Sir William Herschel was a German-born British astronomer who made many important contributions to astronomy

Originally named Friedrich Wilhelm Herschel, he was born in Hannover, Germany. At the age of 19 he went to England, working as a music teacher and organist but devoting all his spare time to astronomy and mathematics.

Unable to procure adequate instruments, he constructed and constantly improved his own telescopes. In 1774, with the aid of his sister Caroline (also an astronomer), he began a comprehensive and systematic survey of the heavens. In 1781 he discovered a new planet, which he named Georgium Sidus in honor of George III, king of the United Kingdom of Great Britain and Ireland, but which is now universally called Uranus.

A year later he was appointed private astronomer to the king, a position that enabled him to devote all his time to his astronomic pursuits. He erected a telescope at Slough with a 48-in (1.22-m) mirror and a focal length of 40 ft (12.2 m). Using this, he discovered two satellites of Uranus and the sixth and seventh satellites of Saturn.

He studied the rotation period of many planets and the motion of double stars, and also cataloged more than 800 double stars . He studied nebulas, contributing new information on their constitution and increasing the number of observed nebulas from about 100 to 2500. Herschel was the first to propose that these nebulas were composed of stars. He was elected to the Royal Society in 1781 and knighted in 1816. He is considered the founder of sidereal astronomy.