Which American astronomer discovered the dwarf planet Pluto?

Clyde William Tombaugh (February 4, 1906 – January 17, 1997) was an American astronomer. He discovered Pluto in 1930, the first object to be discovered in what would later be identified as the Kuiper belt. At the time of discovery, Pluto was considered a planet but was later reclassified as a dwarf planet in 2006. Tombaugh also discovered many asteroids. He also called for the serious scientific research of unidentified flying objects, or UFOs.

Following his discovery of Pluto, Tombaugh earned bachelor's and master's degrees in astronomy from the University of Kansas in 1936 and 1938. During World War II he taught naval personnel navigation at Northern Arizona University. He worked at White Sands Missile Range in the early 1950s, and taught astronomy at New Mexico State University from 1955 until his retirement in 1973.