Astronomers have identified what could be the coldest, faintest white dwarf star ever seen, so cold that its carbon has crystallized — not unlike a diamond. The work was published in the Astrophysical Journal this week.

White dwarfs are end-state stars that have collapsed to form hot, extremely dense, Earth-sized objects composed mostly of carbon and oxygen. While they can be as massive as the sun, white dwarfs are so dense they’re only about the size of Earth.

The 11-billion-year-old, uncommonly cool white dwarf couldn’t be more than 2,700 degrees Celsius; the center of the sun is 5,000 times hotter. Astronomers believe such a cool ancient stellar remnant would be largely crystallized carbon — which makes it, in effect, a diamond.

Read the full post at IFLS.