Down the Stellar Hatch

7 August 2007 (All day)

Traces of an Earth-like planet have turned up in an unlikely place: inside a star. The discovery bolsters astronomers' suspicion that solar systems similar to ours must exist around other stars.

Despite the recent surge in extrasolar planet discoveries, astronomers have struggled to find worlds like our own. Of the 240 known planets orbiting other stars, only one is small and rocky like Earth (ScienceNOW, 11 June 2007). The rest are hefty gas giants resembling Jupiter. Now, that Earth-like planet may have some company thanks to readings from an unusual star known as GD 362.

Most small, hot stars--known as white dwarfs--have atmospheres that consist almost entirely of helium and hydrogen. But GD 362 is different. Using spectrometers attached to the Keck I and II telescopes at Mauna Kea Observatory in Hawaii and to several other telescopes, a team of astronomers including Michael Jura of the University of California, Los Angeles, identified the signatures of 17 elements in GD 362, including sodium, magnesium, aluminum, iron, and nickel. What's more, the levels of these elements in GD 362's atmosphere occur in similar proportions as those on Earth. That likely means that GD 362 swallowed a planetoid much smaller than Earth sometime in its history, the team reports in an upcoming issue of The Astrophysical Journal.

The discovery is "an exciting new development," says astrophysicist Alan Boss of the Carnegie Institution of Washington, D.C. "It gives us more proof that planetary systems resembling our own are likely to be common in the galaxy, and that life may be commonplace in the universe."

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