Posted By: wwh astronomy words - 05/29/02 06:45 PM
from new word site:
0/17/2000: An apsisis a "turning point" of an elliptical celestial orbit... a point where a satellite is either closest to, or is farthest away from its primary. For a satellite of the earth, the point of closest approach to the earth is the perigee and the point farthest from the earth is the apogee. Both the perigee and the apogee would be syzygies or apses. For a body in orbit around the sun the point where it's closest to the sun is called the perihelion and the point where it's farthest from the sun is the aphelion.

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