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.

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