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Review: The Crowded Universe

The Crowded Universe: The Search for Living Planets
by Alan Boss
Basic Books, 2009
hardcover, 256 pp., illus.
ISBN 978-0-465-00936-7

One of the most dynamic fields of astronomy in the last 15 years has been the search for extrasolar planets, or exoplanets. Until the mid-1990s the existence of such planets was almost entirely theoretical, other than a few planets discovered by chance around a pulsar. Were solar systems like our own rare or commonplace? The answer appears more likely to be the latter, based on the wave of exoplanet discoveries since the mid-90s: over 300 to date, a number increasing almost weekly. And these discoveries promise to accelerate with missions like NASA’s Kepler spacecraft, scheduled for launch early next month, that will be able to detect even smaller exoplanets that current possible—including, scientists hope, Earth-sized worlds.

In The Crowded Universe, Alan Boss, a theoretical astrophysicist who as studied models of planet formation, provides a broad, general review of the recent history of exoplanet discovery. Starting from the mid-1990s and going through late 2008, Boss reviews the discoveries of the first exoplanets around Sun-like stars and major discovery milestones that have occurred since then, including finding multiple-planet systems, directly imaging exoplanets, and discoveries of atmospheres and their compositions of some of these distant worlds. He expands his scope beyond just discoveries, though, to cover topics like the theory of planet formation, development of spacecraft missions, and some of the related policy issues, including changes in NASA leadership and the struggles to secure funding for and manage some key exoplanet missions like Kepler, which was in danger of cancellation as recently as 2007.

It seems that looking for planets around other stars, like so many other efforts, brings out a competitive streak in people.

The strictly chronological approach that Boss takes—each section is datestamped—allows the reader to follow the flow of discoveries and other work in this field, although it can be a little jarring to go from a passage about a scientific discovery to one about the difficulties developing a spacecraft mission designed to study these worlds. In addition, the final few chronological entries are actually predictions of near-term events, like the launch of Kepler; the only clue is that they’re written in the future and not the past tense, something that might confuse people who read the book down the road.

Besides the obvious theme of exoplanet discovery, Boss weaves a secondary theme into the book: one of competition in the search for these worlds and understanding their nature. In various parts of the book he pits exoplanet pioneers Geoff Marcy and Paul Butler against Michel Mayor and Didier Queloz (and, later, others) in a race to see who would find the first and the most exoplanets; Kepler against a similar French spacecraft, CoRoT, in the hunt to find the first Earth-sized exoplanets (something Boss calls the “Extrasolar Planet Space Race”, likening CoRoT to Sputnik); and two models of solar system formation, called core accretion and disk instability, the latter championed by the author. It seems that looking for planets around other stars, like so many other efforts, brings out a competitive streak in people.

For those who have followed the field of exoplanet discovery in the last 15 years, there won’t be much new in The Crowded Universe: the science is covered at a very high level to make it accessible to the broadest possible audience. What makes the book useful is that it ties together not just the science but also the technical and political issues that make it possible (or, sometimes, impossible) to perform the science. Some of this content becomes digressions that add little to the story, like the tale of the “meteorite” that hit a New Jersey house in 2007; it turns out it’s a bit of space debris, perhaps from the upper stage of the Soyuz rocket that launched CoRoT a few days earlier. Others, though, will be enlightening even for those who more closely follow the field, such as when Boss recalls hearing a “strangely familiar” voice on a 2007 airline flight talking about NASA. That person turned out be former administrator Dan Goldin, who said little publicly about NASA after leaving the agency in 2001 but in this anecdote was expressing his concern about the fate of the Terrestrial Planet Finder missions that he championed when he led NASA but were now languishing. While the pace of exoplanet discoveries will quickly date this book, The Crowded Universe does offer a good way to quickly get up to speed on the state of and prospects for exoplanet research.