Positing New Planets Divides Astronomers

"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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On the Net:

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