www.baltimoresun.com/health/maryland-health/la-sci-sn-hubble-debris-polluting-dying-stars-20130509,0,582357.story

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Hubble spots Earth-like debris polluting dying stars

By Deborah Netburn

This post has been corrected, as indicated below.

7:48 PM EDT, May 9, 2013

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In the Hyades star cluster, located 150 light years from Earth, scientists discovered two white dwarf stars that have Earth-like materials in their atmosphere.

A white dwarf star is a dim remnant of a star that was once like our sun. Usually its atmosphere would contain only light elements like hydrogen and helium because heavier elements like silicon and carbon would sink quickly into its core.

But it is exactly silicon, and just a bit of carbon -- the same stuff that rocky planets and asteroids are made of -- that scientists discovered in the atmosphere of the two white dwarf stars.

Photos: Amazing images from space

"That means those elements are not only there, but are continually being replenished," said Jay Farihi, lead author of a new study in the Monthly Notices of the Royal Astronomical Society. "And we can calculate how fast they need to be replenished because we know how fast they sink."

So where is this river of silicon-rich material coming from? Farihi and his team say it is probably coming from rocky asteroids that veered too close to the star and were shredded by the white dwarf's gravity. The shredded material likely formed a ring of debris around the white dwarf, which then funneled the material into the dead star. 

And here's the cool part: Where there are rocky asteroids, there are probably rocky planets as well.

"If you have giant rocks that are many kilometers in size flying about, it is almost certain that planet formation has happened," Farihi told the Los Angeles Times. "It's like seeing a bunch of Lego blocks strewn around a kid's room. You know they were building something, but you don't know exactly what they are building."

It's unclear if these planets, if they existed, are still around. In the process of becoming a white dwarf, the star expanded, and then contracted and some or all of the planets may have been lost during that process. But Farihi said there is an excellent chance that some of the planets have remained, and that is what is pushing these rocky asteroids toward the star.

"I hope this study will inspire people to take a closer look," he said.


[For the record, 10:20 p.m., May 9: A previous version of this post misspelled Jay Farihi's last name in one reference.]