Neso (moon)
| Neso | |
|---|---|
| Provisional or systematic name | S / 2002 N 4 |
| Central body | Neptune |
| Properties of the orbit | |
| Major semi-axis | 49,285,000 km |
| Periapsis | 21,123,500 km |
| Apoapsis | 77,446,500 km |
| eccentricity | 0.5714 |
| Orbit inclination to the equator of the central body | 147.87 ° |
| Orbit inclination to the ecliptic | 136.439 ° |
| Orbital time | 9740.73 d |
| Mean orbital velocity | 0.35 km / s |
| Physical Properties | |
| Albedo | ≈ 0.16 |
| Apparent brightness | 25.6 mag |
| Medium diameter | ≈ 60 km |
| Dimensions | ≈ 1.6485 10 17 kg |
| Medium density | ≈ 1.5 g / cm 3 |
| Acceleration of gravity on the surface | ≈ 0.010 m / s 2 |
| discovery | |
| Explorer |
Matthew J. Holman et al. |
| Date of discovery | August 14, 2002 |
| Remarks | largest and longest orbit of a natural satellite in the solar system |
Neso (also Neptune XIII ) is the outermost of the known moons of the planet Neptune . It is one of Neptune's outer retrograde irregular moons . It has the furthest distance to the central body and the longest orbit of a planetary moon in the solar system.
Discovery and naming
Neso was founded on August 14, 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 August 14, 2002 to September 30, 2003. The recordings were made with the 4-meter Blanco telescope at the Cerro Tololo Inter-American Observatory in Chile . Several images were digitally combined until the moon appeared point-like in contrast to the line-shaped stars. The moon was initially lost again before the orbit was determined until it was found again by the same team in August 2003. The discovery was announced on September 30, 2003; the moon was initially given the provisional designation S / 2002 N 4 .
On February 3, 2007 the moon was named after Neso (Greek for “island”), one of the 50 or so Nereid sea nymphs from Greek mythology . They are the beautiful daughters of the wise old man Nereus , who was said to be prophecy and constant metamorphosis, and his wife, the Oceanid Doris .
Track properties
Neso orbits Neptune on a retrograde , highly elliptical orbit between 21,123,500 and 77,446,500 km from its center (major orbit half-axis 49,285,000 km or 1,990,187 Neptune radii). The orbital eccentricity is 0.5714 (the second highest in the Neptun system ), the web is 147.87 ° relative to the equator of Neptune inclined . It can be assumed that these parameters are variable due to orbital disturbances by the sun , since the eccentricity is also 0.495 and 0.6221734, the orbit inclination (compared to the ecliptic ) with 132.6 and 140.66691 ° and the major orbit half-axis between 48.387 and 49.190 million km is specified.
The moon has the largest known orbit - regardless of whether you measure in kilometers or in planetary radii - and the longest orbit of a moon in the solar system ; Neso's mean distance to Neptune almost corresponds to the distance of the planet Mercury to the sun, in its aphelion , the maximum distance to the central body, it even exceeds this planet significantly.
Since the two outermost retrograde moons Psamathe - which is on average about 2,590,000 km from Neso's orbit - and Neso form a group due to the similar inclinations and the major semi-axes, this is called the Neso group after the first discovered moon . It was likely formed from a single asteroid that was captured by Neptune and shattered. The orbits of these two moons are close to the most theoretical stable distance from Neptune for bodies with retrograde orbits. The gravitational zone of influence of a planet is defined by its Hill sphere , which at Neptune is about 116,000,000 km; this is the largest of all bodies in the solar system. It is assumed that satellites are stable up to 67% (corresponding to 76,300,000 km) of this area.
Neso orbits Neptune in 9740 days, 17 hours and 31 minutes, that is almost 27 earth years. The moon needs more than twice as much time for its orbit as Jupiter for one orbit around the sun and almost a Saturn year. There are also different information for the orbital period between 9374 and 9595.61 days.
Physical Properties
The reflectivity is reduced to 16%. estimated. That would make the surface relatively dark. This results in a diameter of approx. 60 km for Neso. The density is estimated at 1.5 g / cm 3 . This means that the moon is mostly composed of water ice .
exploration
Due to the great distance to Neptune and the weak brightness of 25.6 mag, which is 1: 12,200,000 compared to the central planet, Neso was not found when Voyager 2 flew by in 1989. Since its discovery in 2002, Neso could only be observed through terrestrial telescopes, but this could determine its orbital elements and their brightness.
Web links
- IAUC 8213: S / 2001 U 2 and S / 2002 N 4 October 1, 2003 (discovery)
- IAUC 8802: Satellites of Neptune February 3, 2007 (numbering and naming)
- IAU: Natural Satellites Ephemeris Service IAU: Orbital parameters and ephemeris of irregular moons
- NASA: Planetary Satellite Physical Parameters NASA: Physical Parameters (English)
- NASA: Planetary Satellite Mean Orbital Parameters NASA: Orbital Parameters (English)
- NASA: Neptunian Satellite Fact Sheet NASA: List of Parameters
- Scott S. Sheppard: Neptune's Known Satellites List with parameters of the Neptune system (English)
- USGS: Planet and Satellite Names and Discoverers Names of planets and satellites
- Polish moon page: Neso description and further links (English)