Astronomers have identified what might be one of the strangest stars in our galaxy: an incredibly cold, ancient and faint white dwarf that has crystallized into a diamond the size of Earth.

“It’s a really remarkable object,” said Professor David Kaplan of the University of Wisconsin-Milwaukee in a press release. “These things should be out there, but because they are so dim they are very hard to find.”

White dwarfs are stars at the end of their life span when the fusion reaction that has pumped out heat and energy during has all but stopped, leaving the remaining carbon and oxygen to compact into an incredibly dense and cold state.

In the case of this recently discovered white dwarf, astronomers believe that it has cooled and crystallized all the way to diamond, estimating that the once-fiery star is 11 billion years old – making it the same age as the Milky Way.

Stars like this aren’t rare (around 97 per cent of stars are thought to turn into white dwarfs and we’ve even discovered planets made of diamond) but they are incredibly difficult to find – simply because their light is too faint to make its way through the cosmos to telescopes on Earth.

Thankfully, this particular white dwarf had a partner that gave away its presence to astronomers on Earth: a companion pulsar star dubbed PSR J2222-0137…. see more