Born Wermland, Sweden, 28 April 1846
Died Pulkovo, Russia, 29 August 1916
Jöns Backlund is best known for his lifelong research on the motion and brightness of comet 2P/Encke. A mathematician and theoretical astronomer, Backlund earned his doctorate degree in astronomy from the University of Uppsala, Sweden, in 1875. He was hired as assistant director of the Russian Royal Observatory at Pulkovo in 1879 by Otto Wilhelm Struve . In 1883, Backlund was elected to the Imperial Russian Academy of Sciences of Petrograd, which allowed him to move to Saint Petersburg. Backlund was called upon by the Russian Academy to become the director of Pulkovo Observatory in 1895, following the resignation of Fedor Bredikhin . Backlund served in this capacity for 21 years, during which time he successfully improved the work of the observatory by employing large numbers of staff.
Backlund devoted himself to what became the passion of his lifetime, computing the orbit of the comet named for Johann Encke , who had devoted much of his own career to computing its puzzling orbit. Encke had proposed that there was a resisting medium near the Sun, which affected the comet’s orbit. Following Encke’s death, this problem was taken up by Friedrich von Asten until his death in 1878. Subsequently, Backlund devoted his major research efforts for the rest of his life to computing the orbit of this comet. Because of the contradictory implications of earlier observations, Backlund decided that it was necessary to recalculate the gravitational perturbations of the planets from Mercury to Saturn on Comet Encke’s orbit.
Backlund participated in several international scientific projects and conferences. He also published a large volume of papers summarizing his observations related to the motion of Encke’s comet. Backlund won worldwide renown for his accurate and thorough investigations; he was honored by Cambridge University with a “Doctor in Science” in 1904. He was also awarded the Royal Astronomical Society Gold Medal in 1909. In 1914, he was presented the Bruce Gold Medal of the Astronomical Society of the Pacific for his work on Encke’s comet, as well as for his other notable scientific achievements and contributions to theoretical astronomy. Backlund has a lunar crater named for him, along with a minor planet (856) Backlunda.