Featured planetary moon
Nereid
A small outer moon tracing an unusually stretched orbit.
Nereid travels on a highly eccentric orbit, changing its distance from Neptune dramatically over each revolution. That path distinguishes it from the more regular inner satellite system.
- Orbit representation
- Representative mean elements
- Surface
- procedural reconstruction
Reference measurements
The numbers that shape this world
- Mean radius
- 170 km
- Mean orbital distance
- 5,513,900 kmSemi-major axis around the parent body.
- Orbital period
- 360.133 days
- Eccentricity
- 0.751
- Inclination
- 5.1°Earth mean ecliptic at J2000
- Rotation
- Rotation unresolved
World portrait
Distance that changes by design
Nereid is a reminder that a single semi-major axis cannot describe the experience of an eccentric orbit. The page keeps eccentricity beside period and reference frame.
System geometry
Nereid in motion around Neptune
Nereid travels at a mean orbital distance of 5,513,900 km and completes a circuit in 360.133 days. Its eccentricity of 0.751 and 5.1° inclination are read against Earth mean ecliptic at J2000. The rotation state remains unresolved instead of being assigned a decorative spin.
Representation notes
What Explore is showing
JPL fitted mean elements describe general orbit shape and orientation; they are not an accurate ephemeris.
Reference-guided visual reconstruction based on cited mission records; no source raster is reproduced.
Provenance