 Discovery images of Psamathe by theSubaru Telescope in 2003 | |
| Discovery[1][2] | |
|---|---|
| Discovered by | |
| Discovery date | 19 August 2003 |
| Designations | |
Designation | Neptune X |
| Pronunciation | /ˈsæməθiː/ |
Named after | ΨαμάθηPsamathē |
| S/2003 N 1 | |
| Adjectives | Psamathean/sæməˈθiːən/ |
| Orbital characteristics | |
| Epoch 1 January 2000(Proper orbital element) | |
| Observation arc | 20.97yr (7,660 days)[3] |
| 183.3°(proper) | |
| Satellite of | Neptune |
| Group | Neso group |
| Proper orbital elements[4] | |
Propersemi-major axis | 47,615,100 km = 0.318 AU |
Propereccentricity | 0.414 |
Properinclination | 127.8° |
Propermean motion | 14.371255 deg / yr |
Properorbital period | 25.05yr (9149.514d) |
Precession ofperihelion | 874.6486 arcsec / yr |
Precession of theascending node | 972.3189 arcsec / yr |
| Physical characteristics | |
| 40 km(for albedo 0.04)[5] | |
| Albedo | 0.04(assumed)[5] |
Psamathe/ˈsæməθiː/, also known asNeptune X, is aretrogradeirregular satellite ofNeptune. It is named afterPsamathe, one of theNereids. Psamathe was discovered byScott S. Sheppard andDavid C. Jewitt in 2003 using the 8.2 meterSubaru Telescope.[5] Before it was officially named on February 3, 2007 (IAUC 8802), it was known by theprovisional designationS/2003 N 1.[6]
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 thetheoretical stable separation from Neptune for a body in a retrograde orbit. Given the similarity of Psamathe's orbital parameters withNeso (S/2002 N 4), it was suggested that both irregular satellites could have a common origin in the breakup of a larger moon.[5] Both are farther from their primary than most other known moons in the Solar System (although not as far asS/2021 N 1).[7]
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