Psamathe (moon)
| Psamathe | |
|---|---|
| Provisional or systematic name | S / 2003 N 1 |
| Central body | Neptune |
| Properties of the orbit | |
| Major semi-axis | 46,695,000 km |
| Periapsis | 25,687,000 km |
| Apoapsis | 67,703,000 km |
| eccentricity | 0.4499 |
| Orbit inclination to the equator of the central body | 146.60 ° |
| Orbit inclination to the ecliptic | 137.391 ° |
| Orbital time | 9115.9 d |
| Mean orbital velocity | 0.37 km / s |
| Physical Properties | |
| Albedo | ≈ 0.16 |
| Apparent brightness | 24.6 mag |
| Medium diameter | ≈ 38 km |
| Dimensions | ≈ 1.4987 10 16 kg |
| Medium density | ≈ 1.5 g / cm 3 |
| Acceleration of gravity on the surface | ≈ 0.0028 m / s 2 |
| Escape speed | ≈ 10.27 m / s |
| discovery | |
| Explorer |
Scott S. Sheppard , David C. Jewitt , |
| Date of discovery | August 29, 2003 |
| Remarks | second smallest known Neptune moon |
Psamathe (also Neptune X ) is the second outermost moon on the planet Neptune . It is one of Neptune's outer retrograde irregular moons .
Discovery and naming
Psamathe was recorded on August 29, 2003 by a team consisting of Scott S. Sheppard , David C. Jewitt , Jan Kleyna and John J. Kavelaars on recordings from July 4 to August 30, 2003 as well as from August 11, 2001 and from 14 . discovered by August 16, 2002. The images were taken through the 8.2 meter Subaru telescope at the Mauna Kea Observatory in Hawaii . Several images were digitally combined until the moon appeared point-like in contrast to the line-shaped stars. Almost at the same time, Matthew J. Holman's team discovered the moon at the 4-meter Blanco telescope at the Cerro Tololo Inter-American Observatory in Chile . The discovery was announced on September 3, 2003; the moon was initially given the provisional designation S / 2003 N 1 . It was the last Neptune moon to be discovered until 2013 .
On February 3rd, 2007 the moon was named after Psamathe (Greek for "sand"), one of the 50 or so Nereids , 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 . Psamathe was the wife of Proteus .
Track properties
Psamathe orbits Neptune on a retrograde , very elliptical orbit between 25,687,000 and 67,703,000 km from its center (major orbit half-axis 46,695,000 km or 1,885,600 Neptune radii). The orbital eccentricity is 0.4499, the web is 146.60 ° 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 0.2430713 and 0.3809, the orbit inclination (compared to the ecliptic ) with 124.4634 and 126.312 ° and the major orbit half-axis between 46.695 and 49.393 million km is specified. Psamathe's distance to Neptune is almost the same as the distance between the planet Mercury and the sun.
The orbit of the next inner prograde moon Laomedeia is on average about 25.9 million km away from Psamathe's orbit, the distance of the orbit of the next outer retrograde moon Neso is only about 2,590,000 km on average.
Since the two outermost retrograde moons Psamathe 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 satellite orbits are stable up to 67% (corresponding to 76,300,000 km) of this area.
Psamathe orbits Neptune in around 9115 days or around 24.975 earth years, so it takes almost as long as Saturn does for its orbit around the sun. For the period of rotation there are also different information between 9074.3 and 9654.93 days.
Physical Properties
Psamathe is estimated to have a diameter of 38 km, based on an assumed retroreflective power of 16%. The surface is therefore relatively dark. Based on this estimate, Psamathe appears to be the second smallest known Neptune moon to date. Their 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 24.6 mag, which is 1: 5,250,000 compared to the central planet, Psamathe was not found during the flyby of Voyager 2 in 1989. Since its discovery in 2003, Psamathe could only be observed through earth-based telescopes and its orbital elements and their brightness could be determined.
Web links
- IAUC 8193: Satellites of Neptune September 3, 2003 (rediscovery)
- 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: Psamathe description and further links (English)
- German moon page: The outer moons of Neptune images from Psamathe