Question: What are the stars made of?

Nawapat Kaweeyanun answered on 15 Nov 2019:

Stars are a huge ball of gas which is mostly hydrogen. Hydrogen is the smallest/lightest atom in the universe. A huge ball of hydrogen will crunch inward because of the massive gravity, pressing the hydrogen atoms together hard enough that they fuse into a heaver atom called helium. This “fusion” process releases an energy growing outward opposing gravity, preventing the gas ball from collapsing further so the star has a stable shape. Hydrogen fusion will continue until the very last hydrogen atom is used, and that’s when the star will die. How a star dies is a story for another day though …