ESA Science & Technology - Artist's impression of crystallisation in white dwarf

Illustration of a white dwarf, the dead remnant of a star like our Sun, with a crystallised, solid core.

White dwarfs are the remains of medium-sized stars similar to our Sun. Once these stars have burnt all the nuclear fuel in their core, they shed their outer layers, leaving behind a hot core that starts cooling down.

Data captured by ESA's galaxy-mapping spacecraft Gaia has revealed for the first time how white dwarfs turn into solid spheres as the originally hot matter inside their core starts crystallising, becoming solid.