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
Definition of planet to 400 astronomical units from the star. A Mars-mass body at the orbit of Pluto clears its orbit. This metric, which leaves Pluto as a dwarf planet, applies to both the Solar System and to extrasolar systems. Some opponents of the definition have claimed that "clearing the neighbourhood" is an ambiguous concept. Mark Sykes, director of the Planetary Science Institute in Tucson, Arizona, and organiser of the petition, expressed this opinion to National Public Radio. He believes that the definition does not categorise a planet by composition or formation, but, effectively, by its location. He believes that a Mars-sized or