Apsis
This article is about the astronomical term. In architecture, apsis is also the plural of apse.
Apogee is also the name of a major video game publisher.
In astronomy, an apsis is the point of greatest or least distance of the elliptical orbit of a celestial body from a center of attraction. The point of closest approach is called the periapsis and the point of farthest approach is the apoapsis.
According to Kepler's laws of planetary motion, as a body approaches the periapsis it will increase in velocity and as a body approaches the apoapsis it will decrease in velocity.
When the body the orbit is around is known, more specific names are often used.
| Body being orbited | Closest approach | Farthest approach |
|---|---|---|
| Earth | perigee | apogee |
| The Sun | perihelion | aphelion |
| The Moon | perilune | apolune |
| Jupiter | perijove | apojove |
| A black hole | perimelasma | apomelasma |