The search for our solar system's ninth planet | Mike Brown

翻译人员: Yiwei Chen 校对人员: Jiasi Hao

我要给你们讲述一个 从 200 年前开始的故事。

I'm going to tell you a story from 200 years ago.

In 1820, French astronomer Alexis Bouvard

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。

almost became the second person in human history to discover a planet.

He'd been tracking the position of Uranus across the night sky

他当时在用原始的星表 追踪夜间天王星

using old star catalogs,

划过天空的位置，

and it didn't quite go around the Sun

然而天王星并没有像他预测的那样

the way that his predictions said it should.

围绕着太阳转。

Sometimes it was a little too fast,

有时，它转得有点太快了，

sometimes a little too slow.

有时，又转得有点太慢。

布瓦尔知道他的预测是完美的，

Bouvard knew that his predictions were perfect.

So it had to be that those old star catalogs were bad.

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，

He told astronomers of the day,

"Do better measurements."

“做更好的测量。”

So they did.

于是他们照做了。

Astronomers spent the next two decades

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，

meticulously tracking the position of Uranus across the sky,

but it still didn't fit Bouvard's predictions.

但是结果仍然 和布瓦尔的预测不一样。

By 1840, it had become obvious.

直到 1840 年，事情变得很明显：

The problem was not with those old star catalogs,

问题不是出在那些陈旧的星表上，

而是在于那些预测。

the problem was with the predictions.

同时，天文学家们 知道这是为什么。

And astronomers knew why.

They realized that there must be a distant, giant planet

他们意识到， 一定是有一个遥远的巨大行星，

just beyond the orbit of Uranus

刚好在天王星轨道的后面，

that was tugging along at that orbit,

影响着天王星的运行速度。

sometimes pulling it along a bit too fast,

有时推着它，导致它移动得太快，

sometimes holding it back.

有时又会拽住它， 减慢它的运行速度。

Must have been frustrating back in 1840

回到 1840 年，科学家一定很崩溃，

to see these gravitational effects of this distant, giant planet

因为你能看到这些 相距遥远的巨行星重力效应，

but not yet know how to actually find it.

却还不知道如何找到它。

相信我，这真的很让人崩溃。

Trust me, it's really frustrating.

(Laughter)

（笑声）

But in 1846, another French astronomer,

但是到了 1846 年， 另外一个法国天文学家

Urbain Le Verrier,

奥本·勒维耶（Urbain Le Verrier），

worked through the math

通过数学计算，

and figured out how to predict the location of the planet.

找到了如何预测行星位置的方法。

He sent his prediction to the Berlin observatory,

他把他的预测结果发给了柏林天文台，

they opened up their telescope

他们打开了望远镜，

and in the very first night they found this faint point of light

然后就在第一天晚上， 观测到了一个很微弱的光点，

slowly moving across the sky

缓慢的从天空划过，

and discovered Neptune.

然后发现了天王星。

It was this close on the sky to Le Verrier's predicted location.

它的位置和勒维耶的预测结果 在天空中就只差这么一点。

The story of prediction and discrepancy and new theory

这段关于预测、区别、新理论

and triumphant discoveries is so classic

以及成功发现的故事堪称经典，

and Le Verrier became so famous from it,

勒维耶也因此成名，

that people tried to get in on the act right away.

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，

In the last 163 years,

dozens of astronomers have used some sort of alleged orbital discrepancy

数十位天文学家 利用所谓的轨道偏差，

to predict the existence of some new planet in the solar system.

来预测太阳系中是否存在新行星。

They have always been wrong.

但他们的预测 却一直出现各种问题。

最有名的一个错误预测

The most famous of these erroneous predictions

came from Percival Lowell,

来自于帕西瓦尔·罗威尔 （Percival Lowell），

who was convinced that there must be a planet just beyond Uranus and Neptune,

他坚信，在天王星和海王星后， 一定还有一个行星，

messing with those orbits.

在干扰那些轨道。

And so when Pluto was discovered in 1930

因此在 1930 年冥王星被发现于

at the Lowell Observatory,

洛厄尔天文台时，

everybody assumed that it must be the planet that Lowell had predicted.

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。

They were wrong.

It turns out, Uranus and Neptune are exactly where they're supposed to be.

结果表明，天王星和海王星 就在它们应该在的地方。

It took 100 years,

这件事花费了 100 年的时间，

but Bouvard was eventually right.

但是最终，人们发现布瓦尔是对的。

Astronomers needed to do better measurements.

天文学家们需要做更好的测量。

And when they did,

他们这么做了之后，

those better measurements had turned out that

那些更好的测量表明，

there is no planet just beyond the orbit of Uranus and Neptune

在天王星和海王星的轨道后面 并没有行星的出现，

and Pluto is thousands of times too small

并且冥王星的体积 比预测的要小几千倍，

to have any effect on those orbits at all.

以至于对那些轨道 不会产生任何影响。

因此，尽管冥王星后来被证实

So even though Pluto turned out not to be the planet

并非本意想要预测的那颗行星，

it was originally thought to be,

it was the first discovery of what is now known to be

但这是目前对在已知行星外轨道上

thousands of tiny, icy objects in orbit beyond the planets.

存在的数千个微小的 结冰天体（柯伊伯带）的首次发现。

Here you can see the orbits of Jupiter,

这里你可以看到木星、

Saturn, Uranus and Neptune,

土星、天王星和海王星的轨道，

and in that little circle in the very center is the Earth

以及在那个小圆圈里， 最中间的地方就是地球，

and the Sun and almost everything that you know and love.

和太阳，以及所有 你知道并喜爱的一切。

And those yellow circles at the edge

那些边缘发黄的圈，

是在行星外围的结冰天体。

are these icy bodies out beyond the planets.

These icy bodies are pushed and pulled

这些结冰天体

by the gravitational fields of the planets

会因为行星的重力场，

in entirely predictable ways.

按照完全可预测的方式被推拉。

Everything goes around the Sun exactly the way it is supposed to.

所有的行星基本上都在 以它们该有的方式

Almost.

围绕着太阳转。

So in 2003,

在 2003 年，

I discovered what was at the time

我发现了

the most distant known object in the entire solar system.

当时在太阳系中探测到 的最遥远的已知天体。

It's hard not to look at that lonely body out there

很难忽视远方那颗孤独的天体，

and say, oh yeah, sure, so Lowell was wrong,

然后说，是的， 罗威尔错了，

there was no planet just beyond Neptune,

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。

but this, this could be a new planet.

我们真正要问的是，

The real question we had was,

what kind of orbit does it have around the Sun?

它以什么样的轨道围绕着太阳转？

Does it go in a circle around the Sun

它是否就像其他行星一样

like a planet should?

绕着太阳以圆形的轨道旋转？

Or is it just a typical member of this icy belt of bodies

还是就像冰带中 其他典型的结冰天体一样，

that got a little bit tossed outward and it's now on its way back in?

只是先前不小心被抛出去了， 现在在回归原轨道的路上？

This is precisely the question

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。

the astronomers were trying to answer about Uranus 200 years ago.

They did it by using overlooked observations of Uranus

他们是利用在发现天王星的 91 年前

from 91 years before its discovery

所被忽略的观测资料，

to figure out its entire orbit.

从而找到它的整个轨道的。

We couldn't go quite that far back,

我们无法追溯回那么早的资料，

but we did find observations of our object from 13 years earlier

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。

that allowed us to figure out how it went around the Sun.

这些资料让我们弄清了 它是如何绕太阳转的。

So the question is,

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，

is it in a circular orbit around the Sun, like a planet,

or is it on its way back in,

还是像那些结冰天体一样

like one of these typical icy bodies?

在回程途中？

And the answer is

答案是，

皆非。

no.

It has a massively elongated orbit

它拥有非常巨大的椭圆轨道，

that takes 10,000 years to go around the Sun.

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），

We named this object Sedna

after the Inuit goddess of the sea,

是因纽特人海洋女神的名字，

in honor of the cold, icy places where it spends all of its time.

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

We now know that Sedna,

it's about a third the size of Pluto

约是冥王星的三分之一，

and it's a relatively typical member

且是海王星外的那些结冰天体中，

of those icy bodies out beyond Neptune.

相对比较典型的一个天体。

Relatively typical, except for this bizarre orbit.

相对比较典型， 但不包括它的奇特的轨道。

You might look at this orbit and say,

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”，

"Yeah, that's bizarre, 10,000 years to go around the Sun,"

but that's not really the bizarre part.

但这还不是它奇特的地方，

The bizarre part is that in those 10,000 years,

奇特的是，在那一万年中，

Sedna never comes close to anything else in the solar system.

塞德娜完全不接近 太阳系中的任何其他东西。

Even at its closest approach to the Sun,

即使是在它离太阳最近的位置，

Sedna is further from Neptune

塞德娜和海王星的距离

than Neptune is from the Earth.

也比海王星和地球之间的距离更远。

假如塞德娜有这样的轨道：

If Sedna had had an orbit like this,

that kisses the orbit of Neptune once around the Sun,

绕行太阳一圈就会和 海王星的轨道接触一次，

that would have actually been really easy to explain.

那这就很容易解释了。

That would have just been an object

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，

that had been in a circular orbit around the Sun

in that region of icy bodies,

有一瞬间太靠近海王星，

had gotten a little bit too close to Neptune one time,

因此被弹了出去，

and then got slingshot out and is now on its way back in.

现在正在返回的途中。

But Sedna never comes close to anything known in the solar system

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。

that could have given it that slingshot.

Neptune can't be responsible,

既然不是海王星造成的，

but something had to be responsible.

那一定有别的原因。

This was the first time since 1845

这是自 1845 年以来

that we saw the gravitational effects of something in the outer solar system

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，

and didn't know what it was.

但不知道它是什么。

我曾经以为自己知道答案。

I actually thought I knew what the answer was.

的确，它有可能是外太阳系一颗

Sure, it could have been some distant, giant planet

in the outer solar system,

很遥远的巨大行星，

but by this time, that idea was so ridiculous

但在这个情况中，这个想法很荒谬，

and had been so thoroughly discredited

完全不足为信，

that I didn't take it very seriously.

所以我没有很严肃的对待它。

But 4.5 billion years ago,

但在 45 亿年前，

when the Sun formed in a cocoon of hundreds of other stars,

当太阳在其它上百个天体的 包裹下形成时，

any one of those stars

那些天体中的任何一个

都有可能太靠近塞德娜，

could have gotten just a little bit too close to Sedna

and perturbed it onto the orbit that it has today.

从而影响它， 让它进入现今的这个轨道中。

When that cluster of stars dissipated into the galaxy,

当那群天体消散在星系中，

the orbit of Sedna would have been left as a fossil record

塞德娜的轨道应该会变成 太阳最早期历史中

of this earliest history of the Sun.

的化石记录。

I was so excited by this idea,

这个想法让我很兴奋，

by the idea that we could look

这表示我们可以去研究

太阳诞生的化石历史，

at the fossil history of the birth of the Sun,

that I spent the next decade

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。

looking for more objects with orbits like Sedna.

In that ten-year period, I found zero.

在那十年间，我一个也没找到。

(Laughter)

（笑声）

But my colleagues, Chad Trujillo and Scott Sheppard, did a better job,

但我的同事，查理·楚基罗 和史考特·雪柏，有了些发现。

and they have now found several objects with orbits like Sedna,

他们现在已经找到了 好几个轨道类似塞德娜的天体。

which is super exciting.

这非常令人兴奋。

But what's even more interesting

但更让人激动的是，

is that they found that all these objects

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，

are not only on these distant, elongated orbits,

they also share a common value of this obscure orbital parameter

而且具有相同的复杂轨道参数特征。

that in celestial mechanics we call argument of perihelion.

在天体力学中， 我们把这个参数称为近日点幅角。

When they realized it was clustered in argument of perihelion,

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，

they immediately jumped up and down,

因为他们认为一定有个 遥远的巨大行星存在。

saying it must be caused by a distant, giant planet out there,

这真的让人很兴奋， 只是完全不合理罢了。

which is really exciting, except it makes no sense at all.

让我试着用一个比喻 来解释为什么。

Let me try to explain it to you why with an analogy.

Imagine a person walking down a plaza

试想，一个人走在广场上，

and looking 45 degrees to his right side.

看向他右边 45 度的方向。

这可能有很多理由，

There's a lot of reasons that might happen,

很容易解释，不是什么大事儿。

it's super easy to explain, no big deal.

现在试想，有很多不同的人

Imagine now many different people,

都在广场上朝不同的方向走，

all walking in different directions across the plaza,

but all looking 45 degrees to the direction that they're moving.

但都看向他们行进方向的 45 度角。

Everybody's moving in different directions,

大家行进的方向不同，

everybody's looking in different directions,

大家看去的方向也不同，

but they're all looking 45 degrees to the direction of motion.

但他们看去的 都是行进方向的 45 度处，

What could cause something like that?

这个现象背后的原因会是什么？

I have no idea.

我不知道。

It's very difficult to think of any reason that that would happen.

非常难想象出任何理由 会造成这个现象。

(Laughter)

（笑声）

And this is essentially what that clustering

基本上，这就是 一堆相近的近日点幅角

in argument of perihelion was telling us.

告诉我们的事。

Scientists were generally baffled and they assumed it must just be a fluke

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。

and some bad observations.

They told the astronomers,

他们告诉天文学家，

“把观测做得更好一点”。

"Do better measurements."

I actually took a very careful look at those measurements, though,

我其实非常仔细地 研究过这些测量值，

and they were right.

但它们是对的。

这些天体真的都用

These objects really did all share

同样的近日点幅角值，

a common value of argument of perihelion,

and they shouldn't.

但是这不应该。

背后一定有原因。

Something had to be causing that.

谜团的最后一片出现在 2016 年，

The final piece of the puzzle came into place in 2016,

when my colleague, Konstantin Batygin,

当我和隔壁办公室的同事

康斯坦丁·巴蒂金意识到

who works three doors down from me, and I

realized that the reason that everybody was baffled

大家之所以那么受挫

was because argument of perihelion was only part of the story.

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，

If you look at these objects the right way,

它们实际上在宇宙中 呈队列排布，并面朝同样的方向，

they are all actually lined up in space in the same direction,

and they're all tilted in space in the same direction.

以同样的角度倾斜。

It's as if all those people on the plaza are all walking in the same direction

就好像在广场上的那些人们 都朝向相同的方向行进，

and they're all looking 45 degrees to the right side.

并且他们都看向右边 45 度。

That's easy to explain.

这很容易解释。

因为他们都在看向某个东西。

They're all looking at something.

These objects in the outer solar system are all reacting to something.

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？

But what?

Konstantin and I spent a year

我和康斯坦丁花了一年的时间，

trying to come up with any explanation other than a distant, giant planet

尝试去找出一个不同的解释， 不同于在外太阳系中

in the outer solar system.

有遥远且巨大行星的解释。

We did not want to be the 33rd and 34th people in history to propose this planet

我们并不想要成为第 33 和 34 位 提出这个行星存在

to yet again be told we were wrong.

又被告知弄错了的人。

But after a year,

但一年后，

there was really no choice.

真的没有别的选择。

We could come up with no other explanation

除了之前的那个解释，

我们想不出其他的解释了：

other than that there is a distant,

massive planet on an elongated orbit,

可能有个遥远的巨大行星 沿着椭圆的轨道运行，

inclined to the rest of the solar system,

倾斜向这个太阳系的其他部分，

从而被迫形成这些

that is forcing these patterns for these objects

in the outer solar system.

外太阳系天体的模式。

Guess what else a planet like this does.

猜一下这样的行星还会做什么？

Remember that strange orbit of Sedna,

还记得塞德娜那奇特的轨道吗？

how it was kind of pulled away from the Sun in one direction?

那个轨道似乎被朝着 一个方向拉离太阳。

A planet like this would make orbits like that all day long.

这样的一个行星会 不分昼夜地产生那样的轨道。

We knew we were onto something.

我们知道事情有些眉目了。

So this brings us to today.

这就把我们带到了今天。

We are basically 1845, Paris.

我们的处境基本上 就是 1845 年的巴黎。

（笑声）

(Laughter)

We see the gravitational effects of a distant, giant planet,

我们看到遥远的巨大行星 造成的重力效应，

and we are trying to work out the calculations

于是我们试着计算出

to tell us where to look, to point our telescopes,

望远镜应该转向的方向，

to find this planet.

希望能找到这个行星。

We've done massive suites of computer simulations,

我们做过大量的电脑模拟，

massive months of analytic calculations

投入无数个月做分析计算，

and here's what I can tell you so far.

目前我能告诉各位的是：

First, this planet, which we call Planet Nine,

首先，我们把这颗行星 称为第九行星，

因为它就是第九个。

because that's what it is,

Planet Nine is six times the mass of the Earth.

第九行星的质量是地球的 6 倍。

这并非“它比冥王星小一点，

This is no slightly-smaller-than-Pluto,

let's-all-argue-about- whether-it's-a-planet-or-not thing.

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。

This is the fifth largest planet in our entire solar system.

For context, let me show you the sizes of the planets.

我先让各位对比一下 这些行星的大小。

在后方，你可以看到 巨大的木星和土星。

In the back there, you can the massive Jupiter and Saturn.

Next to them, a little bit smaller, Uranus and Neptune.

在它们旁边是稍小一点 的天王星和海王星。

Up in the corner, the terrestrial planets, Mercury, Venus, Earth and Mars.

在上面角落的是类地行星： 水星、金星、地球、火星。

You can even see that belt

你甚至可以看到

of icy bodies beyond Neptune, of which Pluto is a member,

海王星外面的结冰带， 而且冥王星也是其中一员。

good luck figuring out which one it is.

看看你们能不能分清谁是谁。

And here is Planet Nine.

这里是第九行星。

Planet Nine is big.

第九行星很大。

第九行星大到

Planet Nine is so big,

you should probably wonder why haven't we found it yet.

你应该纳闷，为什么 我们还没有找到它。

Well, Planet Nine is big,

第九行星的确很大，

but it's also really, really far away.

但它也非常、非常的远。

It's something like 15 times further away than Neptune.

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。

And that makes it about 50,000 times fainter than Neptune.

此外，天空真的是一个很大的空间。

And also, the sky is a really big place.

We've narrowed down where we think it is

我们已经把它的定位范围

to a relatively small area of the sky,

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

but it would still take us years

to systematically cover the area of the sky

才能系统性地覆盖到整个区域，

with the large telescopes that we need

而且还得使用很大的望远镜

to see something that's this far away and this faint.

才能看到那么遥远，那么微弱的行星。

Luckily, we might not have to.

幸运的是，我们可能不用这么做。

Just like Bouvard used unrecognized observations of Uranus

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，

from 91 years before its discovery,

I bet that there are unrecognized images

我敢说一定有那些 未能识别出的影像

that show the location of Planet Nine.

可以显示出第九行星的位置。

It's going to be a massive computational undertaking

这势必要用到非常大量的计算

to go through all of the old data

才能分析完所有的旧资料，

and pick out that one faint moving planet.

并挑出那一个亮度微弱的移动行星。

But we're underway.

我们正在做这件事了，

And I think we're getting close.

并且我认为 我们离成功越来越近了。

所以，我要说的是，准备好。

So I would say, get ready.

We are not going to match Le Verrier's

我们并不是要追赶勒维耶的记录：

"make a prediction,

“做一个预测，

have the planet found in a single night

第一个晚上就在离预测位置

that close to where you predicted it" record.

不远处找到了行星”。

But I do bet that within the next couple of years

但我敢说，在接下来几年内，

some astronomer somewhere

某地的某个天文学家

will find a faint point of light,

会发现一个微弱的光点

slowly moving across the sky

缓慢的在天空中移动，

and triumphantly announce the discovery of a new,

并得意洋洋地宣布 一颗新行星的发现，

and quite possibly not the last,

而且可能还不是我们太阳系中

real planet of our solar system.

·真实存在的最后一颗行星。

Thank you.

谢谢。

(Applause)

（掌声）