Dead stars surrounded by fields of dust from pulverized asteroids may seem to make up a forbidding and ominous picture, but researchers who studied six such star systems say the dust should actually fuel the optimism of people who dream of finding extraterrestrial life. The dust’s composition suggests that rocky planets like our own Earth may be common in the universe, researchers say, which ups the chance that life as we know it has evolved somewhere out there.

The dust in question was found surrounding small, dense white dwarf stars. As stars like our own sun near the end of their life, they puff up into red giants that consume their innermost planets and jostle the orbits of outer planets and asteroids. Eventually the stars blow off their outer layers and shrink down into white dwarfs. Occasionally, a perturbed asteroid will wander too close to the white dwarf, whose gravity rips the rocky body to shreds, forming debris [SPACE.com].

That debris is what researchers studied with NASA’s Spitzer Space Telescope. By viewing the stars through a spectrograph, which separates out light from different wavelengths, the scientists were able to observe the telltale signatures of certain chemicals in the light. Since that starlight is passing through the film of the asteroid debris, the light picked up signatures of the asteroids’ composition, too [Wired News]. Lead researcher Michael Jura announced at the ongoing American Astronomical Society meeting that the composition of the asteroid dust was remarkably similar to that of the rocky planets in our solar system.

“If you ground up our asteroids and rocky planets, you would get the same type of dust we are seeing in these star systems,” Jura said. For example, the systems all contain glassy silicates similar to a mineral called olivine that is common in Earth’s crust. The systems are also low in carbon, which is similarly lacking in the geologic profile of our sun’s rocky planets [National Geographic News].

Asteroids can convey information about planets because both types of bodies are made of the same raw material: The dust that circles around young stars and eventually clumps together into planets and asteroids. “Asteroids are leftover building blocks that didn’t get incorporated into the planets,” Jura said. “What we have now is a tool to measure the bulk composition of planets” [Wired News]. Researchers had previously found two white dwarfs surrounded by dust with a similar composition, but the discovery of six more suggests that the arrangement may be common. “What was once kind of a freak is now a systematic pattern,” Jura said [New Scientist].

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Image: NASA / JPL-Caltech

January 7th, 2009 7:09 AM Tags: asteroids, exoplanets, extraterrestrial life, NASA, stars, telescopes
by Eliza Strickland in Space | 3 comments | RSS feed | Trackback >