out of hydrogen, the outer layers start to expand and the star becomes a red giant, dozens to hundreds of times its original size. The core shrinks in size once there is no energy production to maintain it against gravity. Then nuclear fusion of hydrogen starts in a shell surrounding the core and, when the temperature of the core is high enough, helium fusion into carbon is achieved. In its last evolutionary stages, the star ejects its outer layers and only a degenerate core is left.

White dwarfs do