Herschel, (Frederick) William (1738 1822)

German-born English astronomer. He was a skilled telescope maker, and pioneered the study of binary stars and nebulae. He discovered the planet Uranus 1781 and infrared solar rays 1801. He catalogued over 800 double stars, and found over 2,500 nebulae, catalogued by his sister Caroline Herschel; this work was continued by his son John Herschel. By studying the distribution of stars, William established the basic form of our Galaxy, the Milky Way. Herschel discovered the motion of binary stars around one another, and recorded it in his Motion of the Solar System in Space 1783. In 1789 he built, in Slough, Berkshire, a 1.2-m/4-ft telescope of 12 m/40 ft focal length (the largest in the world at the time), but he made most use of a more satisfactory 46-cm/18-in instrument. He discovered two satellites of Uranus and two of Saturn. Herschel was born in Hanover and joined a regimental band at 14. He went to England 1757 and worked as a musician and composer while instructing himself in mathematics and astronomy, and constructing his own reflecting telescopes. The discovery of Uranus brought him fame and, in 1782, the post of private astronomer to George III. In 1800, Herschel examined the solar spectrum using prisms and temperature-measuring equipment, and found that the hottest radiation was infrared. This was the beginning of the science of stellar photometry. He also established the motion and velocity of the Sun.