[uh-fee-lee-uh
n, uh-feel-yuhn, ap-hee-lee-uhn] 
[uh-fee-lee-uh, uh-feel-yuh, ap-hee-lee-uh] . | Astronomy. the point in the orbit of a planet or a comet at which it is farthest from the sun. |
lion (diástēma) off-sun (distance), neut. of *aphlios (adj.), equiv. to ap- ap- 2 + hli(os) sun + -os adj. suffix. See apogee aphelion (ə-fē'lē-ən) Pronunciation Key
(click for larger image in new window) The point at which an orbiting body, such as a planet or comet, is farthest away from the Sun. Compare apogee, perihelion. |