MPhys Physics with Astrophysics

Year of entry: 2024

Course unit details:
Stars and Stellar Evolution

Course unit fact file
Unit code PHYS30692
Credit rating 10
Unit level Level 3
Teaching period(s) Semester 2
Offered by Department of Physics & Astronomy
Available as a free choice unit? No


Stars and Stellar Evolution


Unit title Unit code Requirement type Description
Introduction to Astrophysics and Cosmology PHYS10191 Pre-Requisite Compulsory
Electromagnetism PHYS20141 Pre-Requisite Compulsory
Statistical Mechanics PHYS20352 Pre-Requisite Compulsory

Follow - Up units

PHYS40591 - Radio Astronomy

PHYS40771 - Gravitation


To apply the fundamental physics laws to understand the physics of stellar structure.

Learning outcomes

On completion successful students will be able to:
1. describe the basics of observational classification of stars in terms of spectral type, luminosity class, and the Hertzsprung-Russell diagram
2. assemble a set of equations of stellar structure from the physics of pressure balance, conservation of mass and luminosity, and the transport of energy
3. contrast the different versions of the equation of state in stellar interiors with respect to the contributions to the pressure of radiation, degenerate and non-degenerate gases
4. predict the dominant form of energy transport inside stars, based on the opacity to the transfer of radiation
5. identify the networks of nuclear reactions that operate in stellar cores, with reference to the core temperature, composition, stellar mass, and evolutionary state
6. outline, with respect to the initial mass and composition, the key phases of stellar evolution and the endpoints of such evolution
7. manipulate equations derived from analytical approximations to the stellar structure equations



1. Observed properties of stars
Measurement of stellar distances, luminosities, temperatures.  Masses and radii.  The Hertzsprung-Russell diagram.

2. Equations of Stellar structure
Time scales.  Fundamental equations:  mass conservation, hydrostatic equilibrium, energy transport.  The virial theorem.  Radiative transport and convection.

3. Equations of State
Pressure as function of temperature and density for:  Photons, Ideal gas, Degenerate electron gas.  Mean molecular weight.  Ionization.

4. Radiative transfer and opacity                                                                                                       Optical depth. Rosseland Mean Opacity. Opacity mechanisms. Applications to stars 

5. Nuclear fusion in stars                                                                                                                     Energy yields. Cross sections: the Gamow peak, reaction rates, and their temperature dependence. Reaction chains in stars. Neutrinos. 

6. Stellar modelling
Limits to the mass.  Solving the coupled equations.  Simple analytic stellar models:  polytropes and other relations.  Numerical models.  The Eddington luminosity.  Dimensional analysis and mass-radius relations.  The HR diagram.

7. Asteroseismology                                                                                                                               Pressure and gravity waves; helioseismology; application to other stars 

8. Early stellar evolution
The Hayashi line.  Onset of nuclear burning.  Main sequence evolution.  Life times.

9. Post-main sequence evolution
Isothermal cores.  Shell burning.  Degeneracy:  the helium flash.  The RGB and the AGB.  Mass loss.  White dwarfs.  Core collapse.  Supernovae.

Assessment methods

Method Weight
Written exam 100%

Feedback methods

Feedback will be available on students’ individual written solutions to examples sheets and online tests, and model answers will be issued.

Recommended reading

Recommended text 
Prialnik, D. An Introduction to the Theory of Stellar Structure and Evolution 2nd Ed (CUP 2009) 

Useful references 
Kippenhahn, Weiss & Weigert: Stellar Structure and Evolution, 2nd Ed, (Springer 2012) 

Clayton, D.D. Principles of Stellar Evolution and Nucleosynthesis (University of Chicago 1984)

Study hours

Scheduled activity hours
Assessment written exam 1.5
Lectures 23
Independent study hours
Independent study 75.5

Teaching staff

Staff member Role
John Leahy Unit coordinator

Return to course details