Abstract:
The principle factors governing the modelling of stellar atmosphere are reviewed, and it is noted that modern observations, which span wavelengths from 1000 /sup0/A to several mm, reveal parts of stars which are not included in the classical models. The evidence across the HR diagram shows that four components may be present in addition to the photosphere, namely a hot chromosphere/corona, a coll extended atmosphere of atoms and ions, dust, and an escaping wind. Some suggestions are made concerning the direction future research might take in order to solve the problems that are not handled successfully by classical methods of modelling stellar atmosphere
