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An Earth-size planet has been spotted orbiting a nearby star at a distance that would makes it not too hot and not too cold - comfortable enough for life to exist, researchers announced September 29.
據美國太空網9月29日報道，研究人員最新宣稱探測到一顆類似地球的行星，其環繞鄰近恒星距離適中，得以保持適宜的氣候和溫度——舒適程度足以讓生命存活下來。
If confirmed, the exoplanet, named Gliese 581g, would be the first Earth-like world found residing in a star's habitable zone - a region where a planet's temperature could sustain liquid water on its surface. And the planet's discoverers are optimistic about the prospects for finding life there.
如果得以證實，這顆被命名為“Gliese 581g”的系外行星將成為第一顆類似地球的世界——該行星的溫度可維持表面存在液態水。而探測者們則因此對找到外星生命充滿希望。
"Personally, I would say, my own personal feeling is that the chances of life on this planet are 100 percent," said Steven Vogt, a professor of astronomy and astrophysics at the University of California. "I have almost no doubt about it."
“就個人角度而言，我認為這顆行星上存在生命的概率為100%，”美國加州大學圣塔克魯茲分校天體物理學家史蒂文-沃格特說?！皩Υ宋規缀鹾敛恢靡伞?/FONT>
Gliese 581g is one of two new worlds the team discovered orbiting the red dwarf star Gliese 581, bumping that nearby star's family of planets to six. The other newfound planet, Gliese 581f, is outside the habitable zone, researchers said.”
Gliese 581g是環繞紅矮星Gliese 581兩顆行星中的其中一顆，它的發現使該行星系內行星數量增加至6顆。研究人員稱，另一顆新發現的行星是Gliese 581f，位于適宜居住區域之外。
The star is located 20 light-years from Earth in the constellation Libra. Red dwarf stars are about 50 times dimmer than our sun. Since these stars are so much cooler, their planets can orbit much closer to them and still remain in the habitable zone. Estimates suggest Gliese 581g is 0.15 astronomical units (One astronomical unit is the average distance between the Earth and sun) from its star, close enough to its star to be able to complete an orbit in just less than 37 days.
而紅矮星Gliese 581位于天秤星座，距離地球20光年，大約比太陽昏暗50倍。由于這樣的恒星溫度相對較低，它的行星在近距離環繞其運行的同時還能保持著適宜的氣候和溫度。初步分析認為Gliese 581g與恒星的距離為0.15個天文單位（一個天文單位約等于地球至太陽的平均距離），較近的軌道距離使得該行星公轉一周只需37天。
Gliese 581g has a mass three to four times Earth's, the researchers stimated. From the mass and estimated size, they said the world is probably a rocky planet with enough gravity to hold onto an atmosphere. Just as Mercury is locked facing the sun, the planet is tidally locked to its star, so that one side basks in perpetual daylight, while the other side remains in darkness. This locked configuration helps to stabilize the planet's surface climate, Vogt said. Between blazing heat on the star-facing side and freezing cold on the dark side, the average surface temperature may range from minus 31 to minus 12 degrees Celsius, the researchers said.
研究人員估測Gliese 581g行星的質量大約是地球的3到4倍?；谠撔行堑馁|量和預測體積，研究人員稱該行星很可能是一顆巖石行星，具有足夠的引力維持大氣層。與水星總有一半固定地面對太陽相似，該行星總是始終保持一面朝向恒星，使得星球的一半永久處于陽光之中，而另一半則永久位于黑暗。沃格特稱，這種特征有助于穩定行星的表面氣候。研究人員還稱，在熾熱和寒冷的兩個半球之間，該星球平均表面溫度為零下31攝氏度至零下12攝氏度。
