Franz Friedrich Ernst Brünnow (1821-1891), German astronomer, was born in Berlin on the 18th of November 1821. Between the ages of eight and eighteen he attended the Friedrich-Wilhelm gymnasium. In 1839 he entered the university of Berlin, where he studied mathematics, astronomy and physics, as well as chemistry, philosophy and philology. After graduating as Ph.D. in 1843, he took an active part in astronomical work at the Berlin observatory, under the direction of J. F. Encke, contributing numerous important papers on the orbits of comets and minor planets to the Astronomische Nachrichten. In 1847 he was appointed director of the Bilk observatory, near Düsseldorf, and in the following year published the well-known Mémoire sur la comète elliptique de De Vico, for which he received the gold medal of the Amsterdam Academy. In 1851 he succeeded J. G. Galle as first assistant at the Berlin observatory, and accepted in 1854 the post of director of the new observatory at Ann Arbor, Michigan, U.S.A. Here he published, 1858-1862, a journal entitled Astronomical Notices, while his tables of the minor planets Flora, Victoria and Iris were severally issued in 1857, 1859 and 1869. In 1860 he went, as associate director of the observatory, to Albany, N. Y.; but returned in 1861 to Michigan, and threw himself with vigour into the work of studying the astronomical and physical constants of the observatory and its instruments.
In 1863 he resigned its direction and returned to Germany; then, on the death of Sir W. R. Hamilton in 1865, he accepted the post of Andrews professor of astronomy in the university of Dublin and astronomer-royal of Ireland. His first undertaking at the Dublin observatory was the erection of an equatorial telescope to carry the fine object-glass presented to the university by Sir James South; and on its completion he began an important series of researches on stellar parallax. The first, second and third parts of the Astronomical Observations and Researches made at Dunsink contain the results of these labours, and include discussions of the distances of the stars α Lyrae, σ Draconis, Groombridge 1830, 85 Pegasi, and Bradley 3077, and of the planetary nebula H. iv. 37. In 1873 the observatory, on Dr Brünnow's recommendation, was provided with a first-class transit-circle, which he proceeded to test as a preliminary to commencing an extended programme of work with it, but in the following year, in consequence of failing health and eyesight, he resigned the post and retired to Basel. In 1880 he removed to Vevey, and in 1889 to Heidelberg, where he died on the 20th of August 1891. The permanence of his reputation was secured by the merits of his Lehrbuch der sphärischen Astronomie, which were at once and widely appreciated.
In 1860 part i. was translated into English by Robert Main, the Radcliffe observer at Oxford; Brünnow himself published an English version in 1865; it reached in the original a 5th edition in 1881, and was also translated into French, Russian, Italian and Spanish.
See Month. Notices Roy. Astr. Society, lii. 230; J. C. Poggendorff's Biog. Lit. Handwörterbuch, Bd. iii.; Nature, xliv. 449.