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Uranus and its 5 major moons (Titania, Oberon, Ariel, Umbriel, and Miranda)

Uranus is the seventh planet from the Sun; it is an ice giant. It is named after than Icons-flag-gr.png Greek god of the atmosphere; the planet's name in eastern Asian languages literally translates as "heaven king star" (天王星, Icons-flag-jp.png Tennosei).[1][2][3][4]

Properties and Discovery

Uranus is a large planet, with a diameter of 50,724 km. It is composed of mostly Hydrogen and Helium and contains trace amounts of Methane and Hydrogen Sulphide. Uranus has powerful winds up to 901.2 kilometers per hour. Furthermore, Uranus gets as cold as -227 oC. Uranus is so dim in the sky, it was recognized as a star for a very long time until 1783, when William Herschel (also discoverer of IC 1101) discovered it. Sir William Herschel observed Uranus on 13 March, 1781 from the garden of his house at 19 New King Street in Bath, Somerset, Icons-flag-gb-eng.png England (now the Herschel Museum of Astronomy),[5] and initially reported it (on 26 April 1781) as a comet.[6] Herschel "engaged in a series of observations on the parallax of the fixed stars",[7] using a telescope of his own design.

Herschel recorded in his journal that "in the quartile near ζ Tauri ... either [a] Nebulous star or perhaps a comet."[8] On 17 March he noted: "I looked for the Comet or Nebulous Star and found that it is a Comet, for it has changed its place."[9] When he presented his discovery to the Royal Society, he continued to assert that he had found a comet, but also implicitly compared it to a planet:[7]

The power I had on when I first saw the comet was 227. From experience I know that the diameters of the fixed stars are not proportionally magnified with higher powers, as planets are; therefore I now put the powers at 460 and 932, and found that the diameter of the comet increased in proportion to the power, as it ought to be, on the supposition of its not being a fixed star, while the diameters of the stars to which I compared it were not increased in the same ratio. Moreover, the comet being magnified much beyond what its light would admit of, appeared hazy and ill-defined with these great powers, while the stars preserved that lustre and distinctness which from many thousand observations I knew they would retain. The sequel has shown that my surmises were well-founded, this proving to be the Comet we have lately observed.[7]

Ring System and Satellites

Uranus's axis is tilted more than 90 degrees. Uranus has 13 rings; all of which are faint. Uranus has 27 moons, some of them named after William Shakespeare's characters; the six largest ones are Ariel, Umbriel (named for a character by Alexander Pope; there is also a character created by him named Ariel), Oberon, Titania, Puck, and Miranda. May of the inner and outer smaller and irregular satellites have chaotic orbits and are expected to collide within the short span of a few million years. The outer satellites are mostly captured, small, and irregular, and were originally given names from a single Shakespearean play, The Tempest, but with Margaret being named after a character from Much Ado About Nothing that trend has ended.

These moons were named after Shakespeare's characters with the basis that since some of them are air spirits, Uranus, the Greek personification of the atmosphere, should be attended by air spirits. Shakespeare and Herschel were both from England as well. However, the majority of moons are named after Shakespearean characters (except two or three), regardless whether they are fairies or human mortals; the airy spirits trend ended with Miranda (from The Tempest and not a air spirit) and only continued by Cupid (named by Shakespeare for the Roman counterpart of Eros, the son of Venus or Aphrodite who is coincidentally said to be born from Uranus's severed genitals), Mab, and Puck.

It is believed that most of these moons and the rings of Uranus were created by the exact same impact which gave Uranus its large axial tilt (see below).[10]


Uranus's axis is tilted by more than 90 degrees, due to a massive impact with a planet twice the size of Earth early in the planet's history.[10] This also means that the planet will appear at first glance to rotate clockwise along its axis as seen from its north pole, just like Venus. The planet's magnetic field also rotates, occasionally exposing the planet to harmful radiation from the Sun.


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  4. "Asian Astronomy 101". Hamilton Amateur Astronomers 4 (11). 1997. Archived from the original on 18 October 2012. https://www.webcitation.org/6BVZMMrHn?url=http://amateurastronomy.org/EH/Oct97.txt. Retrieved 5 August 2007.
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  6. Herschel, William; Watson, Dr. (1781). "Account of a Comet, By Mr. Herschel, F. R. S.; Communicated by Dr. Watson, Jun. of Bath, F. R. S". Philosophical Transactions of the Royal Society of London 71: 492–501. Bibcode 1781RSPT...71..492H. doi:10.1098/rstl.1781.0056.
  7. 7.0 7.1 7.2 Journal of the Royal Society and Royal Astronomical Society 1, 30, quoted in Miner, p. 8.
  8. Royal Astronomical Society MSS W.2/1.2, 23; quoted in Miner p. 8.
  9. RAS MSS Herschel W.2/1.2, 24, quoted in Miner p. 8.
  10. 10.0 10.1 https://www.space.com/39123-crash-that-tilted-uranus-made-moons.html