Mercury may be a burnout case, and Mars isn't what he used to be. Venus is a hottie, but she'll make your life hell. With Saturn, it's all about the rings and the bling. Jupiter takes himself waaaay too seriously. Uranus won't stop with the off-color puns, while Neptune's jokes will leave you cold. But Pluto? Now that's one funny planet!
In the decades since Pluto was discovered in 1930, the ice dwarf was adopted as a sentimental favorite for kids and one of the most anthropomorphized bodies in the solar system, even for grown-ups.
Astrophysicist Neil deGrasse Tyson, the planetarium director who left Pluto out of the parade of planets at the American Museum of Natural History, thinks its appeal is all about the dog—the fact that generations of kids have linked the tiny world with Walt Disney's orange cartoon character. And that's certainly a factor, at least for kids like eleven-year-old Michael O'Sullivan, who was told about the International Astronomical Union's ruling during a field trip to the National Air and Space Museum.
"Seriously! Pluto is not a planet?" he asked. Then, after a moment of reflection, he added, "At least Pluto the dog doesn't have to compete with the planet anymore."
The Disney Company, which had capitalized on the newfound planet's popularity seventy-five years earlier, was philosophical about the planetary putdown. "Pluto is taking this news in stride," company spokesman Donn Walker said, "and we have no reason to believe he might bite an astronomer."1 But the varied reactions to the IAU's reclassification scheme indicated that the sympathy for Pluto went deeper than Disney. Pluto struck a chord as the cute little runt of the solar system's family, kicked out by the big shots of the cosmos. One editorial cartoon showed a scrawny kid pleading to be let into the treehouse for the "Solar System Club," only to be told, "Beat it, Pluto—you little ice ball!"2
The episode in Prague inspired comedians half a world away. "Today Pluto packed up and moved out. It said it is now going to spend more time with the family. Even sadder, it hung out around Saturn all day trying to get a job as a moon," David Letterman quipped on CBS 's The Late Show.3
The perils of Pluto even provided material for one of the summer's biggest Internet sensations. "Lonelygirl15," the main character in a wildly popular faux-reality video series, snipped Pluto off a solar system mobile and related the little world's fate to her own teenage angst: "Ceres? Xena? UB313? These are Pluto's new friends. Do they sound like the kids that you want to eat lunch with? No way!"4
Chicago stand-up comedian Ricky Marsh made it sound as if Pluto's kindred spirit wasn't Xena the Warrior Princess but rather Woody Allen: "Pluto was this little nebbish, never bothering anybody. Sure, it was a long distance from home, and it never called, sent a card or came for Shabbos dinner . . . but it's harmless. . . . Jews are always defending the little guy, so why should we stand by and do nothing about the inquisition of Pluto? "5
When it comes to Pluto's appeal, it's not all about the dog. It's all about the underdog.
There was plenty to laugh at in the way the IAU's definition turned out—particularly the definition of "dwarf planets" as nonplanets. It didn't take long for the "dwarf " label to get attached to anything that didn't quite measure up to expectations.
"How dare they say that Pluto is a Dwarf Planet?" one blurb asked on a Web site selling dwarf-planet apparel. "That's like saying Ottumwa is a Dwarf City, or like saying the Chicago Cubs are a Dwarf Baseball Team, or like saying George W. Bush is a Dwarf President . . . um, okay."6
Some columnists joked that the arrangement actually brought Pluto back into the planetary fold through the back door. "'Dwarf,' in addition to being politically incorrect, is only an adjective. 'Planet' is a noun, solid and palpable. Pluto, put plainly, is still a planet," Cox Newspapers' Tom Teepen wrote. "The astronomers outsmarted themselves. Which, on the evidence, may not have been all that difficult."7
The reactions from astronomers weren't all played for laughs: On one hand, Xena's discoverer, Mike Brown, declared that "Pluto is dead."8 (And yet it moves.) "I'm of course disappointed that Xena will not be the tenth planet, but I definitely support the IAU in this difficult and courageous decision," Brown said. "It is scientifically the right thing to do, and is a great step forward in astronomy."9
On the other hand, Alan Stern—the planetary scientist who worked for a decade and a half to get a probe sent to Pluto—said the IAU's definition was "scientifically ludicrous and publicly embarrassing."
" It's going to be a laughingstock," he said. " It's going to be a mess for schoolkids. I don' t think textbooks will even accept it."10
Clyde Tombaugh's widow, Patsy, reacted more in sadness than in anger. Since her husband's death nine years earlier, she was the one most called upon to give the perspective of Pluto's discoverer: "It kind of sounds like I just lost my job. But I understand science is not something that just sits there. It goes on. Clyde finally said before he died, 'It's there. Whatever it is, it is there.'"11
Patsy and other family members were the guests of honor at a protest rally at New Mexico State University in Las Cruces, where Clyde Tombaugh spent the last years of his career and his life. About fifty supporters listened to speeches and carried signs proclaiming "Size Doesn't Matter."
Meanwhile, Mark Sykes and Alan Stern started up an online petition drive, protesting the IAU planet definition as unusable and rejecting it. More than three hundred scientists and astronomers signed the petition, including some who thought Pluto shouldn' t be classified as a planet but objected to the IAU's handling of the issue. The petition was removed from the Web after only a few days. "Notice of the petition began to appear on blogs, and we did not want to be swamped by signatures from the general public," Sykes said.
Lawmakers joined the fray as well, although they took their vote a little less seriously than the astronomers did. New Mexico's state House of Representatives approved a proclamation declaring Pluto to be a planet, with Patsy Tombaugh looking on from the gallery.12 In Wisconsin, the city of Madison passed a resolution designating Pluto as "its ninth planet" while supporting "planets that take a different path, such as Ceres and Xena."13 And in California, a tongue - in - cheek resolution condemning the "mean - spirited
International Astronomical Union" was introduced in the State Assembly. 1 4 (None of the measures was legally binding.)
Despite what Stern said, textbook authors at least took note of the planethood paradigm shift. In an ironic twist, Stern's own teenage son was caught up in the shift, when his science teacher marked a test answer wrong because it didn't conform to the eight-planet paradigm.
Most textbooks didnl require that much of a change, because Plutos place had already been put in perspective thanks to the previous decade's discoveries about the Kuiper Belt. The SETI Institutes Dana Backman, who is the coauthor of the textbook Perspectives on Astronomy as well as a researcher specializing in planetary disks, joked that he was "sort of an anti-Pluto cult leader" even before the IAU's decision. "I had always taught the material that Pluto was not a planet," Backman said. "That caused people to wake up a little bit."
In some textbooks, Pluto was wiped out entirely.15 In others, the outcome of the IAU meeting was only half digested. For example, one set of worksheets for McDougal Littells middle school science series asked students to add entries for five outer planets, but highlighted only the four Jovian planets (Jupiter, Saturn, Uranus, and Neptune). Pluto was still mentioned in a side note, however, as "the smallest and coldest planet in our solar system."16
Astronomer Thomas Arny, one of the coauthors of an introductory astronomy textbook, had to revise the chapters on the solar system twice, thanks to the IAU's pronouncements. "I honestly just don't understand what the fuss is about," he said. "There are big planets, and there are little planets. So what?"
His fellow coauthor, Stephen Schneider, just wanted to have the planethood question settled, one way or another, for the sake of the teachers. "Most of them were willing to go with the new definition—they just didn't want it to keep changing," he said.
Some teachers quickly adapted their old curriculum to reflect the new IAU view. At Jamestown High School in Virginia, Earth sciences teacher Tricia Dillon traditionally had students do up travel brochures for the solar system's planets. In the fall of 2006, the brochures carried a disclaimer: "The trip to Pluto has been canceled due to its reduced status in the solar system." Dillon used the planethood debate to teach her students about the scientific process—which, in this case, was a hard lesson to absorb. "A lot of them were sad," she said.17
Other teachers kept Pluto in the classroom no matter what the textbooks said. Bev Grueber, a science teacher at North Bend Elementary School in Nebraska, said Pluto is still one of the subjects handed out to her fourth-graders for oral reports on the solar system. "Everyone jumps for joy when they get Pluto," she said. "Last year, I left Pluto out of the draw and they asked where it was, so they still consider it a planet regardless of what the space scientists tell us the definition of that planet is."18
In an effort to raise awareness about NASA's New Horizons mission, Stern recruited a group of children called "Pluto's Pals" who were born on the same day that the spacecraft was launched. Two of those pals are twins Nora and Hana Fennell, who will be nine years old by the time New Horizons reaches Pluto. What will they be learning about Pluto by that time? Their mother, Risha Raven, couldn't predict.
"I asked their twelve-year-old sister what she thought," Raven said. "She said she's been told that Pluto was not a planet, and she really doesn't understand why."
The authors of children's books wrestled with the planetary paradigm shift as much as teachers did. Most of the newly written books reflected the IAU's view and explained Pluto's passage from planet to dwarf planet. But if you were inclined to add Pluto and Xena, you could read Ten Worlds to your child, and if you wanted to make sure Ceres was also covered, you could go with 11 Planets instead.
A vigorous debate swirled around what to do with the classic memory aid for the names of the planets. The old phrase "My Very Excellent Mother Just Served Us Nine Pizzas" could be shortened by turning those " Nine Pizzas" into " Nachos." But it could just as well be lengthened by adding Ceres and Xena's new name, Eris, to the jingle: "My Very Exciting Magic Carpet Just Sailed Under Nine Palace Elephants."19
So how many do you memorize? One of the silliest arguments for going with eight planets, period, was that kids would eventually be forced to commit twenty or thirty or three hundred planetary names to memory. Do students have to know all 191 United Nations member states? If teachers can draw the line at remembering the five permanent UN Security Council members for social studies class, they can draw the line wherever it's appropriate for science class.
"Basically, it's a teachable moment for science teachers, because it shows the dynamic nature of science," said Gerry Wheeler, executive director of the National Science Teachers Association.20
If Neil deGrasse Tyson had his way, science teachers would downplay the nine-planet versus eight-planet question altogether. "The question should not be how many planets there are," he said. "There's no science in that question." The important thing is to learn about the different classes of objects in the solar system—ranging from the gas giants (Jupiter and Saturn) and the ice giants (Uranus and Neptune) to the terrestrials (Mercury, Venus, Earth, and Mars), as well as the round rocky dwarfs (Ceres) and ice dwarfs (Pluto and Xena), plus the gnarlier asteroids and comets.
The nine-versus-eight dilemma played out in spheres outside as well as inside the classroom. Musicians mostly gave up on adding Pluto to The Planets, Gustav Holst's famous orchestral suite. (Which was no big deal: Pluto was never part of the original music because it was written before Tombaugh made his discovery.) The National Air and Space Museum kept Pluto' s plaque in its own outdoor parade of planets on Washington's National Mall, but stuck a black square over Pluto's symbol in its indoor planetary exhibit. Was the museum in mourning? It even put up an "In Memoriam: Pluto" poster, as if the 29-sextillion-pound world had wasted away to nothingness.21
In the toy world, some companies continued to sell mobiles and posters with nine planets, while others switched to eight. Some sold both, occasionally throwing in moons and stars as extras. Scholastic News artfully tried to have it both ways by offering a "Little Big Box of Planets . . . and Pluto, Too!"
When you think about it, what kid would complain about having an extra planet in the toy box? On the flip side, it's a letdown to get just eight toy planets when you were looking for nine. Blogger Jason Kottke was so disappointed to find that his fourteen-month-old son's "Solar System Ball" lacked a Pluto that he took a black marker and drew one on. "One ball at a time, people," he wrote, "that's how we win."22
While textbook writers, teachers, and parents absorbed what the IAU had done—and tried to figure out whether they were for or against it—astronomers tied up some of the loose ends left behind from Prague.
The top item on the to-do list was naming the dwarf planets—the very issue that sparked the Battle of Prague in the first place. After all the trouble he'd been through, Mike Brown decided the world just wasn't ready to have the biggest known dwarf planet named after a TV warrior princess. He sought a more dignified name for Xena as well as its moon, which had been detected several months after Xena's discovery. (The moon had been temporarily nicknamed Gabrielle, after Xena's sidekick on the TV show.)
Brown's choices for the official names—Eris for the dwarf planet, Dysnomia for the moon—were something of an in-joke, and a commentary on the year's turmoil. The names were taken from Greek mythology: Eris was the goddess of strife, and Dysnomia was her daughter, the spirit of lawlessness.
Eris and Dysnomia didn't conform to the IAU's custom of naming newfound objects beyond Neptune after creation deities from mythologies other than Greek and Roman. But after all, Xena had once been considered the tenth planet, and its discovery certainly brought the IAU more than its share of strife. That was a good enough excuse for the IAU working groups newly designated to sign off jointly on the names of dwarf planets—the Working Group for Planetary System Nomenclature and the Committee on Small Body Nomenclature. So, just three weeks after the IAU created the dwarf planet definition, Xena and Gabrielle were officially christened Eris and Dysnomia.
In addition to a permanent name, Eris was given a minor-planet number, 136199—signaling that, at least for the time being, the IAU's Minor Planet Center would be keeping track of dwarf planets as well as asteroids and the smaller solar system objects beyond Neptune's orbit. Pluto, too, was given a number, 134340, following through on the half-joking suggestion that Brian Marsden made twenty-six years earlier during the onetime ninth planet's fiftieth anniversary party.
Marsden felt some satisfaction that Pluto was finally being put in its place, just as he was giving up the reins of the Minor Planet Center. In fact, his last official day as the center's director was the very day that the IAU voted to put Pluto in the dwarf-planet category. "Pluto and I were retired on the same day, you might say," Marsden said.
Some astronomers thought Pluto' s forgettable number might have been meant as a subtle kind of payback, coming from a person who put great stock in the significance of numbers and names. Gingerich recalled that Marsden was "swatted down" back in 1999 for suggesting a dual-status classification for Pluto. "He got his revenge by getting this extraordinarily ugly number for Pluto, which did not win him any brownie points," Gingerich said.
It definitely didn't win him brownie points from Annette Tombaugh-Sitze, the daughter of Pluto's late discoverer. "If it was the last thing he did, he was going to put an asteroid number on Pluto," she said. "And it was the last thing he did."
Another loose end was left hanging in Prague: What should the IAU call the dwarf planets beyond the orbit of Neptune? The idea was to give Pluto and the Plutophiles a consolation prize, to balance the icy world's demotion from the planetary ranks.
The first suggestion was to call them "plutons," but geologists nixed that idea. Then there was the resolution put forward in Prague to call them "plutonian objects"—a suggestion that narrowly went down to defeat. The IAU's
Executive Committee was left with the task of coming up with its own catchall term.
After more than a year of discussion, Marsden and other experts came up with the name "plutoids" to describe dwarf planets beyond Neptune's orbit, and "ceroids" for Ceres and any other dwarfs in the asteroid belt. Just as "asteroid" stood for starlike objects in William Herschel's day, the plutoid category would take in Pluto-like objects—ice dwarfs massive enough to crush themselves into a round shape. Ceroids, similarly, would be used for Ceres-like worlds.
The IAU's Executive Committee went along with the "plu-toid " idea but tossed out "ceroid," declaring that scientists didn't expect to find anything other than Ceres that fit the dwarf planet category. "That is news to me," Marsden said.23
There were those on both sides of the planet debate who thought bringing in the new category of plutoids was just plain unnecessary. David Jewitt, the codiscoverer of the first Kuiper Belt object beyond Pluto, said he regarded the "so-called 'plutoids'" as nothing more than big Kuiper Belt objects. The only potential benefit, he said, would be if the IAU's action closed off "the equally irrelevant and politically motivated" claims for Pluto's planethood.24
There was little chance of that. Alan Stern, who had devoted just about as much of his life to getting a mission to Pluto as Jewitt had to studying Kuiper Belt objects, agreed that the newly coined word was irrelevant—but for a completely different reason. "It sounds like 'hemorrhoid' and it sounds like 'asteroid,' and of course these objects are planets and not asteroids," he said.25
Stern wondered whether this would be the last straw for those who were fed up with IAU officials and their planet definition. "They're almost needling the planetary community to go their own way," he said.
In fact, in the summer of 2008, Stern and other planetary scientists did go their own way, organizing a "Great Planet Debate" that finally gave the solar system's underdogs their day.
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