Psamathe, also known as Neptune X and previously as S/2003 N 1, is an irregular moon of Neptune. It was discovered by Scott Sheppard, David Jewitt, and Jan Kleyna at Mauna Kea Observatory on 29 August
Irregular moons of all four giant planets, plotted by average distance from their planet (semi-major axis in Hill radii) and orbital inclination (degrees with respect to ecliptic). The Neso group is the cluster of retrograde moons labeled in blue.