That's dozens of chances to discover the first alien life.

這樣有非常多的機會初次發現外星生命。

Or, you know, plenty of places we could park our first interstellar colonies.

或者，你知道，會有許多地方可能可以成為我們的星際殖民地。

But with so many options, how do we know which is best?

但既然有這麼多選項，我們該如何知道哪個是最佳選擇呢？

You might think that most Earth-like planets should be at the top of our list.

你或許會覺得大部分類似地球的星球，都會列在我們移民清單的首選吧？

After all, we've got everything we need.

畢竟，這些星球都有我們所需的一切。

Water, land, an atmosphere, and trillions of life forms lapping it all up.

水、土地、大氣、數萬億的生命構成了全部。

But according to a small group of researchers, there are bigger and better planets out there.

但根據小部分的研究學者表示，宇宙裡有比地球更大、更好的星球。

They're called super-Earths.

它們被稱為「超級地球」。

Super-Earths may be some of the most common planets in our galaxy.

超級地球是我們銀河系中最常出現的星球。

Since 2009, Kepler Space Telescope has discovered about 4000 exoplanets.

自從 2009 年起，克卜勒太空望遠鏡已經發現了約 4000 顆系外行星。

30 percent of them are super-Earths, and a few percent of those super-Earths orbit within their host star's habitable zone.

其中有 30％ 是超級地球，而這些超級地球的百分之幾在其所在恆星的宜居區域內運行。

That's the Goldilocks Zone, where the planet's surface is just the right temperature for liquid water.

這是稱為 Goldilocks Zone (宜居帶)，在這裡星球表面溫度仍可讓水保持液態。

Not too cold, not too hot.

不會太冷也不會太熱。

Now, there's a chance some of these super-Earths aren't rocky worlds like Earth.

有些超級地球或許不像地球一樣為岩石地表。

The larger ones could be made out of mostly hydrogen and helium gas, like Jupiter and Saturn, which would not be very hospitable for life.

比較大的可能是大部分是由氫氣和氦氣組成，如木星和土星，而這些對生命不不太友善。

But the reality is, astronomers are still gathering details as more data comes in.

但事實上，天文學家仍在收集更多數據。

So, in the meantime, let's explore what life on a rocky, habitable super-Earth might be like.

因此與此同時，讓我們來探索在有岩層表面又宜居的超級地球上的生活會是如何吧！

Liquid water is just the start.

液態水只是個開始。

These planets can be almost double Earth's radius, and up to ten-times more massive.

這些星球的半徑幾乎可以是地球半徑的兩倍，並且質量可以高達其十倍。

And all that extra mass is what researchers think could really make super-Earths the perfect home.

研究人員認為，所有這些額外的質量可以使超級地球成為理想的居住地。

That's because more massive planets have a stronger gravitational pull.

那是因為更大的星球具有更強的引力。

Super-Earth Kepler 20b, for example is nearly double the size of Earth, and it's ten-times more massive.

例如超級地球柯卜勒 20b，它將近是地球的兩倍大、10 倍重。

This makes its surface gravity almost three-times stronger.

這讓表面重力強了三倍。

That stronger gravity means that the planet can hold on to more air molecules and form a thicker atmosphere, which is great for protecting against harmful space radiation.

較強的引力意味著星球可以保留更多的空氣分子並形成較厚的大氣層，這對於防止有害的空間輻射非常有用。

It also means mountains and hills would erode a lot faster, leaving a relatively flatter surface, compared to Earth.

這也意味著與地球相比，山丘會更快地被侵蝕並留下相對平坦的地表。

Now that might sound boring, but scientists think this could actually spawn dozens of shallow islands all across the planet.

聽起來可能很無聊，但科學家們認為這個現象可能在地球上產生了數十個淺島嶼。

Those in turn, could be the perfect place for life to form and evolve.

而反過來說，這些地方可是生命產生和進化的最佳地點。

Just as biodiversity in Earth's oceans is richest in shallow waters near coastlines, such an "archipelago world" might be enormously advantageous to life.

就像在地球上，海洋接近岸邊的淺灘是生物多樣性最高的地方，這樣「群島世界」或許會對生命有極大的好處。

There's just one problem, leaving this tropical paradise would be extremely difficult.

還有另一個問題，就是要離開熱帶會極度困難。

The escape velocity on Kepler 20b is more than double compared to Earth's, which means either rockets would need more fuel to reach their destinations...

在柯卜勒 20b 上的離開速度需要是地球上的兩倍，意味著需要有更多的燃油來到達目的地…

Like for example, a mission similar to the Apollo Moon Landing would require twice the amount of fuel.

舉例來說，類似於阿波羅登月計劃的任務將需要兩倍的燃料量。

Or, rockets would have to carry only a fraction of the payload.

或者，火箭需要只能搭載一小部分的載貨量。

For instance, SpaceX's Falcon Heavy can launch 50,000 kilograms of payload into Earth's orbit.

例如，SpaceX 的 Falcon Heavy 可以像地球軌道發射 5 萬公斤的載貨量。

Whereas it could only launch 40 kilograms into orbit around a super-Earth like Kepler 20b.

而在柯卜勒 20b 這種超級地球只能發射 40 公斤的載貨重量。

That's about the weight of a German Shepherd.

這大概是一隻德國牧羊犬的重量而已。

Suffice it to say, leaving a super-Earth would be a far greater challenge.

這也足以說明，要離開超級地球會是個多大的挑戰。

But if it looked like this, would you really want to say goodbye?

但如果它看起來像這樣，你真的會想離開這裡嗎？

We'll never know for sure until we visit one.

直到我們能造訪這個地方，我們永遠無法得知。

What questions do you have about space?

對於宇宙你還有什麼問題嗎？

Leave your queries and the comments below.

將你的問題留在下方留言處。

And thanks for watching.

謝謝收看。