本帖最后由 人与自然 于 2012-12-21 01:34 编辑
http://www.dailymail.co.uk/sciencetech/article-2250451/Habitable-world-discovered-orbiting-Sun-twin-just-12-light-years-away-visible-Earth.html
A planet that could support life orbits a twin of our own Sun which is so close it is visible to the naked eye, scientists revealed today.
The world is one of five thought to be circling Tau Ceti, a star just 12 light years away which 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'.
An artist's impression of the Tau Ceti system: A planet with conditions that could support life orbits the system, whose star is almost a twin of our own Sun, scientists revealed today
Also known as the 'Goldilocks zone', this is the orbital region that is neither to hot nor too cold to allow liquid surface water and, potentially, life.
Tau Ceti can be seen in the night sky in the constellation of Cetus, the whale. 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.
Scientists from Australia, Britain, Chile and the U.S. found the planets using a highly sensitive technique that combined data from more than 6,000 observations from three different telescopes.
They used the radial velocity method which looks for 'wobble' in a star's movement caused by the gravitational tug of planets.
Visible to the naked eye: Tau Ceti is just 12 light years from our own corner of the galaxy and can be seen in the night sky, but scientists had to use delicate measurements to detect and describe its planets
Dr James Jenkins, a member of the international team from the University of Hertfordshire, said: 'Tau Ceti is one of our nearest cosmic neighbours and so bright that we may be able to study the atmospheres of these planets in the not-too-distant future.
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