The story of 'Oumuamua, the first visitor from another star system | Karen J. Meech | TED

翻译人员: Hong Li 校对人员: Yuanqing Edberg

NASA's always on the lookout for possible asteroid collision hazards,

美国航空航天局（NASA）一直在进行 天文观测，以避免小行星碰撞的危险，

so the Pan-STARRS telescope is scanning the sky every night.

因此泛星计划的望远镜 每晚都在扫描天空。

Each morning, candidate objects are examined by Pan-STARRS staff

每天早上，泛星计划的工作人员 都会检查那些候选星体，

and usually discovered to be no big deal.

通常的结果都是：没有问题。

But on October 19, 2017,

但是2017年的10月19日，

Pan-STARRS spotted an object moving rapidly between the stars,

泛星计划发现了一个 在星系间快速移动的物体，

and this time the usual follow-up measurements of position and speed

这一次，例行的 位置和速度测量结果

showed something completely different.

显示了完全不一样的结果。

By October 22nd, we had enough data

到10月22日，我们有了足够的数据

to realize that this object wasn't from our solar system.

证明这个物体不是来自太阳系。

Holy cow.

我的天。

That's when I got the phone call,

我就是在那天接到的电话，

the phone call that all solar system astronomers are waiting for.

所有研究太阳系的天文学家 都在等这个电话。

Let me tell you how exciting this was.

我来告诉你们这件事有多让人激动。

(Laughter)

（笑声）

NASA's been expecting to see an interstellar comet

从20世纪70年代开始， NASA就想找到一颗

pass through the solar system since the 1970s,

跨星际飞行的彗星，能横穿太阳系，

but until now, we'd never seen anything.

但直到现在都没有任何发现。

Our own solar system is huge,

我们的太阳系很大，

so even getting a package from the nearest star system

即使从最近的、 离我们4.4光年的恒星系统

4.4 light years away

发点东西过来，

would take over 50,000 years.

也需要5万年那么久。

So this is a really big deal.

因此这件事真的非常重要。

The interstellar visitor entered our solar system

这位星际访客是从行星平面上方，

from above the plane of the planets,

从天琴座的方向

coming from the direction of the constellation Lyra,

进入我们的太阳系的，

and it passed closest to the Sun on September 9th,

它在9月9日经过了近日点，

passing inside the orbit of Mercury.

从水星轨道内穿过。

Now this isn't a particularly close approach or unusual distance.

这个距离其实不算近， 属于正常范围。

It's just much easier to see objects close by.

但是已经让我们的观测 变得容易多了。

On October 14th,

在10月14日，

before we discovered it, it made its closest approach to the Earth,

在我们发现它之前， 它已经掠过了近地点，

within about 15 million miles.

差不多在1500万英里之内。

This is really close by astronomical standards.

就天文学的标准来说， 这已经相当近了。

Now rather than call this by its unwieldy catalog name,

我们没有按照枯燥的 目录命名来称呼它，

we briefly called it "Rama,"

我们叫它“拉玛”，

after the cylindrical spacecraft that passed through the solar system

名字来自于阿瑟 · C · 克拉克 1973年的经典科幻小说

in Arthur C. Clarke's classic science fiction story in 1973.

里面那艘穿过太阳系的 圆柱形宇宙飞船。

But this wasn't quite right either,

但其实这个名字也不太合适，

so in honor of it being discovered by a telescope in Hawaii,

因为发现它的望远镜是在夏威夷，

we consulted two experts on Hawaiian culture --

于是我们找了两位夏威夷文化的专家，

a Hawaiian navigator and a linguist --

一位夏威夷向导和一位语言学家，

to propose a name.

来想一个名字。

And they suggested "'Oumuamua,"

他们提议叫“奥陌陌”，

which means scout or messenger from the distant past reaching out to us.

意思是经过长途跋涉 找到我们的侦察兵或者信使。

Now this discovery was important for many reasons,

这个发现之所以重要，有很多原因，

but to me the most significant is for what 'Oumuamua can tell us

但我认为最有意义的是， 奥陌陌能告诉我们

about the past of our solar system.

我们太阳系的过去。

The process of the birth of a new solar system and the growth of planets

一个新的恒星系统的诞生 和行星的成长

can be a violent and messy business.

是一个剧烈而混乱的过程。

Leftover icy and rocky debris gets ejected from the new solar system

多余的冰和岩石碎屑 被甩出这个新生的恒星系统。

as the giant planets migrate through the dusty disk

巨大的行星从它们诞生的尘埃中

out of which they're formed.

穿越而过。

Now have you ever felt an emotional chill,

你们有没有感受过情绪的震颤，

something that's so exciting that a shiver runs up and down your spine?

就是有件事让你很激动， 一阵颤抖的感觉沿着你的脊柱上下？

Or something that's very emotionally moving?

或者让你觉得非常受感动？

Well this was it for me.

我当时就是这种感觉。

This was my wow moment.

这是我的惊喜时刻。

We actually had a piece of material from another solar system

有一块从其他星系过来的物质

coming close enough for us to observe.

离得够近，可以让我们观察。

So what would you like to know about 'Oumuamua,

关于奥陌陌，你们想知道些什么呢，

the very first visitor from another star system?

它是第一位来自另一个星系的访客。

Well, I could think of a million things,

我可以想到一百万件事，

but there's what you want and what you can have,

但是现实和理想总是有差距的，

and 'Oumuamua was moving away and fading very rapidly.

奥陌陌当时正在离我们而去， 消失得非常快。

In the span of about a week,

在差不多一周的时间里，

it had dropped in brightness by a factor of [10].

它的亮度就下降了百分之一。

So this is about all the time we were going to have

因此我们能用来方便地研究它的时间

to study it easily.

非常有限。

So we had to distill the process of getting telescope time --

因此我们要加快申请使用望远镜，

normally a very competitive, peer-reviewed proposal process

申请过程充满竞争、手续繁杂，

that can take up to months --

通常要花几个月的时间，

down to less than a few days.

而我们只有几天的时间。

So began a "polite" competition for resources.

于是开始了一场 “礼貌地”争夺资源的竞争。

OK, let me not mince words. It was a fierce battle.

好吧，还是不要说反话了。 那是一场激烈的战斗。

We dropped everything,

我们放下了所有的事情，

working around the clock,

跟时间赛跑，

trying to craft perfectly crafted proposal words

试图写出一篇完美的申请报告

to send to the observatory directors.

发给天文台台长。

Well, good news. We got the time.

好在事遂人愿， 我们申请到了使用时间。

Now, from a perfectly selfish point of view,

从非常私人的观点出发，

the first thing we might like to know is how massive 'Oumuamua is.

我们想要了解的第一件事 可能是奥陌陌的质量是多少。

Because after all, it passed very close to the Earth,

因为毕竟它曾经离地球非常近，

and we didn't know about it until afterwards.

而我们发现它的时候它已经远离了。

How bad would this have been had it not missed the Earth?

如果它撞上地球，会有多糟糕？

Well, the impact energy

撞击的能量

depends on the square of the velocity times its mass,

取决于速度的平方乘以它的质量，

and the mass depends on how big it is and what it's made of.

而质量取决于它有多大， 以及由什么物质组成。

So how big is 'Oumuamua, and what's its shape?

那么奥陌陌有多大呢？ 形状又是什么样？

Well, we can get this from its brightness.

我们能从它的亮度上来判断。

Now, if you don't believe me, think of comparing the brightness

如果你不相信的话， 想象一下，我们来比较两者的亮度，

一个是你后院的萤火虫

of a firefly in your backyard

to the navigation lights on a distant airplane.

一个是远处飞机上的导航灯。

You know the airplane is much brighter --

飞机的灯肯定更亮，

it just appears faint because it's so far away.

它看起来比较暗淡是因为离得远。

We're also going to need to know

我们还需要知道

how reflective the surface of 'Oumuamua is,

奥陌陌的表面反射情况，

and we don't have any clue,

我们没有任何线索，

but it's reasonable to assume it's very similar to small asteroids

但是可以有依据地猜测， 应该跟我们太阳系中的

and comets in our solar system,

小行星和卫星很相似。

or in technical terms,

或者用技术性的描述，

something between the reflectivity of charcoal and wet sand.

它的反射率应该介于 木炭和潮湿的沙子之间。

Nowadays, most of the big telescopes are used in what's called a service mode,

如今，大多数大型望远镜 都在以所谓服务模式运行，

meaning we have to carefully develop all the instructions

就是说我们要仔细地准备 所有的操作流程，

and send them to the telescope operator,

然后发给望远镜操作员，

and then anxiously wait for the data to come back,

之后就是焦急地等待数据发过来，

praying to the weather gods.

同时向天气之神祈祷。

Now I bet most of you don't have careers

我打赌你们都没做过这种工作，

that critically depend on whether or not it's cloudy last night.

成败与否极度依赖于头天晚上 是不是多云的天气。

Well, we weren't going to get any second chances here.

我们不再会有第二次机会。

Because the weather was great, 'Oumuamua decided not to be.

因为天气很不错，于是奥陌陌 给我们带来一点挑战。

Its brightness wasn't constant.

它的亮度不是很恒定。

Now here we see 'Oumuamua racing between the stars.

我们现在看到的是奥陌陌 在星星之间穿梭。

It's centered in the middle.

它被放在了中间。

The stars are trailed out because the telescope is following its motion.

星星在移动，因为望远镜 是跟着奥陌陌走的。

It started faint and then it got brighter, fainter, brighter, and fainter again,

它一会儿变暗，一会儿变亮，不停反复，

as sunlight is reflected off of four sides of an oblong object.

因为这个长方形物体的 四个面都会反射阳光。

The extreme brightness change

这种急剧的亮度变化

led us to an unbelievable conclusion about its shape.

让我们得出了关于它形状的 非常难以置信的结论。

As shown in this artist's impression,

根据艺术家制作的效果图，

'Oumuamua is apparently very long and narrow,

奥陌陌显然又长又窄，

with an axis ratio of about 10 to one.

长短轴比差不多是10比1。

Assuming it's dark, this means it's about half a mile long.

假设它是黑色的， 那就意味着它有800米长。

Nothing else in our solar system looks like this.

太阳系里从未有过这样的天体。

We only have a handful of objects that even have an axis ratio

我们观测到的长短轴比 超过5比1的天体

bigger than five to one.

也非常少。

So we don't know how this forms,

我们不清楚它是怎么形成的，

but it may be part of its birth process in its home solar system.

但可能跟它在自己星系中的 形成过程有关。

'Oumuamua was varying in brightness every 7.34 hours,

奥陌陌的亮度 每7.34小时就发生变化，

or so we thought.

至少我们是这么认为的。

As more data started to come in from other teams,

其他团队的数据陆续发来，

they were reporting different numbers.

他们上报的数据有所不同。

Why is it the more we learn about something,

为什么我们对一件事情了解越多，

the harder it gets to interpret?

就越难将它解释清楚呢？

Well, it turns out that 'Oumuamua is not rotating in a simple way.

事实上，奥陌陌并不是简单地在旋转。

It's wobbling like a top.

而是像陀螺一样在摇晃。

So while it is rotating around its short axis,

它在绕自己短轴旋转的同时，

it's also rolling around the long axis

也在绕长轴翻转，

and nodding up and down.

同时上下摇晃。

This very energetic, excited motion

这种有力的、激烈的运动形式，

is almost certainly the result of it being violently tossed

几乎可以肯定，是因为它被猛烈地

out of its home solar system.

抛出了自己的太阳系。

Now how we interpret the shape from its brightness

我们如何通过它的亮度 来解释它的形状，

depends very critically on how it's spinning,

很大程度上取决于它的旋转方式，

so now we have to rethink what it may look like,

因此我们不得不重新猜测它的样子，

and as shown in this beautiful painting by space artist Bill Hartmann,

正如太空画家比尔 · 哈特曼 这幅漂亮的画作所展示的一样，

we think that 'Oumuamua may be more of a flattened oval.

我们认为奥陌陌可能 更像一个扁平的椭圆。

So let's get back to the energetics.

让我们说回它的能量。

What is it made of?

它是由什么构成的？

Well, ideally we would love to have a piece of 'Oumuamua

当然，最理想的方式是 我们能拿到一片奥陌陌的样本，

into the laboratory, so we could study it in detail.

送到实验室仔细研究。

But since even private industry can't manage to launch

但是即便是私人企业也无法在一周内

a spacecraft within a week

发射宇宙飞船，

to something like this,

飞往这样一个目标，

astronomers have to rely on remote observations.

天文学家们不得不依靠遥控观测，

So astronomers will look at how the light interacts with the surface.

他们观察光线如何与表面互动。

Some colors may get absorbed, giving it a chemical fingerprint,

有些颜色的光线可能会被吸收， 给它留下一个化学指纹，

whereas other colors may not.

而其他的颜色则不会。

On the other hand, some substances may just reflect more blue

换句话说，有些物体 会反射更多蓝色的光

or red light efficiently.

或者红色的光。

In the case of 'Oumuamua, it reflected more red light,

而奥陌陌，会反射更多的红光，

making it look very much like the organic rich surface of the comet recently visited

使它看起来很像罗塞塔号 最近造访的那颗彗星

by the Rosetta spacecraft.

富含有机物的表面。

But not everything that looks reddish has the same composition.

但并不是所有看起来 发红的物体都有相同的成分。

In fact, minerals that have tiny little bits of iron in the surface

实际上，表面含有少量铁的矿物质

can also look red,

看起来也是红色的，

as does the dark side of Saturn's moon Iapetus,

就像土星的卫星伊阿珀托斯的暗面，

shown in these images from the Cassini spacecraft.

从卡西尼号航天器 拍下的照片中就可以看出来。

Nickel-iron meteorites, in other words, metal,

镍铁陨石，换句话说，就是金属，

can also look red.

也可能呈红色。

So while we don't know what's on the surface,

既然我们无法得知表面有什么，

we know even less about what's on the inside.

就更无从知晓 它的内部由什么构成了。

However, we do know that it must at least be strong enough

但我们至少确定它足够坚固

to not fly apart as it rotates,

才不会在旋转中解体，

so it probably has a density similar to that of rocky asteroids;

因此它的密度 应该跟石质的小行星类似，

perhaps even denser, like metal.

也许更大，接近金属。

Well, at the very least, I want to show you

至少，我想给大家看一眼

我们的一架地基天文望远镜

one of the beautiful color images that we got

from one of the ground-based telescopes.

拍到的一张漂亮的彩色照片。

All right, I admit, it's not all that spectacular.

好吧，我承认，并没有那么漂亮。

(Laughter)

（笑声）

We just don't have the resolution.

分辨率不够高。

Even Hubble Space Telescope

即便是哈勃太空望远镜

doesn't present a much better view.

也无法拍得更好。

But the importance of the Hubble data was not because of the images,

但是哈勃提供的数据的重要性， 并不在于它拍摄的照片，

but because it extended our observations out

而是它将我们的观察期

to two and a half months from the discovery,

延长到了自发现起的2个半月，

meaning we get more positions along the orbit,

意味着我们能获得它 轨道的更多位置，

which will hopefully let us figure out where 'Oumuamua came from.

也就有希望弄清楚奥陌陌来自哪里。

So what exactly is 'Oumuamua?

那么，奥陌陌到底是什么？

We firmly believe it's likely to be a leftover archaeological remnant

我们坚信，它应该是另一个行星系统

from the process of the birth of another planetary system,

在诞生时留下的遗迹，

some celestial driftwood.

一些天体漂流木。

Some scientists think that maybe 'Oumuamua formed

有些科学家认为， 奥陌陌在形成的时候

very close to a star that was much denser than our own,

离一颗恒星非常近， 这颗恒星比太阳密度要大，

and the star's tidal forces shredded planetary material

在它形成的早期，潮汐力将

early in the solar system's history.

许多行星物质撕裂了。

Still others suggest that maybe this is something that formed

而另一些人认为， 奥陌陌也许诞生于

during the death throes of a star,

某颗恒星生命的晚年，

perhaps during a supernova explosion,

也许是在超新星爆发阶段，

as planetary material got shredded.

行星物质被撕碎。

Whatever it is, we believe it's a natural object,

无论原因是什么， 我们都相信它是自然形成的，

but we can't actually prove that it's not something artificial.

但我们也无法证明它不是人造的。

The color, the strange shape, the tumbling motion

它的颜色，奇怪的形状， 翻滚的动作模式，

could all have other explanations.

都有可能完全是另一种解释。

Now while we don't believe this is alien technology,

既然我们不相信 这是外星人的技术，

why not do the obvious experiment and search for a radio signal?

那为什么不做个简单的实验， 搜索一下无线电信号呢？

That's exactly what the Breakthrough Listen project did,

这就是“突破监听计划”在做的，

but so far, 'Oumuamua has remained completely quiet.

但到目前为止， 奥陌陌依然是静默状态。

Now could we send a spacecraft to 'Oumuamua

那我们能不能发射 一艘宇宙飞船去追赶奥陌陌，

and answer this question once and for all?

一次性搞清楚所有的问题呢？

Yes, we do actually have the technology,

没错，从技术上来说完全可行，

but it would be a long and expensive voyage,

但这将是一场漫长而昂贵的远航，

and we would get there so far from the Sun

我们会离开太阳非常远，

that the final approach trajectory would be very difficult.

计算最后的对接轨道将非常困难。

So I think 'Oumuamua probably has many more things to teach us,

因此我觉得，奥陌陌 还可以教我们很多事情，

and in fact there might be more surprises in store

事实上，随着包括我在内的 科学家们继续研究数据，

as scientists such as myself continue to work with the data.

应该还有更多惊喜在等着我们。

More importantly, I think this visitor from afar

更重要的是，这位远道而来的访客

has really brought home the point that our solar system isn't isolated.

证明了一点，我们的太阳系 并不是孤立的。

We're part of a much larger environment,

我们是一个更大世界的一部分，

and in fact, we may even be surrounded by interstellar visitors

实际上，我们周围 可能有许多星际访客，

and not even know it.

而我们还没有察觉。

This unexpected gift

这件意外的礼物

has perhaps raised more questions than its provided answers,

带来的疑问可能 比它解答的问题还要多，

but we were the first to say hello to a visitor from another solar system.

但我们是第一批对来自 其他星系的客人打招呼的人。

Thank you.

谢谢大家。

(Applause)

（掌声）

Jedidah Isler: Thanks, Karen.

吉迪达 · 伊斯勒：谢谢凯伦。

I of course enjoyed that talk very much. Thank you.

我非常喜欢这次演讲，谢谢你。

As I recall, we found it pretty late in its journey towards us.

我回顾了一下演讲内容，我们 发现它的时候已经非常晚了。

Will future technologies like the Large Synoptic Survey Telescope

未来的科技，比如 大型综合巡天望远镜，

help us detect these things sooner?

是否能帮我们更早一点 发现这样的物体呢？

Karen Meech: Yeah. We're hoping that we'll start to see a lot of these things,

凯伦 · 梅赫：是的，我们希望 能发现很多这样的天体，

理想的是，最好能有一颗 正在向太阳靠近，

and ideally, you'd love to find one as it's approaching the Sun,

because you want to have time to do all the science,

这样就有时间来进行研究，

or even more ideal,

更理想的是，

you'd get a spacecraft ready to go,

有一艘飞船时刻准备着，

parked somewhere in the L4 or L5 position,

停在L4或者L5的位置，

somewhere near Earth,

靠近地球，

so that when something comes by, you can chase it.

这样如果有东西飞过， 就能进行追踪。

JI: Awesome, thanks so much. Let's thank Karen again.

吉迪达 · 伊斯勒：太棒了， 非常感谢。再次感谢凯伦。

(Applause)

（掌声）