[extropy-chat] New IAU definitions for planets and dwarf planets

[Alfio Puglisi]

>From http://www.iau2006.org/mirror/www.iau.org/iau0603/index.html

(1) A "planet"1 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) shape2 , (c) has not cleared the neighbourhood around its
orbit, and (d) is not a satellite.


If I understand correctly:

1) there are eight planets: Mercury, Venus, Earth, Mars, Jupiter,
Saturn, Uranus and Neptune
2) there are, for now, four dwarf planets: Ceres, Pluto, Charon and Xena.

Point (d) of the second statement is to avoid that all round moons
become dwarf planets.

Status of the biggest asteroids in the outer solar system (Quaoar,
2003 EL61, 2005 FY9, Sedna and many others) to be decided. Most of
them can be considered dwarf planets.

Alfio