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
Solar System icy objects. Astronomers sometimes informally divide this structure into separate regions. The inner Solar System includes the four terrestrial planets and the asteroid belt. The outer Solar System is beyond the asteroids, including the four giant planets. Since the discovery of the Kuiper belt, the outermost parts of the Solar System are considered a distinct region consisting of the objects beyond Neptune. Most of the planets in the Solar System have secondary systems of their own, being orbited by planetary objects called natural satellites, or moons (two of which, Titan and Ganymede, are larger than the planet Mercury), and, in