crazyWhat I actually mean is that the definition the IAU used to define a planet is that it must a) orbit a star but not be another star or a moon; b) be round due to its gravity; and c) has cleared the neighborhood around its orbit. Since Pluto (and Eris and Ceres) fulfill the first two only, they're dwarf planets.
What have we learned? Clean your room, or else you might have your person status revoked.
(We have also learned that astronomy texts should not be read at 3a, but that's another thing.)
