Naiad is the innermost satellite of Neptune and also the smallest among the inner moons. Naiad is the 8th overall largest and 59th largest moon in the Solar System currently known.
Discovery
Naiad was discovered sometime before mid-September 1989 from the images taken by the Voyager 2 spacecraft. Naiad was the last moon to be discovered during the Voyager 2 spacecraft flyby.
Naming
The moon was given the temporary designation S/1989 N6.
Naiad the moon was named after the Naiads of Greek legend.
In Greek mythology, the Naiads or Naiades were a type of nymph who presided over fountains, wells, springs, streams, and brooks. They are distinct from river gods, who embodied rivers, and the very ancient spirits that inhabited the still waters of marshes, ponds and lagoon-lakes, such as pre-Mycenaean Lerna in the Argolid.
Stats
Diameter (mean): 66 km
Semi-major axis: 48,227 km
Orbital Period: 0.294 days
Orbit
Naiad orbits about 23,500 km above Neptune's cloud tops. Since this is below the synchronous orbit radius, its orbit is slowly decaying due to tidal deceleration and may eventually impact Neptune's atmosphere, or break up into a planetary ring upon passing its Roche limit due to tidal stretching.
Naiad orbits Neptune well within its fluid Roche limit, and its density is expected to be low enough that it may be very close to its actual Roche limit already.
Naiad takes as long to rotate on its axis as it does to make one orbit of Neptune; and therefore always keeps the same hemisphere pointed to Neptune.
Physical characteristics
Naiad is irregularly shaped and probably has not been modified by any internal geological processes after its formation.
Little else is known about Naiad. Naiad is likely, like the other satellites inward of Triton, a rubble pile re-accreted from fragments of Neptune's original satellites, which were smashed up by perturbations from Triton soon after that moon's capture into a very eccentric initial orbit.
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