宇宙中的最後一顆恆星——紅矮星解析：英語精讀講義

One day the last star will die

有一天，最後一顆恆星將會死去，

and the universe will turn dark forever. 文法

宇宙將永遠陷入黑暗。

It will probably be a red dwarf,

它可能是一顆紅矮星，

a tiny kind of star

一種微小的恆星，

that's also one of our best bets to find alien life 慣用語

這也是我們尋找外星生命的絕佳目標之一，

and might be the last home of humanity

並可能是人類最後的家園，

before the universe becomes uninhabitable.

直到宇宙變得不再適宜居住。

So what do we know about them

那麼我們對它們了解多少？

and why are they our last hope?

為什麼它們是我們最後的希望？

At least 70% of stars in the universe are red dwarfs.

宇宙中至少有70%的恆星是紅矮星。

They are the tiniest stars out there

它們是已知最小的恆星，

with only about 7 to 50% of the mass of our sun,

質量只有我們太陽的7%到50%，

not that much bigger than our planet Jupiter,

並不比我們的木星大多少，

which is still huge though.

儘管那仍然十分巨大。

They are also very dim.

它們也非常暗淡。

It's impossible to see them with the naked eye. 片語搭配

肉眼根本無法看到它們。

You've never seen one in the night sky.

你在夜空中從未見過它們。

Even with all our technology, 文法

即使擁有最先進的技術，

we can only clearly observe red dwarfs in our neighborhood. 慣用語

我們也只能清晰地觀察到我們附近的紅矮星。

Approximately 20 of the 30 stars close to Earth are red dwarfs.

在距離地球最近的30顆恆星中，大約有20顆是紅矮星。

Like all stars, red dwarfs fuse hydrogen into helium.

和所有恆星一樣，紅矮星將氫聚變成氦。

But while more massive stars accumulate all the fused helium in their cores,

但是，質量較大的恆星會將聚變產生的氦全部積聚在核心，

red dwarfs stay convective,

紅矮星則保持對流，

meaning that the helium and hydrogen constantly mix.

這意味著氦和氫會不斷混合。

So they use up their fuel incredibly slowly 片語動詞

因此，它們消耗燃料的速度慢得驚人，

before they're extinguished.

直至最終熄滅。

Red dwarfs burn so slowly that their average lifespan 文法

紅矮星燃燒得如此緩慢，以至於它們的平均壽命

is between 1 and 10 trillion years.

在1萬億到10萬億年之間。

By comparison, the sun will survive for another 5 billion years. 表達脈絡

相比之下，太陽只能再存活大約50億年。

Because the universe is only 13.75 billion years old,

因為宇宙只有137.5億年的歷史，

not a single red dwarf has reached later development stages. 文法

所以沒有一顆紅矮星達到了演化的後期階段。

Every single one of the trillions that exist is still a baby. 慣用語

現存的數萬億顆紅矮星每一顆都還是個嬰兒。

Speaking of babies, 表達脈絡

說到嬰兒，

the smallest star in the entire universe is also a red dwarf

全宇宙最小的恆星也是一顆紅矮星，

because small red dwarfs are right on the verge of being a star at all. 片語搭配

因為質量極小的紅矮星正好處於成為恆星的邊緣。

Just a tiny bit less hydrogen 文法

只要氫再少那麼一點點，

and they are mere brown dwarfs, 用詞

它們就只會變成棕矮星，

failed stars that cannot sustain a fusion reaction for long. 用詞

即無法長久維持聚變反應的失敗恆星。

So what about aliens or a new home for humanity?

那麼關於外星人或人類的新家園呢？

Since our sun will die one day,

既然我們的太陽終有一天會死去，

we'll eventually need to look for a new home.

我們最終將需要尋找一個新家園。

And where there are habitable planets, 文法

而在有宜居行星的地方，

there might also be aliens.

也可能存在外星人。

The Kepler space observatory found 文化背景

克卜勒太空望遠鏡發現，

that at least half of all red dwarfs host rock planets 用詞

至少一半的紅矮星擁有岩石行星，

between half and four times the mass of our Earth.

質量在我們地球的一半到四倍之間。

Many of them are in the habitable zone, 用詞

其中許多位於適居帶內，

the area around a star where water can be liquid.

即恆星周圍能讓液態水存在的區域。

But since red dwarfs burn at relatively cold temperatures,

但由於紅矮星燃燒的溫度相對較低，

a planet would need to be really close to be hospitable,

行星必須靠得非常近才能適宜居住，

probably as close as Mercury to our sun or even closer. 文法

也許要像水星離太陽那樣近，甚至更近。

Which brings with it all kinds of problems. 表達脈絡

這就帶來了各種問題。

For example, a planet this close to a star

例如，離恆星這麼近的行星

would probably be tidally locked, 用詞

很可能會被潮汐鎖定，

meaning the same side would always face it.

這意味著它總是以同一面朝向恆星。

This side would be incredibly hot,

這一面會酷熱無比，

while the shadow side would be frozen, 文法

而陰影面則會被冰凍，

which makes it hard for life to develop. 文法

這使得生命很難在此孕育。

Although a planet with a big enough ocean

雖然，一顆擁有足夠大海洋的行星

might be able to distribute the star's energy

也許能夠將恆星的能量分散開來，

and create some kind of stability.

從而創造出某種穩定性。

Or the gravitational forces of the red dwarf

又或者，紅矮星的引力

could squeeze the planet

可能會擠壓行星，

and heat it up so much 文法

使其溫度升得如此之高，

that it might lose all its water over time.

以至於它可能隨著時間的推移失去所有的水。

These planets could end up like Venus, 片語動詞

這些行星最終可能會變得像金星一樣，

a hot, burning hell.

成為一個酷熱燃燒的地獄。

Another problem is that many red dwarfs

另一個問題是，許多紅矮星

vary in their energy output. 片語搭配

它們的能量輸出是不穩定的。

They can be covered in star spots

它們表面可能會佈滿星斑，

that can dim their emitted light

這些星斑會讓它們發出的光變暗

by up to 40% for months, 文法

長達數月之久，最高可減弱40%，

which would cause oceans on planets to freeze over. 片語動詞

這會導致行星上的海洋結冰。

At other times, they can emit powerful solar flares, 講解

在另一些時候，它們能釋放強大的閃焰，

sudden outbursts of energy,

即能量的突然爆發，

incredibly powerful.

威力驚人。

These red dwarfs can double their brightness in minutes,

這些紅矮星能在幾分鐘內亮度翻倍，

which could strip away sizable portions of a planet's atmosphere 片語動詞

這可能會剝離行星相當大一部分的大氣層，

and burn it,

並將其灼燒，

rendering it sterile. 文法

使其變得寸草不生。

On the other hand, 表達脈絡

另一方面，

their extremely long lifespan is a big plus. 用詞

它們極長的壽命是一個巨大的加分項。

A red dwarf with just moderate levels of activity

一顆活躍度適中的紅矮星

could be an amazing place for a planet that hosts life.

可能成為孕育生命的行星的絕佳場所。

Life on Earth has existed for about 4 billion years 文法

地球上的生命已存在了大約40億年，

and we have about a billion years left 片語搭配

我們大約還剩下10億年的時間，

before the sun becomes so hot

之後太陽將變得異常灼熱，

that complex life on Earth will become impossible.

以至於地球上無法再存在複雜的生命。

We will either die 文法

我們要麼滅絕，

out or leave Earth and look for a new home.

要麼離開地球去尋找一個新家園。

We could build a civilization

我們也許能建立一個文明，

for potentially trillions of years

延續可能長達數萬億年，

around a red dwarf with the right conditions.

圍繞著一顆條件適宜的紅矮星。

About 5% of the red dwarfs in the Milky Way

銀河系中大約5%的紅矮星

may host habitable,

可能擁有宜居的、

roughly Earth-sized planets.

差不多地球大小的行星。

That would be more than 4 billion in total.

總數將超過40億顆。

But life may not even need a planet like Earth. 文法

但生命甚至可能不需要像地球一樣的行星。

Candidates for life around a red dwarf

紅矮星周圍可能孕育生命的候選地，

may be the moons of gas giants

可能是氣態巨行星的衛星，

or so-called super-Earths, 用詞

或者是所謂的「超級地球」，

really massive rocky planets.

即質量極大的岩石行星。

All in all, there are an estimated 60 billion 表達脈絡

總而言之，據估計約有600億顆

potentially habitable planets around red dwarfs

潛在宜居的行星圍繞著紅矮星，

and that's in the Milky Way alone.

而且這僅僅是在銀河系內。

So red dwarfs might become really important

因此，紅矮星可能會變得非常重要，

for our survival in the future.

對於我們未來的生存而言。

But everything has to die at some point,

但萬物終有一死，

even red dwarfs.

哪怕是紅矮星。

When in trillions of years

當幾萬億年後，

the life of the last red dwarf in the universe

宇宙中最後一顆紅矮星的生命

is about to end, 文法

即將走向終點時，

it will not be a very spectacular event.

這不會是一個非常壯觀的事件。

As its hydrogen runs out, it shrinks, 片語動詞

隨著它的氫耗盡，它會收縮，

becoming a blue dwarf,

變成一顆藍矮星，

burning out completely. 片語動詞

直至徹底燃盡。

After its fuel is spent,

燃料耗盡後，

it's transformed into a white dwarf, 片語搭配

它轉變為一顆白矮星，

an object about as small as Earth,

這是一個大小跟地球差不多、

packed very densely and made of degenerate gases, 文法

極其緻密、由簡併氣體構成的天體，

mostly of helium-4 nuclei.

主要成分是氦-4原子核。

Having no more source of energy, 文法

既然沒有了能量來源，

it will cool extremely slowly over trillions of years

它將在數萬億年的時間裡極其緩慢地冷卻，

until it becomes its final form,

直到變成它的最終形態——

a cold black dwarf.

一顆冰冷的黑矮星。

White and black dwarfs are so fascinating

白矮星和黑矮星如此令人著迷，

that they deserve their own video.

值得專門做一期影片來講述。

Anyway, it's going to be a long time 文法

無論如何，還要過很久很久，

before the last stars in the universe vanish.

宇宙中最後的恆星才會消失。

It's kind of uplifting to know 語氣意圖

知道這點算是讓人有些欣慰：

that if humanity succeeds in venturing into space, 片語搭配

如果人類成功探索太空，

we have plenty of time

我們還有充足的時間，

before the universe turns out the lights. 慣用語

在宇宙熄滅所有燈光之前。

Our videos are made thanks to your support

我們的影片得益於你們在

on patreon.com.

patreon.com上的支持。

If you want to help us make more of them,

如果你想幫助我們製作更多影片，

we really appreciate your support.

我們非常感謝你的支持。