**Homepage for 171.613 (Fall 2023): Radiative Astrophysics**

**Instructor: ** Marc Kamionkowski

Bloomberg 439

Office Hours:** **Thursday, 10am-11am or email for an appointment

**Grader: ** Ray Shi

Bloomberg 229

Office Hours:** **Tuesday, 4-5pm

**Class times/location: ** MW 1:30pm—2:45pm, Bloomberg 361

**COURSE OVERVIEW AND COMMENTS:**

Photons, or light, provide the principal communicator of information from astrophysical sources to us. Yes, we’ve now seen gravitational waves and neutrinos from a variety of astrophysical sources, but photons still carry most of the information.

The purpose of this class is to understand the physical phenomena that produce that light and how that light propagates to us. The relevant physics is for the most part stuff you’ve learned as an undergraduate—quantum mechanics, special relativity, electromagnetism, etc. But in this class its all put together in a way that is relevant for astrophysics.

Fortunately for all of us, Rybicki and Lightman wrote a spectacular little book that we will follow. The lectures and most of the homework will follow it quite closely.

**Prerequisites:** I am assuming that you have a grasp of quantum mechanics, electromagnetism, and special relativity.

**Homework/Grades: **I will assign weekly homeworks. Although they will be frequent, they should be relatively simple. The reason I assign weekly homeworks is because I think you will learn more effectively if you spend a little time every week, rather than cramming a huge chunks of time less often. I encourage you to keep on schedule with the homeworks. Feel free to work with other students and consult with other books, more senior students, patient postdocs, and the internet for help, but then try, once you’ve figured things out, to write the solutions on your own. We’ll then have a take home final exam. The final grade will be 75% homework and 25% final eam.

**REQUIRED TEXTBOOK:**

** Radiative Processes in Astrophysics **by Rybicki and Lightman

Available at the University bookstore or online (free with your JHED)

https://onlinelibrary.wiley.com/doi/book/10.1002/9783527618170

Other books:

*Radiation*, by Frank Shu, is a nice book and has some overlapping material

*Physics of the Interstellar and Intergalactic Medium, *by Bruce Draine, is a great book that is really about the physics of the interstellar medium, but also has lots of overlap with the subjects in this class.

**SYLLABUS, READING ASSIGNMENTS AND HOMEWORK PROLEMS:**

Chapter and problem numbers refer to Rybicki-Lightman

Lecture Date Subject / Reading / Homework problems

1 8/28 Introduction, specific intensity, and moments, 1.1-1.3

2 8/30 Radiative transfer equation and moments, 1.4; Problems 1.1, 1.2, 1.3

3 9/6 Blackbody and thermal radiation, 1.5

4 9/1 Einstein coefficients, 1.6 Problems 1.4, 1.5, 1.7

5 9/13 Scattering, 1.7

6 9/18 Radiative diffusion, 1.8 Problems 1.8, 1.9, 1.10

7 9/20 Maxwell’s equations, Fourier transforms, 2.1-2.3

8 9/25 Polarization, 2.4 Problems 2.2, 2.3

9 9/27 Electromagnetic potentials and the Liener-Wiechert potentials, 2.5, 3.1

10 10/2 Radiation fields, dipole approximation, 3.2 Problems 3.1, 3.2, 3.3

11 10/4 Thomson scattering, harmonic oscillator, 3.4-3.6

12 10/09 Lorentz transformations and 4-vectors, 4.1-4.2 Problems 3.4, 3.5, 3.6

13 10/11 Emission from relativistic particles, 4.8

14 10/16 Bremsstrahlung I, 5 Problems 4.1, 4.12, 4.13

15 10/18 Bremsstrahlung II, 5

16 10/23 Bremsstrahlung III, 5 Problems 5.1, 5.2

17 10/25 Synchrotron radiation I, 6

18 10/30 Synchrotron radiation II, 6

19 11/1 Synchrotron radiation III / Compton scattering I, 6 Problems 6.1, 6.2, 6.4

20 11/6 Compton scattering I, 7

21 11/8 Compton scattering II, 7 Problems 7.1, 7.2, 7.3

22 11/13 Plasma effects, 8

23 11/15 Atoms, 9

24 11/27 Atoms, 9 Problems 8.3, 9.2, 9.3, 9.4

25 11/29 Radiative transitions, 10

26 12/4 molecules, 11 Problems 10.2, 10.5, 11.1

27 12/6 TBD

**Homework due dates:**

Here,

- ‘DDL’ means homework submitted after that day will be treated as ‘late’, and the late penalty is to give at most 60% of the points (i.e. 6 for ‘solve’ and 4 for ‘make a good-faith effort to solve’).

- ‘Return graded’ means the graded homework is supposed to be returned to the students; ‘DDL (late)’ means that any homework submitted after that will be treated as invalid (0 pt) unless the student has a solid reason for the late submission.

Homeworks can be turned in in class or directly to Rui.

Last updated 31 August 2023