Garik Israelian: What's inside a star?

譯者: Joan Liu 審譯者: Shelley Krishna Tsang

I have a very difficult task.

我有一個困難的任務。

I'm a spectroscopist.

我是個光譜學家。

I have to talk about astronomy without showing you

我要講天文學可是我不要給你們看

any single image of nebulae or galaxies, etc.

任何一張有星雲或銀河的圖片

because my job is spectroscopy.

因為我的工作是光譜學

I never deal with images.

我從來不看實際圖像。

But I'll try to convince you

可是我要試著說服你們

that spectroscopy is actually something which can

光譜學圖片是真的能夠

change this world.

改變世界的。

Spectroscopy can probably answer the question,

光譜學或許可以回答下面這樣的問題：

"Is there anybody out there?"

「真的有外星人嗎?」

Are we alone? SETI.

是只有我們嗎?SETI(尋找外太空星球智慧生命計畫)

It's not very fun to do spectroscopy.

做光譜學不是很有趣。

One of my colleagues in Bulgaria,

我一個在保加利亞的同事

Nevena Markova, spent about 20 years

Naviana Markova花了大約二十年的時間

studying these profiles.

研究這些資料。

And she published 42 articles

她發表了42篇文章

just dedicated to the subject.

就只討論這個主題。

Can you imagine? Day and night, thinking,

你可以想像嗎？二十年來日以繼夜地思考、

observing, the same star for 20 years

觀察同樣的星星，

is incredible.

太不可思議了。

But we are crazy. We do these things.

可是我們是瘋狂的。我們做這樣的事情。

(Laughter)

(笑聲)

And I'm not that far.

我還沒那麼瘋狂。

I spent about eight months working on these profiles.

我花了八個月研究這些資料。

Because I've noticed

因為我發現

a very small symmetry

一個很小的對稱性

in the profile of one of the planet host stars.

在主恆星的資料裡。

And I thought, well maybe there is Lithium-6 in this star,

然後我想，或許這個星星含有鋰6(Lithium-6)，

which is an indication that this star

這暗示著這個星星

has swallowed a planet.

可能曾經吞噬過另一個星球。

Because apparently you can't have this fragile isotope

因為顯然的像鋰6(Lithium-6)這樣不穩定的同位素

of Lithium-6 in the atmospheres of sun-like stars.

不可能存在於恆星的環境中。

But you have it in planets and asteroids.

但是在星球和小行星中都含有這個東西。

So if you engulf planet or large number of asteroids,

所以如果吞噬了行星和很多個小行星，

you will have this Lithium-6 isotope

那麼就會有鋰6(Lithium-6)這個同位素

in the spectrum of the star.

在行星的光譜中。

So I invested more than eight months

所以我花了超過八個月的時間

just studying the profile of this star.

就是來研究這個星星資料中的鋰線。

And actually it's amazing,

而且事實上是非常驚人的，

because I got phone calls from many reporters asking,

因為我接到很多記者的電話問我

"Have you actually seen the planet going into a star?"

「你真的有看到一個行星進入一個星星嗎？」

Because they thought that if you are having a telescope,

因為他們以為可以有一個望遠鏡

you are an astronomer so what you are doing

你是天文學家而你做的事情

is actually looking in a telescope.

就是透過望遠鏡看。

And you might have seen the planet going into a star.

然後你有可能有看到一個行星進入一個星星。

And I was saying, "No, excuse me.

然後我會說：「不，對不起。

What I see is this one."

我看到的是這個。」

(Laughter)

(笑聲)

It's just incredible. Because nobody understood really.

這是很不可思議的。因為沒有人真正了解。

I bet that there were very few people

我賭只有非常少數的人

who really understood what I'm talking about.

真正知道我在講什麼。

Because this is the indication that the planet went into the star.

因為這正是代表著一個行星進入一個星星。

It's amazing.

這是驚人的。

The power of spectroscopy

光譜學的能耐

was actually realized

事實上是在1973年

by Pink Floyd already in 1973.

被Pink Floyd發現的。

(Laughter)

(笑聲)

Because they actually said that

因為他們真的曾經說過

you can get any color you like

你可以在光譜中得到

in a spectrum.

任何你想要的顏色。

And all you need is time and money

你需要的只是時間和金錢

to make your spectrograph.

來製作你的光譜。

This is the number one high resolution,

這是個這個星球上解析度最高、

most precise spectrograph on this planet, called HARPS,

最精準的光譜儀器，叫做HARPS，

which is actually used to detect

是用來偵測

extrasolar planets and sound waves

外太陽系行星和星星大氣層中

in the atmospheres of stars.

的聲波。

How we get spectra?

我們怎麼得到光譜呢？

I'm sure most of you know from school physics

我想你們從學校教得物理得知

that it's basically splitting a white light

事實上是把白光

into colors.

分成其他顏色。

And if you have a liquid hot mass,

而且如果你有液態熱體，

it will produce something which we call a continuous spectrum.

他會產生連續光譜。

A hot gas is producing emission lines only,

熱氣只釋放出線條，

no continuum.

不會連續。

And if you place a cool gas in front of a

如果你把冷氣團放在

hot source,

熱源前面，

you will see certain patterns

你會看到特定的圖樣，

which we call absorption lines.

我們稱為吸收光譜。

Which is used actually to identify chemical elements

這就是我們鑑定冷質中

in a cool matter,

化學組成的方法，

which is absorbing exactly at those frequencies.

就是吸收一樣的頻率。

Now, what we can do with the spectra?

現在，光譜能做什麼呢？

We can actually study line-of-sight velocities

我們可以研究天體的

of cosmic objects.

視相速度。

And we can also study chemical composition

我們也可以研究星星、星系、星雲

and physical parameters of stars,

的化學組成

galaxies, nebulae.

及物理參數。

A star is the most simple object.

星星是做簡單的物體。

In the core, we have thermonuclear reactions going on,

在中心有一個熱核能反應

creating chemical elements.

製造化學元素。

And we have a cool atmosphere.

而我們有一個涼的大氣層。

It's cool for me.

這對我來說是涼的。

Cool in my terms is three or four or five thousand degrees.

涼在我的定義中是三或四或五千度。

My colleagues in infra-red astronomy

我的同事研究紅外線天文學

call minus 200 Kelvin is cool for them.

他說對他們來說負兩百凱爾文是涼。

But you know, everything is relative.

但是你們知道，所有事情都是相對的。

So for me 5,000 degrees is pretty cool.

對我來說，五千度是蠻涼的。

(Laughter)

(笑聲)

This is the spectrum of the Sun --

這是太陽的光譜。

24,000 spectral lines,

兩萬四千條光譜線

and about 15 percent of these lines is not yet identified.

而且大約百分之十五的線還沒被鑑定出來。

It is amazing. So we are in the 21st century,

這是很驚人的。我們在二十一世紀，

and we still cannot properly understand

但我們仍然沒有辦法正確了解

the spectrum of the sun.

太陽的光譜。

Sometimes we have to deal with

有時候我們必須從

just one tiny, weak spectral line

一條又小又微弱的光譜線中

to measure the composition of that chemical element in the atmosphere.

找出氣層中的化學成分組成。

For instance, you see the spectral line of the gold

譬如說你看到金的光譜線

is the only spectral line in the spectrum of the Sun.

是太陽光譜裡面唯一的一條線。

And we use this weak feature

我們就用這個微薄的特色

to measure the composition

來測量太陽大氣層中

of gold in the atmosphere of the Sun.

金的含量。

And now this is a work in progress.

現在這是個正在進行的研究。

We have been dealing with a similarly very weak feature,

我們在研究鋨的時候

which belongs to osmium.

也同樣面對類似的微弱信號。

It's a heavy element produced in thermonuclear

鋨是一個重金屬元素

explosions of supernovae.

在超級新星的熱合爆炸中產生。

It's the only place where you can produce, actually, osmium.

事實上這是唯一可以產生鋨的狀況。

Just comparing the composition of osmium

單單只是比較其中一個主行星

in one of the planet host stars,

的鋨成分，

we want to understand why there is so much

我們想要了解為什麼

of this element.

有這麼多這種元素。

Perhaps we even think that maybe

或許我們更會想

supernova explosions trigger formations of planets and stars.

或許超級新星的爆炸會導致行星及星星的誕生。

It can be an indication.

這有可能是個暗示。

The other day, my colleague from Berkeley,

那天我在柏克萊的同事

Gibor Basri, emailed me

Gibor Basri用電郵傳了

a very interesting spectrum,

一張非常有趣的光譜圖給我，

asking me, "Can you have a look at this?"

問我：「你可以看看這個嗎？」

And I couldn't sleep, next two weeks,

然後我接下來兩個禮拜都沒有睡覺，

when I saw the huge amount of oxygen

當我看到有大量的氧氣

and other elements in the spectrum of the stars.

和其他元素出現在星星的光譜中，

I knew that there is nothing like that observed in the galaxy.

我知道沒有其他星系跟這個一樣。

It was incredible. The only conclusion we could make from this

這是非常驚人的。我們唯一可以從中得到的

is clear evidence that there was a supernova explosion

確切結論是這代表著在這個系統中曾經有個

in this system, which polluted the atmosphere

超級新星爆炸，且汙染了這個星星的

of this star.

大氣層。

And later a black hole was formed

然後在這二原體系下

in a binary system,

一個黑洞產生了，

which is still there with a mass of about

它現在還在那裡且集中了

five solar masses.

五個太陽的質量。

This was considered as first evidence that actually black holes

這被認為是第一個證明黑洞是從

come from supernovae explosions.

超級新星爆炸來的的證據。

My colleagues, comparing composition of chemical elements

我的同事在比較不同星系的

in different galactic stars,

化學成分組成，

actually discovered alien stars in our galaxy.

他發現我們星系有外來星星。

It's amazing that you can go so far

能夠只從星星的化學成分資料

simply studying the chemical composition of stars.

得到這麼多訊息是很驚人的。

They actually said that one of the stars you see in the spectra

他們還說其中一顆在光譜上看到的星星事實上是

is an alien. It comes from a different galaxy.

外來星。它是從其他星系來的。

There is interaction of galaxies. We know this.

星系之間是有相互作用的。我們知道這個。

And sometimes they just capture stars.

有時候他們捕捉星星。

You've heard about solar flares.

你們有聽過太陽耀斑。

We were very surprised to discover

我們很驚訝地發現

a super flare,

一個太陽耀斑，

a flare which is thousands of millions of times

一個比我們現在看到的太陽威力大

more powerful than those we see in the Sun.

幾十億倍的耀斑。

In one of the binary stars in our galaxy

在我們星系中的一個雙星系

called FH Leo,

叫做FH Leo，

we discovered the super flare.

我們發現了這個超級耀斑。

And later we went to study the spectral stars

後來我們去研究光譜線

to see is there anything strange with these objects.

來看看有沒有其他奇怪的事情。

And we found that everything is normal.

我們發現所有事情都是正常的。

These stars are normal like the Sun. Age, everything was normal.

這些星星就跟太陽一樣正常。年紀什麼都是正常的。

So this is a mystery.

所以是個謎。

It's one of the mysteries we still have, super flares.

超級耀斑是到現在仍然存在的謎。

And there are six or seven similar cases

而且在文獻上大約有

reported in the literature.

六到七個類似的例子。

Now to go ahead with this,

現在我們繼續往下走，

we really need to understand chemical evolution of the universe.

我們很需要了解這個宇宙的化學演化。

It's very complicated. I don't really want you to

這很複雜。我沒有很希望你們

try to understand what is here.

試圖去了解。

(Laughter)

(笑聲)

But it's to show you how complicated is the whole story

可是現在是要給你們看整個化學元素的產生

of the production of chemical elements.

有多們複雜。

You have two channels --

你有兩個管道：

the massive stars and low-mass stars --

一個高質量星星和一個低質量星星

producing and recycling matter and chemical elements in the universe.

正在產生和回收宇宙間的質體和化學元素。

And doing this for 14 billion years,

一百四十億年來一直這麼做，

we end up with this picture,

我們就有了這張圖片。

which is a very important graph,

這是張非常重要的圖表，

showing relative abundances of chemical elements

顯示了恆星及星際介質中

in sun-like stars

各種化學成分的

and in the interstellar medium.

相對含量。

So which means that it's really impossible

也就是說是不可能找到

to find an object where you find about 10 times more sulfur than silicon,

一個物體其硫含量是矽含量的十倍，

five times more calcium than oxygen. It's just impossible.

或是鈣含量比氧含量多五倍。就是不可能。

And if you find one, I will say that

而且如果你真的找到這樣的物體我會說

this is something related to SETI,

這一定跟SETI(尋找外太空智慧)有關。

because naturally you can't do it.

因為自然界中是不可能的。

Doppler Effect is something very important

都普勒效應是基礎物理學中

from fundamental physics.

非常重要的。

And this is related to the change of the frequency

而且這個跟移動源頭的

of a moving source.

頻率有關。

The Doppler Effect is used to discover extrasolar planets.

都普勒效應是用來發現太陽系外的行星。

The precision which we need

要找到一個

to discover a Jupiter-like planet

像木星的行星，

around a sun-like star

我們需要的精準度

is something like 28.4 meters per second.

是大約每秒28.4公尺。

And we need nine centimeters per second

要發現一個像地球的行星，

to detect an Earth-like planet.

我們需要每秒九公分。

This can be done with the future spectrographs.

這個在未來的光譜研究上可以做到。

I, myself, I'm actually involved in the team

我，我自己有餐與一個團隊，

which is developing a CODEX,

在研發一種規則，

high resolution, future generation spectrograph

高解析度，新一代的的光譜法

for the 42 meter E-ELT telescope.

可以用在42米E-ELT望遠鏡上。

And this is going to be an instrument

這會是一個未來可以探測

to detect Earth-like planets

在似太陽星星附近

around sun-like stars.

像地球這樣的行星。

It is an amazing tool called astroseismology

這是個驚人的工具叫做星震學。

where we can detect sound waves

我們可以用來探測星星大氣層中

in the atmospheres of stars.

的聲波。

This is the sound of an Alpha Cen.

這是半人馬座阿爾法星的聲音。

We can detect sound waves

我們可以探測到

in the atmospheres of sun-like stars.

恆星大氣層中的聲波。

Those waves have frequencies

這些波有頻率，

in infrasound domain, the sound actually nobody knows, domain.

在亞聲區塊，就是沒有人知道是什麼聲音的區塊。

Coming back to the most important question,

回到最重要的問題：

"Is there anybody out there?"

「外面到底有沒有人？」

This is closely related

這跟行星的地質構造及

to tectonic and volcanic activity of planets.

火山活動是非常有關係的。

Connection between life

生命跟放射性原子核

and radioactive nuclei

中間的關係

is straightforward.

是很直接的。

No life without tectonic activity,

沒有地質構造的改變

without volcanic activity.

或是沒有火山活動就沒有生命。

And we know very well that geothermal energy

我們知道地熱

is mostly produced by decay of uranium, thorium, and potassium.

大部分來自鈾、釷和鉀的衰變。

How to measure, if we have planets

怎麼測量？如果我們有一個行星，

where the amount of those elements is small,

這些元素的含量非常少，

so those planets are tectonically dead,

就是說沒有地質構造的改變，

there cannot be life.

那麼不可能有生命。

If there is too much uranium or potassium or thorium,

如果有太多鈾或鉀或釷，

probably, again, there would be no life.

那麼，或許，也不會有生命。

Because can you imagine everything boiling?

因為你可以想像所有東西都在沸騰嗎？

It's too much energy on a planet.

那對一個行星來說是太多能量的。

Now, we have been measuring abundance

現在我們正在測量

of thorium in one of the stars with extrasolar planets.

一個外星系行星的釷含量。

It's exactly the same game. A very tiny feature.

這是完全一樣的。一個很小的特徵。

We are actually trying to measure this profile

我們真的在試圖測量這個資料

and to detect thorium.

去探測釷。

It's very tough. It's very tough.

這很困難。這很困難。

And you have to, first you have to convince yourself.

而且你必須先說服你自己。

Then you have to convince your colleagues.

然後必須說服你的同事們。

And then you have to convince the whole world

然後你必須說服全世界

that you have actually detected something like this

你真的有在百秒差距外

in the atmosphere of an extrasolar planet

一個外星系主行星的大氣層中

host star somewhere in 100 parsec away from here.

探測到這樣的東西。

It's really difficult.

這非常艱難。

But if you want to know about a life on extrasolar planets,

但是如果你想要知道外太陽系行星上的生命，

you have to do this job.

你就必須做這種工作。

Because you have to know how much of radioactive element you have

因為你需要知道在這些系統中

in those systems.

有多少放射性物質。

The one way to discover about aliens

一個可以發現外星人的方法，

is to tune your radio telescope and listen to the signals.

是調整收音機望遠鏡且傾聽信號。

If you receive something interesting,

如果你收到有趣的東西，

well that's what SETI does actually,

事實上SETI就是這麼做，

what SETI has been doing for many years.

SETI已經好幾年都在這麼做了。

I think the most promising way

我認為最有希望的方法

is to go for biomarkers.

是找生物印記。

You can see the spectrum of the Earth, this Earthshine spectrum,

你可以看到地球的光譜，這個地球反照光譜，

and that is a very clear signal.

有非常清楚的信號。

The slope which is coming, which we call a Red Edge,

這個傾斜的地方我們稱之為紅邊(Red Edge)，

is a detection of vegetated area.

是代表著植被區。

It's amazing that we can detect vegetation

我們可以從光譜針測到植被

from a spectrum.

是非常驚人的。

Now imagine doing this test

現在想像對其他行星

for other planets.

做這樣的測試。

Now very recently, very recently,

現在很近期，非常近期，

I'm talking about last six, seven, eight months,

我是在講說大約這六、七、八個月，

water, methane, carbon dioxide

水、甲烷、二氧化碳

have been detected in the spectrum

在一個外星系行星的光譜上

of a planet outside the solar system.

被偵測到了。

It's amazing. So this is the power of spectroscopy.

這很驚人。這就是光譜學的厲害。

You can actually go and detect

你可以真的去偵測

and study a chemical composition of planets

和研究一個離太陽系很遠很遠的行星

far, far, far from solar system.

的化學組成。

We have to detect oxygen or ozone

我們必須偵測到氧氣或是臭氧

to make sure that we have all necessary conditions

才能確定我們有生命存在

to have life.

必須的條件。

Cosmic miracles are something

宇宙奇蹟是一些

which can be related to SETI.

跟SETI有關的現象。

Now imagine an object, amazing object,

現在想像一個物體，一個驚奇的物體，

or something which we cannot explain

或是一個我們無法解釋的東西

when we just stand up and say,

我們只能站起來然後說：

"Look, we give up. Physics doesn't work."

「好吧！我們放棄，物理不適用。」

So it's something which you can always refer to SETI and say,

所以這是你們可以永遠歸因於SETI然後說：

"Well, somebody must be doing this, somehow."

「嗯，總有人用某種方法在做這個。」

And with the known physics etc,

以現知的物理，

it's something actually which has been pointed out

這事實上是個已經被Frank Drake

by Frank Drake,

在好幾年前

many years ago, and Shklovsky.

指出的事情。

If you see, in the spectrum of a planet host star,

如果你看到一個主行星的光譜，

if you see strange chemical elements,

如果你看到奇怪的化學元素，

it can be a signal from a civilization

這有可能是文明的信號。

which is there and they want to signal about it.

文明存在而且他們想要示意。

They want to actually signal their presence

他們想要示意他們的存在，

through these spectral lines,

利用光譜線，

in the spectrum of a star, in different ways.

用不同的方式表現在星星的光譜中。

There can be different ways doing this.

有不同種方式可以達成這個目的。

One is, for instance, technetium

其中一個方式是用鎝元素，

is a radioactive element

一個大約42萬年才會衰退的

with a decay time of 4.2 million years.

放射性元素。

If you suddenly observe technetium

如果你突然在一個類太陽星星

in a sun-like star,

的大氣層中

you can be sure that somebody has put this

發現鎝元素，你可以確定

element in the atmosphere,

有人把他放在那的，

because in a natural way it is impossible to do this.

因為自然界中不可能發生。

Now we are reviewing the spectra of about

現在我們正在研究

300 stars with extrasolar planets.

大約300個外星系行星的光譜。

And we are doing this job since 2000

我們從2000年開始這麼做，

and it's a very heavy project.

這是個很龐大的計劃。

We have been working very hard.

我們很認真地做，

And we have some interesting cases,

而且我們也有些非常有趣的例子，

candidates, so on, things which we can't really explain.

一些我們無法解釋的例子。

And I hope in the near future

我希望在不遠的將來

we can confirm this.

我們可以確認這個。

So the main question: "Are we alone?"

所以主要的問題是：「我們是孤獨的嗎？」

I think it will not come from UFOs.

我覺得不會從UFO中得到答案。

It will not come from radio signals.

我覺得不會從收音訊號中得到答案。

I think it will come from a spectrum like this.

我覺得會從這類的光譜中得到答案。

It is the spectrum of a planet like Earth,

這是個類地行星的光譜

showing a presence of nitrogen dioxide,

顯示著氮氧化物，

as a clear signal of life,

明確代表生命存在，

and oxygen and ozone.

和氧和臭氧。

If, one day, and I think it will be

如果哪一天，而且我覺得

within 15 years from now, or 20 years.

大約再十五年或二十年

If we discover a spectrum like this

我們發現一個像這樣的光譜，

we can be sure that there is life on that planet.

那麼我們可以確定那顆行星上有生命。

In about five years we will discover

大約再五年我們會發現

planets like Earth, around sun-like stars,

其他類地行星在類太陽恆星附近，

the same distance as the Earth from the Sun.

距離大約與地球和太陽間距相似。

It will take about five years.

這大概需要五年。

And then we will need another 10, 15 years

然後我們需要十、十五年

with space projects

利用太空計劃

to get the spectra of Earth-like planets like the one I showed you.

來取得像我剛剛給你們看的類地行星的光譜。

And if we see the nitrogen dioxide

然後如果我們看到氮氧化物

and oxygen,

或氧，

I think we have the perfect E.T.

我想我們就有E.T.(外星人)了。

Thank you very much.

非常謝謝你們。

(Applause)

(掌聲)