EMILIO SEGRE VISUAL ARCHIVES / AMERICAN INSTITUTE OF PHYSICS / SCIENCE PHOTO LIBRARY EMILIO SEGRE VISUAL ARCHIVES / AMERICAN INSTITUTE OF PHYSICS / SCIENCE PHOTO LIBRARY
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Harlow Shapley (1885-1972), US astronomer (left), with the Danish astronomer Ejnar Hertzsprung (1873-1967). Both worked on Cepheid variable stars. Hertzsprung determined the distance to several of these stars, allowing him to calibrate the relationship between Cepheid period and luminosity. Shapely studied the distribution of Cepheid stars in globular clusters (huge spherical star clusters). From his work he was able to determine that the Milky Way was disc-shaped, that globular clusters were distributed around its centre both above and below the disc, and that the Sun was a considerable distance from the centre. Photographed at a meeting of the International Astronomical Union in Moscow, Russia.
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