Alfred Harrison Joy (September 23, 1882 in

Greenville, Illinois : Greenville is a city in Bond County, Illinois, United States, east of St. Louis. The population as of the 2020 census was 7,083, up from 7,000 at the 2010 census. It is the county seat of Bond County. Greenville is part of the St. Louis M ...

– April 18, 1973 in

Pasadena, California Pasadena ( ) is a city in Los Angeles County, California, northeast of downtown Los Angeles. It is the most populous city and the primary cultural center of the San Gabriel Valley. Old Pasadena is the city's original commercial district. I ...

) was an

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, natural satellite, moons, comets and galaxy, g ...

best known for his work on stellar distances, the radial motion of stars, and variable stars. A crater on the moon has been named in his honor.

Early years

He was born in

, the son of F.P. Joy, a prominent clothing merchant in Greenville and one-time mayor of the town.Allan H. Keith
''Historical Stories: About Greenville and Bond County, IL''
Consulted on August 15, 2007. He received a BA from Greenville College in 1903 and an MA from

Oberlin College Oberlin College is a Private university, private Liberal arts colleges in the United States, liberal arts college and conservatory of music in Oberlin, Ohio. It is the oldest Mixed-sex education, coeducational liberal arts college in the United S ...

the next year.

Career

After graduating, Joy went on to work at the

American University of Beirut The American University of Beirut (AUB) ( ar, الجامعة الأميركية في بيروت) is a private, non-sectarian, and independent university chartered in New York with its campus in Beirut, Lebanon. AUB is governed by a private, aut ...

in the Syrian Protestant College as a professor of astronomy and the director of the observatory. He was forced to return to the U.S. in 1915 because of

World War I World War I (28 July 1914 11 November 1918), often abbreviated as WWI, was one of the deadliest global conflicts in history. Belligerents included much of Europe, the Russian Empire, the United States, and the Ottoman Empire, with fightin ...

. In the United States, he worked at the

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 observat ...

from 1915 to 1952. There, he and his colleagues ascertained the

spectral type In astronomy, stellar classification is the classification of stars based on their stellar spectrum, spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a Prism (optics), prism or diffraction grati ...

absolute magnitude Absolute magnitude () is a measure of the luminosity of a celestial object on an inverse Logarithmic scale, logarithmic Magnitude (astronomy), astronomical magnitude scale. An object's absolute magnitude is defined to be equal to the apparent mag ...

, and stellar distance of over 5,000 stars. Joy also initially defined the T-Tauri type star. He studied the Doppler displacement of the spectral lines of stars to determine their radial velocities deducing a star's absolute dimensions, masses, and the orbital elements of some specific stars. He won 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 fi ...

in 1950. He was president of the Astronomical Society of the Pacific in 1931 and 1939.

References

External links

Bruce Medal biographyknn

Smithsonian/NASA Astrophysics Data System (ADS) obituaryNational Academy of Sciences Biographical Memoir
{{DEFAULTSORT:Joy, Alfred Harrison 1882 births 1973 deaths American astronomers American University of Beirut People from Greenville, Illinois Greenville College people