Burrau, Carl Jensen

(b. Elsinore, Denmark, 29 July 1867; d. Gentofte, Denmark, 8 October 1944)

astronomy, actuatial mathematics.

Burrau studied mathematics at Corpenhagen University and was an assistant astronomer at the university observatory from 1893 to 1898. He subsequently worked as an actuary. From 1906 to 1912 he lectured at Copenhagen University on practical mathematics. In his researches as an astronomer and as an actuary he was a disciple of T.N. Thiele.

In 1892 the Royal Danish Academy, at Thiele’s suggestion, presented an astronomical prize problem concerning librations in the Problème restreint with two equal masses in circular movement round their common center of gravity. In his solution, Burrau was the first to point out that a series of periodic orbits, into which the third (massless) body moves, develops into a limiting orbit of ejection from (or collision with) one of the masses. It was a pioneer achievement, the first step taken in the systematic search for periodic orbits in the three-body problem that was later carried out by E. Strömgren and his pupils (in its early years, in collaboration with Burrau).

Burrau’s dissertation (1895) deals with the derivation of the constants of a measuring machine for photographic determination of star positions. He suggested a development of Bessel’s classic method and discussed previously proposed simplifications.

The “distance” from these studies to actuarial work is short. In an obituary, Kristensen, who audited Burrau’s lectures on practical mathematics, mentions “his ability to combine scientific points of view with instructions for using them in practice.” Burrau’ little book on actuarial mathematics, Forsikringsstatistikens Grundlag, which was originally written as a series of lectures and appeared in Danish, German, and Italian, is a similar attempt to use his mathematical knowledge in the domain in which he worked for most of his life. Later, he and B. Strömgren published a paper on dividing a frequency curve into its components.

BIBLIOGRAPHY

I. Original Works, Burrau’s writings include “Recherches numériques concernant des solutions périodiques d’un cas spécial du problème des trois corps,” in Astronomische Nachrichten, 135 (1894), 233–240; 136 (1894), 161–174; “Undersøgelser over Instrumentkonstanter ved Kjøbenhavns Universitets Astronomiske Observatoriums Maaleapparat for fotografiske Plader,” his dissertation, Univ. of Copenhagen (1895); a review of Darwin’ Periodic Orbits (1897), in Vierteljahrsschrift der Astronomischen Gesellschaft, 33 (1898), 21–33, containing information on the early development of the three-body problem; “Über einige in Aussicht genommene Berechnungen betreffend einen Spezialfall des Dreikörper-Problems,” ibid., 41 (1906), 261–26; and Forsikringsstatistikens Grundlag (Copenhagen, 1925), originally published in German in Wirtschaft und Recht der Versicherung, 56 (1924). Papers are in Publikationer og mindre Meddelelser fra københavns Observatorium (1913–1934).

II. Secondary Literature. Articels on Burrau are Dansk Biografisk Leksikon, IV (1934), 365–36; and S. Kristensen, in Skandinavisk Aktuarietidskrift, 28 (1945), 128–130.

Axel V. Nielsen