The book I read was called “100 Things You Should Know About Space.” In the text it says,”stars begin to die when they run out of gas to make energy. The middle of the star begins to shrink but the outer part expands, making the star much larger.” When an ordinary star dies it expands then theres a chain. When the ordinary star dies it becomes a red giant star, then it splits. Part of it turns into a supernova explosion, then it turns into a black hole. The other part the star becomes smaller then turns into a white dwarf star, then into a black dwarf star.