Sun-Like Stars Littered with Rocky Remains

THE GIST:

• Metal pollutants have been discovered in the atmosphere of ancient, sun-like stars.
• The remains are believed to be rocky bodies that crashed into their parent stars.
• Rocky, possibly watery worlds like Earth could exist beyond our solar system.

Ancient, sun-like stars possess metal contaminants that scientists believe are remnants of rocky, potentially water-bearing bodies that crashed into their mother stars, according to a comprehensive study.

The finding increases prospects that Earth-like planets formed in other solar systems.

The new research dismisses the possibility that telltale traces of calcium, magnesium, silicon and iron found in the atmospheres of white dwarf stars came from dust in interstellar space, leaving indigenous planetary systems as the most viable explanation.

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"We've suspected for a few years that the interstellar medium was not the solution because there were some problems with it. This seems to be the final nail in the coffin," University of Montreal astronomer Patrick Dufour told Discovery News.

Using data collected by the Sloan Digital Sky Survey, researchers studied 300 white dwarf stars, which are stars similar to our sun but in the last stage of their existence.

The study targeted 300 white dwarfs -- some as young as 10,000 to 100,00 years old and others as old as 8 billion to 9 billion years -- with nearly pure helium atmospheres. Chemical analysis of the stars showed about 3 percent of them contained trace metals consistent with rocky, possibly watery bodies like asteroids.

Since asteroids are the leftover building blocks of planets in our solar system, scientists believe the discovery builds a case for terrestrial-like worlds such as Earth around other sun-like stars.

"Asteroids are really failed planets," University of Leicester astronomer Jay Farihi told Discovery News. "What we're saying about these white dwarf metals is that they're either leftover rocks or leftover remains of a planet."

Planets as close to their parent stars as Earth would have been consumed as the stars ballooned into red giants, with the rocky bodies' remains entombed in the stars' cores. Asteroids beyond Mars' orbit would survive the parent stars' expansion. The study suggests, however, that occasionally one or more would come crashing into the star's cooling body.

The study focused on white dwarfs with helium-rich atmospheres so any trace metals would show up more distinctly. The analysis was sensitive enough to detect the remains of an object with the mass of a large asteroid.

"It doesn't take that much to pollute the star," Farihi said.

The team compared white dwarf stars that were near or had passed through dusty regions of interstellar space, with those that travel through clearer skies. They found no difference in the level and frequency of metal contaminants in the stars' atmospheres, leading scientists to conclude that interstellar space was not the source.

The research is being published in this month's issue of the Monthly Notices of the Royal Astronomical Society.