Psamathe (moon)
Moon of Neptune
From Wikipedia, the free encyclopedia
Psamathe /ˈsæməθiː/, also known as Neptune X, is a retrograde irregular satellite of Neptune. It is named after Psamathe, one of the Nereids. Psamathe was discovered by Scott S. Sheppard and David C. Jewitt in 2003 using the 8.2 meter Subaru Telescope.[4] Before it was officially named on February 3, 2007 (IAUC 8802), it was known by the provisional designation S/2003 N 1.[6]
 Discovery images of Psamathe by the Subaru Telescope in 2003 | |
| Discovery[1][2] | |
|---|---|
| Discovered by | |
| Discovery date | 19 August 2003 |
| Designations | |
Designation | Neptune X |
| Pronunciation | /ˈsæməθiː/ |
Named after | Ψαμάθη Psamathē |
| S/2003 N 1 | |
| Adjectives | Psamathean /sæməˈθiːən/ |
| Orbital characteristics | |
| Satellite of | Neptune |
| Group | Neso group |
| Proper orbital elements[3] | |
Proper semi-major axis | 47,646,600 km (0.318498 AU) |
Proper eccentricity | 0.413 |
Proper inclination | 127.8° |
Proper orbital period | 25.05 years (9,149 d) |
Precession of perihelion | 874.6486 arcsec / yr |
Precession of the ascending node | 972.3189 arcsec / yr |
| Physical characteristics | |
| 40 km (for albedo 0.04)[4] | |
| Albedo | 0.04 (assumed)[4] |
| 10.8[5] | |
Psamathe is about 38 kilometers in diameter. It orbits Neptune at a distance of between 25.7 and 67.7 million km (for comparison, the Sun–Mercury distance varies between 46 million and 69.8 million km) and requires almost 25 Earth years to make one orbit. The orbit of this satellite is close to the theoretical stable separation from Neptune for a body in a retrograde orbit. Given the similarity of Psamathe's orbital parameters with Neso (S/2002 N 4), it was suggested that both irregular satellites could have a common origin in the breakup of a larger moon.[4] Both are farther from their primary than most other known moons in the Solar System (although not as far as S/2021 N 1).[7]
