Seth Barnes Nicholson (November 12, 1891 – July 2, 1963) was an American astronomer.[1] He worked at the Lick observatory in California, and is known for discovering several moons of Jupiter in the 20th century.
Nicholson was born in Springfield, Illinois, and was raised in rural Illinois. He was educated at Drake University, where he became interested in astronomy.[2] On May 29, 1913, he was married to Alma Stotts, a fellow student at Drake then the University of California at Berkeley. They would have three children: Margaret, Donald, and Jean.[3]
In 1914, at the University of California's Lick Observatory, while observing the recently discovered JupitermoonPasiphaë, he discovered a new one, Sinope, whose orbit he computed for his Ph.D. thesis in 1915.
Sinope, Lysithea, Carme, and Ananke were simply designated as "Jupiter IX", "Jupiter X", "Jupiter XI", and "Jupiter XII". They were not given their present names until 1975. Nicholson himself declined to propose names.[4]
At Mt. Wilson, his main assignment concerned solar activity and he produced for decades annual reports on sunspot activity. He also made a number of eclipse expeditions to measure the brightness and temperature of the Sun's corona.
In the early 1920s, he and Edison Pettit made the first systematic infrared observations of celestial objects.
They used a vacuum thermocouple to measure the infrared radiation and thus the temperature of the Moon which led to the theory that the Moon was covered with a thin layer of dust acting as an insulator, and also of the planets, sunspots and stars.
Their temperatures measurements of nearby giant stars led to some of the first determinations of stellar diameters.
^Judit M. Pap, Peter A. Fox, "Solar variability and its effects on climate", Volume 141 of Geophysical monograph, American Geophysical Union, publ. American Geophysical Union, 2004, ISBN0875904068, 9780875904061, length 366 pages, page 51.