Seth Barnes Nicholson

Seth Barnes Nicholson ( born November 12, 1891 in Springfield, Illinois, † July 2, 1963 in Los Angeles ) was an American astronomer.


Nicholson grew up in the rural area of ​​Illinois and later attended Drake University where be became interested in astronomy.

In 1914 he observed at the Lick Observatory of the University of California the newly discovered moon of Jupiter, which was later named Pasiphae. He discovered another moon in Jupiter ( Sinope ), which received the designation Jupiter moon IX. Nicholson calculated the orbit of the moon in 1915 as part of his doctoral thesis. In 1916 he discovered the asteroid ( 878 ) Mildred.

He spent his future career at Mount Wilson Observatory, where he three other moons of Jupiter, Lysithea, Carme (both 1938) and Ananke (1951 ) and the Trojan asteroids ( 1647) Menelaus discovered. He also calculated the orbits of several comets and the dwarf planet Pluto.

Sinope, Lysithea, Carme and Ananke were initially just as the moons of Jupiter IX, X, XI and XII called. Only in 1975 did they get their names by the International Astronomical Union ( IAU ), with Nicholson had argued against naming.

His main task at the Mount Wilson Observatory, however, was to study the solar activity, which he created annual reports on sunspot activity over decades. He took part in several expeditions to observe solar eclipses to determine the brightness and temperature of the solar corona.

In the early 1920s he led together with Edison Pettit by the first systematic investigations of celestial bodies in the infrared range. Measuring the infrared radiation of the Moon and the derived temperatures led to the proper assumption that the moon's surface is coated with a thin layer of dust, which has a heat insulating effect. The temperature measurements of red giant stars revealed the first evidence for the determination of stellar diameters.

From 1943 to 1955 he worked as editor and vice president of the Astronomical Society of the Pacific. 1963 was awarded to him for his services, the Bruce Medal.

The lunar crater Nicholson, Mars crater Nicholson and Nicholson Regio on Jupiter's moon Ganymede is named after him.