1735 Mathematical calculations suggest that it is on this day that dwarf planet Pluto moved inside the orbit of Neptune for the last time before 1979.
1915 Pluto is photographed for the first time but is not recognized as a planet.
1930 While studying photographs taken in January, Clyde Tombaugh discovers Pluto.
1930 The news of the discovery of Pluto is telegraphed to the Harvard College Observatory.
1930 The dwarf planet Pluto is officially named.
1978 Charon, a satellite of the dwarf planet Pluto, is discovered by American astronomer James Christy.
1979 Pluto moves inside Neptune's orbit for the first time since either was discovered.
1983 Pioneer 10 travels beyond Pluto's orbit.
2006 The New Horizons probe is launched by NASA on the first mission to Pluto.
2006 Pluto's newly discovered moons are officially named Nix & Hydra.
2006 The International Astronomical Union (IAU) redefines the term "planet" such that Pluto is now considered a Dwarf Planet.
2007 Jupiter flyby of the New Horizons Pluto-observer spacecraft.