On this day in 1781, William Herschel realised that what he initially thought was a comet was, in fact, Uranus, which he would name after the ruling monarch King George III. Though the name ‘Georgium sidus’ would not stick, Herschel’s discovery earned him favour with the King and led to him being appointed “The King’s Astronomer”.
Over the coming decade, Herschel would make many more discoveries including two of Saturn’s moons and two of Georgium sidus’ moons. He would also measure the tilt of Mars and discover the Martian Ice Caps.
More than just these, he would discover infrared radiation after pushing sunlight through a prism in 1800, which would lead Johann Ritter to repeat his experiment and discover ultraviolet radiation a year later.