Astronomers find rocky planet outside solar system

[September 16, 2009]  WASHINGTON (AP) -- Astronomers have finally found a place outside our solar system where there's a firm place to stand -- if only it weren't so broiling hot.

As scientists search the skies for life elsewhere, they have found more than 300 planets outside our solar system. But they all have been gas balls or can't be proven to be solid. Now a team of European astronomers has confirmed the first rocky extrasolar planet.

Scientists have long figured that if life begins on a planet, it needs a solid surface to rest on, so finding one elsewhere is a big deal.

"We basically live on a rock ourselves," said co-discoverer Artie Hartzes, director of the Thuringer observatory in Germany. "It's as close to something like the Earth that we've found so far. It's just a little too close to its sun."

So close that its surface temperature is more than 3,600 degrees Fahrenheit, too toasty to sustain life. It circles its star in just 20 hours, zipping around at 466,000 mph. By comparison, Mercury, the planet nearest our sun, completes its solar orbit in 88 days.

"It's hot, they're calling it the lava planet," Hartzes said.

This is a major discovery in the field of trying to find life elsewhere in the universe, said outside expert Alan Boss of the Carnegie Institution. It was the buzz of a conference on finding an Earth-like planet outside our solar system, held in Barcelona, Spain, where the discovery was presented Wednesday morning. The find is also being published in the journal Astronomy and Astrophysics.

The planet is called Corot-7b. It was first discovered earlier this year. European scientists then watched it dozens of times to measure its density to prove that it is rocky like Earth. It's in our general neighborhood, circling a star in the winter sky about 500 light-years away. Each light-year is about 6 trillion miles.

Four planets in our solar system are rocky: Mercury, Venus, Earth and Mars.

In addition, the planet is about as close to Earth in size as any other planet found outside our solar system. Its radius is only one-and-a-half times bigger than Earth's and it has a mass about five times the Earth's.

Now that another rocky planet has been found so close to its own star, it gives scientists more confidence that they'll find more Earth-like planets farther away, where the conditions could be more favorable to life, Boss said.

"The evidence is becoming overwhelming that we live in a crowded universe," Boss said.

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On the Net:

European Southern Observatory: http://www.eso.org/

[Associated Press; By SETH BORENSTEIN]

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