Amici’s double star observations

In April 1824, as part of an extended tour through Europe following the death of his father William, the British astronomer and polymath John Herschel (1792–1871) met the Italian astronomer Giovanni Battista Amici (1786–1863) at the latter’s observatory in Modena. At the time, along with Herschel and Wilhelm Struve (1793–1864) in Dorpat, Amici was among the few astronomers measuring double stars. Their study, pioneered by Herschel’s father, was of interest because (in the case of optical doubles) they provided opportunity for measuring parallax or (in the case of true binaries) a chance to derive orbital parameters from observational data, as Felix Savary (1797–1841) would do for the first time in 1827. Measuring double stars was at the edge of observational precision, and determining orbital parameters depended on high-quality optics, precise micrometers, and data from as many different observers as possible. The younger Herschel encouraged a network of double star observers wherever he went, and much of his later work in astronomy involved synthesizing and publishing this data. Unlike Struve and Herschel, however, Amici never published his own extensive double star observations. Amici’s double star observations, stretching from 1815 to 1851 (although most are from 1824–1826), are now available in a handsome edition by Edizioni Tassinari as the second volume of Edizione Nazionale delle Opere e della Corrispondenza di Giovanni Battista Amici. The volume includes a 23-page introduction in Italian and English providing context on double star research in the 19th century as well as a discussion of Amici’s instruments and a survey of his correspondence related to double stars. The introduction explains why Amici and his instruments were important to double star research but not, however, why double star research was important to Amici. No doubt other volumes in the series contain Amici’s biographical details, but without a sketch of his life and career a reader of this volume alone will not know what role double stars played in Amici’s work, his institutional affiliations, or why he moved from Modena to Florence in 1831. The bulk of the volume (200 pp) is devoted to a high-quality, page-by-page reproduction of Amici’s six unpublished double star notebooks. The first notebook forms what would have been the introduction to Amici’s catalogue, showing the influence of William Herschel’s double star classes. The other notebooks contain his observations, organized roughly chronologically. 1032417 JHA0010.1177/00218286211032417Journal for the History of AstronomyBook Reviews book-review2021