Charles-Eugène Delaunay (; 9 April 1816 – 5 August 1872) 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 ...

and mathematician. His lunar motion studies were important in advancing both the theory of

planet A planet is a large, Hydrostatic equilibrium, rounded Astronomical object, astronomical body that is generally required to be in orbit around a star, stellar remnant, or brown dwarf, and is not one itself. The Solar System has eight planets b ...

ary motion and mathematics.

Life

Born in Lusigny-sur-Barse, France, to Jacques-Hubert Delaunay and Catherine Choiselat, Delaunay studied under

Jean-Baptiste Biot Jean-Baptiste Biot (; ; 21 April 1774 – 3 February 1862) was a French people, French physicist, astronomer, and mathematician who co-discovered the Biot–Savart law of magnetostatics with Félix Savart, established the reality of meteorites, ma ...

at the Sorbonne. He worked on the mechanics of 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 ...

as a special case of the

three-body problem In physics, specifically classical mechanics, the three-body problem is to take the initial positions and velocities (or momenta) of three point masses orbiting each other in space and then calculate their subsequent trajectories using Newton' ...

. He published two volumes on the topic, each of 900 pages in length, in 1860 and 1867. The work hints at chaos in the system, and clearly demonstrates the problem of so-called "small denominators" in perturbation theory. His

infinite series In mathematics, a series is, roughly speaking, an addition of infinitely many terms, one after the other. The study of series is a major part of calculus and its generalization, mathematical analysis. Series are used in most areas of mathemati ...

expression for finding the position of the Moon converged too slowly to be of practical use but was a catalyst in the development of

functional analysis Functional analysis is a branch of mathematical analysis, the core of which is formed by the study of vector spaces endowed with some kind of limit-related structure (for example, Inner product space#Definition, inner product, Norm (mathematics ...

O'Connor & Edmund and

computer algebra In mathematics and computer science, computer algebra, also called symbolic computation or algebraic computation, is a scientific area that refers to the study and development of algorithms and software for manipulating expression (mathematics), ...

. Delaunay became director of the

Paris Observatory The Paris Observatory (, ), a research institution of the Paris Sciences et Lettres University, is the foremost astronomical observatory of France, and one of the largest astronomical centres in the world. Its historic building is on the Left Ban ...

in 1870 but drowned in a boating accident near

Cherbourg Cherbourg is a former Communes of France, commune and Subprefectures in France, subprefecture located at the northern end of the Cotentin peninsula in the northwestern French departments of France, department of Manche. It was merged into the com ...

, France, two years later. He was followed by Jean Claude Bouquet at the Academy.

Peter Guthrie Tait Peter Guthrie Tait (28 April 18314 July 1901) was a Scottish Mathematical physics, mathematical physicist and early pioneer in thermodynamics. He is best known for the mathematical physics textbook ''Treatise on Natural Philosophy'', which he ...

in his book ''An Elementary Treatise on Quaternions'' edition 1867 on page 244 named Didonia in honour of Delaunay.

Honours

*Member of the ''

Académie des 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 ...

'', (1855) non.(2001) *

Gold Medal of the Royal Astronomical Society The Gold Medal of the Royal Astronomical Society is the highest award given by the Royal Astronomical Society (RAS). The RAS Council have "complete freedom as to the grounds on which it is awarded" and it can be awarded for any reason. Past awar ...

, (1870) *His name is one of the 72 names inscribed on the Eiffel Tower.

References

Bibliography

By Delaunay

* * * * * * *

About Delaunay

* non.(2001) "Delaunay, Charles-Eugène", ''

Encyclopædia Britannica The is a general knowledge, general-knowledge English-language encyclopaedia. It has been published by Encyclopædia Britannica, Inc. since 1768, although the company has changed ownership seven times. The 2010 version of the 15th edition, ...

'', Deluxe edition CD-ROM *
Some of Delaunay's works are digitalized
on

digital library. {{DEFAULTSORT:Delaunay, Charles-Eugene École Polytechnique alumni Mines Paris - PSL alumni Corps des mines 19th-century French astronomers 19th-century French mathematicians Recipients of the Gold Medal of the Royal Astronomical Society 1816 births 1872 deaths Foreign members of the Royal Society Members of the French Academy of Sciences Boating accident deaths Accidental deaths in France