- Astronomy. the point in the orbit of a planet or a comet at which it is farthest from the sun.
Origin of aphelion
Examples from the Web for aphelion
The motion of Newton's comet at aphelion may be equally slight.The Education of Henry Adams
After the fourth go round he was fully five diameters out at aphelion.The Pirates of Ersatz
The apogee of the sun is synonymous with the aphelion of the earth.
An irregularity in the motion of a planet by which it deviates from the aphelion or apogee.
In the orbit of a planet, means the line joining its aphelion and perihelion.
- the point in its orbit when a planet or comet is at its greatest distance from the sunCompare perihelion
Word Origin and History for aphelion
"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.