首次發現系外星球上的有機分子（圖）
07-16
首次發現系外星球上的有機分子（圖）
巨型行星HD 189733b 溫度太高，上面的甲烷和水蒸氣不會導致生命的產生。
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. | 研究人員首次發現，有機分子以甲烷的形式存在於太陽系以外的一顆行星上。這顆巨大的行星距離其主恆星太近，上面的甲烷不可能導致生命的產生。然而，該發現為天文學家們提供了希望，有朝一日他們將能夠分析類地行星上的大氣。 |
| 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. | 美國加州理工學院的天文學家馬克·斯溫和高特姆·瓦西斯特、英國倫敦大學學院的天文學家喬瓦納·蒂耐提利用哈勃太空望遠鏡觀察了巨型行星HD189733b，其質量比木星略大，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. | 由於從地球上看來該行星不斷從其主恆星的前面經過，部分恆星光線周期性地通過行星的大氣層滲透過來，大氣層中不同的化學物質吸收的波長也各不相同。 |
| The observations confirm an earlier tentative detection of water vapour and reveal the presence of methane gas. | 此次觀察不但證實了先前的推測——其大氣中存在水蒸氣，而且還發現了甲烷氣體的存在。 |
| "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. | 美國劍橋麻省理工學院的薩拉·西格沒有參與這項研究，但她說：「我起初覺得，這個發現非常令人驚訝。」因為HD 189733b距離其主恆星太近，只相當於水星到太陽距離的10％，其溫度很高，大氣的溫度約為700攝氏度。西格說：「當溫度這麼高的時候，主要形式的含碳成分應該是一氧化碳，而不應是甲烷。」 |
| 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. | 研究人員提出，這也許是由於對某個化學過程的理解出了問題：要麼只是將甲烷集中到了大氣溫度較低的區域，要麼就是直接產生了過剩的甲烷。西格說，或許甲烷的出現僅僅意味著該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. | 若不是處於熾熱氣態行星大氣這樣惡劣的區域中，水和有機分子的出現會使該行星成為有望擁有生命的星球。 |
| 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，歸根到底天文學家們希望能夠分析較小的、更類似地球的行星大氣，而這項新研究向那個目標跨出了一大步。「我們的目標是研究固態行星，」她告訴《新科學家》雜誌的記者說，「對此我感到極為興奮！」 |
| The study will be detailed in the forthcoming issue of Nature. | 該研究的詳細情況刊登在即將出版的《自然》雜誌上。 |
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