noun, plural a·phe·li·a [uh–fee-lee-uh, uh–feel-yuh, ap-hee-lee-uh] /əˈfi li ə, əˈfil yə, æpˈhi li ə/.
- Astronomy. the point in the orbit of a planet or a comet at which it is farthest from the sun.
noun plural -lia (-lɪə)
- the point in its orbit when a planet or comet is at its greatest distance from the sunCompare perihelion
“point farthest from the sun” (of a celestial body’s orbit), 1670s, a Grecianized form of Modern Latin aphelium, altered by Johannes Kepler based on Greek apo heliou “away from the sun,” from apo “away from” (see apo-) + heliou, genitive of helios “sun” (see sol). The whole was formed on the model of Ptolemaic apogaeum (see apogee) to reflect the new helio-centric model of the universe.
- The point at which an orbiting body, such as a planet or comet, is farthest away from the Sun. Compare apogee perihelion.