On this day in 1781, astronomer Sir William Herchel discovered Uranus. Of course Uranus had been observed before, indeed Hipparchos took great interest in Uranus way back in 128 BC. However, previous observers had assumed it was a star and it would not be until Herschel was able to take a really good look at it that Uranus was identified as what it truly is – a planet.
William Herschel was born November 15th 1738 in Hanover, which was then part of the Holy Roman Empire. At the time the crowns of Great Britain and Hanover were united under King George II and the Herschel family were employed in the two nation's joint army. William and his brother Jakob joined as oboists in the regimental band of a Hanoverian Guards regiment and were deployed when the Seven Years’ War broke out in 1756. A year later France invaded Hannover and the brothers were present at the Battle of Hastenbeck where a British and German army was defeated. Soon after the brothers’ father sent them both to seek refuge in England. Although Jakob had received his dismissal from the Hanoverian Guards, Wilhelm was accused of desertion.
In England, William quickly learnt English and became an accomplished musician and composer, adding the violin, harpsichord and organ to his repertoire and composing a number of symphonies. He would eventually settle in Bath where his intellectual curiosity and interest in music eventually led him to astronomy. After reading Robert Smith's Harmonics, or the Philosophy of Musical Sounds (1749), he took up Smith's A Compleat System of Opticks (1738), which described techniques of telescope construction. He took lessons from a local mirror-builder and having obtained both tools and a level of expertise, started building his own reflecting telescopes. He relied on the assistance of other family members, particularly his sister Caroline and his brother Alexander, a skilled mechanical craftsperson.
He "began to look at the planets and the stars" in May 1773 and on March 1st 1774 began an astronomical journal by noting his observations of Saturn's rings and the Great Orion Nebula (M42). By 1779, Herschel made the acquaintance of Sir William Watson, who invited him to join the Bath Philosophical Society. Herschel became an active member and through Watson would greatly enlarge his circle of contacts.
Herschel observed Uranus on March 13th 1781 from the garden of his house at 19 New King Street in Bath and initially reported it as a comet. This is how he presented his discovery to the Royal Society, though he also implicitly compared it to a planet.
Although Herschel continued to describe his new object as a comet, other astronomers had already begun to suspect otherwise. The object was soon universally accepted as a new planet and by 1783, Herschel too acknowledged this to Royal Society president Joseph Banks:
"By the observation of the most eminent Astronomers in Europe it appears that the new star, which I had the honour of pointing out to them in March 1781, is a Primary Planet of our Solar System."
In recognition of his achievement, King George III gave Herschel an annual stipend of £200 on condition that he move to Windsor so that the Royal Family could look through his telescopes (equivalent to £24,000 in 2019). As a bonus, George also pardoned him of his apparent desertion.
Despite only becoming a professional astronomer at the age of 43, Herschel made other valuable contributions to the field, building increasingly powerful telescopes to make observations of nebulae and form theories on their formation and evolution. He made numerous other discoveries, including two moons of Saturn, Mimas and Enceladus; as well as two moons of Uranus, Titania and Oberon.
He died on August 25th 1822 with the epitaph:
Coelorum perrupit claustra
(He broke through the barriers of the heavens)
His house at 19 New King Street in Bath, Somerset, where he made many telescopes and first observed Uranus, is now home to the Herschel Museum of Astronomy.
This scene was created by Colin Parry as part of a series of models on British history. Follow us on Facebook, Twitter and Instagram to see them first.
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