Ludendorff, F. W. Hans

Ludendorff, F. W. Hans

(b. Thunow, near Koszalin, Germany, 26 May 1873; d. Potsdam, Germany, 26 June 1941)

astronomy.

Ludendorlf was the youngest son of Ludendorff, a farmer, and his wife, the former Clara von Tempelhof, a descendant of the old Prussian military family. After an elementary education at home from a tutor, Ludendorff’ attended the Falk Realgymnasium in Berlin, then he qualified for admission to the University of Berlin in 1892. He studied astronomy, mathematics, and physics and received the Ph.D. in 1897. His main teachers were Forster and Bauschinger. After a year at the Hamburg observatory under Rumcker, Ludendorff joined the astrophysical observatory at Potsdam in 1898 and remained there until his retirement in 1939. In 1905 he became observer, and in 1915, chief observer; in 1921-1939 he was director of the famous institute. Ludendorlf was elected a member of the Preussische Akademie der Wissenschaften at Berlin in 1921, a position that carried with it the title of professor and the right to lecture at the University of Berlin.

During his student years, at Hamburg, and early in his stay at Potsdam, Ludendorlf was active in both theoretical and measurement astronomy. In 1899 the Potsdam part of the Photographische Himmelskarte was completed. Ludendorlf assisted in this work and also in the evaluation of the plates until 1900. However, from 1901 to 1921 he worked only in spectrography, to some extent with Eberhard. After becoming director of the observatory, Ludendorff could no longer spend the nights observing and gave up that work. At the beginning of his spectroscopic studies Ludendorlf investigated the radial velocities of many stars. He later determined the orbits of spectroscopic binaries, calculated their masses, and regularly published catalogs of their orbital elements. Thus he found that the masses of the B stars are three times greater than the masses of the stars of classes A-K. He was also occupied with the statistics of spectroscopic binaries and classified helium stars. Attempting to treat the δ Cephei and ζ Geminorum variables as binaries, Ludendorff found in 1913 that they could not be double stars. Subsequently he investigated the relationship of these stars and of the planetary nebulae to the helium stars, problems which led him more and more to variable star investigations. Among Ludendorff’s spectroscopic work his measurements of radial velocities of the Ursa Major group, especially of star ε, should be mentioned.

The last two decades of Ludendorff’s life were devoted to the variable stars and to writing. In particular he investigated ∊ Aurigae, R Coronae Borealis, and such long-period variables as o Ceti (Mira). Here he did not carry out observations but did critical sifting. He also proposed a new classification of variable stars. With G. Eberhard and A. Kohlschutter he edited the Handbuch für Astrophysik, writing parts of volumes VI and VII. He also helped to revise some popular astronomy books.

From the time of a visit to Mexico to observe a solar eclipse in 1923—he observed the solar corona, photometering its spectrum—and to Bolivia, where he erected a branch observatory for the spectrographic Durchmusterung. of the southern sky in 1926, Ludendorff was interested in the astronomical knowledge of the older American civilizations, especially of the Mayans. He passionately investigated various Mayan inscriptions, relating them to conspicuous constellations long before the Christian era.

From 1933 to 1939 Ludendorlf was president of the Astronomische Gesellschaft and presided over three of its congresses. He was also a member of many scientific societies, including the Royal Astronomical Society,

Ludendorff was the youngest brother of General Erich Ludendorff, well-known for his service during World War 1 and later for his extremist political ideas, of which Hans never approved. Hans Ludendorff served for only a short time as military meteorologist, and though a lance-corporal, he sometimes dined with Hindenburg and his brother Erich. In 1907 Ludendorff married Käthe Schallehn; they had two sons and one daughter.

BIBLIOGRAPHY

Ludendorff’s writings include Die Jupiter-Störungen der kleinen Plane ten υon Hecuba-Typus (Berlin, 1896), his dissertation; “Untersuchungen über die Kopien des Gitters Gautier No. 42 und über Schichtverzerrungen auf photographische Platten,” in Publikationcn des Astrophysikalischen Obserυatoriums zu Potsdam, 49 , pt, 15 (1903); “Der grosse Sternhaufen im Hercules Messier 13 ,” ibid., 50 , pt. 15 (1905); “Der Veränderliche Stern R Coronae Borealis,” ibid, 57 , pt. 19 (1908); “Erweitertes System des Grossen Bären,” in Astronomische Nachrichten, 180 (1908), 183; “Verzeichn. d. Bahnelem, spektroskop. Dop-pelstene,” in Vierteljahrschrift der Astronomische Gesellschaff, 45-50, 62 (1910-1915, 1927); Über die Bezieh. d. veräschied. Klass. Veränderl. Sterne.” in Seeliger Festschrift (Berlin, 1924), pp. 89-93; “Radialgesch. v. ∊ Aurigae,” in Sitziungsberichte der Preussischen Akademie der Wissen-schaften zu Berlin (1924), 49-69; “Spektroskop. Untersuchungen Über d. Sonnenkorona,” ibid. (1925), 83-113; “über d. Abhängigkeit d. Form d. Sonnenkorona v. d. Sonnenfleckenhäufigkeit,” ibid. (1928), 185-214; 13 papers with the general title, “Untersuchungen zur Astronomie der Maya,” ibid. (1930-1937); and “über d, Lichtkurven d. Mira-Sterne,” ibid. (1932), 291-325.

In addition, Ludendort was editor of Handbuch der Astrophysik from 1920 to 1930.

A biography is P. Guthnik, “Hans Ludendorff,” in Viertel/ahrschrift der Astronomisclren Gesellschaft, 77 (1942).

H. Christ. Freiesleben