Smaller objects can be square shaped, or any other shape. The asteroid Eros looks like a ballet slipper. However, when an object gets big enough it's gravity becomes stronger than the bonds that hold it's molecules together, and the object conforms to a round shape. Somewhere around five hundred to a thousand kilometers in diameter seems to be the critical size [depending on density, and structural strength of the material].
Originally posted by ashok_bitsboymech
@Jan 29 2005, 05:35 PM
why can't all the planets be in square shape.why no heavernly boidies are not in a square shape.
Concerning the Sun, gravity keeps it round. There are about six hundred thousand kilometers of gas pressing in on the reaction area, keeping the sun from getting deformed by the reaction's variation in intensity. It is also the case the the reaction intensity probably doesn't vary much over time, and so the core of the Sun is at pretty close to a short term equilibrium.
Forming opinions as we speak