Irregular moon Irregular moon In astronomy, an irregular moon, irregular satellite or irregular natural satellite is a natural satellite following a distant, inclined, and often eccentric and retrograde orbit. They have been captured by their parent planet, unlike regular satellites, which formed in orbit around them. As of July 2018, 125 irregular moons are known, orbiting all four of the outer planets (Jupiter, Saturn, Uranus and Neptune). The largest of each planet are Himalia of Jupiter, Phoebe of Saturn, Sycorax of Uranus, and Triton of Neptune. It is currently thought that the irregular satellites were captured from heliocentric orbits near their current
Supersynchronous orbit Ariane 5 flight VA241. However, due to launch crew error resulting in anomaly and a deviation of the trajectory, the satellites were not inserted into the intended orbit, causing a reschedule of their maneuvering plan. Most natural satellites in the Solar System are in supersynchronous orbits. The Moon is in a supersynchronous orbit of Earth, orbiting more slowly than the 24-hour rotational period of Earth. The inner of the two Martian moons, Phobos, is in a subsynchronous orbit of Mars with an orbital period of only 0.32 days. The outer moon Deimos is in supersynchronous orbit around Mars. The Mars