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A super-Earth is an extrasolar planet with a mass higher than Earth's, but substantially below the mass of the Solar System's ice giants Uranus and Neptune, which are 15 and 17 Earth masses respectively.〔 〕 The term ''super-Earth'' refers only to the mass of the planet, and does not imply anything about the surface conditions or habitability. The alternative term "gas dwarfs" may be more accurate for those at the higher end of the mass scale, as suggested by MIT professor Sara Seager, although mini-Neptunes is more common. == Definition == In general, super-Earths are defined exclusively by their mass, and the term does not imply temperatures, compositions, orbital properties, habitability, or environments are cited in definitions of super-Earths. While sources generally agree on an upper bound of 10 Earth masses,〔〔 〕〔 〕 (~69% of the mass of Uranus, which is the Solar System gas giant with the least mass), the lower bound varies from 1〔 or 1.9〔 to 5,〔 with various other definitions appearing in the popular media.〔 〕〔 〕〔 〕 The term Super-Earth also is used by astronomers to define planets bigger than Earth-like planets (from 0.8 Earth-radii till 1.25), but smaller than mini-Neptunes (from 2 Earth-radii till 4).〔 〕 This definition was made by the Kepler Mission.〔 〕 Some authors further suggest that the term be limited to planets without a significant atmosphere, or planets that have not just atmospheres but also solid surfaces or oceans with a sharp boundary between liquid and atmosphere, which the four giant planets in our solar system do not have. Planets above 10 Earth masses are termed massive solid planets〔(MASS-RADIUS RELATIONSHIPS FOR SOLID EXOPLANETS ), S. Seager, M. Kuchner, C. A. Hier-Majumder, B. Militzer, February 1, 2008〕/mega-Earths〔(Astronomers find a new type of planet: The 'mega-Earth' )〕〔(EXOPLANETS: FROM EXHILARATING TO EXASPERATING ), 22:59, Kepler-10c: The "Mega-Earth", Dimitar Sasselov, June 2, 2014〕 or gas giant planets depending on whether they are mostly rock/ice or mostly gas. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Super-Earth」の詳細全文を読む スポンサード リンク
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