The Sun
The Sun is the star at the center of the Solar System. It is by far the most important source of energy for life on Earth. Its mass is about 330,000 times that of Earth. It formed approximately 4.6 billion 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.
