Ejnar Hertzsprung, a Danish chemist and astronomer, born on 8 October, 1873 (died 21 October 1967). He studied as a chemist, briefly worked as a chemist and volunteered his time at the Urania Observatory in Copenhagen. It was his interest in the theory of blackbody radiation and its relation to the radiation of stars that initially stimulated his interest in astronomy. In 1905 he published his first paper on astronomy, proposing a relationship between the spectrum and luminosity of stars. In 1906, Hertzsprung plotted the absolute magnitude of stars in relation to their luminosity, classification, and effective temperature. In a 1907 paper Hertzsprung referred to the open star clusters as a method for deriving the relation between the radiation of a star and its colour. Since the physical members of such a cluster would be of equal distance, or nearly so, their apparent magnitudes and colours should reveal this relation. He finally switched careers in 1909 and in 1910 he met with American astronomer Henry Norris Russell, who had reached very similar conclusions independently, and the two astronomers merged their results as the Hertzsprung-Russell (or H-R) diagram, published in 1913. This remains a cornerstone of modern astrophysics. Also in 1913 he determined the distances to several Cepheid variable stars by statistical parallax and was thus able to calibrate the relationship discovered by Henrietta Leavitt between Cepheid period and luminosity. One of the principal reasons why Hertzsprung was awarded the gold medal of the Royal Astronomical Society was his determination of the distance to the Small Magellanic Cloud in 1913. He discovered two asteroids, 1627 Ivar on 25 September, 1929 and 1702 Kalahari on 7 July 1924. Hertzsprung (crater) on the Moon and asteroid 1693 Hertzsprung were named after him. He spent 25 years at the Leiden Observatory, the last nine years as Director, and was among the last self-taught astronomers to oversee a major observatory. Reference: nndb/people/225/000169715/, Retrieved 19 April, 2012, encyclopedia/topic/Ejnar_Hertzsprung.aspx, Retrieved 19 April, 2012
Posted on: Wed, 08 Oct 2014 05:30:00 +0000
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