了解宇宙是如何运行的（2010）

How the Universe Works S06E09

Part 2 Dec. 22, 2021, 7:23 p.m.

The temperatures, the distances from the star,
我们发现热木星的地方非常热
where we find hot Jupiters are so hot,
很难想象有什么物质
it's hard to imagine any material
会从恒星云中凝结出来
condensing out of the solar nebula.
这就引发了这样一种想法
This kick-started the idea
也许这些被称为热木星的行星
that maybe these hot Jupiters, as they were called,
实际上可能是在更远的地方形成的
may have actually formed farther out,
就像我们的木星现在所在的地方一样
like near where our Jupiter is now,
在恒系早期
and in the early solar system
它们开始向恒星内部迁移
they started migrating inward toward their star.
那么当木星大小的行星向内移♥动♥时
So what happens when a planet the size of Jupiter
会发生什么呢？
moves inward?
这是否有助于解释太阳系内部质量的缺失
Can this help explain the inner solar system's missing mass
并解释为什么我们没有热木星？
and answer why we don't have a hot Jupiter?
为了找到答案，凯文·沃尔什和他的同事们
To find out, Kevin Walsh and colleagues simulate
模拟了太阳系最初的1000万年
the first 10 million years of the solar system.
他们称这种模式为大轨迹
They call this model the grand tack.
大轨迹模型是一个场景
The grand tack model is a scenario
旨在帮助我们理解
designed to help understand
类地行星是如何形成的
how the terrestrial planets could have formed,
思考巨型行星在太阳系早期可能做了什么。
thinking about what the giant planets
可能做了什么
might have been doing in the early solar system.
这些行星是在环绕新形成的太阳的
The planets form within a thick disk of gas and debris
由气体和碎片组成的厚圆盘中形成的
that surrounds the newly-formed sun.
大轨迹模型模拟了木星通过这个圆盘
The grand tack model simulates what happens if Jupiter moves
向太阳移♥动♥时会发生什么
in towards the Sun through this disk.
它把所有的小行星
It's pushing all of the asteroids in its path
都推到太阳系内部
into the inner solar system.
所有这些物质都会聚集在一起
All of that material is what is going to come together
形成岩态行星
to form the rocky planets.
木星巨大的引力
Jupiter's immense gravity pulls in more
吸引了越来越多的物质
and more material,
形成了密集的碎片波
forming a dense wave of debris bulging out behind it.
隆起的压力将木星进一步向内推
The pressure of this bulge pushes Jupiter further inwards.
就像一个毁灭球一样，木星会清除掉
Like a wrecking ball, Jupiter should clear out
整个太阳系内部
all the planet-building material
所有的行星构成物质
from the entire inner solar system
变成一个充满阳光的炎热的木星
and become a sun-hugging hot Jupiter,
但有些东西阻止了木星的毁灭之路
but something checks Jupiter's path of destruction.
如果木星在太阳系内部停留的时间
If Jupiter had hung around much longer
再长一些，我们就不会在这里了
in the inner solar system, we wouldn't be here,
所以一定有什么东西把它迅速地拉了出来
so something must have drawn it out very rapidly.
是什么能让一个巨大的行星快速移♥动♥呢？
And what could possibly move a big, massive planet rapidly?
答案是另一颗巨大的巨行星
And the answer is another big, massive planet.
土星……
Saturn...
它是在木星之后形成的
It forms just after Jupiter,
当它也向太阳移♥动♥时
and is hot on Jupiter's heels,
它紧跟在木星的后面
as it, too, migrates towards the Sun.
土星本身就很大
Saturn is pretty big itself.
两颗巨行星的迁移
The combined effect of the two giant planets
其综合效应就是
migrating is that once
一旦土星足够大，它实际上可以改变
Saturn is large enough, it can actually change the way
气体盘与两颗行星♥相♥互作用的方式
that the gas disk is interacting with both the planets.
它可以阻止木星向内迁移，并帮助木星
And it can stop Jupiter's inward migration and help to turn
改变方向
Jupiter around
几乎把它拉回外太阳系
and almost pulls it back to the outer solar system.
就像一艘改变方向的帆船
Like a sailboat switching direction,
木星逐渐远离太阳
Jupiter tacks away from the Sun.
巨大的外行星的行为
The behavior of the giant outer planets
使我们的太阳系没有炽热的木星
leaves our solar system with no hot Jupiter
也对较小的内行星产生了巨大的影响
and has dramatic effect on the small inner planets, too.
当它向外返回时
As it's coming back outwards,
木星对太阳系内部做了什么？
what has Jupiter done to the inner solar system?
它移走了沿途的所有物质
It has removed all of the material in its path,
直到我们今天地球所在的地方
all the way down to where we find the Earth today.
所有这些物质被推入太阳系内部的一个窄带中
And all of that material pushed into essentially a narrow band
它们会聚集在一起形成了
in the inner solar system is what is going to come together
我们今天所见的岩态行星
to form the rocky planets as we find them today.
根据大轨迹模型
According to the grand tack model,
如果没有木星，内太阳系的岩质类地行星
without Jupiter, the rocky terrestrial planets
可能永远不会形成
of the inner solar system might have never formed.
其中一个行星就是地球
One of those planets is Earth.
所以，我们的存在很大程度上归功于木星
So as much as we owe our existence to Jupiter,
同时也归功于土星
we also owe it to Saturn
因为如果木星一直靠近太阳
because if Jupiter had kept moving in closer to the Sun,
我们几乎肯定不会在这里
we almost certainly wouldn't be here now.
大轨迹模型可能为地球形成的故事
The grand tack may provide a vital chapter
提供了至关重要的一章
in the story of Earth's formation.
这就解释了为什么我们错过了炽热的木星
That answers why we're missing a hot Jupiter
但却无法解释为什么
but doesn't explain why there's nothing
水星和太阳之间什么都没有
between Mercury and the Sun,
也无法解释为什么我们错过了整个银河系中
nor why we're missing one of the most common types of planet
最常见的行星之一
in the whole galaxy,
一个巨大的岩石世界
a giant rocky world up to 10 times
大小是地球的10倍……一个“超级地球”
the size of Earth... A super-Earth.
开普勒太空望远镜
The Kepler space telescope
寻找其他恒星周围的系外行星
leads the charge in the hunt
一直走在最前面
for exoplanets around other stars.
已经确认了超过2000个新世界
It's confirmed over 2,000 new worlds.
这是迄今为止最大的单一发现
The single-largest finding to date,
其中超过三分之一的行星是超级地球
over one-third of those planets are super-Earths.
超级地球是一种岩石行星
A super-Earth is a type of rocky planet
其质量是地球质量的几倍
that has a mass a few times the mass of the Earth,
当我们环顾银河系时，到处都能找到它们
and as we look around the galaxy, we find them all over.
但我们的太阳系没有
Our solar system doesn't have one,
你不得不问这个问题……为什么没有呢？
and you have to ask the question... why not?
我们有什么不同？
What's different about us?
在我们的太阳系中，行星的质量各不相同
In our solar system, planets range in mass,
木星是最大的
with Jupiter being the largest
水星是最小的
and Mercury the smallest.
但奇怪的是，在地球和天王星之间的范围内
But weirdly, we have nothing in the super-Earth-size range,
我们没有任何的像超级地球这样的行星
which is between Earth and Uranus.
为什么地球和天王星之间
Why is there such a big gap in masses
有这么大的质量差距
between the Earth and Uranus,
大约是地球质量的十几倍？
which is roughly a dozen times the Earth's mass?
从一个到一打，这是一个很大的飞跃
It's a big jump from one to a dozen.
为什么？
Why?
2015年
In 2015,
康斯坦丁·巴蒂金(Konstantin Batygin)
Konstantin Batygin tries to find the answer
试图找到为什么我们没有超级地球
to why we have no super-Earths,
以及为什么水星轨道内什么都没有的答案
and why there is nothing within the orbit of Mercury.
他重建了大轨迹模型，但有一个关键的区别…
He reconstructs the grand tack model with one key difference...
从六个超级地球开始模拟
The simulations start with six super-Earths
它们位于我们太阳系的中心
in our solar system center
围绕太阳的紧密轨道上
in a tight orbit around the Sun,
这是我们观察到的其他恒星系的典型特征
typical of other systems we've observed.
他称这种新模式为“大攻击”
He calls this new model the grand attack.
在研究大轨迹的过程中
One of the realizations that has come out
我们认识到
of studying the grand tack scenario
木星的迁移
is that Jupiter's migration would have really unleashed
会对太阳系内部
a veritable grand attack
造成真正的巨大冲击
upon the inner solar system.
大攻击模型增强了木星的活动能力
The grand attack model ramps up Jupiter's action
因此它将成群的大量小行星和行星胚胎
so it sends swarms of giant asteroids and planetary
在紧密重叠的轨道上
embryos into the inner solar system on tight-knit,
送入太阳系内部
overlapping orbits.
结果呢？
The result?
一场大屠♥杀♥
Carnage.
每20到200个轨道上
Each big body will experience a collision
每个大天体都会经历一次与另一个大天体的碰撞
with another big body once every 20 to 200 orbits.
这在宇宙时间尺度上是非常快的