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super-Earth

(superearth)
(exoplanet more massive than Earth but substantially less than Neptune)

Super-Earth (or superearth) is a common term for extra-solar planets more massive than the Earth but substantially less massive than Uranus and Neptune, basically 2-10 Earth masses though there is no consensus on exact limits. Often the radius is known but not the mass (e.g., from the transit method), and the term super-Earth might be applied to a planet because it has a somewhat larger radius than Earth, presumably a radius consistent with the above mass range.

Usage of the term super-Earth regarding the planet's constituents and structure varies. Sometimes the term is only meant to indicate the mass, even if the planet has a large atmosphere in the manner of a gas giant. In other instances, it is meant to be Earth-like, i.e., a rocky planet with on the order of 1% of its mass as atmosphere which is considered the most likely atmosphere percentage in the super-Earth mass range. In the latter case, other terms have been used for gas planets of such a mass, such as mini Neptune, sub Neptune, gas dwarf, mini gas giant, or transitional planet for planets with large atmospheres in the manner of Neptune, etc. The term super-puff means essentially a larger-than-Earth (super-Earth) rocky core, but with a large, non-Earth-like atmosphere. Super-Earth statistics show two peaks in radius (1.3 versus 2.4 Earth radii) suggesting two types of planets and planet formation. The term evaporation valley refers to a hypothesis about the difference, that a planet positioned so as to be sufficiently warmed by the star loses the non-metals in its atmosphere, sufficiently quickly that they are generally either wiped out or left essentially intact.

Current statistics and analysis suggest super-Earth's are very common, perhaps the most common type of planet, in late 2018 being roughly 1000 out of the 4000 exoplanets known. Current thought is about a third of systems have a super-Earth, compared to perhaps a sixth with gas giants, in contrast to the solar system that has gas giant Jupiter but no super-Earth. The super-Earth ubiquity needs explanation. Some models suggest the larger ones would naturally experience runaway accretion and become gas giants, and the fact that they didn't suggests the gas supply was cut off, i.e., the disk (transitional disk) dispersed after a short lifetime.


(planet type,exoplanets)
http://en.wikipedia.org/wiki/Superearth

Referenced by:
Automated Planet Finder (APF)
exoearth
extra-solar planet
55 Cancri e (55 Cnc e)
GJ 1214 b
mega-Earth
planet type
rocky planet
solar system

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