First rocky planet outside our solar system found.

(CNN) -- Scientists have discovered the first confirmed Earthlike planet outside our solar system, they announced Wednesday.

"This is the first confirmed rocky planet in another system," astronomer Artie Hatzes told CNN, contrasting the solid planet with gaseous ones like Jupiter and Saturn.

But "Earthlike" is a relative term.

The planet's composition may be similar to that of Earth, but its environment is more like a vision of hell, the project's lead astronomer said.

It is so close to the star it orbits "that the place may well look like Dante's Inferno, with a probable temperature on its 'day face' above 3,600 degrees Fahrenheit (2,000 degrees Celsius) and minus-328 degrees Fahrenheit (minus 200 degrees Celsius) on its night face," said Didier Queloz of Geneva Observatory in Switzerland, the project leader.

Hatzes, explaining that one side of the body is always facing the star and the other side always faces away, said the side "facing the sun is probably molten. The other side could actually have ice" if there is water on the planet.

"We think it has no atmosphere to redistribute the heat," Hatzes told CNN from Barcelona, Spain, where he is attending the "Pathways Towards Habitable Planets" conference.

The astronomers were stunned to find a rocky planet so near a star, he said.

"We would have never dreamed you would find a rocky planet so close," he said. "Its year is less than one of our days."

The planet, known as CoRoT-7b, was detected early last year, but it took months of observation to determine that it had a composition roughly similar to Earth's, the European Southern Observatory said in a statement.

Astronomers were able to measure the dimensions of the planet by watching as it passed in front of the star it orbits, then carried out 70 hours of study of the planet's effect on its star to infer its weight.

With that information in hand, they were able to calculate its density -- and were thrilled with what they found, Hatzes said.

"What makes this exciting is you compare the density of this planet to the planets in our solar system, it's only Mercury, Venus and Earth that are similar," Hatzes, of the Thuringer observatory in Germany, told CNN.

They were helped by the fact that CoRoT-7b is relatively close to Earth -- about 500 light years away, in the constellation of Monoceros, the Unicorn.

"It's in our solar neighborhood," Hatzes said. "The thing that made it easier is it's relatively close, so it's relatively bright. If this star was much much farther away, we wouldn't have been able to do these measurements."

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