ffirs.qxd 3/5/08 6:26 AM Page i THE BRIGHTEST STARS DISCOVERING THE UNIVERSE THROUGH THE SKY’S MOST BRILLIANT STARS Fred Schaaf John Wiley & Sons, Inc. flast.qxd 3/5/08 6:28 AM Page vi ffirs.qxd 3/5/08 6:26 AM Page i THE BRIGHTEST STARS DISCOVERING THE UNIVERSE THROUGH THE SKY’S MOST BRILLIANT STARS Fred Schaaf John Wiley & Sons, Inc. ffirs.qxd 3/5/08 6:26 AM Page ii This book is dedicated to my wife, Mamie, who has been the Sirius of my life. This book is printed on acid-free paper. Copyright © 2008 by Fred Schaaf. All rights reserved Published by John Wiley & Sons, Inc., Hoboken, New Jersey Published simultaneously in Canada Illustration credits appear on page 272. Design and composition by Navta Associates, Inc. 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Wiley also publishes its books in a variety of electronic formats. Some content that appears in print may not be available in electronic books. For more information about Wiley products, visit our web site at www.wiley.com. Library of Congress Cataloging-in-Publication Data: Schaaf, Fred. The brightest stars : discovering the universe through the sky's most brilliant stars / Fred Schaaf. p. cm. Includes bibliographical references and index. ISBN 978-0-471-70410-2 (cloth : alk. paper) 1. Stars—Luminosity function—Amateurs’ manuals. 2. Stars—Amateurs’ manuals. 3. Astronomy—Amateurs’ manuals. I. Title. QB815.S33 2008 523.8--dc22 2008000278 Printed in the United States of America 10 9 8 7 6 5 4 3 2 1 ftoc.qxd 3/5/08 6:27 AM Page iii CONTENTS Acknowledgments v Introduction 1 PART ONE Stars in the Sky 1 How Bright Is Bright? 7 2 Meet the 1st-Magnitude Stars 13 3 The Locations, Yearly Motions, and Names of the Stars 25 4 Seeing Stars Better (Skies, Eyes, and Telescopes) 39 PART TWO Stars in the Universe 5 Parts, Structure, Distances, and Motions in the Universe 51 6 The Varieties of the Stars 63 7 The Lives and Deaths of the Stars 71 PART THREE Profiles of the Brightest Stars 8 Sirius 83 9 Canopus 104 10 Alpha Centauri 115 11 Arcturus 126 12 Vega 136 13 Capella 146 14 Rigel 157 15 Procyon 163 16 Achernar 170 Contents | iii ftoc.qxd 3/5/08 6:27 AM Page iv 17 Betelgeuse 174 18 Beta Centauri 182 19 Alpha Crucis 185 20 Altair 188 21 Aldebaran 196 22 Spica 208 23 Antares 215 24 Pollux 224 25 Fomalhaut 230 26 Beta Crucis 238 27 Deneb 241 28 Regulus 247 Appendix A The Brightest Stars: Position, Spectral Type, Apparent and Absolute Magnitude, and Distance 255 Appendix B The Brightest Stars: Spectral Type, Color Index, Color, and Surface Temperature 256 Appendix C Midnight and 9:00 P.M. Culminations, Season of Prime Evening Visibility 257 Appendix D Diameters and Masses of the Brightest Stars 258 Appendix E Motions of the Brightest Stars 259 Appendix F The 200 Brightest Stars 260 Glossary 266 Sources 269 Illustration Credits 272 Index 273 iv | Contents flast.qxd 3/5/08 6:28 AM Page v ACKNOWLEDGMENTS The first person I want to thank in connection with this book is Kate Brad- ford. Kate acted as acquisitions editor for two books of mine at the same time: The Brightest Stars and The 50 Best Sights in Astronomy. Now that both books have come to fruition (50 Best Sights was published by John Wiley & Sons in 2007), I feel extremely gratified to have been able to bring them into being. But the whole process could not have gotten off the ground without Kate’s skilled help and support. The next person I worked with on these two books was editor Teryn John- son. I’ve not forgotten her congenial support. The person who has worked the most, and the most vitally, with me on these books, however, has been Christel Winkler. She has been patient and understanding under trying cir- cumstances. I wish to give my deepest thanks to her for her tremendous and conscientious efforts to keep these books on schedule. Now let me turn to the diagrams, maps, and artwork produced for The Brightest Stars. Many of them were created by two old friends of mine, Guy Ottewell and Doug Myers. Their work is always unique and brilliant. I owe an enormous debt of gratitude to both of them. Vital maps were also provided by Robert C. Victor and D. David Batch, who produce the Abrams Planetarium Sky Calendar. Sky Calendar is a won- derful resource for all knowledge levels of skywatchers, and teachers, too. It is available from the Abrams Planetarium, Michigan State University, East Lansing, Michigan 48824. You can also check out the associated Skywatcher’s Diary at www.pa.msu.edu/abrams/diary.html. Acknowledgments| v flast.qxd 3/5/08 6:28 AM Page vi cintro.qxd 3/5/08 6:32 AM Page 1 INTRODUCTION he season was winter. It was probably the winter I turned six years old. TAll I know for sure is that things got started when I read a section of a book at school. The section told about the brightest stars and constellations of winter. That night, I lay awake in my dark bedroom, peering out through the slits between the big window’s venetian blinds. And that was how I first really made contact with one of the greatest inspirations of my life: the stars. But it was not just any stars I was seeing through the blinds and outside between the bare winter tree branches. These were the brightest stars. First, the blue-white star Rigel, which the book had talked about, glittered through the trees and truly pierced my heart with its beauty and wonder. Only I didn’t know initially that it was Rigel. It was so splendid I thought it must be Sirius, the blue-white brightest-of-all star that the book had also told me about. It wasn’t until minutes later, as I lay watching and pondering Rigel, that I suddenly caught sight of a second spark of blue radiance. My already wonderstruck mind reeled because this blue light burned several whole qual- itative levels of brightness greater than the first star. I was gazing, for the first time, upon Sirius, star of stars, the brightest of all stellar jewels in the firma- ment. And I would never be the same again, for I had started to make the acquaintance of the brightest stars. Welcome to a book devoted to the brightest stars. Much has been written about the planets of our solar system, and rightfully so, for they are mar- velous. But when we look up in the sky we see twenty-one stars that are usu- ally brighter than Mars. One of them—my childhood flame, Sirius—is almost always brighter than any of the planets except Venus and Jupiter. And these stars do not shine with the steady light of the planets. Stars twinkle. That twin- kling, although it is caused by Earth’s atmosphere, beckons us to beyond— beyond our planets, beyond this solar system, beyond the reach of our spaceships for the foreseeable future, the stars call to us. And the message of starlight is first that these pretty pieces of trembling fire are suns in some essential ways like our own. Even without close inspection, we can realize that we are seeing suns and imagine that some, perhaps many, of the stars have their own sets of planets. We can even imagine that maybe sentient beings like Introduction | 1 cintro.qxd 3/5/08 6:32 AM Page 2 ourselves are staring back and wondering about the stars in their sky, includ- ing our own Sun. The brightest stars deserve a book of their own. Stars are the most impor- tant units of the universe at large. The very word astronomy means “ordering of the stars.” When we look up in the natural night sky, almost every one of the multitude of lights we see is a star.