Pluto Demoted!
Pluto the planet, R.I.P. — 1930 – 2006
The International Astronomical Union giveth, and the International Astronomical Union taketh away. The IAU stripped Pluto of its planetary status this week after setting some solid guidelines as to what constitutes a planet — guidelines that exclude Pluto.
Here are the official resolutions from IAU's news posting:
RESOLUTION 5A
The IAU therefore resolves that "planets" and other bodies in our Solar System be defined into three distinct categories in the following way:
- A "planet" is a celestial body that
- is in orbit around the Sun,
- has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and
- has cleared the neighbourhood around its orbit.
- A "dwarf planet" is a celestial body that
- is in orbit around the Sun,
- has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape,
- has not cleared the neighbourhood around its orbit, and
- is not a satellite.
- All other objects except satellites orbiting the Sun shall be referred to collectively as "Small Solar-System Bodies".
The resolutions continue on to set Pluto's status as a non-planet:
RESOLUTION 6A
The IAU further resolves:Pluto is a "dwarf planet" by the above definition and is recognized as the prototype of a new category of trans-Neptunian objects.
Well, Pluto, it was fun while it lasted.
I wonder if Venetia Phair (Venetia Burney) needs to give her five pounds back now. (As a note, Disney's Pluto coincidentally came out the same year that Pluto was named.)
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