William Herschel, a German-born English astronomer, was born Nov. 15, 1738. Herschel had come to England from Hannover in 1756, following in the footsteps of King George III of England, and although a musician by trade, Herschel became interested in optics, read a book on the subject, and then taught himself to make telescopes. He was especially interested in building a reflecting telescope, which uses a mirror rather than a lens to gather the light. The reflecting telescope had been invented by Isaac Newton a century earlier, but no one had solved the problems of building even a moderate sized reflector. Herschel apparently taught himself well, for he soon had a 7-foot reflector that was quite excellent. Now that he had learned telescope-making, Herschel then had to learn astronomy. Again, he taught himself, by “sweeping the sky,” night after night, with his 7-foot reflector.
It was on one of those nights, Mar. 13, 1781, to be specific, that Herschel spotted a small disc of light between Taurus and Gemini that had not been there on the previous sweep. He thought at first that it was a comet, and published a short paper to that effect, but several months of observations convinced him and others that this was not a comet, but a new planet. Wise to the ways of the world, and following the lead of Galileo and his Medicean stars, Herschel named the new planet “Georgium sidus”–“King George’s star”–and before long he had a comfortable pension and a royal appointment. It was a German, Johann Bode, who gently suggested that Uranus might be a more suitable name than George. The same Bode, in his star atlas of 1801, the Uranographia, inserted a marker and a label in his plate of Taurus and Orion, just above the end of Orion’s club, saying “ab Herschel detect. 1781 Mart. 13” (third image).
The Herschel museum in Bath has as replica of the telescope that Herschel used to discover Uranus (first image), nicely displayed in what was at that time Herschel’s home, but Teylers Museum in Haarlem in the Netherlands has an original Herschel 7-footer that Herschel built about 1790 (fourth image). The Science Museum in London has a mirror-grinding machine that was used by Herschel (second image). There were many portraits of Herschel; the one above (fifth image) was by John Russell and is in the National Maritime Museum in Greenwich.
Herschel later made much larger telescopes that he used to catalog nebulae, but that will be a subject for another occasion.
Dr. William B. Ashworth, Jr., Consultant for the History of Science, Linda Hall Library and Associate Professor, Department of History, University of Missouri-Kansas City. Comments or corrections are welcome; please direct to firstname.lastname@example.org.