noun
- the point in the orbit of a celestial body (such as a planet or comet) that is farthest from the sun
Usage: astronomy; plural: aphelia or aphelions
Examples
- Earth reaches its aphelia in early July each year.
- The comet's aphelia occurs once every 76 years.
- At aphelia, planets move more slowly in their orbits.
- Astronomers calculate the distance from the sun at aphelia for all known planets.