Apoapsis

Given two objects, A and B (two planets for example), if object B orbits around object A, apoapsis is the point in the orbit of B which is furthest (greatest distance) from A.

• If object A is Earth, it's also known as apogee.
• If object A is the Sun, it's also known as aphelion.
• If object A is the Moon, it's also known as apolune.

According to Kepler's laws of planetary motion; as a planet travels in an elliptical orbit, around a star; as the planet approaches the periapsis, it will increase in velocity.

The point of closest approach is the periapsis.