Psamathe (sam'-a-thee, Greek Ψαμαθεια, Latin Psamathē) is an irregular natural satellite of Neptune. It is also known as Neptune X (that is, the tenth named moon of Neptune). Moons of solar system scaled to Earths Moon The common noun moon (not capitalized) is used to mean any natural satellite of the other planets. ... Atmospheric characteristics Surface pressure ≫100 MPa Hydrogen - H2 80% ±3. ...
Psamathe was discovered by Scott S. Sheppard and David C. Jewitt in 2003. It orbits Neptune at a distance of about 46,695,000 km and is about 24 kilometers in diameter. Scott S. Sheppard is an astronomer based at the Institute for Astronomy at the University of Hawaii. ... David C. Jewitt is a Professor of astronomy at the University of Hawaii Institute for Astronomy. ... 2003 (MMIII) is a common year starting on Wednesday of the Gregorian calendar. ...
It is named after Psamathe, one of the Nereids. It was formerly known by the provisional designationS/2003 N 1. In Greek mythology, there were two people named Psamathe. ... In Greek mythology, the Nereids (NEER-ee-eds) are sea nymphs, the fifty daughters of Nereus and Doris. ... The provisional designation of comets and asteroids are similar to each other: they both follow a pattern set in 1925 by the Minor Planet Center of the IAU. Historical designations At first, astronomers strove to assign symbols to the minor planets: 1 Ceres a stylized sickle 2 Pallas a lozenge...
Eccentricity: 0.4499
Orbital inclination: 146.60° (to Neptune's equator), 124.39° (to the ecliptic)
Triton is unique among all large moons in the solar system for its retrograde orbit around the planet (i.e., it orbits in a direction opposite to the planet's rotation).
The small outer moons of Jupiter and Saturn also have retrograde orbits, as do three of Uranus' outer moons, but the largest of them (Phoebe) has only 8% of the diameter (and 0.03% of the mass) of Triton.
Moons in retrograde orbits cannot form out of the same region of the solar nebula as the planets they orbit, but must be captured from elsewhere; it is thought that Triton may be a captured Kuiper belt object.
Several moons are thought to be captured asteroids; others may be fragments of larger moons shattered by impacts, or (in the case of Earth's Moon) a portion of the planet itself blasted into orbit by a large impact.
Most moons in the solar system are tidally locked to their primaries, meaning that one side of the moon is always turned toward the planet.
Exceptions are Saturn's moon Hyperion, which rotates chaotically due to a variety of external influences, and the outermost moons of the gas giants, which are too far away to become 'locked' (an example is Saturn's moon Phoebe).
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