HD 10180 c is an extrasolar planet approximately 130 light-year

Light-year

A light-year, also light year or lightyear is a unit of length, equal to just under 10 trillion kilometres...

s away in the constellation Hydrus

Hydrus

Hydrus is a small constellation in the southern sky, created in the sixteenth century. Its name means "male water snake", and it should not be confused with Hydra, a much larger constellation which represents a female water snake.-History:...

. With a minimum mass comparable to that of Neptune

Neptune

Neptune is the eighth and farthest planet from the Sun in the Solar System. Named for the Roman god of the sea, it is the fourth-largest planet by diameter and the third largest by mass. Neptune is 17 times the mass of Earth and is slightly more massive than its near-twin Uranus, which is 15 times...

, it is of the class of planets known as Hot Neptune

Hot Neptune

A hot Neptune is an extrasolar planet in an orbit close to its star , with a mass similar to that of Uranus or Neptune. Recent observations have revealed a larger potential population of hot Neptunes than previously thought...

s. Dynamical simulations suggest that if the mass gradient was any more than a factor of two, the system would not be stable.

While planet c does not exist in any mean motion resonances

Orbital resonance

In celestial mechanics, an orbital resonance occurs when two orbiting bodies exert a regular, periodic gravitational influence on each other, usually due to their orbital periods being related by a ratio of two small integers. Orbital resonances greatly enhance the mutual gravitational influence of...

, both planets with adjacent orbits (b and d) share near resonances with c.