Person: Encke, Johann Franz
Johann Franz Encke was a German astronomer. 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
Mathematical Profile (Excerpt):
- Gauss was impressed with Encke's talents in astronomical observation and tried to have him work as an assistant in a small observatory in Ofen (another name for Buda, not part of Budapest).
- However, war interrupted Encke's studies and, in March 1813, he enlisted to fight against Napoleon.
- Encke was discharged in July 1814 and returned to his studies, but he was again interrupted in March 1816, when Napoleon escaped from the island of Elba.
- Not only did Gauss support his application for the position, but Encke had met the director of the observatory, Bernhrd von Lindenau (1780-1854), during his time in military service.
- Encke dedicated his time to astronomical observations and the computation of orbits of comets and minor planets.
- During his time in Seeberg, Encke used the records of the transits of Venus (from 1761 and 1769) to derive the solar parallax with surprising accuracy.
- Encke's value of 8.571", given in 1835, was accepted for some years but by 1860 the accepted value became 8.95".
- He is most famous for giving his name to Encke's comet.
- In fact, Encke always referred to it as Pons's comet.
- Encke observed it in December 1818 and computed its orbit in January 1819.
- Encke identified the comet with the ones observed by Pierre François-André Méchain (1786), Caroline Herschel (1795) and Pons (1805).
- Because of the comet's short period, Encke was able to observe it a number of times.
- Considering the observatory in Berlin to be inadequate, Encke decided to move to a new building, equipped with better instruments (including a large Fraunhofer refractor).
- Though Encke had been promised a new observatory when he took office, the promise would have not been realised so soon were it not for Alexander von Humboldt, who in 1828 appealed for aid to King Frederick William III.
- Encke was in charge of the Astronomisches Jahrbuch (Astronomical Yearbook), founded by his predecessor, Johann Elert Bode, who edited it for fifty years.
- Encke worked to improve the publication: he dropped the announcements, kept the articles (writing many of them himself) and radically improved the ephemerides.
- The Astronomisches Jahrbuch was, under Encke's direction, considered to have the best ephemerides in Europe, and was the cause of many reforms in similar publications like the British Nautical Almanac.
- The Royal Astronomical Society recognised Encke's efforts and gave him a second Gold Medal in 1830.
- The history of astronomical ephemerides is not a little varied and curious; a concise account of it will be found in the fourth volume of the 'Memoirs' of the Royal Astronomical Society, on the occasion of the council of the Society presenting Encke, through their President, with a gold medal, for the part which he had taken in the improvement of the Berlin Ephemeris.
- It would be superfluous to dwell upon the merits of this well-known work, which, far outstripping all rivalry, must be considered as the only Ephemeris on a level with the present wants of the sciences." On presenting the medal, Sir James South, the President, adds, "With the 'Berlin Ephemeris', an observatory scarcely wants a single book; without it, every one." It would, however, be disloyal, though in any other aspect it may be needless, not to add that what has just been said of the Berlin Ephemeris of 1830, may with equal truth be predicated of the 'Nautical Almanacs' from 1834 to the present date; nevertheless the first impulse came from Encke and Berlin.
- Encke was involved in the discovery of the planet Neptune.
- He initially opposed the use of the telescope for the search of Neptune, but he eventually gave permission to Johann Gottfried Galle and Heinrich d'Arrest, two of his students, to carry it out, using a chart of the night sky printed by Encke between 1830 and 1859.
- Neptune was found just before midnight on Encke's 55th birthday, in 1846.
- Encke was taken out of his birthday party to confirm the discovery and became the third person to see Neptune, at least knowing what he was looking at.
- As Director, Encke communicated the discovery to Astronomisches Nachrichten (Astronomical News).
- Encke did not mention d'Arrest in this notice, something he would come to regret later in life.
- Through observations, in 1837, he found Encke's division (or Encke's gap) in the outer ring of Saturn.
- Encke also derived a method to calculate perturbations on the orbits of minor planets in 1851, which was more convenient than Gauss's previous method.
- So it fared with Encke.
- A man such as this, absorbed in his work, and shutting himself away from the outer world, was likely to be sometimes abrupt, or laconic, or even incautious, in his utterances; these utterances, from their bluntness or their truthfulness, occasionally gave offence, and involved Encke in trouble.
- Encke died that same year, at the age of seventy-four.
Born 23 September 1791, Hamburg, Germany. Died 26 August 1865, Spandau, Germany.
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Tags relevant for this person:
Astronomy, Origin Germany, Physics
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References
Adapted from other CC BY-SA 4.0 Sources:
- O’Connor, John J; Robertson, Edmund F: MacTutor History of Mathematics Archive
