The development of spectroscopy and its applications to the constitution of the universe during the nineteenth century

Abstract

The thesis looks at the discovery of spectrum analysis by Bunsen and Kirchhoff and how application was made of this analysis in attempting to understand the structure of the sun, stars, comets and nebulae by observation of their spectra. The early part of the thesis looks at the preliminary studies of Melvill, Fox Talbot and Wollaston on the spectra of flames. Then the ever increasing interest in spectra by a whole series of notable scientists is touched upon where mention is made of Fraunhofer's major contribution due to his perfection of the manufacture of glass prisms. The thesis points out that although there was considerable interest in the subject, progress was hampered by great technical difficulties. The breakthrough came during 1859-1862 with the work of Bunsen and Kirchhoff, but with the credit going to Kirchhoff alone for its celestial applications. Their observations convinced them that gases and vapours had the power of absorbing those very rays which they themselves gave out when in a state of incandescence. Once the work of Kirchhoff had been published there was a rush to use it in the study of the structure of the various heavenly bodies. Faye, Huggins and Lockyer (amongst others) were all interested in the structure of sun spots and the corona. Techniques were devised to observe the coronal spectrum during an eclipse and photographic methods started to make an ever increasing contribution towards the research work. These techniques led to arguments as to the correct classification of protuberances mainly between Respighi, Secchi and Zollner. Considerable work was done on the study of chromospheric lines (Lockyer, Respighi and Young) and various methods were devised for viewing the prominences. From 1864 onwards work was done on the structure of comets indicating that the coma has a different spectrum from that of the nucleus. The spectra of the fixed stars were observed and Secchi proposed a star classification (1868) which held a linkage with their colours. Further, the technique of using a shift in the position of spectral lines was used to determine the motion of stars in the line of sight. Finally, the thesis looks at the detailed research work on variable stars and nebulae ending with some notes on the instruments and techniques used by the observers.