天外有生命?

An organic molecule has been detected for the first time in the atmosphere of a planet outside the solar system.

Astronomers say the discovery, published today in the journal Nature, is an important step towards eventually identifying signs of life on a planet orbiting another star.

A team of astronomers from the US and Britain, using the Hubble Space Telescope, found the tell-tale “spectroscopic” signature of methane molecules in the atmosphere of a planet 63 light years from Earth.

The planet, called HD 189733b, is about the size of Jupiter but it orbits very close to its parent star and is therefore too hot to support life as we know it.

Giovanna Tinetti of University College London said: “We haven't found life on another planet yet, but this is an exciting step towards showing that we can detect these signature molecules where they are present in the universe.”

Methane is the simplest possible organic molecule, with a single carbon atom surrounded by four hydrogen atoms.

Under the right circumstances methane can play a key role in “prebiotic” chemistry – the reactions considered necessary to form carbon-based life.

Although methane has been detected on most of the planets in the solar system, this is the first time an organic molecule has been detected on any of the 270 planets discovered in orbit around other stars.

The discovery demonstrates the principal that organic molecules can be detected on extrasolar planets through spectroscopy, which splits light into its components to reveal the “fingerprints” of various chemicals.

天文学家首次在太阳系以外一颗行星的大气层中发现了有机分子的存在。

这一发现发表在今天的《自然》(Nature)杂志上。天文学家表示，这向在环绕另一颗恒星公转的行星上最终发现生命迹象迈出了重要一步。

来自英美两国的一些天文学家使用哈勃太空望远镜(Hubble Space Telescope)，在距离地球63光年的一颗行星的大气层中，发现了揭开谜底的有机分子“光谱”特征。

这颗行星名为HD 189733b，大小与木星相仿，其轨道非常靠近其母恒星，因而温度过高，据我们所知无法承载生命。

伦敦大学学院的吉奥瓦纳•蒂内迪(Giovanna Tinetti)表示：“我们迄今为止尚未在另一颗行星发现过生命，但这是令人鼓舞的一步，表明我们已能宇宙中发现此类特征分子。”

甲烷是可能存在的最简单的有机分子，由4个氢原子围绕1个碳原子组成。

在适当环境中，甲烷可以在“生命起源前(prebiotic)”的反应中扮演关键角色，人们认为，此类化学反应是形成碳基生命的必要步骤。

尽管在太阳系的多数行星上都发现了甲烷，这却是人类首次在围绕其他恒星旋转的270颗已知行星中发现有机分子。

此项发现验证了通过光谱分析能够在太阳系以外的行星中发现有机分子的原则，光谱分析是将光划分为光谱，之后揭示出不同化学物质的“指纹”。