Why is Pluto not a planet anymore?

  • Thread starter Thread starter EMILY
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EMILY

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This really makes me mad. Who decided this nonsense and who made him the boss of the planets?
 
Not just one person - it was decided by a vote of the International Astronomical Union in August 2006 (2412 astronomers were at that particular General Assembly).

A planet was defined as an object that:
1. Orbits the sun (and not another planet)
2. Is spherical due to its mass and gravity
3. Has cleared its orbital path of debris.

Pluto meets #1 and #2, but not #3.
Pluto orbits within the Kuiper Belt, a huge region full of debris.
So along with Makemake, Eris, and Haumea (and possibly dozens of other objects) is called a "dwarf planet".
Dwarf planets beyond Neptune are also called "plutoids".
And the same definition promoted Ceres (in the asteroid belt) to "dwarf planet" as well.
 
Yeah, I was just getting used to all the names and could finally say Uranus without giggling.
 
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