[INTRO ♪]
[前奏]
Jupiter is more than twice as massive as all the other planets in our solar system combined,
木星比太阳系中其他所有行星加起来的两倍还要大
and it has a history of throwing that weight around.
而且它的质量一直都在向四周散失
In fact, it likely used its gravity to shape the way our solar system looks today.
事实上 木星可能凭其质量塑造了太阳系今天的样子
And that’s generally a good thing for us!
整体上来说 这对我们是好事
We have a nice stable orbit at a cozy distance from our star,
地球与太阳距离适中 公转轨道平稳
and things are usually pretty calm in our planetary neighborhood.
周边行星环境相当平静
So, here on Earth, we have a lot to thank Jupiter for…
所以 我们地球有很多需要感谢木星的
but it isn’t always the nicest neighbor.
但它并非一直是个好邻居
Now and then, it also sends some hazards our way.
它也时不时的使地球处于危险中
That makes sharing a solar system with Jupiter … complicated.
这使得与木星同处一个太阳系的感情变得复杂了
On a good day, Jupiter’s got our back.
好的时候 木星在背后支持我们
When comets from the outermost reaches of the solar system head toward Earth,
比如彗星从宇宙深处来到太阳系冲向地球时
Jupiter’s gravity often acts like a shield by chucking them straight into interstellar space.
木星的引力像护盾一样 将它们直接抛到星际空间
And we’ve even seen Jupiter take some pretty big hits for us.
我们见识过木星帮我们挡掉一些相当严重的撞击
In 1994, fragments of the comet Shoemaker-Levy 9 smashed into Jupiter.
1994年 彗星Shoemaker-Levy 9的碎片撞击了木星
As the impact site rotated into the Earth’s view,
当撞击点旋转到面向地球时
scientists could see dark scars on the surface of the planet
科学家观测到了木星表面上的黑斑
and plumes of debris rising in its atmosphere.
还有碎片尘埃漂浮在大气层中
If a comet like this had hit Earth,
假如类似的彗星撞击地球
it would have kicked up an enormous cloud of dust that would have blotted out the Sun
将会扬起巨大的尘埃云 遮蔽阳光
and caused mass extinctions on par with the ones that took out the dinosaurs.
造成地球生物大灭绝 规模与恐龙灭绝那次不相上下
So not only does Jupiter routinely protect us from comets like Shoemaker-Levy 9,
所以木星不仅日常保护地球不受类似Shoemaker-Levy 9彗星的撞击
but that dramatic collision gave astronomers a wake-up call
它被撞击也给天文学家提了个醒
—if it happened to our neighbor, it could also happen to us.
能发生在邻星上 那也能发生在地球上
Just four years later, in 1998,
就在四年后的1998年
NASA got serious about tracking near-Earth objects, or NEOs,
NASA开始重视追踪近地天体 简称NEOs
that could have catastrophic effects if they hit our planet.
指撞击后会导致地球灾难性后果的天体
And now NASA estimates that we’ve found almost all of the thousand or so NEOs
NASA目前估算已找到近千个
big enough to cause apocalyptic worldwide destruction.
几乎所有大到能导致地球末日的NEOs
There are, of course, still plenty of smaller ones that could potentially do some serious damage,
虽然仍有许多可能造成严重破坏的较小近地天体
but thanks to Jupiter’s wake-up call in the ’90s,
但还是要感谢木星在90年代的提醒
we have a pretty good handle on the scariest threats.
让我们对其中最具威胁的彗星做好了应对措施
So, Jupiter deflects some dangerous comets
木星使一些彗星偏离方向
and reminds us to keep a lookout for incoming asteroids,
并提醒我们注意将到来的小行星
but the biggest planet in the neighborhood doesn’t always play nice.
但这个最大的行星邻居并不总是那么友好
For example, in 1770, the comet Lexell flew past it,
比如1770年 彗星Lexell掠过木星时
and Jupiter’s huge gravity directed the comet right at Earth.
其巨大引力使该彗星直冲地球
It came within 2.3 million kilometers of us!
最近时离我们只有230万千米
That’s how far Earth travels in just 21 hours.
相当于地球公转21小时的距离
So we dodged it by less than a day!
所以我们躲开它时只剩不到一天
And research suggests that this type of event—
而且研究表明 类似事件像
where Jupiter throws things into the inner solar system rather than sending them out
木星吸引小行星到太阳系内部而不是将其抛向外太空
—might be happening more often than we thought.
发生频率可能比我们想象的更多
Like, one simulation of 30,000 space objects
比如一个包含3万个天体的模拟
showed that Jupiter might even be teaming up with Saturn
显示木星甚至可能与土星协作
to send threatening space rocks our way.
将颇具威胁的太空岩石抛向地球
In the model, each simulated object began in a non-threatening orbit somewhere in the outer solar system.
模拟开始时 每个天体运行轨道在外太空某个地方
But by the end of the simulation, 8% of those objects were crossing paths with Earth.
而到最后 有8%的轨道会与地球相交
And while Jupiter’s gravity was the real culprit slinging objects inward,
虽然是木星将它们吸引到太阳系 堪称罪魁祸首
Saturn was guiding objects toward Jupiter.
但是土星将它们引向木星 也“功”不可没
In the real world, a good deal of Jupiter’s ammo is likely made up of objects called Centaurs.
现实中 木星的“弹药”可能大部分由半人马小行星构成
They’re named after the mythical creature that’s half-person, half-horse,
它们的名字来源于半人半马的神话动物
and Centaurs are like hybrids between asteroids and comets:
而它们也像是小行星和彗星的“混血”
They can have the same make-up as asteroids,
它们与小行星组成成分相同
but many of them have comet-like properties like tails of debris.
同时很多还有彗星的特征 比如彗尾
For the most part, Centaurs stick to the outermost solar system.
大多时候 半人马小行星呆在外太空
But if they get close enough to Jupiter,
但一旦它们离木星足够近
the planet’s gravity can alter their path
木星的引力就能改变它们的轨道
and throw them into the inner solar system,
把它们吸引到太阳系
potentially on a collision course with Earth.
并可能与地球发生激烈碰撞
Even when it’s not hurling Centaurs our way,
就算木星没有把它们投向地球
Jupiter may make ordinary comets more of a threat than they already are.
它也能使本具威胁的彗星变本加厉
Although it throws some of them out of the solar system altogether,
尽管木星把一些彗星清出了太阳系
in other cases, a run-in with Jupiter can tighten a comet’s orbit.
但其他时候 木星的干扰会缩短彗星的轨道
That means it’ll go around the Sun faster,
意味着彗星将加速环绕太阳运行
giving it more chances to hit Earth.
增加撞击地球的可能性
In fact, that’s exactly what happened with the famous Comet Hale-Bopp.
事实上 这正是著名的海尔波普彗星发生的事情
It last swung by the Sun in 1997,
它最近一次掠过近日点是在1997年
and that was the first time it was visible in 4,000 years.
这是它4000年来第一次被观测到
But around the same time, an encounter with Jupiter cut its orbital period almost in half,
就在那时 木星的干扰使其公转周期缩短将近一半
meaning it’ll come by again in just over 2,000 years!
意味着它最快将于二千多年后回归
And just to keep us on our toes, Jupiter’s gravity can also pluck rocks from the Asteroid Belt
需要警惕的是 木星引力可以将岩石从小行星带剥离
and send them our way too—which isn’t very neighborly!
朝地球扔来 这不是好邻居该做的
But even if we have to give Jupiter a little side-eye now and then,
不过尽管我们不得不经常对木星侧目
it could have helped make life on Earth possible.
它有可能帮助了地球生物出现
During the formation of the solar system,
太阳系形成之初
its enormous gravity likely helped carve space for our planet to form in the first place.
首先 木星巨大的引力可能为地球的形成创造了空间
And even when Jupiter seemed like our enemy,
尽管木星看起来像敌人
the space debris it sent our way during Earth’s early years
地球形成初期 木星送过来的太空碎片
may also have delivered organic material that helped life form.
可能含有机物 帮助孕育生命
So thanks, Jupiter, for helping to get us going early on!
所以 谢谢你木星 帮助我们早期出现
You can stop sending us all those asteroids and comets, though.
不过 你可以停止向我们扔小行星和彗星了
Beyond helping us learn how to defend our own planet,
除了帮助我们学习如何保卫地球之外
understanding Jupiter’s role in our solar system could help us search for life beyond it.
弄清木星在太阳系中的职能可以帮助我们搜寻太阳系外的生命
When we look for habitable worlds orbiting other stars,
在我们寻找围绕其他恒星公转的宜居行星时
it might be useful not just to look for Earth-like planets,
不要只关注类地行星
but also to see what a Jupiter-like frenemy might be up to nearby.
也看看附近亦敌亦友的类木行星会比较好
Thanks for watching this episode of SciShow Space!
感谢观看本期《太空科学秀》
If you want to learn more about how Jupiter tosses its weight around in the solar system,
如何你想知道更多关于木星如何在太阳系“减重”
you might like our video about the group of asteroids Jupiter has held prisoner
你可能会喜欢我们的视频 木星“囚禁”的小行星群
—possibly for billions of years!
可能已经“囚禁”了几十亿年
You can find out more about Jupiter’s Trojan asteroids after this.
之后你可以了解更多关于木星的特洛伊小行星介绍
[OUTRO ♪]
[结束曲]

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