For the same reason that most astronomical phenomena happen; GRAVITY! The downward pull of gravity causes everything to fall down, and at high enough pressure and heat, rock itself becomes a fluid.
In fact, most of the planets are not exactly spherical; the Earth, for example, bulges out a little around the equator, caused by the centrifugal force of the spinning Earth. Jupiter spins in just 10 hours, and is noticeably bulgy at the equator. Venus, which rotates very slowly, may be the most nearly spherical planet.
While some stars (like the Sun) are very nearly spherical, others are not. The star Altair in the constellation Aquila rotates very rapidly, causing its equator to bulge outward significantly. Altair looks a bit like a beach ball being sat upon. The reason the Sun and other slowly rotating stars are spherical is gravity pulling inward, and the fact that they are made of gas, not solid material. Any gas in the Sun that was further from the center than gas around it would be pulled back down--there's nothing solid beneath it to support it against gravity's downward pull.
It's pretty much spherical. but because it is spinning so fast, the equatorial regions are pushed up just a little. The shape is called "oblate spheroid" which is Latin for "vaguely egg-shaped sphere".
Because of its gravitational pull to its centre.
Round is the definition of "sphere".
PLANET
moon
It sounds like a planet to me.
Yes As in spherical? Pretty much.
It's spherical and it orbits the sun.
The sun's cure is spherical.
Spherical
No. The sun is a circle not square. It is round, what you can call spherical.
The sun is a sphere and the moon is a sphere.
PLANET
The Sun is spherical (round), with a diameter of about 1.4 million km.
No but they are of a spherical shape
moon
It is an adjective, so you could say: "The Sun is a bright spherical object in the sky during the day".
The Moon of the Earth has a spherical shape regardless to its position compared to the Sun.
Stars are spherical just like our Sun
Yes, all spherical planetary bodies have an axis