Nereid

Image of Nereid taken by Voyager 2
Date of discovery |  May 1, 1949[1]
Name of discoverer |  Gerard P. Kuiper[1][2]
Name origin |  Any of fifty women, daughters of Nereus and Doris, who attended Neptune
Orbital characteristics
Primary | Neptune
Order from primary |  8
Periposeidion | 1,371,734 km[3]
Apoposeidion | 9,655,066 km[3]
Semi-major axis | 5,513,400 km[4]
Orbital eccentricity | 0.7512[4]
Sidereal month | 360.13619 da[4]
Avg. orbital speed | 1.12 km/s[5]
Inclination | 27.6°[5] to Neptune's equator
Rotational characteristics
Sidereal day |  11.52 hr[6]
Rotational speed |  0.02576 km/s[3]
Physical characteristics
Mass |  3.09 * 1019 kg[3]
Density |  1,500 kg/m³[7]
Mean radius |  170 km[7]
Surface gravity |  0.713 m/s²[3]
Escape speed |  0.156 km/s[3]
Surface area |  363,158 km²[3]
Composition |  Ice and silicates[8]
Color |  Neutral gray
Albedo |  0.155[7]
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.

## Contents

* 1 Discovery and naming
* 2 Orbital characteristics
* 3 Rotational characteristics
* 4 Physical characteristics
* 5 Observation and Exploration
* 6 References

## Discovery and naming[edit]

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[edit]

Nereid is in a highly eccentric orbit around Neptune, and in fact its orbit is the most eccentric orbit of any solar system body.[9] 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.[4] 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.[10]

## Rotational characteristics[edit]

Nereid's sidereal day is 11.52 hours and is considered regular.[6]

## Physical characteristics[edit]

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.[11]

## Observation and Exploration[edit]

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

## References[edit]

1. ↑ 1.0 1.1 "Gazetteer of Planetary Nomenclature: Planetary Body Names and Discoverers." US Geological Survey, Jennifer Blue, ed. March 31, 2008. Accessed May 9, 2008.
2. ↑ Kuiper, Gerard P. "The Second Satellite of Neptune." Publications of the Astronomical Society of the Pacific, 61:175-176, 1949. Accessed June 8, 2008.
3. ↑ 3.0 3.1 3.2 3.3 3.4 3.5 3.6 Calculated
4. ↑ 4.0 4.1 4.2 4.3 Neptunian Satellite Fact Sheet, NASA, January 22, 2008. Accessed May 9, 2008.
5. ↑ 5.0 5.1 Hamilton, Calvin J. "Entry for Nereid." Views of the Solar System, 2000. Accessed June 8, 2008.
6. ↑ 6.0 6.1 Grav, Tommy, Holman, Matthew J., and Kavelaars, J. J. "The Short Rotation Period of Neptune." Astrophysical Journal Letters 591:L71-L74, July 1, 2003. arXiv:astro-ph/0306001 doi:10.1086/377067 Accessed June 8, 2008.
7. ↑ 7.0 7.1 7.2 "Planetary Satellite Physical Parameters." JPL, NASA. Retrieved June 8, 2008.
8. ↑ "Nereid." Encyclopædia Britannica. 2008. Encyclopædia Britannica Online. 8 June 2008.
9. ↑ Arnett, Bill. "Entry for Nereid." The ~~Nine~~ 8 Planets, May 6, 1995. Accessed June 8, 2008.
10. ↑ Tytell, David. "Neptune's Stowaway." Sky and Telescope, September 11, 2003. Accessed June 8, 2008.
11. ↑ Grav, T., Holman M. J., and Fraser W. "Photometry of Irregular Satellites of Uranus and Neptune." Astrophys. J. 613(2004):L77-L80. arXiv:astro-ph/0405605v1 Accessed June 8, 2008.

v • d • e

The Solar System

Star|

Sol

Terrestrial Planets|

Mercury · Venus · Earth · Mars

Gas Giants|

Jupiter · Saturn · Uranus · Neptune

Dwarf Planets|

Ceres · Haumea · Makemake · Pluto · Eris

Asteroid Belt|

Major asteroids · C-type asteroids · S-type asteroids · M-type asteroids

Trans-Neptunian Objects|

Kuiper belt · Scattered disk · Oort Cloud · Nemesis

Satellites|

Moon · Phobos · Deimos · Io · Europa · Ganymede · Callisto · Mimas · Enceladus · Tethys · Dione · Rhea · Titan · Hyperion · Iapetus · Miranda · Ariel · Umbriel · Titania · Oberon · Triton · Nereid · Charon · Nix · Hydra · Dysnomia

Categories