Principles of Stellar Evolution and Nucleosynthesis 0226109526, 0226109534

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Principles of Stellar Evolution and Nucleosynthesis With a new Preface

Donald D. Clayton

The University of Chicago Press Chicago and London

The University of Chicago Press, Chicago 60637 The University of Chicago Press, Ltd., London

© 1968, 1983 by Donald D. Clayton All rights reserved. Published 1968 University of Chicago Press edition 1983 Printed in the United States of America 90 89 88 87 86 85 84 83

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Library of Congress Cataloging in Publication Data

Clayton, Donald D. Principles of stellar evolution and nucleosynthesis. Reprint. Originally published: New York: McGraw-Hill, [1968] Includes bibliographical references and index. 1. Stars-Evolution. 2. Nucleosynthesis. 1. Title. QB806.C55 1983 521 '.58 83-5106 ISBN 0-226-10952-6 ISBN 0-226-10953-4 (pbk.)

CONTENTS Preface (1983)

ix

Preface (1968)

xx

chapter 1. A PHYSICAL INTRODUCTION TO THE STARS 1-1. 1-2. 1-3. 1-4. 1-5. 1-6. 1-7. 1-8. 1-9.

Luminosity 3 Stellar Temperatures 14 Mass 39 Radius 40 Energetics 41 The Hertzsprung-Russell Diagra,m Stellar Populations 51 Stellar Evolution 62 N ucleosynthesis 69

46

chapter 2. THERMODYNAMIC STATE OF THE STELLAR INTERIOR 77 2-1. Mechanical Pressure of a Perfect Gas 2-2. Quasistatic Changes of State 112 2-3. The Ionized Real Gas 139 2-4. Polytropes 155

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CONTENTS

vi

chapter 3. ENERGY TRANSPORT IN THE STELLAR INTERIOR 166 3-1. 3-2. 3-3. 3-4. 3-5.

Energy Balance 167 Radiative Transfer 170 Opacity of Stellar Matter 185 Conduction 232 Convective Instability of the Temperature Gradient 3-6. Neutrino Emission 259

chapter 4. THERMONUCLEAR REACTION RATES 4-1. 4-2. 4-3. 4-4. 4-5. 4-6. 4-7. 4-8.

Kinematics and Energetics 284 Cross Section and Reaction Rate 288 Nonresonant Reaction Rates 296 Nuclear States 309 Penetration Factors 333 Maximum Cross Section and Resonant Reactions Resonant Reaction Rates in Stars 348 Electron Shielding 357

252

283

342

chapter 5. MAJOR NUCLEAR BURNING STAGES IN STELLAR EVOLUTION 362 5-1. 5-2. 5-3. 5-4. 5-5. 5-6. 5-7.

The Proton-Proton Reaction 366 PPI Chain 369 PPII and PPIII Chains 378 The CNO Bi-cycle 390 Helium Burning 411 Advanced Burning Stages 430 Photodisintegration 433

chapter 6. CALCULATION OF STELLAR STRUCTURE 6-1. 6-2. 6-3. 6-4. 6-5. 6-6. 6-7. 6-8. 6-9. 6-10.

Boundary Conditions 438 M as the Independent Variable 442 Composition Changes 4# Numerical Techniques 446 Contraction to the Main Sequence 462 The Main Sequence 470 Advanced Stellar Evolution 484 Rotation 497 Mass Loss 501 Pulsation 504

436

CONTENTS

vII

chapter 7. SYNTHESIS OF THE HEAVY ELEMENTS

516

7-1. Photodisintegration Rearrangement and Silicon Burning 7-2. Nuclear Statistical Equilibrium and the e Process 533 7-3. Nucleosynthesis of Heavy Elements by Neutron Capture

Index

607

517 546

PREFACE (1983) The Preface that I wrote fifteen years ago for the first edition of this textbook is still applicable to the specific role that it plays in the education of astrophysicists. Were that not so, a reprint edition would not be as useful as many of my colleagues appear to believe that it will be. Some have urged me to write instead an expanded and updated version; but most have reinforced my own opinion that the understanding of principles needed by students remains about what it was. That being the case, we have chosen to keep the cost accessible to students by offering this reprint edition. Of course, scientific research itself has increased by leaps and bounds, both in stellar evolution and in nucleosynthesis. The number of research papers and the complexity of their results dwarf what was known fifteen years ago. But this textbook was not conceived to be a review paper then, and neither need it be today. What we choose instead is to provide in this Preface a brief commentary with selected references to recent literature. These will be useful to students seeking to bridge the text to recent research. In making these remarks, I strive for brevity. The recent references that I selected update those topics that are addressed explicitly or implicitly in the first edition. Rather than trying to be fairly complete in the references, I have singled out some that Will help the student continue study of a particular topic, either because they are readable accounts, or especially influential papers, or reviews possessing a good reference list. In regard to stellar evolution, the Annual Reviews qf Astronomy and Astrophysics are so useful that they are designated explicitly in this Preface (Ann. Rev.) as well as listed in the reference list at the end. The many lAD Symposia published by D. Reidel are also excellent sources to today's stellar evolution problems. One book alone, Essaysin Nuclear Astrophysics, C. A. Barnes, D. D. Clayton, and D. N. Schramm,

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PREFACE (1983)

eds. (Cambridge University Press, Cambridge 1982), contains such a collection of authoritative and interestingly written articles as to serve as a major reference source for nuclear astrophysics. Many references will be to its contents. It is identified in this text for convenience as EssNA. Most instructors will, in any case, have their own references and supplementary material that fit their own emphases for the course. Knowledge of the abundances of the elements in the solar system has greatly improved and continues to provide the basic impetus for nucleosynthesis theory. This includes improved knowledge of the abundances in meteorites, in the sun, and in the solar wind. Two outstanding recent compilations are those of Cameron (1982, in EssNA) and of Anders and Ebihara (1982), whose tables also indicate the nuclear processes believed to be responsible for the synthesis of the abundance of each isotope. A thrilling development was the discovery in the 1970s of small variations in isotopic composition between differing meteoritic samples. The differences strongly point to validation of key ideas of nucleosynthesis theory, ideas that had heretofore been accepted on faith; specifically, that the solar system abundances comprise a mixture of nuclei with different nucleosynthesis histories. I have myself taken pains (Clayton 1979) to demonstrate that these isotopic variations are not random but support the expectations of nucleosynthesis theory. Their interpretation gives birth to a new field of astronomy based on the chemical history of presolar dust (Clayton 1981). Significant observations of overabundances of iron (Kirshner and Oke 1975) and of the products of explosive oxygen burning (Chevalier and Kirshner 1979) in young supernova remnants have provided a long-sought demonstration of the significance of supernovae to nucleosynthesis (Woosley and Weaver 1982a, 1982b, in EssNA). The discovery of pulsars was not anticipated by the text material. The subsequent attention to neutron stars emphasized that the equation of state of matter at very high derisities, up to and beyond the density of nuclear matter on earth (2 X 1014 g/cm''), is an essential part of the problem of stellar evolution. The pressure in the idealized (but unrealistic) case of a perfect neutron gas (degenerate) requires only that its mass MNreplace the electron mass M,in chapter 2; however, that analysis gives a maximum "Chandrasekhar mass" of only 0.7 M