Patrick Moore's Yearbook of Astronomy 2014: Special Memorial Edition 144724396X, 9781447243960

Citation preview

Yearbook of Astronomy 2024

Astronomy 2024.indb 1

07/02/2023 22:40

Front Cover: Hoag’s Object: This unusual galaxy was discovered in 1950 by astronomer Art Hoag. Hoag initially thought the smoke-ring-like object resembled a planetary nebula, the glowing remains of a Sun-like star, but he quickly discounted that possibility, suggesting that the mysterious object was most likely a galaxy. Hoag’s Object lies at a distance of 600 million light-years away in the constellation Serpens. The Hubble Wide Field and Planetary Camera 2 took this image on 9 July 2001. For more information on this and other unusual galaxies, see the article Recent Advances in Astronomy. (NASA and the Hubble Heritage Team (STScI/AURA); Acknowledgment: Ray A. Lucas (STScI/AURA))

Astronomy 2024.indb 2

07/02/2023 22:40

2024 EDITED BY

Astronomy 2024.indb 3

07/02/2023 22:40

First published in Great Britain in 2023 by WHITE OWL An imprint of Pen & Sword Books Ltd Yorkshire – Philadelphia Copyright © Brian Jones, 2023 ISBN 978 1 39904 401 1 The right of Brian Jones to be identified as Author of this work has been asserted by him in accordance with the Copyright, Designs and Patents Act 1988. A CIP catalogue record for this book is available from the British Library. All rights reserved. No part of this book may be reproduced or transmitted in any form or by any means, electronic or mechanical including photocopying, recording or by any information storage and retrieval system, without permission from the Publisher in writing. Typeset in Dante By Mac Style Printed and bound by Short Run Press Limited, Exeter.

Pen & Sword Books Ltd incorporates the Imprints of Pen & Sword Books Archaeology, Atlas, Aviation, Battleground, Discovery, Family History, History, Maritime, Military, Naval, Politics, Railways, Select, Transport, True Crime, Fiction, Frontline Books, Leo Cooper, Praetorian Press, Seaforth Publishing, Wharncliffe and White Owl. For a complete list of Pen & Sword titles please contact PEN & SWORD BOOKS LIMITED 47 Church Street, Barnsley, South Yorkshire, S70 2AS, England E-mail: [email protected] Website: www.pen-and-sword.co.uk or PEN AND SWORD BOOKS 1950 Lawrence Rd, Havertown, PA 19083, USA E-mail: [email protected] Website: www.penandswordbooks.com

Astronomy 2024.indb 4

07/02/2023 22:40

Contents Editor’s Foreword 8 Preface13 About Time 14 Using the Yearbook of Astronomy as an Observing Guide 16 The Monthly Star Charts Northern Hemisphere Star Charts  David Harper27 Southern Hemisphere Star Charts  David Harper53 The Planets in 2024  Lynne Marie Stockman78 Mars finder chart – April 2024 to December 2024 81 Jupiter finder chart – January 2024 to December 2024 82 Saturn finder chart – January 2024 to December 2024 83 Uranus finder chart – January 2024 to December 2024 84 Neptune finder chart – January 2024 to December 2024 85 Phases of the Moon in 2024 86 Lunar Occultations in 2024 87 Eclipses in 2024 89 Monthly Sky Notes and Articles 2024 Evening Apparition of Venus – August 2023 to June 2024

92

Monthly Sky Notes January93 99942 Apophis: A Killer at Our Doorstep  Neil Norman 96 Monthly Sky Notes February100 James Short  Gary Yule103 Monthly Sky Notes March106 The Heavens on Stone Canvas: How Our Ancestors Captured the Universe   Jonathan Powell109

Astronomy 2024.indb 5

07/02/2023 22:40

6  Yearbook of Astronomy 2024 Monthly Sky Notes April113 Buran: The Soviet ‘Space Shuttle’  Jonathan Powell116 Monthly Sky Notes May119 The Peregrinations of Pallas  David Harper123 Evening Apparition of Venus – June 2024 to March 2025

126

Monthly Sky Notes June127 Where Are the Sunspots?  John McCue130 Monthly Sky Notes July135 The Great Comet Crash of 1994  Neil Norman138 Monthly Sky Notes August141 A History of the Smith-Clarke Reflector  Gary Yule143 Monthly Sky Notes September147 The Strange Spin of Venus  John McCue150 Monthly Sky Notes October154 Saturn at its Equinox: Mutual Occultations and Eclipses of the Satellites  2024–2025 David Harper157 Monthly Sky Notes November161 Gone But Not Forgotten: Musca Borealis  Lynne Marie Stockman163 Monthly Sky Notes December167 A Howl Across the Void: The Fate of Beagle 2  Jonathan Powell170 Comets in 2024  Neil Norman173 Minor Planets in 2024  Neil Norman180 Meteor Showers in 2024  Neil Norman188 Article Section Recent Advances in Astronomy  Rod Hine Recent Advances in Solar System Exploration  Peter Rea Anniversaries in 2024  Neil Haggath

Astronomy 2024.indb 6

199 204 215

07/02/2023 22:40

Contents 7 Astronomy in Antarctica  Michael Burton222 Things Fall Apart: Chaos in the Solar System  David Harper237 Male Mentors for Women in Astronomy  Mary McIntyre244 Communicating From the Edge of the Solar System  Peter Rea254 Skies over Ancient America  P. Clay Sherrod260 Tracking Older Artificial Satellites  Steve Harvey271 Inner Lives of Dead Stars  Matt Caplan278 Riccardo Giacconi: X-ray Astronomy Pioneer  David M. Harland286 The Astronomers’ Stars: In the Neighbourhood  Lynne Marie Stockman298 Mission to Mars: Countdown to Building a Brave New World: The Right Stuff   at the Right Time  Martin Braddock306 A Triumvirate of Telescope Makers: Thomas Cooke, Howard Grubb and   Alvan Clark  John McCue and John Nichol315 Miscellaneous Some Interesting Variable Stars  Tracie Heywood323 Some Interesting Double Stars  Brian Jones334 Some Interesting Nebulae, Star Clusters and Galaxies  Brian Jones337 Astronomical Organizations 339 Our Contributors 345 Society for the History of Astronomy (Advertisement) The Federation of Astronomical Societies (Advertisement)

Astronomy 2024.indb 7

351 352

07/02/2023 22:40

Editor’s Foreword

The Yearbook of Astronomy 2024 is the latest edition of what has long been an indispensable publication, the annual appearance of which has been eagerly anticipated by astronomers, both amateur and professional, for well over half a century. As ever, the Yearbook is aimed at both the armchair astronomer and the active backyard observer. Within its pages you will find a rich blend of information, star charts and guides to the night sky coupled with an interesting mixture of articles which collectively embrace a wide range of topics, ranging from the history of astronomy to the latest results of astronomical research; space exploration to observational astronomy; and our own celestial neighbourhood out to the farthest reaches of space. The Monthly Star Charts have been compiled by David Harper and show the night sky as seen throughout the year. Two sets of twelve charts have been provided, one set for observers in the Northern Hemisphere and one for those in the Southern Hemisphere. Between them, each pair of charts depicts the entire sky as two semi-circular half-sky views, one looking north and the other looking south. Commencing with this edition of the Yearbook, the charts use the stereographic map projection, which noticeably reduces the distortion of the shapes of the constellations, especially near to the semi-circular edge of each chart. Lists of Phases of the Moon in 2024, Lunar Occultations in 2024 and Eclipses in 2024 are also provided, together with general summaries of the observing conditions for each of the planets in The Planets in 2024. Apparition charts for all the major planetary members of our Solar System have been compiled by David Harper. Further details of these are given in the article Using the Yearbook of Astronomy as an Observing Guide, the apparition charts themselves following the article The Planets in 2024. As with The Planets in 2024, the Monthly Sky Notes have been compiled by Lynne Marie Stockman and give details of the positions and visibility of the planets for each month throughout 2024. At the beginning of each of the monthly notes is a list of the significant Solar System events occurring during that particular month, and which collectively replace the single list of events that has been a feature in previous editions of the Yearbook of Astronomy. Each section of the Monthly Sky Notes

Astronomy 2024.indb 8

07/02/2023 22:40

Editor’s Foreword  9 is accompanied by a short article, the range of which includes items on a variety of astronomy- and space-related topics including an interesting item by Lynne Marie Stockman, in which we discover that, although constellations come and constellations go, some leave behind traces of their former existence. In the first instalment of her Gone But Not Forgotten series, Lynne examines the many lives of a small faint asterism in Aries known most recently in the West as Musca Borealis. The Monthly Sky Notes and Articles section of the book concludes with a trio of articles penned by Neil Norman, these being Comets in 2024, Minor Planets in 2024 and Meteor Showers in 2024, all three titles being fairly self-explanatory describing as they do the occurrence and visibility of examples of these three classes of object during and throughout the year. In his article Recent Advances in Astronomy Rod Hine has selected just few of the many notable events and papers published during the year. From unusual “Ring Galaxies” to the first spectacular images from the James Webb Space Telescope, via possibly the oldest galaxy, Rod discusses the exciting work done by a variety of astronomers and their colleagues. A common theme is the multidisciplinary nature of astronomy today where a review of old observations leads to new ideas which are then refined with the latest observations from new instruments. This is followed by Recent Advances in Solar System Exploration in which Peter Rea updates us on the progress of a number of planetary missions. In a change from previous yearbooks, this will not be done mission by mission but rather start at the Sun and move outward to the Kuiper belt. We will stop off at each planet in turn to explain what planetary missions are currently operating or en route. We will pause in the asteroid belt between Mars and Jupiter as a number of missions to asteroids are currently on their way to explore this fascinating region of the solar system. One of the cornerstones of modern cosmology was laid a century ago, when Edwin Hubble determined the distance of M31, proving that “spiral nebulae” are other galaxies outside our own. In his article Anniversaries in 2024 Neil Haggath commemorates this event. He also notes the pioneering space probe Mariner 10, the birth of Sir William Huggins and the death of Fritz Zwicky, the “grumpy genius” who predicted neutron stars decades before they were found to exist. The Antarctic Plateau is the driest and coldest region on the surface of our planet. This offers superlative conditions for many kinds of astronomical observations, especially across infrared to millimetre wavelengths. The vast quantity of pure ice also enables imaging of cosmic sources of neutrinos. In the article Astronomy from Antarctica Michael Burton, Antarctic astronomer and Director of the UK’s oldest observatory in Armagh, overviews astronomy on this frozen continent and the remarkable science it has engendered.

Astronomy 2024.indb 9

07/02/2023 22:40

10  Yearbook of Astronomy 2024 In Things Fall Apart: Chaos in the Solar System, David Harper discovers that the Solar System was an exciting and dynamic place in its very early years, as Jupiter and Saturn tacked inwards and veered outwards across hundred of millions of kilometres before settling into their present orbits. In the far future, as the Sun enters its planetary nebula phase, further dramatic changes are likely to happen, as passing stars disrupt the Solar System, ejecting the gas and ice giants into interstellar space. In the third and final part of her Male Mentors for Women in Astronomy series, Mary McIntyre brings the story forward, telling the fascinating tales of some the exceptional female astronomers who were working during the late-eighteenth century, through to the “Lady Computers” who worked at Harvard College and the Royal Greenwich Observatory during the nineteenth century. In his article Communicating from the Edge of the Solar System Peter Rea explains how signals from spacecraft a long way away from Earth get their information back. Talking to spacecraft in Earth orbit only takes a fraction of a second but from Pluto or beyond it can take many hours one way. This becomes significant if a spacecraft emergency occurs as happened with the New Horizons spacecraft as it was approaching Pluto in 2015. Signals to New Horizons were taking nine hours, and when your spacecraft is in trouble, the speed of light seems agonisingly slow. We now know that prehistoric cultures in North America developed methods of time keeping – calendars – to predict the passage of time. But to what extent? In the second of his three-part series of articles Skies over Ancient America, astronomer and archaeologist P. Clay Sherrod discusses our attempts to study the huge stonecovered earthen mounds, calendar monuments. Are these curious structures and markers indeed predictors of the passages of the seasons or – as we assume in many prehistoric cultural sites – merely a coincidental arrangement that modern mankind has assigned to be ancient celestial time pieces? SpaceX satellite cluster launches seem to have dominated the press recently. However, thanks to the Space Race, satellites have been orbiting the planet for well over 60 years. It may be interesting to know that some of the very earliest satellites are still in orbit (although not necessarily operating as originally intended). In the article Tracking Older Artificial Satellites by Steve Harvey, we take a look at both the software and hardware needed to enable us to track and observe these relics of the Space Age. As we learn from his article Inner Lives of Dead Stars by Matt Caplan, dead stars are far from dead. Deep inside the cores of white dwarfs, the incredible pressures and strange mixtures of elements produce new phases of matter unlike any that existed during the star’s life. But while their cores try to hide these phases

Astronomy 2024.indb 10

07/02/2023 22:40

Editor’s Foreword  11 from us deep inside the star, the starlight gives away the rich secrets of their inner lives. In his article Riccardo Giacconi: X-ray Astronomy Pioneer, regular contributor David M. Harland looks back at the work of the Italian-born physicist Riccardo Giacconi who, after moving to America in the 1950s, made pioneering observations of cosmic rays. Giacconi subsequently developed instruments to measure X-rays which he sent aloft – initially on sounding rockets and later on satellites – to study the Sun and to make the first all-sky survey of X-ray sources with the Uhuru satellite, launched in 1970. Lynne Marie Stockman continues her exploration of the unusual stars named after the astronomers who discovered them as she visits the solar neighbourhood in her article The Astronomers’ Stars: In the Neighbourhood. From van Maanen’s Star, the nearest solitary white dwarf, to tiny Teegarden’s Star which is just large enough to initiate nuclear fusion in its core, to the solar-system-skimming Scholz’s Star, our nearest neighbours are an eclectic collection of astronomical oddballs. This is followed by Mission to Mars: Countdown to Building a Brave New World by Martin Braddock, the fourth in a series of articles scheduled to appear in the Yearbook of Astronomy throughout the 2020s and which will keep the reader fully up to date with the ongoing preparations geared towards sending a manned mission to Mars at or around the turn of the decade. Penned by John McCue, an enthusiast of astronomical history, and John Nichol, a renowned telescope maker of long experience, the article A Triumvirate of Telescope Makers: Thomas Cooke, Howard Grubb and Alvan Clark brings together the tales of arguably the greatest makers of refractors in history. The stories of Englishman Thomas Cooke, Irishman Howard Grubb and American Alvan Clark, are intertwined and contemporary and they probably spurred each other to greater heights. Their legacy is the 40-inch Yerkes refractor, still a giant among refractors. The final section of the book starts off with Some Interesting Variable Stars by Tracie Heywood which contains useful information on variables as well as predictions for timings of minimum brightness of the famous eclipsing binary Algol for 2024. Some Interesting Double Stars and Some Interesting Nebulae, Star Clusters and Galaxies present a selection of objects for you to seek out in the night sky. The lists included here are by no means definitive and may well omit your favourite celestial targets. If this is the case, please let us know and we will endeavour to include these in future editions of the Yearbook of Astronomy. Next we have a selection of Astronomical Organizations, which lists organizations and associations across the world through which you can further pursue your interest and participation in astronomy (if there are any that we have omitted

Astronomy 2024.indb 11

07/02/2023 22:40

12  Yearbook of Astronomy 2024 please let us know) and Our Contributors, which contains brief background details of the numerous writers who have contributed to this edition of the Yearbook. New topics and themes are occasionally introduced into the Yearbook of Astronomy, allowing it to keep pace with the increasing range of skills, techniques and observing methods now open to amateur astronomers, this in addition to articles relating to our rapidly-expanding knowledge of the Universe in which we live. There is always an interesting mix, some articles written at a level which will appeal to the casual reader and some of what may be loosely described as at a more academic level. The intention is to fully maintain and continually increase the usefulness and relevance of the Yearbook of Astronomy to the interests of the readership who are, without doubt, the most important aspect of the Yearbook and the reason it exists in the first place. With this in mind, suggestions from readers for further improvements and additions to the Yearbook content are welcomed. All thoughts and comments can be sent via the Yearbook of Astronomy website at yearbookofastronomy.com After all, the book is written for you … As ever, grateful thanks are extended to those individuals who have contributed a great deal of time and effort to the Yearbook of Astronomy 2024, including David Harper, who has provided updated versions of his Monthly Star Charts. These were generated specifically for what has been described as the new generation of the Yearbook of Astronomy, and the charts add greatly to the overall value of the book to star gazers. Equally important are the efforts of Lynne Marie Stockman who has put together the Monthly Sky Notes. Their combined efforts have produced what can justifiably be described as the backbone of the Yearbook of Astronomy. Also worthy of mention is Mat Blurton, who has done an excellent job typesetting the Yearbook. Also Jonathan Wright, Charlotte Mitchell, Lori Jones, Janet Brookes, Paul Wilkinson, Charlie Simpson and Rosie Crofts of Pen & Sword Books Ltd for their efforts in producing and promoting the Yearbook of Astronomy 2024, the latest edition of this much-loved and iconic publication. Brian Jones – Editor Bradford, West Riding of Yorkshire October 2022

Astronomy 2024.indb 12

07/02/2023 22:40

Preface

The information given in this edition of the Yearbook of Astronomy is in narrative form. The positions of the planets given in the Monthly Sky Notes often refer to the constellations in which they lie at the time. These can be found on the star charts which collectively show the whole sky via two charts depicting the northern and southern circumpolar stars and forty-eight charts depicting the main stars and constellations for each month of the year. The northern and southern circumpolar charts show the stars that are within 45° of the two celestial poles, while the monthly charts depict the stars and constellations that are visible throughout the year from Europe and North America or from Australia and New Zealand. The monthly charts overlap the circumpolar charts. Wherever you are on the Earth, you will be able to locate and identify the stars depicted on the appropriate areas of the chart(s). There are numerous star atlases available that offer more detailed information, such as Sky & Telescope’s POCKET SKY ATLAS and Norton’s STAR ATLAS and Reference Handbook to name but a couple. In addition, more precise information relating to planetary positions and so on can be found in a number of publications, a good example of which is The Handbook of the British Astronomical Association, as well as many of the popular astronomy magazines such as the British monthly periodicals Sky at Night and Astronomy Now and the American monthly magazines Astronomy and Sky & Telescope.

Astronomy 2024.indb 13

07/02/2023 22:40

About Time

Before the late eighteenth century, the biggest problem affecting mariners sailing the seas was finding their position. Latitude was easily determined by observing the altitude of the pole star above the northern horizon. Longitude, however, was far more difficult to measure. The inability of mariners to determine their longitude often led to them getting lost, and on many occasions shipwrecked. To address this problem King Charles II established the Royal Observatory at Greenwich in 1675 and from here, Astronomers Royal began the process of measuring and cataloguing the stars as they passed due south across the Greenwich meridian. Now mariners only needed an accurate timepiece (the chronometer invented by Yorkshire-born clockmaker John Harrison) to display GMT (Greenwich Mean Time). Working out the local standard time onboard ship and subtracting this from GMT gave the ship’s longitude (west or east) from the Greenwich meridian. Therefore mariners always knew where they were at sea and the longitude problem was solved. Astronomers use a time scale called Universal Time (UT). This is equivalent to Greenwich Mean Time and is defined by the rotation of the Earth. The Yearbook of Astronomy gives all times in UT rather than in the local time for a particular city or country. Times are expressed using the 24-hour clock, with the day beginning at midnight, denoted by 00:00. Universal Time (UT) is related to local mean time by the formula: Local Mean Time = UT – west longitude In practice, small differences in longitude are ignored and the observer will use local clock time which will be the appropriate Standard (or Zone) Time. As the formula indicates, places in west longitude will have a Standard Time slow on UT, while those in east longitude will have a Standard Time fast on UT. As examples we have:

Astronomy 2024.indb 14

07/02/2023 22:40

About Time  15 Standard Time in New Zealand Victoria, NSW Japan Western Australia India Pakistan Kenya South Africa British Isles Newfoundland Standard Time Atlantic Standard Time Eastern Standard Time Central Standard Time Mountain Standard Time Pacific Standard Time Alaska Standard Time Hawaii-Aleutian Standard Time

UT +12 hours UT +10 hours UT + 9 hours UT + 8 hours UT + 5 hours 30 minutes UT + 5 hours UT + 3 hours UT + 2 hours UT UT 3 hours 30 minutes UT 4 hours UT 5 hours UT 6 hours UT 7 hours UT 8 hours UT 9 hours UT 10 hours

During the periods when Summer Time (also called Daylight Saving Time) is in use, one hour must be added to Standard Time to obtain the appropriate Summer/ Daylight Saving Time. For example, Pacific Daylight Time is UT 7 hours.

Astronomy 2024.indb 15

07/02/2023 22:40

Using the Yearbook of Astronomy as an Observing Guide

Notes on the Monthly Star Charts The star charts on the following pages show the night sky throughout the year. There are two sets of charts, one for use by observers in the Northern Hemisphere and one for those in the Southern Hemisphere. The first set is drawn for latitude 52°N and can be used by observers in Europe, Canada and most of the United States. The second set is drawn for latitude 35°S and show the stars as seen from Australia and New Zealand. Twelve pairs of charts are provided for each of these latitudes. Each pair of charts shows the entire sky as two semi-circular half-sky views, one looking north and the other looking south. A given pair of charts can be used at different times of year. For example, chart 1 shows the night sky at midnight on 21 December, but also at 2am on 21 January, 4am on 21 February and so forth. The accompanying table will enable you to select the correct chart for a given month and time of night. The caption next to each chart also lists the dates and times of night for which it is valid. The charts are intended to help you find the more prominent constellations and other objects of interest mentioned in the monthly observing notes. To avoid the charts becoming too crowded, only stars of magnitude 4.5 or brighter are shown. This corresponds to stars that are bright enough to be seen from any dark suburban garden on a night when the Moon is not too close to full phase. Each constellation is depicted by joining selected stars with lines to form a pattern. There is no official standard for these patterns, so you may occasionally find different patterns used in other popular astronomy books for some of the constellations. Any map projection from a sphere onto a flat page will by necessity contain some distortions. This is true of star charts as well as maps of the Earth. The distortion on the half-sky charts is greatest near the semi-circular boundary of each chart, where it may appear to stretch constellation patterns out of shape. The charts also show selected deep-sky objects such as galaxies, nebulae and star clusters. Many of these objects are too faint to be seen with the naked eye, and you will need binoculars or a telescope to observe them. Please refer to the table of deep-sky objects for more information.

Astronomy 2024.indb 16

07/02/2023 22:40

Using the Yearbook of Astronomy as an Observing Guide  17

Planetary Apparition Diagrams The diagrams of the apparitions of Mercury and Venus show the position of the respective planet in the sky at the moment of sunrise or sunset throughout the entire apparition. Two sets of positions are plotted on each chart: for latitude 52º North (blue line) and for latitude 35º South (red line). A thin dotted line denotes the portion of the apparition which falls outside the year covered by this edition of the Yearbook. A white dot indicates the position of Venus on the first day of each month, or of Mercury on the first, eleventh and 21st of the month. The day of greatest elongation (GE) is also marked by a white dot. Note that the dots do NOT indicate the magnitude of the planet. The finder chart for Mars shows its path from April to December of 2024. In April it is a morning object as it emerges from conjunction with the Sun in November of last year. By December, it is visible for most of the night, and it is approaching opposition in January 2025. Mars traverses 150° in ecliptic longitude during this period, moving from Aquarius in April to Cancer in December, so the chart is based upon the ecliptic, which runs across the centre of the chart from right to left. The position of Mars is indicated on the 1st of each month, and at its most easterly on 7 December, when its motion becomes retrograde. Stars are shown to magnitude 5.5. Note that the sizes of the Mars dots do NOT indicate its magnitude. The finder charts for Jupiter, Saturn, Uranus and Neptune show the paths of the planets throughout the year. The position of each planet is indicated at opposition and at stationary points, as well as the start and end of the year and on the 1st of each month (1st of April, July and October only for Uranus and Neptune) where these dates do not fall too close to an event that is already marked. Stars are shown to magnitude 5.5 on the charts for Jupiter and Saturn. On the Uranus chart, stars are shown to magnitude 8; on the Neptune chart, the limiting magnitude is 10. In both cases, this is approximately two magnitudes fainter than the planet itself. Right Ascension and Declination scales are shown for the epoch J2000 to allow comparison with modern star charts. Note that the sizes of the dots denoting the planets do NOT indicate their magnitudes.

Selecting the Correct Charts The table below shows which of the charts to use for particular dates and times throughout the year and will help you to select the correct pair of half-sky charts for any combination of month and time of night. The Earth takes 23 hours 56 minutes (and 4 seconds) to rotate once around its axis with respect to the fixed stars. Because this is around four minutes shorter than a full 24 hours, the stars appear to rise and set about 4 minutes earlier on

Astronomy 2024.indb 17

07/02/2023 22:40

18  Yearbook of Astronomy 2024 each successive day, or around an hour earlier each fortnight. Therefore, as well as showing the stars at 10pm (22h in 24-hour notation) on 21 January, chart 1 also depicts the sky at 9pm (21h) on 6 February, 8pm (20h) on 21 February and 7pm (19h) on 6 March. The times listed do not include summer time (daylight saving time), so if summer time is in force you must subtract one hour to obtain standard time (GMT if you are in the United Kingdom) before referring to the chart. For example, to find the correct chart for mid-September in the northern hemisphere at 3am summer time, first of all subtract one hour to obtain 2am (2h) standard time. Then you can consult the table, where you will find that you should use chart 11. The table does not indicate sunrise, sunset or twilight. In northern temperate latitudes, the sky is still light at 18h and 6h from April to September, and still light at 20h and 4h from May to August. In Australia and New Zealand, the sky is still light at 18h and 6h from October to March, and in twilight (with only bright stars visible) at 20h and 04h from November to January. Local Time

18h

20h

22h

0h

2h

4h

6h

January

11

12

 1

 2

 3

 4

 5

February

12

 1

 2

 3

 4

 5

 6

March

 1 

 2

 3

 4

 5

 6

 7

April

 2

 3

 4

 5

 6

 7

 8

May

 3

 4

 5

 6

 7

 8

 9

June

 4

 5

 6

 7

 8

 9

10

July

 5

 6

 7

 8

 9

10

11

August

 6

 7

 8

 9

10

11

12

September

 7

 8

 9

10

11

12

 1

October

 8

 9

10

11

12

 1

 2

November

 9

10

11

12

 1

 2

 3

December

10

11

12

 1

 2

 3

 4

Astronomy 2024.indb 18

07/02/2023 22:40

Using the Yearbook of Astronomy as an Observing Guide  19

Legend to the Star Charts

STARS

Symbol

Magnitude

DEEP-SKY OBJECTS

Symbol

Type of object

0 or brighter 1 2 3 4 5

Open star cluster Globular star cluster Nebula Cluster with nebula Planetary nebula Galaxy

Double star Variable star

Magellanic Clouds

Star Names There are over 200 stars with proper names, most of which are of Roman, Greek or Arabic origin although only a couple of dozen or so of these names are used regularly. Examples include Arcturus in Boötes, Castor and Pollux in Gemini and Rigel in Orion. A system whereby Greek letters were assigned to stars was introduced by the German astronomer and celestial cartographer Johann Bayer in his star atlas Uranometria, published in 1603. Bayer’s system is applied to the brighter stars within any particular constellation, which are given a letter from the Greek alphabet followed by the genitive case of the constellation in which the star is located. This genitive case is simply the Latin form meaning ‘of ’ the constellation. Examples are the stars Alpha Boötis and Beta Centauri which translate literally as ‘Alpha of Boötes’ and ‘Beta of the Centaur’. As a general rule, the brightest star in a constellation is labelled Alpha (α), the second brightest Beta (β), and the third brightest Gamma (γ) and so on, although there are some constellations where the system falls down. An example is Gemini where the principal star (Pollux) is designated Beta Geminorum, the second brightest (Castor) being known as Alpha Geminorum. There are only 24 letters in the Greek alphabet, the consequence of which was that the fainter naked eye stars needed an alternative system of classification. The system in popular use is that devised by the first Astronomer Royal John Flamsteed in which the stars in each constellation are listed numerically in order from west to

Astronomy 2024.indb 19

07/02/2023 22:40

20  Yearbook of Astronomy 2024 east. Although many of the brighter stars within any particular constellation will have both Greek letters and Flamsteed numbers, the latter are generally used only when a star does not have a Greek letter.

The Greek Alphabet α

Alpha

ι

Iota

ρ

β

Beta

κ

Kappa

σ

Sigma

γ

Gamma

λ

Lambda

τ

Tau

δ

Delta

μ

Mu

υ

Upsilon

ε

Epsilon

ν

Nu

φ

Phi

ζ

Zeta

ξ

Xi

χ

Chi

Rho

η

Eta

ο

Omicron

ψ

Psi

θ

Theta

π

Pi

ω

Omega

The Names of the Constellations On clear, dark, moonless nights, the sky seems to teem with stars although in reality you can never see more than a couple of thousand or so at any one time when looking with the unaided eye. Each and every one of these stars belongs to a particular constellation, although the constellations that we see in the sky, and which grace the pages of star atlases, are nothing more than chance alignments. The stars that make up the constellations are often situated at vastly differing distances from us and only appear close to each other, and form the patterns that we see, because they lie in more or less the same direction as each other as seen from Earth. A large number of the constellations are named after mythological characters, and were given their names thousands of years ago. However, those star groups lying close to the south celestial pole were discovered by Europeans only during the last few centuries, many of these by explorers and astronomers who mapped the stars during their journeys to lands under southern skies. This resulted in many of the newer constellations having modern-sounding names, such as Octans (the Octant) and Microscopium (the Microscope), both of which were devised by the French astronomer Nicolas Louis De La Caille during the early 1750s. Over the centuries, many different suggestions for new constellations have been put forward by astronomers who, for one reason or another, felt the need to add new groupings to star charts and to fill gaps between the traditional constellations. Astronomers drew up their own charts of the sky, incorporating their new groups

Astronomy 2024.indb 20

07/02/2023 22:40

Using the Yearbook of Astronomy as an Observing Guide  21 into them. A number of these new constellations had cumbersome names, notable examples including Officina Typographica (the Printing Shop) introduced by the German astronomer Johann Bode in 1801; Sceptrum Brandenburgicum (the Sceptre of Brandenburg) introduced by the German astronomer Gottfried Kirch in 1688; Taurus Poniatovii (Poniatowski’s Bull) introduced by the Polish-Lithuanian astronomer Martin Odlanicky Poczobut in 1777; and Quadrans Muralis (the Mural Quadrant) devised by the French astronomer Joseph-Jerôme de Lalande in 1795. Although these have long since been rejected, the latter has been immortalised by the annual Quadrantid meteor shower, the radiant of which lies in an area of sky formerly occupied by Quadrans Muralis. During the 1920s the International Astronomical Union (IAU) systemised matters by adopting an official list of 88 accepted constellations, each with official spellings and abbreviations. Precise boundaries for each constellation were then drawn up so that every point in the sky belonged to a particular constellation. The abbreviations devised by the IAU each have three letters which in the majority of cases are the first three letters of the constellation name, such as AND for Andromeda, EQU for Equuleus, HER for Hercules, ORI for Orion and so on. This trend is not strictly adhered to in cases where confusion may arise. This happens with the two constellations Leo (abbreviated LEO) and Leo Minor (abbreviated LMI). Similarly, because Triangulum (TRI) may be mistaken for Triangulum Australe, the latter is abbreviated TRA. Other instances occur with Sagitta (SGE) and Sagittarius (SGR) and with Canis Major (CMA) and Canis Minor (CMI) where the first two letters from the second names of the constellations are used. This is also the case with Corona Australis (CRA) and Corona Borealis (CRB) where the first letter of the second name of each constellation is incorporated. Finally, mention must be made of Crater (CRT) which has been abbreviated in such a way as to avoid confusion with the aforementioned CRA (Corona Australis). The table shown on the following pages contains the name of each of the 88 constellations together with the translation and abbreviation of the constellation name. The constellations depicted on the monthly star charts are identified with their abbreviations rather than the full constellation names.

Astronomy 2024.indb 21

07/02/2023 22:40

22  Yearbook of Astronomy 2024

The Constellations Andromeda

Andromeda

AND

Delphinus

The Dolphin

DEL

Antlia

The Air Pump

ANT

Dorado

The Goldfish

DOR

Apus

The Bird of Paradise

APS

Draco

The Dragon

DRA

Equuleus

The Foal

EQU

Aquarius

The Water Carrier

AQR

Eridanus

The River

ERI

Aquila

The Eagle

AQL

Fornax

The Furnace

FOR

Ara

The Altar

ARA

Gemini

The Twins

GEM

Aries

The Ram

ARI

Grus

The Crane

GRU

Auriga

The Charioteer

AUR

Hercules

Hercules

HER

Boötes

The Herdsman

BOO

Horologium

The Graving Tool

CAE

The Pendulum Clock

HOR

Caelum

CAM

Hydra

The Water Snake

HYA

Hydrus

The Lesser Water Snake

HYI

Indus

The Indian

IND

Lacerta

The Lizard

LAC

Leo

The Lion

LEO

Leo Minor

The Lesser Lion

LMI

Lepus

The Hare

LEP

Libra

The Scales

LIB

Lupus

The Wolf

LUP

Lynx

The Lynx

LYN

Lyra

The Lyre

LYR

Mensa

The Table Mountain MEN

Microscopium

The Microscope

MIC

Camelopardalis The Giraffe Cancer

The Crab

CNC

Canes Venatici

The Hunting Dogs

CVN

Canis Major

The Great Dog

CMA

Canis Minor

The Little Dog

CMI

Capricornus

The Goat

CAP

Carina

The Keel

CAR

Cassiopeia

Cassiopeia

CAS

Centaurus

The Centaur

CEN

Cepheus

Cepheus

CEP

Cetus

The Whale

CET

Chamaeleon

The Chameleon

CHA

Circinus

The Pair of Compasses

CIR

Columba

The Dove

COL

Monoceros

The Unicorn

MON

COM

Musca

The Fly

MUS

Corona Australis The Southern Crown CRA

Norma

The Level

NOR

Corona Borealis

The Northern Crown

CRB

Octans

The Octant

OCT

Ophiuchus

The Serpent Bearer

OPH

Corvus

The Crow

CRV

Orion

Orion

ORI

Crater

The Cup

CRT

Pavo

The Peacock

PAV

Crux

The Cross

CRU

Pegasus

Pegasus

PEG

Cygnus

The Swan

CYG

Perseus

Perseus

PER

Coma Berenices Berenice’s Hair

Astronomy 2024.indb 22

07/02/2023 22:40

Using the Yearbook of Astronomy as an Observing Guide  23

Phoenix

The Phoenix

PHE

Sextans

The Sextant

SEX

Pictor

The Painter’s Easel

PIC

Taurus

The Bull

TAU

Pisces

The Fish

PSC

Telescopium

The Telescope

TEL

Piscis Austrinus The Southern Fish

PSA

Triangulum

The Triangle

TRI

Puppis

The Stern

PUP

The Mariner’s Compass

PYX

The Southern Triangle

TRA

Pyxis

Triangulum Australe Tucana

The Toucan

TUC

Reticulum

The Net

RET

Ursa Major

The Great Bear

UMA

Sagitta

The Arrow

SGE

Ursa Minor

The Little Bear

UMI

Sagittarius

The Archer

SGR

Vela

The Sail

VEL

Scorpius

The Scorpion

SCO

Virgo

The Virgin

VIR

Sculptor

The Sculptor

SCL

Volans

The Flying Fish

VOL

Scutum

The Shield

SCT

Vulpecula

The Fox

VUL

Serpens Caput and Cauda

The Serpent

SER

Astronomy 2024.indb 23

07/02/2023 22:40

Astronomy 2024.indb 24

07/02/2023 22:40

The Monthly Star Charts

Astronomy 2024.indb 25

07/02/2023 22:40

Astronomy 2024.indb 26

07/02/2023 22:40

M

51

Northern Hemisphere Star Charts

UMA

UMI

DRA Polaris

Capella

CAM

M 52

CAS

Deneb M 39

N G

C

88

4

N G

C

86

9

CEP

This chart shows stars lying at declinations between +45 and +90 degrees. These constellations are circumpolar for observers in Europe and North America.

Astronomy 2024.indb 27

07/02/2023 22:40

Astronomy 2024.indb 28

WEST

Algenib

October 6 at November 6 at December 6 at January 6 at February 6 at

M

AND

Alpheratz

Markab

PEG

33

5h 3h 1h 23h 21h

Scheat

31 M

34 M

C

4

88

LAC

G

N

9

86

52

29 M

39 M

M

CAS

C

G

N

CYG LYR

Deneb

CEP

CAM

NORTH

Vega

DRA

Polaris

ZENITH

92 M

UMI

M

13

BOO

UMA

M

51

M

3

CVN

COM

LMI

Zosma

4h 2h 0h 22h 20h

EAST

October 21 at November 21 at December 21 at January 21 at February 21 at

1N

07/02/2023 22:40

Astronomy 2024.indb 29

EAST

LEO

SEX

Regulus

5h 3h 1h 23h 21h

Algieba

October 6 at November 6 at December 6 at January 6 at February 6 at

Alphard

HYA

44 M

CNC

PUP

MON

GEM

Castor

CMI Procyon

Pollux

LYN

41

M

M

LEP

Saiph

ORI

36

M

SOUTH

CMA

Sirius

35

37

M

Betelgeuse

AUR

ZENITH

Aldebaran

79 M

Rigel

Bellatrix

42

M

M

1

38

M

Capella

TAU

ERI

PER

Algol

Mira

CET

ARI

TRI

PSC

4h 2h 0h 22h 20h

WEST

October 21 at November 21 at December 21 at January 21 at February 21 at

1S

07/02/2023 22:40

Astronomy 2024.indb 30

WEST

ARI

TRI

5h 3h 1h 23h 21h

PSC

November 6 at December 6 at January 6 at February 6 at March 6 at

33

M

Algol

PER

34 M

Alpheratz

AND

31 M

C

G

N

4 88

Capella

N

G

C

9

86

CAS

CAM

LAC

M

52

39 M

CEP

CYG

NORTH

9

Deneb

Polaris

ZENITH

LYR

Vega

DRA

UMI

M

92

UMA

M

13

51

CRB

BOO

M

Izar

CVN

3 M

Arcturus

COM

4h 2h 0h 22h 20h

EAST

November 21 at December 21 at January 21 at February 21 at March 21 at

2N

07/02/2023 22:40

Astronomy 2024.indb 31

EAST

VIR

November 6 at December 6 at January 6 at February 6 at March 6 at

5h 3h 1h 23h 21h

4

10

M

CRT

Zosma

LEO

LMI

SEX

Regulus

Algieba

ANT

Alphard

HYA

PYX

M

SOUTH

M

AUR

LEP

Saiph

Betelgeuse

Sirius 41 CMA

MON

GEM

Castor

CMI

PUP

Procyon

CNC

44

Pollux

LYN

ZENITH

37

79

M

M

42

ORI

35

M

M

M

M

1

Rigel

ERI

TAU

Aldebaran

38

Bellatrix

36

M

4h 2h 0h 22h 20h

WEST

Mira

November 21 at December 21 at January 21 at February 21 at March 21 at

2S

07/02/2023 22:40

Astronomy 2024.indb 32

WEST

TAU

Aldebaran

M

December 6 at January 6 at February 6 at March 6 at April 6 at

37

M

36

5h 3h 1h 23h 21h

38 M

TRI

Algol

Capella

PER

ARI

AUR

34 M

M

33

C

G

N

8

84

AND

N

9

86

31 M

C

G

CAM

CAS M

LAC

CEP

NORTH

52

UMI

39 M

Polaris

UMA

ZENITH

29 M

Deneb

CYG

LYR

DRA

M

57

Vega

M

92

51

HER

M

M

13

CRB

BOO

Izar

SER

4h 2h 0h 22h 20h

EAST

December 21 at January 21 at February 21 at March 21 at April 21 at

3N

07/02/2023 22:40

Astronomy 2024.indb 33

EAST

December 6 at January 6 at February 6 at March 6 at April 6 at

Arcturus

5h 3h 1h 23h 21h

3 M

Spica

VIR

COM

CVN

CRV

4

10 M

CRT

LEO

Zosma

LMI

SOUTH

ANT

SEX

Regulus

Algieba

ZENITH

PYX

Alphard

HYA

Procyon

CNC

44

PUP

M

M

CMA

41

Sirius

GEM

Castor

MON

CMI

Pollux

LYN

LEP

Saiph

Betelgeuse

M

42

Rigel

ORI

35 M

Bellatrix

1 M

4h 2h 0h 22h 20h

WEST

December 21 at January 21 at February 21 at March 21 at April 21 at

3S

07/02/2023 22:40

Astronomy 2024.indb 34

WEST

etelgeuse

ORI

GEM

January 6 at February 6 at March 6 at April 6 at May 6 at

35

M

1

37 M

Aldebaran

M

Castor

5h 3h 1h 23h 21h

M

36

38

M

AUR

LYN

Capella

PER

C

G N Algol 34 M

CAM

8

84

UMA

C

G

N

9

86

M

NORTH

31

CAS

52 M

Polaris

UMI

ZENITH

CEP

LAC

M

39

M

29

Deneb

DRA

CYG

LYR

M

VUL 27

57

92

M

Vega

M

13

HER

M

4h 2h 0h 22h 20h

EAST

January 21 at February 21 at March 21 at April 21 at May 21 at

4N

07/02/2023 22:40

Astronomy 2024.indb 35

EAST

OPH

10

M

January 6 at February 6 at March 6 at April 6 at May 6 at

12

M

SER

CRB

5h 3h 1h 23h 21h

LIB

Izar

BOO

Arcturus

Spica

3 M

51

M

VIR

COM

4

CRT

SOUTH

CRV

10

M

CVN

ZENITH

SEX

ANT

LEO

Zosma

LMI

Alphard

HYA

Regulus

Algieba M

Procyon

CNC

44

MON

CMI

Pollux

4h 2h 0h 22h 20h

WEST

January 21 at February 21 at March 21 at April 21 at May 21 at

4S

07/02/2023 22:40

Astronomy 2024.indb 36

WEST

Procyon

CNC

CMI

M

44

January 6 at February 6 at March 6 at April 6 at May 6 at

Pollux

7h 5h 3h 1h 23h

GEM

Castor

36 M

AUR

7

35 M3

M

LYN

38 M

UMA

Capella C G N

PER Algol

CAM C G N

NORTH

34 M

4 88

9 86

Polaris

UMI

ZENITH

CAS

31 M

M

52

CEP

DRA

LAC

M

39

M

Deneb 29

M

LYR

CYG

92

Vega

SGE

VUL 27 M

DEL

57 M

Altair

6h 4h 2h 0h 22h

EAST

January 21 at February 21 at March 21 at April 21 at May 21 at

5N

07/02/2023 22:40

Astronomy 2024.indb 37

EAST

January 6 at February 6 at March 6 at April 6 at May 6 at

M

SCT

11

7h 5h 3h 1h 23h

17

HER

16 M

OPH 10

M

13

M

Antares

12

M

4 M

SCO

SER

CRB

LIB

Izar

BOO

SOUTH

3

M

Spica

Arcturus

ZENITH

VIR

51

M

CRV

4 10 M

COM

CVN

CRT

SEX

LEO

Zosma

Alphard

HYA

Regulus

Algieba

LMI

6h 4h 2h 0h 22h

WEST

January 21 at February 21 at March 21 at April 21 at May 21 at

5S

07/02/2023 22:40

Astronomy 2024.indb 38

WEST

LEO

Regulus

Algieba

March 6 at April 6 at May 6 at June 6 at July 6 at

5h 3h 1h 23h 21h

LMI

44 M

Pollux

Castor

LYN

UMA

51

M

AUR

PER

C G N

Polaris

NORTH

Capella

CAM

UMI

ZENITH

Algol

4 88

M

34

G N

C

CAS 9 86

DRA

M

52

CEP

M

AND

31

Scheat

PEG

LAC

39

Alpheratz

M

9

Deneb M2

CYG

Markab

Enif

15 M

4h 2h 0h 22h 20h

EAST

March 21 at April 21 at May 21 at June 21 at July 21 at

6N

07/02/2023 22:40

Astronomy 2024.indb 39

EAST

EQU

DEL

March 6 at April 6 at May 6 at June 6 at July 6 at

VUL

Altair

SGE

27 M

5h 3h 1h 23h 21h

AQL

LYR

M

57

Vega

SCT

11

M

17 M

16 M

8 M

20

M

HER

10

6

M

M

OPH

92

M

Antares

12

M

13

M

SOUTH

SCO

4 M

SER

CRB

ZENITH

LIB

Izar

BOO

Spica

Arcturus

3

M

CRV

VIR

M

4 10

CRT

COM

CVN

4h 2h 0h 22h 20h

WEST

Zosma

March 21 at April 21 at May 21 at June 21 at July 21 at

6S

07/02/2023 22:40

Astronomy 2024.indb 40

WEST

COM

May 6 at June 6 at July 6 at August 6 at September 6 at

3h 1h 23h 21h 19h

LEO

Zosma

CVN

Algieba

LMI

51

M

UMA

LYN

UMI

Capella

CAM

Polaris

NORTH

AUR

DRA

ZENITH

9 86

52

34

M

M

Algol

G N

PER

C G N

4 88

C

CAS

CEP

TRI

M

33

31

M

M

39

Deneb

AND

LAC

Alpheratz

Algenib

PEG

Scheat

2h 0h 22h 20h 18h

EAST

May 21 at June 21 at July 21 at August 21 at September 21 at

7N

07/02/2023 22:40

Astronomy 2024.indb 41

EAST

Markab

May 6 at June 6 at July 6 at August 6 at September 6 at

AQR

3h 1h 23h 21h 19h

Sadalmelik

Enif

15 M

EQU

DEL

29 M

CAP

Altair

SGE

AQL

27 M VUL

CYG

LYR

M

11

M 8 M

M

16 20 M

SOUTH

17

SGR

SCT

M

57

Vega

ZENITH

6 M

4 M

12 M

SCO

Antares

10 M

OPH

HER

92

M

M

13

LIB

SER

CRB

Spica

Izar

BOO

Arcturus

VIR

3 M

2h 0h 22h 20h 18h

WEST

May 21 at June 21 at July 21 at August 21 at September 21 at

7S

07/02/2023 22:40

Astronomy 2024.indb 42

WEST

1h 23h 21h 19h 17h

Arcturus

Izar

July 6 at August 6 at September 6 at October 6 at November 6 at

3

COM

M

BOO

CVN

M

51

LMI

UMA

DRA

UMI

NORTH

LYN

Polaris

ZENITH

AUR

CAM

CEP

36

M

38

Capella

N

C G

4 88

52

CAS

M

N

C G

PER

9 86

34

Algol

M

M

31

TRI ARI

33 M

AND

0h 22h 20h 18h 16h

EAST

July 21 at August 21 at September 21 at October 21 at November 21 at

8N

07/02/2023 22:40

Astronomy 2024.indb 43

EAST

PSC

Alpheratz

1h 23h 21h 19h 17h

Algenib

July 6 at August 6 at September 6 at October 6 at November 6 at

PEG Markab

Scheat

AQR

LAC

PSA

15

M

Sadalmelik

Enif

M

39

EQU

MIC

CAP

DEL

M

29

Deneb

AQL

VUL

SOUTH

Altair

SGE

27

M

CYG

ZENITH

M

SGR

M

M

17

57

M

11

SCT

LYR

8

M

M

16

M

20

Vega

6

M

10

OPH

HER

M

M

12

92

M

13

SER

CRB

0h 22h 20h 18h 16h

WEST

July 21 at August 21 at September 21 at October 21 at November 21 at

8S

07/02/2023 22:40

Astronomy 2024.indb 44

WEST

SER

1h 23h 21h 19h 17h

HER

August 6 at September 6 at October 6 at November 6 at December 6 at

CRB

13 M

Arcturus

Izar

BOO

92 M

3 M

51

CVN

M

DRA

UMI

NORTH

UMA

Polaris

CEP

ZENITH

LYN

CAS

52

M

CAM

4 88

AUR

C G N

9 86

M

M 37

36

Capella

C G N

35

38

M

M

1

PER

M

34

Algol

M

Aldebaran

TAU

0h 22h 20h 18h 16h

EAST

August 21 at September 21 at October 21 at November 21 at December 21 at

9N

07/02/2023 22:40

Astronomy 2024.indb 45

EAST

1h 23h 21h 19h 17h

ARI

TRI

August 6 at September 6 at October 6 at November 6 at December 6 at

Mira

M

33

CET

PSC

Algenib

AND

31 M

Alpheratz

PEG

SCL

Fomalhaut

Sadalmelik

Enif

SOUTH

PSA

AQR

Markab

Scheat

LAC

ZENITH

MIC

DEL

CAP

EQU

15

M

M

39

M

29

Deneb

27

AQL

Altair

SGE

M

VUL

CYG

M

11

17

SCT

M

M

LYR

16

M

57

Vega

10 M

OPH 12 M

0h 22h 20h 18h 16h

WEST

August 21 at September 21 at October 21 at November 21 at December 21 at

9S

07/02/2023 22:40

Astronomy 2024.indb 46

WEST

August 6 at September 6 at October 6 at November 6 at December 6 at

3h 1h 23h 21h 19h

M

57

HER

Vega

LYR

CYG

M

29

CRB

13 M

M

92

Deneb

39 M

BOO

DRA

CEP

51 M

Polaris

CAS

NORTH

UMI

52

M

ZENITH

UMA

C

G

N

CAM

4

88

C

G

N

LYN

9

86

Pollux

Castor

AUR

M

36 37

M

GEM

Capella

PER

M

38

35 M

Betelgeuse

1 M

2h 0h 22h 20h 18h

EAST

August 21 at September 21 at October 21 at November 21 at December 21 at

10N

07/02/2023 22:40

Astronomy 2024.indb 47

EAST

ORI

Bellatrix

Aldebaran

3h 1h 23h 21h 19h

Rigel

TAU

August 6 at September 6 at October 6 at November 6 at December 6 at

Algol

ERI

34 M

ARI

TRI

Mira

PSC

CET

33 M

AND

31

M

SOUTH

Fomalhaut

SCL

Algenib

Scheat

PEG

Alpheratz

ZENITH

PSA

AQR

Markab

Sadalmelik

Enif

LAC

EQU

CAP

M

15

DEL

AQL

Altair

SGE

27 M

11 M

VUL

2h 0h 22h 20h 18h

WEST

August 21 at September 21 at October 21 at November 21 at December 21 at

10S

07/02/2023 22:40

Astronomy 2024.indb 48

WEST

Altair

SGE

September 6 at October 6 at November 6 at December 6 at January 6 at

VUL

M

27

3h 1h 23h 21h 19h

29 M

CYG

LAC

57 M

LYR

Deneb

HER

Vega

39

M

M 13

M

92

DRA

CEP

M

52

CAS

4

88

NORTH

M

51

C

G

N

Polaris

UMI

N

G

C

ZENITH 8

69

CVN

UMA

CAM

LMI

LYN

Capella

AUR

Pollux

44 M

Castor

CNC

GEM

2h 0h 22h 20h 18h

EAST

CMI

September 21 at October 21 at November 21 at December 21 at January 21 at

11N

07/02/2023 22:40

Astronomy 2024.indb 49

EAST

n

MON

September 6 at October 6 at November 6 at December 6 at January 6 at

35

36 M

Betelgeuse

M

M

37

3h 1h 23h 21h 19h

Saiph

ORI

1

M

38

M

LEP

42 M

Bellatrix

79 M

TAU

Rigel

Aldebaran

PER

ERI

Algol

TRI

PSC

33

M

CET

SOUTH

Mira

ARI

FOR

34

M

ZENITH

31

SCL

AND

M

Algenib

AQR

Markab

Scheat

PEG

Alpheratz

Sadalmelik

Enif

EQU

15 M

2h 0h 22h 20h 18h

WEST

DEL

September 21 at October 21 at November 21 at December 21 at January 21 at

11S

07/02/2023 22:40

Astronomy 2024.indb 50

WEST

Enif

3h 1h 23h 21h 19h

M

15

Scheat

October 6 at November 6 at December 6 at January 6 at February 6 at

LAC

31 M

27 M

29

M

CYG

Deneb

39

M

57 M

LYR

4

88

Vega

CEP

52 M

CAS

G

N

C

N

C

G

9

86

92 M

DRA

NORTH

UMI

Polaris

CAM

ZENITH

M

51

CVN

UMA

LYN

LMI

Zosma

LEO

Algieba Regulus

2h 0h 22h 20h 18h

EAST

October 21 at November 21 at December 21 at January 21 at February 21 at

12N

07/02/2023 22:40

Astronomy 2024.indb 51

EAST

HYA

M

44

Pollux

3h 1h 23h 21h 19h

CNC

October 6 at November 6 at December 6 at January 6 at February 6 at

Procyon

CMI

Castor

GEM

MON

35

M

37 M

41

M

CMA

1 M

Aldebaran

LEP

42

M

79

M

Rigel

Bellatrix

38

M

ORI

36

M

Saiph

Sirius

Betelgeuse

AUR

Capella

TAU

PER

SOUTH

ERI

ZENITH

FOR

Algol

M

CET

TRI

ARI

Mira

34

PSC

M

33

Alpheratz

Algenib

AND

AQR

PEG

WEST

Sa

2h 0h 22h 20h 18h

Markab

October 21 at November 21 at December 21 at January 21 at February 21 at

12S

07/02/2023 22:40

Astronomy 2024.indb 52

07/02/2023 22:40

Southern Hemisphere Star Charts

PHE Alnair

Achernar

TUC IND 4

HOR

C

10

Peacock

N G

HYI

RET PAV

TEL

N

G

C

20

70

DOR

OCT

MEN

PIC

Canopus

APS VOL

ARA

CHA

TRA

CAR

NOR

47 G C

CEN

CRU

N

G C

51

39

VEL

N

N

G

C

33

55

72

IC

26

23 IC

CIR

02

91

MUS

This chart shows stars lying at declinations between 45 and 90 degrees. These constellations are circumpolar for observers in Australia and New Zealand.

Astronomy 2024.indb 53

07/02/2023 22:40

Astronomy 2024.indb 54

WEST

CET

October 6 at November 6 at December 6 at January 6 at February 6 at

PSC

5h 3h 1h 23h 21h

Mira

ARI TRI

ERI

PER

Algol 34 M

TAU Aldebaran

Bellatrix

Rigel M

42

M

AUR

37 36 M

35 M

NORTH

Capella

38

M

1

Castor

LYN

M

44

CNC

Procyon

Pollux

CMI

MON

41 M Sirius

GEM

CMA

Betelgeuse

Saiph

LEP

ORI

M

79

M

ZENITH

LEO

Regulus

Algieba

HYA

Alphard

SEX

4h 2h 0h 22h 20h

EAST

October 21 at November 21 at December 21 at January 21 at February 21 at

1N

07/02/2023 22:40

Astronomy 2024.indb 55

EAST

CRT

October 6 at November 6 at December 6 at January 6 at February 6 at

CRV

5h 3h 1h 23h 21h

ANT

PYX

VEL

PUP

C

G

N

N

C

CIR

55

TRA

CHA

VOL

NOR

CAR

MUS

02

26

47

IC

72

33

1

9 23

G

N

C

G

IC

CEN

51

39

CRU

Naos

70

20

PAV

OCT

SOUTH

APS

N

C

G

DOR

MEN

PIC

Canopus

COL

ZENITH

RET

C

Peacock

GRU

Achernar

Alnair

TUC

4

10

IND

G N

HYI

HOR

CAE

Fomalhaut

PHE

SCL

FOR

4h 2h 0h 22h 20h

WEST

October 21 at November 21 at December 21 at January 21 at February 21 at

1S

07/02/2023 22:40

Astronomy 2024.indb 56

WEST

Mira

ERI

November 6 at December 6 at January 6 at February 6 at March 6 at

5h 3h 1h 23h 21h

TAU

Rigel

79 M

ORI

42

M

Saiph

Aldebaran

Bellatrix

LEP

38

M

1 M

AUR

Castor

NORTH

LYN

Pollux

44 M

CNC

Procyon

CMI

GEM

MON

Capella

M 36 M

35 M 37

41 M Sirius

Betelgeuse

CMA

PUP

ZENITH

LMI

SEX

LEO

Regulus

Alphard

Algieba

HYA

PYX

Zosma

COM

CRT

VIR

4h 2h 0h 22h 20h

EAST

4 10 M

November 21 at December 21 at January 21 at February 21 at March 21 at

2N

07/02/2023 22:40

Astronomy 2024.indb 57

EAST

Spica

CRV

November 6 at December 6 at January 6 at February 6 at March 6 at

5h 3h 1h 23h 21h

G

N

CEN

LUP

C

G

N C

NOR

CIR

55

47

9 3CRU

51

ANT

ARA

IC

SOUTH

PAV

MEN

Peacock

VOL

CAR

OCT

91

23

CHA

APS

02

26

MUS

IC

72

33

TRA

N

G

C

VEL

Naos

ZENITH

C

4

10

HYI

RET

G N

DOR 70

20

TUC

N

C

G

PIC

Canopus

PHE

Achernar

HOR

COL

CAE

FOR

CET

4h 2h 0h 22h 20h

WEST

November 21 at December 21 at January 21 at February 21 at March 21 at

2S

07/02/2023 22:40

Astronomy 2024.indb 58

WEST

Rigel

42

Bellatrix

M

41

M

ORI

3h 1h 23h 21h 19h

Saiph

January 6 at February 6 at March 6 at April 6 at May 6 at

1 M

35 M

MON

Betelgeuse

Sirius

37 M

Castor

GEM

CMI

Procyon

Pollux

CNC

LYN

44

M

PYX

HYA

LMI

LEO

Algieba

Regulus

SEX

NORTH

Alphard

ANT

ZENITH

Zosma

CVN

COM

CRT

M

3

CRV

M

VIR

4 10

Arcturus

Spica

2h 0h 22h 20h 18h

EAST

January 21 at February 21 at March 21 at April 21 at May 21 at

3N

07/02/2023 22:40

Astronomy 2024.indb 59

EAST

LIB

January 6 at February 6 at March 6 at April 6 at May 6 at

3h 1h 23h 21h 19h

SCO

4 M Antares

LUP

6 M

ARA

NOR

CIR

39

51

CEN

N

C

G

TRA

TEL

G

N

C

55

47

CRU

Peacock

PAV

APS

MUS

02

26

TUC

SOUTH

OCT

IC

3

CHA

C

G

N

2 37

VEL

ZENITH

C G N

PIC

PHE

Achernar

HOR

DOR

70

20

RET

G

N

C

CAR

91

23

4 10HYI

MEN

VOL

IC

Canopus

Naos

PUP

FOR

CAE

COL

79 M

ERI

CMA

LEP

2h 0h 22h 20h 18h

WEST

January 21 at February 21 at March 21 at April 21 at May 21 at

3S

07/02/2023 22:40

Astronomy 2024.indb 60

WEST

MON

February 6 at March 6 at April 6 at May 6 at June 6 at

3h 1h 23h 21h 19h

CMI

Procyon

CNC

Pollux

44 M

HYA

Alphard

SEX

LEO

LMI

Algieba

Regulus

COM

CRV

CVN

NORTH

Zosma

CRT

ZENITH

51 M

4

10

M

VIR

M

3

Spica

BOO

Izar

Arcturus

CRB

SER

LIB

12 M

OPH

10 M

2h 0h 22h 20h 18h

EAST

February 21 at March 21 at April 21 at May 21 at June 21 at

4N

07/02/2023 22:40

Astronomy 2024.indb 61

EAST

M

16

February 6 at March 6 at April 6 at May 6 at June 6 at

20

M

17

M

8 M

4 M SCO Antares

3h 1h 23h 21h 19h

SGR

M

6

CRA

LUP

TEL

ARA

NOR

CIR

IND

N

C

G

47 IC

26

02

SOUTH

C G N

C

G

N

VOL

72

33

Achernar

N

C G

IC

PIC

ANT

CAE

Canopus

91

23

CAR

VEL

DOR

70 20

HOR

RET

MEN

HYI

4 10

CHA

MUS

OCT

TUC

55

CRU

39

51

APS

Peacock

PAV

TRA

CEN

G

N

C

ZENITH

COL

Naos

PYX

PUP

M

79

LEP

41

CMA M

Saiph

Sirius

2h 0h 22h 20h 18h

WEST

February 21 at March 21 at April 21 at May 21 at June 21 at

4S

07/02/2023 22:40

Astronomy 2024.indb 62

WEST

HYA

Alphard

March 6 at April 6 at May 6 at June 6 at July 6 at

3h 1h 23h 21h 19h

SEX

Regulus Algieba

LEO

LMI

CRT

Zosma

CRV 4

10

M

CVN

COM

VIR

Spica

NORTH

51 M

3

M

BOO

Izar

Arcturus

ZENITH

CRB

LIB

M

13

SER

HER

M

12

10

OPH

M

4 M Antares

16 M

11 M

2h 0h 22h 20h 18h

EAST

SCT

17 M

March 21 at April 21 at May 21 at June 21 at July 21 at

5N

07/02/2023 22:40

Astronomy 2024.indb 63

EAST

AQL

M

20

March 6 at April 6 at May 6 at June 6 at July 6 at

M

8

3h 1h 23h 21h 19h

CAP

SGR

6 M

MIC

CRA

SCO

GRU

IND

TEL

Alnair

Peacock

ARA

APS

TRA

CIR

TUC

PAV

NOR

LUP

Achernar

HYI

1

04

SOUTH

C

G

N

OCT

CEN

ZENITH

HOR

RET

MEN

CHA

MUS

N

C

G

55

02

26

70 20

DOR

G N

C

VOL

IC

47

39

51

CRU

C

G

N

PIC

N

C

G

COL

23

91

VEL IC

Canopus

CAR

72

33

Naos

PUP

ANT

PYX

2h 0h 22h 20h 18h

WEST

March 21 at April 21 at May 21 at June 21 at July 21 at

5S

07/02/2023 22:40

Astronomy 2024.indb 64

WEST

CRT

March 6 at April 6 at May 6 at June 6 at July 6 at

CRV

5h 3h 1h 23h 21h

Zosma

1

M

04

VIR

Spica

COM

CVN

3

M

51 M

Arcturus

BOO

Izar

LIB

NORTH

CRB

SER

ZENITH

13 M

12

M

92 M

Vega

OPH

10

M

HER

4 M Antares

SCO

LYR

M

M

6

M

20

CYG

57

M

16

8

M

11

M

27

SGE

M

SCT

17

VUL

M

Altair

DEL

AQL

EQU

4h 2h 0h 22h 20h

EAST

March 21 at April 21 at May 21 at June 21 at July 21 at

6N

07/02/2023 22:40

Astronomy 2024.indb 65

EAST

CAP

March 6 at April 6 at May 6 at June 6 at July 6 at

5h 3h 1h 23h 21h

Fomalhaut

PSA

MIC

SGR

SCL

GRU

IND

Alnair

CRA

PHE

TUC

Peacock

TEL

APS

TRA

NOR

10

4 7

DOR PIC

C G N

N

C

G

Canopus

IC

02 26

CRU

CAR

55

47

CEN

MUS

VOL 0 20

CHA

LUP

MEN

CIR

SOUTH

HOR

RET

OCT

HYI

C

G

N

Achernar

PAV

ARA

ZENITH

N

Naos

VEL 91 23

39

51

72 33

IC

C G

N

C

G

PYX

ANT

SEX

4h 2h 0h 22h 20h

WEST

March 21 at April 21 at May 21 at June 21 at July 21 at

6S

07/02/2023 22:40

Astronomy 2024.indb 66

WEST

Spica

VIR

April 6 at May 6 at June 6 at July 6 at August 6 at

5h 3h 1h 23h 21h

LIB

3 M

Arcturus

BOO

Izar

CRB

SER

4 M Antares

SCO

12

M

13

M

OPH

10

M

20

M

Vega

M

16

8

M

NORTH

92 M

HER

M

6

ZENITH

M

57

SCT

VUL

11

M

LYR CYG

17

M

SGR

29

Deneb

M

M

27

SGE

Altair

AQL

DEL

EQU 15 Enif M

CAP

Markab

Sadalmelik

AQR

4h 2h 0h 22h 20h

EAST

April 21 at May 21 at June 21 at July 21 at August 21 at

7N

07/02/2023 22:40

Astronomy 2024.indb 67

EAST

5h 3h 1h 23h 21h

Fomalhaut

April 6 at May 6 at June 6 at July 6 at August 6 at

SCL

PSA

GRU

MIC

PHE

Alnair

HOR

HYI

C

G

N

Peacock

Achernar

TUC

IND

RET

C

SOUTH

CAR

VOL

0

7 20

CHA

TRA

ARA

APS

PIC

N

G

MEN

OCT

DOR

PAV

TEL

4

10

CRA

ZENITH

MUS

NOR

IC

26

C G

VEL

N

02

55 47

91 23

IC

C G N

CIR

72 33

CRU

C G N

CEN

LUP

39 51

CRT

CRV

4h 2h 0h 22h 20h

WEST

4 10 M

April 21 at May 21 at June 21 at July 21 at August 21 at

7S

07/02/2023 22:40

Astronomy 2024.indb 68

WEST

May 6 at June 6 at July 6 at August 6 at September 6 at

5h 3h 1h 23h 21h

SER

M

12

OPH

CRB

10 M

20

M

8

M

HER 13

M

16

M

17

M

M

92

SCT

SGR

Vega

11

M

LYR

57

M

NORTH

M

27

SGE

Altair

CYG

VUL

AQL

ZENITH

Deneb

29 M

DEL

LAC 39 M

EQU

CAP

M

15 Enif

PEG Scheat

Algenib

Alpheratz

Markab

AQR Sadalmelik

PSC

4h 2h 0h 22h 20h

EAST

May 21 at June 21 at July 21 at August 21 at September 21 at

8N

07/02/2023 22:40

Astronomy 2024.indb 69

EAST

CET

May 6 at June 6 at July 6 at August 6 at September 6 at

5h 3h 1h 23h 21h

FOR

SCL

Fomalhaut

PSA

PHE

HOR C

G

2

CHA

SOUTH

VOL

CAR Canopus

N

OCT

PAV

Peacock

70

MEN 0

4

10

IND

PIC

C

G

N

DOR

RET

HYI

TUC

Alnair

Achernar

GRU

MIC

ZENITH

IC

MUS

APS

N

G

C

2

72 33

TRA

0 26

TEL

CRA

CRU

C

G

N

CEN 55 47

CIR

NOR

ARA

C G N

6

39 51

LUP

M

SCO

Antares 4 M

LIB

4h 2h 0h 22h 20h

WEST

May 21 at June 21 at July 21 at August 21 at September 21 at

8S

07/02/2023 22:40

Astronomy 2024.indb 70

WEST

M

12

M

10

OPH

June 6 at July 6 at August 6 at September 6 at October 6 at

16

M

17 M

5h 3h 1h 23h 21h

SCT

11 M

Vega

AQL

LYR

57

M

VUL

27 M

CYG

SGE

Altair

CAP

DEL

M

29

EQU 15

Deneb

M

39

LAC

Sadalmelik

NORTH

M

Enif

Scheat

PEG

Markab

Fomalhaut

AQR

PSA

ZENITH

M

31

AND

Alpheratz

Algenib

M

33

TRI

PSC

ARI

CET

Mira

4h 2h 0h 22h 20h

EAST

June 21 at July 21 at August 21 at September 21 at October 21 at

9N

07/02/2023 22:40

Astronomy 2024.indb 71

EAST

ERI

June 6 at July 6 at August 6 at September 6 at October 6 at

5h 3h 1h 23h 21h

FOR

CAE

HOR

PHE

SCL

HYI

G

C

G

N

VOL

0

7 20

MEN C

N

CAR

Canopus

PIC

DOR

RET

Achernar

4

CHA

OCT

SOUTH

10

TUC

Alnair

GRU

ZENITH

C

72 33

02 26 G N

IC

MUS

APS

PAV

C G N

CRU

55 47

TRA

Peacock

IND

MIC

N

C G

CEN

39 51

CIR

ARA NOR

TEL

LUP

CRA

SCO

SGR

M

6

LIB

Antares 4 M

8 M 20 M

4h 2h 0h 22h 20h

WEST

June 21 at July 21 at August 21 at September 21 at October 21 at

9S

07/02/2023 22:40

Astronomy 2024.indb 72

WEST

M

11

CAP

5h 3h 1h 23h 21h

AQL

July 6 at August 6 at September 6 at October 6 at November 6 at

Altair

VUL

SGE 27

M

DEL

EQU

Enif

29

M

M

15

Sadalmelik

AQR

PSA Fomalhaut

M

39

LAC

Scheat

AND M

31

Alpheratz

Algenib

NORTH

PEG

Markab

SCL

ZENITH

33 M

PSC

M

TRI

34

PER

Algol

ARI

CET

Mira

Aldebaran

TAU

ERI

Bellatrix

ORI

4h 2h 0h 22h 20h

EAST

July 21 at August 21 at September 21 at October 21 at November 21 at

10N

07/02/2023 22:40

Astronomy 2024.indb 73

M

42

EAST

gel

Saiph

79

CMA

Sirius 41 M

M

5h 3h 1h 23h 21h

LEP

July 6 at August 6 at September 6 at October 6 at November 6 at

COL

CAE

FOR

Naos

CAR

Canopus

PIC

DOR

HOR

IC

70

20

VOL

1 39

2

C

GMEN

N

RET

HYI

Achernar

N

4

10

SOUTH

CRU

C G N

55

CEN

CIR

PAV

TRA

APS

47

TUC

OCT

C

G

N

MUS 02 26 72 IC 33 C G

CHA

PHE

ZENITH

LUP

NOR

ARA

TEL

Peacock

IND

GRU

Alnair

SCO

CRA

MIC

M

6

SGR

M

20

8 M

16 M

17 M

4h 2h 0h 22h 20h

WEST

SCT

July 21 at August 21 at September 21 at October 21 at November 21 at

10S

07/02/2023 22:40

Astronomy 2024.indb 74

WEST

5h 3h 1h 23h 21h

DEL

EQU

August 6 at September 6 at October 6 at November 6 at December 6 at

Enif

15

M

Sadalmelik

AQR

Scheat

PEG

Markab

AND

Alpheratz

Algenib

M

31

PSC

CET

TRI

NORTH

33

M

ARI

ZENITH

M

PER

34 Algol

Mira

FOR

ERI

M

38

M

36

M

37

1

M

M

35

Bellatrix Aldebaran

TAU

ORI

Rigel 42

Betelgeuse

M

Saiph

LEP

4h 2h 0h 22h 20h

EAST

Procyon

MON

August 21 at September 21 at October 21 at November 21 at December 21 at

11N

07/02/2023 22:40

Astronomy 2024.indb 75

EAST

M

41

Sirius

5h 3h 1h 23h 21h

CMA

August 6 at September 6 at October 6 at November 6 at December 6 at

79 M

PUP

PYX

COL

Naos

CAE

VEL

IC

CAR 91

23

Canopus PIC

C

G

N

72

VOL

33

DOR C

IC 47

55

HYI 4

10

CIR

TRA

APS

OCT

C

G

N

Achernar

SOUTH

C G N

CRU

MUS

02

26

CHA

MEN

G

N

20

70

RET

HOR

ZENITH

NOR

ARA

PAV

TUC

PHE

TEL

IND

SGR

GRU

CRA

Peacock

Alnair

PSA

MIC

Fomalhaut

SCL

CAP

4h 2h 0h 22h 20h

WEST

August 21 at September 21 at October 21 at November 21 at December 21 at

11S

07/02/2023 22:40

Astronomy 2024.indb 76

WEST

Sadalmelik

AQR

September 6 at October 6 at November 6 at December 6 at January 6 at

5h 3h 1h 23h 21h

Markab

PEG

Algenib

CET

AND

Alpheratz

PSC

31 M

33 M

TRI

ARI

Mira

FOR

34 M

NORTH

Algol PER

ERI

M

Capella

38

M

1

7M

AUR

35

ORI

36 M3 M

Bellatrix

Rigel

Aldebaran

TAU

ZENITH

M

Castor

GEM

Betelgeuse

Saiph

LEP

79

42

M

Pollux

CMI

Procyon

M

44

CNC

MON

41 M Sirius

CMA

4h 2h 0h 22h 20h

EAST

HYA

September 21 at October 21 at November 21 at December 21 at January 21 at

12N

07/02/2023 22:40

Astronomy 2024.indb 77

EAST

Alphard

September 6 at October 6 at November 6 at December 6 at January 6 at

5h 3h 1h 23h 21h

PYX

ANT

PUP Naos

VEL

COL

IC

2

1 39

CAR

G

N

CRU

55

47

CEN

N

G

C

G

N

C

SOUTH

CIR

TRA

APS

HYI

HOR

OCT

70RET

20

MEN

CHA

DOR

MUS

72 02 33 26 C IC

VOL

PIC

Canopus

CAE

ZENITH

TUC

TEL

PAV Peacock

C

G

N

4

10

Achernar

IND

PHE

MIC

GRU

Alnair

PSA

Fomalhaut

SCL

4h 2h 0h 22h 20h

WEST

September 21 at October 21 at November 21 at December 21 at January 21 at

12S

07/02/2023 22:40

The Planets in 2024 Lynne Marie Stockman

Mercury never stays in one place long, zipping back and forth between the morning and evening skies several times during the year. It begins and ends 2024 in dawn skies, with the best morning apparition for those in the tropics occurring at the beginning of the year, for southern hemisphere early risers in April–June, and in August–September for observers in northern temperate latitudes. These planet-watchers get their best evening views of Mercury during the March–April apparition with everyone else in equatorial and southern latitudes getting their chance between June and August. Morning apparitions begin at inferior conjunction and end at superior conjunction, and are characterised by the planet getting brighter throughout. Evening apparitions are exactly the opposite, with Mercury brightest at the beginning of its western appearance. Mercury undergoes one lunar occultation during daylight hours and passes by all of the planets in the first half of the year. Apparition diagrams showing the position of Mercury above the eastern and western horizons can be found throughout the Monthly Sky Notes. Venus is found in the morning sky as the year begins. Located in the southeast before sunrise, it slowly declines in altitude before disappearing in late May/early June. After superior conjunction on 4 June, Venus adorns the west as the evening star for the remainder of the year. The brightest planet in the sky stays low to the western horizon until November/December for sky watchers in northern temperate latitudes. Those living farther south get much the best views of Venus during the last half of the year. Venus is occulted by the Moon twice in 2024 but one event occurs during daylight hours and the other is visible primarily from Antarctica. The morning star has conjunctions with all of the other planets but after superior conjunction, Venus meets only Mercury in the sky. Apparition diagrams showing the position of Venus above the eastern and western horizons can be found in the January and June Sky Notes respectively. Mars was at conjunction in November 2023 and is emerging from the Sun’s glare as the year begins. It starts out at a relatively faint magnitude +1.4 in the constellation of Sagittarius and slowly brightens as it makes its away across the

Astronomy 2024.indb 78

07/02/2023 22:40

The Planets in 2024  79 sky, passing through Capricornus, Aquarius, Pisces (with a short foray into Cetus), Aries, Taurus, Gemini and finally Cancer where it ends the year. The red planet is occulted twice by the Moon, once in May and again in December. It also passes by all of the other planets in the sky. By the end of the year Mars is in retrograde and brighter than –1 magnitude. A finder chart showing the position of Mars throughout the last nine months of 2024 follows this article. Jupiter spends the first four months of 2024 in Aries before moving into Taurus. It is visible in the evening as the year commences and undergoes a relatively rare conjunction with Uranus in April. Conjunction with the Sun is less than a month later. Jupiter encounters both Mercury and Venus shortly afterwards and meets Mars in August. A morning sky object from late May, Jupiter begins to rise before midnight in late August and reaches opposition in early December. The bright planet travels south of the Pleiades and north of the Hyades star clusters, never coming closer than 4.7° to the Aldebaran, brightest star in Taurus. The Moon also keeps its distance this year; at the beginning of 2024 it passes less than 3° north of the planet but by September, the Moon is nearly 6° north of Jupiter when the two bodies are in conjunction. A finder chart showing the position of Jupiter throughout 2024 follows this article. Saturn is located in Aquarius for the entire year. It begins 2024 as an evening sky object but solar conjunction takes place at the end of February and Saturn moves to the morning sky. It appears in the east before midnight from May (southern hemisphere) or June (northern temperate latitudes) and reaches opposition in early September. Mercury’s close approach in February takes place too close to the Sun to be visible but Venus comes to call in March, followed by Mars in April. A series of lunar occultations begins in April. The tilt of the rings diminishes to just under 2° in June but Saturn’s ring-plane crossing does not take place until next year. A finder chart showing the position of Saturn throughout 2024 follows this article. Uranus has a relatively quiet year in 2024. The Moon never approaches closer than 3° and although four bright planets come to call, only the conjunctions with Jupiter in April and with Mars in July are visible. The Jupiter–Uranus conjunction is an uncommon event; the last time this happened was in 2010–2011 when the two gas giants met three times. Uranus is an evening sky object in Aries at the outset of the year, undergoing conjunction in May and moving into Taurus. It is again visible before midnight from mid-July and reaches opposition in November. Retrograde

Astronomy 2024.indb 79

07/02/2023 22:40

80  Yearbook of Astronomy 2024 motion brings the faint planet back to Aries just before the year ends. A finder chart showing the position of Uranus throughout 2024 follows this article. Neptune inhabits the constellation of Pisces for the entire year and is occulted by the Moon every month. It opens the year as an evening sky object but moves to the morning sky after conjunction in March. It begins rising before midnight in June–July and reaches opposition in September. It ends the year as it began, visible in the evening sky. Neptune encounters Mercury shortly before conjunction and Venus shortly afterwards; both events will be difficult to observe in the twilight. A finder chart showing the position of Neptune throughout 2024 follows this article.

Astronomy 2024.indb 80

07/02/2023 22:40

β

CNC

α

α

CMI

κ

β

β

MON

λ

δ

ι

GEM

α

ct

ζ

1O

ξ

θ

ε

γ

γ

µ η

AUR

θ

ν

η

α

ζ

κ

λ

ι

ζσε

ORI

ζ

δ

β

ε

τ

ηζ

η

γ

α

β

ι

µ

β

Background stars are shown to magnitude +5.5.

δ

ov

ec

31 D

1N

β

ept

38

Dec

7

LYN

1S

10

π

5

3

π4 π

1A

ε

ν

TAU

δ

α

ν

λ

ζ ο

ν PER

53

ε δ2 αθ γ

ug

δ κ β ρ

γ

δ

ξο

41

γ

ε ERI

α

l

κι

1 Ju

η

1

τ

α

α

ARI

4

η

γ

TRI

β

51

β

ο

β

µ

η

PSC

δ

AND

ζ

n

γ τ

1 Ju

θ

τ

CET

θ

α

η

γ

PEG

β

ay

β

ι

1M

Mars April to December 2024 η

α

µλ

γ

ζ

ι

δ

SCL

98 88

λ

AQR

γ

θ

pr 1A

Astronomy 2024.indb 81

07/02/2023 22:40

α

α

ε

115 111

114

15

π

1

6

ο

ec

2

7D

5h 0m

11

ι

π

4

π

3

2

1

π

ο

97

τ

4h 40m

ρ

α

88

90 93

1A ug 31 D ec

68 δ

83 79

π

γ 58

µ

56 53 ω

4h 20m

66

75 81 71

ε

υ

χ

Background stars are shown to magnitude +5.5.

14

106

ept

104

1S

16

ORI

9O ct 1N ov

5h 20m

10°

15°

20°

25°

l 1 Ju

46

47

TAU

44

λ

1 Ju

n

4h 0m

ν 40

37

36

41

30

3h 40m

29

Pleiades

4

5

ο

ay

ζ

3h 20m

1M

ξ

τ 63 δ

ε

3h 0m

λ

pr

ϕ

1A

118

35

σ

µ

38

33

ν

ar

ν

1M

2h 40m

CET

π

ARI

41

ξ

η

14

2h 20m

2

ξ

1 Fe

b

Jupiter January to December 2024

κ

α

n

ξ

1 Ja

Astronomy 2024.indb 82

07/02/2023 22:40

1

λ

ι

2

ω

23h 40m

ω

1

23h 30m

ψ

3

1 Ju

n

30 J

un ug 1A

23h 20m

94

ψ

2

χ

1M

ψ

1

1S ep

ay

AQR

23h 10m

Background stars are shown to magnitude +5.5.

−14°

−12°

−10°

−8°

ϕ

ec ct

−6°

31 D 1O

−4°

ec

pr 1D

1A

23h 0m

1N 16 N ov ov

t ept

8S

τ

2

ar

22h 50m

λ

κ

22h 40m

Saturn January to December 2024

1M

Astronomy 2024.indb 83

07/02/2023 22:40

b

22h 30m

σ n

ρ

θ

42

22h 20m

1 Ja

1 Fe

ι

22h 10m

38

4h 10m

1 Ju

n

4h 0m

3h 50m

ept

3h 40m

TAU

1M

ay

3h 30m

63

31 D

ec

3h 20m

τ ζ

δ

3h 10m

ε

3h 0m

2h 50m

σ

π

2h 40m

ν

1M

ar

an

Background stars are shown to magnitude +8.0. Because Jupiter and Uranus are in conjunction on 21 April 2024, the path of Jupiter from March through May is also shown here. Uranus is depicted by green dots and Jupiter by yellow dots.

16°

18°

1S ct 1O

l ov

1 Ju 17 N

20°

37

pr

22°

η

1A

36

23 J 1 Ja n

24°

pr

Uranus January to December 2024

1A

Astronomy 2024.indb 84

07/02/2023 22:40

0h 5m

33

PSC

3 Ju

l

0h 0m

30

29 27

1A

ept

23h 55m

21 S

Background stars are shown to magnitude +10.0.

−6° 0h 10m

−5°

−4°

−3°

−2°

−1°

31 D

ec ec

23h 50m

8D

0°

ct

1O

20

23h 45m

23h 40m

Neptune January to December 2024

1 Ja

n

Astronomy 2024.indb 85

07/02/2023 22:40

pr

23h 35m

23h 30m

AQR 23h 25m

23h 20m

Phases of the Moon in 2024

New Moon

First Quarter

Full Moon

Last Quarter   4 January

11 January

18 January

25 January

  2 February

  9 February

16 February

24 February

  3 March

10 March

17 March

25 March

  2 April

  8 April

15 April

23 April

  1 May

  8 May

15 May

23 May

30 May

  6 June

14 June

22 June

28 June

  5 July

13 July

21 July

28 July

  4 August

12 August

19 August

26 August

  3 September

11 September

18 September

24 September

  2 October

10 October

17 October

24 October

  1 November

  9 November

15 November

23 November

  1 December

  8 December

15 December

22 December

30 December The dates given in the above table are based on Universal Time (UT)

Astronomy 2024.indb 86

07/02/2023 22:40

Lunar Occultations in 2024

A lunar occultation occurs when the Moon passes in front of a more distant celestial body as seen from Earth, partially or totally obscuring this object and blocking its light. Like total solar eclipses, occultations are seen only at particular times and from particular places, but they have been noticed for centuries; the first known observation dates to 357 BC when Aristotle spotted Mars disappearing behind the Moon’s disk. Occultation data can help astronomers measure the heights and depths of lunar features and improve knowledge about the lunar orbit; such information can be used to detect close companions in multiple star systems and improve the precision of stellar positions. Lunar occultation data was even employed to pinpoint the location of 3C 273, the first quasar to be identified by astronomers. The Moon occults countless faint objects every month but it also moves in front of the occasional planet or bright star, including four first-magnitude stars: α Leonis (Regulus), α Scorpii (Antares), α Tauri (Aldebaran) and α Virginis (Spica). This year is a particularly busy one for the Moon. The latest occultation series of Antares began last year in August and will continue through August 2028. An occultation series of Spica begins on 16 June, finishing in November next year. The open star cluster M45 (Pleiades) or rather, the third-magnitude star η Tauri (Alcyone), has been regularly occulted by the Moon since September last year and will continue to vanish behind the Moon’s disk until July 2029. The Moon is slowly closing in on Regulus; that occultation series will commence next year. For the time being, only Aldebaran remains safely out of reach of the Moon. Neptune is occulted every month in 2024, with Saturn joining in from April as the two planets get ever nearer to one another in the sky. Venus and Mars are also twice victims of the Moon this year and Mercury is occulted once.

Astronomy 2024.indb 87

07/02/2023 22:40

88  Yearbook of Astronomy 2024

Table of Lunar Occultations in 2024 α Scorpii (Antares)

Jan

Feb

Mar

Apr

May

8

5

3, 30

26

24

20

16

15

11

8

α Virginis (Spica) M45 (Pleiades) Mercury

Aug

Sep

Oct

17

14

10

7

16

14

10

6

3, 31

27

24

5

2, 29

26

22

19

16

13

20

Jul

Nov 4

Dec 1, 28

11

Venus

7

Mars

5 5

Saturn Neptune

Jun

15

12

10

18

6

3, 31

27

24

21

17

14

11

8

7

4

1, 28

25

21

18

15

12

9

The dates given in the above table are based on Universal Time (UT)

Details of individual occultations listed in the above table can be found in the corresponding sections of the Monthly Sky Notes. For more information on occultations, including observing predictions for this year, visit the International Occultation Timing Association (IOTA) online at occultations.org

Astronomy 2024.indb 88

07/02/2023 22:40

Eclipses in 2024

There are a minimum of four eclipses in any one calendar year, comprising two solar eclipses and two lunar eclipses. Most years have only four, as is the case with 2024, although it is possible to have five, six or even seven eclipses during the course of a year. There are a total of four eclipses in 2024, comprising two solar eclipses and two lunar eclipses. It is important to note that the times quoted for each event below refer to the start, maximum and ending of the eclipse on a global scale rather than with reference to specific locations. As far as lunar eclipses are concerned, these events are visible from all locations that happen to be on the night side of the Earth. Depending on the exact location of the observer, the entire eclipse sequence may be visible, although for some the Moon will be either rising or setting while the eclipse is going on. The first eclipse of the year is the penumbral lunar eclipse of 25 March, visible in whole or in part throughout most of southern and western Europe, most of Africa, the Atlantic Ocean, Greenland, North America, South America, the Pacific Ocean, eastern regions of Asia, most of Australia and the Arctic and Antarctica. Maximum eclipse takes place at 07:12 UT, the eclipse beginning at 04:53 UT and ending at 09:32 UT. On 8 April there will be a total solar eclipse which will pass from the southern Pacific to the northern Atlantic. Totality will be visible from parts of Mexico, the southern and eastern regions of the United States – from Texas through to Maine – and the Canadian provinces of Ontario, Quebec and Newfoundland. The eclipse begins at 15:42 UT and ends at 20:52 UT with total eclipse taking place between 16:38 UT and 19:55 UT and maximum eclipse occurring at 18:17 UT. A partial lunar eclipse will take place on 18 September, the entirety or parts of which will be visible throughout southern and western Asia, the Indian Ocean, Europe, the whole of Africa, the Atlantic Ocean, North America, South America, the eastern Pacific Ocean and most of the Arctic and Antarctica. The penumbral phase of the eclipse commences at 00:41 UT and ends at 04:47 UT. The Moon begins to enter the Earth’s umbra (full shadow) at 02:12 UT, with maximum eclipse occurring at 02:44 UT. The Moon leaves the umbra at 03:15 UT.

Astronomy 2024.indb 89

07/02/2023 22:40

90  Yearbook of Astronomy 2024 The path of the annular solar eclipse of 2 October will pass from the middle of the Pacific Ocean across the southern tip of South America to the southern Atlantic, making landfall only in a narrow region of Chile and Argentina. A partial eclipse will be visible from most parts of southern South America, the south eastern Pacific Ocean, the southern Atlantic Ocean, the Falkland Islands and much of Antarctica. The eclipse begins at 15:43 UT and ends at 21:47 UT with full eclipse occurring between 16:50 UT and 20:39 UT and maximum eclipse taking place at 18:45 UT.

Astronomy 2024.indb 90

07/02/2023 22:40

Monthly Sky Notes and Articles

Astronomy 2024.indb 91

07/02/2023 22:40

Astronomy 2024.indb 92

07/02/2023 22:40

NE

ct

1O

1 Sep

52° North 35° South

1 Jun

1 May

y

t)

es

a 1M

t( Oc 23 1 Nov

w GE

E

1 Apr

1 Dec

1 Jan

1 Apr

1 Sep

1 Mar

1 Feb

1 Oct

1 Mar

Morning Apparition of Venus August 2023 to June 2024

SE

23

Oc

1 Feb

t)

s we

1 Nov

E t (G

1 Jan

1 Dec

S

0°

10°

20°

30°

40°

50°

Monthly Sky Notes and Articles 2024  93

January

 3/4

Earth

Quadrantid meteor shower (ZHR 120)

 4

Moon

Last Quarter

 5

Mars

1.0° north of M20 (Trifid Nebula)

14°

 6

Mars

0.4° north of M8 (Lagoon Nebula)

14° 

 6

Mars

1.5° north of M21

14°

 8

Moon

Lunar occultation of α Scorpii (Antares)

38°

11

Moon

New

12

Mars

1.1° north of M28

16°

12

Mercury

Greatest elongation west

24°

15

Moon, Neptune

Lunar occultation of Neptune

60° 17°

16

Mars

0.3° north of M22

18

Moon

First Quarter

20

Moon

Lunar occultation of M45 (Pleiades)

119°

24

Moon

1.7° south of β Geminorum (Pollux)

168°

25

Moon

Full

27

Jupiter

East quadrature

90°

27

Mercury, Mars

0.2° apart

20°

Dates are based on UT. Peak activity dates for meteor showers are estimates. The last column gives the approximate elongation from the Sun.

Mercury continues last year’s final morning apparition this month. Still on the upswing from December’s inferior conjunction, Mercury steadily brightens from magnitude +0.6 to −0.3 as it reaches greatest elongation west (23.5°) on 12 January and then passes through its descending node on 23 January. The tiny planet appears just 0.2° south of a somewhat dimmer Mars four days later on 27 January. This is the best morning apparition of Mercury this year for observers in equatorial regions. Venus is Φωσφόρος or Phosphorus, the bearer of light, the morning star. It is high in the southeast for observers in the tropics but rather lower in altitude for those in northern temperate latitudes, and descending every day. It appears almost stationary in the sky early in the month for those in the southern hemisphere

Astronomy 2024.indb 93

07/02/2023 22:40

94  Yearbook of Astronomy 2024

Morning Apparition of Mercury 22 December to 28 February 52° North 35° South 12 Jan (GE west)

30° 20°

21 Jan 1 Feb

1 Jan 11 Feb

1 Jan

21 Feb 11 Feb

E

12 Jan (GE west) 21 Jan

10°

1 Feb

SE

0°

before the planet starts to dip toward the horizon. Shining at a brilliant magnitude −4.0, the morning star is slowly drawing away from Earth, its disk appearing in its waxing gibbous phase through a telescope. Earth arrives at perihelion, the point in its orbit when it is nearest to the Sun, on 3 January. The date of perihelion varies slightly from year to year but always coincides with the Quadrantid meteor shower in early January. More information on the Quadrantids appears in the article Meteor Showers in 2024. The waning crescent Moon occults first-magnitude Antares on 8 January. On 20 January, the waxing gibbous Moon passes in front of the Pleiades open star cluster which is located in the constellation of Taurus. Four days later, the nearly full Moon appears 1.7° south of Pollux, the brightest star in the constellation of Gemini. Mars was at solar conjunction in November 2023 and remains a denizen of the morning sky this month. The red planet passes by a number of interesting deep sky objects, including the Trifid Nebula, the Lagoon Nebula, the open cluster M21 and the globular clusters M28 and M22, not to mention some of the brighter stars of Sagittarius. Unfortunately, most of these events occur when Mars is still less than 20° from the Sun and rising during morning twilight. Observers in the southern hemisphere will have the best glimpses of this rocky planet. Mars is at its maximum southerly declination on 7 January and Mercury is in close attendance on 27 January when the two planets are just 0.2° apart.

Astronomy 2024.indb 94

07/02/2023 22:40

Monthly Sky Notes and Articles 2024  95 Jupiter shines at magnitude −2.5 in the constellation of Aries. It is an evening sky object, better viewed from northern temperate latitudes (setting after midnight) than from the south (setting before midnight). It is at its maximum declination south at the beginning of the month and reaches east quadrature on 27 January. Watch it slowly close the distance to Uranus over the next four months. Saturn is visible in the western sky after sunset but sets by mid-evening. The ringed planet is located in Aquarius and is at its most southerly declination for the year on 1 January. Its celebrated ring system is also at its most open on this day, tilted at an angle of 9.2° as seen from Earth. The rings will appear to close for the next few months but will not appear edge-on until next year. Uranus enters the year in reverse, not returning to direct or prograde motion until around 25 January, the day it reaches its maximum declination south for 2024. Located in Aries, Uranus is best seen from northern latitudes where it sets well after midnight. However, it is strictly an evening sky object for southern hemisphere observers. Uranus is only sixth-magnitude; choose a moonless night in the first half of the month to observe this faint planet. Neptune opens 2024 at its most southerly declination of the year. Found in the evening sky in the constellation of Pisces, this eighth-magnitude object is slightly better placed for viewing from the northern hemisphere than from the south. On 15 January, the waxing crescent Moon occults Neptune as seen from the southern coast of Brazil from around 22:00 UT.

Astronomy 2024.indb 95

07/02/2023 22:40

96  Yearbook of Astronomy 2024

99942 Apophis A Killer at Our Doorstep Neil Norman

The asteroid 99942 Apophis was discovered on 19 June 2004 by astronomers Roy A. Tucker, David J. Tholen and Fabrizio Bernardi working at the Kitt Peak National Observatory, Arizona. At the time of discovery the asteroid was located within the constellation of Leo and situated at a heliocentric distance of 1.01 au and geocentric distance of 1.14 au respectively. As with all new discoveries, an orbit was quickly calculated, and it became very apparent that this asteroid belonged to a group of objects that have a potential to impact Earth and cause disruption on a global scale. Another thing soon became obvious; this asteroid was substantial, and an impact with an object this size could become a grave concern for our planet. Orbital calculations indicated that the asteroid would be passing by Earth on 21 December 2004 at a distance of 0.09638 au (14.42 million kilometres). In June 2005 – once the orbit was well defined – the asteroid was allocated the permanent number 99942, and in July of that year was given the name Apophis by the discoverers (it was previously designated 2004 MN4 ). The name Apophis comes from the Greek name Apep, an enemy of the Ancient Egyptian sun-god Ra. In addition, two of the discoverers – Tucker and Tholen – were fans of the TV show Stargate SG-1, a villain of the show being an alien named Apophis. Given its apparent brightness curve, Apophis was at first estimated to be around 450 metres in diameter, although this estimate was lowered to 350 metres following observations made by NASA’s Infrared Telescope Facility in Hawaii. The NASA impact page – which can be accessed by going to cneos.jpl.nasa.gov/sentry – lists Apophis as 330 metres and gives the estimate of the mass as 4 3 1010 kg, a value based on an assumed density of 2.6 g/cm. It must be noted here that the mass estimate is only a rough approximation compared with the better known diameter size but is accurate to within a factor of three. The composition of Apophis is probably closely matched to that of a LL chondrite (stony) meteorite. It is interesting to note that the Goldstone and Arecibo radar images gathered during 2012 and 2013 indicate that Apophis is elongated, and may be a contact binary object (very plausible as we have in recent years encountered two objects of similar

Astronomy 2024.indb 96

07/02/2023 22:40

Monthly Sky Notes and Articles 2024  97

Images of Apophis obtained over three days during the close approach to Earth on 8, 9 and 10 March 2021. The 70-metre antenna at the Goldstone Deep Space Communications Complex in California and the 100-metre Green Bank Telescope in West Virginia joined forces to gather these pictures. At the time of imaging, the asteroid was around 17 million kilometres from the Earth. For reference, each pixel has a resolution of 38.75 metres. (NASA/JPL-Caltech and NSF/AUI/GBO)

construction, Comet 67P/Churyumov-Gerasimenko and the trans-Neptunian object 486958 Arrokoth). It is also known that the rotation is in retrograde with one full revolution taking 30.4 hours to complete. Apophis is currently in a low inclination orbit of just 3.3° which carries it from just outside the orbit of Venus to a little beyond that of the Earth. Following the close approach to our planet in April 2029, the orbit will be perturbed by Earth’s gravity, placing Apophis in an orbit with a perihelion just inside the orbit of the Earth and an aphelion slightly beyond the orbit of Mars. Previous and future approaches of Apophis to Earth are as follows: DATE

GEOCENTRIC PASS DISTANCE (AU / KILOMETRES)

21 Dec 2004

0.09638 au (14.42 million kilometres)

  9 Jan 2013

0.09666 au (14.46 million kilometres)

13 Apr 2029

0.000254128 au (38,017 kilometres)

27 Mar 2036

0.309756 au (46.34 million kilometres)

20 Apr 2051

0.041455 au (6.20 million kilometres)

16 Sep 2066

0.069562 au (10.41 million kilometres)

12 Apr 2116

0.019462 au (2.91 million kilometres)

Astronomy 2024.indb 97

07/02/2023 22:40

98  Yearbook of Astronomy 2024

Diagram depicting the close approach Apophis will make to Earth on 13 April 2029. The Earth’s gravity will deflect the object and change the orbit of Apophis from that of an Aten class asteroid to that of an Apollo class. The white error bar at centre denotes the uncertainty of the approach distance. (NASA/Marco Polo/Wikimedia Commons)

The pass of 2029 must be flagged up instantly as one of concern; it will be noticed that, unlike the other dates, the distance from Earth is measured in thousands of kilometres rather than millions of kilometres. The approach is timed for 21:46 UT on 13 April. By astronomical standards, this pass is a very close shave indeed, being only around a tenth of the distance of the Moon and closer than several hundred geostationary satellites – a record in terms of a close approach by an asteroid of this size.

Astronomy 2024.indb 98

07/02/2023 22:40

Monthly Sky Notes and Articles 2024  99 At the time of closest approach, 99942 Apophis will be ideally situated for observers in Europe, Africa and Asia, shining as a magnitude 3.1 point of light and easily visible with the naked-eye or binoculars. The pass will be so close that the Earth’s gravity will actually perturb the asteroid and change it from an Aten-class asteroid with a semi -major axis of 0.92 au to an Apollo-class object with a semi major axis of 1.1 au. This will increase the perihelion distance from 0.74 au to 0.89 au resulting in an increase in aphelion distance from 1.09 au to 1.31 au.

The Effect of an Impact with Apophis Although orbital modelling has now shown that the Earth is not in any danger of an impact with Apophis for at least the next 100 years, what would happen if the Earth was to encounter an asteroid of this size? An impact with an object like Apophis would create kinetic energy equivalent of 1,200 megatons of TNT. For comparison, the impact that formed the Barringer Crater in Arizona and the 1908 Tunguska event had similar power, somewhere between three and ten megatons of TNT. The largest hydrogen bomb ever detonated, the Russian nuclear weapon known as the Tsar Bomba – detonated on 10 October 1961 – yielded the equivalent of between 50 and 58 megatons of TNT. One thing for certain is that a collision with Apophis would be felt globally, and an impact into sedimentary rock would create a crater five kilometres in diameter. It is perhaps reassuring to know that the statistics point to a collision with asteroids of this size occurring on average once every 800,000 years. Coincidentally, the last impact by an object of these proportions – thought to have been a kilometre-size asteroid – took place around 800,000 years ago in south eastern Asia. A sobering thought indeed. One must also remember that objects of this size litter space, and could be perturbed our way at any time by Jupiter, and we may have little warning of their impending impact (Apophis was just six months away from close approach at discovery). It is a concern that Apophis has been lurking on Earth’s doorstep – unnoticed – for at least the past 500 years.

Astronomy 2024.indb 99

07/02/2023 22:40

100  Yearbook of Astronomy 2024

February

 1

Moon

1.7° north of α Virginis (Spica)

 2

Moon

Last Quarter

 5

Moon

Lunar occultation of α Scorpii (Antares)

67°

 8

Uranus

East quadrature

90°

 9

Moon

New

11

Moon, Saturn

1.8° apart

15°

12

Moon, Neptune

Lunar occultation of Neptune

33°

16

Moon

First Quarter

16

Moon

Lunar occultation of M45 (Pleiades)

92°

21

Moon

1.6° south of β Geminorum (Pollux)

141°

22

Venus, Mars

0.6° apart

24

Moon

Full

28

Mercury

Superior conjunction

28

Moon

1.5° north of α Virginis (Spica)

28

Mercury, Saturn

0.2° apart

2°

28

Saturn

Conjunction

2°

109°

26° 2° 136°

Dates are based on UT. The last column gives the approximate elongation from the Sun.

Mercury is visible in the morning sky but is already on its way back to the horizon, brightening as it loses altitude. It vanishes before the end of the month, undergoing superior conjunction and a close pass by Saturn on 28 February. Earlier, on the second day of the month, Mercury reaches aphelion for the first time in 2024. Venus continues to rule the morning sky. It is rather low in the southeast for early risers in northern temperate latitudes but is still quite high above the horizon for those much farther south. It is descending, however, and appears a little lower in the sky every morning. When viewed through a telescope, Venus is in its waxing gibbous phase as it heads toward superior conjunction later this year. As the phase increases, the apparent size of diameter of the disk decreases as the planet draws away from Earth. The net effect is that Venus gets slightly dimmer, decreasing from magnitude −4.0 to −3.9 over the course of the month. Venus reaches its descending node on 14 February, crossing the ecliptic plane north to south. On 22 February,

Astronomy 2024.indb 100

07/02/2023 22:40

Monthly Sky Notes and Articles 2024  101 Venus and Mars team up in the southeast before sunrise when the two planets are just over half a degree apart. The Moon continues its series of occultations and near misses of bright stars this month. The Moon is in its waning gibbous phase when it passes less than 2° north of first-magnitude Spica on both the first and last days of February. On 5 February, the waning crescent Moon occults Antares. The First Quarter Moon occults the brightest member of the Pleiades, the famous open star cluster in Taurus, on 16 February. Five days later, the waxing gibbous Moon is in Gemini and moving 1.6° south of Pollux. The Full Moon of 24 February takes place less than a day before apogee, making this Full Moon the ‘smallest’ one of the year, that is to say, the one with the smallest apparent diameter. (The ‘largest’ Full Moon of 2024 occurs in October.) Mars and Venus come to within 0.6° of each other on 22 February, ten days after the red planet crosses into the constellation of Capricornus. Mars is slowly brightening but is only magnitude +1.3 to Venus’s brilliant −4.0. Both planets are in the morning sky, with Mars hugging the horizon as seen from northern latitudes. Southern hemisphere astronomers have the best views, with Mars appearing in the east before dawn brightens the sky. Jupiter dims slightly as it moves away from last year’s opposition toward this year’s solar conjunction, shining at magnitude −2.3 in Aries. It is visible in the evening sky but sets mid- to late evening for all latitudes so look for it in the west as soon as it gets dark. Saturn sets during twilight hours. The very young crescent Moon passes 1.8° south of Saturn on 11 February but the planet is getting close to the Sun by this point. Conjunction takes place on 28 February. Uranus is at east quadrature on 8 February, placing it 90° away from the Sun in the evening sky. The sixth-magnitude object inhabits the constellation of Aries and is most easily viewed from the northern hemisphere where it sets around midnight. Planet watchers in southern latitudes lose Uranus mid-evening. Choose a moonless night during the first part of the month to catch this faint planet. Neptune is occulted by the young crescent Moon on 12 February. This event begins around 08:00 UT and is visible from Melanesia, including Papua New Guinea,

Astronomy 2024.indb 101

07/02/2023 22:40

102  Yearbook of Astronomy 2024 the Solomon Islands and New Caledonia. The eighth-magnitude object is only 0.1°  north of the fifth-magnitude K-type giant star 20 Piscium on 22 February, providing an interesting colour contrast through the astrophotographer’s lens. An evening sky object, Neptune is low in the west as night falls and is best seen from the northern hemisphere.

Astronomy 2024.indb 102

07/02/2023 22:40

Monthly Sky Notes and Articles 2024  103

James Short Gary Yule

The Scottish mathematician and manufacturer of optical instruments James Short was born in Edinburgh on 21 June 1710 to William Short and Margaret Grierson. James was orphaned at the age of ten, and was subsequently accepted at George Heriot’s Hospital Orphanage, transferring a few years later to the Royal High School where he excelled in his studies. In 1724 he entered the University of Edinburgh to study divinity (theology/ministry), although it seems he was more inspired by the lectures of Colin Maclaurin, a professor of mathematics who was teaching at Edinburgh at the time; thus begun Short’s lifelong interest in astronomy. Eventually giving up on the ministry, Short gained the patronage of Maclaurin – a follower A portrait of James Short attributed to the English painter Benjamin Wilson. and friend of Isaac Newton – by displaying a (The Crawford collection of the Royal great skill in handcrafting and an interest in Observatory Edinburgh) telescopes. The practicality of Newton’s reflecting telescopes had been under scrutiny at the Royal society and still had not yet been perfected. Maclaurin set Short to work in his own room at the University to work on the making of mirrors for reflecting telescopes and to perfect the design of a truly parabolic mirror. Short worked mainly on telescopes of the Gregorian design, going on to perfect this in 1734. As a result, Maclaurin wrote to the English mathematician Robert Smith who published an account of Short’s work in his Optiks. This brought James Short into the spotlight and before long he became a Fellow of the Royal Society in 1737. He went on to gain an excellent reputation, establishing a successful telescope-making business in Edinburgh, before moving to London in 1738. Short became known to the natural philosopher James Douglas, 14th Earl of Morton, who became a patron of James Short by appointing him tutor to his

Astronomy 2024.indb 103

07/02/2023 22:40

104  Yearbook of Astronomy 2024

A replica of Isaac Newton’s second telescope of 1672. Newton’s work on optics led him to believe that all refracting telescopes would suffer from chromatic aberration. His new design of telescope, known as a Newtonian reflector and incorporating mirrors, minimized this problem. (Wikimedia Commons/Solipsist (Andrew Dunn)

children. In 1739 Short went with Douglas on a surveying project to Orkney where they started work on determining the length of degree of latitude. Upon returning to London, Short’s business began to thrive. His telescopes became well known and he went on to produce over 1,300 during his 35-year career, of which it is believed 110 are still around today, including two that travelled with the explorer and navigator James Cook during his voyage to Tahiti aboard HMS Endeavour during the late-1760s. Two of the biggest astronomical events of the mid-eighteenth century were the transits of Venus in 1761 and 1769. Many astronomers from around the globe wanted to observe these transits in order to be able to calculate solar parallax and discover the dimensions of the solar system. They were eager to acquire the finest

Astronomy 2024.indb 104

07/02/2023 22:40

Monthly Sky Notes and Articles 2024  105 optics available, turning their attention to London because of its fine reputation for telescope and astronomical instrument makers, including James Short, who was well known and respected for his superior telescope designs. In his spare time Short made observations from his own observatory in Surrey, using one of his own 5-inch telescopes, and had many papers published. He was a good friend of his potential rival, the accomplished optician John Dollond, and encouraged his work on the correction of chromatic aberration in refracting telescopes. He also gave active support to the carpenter and clock-maker John Harrison, famous for his invention of the A fine example of a Gregorian telescope, marine chronometer. based on an original design by James Short championed the difficult and Gregory in the seventeenth century and unpopular Harrison in his disputes with later refined and perfected by James Short. Board of Longitude, although the help that The image shown is an example made by Short gave to Harrison annoyed the Earl of Short in 1741. (Wikimedia Commons/ Morton, James Douglas, who consequently York Museums Trust) opposed Short’s appointment to the Royal Observatory. James Short did, however, become one of the founding members of the Philosophical Society of Edinburgh. He was also the founding member of the Society for the Encouragement of Arts, Manufactures and Commerce in 1754 and, in 1757, became a foreign member of the Royal Swedish Academy of Sciences. His dedication to work led to James Short being a lifelong bachelor, although his telescope-making skills brought him worldwide recognition and success, so much so that he went on to bequeath a fortune of £20,000 on his passing at Newington Butts, Surrey on 14 June 1768, age 57.

Astronomy 2024.indb 105

07/02/2023 22:40

106  Yearbook of Astronomy 2024

March

 3

Moon

Lunar occultation of α Scorpii (Antares)

 3

Moon

Last Quarter

 3

3 Juno

Opposition

178°

 3

324 Bamberga

Opposition

176°

 8

Mercury, Neptune

0.4° apart

9°

 9

Moon, Saturn

1.5° apart

9°

10

Moon

New

10

Moon, Neptune

Lunar occultation of Neptune

6°

11

Moon, Mercury

Lunar occultation of Mercury

10°

15

Moon

Lunar occultation of M45 (Pleiades)

65°

17

Moon

First Quarter

17

Neptune

Conjunction

19

Moon

1.5° south of β Geminorum (Pollux)

21

Venus, Saturn

0.3° apart

19°

24

Mercury

Greatest elongation east

19°

25

Moon

Full – penumbral lunar eclipse

26

Moon

1.4° north of α Virginis (Spica)

163°

30

Moon

Lunar occultation of α Scorpii (Antares)

120°

94°

1° 114°

Dates are based on UT. The last column gives the approximate elongation from the Sun.

Mercury makes it first evening appearance of 2024 this month. This is the best evening apparition of the year for planet-chasers in northern temperate latitudes. Mercury passes near Neptune on 8 March and is occulted by the day-old crescent Moon three days later but both events occur during daylight hours. Mercury continues its ascent in the western skies until late in March, dimming from magnitude −1.8 to +1.5 over the course of the month. The tiny planet passes through its ascending node on 13 March, moving from south to north across the plane of the ecliptic, and reaches perihelion four days later. A greatest elongation east of 18.7° takes place on 24 March; this is the smallest of three greatest elongations east this year.

Astronomy 2024.indb 106

07/02/2023 22:40

Monthly Sky Notes and Articles 2024  107

Evening Apparition of Mercury 28 February to 11 April 52° North 35° South

30°

21 Mar

24

ar

1 Mar

20°

1 Apr

11 Mar

SW

r(

Ma

t)

as

e GE

1M

W

r Ma r 11 Ma 21

24

r(

Ma

t)

as

e GE

10°

1 Apr

11 Apr

0° NW

Venus reaches aphelion on 19 March, the point in its orbit when it is farthest from the Sun. The morning star shines at magnitude −3.9 all month as it slowly descends toward the horizon. In fact, it is already quite low as viewed from northern temperate latitudes. Venus passes by Saturn on 21 March, appearing 0.3° south of the ringed planet. Earth is at an equinox on 20 March, marking the start of astronomical spring in the northern hemisphere and astronomical autumn in the southern hemisphere. (Meteorologists have their own ideas about the dates of the seasons!) The first eclipse of 2024 takes place five days later when the Full Moon undergoes a faint penumbral eclipse. The article Eclipses in 2024 gives more details. This Full Moon is the ‘Harvest Moon’ of the southern hemisphere. The nearest perigee of the year coincides with the New Moon. The waning gibbous Moon occults first-magnitude star Antares twice this month, on 3 March and again on 30 March. The Pleiades and the waxing crescent Moon present an attractive site on 15 March when our satellite occults the open star cluster. Four days later, the waxing gibbous Moon flies past Pollux and on 26 March, the day after the lunar eclipse, the waning gibbous Moon is only 1.4° north of Spica. Mars begins the month in Capricornus, passing 1.4° north of Deneb Algedi (δ Capricorni), the brightest star in the constellation, on 15 March. A few days later

Astronomy 2024.indb 107

07/02/2023 22:40

108  Yearbook of Astronomy 2024 the red planet moves into the neighbouring constellation of Aquarius. Mars is best viewed from the southern hemisphere, where it rises two hours or more before the Sun. As seen from northern temperate latitudes, Mars does not appear until the sky is already well alight. 324 Bamberga reaches opposition in ecliptic longitude on 3 March with maximum elongation from the Sun (176°) taking place at around the same time. Opposition in right ascension occurs the previous day. Found in the constellation of Leo, the twelfth-magnitude asteroid is nearest to Earth in late February but brightest in early March. See Minor Planets in 2024 for more information relating to 324 Bamberga and 3 Juno. 3 Juno mimics the behaviour of its asteroidal neighbour 324 Bamberga this month. Also found in Leo, 3 Juno comes to opposition on 3 March with opposition in right ascension taking place the previous day. Despite being the more distant of the two objects, ninth-magnitude 3 Juno is much brighter than 324 Bamberga. Jupiter continues to dominate the constellation of Aries, shining a brilliant magnitude −2.2 this month. It is easiest to see from northern temperate latitudes where it does not set until late evening; observers in the southern hemisphere lose it in the west much earlier. Saturn was at conjunction late last month and is difficult to see in the morning sky. Southern hemisphere observers will have the best chance of spotting the firstmagnitude object from mid-month onwards but Saturn remains very near to the eastern horizon for those up early in northern temperate latitudes. Located in Aquarius, Saturn has a close encounter with the morning star on 21 March when the two planets are just 0.3° apart. Uranus is a faint sixth-magnitude planet in Aries. It sets during the early evening hours when sought from southern vantage points but remains aloft until quite late in the evening for observers in northern temperate latitudes. Dark skies are a must if you want to see this green ice giant with the naked eye. Neptune is at conjunction with the Sun mid-month and is lost to view. It will reappear in the morning sky at the end of the month where it is most easily viewed in the autumnal southern hemisphere skies.

Astronomy 2024.indb 108

07/02/2023 22:40

Monthly Sky Notes and Articles 2024  109

The Heavens on Stone Canvas How Our Ancestors Captured the Universe Jonathan Powell

When one imagines the work of an artist, perhaps conjured to mind are images of a landscape or portrait on a canvas, perhaps still resting in its easel, or framed and on show in a public gallery. The canvas though represents just one medium in which the artist can capture the world around themselves, with sculptures and models also a way to encapsulate a vision. To early humankind, cave walls provided the canvas, and alongside the sketches of animals, people, and landscapes, the night sky was to also feature.

Understanding Cave Art Cave paintings made in what are now modern-day Turkey, Spain, France and Germany suggest that, perhaps as far back as 40,000 years ago, humans kept track

An early drawing on which the aurora is depicted as candles in the sky, 1570. (Crawford Library, Royal Observatory, Edinburgh)

Astronomy 2024.indb 109

07/02/2023 22:40

110  Yearbook of Astronomy 2024 of the passage of time using knowledge of how the position of the stars slowly changed over thousands of years. Major celestial events have also been recorded. One such notable piece of art is the ‘Shaft Scene’ situated in the Lascaux Caves in France which depicts a dying man along with several animals. Research suggests that the artwork may represent a comet strike on Earth around 15,200 BC. The longevity and survival of the cave art is attributable to the use of mineral pigments, most commonly manganese, hematite, malachite, gypsum, limonite, clays and various oxides. Reddening colours were made with iron oxides (hematite), whilst for black, manganese dioxide and charcoal were used. Analysis of the ‘rock art’ has produced some intriguing theories. Some researchers claim that a sort of “key” or “code” possibly exists within the artwork and that the paintings may have been a way of transmitting or relaying information, whilst a more rational explanation suggests a religious or ceremonial purpose. It has been suggested that prehistoric civilizations may have painted animals on a cave wall to “catch” their soul or spirit in order to hunt them with more ease, or that the cave wall was merely some way of paying homage to the surrounding nature and environment in which the artist lived.

Supernova In July 1054, a brilliant supernova, appearing six times as bright as Venus and clearly visible even at high noon, was sighted and recorded across the world. Thought not to have faded from sight for around two years, the remnants of the outburst still grace our skies in the form of the Crab Nebula in Taurus. Aside reports from Europe, the sighting was recorded in China, Japan, Korea, and modern-day Iraq, along with a possible account by aboriginal Australians. Perhaps, though, one of the most intriguing depictions is a pictograph associated with the Ancestral Puebloan culture found at Chaco Canyon, near the Peñasco Blanco site in New Mexico.

Alternative Records of the Night Sky Discovered inside the Geißenklösterle cave in the Swabian Alps of south-western Germany, the Ach Valley tusk fragment bears the image of an upright figure that is thought may represent the constellation of Orion the Hunter. Carved from a mammoth ivory fragment during the Ice Age, it would make for the oldest known interpretation of a star map, with an age in excess of 32,000 years. The Dendera Zodiac is the name given to an interesting bas-relief found on the ceiling of a chapel in the Temple of Hathor, which is part of the Dendera Temple complex in Upper Egypt. It is an ancient astronomical map that contains all the

Astronomy 2024.indb 110

07/02/2023 22:40

Monthly Sky Notes and Articles 2024  111

The 32,000 year-old small sliver of a mammoth tusk known as the Ach Valley tusk fragment depicts a man-like figure which some believe represents the constellation of Orion. The carving – found in a cave in 1979 in the Alb-Danube region of Germany – measures 38 × 14 × 4 millimetres. If the figure is a representation of Orion, the artefact would make for the oldest image of a star pattern known to humankind. (Wikimedia Commons/Thilo Parg/CC BY-SA 3.0)

Believed to date from the Bronze Age – although some researchers date the piece later in the Iron Age – the Nebra disc, the oldest map of the stars, has a blue-green patina emblazoned with gold symbols that represent the Sun, Moon, and stars, along with the solstices and other astronomical phenomena. (Wikimedia Commons/Frank Vincentz)

information necessary to calculate the journey of Earth from one Zodiac sign to another over 29,920 years. The Nebra disc, thought by many researchers to be the oldest known realistic representation of the cosmos, is made of bronze and measures 32 cm in diameter, with a weight of 2.2 kg. The disc has been dated to 1600 BC, with a manufacture date of 200 years before that. The piece was discovered by treasure hunters in 1999 while metal detecting at a prehistoric enclosure encircling Mittelberg, near the town of Nebra in the Ziegelroda Forest, approximately 180 kilometres south-west of Berlin. The astrolabe, which some quarters refer to as a hand-held model of the Universe, was crafted and used for centuries in European and Islamic cultures, the modern-day equivalent of a smart device with a range of capabilities. Dating back to the sixth century, astrolabes were multi-functional devices used by astronomers and navigators to measure the altitude above the horizon of a celestial object, day or night.

Astronomy 2024.indb 111

07/02/2023 22:41

112  Yearbook of Astronomy 2024 With the advent of the digital era, the capturing and storage of data from the night sky would now perhaps seem to be confined to one method, but in order to have reached this point, we must not forget all that has gone before and the wealth of information gathered by so many different means.

Astronomy 2024.indb 112

07/02/2023 22:41

Monthly Sky Notes and Articles 2024  113

April

 2

Moon

Last Quarter

 3

Venus, Neptune

0.3° apart

16°

 6

Moon, Mars

2.0° apart

37°

 6

Moon, Saturn

Lunar occultation of Saturn

33°

 7

Moon, Neptune

Lunar occultation of Neptune

20°

 7

Moon, Venus

Lunar occultation of Venus

15°

 8

532 Herculina

Opposition

 8

Moon

New – Total solar eclipse

10

Mars, Saturn

0.4° apart

37°

11

Moon

Lunar occultation of M45 (Pleiades)

38°

11

Mercury

Inferior conjunction

152°

2°

15

Moon

1.5° south of β Geminorum (Pollux)

15

Moon

First Quarter

19

Mercury, Venus

1.7° apart

12°

21

12P/Pons-Brooks

Perihelion

23°

21

Jupiter, Uranus

0.5° apart

20°

22/23

Earth

Lyrid meteor shower (ZHR 18)

23

Moon

1.5° north of α Virginis (Spica)

23

Moon

Full

26

Moon

Lunar occultation of α Scorpii (Antares)

29

Mars, Neptune

0.03° apart

87°

170° 147° 41°

Dates are based on UT. Peak activity dates for meteor showers are estimates. The last column gives the approximate elongation from the Sun.

Mercury appears in the west after sunset but only briefly; inferior conjunction takes place on 11 April after which the tiny planet returns to the morning sky. A period of retrograde motion always takes place around the time of inferior conjunction. In this case, Mercury reaches a stationary point on the first day of the month and then returns to direct motion on 24–25 April. Mercury passes its brighter inferior planet colleague Venus on 19 April and then returns to the south side of the ecliptic plane the following day when it passes through its descending node. The second aphelion of 2024 occurs on the final day of the month. This is the best morning

Astronomy 2024.indb 113

07/02/2023 22:41

114  Yearbook of Astronomy 2024 apparition of Mercury in 2024 for early risers in the southern hemisphere. At sixth magnitude during conjunction, Mercury brightens to magnitude +1.1 by the beginning of  May. Venus and Neptune have a close encounter on the third day of the month but this will be difficult to observe from northern locations. The very old crescent Moon occults Venus on 7 April. Given that the Moon is in its new phase the next day, it is unlikely that anyone in the mid-Pacific Ocean will observe this event. Venus and Mercury team up later in the month when they are a little under 2° apart on 19 April. The morning star is desperately close to the horizon as seen from northern temperate latitudes but still is 10° or more in altitude when observed from the southern hemisphere. 12P/Pons-Brooks reaches perihelion in the latter half of April, its first visit to the inner solar system since 1954 and only its fourth fly-by of the Sun since the comet’s formal discovery in 1812. It is expected to be visible to the naked eye this month and will be nearest to Earth in early June. The comet is approaching the Sun from north of the ecliptic which favours observers in the northern hemisphere. Look for it after sunset low in the northwest as it passes southward through the constellations of Aries and Taurus. To learn more about this famous comet and where to find it in the sky, see Comets in 2024. Earth experiences a total solar eclipse on 8 April. Observing hints and timing details are outlined in Eclipses in 2024. The waxing crescent Moon occults the Pleiades star cluster in Taurus on 11 April and passes 1.5° south of Pollux four days later. The waxing gibbous Moon is 1.5° north of Spica on 23 April with our satellite reaching its full phase later that day at 23:49 UT (which is 0:49 BST on 24 April). The final major lunar occultation of the month occurs on 26 April when Antares disappears behind the disk of the waning gibbous Moon. The annual appearance of the Lyrid meteor shower takes place late in the month; see Meteor Showers in 2024 for additional information. Mars glides past Saturn on 10 April with the two celestial bodies less than half a degree apart. The two planets are about the same brightness (around magnitude +1.1) but Mars looks rather more reddish in hue. After crossing the border into Pisces late in the month, Mars is found only 0.03° north of eighthmagnitude Neptune on 29 April. As Mars is still close to the horizon at dawn as viewed from northern temperate latitudes, a trip to the southern hemisphere (with a telescope) is necessary to view this event in dark skies.

Astronomy 2024.indb 114

07/02/2023 22:41

Monthly Sky Notes and Articles 2024  115 532 Herculina reaches opposition in ecliptic longitude on 8 April in the constellation of Boötes, but opposition in right ascension does not take place until ten days later. The object is thought to be one of the larger members of the main asteroid belt between Mars and Jupiter but is no brighter than ninth magnitude. See Minor Planets in 2024 for more information on this interesting body. Jupiter finally overtakes Uranus on 21 April, moving past the fainter planet at a distance of half a degree. Optical aids will be necessary to see both bright Jupiter and faint Uranus in the constellation of Aries. Visible in the evening sky just as twilight ends, the two worlds set soon afterwards. This rare conjunction occurs only once every 14 years or so; the next opportunity to see Jupiter and Uranus together will be the triple conjunction of 2037–8. A week after the Jupiter–Uranus conjunction, Jupiter enters Taurus where it will remain for the rest of the year. Saturn undergoes a lunar occultation on 6 April when the waning crescent Moon moves in front of the planet as seen from parts of Antarctica. The red planet approaches the ringed planet four days later on 10 April, moving past 0.4° south of Saturn. Saturn is in the constellation of Aquarius. It is strictly a morning sky object and much easier to see from southern latitudes than from the north. Uranus has a visitor on 21 April when bright Jupiter passes 0.5° north of the sixthmagnitude planet. Uranus and Jupiter were last seen together in 2010–11 when they underwent a triple conjunction. This event takes place in the western sky after sunset with the Sun only 20° away. Skies should still be dark but Uranus is approaching solar conjunction next month and sets during twilight by the end of  April. Neptune is just past solar conjunction and visible ahead of sunrise in the constellation of Pisces. At eighth magnitude, optical aids are required to see it. On 3 April, brilliant Venus comes to within 0.3° of Neptune but you will need to be in the southern hemisphere in order to see it in dark skies; northern skies are already brightening with the dawn. The lunar occultation four days later is only visible from the southern Atlantic Ocean. Neptune and the red planet enjoy a very close conjunction on the penultimate day of the month when the two planets are only 0.03° apart.

Astronomy 2024.indb 115

07/02/2023 22:41

116  Yearbook of Astronomy 2024

Buran The Soviet ‘Space Shuttle’ Jonathan Powell

NASA’s Space Shuttle program was a landmark achievement with the introduction of the first reusable spacecraft that could be used to deliver humans and payloads – such as satellites – beyond Earth’s atmosphere, and return them if necessary. In essence, the program’s vision pioneered the way for a future that could now show a whole new spectrum of possibilities. A new era had begun in humankind’s quest to conquer space. The planning for such a revolution started back as the early late-1960s, with NASA envisaging the concept as the next progressive stage to gain entry and work effectively in space, and perhaps as well to silence critics of NASA’s budget which was – and always will be – under public scrutiny. NASA’s dream became a reality when, following test flights of the Space Shuttle Enterprise in 1977, the Space Shuttle Columbia spearheaded the program when it powered into the skies in 1981, starting a rollercoaster of both success, and sadly tragedy, for the many launches that followed. However, with NASA firmly in the limelight, the Soviet Union had been duly taking note, with plans of their own to rival this new breed of space vehicle. With striking similarities to the Space Shuttle, ‘Buran’ was conceived and born.

The Birth of Buran Buran, which translates as ‘Snowstorm’ and of which there were seven variants in the proposed fleet, would have brought the Soviet Union very much in line with the USA. In reality, if Buran had succeeded, affairs would have been significantly different in the world of spaceflight that we know today. At the time of Buran’s conception, whilst space was seemingly part of the focus of the Soviets, it was the military possibilities that caused the greatest interest. With construction underway around the time of NASA’s first launch, the first full-scale Buran orbiter was completed several years after, and upon Buran’s completion it seemed that Russia had also entered into this brave new era. The ‘umbrella’ for all of the work that followed on Buran came under the Soviet Reusable Space System program, or MKS, which was to include alongside Buran,

Astronomy 2024.indb 116

07/02/2023 22:41

Monthly Sky Notes and Articles 2024  117

The Soviet Buran reusable space ship pictured in Gorky Park, Moscow. Buran was built to rival the US Space Shuttle but only made one flight. (© Can Stock Photo / demerzel21)

the Energia heavy-lift vehicle which was to propel the craft into space. The Buran concept saw the country draw on an extensive network of resources, with the involvement of over a million people from 1,286 companies and 86 ministries and departments. Several more years were to pass until in late-November 1988, Buran was to reach for the heavens. Taking off from the Baikonur Cosmodrome on 15 November, and powered by a specially designed Energia rocket, the crewless Buran flew under automatic guidance, completing a near faultless test flight and returning to the launch site via a familiar horizontal runway landing. With Buran complete and a successful test flight reflecting that the structure of the craft and its internal components were working effectively, there was every indication to the outside world that Buran and its newly constructed sister craft, nicknamed Ptichka, would fly again, with a second crewless flight planned and expected to be performed by 1993.

Astronomy 2024.indb 117

07/02/2023 22:41

118  Yearbook of Astronomy 2024

Alike but Unlike Whilst there are undoubtedly parallels to be made between the US Space Shuttle and the Soviet Buran craft there were a number of differences, one of the chief of which was the ability to fly Buran automatically with no pilot required throughout the entire flight from take-off to landing. Buran also had a higher orbital and deorbital carrying capacity compared to the Space Shuttle, with Buran’s two rear engines allowing the craft to fly during re-entry into the atmosphere. Buran was adorned with superior heat shields, and interestingly, the docking compartment featured an extendable tunnel, which would have given greater clearance between Buran and any orbiting station is was to dock with.

Buran’s Demise Despite Buran’s demonstration of capability, with its test flight completing two orbits of the Earth and landing virtually metres away from its intended touchdown target area on the runway, Buran was never to fly again. In reality, by the end of 1991 Buran and Ptichka were the only fully completed craft in the program, with work on three more suspended and then never completed. The dissolution of the Soviet Union saw funding terminated, which left the project stranded. The total cost of the program had reached unacceptable proportions – 16.4 billion roubles in 1992 – and with the economy teetering somewhat, financial assistance was withdrawn. By 1993, it had been publicly declared that the project was finished, with a roof collapse at Baikonur not only tragically killing eight workers, but destroying Buran. Whilst a full-scale prototype exists for display purposes, Russia’s dream of its own reusable spacecraft was over. What should have been a glorious new era ushered in by Buran never arrived, with Russia left to seek other avenues in their own conquest of space.

Astronomy 2024.indb 118

07/02/2023 22:41

Monthly Sky Notes and Articles 2024  119

May

 1

Moon

Last Quarter

 3

Moon, Saturn

Lunar occultation of Saturn

57°

 4

Moon, Neptune

Lunar occultation of Neptune

46°

 5

Moon, Mars

Lunar occultation of Mars

42°

 6/7

Earth

Eta Aquariid meteor shower (ZHR 30)

 8

Moon

New

 8

Moon

Lunar occultation of M45 (Pleiades)

12°

 9

Mercury

Greatest elongation west

26°

12

Moon

1.6° south of β Geminorum (Pollux)

61°

13

Uranus

Conjunction

15

Moon

First Quarter

18

Venus, Uranus

0.5° apart

5°

18

Jupiter

Conjunction

1°

19

2 Pallas

Opposition

133°

20

Moon

1.4° north of α Virginis (Spica)

143°

23

Venus, Jupiter

0.2° apart

23

Moon

Full

24

Moon

Lunar occultation of α Scorpii (Antares)

30

Moon

Last Quarter

31

Mercury, Uranus

1.3° apart

16°

31

Moon, Saturn

Lunar occultation of Saturn

82°

0°

3° 172°

Dates are based on UT. Peak activity dates for meteor showers are estimates. The last column gives the approximate elongation from the Sun.

Mercury continues its excellent morning apparition for the early birds of equatorial and southern latitudes. Brightening from magnitude +1.1 to −0.8, it ascends above the eastern horizon for the first half of the month before heading back toward the ground. Greatest elongation west – the largest of the year at 26.4° – occurs on 9 May. Mercury is found 1.3° north of Uranus on the last day of the month but faint Uranus is probably too near solar conjunction to be visible.

Astronomy 2024.indb 119

07/02/2023 22:41

120  Yearbook of Astronomy 2024

Morning Apparition of Mercury 11 April to 14 June 52° North 35° South

9 May (GE west) 21 May

1 Jun

11 Jun

NE

30° 1 May

20°

21 Apr

n Ju 11 1 Jun 11 Apr

21

ay

M

ay

E

(G

M 9 1 May 21 A pr

E

)

st

we

10° 0°

Venus encounters Uranus on 18 May, just five days after the ice giant’s conjunction with the Sun. It then passes by Jupiter on 23 May, again, five days after that gas giant’s conjunction with the Sun. However, these events will not be visible due to the planets’ proximity to our star. Venus itself will undergo superior conjunction in early June, making it difficult to observe the morning star this month. Earth enjoys dark moonless skies for the 2024 appearance of the Eta Aquariid meteor shower during the first week of the month. The article Meteor Showers in 2024 has more information. The occultation of the Pleiades by the New Moon is unobservable on 8 May but stargazers should have a better chance of catching sight of the waxing crescent Moon passing 1.6° south of Pollux four days later. It is slightly closer to Spica (1.4° north of the first-magnitude star) on 20 May and is just one day past full when occulting Antares on 24 May. Mars is occulted by the waning crescent Moon on 5 May. Beginning around 00:00 UT, residents of Madagascar and the islands of the western Indian Ocean will see the red planet vanish behind the disk of the Moon in the early morning hours. Mars reaches perihelion three days later. The red planet remains a morning sky object slowly traversing the constellation of Pisces, briefly dipping into Cetus 9–13 May, and is most easily viewed from the southern hemisphere.

Astronomy 2024.indb 120

07/02/2023 22:41

Monthly Sky Notes and Articles 2024  121 2 Pallas is found far from the ecliptic in the constellation of Hercules. Opposition in ecliptic longitude occurs on 19 May, with opposition in right ascension taking place eight days later. For more information on the weird and wonderful orbit of 2 Pallas, see The Peregrinations of Pallas following this article. Jupiter is at conjunction with the Sun on 18 May and is unobservable. Saturn is twice occulted by the waning crescent Moon this month, on the third, and again on the last day of May. The first occultation, like the one last month, is visible from Antarctica but the second may be seen from around 06:30 UT in Chile, Argentina, Uruguay and the southernmost tip of Brazil. Shining at magnitude +1.2 in the constellation of Aquarius, Saturn is best viewed from the southern hemisphere where it rises before midnight. It remains a morning sky object mired in twilight for observers in northern temperate latitudes. Uranus is at conjunction with the Sun on 13 May, five days before Jupiter’s conjunction, and is lost to view this month. Neptune rises just ahead of the Sun as viewed from northern temperate latitudes but is well aloft in dark skies as seen from the southern hemisphere. Located in Pisces, the eighth-magnitude planet is occulted by the waning crescent Moon on the fourth day of the month. This event is visible from south eastern Australia and New Zealand, beginning around 17:15 UT (which will be early morning on 5 May at these locations).

Astronomy 2024.indb 121

07/02/2023 22:41

122  Yearbook of Astronomy 2024 59

ν 53

21

ρ

ζ

ε

ξ

30°

ι

Her

CrB ε

1 Jun

25°

δ 1 Jul

51 1 May

π β

ρ 1 Aug

20°

γ

54

5 κ

1 Apr

γ

15°

ω

1 Sept

29

10°

ι 43

1 Mar

Ser

47

5°

45

9

λ

16h 40m

16h 20m

16h 0m

The path of Pallas from 1 March to 1 September 2024. Stars are shown to magnitude 6.0. Pallas is never brighter than magnitude 9.0, and the red dots do not denote its brightness. (David Harper)

Astronomy 2024.indb 122

07/02/2023 22:41

Monthly Sky Notes and Articles 2024  123

The Peregrinations of Pallas David Harper

The asteroid 2 Pallas comes to opposition in 2024 on 19 May, and again on 27 May. How is such a thing possible? Well, it depends upon how you define opposition. The Astronomical Almanac says that opposition is the instant when a planet’s ecliptic longitude, seen from Earth, differs by exactly 180° from that of the Sun. For the major planets, which all move close to the ecliptic, this is the day when they rise at sunset, are highest at local midnight, and set at sunrise. Pallas, by contrast, has an orbit around the Sun which is tilted at almost 35° to the ecliptic. As a result, when it is 180° from the Sun in ecliptic longitude on 19 May, it is 47° north of the ecliptic seen from the Earth, on the border between Hercules and Corona Borealis. On this night, Pallas is due south – and hence highest in the sky – 44 minutes after local midnight, even though it is at opposition. Eight days later, on 27 May, it is opposite the Sun in Right Ascension, so it is highest at local midnight. On neither of these dates is it 180° from the Sun, nor is it even at its greatest elongation from the Sun. That happens on 17 May – two days before the “official” date of opposition – when Pallas is 133° from the Sun. It is also not at its closest to the Earth, or at its brightest, on any of the dates mentioned so far in this article. As well as being tilted, the orbit of Pallas is also markedly eccentric (e=0.23). In 2024, its closest approach to Earth is on 7 May, when it is 2.15 au (322 million kilometres) away. This is also the date when it is brightest, at magnitude 9.0. Between March and September, it performs a wide loop – 20° north/south and 12° east/west – through the southern region of Hercules, between Ophiuchus and Serpens Cauda, as shown in the accompanying chart. Here are the significant events for Pallas in 2024, in the order in which they happen:   7 May 17 May 19 May 27 May

Astronomy 2024.indb 123

Closest to Earth, and brightest. Greatest elongation from the Sun. Opposition in ecliptic longitude (“official” opposition). Opposition in Right Ascension (highest at midnight).

07/02/2023 22:41

124  Yearbook of Astronomy 2024 The extreme tilt and eccentricity of Pallas’s orbit means that oppositions can vary significantly in character. During January 2023 Pallas reached magnitude 7.7 among the stars of Canis Major in January and February, but it will not be visible to observers with binoculars or small telescopes in 2024, or at next year’s opposition in August, when it will be even fainter at magnitude 9.5. The opposition in October 2026 is almost as unfavourable, because Pallas shines no brighter than magnitude 8.3. The opposition of March 2028 offers much better prospects. At its closest approach to the Earth on 9 March, Pallas is just 1.29 au from our planet. It reaches magnitude 6.7 for a couple of days either side of opposition in ecliptic longitude on 14 March, when it is only one degree from the ecliptic and lies just west of Zavijava (β Virginis). It is magnitude 7.5 or brighter from mid-February to early April. It is no coincidence that Pallas was discovered by the German astronomer Heinrich Olbers at another March opposition, 226 years earlier in 1802. This was also a favourable apparition, when Pallas was 1.36 au from the Earth and easily visible through a small telescope at magnitude 7.2. It was also just 12° from the ecliptic, at the western end of Virgo, between Vindemiatrix (ε Virginis) and Denebola (β Leonis). Olbers was hunting for asteroids in a region of sky on either side of the ecliptic. He was lucky that Pallas was so near the ecliptic in 1802. In most years, Pallas comes to opposition more than 20° from the ecliptic, and sometimes in excess of

Pallas resembles a golf ball in these remarkable high-resolution images obtained by Pierre Vernazza and colleagues using adaptive optics on the Very Large Telescope. (ESO/M. Marsset et al./MISTRAL algorithm (ONERA/CNRS))

Astronomy 2024.indb 124

07/02/2023 22:41

Monthly Sky Notes and Articles 2024  125 50° away. He was also very fortunate that it was so bright – at many oppositions, it is no brighter than ninth magnitude. Between now and 2040, there are only two apparitions when Pallas is seventh magnitude or brighter: March 2028, as described above, and January–March 2037, when it moves rapidly northward along the line marking 9h of Right Ascension, from the northern edge of Pyxis and through Hydra, passing 10° west of Alphard (α Hydrae) in early March. It is magnitude 7.5 or brighter from mid-January to mid-March.

Acknowledgements This article has made use of the Minor Planet Ephemeris Service at the IAU Minor Planet Center minorplanetcenter.net and the NASA/JPL Horizons ephemeris service ssd.jpl.nasa.gov/horizons to calculate the positions and magnitudes of Pallas.

Astronomy 2024.indb 125

07/02/2023 22:41

Astronomy 2024.indb 126

07/02/2023 22:41

S

1 Dec

1 Jan

9 Jan (GE east)

52° North 35° South

ov

1N

1 Feb

SW

ct

1O

1 Mar

1 Nov

ep 1S

W

1 Oct

1 Dec

Evening Apparition of Venus June 2024 to March 2025

ug 1A

1 Sep

1 Mar

1 Feb

1 Jan 9 Jan (GE east)

ul 1 J ul 1J

1 Aug

NW

0°

10°

20°

30°

40°

50°

Monthly Sky Notes and Articles 2024  127

June

 1

Moon, Neptune

Lunar occultation of Neptune

72°

 2

12P/Pons-Brooks

Closest approach to Earth

45°

 4

Mercury, Jupiter

0.1° apart

12°

 4

Venus

Superior conjunction

 5

Moon

Lunar occultation of M45 (Pleiades)

 6

Moon

New

 9

Earth

Tau Herculid meteor shower (ZHR low)

 9

Moon

1.7° south of β Geminorum (Pollux)

35°

 9

Saturn

West quadrature

90°

14

Moon

First Quarter

14

Mercury

Superior conjunction

16

Moon

Lunar occultation of α Virginis (Spica)

17

Mercury, Venus

0.9° apart

20

Moon

Lunar occultation of α Scorpii (Antares)

20

Neptune

West quadrature

22

Moon

Full

25

Saturn

Minimum ring opening

105°

27

Moon, Saturn

Lunar occultation of Saturn

107°

28

Moon, Neptune

Lunar occultation of Neptune

28

Moon

Last Quarter

0° 15°

1° 117° 4° 159° 90°

97°

Dates are based on UT. Peak activity dates for meteor showers are estimates. The last column gives the approximate elongation from the Sun.

Mercury concludes an excellent morning apparition for those south of the equator. On 4 June, it is only 0.1° north of Jupiter; at magnitude −1.1, it gives Jupiter’s −2.0 close competition in brightness. Mercury passes through its ascending node on 9 June and four days later reaches perihelion for the second time this year. Mercury disappears from view a few days before superior conjunction on 14 June; its close approach to Venus just three days later takes place too near to the Sun to see. Mercury reaches its maximum northerly declination of the year on 20 June. The closest planet to the Sun reappears in the west after sunset shortly after conjunction to begin its best evening apparition for planet-watchers in the tropics and the southern hemisphere.

Astronomy 2024.indb 127

07/02/2023 22:41

128  Yearbook of Astronomy 2024 Venus arrives at superior conjunction on 4 June, exchanging dawn skies for evening twilight. It is visible in the west by the end of the month and is best viewed from equatorial and southern regions. Venus returns to the north side of the ecliptic plane on 6 June when it passes through its ascending node. The close encounter with Mercury on 17 June takes place just 4° away from the Sun, too close to our star to observe. Venus reaches its maximum declination north for 2024 on 20 June, a few hours after Mercury does the same. Earth has excellent viewing conditions for the little-understood Tau Herculid meteor shower which peaks in the first half of the month. See Meteor Showers in 2024 for more details. The solstice arrives on 20 June, heralding summer in the northern hemisphere and winter in the south. The nearest apogee of the year takes place on 14 June, followed on 27 June by the most distant perigee of 2024. As with last month, the lunar occultation of the Pleiades takes place too close to the Sun to be observed, occurring the day before New Moon. The waxing crescent Moon moves to within 1.7° of Pollux on 9 June. The Moon has been getting closer to Spica month by month and on 16 June, finally occults the brightest star in Virgo. This occultation series will continue into November next year. The occultation of Antares by the waxing gibbous Moon occurs on 20 June. 12P/Pons-Brooks is at its nearest to Earth at the beginning of the month but it never approaches closer than 1.5 au. It is fading from view for southern hemisphere observers, passing through the constellations of Lepus, Canis Major, and Puppis, and is found in both the evening and morning skies. See Comets in 2024 for more information. Mars moves from Pisces to Aries on 10 June. Shining at magnitude +1.0, it is starting to look vaguely gibbous in the eyepiece of a telescope. It remains a resident of the morning sky, rising just after midnight, and is most easily observed from the southern hemisphere. Jupiter is found in the constellation of Taurus as a bright magnitude −2.0 object located somewhat south of the Pleiades star cluster and hurtling toward the ‘head’ of the ‘bull’. Its close encounter with Mercury on the fourth day of the month may be too near to the Sun to observe. Jupiter is a morning sky object but rises not much before the Sun.

Astronomy 2024.indb 128

07/02/2023 22:41

Monthly Sky Notes and Articles 2024  129 Saturn reaches west quadrature on 9 June in Aquarius. This, combined with a minimum ring opening of 1.9° on 25 June, provides some interesting opportunities for astrophotographers. The nearly edge-on rings reduces the overall brightness of the planet, making the satellites easier to see, and quadrature leads to some intriguing shadow effects. Saturn reaches its maximum declination north for the year on 24 June and is occulted by the waning gibbous Moon three days later. This event is visible from around 13:00 UT in eastern Australia, northern New Zealand, New Caledonia, Vanuatu, Fiji and other nearby islands. (This event will take place very early in the morning on 28 June for some of these locations.) Retrograde motion begins at the end of the month. Best seen from southern vantage points, the ringed planet rises before midnight for everyone by the end of June. Uranus is in Taurus, a constellation which is visible in the morning sky at this time of year. Now past solar conjunction, the sixth-magnitude planet is best seen from the southern hemisphere where it rises before dawn. Uranus appears during morning twilight when viewed from northern temperate latitudes. Neptune starts the month with a lunar occultation. The waning crescent Moon, just past Last Quarter, glides in front of the faint blue ice giant on 1 June in an event visible from southern Africa and Madagascar, and beginning around 01:00 UT. Neptune reaches quadrature on 20 June and then undergoes yet another lunar occultation on 28 June. This second event begins at approximately 06:30 UT and is visible from Costa Rica, Panama and northern South America. The planet also reaches its maximum declination north for the year on this date. Neptune is located in Pisces and is primarily a morning sky object although it rises before midnight for southern hemisphere observers.

Astronomy 2024.indb 129

07/02/2023 22:41

130  Yearbook of Astronomy 2024

Where Are the Sunspots? Carrington’s Method John McCue

You know precisely where your house is, dear reader, and its position on the earth’s surface, given as latitude and longitude, is certainly important to observers of the universe. One such observer was the English amateur astronomer Richard Christopher Carrington, who was born on 26 May 1826 at Chelsea, Middlesex into a wealthy brewing family. He established an impressive observatory at Redhill, Surrey, with a commissioned 4½-inch refractor, a transit circle and regulator clock.1 With this equipment, he won the Royal Astronomical Society’s Gold Medal for his catalogue of 3,735 circumpolar stars down to tenth magnitude. He then turned his attention to the Sun, and developed a simple method for working out the latitude and longitude of a sunspot on the solar surface. The appearance of sunspots is symptomatic of the comprehensive activity level of the Sun. We regard the Sun as benign, reliable and steadily giving us life support in terms of light and warmth. Yet, although we bask in its glow, in reality it is a cauldron of dangerous turbulence. Prominences – huge outward surges of hydrogen gas – arch thousands of kilometres into space from the solar surface; and the solar wind – gusts of charged particles – reaches out to the planets. Flares – catastrophic explosions on the surface (first observed by Carrington) – add storms to the solar wind, which in turn give rise to beautiful auroral displays in our atmosphere, but which can also create havoc with electrical systems. Hydrogen fusion is the source of solar energy, and is so prolific that a postage stamp-sized piece of the solar surface would shine as bright as five hundred 60 watt bulbs.2 A by-product of this internal nuclear reaction is a ferocious and eternal blast of neutrinos, which escape the Sun. Having zero interaction, they reach the Earth, with trillions of them passing through our body every second without us even noticing. The numbers of sunspots are a visible sign of this changing story. Counting these spots, and noting their latitude and longitude positions on the sun, is crucial to understanding how the Sun works. Carrington’s method of doing this lends itself to direct visual observation of the Sun, as well as to projection of the solar image onto a screen behind the eyepiece. 1.  The Victorian Amateur Astronomer, Allan Chapman, Wiley, 1998. 2. The Cosmic Mind-boggling Book, Neil McAleer, Hodder & Stoughton, 1982.

Astronomy 2024.indb 130

07/02/2023 22:41

Monthly Sky Notes and Articles 2024  131 The author follows – and recommends – the second method, on the grounds of safety. Optical views of the Sun will cause permanent blindness, though modern fullaperture solar filters are available and can be safely used by experienced observers. Using a solar projection box, the author used Carrington’s method from August 1997 until December 1998. Perpendicular cross-lines are drawn on the projection screen, and a stop watch is used to time, and note, the passage of the preceding limb of the Sun over lines A and B; the sunspot over lines A and B; and finally the following limb over lines A and B (see Figure 1). The only requirement is for the cross-lines to be roughly at 45 degrees to the direction of the Sun’s drift, and the line A to be the north-eastern arm. These timings can then be used to calculate the latitude and longitude of the chosen sunspot on the solar surface.3 The author’s calculated positions have been plotted on the horizontal axes of Figures 2 and 3, and then compared with the positions reported by the U.S. Space Weather Prediction Center (SWPC), located in Boulder, Colorado and administered by the National Oceanic and Atmospheric Administration. These are plotted on the vertical axes of Figures 2 and 3. With perfect agreement, the points would lie on the drawn sloping lines. There are more points than sunspots since the author measured some again on different days. Modern amateur astronomers can certainly use the aforementioned solar filters and digital cameras to record a solar image – then using analytical software to determine the sunspots’ positions – although Carrington’s method does not require these photographic and digital skills, and is much more fun! The Sun goes through an 11-year cycle of activity, with the numbers of sunspots correspondingly rising and falling. Every year we see more evidence that large numbers of them give rise to better weather here on Earth. A notable scarcity of sunspots – known as the Maunder Minimum – occurred between 1645 Figure 1: The projection screen as seen when and 1715, during which period the using Carrington’s timing method. ( John McCue) 3. ‘Carrington’s method of determining sunspot positions’, E.T.H. Teague, Journal of the British Astronomical Association, 106, 2, 82–85 (1996) adsabs.harvard.edu/full/ 1996JBAA..106...82T

Astronomy 2024.indb 131

07/02/2023 22:41

132  Yearbook of Astronomy 2024

Figure 2: Comparison of the calculated sunspot latitudes with the reported figures from the Space Weather Prediction Center. (SWPC/WDC-SILSO/Royal Observatory of Belgium)

global average temperature fell, causing such severe winters that the River Thames froze many times. At the start of any cycle, taken at minimum activity, Carrington discovered that sunspots first appeared at higher latitudes (in both hemispheres), any newer spots then emerging at lower latitudes as the cycle progresses. They are then seen close to (but never at) the solar equator at the end of the cycle – the next minimum. When these latitudes are time-plotted, the pattern formed is known as a butterfly diagram, an appropriate name based on its appearance. At the end of 1997, the Sun was at a minimum period of activity (see Figure 4) and about to enter solar cycle number 23. The author’s measurements were taken when this new flow was just getting under way.

Astronomy 2024.indb 132

07/02/2023 22:41

Monthly Sky Notes and Articles 2024  133

Figure 3: Comparison of the calculated sunspot longitudes with the reported figures from the Space Weather Prediction Center. (SWPC/WDC-SILSO/Royal Observatory of Belgium)

It will not surprise the reader to learn that Carrington – by noting the longitude drift of sunspots at certain latitudes while they survived – deduced that the Sun does not rotate as a solid body, even though it looks like one. The spots near the equator reveal that the Sun rotates on its axis every 25 days in that zone, but it takes several days longer nearer the poles. This asynchronous rotation causes the internal magnetic field lines of the Sun to bend and twist, eventually being forced to break out above the photosphere in places. These tangled field lines prevent energy from reaching the surface in these areas, causing the surface to appear dark in comparison to the surrounding and brighter photosphere, resulting in the appearance of a sunspot. Large sunspot groups can be very complex, as shown by the Figure 5 drawings, made on one of the author’s observation days.

Astronomy 2024.indb 133

07/02/2023 22:41

134  Yearbook of Astronomy 2024 Figure 4: The transition between solar cycle 22 and solar cycle 23, as depicted by the Space Weather Prediction Center. (SWPC/ WDC-SILSO/Royal Observatory of Belgium)

Figure 5: The Space Weather Prediction Center’s observer drawing of the solar disc on 9 September 1997, one of the most spectacular days of the author’s run of sunspot observations. (Drawing by kind permission of the observers at the 150-Foot Solar Tower at Mount Wilson Observatory)

Richard Christopher Carrington died at Churt, Surrey on 27 November 1875, aged just 49, and is remembered as an immensely practical and meticulous astronomer.4 4. The Hutchinson Dictionary of Scientific Biography, Roy Porter (Editor) and Marilyn Bailey Ogilvie, Helicon, 2000.

Astronomy 2024.indb 134

07/02/2023 22:41

Monthly Sky Notes and Articles 2024  135

July

 2

Moon

Lunar occultation of M45 (Pleiades)

 5

Moon

New

 6

1 Ceres

Opposition

42° 173°

 6

Moon

1.7° south of β Geminorum (Pollux)

10°

 6

Mercury

0.1° south of M44 (Beehive/Praesepe)

22°

13

Moon

First Quarter

14

Moon

Lunar occultation of α Virginis (Spica)

91°

15

Mars, Uranus

0.5° apart

57°

17

Moon

Lunar occultation of α Scorpii (Antares)

21

Moon

Full

134°

22

Mercury

Greatest elongation east

23

134340 Pluto

Opposition

177°

27°

24

Moon, Saturn

Lunar occultation of Saturn

133°

25

Mercury

1.7° south of α Leonis (Regulus)

25

Moon, Neptune

Lunar occultation of Neptune

28

Moon

Last Quarter

28/29

Earth

Delta Aquariid meteor shower (ZHR 20)

29

Moon

Lunar occultation of M45 (Pleiades)

27° 123°

67°

Dates are based on UT. Peak activity dates for meteor showers are estimates. The last column gives the approximate elongation from the Sun.

Mercury is visible in the northwest after sunset, presenting the best evening apparition of the year for observers in the southern hemisphere and the tropics. It rapidly climbs high into the darkening evening sky, reaching greatest elongation east (26.9°, the largest of 2024) on 22 July, before heading back toward the Sun. It is brightest at the beginning of the month, magnitude −0.6, and dims to first magnitude before the start of August. It is 0.1° south of the open cluster called Praesepe or the Beehive in the constellation of Cancer on 6 July. Mercury passes through its descending node on 17 July and appears less than 2° away from firstmagnitude Regulus on 25 July. Aphelion, the third this year, takes place two days later.

Astronomy 2024.indb 135

07/02/2023 22:41

136  Yearbook of Astronomy 2024

Evening Apparition of Mercury 14 June to 19 August 52° North 35° South

30° 22 Jul (GE east)

1 Aug

11 Aug 22 Jul (GE east) 1 Aug

W

ul

J 11

11 Jul

l

u 1J

20°

1 Jul

10°

21 Jun 21 Jun

NW

0°

Venus reaches perihelion on 10 July but with a nearly circular orbit, Venus’s distance from the Sun does not vary by much. Εσπερος (Hesperus), the evening star, shines at a steady magnitude −3.9 all month but remains quite close to the western horizon for stargazers in northern temperate latitudes. The bright planet gains altitude much more rapidly as viewed from tropical latitudes and the southern hemisphere. Earth reaches aphelion on 5 July. At 1.017 au, this is the most distant Earth is from the Sun this year. Near the end of the month, Earth is treated to a display of Delta Aquariid meteors. See Meteor Showers in 2024 for more information. The waning crescent Moon occults the Pleiades star cluster twice this month, on 2 July and again on 29 July. The Moon’s close passage by Pollux occurs too near to New Moon to be visible. However, the waxing crescent Moon’s occultation of Spica on 14 July and of Antares three days later are easily observable. Mars departs Aries for Taurus on 11 July and passes 0.5° north of Uranus four days later. Mars, at magnitude +1.0, is far brighter than Uranus at +5.8. Hopefully the waxing gibbous Moon will not provide too much natural light pollution for this event. By the end of the month, Mars is rising shortly after midnight.

Astronomy 2024.indb 136

07/02/2023 22:41

Monthly Sky Notes and Articles 2024  137 1 Ceres reaches opposition, first in ecliptic longitude and then in right ascension, on 6 July, with its maximum elongation from the Sun (173°) taking place just before both events. The dwarf planet shines at approximately magnitude +7.5 in the constellation of Sagittarius. Jupiter spends July traversing the region just north of the V-shaped asterism marking the head of Taurus, the Bull, coming no closer than 4.7° to α Tauri (Aldebaran) early in the month. Jupiter rises in the early morning hours and is best observed from the dark winter skies of the southern hemisphere. Saturn is again occulted by the Moon this month. On 24 July, beginning at approximately 21:00 UT, residents of China, eastern Mongolia, North and South Korea, Japan and south eastern Russia may see the waning gibbous Moon move in front of Saturn. Saturn is a first-magnitude object in the constellation of Aquarius and rises during early to mid-evening hours. Uranus and Mars get together on 15 July when the two planets are only half a degree apart in the morning sky. Bright Mars outshines Uranus by nearly five magnitudes. Located in Taurus, Uranus rises around midnight by the end of the month. Neptune begins retrograde motion in the first few days of July. On 25 July, the eighth-magnitude world is occulted by the waning gibbous Moon. Beginning around 12:30 UT, this occultation event is visible from Melanesia, including Papua New Guinea and the Solomon Islands. Located in Pisces, Neptune rises midevening for southern hemisphere observers and appears later in the evening for those seeking the faint planet from northern temperate latitudes. 134340 Pluto is a fifteenth-magnitude object in the constellation of Capricornus. Both oppositions – ecliptic longitude and right ascension – occur on 23 July. Like 1 Ceres, 134340 Pluto was once categorised as a planet but is now known as a ‘dwarf planet’.

Astronomy 2024.indb 137

07/02/2023 22:41

138  Yearbook of Astronomy 2024

The Great Comet Crash of 1994 Neil Norman

This year marks the 30th anniversary of the impact of Comet Shoemaker-Levy 9 into the atmosphere of Jupiter. This was a pinnacle point in astronomy as it was the first time mankind had witnessed a collision between two bodies within the Solar system. The highly successful comet discovery team of Carolyn and Gene Shoemaker and David Levy discovered the comet on two photographic plates taken in March 1993 at the California Institute of Technology’s Palomar Observatory. Astronomers calculated an orbit and quickly realised that the comet was not orbiting the Sun – as every other comet until then had been – but was in fact orbiting the planet Jupiter instead. The loosely-bound orbit was around two years long and it appeared that the comet had been locked in this orbit for several decades prior to discovery. The area of space within which an object is said to orbit Jupiter is known Jupiter’s Hill

Discovery images of Comet Shoemaker-Levy 9, taken on the morning of 24 March 1993 with the 18-inch (0.46 metre) Schmidt telescope at Palomar Observatory, California. The images were taken around two hours apart and clearly show the movement of the comet as seen against the background stars during that period. (Palomar Observatory/David H. Levy)

Astronomy 2024.indb 138

07/02/2023 22:41

Monthly Sky Notes and Articles 2024  139 sphere. When the comet passed Jupiter during the late-1960s or early-1970s it was near aphelion, placing it slightly inside the Hill sphere of Jupiter, resulting in the planet’s gravity pulling the comet closer towards it. Between 16 and 22 July 1994 Jupiter’s atmosphere was bombarded by 21 fragments of the comet. The six-day spectacle left huge black scars on the face of the planet which were detectable for months afterwards and widely observed from Earth by people equipped with only moderately-sized telescopes. Several of these features were even more noticeable than Jupiter’s famous Great Red Spot – a huge hurricane system some three times the diameter of Earth. NASA used its fleet of telescopes and spacecraft to observe this unique event, one of these being the Galileo probe, which was on its way to study Jupiter. Although still around 18 months from arrival Galileo was able to gather images of the impact sites in the planet’s southern hemisphere. The NASA Deep Space Network antennas looked for disturbances in the radio emissions from the planet’s radiation belt. The Hubble Space Telescope was also ideally situated to document this historic event, as were the Ulysses and Voyager 2 space probes. Another close pre-discovery pass of Jupiter occurred in early-July 1992, when the comet passed within only around 40,000 kilometres from the cloud tops of Jupiter. This was inside the planet’s Roche limit and the resulting tidal forces helped to pull the comet apart. The fragments then started to draw away from each other, giving the effect of a ‘string of pearls’, as clearly shown on the accompanying image. When the 21 fragments began impacting Jupiter at 20:13 UT on 16 July, at a speed of 60km/s, fireballs with temperatures of 24,000 degrees Celsius were recorded and a plume of over 3,000 kilometres in length was recorded from fragment A alone. The largest impact occurred on 18 July at 07:33 UT when fragment G impacted the

This Hubble Space Telescope (HST) image (actually a composite of six individual images taken with the HST Wide Field Planetary Camera 2) shows the 21 fragments of Comet ShoemakerLevy 9, resembling a string of pearls due to the tidal forces of Jupiter pulling the main nucleus apart. (NASA/ESA/H.Weaver/E.Smith (STScI))

Astronomy 2024.indb 139

07/02/2023 22:41

140  Yearbook of Astronomy 2024 Jovian atmosphere, creating a dark scar of around 12,000 kilometres in diameter (almost equal to the diameter of the Earth) and with an estimated energy release of six million megatons of TNT – 600 times the entire world’s arsenal. Two other fragments hit 12 hours apart on 19 July, generating scars almost equal in size to that formed from the impact of fragment G.

The Legacy of Shoemaker-Levy 9 This historical event also created a desire for mankind to hunt for objects whose orbits bring them close to the Earth and may therefore potentially impact our planet. Indeed, the multiple impacts of Shoemaker-Levy 9 on Jupiter would have created a mass extinction event on Earth. NASA was subsequently authorised to hunt for these objects, which are now known as NEOs (Near Earth Objects). The NASA department formed to search for and catalogue these threats of asteroid and comet impacts currently monitors thousands of such objects, with discoveries being made on a monthly basis. The impact of Comet Shoemaker-Levy 9 on Jupiter in 1994 certainly revealed to the people of planet Earth just how fragile we are as a species – the Solar System seems to enjoy playing the game of cosmic pinball.

Astronomy 2024.indb 140

07/02/2023 22:41

Monthly Sky Notes and Articles 2024  141

August

 1

Moon

1.8° south of β Geminorum (Pollux)

 4

Moon

New

 4

Venus

1.0° north of α Leonis (Regulus)

17°

 5

Moon, Venus

1.7° apart

17°

10

Moon

Lunar occultation of α Virginis (Spica)

65°

12

Moon

First Quarter

12/13

Earth

Perseid meteor shower (ZHR 80)

14

Moon

Lunar occultation of α Scorpii (Antares)

14

Mars, Jupiter

0.3° apart

19

Mercury

Inferior conjunction

19

Uranus

West quadrature

19

Moon

Full

21

Moon, Saturn

Lunar occultation of Saturn

161°

21

Moon, Neptune

Lunar occultation of Neptune

150°

26

Moon

Lunar occultation of M45 (Pleiades)

26

Moon

Last Quarter

30

Moon

1.7° south of β Geminorum (Pollux)

30°

107° 66° 5° 90°

93° 44°

Dates are based on UT. Peak activity dates for meteor showers are estimates. The last column gives the approximate elongation from the Sun.

Mercury is visible in the evening sky for the first part of the month but is descending toward the horizon. It enters into retrograde motion early in the month and passes by Venus on its way to inferior conjunction on 19 August. Direct motion resumes on 28 August after Mercury returns to the morning sky. This dawn apparition, which continues into late September, is the best one for observers in northern temperate latitudes. Mercury is first magnitude at the beginning of month but dims to sixth as it undergoes conjunction. Its brightness recovers to +0.6 by the end of August. Venus appears a degree north of Regulus on 4 August. However, the sky will still be light and first-magnitude Regulus may not be visible in the twilight. The very young crescent Moon is 1.7° north of Venus on the following day. Mercury makes a distant pass on 8 August when the two planets are 5.7° apart but again, this occurs during twilight and, for observers in northern temperate latitudes, very near to

Astronomy 2024.indb 141

07/02/2023 22:41

142  Yearbook of Astronomy 2024 the horizon. The evening star gains little altitude over the month for northern observers but planet-watchers in the southern hemisphere have much better views as Venus climbs rapidly. Venus remains at magnitude −3.9 throughout the month. Earth welcomes the annual display of Perseid meteors this month, with the light of the First Quarter Moon not too much of a hindrance. The article Meteor Showers in 2024 has more information about viewing conditions. The lunar occultations of Spica on 10 August and Antares on 14 August flank the peak of the Perseids. The open star cluster known as the Pleiades vanishes behind the Last Quarter Moon on 26 August. And the waning crescent Moon passes less than 2° south of Pollux twice, on the first and penultimate days of August. Interestingly, the Full Moon of August is the third of four this season (summer in the north, winter in the south); this is the original definition of a ‘Blue Moon’ in farmers’ almanacs. Mars chases down Jupiter in the constellation of Taurus and overtakes the brighter planet on 14 August. The red planet appears just 0.3° south of the gas giant. Mars is finally positioned to be better seen from the northern hemisphere than the south, with the first-magnitude planet rising well before midnight by the end of the month. Jupiter and Mars are in conjunction on 14 August, with Jupiter much the brighter object. The gas giant continues its sojourn through Taurus and rises before midnight by the end of August. Saturn shines at magnitude +0.8 as it retrogrades through the constellation of Aquarius. It rises in the early evening hours and is readily visible later in the night. The ringed planet is occulted by the waning gibbous Moon on 21 August. This event is visible from about 01:00 UT from Central America, northern South America, north western Africa and western Europe. Uranus is at west quadrature on 19 August. This position places the planet 90° away from the Sun as seen from Earth. Now rising before midnight in the constellation of Taurus, Uranus is best viewed when the Moon is absent. Optical aids are helpful in finding this sixth-magnitude planet. Neptune is in retrograde in the constellation of Pisces. It rises in the early evening hours but at only eighth magnitude, requires a telescope to spot it. Beginning at approximately 20:00 UT on 21 August, the blue ice giant is occulted by the waning gibbous Moon as seen from northern Africa, the eastern Mediterranean Sea, the Middle East, southern and eastern Europe, central Asia and Russia.

Astronomy 2024.indb 142

07/02/2023 22:41

Monthly Sky Notes and Articles 2024  143

A History of the Smith-Clarke Reflector Gary Yule

Salford Astronomical Society was founded in 1965 and the observatory at Chaseley Field in Salford has stood since 1971. However, its main optical telescope – the Smith-Clarke Reflector – has a much longer history, having started life in 1921 as the design of the automotive engineer and designer Captain George Thomas SmithClarke. Born at Lower Park, Bewdley, Worcestershire on 23 December 1884, he later became a resident of Coventry where, in 1922, he joined the staff of the Alvis Car and Engineering Company as an engineer. The company turned to military manufacture during World War II and during this period, Smith-Clarke was made responsible George Thomas Smith-Clarke. for several factories, and became inspector of ( John McCue) all the aero engines produced in Coventry, Birmingham, Derby and Dumfries. Smith-Clarke also had a great interest in astronomy, and owned several telescopes in his youth. He decided to use his engineering skills to construct a telescope of his own. Obviously this could not be of small proportions, so he set about designing and building the 47-centimetre diameter Newtonian reflector housed as Chaseley field today. The telescope was of a truss tube design, made from aluminium and steel hexagonal rings, with a large solid brass primary cell housing the 47-centimetre mirror. The mirror was made from two pieces of glass laminated together, and the story goes that it was of Grubb Parsons design. However, according to research carried out by Adrian Padfield – who wrote a biography championing the achievements of Smith-Clarke as an unsung hero of the engineering age of Coventry – the mirror was, according to family tradition, ground by Smith-Clarke himself in his workshop.

Astronomy 2024.indb 143

07/02/2023 22:41

144  Yearbook of Astronomy 2024 The telescope was mounted on a large, cast steel equatorial fork mounting, which must weigh at least 800 kilograms, and was driven in right ascension by a large brass worm wheel acquired from David Brown Engineering. The overall design of the telescope aroused such interest in astronomy circles that SmithClarke was asked for advice regarding the proposed design of the 100-inch Isaac Newton Telescope to be housed at Herstmonceux. Smith-Clarke became known to Bernard Lovell, the founder of Jodrell Bank Observatory, and in around 1954 he decided to donate the 47-centimetre Newtonian – along with a spectrohelioscope of his own design – to Manchester University. It was housed in a corner of the observatory site in small observatory with 15-foot diameter rotating dome, made of steel frame and aluminium sheeting. This was around the time that Zdeněk Kopal became Professor of Astronomy at Manchester University, the 47-centimetre Newtonian falling under his care. It was used for many years for variable and binary star research and as a training telescope for students. Unfortunately, with the advances of radio astronomy at Jodrell Bank, the telescope fell redundant and was not used for several years. It was decided that it should be given back to the University to use, albeit not at the Jodrell Bank site. However, with them already having the Godlee Observatory housed at the Sackville Street University building, they had no use for it.

Many hands make light work, the Smith-Clarke Reflector being restored by members of Salford Astronomical Society in the basement of the Chaseley Field Centre circa 1970. (Gary Yule)

Astronomy 2024.indb 144

07/02/2023 22:41

Monthly Sky Notes and Articles 2024  145 This brings me on to Salford Astronomical Society’s involvement. The society roots go back to 1962 when – in a pub on Irlam o’th Height, a suburb of Salford – local astronomy enthusiast Arthur Taylor established a group of like-minded people. Interest grew, and the newly-formed group started to hold astronomy classes at the local Chaseley Field Centre. With several of its members being linked to either Salford or Manchester Universities, the story of a large reflecting telescope perhaps being available was too good an opportunity to turn down. They applied for a grant from the Local Education Authority, and were awarded £10,000 to build an observatory at Chaseley Field where the telescope would be available for public use. Terms were agreed with Manchester University and the telescope was transported, along with its dome, from Jodrell Bank to the Chaseley site, where a 7 metre × 7 metre building had been constructed to house it. The building contains an 8-foot concrete pier, which reaches down to the bedrock below, making it completely separate to the main building to prevent it moving with subsidence. The 47-centimetre Newtonian proudly stands atop the pier and under the 15-foot dome, the doors to the observatory being opened to the public in 1971 by Patrick Moore. The Smith-Clarke Reflector has been in the hands of Salford Astronomical Society for over half a century now. It has been used for research projects by Salford University and by society members, as well as being used as a public outreach facility by Salford residents and astronomy enthusiasts everywhere. In 1979 the telescope underwent a few upgrades, including a full strip down and repaints. A slow-motion remote control was also added to the drive to help fine tune the positioning of targets within the eyepiece, all this work being carried out by members of the society. I became a member of the Salford Astronomical Society in 2015, and was obviously very eager to observe with the telescope. My first detailed views of the lunar surface and of Jupiter and Saturn were outstanding and something I will never forget. Hence began my love affair with this old but magnificent telescope. With a passion for using the telescope, and wanting to look after and maintain it, I was quickly moved through the ranks at the observatory, and eventually became Director of Observatory and Curator of Instruments. In 2018 a decision was made to recoat the primary and secondary mirrors, which were subsequently shipped off to Orion Optics UK where they were given their HILUX ultra-high contrast coatings. This brought a far better resolution to celestial targets, as well as a desire that the telescope should also be used for astrophotography. We managed to gain funding via Salford City Council to upgrade the telescope yet again, this time to a fully go-to and remote access platform with a new dual-

Astronomy 2024.indb 145

07/02/2023 22:41

146  Yearbook of Astronomy 2024 Looking a lot more modern, the SmithClarke Reflector today at the Chaseley Field Observatory with full goto upgrade, housed under the recently-restored 15-foot dome. (Gary Yule)

speed focuser, declination drive, upgraded stepper motors and ST-5 units. In addition we have an intelligent handset, designed by AWR Technology and which is connected to our computer and can be controlled via planetarium software. Supplied by Beacon Hill Telescopes, the declination worm wheel now gives more time to observe targets on our public observing sessions. The Smith-Clarke Reflector has seen a lot of use over its long lifetime. Having being made by an amateur astronomer – and initially housed in his own back garden – it has been used to observe thousands of targets ranging from objects within our own Solar System out to the reaches of deep space. It has also provided help to students with their doctorates, and revealed the wonders of the universe to the public. With the dedication of the Salford Astronomical Society, this fine instrument will continue in its mission for many a year to come.

Astronomy 2024.indb 146

07/02/2023 22:41

Monthly Sky Notes and Articles 2024  147

September

 3

Moon

New

 5

Mercury

Greatest elongation west

18°

 5

Moon, Venus

Lunar occultation of Venus

26°

 6

Moon

Lunar occultation of α Virginis (Spica)

39°

 7

Mars

0.9° south of M35

74°

 8

Saturn

Opposition

 9

Mercury

0.4° north of α Leonis (Regulus)

17°

10

Moon

Lunar occultation of α Scorpii (Antares)

81°

11

Moon

First Quarter

12

Jupiter

West quadrature

17

Moon, Saturn

Lunar occultation of Saturn

18

Moon

Full Moon – Partial lunar eclipse

18

Moon

Lunar occultation of Neptune

177°

20

Neptune

Opposition

179°

22

Moon

Lunar occultation of M45 (Pleiades)

120°

24

Moon

Last Quarter

26

Moon

1.6° south of β Geminorum (Pollux)

30

Mercury

Superior conjunction

178°

90° 170°

70° 1°

Dates are based on UT. The last column gives the approximate elongation from the Sun.

Mercury is still gaining altitude in the east during this morning apparition, the best one for astronomers in northern temperate latitudes. Mercury is found north of the ecliptic from 4 September and reaches greatest elongation east – the smallest of the year at only 18.1° – the following day. After this the tiny planet heads back toward the horizon. Mercury passes 0.4° north of first-magnitude Regulus on 9 September, reaching perihelion on the same day. The nearest planet to the Sun vanishes late in the month, some days before superior conjunction on 30 September. Although Mercury steadily brightens throughout the month, look for it early in September when it is at its highest in the sky.

Astronomy 2024.indb 147

07/02/2023 22:41

148  Yearbook of Astronomy 2024

Morning Apparition of Mercury 19 August to 30 September 52° North 35° South

30°

5 Sep

(GE we

st) 1 Sep

20° 11 Sep

5 Sep (GE west) 1 Sep g 21 Sep Au 11 Sep 21 21 Au 21 Sep g

NE

E

10° 0°

Venus is occulted by the waxing crescent Moon on the fifth day of the month but this event is only visible from the Antarctic. The evening star is magnitude −3.9 and still close to the horizon for those seeking it from northern temperate latitudes, but it is high above the western horizon as seen from the tropics and the southern hemisphere. Venus reaches its descending node on 25 September and will remain below the ecliptic through the rest of the year. Earth passes through an equinox on 22 September. On this day astronomical spring returns to the southern hemisphere and autumn commences in the north. The waxing crescent Moon occults Spica on 6 September and Antares four days later on the tenth. The Pleiades open star cluster is blotted out by the waning gibbous Moon on 22 September and the waning crescent Moon comes to within 1.6° of Pollux four days after that. The Full Moon on 18 September is a particularly interesting one: it undergoes a partial lunar eclipse, it is at perigee, and it is also the famous ‘Harvest Moon’ of the northern hemisphere. For more information on eclipses, see Eclipses in 2024. Mars moves from Taurus to Gemini on 5 September and passes through its ascending node the following day. On 7 September, the red planet is less than a degree south of M35, a sprawling open star cluster that should not be confused with the nearby dense open cluster NGC 2158. Mars rises in late evening as viewed

Astronomy 2024.indb 148

07/02/2023 22:41

Monthly Sky Notes and Articles 2024  149 from northern temperate latitudes but only around midnight for observers farther south. It brightens steadily throughout the month, beginning September at magnitude +0.7 and ending at +0.5. Jupiter is at west quadrature on 12 September, sitting 90° away from the Sun. This is an excellent time to observe interplay of shadows of the Galilean satellites upon Jupiter and vice versa; quadrature is when the shadows are cast most obviously a little to the side. For all of the bright stars in Taurus and nearby constellations, Jupiter outshines them all at magnitude −2.4. Look for the largest planet in the solar system very late in the evening as it now rises before midnight. Saturn reaches opposition on 8 September, shining at magnitude +0.7. When viewed through a telescope, the rings are tilted at an angle of 3.7°, slightly up from the minimal tilt in June. Located in Aquarius, Saturn is visible all night. The nearly full Moon occults Saturn on 17 September in an event beginning around 08:15 UT and visible from north eastern Australia, Melanesia, Hawaii and western North America. Uranus reaches a stationary point in both ecliptic longitude and right ascension on the first day of the month, and begins retrograde motion. The planet will remain in retrograde for the remainder of the year. This coincides with the planet’s maximum declination north for the year. The green ice giant rises in mid- to late evening in Taurus, depending on the observer’s latitude, and remains above the horizon through to dawn. Neptune is occulted by the Full Moon on 18 September, shortly after the partial lunar eclipse ends. This event is visible from Hawaii and most of North America from around 05:15 UT. Neptune attains opposition two days later on 20 September. It is at its brightest at magnitude +7.8 but this is still well below the naked-eye limit, even in dark skies. The telescope reveals a tiny blue disk just 2.53 arc-seconds across. Neptune is in Pisces, rising at sunset and setting at sunrise.

Astronomy 2024.indb 149

07/02/2023 22:41

150  Yearbook of Astronomy 2024

The Strange Spin of Venus John McCue

Nearly five billion years ago, the Sun was without planets but was about to acquire them, a gift from an approaching cool, red proto-star, according to a fairly recent proposal. A similar idea was put forward early in the twentieth century by Sir James Jeans, who envisaged the solar system forming as a result of an encounter between the sun and a mature passing star, the former pulling the planet-making material from the latter. Eventually, there were objections to this notion, principally that the material pulled gravitationally from the wandering star would be too hot to collapse and form cool planets. Nowadays most astronomers de-facto agree broadly with an alternative idea – Laplace’s nebular hypothesis. Our planets formed from the left-over gas and dust of the nebula that created the Sun. This by-product formed a spinning disc of gas and dust, which gradually cooled and accreted into the eight planets we know and love, like rolling a snowball into a big snowman! Our Sun and planets were thus formed simultaneously, a monistic event. Some think this concept has a lingering flaw though – there has not been enough time since the creation of the sun to form the gas giants such as Jupiter. Jeans’ idea was hence re-visited and given a spring-clean in the 1970s by John Dormand (Teesside University) and Michael Woolfson (York University).1 They proposed, in this Capture Theory, that the passing star was instead this cool, red protostar. As it passed by, it gave up fragments of itself under the pull of the Sun’s gravity (see figure 1). The planets were thus formed later than the Sun, an example of a dualistic theory. (An aside – over 5,000 exoplanets have now been found and astronomers are broad-minded enough to concede that planet formation may well take place in different ways under different circumstances). Circling the Sun in wild, highly eccentric orbits, these globules became even cooler, condensing into our recognisable planets. Jupiter, Saturn, Uranus and Neptune were there, but the inner planets, including Venus, of course, were 1. Dormand, J.R. and Woolfson, M.M., ‘The Capture Theory and Planetary Condensation’, Monthly Notices of the Royal Astronomical Society, 151, 3, 307–331 (1971) academic.oup.com/mnras/article/151/3/307/2604521

Astronomy 2024.indb 150

07/02/2023 22:41

Monthly Sky Notes and Articles 2024  151

Figure 1: The Capture Theory of the origin of the solar system, as the sun captures cool planetmaking material (not to scale). ( John McCue)

not. To be truthful, the terrestrial planets played only a minor part in this story. The Capture Theory’s computer simulation predicts the formation of two other planets, A and B, both with masses less than Neptune, but much greater than the Earth’s, and both with satellites. In their highly eccentric orbits, collisions between all the early planets would be inevitable, and this indeed was the fate of A and B. As the debris of this destruction cleared, planet A was ejected from the solar system, while planet B broke into two main parts (see figure 2), which became Venus and Earth.2 Mercury formed from a fragment of this doomed planet B. (Another aside – the shrapnel from this catastrophic impact peppered the two satellites of A, making each of them a body of two differing hemispheres. One could have become our Moon, the other Mars. (Other explanations of these hemispherical anomalies are hard to come by!). 2.  Dormand, J.R. and Woolfson, M.M., ‘Interactions in the early solar system’, Monthly Notices of the Royal Astronomical Society, 180, 2, 243–279 (1977) academic.oup.com/mnras/article/180/2/243/1034308

Astronomy 2024.indb 151

07/02/2023 22:41

152  Yearbook of Astronomy 2024

Figure 2: The collision of planets A and B, showing a possible origin of the terrestrial planets and the Moon (not to scale). ( John McCue)

A few million years after being torn from the protostar, the planets were in reasonably circular orbits and the era thus ended of planet-splitting encounters. Yet violent impacts continued as remaining debris was swept up, leaving pockmarks that are still to be seen everywhere, especially on our Moon, Mars, and even Earth. Venus took up its position as second planet from the Sun, and we see it now in a very strange state – and posing an enigma still unsolved; how did it lose its spin? The major planets rotate on their axes with periods ranging from about 10 to 24 hours, with the exceptions of Venus and Mercury. The 59-day pirouette of the latter is understandable, given the braking it has endured by the sun’s gravitational tidal forces (though in a non-captured rotation with the Sun, unlike our Moon and Earth). But how can we explain the fact that Venus is so sluggish, turning daily on its axis, as it does, every 243 earth-days, longer than its year of 225 earth-days? Venus’ day is longer than its year! If that wasn’t hard enough to contemplate, Venus also spins backwards, specifically in the opposite direction to the Earth’s rotation, a

Astronomy 2024.indb 152

07/02/2023 22:41

Monthly Sky Notes and Articles 2024  153 retrograde state. Might a collision have had a controlling interest in this appearance as well? Venus has an extremely dense atmosphere comprising the heavy gas carbon dioxide, almost in its entirety. This ensures that the sun can exert a strong gravitational torque on the tide that is generated in its atmosphere, as well as on its planetary body tide, in much the same way that our Moon pulls on the ocean tide as well as the Earth’s body tide. Computer simulations3 show that if Venus originally had a retrograde spin of about 40 earth-days, the Sun’s atmospheric torque would have slowed the planet down to its present configuration. But how could Venus have started with a retrograde spin, when the evidence of our eyes suggests that all the planets started with prograde spins? A large collision with an asteroid-sized body would service this, probably three times the size of Ceres. If this impact took place on the approaching side of Venus, the effect would have been of someone passing through a revolving door in the opposite direction, only possible by reversing the door! The jury is still out, deciding whether a collision like this is necessary to explain Venus’ present state, though the jury has seen the evidence that these crashes, both big and small, undoubtedly took place. Another possibility is that Venus, during its early life, captured a moon, but in such a way that it took up a backwards orbit. Tidal forces from Venus to this moon would then have inexorably pulled the moon in until it fragmented and rained down on the surface in a shower of fragments, slowing, and possibly halting its rotation. Maybe we shall never know the entire history of our solar system, but we have found so many exoplanets, and are now studying them with remarkable new telescopes, that we could build up one or more evolutionary sequences for planets in the same way that we have done for stars.

3.  McCue, J. and Dormand, J. R., Earth, Moon and Planets, 63, 209–225, (1993)

Astronomy 2024.indb 153

07/02/2023 22:41

154  Yearbook of Astronomy 2024

October

 2

Moon

New – Annular solar eclipse

 3

Moon

Lunar occultation of α Virginis (Spica)

 7

Earth

Arid meteor shower (ZHR unknown)

 7

Moon

Lunar occultation of α Scorpii (Antares)

 7/8

Earth

Draconid meteor shower (ZHR 10)

10

Earth

Southern Taurid meteor shower (ZHR 5)

10

Moon

First Quarter

14

Mars

West quadrature

14

Moon, Saturn

Lunar occultation of Saturn

142°

15

Moon, Neptune

Lunar occultation of Neptune

155°

17

Moon

Full

19

Moon

Lunar occultation of M45 (Pleiades)

21/22

Earth

Orionid meteor shower (ZHR 20)

23

Moon

1.7° south of β Geminorum (Pollux)

24

Moon

Last Quarter

31

Moon

Lunar occultation of α Virginis (Spica)

6° 55°

90°

148° 97° 14°

Dates are based on UT. Peak activity dates for meteor showers are estimates. The last column gives the approximate elongation from the Sun.

Mercury undertakes its final evening apparition of 2024 this month. It barely clears the horizon as viewed from northern temperate latitudes but is much easier to see from the southern hemisphere. It climbs steadily throughout the month, even as it gets dimmer (beginning at magnitude −1.7 and ending at −0.3). The day-old Moon passes less than 2° south of Mercury on 3 October but this takes place just 3° away from the Sun and is unlikely to be visible. Mercury passes through its descending node on 13 October and undergoes yet another aphelion ten days later. Venus is visible in the west after sunset. It remains very low as viewed from northern temperate latitudes but is high in the sky for those viewing it from more southerly vantage points. The evening star brightens slightly to magnitude −4.0 by the end of the month as the planet slowly approaches Earth.

Astronomy 2024.indb 154

07/02/2023 22:41

Monthly Sky Notes and Articles 2024  155

Evening Apparition of Mercury 30 September to 6 December 52° North 35° South

30° 16 Nov (GE east) v No 21

11 Nov 1 Nov

20°

21 Oct ov v 1 N ov 16 Nov (GE east) 2 11 N 1 No c e 1D

SW

1 Dec t c t O Oc 21 11

11 Oct ct 1 OOct 1

W

10° 0°

Earth enjoys the last eclipse of the year on 2 October when a spectacular annular solar eclipse takes place. For information on observing this event, see Eclipses in 2024. Spica is occulted by the young Moon the following day but this takes place too close to the Sun to be visible. However, the lunar occultation of Antares on 7 October should be easily observable. The waning gibbous Moon occults the Pleiades, the famous open star cluster in the constellation of Taurus, on 19 October, and passes 1.7° south of Pollux on 23 October. Another challenging lunar occultation of Spica takes place on the last day of the month. The farthest apogee of the year occurs on the second day of the month, and the Full Moon on 17 October occurs less than 12 hours after perigee, leading to the ‘largest’ Full Moon – the Full Moon with the largest apparent diameter – of the year. (See February for the ‘smallest’ Full Moon of 2024.) October hosts several meteor showers, including the newlydiscovered Arids, early in the month. Occurring around the same time or a few days after the Arids are the Draconids and the Southern Taurids. The Moon is a waxing crescent during peak activity of these showers, thus limiting the amount of lunar light pollution. The Orionid meteor shower peaks a few days after Full Moon and is largely washed out. See Meteor Showers in 2024 for more information on all of these October meteoric events. Mars reaches west quadrature on 14 October. At magnitude +0.3, the planet looks distinctly gibbous when viewed through a telescope, with 88% of the surface

Astronomy 2024.indb 155

07/02/2023 22:41

156  Yearbook of Astronomy 2024 illuminated. Mars spends most of the month in Gemini, moving to the constellation of Cancer on 28 October. It rises during the late evening hours. Jupiter is at its most northerly declination for the year on 6 October, reaching a stationary point two days later before reversing course back toward the V-shaped head of the bull Taurus. A superior planet always enters retrograde before opposition and on average, Jupiter spends approximately 17 weeks in retrograde motion. This means opposition will occur in about eight to nine weeks. Jupiter is best viewed from the northern hemisphere where the magnitude −2.6 planet rises during the early evening hours. Observers in southern latitudes will catch a glimpse of the bright planet rising slightly later in the evening. Saturn is located in Aquarius as a first-magnitude object visible in the evening sky and not setting until after midnight. The rings were at their smallest tilt in June and have been opening slightly ever since. This will continue through next month, after which the rings will close until Saturn undergoes a ring-plane crossing early next year. As Saturn approaches its equinox, its major satellites, which are confined to its equatorial plane, begin occulting one another. The first such occultations take place this year. For more information, see the article Saturn at its Equinox: Mutual Occultations and Eclipses of the Satellites 2024–2025 following this month’s sky notes. Saturn is occulted by the waxing gibbous Moon on 14 October, beginning around 16:30 UT. The event is visible from southern Africa, Madagascar, southern Saudi Arabia, Yemen, Oman, the United Arab Emirates and southern Asia. Uranus is in retrograde in Taurus and rises a little earlier every day. It is visible from early evening. Only the keen-sighted with dark skies will be able to spot this sixthmagnitude planet with the naked eye. Neptune is an evening sky object in Pisces, already aloft as the sky darkens and not setting until dawn. Beginning around 15:30 UT on 14 October, the waxing gibbous Moon occults the eighth-magnitude planet. This event is visible from central Africa, the Middle East, India and central Asia.

Astronomy 2024.indb 156

07/02/2023 22:41

Monthly Sky Notes and Articles 2024  157

Saturn at its Equinox Mutual Occultations and Eclipses of the Satellites 2024–2025 David Harper

Every 14 or 15 years, the Sun and Earth pass through the plane of Saturn’s rings. For a few months, the rings are invisible, except in the largest telescopes. This presents an opportunity for observations that are impossible at any other time, such as the discovery of the small moons Janus, Helene, Telesto and Calypso. The larger moons orbit Saturn near the plane of the rings, and for several months either side of the ring-plane crossing, they occult and eclipse one another. A series of these events begins in May 2024, ahead of the ring-plane crossing in spring 2025, and continues until February 2026. Almost 200 mutual occultations and eclipses will be visible from Earth. These mutual events have been observed by professional astronomers at every ring-plane crossing since 1980 because they provide highly accurate positional information which can be used to improve the orbital parameters of the satellites. This, in turn, has helped the planners of missions including Voyager 2 and Cassini. Astronomers first became interested in the orbits of the satellites of Saturn in the late nineteenth century. If their orbital periods and distances could be measured accurately, this would allow the mass of Saturn itself to be determined with high precision, and that was crucial in the calculation of the gravitational pull it exerted on the other planets of the Solar System. The national almanac offices of Britain, France and the United States were keen to improve the accuracy of the ephemerides that they published for astronomers and sailors. A campaign of astrometric observations of the satellites of Saturn began in 1874 and continued for several decades. With the rise of astrophysics in the early twentieth century, however, celestial mechanics suffered a serious decline, and there was little interest in the orbits of planetary satellites until the mid-1960s, when NASA began making plans to send spacecraft to the outer solar system. Belatedly, it was realised that the existing models of the orbits of the satellites of Saturn were woefully inadequate, and steps needed to be taken to obtain new astrometric observations of very high accuracy.

Astronomy 2024.indb 157

07/02/2023 22:41

158  Yearbook of Astronomy 2024

NASA’s Cassini spacecraft captured this image of the edge of Saturn’s B ring two weeks before the Sun crossed the ring-plane in August 2009. Vertical structures as high as 2.5 kilometres cast long shadows across the ring. (NASA/JPL/SSI)

The first observations of mutual events of the Saturnian satellites took place in 1980. Observers in Europe, Japan and the United States mostly used photoelectric photometers to measure the brief dip in the combined light of each pair of satellites during an occultation or eclipse. These were difficult and challenging observations to make, due to the presence of the overwhelmingly-bright planet within a few arcseconds of the satellites involved in the event. Gérard Dourneau, using the 33 cm Carte du Ciel astrograph at the University of Bordeaux observatory, took multiple photographic plates of the occultation of

Astronomy 2024.indb 158

07/02/2023 22:41

Monthly Sky Notes and Articles 2024  159

The Pic du Midi Observatory is situated in the Pyrenees at an altitude of 2,877 metres above sea level. It is a major research observatory and contributed observations of mutual events during both the 1995 and 2009 campaigns. Saturn’s small moon Helene was discovered at Pic du Midi at the 1980 ring-plane crossing. (Wikimedia Commons/ Pascalou petit)

Dione by Tethys on 5 April 1980, then measured the separation between the two satellites on each plate to create a plot of distance versus time. This technique allowed him to determine the moment of closest approach to within a minute. At the next ring-plane crossing, in 1995, an international campaign dubbed PHESAT95 was led by William Thuillot and Jean-Eudes Arlot of the Institut de Mécanique Céleste et de Calcul des Éphémérides (IMCCE, formerly the Bureau des Longitudes). Sixteen observatories took part, using telescopes from 30 cm to 1.5 metre diameter. Some observations were made using photoelectric photometers – as in 1980 – but CCD cameras were also used to directly capture a sequence of images of the satellites during each event, allowing the distance between the satellites to be measured during occultations, and their reductions in brightness to be determined during eclipses. Another international campaign was coordinated by Thuillot and Arlot for the ring-plane crossing in 2009. They reported the results in a paper in 2012. This time,

Astronomy 2024.indb 159

07/02/2023 22:41

160  Yearbook of Astronomy 2024 amateur astronomers were also able to contribute observations, thanks to the wide availability of CCD cameras and the software to drive them. They included the Sparta Astronomical Society in Greece, and pupils at two grammar schools in Northern Ireland. Analysis of the observations, comparing them with the best available model for the orbits of the satellites, demonstrated that they could pin down the relative positions of each pair of satellites to within 4 milli-arcseconds as seen from Earth, which corresponds to 24 kilometres at Saturn. Details of the mutual occultations and eclipses which will occur between May 2024 and February 2026 can be obtained from the IMCCE web site via the Natural Satellites Database service nsdb.imcce.fr which provides customised lists of events visible from a list of more than 2,000 locations worldwide.

Further Reading

Dourneau, G. (1982), ‘Observation of 2 Mutual Events Involving the Satellites of Saturn in April 1980’, Astronomy & Astrophysics, 112, 73–75 Aksnes, K., Franklin, F., et al. (1984), ‘Mutual Phenomena of the Galilean and Saturnian Satellites in 1973 and 1979/1980’, The Astronomical Journal, 89, 280–288 Thuillot, W., Arlot, J. -E., et al. (2001), ‘The PHESAT95 catalogue of observations of the mutual events of the Saturnian satellites’, Astronomy & Astrophysics, 371, 343–349 dx.doi.org/10.1051/0004-6361:20010321 Arlot, J.-E., Emelyanov, N.V., et al. (2012), ‘Astrometric results of observations of mutual occultations and eclipses of the Saturnian satellites in 2009’, Astronomy & Astrophysics, 544, A29 dx.doi.org/10.1051/0004-6361/201118509

Astronomy 2024.indb 160

07/02/2023 22:41

Monthly Sky Notes and Articles 2024  161

November

 1

Moon

New

 4

Moon

Lunar occultation of α Scorpii (Antares)

 9

Moon

First Quarter

11

Moon, Saturn

Lunar occultation of Saturn

12

Earth

Northern Taurid meteor shower (ZHR 5)

12

Moon, Neptune

Lunar occultation of Neptune

15

Moon

Full

16

Moon

Lunar occultation of M45 (Pleiades)

16

Mercury

Greatest elongation east

17

Uranus

Opposition

17/18

Earth

Leonid meteor shower (ZHR varies)

20

Moon

1.9° south of β Geminorum (Pollux)

23

Moon

Last Quarter

27

Moon

Lunar occultation of α Virginis (Spica)

28° 114° 127° 173° 23° 180° 124° 42°

Dates are based on UT. Peak activity dates for meteor showers are estimates. The last column gives the approximate elongation from the Sun.

Mercury continues its ascent in the west, reaching greatest elongation east (22.5°) on 16 November, before heading back toward the horizon. The tiny planet attains its maximum southerly declination for the year three days later. This final evening apparition is best viewed from the tropics and the southern hemisphere. Retrograde motion begins on 26 November, signalling that inferior conjunction is not far off. Venus is the evening star, brightening from magnitude −4.0 to −4.2 over the course of the month. Venus is approaching Earth; when viewed through a telescope, the disk of the planet is getting larger even as its phase is decreasing from 77% to 68%. The planet continues to climb higher above the western horizon and is best seen from the southern hemisphere and equatorial regions. On November 14, Venus reaches it maximum declination south for the year. Earth collides with more comet debris this month, resulting in the Northern Taurid and Leonid meteor showers. The article Meteor Showers in 2024 gives more details. The waxing crescent Moon occults Antares on the fourth day of the month.

Astronomy 2024.indb 161

07/02/2023 22:41

162  Yearbook of Astronomy 2024 The Pleiades star cluster is next, with the waning gibbous Moon, just a day past full, obscuring M45 on 16 November. Pollux is nearly 2° north of the Moon when our satellite comes to call on 20 November but a week later, the waning crescent Moon occults Spica. Mars continues to distance itself from the Sun, rising mid- to late-evening depending upon the observer’s latitude. It brightens over half a magnitude this month, ending November at a brilliant –0.5. It is getting larger and rounder in the telescopic eyepiece as it gets nearer to Earth and opposition next year. The red planet is found in the constellation of Cancer. Jupiter continues to retrace its steps back across Taurus this month as it approaches opposition in December. At magnitude −2.7, it is the brightest starlike object in a region of sky full of brilliant stars. Jupiter rises during evening twilight when viewed from northern temperate latitudes but is well-situated for astronomers in the southern hemisphere as well. Saturn vanishes behind the waxing gibbous Moon on 11 November. The occultation begins around 01:30 UT for observers in Central America and north western South America. Two days later, the rings open to a value of 5.2°; they will now close down to 0° during the ring-plane crossing next year. Saturn returns to direct motion mid-month. Located in Aquarius, Saturn shines at magnitude +0.8 and sets around midnight. Uranus reaches opposition on 17 November in Taurus, the constellation of the Bull. At magnitude +5.6, it is at its brightest this year. A telescope reveals the planet as a fuzzy green disk 3.69 arc-seconds across. Uranus rises at sunset and vanishes below the horizon as the Sun reappears. Neptune is occulted by the waxing gibbous Moon on 12 November. This event is visible from Mexico and most of North America beginning around 01:00 UT. Neptune is located in Pisces and is an evening sky object, setting around midnight by the end of the month. At eighth magnitude, a small telescope is necessary to observe it.

Astronomy 2024.indb 162

07/02/2023 22:41

Monthly Sky Notes and Articles 2024  163

Gone But Not Forgotten Musca Borealis Lynne Marie Stockman

Situated near the northern border of Aries, between the constellation of Triangulum and the bright open cluster M45 (Pleiades), is a small Y-shaped asterism. This tiny group is comprised of just four stars – 33 Arietis, 35 Arietis, 39 Arietis, 41 Arietis – none of which are brighter than magnitude +3.5, but they represent a named entity in several astronomical traditions. Ancient Chinese astronomers were grouping the stars into constellations over 3,000 years ago. The night sky was divided into five regions. The middle section, centred on the north celestial pole, contained the Three Enclosures and represented the heavenly counterparts of the emperor, his family, and his court. The remainder of the visible heavens was divided into the Four Symbols, each containing seven Mansions. Each Symbol had an associated animal and attributes: the Black Tortoise (north, winter), the Blue Dragon (east, spring), the Red Bird (south, summer), and β

ξ

35°

PER

γ ζ

41

τ

TAU

δ

ζ

α κ

ν

ε

PSC

λ

ϕ

χ β

η

ρ

γ

δ ι

γ

4h 20m

υ 35 33

ARI

Pleiades ω

20°

α

39

ϕ

υ κ

TRI τ

χ

25°

β

ο

ψ

30°

δ

π

4h 0m

3h 40m

3h 20m

3h 0m

η

2h 40m

2h 20m

2h 0m

1h 40m

1h 20m

Dark skies are required to see Musca Borealis (circled in red) located in Aries between the Pleiades and Triangulum. Fourth-magnitude 41 Ari (Bharani) is the brightest member of the group. This constellation is best seen in the evening between mid-October and mid-January. Stars are shown to magnitude +6.0. (David Harper)

Astronomy 2024.indb 163

07/02/2023 22:41

164  Yearbook of Astronomy 2024 the White Tiger (west, autumn). The third Mansion of the White Tiger was called 胃 (Wèi) which means ‘stomach’ and was represented in the sky by 35 Ari, 39 Ari, and 41 Ari. Indian astronomy has similarly deep roots. The sky was originally divided into 28 regions of varying size but this was reduced to 27 equally-spaced sectors called Nakshatras. The second Nakshatra was भरणी (Bharani) and was comprised of the stars 35 Ari, 39 Ari, and 41 Ari. Astrologically it was associated with the planet Venus and the deity Yama who rendered judgement over the dead. Arab astronomers also recognised the grouping of 35 Ari, 39 Ari, and 41 Ari. ) ( ‫َﻄ‬    (al-Bu Known as ' ṭayn), it represented the ‘little belly’ of al-Ḥamal, the first-year #ُ‫اﻟ‬ lamb. The lamb roughly corresponded to the modern Aries, with the two budding horns of the beast given by α Ari (Hamal) and β Ari (Sheratan) and its fatty tail by the Pleiades. In his Almagest, Greek mathematician Ptolemy (c100–c170) left the foursome ‘unformed’ in his constellation of the ram, listing them as outside Aries and describing them as the four stars over the rump, with the rearmost, 41 Ari, as the brightest. And there they remained until the early-seventeenth century when Dutch-Flemish astronomer and cartographer Petrus Plancius (1552–1622) decided to re-introduce them as a new constellation Apes, the bees. Perhaps he imagined the faint grouping as a swarm of bees. As Apes (bees plural) or Apis (bee singular), this constellation appeared on a number of celestial globes and stellar atlases from 1613 onwards. Unfortunately, there was already a southern hemisphere constellation called Apis, the bee. Plancius himself had made up the constellation nearly twenty years earlier and named it after the fly, but it was better known as Apis, the title given to it by German uranographer Johann Bayer (1572–1625) in his celebrated Uranometria of 1603. Perhaps it was for this reason that German astronomer Jakob Bartsch (c1600–1633) renamed the swarm as Vespa, the wasp. In 1624, Bartsch published Usus Astronomicus Planisphærii Stellati which included star charts and accompanying descriptions. The charts clearly showed a large insect labelled Vespa hovering menacingly over the ram’s back, but the associated text still referred to the constellation as Apes. Further confusing the issue, he also likened it to either ‘Beelzebub, deum muscarum notet’ (Ba’al-zəbûb, the lord of the flies) or the honeybees that were found in the corpse of a lion slain by the biblical figure Samson. Vespa never really took flight, and Apis or Apes remained the preferred name for the tiny asterism for some time. Polish astronomer Johannes Hevelius (1611–1687) entered the fray when he replaced the bees or the wasp with a fly, Musca, in his 1687 work Firmamentum

Astronomy 2024.indb 164

07/02/2023 22:41

Monthly Sky Notes and Articles 2024  165 Sobiescianum sive Uranographia. However, this did not help with the conflict with the older southern hemisphere insectoid constellation. Originally a fly (Plancius), it had become a bee (Bayer), and then had transmogrified back into a fly. To avoid confusion, the southern fly began to have ‘Australis’ appended to it. In the nineteenth century, Scottish schoolmaster Alexander Jamieson (1782–1850) transformed the northern fly into Musca Borealis (Celestial Atlas, 1822) and ‘Australis’ was eventually dropped for the southern insect. Not to be outdone, the French also decided to co-op this group of stars. Jesuit priest Ignace-Gaston Pardies (1636–1673) placed an unlabelled fleur-de-lys over the asterism in his 1674 star atlas Globi coelestis in tabulas planas redacti descriptio. Five years later, architect Augustin Royer published his own star map in which he labelled this figure as Lilium, the fleur-de-lys. Astronomer Nicolas-Louis de Lacaille (1713–1762) embraced the tiny constellation, designating 39 Ari as Lilii Borea (the

Musca Borealis hovers over the back of Aries in Plate XIII from Alexander Jamieson’s 1822 Celestial Atlas. (Wikimedia Commons/Alexander Jamieson/United States Naval Observatory Library)

Astronomy 2024.indb 165

07/02/2023 22:41

166  Yearbook of Astronomy 2024 north of the lily) and 41 Ari as Lilii Australis (the south of the lily) in his 1757 publication Astronomiæ Fundamenta Novissimis. Bees or wasp, lily or fly, these names were never embraced by the scientific establishment and one by one they fell out of use. Musca Borealis continued to appear on popular sky charts through the nineteenth century but failed to make the cut in 1922 when the International Astronomical Union (IAU) canonised the set of 88 constellations. In 1930, the boundaries of Aries were carefully drawn to revert to Ptolemy’s original description of four unformed stars over the rump of the ram. However, some of the historical names survive to this day. As of this writing, the two brighter stars have received official names from the IAU. Lacaille’s Lilii Borea is the name of the golden giant star 39 Ari. The blue main sequence star 41 Ari, at magnitude +3.6 the brightest member of the group, is now known as Bharani. This star is the third brightest in the constellation but was oddly overlooked by Bayer. It also holds the distinction of being the brightest star with a Flamsteed designation but lacking a Bayer Greek letter. The fifth-magnitude stars 33 Ari and 35 Ari are known only through their catalogue numbers, but perhaps the IAU will someday bestow names upon them. Vespa and Wèi anyone?

Further Reading

Allen, Richard Hinkley, (1963), Star Names: Their Lore and Meaning, Dover Publications, Inc. Balantine, John C., (2016), The Lost Constellations: A History of Obsolete, Extinct, or Forgotten Star Lore, Springer Praxis Books. Ridpath, Ian, (2018), Star Tales: Revised and Expanded Edition, The Lutterworth Press.

Astronomy 2024.indb 166

07/02/2023 22:41

Monthly Sky Notes and Articles 2024  167

December

 1

Moon

New

 1

Moon

Lunar occultation of α Scorpii (Antares)

 3

Mars

1.3° north of M44 (Beehive/Praesepe)

 4

Saturn

East quadrature

 6

Mercury

Inferior conjunction

 7

Jupiter

Opposition

 8

Moon, Saturn

Lunar occultation of Saturn

 8

Moon

First Quarter

 9

Moon, Neptune

Lunar occultation of Neptune

100°

13

Moon

Lunar occultation of M45 (Pleiades)

157°

13/14

Earth

Geminid meteor shower (ZHR 75+)

15

Moon

Full

18

Moon, Mars

Lunar occultation of Mars

18

Neptune

East quadrature

22

Moon

Last Quarter

22/23

Earth

Ursid meteor shower (ZHR 10)

24

Moon

Lunar occultation of α Virginis (Spica)

70°

25

Mercury

Greatest elongation west

22°

28

Moon

Lunar occultation of α Scorpii (Antares)

28°

30

Moon

New

5° 126° 90° 1° 179° 87°

142° 90°

Dates are based on UT. Peak activity dates for meteor showers are estimates. The last column gives the approximate elongation from the Sun.

Mercury vanishes from view in the west during the first few days of December, undergoing inferior conjunction (and coincidentally perihelion) on 6 December. It returns to the morning sky where it began 2024, brightening as it rises above the eastern horizon before sunrise. Retrograde motion ceases mid-month and Mercury reaches great elongation west (22.0°) on 25 December, after which it heads back toward the horizon. Mercury ends the year north of the plane of the ecliptic, having passed through its ascending node on the first day of the month.

Astronomy 2024.indb 167

07/02/2023 22:41

168  Yearbook of Astronomy 2024

Morning Apparition of Mercury 6 December to 9 February 52° North 35° South 25 D

ec (

GE

wes

21

t) ec

D

20°

an 1J 11 Jan

11 Dec

E

30°

21 Jan 1 Feb

c De 21 25 Dec (GE west) 1 Jan

11 Dec

10°

11 Jan 21 Jan

SE

0°

Venus continues to brighten in the west after sunset, increasing in magnitude from −4.2 to −4.4. The evening star begins to decline in altitude as seen from southern latitudes but continues to climb above the horizon for all other observers. Earth reaches the solstice on 21 December, with summer commencing in the southern hemisphere and winter taking hold in the north. The strong Geminid meteor shower peaks just before Full Moon so observations will be badly hampered by moonlight. The Ursids are at their peak just after Last Quarter Moon so viewing conditions should be a little better. The article Meteor Showers in 2024 gives more details. Antares is occulted by the Moon twice although the first event is unobservable, with the Moon in its new phase. The second occultation takes place on 28 December. The waxing gibbous Moon occults the Pleiades at around the time that the Geminids peak, whilst the waning crescent Moon passes in front of Spica during Ursids activity. The Moon reaches its new phase twice this month; the second New Moon in a calendrical month is sometimes referred to as a ‘Black Moon’. Mars is just over a degree north of M44, Praesepe or the Beehive Cluster, on the third day of the month. Four days later, it enters into retrograde motion and begins to loop back on itself. A lunar occultation takes place on 18 December; the waning gibbous Moon moves in front of bright Mars beginning around 08:00 UT as seen

Astronomy 2024.indb 168

07/02/2023 22:41

Monthly Sky Notes and Articles 2024  169 from Arctic regions including northern Alaska and Canada, Greenland, northern Europe and northern Asia. By the end of the year, Mars is at its most northerly declination and blazing away at magnitude −1.2 in the constellation of Cancer. Look for it in the east from early evening. Jupiter finally reaches opposition on 7 December. It shines at a blinding magnitude −2.8 and in a telescope, appears as a banded disk 48.16 arc-seconds across. Found in Taurus, the gas giant is visible throughout the hours of darkness. Saturn reaches east quadrature on the fourth day of the month. Its final lunar occultation of the year takes place 8 December. Beginning at approximately 09:00 UT, the waxing crescent Moon will obscure the ringed planet as seen from Japan. Look for the first-magnitude body in Aquarius before both planet and constellation set in the late evening hours. Uranus finishes 2024 retrograding through Taurus, re-entering Aries just before the end of the month. Opposition took place last month which means that Uranus is currently an evening sky object. It is well-placed for observation from both hemispheres and sets just before dawn. Neptune returns to direct motion across the constellation of Pisces on 8 December. The following day, the waxing gibbous Moon occults the faint planet in an event visible from north eastern China, Mongolia, north eastern Russia, Japan and western Alaska and beginning at approximately 08:15 UT. East quadrature takes place on 18 December. Look for eighth-magnitude Neptune as soon as the skies get dark; the planet sets at or before midnight by the end of the month.

Astronomy 2024.indb 169

07/02/2023 22:41

170  Yearbook of Astronomy 2024

A Howl Across the Void The Fate of Beagle 2 Jonathan Powell

The points of light that flicker away in the night sky proved a perplexing mystery to the early pioneers on Earth, whose conquests were confined to the land and sea. However, with space patiently waiting for humankind and the advancement of technology, a time would soon be within reach when, having forged the atmospheric moat that encompasses Earth, a new era of pioneering would begin. From early satellites to crewed missions, we then dared to dream of the possibility of going to the Moon, and when that realization was fulfilled, our eager eyes turned to thoughts of pushing even further out into space. Whereas early adventurers were quite happy to be at the forefront of their exploratory voyages, technology over time has allowed the human element to be withdrawn from unnecessary risk, albeit to a limited extent. Granted, human

Professor Colin Pillinger (right), pictured with Dr Roger Bonnet, (left), former ESA Director of Scientific Programs. (© ESA – European Space Agency)

Astronomy 2024.indb 170

07/02/2023 22:41

Monthly Sky Notes and Articles 2024  171 participation in such endeavours as the Apollo missions or onboard the International Space Station has been vital, but in some cases, not essential. As a scout seeks out the terrain in a forward position whilst the main bulk of the army awaits the outcome of the reconnaissance, probes have afforded a look into space in a similar fashion, relaying information back to Earth with no risk to human life. Such probes, alongside the deployment of powerful telescopes, have given us a serious ‘head’s up’ into the universe in which we live, including the extremes of temperature, the barren lands, and ultimately on each search, the quest for life beyond Earth. With the risk to human life removed, the variables as to the success of failure of any mission still remain – even with the best technology and equipment to hand, problems inevitably arise. Such an occasion arose with the Beagle 2, a spacecraft despatched to search for evidence of past life on Mars. Named after HMS Beagle – the iconic sailing vessel which took Charles Darwin on his historic round-the-world journey during the 1830s – Beagle 2 was assigned a six-month tour of duty on the Martian surface. Having been successfully transported to the red planet courtesy of the European Space Agency’s Mars Express mission – launched from Baikonur on 2 June 2003 – Beagle 2 was duly deployed later that year on 19 December, with its scheduled landing on the surface of Mars due to take place on 25 December. At first, all seemed to be going to plan. However, following a successful deployment, a signal from Beagle 2 to acknowledge its safe arrival on the planet’s surface was not forthcoming. The intended signal would have initially reached NASA’s Mars Odyssey spacecraft. Having failed to detect any signal, hopes turned to Jodrell Bank back on Earth to pick up any communication, but still nothing was heard. NASA’s Mars Express was subsequently called upon to assist by attempting to establish contact, again to no avail. In essence, Beagle 2 was unable to tell its masters it had arrived, and a bark of acknowledgement to Earth became a lonely howl that was never to be heard. The man at the very centre of operations was the planetary scientist and founding member of the Planetary and Space Sciences Research Institute at Open University, Professor Colin Pillinger (1943–2014). Beagle 2 was primarily the brainchild of the Open University and the University of Leicester. Pillinger’s vision was to emulate Darwin’s epic voyage of discovery, the passion and belief for Beagle 2 being evident in both his mindset and fervent belief in the project. A testimony to the upholding of space mission ethics, his attachment to Beagle 2 was transparent, which makes the news of Beagle’s later discovery – eight months after Pillinger’s passing – even more heartfelt.

Astronomy 2024.indb 171

07/02/2023 22:41

172  Yearbook of Astronomy 2024

Artist’s impression of how Beagle 2 would have appeared on the Martian surface if all of its four solar panels had deployed. (© ESA/Denman Productions)

During the repeated attempts to re-establish communications after 25 December, Pillinger had suggested that perhaps Beagle 2 had inadvertently come down to rest in a crater at the landing site, or that high concentrations of dust levels had hindered parachute deployment, and in turn failed to slow Beagle 2 sufficiently before it landed on Mars. Neither of these notions provided satisfactory answers to the loss of Beagle 2 and the ability to bring the necessary closure it demanded. By February 2004 all hope had vanished and Beagle 2 was deemed lost. However, in January 2015 a series of images taken by Mars Reconnaissance Orbiter revealed just why Beagle 2 had not contacted Earth some 11 years previously. Whilst Beagle 2 had indeed touched down safely on the surface, two of its four solar panels had failed to unfurl. This had the effect of blocking the spacecraft’s antenna, subsequently preventing the craft from communicating with home. Beagle 2 had arrived on the planet and survived the descent to its surface but was simply not able to let everybody know that it had done so. Despite Beagle 2 never achieving its intended goal, some comfort can be taken from knowing that it actually made it to its intended destination. For some spacecraft, the fate of simply being lost in space has regrettably become a reality.

Astronomy 2024.indb 172

07/02/2023 22:41

Comets in 2024 Neil Norman

When writing for the comet section of the Yearbook of Astronomy, one can only include the objects that are known with certainty to return during the relevant year. Because of this there have been many instances when a bright comet has come along completely by surprise, and has therefore not been included in the articles for the years in question. Recent notable examples include C/2019 Y4 (ATLAS), discovered as a magnitude 19.6 object in Ursa Major by the Asteroid Terrestrial-impact Last Alert System (ATLAS) on 28 December 2019, but which disintegrated as it approached the Sun during the early part of 2020. Another case in point is C/2020 F8 (SWAN), which first came to light on 25 March 2020 before passing perihelion on 27 May and commencing its journey back towards the outer reaches of the solar system. Also not included was the bright comet C/2020 F3 (NEOWISE), its discovery on 27 March 2020 precluding it from being mentioned in the Yearbook for that particular year, but which became one of the brightest northern hemisphere comets since the appearance of Hale-Bopp in 1997. Our final example is C/2021 A1 (Leonard), discovered on 3 January 2021 by American astronomer Greg Leonard from the Mount Lemmon Observatory in Arizona, and going on to become a prominent naked-eye object in December of that year. An image of this comet can be seen along with a Geminid meteor in the article ‘Meteor Showers in 2024’ elsewhere in this volume. For the very latest comet discoveries it is advised that the reader regularly pays a visit to the British Astronomical Association (BAA) Comet Section website at www.ast.cam.ac.uk/~jds which is regularly maintained and updated with all the latest discoveries and news.

Best Prospects for 2024 At the time of writing, a large number of comets are due to return to perihelion during 2024, of which the vast majority are fairly dim. Belonging to the Jupiter family of comets, these objects generally require relatively large aperture equipment to observe them, although there are four comets that are of particular interest this time around.

Astronomy 2024.indb 173

07/02/2023 22:41

174  Yearbook of Astronomy 2024

12P/Pons-Brooks We begin with a comet whose return has been eagerly anticipated for several decades. Originally discovered by French astronomer Jean Louis Pons on 12 July 1812, the object was accidentally recovered on 2 September 1883 by the prolific comet discoverer William Robert Brooks during a routine search for comets. German astronomer Johann Franz Encke deduced that the sightings of 1812 and 1883 were of one and the same object and calculated an orbit of 70.68 years for the comet, which was eventually named after the two original discoverers. Comet 12P/Pons-Brooks next came to perihelion on 22 May 1954 when at a distance of 1.7 au from Earth. Widely observed and documented, the comet underwent several outbursts during the 1954 return. On 10 June 2020, the comet was recovered on its way back to perihelion in 2024 at a magnitude of 23 by a team using the Lowell Discovery Telescope. At the time the comet was located 12 au from the Sun and in the constellation of Hercules.

Three sketches of 12P/Pons-Brooks by George Alcock from Peterborough, Northamptonshire, England drawn between 31 March and 19 April 1954. (British Astronomical Association/George Alcock)

Astronomy 2024.indb 174

07/02/2023 22:41

Comets in 2024 175 The 2024 return will see the comet approach to within around 1.5 au of the Earth on 2 June, yet despite this fairly large distance it should still peak at around fourth magnitude in April. Due to the unpredictable nature of 12P/Pons-Brooks, a close watch is advised for outbursts. It is worth mentioning that the total solar eclipse on 8 April this year should allow observers situated within the path of totality an opportunity to see 12P/Pons-Brooks as it will be placed just above Jupiter. DATE

RA

DECLINATION

MAGNITUDE

CONSTELLATION

  1 Jan 2024

19 37 14

+37 46 31

9.7

Cygnus

15 Jan 2024

20 20 06

+37 58 46

9.3

Cygnus

  1 Feb 2024

21 23 31

+38 13 45

8.8

Cygnus

15 Feb 2024

22 25 41

+37 44 22

8.3

Lacerta

  1 Mar 2024

23 39 54

+35 32 02

7.8

Andromeda

15 Mar 2024

00 50 49

+31 09 42

6.1

Pisces

  1 Apr 2024

02 10 17

+22 39 31

5.1

Aries

15 Apr 2024

03 06 36

+13 38 53

4.5

Aries

  1 May 2024

04 02 20

+02 21 53

4.9

Taurus

15 May 2024

04 48 25

−07 30 28

5.4

Eridanus

  1 Jun 2024

05 48 00

−19 02 03

6.4

Lepus

62P/Tsuchinshan 1 A member of the Jupiter family of comets, 62P/Tsuchinshan 1 was discovered as a magnitude 15 object in Gemini on a photographic plate taken on 1 January 1965 from the Purple Mountain Observatory in Nanking, China. Interestingly, the discovery was not actually announced for several weeks, the first observation recorded outside China being that made on 9 February by Philip Veron from Palomar Observatory, California, USA. The orbital period of Comet 62P/Tsuchinshan 1 is 6.63 years, and all returns have been observed except for that of 2011 when the comet was badly placed for Earth-based observers. The comet comes to perihelion on Christmas Day 2023, but will be best seen from January through March 2024 during which time its magnitude will range from 8 to 10 as it travels from Leo into the neighbouring constellation of Virgo.

Astronomy 2024.indb 175

07/02/2023 22:41

176  Yearbook of Astronomy 2024

In this image of Comet 62P/Tsuchinshun, captured on 12 November 2017 from Nairobi, Kenya, the comet displays a small but noticeable tail in the 3 o’clock position. (Michael Jäger)

DATE

RA

DECLINATION

MAGNITUDE

CONSTELLATION

  1 Jan 2024

11 38 45

+12 17 44

 8.1

Leo

15 Jan 2024

12 14 48

+10 15 49

 8.2

Virgo

  1 Feb 2024

12 42 15

+08 54 49

 8.5

Virgo

15 Feb 2024

12 50 27

+08 42 36

 8.9

Virgo

  1 Mar 2024

12 46 13

+09 00 40

 9.5

Virgo

15 Mar 2024

12 34 36

+09 14 06

10.1

Virgo

13P/Olbers The German astronomer Heinrich Wilhelm Matthias Olbers discovered this comet on 6 March 1815, recording it as a small and diffuse magnitude 7.5 object in Camelopardalis. Observing it again a day later he noted: “The comet goes thus slowly to the north and the east to the body of Perseus. It is small, has a badly

Astronomy 2024.indb 176

07/02/2023 22:41

Comets in 2024 177 defined nucleus, and a very pale transparent coma, and was visible in the cometseeker”. The newly-discovered comet reached a peak magnitude of 5 during perihelion in late-April, and a tail of around 1 degree in length was observed. The comet returned in 1887, and then again in 1956 when it attained a maximum magnitude of 6.5 and once more displayed a 1 degree maximum tail length. Comet 13P/Olbers will return to perihelion on 30 June 2024 and become easily visible to observers during April 2024, remaining well placed until September. The subsequent return will see the comet pass to within 0.756 au of Earth on 10 January 2094.

Heinrich Wilhelm Matthias Olbers, as depicted in a lithograph by German portrait painter Rudolph Suhrlandt. (Wikimedia Commons/Rudolph Suhrlandt)

DATE

RA

DECLINATION

MAGNITUDE

CONSTELLATION

  1 Apr 2024

03 40 49

+15 05 02

10.5

Taurus

15 Apr 2024

04 04 29

+20 14 23

10.1

Taurus

  1 May 2024

04 38 11

+26 09 27

 9.6

Taurus

15 May 2024

05 14 56

+31 14 14

 9

Auriga

  1 Jun 2024

06 11 28

+36 52 40

 8.5

Auriga

15 Jun 2024

07 10 09

+40 26 44

 8

Auriga

  1 Jul 2024

08 30 31

+42 09 42

 7.6

Lynx

15 Jul 2024

09 46 51

+40 39 33

 7.2

Leo Minor

  1 Aug 2024

11 14 15

+34 57 12

 7

Ursa Major

15 Aug 2024

12 15 26

+28 07 20

 6.8

Coma Berenices

  1 Sep 2024

13 16 16

+19 06 01

 7

Coma Berenices

15 Sep 2024

13 57 46

+12 06 11

 7.4

Boötes

The Japanese amateur astronomer Yoshio Kushida discovered this comet on a photograph taken on 8 January 1994 at the Yatsugatake South Base Observatory. The magnitude was given as 13.5 and the comet displayed a strong inner condensation within a coma measuring between 1 and 2 arc minutes in diameter. This object also belongs to the Jupiter family of comets, and has an orbital period

Astronomy 2024.indb 177

07/02/2023 22:41

178  Yearbook of Astronomy 2024

Comet 144P/Kushida imaged on 26 December 2008 from Bury St Edmunds, Suffolk, England. (Martin P. Mobberley)

of 7.6 years and perihelion distance of 1.439 au. The rate of brightening is rapid pre-perihelion and the comet has a rather dim absolute magnitude of 13.4 meaning only close Earth approaches allow it to become visible to observers with modest equipment. Perihelion will take place on 25 January 2024, and this return should be quite favourable, the comet possibly attaining a magnitude of 7.3 when at its brightest in January.

Astronomy 2024.indb 178

07/02/2023 22:41

Comets in 2024 179 DATE

RA

DECLINATION

MAGNITUDE

CONSTELLATION

  1 Jan 2024

03 04 52

+14 22 32

 7.3

Aries

15 Jan 2024

03 28 51

+14 37 03

 7.3

Taurus

  1 Feb 2024

04 09 17

+15 39 15

 7.5

Taurus

15 Feb 2024

04 49 03

+16 38 23

 7.9

Taurus

  1 Mar 2024

05 35 08

+17 23 17

 8.3

Taurus

15 Mar 2024

06 18 55

+17 33 34

 8.9

Orion

  1 Apr 2024

07 10 35

+16 58 31

 9.7

Gemini

15 Apr 2024

07 50 38

+15 53 33

10.3

Gemini

Astronomy 2024.indb 179

07/02/2023 22:41

Minor Planets in 2024 Neil Norman

Minor planets – often referred to as asteroids – are a collection of varying sized pieces of rock left over from the formation of the Solar system around 4.6 billion years ago. Millions of them exist, and to date almost 800,000 have been seen and documented, with around 550,000 having received permanent designations after being observed on two or more occasions and their orbits being known with a high degree of certainty. Different family types of asteroids also exist, such as Amor asteroids which are defined by having orbital periods of over one year and orbital paths that do not cross that of the Earth. Apollo asteroids have their perihelion distances within that of the Earth and thus can approach us to within a close distance and Trojan asteroids have their home at Lagrange points both 60 degrees ahead and behind the planet Jupiter respectively. These asteroids pose no problems to the Earth.

This image of NEO 2021 YQ was taken on 3 January 2022 when the asteroid was 0.02 au from Earth in the constellation of Lynx. The object passed perihelion on 16 February 2022 at a distance of 0.77 au from the Sun. (Northolt Observatory, London, England)

Astronomy 2024.indb 180

07/02/2023 22:41

Minor Planets in 2024 181 Most asteroids travel around the Sun in the main asteroid belt, which is located between the orbits of Mars and Jupiter. However, some asteroids have more elliptical orbits which allow them to interact with major planets, including the Earth. In all, there are around 2,000 which can approach to within a close distance of our planet. These objects are referred to as Potentially Hazardous Asteroids (PHAs). To qualify as a PHA these objects must have the capability to pass within 8 million kilometres of Earth and to be over 100 metres across. However, some asteroids have orbits which allow them to interact with major planets, including Earth. Over 20,000 asteroids have orbits that can bring them into close proximity to our planet. Such an object is referred to as a Near Earth Asteroid (NEA). To be classed as an NEA, an object must have an orbit which allows it to pass within a distance of 1.3 au of the Earth. A Potentially Hazardous Asteroid (PHA) on the other hand is defined as being one which can approach to within 0.05 au (19.5 lunar distances) of our planet, and have a diameter of at least 140 metres. Objects of this size could pose a serious threat if on a collision course with Earth. It is estimated that several thousand exist with diameters of over 100 metres, and with around 150 of these being over a kilometre across. A large number of smaller asteroids, measuring anything between just a few meters in diameter to several tens of meters wide, pass close to our planet on a regular basis, with considerable numbers of smaller ones entering the Earth’s atmosphere every day, burning up harmlessly as meteors. Those observers with a particular interest in following these objects should go to the home page of the Minor Planet Center. It is their job to keep track of these objects and determine orbits for them. This page can be accessed by going to minorplanetcenter.net where you will find a table of newly discovered minor planets and Near Earth Objects (NEOs). At the top of the page is a search box that you can use to locate information on any object that you are interested in, and from this you can obtain ephemeredes of the chosen subject. The Minor Planet Center site is the one that all dedicated asteroid observers should consult on a regular basis. Observers who are beginning the hobby of asteroid hunting should remember that these objects will appear as nothing more than points of light in your field of view. You therefore need to compare your observations with detailed star charts (especially for the dimmer objects) to ascertain that you have indeed observed your intended target. Details of a selection of the brightest minor planets that are at their greatest elongations from the Sun – and thus well placed for observation – and which are visible in binoculars or small telescopes during 2024 are given below.

Astronomy 2024.indb 181

07/02/2023 22:41

ay

χ

1

3

ψ

1A

pr 1 Ju

l

τ

19h 30m 19h 20m 19h 10m

n

χ

19h 0m

ζ

ϕ

1A

ug 1O

ct

24

λ

ε

δ

11

γ

18h 50m 18h 40m 18h 30m 18h 20m 18h 10m

σ

28

ept

4

18h 0m

7

The path of 1 Ceres from 1 April to 1 October 2024 in Sagittarius. Opposition occurs on 6 July when Ceres is at magnitude 7.5. Stars are shown to magnitude 8.5. Ceres is brighter than magnitude 8.5 from mid-May to late-August. (David Harper)

−34°

−32°

−30°

−28°

−26°

52

1M

1 Ju

−24°

2 1

νν

1S

Astronomy 2024.indb 182

07/02/2023 22:41

Minor Planets in 2024 183

1 Ceres This is no doubt the star of the show and arguably the best known of the minor planets. With a diameter of 945 kilometres Ceres is the largest object in the asteroid belt. Discovered by Italian astronomer Giuseppe Piazzi from Palermo Observatory, Sicily on 1 January 1801, Ceres was initially believed to be a planet until the 1850s when it was reclassified as an asteroid following the discoveries of many other objects in similar orbits. 1 Ceres comes to opposition in early July in the constellation of Sagittarius, reaching a maximum elongation of 173° from the Sun at around the same time. DATE

R.A.

DEC

MAG

CONSTELLATION

  1 Apr 2024

19 11 55

−23 24 06

9.0

Sagittarius

15 Apr 2024

19 24 18

−23 40 44

8.9

Sagittarius

  1 May 2024

19 33 48

−24 12 55

8.7

Sagittarius

15 May 2024

19 37 17

−24 56 55

8.5

Sagittarius

  1 Jun 2024

19 34 42

−26 11 34

8.2

Sagittarius

15 Jun 2024

19 26 59

−27 25 31

7.9

Sagittarius

  1 Jul 2024

19 13 24

−28 50 07

7.6

Sagittarius

15 Jul 2024

18 59 52

−29 50 58

7.6

Sagittarius

  1 Aug 2024

18 45 40

−30 37 50

8.0

Sagittarius

15 Aug 2024

18 38 29

−30 54 50

8.3

Sagittarius

  1 Sep 2024

18 36 49

−30 56 23

8.6

Sagittarius

2 Pallas Pallas has a diameter of 512 kilometres and was the second asteroid to be discovered when first spotted by the German astronomer Heinrich Wilhelm Matthias Olbers on 28 March 1802. Pallas has an orbital period of 1,686 days, its path around the Sun being highly eccentric and steeply inclined to the main plane of the asteroid belt, rendering it fairly inaccessible to spacecraft. 2 Pallas reaches a maximum elongation of 133° degrees from the Sun on 17 May. DATE

R.A.

DEC

MAG

CONSTELLATION

  1 Mar 2024

16 36 12

+09 07 58

9.5

Hercules

15 Mar 2024

16 45 35

+12 17 59

9.4

Hercules

  1 Apr 2024

16 50 56

+16 29 52

9.2

Hercules

15 Apr 2024

16 49 52

+19 56 45

9.1

Hercules

  1 May 2024

16 42 48

+23 23 50

9.0

Hercules

Astronomy 2024.indb 183

07/02/2023 22:41

τ 75

11h 20m

11h 40m

79

σ

υ

ω

69

58

59

LEO

11h 0m

χ

53

10h 40m

1A 1M pr ay

48

ρ

β

ay

SEX 10h 20m

1M

α

31

10h 0m

π

Juno and Bamberga in 2024 The paths of 3 Juno (blue) and 324 Bamberga (magenta) between 1 January and 1 May 2024. Both asteroids are at opposition on 3 March when Juno is at magnitude 8.8 and Bamberga at 11.8. Stars are shown to magnitude 9.0. The grey dashed line is the ecliptic. (David Harper)

0°

5°

ν

4 ξ

VIR

n

ar 1M ar 1M

10°

n

1 Ja

ι

b 1 Fe b 1 Fe 1 Ja

pr 1A

Astronomy 2024.indb 184

07/02/2023 22:41

Minor Planets in 2024 185 DATE

R.A.

DEC

MAG

CONSTELLATION

15 May 2024

16 32 35

+25 34 52

9.0

Hercules

  1 Jun 2024

16 18 05

+26 47 35

9.2

Corona Borealis

15 Jun 2024

16 07 08

+26 33 00

9.3

Corona Borealis

  1 Jul 2024

15 58 19

+25 06 45

9.5

Serpens Caput

15 Jul 2024

15 54 24

+23 07 48

9.7

Serpens Caput

  1 Aug 2024

15 56 22

+20 12 34

9.9

Serpens Caput

3 Juno With a mean diameter of around 270 kilometres, Juno ranks as the twelfth largest asteroid and is one of the two largest stony (S-type) asteroids, comprising around 1% of the mass of the entire asteroid belt and being the second largest stony asteroid after 15 Eunomia. Discovered by the German astronomer Karl Ludwig Harding on 1 September 1804, its mean distance from the Sun is 2.6 au, its journey around our star taking 4.36 years to complete. 3 Juno comes to opposition in early March in the constellation of Leo, reaching a maximum elongation of 178° from the Sun at around the same time. DATE

R.A.

DEC

MAG

CONSTELLATION

  1 Jan 2024

11 19 42

−01 56 27

 9.8

Leo

15 Jan 2024

11 22 39

−01 44 06

 9.6

Leo

  1 Feb 2024

11 19 20

00 30 55

 9.4

Leo

15 Feb 2024

11 11 25

+01 15 36

 9.1

Leo

  1 Mar 2024

10 59 44

+03 40 35

 8.8

Leo

15 Mar 2024

10 48 34

+06 00 42

 9.0

Sextans

  1 Apr 2024

10 38 27

+08 22 34

 9.5

Leo

15 Apr 2024

10 34 44

+09 43 28

 9.9

Leo

  1 May 2024

10 36 05

+10 29 36

10.2

Leo

4 Vesta Discovered by German astronomer Heinrich Wilhelm Matthias Olbers on 29 March 1807, Vesta is one of the largest of the asteroids with a diameter of 525 kilometres and an orbital period of 3.63 years. Vesta holds the distinction of being the brightest of the minor planets visible from Earth.

Astronomy 2024.indb 185

07/02/2023 22:41

186  Yearbook of Astronomy 2024 4 Vesta was at opposition last year, and at the beginning of 2024 is at an elongation of 167° from the Sun in the constellation of Taurus. Conjunction takes place in August. DATE

R.A.

DEC

MAG

CONSTELLATION

  1 Jan 2024

05 47 41

+20 59 39

6.9

Taurus

15 Jan 2024

05 34 29

+21 35 57

7.2

Taurus

  1 Feb 2024

05 25 28

+22 19 01

7.6

Taurus

15 Feb 2024

05 24 58

+22 54 34

7.9

Taurus

  1 Mar 2024

05 31 01

+23 31 57

8.1

Taurus

15 Mar 2024

05 41 54

+24 03 45

8.3

Taurus

  1 Apr 2024

06 00 31

+24 33 49

8.5

Taurus

15 Apr 2024

06 19 18

+24 47 53

8.6

Gemini

  1 May 2024

06 43 39

+24 48 28

8.9

Gemini

324 Bamberga Discovered by Johann Palisa on 25 February 1892 and with a mean diameter of 229 kilometres, asteroid 324 Bamberga is one of the top twenty largest main belt asteroids. It has a rotational period of just over 29 hours, which is unusually long for asteroids over 150 kilometres in diameter. Interestingly, 324 Bamberga is classed as intermediate type, falling as it does between the C-type (carbonaceous) and P-type (organic- rich silicate carbon and anhydrous) types. 324 Bamberga comes to opposition in early March in the constellation of Leo, reaching a maximum elongation of 176° at around the same time. DATE

R.A.

DEC

MAG

CONSTELLATION

  1 Jan 2024

11 28 18

+01 37 52

12.8

Leo

15 Jan 2024

11 27 07

+01 07 23

12.6

Leo

  1 Feb 2024

11 20 01

+01 03 08

12.3

Leo

15 Feb 2024

11 10 05

+01 25 37

12.1

Leo

  1 Mar 2024

10 56 57

+02 09 00

11.8

Leo

15 Mar 2024

10 44 29

+02 57 10

12.0

Sextans

  1 Apr 2024

10 32 03

+03 49 23

12.4

Sextans

15 Apr 2024

10 25 37

+04 17 30

12.6

Sextans

1 May 2024

10 23 07

+04 27 28

12.9

Sextans

Astronomy 2024.indb 186

07/02/2023 22:41

Minor Planets in 2024 187 This image of minor planet 324 Bamberga was captured by Loren Ball on 16 August 2017 from Emerald Lane Observatory, Decatur, Alabama, USA. (Loren Ball)

532 Herculina Asteroid 532 Herculina was discovered by German astronomer Max Wolf on 20 April 1904. One of the largest members of the asteroid belt, it has been noted for its complex light curves which have made it difficult to determine both a size and shape for this object, although it is believed to be ~167.8 kilometres in diameter. 532 Herculina occulted the star SAO 120774 in 1978, observations of this event confirming that Herculina had a moon in orbit around it. This object is believed to be around 45 kilometres in diameter and to travel around its parent at a mean distance of ~1,000 kilometres. Herculina was the first asteroid discovered to have a moon. 532 Herculina comes to opposition in early April in the constellation of Boötes, reaching a maximum elongation of 152° at around the same time. DATE

R.A.

DEC

MAG

CONSTELLATION

15 Feb 2024

14 02 45

+11 18 03

 9.8

Boötes

  1 Mar 2024

14 08 44

+13 25 10

 9.5

Boötes

15 Mar 2024

14 08 05

+15 39 44

 9.3

Boötes

  1 Apr 2024

13 59 39

+18 05 25

 9.1

Boötes

15 Apr 2024

13 48 37

+19 15 23

 9.1

Boötes

  1 May 2024

13 35 49

+19 12 33

 9.3

Boötes

15 May 2024

13 27 47

+17 57 40

 9.6

Coma Berenices

  1 Jun 2024

13 24 31

+15 17 04

 9.9

Coma Berenices

15 Jun 2024

13 27 23

+12 28 12

10.1

Virgo

  1 Jul 2024

13 36 06

+08 54 11

10.4

Virgo

Astronomy 2024.indb 187

07/02/2023 22:41

Meteor Showers in 2024 Neil Norman

A shooting star dashing across the sky is a wonderful sight that often captures the imagination of many young minds and perhaps sparks an interest for astronomy in them. On any given night of the year you can expect to see several of these, and they belong to two groups – sporadic and shower. Quite often the ones you see will be ‘sporadic’ meteors, that is to say they can appear from any direction and at any time during the observing session. These meteors arise when a meteoroid – perhaps a particle from an asteroid or a piece of cometary debris orbiting the Sun – enters the Earth’s atmosphere and burns up harmlessly high above our heads, leaving behind the streak of light we often refer to as a “shooting star”. The meteoroids in question are usually nothing more than pieces of space debris that the Earth encounters as it travels along its orbit, and range in size from a few millimetres to a couple of centimetres in size. Meteoroids that are large enough to at least partially

This image, taken during the 1999 Leonid meteor storm from NASA’s Leonid Multi-Instrument Aircraft Campaign (Leonid MAC) through a 50mm camera, shows Leonid meteors during an outburst at 38,000 feet (11,600 metres), and displays the various sizes of meteoroids entering the atmosphere. (NASA/Ames Research Center/ISAS/Shinsuke Abe and Hajime Yano)

Astronomy 2024.indb 188

07/02/2023 22:41

Meteor Showers in 2024 189 survive the passage through the atmosphere, and reach the Earth’s surface without disintegrating, are known as meteorites. At certain times of the year the Earth encounters more organised streams of debris that produce meteors over a regular time span and which seem to emerge from the same point in the sky. These are known as meteor showers. These streams of debris follow the orbital paths of comets, and are the scattered remnants of comets that have made repeated passes through the inner solar system. The ascending and descending nodes of their orbits lie at or near the plane of the Earth’s orbit around the Sun, the result of which is that at certain times of the year the Earth encounters and passes through a number of these swarms of particles. The term ‘shower’ must not be taken too literally. Generally speaking, even the strongest annual showers will only produce one or two meteors a minute at best, this depending on what time of the evening or morning that you are observing. One must also take into account the lunar phase at the time, which may significantly influence the number meteors that you see. For example, a full moon will probably wash out all but the brightest meteors. The following is a table of the principle meteor showers of 2024 and includes the name of the shower; the period over which the shower is active; the Zenith Hourly Rate (ZHR); the parent object from which the meteors originate; the date of peak shower activity; and the constellation in which the radiant of the shower is located. Most of the information given is self-explanatory, but the Zenith Hourly Rate may need some elaborating. The Zenith Hourly Rate is the number of meteors you may expect to see if the radiant (the point in the sky from where the meteors appear to emerge) is at the zenith (or overhead point) and if observing conditions were perfect and included dark, clear and moonless skies with no form of light pollution whatsoever. However, the ZHR should not be taken as gospel, and you should not expect to actually observe the quantities stated, although ‘outbursts’ can occur with significant activity being seen. The observer can make notes on the various colours of the meteors seen. This will give you an indication of their composition; for example, red is nitrogen/ oxygen, yellow is iron, orange is sodium, purple is calcium and turquoise is magnesium. Also, to avoid confusion with sporadic meteors which are not related to the shower, trace the path back of the meteor and if it aligns with the radiant you can be sure you have seen a genuine member of the particular shower.

Astronomy 2024.indb 189

07/02/2023 22:41

190  Yearbook of Astronomy 2024

Meteor Showers in 2024 SHOWER

DATE

ZHR

PARENT

PEAK

CONSTELLATION

Quadrantids

  1 Jan to 5 Jan

120

2003 EH1 (asteroid)

3/4 Jan

Boötes

Lyrids

16 Apr to 25 Apr

18

C/1861 G1 Thatcher

22/23 Apr

Lyra

Eta Aquariids

19 Apr to 28 May

30

1P/Halley

6/7 May

Aquarius

Tau Herculids

19 May to 19 Jun

Low

73P/Schwassmann– Wachmann

9 Jun

Hercules

Delta Aquariids

12 Jul to 23 Aug

20

96P/Machholz

28/29 Jul

Aquarius

Perseids

17 Jul to 24 Aug

80

109P/Swift–Tuttle

12/13 Aug

Perseus

Draconids

  6 Oct to 10 Oct

10

21P/Giacobini–Zinner

7/8 Oct

Draco

Southern Taurids

10 Sep to 20 Nov

5

2P/Encke

10 Oct

Taurus

Arids

28 Sep to 14 Oct

?

15P/Finlay

7 Oct

Ara

Orionids

  2 Oct to 7 Nov

20

1P/Halley

21/22 Oct

Orion

Northern Taurids

20 Oct to 10 Dec

5

2004 TG10 (asteroid)

12 Nov

Taurus

Leonids

  6 Nov to 30 Nov

Varies

55P/Tempel–Tuttle

17/18 Nov

Leo

Geminids

  4 Dec to 17 Dec

75+

3200 Phaethon (asteroid) 13/14 Dec

Gemini

Ursids

17 Dec to 26 Dec

10

8P/Tuttle

Ursa Minor

22/23 Dec

Quadrantids The parent object of the Quadrantids has been identified as the near-Earth object of the Amor group of asteroids 2003 EH1 which is likely to be an extinct comet. With peak rates known to exceed 100 meteors per hour, the Quadrantids rivals the August Perseids, although there is a drawback in that the period of maximum activity takes place over a very short period of between two and three hours. The radiant lies a little to the east of the star Alkaid (η Ursae Majoris) and the meteors are fast moving, reaching speeds of 40 km/s. Maximum activity occurs on the night of 3/4 January when observation may be hindered by a waning gibbous Moon.

Lyrids Produced by particles emanating from the long-period comet C/1861 G1 Thatcher – which last came to perihelion on 3 June 1861 – these are very fast moving meteors that approach speeds of up to 50km/s. The peak falls on the night of 22/23 April with the radiant lying near the prominent star Vega in the constellation of Lyra. This year the glare from a Moon almost at full phase will obscure all but the brightest meteors.

Astronomy 2024.indb 190

07/02/2023 22:41

Meteor Showers in 2024 191

Eta Aquariids One of the two showers associated with 1P/Halley, the Eta Aquariids are active for a full month between 19 April and 28 May. The radiant lies just to the east of the star Sadalmelik (α Aquarii), from where up to 30 meteors per hour are normally expected during the period of peak activity, although displays of up to 60 meteors per hour can occasionally be seen. Maximum activity occurs in the pre-dawn skies of 7 May when an almost New Moon will result in dark skies and the potential for perfect observing conditions.

Tau Herculids Appearing to originate from the star Tau (τ) Herculis, this shower runs from 19 May to 19 June with peak activity taking place on 9 June. The Tau Herculids were first recorded in May 1930 by observers at the Kwasan Observatory in Kyoto, Japan. The parent body has been identified as the periodic comet 73P/Schwassmann–Wachmann, discovered on 2 May 1930 by the German astronomers Arnold Schwassmann and Arno Arthur Wachmann during a photographic search for minor planets being carried out from Hamburg Observatory in Germany. 73P/Schwassmann–Wachmann has an orbital period of 5.36 years. During 1995 the comet began to fragment, and by the time of its 2006 return, at least eight individual fragments were observed (although the Hubble Space Telescope spotted dozens more). 73P/Schwassmann–Wachmann appears to be close to total disintegration. The observed rate of meteors from this shower is low, although with peak activity in 2024 occurring just a few days after New Moon, there is a more than reasonable chance that some meteors from this shower will be seen.

Delta Aquariids Probably linked to the short-period sungrazing comet 96P/Machholz, the Delta Aquariids is a fairly average shower which coincides with the more prominent Perseids. However, Delta Aquariid meteors are generally much dimmer than those associated with the Perseids, making their identification somewhat easier. The radiant lies to the south of the Square of Pegasus, close to the star Skat (δ Aquarii). Located to the north of the bright star Fomalhaut in Pisces Austrinus, the radiant is particularly well placed for those observers situated in the southern hemisphere. The shower peaks during the early hours of 29 July when a Moon one day after last quarter phase may slightly hinder observations of dimmer meteors.

Astronomy 2024.indb 191

07/02/2023 22:41

192  Yearbook of Astronomy 2024

Perseid meteors captured on the night/morning of 12/13 August 2021 by the UK Meteor allnight camera located in Oxfordshire, England. From the image you can see the magnitude variations of the meteors, together with the duration of each apparition, ranging from short trails lasting for a fraction of a second or so to longer trails a few seconds long. (UK Meteor Network/Mark and Mary McIntyre)

Perseids Associated with the parent comet 109P/Swift-Tuttle – and radiating from a point in northern Perseus, close to the border with the adjoining constellation Cassiopeia – the Perseids are a beautiful sight, with fast moving meteors appearing as soon as night falls and up to 80 meteors per hour often recorded. This is usually one of the best meteor showers to observe, with large numbers of very bright meteors often being seen. At the time of peak activity on the night/morning of 12/13 August, a first quarter Moon will be setting shortly after midnight, leaving skies dark enough to allow for a reasonably good early morning display.

Southern Taurids/Northern Taurids Running collectively from 10 September to 10 December, the Taurids are two separate showers, with southern and northern components, the Southern Taurids linked to the periodic comet 2P/Encke and the Northern Taurids to the asteroid 2004 TG10. Meteors from both components emanate from the western regions of Taurus, the radiant for the Southern Taurids being located a little to the north of the star Xi (ξ) Tauri – close to the border with neighbouring Cetus – and that

Astronomy 2024.indb 192

07/02/2023 22:41

Meteor Showers in 2024 193 for the Northern Taurids immediately to the south east of the Pleiades open star cluster. The southern hemisphere encounters the first part of the stream, followed later by the northern hemisphere encountering the second part. The ZHR of these showers is low (between 5 and 10 per hour), although they can be beautiful to watch as they glide across the sky. The Southern Taurids peak on 10 October when a first quarter Moon may leave only the brightest meteors visible. For the Northern Taurid peak on 12 November, the Moon will be just a few days before full phase, which means that both showers will be disappointing this year.

Arids In 1999 astronomers began speculating that a new meteor shower could be forming, with a radiant in the southern constellation Ara (the Altar) and resulting due to the Earth encountering the debris left behind by the periodic comet 15P/Finlay. In September 2021, the Central Bureau for Astronomical Telegrams (CBAT) released a circular announcing the discovery of the new meteor shower as predicted. Peter Jenniskens (SETI Institute and NASA Ames Research Center); Timothy Cooper (Astronomical Society of Southern Africa); and Dante Lauretta (University of Arizona), reported that Cameras for Allsky Meteor Surveillance (CAMS) videobased meteoroid orbit survey networks in New Zealand and Chile detected the new meteor shower. Fireballs resulting from the Earth running into the stream left behind from the 1995 return of the comet were first observed on the evening of 28/29 September 2021. Activity lasted into October with our planet encountering the debris left behind by the comet during its 2014/15 return. A total of thirteen slow moving meteors were detected during the period of visibility. The Arids is a new shower and activity will be unpredictable. Some years will see a limited number of meteors and other years perhaps showing greater activity. This is certainly a meteor shower for observers in the southern hemisphere to monitor closely. As far as the 2024 shower is concerned, at the time of predicted peak activity on 7 October the Moon will be approaching first quarter and should allow for monitoring of any activity.

Draconids Also known as the Giacobinids, the Draconid meteor shower emanates from debris left behind by the periodic comet 21P/Giacobini-Zinner. The duration of the shower is just 4 days from 6 October to 10 October, with the shower peaking on 7/8 October. The ZHR of this shower varies with poor displays in 1915 and 1926 but stronger displays in 1933, 1946, 1998, 2005 and 2012. Radiating from the “head” of Draco, the meteors from this shower travel at a relatively modest 20 km/s. The

Astronomy 2024.indb 193

07/02/2023 22:41

194  Yearbook of Astronomy 2024 Draconids are generally quite faint, but this year a waxing crescent Moon will have set before the shower starts leaving the potential for a good peak activity show.

Orionids The second of the meteor showers associated with 1P/Halley, the Orionids radiate from a point a little to the north of the star Betelgeuse in Orion. Best viewed in the early hours when the constellation is well placed, the shower takes place between 2 October and 7 November with a peak on the night of 21/22 October. The velocity of the meteors entering the atmosphere is a speedy 67 km/s. This year, a waning gibbous Moon may drown out some of the fainter Orionids, although the post-midnight skies should be dark enough to reveal some of the brighter meteors emanating from this shower.

Leonids Running from 6 November to 30 November, this is a fast moving shower with particles varying greatly in size and which can create lovely bright meteors that occasionally attain magnitude −1.5 (or about as bright as Sirius) or better. The radiant is located a few degrees to the north of the bright star Regulus in Leo. The parent of the Leonid shower is the periodic comet 55P/Tempel-Tuttle which orbits the Sun every 33 years. It was last at perihelion in 1998 and is due to return in May 2031. The Zenith Hourly Rates vary due to the Earth encountering material from different perihelion passages of the parent comet. For example, the storm of 1833 was due to the 1800 passage, the 1733 passage was responsible for the 1866 storm and the 1966 storm resulted from the 1899 passage (for additional information see Courtney Seligman’s article Cometary Comedy and Chaos in the Yearbook of Astronomy 2020). The Leonid shower peaks on the night of 17/18 November when the light from a waning gibbous Moon will block out all but the brightest shower members.

Geminids The Geminid meteor shower was originally recorded in 1862 and originates from the debris of the asteroid 3200 Phaethon. Discovered in October 1983, this rocky five kilometre wide Apollo asteroid has an unusual orbit that carries it closer to the Sun than any other named object of its type. Classified as a potentially hazardous asteroid (PHA), 3200 Phaethon made a relative close approach to Earth on 10 December 2017, when it came to within 0.069 au (10.3 million kilometres/ 6.4 million miles) of our planet. The Geminid radiant lies near the bright star Castor in Gemini and the shower peaks on the night of 13/14 December. This is considered by many to be the best shower of the year, and it is interesting to note

Astronomy 2024.indb 194

07/02/2023 22:41

Meteor Showers in 2024 195

A Geminid meteor fleetingly shares the sky with Comet Leonard, as imaged from a site near Carberry, Manitoba, Canada during the early hours of 4 December 2021. For more information on Comet Leonard, see the article Comets in 2024 elsewhere in this volume. ( Justin Anderson/ aurorajanderson.com)

Astronomy 2024.indb 195

07/02/2023 22:41

196  Yearbook of Astronomy 2024 that the number of observed meteors appears to be increasing annually. This year a Moon approaching full phase will greatly hinder observations, blocking out the light from all but the brightest meteors.

Ursids Discovered by William Frederick Denning during the early twentieth century, this shower is associated with comet 8P/Tuttle and has a radiant located near Beta (β) Ursae Minoris (Kochab). With relatively low speeds of around 33 km/s, the Ursids are seen to move gracefully across the sky. Research jointly carried out by Dutch/ American astronomer Peter Jenniskens and his colleague, the Finnish astronomer Esko Lyytinen (1942–2020), revealed that outbursts may occur when 8P/Tuttle is at aphelion due to some meteoroids being trapped in a 7/6 orbital resonance with Jupiter. The Ursids run from 17 December to 26 December with peak activity taking place on the night of 22/23 December. This year, a last quarter Moon may result in the light from many of the fainter meteors being drowned out.

Astronomy 2024.indb 196

07/02/2023 22:41

Article Section

Astronomy 2024.indb 197

07/02/2023 22:41

Astronomy 2024.indb 198

07/02/2023 22:41

Recent Advances in Astronomy Rod Hine

Unusual Galaxies Many readers will be familiar with the scheme for classifying galaxies devised by Edwin Hubble in around 1926. Based almost entirely on the appearance it suffices for most purposes, yet some galaxies fall entirely outside its remit. One such class of galaxies is the Ring Galaxy, of which a few dozen examples are now known,

Hoag’s Object. (NASA and The Hubble Heritage Team (STScI/AURA); Acknowledgment: Ray A. Lucas (STScI/AURA)

Astronomy 2024.indb 199

07/02/2023 22:41

200  Yearbook of Astronomy 2024 where typically a relatively normal-looking galactic core is surrounded by distinct rings rather than spiral arms. Discovered in 1950 by Art Hoag, the prototype for Ring Galaxies is PGC54559 in Serpens, better known as Hoag’s Object and is the cover image for this volume. Arthur Hoag was at the time studying for his PhD at Harvard under the supervision of Bart Bok, and he later went on to a distinguished career culminating in the Directorship of the Lowell Observatory in Flagstaff, Arizona, from 1977 to 1986. Hoag originally thought the ring might be the product of gravitational lensing, but later work showed that all parts of the galaxy had a similar red shift. Gravitational lensing had been discussed since the 1930s but wasn’t confirmed by observation until 1979. The beautiful image taken by the Hubble Space Telescope clearly shows the compact older yellow nucleus surrounded by an almost perfect ring of younger hot blue stars. Very little is visible in the large gap between, although there is slight evidence of very faint star clusters. The core has a diameter of about 17,000 light years and the ring an inner diameter of 75,000 light years and an outer diameter of 121,000 light years. It is in the constellation of Serpens at a distance of around 600 million light years. Just how these unusual galaxies form is far from clear. There are three major theories in play at the moment. One possibility is that a core of older stars might accrete a disc of cooling intergalactic gas which settles as a ring rather than as spiral arms. A second possibility is that a collision between two galaxies could result in the spiral arms of a larger galaxy being pushed outwards by the passage of a smaller galaxy. A third possibility is that a barred spiral galaxy might form and then the bar could become unstable and disperse, leaving the core and the outer starforming ring intact. In 2013 the Israeli astronomer Noah Brosch and a small team used the Westerbork Synthesis Radio Telescope (WSRT) at Dwingeloo, in the Netherlands, to show the existence of a huge ring of neutral hydrogen surrounding the whole object,1 leading to even more uncertainty about the origin of such galaxies. Brosch has suggested that perhaps this is an example of “bar instability” but others remain sceptical, favouring the accretion model. There are many variations within the broad classification of Ring Galaxies, including rings without any obvious central nucleus such as Zw 11 28 in this picture from HST. 1. For further details see ‘HI in HO: Hoag’s object revisited’ by Noah Brosch, Ido Finkelman et al, at arxiv.org/abs/1307.6368

Astronomy 2024.indb 200

07/02/2023 22:41

Recent Advances in Astronomy 201

Zw 11 28 ring galaxy without obvious nucleus. (ESA/Hubble and NASA)

Meanwhile it is nice to reflect on the fact that the cover image also shows, at about one o’clock inside the ring, another more distant ring galaxy that is less romantically named “SDSS J151713.93+213516.8”. An amazing coincidence that the first discovered example of a rare object should so nicely frame another similar object.

HD1 – The Most Distant Galaxy Observed so Far? An international team lead by Yuichi Harikane2 of the Institute for Cosmic Ray Research, University of Tokyo, has found a possible candidate for the most distant galaxy so far observed. Named HD-1, the team found it amongst 700,000 possible 2. For further details see ‘A Search for H-Dropout Lyman Break Galaxies at z ~ 12 – 16’ by Yuichi Harikane et al, at arxiv.org/pdf/2112.09141.pdf

Astronomy 2024.indb 201

07/02/2023 22:41

202  Yearbook of Astronomy 2024 objects in 1,200 hours of observations from the Subaru Telescope, the VISTA telescope, the UK Infrared Telescope (UKIRT) and the Spitzer Space Telescope. They were looking for very specific features in the spectrum that suggest a redshift z-factor between 12 and 13, corresponding to distance of about 13.5 billion light-years. A follow-up observation using the Atacama Large Millimetre Array (ALMA) seems to confirm this although not yet to the usual gold-standard accuracy needed to be sure. The key feature is the apparent presence of a spectral emission line of ionised oxygen (OIII) at a wavelength of 88 microns. The extreme red-shift brings this line comfortably within ALMA’s capability at 237.8 GHz but the weak signal and noise make the measurement very difficult. Being ground-based and despite The James Webb Space Telescope main mirror under being at very high altitude, construction in 2016. (NASA/Wikimedia Commons) ALMA has to peer through the atmosphere where numerous absorption lines confound the results. However, the discovery of HD-1 is so significant that it will be one of the objects soon to be studied by the James Webb Space Telescope ( JWST). Following the successful launch and deployment of the JWST it will take its impressive infrared capability to confirm whether galaxy HD1 really is 13.5 billion light-years away. Unhampered by atmospheric absorption, JWST should be able to repeat the ALMA measurements with much greater accuracy. If this is confirmed then it will surpass the current oldest known galaxy, GN-z11, discovered by the Hubble Space Telescope.

Astronomy 2024.indb 202

07/02/2023 22:41

Recent Advances in Astronomy 203

The James Webb Space Telescope – First Images The James Webb Space Telescope ( JWST) was launched at Christmas 2021 after many delays, but very soon began to thrill astronomers and the general public with the unprecedented clarity of its images. Amongst these were images of the group of galaxies known as Stephan’s Quintet in the constellation of Pegasus. Constructed from over a thousand separate image files, this composite image was captured by two of the JWST’s instruments operating in near- and midinfrared. Already well studied by the Hubble Space Telescope, the new images reveal details previously shrouded by dust. Of particular interest are the shockwaves and tidal effects that should give insights into the way these galaxies have evolved and interacted.

Stephan’s Quintet in Pegasus. (NASA/STScl)

Astronomy 2024.indb 203

07/02/2023 22:41

Recent Advances in Solar System Exploration Peter Rea

This article was written in the spring of 2022. As the missions mentioned are either active or due for launch imminently, the status of some missions may change after the print deadline. Starting with this issue of the Yearbook of Astronomy the article will look at solar system exploration from a planetary body point of view rather than mission by mission. All mission websites are listed at the end of the article.

Sun Comprising 99.8% of the mass of the solar system and with an estimated age of 4.6 billion years our Sun is just an ordinary yellowish G-type star. Its light and solar energy helped life evolve on the third planet out. That same energy will one day

On 31 August 2012, a long filament of solar material that had hitherto been hovering in the Sun’s atmosphere (the corona) erupted out into space at 4:36 p.m. EDT. Travelling at around 1,500 kilometres per second, the coronal mass ejection did not move directly toward Earth, but did connect with Earth’s magnetic environment, or magnetosphere, causing aurora to appear on the night of Monday, 3 September. (NASA Goddard Spaceflight Center)

Astronomy 2024.indb 204

07/02/2023 22:41

Recent Advances in Solar System Exploration 205 see an end to life on Earth. Even today with the Sun halfway through its life cycle, that solar energy can erupt and send huge amounts of energy toward the Earth which can seriously damage satellites in orbit and play havoc with the power grid. Astronomers called these outbursts Coronal Mass Ejections (CMEs). If we are to survive these, we need to understand why and when these events will occur. For the past few decades, satellites in orbit around the Earth and the Sun have been building up a picture of how “our star” works. A list of past and current missions can be found in the further reading section at the end of this article. I would like to single out two very recent missions which are making profound discoveries about the Sun. The NASA mission Parker Solar Probe launched on 12 August 2018 is in a highly elliptical orbit around the Sun which takes it out to the orbit of Venus and when it comes back to the Sun it passes into the solar corona. For the last year or so the perihelion distance has been around ten million kilometres, or fifteen solar radii. Using the gravity of Venus to slightly reshape the spacecrafts orbit, the Parker Solar Probe is gradually reducing the perihelion distance. By 2025, after 24 orbits of the Sun and seven flybys of Venus, the perihelion distance will be around 6.9 million kilometres, or just under ten solar radii. The European Space Agency’s mission Solar Orbiter was launched on 10 February 2020 and was placed into a highly eccentric orbit with a perihelion or closest point to the Sun of 0.28 au and an aphelion or furthest point from the Sun of 0.91 au. The perihelion brings Solar Orbiter inside the orbit of Mercury. The orbital period is around six months. The orbit is highly inclined at 24° and could be raised to 33° in a possible extended mission. The goal of the mission is to take high resolution imagery of the polar regions of the Sun, not possible from Earth and make observations of the heliosphere. Solar Orbiter will also observe the magnetic activity in the atmosphere which causes solar flares and coronal mass ejections. These observations will complement those of the Parker Solar Probe.

Mercury The first mission to Mercury was Mariner 10. Launched on 3 November 1973, it used the gravity of Venus to slingshot it toward Mercury for a first encounter on 29 March 1974 (see “Gravity Assists – Something for Nothing” in the Yearbook of Astronomy 2022). Mariner 10 returned to Mercury in September 1974 and again in March 1975. Because of the shape of the orbit around the Sun, the three flybys all viewed the same hemisphere. Nothing was known of the other hemisphere, and it was to be another 36 years before we could glimpse it. The NASA Mercury Surface, Space Environment, Geochemistry, and Ranging (MESSENGER) mission launched in

Astronomy 2024.indb 205

07/02/2023 22:41

206

Yearbook of Astronomy 2024

The joint European-Japanese BepiColombo mission captured this view of Mercury on 1 October 2021 as the spacecraft flew past the planet for the first time. (ESA/ BepiColombo/MTM)

2004 took seven years, with one Earth, two Venus and three Mercury flybys, before it was placed into orbit around Mercury in March 2011 and was the first spacecraft to orbit Mercury. It spent the next four years imaging almost 100% of the planet. This highly successful mission returned huge amounts of data. Yet questions about the history of Mercury remained open. The European Space Agency (ESA) in conjunction with the Japanese Aerospace Exploration Agency ( JAXA) put together a two-part spacecraft named BepiColombo after Giuseppi Colombo, the Italian mathematician and engineer whose work on gravity assists helped Mariner 10 and Messenger get to Mercury. BepiColombo consists of the Mercury Planetary Orbiter provided by ESA and the Mercury Magnetospheric Orbiter provided by the Japan Aerospace Exploration Agency ( JAXA). Launched on 20 October 2018, it will take the spacecraft until December 2025 to be placed into an orbit around Mercury. As with Messenger, BepiColombo will perform nine gravity assists, one of Earth, two of Venus and six of Mercury. Both spacecraft will be placed into a polar orbit with the ESA spacecraft orbiting much closer to Mercury with a 2.3 hour period and the JAXA spacecraft in a much more elliptical orbit with a 9.3 hour period. The mission website given at the end of this article gives a full account of the instrumentation carried and mission objectives.

Venus The planet Venus, often called the “morning star” or “evening star”, is the third brightest object in the sky after the Sun and the Moon. Away from city lights in a dark location it can cast a shadow. The dense atmosphere reflects a lot of

Astronomy 2024.indb 206

07/02/2023 22:41

Recent Advances in Solar System Exploration 207 sunlight and observers can see it going through phases as it travels around the Sun. That dense atmosphere also makes it very difficult to land on the surface and the very high pressure and temperature, hot enough to melt lead makes it even more difficult for a spacecraft to survive on the surface. A total of 46 spacecraft have been launched to Venus, not all of these surviving the rigours of launch and the journey to the second planet out from the Sun. Some of these missions were not specifically destined to go into orbit or land but used the gravity of Venus to slingshot them onto other destinations. Nonetheless the Venus flyby provided a good opportunity to evaluate the cameras and other instruments. At this writing there is only one spacecraft operating at the planet, a Japanese spacecraft called Akatsuki, meaning “Dawn” in Japanese. It was launched on 20 May 2010 and approached Venus on 6 December 2010. Unfortunately, the orbit insertion manoeuvre did not take place and Akatsuki flew past Venus into an orbit around the Sun. A backup plan slightly adjusted the shape of the orbit allowing the spacecraft to return to Venus on 7 December 2015. Backup thrusters were used because of a failed main engine, and these could only place Akatsuki in a very elliptical orbit with a 14 day period later reduced to 10 days. This was a more elliptical than the intended orbit, but it saved the mission. The spacecraft has been returning data ever since. Interested readers can follow the spacecraft at the mission website. ESA and NASA now have plans to return to Venus and these will be mentioned in future Yearbooks.

Moon It seems a long time ago now when, as a 17 year old I stayed up all night to watch Neil Armstrong make his “giant leap for mankind”. I never thought at the time that it would be over half a century before new boot prints would be placed on the lunar surface. In the next few years, the next man and the first woman will make that 384,000 kilometre journey to Earth’s only natural satellite. This is Project Artemis named for the sister of Apollo. Running alongside Artemis will be the NASA Commercial Lunar Payload Services (CLPS) program. The aim is to deliver an assortment of payloads to the lunar surface on a commercial basis rather than being run by NASA. The first of the CLPS missions is Peregrine Mission One using the Peregrine lander developed by Astrobotic Technology of Pittsburgh. At the time of writing this mission is due for launch the lander to the Lacus Mortis region of the Moon on the maiden flight of the Vulcan Centaur launch vehicle toward the end of 2022. More will follow and interested readers are advised to follow the CLPS website link at the end of this article.

Astronomy 2024.indb 207

07/02/2023 22:41

208  Yearbook of Astronomy 2024

A view of the proposed Peregrine lander from Astrobotics on the lunar surface. The launch will be the maiden flight of the new Vulcan Centaur launch vehicle toward the end of 2022. (Photo courtesy of Astrobotics)

Mars The so called “Red Planet” has been the centre of attention for exploration for some time and will remain so for the foreseeable future. The table below shows the current active missions at Mars, but the NASA Mission InSight may well have ceased operations by the time this publication comes out. I would like to give special mention to the NASA Perseverance rover which landed in Jezero Crater on 18 February 2021. This 45 kilometre crater is believed to have once been filled with water. A large fan delta from an ancient river penetrates the crater rim and has deposited clays and other minerals within range of the rover and will be an area of intensive study. Carried underneath the main body of the rover for the journey to Mars was an experimental helicopter. After landing, the helicopter, called Ingenuity, was lowered onto the surface. This experimental helicopter is the first time any spacecraft has flown in the atmosphere of another planet. It weighs just 1.8kg and has two counter-rotating blades that spin up to 2,700rpm. It is remarkable the helicopter can fly at all considering the atmosphere of Mars is only about 1% that

Astronomy 2024.indb 208

07/02/2023 22:41

Recent Advances in Solar System Exploration 209

This enhanced colour image of Mars’ Jezero Crater was taken by the Mastcam-Z instrument aboard NASA’s Perseverance rover on 18 April 2021. The foreground flat-topped hill, informally named “Kodiak,” is 250 metres wide and located 2.2 kilometres from the rover. It exposes ancient, layered rocks that indicate gradual deposition of sediments in a river delta, followed by floods. (NASA/JPL-Caltech/ASU/MSSS)

of Earth at sea level. It usually rises to a maximum of ten metres above the ground and at the time of writing has travelled a total of 7 kilometres during 29 flights. Ingenuity must stay within line of sight of the Perseverance rover as it cannot communicate with mission controllers back in Pasadena, California. It needs to relay data via the rover which can communicate directly with Earth or relay the

Astronomy 2024.indb 209

07/02/2023 22:41

210  Yearbook of Astronomy 2024 NASA’s Ingenuity Mars helicopter is seen here in a close-up taken by Mastcam-Z, a pair of zoomable cameras aboard the Perseverance rover. This image was taken on 5 April 2021, the 45th Martian day, or sol, of the mission. (NASA/JPL)

data through one of the orbiting satellites listed in the table which can return data at a much faster rate. Perseverance has been busy collecting samples from the coring tubes on the end of a robotic arm. These samples are being placed into special sealed tubes then cached inside the rover body. These tubes will be left on the surface of Mars for a proposed sample return mission conducted jointly by the European Space Agency and NASA. This mission is being designed for a late-2020s launch, more details of which will feature in future Yearbooks. In the meantime Perseverance continues its exploration of Jezero Crater. Mission

Origin

Type

Orbital Insertion

Mars Odyssey

USA

Orbiter

24 Oct 2001

Mars Express

Europe

Orbiter

25 Dec 2003

Mars Reconnaissance Orbiter USA

Orbiter

10 Mar 2006

Mars Science Laboratory – Curiosity

USA

Lander

Maven

USA

Orbiter

22 Sep 2014

Mars Orbiter Mission – Mangalyaan

India

Orbiter

24 Sep 2014

ExoMars – Trace Gas Orbiter Europe

Orbiter

19 Oct 2016

InSight

USA

Lander

Hope Mars Mission

UAE

Orbiter

Tianwen-1

China

Orbiter/Lander

Perseverance Rover

USA

Lander

Astronomy 2024.indb 210

Landed

  6 Aug 2012

26 Nov 2018 9 Feb 2021 10 Feb 2021

14 May 2021 18 Feb 2021

07/02/2023 22:41

Recent Advances in Solar System Exploration 211

Asteroids Occupying a region of our solar system between the orbits of Mars and Jupiter are millions of rocks. We call this region the asteroid belt. Diagrams or artists impressions of the asteroid belt are highly misleading. They show asteroids nose to nose making it impossible for any spacecraft to travel through it. In reality, the asteroid belt is mostly empty. Its total mass is only about 4% of our Moon. Pioneer 10 the first spacecraft to pass through this region never came closer than eight million kilometres to any known asteroid. See article “Diary of a Long Distant Pioneer” in the Yearbook of Astronomy 2023. It is not clear how the asteroid belt came into existence. Interested readers can type “formation of asteroid belt” into their preferred search engine for the latest research in this area. The rocky bodies making up the asteroid belt fall mainly, but not exclusively, into three groups, these being the C-type or carbonaceous, S-type or siliceous and M-type or metal-rich. Spacecraft have visited 14 asteroids so far and returned samples from two of them. The samples returned were both from carbonaceous asteroids. JAXA the Japanese Aerospace Exploration Agency returned samples of 162173 Ryugu on 5 December 2020 with their Hayabusa2 spacecraft and the NASA mission OSIRIS REx should return samples of 101955 Bennu on 23 September 2023. At the time of writing there are two missions en route to various asteroids. The Lucy mission launched in

This artist’s concept depicts the Lucy spacecraft flying past the Trojan asteroid (617) Patroclus and its binary companion Menoetius. Lucy will be the first mission to explore Jupiter’s Trojan asteroids – ancient remnants of the outer solar system trapped in the giant planet’s orbit. (NASA’s Goddard Space Flight Center/Conceptual Image Lab/Adriana Gutierrez)

Astronomy 2024.indb 211

07/02/2023 22:41

212  Yearbook of Astronomy 2024

An illustration of NASA’s Psyche spacecraft, which is targeted to arrive at the main asteroid belt in January 2026 to investigate the metal-rich asteroid 16 Psyche. (NASA/JPL-Caltech/ASU)

October 2021 will use two gravity assists of Earth to increase heliocentric velocity enabling Lucy to reach the orbit of Jupiter to study asteroids located at the fourth and fifth Lagrange points, that is 60° ahead (L4) and 60° behind (L5) Jupiter. On the way to these so-called Trojan asteroids, the spacecraft will perform a flyby of the 4 kilometre diameter asteroid 52246 Donaldjohanson in 2025. In 2027 Lucy will arrive at the L4 location where she will visit a total of four Trojan asteroids, starting with 3548 Eurybates and 15094 Polymele. These visits will be followed by flybys of 11351 Leucus and 21900 Orus, after which Lucy will change her trajectory in order to reach the next target. The spacecraft will return to the Earth for another gravity assist to send her onward to the L5 or trailing camp of Trojans in 2033 for a flyby of the binary asteroid 617 Patroclus and Menoetius. This should be a fascinating mission to follow. Unlike most other asteroids, which are rocky or icy bodies, scientists believe the M-type (metallic) asteroid Psyche is comprised mostly of nickel and iron, like the Earth’s core. A NASA mission, also called Psyche, is due to launch in the summer of 2023. On arrival at Psyche the initial orbit would be about 700 kilometres above the surface of the asteroid, gradually being reduced to about 85 kilometres. The metallic asteroid will be explored for about two years. This will be the first metallic asteroid to be explored.

Astronomy 2024.indb 212

07/02/2023 22:41

Recent Advances in Solar System Exploration 213

Jupiter Looking down on Jupiter from above it looks like another version of our solar system with a retinue of 80 natural satellites or moons, four of which are planetary size. These four moons were first recorded by Galileo in 1610 and are named Io, Europa, Ganymede, and Callisto after the lovers of Zeus ( Jupiter), the King of the Gods in Greek mythology. It is to three of these large moons that two spacecraft are being targeted – one American and one European. First to be launched is the Jupiter Icy Moons Explorer ( JUICE) mission in April 2023 followed by Europa Clipper in October 2024. The science goals of JUICE are a thorough exploration of Jupiter, Europa, Ganymede, and Callisto. Previous missions to Jupiter have indicated the possibility of a sub-surface ocean on these three moons. The Cassini mission to Saturn produced strong evidence for a sub-surface ocean on the moon Enceladus. JUICE will explore Europa and Callisto with a series of flybys and later in the mission will go into orbit around Ganymede. NASA’s Europa Clipper will concentrate solely on Europa as this is the moon with the strongest evidence for the presence of water. During its primary mission it will conduct around 50 flybys, some coming within 25 kilometres of Europa’s surface. Interested readers are

This artist’s rendering depicts the Europa Clipper spacecraft, which is due for launch toward Jupiter and its moon Europa in 2024. (NASA/JPL)

Astronomy 2024.indb 213

07/02/2023 22:41

214  Yearbook of Astronomy 2024 encouraged to visit the mission websites listed at the end of the article. At the time of writing the NASA mission Juno launched in 2011 continues to return excellent data from Jupiter. The mission website catalogues a huge number of images and other data.

Kuiper Belt and Beyond The New Horizons mission that flew past the Pluto/Charon system in 2015 and Kuiper Belt Object (KBO) Arrokoth in 2019 continues to search for other KBOs to study. The Voyager 1 and Voyager 2 spacecraft launched in 1977 continue to maintain contact with Earth, although their power levels are now dangerously low, and these long-lasting explorers of the solar system will not be able to stay in touch for very much longer. As always, Solar System exploration continues to excite and inspire, and next year promises to be no different.

Further Reading

Parker Solar Probe website: parkersolarprobe.jhuapl.edu Solar Orbiter website: sci.esa.int/web/solar-orbiter Akatsuki mission to Venus: www.isas.jaxa.jp/en/missions/spacecraft/current/ akatsuki.html Commercial Lunar Payload Services: nasa.gov/content/commercial-lunar-payloadservices Mars Perseverance Rover: mars.nasa.gov/mars2020 Ingenuity Mars Helicopter: mars.nasa.gov/technology/helicopter Lucy mission to Asteroids: lucy.swri.edu Psyche mission to Metallic Asteroid: psyche.asu.edu Europa Clipper mission: europa.nasa.gov Juice mission to Galilean Moons: sci.esa.int/web/juice Juno mission to Jupiter: missionjuno.swri.edu New Horizons mission to Pluto and the Kuiper Belt: pluto.jhuapl.edu

Astronomy 2024.indb 214

07/02/2023 22:41

Anniversaries in 2024 Neil Haggath

Sir William Huggins (1824–1910) This year sees the bicentenary of the birth of one of the pioneers of the modern science of astrophysics – yet he was an amateur with no scientific qualifications. William Huggins was born in Cornhill, Middlesex on 7 February 1824. While he bought a telescope as a boy, and learned his way around the sky, he had little scientific education, and worked in, and later took over, his family’s drapery business. At 30, he sold the business and moved to Tulse Hill in outer London, where he was able to devote himself to astronomy, building an observatory with an 8-inch refractor. In 1859, Kirchoff and Bunsen explained the dark lines in the Sun’s spectrum, discovered by Joseph von Fraunhofer, Sir William Huggins, portrait by English artist John Maler Collier, date unknown. as being due to the absorption of light (Wikimedia Commons/John Collier/ at specific wavelengths by different National Portrait Gallery) elements, and therefore identified many elements present in the Sun. Huggins reasoned that the same could perhaps be done for other stars. Together with his friend William Allen Miller, a professor of chemistry, he built a spectroscope which could be attached to his telescope. They obtained spectra of Betelgeuse and Aldebaran, and found that they contained absorption lines similar to those in that of the Sun. They soon did the same for several other stars, and published a paper in 1863, Lines in the Spectra of Some of the Fixed Stars. They were able to identify elements in the spectra, and Huggins correctly reasoned that the differences in the spectra of different stars were due to their surface temperatures.

Astronomy 2024.indb 215

07/02/2023 22:41

216  Yearbook of Astronomy 2024 Ironically, only 33 years earlier, the French philosopher Auguste Comte had cited “the chemical composition of the stars” as an example of something which could never possibly be known! In 1868, Huggins achieved another first; he realized that the spectrum of Sirius was red shifted, and determined its speed of motion. He was also a pioneer of astrophotography, and one of the first to photograph stellar spectra. Later in life, Huggins was assisted by his wife Margaret, whom he married in 1875, and who became an accomplished spectroscopist in her own right. In 1899, they jointly published the Atlas of Representative Stellar Spectra. Huggins was elected a Fellow of the Royal Society in 1865, and served as President of the Royal Astronomical Society from 1876–78. He was knighted by Queen Victoria in 1897. He died at his home on 10 May 1910, aged 86.

The Dorpat Refractor Today, every astronomer is familiar with equatorially mounted telescopes, which are rotated around an axis aligned with the North or South Celestial Pole, usually by a mechanical or electric drive, to counter the Earth’s rotation. The first such instrument was built 200 years ago. Dorpat Observatory – later renamed Tartu Observatory – was established in 1810 in Estonia, which was then part of the Russian Empire. The renowned Russian-German astronomer Friedrich Georg Wilhelm Struve (1793–1864) was its Director from 1818 until 1839. Under his leadership, the observatory was equipped with its largest and finest instrument, a 9-inch apochromatic refractor, built by the renowned German astronomer and optician Joseph von Fraunhofer (1787–1826), and completed in 1824. This was the largest refractor in the world at the time, but more importantly, it was the first telescope to be equatorially mounted

Astronomy 2024.indb 216

Janet Laidla, Director of Tartu Old Observatory, standing alongside the 9-inch Fraunhofer Refractor. (Wikimedia Commons/Elen Torb)

07/02/2023 22:41

Anniversaries in 2024 217 and equipped with a clockwork drive. Its mounting was in fact the prototype of the design which we still call a German equatorial. Among other important work achieved with the telescope, Struve measured the parallax of Vega, becoming only the second person to determine the distance of a star. Tartu Observatory remained in use until 1964, when it was replaced by a modern facility; it is now preserved as a museum, and Fraunhofer’s great refractor still exists.

Edwin Hubble and M31 In the early twentieth century, one of the biggest questions in astronomy concerned the so-called “spiral nebulae” – were they separate distant galaxies, or much smaller structures within our own Galaxy? This was the subject of the “Great Debate” in 1920 between Harlow Shapley and Heber D. Curtis. (See the author’s article ‘Anniversaries in 2020’ in the Yearbook of Astronomy 2020) The matter was finally settled a century ago this year, when Edwin Hubble (1889–1953) determined the distance of Messier 31, then known as the Andromeda Nebula, proving that it is indeed an external galaxy. This was made possible by two previous Edwin Hubble. (Wikimedia Commons/ discoveries. In 1912, Henrietta Swan Leavitt Johan Hagemeyer) (1868–1921) discovered the Period-Luminosity Relationship for Cepheid variable stars – now rightly but belatedly named Leavitt’s Law. (See the article ‘Henrietta Swan Leavitt and her Work’ by David M. Harland in the Yearbook of Astronomy 2021.) She discovered this by studying Cepheids in the Small Magellanic Cloud, which could be regarded as all at roughly the same distance from us – though no-one yet knew what that distance was. Two years later, Ejnar Hertzsprung (1873–1967) and Henry Norris Russell (1877–1957) independently developed what we now know as the HertzsprungRussell Diagram, which relates the colours of stars – which indicate their surface temperatures – with their intrinsic luminosities – thereby providing a method of determining the distances of stars which are too distant to be directly measured by parallax.

Astronomy 2024.indb 217

07/02/2023 22:41

218  Yearbook of Astronomy 2024 Using the H-R Diagram to deduce the distances of relatively nearby Cepheids, astronomers were able to calibrate Leavitt’s Law, and therefore use Cepheids as “standard candles” to determine the distances of the Magellanic Clouds and of globular clusters. Harlow Shapley (1885–1972) used them to map the size and shape of our Galaxy. As Cepheids are intrinsically extremely bright – hundreds of times the luminosity of the Sun – they can be identified at great distances. Hubble identified a number of them in M31, and deduced that its distance was 750,000 light years. That was far too small, and was later revised to over two million – but as even that initial value was far greater than the size of our Galaxy, it proved that the “nebula” is another galaxy, comparable in size with our own. His conclusion was published in The New York Times on 23 November 1924. Hubble later determined the distances of 24 other galaxies. Back in 1912, Vesto M. Slipher (1875–1969) had found that the spectra of almost all “spiral nebulae” – apart from those in what we now call the Local Group – are redshifted, showing that they are moving away from us. In 1929, by comparing Slipher’s redshift measurements with his own measurements of galactic distances, Hubble discovered that a galaxy’s velocity of recession is proportional to its distance. This was independently proposed by Georges Lemâitre (1894–1966), so it is now called the Hubble-Lemâitre Law. Hubble had in fact discovered the expansion of the Universe, one of the cornerstones of modern cosmology.

Fritz Zwicky (1898–1974) One of astronomy’s great maverick thinkers died fifty years ago – a man who was in some ways far ahead of his time. Fritz Zwicky was born in Bulgaria on 14 February 1898, of a Swiss father and Czech mother. In 1925, he took a position at the California Institute of Technology, and spent the rest of his life in the US, though he remained a citizen of Switzerland. He became Professor of Astronomy at Caltech in 1942, and was a staff member at both Mount Wilson and Palomar Observatories. In 1933, by studying the rotation of several galaxies in the Coma Cluster, Zwicky concluded that they contained far more mass than that of their visible stars. He postulated the existence of what he called in German dunkle Materie – dark matter – decades before it became a mainstream theory. The following year, he and Walter Baade (1893–1960) wrote a paper in which they coined the term “supernova”, and proposed that massive stars, after such deaths, would collapse to form what we now call neutron stars. This was only two

Astronomy 2024.indb 218

07/02/2023 22:41

Anniversaries in 2024 219 years after the discovery of the neutron, and thirty years before neutron stars were shown to exist. In 1937, he proposed the concept of galaxies acting as gravitational lenses – a phenomenon which was not observed until 1979. Much of Zwicky’s work involved galaxies, and between 1961 and 1968, he published his six-volume Catalogue of Galaxies and of Clusters of Galaxies. He was quite a polymath, and between 1943 and 1961, did important work on jet engines and rocketry. A little known fact is that he was the first person ever to launch an object into deep space! On 16 October 1957, just twelve days after Sputnik 1, he launched Fritz Zwicky. ( John McCue) an Aerobee sounding rocket into the upper atmosphere; while it didn’t reach orbit, an explosive charge in its nosecone accelerated some metal pellets to far greater velocities. It’s believed that some of the pellets exceeded the Earth’s escape velocity and went into orbits around the Sun. Zwicky was notoriously grumpy, opinionated and difficult to work with. Sadly, his personality may have contributed to him not gaining the recognition he deserved during his lifetime and beyond; Neil DeGrasse Tyson described him to TV viewers as “the most brilliant man you’ve probably never heard of ”. Yet he was also a noted humanitarian; after the Second World War, he organised the shipment of tons of scientific books to war-damaged libraries across Europe. Zwicky died in California on 8 February 1974, six days short of his 76th birthday.

Mariner 10: Three Firsts in One! Fifty years ago, a single NASA space probe achieved no less than three separate “firsts” – the first probe to fly by Mercury, the first to use a gravity assist and the first to make multiple flybys of a planet. Mariner 10 was launched by an Atlas-Centaur rocket on 3 November 1973. It was similar to the previous Mariners which had been sent to Venus and Mars, with a mass of 503 kg at launch. Its instruments included TV cameras, spectrometers, magnetometers and a plasma analyser.

Astronomy 2024.indb 219

07/02/2023 22:41

220  Yearbook of Astronomy 2024

A photo mosaic of Mercury’s southern hemisphere captured by Mariner 10 during its initial flyby of the planet in March 1974. The gaps at the top of image are due to incomplete camera coverage. (NASA/JPL)

In order to reach Mercury, the probe first had to fly past Venus, using gravity assist to propel itself onward to the latter planet – the first time this was done. For an explanation of the technique, see Peter Rea’s article ‘Gravity Assists: Something for Nothing?’ in the Yearbook of Astronomy 2022. Mariner 10 suffered several equipment problems after launch. The plasma analyser door jammed, the camera heaters failed, and most importantly, its gyroscopes failed, and it had to switch to using sightings of the Sun and Canopus to maintain its attitude, instead of inertial control. The probe flew within 6,000 kilometres of Venus on 5 February 1974, taking ultraviolet images which revealed for the first time the circulation patterns in the planet’s atmosphere. The gravity assist placed the probe into a solar orbit which was in a resonance with that of Mercury, causing it to make repeated passes of the planet at six-month intervals. The first flyby took place on 29 March 1974, with a closest approach

Astronomy 2024.indb 220

07/02/2023 22:41

Anniversaries in 2024 221 at only 703 kilometres. The first close-up images discovered many craters, and the large feature now called the Caloris Basin. It also discovered Mercury’s magnetic field. The second flyby occurred on 21 September, but at a much greater distance, over 48,000 kilometres; it was decided to save fuel for later course corrections, to enable the third flyby to be even closer than the first. The third, on 16 March 1975, had a closest approach of only 327 kilometres, resulting in images with a resolution of 140 metres. Unfortunately, all three flybys occurred over the same hemisphere of Mercury, so only about half of the planet’s surface was imaged close up. Nevertheless, despite its multiple problems, Mariner 10 was a major success. No other probe would be launched to Mercury for thirty years.

Astronomy 2024.indb 221

07/02/2023 22:41

Astronomy in Antarctica Michael Burton

Why Antarctica? Advancing the frontiers of astronomy requires the building of telescopes that are capable of measuring ever fainter radiation fluxes across the spectrum, as we seek to understand better how the planets, stars, galaxies and even the universe form and evolve. Telescopes in space are usually best suited to such pursuits, placed above the debilitating effects of the Earth’s atmosphere, which not only blocks much of the cosmic radiation reaching us on the ground, but also blurs the light when it does. However, space telescopes are extremely costly to build, with minimal opportunity to maintain, let alone upgrade, once launched. Ground-based telescopes offer flexibility and can accommodate enormous and/or complex instrumentation that is not feasible in space. Nevertheless, they remain limited by conditions at the sites where they are located. As astronomy has developed, front line observatories have

Leaving for work at Dome C! Heading to the observatory on skidoo with the twin towers of the French-Italian Concordia Station in the background. (Karim Agabi)

Astronomy 2024.indb 222

07/02/2023 22:41

Astronomy in Antarctica 223 moved to ever more remote locations around the globe, seeking high, dry and dark mountain top sites for their leading telescopes. There is no more remote a location on Earth than the Antarctic Plateau, the driest and coldest region on its surface. This is the next best place to space for many kinds of observation, as well as being far cheaper to access. Of course, operating telescopes in Antarctica presents more challenges than at temperate latitude observatories. There still needs to be a driving scientific rationale behind going to Antarctica to merit this extra effort. This article will introduce you to this great continent, its potential for astronomy, some of the telescopes that have been built there and the science they are undertaking.

The Antarctic Continent and its High Ice Plateau Antarctica is the highest, driest and coldest of the continents. It is the end of the Earth, literally as well metaphorically. As with all endeavours there, it was the

Topographic map of Antarctica showing the vast bulk of the Antarctic Plateau and the positions of the ice domes where the astronomical observatories mentioned in this article are sited. The scale bar shows a distance of 2,000 kilometres, and the colour elevation, ranging from sea level (purple) to 4,000 metres (red). Based on an original image from the United States Geological Survey. (USGS/Michael Burton)

Astronomy 2024.indb 223

07/02/2023 22:41

224  Yearbook of Astronomy 2024 last continent from where humans conducted astronomical observations. While the first astronomical discovery was actually made a century ago it has only been in the past three decades that major ventures in the field have taken place. With today’s technology astronomy is no longer difficult to pursue in Antarctica when the necessary resources are available to support it. The amount of exposed land in Antarctica is tiny and confined almost entirely to the coastal fringe. From an astronomer’s perspective it is the great ice mass of the Antarctic Plateau that draws the attention. For, while the continent is crossed by one of the world’s great mountain ranges – the Trans Antarctic Mountains – all but its highest peaks (the nunataks) are obscured from view, buried under the vast ice sheet that makes up the Antarctic Plateau. The land itself lies under several kilometres of ice, with the ice surface very gradually rising from the coast to reach over 4,000 metres at Dome A. The area of ice over 3,000 metres elevation is the size of Western Europe. This is the Antarctic Plateau. Its great extent makes Antarctica the highest continent, as measured by average elevation. It also contains the coldest and driest regions of our planet. Winter temperatures are typically around –60°C. Precipitable water vapour columns1 can fall below 0.1 mm at times, opening new windows in the spectrum into space. Of crucial importance for the conduct of astronomy is that there is little wind on top of the plateau. The wind is katabatic in origin, starting from the highest points and picking up speed as it falls towards the coast, under gravity. With an average slope of a tenth of a degree, the wind is also gentle. Over the highest parts of the plateau typical wind speeds are only 1–2 metres per second. Nearer the coast, as the gradient increases the wind speed picks up – and can lead to the ferocious storms that are a part of Antarctic folklore. The summits of the plateau, in contrast, are passive. Telescopes can be placed outside through the winter with minimal protection.

Sites for Astronomy on the Antarctic Plateau The South Pole, at 2,835 metres elevation, lies on the flank of the Antarctic Plateau. While there are better places in Antarctica for observation, the logistics of ready access have made the Pole the place where most of the astronomy has so far been 1. This is the height of the water column if the vapour is extracted from the atmosphere and converted to liquid form. For the best temperate observatory sites typical precipitable water vapour columns are around 1 mm. In contrast, humans generally live where these columns are many centimetres thick.

Astronomy 2024.indb 224

07/02/2023 22:41

Astronomy in Antarctica 225 conducted, at the US Amundsen-Scott South Pole station. Named after the famous explorers who first reached the Pole in 1911–12, the station was established in 1957 during the International Geophysical Year (IGY). Access to the site is via skiequipped aircraft from McMurdo station on the coast, with daily flights over the summer period from November to February. Concordia station at Dome C, built by France and Italy, was opened for winter operation in 2005. At 3,268 metres Dome C is one of the high points of the Plateau, where the conditions are at their most stable. Dome C is accessed by overland tractor traverses for cargo and supplies, whereas scientists are generally flown in. The highest location on the plateau is the 4,083 metre Dome A, the first visit to which was made by a Chinese team as recently as 2005. In 2009 China began the construction of Kunlun Station there, and several astronomical experiments are now underway. Kunlun is only accessed by a summer traverse; no humans have yet wintered there.

Site Conditions Two primary factors have driven much of the current interest in Antarctic astronomy – the coldest and the driest conditions found on Earth. The cold dramatically

The 10-metre diameter South Pole Telescope (SPT) under moonlight probing relic radiation from the Big Bang at microwave frequencies. (Daniel Luong-Van)

Astronomy 2024.indb 225

07/02/2023 22:41

226  Yearbook of Astronomy 2024 reduces the background sky fluxes in the infrared, whereas across the infrared to millimetre bands the dry air opens many spectral windows to observation. A host of secondary factors provide additional reasons for conducting astronomy from Antarctica. These include the stability of the atmosphere and its thin surface boundary layer, low levels of pollution and dust aerosols in the air, high cloud-free fractions, the ability to conduct continuous or long-duration monitoring, increased low-energy cosmic-ray fluxes arising from the proximity to the magnetic pole, low levels of seismic activity and the vast quantities of pure ice available as an absorber of particles. Some of these secondary factors have proven to be particularly potent. For instance, the ice is used for a neutrino detector at the South Pole (IceCube). The confinement of most of the turbulence to a thin layer at the summits of the plateau creates conditions with extraordinary good seeing, if a telescope were to be raised just a few metres above the ice.

Conducting Science in Antarctica

In Antarctica logistics determines what it is possible to do. Without pre-existing infrastructure and support capability, conducting frontier science is not possible. While an adventurer might still forge new routes across the Trans Antarctic Mountains, the age of the Antarctic hero is long over. For the modern explorer the challenges lie elsewhere, in making sophisticated instrumentation work in conditions very different to the laboratory back home. Life in a modern Antarctic station is certainly no luxury experience, but it is not arduous either. One might have to share rooms for sleeping, limit showers to two minutes, twice a week, and deal with high-altitude acclimatisation, but these merely serve to make you slightly uncomfortable. Dealing with continuous daylight in summer can be more of a problem, but this is only a matter of upsetting circadian rhythms. In one crucial aspect life has become much easier than even a couple of decades ago – communications. No-one is truly alone anymore in Antarctica through the long, dark winters. Internet video conferencing can be arranged among members of the research team, scattered around the globe, as indeed we have all become familiar with through the Covid pandemic.

Antarctic Astronomy Today

In this section we look at some of the astronomy taking place at the South Pole and two of the summits of the Antarctic plateau, Domes A and C. There are, however, many more astronomical endeavours taking place across the continent than can be covered in this brief overview.

Astronomy 2024.indb 226

07/02/2023 22:41

Astronomy in Antarctica 227

South Pole Cosmic Microwave Background Radiation (CMBR) All of space is pervaded by a relic radiation produced soon after the Big Bang. It is detected as static at microwave frequencies, emitting with a temperature of just 3° above absolute zero. This is the Cosmic Microwave Background Radiation (CMBR). Small fluctuations in the CMBR provide a probe of conditions at the birth of the Universe that led to the galaxies, stars and planets that we see around us today. Measurement of these anisotropies in the CMBR has provided the most prominent science to emerge from astronomy in Antarctica. The high precision that is required is facilitated by the stability of the microwave sky emission, a consequence of the dry conditions. The Background Imaging of Cosmic Extragalactic Polarization (BICEP) experiment aims to measure polarization of the CMBR, in particular of its B-modes. These are the components of the polarization signal that are oriented at 45° to the direction the CMBR photons are travelling. They can be generated by gravitational waves produced during the epoch of inflation in the primordial universe, when

The South Pole Telescope (left) and BICEP telescope (right) at the Martin A Pomerantz Observatory (MAPO) at the South Pole, where they are being used to measure the cosmic microwave background radiation. The Milky Way can be seen at the top right and a spectacular aurora along the horizon. (South Pole Telescope collaboration)

Astronomy 2024.indb 227

07/02/2023 22:41

228  Yearbook of Astronomy 2024 the size of the universe expanded at an exponential rate (as opposed to the nearsteady expansion rate of today). These B-modes are predicted to cause anisotropies of less than one millionth of a degree in the CMBR.2 If they could be detected it would provide a probe of this extraordinary early phase of the Universe. BICEP is now in its fourth generation (“BICEP Array”) at the South Pole. When complete it will comprise four microwave (radio) telescopes of 0.5 metres diameter with over 30,000 detectors, measuring radiation around one millimetre in wavelength. The largest telescope in Antarctica is the 10 metre diameter South Pole Telescope (SPT), working in the same waveband. In its third generation, SPT complements BICEP’s measurements of the B-mode polarization, as well as tackling several other science projects involving cosmology and the search for the first galaxies to form in the Universe. SPT also participates in the Event Horizon Telescope (EHT), a worldwide network of radio telescopes used to probe the event horizon around super massive black holes at the centres of galaxies. Millimetre-wavelength radiation is combined by the technique of interferometry to produce an image whose angular resolution is equivalent to that of a single telescope the diameter of the Earth. SPT was a key contributor to the image obtained by the EHT in 2022 of the 4 million solar mass black hole at the centre of our Milky Way galaxy, whose angular size is just 50 millionths of an arc second (equivalent to resolving a tennis ball on the Moon).

Neutrinos The IceCube Neutrino Observatory is located at the South Pole, where it uses the clear Antarctic ice as an absorber to detect neutrinos and cosmic rays over a wide range of energies. IceCube is buried deep beneath the ice, encompassing a volume of one cubic kilometre. It comprises long strings drilled into the ice that collectively support over 5,000 detector modules. The modules record (blue) Cherenkov radiation produced from the exceedingly rare encounters of neutrinos with ice or rock nuclei. The clear ice permits the blue light to traverse with little attenuation. The modules point downwards to shield from the vastly greater fluxes from downward-travelling muons (produced by interactions of cosmic rays in the atmosphere). Hence IceCube serves as a telescope for upward-travelling neutrinos, so mapping the northern skies for their cosmic sources. A set of modules at the surface (IceTop) also helps discriminate against other events that can produce particle showers. A further set of eight closely packed 2.  The deepest polarization map achieved so far by BICEP has a depth of 3μK per arc minute, close to but not yet capable of measuring this level.

Astronomy 2024.indb 228

07/02/2023 22:41

Astronomy in Antarctica 229

A schematic of the IceCube Neutrino Observatory buried deep beneath the ice at the South Pole. Strings containing the optical modules which detect the Cherenkov radiation produced by neutrino interactions are buried deep beneath the ice and just above the bedrock beneath. The size of the Eiffel Tower is shown for comparison. (Yang/IceCube/NSF)

strings at the centre of the array extends the energy range of the observatory, with the result that the telescope is sensitive to neutrinos across four orders of magnitude in energy.3 In 2018 IceCube, working with the gamma-ray telescopes Fermi (in space) and Major Atmospheric Gamma Imaging Cherenkov Telescopes (MAGIC) in the Canary Islands, made the first-ever identification of a source of both extragalactic neutrinos and high energy cosmic rays, the blazar TXS 0506+056.4 This is 3. This is from 1014 – 1018 eV. Here eV is an “electron-volt”, a unit that particle physicists typically use for measuring extreme energies. Phenomena producing optical photons are generally around an eV, so vastly less energetic. 4. Blazars are active galaxies powered by massive black holes in their cores that are also ejecting jets of matter at relativistic speeds pointed towards Earth. They are among the brightest objects known in the universe.

Astronomy 2024.indb 229

07/02/2023 22:41

230  Yearbook of Astronomy 2024

The IceCube Laboratory at the Amundsen-Scott South Pole Station. It contains the computers that collect raw data from the neutrino telescope and undertake the first stage of data processing. Events that are selected as “interesting” are then sent to the University of Wisconsin in the USA for further analysis. (IceCube/NSF).

an example of multi-messenger astrophysics in action, studying the same source by using entirely different probes, here investigating the highest energy processes in nature. IceCube has also been used to test fundamental physics, notably a phenomenon known as a Glashow resonance event in the Standard Model of particle physics. The prediction was for a particular kind of neutrino – an electron antineutrino – to be produced during a resonance reaction between an electron and a new particle postulated to exist by Glashow, the W− boson. IceCube detected an anti-neutrino with precisely this energy,5 so lending support to the Standard Model. An upgrade to IceCube is now in the planning stage – IceCube Gen2. This will involve extending the volume of the array to include eight cubic kilometres of ice, providing a more densely instrumented core, and adding a radio array on the surface which extends over 500 square kilometres. Together, these enhancements will greatly increase the rate at which astrophysical neutrinos are detected as well as the sensitivity of the telescope to finding individual cosmic sources of  neutrinos. 5.  6.3 peta-electron-volts (6.3 × 1015 eV)

Astronomy 2024.indb 230

07/02/2023 22:41

Astronomy in Antarctica 231

Dome C Observations of time variable phenomena can be hampered at temperate sites by the regular day-night cycle, especially when these might be short, transient events occurring every few days. The four-month Antarctic night of mid-winter, combined with the exceptionally stable sky conditions, offers important opportunities here.

The ASTEP telescope in mid-winter at Concordia Station, Dome C. The Milky Way runs across the right side of the photograph, with the two bright stars of the Pointers (α and β Centauri) at top and a satellite trail visible just below. A spectacular aurora runs in front of the background stars. (PNRA, IPEV, ASTEP & Marco Buttu)

Astronomy 2024.indb 231

07/02/2023 22:41

232  Yearbook of Astronomy 2024 These facets minimise the aliasing caused by the diurnal cycle and facilitate high photometric precision, needed for making detections when the changes in light level are small. This is the domain for transiting exoplanet searches, looking for small dips in the brightness of a star caused by the passage of a planet in front of it. This has provided the rationale behind the Antarctic Search for Transiting ExoPlanets (ASTEP) programme conducted at the French-Italian Concordia Station at Dome C. ASTEP began with a small (10 centimetre) telescope, which over the course of four winters measured light curves for 6,000 stars, as well as demonstrating excellent observing conditions for two-thirds of the time. The current programme now uses a 40 centimetre telescope imaging over a 1° field of view. It is being used to follow-up candidate exoplanets identified by the Transiting Exoplanet Survey Satellite (TESS) with transit durations longer than five hours and orbital periods of many days, for which the diurnal cycle makes observation difficult from temperate sites. ASTEP contributed to the discovery of the temperate Neptune-sized exoplanet TOI-1231 b, for instance. The data are also being used to aid exoplanet observations using the JWST and ESA’s future Ariel space telescopes.

Dome A and Ridge A The highest site on the Antarctic Plateau is Dome A where China operates Kunlun Station. With similar characteristics to Dome C, the initial endeavours here have also focussed on time domain astronomy. The first telescope was the 15 centimetre

Panorama of the Chinese observatory at Kunlun Station, Dome A, the highest place on the Antarctica Plateau. The first two AST3 telescopes are to left, together with the CSTAR telescope. The yellow and green buildings are the instrument and power modules of the Australian PLATO observatory. A wind turbine and solar panels can also be seen, used for power generation. (Ce Yu from Tianjing University)

Astronomy 2024.indb 232

07/02/2023 22:41

Astronomy in Antarctica 233 Chinese Small Telescope Array (CSTAR). With a fixed orientation viewing towards the South Celestial Pole, and so utilising the relatively small sky rotation to limit image smear, it produced a catalogue of 10,000 stars. This was followed by the three Antarctica Survey Telescopes (AST3) project, 0.5 metre-sized telescopes. The first two operated at optical wavelengths at Dome A, respectively. The third, intended for the infrared, is now being commissioned in China prior to deployment. Just 100 kilometres away, and 30 metres lower in elevation, is Ridge A. Here, the 62 centimetre diameter terahertz frequency High Elevation Antarctic Telescope (HEAT) was placed by the USA and Australia, taking advantage of the very driest conditions on the Antarctic plateau. HEAT uses a fixed mirror to act as a transit telescope, imaging at a pre-set elevation when a source crosses the meridian. HEAT mapped the carbon emission associated with a cold molecular cloud that is condensing out of the surrounding atomic gas, a precursor stage to the formation of new stars.

The High Elevation Antarctic Telescope (HEAT) at Ridge A, exploiting the extremely dry air to measure radiation at terahertz frequencies. The flat mirror to left directs the radiation off the main mirror to right and into the dewar containing the detectors in centre. (Craig Kulesa, University of Arizona)

Astronomy 2024.indb 233

07/02/2023 22:41

234  Yearbook of Astronomy 2024

The Infrared Some astronomical events shine brightest in the infrared due to phenomena such as self-enshrouding, dust extinction and/or low temperatures. In the first counterpart seen to gravitational waves measured from a binary neutron star merger, it was the rapid reddening due to atomic opacity and infrared spectral features that revealed the synthesis of the heaviest elements in the periodic table. Unveiling such counterparts to neutron star – black hole mergers in the future requires sensitive wide-field infrared survey telescopes. The South Pole Infrared Telescope (SPIREX) was a 60 centimetre pathfinder infrared telescope that operated at the South Pole at the turn of the millennium, imaging buried star forming regions in our Galaxy. In a waveband known as KDark (2.4µm) the extreme cold minimises the thermal radiation that dominates the background noise for a telescope on Earth. The convergence of several new technologies will soon enable high cadence surveys of the infrared sky in Antarctica. Two projects are now under development, the Kunlun Infrared Sky Survey (KISS) and Cryoscope.

The South Pole Infrared Explorer (SPIREX) telescope at the South Pole. This was used to measure infrared emission from embedded star formation complexes in the southern Milky Way. (Michael Burton)

Astronomy 2024.indb 234

07/02/2023 22:41

Astronomy in Antarctica 235

Final Words Antarctica is a land of extremes. Descriptors such as coldest, driest, highest, windiest and calmest can all be applied to the continent. It is barely a century since the first explorers ventured into the interior. The Antarctic plateau has been shown to provide the pre-eminent conditions for many kinds of astronomical observations from Earth. Antarctica remains a challenging place to work, but technology now provides ready access to its interior where sophisticated scientific experiments can be carried out. Human perceptions of the continent have not, however, caught up with recent accomplishments. While the ‘heroic age’ of Antarctic exploration is long over, it still stirs the imagination. Paradoxically, this has also limited our ability to fully exploit the unique conditions to conduct front-line science, as much of our thinking is still mired by pre-conceptions informed by the survival tales from the heroic age. The Antarctic Plateau provides sites where the ultimate Earth-based telescopes may be built, if we can find a way to build on the pioneering scientific endeavours of the past few decades and to establish the infrastructure needed to support these future grand-design facilities.

Design drawings for the proposed KISS project by China and Australia at Dome A, a 0.5m diameter infrared survey telescope. The aim is to detect time varying objects in the KDark (2.4µm) waveband, such as supernovae, protostars, dying stars and the nuclei of galaxies. ( Jon Lawrence, Australian Astronomical Observatory)

Astronomy 2024.indb 235

07/02/2023 22:41

236  Yearbook of Astronomy 2024

Further Information

For an in-depth discussion on Antarctic Astronomy, the reader might like to read a review article written by the author and published in Astronomy and Astrophysics Review: arxiv.org/pdf/1007.2225.pdf

Some Websites

BICEP Cosmic Microwave Background experiment: bicepkeck.org The IceCube Neutrino Observatory: icecube.wisc.edu South Pole Telescope (SPT): pole.uchicago.edu/public/Home.html The PLATeau Observatory (PLATO) at Dome A: web.archive.org/web/20100324134431/ http://mcba11.phys.unsw.edu.au/~plato/plato.html

Acknowledgements A great many colleagues have helped and supported me during my days as an Antarctic astronomer. I particularly want to acknowledge John Storey and Michael Ashley; we worked as a triumvirate at the University of New South Wales for over two decades pursuing the dream of building telescopes at the bottom of the world. For help in writing this article I would like to thank Tony Travouillon, Jim Madsen (IceCube), Benjamin Schmitt (BICEP), Tristan Guillot (ASTEP) and Xuefei Gong (Dome A).

Astronomy 2024.indb 236

07/02/2023 22:41

Things Fall Apart Chaos in the Solar System David Harper



Things fall apart; the centre cannot hold; Mere anarchy is loosed upon the world. William Butler Yeats, The Second Coming

Worlds in Collision? In 1950, the writer Immanuel Velikovsky published a book called Worlds in Collision in which he suggested that around the year 1500 BC, an Earth-sized chunk of material was ejected from Jupiter towards the inner Solar System. According to Velikovsky, this “comet” passed very close to the Earth, changing its orbit and triggering worldwide catastrophes which were still remembered in folklore. The “comet” subsequently settled into a circular orbit around the Sun to become the planet Venus, but not before it destabilised the orbit of Mars, which itself made several close passes of the Earth, causing further disasters. Velikovsky’s bizarre claims were met with scorn by scientists, because they violated the laws of physics. Carl Sagan was a prominent critic. But questions such as “Is the Solar System stable?” and “Have the planets always been in their current orbits?” have been the subject of research by astronomers and mathematicians since the time of Isaac Newton, and this remains an active field of study.

It’s Bad News for Mercury Classical celestial mechanics, involving algebraic manipulation of the equations of motion, has successfully explored the stability of two- and three-body systems, but it is of limited usefulness when applied to the full Solar System. All of the work that I will describe in this article is based on numerical simulations carried out on increasingly powerful computers over the past four decades. In the 1980s, two groups of astronomers, one in Europe and the other in the United States, sought to numerically integrate the orbits of the major planets to explore their dynamical behaviour over a span of up to two hundred million years. Most mainframe computers were not yet fast enough to accomplish this, so the European team, known as Project LONGSTOP, used a Cray-1S supercomputer,

Astronomy 2024.indb 237

07/02/2023 22:41

238  Yearbook of Astronomy 2024 which was the most powerful generalpurpose computer yet built. The American group took a different approach, building a customised computer which they called the Digital Orrery. This comprised ten identical “planet computer” modules, each of which could calculate the orbit of a single planet. These “planet computers” were linked together in a ring to enable them to exchange data with one another. Neither project found any evidence of chaotic behaviour over the timescales of their integrations, but they did demonstrate that the slow changes in the orbits of the planets on a scale of millions of years agreed closely with the predictions of classical Pierre-Simon de Laplace (1749–1827) investigated the stability of the Solar celestial mechanics. System without the benefit of computers. The French astronomer Jacques Laskar, ( Johann Ernst Heinsius (portrait); writing in Nature in 1989, reported that his Sergeiprivet/Wikimedia Commons own numerical experiments, covering a 200 (photograph)) million year span, showed that the Solar System is indeed chaotic on timescales of tens of millions of years. He commented that this does not mean catastrophic events such as Venus crossing the orbit of the Earth, but rather that we cannot say exactly where each planet will be in its orbit more than a few million years into the future, no matter how accurately we know their masses, positions and velocities at the present day. Laskar continued his exploration of the stability of the Solar System in the early1990s in a series of numerical integrations which greatly extended the time span of his earlier work. He described his findings in a paper in Astronomy & Astrophysics in 1994. His approach differed from Project LONGSTOP and the Digital Orrery. They had integrated the full equations of motion, but Laskar used a mathematical technique called “averaging” which allowed him to ignore the small, short-period perturbations that each planet produces on the others, to focus on the long-period effects. With this refinement, Laskar was able to run a one billion year simulation in a single day on a dedicated IBM RS6000 workstation. Running his simulations over a time span of 25 billion years, Laskar monitored the eccentricities and inclinations of the planetary orbits. Most of the planets remained in near-circular, low-inclination orbits, similar to the ones that they

Astronomy 2024.indb 238

07/02/2023 22:41

Things Fall Apart: Chaos in the Solar System 239

3D rendering of a Cray 1 supercomputer, with figures for scale. (FlyAkwa/Wikimedia Commons)

follow today. The orbit of Mercury, however, underwent large and rapid changes in both eccentricity and inclination. At one point during the simulation, Mercury’s eccentricity exceeded 0.5. Whilst this was not large enough to allow Mercury to cross the orbit of Venus, it raised the intriguing possibility that this might happen in another simulation with slightly different starting conditions. To test this idea, Laskar carried out further simulations, running a series of parallel integrations, each with the starting position of the Earth shifted by 150 metres in different directions, and then selecting the integration which yielded the largest eccentricity for Mercury. Repeating this shift/integrate/select procedure several times, he found that he could drive the eccentricity towards 1 in less than 4 billion years. He described these experiments as “guiding Mercury somewhat towards the exit”, but cautioned that in the real Solar System, “it should not be too easy to get rid of Mercury, otherwise it would be difficult to explain its presence”. However, the most likely fate of Mercury is that it will be engulfed by the Sun during its red giant phase.

In the Beginning Dramatic and rapid changes were also a feature of the very early Solar System. A team led by Kevin Walsh explored the evolution of the orbits of the four gas giants in a paper published in Nature in 2011. Building on research published a decade earlier by Richard Nelson and colleagues at Queen Mary University of London,

Astronomy 2024.indb 239

07/02/2023 22:41

240  Yearbook of Astronomy 2024 they ran simulations of the orbits of the gas giants within the proto-planetary disk of gas and dust from which they formed. In their model, Jupiter begins as a fullyformed planet at 3.5 au from the Sun, whilst Saturn is approximately a third of its present-day mass at 4.5 au. Uranus and Neptune are at 6 and 8 au respectively, and also about a third of their present-day masses. As the simulation runs forward, Jupiter’s orbit shrinks rapidly until it is only 1.5 au from the Sun after just 100,000 years. Over the same time span, Saturn doubles its mass through accretion of gas from the surrounding disk whilst maintaining its orbital distance. However, as Jupiter approaches its minimum distance from the Sun, Saturn’s orbit shrinks extremely rapidly from 4.5 au to 2 au in less than 10,000 years! At this point in the simulation, Jupiter and Saturn are locked in a 3:2 orbital resonance, and as Jupiter begins to migrate outwards, Saturn’s orbit is forced to expand in lock-step. At 200,000 years in the simulation, Uranus and Neptune are also captured into resonances, forcing their orbits to migrate outwards as well, as they continue to accrete gas from the proto-planetary disk. By 600,000 years, all four planets are at their present-day masses, and Jupiter has reached its current orbital distance at 5.2 au. The other three planets are all still within 13 au of the Sun, and locked in a series of orbital resonances similar to that of the Galilean moons of Jupiter today. Alessandro Morbidelli – one of the co-authors of the study – had already explored the next stage in the evolution of the Solar System in a paper with other colleagues in The Astronomical Journal in 2007. They began each of their simulations with the four gas giants in a similar configuration to the end state of the 2011 study, and experimented with several different scenarios: a graduallydissipating proto-planetary disk, a fifth Neptune-size gas giant, and collections of trans-Neptunian planetesimals. Many of these experiments resulted in Solar Systems that became unstable in a few tens of millions of years, with the orbits of Uranus and Neptune undergoing rapid changes when Jupiter and Saturn ALMA image of the protoplanetary disk passed through the 5:3 mean-motion surrounding HL Tauri. (ALMA (ESO/NAOJ/ NRAO)) resonance.

Astronomy 2024.indb 240

07/02/2023 22:41

Things Fall Apart: Chaos in the Solar System 241 However, in one simulation, involving a trans-Neptunian disk of planetesimals with a total mass equal to 50 Earths, both Uranus and Neptune migrated outwards from 10 and 12 au to 17 and 30 au respectively over 100 million years. Their present orbital distances are 19 and 30 au, so this may indeed be the way in which our Solar System was built.

Close Encounters of the Stellar Kind Jon Zink, Konstantin Batygin and Fred Adams considered the long-term future of the Solar System in a paper published in 2020 in The Astronomical Journal. In the first part of their study, they integrated the orbits of the four gas giants from the present day, through the period when the Sun leaves the main sequence, and into its planetary nebula phase, when it loses around 46% of its mass via stellar winds. Most of this mass loss occurs in the final million years, but this is far longer than the orbital periods of the planets, so their response is gradual and – unlike in the early Solar System – there are no sudden changes. At the end of this chapter in the history of the Solar System, the orbital distance of each planet is 1.85 times its present day value. Jupiter is orbiting the Sun where Saturn used to be, Saturn has moved almost to Uranus’s present-day orbit, and Uranus is a little way beyond Neptune’s current distance. Neptune itself orbits at 55 au. Their simulation also introduced random flyby encounters with other stars in the galaxy. They drew a 10,000 au sphere around the Solar System to define a zone where encounters with passing stars could affect the orbits of the planets. Current models of the size distribution and kinematics of stars in the galactic disk suggest that a passing star of between 0.08 and 1 solar masses would enter this zone once every 23  million years on average. They found that close stellar flybys had little effect on the Solar System before the planetary nebula phase of the integration, but after the orbits of the gas giants had expanded, they became more vulnerable to such encounters. Zink and colleagues ran ten simulations of the Solar System beyond the planetary nebula phase, each with a different random series of close stellar flybys. In all ten, the outcome was broadly the same. All four planets were ejected from the Solar System within one trillion (1012) years. The first planet was ejected after about 30 billion years, on average. They noted that there was no fixed order in which the planets were ejected, although the most frequent scenario was that the ice giants Uranus and Neptune would be removed first, followed by Saturn, and finally Jupiter. However, in one simulation, Jupiter was the first to be ejected, whilst Saturn was the first to go in two other simulations.

Astronomy 2024.indb 241

07/02/2023 22:41

242  Yearbook of Astronomy 2024

An early nineteenth-century brass orrery showing the planets out to Uranus, with their satellites. (Robert Brettell Bate (maker); Birmingham Museums Trust/Wikimedia Commons (photograph))

After the first planet was ejected, two more would usually follow within 5 billion years, leaving a single planet – most often Jupiter, but on one occasion Neptune – to follow a lonely path around the Sun for, on average, another 50 billion years before being evicted. In most cases, this final act was the result of another star passing within 200 au of the Sun.

Conclusion The present-day Solar System does not see the planets careening around like billiard balls in Velikovsky-style disaster movie scenarios, but it did undergo largescale changes in its very early history, and this will happen again far in the future. The Solar System was a fast-moving place four and a half billion years ago. Today, thankfully, it is much more sedate.

References

Applegate, J.H., Douglas, M.R., Gürsel, Y., Hunter, P., Seitz, C.H., Sussman, G.J. 1985, “A Digital Orrery”, IEEE Transactions on Computers, C-34, 822–831. Applegate, J.H., Douglas, M.R., Gürsel, Y., Sussman, G.J., Wisdom, J. 1986, “The Outer Solar System for 200 Million Years”, The Astronomical Journal, 92, 176–194.

Astronomy 2024.indb 242

07/02/2023 22:41

Things Fall Apart: Chaos in the Solar System 243 Laskar, J. 1989, “A numerical experiment on the chaotic behaviour of the Solar System”, Nature, 338, 237–238. Laskar, J. 1994, “Large-scale chaos in the solar system”, Astronomy & Astrophysics, 287, L9–L12. Morbidelli, A., Tsiganis, K., Crida, A., Levison, H.F. 2007, “Dynamics of the giant planets of the Solar System in the gaseous protoplanetary disk and their relationship to the current orbital architecture”, The Astronomical Journal, 134, 1790–1798. Nobili, A. 1988, “Long term dynamics of the outer Solar System: Review of Project LONGSTOP”, in M.J. Valtonen (ed.), “The Few Body Problem” (Kluwer Academic Publishers), 147–163. Walsh, K.J., Morbidelli, A., Raymond, S.N., O’Brien, D.P., Mandell, A.M. 2011, “A low mass for Mars from Jupiter’s early gas-driven migration”, Nature, 475, 206–209. Zink, J.K., Batygin, K., Adams, F.C. 2020, “The Great Inequality and the Dynamical Disintegration of the Outer Solar System”, The Astronomical Journal, 160, 232.

Astronomy 2024.indb 243

07/02/2023 22:41

Male Mentors for Women in Astronomy Mary McIntyre

Part two of our series covered the life of Caroline Herschel, the first high status female astronomer to be paid for her work and the first to receive royal patronage. This changed the landscape for women and during the nineteenth century there were more prominent female astronomers than ever before. In the early nineteenth century women were still not permitted to study at university or indeed even enter a library, so they often had a male mentor. It is impossible to include every female astronomer in this article; what follows is a selection. Wang Zhenyi (1768–1797) was born in China, sixteen years after Caroline Herschel. She breached feudal customs of the time and educated herself in many subjects. Her grandfather, Wang Zhefu, was her first astronomy teacher and following his death she gained extensive knowledge by studying his vast book collection. Zhenyi was known for her mathematics and astronomy and studied the mechanics of lunar eclipses using models in her garden. She had written twelve books by the time she died, aged just twenty nine. Mary Somerville (1780–1872) was born in Scotland and carved herself out an illustrious career. Her father was determined that Mary should be schooled but she was frustrated at the inequality of the teaching. In her memoirs she felt it “… unjust that women should have been given a desire for knowledge if it were wrong to acquire it.” Additionally, she “… resented the injustice of the world in denying all those privileges of education to my sex which were so lavishly bestowed on men.” Encouraged Oil on canvas painting of Mary Fairfax by her uncle she taught herself Latin and (Mary Somerville’s maiden name) in 1834 Greek so she could read science books. He by the English portrait painter Thomas assured her that many women had become Phillips. (Thomas Phillips/Wikimedia Commons) scholars before her.

Astronomy 2024.indb 244

07/02/2023 22:41

Male Mentors for Women in Astronomy 245

Scottish £10 note featuring Mary Somerville. This bank note was issued in 2017. (Image courtesy of Royal Bank of Scotland, 175 Glasgow Road, Edinburgh)

Her first husband didn’t approve of her education, but following his death in 1807 she continued studying. She loved to spend her time solving mathematical problems and was awarded a silver medal 1811 after solving a Diophantine problem. In 1812 she married her second husband and he encouraged her studies. Mary became maths tutor for Ada Lovelace, and both became acquainted with Charles Babbage. She became famous when she translated and expanded the five volumes of PierreSimon Laplace’s series Mécanique Céleste. It was published in 1831 to great acclaim because she had translated Laplace’s work from algebra into common language. Maria Mitchell and her student Mary Whitney in the Vassar College Observatory, about 1877 by Eva March Tappan. (Eva March Tappan/ Wikimedia Commons)

Astronomy 2024.indb 245

07/02/2023 22:41

246  Yearbook of Astronomy 2024 Mary published books on geography and microscopy and in recognition of her eminence in science and literature the Crown granted her a civil pension of £200. In 1834 Mary was elected honorary member of several societies. Oxford University’s Somerville College is named in her honour and her image was featured on the Royal Bank of Scotland £10 note in 2017. Maria Mitchell (1818–1889) was born in Nantucket, Massachusetts. Maria and her nine siblings were brought up in the Quaker religion, which fostered an atmosphere of equality. Her father was a teacher and amateur astronomer and educated all of his children in science Maria Mitchell’s telescope, as displayed at the and astronomy. Smithsonian National Museum of American Maria attended a local grammar History. (Dpbsmith/Wikimedia Commons) school, but when she was eleven, her father founded his own school. She began to study there and worked as a teaching assistant. In 1835 Maria founded her own school which trained girls in mathematics and science. Education was still segregated at this time, but Maria made the controversial decision to allow non-white pupils to attend her school. Maria showed a natural talent for astronomy and thanks to her father she knew how to use a variety of astronomical equipment. In 1836 she began working as first librarian of the Nantucket Atheneum. The limited operating hours gave her time to work alongside her father doing observations and calculations for the US Coast Survey. They worked in a small rooftop observatory where they looked for nebulae, double stars and lunar occultations. On 1 October 1847 Maria discovered comet 1847 V1 (modern designation C/1847 T1), also known as “Miss Mitchell’s Comet”. This discovery made her famous and earned her a gold medal from the King of Denmark. Despite not having a university education, Maria was appointed Professor of Astronomy at Vassar in 1865, thus becoming the first ever female professor. She was paid much less than her male peers. Maria defied the belief that women should not observe at night because the cold night air was feared to be “… dangerous to the delicate female disposition …” and she took her female students out after dark for observing practice.

Astronomy 2024.indb 246

07/02/2023 22:41

Male Mentors for Women in Astronomy 247 Maria’s observations were widely published and she continued her research during retirement. She left behind an incredible legacy. A crater on the Moon was named after her and she was inducted into the National Women’s Hall of Fame in 1994. Elizabeth Brown (1830–1899) was the daughter of Thomas Brown, a keen astronomer and meteorologist. He introduced Elizabeth to science and she assisted him with meteorological and astronomical observations. Although Elizabeth focused on solar observing and producing meticulous sunspot sketches, she also observed many other astronomical objects, publishing her work in several journals. She was one of the first women to have her own observatory and was the first to be photographed in one.

Sunspot sketches by Elizabeth Brown, from the British Astronomical Association Solar Section report of July 1893. Elizabeth was the first director of the BAA Solar Section and she created meticulous sketches of sunspots. (British Astronomical Association, BAA Memoirs, 1, 1893, plates 1 and 2)

Astronomy 2024.indb 247

07/02/2023 22:41

248  Yearbook of Astronomy 2024 From 1871 until her father’s death in 1883, Elizabeth took over her father’s meteorological observations. Following his death she became a member of Liverpool Astronomical Society and was soon appointed as head of their solar section. In 1890 Elizabeth was instrumental in the formation of the British Astronomical Association (BAA), a society which, unlike the Royal Astronomical Society (RAS), accepted female members. She became Director of the Solar Section but also assisted several other sections. She travelled the world, including trips to observe three solar eclipses. She sadly died whilst still planning her fourth eclipse trip. Elizabeth Isis Pogson (1852–1945) was born in Oxford, England. Her father, Norman, was an accomplished astronomer and was director of the Radcliffe Observatory in Oxford. In 1860 her father was appointed as Government Superintendent of the Madras Observatory, so Isis relocated there with her parents, with Isis working as his assistant and as a “computer”. When her father died in 1891 she was appointed director in his place. Isis was the first woman to be nominated to be elected a Fellow of the RAS, but her nomination was unsuccessful because of a legal quibble over the male pronouns used in their founding charter. In 1892 a secret ballet was held regarding a rule change, but it was unsuccessful, with one Fellow commenting this was simply a proposal to introduce social dancing to the meetings. Isis was successfully elected in 1920 following a change of the rules. Mary Proctor (1862–1957) was born in Ireland and moved to Missouri in 1881. She was taught astronomy by her father, the English astronomer Richard Anthony Proctor, and is known to have observed solar eclipses. Her father was an astronomy populariser, writer and lecturer. Mary assisted him with his observations from a young age and she helped to look after his library and proof read his books. Together, Mary and her father founded the science magazine Knowledge: An Illustrated Magazine of Science in 1881. Mary taught astronomy in private schools while she studied at University, but later forged a career as an astronomy lecturer. She was a prolific writer, particularly well known for her articles and books aimed at children; she became known as the Children’s Astronomer and a lunar crater was named in her honour. By the late-1800s women were taking jobs that did not require physical strength, and were deemed by men as being suitable for the “essentially docile female mind”. From the mid-1800s several women’s colleges were founded in the UK, so women could finally get a university education, but at many universities in the UK women were not actually allowed to graduate until the 1920s. Imagine putting in all that work and expense yet at the end of it not officially graduating! Women were

Astronomy 2024.indb 248

07/02/2023 22:41

Male Mentors for Women in Astronomy 249 also studying at post-graduate level, and in 1893 Dorothea Klumpke Roberts became the first lady to be awarded a doctorate in astronomy in Paris. Two male mentors who had a huge impact on women who wanted to become astronomers were Professor Edward Charles Pickering from Harvard College Observatory and Sir William Christie from the Greenwich Observatory. Both gave women the opportunity to become “lady computers”, i.e. ladies who did calculations and analysed photographic plates and spectra, captured by men at night. Over the years over forty women worked as computers for Pickering, a group very unkindly referred to as “Pickering’s Harem”.

Dorothea Klumpke Roberts, c.1886. Dorothea was the first woman to be awarded a doctorate in astronomy. (Unknown author/Wikimedia Commons)

The Harvard Computers, c.1890 at the Harvard College Observatory. The group included Henrietta Swan Leavitt, Annie Jump Cannon, Williamina Fleming and Antonia Maury. Over 40 female computers were employed by observatory director Edward Charles Pickering. (Harvard College Observatory/Wikimedia Commons)

Astronomy 2024.indb 249

07/02/2023 22:41

250  Yearbook of Astronomy 2024 Pickering believed women were capable of the work but also knew that he could pay them far less than men. Dr Henry Draper’s widow Mary wanted to continue her husband’s work studying the chemical composition of stars so she donated money and equipment to help pay for the computers. Nettie Farrar had originally

The photographic plate on which Williamina Fleming discovered the Horsehead Nebula in 1888. As women were not expected to work at night the photographic plate was produced by William Henry Pickering, brother of Edward Charles Pickering. The analysis and discovery was by Williamina, but the first Dreyer Index Catalogue failed to credit her with it. (Plate B02312, Harvard College Observatory, Photographic Glass Plate Collection)

Astronomy 2024.indb 250

07/02/2023 22:41

Male Mentors for Women in Astronomy 251 begun work on the Henry Draper Catalogue but she had to give up work when she got engaged. Williamina Paton Stevens Fleming (1857–1911) was one of the founding members of the Harvard lady computers. She was born in Dundee, Scotland but emigrated to the USA in 1878 and worked as a maid for Pickering. He realised she had talents beyond her current position so he invited her to work at the observatory, where she devised a better stellar classification system; work that led to her being elected as a Fellow of the RAS in 1907. During her career Williamina discovered 59 nebulae, the most notable being the Horsehead Nebula in Orion. She also discovered white dwarfs, 310 Henrietta Swan Leavitt in middle age, exact variable stars and 10 novae. Asteroid 5747 date of image unknown. Henrietta worked as a Harvard Computer from 1902 until Williamina was named in her honour, 1921, and discovered the period-luminosity along with a lunar crater. relationship in Cepheid variable stars. Antonia Maury (1866–1952) was (Unknown author/Wikimedia Commons) Henry Draper’s niece and a graduate of Vassar College. She worked as a Harvard Computer from 1888 until 1933, working on reclassifying some of the stars published in the Henry Draper Catalogue. Henrietta Swan Leavitt (1868–1921) was born in Lancaster, Massachusetts. She received her bachelor’s degree in 1892 and went on to work as a Harvard Computer from 1902 until 1921. She measured variable star magnitudes on photographic plates and catalogued them. She discovered the Period-Luminosity relationship of Cepheid Variables; this had a huge scientific impact for cosmology for their application as “standard candles”. Asteroid 5383 Leavitt and a lunar crater were named in her honour. Annie Jump Cannon (1863–1941) was born in Dover, Delaware. Her first astronomy teacher was her mother, who encouraged Annie to pursue a career in astronomy. She graduated with a physics degree in 1884 and worked as Harvard Computer from 1896 until 1940. She classified the spectra of over 225,000 stars and went on to simplify and redesign the stellar classification system devised by Williamina Fleming. She was the first professional female astronomer to directly study variable stars at night.

Astronomy 2024.indb 251

07/02/2023 22:41

252  Yearbook of Astronomy 2024 The Royal Greenwich Observatory also employed some female computers. To be a computer, a woman needed to have studied to degree level. This was not the case for the male employees, who could be employed straight from school and with no qualifications! Annie Scott Dill Maunder (1868–1947) worked as a Greenwich computer from 1890 until 1895 and was one of the first women in England to be paid to work in astronomy. Annie and her husband Walter photographed sunspots, including the “giant sunspot of July 1892”, the largest sunspot ever recorded from Greenwich at that time. They also discovered the 22-year solar cycle. In 1894 Annie became Annie Scott Dill Maunder, 7 December 1931. She was the first lady computer at the Royal the editor of the BAA Journal. After she Greenwich Observatory, working from left, it was another forty years before 1890 until 1895, and becoming one of the another female astronomer was hired first women in England to be paid to work in astronomy. (Lafayette/National Portrait there. Whilst many lady computers had great Gallery/Wikimedia Commons) careers, the work they carried out was mostly assigned to them by their male colleagues. There was little opportunity for further education, promotion or career advancement; the “glass ceiling”1 was very much in place. In the years since the lady computers there have been numerous female shining lights in astronomy, but they have faced many challenges. Cambridge University did not accept females until 1947 and Queen’s College at Oxford University did not 1. The Glass Universe, Dava Sobel, 4th Estate (2016). The book title is a play on the term “glass ceiling”; i.e. the invisible barrier that prevents women from being offered the same promotional opportunities as their male colleagues. The Glass Universe tells the story of the remarkable women who worked as “Lady Computers” at Harvard College Observatory. These women performed calculations and analysed stellar spectra and photographic plates that were captured at night by men. In so doing, they made remarkable discoveries that completely revolutionised our understanding of the stars and cosmology. Whilst the women themselves were constrained by the glass ceiling, their discoveries smashed through it and up to the Glass Universe.

Astronomy 2024.indb 252

07/02/2023 22:41

Male Mentors for Women in Astronomy 253 accept them until 1979 – four years after the Sex Discrimination Act! Women still face prejudice today, and a gender pay gap still exists in many institutions. As of 2021, the membership statistics of the International Astronomical Union showed that, in the 55 to 100 age bracket 14% were female, the figure being 31% for the 25 to 55 bracket. Perhaps there have been more opportunities available to younger women. It may also suggest, however, that the glass ceiling is still very much in place, and that women are not being given opportunities for promotion to senior positions later in their career. We are still a long way from equality, although things are improving. The message to the amateur or professional female astronomers reading this article is to get involved with outreach activities for younger audiences. Our young girls need positive female role models, and you could just be the spark that ignites the passion of a promising young female who dreams of a career in astronomy.

Astronomy 2024.indb 253

07/02/2023 22:41

Communicating From the Edge of the Solar System A Very Long Distance Phone Call Peter Rea

Introduction I spoke to my daughter recently. Nothing unusual with that I hear you say. However she is on the other side of the world in Australia and it requires our voices to be sent about a tenth of the way to the Moon and back again via a communication satellite positioned above the equator. There is hardly any delay and we can speak quite comfortably without crashing into each other’s sentences. There was a noticeable delay when the mission control in Houston spoke to the Apollo astronauts on the Moon. It took the signal about a second to travel from the Earth to the Moon. However, communicating with spacecraft at the edge of the Solar System can take many hours for a one way trip and presents unique challenges which will now be discussed.

The Deep Space Network The NASA Deep Space Network (DSN) is operated by the Jet Propulsion Laboratory in Pasadena, California. It consists of three sites spaced roughly 120 degrees of

Photo of the 70-meter antenna at the Goldstone Deep Space Communications Complex in the Mojave Desert in California, officially named Deep Space Station 14. This complex is one of three comprising NASA’s Deep Space Network, the others being at Madrid, Spain and Tidbinbilla near Canberra, Australia. (NASA/JPL)

Astronomy 2024.indb 254

07/02/2023 22:41

Communicating From the Edge of the Solar System 255

Deep Space Station 43 is the 70-meter radio antenna at the Deep Space Network’s Canberra facility in Australia. It is the only antenna that can send commands to the Voyager 2 spacecraft. (NASA/Canberra Deep Space Communication Complex)

longitude apart, the sites being Goldstone Deep Space Communications Complex located close to Barstow in the Mohave Desert in California; Madrid Deep Space Communications Complex located about 60 kilometres from Madrid in Spain and the Canberra Deep Space Communications Complex located at Tidbinbilla, around 20 kilometres from Canberra in Australia. From these locations a spacecraft in deep space will be above the horizon of at least one of the sites. Each site consists of one large 70-metre dish and some smaller 34-metre dishes. For communication to Voyager and New Horizons at the edge of the solar system, only the larger dishes can pick up the very weak signal. These dishes can, if required, be arrayed (linked) with the smaller 34-metre dish to assist in picking up these weak signals. When Voyager 2 passed Neptune in 1989 the gravity of Neptune deflected the path of Voyager 2 downwards below the plane of the Solar System so only the Canberra 70-metre dish in the southern hemisphere can communicate with Voyager 2. The Deep Space Network website is at deepspace.jpl.nasa.gov

Astronomy 2024.indb 255

07/02/2023 22:41

256  Yearbook of Astronomy 2024

As the Earth rotates at least one large antenna will be able to “see” the spacecraft, with slight overlaps. (Peter Rea)

Getting Data Back to Mission Control To give an idea of the technical difficulties when communicating with spacecraft at the edge of the solar system consider that Voyager 1 and 2 use a 22 watt transmitter. I have two LED lamps on my desk – their total consumption is about that. As the signal from Voyager 1 starts is long journey back to Earth it progressively spreads out. Even from Saturn, about a quarter of the way to Pluto, the beam has spread out to around 100 Earth diameters. By the time the faint signal reaches a DSN antenna that 22 watt output has been reduced to a billion-billionth of a watt. Once received at one of the DSN antennas, a ground communications facility provides communications via landlines, submarine cable, microwave links and communications satellites linking the three complexes to the operations centres at JPL, for Voyager or the Applied Physics Laboratory for New Horizons. All communications have primary and backup routes to ensure time sensitive data can always get to and from the DSN stations. To view which DSN dishes are currently in use and with which spacecraft they are communicating, visit the Deep Space Network Now website at eyes.nasa.gov/dsn/dsn.html

Astronomy 2024.indb 256

07/02/2023 22:41

Communicating From the Edge of the Solar System 257

New Horizons Emergency The New Horizons spacecraft, after many years of planning, arguing over funding, designing, and building, was due to fly past the Pluto/Charon system on Tuesday 14 July 2015. After a journey of 5.2 billion kilometres taking almost ten years, the end game was only a few days away. Many of the engineers had spent the best part of their professional careers on this mission. With just 10 days to go before the encounter most Americans were out celebrating the 4 July Independence Day weekend. Off duty mission engineers were with their families. The burgers, hotdogs and beer were consumed with vigour. The “core load” of final instructions was being transmitted to New Horizons on this Saturday, 4 July. This large file took four and a half hours to reach New Horizons, and many hours to send the whole file. All the coding had been completed some time ago. The updated timings on when and where New Horizons should point the cameras and spectrometers were all included. Press the “send” button and you have nine hours to wait before confirmation that these data have started to arrive aboard the spacecraft. Time, perhaps, for another beer and hotdog. Then, just before 2.00 pm, the signal from New Horizons suddenly stopped. The DSN station in Australia (the one communicating with New Horizons at the time) was contacted to check their system configuration and settings. Was the fault down here on the ground? The answer soon came back that the issue was not with the DSN. They were simply not receiving a signal from New Horizons. The core load was due to start running the spacecraft in three days – 7 July – for the close approach science and a final look for small moons or debris that could pose a threat. The MOC had a scant 72 hours to get New Horizons signal back, made

The Deep Space Network has three sites spaced approximately 120 degrees of longitude apart to provide continuous coverage as the Earth rotates. (Peter Rea)

Astronomy 2024.indb 257

07/02/2023 22:41

258  Yearbook of Astronomy 2024

New Horizons Principal Investigator Alan Stern of Southwest Research Institute celebrates with mission flight controllers after they received confirmation from the spacecraft that it had successfully completed the flyby of Pluto – on Tuesday 14 July 2015 – in the Mission Operations Center at the Applied Physics Laboratory, Johns Hopkins University, Howard County, Maryland. (NASA/Bill Ingalls)

more difficult by the nine hour send and return time. The speed of electromagnetic radiation is incredibly fast but when you have a spacecraft emergency at the edge of the solar system and have three days to fix it, it must seem agonisingly slow. It was surmised in the Mission Operations Center (MOC) that receiving the upload of the large file and running a programme to compress some recently taken images to free up memory may have overloaded the main computer. If that were the case then New Horizons would automatically stop what it was doing, switch to a backup computer and phone home for instructions. Engineers call this going into safe mode. If that was the case, then in a few hours the MOC should receive that phone home signal. After a tense wait, that signal did arrive confirming New Horizons was in safe mode and working off the backup computer. At least they were back in contact. It cannot be over emphasised the pressure the MOC was under. They only have three days to get the core load running – time was not on their side.

Astronomy 2024.indb 258

07/02/2023 22:41

Communicating From the Edge of the Solar System 259 Studying the telemetry indicated that the core load had been erased when the spacecraft re-booted on the backup computer. The MOC had to get New Horizons to switch to the primary computer and discover if any more software had been erased or corrupted. Doing this on your own computer can be time consuming, so try doing it with a nine hour communications round trip. Working in shifts around the clock the switch to primary computer was achieved and the core load sent again to New Horizons. Some of the approach science was dumped to allow controllers full access to the main computer and have New Horizons keep the antenna pointing back to Earth. New Horizons did not have a moveable camera so any picture taking required the antenna to be pointed away from Earth to allow cameras to point at the target. After three days – and just in time on the 7 July – the core load started the approach science with seven days left to encounter. The New Horizons mission had come dangerously close to missing the Pluto encounter. Cool heads saved the day, and the rest is history. The New Horizons website is at pluto.jhuapl.edu

Communication Times To get a feel of the time needed to send a signal one way to the edge of the Solar System consider that it currently (at time of writing) takes nearly seven and a half hours to reach the New Horizons spacecraft, far beyond Pluto; just over 18 hours to reach Voyager 2; and nearly 22 hours to reach Voyager 1. It is much quicker to phone my daughter in Australia. These times are increasing all the time. For live updates of distance to Voyagers 1 and 2 visit voyager.jpl.nasa.gov/mission/status The Voyager Mission Website can be found at voyager.jpl.nasa.gov New Horizons distances are available on the mission website listed above.

Further Reading

Uplink-Downlink: A History of the Deep Space Network, 1957-1997 (The NASA History Series) by Douglas J. Mudgway, 2001 Chasing New Horizons: Inside the Epic First Mission to Pluto by Alan Stern and David Grinspoon, 2018 Planets Beyond: Discovering the Outer Solar System by Mark Littmann, 1988

Astronomy 2024.indb 259

07/02/2023 22:41

Skies over Ancient America The Evolution of Ancient Skywatching as Cultures Move Northward in the Americas P. Clay Sherrod

In the first part of this article – published in the Yearbook of Astronomy 2022 – we identified and summarized the earliest organized cultures in the western hemisphere and the state of technological advancement in some of those diverse groups. Their obsession with the night (and day) sky came from a natural curiosity of the heavens and what the orbs of the heavens must mean to the humans below. However, as the mental logic of early American cultures advanced, so did their skills in domestic agriculture, and their ability to predict the annual migrations of animal for both food and resources. Part 2 of ‘Skies over Ancient America’ discusses our attempts to study huge stone-covered earthen mounds, calendar monuments and whether or not all of these are indeed predictors of the passages of the seasons or, as we assume in many prehistoric cultural sites, merely a coincidental arrangement that modern mankind “wants to believe” are ancient celestial time pieces.

In the Americas North of Mesoamerica Prehistoric Site Astronomical Alignments – Intended or Coincidental? Hundreds, if not thousands, of archaeological sites have been reported to have some indication that a worship or study of the sky was of importance to those who built them. Certainly we have learned that agriculture – including knowledge of the coming of planting season, impending drought periods and the first frost – plays a great role in community development, as it did in the early Americas, and a calendar is essential to understanding when those times are approaching. But does every archaeological site – from bluff shelters, to mound communities, to tribal cities – have to demonstrate some association with the sky? Are many of those reported actual calendar sites, or do they perhaps simply coincidentally show random alignments that happen to fall on the rising and setting of stars, planets, the sun and moon?

Astronomy 2024.indb 260

07/02/2023 22:41

Skies over Ancient America: The Evolution of Ancient Skywatching  261

The rising of a bright planet, moon or sun against a foreground object could have been used as mankind’s first astronomical calendar. (Clarke L. Sherrod)

Astronomy 2024.indb 261

07/02/2023 22:41

262  Yearbook of Astronomy 2024

Surveying position angles via neighbourhood houses in Memphis, Tennessee. (P. Clay Sherrod)

To accept this coincidence is very simple. Imagine that it had been suggested that a neighbourhood group of houses – say 150 homes – were aligned to the rising and setting of stars. Without prior identification of the rising and setting of any stars at all, we can stand on the rooftop of OUR home in the subdivision of homes and watch throughout the year with this preconceived idea. As we scan the east and west over the course of 365 days, we can see actual “alignments” of nearly ALL of the bright stars in our skies during rising and setting of these orbs over one of our neighbours’ homes. Did the developer actually build all these houses with a transit from my rooftop so that they would align to the azimuths of those stars? Of course not; this is random coincidence, just as the huge posts at Cahokia and the stones in the medicine wheels (discussed below) may be.

Solstice Markers Throughout the western hemisphere are markers of one type or another that prehistoric cultures may have concocted to mark the exact dates of winter and summer solstice, or the east and west rising and setting positions of the sun on the Equinoxes. Every local rock art site is reported to have “sun signs” and shadows marking these exact dates, only for us to find that most are deemed coincidental or happenstance at best. There are some exceptions, and only a selection of the most notable of these is given here. Many on-line resources are available discussing sites across the globe as can be seen at archaeoastronomy.com/usa.html

Astronomy 2024.indb 262

07/02/2023 22:41

Skies over Ancient America: The Evolution of Ancient Skywatching  263

Mayan at Chich’en Itza The Pyramid of Kukulcán (often referred to as just Kukulcán) – and known to the Spanish Conquistadors as El Castillo – is the main and most prominent of the structures at Belize’s Chichen Itza. The location of the mound in terms of importance was in use long before El Castillo was constructed, it being built over a pre-existing temple that occupied the site during the ninth century. It is the biggest pyramid in Chichen Itza, its base measuring 53.3 metres wide on all four sides. The sides of this monument are steep, with steps covering all four sides; the top temple, at 24 metres high, towers above the other stone structures, and on the flat top terrace was constructed a 6-metre temple. Upon completion in around AD 800, the view from the top temple was so grand that – on a clear day – the top of the grand pyramid at the neighbouring city of Ek Balam can be seen. No matter what the legend may or may not have been, some incredible engineering and symbolism combine with the natural seasons of the Earth to

Shadows develop the form of a writhing serpent descending the El Castillo mound at Chichen Itza. Each of the four sides of El Castillo has 91 steps ascending it – a total of 364 steps; if the flat observing surface and temple platform of the structure is also counted as a step, the total number of steps for this ceremonial structure is equal to the number of days between each seasonal equinox, spring to spring and/or autumn to autumn. (Pyramidomania.com)

Astronomy 2024.indb 263

07/02/2023 22:41

264  Yearbook of Astronomy 2024 create an unmistakable – and occasionally disturbing – image of a giant snake crawling down the temple. For five hours an illusion of light and shadow creates seven triangles on the side of the staircase starting at the top and inching its way down until it connects the top platform with the giant stone head of the feathered serpent at the bottom. Twice yearly – for 45 minutes at each equinox – the impressive shadow cast from the steps remains in its entirety before appearing to actually slither downward, descending the pyramid and eventually disappearing.

North American at Chaco Canyon Chaco Canyon in New Mexico is a result of wind and water erosion which has carved out one of the most spectacular of all south-western United States landmarks. The resulting canyon runs northwest to southeast and is the home of dozens of significant North American native cultural sites, notable among them the Anasazi, or Pueblo, of rock art fame. Not all western US rock art is of Anasazi origin, although tens of thousands of glyphs were left by these people alone as they ventured into a new world, probably in around 6,000 BC. The centre of their activity some 1,500 years ago was what is today Utah and New Mexico. Most are anthropomorphic figures, likely self-portraits

The remarkable geological feature known as Fajada Butte can be seen for many miles in all directions, and seems an ideal location for securing the importance of the intricate Sun Dagger of the south-western United States indigenous people. (Wikimedia Commons/Rationalobserver)

Astronomy 2024.indb 264

07/02/2023 22:41

Skies over Ancient America: The Evolution of Ancient Skywatching  265 Fajada Butte features a dagger of sunlight which pierces surrounding stones and travels across the middle of this carved spiral petroglyph. (Public Domain, State of New Mexico)

of hunting and dramatic incidences of daily life, but others are curious geometric shapes among zoomorphic symbols and some might represent images of the night sky, comets and even solstice calendars. Such is the case at Fajada Butte (Banded Butte), which rises prominently out of the rugged desert terrain just a few kilometres from the complex of Anasazi sites, which includes Pueblo Bonito, Kin Kletso, and Chetro Ketl. During the times around the summer solstice, the sun sets roughly behind Fajada Butte as seen from Pueblo Bonito.

Diagrams showing the aspects of the Fajada Butte Sun Dagger at solstices and equinoxes. (US National Park Service)

Astronomy 2024.indb 265

07/02/2023 22:41

266  Yearbook of Astronomy 2024 On the flanks of Fajada Butte is the Sun Dagger, a now-infamous spiral petroglyph carved in the cliffs and surrounded by huge jagged breakdown boulders. On the summer solstice – the longest day of the year on or around 21 June – a daggershaped streak of light shines between the breakdown boulders and can be seen to precisely cross the centre of the carved spiral. At the times of the spring and fall equinoxes, yet another streak of light will appear on the petroglyph face, halfway between the centre and outer circle of the spiral. To make this likely calendar marker even more complex, during the winter solstice – the shortest day of the year – a pair of daggers touches the left and right outer lines of the spiral, yet they do not A human figure standing beneath a figure enter the spiral itself. of the sun, depictions of this nature being However, as is the case with many very common in Anasazi/Pueblo rock art. significant archaeological sites across the (P. Clay Sherrod) world, the Fajada Butte sun dagger is no longer functioning in its original state, as it was when discovered by American artist Anna Sofaer in 1977. Heavy human traffic – and perhaps the wear and tear of a thousand years – has resulted in significant shifting of the huge rock slabs that shadow the petroglyph, and the phenomenon has been lost to modern observers. The importance of the sun to the ancient people of Chaco Canyon was not reserved for just this one calendar site however; many “medicine wheels” (see below) and pictographs/petroglyphs showing human figures aligned with indisputable sun figures are seen to dominate the landscape.

Calendar Circles Henges In the 1960s, archaeologist Melvin L. Fowler (1924–2008) of the University of Wisconsin, Madison led a team of student excavators on what started as a routine study of what was thought to be a heavily populated living area west of the huge Monks Mound at the Cahokia Mound Site in Collinsville, Illinois (see description

Astronomy 2024.indb 266

07/02/2023 22:41

Skies over Ancient America: The Evolution of Ancient Skywatching  267 following). In addition to finding considerable lithic debris throughout the large area, there was evidence of hundreds, if not thousands, of wooden posts which had left their characteristic circular colour within the excavated earth. Such posts were used throughout the site for housing construction, tanning and other applications. However, seemingly scattered among those many posts were a considerable number that did not appear to have any reasonable purpose. They were huge – up to a metre across – and he quickly unearthed enough of them for fellow archaeologist Warren Wittry (1927–1995) to suggest they represented the circular feature now known as the Cahokia Woodhenge, an American equivalent of the ancient Stonehenge in Wiltshire, England. The “woodhenge” label not only stuck to these features, but opened the way for subsequent “discoveries” of similar wooden circles throughout many other North American pre-Columbian cultures. The concept for these was offered as being similar to that of the “medicine wheels” of later western Native American tribes, with circles of huge vertical posts serving as horizon markers for the rising and setting of 24 celestial objects throughout the year. In later years, three more, with differing numbers of posts, were discovered in other areas of Cahokia. Re-examination of this excavated area at Cahokia by Sherrod and Rollingson1 revealed far more, and seemingly randomly spaced one-metre poles had been erected in this residential area, far too many to account for what had been cherrypicked to form a circle. In short, something as important as a celestial calendar for the Cahokian priests would never have been constructed in a residential neighbourhood, which these posts were. Although still popular for visitors, this concept has largely been discredited. Even today, those who care for the site continue to compare the “Woodhenge” of Cahokia to the Stonehenge of England. Based on the domestic scatter on excavation maps of the Cahokia Woodhenge area, nothing could be further from reality. In Ohio, archaeologists suspect woodhenges at seven sites to be linked to the very ancient Hopewell culture, which flourished from 2,200 to 1,700 years ago.2 In all, these woodhenges purportedly signify the positions of the rising and setting of the sun during the two annual solstices, as well as the east and west rising and setting points of the sun during the spring and autumn equinoxes. However, as stated, the accuracy of these claims is diminished when we consider that, in 1. ‘Surveyors of the Prehistoric Mississippi Valley’, Sherrod, P. Clay and Martha Rollingson, Arkansas Archaeological Survey Research Series, 28, 1987 2.  ‘A Hopewell Woodhenge’, Dave Ghose, American Archaeology, 18, No. 4 (Winter 2014-15)

Astronomy 2024.indb 267

07/02/2023 22:41

268  Yearbook of Astronomy 2024 Art by Herb Roe of the Woodhenge concept at Cahokia Mounds. (Wikipedia/Herb Roe)

all cases, only post holes which conform to a preconceived notion of a calendar “henge” have been selected to outline these features, with dozens of additional similar  post  holes  – for which there are no identified purposes – seemingly being ignored.

Medicine Wheels There is a similar, non-structurally different, type of suspected calendar circle in western North America. Known as medicine wheels, these features are made of rocks that appear to somehow align to azimuths of the solstices – and perhaps even to some brighter stars – during rising and setting. Archaeologists and archaeoastronomers have located more than 100 of these medicine wheels, mainly in Alberta and Saskatchewan, Canada, with a few identified in Montana and Wyoming in the United States. It is important to point out that agriculture and cultivation of domestic crops was practiced by all of the ethnic and cultural groups associated with the medicine wheel, yet there is some disagreement that domestic agriculture was perhaps not in use in some, if not many, of the years in which rock art solstice markers were thought to have been devised. Nonetheless, even migrations of animals throughout any local region can be forecast if one knows the approximate times of solstices and/or equinoxes. The overall diameters of these circles range from just a few metres to more than 100 metres, and nearly all are placed atop a hill, offering good views of the surrounding horizons, and thereby adding some credibility as to the intended purpose of these stone earthworks.

Astronomy 2024.indb 268

07/02/2023 22:41

Skies over Ancient America: The Evolution of Ancient Skywatching  269 The Majorville, Alberta, Canada Cairn/Medicine Wheel. (Alberta Department of Tourism)

One of the largest and oldest such design is the Majorville Medicine Wheel, located to the south of Bassano in southern Alberta, Canada, where archaeologists have found spear points and stone tools dating the site to perhaps 4,500 years ago. Although now badly damaged through the centuries, there may originally have been 28 “spokes” radiating from a large central mound of stones, or cairn; some of these spokes suggest alignment to the summer solstice sunrise, and the rising azimuths of the bright stars Sirius, Aldebaran, Fomalhaut, and Rigel. Another more recently constructed medicine wheel, the Big Horn Medicine Wheel in Wyoming, was built sometime between AD 1200 and 1700. As with some other less astronomically-convincing western USA wheels, this and others appear to point to the azimuth of matching stars. This could also be random coincidence, as the woodhenges in question appear to have too many posts and convenient “alignments” to random stars, with many posts in positions not relevant to the sky. Whether or not these ‘wheels’ are intentionally constructed to depict the passage of the cosmos above our Earth, the ancient people did use markers such as this to mark the passage of calendar time. Consequently, we must not discount ALL such as coincidences, and should keep an open mind about those with obvious (such as solsticial) alignments. * * * As the great Laurentide Ice Sheet receded, during the period prior to around 11,000 years ago, the climate in northern latitudes began to warm up, the rivers and creeks that formed increasingly provided optimum hunting and growing

Astronomy 2024.indb 269

07/02/2023 22:41

270  Yearbook of Astronomy 2024 conditions, particularly in the lands now known as the United States. Early cultures from South and Central America began moving northward as these fertile lands opened up, and with the cultures the technological values that they had developed over thousands of years before went with them. The entire trek, from a time prior to Columbian discovery through to subsequent habitation, would take nearly a thousand years. During that period, the need for calendars never ceased, for it was through the ability to predict the passage of time that animal migrations, agricultural planting and seasonal sustainability was made possible. Nonetheless, without the written word, the passage of traditional engineering and astronomical protocol from generation to generation was not perfect; in fact, it would be the slight changes over the next millennia that would allow scientists to discern slight cultural and anthropological differences of the people who would ultimately follow the fertile lands of the Mississippi River and its tributaries into a new world. The next, and final, instalment of ‘Skies Over Ancient America’, will appear in the Yearbook of Astronomy 2025. In this, we will explore how these slight changes evolved enough to allow modern investigators to examine a prehistoric settlements and ascertain an approximate time of construction, as well as even slight diversions in cultural association, all based on the principles of solstice and equinox markers, and a unit of measure we know today as the Toltec Module.

Astronomy 2024.indb 270

07/02/2023 22:41

Tracking Older Artificial Satellites Steve Harvey

Introduction Recently we have seen hundreds of new SpaceX satellites being launched into orbit, adding to the thousands of older satellites that are already orbiting the planet. On 4 October 1957 Sputnik 1 became the first artificial Earth satellite. It only remained in orbit for three months before atmospheric drag returned it to Earth. However, not all of these early vehicles have suffered such a fate, some still remaining in orbit to this date. It may be surprising to discover even some of the satellites from the 1950s are still in orbit.

Targets The North American Aerospace Defense Command (NORAD) is partly tasked with tracking all orbiting bodies greater than 10 centimetres across. Currently exceeding 47,000 objects (including 12,000 satellites) this list, and the associated Two-Line Element (TLE) data1 is publicly available via the space-track website space-track.org. CelesTrak also publish a partial list of this catalogue at celestrak.org and provide a very comprehensive set of search software and visualisation tools. Many other websites are available to provide a list of targets, including the ubiquitous Heavens Above at heavens-above.com/Satellites.aspx The following table details the ten oldest artificial satellites still in orbit. It is worth noting that some rocket shrouds and debris from these earlier flights are also still in orbit, although we will exclude these from our list. The satellites listed are all in low Earth orbit (less than 2,000 kilometres altitude), thereby taking a couple of hours or less to travel around our planet and (occasionally) presenting two opportunities to view them during an evening.

1. Two Line Element (TLE) is the standard data format to specify the orbit of an artificial satellite.

Astronomy 2024.indb 271

07/02/2023 22:41

272  Yearbook of Astronomy 2024 Satellite ID (NORAD)

Name

Designation (COSPAR)

Name in Spacetrack Catalogue

Orbit km × km / inclination

Magnitude intrinsic/ maximum

  5

Vanguard 1

1958-002-B

VANGUARD 1

648 × 3833 / 34.2°

10.2 / 8.3

 11

Vanguard 2

1959-001-A

VANGUARD 2

552 × 2934 / 32.9°

  8.2 / 5.6

 20

Vanguard 3

1959-007-A

VANGUARD 3

507 × 3258 / 33.3°

  7.7 / 4.8

 22

Explorer 7

1959-009-A

EXPLORER 7

482 × 668 / 50.3°

  8.2 / 5.0

 29

Tiros 1

1960-002-B

TIROS 1

629 × 662 / 48.4°

  8.2 / 6.2

 45

Transit 2A

1960-007-A

TRANSIT 2A

601 × 956 / 66.7°

  6.7 / 4.5

 58

Courier 1B

1960-013-A

COURIER 1B

962 × 1209 / 28.3°

  7.7 / 7.5

116

Transit 4A

1961-015-A

TRANSIT 4A

867 × 977 / 66.8°

  8.2 / 7.6

117

Injun/Solrad 3

1961-015-B

SOLRAD 3 / INJUN 1

871 × 987 / 66.8°

  8.2 / 7.6

120

Tiros 3

1961-017-A

TIROS 3

712 × 777 / 47.9°

  8.7 / 7.2

Satellite ID This is the NORAD identification which is a sequential nine-digit number assigned by the United States Space Command (USSPACECOM) in the order of launch to all artificial objects in the orbits of Earth and those that left Earth’s orbit. Name The common name used to identify the satellite. Designation The Committee on Space Research (COSPAR) designation is an international identifier assigned to artificial objects in space. It consists of the launch year, a three-digit incrementing launch number of that year and up to a three-letter code representing the sequential identifier of a launched item. See cosparhq.cnes.fr Name in Spacetrack Catalogue This is the name used for the object in the Spacetrack catalogue. Orbit Orbital information showing apogee, perigee and inclination. Magnitude Intrinsic magnitude (defined as at 1,000 kilometres distance and 50% illuminated) is more representative of typical viewing, whereas maximum is the theoretical maximum. The magnitude will be degraded by inclination (your viewing angle). Important note: the orbital data listed in the table was correct as of 1 September 2022. Orbital data may change over time – check a website such as heavens-above.com for latest information.

How From the above table we can see that – unfortunately – the targets are rarely within the visual limit of magnitude 6 (at least for observers in the UK). Also, with such low inclinations, the Vanguard series never appear high in the sky for UK observers,

Astronomy 2024.indb 272

07/02/2023 22:41

Tracking Older Artificial Satellites 273 and magnitudes of 11 or 12 are the norm. However, there are still ways in which we can track, view and image these objects, either through magnification or imaging.

Software Prior to imaging or viewing the satellites, one must determine when such targets will be visible from the intended viewing location. Several websites are available to produce these types of data and allow the production of a viewing list as well as the option to print out a viewing guide showing the projected path of the satellite across the sky. Generally, a search window of ten days is provided and thus allowing the observer to select the most favourable apparitions – i.e. the brightest and highest declination for the observation site provided. Using a laptop outside ‘in the field’ will make locating easier, by not having to print things prior to observing. It will also make it possible to control the telescope mount (using the ASCOM or INIDGO interface) if attempting to slew to and track the targets. Software is abundant, sources including Orbitron at stoff.pl Stellarium at stellarium.org and SkyTrack at heavenscape.com A comprehensive index may be found at celestrak.org/software/satellite/ sat-trak.php For many people though, the preferred choice would be using a tablet with Wi-Fi connection. Again many software packages (apps) are available depending upon the Operating System. I have tried many iOS apps, one of the best I have found being Luminos. This allows the user to create custom lists of satellites (using TLE data links from the CelesTrak website celestrak.org) and to view visible passes, whilst having the tablet match its view to where it is being pointed. This allows for perfect alignment and framing of images when performing static photography of satellite tracks. Smartphones are also a great help, having equally good software to help with accurate timings and alignment. The Orbitrack app (southernstars.com/ products) is available for both iOS and android.

Viewing With the necessary list of predictions in hand one may then attempt observations …

Using Binoculars A good pair of 7 × 50 binoculars will provide optimum weight versus relative brightness (higher magnification leads to a dimmer image). These should typically allow the viewing of objects down to around ninth magnitude or so. Image

Astronomy 2024.indb 273

07/02/2023 22:41

274  Yearbook of Astronomy 2024 stabilised binoculars may allow viewing of even dimmer objects. There are many variables in determining the limiting magnitude for a particular location and the equipment used. Dark skies are preferable when visually observing (away from any ambient street lighting and so forth). Allowing your eyesight to dark adapt will also help with the chances of viewing these dim objects. Also remember to use red torchlight and to ensure any electronic screens are set to night vision mode or red filtered.

Using a Telescope The use of a telescope is a lot trickier and takes far more preparation than the pointand-shoot technique required for binoculars. If the mount is manually manoeuvred then keeping the object within the eyepiece is an error-prone and probably fruitless way to try. If the mount is automated through the use of a hand controller, this will also probably end in frustration as the effective speed of the moving satellite will fail to correspond with the speed of the telescope motor (note that satellites appear to move quicker when overhead). A preferable method would be to allow the mount to follow the object across the sky. Some hand controllers already have A Sky-watcher AZ-GTi Mount, connected over Wi-Fi satellites in their database, whilst to an iPad running the Luminos software which allows others allow uploading of the control of the mount. (Steve Harvey) necessary TLE data1. You could also use computer/tablet software to control the mount. Note that an aperture of at least 80mm, with a minimum limiting magnitude of 12, is needed to view the Vanguard satellites from the UK.

Astronomy 2024.indb 274

07/02/2023 22:41

Tracking Older Artificial Satellites 275

Still Photography This is by far and away the simplest method to record the tracks of the satellites as they move across the background of apparently static stars. Using a digital SLR on a solid tripod is a great start. Using a wide-angle lens with a high f/ratio (less than f/2.8 is preferable) to give a wide field of view of the predicted path of the satellite. Focussing can be fraught, as most DSLR setups do not have a set infinity focus point. Using a bahtinov mask, Live View or pre-focussing on a bright star will help. Alternatively, take a picture, review the magnified image on screen and adjust focus and repeat until happy. Set the DSLR to Manual, adjust aperture to the maximum aperture that the lens allows and adjust exposure time to a suitably long duration – typically less than 1 minute for urban locations. Setting to Bulb and using a remote release cable really helps. A few test shots will allow the determination of the optimum ISO setting. In an urban location images will just become fogged out above a certain ISO value for longer duration exposures. The examples shown in these two images – obtained using two different lenses – have both been inverted and stretched (using Lightroom) so that the satellite tracks appear bolder.

Transit 4A (24mm, f1.4, 15sec) appearing to pass close to Orion’s Belt. (Steve Harvey)

Astronomy 2024.indb 275

07/02/2023 22:41

276  Yearbook of Astronomy 2024

Tiros 1 (100mm, f2.8, 15sec) plus one interloper at top of image. The elongated smudge seen to the right of the lower satellite trail is the Andromeda Galaxy (M31). (Steve Harvey)

Moving Image Photography Using a video camera with very sensitive optics is probably still not going to be sensitive enough to record even the brightest objects in our list. Most dedicated astro ‘video’ cameras would still need several seconds’ exposure to capture – so even with very good tracking the end result will simply be a dot in the middle of the video.

Alternatives Other camera techniques such as all sky cameras and meteor camera recording kits are probably not sensitive enough to record such dim objects

Astronomy 2024.indb 276

07/02/2023 22:41

Tracking Older Artificial Satellites 277

When Not all days are suitable for viewing, even if the prediction software tells you that there is a visible pass occurring. Apart from the obvious throes of inclement weather, we also must consider the Moon and the amount of moonlight. Generally, the middle two weeks of a lunation, centred around Full Moon will be the worse – drowning out all but the brightest of stars. The ability to see a satellite is determined by it being lit by sunlight (when the sun for the local observer is below the horizon). Therefore, the opportunities for observation increase for northern hemisphere locations during the summer months (equinox to equinox). Whether viewing or imaging, unfortunately one will not be able to see more than a point of light (no distinct outlines of solar arrays). However, the satisfaction of viewing an object that was put into orbit over 60 years ago is quite rewarding. So why not have a go at ticking off a few from the top 10 list, which could involve as much or as little time, money and effort as you wish. Also, there is no rush, as Vanguard 1 has a predicted lifespan of approximately 240 more years in orbit. So, there is plenty of time to hone your skills required for telescopic satellite tracking. Perhaps one could then progress to radio satellite tracking and find the oldest of these still active.

Astronomy 2024.indb 277

07/02/2023 22:41

Inner Lives of Dead Stars Matt Caplan

The deaths of stars receive a disproportionate amount of attention in media, and rightly so. Despite being relatively quick phenomena, supernovae as bright as galaxies and giant stars that can swallow our solar system make for great observing, their pictures exciting us like a shiny nickel excites a magpie. The remnants too

The Ring Nebula is one of the most famous and most photographed planetary nebula, showing the remains of a star that is in the final stages of becoming a white dwarf, still visible as a faint dot in the centre. (The Hubble Heritage Team (AURA/STScI/NASA))

Astronomy 2024.indb 278

07/02/2023 22:41

Inner Lives of Dead Stars 279 – especially neutron stars and black holes – compete for superlative titles even if they’re little more than a dot through a telescope. But what of the white dwarfs, the low mass remnants of stars like our sun? Most of us probably just know the basics – after a grand finale as a red giant, a low mass star sheds its outer layers forming a planetary nebula, leaving behind its core. While ‘white’ hot (as star cores tend to be) they are very much so ‘dwarfs’ compared to their earlier selves, being not much larger than our own earth. Without any heat source they should just cool and dim, like a hot skillet taken off the burner, until they fade from view entirely. This property has made white dwarfs excellent clocks, as the heat leaks out of the white dwarf like sand leaks into the bottom of an hourglass. If you measure the temperature of white dwarfs in a cluster then you know their age and thus the ages of the stars around them, an incredibly powerful tool for cosmologists. But in recent years, the Gaia space telescope has showed us that white dwarfs aren’t so simple. Thanks to Gaia, we have an unprecedented census of billion stars in our galaxy, including a quarter of a million white dwarfs. Many of these white dwarfs are just too warm to make sense of, as if they had some extra source of heat sustaining them in death. There is an obvious solution, which it turns out is wrong. Maybe these white dwarfs aren’t too hot for their age; maybe they’re just older than we think? This is easy enough to check. Since we know the rate that stars form in our galaxy, we’d expect similar numbers of white dwarfs of a given mass with every temperature. But when we look at their masses and temperatures, it seems many of them have ‘piled up’ with similar surface temperatures and brightnesses, as if they’ve stopped cooling after a few billion years. The best explanation, as crazy as it may seem, is that long after nuclear fusion stops a new heat source turns on. To understand the inner lives of these dead stars a bit better, let’s start at the beginning.

Our Sun and Dying Stars Once formed, a sunlike star spends the majority of its life fusing hydrogen to helium in its core in a phase called the ‘main sequence.’ Indeed, our sun is in this stage – it has been almost five billion years, and it will continue for about five more. This cosmic bonfire will burn until the core hydrogen is spent, all fused to helium, but unlike a bonfire this doesn’t mean it will fizzle out. The core contracts and ignites helium burning, creating elements like carbon and oxygen, while the rest of the star swells into a red giant before finally casting off its outer layers.

Astronomy 2024.indb 279

07/02/2023 22:41

280

Yearbook of Astronomy 2024

The proton-proton chain is the dominant power source in sun-like stars, and is responsible for 99% of our sun’s present power output. (Wikimedia Commons/Doctor C)

Many stars died just like this long before our sun, and have mixed some of the metals they made, like carbon and oxygen, back into the galaxy.1 As a result, our sun formed from gas containing all the metals of these past generations of stars, chief among them are carbon and oxygen, supplied in roughly equal parts by past supernova and the winds of dying red giants. Along with core hydrogen fusion, these metals act as the second largest power source in the core of the sun today. This may seem strange to you – if the sun cannot use these elements as fuel, how can they power the star? Sure enough, even though the sun isn’t hot enough to produce its own carbon and oxygen yet, it can use these nuclei forged from the stars that came before it as a catalyst. Through a 1. This sentence might seem strange to you. Why would astronomers call everything heavier than hydrogen and helium a ‘metal’? Certainly, if carbon and oxygen (the mainstays of the human body and organic chemistry) are metals then we would all shine like C3PO! The truth is that astronomers and chemists mean different things by the word ‘metals.’ Even noble gasses like neon and xenon count as metals in an astronomer’s definition. If that seems strange, here’s a helpful rule to remember the convention. If it was made in the big bang, astronomers call it “hydrogen and helium” and if it was made by stars it’s a “metal.”

Astronomy 2024.indb 280

07/02/2023 22:41

Inner Lives of Dead Stars 281

The CNO cycle, beginning with one carbon-12 nucleus, consists of the capture of four protons and two beta decays (which convert two protons intro neutrons), followed by the emission of a helium-4 nucleus. The end result is the same as the proton-proton chain, which is the conversion of four hydrogen into one helium nucleus. The carbon-12 nucleus is recovered at the end, and the cycle repeats. (Wikimedia Commons/Borb)

series of nuclear reactions capturing hydrogen, they slowly build themselves up from carbon to oxygen before expelling a helium nucleus and becoming carbon. This sequence of reactions is called the ‘CNO cycle’, named for the series of carbon, nitrogen, and oxygen isotopes involved. Though only one in a thousand nuclei in the core of the sun may be a suitable catalyst, this cycle is responsible for almost 1.6% of the sun’s power output, which we know very precisely thanks to detailed observations of solar neutrinos.

Astronomy 2024.indb 281

07/02/2023 22:41

282  Yearbook of Astronomy 2024 So what becomes of the CNO nuclei as the star enters the giant phase? You might think they just mix away into the ashes of the helium burning, becoming indistinguishable from the bulk of 12-carbon and 16-oxygen. Strangely enough, these foreign nuclei retain their identity through yet another series of nuclear reactions. Since the slowest step of the cycle involves 14-nitrogen (with 7 protons and 7 neutrons) capturing a proton, our catalyst nuclei spend longer and longer waiting at this step of the cycle as core hydrogen runs out. Toward the end of the hydrogen burning phase, almost all of the original carbon and oxygen has been converted to nitrogen. Then, as the temperature rises and core helium begins to burn, some helium nuclei will fuse with these 14-nitrogen nuclei converting them first to 18-flourine and finally to 22-neon. At the end of the giant phase, we are left with roughly equal amounts of 12-carbon and 16-oxygen and a pinch of 22-neon in our white dwarf. These 22-neon nuclei are special, at least in a white dwarf. Though they only comprise 2% of the mass of the star, they are the key to keeping white dwarfs so warm. Unlike every other nuclei in the white dwarf, which has equal numbers of protons and neutrons, 22-neon is different. It has 12 neutrons and 10 protons. With these extra neutrons, a 22-neon nucleus is just a pinch denser than the surrounding 12-carbon and 16-oxygen, causing it to sink toward the core like a pebble in a pond. In the incredible gravity and pressure of a white dwarf, this is more than a theoretical novelty. As these nuclei sink they release a tremendous amount of energy through friction and collisions with their neighbours, warming the dead star.2 So even without nuclear reactions, the properties of fluids and buoyancy give us a pinch of heat, extending the life of our white dwarf into death. But this is still not enough.

2. This is, strangely enough, very similar to how we perform isotopic separation on earth. While 235-uranium is fissile and useful for nuclear reactors and weapons, 238-uranium is not. The 235U (having a much shorter half-life than 238U) has mostly decayed away since the formation of the earth, so uranium ore mined earth has a very low fraction of 235U which must be separated from the 238U to build a fuel assembly or bomb core. To separate these isotopes, uranium is bound with fluorine to create uranium hexafluoride gas which is then spun in a centrifuge. The large centrifugal force causes the UF6 molecules with a 238 U to ‘sinks’ to the edges, while the 235U ‘floats’ to the centre. Note that it is not illegal for you to know this or for me to tell you this.

Astronomy 2024.indb 282

07/02/2023 22:41

Inner Lives of Dead Stars 283

Dead Stars and Freezing Cold The gravitational settling of neutron rich elements can explain some but not all of the heat needed to understand the galaxy’s dying white dwarfs. For that, they must freeze. Phase transitions can consume or release huge amounts of energy, depending on the material. Consider water, as an easy example. It requires almost as much energy to melt ice to water (without changing temperature at all!) as it does to heat ice cold water up to boiling. For example, when you add ice to your drink the drink will stay at exactly freezing temperature so long as the ice has not fully melted and you stir every once in a while. Microscopically, this is because the crystal structure requires an enormous amount of energy to disassemble. The atoms are very comfortable when arranged in a nice regular grid, and so they need a lot of energy to get kicked out of it. And, going the other direction, freezing water into ice releases just as much as the atoms settle into their lattice. While the core of a white dwarf is a bit hotter than a cup of ice water (about 100,000 Kelvin hotter, if we’re being exact), the same physics applies. Nuclei here are fully ionized, stripped of their electrons, and constantly bumping into and

To melt ice or to freeze a substance requires an enormous amount of energy, but so long as the two phases coexist right at freezing temperature the temperature of the mixture will not change. In a warming cup on earth, this keeps your drink cold until all the ice has melted. In a cooling white dwarf in space, this will keep the star warm until the core has almost completely crystallized. (Matt Caplan)

Astronomy 2024.indb 283

07/02/2023 22:41

284  Yearbook of Astronomy 2024

These simulations of plasmas in the core of white dwarfs show the regular repeating crystal pattern of the solid and the messy disorganization of the liquid, with each dot representing one nucleus. The simulations are in 3D so those nuclei that appear close together are really separated in the third dimension which has been flattened to make these images. Both simulations are run at densities millions of times greater than matter on earth, at temperatures of a hundred thousand Kelvin. Moreover, they are run at the exact same temperature and density, and may be thought of as the same as a cup of ice at 0° C and a cup of water at 0° C. (Matt Caplan)

bouncing off each other thanks to their mutual repulsive electric force. But as the star cools, the nuclei find themselves moving slower and slower. Eventually, they move so slowly they can barely slip past each other, their mutual electric energies now much greater than their kinetic energies. With gravity and the weight of the star pressing down on them, nuclei begin to assemble into a crystal lattice in the core of the star. One by one nuclei join the crystal, each releasing a pinch of energy.3 It is ultimately this crystallization occurring in the core which is responsible for the observed ‘pile-up’ in the white dwarfs that seem to have stopped cooling. If their cores did not crystallize, then we’d observe a smooth distribution of white 3. This is a very subtle point. Phase transitions on earth, like converting liquids into solids, typically involve electrons bonds forming between neighbouring atoms. These electric bonds are then responsible for consuming, or releasing, much of the energy associated with a phase transition. In a white dwarf it is very different. Due to the high pressure, the electrons cannot form atoms and instead form a sort of quantum mechanical gas permeating the white dwarf. The ‘freezing’ in white dwarfs is entirely due to the electric repulsion between the positively charged nuclei, with no electrons needed. The cores of stars are a very weird place.

Astronomy 2024.indb 284

07/02/2023 22:41

Inner Lives of Dead Stars 285 dwarf temperatures. Instead, we see many white dwarfs all stalling at about the same temperature, completely consistent with observations. And that brings us back to today. By the time you read this the Gaia satellite will have had its third data release, and astronomers will be sharpening their models and tightening their error bars. These white dwarfs are complicated, with rich inner lives of neon rain and freezing cores. What’s more, we will be able to correct for this extra heating and use white dwarfs as clocks to determine the true ages of star clusters around our Milky Way. In the next few years, we hope to better understand the crystal structure of the core as well as the effects of other neutron-rich nuclei similar to 22-neon, such as 23-sodium and 56-iron. Moreover, we hope to understand the effects these core crystals might have on type 1a supernova, which are the result of explosive burning of carbon and oxygen in white dwarfs. If the core is made of dud nuclei that are too heavy to be burnt, will this change anything about the explosion? Since type 1a supernova are used to measure the accelerating expansion of the universe, could a frozen core affect these measurements too? Even though we don’t know the answers to these questions now thanks to Gaia we know exactly what to do next, and within a few short years the curious case of the warm white dwarfs may be solved.

Astronomy 2024.indb 285

07/02/2023 22:41

Riccardo Giacconi X-ray Astronomy Pioneer David M. Harland

Riccardo Giacconi was born in Genoa, Italy, on 6 October 1931 but was raised in Milan. When he was six years old his parents separated. In his early years at school he was such an inattentive student that his mother, who taught mathematics, arranged for him to repeat a year. After that, his interest picked up and in 1942 he showed an aptitude for mathematics. In the autumn of 1945 Giacconi started high school, where he faced the choice of either a classical or a scientific curriculum. He decided on the latter. He was determined to achieve the highest grades in order to skip the final (fifth) year of school and pass straight on to university. He was successful and enrolled at the University of Milan at the age of 18 to study physics, a course which ended with a doctorate. On graduating in 1954 with a thesis on the detection of cosmic-rays, he remained in place and taught experimental physics. He moved to the United States in September 1956 with a Fulbright Fellowship and worked on instrumentation for experimental particle physics at the University of Indiana at Bloomington. This gave him an appreciation of the importance of setting clear scientific goals prior to initiating a physics experiment, and then designing the apparatus for efficient collection, reduction and analysis of data. In February 1958 he moved to Princeton University, New Jersey, as a research associate in the Cosmic Ray Laboratory. With his Fulbright Fellowship nearing expiry, in September 1959 he was hired by American Science and Engineering (AS&E) in Cambridge, Massachusetts, a private research corporation set Riccardo Giacconi. (AIP Emilio up in 1958 by a group of scientists and engineers Segrè Visual Archives, Physics Today from Massachusetts Institute of Technology Collection)

Astronomy 2024.indb 286

07/02/2023 22:41

Riccardo Giacconi: X-ray Astronomy Pioneer 287 (MIT). In 1959 it was funded primarily by grants from the Department of Defense to pursue research in space physics. MIT professor Bruno B. Rossi was the chairman of the company and also a member of the Space Science Board, which had been formed by the National Academy of Sciences in 1958, in response to Sputnik, “to survey the scientific problems, opportunities, and implications of man’s advance into space”. One enticing prospect was to observe the universe in regions of the electromagnetic spectrum otherwise unavailable due to the presence of our atmosphere, particularly the X-ray region. In fact, on the presumption that the Sun must be the brightest object in the sky, Herbert Friedman’s group at the Naval Research Laboratory in Washington, D.C., had started launching detectors on high-altitude rockets in 1948. Their detectors were similar to Geiger counters, in that X-rays that entered the detector would ionise the gas contained within, and the free electrons would be drawn to a wire held at a high positive charge to create an electrical pulse. The first flight confirmed that the Sun emits X-rays. However, it was calculated that if the Sun were to be relocated as little as 1 light-year away then its emission would be 1,000 times weaker than the detection limit of the observations. Clearly, the sensitivity of instruments would need to be greatly increased for non-solar X-ray astronomy to become viable. At that time, optics for focusing X-rays were in a rudimentary state, and imageforming systems were non-existent. Rossi asked Giacconi to review the literature. In an optical telescope, light rays are brought to a focus by a lens or a mirror. The wider the aperture, the greater the amount of light which is concentrated on the detector. Hence an astronomer looking through a telescope is able to see fainter objects than are visible to the naked eye. It is not possible to use a conventional mirror to focus X-rays because the surface absorbs, rather than reflects, the energy. On reading of a failed attempt to employ external-reflection grazing-incidence optics for microscopy, Giacconi realised that scaling up such a configuration for a telescope would eliminate the difficulties that had precluded its use in microscopy. It would be possible to create a mirror that could concentrate X-rays by using the edges of a paraboloid, where grazing-incidence occurs, and thereby raise the sensitivity by a factor of 1,000 to 100,000 times. A further refinement to increase sensitivity was suggested by Rossi. This nested reflecting surfaces one within another, in a configuration of confocal paraboloids. They jointly published this proposal in February 1960.1 1.  ‘A ‘telescope’ for Soft X Ray Astronomy’. 1960, R. Giacconi and B. B. Rossi, Journal of Geophysical Research, 65, 773–775.

Astronomy 2024.indb 287

07/02/2023 22:41

288  Yearbook of Astronomy 2024 However, this design was limited to a very narrow field of view. It could measure a single point source at a greatly increased sensitivity, but would require being raster-scanned in order to study an extended object. For example, the disk of the Sun spans 1,800 seconds of arc, so scanning it using a spot that provided a resolution of 5 seconds of arc would require almost 130,000 exposures. Nevertheless, solar scientists were delighted at the prospect of studying X-rays from the Sun in this manner. In October 1960 NASA contracted AS&E to develop such an X-ray instrument for one of the Orbiting Solar Observatories scheduled for launch in the middle of the decade, to enable the Goddard Space Flight Center in Greenbelt, Maryland, to undertake solar studies. While the X-ray instrument for the Orbiting Solar Observatory was being developed, Giacconi decided to apply his knowledge of cosmic rays to improve the type of detector being used by the NRL team.

Technicians preparing an Orbiting Solar Observatory for launch in 1967. The lower section spun while the upper section maintained its instruments facing the Sun. (NASA)

Astronomy 2024.indb 288

07/02/2023 22:41

Riccardo Giacconi: X-ray Astronomy Pioneer 289 The problem with using a Geiger counter for X-ray astronomy on a highaltitude rocket was that the background count from cosmic rays would swamp the expected strength of the signals from celestial X-ray sources. Giacconi borrowed the anti-coincidence technique commonly used by particle physicists. He wrapped a scintillation counter around his Geiger counter, leaving only its ‘window’ exposed. Whereas X-rays penetrating the window would trigger only the Geiger counter, cosmic rays would trigger both detectors simultaneously, enabling them to be discounted. He reckoned that by subtracting most of the background he could achieve a 50-fold improvement in sensitivity to X-rays. Furthermore, the tiny window of the NRL detector provided a field of view spanning just 3 degrees. While this was swept across the sky by the rotation of the rocket it would not only sample a tiny portion of the sky, it would also spend very little time sampling in a given direction. Giacconi therefore opened up the field of view of his detector to an angle of 120 degrees in order both to observe more of the sky and also to sample a given direction for longer. In addition, a trio of detectors could be arranged to simultaneously observe different directions, thus maximising the overall coverage. In the early 1960s those seeking funds from NASA to develop non-solar X-ray astronomy faced the dilemma that it had yet to be shown that there were such sources. However, the Air Force Cambridge Research Laboratories was also funding space physics, and invited AS&E to test a detector of the kind proposed by Giacconi. After several failures, the project succeeded on 18 June 1962 with a launch from the White Sands Missile Range in New Mexico. The rocket spent 350 seconds above an altitude of 80 km, rotating on its axis twice per second. With the Moon just a day off its ‘full’ phase, the plan was to attempt to detect its surface fluorescing in response to illumination by solar X-rays. The instrument detected a much stronger source than had been expected and, significantly, it was not the Moon. (In fact, the Moon was not detectable at all in this data.) With such a wide field of view it was not possible to pinpoint the source on the sky. The fact that it was within the constellation of Scorpius led to it being designated ‘Sco X-1’. This fortuitous discovery kick-started non-solar X-ray astronomy.2 But flying instruments on high-altitude rockets could provide only occasional, and brief, opportunities for observations. What was needed was a satellite capable of providing the first all-sky survey. 2. ‘Evidence for X Rays from Sources Outside the Solar System’. 1962, R. Giacconi, H. Gursky, F. Paolini and B. B. Rossi, Physical Review Letters, 9, 439–443.

Astronomy 2024.indb 289

07/02/2023 22:41

290  Yearbook of Astronomy 2024 On 8 April 1964 AS&E submitted a proposal to NASA entitled ‘An X-ray Explorer to Survey Galactic and Extragalactic Sources’. Giacconi argued that, unlike the Orbiting Solar Observatory, one part of which would spin rapidly while the other was maintained facing the Sun, an allsky survey required a satellite to spin slowly to maximise the time that each source was in the field of view, with the timing indicating the direction of a measurement. Furthermore, it would have to tilt its axis over time in order to obtain coverage of the entire celestial sphere. Giacconi had expected AS&E to build both the science package and Marjorie Townsend and Bruno Rossi preparing the satellite and to have it ready for the Uhuru satellite, which has its solar panels launch within 18 months of being draped down over the support structure. (NASA/ given the go-ahead, but NASA did Goddard Space Flight Center) not run is science programs in that way. Satellites were to be designed and constructed by one of its field centres, and the developers of the science packages (the raison d’être for the flight) were treated as subcontractors. As a result, the mission was not ready for launch until the end of the decade, by which time it was the first in a series of Small Astronomy Satellites. The project was given to the Goddard Space Flight Center. The project manager was Marjorie Townsend, an electrical engineer with experience of a number of space projects. The spacecraft was built by the Applied Physics Laboratory in Laurel, Maryland, an adjunct of Johns Hopkins University, with a track record for developing military satellites. While NASA developed the Small Astronomy Satellite, Giacconi’s group continued to launch rockets with ever more capable detectors to further observe known non-solar X-ray sources, in particular to localise their positions on the celestial sphere, to measure their angular sizes, and to determine their spectra. For example, in 1964 they measured the position of Sco X-1 to within half a degree (a great improvement, but comparable to the angular diameter of the lunar disk), determined its angular size to be less than 7 minutes of arc, and measured its

Astronomy 2024.indb 290

07/02/2023 22:41

Riccardo Giacconi: X-ray Astronomy Pioneer 291 spectrum across the range 1 to 25 keV.3 By 1966 they had reduced its angular size to less than 20 seconds of arc and trimmed the ‘error box’ sufficiently for astronomers at Tokyo Observatory and the Carnegie Observatories in California to settle on a single optical counterpart.4 This identification confirmed that stellar objects could produce X-ray luminosities 1,000 times greater than their optical output, implying that the means of generation was entirely different to that by which the Sun emitted X-rays.5 The mission of Explorer 42, the first Small Astronomy Satellite, was to survey the entire X-ray sky. Because it was launched from a platform off the coast of Kenya on 12 December 1970, which was the anniversary of that nation’s independence, the satellite was named Uhuru, meaning ‘freedom’ in Swahili. The near-equatorial circular orbit at an altitude of about 530 km minimised interference from the charged particles where the inner van Allen radiation belt dips down to low altitude to produce the so-called South Atlantic Anomaly. The science package provided by AS&E was built using two almost identical sections, mounted back to back. Each section included a bank of proportional counters using windows of beryllium, a collimator to define the field of view, a star sensor, and a Sun sensor. The electronics were mounted in a box underneath. The X-ray signals were processed using a discriminator that analysed the shape of a pulse to reject signals from gamma rays and cosmic rays, a technique that was demonstrated by the AS&E group on a rocket flight in 1967.6 The collimators were arrangements of rectangular cells. One gave a field of view of 5 3 5 degrees. This provided high sensitivity for diffuse sources. The other had a rectangular field of 0.5 3 5 degrees that gave greater angular resolution for studying individual point sources. Each section of the package had 3.  The wavelengths of X-rays are shorter than those of ultraviolet light and typically longer than those of gamma rays. In fact, there is some overlap with gamma rays due to a difference in the way that they are produced; namely with X-rays being emitted by electrons and gamma rays by atomic nuclei. The quantum energies in the X-ray range are measured in units called electron volts (eV), and span from about 1 eV to 100,000 eV. 4.  ‘On the Identification of Sco X-1’. 1966, A. R. Sandage, P. Osmer, R. Giacconi, P. Gorenstein, H. Gursky, J. R. Waters, H. Brant, G. Garmire, B. Sreekantan, M. Oka, K. Osawa and J. Jugaku, Astrophysical Journal, 146, pp. 316–321. 5.  Sco X-1 was later identified as a neutron star in the act of accreting matter from a lowmass stellar companion. 6.  ‘Reduction of Cosmic Background in an X-ray Proportional Counter Through Rise Time Discrimination’. 1968, P. Gorenstein and S. Mickiewicz, Review of Scientific Instruments, 39, 816–820.

Astronomy 2024.indb 291

07/02/2023 22:41

292  Yearbook of Astronomy 2024

Uhuru schematic, showing its axis of rotation and the side-viewing X-ray detectors. (NASA)

its own star sensor, capable of seeing stars down to about 4th magnitude. As the satellite slowly spun on its axis, scanning the sky, the detector generated an electrical signal whenever an X-ray source entered the field of view. The position on the sky was calculated from the timing and the orientation of the satellite relative to the stars. The significance of the Uhuru mission can be appreciated from the fact that the data from a single 96-minute orbit exceeded the total data from all of the rocket flights. It suffered a number of malfunctions but continued to supply data through to March 1973, by which time it had increased from 30 to 339 the number of known celestial X-ray sources, many of them so near the plane of the Milky Way they had to lie within our galaxy, and the rest were other galaxies and quasars. Remarkably, some sources displayed variations in signal strength on a wide range of timescales.

Astronomy 2024.indb 292

07/02/2023 22:41

Riccardo Giacconi: X-ray Astronomy Pioneer 293

An all-sky map of the 339 X-ray sources detected by Uhuru. The plane of the Milky Way spans the horizontal axis. The indicated diameter of a source marker is proportional to the logarithm of its peak intensity. (Ref: ‘The Fourth Uhuru Catalogue of X-ray Sources’, 1978, W. Forman, C. Jones, L. Cominsky, P. Julien, S. Murray, G. Peters, H. Tananbaum and R. Giacconi, Astrophysical Journal Supplement, 38, 357–412)

The raster-scanned instrument developed by AS&E for the Orbiting Solar Observatory was superseded by an imaging system which could function as a camera. After trials on rockets, this was incorporated into the Skylab space station that was launched in 1973. The optics of this X-ray spectrographic telescope (Experiment S-054 in NASA terminology) employed a pair of coaxial and confocal grazing-incidence mirrors in a hybrid design whereby an incoming X-ray would reflect off the 30-cm-diameter paraboloid onto the 23-cm-diameter hyperboloid on its way to the point of focus. The image was recorded on photographic film, later retrieved by the astronauts for return to Earth.7 In 1973, Giacconi accepted a professorship at Harvard and headship of the High Energy Astronomy Division of the Harvard-Smithsonian Center for Astrophysics in Cambridge. This collaborated with AS&E to build the imaging X-ray telescope for the second in the series of NASA High Energy Astronomy Observatories. When 7.  ‘The S-054 X-ray Telescope Experiment on Skylab’. 1977, G. S. Vaiana, L. Van Speybroeck, M. V. Zombeck, A. S. Krieger, J. K. Silk and A. Timothy, Space Science Instrumentation, 3, 19–76.

Astronomy 2024.indb 293

07/02/2023 22:41

294  Yearbook of Astronomy 2024

Focusing X-rays by double grazing-incidence reflection. (Redrawn from Fig. 3 of ‘The Einstein (HEAO 2) X-ray Observatory’, R. Giacconi et al., Astrophysical Journal, 230, 540–550, 1979)

Einstein Observatory schematic. (NASA/Harvard-Smithsonian Center for Astrophysics)

Astronomy 2024.indb 294

07/02/2023 22:41

Riccardo Giacconi: X-ray Astronomy Pioneer 295

The Einstein Observatory optics had four pairs of mirrors in a nested configuration. (NASA/ Goddard Astrophysics Science Division)

launched in November 1978 it was named in honour of Albert Einstein. The optical system was similar to that used for Skylab but in this case employing four confocal, concentric paraboloid-hyperboloid mirror pairs with diameters ranging from 0.34 to 0.58 metres.8 This was the first focusing X-ray telescope for non-solar astronomy, and the high surface smoothness and efficiency of the fused quartz mirrors made it 100 times more sensitive than Uhuru. A turntable enabled four different detectors to be placed at the focus. The increase in sensitivity and seconds-of-arc resolution was a turning point for astronomy in general. All of this was a prelude to what would become the Chandra X-Ray Observatory. This project spent a long time in development, but it was finally ferried into orbit by Space Shuttle in 1999. The High Resolution Mirror Assembly from the Center for Astrophysics was a refinement of that of the Einstein Observatory, using larger mirrors, and yielded even more spectacular results.9

8.  ‘The Einstein (HEAO 2) X-ray Observatory’, R. Giacconi, et al. 1979, Astrophysical Journal, 230, 540–550. 9.  ‘In-flight Performance of the Chandra High Resolution Camera’, S. S. Murray, et al. 2000, Proc. SPIE, 4012, 68–80.

Astronomy 2024.indb 295

07/02/2023 22:41

296  Yearbook of Astronomy 2024

Chandra X-ray Observatory schematic. (NASA/CXC/NGST)

Postscript In 1981 NASA appointed Giacconi as the first director of the Space Telescope Science Institute, located at the Johns Hopkins University in Baltimore, Maryland, to plan the science program for the Hubble Space Telescope whose launch was then expected in the middle of the decade. On returning to Europe in 1993 he became Director-General of the European Southern Observatory in Garching, Germany. He supervised the construction of the world’s greatest array of optical telescopes, the Very Large Telescope at Cerro Paranal in the Atacama Desert of Chile, and also the early development, in concert with Japan and the USA, of the Atacama Large Millimetre/submillimetre Array (ALMA). Back in the USA in 1999 he was appointed as president of Associated Universities, Inc., which manages the various facilities of the National Radio Astronomy Observatory. In 1981 Giacconi won the Dannie Heineman Prize, jointly awarded by the American Institute of Physics and the American Astronomical Society for outstanding work in astrophysics. Then in 1982 he received the Gold Medal of the Royal Astronomical Society. But the pinnacle of recognition came in 2002 when he shared the Nobel Prize in Physics for his pioneering contributions to astrophysics.

Astronomy 2024.indb 296

07/02/2023 22:41

Riccardo Giacconi: X-ray Astronomy Pioneer 297 Giacconi served as a professor of physics and astronomy at Johns Hopkins University from 1999 to his death on 9 December 2018 at the age of 87. He was without doubt the ‘father’ of X-ray astronomy. During his career, the sensitivity of celestial X-ray observations was increased by a factor of a billion, opening an astonishing window on the universe.

Further Reading

Secrets of the Hoary Deep: A Personal History of Modern Astronomy by Riccardo Giacconi, Johns Hopkins University Press, 2008.

Astronomy 2024.indb 297

07/02/2023 22:41

The Astronomers’ Stars In the Neighbourhood Lynne Marie Stockman

The Celestial Sphere. The ancients looked up at the sky and imagined that the fixed stars were attached to a distant crystalline sphere centred upon Earth and rotating about it. Some stars were bright, some were faint, but all were the same unknowable distance away. The celestial sphere began to crack during the scientific revolution of the late European Renaissance, but the first accurate determination of a stellar distance would not come until 1838 when German astronomer Friedrich Wilhelm Bessel measured the parallax of Piazzi’s Flying Star (61 Cygni), a star with a large proper motion. Born in Sneek, Holland, Adriaan van Maanen (1884–1946) was educated at the University of Utrecht, earning his doctorate in 1911. During his graduate studies at the Groningen Astronomical Laboratory, he worked alongside Jacobus Cornelius Kapteyn. He was a volunteer assistant at Yerkes Observatory after earning his degree and went to Mount Wilson Observatory the following year. His early research at Mount Wilson involved solar observations, including spectroscopy. His work measuring minute Zeeman splitting in solar spectral lines would later contribute to the discovery of the Sun’s magnetic field. Later, van Maanen principally concerned himself with measuring proper motions and parallaxes of stars and investigating the distribution of stars in the solar neighbourhood, but he was also interested in the internal rotation of spiral nebulae which are now known to be galaxies outside of our own. He was a member of numerous learned societies, including the Royal Astronomical Society and the Astronomische Gesellschaft, and served on several commissions of the International Astronomical Union (Anonymous 1947). Now thought to be the closest known solitary white dwarf star to the Sun, van Maanen’s Star (also called van Maanen 2) was discovered by van Maanen to have a high proper motion whilst he was searching for the companion of another nearby star (van Maanen 1917): In a search for companions of stars with large proper motion two plates of the region of Lalande 1299 were taken on September 15, 1914, and two on September 12, 1917. The plates do not show any companion of Lalande 1299

Astronomy 2024.indb 298

07/02/2023 22:41

The Astronomers’ Stars: In the Neighbourhood

299

(μ = 10.37 in p = 146°.9), but reveal a star which has an even larger motion. This star is located 99 north and 119 east of Lalande 1299; its annual proper motion with respect to some stars in the neighborhood, as derived from the two pairs of plates, is: μ = 30.01 in p = 156°. Gaia values give an annual proper motion of 20.98. The star was first identified as a white dwarf by Willem Jacob Luyten, but it took some years before the peculiar properties of these degenerate stars were fully recognised (Luyten 1923). Van Maanen’s Star was the third star to be recognised as a white dwarf, after Sirius B and 40 Eridani B, but unlike those two objects, it is a solitary star, not part of a multiple system. Initial analysis of the spectrum of the object led to a classification of F0, a star slightly hotter than the Sun. This was called into question when the star was finally recognised as a white dwarf. The heavy elements present in the spectrum of van Maanen’s Star could not have been produced by the star itself; these elements would have quickly sunk to the centre under the white dwarf ’s massive gravitational field. Instead, such surface contamination must have come from outside the star, but how? Since 2005, several dozen so-called ‘polluted’ white dwarfs have been identified. It is now accepted that these white dwarf stars are surrounded by dry,

NASA’s Spitzer Space Telescope has confirmed the existence of several dozen white dwarf stars surrounded by dry, dusty disks. In this artist’s impression, a white dwarf similar to van Maanen’s Star is surrounded by the remains of countless shredded asteroids, the remnants of which may end up contaminating the surface of the central star. (Lynne Marie Stockman)

Astronomy 2024.indb 299

07/02/2023 22:41

300  Yearbook of Astronomy 2024 dusty disks comprised of tidally-disrupted asteroids and probably at least one exoplanet. The exoplanet disturbs the debris in the circumstellar disk, sending it spiralling into the star where it eventually ends up contaminating the surface of the white dwarf. Although it was not recognised at the time, the original 1917 glass plate spectrogram of van Maanen’s Star was the first detection of an exoplanetary system (Farihi 2016). This evidence for extrasolar bodies pre-dates the discovery of the first exoplanets by 75 years. Robert Thorburn Ayton Innes (1861–1933), a native of Edinburgh, Scotland, had no formal training in astronomy, yet he was elected to the Royal Astronomical Society at the age of 18. His 1891 and 1893 papers on the secular perturbations of the Earth by Mars and Venus led to his later investigations of the variability of the rotation of our planet. He discovered a number of double stars whilst observing in Australia and was soon invited to South Africa to take up the post of secretary at the Royal Observatory, Cape of Good Hope. He continued his work on visual binaries, eventually publishing a catalogue of southern double stars. On the recommendation of Sir David Gill, he was appointed director of the Transvaal Observatory in Johannesburg in 1903 which nine years later became the Union Observatory of South Africa. His interest in double stars never waned but he worked in other areas as well. He was closely involved in ‘blinking’ astrophotographic plates to look for proper motions of stars. His most famous discovery was undoubtedly Proxima Centauri, the nearest star to the Sun and one member of the Alpha (α) Centauri trinary system. He retired in 1927, dying suddenly in 1933 six months after returning to Britain (Anonymous 1933). The blink technique used by Innes revealed a high-proper motion star in the constellation of Carina (Worssell 1920): While examining the Sydney plates in the blink apparatus a star of about 12th magnitude, at R.A. 11h 13m, Dec. −57° 89, was found by Mr. Innes to have the large proper motion of 2710.8 a century towards 292°.6. This dim red dwarf star, subsequently catalogued as GJ 422 (star number 422 in the Gliese Catalogue of Nearby Stars), is now known as Innes’ Star. It was observed by the Gaia spacecraft which confirmed a high proper motion of 2730.78 per century. Erroneous parallax measurements at the time led to a distance calculated to around 10 light years, making it one of the nearest stars to the Sun, but modern parallax values place the star four times farther away. Innes’ Star may have a large planet in orbit within its habitable zone (Tuomi et al 2014).

Astronomy 2024.indb 300

07/02/2023 22:41

The Astronomers’ Stars: In the Neighbourhood

301

Red dwarf stars are the most common type of stars in the solar neighbourhood and indeed the Galaxy. However, young red dwarfs are active stars. Magnetically dynamic, they are surrounded by huge arcing prominences and their surfaces are pockmarked with large starspots. They also erupt with intense ultraviolet flares which have the potential to damage or destroy the atmosphere of (and any life forms on) an orbiting planet. This artist’s impression shows an active red dwarf and its imperilled planet. (Lynne Marie Stockman)

Willem Jacob Luyten (1899–1994) was born and spent his earliest years in Semarang, Java, which was then part of the Dutch East Indies. He became interested in astronomy whilst living there and continued this pursuit when he and his family returned to the Netherlands, obtaining a doctorate in the subject at the University of Leiden. He was particularly interested in the properties of stars in the solar neighbourhood, and his proper motion studies proved useful in calibrating the Hertzsprung-Russell diagram. He worked at Lick Observatory for two years before moving to Harvard College Observatory at the invitation of Harlow Shapley. He also spent two years at the Boyden Observatory in Bloemfontein, South Africa. After returning to the United States in 1931, Luyten joined the faculty at the University of Minnesota where he remained until his death in 1994 (Upgren 1995). The star GJ 273 is often called Luyten’s Star after Luyten who, with his colleague Edwin G. Ebbinghausen, discovered its unusually high proper motion (Luyten and Ebbinghausen 1935): A Faint Star of Large Proper Motion. — During the proper motion survey of the northern hemisphere, on plates lent by the Harvard Observatory, the

Astronomy 2024.indb 301

07/02/2023 22:41

302  Yearbook of Astronomy 2024 star B.D. +5° 1668 was found to possess the very large proper motion of 30.7 annually. The photographic magnitude is estimated at 11.5, and an objective prism plate taken for the purpose at Harvard indicates that the spectrum is of late type, probably M. Luyten’s Star is a tenth-magnitude red dwarf star. Gaia data published in 2020 suggest an annual proper motion of 30.74. It is currently heading away from the solar system but it came to within 3.666 pc of the Sun approximately 13,900 years ago (Garciá-Sánchez et al 2001). Two planets were discovered in orbit around Luyten’s Star in 2017. The larger of the two, a so-called ‘Super Earth’, lies just within the habitable zone of the star (Astudillo-Defru et al 2017). New nearby stars continue to come to light. The Near-Earth Asteroid Tracking programme surveyed the sky for near-Earth objects between 1995 and 2007. American astrophysicist Bonnard John Teegarden from NASA’s Goddard Space Flight Center realised that the data collected by the survey was a potential gold mine for stellar proper motion studies. Using CCD images from the programme, he announced the discovery of a new nearby star (Teegarden et al 2003): We report the discovery of a nearby star with a very large proper motion of 50.05 ± 00.03 yr−1. The star is called SO 025300.5+165258…There are currently only seven known stars with proper motions greater than 50 yr−1. Teegarden’s Star is a very faint red dwarf star, less than 0.1 of a solar mass in size and only just large enough to initiate fusion in its core. With an effective surface temperature of under 3000 K, most of its energy is radiated in the infrared. (By comparison, the effective surface temperature of the Sun is around 5800 K.) Gaia measurements give the star a slightly higher proper motion of 50.12 per year and position it just 3.83 pc away from the Sun. In 2019, two Earth-mass planets were discovered in orbit about this ultra-cool dwarf, placing them amongst the smallest exoplanets yet discovered (Zechmeister et al 2019). In 2013, German astronomer Ralf-Dieter Scholz examined data from the Widefield Infrared Survey Explorer mission, focusing on nearby low-mass red and brown dwarf stars hiding in the dusty galactic plane. He uncovered a likely prospect with the unwieldy name WISE J072003.20−084651.2 (Scholz 2014): Here, we introduce a previously missing possible 8 pc sample member in the Galactic plane, WISE J072003.20−084651.2 (hereafter WISE J0720−0846), which was identified among bright candidates selected from Wide-field

Astronomy 2024.indb 302

07/02/2023 22:41

The Astronomers’ Stars: In the Neighbourhood 303 Infrared Survey Explorer (WISE; Wright et al. 2010) data (Sect. 2). Despite its relatively small proper motion (Sect. 3), the preliminary trigonometric parallax, based on the available 12 epochs of observations (Sect. 3), leads to a distance of about 7 pc. A year after this result was published, American astronomer Eric E. Mamajek and his collaborators calculated that WISE J072003.20−084651.2 had passed through the outer Oort cloud some 70,000 years ago, the nearest flyby of the solar system by another star yet discovered (Mamajek et al 2015). It was Mamajek who named this visitor Scholz’s Star. At closest approach, the star would have been just 0.25 pc or 52,000 au away but shining at a meagre tenth-magnitude as seen from Earth.

A few million years ago, something jostled the Oort cloud and sent an icy body plummeting toward the Sun on a hyperbolic orbit. The comet was finally discovered in September 2012 and designated C/2012 S1 (ISON). Comet ISON reached perihelion for the first (and last) time in November 2013, disintegrating as it swept just 0.01 au past the Sun. The passage of Scholz’s Star through the Oort cloud 70,000 years ago may result in similar comets visiting the inner solar system a few million years from now. In this photograph from 27 October 2017, Comet ISON is seen traversing a colourful collection of eighth-, ninth- and tenth-magnitude stars located between Rho (ρ) Leonis and Chi (χ) Leonis. (Damian Peach)

Astronomy 2024.indb 303

07/02/2023 22:41

304  Yearbook of Astronomy 2024 Scholz’s Star is an active, ultra-cool, low-mass red dwarf with a brown dwarf companion. Red dwarfs are known to flare by as many as nine magnitudes so it is possible that our distant ancestors might have seen the star suddenly blaze to life in the night sky for minutes or even hours at a time. Theoretically, the passage of a star near or through the Oort cloud should disrupt the orbits of some of the icy bodies which inhabit the outer solar system. These comets may be ejected from the solar system or directed inward toward the Sun. Mamajek conjectured that Scholz’s Star was too small to do much damage but a later analysis of over 300 comets on known hyperbolic orbits suggests that several dozen might be on their way in due to perturbations caused by the fly by of the tiny binary system (de la Fuente Marcos et al 2018). When can we expect this influx of comets? Stick around for a couple of million years to find out!

The Astronomers’ Stars: The Quick and the Close Name

Designation

Barnard’s Star *

GJ 699 (V2500 Ophiuchi)

Argelander’s Second Star * GJ 411

Spectral Type M4V

Distance Annual (light years) Proper Motion 5.96

100.39

M2V

8.30

40.81

Piazzi’s Flying Star/ Bessel’s Star *

GJ 820B (61 Cygni B)

K7V

11.40

50.18

GJ 820A (61 Cygni A)

K5V

11.40

50.28

Luyten’s Star

GJ 273

M3.5V

12.35

30.74

Teegarden’s Star

WISEA J025303.34+165213.2

M7V

12.50

50.12

Kapteyn’s Star *

GJ 191 (VZ Pictoris)

M1.5V

12.83

80.64

van Maanen’s Star

GJ 35

DZ7.5

14.07

20.98

Scholz’s Star

WISEA J072003.20−084651.3

M9.5+T5

22.19

00.13

Argelander’s Star *

GJ 451

K1V

29.91

70.06

Innes’ Star

GJ 422

M3.5

41.34

20.74

Stars marked with an asterisk * are discussed in the earlier article, ‘The Astronomers’ Stars: Life in the Fast Lane’, which appeared in the Yearbook of Astronomy 2023. Distances and proper motions are derived from the SIMBAD astronomical database (accessed October 2022). Spectral types are taken from a variety of sources. Note that many of our nearest neighbours are cool K- and M-type dwarfs.

Acknowledgements This research has made use of NASA’s Astrophysics Data System Bibliographic Services, operated at the Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts, USA, and the SIMBAD astronomical database, operated at CDS, University of Strasbourg, France. The author would like to thank Dr David Harper for his enthusiastic encouragement and helpful comments.

Astronomy 2024.indb 304

07/02/2023 22:41

The Astronomers’ Stars: In the Neighbourhood 305

References

[Anonymous] 1933, ‘Obituary: Robert T.A. Innes’, The Observatory, 56, 129–131. [Anonymous] 1947, ‘Obituary: Adrian van Maanen’, Monthly Notices of the Royal Astronomical Society, 107, 54–56. Astudillo-Defru, N., Forveille, T., Bonfils, X., and 10 others. 2017, ‘The HARPS search for southern extra-solar planets. XLI. A dozen planets around the M dwarfs GJ 3138, GJ 3323, GJ 273, GJ 628, and GJ 3293’, Astronomy & Astrophysics, 602, A88. doi.org/10.1051/0004-6361/201630153 de la Fuente Marcos, Carlos, de la Fuente Marcos, Raúl, Aarseth, Sverre J. 2018, ‘Where the Solar system meets the solar neighbourhood: patterns in the distribution of radiants of observed hyperbolic minor bodies’’, Monthly Notices of the Royal Astronomical Society, 476 (1), L1–L5. doi.org/10.1093/mnrasl/sly019 Farihi, J. 2016, ‘Circumstellar debris and pollution at white dwarf stars’, New Astronomy Reviews, 71, 9–34. doi.org/10.1016/j.newar.2016.03.001 Garciá-Sánchez, J., Weissman, P.R., Preston, R.A., and 5 others. 2001, ‘Stellar encounters with the solar system’, Astronomy & Astrophysics, 379 (2), 634–659. doi.org/10.1051/0004-6361:20011330 Luyten, Willem J. 1923, ‘A Study of Stars with Large Proper Motions’, Lick Observatory Bulletin, 11 (344), 1–32. Luyten, W.J., Ebbinghausen, E.G. 1935, ‘A Faint Star of Large Proper Motion’, Harvard College Observatory Bulletin, 900, 1–3. Mamajek, Eric E., Barenfeld, Scott A., Ivanov, Valentin D., and 4 others. 2015, ‘The Closest Known Flyby of a Star to the Solar System’, The Astrophysical Journal Letters, 800, L17–L20. doi.org/10.1088/2041-8205/800/1/L17 Scholz, R.-D. 2014, ‘Neighbours hiding in the Galactic plane, a new M/L dwarf candidate for the 8 pc sample’, Astronomy & Astrophysics, 561, A113. doi.org/10.1051/0004-6361/201323015 Teegarden, B.J., Pravdo, S.H., Hicks, M., and 7 others. 2003, ‘Discovery of a New Nearby Star’, The Astrophysical Journal, 589 (1), L51–L53. doi.org/10.1086/375803 Tuomi, Mikko, Jones, Hugh R.A., Barnes, John R., and 2 others. 2014, ‘Bayesian search for low-mass planets around nearby M dwarfs – estimates for occurrence rate based on global detectability statistics’, Monthly Notices of the Royal Astronomical Society, 441 (2), 1545–1569. doi.org/10.1093/mnras/stu358 Upgren, Arthur R. 1995, ‘Willem Jacob Luyten (1899–1994)’, Publications of the Astronomical Society of the Pacific, 107 (713), 603–605. van Maanen, A. 1917, ‘Two Faint Stars with Large Proper Motions’, Publications of the Astronomical Society of the Pacific, 29 (172), 258–259. Worssell, W.M. 1920, ‘Parallax and Proper Motion of a Faint Star in the Sydney Zone’, Circular of the Union Observatory, 49, 55. Zechmeister, M., Dreizler, S., Ribas, I., and 180 others. 2019, ‘The CARMENES search for exoplanets around M dwarfs. Two temperate Earth-mass planet candidates around Teegarden’s Star’, Astronomy & Astrophysics, 627, A49. doi.org/10.1051/0004-6361/201935460

Astronomy 2024.indb 305

07/02/2023 22:41

Mission to Mars Countdown to Building a Brave New World The Right Stuff at the Right Time Martin Braddock

Introduction The last article entitled ‘The Bare Necessities of Life’ in Yearbook of Astronomy 2023 introduced some of the mental and physical challenges which will be faced by colonists. The initiating concepts centred around basic human needs in the first instance and human wants in the second. Accepting that the boundary between need and want is not clearly defined and will drift over time to the latter, at least until the point of acceptance is reached; it is relevant for us to develop these concepts further. Some concepts presented are philosophical in nature, though they have clear groundings in reported fact based on terrestrial events and it would be prudent, if not essential, for mission planners to consider implications and develop implementable procedures in order to provide the best opportunity for the growth of a sustainable and thriving Martian colony. The world has changed since the outbreak of the Covid-19 pandemic. At the time of writing this article in October 2022, most countries are slowly returning to a semblance of pre-pandemic normality and we have learnt much about ourselves as human beings and how we function across society. We have seen the rise of nationalism1 (Bieber 2022, Mylonas and Whalley 2022), direct effects of the Covid-19 pandemic on global economies and ways of life2,3,4 (Priya et al

1. Wang Z. (2021). ‘From Crisis to Nationalism? The Conditioned Effects of the COVID-19 Crisis on Neo-nationalism in Europe’. Chinese Political Science Review, 6:1, 20–39. 2. Onyeaka H, Anumudu CK, Al-Sharify ZT, Egele-Godswill E, Mbaegbu P. (2021). ‘COVID-19 pandemic: A review of the global lockdown and its far-reaching effects’ Science Progress doi:10.1177/00368504211019854 3. kff.org/global-health-policy/issue-brief/economic-impact-of-covid-19-on-pepfarcountries 4. statista.com/study/71343/economic-impact-of-the-coronavirus-covid-19-pandemic

Astronomy 2024.indb 306

07/02/2023 22:41

Mission to Mars: Countdown to Building a Brave New World 307 2021), heightened awareness of individual and community well-being5,6 including those who care for others (De Kock et al 2021), adaptation and resilience in some but not all individuals7 and the rise in enabling technologies which connect people who have access to current and ever evolving forms of communication (Gabbiadini et al 2020, Nguyen et al 2020). In parallel, we have also witnessed remarkable advances in space exploration which include landing and deployment of rovers on Mars by the United States (US) and China; the discovery of a Martian aurora by the United Arab Emirates’ Hope probe; the discovery of an ocean on Mimas, a moon of Saturn; the first image of the black hole Sgr A* at the heart of the Milky Way; dedicated international efforts with public and private enterprise collaboration to make returning to the Moon a reality; and in July 2022, the return of images of the deep cosmos seen for the first time with the James Webb Space Telescope.

What Actually is the Right Stuff ? The origin of the term dates back to the early days of space exploration in the US galvanized by the ‘conquest of space’ – the space race with the former Soviet Union from 1945 to 1963 (Wolfe 1979). Having the Right Stuff was driven by the need to win and not be disadvantaged in the first instance and to explore and define new boundaries which could subsequently be utilised in the second. In 1957 the Soviet Union shocked the world and especially the US by launching Sputnik, the world’s first satellite into orbit. This led to the creation of NASA in 1958 and the start of the US space programme for humans in space called Project Mercury and in 1959, selection of the ‘Mercury Seven’, astronauts all deemed suitable to enter space. Soviet astronaut Yuri Gagarin was the first man to enter space on 12 April 1961, US astronaut Alan Shepard became the second man on 5 May 1961 and John Glenn, another member of the Mercury Seven, orbited the Earth three times aboard Friendship 7 on 20 February 1962. Having the right stuff essentially meant keeping your fears to yourself, and was often masked by machismo behaviour, aspirations for fame and hero status aligned with a driven goal to be a willing and honoured participant in defining a new frontier and be remembered for it. This constrained 5. kff.org/coronavirus-covid-19/issue-brief/the-implications-of-covid-19-for-mentalhealth-and-substance-use 6. who.int/europe/emergencies/situations/covid-19/mental-health-and-covid-19 7. gov.uk/government/publications/covid-19-mental-health-and-wellbeing-surveillancereport/2-important-findings-so-far

Astronomy 2024.indb 307

07/02/2023 22:41

308  Yearbook of Astronomy 2024

The Mercury Seven: From left to right: Gordon Cooper, Walter Schirra, Alan Shepard, Virgil Grissom, John Glenn, Donald Slayton and Scott Carpenter. Credit NASA photo S63-18853. (Wikimedia Commons/NASA photo S63-18853)

mental fortitude and resilience was accompanied by extreme physical fitness and discipline and underpinned astronaut selection criteria which during this period were restricted to military test pilots only.

Is the ‘Old’ Right Stuff Applicable for Today’s Space Exploration? Today, the need for diversity and inclusion as much as is practicable is more important than ever with far more recognition of equality that appeared to be the case 60 years ago.8 NASA’s Artemis project9 which is to return to the Moon in the 2020s is to include a female astronaut and an astronaut of colour. Although a proportion of astronauts have military experience, today’s selection criteria do not demand it and 8. National Academies of Sciences, Engineering, and Medicine. 2022. ‘Advancing Diversity, Equity, Inclusion, and Accessibility in the Leadership of Competed Space Missions’. Washington, DC: The National Academies Press. doi.org/10.17226/26385 9. nasa.gov/specials/artemis-team

Astronomy 2024.indb 308

07/02/2023 22:41

Mission to Mars: Countdown to Building a Brave New World 309 an increasing number of astronauts are civilians. Clearly, as is the case for terrestrial exploration, candidate astronauts must be physically fit and mentally prepared to endure, cope with and manage stressful situations. As part of the training program, candidates are required to complete military water survival before beginning their flying programme, pass a swimming test and become qualified SCUBA divers to prepare for spacewalk training. Mental fitness assessment includes psychological and psychiatric evaluation of the ability to work as an individual and in a team, under stressful situations and to demonstrate judgement, leadership, communication and motivational skills. With the capability of judgement and leadership, as on Earth, come the softer skills of consideration for others, empathy, encouragement and open discussion of anxieties and concerns, some of which would have been deemed as weaknesses in individuals in the very early space missions. Scott Kelly’s excellent narrative (Kelly and Dean 2017) describe both the voyage in space and the voyage of self-understanding and how the environment shapes personal perspective. Today’s NASA’s Right Stuff now includes qualification to at least Master’s degree level in a scientific or medical discipline. In the last article ‘The Bare Necessities of Life’ I described some of the analogue environments used to assess team dynamics and behaviours which are essential to get right first time for building and maintaining a Martian colony. The active exclusion of women from NASA’s Apollo and Skylab programmes (as women could not become test pilots and being a test pilot was mandatory for selection) has now been relaxed. The first and youngest female cosmonaut, Valentina Tereshkova flew on Vostok 6 on 16 June 1963. To date approximately 90% of astronauts and cosmonauts are men, however, the representation of women as equally capable contributors in all activities has rightfully – if not slowly – been recognised and is now a staple part of future mission planning. With the long-term view of Mars, colonisation and societal growth, human procreation obviously requires both sexes and the philosophy and ethics associated with this topic will be discussed in a future article. Our new Right Stuff respects racial – in addition to gender – inclusivity. To prepare for the Apollo-Soyuz docking mission in 1975, astronauts lived and trained in Russia and cosmonauts did the same in the US. Both Russia and the US flew astronauts from different countries in Europe, the Americas and India and the International Space Station has representatives from 19 countries. In parallel, both professional and amateur space agencies, organisations and academic foundations have developed throughout many nations each with their own goals to represent country expertise in the best way possible. In the last 30 years, China has entered the field; in 2003 Yang Liwei became the first Chinese citizen in space and China is also planning on sending people to the Moon as a stepping stone to Mars. The

Astronomy 2024.indb 309

07/02/2023 22:41

310

Yearbook of Astronomy 2024 The basic principles of leadership. (M. Braddock)

logical extension for true diversity is that acceptance of both non-religious and religious beliefs and cultural differences, which may in their simplest form mean food and beverage and ‘down time’ preference, particularly over long periods of time and most certainly over a lifetime. We must acknowledge that we human beings will respond differently to our environment and can often become in awe of our surroundings. Many astronauts and cosmonauts have reported that one of the most emotionally fulfilling things to do once in space is to look back at planet Earth. The view can be so captivating that it can, for some, alter their views of themselves, their purpose in life and humanity and its place in the universe, a phenomenon known as the overview effect. For others, the view can enhance their existing religious beliefs and their place in the universe and, as has been evidenced with the Covid-19 pandemic, positive religious coping may be able to moderate some aspects of physical, interpersonal, and psychological loss (Cowden et al 2021). It is noteworthy that Space Agencies in general support astronauts to practice their religious beliefs either in public or in private. This topic is now mainstream in NASA scientist and European researcher’s planning schedules.10 At the outset, however, it would appear appropriate to have colonists exhibit a balanced outlook on life, have neither strong non-secular or secular beliefs, be able to seek out the best in everybody, be tolerant of the views of others, especially if their opinions differ from one’s own and above all, put the team and mission ahead of personal achievement. These are some of the standard components of being part of and leading any team, whether it be in a board room in an international corporate 10. nasa.gov/hrp/spaceflightforeverybody

Astronomy 2024.indb 310

07/02/2023 22:41

Mission to Mars: Countdown to Building a Brave New World 311 conglomerate or as part of a local sports team – leadership requiring vision and unwavering drive is essential. Qualities required for a Mars colonial leader do have some additional and unique features, shared with missions being undertaken in extreme environments, including military exercises though unlike their terrestrial counterparts, include acceptance that the mission is likely ‘no return’. The ability to delegate, communicate and encourage when needed, celebrate the successes and share in the ‘not-so’ successes is tantamount and together with an overriding sense of purpose, optimism and realism where terrestrial norms may no longer apply, make for leading the pioneers of this new frontier.

The Right Stuff Needs to Include Patience! As of October 2022, no sign of past or present life has been found on, or in rock samples drilled from the surface of the planet. However, plenty of evidence supports the notion that the surface has been and continues to be weathered by both wind and water, similar to many places on Earth. Both NASA’s Perseverance and the CNSA’s Zhurong rovers have made important discoveries from their exploration of the Martian surface over the last 12 months. Perseverance, which landed in the Jezero crater in March 2021 has uncovered a specific type of fine-grained rock in an area known as the Hogwallow Flats11 which may provide us with the best evidence for past life. The crater floor comprises igneous rocks formed as molten rock cooled and solidified billions of years ago and is surprising, as the rocks were expected to be sedimentary, created by the deposition of layers of sediment over time by wind and water and widely found in the delta region of the crater. The identification of igneous rocks provides geologists with a unique opportunity as scientists can analyse the radioactive decay of elements inside them to determine their age. Moreover the identification of salt-rimmed holes in one of the drilled samples is intriguing as the holes are likely formed by the passage of water flowing through the rock. This early finding is significant as it supports the original astrobiology objective of identifying an ancient volcanic rock that had interacted with water, suggestive of a life-friendly environment such has never been seen before on Mars. This rock formation, called Maaz, covers much of Jezero’s floor (Witze 2022). Together six samples from a total of up to 30 to be collected have been cached so far for return to Earth at a later date. In parallel, Zhurong which landed in May 2021 in the Utopia Planititia which is believed to be an ancient ocean, has detected the presence of etchings and grooves in the rock which suggest intense wind erosion from sand. The flaky texture of rocks implies past interaction with 11. mars.nasa.gov/mars2020/mission/status/387/fine-grained-rocks-at-hogwallow-flats

Astronomy 2024.indb 311

07/02/2023 22:41

312  Yearbook of Astronomy 2024 water and the finding of wind-sculpted structures called mega ripples spanning a few metres support the notion of past and present Martian weathering. Taken together, both rovers have made excellent progress in being able to safely navigate the Martian surface, collect data for return to Earth for scientists to study and analyse and collect samples. Patience is now a key component of the Right Stuff and it is essential to allow time for thorough experimentation and interpretation of data and manage the expectations of both professional space scientists and the general public – both of whose understanding is required to maintain momentum for allowing the next wave of new discoveries to be made.

Designer Right Stuff of the Future? In Einstein’s, open letter to the General Assembly of the United Nations in October 1947 he states: ‘Because of our inability to solve the problem of international organization, it has actually contributed to the dangers which threaten peace and the very existence of mankind’ This statement is undoubtedly correct, perhaps especially so today with the realisation of climate change, acceptance that change towards carbon net zero needs to accelerate and the omnipresent threat of world conflict. However, this situation is likely to always be the case in any society where nationalistic pride, and with some justification predominates and where, perhaps country insecurity contributes as a confounder. How utopian would it be for everybody interested in exploring Mars and space in general to share funding, data, mission plans for the future? Picture a world where the boundaries between natural and synthetic biology have become blurred, where digital technology is accessible to everyone, where bioelectronics is able to augment human physiological processes, where gene editing and new medicines are able to modify human beings to be less susceptible to the effects of radiation, microgravity and irrational judgement and actions. Science fiction and utopian fantasy? At present, perhaps yes, although the pace of technology development is accelerating and within the next five years is set to make major breakthroughs in what it means to be human and how these advances can best be put to use on Earth and in Space (Braddock 2021, Cahill and Braddock 2021, Sharpe and Braddock 2021) and how robotics may lead the future exploration of space (Goldsmith and Rees 2022). Maybe, just maybe, we will see nations representing Homo sapiens come together to pool their knowledge, share and solve their challenges and celebrate their successes together.

Astronomy 2024.indb 312

07/02/2023 22:41

Mission to Mars: Countdown to Building a Brave New World 313

A new world, where digital bioelectronics, artificial intelligence and human physiology may play a role in defining the Right Stuff of the future. (Pixabay)

Indeed and as quoted from Christa McAuliffe a payload specialist and American teacher and astronaut killed on the Space Shuttle Challenger in 1986: ‘Space is for everybody. It’s not just for a few people in science or math, or for a select group of astronauts. That’s our new frontier out there, and it’s everybody’s business to know about space’. The next article in the series will assess the current state of the art for human enhancement as applied to space travel and introduce humanoid robots as our partners for Mars colonisation and habitation.

References

Bieber, F. (2022). ‘Global Nationalism in Times of the COVID-19 Pandemic’. Nationalities Papers, 50, #1, 13–25 Braddock, M. (2021). ‘Limitations for colonisation and civilisation built and the potential for human enhancements. Human enhancements for lunar, Martian and future missions to the outer planets’. Hardcover ISBN 978-3-030-42035-2, eBook ISBN 978-3-030-42036-9, Springer Publishing

Astronomy 2024.indb 313

07/02/2023 22:41

314  Yearbook of Astronomy 2024 Cahill, B. and Braddock, M. K (2021). ‘Back to the future: the rise of human enhancement and potential applications for space missions’. Studia Humana, 10:4, 1–6. Sharpe, R. and Braddock, M. (2021). ‘Sustaining resources for Homo Martis: the potential of synthetic biology for the settlement of Mars’. Studia Humana, 11:1, 1–16. Cowden, R.G., Rueger, S.Y., Davis, E.B., Counted, V., Kent, B.V., Chen, Y., Van der Weele, T.J., Rim, M., Lemke, A.W., Worthington, E.L. (2022). ‘Resource loss, positive religious coping, and suffering during the COVID-19 pandemic: a prospective cohort study of US adults with chronic illness’, Mental Health, Religion & Culture, 25:3, 288–304. De Kock, J.H., Latham, H.A., Leslie, S.J., Grindle, M., Munoz, S.-A., Ellis, L., Polson, R., O’Malley, C.M. (2021). ‘A rapid review of the impact of COVID-19 on the mental health of healthcare workers: implications for supporting psychological well-being’. BMC Public Health, 21, 104. doi.org/10.1186/s12889-020-10070-3 Gabbiadini, A., Baldissarri, C., Durante, F., Valtorta, R.R., De Rosa, M., Gallucci, M. (2020). Together Apart: The Mitigating Role of Digital Communication Technologies on Negative Affect During the COVID-19 Outbreak in Italy’. Frontiers in Psychology, doi=10.3389/fpsyg.2020.554678 Goldsmith, D., Rees, M. (2022). The End of Astronauts: Why Robots Are the Future of Exploration. ISBN 978-0-674-25772-6, Belknap Press. Kelly, S., Dean, M. L. (2017). Endurance: A Year in Space, A Lifetime of Discovery. Published by Alfred A. Knopf, Inc (US) and Viking Press (UK), ISBN 978-1-5247-3159-5. Mylonas, H., Whalley, N. (2022). ‘Pandemic Nationalism’, Nationalities Papers, 50, #1, 3–12. Nguyen, M.H., Gruber, J., Fuchs, J., Marler, W., Hunsaker, A., Hargittai, E. (2020). ‘Changes in Digital Communication During the COVID-19 Global Pandemic: Implications for Digital Inequality and Future Research’, Social Media + Society. doi:10.1177/2056305120948255 Priya, S.S., Cuce, E., Sudhakar K. (2021). A perspective of COVID 19 impact on global economy, energy and environment, International Journal of Sustainable Engineering, 14, #6, 1290–1305. Witze, A. (2022). ‘A Year on Mars: How NASA’s Perseverance rover hit a geological jackpot’, Nature, 603, 18–19. Wolfe, T. (1979). The Right Stuff, Farrar, Straus and Giroux (Publishers)

Astronomy 2024.indb 314

07/02/2023 22:41

A Triumvirate of Telescope Makers Thomas Cooke, Howard Grubb and Alvan Clark John McCue and John Nichol

There was an Englishman, an Irishman and an American – separated by national boundaries but joined, almost to a point, by birth at the beginning of the nineteenth century. Thomas Cooke was born in Allerthorpe, near Pocklington, East Riding of Yorkshire on 8 March 1807; Thomas Grubb in Portlaw, County Waterford, Ireland on 4 August 1800; and Alvan Clark in Ashfield, Massachusetts on 8 March 1804. They ruled the world of refracting telescope-making until the end of the century, engaging each other in a dramatic leapfrog combat to build the largest refractor in the world, a contest won by Clark with the 40-inch diameter lens in the Yerkes Thomas Cooke. ( John McCue) Observatory refractor. That building was opened in 1897, poignantly the year of Alvan Graham Clark’s death, Clark’s second son, the father himself dying in 1887. Moreover, and importantly for astronomical research, all three launched successful family enterprises, emphasising their stamp on history. Thomas Cooke’s family were poor, his father being a shoemaker in the village of Allerthorpe. Thomas wanted to follow his hero, James Cook, on voyages of exploration,1 and he was even ready to board a ship at Hull, but his mother persuaded him to stay. He opened a successful village school, teaching the children of wealthy locals, and was clearly a well-liked communicator. Moving to York in 1829, he made his first telescope, fashioning the lens from the base of a whisky tumbler, and the tube from tin. His first shop, opened in 1837, was an instant success, turning his remarkable talent to many aspects of optics such as microscopes, spectacles 1.  Thomas Cooke Telescopes, Martin Lunn, thomascooketelescopes.wordpress.com

Astronomy 2024.indb 315

07/02/2023 22:41

316  Yearbook of Astronomy 2024 and opera glasses. The telescope business boomed, and he constantly had to move to larger premises. Thomas Grubb was born into a wealthy farming family, and he began his career in billiard table manufacture before an interest in astronomy took him, and he founded the Grubb Telescope Company in 1833. The firm was eventually bought in 1925 by the shipping engineer Sir Charles Parsons and a factory was established on Tyneside, north-eastern England. They traded until 1985 and were responsible for a number of large professional telescopes, such as the Isaac Newton telescope with its 2.5-metre mirror, and the 4.2-metre Howard Grubb. ( John McCue) William Herschel Telescope, both on La Palma in the Canary Islands. His son Howard Grubb, born in 1844, was able to benefit from the vast experience of his father. He extended the size and quality of the telescopes produced by the family business, and was knighted in 1877 at Dublin Castle. Alvan Clark was from a family of Cape Cod whalers and discovered telescope making at the relatively late age of 40. Like Thomas Cooke, he was self-taught and until his optical epiphany he was a portrait artist and engraver. Alvan had two sons, Alvan Graham and George Bassett. The latter was instrumental in sparking his father’s interest in telescope making – as a student George attempted to melt down some metal from a broken bell in the hope of casting a telescope mirror (it was not until 1864 that glass was first used to make telescope mirrors following the pioneering work of Leon Foucault). Alvan became interested in his son’s project which eventually drew him to make several reflecting telescopes. He was never really satisfied with their performance, and around 1846 turned to making lenses, an area in which he made rapid progress. It was not long before he was able to recognise figuring errors in the 15-inch Harvard telescope. In those early days of telescope making, optical testing methods were not well established, and to assess the quality of a lens, double stars of known close separation were often used. As a result of this several new binaries were discovered. Clark was in correspondence with the acclaimed English observer William Rutter Dawes who greatly admired the quality of Clark’s lenses. Indeed, he purchased five Clark objectives with apertures around 7 to 8 inches in diameter. Around this time

Astronomy 2024.indb 316

07/02/2023 22:41

A Triumvirate of Telescope Makers 317 in the US, little interest was shown in Clark’s work and he himself attributed his eventual success to Dawes’ praise of his optics. In 1858 one of the 8-inch lenses bought by Dawes was sold to the English pioneer of astrophysics William Huggins for £200, the lens being remounted by Thomas Cooke. In 1860 the University of Mississippi placed an order with the Clarks for what would then be the largest refractor in the world, with an aperture of 18½ inches. Before this, the largest lens made by the Clarks was 12 inches in diameter, so the Mississippi scope was a major step forward. The Civil War prevented payment reaching the Clarks so the telescope was installed, in 1866, at the Dearborn Observatory in Chicago. During testing of this lens, Alvan Graham Clark discovered Sirius’ companion star, whose existence had been predicted by Bessel as a result its inconsistent proper motion. The success of the 18.5-inch was followed by more refractors each of which was to hold the title as the world’s largest refractor when constructed. 1873 saw the completion of the 26-inch for the US Naval Observatory, for which the Clarks received a payment of $20,000. This was the telescope destined to displace Thomas Cooke’s 25-inch Newall Telescope as the world’s largest refractor. Using the 26-inch telescope, Asaph Hall discovered Phobos and Deimos, the moons of Mars, on 12 August 1877. Previously, Johannes Kepler speculated that Mars might have two moons; this may have been picked up by Jonathan Swift who, in his book of 1726 Gulliver’s Travels, tells how the scientists of Laputa discovered two satellites of Mars. The Clarks’ record for producing the world’s largest refractor continued in 1883 with the 30-inch for the Pulkova Observatory, near Leningrad. Unfortunately, this telescope was destroyed in the Second World War, although the lens survived. 1887 saw the 36-inch for the Lick Observatory, and finally, in 1897, they built the 40-inch for the Yerkes observatory which still holds the title of the world’s largest refractor. It is said that Alvan Clark never set foot in another optical shop so, not seeing what his rivals were doing, he could not say which of his techniques was original to him. His son Alvan Graham did visit Europe though, which included a call on Howard Grubb, perhaps the Clarks’ greatest competitor. While openly recognising the quality of the Alvan Clark. ( John McCue)

Astronomy 2024.indb 317

07/02/2023 22:41

318  Yearbook of Astronomy 2024 Clark lenses, Grubb was less complimentary about their telescope mountings, believing the axes to be too small for the size of the telescope tube. Grubb also thought that the mounts were cumbersome. This seems borne out by the 26-inch Clark refractor in the US Naval Observatory, which was subsequently re-mounted by Warner and Swasey. Before Alvan Graham Clark’s European trip, the Clarks employed wooden tubes for their instruments. Following the trip, however, they used riveted steel tubes, after Alvan Graham saw the Newall 25-inch telescope (the largest refractor in the world in 1869) made by Thomas Cooke. Alvan Graham, like his father, believed that it was impossible to make a perfect reflector and this was vocalised during his meeting with Howard Grubb who did not agree with this assertion. This led to a heated discussion between the two. Now, when the trustees of the Lick Observatory were considering the purchase of a large telescope, both Clark and Grubb were rival bidders. Howard Grubb lobbied hard, assuring the trustees he was able to supply the instrumentation that they needed, saying he could produce a reflector better than anyone else. On refractors however, Grubb conceded that

The world-beating 40-inch refractor at Williams Bay, Wisconsin. Built by the Clarks between 1895 and 1897, and financed by Chicago millionaire Charles Yerkes, this fine instrument was used in research by Chicago University for over 100 years. It was (at time of writing) expected to re-open in 2022 as a public outreach facility. (Ryan Benshiemer/Ideal Impressions Photography)

Astronomy 2024.indb 318

07/02/2023 22:41

A Triumvirate of Telescope Makers 319 he could not promise to make a better objective lens than Mr. Clark, but he would make a superior mount. In the event, the Lick trustees hedged their bets and gave the contract for the 36-inch lens to Alvan, the mount and dome contract going to Warner and Swasey. Howard Grubb was left bitterly disappointed that the Lick trustees gave him nothing, although he was magnanimous enough to suggest the rising floor idea in the dome. December 1880 was around the time that Howard Grubb was leading the race to build the world-beater; he had completed the 27-inch refractor for the Vienna observatory, the largest refractor in the world at that time. History teaches us that the Clarks excelled at lens-making with few others, if any, able to match their quality. However, in other areas, things were different. As we have seen, Clark mounts were of questionable quality and as a result we see Clark objectives mated with third party mounts and accessories. The story with Howard Grubb could not be more dissimilar. Grubb made lenses, mirrors, mounts and accessories (such as electrical clock drives) of the highest quality often with innovative designs. Howard began working with his father on the 48-inch Melbourne telescope, which was completed in 1867. At the time it was the second largest reflector in the world, surpassed only by the 72-inch instrument of Lord Rosse. The 48-inch telescope set the standard for observatory telescopes that followed. It was mounted equatorially and had a Cassegrain optical configuration. The largest refractor made by Howard Grubb was for the Royal Greenwich Observatory; installed in 1893 it had an aperture of 28 inches. It was briefly moved to Herstmonceux in 1947, but was returned to Greenwich in 1971 in time for the tri-centennial of the observatory in 1975 when it was recommissioned by Queen Elizabeth II. Grubb produced seven refractors in the range 24 to 28 inches. Some of these were designed for photographic work, an example being the 26-inch Thompson refractor at Herstmonceux, which was used to take 60,000 photographs between 1897 and 1988. In the late-nineteenth century a large group of observatories from around the world took part in an ambitious project to catalogue and map the night sky. The Carte du Ciel and the Astrographic Catalogue were parts of this initiative. The telescopes to be used would have an aperture of 13 inches and be optimised for photography. Seven of these telescopes were made in Dublin by Grubb between 1889 and 1896 and sent to different observatories around the world including Greenwich, where photography for the project started in 1892. This same Greenwich lens was to play a vital role in proving Einstein’s general theory of relativity, being used in Brazil during the total solar eclipse of 29 May 1919 to photograph stars near the sun. The Astronomer Royal, Frank Watson Dyson, predicted that if Einstein was right

Astronomy 2024.indb 319

07/02/2023 22:41

320  Yearbook of Astronomy 2024 a small deflection in the position of the star would be seen due to the gravitational effect of the Sun. This was, in fact, found to be the case, and Einstein became a world-wide overnight celebrity. The power and precision of Grubb’s lens had enabled this observation to be made. Cooke, Grubb and Clark were microscopically aware of each other’s work throughout their careers and no doubt occasionally their reputations bumped in the endeavours of individuals. One well-known example is the aforementioned William Huggins, the father of modern spectroscopy. He possessed an 8-inch refractor with a Clark lens mounted by Thomas Cooke. He considered buying a new telescope to develop his research on the constituents of the stars and nebulae, but from whom should he buy it? In early 1868, Thomas Grubb was just taking over from his father, Howard, and he paid a visit to the Huggins’ observatory. Huggins confided in his friend, Thomas Romney Robinson that he had nonetheless already been in contact with Thomas Cooke,2 maybe because Grubb’s estimate of £800 was beyond his budget, even with the expected £560 from the sale of his Alvan Clark telescope. Huggins wanted a larger aperture than his existing 8-inch Clark, possibly a 12-inch, but such a large refractor would not fit in his existing observatory building if it was built to the same aperture to focal length ratio as the 8-inch, this being 1:15. Presumably to solve this, Cooke offered to build Huggins a “dumpy” refractor of 11-inches lens diameter and a focal length of only 10 feet. Sadly, Cooke died in the autumn of that year, and not long after, Huggins’ mother died. These tragedies threw his plans into disarray. With support Huggins recovered, and his friend Robinson approached the Royal Society for their financial help.3 Howard Grubb was thus commissioned to build a 15-inch refractor for Huggins, and the observatory was modified to accommodate it. Thus was spectroscopy, the crucial new branch of astronomy, saved.

2. Barbara J. Becker, Ph.D. thesis, ‘Eclecticism, Opportunism and the Evolution of a New Research Agenda: William and Mary Huggins’, submitted to John Hopkins University. See faculty.humanities.uci.edu/bjbecker/huggins (Chapter 3, Part 3) 3. The Victorian Amateur Astronomer, Allan Chapman, Wiley, 1998, p.116.

Astronomy 2024.indb 320

07/02/2023 22:41

Miscellaneous

Astronomy 2024.indb 321

07/02/2023 22:41

Astronomy 2024.indb 322

07/02/2023 22:41

Some Interesting Variable Stars Tracie Heywood

You may have considered taking up variable star observing but how should you choose which stars to observe? There are so many variable stars in the night sky and you don’t want to waste your time attempting to follow the “boring” ones. Your choice of stars will, of course, depend on the equipment that you have available, but also needs to be influenced by how much time you can set aside for observing. This article splits some of the more interesting variable stars into three groups. The group that is most suited to you will depend on how often you can observe each month and for how long you can observe on a clear night. The light curves included have been constructed from observations stored in the Photometry Database of the British Astronomical Association Variable Star Section. Comparison charts for most of these stars can be found on the BAA Variable Star Section website at britastro.org/vss

One-Nighters These are stars that can go through most of their brightness variations in the course of a single (reasonably long) night and would suit people who can only observe occasionally, but can then observe well into the night. STAR

TYPE

RA

DEC

H

M

º

9

MAX / MIN

PERIOD

OO Aquilae

EW

19

48

+09

19

9.2 / 9.9

0.506793 days (~12.16 hours)

U Cephei

EA

01

02

+81

53

6.7 / 9.3

2.493087 days (~60 hours)

TW Draconis

EA

15

34

+63

54

7.3 / 8.9

2.806847 days (~67 hours)

Beta (β) Persei (Algol)

EA

03

08

+40

57

2.1 / 3.4

2.867 days (~69 hours)

OO Aquilae is a W UMa type eclipsing variable. These are ‘contact’ binary systems that show no period of constant brightness between eclipses. Predictions for upcoming eclipses can be found at as.up.krakow.pl/minicalc/AQLOO.HTM

Astronomy 2024.indb 323

07/02/2023 22:41

324  Yearbook of Astronomy 2024 U Cephei is an Algol-type eclipsing variable. Primary eclipses last for about 9 hours and are flat-bottomed, indicating that they are total eclipses. Predictions for upcoming eclipses can be found at as.up.krakow.pl/minicalc/CEPU.HTM TW Draconis is another Algol-type eclipsing variable star. Predictions for upcoming eclipses can be found at as.up.krakow.pl/minicalc/DRATW.HTM Beta Persei (Algol) is an eclipsing variable that shows deep primary eclipses but only very shallow secondary eclipses. Although circumpolar from the UK, it is too low in the sky for observation from April to June

Most Clear Nights These are stars that vary a bit more slowly, but which can display significant changes over a week or two. They would suit people who can observe for a short while on (nearly) every clear night. STAR

TYPE

RA

DEC º

MAX / MIN

PERIOD

H

M

T Coronae Borealis

Rec Nova

16

00

+25 55

2.0 / 10.8

227.6 days (orbital)

V367 Cygni

EB

20

48

+39 17

7.2 / 8.2

18.60 days

SV Sagittae

RCB

19

08

+17 38

10.3 / 17.1

None

SU Tauri

RCB

05

49

+19 04

9.1 / 18.0

None

9

T Coronae Borealis is a recurrent nova system that produced outbursts in 1866 and 1946. It has shown increased activity in recent years, although we can’t assume that the next outburst will occur exactly 80 years on from that of 1946. V367 Cygni is a Beta Lyrae type eclipsing variable that can be followed using binoculars. Both primary and secondary eclipses can be observed visually SV Sagittae and SU Tauri are similar types of variable star to R Coronae Borealis. They can show deep fades, unpredictable in advance, and these can last for many months, especially so in the case of SU Tauri. A good-sized telescope is needed to follow them all they way down to minimum. Some minima of SU Tauri have been so deep that they have only been visible to CCD observers rather than to visual observers.

Astronomy 2024.indb 324

07/02/2023 22:41

Some Interesting Variable Stars  325

Several Times per Month Slower variables whose brightness will change significantly over several months or a year. These variables would suit people who can observe several times per month, but not necessarily on every clear night. STAR

TYPE

RA

DEC

H

M

º

9

MAX / MIN

PERIOD

S Coronae Borealis

Mira

15

21

+31

22

5.8 / 14.1

360 days

W Cygni

SR

21

36

+45

22

5.6 / 7.5

131 days / 260 days

Chi Cygni

Mira

19

51

+32

55

3.4 / 14.2

407 days

U Delphini

SR

20

46

+18

06

6.2 / 7.7

120 days

g Herculis

SR

16

29

+41

53

4.6 / 6.0

89 days / 875 days

Tau4 Serpentis

SR

15

36

+15

05

6.0 / 7.5

87 days

RY Ursae Majoris

SR

12

20

+61

19

6.9 / 8.5

310 days

S Coronae Borealis is a Mira type variable. As for other Mira type variables, some maxima are brighter than others. As the accompanying light curve shows, the 2022 maximum was unusually bright. The 2024 maximum is predicted to occur in late June. Chi Cygni is another Mira type variable, lying not far from Eta (η) Cygni. It is poorly placed for observation at the start of the year but better placed from the spring onwards. Maximum in 2024 is predicted to occur during July. W Cygni, U Delphini, g Herculis, Tau4 Serpentis and RY Ursae Majoris are semiregular variables that can be followed using binoculars. “Semi-regular” indicates that the brightness variations repeat only roughly from one cycle to the next. The observed brightness range differs between cycles, sometimes covering the whole of the listed range, but more often being somewhat smaller.

Astronomy 2024.indb 325

07/02/2023 22:41

The BAA VSS finder chart for Beta (β) Persei (Algol). (BAA Variable Star Section)

Astronomy 2024.indb 326

07/02/2023 22:41

Minima of Algol in 2024 Beta (β) Persei (Algol): Magnitude 2.1 to 3.4 / Duration 9.6 hours Jan

May

Sep

 1  4  7  9 12 15 18 21 24 27 29

h  7.4  4.2  1.0 21.8 18.6 15.5 12.3  9.1  5.9  2.7 23.5

 3  6  9 12 15 17 20 23 26 29

14.5 11.3  8.1  4.9  1.7 22.5 19.4 16.2 13.0  9.8

 1  3  6  9 12 15 18 21 23 26 29

 0.7 21.6 18.4 15.2 12.0  8.8  5.6  2.5 23.3 20.1 16.9

Feb * * *

 1  4  7 10 13 16 19 21 24 27

h 20.3 17.2 14.0 10.8  7.6  4.4  1.2 22.1 18.9 15.7

 1  4  7  9 12 15 18 21 24 27 29

 6.6  3.4  0.3 21.1 17.9 14.7 11.5  8.3  5.2  2.0 22.8

Jul

 2  5  8 11 14 16 19 22 25 28 31

13.7 10.5  7.4  4.2  1.0 21.8 18.6 15.4 12.2  9.1  5.9

Nov

*

Mar

* * *

* Jun

* *

* * *

Oct

* * *

 1  4  7 10 12 15 18 21 24 27 30

h 12.5  9.3  6.1  3.0 23.8 20.6 17.4 14.2 11.0  7.9  4.7

 2  5  8 11 14 17 20 22 25 28 31

19.6 16.4 13.2 10.1  6.9  3.7  0.5 21.3 18.1 14.9 11.8

 3  5  8 11 14 17 20 23 26 28

 2.7 23.5 20.3 17.1 14.0 10.8  7.6  4.4  1.2 22.0

Apr

* *

Aug

*

* * *

* *

Dec

 2  4  7 10 13 16 19 22 24 27 30

h  1.5 22.3 19.1 15.9 12.8  9.6  6.4  3.2  0.0 20.8 17.6

 3  6  9 11 14 17 20 23 26 29

 8.6  5.4  2.2 23.0 19.8 16.7 13.5 10.3  7.1  3.9

 1  4  7 10 13 16 18 21 24 27 30

18.9 15.7 12.5  9.3  6.1  2.9 23.8 20.6 17.4 14.2 11.0

*

* *

*

* * * *

Eclipses marked with an asterisk (*) are favourable from the British Isles, taking into account the altitude of the variable and the distance of the Sun below the horizon (based on longitude 0° and latitude 52°N) All times given in the above table are expressed in UT/GMT.

Astronomy 2024.indb 327

07/02/2023 22:41

The BAA VSS finder chart for g Herculis, with four suitable comparison stars labelled. (BAA Variable Star Section)

Astronomy 2024.indb 328

07/02/2023 22:41

Astronomy 2024.indb 329

07/02/2023 22:41

A BAA VSS light curve showing CCD observations, by member David Conner, of a secondary eclipse of OO Aquilae during the evening of 2 October 2019. The observations were made using the objective lens and tube of a 9 × 50 finder scope coupled to an Atik Titan monochrome CCD camera. All 448 observations were unfiltered. (David Conner/BAA Variable Star Section)

Astronomy 2024.indb 330

07/02/2023 22:41

The BAA VSS light curve for the R Coronae Borealis (RCB) type variable SU Tauri from early 2016 to spring 2022. Gaps in the light curve coincide with Taurus being near solar conjunction. (BAA Variable Star Section)

Astronomy 2024.indb 331

07/02/2023 22:41

The BAA VSS light curve for the Mira type variable S Coronae Borealis from January 2015 to July 2022. Note how the brightness at maximum in 2022 was considerably higher than that in earlier cycles. (BAA Variable Star Section)

Astronomy 2024.indb 332

07/02/2023 22:41

A BAA VSS light curve showing the observations of the Mira-type variable Chi Cygni between January 2002 and summer 2022 made by John Toone, one of the UK’s most prolific variable star observers. ( John Toone/BAA Variable Star Section)

Astronomy 2024.indb 333

07/02/2023 22:41

The BAA VSS visual light curve for the semi-regular variable RY Ursae Majoris between summer 2018 and summer 2022. (BAA Variable Star Section)

Some Interesting Double Stars Brian Jones

The accompanying table describes the visual appearances of a selection of double stars. These may be optical doubles (which consist of two stars which happen to lie more or less in the same line of sight as seen from Earth and which therefore only appear to lie close to each other) or binary systems (which are made up of two stars which are gravitationally linked and which orbit their common centre of mass). Other than the location on the celestial sphere and the magnitudes of the individual components, the list gives two other values for each of the double stars listed – the angular separation and position angle (PA). Further details of what these terms mean can be found in the article Double and Multiple Stars published in the 2018 edition of the Yearbook of Astronomy. Double-star observing can be a very rewarding process, and even a small telescope will show most, if not all, the best doubles in the sky. You can enjoy looking at double stars simply for their beauty, such as Albireo (β Cygni) or Almach (γ Andromedae), although there is a challenge to be had in splitting very difficult (close) double stars, such as the demanding Sirius (α Canis Majoris) or the individual pairs forming the Epsilon (ε) Lyrae ‘Double-Double’ star system. The accompanying list is a compilation of some of the prettiest double (and multiple) stars scattered across both the Northern and Southern heavens. Once you have managed to track these down, many others are out there awaiting your attention …

Astronomy 2024.indb 334

07/02/2023 22:41

Some Interesting Double Stars  335 Star Beta1,2 (β1,2) Tucanae

Declination h m ° ‘ 00 31.5 62 58

4.36 / 4.53

Separation PA (arcsec) ° 27.1 169

Achird (η Cassiopeiae) Mesarthim (γ Arietis) Almach (γ Andromedae)

00 49.1 +57 01 53.5 +19 02 03.9 +42

3.44 / 7.51 4.58 / 4.64 2.26 / 4.84

13.4  7.6  9.6

324   1  63

32 Eridani Alnitak (ζ Orionis)

03 54.3 02 57 05 40.7 01 57

4.8 / 6.1 2.0 / 4.3

 6.9  2.3

348 167

Gamma (γ) Leporis

05 44.5 22 27

3.59 / 6.28

95.0

350

Sirius (α Canis Majoris)

06 45.1 16 43

1.4 / 8.5

Castor (α Geminorum)

07 34.5 +31

53

1.93 / 2.97

 7.0

 55

Gamma (γ) Velorum

08 09.5 47 20

1.83 / 4.27

41.2

220

Upsilon (υ) Carinae

09 47.1 65 04

3.08 / 6.10

 5.03

129

Algieba (γ Leonis)

10 20.0 +19

50

2.28 / 3.51

 4.6

126

Acrux (α Crucis)

12 26.4 63 06

1.40 / 1.90

 4.0

114

Porrima (γ Virginis)

12 41.5 01 27

3.56 / 3.65

Cor Caroli (α Canum Venaticorum) Mizar (ζ Ursae Majoris)

12 56.0 +38

19

2.90 / 5.60

19.6

229

13 24.0 +54

56

2.3 / 4.0

14.4

152

Alpha (α) Centauri

14 39.6 60 50

0.0 / 1.2

Izar (ε Boötis)

14 45.0 +27

04

2.4 / 5.1

 2.9

344

Omega1,2 (ω1,2) Scorpii

16 06.0 20 41

4.0 / 4.3

14.6

145

Epsilon1 (ε1) Lyrae

18 44.3 +39

40

4.7 / 6.2

 2.6

346

Epsilon2 (ε2) Lyrae

18 44.3 +39

40

5.1 / 5.5

 2.3

 76

Theta1,2 (θ1,2) Serpentis

18 56.2 +04

12

4.6 / 5.0

22.4

104

Astronomy 2024.indb 335

RA

49 18 20

Magnitudes

Comments Both stars again double, but difficult Easy double Easy pair of white stars Yellow and blue-green components Yellowish and bluish Difficult, can be resolved in 10cm telescopes White and yelloworange components, easy pair Binary, period 50 years, difficult Binary, 445 years, widening Pretty pair in nice field of stars Nice object in small telescopes Binary, 510 years, orange-red and yellow Glorious pair, third star visible in low power Binary, 170 years, widening, visible in small telescopes Easy, yellow and bluish Easy, wide naked-eye pair with Alcor Binary, beautiful pair of stars Fine pair of yellow and blue stars Optical pair, easy The Double-Double, quadruple system with ε2 Both individual pairs just visible in 80mm telescopes Easy pair, mag 6.7 yellow star 7 arc minutes from θ2

07/02/2023 22:41

336  Yearbook of Astronomy 2024 Star Albireo (β Cygni)

RA Declination h m ° ‘ 19 30.7 +27 58

3.1 / 5.1

Separation PA (arcsec) ° 34.3  54

Algedi (α1,2 Capricorni) Gamma (γ) Delphini

20 18.0 12 32 20 46.7 +16 07

3.7 / 4.3 5.14 / 4.27

 6.3  9.2

292 265

61 Cygni

21 06.9 +38

5.20 / 6.05

31.6

152

Theta (θ) Indi

21 19.9 53 27

4.6 / 7.2

 7.0

275

Delta (δ) Tucanae

22 27.3 64 58

4.49 / 8.7

 7.0

281

Astronomy 2024.indb 336

45

Magnitudes

Comments Glorious pair, yellow and blue-green Optical pair, easy Easy, orange and yellow-white Binary, 678 years, both orange Fine object for small telescopes Beautiful double, white and reddish

07/02/2023 22:41

Some Interesting Nebulae, Star Clusters and Galaxies Brian Jones

Object 47 Tucanae (in Tucana) M31 (in Andromeda) Small Magellanic Cloud NGC 362 (in Tucana)

h 00 00 00 01

m 24.1 40.7 52.6 03.3

Declination ° ‘ 05 72 +41 05 49 72 51 70

M33 (in Triangulum) NGC 869 and NGC 884 M34 (in Perseus) M45 (in Taurus) Large Magellanic Cloud 30 Doradus (in Dorado)

01 02 02 03 05 05

31.8 20.0 42.1 47.4 23.5 38.6

+30 +57 +42 +24 69 69

28 08 46 07 45 06

M1 (in Taurus) M38 (in Auriga) M42 (in Orion) M36 (in Auriga) M37 (in Auriga) M35 (in Gemini) M41 (in Canis Major) M44 (in Cancer) M81 (in Ursa Major) M82 (in Ursa Major) Carina Nebula (in Carina)

05 05 05 05 05 06 06 08 09 09 10

32.3 28.6 33.4 36.2 52.3 06.5 46.0 38.0 55.5 55.9 45.2

+22 +35 05 +34 +32 +24 20 +20 +69 +69 59

00 51 24 08 33 21 46 07 04 41 52

M104 (in Virgo) Coal Sack (in Crux) NGC 4755 (in Crux) Omega (ω) Centauri

12 12 12 13

40.0 50.0 53.6 23.7

11 62 60 47

37 30 22 03

M51 (in Canes Venatici) M3 (in Canes Venatici)

13 13

29.9 40.6

+47 +28

12 34

Astronomy 2024.indb 337

RA

Remarks Fine globular cluster, easy with naked eye Andromeda Galaxy, visible to unaided eye Satellite galaxy of the Milky Way Globular cluster, impressive sight in telescopes Triangulum Spiral Galaxy, quite faint Sword Handle Double Cluster in Perseus Open star cluster near Algol Pleiades or Seven Sisters cluster, a fine object Satellite galaxy of the Milky Way Star-forming region in Large Magellanic Cloud Crab Nebula, near Zeta (ζ) Tauri Open star cluster Orion Nebula Open star cluster Open star cluster Open star cluster near Eta (η) Geminorum Open star cluster to south of Sirius Praesepe, visible to naked eye Bode’s Galaxy Cigar Galaxy or Starburst Galaxy NGC 3372, large area of bright and dark nebulosity Sombrero Hat Galaxy to south of Porrima Prominent dark nebula, visible to naked eye Jewel Box open cluster, magnificent object Splendid globular in Centaurus, easy with naked eye Whirlpool Galaxy Bright Globular Cluster

07/02/2023 22:41

338  Yearbook of Astronomy 2024 Object M4 (in Scorpius) M12 (in Ophiuchus) M10 (in Ophiuchus) M13 (in Hercules)

h 16 16 16 16

RA m 21.5 47.2 57.1 40.0

Declination ° ‘ 26 26 57 01 06 04 +36 31

M92 (in Hercules) M6 (in Scorpius) M7 (in Scorpius) M20 (in Sagittarius) M8 (in Sagittarius) M16 (in Serpens) M17 (in Sagittarius) M11 (in Scutum) M57 (in Lyra) M27 (in Vulpecula) M29 (in Cygnus) M15 (in Pegasus) M39 (in Cygnus) M52 (in Cassiopeia)

17 17 17 18 18 18 18 18 18 19 20 21 21 23

16.1 36.8 50.6 02.3 03.6 18.8 20.2 49.0 52.6 58.1 23.9 28.3 31.6 24.2

+43 32 34 23 24 13 16 06 +32 +22 +38 +12 +48 +61

11 11 48 02 23 49 11 19 59 37 31 10 25 35

Remarks Globular cluster, close to Antares Globular cluster Globular cluster Great Globular Cluster, just visible to naked eye Globular cluster Open cluster Bright open cluster Trifid Nebula Lagoon Nebula, just visible to naked eye Eagle Nebula and star cluster Omega Nebula Wild Duck open star cluster Ring Nebula, brightest planetary Dumbbell Nebula Open cluster Bright globular cluster near Epsilon (ε) Pegasi Open cluster, good with low powers Open star cluster near 4 Cassiopeiae

M = Messier Catalogue Number     NGC = New General Catalogue Number The positions in the sky of each of the objects contained in this list are given on the Monthly Star Charts printed elsewhere in this volume.

Astronomy 2024.indb 338

07/02/2023 22:41

Astronomical Organizations

American Association of Variable Star Observers 49 Bay State Road, Cambridge, Massachusetts, 02138, USA aavso.org The AAVSO is an international non-profit organization of variable star observers whose mission is to enable anyone, anywhere, to participate in scientific discovery through variable star astronomy. We accomplish our mission by carrying out the following activities: • observation and analysis of variable stars • collecting and archiving observations for worldwide access • forging strong collaborations between amateur and professional astronomers • promoting scientific research, education and public outreach using variable star data

American Astronomical Society 1667 K Street NW, Suite 800, Washington, DC 20006, USA aas.org Established in 1899, the American Astronomical Society (AAS) is the major organization of professional astronomers in North America. The mission of the AAS is to enhance and share humanity’s scientific understanding of the universe, which it achieves through publishing, meeting organization, education and outreach, and training and professional development.

Association of Lunar and Planetary Observers (ALPO) Matthew L. Will (Secretary), P.O. Box 13456, Springfield, IL 62791-3456, USA alpo-astronomy.org Founded in 1947 by Walter Haas, the ALPO is an international non-profit organization that studies all natural bodies in our solar system. ALPO Sections include Lunar, Solar, Mercury, Venus, Mars, Minor Planets, Jupiter, Saturn, Remote Planets, Comets, Meteors, Meteorites, Eclipses, Exoplanets, Outreach and Online, many with separate “Studies Programs” within these Sections. Minimum

Astronomy 2024.indb 339

07/02/2023 22:41

340  Yearbook of Astronomy 2024 membership is very reasonable and includes the quarterly full colour digital Journal of the ALPO. Interested observers of any experience are welcome to join. Many members stand ready to improve the skills and abilities of novices.

Astronomical Society of the Pacific 390 Ashton Avenue, San Francisco, CA 94112, USA astrosociety.org Formed in 1889, the Astronomical Society of the Pacific (ASP) is a non-profit membership organization which is international in scope. The mission of the ASP is to increase the understanding and appreciation of astronomy through the engagement of our many constituencies to advance science and science literacy. We invite you to explore our site to learn more about us; to check out our resources and education section for the researcher, the educator, and the backyard enthusiast; to get involved by becoming an ASP member; and to consider supporting our work for the benefit of a science literate world!

Astrospeakers.org astrospeakers.org A website designed to help astronomical societies and clubs locate astronomy and space lecturers which is also designed to help people find their local astronomical society. It is completely free to register and use and, with over 50 speakers listed, is an excellent place to find lecturers for your astronomical society meetings and events. Speakers and astronomical societies are encouraged to use the online registration to be added to the lists.

British Astronomical Association Burlington House, Piccadilly, London, W1J 0DU, England britastro.org The British Astronomical Association is the UK’s leading society for amateur astronomers catering for beginners to the most advanced observers who produce scientifically useful observations. Our Observing Sections provide encouragement and advice about observing. We hold meetings around the country and publish a bi-monthly Journal plus an annual Handbook. For more details, including how to join the BAA or to contact us, please visit our website.

Astronomy 2024.indb 340

07/02/2023 22:41

Astronomical Organizations  341

British Interplanetary Society Arthur C. Clarke House, 27/29 South Lambeth Road, London, SW8 1SZ, England bis-space.com The British Interplanetary Society is the world’s longest-established space advocacy organisation, founded in 1933 by the pioneers of British astronautics. It is the first organisation in the world still in existence to design spaceships. Early members included Sir Arthur C Clarke and Sir Patrick Moore. The Society has created many original concepts, from a 1938 lunar lander and space suit designs, to geostationary orbits, space stations and the first engineering study of a starship, Project Daedalus. Today the BIS has a worldwide membership and welcomes all with an interest in Space, including enthusiasts, students, academics and professionals.

Canadian Astronomical Society Société Canadienne D’astronomie (CASCA) 100 Viaduct Avenue West, Victoria, British Columbia, V9E 1J3, Canada casca.ca CASCA is the national organization of professional astronomers in Canada. It seeks to promote and advance knowledge of the universe through research and education. Founded in 1979, members include university professors, observatory scientists, postdoctoral fellows, graduate students, instrumentalists, and public outreach specialists.

Royal Astronomical Society of Canada 203-4920 Dundas St W, Etobicoke, Toronto, ON M9A 1B7, Canada rasc.ca Bringing together over 5,000 enthusiastic amateurs, educators and professionals RASC is a national, non-profit, charitable organization devoted to the advancement of astronomy and related sciences and is Canada’s leading astronomy organization. Membership is open to everyone with an interest in astronomy. You may join through any one of our 29 RASC centres, located across Canada and all of which offer local programs. The majority of our events are free and open to the public.

Federation of Astronomical Societies The Secretary, 147 Queen Street, Swinton, Mexborough, S64 8NG fedastro.org.uk The Federation of Astronomical Societies (FAS) is an umbrella group for astronomical societies in the UK. It promotes cooperation, knowledge and

Astronomy 2024.indb 341

07/02/2023 22:41

342  Yearbook of Astronomy 2024 information sharing and encourages best practice. The FAS aims to be a body of societies united in their attempts to help each other find the best ways of working for their common cause of creating a fully successful astronomical society. In this way it endeavours to be a true federation, rather than some remote central organization disseminating information only from its own limited experience. The FAS also provides a competitive Public Liability Insurance scheme for its members.

International Dark-Sky Association darksky.org The International Dark-Sky Association (IDA) is the recognized authority on light pollution and the leading organization combating light pollution worldwide. The IDA works to protect the night skies for present and future generations, our public outreach efforts providing solutions, quality education and programs that inform audiences across the United States of America and throughout the world. At the local level, our mission is furthered through the work of our U.S. and international chapters representing five continents. The goals of the IDA are: • Advocate for the protection of the night sky • Educate the public and policymakers about night sky conservation • Promote environmentally responsible outdoor lighting • Empower the public with the tools and resources to help bring back the night

The Planetary Society 60 South Los Robles Avenue, Pasadena, CA 91101, USA planetary.org The Planetary Society was founded by Carl Sagan, Louis Friedman and Bruce Murray in 1980 in direct response to the enormous public interest in space, and with a mission to introduce people to the wonders of the cosmos. With a global membership in excess of 50,000 from over 100 countries, it is the largest and most influential non-profit space organization in the world. The Planetary Society bridges the gap between the scientific community and the general public, inspiring and educating people from all walks of life and empowering the world’s citizens to advance space science and exploration.

Astronomy 2024.indb 342

07/02/2023 22:41

Astronomical Organizations  343

Royal Astronomical Society of New Zealand PO Box 3181, Wellington, New Zealand rasnz.org.nz Founded in 1920, the object of The Royal Astronomical Society of New Zealand is the promotion and extension of knowledge of astronomy and related branches of science. It encourages interest in astronomy and is an association of observers and others for mutual help and advancement of science. Membership is open to all interested in astronomy. The RASNZ has about 180 individual members including both professional and amateur astronomers and many of the astronomical research and observing programmes carried out in New Zealand involve collaboration between the two. In addition the society has a number of groups or sections which cater for people who have interests in particular areas of astronomy.

Astronomical Society of Southern Africa Astronomical Society of Southern Africa, c/o SAAO, PO Box 9, Observatory, 7935, South Africa assa.saao.ac.za Formed in 1922, The Astronomical Society of Southern Africa comprises both amateur and professional astronomers. Membership is open to all interested persons. Regional Centres host regular meetings and conduct public outreach events, whilst national Sections coordinate special interest groups and observing programmes. The Society administers two Scholarships, and hosts occasional Symposia where papers are presented. For more details, or to contact us, please visit our website.

Royal Astronomical Society Burlington House, Piccadilly, London, W1J 0BQ, England ras.org.uk The Royal Astronomical Society, with around 4,000 members, is the leading UK body representing astronomy, space science and geophysics, with a membership including professional researchers, advanced amateur astronomers, historians of science, teachers, science writers, public engagement specialists and others.

Society for the History of Astronomy Birmingham and Midland Institute, 9 Margaret Street, Birmingham, B3 3BU shastro.org.uk The Society for the History of Astronomy was founded in 2002 to promote the study of the history of astronomy by hosting talks by members and publishing new research into the field. One of the main objectives was to encourage research

Astronomy 2024.indb 343

07/02/2023 22:41

344  Yearbook of Astronomy 2024 into past astronomers who have previously been neglected within the history of science. Some of its members are professional historians of science but most are amateur historians. The Society hosts several one-day conferences at venues across the United Kingdom each year. A Bulletin is published twice yearly containing articles and news items about astronomical history along with short reports of original research by members. The SHA also issues a quarterly electronic newsletter “e-News” which supplements the email messages from the society with updated events/meetings, and general news from council and SHA library. A library of publications of importance to the history of the science is maintained by the Society at the Birmingham and Midland Institute.   One of the Society’s major activities is organising a Survey of Astronomical History in the form of lists of historical astronomers and observatories in every part of Britain and Ireland. This has been motivated by a desire to promote research into local astronomical activities that may have previously been neglected. The Society publishes annually a refereed journal called The Antiquarian Astronomer containing new research into the history of astronomy, particularly articles written by members. Published papers have discussed activities in major observatories, scientific research by individuals of particular note, scientific instrument makers, and the activities of prominent amateurs.

Society for Popular Astronomy Secretary: Guy Fennimore, 36 Fairway, Keyworth, Nottingham, NG12 5DU popastro.com The Society for Popular Astronomy is a national society that aims to present astronomy in a less technical manner. The bi-monthly society magazine Popular Astronomy is issued free to all members.

Webb Deep-sky Society Secretary: Steve Rayner, 11 Four Acres, Weston, Portland, Dorset, DT5 2JG webbdeepsky.com Founded in 1967 – and named after Thomas William Webb, author of Celestial Objects for Common Telescopes – the Webb Deep-Sky Society is one of the leading international deep sky organisations, and publishes a journal The Deep-Sky Observer together with a regular double star Circular. The original aim of the society was to update Webb’s publications, and this was achieved through a series of eight handbooks. It still publishes material that it believes is relevant to deep sky observing. The society welcomes all levels of observers and has a number of sections dedicated to the observations of Double Stars, Nebulae and Clusters, and Galaxies.

Astronomy 2024.indb 344

07/02/2023 22:41

Our Contributors

Martin Braddock is a professional scientist and project leader in the field of drug discovery and development with 34 years’ experience of working in academic institutes and large corporate organizations. He holds a BSc in Biochemistry and a PhD in Radiation Biology and is a former Royal Society University Research Fellow at the University of Oxford. He was elected a Fellow of the Royal Society of Biology in 2010, and in 2012 received an Alumnus Achievement Award for distinction in science from the University of Salford. Martin has published over 170 peer-reviewed scientific papers, filed nine patents, and edited two books for the Royal Society of Chemistry. He also serves as a proposal evaluator for multiple international research agencies. Martin holds further qualifications from the University of Central Lancashire and Open University. He is a member of the Mansfield and Sutton Astronomical Society and was elected a Fellow of the Royal Astronomical Society in May 2015. An ambassador for science, technology, engineering and mathematics (STEM), Martin seeks to inspire the next generation of young scientists to aim high and be the best they can be. To find out more about him visit science4u.co.uk Michael Burton is Director of the Armagh Observatory and Planetarium, which was founded in 1790 and is the oldest continuously-operating observatory in the British Isles still used for its original purpose of undertaking astronomical research. While at the University of New South Wales in Sydney, he chaired the International Astronomical Union’s Working Group for the Development of Antarctic Astronomy for nearly two decades from 1994, including organising the first IAU Symposium in the field (Beijing, 2012). His contributions to Antarctic astronomy included site testing the South Pole for the quality of astronomical observations; pioneering observations in the infrared and terahertz bands in Antarctica with the SPIREX (South Pole) and HEAT (Ridge A) telescopes; and writing science cases underpinning the development of telescopes on the Antarctic Plateau. Matt Caplan is a theoretical nuclear astrophysicist and currently a professor of physics at Illinois State University where he studies white dwarfs, neutron stars, and

Astronomy 2024.indb 345

07/02/2023 22:41

346  Yearbook of Astronomy 2024 microscopic black holes. Dr. Caplan received his PhD from Indiana University and his BS from the University of Virginia. Before beginning at ISU he was a Canadian Institute for Theoretical Astrophysics National Fellow at McGill University, and is an inaugural fellow of the Physicists Coalition for Nuclear Threat Reduction. Beyond academia, he is a scriptwriter for PBS Digital Studios and Kurzgesagt. Neil Haggath has a degree in astrophysics from Leeds University and has been a Fellow of the Royal Astronomical Society since 1993. A member of Cleveland and Darlington Astronomical Society since 1981, he has served on its committee since 1989. Neil is an avid umbraphile, clocking up six total eclipse expeditions so far to locations as far flung as Australia and Hawai’i. Four of them were successful, the most recent being in Jackson, Wyoming on 21 August 2017. In 2012, he may have set a somewhat unenviable record among British astronomers – for the greatest distance travelled (6,000 miles to Thailand) to NOT see the transit of Venus. He saw nothing on the day … and got very wet! David M. Harland gained his BSc in astronomy in 1977 and his PhD in computer science in 1981. He has lectured in computer science, worked in industry and managed academic research. In 1995 he ‘retired’ in order to write on space themes. David Harper, FRAS has had a varied career which includes teaching mathematics, astronomy and computing at Queen Mary University of London, astronomical software development at the Royal Greenwich Observatory, bioinformatics support at the Wellcome Trust Sanger Institute, and a research interest in the dynamics of planetary satellites, which began during his PhD at Liverpool University in the 1980s and continues in an occasional collaboration with colleagues in China. He is married to fellow contributor Lynne Marie Stockman. Steve Harvey has a software engineering background. A keen astronomer from an early age, he is a member of his local astronomy club in Horsham, and currently sits on the council of the British Astronomical Association as the director of the Computing Section. Steve is responsible for producing their annual Handbook as well as data used in the Royal Astronomical Society diaries. He is also a Fellow of the RAS, a keen photographer and supporter of the Target Asteroids! and International Astronomical Search Collaboration (IASC) programs. Tracie Heywood is an amateur astronomer from Leek in Staffordshire and is one of the UK’s leading variable star observers, using binoculars to monitor the

Astronomy 2024.indb 346

07/02/2023 22:41

Our Contributors  347 brightness changes of several hundred variable stars. Tracie currently writes a monthly column about variable stars for Astronomy Now magazine. She has previously been the Eclipsing Binary coordinator for the Variable Star Section of the British Astronomical Association and the Director of the Variable Star Section of the Society for Popular Astronomy. Rod Hine was aged around ten when he was given a copy of The Boys Book of Space by Patrick Moore. Already interested in anything to do with science and engineering he devoured the book from cover to cover. The launch of Sputnik I shortly afterwards clinched his interest in physics and space travel. He took physics, chemistry and mathematics at A-level and then studied Natural Sciences at Churchill College, Cambridge. He later switched to Electrical Sciences and subsequently joined Marconi at Chelmsford working on satellite communications in the UK, Middle East and Africa. This led to work in meteorological communications in Nairobi, Kenya and later a teaching post at the Kenya Polytechnic. There he met and married a Yorkshire lass and moved back to the UK in 1976. Since then he has had a variety of jobs in electronics and industrial controls, and until recently was lecturing part-time at the University of Bradford. Rod got fully back into astronomy in around 1992 when his wife bought him an astronomy book, at which time he joined Bradford Astronomical Society. He is currently working part-time at Leeds University providing engineering support for a project to convert redundant satellite dishes into radio telescopes in developing countries. Brian Jones hails from Bradford in the West Riding of Yorkshire and was a founder member of the Bradford Astronomical Society. He developed a fascination with astronomy at the age of five when he first saw the stars through a pair of binoculars, although he spent the first part of his working life developing a career in mechanical engineering. However, his true passion lay in the stars and his interest in astronomy took him into the realms of writing sky guides for local newspapers, appearing on local radio and television, teaching astronomy and space in schools and, in 1985, leaving engineering to become a full time astronomy and space writer. His books have covered a range of astronomy and space-related topics for both children and adults and his journalistic work includes writing articles and book reviews for several astronomy magazines as well as for many general interest magazines, newspapers and periodicals. His passion for bringing an appreciation of the universe to his readers is reflected in his writing. You can find out more by visiting his blog at starlight-nights.co.uk from where you can also access his Facebook group Starlight Nights.

Astronomy 2024.indb 347

07/02/2023 22:41

348  Yearbook of Astronomy 2024 John McCue graduated in astronomy from the University of St Andrews and began teaching. He gained a PhD from Teesside University studying the unusual rotation of Venus. In 1979 he and his colleague John Nichol founded the Cleveland and Darlington Astronomical Society, which then worked in partnership with the local authority to build the Wynyard Planetarium and Observatory in Stockton-onTees. John is currently double star advisor for the British Astronomical Association. Mary McIntyre is an amateur astronomer and astronomy communicator based in Oxfordshire, England. She is a keen astrophotographer but also loves creating and teaching astronomy sketching and art. She delivers astronomy related presentations to astronomy societies, camera clubs, history clubs, U3A groups, the Women’s Institute and other local community groups. She also delivers astronomy talks and runs astronomy sketching and craft workshops for children in schools, Beavers/Cubs/Scouts and children’s astronomy clubs. She is passionate about astronomy outreach and was awarded the 2021 Sir Patrick Moore Prize by the British Astronomical Association for her outreach activities. She is a Fellow of the Royal Astronomical Society and a regular contributor to Sky at Night magazine and the Yearbook of Astronomy. She has made numerous radio appearances, is a co-presenter of the Comet Watch radio show and a regular panel member on the Space Oddities live panel show. She also runs the UK Women in Astronomy Network which helps to provide inspiration to women and girls who want to pursue a career in astronomy. John Nichol graduated from Newcastle University in 1976 with a degree in science, subsequently completing an MSc at Teesside University. Along with John McCue he was the co-founder of the Cleveland and Darlington Astronomical Society. He has had a lifelong interest in astronomy and optics and since 2010 he has been a professional telescope mirror maker. Neil Norman, FRAS first became fascinated with the night sky when he was five years of age and saw Patrick Moore on the television for the first time. It was the Sky at Night programme, broadcast in March 1986 and dedicated to the Giotto probe reaching Halley’s Comet, which was to ignite his passion for these icy interlopers. As the years passed, he began writing astronomy articles for local news magazines before moving into internet radio where he initially guested on the Astronomyfm show ‘Under British Skies’, before becoming a co-host for a short time. In 2013 he created Comet Watch, a Facebook group dedicated to comets of the past, present and future. His involvement with Astronomyfm led to the creation of the monthly

Astronomy 2024.indb 348

07/02/2023 22:41

Our Contributors  349 radio show Comet Watch, which is now in its fourth year. Neil lives in Suffolk with his partner and three children. Perhaps rather fittingly, given Neil’s interest in asteroids, he has one named in his honour, this being the main belt asteroid 314650 Neilnorman, discovered in July 2006 by English amateur astronomer Matt Dawson. Jonathan Powell worked at BBC Radio Wales as their astronomy correspondent and is currently astronomy and space correspondent for The National (an online newspaper for Wales) and a columnist at the South Wales Argus. He is also a contributor to CAPCOM, an online magazine which promotes astronomy and spaceflight to the general public, in addition to which he has presented on commercial radio at Sunshine FM in Worcester, Brunel FM in Swindon, Bath FM in Bath, and on the astronomy and space dedicated radio station Astro Radio UK. Jonathan has also written three books on astronomy – Cosmic Debris: What It Is and What We Can Do About It; Rare Astronomical Sights and Sounds (which was selected by Choice magazine as an Outstanding Academic Title for 2019); and From Cave Art to Hubble: A History of Astronomical Record Keeping. Peter Rea has had a keen interest in lunar and planetary exploration since the early 1960s and frequently lectures on the subject. He helped found the Cleethorpes and District Astronomical Society in 1969. In April of 1972 he was at the Kennedy Space Centre in Florida to see the launch of Apollo 16 to the moon and in October 1997 was at the southern end of Cape Canaveral to see the launch of Cassini to Saturn. He would still like to see a total solar eclipse as the expedition he was on to see the 1973 eclipse in Mali had vehicle trouble and the meteorologists decided he was not going to see the 1999 eclipse from Devon. He lives in Lincolnshire with his wife Anne and has a daughter who resides in Melbourne, Australia. P. Clay Sherrod is the director and founder (in 1971) of Arkansas Sky Observatories – the oldest entirely privately-funded astronomical and earth science research facility in the USA. He is the author of 36 books in science and nature, as well as two novels, a book of poetry and a popular cookbook. Sherrod is known worldwide for his creative writings and lectures in the sciences and has contributed over five decades of research in astronomy, palaeontology, archaeology, environmental and earth sciences, and in the fields of molecular biology and research into the origin of life. His publications are detailed at arksky.org/publications and the Arkansas Sky Observatories can be accessed at arksky.org

Astronomy 2024.indb 349

07/02/2023 22:41

350  Yearbook of Astronomy 2024 Lynne Marie Stockman holds degrees in mathematics from Whitman College, the University of Washington and the University of London. She has studied astronomy at both undergraduate and postgraduate levels, and is a member of the Astronomical Society of the Pacific. A native of North Idaho, Lynne has lived in Britain since 1992. She was an early pioneer of the World Wide Web: with her husband and fellow Yearbook contributor David Harper, she created the web site obliquity.com in 1998 to share their interest in astronomy, computing, family history and cats. Gary Yule developed an interest in astronomy at the age of seven when his father woke him in the middle of the night to observe Halley’s Comet. Since then he has become a keen amateur astronomer and his journey has taken him down many avenues, ranging from the history of astronomy to astrophotography. Gary has a particular interest in antique telescopes and the stories behind them, and is the Chairperson and Curator of Instruments for Salford Astronomical Society where he dedicates most of his time. He is also involved in the organisation of the North West Astronomy Festival and heads up various astronomy and astrophotography pages on social media, in addition to which he buys and sells telescopes and mounts, many of which are antique.

Astronomy 2024.indb 350

07/02/2023 22:41

All are welcome

Members receive the Society’s publications: eNews, Bulletin and Antiquarian Astronomer. There are also meetings and visits to places of interest, use of our unique library and access to research grants.

@SocHistAstro @SocHistAstro Contact - [email protected]

societyforthehistoryofastronomy.com

Astronomy 2024.indb 351

07/02/2023 22:41

Astronomy 2024.indb 352

07/02/2023 22:41