Sao is a prograde

irregular satellite 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 ...

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 ...

. It was discovered by Matthew J. Holman ''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 fraction of sunlight that is Diffuse reflection, diffusely reflected by a body. It is measured on a scale from 0 (corresponding to a black body that absorbs all incident radiation) to 1 (corresponding to a body that reflects ...

of 0.04). Sao follows an exceptionally inclined and moderately 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 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. The satellite is in Kozai resonance, 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 ( ; ; , 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 ...

; 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) Sao group Moons of Neptune Irregular satellites Discoveries by Tommy Grav 20020814 Moons with a prograde orbit Kozai mechanism