了解宇宙是如何运行的（2010）

How the Universe Works S06E05

Part 6 Dec. 22, 2021, 7:22 p.m.

from supernovas and black holes.
如果不加以控制，星系就会自我耗尽
Left unchecked, the galaxy burns itself out.
但有些星系会有一个宇宙守护者
But some galaxies have a cosmic guardian
创造了安静，和平的社区
creating quiet, peaceful neighborhoods.
有什么东西在控制着恒星的诞生
Something is controlling star birth.
为了形成恒星
In order for stars to form,
你需要冷却的气体，氢分子
you need cool gas, molecular hydrogen,
而类星体绝不是冷的
and a quasar is anything but cool.
它们听起来很酷
They're cool to think about,
但如果你离它们很近的话，它们真的很热
but they're really hot if you're near one.
如果你是一个星系，你准备好
If you're a galaxy, and you're ready to just
要形成一堆恒星
form a bunch of stars,
但这时你的内心出现了一个类星体
but then a quasar turns on in your heart,
这将影响这些恒星的形成方式
that's going to impact how those stars form.
所以星系中低温气体的命运
So the fate of cold gas in a galaxy is incredibly tightly
与整个星系中恒星的形成
coupled to the fate of star formation
紧密相连
throughout that galaxy,
我们认为类星体在它们周围的环境中
and we think that quasars deposit so much energy
沉积了大量的能量
into their ambient surroundings
它们可以通过加热来阻止
that they can prevent the formation
非常非常冷的气体的形成
of very, very cold gas by heating it up.
类星体将大量的热量
Quasars pump huge amounts of heat
输送到它们的环境中
into their environment.
一种方法是通过一种叫做类星体风的
One way they do this is through an extreme cosmic hurricane
极端宇宙飓风
called a quasar wind.
是一种明亮的光之风
You have a wind of light.
这个超大质量黑洞周围
There's just so much light that's being powered
旋转的物质盘，为这些光风
by this spinning disk of material
提供了非常多的能量
around this supermassive black hole
这些光风可以推动星系核心的
that that light can actually push on the dust
尘埃和气体并将它们
and the gas in the core of the galaxy
快速地向外推
and push it outwards very rapidly,
这些“风”速度可以非常快
and these winds can be really fast.
这种可不是你和我
It's not the kind of wind you and I
习以为常的那种风
are used to thinking about.
它实际上是一股高能粒子流
It's actually a stream of high-energy particles.
在某些情况下，这些粒子可以
In some cases, these particles can be traveling
以每小时数亿英里的速度运动
at hundreds of millions of miles an hour.
星系中形成恒星的冷物质
The cool, star-forming material in the galaxy
就会变得炙热而混乱
becomes hot and turbulent.
原来这些宁静的氢分子云
Instead of having these nice, tranquil clouds
会在重力作用下
of molecular hydrogen
坍塌，而现在却被一股巨大的
collapsing under gravity, now here comes this big,
令人讨厌的类星体风，扰乱了一切
giant nasty quasar wind disrupting everything.
它会使星系的温度升高很多
It's going to basically warm the galaxy too much,
致使那个星系会有
and that galaxy is going to have
我们所说的淬火恒星的形成
what we call quenched star formation,
所以这个星系的新恒星形成的速率
so it's going to have a lower rate of forming new stars
会比我们所预期的更低
than we would expect it to.
在宇宙武器库中，类星体还是一个
Quasars have another star-suppressing weapon
抑制恒星的武器
in their cosmic armory.
有另一种我们认为存在的模式
There's another mode that we think exists,
那就是机械的，或动力学的反作用力
and that is mechanical, or kinetic, feedback,
就是字面上的这个意思吧？
and that is literally this. Right？
那就是动量注入
That is momentum injection.
这是一列由星系的超大质量黑洞
That is a freight train plowing through a galaxy
为动力，以喷射物为货物的“货运火车”
in the form of a jet launched by the supermassive black hole,
而这种喷射物，就像一辆在积雪的街道上铲雪的卡车
and that jet, just like a truck plowing a snowy street,
把物质推开
pushes material out of the way.
喷流把气体推挤到星系的边缘
The jets pulled off the gas to the outskirts of the galaxy.
并释放出巨大的能量
They blow out tremendous amounts of energy.
它们把气体吹走，导致的结果就是
They spit out gas, and what happens
阻止了恒星的形成过程
is it stops the process of star formation.
产生新恒星所需的燃料更少了
There's less fuel for new stars to be made.
类星体变化无常，喷流的作用比看上去更复杂
在某些情况下，他们甚至可能负责制♥造♥恒星
这被称为喷流触发的恒星形成
而且有越来越多的证据表明它的存在
至少在一些星系中，或者至少在整个星系的某些空间尺度上
2017年，天文学家利用“阿尔玛”在凤♥凰♥星团中心喷流的尾迹中
发现了新恒星的形成
喷流驱动恒星形成气体，那么它们又是如何导致恒星形成的呢？
那么这是如何发生的呢？你必需要有一堆冷的气体云
否则就产生不了任何东西
这样沿着喷流轴的那条线上就会增加恒星形成的数量
因为就像扫雪机一样
你把积雪压紧在一起
有了这些“雪”或冷的分子气体中就会在星系中诞生恒星
类星体是个矛盾体
有时会带来破坏
有时会带来创造
它们甚至似乎可以给星系带来平衡
然而，如果它们持续喷出气体
However, if they continue ejecting gas,
就会永久阻止恒星的诞生
they would permanently shut off star birth,
然后杀死它们的星系
killing their galaxy.
幸运的是，它们在造成致命伤害之前就停止了
Luckily, they stop before causing fatal damage.
最终，当星系中心的气体
Eventually, the gas in the center of that galaxy
消耗殆尽时
is going to run out,
就像是一个电灯开关
and when it does, it's like a light switch,
把类星体给关掉了
and you're turning the quasar off.
类星体的燃料是冷却的气体
Quasars are fueled by cool gas.
吹走了它的燃料后，类星体本身就会死亡
Having blown away its fuel, the quasar itself will die.
气体云再次冷却，恒星开始再次重新形成
Gas clouds cool, and stars begin to form again.
但是冷却的气体同样会
But the cooling gas also falls back
流回到超大质量黑洞
towards the supermassive black hole,
于是为类星体的重新点燃提供了新的燃料
providing new fuel for the quasar to reignite.
所以黑洞，在很多方面，可以自动关闭
And so the black hole, in a lot of ways, can shut itself off,
就像你客厅里的恒温器
just like a thermostat in your living room,
如果房♥间太冷，恒温器就会启动
where, if the room gets too cold, your thermostat kicks in.
当温度升高到一定程度时
The heat turns on and gets to a point
房♥间就会变得太热，然后自动调温器就会关闭
where the room is now too hot, and the thermostat kicks off.
当类星体启动时，恒星就会停止形成
When the quasar turns on, it's like you stop star formation,
而当类星体关闭时
and then when it turns off,
恒星又会恢复形成
it's like you've turned star formation back on.
正因为类星体有调节恒星形成的能力，所以
Quasars regulate star formation so that not too many stars
就不会有太多的恒星同时形成
are formed all at the same time.
通过调节恒星的形成
By regulating star formation,
类星体控制了星系未来的恒星形成
quasars control the future star formation of the galaxy.
所以我们以为类星体具有令人难以置信的暴♥力♥现象
So we think as quasars as these incredibly violent phenomenon,
但实际上，它们比你想象的
but in actuality, they are much more subtle and elegant
要微妙和优雅得多
than you might think.
在某种意义上，它们也是一种创造的力量
In a sense, they're a force for creation, as well,
因为它们减缓了恒星在星系中形成的过程
because they are mitigating how stars are forming in galaxies.
类星体的活动很可能
It's very likely that quasar activity
对星系的发展至关重要
is essential for galaxy development,
所以从这个意义上说，类星体的活动
so in that sense, we have an equilibrium generated
产生了一个平衡
by quasar activity.
你可以让他们保持平稳
You could keep them on an even keel.
类星体是年轻星系的必经之路
Quasars are a rite of passage for young galaxies,
从混沌的恒星形成的青少年阶段逐渐过渡到
graduating from chaotic star-forming adolescence
成熟、稳定的星系，就像我们的星系一样
into mature, stable galaxies like our own.
类星体的存在
The existence of quasars
可能对星系的健康至关重要
may be essential to the health of a galaxy.
但我们认为在整个宇宙时间的星系演化中
But we think they play an incredibly important role
它们扮演着极其重要的角色
in the evolution of galaxies throughout cosmic time.
类星体是宇宙中能量最大的
Quasars are the most energetic objects
天体
in the universe.
它们似乎几乎违背了自然法则
They seem to almost defy the laws of nature,
但它们同样也是工具
but they're also tools.
们是让我们了解自己起源的工具
They're tools that allow us to understand our own origins.
我们可以用类星体
We can use quasars to help understand
来帮助我们理解星系的起源，恒星的起源
the origins of galaxies, the origins of stars.
类星体有助于创造稳定的星系
Quasars help create stable galaxies,
而这种稳定的星系可以维持生命
the kind of galaxies that could sustain life.
我们以一种美丽而基本的方式
We are connected to the universe
与宇宙紧密联♥系♥在一起
in a beautiful and fundamental way.
所以类星体，虽然非常狂暴，但它们
So quasars, even though they're incredibly violent,
是星系的一部分
they're a part of galaxies,
也是星系进化的一部分
and they're a part of galactic evolution.
有时候，为了创造，你必须要先毁灭