noun
- the two points in an elliptical orbit that are farthest from and closest to the center of attraction
Usage: astronomy; plural of apsis
Examples
- The apsides of Earth’s orbit around the Sun are called aphelion and perihelion.
- Astronomers calculate the apsides to determine orbital characteristics.
- The Moon’s apsides shift gradually over time due to gravitational influences.
- Spacecraft trajectories must account for the apsides of planetary orbits.
- The distance between the two apsides defines the major axis of an elliptical orbit.