Uranus

Uranus

Uranus is hardly visible in the bare eye on very clear night, it appears, even with powerful instruments as under the shape of a small greenish disk.
Uranus is the seventh planet of the solar system, a gaseous giant and the third in size.
It was discovered on March 13th, 1781 by William Herschel.
Its name comes from the god Uranus, Roman god of the sky, the equivalent of the Greek god Ouranos. It has an axis of rotation tilted to 98 ° (That of the Earth is 23,27 °, and that of the Jupiter of 3,22 °). Uranus is lying thus almost on its orbit.
Uranus is a gaseous huge planet, as Jupiter, Saturn and Neptune.
In theory, it would consist of a solid nucleus of silicates and of iron about 7500 km in diameter, surrounded with a coat consisted of clouds of molecular hydrogen, of helium, methane and ammonia on a 10 000 km thickness, then a superficial layer of hydrogen and liquid helium, thickens 7600 km which bottom gradually in the atmosphere.
Unlike Jupiter and Saturn, Uranus is not rather massive so that the hydrogen exists in the metal state around the nucleus.

La 7ème planète

category : planets

Uranus is the 7th solar planet of the system and the 3rd biggest.
It is Friedrich Wilhelm Herschel who discovered it accidentally on March 13th, 1781 and he thought first of all of having to deal with a comet.
Uranus had already been observed previously but it was ignored and cataloged as simple star (the first observation recorded by Uranus dates 1690 when John Flamsteed cataloged it as the star 34 Tauri).
Having correctly determined the nature of the celestial body, Herschel called it the Georgian Planet in honor of King of England Georges III
The thrower, a rocket Soyuz 2.1B, unstuck at 3:23 pm (the hour Paris time) on December 27th, 2006 of his shooting range of the Baikonur cosmodrome.

Uranus showed irregularities in its orbit around the Sun that the law of the universal gravitation could not explain.
An eighth planet was needed to explain these irregularities.
A psychological bolt had jumped, the dimensions of the solar system doubled at one go. Most of the planets make their rotation on an almost perpendicular axis in the plan of the ecliptic but the axis of Uranus is almost parallel to this plan.
Uranus mainly consists of cliffs and ices, with only 15 % of hydrogen and a little helium, while Jupiter and Saturn almost completely consist of hydrogen.

The atmosphere of Uranus is constituted about 83 % of hydrogen, 15 % of helium and 2 % of methane.
The blue color of Uranus is the result of the absorption of the red light by the methane in the superior atmosphere.
Uranus possesses rings as other gas giants, overdrafts that in 1979.
They are very dark as those of Jupiter and consisted of relatively big particles, up to 10 meters in diameter besides fine dusts, as rings of Saturn.
There are 11 known rings, all very weak, the most glittering being the ring Epsilon.

Les 27 satellites d'Uranus

category : planets

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Astronomy - october 15th 2007