Astrophysics For Physicists

This page intentionally left blank Astrophysics for Physicists Designed for teaching astrophysics to physics students at advanced undergraduate or beginning graduate level, this textbook also provides an overview of astrophysics for astrophysics graduate students, before they delve into more specialized volumes. Assuming background knowledge at the level of a physics major, the textbook develops astrophysics from the basics without requiring any previous study in astronomy or astrophysics. Physical concepts, mathematical derivations and observational data are combined in a balanced way to provide a unified treatment. Topics such as general relativity and plasma physics, which are not usually covered in physics courses but used extensively in astrophysics, are developed from first principles. While the emphasis is on developing the fundamentals thoroughly, recent important discoveries are highlighted at every stage. ARNAB RAI CHOUDHURI is a Professor of Physics at the Indian Institute of Science. One of the world’s leading scientists in the field of solar magnetohydrodynamics, he is author of The Physics of Fluids and Plasmas (Cambridge University Press, 1998). Astrophysics for Physicists Arnab Rai Choudhuri Indian Institute of Science CAMBRIDGE UNIVERSITY PRESS Cambridge, New York, Melbourne, Madrid, Cape Town, Singapore, São Paulo, Delhi, Dubai, Tokyo Cambridge University Press The Edinburgh Building, Cambridge CB2 8RU, UK Published in the United States of America by Cambridge University Press, New York www.cambridge.org Information on this title: www.cambridge.org/9780521815536 © A. Choudhuri 2010 This publication is in copyright. Subject to statutory exception and to the provision of relevant collective licensing agreements, no reproduction of any part may take place without the written permission of Cambridge University Press. First published in print format 2010 ISBN-13 978-0-511-67742-7 eBook (NetLibrary) ISBN-13 978-0-521-81553-6 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. Contents Preface A note on symbols page xiii xviii 1 1 Introduction 1.1 Mass, length and time scales in astrophysics 1 1.2 The emergence of modern astrophysics 4 1.3 Celestial coordinates 6 1.4 Magnitude scale 8 1.5 Application of physics to astrophysics. Relevance of general relativity 9 1.6 Sources of astronomical information 12 1.7 Astronomy in different bands of electromagnetic radiation 14 1.7.1 Optical astronomy 15 1.7.2 Radio astronomy 18 1.7.3 X-ray ast