• A star is a massive, bright, sphere of very hot gas called plasma which is held together by its own gravity.
• Stars radiate energy created from nuclear fusion, which is a process that takes place in a star's core and involves hydrogen fusing (burning) to make helium.
• As a star is near the end of its life, it begins to change the helium into heavier chemical elements, such carbon and oxygen, and the star will begin to change color, density, mass and size.