Stars Stars Are Self-Luminous Gaseous Spheres. How they do this is the subject of question number two. Being self-luminous makes stars different from planets, moons, asteroids, and comets, all of which shine by reflecting sunlight.
Stars are different in other ways as well.
They possess far more mass, have different compositions, are hotter, and most are bigger than planetary objects. It is a self-luminous, gaseous sphere. It has no solid surface. Its size is about 100 times that of the Earth and its mass is roughly 300,000 times that of the Earth. The Sun is composed mainly of hydrogen and some helium.