ExoplanetsⅢ

系外行星(三)

Amateur Astronomer - - 宇宙奥秘 -

Like most people, many scientists believe there’s some type of life on other planets. It could be as simple as microbes, or as complex as the plant and animal life here on Earth.

和多数人一样,很多科学家也相信其他行星上会存在一些种类的生命。它们可能像细菌一样简单,也可能像我们地球上的植物和动物一样复杂。 But there’s a huge gap between believing that something’s there and actually proving it. And so far, there’s no confirmed evidence of life on any world other than our own. Yet astronomers are already trying to tease out that evidence on exoplanets — worlds that orbit stars other than the Sun.

但是相信它们存在和实际证明它们存在之间有着巨大的鸿沟。到目前为止,除了我们的世界,其他任何地方都没有生命存在的有力依据。然而天文学家们已经试图去梳理在系外行星,太阳以外其他恒星的行星上存在生命的证据了。 They’re doing so by taking advantage of the fact that most of the worlds discovered so far pass in front of their stars. Astronomers take a spectrum of the star when no planet is in front of it, revealing the star’s chemistry. Then they take another spectrum when the planet passes in front of the star. If the planet has an atmosphere, then some of the star’s light passes through it. Comparing the spectra can reveal the chemistry of that atmosphere.

他们利用这一事实来进行梳理:到目前为止发现的绝大多数行星都从它们的恒星前经过。天文学家们拍摄没有行星经过时恒星的光谱,了解恒星的化学成分;之后,他们再拍摄有行星经过时的恒星光谱。如果有大气层,那么一些星光会穿过大气层。对比两个光谱可以发现行星大气的化学物质。 They’ve already discovered several giant planets that are in the habitable zone — the distance from the star where temperatures are just right for liquid water. The planets are too much like Jupiter and Saturn for Earth-like life. But if they have big moons, those worlds could be good abodes for life — small, rocky worlds with lots of water.

他们已经在宜居带(与恒星距离合适,其温度适宜液态水存在)发现了数颗巨行星。对于类地生命来说,这些行星太像木星和土星了。但是,如果它们有大型卫星,那里可能很适宜生命居住——小而且拥有很多水的岩石世界。 右面这幅美术作品中G lie s e 1 2 1 4 b正从其恒星前经 过 。 G lie s e 1214b也被称为G J 1 2 1 4 b ,曾经被看成是“超级地球”,它比地球大,大概有海王星那么大。整个G lie se 1 2 1 4是迄今为止发现的离太阳最近的恒星系统,约在4 2光年之外。图片来源:欧洲南方天文台(E S O ) Life on Earth produces elements and compounds that are rarely found without life, such as oxygen and methane. So if one of these “biomarkers” turns up in a planet’s atmosphere, it increases the odds that something is living there. And if more than one biomarker is found, especially at high concentrations, then it’s a good bet that it’s a living world.

地球上的生命制造了没有生命的世界里很难找到的元素和化合物,比如氧气和甲烷。如果有一个这种“生命指标”出现在行星的大气层中,这就增加了有生命在那里存在的可能性。如果发现超过一项的指标,尤其是高浓度的,就可以赢率很高地打赌说这是一个有生命存在的世界了。 Astronomers have used this technique to study the atmospheres of several planets. So far, though, they haven’t found any biomarkers — the signature of life on another world.

天文学家们通过这一方法研究了几颗行星的大气层。但是,到目前为止,他们都没有发现任何指标,那些在另一个世界存在生命的信号。 Recent simulations by researchers at McMasters University found that such “exomoons” could grow to about twice the mass of Mars — bigger than any moon in the solar system. Such a heavy world could hold on to its water and atmosphere for billions of years — providing plenty of time for life to develop.

最近,麦克马斯特大学的研究人员通过模拟发现,这类“系外卫星”可能达到大约火星质量的2倍,比太阳系里所有的卫星都要大。如此重大的世界可以在数十亿年中牢牢吸引水和大气层,为生命的进化提供足够的时间。 So far, no one has seen any exomoons. They’re quite hard to detect with current technology. But new telescopes on the ground and in space should have the ability to pluck them from the observations of exoplanets — perhaps revealing some distant homes for life.

到目前为止,没有人见过任何系外卫星。以今天的科技来探测它们确实太难了。但是,地面上和太空中的新型望远镜可能拥有通过观察系外行星捕获它们的能力,这也许会揭示一些遥远的生命居所。 2016.11

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