Édouard Albert Roche (; 17 October 1820 – 27 April 1883) 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, natural satellite, moons, comets and galaxy, g ...

and

mathematician A mathematician is someone who uses an extensive knowledge of mathematics in their work, typically to solve mathematical problems. Mathematicians are concerned with numbers, data, quantity, structure, space, models, and change. History On ...

, who is best known for his work in the field of

celestial mechanics Celestial mechanics is the branch of astronomy that deals with the motions of objects in outer space. Historically, celestial mechanics applies principles of physics (classical mechanics) to astronomical objects, such as stars and planets, to ...

. His name was given to the concepts of the

Roche sphere The Hill sphere of an astronomical body is the region in which it dominates the attraction of satellites. To be retained by a planet, a moon must have an orbit that lies within the planet's Hill sphere. That moon would, in turn, have a Hill sp ...

Roche limit In celestial mechanics, the Roche limit, also called Roche radius, is the distance from a celestial body within which a second celestial body, held together only by its own force of gravity, will disintegrate because the first body's tidal forc ...

, and

Roche lobe In astronomy, the Roche lobe is the region around a star in a binary system within which orbiting material is gravitationally bound to that star. It is an approximately teardrop-shaped region bounded by a critical gravitational equipotential, wit ...

. He also was the author of works in

meteorology Meteorology is a branch of the atmospheric sciences (which include atmospheric chemistry and physics) with a major focus on weather forecasting. The study of meteorology dates back millennia, though significant progress in meteorology did not ...

Biography

He was born in

Montpellier Montpellier (, , ; oc, Montpelhièr ) is a city in southern France near the Mediterranean Sea. One of the largest urban centres in the region of Occitania (administrative region), Occitania, Montpellier is the prefecture of the Departments of ...

, and studied at the

University of Montpellier The University of Montpellier (french: Université de Montpellier) is a public university, public research university located in Montpellier, in south-east of France. Established in 1220, the University of Montpellier is one of the oldest univ ...

, receiving his D.Sc. in 1844 and later becoming a professor at the same institution, where he served in the Faculté des Sciences starting in 1849. Roche made a mathematical study of Laplace's

nebular hypothesis The nebular hypothesis is the most widely accepted model in the field of cosmogony to explain the formation and evolution of the Solar System (as well as other planetary systems). It suggests the Solar System is formed from gas and dust orbitin ...

and presented his results in a series of papers to the Academy of Montpellier from his appointment until 1877. The most important were on

comets A comet is an icy, small Solar System body that, when passing close to the Sun, warms and begins to release gases, a process that is called outgassing. This produces a visible atmosphere or coma, and sometimes also a tail. These phenomena are ...

(1860) and the nebular hypothesis itself (1873). Roche's studies examined the effects of strong gravitational fields upon swarms of tiny particles. He is perhaps most famous for his theory that the

planetary ring A ring system is a disc or ring, orbiting an astronomical object, that is composed of solid material such as dust and moonlets, and is a common component of satellite systems around giant planets. A ring system around a planet is also known as ...

s of

Saturn Saturn is the sixth planet from the Sun and the second-largest in the Solar System, after Jupiter. It is a gas giant with an average radius of about nine and a half times that of Earth. It has only one-eighth the average density of Earth; h ...

were formed when a large icy

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 ...

came too close to Saturn and was pulled apart by

gravitation In physics, gravity () is a fundamental interaction which causes mutual attraction between all things with mass or energy. Gravity is, by far, the weakest of the four fundamental interactions, approximately 1038 times weaker than the stron ...

al forces. He described a method of calculating the distance at which an object held together only by gravity would break up due to

tidal force The tidal force is a gravitational effect that stretches a body along the line towards the center of mass of another body due to a gradient (difference in strength) in gravitational field from the other body; it is responsible for diverse phenomen ...

s; this distance became known as the Roche limit. His other best known works also involved orbital mechanics. The Roche sphere describes the limits at which an object which is in orbit around two other objects will be captured by one or the other, and the Roche lobe approximates the gravitational sphere of influence of one

astronomical body An astronomical object, celestial object, stellar object or heavenly body is a naturally occurring physical entity, association, or structure that exists in the observable universe. In astronomy, the terms ''object'' and ''body'' are often us ...

in the face of perturbations from another heavier body around which it

orbit In celestial mechanics, an orbit is the curved trajectory of an object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an artificial satellite around an object or position in space such as a p ...

Works

Roche's works are in French, his vernacular language.

Lists of works

List of works
on the site 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 the ...

(31 items) (Includes—unnumbered—works commenting that of Roche. Also includes works in meteorology) * , in ''Mémoires de la Société des sciences, de l'agriculture et des arts de Lille'', 1885 (34 items)

References

* Z. Kopal, ''The Roche problem'',

Kluwer Academic Publishers Springer Science+Business Media, commonly known as Springer, is a German multinational publishing company of books, e-books and peer-reviewed journals in science, humanities, technical and medical (STM) publishing. Originally founded in 1842 in ...

, Dordrecht, 1989 . {{DEFAULTSORT:Roche, Edouard 1820 births 1883 deaths Scientists from Montpellier 19th-century French astronomers 19th-century French mathematicians Tidal forces

Biography

Works

Lists of works

See also

References