Despite earlier indications that the International Astronomical Union might adopt a broad definition of a planet that includes Pluto and additional objects in the list of planets, they’ve decided that Pluto isn’t a planet after all, and neither are the other three objects they had been considering: Charon, Ceres, and 2003 UB313.
The good news, I guess, is that now that UB313 won’t be a planet, it will probably be allowed to keep its way-cool nickname: Zena. (Yes, named after the television character.)
In addition to the earlier parts of the definition (round, orbits the sun) they’ve also added a provision that planets must have cleared their orbit of other debris. Pluto and its moon, Charon, are in an orbit that crosses Neptune’s orbit, so obviously there’s other stuff there.
Then again, mighty Neptune (eight thousand times more massive) hasn’t yet hurled Pluto out of the solar system (or into the inner system) so how come it’s still considered a planet? Sounds like fuzzy thinking by Pluto-haters.
The meeting was held in Prague, but somehow I suspect the French are behind this…
Robert F. Brown says
The planet Pluto should be reinstated to full planethood immediately and given an aplogy by the IAU.