Thalassa appears to be about 80 kilometers (50 miles) in diameter. It orbits Neptune in 7 hours, 30 minutes about 25,200 kilometers (15,700 miles) above the cloud tops. It is irregularly shaped and shows no sign of any geological modification. Thalassa circles the planet in the same direction as Neptune rotates. The above image has been slightly smeared so that Thalassa appears highly elongated.
Discovered by Voyager 2
Date of discovery 1989
Mass (kg) ?
Equatorial radius (km) 40
Equatorial radius (Earth = 1) 6.2716e-03
Mean density (gm/cm^3) ?
Mean distance from Neptune (km) 50,000
Rotational period (days) ?
Orbital period (days) 0.311485
Mean orbital velocity (km/sec) 11.68
Orbital eccentricity 0.0002
Orbital inclination (degrees) 0.21
Visual geometric albedo 0.06
Magnitude (Vo) 23.8
Neptune Naiad Despina
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