Seth Barnes Nicholson (November 12, 1891 – July 2, 1963) was an American

astronomer An astronomer is a scientist in the field of astronomy who focuses their studies on a specific question or field outside the scope of Earth. They observe astronomical objects such as stars, planets, moons, comets and galaxies – in either o ...

. 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 Springfield is the capital of the U.S. state of Illinois and the county seat and largest city of Sangamon County. The city's population was 114,394 at the 2020 census, which makes it the state's seventh most-populous city, the second largest ...

, and was raised in rural Illinois. He was educated at

Drake University Drake University is a private university in Des Moines, Iowa. It offers undergraduate and graduate programs, including professional programs in business, law, and pharmacy. Drake's law school is among the 25 oldest in the United States. Hi ...

, where he became interested in astronomy. In 1914, at the University of California's Lick Observatory, while observing the recently discovered

Jupiter Jupiter is the fifth planet from the Sun and the largest in the Solar System. It is a gas giant with a mass more than two and a half times that of all the other planets in the Solar System combined, but slightly less than one-thousandt ...

moon The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width ...

Pasiphaë In ancient Greek religion and Greek mythology, Pasiphaë (; grc-gre, Πασιφάη, Pasipháē, lit=wide-shining derived from πάσι (archaic dative plural) "for all" and φάος/φῶς ''phaos/phos'' "light") was a queen of Crete, and wa ...

, he discovered a new one, Sinope, whose

orbit In celestial mechanics, an orbit is the curved trajectory of an object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an artificial satellite around an object or position in space such a ...

he computed for his Ph.D. thesis in 1915. He spent his entire career at

Mount Wilson Observatory The Mount Wilson Observatory (MWO) is an astronomical observatory in Los Angeles County, California, United States. The MWO is located on Mount Wilson, a peak in the San Gabriel Mountains near Pasadena, northeast of Los Angeles. The observ ...

, where he discovered three more Jovian moons: Lysithea and Carme in 1938, and

Ananke In ancient Greek religion, Ananke (; grc, Ἀνάγκη), from the common noun , "force, constraint, necessity") is the personification of inevitability, compulsion and necessity. She is customarily depicted as holding a spindle. One of the ...

in 1951. While at the

Palomar Observatory Palomar Observatory is an astronomical research observatory in San Diego County, California, United States, in the Palomar Mountain Range. It is owned and operated by the California Institute of Technology (Caltech). Research time at the observat ...

in 1957, he discovered 1647 Menelaus, an asteroid near Jupiter. Other work included computing the orbits of several

comet A comet is an icy, small Solar System body that, when passing close to the Sun, warms and begins to release gases, a process that is called outgassing. This produces a visible atmosphere or Coma (cometary), coma, and sometimes also a Comet ta ...

s and also that of

Pluto Pluto (minor-planet designation: 134340 Pluto) is a dwarf planet in the Kuiper belt, a ring of bodies beyond the orbit of Neptune. It is the ninth-largest and tenth-most-massive known object to directly orbit the Sun. It is the largest k ...

. 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. At Mt. Wilson, his main assignment concerned

solar activity Solar phenomena are natural phenomena which occur within the atmosphere of the Sun. These phenomena take many forms, including solar wind, radio wave flux, solar flares, coronal mass ejections, coronal heating and sunspots. These phenomena a ...

and he produced for decades annual reports on sunspot activity. He also made a number of

eclipse An eclipse is an astronomical event that occurs when an astronomical object or spacecraft is temporarily obscured, by passing into the shadow of another body or by having another body pass between it and the viewer. This alignment of three ce ...

expeditions to measure the brightness and temperature of the Sun's corona. In the early 1920s, he and

Edison Pettit Edison Pettit (September 22, 1889 – May 6, 1962) was an American astronomer. He was born in Peru, Nebraska. Pettit received his bachelor's degree from the Nebraska State Normal School in Peru. He taught astronomy at Washburn College in ...

made the first systematic

infrared Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from aroun ...

observations of celestial objects. They used a vacuum

thermocouple A thermocouple, also known as a "thermoelectrical thermometer", is an electrical device consisting of two dissimilar electrical conductors forming an electrical junction. A thermocouple produces a temperature-dependent voltage as a result of th ...

to measure the infrared radiation and thus the temperature of the

Moon The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width ...

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 star A giant star is a star with substantially larger radius and luminosity than a main-sequence (or ''dwarf'') star of the same surface temperature.Giant star, entry in ''Astronomy Encyclopedia'', ed. Patrick Moore, New York: Oxford University Press ...

s led to some of the first determinations of stellar diameters. Nicholson, together with astronomer

George Ellery Hale George Ellery Hale (June 29, 1868 – February 21, 1938) was an American solar astronomer, best known for his discovery of magnetic fields in sunspots, and as the leader or key figure in the planning or construction of several world-lead ...

, lend their name to the " Hale-Nicholson law" concerning the magnetic polarity of sunspots.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, , 9780875904061, length 366 pages
page 51
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 Los Angeles ( ; es, Los Ángeles, link=no , ), often referred to by its initials L.A., is the largest city in the state of California and the second most populous city in the United States after New York City, as well as one of the wor ...

. His final resting place is in dispute, but he was cremated and his remains were likely dispersed by his son.

Awards and honors

* Awarded the

Bruce Medal The Catherine Wolfe Bruce Gold Medal is awarded every year by the Astronomical Society of the Pacific for outstanding lifetime contributions to astronomy. It is named after Catherine Wolfe Bruce, an American patroness of astronomy, and was f ...

(1963) * The asteroid

1831 Nicholson 1831 Nicholson, provisional designation , is a stony asteroid of the Baptistina family from the inner regions of the asteroid belt, approximately in diameter. It was discovered on 17 April 1968, by Swiss astronomer Paul Wild at the Zimmerwald ...

, the lunar crater

Nicholson Nicholson may refer to: People *Nicholson (name), a surname, and a list of people with the name Places Australia * Nicholson, Victoria * Nicholson, Queensland * Nicholson County, New South Wales * Nicholson River (disambiguation) * Nicholson Road ...

, the Martian crater

, and the feature Nicholson Regio on Ganymede were named after him.

References

External links

* * {{DEFAULTSORT:Nicholson, Seth Barnes 1891 births 1963 deaths 20th-century American astronomers Discoverers of asteroids Discoverers of moons Discoveries by Seth Nicholson People from Springfield, Illinois Scientists from Illinois

Awards and honors

See also

References

External links