Moons of Pluto meters per pixel were returned of Nix and up to 1.1 kilometers per pixel of Hydra. Lower-resolution images were returned of Styx and Kerberos. Author Edmond Hamilton referred to three moons of Pluto in his 1940 novel "Calling Captain Future", naming them , , and . Charon was listed as the largest of them. All three moons would not be discovered until the year 1970, according to Hamilton. The real Charon was discovered in 1978. Moons of Pluto The dwarf planet Pluto has five moons down to a detection limit of about 1 km in diameter. In order of distance
Eris (dwarf planet) Eris appeared to be larger than Pluto, NASA initially described it as the Solar System's tenth planet. This, along with the prospect of other objects of similar size being discovered in the future, motivated the International Astronomical Union (IAU) to define the term "planet" for the first time. Under the IAU definition approved on August 24, 2006, Eris is a "dwarf planet", along with objects such as Pluto, Ceres, Haumea and Makemake, thereby reducing the number of known planets in the Solar System to eight, the same as before Pluto's discovery in 1930. Observations of a stellar occultation by Eris