Ejnar Hertzsprung

Ejnar Hertzsprung (Danish: [ˈɑjnɐ ˈhɛɐ̯tsˌpʁɔŋ]; 8 October 1873 – 21 October 1967) was a Danish chemist and astronomer born in Copenhagen. In the period 1911–1913, together with Henry Norris Russell, he developed the Hertzsprung–Russell diagram.

Ejnar Hertzsprung
Hertzsprung (right) and Karl Schwarzschild in front of the Göttingen Observatory building (1909)
Born(1873-10-08)8 October 1873
Copenhagen, Denmark
Died21 October 1967(1967-10-21) (aged 94)
Roskilde, Denmark
Alma materCopenhagen Polytechnic (DTU)
Known forHertzsprung–Russell diagram
AwardsBruce Medal 1937
Scientific career
FieldsChemistry, Astronomy
InstitutionsLeiden Observatory

In 1913 he determined the distances to several Cepheid variable stars by parallax,[1] and was thus able to calibrate the relationship, discovered by Henrietta Leavitt, between Cepheid period and luminosity. In this determination he made a mistake, possibly a slip of the pen, putting the stars 10 times too close. He used this relationship to estimate the distance to the Small Magellanic Cloud. From 1919 to 1946, Hertzsprung worked at Leiden Observatory in the Netherlands, from 1937 as director. Among his graduate students at Leiden was Gerard Kuiper.

Perhaps his greatest contribution to astronomy was the development of a classification system for stars to divide them by spectral type, stage in their development, and luminosity. He used the earlier classification system developed by Antonia Maury in his work.[2] The so-called "Hertzsprung–Russell Diagram" has been used ever since as a classification system to explain stellar types and stellar evolution. He also discovered two asteroids, one of which is 1627 Ivar, an Amor asteroid.[3]

His wife Henrietta (1881–1956) was a daughter of the Dutch astronomer Jacobus Kapteyn. Hertzsprung died in Roskilde in 1967. The asteroid 1693 Hertzsprung was named in his honour.[4]

Asteroids discovered
  • 1627 Ivar (25 September 1929)
  • 1702 Kalahari (7 July 1924)

Honors
Awards
Named after him

Sources
  • Sky & Telescope, January, 1968, Sky Publishing Corporation, Cambridge

References
  1. Hertzsprung, E. (1913). "Über die räumliche Verteilung der Veränderlichen vom δ Cephei-Typus" [On the spatial distribution of variable [stars] of the δ Cephei type]. Astronomische Nachrichten (in German). 196 (4692): 201–208. Bibcode:1913AN....196..201H.
  2. Hoffleit, D. "Reminiscences on Antonia Maury and the c-Characteristic." The MK Process at 50 Years: A Powerful Tool for Astrophysical Insight. Vol. 60. 1994.
  3. Schmadel, Lutz D. (2003). "(1627) Ivar". Dictionary of Minor Planet Names – (1627) Ivar. Springer Berlin Heidelberg. p. 129. doi:10.1007/978-3-540-29925-7_1628. ISBN 978-3-540-29925-7.
  4. Schmadel, Lutz D. (2003). "(1693) Hertzsprung". Dictionary of Minor Planet Names – (1693) Hertzsprung. Springer Berlin Heidelberg. p. 135. doi:10.1007/978-3-540-29925-7_1694. ISBN 978-3-540-29925-7.

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