Mean Motion
The angular speed required for a body to make one orbit around an ideal ellipse with a specific semi-major axis. It is equal to 2 times pi (π) divided by the orbital period.
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Mean Motion
In undisturbed elliptic motion, the constant angular speed required for a body to complete one revolution in an orbit of a specified semi-major axis.
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mean motion (NASA SP-7, 1965) (symbol n, µ)
Of an object in orbit, a measure of angular velocity, n = / P where P = period.
M = n (t - T) where n is mean motion; t is time of the computation; and T is time of perifocus. The eccentric anomaly E and the mean anomaly M are related by the Kepler equation
M = E - e sin E where e is eccentricity of the ellipse.
In the following year his memoir on the secular acceleration of the moon's mean motion partially invalidated Laplace's famous explanation, which had held its place unchallenged for sixty years.
The motions of individual stars, it is true, vary widely, but if the mean motion of a number of stars is considered this tendency is always to be found.
When an object's orbital period is an exact ratio of Neptune's (a situation called a mean motion resonance), then it can become locked in a synchronised motion with Neptune and avoid being perturbed away if their relative alignments are appropriate.
Pluto lies in the 3:2 mean motion resonance of Neptune: for every three orbits of Neptune around the Sun, Pluto makes two. The two objects then return to their initial positions and the cycle repeats, each cycle lasting about 500 years.
For nearby clusters of appreciable angular extent (like the Hyades) perspective makes the proper motions of individual stars not parallel, but directed toward a point in the sky parallel to the cluster's mean motion relative to the Sun.
Resonance KBOs inhabit one of the mean motion resonances with Neptune. The most populated is the 3:2 resonance, which contains Pluto and almost 25% of the detected KBOs (for obvious reasons called plutinos).
In undisturbed elliptic motion, the product of the mean motion of an orbiting body and the interval of time since the body passed pericenter.
The Moon itself would move uniformly (with some mean motion in anomaly) on a secondary circular orbit, called an epicycle, that itself would move uniformly (with some mean motion in longitude) over the main circular orbit around the Earth, ...
Gordon, M.K., C.D. Murray, and M.R. Showalter, Satellite Mean Motion Resonances in Saturn's Rings, Bull. Amer. Astron. Soc. 38, 560, 2006.
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Positions of jet streams in the atmosphere. Arrows indicate directions of mean motions in a meridional plane.
Callippus or Calippus was a Greek astronomy and mathematician.Callippus was born at Cyzicus, and studied under Eudoxus of Cnidus at the Academy of Plato....
, 330 B. C.). The attribution of a mean motion to so complex a motion as the moon's ...
The debris belt detected is located around one AU from HD 69830, "coincident" with the 2:1 and 5:2 mean motion resonances of the outermost of three Neptune-sized planets also discovered in early 2006 (more below). ...
 See also: Planet, Solar, Orbit, Period, Earth
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