NICHOLSON, SETH BARNES

(b. Springfield, Illinois, 12 November 1891; d. Los Angeles, California, 2 July 1963)

observational astronomy.

Nicholson spent his youth in rural communities in Illinois, where his father, a somewhat trained geologist, alternated between farming and teaching in elementary and high schools. At Drake University, Nicholson’s career choice was influenced by the professor of astronomy, D. W. Morehouse, who was well-known for his discovery in 1908 of a particularly bright comet. In 1912 Nicholson and Alma Stotts, a classmate at Drake whom he soon married, enrolled as graduate students in astronomy at Berkeley; from then on, they were part of the West Coast astronomical community.

Nicholson’s most noted astronomical work was his discovery of four faint moons of Jupiter. In 1914, while at Lick Observatory photographing Jupiter VIII, which had been found by P. Melotte a few years before, Nicholson discovered Jupiter IX. This small satellite was at the limit of detectability of the thirty-six-inch telescope and the then available photographic plates, and for many years other astronomers had to take Nicholson’s word for its existence. Nicholson’s Ph.D. dissertation concerned the discovery of Jupiter IX and calculations of its orbit. After receiving his doctorate Nicholson was appointed to the staff at the Mt. Wilson Observatory, where he found Jupiter X and Jupiter XI in 1938, and Jupiter XII in 1951.

In addition to his work on the minor bodies of the solar system, Nicholson tackled several astrophysical problems. He made long-term and detailed observations of the surface features and spectrum of the sun. With Edison Pettit he used a vacuum thermocouple to measure the temperatures of stars, planets, and the eclipsed moon. He charted the profiles of spectral lines in Cepheid stars, and from spectrograms of Venus he derived a value for the solar parallax and a verification of the absence of oxygen and water vapor from the Venusian atmosphere.

A mentor to numerous young astronomers, Nicholson was an active member of the Astronomical Society of the Pacific and several other astronomical and civic organizations. He received the Catherine Bruce Gold Medal of the Astronomical Society of the Pacific (1963) and was elected to membership in the National Academy of Sciences (1937).

BIBLIOGRAPHY

For biography and bibliography see Paul Herget, “Seth Barnes Nicholson;“in Biographical Memoirs. National Academy of Sciences, 42 (1971), 201–227. See also R. M. Petrie, “Award of the Bruce Gold Medal to Seth B. Nicholson,” in Publications of the Astronomical Society of the Pacific, 75 (1963), 305–307.

Deborah Jean Warner