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The Secret Code of the Stars – A New Landscape of the Sky and the Birth of Astrophysics

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Project description

It was not for another 40 years that the discovery of dark lines in the solar spectrum by Joseph Fraunhofer in 1817 led to the development of astronomical spectroscopy. The lines are produced by the absorption of characteristic colours from specific chemical elements in the solar atmosphere. These ‟lined” spectra, different for each star, showed a new landscape of the sky, aesthetically impressive, while looking totally strange. Parallel to this new picture of the sky, romantic and impressionist landscape painting arose. It also disturbed contemporaries and struggled for academic acceptance.
Spectroscopy radically changed our simple image of light points in the night sky, just as the new painting of the 18th century everted the traditional picture of colours and forms in nature.

The project will be continued by further studies. Since 2019, three letters by Fraunhofer to Samuel Thomas Sömmering were analysed, which up until now had been unknown. Unfortunately, they were heavily damaged by firefighting water at the end of World War II. In cooperation with the archives of the Goethe-Museum Frankfurt (as owner of the letters) and with the department of material sciences and art technology at the institute of preservation and restoration of the Bayerische Staatsbibliothek, Munich, these letters were photographed in ultraviolet light. Much of the washed-out handwriting became readable this way. Especially important is a letter (see picture), in which Fraunhofer describes attempts to colourise his copper etching of the solar spectrum. Until now we didn’t know anything about such attempts. This letter is also important in relation to the – hitherto unknown – technical provenience of the three preserved hand-coloured Fraunhofer spectra, two of them in the Deutsches Museum, one in the Goethe-Nationalmuseum Weimar. In respect to these three Fraunhofer letters, work on a longer article is in progress. The interrelation of astronomy and cultural history in the 19th century will be further examined, especially the relationship of romantic and impressionistic painting to physical optics. Spectral colours became more and more important. But we will also further explore the revolution which took place with a new understanding of a fragmented nature.


November 2017 – April 2018 exhibition in the Deutsches Museum for the 200-year-anniversary of Fraunhofer’s dark lines from 1817.


[Translate to English:]

  • Eine neue ′Landschaft′ des Unsichtbaren - Dunkle Linien im Spektrum der Sterne. In: Jahrbuch für Europäische Wissenschaftskultur 6 (2011), erschienen 2013, S.273–325.
  • From William Hyde Wollaston to Alexander von Humboldt - Star Spectra and Celestial Landscape. In: Annals of Science 71 (1), 2014, S. 27-60.


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