了解宇宙是如何运行的（2010）

How the Universe Works S06E06

Part 5 Dec. 22, 2021, 7:23 p.m.

Imagine you're living in the far future of the galaxy
你看到夜空中
and you see the night sky
银河系和仙女座正在碰撞
while the Milky Way and Andromeda are colliding.
它看起来将是一个完全不同的地方
It will look like a very different place.
不再是一个横跨夜空的波段
Rather than one band across the night sky,
你会看到有两个，因为两个圆盘聚集在一起
you might have two as the two disks come together.
这将是一个奇迹般的景象
It will be a miraculous sight,
但将是一个与我们今天非常、非常不同的地方
but a very, very different place than we have today.
有了气体云，就能创造出新的恒星
不仅止于此，而且随着新恒星的诞生，它们会产生能量
这是整个银河系的一个连锁反应
新的气体云碰撞，作为回应，新的恒星诞生了
这就是整个系统的连锁反应
这就意味着我们的天空将在数十亿年后再一次点亮
This means our sky will light up for the first time in billions of years.
恒星的形成将在整个星系中闪耀
Star formation will flare across the galaxy.
但现在庆祝是不是太早了？
But is it too soon to celebrate?
两个星系合并期间的
This new round of star formation
这一轮恒星的形成……
during the merger of our two galaxies...
虽然这很酷，但一旦结束
While it's very cool for a little bit,
就会把新星系送入
once it's over, that kind of sends the new galaxy
死亡漩涡
into a death spiral.
当新恒星在这个新星系中诞生时
When new stars are born in this new galaxy,
它们中的许多都将是又热又大的蓝色恒星
many of them are going to be hot, large, blue stars.
最终，这些年轻、炙热的恒星将快速消亡
Eventually, those young, hot stars are going to start to die,
当它们消亡时，它们将以超新星的形式
and when they do, they're going to explode
剧烈爆♥炸♥
violently as supernovae.
这些超新星将开始
And those supernovae are going to start
将气体喷发出星系
blasting gas out of the galaxy.
所有的气体都将消失
All of the gas is gone.
没有更多的物质可以形成恒星
There's no more stuff to form stars.
这就是星系灭亡的原因
And that's what kills a galaxy.
当然“银女星系”要花上亿年
It'll take hundreds of millions of years
才能耗尽造星气体
for Milkomeda to run out of star-building gas.
然后我们的新椭圆星系就会饿死
And then our new elliptical galaxy will starve.
但最后的打击还在后面
But the final blow is still to come.
另一个需要考虑的问题是
Another issue to consider is what happens
两个星系核心的两个超大质量黑洞
to the two supermassive black holes
会发生什么事件
at the cores of the two galaxies.
一开始，它们会绕着彼此旋转
Well, initially, they're going to orbit each other,
并激起很多湍流，然后它们会合并
stirring up a lot of turbulence, and they're going to combine.
因为有很多新的、热的、新鲜的气体
And because there's a lot of new, hot, fresh gas,
我们的新星系将会成为类星体
our new galaxy is going to be a quasar.
这颗类星体会增加热量
And that quasar is going to turn up the heat,
增加湍流
it's going to turn up the turbulence,
这意味着恒星的形成会再次中断
and this means star formation is going to be shut off.
在这些超大质量黑洞的综合力量的
The combined power of the supermassive black holes
帮助下会创造了一个撕裂整个星系的类星体
help create a quasar that tears through the galaxy.
它释放出猛烈的辐射束
It releases ferocious beams of radiation
会穿透银女星系中的形成恒星的气体
that blast through Milkomeda's star-forming gas.
刚刚重生的星系
It's only just been reborn,
刚刚扩大的星系却再次进入死亡倒计时
but our newly enlarged galaxy is once again dying.
像银女星系这样的巨大星系，似乎从一开始就注定要灭亡
Vast galaxies, like Milkomeda, seem doomed from the start.
它们的大小给恒星的形成带来了太多的问题
Their size creates too many problems for star formation.
或者……所以我们在想
Or... so we thought.
我们看到的星系越多
The more galaxies we see, the more we realize
我们就越意识到还有很多我们没有发现的星系
there's a lot out there we haven't discovered,
而且最近又发现了
and there's a new class of galaxies
一类新的星系
only recently identified.
这些星系的质量是银河系的10倍以上
These galaxies are more than 10 times the mass of the Milky Way.
有趣的是，它们仍在形成恒星
And, intriguingly, they're still forming stars.
显然我们遗漏了什么
Apparently we've missed something.
40亿年后，银河系将不复存在，在与仙女座碰撞后，它重生为
一个巨大的椭圆形星系，叫做银女星系
科学家们认为这么大的星系注定要灭亡
4 billion years from now, the Milky Way is no more.
After colliding with Andromeda, it's reborn
as a giant elliptical galaxy called Milkomeda.
Scientists thought galaxies this big were doomed.
那么这是否意味着希望已经出现了吗？
So does this mean there is hope on the horizon?
斯隆数字巡天项目花了10年时间研究了
The Sloan digital sky survey has spent a decade
超过100万个星系
studying over a million galaxies.
它发现了一种罕见但巨大的星系……
It's discovered a rare but enormous kind of galaxy...
一个超级螺旋星系
A super spiral.
这些超级螺旋星系是难以置信的
These super-spiral galaxies are spiral galaxies
超级螺旋星系
that are incredibly super,
我说的“超级”是指它们有4倍的尺寸
and by "super," I mean they have four times the size,
10倍的质量
10 times the mass,
它们非常奇怪因为它们已经
and they're weird because they exceed
超过了螺旋星系的假定重量极限
the supposed weight limit for spiral galaxies.
所以它们不应该有新的恒星，然而并不
So they shouldn't have new stars, but they do.
它们是非常健康的星系
They're very healthy galaxies.
科学家们只发现了53个超级螺旋星系
Scientists have found just 53 super spirals.
超级螺旋星系表明，在极少数情况下
Super-spiral galaxies show that in rare situations,
大质量星系会继续产生新的恒星
massive galaxies continue to produce new stars.
所以，这会是银女星系的生命线吗？
So, is this a lifeline for Milkomeda?
当我们想到两个星系相撞时
When we think about two galaxies colliding,
很多计算机模型都表明
a lot of our computer models suggest
它们会把对方搞得一团糟
that they really mess each other up.
事情变得非常混乱
Things get very chaotic.
但随着时间的推移，它们会回到螺旋形吗？
But over time, could they settle back down into a spiral shape?
事实上，这可能就是超级螺旋的情况
And, in fact, that may be what happens with super spirals.
其中一个线索是，许多超级螺旋星系
One of the clues is that many super-spiral galaxies
有两个核心
have double cores.
不是只有一个超大质量黑洞
Instead of there just being one supermassive black hole,
而是有两个黑洞在相互绕行
there are actually two orbiting each other.
事实上，我们看到的超级螺旋星系有两个核心
The fact that we see spiral galaxies with two cores
它们很可能会碰撞
makes it possible that you could have a collision
并仍然作为一个螺旋星系而存在
and still survive as a spiral galaxy.
因此，也许甚至银河系也有希望在与仙女座碰撞后
So maybe there's hope that even the Milky Way will be a spiral
变成螺旋状星系
once it collides with Andromeda.
这是60亿年后的现场照片……
Picture the scene... 6 billion years in the future.
银女星系在宇宙中漂流……
Milkomeda drifts through the universe...
不是椭圆星系，而是超级螺旋星系
not as an elliptical galaxy, but as a super spiral.
这种形状意味着星系更加稳定
This shape means the galaxy is far more stable.
银女星系的超大质量黑洞
The damaging heat and turbulence
所产生的破坏性热量和乱流
generated by Milkomeda's supermassive black holes
无法扰乱螺旋臂里的造星气体
can't disrupt star-building gas way out in the spiral arms.
我们的银河系非但没有消亡，反而继续存在……
Far from dying off, our galaxy lives on...
比以往任何时候都大
Larger than ever before.
我们已经开始制♥作♥
关于银河系和仙女座星系如何碰撞的计算机模型
所以这两个旋涡星系有可能不会变得一团糟
我们可能会安顿下来，自己成为一个超级螺旋
银河系有一天会成为一个超级螺旋
但这并不是故事的结局
But that isn't the end of the story.
从现在起，数百亿年之后
Tens of billions of years from now,
银河系会继续增长吗？
could the galaxy continue to grow?
我们的本星系群……
Our local group of galaxies...
银河系、仙女座、三角座……
Milky Way, Andromeda, Triangulum...
然后是一系列矮星系……
And then a collection of dwarf satellite galaxies...
都被引力捆绑在一起
Is gravitationally bound together,
最终，我们都被粘在一起
and eventually, we're all glued together
成为一个巨大的物体
into a single massive object.
这意味着什么？
What does this mean?
这意味着我们可能是宇宙中最大结构之一的
This means we might be part of one of the largest structures
一部分
in the universe.
在它十亿年的生命历程中
During its billion years of life,
银河系将变得面目全非
the Milky Way changes beyond recognition.
它经历了无数次的碰撞
It suffers countless collisions,
吞噬了许多较小的星系
feasts on many smaller galaxies,
并产生了无数的恒星
and gives birth to innumerable stars.
我们谈论星系的生命周期……
We talk about the life cycle of galaxies...
它们是如何诞生的，如何以健康的方式创造新恒星
How they're born, how they live healthy lives making new stars,
以及最终如何消亡
and eventually how they die away.
其实并没有那么令人沮丧
It's really not as depressing as that.
宇宙中的一切都在变化
Everything in the universe changes.
像我们这样的星系一直处于不断变化的状态
Galaxies like ours are in a constant state of flux.
所以说到银河系
So when it comes to the Milky Way,
死亡真的不是终结
death really isn't the end.