(单词翻译:单击)
Even though we spend tons of time studying them,
我们即使花了大量时间研究其他星系，
it's impossible for us to visit other star systems, at least, right now.
也不可能造访它们，至少现在不能。
But recently, a visitor from another system came to see us.
但最近，一个其他星系的访客来看我们了。
On October 19, astronomers at the University of Hawaii noticed something new in the sky,
10月19号，夏威夷大学的天文学家们注意到天空中出现了一些新东西，
and at first, it seemed like a regular asteroid, less than half a kilometer wide.
刚开始，它看起来像正常的小行星，直径不到半公里宽。
Except, when they mapped its path through space,
但当他们绘制它在太空的路径时，
they found that it's moving way too fast to be orbiting the sun.
发现它移动得太快了，无法围绕太阳旋转。
That means, as far as anyone can tell,
也就是说，就我们所知，
this newly discovered asteroid is the first one we've ever seen from outside the solar system!
这颗新发现的小行星是我们看到的第一颗太阳系外小行星！
The asteroid is currently known as A/2017 U1,
这颗小行星目前命名为A/2017 U1，
and astronomers have searched for objects like it for decades.
对于这样的天体，天文学家已经搜寻数十年了。
They expect that, when new planetary systems form,
他们认为，当新的行星系形成时，
the planets' gravity should occasionally slingshot some leftover rocks into interstellar space.
行星引力偶尔会将一些剩余的岩石弹射到星际空间。
And every once in awhile, one of those lonely rocks should enter another star system, like ours,
每隔一段时间，某个孤独的岩石就会进入另一个恒星系中，比如我们的太阳系，
carrying chemical clues about the neighborhood it came from.
从而我们也得知了它所在恒星系的化学成分。
But we've never actually seen one of these interstellar tourists before,
但我们之前从没见过星际访客，
which is why A/2017 U1 is so exciting.
这就是A/2017 U1令人兴奋的原因。
At first, astronomers thought that U1 was just a Near-Earth Object,
刚开始，天文学家们以为U1只是个近地天体，
our name for any large rock whose orbit passes near Earth's.
任何经过地球附近的大型岩石轨道都是这么命名的。
But when they calculated its speed and trajectory, they discovered that it can't be an NEO:
但当他们计算了它的速度和轨迹时，发现它不可能是近地天体：
Those all orbit the sun, and U1 is just going too fast to be held, or even slowed down, by the sun's gravity.
近地天体都围绕太阳旋转，但U1的速度太快，太阳引力承受不住，甚至降不下它的速度。
And we don't know of anything along its path that could've sped it up so much.
我们不知道它的路径上有什么能够加速的东西。
Which means it must've fallen toward the sun from somewhere else,
也就是说它一定是从别处落向太阳的，
probably from the direction of the constellation Lyra.
可能是从天琴座的方向来的。
Right now, U1 is rocketing out of the solar system at about 44 kilometers per second,
现在，U1以每秒44公里的速度冲出太阳系，
or almost twice as fast as the average asteroid.
速度几乎是普通小行星的两倍。
And unfortunately, it'll probably never come back.
遗憾的是，它可能不会再回来了。
Researchers all over the world will spend the next few weeks frantically pointing telescopes at U1,
世界各地的研究人员将在接下来的几周疯狂地用望远镜观察U1，
hoping to learn as much as they can about its trajectory, composition, and behavior before it leaves for good.
希望在它永远离开前能尽可能多地了解它的轨迹、构成和行为。
But they don't have long.
但他们时间不多。
After a month or so, it'll be so far from the sun that even our best telescopes won't be able to see it any more.
大约一个月后，它就会远离太阳，即使是最好的望远镜也看不到了。
Now, it's completely possible that all this research will end up revealing a much more normal explanation of U1's impressive speed.
现在所有这些研究结果完全有可能更好地解释U1拥有惊人速度的原因。
After all, it was just discovered, so we hardly know anything about it.
毕竟，它刚刚被发现，所以我们对它几乎一无所知。
And even if it is from somewhere else,
它来自其他地方，
we might not have enough time with U1 to learn much more about where it came from or what it's made of.
我们可能没有足够的时间来了解U1，了解它来自哪里或者由什么组成。
But for now, this rock seems like it's the closest we've ever been to a piece of another star system.
但就目前而言，这块岩石似乎是最接近我们的另一颗恒星系岩石。
So, thanks for swinging by, U1!
所以，U1，谢谢你的光临！
Now, as far as we know, everything else around the sun has been here since the beginning.
目前，就我们所知，太阳周围的一切自诞生就一直在这里。
And one of those rocks is the dwarf planet Ceres in the asteroid belt,
其中就包括小行星带中的矮行星谷神星，
where NASA's Dawn spacecraft has been orbiting for more than two years.
宇航局的“黎明”号已经围着它运行两年多了。
Two new studies, published this month have used data from Dawn to support the idea that Ceres used to have oceans,
本月发表的两项新研究利用了“黎明”号的数据，它们支持谷神星曾经拥有海洋的观点，
by finding ways that the ocean's remnants could still be affecting its surface.
方法是寻找可能仍在影响其表面的海洋残留物。
The first study, published in the Journal of Geophysical Research Planets,
第一项研究发表在《地球物理研究杂志》行星上：
used measurements of Ceres's gravity and shape to calculate the density of rocks on and beneath its surface.
通过测量谷神星的重力和形状来计算其表面和下面岩石的密度。
When there are denser rocks, or something with a lot of mass, like a mountain,
当有密度较大的岩石或质量很重的物体时，比如一座山，
the gravitational pull of that spot will be stronger.
那个地方的万有引力就会强些。
And that can help us figure out what an object is made of.
这能帮助我们计算出物体的构成。
Using this data, the researchers found that Ceres's crust just isn't dense enough to be made of regular rocks,
利用这些数据，研究人员发现谷神星的地壳不够致密，构不成普通岩石，
which we basically already knew.
我们早就知道这些了。
But in this new paper, the scientists proposed that there's water-ice mixed in with the rocks,
但在这篇新论文中，科学家们提出岩石中有水冰，
along with salts and something known as clathrate hydrate, or trapped gas bubbles surrounded by water molecules.
还有盐和被称为笼形水合物的物质，或是被水分子包围的气泡。
And the second study, published in Earth and Planetary Science Letters, found the same thing.
第二项发表在《地球和行星科学快报》上的研究发现了同样的事。
It confirmed and added to those findings by looking more closely at how Ceres's surface seems to have changed over time.
它通过更仔细地观察谷神星表面如何随时间变化，证实并补充了这些发现。
We know that harder rocks like iron tend to keep their shape better than softer or waterlogged rocks do,
我们知道，铁这样的坚硬岩石往往比较软或浸水岩石更能保持形状，
so the more flattened areas on Ceres's surface are probably made of softer, less dense rock.
因此，谷神星表面更平坦的区域可能是由较软、密度较小的岩石构成的。
Except, these researchers also found that Ceres is made of pretty strong stuff.
除此之外，这些研究人员还发现谷神星是由相当坚硬的物质构成的。
So the only way they could reconcile Ceres's low density with its strong crust was
因此，唯一能使谷神星的低密度与坚固地壳协调一致的方法是
if the crust was made of a combination of rocks, ice, salts, and clathrate hydrate.
地壳由岩石、冰、盐和笼型水合物组成。
And if that sounds familiar, that's because that's exactly what the first study's authors found,
这听起来很熟悉，因为它和第一项研究的作者发现得相同。
based on different measurements and methods.
只不过测量方法不同。
All that water in Ceres's crust supports the idea
谷神星地壳中的水支持了这一观点，
that Ceres originally had oceans on its surface that have since frozen or escaped into space.
谷神星表面最初有海洋，它们结冰或者逃到太空了。
Which is pretty awesome for a dwarf planet.
对于一颗矮行星来说，这相当了不起。
The second study's authors also pointed out that Ceres's insides seem weaker than the outer crust,
第二项研究的作者还指出，谷神星内部似乎比外部地壳脆弱，
which could mean that there's still some liquid water leftover after all.
意思是它可能仍残有一部分液态水。
But before you get your submarines ready, we still need more data to be sure.
但在你准备好潜艇之前，我们需要更多的数据来确认。
Fortunately, NASA announced that they'll be extending the Dawn mission a second time,
幸运的是，宇航局宣布他们会延长“黎明”号的任务时间，
and it'll be closer to Ceres than ever before until it runs out of fuel sometime late next year.
它将比以往任何时候都更接近谷神星，直到明年晚些时候耗尽燃料。
So, our interstellar visitor U1 might be speeding away from the solar system,
我们的星际访客U1可能正在远离太阳系，
but we still have lots of cool stuff to study here, too.
但我们仍有很多有趣的东西可以研究。
Thank you for watching this episode of SciShow Space News,
感谢您收看本期的太空科学秀，
which can only exist because of our awesome Patrons on Patreon!
这多亏了Patrons的大力支持！
Thank you to Patrons like Alaina, Zane, and someone who just goes by uh Mike.
感谢阿莱娜、赞恩和刚来串门的麦克。
Not only do you guys have awesome names,
你们不仅名字好听，
you make everything we do at SciShow possible, so thank you.
也在支持太空秀，所以谢谢你们。
If you want to help make SciShow, you can go to patreon.com/scishow,
如果你想帮助制作太空科学秀，请登录patreon.com/scishow。
and we're also conducting an audience survey right now too.
我们会立刻做一份观众调查。
If you want to tell us more about yourself, please click on the link in the description.
如果你想告诉我们更多你的事情，请点击描述中的链接。
