Neso (moon)
Discovery | |
---|---|
Discovered by |
|
Discovery site | Cerro Tololo Obs. |
Discovery date | 14 August 2002 |
Designations | |
Designation | Neptune XIII |
Pronunciation | /ˈniːsoʊ/ |
Named after | Νησώ Nēsō |
S/2002 N 4 | |
Adjectives | Nesoan /nɪˈsoʊ.ən/ or Nesoian /nɪˈsoʊ.iən/ |
Orbital characteristics | |
Epoch 10 June 2003 | |
Observation arc | 19.96 yr (7,292 days) |
Periapsis | ~21,215,700 km (0.141 AU) |
Apoapsis | ~77,784,500 km (0.518 AU) |
0.33 AU (~49,500,000 km), 3,220 Neptune radii, 49.285 Gm | |
Eccentricity | 0.5714 |
9740.73 d (26.67 y) | |
Inclination | 136.439° |
Satellite of | Neptune |
Physical characteristics | |
Mean diameter | 60 km (for albedo 0.04) |
Albedo | 0.04 (assumed) |
Spectral type | V–R = 0.58±0.13 V–I = 1.0±0.4 R–I = 0.7±0.4 |
25.6±0.3 (V-band) | |
10.67 | |
Neso /ˈniːsoʊ/, also known as Neptune XIII, is the outermost known natural satellite of Neptune. It is a retrograde irregular moon discovered by Matthew J. Holman, Brett J. Gladman, et al. on 14 August 2002, though it went unnoticed until 2003. Neso orbits Neptune at a distance of more than 48 Gm (billion m), making it (as of 2015) the most distant known moon of any planet. At apocenter, the satellite is more than 72 Gm from Neptune. This distance exceeds Mercury's aphelion, which is approximately 70 Gm from the Sun.
Neso is also the moon with the longest orbital period, 26.67 years. It follows a retrograde, highly inclined, and highly eccentric orbit illustrated on the diagram in relation to other irregular satellites of Neptune. The satellites above the horizontal axis are prograde, the satellites beneath it are retrograde. The yellow segments extend from the pericentre to the apocentre, showing the eccentricity.
Neso is about 60 km (37 mi) in diameter based on an assumed albedo.
Given the similarity of the orbit's parameters with Psamathe (S/2003 N 1), it was suggested that both irregular satellites could have a common origin in the break-up of a larger moon.
Neso is named after one of the Nereids. Before it was officially named on 3 February 2007 (IAUC 8802), Neso was known by its provisional designation, S/2002 N 4.