Tombaugh, Clyde William


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Tombaugh, Clyde William

(tŏm`bô), 1906–97, American astronomer, b. Streator, Ill. Although lacking formal training or a college degree, he was hired in 1929 as an assistant by the Lowell ObservatoryLowell Observatory,
astronomical observatory located in Flagstaff, Ariz.; it was founded in 1894 by Percival Lowell, the American astronomer who popularized the idea that Mars might support intelligent life. Its original telescope, still in operation, is a 24-in.
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 to continue the search for a planet beyond Neptune, which had been initiated by Percival LowellLowell, Percival,
1855–1916, American astronomer, b. Boston, grad. Harvard, 1876; brother of Abbott Lawrence Lowell and Amy Lowell. He visited Korea and Japan, where he acted as counselor and foreign secretary to the Korean Special Mission to the United States and wrote
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. Tombaugh used a blink microscopeblink microscope,
in astronomy, device for determining a change in position or magnitude (brightness) of a star relative to other stars in the background. Two photographs of the same field or area of the sky are projected so that they precisely coincide.
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 to compare photographs of a small part of the night sky and detect the planet. After ten months of painstaking comparisons, on Feb. 18, 1930, he found PlutoPluto,
in astronomy, a dwarf planet and the first Kuiper belt, or transneptunian, object (see comet) to be discovered (1930) by astronomers. Pluto has an elliptical orbit usually lying beyond that of Neptune.
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 (now regarded as a Kuiper belt object [see cometcomet
[Gr.,=longhaired], a small celestial body consisting mostly of dust and gases that moves in an elongated elliptical or nearly parabolic orbit around the sun or another star. Comets visible from the earth can be seen for periods ranging from a few days to several months.
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] and a dwarf planetdwarf planet,
a nonluminous body of rock or gas that orbits the sun and has a rounded shape due to its gravity. Unlike a planet, a dwarf planet is not capable of clearing its orbit of smaller objects by collision, capture, or other means.
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) in the constellation Gemini. After several weeks of observation by the observatory staff to validate the discovery, it was announced on Mar. 13, the 75th anniversary of Lowell's birth. Tombaugh received a scholarship from the Univ. of Kansas, where he obtained his bachelor's (1936) and master's (1939) degrees. He subsequently returned to the observatory and also held several academic posts. He focused on planetary observations, particularly of Mars, and in 1965 images returned by the space probe Mariner 4 confirmed his prediction that the Martian surface would have craters caused by asteroid impacts. He wrote Out of the Darkness: The Planet Pluto (1980) with Patrick Moore.

Bibliography

See biography by D. H. Levy (1992).

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