The seventh most distant planet from the Sun, discovered by William Herschel in 1781. It is bluish green because of methane in the atmosphere. Its atmosphere is composed of hydrogen and helium, its mantle is water and ammonia ice, and its core is rocky. Uranus has 9 faint rings
New research suggests that the giant planet may have suffered two massive impacts early in its history, which would account for its extreme, mysterious axial tilt. Uranus orbits nearly on its side; its axis of rotation is skewed by 98 degrees relative to an ordinary upright orientation, perpendicular to the orbital plane.
"If we are right, Uranus was hit at least twice by big objects, about the mass of the Earth," said Alessandro Morbidelli of the Observatory of Côte d’Azur in Nice, France.
“When you go to Uranus and Neptune you find their composition is dominated a lot more by rock and ice. There is a lot more water in their atmospheres, a lot more methane.” Dr Chris Arridge, of University College London’s Mullard Space Science Laboratory in Surrey.
Uranus takes 84 years to orbit the Sun which leads to extreme seasons. Dr Arridge said: “Because there is so little heat coming from inside Uranus, its atmosphere is completely driven by force of sunlight. And because it has got this large tilt in its axis one pole is continually in sunlight for 42 years while the other is in darkness and then the situation is reversed for 42 years.”
Like the other gas giant planets, Uranus has no solid surface. It gets its bluish surface colour from tiny frozen ammonia crystals. The atmosphere is thought to be mainly hydrogen and helium.
Astronomers have discovered new rings and small moons around Uranus and found surprising changes in satellite orbits around the giant planet. NASA's Hubble Space Telescope photographed a pair of previously unknown rings.
Auroras on Uranus are fainter than they are on Earth, and the planet is more than 4 billion kilometers (2.5 billion miles) away. Previous Earth-bound attempts to detect the faint auroras were inconclusive.
In the new observations, which are the first to glimpse the Uranian aurora with an Earth-based telescope, the researchers detected the luminous spots twice on the dayside of Uranus
Uranus measures a mighty four-times the diameter of Earth and orbits the sun at an average distance of 2.9 billion kilometers (around 20 times the Earth-sun distance). From that distance it's only just visible to the naked eye under dark skies, but telescopes are needed to see any detail.
Herschel first called the new planet the Georgian Star, after King George III, and that name was used by the Nautical Almanac until as late as 1850. The name Uranus was proposed by Johann Bode when the planet was discovered, on the basis that Mars, Jupiter, Saturn, and Uranus constituted a sequence of generations in mythology.
Using infrared images taken by the 10-meter Keck II telescope in Hawaii, Imke de Pater of the University of California, Berkeley, and colleagues report in Science Express, that the rings have been going through some changes since they were first photographed in 1986 by Voyager 2.