The energy released by a body falling in a gravitational field. It is a form of potential energy. When an interstellar gas cloud collapses to form a protostar, the gravitational energy released heats its interior to the point at which nuclear reactions can commence. Gravitational energy also supplies the energies for stars condensing into white dwarfs, and plays a major role in the processes operating inside supernovae. Large amounts of gravitational energy are released by material falling into the accretion disks around black holes, and may provide the power source for quasars, Seyfert galaxies, and other active galactic nuclei.