演講MP3+雙語文稿:尋找太陽系的第九顆行星

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【演講人及介紹】Mike Brown

行星天文學(xué)家邁克·布朗（Mike Brown）掃描天空，尋找并深入研究太陽系中的遙遠(yuǎn)天體，以期深入了解我們的行星及其周圍的行星是如何形成的。

【演講主題】尋找我們太陽系的第九顆行星

【演講文稿-中英文】

翻譯者 Yiwei Chen 校對 Jiasi Hao

00:13

I'm going to tell you a story from 200years ago. In 1820, French astronomer Alexis Bouvard almost became the secondperson in human history to discover a planet. He'd been tracking the positionof Uranus across the night sky using old star catalogs, and it didn't quite goaround the Sun the way that his predictions said it should. Sometimes it was alittle too fast, sometimes a little too slow. Bouvard knew that his predictionswere perfect. So it had to be that those old star catalogs were bad. He told astronomersof the day, "Do better measurements." So they did. Astronomers spentthe next two decades meticulously tracking the position of Uranus across thesky, but it still didn't fit Bouvard's predictions.

我要給你們講述一個(gè)從 200 年前開始的故事。1820 年，法國天文學(xué)家阿列西·布瓦爾（Alexis Bouvard）差點(diǎn)成為了人類歷史上第二個(gè)發(fā)現(xiàn)行星的人。他當(dāng)時(shí)在用原始的星表追蹤夜間天王星劃過天空的位置，然而天王星并沒有像他預(yù)測的那樣圍繞著太陽轉(zhuǎn)。有時(shí)，它轉(zhuǎn)得有點(diǎn)太快了，有時(shí)，又轉(zhuǎn)得有點(diǎn)太慢。布瓦爾知道他的預(yù)測是完美的，因此這一定是陳舊星表的不準(zhǔn)確性所導(dǎo)致的。那天，他跟天文學(xué)家們說，“做更好的測量。”于是他們照做了。天文學(xué)家們花費(fèi)了將近 20 年，一絲不茍的追蹤天王星劃過天空的軌跡，但是結(jié)果仍然和布瓦爾的預(yù)測不一樣。

01:01

By 1840, it had become obvious. The problemwas not with those old star catalogs, the problem was with the predictions. Andastronomers knew why. They realized that there must be a distant, giant planetjust beyond the orbit of Uranus that was tugging along at that orbit, sometimespulling it along a bit too fast, sometimes holding it back.

直到 1840 年，事情變得很明顯：問題不是出在那些陳舊的星表上，而是在于那些預(yù)測。同時(shí)，天文學(xué)家們知道這是為什么。他們意識到，一定是有一個(gè)遙遠(yuǎn)的巨大行星，剛好在天王星軌道的后面，影響著天王星的運(yùn)行速度。有時(shí)推著它，導(dǎo)致它移動(dòng)得太快，有時(shí)又會(huì)拽住它，減慢它的運(yùn)行速度。

01:24

Must have been frustrating back in 1840 tosee these gravitational effects of this distant, giant planet but not yet knowhow to actually find it. Trust me, it's really frustrating.

回到 1840 年，科學(xué)家一定很崩潰，因?yàn)槟隳芸吹竭@些相距遙遠(yuǎn)的巨行星重力效應(yīng)，卻還不知道如何找到它。相信我，這真的很讓人崩潰。

01:36

(Laughter)

（笑聲）

01:37

But in 1846, another French astronomer,Urbain Le Verrier, worked through the math and figured out how to predict thelocation of the planet. He sent his prediction to the Berlin observatory, theyopened up their telescope and in the very first night they found this faintpoint of light slowly moving across the sky and discovered Neptune. It was thisclose on the sky to Le Verrier's predicted location.

但是到了 1846 年，另外一個(gè)法國天文學(xué)家奧本·勒維耶（Urbain Le Verrier），通過數(shù)學(xué)計(jì)算，找到了如何預(yù)測行星位置的方法。他把他的預(yù)測結(jié)果發(fā)給了柏林天文臺，他們打開了望遠(yuǎn)鏡，然后就在第一天晚上，觀測到了一個(gè)很微弱的光點(diǎn)，緩慢的從天空劃過，然后發(fā)現(xiàn)了天王星。它的位置和勒維耶的預(yù)測結(jié)果在天空中就只差這么一點(diǎn)。

02:01

The story of prediction and discrepancy andnew theory and triumphant discoveries is so classic and Le Verrier became sofamous from it, that people tried to get in on the act right away. In the last163 years, dozens of astronomers have used some sort of alleged orbitaldiscrepancy to predict the existence of some new planet in the solar system.

這段關(guān)于預(yù)測、區(qū)別、新理論以及成功發(fā)現(xiàn)的故事堪稱經(jīng)典，勒維耶也因此成名，那些試圖進(jìn)入該領(lǐng)域的人也立馬行動(dòng)了起來。在過去的 163 年里，數(shù)十位天文學(xué)家利用所謂的軌道偏差，來預(yù)測太陽系中是否存在新行星。

02:28

They have always been wrong.

但他們的預(yù)測卻一直出現(xiàn)各種問題。

02:32

The most famous of these erroneouspredictions came from Percival Lowell, who was convinced that there must be aplanet just beyond Uranus and Neptune, messing with those orbits. And so whenPluto was discovered in 1930 at the Lowell Observatory, everybody assumed thatit must be the planet that Lowell had predicted. They were wrong. It turns out,Uranus and Neptune are exactly where they're supposed to be. It took 100 years,but Bouvard was eventually right. Astronomers needed to do better measurements.And when they did, those better measurements had turned out that there is noplanet just beyond the orbit of Uranus and Neptune and Pluto is thousands oftimes too small to have any effect on those orbits at all.

最有名的一個(gè)錯(cuò)誤預(yù)測來自于帕西瓦爾·羅威爾（Percival Lowell），他堅(jiān)信，在天王星和海王星后，一定還有一個(gè)行星，在干擾那些軌道。因此在 1930 年冥王星被發(fā)現(xiàn)于洛厄爾天文臺時(shí)，所有人都以為，那顆行星一定就是羅威爾曾預(yù)測的那顆。但他們錯(cuò)了。結(jié)果表明，天王星和海王星就在它們應(yīng)該在的地方。這件事花費(fèi)了 100 年的時(shí)間，但是最終，人們發(fā)現(xiàn)布瓦爾是對的。天文學(xué)家們需要做更好的測量。他們這么做了之后，那些更好的測量表明，在天王星和海王星的軌道后面并沒有行星的出現(xiàn)，并且冥王星的體積比預(yù)測的要小幾千倍，以至于對那些軌道不會(huì)產(chǎn)生任何影響。

03:20

So even though Pluto turned out not to bethe planet it was originally thought to be, it was the first discovery of whatis now known to be thousands of tiny, icy objects in orbit beyond the planets.These icy bodies are pushed and pulled by the gravitational fields of theplanets in entirely predictable ways. Everything goes around the Sun exactlythe way it is supposed to.

因此，盡管冥王星后來被證實(shí)并非本意想要預(yù)測的那顆行星，但這是目前對在已知行星外軌道上存在的數(shù)千個(gè)微小的結(jié)冰天體（柯伊伯帶）的首次發(fā)現(xiàn)。這些結(jié)冰天體 會(huì)因?yàn)樾行堑闹亓?，按照完全可預(yù)測的方式被推拉。所有的行星基本上都在以它們該有的方式圍繞著太陽轉(zhuǎn)。

04:02

Almost.

幾乎是所有東西。

04:04

So in 2003, I discovered what was at thetime the most distant known object in the entire solar system. It's hard not tolook at that lonely body out there and say, oh yeah, sure, so Lowell was wrong,there was no planet just beyond Neptune, but this, this could be a new planet.The real question we had was, what kind of orbit does it have around the Sun?Does it go in a circle around the Sun like a planet should? Or is it just atypical member of this icy belt of bodies that got a little bit tossed outwardand it's now on its way back in?

在 2003 年，我發(fā)現(xiàn)了當(dāng)時(shí)在太陽系中探測到的最遙遠(yuǎn)的已知天體。很難忽視遠(yuǎn)方那顆孤獨(dú)的天體，然后說，是的，羅威爾錯(cuò)了，海王星之外并沒有其他行星，但這一顆——這一顆可能是新的行星。我們真正要問的是，它以什么樣的軌道圍繞著太陽轉(zhuǎn)？它是否就像其他行星一樣繞著太陽以圓形的軌道旋轉(zhuǎn)？還是就像冰帶中 其他典型的結(jié)冰天體一樣，只是先前不小心被拋出去了，現(xiàn)在在回歸原軌道的路上？

04:36

This is precisely the question theastronomers were trying to answer about Uranus 200 years ago. They did it byusing overlooked observations of Uranus from 91 years before its discovery tofigure out its entire orbit. We couldn't go quite that far back, but we didfind observations of our object from 13 years earlier that allowed us to figureout how it went around the Sun.

這正是在 200 年前，天文學(xué)家在研究天王星時(shí)努力想要解答的問題。他們是利用在發(fā)現(xiàn)天王星的 91 年前所被忽略的觀測資料，從而找到它的整個(gè)軌道的。我們無法追溯回那么早的資料，但是我們在 13 年前的資料里找到了對目標(biāo)天體的觀測記錄。這些資料讓我們弄清了它是如何繞太陽轉(zhuǎn)的。

05:00

So the question is, is it in a circularorbit around the Sun, like a planet, or is it on its way back in, like one ofthese typical icy bodies? And the answer is no.

那么問題是，它是像行星一樣在圓形的軌道上繞著太陽轉(zhuǎn)呢，還是像那些結(jié)冰天體一樣在回程途中？ 答案是，皆非。

05:11

It has a massively elongated orbit thattakes 10,000 years to go around the Sun. We named this object Sedna after theInuit goddess of the sea, in honor of the cold, icy places where it spends allof its time. We now know that Sedna, it's about a third the size of Pluto andit's a relatively typical member of those icy bodies out beyond Neptune.Relatively typical, except for this bizarre orbit. You might look at this orbitand say, "Yeah, that's bizarre, 10,000 years to go around the Sun,"but that's not really the bizarre part. The bizarre part is that in those10,000 years, Sedna never comes close to anything else in the solar system.Even at its closest approach to the Sun, Sedna is further from Neptune thanNeptune is from the Earth.

它擁有非常巨大的橢圓軌道，使它繞太陽一周需要一萬年的時(shí)間。我們將這個(gè)天體命名為塞德娜（Sedna），是因紐特人海洋女神的名字，以致敬它一生都在冰凍的環(huán)境中。我們現(xiàn)在知道塞德娜的體積約是冥王星的三分之一，且是海王星外的那些結(jié)冰天體中，相對比較典型的一個(gè)天體。相對比較典型，但不包括它的奇特的軌道。你看著這個(gè)軌道可能會(huì)說，“繞著太陽能走一萬年確實(shí)很奇特”，但這還不是它奇特的地方，奇特的是，在那一萬年中，塞德娜完全不接近太陽系中的任何其他東西。即使是在它離太陽最近的位置，塞德娜和海王星的距離也比海王星和地球之間的距離更遠(yuǎn)。

05:59

If Sedna had had an orbit like this, thatkisses the orbit of Neptune once around the Sun, that would have actually beenreally easy to explain. That would have just been an object that had been in acircular orbit around the Sun in that region of icy bodies, had gotten a littlebit too close to Neptune one time, and then got slingshot out and is now on itsway back in.

假如塞德娜有這樣的軌道：繞行太陽一圈就會(huì)和海王星的軌道接觸一次，那這就很容易解釋了。那它就是在結(jié)冰天體的區(qū)域中以圓形軌道繞行太陽的天體，有一瞬間太靠近海王星，因此被彈了出去，現(xiàn)在正在返回的途中。

06:19

But Sedna never comes close to anythingknown in the solar system that could have given it that slingshot. Neptunecan't be responsible, but something had to be responsible. This was the firsttime since 1845 that we saw the gravitational effects of something in the outersolar system and didn't know what it was.

但是塞德娜從未接近過太陽系中任何已知的東西，不可能造成那樣的彈射。既然不是海王星造成的，那一定有別的原因。這是自 1845 年以來我們第一次看到了在外太陽系的某個(gè)東西產(chǎn)生了重力效應(yīng)，但不知道它是什么。

06:42

I actually thought I knew what the answerwas. Sure, it could have been some distant, giant planet in the outer solarsystem, but by this time, that idea was so ridiculous and had been sothoroughly discredited that I didn't take it very seriously. But 4.5 billionyears ago, when the Sun formed in a cocoon of hundreds of other stars, any oneof those stars could have gotten just a little bit too close to Sedna andperturbed it onto the orbit that it has today. When that cluster of starsdissipated into the galaxy, the orbit of Sedna would have been left as a fossilrecord of this earliest history of the Sun.

我曾經(jīng)以為自己知道答案。的確，它有可能是外太陽系一顆很遙遠(yuǎn)的巨大行星，但在這個(gè)情況中，這個(gè)想法很荒謬，完全不足為信，所以我沒有很嚴(yán)肅的對待它。但在 45 億年前，當(dāng)太陽在其它上百個(gè)天體的包裹下形成時(shí)，那些天體中的任何一個(gè)都有可能太靠近塞德娜，從而影響它，讓它進(jìn)入現(xiàn)今的這個(gè)軌道中。當(dāng)那群天體消散在星系中，塞德娜的軌道應(yīng)該會(huì)變成太陽最早期歷史中的化石記錄。

07:20

I was so excited by this idea, by the ideathat we could look at the fossil history of the birth of the Sun, that I spentthe next decade looking for more objects with orbits like Sedna. In thatten-year period, I found zero.

這個(gè)想法讓我很興奮，這表示我們可以去研究太陽誕生的化石歷史，于是我用接下來十年的時(shí)間，去尋找更多有著類似塞德娜軌道的天體。在那十年間，我一個(gè)也沒找到。

07:34

(Laughter)

（笑聲）

07:35

But my colleagues, Chad Trujillo and ScottSheppard, did a better job, and they have now found several objects with orbitslike Sedna, which is super exciting.

但我的同事，查理·楚基羅和史考特·雪柏，有了些發(fā)現(xiàn)。他們現(xiàn)在已經(jīng)找到了好幾個(gè)軌道類似塞德娜的天體。這非常令人興奮。

07:43

But what's even more interesting is thatthey found that all these objects are not only on these distant, elongatedorbits, they also share a common value of this obscure orbital parameter thatin celestial mechanics we call argument of perihelion. When they realized itwas clustered in argument of perihelion, they immediately jumped up and down,saying it must be caused by a distant, giant planet out there, which is reallyexciting, except it makes no sense at all.

但更讓人激動(dòng)的是，他們發(fā)現(xiàn)，所有這些天體，不僅是在遙遠(yuǎn)，橢圓形的軌道上運(yùn)行，而且具有相同的復(fù)雜軌道參數(shù)特征。在天體力學(xué)中，我們把這個(gè)參數(shù)稱為近日點(diǎn)幅角。當(dāng)他們發(fā)現(xiàn)那些特征參數(shù)集聚在近日點(diǎn)幅角時(shí)，立即手舞足蹈起來，因?yàn)樗麄冋J(rèn)為一定有個(gè)遙遠(yuǎn)的巨大行星存在。這真的讓人很興奮，只是完全不合理罷了。

08:13

Let me try to explain it to you why with ananalogy. Imagine a person walking down a plaza and looking 45 degrees to hisright side. There's a lot of reasons that might happen, it's super easy toexplain, no big deal. Imagine now many different people, all walking indifferent directions across the plaza, but all looking 45 degrees to thedirection that they're moving. Everybody's moving in different directions,everybody's looking in different directions, but they're all looking 45 degreesto the direction of motion. What could cause something like that? I have no idea.It's very difficult to think of any reason that that would happen.

讓我試著用一個(gè)比喻來解釋為什么。試想，一個(gè)人走在廣場上，看向他右邊 45 度的方向。這可能有很多理由，很容易解釋，不是什么大事兒?，F(xiàn)在試想，有很多不同的人都在廣場上朝不同的方向走，但都看向他們行進(jìn)方向的 45 度角。大家行進(jìn)的方向不同，大家看去的方向也不同，但他們看去的都是行進(jìn)方向的 45 度處，這個(gè)現(xiàn)象背后的原因會(huì)是什么？我不知道。非常難想象出任何理由會(huì)造成這個(gè)現(xiàn)象。

08:51

(Laughter)

（笑聲）

08:53

And this is essentially what thatclustering in argument of perihelion was telling us.

基本上，這就是一堆相近的近日點(diǎn)幅角告訴我們的事。

08:59

Scientists were generally baffled and theyassumed it must just be a fluke and some bad observations. They told theastronomers, "Do better measurements." I actually took a very carefullook at those measurements, though, and they were right. These objects reallydid all share a common value of argument of perihelion, and they shouldn't.Something had to be causing that.

科學(xué)家們很受挫，他們認(rèn)為一定是僥幸和不佳的觀測造成的。他們告訴天文學(xué)家，“把觀測做得更好一點(diǎn)”。我其實(shí)非常仔細(xì)地研究過這些測量值，但它們是對的。這些天體真的都用同樣的近日點(diǎn)幅角值，但是這不應(yīng)該。背后一定有原因。

09:23

The final piece of the puzzle came intoplace in 2016, when my colleague, Konstantin Batygin, who works three doorsdown from me, and I realized that the reason that everybody was baffled wasbecause argument of perihelion was only part of the story. If you look at theseobjects the right way, they are all actually lined up in space in the same direction,and they're all tilted in space in the same direction. It's as if all thosepeople on the plaza are all walking in the same direction and they're alllooking 45 degrees to the right side. That's easy to explain. They're alllooking at something. These objects in the outer solar system are all reactingto something. But what?

謎團(tuán)的最后一片出現(xiàn)在 2016 年，當(dāng)我和隔壁辦公室的同事康斯坦丁·巴蒂金意識到大家之所以那么受挫是因?yàn)榻拯c(diǎn)幅角只是故事的一部分。如果你用對的方式來觀察這些天體，它們實(shí)際上在宇宙中呈隊(duì)列排布，并面朝同樣的方向，以同樣的角度傾斜。就好像在廣場上的那些人們都朝向相同的方向行進(jìn)，并且他們都看向右邊 45 度。這很容易解釋。因?yàn)樗麄兌荚诳聪蚰硞€(gè)東西。在外太陽系的這些天體都受到某個(gè)東西的影響。但那是什么呢？

10:08

Konstantin and I spent a year trying tocome up with any explanation other than a distant, giant planet in the outersolar system. We did not want to be the 33rd and 34th people in history topropose this planet to yet again be told we were wrong. But after a year, therewas really no choice. We could come up with no other explanation other thanthat there is a distant, massive planet on an elongated orbit, inclined to therest of the solar system, that is forcing these patterns for these objects inthe outer solar system.

我和康斯坦丁花了一年的時(shí)間，嘗試去找出一個(gè)不同的解釋，不同于在外太陽系中有遙遠(yuǎn)且巨大行星的解釋。我們并不想要成為第 33 和 34 位提出這個(gè)行星存在又被告知弄錯(cuò)了的人。但一年后，真的沒有別的選擇。除了之前的那個(gè)解釋，我們想不出其他的解釋了：可能有個(gè)遙遠(yuǎn)的巨大行星沿著橢圓的軌道運(yùn)行，傾斜向這個(gè)太陽系的其他部分，從而被迫形成這些外太陽系天體的模式。

10:44

Guess what else a planet like this does.Remember that strange orbit of Sedna, how it was kind of pulled away from theSun in one direction? A planet like this would make orbits like that all daylong. We knew we were onto something.

猜一下這樣的行星還會(huì)做什么？還記得塞德娜那奇特的軌道嗎？那個(gè)軌道似乎被朝著一個(gè)方向拉離太陽。這樣的一個(gè)行星會(huì)不分晝夜地產(chǎn)生那樣的軌道。我們知道事情有些眉目了。

10:57

So this brings us to today. We arebasically 1845, Paris.

這就把我們帶到了今天。我們的處境基本上就是 1845 年的巴黎。

11:05

(Laughter)

（笑聲）

11:06

We see the gravitational effects of a distant,giant planet, and we are trying to work out the calculations to tell us whereto look, to point our telescopes, to find this planet.

我們看到遙遠(yuǎn)的巨大行星造成的重力效應(yīng)，于是我們試著計(jì)算出望遠(yuǎn)鏡應(yīng)該轉(zhuǎn)向的方向，希望能找到這個(gè)行星。

11:18

We've done massive suites of computersimulations, massive months of analytic calculations and here's what I can tellyou so far.

我們做過大量的電腦模擬，投入無數(shù)個(gè)月做分析計(jì)算，目前我能告訴各位的是：

11:25

First, this planet, which we call PlanetNine, because that's what it is, Planet Nine is six times the mass of theEarth. This is no slightly-smaller-than-Pluto, let's-all-argue-about-whether-it's-a-planet-or-not thing. This is the fifth largest planet in ourentire solar system. Planet Nine is big.Planet Nine is so big, you should probably wonder why haven't we found it yet.Well, Planet Nine is big, but it's also really, really far away. It's somethinglike 15 times further away than Neptune. And that makes it about 50,000 timesfainter than Neptune. And also, the sky is a really big place. We've narroweddown where we think it is to a relatively small area of the sky, but it wouldstill take us years to systematically cover the area of the sky with the largetelescopes that we need to see something that's this far away and this faint.Luckily, we might not have to.

首先，我們把這顆行星稱為第九行星，因?yàn)樗褪堑诰艂€(gè)。第九行星的質(zhì)量是地球的 6 倍。這并非“它比冥王星小一點(diǎn)，爭論一下它是不是行星”的情形。這是我們整個(gè)太陽系中第五大的行星。 第九行星很大。第九行星大到 你應(yīng)該納悶，為什么 我們還沒有找到它。第九行星的確很大，但它也非常、非常的遠(yuǎn)。它所在的位置可能比海王星還要遠(yuǎn)十五倍。這同時(shí)意味著它的亮度比海王星還要微弱五萬倍。此外，天空真的是一個(gè)很大的空間。我們已經(jīng)把它的定位范圍縮小成天空中相對很小的一塊區(qū)域。但我們?nèi)匀灰〝?shù)年的時(shí)間才能系統(tǒng)性地覆蓋到整個(gè)區(qū)域，而且還得使用很大的望遠(yuǎn)鏡才能看到那么遙遠(yuǎn)，那么微弱的行星。幸運(yùn)的是，我們可能不用這么做。

12:46

Just like Bouvard used unrecognizedobservations of Uranus from 91 years before its discovery, I bet that there areunrecognized images that show the location of Planet Nine. It's going to be amassive computational undertaking to go through all of the old data and pickout that one faint moving planet. But we're underway. And I think we're gettingclose.

就像布瓦爾使用在天王星被發(fā)現(xiàn)的 91 年前未能識別出天王星的觀測資料，我敢說一定有那些未能識別出的影像可以顯示出第九行星的位置。這勢必要用到非常大量的計(jì)算才能分析完所有的舊資料，并挑出那一個(gè)亮度微弱的移動(dòng)行星。我們正在做這件事了，并且我認(rèn)為我們離成功越來越近了。

13:15

So I would say, get ready. We are not goingto match Le Verrier's "make a prediction, have the planet found in asingle night that close to where you predicted it" record. But I do betthat within the next couple of years some astronomer somewhere will find afaint point of light, slowly moving across the sky and triumphantly announcethe discovery of a new, and quite possibly not the last, real planet of oursolar system.

所以，我要說的是，準(zhǔn)備好。我們并不是要追趕勒維耶的記錄：“做一個(gè)預(yù)測，第一個(gè)晚上就在離預(yù)測位置不遠(yuǎn)處找到了行星”。但我敢說，在接下來幾年內(nèi)，某地的某個(gè)天文學(xué)家會(huì)發(fā)現(xiàn)一個(gè)微弱的光點(diǎn)緩慢的在天空中移動(dòng)，并得意洋洋地宣布一顆新行星的發(fā)現(xiàn)，而且可能還不是我們太陽系中·真實(shí)存在的最后一顆行星。

13:46

Thank you.

謝謝。

13:47

(Applause)

（掌聲）