Previous | Session 28 | Next
A. K. Speck (University of Missouri - Columbia)
Intermediate-mass stars (0.8-8.0 solar masses) eventually evolve to become asymptotic giant branch (AGB) stars. During the AGB phase, these stars develop circumstellar envelopes comprising a mixture of dust and gas. AGB stars are major contributors of new elements to interstellar space. Furthermore, dust formation drives mass loss and thus influences the evolution of such stars. Therefore studying the dust around AGB stars is vital to our understanding of stellar evolution and galactic chemical enrichment. The major factors in determining the mineralogy (the composition and crystal structure) of the dust are the chemistry and density of the gas from which it forms. We discuss how a combination of infrared (IR) spectroscopic observations (both astronomical and laboratory) and theoretical considerations about the kinetics and thermodynamics in play in dust forming environments, together with meteoritic evidence, lead to a detailed understanding of dust formation processes. In addition, we discuss how the evolution of AGB stars (in terms of both chemistry and mass-loss rates), leads to changes in the dust mineralogy.
Previous | Session 28 | Next
Bulletin of the American Astronomical Society, 37 #2
© 2005. The American Astronomical Soceity.