The solar nebula theory is a widely accepted model for the formation of the Solar System. According to this theory, the Solar System formed from a rotating disk of gas and dust called the solar nebula. As the nebula collapsed under its own gravity, it flattened into a disk shape with the Sun forming at the center. Over time, the material in the solar nebula began to clump together to form planetesimals, which eventually coalesced to form the planets, moons, and other objects in the Solar System. The solar nebula theory helps to explain the composition, structure, and characteristics of the planets and other celestial bodies in the Solar System.