Our WWW pages give a flavour of current research. They are less massive than the Sun. Some are extremely helium rich. They are comparatively young stars, with masses 1 - 3 times the Sun. R Coronae Borealis stars fade unpredictably by factors of up to 1000.
Stellar atmospheres are the outermost layers of a star from which light is radiated.
The passage of radiation through the atmosphere modifies the spectrum . This can tells us about the conditions and composition within the atmosphere. Modelling stellar spectra requires sophisticated techniques, and lots of atomic data . Stellar pulsations are observed in many stars across the Hertzsprung-Russell diagram, and in all of the classes of star described above. We can learn about the fundamental properties of stars from their pulsations.