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  • Sci. & Tech.
    'Second Earth' may mean we're not alone


    By Ian Sample

    Scientists have discovered a warm and rocky "second Earth" circling a star, a find they believe dramatically boosts the prospects that we are not alone.

    The planet is the most Earth-like ever spotted and is thought to have perfect conditions for water, an essential ingredient for life. Researchers detected the planet orbiting one of Earth's nearest stars, a cool red dwarf called Gliese 581, that lies 20 light years away in the constellation of Libra.

    Measurements of the planet's celestial path suggest it is 1.5 times the size of our home planet, and orbits close to its sun, with a year of just 13 days. The planet's orbit brings it 14 times closer to its star than Earth is to the sun. But Gliese 581 burns at only 3,000C, half the temperature of our own sun, making conditions on the planet comfortable for life, with average ground temperatures estimated at 0 to 40C. Researchers claim that the planet is likely to have an atmosphere. The discovery follows a three-year search for habitable planets by the European Southern Observatory, which operates a 3.6m telescope at La Silla in Chile.

    "We wouldn't be surprised if there is life on this planet," said Stephane Udry, an astronomer on the project at the Geneva Observatory in Switzerland.

    Two years ago, the same team discovered a giant Neptune-sized planet orbiting Gliese 581. A closer look revealed the latest planetary discovery, along with a third larger planet that orbits the star every 84 days. In astronomical tradition, the planets have been named after their star, with the most Earthlike now called Gliese 581c. The research team spotted the planet by searching the "habitable zone", the rare Goldilocks regions of space where the conditions are "just right" for life to gain a foothold and flourish.

    In a solar system, habitable planets are neither too near the sun, where liquid water would evaporate, nor too far, where they will be too frigid to sustain life. In our solar system the habitable zone is roughly between Venus and Mars.

    Xavier Delfosse, a member of the team at Grenoble University, said: "This planet will most probably be a very important target of the future space missions dedicated to the search for extraterrestrial life. On the treasure map of the universe, one would be tempted to mark this planet with an X." The discovery of an Earth-like planet so near - on cosmic scales - suggests that habitable planets could be numerous in the galaxy, Dr Delfosse said.

    In December, the French space agency CNES and the European Space Agency launched Corot, a second Earth hunter. The craft will gaze at 120,000 stars from an orbit more than 800km above Earth and hopefully spot between 10 and 40 small rocky planets. Many are expected to be capable of supporting an atmosphere.

    Sci. & Tech.


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