Astrophysics of Planet Formation , Philip J. Armitage
Cambridge U. Press, New York, 2010. $65.00 (284 pp.). ISBN 978-0-521-88745-8
The foundations of planet formation research were established from the late 1960s through the 1980s by such noted patriarchs of the field as Chushiro Hayashi, Viktor Safronov, and Stuart Weidenschilling. However, planet formation theories have been invigorated during the past 15 years by an explosion in the discovery of exoplanets, which provide an expanded and exciting playground and a new set of constraints.
The goal of a planet formation theory is to understand the numerous, complex, and interdependent steps between collapse of the nebular cloud and the emergence of giant planets, small planets, and planetoids. In Astrophysics of Planet Formation , Philip Armitage lays out a concise introduction to the most important theoretical concepts in planet formation. He describes or derives the governing equations; gives, when possible, results from numerical modeling; and discusses observational constraints. In a nutshell, the book provides the young astrophysicist with the necessary background and elements to move on to more advanced work.
Astrophysics of Planet Formation is organized into self-contained but connected chapters that generally follow the chronology of planet formation: disk characteristics and evolution, plan-etesimal formation, terrestrial planet formation, and giant planet formation. The book concludes with a brief chapter on the dynamics of planetary systems. Two pedagogical approaches make it an outstanding introductory text: Armitage concentrates on the essentials rather than getting lost in the details, and he carefully walks the reader through the derivation of equations, highlighting their physical meaning. He also gives technical references for in-depth reading at the end of each chapter.
Several chapters stress unresolved challenges and clearly state where and why difficulties arise in such issues as modeling the transport of angular momentum in a disk or understanding how dust particles grow into planetesimals. Armitage has brought his extensive knowledge in modeling the structure and evolution of astrophysical disks and applies that knowledge to problems in planet formation. But he does not fall short on other topics: For example, in the appendix, he discusses the technical aspects of N-body methods—used to predict the motion of gravitationally interacting celestial objects—to demystify the complexity behind astrophysical numerical methods, which are often obscure to those outside the field.
Overall, Armitage delivers on the book’s aim to “provide a concise introduction to the classical theory of planet formation and to more recent developments spurred by new observations.” Astrophysics of Planet Formation would be an excellent main text for a course in astronomy, astrophysics, or planetary science.
Diana Valencia is a Carl Sagan postdoctoral research fellow at MIT in Cambridge. Her research interests include the structure and composition of super-Earths and the thermal evolution of icy terrestrial planets.
