Heidelberg 1999 – scientific programme
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GR: Gravitation und Relativitätstheorie
GR 11: Astrophysics
GR 11.1: Invited Talk
Thursday, March 18, 1999, 14:00–14:40, AM1
Element formation and stellar evolution — •Bodo Baschek — Institut für Theoretische Astrophysik der Universität Heidelberg, Tiergartenstrasse 15, D-69121 Heidelberg
An overwiew is given over the distribution of the chemical elements observed in the universe and over their origin. The present distribution of the nuclides is – except for some light elements – the result of nucleosynthesis taking place inside the stars during their evolution over many stellar generations in about 15· 109 years. On the other hand, observation of abundances of heavier elements in very young galaxies indicate that stellar nucleosynthesis did take place, and hence provide "boundary conditions" for cosmological models.– After briefly presenting the principles of spectral analyses and the observed chemical composition of stars, nebulae, supernovae and their remnants, the basic nuclear reactions in the stellar interiors are discussed together with an outline of the evolution of stars.– Since stars – as well as the interstellar medium – are the essential constituents of galaxies, their individual evolution is closely coupled to that of the entire galactic system. Stars form out of the interstellar medium with different masses, and hence have very different evolutionary time scales. During their evolution they then change the interstellar composition by expelling processed matter. In particular supernova explosions play a vital role in the enrichment of the interstellar medium with heavier elements.