Physics 342
Principles of Astrophysics
Spring 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. In Physics 342 we will focus on the question: How did we get here?

Our story will include the nucleosynthesis of hydrogen and helium in the first few minutes after the Big Bang 13.7 billion years ago, the formation of stars from this primordial gas, and the forging of heavier elements, such as carbon, nitrogen, and oxygen, among all others within these stars' nuclear furnaces. Around at least one star in the Universe some of these heavy elements coagulated to form a rocky planet with a tenuous atmosphere. On this planet Earth, the energy from the star and the gas in the atmosphere were just right to allow the emergence of life. The energy that sustains us originated deep in the Sun, thanks to E=mc2 . The atoms that comprise our bodies were made inside dying stars. Literally, we are star dust. The goal of Physics 342 is to understand the physics of this remarkable story.

Some astrophysical systems are described by equations that are fairly easy to solve, and we will certainly study them. However, many interesting systems cannot be solved exactly. Nevertheless, we can often use physical insight and approximate calculations to understand the salient 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 assume 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. Note that Physics 341 is not a prerequisite for Physics 342; the two courses are designed to be complementary, but independent.

Lectures will be based on the course textbook, Principles of Astrophysics: Using Gravity and Stellar Physics to Explore the Cosmos, by Prof. Chuck Keeton. (It was written specifically for this course.)

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: TBD

Grading Policy

Grading will be based on biweekly problem sets (40%), two in-class conceptual midterms (10% each), iClicker conceptual question scores (20%), and the final exam (20%).

Problem sets will be posted to Sakai. There will be 6 problem sets during the semester, due roughly every other Thursday at the beginning of class. Problem sets can also be turned in as PDF files via Sakai.

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.

You are encouraged to work in groups on the problem sets, 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 use notes, assignments, or solutions from previous years of Physics 341 or 342.

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.

The final exam will occur on Friday, May 6 at 12pm in ARC 105 (our regular classroom).

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
Jan 16,18
dimensional analysis; electron gas
Chapter 1
Jan 23,25
The air we breathe
kinetic theory of gases;
planetary atmospheres;
hydrostatic equilibrium
Ch. 12.1/12.2/12.3
Jan 30, Feb 1
Hot in here
blackbody radiation;
planet temperatures
Ch. 13.1/13.2
PS #1 due Feb 4
Feb 6,8
atmospheric heating;
greenhouse effect
Ch. 13.3/13.4
Feb 13,15
Star light, star bright
stellar atmospheres; HR diagram
Ch. 14.1/14.2
CO-chapter 8
PS #2 due Feb 18
Feb 20,22
first in-class midterm ;
nuclear fusion: energetics
Ch. 15
in-class midterm Feb 23
Feb 27, Mar 1
nuclear fusion: reaction rates;
nuclear reactions in stars
Ch. 15
PS #3 due Mar 3
Mar 6,8
energy transport;
stellar structure
Ch. 16.1/16.2
Mar 13, 15
Mar 20,22
We are star dust
stellar evolution: low-mass stars;
stellar evolution: high-mass stars
Ch. 16.3/16.4
PS #4 due Mar 24
Mar 27,29
white dwarfs; neutron stars
Ch. 17
Apr 3,5
Surveying the Universe
second in-class midterm;
supernovae; cosmic acceleration; dark energy
Ch. 11
in-class midterm April 5
Apr 10, 12
star and galaxy formation
Ch. 8.1.3/19.1/19.2
PS #5 due Apr 14
Apr 17,19
stars, disks, and planets
Ch. 19.3/19.4
Apr 24,26
cosmic microwave background;
Big Bang nucleosynthesis
Ch. 20.1/20.2
PS #6 due Apr 28


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Last updated: April 15, 2016 by Alyson Brooks