Space Station Info :: Uranus

Uranus moons


William Herschel was the astronomer who discovered Uranus and its two moons. Just six years after discovering the planet, Oberon and Titania was found by the English skygazer in 1787. Uranus has 27 known moons, among which most of them weren't found until the space age. It starts from Titania which is 981 miles (1,579 km) in diameter to the Tiny Cupid which is 11 miles, that is just 18 km in diameter. Before the Voyager 2 spacecraft which was launched in 1977, astronomers knew about five moons.


Uranus is the third-largest planetary radius and fourth-largest planetary mass in the Solar System. Uranus was the first planet discovered with a telescope. The interior part of Uranus is mainly composed of ices and rock. Uranus is the seventh planet from the Sun which is similar in composition to Neptune, and both have different bulk chemical composition from that of the larger gas giants Jupiter and Saturn. For this reason only, scientists often classify Uranus and Neptune as "ice giants" to distinguish them from the gas giants. Uranus's atmosphere is similar to Jupiter's and Saturn's but it contains more "ices" such as water, ammonia, and methane, along with traces of other hydrocarbons in its primary composition of hydrogen and helium. It is the coldest planetary atmosphere in the Solar System, which has a minimum temperature of 49 K (-224 C; -371 F), and has a complex layered cloud structure with water. Wind speeds can reach upto 250 metres per second (900 km/h; 560 mph). It is the only planet whose name is derived directly from a figure from Greek mythology, from the Latinised version of the Greek god of the sky Ouranos. Sir William Herschel announced its discovery on 13 March 1781. Like the other giant planets, Uranus has, a magnetosphere, a ring system and numerous moons. Because its axis of rotation is tilted sideways, Uranian system has a unique configuration among those of the planets nearly into the plane of its solar orbit. Images from Voyager 2 showed Uranus as an featureless planet in visible light in 1986.


The outermost part of Uranus's gaseous envelope that is accessible to remote sensing capability which extends down to roughly about 300 km below the 1 bar (100 kPa) level, with a corresponding pressure around 100 bar (10 MPa) and a temperature of 320 K (47 C; 116 F is called its atmosphere. The tenuous thermosphere extends over two planetary radii from the nominal surface, which is defined to lie at a pressure of 1 bar. The Uranian atmosphere is divided into three layers. The troposphere layer which has an altitude of -300 and 50 km (-186 and 31 mi) and a pressure of about 100 to 0.1 bar (10 MPa to 10 kPa). The Stratosphere layer which has an altitude of 50 and 4,000 km (31 and 2,485 mi) and a pressure of 0.1 and 10-10 bar (10 kPa to 10 Pa).


Uranus is generally visible to the naked eye which can be easily viewed with binoculars. It has apparent magnitude which swings between +5.6 and +5.9, visibile at +6.5 to the naked eye from 1995 to 2006. The angular diameter for Uranus is between 3.4 and 3.7 arcseconds, compared with 16 to 20 arcseconds for Saturn and 32 to 45 arcseconds for Jupiter. Uranus appears as light greenish-blue color disk with distinct limb darkening when viewed in larger amateur telescopes with an objective diameter of between 15 and 23 cm. Some of the larger satellites, such as Titania and Oberon or cloud patterns, may be visible with a large telescope of 25 cm or wider.