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 their studies on a specific question or field outside the scope of Earth. They observe astronomical objects such as stars, planets, moons, comets and galaxies – in either ...

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

planet A planet is a large, rounded astronomical body that is neither a star nor its remnant. The best available theory of planet formation is the nebular hypothesis, which posits that an interstellar cloud collapses out of a nebula to create a you ...

ary motion and mathematics.

Life

Born in

Lusigny-sur-Barse Lusigny-sur-Barse (; ) is a commune in the Aube department in the northeastern Grand Est region of France. In 2019, it had a population of 2,207. Geography The Barse flows through the commune. The most recognisable building in Lusigny, throug ...

, 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 physicist, astronomer, and mathematician who co-discovered the Biot–Savart law of magnetostatics with Félix Savart, established the reality of meteorites, made an early ba ...

at the

Sorbonne Sorbonne may refer to: * Sorbonne (building), historic building in Paris, which housed the University of Paris and is now shared among multiple universities. *the University of Paris (c. 1150 – 1970) *one of its components or linked institution, ...

. He worked on the mechanics of the

Moon The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width of ...

as a special case of the

three-body problem In physics and classical mechanics, the three-body problem is the problem of taking the initial positions and velocities (or momenta) of three point masses and solving for their subsequent motion according to Newton's laws of motion and Newton's ...

. 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, a description of the operation of adding infinitely many quantities, one after the other, to a given starting quantity. The study of series is a major part of calculus and its generalization, math ...

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 (e.g. inner product, norm, topology, etc.) and the linear functions defined o ...

O'Connor & Edmund and computer algebra. Delaunay became director of the Paris Observatory in 1870 but drowned in a boating accident near Cherbourg, France, two years later. He was followed by Jean Claude Bouquet at the Academy.

Peter Guthrie Tait Peter Guthrie Tait FRSE (28 April 1831 – 4 July 1901) was a Scottish mathematical physicist and early pioneer in thermodynamics. He is best known for the mathematical physics textbook ''Treatise on Natural Philosophy'', which he co-wrote wi ...

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 (French: ''Académie des 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 research. It was at th ...

'', (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 (Latin for "British Encyclopædia") is a general knowledge English-language encyclopaedia. It is published by Encyclopædia Britannica, Inc.; the company has existed since the 18th century, although it has changed ownership various t ...

, Deluxe edition CD-ROM *
Some of Delaunay's works are digitalized
on Paris Observatory digital library. {{DEFAULTSORT:Delaunay, Charles-Eugene École Polytechnique alumni Mines ParisTech 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