BornSaint-Jean-sur-Tourbe, Marne, France, 27 April 1834
DiedChartres, Eure-et-Loire, France, 4 June 1921
Aimable Gaillot specialized in celestial mechanics and eliminated notable residuals in the orbits of the jovian planets; his values for the masses of these planets were the most accurate ones then available. His parents were Jean Baptiste Gaillot and Marie Catherine Gillet.
Gaillot was recruited in 1861 by Urbain Le Verrier , director of the Paris Observatory. His career was spent entirely in the Service des calculs (Bureau of computation), of which he became the head in 1873. Gaillot remained devoted to Le Verrier, even after the latter’s forced resignation (1870). In this way, he was able to complete the revision of Le Verrier’s planetary theories and was active in several geodetic campaigns.
Gaillot was appointed astronome adjoint in 1868 and astronome titulaire in 1874. When Moritz Löewy was chosen as the new director of the Paris Observatory, he called upon Gaillot to be his deputy director, a position Gaillot held until his retirement in 1903.
Another of Gaillot’s important contributions was his compilation of nearly 400,000 meridian observations of stars (gathered between 1837 and 1881) into the eight-volume Catalogue de l’Observatoire de Paris (1887). He also served as editor of numerous volumes of the Annales de l’Observatoire de Paris, founded by Le Verrier.
Gaillot, however, was chiefly engaged in the refinement of the orbits of the planets. These were successively introduced into the Connaissance des temps (the French nautical almanac) after 1864. Originally, the orbits of Jupiter, Saturn, Uranus, and Neptune displayed residuals on the order of 10 arc-seconds. By a laborious procedure, Gaillot successively derived new orbital elements and masses for these planets, whose final results differed by at most a few arc seconds. For example, Gaillot reduced the discrepancies in Saturn’s mass from one part in a hundred to one part in a thousand, as compared with modern values. Gaillot completed this work in 1913 when he was almost 80 years old.