Seth Barnes Nicholson

Seth Barnes Nicholson
Born	November 12, 1891 Springfield, Illinois
Died	July 2, 1963 (aged 71) Los Angeles
Nationality	American
Fields	astronomy
Institutions	Mount Wilson Observatory
Alma mater	Drake University
Notable awards	Bruce Medal (1963)

Seth Barnes Nicholson (November 12, 1891 – July 2, 1963) was an American astronomer.^[1]

Asteroids discovered: 2
878 Mildred	September 6, 1916
1647 Menelaus	June 23, 1957

Nicholson was born in Springfield, Illinois, and was raised in rural Illinois. He was educated at Drake University where he became interested in astronomy.

In 1914, at the University of California's Lick Observatory, while observing the recently discovered Jupiter moon Pasiphaë, he discovered a new one, Sinope, whose orbit he computed for his Ph.D. thesis in 1915.

He spent his entire career at Mount Wilson Observatory, where he discovered three more Jovian moons: Lysithea and Carme in 1938 and Ananke in 1951, as well as a Trojan asteroid, 1647 Menelaus, and computed orbits of several comets and of Pluto.

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.^[2]

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.

Nicholson, together with astronomer George Ellery Hale, lend their name to the "Hale-Nicholson law" concerning the magnetic polarity of sunspots.^[3][4]

From 1943 to 1955, he served as editor of the Publications of the Astronomical Society of the Pacific, of which he was also twice president.

He died in Los Angeles.

Awards and honors

• Awarded the Bruce Medal (1963)
• The Asteroid 1831 Nicholson, the crater Nicholson on the Moon, the crater Nicholson on Mars, and Nicholson Regio on Ganymede were named after him.

References

1. "Obituary: Seth B. Nicholson". Physics Today 16 (9): 106. September 1963. doi:10.1063/1.3051113.
2. Seth Barnes Nicholson, The Satellites of Jupiter.
3. Astrophysics of the sun, Harold Zirin, Cambridge University Press, 1988, p.307; http://adsabs.harvard.edu/abs/1988assu.book.....Z
4. 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, ISBN 0875904068, 9780875904061, length 366 pages, page 51.

External links

• Works by or about Seth Barnes Nicholson at Internet Archive
• Seth Barnes Nicholson — Biographical Memoirs of the National Academy of Sciences