Kepler-20d is an exoplanet orbiting

Kepler-20 Kepler-20 is a star 929 light-years from Earth in the constellation Lyra with a system of six known planets. The apparent magnitude of this star is 12.51, so it cannot be seen with the unaided eye. Viewing it requires a telescope with an a ...

. It has a mass and radius similar to Neptune. Despite being the furthest planet from the star, it has an orbit similar to Mercury, meaning that it is a

Hot Neptune A hot Neptune or Hoptune is a type of giant planet with a mass similar to that of Uranus or Neptune orbiting close to its star, normally within less than 1 AU. The first hot Neptune to be discovered with certainty was Gliese 436 b in 2007, an exo ...

. Along with the other four planets in the system, Kepler-20d was announced on December 20, 2011.

References

Kepler-20d , Wayback Machine
Exoplanets discovered in 2011 D 20d Hot Neptunes Transiting exoplanets {{Extrasolar-planet-stub