A "super-Earth" is an exoplanet (a planet around another star) whose mass is between about two and ten Earth-masses. Planets larger than this are closer to Uranus and Neptune in size (and perhaps in other physical properties as well). The category of "super-Earth" currently refers only to the mass of the object, and not to its radius, its orbital distance from the star, its surface temperature, or its atmospheric properties, although naturally astronomers are working hard to identify super-Earths that might offer clues about the Earth in these features. Of the 576 exoplanets whose basic parameters are currently approximately known, there are 36 in the super-Earth category.
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