From ExoDictionary
Jump to: navigation, search


(plural apsides)

In celestial mechanics, either of the two orbital points nearest or farthest from the center of attraction. Also called apse . The apsides are the perihelion and aphelion in the case of an orbit about the Sun, and the

perigee and apogee in the case of an orbit about the Earth. The line connecting these two points is called line of apsides . The nearest point is the lower apsis while the farthest point is the higher apsis.

There are various terms related to celestial objects and their respective orbits:

Body Closest approach Farthest approach
Galaxy Perigalacticon Apogalacticon
Star Periastron Apastron
Black hole Perimelasma/Perinigricon Apomelasma/Aponigricon
Sun Perihelion Aphelion
Mercury Perihermion Apohermion
Venus Pericytherion/Pericytherean/Perikrition Apocytherion/Apocytherean/Apokrition
Earth Perigee Apogee
Moon Periselene/Pericynthion/Perilune Aposelene/Apocynthion/Apolune
Mars Periareion Apoareion
Jupiter Perizene/Perijove Apozene/Apojove
Saturn Perikrone/Perisaturnium Apokrone/Aposaturnium
Uranus Periuranion Apouranion
Neptune Periposeidion Apoposedion
Pluto Perihadion Apohadion


This article is based on NASA's Dictionary of Technical Terms for Aerospace Use