Friday, December 18, 2009

Book Review: The Case for Pluto

If readers of this blog have any friends with an interest in astronomy and can get them only one book as a holiday gift, Alan Boyle's The Case for Pluto: How A Little Planet Made A Big Difference is the one to get. As his aptly chosen title says, Boyle makes the case for Pluto and does it so thoroughly and so understandably that even people not familiar with astronomy can easily follow his fascinating narrative.

That is what Pluto's story is--a narrative, a captivating tale complete with history, politics, culture, and humor, very far from the type of dry reading many associate with science books.

Like Dr. David Weintraub in Is Pluto A Planet, Boyle provides a historical background that takes readers from the cornfields of Iowa to 18th and 19th century Europe and controversies over the discoveries of Uranus, Ceres, the first asteroids, and Neptune. Noting that William Herschel, discoverer of Uranus, was the one who initially coined the term asteroid, Boyle illustrates how politics and astronomy in the 18th century startlingly resemble both in the 21st. Critics of the new term argued Herschel coined it partly because he wanted to be the only person alive who discovered a planet, which would be true if Ceres and the asteroids were deemed not planets.

The demotion of Ceres from planet to asteroid is often cited by those who support the demotion of Pluto. But Boyle quotes Dr. Mark Sykes of the Planetary Science Institute, who notes that had Herschel been able to see the disk of Ceres with telescopes of his day, he might not have objected to it being called a planet.

He also chronicles the long effort by astronomer Brian Marsden, former head of the IAU's Minor Planet Center, to have Pluto placed under the MPC's jurisdiction, which was not the case as long as it was considered a major planet. Interestingly, Marsden first suggested classifying Pluto as a major planet at a 1980 celebration commemorating the 50th anniversary of Pluto's discovery, in the presence of discoverer Clyde Tombaugh and his family.

Boyle tells the gripping story of how personalities became intertwined with science, not just in the case of Marsden, but in the effort to fund a robotic mission to Pluto and in the quest to discover Kuiper Belt Objects starting in the early 1990s. From Uranus to Eris, the story of astronomical discoveries is the story of people, their feuds, their insecurities, their personal passions toward a particular goal. 

He recalls the painful admission by astronomer Dr. Owen Gingerich, chair of the original committee assembled by the IAU to address planet definition, about the way things fell apart in Prague partly because Gingerich left before the final debate and vote."Had I been there, I would have worked out a compromise," Gingerich said, both in the book and at the Great Planet Debate. For want of one astronomer, Pluto was lost. Who can say "Greek tragedy?"

Supporters of Pluto's demotion claim people want to cling to Pluto as a planet out of emotion and sentimentality. What Boyle drives home is the fact that the entire history of astronomical discovery, from controversy over what to name newly-discovered Uranus to the brouhaha on the last day of the 2006 IAU General Assembly, all involved emotion, passion, and sentiment. There were and are no Vulcans.

Refreshingly, Boyle devotes a chapter to the Great Planet Debate, ripping away the veneer of finality the IAU has attempted to impose regarding its 2006 decision. "The IAU has no special claim," he quotes Dr. Alan Stern, who added the significant point that many planetary scientists do not even belong to the IAU while most IAU members work in other areas of astronomy such as the study of galaxies. "The people who actually understand the physics, the chemistry, the work on planets, aren't in the IAU," Stern accurately noted.

Two specific points are made very clear throughout the course of the book. One is the existence of two competing views about how to understand the solar system. Boyle accurately notes that the issue is not about being pro or against Pluto but about two competing paradigms--that of the dynamicists, who focus on the way solar system objects move and affect one another, and that of the planetary scientists, who study the individual objects themselves, looking for activity such as geology and weather. This is the crux of the argument, and this is why there is no right or wrong answer, only differing interpretations.

The other critical point Boyle articulates addresses public perception, culture, why people care about Pluto. He accurately dismisses Dr. Neil de Grasse Tyson's claim that people's affinity for Pluto is all about the Disney dog. "When it comes to Pluto's appeal, it's not all about the dog. It's all about the underdog." In one concise sentence, he answers the question that has mystified so many, the reason that so many people reacted to the IAU decision with such outrage.

Notably, Clyde Tombaugh, the man who discovered Pluto, was himself an underdog, having grown up in a farm family and taken the job at Lowell Observatory with only the one-way ticket to Flagstaff he could afford. Tombaugh eventually obtained a Masters in astronomy but never a PhD, a fact that caused him to be snubbed by some astronomers. "I always thought I was a nobody," the planet discoverer shockingly reveals in David Levy's biography of him, expressing surprise at both his and Pluto's popularity.

In a relatively small book, Boyle provides a plethora of information about the five bodies currently designated as dwarf planets, a list of next generation projects searching for exoplanets, a copy of the 2006 IAU resolutions, and, most importantly, a section in the back about how to talk to kids about planets. In clear, non-technical language, he discusses the fact that scientists do not all think the same way about planets, emphasizing that debate is at the heart of the way science works.

As for the question of how many planets revolve around our Sun, "four plus four plus more," referring to four terrestrials, four jovians, and an indeterminate number of "more" planets of a third category, is the most concise, most sensible way I have yet heard this question answered.

The Case for Pluto speaks to all ages, to lay people and scientists alike, demystifying what to many was a convoluted, senseless decision by a remote group of academics that has generated much confusion. "How wrong they were," Boyle says twice of the IAU's confidence that it had resolved the issue in 2006. He makes an amusing but apt inference to Galileo's so-called retraction of his Sun-centered theory before the Inquisition by citing Mike Brown's infamous line "Pluto is dead" and following it with the parenthetical statement (and yet it moves), the words quietly muttered by Galileo in defiance of his forced retraction.

Is there a solution to the debate? Boyle proposes using a model similar to the Herzsprung-Russell Diagram, which has been used to classify stars for almost 100 years, envisioning a similar spectrum for planets. But such a spectrum must also address the amazing diversity of objects being found orbiting other stars. And that most likely means adding more subcategories.

I do admit to a personal reason for favoring this book. In the reference section for Chapter 9, "The Battle of Prague," Boyle's first reference is to the article I originally wrote for my local newspaper, The Somerset Spectator,  later picked up by the UK Space Conference of 2008, "Pluto, the Planet that Was," which can be found here: For more on this wonderful book, visit its web site at

How can anyone put the issue better than this? "Never again can Pluto be the ninth planet. Or the littlest planet. Or the most distant planet. But does that make Pluto a nonplanet? No way."

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