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Remember Oumuamua?
还记得奥陌陌吗？
It was the interstellar asteroid astronomers spotted last fall, and it got everyone all psyched because it's an interstellar asteroid.
它是去年秋天天文学家发现的星级小行星。这个发现让所有人为之兴奋，因为它可是星级小行星啊。
It came from outside our solar system!
也就是说，他来自太阳系之外！
If we want to study a different part of the galaxy we can't do that because we can't get there but sometimes there comes here!
我们是无法研究系外物体的，因为我们到不了系外，但有物体可以到达系外啊！
But, that object was just passing through, though, so scientists didn't have a ton of time to study it.
但是星级小行星一闪而逝，所以科学家还来不及研究。
But this week, according to a paper published Monday in MNRAS: Letters, there's some good news:
但就在本周一，《皇家天文学会月刊》上发表了一篇论文，称有好消息了：
We seem to have found another interstellar asteroid.
我们似乎发现了另一颗星际小行星。
Except, instead of just visiting our solar system, this one permanently moved in.
不过，这颗星并非如同访客一样，而是永久居民。
The object is named 2015 BZ509, or Bee-Zed for short, and it orbits the Sun in a pretty wonky orbit.
这颗星名为2015 BZ509，简称Bee-Zed，它围绕太阳运行的轨迹并不平稳。
For one, it moves backwards, or retrograde.
一方面是因为，这颗星运行方向与其他星体相反。
It circles the Sun clockwise, instead of the counter-clockwise motion we see in all of the rest of the solar system.
它顺时针环绕太阳运动，但太阳系里的其他星体都是逆时针环绕太阳运行的。
Its orbit is also pretty elliptical, and it's inclined 163° below the ecliptic, which means it's at a really strange tilt.
其轨道也是略椭圆的，与黄道呈163°角，也就是说，其倾斜角度非常奇怪。
Astronomers first spotted this asteroid in 2015, like the name suggests,
天文学家第一次发现它是在2015年，从它2015 BZ509的名字里也能看出来，
but they originally thought it was just part of a class of objects called Centaurs.
不过，起初的时候，科学家以为它是半人马族的小行星。
These are objects, both asteroids and other icy bodies, that hang out between Jupiter and Neptune.
在木星和海王星之间有一些小行星和其他含冰物体。
For the most part, scientists believe these objects originally came from the Kuiper Belt or the Oort Cloud, two regions past Neptune,
科学家偏向于认为，这些物体一开始来自凯伯带，也就是奥尔特云，这两个区域已经越过了海王星，
but got pushed in among the planets by gravitational encounters with other objects.
因为与其他物体之间的引力牵绊而受到了推力的作用。
Because of all that, their orbits are pretty chaotic! Like, that's actually the technical term:
正是如此，它们的运行轨道没有规律，用行话来说：
They are in chaotic orbits, with all kinds of tilts, shapes, and directions.
它们轨迹混沌，倾斜角度、形状和方向都是各式各样的。
Still, Bee-Zed was always especially weird among the Centaurs.
虽然如此，Bee-Zed在半人马族中依然总是非常怪异的存在。
And this new paper has a hypothesis about why: It's not from around these parts.
而这篇发表的论文解释了其中的原因：Bee-Zed并不属于半人马族。
The team ran statistical simulations on lots of objects like this asteroid, tracking their possible orbits over the entire life of the solar system.
该研究小组在很多物体上进行了统计模拟，比如这种小行星，并记录下它们在太阳系整个生命中可能的所有运行轨道。
And they found that Bee-Zed specifically has an unusual, but really stable orbit.
然后，他们发现，Bee-Zed的轨道虽然与众不同，但其实非常稳定。
In fact, it appears that it didn't get nudged toward the Sun like other Centaurs:
实际上，Bee-Zed并没有像半人马族一样被推着朝太阳行进。
It's been hanging around there since the time when the planets formed around 4.5 billion years ago.
自45亿年前这些行星形成以来，Bee-Zed就一直在那个区域活动。
But if it's been around for that long, its orbit should be a lot more normal.
但如果45亿年的时间里，它一直是这样运行的话，那它的轨道应该更正常才对呀。
It should've formed from the same spinning disk of matter as everything else.
Bee-Zed应该像其他星体一样形成才对呀。
And that would mean it would have a similar orbit to everything else.
也就是说，它的运行轨道应该跟其他星体相似才对。
The researchers suggest that Bee-Zed could only have such a strange path if it came from outside the solar system,
这些科学家认为，Bee-Zed的轨道如此奇怪，那就只有一种解释：它来自太阳系外，
and was later captured by the Sun's gravity. Basically, billions of years ago, it immigrated to our neighborhood.
某个时候，它受到了太阳引力的作用，大概是数十亿年前，它迁移来到了太阳系内。
Based on those simulations, it probably wasn't the only one, either.
基于这些模拟情况，可以得出，Bee-Zed可能不是唯一一个这样的小行星。
There may be a bunch of other extrasolar asteroids orbiting on even weirder paths.
可能还有其他一些系外小行星，它们的轨道可能更加怪异。
The simulations showed lots of potential objects congregating on an orbit perpendicular to the solar system,
模拟情况显示，与太阳系垂直的轨道上可能聚集着很多物体，
which the researchers dubbed the polar corridor.
所以科学家将这条轨道称为极面走廊。
If it's real, in more than just the math, it would start a long way away from the Sun.
如果这是真的，那么应该是从离太阳很远的地方开始的。
So if these other objects exist, they'd be orbiting really far out there, even into the Oort cloud around 150 million kilometers away.
所以，如果这样的物体确实存在的话，他们的轨道可能非常远，甚至深入到距离1.5亿千米的奥尔特云中。
And that would help explain why we haven't detected them yet: They'd be really hard to see!
这也就能解释为什么我们还没有检测到它们的存在了：观察难度太高了！
Now, even though this paper made a good case, there's still a chance that Bee-Zed came from somewhere closer to home.
不过，即便这篇论文说的有几分道理，但也不排除另一种可能性：Bee-Zed来自离地球更近的地方。
There's still a lot we don't know about the regions beyond Neptune,
海王星之外的区域，我们还知之甚少，
and this simulation also didn't show the asteroid being directly captured by the Sun or anything.
而这次模拟也不能表明这颗小行星就是受到了太阳或者其他什么物体引力的直接作用。
So it's still not a closed case. But it is a good start and hopefully we'll figure out that it definitely is
所以这个问题还没有定论，但这是个良好的开端。希望我们能找到确定的答案，
and then we'll go visit it and it will be like visiting another part of the galaxy without having to have, like, lightspeed drives.
然后去那里观光，就会像去太阳系的另一个部分一样，不用担心用光速行使的问题。
Meanwhile, in this week's more local news, scientists may have figured out why Saturn has such weirdly shaped moons.
本周的另一则新闻是，科学家可能发现土星为何有形状如此怪异的卫星了。
The planet has at least 62 of them, and lots of the smaller, inner ones have just some wild shapes.
土星至少有62个卫星，其中体态不大、轨道偏内的卫星形状都十分放荡不羁。
Like, there's Pan, which is shaped kinda like a little empanada, and Atlas, which looks like a ravioli.
比如，土卫十八的形状有点像头显卷饼，而土卫十五则有点像馄饨。
And then there's Prometheus, which looks vaguely like a burrito. I haven't had lunch yet.
还有土卫十六，看着像个玉米煎饼，说的我都饿了。
We've wondered for a while why these tiny moons are shaped the ways they are,
我们一直都不明白这些小卫星为什么会长成这个样子，
and thanks to a paper published Monday in Nature Astronomy, we think we know! Based on a combination of modeling processes,
不过好在周一的时候，《自然天文学》上发布了一篇文章，我们现在知道为什么了！在集合了数次建模之后，
the authors suggest those moons got their shapes from specific kinds of impacts between smaller objects called moonlets.
本文的几位作者认为，这些卫星是一些小物体（比如小卫星）之间的特定影响形成的。
To get their results, they simulated a bunch of these moonlets using a mix of N-body simulations and smooth particle hydrodynamic, or SPH, modeling.
为了得到结果，他们模拟了一些小卫星，方法是用N体模拟和光滑粒子流体动力学建模。
N-body simulations describe the gravitational interactions of massive objects hanging out together, and SPH modeling is great for impacts.
N体模拟可以描述一起运行的大型物体之间的引力相互作用；而光滑粒子流体动力学建模则可以体现影响情况。
According to these processes, a few things could happen when the moonlets crashed into each other.
根据这些建模过程，如果这些小卫星彼此相撞的话，是会出点儿问题的。
Depending on the angle they collided, they could either merge, stick together for a bit and then separate, or glance off each other in, like, hit-and-runs.
根据相撞角度的不同，小卫星会合体后分开或者是相撞后即可分开，就像肇事逃逸一样。
In those cases, they didn't merge, and they also probably didn't exchange insurance information.
在这些情况下，它们都不会永远地合为一体，也很可能不会交换保险信息。
Most of Saturn's inner moons seem to have formed when the moonlets stuck together.
大多数偏内的土星卫星似乎都是在小卫星聚集在一起的时候形成的。
And their weird shapes were specifically determined by the angle at which they collided.
而它们的奇形怪状就是由相撞的角度决定的。
In the simulation, oblique collision angles gave more oblong, burrito-like shapes, creating moons like Prometheus.
在模拟中，相撞的角度若是倾斜，就会产生椭圆形的、像玉米煎饼一样形状的卫星，类似于土卫十六。
And more direct collision angles made an equatorial ridge, like on Pan and Atlas.
而相撞的角度若是垂直的，就会产生赤道脊，像土卫十八和十五一样。
These models also apply to at least one of Saturn's larger, more distant moons, too: Iapetus, which also has an equatorial ridge.
这些模型也适用于土星的一个体型更大、距离更远的卫星：同样有赤道脊的土卫八。
Of course, we'd figured for a while that collisions were involved somewhere in these funny shapes,
当然了，虽然我们已经知道撞击的情况对于卫星的形状有影响，
but that's also kind of just the astronomer's fall-back.
但那也只是天文学家的理解而已。
Weird shape? Probably something ran into it. Weird orbit? Probably something ran into it.
形状奇怪是吗？应该是撞击导致的。轨道奇怪是吗？应该是撞击导致的。
Covered in lava? Something ran into it. You get the idea.
火山岩浆奇怪是吗？应该是撞击导致的。
Now, we at least have some serious math to back up that hypothesis!
现在，至少有一些不是闹着玩的数学方法来支持这个假说了！
Well, at least for these moons, not for all the other weird stuff in space.
至少上述卫星是符合该假设的，虽然尚不确定是否其他奇怪的物体都符合。
That will hopefully come later. Thanks for watching this episode of SciShow Space News!
这是我们下一步希望弄清楚的，感谢收看本期的《太空科学秀》！
If you'd like to keep up to date with the latest news from the solar system and beyond, please go to youtube.com/scishowspace to subscribe. Please.
如果大家想了解与太阳系及其以外宇宙有关的最新新闻，请登录并订阅youtube.com/scishowspace吧！
