Estimates put it at about 100,000 light-years, from one end to the other.

估計從一端到另一端約為十萬光年。

But you know what's way bigger?

但你知道還有什麼東西更大嗎？

Space itself.

外太空本身。

Because in all of that space we estimate that there are as many as 100 billion galaxies.

因為我們估計在整個外太空中，有多達 1,000 億個星系。

And among all those galaxies, we've found a few that are our twins.

在這些星系中，發現了我們的一些雙胞胎。

That's right, the Milky Way has long-lost twins out there among the stars.

沒錯，銀河系在恆星間有失散多年的雙胞胎。

Although not in a literal sense like our galaxies formed in the same place at the same time.

雖然不像字面意思，我們的星系同時在同一個地方形成。

But finding these twin galaxies can help us learn about our own, because it's pretty

但發現這些雙胞胎星系，可以幫助我們了解自己的星系，因為

hard to figure out what's going on in the Milky Way while we're a part of it.

很難搞懂銀河系中發生了什麼，而且我們還身在其中。

The Milky Way's disk is 1,000 light years thick, and to get a good picture of it, you'd

銀河系的光盤厚度為 1,000 光年，想要拍到好照片，

have to get pretty far above it, like how the Earth is round but you wouldn't see

必須比它高出許多，就像地球很圓，但你看不到曲線，

the curve unless you were way above it, even higher than commercial airliners go.

除非你超越它的高度 ，甚至高於民航機的高度。

And cue the flat Earthers in the comments.

在留言說說地平說學會。

Considering that the Voyager I, the most distant man-made object we've ever made, is about 0.002 light-years

考慮到航海家 1 號是距離地球最遠的人造飛行器，大約是 0.002 光年

away, we're not taking a galactic selfie any time soon.

我們短期內無法進行銀河自拍。

To borrow a metaphor I wish I'd thought of, mapping the Milky Way is like trying to

我借用一個我能想到的暗喻，繪製出銀河系的圖，就像

map a forest while you're tied to one of the trees.

繪製出一座森林，而你被綁在其中一棵樹。

So we've had to piece together what our galaxy looks like based on what we can see.

所以我們要根據我們看到的東西，來拚奏出銀河系的樣貌。

First and most obvious is the Milky Way is flat because we can see it edge-on in our night sky.

首先也是最明顯的是，銀河系是平的，因為我們可以看到它在夜空中嶄露頭角。

The shape of that flat plane has been a bit harder to pin down.

平面的形狀程度有點難確定。

The astronomer Herschel was the first to try it in 1785, and by counting the number of

天文學家赫雪爾是在 1785 年第一位嘗試的人，透過計算他看到的恆星數量，

stars he saw and assuming that more stars meant more galaxy, he came up with a pretty blobby shape.

並假設更多的恆星就代表更多的星系，於是他想出一個漂亮的斑點形狀。

This picture changed in the 1910s when another astronomer, Harlow Shapley, measured the distance

這張圖片在 1910 年代發生變化，當時另一位天文學家哈羅．沙普利測量出

to globular clusters of stars and found that they were in a spherical shape about 100,000 light years in diameter.

恆星的球狀星團距離，並發現它們的球形直徑約 10 萬光年。

Shapley concluded that our galaxy must be a circular disk inside this spherical halo of globular clusters.

沙普利得出結論，星系必定在球狀星團中的球形光暈內。

In the last 75 years, techniques that could see through interstellar dust like radio,

在過去 75 年裡，透過無線電、紅外線和 X 射線天文學等技術，

infra-red, and X-ray astronomy have helped us see just where the arms of our spiral galaxy are.

看見星際塵埃，也幫助我們看到螺旋星系的臂部。

But there's only so much we can do from here.

但我們能從這裡做到就這麼多。

Exactly what the Milky Way looks like on the other side of its central bulge is unknowable to us.

正如銀河系在其中央核球另一端看到的樣子，對我們來說都是未知的。

And our image of what we can see is still changing; we only started to realize the central

我們所看到的影像仍在變化；我們才開始意識到

bar connecting the large spiral arms was thicker and more substantial than we thought in 1996.

連接大型螺旋臂的棒狀結構，比我們在 1996 年想像的更厚、更大。

So now that we have a pretty good idea what we look like, we can seek out similar galaxies that can fill in the gaps.

我們現在已經非常了解自己的樣子，可以來尋找填補空缺的類似星系。

NGC 1073, for example, is a barred spiral in the constellation Cetus.

例如，NGC 1073 是位於鯨魚座的棒旋星系。

Another twin, GAMA202627 has two smaller companion galaxies, much like our own Magellanic clouds.

另一個雙胞胎，GAMA202627 有兩個較小的伴星系，就像我們的麥哲倫雲一樣。

Companions as big as these clouds are a rare find and warrant further study.

像這些雲一樣大的伴星系是罕見的發現，並值得進一步研究。

We've even found a galaxy that could tell us about the Milky Way's ominous future.

我們甚至發現一個星系，可以告訴我們銀河系未來的不祥之兆。

Near Andromeda is a small and incredibly dense galaxy called M32.

仙女座附近有一個小型而非常密集的星系，叫做 M32。

A recent paper proposes that once upon a time it looked like the Milky Way, until Andromeda

近期一篇論文提出，它在很久以前看起來像銀河系，直到仙女座

came barreling through, stealing stars and planets, ballooning in size, and leaving M32 a shadow of its former self.

快速穿過並偷走恆星和行星，讓自己的規模膨脹，讓 M32 成為自己昔日的影子。

Why is this important you ask?

你問為什麼這很重要？

Because Andromeda is on a collision course with our galaxy.

因為仙女座必定和我們的銀河系發生碰撞。

What happened to M32 could be what happens to us.

發生在 M32 的事可能也會發生在我們身上。

Odds are good that as our telescopes and techniques improve, we'll find more of our twins out there that can tell us more about ourselves.

可能性很大，隨著我們的望遠鏡和技術的進步，我們會發現更多雙胞胎，告訴我們更多關於自己的資訊。

Just don't get too attached to the galaxy's shape, because in about 4.5 billion years, it could all change.

只是不要太依賴銀河系的形狀，因為大約在 45 億年後，它可能會完全改變。

Fun Fact: Confirming the Milky Way had a large bar also meant our galaxy had two large arms

有趣的事實：確認銀河系有個大棒狀星系，就代表我們的星系有兩個大臂

that wrapped around it twice, rather than four separate main arms as previously thought.

纏繞它兩次，而不是像先前認為有四個分開的主臂。

If you liked this video, go check out this one Maren did on the universe's first type of molecule.

如果你歡這部影片，去看看 Maren 這部影片，討論宇宙第一類分子。

Thanks for watching, don't forget to subscribe and I'll see you next time on Seeker!

謝謝觀看，別忘了訂閱，我們下次在 Seeker 見！