First came the petitions.

Then the angry mnemonics, like “My! Very educated morons just screwed up numerous planetariums.” And, inevitably, the bumper stickers: “Honk if Pluto is still a planet.”

The United States is arguably a much noisier place, judging by the sheer volume of protests lodged in the two months since several hundred members of the International Astronomical Union voted to define what constitutes a planet, booting Pluto in the process.

Pluto was discovered by Kansas University alumnus Clyde Tombaugh in 1930 while working at Lowell Observatory near Flagstaff, Ariz.

Pluto orbits the sun and is nearly round, but the majority ruled it hadn’t cleared the celestial “neighborhood around its orbit.” The diminutive world just didn’t have the oomph to rid its orbit of interloping ice balls in the Kuiper Belt at the edge of our solar system.

“Ridiculous!” responded Richard Fienberg, the editor in chief of Sky & Telescope magazine. Scores of astronomers joined him in calling the decision process so flawed that it has rendered the definition of a planet all but meaningless.

Petition begins

“Practically, there’s a lot of people who are just going to ignore it,” said Mark Sykes, director of the Planetary Science Institute in Tucson, Ariz., and a driving force behind an online petition that has said as much.

Gonzalo Tancredi, a planetary astronomer at the University of Uruguay in Montevideo, disagreed, defending the “good agreement” as one based on the best available science. “Maybe it’s not a perfect one, but it’s the one that reflects better the present knowledge about the solar system,” he said.

Far beyond the astronomical dispute, though, the demotion of Pluto spurred an upwelling of public sentiment in editorials, petitions and blogs, and spawned a Web-based cottage industry devoted to defending a distant orb one-fifth the mass of the moon. Amid the frenzy, schoolchildren repeatedly lodged the same tearful query: “What happened to Pluto?” As educators are discovering, though, the question may have opened the door to teaching the public about science – and a dirty iceball that clearly holds some sentimental value.

‘It’s an oddball’

“It’s the littlest planet, it’s way out there; it’s an oddball,” said Mark Bullock, a planetary scientist at the Southwest Research Institute in Boulder, Colo. In short, Pluto embodies the underdog. And, of course, it shares a name with the sidekick of a beloved Disney icon.

But what, exactly, defines it?

A working definition of “planet” – essentially, a roundish object that orbits a star – would have expanded our solar system’s planetary clique to 12.

The effort had been necessitated by newly discovered orbs such as the Pluto-plus-sized Xena (since renamed after Eris, goddess of discord). But on the last day of a turbulent meeting in Prague, Czech Republic, the International Astronomical Union’s general assembly did an about-face and dropped the planetary tally to eight, relegating Pluto, Eris and an asteroid named Ceres to “dwarf planets.” Charon, another would-be planet and Pluto’s main moon, didn’t even make that cut.

Less than a week later, Sykes’ petition decrying the decision had been signed by 305 scientists and stargazers from 34 states and a dozen other countries. Richard Wagener, an atmospheric physicist at Brookhaven National Laboratory in New York, said he signed out of dissatisfaction with the fuzzy definition rather than out of any unhappiness that Pluto was excluded from the club.

Requirements troubling

Especially troubling for Wagener and many other petitioners is the “vague” new requirement for a planet’s orbital path to be cleared of debris.

Technically, even Jupiter hasn’t managed that feat, as it is both led and followed in its orbit by a legion of asteroids, he said. And if Neptune’s neighborhood was truly debris free, others point out, periodically trespassing Pluto would have been swept away long ago.

If the back-and-forth had been limited to, say, the Pluto-like body 2005FY9, perhaps few outside of academia would care. But onlookers say Pluto’s demise has revealed a large reservoir of cultural attachment to the littlest planet.

Almost overnight, petitions invoking everything from outraged Disney fans to the presumed immutability of “four seasons, four Beatles, three Stooges and nine planets” popped up online, with sentimentalists adding personal notes (“Get your grubby hands off of Pluto!”) or hawking T-shirts with phrases like “Save the Planet” above a lonely-looking orange-colored blob.

Science isn’t popularity

In an election, Pluto would have reclaimed its lost status in a landslide, judging by the more than 10,000 votes on one Web site, plutopetition.com, or the overwhelming attachment cited by the Discovery Channel Store’s (admittedly non-scientific) poll of schoolchildren.

But science, as scientists are fond of saying, is not a popularity contest.

Others beg to differ, and Sykes hopes a soon-to-be-launched Web site inviting researchers to provide input and work on consensus papers will reinvigorate the scientific process.

Whatever it is now, Pluto is unlikely to go quietly into the night. If nothing else, Sykes and others muse, the dialogue can only help educators tap into a teachable moment that has seized the attention of so many – or at least given them yet another reason to honk.