Sao is a prograde

irregular satellite In astronomy, an irregular moon, irregular satellite or irregular natural satellite is a natural satellite following a distant, inclined, and often eccentric and retrograde orbit. They have been captured by their parent planet, unlike regular s ...

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

. It was discovered by

Matthew J. Holman Matthew J. Holman (born 1967) is a Smithsonian Astrophysical Observatory, Smithsonian astrophysicist and lecturer at Harvard University. Holman studied at MIT, where he received his bachelor's degree in mathematics in 1989 and his PhD in planetar ...

''et al.'' on August 14, 2002. TheIrregulars NEPTUNE GROUPS

Sao orbits Neptune at a distance of about 22.4 million km and is about 44 kilometers in diameter (assuming an

albedo Albedo (; ) is the measure of the diffuse reflection of sunlight, solar radiation out of the total solar radiation and measured on a scale from 0, corresponding to a black body that absorbs all incident radiation, to 1, corresponding to a body ...

of 0.04). Sao follows an exceptionally

inclined Incline, inclined, inclining, or inclination may refer to: *Grade (slope), the tilt, steepness, or angle from horizontal of a topographic feature (hillside, meadow, etc.) or constructed element (road, railway, field, etc.) *Slope, the tilt, steepn ...

and moderately

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 v ...

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 (astronomy), primary body. For example, the apsides of the Earth are called the aphelion and perihelion. General description There are two ...

to the apocentre, showing the eccentricity. The satellite is in

Kozai resonance 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. It is also known as the von Zeipel-Kozai-Lidov, Lidov–Kozai mechanism, Kozai ...

, i.e. its inclination and eccentricity are coupled (the inclination of the orbit decreases while eccentricity increases and ''vice versa''). Sao, or Neptune XI, like many of the outer satellites of Neptune, is named after one of the

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

; Sao was associated with sailing and is referred to as "The rescuer" or "Safety". Before the announcement of its name on February 3, 2007 (IAUC 8802), Sao was known provisionally as S/2002 N 2.

References

* Ephemeri
from MPC
* Mean orbital parameter
from JPL

External links

{{DEFAULTSORT:Sao (Moon) Moons of Neptune Irregular satellites 20020814 Moons with a prograde orbit