Dec. 27 (Bloomberg) -- France today will launch the first satellite dedicated to finding planets outside the solar system, the French National Center of Space Studies said.

The craft, named Corot, carries a telescope that will be used to study about 10,000 stars at a time, examining the same stretch of sky for 150 days and using tiny variations in the light emitted by stars to detect so-called exoplanets, Philippe Goudy, assistant director for orbital projects at the agency, said today in a telephone interview from its control center in Toulouse, southwestern France.

``Because Corot will be looking at a great number of stars, the probability that we will detect exoplanets is high,'' Goudy said. ``What everybody has in mind is this tremendous question of is there life elsewhere in the universe, or are we alone. Corot won't be able to tell us that, but it will be able to tell us what type of planets are orbiting other stars and how common they are.''

Corot, which stands for convection rotation and planetary transits, will be launched from Kazakhstan's Baikonur Cosmodrome at 3:23 p.m. Paris time today, Goudy said. As well as searching for exoplanets, Corot will study astro-seismology, or the internal workings of stars, by analyzing the way light from the stars wobbles over time, according to Goudy.

The 170-million euro ($225-million) mission is led by the French space center in collaboration with the European Space Agency, with assistance from Austria, Belgium, Germany, Spain and Brazil. The 630-kilogram (1,400-pound) craft will be launched on a polar orbit around the Earth at an altitude of 896 kilometers (557 miles).

NASA Mission

The planet-hunting portion of the mission will help prepare the way for the U.S. National Aeronautics and Space Administration's Kepler project, according to Goudy. Kepler, scheduled for launch in October 2008, will scour the skies for planets the size of Earth and smaller. Corot may be able to locate planets about 1 1/2 times the size of Earth by detecting shifts in the amount of light emitted by stars, Goudy said.

``Corot is using the so-called transit approach: detecting a small diminution of the light we receive from a star when the planet orbits in front of it,'' Goudy said. ``Corot can detect changes of less than a hundredth of a percent.''

So far, more than 200 exoplanets have been found by ground- based instruments, with assistance from satellites, according to Goudy. All of them have been so-called gas giants, similar to Jupiter, rather than smaller, rocky planets, such as Earth, Mars, Venus and Mercury.

Smallest Exoplanet

Astronomers in January announced they had found the smallest exoplanet yet. Named OGLE-2005-BLG-390Lb, the exoplanet is about 5.5 times the mass of Earth, a team led by the Astrophysics Institute of Paris said in the journal Nature.

Three orbits are needed to confirm the presence of an exoplanet, so Corot will detect those that take 75 days or less to orbit because it will concentrate on any one area of the sky for about 150 days, Goudy said. The telescope will be analyzing stars in our own galaxy, the Milky Way, most of which are thousands of light-years away.

Mission scientists hope Corot's telescope may be able to detect about 200 exoplanets, Goudy said.

The main contractor in building Corot was Alcatel Alenia Space, a joint venture of Paris-based Alcatel-Lucent and Finmeccanica SpA, based in Rome.

To contact the reporter on this story: Alex Morales in London at amorales2@bloomberg.net.

Last Updated: December 27, 2006 05:44 EST