Nereid (GIF)

Neptune II

Nereid [NEER-ee-ed] was discovered in 1949 by astronomer Gerard Kuiper. Nereid is about 340 kilometers (210 miles) in diameter and is so far from Neptune that it requires 360 days to make one orbit. Voyager's best photos of Nereid were taken from about 4.7 million kilometers (2.9 million miles). The photos show that the moon's surface reflects about 14 percent of the sunlight that strikes it, making it somewhat more reflective than Earth's Moon, and more than twice as reflective as Proteus. Nereid's orbit is the most eccentric in the solar system. Its distance to Neptune ranges from about 1,353,600 kilometers (841,100 miles) to 9,623,700 kilometers (5,980,200 miles).

Nereid Statistics

Discovered by ................................. Gerard Kuiper
Date of discovery ...................................... 1949

Mass (kg) ................................................. ?
Equatorial radius (km) .................................. 170
Equatorial radius (Earth = 1) .................... 2.6654e-02
Mean density (gm/cm^3) .................................... ?

Mean distance from Neptune (km) ................... 5,513,400
Rotational period (days) .................................. ?
Orbital period (days) .............................. 360.1362
Mean orbital velocity (km/sec) ......................... 1.12

Orbital eccentricity ................................. 0.7512
Orbital inclination .................................... 27.6°

Visual geometric albedo ................................ 0.14
Magnitude (Vo) ......................................... 18.7

Neptune Triton

Author: Calvin J. Hamilton.