celestial mechanics, the study of the motions of astronomical bodies as they move under the influence of their mutual gravitation gravitation, the attractive force existing between any two particles of matter .

The Law of Universal Gravitation

Since the gravitational force is experienced by all matter in the universe, from the largest galaxies down to the smallest particles, it
..... Click the link for more information. . Celestial mechanics analyzes the orbital motions of planets, dwarf planets, comets, asteroids, and natural and artificial satellites within the solar system as well as the motions of stars and galaxies. Newton's laws of motion and his theory of universal gravitation are the basis for celestial mechanics; for some objects, general relativity is also important. Calculating the motions of astronomical bodies is a complicated procedure because many separate forces are acting at once, and all the bodies are simultaneously in motion. The only problem that can be solved exactly is that of two bodies moving under the influence of their mutual gravitational attraction (see ephemeris ephemeris (ĭfĕm`ərĭs) (pl.
..... Click the link for more information. ). Since the sun is the dominant influence in the solar system, an application of the two-body problem leads to the simple elliptical orbits as described by Kepler's laws Kepler's laws, three mathematical statements formulated by the German astronomer Johannes Kepler that accurately describe the revolutions of the planets around the sun. Kepler's laws opened the way for the development of celestial mechanics, i.e.
..... Click the link for more information. ; these laws give a close approximation of planetary motion. More exact solutions, which consider the effects of the planets on each other, cannot be found in a straightforward way. However, methods accounting for these other influences, or perturbations perturbation (pŭr'tərbā`shən)
..... Click the link for more information. , have been devised; they allow successive refinements of an approximate solution to be made to almost any degree of precision. In computing the motions of stars and the rotations of galaxies, statistical methods are often used. Columbia Univ. astronomer Wallace Eckert was the first to use a computer for orbit calculations; now computers are used for this work almost exclusively.

celestial mechanics

Branch of astronomy that deals with the mathematical theory of the motions of celestial bodies. Johannes Kepler's laws of planetary motion (1609–19) and Newton's laws of motion (1687) are fundamental to it. In the 18th century, powerful methods of mathematical analysis were generally successful in accounting for the observed motions of bodies in the solar system. One branch of celestial mechanics deals with the effect of gravitation on rotating bodies, with applications to Earth (see tide) and other objects in space. A modern derivation, called orbital mechanics or flight mechanics, deals with the motions of spacecraft under the influence of gravity, thrust, atmospheric drag, and other forces; it is used to calculate trajectories for ascent into space, achieving orbit, rendezvous, descent, and lunar and interplanetary flights.

celestial mechanics [sə′les·chəl mə′kan·iks]

(astrophysics)

The calculation of motions of celestial bodies under the action of their mutual gravitational attractions. Also known as gravitational astronomy.