Published online by Cambridge University Press: 05 April 2014
Stellar spectroscopy before 1860
Fraunhofer first observed stellar spectra in 1814. Using his 2.5-cm aperture theodolite telescope, he found three broad stripes in the spectrum of Sirius . Nine years later, with his 10-cm refractor he described the lines he saw in Sirius, Castor, Pollux, Capella, Betelgeuse and Procyon . The main result from this work was that stars have dark absorption lines in their spectra, yet that the lines present differ from star to star. Sirius, for example, with its three strong lines, was quite dissimilar to sunlight, while Betelgeuse displayed countless lines in its spectrum, some of which corresponded in position to the solar lines (see Chapter 2).
It is perhaps remarkable that the first pioneer to explore line spectra of any source at all systematically should have included stellar spectra in his observations. After Fraunhofer, no significant work was undertaken in stellar spectroscopy for 40 years. It is also surprising that these decades that saw so much activity in solar and laboratory spectroscopy should have seen practically no continuation of the spectroscopic work on stars that Fraunhofer had initiated.
Fraunhofer's 1823 paper describes his objective prism mounted on the 10-cm telescope. One of the few references to stellar spectroscopic observations in the intervening four decades came in 1838 from the Scottish-born German astronomer Johann (John) von Lamont (1805–79), who was then director of the Royal Observatory in Munich . Lamont set up Fraunhofer's apparatus again, and observed spectra of some of the brightest stars.