In celestial mechanics , an apsis , plural apsides -LRB- -RRB- 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 .

In astronomy , an apsis , plural apsides -LRB- IPA : / / -RRB- is the point of greatest or least distance of the elliptical orbit of an astronomical object from its center of attraction , which is generally the center of mass of the system .
