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Article: What's a planet? New riddles beyond the solar system.(Cover story)
- Article from:
- Science News
- Article date:
- December 2, 2006
- Author:
CopyrightCOPYRIGHT 2006 Science Service, Inc. This material is published under license from the publisher through the Gale Group, Farmington Hills, Michigan. All inquiries regarding rights should be directed to the Gale Group. (Hide copyright information)
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"I found a planet!" Caltech astronomer Mike Brown remembers exclaiming during a phone call he made to his wife early in 2005. Little did he know that he'd have to eat his words just 18 months later. Brown had found an outer-solar system object heavier than Pluto, so it seemed reasonable to call the object the tenth planet.
But last August, the International Astronomical Union approved the first formal definition of a planet since the Greeks coined the term some 2,000 years ago. Pluto, got the boot, and Brown's proposed tenth planet, a body now called Eris, was disqualified.
The group of astronomers decided to call Pluto and Eris "dwarf planets'--a class ...