And water is just one of the mysteries about this system. Scientists don’t know for sure if GD 61 had, or has, planets, but they say a giant planet most likely pushed the asteroid in toward its doom near the white dwarf. And they can’t tell how big the asteroid was that deposited this detritus on the star—based on the amount of pollution in the white dwarf’s atmosphere, the researchers estimate the asteroid was at least 90 kilometers wide, but could have been much larger. That would put it in a class of objects known as minor planets, similar to Ceres and Vesta in our own solar system, which are also thought to contain large amounts of water stored under their rocky crusts in the form of buried ice.
The planetary graveyard around GD 61 may be a vision of what’s to come for the sun and its planets in the far future. The sun, like 98 percent of the stars in the galaxy, will also become a white dwarf eventually, and its ferocious gravity will probably strip Earth and other inner planets of their heavy elements. It’s not a pretty picture, but, as Farihi says, “we have five billion years to work on that.”