Today a pioneer in star classification in the history of astronomy is born.
Ejnar Hertzsprung (right) worked with German physicist Carl Schwarzschild (left) from 1909 until his death during World War I. Credit: Göttingen Observatory Photo, courtesy Hartmut Grosser/Public domain, via Wikimedia Commons
On October 8, 1873, Ejnar Hertzsprung was born near Copenhagen, Denmark. His father had studied astronomy and worked in finance, and Hertzsprung himself showed interest in astronomy and mathematics, but pursued a degree in chemical engineering. After graduating from the Polytechnic Institute in Copenhagen, he worked as a chemist in St. Petersburg, Russia, and studied photochemistry in Leipzig, Germany. Upon Hertzsprung’s return to Copenhagen in 1901 he began to take astronomy seriously, publishing papers in 1905 and 1907 disclosing his discovery of dwarf and giant sequences of stars. By 1909, he began working with the German physicist Karl Schwarzschild, first at the Göttingen Observatory and then at the Potsdam Observatory. When World War I meant that most of the observatory’s staff were away for military service – including Schwarzschild – Hertzsprung took charge of almost all the telescopes. His improvements in the technique of photographing double stars allowed extensive measurements and cataloguing. After the war and Schwarzschild’s death, Hertzsprung left Germany for Leiden University in the Netherlands; In 1935, he became director there, a position he held until his retirement in 1944. A pioneer in classification, Hertzsprung is best known for his role in the development of the Hertzsprung–Russell diagram, which charts stars by their size and color.
