Pluto: The votes are in

Harvard-Smithsonian Center for Astrophysics
September 22, 2014
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Harvard-Smithsonian Center for Astrophysics

On Sept. 18, 2014, audience members who attended the Observatory Night talk "What is a Planet?" voted to choose one of three possible definitions for a planet. The result: a planet is "the smallest spherical lump of matter than formed around stars or stellar remnants," and Pluto IS a planet! (Photo courtesy Harvard-Smithsonian Center for Astrophysics)