AST 320 – Introduction to Astrophysics (2023)


M2 in BA 1200, F12 in SS 2117
Marten van Kerkwijk, MP 1203B,; office hours: After class, or by appointment
Teaching assistants
  • Amanda Cook, AB 127, Office hours: W4 (problem set 1)
  • Gavin Noble, TBA, Office hours: TBA
Web page
Lecture notes
pdf (last updated: [2023-04-03 Mon 12:05]
Problem sets
five; set 1 due Jan. 30th, set 2 due Feb. 13th, set 3 due March 6th, set 4 due March 24th, set 5 due April 3rd 5th.
Previous midterms
2009, 2014, 2015
Previous finals
2009, 2014, 2015

Note on e-mail: your teaching assistants and professor will try to answer e-mail within one working day. For questions about the problem sets, please come to the TA office hour; please do not expect that e-mails sent in the weekend will be answered before class on Monday.


This course aims to teach the physics underlying the formation, the equilibrium, and the evolution of structure on all astronomical scales. Two main topics will be discussed:

  • Stars
    • Hydrostatic equilibrium, virial theorem;
    • Collapse of molecular clouds, star formation;
    • Equation of state in stellar interiors;
    • Simple stellar models: polytropes;
    • Radiative energy transport, opacity sources;
    • Convective energy transport;
    • Hayashi track; pre–main sequence evolution;
    • Energy balance: contraction, nuclear fusion;
    • Stellar model building;
    • The main sequence, brown dwarfs;
    • Low-mass stars: giant phases, shell burning;
    • High-mass stars: fusion up to iron;
    • Supernovae.
  • The Universe
    • Cosmological principle, basic parameters;
    • Simple relativistic cosmology;
    • Big Bang nucleosynthesis;
    • Times, distances, horizons, diameters;
    • Cosmic microwave background, inflation;
    • Fluctuations and structure formation.

Course text book

The text book is An Introduction to Modern Astrophysics, 2nd edition, by Carroll & Ostlie (Cambridge University Press, 2016). The focus will be on chapters 9, 10, 12, 13, 15, and 16 (Stars), and 29 and 30 (Universe). A more detailed list will be given in class. Furthermore, handouts will be made available that summarise the material and give additional detail where the text does not go into sufficient depth.

Alternative/Advanced texts

Stellar Structure and Evolution, by Kippenhahn, Weigert & Weiss (Springer-Verlag, 2012); a very good book (recommended by many of the former students of AST 320) for those who want to delve deeper into the subject. This book is available online and is sufficient on its own for the Stars part of the course.


The course prerequisites are AST 221H & 222H, and PHY 252H. These are equivalent to parts of the text book, which will be mentioned explicitly in class.


  • (25%) Five problem sets.
  • (25%) Term test, in class (likely March 10th, TBC).
  • (50%) Final examination.

Problem sets

Roughly every two weeks, there will be a problem set due, which uses material already discussed to prepare for the lecture. These problem sets will be available two weeks beforehand.

The problem sets are meant to apply and test your understanding of the material. Each should take no more than eight hours. If you seem to need more time or space, you are problably making things too complicated, and should come to an office hour!

We strongly encourage you to collaborate on problem sets, and suggest those interested form Recognized study Groups. Groups can consist of up to eight students, though we recommend somewhat smaller ones, of 3 to 5, to ensure everybody contributes. Groups should hand in a single solution and all students in them will get the same mark.

Author: Marten van Kerkwijk

Created: 2023-04-03 Mon 12:10