Ejnar Hertzsprung

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Ejnar Hertzsprung (right) and Karl Schwarzschild

Ejnar Hertzsprung (born October 8, 1873 in Frederiksberg , † October 21, 1967 in Roskilde ) was a Danish astronomer . He is considered one of the pioneers of modern astrophysics ; he is one of the namesake of the Hertzsprung-Russell diagram and other objects.

Life

After studying chemistry in 1898, Hertzsprung worked in Saint Petersburg for several years . In 1901 he went to Leipzig to acquire basic knowledge of photochemistry from Wilhelm Ostwald . In 1902 he returned to Denmark and turned to his first astronomical studies, at the University of Copenhagen and at the private Urania observatory in Frederiksberg . In 1905 and 1907 he published classic articles "On the radiation of the stars" about his attempts to measure the luminosity of stars using their spectra.

Karl Schwarzschild became aware of the young talent and in 1909 gave him an extraordinary professorship at the University of Göttingen . Shortly thereafter, Schwarzschild switched to the Astrophysical Observatory in Potsdam as director and took Hertzsprung with him as an observer. Schwarzschild died in 1916; In addition, the research opportunities for a foreigner in Germany were increasingly limited during the First World War . In 1919, Hertzsprung moved to the Leiden University Observatory (Netherlands), where he was in charge from 1935 to 1944.

In the last year of the war, the now 71-year-old returned to Denmark. He lived in Tølløse (now Holbæk Kommune ), a few kilometers from the Brorfelde Observatory .

Work and meaning

With his research, Hertzsprung made important contributions to the development of modern astrophysics . As early as 1905 he defined the absolute brightness, a measure of the luminosity of a star . He also discovered that giant stars and dwarf stars can occur at stars with the same surface temperature , which is how he created a classification feature. In 1909 Hertzsprung worked on surface temperature-luminosity relationships. In order to answer the question of whether there are cold and hot luminous stars, he developed a temperature-luminosity diagram. In 1911, Hertzsprung discovered slight fluctuations in brightness in the Polar Star , which enabled him to assign it to the Delta Cepheids (stars with periodic changes in brightness).

In 1913 he succeeded in determining the first distance to Cepheids in the Small Magellanic Cloud . Along with the period-luminosity relation of Henrietta Swan Leavitt could as well be determined distances to more distant Cepheids in other galaxies for the first time. However, the calculated distance to the Small Magellanic Cloud of about 3,000 light years was incorrect. We now know that the Small Magellanic Cloud is about 70 times further away. Nevertheless, the determination of the distance at that time was an important astrophysical pioneering act.

Also in 1913 his temperature-luminosity diagram was revised and appropriately published by Henry Norris Russell ( Hertzsprung-Russell diagram , HRD). In 1915 Hertzsprung devoted himself to the double stars , for whose observation he developed a photographic precision method. Hertzsprung also discovered the asteroid (1702) Kalahari and the near-Earth Cupid asteroid (1627) Ivar , which he named after his deceased brother. He also found a relationship between mass and luminosity, which he formulated in 1919 in a general form for the main sequence stars of the HRD.

Since 1921 he was a foreign member of the Royal Netherlands Academy of Sciences (KNAW). In 1927 he was elected to the American Academy of Arts and Sciences , and in 1929 he was awarded the gold medal of the Royal Astronomical Society . In December 1938 he became a corresponding member of the Académie des Sciences in Paris. In 1941 he was accepted into the American Philosophical Society .

In his honor, an asteroid discovered in 1935 was named (1693) Hertzsprung . The Hertzsprung lunar crater is also named after him.

literature

  • Dieter B. Herrmann: Ejnar Hertzsprung. Star research pioneer , Springer, Berlin a. a. 1994. ISBN 3-540-57688-6 .

Individual evidence

  1. ↑ Danmarks natural og Lægevidenskabelige Library
  2. ^ Kraks Blå Bog 1957 .
  3. ↑ Ejnar Hertzsprung: "About the spatial distribution of variables of the δ Cephei type." Astronomical News , 196 p. 201-210 (1914). Online article .
  4. ↑ Simon Singh: Big Bang , dtv, 2007, p. 222.
  5. ^ Past Members: E. Hertzsprung. KNAW, accessed November 27, 2019 .
  6. ^ List of members since 1666: Letter H. Académie des sciences, accessed on November 27, 2019 (French).
  7. ↑ Member History: Ejnar Hertzsprung. American Philosophical Society, accessed September 29, 2018 .

Web links

personal data
SURNAME Hertzsprung, Ejnar
BRIEF DESCRIPTION Danish astronomer
DATE OF BIRTH October 8, 1873
PLACE OF BIRTH Frederiksberg
DATE OF DEATH October 21, 1967
Place of death Roskilde