Discovering Uranus

On this day in 1781 Sir William Herschel officially discovered Uranus. By officially I mean that even though it had been sighted before, Herschel was the person who finally figured it wasn't a star. He thought it was a comet. Well, it was a step in the right direction. In December of 1690 John Flamsteed made the 1st known observation & catalogued it as 34 Tauri. (It was in the constellation Taurus at the time.) He went on to observe it 6 more times. Between 1750-1771 Pierre Charles Le Monnier observed it at least 12 times (including 4 days running). Anyway, after later determining the orbit was more circular unlike the orbit of a comet it was upgraded to a planet. He then named it Georgium Sidus (George's Star) in honour of King George III of Great Britain. After some discussion of naming it after Herschel as well as many other names, including at 1 point, Neptune, Johann Elert Bode came up with Uranus, the Latinized version ofOuranos, the Greek god of the sky.

Uranus is a gas giant & the 3rd largest planet by diameter (4th by mass) in the Solar System. The atmosphere is about 83 percent hydrogen, 15 percent helium, 2 percent methane and traces of acetylene. The interior is most likely made up of compounds of oxygen, carbon, and nitrogen, as well as rocky materials. Unlike the other gas giants the core is not made of metalic hydrogen. Its cyan coloration is due to the methane in the atmosphere. An outer layer covers up the storms that are visible on the other gas giants. Its much lower temperature also helps to keep the storms invisible most of the time. (A spot similar to those on Jupiter showed up in 2006.) It has an unusual axial tilt of 97.77° (probably due to a crash with another body). It had a ring system that was 1st discovered in 1977 & consists of 13 known rings. 27 moons are currenly known. They are named after characters from the works of Shakespeare & Alexander Pope.

So far only Voyager 2 has visited the planet. & while it was officially determined to be a planet by the use of a telescope, under certain circumstances it can actually be seen by the naked eye.

(Photos: Top - Voyager 2, 10 January 1986,

Bottom, Hubble Space Telescope, NASA, Public Domain)