Donner, Anders Severin
BornKokkola(Finland), 5 November 1854
Finnish astronomer Anders Donner should perhaps be remembered as the astronomer primarily responsible for completing on time one of the first zones of the Carte du Cielproject. His parents were Anders Donner and Hilda Rosina Louise Malm. He married Elin Maria Wasastjerna in 1883, and they had six children.
Anders Donner lost his father early. His mother remarried and moved to Helsinki. Donner graduated from the University of Helsinki in 1875 and studied mathematics in Germany, in Leipzig, Königsberg (today Kaliningrad in Russia), and Berlin. In 1877/1878, Donner assisted his former professor of astronomy Karl Krüger in astronomical observations at Gotha in Germany. Donner defended his doctoral thesis on mathematics in Helsinki in 1879.
Donner concentrated on theoretical astronomy, especially on celestial mechanics, in the Observatory of Stockholm under the guidance of Johan Gyldén . Donner was appointed professor of astronomy at the University of Helsinki in 1883.
Oskar Backlund , who worked at the Pulkovo Observatory in Russia, drew Donner’s attention to the possibilities that a brand new observation technique, i.e., photography, offered to astronomy. Photographs of an object were permanent documents that could be looked at later, and the long exposure revealed objects that could not to be seen with eyes, even through a powerful telescope. The importance of the method was soon understood, an international conference was held in Paris in 1887, and a catalog and sky map project of stars based on photography was launched. Donner joined the project that is known by its French name Carte du Ciel.
For the program, a so-called standard astrograph (a kind of telescope) was purchased by the Observatory of Helsinki, and the program started in 1890. The sky was divided among 19 observatories, and Helsinki got the zone between +39° and +47° declination. The aim was to produce a catalog in which the positions of all stars brighter than the 11th magnitude would be measured with great precision and also their brightness would be given. In addition to that, a map would be made in which all stars brighter than the 14th magnitude would be shown. There were 1,008 areas to be photographed in the Helsinki Zone.
All of the required catalog plates had been photographed in Helsinki by 1896, and the maps were completed in 1911. But the most onerous work was to measure the positions and brightnesses of the stars on the plates and to calculate their coordinates and magnitudes with great precision for inclusion in the catalog. While carrying out this work, Donner developed and published many new methods of handling the large quantities of data involved. Photographs of the sky for many other studies were also taken at Helsinki and sent to the observatories that had requested them. Publication of the Helsinki Zone of the Carte du Ciel(astrographic catalog) began in 1903 and was completed in 1939. The 12-volume catalog contains 284,663 stars, and Donner eventually invested a considerable sum from his own resources in the project.
The workload of the project proved much bigger than was expected in the beginning, and many observatories did not finish or postponed their work. As the Carte du Cielof Helsinki was the only one to be completed in decades, the program did not produce the kind of complete material that was originally hoped for, to be used for instance in study of the structure of the Milky Way.
On Donner’s initiative, the photography of sky zones was restarted in 1909. By comparing the new plates to the older ones, proper motions of stars, whose positions had changed during the years, would be found. Donner’s closest colleague, Professor Ragnar Furuhjelm (1879–1944), published in 1916–1947 catalogs of over 4,000 proper motions of stars. Research on proper motions of stars has continued in Helsinki down to the present.
Donner was the rector and chancellor of the University of Helsinki and a member and elected official of many scientific societies. He strongly influenced the organization of many scientific fields in Finland and was also a key figure in the economic life of the country.