Astronomers predict that they will find up to 10 similar objects in the Kuiper Belt that are as large as or larger than Pluto. So unless we want to add 10 more planets to the elementary-school curriculum, we would be wise to downgrade Pluto to the distant iceball it is.
Excuse me? Was this the same newspaper whose page 1 headline blamed Hayden for all of Pluto’s woes? And what’s that about the Hayden Planetarium causing “quite a stir”? Wasn’t it the New York Times that broke the story—a year late—and not some kind of media press release on our part? We had been quietly minding our own planetary business for a year before they even took notice. And what’s that about “we would be wise to downgrade Pluto”? Who’s “we”?
Figure 4.9. Eight trans-Neptunian objects drawn to scale, including Pluto. As the inventory of objects that orbit the Sun beyond Neptune grows, so, too, does the likelihood of finding objects that rival Pluto in size. Already, Eris checks in larger than Pluto. More will surely follow. For size reference, a segment of Earth appears along the lower edge.
All during the previous year, the Times had allied itself with the Pluto-is-a-planet people. But if the Times was now (albeit tacitly) acquiescing to the sensibility of our approach—if the paper was finally seeing what we saw the night of our Pluto panel—then we were happy to have them on our side.
A year later, in November 2003, a reddish ball now named 90377 Sedna, with a diameter somewhere around 1,500 kilometers—about three-quarters that of Pluto—was discovered by Kuiper belt hunters Michael Brown, Chad Trujillo, and David Rabinowitz, again using the Oschin Telescope. It was the most distant known body in the solar system, and planetary scientists were rapidly closing in on the Holy Grail—an object out there bigger than Pluto itself.
In fact, it had already been found the previous month. On October 21, 2003, Brown, Trujillo, and Rabinowitz photographed, but only later revealed, the ninth largest solar system body in orbit around the Sun: 136199 Eris, whose diameter falls somewhere between 2,400 and 3,000 kilometers (Pluto’s checks in at 2,300 kilometers) and whose mass is 27 percent larger than that of Pluto. Brown and his collaborators announced their discovery along with two other (smaller, less planet-shaking) objects on July 29, 2005.
If Eris were to keep its classification as a planet under IAU rules, as Mike Brown argued should happen, then his object was a shoe-in for planet status, making Brown the second American to discover a planet, after Clyde Tombaugh. But the converse must also be true: If Eris were classified as something other than a planet—how about a dwarf planet?—then Eris, being bigger than Pluto, would drag Pluto down with it. Such was the battlefield drawn by the inevitable discovery of Eris.
Before Eris was formally named by the IAU in September 2006, Mike Brown had unofficially been calling the thing Xena, after the buff, buxom, leather-clad, sword-wielding warrior princess of cable television who spends much of each weekly episode kicking medieval butt. Unfortunately (in my opinion), television mythology is not a valid source of names for cosmic objects. The IAU instead references mythologies from a time somewhat before TV was invented. Mike Brown knew this and had proposed the name Eris, the Greek goddess of discord and strife. For Eris’s moon, whose orbit enabled the accurate calculation of Eris’s Plutobeating mass, he proposed Dysnomia, the demon goddess of lawlessness and the daughter of Eris. As you may already know, classical gods led complicated social lives. One of Eris’s pastimes was to instill jealousy and envy among men, driving them to battle. At the wedding of Peleus and Thetis, all the gods were invited with the exception of Eris. Angered by her exclusion, she vengefully instigated a quarrel among the goddesses that precipitated the Trojan War.
Brown had indeed done his classical homework and dutifully captured Eris’s destabilizing influence on the Pluto problem, causing a war of its own.
5
Pluto Divides the Nation
IT’S NOT EASY BEING A PUBLIC ENEMY. NEARLY ALL the paper mail and e-mail that I received following the trouble-making January 22, 2001, New York Times article was negative. Schoolchildren and adults alike branded me a thoughtless, heartless Pluto hater. Some, not paying attention to the one-year delay of the Times article from opening day of the Rose Center, accused the museum of mounting a publicity stunt to drum up attendance.
I personally replied to nearly every inquiry. Most letters presumed that we, the mean, city slicker New Yorkers, had kicked small, defenseless Pluto out of the solar system and that I was somehow personally trying to disrupt the nine-planet family we had all come to befriend in elementary school.
Of course, what we actually did to Pluto was more subtle than this, which prompted me to compose a “media response” to the barrage of inquiries, attempting to clarify our position compared with what someone would think we did based on the New York Times’ “Pluto’s Not a Planet? Only in New York” headline. The content of this 1,000-word statement (see Appendix E for the complete text) includes exact quotes from our exhibits. In the Planet Zone of the Hall of the Universe, we ask the question, “What is a Planet?” to which we reply:
In our solar system, planets are the major bodies orbiting the Sun. Because we cannot yet observe other planetary systems in similar detail, a universal definition of a planet has not emerged. In general, planets are massive enough for their gravity to make them spherical, but small enough to avoid nuclear fusion in their cores.
This paragraph is hardly controversial. Our exhibit goes on to describe “Our Planetary System”:
Five classes of objects orbit our Sun. The inner terrestrial planets are separated from the outer gas giant planets by the asteroid belt. Beyond the outer planets is the Kuiper Belt of comets, a disk of small icy worlds including Pluto. Much more distant, reaching a thousand times farther than Pluto, lies the Oort Cloud of comets.
Another innocuous paragraph. But the persistent (negative) attention received by the museum forced us to temper the storm. After I review the overall layout of the Rose Center, I describe in detail the “offending” part of our Scales of the Universe exhibit but remain firm about our intent:
About midway in the journey [along the Scales of the Universe] you come upon the size scale where the sphere represents the Sun. On that scale, hanging from the ceiling, are the Jovian planets (the most highly photographed spot in the facility) while a set of four small orbs are also on view, attached to the railing. These are the terrestrial planets. No other members of the solar system are represented here. This entire exhibit is about size, and not much else.
I then address the issue head-on:
But the absence of Pluto (even though the exhibit clearly states that it’s the Jovian and terrestrial planets that are represented) has led about ten percent of our visitors to wonder where it is.
Ten percent of the public bewildered is a large enough fraction to concern us as educators. The release continues:
In the interest of sound pedagogy we have decided to…add a sign at the right spot on the size scales exhibit that simply asks “Where’s Pluto?” and gives some attention to why it was not included among the models.
Shortly thereafter, we wrote, designed, manufactured, and bolted a “Where’s Pluto?” plaque to our Scales of the Universe walkway, adjacent to and visible from the rail-mounted models of Mercury, Venus, Earth, and Mars. No longer would people ask Pluto’s whereabouts among our exhibits, but these measures did nothing to stave off the fulmination that would follow.
We released the statement to general audiences on February 2, 2001, but it was specifically intended for the widely read, UK-based Internet chat group called Cambridge Conference Network (CCNet), moderated by social anthropologist Benny J. Peiser, of Liverpool John Moores University. The primary interest of the network was open discussion of asteroids, comets, and their risk to life on Earth, but many other newsy subjects also found their way to these pages.
On January 29, 2001, Peiser posted articles from the Associated Press (AP) and Boston Globe that had been spawned by the original New York Times sto
ry on Pluto a week before.29 The AP article contained a quote from me:
There is no scientific insight to be gained by counting planets. Eight or nine, the numbers don’t matter.
This was followed by a quote from David Levy, amateur astronomer extraordinaire (who we met in the last chapter at the museum’s 1999 panel on Pluto’s status). Levy drew first blood with the barb:
Tyson is so far off base with Pluto, it’s like he’s in a different universe.
Always remember that when an astronomer accuses you of being in a “different universe,” it carries extra meaning.
Sustained, verbal altercations followed immediately in the chat group. University of Hawaii’s David Jewitt, codiscoverer of the Kuiper belt of comets (along with Jane Luu, who we also met in our discussion of the Pluto panel), fully endorsed our exhibit treatment of Pluto:
They’ve done exactly the right thing. It’s an emotional question. People just don’t like the idea that you can change the number of planets. It’s inevitable that other museums will come around, though. The Rose center is just slightly ahead of its time.
Leonard David, journalist from Space.com, quoted space scientist Kevin Zahnle as saying:
Pluto is a true-blue American planet, discovered by an American for America.
I later learned from a colleague that Zahnle, of NASA’s Ames Research Center, in Moffett Field, California, is only capable of such a statement in jest, but others who did not know this took the jingoistic comment seriously. Joshua Kitchener, publisher of a Web-based asteroid-tracking magazine, replied immediately:
Such romanticism has no place in science, a system which must never cease trying to determine the objective truth, a truth free from human prejudice and emotion. Neither does nationalism.
Want to piss off the astronomers?30 Call them astrologers. Space scientist Wendell Mendell, of NASA’s Johnson Space Center in Houston, did just that:
I confess I am disappointed in the learned community that joins with astrologers in holding onto an outdated classification scheme.
I was particularly charmed by the attempt of some to make peace among the combatants. Dale Cruikshank, president of the IAU’s commission for the physical study of the planets and satellites, took both sides of the argument:
My personal view is that Pluto should probably have dual citizenship, in that its planetary status ought to be maintained partly for historical reasons and partly for its physical characteristics. But it seems clear that it is also “object one” in what we now recognize as a large class of Kuiper Belt objects.
David Levy, with perennial concern for the relationship between scientists and the public, commented:
On the whole, I do not agree with the dual status because it complicates matters too much in the public perception.
Levy’s comment here is entirely consistent with his concern-for-the-public testimony at the museum’s Pluto panel. A day earlier, Levy had posted a claim that left you wondering whether he was a personal friend of Pluto:
I believe that until we land on Pluto and find incontrovertible evidence that that world does not wish to be called a planet, that we should leave things as they are.
My professional research interests relate primarily to stars and galaxies. Knowing this, geologist Jeff Moore, from NASA Ames, chose to attack my absence of professional association with the solar system:
First of all, it’s rather amazing that Tyson, an astrophysicist, would even venture into such waters. I feel, as a planetary geologist, equally qualified to demote the Magellanic Clouds 31 to glorified star clusters as opposed to small galaxies. So in that spirit, I think he’s full of baloney.
I have always enjoyed seeing the word baloney used in a sentence.
Returning to the dialogue, Joshua Kitchener could not resist a historical analogy to the proceedings:
It’s not too hard to imagine the same type of people back in Galileo’s age, saying, “I’ve been taught that the Earth is the center of the universe since I was a child. Why change it? I like things the way they are.”
Mark Kidger, of the Institute for Astrophysics in the Canary Islands, followed with a perceptive comment about the trans-Neptunian objects (TNOs) of the Kuiper belt:
Had other TNOs been discovered in 1935 and not in 1992, it is quite possible that we would not be having this debate now.
These views, and many more, were all posted to CCNet within a single 24-hour period. Benny Peiser would now solicit the open letter of rebuttal from me, with a polite appeal that concealed much of the emotion that the raging conversation had engendered:
I regret that you have received a considerable amount of flak and criticism for your pioneering decision, and would like to congratulate you for your courage. As a moderator of CCNet, I have tried to keep this whole debate in the domain of fact and evidence, rejecting right from the start any attempts to intimidate those who suggested changes to the status of Pluto.
Please let me know whether you would be happy to write a little essay-type comment for CCNet and its many readers. I would very much [like] to hear from you.
On February 14, 2001, Benny Peiser decided to post the entire New York Times article that contained the conversation between me and Mark Sykes, chair of the American Astronomical Society’s Division for Planetary Sciences. A week earlier, in a kind of preamble to that posting, Mark Sykes may have been concerned about whether the New York Times article adequately captured his views. So he submitted a 900-word letter to CCNet bluntly recounting his disapproval with what he saw among our exhibits at the Rose Center. He made his point of view quite clear:
…the issue at the Hayden is more one of poor pedagogy than a clarion call for controversy.
The exhibit on planets at best confuses those who look closely enough to catch the inconsistencies….
…scientific and pedagogical integrity would require that they prominently notify the public that they are taking an advocacy position to remove Pluto’s planetary status and acknowledge that at present the IAU officially designates Pluto as a planet.
That letter did not go unheeded. University of Memphis astrophysicist Gerrit Verschuur struck back as though it was he, and not the Rose Center, who had been attacked personally:
I was shocked to read the following from Mark Sykes…“When designing an exhibition, one needs to understand and take into consideration the expectations of the viewer. Given an opportunity, the viewer will see what they expect to see.” Surely an exhibition that does just that contributes nothing. If viewers only see what they expect to see they might as well stay home. Does the Sykes philosophy mean when designing an exhibit about UFOs in which one hopes to educate that one must give the viewers what they expect to see, which is a load of nonsense about aliens flying between the stars?…Surely the point of an exhibit in science is to inform and educate and not just to feed prejudices and expectations.
Verschuur goes on to make an insightful pedagogical observation about teaching Astro 101:
I feel sure most of us who have taught astronomy have felt troubled when we reach the chapter that shows Pluto looking at us from the end of chapters on the gas giants, or even worse, lurking among the terrestrial planets.
Verschuur, author of five popular books on astrophysics, continues with a second insightful observation, referencing the ruffled relations between pure research scientists and scientists who also choose to bring the frontier of science to the public:
Is the problem perhaps that the Pluto controversy has been stirred up by a planetarium, given that many professional astronomers are still inherently prejudiced against anyone who deigns to dedicate their time to the popularization of astronomy?
The hidden folly of it all was succinctly captured by Sonoma State University astronomer Phil Plait:
At the heart of the debate is our very definition of the word “planet.” Currently, there isn’t one. The International Astronomical Union (IAU), a worldwide body of astronomers, is the official keeper of names. It has no strict d
efinition of a planet, but has decreed that there are nine major planets, including Pluto. This, however, is not very satisfying. If the IAU doesn’t really know what a planet is, how can it know there are nine?
Mark Sykes was not alone in his brazen ways. Many of my colleagues felt comfortable telling me directly, via e-mail, what their opinions were regarding our exhibit treatment of Pluto. They wasted no time, most arriving at my in-box within days of the story breaking in the New York Times on January 22, 2001, and with others trickling in over the years that followed.
Robert L. Staehle, of NASA’s Jet Propulsion Laboratories, in Pasadena, California, sure that we were guilty of a simple oversight, candidly wrote:
What gives? Did someone there have a memory lapse? What will it take to get Pluto back up there where it belongs?
Staehle would later follow with an observation of nature that we can all agree with:
In the end, neither Pluto nor anything else in the outer Solar System cares in the slightest what anybody on Earth labels it. These bodies exist, and hold what they have to reveal about our collective natural history, totally without regard to any label assigned by an august body of scientists, or any other living thing that we know of.
Michael A’Hearn, of the University of Maryland, who was kind enough to participate in our Pluto panel two years earlier, shared a perceptive pedagogical observation:
I am struck by the fact that the people who seem most wedded to keeping Pluto a planet are systematically the people who do not have to teach the subject (either to students or the public) on a day to day basis.
Timothy Ferris, the best-selling science writer, was quick to offer support, combined with a prescient statement of the long-term outcome of our decision:
Unhindered by any prejudices on the subject other than a personal liking for Clyde Tombaugh, a good man whose advice was central in my design of Rocky Hill Observatory, I reviewed the case and concluded that, hell, Pluto is not a planet. So I think you guys did the right thing, and will in the long run be viewed as having led the bird when your only alternative was to miss.
The Pluto Files: The Rise and Fall of America's Favorite Planet Page 8