太阳系有8大行星和300多颗卫星 Our solar system, eight planets and over 300 moons
有规律地围绕太阳运行 circling the sun like clockwork.
但起初并非如此 But it didn't start that way.
太阳系经历过一段漫长的狂暴历史 Our solar system has a long history of violence.
我们今天看到的太阳系 The solar system we see today
是早期混沌状态最后的幸存者 is really just the final survivors of the early chaos.
在未来, 混沌状态会卷土重来 And in the future, that chaos will return.
整个太阳系会像纸牌搭的房子 The entire house of cards that is our solar system
彻底瓦解 will completely fall apart.
太阳系来自混沌, 最终会复归混沌 From start to finish, this is how solar systems work.
宇宙有道理 How the Universe Works
第1季第7集：太阳系 Solar Systems
银河系拥有数十亿颗恒星 There are billions of stars in the Milky Way galaxy.
其中一颗是我们的太阳 One of them is our sun.
行星和卫星绕着太阳运行 And around the sun orbits a system of planets and moons...
称为太阳系 a solar system.
太阳系显然是个宝贵的行星系 Our solar system is clearly a precious planetary system.
这引起了一个问题 And it begs the question,
有无类似行星系绕着其它恒星运行 are there other planetary systems like ours orbiting other stars?
为找答案, 马西用凯克望远镜观天 To find out, Marcy scans the skies with the Keck,
它是世界上最大的光学望远镜之一 one of the world's largest optical telescopes.
在海拔1.4万尺夏威夷莫纳克亚山 Perched at 14,000 feet, on top of Mauna Kea in Hawaii,
用于寻找遥远的新太阳系 it hunts for new, distant solar systems.
不可思议的是 The marvellous reality...
银河系拥有大约两千亿颗恒星 is that our own Milky Way galaxy contains some 200 billion stars or so,
其中许多恒星都拥有自己的行星系 and many of those stars have their own planetary systems.
有八大行星的太阳系并非独一无二 Our solar system, with its eight major planets, is not alone.
宇宙中还有数十亿其它行星系存在 There are other brethren planetary systems out there by the billions.
天文学家当然希望找到另一个… Of course, astronomers hope to find another solar system
具有地球这样的行星的太阳系 with a planet like Earth,
他们有个好的开头 and they're off to a good start.
迄今为止, 马西和其它天文学家 So far, Marcy and other astronomers have discovered
已发现360多个有行星系的恒星 over 360 stars with orbiting planets.
其中一个最令人兴奋的发现是 One of the exciting discoveries that we've made is that...
恒星通常不会只有一颗行星 stars tend to be orbited not just by one planet
而是有二至四颗, 甚至更多行星 but usually two, three, four, or a multitude of planets.
行星以族群形式出现 Planets come in families,
与太阳系的情形相似 not unlike the family of planets we enjoy here around our own sun
科学家第一次可以仔细研究它们 For the first time, scientists can study them in some detail.
我们观察到行星绕着太阳运行时 We can actually observe how planets heat up
是如何变热的 as they go around their sun.
比如我们看见行星绕着恒星运行时 For example, we actually saw that one planet
会变热和变冷 got hotter and colder as it orbited its star.
我们发现其实看到它的黑夜面 And we realised that we were actually seeing the night side of the planet
然后看到白昼面 and then the day side of the planet.
所以有温差 That was the temperature difference.
是另一太阳系的行星的日出和日落 We were observing sunrise and sunset on a planet in another solar system.
但是这颗行星与地球大不相同 But that planet is nothing like Earth
多数新发现的太阳系 And most of these newly discovered solar systems
都与我们的太阳系非常不同 are nothing like our own.
它们的行星很巨大, 比木星大得多 Their planets are huge, much bigger than Jupiter.
有些难以约束 Some follow wild orbits
有些逆向而行 Some orbit in the opposite direction,
有些飞速冲向数十亿哩外的太空 and some shoot billions of miles out into space
然后向着恒星俯冲回来 then dive back toward their star.
少数距离恒星太近 A few orbit so close to the star
令表面气化 their surfaces vaporise.
样子虽然算不上吓人但也十分古怪 It's bizarre, at the least, if not completely frightening.
行星系包含结构, 大小, 质量… Planetary systems offer a wide diversity
各不相同的行星 of different architectures, sizes, masses of the planets, and so on,
太阳系只是数千种行星系中的一种 rendering our solar system just one type of a planetary system out of thousands.
也许每个太阳系都是独一无二的 It could be that each and every solar system is a one-of-a-kind.
但它们都有一个共同点 But they all have one thing in common...
每个太阳系最初都只是一颗恒星 each one begins with a star.
首先, 恒星是在气体和尘埃… First, a star is born
所组成的星云中诞生 in a cloud of dust and gas called a nebula.
这是鹰状星云 This is the Eagle Nebula.
这些是创生之柱 These are the Pillars of Creation.
马头星云, 一个巨大的恒星摇篮 And this is the Horsehead Nebula, an enormous star nursery.
科学家们一直在努力探寻 What scientists have been trying to figure out
是甚么引发恒星形成的过程 is what triggers the star-making process.
其中一个可能是 One possibility
一个附近的超新星发生爆炸 is that a nearby supernova explosion took place...
猛烈冲击平静的分子云 and rammed into this otherwise innocuous molecular cloud...
把它击碎 smushing it, smashing it,
然后压缩, 最终被引力控制 compressing it down so that gravity could take over.
一旦被引力控制 Once gravity takes over
分子云就会塌缩 the cloud begins to shrink,
吸入越来越多的气体 sucking in more and more gas
形成一个巨型旋转圆盘 into a giant, spinning disk.
中心的引力将一切压缩成… Gravity at the centre crushes everything
一个密度很大的超热球体 into a dense, super hot ball
它的温度越来越热 that gets hotter and hotter.
突然气体中的原子开始熔化 Suddenly, atoms in the gas begin to fuse
恒星开始燃烧 and the star ignites.
剩余的尘埃和碎片 The leftover dust and debris
形成一个围绕新恒星旋转的圆盘 forms a disk spinning around the new star.
它包含了行星, 卫星, 彗星 It contains the seeds
和小行星的种子 of planets, moons, comets, and asteroids.
2001年, 哈勃太空望远镜… In 2001, the Hubble Space Telescope
在观测猎户座大星云时 was scanning the Orion Nebula...
拍到早期恒星被圆盘围绕的画面 and took this image of a young star surrounded by one of these disks.
这是一个正在诞生的太阳系 It's a picture of a solar system being born.
观看这些美丽的星云图片时 Whenever I look at these beautiful pictures of nebulae,
最令我感动的是… the thing that really gets me
我们的太阳系初生时就是这个样子 is that these are baby pictures of our own solar system.
我们曾经也是这样 We looked like that once.
这些图像为了解行星系的形成 These fuzzy images have opened the door
开启了一扇大门 to understanding how planetary systems form.
我们首次拥有了这一非凡工具 We have this marvellous first ever tool
拍摄到行星在形成过程中的图片 by which we can take pictures of planets caught in the act of formation.
这给了我们极佳机会 It's quite a marvellous opportunity
观测其它行星系的形成 for us to see the planets around other stars forming,
由此可以窥见 thereby giving us a glimpse
我们的太阳系是如何形成的 as to how our own solar system must surely have formed.
科学家已知道恒星从何而来 Scientists understood where stars come from
但不知行星如何从气体和尘埃形成 but not how planets grow from the disk of gas and dust.
国际太空站上一次偶然事件 The answer was discovered by accident
解开了这一谜团 aboard the International Space Station.
航天员佩蒂特用糖和盐 Astronaut Don Pettit was experimenting with grains of sugar and salt
在太空的无重状态做实验 in the weightlessness of space.
洛夫正在地面指挥中心观察 Stanley Love was watching from Mission Control...
当佩蒂特无意中发现… when Pettit stumbled onto the process
宇宙尘埃形成行星的过程 of how planets form from cosmic dust.
其中一个佩的周六早上科研项目 Well, one of Don's... Saturday-morning science projects
要用到我们储存饮料的袋子 was to take the bags that we store drinks in
他将像盐和糖等其它东西放进袋子 and he put other stuff in it, like salt and sugar,
其中一个袋子只放了咖啡粉 and there was one bag that he just left the coffee powder in.
然后给袋子充气 Then he inflated the bags,
由于袋子里有粒子 and with these particles in them,
发觉粒子立即聚成一团 noticed that the particles would just clump up immediately.
形成了积尘 They make a little dust bunny.
我们观察了一段时间 We'll be spending some time watching that.
我说: 佩蒂特, 这太不可思议了 I said, "Don, this is incredible!"
你解决了困扰行星科学40年的问题 "You've just solved a 40-year-old problem in planetary science!"
佩蒂特解开了一个重大谜团 Astronaut Pettit had discovered something big.
在太空的零引力里面 !n the zero gravity of space,
尘埃粒子不会四散悬浮 particles of dust don't float apart,
而是会聚集成一团 they clump together.
宇宙尘埃就是这样形成行星的 This is how mighty planets are made from cosmic dust.
尘埃粒子会碰撞并粘连在一起 The dust particles would collide and stick and grow
形成更大的尘粒 into ever larger dust particles
接着形成岩块, 最终会形成巨石 and eventually rocks and eventually boulders.
巨石越大, 引力就越强 The bigger the boulder, the more gravity it has.
它开始吞噬周边的一切 It begins to eat up everything around it
从而越长越大 and grows bigger.
巨石变得更大, 更重 It becomes larger, heavier,
吞噬的岩块也越来越大 and consumes bigger and bigger rocks.
最后有些巨石变成了行星 Eventually, some of these rocks grow into planets.
这是太阳系在46亿年前发生的事 This is what happened in our solar system 4.6 billion years ago.
有100个年轻行星绕着新太阳运行 There were about a hundred young planets all orbiting the new sun.
碰撞是不可避免的 Collisions were inevitable.
所有太阳系在初时都很狂暴 At the beginning, solar systems are violent.
我们的太阳系也不例外 Ours was no different.
它最初约有100个小行星 It began with about 100 small, new planets.
那么100个小行星如何发展成为… So how did it go from 100 small planets
今天的八大行星呢? to the eight major planets of today?
从研究其它太阳系进化找到了答案 We got the answer by studying the evolution of other solar systems.
我们看到太阳系诞生时期的行星 We see solar systems forming planets...
突然 and all of a sudden,
它们周围出现这些巨大圆盘 they had these giant disks around them.
这些圆盘一定由巨大碰撞产生 Those disks must be from huge collisions.
若其它行星系中的行星会相互撞击 If planets are smashing together in other systems,
那么我们的太阳系也会如此 they probably smashed together in our own.
我们现在知道所有太阳系 We now know that all solar systems do this
在稳定之前都会这样 before they settle down.
这是它们形成的方式 It's the way they're built.
今天看到的整齐有序的太阳系 The nice, neat, orderly solar system that we see today
并非一直如此 has not always been the case.
在早期, 即是在行星开始形成后 In the early days, a few million years, basically,
的数百万年间 after the planets started forming,
有几十个, 甚至数百个早期行星 there were dozens, maybe even hundreds of these young planets
在太阳系周围流窜 that were bouncing around the solar system.
它们相互碰撞 They would smash into each other.
有时会聚集起来成为更大的行星 Sometimes they would collect and get to be bigger planets.
有时会将彼此撞成碎片 Sometimes they would smash each other and turn into little bits.
在新生的太阳系中 There was heavy traffic in the new solar system,
大大小小的物体穿梭往来 objects of all sizes.
难免会发生碰撞 They were bound to collide.
一些行星变得巨大, 碰撞也更剧烈 Some of the planets grew larger, and so did the collisions.
想象一下那会是怎样一番景象 I like to try to imagine what it would have been like
若站在早期地球上抬头仰望夜空 to actually stand on the early Earth and look up into the night sky.
肯定会大异其趣 Things would have looked different.
行星相互撞击 Planet hit planet.
只有最大的才能幸存 Only the largest survive.
其余的难免粉身碎骨 The rest are smashed to pieces.
某个庞然大物撞击早期水星 Something very large struck the young planet Mercury.
将水星外壳撞落, 只剩下铁质内核 It blew the crust off and left behind just the iron core.
早期地球也未能幸免 And the young planet Earth did not escape either.
一个行星大小的物体撞着地球 A planet-sized object slammed into the Earth off-centre
将一大块外壳撞碎 and blew a huge amount of the Earths crust into space.
碎片绕着地球运行 The debris circled around the Earth...
最后聚集在一起形成月球 and eventually coalesced to become the moon.
这场撞车大赛持续了五亿年之久 This demolition derby raged for 500 million years.
现在的火星, 地球, 水星和金星 What we see now, Mars and Earth and Mercury and Venus,
这些内太阳系行星都是幸存者 these planets in the inner solar system, they're the survivors.
它们在这些巨大撞击中生存了下来 They're the ones who lived through these giant impacts.
幼年行星的碎片就形成小行星带 Debris from smashed infant planets ended up in the asteroid belt,
如同一个行星废料堆积场 a junkyard of rocky, leftover planet parts.
大多数大型撞击发生在内太阳系 Most of the big impacts happened in the inner solar system.
但是外行星中的天王星也受到撞击 But one of the outer planets, Uranus, was also hit and knocked on its side.
这是个谜, 因为外行星… A mystery, since the outer planets
主要由气体构成 formed mostly from gas
避开了内太阳系的剧烈撞击 and largely escaped the violence of the inner solar system.
这些岩石内核形成 These rocky cores formed.
气体聚集在内核周围 The gas accumulated around them.
这个过程发生得很快 This process actually happened very rapidly.
只用了大约一百万年 In astronomical terms, in only about a million years.
那就是我们今天看到的巨行星 And those are the giant planets we see today.
在气体巨行星木星和土星之外 Beyond the gas giants, Jupiter and Saturn,
是天王星和海王星 are Uranus and Neptune.
后两者由气体和冰构成 These two are made of gas and ice.
它们之外是柯伊伯带 And beyond them lies the Kuiper Belt,
是沿轨道运行的冰封岩石和矮行星 a band of orbiting icy rocks and dwarf planets.
曾经被当作第九大行星的冥王星 We used to think that one Kuiper Belt object, Pluto,
其实是柯伊伯带天体 was the ninth planet.
冥王星其实是一颗矮行星 We've since decided that Pluto is, in fact, a dwarf planet,
在超过30亿哩之外绕太阳运行 one of many orbiting more than three billion miles from the sun.
哪里有数百万这样的行星 There are millions of these things out there.
它们太遥远和太模糊, 很难看清楚 They're so far away and so faint that they're hard to see.
这些是太阳系形成过程中的残留物 These are left over from the formation of the solar system itself.
柯伊伯带处于太阳影响力的边缘 The Kuiper Belt marks the edge of the sun's influence.
这里没有热力和光线极暗 There is no warmth and not much light way out here.
但柯伊伯带并不是太阳系的边界 But the Kuiper Belt is not the end of our solar system.
更远处还有一个由数万亿冰封物质 A shell of trillions of icy objects,
构成的外壳, 称为奥尔特云 called the Oort Cloud, is even further out.
奥尔特云非常遥远 The Oort Cloud is so far away,
太阳的光要走一整年才能到达哪里 light from the sun takes a full year to reach it.
从寒冷边缘到中心的炽热恒星 From the cold outer edge to the hot star at the centre,
我们的太阳系看来很稳定 our solar system seems stable.
一切都井然有序和在怡当位置 Everything appears orderly and in its proper place.
但有个地方令人大惑不解 But something isn't right.
天王星和海王星的位置不对 Uranus and Neptune are in the wrong place.
太阳系的行星由气体和尘埃形成 The planets of the solar system grew from a giant disk of dust and gas...
四个离太阳较近的岩态行星 the four inner rocky planets close to the sun,
和较远的气体巨行星 and the giant gas planets farther out.
但天王星和海王星看来位置不对 But Uranus and Neptune seem out of place.
离太阳这么远, 根本没有足够物质 There wasn't enough stuff this far from the sun
形成这样巨大的行星 to make such big planets.
那么它们为何跑到这里呢? So, what are they doing out here?
这引出了一个理论 That led us to a theory
天王星和海王星 where Uranus and Neptune
是在离太阳很近的位置形成 formed very close to the sun...
然后被推到了外围 and were actually violently pushed outward.
是甚么推动两个巨大行星 So, what could shove two massive planets
穿越太阳系呢? clear across the solar system?
我们相信土星和木星 We believe that Jupiter and Saturn
形成一种有趣的结构 got into this funny configuration.
木星绕太阳运行两周的时间 where Jupiter went around the sun exactly twice
等于土星绕太阳运行一周的时间 every time Saturn went around once.
这种结构使得它们在相遇时 And that configuration...
产生更大的相互影响 allows the planets to kick each other more as they pass one another,
这导致整个太阳系出现混乱 and that caused the whole system to go nuts.
木星和土星的引力相结合 The combined gravity of Jupiter and Saturn yanked hard on Uranus and Neptune...
猛力将天王星和海王星拖离太阳 and pulled them away from the sun.
当它们向外移动时 As they moved outward,
艰难地穿过小行星群 the two planets ploughed through asteroids and other debris
和其它行星形成时留下的碎片 left over from the formation of the other planets.
数十亿岩块在这过程中四处飞散 This sent billions of chunks of rock flying in all directions.
有些形成了小行星带 Some rocks formed the asteroid belt.
但大部分被甩出外围形成柯伊伯带 But most were thrown out to create the vast Kuiper Belt
我喜欢用保龄球赛做比喻 The analogy I like to use is, think of a bowling match.
当保龄球打过去, 球瓶四处飞散 And the bowling balls go down, and the pins just go kaplooey.
这就是在太阳系外围发生的情况 That's what happened in the outer part of the solar system.
但木星和土星的引力太过强大 The gravitational push from Jupiter and Saturn was so strong,
可能掉换了天王星和海王星的位置 it may have reversed the position of the two planets.
天王星和海王星在形成时 It looks like it's possible... that Uranus and Neptune actually formed
位置可能与现在相反 in the opposite order.
海王星比天王星更靠近太阳 Neptune was closer to the sun than Uranus
但这些引力互动令它们掉换了位置 but these gravitational interactions actually swapped their positions.
天王星和海王星穿过的大量岩石 It was the blizzard of rocks that Uranus and Neptune ran into
起到了刹车作用 that acted like a brake
它们慢慢减速形成了现在的轨道 and slowed them into the orbits they keep today.
行星改变轨道似乎匪夷所思 The idea of planets changing orbits may sound crazy,
但科学家在其它太阳系见到过 but scientists have seen it happen in other solar systems.
所以他们认为这是普遍现象 So now they think it's just the way all solar systems work.
当我们遥望星系 When we look out into the galaxy
观察其它恒星周围的行星时 and look at planets around other stars,
看到许多类似事件发生过的证据 we see lots of evidence of those kind of events happening elsewhere.
在一个遥远星系 In one far-off system,
科学家观察到超乎寻常的现象 scientists have spotted something completely off the charts.,.
一个与木星同样大小的行星 a planet as big as Jupiter,
但它的运行方式与木星截然不同 but it's not acting like the Jupiter we know.
有些这样巨大的行星 Some of these giant planets...
经常在靠近母恒星的地方运行 are found orbiting very close to their host star,
只需几天时间就能绕母恒星一周 taking only days, a few days, to go around the host star.
这些巨行星离恒星太近 Obviously, such close-in Jupiters
显然会受到炙烤 are blowtorched by the star,
行星的温度可达一千或二千度摄氏 raising the temperature of the planet up to 1,000 or 2,000 degrees Celsius.
一个气体巨行星是不可能形成的 There's no way a gas giant could have formed this close in.
这里的温度实在太高 It's way too hot
唯一的解释就是 The only explanation...
它在远处形成, 然后移动到这里 is that it must have formed out there and then moved in here.
我们的太阳系可能发生过同样情况 The same thing could have happened in our own solar system.
科学家已发现太阳表面… Scientists have found large amounts of the element, lithium,
含有大量锂元素 on the surface of the sun.
恒星中通常并没有锂元素 Lithium doesn't normally exist in stars,
但气体巨行星却含有这一元素 but it is found in gas planets.
也许我们的太阳系曾有气体巨行星 Maybe there was another gas giant in our own solar system
撞向太阳 that spiralled in and crashed into the sun.
这解释了为何太阳表面有锂元素 That would explain how the lithium got there.
一定发生过激烈碰撞 Something very violent happened.
是否可能有一颗像木星大小的行星 Could it have been one of these Jupiter-size planets
在很久以前撞入太阳? getting thrown in toward the sun long ago?
太阳系的初期狂暴而混乱 In the beginning, solar systems are violent and messy.
但逐渐安定下来和变得较稳定 But over time, they settle down and become more stable.
但稳定只是假象 But stability is an illusion.
太阳系里的任何一颗行星 Any planet in the solar system
随时都有毁灭危险 is always in danger of total annihilation.
银河系中有各式各样的太阳系 There are all kinds of solar systems in the Milky Way galaxy.
大多数与我们的太阳系大不相同 Most seem strange compared to our own.
有些行星的轨道很混乱 Some planets follow crazy orbits.
有些行星相互撞击 Some smash into each other.
有些甚至会撞入母恒星里 Others dive into their stars.
那么为何我们的太阳系的行星轨道 So why are the orbits of our own planets
如此规则和稳定呢? so regular and stable?
因为所有行星的运动 Well, that's because... all the planets have motion left over
都是太阳系形成所剩下的 from the formation of the solar system.
太阳形成时太阳周围的星云崩塌 When the nebula collapsed around the sun as the sun was forming,
它产生一种内在的运动 there was an intrinsic motion,
使行星获得了速度 and that gave our planet a velocity.
其实我们一直向着太阳自由下落 Literally, we are falling freely toward the sun at all times,
但由于速度太快, 总是不断错过 but we're going so fast, we keep missing it
于是形成轨道运行 That's what an orbit is.
好比旋转木马 Think of a merry-go-round.
转得越快就脱离中心越远 The faster it spins, the farther and farther you're thrown from the centre.
一旦减速就会失去动力掉下来 When it slows down, you lose momentum and fall back inwards.
这跟行星的情形一样 It's something like that with planets.
形成行星的圆盘是在旋转的 The disk that gave birth to the planets was spinning,
它剩下的动力令行星一直运行至今 and the momentum left over from that keeps everything going around to this day.
地球每小时移动66000哩 Moving at 66,000 miles an hour,
需要一年绕太阳运行一周 the Earth takes one year to orbit the sun.
离太阳越远, 轨道半径越大 Planets farther from the sun have bigger orbits,
移动越慢和时间越长 move slower, and take longer.
土星每29年绕太阳一周 Saturn orbits the sun once every 29 years.
海王星需要164年 Neptune takes 164 years.
每个行星都在精确轨道上绕日运行 Each planet stays on a precise path around the sun.
对我们来说, 这是好事 And for us, that's a good thing.
行星之间距离适当 Our solar system has a somewhat fortunate spacing of the planets,
轨道几乎都是圆形 with nearly circular orbits...
令到这座纸牌搭的房子 which keeps the whole house of cards
不会瓦解, 烟消云散 from falling apart, crumbling, scattering to the wind.
若我们的太阳系没有… If our solar system did not have
规则, 稳定, 近乎圆形的轨道 nice, neat, stable, nearly circular orbits,
地球就不可能存在 the Earth wouldn't be here
我们也不可能坐在这里谈论这些 and we wouldn't be here talking about it
行星在安全稳定的轨道上运行 The planets are on safe, stable orbits...
但数十亿颗彗星和小行星则不然 but billions of comets and asteroids are not.
许多会飞快闯入内太阳系 Many come streaking into the inner solar system.
当这情况出现时, 当心 And when they do, watch out.
现在见到的这个陨石坑是五万年前 The meteor crater which we see here today...
一个直径150尺的石铁陨石 formed as a result... of a 150'-foot rocky iron object
撞向地球所造成的 coming in and slamming into the Earth - roughly 50,000 years ago.
有些撞向我们的物体可能大得多 Some of the objects coming our way can be much bigger.
看一下月球 Look at the moon.
哪里满布巨大的陨石坑 It's covered with large impact craters.
地球也曾多次被撞击 Earth has been hit, too. A lot.
但这些陨石坑已被侵蚀 But the craters have eroded.
我们知道6500万年前一颗小行星 We know that a huge asteroid smashed into the Earth,
撞落墨西哥海岸对开 off the coast of Mexico, 65 million years ago.
飞行速度高达每小时45000哩 It was going 45,000 miles an hour,
撞击所产生的能量 and when it hit, it released more energy
超过50亿个广岛原子弹 than five billion Hiroshima bombs.
地球上七成生命毁于一旦 It wiped out 70 percent of life on Earth.
几次这种撞击能毁灭地球一切生命 A few more impacts like that could destroy all life on Earth.
但信不信由你, 地球有个巨型保镖 But believe it or not, Earth has a giant bodyguard.
木星除了是一个美丽的星球 Jupiter is more than just... another pretty face through the telescope.
它对地球上的生命亦至关重要 it's actually really important for life on Earth.
由于木星的引力巨大无比 Jupiter's gravity is so huge
加上它的位置恰到好处 and it's just in the right place in the solar system...
所以能够保护地球免遭彗星的撞击 that it protects the Earth from comets that come from deep in the solar system
它们在太阳的引力下可能撞向地球 and swing by the sun and could possibly hit the Earth.
木星就像太阳系最大的棒球棒 Jupiter plays the role of the biggest baseball bat in the solar system.
当这些彗星袭来时 As these comets come by,
大多数都被木星挡出了太阳系 most of them get knocked out of the solar system by Jupiter.
1994年, 苏梅克列维九号彗星 In 1994, Comet Shoemaker-Levy 9
朝着内太阳系冲过来 raced toward the inner solar system.
但它根本过不了木星这一关 But it never got past Jipiter.
天文学家目睹木星将它撕得粉碎 Astronomers watched as Jupiter tore it to pieces
并把碎片拉到木星表面 and dragged its remains... down to the planet's surface.
我们看到彗星撞入木星 We have seen comets smash into Jupiter,
产生比地球还大的火球 creating fireballs that were bigger than the Earth.
这是我们的太阳系中最大型爆炸 They were the biggest explosions ever seen in our solar system.
若那颗彗星撞到地球就不堪设想 Had that comet hit us, it would have resurfaced the planet
地球所有生命都会灭绝 It would have been the end of life as we know it.
若没有木星, 地球的撞击率 If Jupiter wasn't there, we believe that the impact rate on the Earth
会比现在多1000倍 would be something like a thousand times more than we see today.
幸而地球有一个完美的轨道 Lucky for us, Earth has the perfect orbit.
木星遮挡了小行星和彗星的侵袭 Jupiter protects us from asteroids and comets.
离太阳够近令我们有液态水 We're close enough to the sun for liquid water
但不会近到令水被蒸发掉 but not so close that it boils away.
这种组合对生命来说怡到好处 It's just the right combination for life.
问题是 Question is,
若我们的太阳系能够创造完美条件 if our solar system could create the perfect conditions,
其它太阳系也能够做到吗? could other solar systems do it, too?
行星探测器发现一个太阳系 Planet hunters have spotted a solar system
距离我们20光年 20 light-years away,
有一颗行星大小和位置都恰到好处 and it has a planet just the right size in just the right place.
世界各地的天文学家 Astronomers around the world are looking for new planets
正在寻找遥远的太阳系的新行星 in distant solar systems.
迄今为止, 已发现了420多颗 So far, they've discovered more than 420.
大多数是像木星这样的气体巨行星 Most are huge gas giants, like Jupiter...
但它们不是离恒星太近就是太远 but they're either very close to the star or much farther away.
2005年, 天文学家有一个惊人发现 Then, in 2005, astronomers made an exciting discovery.
就是有一个太阳系也有岩态行星 They detected a solar system with rocky planets like our own.
这些行星绕着恒星格利泽581运行 These planets orbit a star called Gliese 581.
恒星格利泽581和它的四颗行星 This star, Gliese 581, and its four planets
和我们的太阳系相比十分奇异 is, frankly, quite bizarre relative to our solar system.
这四颗行星都与母恒星十分接近 The four planets we know of all orbit very close to the host star,
四颗行星跟母恒星的距离 all foir of them orbiting closer than the planet Mercury, our closest planet,
都比离太阳最近的水星还近 orbits the sun.
格利泽581是一颗小型恒星 But Gliese 581 is a small star.
无论光和热都比不上太阳 It doesn't burn as brightly or give off as much heat as our sun
所以行星可这样近运行而不会气化 so the planets can orbit much closer without being vaporised
我们知道有四个行星绕着恒星运行 We know of four planets going around this star,
而其中几个相当有趣 and a few of them are quite interesting.
其中一个是地球质量的两倍 There's one that's only about twice the mass of Earth.
它离恒星非常近 Now, that particular one... is very close to the star.
大概太热了, 生命不可能存活 It's probably very hot, too hot for life.
但另一个的质量大约是地球的八倍 But there's another one, about eight times the mass of the Earth,
离恒星的距离足够远 which is getting far enough away from the star
哪里也许适宜居住 that it might be in the habitable zone.
这颗行星的轨道跟地球很相似 Like Earth, this planet orbits at a distance
令它拥有液态水 where water is a liquid.
有水就可能有海洋和生命 And where there's liquid water, there could be oceans and life.
2009年3月, 太空总署发射了… In March 2009, NASA launched
开普勒太空望远镜 the Kepler Space Telescope.
任务是在新太阳系中… Its mission, to search for planets
搜寻与我们相似的行星 similar to our own in new solar systems.
也许会发现有沼气大气层的行星 We may find planets that have methane atmospheres...
或者有氨气大气层的行星 that have ammonia atmospheres.
或许找到覆盖着重质有机物的行星 We may find planets that are covered in heavy organics...
一种柏油状物质 a tar-like materia
或许找到一些有水覆盖的行星 We may find some that are covered by water.
未来10至20年间的一项重大探索 I think one of the glorious quests here in the next decade or two
就是了解宇宙中可能存在的… is to learn the full diversity of the family of Earth-like planets
整个类地行星家族 that may be out there in the universe.
天文学家预计利用开普勒望远镜 With Kepler, astronomers expect to discover hundreds, possibly thousands,
有可能发现数百或数千个新太阳系 of new solar systems.
以银河系为例 Think about our own Milky Way galaxy.
它有5000亿至1万亿颗恒星 The galaxy has roughly 500 billion to a trillion stars.
相当大部分恒星拥有行星 Some fairly large percentage of that have planets.
想想有多少个已知的星系 Now, think about how many galaxies we know of.
我们肯定还没发现宇宙中所有星系 We certainly haven't found all the galaxies in the universe yet.
但我们拍摄到的星系已有600亿个 But the ones we can take a picture of are actually about 60 billion galaxies.
当你今晚抬头仰望星空 When you look up at the night sky tonight,
仅在视线范围内 simply in the path of your sight,
即使肉眼无法看到 even if you can't see it,
也存在着数十亿个太阳系 there are billions of solar systems all around you.
很可能有一个太阳系 And there could be a solar system
也拥有像地球一样的行星 with a planet just like Earth.
发生过一次就有可能发生第二次 If it happened once, it could happen again.
太阳系不会永远存在 Solar systems don't last forever.
轨道会瓦解, 行星会相互碰撞 Orbits fall apart. Planets collide.
这也许会发生在我们的太阳系 It might happen to us.
即使不发生, 在50亿年后… But even if it doesn't, in another five billion years,
一场大灾难也会结束我们的太阳系 a catastrophe will end our solar system as we know it
没有甚么是永恒的, 包括太阳系 Nothing lasts forever, not even solar systems.
我们的太阳系现在看似稳定 Ours may seem stable now,
但其实它正在慢慢瓦解 but, actually, it's very slowly coming apart.
若太阳系的过去是混乱的 If the solar system was chaotic in the past,
不表示它现在已完全安定下来 that doesn't mean its all settled down now.
未来仍然可能出现混乱局面 There is still a possibility of a little bit of chaos in the future.
在未来, 行星彼此间的引力 In the future, the gravitational pull of the planets on each other...
会逐渐打乱它们的轨道 will gradually disrupt their cubits.
也许在数十亿年间 Perhaps, over the billions of years...
行星会在引力作用下相互推撞 the planets will jostle each other in this gravitational way
最终两个行星会相互靠近 so that, eventually, two of the planets will come close to each other.
当这种情形发生时 When that happens, and it will...
两个行星会绕着对方转动 those two planets will engage in a sort of a do-si-do;
一个或两个会被掷入偏远的轨道 flinging one or the other of them, maybe both, into wild orbits,
甚至有可能被弹出太阳系 perhaps ejecting one or both of them from the solar system.
火星也许会被抛出太阳系 Mars could be thrown out of the solar system
水星也许会撞入地球 and Mercury might crash into the Earth.
整个纸牌搭的房子, 即是太阳系 The entire house of cards that is our solar system
会完全瓦解 would completely fall apart.
所有太阳系的诞生和死亡 Solar systems begin and end
都伴随着大量的碰撞和毁灭 with a lot of collisions and destruction.
但暂时毋须恐慌 But don't panic yet.
这些都是数十亿年以后的事 This is gonna take billions of years.
但在太阳系的有生之年 But over the lifetime of the solar system,
这些都是会发生的不测事件 these are eventualities that could come to pass.
不管怎样, 我们的太阳系定会毁灭 But one way or another, our solar system is doomed.
像所有太阳系, 当中心恒星灭亡时 Like all solar systems, the end will come
末日就来临了 when the star at the centre dies.
50亿年后, 我们的太阳 In five billion years, our own star
将会耗尽燃料变成一个红巨星 will run out of fuel and become a red giant
温度会升高, 体积会膨胀 It'll heat up, swel
并将吞噬所有内行星 and engulf the inner planets.
地球表面会被烧焦 The Earths surface will be scorched.,.
海洋会蒸发 the seas will evaporate...
陆地会熔化 and the land will melt
太阳会膨胀直至到达地球的轨道 The sun will become about as big as where the Earth's orbit is
所以世界末日的景象可能是 so a likely scenario for the end of the world
我们会短暂地进入太阳 is that we're going to be inside the sun for a while.
地球会被太阳吞噬 The Earth's gonna get swallowed right up into the sun
会被烧烤, 蒸发 and it's gonna be toast, vapour, literally.
没多久红巨星也会瓦解 After a while, the red giant will fall apart, too,
剩下微小的恒星残骸: 白矮星 leaving behind a tiny corpse of a star called a white dwarf.
白矮星的体积与地球相若 It will be about the size of the Earth
但它要经过数百万年甚至数十亿年 and it will cool off
才能冷却下来 over many millions or billions of years.
这将是我们的太阳系的最终结局 That will be the real end of our solar system.
从这个死寂的地球… From the Earth, this dead, rocky planet
它曾经怀有一个充满生气的文明 that used to harbour an enormously vibrant civilisation,
我们向外看 we will look out,
太阳变成了一个非常苍白的小点 and there will be this fairly faint dot which is our sun,
一颗奄奄一息的白矮星 now a white dwarf, a dying, almost dead star.
内行星的残骸会继续绕白矮星运行 The remains of the inner planets will continue to orbit the white dwarf.
但巨大外行星会完好地继续存在 But the giant outer planets will live on untouched.
在太阳成为红巨星时 They will have warmed up
它们的温度会升高 during the red-giant phase of the sun.
但一旦太阳变成白矮星 But once the sun is a white dwarf,
这些巨行星就会照样生存下去 those giant planets will survive just as well,
保留着它们的氢气和氦气 holding on to their hydrogen and helium,
虽然温度将比以前低 albeit colder than they used to be,
因为白矮星不能给它们提供热力 because that white dwarf will no longer be warming them up.
尽管对于我们的太阳系来说 Even though this is five billion years
这会是50亿年后发生的事 in the future for our solar system,
但对于宇宙中很多星系 it may already have happened
这个过程也许已经发生了 to many other systems throughout the universe.
我们的太阳系摆脱了最初混乱 Our solar system emerged from chaos
以至最终孕育了生命 to eventually support life.
我们很幸运 We were lucky.
行星数量不多不少 We've just the right amount of planets, in the right place,
相互距离恰到好处 at the right distance from each other,
而恒星亦正好是合适的类型 all orbiting the right type of star.
但一切都可以截然不同 But it could have been a very different story.
我们的太阳系有很多方面都很幸运 There are so many things that are fortunate about our solar system,
首先就是太阳 starting with the sun.
太阳非常稳定和温和 The sun is a very stable, easy star,
非常适合生命的进化 a perfect thing for life to evolve around.
我们的生存大概并非偶然 That's probably not a coincidence that we're here.
数十亿年间的一连串不寻常的事 An extraordinary chain of events over billions of years
令我们的太阳系成为生命的摇篮 have made our solar system the perfect place for life to evolve.
今天见到的一切并非一向如是 What we see today is not the way things have always been
也并非永远会如是 and not the way things will always be.
我们不是独一无二 We're not unique,
这只是事物发展的方式 but it is just the way things worked out.
地球必须在适当位置 The Earth has to be in the right place.
其它行星必须在适当位置 The planets had to be in the right place.
巨行星必须在适当位置 The giant planets have to be in the right place
才能保护我们免受撞击 to protect us from impacts.
一切都要合适, 地球才会出现生命 All that has to be right in order to get life on Earth.
我们的太阳系是我们所知的 Ours is the only planetary system we know
唯一有生命的行星系 that supports life.
就太阳系来说 As solar systems go,
它令我们非常特别或完全正常? does that make us extraordinary or perfectly normal?
我们不知道 We don't know.
但每周都有新的太阳系被发现 But every week, we're discovering new solar systems with new planets.
最终发现宇宙中有其它生命 It could be just a matter of time before we discover...
可能只是时间问题 we're not alone.
翻译/摘订时间轴/校对：啥时候摇中