Comparative planetary science closest analogue is the Pluto-Charon system, though its axial tilt is completely different. Both our Moon and Charon are hypothesized to have formed via giant impacts. Giant impacts are hypothesized to account for both the tilt of Uranus, and the retrograde rotation of Venus. Giant impacts are also candidates for the Mars ocean hypothesis, and the high density of Mercury. Most giant planets (except Neptune) have retinues of moons, rings, ring shepherds, and moon Trojans analogous to mini-solar systems. These systems are postulated to have accreted from analogous gas clouds, and possibly with analogous migrations during their formation periods. The
Solar eclipses on Uranus Umbriel, Titania and Oberon—are large enough and near enough to eclipse the Sun. All other satellites of Uranus are too small or too distant to produce an umbra. At its distance from the Sun, the Sun's angular diameter is reduced to a tiny disk about 2 arcminutes across. The angular diameters of the moons large enough to fully eclipse the sun are: Cressida, 6–8'; Desdemona, 6–7'; Juliet, 10–12'; Portia, 9–13'; Rosalind, 4–5'; Belinda, 6–8'; Puck, 6–8'; Miranda, 10–15'; Ariel, 20–23'; Umbriel, 15–17'; Titania, 11–13'; Oberon, 8–9'. Solar eclipses on Uranus Solar eclipses on Uranus occur when any of the natural