Physics 341
Principles of Astrophysics
Fall 2016

Tuesdays and Thursdays
3:20 to 4:40pm
ARC 105, Busch campus
Instructor: Alyson Brooks


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.)

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

Students with disabilities should consult the department policy.

Grading Policies

  • Grading will be based on weekly problem sets (50%), one in-class midterm (15%), and iClicker scores (15%), and the final exam (20%).
  • 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.

    Contact Information

    Prof. Alyson Brooks
    Room 306, Serin Physics Building (across Allison Road from the classroom), Busch campus
    Email: abrooks[at]
    Phone: 848-445-8877

    Office hours: Wed 12-2, or by appointment

    The final exam will occur on Friday, Dec 16 at 8am in SEC 209.

    Schedule: Topics and Assignments

    This syllabus may be modified as the semester progresses.

    Note: Under the "Text" column, "Ch" mark the Chapters in Keeton. "CO" refers to Carroll & Ostlie, on reserve at the Library of Science and Medicine

    General concept
    Sept 6, 8 Introduction gravity; estimation; dimensional analysis Ch. 1, Sections 1.1 & 1.2  
    Sept 13, 15 1-body problem Newton's laws of motion and gravitation;
    conservation laws
    Ch. 2;
    CO 1.1,1.2,2.1,2.2
    PS1 due
    Sept 20, 22   deriving Kepler's laws; the Galactic center Ch. 3;
    CO 2.3,6.1,24.4
    PS2 due
    Sept 27, 29   Doppler effect; supermassive black holes Ch. 3, Sections 3.2 and 3.3 PS3 due
    Oct 4, 6 begin 2-body problem 2-body theory; binary stars Ch. 4, Sections 4.1 & 4.2; CO 2.3,5.4,8.1,7.1,7.2,7.3 PS4 due
    Oct 11, 13   binary stars cont'd; extrasolar planets Ch. 4.3; CO 7.5 PS5 due
    Oct 18, 20   tidal forces; midterm exam Ch. 5; CO 19.2 Thurs in-class midterm
    Oct 25, 27 N-body problems and galaxies basic properties of galaxies; spiral galaxy rotation curves Ch. 7.1 - 7.3; CO 25.1,25.2,24.1,24.2  
    Nov 1, 3   dark matter; virial theorem Ch. 7.3 - 7.4;
    CO 24.3
    PS6 due
    Nov 8, 10 gravitational lensing elliptical galaxies
    lensing principles; microlensing
    Ch.8, Ch. 9.1 - 9.2; CO 2.4,25.4,28.4 PS7 due
    Nov 15, 17   galaxy and cluster lensing Ch. 9.3 PS8 due
    Nov 22, 24 relativity special relativity Ch. 10.1 - 10.2;
    CO Ch.4
    Thursday Thanksgiving
    Nov 29, Dec 1   general relativity; applications of general relativity Ch. 10.3 - 10.5;
    CO 17.1,17.2
    PS9 due
    Dec 6, 8   black holes
    expanding Universe; geometry and dynamics
    Ch. 10.6, Ch. 11; CO 17.3,27.1,27.2,29.1 PS10 due
    Dec 13, 16   dark energy; future of the Universe Ch. 11; CO 29.3 final exam
    SEC 209
    Dec 16, 8-11am



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    Last updated: November 1, 2016 by Alyson Brooks