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Rocky Planet Found Outside Solar System

Posted on: Tuesday, 14 September 2004, 06:00 CDT

SWEDEN: A 'super Earth' has been detected in orbit around a star 50 million light years away. The planet is the smallest to have been discovered outside our solar system, and the first with a rocky composition like Earth.

"This is a really wonderful discovery on the way to the ultimate aim of discovering another Earth," said Mr Richard West, senior astronomer at the European Southern Observatory in Chile, which discovered the planet.

The discovery, announced yesterday at the EuroScience forum in Stockholm, is the most important since the first exoplanet - a planet orbiting a star other than the sun - was found in 1995.

"We believe the new planet has a rocky structure, which is more like Earth than any other exoplanet discovered so far," said Didier Queloz of Switzerland's Geneva Observatory.

The planet, whose mass is 14 times greater than Earth, is close to its parent star - only one-tenth of the distance of the sun from the Earth - and therefore too hot to support any known form of life. Mr Queloz estimated the surface temperature to be 650 degrees celsius.

Although planet-hunting technology is advancing rapidly, it will probably be a decade before astronomers can reliably detect Earth- sized planets at the right distance from their parent star to support the chemical processes that could give rise to life.

Exoplanets are too small to observe directly, so astronomers use indirect methods based on planets' interaction with the parent star. Some scientists have speculated that Earth-like planets capable of sustaining life may be rare in our galaxy. But Mr Queloz said it was too early to tell.

"Until we can detect Earth-sized planets, we cannot conclude that our solar system is bizarre or unusual," he said.

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