The most mysterious star in the universe | Tabetha Boyajian

譯者: Helen Chang 審譯者: Hayley Kang

Extraordinary claims require extraordinary evidence,

不平凡的主張， 需要不平凡的證據來證明。

and it is my job, my responsibility, as an astronomer

身為一名天文學家， 我有義務提醒大家，

to remind people that alien hypotheses should always be a last resort.

不到萬不得已，絕不輕易 用外星假說來解釋天文現象。

Now, I want to tell you a story about that.

我現在告訴大家這個故事，

It involves data from a NASA mission,

和NASA任務的資料有關，

ordinary people and one of the most extraordinary stars in our galaxy.

也和一般大眾、及銀河系中 最奇特的星體有關。

It began in 2009 with the launch of NASA's Kepler mission.

故事起始於2009年， NASA的克普勒號任務啟動。

Kepler's main scientific objective

克普勒號在科學上的 主要目的，

was to find planets outside of our solar system.

是找出太陽系之外的 其他行星。

It did this by staring at a single field in the sky,

通過注視天空中的特定區塊，

this one, with all the tiny boxes.

這組，有很多小框框的地方，

And in this one field,

就在這一個區塊，

it monitored the brightness of over 150,000 stars

可以觀測 超過15萬顆以上的星體亮度，

continuously for four years,

為期四年，

taking a data point every 30 minutes.

每30分鐘紀錄一次。

It was looking for what astronomers call a transit.

我們在尋找天文學家所謂的 「凌星」現象，

This is when the planet's orbit is aligned in our line of sight,

意思是當行星軌道平面 和觀測視線平行，

just so that the planet crosses in front of a star.

若行星運行到我方和母恆星之間 三者恰成共線，

And when this happens, it blocks out a tiny bit of starlight,

母恆星光度會因被行星遮蔽 而些微減弱，

which you can see as a dip in this curve.

也就是圖中 曲線突然下凹的部份。

And so the team at NASA had developed very sophisticated computers

為此，NASA的團隊打造了 非常精密複雜的電腦系統，

to search for transits in all the Kepler data.

搜尋克普勒任務 資料中的凌星現象。

At the same time of the first data release,

在第一批資料公佈的當下，

astronomers at Yale were wondering an interesting thing:

耶魯大學的天文學家 設想了個有趣的問題：

What if computers missed something?

如果電腦失算犯錯呢？

And so we launched the citizen science project called Planet Hunters

因此我們發起了名為 「尋找行星」的素人科學計畫，

to have people look at the same data.

讓人類來看相同的資料。

The human brain has an amazing ability for pattern recognition,

人腦很會辨認規律或模式，

sometimes even better than a computer.

有時甚至強過電腦。

However, there was a lot of skepticism around this.

然而也有很多人懷疑這點，

My colleague, Debra Fischer, founder of the Planet Hunters project,

我的同事 Debra Fischer 是「尋找行星」計畫的主持人，

said that people at the time were saying,

他說當時大家都說：

"You're crazy. There's no way that a computer will miss a signal."

「你瘋了， 電腦不可能漏失錯過訊號。」

And so it was on, the classic human versus machine gamble.

於是我們開了賭盤： 傳統人腦對上電腦機器。

And if we found one planet, we would be thrilled.

我們能發現一顆行星， 就非常不得了了。

When I joined the team four years ago,

四年前我加入時，

we had already found a couple.

我們已發現了幾顆，

And today, with the help of over 300,000 science enthusiasts,

時至今日，有超過30萬 熱血天文同好的幫助，

we have found dozens,

我們找到了十幾顆。

and we've also found one of the most mysterious stars

還找到在我們的銀河系中 最神秘的一顆星體。

in our galaxy.

還找到在我們的銀河系中 最神秘的一顆星體。

So to understand this,

讓大家更瞭解， 我們看看

let me show you what a normal transit in Kepler data looks like.

從克普勒傳回來 凌星現象的正常數據長這樣。

On this graph on the left-hand side you have the amount of light,

圖表的左邊表示亮度，

and on the bottom is time.

底下橫軸則代表時間，

The white line is light just from the star,

白線表示來自星體的光線，

what astronomers call a light curve.

天文學家稱之為光曲。

Now, when a planet transits a star, it blocks out a little bit of this light,

好，當凌星發生時 光線會稍微受到阻擋，

and the depth of this transit reflects the size of the object itself.

凌星減弱的光度比例 反應了觀察目標行星的大小。

And so, for example, let's take Jupiter.

以木星為例，

Planets don't get much bigger than Jupiter.

很難找到比木星還大的行星，

Jupiter will make a one percent drop in a star's brightness.

木星經過 恆星光度約會減弱 1%。

Earth, on the other hand, is 11 times smaller than Jupiter,

地球呢，大小只有木星的 十一分之一，

and the signal is barely visible in the data.

因此資料中光度減弱的訊號 很難用肉眼看出。

So back to our mystery.

回到我們剛說的神秘星體。

A few years ago, Planet Hunters were sifting through data looking for transits,

幾年前「尋找行星」計畫 檢視資料並尋找凌星時，

and they spotted a mysterious signal coming from the star KIC 8462852.

他們發現一組謎樣的訊號 來自KIC 8462852星球，

The observations in May of 2009 were the first they spotted,

他們發現的第一筆資料 是2009年5月的觀測，

and they started talking about this in the discussion forums.

大家就在論壇上熱烈討論。

They said and object like Jupiter

他們說亮度掉這麼多，

would make a drop like this in the star's light,

應該是類似木星的大小，

but they were also saying it was giant.

但也有人說那應該是一顆巨星。

You see, transits normally only last for a few hours,

試想，一般凌星只會維持幾小時，

and this one lasted for almost a week.

但這次卻長達近一週。

They were also saying that it looks asymmetric,

另外也提到， 資料看起來並不對稱，

meaning that instead of the clean, U-shaped dip that we saw with Jupiter,

不像木星的亮度減弱 呈現 U 型。

it had this strange slope that you can see on the left side.

圖的左邊可以看到 曲線的斜率有點奇怪，

This seemed to indicate

這可能表示，

that whatever was getting in the way and blocking the starlight

不論凌星是 被什麼樣的不明物體遮蔽，

was not circular like a planet.

都不像行星，不是球體。

There are few more dips that happened,

這樣的光度減弱發生了好幾次，

but for a couple of years, it was pretty quiet.

但中間一兩年平靜無波，

And then in March of 2011, we see this.

直到2011年三月， 我們看到這個：

The star's light drops by a whole 15 percent,

光度減弱了整整15%。

and this is huge compared to a planet,

比起來掉了超多，

which would only make a one percent drop.

因為普通凌星現象只會掉 1%。

We described this feature as both smooth and clean.

我們剛說這個現象的特徵是 曲線平滑乾淨，

It also is asymmetric,

而且不對稱，

having a gradual dimming that lasts almost a week,

光度慢慢減弱， 持續將近一週，

and then it snaps right back up to normal in just a matter of days.

然後在短短幾天內 就跳回正常值。

And again, after this, not much happens

然後，在此之後 又歸於平淡。

until February of 2013.

直到 2013 年 2 月，

Things start to get really crazy.

開始出現非常瘋狂的現象，

There is a huge complex of dips in the light curve that appear,

一大段的光度減弱， 而且是複雜的擾動，

and they last for like a hundred days,

期間持續約 100 天，

all the way up into the Kepler mission's end.

直到克普勒任務結束。

These dips have variable shapes.

這些曲線下凹有各種形狀，

Some are very sharp, and some are broad,

有的很尖、有的很廣，

and they also have variable durations.

且週期長短不一，

Some last just for a day or two, and some for more than a week.

有的只有一兩天， 有的甚至超過一星期。

And there's also up and down trends within some of these dips,

其中有些還會上上下下，

almost like several independent events were superimposed on top of each other.

好像有好幾組獨立事件 同時交疊穿插發生。

And at this time, this star drops in its brightness over 20 percent.

這次恆星亮度一下掉超過20%，

This means that whatever is blocking its light

這表示遮蔽物的大小，

has an area of over 1,000 times the area of our planet Earth.

是地球的 1000 倍。

This is truly remarkable.

這著實值得注意。

And so the citizen scientists, when they saw this,

當素人科學家看到此景 覺得事有蹊蹺，

they notified the science team that they found something weird enough

他們馬上把這特殊現象通知了研究團隊，

that it might be worth following up.

這情況值得我們後續追蹤。

And so when the science team looked at it,

研究團隊看了資料，

we're like, "Yeah, there's probably just something wrong with the data."

覺得：「喔， 資料可能有問題吧。」

But we looked really, really, really hard,

但我們很用力用力用力地看了，

and the data were good.

資料沒有問題。

And so what was happening had to be astrophysical,

因此 這必然是某種天文物理現象，

meaning that something in space was getting in the way

也就是太空中有某種物體 擋在中間阻斷了光線，

and blocking starlight.

也就是太空中有某種物體 擋在中間阻斷了光線。

And so at this point,

到這個地步，

we set out to learn everything we could about the star

我們開始尋找 各種蛛絲馬跡，

to see if we could find any clues to what was going on.

想瞭解到底發生了什麼事。

And the citizen scientists who helped us in this discovery,

而那些發現這樁怪事的 素人科學愛好者們，

they joined along for the ride

也加入我們，

watching science in action firsthand.

親眼見證第一手的科學工作。

First, somebody said, you know, what if this star was very young

剛開始，有人說 是不是這顆星星很新，

and it still had the cloud of material it was born from surrounding it.

可能剛出生， 週邊還圍繞著星雲物質。

And then somebody else said,

另一個人說，

well, what if the star had already formed planets,

會不會是已成形的兩顆行星相撞？

and two of these planets had collided,

會不會是已成形的兩顆行星相撞？

similar to the Earth-Moon forming event.

有點像月球成為地球行星的狀況...

Well, both of these theories could explain part of the data,

嗯，兩者都能解釋 部份的資料，

but the difficulties were that the star showed no signs of being young,

但問題是這星體 看來並不年輕，

and there was no glow from any of the material

也沒有物質因為恆星光線 受熱而發光的跡象。

that was heated up by the star's light,

也沒有物質因為恆星光線 受熱而發光的跡象。

and you would expect this if the star was young

如果這是一顆新星，

or if there was a collision and a lot of dust was produced.

或是有星體相撞， 那會產生大量的星塵。

And so somebody else said,

又有人說，

well, how about a huge swarm of comets

那會不會...是一大群彗星，

that are passing by this star in a very elliptical orbit?

在狹長橢圓的軌道上運行 經過這顆恆星？

Well, it ends up that this is actually consistent with our observations.

好，這假設倒是很符合 我們的觀測資料，

But I agree, it does feel a little contrived.

但我也同意 這感覺有點過於巧合。

You see, it would take hundreds of comets

想想，這需要上百顆彗星經過，

to reproduce what we're observing.

才可能重現我們觀察到的現象。

And these are only the comets

而且那些彗星都要，

that happen to pass between us and the star.

恰好通過我們和那顆星之間。

And so in reality, we're talking thousands to tens of thousands of comets.

也就是說實際上 要有千千萬萬顆彗星經過。

But of all the bad ideas we had,

然而，在一堆爛主意中，

this one was the best.

這個想法是最靠譜的了

And so we went ahead and published our findings.

我們就發表了這個發現，

Now, let me tell you, this was one of the hardest papers I ever wrote.

跟大家說， 這是我寫過最難寫的論文。

Scientists are meant to publish results,

科學家的工作 就是要將研究成果發表，

and this situation was far from that.

但我們根本沒有成果可言。

And so we decided to give it a catchy title,

因此我們決定取巧 想了個吸引人的標題，

and we called it: "Where's The Flux?"

叫做「哪來的搗蛋鬼？」

I will let you work out the acronym.

我想你們會懂 句子縮略語的言下之意。

(Laughter)

〔畫面：縮寫為 WTF 另有「搞屁？」之意〕〔觀眾笑〕

So this isn't the end of the story.

故事還沒完。

Around the same time I was writing this paper,

就在我寫這篇論文的時候，

I met with a colleague of mine, Jason Wright,

我遇到了我同事 Jason Wright，

and he was also writing a paper on Kepler data.

他也剛好用克普勒的資料 在寫論文。

And he was saying that with Kepler's extreme precision,

他寫道克普勒的資料 極度地精準，

it could actually detect alien megastructures around stars,

它甚至可能偵測到 外星文明的巨型建築物。

but it didn't.

但，根本沒有。

And then I showed him this weird data that our citizen scientists had found,

我給我同事看了 素人科學愛好者們的奇特發現，

and he said to me,

我同事就說：

"Aw crap, Tabby.

「歐，慘了，

Now I have to rewrite my paper."

現在我的論文得重寫了...」

So yes, the natural explanations were weak,

因此，是的， 「自然現象」的解釋力很弱，

and we were curious now.

而現在我們燃起了好奇之心。

So we had to find a way to rule out aliens.

我們應該想辦法 排除外星文明這個解釋，

So together, we convinced a colleague of ours

因此我們一同說服了另一位同事，

who works on SETI, the Search for Extraterrestrial Intelligence,

他是SETI計畫的一員， 致力於尋找外星文明，

that this would be an extraordinary target to pursue.

這目標非常特別。

We wrote a proposal to observe the star

我們擬了觀察計畫案 這顆星體，

with the world's largest radio telescope at the Green Bank Observatory.

預計使用綠堤天文台那座 世界最大的電波望遠鏡。

A couple months later,

幾個月後，

news of this proposal got leaked to the press

這個計劃被洩露給媒體了，

and now there are thousands of articles,

現在有數以千計篇文章，

over 10,000 articles, on this star alone.

數以萬計吧，都在報導這顆星。

And if you search Google Images,

如果搜尋 Google 圖片，

this is what you'll find.

你會看到這個，

Now, you may be wondering, OK, Tabby, well,

大家可能會想， 好吧，泰比，好啦，

how do aliens actually explain this light curve?

要怎麼用外星文明 來解釋光曲呢？

OK, well, imagine a civilization that's much more advanced than our own.

好的，請想像有一個 比我們進步一百倍的外星文明，

In this hypothetical circumstance,

假設真的有的話，

this civilization would have exhausted the energy supply of their home planet,

這個文明耗盡了母星球的能源，

so where could they get more energy?

他們需要更多能源，去哪找呢？

Well, they have a host star just like we have a sun,

他們有恆星，就像我們的太陽，

and so if they were able to capture more energy from this star,

因此，如果他們能從此恆星 擷取到更多的能源，

then that would solve their energy needs.

即可解決他們的能源需求問題，

So they would go and build huge structures.

所以他們蓋了巨型建物。

These giant megastructures,

這些外星文明的龐然大物，

like ginormous solar panels, are called Dyson spheres.

例如無敵巨大的太陽能板 被稱為戴森球體。

This image above

上面的這張圖，

are lots of artists' impressions of Dyson spheres.

有很多畫家對戴森球體的想像，

It's really hard to provide perspective on the vastness of these things,

我很難跟大家解釋這東西 到底有多巨大...

but you can think of it this way.

但你們可以這樣想：

The Earth-Moon distance is a quarter of a million miles.

地球到月球的距離是 25 萬英哩，

The simplest element on one of these structures

而我們的巨型結構，

is 100 times that size.

是它的 100 倍。 （編按：2500 萬英哩）

They're enormous.

有夠大的。

And now imagine one of these structures in motion around a star.

想像一下這樣巨大的結構， 繞著星體軌道走，

You can see how it would produce anomalies in the data

可以看到它產生了 很多異常資料，

such as uneven, unnatural looking dips.

也就是這些不對稱、不自然的 下凹曲線，

But it remains that even alien megastructures

但這外星超大結構的行為，

cannot defy the laws of physics.

並不遵守物理定律，

You see, anything that uses a lot of energy

一般大量消耗能量的物質，

is going to produce heat,

必然釋放熱能，

and we don't observe this.

但我們卻沒有看到這樣的現象，

But it could be something as simple

但也有可能是很簡單的答案像是，

as they're just reradiating it away in another direction,

可能只是以輻射形式往其他方向發散，

just not at Earth.

而不是朝著地球方向。

Another idea that's one of my personal favorites

另一種可能， 也是我個人最喜歡的說法，

is that we had just witnessed an interplanetary space battle

就是我們剛好目擊一場 行星間的太空戰爭開打，

and the catastrophic destruction of a planet.

其中一顆行星因此被摧毀了。

Now, I admit that this would produce a lot of dust

當然我承認 這樣應該會產生大量的塵土，

that we don't observe.

但是我們並沒有觀察到。

But if we're already invoking aliens in this explanation,

不過如果我們已經假設 有外星人存在並且打仗，

then who is to say they didn't efficiently clean up all this mess

誰說他們不能快速地 把那些塵土垃圾清乾淨，

for recycling purposes?

為了要...資源回收？

(Laughter)

〔觀眾笑〕

You can see how this quickly captures your imagination.

這說法很有想像力吧！

Well, there you have it.

好，就是這樣。

We're in a situation that could unfold

現在的我們處於一個左右兩難的境地，

to be a natural phenomenon we don't understand

一邊是未知的自然現象，

or an alien technology we don't understand.

另一半是未知外星科技。

Personally, as a scientist, my money is on the natural explanation.

我個人，身為科學家， 我賭自然現象這邊。

But don't get me wrong, I do think it would be awesome to find aliens.

但不要誤會， 要是發現外星人，一定很酷，

Either way, there is something new and really interesting to discover.

無論如何，發掘這些未知的新事物 會有很有趣，

So what happens next?

那接下來會怎樣呢？

We need to continue to observe this star

我們要持續地觀察，

to learn more about what's happening.

收集更多資訊， 看看到底發生什麼事，

But professional astronomers, like me,

但像我這樣的專業天文學者，

we have limited resources for this kind of thing,

我們的資源有限，

and Kepler is on to a different mission.

克普勒也還有自己的任務，

And I'm happy to say that once again,

而我很高興，再次強調，

citizen scientists have come in and saved the day.

素人科學愛好者 又再次派上用場！

You see, this time,

要知道，這次是

amateur astronomers with their backyard telescopes

業餘天文學家 對此立馬挺身而出，

每晚在自家後院，

stepped up immediately and started observing this star nightly

at their own facilities,

用自己的望遠鏡觀察，

and I am so excited to see what they find.

我很期待他們的發現。

What's amazing to me is that this star would have never been found by computers

我覺得最棒的是 電腦不可能發現這顆母恆星，

because we just weren't looking for something like this.

因為我們根本沒想到 會出現這種情形，

And what's more exciting

更令人高興的是，

is that there's more data to come.

未來還會有更多資料，

There are new missions that are coming up

會有新一期的任務，

that are observing millions more stars

通過觀測數以萬計，

存在於天空中的星星，

all over the sky.

And just think: What will it mean when we find another star like this?

大家可以思考：如果我們又找到 類似這樣的星體，這代表什麼？

And what will it mean if we don't find another star like this?

或如果我們再也找不到 類似這樣的星體，又代表什麼呢？

Thank you.

謝謝大家。

(Applause)

〔掌聲｝