Ejnar Hertzsprung

Ejnar Hertzsprung


Date of Birth
October 8, 1873
Date of Death
October 21, 1967

Ejnar Hertzsprung studied chemical engineering in Copenhagen, worked as a chemist in St. Petersburg, and studied photochemistry in Leipzig before returning to Denmark in 1901 to become an independent astronomer. In 1909 he was invited to Göttingen to work with Karl Schwarzschild, whom he accompanied to the Potsdam Astrophysical Observatory later that year. From 1919 to 1944 he worked at the Leiden Observatory in the Netherlands, the last nine years as director. He then retired to Denmark but continued measuring plates into his nineties. He is best known for his discovery that the variations in the widths of stellar lines discovered by Antonia Maury reveal that some stars (giants) are of much lower density than others (main sequence or “dwarfs”) and for publishing the first color-magnitude diagrams. He was the first to calibrate the period-luminosity relation for Cepheid variable stars and he used it to estimate the distance to the Small Magellanic Cloud. He also determined proper motions, colors, and magnitudes of thousands of stars in the Pleiades cluster, and he measured about a million photographic positions of binary stars.

Presentation of Bruce medal

Leuschner, A.O.PASP 49, 65-81 (1937).

Other awards

Royal Astronomical Society, Gold medal, 1929, presented by T.E.R. Phillips, MNRAS 89, 404-17 (1929).

Biographical materials

Andrews, A.D., “Ejnar Hertzsprung’s 90th Birthday,” Irish Astronomical Journal 6, 150-51 (1963).
Beckett, Elizabeth, Holly Bernitt, and Vishwa Chandra, “Ejnar Hertzsprung
Daugherty, Brian, Astronomy in Berlin
Herrmann, Dieter B., Ejnar Hertzsprung - Pionier der Sternforschung (Springer-Verlag, Berlin, NY, 1994). A shorter version appeared in Sterne 72, 1, 60-61 (1996).
Herrmann, Dieter B., Biographical Encyclopedia of Astronomers (Springer, NY, 2007), pp. 496-97.
Poulsen, Erling Rundetaarn Observatory
Strand, K. Aa., Dictionary of Scientific Biography 6, 350-53.
Urania Observatory, Denmark [in Danish].
van Helden, Albert, in K.v. Berkel, A.v. Helden, & L. Palm, eds., A History of Science in The Netherlands (Brill, Leiden, 1999), pp. 460-63.


Hellyer, B., Journ. British Astron. Ass. 83, 460-461 (1973).
Strand, K. Aa. PASP 80, 51-56 (1968).
Wesselink, A., QJRAS 9, 337-41 (1968).
Nielsen, Axel V., Sky & Telescope 35, 4-6 (1968).
Oosterhoff, P.Th., Astron. Nachr. 291, 85-87 (1969) [This is a German translation from Dutch].
More obituaries


AIP Center for History of Physics
Astronomes Amateurs du Luxembourg
Urania Observatory, Denmark

Named after him

Lunar crater Hertzsprung
Minor Planet #1693 Hertzsprung
The Hertzsprung-Russell Diagram (with H.N. Russell)


Papers, etc.

Many of Hertzsprung’s papers, and thousands of pages of original measurements, are at the U.S. Naval Observatory Library. Some papers are at the University of Aarhus and some at the Leiden University Library. The AIP Niels Bohr Library has 347 microfiche of correspondence in 6 languages. Includes 32-page guide. He is also mentioned in many oral history interviews there.

Other References: Historical

Andrews, A. D., “Ejnar Hertzsprung’s 90th Birthday,” Irish Astr. J. 6, 150 (1963).

Baneke, David, “Teach and Travel: Leiden Observatory and the Renaissance of Dutch Astronomy in the Interwar Years” Journal for the History of Astronomy 41, 167-98 (2010).

DeVorkin, D.H., “Steps Toward the Hertzsprung-Russell Diagram,” Physics Today 31, 3, 32-39 (1978).

DeVorkin, David, “Stellar Evolution and the Origin of the Hertzsprung-Russell Diagram,” in Astrophysics and Twentieth-Century Astronomy to 1950, Part A, O. Gingerich, ed. (Univ. of Cambridge Press, Cambridge, UK, 1984), pp. 90-108.

DeVorkin, David, Henry Norris Russell: Dean of American Astronomers (Princeton Univ. Press, Princeton, NJ, 2000).

Dyson, Frank Watson, “The Stars around the North Pole,” Royal Institution Library of Science: Astronomy, 239-242.

Fernie, J.D., “The Period-Luminosity Relation: A Historical Review,” PASP 81, 707-731 (1969).

Hearnshaw, J. B., The Analysis of Starlight (Cambridge University Press, Cambridge, UK, 1986).

Hearnshaw, J. B., The Measurement of Starlight (Cambridge University Press, Cambridge, UK, 1996).

Herrmann, Dieter B., “Ejnar Hertzsprung - ein ‘Tycho’ des 20. Jahrhunderts?” in Bericht ueber das Treffen des Arbeitskreises Astronomiegeschichte 1994.

Hertszprung, Ejnar, “Karl Schwarzschild,” Ap.J. 45, 285-92 (1917).

Hertzsprung-Kapteyn, H., The Life and Works of J.C. Kapteyn (Kluwer, Norwell, MA, 1994). [translation by E.R. Paul of book written by Hertzsprung’s wife, who was Kapteyn’s daughter, in 1928].

Nielsen, Axel V., “Contributions to the History of the Hertzsprung-Russell Diagram,” Centaurus 9, 219-253 (1963).

Sitterly, Bancroft W., “Changing Interpretations of the Hertzsprung-Russell Diagram, 1910-1940: A Historical Note,” Vistas in Astronomy 12, 357-366 (1970).

Strand, K. Aa, “Ejnar Hertzsprung and the Leiden Observatory,” Popular Astronomy 55, 361 (1947).

Waterfield, R.L., “The Story of the Hertzsprung-Russell Diagram,” J. Brit. Astron. Assoc., 67, 1-24 (1956).

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Other References: Scientific

Hertszprung, Ejnar, “Vergleich einiger spektralphtometrischen Resultate,” Physikalische Zeitschrift 5, 34 (1904).

Hertszprung, Ejnar, “Zur Strahlung der Hefnerlampe,” Physikalische Zeitschrift 5, 634-35 (1904).

Hertszprung, Ejnar, “Zur Strahlung der Stern,” Zeitschrift für wissenschaftliche Photographie 3, 429-442 (1905). [The discovery, from the spectra, that some stars are giants and others dwarfs. A translation, with commentary, appears in Lang, Kenneth R. & Owen Gingerich, eds., A Source Book in Astronomy & Astrophysics, 1900-1975 (Harvard Univ. Press, Cambridge, MA, 1979), pp. 208-11.

Hertszprung, Ejnar, “Zur Strahlung der Sterne,” Zeitschrift für wissenschaftliche Photographie 5, 89 (1907).

Hertszprung, Ejnar, “Zur Bestimmung der photographischen Sterngröße,” Astr. Nach. 176, 49-60 (1907).

Hertszprung, Ejnar, “Über die Sterne der Unterabteilungen c und ac nach der Spektralklassifikation von Antonia C. Maury,” Astr. Nach. 179, 373-80 (1909).

Hertzsprung, Ejnar, “On new members of the system of the stars β, γ, δ, ε, ζ Ursae Majoris,” Ap.J. 30, 135-43 (1909).

Hertszprung, Ejnar, “On New Members of the System of the Stars β, γ, δ, ε, ζ Ursae Majoris,” Ap.J. 30, 135-43 (1909).

Hertszprung, Ejnar, “Über die Verwendung photographischer effektiver Wellenlaengen zur Bestimmung von Farbenaequivalenten,” Publikationen des Astrophysikalischen Observatoriums zu Potsdam 22, 1 (1911).

Hertszprung, Ejnar, Über die rümliche Verteilung der Veränderlichen vom δ Cephei-Typus,” Astr. Nach. 196, 201-08 (1913).

Hertszprung, Ejnar, “Effective Wavelengths of 184 Stars in the Cluster N.G.C. 1647,” Ap.J. 42, 92-110 (1915).

Hertszprung, Ejnar, “Effective Wavelengths of Absolutely Faint Stars,” Ap.J. 42, 111-19 (1915).

Hertszprung, Ejnar, “Bemerkungen zur Spektralklassifikation der gelben Sterne,” Astronomische Nachrichten, 208, 265-72 (1919).

Hertszprung, Ejnar, “On the Motion of the Magellanic Clouds,” MNRAS 80, 782-84 (1920).

Hertszprung, Ejnar, “Effective Wave-lengths of 129 Stars within 0°.5 of the North Pole and of the Σ Companion of Polaris.,” Ap.J. 55, 370-79 (1922).

Hertszprung, Ejnar, “List of Stars Nearer than 5 Parsecs,” Bulletin of the Astronomical Institutes of the Netherlands 1, 21-22 (1922).

Hertszprung, Ejnar, “Remark on the Relation between Colour, Proper Motion and Apparent Magnitudes of the Stars,” Bulletin of the Astronomical Institutes of the Netherlands 1, 91-92 (1922).

Hertszprung, Ejnar, “On the Motions of Praesepe and of the Hyades,” Bulletin of the Astronomical Institutes of the Netherlands 1, 150-51 (1922).

Hertszprung, Ejnar, “On the Relation between Period and Form of the Light-curve of Variable Stars of the δ Cephei Type,” Bulletin of the Astronomical Institutes of the Netherlands 3, 115-20 (1926).

Hertszprung, Ejnar, “Observation of a Maximum of EP Carinae,” Bulletin of the Astronomical Institutes of the Netherlands 4, 172 (1928).

Hertszprung, Ejnar, “Provisional Elements of FS Carinae,” Bulletin of the Astronomical Institutes of the Netherlands 4, 175-76 (1928).

Hertszprung, Ejnar, “On the character of the variation of SX Aurigae,” Bulletin of the Astronomical Institutes of the Netherlands 4, 178-80 (1928).

Hertszprung, Ejnar, “The Pleiades,” Observatory 52, 226-31 (1929) [George Darwin Lecture].

Hertszprung, Ejnar, “On the Orbital Motion to be Expected in Double Stars of Given Magnitude Separation and Proper Motion,” Bulletin of the Astronomical Institutes of the Netherlands 6, 57-58 (1930).

Hertszprung, Ejnar, “Discussion on Personal Errors in Photographic Measures of Double Stars,” Bulletin of the Astronomical Institutes of the Netherlands 9, 253-57 (1942).

Hertszprung, Ejnar, “On the Point of Convergence of the Hyades,” Bulletin of the Astronomical Institutes of the Netherlands 9, 283-84 (1942).

Hertszprung, E., “Catalogue de 3259 Etoiles dans les Pleiades,” Ann. Sternw. Leiden 19, 1-89 (1947).

Hertzsprung, Ejnar, “Note on the Diameters of Photovisual Star Images,” Vistas in Astronomy 2, 1123-24 (1956).

Hertszprung, E., “Mouvement relatif linéaire d’étoiles doubles,” Journal des Observateurs 47, 27-30 (1964).

Hertszprung, E., “Sur la luminosité de masse des composantes d’une étoile double,” Journal des Observateurs 47, 31-33 (1964).

Hertszprung, Ejnar, Zur Strahlung der Sterne. Drei Arbeiten von Ejnar Hertzsprung (Akademie Verlags-Gesellschaft, Leipzig, 1976) [contains Herrmann, D. B., Ejnar Hertzsprung, Leben und Werk; Hertzsprung, E., Zur Strahlung der Sterne (I); Hertzsprung, E., Zur Strahlung der Sterne (II); Hertzsprung, E., Über die Sterne der Unterabteilungen c und ac nach der Spektralklassifikation von Antonia C. Maury.]

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Other Works: Popularizations, Fiction, etc.

Hertszprung, Ejnar, “On Collaboration in Astronomy,” PASP 49, 309-16 (1937) [address on receiving the Bruce medal].