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Johann Franz Encke

Born: September 23, 1791, in Hamburg, Germany
Died: August 26, 1865, in Spandau, Germany

Johann Encke began his career in Astronomy in 1811 at Gottingen University, under the tutelage of mathematician Carl Friedrich Gauss. However, his studies were interrupted by military service from 1813 to 1815.

Returning to civilian life in 1816, Encke was immediately hired by Bernhardt August von Lindenau, director of Seeberg Observatory, as his assistant.

While at Seeberg Observatory, Encke completed his research on the Great Comet of 1680 (discovered by Gottfried Kirch), one of the brightest comets of the 17th Century. For his work, he was awarded the Cotta Prize in 1817.

Continuing his research on comets, Encke correctly assigned an orbital period of 71 years to the 1812 comet (discoverd by Jean-Louis Pons). Now formally designated 12P/Pons-Brooks, this periodic comet is due to return in 2024.

Encke also correctly calculated the orbital period of the comet first observed by Pierre Méchain in 1786. It was not classified as a periodic comet until Encke was able to demonstrate by his calculations, published in 1819 in the journal Correspondance Astronomique, that the comet would reappear in 1822. This was verified by astronomer Carl Ludwig Rumker in June 1822, and in honour of Encke's work this comet now bears his name - 2P/Encke.

In 1822, Encke became the director of Seeberg Observatory and during his tenure there turned his attention to computing solar parallax, based on the transits of Venus in 1761 and 1769. His result, 8".57, was considered authoritative for many years. (The correct figure is 8".794.)

Encke moved to Berlin in 1825 as superintendent of the observatory being constructed there. During his career in Berlin, Encke supervised the production of star maps for the Berlin Academy (1830 to 1859); was editor of Astronomisches Jahrbuch; published four volumes of Berlin Observatory's Astronomische Beobachtungen; and worked on determining the orbits of asteriods.

In recognition of his many contributions to Astronomy, the asteroid 9134 Encke was named after him. His name is aslo associated with Saturn's rings. In 1888, while observing Saturn, astronomer James Edward Keeler discovered a gap in Saturn's A Ring. This gap is now referred to as the Encke Gap. It is 325 km (202 miles) wide and is maintained by the tiny moon Pan orbiting within it.

Johann Franz Encke

Saturn's Rings
Saturn's rings - Click for larger view
Image credit: NASA/JPL-Caltech/Space Science Institute

Saturn's moon Pan
Saturn's moon Pan - Click for larger view
Image credit: NASA/JPL-Caltech/Space Science Institute

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