首次发现系外星球上的有机分子（图）   

巨型行星HD 189733b 温度太高，上面的甲烷和水蒸气不会导致生命的产生。

Organic molecules found on alien world for first time

Organic molecules – in the form of methane – have been detected on a planet outside our solar system for the first time. The giant planet lies too close to its parent star for the methane to signal life, but the detection offers hope that astronomers will one day be able to analyse the atmospheres of Earth-like worlds.	研究人员首次发现，有机分子以甲烷的形式存在于太阳系以外的一颗行星上。这颗巨大的行星距离其主恒星太近，上面的甲烷不可能导致生命的产生。然而，该发现为天文学家们提供了希望，有朝一日他们将能够分析类地行星上的大气。
Astronomers Mark Swain and Gautam Vasisht of Caltech in Pasadena, US, and Giovanna Tinetti of University College London, UK, used the Hubble Space Telescope to observe the giant planet HD 189733b, which is slightly more massive than Jupiter and lies 63 light years from Earth.	美国加州理工学院的天文学家马克·斯温和高特姆·瓦西斯特、英国伦敦大学学院的天文学家乔瓦纳·蒂耐提利用哈勃太空望远镜观察了巨型行星HD189733b，其质量比木星略大，距地球63光年。
Because the planet crosses the face of its parent star as seen from Earth, some starlight is periodically filtered through the planet's atmosphere, where different chemicals absorb particular wavelengths.	由于从地球上看来该行星不断从其主恒星的前面经过，部分恒星光线周期性地通过行星的大气层渗透过来，大气层中不同的化学物质吸收的波长也各不相同。
The observations confirm an earlier tentative detection of water vapour and reveal the presence of methane gas.	此次观察不但证实了先前的推测——其大气中存在水蒸气，而且还发现了甲烷气体的存在。
"Initially, that is surprising," says Sara Seager of MIT in Cambridge, US, who was not involved in the study. Because HD 189733b orbits very close to its parent star – just 10% of Mercury's distance from the Sun, it is very hot, with atmospheric temperatures of about 700° Celsius. "When the temperature is this high, the dominant form of carbon should be carbon monoxide, not methane," says Seager.	美国剑桥麻省理工学院的萨拉·西格没有参与这项研究，但她说：“我起初觉得，这个发现非常令人惊讶。”因为HD 189733b距离其主恒星太近，只相当于水星到太阳距离的10％，其温度很高，大气的温度约为700摄氏度。西格说：“当温度这么高的时候，主要形式的含碳成分应该是一氧化碳，而不应是甲烷。”
The authors suggest that some ill-understood chemical process might be responsible, either concentrating the methane in cooler parts of the atmosphere, or generating extra methane directly. Alternatively, the methane might simply mean that the planet happens to be very rich in carbon, Seager says.	研究人员提出，这也许是由于对某个化学过程的理解出了问题：要么只是将甲烷集中到了大气温度较低的区域，要么就是直接产生了过剩的甲烷。西格说，或许甲烷的出现仅仅意味着该行星恰巧富含碳元素。
This combination of water and organic molecules would be a promising one for life if it were found in a less hostile spot than the atmosphere of a searing gas giant.	若不是处于炽热气态行星大气这样恶劣的区域中，水和有机分子的出现会使该行星成为有望拥有生命的星球。
Eventually, astronomers hope to be able to analyse the atmospheres of smaller planets more akin to the Earth, and the new study is a big step in that direction, says Seager. "The path that we're on is towards rocky planets," she told New Scientist. "I'm really excited about this."	西格指出，归根到底天文学家们希望能够分析较小的、更类似地球的行星大气，而这项新研究向那个目标跨出了一大步。“我们的目标是研究固态行星，”她告诉《新科学家》杂志的记者说，“对此我感到极为兴奋！”
The study will be detailed in the forthcoming issue of Nature.	该研究的详细情况刊登在即将出版的《自然》杂志上。