It was the first planet ever in our Solar system to be discovered by a telescope. The planet had been observed on many occasions, but it did not gain recognition; as it was generally mistaken for a star. John Flamsteed and Pierre Lemonnier were the initial astronomers to have observed the planet. However, the planet was officially discovered by Sir William Herschel on 13 March 1781. The planet was discovered when Sir William Herschel was surveying the stars through a homemade telescope. The planet was discovered while observing the stars down to magnitude eight, those which are around ten times dimmer and are visible to the naked eye. One ‘star’ seemed different and within a year the planet was shown to have planetary orbit which was 18 times farther from the Sun than the Earth.
The planet was named Uranus, after the ancient Greek sky deity; Ouranos. Many names were suggested for the newly discovered planet, which included ‘Hypercronius’, ‘Oceanus’, ‘Neptune’, ‘Minerva’ (the Roman goddess of wisdom). Sir William Herschel declared the mythological names to be unsuitable for the present philosophical era. Further, he proposed the name Georgium Sidus for the new planet, in honour of his patron, King George III. However, the idea did not gain popularity, so eventually going with the tradition of naming planets after Roman gods; a mythological name was given to the planet. It is the only planet whose name is derived from Greek mythology, instead of Roman mythology.
Uranus is basically bluish-green in colour, due to the methane present in its hydrogen-helium atmosphere, which absorbs the red light that causes the planet to have a blue cast, which is mainly responsible for the planet’s bluish-green colour. The two main constituents of the Uranian atmosphere are molecular hydrogen and atomic helium. The atmosphere of the planet is composed of about 83% hydrogen, 15% helium and 2% methane. It is often referred as an ‘ice giant’, as 80% or above of its mass comprises fluid mix of methane, water and ammonia ices. Unlike other planets in our solar system, Uranus has an axis tilt of 97.77°, which leads it to orbit the Sun on its side. A collision with a planet sized body after its formation might be a reason for its unusual orientation. The extreme tilt leads to extreme seasons which last for around 20 years, that means for around a quarter of Uranian year, which equals to 84 Earth years. During these seasons, the Sun shines directly over each pole, causing the other half to experience a long, cold and a dark winter.
Uranus comprises a very thin and faint system of rings. In our solar system, it is the second planet to have rings. Its initial observations were done by James L. Elliot, Edward W. Dunham, and Douglas J. Mink in the Kuiper Airborne Observatory and the Perth Observatory in Australia. They viewed the star blinking out briefly several times. The blinking was caused due to the rings which blocked the starlight. When the planet drifted slowly in front of the star, they observed that the star actually blinked out of view five times before it was covered by the planet. Their observations lead to a conclusion that Uranus might be surrounded by a system of five rings. The system of rings was confirmed in the year 1986, when a NASA built space probe- Voyager 2 was sent to the planet. Two new rings were discovered during the voyage, bringing the number to seven. Over the years, after careful analysis and a closer view of Voyager 2 space probe; six more rings were discovered bringing to a total of thirteen now. In order of increasing distance from the planet, the rings are 1986U2R, 6, 5, 4, Alpha, Beta, Eta, Gamma, Delta, Lambda, Epsilon, Nu and Mu. The larger rings in the system are surrounded by belts of fine dust.
Uranus comprises 27 known moons. Unlike other planets which derived its name from Roman or Greek mythology, the natural satellites or moons of Uranus were named after the great works of William Shakespeare and some were named for characters from the works of Alexander Pope’s English literature. All the moons were created by ice and rock. Oberon and Titania are the largest moons, which were discovered in the year 1787 by William Herschel. The expedition of Voyager 2 space probe to Uranian system helped in the discovery of ten known moons.
- Coredelia: It was initially discovered by Voyager 2 in the year 1986. It is the innermost moon of the planet which is named after Lear’s daughter from ‘King Lear’ of Shakespeare. It comprises a diameter of 15km and is also one of the smallest moons in the Solar System.
- Ophelia: It is a natural satellite of the planet Uranus. In Shakespeare’s play ‘Hamlet’, Ophelia was the daughter of Polonius. Ophelia was also discovered by Voyager 2 in the year 1986.
- Bianca: It is a natural satellite of the planet Uranus. In Shakespeare’s play ‘The Taming of the Shrew’, Bianca was the sister of Katherine. Bianca was also discovered by Voyager 2 space probe in the year 1986.
- Cressida: It is a natural satellite of the planet Uranus. In Shakespeare’s play ‘Troilus and Cressida’, Cressida was the daughter of Calchas. It was also discovered by Voyager 2 in the year 1986.
- Desdemona: It is a natural satellite of the planet Uranus. In Shakespeare’s Play, ‘Othello’, Desdemona was the wife of Othello. It was also discovered by Voyager 2 in the year 1986.
- Juliet: It is a natural satellite of the planet Uranus. In Shakespeare’s play ‘Romeo and Juliet’, Juliet was the famous and tragic heroine. It was also discovered by Voyager 2 in the year 1986.
- Portia: It is a natural satellite of the planet Uranus. In Shakespeare’s play ‘Merchant of Venice’, Portia was a rich heiress. Portia was also one of the several new moons which were discovered by Voyager 2 in the year 1986.
- Rosalind: It is a natural satellite of the planet Uranus. In Shakespeare’s play ‘As you like it’, Rosalind was the daughter of the banished Duke. It was discovered by Voyager 2 in the year 1986.
- Belinda: It is a natural satellite of the planet Uranus. It was named the heroine in Alexander Pope’s ‘The Rape of the Lock’. It was one of the several moons to be discovered by Voyager 2 in the year 1986.
- Puck: It is a natural satellite of the planet Uranus. In Shakespeare’s play ‘Midsummer Night’s Dream’, Puck was a mischievous fairy. It was also discovered by Voyager 2 in the year 1986.
Since the Voyager 2 expedition, astronomers have raised the total to 27 known moons with the help of Hubble Space Telescope and improved ground-based telescopes. The other natural satellites of the planet Uranus are:
Miranda, Ariel, Umbriel, Titania and Oberon are the major moons of the planet.
- Miranda: It is a natural satellite of the planet Uranus. It was initially discovered in the year 1948 by Kuiper. Its name is taken from the famous play of William Shakespeare – ‘The Tempest’. It is the innermost and the smallest of five major satellites. It comprises giant fault canyons which consists of terraced layers and surfaces that appear comparatively old.
- Ariel: It is natural satellite of the planet Uranus. It was discovered by William Lassell in the year 1851. Its name is taken from the famous play of William Shakespeare – ‘The Tempest’. It is the brightest among all the moons of Uranus.
- Umbriel: It is a natural satellite of the planet Uranus. It is named after a character in ‘The Rape of the Lock’ by Alexander Pope. It is an ancient and darkest of all the five major moons of Uranus.
- Titania: Titania is the largest natural satellite of the planet Uranus. It is named after the character from William Shakespeare’s famous play ‘Midsummer- Night’s Dream’. Titania was the Queen of Fairies and the Wife of Oberon.
- Oberon: It is the outermost and the second largest natural satellite of the planet Uranus. Oberon was the husband of Titania in William Shakespeare’s famous play ‘Midsummer-Night’s Dream’. It was discovered by William Herschel in the year 1787.