Østervold Observatory
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Østervold Observatory (or Copenhagen University Observatory; ) is a former
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( IAU code 035) in
Copenhagen Copenhagen ( ) is the capital and most populous city of Denmark, with a population of 1.4 million in the Urban area of Copenhagen, urban area. The city is situated on the islands of Zealand and Amager, separated from Malmö, Sweden, by the ...
, Denmark owned and operated by the
University of Copenhagen The University of Copenhagen (, KU) is a public university, public research university in Copenhagen, Copenhagen, Denmark. Founded in 1479, the University of Copenhagen is the second-oldest university in Scandinavia, after Uppsala University. ...
(Københavns Universitet). It opened in 1861 as a replacement for the university's old observatory at
Rundetårn The Round Tower () is a 17th-century tower in Copenhagen, Denmark, one of the many architectural projects of Christian IV. Built as an astronomical observatory, it is noted for its equestrian staircase, a 7.5-turn helical corridor leading to th ...
. The Østervold Observatory building house the ''Institute for Science Didactics'' of the University of Copenhagen.


History

The first astronomical observatory operated by the University of Copenhagen was
Rundetårn The Round Tower () is a 17th-century tower in Copenhagen, Denmark, one of the many architectural projects of Christian IV. Built as an astronomical observatory, it is noted for its equestrian staircase, a 7.5-turn helical corridor leading to th ...
. It had been inaugurated in 1642 as a replacement for
Tycho Brahe Tycho Brahe ( ; ; born Tyge Ottesen Brahe, ; 14 December 154624 October 1601), generally called Tycho for short, was a Danish astronomer of the Renaissance, known for his comprehensive and unprecedentedly accurate astronomical observations. He ...
's Stjerneborg, but during the early 19th century had become outdated as astronomical instruments grew bigger and bigger while the tower could not be expanded. In the same time,
light pollution Light pollution is the presence of any unwanted, inappropriate, or excessive artificial Visible spectrum, lighting. In a descriptive sense, the term ''light pollution'' refers to the effects of any poorly implemented lighting sources, during the ...
from the surrounding city as well as vibrations caused by the still increasing traffic in the streets below had made the observations inaccurate. In 1861 the observatory was moved to Østervold, where a new observatory was constructed on the old bastioned fortifications of the city, which had become outdated and were being abandoned. The well-known Russian-German astronomer, Heinrich Louis d'Arrest, who had been appointed professor in astronomy at the university in 1857, was chosen to plan the new observatory. He used the observatory for his study of
nebula A nebula (; or nebulas) is a distinct luminescent part of interstellar medium, which can consist of ionized, neutral, or molecular hydrogen and also cosmic dust. Nebulae are often star-forming regions, such as in the Pillars of Creation in ...
s, in 1867 publishing an
astronomical catalog An astronomical catalogue is a list or tabulation of astronomical objects, typically grouped together because they share a common type, Galaxy morphological classification, morphology, origin, means of detection, or method of discovery. The olde ...
ue of 1,942 nebulas with 4,900 positions. He also did significant work in
spectroscopy Spectroscopy is the field of study that measures and interprets electromagnetic spectra. In narrower contexts, spectroscopy is the precise study of color as generalized from visible light to all bands of the electromagnetic spectrum. Spectro ...
, and discovered, for the first time, the differences in the evolutionary state and spatial distribution of stars. While d'Arrest used the main telescope, observer H. C. F. C. Schjellerup used the Meridian circle for creating one of the most comprehensive astronomical catalogues of the time of stars of the 8th-9th
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: 10,000 positions on 259 observation nights. The next director of the Østervold Observatory was Thorvald N. Thiele, a skilful mathematician who developed a new method of determining the orbit of
Binary star A binary star or binary star system is a system of two stars that are gravitationally bound to and in orbit around each other. Binary stars in the night sky that are seen as a single object to the naked eye are often resolved as separate stars us ...
s. He founded the tradition for numerical computational mathematics, which has lasted up to modern times. In 1907, Elis Strömgren was appointed professor and director of the observatory, and under his direction the computational work continued. During
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, the
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, founded by Astronomische Gesellschaft in 1882, was moved from
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, Germany, to the Østervold Observatory. It remained located in Copenhagen until 1965, when it was moved to the
Smithsonian Astrophysical Observatory The Smithsonian Astrophysical Observatory (SAO) is a research institute of the Smithsonian Institution, concentrating on Astrophysics, astrophysical studies including Galactic astronomy, galactic and extragalactic astronomy, cosmology, Sun, solar ...
,
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, United States. In 1940 Ellis Strömgren was succeeded by his son Bengt Strömgren, who made the pioneering discovery that
hydrogen Hydrogen is a chemical element; it has chemical symbol, symbol H and atomic number 1. It is the lightest and abundance of the chemical elements, most abundant chemical element in the universe, constituting about 75% of all baryon, normal matter ...
is the most abundant element in the stellar interior. He was also the first to make the correct interpretation of the Hertzsprung–Russell diagram (the relation between the total energy output from a star and its surface temperature was independently found by the Danish chemist and astronomer Ejnar Hertzsprung and the American astronomer Henry Norris Russell). Around 1950, he developed the uvbyß photoelectric system, which is still in use today. In the 1950s, the Østervold Observatory was replaced by the Brorfelde Observatory located near the town of
Holbæk Holbæk () is a town in Denmark and the County seat, seat of Holbæk municipality with a population of 30,903 (1 January 2025).Schmidt telescope with a camera that used photographic film. It houses a 300 double reflector with a focal depth of 4.9m.


Building

The Østervold Observatory is a south-facing, three-winged building, designed by Christian Hansen. The central wing is topped by a
dome A dome () is an architectural element similar to the hollow upper half of a sphere. There is significant overlap with the term cupola, which may also refer to a dome or a structure on top of a dome. The precise definition of a dome has been a m ...
. containing the main instrument. The side wings contained residences for the director, the observer as well as assistants. To secure the best possible foundation of the instruments, the foundation of the building rests on the original, true ground surface, penetrating the entire depth of the ramparts on which the building stands. This took 1/3 of the bricks used for the entire complex. The Østervold Observatory building is no longer used for astronomy, but it was often used among ornithologists. The buildings house the I''nstitute for Science Didactics'' University of Copenhagen.https://web.astronomicalheritage.net/show-entity?identity=240&idsubentity=1


Instruments

The original main instrument of the observatory, housed in the dome, was a 280 mm refractor with a focal distance of 4.9 m. In 1895, this telescope was replaced by a 360 mm refractor with a focal length of 4.9 m and a 200 mm photographic lens with a focal length of 4.8 m. The purchase of the double refractor enabled the observatory to participate in photographic observations without having to give up visual observations. This double refractor is still found in the dome of the Østervold Observatory, while the 1861 refractor is displayed at the Steno Museum in
Ã…rhus Aarhus (, , ; officially spelled Ã…rhus from 1948 until 1 January 2011) is the second-largest city in Denmark and the seat of Aarhus municipality, Aarhus Municipality. It is located on the eastern shore of Jutland in the Kattegat sea and app ...
. c


Directors

1862-1875: Heinrich Louis d'Arrest
1875-1907: Thorvald N. Thiele
1907-1940: Elis Strömgren
1940–1951. Bengt Strömgren


See also

* Brorfelde Observatory *
List of astronomical observatories This is a partial list of astronomical observatories ordered by name, along with initial dates of operation (where an accurate date is available) and location. The list also includes a final year of operation for many observatories that are no lon ...
*
Rundetårn The Round Tower () is a 17th-century tower in Copenhagen, Denmark, one of the many architectural projects of Christian IV. Built as an astronomical observatory, it is noted for its equestrian staircase, a 7.5-turn helical corridor leading to th ...


References


External links


History of Copenhagen University Observatory
{{DEFAULTSORT:Ostervold Observatory 1861 establishments in Denmark Astronomical observatories in Denmark Buildings and structures in Copenhagen parks Historicist architecture in Copenhagen Minor-planet discovering observatories University and college astronomical observatories