ENCKE, JOHANN FRANZ

born Sept. 23, 1791, Hamburg died Aug. 26, 1865, Spandau, Ger. German astronomer who in 1819 established the period of the comet now known by his name (see Encke's Comet). Encke was educated at Hamburg and the University of Gttingen, where he worked under the direction of Carl Friedrich Gauss. In 1816 Encke became assistant at the Seeberg Observatory near Gotha, Ger., where he was made vice director in 1820 and director in 1822. In 1825 he was appointed professor of astronomy and director of the observatory of the University of Berlin. There he planned and supervised the construction of a new observatory, completed in 1835. Besides the comet that bears his name, Encke is also known for his discovery of Encke's Division, in the outermost ring of Saturn. From observations of the transits of Venus recorded in 1761 and 1769, he derived a value for the solar parallax (in effect, for the Sun's distance from the Earth) that, at 8.57, is close to the presently accepted figure. He also established methods for calculating the orbits of minor planets and orbits of double stars.