21 March – 21 June 2016 in Florence, Rome, Naples, Palermo, Padua

GIOVAN BATTISTA DONATI (1826-1873)

“Intorno alle strie degli spettri stellari” (on lines from stellar spectra)

Annals of the R. Museum of Physics and Natural History of Florence for 1865. New Series, vol. I. Florence, with the types of M. Cellini and C. at the Galileiana, 1866.

1 vol, ill., 310 mm

INAF-Arcetri Astrophysical Observatory

Although Donati never proposed a scheme for the spectral classification of stars, his observations conducted around 1859-1860 (see Fi. 01) led to the unexpected discovery of a correspondence between stellar colours and spectra, which would be later confirmed and extended by Angelo Secchi in the following years (cf. Fi. 03 and Fi. 05). This table shows the absorption lines in the spectra of 15 stars grouped according to their colours. Donati observes: the white stars have lines that resemble each other, and the same is true for the yellow stars, the orange, and red. The correlation inferred by Donati is due to the fact that both the spectrum and the colour of a star depend on its effective (photospheric) temperature, a result fully understood only in the 1920’s thanks to studies of the English astronomer (working at the Harvard Observatory) Cecilia Payne (1900-1979). A second plate from this work shows the tube and spectroscope used by Donati for these first observations.

Bibl.: DONATI 1866, CHINNICI 1999, HEARNSHAW 2014.