Pluto demotion seems imminent

The proposal that Ceres, Charon and 2003 UB313 be declared planets under a definition which would also have opened the doors to forty-one other candidates has been defeated by the International Astronomical Union General Assembly.

Thursday (very early; the meeting is in Prague) the Assembly will decide on another option. The most likely outcome is to demote Pluto- easily the smallest current planet, which follows an eccentric orbit and is basically just a big comet- and go with an eight planet solar system. Obviously, that would take 2003 UB313- a similar body to Pluto- out of the running, too.

Pluto and 2003 UB313 are the largest of as many as a hundred similar, icy objects on the fringes of the solar system, in what is known as the Kuiper Belt.

This picture will give you a good idea of the relative sizes of the objects in question.