Experts' vote could mean demotion for Pluto

Astronomy group to offer definition in 'planet' debate

NASA's New Horizons spacecraft is streaking at 43,500 mph toward a 2015 rendezvous with Pluto. When it arrives, will it encounter the solar system's ninth planet or a demoted celestial has-been?

Nearly 3,000 astronomers and planetary scientists from around the globe will gather in Prague, Czech Republic, next week to answer that question by voting on an official definition of "planet."

For decades, schoolchildren have learned that nine planets circle the sun. But that number could drop to eight or soar to dozens, depending on the new International Astronomical Union definition.

The wording of the proposed definition has been a guarded secret since it was drafted in June.

The clandestine nature of the deliberations has heightened anticipation among scientists who have argued about Pluto's status for years. Many say it's time to resolve this thorny issue and move on.

"I have a well-developed opinion on this topic, but I'm willing to abide by whatever the IAU decides,"

University of Colorado planetary scientist Larry Esposito said.

"I'm willing to give up my position for the interest of a good, solid definition that professional astronomers can agree to,"

said Esposito, a team leader on the Cassini mission to Saturn

News leaks about the planet definition began to spout late this week, as the authors prepared to present a draft resolution to the IAU's executive committee Sunday in Prague. The IAU is the official arbiter of all issues related to astronomical nomenclature.

In a story that aired Thursday, unnamed sources told National Public Radio the proposed definition would include Pluto in a new class of small planets. A source also told the Rocky Mountain News on Thursday that a member of the seven-person definition panel said Pluto will remain a planet.

IAU Vice President Bob Williams described the reports as "interesting speculation" but would neither confirm nor deny them.