Urbain Le Verrier

Urbain Le Verrier

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Urbain Le Verrier

Urbain Le Verrier.

Urbain Jean Joseph Le Verrier (March 11, 1811 – September 23, 1877) was a French mathematician who specialized in celestial mechanics and is best known for his part in the discovery of Neptune.

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Life and work

Le Verrier was born in Saint-Lô, France, and studied at the Ecole Polytechnique. Following a brief period studying chemistry under Gay-Lussac, Le Verrier switched to astronomy, particularly celestial mechanics. He accepted a job at the Paris Observatory, where he spent most of his professional life, and eventually became that institution's Director.^[1]

Grave of Le Verrier

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,^[2], Directory 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 August 31, 1846, two days before Adams's final solution, which turned out to be 12° off the mark, was privately mailed to the Royal Greenwich Observatory. Le Verrier transmitted his own prediction by September 18 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, September 23, 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, for reasons that have proved increasingly difficult to defend or define. Scholars' opinion has been moving in recent years to increased awareness that Le Verrier's open prediscovery publication of his predictions merits his credit, heretofore too long denied, as sole mathematical discoverer of Neptune.

Galvanized by his success with Neptune, Le Verrier proceeded to interpret variations in the orbit of Mercury as being due to an unknown planet, tentatively named Vulcan. This triggered a wave of false detections, which lasted until 1915, when Einstein explained Mercury's anomalous motion with his theory of general relativity.

The last quarter century of Le Verrier's life was engaged in establishing the orbits of all eight planets, a project which he only narrowly lived to see completed and printed.

Le Verrier had a wife and children. He died in Paris, France and was buried in the Cimetière Montparnasse. A large stone celestial globe sits over his grave. He will be ever remembered by the phrase attributed to Arago: "the man who discovered a planet with the point of his pen."