2006: Pluto, once the ninth planet from the sun, is downgraded to a mere “dwarf planet.” Our solar system loses a favorite kid brother and now has, officially, only eight planets.
Pluto was discovered by American astronomer Clyde Tombaugh on Feb. 18, 1930. Comparing photographs taken of the same section of sky over several nights in January, Tombaugh identified a moving object against a background of stationary stars.
Based on the predictions of two colleagues at the Lowell Observatory, he’d been searching for a planet outside the orbit of Neptune at the time. The photographs convinced him he had found it.
Tombaugh announced his discovery on March 13. The planet was officially named Pluto, after the Roman god of the underworld, on May 1, 1930.
