Gaillot, Aimable Jean-Baptiste

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Gaillot, Aimable Jean-Baptiste

(b. Saint-Jean-sur-Tourbe, Marne, France, 27 April 1834; d. Chartres, France, 4 June 1921)

astronomy, celestial mechanics.

Gaillot spent his entire career at the Bureau of Computation of the Paris observatory, to which he was assigned at the time of his recruitment by Urbain Le Verrier in 1861, and was director of the bureau from 1873. He became astronomer in 1864 and chief astronomer in 1874, and was made assistant director of the Paris observatory in 1897.

In astronomy Gaillot concentrated on the calculations that would make his colleagues’ observations most useful. He directed the publication of the Catalogue de l’Observatoire de Paris, which classified the 387, 474 meridian observations made between 1837 and 1881. Despite poor health Gaillot saw this twenty-year task to completion before retiring in 1903.

He continued his research in celestial mechanics until he was eighty. His important contributions in this field brought him four awards from the Academy of Sciences, of which he became a corresponding member in 1908.

Gaillot was Le Verrier’s only collaborator. The latter’s widow wrote to him in 1877: “I especially want to express my deep gratitude to the devoted and intelligent collaborator who enabled my beloved husband to complete his colossal project. It pleased him to recognize that without you, this would have been impossible”.

To complete Le Verrier’s work, Gaillot amended the latter’s analytical theories concerning Jupiter, Saturn, Uranus, and Neptune. By using a laborious but effective method of interpolation, he eliminated all discordance: his values for the mass of these planets turned out to be excellent and the positions he calculated were confirmed by observations to an accuracy of one or two seconds. Since their publication Gaillot’s tables have served as a basis for the international ephemerides found in Connaissance des temps.


In celestia; mechanics three broad mémoires covering all of Gaillot’s earlier research concern Le Verrier’s theories on the motion of the planets; two of them furnish, for Saturn and Jupiter, additions to these theories and also corrected tables—see Annales de l’Observatoire de Paris, 24 (1904), 1–512, and 31 (1913), 1–317; the third, concerning Uranus and Neptune, includes Le Verrier’s theory, which is considerably elaborated, and new tables: ibid., 28 (1910), 1–649. See also “Contribution à la recherche des planètes ultraneptuniennes”, in Comptes rendus hebdomadaires des séances de l’Académie des sciences, 148 (1909), 754–758; and “Le Verrier et son oeuvre”, in Bulletin des sciences mathématiques et astronomiques, 2 (1878), 29–40.

In fundamental astronomy, see “Influence de l’attraction luni-solaire sur la verticale, la pesanteur et la marche des pendules”, in Bulletin astronomique, 1 (1884), 113–118, 217–220; “Détermination géométrique des positions des circumpolaires”, ibid., 375–381, 577–583; “Sur la mesure du temps”, ibid., 3 (1886), 221–232; “Changements de la durée de l’année julienne . . .,” in Comptes rendus hebdomadaires des séances de l’Académie des sciences, 97 (1883), 151–154; “Sur les mesures du temps”, ibid., 544–546; “Détermination de la constante de la réfraction . . .,” ibid., 102 (1886), 200–204, 247–250; “Sur les variations de al latitude . . .,” ibid., 111 (1890), 559–561; 112 (1890), 651–563; and “Sur les formulas de l’aberration annuelle”, ibid., 116 (1893), 563–565. On the work on star catalogs, see “Discordances in d’Agelet’s Observations”, in Astronomical Journal, 16 (1896), 182–183; and, especially, the “Introduction” in Catalogue de l’Observatoire de Paris, I (Paris, 1887), (1)–(22).

For information about Gaillot, see B. Baillaud, “Notice nécrologique, A. Gaillot”, in Comptes rendus hebdomadaires des séances de l’Académie des sciences, 172 (1921), 1393–1394.

Jacques R. LÉvy