The Pluto Files: The Rise and Fall of America's Favorite Planet (13 page)

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FTER TWO YEARS OF COMMITTEE DELIBERATION, THE
International Astronomical Union (IAU) could not converge on what exactly a planet should be. And so the IAU formed an ad hoc Planet Definition Committee to see if they could succeed where others had failed. This fresh group of seven—five scientists, a journalist, and a science historian—met for two days before the Prague meeting to cogitate and then decided on what, in their judgment, would be the best solution for all concerned parties, Pluto included. On August 16, 2006, they recommended to IAU membership that a planet be officially defined as an object that (1) is in orbit around a star, but not in orbit around another planet, and (2) is large enough for its own force of gravity to shape it into a sphere, but not so large that it would trigger fusion in its core becoming a star. This definition would have kept Pluto as a planet and added, on the spot, three more objects to the planet list: Ceres, Charon, and Eris, with many more surely to come.

Figure 6.1.
The seven-member Planet Definition Committee of the International Astronomical Union (IAU).
Top row, left to right:
André Brahic, University of Denis Diderot (Paris) planetary scientist and popularizer; Iwan Williams, Queen Mary University (London) planetary theorist; Junichi Watanabe, director of the Outreach Division of the National Astronomical Observatories of Japan; and Richard Binzel, MIT planetary scientist.
Bottom row, left to right:
Catherine Cesarsky, director general of the European Southern Observatories and president-elect of the IAU; Dava Sobel, best-selling science writer and journalist; and Owen Gingerich, Harvard astronomer, historian of science, and chair of the committee.

In spite of the undeniable cosmic expertise represented among the committee members, they were nonetheless absent researchers who specialize in the discovery and analysis of Kuiper belt objects or in the discovery and analysis of exosolar planets, two frontiers of planetary science that bring daily insight to what kind of solar system we live in. Based on the comments and reactions already expressed by Kuiper belt codiscoverers David Jewitt and Jane Luu, for example, had either of them been on the committee, it surely would have led to yet another hung jury.

During the week that passed between the IAU proposal going public and the formal vote on the recommendations, the roundness criterion received substantial media attention. In an appearance on Comedy Central’s
The Colbert Report
, I shared this information with faux ultraconservative host Stephen Colbert, who had been supportive of Pluto all along, but was deeply concerned that if being round was what made you a planet, then “that means anything could be a planet,” and “if everything is a planet, then nothing is a planet.” His concern, shared by many, was simply that the decision was “taking away the specialness of Earth’s planetness.” He then proceeded to trash-talk the other three planet candidates in the solar system, beginning with Pluto’s very round moon Charon:

Next came Ceres, the largest and only round asteroid:

Last was the yet-to-be-named icy Kuiper belt object 2003 UB313 that would later become Eris:

Back in the
real world, the conference attendees hotly debated the roundness criterion for planethood, leading to two additional criteria: (1) that the round object not be in orbit around another, larger world—precluding Charon from being called Pluto’s companion planet; and (2) that the round object has cleared its orbit of wayward debris—the death knell for Pluto, whose orbital regime remains rich with countless thousands of craggy chunks of icy Kuiper belt objects. This leaves the Sun with an eight-planet family instead of either twelve or nine. Coincidentally, on August 16, 2006, my friend and museum colleague Steven Soter (the fellow who first called my attention to the Pluto problem back in 1998) submitted for publication a research paper titled “What Is a Planet?” in which he quantifies what it would mean for an object to clean its orbit.
³³
This criterion is subtle because without a quantitative account of a clean orbit, the requirement can be arbitrarily invoked. For example, as noted earlier, Earth continues to plow through hundreds of tons of wayward meteoroids per day in its annual journey around the Sun. So have we cleared our orbit? Clearly not. The objective is to assess the total mass of cleanable debris and compare it with the mass of the planet in question. If the debris does not amount to much, then you can claim to have cleaned or dominated your orbit. Otherwise, you’re just one of the crowd.

For example, Earth far outweighs the sum of all matter it will ever collide with. Earth can plow through its daily dose of debris for a quadrillion (1,000,000,000,000,000) years and become a mere 2 percent heavier than when it started. A quadrillion years is 10,000 times longer than the current age of the universe. Meanwhile, the countless Kuiper belt comets outweigh Pluto by a factor of at least 15.

Steve Soter’s paper provided perspective on what was, at the time, a hastily added criterion to the original roundness definition of the IAU resolution. Soter and I had collaborated on this paper during its early stages, but by the end, he had done 95 percent of the work while I was (regrettably) distracted by administrative matters. So I withdrew as coauthor but was delighted to be recognized in the paper’s acknowledgments.

Figure 6.2.
The 26th (triennial) General Assembly of the International Astronomical Union, held in Prague. Of the 2,500 attending members, 424 remained for the last day of the conference (August 24, 2006) to vote overwhelmingly (90 percent in favor) on a revised definition of the word
planet
that excluded Pluto, formally “demoting” it to dwarf planet status.

Back at the IAU conference in Prague, anxious reporters waited outside the assembly hall, which was off-limits to the press. They lurked with the kind of silent anticipation one finds only during the election of a new pope by the college of cardinals, for which eager onlookers in St. Peter’s Square search for the smoke to rise from the Vatican Palace chimney—black smoke, a failed ballot; white smoke, a new pope is elected. All week long my e-mail in-box logged more than a hundred inquiries a day on Pluto alone, from concerned citizens and from the press wanting me to comment. When the final vote was cast on August 24, 2006, a revised definition of a planet emerged—and a revised status for Pluto:

More than 90 percent of the 424 voters voted for demotion. (See the full amended resolution 5A in Appendix F.) The same criteria that downgraded Pluto elevated Ceres to the class of dwarf planet from the ranks of asteroids. Eris, the freshly discovered spherical Kuiper belt object, joined Pluto among the ranks of dwarf planets as well.

By now, the Pluto e-mails to my in-box were arriving at about two hundred a day, with assorted subject headers that betrayed the sentiments contained within: “Now Look What You’ve Done!” “Congratulations on Winning the Pluto Is Not a Planet Debate,” and “Honk if you think Pluto is still a planet.” And a dozen major media outlets had called or e-mailed for my reaction to the decision. I happened to be at the beach that entire week, on vacation with my family, and could take no interviews. So this feeding frenzy would have to happen without me.

In the weeks that followed, there were one or two supporters amid the e-mail barrage:

The following comment was not sent directly to me but was posted to “Dome-L,” an Internet chat group that serves planetarium professionals. The fellow reflects on the planetarium community’s resistance to our museum’s treatment of Pluto on the grounds that it was against IAU proclamation; but after the IAU officially demoted Pluto, the same community continued to object, this time ignoring the IAU. Behavior such as this betrays hidden biases that do not tend to be subject to rational argument.

Some people got a bit carried away in their anti-Pluto enthusiasm:

Others took the occasion to lambaste the negotiating talents of well-meaning scientists:

Meanwhile, surface mail continued. Angry third graders from the year 2000 were now in high school, with other (hormonal) priorities to distract them. But, as already noted, there’s always a new crop of elementary schoolers to fill that void. In a stack of letters addressed to me from Mrs.

Debbie Dalton’s third-grade class in the Warren L. Miller Elementary School, in Mansfield, Pennsylvania, Emerson York expresses their sentiment best, complete with seven exclamation marks to end the letter, followed by an illustration of a teary-eyed Pluto (Figure 6.3).

One of my favorites of the angry-kid genre arrived from Madeline Trost, of Plantation, Florida, and was mailed on September 19, 2006. After addressing the envelope to me personally, she bluntly addresses her letter “Dear Scientest” (Figure 6.4), and she can’t contain her flurry of assaults on my integrity, ending with an appeal to accommodate a short-coming of her own. I received another angry letter from a kid, except this one was a little older. As a card-carrying member of the American Museum of Natural History, she also felt comfortable schooling me in Plutonian mythology (Figure 6.5).

For newspaper articles,
journalists hardly ever get to title their own piece. That task usually goes to someone else in the back office. For Pluto and its demotion, the urge to compose an attention-getting headline that poked fun at the entire episode was irresistible—especially for the tabloids. Ones that rise above others include the
Atlanta Journal-Constitution
’s “Planned Planethood” on August 16, 2006. Meanwhile, with the fresh memory of miscounted ballots in Florida during the hotly contested presidential elections of 2000, the
St. Petersburg Times
carried the headline “Pluto’s Hanging Chad” on August 22, 2006.

Those were the real headlines.

In a parody of
The New York Times’
page 1, The People’s Cube (ThePeoplesCube.com) ran a series of Pluto-inspired headlines (accompanied by illegible columns of text) that mirror prevailing political and cultural sentiments in America. Dated August 26, 2006, the page begins with: