# Astronomy 320: Spring 2016

# Theoretical Astrophysics

Modern astronomy has its roots firmly grounded in the fundamental principles of physics (both classical and quantum). Furthermore, many branches of physics as we know them today trace their origins to the search for universal physical laws to explain natural phenomena discovered and analyzed by astronomers.

The goal of theoretical astrophysics is to provide physical and conceptual understanding of the diverse systems that represent our universe. Introductory astronomy courses are often organized by scale (planets, stars, galaxies and the universe as a whole) and observational astronomy courses are often organized by wavelength because of the different technologies. To emphasize the different approach needed for developing a theoretical framework, this course is organized into themes of governing physical principles. For each of the three main themes (gravity, gas physics and quantum physics), we start with fundamental principles and then discuss applications in various astronomical contexts. We will also discuss systems in which several principles interact synergistically and demonstrate how astrophysical theories are developed by successive model refinements and confrontation with data. We will show how application of simple physical laws can explain the observed properties of an astounding range of astronomical objects!

I will assume a basic knowledge of astronomical concepts (up to the ASTR120/ASTR121 level) as well as basic physics (up to the PHYS270/PHYS271/PHYS273 level)

#### Schedule

Instructor: Massimo Ricotti Class: CSS 1113 Lectures: Tuesday and Thursday from 11:00pm to 12:15pm First class: Tue Jan 26 Last class: Tue May 10 TA: Scott Lawrence Reading session (w/Scott): Wednesday from 2:00pm to 2:50pm First reading session: Wed Feb 3rd

#### What's New?

April 26: Online course evaluation open April 25 - May 11 - please participate. |

April 19: Problem Set #6 (the last one!) posted on ELMS (due May 3rd). |

April 5: Problem Set #5 posted on ELMS (due April 14). |

March 21: Problem Set #4 posted on ELMS (due March 31). |

March 1: Midterm sample and solution posted on ELMS. |

March 1: Problem Set #3 posted on ELMS (due March 10). |

Feb 18: Problem Set #2 posted on ELMS (due March 1). |

Feb 8: Problem Set #1 posted on ELMS (due Feb 18). |

Jan 28: From today onward we will use a new lecture room (to accomodate the 31 students taking the class this year): CSS 1113 |

Jan 28: First class |

Jan 27: No reading session on Wed 27 Jan |

Jan 26: Snow day (no class) |

#### Contact info and Notes

- Office: PSC 1156
- E-mail: ricotti "at" astro "dot" umd "dot" edu
- Phone: (301) 405 5097
- Office hours: Mon 12:00pm-2:00pm or by appointment
- Class web page: http://www.astro.umd.edu/~ricotti/NEWWEB/teaching/ASTR320_16.html
- TA: Scott Lawrence
- E-mail: srl "at" umd "dot" edu

#### Course Outline

The Syllabus is available in PDF format.

Date | Lecture | |
---|---|---|

GRAVITY (notes) | ||

#1 | Jan 26 | Snow Day (class cancelled) |

#2 | Jan 28 | Introduction; Recap of Newton’s laws and the conservation of momentum |

#3 | Feb 2 | Newtonian gravity |

#4 | Feb 4 | One body problem - conservation laws and constants of motion |

#5 | Feb 9 | One body problem - solving the equation of motion |

#6 | Feb 11 | Discovery of Gravitational Waves |

#7 | Feb 16 | One body problem - cont. |

#8 | Feb 18 | One body problem - derivation of Kepler's Laws |

#9 | Feb 23 | Two-body problems and binary systems (notes) |

#10 | Feb 25 | Two + one (restricted three) body problem - Lagrange points and effective potential |

#11 | Mar 01 | N-body dynamics - the virial theorem |

#12 | Mar 03 | N-body dynamics - applications of the virial theorem |

- | Mar 08 | MIDTERM (in class) |

GAS PHYSICS (notes) | ||

#13 | Mar 10 | Pressure and the concept of hydrostatic equilibrium |

- | Mar 15 | SPRING BREACK |

- | Mar 17 | SPRING BREACK |

#14 | Mar 22 | Atmospheres in an external gravitational field |

#15 | Mar 24 | Self-gravitating atmospheres |

#16 | Mar 29 | Introduction to thermodynamics and statistical mechanics |

#17 | Mar 31 | Statistical mechanics of ideal gas |

#18 | Apr 05 | Radiation gases |

#19 | Apr 07 | Radiation gases (cont) and applications to Cosmology |

#20 | Apr 12 | Brief introduction to hydrodynamics |

QUANTUM PHYSICS (notes) | ||

#21 | Apr 14 | The Bohr model of the atom |

#22 | Apr 19 | Particle wave duality and particle in a box |

#23 | Apr 21 | Fermions and bosons; Fermi-Dirac and Bose-Einstein statistics |

#24 | Apr 26 | Degeneracy pressure and while dwarf |

#25 | Apr 28 | Type-1a supernovae and neutron stars |

#26 | May 03 | Schrodinger’s approach to Quantum Mechanics |

#27 | May 05 | The structure of the hydrogen atom |

#28 | May 10 | Review |

- | May 12 | Final exam (in class, Thursday 8:00am-10:00am) |

#### Textbooks

- There are no required textbooks
- Texts Recommended for this course are:
- Astrophysics for Physicists, by Arnab Rai Choudhuri,

(Cambridge University Press, 2010) ISBN-13: 978-0521815536 - Astrophysics in a Nutshell, by Dan Maoz,

(Princeton University Press, 2007) ISBN-13: 978-0691125848 - Class participation 10%
- Homework 30%
- Midterm exam 25%
- Final exam 35%
- A 100% - 90%
- B 89.9% - 80%
- C 79.9% - 70%
- D 69.9% - 60%
- F below 60%
- Problem related to perturbation theory (Bungee Cord) Note: we skipped perturbation theory in class, hence this topic will NOT be on the Midterm or Final

#### Course Grading

#### Homework

Homework will be assigned every week or every other week. Their due dates will be announced at the time they are assigned. On the due date the students will be expected to turn in their homework in class. The homework turned in will be graded and returned to the students. I will provide solutions and discuss them in class.

*No homework assigned yet.*

#### Wiki pages related to class's discussions

Class #1 | |

Class #2 | |

Discussion Section #7 | |

Class #8 | |

Class #9 | |

Class #24 and #25 |