Sao (moon)

Sao

Discovery
Discovered by	M.Holman JJ Kavelaars T. Grav W. Fraser D. Milisavljevic
Discovered	August 14, 2002
Mean orbital elements
Epoch June 10, 2003
Semi-major axis	22.228 Gm
Eccentricity	0.1365
Inclination	53.483° *
Orbital period	2912.72 days (7.97 yr)
Physical characteristics
Mean diameter	44 km **
Rotation period	?
Albedo	0.04 assumed
Color	?
Spectral type	?
*to the ecliptic **based on the albedo

Sao (/ˈseɪ.oʊ/ SAY-oh; Greek: Σαώ) is a prograde irregular satellite of Neptune. It was discovered by Matthew J. Holman et al. on August 14, 2002.

Irregular satellites of Neptune.

Sao orbits Neptune at a distance of about 22.4 million km and is about 44 kilometers in diameter (assuming an albedo 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 to the apocentre, showing the eccentricity.

The satellite is in so-called 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; 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

• Ephemeris from MPC
• Mean orbital parameters from JPL

External links

• Matthew Holman's Neptune's page
• David Jewitt's pages
• Scott Sheppard's pages