Neso , also known as Neptune XIII, is the second-outermost known

natural satellite A natural satellite is, in the most common usage, an astronomical body that orbits a planet, dwarf planet, or small Solar System body (or sometimes another natural satellite). Natural satellites are colloquially referred to as moons, a deriv ...

Neptune Neptune is the eighth and farthest known planet from the Sun. It is the List of Solar System objects by size, fourth-largest planet in the Solar System by diameter, the third-most-massive planet, and the densest giant planet. It is 17 t ...

, after S/2021 N 1. It is a

retrograde Retrograde may refer to: Film and television * Retrograde (2004 film), ''Retrograde'' (2004 film), a film by Christopher Kulikowski * Retrograde (2022 American film), ''Retrograde'' (2022 American film), a documentary film by Matthew Heineman * ...

irregular moon In astronomy, an irregular moon, irregular satellite, or irregular natural satellite is a natural satellite following an orbit that is irregular in some of the following ways: Distant; inclined; highly elliptical; retrograde. They have often be ...

discovered by Matthew J. Holman, Brett J. Gladman, ''et al.'' on 14 August 2002, though it went unnoticed until 2003. 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 exceeds Mercury's

aphelion An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. The line of apsides (also called apse line, or major axis of the orbit) is the line connecting the two extreme values. Apsides perta ...

, which is approximately 70 million km from the

Sun The Sun is the star at the centre of the Solar System. It is a massive, nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light a ...

Neso is also the moon with the second-longest orbital period, 26.67 years. It follows a retrograde, highly inclined, and highly

eccentric Eccentricity or eccentric may refer to: * Eccentricity (behavior), odd behavior on the part of a person, as opposed to being "normal" Mathematics, science and technology Mathematics * Off- center, in geometry * Eccentricity (graph theory) of a ...

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 An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. The line of apsides (also called apse line, or major axis of the orbit) is the line connecting the two extreme values. Apsides perta ...

to the apocentre, showing the eccentricity. Neso is affected by the

Kozai mechanism In celestial mechanics, the Kozai mechanism is a dynamical phenomenon affecting the orbit of a binary system perturbed by a distant third body under certain conditions. The mechanism is also named von Zeipel-Kozai-Lidov, Lidov–Kozai, Kozai–Li ...

. Neso is about in diameter based on an assumed albedo of 0.04. Given the similarity of the orbit's parameters with

Psamathe Psamathe may refer to: Greek mythology * Psamathe (Nereid) * Psamathe (Crotopus), Daughter of Crotopus Other

* Psamathe (moon), moon of Neptune * Psamathe (polychaete), ''Psamathe'' (polychaete), polychaete worm genus * Psamathe (Leighton), '' ...

(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 In Greek mythology, the Nereids or Nereides ( ; ; , also Νημερτές) are sea nymphs (female spirits of sea waters), the 50 daughters of the 'Old Man of the Sea' Nereus and the Oceanids, Oceanid Doris (Oceanid), Doris, sisters to their bro ...

. Before it was officially named on 3 February 2007 (IAUC 8802), Neso was known by its provisional designation, S/2002 N 4.

References

MPC: Natural Satellites Ephemeris Service
* Mean orbital parameters fro
JPL

External links

{{DEFAULTSORT:Neso (Moon) Neso group Moons of Neptune Irregular satellites Discoveries by Tommy Grav Discoveries by Brett J. Gladman 20020814 Moons with a retrograde orbit Kozai mechanism

See also

References

External links