Pluto is composed of 70% rock and 30% water ice, with a diameter of 1,454 miles across. It has a metallic-rock core, takes 6.36 Earth days to complete one day, and orbits the Sun once every 248 Earth years from a distance of 3.6 billion miles. Pluto has an atmosphere of nitrogen and carbon monoxide and is orbited by three moons named Nix, Charon, and Hydra.