first planet discovered that was not known in ancient times, named for the god of Heaven, husband of Gaia, the Earth, from Latin Uranus, from Greek Ouranos literally "heaven," in Greek cosmology, the god who personifies the heavens, father of the titans. Cf. Urania, name of the Muse of astronomy, from Greek Ourania, fem. of ouranios, literally "heavenly."
The planet was discovered and identified as such in 1781 by Sir William Herschel (it had been observed before, but mistaken for a star, e.g. in 1690 when John Flamsteed cataloged it as 34 Tauri); Herschel proposed calling it Georgium Sidus, literally "George's Star," in honour of his patron, King George III of England.
I cannot but wish to take this opportunity of expressing my sense of gratitude, by giving the name of Georgium Sidus ... to a star which (with respect to us) first began to shine under His auspicious reign. [Sir William Herschel, 1783]The planet was known in English in 1780s as the Georgian Planet; French astronomers began calling Herschel, and ultimately German astronomer Johann Bode proposed Uranus as in conformity with other planet names. However, the name didn't come into common usage until c.1850.
The seventh planet from the Sun and the third largest, with a diameter about four times that of Earth. Though slightly larger than Nepture, Uranus is the least massive of the four gas giants and is the only one with no internal heat source. A cloud layer of frozen methane gives it a faint bluish-green color, and it is encircled by a thin system of 11 rings and 27 moons. Uranus's axis is tilted 98° from the vertical—the greatest such tilt in the solar system—with the result that its poles are in continuous darkness or continuous sunlight for nearly half of its 84-year orbital period. See Table at solar system.