Henry Norris Russell, Director of the Princeton Observatory, was one of America's most distinguished astronomers. His grasp of all phases of astronomy was truly awesome. The son of a Presbyterian minister, he was a brilliant student at Princeton University, where he received his doctoral degree in 1899. Except for a brief period at Cambridge University in England, Russell spent 36 years of his career at Princeton.
Russell's greatest achievement was his publication in 1913 of the research leading to the Hertzsprung-Russell diagram. The work began in 1903 in collaboration with the British astronomer Hinks at Cambridge, where he undertook a program of deriving stellar parallaxes photographically. The work, which was completed in 1910, was instrumental in his discovery of a relationship between the absolute magnitudes and spectral types of stars. A plot of this relationship showed the existence of two types of red star: one highly luminous, the other quite faint. By 1913, Russell had refined this correlation, now known as the H-R diagram, and was using the terms giants and dwarfs to distinguish between the two groups. Russell proposed in 1913 a path for the evolution of stars from giants onto and down the main sequence to end their lives as cool M dwarfs. Although his theory of stellar evolution was subsequently shown to be wrong, the H-R diagram continues to provide an empirical basis for current theories of stellar evolution.
In the late 1920s, Russell applied the newly developed quantum theory to determining the abundances of elements in stars. From an analysis of the profiles of absorption lines, he derived the relative abundance of some 50 different elements in the solar atmosphere. He also applied this technique to a number of other stars. The research suggested a very high abundance of hydrogen in the Sun and stars, a result of great importance in our understanding of the structure and evolution of stars and in the evolution of chemical elements. Russell also made other important contributions to the theory of stellar structure. He showed that the physical properties of a star at each stage of its evolution can be found solely from its mass, chemical composition, and age (the Vogt-Russell theorem). It is most fitting that a memory to his contributions to astrophysics be perpetuated by the diagram which bears his name.