Urbain Le Verrier

Urbain Le Verrier was a French mathematician and astronomer who predicted the existence and approximate position of the planet Neptune through mathematical analysis alone, before anyone had observed it. Working from small, unexplained irregularities in the observed orbit of Uranus, Le Verrier calculated in 1846 where an as yet unseen planet's gravity would have to be pulling to produce exactly those irregularities, sent his predicted position to the Berlin Observatory, and astronomer Johann Galle located the new planet within about one degree of Le Verrier's predicted position on the very night he looked, a celebrated triumph for Newtonian celestial mechanics. Le Verrier, who led the Paris Observatory for much of his career, also studied a puzzling, much smaller anomaly in the orbit of Mercury, its perihelion precessing slightly faster than Newtonian gravity could account for, and proposed the existence of another unseen planet, which he named Vulcan, to explain it; that planet was never found, and the anomaly was correctly explained only decades later by Einstein's general theory of relativity.