Bob the Alien's Tour of the Solar System
Bob the Alien's Tour of the Solar System

The Discovery of Uranus


Before 1781, nobody knew of the existence of the planet Uranus. People believed that there were only six planets in the Solar System, including Earth. Mercury, Venus, Mars, Jupiter and Saturn are visible from Earth with the naked eye so had been observed by stargazers for tens of thousands of years. The ancient Romans gave the planets their current names, believing that they represented their gods. However, the advent of the scientific age meant that what people knew about the universe around them was about to change.

The invention of the telescope was a huge leap in astronomy. Before it, astronomers had to rely on what they could see with their eyes. With a telescope, suddenly people could look further than the eye could see and for the first time observe worlds that nobody had seen before. Galilei Galileo made one of the first major discoveries using a telescope. In 1610, while looking at Jupiter, he noticed four points of light surrounding the planet. He soon realised that he had spotted four of Jupiter's moons, the first moons to be discovered elsewhere in the Solar System other than the moon orbiting Earth (which is pretty difficult not to see!). Scientists of the time began to get excited that there may be other mysterious worlds in the Solar System, and not just moons orbiting the six known planets. There may be new planets out there that they didn't yet know about waiting to be discovered!

The earliest known observation of a new planet was by John Flamsteed, an English astronomer, in 1690. He spotted an object which he thought to be a star and which he referred to as 34 Tauri. He made several other observations of this "star", again not realising he was looking at a planet. Other astronomers also observed the same object, but as its movement didn't differ from the other stars (the usual way of spotting a planet), they simply didn't recognise it as being a planet.

William Herschel

On 13th March 1781, while observing the night sky, the English astronomer and composer Frederick William Herschel (pictured left) noticed an object which didn't move across the sky like stars do. Initially believing it to be a comet, and naming it Georgium Sidus (George's Star) in honour of King George III, Herschel soon realised that his object may in fact be a planet. This suggestion was made by Nevil Maskelyne, the British Astronomer Royal. After doing a bit of mathematics, it was confirmed that Georgium Sidus was definitely a planet, and Herschel became a national hero, becoming the first person to "discover" a planet! As a reward for discovering this planet (and probably because he named it after the King) he became King's astronomer, meaning that his job was to look into the sky for the King!

The British were very proud of the discovery of the Solar System's seventh planet, and for almost sixty years, were happy to refer to it as George's Star. However, the rest of the world wasn't too happy, mainly because the name of the planet didn't fit in with the mythological names of the other planets, and partly for more political reasons. The Americans and French were especially reluctant to call the planet George's Star. Both countries were in a war against Great Britain and didn't want to refer to a planet named in honour of the King of its enemy. Instead, they knew it as Herschel. It was eventually the scientific community that succeeded in renaming the seventh planet. The name Uranus was chosen, named after the Greek god of the sky.

In 1787, a few years after discovering Uranus, Herschel also found two moons orbiting it. His son John later gave them the names Titania and Oberon after the King and Queen of the Fairies in William Shakespeare's play, A Midsummer Night's Dream (click here for more information about Shakespeare's Moons). Although the name of Herschel's planet had to be changed, the moons kept their names. In addition, all of the moons of Uranus that have been discovered since have continued to be named after Shakespearean characters (with a couple of moons named after characters in Alexander Pope's The Rape of the Lock) instead of after mythological characters like the moons of other planets in the Solar System.

Herschel's discovery doubled the physical size of the known Solar System overnight and encouraged astronomers to look even deeper into space to try to find other worlds. The discovery of Uranus later led to the discovery of Neptune in 1846 (Neptune's location was found not by observing the planet, but by observing the effect its gravity had on Uranus and calculating its position). Neptune's discovery then led to the discovery of Pluto in 1930. Even today, many new small worlds are being discovered in the Solar System and even in orbits around other distant stars. The discoveries of Uranus and two of its moons were not Herschel's only achievements. He also discovered two moons orbiting Saturn and came up with the word "asteroid" to describe small objects in space. Like many other scientists of the time, he also believed that the Solar System was full of life and that all of the planets and even the Sun were inhabited! Despite his other achievements and theories about the universe, Herschel will always be remembered for finding Uranus and therefore becoming the first person ever to "discover" a planet.

Bob the Alien's Tour of the Solar System
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