astroengine send this interesting excerpt from Discovery: "The Hubble Space Telescope has discovered rocky remains of planetary material 'polluting' the atmospheres of two white dwarfs — a sign that these stars likely have (or had) planetary systems and that asteroids are currently being shredded by extreme tidal forces. Although white dwarfs with polluted atmospheres have been observed before, this is the first time evidence of planetary systems have been discovered in stars belonging to a relatively young cluster of stars. 'We have identified chemical evidence for the building blocks of rocky planets,' said Jay Farihi of the University of Cambridge in a Hubble news release. 'When these stars were born, they built planets, and there's a good chance that they currently retain some of them. The signs of rocky debris we are seeing are evidence of this — it is at least as rocky as the most primitive terrestrial bodies in our Solar System.'"