Huge clouds of dust and gas collapse under gravitational forces, forming protostars. These young stars undergo further collapse, forming main sequence stars.
Stars expand as they grow old.
As the core runs out of hydrogen and then helium, the core contacts and the outer layers expand, cool, and become less bright. It will eventually collapse and explode. As stated in our privacy policy , we fully respect your privacy and will not use your e-mail address for any purpose other than the newsletter subscription.