Spaceflight · Physics
Periapsis
Say it: pair-ee-AP-sis IPA: /ˌpɛriˈæpsɪs/ noun
Periapsis: The point in an orbit closest to the body being orbited.
An elliptical orbit has a closest approach and a farthest departure. Periapsis is the general name for the closest point, regardless of the central body's identity.
- Example
- The spacecraft passed periapsis on the low side of its elongated orbit.
- Why astronomers use it
- It helps describe trajectories, flybys, and where orbital conditions are most extreme.
- Tiny cosmic connection
- Perihelion specifies the Sun and perigee specifies Earth; periapsis is the broader term.
Observatory Spaceflight Physics
Where to check it
- NASA Science: Universe glossary (opens in a new tab)
- NASA: Basics of Space Flight glossary (opens in a new tab)
- Wikipedia: Apsis (opens in a new tab)
Written for Cool Moon Facts in its own words; the sources cover the same idea in more depth.