Ceres is a dwarf planet.
Ceres (dwarf planet) . Its diameter is approximately 945 km , making it the largest of the minor planets within the orbit of Neptune . The 33rd-largest known body in the Solar System , it is the only dwarf planet within the orbit of Neptune.Due to its eccentric orbit , the dwarf planet Pluto was also within the orbit of Neptune from 1979 to 1999 , and will be again from approximately 2227 to 2247 . As the largest body in the asteroid belt , the dwarf planet Ceres ( formally `` 1 Ceres '' ) frequently appears in science fiction : Dawn (spacecraft) . Dawn is the first spacecraft to orbit two extraterrestrial bodies , the first spacecraft to visit either Vesta or Ceres , and also the first to visit a dwarf planet , arriving at Ceres in March 2015 , a few months before New Horizons flew by Pluto in July 2015 .