Johan Oskar Backlund (April 28 1846 – August 29 1916) was a Swedish-Russian astronomer. His name is sometimes given as Jöns Oskar Backlund, however even contemporary Swedish sources give "Johan". In Russia, where he spent his entire career, he is known as Oskar Andreevich Baklund (Оскар Андреевич Баклунд). Russian sources sometimes give his dates of birth and death as April 16 1846 and August 16 1916, since Russia still used the Julian calendar at the time.

He was born in Länghem, in Westrogothia, Sweden and graduated from Uppsala University in 1872. In 1876 he emigrated to Russia. He worked at Dorpat Observatory , in today's Tartu, Estonia, 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 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.

He won the Gold Medal of the Royal Astronomical Society in 1909. He won the Bruce Medal in 1914.

The Backlund crater on the Moon is named after him, as is the asteroid 856 Backlunda .

Family

Married Ulrika Catharina Widebeck. Their daughter Elsa Carolina Backlund (February 25, 1880 – April 19, 1974) became a well-known artist (she married Ulrik Fredrik Adolf Hugo Celsing, and was known under the name Elsa Backlund-Celsing). Their son Helge Gotrik Backlund (September 3, 1878 – 1958) was a geologist.

External links

• Bruce Medal page
• Awarding of Bruce Medal
• Awarding of RAS gold medal

• [1] (in Swedish)
• [2] (in Swedish)
• [3] (in Swedish)
• [4] (in Russian)

Obituaries

• AN 203 (1916) 235/236 (in German)
• MNRAS 77 (1916) 310
• Obs 40 (1917) 128–131 (not online)