Why are planets, including sun/moon and others, round?
Because a round shape is the most naturally stable shape there is, due to the spreading of mass around a common center. The earth is 3% out of round, due to it’s spinning force. Several of the gas planets are even MORE out of round, due to their high rotational rates as well. So they are not perfect spheres. Smaller bodies may have formed or clumped out of debris, and don’t have enough gravitational energy to slip into a round shape. There’s some factor of size which will allow a body to go to a round shape. Several of the dwarf planets, like Pluto and the 3 newly discovered ones, are about 500 miles in diameter or more, but much lower, and they could take on the appearance of being a lumpy rock. So size has a bearing on whether or not an object will become round or stay as a lumpy mass of matter.
