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Celestial sprawl: 12 planets?

by editor2
August 18th, 2006

The number of planets in our solar system would jump from nine to 12, and puny, belittled Pluto would remain among them under a proposal by an international body of astronomers meeting in Prague.The definition of planet being proposed today by the International Astronomical Union, if approved, would rewrite the textbooks and discard the simple nine-planet solar system that schoolchildren have memorized for decades.

Under the proposed definition, our solar system would gain three planets immediately. A dozen or more additional planets could be added later, if they qualify.

Supporters of the plan say a burst of discovery over the past decade has forced astronomers to face the fact that our solar system is a far more complicated, messy place than we once thought.

Critics say the new system would be confusing and that the proposed 12-planet cutoff is arbitrary. One prominent planetary scientist labeled the proposal “insane.”

Nearly 2,500 IAU members in Prague are expected to vote on the proposal Aug. 24. The IAU is the official arbiter of issues related to astronomical nomenclature.

“The solar system is different than we thought it was in the 20th century. There are just planets all over the place,” said Boulder planetary scientist Alan Stern.

“Life’s complicated. Get over it,” said Stern, a supporter of the proposed definition and the lead scientist on NASA’s New Horizons mission to Pluto and the Kuiper Belt, a band of icy, sun-orbiting bodies beyond Neptune.

Scientists have argued about Pluto’s status for years. Some say it’s nothing more than a large Kuiper Belt Object and should be tossed from the family of planets.

The need for a bulletproof definition of a planet gained urgency last year after the discovery of a Kuiper Belt Object designated 2003 UB313 and nicknamed Xena.

Hubble Space Telescope photos show that Xena has a diameter of 1,490 miles, plus or minus 60 miles. Pluto is 1,422 miles across.

Source :,1299,DRMN_15_4920464,00.html

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