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Where Does the Solar System End?

欢迎来到SciShow Space 我是CaitlinHofmeister 对天文学来说 看起简单的问题
I’m Caitlin Hofmeister and welcome to SciShow Space. As is often the case in astronomy,
答案可能不那么简单 这是常有的事 比如
a seemingly simple question does not necessarily have a simple answer. For example, where does
our solar system end? As in where does our stellar neighborhood stop and where does the
浩瀚无垠 看不到边的太空起点在哪里这个问题实际上在2013年的夏天引起了
vast expanse of space start? This question actually caused quite a kerfuffle in the summer
相当大的混乱 当时无数新闻媒体发布公告 1977年着陆的航行者1号发射器
of 2013 when many news outlets proclaimed that the Voyager 1 spacecraft, launched in
最终正式留在了太阳系 尽管航行者已经明显比
1977, had finally and officially left the solar system. While it’s clear that Voyager
之前任何一个人造物能到达的地方远得多结果表明 还是不能从真正意义上
has traveled farther than any human-made thing before, it turns out you can’t actually
一劳永逸地说它已经穿过了太阳系 因为关于太阳系实际尽头的定义
say once and for all that it has crossed out of our solar system because there are different
是千差万别的 空间站称 太阳系的尽头真的是极其复杂的
ways of deciding where our solar system actually ends. Space: turns out it’s pretty complicated.
那么还有七个其他的星球 很多矮行星 无数小行星以及彗星
So there are seven other planets, many dwarf planets, countless asteroids and comets, and,
当然了 地球也是绕着太阳运行的 我们都有一个共同点
of course, Earth all orbiting the Sun, and we all have one thing in common that makes
让我们成为了宇宙附近最酷的组合 也就是我们都受太阳的引力效应影响
us members of the coolest club in the cosmological neighbourhood: our gravitational attraction
大多数人的想法是 只要绕太阳运行就靠直觉简单定义为
to the Sun. By most thinking, just orbiting the Sun is an easy and intuitive way to define
太阳系以内了 但是 太阳的引力效应在太阳系也有失效区
the Solar System and its limits. But, the Sun’s gravitational attraction starts to
也是我们称为奥尔特云团 那是一个巨大的零散
fizzle out in part of the Solar System called the Oort cloud which is an enormous and odd
冰状物聚集区 绕行轨道距离太阳150万公里远
collection of icy objects orbiting the Sun 150 trillion kilometers away. That’s 100,000
那是我们与太阳距离的十万倍所以 那里肯定就是太阳系的终点了
times farther from the Sun than we are. So that must be where the Solar System ends,
对吧 没错 但是 那里还不是航行者的终点假如我们以奥尔特云团为界
right? Well, yes, but that’s not where Voyager is. If we use the Oort cloud as our definition
of the boundary, then Voyager actually has a really, really, really long way to go. It
won’t even enter the cloud for another 300 years, and it won’t pass out of it for another
云团 到了那时候 我可能 呃 是个用玻璃罐子保存起来的脑袋 如果有
30,000. By then I’ll just be, like, a preserved head in a glass jar… if there are glass
But this isn’t even the threshold that got the media’s knickers in a twist. Another
way of defining the Solar System is not by the Sun’s gravitational influence, but by
而是其放射物的影响程度 考虑到太阳系之外的东西 在局部星际

the influence of its radiation. Consider what’s outside the Solar System. The local interstellar
之间 众所周知 是由物质 气体 尘埃和
medium, as it’s officially known, is made up of matter; gas and dust and particles that
在星系之间悬浮的微粒组成的 现在太阳推动这些
hang out in the areas of space in between star systems. Now the Sun pushes this interstellar
medium out of the way with a high-speed stream of charged particles called the solar wind.
This stream flows in all directions from the Sun, forming a bubble called the heliosphere.
The boundary of this bubble is where the solar wind can no longer overpower the outside pressure
星际媒介 而太阳风暴首先相互作用更强的的星际媒介
of the interstellar medium. And as the solar wind begins to interact more with the interstellar
medium, it slows abruptly forming a shock wave known as the termination shock. Just
而冲击波之外 太阳系几乎像司机猛踩刹车一样
beyond the shock wave, the solar system kind of piles up suddenly like a driver slamming
快速堆积 把每个冲击波都向外发射 这个地方
on the brakes and sending everyone flying forward. The area where this radiation bunches
的辐射堆积称为日鞘 太阳风暴会持续
up is called the heliosheath. This continues until the pressures of the solar wind and
the interstellar medium balance out forming the final boundary known as the heliopause.
所以穿过这最后的边界线 即太阳风顶层 航行者于2013年八月进入
So it’s through this last border, the heliopause, that Voyager crossed in August of 2013, putting
the spacecraft into what one astronomer called “a mixed transitional region of interstellar
当然了 也没有类似的环形场作为航行者离开
space.’ Of course, that doesn’t have the same ring to it as “Voyager has left the
的场地 因此当我们知道航行者1号进入星际空间的时候
building.’ So while we know Voyager 1 has entered interstellar space, saying it’s
left the Solar System is actually misleading. It still has a rough ride ahead of it through
奥尔特云团的过程 它还将感受到太阳引力效应的拉力
the Oort cloud and it’s going to be feeling the Sun’s gravitational pull for tens of
几万年之久 那么你现在知道了专家知道的 你就放松
thousands of years. So now you know what the experts know and you can sit back and enjoy
the rest of Voyager’s journey, and we’ll give you an update in about 300 years.
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