A planet 20 light years away is the first outside our solar system to be officially declared habitable by scientists.
The "exoplanet" Gliese 581d has conditions that could support Earth-like life, including possible watery oceans and rainfall.
Yet any future space voyagers landing there would find themselves in truly alien surroundings. The sky is likely to be murky red, not blue, and gravity is twice what is on Earth, doubling the weight of anyone standing on the surface.
In addition, the planet's carbon dioxide-rich atmosphere would almost certainly not be breathable by humans.
Scientists were surprised by the discovery because Gliese 581d was previously ruled out as a habitable planet candidate.
But a new computer model capable of simulating extraterrestrial climates has shown the previousassumption to be wrong, and confirmed that Gliese 581d really could harbour life.
Scientists believe the findings could pave the way to more discoveries of potential havens for life among the stars, including some that are strange and unexpected.
Dr Robin Wordsworth, a member of the French team from the Institut Pierre Simon Laplace in Paris, said: "This discovery is important because it's the first time climate modellers have proved that the planet is potentially habitable, and all observers agree that the exoplanet exists.
"If you look at the history of the search for habitable planets, there have been at least two instances so far when scientists have announced that a habitable world has been discovered, only to have the claim contradicted later, either by climate experts or by other observers.
"The Gliese system is particularly exciting to us as it's very close to Earth, relatively speaking. So with future generations of telescopes, we'll be able to search for life on Gliese 581d directly.
"This said the fact that a planet so unlike the Earth could be habitable bodes pretty well for the search for life in general.
"I think it's becoming clearer with every discovery we make in exoplanet science that the variety of worlds out there in the universe is going to be far greater than the few examples we are used to from our Solar System."




天文科学家正式对外宣布，在太阳系之外发现了一颗距离在20光年左右的适合生命体生存的星球。
这颗名为格利泽 581d的外部星提供了可供生命存在所需的条件，在格利泽上可能存在有类似于谁的海洋和降雨。

不过当未来的太空旅行者在那可星球上着落时，可能会发现自己正处于名副其实外形环境，哪儿的天空不是蓝色，而是红色的，引力也可能是地球的两部，任何人站在星球表面，体重都将是地球上的两倍。

此外，这个星球的大气中充满了二氧化碳，人类几乎是无法呼吸的。
科学家们对于这项发现感到非常意外，因为在此前格利泽 581d一直被排除在适宜居住的星球之外。
一项新的电脑建模模拟了外星其后，这推翻了之前错误的假设，并证实格利泽 581d其实是适合生命存在的。

科学家们相信，这项发现可以为今后发现更多的适宜生命生存的行星拓宽道路，其中可能包括怪异和意想不到的星球。

法国的罗宾•华兹华斯教授是巴黎皮埃尔西蒙拉普拉斯研究所的成员之一，他说："这项发现非常重要，是首次通过模拟行星的其后来判断其是否适宜生存，所有的观察员他在这颗外部行星存在的问题上达成了统一的认定。"

"在研究寻找适宜居住行星的历史之后，你会发现目前至少有两个例子，在天文学家宣称找到了适合的目标之后，气象专家或者其他观察员总会将之否定。"


"格利泽的系统尤为使我们感到兴奋，因为它距离地球很近，在将来利用天文望远镜，我们或许就能直接关发到这个星球上是否有生命的存在。"
"也就是说，这样一个与地球非常类似的星球居然适合居住，这也预示着寻找生命存在的大好前景。"

"我认为随着对太阳系以外行星的进一步了解，情况越来越明朗，我们不应该将目光仅限于太阳系内的为数不多的星球，宇宙中还有大量的带我们探索的世界。"

• planet [´plænit] n.行星 (初中英语单词)
• system [´sistəm] n.系统，体系，制度 (初中英语单词)
• standing [´stændiŋ] n.持续 a.直立的 (初中英语单词)
• addition [ə´diʃən] n.加；加法；附加物 (初中英语单词)
• carbon [´kɑ:bən] n.碳；(一张)复写纸 (初中英语单词)
• atmosphere [´ætməsfiə] n.大气；空气；气氛 (初中英语单词)
• computer [kəm´pju:tə] n.计算机；电子计算器 (初中英语单词)
• capable [´keipəbəl] a.有能力；能干的 (初中英语单词)
• previous [´pri:viəs] a.先，前，以前的 (初中英语单词)
• climate [´klaimit] n.气候；特殊气候地带 (初中英语单词)
• unlike [,ʌn´laik] a.不同的 prep.不象... (初中英语单词)
• variety [və´raiəti] n.变化；多样(性)；种类 (初中英语单词)
• gravity [´græviti] n.严肃；严重；重力 (高中英语单词)
• previously [´pri:viəsli] ad.预先；以前 (高中英语单词)
• assumption [ə´sʌmpʃən] n.掌握；担任；假定 (高中英语单词)
• potential [pə´tenʃəl] n.&a.潜在的；可能的 (高中英语单词)
• relatively [´relətivli] ad.比较地；相对地 (高中英语单词)
• universe [´ju:nivə:s] n.天地；全人类；银河系 (高中英语单词)
• officially [ə´fiʃəli] ad.以职员身份；正式 (英语四级单词)
• watery [´wɔ:təri] a.水的；像水的 (英语六级单词)
• landing [´lændiŋ] n.登陆；降落；楼梯平台 (英语六级单词)
• speaking [´spi:kiŋ] n.说话 a.发言的 (英语六级单词)