了解宇宙是如何运行的（2010）

How the Universe Works S05E03

Part 2 April 18, 2021, 7:46 p.m.

但当科学家们进行数学计算
But when scientists did the math
看看这样一个中等质量的黑洞
to see if such an intermediate-mass black hole
是否会成长为超大质量的黑洞时
could grow into a supermassive black hole,
他们遇到了一个障碍
they hit a snag.
自宇宙诞生以来
There hasn't been enough time
还没有足够的时间
since the birth of the universe
让中等质量的黑洞
for an intermediate-mass black hole
吞噬足够多的恒星
to eat enough stars
成长为超大质量的黑洞
to grow into a supermassive black hole.
布洛克:似乎没有足够的时间
Bullock: It doesn't seem like there's enough time
让黑洞变得像我们看到的那样大
for black holes to get as big as we see them.
但超大质量黑洞无处不在
But supermassives are everywhere we look.
他们是怎么会在那里？
How did they get there?
它们是怎么长得这么大的？
And how did they grow so huge?
在我们的宇宙中，我们已经发现了小黑洞
In our universe, we've detected small black holes.
我们见过怪物
And we've seen monsters,
超大质量的黑洞质量
supermassive black holes
是太阳的数十亿倍
billions of times the mass of our sun.
但我们几乎没有找到中间的
But we'd found almost none in between.
那么如何从一个小黑洞变成一个大黑洞呢？
So how do you get from a small black hole to a giant one?
宇宙学中最重要的未解决问题
One of the most important outstanding questions
之一就是
in cosmology is,
特大质量黑洞是如何
how did supermassive black holes
变得如此之大的？
get as big as they are?
那是什么时候发生的？
And when did that happen?
黑洞通常被气体和恒星包围
Black holes are normally surrounded by gas and stars,
就像一个吃到饱的自助餐
an all-you-can-eat buffet.
关于黑洞如何成长的一个最好的观点
One of the best ideas for how black holes grow
就是黑洞会做
is that black holes do
我们所期望的事情
what we expect black holes to do,
那就是吃东西
and that is eat stuff.
对于黑洞来说
For a black hole,
宇宙几乎就是它的餐厅
it's almost as if the universe is its restaurant.
在它的菜单上，你会发现恒星、行星
And on its menu, you'll find stars, planets,
气体云和尘埃
and clouds of gas and dust.
那么，暴食
So is binge-eating the answer
是产生超大质量黑洞的答案吗？
to growing a supermassive black hole?
从理论上讲，黑洞应该会随着
Theoretically, black holes should keep on growing forever
它们消耗越来越多的食物而不断增长
as they consume more and more food.
但最近的发现表明
But recent discoveries suggest
宇宙在让它们节食
that the universe puts them on a diet,
在控制着它们的食量
controlling how much they eat.
黑洞是饥饿的他们喜欢吃
Black holes are hungry. They like to eat.
但有时，它们吃得太多
But sometimes, they eat too much,
就会打嗝
and they burp it up.
2015年2月
February 2015.
天文学家报告说 ngc2276 星系中
Astronomers report something unusual
有一些不寻常的现象
in the galaxy ngc 2276.
它看起来就像
it looked like something had taken a bite
被什么东西咬了一口
out of one of its spiral arms.
只有一个中等质量的黑洞
Sitting alone in the void
它的质量大约是
was an intermediate-mass black hole,
太阳质量的5万倍
about 50,000 times the mass of the sun.
有一种理论认为
One theory was that the black hole
黑洞吞噬了周围的一切
had eaten everything around it,
形成了死区
creating the dead zone.
但对黑洞能量爆发的
But the detection of a burst of energy
探测表明
from the black hole suggests
它可能吃了太多东西
it may have tried to eat too much
在这个过程中破坏了食物来源
and, in the process, destroyed its food source,
它打嗝太厉害，导致食物被炸飞了
burping so hard, its food was blasted away.
事实证明，黑洞实际上是非常邋遢的吞噬者
Turns out that black holes are actually very messy eaters.
很多物质在试图吸收的过程中被甩了出去
A lot of matter gets thrown off as it tries to absorb it.
物质向内移♥动♥，变热
So things move in, gets hot.
但是很多物质又被扔了出来
But then a lot of it gets thrown all the way back out.
艾尔斯勒:黑洞不是空间中的真空
Isler: Black holes are not vacuums in space.
它们不会吃掉周围的所有东西
They do not just eat everything around them.
所以它们很乱有些东西进来了
And so they are messy. Some things get in.
他们吸收那些物质并增加了它们的质量
And they take that on. And it grows their mass.
有些东西在他们吃的时候就被扔掉了
And some things are just flung out as they're eating.
黑洞的巨大引力将气体、尘埃
The enormous gravity of black holes sucks gas, dust,
甚至恒星吸向它们
and even stars towards them.
大家都吃过自助餐
Everybody's been to an all-you-can-eat buffet.
但让我们说实话你所能吃的东西
But let's be honest. There really is a limit
是有限度的
to how much you can eat.
黑洞是贪吃鬼他们是贪婪的
Black holes are gluttons. They're greedy.
他们不知道自己什么时候吃多了
They don't really know when they've eaten too much.
它们不断地塞进越来越多的食物
They just keep on cramming in more and more food.
它不会直接掉进去
It doesn't just fall in.
它或多或少都要被浪费掉
It has to go down the drain, more or less.
所以它在洞周围形成了这个圆盘
And so it forms this disk around the hole.
形成圆盘的时候，会有很多
And as it does that, there's a lot of turbulence
湍流和磁场
and magnetic fields
还有一种女巫的力量在那里
and a witch's brew of forces going on there
使它变得非常热
that get it really hot.
随着气体和尘埃的旋转
As the gas and dust swirls around,
它会变热
it heats up,
将温度推高至数百万华氏度
pushing temperatures to millions of degrees fahrenheit.
这种漩涡叫做吸积盘
This swirl, called the accretion disk,
也会产生强大的磁场
also generates powerful magnetic fields.
这些磁场被黑洞的旋转所牵引
These fields are dragged by the spin of the black hole
集中在两极之上
and become focused above the poles.
随着能量的积累
As energy builds up,
磁场变得非常强大
the magnetic fields become so compressed
它们会爆发出超能量粒子
they blast out super-energized particles.
这些光束实际上非常强烈
These beams can actually be incredibly violent.
物质以接近光速的速度
Matter is flung out
被甩出去
at a large fraction of the speed of light.
它是一股巨大的风
It's a tremendous wind
从黑洞吹出去
that blows very hard away from the black hole.
喷流击中黑洞周围的
The jet hits the gas clouds
气体云
surrounding the black hole,
将“自助餐”吹走
blowing the buffet away.
如果它们吃得太多
If they eat too much,
它们几乎会把周围的一切
they can basically blow everything
全都吹走
that's in their vicinity away.
他们失去了食物供应然后他们就会饿死
They lose their food supply. And then they're gonna starve.
他们可以搬起石头砸自己的脚
They can kind of shoot themselves in the foot.
由于没有食物
With no food available,
黑洞停止生长
the black hole stops growing.
天文学家认为这就是
Astronomers think that's what happened
他们在死区发现的
to the intermediate-mass black hole
中等质量黑洞的情况
they discovered in the dead zone.
这些打嗝可以调节恒星的形成
These burps may regulate star formation
阻止黑洞变得肥胖
and stop the black hole from getting obese.
但随着时间的推移
But over time,
黑洞会再次开始
the black hole will start eating again
吞噬气体
as gas falls back towards it.
但是，一个中等质量的黑洞是否能够吃掉足够多的东西
But can an intermediate-mass black hole eat enough
从而变成一个质量达数十亿个太阳质量的
to become a supermassive black hole
超大质量黑洞呢？
weighing billions of solar masses?
黑洞会因为吃东西而变得如此肥胖吗？
Could that black hole become so obese by eating?
这是一个非常有趣的问题
That's a really interesting question.
你得吃很多才会有
You'd have to eat a heck of a lot
那么多脂肪
to get that fat.
想想看，如果一个星系平均有
When you think about it, if you imagine an average galaxy
1000亿颗恒星
has 100 billion stars,
那么黑洞必须吃掉星系中
the black hole would have to eat one
每五颗恒星中的一颗
in every five stars in the galaxy.
宇宙是古老的但它的年龄真的足够大
The universe is old. But is it really old enough