Given two objects of which one orbits the other, for example a planet and a satellite, periapsis is the point in the satellite's orbit which is closest (at the smallest distance) from the planet.
- If the object orbits the Earth, it's also known as perigee.
- If the object orbits the Sun, it's also known as perihelion.
- If the object orbits the Moon, it's also known as perilune.
The point of farthest approach is the apoapsis
. 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