Rocky planet, just like Earth, found

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(China Daily)
Updated: 2009-09-17 09:15

Corot-7b, which circles its sun in 20 hours, too hot to harbor life...

An artist's impression released by European Southern Observatory yesterday shows the smallest and fastest-orbiting exoplanet known, Corot-7b (foreground), around a star named Corot-7, located towards the constellation of Monoceros (the Unicorn) at a distance of about 500 light-years. [Agencies]

WASHINGTON: 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 between 1,000 and 1,500 degree Celsius, too toasty to sustain life. It circles its star in just 20 hours, zipping around at 749,954 kph. 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 yesterday 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.

To get their measurements, the astronomers used what they dubbed "the best exoplanet-hunting device in the world", called a high accuracy radial velocity planet searcher (HARPS) - which is a spectrograph attached to the European Southern Observatory's telescope at the La Silla observatory in Chile.

"Even though HARPS is certainly unbeaten when it comes to detecting small exoplanets, the measurements of Corot-7b proved to be so demanding that we had to gather 70 hours of observations," said Francois Bouchy, another of the European-wide group of scientists who conducted the study.

Fellow astronomer Artie Hatzes said the work represented a "tour de force" of astronomical measurements.

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.

AP - Reuters