White dwarfs are slowly cooling remnants of stars that once resembled our Sun.

The longer version

When a Sun-like star exhausts its fuel, it sheds its outer layers and leaves behind a compact core supported by electron degeneracy pressure rather than by fusion. No new energy is generated, so the remnant simply radiates its stored heat into space. The material inside is extraordinarily dense.

Over immense spans it fades from white through yellow and red, eventually becoming a cold dark cinder. Before fading it is extremely hot and small, roughly the size of Earth. Many such objects are found orbiting other stars, and they represent a common endpoint of stellar evolution. Their faint glow makes them hard to detect.

Where this entry sits

The night sky looks calm, yet almost everything up there is moving, burning, or slowly changing. These facts cover planets, stars, the Moon, gravity, black holes, comets, and the story of how people began exploring beyond Earth. The full list sits on the Space and Sky page, where every entry is listed in order.