What are perihelion and aphelion?

1 Answer
Feb 14, 2015

The perihelion is the point in the orbit of the Earth, or any planet, comet, asteroid, or orbiting object, where it is closest to the sun

The aphelion is the opposite, the point in the orbit when the object is farthest from the sun

Most orbiting bodies have elliptical orbits, not circular orbits, therefore the bodies are not a fixed distance from the sun at all times.

Here, (1) is the aphelion, (2) is the perihelion, and (3) is the sun (not to scale).

The distance of the Earth to the Sun is:

147.1 million km (91.4 million miles) at perihelion in early January

152.1 million km (94.5 million miles) at aphelion in early July

Both words come from Greek, where 'peri' means 'near', and 'Helios' is the Greek god of the sun, and 'apo' means 'away'.