On February 18, 1930, Clyde Tombaugh, examining photographic plates at Lowell Observatory in Flagstaff, Arizona, noticed a tiny point of light that had shifted position between exposures taken two weeks apart. The object was later named Pluto, fulfilling astronomer Percival Lowell's decades-old quest for a hypothesized 'Planet X.' It was reclassified as a dwarf planet in 2006.
Tombaugh had no formal astronomy degree when Lowell Observatory hired him in 1929, drawn by hand-drawn sketches of Jupiter and Mars he'd sent them from his family farm in Kansas. His task was tedious beyond description: photograph the same patch of sky nights apart, then compare the plates using a blink comparator, a machine that flickered between two images so any moving object would appear to jump.
On the afternoon of February 18, after months of scanning, Tombaugh noticed a faint dot near the star Delta Geminorum shift position between plates taken on January 23 and 29. 'That's it,' he reportedly said, sitting in stunned silence for nearly 45 minutes before telling anyone.
The discovery made headlines worldwide and appeared to vindicate Percival Lowell, who had died in 1916 still searching for the planet whose gravity he believed was tugging at Uranus's orbit. An 11-year-old English girl, Venetia Burney, suggested the name Pluto, god of the underworld — fittingly, given the tiny world's icy, distant obscurity. In 2006 the International Astronomical Union stripped Pluto of full planet status, sparking a controversy that persists among astronomers and the public alike.