了解宇宙是如何运行的（2010）

How the Universe Works S06E06

Part 4 Dec. 22, 2021, 7:23 p.m.

That's what actually creates new stars.
所以当一个矮星系经过银河系时
So as a dwarf galaxy passes by the Milky Way,
银河系巨大的光晕
the tremendously massive halo of the Milky Way,
会从矮星系中吸收所有的气体
all of that gas, can draw off material from the dwarf galaxy,
把它们融入到银河系中
adding it to the Milky Way.
就这样，银河系吸走了
So in this way, the Milky Way drains away
其他星系的生命之血
the lifeblood of other galaxies.
在某种意义上，你可以说它是一个吸血鬼
In some sense, you could say it's a vampire
因为吸血鬼会吸取其他东西的生命
because a vampire sucks the life out of other things
来保持自身的青春
so it can remain young.
在130亿年的生命中，我们的吸血鬼星系饱餐了一顿
In its 13 billion-year life, our vampire galaxy has feasted.
吞噬了受害者的生命之血
Consuming the lifeblood of its galactic victims,
银河系变得肥胖起来
the Milky Way has grown fat.
但是这种疯狂的吞噬会不会是
But could this monstrous feeding frenzy be a factor
银河系消亡的一个因素呢？
in the Milky Way's demise?
关键的证据再一次
Once again, crucial evidence
来自斯隆数字巡天
comes from the Sloan digital sky survey.
这个的望远镜不仅能绘制出银河系中的恒星
Their telescope maps the stars in our galaxy,
还能绘制出宇宙中的星系
but it also maps the galaxies in our universe.
看遥远的星系就像回顾时间一样
Looking at distant galaxies is like looking back in time.
因为它们离地球越远
Because the farther away they are,
它们发出的光到达地球所需的时间就越长
the longer their light takes to reach us.
我们看到的最遥远的星系不是现在的样子
We see the most distant galaxies not as they are now,
而是过去的样子数十亿年前的样子
but as they were... Billions of years ago.
所以，当你观察那些星系时
So, when you look at these galaxies,
你看到的是它们非常年轻时的样子
you're seeing them as they were when they were very young,
而你观察这些星系时，他们是最近的样子
and you're seeing these galaxies as they are more recently,
所以你可以看到它们的演变……
so you can actually look at the evolution...
星系是如何随着宇宙的老化而变化的
How galaxies change over time as the universe ages.
在研究这些数据时
While studying the data,
科学家们有了一个惊人的发现
scientists make a dramatic discovery.
他们发现螺旋星系，就像银河系一样
They find spiral galaxies, just like the Milky Way,
正在宇宙中消亡
dying all over the universe.
它们的相似之处是它们的质量
And what connects them is their mass.
螺旋星系的大小
There seems to be an upper weight limit
似乎有一个重量上限
for the sizes of spiral galaxies.
在达到太阳质量的大约1万亿倍之前
Up to about a trillion times the mass of the Sun,
我们看到螺旋星系在继续形成恒星
we see spiral galaxies that continue to form stars,
但一旦它们超过这个门槛
but once they pass this threshold,
星系就会死亡，耗尽恒星
galaxies tend to die and run out of stars.
在吞噬较小星系的
While devouring the star-building gas
造星气体时
of smaller galaxies,
银河系可能已经变得过于肥胖
the Milky Way may have grown obese,
现在它可能会在自己的晚餐中窒息而死
and now it could be choking to death on its own dinner.
但怎么会这样？
But how?
一旦一个螺旋星系足够大
Once a spiral galaxy is sufficiently big,
它就会有难以置信的引力
it's going to have an incredible gravitational force,
所以它吸引的任何气体
so any gas that it pulls to itself
都会以难以置信的速度吸进来
is going to come in at an incredibly high speed.
这些气体会被加热
That gas is going to be superheated.
这种炽热的气体会移♥动♥得非常快
The superheated gas moves so quickly
以至于它没有落入银河系的银心
that it's prevented from falling into the Milky Way.
这些气体能量太大，我们星系的引力无法将其吸进去
The gas is too energetic for our galaxy's gravity to pull it in.
相反，它会停留在银河系周围的光晕中
Instead, it stays in the halo around the Milky Way,
我们银河系的食物供应被阻断了
and our galaxy's food supply is choked off.
最终，我们的星系将会饿死
Eventually, our galaxy will starve.
这只有在银河系超过
This will only happen if the Milky Way
造星重量限制时才会发生
is over the star-building weight limit.
但是一个星系的体重是多少呢？
But how exactly do you weigh a galaxy?
我们衡量一个星系的一种基本方法是
One basic way we can weigh a galaxy
测量恒星在其中移♥动♥的速度
is measure how fast the stars are moving within it.
所以恒星绕星系中心运行的速度越快
So the faster the stars orbit around the center of the galaxy,
星系的质量就越大
the more massive the galaxy is.
这种衡量银河系的方法依赖于重力
This method of weighing the Milky Way relies on gravity.
快速移♥动♥的恒星需要更大的引力来使它们
Fast-moving stars need more gravity to hold them
保持在轨道上
in their orbits,
而更大的引力意味着更大的星系质量
and more gravity means more galactic mass.
当科学家们利用这些信息进行数学计算时
When scientists use this information to run the math,
可怕的真♥相♥大白了
the horrible truth is revealed.
我们已经通过了一个临界点
We've passed kind of a critical level.
银河系的质量对于它自身的健康来说太大了
The Milky Way is far too massive for its own health,
而我们已经进入了末日的开始
and we've entered the beginning of the end.
我们快没油了，我是说真的
We're running out of gas, and I mean this literally.
气体云形成了恒星
Gas clouds form stars,
在它们形成恒星的过程中
and as they form stars, they're used up,
它们已经被耗尽了，所以我们的油箱
and so our gas tank is getting closer and closer
一天比一天空
to empty every day.
关于银河系毁灭的调查
The investigation into the killing of the Milky Way
已经结束
is closed.
判决结果？
The verdict?
贪婪的银河系正在扼杀自己
The greedy Milky Way is killing itself.
经过数百万年的时间，恒星的形成逐渐停止
Over millions of years, star formation grinds to a halt,
星系也随之消亡
and the galaxy dies.
但银河系能复活吗？
But could the galaxy be resurrected?
我们似乎在讲一个非常悲伤的故事
We seem to be telling a very sad story.
我们谈论的是银河系的消亡……
We're talking about the demise of the Milky Way galaxy...
恒星形成的结束……
The end of star formation...
但也许现在写死亡公告
But maybe it's just a little bit too soon
还为时过早
to write the death announcement yet.
希望就在眼前
Hope could be just over the horizon.
在太空和天体物理学中，一切皆有可能
In space and astrophysics, really anything is possible.
令人震惊的银河系垂死的案子已经解决了
The shocking case of our dying galaxy has been solved.
没有杀手
There was no killer.
事实证明，银河系正在将自己吞噬至死
Turns out, the Milky Way is eating itself to death.
但这真的是终结吗？
But is this really the end?
拯救会向我们走来吗？
Could salvation be heading our way?
即使现在银河系的恒星形成
Even if star formation is turning off
已经停止了
in the Milky Way now,
然而我们知道它将要与仙女座星系
we know that it's on a collision course
发生碰撞
with the Andromeda galaxy.
它们正在以每小时
They're moving toward each other
数十万英里的速度向对方移♥动♥着
at hundreds of thousands of miles per hour.
碰撞听起来总是
A collision sounds like something
具有破坏性的
that's always destructive,
但事实并非如此
but that's not necessarily the case.
银河系与我们巨大的
The Milky Way's collision
星系邻居仙女座星系的碰撞
with our giant galactic neighbor Andromeda
将会在40亿年之后才会发生
won't happen for another 4 billion years.
到那时，这两个星系的恒星形成
By then, star formation in both of these galaxies
将完全停止
will have stopped completely.
但一场盛大的会面可能会改变这一切
But a giant meet-up could change all that.
作为一个孤立的星系
As an isolated galaxy,
银河系已经处于逐渐减少的阶段
the Milky Way is already in its wind-down phase.
它不再像以前那样产生那么多的新恒星
It's not producing as many new stars as it used to.
但是有一种方法可以产生新一轮的恒星形成
But there is one way to generate a new round of star formation,
那就是通过星系合并事件
and that's through a galactic merger event.
当仙女座离得足够近时
When Andromeda gets close enough,
两个星系之间的相互引力
the mutual gravity between the two galaxies
会开始把它们拉出去，像太妃糖一样把它们拉出来
will start to stretch them out, pulling them out like Taffy.
恒星会被拉出这些长而环状的飘带
Stars will be pulled out into these long, looping streamers,
然后星系就会
and then the galaxies
从物理上互相穿过
will physically pass through each other.
最终，这两个星系会缩回一起
Eventually, the two galaxies will draw back together again
并合并成一个巨大的星系
and merge into one gigantic galaxy,
到那时，所有的气体云
and at that point, all of these gas clouds
都会闪着变成恒星
will flash into star formation.
当星系合并时，它们会重生
As the galaxies merge, they'll be reborn.
两个垂死的螺旋形星系
Two dying spiral-shaped galaxies
变成了一个有生命的椭圆星系
become a single living elliptical galaxy
称之为“银女星系”(Milkomeda)
called Milkomeda.
想象一下，你生活在遥远的未来