Hamy, Maurice Théodore Adolphe

(b. Boulogne-sur-Mer, France, 31 October 1861; d. Paris, France, 9 April 1936)

celestial mechanics, astronomy, optics.

Born into a Picard family, Hamy received his secondary education in the various cities where his father, an official in the postal service, was assigned. He came to Paris to prepare for his licence in science, which he obtained in 1884. Next he was a student astronomer at the Paris observatory, where he remained throughout his career, becoming astronomer in 1893 and chief astronomer in 1904. He retired in 1929.

A mathematician and physicist, Hamy did research in various areas of astronomy and in related fields. In celestial mechanics he studied the forms of heavenly bodies and demonstrated that their equipotential surfaces cannot be strictly ellipsoidal unless the ellipsoids are homofocal, a condition which cannot be met in the case of planets. The problem of planetary perturbations led him to consider the asymptotic value of coefficients of high degree. This in turn permitted Hamy to calculate certain long-term inequalities, such as those of the motion of Juno. Through this accomplishment he advanced the research on approximate values of functions of large numbers.

In instrumental astronomy Hamy devised several procedures for improving the determination of the constants of the meridian instrument. He also improved the technique of measuring radial velocities with the objective prism. In the course of his work in spectroscopy he made several important determinations on monochromatic radiations, notably on those of cadmium.

Hamy’s investigations probably of most interest today are those concerning the study of stellar and planetary diameters through interferometry. The use of wide slits, necessary for collecting sufficient light, posed difficult mathematical problems that he overcame. Thus he was able to use the method successfully on the satellites of Jupiter and on Vesta.

Although Hamy suffered until his death from an intestinal disease contracted in 1905 in Spain while observing an eclipse, his activity was considerable. He left more than 100 scientific publications. In 1908 he was elected to the Academy of Sciences and in 1916 to the Bureau of Longitudes, of which he became chairman in 1921.

BIBLIOGRAPHY

Almost all of Hamy’s works appeared in either Comptes rendus hebdomadaires des séances de l’Académie des sciencesor Bulletin astronmique between 1887 and 1928. The most important in mathematics and interferometry are “Étude sur la figure des corps célestes,” in Annales de l’Observatoire de Paris, 19 (1889), F1-F54, his doctoral dissertation; “Théorie générale de la figure des planètes,” in Journal de mathématiques pures et appliquées, 4th ser., 6 (1890), 69–143; “Mesures interférentielles des faibles diamètres,” in Bulletin astronomique, 10 (1893), 489–504, and 16 (1899), 257–274, also in Comptes rendus hebdomadaires des séances de l’Académie des sciences, 127 (1898), 851, 982 (errata); 128 (1899), 583; 174 (1922), 342, 904; 175 (1922), 1123; 176 (1923), 1849; “Développement approché de la fonction perturbatrice...’” in Journal de mathématiques pures et appliquées, 4th ser., 10 (1894), 391–472, and 5th ser., 2 (1896), 381–439; and “L’approximation des fonctions de grands nombres,” ibid., n.s. 4 (1908), 203–281.

There are two biographical notices by E. Picard: “Notice nécrologique,” in Comptes rendus hebdomadaires des séances de l’Académie des sciences, 202 (1936), 1317; and “La vie et l’oeuvre de Maurice Hamy,” in Annuaire publié par le Bureau des longitudes pour l’an 1943, A1–A15.

Jacques R. LÉvy