An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

The point in an orbit where the moving body lies furthest from the celestial body around which it turns.

Apoapsis, from → apo- + → apsis.

Apâhabâk, from apâ-, → apo-, + habâk, → apsis.

The point of greatest or least distance of the orbit of a celestial body from a center of attraction. The closest point is the → periapsis, the further point the → apoapsis.

L. apsis "arch, vault," from Gk. hapsis "loop, arch," from haptein "fasten together".

Mod.Pers. habâk "top of the head; the summit of a mountain".

The angular distance between the → ascending node of an object orbiting a → primary and its periapsis measured from the primary. Argument of periapsis is measured in the → orbital plane in the direction of motion. It is one of the → orbital elements. See also → argument of perigee, → argument of perihelion.

→ argument; → perigee.

The point in an orbit of a body where it is closest to its primary; opposite of → apoapsis.

→ peri- + → apsis.

One of the → orbital elements, the time when the → secondary body reaches → periapsis.

→ time; → periapsis; → passage.