(单词翻译:单击)
Last week, two teams, one from the UK and one from across North America, independently reported a pretty cool discovery.
上周，2个团队，一个来自英国，一个来自北美。这2个团队分别报道了一个很酷的发现。
They found water in the atmosphere of an exoplanet about 110 light-years away, called K2-18b.
他们发现距离我们大概110光年远的一颗系外行星大气层里有水，这颗系外行星名为K2-18b。
Which has implications for our search for life on other worlds, but it’s probably not time to pop the champagne cork just yet.
这表明我们在其他星球搜索生命的事情有了进展，但可能现在庆贺还为时尚早。
See, this isn’t the first time water’s been found in an exoplanet’s atmosphere.
毕竟这不是人类第一次在系外行星的大气层中发现水。
Water is a pretty common molecule in space, after all.
毕竟水是宇宙里十分常见的一种分子。
But what makes this discovery so interesting is that the planet is fairly small, and it’s in its star’s habitable zone, where it’s likely that the water can be in liquid form.
不过，该发现的有趣之处在于——这颗行星体型非常之小。而且这颗行星位于其恒星的宜居地带，所以很有可能水是液态形式的。
To make this discovery, the two teams both used the same data:
为了这项发现，2个团队都使用了相同的数据：
observations of the planet’s host star by the Hubble Space Telescope.
他们用哈勃望远镜观测了这颗行星的主恒星。
They looked at the star’s light signature, or spectrum, at different times:
他们在不同的时间观测了这颗恒星的光谱——
when the planet was in front of the star, and when it wasn’t.
行星在恒星前以及行星不在恒星前的时候。
The obviously the difference between those two spectra gives you a spectrum of the planet’s atmosphere.
显然，两个光谱的区别可以让我们了解到行星大气层的光谱。
And that spectrum tells you what’s in the atmosphere, because different atoms and molecules have characteristic features that let us identify them.
光谱可以告诉我们大气层里有什么，因为不同的原子和分子都有各自的特征，具有可识别性。
So when they looked at that spectrum, they found the signature of good ol’ H2O. Sort of.
所以，他们观测光谱的时候发现了水的痕迹，哪怕是一丢丢吧。
Because these measurements aren’t actually terribly precise.
因为这些测量实际上并不是十分精确。
There’s a bunch of statistical noise. So the UK team applied some more math to the data and created a model of the planet’s atmosphere.
从统计学的角度来讲，会有很多误差。于是，英国团队使用数学方法，创建了一个该行星大气层的模型。
And depending on exactly how they modeled the atmosphere, they concluded it was anywhere from 0.01% to 50% water vapor.
根据他们建模的方式，结论是大气层中水蒸气的含量在0.01%-50%之间。
K2-18b is a type of exoplanet sometimes called a super-Earth, but also sometimes called a mini-Neptune.
K2-18b是系外行星，有时候也称作超级地球，但有时候也叫迷你海王星。
And these are both bad names. This planet isn’t really like Earth or Neptune.
这些名字都不够好，因为该行星其实既不像地球也不像海王星。
It’s probably about 8x the mass of Earth, and 2/3 the density.
其质量是地球的8倍，密度是地球的2/3。
It might be more like a gas giant, or more like a rocky planet with a very thick atmosphere.
它可能更像是气体巨星，或者大气层很厚的岩石行星。
We just don’t know! Although K2-18b is technically in its star’s habitable zone,
我们也还不清楚！虽然该行星从技术角度来讲是在其恒星的宜居地带，
we don’t think anything lives there, water or no water.
但我们觉得那里没有生命存在，不管那里有没有水。
It’s really close to its star, taking only 33 days to orbit.
它距离主恒星非常近，环绕一圈只需要33天。
But the star gives off a lot less light than our Sun.
但其主恒星放出的光比太阳少。
So the planet receives a similar amount of light to Earth.
所以该行星受到的光照量与地球类似。
That doesn’t mean it’s habitable, though. The star is a red dwarf, and those are known to frequently emit violent solar flares.
不过，这也不能证明它就是宜居星球。其恒星是红矮星，而红矮星会频繁释放波动剧烈的太阳耀斑。
And because it’s so close, K2-18b is probably being bombarded with dangerous amounts of UV radiation and cosmic rays that are harmful to life as we know it.
而且由于非常近，所以该行星很有可能会受到大量紫外线和宇宙射线的辐射，对生命有害。
This discovery does prove that current telescope tech is still capable of a lot of interesting science, even as astronomers race to build bigger and better ones.
该发现证明，现在的望远镜技术依然能做许多有趣的科学研究，虽然科学家一直在加快脚步做更大更好的望远镜。
But we still want to learn more about what these planets are made of, and what else is in their atmospheres.
不过，我们依然想了解更多有关该行星组成以及其大气层里还有什么的内容。
For that, we still need to wait for the next generation of space telescopes, like NASA’s James Webb Space Telescope and the European Space Agency’s Ariel mission.
为了这个目标，我们依然需要等下一代望远镜，比如美国宇航局的韦伯望远镜和欧洲太空总署的Ariel任务。
Moving a bit closer to home, our next piece of news is that we have a visitor!
在离我们稍近的地方，下一条重磅消息是——我们有客人来了！
For only the second time, astronomers have found a rock from interstellar space flying through our solar system.
这是科学家仅第2次发现星际空间里有石头穿越太阳系。
You may remember ‘Oumuamua, which briefly visited in 2017.
大家可能记得奥陌陌，它曾于2017年短暂经过。
Well, last week, astronomers announced a new object, given the temporary name of C/2019 Q4 (Borisov), which we’ll just call Borisov for short right now.
上周，天文学家宣布发现一个新物体，临时起了名字叫C/2019 Q4，我们现在先简称为鲍里索夫。
And it has been seen in the neighborhood.
科学家在附近发现的它。
It was found at the end of August by an amateur astronomer in Crimea by the name of Gennady Borisov, hence the name.
是克里米亚一位名为鲍里索夫的业余天文学家在8月末发现的，所以起了这个名字。
It’s actually not yet 100% confirmed to be from outside our solar system, but the evidence is looking good.
现在还不能完全确定它来自于太阳系外，不过证据看起来还是比较充分的。
Like ‘Omuamua, Borisov was probably made in a different star system, and was then flung out of the star’s orbit.
像奥陌陌一样，鲍里索夫很有可能是来自不同的恒星系，然后从轨道脱离出来了。
So now it’s a chunk of rock that’s just randomly floating through space between the stars, and which happened to come near the solar system.
所以，现在它如同一块石头一样在不同的恒星间穿梭，然后又恰好经过了太阳系。
Which means that by learning more about it, and other objects like it, we can maybe learn something about the formation of star systems beyond our own.
也就是说，如果能了解更多与它有关的内容，我们或许可以了解太阳系外的恒星系组成。
For instance, Borisov is probably more comet-like than ‘Oumuamua.
比如，鲍里索夫很有可能比奥陌陌更像彗星。
It looks fuzzy, so we think it probably has a thin, gaseous envelope, or coma, around it, just like a comet.
由于图片失真严重，所以我们认为它很有可能有很稀薄的气体包层/彗形象差，就像彗星一样。
So now we can ask: what do comets from other stars look like?
所以现在要问一个问题：其他恒星的彗星长什么样？
Another neat thing is that we should be able to observe Borisov for up to a year.
还有一件事是：我们应该可以观测它1年的时间。
Oumuamua only stayed around for a few weeks after we detected it.
在我们探测到奥陌陌之后，它只待了几周。
But we’ve spotted Borisov as it’s still getting closer to us.
但我们发现鲍里索夫离我们却越来越近。
And its closest approach is expected to be in December.
最近的时候应该是12月。
At that point, it’ll pass between Mars’ and Jupiter’s orbits.
那时候，它会在火星和木星的轨道之间。
But it’s on what astronomers call a hyperbolic orbit, meaning it’s not actually orbiting the sun;
但它现在在科学家所说的双曲线轨道上，也就是说，它并未环绕太阳。
it’ll take a single big swing past it, and then depart.
它只是经过太阳，然后与太阳分开。
Interstellar rocks like Borisov are rare, but not too rare.
鲍里索夫这样的星际石头很稀少，但也没有稀少到极致。
We think at any given time there’s probably about one interstellar object like this in our solar system.
我们觉得，太阳系里任何时候都会有大概一块这样的星际物体。
But we rarely get a chance to actually watch one pass like this.
但我们很少有机会去观测这种星际物体飞过。
And the European Space Agency may try to send a mission to a future visitor like Borisov to learn even more about these objects, so any data we gather now may help it along.
欧洲太空总署或许可以尝试未来在鲍里索夫等物体上执行任务，了解更多有关这些物体的内容，这样一来，我们收集的任何数据可能都会帮上忙。
But maybe more importantly, it’s a pretty cool reminder that amateur astronomers make awesome new discoveries!
不过，或许更重要的是，它提醒我们业余天文学家也可以做出惊人的发现！
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感谢收看《太空科学秀》，尤其要感谢忠实粉丝，助力节目的发展！
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