'Habitable' planet discovered circling Tau Ceti star

A planet with conditions that could support life orbits a twin neighbor of the sun visible to the naked eye, scientists have revealed.

The world is one of five thought to be circling Tau Ceti, a star just 12 light years away that is almost identical to the sun. Astronomers estimate the Tau Ceti planets to be two to six times bigger than Earth. One of them, with five times the Earth's mass, lies in the star's "habitable zone".

Also known as the "Goldilocks zone", this is the orbital region that is neither too hot nor too cold to allow liquid surface water and, potentially, life. Details of the discovery are to appear in the journal Astronomy & Astrophysics.

Because of the difficulties involved in detecting extra-solar planets, most found so far have had high masses. The Tau Ceti planetary family is thought to be the lowest-mass solar system yet detected.



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