Retrograde and prograde motion orbits about the Sun of all planets and most other objects, except many comets, are prograde, i.e. in the same direction as the Sun rotates. The rotations of most planets, except Venus and Uranus, are also prograde. Most natural satellites have prograde orbits about their planets. Prograde satellites of Uranus orbit in the direction Uranus rotates, which is retrograde to the Sun. Retrograde satellites are generally small and distant from their planets, except Neptune's satellite Triton, which is large and close. All retrograde satellites are thought to have formed separately before being captured by their planets. When a galaxy or
Retrograde and prograde motion Triton (the largest of Neptune's moons) have prograde orbits. The particles in Saturn's Phoebe ring are thought to have a retrograde orbit because they originate from the irregular moon Phoebe. All retrograde satellites experience tidal deceleration to some degree. The only satellite in the Solar System for which this effect is non-negligible is Neptune's moon Triton. All the other retrograde satellites are on distant orbits and tidal forces between them and the planet are negligible. Within the Hill sphere, the region of stability for retrograde orbits at a large distance from the primary is larger than that for prograde orbits.