Nereid

Nereid, or Neptune II, is the second moon of Neptune to be discovered. It is also the third most massive of Neptune's thirteen moons, and eighth in orbit around Neptune.

Discovery and naming
Gerard P. Kuiper discovered Nereid in 1949. He gave it the generic name of the fifty female attendants of Neptune, the Roman god of the sea.

Orbital characteristics
Nereid is in a highly eccentric orbit around Neptune, and in fact its orbit is the most eccentric orbit of any solar system body. Its sidereal month is about 360.14 Julian days. Nereid's orbit is inclined about 28 degrees from Neptune's equator, but is inclined only 7.23 degrees from the local Laplace plane. Almost no astronomer believes that Nereid formed with the planet, and most astronomers believe that Nereid is a captured Kuiper belt or other trans-Neptunian object.

Rotational characteristics
Nereid's sidereal day is 11.52 hours and is considered regular.

Physical characteristics
Nereid has a mass of 3.09 * 1019 kg, the third greatest mass of the moons of Neptune. Its color is neutral-gray. Another moon of Neptune, Halimede (formerly S/2002 N 1), has the same neutral color, leading some astronomers to suggest that Halimede is a fragment of Nereid broken off in a collision with another, unknown object.

Observation and Exploration
Telescopic observation has revealed little about Nereid beyond its orbital elements. The one spacecraft that visited the Neptunian system, Visiting mission::Voyager 2, captured one low-resolution image of Nereid but did not fly close enough to it to discover more.

Related Links

 * Nereid by Wikipedia

Néréide