Seager S. Exoplanets

Tucson: University of Arizona Press, 2011. — 545 p.For the first time in human history, we know for certain the existence of planets around other stars. Now the fastest-growing field in space science, the time is right for this fundamental source book on the topic which will lay the foundation for its continued growth.
Exoplanets serves as both an introduction for the non-specialist and a foundation for the techniques and equations used in exoplanet observation by those dedicated to the field.
This is a unique time in human history - for the first time, we are on the technological brink of being able to answer questions that have been around for thousands of years: Are there other planets like Earth? Are they common? Do any have signs of life? The field of exoplanets is rapidly moving toward answering these questions with the discovery of hundreds of exoplanets now pushing toward lower and lower masses; the Kepler Space Telescope with its yield of small planets; plans to use the James Webb Space Telescope (launch date 2014) to study atmospheres of a subset of super Earths; and ongoing development for technology to directly image true Earth analogs. Theoretical studies in dynamics, planet formation, and physical characteristics provide the needed framework for prediction and interpretation. People working outside of exoplanets often ask if the field of exoplanets is like a dot.com bubble that will burst, deflating excitement and progress. In my opinion, exciting discoveries and theoretical advances will continue indefinitely in the years ahead, albeit at a slower pace than in the first decade. The reason is that observations uncover new kinds and new populations of exoplanets -- and these observations rely on technological development that usually takes over a decade to mature. For example, in the early 2000s all but one exoplanet was discovered by the radial velocity technique. At that time, many groups around the world were working on wide-field transit surveys. But it was not until recently, a decade into the twenty-first century, that the transit technique is responsible for almost one-quarter of known exoplanets. The planet discovery techniques astrometry (as yet to find a planet) and direct imaging have not yet matured; when they do, they will uncover planets within a new parameter space of planet mass and orbital characteristics. In addition, people are working hard to improve the precision for existing planet discovery techniques to detect lower-mass planets and those further from the star. All in all, technology enables slow but sure progress, and this fuels ongoing discovery. Theory, like observations, also takes time to unfold and mature. We can anticipate an "ultimate" planet formation model similar to the "millenimum simulation" for galaxy formation and evolution. In time, incorporating detailed physics as well as being able to reproduce the generic outcome of planet populations (mass, radius, and orbital characteristics, including period) will enable a deeper understanding of planet formation and migration. Similarly, the ideal exoplanet atmosphere code of the future could be a three-dimensional Monte Carlo code that includes radiative transfer with inhomogeneous cloud coverage and surface features, a code that also solves for the temperature structure and combines with a hydrodynamical simulation to calculate the three-dimensional temperature and wind structure. Classical orbital mechanics, already reinvigorated by interesting exoplanet systems (e.g., planets in resonant orbits, hot Jupiter exoplanets that orbit in the direction opposite to the stellar rotation), also has a role to play in explaining fundamental mechanisms of how planetary system configurations came to be. Orbital dynamics modeling is driving the search for moons and other unseen planet companions by their perturbations on transiting planet signatures. Exoplanets is a unique science because it involves so many disciplines within and beyond planetary science and astrophysics. The other disciplines include geophysics, high-pressure mineral physics, quantum mechanics, chemistry, and even microbiology. While exoplanet observations clearly belong under the branch of astronomy, for many years the whole discipline of exoplanets lacked a true home. Physics departments have said "Exoplanets: It's interesting, but is it physics?" Planetary and Earth science departments used to collecting real data in their hands from Earth and in situ measurements from solar system planets were, in the early 2000s, reluctant to believe there would ever be enough high-quality data to take the research field of exoplanets seriously. With hundreds of known exoplanets and many fascinating observational and theoretical discoveries, the whole world is embracing exoplanets, a field that can now find its home both in and spanning across planetary science, astronomy and astrophysics, and astrobiology. We use the term "exoplanets" and not "extrasolar planets" in this book. Exoplanets is the most direct derivative from the Greek language, from which the word "planet" originates. (Note that the word "extrasolar" is derived from Latin.) It is most fitting that the field be named as traditionally as possible, and there is none more traditional than Greek. The goal of this volume is to cover the range of topics in exoplanet observation and theory at the graduate student level. Each chapter of this volume aims to cover the fundamentals and recent discoveries in such a way as to be a cross between a textbook and a review article. Because the field of exoplanets moves so rapidly, we have tried to arrange each chapter so that the first two sections (the introduction and and an explanation of the basic concepts/fundamental equations) will not go out of date. The next two sections (covering recent highlights and future progress) will go out of date eventually, but serve to capture and review what is going on in a subfield. Some chapters deviate from the standard structure and, by nature of construction, the level of technical detail and writing style will vary in an edited volume with different authors for each chapter. We intend that this book will serve to inspire professional researchers and engineers and students to build a foundation for the next generation of exoplanet observational and theoretical discoveries. Exoplanets is the 37th book in the University of Arizona Press Space Science Series, the first dedicated to planets beyond our solar system. As editor of this volume, I foremost thank General Editor Richard Binzel for believing in my vision for this book and for his advice and fast turnaround on practical matters. I am extremely grateful to Renée Dotson of the Lunar and Planetary Institute for her patience and careful efforts in compiling and production of the book. The book would not have been possible without the contribution and dedication of each of the chapter authors, often going far beyond what the authors had initially anticipated. The chapter reviewers played an invaluable role in improving the quality of this book. Appreciation to William Hartmann for his original painting that graces the book's cover. Last but not least, I am grateful to Wes Traub of NASA Jet Propulsion Laboratory for his financial support, which has enabled the book to be available for a practical purchase price. Close to two decades since the first exoplanets were discovered, the field of exoplanets has grown without bound. So many surprising discoveries have been made that by now we know to expect the unexpected. I always like to say that, for exoplanets, anything is possible within the laws of physics and chemistry. And, when asked about which planet or discovery is my favorite one, I like to reply that it is the next one, because in exoplanets, the best is yet to come. I hope you, the reader, will use this book to learn about whichever subdiscipline interests you and to build your knowledge to play a role in the future of exoplanet research.