US astronomer best known for his independent discovery of the Hertzsprung–Russell diagram.
The son of a Presbyterian minister, Russell was educated at Princeton, where he gained his PhD in 1899. After two years further study in Britain, Russell returned to Princeton, where he became professor of astronomy and director of the observatory from 1911 until his retirement in 1947.
In his classic paper The Spectrum Luminosity Diagram (1914) Russell plotted stellar brightness (absolute magnitude) against spectral type. The result, independently suggested by Ejnar Hertzsprung, is now known as the Hertzsprung–Russell diagram. Russell also suggested an evolutionary scheme in which hot giant stars become small cold dwarfs. Although this turned out to be too simple, the diagram itself has remained as the basis for an account of stellar evolution. In 1929 Russell made the first reliable estimates of the composition of the sun. Using solar spectra he argued that 60 per cent of the sun's volume was composed of hydrogen. Although now recognized as an underestimate, it was then such a surprisingly high figure that it posed a major challenge to cosmologists.
Subjects: Science and Mathematics.