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 Formation and evolution of the Solar System The formation and evolution of the Solar System began 4.6 billion years ago with the gravitational collapse of a small part of a giant molecular cloud. Most of the collapsing mass collected in the center, forming the Sun, while the rest flattened into a protoplanetary disk out of which the planets, moons, asteroids, and other small Solar System bodies formed. This model, known as the nebular hypothesis was first developed in the 18th century by Emanuel Swedenborg, Immanuel Kant, and Pierre-Simon Laplace. Its subsequent development has interwoven a variety of scientific disciplines including