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Ejnar Hertzsprung (October 8, 1873, Copenhagen – October 21, 1967, Roskilde) was a Danish chemist and astronomer.

In the period 1911-1913 with Henry Norris Russell, he developed the Hertzsprung-Russell diagram.

In 1913 he determined the distances to several Galactic Cepheid stars by statistical 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. 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-Russel Diagram" was used for many years as a classification system to explain stellar types and evolution.

He discovered two asteroids, one of which is the Amor asteroid 1627 Ivar.

"Hertzsprung Russel Diagram"

[edit] Honors

Awards

• Gold Medal of the Royal Astronomical Society in 1929
• Bruce Medal in 1937.

Named for him

• Hertzsprung crater on the Moon.
• Asteroid 1693 Hertzsprung.

[edit] External links

• Bruce Medal page
• Awarding of Bruce Medal: PASP 49 (1937) 65
• Awarding of RAS gold medal: MNRAS 89 (1929) 404

[edit] Further reading

• "Sky & Telescope" magazine for January, 1968, Sky Publishing Corporation, Cambridge, MA.

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