Édouard Roche
Encyclopedia
Édouard Albert Roche was a French
astronomer and mathematician
, who is best known for his work in the field of celestial mechanics
. He gave his name to the concepts of the Roche sphere, Roche limit
and Roche lobe
.
He was born in Montpellier
, and studied at the University of Montpellier
, 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 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 (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
s of Saturn
were formed when a jumbo moon
came too close to Saturn and was pulled apart by gravitation
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
s; this distance became known as the Roche limit.
His other best known works also involved orbital mechanics. The Roche lobe 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 sphere approximates the gravitational sphere of influence of one astronomical body in the face of perturbations from another heavier body around which it orbit
s.
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
astronomer and mathematician
Mathematician
A mathematician is a person whose primary area of study is the field of mathematics. Mathematicians are concerned with quantity, structure, space, and change....
, who is best known for his work in the field of celestial mechanics
Celestial mechanics
Celestial mechanics is the branch of astronomy that deals with the motions of celestial objects. The field applies principles of physics, historically classical mechanics, to astronomical objects such as stars and planets to produce ephemeris data. Orbital mechanics is a subfield which focuses on...
. He gave his name to the concepts of the Roche sphere, Roche limit
Roche limit
The Roche limit , sometimes referred to as the Roche radius, is the distance within which a celestial body, held together only by its own gravity, will disintegrate due to a second celestial body's tidal forces exceeding the first body's gravitational self-attraction...
and Roche lobe
Roche lobe
The Roche lobe is the region of space around a star in a binary system within which orbiting material is gravitationally bound to that star. If the star expands past its Roche lobe, then the material can escape the gravitational pull of the star. If the star is in a binary system then the material...
.
He was born in Montpellier
Montpellier
-Neighbourhoods:Since 2001, Montpellier has been divided into seven official neighbourhoods, themselves divided into sub-neighbourhoods. Each of them possesses a neighbourhood council....
, and studied at the University of Montpellier
University of Montpellier
The University of Montpellier was a French university in Montpellier in the Languedoc-Roussillon région of the south of France. Its present-day successor universities are the University of Montpellier 1, Montpellier 2 University and Paul Valéry University, Montpellier III.-History:The university...
, 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
Pierre-Simon Laplace
Pierre-Simon, marquis de Laplace was a French mathematician and astronomer whose work was pivotal to the development of mathematical astronomy and statistics. He summarized and extended the work of his predecessors in his five volume Mécanique Céleste...
nebular hypothesis 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 (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
Planetary ring
A planetary ring is a ring of cosmic dust and other small particles orbiting around a planet in a flat disc-shaped region.The most notable planetary rings known in Earth's solar system are those around Saturn, but the other three gas giants of the solar system possess ring systems of their...
s of Saturn
Saturn
Saturn is the sixth planet from the Sun and the second largest planet in the Solar System, after Jupiter. Saturn is named after the Roman god Saturn, equated to the Greek Cronus , the Babylonian Ninurta and the Hindu Shani. Saturn's astronomical symbol represents the Roman god's sickle.Saturn,...
were formed when a jumbo moon
Natural satellite
A natural satellite or moon is a celestial body that orbits a planet or smaller body, which is called its primary. The two terms are used synonymously for non-artificial satellites of planets, of dwarf planets, and of minor planets....
came too close to Saturn and was pulled apart by gravitation
Gravitation
Gravitation, or gravity, is a natural phenomenon by which physical bodies attract with a force proportional to their mass. Gravitation is most familiar as the agent that gives weight to objects with mass and causes them to fall to the ground when dropped...
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
Tidal force
The tidal force is a secondary effect of the force of gravity and is responsible for the tides. It arises because the gravitational force per unit mass exerted on one body by a second body is not constant across its diameter, the side nearest to the second being more attracted by it than the side...
s; this distance became known as the Roche limit.
His other best known works also involved orbital mechanics. The Roche lobe 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 sphere approximates the gravitational sphere of influence of one astronomical body in the face of perturbations from another heavier body around which it orbit
Orbit
In physics, an orbit is the gravitationally curved path of an object around a point in space, for example the orbit of a planet around the center of a star system, such as the Solar System...
s.