US astronomer who established that the Galaxy was much larger than previously thought. The Sun was not at the centre of the Galaxy as then assumed, but two-thirds of the way out to the rim; globular clusters were arranged in a halo around the Galaxy.
Shapley was born in Missouri and studied at Laws Observatory. He worked at Mount Wilson Observatory, California, 1914-21, and was then appointed director of the Harvard College Observatory. Alleged by Senator Joseph McCarthy in 1950 to be a communist, he was interrogated by the House of Representatives Committee on Un-American Activities.
Shapley obtained nearly 10,000 measurements of the sizes of stars in order to analyse some 90 eclipsing binaries. He also showed that Cepheid variable stars were pulsating single stars, not double stars. He discovered many previously unknown Cepheid variables and devised a statistical procedure to establish the distance and luminosity of a Cepheid variable. Shapley's surveys recorded tens of thousands of galaxies in both hemispheres.