What is the largest known rocky planet

The planet Uranus was first sighted in 1690. However, it was not recognized as the seventh planet in the solar system until 1781. Up to then it was the first planet that was not already known in antiquity. Due to its great distance from the Sun of 19.2 AU, it takes 84 years to make one orbit. The rotation time around its own axis is approx. 17 hours, with the rotation axis with an inclination of 97.77 ° lying almost exactly on the plane of the orbit. The axis of Uranus, like the earth's axis, is always aligned in the same way in relation to the fixed star sky. This results in distinct “seasons” and the sun does not rise at the poles for almost 40 earth years. Like Jupiter and Saturn, Uranus is a gas planet, but with a larger inner solid core and a mass of 8.7x1025 kg.

The atmosphere has a higher proportion of helium and methane than the gas planets closer to the sun. This methane gas absorbs the sun's reddish light, making Uranus appear blue-green. Images of the Voyager 2 probe flying past Uranus from 1986 showed only a slight cloud structure. This seems to be changing, however, because in recent years it has been possible to discover visible cloud structures with telescopes.

The planet Uranus is surrounded by a narrow ring system. These rings can be seen as thin, sharply defined areas with modern space telescopes. In addition, Uranus is orbited by several moons. 27 satellites are known by 2019. The five largest had already been discovered from Earth before the Voyager 2 probe flew by in January 1986. All five are likely 50% ice and 50% rock, and most of their surface is littered with craters.

The irregular surface of the moon Miranda led to the hypothesis that Miranda was shattered once and that the debris reassembled afterwards. In 1986, images from the Voyager 2 probe revealed 10 other moons. Voyager 2 was the only flight of a probe to the planet Uranus after a flight time of 8.5 years. Most of the images currently known come from this mission. At the moment there are no plans for another space mission to Uranus.