Sao (moon)

Matthew J. Holman et al.

Sao ( Neptune XI) is the fourth outermost moon of the planet Neptune. He is one of prograde irregular moons of Neptune.

Discovery and designation

Sao was on 14 August 2002 by a team consisting of Matthew J. Holman, John J. Kavelaars, Tommy Grav, Brett J. Gladman, Wesley C. Fraser, Dan Milisavljevic, Philip D. Nicholson, Joseph A. Burns, Valerio Carruba, Jean -Marc Petit, Philippe Rousselot, Oliver Mousis, Brian G. Marsden and Robert A. Jacobson on recordings from 14 August to 4 September 2002, and on 10 August 2001 discovered along with Halimede and Laomedeia. The images were taken by the 4.0 -meter Blanco telescope at the Cerro Tololo Inter- American Observatory in Chile, and the 3.6 -meter Canada -France - Hawaii Telescope in Hawaii. Several recordings were digitally combined until the moons as opposed to the line-shaped stars appeared point-like. The discovery was announced on 13 January 2003; the moon first received the provisional designation S/2002 N 2

On 3 February 2007, the moon was then named ( " the -saving " for Greek), one of about 50 sea nymphs Nereids in Greek mythology to Sao. They are the beautiful daughters of the wise old man Nereus, the prophecy and constant transformation have been rumored, and his wife, Doris of Oceanid. Sao been associated with sailing.

Web properties

Sao orbits Neptune on a prograde, elliptical path 19054600-25309430 km Distance to the center ( large semi-major axis 22,182,010 895.736 or Neptun radii ). The orbital eccentricity of 0.1409888, the orbit is inclined 65.22 ° relative to the equator of Neptune. The moon is in a so-called Kozai - orbital resonance, which means that its orbital inclination and eccentricity are coupled to each other ( the orbital inclination decreases when increasing the eccentricity, and vice versa). It can therefore be assumed that these parameters are variable, since the eccentricity is specified with 0.2931, the orbital inclination ( with respect to the ecliptic ) with 48.511 ° and the Great semi-major axis from 22.228 to 22.422 Millionen km.

The orbit of the next inner moon Halimede is on average about 5.6 million km away from Saos orbit, the distance of the path of the next outer moon Laomedeia averages around 1.3 million km.

Sao orbits Neptune in about 2905 days 15 hours and 22 minutes or about 7,961 Earth years, ie longer than the four inner planets, the dwarf planet Ceres and the majority of the asteroids of the main belt need around the sun.

Physical Properties

Sao has a diameter of 44 km estimated, based on the assumed for them albedo of 16%. The surface is thus relatively dark. Their density is estimated to be 1.5 g/cm3. So the moon is likely to be composed predominantly of water ice.

It is believed that the moon is a captured asteroid.

Research

Because of the great distance to Neptune and weak brightness of 25.4 like the 1:12000000 is opposite to the central planet, Sao was not found during the flyby of Voyager 2 in 1989. Since the discovery in 2002 Sao could only be observed by ground-based telescopes, while their orbital elements and their brightness can be determined.