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

美國太空總署一直小心觀察著 潛在小行星碰撞的危險，

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

所以泛星計畫的望遠鏡 每晚都在掃描天空。

and usually discovered to be no big deal.

每天早上，泛星計畫的工作人員 會檢查候選的對象，

But on October 19, 2017,

通常沒發現什麼大不了的狀況。

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

但是在 2017 年 10 月 19 日，

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

泛星計畫發現一顆 在恆星之間快速移動的物體，

showed something completely different.

而這次例行的後續追蹤 所測量出的位置和速度，

By October 22nd, we had enough data

顯示出完全不同的東西。

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

到 10 月 22 日，我們有足夠的數據

Holy cow.

瞭解到這物體並非來自我們太陽系。

That's when I got the phone call,

天啊。

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

我接到電話，

Let me tell you how exciting this was.

是所有太陽系的天文學家 都在等待的電話。

(Laughter)

讓我告訴你這多麼令人興奮。

NASA's been expecting to see an interstellar comet

（笑聲）

pass through the solar system since the 1970s,

美國太空總署一直期待看到 穿過太陽系的星際彗星，

but until now, we'd never seen anything.

但自 20 世紀 70 年代 以來直到現在，

Our own solar system is huge,

我們未曾見過任何東西。

so even getting a package from the nearest star system

我們自己的太陽系很巨大，

4.4 light years away

即使從距離 4.4 光年的 最近星系接收包裹

would take over 50,000 years.

也需要 5 萬年。

So this is a really big deal.

所以這事至關重要。

The interstellar visitor entered our solar system

星際訪客從黃道面的上方

from above the plane of the planets,

進入我們的太陽系，

coming from the direction of the constellation Lyra,

來自天琴座（Lyra）的方向，

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

於 9 月 9 日經過近日點，

passing inside the orbit of Mercury.

經水星軌道內側穿越。

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

這距離不算特別接近， 也不算非比尋常，

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

只是近距離觀察物體要容易得多。

On October 14th,

在我們發現它之前，

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

它在 10 月 14 日最接近地球，

within about 15 million miles.

距離約在 1500 萬英里內。

This is really close by astronomical standards.

以天文的標準而言，是非常近的。

Now rather than call this by its unwieldy catalog name,

我們不用難懂的目錄名稱來稱呼它，

we briefly called it "Rama,"

我們簡稱它為「拉瑪」，

after the cylindrical spacecraft that passed through the solar system

那是亞瑟·查理斯·克拉克 1973 年的經典科幻小說裡

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

穿過太陽系的圓柱形太空船的名字。

But this wasn't quite right either,

但這也不那麼合適，

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

所以為了紀念夏威夷的望遠鏡發現它，

we consulted two experts on Hawaiian culture --

我們諮詢了兩位夏威夷文化專家，

a Hawaiian navigator and a linguist --

他們是夏威夷航海家和語言學家，

to propose a name.

提出一個名字。

And they suggested "'Oumuamua,"

他們建議「斥侯星」，

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

意思是來自遙遠的過去， 向我們伸手的偵察員或使者。

Now this discovery was important for many reasons,

這個發現很重要的原因相當多，

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

但對我而言，最重要的是

about the past of our solar system.

斥侯星可以告訴我們太陽系的過去。

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

新太陽系的誕生和行星生成的過程

can be a violent and messy business.

可能很猛烈、很混亂。

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

當巨大的行星穿過 形成它們的塵埃盤時，

as the giant planets migrate through the dusty disk

殘餘的冰冷岩石碎片

out of which they're formed.

便被逐出這個新生的太陽系。

Now have you ever felt an emotional chill,

你有沒有感受到一種情緒的寒意？

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

一種令人興奮的東西 讓你的脊椎上下顫抖？

Or something that's very emotionally moving?

或是某種情緒激動？

Well this was it for me.

對我來說就是這樣。

This was my wow moment.

這是我的驚嘆時刻。

We actually had a piece of material from another solar system

我們實際上有一塊 來自另一個太陽系的物質

coming close enough for us to observe.

近到讓我們能夠觀察它。

So what would you like to know about 'Oumuamua,

你想了解斥侯星

the very first visitor from another star system?

這另一星系的首位訪客那些事呢？

Well, I could think of a million things,

我可以想到一百萬件事，

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

但是想要的和得到的是兩碼事，

and 'Oumuamua was moving away and fading very rapidly.

而斥侯星正迅速、逐漸地消失。

In the span of about a week,

在大約一周的時間內，

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

它的亮度下降到十分之一。

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

一個星期就是我們能便於 研究它的全部時間。

to study it easily.

因此我們必須快馬加鞭 取得使用望遠鏡的時間，

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

這個由同行評審的提案流程 通常競爭激烈，

normally a very competitive, peer-reviewed proposal process

審核期可能長達數個月，

that can take up to months --

被縮減到短短幾天。

down to less than a few days.

一場「禮貌」的資源競爭開始了。

So began a "polite" competition for resources.

好吧，我不再矯言了。 這是一場激烈的戰鬥。

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

我們擱下所有的工作，

We dropped everything,

不分晝夜地

working around the clock,

試圖趕製出完美的提案，

trying to craft perfectly crafted proposal words

送交給天文台的主管們。

to send to the observatory directors.

好消息。我們獲得了使用的時間。

Well, good news. We got the time.

從一個完全自私的角度來看，

Now, from a perfectly selfish point of view,

首先我們想知道斥侯星有多大。

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

因為它畢竟曾非常接近地球，

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

這是事後我們才知道的。

and we didn't know about it until afterwards.

如果它擊中地球會多糟糕？

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

衝擊的能量取決於 速度的平方乘以質量，

Well, the impact energy

質量取決於它的大小和組成。

depends on the square of the velocity times its mass,

那麼斥侯星有多大，是什麼形狀？

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

我們可從它的亮度得知。

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

如果你不相信我，

Well, we can get this from its brightness.

可以比較後院的螢火蟲亮度

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

與遙遠飛機上的導航燈亮度。

of a firefly in your backyard

你知道飛機比較亮，

to the navigation lights on a distant airplane.

它的亮度顯得微弱只因為距離遠。

You know the airplane is much brighter --

我們還需要知道

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

斥侯星表面的反射程度。

We're also going to need to know

我們沒有任何線索，

how reflective the surface of 'Oumuamua is,

但我們認為它與太陽系中的

and we don't have any clue,

小行星和彗星非常相似，

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

或以技術用詞來說，

and comets in our solar system,

它的反射率類似介於木炭和濕沙之間。

or in technical terms,

如今，大多數大型望遠鏡 採用所謂的服務模式，

something between the reflectivity of charcoal and wet sand.

意思是我們必須仔細闡述所有的指令，

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

並將它們發送給望遠鏡操作員，

meaning we have to carefully develop all the instructions

然後焦急地等待收回數據，

and send them to the telescope operator,

向天氣之神祈禱。

and then anxiously wait for the data to come back,

我敢打賭，你們大多數人的職涯

praying to the weather gods.

不取決於昨晚是不是陰天。

Now I bet most of you don't have careers

我們不會有任何第二次機會。

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

天氣很好，而斥侯星則否。

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

它的亮度不恆定。

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

我們看到斥侯星在星星間急駛。

Its brightness wasn't constant.

中間就是它。

Now here we see 'Oumuamua racing between the stars.

星星拖出尾巴， 因為望遠鏡追著斥侯星移動。

It's centered in the middle.

它的亮度轉弱，再次變亮， 變暗，變亮，又變暗。

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

由於陽光從長方形物體的四面反射。

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

極端的亮度變化使我們對其形狀

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

產生了令人難以置信的結論。

The extreme brightness change

正如這位藝術家的圖象所示，

led us to an unbelievable conclusion about its shape.

斥侯星顯然非常長而窄，

As shown in this artist's impression,

軸比約為 10 比 1。

'Oumuamua is apparently very long and narrow,

假設它很暗， 意思是它大約半英里長。

with an axis ratio of about 10 to one.

我們的太陽系中沒有像這樣的物體。

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

我們只有少數幾個

Nothing else in our solar system looks like this.

軸比大過 5 比 1 的物體。

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

因此我們不知道這是如何形成的，

bigger than five to one.

但可能是其太陽系 誕生過程中的一部分。

So we don't know how this forms,

斥侯星的亮度每 7.34 小時變化一次，

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

或者這是我們認為的數字。

'Oumuamua was varying in brightness every 7.34 hours,

隨著其他團隊的數據開始加了進來，

or so we thought.

他們報告的數字不同。

As more data started to come in from other teams,

為什麼我們越了解某事，

they were reporting different numbers.

就越難以解釋？

Why is it the more we learn about something,

原來斥侯星不以簡單的方式旋轉。

the harder it gets to interpret?

它像陀螺一樣搖擺不定。

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

因此，它圍繞短軸旋轉，

It's wobbling like a top.

也圍繞長軸滾動，

So while it is rotating around its short axis,

並且上下搖擺。

it's also rolling around the long axis

這種充滿活力、活躍的運行方式，

and nodding up and down.

幾乎可以肯定它是從自己的太陽系

This very energetic, excited motion

被猛烈拋出的結果。

is almost certainly the result of it being violently tossed

我們如何從亮度解釋形狀

out of its home solar system.

關鍵取決於它是如何旋轉的，

Now how we interpret the shape from its brightness

所以我們必須重新思考它的外觀。

depends very critically on how it's spinning,

正如空間藝術家比爾 · 哈特曼 這幅美麗的畫作所示，

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

我們認為斥侯星 更可能是個扁平的橢圓形。

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

讓我們回到能量學。

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

它的組成是什麼？

So let's get back to the energetics.

理想情況下，我們希望 帶塊斥侯星的碎片到實驗室，

What is it made of?

讓我們可以詳細研究它。

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

但是，由於在這情形下，

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

即使是私營企業

But since even private industry can't manage to launch

也無法在一周內成功發射太空船，

a spacecraft within a week

天文學家不得不仰賴遠程觀測。

to something like this,

因此，天文學家研究 光線如何與表面相互作用。

astronomers have to rely on remote observations.

有些顏色可能被吸收， 留下化學指紋，

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

而其他顏色可能沒被吸收、沒指紋。

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

另一方面，某些物質可能只是

whereas other colors may not.

更有效地反射藍光或紅光。

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

斥侯星的情況是它反射更多的紅光，

or red light efficiently.

使它看起來非常像

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

羅塞塔號太空船最近訪問的彗星

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

所遇到的富含有機物的表面。

by the Rosetta spacecraft.

但並非所有看起來偏紅的 東西，成分都相同。

But not everything that looks reddish has the same composition.

事實上，表面上含有少量鐵的礦物質

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

也可能看起來紅紅的，

can also look red,

土星的月亮「土衛八」的 黑暗面正是如此，

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

這些圖像來自卡西尼號太空船。

shown in these images from the Cassini spacecraft.

鎳鐵隕石，換句話說，金屬，

Nickel-iron meteorites, in other words, metal,

看起來也紅紅的。

can also look red.

因此，我們不知道表面是什麼，

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

對內部所知更少。

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

然而，我們確實知道 它必須至少要夠堅固，

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

在旋轉時才不會分開，

to not fly apart as it rotates,

所以它的密度可能 與岩石小行星的密度相似，

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

也許更密些，像金屬那樣。

perhaps even denser, like metal.

我至少想展示美麗的彩色圖像之一，

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

是我們的地面望遠鏡獲得的。

one of the beautiful color images that we got

好吧，我承認，它不是那麼壯觀。

from one of the ground-based telescopes.

（笑聲）

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

只是解析度不夠。

(Laughter)

甚至哈伯太空望遠鏡 也沒有更好的視野。

We just don't have the resolution.

但哈伯數據的重要性不在於圖像，

Even Hubble Space Telescope

而是它將我們的觀察結果

doesn't present a much better view.

延伸到發現它之後的兩個半月，

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

意思是我們獲得軌道上更多的位置，

but because it extended our observations out

有望讓我們弄明白斥侯星來自哪裡。

to two and a half months from the discovery,

那麼斥侯星究竟是什麼？

meaning we get more positions along the orbit,

我們堅信，它可能是

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

另一個行星系統誕生過程中 剩餘的考古遺跡，

So what exactly is 'Oumuamua?

是天體的漂流木。

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

一些科學家認為，也許斥侯星形成時

from the process of the birth of another planetary system,

很靠近一顆比我們太陽 密度更大的恆星，

some celestial driftwood.

而那恆星的潮汐力

Some scientists think that maybe 'Oumuamua formed

在它自己太陽系的歷史早期 就弄碎了行星物質。

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

還有一些人認為

and the star's tidal forces shredded planetary material

它可能是一顆恆星 在痛苦的死亡過程中形成的，

early in the solar system's history.

可能是在超新星爆炸的期間，

Still others suggest that maybe this is something that formed

行星的物質被粉碎了。

during the death throes of a star,

不管是什麼，我們相信 這是一個自然物體，

perhaps during a supernova explosion,

但實際上我們無法證明 這不是人為的東西。

as planetary material got shredded.

顏色、奇怪的形狀、翻滾動作

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

可能有其他的解釋。

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

既然我們不相信這是外星人的技術，

The color, the strange shape, the tumbling motion

為什麼不做明顯的實驗， 蒐索無線電信號呢？

could all have other explanations.

這正是「突破聆聽」計劃所做的，

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

但到目前為止，斥侯星仍然完全安靜。

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

我們現在可以將宇宙飛船送到斥侯星

That's exactly what the Breakthrough Listen project did,

並一勞永逸地回答這個問題嗎？

but so far, 'Oumuamua has remained completely quiet.

是的，我們的確擁有這項技術，

Now could we send a spacecraft to 'Oumuamua

但那將會是個既貴又長的旅程，

and answer this question once and for all?

到達時，會離太陽那麼的遠，

Yes, we do actually have the technology,

最終的接近軌跡將會極端困難。

but it would be a long and expensive voyage,

所以我認為斥侯星可能 還有很多東西要教我們。

and we would get there so far from the Sun

事實上，隨著像我這樣的科學家 繼續使用這些數據，

that the final approach trajectory would be very difficult.

可能會有更多的驚喜。

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

更重要的是，我認為這位遠到的訪客

and in fact there might be more surprises in store

確實帶回一個觀點：

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

那就是我們的太陽系並不孤立，

More importantly, I think this visitor from afar

我們是更寬廣宇宙的一部分，

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

事實上，我們甚至可能 被星際訪客包圍著，

We're part of a much larger environment,

只是自己不知道。

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

這個意想不到的禮物

and not even know it.

所衍生的提問 可能比帶來的答案還更多，

This unexpected gift

但我們首次

has perhaps raised more questions than its provided answers,

向另一個太陽系的訪客打招呼。

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

謝謝。

Thank you.

（掌聲）

(Applause)

吉迪達 · 伊斯勒：謝謝，凱倫。 我當然非常喜歡這個話題。謝謝。

Jedidah Isler: Thanks, Karen.

我記得你說到，我們在 它行經我們的旅程後期才發現它。

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

未來的大型天氣測量望遠鏡技術等等