Astrophysics for Physicists

Astrophysics for Physicists, Arnab Rai Choudhuri, Cambridge U. Press, New York, 2010. $60.00 (471 pp.). ISBN 978-0-521-81553-6

Essentially all branches of basic physics find applications in astrophysics. Therefore, the first major challenge for any author attempting to craft an astrophysics textbook is to lay out the basic physics before moving on to the subject at hand. Even an ideal undergraduate text, though, would serve only temporarily as a comprehensive text in a field that is evolving so rapidly. For example, the must-cover topic of general relativity, though now a classical subject, is seeing its applications expand at an increasing rate.

With Astrophysics for Physicists, Indian Institute of Science physics professor Arnab Rai Choudhuri introduces the topic at the advanced undergraduate level. The book is designed for a one-semester course covering stellar astrophysics and relativistic astrophysics with cosmology; those two topics are often taught over two semesters in two separate courses using two separate textbooks. Such courses often use Dale Ostlie and Bradley Carroll’s An Introduction to Modern Stellar Astrophysics (Benjamin Cummings, 1995), Peter Hoyng’s Relativistic Astrophysics and Cosmology: A Primer (Springer, 2006), or Barbara Ryden’s Introduction to Cosmology (Benjamin Cummings, 2003), reviewed in PHYSICS TODAY (October 2004, page 77 ).

Astrophysics for Physicists can be divided into three sections. The first discusses the tools of astronomy and covers such topics as coordinate systems, celestial mechanics, telescopes, and the basic properties of light. The second discusses the nature of stars, beginning with the determination of stellar parameters from their observable properties (positions, spectra, luminosities, and so forth) and proceeding to the physical principles that govern stellar atmospheres and interiors. The book also explains the formation, evolution, and death of stars. The third section covers the most interesting and important applications of Einstein’s general relativity in present-day astrophysics and cosmology: black holes, neutron stars, gravitational waves, and the cosmic microwave background.

Any text for a one-semester course will necessarily be limited in its coverage; its content would naturally reflect the interest and expertise of the author. As one would anticipate from the author’s background in solar magnetohydrodynamics, Astrophysics for Physicists contains good passages on fluids, plasmas, magnetic fields, and general relativity, and it provides strong mathematically based discussions of many of the important areas of astrophysics. It stresses theory, but also discusses several experimental and observational topics, such as gamma-ray bursts, interferometer detectors of gravitational waves, and the angular power spectrum of the cosmic microwave background.

The book tends to be more extensive and technical in stellar astrophysics, plasma, magnetic effects, and general relativity. Rapidly developing areas including cosmology, relativistic jets, black hole thermodynamics, and relativistic compact objects such as quasars are given less thorough treatments. Though the text does cover the developing area of pulsars, some equally worthy topics are mentioned only briefly. An example is the book’s one-page (page 123) discussion of extrasolar planets. Not only is that one of the hot topics in astrophysics, it also could have provided an opportunity to explore relevant basic physics. To Choudhuri’s credit, the book is overall fairly up to date in most areas.

It is also unfortunate that the book’s first section must dwell so much on the arcane units of astronomical observations, many of which were created to quantify observations when the observers had no idea of the underly-ing physics. Much old astronomical terminology continues to persist for hundreds of years, but current generations of students would be better served if those units are rationalized and made to match the underlying astrophysics.

Astrophysics for Physicists represents a useful learning framework and theoretical reference tool for the newcomer and a quick reference for those working in related areas. Overall I rate it as a solid up-to-date text.