♅ Uranus

Named for the Greek god Uranus (Greek: Ouranos · Roman: Caelus)

The sky The heavens

Which sign is Uranus in now?

Detail of Uranus and the Dance of the Stars by Karl Friedrich Schinkel
Uranus and the Dance of the Stars Karl Friedrich Schinkel, 1834 Architekturmuseum der TU Berlin Detail of the upper middle of the picture. Public domain, via Wikimedia Commons

The sky as a god, and father of the Titans.

The god

Uranus is the Latin form of Ouranos, Greek for the sky, and in Greek myth he is the sky itself as a god. In Hesiod’s Theogony, the account most Greeks came to accept, Gaia, the Earth, “first bore starry Heaven, equal to herself, to cover her on every side.” Together they were the parents of the twelve Titans, the three Cyclopes and the three Hundred-Handed Ones, and his son Kronos (Saturn) overthrew him. The Romans knew him as Caelus. Uranus is the only planet named for a Greek god rather than a Roman one.

How the planet got its name

Uranus moves so slowly against the stars that it wasn’t recognized as a planet until William Herschel observed it on March 13, 1781 from the garden of his house in Bath, England. He wanted to call it Georgium Sidus, “George’s Star,” after his patron King George III. Johann Bode argued that, just as Saturn was the father of Jupiter, the new planet should be named for the father of Saturn, and Uranus became universal in 1850, when Britain’s Nautical Almanac Office, the last holdout, switched over. The element uranium, discovered in 1789, was named in support of Bode’s choice, and the planet’s moons are named for characters from Shakespeare and Alexander Pope.

Symbols

Stars

The planet

An ice giant. At least 80% of its mass is a hot, dense fluid of “icy” materials (water, methane and ammonia) above a small rocky core, and methane in its atmosphere gives it its blue-green color. Uranus is the only planet whose equator is nearly at a right angle to its orbit, tilted 97.77°, perhaps because of a collision with an Earth-sized object long ago. It has 13 faint rings and takes about 84 Earth years to circle the Sun.

Diameter
51,118 km 4 × Earth
Mass
86.8 × 10²⁴ kg 15 × Earth
Gravity
8.7 m/s² 0.89 × Earth's
Length of day
17.2 hours sunrise to sunrise
Length of year
83.7 Earth years one trip around the Sun
Distance from the Sun
2,867 million km 19.16 AU (Earth = 1)
Average temperature
-195 °C -319 °F
Moons
28 NASA’s count
Rings
Yes

Figures from NASA’s Planetary Fact Sheet; the temperature is its “mean temperature.” Comparisons with Earth are worked out from the same sheet.

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