Physics 341: Principles of Astrophysics

Fall 2015

3:20-4:40 T Th
Room: ARC 105
Text: Principles of Astrophysics by Charles Keeton

Course Description

Astrophysics is the application of physical principles to astronomical systems. In Physics 341 and 342 you will learn how to use gravity, electromagnetism, and atomic, nuclear, and gas physics to understand planets, stars, galaxies, dark matter, and the Universe as a whole. Gravity is the dominant force in many astronomical systems, and it will be our focus in Physics 341.

Some astrophysical systems are described by equations that are fairly easy to solve, and we will study them. However, many interesting systems cannot be solved exactly. Nevertheless, we can often use physical insight and carefully chosen approximations to understand the key features of a system without sweating the details. One goal of the course is to develop that skill. As you will see, it will take us very far (through the whole Universe, in fact!). Another goal is to learn about recent advances in astrophysics, a very dynamic field of research.

Prerequisites for this class are two semesters of physics and two semesters of calculus. I will briefly review physical principles as we need them, but it is assumed that you have seen them before. I will also assume familiarity with vector calculus. Some of the assignments may involve a bit of computation that can be done with programs like Excel, Google Spreadsheets, Maple, Matlab, or Mathematica.

The recommended textbook for Physics 341 (and 342) is Principles of Astrophysics: Using Gravity and Stellar Physics to Explore the Cosmos, by Prof. Chuck Keeton. (It was written specifically for this course.)

Grading Policies

  • Grading will be based on weekly problem sets (60%), an in-class midterm (10%), the final exam (10%), and iClicker scores (20%, with a bonus for active class participation).
  • Weekly problem sets will be posted to Sakai on Thursday afternoons, and will be due the following Thursday at the beginning of class. Problem sets can also be turned in via our Sakai website in PDF format.
  • Collaboration with other students is strongly encouraged, but your write-up of the solutions must be your own. You must write down the names of your collaborators on your write-up. You must also cite any external sources you use (other than the textbook). You may not refer to notes, assignments, or solutions from previous years of Physics 341 or 342.
  • Always show your work. You will not receive full credit if you do not show your work. I will never look for a specific answer. Rather, I am always looking for the reasoning behind the answer.
  • In general, late homework will automatically receive a maximum of half points. Seek arrangement with me at least 24 hours in advance if you think you have a legitimate excuse for late work. After I have graded and handed back homework, I will not accept that homework anymore.

    Auditors are welcome. Please let me know if you are interested in auditing the class.

    Students with disabilities, please visit this link.

    Contact Information
    email: mbuckley at
    office: 329 Serin
    office hours: Mon: 3:30-4:30, Wed 2:30-3:30, after class, and by appointment.

    Tentative Schedule
    Date General Concept Topic(s) Text Due
    Sept 1, 3 Introduction gravity; estimation; dimensional analysis Ch. 1, Sections 1.1 & 1.2  
    Sept 10, 15, 17 1-body problem Newton's laws of motion and gravitation;
    conservation laws
    Ch. 2 PS1 due
    Sept 22, 24   deriving Kepler's laws; the Galactic center Ch. 3 PS2 due
    Sept 29, Oct 1 begin 2-body problem Doppler effect; supermassive black holes;
    2-body theory
    Ch. 3, Sections 3.2 and 3.3
    Ch. 4, Section 4.1
    PS3 due
    Oct 6, 8   binary stars; extrasolar planets Ch. 4, Sections 4.2 & 4.3 PS4 due
    Oct 13, 15   tidal forces; 3-body problem Ch. 5; Ch. 6 PS5 due
    Oct 20, 22 3-body problem 3-body problems continued; midterm exam Ch. 6 Thurs in-class midterm
    Oct 27, 29 N-body problems and galaxies basic properties of galaxies; spiral galaxy rotation curves; dark matter Ch. 7 No Homework
    Oct Nov 3, 5   galactic structure beyond rotation; virial theorem; elliptical galaxies; galaxy interactions Ch. 8 PS6 due
    Nov 10, 12 gravitational lensing basic principles; microlensing; galaxy and cluster lensing Ch. 9 PS7 due
    Nov 17, 19, 24 relativity special and general relativity Ch. 10, Sections 10.1 - 10.3 PS8 due
    Dec 1, 3   applications of general relativity; black holes Ch. 10, Sections 10.4 - 10.6 PS9 due
    Dec 8, 10   expanding Universe; geometry and dynamics;
    dark energy; future of the Universe, Exam Review
    Ch. 11 PS10 due
    Dec 17   Final Exam