Exoplanets

Abstract

Exoplanets , edited by Seager, S. . Tucson, Arizona : The University of Arizona Press , 2010 , Space Science Series, 500 p. $35, cloth (ISBN #978-0-8165-2945-2) . With the discovery of now more than 500 extrasolar planets and over 1200 planetary candidates, exoplanetary science has reached a point where it is widely recognized as a well-established and independent field of astronomy. The diverse characteristics of the currently known extrasolar planets, both in orbital architecture and physical properties, have given this young field a great potential for connecting to other fields of planetary science, and to develop new disciplines. As one of the most rapidly growing fields of astronomy, exoplanetary science covers a vast variety of topics from observational techniques, to celestial mechanics and computational modeling, to geophysics and geodynamics, as well as atmospheric circulations and biosignatures. The rapid progression of this field during the past few years has made it impossible to portray a comprehensive picture of exoplanetary science by simply writing a conventional review article. An all-encompassing review would require thorough contributions from many experts. Exoplanets is the only book to date that has succeeded in doing so. As a book that aims to cover all topics related to extrasolar planets, Exoplanets is comprehensive and coherent, with a fluid connectivity between its different chapters. The book has been divided into five sections with the first part devoted to familiarizing the reader with the fundamentals of exoplanetary science. It briefly summarizes the history of searching for extrasolar planets, and it prepares the reader for the technical discussions of the upcoming chapters by presenting a review of different topics of planetary science, including the necessary background in orbital dynamics and celestial mechanics. Part II discusses observational techniques. The sequence of chapters in this section follows an important logical trend—they are presented in the order of the employment of their corresponding observational techniques in searching for extrasolar planets. This also directly relates to the contribution of each technique to the number of detected planets. Naturally, the radial velocity technique is discussed first, followed by transit photometry, microlensing, and imaging. A unique feature of these chapters (or for that matter, all chapters in the book) is the level of their technicality. Each chapter presents an in-depth and technical review of a specific observational technique that makes it greatly suitable for training purposes. Combined with their large number of references and a thorough review of the literature, in particular in the last chapter where a statistical analysis of the state of the detected planets is presented, the chapters in part II present a valuable tool for teaching methods of observing extrasolar planets to graduate students, and preparing them for proper data reduction and analysis. The technical level of Exoplanets, its thoroughness, and its potential for being the field’s reference textbook is seen throughout all of its chapters. In part III, the book covers the theoretical developments in planetary dynamics that stem from the (surprising) orbital architecture of extrasolar planets. The orbital diversity of these bodies, in particular the existence of short-period giant planets, requires detailed considerations when using computational modeling to fit the observational data. The chapter by Fabrycky reviews these issues within the context of the currently known detection techniques, and presents a clear, subtle, and analytically sound approach to resolving them. The next chapter on the effects of tides is a marvelous presentation of this phenomenon in planetary systems. Corriea and Laskar show an elegant mathematical treatment of tides in planetary systems and portray a detailed picture of their connection to extrasolar planets and their dynamical evolution. As a natural progression to part III, the formation of extrasolar planets and the properties of planet-forming environments are discussed in part IV. The opening chapter of this section is a thorough and fundamental review of protoplanetary and debris disks by Roberge and Kamp. In this chapter, the authors present a detailed discussion of the observational properties, structure, composition, and models of the formation and evolution of debris and protoplanetary disks. The next two chapters focus on the growth of planetesimals to planetary embryos and subsequently to giant and terrestrial planets. As always, Chambers skillfully describes the formation of terrestrial planets and the architecture of an asteroid belt, and sets the grounds for D’Angleo and his colleagues who present a complete review of the current state of research on the formation of giant planets through the core accretion and disk instability models. The section ends with a well-structured chapter on planet–disk interaction and planetary migration, and the way that theories of planet formation can be used to explain the existence of giant planets in short-period orbits. The last section of the book is a collection of inclusive articles on the physical properties of extrasolar planets. The successful operations of the Spitzer, CoRoT, and Kepler space telescopes have not only contributed to the detection of extrasolar planets, they also have enabled us to gain insight into the possible composition and internal structure of these objects. The first two chapters in this section present the latter by reviewing the current models of the interiors of giant and terrestrial planets in our solar system, and discussing the applicability of these models to extrasolar planetary systems. The next two chapters extend this analysis to the atmospheres of these bodies. Burrows and Orton offer a detailed review of the models of giant planet atmospheres and a wonderful discussion on their implications for the atmospheric compositions of extrasolar planets. Meadow and Seager skillfully extend these discussions to terrestrial planets where they give an elegant analysis of habitability and biosignatures. The book ends with a masterfully developed chapter on atmospheric circulations of extrasolar planets. With its well-crafted review chapters, Exoplanets is clearly the most comprehensive reference on all topics related to extrasolar planetary science. It presents a fundamental review of the current state of the field with an appropriate level of technicality that not only serves nonexpert readers, but also has turned the book into an invaluable resource for teaching and training purposes. This is a book that anyone working on any aspect of extrasolar planets should not be without.