In this illustration, an asteroid is literally falling apart. This type of impactor can result in a chain of smaller craters rather than one large crater.
This artist's concept illustrates one such dead star, or "white dwarf," surrounded by the bits and pieces of a disintegrating asteroid. These observations help astronomers better understand what rocky planets are made of around other stars.
Asteroids are leftover scraps of planetary material. They form early in a star's history when planets are forming out of collisions between rocky bodies. When a star like our sun dies, shrinking down to a skeleton of its former self called a white dwarf, its asteroids get jostled about. If one of these asteroids gets too close to the white dwarf, the white dwarf's gravity will chew up the asteroid, leaving a cloud of dust.
The Spitzer Space Telescope's infrared detectors can see these dusty clouds and their various constituents. So far, the telescope has identified silicate minerals in the clouds polluting eight white dwarfs. Because silicates are common in our Earth's crust, the results suggest that planets similar to ours might be common around other stars.
Last Update: 24 Mar 2011 (AMB)