SUNDMAN, KARL FRITHIOF

(b. Kaskö, Finland, 28 October 1873; d. Helsinki, Finland, 28 September 1949)

astronomy.

After studying at the University of Helsinki and the Pulkovo Observatory, Sundman was appointed assistant professor at Helsinki in 1902 and later, in 1907, associate professor. In 1918 he was made full professor and director of the Helsinki observatory, which positions he held until his retirement in 1941.

Sundman’s scientific work was devoted principally to problems of celestial mechanics, and his name is connected with two important achievements. First, he extended Laplace’s propositions concerning the convergence of the series in unperturbed elliptic motion to the perturbation problem. His second achievement concerned the fundamental problem of celestial mechanics, the so-called three-body problem, which he reported in two papers (1907,1909) and summarized, in 1912, in “Mé moire sur le problème des trois corps.” The method he used results in a general solution to the three-body problem because the series developments he derived of the coordinates of the three bodies represent the future motion even if the convergence of the series becomes slower with increasing time.

Sundman’s later papers include a description of a machine for the computation of planetary perturbations (1915), studies of the invariability of the axes of planetary orbits (1940), and numerical calculation of the motion of the sun and the moon at the time of the total solar eclipse on 9 July 1945 (1948).

Although Sundman’s main interest lay in theoretical astronomy, he promoted practical work at the Helsinki observatory. He also continued the work on the photographic star catalogue that had been initiated by his predecessor, A. Donner.

BIBLIOGRAPHY

I. Original Works. Sundman’s works include “Utvecklingarna af e och e² uti kedjebråk med alla partialtäljare lika med ett,” in Öfversikt af Finska Vetenskaps societetens förhandlingar, 38 (1896); “Om den personliga eqvationen vid ringmikrometerobservationer,” ibid,; “Über die Störungen der kleinen Planeten, speciel derjenigen, deren mittlere Bewegung annähernd das Doppelte Jupiters beträgt” (1901), Sundman’s dissertation: “Über eine direkte Herleitung der Gyldéné schen A- und B-Koeffizienten als Funktionen Von θ Transcendenten,” in Förhandlingar vid Nordiska naturforskare-och läkarmötet (1902); “Recherches sur le problème des trois corps,” in Finska Vetenskapssocietetens Acta, 34 (1907), 6; “Nouvelles Recherches sur le problème des trois corps,” ibid., 35 (1909), 9; “Om planeternas banor,” in Öfversikt af Finska Vetenskapssocietetens forhandlingar, 51C (1909), 3; and “Sur les singularités réelles dans le problème des trois corps,” in Comptes rendus du Congrès des mathematiciens scandinaves (1910).

See also “Mémoire sur le problème des trois corps,” in Acta Mathematica, 36 (1912); “Theorie der Planeten,” in Encyklopädie der mathematischen Wissenschaften, 6 (1915), 2; “Plan d’une machine destinée à donner les perturbations des planètes,” in Festskrift für A.S. Donner (1915); “Sur les conditions nécessaires et suffisantes pour la convergence du développement de la fonction perturbatrice dans le mouvement plan,” in Öfversikt af Finska Vetenskapssocietetens förhandlingar, 58A (1916), 24; “Observations de l’éclipse du soleil à Kumlinge le 21 août 1914,” ibid., 59A (1916), 1; “Étude d’un cliché pris avec le tube polaire de l’observatoire de Helsingfors,” ibid., 59A (1916), 5; “Om de astronomiska rörelseteorierna,” ibid, 61B (1919), 4; “Uber die Richtungslinien für fortgesetzte Untersuchungen in den Planet- und Trabant-theorien,” in Redog, f. 5 Skand, Matem, Kongr, 1922 (1923); “La gravitation universelle et sa vitesse de propagation,” in Festskrift till Ernst Lindelöf (1929); “Über die Bestimmung geradliniger Bahnen,” in Vierteljahrschrift der Astronomischen Gesellschaft, 70 (1935); “Démonstration nouvelle du théorème de Poisson sur l’invariabilité des grands axes,” in Festschrift für Elis Strömgren (1940) 263; and “The Motions of the Moon and the Sun at the Solar Eclipse of 1945, July 9th,” in L’activié de la Commission géodésique Baltique pendant les années 1944 – 47 (1948).

C. SchalÉn