» For Edenbridge's album, see Aphelion (album). For the literary journal Perigee, see . In celestial mechanics, an apsis, plural apsides 's the point of greatest or least distance of the elliptical orbit of an object from its center of attraction, which's generally the center of mass of the system. The point of closest approach (the point at which two bodies are the closest)'s called the periapsis or pericentre, from Greek περὶ, peri, around. The point of farthest excursion… (More on Aphelion)