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Astro*Dictionary by Michael Erlewine





2 articles for "Apsis"

Apsis [Astro*Index]

Plural, Line of Apsides.

The points in the orbit of the moon or a planet closest to and furthest from the center of attraction. The first is called the lower apsis and is the same, for bodies which orbit the sun, as the perihelion; the second is called the higher apsis and corresponds to aphelion. For the moon's orbit around the earth the coresponding terms are perigee and apogee. The line of apsides is the major axis of an elliptical orbit. The line connecting the aphelion and perihelion points of an elliptical orbit. The line of apsides precesses due to the mutual perturbation of the planets, whose orbits shift in their own planes.

See also:
♦ Perihelion ♦ Aphelion ♦ Perturbation ♦ Apsides, Line of
Apsis [DeVore]

n. (pl., apsides).

The points of greatest and least distance of a heavenly body from its centre of attraction. (v. Orbit.)

See also:
♦ Perihelion ♦ Aphelion ♦ Orbit


Astro*Index Copyright © 1997 Michael Erlewine