The Cambridge Encyclopedia of Stars

This unique encyclopedia provides a fascinating and fully comprehensive description of stars and their natures and is filled with beautiful color images. The book begins with ancient astronomy – with constellations and star names – and then proceeds to modern coordinate systems. Further chapters explain magnitudes, distances, motions, and the Galaxy at large. Double stars, clusters, and variables are introduced, and, once the different kinds of stars are in place, later chapters examine stellar evolution, beginning with the interstellar medium and star formation, proceeding to our Sun and its characteristics, and ending with the ageing processes of solar-type and high-mass stars. The book ends by showing how this information can be combined into a grand synthesis. Detailed cross-referencing enables the reader to explore topics in depth and makes this an invaluable work both for beginners and for those with a more advanced interest in stars and stellar evolution.

DR. JAMES B. KALER is Professor Emeritus of Astronomy at the University of Illinois at Urbana-Champaign. His research involved dying stars, specifically the graceful shells and rings of gas ejected in stellar death called “planetary nebulae.” Long interested in science education and popularization, Dr. Kaler has written for a variety of magazines that include 1’Astronomia (Italy), Astronomy, Sky and Telescope, StarDate, and Scientific American. He was a consultant for Time-Life Books on their “Voyage Through the Universe” series, has appeared frequently on regional Illinois television and radio, and lectures widely. He received the 1999 Armand Spitz Memorial Lectureship from the Great Lakes Planetarium Association for his work, has written several books including Stars and their Spectra, Extreme Stars: At the Edge of Creation, and The Ever-Changing Sky: A Guide to the Celestial Sphere, all published by Cambridge University Press. Dr. Kaler has an asteroid named after him in honor of his outreach work.

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THE CAMBRIDGE ENCYCLOPEDIA OF STARS

James B. Kaler

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CAMBRIDGE UNIVERSITY PRESS
Cambridge, New York, Melbourne, Madrid, Cape Town, Singapore, São Paulo

Cambridge University Press
The Edinburgh Building, Cambridge CB2 2RU, UK

Published in the United States of America by Cambridge University Press, New York

www.cambridge.org
Information on this title: www.cambridge.org/978-0-521-81803-2

© Cambridge University Press 2006

This publication is in copyright. Subject to statutory exception
and to the provisions of relevant collective licensing agreements,
no reproduction of any part may take place without
the written permission of Cambridge University Press.

First published 2006

Printed in the United Kingdom at the University Press, Cambridge

A catalogue record for this publication is available from the British Library

ISBN-13 978-0-521-81803-2 hardback
ISBN-10 0-521-81803-6 hardback

Cambridge University Press has no responsibility for the persistence or accuracy of URLs for external or third-party internet websites referred to in this publication, and does not guarantee that any content on such websites is, or will remain, accurate or appropriate.

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To my Family

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Contents

		Preface	page xi
		Acknowledgements	xiii
1		Stars and constellations	1
		1.1  Classical constellations	3
		1.2  Modern constellations	11
		1.3  Common star names	13
		1.4  Catalogue names	18
		1.5  Non-stellar objects	22
2		Location	23
		2.1  Earth	25
		2.2  The celestial sphere	26
		2.3  Coordinates on the celestial sphere	28
		2.4  Precession	37
		2.5  Nutation, aberration, and the rest of it	40
		2.6  Astrometry	41
3		Magnitudes	43
		3.1  Apparent magnitudes	45
		3.2  Absolute magnitudes	52
		3.3  Bolometric magnitudes	53
		3.4  Color	54
		3.5  Interstellar extinction	56
4		Distances	59
		4.1  The cosmic distance ladder	61
		4.2  Parallax	62
		4.3  Distances from motions	66
		4.4  Photometric methods	69
		4.5  Expansion parallaxes	76
		4.6  Binary stars	77
5		The Galaxy in motion	79
		5.1  The Galaxy	81
		5.2  Relative motion	84
		5.3  Solar motion and Galactic rotation	87
		5.4  Evolution	94
6		Spectra and the HR diagram	97
		6.1  The solar spectrum	99
		6.2  The spectral sequence	102
		6.3  The second dimension	108
		6.4  The third dimension	114
7		Stellar properties	119
		7.1  Radiation laws	121
		7.2  Gross properties	131
		7.3  Chemical composition	136
		7.4  Magnetism and winds	140
8		Double and multiple stars	141
		8.1  Organization	143
		8.2  Visual binaries	144
		8.3  Spectroscopic binaries	149
		8.4  Eclipsing binaries	152
		8.5  Interacting binaries	155
		8.6  Multiple stars	161
9		Star clusters and associations	163
		9.1  Forms	165
		9.2  Open clusters	167
		9.3  Associations	173
		9.4  Globular clusters	176
10		Variable stars	185
		10.1  Kinds of variation	187
		10.2  Names	190
		10.3  Cepheid variables	191
		10.4  Near and below the main sequence	196
		10.5  The red giant realm	198
		10.6  Eruptive variables	202
		10.7  Spots and flares	205
11		Star formation	207
		11.1  The interstellar medium	209
		11.2  Evidence for star birth	215
		11.3  The process	220
		11.4  Planets	224
12		Sun and main sequence	229
		12.1  The Sun	231
		12.2  Inside the Sun	237
		12.3  Oscillations	242
		12.4  The main sequence	244
13		Stellar evolution	247
		13.1  Domains of the main sequence	249
		13.2  Early intermediate-mass evolution	251
		13.3  Late intermediate-mass evolution	257
		13.4  Planetary nebulae	260
		13.5  White dwarfs at last	266
		13.6  Binary evolution	267
14		High-mass evolution	269
		14.1  Supergiants	271
		14.2  Supernovae	275
		14.3  The remains	282
		14.4  Synergy	291
		Appendix 1 The Messier Catalogue	293
		Appendix 2 The 51 brightest stars (to Polaris, magnitude 2.02)	297
		Appendix 3 The stars within four parsecs (plus 2)	300
		Appendix 4 The chemical composition of the Sun	303
		Appendix 5 Endpaper: riches at the anticenter	310
		Further reading	313
		Index	314

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Preface

In the summer of 1947, when I was eight years old, I wrote a five-page “book” called “Things That I Know About Stars.” It calls out some of the constellations I had found. And it contains a few gems: “The Sun may expand to about 3 or 4 tims it’s size”; “There are two kinds of stars (dwarfs and gaints)”; “A white dwarf may enter the solar system”; [The Sun] “is a fixed star traveling at about 12 miles per secend [sic].” I have no idea where these came from: eight-year-olds are not much into citations. And I clearly could have used an editor. But the statements are, even after nearly 60 years, all basically true.

   I’m still writing the same book. It’s just become a little bigger. I also found an editor. And it is not what I know, but what generations of astronomers have learned and allowed us all to know about the stellar science. Decades of research have not only supported the knowledge of the 1940s and earlier, but have added to it to an astonishing degree, to the point at which we have a good understanding of the beasts of the stellar zoo, and how they all link together. That is hardly to say that we have found all the answers. Indeed, for every discovery, there seems to unfold another mystery.

   The Cambridge Encyclopedia of Stars is not laid out in traditional encyclopedic – alphabetic – format. Nor is it designed as a pedagogical textbook in which one chapter leads smoothly and logically into the next. It falls instead somewhere in between. Chapters concentrate on particular aspects of stellar astronomy – distances, double stars – and are meant to stand alone. At the same time, the reader is led continuously deeper and deeper into the subject. Discussion in one chapter assumes knowledge to be found in other chapters. Continuity is achieved by using both forward and backward referencing. For example, the chapter on distances discusses the Cepheid variable method, but does not treat either their creation or structure, which are reserved for later chapters and sections, and which are referenced with square brackets. The book is designed such that a reader can pursue it either from beginning to end or can dip into it at any point and read any particular chapter, in either case referring to the cross-referencing as needed.

   The Cambridge Encyclopedia of Stars begins with two chapters on astronomical fundamentals that discuss constellations, star names, and coordinates. These are followed by another pair that examine stellar fundamentals: magnitudes and distances. An interlude places stars within the context of the Galaxy by looking at solar and stellar motions. The next pair attack the spectral sequence, the HR diagram, the various kinds of stars, and physical properties such as temperature, chemical composition, and the like. A trio then discusses binary systems, clusters, and variable stars. With these stellar characteristics in place, the book concludes with a set of four chapters on stellar structure and evolution that examine the interstellar medium and star formation, the Sun and the main sequence, the evolution of lower mass stars to white dwarfs, the evolution of higher masses to neutron stars and black holes.

   Though the format is largely descriptive, equations are used where they enhance clear discussion. Calculus is not employed except by discussion of it in the section on stellar structure, in which the concepts are developed. Background and peripheral material is placed into boxed sidebars. The biggest problem, as always, was the selection of what to include within the limits of space allotted. I have tried to bring a balance to the book by maintaining what I consider to be consistent levels from one chapter to the next to give an overall uniform view of what is known about stars, and equally important, what is not known. I hope you enjoy the results.

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Acknowledgements

As in any page of acknowledgements, especially for a book of this scope, there are many sets of people to thank. Foremost are the research astronomers who through their hard and dedicated work gleaned the knowledge that is presented here. The data in the many tables that appear in the text and appendices are a synthesis of a vast number of compilations and research papers by generations of scientists. Deep thanks and appreciation to them all.

   Next are the individuals who made this labor of love possible. First to thank is Simon Mitton, who was responsible for getting the project started in the first place at the January 2001 meeting of the American Astronomical Society in San Diego. We were discussing the Cambridge encyclopedia projects, and I said “How about one on stars?”. Four years later, the work was finally complete. To Simon, thanks. Following closely are my editor, Jacqueline Garget, who has patiently followed my progress through the forest of stellar astronomy, and has guided the book to fulfillment. Thanks also to editors Vince Higgs and Jo Bottrill, copy editor Peter Sinclair, and to designer Chris McLeod. I express great thanks as well for the fine new graphics rendered by Precision Graphics of Champaign, and for their diligence in preserving the old ones.

   Third are the many professional and amateur astronomers who have allowed me the use of their wonderful imagery and who have helped make the book come alive. Following are the various observatories and organizations (and their personnel) who have been kindly cooperative and that include the American Association of Variable Star Observers (AAVSO), the Anglo-Australian Observatory, Big Bear Solar Observatory, the California Institute of Technology (Mt. Wilson and Palomar), the Chandra X-ray Observatory, the Institute for Solar Physics, Royal Swedish Academy of Sciences, Lick Observatory, Lowell Observatory, the National Optical Astronomy Observatories (NOAO), the Okayama Astrophysical Observatory, the Space Telescope Science Institute (Hubble Space Telescope, HST), the Subaru Telescope, and Yerkes Observatory. Thanks also to Sky Publishing Company and to the Special Collections and Rare Book Room of the University of Illinois. A very special thanks goes to Adam Black and to Addison-Wesley for allowing the use of numerous graphics from my textbook Astronomy!.

   Last and hardly least are the many astronomers who taught me their craft, patiently answered my questions, and set me on corrected paths. Thanks to you all.

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