The New International Encyclopædia/Encke, Johann Franz
ENCKE, Johann Franz (1791–1865.) A German astronomer, born in Hamburg, where his father was a clergyman. After studying at Göttingen, under Gauss, he look part in the campaign of 1813-14, and in 1815 served in the Prussian Army as lieutenant of artillery. On the establishment of peace, he left the service and became assistant and afterwards principal astronomer in the Observatory of Seeberg, near Gotha. In 1825, chiefly at the instance of Bessel, he was called to Berlin to become secretary of the Academy of Sciences and director of the observatory. While at Gotha, the astronomical prize offered by Cotta was awarded to Encke by the judges, Gauss and Olbers, for his determination of the orbit of the comet of 1680. This led him to investigate another problem — viz. the determination of the distance of the sun from the earth. Encke's results, based upon the two transits of Venus, in 1761 and 1709, were published in two separate tracts, entitled Die Entfernung der Sonne (1822-24). His best-known work, however, is his discussion of the orbit of the comet discovered by Pons, November 26, 1819, which has a short period of about 1200 days, and which has since gone by the name of Encke's comet and has appeared regularly. (See Comet.) Encke's researches on this subject are contained in the transactions of the Berlin Academy. He endeavored to explain a remarkably regular change in the comet's period of revolution as the result of some resisting substance in the space traversed by the comet. There is, however, much doubt among astronomers as to the correctness of this hypothesis. In 1830 he undertook to edit the Berlin Astronomisches Jahrbuch, in which he published a number of astronomical papers. He issued four volumes of Astronomische Beobachtungen auf der Sternwarte zu Berlin (1840-56).