An Invitation to Astrophysics Thanu Padmanabhan , World Scientific, Hackensack, NJ, 2006. $66.00, $36.00 paper (362 pp.). ISBN 978-981-256-638-6, ISBN 978-981-256-687-4 paper
No field of physics is more vibrant today than astronomy. And the power of astronomy to excite students and draw them into physics is universally recognized. As a result, some physicists who never took a course in astronomy probably wish that they had. Now they have a chance to catch up.
An Invitation to Astrophysics by Thanu Padmanabhan is targeted at physicists interested in taking a tutorial in astronomy. In just 362 pages, Padmanabhan, a respected cosmologist at the Inter University Centre for Astronomy and Astrophysics in Pune, India, aims to bring readers from square one to a position from which they can understand current research across almost the whole field of astronomy from normal and degenerate stars to the dynamics and evolution of normal and active galaxies, and from the Big Bang to the formation of stars and galaxies. The exposition is quantitative throughout and firmly based on basic physical principles.
To benefit from the book, readers need to have a good knowledge of undergraduate physics, including electromagnetism, special relativity, and quantum mechanics. They also need a sophistication in the handling of physical concepts that few undergraduates possess. Readers having those prerequisites will be able to grasp the basic principles of such diverse areas as gravitational lensing, accretion onto degenerate stars and black holes, the workings of astrophysical plasmas in interstellar space and relativistic jets, cosmic nucleosynthesis, the use of the cosmic background radiation as a cosmic probe, and the dynamics of dark matter.
The reader, however, will have to work hard: A serious session with Padmanabhan s book does for the mind what a vigorous workout in the gym does for the body. Each of the nine chapters has about 80 equations and finishes with about 15 exercises, so ideally one would work through the book with pen and paper at hand. I m not sure how many of my colleagues have the time for such an exercise, but most would benefit from it. I would warmly recommend the book to a good graduate student of astronomy who is preparing for general exams, or to a graduate student working in particle physics who is shifting to the astroparticle side. The text could also serve as a focus for an inspirational graduate seminar that would broaden and deepen students under standing of physics and the way it enables us to understand environments wildly unlike our own.
Inevitably, some of the author s statements are oversimplifications or just downright wrong. For example, Padmanabhan states that the first stars belong to population II. But population II stars actually contain enough heavy elements to function in ways significantly different from the first stars, and astronomers are still hunting for those first stars, the denizens of population III. In reality, however, those stars may all be extinct. Newtonian gravity is not adequate so long as the gravitational potential satisfies φ ≪c 2, but only when this condition is combined with ν ≪c. Moreover, the author s discussion of the precession of the equinoxes is confusing because he first estimates the sub dominant effect of the Sun and then makes a correction for the dominant contribution of the Moon.
Yet the blemishes are minor. The author often derives familiar results in an unusual order or from an unconventional perspective; thus even the most distinguished professor of astrophysics will gain fresh insights from An Invitation to Astrophysics . It is an unconventional but very worthwhile book.
