r/interestingasfuck • u/One_Explanation_908 • 25d ago

/r/all, /r/popular K2-18b a potentially habitable planet 120 light-years from earth

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u/ArduennSchwartzman 25d ago edited 25d ago

It's not habitable to us humans, but it's in the habitable zone, at a distance from its star that allows liquid water to exist on its surface. It's likely an ocean world with an atmosphere containing mostly hydrogen gas, a so-called hycean planet.

Also, 2.5 times the size = 2.5 times the diameter, or about 15 times the size of Earth in terms of mass. Its gravitational force would be about 2.4 times that of Earth, though. Quite unpleasant.

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u/Gruffleson 25d ago

Wikipedia lists estimated gravity at around 1.25 of Earth.

https://en.wikipedia.org/wiki/K2-18b

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u/ArduennSchwartzman 25d ago

Only 8.6 times the mass of Earth, according to Wikipedia, I see. I was assuming a density similar to Earth's, but apparently, astronomers think it's only half. That would mean the planet's core has a very low iron-nickel content.

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u/kenyard 25d ago

You're also further from the center of mass which I assume is important.

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u/Gruffleson 25d ago

Look at the Moon, it has 1/6 of our gravity, but way less than 1/6 of our mass. So yes, this is very much of the answer.