The galactic recipe for a living planet | Karin Öberg

Transcriber: Ivana Korom Reviewer: Krystian Aparta

翻译人员: Meng Ren 校对人员: Yolanda Zhang

So I'm pretty sure that I'm not the only one in this room

你是否曾在某个时刻， 望着天上的星星，

who at some point have found myself, you know, looking up towards the stars,

思索着：“我们是唯一的吗？ 宇宙中还有像地球一样的

and wondered, you know, "Are we it,

有生命存活的星球吗？”

or are there other living planets out there such as our own?"

我确信我不是这个房间里 唯一一个这样做过的人。

I guess it is possible that I'm then the only person

但我可能是唯一一个

对这个问题痴迷到

who has obsessed enough about that question

to make it my career.

把解开它当作毕生事业的人。

But moving on.

那么言归正传。

How do we get to this question?

我们为什么会思考这个问题呢？

Well, I would argue the first thing to do

我建议，咱们先把目光 从天空中收回，

is to turn our eyes back down from the sky to our own planet, the Earth.

回到我们赖以生存的地球上。

And think about just how lucky did the Earth have to be

然后想一想，地球成为这样一个 有生命力的行星，

to be the living planet it is.

是多么幸运的一件事儿。

Well, it had to be at least somewhat lucky.

多少得靠点运气吧。

Had we been sitting closer to the Sun

如果我们距离太阳再近点儿，

or a bit further away,

或者再远点儿，

any water that we have had would have boiled off or frozen over.

那地球上所有的水要么 因过热而蒸发，要么因寒冷被冻住。

And I mean, it's not a given that a planet has water on it.

不是所有的行星都有水存在。

So had we been a dry planet,

如果地球是干的，

there would not have been a lot of life on it.

那么它将无法孕育生命。

And even if we had had all the water that we have today,

即使地球上存在我们今天 所拥有的水资源，

if that water had not been accompanied

但如果没有

by the right kind of chemicals to get life going,

适合生命生存的化学物质，

we would have a wet planet, but just as dead.

那地球也只会是一个 死气沉沉的大水球。

So it's so many things that can go wrong,

可能导致失败的因素这么多，

what are the chances that they go right?

那么成功的几率有多大呢？

What are the chances that the planet forms

在一颗行星上，

with at least the basic ingredients needed

存在着有助于生命起源的 基本元素的概率

to have an origins of life happening?

到底有多大呢？

Well, let's explore that together.

那么，我们一起来看一看。

So if you're going to have a living planet,

一颗可孕育生命的行星，

the first thing you're going to need

至少应该是

is a planet.

一颗行星。

(Laughter)

（笑声）

But not any planet will do.

但并不是随便一颗行星就可以了。

You're probably going to need a rather specific and earthlike planet.

至少应该是一颗类地行星，

A planet that is rocky,

有着岩石表面，

so you can have both oceans and land,

拥有海洋和陆地两种地表形态。

and it's sitting neither too close nor too far away from its star,

与恒星的距离不太远也不太近，

but at the just-right temperature.

要在温度适宜的距离内。

And it's just right for liquid water, that is.

也就是说， 水以液态形式存在。

So how many of these planets do we have in our galaxy?

在银河系中，这样的行星有多少呢?

Well, one of the great discoveries of the past decades

过去几十年间，我们 取得的重大发现之一就是，

is that planets are incredibly common.

行星是再常见不过的了。

Almost every star has a planet around them.

几乎所有的恒星都有 一颗围绕其转动的行星。

Some have many.

有的拥有许多颗。

And among these planets,

在这些行星中，

on the order of a few percent are earthlike enough

约百分之几可被视为类地行星，

that we would consider them potentially living planets.

我们认为它们是 可能孕育生命的行星。

So having the right kind of planet is actually not that difficult

因此，合适的行星并不难寻，

when we consider that there's about 100 billion stars in our galaxy.

考虑到整个银河系 大约有一千亿颗恒星，

So that gives you about a billion potential living planets.

那么潜在的宜居行星 大约有十亿颗。

But it's not enough to just be at the right temperature

但是适宜的气温或环境组成

还不够，

or have the right overall composition.

You also need the right chemicals.

还需要合适的化学物质。

And what the second and important ingredient to make a living planet is --

可孕育生命的行星所需的 第二重要的物质，

I think it's pretty intuitive --

我们不难猜想——

it's water.

那就是水。

After all, we did define our planet as being potentially living

毕竟，温度之所以能定义 环境是否可生存，

if it had the right temperature to keep water liquid.

是因为它能决定 水是否以液态形式存在。

And I mean, here on Earth, life is water-based.

在地球上， 水是生命结构的基本构成。

But more generally,

更广泛地讲，

water is just really good as a meeting place for chemicals.

水是一种非常优良的化学反应介质。

It is a very special liquid.

它是一种很特别的液体。

So this is our second basic ingredient.

所以水是第二个基本要素。

Now the third ingredient, I think,

现在来谈第三个要素，

is probably a little bit more surprising.

它可能会让你们有点吃惊。

I mean, we are going to need some organics in there,

我们现在需要一些有机物，

since we are thinking about organic life.

因为我们想要有机生命体。

But the organic molecule

这种能组成化学物质，

that seems to be at the center of the chemical networks

并进一步组成生物分子的 核心有机分子

that can produce biomolecules is hydrogen cyanide.

就是氰化氢。

So for those of you who know what this molecule is like,

如果你了解这种物质，

you know it's something that it's a good idea to stay away from.

你就知道，我们应该 尽量离它远点儿。

But it turns out

但事实证明，

that what's really, really bad for advanced life forms,

对高等生物体，比如人类

such as yourselves,

非常有害的物质，

is really, really good to get the chemistry started,

可能对化学反应的发生十分有利，

the right kind of chemistry that can lead to origins of life.

而适当的化学反应 将带来生命的起源。

So now we have our three ingredients that we need,

那么现在，三种要素都有了，

you know, the temperate planet,

适宜的行星、

water and hydrogen cyanide.

液态水，以及氰化氢。

So how often do these three come together?

那么，三者同时出现的 概率有多大呢？

How many temperate planets are there out there

在所有适宜的行星中，

同时存在着液态水和氰化氢的 又有多少呢？

that have water and hydrogen cyanide?

Well, in an ideal world,

理想状态下，

we would now turn one of our telescopes towards one of these temperate planets

我们打开望远镜， 对着这些行星，

and check for ourselves.

看一下就好了。

Just, "Do these planets have water and cyanides on them?"

无非就是确认 “行星上有没有液态水和氰化物？”

Unfortunately, we don't yet have large enough telescopes to do this.

不幸的是，我们还没有 具备理想观测能力的望远镜。

We can detect molecules in the atmospheres of some planets.

我们能对一部分行星的 大气层分子进行探测。

But these are large planets

但仅限于大型的

sitting often pretty close to their star,

且与其所环绕的恒星 距离很近的行星。

nothing like these, you know, just-right planets

并不是我们所说的

that we're talking about here,

那些刚好符合条件的行星，

which are much smaller and further away.

它们更小也更远。

So we have to come up with another way.

因此我们必须另想一个办法。

And the other way that we have conceived of and then followed

我们想到并实施的另一个办法是，

is to instead of looking for these molecules

与其从现存的行星里

in the planets when they exist,

寻找这些物质分子，

is to look for them in the material that's forming new planets.

不如着眼于 正在合成新行星的物质。

So planets form in discs of dust and gas around young stars.

行星由年轻恒星周围的 气体尘埃盘构成。

And these discs get their material from the interstellar medium.

这些盘状物由星际介质组成。

Turns out that the empty space you see between stars

事实上，当你凝望天空， 思索存在主义问题时

when you are looking up towards them, asking existential questions,

所目睹的恒星之间的空隙，

is not as empty as it seems,

并非像看起来的那么空空荡荡。

but actually full of gas and dust,

那里面充满了气体和尘埃，

which can, you know, come together in clouds,

汇合在一起形成了星云，

then collapses to form these discs, stars and planets.

星云坍缩后形成了气体尘埃盘、 恒星，和行星。

And one of the things we always see when we do look at these clouds

当观察星云时， 你总能发现一种物质，

is water.

那就是水。

You know, I think we have a tendency to think about water

我想，人们总是倾向于将水

as something that's, you know, special to us.

视为一种特别的存在。

Water is one of the most abundant molecules in the universe,

水是宇宙中含量最高的物质之一，

including in these clouds,

在这些星云中也不例外。

these star- and planet-forming clouds.

这些形成恒星与行星的星云。

And not only that --

不仅如此——

water is also a pretty robust molecule:

水还是一种非常稳定的分子：

it's actually not that easy to destroy.

它不易被破坏。

So a lot of this water that is in interstellar medium

因此，星际介质中包含的水分子，

will survive the rather dangerous, collapsed journey from clouds

在危险的星云坍缩过程中 被保存了下来，

to disc, to planet.

进入气体尘埃盘， 最后成为行星的一部分。

So water is alright.

所以，水是存在的，

That second ingredient is not going to be a problem.

搜寻这第二种元素并不难。

Most planets are going to form with some access to water.

大多数行星的形成 多多少少会有水的参与。

So what about hydrogen cyanide?

那么，有没有氰化氢呢？

Well, we also see cyanides and other similar organic molecules

首先，我们在这些星际介质中

也观测到了氰化物 和其他相似的有机分子。

in these interstellar clouds.

But here, we're less certain about the molecules surviving,

但是，从星云过渡到气体尘埃盘时， 多少分子能存活下来，

going from the cloud to the disc.

我们不太有信心。

They're just a bit more delicate, a bit more fragile.

它们相对比较精巧，比较脆弱。

So if we're going to know that this hydrogen cyanide

所以，如果我们想确定氰化氢

is sitting in the vicinity of new planets forming,

存在于正在形成的行星附近，

we'd really need to see it in the disc itself,

我们就必须 从正在形成这颗行星的

in these planet-forming discs.

气体尘埃盘中找到它。

So about a decade ago,

大约十年前， 我成立了一个项目，

I started a program to look for this hydrogen cyanide

从形成某颗行星的气体尘埃盘中

and other molecules in these planet-forming discs.

寻找氰化氢和其他分子物质。

And this is what we found.

我们找到了这些。

好消息是，在这六张图片中

So good news, in these six images,

those bright pixels represent emissions originating from hydrogen cyanide

那些较亮的像素点代表 在几百光年之外，

行星气体尘埃盘中氰化氢的释放。

in planet-forming discs hundreds of light-years away

that have made it to our telescope,

它们进入了望远镜观测范围内，

onto the detector,

被探测器捕捉到，

allowing us to see it like this.

于是被我们所看见了。

So the very good news

那么，好消息是我们能确定

is that these discs do indeed have hydrogen cyanide in them.

这些气体尘埃盘中 确实存在着氰化氢，

That last, more elusive ingredient.

这最后一种难以捉摸的物质。

坏消息是，我们无法探测出 气体尘埃盘中氰化氢的具体方位。

Now the bad news is that we don't know where in the disc it is.

If we look at these,

我们来看看这几幅图。

I mean, no one can say they are beautiful images,

没人觉得它们很美吧，

even at the time when we got them.

我们收到时也不觉得。

You see the pixel size is pretty big

看得出来这些像素点挺大的，

and it's actually bigger than these discs themselves.

实际上比它们所在的 气体尘埃盘还大。

So each pixel here

这里的每一个像素点

represents something that's much bigger than our solar system.

都代表着一个 远远大于太阳系的空间。

And that means

也就是说，我们也不知道

that we don't know where in the disc the hydrogen cyanide is coming from.

氰化氢到底位于 气体尘埃盘的哪个方位。

And that's a problem,

这就比较麻烦了，

because these temperate planets,

因为对于适宜的行星来说，

they can't access hydrogen cyanide just anywhere,

不是任何的氰化氢都有用，

but it must be fairly close to where they assemble

它们必须与行星的距离够近，

for them to have access to it.

才能被行星利用。

So to bring this home, let's think about an analogous example,

为了讲得更明白一点， 我们来做个类比，

that is, of cypress growing in the United States.

就拿在美国种柏树来举例好了。

So let's say, hypothetically,

假设，

that you've returned from Europe

你去了一趟欧洲，

where you have seen beautiful Italian cypresses,

在那儿看到了美丽的意大利柏树，

and you want to understand, you know,

于是你想知道

does it make sense to import them to the United States.

把柏树引入到美国的可能性。

Could you grow them here?

你能在美国种柏树吗？

So you talk to the cypress experts,

于是你去咨询了柏树专家，

they tell you that there is indeed

他们告诉你的确有一个横跨美国、

a band of not-too-hot, not-too-cold across the United States

气候温和的带状区域，

where you could grow them.

能种植柏树。

And if you have a nice, high-resolution map or image like this,

如果你有一张像这样的 完整高清的地图，

it's quite easy to see that this cypress strip

就不难发现这块适合 柏树生长的带状区域

overlaps with a lot of green fertile land pixels.

覆盖了许多代表 肥沃绿色植被带的像素点。

Even if I start degrading this map quite a bit,

即使我降低地图的清晰度，

making it lower and lower resolution,

一点一点降低它的分辨率，

it's still possible to tell

我们还是能看出

that there's going to be some fertile land overlapping with this strip.

有一些土壤肥沃的地带 与带状区域重合。

But what about if the whole United States

那么，如果整个美国

is incorporated into a single pixel?

被包含在一个像素点内呢？

If the resolution is that low.

如果分辨率这么低，

What do you do now,

你怎么办？

how do you now tell whether you can grow cypresses in the United States?

现在你如何判断在美国的 哪个区域能种植柏树？

Well the answer is you can't.

你无法判断。

I mean, there's definitely some fertile land there,

我们能确定那儿 有一些适合的土壤，

or you wouldn't have that green tint to the pixel,

否则图中的像素点 不会是绿色的，

but there's just no way of telling

但我们无法得知，

whether any of that green is in the right place.

绿色地带的具体位置。

And that is exactly the problem we were facing

这就是当我们只能拍摄到

with our single-pixel images of these discs

含氰化氢的气体尘埃盘的 单像素图像时，

with hydrogen cyanide.

所面临的问题。

So what we need is something analogous,

所以，我们需要的 也是类似的东西，

at least those low-resolution maps that I just showed you,

至少也是一张低像素的图像， 就像那张美国地图，

to be able to tell whether there's overlap between where the hydrogen cyanide is

使我们能够判断 氰化氢所处的方位

and where these planets can access it as they are forming.

和形成中的行星之间 是否存在重合。

So coming to the rescue, a few years ago,

那么我们在几年前 找到的解决办法，

is this new, amazing, beautiful telescope ALMA,

就是这组无与伦比的 新型 ALMA 望远镜——

the Atacama Large Millimeter and submillimeter Array

位于智利北部的“阿塔卡马

in northern Chile.

大型毫米波/亚毫米波阵列”。

So, ALMA is amazing in many different ways,

ALMA 在各个方面都卓越非凡，

but the one that I'm going to focus on

但我想着重讲的是，

is that, as you can see, I call this one telescope,

正如你们所见， 我们称它为一个望远镜，

但这张图里有许多个天线盘。

but you can there are actually many dishes in this image.

And this is a telescope that consists of 66 individual dishes

这是一个拥有 66 座 独立天线盘的望远镜，

that all work in unison.

它们协同工作。

And that means that you have a telescope

这就意味着，

每座天线盘间隔的 最大距离相加，就能得到

that is the size of the largest distance that you can put these dishes

away from one another.

这座望远镜的最大尺寸，

Which in ALMA's case are a few miles.

也就是说， ALMA 的尺寸可达好几英里。

So you have a more than mile-sized telescope.

这是一座几英里大的望远镜。

And when you have such a big telescope,

透过如此巨型的望远镜，

you can zoom in on really small things,

你可以聚焦到非常细微的物体上，

including making maps of hydrogen cyanide in these planet-forming discs.

比如，绘制正在形成行星的 气体尘埃盘里的氰化氢分布图。

So when ALMA came online a few years ago,

几年前当 ALMA 首次上线时，

that was one of the first things that I proposed that we use it for.

这就是我提议的项目之一。

And what does a map of hydrogen cyanide look like in a disc?

那么，气体尘埃盘里的氰化氢分布图 到底长什么样呢？

Is the hydrogen cyanide at the right place?

氰化氢所在的方位合理吗？

And the answer is that it is.

答案是肯定的。

So this is the map.

这就是分布图。

You see the hydrogen cyanide emission being spread out across the disc.

你可以看到被释放的氰化氢 分散在整个气体尘埃盘内，

First of all, it's almost everywhere,

几乎无处不在，

which is very good news.

这是个好消息。

But you have a lot of extra bright emission

而且你还可以看到 一些特别光亮的释放物，

coming from close to the star towards the center of the disc.

从气体尘埃盘中心处的恒星 散发出来。

And this is exactly where we want to see it.

这正是我们希望看到的 氰化氢的位置。

This is close to where these planets are forming.

行星们将在这附近形成。

And this is not what we see just towards one disc --

不只一个气体尘埃盘 呈现出了这样的景象，

here are three more examples.

这儿还有三个例证。

You can see they all show the same thing --

你可以看到他们都展示了 相同的现象——

lots of bright hydrogen cyanide emission

大量光亮的氰化氢

coming from close to the center of the star.

从恒星的中心附近被释放出来。

For full disclosure, we don't always see this.

然而，情况不总是这样的。

There are discs where we see the opposite,

我们也观察到一些 情况相反的气体尘埃盘，

where there's actually a hole in the emission towards the center.

它们的中心形成了一个 氰化氢中空地带。

So this is the opposite of what we want to see, right?

这恰恰不是我们 想要的，对吧？

This is not places where we could research

这不是我们所需要的

if there is any hydrogen cyanide around where these planets are forming.

氰化氢与正在形成的行星 所重合的区域。

But in most cases,

但是，大多数情况下，

we just don't detect hydrogen cyanide,

我们不光探测氰化氢是否存在，

but we detect it in the right place.

还要看它是否存在于正确的位置。

So what does all this mean?

这一切意味着什么呢？

Well, I told you in the beginning

正如我在开场时所说的，

that we have lots of these temperate planets,

宇宙中适宜的行星非常多，

maybe a billion or so of them,

大约有十亿个，

that could have life develop on them

它们只要满足必需的物质条件，

if they have the right ingredients.

就可能出现生命。

And I've also shown

我也展示了

that we think a lot of the time, the right ingredients are there --

在很多时候， 必要的物质是存在的——

we have water, we have hydrogen cyanide,

我们发现了水和氰化氢，

there will be other organic molecules as well

还有其他的有机分子

coming with the cyanides.

随氰化物一起出现。

This means that planets with the most basic ingredients for life

这说明能够孕育生命的行星

are likely to be incredibly common in our galaxy.

可能在银河系中极其常见。

And if all it takes for life to develop

那么，如果只要有这些基础物质，

is to have these basic ingredients available,

生命就会出现的话，

there should be a lot of living planets out there.

拥有生命的行星 应该是数不胜数。

But that is of course a big if.

但我说的是“如果”。

And I would say the challenge of the next decades,

我认为，在下一个十年，

for both astronomy and chemistry,

天文学和化学将 面临的挑战是，

is to figure out just how often

我们将研究

we go from having a potentially living planet

在可能孕育生命的行星里，

to having an actually living one.

实际产生生命的行星的比率。

Thank you.

谢谢大家。

(Applause)

（掌声）