[BRIEF NOTE] Not 12 planets, but 8

[rfmcdonald]

From the BBC:

Amid dramatic scenes which saw astronomers waving yellow ballot papers in the air, the IAU meeting voted through new definition criteria.

They agreed that to qualify as a planet, a celestial body must be in orbit around a star while not itself being a star. It also must be large enough in mass "for its self-gravity to overcome rigid body forces so that it assumes a... nearly round shape, and has cleared the neighbourhood around its orbit."

Pluto was automatically disqualified because its oblong orbit overlaps with Neptune's.

It will now join a new category of "dwarf planets".

Pluto's status has been contested for many years as it is further away and considerably smaller than the eight other "traditional" planets in our Solar System.

Its orbit around the Sun is also highly inclined to the plane of those big planets.

In addition, since the early 1990s, astronomers have found several objects of comparable size to Pluto in an outer region of the Solar System called the Kuiper Belt.

I had such high hopes for Ceres. Alas. At least it--and Pluto, for that matter--are now dwarf planets.