地球般的行星有可能会有生命存在

紫色辣椒

Astronomers have spotted "the first habitable Earth-like planet" outside the solar system, a find so enticing that Canada's space telescope is being redirected to take a closer look.

3 J4 m( A; N" T0 Z* DThe "super-Earth" appears to be 50-per-cent larger than Earth and orbiting around a star in a "habitable zone" where temperatures are so balmy that water -- the elixir of life -- would be liquid.
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" u" G# W- X7 d9 s3 U5 h"We have estimated that the mean temperature of this super-Earth lies

; T) g0 d+ k3 _% rbetween 0 and 40 degrees Celsius, and water would thus be liquid," says Stephane Udry, of the Geneva Observatory, who leads the European team that reported the discovery Tuesday in the journal Astronomy and Astrophysics.
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, A. `8 H. f3 Z6 HThe planet, believed to be either rocky like Earth or covered with oceans, is seen as a promising target in the search for extraterrestrial life.
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, |6 y+ y1 ]* Y, i3 L8 l9 w"On the treasure map of the universe, one would be tempted to mark this planet with an X," says team member Xavier Delfosse of Grenoble University.

Since the discovery in 1995 of the first "exoplanet" orbiting a star other than the sun, more than 200 planets have been found. Most are gas giants on extreme orbits around stars that make them either scorching hot or far too cold to maintain life as we know it.

) S3 e5 n# a  Y" |+ ~The Europeans say the new planet is the smallest exoplanet and "most Earth-like" so far. They have deduced that it orbits its star in 13 days and is 14 times closer to its star than the Earth is to the sun.
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' p; V. @) v5 ?3 k: k. |The scientists found the planet using a super-sensitive planet-hunting machine fitted onto a European telescope in Chile. It detects the tiny changes -- or wobbles -- produced as planets orbit around stars. The planet's host star, a red dwarf called Gliese 581, is much smaller and colder than the sun, which means the planet can be close to its star but still be in the so-called "habitable zone," the region around a star where water would be liquid.

Gliese 581 is among the 100 closest stars to Earth, located 20.5 light-years away in the constellation Libra. This means light takes 20.5 years to travel from Gliese 581 to Earth.

Astronomer Jaymie Matthews of the University of British Columbia cautions there is no evidence so far showing the planet actually harbours water, let alone "extras from Star Trek." All that scientists can say for certain is that the planet appears to exist, and could have a solid surface and habitable temperatures.
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+ \' H/ W9 x) t: K" S+ r/ ]. ^But the European evidence is so exciting, Matthews says, that he and his colleagues have agreed to focus Canada's suitcase-sized space telescope, known as MOST, on the alien solar system.
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"We're putting it on a stakeout," says Matthews, who leads the MOST team and is currently in Vienna. (MOST stands for "microvariabilty and oscillations of stars.")
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  Y  |- W; x: h% I0 |' b7 ]He expects to have the planetary system in the microsatellite telescope's sights by late next week. "We've been working on this for a few weeks," he said by telephone.

Matthews says it will be possible to look for the "super-Earth" without too big an impact on other MOST projects.
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"We'll be squeezing it into to our regularly scheduled programming. That's the beauty of having something like MOST.

"It's almost like having your own private space telescope in the sense that it's possible for us to take advantage of these targets of opportunity and adapt very, very quickly."

With luck, Matthews says MOST, which has a much clearer view from its orbit above Earth, will be able to actually see the planet orbiting across the face of the star and confirm its existence.
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: N' ^. m! b! K) o/ V, j" N2 s; UThe odds that MOST will be in the right vantage point to observe such a "transit" is about one in 20.
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"It's a long shot," he says, but well worth taking because the results could be huge.

% x- ~0 y+ r( i4 a2 j! J! {"A few hundred years from now, people will look back at this era the same way we look back at the time of Galileo. This is the first time in history that we are actually able to look and find places elsewhere in the universe where creatures like us could possibly live."
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Two years ago, the European astronomers found a much bigger planet around the Gliese 581, similar in size to Neptune, and they suspect there may be a third planet about eight times heavier than Earth.