Americanastronomer. With Philip Childs Keenan (1908–2000) he developed the Morgan–Keenan classification of stellar spectra, set out in An Atlas of Stellar Spectra (1943). Morgan and Keenan devised a series of standard spectra against which a star's spectrum may be identified by visual comparison to yield its mass and luminosity (and hence distance). In 1951, Morgan inferred the spiral structure of the Galaxy from the distribution of O- and B-type stars near the galactic equator. In 1953 he helped to originate the system of UBV photometry by which a star's colour index may be determined (see Johnson Photometry). He also developed classification systems for galaxies and clusters of galaxies (see Morgan's Classification; Bautz–Morgan class).
Subjects: Astronomy and Astrophysics.