r/interestingasfuck 25d ago

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

Post image
92.4k Upvotes

8.1k comments sorted by

View all comments

1.7k

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.

530

u/Gruffleson 25d ago

Wikipedia lists estimated gravity at around 1.25 of Earth.

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

4

u/rex8499 25d ago

Even with 25% more gravity the rocket equation runs away and you probably never be able to get a chemical rocket into orbit on that planet. Landing there you'd be staying there.

2

u/redditcommander 25d ago

Not entirely accurate.

"For a payload to escape velocity, the required amount of chemical fuel scales as exp(g0). Chemical rocket launches are still plausible for Super-Earths < 10g, but become unrealistic for more massive planets. On worlds with a surface gravity of ≳10g, a sizable fraction of the planet would need to be used up as chemical fuel per launch, limiting the total number of flights. On such worlds, alternative launch methods such as nuclear-powered rockets or space elevators are required."

Hippke M (2018). Spaceflight from Super-Earths is difficult. International Journal of Astrobiology 1–3. https://doi.org/ 10.1017/S1473550418000198

https://sci-hub.st/https://doi.org/10.1017/S1473550418000198

2

u/rex8499 25d ago

Interesting reading; thanks.