Leverrier, Urbain Jean Joseph (1811-1877)

French astronomer. He predicted the existence and position of the planet Neptune from its influence on the orbit of the planet Uranus. It was discovered in 1846.

The possibility that another planet might exist beyond Uranus, influencing its orbit, had already been suggested. Leverrier calculated the orbit and apparent diameter of the hypothetical planet, and wrote to a number of observatories, asking them to test his prediction of its position. Johann Galle at the Berlin Observatory found it immediately, within 1° of Leverrier's coordinates.

Unbeknown to Leverrier, English astronomer John Couch Adams had carried out virtually identical calculations a year earlier, but had failed to persuade anyone to act on them.

Leverrier was born in St Lô, Normandy, and studied in Paris at the Ecole Polytechnique, joining the staff 1837. He became professor in 1847, and in 1849 a chair of celestial mechanics was established for him at the Sorbonne. He was politically active in the revolutions of 1848, serving as a member of the legislative assembly in 1849 and as senator in 1852. In 1854 he became director of the Paris Observatory. His career was devoted to celestial mechanics, especially the problem of the stability of the Solar System.

After his discovery of Neptune, Leverrier compiled a comprehensive analysis of the masses and orbits of the planets of the Solar System. This was published after his death, in the Annals of the Paris Observatory.

Leverrier was also instrumental in the establishment of a meteorological network across continental Europe.