Quick facts
Parent planet
Diameter (mean)
44 km
Mass
5.5 × 10¹⁶ kg
7.5e-07 Moon masses
Mean orbital radius
22,228,000 km
Orbital period
2912.7 Earth days
Discovery year
2002
Discoverer
Matthew J. Holman et al.
Naming origin
One of the Nereids
Surface conditions
Sao is a prograde outer irregular moon of Neptune. Together with Laomedeia, Sao is one of only two known prograde irregulars at Neptune.
Missions and observations
Every Neptune-system mission has had an opportunity to image or characterize Sao. The list below is the Neptune-system mission catalog; specific Sao encounters are documented in mission archives.
| Mission | Year at Neptune | Status |
|---|---|---|
|
Voyager 2 NASA |
1989 | Completed |
Naming etymology
Sao was one of the Nereid sea nymphs. Adopted by the IAU in 2007.
Methodology & sources
Diameter, mass, and orbital parameters from JPL Solar System Dynamics — Physical Parameters. Discovery year and discoverer from the JPL Satellite Discovery Circumstances. Naming etymology from the IAU Working Group for Planetary System Nomenclature. Stylized SVG hero composed from NASA / JPL imagery as visual reference; no photographs are reproduced.