Sun

Sun

The Sun is a G-type main-sequence star (G2V) based on its spectral class , and is informally referred to as a yellow dwarf. It formed approximately 4.6 billion [a] [9] [18] years ago from the gravitational collapse of matter within a region of a large molecular cloud . Most of this matter gathered in the center, whereas the rest flattened into an orbiting disk that became the Solar System . The central mass became so hot and dense that it eventually initiated nuclear fusion in its core . It is thought that almost all stars form by this process .