Souillart, Cyrille Joseph

Born Bruay-en-Artois (Pas-de-Calais), France 20 January 1828

Died Lille, France 9 May 1898

Cyrille Souillart was a professor of mechanics and astronomy at the University of Lille who had a lifelong interest in the theory of Jupiter’s satellites.

Souillart was of modest origin. His father was a primary school teacher. In 1851 he was accepted at Ecole Normale Supérieure, where Victor Puiseux’s lectures sparked his interest in celestial mechanics. He was a high school teacher from 1854 to 1874. Souillart defended a thesis entitled Analytical theory of Jupiter’s satellites at the University of Paris in 1865. In 1873 he was named professor of rational and applied mechanics and in 1887 full professor of astronomy, at the University of Lille, where he was a colleague of Joseph Boussinesq.

The theory of motion for Jupiter’s satellites was first developed by Pierre-Simon de Laplace in book eight of his Treatise of Celestial Mechanics. Laplace determined an approximate analytical solution for...