Encke, Johann Franz (1791-1865)

Johann Franz Encke was born on 23. September 1791 in Hamburg. His father was Johann Michael (1749-95), his mother Marie, née Misler (1755-1811).

From 1811 on Encke studied mathematics in Goettingen as pupil of C.F. Gauss. In May 1816 he moved to Seeberg near Gotha to work as observer at the observatory there. In 1822 he was promoted Director of that observatory and in 1825 followed a call to be the Director of the Observatory at Berlin. He supervised the new construction of the observatory from 1832-35. In 1844 he became ordinary professor at the University of Berlin and was allowed to lecture without receiving a doctorate.

Probably best known is his calculation of an cometary orbit. Encke followed a suggestion by J.-L. Pons, who suspected one of the three comets discovered in 1818 to be the same one already discovered by him1 in 1805, and calculated the elements of the orbit. The comet was found to have a period of 3.3. years and Encke predicted its return for 1822. This return was only observable from the southern hemisphere and seen by K. Ruemker from Australia. In 1825 Encke was visited by K. Knorre, who joined him for observations of the comet during this years return at the Seeberg Observatory near Gotha.

The comet was previously seen by Pierre-Francois Méchain in 1786 and Caroline Herschel of England in 1795.

The importance of the predicted return based on the calculation by Encke was rewarded by the Astronomical Society in London by presenting the gold medal to him in 1823. In this year Encke married Amalie Becker (1787-1879), daughter of a bookseller. They had three sons and two daughters.

During Encke's directorship the work at the Berlin observatory concentrated on the calculation of the orbits of asteroids and the influence of the big planets on these orbits. 1846 J.G. Galle discovered the planet Neptune with the help of star charts edited by Encke. Encke, with the help of his assistants J.P. Wolfers and Bremiker, also published 37 volumes (1830-66) of the 'Berliner Astronomisches Jahrbuch', an annual publication. These contain some still valuable articles on the problems of the calculating astronomy.

Encke died in Spandau, near Berlin, on 28. August 1865. He is honored by a lunar crater named after him. An 1838 discovered division between the A- and F-ring around the planet Saturn also bears his name (Encke gap).

Find more about Encke at:  http://www.in-berlin.de/User/jd/himmel/astro/Encke-e.html

1 Chapin suggests that Encke had seen the comet in 1805. I doubt this, since Encke was only 14 years of age at that time.

References:
1. KOPFF, A., in: Neue Deutsche Biographie, Vol. 4, p. 489-90
2. FREIESLEBEN, H.C., in: Dictionary of Scientific Biography, Vol. 4, p. 369-70
     Chapin, Seymour L. in: Dictionary of Scientific Biographies, Vol. 11
3. AUDOUZE, J. & ISRAËL, G., Cambridge Atlas of Astronomy, 3. Ed., p. 110
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