了解宇宙是如何运行的（2010）

How the Universe Works S05E05

Part 6 April 18, 2021, 7:47 p.m.

铁核变得很不稳定
That iron core becomes unstable
致使恒星塌缩成中子星
and collapses to a neutron star.
如果中子星在快速旋转……
If that neutron star is rapidly rotating ...
这意味着如果它每秒旋转1000次……
that means if it's spinning about 1,000 times a second ...
它会储存大量的转动能
it will have a huge store of rotational energy.
由于中子星强大的磁场的限制
This energy is concentrated as the star shrinks,
这种能量在恒星塌缩时集中在一起
constrained by the neutron star's powerful magnetic fields.
最终，由于无处可去
Eventually, with nowhere else to go,
被压抑的能量从中子星的两极
the pent-up energy bursts from the poles
爆发了出来
of the neutron star.
汤普森: 它可以产生喷射
Thompson: It can make a jet,
就像挤压一管牙膏一样
almost like squeezing a tube of toothpaste.
喷流可以从两端穿透中子星喷射出来
The jet can go punching through the star in each direction.
它本质上是一个磁化炸♥弹♥
It essentially sets off a magnetized bomb
然后产生这些喷射流
that then produces these jets
沿着一个方向穿过中子星
that just go ripping through the star in one direction
并从南北两极喷射而出
and out each pole, the north and the south pole.
这些光束中蕴含的大量能量
And the amount of energy that is packed into these beams
使它们成为死亡射线
make them death rays.
这些都是现代宇宙中
These are the single most energetic events
能量最大的事件
going on in the modern universe.
那么直接撞击地球的可能性有多大？
So what's the likelihood of a direct hit on earth?
有简单的答案吗？我们只是不知道
The simple answer? We just don't know.
伽玛射线暴的问题是
The problem with gamma ray bursts
它们从很远的地方就很危险
is that they're so dangerous from so far away.
实际上可能会有恒星
There actually may be stars out there
即将爆发伽马射线
about to go gamma ray burst
并指向我们，而我们甚至什么都不知道
that are pointed towards us we don't even know about.
我们对天空进行了勘测
We've made a survey of the sky,
我们确实发现了一些危险的恒星
we've identified which stars we think are dangerous,
但似乎并没有看到那根对着我们的“枪管”
and we don't appear to be looking right down
所以也许现在，我们是安全的
the gun barrel, so maybe for now, we're safe.
我们不必熬夜担心
We don't have to stay up late at night worrying about
被伽玛射线暴杀死
being killed by gamma ray bursts,
但宇宙又大又古老
but the universe is big and old,
这就意味着奇怪的事情一直在发生
and that means weird things happen all the time.
在未来我们的太阳系很可能
Our solar system could well be taken out
会被伽玛射线暴摧毁
by a gamma ray burst in the future.
但这是个大宇宙，我们只是个小目标
But it's a big universe, we're a small target,
这对我们来说是很有利的
and that stacks the odds in our favor.
与此同时，天文学家发现了
In the meantime, astronomers have caught
另一个杀手
another killer in the act, and they think that
他们认为这种邪恶的恒星类型
this sinister star type will almost certainly be
几乎肯定会是最终摧毁地球的终极杀手
the same killer that finally destroys the earth.
我们现在知道我们的宇宙
We now know that our universe
充满了杀手恒星
is filled with killer stars
而现在，某处的某个行星
and that right now, some planet somewhere
即将被烤焦
is about to be toast.
但直到最近，我们掌握的
But until very recently, the evidence we had
这场大规模行星屠♥杀♥的证据都是间接的
for this mass planetary slaughter was indirect.
我们已经看到有很多死亡恒星
We've seen that there are a lot of death stars out
一直在炙烤着行星
there that are frying planets all the time.
现在，我们还从未见过
Now, we've never seen any of these planets
那些被恒星摧毁的行星
actually get destroyed by these stars,
有一次除外，事实证明这是一颗
except once, and it turns out that was a planet
可能曾经很像地球的行星
that may have once been much like earth
它绕着一颗曾经很像太阳的恒星运行
and it was orbiting a star that was once much like the sun.
2015年
2015.
天文学家大卫·基平正在仔细研究开普勒望远镜的数据
Astronomer David kipping is poring over data from kepler,
这架太空望远镜用于寻找系外行星，当行星
a space telescope designed to spot alien planets
经过其主恒星前面时就能发现它们
as they pass in front of their host stars.
一颗有着不寻常特征的
A white dwarf star
白矮星吸引了他的眼球
with a very unusual signature catches his eye.
这颗小恒星并没有被一颗
Instead of being dimmed by a neat, round planet,
有序的圆形行星弄得暗淡无光
the tiny star appeared to be surrounded
它的周围似乎环绕着大量正在分解的岩石和尘埃
by vast chunks of disintegrating rock and dust.
我们从这颗白矮星上看到的是
What we're seeing from this white dwarf
它的亮度多次地下降
are multiple dips in its brightness,
有时高达40%的光被遮挡
sometimes as much as 40 percent of the light being blocked,
它们的周期略有不同
and they're all on slightly different periods,
但都大约在5个小时左右
but all roughly about five hours,
这意味着有东西在非常近的轨道上运行
which means we have something orbiting very close in,
并且是成群结队的团簇
but it's in clumps.
这些团簇是什么呢
What could these clumps be?
它们的密度太大，不可能是一群小行星
They were too tightly packed for a swarm of asteroids
而且它们离主恒星太近，也不可能是冰冷的彗星
and too close to their host star to be icy comets.
最好的解释是
The best explanation we had
这颗白矮星周围
was that this wasn't just one planet
并不只有一颗行星
going around this white dwarf star.
它们是非常小的星子
They were very small planetesimals
可能是行星分♥裂♥的产物
that were probably the product of a disintegrating planet.
发现这颗白矮星正在
The white dwarf star had been caught in the act
谋杀它自己的行星
of murdering its own planet.
所以当一颗行星离白矮星非常近时
So a planet which is so close to that white dwarf star
潮汐力与
that the tidal forces,
白矮星的引力相互作为下，撕裂了这颗行星
the gravity of that white dwarf, has ripped apart the planet,
现在我们看到碎片
and now we're seeing the fragments
落到了白矮星的表面
fall into the surface of the white dwarf.
这是一个美丽的发现
It was a beautiful discovery.
我的意思是，我们曾怀疑会发生这个事情
I mean, we had suspected this was happening,
而现在实际上看到了直接证据……
but to actually see the direct evidence with ...
几乎用你自己的眼睛
with almost your own eyes,
你知道，看到这个光曲线
you know, seeing this light curve,
就好比看到一颗行星在你面前解体
seeing a planet disintegrating right before you,
并证实了
was confirmation of something
我们长♥期♥以来的猜测
we had suspected for a long time.
我们只看到一颗恒星杀死了一颗行星
We've only seen one star killing one planet,
但科学家们怀疑，同样的谋杀行为
but scientists suspect this same act of murder
可能在整个宇宙中发生着
could be happening all over the cosmos.
如果白矮星可以摧毁行星
If white dwarfs can destroy planets,
那就意味着90%的恒星
then that means that 90 percent of stars
实际上是有能力摧毁行星的
are actually capable of destroying planets,
所以最终行星是没有安全避难所的
so there's ultimately no safe haven for planets.
这也是一个令人心寒的未来展望
It's also a chilling look into the future.
几十亿年后，我们的太阳
In a few billion years' time, our sun will begin
也将开始转变成白矮星
its transformation into a white dwarf.
首先，它会膨胀
At first, it'll swell up,
吞没内部的岩石行星
engulfing the inner rocky planets,
水星和金星
Mercury and Venus.
现在，这意味着行星
Now, that means that the planets
将在太阳的内部沿着轨道运行
will be orbiting around inside the sun.
通常行星是在空无一物的空间中绕轨道运行
Usually we orbit through empty space.
没有什么能真正改变
There's nothing really to change the way
行星围绕恒星运行的方式
we move around the star.
但太阳内部有大量的气体
But inside the sun is a lot of gas.
会产生阻碍行星的牵引力
We'll be dragging against that.
并会带走行星的能量
And that will take energy away from the planets
行星就会螺旋状地，越来越接近恒星
and they will spiral in, closer and closer to the star.
我们膨胀的恒星会将其外层完全吹走
Our bloated star blows off its outer layers completely,
留下一颗又小又密的白矮星
leaving behind a tiny, dense white dwarf
此时被炙烤的地球
and revealing the scorched earth,
现在正以一个不断减少的死亡螺旋进入太阳
now on an ever-decreasing death spiral into the sun.
如果你离白矮星越来越近
If you're getting closer and closer to the white dwarf,
你就完蛋了，因为最终
you're doomed, because eventually,
你的岩石行星会分崩离析
your rocky planet will be ripped apart.
白矮星太阳的强大引力
The intense gravity of our white dwarf sun
会把内部行星的烧焦残骸
pulls on the charred remains of the inner planets,
一片一片地拉散
and piece by piece, they break apart.
所以如果行星在太阳的外层中存活下来
So if the planets do survive being in the sun's envelope
它们现在就会在这颗白矮星的
and they're now orbiting close to the surface