White Dwarf

When an average star like our Sun runs out of fuel, nuclear fusion halts and the stellar equilibrium is disrupted. The star begins to collapse unto itself under its own weight, before the whole process is halted once again by the formation of a white dwarf. The collapsing material bounces back out and is ejected into space, creating a planetary nebula and slowly exposes the white dwarf at its center.

A white dwarf is made of electron-generate matter and is prevented from further collapse due to the pressure from fast-moving electrons on its surface. These objects are roughly the size of Earth and have a mass limit of 1.4 solar masses—any more mass and the electrons will not be able to sustain the pressure, causing them to go supernova.