Shapley, Harlow

(born Nov. 2, 1885, Nashville, Mo., U.S.—died Oct. 20, 1972, Boulder, Colo.) U.S. astronomer. In 1911 he began a determination of the dimensions of the components of numerous binary stars from measurements of their light variation when they eclipse one another; he also proposed (correctly) that Cepheid variables are pulsating variable stars, not eclipsing binaries (see eclipsing variable star). In 1914 he joined the staff of Mount Wilson Observatory. His study of the distribution of globular clusters in the Milky Way Galaxy led him to deduce that the Sun, previously thought to lie near the centre of the Galaxy, was 50,000 light-years from the centre (now estimated at about 27,000), leading to the first realistic estimate of the Galaxy's size. Shapley also studied neighbouring galaxies, especially the Magellanic Clouds, and found that galaxies tend to occur in clusters.

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