宇宙（2007）

The Universe S02E01

Part 5 April 23, 2021, 10:04 a.m.

I'm so excited about Gliese 436.I'm almost jumping out of my clothes.
它是飞马座51以来最重大的发现
It's the most importantdiscovery since 51 Pegasi,
可能还要重要
maybe even more important.
让杰夫.马西如此兴奋的是
What has Geoff Marcy so excited
发现这颗行星的密度是每立方厘米2.1克
is that this planet was found to have adensity of 2.1 grams per cubic centimeter.
这意味着什么?是个了不起的数字
What does that mean?it's a spectacular number,
因为每个小学生都知道
because every schoolchild knows that
水的密度是每立方厘米1克
the density of water is onegram per cubic centimeter,
我们同样知道从街上随便拾起来的石块
and we also know that rocksthat you pick up on the street,
我们地球的密度例如这石块
the density of our Earth,for example, as a rock,
每立方厘米大约为5克
is about five gramsper cubic centimeter.
因此这颗行星围绕着格雷司436
And therefore, thisplanet, around 436,
是石头和水的混合体
is composed of a mixtureof rock and water.
由石头和水组成的行星听起来象地球
A planet made of rock and watersounds tantalizingly Earth-like,
但格雷司436 b的水太多
but gliese 436 b has so much water
根本就不会有陆地
that there would be nolandmasses exposed at all.
你不会想去那个水世界游泳的吧
And you wouldn't wanna take a swim inthe oceans of this watery alien world.
可能其表面有层液态水
There may be a layer ofliquid water on the surface,
但是下面的东西就有点神秘了
but below that, thingsbegin to get a little weird.
有如此多的水
There's so much water
水分子很轻的引力将向中心挤压
that the sheer gravitational force
of the water moleculespressing down toward the center
将水紧紧地挤压在一起
will crush the water so tightly
水分子将相互紧挨着
that the water molecules arealmost touching each other.
这是种很奇怪的水事实上我们称它为"冰" 即使它不冷
It's a very odd type of water. In fact,we call it "ice" even though it's not cold
因为水分子将被排列组合成冰的结构
because the watermolecules will be arranged
但是仅仅是因为高压
in a structure like ice, butonly due to its high pressure.
显然格雷司436 b不完全是类地行星
Clearly, gliese 436 b isn'tquite an Earth-like planet,
那么这颗日外行星是什么呢?
but what about this alien world?
什么样的行星才是真正的类地行星呢?
What would make an alienplanet truly Earth-like?
应该是主要由岩石构成
It should be made primarily of rock
有充分的水组成的海洋
with enough water for oceans,
但水又不能太多陆地不能完全被淹没
but not so much water that the landmasses are completely submerged.
也必须在它的恒星系里是适宜居住的地方
It would also have to be inits star's habitable zone.
适宜居住的典型的概念是
The typical idea for a habitable zone
它与恒星的距离能够在其表面存在液态水
is the range of distances froma star where an Earth-like planet
could have liquid water at its surface.
这个概念就是如果将地球推近点
The idea would be that if you tookEarth and pushed it in too far,
海洋就会沸腾就不利于生存
the oceans will all boilaway, and that's bad for life;
而如果将地球推远点
or if you took the Earthand pushed it out too far,
海洋将通通接成冰也不利于生存
the oceans would all freeze,and that's bad for life.
在我们的太阳系里
In our own solar system,
适宜居住的区域是从火星的轨道
the habitable zoneranges from Mars' orbit
到金星的轨道之间
into as close as to where Venus orbits.
然而日外太阳系里的可居住区域各不相同
But the habitable zone inalien solar systems varies
有赖于其宿主星的温度有多高
depending on how hot the star is.
当前我们找到可居住的类地行星的最大希望
Currently, our best hope forfinding habitable Earth-like planets
是针对相对较冷较暗的恒星进行调查
is to look around cool, dim stars
此类恒星叫做"红矮星'即"中矮星"
called "red dwarfs" or "m dwarfs."
中矮星本身是种很特殊的恒星
The m dwarfs themselvesare very special stars.
如果我们的太阳是100W的灯泡的话
So our sun might be 100-watt lightbulb,
中矮星大概就是10W的灯泡
an m dwarf is perhapsa 10-watt light bulb,
因此就意味着还是够温暖的
and so what that means isthat to stay warm enough
会有液态的水而不是冰
so that you have liquid water, not ice,
但是还是不够热行星要靠得很近才行
but still not too hot, youmove the planet in much closer.
那些靠得很近的行星很容易通过手段被发现
And those close planetsare easier for us to detect
因为它们拽拉宿主星会更强些
with our technique becausethey tug on the star a bit more.
其中一颗中矮星格雷司876
One of these m dwarfs,called "Gliese 876"
已经发现至少有3颗行星
has been found to have atleast three planets orbiting it.
其中两颗是气体巨星
Two of them are gas giants,
但是第三颗格雷司876 d
but the third, Gliese 876 d,
是到目前为止发现的最小的行星
is one of the smallestplanets discovered so far,
大概是地球质量的6到7倍
at roughly six or seventimes the mass of the Earth.
它也刚好处在其宿主星的可居住区的边缘
It's also just on the edgeof its star's habitable zone.
它绕宿主星一圈只需要1.9天
The planet orbits in just1.9 days around its host star,
但是因为宿主星的亮度很暗
but because the host staris so low in luminosity,
它所处的位置可以想象得出可居住区域是什么样子
it puts it on the edge of what youmight imagine a habitable zone to be.
会有一些地方绕着行星背后一圈
There could be some region, a ringaround the planet towards the backside
那里的温度刚好使得液态水存在
where the temperature's actuallyjust right for liquid water to exist.
当它第一次被发现时
When it was first discovered,
科学家们高度称赞它是第一颗超级行星
scientists hailed this planetas the first of the super Earths.
是地球质量的7倍
Seven times the mass of the Earth
听起来很接近我们地球
sounds so close to the size of our Earth
怀疑它可能是颗岩石行星
that you wonder whetheror not it's a rocky planet,
或许还有厚厚的大气层
maybe with a thick atmosphere.
然而现在专家学者还是没有把握
But today, the experts are unsure
究竟是不是颗岩石大行星
whether this is a large,rocky planet at all.
格雷司876 b
Like Gliese 436 b,
可能完全覆盖着致密水的海洋
it may be completely covered inan ocean of super dense water.
把它称为超级行星暗示着
To call it a "super Earth" is to suggest
我们已经找到了一颗地球亲密的堂兄了
that we've found a planet that'sa close cousin of our Earth.
现在我宁愿它是个远房♥亲戚
I would now rather thinkof it as a distant cousin,
与地球不无关系
not unrelated to our Earth,
但是离得太远其实它更象是太阳系里的海王星
but far enough away,indeed, more like neptune
有个大的岩石核
in our own solar system,that has a big, rocky core,
但是包裹着水的外壳
but surrounded by abig envelope of water.
因此发现类地行星的竞赛在继续进行
So the race continues todiscover the first truly
Earth-like planet.
在亚利桑那大学
At the university of Arizona,
天文学家莱尔德.克洛斯正期待
astronomer laird closeis hoping to capture
获得第一颗日外地球的照片
the first picture of an alien Earth.
然而要达到这个目标望远镜技术需要有个大的飞跃
But to do that will take a giantleap in telescope technology.
这里是斯图尔特天文镜面实验室
Here at the stewardobservatory mirror lab,
在大学足球场看台下面的大空间里
in a cavernous spaceunderneath the bleachers
of the university's football stadium,
工程师们正在制♥作♥下一代的天文望远镜
engineers are working on the nextgeneration of supertelescopes.
这是迄今为止最大的镜面
This is the largest mirrorthat's ever been made.
镜面直径8.4米
This mirror is 8.4 meters across,
然而这只是巨型麦哲仑望远镜的7块镜面中的一块
but it's just 1/7th
of the size that's needed forthe giant magellan telesce.
当把7块这样大小的镜面拼起来
And together, when combinedwith seven other mirrors like it
组合成巨型麦哲仑望远镜后
with the giant magellan telescope,
我们就能够直接看到日外行星
we will be able toactually directly image
extrasolar planets and maybe even
甚至还可能看到日外类地行星了
Earth-like planets around alien suns.
预计会在2016年完成
Scheduled for completion in 2016,
这个望远镜拍到的会比哈勃太空望远镜拍到的
this telescope will be able tomake images up to 10 times sharper
图象清晰10倍
than the hubble space telescope.
美国航♥天♥局和欧洲航♥天♥局
Nasa and the European Space Agency
也正在进行几项任务
are also developing several missions
用太空望远镜来搜索我们的行星亲戚
that will use space-based telescopes
to search the starsfor our planetary kin.
这对人类来说无法想象会有多么振奋不管那些小光点周围是否存在行星
This will be incrediblyexciting for humankind
to know whether or not aroundthose little points of light
我们观察夜晚的星空
that we see in the night sky,whether there's Earth-like planets
不管那些恒星周围有没有类地行星
tied in an orbit around those stars.
随着技术的提高
As technology improves,
我们将会找到更象地球的行星
we're gonna be able to find planetsthat look much more like the Earth,
或许那些行星上会有生命存在
planets that, perhaps,have life on them,
甚至还可能存在森林火车
and maybe even planets thathave forests and steam trains.
天文学家们已经将自己的毕生奉献在这个事业中了
The astronomers who havededicated their lives to this quest
大家都相信找到第一颗真正的类地行星
all believe it's only amatter of time before we find
唯一重要的就是时间
the first truly Earth-like planet.
我可以告诉你最让人激动的是
The most exciting thingI can tell you is that
我们现在经常发现
we are now routinely discovering,
普遍发现那种是地球质量5到10倍的行星
commonly discovering planets
that are a mere five or 10times the mass of our Earth.
我们不会满天空地去找行星
We're not quite to the pointwhere we're finding Earths,
而是完全有目标的去找的
and that's where we really want to be.
我们在找和我们的地球家园
But we're finding planetsthat are ever so close
非常亲近的行星
to our home planet.
所以说其实一旦跨过最后的一道槛
So when we actually do cross thatfinal threshold and do find evidence
找到存在可居住行星的证据
that there's a habitableplanet out there,
那对人类来说将是个划时代的事件
this is gonna be a quite anepochal event for humanity.
然而大家不必过多地担心
People should not worry too much yet,