​APHELION (from Gr. ἀπό, from, and ἥλιος, sun), in astronomy, that point of the orbit of a planet at which it is most distant from the sun. Apogee, Apocentre, Aposaturnium, &c. are terms applied to those points of the orbit of a body moving around a centre of force—as the Earth, Saturn, &c.—at which it is farthest from the central body.