PRINCIPLES OF STELLAR STRUCTURE AND EVOLUTION PRINCIPLES OF STELLAR STRUCTURE AND EVOLUTION CESARE CHIOSI UNIVERSITY OF PADOVA, ITALY

The stars Emit radiation Magnitudes, colors, spectra Magnitudes, colors, spectra Emit matter Stellar winds, ISM enrichment Stellar winds, ISM enrichment Synthsize elements Generate the elemental species we know Generate the elemental species we know Run as clocks Ages (stars, clusters, galaxies), cosmology Ages (stars, clusters, galaxies), cosmology

Which engine? Gravity is the main engine running the formation, structure and evolution of a star However many physical phenomena contrast, delay, balance the gravity and oppose to this in reaching very soon the final stage How to decipher the star phenomenum? Delberately we will focus on the physics of the inner processes and not On the appearance of the star in the Hertzsprung-Russel Diagram

Introduction Stars lose energy a source is requirred to balance Stars are in mechanical and thermal equilibrium (almost exactly) Three important time scales can be defined: Free-fall time scale (mechanical equilibrium) hours days Thermal time scale (gravitazional energy release by contracttion) Nuclear time scale (realse of energy by nuclear reactions)