AST 301: Introduction to Astrophysics

3 credits | Prerequisites: AST 201 for A&A Minor; PHY 101, MAT 104 for Physics Minor

Course rationale

This is an elective course designed for students majoring in physics, mathematics, engineering or computer science. Students can take it as part of a minor or specialization in astronomy and astrophysics or as a free elective. The course intends to give an overview of the theoretical understanding and observational evidence of our current picture of the universe and its large-scale constituents. However, more emphasis will be put on astrophysical observations than theory. For a more rigorous theoretical approach to cosmology, please refer to PHY 402: Cosmology.

Course content

Observing the universe: fundamental cosmological observations and their consequences: Olber’s paradox, homogeneity and isotropy, recession of galaxies, abundance of helium, age of globular clusters, CMB anisotropies, number counts of radio galaxies. Standard model of cosmology: Newtonian cosmology, kinematics and dynamics of the universe, laws of thermodynamics. Expansion equations: Friedmann-Lemaître equations and their consequences, big bang, age of the universe, redshift, Einstein-de Sitter model. Thermal history of the universe: radiation-dominated phase, decoupling of neutrinos, pair annihilation, primordial nucleosynthesis, deuterium formation, helium abundance, baryons and dark matter. Blackbody radiation: Planck’s law, Rayleigh-Jeans and Wien approximations, luminosity of a spherical black body, radiation pressure, limits of intensity. Cosmic microwave background: recombination, origin of CMB, dipole anisotropy, spectral evolution, temperature anisotropy, angular fluctuations, polarization. Formation of structures: galaxy redshift surveys, gravitational instability, linear perturbation theory, density fluctuations, correlation functions, power spectrum. Evolution of structures: the initial power spectrum, growth of density perturbations, cold and hot dark matter, spherical collapse, dark matter haloes, numerical simulations of structure formation, substructures, peculiar velocities. Hydrogen spin-flip radiation: Sky at 1420 MHz or 21 cm, quantization fundamentals, hyperfine transition: line splitting, the interaction terms, magnetic field inside proton, spin-spin coupling, energy difference, Zeeman effect. Dark ages and cosmic dawn: galaxies at high redshift, active and starburst galaxies, galaxy formation and evolution, cosmic star-formation history. Epoch of reionization: the first stars, the reionization process, detection of the 21-cm signal from this epoch. Cosmological parameters: determining cosmological parameters using observations: CMB, distant supernovae, cosmic shear, Lyman-α forest, intensity mapping of hydrogen.

Course objectives

  1. Understand the observational basis of our current standard model of the universe.
  2. Describe the evolution of the early universe until formation of stars and galaxies using equations of motion.
  3. Introduce the physical mechanisms behind the continuum blackbody radiation and the 21-cm line radiation.
  4. Extract scientifically useful information from cosmic blackbody and 21-cm radiation.
  5. Understand the importance of the radiation of 21-cm wavelength from hydrogen in creating a 4D map of the universe.


  1. Peter Schneider, Extragalactic Astronomy and Cosmology: An Introduction, Springer, 2006.
  2. Andre Liddle, An Introduction to Modern Cosmology, 3rd edition, Wiley, 2015.
  3. Hale Bradt, Astrophysics Processes: The Physics of Astronomical Phenomena, Cambridge University Press, 2008.
  4. Bradley Carroll & Dale Ostlie, An Introduction to Modern Astrophysics, 2nd edition, Cambridge University Press, 2017.