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
Formation and evolution of the Solar System further hypothesized that the Mars-sized object may have formed at one of the stable Earth–Sun Lagrangian points (either or ) and drifted from its position. The moons of trans-Neptunian objects Pluto (Charon) and Orcus (Vanth) may also have formed by means of a large collision: the Pluto–Charon, Orcus–Vanth and Earth–Moon systems are unusual in the Solar System in that the satellite's mass is at least 1% that of the larger body. Astronomers estimate that the Solar System as we know it will not change drastically until the Sun has fused almost all the hydrogen fuel in its core into helium,