URANUS
Uranus is the seventh planet from the Sun. The name "Uranus" is a reference to the Greek god of the sky, Uranus. According to Greek mythology, Uranus was the grandfather of Zeus (Jupiter) and father of Cronus (Saturn). It has the third-largest planetary radius and fourth-largest planetary mass in the Solar System. Uranus is similar in composition to Neptune, and both have bulk chemical compositions which differ from that of the larger gas giants Jupiter and Saturn. For this reason, scientists often classify Uranus and Neptune as "ice giants" to distinguish them from the gas giants. Uranus' atmosphere is similar to Jupiter's and Saturn's in its primary composition of hydrogen and helium, but it contains more "ices" such as water, ammonia, and methane, along with traces of other hydrocarbons. It has the coldest planetary atmosphere in the Solar System, with a minimum temperature of 49 K (−224 °C; −371 °F), and has a complex, layered cloud structure with water thought to make up the lowest clouds and methane the uppermost layer of clouds. The interior of Uranus is mainly composed of ices and rock.
Like the other giant planets, Uranus has a ring system, a magnetosphere, and numerous moons. The Uranian system has a unique configuration because its axis of rotation is tilted sideways, nearly into the plane of its solar orbit. It's north and south poles, therefore, lie where most other planets have their equators. In 1986, images from Voyager 2 showed Uranus as an almost featureless planet in visible light, without the cloud bands or storms associated with the other giant planets. Voyager 2 remains the only spacecraft to visit the planet.] Observations from Earth have shown seasonal change and increased weather activity as Uranus approached its equinox in 2007. Wind speeds can reach 250 metres per second (900 km/h; 560 mph).
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INTERNAL STRUCTURE
Uranus' mass is roughly 14.5 times that of Earth, making it the least massive of the giant planets. Its diameter is slightly larger than Neptune's at roughly four times that of Earth. A resulting density of 1.27 g/cm3 makes Uranus the second least dense planet, after Saturn. This value indicates that it is made primarily of various ices, such as water, ammonia, and methane. The total mass of ice in Uranus' interior is not precisely known, because different figures emerge depending on the model chosen; it must be between 9.3 and 13.5 Earth masses. Hydrogen and helium constitute only a small part of the total, with between 0.5 and 1.5 Earth masses. The remainder of the non-ice mass (0.5 to 3.7 Earth masses) is accounted for by rocky material.
The standard model of Uranus' structure is that it consists of three layers: a rocky (silicate/iron–nickel) core in the centre, an icy mantle in the middle and an outer gaseous hydrogen/helium envelope. The core is relatively small, with a mass of only 0.55 Earth masses and a radius less than 20% of Uranus'; the mantle comprises its bulk, with around 13.4 Earth masses, and the upper atmosphere is relatively insubstantial, weighing about 0.5 Earth masses and extending for the last 20% of Uranus' radius. Uranus' core density is around 9 g/cm3, with a pressure in the centre of 8 million bars (800 GPa) and a temperature of about 5000 K. The ice mantle is not in fact composed of ice in the conventional sense, but of a hot and dense fluid consisting of water, ammonia and other volatiles. This fluid, which has high electrical conductivity, is sometimes called a water–ammonia ocean.
The extreme pressure and temperature deep within Uranus may break up the methane molecules, with the carbon atoms condensing into crystals of diamond that rain down through the mantle like hailstones. Very-high-pressure experiments at the Lawrence Livermore National Laboratory suggest that the base of the mantle may comprise an ocean of liquid diamond, with floating solid 'diamond-bergs'. Scientists also believe that rainfalls of solid diamonds occur on Uranus, as well as on Jupiter, Saturn, and Neptune.
The bulk compositions of Uranus and Neptune are different from those of Jupiter and Saturn, with ice dominating over gases, hence justifying their separate classification as ice giants. There may be a layer of ionic water where the water molecules break down into a soup of hydrogen and oxygen ions, and deeper down superionic water in which the oxygen crystallises but the hydrogen ions move freely within the oxygen lattice.
Although the model considered above is reasonably standard, it is not unique; other models also satisfy observations. For instance, if substantial amounts of hydrogen and rocky material are mixed in the ice mantle, the total mass of ices in the interior will be lower, and, correspondingly, the total mass of rocks and hydrogen will be higher. Presently available data does not allow a scientific determination of which model is correct. The fluid interior structure of Uranus means that it has no solid surface. The gaseous atmosphere gradually transitions into the internal liquid layers. For the sake of convenience, a revolving oblate spheroid set at the point at which atmospheric pressure equals 1 bar (100 kPa) is conditionally designated as a "surface". It has equatorial and polar radii of 25,559 ± 4 km (15,881.6 ± 2.5 mi) and 24,973 ± 20 km (15,518 ± 12 mi), respectively. This surface is used throughout this article as a zero point for altitudes.
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URANUSITE FACTS
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William Herschel discovered Uranus in 1781. The planet is too dim to have been seen by ancient civilizations. Herschel himself believed that Uranus was a comet at first, but several years later it was confirmed as a planet – making Uranus the first planet discovered in modern history. The original name proposed by Herschel was “Georgian Sidus” after King George III but the scientific community didn’t take to it. Instead, Uranus was proposed and accepted by astronomer Johann Bode and it comes from ancient Greek god Ouranos.
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Uranus rotates on its axis once every 17 hours and 14 minutes. Like Venus, it turns in a retrograde direction which is opposite to the direction Earth and the other six planets turn.
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It takes Uranus 84 Earth days to orbit the Sun. Its axis is at 98 degrees, which means it almost lies sideways as it orbits the Sun. This means that the north and south poles of Uranus lie near where the equator is on Earth. During parts of its orbit one or other of the poles directly face the Sun which means the planet gets around 42 years of direct sunlight followed by 42 years of darkness.
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A collision may have caused the unusual tilt of Uranus. The theory is that an Earth-sized planet may have collided with Uranus which forced its axis to drastically shift.
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Uranus wind speeds can reach up to 900 km per hour. This is roughly 560 miles per hour.
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The mass of Uranus is about 14.5 times the mass of Earth, making it the lightest of the four gas giants of the outer solar system.
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Uranus is often referred to as the “ice giant”. While it has a hydrogen and helium upper layer like the other gas giants, Uranus also has an icy mantle which surrounds its rock and iron core. The upper atmosphere of water, ammonia and methane ice crystals gives Uranus its distinctive pale blue colour.
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Uranus is the second least dense planet in the solar system, after Saturn.
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The Voyager 2 is the only spacecraft to have flown by Uranus. This happened in 1986 and it flew past the planet at a distance of around 81,500 km. This mission returned the very first close-up images of the planet, its ring system and its orbiting moons.
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Uranus has 13 presently known rings. All except two Uranian are extremely narrow – they are usually a few kilometres wide. It is believed that the rings are probably quite young. The matter within the rings is thought to be parts of a moon or moons that were shattered by high-speed impacts with an object such as a comet or asteroid
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The chemical element Uranium, discovered in 1789, was named after the newly discovered planet Uranus.
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Uranus is the coldest planet in the solar system. The minimum surface temperature on Uranus is -224°C – making it the coldest of the eight planets. Its upper atmosphere is covered with a haze made mostly of methane which hides the storms taking place in its cloud decks.
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The Uranian moons are named for characters created by Alexander Pope and William Shakespeare. For example, Oberon, Titania and Miranda. All these worlds are frozen with dark surfaces and some are a mixture of ice and rock. Of the Uranian moons, the most interesting is Miranda which has ice canyons, terraces and many strange-looking surface area.