Apsis

Apsis

(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

References

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