# Physical Processes in Astronomy

This course discusses physical processes relevant for astrophysics and consists of three parts. Part I covers fluid dynamics. We will derive the continuity, momentum & energy equations, discuss hydrostatic equilibrium, viscous flows, fluid instabilities, equations of state, shocks, turbulence and focus on various astrophysical applications such as stellar structure and accretion disks. Part II deals with collisionless fluids. We will derive the Jeans equations, contrast them to Euler equations of collisional fluids, and study some applications of collisionless dynamics, including the virial theorem, dynamical friction and the impulse approximation. Finally, in Part III, we address radiative processes. We discuss both thermal and non-thermal emission mechanisms, study the interaction of radiation and matter, and delve into radiative transfer.

**Lecture hours:** TTh 9.00-10.15am (room WTS B60)

**Office hours: **Wed 4.00 – 5.00 pm, office 52HH#320 or via zoom.

**Syllabus:** Click here for download

**Lecture Notes:** PDF document (~200 pages). Click here for download. NOTE: lecture notes may be updated throughout the semester. **Check back regularly for updates**.

**Grading: – **35% final exam

– 30% midterm exam

– 35% problem sets

For more information, use the Yale Canvas System.

**Textbook(s)**

Although no textbook is required (detailed lecture notes are available), students are strongly encouraged to buy the textbook “The Physics of Fluids and Plasmas: An Introduction for Astrophysicists” by Arnab Rai Choudhuri, which covers most of the material covered in class and at the right level. Additional textbooks that are recommended are listed below:

**Problem Sets**

Problem sets (and their solutions) will be made available for download here.

Problem Set 0: voluntary, will NOT be graded [solutions]

Problem Set 1: due date Feb 6

Problem Set 2: due date Feb 16

Problem Set 3: due date Mar 9

Problem Set 4: due date Apr 25

NOTE: Don’t forget to indicate your name, staple your work, **and always explain your answers to the problem sets**. Points will be subtracted if you fail to explain how you came to the solution, even if it is correct.