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Marie-Henri Andoyer, who died on June 12, was one of the most distinguished French scientists. His work extended through all branches of mathematical astronomy, he constructed extensive tables of mathematical functions, and in his earlier years he was active as an observer at Toulouse Observatory. By steady and unremitting labour for the last forty-five years he accomplished much enduring work. Throughout most of this time he was a teacher who loved teaching, and his contributions to astronomy have been enhanced by several excellent textbooks. For twenty years he was a member of the Bureau des Longitudes and in 1911 he succeeded Radau as editor of the Connaissance des Temps, in which he played an important part in the development of astronomical ephemerides. It appeared that his work might finally be crowned by the directorship of the Paris Observatory, but this distinction he refused.
Andoyer was born in Paris on October 1, 1862. His early education was at the Lycée St. Louis, and from this school he went at the age of nineteen to the École Normale Supérieure. Here he specialized in pure mathematics, turning later towards celestial mechanics, in which subject he took his doctorate. For eight years from 1884 he was engaged in Toulouse, filling the dual role of teacher at the Faculty of Sciences and assistant at the observatory. During this period he dedicated himself to a marked degree to the manifold activities that characterize life. His theoretical research at this time concerned equations of celestial mechanics, the constancy of the semi-spheric planetary orbits, and the inequalities in the motion of the moon. Up to the time of his marriage he lived in a room allotted to him at the observatory. He was in charge of the astrographic work, prepared the list of reference stars, and took the first plates. He also made observations of the eclipses of the satellites of Jupiter and Saturn, and made various other miscellaneous observations.
In 1892 he was recalled to Paris to assist at the Sorbonne in the mathematical department and to give lectures on celestial mechanics and practical astronomy. In 1903 he was elected professor and, as already stated, he became director of the Connaissance des Temps in 1911
As is well known, the most exhaustive attempt to give a completely general algebraic theory of the motion of the moon was made by Delaunay. For practical purposes, it is known that a greater degree of numerical accuracy with less labour can be obtained by starting with a numerical value of the mean motion, such as had been done by Hansen and has since been done by Brown. Much of Andoyer's labour was concerned with verifying Delaunay's expressions. When at Toulouse, he had found some errors in Delaunay's work involving terms of the eighth and higher orders (e.g., mesin 2D). In his Recherches supplémentaires de Delaunay, he stated that beyond the seventh order, all the terms are inexact, although the initial terms are correct.
By using two methods that give results in agreement with each other and with Brown's theory, he was able to find many errors in Delaunay. He carried on this work until the end of his life, the last paper on the subject being published in 1928.
Another branch of celestial mechanics treated by Andoyer was the theory of intermediate orbits, following the lines of Gylden. In this problem, he dealt with cases of near commensurability, especially with reference to planets of the Hecuba type. In 1906, he wrote on the relative equilibrium of bodies and on periodic orbits near the positions of relative equilibrium
Andoyer was an excellent teacher who took great pains over his lectures, many of which he published for the use of students in general. His purely mathematical books include, besides numerous smaller works, Leçons sur la théorie des formes et la géométrie analytique supérieure. This book indicates his great skill in handling problems in analytical geometry, a subject on which he wrote a number of original papers. His Cours d'Astronomie, including volumes on theoretical and practical astronomy, has gone to several editions. A little book, Théorie de la Lune, giving all the inequalities in the three coordinates to the fourth order of small quantities, may be recommended to anyone wishing to read an introduction to the complexities of the moon's motion. His more recent work, Cours de mécanique céleste, in two volumes, may be described as an intermediary between the works of Tisserand and Poincaré. The aim is to provide a simple, yet complete, practical solution to the real problems of celestial dynamics. After dealing with the general problem of elliptic motion and its perturbations, he considered the special cases of the major planets, the moon, and the great satellites of Jupiter.
One would have thought that Andoyer would have found his time fully occupied by teaching, writing, direction of the Connaissance des Temps, and original research, but his unwearied spirit drove him to the apparently mechanical labour of computing tables of mathematical functions. Between 1911 and 1918, he published four large folio volumes: (1) Tables of Logarithms of Trigonometric Functions to 14 Decimals (1911); (2) Tables of the Natural Trigonometric Functions to 15 Decimals, three volumes (1915, 1916, 1918). He also made calculations for tables of addition and subtraction logarithms, and for tables of logarithms of numbers to a large number of decimals. For several years, he regularly devoted three hours daily to this work
Enough has been said to show that he was a man of boundless energy. Many British astronomers will have pleasant remembrances of his whole-hearted enthusiasm at the various meetings of the International Astronomical Union, of which he was a vice-president at the time of his death, having acted as president of the Commissions on Celestial Mechanics and Ephemerides. In the words of the president of the Academy of Sciences, of which he became a member in 1919: "D'une rare modestie, Andoyer masquait sous une bonhomie, un peu brusque, un cœur excellent, il sera vivement regretté parmi nous." We may add that his death will be deeply regretted in other countries besides his own.
He married when at Toulouse and had two sons and a daughter. The death of the eldest son, killed early in the war, was a heavy blow.
He was an Officer of the Legion of Honour
He was elected an Associate of the Society on November 13, 1914.
J. J
Andoyer was born in Paris on October 1, 1862. His early education was at the Lycée St. Louis, and from this school he went at the age of nineteen to the École Normale Supérieure. Here he specialized in pure mathematics, turning later towards celestial mechanics, in which subject he took his doctorate. For eight years from 1884 he was engaged in Toulouse, filling the dual role of teacher at the Faculty of Sciences and assistant at the observatory. During this period he dedicated himself to a marked degree to the manifold activities that characterize life. His theoretical research at this time concerned equations of celestial mechanics, the constancy of the semi-spheric planetary orbits, and the inequalities in the motion of the moon. Up to the time of his marriage he lived in a room allotted to him at the observatory. He was in charge of the astrographic work, prepared the list of reference stars, and took the first plates. He also made observations of the eclipses of the satellites of Jupiter and Saturn, and made various other miscellaneous observations.
In 1892 he was recalled to Paris to assist at the Sorbonne in the mathematical department and to give lectures on celestial mechanics and practical astronomy. In 1903 he was elected professor and, as already stated, he became director of the Connaissance des Temps in 1911
As is well known, the most exhaustive attempt to give a completely general algebraic theory of the motion of the moon was made by Delaunay. For practical purposes, it is known that a greater degree of numerical accuracy with less labour can be obtained by starting with a numerical value of the mean motion, such as had been done by Hansen and has since been done by Brown. Much of Andoyer's labour was concerned with verifying Delaunay's expressions. When at Toulouse, he had found some errors in Delaunay's work involving terms of the eighth and higher orders (e.g., mesin 2D). In his Recherches supplémentaires de Delaunay, he stated that beyond the seventh order, all the terms are inexact, although the initial terms are correct.
By using two methods that give results in agreement with each other and with Brown's theory, he was able to find many errors in Delaunay. He carried on this work until the end of his life, the last paper on the subject being published in 1928.
Another branch of celestial mechanics treated by Andoyer was the theory of intermediate orbits, following the lines of Gylden. In this problem, he dealt with cases of near commensurability, especially with reference to planets of the Hecuba type. In 1906, he wrote on the relative equilibrium of bodies and on periodic orbits near the positions of relative equilibrium
Andoyer was an excellent teacher who took great pains over his lectures, many of which he published for the use of students in general. His purely mathematical books include, besides numerous smaller works, Leçons sur la théorie des formes et la géométrie analytique supérieure. This book indicates his great skill in handling problems in analytical geometry, a subject on which he wrote a number of original papers. His Cours d'Astronomie, including volumes on theoretical and practical astronomy, has gone to several editions. A little book, Théorie de la Lune, giving all the inequalities in the three coordinates to the fourth order of small quantities, may be recommended to anyone wishing to read an introduction to the complexities of the moon's motion. His more recent work, Cours de mécanique céleste, in two volumes, may be described as an intermediary between the works of Tisserand and Poincaré. The aim is to provide a simple, yet complete, practical solution to the real problems of celestial dynamics. After dealing with the general problem of elliptic motion and its perturbations, he considered the special cases of the major planets, the moon, and the great satellites of Jupiter.
One would have thought that Andoyer would have found his time fully occupied by teaching, writing, direction of the Connaissance des Temps, and original research, but his unwearied spirit drove him to the apparently mechanical labour of computing tables of mathematical functions. Between 1911 and 1918, he published four large folio volumes: (1) Tables of Logarithms of Trigonometric Functions to 14 Decimals (1911); (2) Tables of the Natural Trigonometric Functions to 15 Decimals, three volumes (1915, 1916, 1918). He also made calculations for tables of addition and subtraction logarithms, and for tables of logarithms of numbers to a large number of decimals. For several years, he regularly devoted three hours daily to this work
Enough has been said to show that he was a man of boundless energy. Many British astronomers will have pleasant remembrances of his whole-hearted enthusiasm at the various meetings of the International Astronomical Union, of which he was a vice-president at the time of his death, having acted as president of the Commissions on Celestial Mechanics and Ephemerides. In the words of the president of the Academy of Sciences, of which he became a member in 1919: "D'une rare modestie, Andoyer masquait sous une bonhomie, un peu brusque, un cœur excellent, il sera vivement regretté parmi nous." We may add that his death will be deeply regretted in other countries besides his own.
He married when at Toulouse and had two sons and a daughter. The death of the eldest son, killed early in the war, was a heavy blow.
He was an Officer of the Legion of Honour
He was elected an Associate of the Society on November 13, 1914.
J. J
Marie Henri Andoyer's obituary appeared in Journal of the Royal Astronomical Society 90:4 (1930), 384-386.