Joseph Ashbrook (April 4, 1918 – August 4, 1980) was an American

astronomer An astronomer is a scientist in the field of astronomy who focuses on a specific question or field outside the scope of Earth. Astronomers observe astronomical objects, such as stars, planets, natural satellite, moons, comets and galaxy, galax ...

Biography

Ashbrook was born in

Philadelphia Philadelphia ( ), colloquially referred to as Philly, is the List of municipalities in Pennsylvania, most populous city in the U.S. state of Pennsylvania and the List of United States cities by population, sixth-most populous city in the Unit ...

Pennsylvania Pennsylvania, officially the Commonwealth of Pennsylvania, is a U.S. state, state spanning the Mid-Atlantic (United States), Mid-Atlantic, Northeastern United States, Northeastern, Appalachian, and Great Lakes region, Great Lakes regions o ...

. He received a doctorate from

Harvard University Harvard University is a Private university, private Ivy League research university in Cambridge, Massachusetts, United States. Founded in 1636 and named for its first benefactor, the History of the Puritans in North America, Puritan clergyma ...

in 1947 and taught at

Yale University Yale University is a Private university, private Ivy League research university in New Haven, Connecticut, United States. Founded in 1701, Yale is the List of Colonial Colleges, third-oldest institution of higher education in the United Stat ...

from 1946 to 1950, and at Harvard from 1950 to 1953. He started to work at ''

Sky and Telescope ''Sky & Telescope'' (''S&T'') is a monthly magazine covering all aspects of amateur and professional astronomy, including what to see in the sky tonight and new findings in astronomy. Other topics covered include: *observing guides for planets, ...

'' 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."Ashbrook, Joseph", by Leif L. Robinson, pp. 65-66 in ''The Biographical Dictionary of Astronomers'', eds. Thomas Hockey et al., Springer: New York, 2007, , . Ashbrook was one of the first to study

Cepheid variable A Cepheid variable () is a type of variable star that pulsates radially, varying in both diameter and temperature. It changes in brightness, with a well-defined stable period (typically 1–100 days) and amplitude. Cepheids are important cosmi ...

s as tools for establishing galactic distances. He was a longtime member of the

AAVSO The American Association of Variable Star Observers (AAVSO) is an international nonprofit organization. Founded in 1911, the organization focuses on coordinating, analyzing, publishing, and archiving variable star observations made largely by amat ...

. He went through old archives of observations from centuries past to determine a highly precise value for the

rotation period In astronomy, the rotation period or spin period of a celestial object (e.g., star, planet, moon, asteroid) has two definitions. The first one corresponds to the '' sidereal rotation period'' (or ''sidereal day''), i.e., the time that the objec ...

Mars Mars is the fourth planet from the Sun. It is also known as the "Red Planet", because of its orange-red appearance. Mars is a desert-like rocky planet with a tenuous carbon dioxide () atmosphere. At the average surface level the atmosph ...

—to within a few thousandths of a second. He co-discovered the periodic comet 47P/Ashbrook-Jackson in 1948.

Honors

* Member of the

American Astronomical Society The American Astronomical Society (AAS, sometimes spoken as "double-A-S") is an American society of professional astronomers and other interested individuals, headquartered in Washington, DC. The primary objective of the AAS is to promote the adv ...

and

International Astronomical Union The International Astronomical Union (IAU; , UAI) is an international non-governmental organization (INGO) with the objective of advancing astronomy in all aspects, including promoting astronomical research, outreach, education, and developmen ...

. * Crater Ashbrook on the

Moon The Moon is Earth's only natural satellite. It Orbit of the Moon, orbits around Earth at Lunar distance, an average distance of (; about 30 times Earth diameter, Earth's diameter). The Moon rotation, rotates, with a rotation period (lunar ...

named after him. * Minor planet

2157 Ashbrook Year 157 ( CLVII) was a common year starting on Friday of the Julian calendar. At the time, it was known as the Year of the Consulship of Civica and Aquillus (or, less frequently, year 910 ''Ab urbe condita''). The denomination 157 for this ye ...

named after him.

References

External links

Obituaries

* Journal of the American Association of Variable Star Observers 9 (1980) 43 * ''

'' 60 (1980) 281 1918 births 1980 deaths 20th-century American astronomers Harvard University alumni Yale University faculty Harvard University faculty {{US-astronomer-stub