Uranus (IPA: /jʊˈreɪ.nəs, ˈjʊr.ə.nəs/) is the seventh planet from the Sun, and the first discovered in modern times. Although, like the five classical planets, Uranus is visible to the naked eye, its dimness and slow motion across the sky meant that it was never recognised as a planet by ancient observers. The planet remained unknown Sir William Herschel announced its discovery on March 13, 1781, expanding the known boundaries of the solar system for the first time in modern history. Uranus was also the first planet discovered using technology (a telescope) rather than the naked eye.
Uranus is named after the ancient Greek deity of the sky (Uranus, Οὐρανός), Its astronomical symbol is . The symbol is a combination of the symbols for the Sun and Mars, as Uranus was the personification of heaven in Greek mythology, dominated by the light of the Sun and the power of Mars. It is also the alchemical symbol of platinum. The element uranium was named in its honour.
The adjective of Uranus is "Uranian". Although it is a gas giant, like Jupiter and Saturn, it is far less massive than either and has a markedly different internal composition, with much less hydrogen and helium and a far greater abundance of "ices", such as water, ammonia, and methane. Neptune is of a similar mass and composition to Uranus, and astronomers have begun to employ a new category to describe them collectively: "Uranian planets" or "ice giants" as distinct from the Jovian planets Jupiter and Saturn.
Like the other giant planets, Uranus possesses a ring system, a magnetosphere, and numerous moons. Uranus is unique though in that it, its moons, and its rings orbit the sun virtually sideways; their north and south poles lie where the other planets have their equators. Seen from Earth, Uranus's rings appear to circle the planet like an archery target, while its moons revolve around it like the hands of a clock. When Voyager 2 first imaged Uranus in 1986, it found it virtually featureless, with none of the cloud bands or storms associated with the other giants. Now, as Uranus approaches its equinox, ground-based observations are beginning to see signs of weather activity on its surface.