Falling Rocks

Watch for falling [rocks:stones] . Those are words to keep in mind when you're driving a mountain road. Or, it seems, when you're cruising past a white dwarf star. White dwarfs are small, [dense:Thick] remnants of normal stars that have [expended:intended] their fuel. Now researchers have identified rocky, asteroid-like material raining down on two white dwarfs. The [rocky:funky] material is akin to the [building:holding] blocks of planets - and its presence suggests that the two stars formed planetary systems before they expired and became white dwarfs. That's the conclusion of a study in the Monthly Notices of the Royal Astronomical Society. [Astronomers:Association] identified the silicon-rich rocky material by training the Hubble Space Telescope on the nearby Hyades star [cluster:blaster] . Finding rocky material means the stars once had the raw [ingredients:residents] to make exoplanets - although almost no known planets orbit stars inside of clusters.