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Review: Beyond Pluto

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Beyond Pluto: Exploring the Outer Limits of the Solar System
by John Davies
Cambridge Univ. Press, 2011
softcover, 242 pp., illus.
ISBN 978-1-107-40261-4

Over the last decade astronomers and planetary scientists have reshaped our knowledge of the Kuiper Belt and the outer solar system. Their work includes the discovery of a number of large bodies in the outskirts of the solar system, notably Eris, Quaoar, and Sedna. This, in turn, helped push the International Astronomical Union in 2006 to approve a formal definition of the term “planet” that demoted Pluto to the new category of “dwarf planet”, along with some of these newly-discovered bodies. These discoveries and other research would provide plenty of material for a book about our knowledge of the outer solar system—after all, several books have been written about Pluto’s standing as a (dwarf) planet in the last few years alone.

Once you take into account the fact that its contents are a decade old, the book is actually quite a good examination of our knowledge of the Kuiper Belt up until the turn of the century.

Unfortunately, despite its title, Beyond Pluto is not that book. The book recently published by Cambridge University Press is actually reprinting of a book originally released back in 2001. There is no new material in this book: no revisions of existing chapters nor inclusion of additional chapters. This fact may be subtle to some readers: it’s mentioned on the back cover of the book but hardly anywhere else. Similarly, the only hint on its page (linked to above) that the book is a reprint of an older work are the words “Edition: Reissue”; a similar caveat is the sole clue in its listing on the Barnes & Noble web site.

It’s not clear why the publishers decided to simply reprint, instead of update, the book. That’s a shame, because once you take into account the fact that its contents are a decade old, the book is actually quite a good examination of our knowledge of the Kuiper Belt up until the turn of the century. British astronomer John Davies goes through the history of observations of small outer solar system bodies as well as some of the theory about the those bodies, dating back to the original papers by Gerard Kuiper and Kenneth Edgeworth that predicted the existence of a population of such bodies decades before astronomers found the first Kuiper Belt object. Davies goes beyond the science and provides backgrounds of some of the key scientists, their personalities, and the interactions with others in the field.

While Beyond Pluto offers no new information on the last decade of outer solar system research, it becomes—inadvertently—something of a time capsule of our knowledge of the field and some of the key questions it faced at the time. In the book’s final chapter, titled “Will we ever get our names right?”, Davies examines the controversy of the classification of Pluto in the 1990s when some astronomers proposed giving Pluto a dual classification with its own minor planet number, 10000. That effort failed, but Davies suggested that “astronomers may live to regret this decision if an object bigger that Pluto is ever found” in the outer solar system. Indeed, it was the discovery of Eris, which initially appeared to be larger in diameter (and is more massive) than Pluto that triggered the ultimate reassessment of Pluto’s classification. (Pluto ended up with the minor planet number 134340 after its reclassification by the IAU.)

Davies is less successful in another bid to win recognition for Edgeworth as the first to propose the existence of the belt of objects (he goes as far to suggest that Kuiper knew of Edgeworth’s 1949 paper when he wrote his 1951 book chapter). Davies proposed that, since the name “Kuiper Belt” has already stuck in the astronomical community, that the objects that populate it be known as Edgeworth-Kuiper Objects (EKOs) rather than Kuiper Belt Objects (KBOs). That recognition doesn’t appear to have caught on: a Google search—a quick, if imprecise, measure of the frequency of use of term—returns 289,000 results for “Kuiper Belt object” but only 3,400 results for “Edgeworth-Kuiper object”. Perhaps a revised edition of the book will one day be published that revisits these and other issues regarding the distant, but hardly uninteresting, outer regions of our solar system.