 Neso imaged by theVery Large Telescope's FORS1 imager in September 2002 | |
| Discovery[1][2] | |
|---|---|
| Discovered by |
|
| Discovery site | Cerro Tololo Obs. |
| Discovery date | 14 August 2002 |
| Designations | |
Designation | Neptune XIII |
| Pronunciation | /ˈniːsoʊ/ |
Named after | ΝησώNēsō |
| S/2002 N 4 | |
| Adjectives | Nesoan/nəˈsoʊ.ən/ orNesoian/nəˈsoʊ.iən/ |
| Orbital characteristics | |
| Observation arc | 19.96yr (7,292 days)[3] |
| Satellite of | Neptune |
| Group | Neso group |
| Proper orbital elements[4] | |
Propersemi-major axis | 49,897,800 km (0.333546 AU) |
Propereccentricity | 0.455 |
Properinclination | 128.4° |
Properorbital period | 26.84 years (9,805 d) |
Precession of theascending node | 1161.29032 arcsec / yr |
| Physical characteristics | |
| 60 km(for albedo 0.04)[5] | |
| Albedo | 0.04(assumed)[5] |
Spectral type | V–R =0.58±0.13[6] V–I =1.0±0.4[7] R–I =0.7±0.4[7] |
| 25.6±0.3 (V-band)[7] | |
| 10.67[3] | |
Neso/ˈniːsoʊ/, also known asNeptune XIII, is the second-outermost knownnatural satellite ofNeptune, afterS/2021 N 1. It is aretrogradeirregular moon discovered byMatthew J. Holman,Brett J. Gladman,et al. on 14 August 2002, though it went unnoticed until 2003.[2][8] Neso is the second-most distant moon of Neptune, with an average orbital distance of nearly 49.6 million km. At its farthest point of its orbit, the satellite is more than 72 million km from Neptune. This distance exceedsMercury'saphelion, which is approximately 70 million km from theSun.
Neso is also the moon with the second-longest orbital period, 26.8 years.[4] It follows a retrograde, highlyinclined, and highlyeccentric orbit illustrated on the diagram in relation to other irregular satellites of Neptune. The satellites above the horizontal axis areprograde, the satellites beneath it are retrograde. The yellow segments extend from thepericentre to theapocentre, showing the eccentricity.
Neso is affected by theKozai mechanism.[9]
Neso is about 60 km (37 mi) in diameter based on an assumed albedo of 0.04.
Given the similarity of the orbit's parameters withPsamathe (S/2003 N 1), it was suggested that both irregular satellites could have a common origin in the break-up of a larger moon.[5]
Neso is named after one of theNereids. Before it was officially named on 3 February 2007 (IAUC 8802), Neso was known by its provisional designation,S/2002 N 4.
Listed in approximately increasing distance fromNeptune | |||||||||||
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| Irregular |
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| Geography |  | ||||||
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