Encke, Johann Franz (1791-1865)

German astronomer. His work on star charts during the 1840s contributed to the discovery of the planet Neptune in 1846. He also worked out the path of the comet that bears his name. The new star charts were compiled from both old and new observations. They were completed in 1859 but were soon improved upon by those of Friedrich Argelander.

Encke carried out continuous research on comets and the perturbations of the asteroids. What subsequently became known as Encke's comet had been reported by French astronomer Jean-Louis Pons, but little was known of its behaviour. Encke showed that the comet had an elliptical orbit with a period of just less than four years, the shortest period known.

Encke was born in Hamburg and studied at the University of Göttingen. On completing his studies there he became assistant at the observatory at Seeberg, and in 1822 director. He was a professor at the Academy of Sciences in Berlin and was Bode's successor as director of the Berlin Observatory 1825-65. He supervised the execution of the star maps of the Berlin Academy 1830-59 and the erection of the new observatory 1832-35.