HST image of the M16 nebula: pillars of creation

Physics 342
Principles of Astrophysics
Spring 2020

Tuesdays and Thursdays
3:20 to 4:40pm
ARC 105, Busch campus
Instructor: Prof. Eric Gawiser


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.) Optional, supplementary information can be found in An Introduction to Modern Astrophysics (2nd edition) by Bradley W. Carroll and Dale A. Ostlie (affectionately known as the Big Orange Book). Both of these textbooks are on reserve at the Library of Science and Medicine.

Contact Information

Prof. Eric Gawiser
Room 303, Serin Physics Building (across Allison Road from the classroom), Busch campus
Email: gawiser[at]physics.rutgers.edu
Phone: 848-445-8874

Virtual Office Hours: Thursday 12-1PM

Grading Policy

Grading will be based on problem sets (50%), an in-class midterm (20%), iClicker conceptual question scores (10%), and the final exam (20%). Due to the COVID-19 interruption in in-person instruction, lectures after Spring Break will be offered via WebEx, and the final exam will be optional.

There will be 6 problem sets during the semester, due every other Thursday at the beginning of class. Problem sets can be turned in as PDF files via Sakai. It is your responsibility to meet the deadline! Late assignments will not be accepted.

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 class notes I post or the textbook). You may not use notes, assignments, or solutions from previous years of Physics 341 or 342.

The optional final exam will occur on Friday, May 8 from 12-3pm.

Students are expected to maintain the highest level of academic integrity. You should be familiar with the university policy on academic integrity. Violations will be reported and enforced according to this policy. The use of external sources to obtain solutions to homework assignments or exams is cheating and a violation of the University Academic Integrity policy. Cheating in the course may result in penalties ranging from a zero on an assignment to an F for the course, or expulsion from the University. Posting of homework assignments, solutions, conceptual or exam questions, recorded lectures, or other lecture materials to external sites without the permission of the instructor is a violation of copyright and constitutes a facilitation of dishonesty, which may result in the same penalties as explicit cheating.

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 21,23
dimensional analysis; electron gas
Chapter 1
Jan 28,30
the air we breathe
kinetic theory of gases;
planetary atmospheres;
hydrostatic equilibrium
Ch. 12.1/12.2/12.3
CO 8.1/10.2/10.1
Feb 4,6
hot in here
blackbody radiation;
planet temperatures
Ch. 13.1/13.2
CO 3.4-5
PS #1 due Feb 6
Feb 11,13
atmospheric heating; greenhouse effect
Ch. 13.3/13.4/13.5
CO 9.2/20.2
Feb 18,20
star light, star bright
stellar atmospheres; HR diagram
Ch. 14
CO 8
PS #2 due Feb 20
Feb 25,27
nuclear fusion: energetics, reaction rates
Ch. 15.1/15.2
CO 10.3
Mar 3,5
nuclear reactions in stars; solar neutrinos
Ch. 15.3/15.4
CO 10.3
PS #3 due Mar 5
Mar 10,12
in-class midterm;
Rutgers canceled Mar. 12 class
in-class midterm Mar 10
Mar 17,19
Mar 24
energy transport; stellar structure
Ch. 16.1/16.2
CO 9.3/10.4-6/11.1
Mar 26
we are star dust
stellar evolution: low-mass stars
Ch. 16.3
CO 13
Mar 31
stellar evolution: high-mass stars
Ch. 16.4
CO 15.1-3
Apr 2,7
white dwarfs; neutron stars
Ch. 17
CO 4.4/16
PS #4 due Apr 2
Apr 9 surveying the Universe
stellar pulsation; Cepheids
Ch. 18
CO 29.1
Apr 14
supernovae; cosmic acceleration; dark energy
Ch. 11
CO 29.3-4
Apr 16,21
cooling; star and galaxy formation
Ch. 8.1.3/19.1/19.2/19.3
CO 12.2/2.4/26.2
PS #5 due Apr 16
Apr 23
planet formation
Ch. 19.4
CO 18.2/23.2
Apr 28,30
cosmic microwave background;
Big Bang nucleosynthesis
Ch. 20
CO 29.2
PS#6 due Apr 30
May 8
optional final exam 12-3pm


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Last updated: May 1, 2020 by Eric Gawiser