Description

The study of stellar systems encompasses a wide range of physics, including gravitation, quantum mechanics, and thermodynamics. This module takes these fundamental physical concepts, learned in the core modules, and uses them to derive the properties of stars. The basic internal structure of stars is described in the first sections, while later sections deal with the ageing and death of both high- and low-mass objects. The final sections describe how stars form.

Module Aims

This module aims to develop familiarity with topics at the forefront of current astrophysical research, such as star formation and a detailed understanding of the physics that govern stellar structure and evolution.

Intended Learning Outcomes (ILOs)

A student who has passed this module should be able to:

• Module Specific Skills and Knowledge:
  1. describe the fundamental properties of stars;
  2. use the equation of hydrostatic equilibrium to estimate the core properties of stars;
  3. calculate the dynamical, thermal, and nuclear timescales of stars;
  4. describe the main nuclear reactions that power high and low mass stars;
  5. describe how radiation is transported from the stellar core to the surface;
  6. discuss post-main sequence evolution for high and low mass stars;
  7. describe the physics of compact stars and derive the mass-radius relationship for white dwarfs;
  8. discuss the terminal stages of stellar evolution;
  9. calculate the Jeans mass and describe the process of star formation;
• Discipline Specific Skills and Knowledge:
  10. solve mathematical problems;
  11. apply quantum and classical mechanics, and thermal physics to stellar systems;
• Personal and Key Transferable / Employment Skills and Knowledge:
  12. develop self-study skills;
  13. solve problems.

Syllabus Plan

1. General Properties of stars
   1. Definition of a star
   2. Observable quantities
   3. Distance determination
   4. Mass determination
   5. Luminosity and effective temperature
   6. Black body radiation
   7. Magnitude, colors and spectral types
2. Basic approach: Dimensional analysis
   1. Hydrostatic Equilibrium
   2. Virial theorem
   3. Characteristic timescales
      1. Dynamical or 'free fall' timescale
      2. Thermal timescale or Kelvin-Helmholz timescale
      3. Nuclear timescale
      4. Stellar lifetime on the Main Sequence
   4. Mass-luminosity relationship
3. Stellar structure equations
   1. Coordinates and mass distribution
      1. Eulerian description
      2. Lagrangian description
   2. Hydrostatic equilibrium
   3. Equation of motion for spherical symmetry
   4. Energy conservation
   5. Energy transport mechanisms
      1. Radiative transport of energy
      2. Convective transport of energy
      3. Conductive transport of energy
4. Thermodynamical properties of matter
   1. Ideal gas with radiation
      1. Fully ionized matter
      2. Partial ionisation
   2. Degenerate electron gas
      1. Consequence of Pauli's principle
      2. Complete degenerate electron gas
      3. Partial degeneracy
   3. Effect of degeneracy on stellar evolution
   4. Non ideal effects
5. Nuclear reactions and main burning phases in stars
   1. Basics of thermonuclear reactions
      1. Mass excess
      2. Binding energy
      3. Coulomb barrier
      4. Tunnel effect or quantum tunneling
      5. Cross sections and reaction rates
   2. Major nuclear burning phases in stars
      1. Hydrogen burning
      2. Helium burning
      3. Advanced stages
   3. Ultimate stages
6. Energy transport properties
   1. Opacity of stellar matter
      1. Bound-bound absorption
      2. Bound-free absorption
      3. Free-free absorption
      4. Electron scattering (Thomson scattering)
7. Principles of stellar evolution
   1. Polytropes
      1. The Lane-Emden equation
      2. The polytropic equation of state
      3. Analytical solutions to the Lane-Emden equation
      4. Masses and radii of polytropes
   2. Numerical models
      1. Contraction toward the Main Sequence
      2. Evolution on the Main Sequence
      3. Final stages: the death of stars
         White dwarfs; Supernovae, Remnants of supernovae: Neutron stars, black holes
8. Instabilities and stellar pulsations
   1. Stability considerations
   2. Stellar pulsations
      1. Special case of Cepheids
      2. Basics of stellar pulsation theory
9. Star formation
   1. Properties of interstellar medium and clouds
   2. The Jeans length and mass
      1. Gravitational instability criterion
   3. Fragmentation process
10. Massive star formation
    1. Spherical accretion and the Eddington limit
    2. The role of rotation
11. Binary star evolution
    1. The lagrange points
    2. The Roche lobe
    3. Detached binaries
    4. Semi-detached binaries
    5. Contact binaries
12. Protostellar discs
    1. Kinematical and thermal structure
    2. The source of viscosity
    3. The inner disc and the sublimation radius
    4. Magnetospheric accretion

Learning and Teaching

Learning Activities and Teaching Methods

Assessment

Resources

The following list is offered as an indication of the type & level of information that students are expected to consult. Further guidance will be provided by the Module Instructor(s).

Core text:

• Not applicable

Supplementary texts:

• Bowers R.L. and Deeming T. (1984), Astrophysics 1 - Stars, Jones and Bartlett, ISBN 0-86720-018-9 (UL: 523.01 BOW/X)
• Phillips A.C. (1999), The Physics of Stars (2^nd edition), Wiley, ISBN 0-471-98797-2 (UL: 523.8 PHI)
• Prialnik and D. (2010), An Introduction to the Theory of Stellar Structure and Evolution (2^nd edition), Cambridge University Press, ISBN 978-0-521-86604-0 (UL: 523.88 PRI)

ELE:

• http://newton.ex.ac.uk/redirects/ELE/PHY3066

Further Information

Prior Knowledge Requirements

Re-assessment

Re-assessment is not available except when required by referral or deferral.

Notes: See Physics Assessment Conventions.

KIS Data Summary

Miscellaneous