New dwarf planet discovered?
A planet is a body that
- Is in orbit around the Sun.
- Has sufficient mass to be close to spherical.
- Has cleared its orbit (this last definition has already been footnoted into oblivion, because several of the classical planets, including earth, have managed to accumulate a good number of asteroids in their trojan points.)
A dwarf planet, on the other hand, has to fulfill definition #1 and #2. Okay, fine and good, so we've got this spiffy little definition that keeps hoi polloi away from the exclusive club that are all of the planets (except Ceres) that were discovered before that pesky American came along and spoiled the game.
But if you found a planet that had a large number of asteroids sharing its orbit that which may have been there since the time of planetary accretion, you'd think that it hadn't actually cleared its orbit, right?
I'm sure that yet another footnote1,2 will be cranked out pretty quickly, but for now, I'd like to say hello to the dwarf planet Neptune; a dwarf gas giant that's only five times the diameter of earth.
(via James Nicoll)
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I suspect it will be piggybacked under relative masses, but some of the objects that have been discovered are in the 40km diameter range, which is big enough to cause an extinction event if one went astray and rammed into our planet. It seems somewhat unsporting to call an extinction-event sized object irrelevant debris.
Or, alternatively, they could just junk the silly "dwarf planet" classification and welcome Ceres, Pluto/Persephone, and the small collection of planet-sized-and-shaped Kuiper Belt Objects that have already been discovered back into the planetary treehouse.