Early years Urbain Le Verrier was born at
Saint-Lô, Manche, France, to a modest bourgeois family, his parents being Louis-Baptiste Le Verrier and Marie-Jeanne-Josephine-Pauline de Baudre. He studied at the
École Polytechnique – briefly chemistry, under
Gay-Lussac, writing papers on the combinations of phosphorus and hydrogen, and of phosphorus and oxygen. In 1846 Le Verrier became a member of the
French Academy of Sciences, and in 1855 was elected a foreign member of the
Royal Swedish Academy of Sciences. His name is one of the
72 inscribed on the Eiffel Tower.
Career Early work Le Verrier's first work in astronomy was presented to the
Académie des Sciences in September 1839, entitled
Sur les variations séculaires des orbites des planètes (
On the Secular Variations of the Orbits of the Planets). This work addressed the then most-important question in astronomy: the
stability of the Solar System, first investigated by
Laplace. He was able to derive some important limits on the motions of the system, but due to the inaccurately-known masses of the planets, his results were tentative. From 1844 to 1847, Le Verrier published a series of works on periodic
comets, in particular those of
Lexell,
Faye and
DeVico. He was able to show some interesting interactions with the planet
Jupiter, proving that certain comets were actually the reappearance of previously-known comets flung into different orbits.
Discovery of Neptune Le Verrier's most famous achievement is his prediction of the existence of the then unknown planet Neptune, using only mathematics and astronomical observations of the known planet Uranus. Encouraged by physicist
Arago, Director of the Paris Observatory, Le Verrier was intensely engaged for months in complex calculations to explain small but systematic discrepancies between
Uranus's observed
orbit and the one predicted from the
laws of gravity of
Newton. At the same time, but unknown to Le Verrier, similar calculations were made by
John Couch Adams in England. Le Verrier announced his final predicted position for Uranus's unseen perturbing
planet publicly to the French Academy on 31 August 1846, two days before Adams's final solution was privately mailed to the
Royal Greenwich Observatory. Le Verrier transmitted his own prediction by 18 September in a letter to
Johann Galle of the
Berlin Observatory. The letter arrived five days later, and the planet was found with the Berlin Fraunhofer refractor that same evening, 23 September 1846, by Galle and
Heinrich d'Arrest within 1° of the predicted location near the boundary between
Capricorn and
Aquarius. There was, and to an extent still is, controversy over the apportionment of credit for the discovery. There is no ambiguity to the discovery claims of Le Verrier, Galle, and d'Arrest. Adams's work was begun earlier than Le Verrier's but was finished later and was unrelated to the actual discovery. Not even the briefest account of Adams's predicted orbital elements was published until more than a month after Berlin's visual confirmation. Adams made full public acknowledgement of Le Verrier's priority and credit (not forgetting to mention the role of Galle) when he presented his work to the
Royal Astronomical Society in November 1846:
Tables of the planets Early in the 19th century, the methods of predicting the motions of the planets were somewhat scattered, having been developed over decades by many different researchers. In 1847, Le Verrier took on the task to "... embrace in a single work the entire planetary system, put everything in harmony if possible, otherwise, declare with certainty that there are as yet unknown causes of perturbations...", a work which would occupy him for the rest of his life. Le Verrier began by re-evaluating, to the 7th order, the technique of calculating the
planetary perturbations known as the perturbing function. This derivation, which resulted in 469 mathematical terms, was complete by 1849. He next collected observations of the positions of the planets as far back as 1750. Examining these and correcting for inconsistencies with the most recent data occupied him until 1852. (Other explanations considered included a slight oblateness of the Sun.) The success of the search for
Neptune based on its perturbations of the orbit of
Uranus led astronomers to place some faith in this possible explanation, and the hypothetical planet was even named
Vulcan. However, no such planet was ever found, and the anomalous precession was eventually explained by
general relativity theory.
Later life Le Verrier's methods of management were disliked by the staff of the
Observatoire, and the disputes became so great that he was driven out in 1870. He was succeeded by
Delaunay, but was reinstated in 1873 after Delaunay accidentally drowned. Le Verrier held the position until his death in 1877. and had three children. In 1847, he was elected to the
American Philosophical Society. He died in Paris, France and was buried in the
Montparnasse Cemetery. A large stone celestial globe sits over his grave. He will be remembered by the phrase attributed to
Arago: "the man who discovered a planet with the point of his pen." ==Honours==