aphelion

noun

Etymology: From New Latin aphēlium (whence English aphelium, now displaced) + -ion (used in the names of other apsides). Aphelium was formed from Ancient Greek ἀπο- (apo-, prefix meaning ‘away, from, off’) + ἥλῐος (hḗlĭos, “the sun”) (ultimately from Proto-Indo-European *sóh₂wl̥ (“the sun”)), modelled after New Latin apogaeum (“apogee”). The plural form aphelia is from aphelion + -a (plural form of the suffix -on).

1. The point in the elliptical orbit of a comet, planet, or other astronomical object, where it is farthest from the Sun.

   “[I]t follows from the theory of gravity, that the aphelia of Mercury, Venus, the Earth, and Mars, slightly progress.”