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It might not always seem like much, but the solar system is a really big place.
太阳系似乎没多大，但它实际上很辽阔。
It's almost stupidly big.
它大得惊人。
Normally, we just think about the planets and maybe the asteroid belt,
通常，我们只想到行星或者小行星带，
but it includes a lot more than that.
但它不只是这些天体。
And to make sense of it all, astronomers break things up into regions where the objects are more or less similar.
为了理清这一切，天文学家按照天体的相似程度划分区域。
Beyond Neptune, and before you get to a group of icy objects called the Oort Cloud,
在海王星和一组被称为奥尔特云的冰冻天体之间，
there are two big transition regions called the Kuiper Belt and the scattered disc,
有两个过渡区域，叫做柯伊伯带和离散盘，
and together, they form the frontier of modern planetary science.
它们一起构成了现代行星科学的前沿。
The Kuiper Belt stretches from about 30 to 55 astronimical units, or AU.
柯伊伯带从距日大约30个天文单位延伸到55个天文单位（AU），
One AU is the average distance from the Earth to the sun,
一个天文单位是地球到太阳的平均距离，
and astronomers use it to describe large distances.
是天文学家用来描述远距离用的。
After about 55 AU, the scattered disc starts.
55个天文单位之后是离散盘。
The objects in both these regions are the frozen leftovers of when the planets formed.
这两个区域的天体都是行星形成时的冰冻残留物。
Back in the early history of the solar system,
回到太阳系的早期历史，
they were all tossed around when the giant planets migrated outward.
当巨大行星向外迁移时，它们都被甩在了周围。
Kind of like when you go grocery shopping and push your leftovers to the back of the fridge.
这有点儿像你去杂货店购物，然后把你的剩余物推到冰箱里面。
Now, the Kuiper Belt is mostly known for being full of icy objects,
现在，柯伊伯带因满是冰冻天体而闻名，
like comets, or for being home to Pluto.
比如彗星，或冥王星的家。
But it's actually defined by something a heck of a lot bigger: Neptune.
但它实际上是由更大的天体定义的：海王星。
Neptune basically rules the Kuiper Belt.
海王星基本上统治着柯伊伯带。
It influences the orbits of most objects that exist there because of an effect called a mean motion resonance.
因为一种平均运动共振效应，它影响着这里大部分天体的轨迹，
These resonances happen at spots where Kuiper Belt objects orbit the sun in a nice, even ratio with Neptune.
当柯伊伯带天体的轨道周期与海王星的比率接近甚至相等时，就会发生共振效应。
For example, Pluto's trapped in a 2:3 resonance,
例如，冥王星的共振比值是2:3，
meaning it orbits the sun exactly twice for every three orbits Neptune makes.
也就是说冥王星围绕太阳转2圈时，海王星恰好转3圈。
And that keeps Pluto from flying off course.
这使得冥王星无法偏离轨道。
Not all Kuiper Belt objects are in resonance with Neptune,
并不是所有的柯伊伯带天体都与海王星共振，
but they're still close enough to be affected by it in some way.
但它们很接近共振，仍会受到某种程度的影响。
And in the region as a whole,
在整个柯伊伯带区域，
these resonances are a stabilizing force and define what it means to be in the Kuiper Belt.
这些共振作为一种稳定力量，定义了它在柯伊伯带的意义。
Beyond about 55 AU, Neptune's influence become weaker and less important.
在距日55个天文单位之外的地方，海王星的影响越来越弱，越来越不重要。
That's where the scattered disc starts,
于是离散盘区开始了，
and it extends all the way to the edge of the Oort Cloud, thousands of AU from the Sun.
它一路延伸到距日数千个天文单位的奥尔特云边缘。
Objects in the scattered disc are...well, scattered.
离散盘区域的天体都是...分散的。
For once, astronomers actually gave something a useful name.
这一次，天文学家给出的名字很有用。
Instead of being neatly ordered by Neptune's gravity,
这些天体没有在海王星的引力下整齐排列，
these objects are much more likely to be disrupted by it,
而更像是被它破坏了，
and that can throw them into some extreme orbits.
被扔到了一些极端轨道上。
Take Eris, a dwarf planet in the scattered disc.
以阋神星为例，它是离散盘区的矮行星。
Its orbit carries it anywhere from 38 to 98 AU, and it's also tilted by 45 degrees,
它的轨道距太阳有38到98个天文单位，45度倾斜，
which means it usually is way above or below the plane of the solar system.
这意味着它通常是在太阳系平面之上或之下。
Now, even though we use physics to draw distinctions between the Kuiper Belt and the scattered disc,
现在，即使我们用物理区分出柯伊伯带和离散盘，
the worlds in both regions are probably pretty similar.
这两个区域的世界仍相当相似。
They're mostly big balls of ice, but that is definitely not as boring as it sounds.
它们大多数是冰球，但绝不像听起来那么无聊。
These regions are normally way more exciting and interesting than anything we could've imagined.
这些区域通常比我们想象的更令人兴奋和有趣。
In 2015, when New Horizons flew by Pluto and its moon Charon,
在2015年，当“新地平线”号飞到冥王星和它的卫星冥卫一时，
it was our first real experience with the Kuiper Belt, and it showed us a ton of weird stuff.
我们有了柯伊伯带的第一次真实经历，它向我们展示了很多奇怪的东西。
For one, their surfaces are covered in a strange organic substance astronomers call tholins,
首先，它们的表面覆盖着一种天文学家称之为“索林”的奇怪有机物质，
and they even seem to exchange the ingredients to make tholins back and forth.
它们甚至会交换成分，使得索林来回摆动。
Also two of Pluto's smaller moons, Nix and Hydra, both rotate chaotically,
而且冥王星的两个小卫星冥卫二和冥卫三，轨迹混乱，
which means it's literally impossible to predict how they'll spin in the future.
也就是说，我们根本无法预测它们未来会怎么旋转。
Then outside the Pluto system, there's Haumea,
在冥王星系统之外是妊神星，
another object in the Kuiper Belt slightly smaller than Pluto.
柯伊伯带里另一颗比冥王星略小的天体。
This year, scientists discovered that Haumea has a ring,
今年，科学家们发现妊神星有一个光环，
making it the farthest known ring system in the entire solar system!
这使它成为整个太阳系中已知的最远行星环！
Basically, the Kuiper Belt is packed with variety,
基本上，柯伊伯带的天体多种多样，
and we're still figuring out what other objects might exist there.
我们仍需弄清楚它还存在什么其他天体。
And since many objects in the scattered disc have extremely elongated orbits,
由于许多离散盘区的天体都有极其细长的轨道，
they might be totally new kinds of strange.
我们对它们可能完全陌生。
Even in the Kuiper Belt, changing temperatures over Pluto's elliptical orbit
在柯伊伯带，改变冥王星椭圆轨道的温度，
means that its atmosphere can more than triple in pressure over the course of a Pluto year,
意味着冥王星一年里的大气压力会增加三倍以上，
which is pretty dang weird.
这相当怪了。
Imagine being on Earth and getting squished by the atmosphere every few months.
想象一下，在地球上每隔几个月就被大气层压扁的样子。
So who knows what's hiding in the scattered disc.
谁知道离散盘区藏着什么呢。
To find out the true range of possibilities, we'll need to study some more objects.
为了找出它真正的可能范围，我们需要研究更多的天体。
Unfortunately, the scattered disc is hard to research because it's really dark that far from the sun,
不幸的是，离散盘很难研究，因为它距太阳远，非常黑暗，
and it's hard to get clear images with our telescopes.
而且我们用望远镜很难得到它清晰的图像。
And sending a probe there would take decades.
发送一枚探测器可能需要数十年的时间。
So for now, we'll focus on learning more about the Kuiper Belt.
所以，目前为止，我们将集中学习更多关于柯伊伯带的知识。
And New Horizons is gonna make that happen.
“新地平线”号将使一切得以实现。
On New Year's Day 2019, it'll fly by a Kuiper Belt object called 2014 MU69.
在2019年元旦，它将飞到柯伊伯带名为“2014 MU69”的天体上。
It might be what scientists call a contact binary,
2014 MU69可能是科学家所说的密接双星，
a pair of objects that orbit each other so closely that they might even touch!
即一对天体紧密旋转，甚至接触！
But we'll know more soon.
但我们不久就知道更多信息了。
Sadly, after New Horizons is finished,
难过地是，“新地平线”号完成任务后，
the Kuiper Belt and scattered disc will go back to just being points of light to us.
柯伊伯带和离散盘对于我们来说只是亮点。
But we've already learned a ton about them,
但我们已经对它们很了解了，
and now we've got a whole new appreciation for all those weird worlds out there.
现在我们对所有这些怪异的世界有了全新的认识。
Thanks for watching this episode of SciShow Space!
感谢您收看本期的太空科学秀！
If you'd like to learn more about what comes after the scattered disc,
如果你想了解更多关于离散盘之外的内容，
you can check out another one of our episodes, where I tell you all about the Oort Cloud!
你可以观看我们的另一期节目，我会告诉你所有奥尔特云的消息！
