Johann Franz Encke

Johann Franz Encke (; 23 September 179126 August 1865) was a German astronomer. Among his activities, he worked on the calculation of the periods of comets and asteroids, measured the distance from the Earth to the Sun, and made observations of the planet Saturn.

Biography Encke was born in Hamburg, where his father was the Pastor at St. James' Church, Hamburg. He was the youngest of eight children, and at the time his father died, when he was four years old, the family was in straitened circumstances. Thanks to the financial assistance of a teacher, he was able to be educated at the Gelehrtenschule des Johanneums. He studied mathematics and astronomy from 1811 at the University of Göttingen under Carl Friedrich Gauss, but he enlisted in the Hanseatic Legion for the campaign of 1813–1814, serving as a sergeant in the artillery of the Prussian army, in Holstein and Mecklenburg. In 1814 he resumed his studies at the University, but after Napoleon's escape from Elba he returned to the military, serving until 1815 by which time he had become a lieutenant.

Having returned to Göttingen in 1816, he was at once appointed by Bernhardt von Lindenau as his assistant in the observatory of Seeberg near Gotha (he had become acquainted with von Lindenau during his military service). There he completed his investigation of the comet of 1680, for which the Cotta prize was awarded to him in 1817 by judges Gauss and Olbers. He correctly assigned a period of 71 years to the comet of 1812, now known as 12P/Pons-Brooks.

Eight masterly treatises on the comet's movements were published by him in the Berliner Abhandlungen (1829–1859). From a fresh discussion of the transits of Venus in 1761 and 1769 he deduced a solar parallax of 8.57 arcsecond. This and the corresponding distance to the sun were long accepted as authoritative. and a Foreign Honorary Member of the American Academy of Arts and Sciences in 1849. Incipient brain-disease compelled him to withdraw from official life in November 1863. He still was director of the Berlin observatory until his death on 26 August 1865 in Spandau. His successor was Wilhelm Julius Foerster.

He contributed extensively to the periodical literature of astronomy.

Encke's grave is preserved at a cemetery in the Kreuzberg section of Berlin, the Friedhof II der Jerusalems- und Neuen Kirchengemeinde (Cemetery No. II of the congregations of Jerusalem's Church and New Church) (entrance: opposite to 58–60, Zossener Str.; 61, Baruther Str. only for vehicles of the cemetery). His grave is close to that of the mathematician Carl Gustav Jacob Jacobi.

Honors Twice, in 1824 and 1830, the recipient of the Gold Medal of the Royal Astronomical Society. The crater Encke on the Moon is named after him. Asteroid 9134 Encke is named in his honour. The Encke gap of Saturn's rings is named after him. Comet Encke is named after him for his calculation of its orbit.