Shapley, Harlow (1885–1972)

US astronomer. He established that our Galaxy was much larger than previously thought. His work on the distribution of globular clusters showed that 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 Nashville, Missouri, and graduated from Laws Observatory, Columbia, Missouri, where he also gained an MA. He worked at Mount Wilson Observatory, California, 1914–21, and then moved to Harvard University, Cambridge, Massachusetts, where he was professor of astronomy and director of Harvard College Observatory 1921–52. Alleged by Senator Joseph McCarthy to be a communist 1950, 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 (binary stars in which the two stars periodically pass in front of each other as seen from Earth). 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.