评论
打印
In 2015, the New Horizons mission introduced Pluto to the world, bringing with it almost as many questions as answers.
2015年，新视野号发现了冥王星的存在。冥王星的发现在解答了一些疑惑的同时，也带来了一些疑惑。
And in a paper published last week in the journal Icarus, astronomers from the Southwest Research Institute tackled one of the most basic of those questions: how did Pluto form?
上周，《伊卡洛斯》期刊上发表了一篇论文，美国西南研究院的宇航员解决了这其中最基本的一个问题：冥王星是怎么来的。
Turns out, it might be more like a giant super-comet than anything else.
他们发现，冥王星更像是一个大型的超级彗星。
Before New Horizons, most astronomers thought Pluto formed like the full-fledged planets, from the protoplanetary disk — the collection of gas, dust, and ice that swirled around the Sun in the early solar system.
在新视野号发现冥王星之前，大多数天文学家认为，冥王星是从行星盘形成的完整星体——由气体、尘埃、冰形成。在太阳系初期就围绕太阳旋转。
But the Southwest researchers realized the data from the flyby supports a very different idea: that Pluto is made out of a bunch of comets crushed together.
但西南研究院的研究人员根据飞近探测得到的数据发现了另一个可能性：冥王星是由许多彗星撞击在一起形成的。
Possibly a billion of them.
数量可能有十亿那么多。
The main evidence for this comes from Pluto's heart, the region known as Tombaugh Regio.
主要证据来自冥王星的内核，这个区域叫汤博区。
Specifically, the left half of it, which is basically one big nitrogen glacier.
确切来说，是汤博区的左半部分，这里基本上就是氮元素组成的冰川。
Nitrogen drives many of the geologic processes on Pluto.
氮是为冥王星的很多地质作用提供了驱动力。
It flows across the surface, might erupt from cryovolcanoes, and makes up the atmosphere.
冥王星的表面到处有氮气流动，冰火山下面也蕴藏着氮气，氮气还是大气层的组成成分。
The thing is, all that nitrogen had to come from somewhere.
问题是，这氮气是从何而来的呢？
Now, it is possible that it came from ice in the protoplanetary disk, which would have had a bunch of nitrogen in it.
有一种可能是：氮气来自行星盘的冰层中，
But it could have also come from comets.
但氮气也有可能是从彗星来的。
We don't know exactly how much nitrogen is in the typical comet, but we do know how much is in 67P, thanks to the Rosetta orbiter.
虽然我们不知道彗星上一般情况下含有多少氮，但我们知道67P的含量有多少，这都归功于罗塞塔号卫星。
Based on that, the researchers came up with a broad estimate for the nitrogen we'd expect to find in comets in general.
基于从罗塞塔号得到的数据，研究人员大致估测了氮的含量。我们认为，其氮含量与一般彗星的氮含量相同。
And when they crunched the numbers, they found that if a billion of those comets came together, they could form a world just like Pluto.
他们结合数据后发现，如果有十亿颗彗星相聚在一起，就会形成像冥王星一样的世界。
At this point, it's hard to tell which theory is more likely.
目前，很难判断哪种理论的可能性更大。
It mostly depends on how much nitrogen Pluto has lost to space over the years.
这主要取决于过去这些年间，冥王星散失了多少氮到宇宙中。
If a lot of it has been lost over time, the idea that Pluto came from the protoplanetary disc is probably a better fit, because it could have formed a world with much more nitrogen than Pluto has now.
如果冥王星散失了很多氮元素的话，那么认为冥王星来自于行星盘的理论可能性就更大，因为冥王星散失的氮元素完全可以组成比冥王星更大的星球。
But if Pluto hasn't lost too much nitrogen, the giant comet model might work better.
但如果冥王星散失了过多的氮元素，大型彗星模型也就具备了极高的可能性。
We just don't have enough data on Pluto yet to know how its nitrogen content has changed.
我们只是没有关于冥王星的充足数据，所以无法得知其氮元素的变化情况。
It wouldn't hurt to get nitrogen measurements for more comets, either.
测量其他彗星的氮元素含量也是多多益善的。
In the meantime, New Horizons isn't done yet.
与此同时，新视野号还没有结束任务。
It's headed for a flyby of another, much smaller object out there, called MU69, on New Year's day of 2019.
新视野号正在前往另一个星球的飞近探测。这个星球体型更小些，名为MU69。新视野号将在2019年新年那天进行飞近探测。
What it discovers could tell us a lot more about what's floating around in the space near Pluto, and might get us closer to understanding how it formed.
新视野号的发现成果可能让我们了解冥王星附近空间里漂浮着的物体是什么，也可能让我们进一步理解冥王星的组成。
Speaking of the more remote ends of our solar system …
现在我们来谈谈太阳系更远的尽头都有什么……
You might have heard of Planet Nine: the unknown planet that might or might not exist far out in the solar system, orbiting between 200 and 1200 times the distance from Earth to the Sun.
大家可能听说过九号行星：这颗不知名的行星可能存在于太阳系里遥远的地方，也可能压根就不存在。如果存在的话，它应该在地球到太阳距离的200倍-1200倍之间的地方运转。
And in a paper posted online this week, researchers discovered even more evidence for it.
在本周网上发表的一篇论文中，研究人员发现了其存在的更多证据。
Planet Nine is probably about 10 times the mass of Earth, a type of planet known as a super-Earth in between smaller rocky worlds like ours and gas giants.
九号行星很可能质量是地球的近10倍。这种行星就是超级地球，它存在于更小的岩石星球（比如地球）和气体巨星之间。
If it's really out there, that is.
如果九号行星当真存在，那其质量就是上面描述的那样。
We've never actually seen Planet Nine, which is why it stays theoretical.
我们从来没有亲眼见到过九号行星，所以说，它一直存在于理论中。
But we have seen a handful of dwarf planets and other small bodies beyond Neptune that all have the same weird, oblong orbits and bizarre inclinations above the flat plane of the solar system.
不过，我们已经在海王星之外发现了许多矮行星等小型星体，它们的轨道都是椭圆形的，十分奇怪。倾斜角度也十分怪异：是太阳系平面向上抬起的角度。
And many researchers don't think that's a coincidence.
很多研究人员认为，这不是巧合。
Instead, they think these orbits come from the gravitational pull of an undiscovered planet, in what's become known as the Planet Nine Hypothesis.
相反，它们认为，之所以会有这样的轨道是因为某个尚不为人所知的行星施加了引力的作用，这个理论也成为九号行星假说。
The team that proposed the current version of the hypothesis in 2016 based their calculations on just six objects with these weird characteristics.
2016年提出该假说现行版本的团队对具备这些奇怪特征的6个物体进行了计算。
But as astronomers have discovered more objects with similar qualities, the evidence for Planet Nine has grown.
但由于天文学家发现的有类似特征的物体越来越多，所以九号行星存在的证据也就越来越多了。
Last week's paper brings the number up to 14.
上周有一篇论文提出，目前已有14个具备这些特征的物体。
The team discovered a new object beyond Neptune, called 2015 BP519, which they nicknamed Caju.
该团队在海王星之外发现了一个新物体，名为2015 BP519，简称Caju。
And it has an even more extreme orbit than the others, following a path researchers had seen in computer models but never in real life.
Caju的轨道比其他物体的更为怪异——这种轨道只在模型里出现过，但在现实生活里还没有人见过。
It also happens to be big enough to possibly qualify as a new dwarf planet.
Caju的体型也十分庞大，可以说是“新型”矮行星了。
It's worth noting that this paper hasn't been accepted for publication yet.
值得注意的是，这篇论文尚未获准发表。
The authors posted it to the preprint website arXiv, but it hasn't been peer reviewed.
文章的几位作者将其递交给了预印网站arXiv，但还没有经过同行审查。
Still, assuming it passes the peer review process, the researchers have just added another big piece to the body of evidence for Planet Nine … at least for those who agree with the hypothesis.
而且，就算这篇文章经过了同行审查，研究人员也要将另一个与九号行星类似的新发现加进去……受众至少有认可该假说的人。
Which not everyone does!
毕竟不是所有人都相信九号行星的存在。
Some think it's possible that these orbits are just a coincidence.
一些人认为，这些奇异轨道的存在可能只是一场巧合。
They could be within the range of what you'd expect, statistically.
从统计数据的角度看，轨道是可以预期到的。
And there could be some bias toward discovering a higher proportion of objects with these weird orbits because of the methods we use to look for things beyond Neptune.
而且也可能有些人会持有偏见，认为不可能再发现更多有这种奇怪轨道的物体了，他们认为我们用来寻找海王星之外物体的方法只能止步于此了。
One way to settle the debate would be to actually, you know, find it.
解决争议的一个方法是找到九号行星。
But first we have to figure out where it is, which researchers are trying to do based on the weird orbits we've found so far.
但首先我们要知道九号行星的位置在哪里。关于这一点，许多研究人员已经在努力根据我们目前发现的奇怪轨道来确认了。
From there, we'd have to spot it moving against the background of stars.
如果真有九号行星，那么在它的发现点，我们一定会看到它像星海移动。
But we'll need a powerful telescope to find it, because even the closest point in its orbit is incredibly far away, and it's dark out there.
但要观测到其存在，我们需要功能强大的望远镜，因为即便是在轨道上离我们最近的点，其实也是非常遥远灰暗的。
Researchers are working on it, but unless we can narrow down the area where Planet Nine might be, there's a lot of sky to cover.
虽然研究人员已经在着手寻找九号行星了，但如果我们无法缩小可能的范围，那就有的找了。
For now, we'll just have to keep looking.
就现在来看，我们还是要不断寻找查看的。
Thanks for watching this episode of SciShow Space News!
感谢收看本期的《太空科学秀》！
If you're interested in learning more about Planet Nine, you can check out our episode about the landmark 2016 research.
如果您想了解更多有关九号行星的知识，就请查看我们关于里程碑式的2016年调查的集锦吧！
