Nereid
Moon· orbits Neptune
Nereid is a small, distant moon of Neptune on one of the most eccentric orbits of any moon, swinging from ~1.4 to ~9.7 million km.
Open in 3D viewSee Nereid in the live, interactive 3D map
Key facts
Radius
170 km
10% of our Moon's radius
Orbit around Neptune
360 Earth days
0.99 Earth years
Science
Physical
- Radius
- 170 km · 10% of our Moon's radius
Orbit around Neptune
- Distance from Neptune
- 6,471,331 km
- Orbital period
- 360.1 days
- Eccentricity
- 0.751
- Inclination
- 5.10 °
Rotation
- Rotation
- Uncertain and not synchronous — light-curves have suggested a period near ~11 hours, but the measurement remains debated. Not tidally locked.
Composition
- Bulk composition
- A small icy body; its make-up is poorly known but presumed to be water ice and rock.
Radiation & temperature
- Insolation
- 0.00112 S⊕ · 1/893 of the sunlight Earth receives
- Geometric albedo
- 0.24
- Equilibrium temperature
- 48 K (-226 °C)
Discovery & history
- Discovered
- May 1, 1949
- By
- Gerard P. Kuiper
- Method
- Photographic plates
- Name
- The Nereids, the fifty sea-nymph daughters of Nereus in Greek myth.
Kuiper discovered Nereid in 1949. It follows one of the most eccentric orbits of any moon, swinging from roughly 1.4 to 9.6 million km from Neptune, so its distance and brightness change dramatically over its nearly year-long orbit.
Images
Nereid has never been resolved. Voyager 2's 1989 flyby — the only spacecraft ever to pass Neptune — imaged it from about 4.7 million km as a faint point just a few pixels across, revealing no surface detail. No true image of Nereid exists.