B1 中級 美國腔 1995 分類 收藏
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Astronomers have found dozens of potentially habitable planets outside of our solar system.
That's dozens of chances to discover the first alien life.
Or, you know, plenty of places we could park our first interstellar colonies.
But with so many options, how do we know which is best?
You might think that most Earth-like planets should be at the top of our list.
After all, we've got everything we need.
Water, land, an atmosphere, and trillions of life forms lapping it all up.
But according to a small group of researchers, there are bigger and better planets out there.
They're called super-Earths.
Super-Earths may be some of the most common planets in our galaxy.
Since 2009, Kepler Space Telescope has discovered about 4000 exoplanets.
30 percent of them are super-Earths, and a few percent of those super-Earths orbit within their host star's habitable zone.
That's the Goldilocks Zone, where the planet's surface is just the right temperature for liquid water.
Not too cold, not too hot.
Now, there's a chance some of these super-Earths aren't rocky worlds like Earth.
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.
But the reality is, astronomers are still gathering details as more data comes in.
So, in the meantime, let's explore what life on a rocky, habitable super-Earth might be like.
Liquid water is just the start.
These planets can be almost double Earth's radius, and up to ten-times more massive.
And all that extra mass is what researchers think could really make super-Earths the perfect home.
That's because more massive planets have a stronger gravitational pull.
Super-Earth Kepler 20b, for example is nearly double the size of Earth, and it's ten-times more massive.
This makes its surface gravity almost three-times stronger.
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.
It also means mountains and hills would erode a lot faster, leaving a relatively flatter surface, compared to Earth.
Now that might sound boring, but scientists think this could actually spawn dozens of shallow islands all across the planet.
Those in turn, could be the perfect place for life to form and evolve.
Just as biodiversity in Earth's oceans is richest in shallow waters near coastlines, such an "archipelago world" might be enormously advantageous to life.
There's just one problem, leaving this tropical paradise would be extremely difficult.
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...
Like for example, a mission similar to the Apollo Moon Landing would require twice the amount of fuel.
Or, rockets would have to carry only a fraction of the payload.
For instance, SpaceX's Falcon Heavy can launch 50,000 kilograms of payload into Earth's orbit.
Whereas it could only launch 40 kilograms into orbit around a super-Earth like Kepler 20b.
That's about the weight of a German Shepherd.
Suffice it to say, leaving a super-Earth would be a far greater challenge.
But if it looked like this, would you really want to say goodbye?
We'll never know for sure until we visit one.
What questions do you have about space?
Leave your queries and the comments below.
And thanks for watching.
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宇宙間究竟有沒有另一個「地球」? (Is There A Better Planet Out There For Us?)

1995 分類 收藏
Seraya 發佈於 2020 年 7 月 8 日    Seraya 翻譯    adam 審核
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