U R A N U S
CharacteristicsUranus was the first discovered planet that he was not well-known in the antiquity, although yes had been observed and confused with stars in many occasions. The registry older than is of him must to John Flamsteed, who catalogued it as the star 34 Tauri in 1690.
Sir William Herschel, a German musician in the cut of king Jorge III of England, discovered the planet in 1781 using a telescope constructed by he himself. Initially it gave the name him Georgium Sidus (the star of Jorge) in honor to the king who finished losing the British colonies in America, but had gained a star. Nevertheless, the name did not last beyond Great Britain, and Lalande, a French astronomer, proposed to call it Herschel in honor of its discoverer. Finally, German astronomer Johann Elert Bode proposed the name of Uranus in honor to the Greek God, father of Cronos - whose equivalent Roman gave name to Saturn -. Towards 1827, Uranus was the used name more for the planet even in Great Britain. The HM Nautical Almanac continued listing it like Georgium Sidus until the year of 1850.
Uranus has a nucleus composed of rocks and last ice of different type being these much more abundant ones. The planet counts on a heavy atmosphere formed by a mixture of hydrogen and helium that can represent until a 15% of the planetary mass. Uranus (as Neptune) is in many aspects an interrupted gaseous giant in its accumulated growth without having the great masses of gases of the inner giant planets Jupiter and Saturn.
The Uranus rotation, like the one of Venus, is retrograde, being its axis of inclined rotation almost ninety degrees on the plane of its orbit. During his orbital period of 84 years one of the poles permanently it is illuminated by the Sun whereas the other remains in the shade. Consequently one hopes that this one planet has important seasonal effects in its atmosphere. The reasons are not known by which the axis of the planet is inclined in so high degree although it is speculated on that perhaps during its formation the planet could have collided with a great protoplaneta able to have produced this anomalous direction. Other possibilities are the gravitational disturbances exerted by other giant planets of the Solar System. At the time of the passage of Voyager 2, in 1986, the Uranus South Pole was practically aiming towards the Sun. Then the clouds of the planet weakly were distributed in bands and hardly perceivable zones. The more recent observations of the Space Telescope Hubble show one more a more dynamic structure as the solar rays have been reaching the equatorial latitudes. In the 2007 Sun will directly illuminate the equator of the planet.
Seventh planet of the Solar System
The Uranus brightness reaches a magnitude of between +5,5 and +6,0, reason why it can at first be seen of very tenuous way in an exceptionally dark sky, although it can be with facility with simple binoculars. From the Earth it presents/displays an apparent diameter of 4": in order to appreciate it comfortably 100 increases are needed more than, appearing in the telescope as a blurred disc of greenish or yellowish color with the darkest edges. In most of the professional telescopes details cannot stand out on their disc but thanks to the revolution of the digital astronomical photography it is possible to obtain photometry differential of the latitudes of the planet with relatively modest telescopes. The use of techniques of adaptive optics in some of the greater telescopes of the world as the Keck telescope multitude of details in his revitalized atmosphere has allowed to obtain some of the best images of this planet being shown.
Their greater and external satellites can be appraised with difficulty with telescopes of 20 cm, on condition that to count on dark skies; instruments of 30-40 cm of diameter allow to appreciate four more brilliants without much difficulty. Nevertheless a camera CCD connected to any small telescope (20-25 cm) allows to its capture and pursuit.
|Average Dist. of the Sun||19.18 UA|
|Average radio||1.783.000.000 km|
|Orbital period (sidereal)||84.01 years|
|Period of rotation||17h. 14m.|
|Orbital speed average||6,81 km/s|
|Inclination of the axis||97,92°|
|Number of satellites||20|
|Equatorial diameter||50,800 km|
|Average density||1,18 g/cm³|
|Superficial gravity||0.79 Earth|
|Speed of escape||21,22 km/s|
|Average Temp. superf.: Day||---|
|Average Temp. superf.: Night||---|
In the page Web you can obtain more data of each one of our planets and the dwarf planets defined by the IAU of our Solar System.
Masm Last update 2006-10-20)