# Orbit - Perturbation Theory, Types Of Orbits, Orbits Of Double And Multiple Stars

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bodies body elements elliptical

An orbit is the path followed by a celestial body moving in a gravitational field. When a single object, such as a **planet**, is moving freely in a gravitational field of a massive body, such as a **star**, the orbit is in the shape of a conic section, that is, elliptical, parabolic, or hyperbolic. Most orbits are elliptical.

The exact path and position of an object in space can be determined by taking into account seven orbital elements. These elements deal with the mathematical relationships between the two bodies. To determine the orbit of a celestial body, it must be observed and precise measurements taken at least three times. However, at least 20 precise observations, covering at least one full revolution, are needed for accurate orbital elements to be determined. If two bodies that move in elliptical orbits around their common center of **mass** (for example, the **Sun** and **Jupiter**) were alone in an otherwise empty universe, we would expect that their orbits would remain constant. However, the **solar system** consists of the Sun, eight major planets, and an enormous number of much smaller bodies all orbiting around the solar system's center of mass. The masses of these objects all influence the orbits of each other in small and large ways.

## Additional Topics

The Sun's gravitational attraction is the main force acting on each planet, but there are much weaker gravitational forces between the planets, which produce perturbations of their elliptical orbits; these make small changes in a planet's orbital elements with time. The planets which perturb the Earth's orbit most are Venus, Jupiter, and Saturn. These planets and the sun also …

A synchronous orbit around a celestial body is a nearly circular orbit in which the body's period of revolution equals its rotation period. This way, the same hemisphere of the satellite is always facing the object of its orbit. This orbit is called a geosynchronous orbit for the Earth where, with its sidereal rotation period of 23 hours 56 minutes 4 seconds, the geosynchronous orbit is 21,…

The orbits of double stars, where the sizes of the orbits have been determined, provide the only information we have about the masses of stars other than the Sun. Close doublestars will become decidedly non-spherical because of tidal distortion and/or rapid rotation, which produces effects analogous to those described above for close artificial planetary satellites. Also, such stars often have gas…

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