Physics 341
Principles of Astrophysics
Fall 2018

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 (35%), two in-class midterms (15% each), a final exam (20%), and iClicker scores (15%).
  • 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 2-3:30 (or by appointment)

    The final exam will occur on Friday, Dec 14 at 8am, location 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. Both books are on reserve at the Library of Science and Medicine.

    General concept
    Sept 4, 6 Introduction gravity; estimation; dimensional analysis Ch. 1, Sections 1.1 & 1.2  
    Sept 11, 13 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 18, 20   deriving Kepler's laws; the Galactic center Ch. 3;
    CO 2.3,6.1,24.4
    PS2 due
    Sept 25, 27   Doppler effect; supermassive black holes Ch. 3, Sections 3.2 and 3.3 PS3 due
    Oct 2, 4 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 9, 11   binary stars cont'd; midterm exam Ch. 4.3; CO 7.5 Thurs in-class midterm
    Oct 16, 18   extrasolar planets; tidal forces Ch. 5; CO 19.2 PS5 due
    Oct 23, 25 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 PS6 due
    Oct 30, Nov 1   dark matter; virial theorem Ch. 7.3 - 7.4;
    CO 24.3
    PS7 due
    Nov 6, 8 gravitational lensing elliptical galaxies
    lensing principles
    Ch.8, Ch. 9.1 - 9.2; CO 2.4,25.4,28.4 PS8 due
    Nov 13, 15   lensing principles; microlensing Ch.8, Ch. 9.1 - 9.2; CO 2.4,25.4,28.4 Thurs in-class midterm
    Nov 20, 22   galaxy and cluster lensing Ch. 9.3 Thursday Thanksgiving
    Nov 27, 29 relativistic cosmology the expanding Universe; the accelerating Universe Ch. 11; CO 27.1,
    PS9 due
    Dec 4, 6   general relativity; applications of general relativity Ch. 10.3 - 10.5;
    CO 17.1,17.2
    PS10 due
    Dec 11, 13   black holes Ch. 10.6, Ch. 11;
    CO 17.3
    final exam
    SERC 209
    Dec 14, 8-11am



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    Last updated: Aug 02, 2017 by Alyson Brooks