Ejnar Hertzsprung

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.
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