Gallic Group. Inuit Group. Irregular moon. In astronomy, an irregular moon is a natural satellite following a distant, inclined, and often eccentric and retrograde orbit.
They are believed to have been captured by their parent planet, unlike regular satellites, which formed in situ. Definition[edit] In practice, the satellite's semi-major axis is compared with the planet's Hill sphere (that is, the sphere of its gravitational influence) . Irregular satellites have semi-major axes greater than 0.05. Moons of Saturn. Artist's concepts of the Saturnian ring–moon system Saturn, its rings and major icy moons—from Mimas to Rhea Images of several moons of Saturn.
From left to right: Mimas, Enceladus, Tethys, Dione, Rhea; Titan in the background; Iapetus (top) and irregularly shaped Hyperion (bottom). Some small moons are also shown.