Measurements of the Angular Diameters of Stars

Abstract

AFTER the successful measurement of Capella as a double star by Prof. A. Michelson's interferometer method applied to the 100-in. reflector at Mount Wilson, it was known that he intended to attempt the more difficult feat of measuring stellar diameters. The most hopeful stars to choose for the purpose are the giant red stars. Prof. Eddington made some estimates of their angular diameters in his inaugural address to Section A of the British Association last August (NATURE, September 2, 1920, p. 14). Taking the temperature and surface brightness derived from the distribution of energy in the spectrum, the angular diameter (which is independent of the assumed distance) is deducible from the apparent magnitude. The highest estimate for any star was that for Betelgeux, the value being 0.051″.