A super-Neptune is a

planet A planet is a large, Hydrostatic equilibrium, rounded Astronomical object, astronomical body that is generally required to be in orbit around a star, stellar remnant, or brown dwarf, and is not one itself. The Solar System has eight planets b ...

that is more massive than the planet

Neptune Neptune is the eighth and farthest known planet from the Sun. It is the List of Solar System objects by size, fourth-largest planet in the Solar System by diameter, the third-most-massive planet, and the densest giant planet. It is 17 t ...

. These planets are generally described as being around 5–7 times as large as Earth with estimated masses of 20–80 ; beyond this they are generally referred to as

gas giants A gas giant is a giant planet composed mainly of hydrogen and helium. Jupiter and Saturn are the gas giants of the Solar System. The term "gas giant" was originally synonymous with "giant planet". However, in the 1990s, it became known that Uranu ...

. A planet falling within this mass range may also be referred to as a sub-Saturn. There have been relatively few discoveries of planets of this kind. The mass gap between Neptune-like and

Jupiter Jupiter is the fifth planet from the Sun and the List of Solar System objects by size, largest in the Solar System. It is a gas giant with a Jupiter mass, mass more than 2.5 times that of all the other planets in the Solar System combined a ...

-like planets is thought to exist because of "runaway accretion" occurring for

protoplanet A protoplanet is a large planetary embryo that originated within a protoplanetary disk and has undergone internal melting to produce a differentiated interior. Protoplanets are thought to form out of kilometer-sized planetesimals that gravitatio ...

s of more than —once this mass threshold is crossed, they accumulate much additional mass (due to

gravity In physics, gravity (), also known as gravitation or a gravitational interaction, is a fundamental interaction, a mutual attraction between all massive particles. On Earth, gravity takes a slightly different meaning: the observed force b ...

increasing with mass and the presence of material in an

accretion disk An accretion disk is a structure (often a circumstellar disk) formed by diffuse material in orbital motion around a massive central body. The central body is most frequently a star. Friction, uneven irradiance, magnetohydrodynamic effects, and ...

) and grow into planets the size of Jupiter or even larger. Known examples include Kepler-101b,

HAT-P-11b HAT-P-11b (or Kepler-3b) is an extrasolar planet orbiting the star HAT-P-11. It was discovered by the HATNet Project team in 2009 using the transit method, and submitted for publication on 2 January 2009. This planet is located approximatel ...

, and K2-33b.

Mass-radius relationship

Through modelling, and analysis of discovered exoplanets, the relationship between mass and radius has given a much higher upper limit for the transition boundary between Neptune and Jupiter worlds than had been previously defined empirically from observing the planets within the

Solar System The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Sola ...

, for example Chen & Kipping (2017) defined the transition point between Neptunian and Jovian worlds at around 130 . In studies looking into this relationship between mass-radius, Saturn, though never defined as an ice giant, is however found to sit just within the mass-radius limits for a Neptunian world, close to the transition point between super-Neptune and Jupiter world.

References

Types of planet * {{extrasolar-planet-stub

Mass-radius relationship

See also

References