The distant planet Pluto and its moon, Charon, as revealed by NASA's Hubble Space Telescope (Feb 1994) when the planet was 2.6 billion miles from Earth; or nearly 30 times the separation between Earth and the sun. Pluto's diameter of 1440 miles and Charon's diameter of 790 miles. Pluto was discovered in 1930 but Charon wasn't detected until 1978 because the moon is so close to Pluto that the two worlds are typically blurred together when viewed through ground-based telescopes.