The Planetary Society Blog
By Emily Lakdawalla
Society Note: It's Official: Pluto is NOT a Planet
Aug. 24, 2006 | 10:05 EDT | 14:05 UTC
by Jennifer Vaughn
Today the International Astronomical Union (IAU) decided that Pluto will not be keeping its "planet" title. Instead, Pluto, as well as asteroid Ceres and the larger-than-Pluto 2003 UB313 are now classified as "dwarf planets." According to the IAU, a "planet" is rounded by self gravity and has cleared its orbital zone, a "dwarf planet" is rounded by self gravity but has NOT cleared its orbital zone, and "small solar system bodies" are not rounded by self gravity. Because Pluto is part of the Kuiper belt and Ceres is part of the asteroid belt, neither has "cleared" its neighborhood, so they don't qualify as planets.
The IAU did give a "nod" to the public interest in Pluto by agreeing that it is a prototype of a new -- still unmaned -- class of Trans-Neptunian object.
The Planetary Society issued a statement today saying, planet or not, these bodies are still interesting and worth exploring. We're also asking for opinions from the general public to see what kind of response this decision is generating.
Amir Alexander has written a good background story on the planet definition debate, and A.J.S. Rayl posted a news story about the IAU's decision. Also, for Planetary Society members, Lou Friedman started a discussion in the forum.
I imagine this will just be the beginning of a much larger discussion. Stay tuned...
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