Hertzsprung, Ejnar(ī`när hĕrts`spro͞ong), 1873–1967, Danish astronomer. Although trained as a chemical engineer, Hertzsprung made his career in astronomy, specializing in exacting photographic observations of stars. In 1905 he discovered high-luminosity, or giant, stars. In 1913 he calculated the distance to the Small Magellanic Cloud by a method still used for measuring galactic and intergalactic distances. His 1922 catalog of star colors and luminosities disclosed the absence of bright stars of intermediate color, called the Hertzsprung gap. Working independently, both Hertzsprung and the American astronomer H. N. Russell developed a graph in which the luminosity of a star is plotted against its surface temperature. Such a graph is now called a Hertzsprung-Russell diagramHertzsprung-Russell diagram
[for Ejnar Hertzsprung and H. N. Russell], graph showing the luminosity of a star as a function of its surface temperature. The luminosity, or absolute magnitude, increases upwards on the vertical axis; the temperature (or some temperature-dependent
..... Click the link for more information. and is the fundamental piece of observational evidence that the theory of stellar evolution must explain.
Born Oct. 8, 1873, in Frederiksberg, Denmark; died Oct. 21, 1967, in Tølløse, Denmark. Astronomer. Member of the Dutch and Danish academies of sciences and corresponding member of the Paris Academy of Science.
Hertzsprung, who was educated as a chemical engineer, was a professor of astronomy at Göttingen, Potsdam, and Leiden. From 1935 to 1945 he was director of the Leiden Observatory. He discovered (1905, 1907) the division of stars of spectral classes G, K, and M into “giants” and “dwarfs” and the existence of a relationship between the absolute magnitude and spectral class of stars. (Subsequently this relationship was examined in detail by the American astronomer H. Russell and was named the Hertzsprung-Russell diagram.) Hertzsprung applied photography for the first time (1914-19) to the study of binary stars.
REFERENCESPannekoek, A. Istoriia astronomii. Moscow, 1966. (Translated from English.)
Strand, K. “Ejnar Hertzsprung, 1873-1967.” Astronomical Society of the Pacific. Publications, 1968, vol. 80, no. 472, pp. 50-56.