February 3, 2009 / 5:52 PM / 11 years ago

Scientists discover smallest exoplanet

LONDON (Reuters) - French scientists have discovered the smallest planet yet located out of our solar system, a celestial find less than twice the size of Earth and which orbits a Sun-like star.

The so-called exoplanet may be rocky like Earth but its temperature is so high it could be covered in lava or water vapour, according to findings from a mission led by the French Space Agency.

“This discovery is a very important step on the road to understanding the formation and evolution of our planet,” Malcolm Fridlund of the European Space Agency, which is participating in the mission, said Tuesday.

“For the first time, we have unambiguously detected a planet that is ‘rocky’ in the same sense as our own Earth.”

About 330 exoplanets have been found orbiting other stars besides the Earth’s sun, most of which are gas giants with characteristics similar to Jupiter and Neptune.

The new find — called COROT-Exo-7b — is different. It orbits closely around its star once every 20 hours, with a high temperature between 1,000 and 1,500 Celsius.

Astronomers using an orbiting telescope made the discovery when the planet passed its sun, dimming the light from the star as it moved in front of it, the team said.

Scientists say the discovery is important because recent measurements have indicated the existence of planets of small masses but their sizes remained undetermined until now.

Most exoplanets have been spotted using indirect measurements, mostly looking at their effects on the gravitational fields of their suns.

In this case, the researchers said they were able to directly measure the size of the surface of the planet, which may be rocky like Earth and covered in liquid lava.

It may also belong to a class of planets thought to be made up of water and rock in almost equal amounts, they said.

Reporting by Michael Kahn; Editing by Maggie Fox and Richard Balmforth

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