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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.

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.