Herschel, Sir (Frederick) William, originally Friedrich Wilhelm Herschel 1738-1822
British astronomer

Born in Hanover, Germany, he was the son of a musician who instructed his sons in the same profession. William joined the Hanoverian Guards band as an oboist and moved in 1755 to England where he built up a successful career in music, eventually settling in Bath in 1766, where his interest in astronomy began. He built his own telescopes, learning to cast his own metal discs for his mirrors. In 1781 he discovered the planet Uranus, the first to be found telescopically, which he named Georgium Sidus in honour of King George III, who a year later appointed him his private astronomer. At Slough, near Windsor, assisted by his sister Caroline Herschel, he continued his research and built ever larger telescopes. Herschel's discoveries included two satellites of Uranus (1787) and two of Saturn (1789), but his epoch-making work lay in his studies of the stellar universe. He drew up his first catalogue of double stars (1782), later demonstrating that such objects constitute bodies in orbit around each other (1802), and observed the Sun's motion through space (1783). His famous paper, On the Construction of the Heavens (1784), produced a model of the Milky Way as a non-uniform aggregation of stars; such studies occupied him for the rest of his life. Following the publication of Charles Messier's catalogue of nebulae and star clusters (1781), he began a systematic search for such non-stellar objects which revealed a total of 2,500, published in three catalogues (1786, 1789, 1802). He distinguished different types of nebulae, realizing that some were distant clusters of stars while others were nebulosities. Herschel was knighted in 1816. The epitaph on his tomb sums up his immense influence on the course of astronomy: Coelorum perupit claustra 'he broke the barriers of the heavens'.

Bibliography: A Armitage, William Herschel (1962)