Getting to know the Satellites
The Solar System’s planets and officially recognised dwarf planets are known to be orbited by 182 natural satellites, or moons. 19 moons in the Solar System are large enough to be gravitationally rounded, and thus would be considered planets or dwarf planets if they were in direct orbit around the Sun.
Moons are classed in two separate categories according to their orbits: regular moons, which have prograde orbits (they orbit in the direction of their planets’ rotation) and lie close to the plane of their equators, and irregular moons, whose orbits can be pro- or retrograde(against the direction of their planets’ rotation) and often lie at extreme angles to their planets’ equators. Irregular moons are probably minor planets that have been captured from surrounding space. Most irregular moons are less than 10 kilometres (6.2 mi) in diameter.