Neso (moon)
Matthew J. Holman et al.
Neso ( Neptune XIII ) is the outermost of the known moons of the planet Neptune. He is one of Neptune's outer retrograde irregular moons. He has the furthest distance from the central body and the longest orbit of a planet moon in the solar system.
Discovery and designation
Neso 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 of 14 August 2002 discovered until 30 September 2003. The images were taken by the 4.0 -meter Blanco telescope at Cerro Tololo Inter- American Observatory in Chile. Several recordings were digitally combined until the moon is in contrast to the line-shaped stars appeared point-like. The moon was initially lost again until he was found again in August 2003 by the same team before the orbit determination. The discovery was announced on 30 September 2003; the moon first received the provisional designation S/2002 N 4
On 3 February 2007, the moon was then Neso (Greek for "island" ), one of about 50 sea nymphs Nereids in Greek mythology, named. They are the beautiful daughters of the wise old man Nereus, the prophecy and constant transformation have been rumored, and his wife, Doris Oceanid.
Web properties
Neso orbits Neptune in a retrograde, highly elliptical orbit 21123500-77446500 km Distance to the center (large semi-major axis 49.285 million km or 1990.187 Neptune radii ). The orbital eccentricity is 0.5714 ( the second highest in the Neptune system ), the orbit is inclined 147.87 ° relative to the equator of Neptune. It can be assumed that the sun, these parameters are variable due to perturbations, as the eccentricity with 0.495 and 0.6221734, the orbital inclination ( with respect to the ecliptic ) with 132.6 and 140.66691 ° and the large semi-major axis from 48.387 to 49.190 Millionen km is specified.
The moon has the largest known orbit - regardless of whether you measure in kilometers or in planetary radii - and the longest orbital period of a moon in the solar system; Nesos average distance to Neptune is almost equal to the distance of the planet Mercury to the Sun, in its aphelion, the maximum distance to the central body, it surpasses this planet even significantly.
Since the two outermost retrograde moons Psamathe - which is removed on the average about 2.59 million km of Nesos orbit - and Neso due to the similar inclinations and semi-major axes form a group, called this after the erstentdeckten Moon Neso group. They probably originated from a single asteroid that was captured by Neptune and broke. The orbits of the two moons are close to the theoretical extreme stable distance to Neptune for body with retrograde orbit. The gravitational zone of influence of a planet is defined by its Hill sphere, which in the case of Neptune about 116 million kilometers; this is the greatest of all bodies in the solar system. It is assumed that satellite to 67% (corresponding to 76.3 million km ) of this range are stable.
Neso orbits Neptune in about 9740 days, 17 hours and 31 minutes, respectively, in approximately 26.868 Earth years, so it requires more than twice as much time as Jupiter. An orbit around the Sun and Saturn for nearly a year Also exist differing data from 9374 to 9595.61 days for the round trip time.
Physical Properties
The albedo is 16%. estimated. Thus, the surface would be relatively dark. The result for Neso a diameter of about 60 km. The density is estimated to be 1.5 g/cm3. So the moon is likely to be composed predominantly of water ice.
Research
Due to the large distance to Neptune and weak brightness of 25.6 like the 1:12.200.000 is opposite to the central planet, Neso was not found during the flyby of Voyager 2 in 1989. Since the discovery in 2002 Neso could only be observed by ground-based telescopes, so, however, their orbital elements and their brightness could be determined.