Clyde William Tombaugh was an American astronomer best known for discovering Pluto in 1930 while working at Lowell Observatory in Flagstaff, Arizona. He later held positions at White Sands Proving Ground and served on the faculty of New Mexico State University from 1955 until his retirement in 1973.
In August 1949 Tombaugh reported seeing a group of rectangular lights in the night sky above Las Cruces, New Mexico. He described the brief, silent sighting to Air Force personnel and repeated the account in later public statements.
- Discovered Pluto on February 18, 1930, at Lowell Observatory.
- Observed rectangular lights on or about August 20, 1949, in Las Cruces, New Mexico, with wife and mother-in-law.
- Served as optical physicist tracking missiles at White Sands Proving Ground 1946–1955.
- Led planetary research program at New Mexico State University 1955–1973.
- Died January 17, 1997, in Las Cruces, New Mexico.
- United StatesBorn and lifelong resident
- Lowell ObservatoryPlanet search 1929–1946
- White Sands Proving GroundOptical physicist 1946–1955
- New Mexico State UniversityFaculty 1955–1973
- University of KansasBS 1936, MA 1939
- Jackson-Gwilt MedalRoyal Astronomical Society 1931
Background
Clyde William Tombaugh was born on February 4, 1906, on a farm near Streator, Illinois. He developed an early interest in astronomy and built his own telescopes while growing up on a Kansas farm after his family moved there in 1922. Tombaugh graduated from Burdett High School in 1925 and sent detailed drawings of Mars to Lowell Observatory in 1928.
Lowell Observatory director Vesto Melvin Slipher hired Tombaugh in January 1929 to conduct a photographic search for a predicted ninth planet. Using a 13-inch astrograph, Tombaugh compared plates with a blink comparator and identified Pluto on February 18, 1930. The discovery was announced on March 13, 1930. He remained at Lowell until 1946, cataloging thousands of galaxies, asteroids, and other objects.
Tombaugh earned a bachelor's degree from the University of Kansas in 1936 and a master's degree in 1939 while continuing summer work at Lowell. He taught navigation for the U.S. Navy during World War II at Arizona State College. In 1946 he moved to Las Cruces, New Mexico, and joined the civilian staff at White Sands Proving Ground.
At White Sands Tombaugh served as Chief of the Optical Measurements Section from 1946 to 1950, setting up tracking telescopes for ballistic missile tests. He continued as an optical physicist in the Systems Engineering Branch until 1955. During this period he also founded the Las Cruces Astronomical Society in 1951.
In 1955 Tombaugh joined the faculty of New Mexico State University. He established a major planetary research program there, including the Planetary Patrol project that monitored Jupiter's Great Red Spot and studied Mercury's rotation. He retired from full-time faculty duties in 1973 but remained active as an observer and adviser.
On an evening in August 1949 Tombaugh was in the backyard of his Las Cruces home with his wife and mother-in-law when he saw a geometric formation of faint bluish-green rectangular lights near the zenith. The lights moved south-southeasterly, foreshortened, and faded after about three seconds with no sound. He later wrote a detailed statement for Air Force investigators.
Tombaugh reported the sighting to Project Blue Book personnel. Popular accounts sometimes described the rectangles as illuminated windows or portholes on a craft, though Tombaugh's own account compared them to the Lubbock Lights and noted their low luminosity. He stated he had never seen anything so strange in thousands of hours of sky watching.
In 1957 Tombaugh confirmed the details of the sighting in public statements. He also reported seeing green fireballs over New Mexico in the late 1940s and early 1950s. Later in life he expressed openness to scientific study of unidentified aerial phenomena while favoring natural explanations such as temperature inversions for his 1949 observation.
Tombaugh received the Jackson-Gwilt Medal from the Royal Astronomical Society in 1931. He authored books including Out of Darkness: The Planet Pluto with Patrick Moore in 1980. He continued telescope making and public lectures after retirement, supporting observational astronomy programs at New Mexico State University.
Legacy
Clyde Tombaugh died on January 17, 1997, at age 90 in Las Cruces, New Mexico. His discovery of Pluto remains a landmark in solar system astronomy, and the 1949 sighting is frequently cited in discussions of astronomer-reported unidentified aerial phenomena.
New Mexico State University maintains programs and facilities honoring his contributions to planetary science. The asteroid 1604 Tombaugh is named after him.
Last updated 25 October 2026