Joseph von Fraunhofer - craftsman of light

Joseph Fraunhofer was born in Straubing on 6 March 1887 as the eleventh child of master glazier Franz Xaver Fraunhofer and his wife Anna Maria. After the death of his parents, at the age of eleven he was given by his guardian to the mirror maker and ornamental glass cutter Philipp Anton Weichselberger for a six-year apprenticeship as a mirror cutter in Munich. There he survived the collapse of his master's house in 1801.

In 1806, Fraunhofer joined the optical department of the Mathematical-Fine Mechanical Institute of Reichenbach, Utzschneider and Liebherr for the manufacture of astronomical and geodetic instruments (initially in Munich, from 1807 in Benediktbeuern). From 1809 he was a member of the management team, and from 1811 also the manager of the glass melting plant, developing new grinding machines and glass types for optical glass that improved lens quality.

From 1814, Fraunhofer is a partner in the Optical Institute; he is responsible for improving the achromatic lens pair for astronomical observations.
It was probably in this year that he discovered the lines in the solar spectrum.

In 1817, Joseph von Fraunhofer published his discovery of the dark lines in the solar spectrum in the memoranda of the Academy of Bavarian Sciences. A good 40 years later, spectral analyses by Kirchhoff and Bunsen showed that Fraunhofer had thus provided the key to the secret code of the stars: Because each chemical element is associated with a specific number and arrangement of spectral lines, it is possible to determine the composition of the atmosphere and celestial bodies.

In the year of publication, Fraunhofer is admitted to the Bavarian Academy of Sciences as a corresponding member, and from 1821 he is listed there as an associate member. From 1823, he was a salaried professor and curator of the physics cabinet.
In 1824, Fraunhofer was honoured with the Knight's Cross of the Order of Merit of the Bavarian Crown and elevated to the personal nobility.

In 1824, Joseph von Fraunhofer completed the construction of his largest telescope for the Russian observatory in Dorpat (now Tartu, Estonia). The astronomer Friedrich Georg Wilhelm Struve used this telescope with an aperture of 24.4 cm and a focal length of 4.33 metres to study double stars in particular. The Berlin observatory received a second, identical telescope in 1829. Johann Gottfried Galle uses it to discover Neptune in 1846.

Joseph von Fraunhofer did not live to see this discovery or the completion of his heliometer for the Königsberg observatory. He died of pulmonary tuberculosis on 7 June 1826 at the age of 39.

Objects, documents, correspondence: On Deutsches Museum Digital you can further explore Joseph von Fraunhofer in the collection of the Deutsches Museum.