Uranus is the third gaseous giant in size of the solar system. Discovered on March 13th, 1781 by William Herschel, 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 possesses at least 13 main rings. Five were discovered in 1977 thanks to the observations of eclipses of stars by Uranus. Six others were observed to Travel 2 between 1985 and 1986. Both last ones were discovered thanks to the spatial telescope Hubble in December, 2005. The rings of Uranus, little visible consist of particles of the order of the centimeter. Uranus possesses at least 27 natural satellites.

Both first ones (Titania and Oberon) were discovered by William Herschel in 1787. Two other moons, Ariel and Umbriel, were discovered by William Lassell in 1851. It is John Herschel, the son of William who gave their names to the first four moons of Uranus (Oberon, Titania, Ariel, Umbriel). Names are pulled by the characters of the " Dream of a summer night " of William Shakespeare. Gerard Kuiper discovered Miranda in 1948. Ten other moons were discovered during the passage of Voyager 2 in 1986 and the other one, Perdita, was discovered thirteen years later among the successful photos. Eleven other moons were since identified, by using ground telescopes.

Titania

category : satellites of planets

Titania is the biggest moon of Uranus. It was discovered in 1787 by William Herschel. It carries the name of Titania, the queen of Fairies in " The Dream of a summer night " of William Shakespeare. Titania consists about 50 % of ice, 30 % of silicates and 20 % of organic compounds close to some methane. One of its main physical characteristics is the presence of an immense canyon, widely bigger than a Big canyon on Earth, the same order of height as Valles Marineris on Mars or Ithaca Chasma on Tethys, the moon of Saturn.

[source NASA]

Obéron

category : satellites of planets

Obéron is the most remote from the big satellites of Uranus and the second in size. It was discovered in 1787 by Herschel.
Obéron consists about 50 % of ice of water, 30 % of silicates, and 20 % of compounds of methane, carbon and nitrogen. Its surface is covered with craters, and indicates a very weak internal activity if we except a not identified dark material which fills the floors of numerous craters.

[source NASA]

Umbriel

category : satellites of planets

Umbriel is the third biggest satellite of Uranus. It was discovered in 1851 by William Lassell. Umbriel is the most somber satellite of Uranus and also the least active geologically, consisted mainly of ice of water, the rest being constituted by silicates and to 20 % of ice of methane ( CH4). One of the characteristics of the surface of Umbriel is the crater Wunda, a wide brilliant ring 140 km in diameter of materials close to the equator. The nature of this ring is not known, but he could involve a deposit of ice, maybe following an impact.

[source NASA]

Ariel

category : satellites of planets

Ariel is the fourth biggest satellite of Uranus. It was discovered in 1851 by William Lassell. Ariel would consist in 50 % of ice of water, in 30 % of silicates and in 20 % of ice of methane ( CH4) and it seems that certain regions of its surface are recently frozen. Widely deprived by craters of impact, Ariel seems to have undergone a period of intense geologic activity which produced a complex network of canyons and drainage of liquid water on its surface.

  [ Photography taken on January 24th, 1986 at a distance about 130 mm]

Miranda

category : satellites of planets