Discovery of Enceladus by William Herschel

Background. Frederick William Herschel (1738–1822) was a German–British astronomer and composer who frequently collaborated with his younger sister Caroline, often taking notes while he observed. He had earlier made many telescopes at his house at 19 New King Street in Bath, Somerset, where he first observed Uranus.

The Discovery. Enceladus was discovered by William Herschel on 28 August 1789, during the first use of his new 1.2 m (47 in) 40-foot telescope, then the largest in the world, at Observatory House in Slough, England. Little was known about the moon until the Voyager spacecraft flew by Saturn in 1980 and 1981.

Context in Herschel's Work. The Enceladus discovery came in Herschel's later career, in which he also discovered Mimas, another moon of Saturn, and Titania and Oberon, moons of Uranus. In 1789, shortly after the 40-foot instrument became operational, he discovered Mimas, only 250 miles (400 km) in diameter.