Chromospheres, Coronae, Gas and Dust Around Luminous Stars
From a fundamental point of view there is not much reason to distinguish between the various parts of outer stellar envelopes, such as chromospheres, coronae, dust shells, etc. Such a distinction might easily leave the reader with the false impression that these layers are separate physical entities. The contrary is true: the complicated interplay between the mechanical, magnetic, radiative and conductive fluxes, in addition to stellar winds in outer atmospheric regions can lead to the formation of extended envelopes, with a complicated temperature and density distribution. Conventionally, different names are assigned to the various temperature regions — cf. Section 1.8. In the extreme parts of these envelopes where the gas has low temperatures, molecules and even dust particles may form. In other cases youngly formed stars may still partly be embedded in the gas and dust cloud out of which they originated.
KeywordsDust Particle Spectral Type Stellar Wind Dust Cloud Coronal Heating
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