|
( Apsis)
In celestial mechanics, an apsis, plural apsides (pronounced /'æps?d??z/) is the point of greatest or least distance of the elliptical orbit of an object from its center of attraction, which is generally the center of mass of the system. The point of closest approach is called the periapsis or pericentre and the point of farthest excursion is called the apoapsis (Greek ap?, from, which becomes ap before a vowel, and af before rough breathing), apocentre or apapsis (the latter term, although etymologically more correct, is much less used). A straight line drawn through the periapsis and apoapsis is the line of apsides. This is the major axis of the ellipse, the line through the longest part of the ellipse. Derivative terms are used to identify the body being orbited. The most common are perigee and apogee, referring to orbits around the Earth (Greek ?? gê earth), and perihelion and aphelion, referring to orbits around the Sun (Greek ‘????? helios sun). During the Apollo program, the terms pericynthion and apocynthion were used when referring to the moon. These formulae characterize the periapsis and apoapsis of an orbit
|
Apsis Subcategories
Apsis Articles
|
|
