superEarths

Super-Earths are exoplanets with masses larger than Earth's but well below those of the ice giants Uranus and Neptune. The term is commonly used for planets with roughly 1 to 10 Earth masses and radii near 1.25 to 2.0 Earth radii, though composition can vary and the category overlaps with other classes. It is a descriptive label rather than a precise dynamical definition, and it does not imply Earth-like conditions.

The internal structure of super-Earths can range from predominantly rocky to volatile-rich, with the possibility of substantial atmospheres. Mass–radius measurements indicate a continuum from high-density, rocky worlds to bodies with thick envelopes of volatiles or gas. Some super-Earths are likely terrestrial; others may be mini-Neptunes with significant gaseous layers.

Most known super-Earths orbit close to their stars, but a substantial number reside at wider separations. They are discovered mainly through transit observations, which yield radius, and radial-velocity measurements, which provide mass. Together these data constrain density and possible composition. Formation scenarios include core accretion with varying gas accretion histories and inward migration; atmospheric loss due to stellar irradiation can alter a planet’s apparent size and composition over time.

Habitability depends on multiple factors beyond mass, including equilibrium temperature, atmosphere, and geologic activity. Some super-Earths receive stellar flux compatible with liquid water under favorable conditions, but many experience harsh environments or tidal effects around M-dwarf hosts.

Notable examples include 55 Cancri e and several Kepler discoveries. Ongoing and future observations aim to refine mass, radius, and atmospheric properties to improve classification.