听力课堂TED音频栏目主要包括TED演讲的音频MP3及中英双语文稿，供各位英语爱好者学习使用。本文主要内容为演讲MP3+双语文稿:寻找太阳系的第九颗行星，希望你会喜欢！

【演讲人及介绍】Mike Brown

行星天文学家迈克·布朗（Mike Brown）扫描天空，寻找并深入研究太阳系中的遥远天体，以期深入了解我们的行星及其周围的行星是如何形成的。

【演讲主题】寻找我们太阳系的第九颗行星

【演讲文稿-中英文】

翻译者 Yiwei Chen 校对 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.

我要给你们讲述一个从 200 年前开始的故事。1820 年，法国天文学家阿列西·布瓦尔（Alexis Bouvard）差点成为了人类历史上第二个发现行星的人。他当时在用原始的星表追踪夜间天王星划过天空的位置，然而天王星并没有像他预测的那样围绕着太阳转。有时，它转得有点太快了，有时，又转得有点太慢。布瓦尔知道他的预测是完美的，因此这一定是陈旧星表的不准确性所导致的。那天，他跟天文学家们说，“做更好的测量。”于是他们照做了。天文学家们花费了将近 20 年，一丝不苟的追踪天王星划过天空的轨迹，但是结果仍然和布瓦尔的预测不一样。

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，事情变得很明显：问题不是出在那些陈旧的星表上，而是在于那些预测。同时，天文学家们知道这是为什么。他们意识到，一定是有一个遥远的巨大行星，刚好在天王星轨道的后面，影响着天王星的运行速度。有时推着它，导致它移动得太快，有时又会拽住它，减慢它的运行速度。

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，科学家一定很崩溃，因为你能看到这些相距遥远的巨行星重力效应，却还不知道如何找到它。相信我，这真的很让人崩溃。

01:36

(Laughter)

（笑声）

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，另外一个法国天文学家奥本·勒维耶（Urbain Le Verrier），通过数学计算，找到了如何预测行星位置的方法。他把他的预测结果发给了柏林天文台，他们打开了望远镜，然后就在第一天晚上，观测到了一个很微弱的光点，缓慢的从天空划过，然后发现了天王星。它的位置和勒维耶的预测结果在天空中就只差这么一点。

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.

这段关于预测、区别、新理论以及成功发现的故事堪称经典，勒维耶也因此成名，那些试图进入该领域的人也立马行动了起来。在过去的 163 年里，数十位天文学家利用所谓的轨道偏差，来预测太阳系中是否存在新行星。

02:28

They have always been wrong.

但他们的预测却一直出现各种问题。

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.

最有名的一个错误预测来自于帕西瓦尔·罗威尔（Percival Lowell），他坚信，在天王星和海王星后，一定还有一个行星，在干扰那些轨道。因此在 1930 年冥王星被发现于洛厄尔天文台时，所有人都以为，那颗行星一定就是罗威尔曾预测的那颗。但他们错了。结果表明，天王星和海王星就在它们应该在的地方。这件事花费了 100 年的时间，但是最终，人们发现布瓦尔是对的。天文学家们需要做更好的测量。他们这么做了之后，那些更好的测量表明，在天王星和海王星的轨道后面并没有行星的出现，并且冥王星的体积比预测的要小几千倍，以至于对那些轨道不会产生任何影响。

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，尽管冥王星后来被证实并非本意想要预测的那颗行星，但这是目前对在已知行星外轨道上存在的数千个微小的结冰天体（柯伊伯带）的首次发现。这些结冰天体 会因为行星的重力场，按照完全可预测的方式被推拉。所有的行星基本上都在以它们该有的方式围绕着太阳转。

04:02

Almost.

几乎是所有东西。

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，我发现了当时在太阳系中探测到的最遥远的已知天体。很难忽视远方那颗孤独的天体，然后说，是的，罗威尔错了，海王星之外并没有其他行星，但这一颗——这一颗可能是新的行星。我们真正要问的是，它以什么样的轨道围绕着太阳转？它是否就像其他行星一样绕着太阳以圆形的轨道旋转？还是就像冰带中 其他典型的结冰天体一样，只是先前不小心被抛出去了，现在在回归原轨道的路上？

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.

这正是在 200 年前，天文学家在研究天王星时努力想要解答的问题。他们是利用在发现天王星的 91 年前所被忽略的观测资料，从而找到它的整个轨道的。我们无法追溯回那么早的资料，但是我们在 13 年前的资料里找到了对目标天体的观测记录。这些资料让我们弄清了它是如何绕太阳转的。

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.

那么问题是，它是像行星一样在圆形的轨道上绕着太阳转呢，还是像那些结冰天体一样在回程途中？ 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.

它拥有非常巨大的椭圆轨道，使它绕太阳一周需要一万年的时间。我们将这个天体命名为塞德娜（Sedna），是因纽特人海洋女神的名字，以致敬它一生都在冰冻的环境中。我们现在知道塞德娜的体积约是冥王星的三分之一，且是海王星外的那些结冰天体中，相对比较典型的一个天体。相对比较典型，但不包括它的奇特的轨道。你看着这个轨道可能会说，“绕着太阳能走一万年确实很奇特”，但这还不是它奇特的地方，奇特的是，在那一万年中，塞德娜完全不接近太阳系中的任何其他东西。即使是在它离太阳最近的位置，塞德娜和海王星的距离也比海王星和地球之间的距离更远。

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.

假如塞德娜有这样的轨道：绕行太阳一圈就会和海王星的轨道接触一次，那这就很容易解释了。那它就是在结冰天体的区域中以圆形轨道绕行太阳的天体，有一瞬间太靠近海王星，因此被弹了出去，现在正在返回的途中。

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.

但是塞德娜从未接近过太阳系中任何已知的东西，不可能造成那样的弹射。既然不是海王星造成的，那一定有别的原因。这是自 1845 年以来我们第一次看到了在外太阳系的某个东西产生了重力效应，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.

我曾经以为自己知道答案。的确，它有可能是外太阳系一颗很遥远的巨大行星，但在这个情况中，这个想法很荒谬，完全不足为信，所以我没有很严肃的对待它。但在 45 亿年前，当太阳在其它上百个天体的包裹下形成时，那些天体中的任何一个都有可能太靠近塞德娜，从而影响它，让它进入现今的这个轨道中。当那群天体消散在星系中，塞德娜的轨道应该会变成太阳最早期历史中的化石记录。

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.

这个想法让我很兴奋，这表示我们可以去研究太阳诞生的化石历史，于是我用接下来十年的时间，去寻找更多有着类似塞德娜轨道的天体。在那十年间，我一个也没找到。

07:34

(Laughter)

（笑声）

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·楚基罗和史考特·雪柏，有了些发现。他们现在已经找到了好几个轨道类似塞德娜的天体。这非常令人兴奋。

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.

但更让人激动的是，他们发现，所有这些天体，不仅是在遥远，椭圆形的轨道上运行，而且具有相同的复杂轨道参数特征。在天体力学中，我们把这个参数称为近日点幅角。当他们发现那些特征参数集聚在近日点幅角时，立即手舞足蹈起来，因为他们认为一定有个遥远的巨大行星存在。这真的让人很兴奋，只是完全不合理罢了。

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.

让我试着用一个比喻来解释为什么。试想，一个人走在广场上，看向他右边 45 度的方向。这可能有很多理由，很容易解释，不是什么大事儿。现在试想，有很多不同的人都在广场上朝不同的方向走，但都看向他们行进方向的 45 度角。大家行进的方向不同，大家看去的方向也不同，但他们看去的都是行进方向的 45 度处，这个现象背后的原因会是什么？我不知道。非常难想象出任何理由会造成这个现象。

08:51

(Laughter)

（笑声）

08:53

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

基本上，这就是一堆相近的近日点幅角告诉我们的事。

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.

科学家们很受挫，他们认为一定是侥幸和不佳的观测造成的。他们告诉天文学家，“把观测做得更好一点”。我其实非常仔细地研究过这些测量值，但它们是对的。这些天体真的都用同样的近日点幅角值，但是这不应该。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?

谜团的最后一片出现在 2016 年，当我和隔壁办公室的同事康斯坦丁·巴蒂金意识到大家之所以那么受挫是因为近日点幅角只是故事的一部分。如果你用对的方式来观察这些天体，它们实际上在宇宙中呈队列排布，并面朝同样的方向，以同样的角度倾斜。就好像在广场上的那些人们都朝向相同的方向行进，并且他们都看向右边 45 度。这很容易解释。因为他们都在看向某个东西。在外太阳系的这些天体都受到某个东西的影响。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时间，尝试去找出一个不同的解释，不同于在外太阳系中有遥远且巨大行星的解释。我们并不想要成为第 33 和 34 位提出这个行星存在又被告知弄错了的人。但一年后，真的没有别的选择。除了之前的那个解释，我们想不出其他的解释了：可能有个遥远的巨大行星沿着椭圆的轨道运行，倾斜向这个太阳系的其他部分，从而被迫形成这些外太阳系天体的模式。

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.

猜一下这样的行星还会做什么？还记得塞德娜那奇特的轨道吗？那个轨道似乎被朝着一个方向拉离太阳。这样的一个行星会不分昼夜地产生那样的轨道。我们知道事情有些眉目了。

10:57

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

这就把我们带到了今天。我们的处境基本上就是 1845 年的巴黎。

11:05

(Laughter)

（笑声）

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.

我们看到遥远的巨大行星造成的重力效应，于是我们试着计算出望远镜应该转向的方向，希望能找到这个行星。

11:18

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

我们做过大量的电脑模拟，投入无数个月做分析计算，目前我能告诉各位的是：

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，我们把这颗行星称为第九行星，因为它就是第九个。第九行星的质量是地球的 6 倍。这并非“它比冥王星小一点，争论一下它是不是行星”的情形。这是我们整个太阳系中第五大的行星。 第九行星很大。第九行星大到 你应该纳闷，为什么 我们还没有找到它。第九行星的确很大，但它也非常、非常的远。它所在的位置可能比海王星还要远十五倍。这同时意味着它的亮度比海王星还要微弱五万倍。此外，天空真的是一个很大的空间。我们已经把它的定位范围缩小成天空中相对很小的一块区域。但我们仍然要花数年的时间才能系统性地覆盖到整个区域，而且还得使用很大的望远镜才能看到那么遥远，那么微弱的行星。幸运的是，我们可能不用这么做。

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.

就像布瓦尔使用在天王星被发现的 91 年前未能识别出天王星的观测资料，我敢说一定有那些未能识别出的影像可以显示出第九行星的位置。这势必要用到非常大量的计算才能分析完所有的旧资料，并挑出那一个亮度微弱的移动行星。我们正在做这件事了，并且我认为我们离成功越来越近了。

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，我要说的是，准备好。我们并不是要追赶勒维耶的记录：“做一个预测，第一个晚上就在离预测位置不远处找到了行星”。但我敢说，在接下来几年内，某地的某个天文学家会发现一个微弱的光点缓慢的在天空中移动，并得意洋洋地宣布一颗新行星的发现，而且可能还不是我们太阳系中·真实存在的最后一颗行星。

13:46

Thank you.

谢谢。

13:47

(Applause)

（掌声）