Extraordinary claims require extraordinary evidence, and it is my job, my responsibility, as an astronomer to remind people that alien hypotheses should always be a last resort.
不平凡的主張, 需要不平凡的證據來證明。 身為一名天文學家, 我有義務提醒大家, 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. It involves data from a NASA mission, ordinary people and one of the most extraordinary stars in our galaxy.
我現在告訴大家這個故事, 和NASA任務的資料有關, 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. Kepler's main scientific objective was to find planets outside of our solar system. It did this by staring at a single field in the sky, this one, with all the tiny boxes. And in this one field, it monitored the brightness of over 150,000 stars continuously for four years, taking a data point every 30 minutes. It was looking for what astronomers call a transit. This is when the planet's orbit is aligned in our line of sight, just so that the planet crosses in front of a star. And when this happens, it blocks out a tiny bit of starlight, which you can see as a dip in this curve.
故事起始於2009年, NASA的克普勒號任務啟動。 克普勒號在科學上的 主要目的, 是找出太陽系之外的 其他行星。 通過注視天空中的特定區塊, 這組,有很多小框框的地方, 就在這一個區塊, 可以觀測 超過15萬顆以上的星體亮度, 為期四年, 每30分鐘紀錄一次。 我們在尋找天文學家所謂的 「凌星」現象, 意思是當行星軌道平面 和觀測視線平行, 若行星運行到我方和母恆星之間 三者恰成共線, 母恆星光度會因被行星遮蔽 而些微減弱, 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 to search for transits in all the Kepler data.
為此,NASA的團隊打造了 非常精密複雜的電腦系統, 搜尋克普勒任務 資料中的凌星現象。
At the same time of the first data release, astronomers at Yale were wondering an interesting thing: What if computers missed something?
在第一批資料公佈的當下, 耶魯大學的天文學家 設想了個有趣的問題: 如果電腦失算犯錯呢?
And so we launched the citizen science project called Planet Hunters to have people look at the same data. The human brain has an amazing ability for pattern recognition, sometimes even better than a computer. However, there was a lot of skepticism around this. My colleague, Debra Fischer, founder of the Planet Hunters project, said that people at the time were saying, "You're crazy. There's no way that a computer will miss a signal." And so it was on, the classic human versus machine gamble. And if we found one planet, we would be thrilled. When I joined the team four years ago, we had already found a couple. And today, with the help of over 300,000 science enthusiasts, we have found dozens, and we've also found one of the most mysterious stars in our galaxy.
因此我們發起了名為 「尋找行星」的素人科學計畫, 讓人類來看相同的資料。 人腦很會辨認規律或模式, 有時甚至強過電腦。 然而也有很多人懷疑這點, 我的同事 Debra Fischer 是「尋找行星」計畫的主持人, 他說當時大家都說: 「你瘋了, 電腦不可能漏失錯過訊號。」 於是我們開了賭盤: 傳統人腦對上電腦機器。 我們能發現一顆行星, 就非常不得了了。 四年前我加入時, 我們已發現了幾顆, 時至今日,有超過30萬 熱血天文同好的幫助, 我們找到了十幾顆。 還找到在我們的銀河系中 最神秘的一顆星體。 還找到在我們的銀河系中 最神秘的一顆星體。
So to understand this, let me show you what a normal transit in Kepler data looks like. On this graph on the left-hand side you have the amount of light, and on the bottom is time. The white line is light just from the star, what astronomers call a light curve. Now, when a planet transits a star, it blocks out a little bit of this light, and the depth of this transit reflects the size of the object itself. And so, for example, let's take Jupiter. Planets don't get much bigger than Jupiter. Jupiter will make a one percent drop in a star's brightness. Earth, on the other hand, is 11 times smaller than Jupiter, and the signal is barely visible in the data.
讓大家更瞭解, 我們看看 從克普勒傳回來 凌星現象的正常數據長這樣。 圖表的左邊表示亮度, 底下橫軸則代表時間, 白線表示來自星體的光線, 天文學家稱之為光曲。 好,當凌星發生時 光線會稍微受到阻擋, 凌星減弱的光度比例 反應了觀察目標行星的大小。 以木星為例, 很難找到比木星還大的行星, 木星經過 恆星光度約會減弱 1%。 地球呢,大小只有木星的 十一分之一, 因此資料中光度減弱的訊號 很難用肉眼看出。
So back to our mystery. A few years ago, Planet Hunters were sifting through data looking for transits, and they spotted a mysterious signal coming from the star KIC 8462852. The observations in May of 2009 were the first they spotted, and they started talking about this in the discussion forums.
回到我們剛說的神秘星體。 幾年前「尋找行星」計畫 檢視資料並尋找凌星時, 他們發現一組謎樣的訊號 來自KIC 8462852星球, 他們發現的第一筆資料 是2009年5月的觀測, 大家就在論壇上熱烈討論。
They said and object like Jupiter would make a drop like this in the star's light, but they were also saying it was giant. You see, transits normally only last for a few hours, and this one lasted for almost a week.
他們說亮度掉這麼多, 應該是類似木星的大小, 但也有人說那應該是一顆巨星。 試想,一般凌星只會維持幾小時, 但這次卻長達近一週。
They were also saying that it looks asymmetric, meaning that instead of the clean, U-shaped dip that we saw with Jupiter, it had this strange slope that you can see on the left side. This seemed to indicate that whatever was getting in the way and blocking the starlight was not circular like a planet. There are few more dips that happened, but for a couple of years, it was pretty quiet.
另外也提到, 資料看起來並不對稱, 不像木星的亮度減弱 呈現 U 型。 圖的左邊可以看到 曲線的斜率有點奇怪, 這可能表示, 不論凌星是 被什麼樣的不明物體遮蔽, 都不像行星,不是球體。 這樣的光度減弱發生了好幾次, 但中間一兩年平靜無波,
And then in March of 2011, we see this. The star's light drops by a whole 15 percent, and this is huge compared to a planet, which would only make a one percent drop. We described this feature as both smooth and clean. It also is asymmetric, having a gradual dimming that lasts almost a week, and then it snaps right back up to normal in just a matter of days.
直到2011年三月, 我們看到這個: 光度減弱了整整15%。 比起來掉了超多, 因為普通凌星現象只會掉 1%。 我們剛說這個現象的特徵是 曲線平滑乾淨, 而且不對稱, 光度慢慢減弱, 持續將近一週, 然後在短短幾天內 就跳回正常值。
And again, after this, not much happens until February of 2013. Things start to get really crazy. There is a huge complex of dips in the light curve that appear, and they last for like a hundred days, all the way up into the Kepler mission's end. These dips have variable shapes. Some are very sharp, and some are broad, and they also have variable durations. Some last just for a day or two, and some for more than a week. And there's also up and down trends within some of these dips, almost like several independent events were superimposed on top of each other. And at this time, this star drops in its brightness over 20 percent. This means that whatever is blocking its light has an area of over 1,000 times the area of our planet Earth.
然後,在此之後 又歸於平淡。 直到 2013 年 2 月, 開始出現非常瘋狂的現象, 一大段的光度減弱, 而且是複雜的擾動, 期間持續約 100 天, 直到克普勒任務結束。 這些曲線下凹有各種形狀, 有的很尖、有的很廣, 且週期長短不一, 有的只有一兩天, 有的甚至超過一星期。 其中有些還會上上下下, 好像有好幾組獨立事件 同時交疊穿插發生。 這次恆星亮度一下掉超過20%, 這表示遮蔽物的大小, 是地球的 1000 倍。
This is truly remarkable. And so the citizen scientists, when they saw this, they notified the science team that they found something weird enough that it might be worth following up. And so when the science team looked at it, we're like, "Yeah, there's probably just something wrong with the data." But we looked really, really, really hard, and the data were good. And so what was happening had to be astrophysical, meaning that something in space was getting in the way and blocking starlight. And so at this point, we set out to learn everything we could about the star to see if we could find any clues to what was going on. And the citizen scientists who helped us in this discovery, they joined along for the ride watching science in action firsthand.
這著實值得注意。 當素人科學家看到此景 覺得事有蹊蹺, 他們馬上把這特殊現象通知了研究團隊, 這情況值得我們後續追蹤。 研究團隊看了資料, 覺得:「喔, 資料可能有問題吧。」 但我們很用力用力用力地看了, 資料沒有問題。 因此 這必然是某種天文物理現象, 也就是太空中有某種物體 擋在中間阻斷了光線, 也就是太空中有某種物體 擋在中間阻斷了光線。 到這個地步, 我們開始尋找 各種蛛絲馬跡, 想瞭解到底發生了什麼事。 而那些發現這樁怪事的 素人科學愛好者們, 也加入我們, 親眼見證第一手的科學工作。
First, somebody said, you know, what if this star was very young and it still had the cloud of material it was born from surrounding it. And then somebody else said, well, what if the star had already formed planets, and two of these planets had collided, similar to the Earth-Moon forming event. Well, both of these theories could explain part of the data, but the difficulties were that the star showed no signs of being young, and there was no glow from any of the material that was heated up by the star's light, and you would expect this if the star was young or if there was a collision and a lot of dust was produced. And so somebody else said, well, how about a huge swarm of comets that are passing by this star in a very elliptical orbit? Well, it ends up that this is actually consistent with our observations. But I agree, it does feel a little contrived. You see, it would take hundreds of comets to reproduce what we're observing. And these are only the comets that happen to pass between us and the star. And so in reality, we're talking thousands to tens of thousands of comets. But of all the bad ideas we had, this one was the best. And so we went ahead and published our findings.
剛開始,有人說 是不是這顆星星很新, 可能剛出生, 週邊還圍繞著星雲物質。 另一個人說, 會不會是已成形的兩顆行星相撞? 會不會是已成形的兩顆行星相撞? 有點像月球成為地球行星的狀況... 嗯,兩者都能解釋 部份的資料, 但問題是這星體 看來並不年輕, 也沒有物質因為恆星光線 受熱而發光的跡象。 也沒有物質因為恆星光線 受熱而發光的跡象。 如果這是一顆新星, 或是有星體相撞, 那會產生大量的星塵。 又有人說, 那會不會...是一大群彗星, 在狹長橢圓的軌道上運行 經過這顆恆星? 好,這假設倒是很符合 我們的觀測資料, 但我也同意 這感覺有點過於巧合。 想想,這需要上百顆彗星經過, 才可能重現我們觀察到的現象。 而且那些彗星都要, 恰好通過我們和那顆星之間。 也就是說實際上 要有千千萬萬顆彗星經過。 然而,在一堆爛主意中, 這個想法是最靠譜的了 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. Scientists are meant to publish results, and this situation was far from that. And so we decided to give it a catchy title, and we called it: "Where's The Flux?" I will let you work out the acronym.
跟大家說, 這是我寫過最難寫的論文。 科學家的工作 就是要將研究成果發表, 但我們根本沒有成果可言。 因此我們決定取巧 想了個吸引人的標題, 叫做「哪來的搗蛋鬼?」 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. Around the same time I was writing this paper, I met with a colleague of mine, Jason Wright, and he was also writing a paper on Kepler data. And he was saying that with Kepler's extreme precision, it could actually detect alien megastructures around stars, but it didn't. And then I showed him this weird data that our citizen scientists had found, and he said to me, "Aw crap, Tabby. Now I have to rewrite my paper."
故事還沒完。 就在我寫這篇論文的時候, 我遇到了我同事 Jason Wright, 他也剛好用克普勒的資料 在寫論文。 他寫道克普勒的資料 極度地精準, 它甚至可能偵測到 外星文明的巨型建築物。 但,根本沒有。 我給我同事看了 素人科學愛好者們的奇特發現, 我同事就說: 「歐,慘了, 現在我的論文得重寫了...」
So yes, the natural explanations were weak, and we were curious now. So we had to find a way to rule out aliens. So together, we convinced a colleague of ours who works on SETI, the Search for Extraterrestrial Intelligence, that this would be an extraordinary target to pursue. We wrote a proposal to observe the star with the world's largest radio telescope at the Green Bank Observatory.
因此,是的, 「自然現象」的解釋力很弱, 而現在我們燃起了好奇之心。 我們應該想辦法 排除外星文明這個解釋, 因此我們一同說服了另一位同事, 他是SETI計畫的一員, 致力於尋找外星文明, 這目標非常特別。 我們擬了觀察計畫案 這顆星體, 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, news of this proposal got leaked to the press and now there are thousands of articles, over 10,000 articles, on this star alone. And if you search Google Images, this is what you'll find.
幾個月後, 這個計劃被洩露給媒體了, 現在有數以千計篇文章, 數以萬計吧,都在報導這顆星。 如果搜尋 Google 圖片, 你會看到這個,
Now, you may be wondering, OK, Tabby, well, how do aliens actually explain this light curve? OK, well, imagine a civilization that's much more advanced than our own. In this hypothetical circumstance, this civilization would have exhausted the energy supply of their home planet, so where could they get more energy? Well, they have a host star just like we have a sun, and so if they were able to capture more energy from this star, then that would solve their energy needs. So they would go and build huge structures. These giant megastructures, like ginormous solar panels, are called Dyson spheres.
大家可能會想, 好吧,泰比,好啦, 要怎麼用外星文明 來解釋光曲呢? 好的,請想像有一個 比我們進步一百倍的外星文明, 假設真的有的話, 這個文明耗盡了母星球的能源, 他們需要更多能源,去哪找呢? 他們有恆星,就像我們的太陽, 因此,如果他們能從此恆星 擷取到更多的能源, 即可解決他們的能源需求問題, 所以他們蓋了巨型建物。 這些外星文明的龐然大物, 例如無敵巨大的太陽能板 被稱為戴森球體。
This image above are lots of artists' impressions of Dyson spheres. It's really hard to provide perspective on the vastness of these things, but you can think of it this way. The Earth-Moon distance is a quarter of a million miles. The simplest element on one of these structures is 100 times that size. They're enormous. And now imagine one of these structures in motion around a star. You can see how it would produce anomalies in the data such as uneven, unnatural looking dips.
上面的這張圖, 有很多畫家對戴森球體的想像, 我很難跟大家解釋這東西 到底有多巨大... 但你們可以這樣想: 地球到月球的距離是 25 萬英哩, 而我們的巨型結構, 是它的 100 倍。 (編按:2500 萬英哩) 有夠大的。 想像一下這樣巨大的結構, 繞著星體軌道走, 可以看到它產生了 很多異常資料, 也就是這些不對稱、不自然的 下凹曲線,
But it remains that even alien megastructures cannot defy the laws of physics. You see, anything that uses a lot of energy is going to produce heat, and we don't observe this. But it could be something as simple as they're just reradiating it away in another direction, just not at Earth.
但這外星超大結構的行為, 並不遵守物理定律, 一般大量消耗能量的物質, 必然釋放熱能, 但我們卻沒有看到這樣的現象, 但也有可能是很簡單的答案像是, 可能只是以輻射形式往其他方向發散, 而不是朝著地球方向。
Another idea that's one of my personal favorites is that we had just witnessed an interplanetary space battle and the catastrophic destruction of a planet. Now, I admit that this would produce a lot of dust that we don't observe. But if we're already invoking aliens in this explanation, then who is to say they didn't efficiently clean up all this mess for recycling purposes?
另一種可能, 也是我個人最喜歡的說法, 就是我們剛好目擊一場 行星間的太空戰爭開打, 其中一顆行星因此被摧毀了。 當然我承認 這樣應該會產生大量的塵土, 但是我們並沒有觀察到。 不過如果我們已經假設 有外星人存在並且打仗, 誰說他們不能快速地 把那些塵土垃圾清乾淨, 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. We're in a situation that could unfold to be a natural phenomenon we don't understand or an alien technology we don't understand. Personally, as a scientist, my money is on the natural explanation. But don't get me wrong, I do think it would be awesome to find aliens. Either way, there is something new and really interesting to discover.
好,就是這樣。 現在的我們處於一個左右兩難的境地, 一邊是未知的自然現象, 另一半是未知外星科技。 我個人,身為科學家, 我賭自然現象這邊。 但不要誤會, 要是發現外星人,一定很酷, 無論如何,發掘這些未知的新事物 會有很有趣,
So what happens next? We need to continue to observe this star to learn more about what's happening. But professional astronomers, like me, we have limited resources for this kind of thing, and Kepler is on to a different mission.
那接下來會怎樣呢? 我們要持續地觀察, 收集更多資訊, 看看到底發生什麼事, 但像我這樣的專業天文學者, 我們的資源有限, 克普勒也還有自己的任務,
And I'm happy to say that once again, citizen scientists have come in and saved the day. You see, this time, amateur astronomers with their backyard telescopes stepped up immediately and started observing this star nightly at their own facilities, and I am so excited to see what they find.
而我很高興,再次強調, 素人科學愛好者 又再次派上用場! 要知道,這次是 業餘天文學家 對此立馬挺身而出, 每晚在自家後院, 用自己的望遠鏡觀察, 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 because we just weren't looking for something like this. And what's more exciting is that there's more data to come. There are new missions that are coming up that are observing millions more stars all over the sky.
我覺得最棒的是 電腦不可能發現這顆母恆星, 因為我們根本沒想到 會出現這種情形, 更令人高興的是, 未來還會有更多資料, 會有新一期的任務, 通過觀測數以萬計, 存在於天空中的星星,
And just think: What will it mean when we find another star like this? And what will it mean if we don't 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? 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}