Final Definition
The final definition, as passed on 24 August 2006 under the Resolution 5A of the 26th General Assembly is:
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The IAU...resolves that planets and other bodies, except satellites, in the Solar System be defined into three distinct categories in the following way: (1) A planet is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighbourhood around its orbit. (2) A "dwarf planet" is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, (c) has not cleared the neighbourhood around its orbit, and (d) is not a satellite. (3) All other objects, except satellites, orbiting the Sun shall be referred to collectively as "Small Solar System Bodies". Footnotes: The eight planets are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. |
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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.
Footnote: An IAU process will be established to select a name for this category. |
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The IAU also resolved that "planets and dwarf planets are two distinct classes of objects", meaning that dwarf planets, despite their name, would not be considered planets.
Read more about this topic: IAU Definition Of Planet
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