Lund Observatory
Lund University

Stellar Atmospheres, Investigated by Means of Infrared Spectroscopy


I have made major contributions to the interpretation of high-resolution, mid-infrared spectra of stars, especially those of red supergiants. For instance, I discovered unexpected water vapour in the atmospheres of warm giant stars. These observations are very useful to test models of the outer atmospheric structures. We still do not know whether inhomogeneities are important or whether there are further circumstellar regions with matter not accounted for. The interpretations of the water vapour lines have caused a lively debate in the literature. Our powerful observations of a whole range of stars will be decisive in this context.

  • The Mg I lines emission at 12 microns

Furthermore, I detected and modelled successfully the first observations of stellar (non-solar) Mg I emission lines at 12 microns. These Zeeman sensitive lines are potentially useful for measuring stellar magnetic fields (In November 2006 we will explore this possibility at the Gemini North telescope).


The outer atmospheric and circumstellar environments of red giant stars are very complicated structures and studying them by high-resolution, infrared spectroscopy is providing us with new insights and constraints. I have been leading several successful scientific projects from the start to the final publications. As a result of my research, I have detected and studied carbon-dioxide line emisson, and I have developed the method of 'stellar wind archaeology' and investigated winds in light scattered on wind molecules. 

In 2000, work along these lines resulted in my thesis `Infrared Spectroscopic Investigations of Stellar Winds from Red Giants' (Acta Universitatis Upsaliensis. Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology; 515. 51 pp. Uppsala. ISBN 91-554-4669-8).  Available are also the press release in Swedish, the spikblad, and the abstract of the thesis.

Docent Nils Ryde
Lund Observatory 
Box 43
SE-221 00 Lund, Sweden

Office: B207, Sölvegatan 27 
Phone: +46-46-222 1574, Fax: +46-46-222 4614