What happens when a red giant star becomes a white dwarf?
When a low- to medium-mass star (a red giant) exhausts the nuclear fuel in its core, it collapses under the gravitational pressure of its own weight into an extremely compact, dense star known as a white dwarf. As a more massive star (6 to 8 solar masses) collapses to a white dwarf, it blows off more than half of its outer layer into space as a planetary nebula–gas and dust that may provide building material for planets in newly forming solar systems. Although dimmer than the original star, a white dwarf will continue radiating light for several billion years from thermal energy (heat energy) trapped in its interior.
