Uranus. Artwork of the planet Uranus and its moons seen from space. Uranus is the seventh planet from the Sun. It has a diameter of four times that of Earth and a volume of 64 Earths. It is a gas giant with an atmosphere of mostly hydrogen and helium, but much of the planet is solid rock and ice below the atmosphere. It has a ring system, and is shown tipped on its side. This is probably due to a big impact event in its early history. The temperature is a freezing -193 degrees Celsius. Uranus has over 20 moons. The bright band of stars of the Milky Way is seen in the background.