Uranus is the seventh planet from the Sun and the first to be discovered with a telescope — William Herschel spotted it on 13 March 1781. It is classified as an ice giant, distinct from Jupiter and Saturn: its interior is dominated by a hot, dense fluid of “icy” materials — water, methane, and ammonia — above a small rocky core.

Uranus rotates on its side, with an axial tilt of 97.77°. During the 84-Earth-year Uranian orbit, each pole spends 42 years in continuous sunlight followed by 42 years in darkness, producing the most extreme seasons of any planet. Its pale blue-green color is produced by methane in its atmosphere absorbing red wavelengths of sunlight.

Uranus has 13 known rings — dark, narrow, and composed of dust to meter-sized particles — and 28 known moons, all named after characters from Shakespeare and Alexander Pope. The largest five are Miranda, Ariel, Umbriel, Titania and Oberon. Voyager 2’s January 1986 flyby remains the only close-up study of the Uranian system, and the 2023 NASA Planetary Science Decadal Survey identified a Uranus orbiter and probe as its highest-priority flagship mission of the 2030s.