When Was Pluto Discovered?

Percival Lowell predicted a "Planet X" beyond Neptune based on perceived perturbations in the orbits of Uranus and Neptune, and began searching for it in 1906. After Lowell death in 1916, the search continued. In 1929, 23-year-old Clyde Tombaugh, a Kansas farmboy and amateur astronomer, was hired to continue the painstaking work. Using a blink comparator to detect moving objects between photographic plates taken days apart, Tombaugh found Pluto on 18 February 1930. The name "Pluto" was suggested by Venetia Burney, an 11-year-old English schoolgirl. Pluto was classified as the ninth planet for 76 years until the IAU reclassified it as a dwarf planet in 2006, after the discovery of similar Kuiper Belt objects (especially Eris). When NASA New Horizons probe flew past Pluto in 2015, it carried a small container of Tombaugh ashes.