VII Semester 2+2, VIII Semester 2+2

**INTRODUCTION.** Theory and Problems in Stellar Structure and
Evolution. Observed Physical Characteristics of Stars. Empirical
Relations and Diagrams.

**DESCRIPTION OF STELLAR INTERIORS - PHYSICAL PRINCIPLES.**
General Distribution Law of Matter. Distributions of
Gas Particles and Photons in Statistical Equillibrium.
Conditions for LTE.
Degenerate States. Simple Perfect Gas and Black Body Radiation.
Free Electron Density. Mean
Molecular Weight. Radiation Field Parameters. Equation of State. Polytropic
Processes. Adiabatic Changes. Some Thermodynamic Relations. Absorption
Mechanisms and Processes under Typical Conditions in Stellar Interiors.
Monochromatic Mass Absorption Coefficients: Bound-Free and Free-Free
Transitions. Scattering on Free Electrons. Total Opacity.
Rosseland Mean Opacity. Approximate
Formulae. Kramers' Law. The Influence of Heavier
Elements on the Opacity. Energy Transfer. Thermal (Energetic) Equilibrium.
Radiative equilibrium. Energy Flux in Radiative Equilibrium. Thermal
Conduction. Convective Equilibrium. Temperature Gradients in the
Convective Zone. Average Speed of Convecting Elements. Conditions for
Turbulence to Appear. Convective Flux and Methods for its Computation.
Stability of Transfer Mechanisms. Stellar Energy Sources. Thermonuclear
Reactions. Hydrogen and Helium Burning Reactions. Heavier Isotopes
Burning Reactions. Energy Production Rate.
Approximate Formulae. Neutrino Energy Losses. Gravitational Potential
Energy of a Star. Conditions for Gravitational Contraction. Local Energy
Release from Gravitational Contraction. The Virial Theorem.
Internal and Total Energy of a Star. Dynamical Stability.

**STELLAR MODELS AND EVOLUTION.** Hydrostatic (Gravitational)
Equilibrium for Spherical Symmetry. Integral Theorems for Equilibrium of Stars. Vogt-Russell
Theorem. Formal-Mathematical Proof. Physical Interpretation. Analytical
Models. Polytropic Stars. Standard Model. Uniform Energy Source Model.
Point-Source Model. Stellar Envelopes in Radiative Equilibrium. Convective
Stellar Envelopes. Temperature Distribution in the Envelope (Problems).
Computation of Stellar Models. Equations of Structure.
Boundary Conditions. Dimensionless Variables. Transformations for
Integration from the Surface. Variables for Integration from the Center.
Invariants and the U-V Plane. Numerical Integration. Schwarzschild
Technique. Henyey Technique. Hydrodynamic Technique. Variable Chemical
Composition. Basic Phases of Stellar Evolution. Initial Phase (The Jeans
Instability, Formation and Evolution of Proto-Stars, Hayashy Sequences ,
Zero-Age Sequence). Main Sequence Phase (Evolution Rate Depending on
Mass, Main Sequence Theoretical Limits, Global Structure of Hot and Cold
Stars). Evolution of Massive Stars After the Main Sequence (Thermal
Instability, Gravitational Contraction of Central Core, Hydrogen Reactions
in the Stellar Envelope, Red Giant Stage - Spending of Helium in the
Central Core, Hydrogen and Helium Burning Reaction in Stellar Envelopes,
Pulsational Instability). Final Stages (Conditions for Dynamical Instability:
Planetary Nebula, Supernovae - White Dwarfs, Neutron Stars, Black Holes).
Developing Sequences of Models. Evolution with Variable Mass. Homologous
Models. Time Scales of Evolution. Gravitational Collapse. Dynamical
Expansion. Heating and Cooling. Kelvin's Scale. Scale of Nuclear Evolution.
Evolution of Chemical Elements. Contemporary Composition of Interstellar
Matter. Heavy Elements Production in Supernovae Explosion. Young and Old
Stars.