Pluto: An American Planet... Aug 14, 2006 0:48:48 GMT -6
Post by Chicago Astronomer Joe on Aug 14, 2006 0:48:48 GMT -6
9th rock from sun, Pluto, under cosmic debate: Is it planet?
WASHINGTON -- Ask most schoolchildren how many planets there are in our solar system, and they'll tell you nine.
It has been that way since 1930, when a Kansas farm boy with a passion for astronomy detected Pluto, the ninth planet.
But soon, there could be only eight. Pluto faces demotion.
At a conference in Prague, Czech Republic, this month, the International Astronomical Union, which oversees such matters, is scheduled to consider a resolution that defines a planet.
Driven largely by controversy over the status of Pluto, which doesn't share several key attributes of the eight other planets, the resolution could mean Pluto's dismissal from that group.
Instead, it could be defined as simply one of thousands of small, icy objects in the less glamorous Kuiper Belt, just beyond Neptune.
An alternative would be to maintain Pluto's planetary credentials, but that potentially opens the door to dozens more planets.
"This is such a hot issue," said Stephen Maran, author of "Astronomy for Dummies."
The committee writing the resolution has worked in secret. Few people know what it will recommend. Those who know aren't talking. Egos are involved. Some say U.S. pride has emerged; Pluto is the only one of the nine discovered by an American. And there's no guarantee that the conference will accept the recommended resolution, whatever it is.
From a purely scientific perspective, downgrading Pluto is no big deal, said Daniel Green of the Smithsonian Astrophysical Observatory.
"All through history, we have changed the number of planets," Green said. "There used to be only seven planets. People thought the sun and the moon were planets and the Earth wasn't. Things change."
Virtually since its discovery, questions dogged Pluto. It wasn't like the other planets. Too small. Erratic orbit. Not enough of a rocky center.
Many scholars questioned Pluto's inclusion as a planet.
In 2000, the Hayden Planetarium at the American Museum of Natural History in New York City opened a solar system exhibit. Conspicuously missing as a planet was Pluto. The argument that had long engulfed scientific circles exploded into public view.
"My files are overfilled with hate mail from elementary students," said Neil deGrasse Tyson, the planetarium's director, who called Pluto "a vagabond of the solar system."
The arguments for keeping Pluto as a planet: It's a large, round object that orbits the sun. It has an atmosphere. It has moons.
"It just fits into the bag of being a planet better," said Mark Sykes, director of the Planetary Science Institute in Arizona. "We know enough to know it's not just an inert ball of ice."
I say, if Mercury is a planet, so stays Pluto.