Nuclear fusion is the process by which atoms combine to form larger atoms. This process releases a tremendous amount of energy, which powers the star and makes it shine.
Stars are huge spheres of hot gas and plasma. The star is constantly being pushed and held together by its own gravity, and because of these, nuclear reactions start happening in its core, constantly releasing light and heat.
Stars form in large clouds of gas and dust called molecular clouds. Molecular clouds range from 1,000 to 10 million times the mass of the Sun and can span as much as hundreds of light-years. Molecular clouds are cold which causes gas to clump, creating high-density pockets. Some of these clumps can collide with each other or collect more... See more