Pieter Oosterhoff
Encyclopedia
Pieter Theodorus Oosterhoff (30 March 1904, Leeuwarden - 14 March 1978, Leiden) was a Dutch
astronomer
.
He was the co-administrator, along with Jan Oort
, of the Leiden Observatory
in the Netherlands.
His published papers are primarily in regard to variable star
s and photometry
. He is most noted for his 1939 observation that there appear to be two populations of globular clusters based on the periodicities of their RR Lyrae variable
stars. These two populations would come to be known as Oosterhoff groups after him.
Between 1951 and 1952 he served as assistant general secretary of the International Astronomical Union
, and served as general secretary from 1952 until 1958. In 1954 he was one of twelve European astronomers who drafted a statement that would lead to the formation of the ESO
.
The asteroid
1738 Oosterhoff is named after him.
Netherlands
The Netherlands is a constituent country of the Kingdom of the Netherlands, located mainly in North-West Europe and with several islands in the Caribbean. Mainland Netherlands borders the North Sea to the north and west, Belgium to the south, and Germany to the east, and shares maritime borders...
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...
.
He was the co-administrator, along with Jan Oort
Jan Oort
Jan Hendrik Oort was a Dutch astronomer. He was a pioneer in the field of radio astronomy. The Oort cloud of comets bears his name....
, of the Leiden Observatory
Leiden Observatory
Leiden Observatory is an astronomical observatory in the city of Leiden, Netherlands. It was established by Leiden University in 1633, to house the quadrant of Snellius, and is the oldest operating University observatory in the world Leiden Observatory (Sterrewacht Leiden in Dutch) is an...
in the Netherlands.
His published papers are primarily in regard to variable star
Variable star
A star is classified as variable if its apparent magnitude as seen from Earth changes over time, whether the changes are due to variations in the star's actual luminosity, or to variations in the amount of the star's light that is blocked from reaching Earth...
s and photometry
Photometry (astronomy)
Photometry is a technique of astronomy concerned with measuring the flux, or intensity of an astronomical object's electromagnetic radiation...
. He is most noted for his 1939 observation that there appear to be two populations of globular clusters based on the periodicities of their RR Lyrae variable
RR Lyrae variable
RR Lyrae variables are periodic variable stars, commonly found in globular clusters, and often used as standard candles to measure galactic distances.This type of variable is named after the prototype, the variable star RR Lyrae in the constellation Lyra....
stars. These two populations would come to be known as Oosterhoff groups after him.
Between 1951 and 1952 he served as assistant general secretary of the 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...
, and served as general secretary from 1952 until 1958. In 1954 he was one of twelve European astronomers who drafted a statement that would lead to the formation of the ESO
European Southern Observatory
The European Southern Observatory is an intergovernmental research organisation for astronomy, supported by fifteen countries...
.
The asteroid
Asteroid
Asteroids are a class of small Solar System bodies in orbit around the Sun. They have also been called planetoids, especially the larger ones...
1738 Oosterhoff is named after him.