宇宙时空之旅（2014）

Cosmos: A SpaceTime Odyssey S01E08

Part 3 April 25, 2021, 12:40 p.m.

恒星大气理论
塞西莉亚·佩恩
那你就要捍卫你的理论
you should defend your position.
权威的话语
The words of the powerful
在人类其他经验性的领域可能会占上风
may prevail in other spheres of human experience,
但是在科学中唯一能让大家信服的只有
but in science, the only thing that counts is the evidence
观点当中的证据和逻辑推理
and the logic of the argument itself.
塞西莉亚·佩恩对于
Cecilia Payne's interpretation
安妮·坎农的恒星光谱分类法的解释
of Annie Jump Cannon's sequence of stellar spectra
让我们第一次有能力去了解
made it possible for us
恒星一辈子的故事
to read the life stories of the stars
并且可以从恒星激烈的死亡中
and to trace the story of life itself back to its beginnings
推断出它生命的开始
in their fiery deaths.
我们的宇宙中有很多种恒星
There are many kinds of stars.
有些如太阳一样明亮
Some are bright like the Sun.
有些则昏暗
Some are dim.
最大的恒星在质量上要比最小的恒星
The greatest stars are ten million times larger
大一千万倍
than the smallest ones.
有些恒星已经有一百亿岁
Some stars are old beyond imagining,
古老得不可想象
more than ten billion years of age.
还有一些此时此刻正在诞生
Others are being born right now.
当原子在恒星中心聚变的时候
When atoms fuse in the hearts of stars,
星光就产生了
they make starlight.
恒星是在残骸中产生的
Stars are born in litters,
组成它们的是星际云中的气体和尘埃
formed from the gas and dust of interstellar clouds.
而残骸中诞生的恒星的质量
The mass of the individual stars in a litter
可以从矮星
can range from the runts
并不比最大的行星大多少
not much larger than the largest planets--
一直到令太阳显得小巧玲珑的超级巨星
to the supergiant stars that dwarf the Sun.
猎户座腰带下面星云中的恒星都是新生的
The stars in the nebula below Orion's Belt are newborns,
大概也就五百万年左右
around five million years old,
它们依旧被包裹在孕育它们的气体尘埃中
and still swaddled in the gas and dust that gave birth to them.
而昴星团中的恒星已经是咿呀学语的小孩子了
The stars in the Pleiades are already toddlers,
大概有一亿年左右
about 100 million years old.
它们已经抛掉了气体和尘埃的包裹层
They've shed their blankets of gas and dust,
但是它们还是被彼此之间的引力所束缚着
but they're still bound together by their mutual gravity.
再过几亿年
Another few hundred million years,
它们就会飘散各奔东西
and they'll drift apart and go their separate ways,
后会无期了
never to meet again.
北斗七星中的大部分恒星都是青春期的少年了
Most of the stars of the Big Dipper are adolescents,
大概有五亿岁左右
roughly half a billion years old.
虽然它们已经从诞生的星云当中飘散开来
They've already drifted apart from their birth cluster,
但是我们还是可以追寻到它们共同的祖先
although we can still trace their common ancestry.
最终它们会在银河系当中完全分散开
Eventually, they'll spread out around the Milky Way galaxy.
但是我们所熟悉的那些星座
But most of the familiar constellations
大部分是由根本不相干的恒星组成的
are a mix of entirely unrelated stars,
有些离得近但是比较暗
some faint and nearby,
有些离得远但是很亮
others bright and far away.
我们的太阳
Our own Sun?
就算从几光年的距离上来看
From the distance of even a few light-years,
我们也很难分辨出太阳
it's hard to find amidst the other stars.
就那个
It's that one.
太阳现在处在中年阶段
Our Sun is middle-aged
距离诞生地已经飘离很远
and a long way from where it was born.
它的姐妹星
Its sister stars,
就是从同一块星际云当中诞生的恒星
hatched from the same interstellar cloud,
已经分散在整个银河系了
are dispersed throughout the galaxy.
它们中的许多都有自己的行星
Many of them have their own planets.
或许还有一些行星培育出了
Perhaps some of them nurture
生命允许生命进行演化产生出智慧
the evolution of life and intelligence.
夜空中的大部分恒星
Most of the stars in our night sky
实际上都有至少一个互相绕行的伴星
actually orbit around one or more stellar companions.
如果只用肉眼
With the naked eye,
在这些双星或多星系统当中我们
we usually can't see the fainter members
没有办法看到那些比较暗的成员
in such double and multiple star systems.
如果一个世界有三个太阳
On a world with three suns,
夜空就会很罕见
the nights would be rare
而白昼也会在红与蓝之间交替变换
and the days might alternate between red and blue.
塌缩是恒星不可逃避的命运
It is the destiny of stars to collapse.
每次你抬头在夜空中看到的成百上千的繁星
Of the thousands of stars you see when you look up at the night sky,
其实都是活在
every one of them is living
两次塌缩之间
in an interval between two collapses...
第一次塌缩是从昏暗的星际气体云中
an initial collapse of a dark, interstellar gas cloud
形成恒星
to form the star,
最终塌缩就是这颗明亮的恒星
and a final collapse of the luminous star
奔赴命运终点
on its way to its ultimate fate.
除非有某种力的干扰
Gravity makes stars contract,
否则引力就会让恒星收缩
unless some other force intervenes.
太阳是一个无比巨大的炽热的气体球
The Sun is a great, big ball of incandescent gas.
太阳核心无比炽热的气体推着太阳向外膨胀
The super hot gas in its core pushes the Sun to expand outward.
与此同时太阳自身的引力
At the same time, the Sun's own gravity
也拉着自己向内收缩
pulls it inward to contract.
太阳现在就在向内的引力
And our Sun is poised between these two forces
和向外的压力之间保持着稳定的动态平衡
in a stable equilibrium between gravity and nuclear fire,
而这种动态平衡还会持续四十亿年
a balance it will maintain for another four billion years.
但随着太阳不停地消耗掉氢
But as the Sun consumes hydrogen,
它的核心会慢慢缩小
its core very slowly shrinks,
同时太阳的表面会相应的逐渐向外扩张
and the Sun's surface gradually expands in response.
这种变化非常缓慢
It happens very slowly,
在长达
imperceptibly,
百万年的过程当中根本无法察觉
over the course of millions of years.
但是大概在十亿年之后
But in about a billion years,
太阳就会比今天亮百分之十左右
the Sun will be ten percent brighter than it is today.
百分之十听起来可能不多
Ten percent may not sound like much,
但多出来的热量对地球有巨大影响
but that extra heat will have a big effect on Earth.
大概四十亿到五十亿年之后
When the Sun finally exhausts its nuclear fuel
当太阳完全耗尽自己的核燃料时
four or five billion years from now,
它的气体就会逐渐变冷压力就会下降
its gas will cool and the pressure will fall.
当太阳的内部压力没办法再承受
The Sun's interior can no longer support the weight
外层的重力时
of the outer layers,
形成恒星的那个初始塌缩就会继续
and the initial collapse will resume.
天下没有不散的筵席
Nothing lasts forever.
纵使恒星也会死
Even the stars die.
氢在一百亿年的聚变过程中
Helium, the ash of ten billion years of hydrogen fusion,
在恒星内核产生了大量的氦
has built up in the core.
没有了核聚变支撑外壳
With no nuclear fire to sustain its weight,
内核会继续塌缩直到温度足够高
the core collapses until it becomes hot enough
点燃氦聚变成碳和氧
to start fusing helium into carbon and oxygen.
现在太阳的内核已经比以前热了太多
The core of the Sun is now much hotter than it was before.
它的大气层不断扩张
Its atmosphere rapidly expands.
在接下来的几十亿年中它就会变成一颗红巨星
Over the next billion years, it'll become bloated
这时候它的大小将会变成
to more than 100 times its original size--
现在的一百倍
a red giant star.
它会包裹并且吞噬水星
It will envelop and devour the planets Mercury...
之后是金星
...and Venus...
甚至最后吞噬地球
...and possibly the Earth.
我倒是希望
I like to think that
在那个遥远的将来到来之前
tens of millions of years before that far distant future,
地球上如果还有生命的话
if there still be life born of Earth,
它们能在群星之中找到新的家
it will have found new homes among the stars.
一旦太阳燃尽了它所有的氦
Once the Sun burns through its helium,
它就会变得非常不稳定
it will become highly unstable,
并且会把它的外层物质抛射到空间中
casting off its outer layers into space.
而裸♥露♥在外无比巨热的内核将会用高能紫外线
The exposed, super hot core will flood its surroundings
淹没周围的一切
with high-energy ultraviolet light.
原子将会上演一出狂野的荧光之舞
The atoms will perform a wild, fluorescent dance.
太阳将会像蛋奶酥一样塌缩
The Sun will collapse like a souffle.
缩小到原来的百分之一跟地球差不多
shrinking a hundredfold to the size of the Earth.
而到那个时候太阳本身会变得如此致密
And at that point, the Sun will be so dense
过于拥挤的电子开始产生向外的推力
that its overcrowded electrons will push back,
这就停止了进一步的收缩
stopping any further contraction.