Peter Andreas Hansen

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Peter Andreas Hansen
Photography around 1865

Peter Andreas Hansen (born December 8, 1795 in Tondern ( Schleswig ), † March 28, 1874 in Gotha ) was a German astronomer and geodesist who began his scientific career as an amateur researcher . He is known for his work in astrometry and mathematical geodesy.

Life and family

Peter Andreas Hansen was the only son from the first marriage of gold and silversmith Nicolay Hansen (1755-1835) in Tondern. Early on, Peter Andreas distinguished himself with special skills and an interest in physics. He learned math, foreign languages ​​and playing musical instruments very easily. He would have liked to have attended secondary school, but the untimely death of his mother Anna Henriette (1760–1808) prevented these plans.

Hansen learned the art of watchmaking in Flensburg and established himself as a watchmaker in Tondern in 1819. The family doctor Peter Dircks recognized the young man's abilities and recommended him to his friend Heinrich Christian Schumacher for a scientific career. So Hansen went to Copenhagen and in 1821 got a job at the Danish degree measurement in Holstein led by Schumacher and in 1822 at his observatory in Altona . In 1823 he wrote his first own publications in the Astronomical News founded by Schumacher . When Johann Franz Encke's position at the Gotha observatory became vacant due to his appointment to Berlin, Schumacher, Olbers and Gauß recommended him for this position.

In 1825 he was appointed director of the Seeberg observatory near Gotha to succeed Johann Franz Encke . At that time Gotha was considered one of the most famous sites of astronomical science. Hansen's achievements were varied. He also proved himself as a geodesist and promoted the work of the European degree measurement, in whose permanent commission he was chairman for many years. Hansen and his family suffered greatly from the poor living and working conditions and the increasing deterioration of the observatory, as well as from the poor support from the Duke. The decay of the observatory, which is remote in the forest on the Seeberg and heavily exposed to the weather, prompted Hansen to apply for a move closer to the city. In 1839 the Hansen family was able to move into their own house on the southern edge of Gotha. Here, in 1859, Hansen set up an interim observatory with a meridian circle and an astronomical clock . This is where his children, three daughters and four sons grew up, and this is where his most important theoretical works were written. Hansen's main merits were particularly in the theoretical field, especially in the perturbation theory of the planets and in the creation of the lunar tables, a work that was used for decades for sea navigation. Through his technical skills he had introduced new, practical methods in the use of important astronomical instruments and had done much to improve them.

His daughter Emma (1836–1892) married the Pulkowo astronomer August Wagner (1828–1886), who spent his entire two-year stay abroad in Gotha. His daughter Marie (1829–1925) married the American writer and diplomat Bayard Taylor (1825–1878). In her autobiographical novel From Two Parts of the World , she described life in the Hansen household. It was also the case that the older father's chatter got on his nerves so much that he no longer had his hair cut. The daughter Ida (1844–1873) married the Hamburg mechanic and instrument maker Johann Adolf Repsold (1838–1919). His son Wilhelm (1832–1906) founded an iron foundry and turbine factory in Gotha, which was to grow into the largest industrial enterprise in the duchy.

Hansen worked with great success until his death in the observatory on Jägerstrasse. Hansen has received high honors from home and abroad for his scientific work. With Peter Andreas Hansen, however, the heyday of astronomy in Gotha ended.

Peter Andreas Hansen died on March 28, 1874. His burial in Gotha Cemetery IV took place with great interest from the population.

The city of Gotha honored their son by naming a street in the north of Gotha and a school in Wilhelm-Bock-Straße.

Hansen as director of the Seeberg Observatory

Peter Andreas Hansen
painting by Paul Emil Jacobs

As head of the observatory as part of the foundation of Duke Ernst II of Saxe-Gotha-Altenburg, Hansen received only a moderate salary, but a very well-equipped observatory. The inventory list drawn up by him showed the extensive inventory of astronomical instruments. Since 1839 the interim observatory in his Gotha town house has been the focus of his astronomical activity, he only visited the observatory on the Seeberg once a week.

Hansen as an astronomical observer

Hansen's first observations in Gotha were on comet 1825 III. He was able to get to know the capabilities of Gothaer instruments. As a trained mechanic, he put the findings together and published them as theories of the individual devices. Further observations followed continuously to determine the orbit of the planetary bodies and especially of the moon as the basis of his perturbation theories .

Later he also constructed an equatoreal , which he had built for his new observatory at Repsold & Sons in Hamburg .

Hansen as a theoretical astronomer

From the observations of the moving celestial bodies, he derived their orbital elements and turned to calculating the recognizable disturbances of these movements. He developed generally applicable solutions, which he published in Gotha from 1829. His specialty eventually became the movement of the moon . In doing so, he improved the theory of disturbances . He used the Hansen coefficients named after him.

This work on the lunar theory finally culminated in his main work Tables de la lune d'après le principe Newtonien de la gravitation universelle , which was published in London in 1857 on behalf of the British government . This work, which was initially irreplaceable for navigation, was created by him in England with several computers and in collaboration with George Biddell Airy , the director of the Greenwich Observatory , since there was no way to do so in Gotha .

Hansen as a geodesist

Hansen had already taken part in geodetic work in Denmark and on Heligoland under Schumacher's direction . In 1837 he was commissioned to measure the Gothaer Land. Here, too, he was involved in both the practical work and the theory of measurements. The so-called " Hansen task " became a standard method of trigonometric point determination in geodesy . Hansen headed the permanent commission of the European degree measurement for several years and was also a member of the German commission for the observation of the passage of Venus in 1874.

Gotha's New Ducal Observatory

It is probably thanks to his increasing scientific fame and his work in the geodetic development of the Gothaer Land that the Gotha Landtag approved the construction of a new observatory in the Gotha city area. The preparations for the construction, which according to Hansen's plans should offer the best opportunities for a practical and theoretical astronomer, began in the 1850s. The stones of the meridian hall of the Seeberg observatory and the former grotto of the park of Friedrichstal Palace were used for this purpose. The new building was completed in 1859.

An astronomical prototype

Hansen's observatory in Gotha, today's sight (Jägerstrasse)

In addition to a spacious residential building, which also contained work and lecture rooms for scientific work, an octagonal tower with a rotating dome, a meridian hall and, as a special feature, an observation room in the first quarter. The instrumental equipment could be put together from the previous inventory. Hansen only designed a new instrument for the tower, an equatoreal . Hansen improved the observation methods by introducing electrical timekeeping. A prototype of an astronomical observatory was thus built in Gotha again. Hansen had oriented the way of working entirely on astrometric research, so that the observatory offered no possibilities for the emerging astrophysical research.

According to the will of Duke Ernst II of Saxe-Gotha-Altenburg, the Gotha observatory was to be the only public monument of his life. Hansen therefore had a plaque with a Latin text placed above the entrance to the observatory. In 2007, the plaque, which had been damaged by the effects of the war, was restored to the public with funds from the Gotha Cultural Foundation. The text is now again:

SPECULA ERNESTINA

IN VICINO MONTE OLIM CONDITA FROM ERNESTO II: DG ET A.
OPPORTUNIORE LOCO NUNC REST. AB ERNESTO II. DC ET G.

MDCCCLVII

(Ernestine observatory, once donated by Ernst II Duke of Gotha and Altenburg, on a neighboring mountain, now restored at a more favorable location by Ernst II Duke of Coburg and Gotha, 1857)

On April 18, 2007, the German Association for Surveying Inaugurated a donated plaque in honor of Hansen's astronomical and geodetic activities next to the entrance to the residential building.

Hansen's character has been described as a bit difficult. As an autodidact, he had developed his own working style, which sometimes led to unusual solutions and expressions. He clung to what he knew correctly and defended his opinion. But he had a number of friends and employees, some of whom stayed longer in Gotha. There are only BA Gould (1824–1896) from Cambridge , Friedrich Georg Wilhelm Struve (1793–1864) and Otto Wilhelm von Struve (1819–1905) from Pulkowo , George Biddell Airy (1801–1892) from Greenwich and Johann Littrow ( 1781–1840) from Vienna . Wilhelm Scheibner (1826–1908) worked from 1848 to 1853 as a student and assistant at Hansen in Gotha . Later he edited Hansen's writings as a professor of mathematics in Leipzig .

Hansen's extensive correspondence is in the Hamburg State Archives and is still awaiting scientific processing. Hansen's correspondence with Carl Friedrich Gauß is handwritten in the Gauß letter database. The University and Research Library Erfurt / Gotha owns numerous Hanseniana .

Honors

Main cemetery in Gotha Tomb of the married couple Hansen

Hansen received many honors in the last years of his life. In Gotha he was a member of the government as a Privy Councilor for surveying issues. He was awarded an honorary doctorate from the University of Jena, a member of many academies and received several awards:

In 1935 the Christian-Albrechts-Universität zu Kiel had a memorial stone erected in Hansen's place of birth, Tondern.

When the cemetery was cleared in 1951, the tombstone of Hansen and his wife was secured and is now in the main cemetery in the Ehrenhain next to the stones of other important Gotha personalities. In addition, the Hansenstraße and the Hansenschule in Gotha are a reminder of the astronomer. In 1995 a memorial stone was erected on the Großer Inselsberg for the geodetic significance of Hansen's measurements.

In addition, the lunar crater Hansen (moon crater) and the asteroid (4775) Hansen were named after him.

Works

  • Detailed method of making observations with the Fraunhofer heliometer. Gotha 1827.
  • Investigations into the mutual disturbances of Jupiter and Saturn. Berlin 1831.
  • Determination of the absolute disturbances in ellipses of any eccentricity and inclination. Gotha 1843.
  • Discussion of an expedient method for calculating the absolute disturbances of the small planets. Dept. 1–3. Leipzig 1856-1859.
  • Fundamenta nova investigationis orbitae verae, quam luna perlustrat. Gotha 1838.
  • Tables de la lune. London 1857.
  • Presentation of the theoretical calculation of the disturbances used in the lunar tables. 2 parts. Leipzig 1862–1864.
  • The theory of the equatorial. Leipzig 1855.
  • Theory of solar eclipses and related phenomena. Leipzig 1858.
  • Disturbances of the great planets: especially Jupiter. Leipzig 1875.

literature

Web links

Commons : Peter Andreas Hansen  - Collection of images, videos and audio files

Individual evidence

  1. ^ Gaussian letter database .
  2. ↑ Holger Krahnke: The members of the Academy of Sciences in Göttingen 1751-2001 (= Treatises of the Academy of Sciences in Göttingen, Philological-Historical Class. Volume 3, Volume 246 = Treatises of the Academy of Sciences in Göttingen, Mathematical-Physical Class. Series 3, volume 50). Vandenhoeck & Ruprecht, Göttingen 2001, ISBN 3-525-82516-1 , p. 103.
  3. ^ Inge Adriansen: Erindringssteder i Danmark. Monuments, minesmærker and mødesteder. Museum Tusculanum, Copenhagen 2011, ISBN 978-87-635-3173-3 , p. 253.


personal data
SURNAME Hansen, Peter Andreas
BRIEF DESCRIPTION German astronomer
DATE OF BIRTH December 8, 1795
PLACE OF BIRTH Tondern
DATE OF DEATH March 28, 1874
Place of death Gotha