The galactic recipe for a living planet | Karin Öberg

Transcriber: Ivana Korom Reviewer: Krystian Aparta

譯者: Lilian Chiu 審譯者: Helen Chang

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

我相信，除了我以外， 在座還有其他人

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

曾經在某個時點 抬頭看向天上的星星，

and wondered, you know, "Are we it,

心想：「只有我們嗎？

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

或者還有其他像地球一樣 有生命的行星存在？」

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

我想，可能只有我一個人

who has obsessed enough about that question

對那個問題著迷到足以 把它變成我的職涯。

to make it my career.

But moving on.

但，換個話題。

How do we get to this question?

我們是怎麼來到這個問題的？

Well, I would argue the first thing to do

我認為，第一件要做的事，

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

就是轉個方向， 從天空看向我們的地球。

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

想想地球是多麼幸運

to be the living planet it is.

才能成為這個有生命的行星。

Well, it had to be at least somewhat lucky.

一定有些運氣的成份在。

Had we been sitting closer to the Sun

如果地球的位置離太陽近一點

or a bit further away,

或遠一點，

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

地球上所有的水就會蒸發或結冰。

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

行星並不一定有水。

So had we been a dry planet,

如果地球是個乾燥的行星，

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

地球上就不會有多少生命。

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

就算有了現今所有的這些水，

if that water had not been accompanied

如果那些水沒有配合

by the right kind of chemicals to get life going,

對的化學物質讓生命能夠形成，

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

地球也不過是個濕的死行星。

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

有許多地方都可能出錯，

what are the chances that they go right?

它們通通沒出錯的機率有多高？

What are the chances that the planet forms

有多高的機率，地球在形成時，

with at least the basic ingredients needed

也至少有促成生命起源

to have an origins of life happening?

所必要的基本要素？

Well, let's explore that together.

咱們一起來探討一下。

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

若要產生一個有生命的行星，

the first thing you're going to need

首先需要的

is a planet.

就是一個行星。

(Laughter)

（笑聲）

But not any planet will do.

但並非任何行星都可以。

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

你可能會需要一個特殊 且像地球的行星。

A planet that is rocky,

要是個多岩的星球， 才能同時有海洋又有陸地，

so you can have both oceans and land,

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

且它不能離它的恆星太遠或太近，

but at the just-right temperature.

溫度要剛剛好。

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

液態水要能存在於這個溫度下。

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

在我們的銀河系中， 有多少個這樣的行星？

Well, one of the great discoveries of the past decades

過去幾十年間最偉大的發現之一，

is that planets are incredibly common.

就是行星非常常見。

Almost every star has a planet around them.

幾乎每個恆星都有行星繞行，

Some have many.

有的還有很多個。

And among these planets,

在這些行星中，

on the order of a few percent are earthlike enough

大約有幾個百分比和地球夠相近，

that we would consider them potentially living planets.

我們可以將它們視為 可能有生命的行星。

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

所以，要找到對的行星 並沒有那麼困難，

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

畢竟在我們的銀河系 就有大約一千億個恆星。

So that gives you about a billion potential living planets.

這樣算起來約有十億個行星 可能會有生命存在。

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

但是僅僅是溫度 和整體構成條件對了還不夠，

or have the right overall composition.

You also need the right chemicals.

還需要有對的化學物質。

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

所以，要製造出有生命的行星， 第二項重要的要素是——

I think it's pretty intuitive --

我想，這點十分直覺——

it's water.

要有水。

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

畢竟，我們把可能 有生命的行星定義為

if it had the right temperature to keep water liquid.

要有對的溫度來讓水維持在液態。

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

在地球上，生命的基礎就是水。

But more generally,

但更廣泛來說，

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

水是適合化學反應的地方，

It is a very special liquid.

它是種非常特別的液體。

So this is our second basic ingredient.

這是我們的第二項基本要素。

Now the third ingredient, I think,

至於第三項要素，我認為

is probably a little bit more surprising.

可能會比較讓人驚訝一些。

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

在行星上會需要有一些有機物質，

since we are thinking about organic life.

畢竟我們在談的是有機生命。

But the organic molecule

但，似乎位在化學網絡

that seems to be at the center of the chemical networks

中心位置的有機分子，

that can produce biomolecules is hydrogen cyanide.

且能夠產生出生物分子的 有機分子就是氰化氫。

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

如果你知道這種分子 是什麼樣的分子，

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

你就會知道離它遠一點會比較好。

But it turns out

但結果發現， 對於先進的生命形式，

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

比如各位，非常非常不好的東西，

such as yourselves,

is really, really good to get the chemistry started,

竟然對於啟動化學作用 非常非常有幫助，

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

且是能夠造成生命起源的 那一種化學作用。

So now we have our three ingredients that we need,

現在，必要的三項要素都有了，

you know, the temperate planet,

氣候溫和的行星、

water and hydrogen cyanide.

水，以及氰化氫。

So how often do these three come together?

這三項要素同時 存在的機會有多大？

How many temperate planets are there out there

天上有多少氣候溫暖的行星

that have water and hydrogen cyanide?

同時有水和氰化氫？

Well, in an ideal world,

理想的情況，

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

我們現在就會把望遠鏡

轉向其中一個氣候溫暖的行星，

and check for ourselves.

自己做確認。

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

看「這些行星有水和氰化氫嗎」？

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

不幸的是，

我們的望遠鏡不夠大，無法辦到。

We can detect molecules in the atmospheres of some planets.

我們可以偵測到一些行星 在大氣中有分子存在。

But these are large planets

但這些都是大型行星， 通常都非常接近它們的恆星，

sitting often pretty close to their star,

nothing like these, you know, just-right planets

並不像是我們剛才 談到的「對的行星」，

that we're talking about here,

which are much smaller and further away.

對的行星要比較小、比較遠。

So we have to come up with another way.

所以我們得想出其他辦法。

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

我們想出來並採取的另一種方法，

is to instead of looking for these molecules

並不是在行星已經存在時

in the planets when they exist,

去找這些分子，

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

而是去形成新行星的材料 當中尋找這些分子。

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

行星形成的地方，是新恆星周圍 由塵埃與氣體組成的星盤。

And these discs get their material from the interstellar medium.

這些星盤的材料來自星際介質。

Turns out that the empty space you see between stars

結果發現，當你仰望星空 詢問生命相關問題時，

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

看到星球之間的空間，

is not as empty as it seems,

並不是看起來的那麼空，

but actually full of gas and dust,

其實滿是氣體和塵埃，

which can, you know, come together in clouds,

它們會聚集成星雲，

then collapses to form these discs, stars and planets.

接著崩塌形成星盤、恆星、行星。

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

當我們看見這些星雲時，

一定會看到水。

is water.

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

我想，我們傾向於認為水很特別，

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

僅僅我們才有。

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

水是宇宙中最充足的分子之一，

including in these clouds,

也存在於這些星雲中，

these star- and planet-forming clouds.

這些會形成恆星和行星的星雲。

And not only that --

不僅如此——

water is also a pretty robust molecule:

水也是一種很結實的分子：

it's actually not that easy to destroy.

要摧毀水其實並不容易。

So a lot of this water that is in interstellar medium

所以，在星際介質中的許多水

will survive the rather dangerous, collapsed journey from clouds

在星雲崩塌成為星盤、

行星的過程中能夠存留下來。

to disc, to planet.

So water is alright.

所以，水沒問題。

That second ingredient is not going to be a problem.

第二項要素也不會成為問題。

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

行星在形成時多半都能取得水。

So what about hydrogen cyanide?

那氰化氫呢？

Well, we also see cyanides and other similar organic molecules

我們在這些星際雲之中也會看到

氰化氫及其他類似的有機分子。

in these interstellar clouds.

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

但，在這裡我們比較無法肯定

在星雲變成星盤的過程中 分子能留存下來。

going from the cloud to the disc.

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

它們比較脆弱，比較容易損壞。

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

如果我們要確定在新行星形成的

is sitting in the vicinity of new planets forming,

鄰近區域有氰化氫存在，

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

我們就得確保星盤本身就有氰化氫，

in these planet-forming discs.

在這些形成行星的星盤中。

So about a decade ago,

大約十年前，

I started a program to look for this hydrogen cyanide

我開始一項計畫，目的就是

在這些形成行星的星盤中 尋找氰化氫和其他分子。

and other molecules in these planet-forming discs.

And this is what we found.

這是我們的發現。

So good news, in these six images,

好消息是，在這六張影像中，

those bright pixels represent emissions originating from hydrogen cyanide

那些亮點代表

由氰化氫放出的光，

in planet-forming discs hundreds of light-years away

這些光從數百光年外形成行星的星盤

that have made it to our telescope,

一路來到我們的望遠鏡，

onto the detector,

進入偵測器，

allowing us to see it like this.

讓我們能以這種方式看見它們。

So the very good news

非常好的消息是，

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

這些星盤當中的確有氰化氫。

That last, more elusive ingredient.

那就是比較難捉摸的 最後一項要素。

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

壞消息是，

我們不知道它們 位在星盤中的何處。

If we look at these,

若看看這些……

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

沒有人說它們是漂亮的影像，

even at the time when we got them.

就連我們剛入手時也一樣。

You see the pixel size is pretty big

各位可以看見像素非常大，

and it's actually bigger than these discs themselves.

且像素其實比星雲本身還大。

So each pixel here

所以這裡的每個像素代表的範圍

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

實際上都比我們的太陽系還大。

And that means

那就表示，

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

我們不知道氰化氫 是來自星雲中的何處。

And that's a problem,

那是個問題，

because these temperate planets,

因為這些氣候溫暖的行星

they can't access hydrogen cyanide just anywhere,

並不是任何地方的 氰化氫都可以取用，

but it must be fairly close to where they assemble

它們只能取用

距離它們形成處夠近的氰化氫。

for them to have access to it.

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

讓我用個比喻來協助 大家清楚了解這一點，

that is, of cypress growing in the United States.

這個比喻就是生長在美國的柏樹。

So let's say, hypothetically,

比如，做個假設，

that you've returned from Europe

你剛從歐洲回來，

where you have seen beautiful Italian cypresses,

你在歐洲看到了 美麗的義大利柏樹，

and you want to understand, you know,

你想要知道，

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

把它們進口到美國是否行得通。

Could you grow them here?

它們能在這裡生長嗎？

So you talk to the cypress experts,

於是你去找柏樹專家談，

they tell you that there is indeed

他們告訴你，在美國的確

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

有一塊不太熱、不太冷的地帶

where you could grow them.

可以種植它們。

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

如果你有一張像這樣 高解析度的地圖或影像，

it's quite easy to see that this cypress strip

很容易就可以看出這個柏樹帶

overlaps with a lot of green fertile land pixels.

和許多肥沃土地的綠色像素重疊。

Even if I start degrading this map quite a bit,

就算我開始把這張地圖變差，

making it lower and lower resolution,

讓解析度越來越低，

it's still possible to tell

仍然可以判斷

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

有一些肥沃的土地 和這條柏樹帶重疊。

But what about if the whole United States

但，如果整個美國

is incorporated into a single pixel?

都被放進單一個像素中呢？

If the resolution is that low.

如果解析度就是那麼低，

What do you do now,

你要怎麼辦？

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

現在你要如何辨視出 在美國的哪些地方能種柏樹？

Well the answer is you can't.

答案是，辦不到。

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

肯定在某處會有肥沃的土地，

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

要不然這個像素就不會帶有綠色，

but there's just no way of telling

但就是沒辦法辨視出

whether any of that green is in the right place.

那綠色的區域是否在對的地方。

And that is exactly the problem we were facing

同樣的問題也發生在我們

with our single-pixel images of these discs

使用單一像素星盤影像

with hydrogen cyanide.

來找氰化氫時。

So what we need is something analogous,

所以我們需要類似的東西，

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

至少要有我剛才給各位 看的那些低解析度地圖，

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

才能分辨出氰化氫是否位在

行星在形成時能夠取得的位置。

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

So coming to the rescue, a few years ago,

幾年前，救星出現了，

is this new, amazing, beautiful telescope ALMA,

救星就是一種很了不起 且很美麗的新望遠鏡叫做 ALMA，

the Atacama Large Millimeter and submillimeter Array

阿塔卡瑪大型毫米及次毫米波陣列，

in northern Chile.

位在智利北部。

So, ALMA is amazing in many different ways,

ALMA 在許多方面都很棒，

but the one that I'm going to focus on

但我要強調的部分，

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

各位可以在圖上看到， 它被稱為「一個」望遠鏡，

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

但各位可以在影像中看到， 它其實有許多碟形天線。

And this is a telescope that consists of 66 individual dishes

這個望遠鏡包含 六十六個個別的天線，

that all work in unison.

一起配合運作。

And that means that you have a telescope

那就表示，這個望遠鏡的大小

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

取決於能將這些天線擺放到

away from one another.

距離彼此多遠的距離。

Which in ALMA's case are a few miles.

就 ALMA 來說， 這個距離是幾英里。

So you have a more than mile-sized telescope.

所以你有一台超過 一英里大的望遠鏡。

And when you have such a big telescope,

有這麼大的望遠鏡，

you can zoom in on really small things,

你就可以將非常小的東西放大，

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

也可以針對這些形成行星的星盤 來製作氰化氫的地圖。

So when ALMA came online a few years ago,

幾年前 ALMA 上線時，

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

我最先提議的用途之一 就是用來製作這種地圖。

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

在星盤中的氰化氫地圖 看起來會是什麼樣子？

Is the hydrogen cyanide at the right place?

氰化氫有在對的位置嗎？

And the answer is that it is.

答案是，有的。

So this is the map.

就是這張地圖。

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

各位可以看見，在整個星盤 各處都有氰化氫釋放出的光。

First of all, it's almost everywhere,

首先，它幾乎到處都有，

which is very good news.

這是非常好的消息。

But you have a lot of extra bright emission

但還有許多額外釋放出來的亮光，

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

從接近恆星的地方， 朝向星盤的中心。

And this is exactly where we want to see it.

我們就是希望在這裡看到它。

This is close to where these planets are forming.

這裡很接近行星形成的位置。

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

並不是只有一個星盤 可以看到這種現象——

here are three more examples.

這裡還有三個例子。

You can see they all show the same thing --

可以看到它們都呈現 一樣的狀況——

lots of bright hydrogen cyanide emission

許多氰化氫所釋放的光，

coming from close to the center of the star.

從接近恆星中心的位置釋放出來。

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

老實說，不見得都能看到這種現象。

There are discs where we see the opposite,

在一些星盤中會看到相反的現象，

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

在中心的部分有一個洞 沒有光線釋放。

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

這和我們想看見的畫面 完全相反，對吧？

This is not places where we could research

我們不可能研究在這些星盤中

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

行星形成的位置附近 有沒有氰化氫存在。

But in most cases,

但在大部分的情況下， 我們不只偵測氰化氫，

we just don't detect hydrogen cyanide,

but we detect it in the right place.

而是在對的地方偵測氰化氫。

So what does all this mean?

這是什麼意思？

Well, I told you in the beginning

在一開始時我有說過，

that we have lots of these temperate planets,

有許多氣候溫暖的行星存在，

maybe a billion or so of them,

也許有十億個，

that could have life develop on them

如果這些行星有對的要素，

if they have the right ingredients.

上面都有可能會有生命發展。

And I've also shown

我也說明了

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

大部分時候，對的要素都在——

有水、有氰化氫，

we have water, we have hydrogen cyanide,

there will be other organic molecules as well

也有隨著氰化物而來的 其他有機分子。

coming with the cyanides.

This means that planets with the most basic ingredients for life

這就表示，在我們的銀河系中，

有相當多行星具備形成生命 所必要的最基本要素。

are likely to be incredibly common in our galaxy.

And if all it takes for life to develop

如果只要有這些基本要素

is to have these basic ingredients available,

就可以發展出生命，

there should be a lot of living planets out there.

那在宇宙中應該會有 許多有生命的行星。

But that is of course a big if.

但當然這是個很大的「如果」。

And I would say the challenge of the next decades,

我認為接下來數十年，

for both astronomy and chemistry,

天文學和化學所面對的挑戰

is to figure out just how often

就是要找出有多大的可能性，

we go from having a potentially living planet

我們能夠從認為 一個行星可能有生命存在，

to having an actually living one.

變成確定那裡真的有生命存在。

Thank you.

謝謝。

(Applause)

（掌聲）