评论
打印
Dark matter, dark energy, there are all kinds of things in space that we have yet to figure out.
包括暗物质、暗能量在内，宇宙里有各式各样有带我们探寻的东西。
But your real hipster astronomers don’t worry about famous mysteries like that.
但淘气的天文学家并不沉浸于上述众所周知的谜题。
They worry about stuff like the missing baryon problem: the fact that around a third of the regular, ordinary matter in the universe has refused to show up on any telescopes.
他们感兴趣的是重子失踪问题：宇宙里有1/3的常规物质即便通过望远镜也看不到。
At least, until now. In last week’s issue of the journal Nature, an international team of astronomers reported that they’ve finally found evidence of the missing matter.
至少目前为止，有一组国际天文学家上周在《自然》杂志里发表的文章指出，他们终于发现了消失物质的证据。
Honestly, it was right where everyone expected it.
其实，它就在大家都能想到的地方。
But it took decades of new techniques, new telescopes, and new knowledge to finally find it.
但我们动用了许多新技术、望远镜和新了解的情况才最终发现了它。
We have lots of ways of figuring out how much stuff is in the universe.
我们有很多办法能确定宇宙里物质的含量。
For example, we can look at the Cosmic Microwave Background, the echo of the Big Bang whose colorful pattern depends on the universe’s early makeup.
比如，我们可以通过观测宇宙微波背景，也即宇宙大爆炸的回声来确定含量，因为它的颜色模式取决于宇宙初期的组成情况。
Or we can see how quickly the universe expands, which depends partially on the gravitational pull of all of its matter on all of the other matter.
我们还可以通过宇宙扩张的速度来确定含量，因为该速度在一定程度上要受到它与其他物质之间引力作用的影响。
We can also look at how quickly early structures formed.
我们还可以通过初期结构的组成方式来确定含量。
The list goes on from there, but one of the greatest achievements of modern astronomy is that all our independent measurements using different techniques tell pretty much the same story.
可以依据的元素有很多，但现代天文学最伟大的成就之一就是使用不同技术进行的独立测量都指向了同一个结果：
Most of the universe is dark energy, a poorly-understood, nonstop pressure spreading apart space.
宇宙大部分是由暗能量组成的，我们对暗能量知之甚少，只知道它是在宇宙里延伸开来的、不间断的压力。
Then, most of the rest is dark matter, a kind of something that exerts a lot of gravity but doesn’t emit or absorb any light.
此外，剩下的大部分都是暗物质。暗物质对其他物体有极大的引力作用，但不会发光，也不会吸收光。
Finally, a measly 5% of the universe is ordinary matter, or baryonic matter, it’s the kind that we and the Earth and the stars are made of.
最后一点是：宇宙里只有5%的部分是普通物质，也就是重子物质。正是重子物质组成了人类和地球。
Everything we’ve ever seen or touched, all the countless stars and planets, all of that is just 5% of what’s out there, with the rest being stuff that we fundamentally don’t understand.
我们所见所感的一切、那些数不清的恒星和行星，所有这些加起来不过占了5%。剩下的所有东西，我们都根本不了解。
Except, there’s also a problem: We can’t actually find a big chunk of that ordinary matter.
此外，我们还遇到了一个瓶颈：连重子物质，我们也只找到了冰山一角而已。
When we count up the matter in all the stars, galaxies, and gas clouds we can see and then extrapolate, we find that ordinary matter makes up only about 3% or so of the universe.
在细数我们能观测到的以及能推测出的所有恒星、星系、气体云中所含的物质后，我们发现，重子物质只占宇宙的3%左右。
That means around a third of it is missing from our observations: We know it’s there from all those other measurements, but we haven’t seen it with our telescopes.
也就是说，有1/3的部分是我们观测不到的：我们通过观测得知这1/3确有其事，但通过望远镜却观测不到。
And this is just normal matter!
而且这只是普通物质啊！
This is the stuff that should be relatively easy to find!
普通物质找起来应该相对容易才对呀！
Astronomers have dubbed this “the missing baryon problem”, where baryonic matter is stuff made of protons, neutrons, and electrons.
天文学家将这种现象称为“重子失踪问题”。所谓重子就是由质子、重子、电子组成的物质。
Most physicists have a slightly different definition of baryon, but this is the one many astronomers use.
大多数物理学家对重子的定义都稍有不同，但上面这个是许多天文学家都认可的一个定义。
So far, researchers have mostly assumed that the missing baryons are hidden in certain immense filaments of gas that sit between galaxies, generally known as the Intergalactic Medium, or IGM.
目前为止，研究人员基本上的假设是：失踪的重子隐藏在了星系之间的大量气体中，也就是星系际介质中。
The IGM can be millions of degrees Celsius, but the gas in it is so sparse that it would feel cold if you were in the middle of it.
星系际介质温度可达数百万摄氏度，但由于其中空气稀疏，所以人类置身其中会感觉很冷。
Astronomers think that a huge fraction of the universe’s mass is tied up in these filaments, but the IGM is hard to investigate directly.
天文学家认为，宇宙中的许多物体都隐藏其中，但很难直接探测到。
See, it’s mostly ionized hydrogen, or hydrogen that has lost its one and only electron.
基本上这里面都是氢离子，也就是失去了唯一离子的氢原子。
But atoms give off and absorb light when the arrangement of their electrons changes.
但当原子的电子排布发生变化时，原子会释放或者吸收光。
So if the hydrogen in the IGM has no electrons, it won’t absorb or emit any light.
所以，如果星系际介质中的氢原子失去了电子，那么它就不会再释放或者吸收光了。
Which makes it really difficult to study.
这样就使得研究难度加大了。
Thankfully, research over the last few decades has also indicated that there should be a tiny amount of ionized oxygen in the gas, too.
不过！过去几十年的研究表明，空气中也有少量氧离子。
Oxygen starts out with more electrons than hydrogen, so when it loses some and becomes ionized, it still has others left over.
由于氧原子的离子比氢原子多，所以即便失去几个离子变为氧离子后，也还有富余。
So we can try to see it.
所以氧离子就是可见的了。
And from there, we can extrapolate how much other stuff is in those filaments of the IGM.
据此，我们可以推断出星系际介质还有多少其他物质。
To find evidence of that miniscule amount of oxygen, the astronomers in this new paper used the European Space Agency’s XMM-Newton, an orbiting X-ray telescope that can see the kind of light that interacts with ionized oxygen.
为了寻找少量氧离子的蛛丝马迹，撰写这篇论文的天文学家就使用了欧洲太空总署的射线成象望远镜-牛顿卫星，这颗卫星也是一个X光望远镜，可以看到跟氧离子相互作用的光。
But there’s so little oxygen in the IGM that it doesn’t just shine like a star;
但星系际介质中的氧含量太少了，所以亮度远比不上恒星；
you need a huge flashlight lighting it up.
要用巨型手电筒照亮才会看到。
For this team, that flashlight was a distant type of quasar sitting conveniently far behind the gas.
就这篇论文的情况来说，星系际介质背后很远的地方有一个类星体可以起到巨型手电筒的作用。
These are objects powered by black holes that emit tons of radiation, more than many galaxies.
这种类星体的能量从黑洞而来，而黑洞放出的辐射巨大，超过了许多星系加起来的总量。
They looked at the quasar for about 18 days total over the course of two years, and all their observations told them that some of the its light was getting absorbed by the IGM’s oxygen on its way to Earth.
他们在两年的时间里总共花费了近18天的时间来观测这颗类星体。观测结果表明：其中部分光在传播到地球的途中就被星系际介质中的氧离子吸收了。
Based on how much light was absorbed, and how much oxygen we think is in the IGM compared with other elements, the team concluded that there’s exactly enough matter in the IGM to account for the missing baryons.
根据吸收光的总量以及我们估算的星系际介质中氧离子与其他元素的比例，研究人员推断，星系际介质中物质的总量已经达到了失踪重子质量的标准。
Even with two years of observations, though, this isn’t the end of the mystery.
虽然观测已经进行了两年，但谜题还是没有完全解开。
The team admits that there’s still a lot of uncertainty, and that we need to look at more filaments of IGM before the problem will truly be solved, just in case this gas is an anomaly.
该研究小组承认还有很多不确定的地方，也承认我们需要观测更多的星系际介质才能真正解决失踪重子的问题。毕竟，这些气体就是个奇葩也说不准呢。
But this paper does show that there’s a light at the end of the tunnel and that our hypotheses are on the right track.
但这篇论文确能证明的是：隧道的尽头是有光的，而且我们的假设方向是对的。
And once the missing baryon problem is solved, we’ll just need to figure out the other 95% of the universe, and we’ll be all set!
先解决失踪重子的问题，再弄明白其余95%的物质，就完活儿了！
Thanks for watching this episode of SciShow Space!
感谢收看本期的《太空科学秀》！
If you would like to keep learning more about the universe and how weird and cool it is, and stay up-to-date with astronomers’ newest findings, we’ve got you covered.
如果您想持续了解宇宙，了解它的怪异、它的奇妙，就请持续关注天文学家的最新发现吧！我们节目里都有哦！
You can go to youtube.com/scishowspace for more videos and to subscribe.
您还可以订阅youtube.com/scishowspace，以观看更多的精彩视频。
