A group of three papers from the family of a well-known Swedish-Russian astronomer Johan Oskar Backlund containing a signed by J. O. Backlund letter, invitation card, envelope addressed to the Croatian astrophysicist and doctor Branimir Alexander Truhelka. Dimensions: letter (20 x 16 cm); invitation card (11 x 7 cm); envelope (11.5 x 8 cm). Light staining and foxing.
Backlund, Johan Oskar (1846-1916) - was a Swedish-Russian astronomer. His name is sometimes given as Jöns Oskar Backlund. In Russia, where he spent his entire career, he is known as Oskar Andreevich Baklund (Оскар Андреевич Баклунд). He was born in Sweden and graduated from Uppsala University in 1872. After getting his doctorate in 1875, he emigrated to Russia in 1876. He worked at Dorpat Observatory, and then in 1879, worked at Pulkovo Observatory, becoming director of the observatory from 1895 until his death. He specialized in celestial mechanics and notably worked on calculating the orbit of Comet Encke, taking into account the perturbations of various planets. He used observations of Comet Encke to try to estimate the mass of Mercury. Russian sources sometimes referred to the comet as Comet Encke-Backlund. He also carried out geodesic studies in Spitzbergen from 1898 to 1900. He became a member of the Saint Petersburg Academy of Sciences in 1883, a member of the Royal Swedish Academy of Sciences in 1897, and a Fellow of the Royal Society in 1911. He was elected a Foreign Honorary Member of the American Academy of Arts and Sciences in 1914. He was married to Ulrika Catharina Widebeck. Their daughter Elsa Celsing became a well-known artist, and their son Helge Gotrik Backlund was a geologist and explorer.