Joseph Ashbrook
Encyclopedia
Joseph Ashbrook was an American
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 astronomer
Astronomer
An astronomer is a scientist who studies celestial bodies such as planets, stars and galaxies.Historically, astronomy was more concerned with the classification and description of phenomena in the sky, while astrophysics attempted to explain these phenomena and the differences between them using...

.

Life

Ashbrook was born in Philadelphia
Philadelphia, Pennsylvania
Philadelphia is the largest city in the Commonwealth of Pennsylvania and the county seat of Philadelphia County, with which it is coterminous. The city is located in the Northeastern United States along the Delaware and Schuylkill rivers. It is the fifth-most-populous city in the United States,...

, Pennsylvania
Pennsylvania
The Commonwealth of Pennsylvania is a U.S. state that is located in the Northeastern and Mid-Atlantic regions of the United States. The state borders Delaware and Maryland to the south, West Virginia to the southwest, Ohio to the west, New York and Ontario, Canada, to the north, and New Jersey to...

. He received a doctorate from Harvard University
Harvard University
Harvard University is a private Ivy League university located in Cambridge, Massachusetts, United States, established in 1636 by the Massachusetts legislature. Harvard is the oldest institution of higher learning in the United States and the first corporation chartered in the country...

 in 1947 and taught at Yale University
Yale University
Yale University is a private, Ivy League university located in New Haven, Connecticut, United States. Founded in 1701 in the Colony of Connecticut, the university is the third-oldest institution of higher education in the United States...

 from 1946 to 1950, and at Harvard from 1950 to 1953. He started to work at Sky and Telescope in 1953, where he wrote the column "Astronomical Scrapbook" from 1954 to 1980, and remained on its staff until his death; he also edited the magazine from 1964 on.

Work

Ashbrook was one of the first to study Cepheid variable
Cepheid variable
A Cepheid is a member of a class of very luminous variable stars. The strong direct relationship between a Cepheid variable's luminosity and pulsation period, secures for Cepheids their status as important standard candles for establishing the Galactic and extragalactic distance scales.Cepheid...

s as tools for establishing galactic distances. He was a longtime member of the AAVSO
American Association of Variable Star Observers
Since its founding in 1911, the American Association of Variable Star Observers has coordinated, collected, evaluated, analyzed, published, and archived variable star observations made largely by amateur astronomers and makes the records available to professional astronomers, researchers, and...

.

He went through old archives of observations from centuries past to determine a highly precise value for the rotation period
Rotation period
The rotation period of an astronomical object is the time it takes to complete one revolution around its axis of rotation relative to the background stars...

 of Mars
Mars
Mars is the fourth planet from the Sun in the Solar System. The planet is named after the Roman god of war, Mars. It is often described as the "Red Planet", as the iron oxide prevalent on its surface gives it a reddish appearance...

 —to within a few thousandths of a second.

He co-discovered the periodic comet 47P/Ashbrook-Jackson
47P/Ashbrook-Jackson
47P/Ashbrook–Jackson is a periodic comet in our solar system.The comet nucleus is estimated to be 5.6 kilometers in diameter.- History :Comet 47P/Ashbrook–Jackson was discovered by American and South African scientists in 1948.- Name :...

 in 1956.

Honors

  • Member of the American Astronomical Society
    American Astronomical Society
    The American Astronomical Society is an American society of professional astronomers and other interested individuals, headquartered in Washington, DC...

     and International Astronomical Union
    International Astronomical Union
    The International Astronomical Union IAU is a collection of professional astronomers, at the Ph.D. level and beyond, active in professional research and education in astronomy...

    .
  • Crater Ashbrook
    Ashbrook (crater)
    Ashbrook is a large lunar impact crater that is located in the vicinity of the south pole on the far side of the Moon, and so cannot be viewed directly from the Earth. The eastern face of the crater has been overlain by the similar-sized Drygalski, and more than half the interior floor of Ashbrook...

     on the Moon
    Moon
    The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...

     named after him.
  • Minor planet 2157 Ashbrook
    2157 Ashbrook
    2157 Ashbrook is a main-belt asteroid discovered on March 7, 1924 by K. Reinmuth at Heidelberg.- External links :*...

     named after him.

Obituaries

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