Philippe Gustave Doulcet, Comte de Pontécoulant (1795–1874) was a French

astronomer An astronomer is a scientist in the field of astronomy who focuses on a specific question or field outside the scope of Earth. Astronomers observe astronomical objects, such as stars, planets, natural satellite, moons, comets and galaxy, galax ...

. He was the younger son of Louis Gustave le Doulcet, Comte de Pontécoulant and was the brother of Louis-Adolphe Pontécoulant. After 1811 he served in the army until 1849. Following his retirement he dedicated himself to the study of mathematics and astronomy. In 1829 he used the mathematical methods of Poisson and Lagrange to successfully predict the return of

Halley's Comet Halley's Comet is the only known List of periodic comets, short-period comet that is consistently visible to the naked eye from Earth, appearing every 72–80 years, though with the majority of recorded apparitions (25 of 30) occurring after ...

with good precision. His prediction of the

perihelion An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. The line of apsides (also called apse line, or major axis of the orbit) is the line connecting the two extreme values. Apsides perta ...

passage was correct to within two days.George Forbes, "History of Astronomy". He was a member of the

French Academy of Sciences The French Academy of Sciences (, ) is a learned society, founded in 1666 by Louis XIV at the suggestion of Jean-Baptiste Colbert, to encourage and protect the spirit of French Scientific method, scientific research. It was at the forefron ...

. The crater Pontécoulant on the

Moon The Moon is Earth's only natural satellite. It Orbit of the Moon, orbits around Earth at Lunar distance, an average distance of (; about 30 times Earth diameter, Earth's diameter). The Moon rotation, rotates, with a rotation period (lunar ...

is named after him. File:Pontécoulant-1.jpg, Volumes I-III of ''Theorie analytique du systeme du monde'' (1829-1834) File:Pontécoulant-2.jpg, Title page to volume I of ''Theorie analytique du systeme du monde'' (1829) File:Pontécoulant-4.jpg, Table of contents to volume I of ''Theorie analytique du systeme du monde'' (1829) File:Pontécoulant-7.jpg, First page to volume I of ''Theorie analytique du systeme du monde'' (1829)

Bibliography

1829-1846, "Théorie Analytique du Système du Monde", Paris.
* 1840, "Traité élémentaire de Physique Céleste", Paris, 2 volumes. * 1864, "Notice sur la comète de Halley et ses apparitions successives de 1531 à 1910", ''Comptes rendus hebdomadaires des séances de l’Académie des sciences'', 58, 706-709

References

External links

Portrait of Gustave Pontecoulant from the Lick Observatory Records Digital Archive, UC Santa Cruz Library's Digital Collections
1795 births 1874 deaths 19th-century French astronomers Members of the French Academy of Sciences Counts of Pontécoulant 19th-century French mathematicians French military personnel of the Napoleonic Wars {{france-astronomer-stub