Naiad or Neptune III is the closest moon to Neptune named after the Naiads of Greek legend. It was found sometime before mid-September, 1989 from the images taken by the Voyager 2 probe. The last moon to be discovered during the flyby, it was designated S/1989 N 6. Naiad is not a sphere and probably has not been changed by any internal geological processes after its formation. It orbits about 23,500 km above Neptune's cloud tops.
|Discovered by||Voyager Imaging Team|
|Discovered in||September 1989|
|Semi-major axis||48 227 ± 1 km|
|Eccentricity||0.0004 ± 0.0003|
|Orbital period||0.2943958 ± 0.0000002 d|
|Inclination||4.75 ± 0.03° (to Neptune equator)|
4.75° (to local Laplace plane)
|Is a moon of||Neptune|
|Mass||~1.9×1017 kg |
(based on assumed density)
|Mean density||~1.2 g/cm3 (estimate)|
|Rotation period||assumed synchronous|
|Axial tilt||~zero presumably|
|Surface temp.||~51 K mean (estimate)|
Since the Voyager 2 flyby, the Neptune system has been studied a lot from ground-based observatories and the Hubble Space Telescope as well. In 2002-03, Keck telescope looked at the system using adaptive optics and detected easily the biggest four closer satellites. Thalassa was found with some image processing, but Naiad was not located.