In 1905, Danish astronomer Ejnar Hertzsprung (1873-1967) became the first to suggest an absolute standard of brightness for stars ("absolute magnitude"). He defined it as the magnitude of a star as seen from a distance of ten parsecs (32.6 light-years). A year later, he published a paper in which he compared the absolute magnitudes of stars in the Pleiades with their colors and spectral types, plotting them on a graph and noting the relationship between the two, as well as the existence of bright "giants" and dim "dwarfs." However, Hertzsprung published his work in an obscure German photographic journal, and it went unnoticed until 1913, when the American Henry Russell (1877-1957) presented his own work, independently developed, to the Royal HENRY RUSSELL Astronomical Society.
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