(daily way in the model 0.58 m) 

Counted from the sun it is the 7th planet, and it belongs, like Jupiter, Saturn and Neptune, to the gas planets. Its atmosphere consists of 83% hydrogen, 15% helium and 2% methane and other molecular compounds. Inside the planet there is a relatively solid silicate/iron core, which is surrounded by a layer of frozen substances (water, methane, etc.). Uranus doesn't belong to the classic planets, because its existence wasn't known about in ancient times, despite its being just about recognizable with the naked eye in the right conditions. Its diameter is 51,118 km, its distance from the sun 19.18 AU and its mass about 15 times that of the earth's. On its almost circular orbit, which is only tilted at 0.77° to the ecliptic, Uranus takes 84 years to circle the sun, rotating once around its own axis every 17.9 hours. This axis almost lies on the ecliptic plane (97° slant to the polar axis of the ecliptic), which means that Uranus, to some extent, "rolls" on its side along its orbital path, allowing people on earth now and then to have a perpendicular view of one of its poles and its weak ring system. (Picture).  The rings are located in the planet's equatorial plane and consist of particles varying in size from fine particles of dust to big boulders of about 10m.  In about 2007 the sun will lie on the same plane, which means that on Uranus there will be equinox. Afterwards the polar cap which is presently averted to the sun will be subjected to an increased amount of sunlight, and people hope to observe phenomena similar to our weather and according to the seasons on earth on the surface of the planet, which is covered by clouds. Through a telescope Uranus appears as a blue-green disc, but the rings stay invisible.  Uranus` magnetic field is remarkably shifted at about 60° to the rotational axis of the planet. At a distance of between 50 000 and 17 million km, 21 known moons, sized between 13 and 1600 km, accompany Uranus. The number of these moons could increase following some more recent observations. The two biggest moons are called Titania and Oberon. They are situated at a distance of about 0.5 million km from the planet. With the help of the probe Voyager 2 (1986) and the Hubble Space Telescope (HST) we obtained much of our more recent knowledge about Uranus, its moons and its ring system.

The discovery of Uranus completes a thrilling chapter in the modern history of astronomy. It was located for the first time as a fixed star on one of Flamsteed's star charts (1690) and had been observed and presumed to be a fixed star by Bradley, Mayer and Lemonnier, as one can see from their boards of fixed stars and as Leverrier realized afterwards in 1846. Its first realistic discovery was made by William Herschel, who observed it on March 13th, 1781 in the zodiac sign Gemini. He first thought it to be a comet and named it  "Georgium Sidus" in honour of the English King George III. After further observation and calculation of the orbital paths by Zach, Gauss and Bode  its true identity was revealed and it was named Uranus by Bode in 1850. This name goes back to Greek mythology. Herschel also discovered the two big moons Titania and Oberon, which are named like other moons after characters from "A Midsummer Night`s Dream", a play in which Shakespeare took up a mythological topic from ancient times.

In ancient Greece Uranos was considered to be the father of the titans, whose most famous representatives were Kronos/Saturn and Prometheus. Uranus himself, however, was, as myth tells it, created by the broad-chested Earth at that time when Chaos was still reigning. Earth created Uranos, the Heaven, so that she could be surrounded by the sky and so that the gods would have a permanent place to live in it. As a cruel father, however, Uranus abandoned his children in deep ravines, till he was finally taken revenge on by Kronos, who took his manhood from him and threw it into the sea. Out of the foam Aphrodite was created . The beginning of a father-son conflict, which also manifested into a generation-conflict and has erupted many times in the history of mankind, seems also to be contained within this myth of heavenly creation. The planet's name is also related etymologically to Orion, the most prominent constellation on the celestial equator and Urania, the Greek muse of astronomy.

Uranus und sein Ringsystem
Picture: Uranus and its ring system.