The seventh planet from the Sun is Uranus. Uranus is the third largest planet in the solar system and is known to be an "ice giant". It has a complex layered cloud structure and a marked axial tilt of 97.8° with a retrograde rotation rate of 17 hours. Uranus is visible to the naked eye, but it is very dim and was not classified as a planet until 1781, when it was first observed by William Herschel.