8 October 1873|
|Died||21 October 1967
|Alma mater||Copenhagen Polytechnic|
|Known for||Hertzsprung–Russell diagram|
|Notable awards||Bruce Medal 1937|
Ejnar Hertzsprung (Danish pronunciation: [ɑjnɐ ˈhæɐ̯d̥sb̥ʁɔŋ], 8 October 1873 – 21 October 1967) was a Danish chemist and astronomer, born in Copenhagen, Denmark. In the period 1911–1913, together with Henry Norris Russell, he developed the Hertzsprung–Russell diagram.
In 1913 he determined the distances to several Cepheid variable stars by statistical[clarification needed] parallax, 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. 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.
Named after him
- Sky & Telescope, January, 1968, Sky Publishing Corporation, Cambridge
- Hertzsprung, E., "Über die räumliche Verteilung der Veränderlichen vom δ Cephei-Typus." Astronomischen Nachrichten, 196 p. 201–210 (1913)
- Schmadel, Lutz D. (2003). Dictionary of Minor Planet Names – (1627) Ivar. Springer Berlin Heidelberg. p. 129. ISBN 978-3-540-29925-7. Retrieved November 2015.
- Schmadel, Lutz D. (2003). Dictionary of Minor Planet Names – (1693) Hertzsprung. Springer Berlin Heidelberg. p. 135. ISBN 978-3-540-29925-7. Retrieved November 2015.
- Bruce Medal page
- Awarding of Bruce Medal: PASP 49 (1937) 65
- Awarding of RAS gold medal: MNRAS 89 (1929) 404
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