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Here's a simple question with a not-so-simple answer: What's it like at the edge of the solar system?
有一个复杂的问题可以用简单的答案来回答，这个问题是：太阳系的边缘是什么样子？
You'd think that space would basically be the same anywhere, except punctuated by different kinds of stars and objects.
大家可能会认为宇宙各处基本上都一模一样，除非受到不同恒星和物体的撞击。
But that's not actually true. The region inside our solar system is distinctly different from the cold, black void outside of it.
但事实并非如此：太阳系内的区域与调养西外面寒冷、黑暗的虚无之地完全不同。
But we didn't know much about those differences until NASA launched the Interstellar Boundary Explorer, or IBEX, ten years ago.
但之前我们不是很了解太阳系内外的区别，直到10年前美国宇航局发射了星际边界探测器(IBEX)。
For almost a decade, IBEX has been mapping out the size and shape of our nice, calm region of space, all without leaving the safety of Earth's orbit!
这10年来，星际边界探测器一直都在勾勒美妙而又平和的宇宙的广度和形态，不过它始终没有离开地球的轨道哦！
And in that time, it's shown us a lot, both about interstellar space and about how special our neighborhood is.
在这期间，星际边界探测器确实向我们展示了很多，其中既包括宇宙空间，也包括我们附近的特殊区域。
It's even debunked at least one popular hypothesis. Now, it's easy to imagine a few different definitions for the edge of the solar system.
星际边界探测器甚至还证实了一个知名假说的错误，现在很容易就能想象出太阳系边缘的几种不同的景象。
You could figure out how far the Sun's light goes or where the influence of its gravity ends,
我们可以知道太阳的光线能传播多远，或者重力的影响范围有多广，
or you could even mark the orbit of the farthest object that travels around it.
甚至也可以勾勒出太阳最远的卫星的轨道是怎样的。
But those all have their own problems. Like, the Sun's light actually travels an infinite distance.
但这几个问题也有各自的症结所在，比如，实际上，太阳光可以无限传播。
And the farthest object orbiting the Sun is far beyond what we can see, so we can't actually measure it.
而且太阳最远的卫星已经超过了我们的视距，所以无法测量。
So to get at an idea of the solar system's boundary, scientists often use what's called the heliosphere.
所以，要想得知太阳系的边界，科学家就要用到日球层。
The heliosphere is the region of space dominated by the Sun's solar wind,
日球层是太空里的一个区域，要受到太阳风导向的控制，所谓太阳风，
a stream of electrically-charged particles that pours nonstop out of its surface in all directions.
就是一股带电粒子，从太阳表面的各种方向源源不断地流出。
The farther away from the Sun you get, the weaker the solar wind is and, eventually, there'd be more particles from interstellar space than from the Sun.
离太阳越远的地方，太阳风就越弱。所以最终从太空里获得的粒子要比从太阳获得的多。
That change happens at a place called the heliopause, and it's a convenient definition for the solar system's edge.
但在日球层顶的时候会发生变化，所以用日球层顶来界定太阳边界是非常方便的。
This is the boundary IBEX is studying, along with a little help from its friend Voyager 1.
这也是星际边界探测器在研究的边界，过程中得到了旅行者1号的一些帮助。
Back in 2012, Voyager 1 became the first human-made object to cross this border and enter interstellar space.
2012年，旅行者1号是第一个穿越此边界并进入太空的人造物体。
It found the heliopause to be about 120 times farther from the Sun than the Earth is, but it could only take measurements of one tiny spot.
虽然旅行者1号发现日球层顶距离太阳的距离是地球的近120倍，但旅行者1号当时只能测量一个小点而已。
Fortunately, that's where IBEX comes in. Even though its orbit never takes it beyond the Moon, IBEX has spent the last decade mapping the entire heliopause.
幸运的是，出现了星际边界探测器，虽然星际边界探测器距离地球非常近，但它用了十年的时间还是得以描绘出整个日球层顶。
It does this by measuring particles called energetic neutral atoms, or ENAs.
方式是测量一种叫高能量中性粒子(ENA)的微粒。
ENAs form at the heliopause when the solar wind slams into the interstellar medium,
高能量中性粒子是在日球层顶形成的，需要有太阳风进入星际介质中，
the collection of gas that fills in the gaps between star systems. It's sometimes called the ISM for short.
所谓星际介质就是各星系之间的桥梁，有时候会用ISM来代指星际介质。
When the solar wind's electrically-charged particles strike the neutral molecules of the ISM, they sometimes steal electrons and become neutral themselves.
太阳风的带电粒子撞击星际截止的中性粒子时，有时候会带走一些电子，从而变为中性粒子。
Then, those freshly-minted ENAs can suddenly travel in straight lines because, without charge, they're no longer deflected by magnetic fields.
随后，这些高能中性粒子可以突然沿直线移动，因为变为中性粒子后，就不再受到磁场的作用。
A tiny portion of them bounce back towards Earth, and an even tinier portion strike the detectors carried by IBEX.
其中一小部分会在受到弹射作用后往地球移动，还有更小的一部分会为星际边界探测器所捕捉。
Seriously, these events are rare: Sometimes, ENAs strike the spacecraft at a rate of only one per hour.
以下情况比较少见：极少数时候，高能量中性粒子每小时只会撞击宇宙飞船一次。
Given that, it's pretty impressive that it took just six months for IBEX to make its first major discovery, which happened in October 2009.
鉴于此，星际边界探测器能在仅半年的时间里，于2009年10月就实现第一次重大发现，这是非常让人印象深刻的。
The spacecraft created our most comprehensive map of the heliopause ever.
星际边界探测器实现了对日球层顶最全面的一次测绘，
And in doing so, it found that one spot was just a bit different than all the others.
继而发现，有一个点与其他点有些许不同。
In one very narrow region of space, a lot more ENAs were being made than anywhere else.
这个点代表着宇宙里有非常小的一个区域，这里产生的高能量中性粒子要比其他地方都要多。
Scientists had long expected to find at least a little variation in the production of ENAs across the heliopause, but this spot was especially surprising.
长期以来，科学家一直希望能在日球层顶发现高能量中性粒子产生的方式有哪怕一丁点儿不同，但这个点的发现尤为惊人。
Astronomers aren't exactly sure why it's happening, but it probably has to do with the influence of interstellar magnetic fields.
天文学家还不确定这个点是如何形成的，八成是跟星际磁场的作用有关。
In the years since, this ribbon-like region has also continued to change, suggesting that the solar system is embedded in a surprisingly dynamic environment.
从发现这个点后的数年来，这个像缎带一样的区域一直都在变化。这表明，太阳系处在一个动态的环境中。
Interstellar space might not look like much, but there's probably a lot going on out there.
星际空间看起来波澜不惊，其实很可能正在发生很多变化。
IBEX also took some of the first measurements of oxygen, neon, and hydrogen atoms coming into our neighborhood from interstellar space.
星际边界探测器还对从星际空间进入太阳系的氧原子、氖原子、氢原子进行了首次测试。
And by comparing the ratio of oxygen and neon atoms it detects, it's shown that our solar system is oxygen-rich compared to the surrounding galactic neighborhood.
而通过对比星际边界探测器测量到的氧原子和氖原子比例，我们发现，太阳系比银河系里的其他区域含氧量高。
Since oxygen is a key component of water, and water is a key component of life here on Earth, this could be a big deal for understanding where we came from.
而鉴于氧是水的主要组成元素，而水又是地球生命的主要成分，所以这从很大程度上可以解释我们从何而来。
Not to mention that we need oxygen to, you know, breathe. But as for why we have so much extra oxygen, scientists aren't sure.
不仅如此，我们还需要氧气才能呼吸，至于为什么地球有如此丰富的含氧量，科学家尚未确定答案。
It could be dumb luck. Elements are spread a little unevenly through the galaxy, and we might've just ended up in an oxygen-rich area.
或许就是一种运气吧，星系中元素的分配有些不均匀，而我们恰好在含氧量丰富的地方。
And it's always possible that we're not really special after all.
非常可能的情况是：我们一点都不特殊。
Oxygen in the ISM could just be locked up in things like ice that don't produce energetic neutral atoms.
星际介质中的氧可以存在于冰等物质中，而冰这种物质是不会产生高能量中性粒子的。
Probably IBEX's biggest discovery to date, though, is actually something it didn't find: a bow shock.
或许目前为止，星际边界探测器最大的发现就是它还没有发现的东西：弓形激波。
Bow shocks are the space equivalent of a sonic boom, and scientists thought one would form where the heliosphere slammed into the interstellar medium.
弓形激波相当于宇宙里的超音波爆声。以前，科学家认为，弓形激波会在日球层顶进入星际介质的时候形成。
But instead, IBEX showed that the Sun is actually moving more slowly relative to the interstellar medium than we'd previously thought.
但根据星际边界探测器获得的数据，太阳在星际介质中的移速要比我们以前所想的更慢。
Combine that with the direct measurements of these interstellar magnetic fields from the Voyagers, and the math just doesn't work out for a bow shock.
将这一点与从旅行者系列星际磁场处获得的直接测量数据放在一起考虑，却无法通过计算得出弓形激波的存在。
So score one for more peaceful interactions with outer space! A decade in, and IBEX has lasted about five times longer than it was designed to.
庆幸我们与外太空之间可以更加和平的相处吧！10年了，星际边界探测器的寿命是当初设计时候的近5倍。
And with no end in sight, it'll keep circling the Earth with its eyes on the solar system's literal final frontier.
在目之所及没有边界的情况下，星际边界探测器将继续环绕地球，探测太阳系的边界究竟在何处。
Thank you for watching this episode of SciShow Space, which is produced by Complexly.
感谢收看本期的《太空科学秀》，由Complexly制作哦。
Complexly also produces a new channel called Nature League, where my friend Brit talks about all things nature,
初次之外，Complexly还创设了一个新的频道，叫做自然联盟，主持人是我的朋友布雷特，节目是与自然有关的内容。
and she has a really great video about organisms that can survive without oxygen that you might want to check out, and we'll link to it in the description. Thanks!
其中有一期视频介绍的生物体可以在没有氧的情况下存活，这期非常棒，大家可能会感兴趣，所以我们将链接放在了描述里。感谢大家收看！
