1938-

American astronomer who co-discovered Pluto's moon, Charon, in 1978. Pluto, the furthest planet from the Sun, was discovered in 1930 by Clyde Tombaugh. However, because of its distance from the Sun, very little was known about it except for its orbital parameters. The discovery of Charon by Christy and Robert Harrington made it possible to determine Pluto's size and mass through application of basic physics governing planet-moon systems.