The smallest rocky planet ever spotted outside Earth’s solar system has been found by the Kepler observatory, the US space agency said Monday.

The planet called Kepler—10b is the first Earth—sized planet confirmed found by Kepler, which was launched in 2009 to find small planets orbiting distant stars. It is about 1.4 times the size of Earth, according to data gathered during eight months of observations, NASA said.

The newly discovered planet, however, is too close to its sun to harbour life, scientists said.

“The discovery of Kepler—10b is a significant milestone in the search for planets similar to our own,” said Douglas Hudgins, Kepler programme scientist at NASA. “Although this planet is not in the habitable zone, the exciting find showcases the kinds of discoveries made possible by the mission and the promise of many more to come.” The Kepler mission is designed to discover other Earth-like planets in the Milky Way galaxy, but for those planets to be capable of harbouring life, they must be located in what scientists dub the “Goldilocks” zone — neither too hot nor too cold.

Last year, Kepler scientists reported the discovery of a small planetary system orbiting another star, a first for the orbiting telescope. It might also include a small, rocky planet orbiting near its sun.

The Kepler space telescope is finely tuned enough to detect Earth— sized planets orbiting distant stars. The 590—million—dollar telescope programme is to spend at least the next three and a half years pointed at a large swath of the Milky Way galaxy, which contains about 4.5 million stars.

The most advanced cameras ever used in space are focussing on 100,000 to 150,000 stars deemed most likely to have orbiting planets, scientists said at a prelaunch press briefing. Data from the cameras are to be used to find planets by looking for distortions in the light being emitted as an orbiting planet crosses in front of the star.

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