了解宇宙是如何运行的（2010）

How the Universe Works S06E05

Part 4 Dec. 22, 2021, 7:22 p.m.

是什么引发了类星体的点燃？
What triggers a quasar to ignite？
科学家们现在推断，类星体可能是
Scientists now theorize the quasars switching on
星系生命的自然组成部分
may be a natural part of a galaxy's life.
星系不是固定不变的东西
Galaxies are not fixed things.
它们在不断地变化，进化
They're constantly changing, evolving.
当然，我们也会突然看到这些东西启动了
It's also true that suddenly we see these things switch on,
想象一下这种情形是很令人着迷的
and it's kind of mesmerizing to imagine the situation.
在一年的时间内，一个星系可以从正常状态
Within a year's time, a galaxy could go from being normal
变为活跃状态
to being active.
大多数人认为，如果不是全部的话
It's thought that most, if not all,
星系都会经历一个包括形成类星体的
galaxies go through a phase of development
发展阶段
that includes forming a quasar,
类星体是星系成长过程中的一个正常部分
that it's a normal part of a galaxy growing up.
类星体的行为很像一个青少年
Quasars can act a lot like a teenager,
会发脾气
tantrums and all.
这时它们会闪闪发光
This was when they were shining brightly,
以惊人的速度进食
eating mass at an incredible rate.
就像你的青少年时期，你知道吗？
It's almost like your teenage years, you know？
你把看到的东西都吃了，却弄得一团糟
You ate everything in sight, and things were pretty messy.
你可能经历过很多情绪波动
You might have undergone a lot of mood swings.
这有点像类星体
It's kind of like that with a quasar.
当类星体感到饥饿
When a quasar gets hungry
并袭击“冰箱”时，它就可以打开“冰箱”
and raids the refrigerator, it can switch on.
那么是什么触动了这个开关呢？是什么在开启和关闭类星体？
So what flips the switch？ What turns a quasar on and off？
它基本上与气体
It fundamentally has to do with gas
进入星系中心有关
getting into the centers of galaxies.
当物质进入黑洞时，黑洞就等在那里
When stuff gets in there, a black hole is waiting,
然后它就变亮了
and then it gets bright.
那么类星体从哪里找到足够的气体来享用呢？
So where does a quasar find enough gas to feast on？
要开启类星体，需要一定的条件
To turn on a quasar, you need certain conditions.
你需要一个超大质量的黑洞
You need a supermassive black hole,
还需要大量的物质倾倒在它上面
and you need a lot of material dumped on it.
这意味着什么？一个星系碰撞
What does this？ A galaxy collision.
星系不是固定在一个地方的
Galaxies are not locked in place.
它们在太空中移♥动♥
They move through space.
有时,它们会碰撞
Sometimes, they collide.
我们认为，处于核心的
We think that the supermassive black holes,
超大质量黑洞会发生碰撞与合并
at their cores, will collide and merge,
合并后星系的气体供应
and the gas supply from the combined galaxies
流向新的超大质量黑洞
streams towards the new supermassive black hole.
这就像是，当这两个星系合并时
It's almost like, when you have these two galaxies merging,
它们就有了新的食物
that they have all new food.
这是一个全新的餐盘
It's a brand-new dinner plate,
一个全新的自助餐
a brand-new buffet of food to eat.
好吧，那是一个进食源，对吧？
Well, that's a feeding source, right？
你会开始疯狂地
You're going to start a feeding frenzy
吞噬这个黑洞
on the black hole that's sitting there.
气体螺旋进入，加热到几百万度
The gas spirals in, heats up to millions of degrees.
星系核会亮起来
The galactic core lights up.
类星体就这样诞生了
And a quasar is born.
似乎星系合并
It seems galaxy mergers provide
提供了类星体形成的最佳条件
the best conditions for quasar formation,
但当天文学家研究这些不寻常的类星体的
but when astronomers studied the rapid ignition
快速点燃时
of these unusual quasars,
他们并没有发现星系合并的证据
they didn't find evidence of a galaxy merger.
一定是别的什么东西启动了它们
Something else must switch them on.
当我们考虑到一个典型类星体的大小尺度时
When we think about the size scales of a typical quasar,
我们认为它必须花费数年才能真正启动
we think it must take years to really turn on.
如果你认为是一股气流
And if you're thinking about a flow of gas
穿过星系的中心
passing through the central parts of a galaxy
与黑洞相遇，然后激活“发电机”
to encounter the black hole, to activate the dynamo,
并发射喷流
to launch a jet,
这应该需要相当长的时间
this should take a healthy amount of time.
这是……这是一件大事
This... this is big stuff.
那么，什么能加快这一进程呢？
So what could speed this up？
一种观点认为，黑洞周围的气体圈
One idea is that something catastrophic happens
即吸积盘
inside the accretion disk,
内部发生了灾难性的事件
the ring of gas surrounding the black hole.
一个活跃的类星体意味着黑洞正在吞噬一些东西
An active quasar means that a black hole is eating something,
所以当你看到类星体启动时
so when you see a quasar turn on,
你就知道黑洞周围发生了
you know that something
非常严重的问题
went very wrong around the black hole.
也许碟片中的有些东西掉进去了
Maybe some of the disk fell in.
甚至可能有一颗恒星靠得太近了
Maybe even a star got a bit too close.
吸积盘不仅仅是气体和尘埃
Accretion disks are not just gas and dust.
黑洞会把所有东西都拖进去
Black holes will drag in anything and everything.
有恒星有气体
There are stars. There's gas.
气体云中，有恒星正在形成
There's gas clouds. There's stars in formation.
也有恒星正在死亡
There are stars dying.
那里发生了很多事情，但基本上，发生的就是
A lot is happening there, but basically, what happens
恒星靠得太近了
is that star veers too close,
它基本上被剥离了
and it is basically stripped.
它的一部分被分开了
It's pulled apart.
黑洞的巨大引力可以把一颗恒星
The enormous gravity of the black hole
撕成碎片
could tear a star to pieces,
在吸积盘内产生了
giving rise to a sudden surge of energy
突然激增的能量
within the accretion disk.
或者，一颗爆♥炸♥的恒星
Or perhaps, an exploding star
可能是类星体点火的催化剂
could be the catalyst for quasar ignition.
因此，有可能是一颗超新星在吸积盘中爆♥炸♥
So it could be that a supernova going off in the accretion disk
引发了物质的雪崩
triggers an avalanche of material
这些物质就能够突然落入黑洞
suddenly being able to fall in on the black hole.
在这两种情况下，一股突然涌入的热气
In both cases, a sudden rush of hot gas
会加热吸积盘
would heat up the accretion disk,
然后启动了类星体
switching on the quasar.
你需要对一个星系做一些剧烈的事情
You need to do something violent to a galaxy
让它真正得到足够的物质来创造类星体活动
to let it really feed enough to create a quasar activity.
一旦被激活
Once activated,
类星体可以闪耀数百万年
a quasar can shine for millions of years,
并释放出能量和毁灭性的喷流
blasting out energy and destructive jets.
我们就能在宇宙中看到它们
We see them across the universe.
看起来基本的原料是相当常见的
It seems the basic ingredients are quite common,
即使在我们自己的社区
even in our own neighborhood.
我们把这些放在一起
Let's put all this together.
类星体需要什么？需要一个星系
What do you need for a quasar？ You need a galaxy.
你需要在星系中心有一个超大质量黑洞
You need a central supermassive black hole.
你还需要气体，你需要掉进黑洞的物质
You need gas, and you need stuff falling into that black hole
来创造类星体现象
to create the quasar phenomenon.
嗯，我们生活在一个星系，银河系
Well, we live in a galaxy, the milky way,
它的中心就有一个超大质量黑洞
and it has a central supermassive black hole,
附近有气体绕着它运行
and there's gas orbiting around near there.
听起来似乎不太好
That doesn't sound good.
我们的未来看来并不光明
Our future certainly does not look bright.
如果喷射流穿过银河系，热量和宇宙风从核心爆发
就有一个问题……我们会生存下去吗？
Jets ripping through the milky way,
heat and cosmic winds bursting out from the core,
posing the question... Would we survive？
我们习惯地认为我们的星系是和平的
We're used to thinking of our galaxy as peaceful.
如果它隐藏着暴♥力♥的过去呢？
What if it's hiding a violent past？
最近的发现令人着迷
What's been discovered recently is kind of fascinating.
有两个巨大的空气泡
There's two large evacuated bubbles
从我们的星系中心散发出来
emanating from the center of our galaxy.
这些气泡充满了过热的气体
The bubbles are full of superheated gas,
它们正以每小时200万英里的速度
and they're moving out of our galaxy
远离我们的星系
at 2 million miles per hour.
这些泡沫很大
These bubbles are huge.
它们的规模堪比银河系本身
They're on the scale of the galaxy itself.
它们有5万光年长
They're 50,000 light-years long.
它们非常巨大，如果你要在天空中绘制它们
They're so big that if you were to map them out on the sky,
它们会从一个地平线延伸到另一个地平线
they would stretch from horizon to horizon.
这些气泡看起来类似于
These gas bubbles look similar to those seen
那些在遥远的星系团中看到的，比如 hydra a(海德拉 a)