Aphelion
Aphelion is the point in an orbit where an object is farthest from the Sun.
Aphelion is the point in an orbit farthest from the Sun, the opposite of perihelion. Earth reaches aphelion in early July, when it is about 152 million kilometres away. It is a common surprise that this happens during northern summer: seasons are caused by the tilt of Earth's axis, not its distance from the Sun.
For asteroids and comets, aphelion reveals where they spend most of their time. Objects move slowest at aphelion, so an object with an aphelion in the asteroid belt spends long periods there. Many meteorites have orbits with aphelia between about 2 and 4 astronomical units, inside or near the main asteroid belt, the region they came from.
Comets from the outer Solar System can have aphelia thousands of times farther away than Earth's distance from the Sun, deep in the Oort Cloud. The difference between perihelion and aphelion is set by an orbit's eccentricity.
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Level: Explorer Ages 10 and up