Laomedeia (LAY-o-meh-DEE-uh, or LAY-o-meh-DYE-uh) is a small irregular satellite (a satellite with a distant, often highly inclined, eccentric or retrograde orbit) of Neptune. Its average distance from Neptune is a little less than 15 million miles, but it has a very eccentric orbit and is less than 9 million miles distant at perineptune, and almost 21 million miles away at aponeptune. The orbit is highly inclined, making an angle of about 40 degrees with the rotational plane of the planet, but does have prograde or direct motion, meaning it orbits in the same direction as the planet's rotation. Given its large distance from Neptune its rotational period cannot have any relationship to its orbital motion and is therefore unknown.
All the outer moons of Neptune are assumed to have albedos (or reflectivity) of about 4%. If that is correct, Laomedeia's brightness corresponds to an object about 25 miles in diameter. If it were assumed to have a density between 1 and 2 times that of water, its mass would be 40 to 80 trillion tons (4 to 8 times 10 to the 13th power). However, since the albedo could be substantially higher (or even a little lower) than the assumed value, its size and mass are essentially unknown.
|Data for Laomedeia|
Discovered by J. Kavelaars et al at Cerro Tololo, August 13, 2002 (as S/2002 N3; named in 2007)
Named after one of the Nereids
Orbital size 24 million km (about 15 million miles)
Orbital eccentricity 40%
Orbital inclination 38 degrees
Orbital period 3171 days = 8.68 years
Rotational period unknown
Diameter about 40 km (about 25 miles) (based on assumed albedo)
Albedo (reflectivity) 4% (assumed)