Dead Stars Harbor Asteroids

This artist's concept illustrates a dead star, or white dwarf, surrounded by the bits and pieces of a disintegrating asteroid. The scene suggests the raw material for planets like Earth are common. (Image credit: NASA/JPL-Caltech)

LONG BEACH,Calif. ? New observations of chewed-up asteroids around old dead ?stars calledwhite dwarfs bolster the idea that the Earth and other rocky planets in oursolar system are far from alone in the universe.

Astronomersused NASA's SpitzerSpace Telescope to peer at six such white dwarf stars and found thesignature of asteroid debris circling the stars. An analysis of the lightcoming from the systems show the rings are made of some of the same materialsas rocky bodies in our own solar system.

"Itstrengthens suspicions that Earth-like planets are common," said MichaelJura of UCLA here Monday at the 213th meeting of the American AstronomicalSociety.

Asteroidsand planets form from the dust and gas that swirls around young stars. As thedust sticks together, it forms clumps that eventually become full-fledgedplanets, according to the leading theory. Asteroids are the "leftoverbuilding blocks that didn?t get incorporated in the planets," Jura said.

Occasionally,a perturbed asteroid will wander too close to the white dwarf, whose gravityrips the rocky body to shreds, forming debris. (This is similar to whathappened to Comet Shoemaker-Levy 9 when it was tornapart by Jupiter's gravity before impacting the planet in 1994.)

"Nowwe?ve got a bigger sample of these polluted white dwarfs, so we know thesetypes of events are not extremely rare," Jura said, noting that they about1 percent of white dwarfs are estimated to have these signatures.

"Thisis one clue that the rocky material around these stars has evolved very muchlike our own," Jura said.

The spectra(light broken into its components) of the asteroid debris also showed no carbonsignature ? what Jura calls a "carbon desert" ? another similarity tothe asteroids and rocky planets in our own solar system, which have relativelylittle carbon.

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Andrea Thompson is an associate editor at Scientific American, where she covers sustainability, energy and the environment. Prior to that, she was a senior writer covering climate science at Climate Central and a reporter and editor at Live Science, where she primarily covered Earth science and the environment. She holds a graduate degree in science health and environmental reporting from New York University, as well as a bachelor of science and and masters of science in atmospheric chemistry from the Georgia Institute of Technology.