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