Positing New Planets Divides Astronomers

Michael Brown, an astronomer at the California Institute of Technology in Pasadena, Calif., poses on the campus Friday, Aug. 18, 2006. Few planet hunters stand to gain as much as Brown if our solar system balloons to 12 planets under a proposed new definition. He's spotted more than a dozen objects that might qualify as planets. So why is he upset? "When I was a kid, planets were special," he said. "This definition takes the magic out of the solar system." It was Brown's discovery of an icy rock bigger than Pluto that helped lead astronomers to rethink their definition of what a planet is. But Brown doesn't think his discovery, or even Pluto, which was spotted in 1930, should qualify as true planets. (Photo/Damian Dovarganes) (Damian Dovarganes - AP)

"It's impossible to draw the line between the new dwarf planets and large asteroids," said Mark Bailey, director of Britain's Armagh Observatory.

And forget the term "pluton" _ it's already history.

Under pressure from a growing faction of astronomers, the planet definers have been tossing around other options: plutoids, plutonids, plutonoids, plutians, or Tombaugh objects or planets in honor of Clyde Tombaugh, the American who discovered Pluto in 1930.

Among the scientists who torpedoed "pluton" were geologists, who pointed out _ somewhat embarrassingly to astronomers _ that it's already a prominent term in volcano science for deep igneous rock formations.

"What were they thinking? The reaction in the geologic community was rolling of eyes," said Allen F. Glazner, a geologist at the University of North Carolina. "It would be like botanists trying to distinguish between trees and shrubs and coming up with the term 'animal.'"

Harvard's Owen Gingerich, who chairs the planet definition panel, conceded: "We perhaps stumbled."

After the panel got dozens of objecting e-mails, "we backed off," he added.

Suddenly, the future looks dim for much-maligned Pluto, which is smaller than Earth's moon.

Its underdog status has inspired scores of tributes, including one by folk singer Christine Lavin that laments: "I guess if Pluto showed up at a planet convention, the bouncer at the door might have to ban it."

"Some say, 'No, Pluto is a nice planet'" and should remain one, Watanabe said.

"It's an important object that has played an important role," he said. "But this is a natural way to draw a line."

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