Space Telescope Science
Deep inside the Hyades star cluster, a pair of burned-out stars are yielding clues to the presence of rocky planets that may have whirled around them. Asteroid debris is 'raining' into the hot atmospheres of these white dwarfs. Asteroids should consist of the same material that form terrestrial planets, and seeing evidence of asteroids points to the possibility of Earth-sized planets in the same system.
Hubble's Cosmic Origins Spectrograph observed silicon and only low levels of carbon in the white dwarfs' atmospheres. Silicon is a major ingredient of the rocky material that constitutes Earth and other solid planets in our solar system. Astronomers used sophisticated computer models of white dwarf atmospheres to determine the abundances of various elements that can be traced to planets in the Hubble spectrograph data.