- Astronomy. the planet seventh in order from the sun, having an equatorial diameter of 32,600 miles (56,460 km), a mean distance from the sun of 1,784 million miles (2,871 million km), a period of revolution of 84.07 years, and 15 moons.
- Also Ouranos. Classical Mythology. the personification of Heaven and ruler of the world, son and husband of Gaea (Earth) and father of the Titans, who was castrated and dethroned by his youngest son, Cronus, at the instigation of Gaea.
- Greek myth the personification of the sky, who, as a god, ruled the universe and fathered the Titans and Cyclopes on his wife and mother Gaea (earth). He was overthrown by his son Cronus
- one of the giant planets, the seventh planet from the sun, sometimes visible to the naked eye. It has 27 satellites, a ring system, and an axis of rotation almost lying in the plane of the orbit. Mean distance from sun: 2870 million km; period of revolution around sun: 84 years; period of axial rotation: 17.23 hours; diameter and mass: 4 and 14.5 times that of earth respectively
Word Origin for Uranus
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.