Uranus
Seventh planet from the Sun, discovered by German-born British astronomer William Herschel in 1781. It is twice as far out as the sixth planet, Saturn. Uranus has a mass 14.5 times that of Earth. The spin axis of Uranus is tilted at 98°, so that one pole points towards the Sun, giving extreme seasons.
Mean distance from the Sun
2.9 billion km/1.8 billion mi
Equatorial diameter
50,800 km/31,600 mi
Rotation period
17 hours 12 minutes
Year
84 Earth years
Atmosphere
deep atmosphere composed mainly of hydrogen and helium
Surface
composed primarily of rock and various ices with only about 15% hydrogen and helium, but may also contain heavier elements, which might account for Uranus's mean density being higher than that of Saturn
Satellites
27 moons were known by the end of 2005
Rings
11 rings, composed of rock and dust, around the planet's equator, were detected by the US space probe Voyager 2 in 1977. The rings are charcoal black and may be debris of former ‘moonlets’ that have broken up. The ring furthest from the planet centre (51,000 km/31,800 mi), Epsilon, is 100 km/60 mi at its widest point. In 1995, US astronomers determined that the ring particles contained long-chain hydrocarbons. Looking at the brightest region of Epsilon, they were also able to calculate the precession of Uranus as 264 days, the fastest known precession in the Solar System
Uranus has a peculiar magnetic field, in that it is tilted at 60° to the axis of spin, and is displaced about a third of the way from the planet's centre to its surface. Uranus spins from east to west, the opposite of the other planets, with the exception of Venus and possibly the dwarf planet Pluto. The rotation rate of the atmosphere varies with latitude, from about 16 hours in mid-southern latitudes to longer than 17 hours at the equator.
| Titania, the largest moon, has a diameter of 1,580 km/980 mi. Voyager 2 flew by Uranus in January 1986, and revealed that Uranus is covered with a cloud layer under which a hot ocean of superheated water exists. The pressure caused by the thick atmosphere keeps the water from boiling away and the heat keeps the pressure from solidifying the water. This has led to suggestions that the planet may have formed from the coalescence of comets. Other discoveries were that the pole facing the Sun is no hotter than the pole facing away, and that four known methane clouds in the atmosphere rotate with the planet, not in the expected opposite direction. |
Uranus
In Greek mythology, the primeval sky god, whose name means ‘Heaven’. He was responsible for both the sunshine and the rain, and was the son and husband of Gaia, the goddess of the Earth. Uranus and Gaia were the parents of Kronos and his fellow Titans, the one-eyed giant Cyclops, and the 100-handed Hecatoncheires.
| Uranus was deposed and emasculated by Kronos, the blood from his wounds falling on the Earth and giving rise to the three Furies. In later traditions Aphrodite, goddess of love, was born from the foam which arose from his genitals or blood falling into the sea. |
)
)
