CHARON

only known natural satellite of Pluto. It was discovered in 1978 by James W. Christy and Robert S. Harrington at the United States Naval Observatory in Washington, D.C. Earlier attempts to detect a moon of Pluto had proved unsuccessful because Pluto is so remote. Moreover, Charon is unusually close to the planet and so had been obscured by the glare of its light. Charon orbits Pluto in 6.3871 days on a circular orbit with a radius of approximately 19,700 km (12,210 miles). Its diameter is thought to be roughly half that of Pluto, or as little as 1,284 km. Charon, unlike Pluto, seems to have little methane. Its surface is believed to be composed of water-ice and a residual of carbonaceous or silaceous impurities (or both), which together would give it a morainic appearance. in Greek mythology, the son of Erebus and Nyx (Night), whose duty it was to ferry over the Rivers Styx and Acheron those souls of the deceased who had received the rites of burial. In payment he received the coin that was placed in the mouth of the corpse. In art Charon was represented as a morose and grisly old man. In Etruscan he was known as Charun and appeared as a death demon, armed with a hammer. Eventually he came to be regarded as the image of death and of the world below. As such he survives in Charos, or Charontas, the angel of death in modern Greek folklore.