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Basic Information

Super-Earths are planets larger than Earth but not so large as a Gas Giant. So, from just a little more massive than the Earth, up to about 10 times the mass of the Earth.

There are no such planets in our own Solar System. All our Jovian Planets and Ice Giants are at least 14 times as massive as Earth, and there's no terrestrial planets in our system larger than Earth. However, extrasolar super-earths have been detected in orbit of the stars Gliese 581 and Gliese 876.

Sometimes the term "Super-Earths" is used to specifically discuss terrestrial planets that fit that size category. However, technically the term also includes icy and watery worlds beyond the snow line.

Terrestrial Super-Earths are likely to exhibit extremely high surface gravity, probably more so than the gravity of slightly larger Gas Giant, as the gas giant would be less dense. Some of the detected Terrestrial Super-Earths seem to have very large iron cores - so while their radius or size might be just 1.5 earths, their mass is 5 earths or more. This is likely to make the largest Super-Earths very active geologically and volcanically. The density and mass of the planet might prevent Plate Tectonics from being a factor on the planet at all. If so, the result may be a Venus-like planet. An only-slightly-super-earth, however, could still be very earth-like.

For ideas on what impact the hypergravity would have on the creatures that live and evolve there, see Heavyworlder.



Game and Story Use

  • A planet that's a little bigger than earth will have more resources and surface area, and thus support a larger population.
    • If such a world got in a war with us, they'd have a little more to expend on it.
      • Their soldiers might also be stronger or tougher, because the square-cube law says the other planet will have more mass and thus stronger gravity. They'll be adapted to it. See also Heavyworlder.
        • Yes, but will they be able to leap tall buildings in a single bound?
          • They might, but landing is likely to be pretty rough, at least on their homeworld. If they come to visit us, they may exhibit something akin to superstrength, or it may be that their bodies just aren't built for the rapid movements needed to jump well.
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