Dead stars shed new light on planet birth

January 6th, 2009 - 5:40 pm ICT by ANI  

Washington, Jan 6 (ANI): Observations made with NASAs Spitzer Space Telescope has revealed six dead white dwarf stars littered with the remains of shredded asteroids, which may shed new light on the birth of planets.

So far, the results suggest that the same materials that make up the Earth and our solar systems other rocky bodies could be common in the universe.

If you ground up our asteroids and rocky planets, you would get the same type of dust we are seeing in these star systems, said Michael Jura of the University of California, Los Angeles.

This tells us that the stars have asteroids like ours, and therefore could also have rocky planets, he added.

Asteroids and planets form out of dusty material that swirls around young stars. The dust sticks together, forming clumps and eventually full-grown planets. Asteroids are the leftover debris.

When a star like our sun nears the end of its life, it puffs up into a red giant that consumes its innermost planets, while jostling the orbits of remaining asteroids and outer planets.

As the star continues to die, it blows off its outer layers and shrinks down into a skeleton of its former self - a white dwarf.

Sometimes, a jostled asteroid wanders too close to a white dwarf and meets its demise - the gravity of the white dwarf shreds the asteroid to pieces.

Spitzer observed shredded asteroid pieces around white dwarfs with its infrared spectrograph, an instrument that breaks light apart into a rainbow of wavelengths, revealing imprints of chemicals.

Previously, Spitzer analyzed the asteroid dust around two so-called polluted white dwarfs; the new observations bring the total to eight.

Now, weve got a bigger sample of these polluted white dwarfs, so we know these types of events are not extremely rare, said Jura.

In all eight systems observed, Spitzer found that the dust contains a glassy silicate mineral similar to olivine and commonly found on Earth.

This is one clue that the rocky material around these stars has evolved very much like our own, said Jura.

The Spitzer data also suggest there is no carbon in the rocky debris - again like the asteroids and rocky planets in our solar system, which have relatively little carbon.

By continuing to use spectrographs to analyze the visible light from this fine dust, astronomers will be able to see exquisite details, including information about what elements are present and in what abundance.

This will reveal much more about how other star systems sort and process their planetary materials.

Its as if the white dwarfs separate the dust apart for us, said Jura. (ANI)

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