Extraterrestrial skies celestial equator to the North and in 2029 the North Pole of Uranus will be nearly pointed at the Sun. None of Uranus's moons would appear as large as a full moon on Earth from the surface of their parent planet, but the large number of them would present an interesting sight for observers hovering above the cloudtops. The angular diameters of the five large moons are as follows (for comparison, Earth's moon measures on average 31′ for terrestrial observers): Miranda, 11–15′; Ariel, 20–23′; Umbriel, 15–17′; Titania, 11–13′; Oberon, 8–9′. Unlike on Jupiter and Saturn, many of the inner moons
Definition of planet object can be irregular in shape, but beyond that point gravity begins to pull an object towards its own centre of mass until the object collapses into an ellipsoid. (None of the large objects of the Solar System are truly spherical. Many are spheroids, and several, such as the larger moons of Jupiter and Saturn and the dwarf planet , have been further distorted into ellipsoids by rapid rotation or tidal forces, but still in hydrostatic equilibrium.) However, there is no precise point at which an object can be said to have reached hydrostatic equilibrium. As Soter noted in his