Nicholson, Seth Barnes (1891–1963)
American astronomer who discovered Jupiter's
moons Lysithea, Ananke,
Carme, and Sinope,
and also did important work on sunspots.
Nicholson was educated at Drake University, Des Moines, Iowa, and at the
University of California (Ph.D., 1915). As a graduate student at the University
of California he was photographing the recently-discovered eighth moon of
Jupiter (now known as Pasiphae) with the 36-inch Crossley reflector when
he discovered a ninth (Sinope). He computed its orbit for his Ph.D. dissertation.
At Mount Wilson Observatory, where he
spent his entire career, he discovered three more Jovian satellites, as
well as a Trojan asteroid, and computed the orbits of several comets and
of Pluto. His main work at Mount Wilson involved
observing the Sun with the observatory's tower telescope, and he produced
annual reports on sunspot activity and magnetism for decades. He and Edison
Pettit used a vacuum thermocouple to measure the temperatures of the Moon,
planets, sunspots, and stars in the early 1920s. Their temperature measurements
of nearby giant stars led to some of the first determinations of stellar
diameters.
Adapted in part from the biographical
entry at The Bruce Medalists website
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