PHYS 321: Stellar AstrophysicsUniversity of British Columbia, Okanagan Campus

Academic Year 2011/2012, Winter Term 2 (a.k.a. Spring)Tuesday, Thursday 12:30 - 2:30 p.m.

Current Course Schedule: http://goo.gl/ifQNdProf. Erik Rosolowskyemail: erik.rosolowsky@ubc.ca (if you need to reach me for ANY reason, this is the place to start)Calendar: http://goo.gl/PnfqnOffice: ASC 354Office Phone: (250) 807-9623Office Hours: Officially Wednesdays 9 a.m. - 11 a.m. Also (and especially), by appointment! You can use the calendar link above to find a time that’s free for me and works better for you. Then, send me an email and I’ll block the time for you. Course Website: http://www.vista.ubc.ca/ Calendar Description -- Stellar structure and evolution. Hydrostatics, radiative transfer, fusion, equations of state. Main sequence stellar models. Low and high mass stellar post main sequence evolution. Stellar remnants. [3-0-0]Prerequisite: All of PHYS 200, PHYS 216.

Course Description -- Astrophysics concerns the applications of physics to the Universe as a whole. Since nearly all of the Universe is inaccessible for direct physical experiment, astrophysics is a dialogue between physical reasoning and observations. This course will present an introduction to astrophysics in two parts. First, we will explore the physics behind stars and stellar evolution which represents the best-solved problem in astrophysics. The dominant physics in stellar evolution combines basic applications of gravitation and thermodynamics with flourishes of quantum mechanics and radiation theory. After discussing stellar structure and evolution, we will digress into the related, but far more active topics of star formation and stellar death. Since these phenomena are significantly less well-understood, the physics behind them is necessarily more cursory. We will be forced into the domain of modern astrophysics based around physical conjecture, estimation and evaluation of hypotheses with observations.

Course Objectives -- My goals in this course are to:• Demonstrate the interplay between the many branches of physics in establishing the modern

theory of stellar structure and evolution.• Develop your physical reasoning through estimation and critical evaluation of physical

scenarios. • Give you the opportunity to scientifically interact with your peers on topics that are new to you

and apply the physics you have learned to a variety of astrophysical problems. If there is anything that you think I can do to help meet my goals, please let me know. A more detailed explanation of your content objectives is given at the end of this document.

Physics 321 • Stellar Astrophysics • Prof. Rosolowsky • Course Outline • p. 1

© Dr. Erik Rosolowsky, 2011-2012, All Rights Reserved

Required Materials -- The textbook: Introduction to Modern Astrophysics (2nd edition) by Carroll and Ostlie (ISBN 9780805304022). The textbook is only somewhat required. We will have a broad range of reading materials, but this book will be the core of the readings. There are

Supplementary Materials -- The following texts are on two hour reserve in the library.1. Structure and Evolution of the Stars by Martin Schwarzschild (that’s the son of the black hole

guy: Karl Schwarzschild)2. Theory of Stellar Structure and Evolution (2nd edition) by Prialnik3. The Physics of Stars by Phillips4. The Observation and Analysis of Stellar Photospheres by Gray5. Principles of Stellar Evolution and Nucleosynthesis by Clayton6. Stellar Structure and Evolution by Kippenhahn and Wigert7. An Introduction to Stellar Astrophysics Volume I by Böhm-Vistense8. The required textbook9. The first half of the required textbook entitled An Introdcution to Modern Stellar

Astrophysics by Ostlie and CarrollReadings are assigned primarily from the main textbook but also from the reserve readings and from journals in the library holdings. An itemized syllabus is posted on Vista with direct links to the library resources. Note that journal article holdings can only be accessed from UBC computers or by using the UBC library VPN. We will discuss the setup to this in more detail during class.

Expectations of the Professor -- This is an upper-division physics course designed for students with an active interest and some experience in physics. In this document, I will try to outline my expectations and requirements for the course in sufficient detail that you will know what you should do to have success in the course. You may meet those expectations however you choose. This is a three-credit class meaning that you can expect to spend roughly nine hours of effort weekly in the course. Pre-requisites -- PHYS 200 and 216. You will need to have a basic command of mechanics and electromagnetism as well as thermal physics and quantum mechanics at the level typically taught in the first and second year of physics at UBC Okanagan. We will need to take that lovely elegant physics and do horrible things to it (i.e., wildly inaccurate approximations) that will make you cringe. If you have any questions about whether you are sufficiently prepared for the course, feel free to look at the first homework set or come to speak with me about what you have done so far.

Grading Policy -- You will be evaluated on the quality and accuracy of your written work and oral presentations of course material. There is no enforced curve, but you will be held to a content standard. To receive high marks in the class, you should meet the vast majority of the content goals presented below. You will have several opportunities to present your work for evaluation and they will be weighted as follows.

Physics 321 • Stellar Astrophysics • Prof. Rosolowsky • Course Outline • p. 2

© Dr. Erik Rosolowsky, 2011-2012, All Rights Reserved

Component Weight

Reading Quizzes 15%

Homework (10) 30%

Quizzes (6) 25%

Final Exam 30%

Grading will be on the UBC standard scale. The main goal of the numerous assignments is to provide you with a constant and predictable level of work with many opportunities to demonstrate your skill level. The different components of the course will provide you with ample opportunities to demonstrate how you are meeting the course objectives.• Reading Quizzes -- Before every class in which reading is assigned, there will be a short

reading quiz covering the assigned reading. The quizzes serve a two-fold role. First, the ensure that you are are doing the reading before class in order to success. They will also solicit specific feedback for the class that I will use to shape lectures and address questions for class. Because of their incentivizing nature, reading quizzes cannot be completed after they are due. However, you will be excused for 10% of the quiz points automatically. Reading quizzes are due 1 hour before class.

• Homework -- Homework is an essential portion of the class and will consist of a few relatively complex problems aimed at developing your understanding of the material. You are strongly encouraged to collaborate with your classmates, but (this is important) you should prepare your submitted homework on your own. No direct copying or paraphrasing. The presentation for homework will not be marked for formal presentation (as I do in some other classes), but good style is essential for clarity and maximum partial credit. Acknowledgements are required on all submitted homework sets. Failure to include Acknowledgements will result in a penalty on the assignment of 20% of the maximum possible score (minimum score is 0). Homework will be assessed a penalty of up to 20% of the maximum possible score per day late.

• Quizzes -- Roughly every other week there will be a short (25 minute) quiz at the beginning of class. Quizzes cover material in the preceding two weeks of class and are designed to make sure you are keeping up with the material. You will have access to a formula sheet which is a two-sided sheet of paper with whatever you can hand write on it. You will be able to use one formula sheet through the term and just add to it, as you desire. The quizzes are given in lieu of midterms. Your grade on any quizzes for which you are absent will be replaced with your final exam score.

• Final Exam -- There will be a three hour written final examination. You will have access to your formula sheet and a calculator.

This may, initially, seem like a lot of work. Don’t Panic. Each assignment should be sufficiently small so that the course does not consume an excessive portion of your time. In general, I prefer to create many opportunities to provide you with feedback on your work so you know how well you are doing and can adjust your expectations and efforts accordingly.

Physics 321 • Stellar Astrophysics • Prof. Rosolowsky • Course Outline • p. 3

© Dr. Erik Rosolowsky, 2011-2012, All Rights Reserved

Finally, two important points that UBCO wishes all students to be aware of:ACADEMIC INTEGRITY

The academic enterprise is founded on honesty, civility, and integrity. As members of this enterprise, all students are expected to know, understand, and follow the codes of conduct regarding academic integrity. At the most basic level, this means submitting only original work done by you and acknowledging all sources of information or ideas and attributing them to others as required. This also means you should not cheat, copy, or mislead others about what is your work. Violations of academic integrity (i.e., misconduct) lead to the break down of the academic enterprise, and therefore serious consequences arise and harsh sanctions are imposed. For example, incidences of plagiarism or cheating may result in a mark of zero on the assignment or exam and more serious consequences may apply if the matter is referred to the President’s Advisory Committee on Student Discipline. Careful records are kept in order to monitor and prevent recurrences. A more detailed description of academic integrity, including the policies and procedures, may be found athttp://okanagan.students.ubc.ca/calendar/index.cfm?tree=3,54,111,0

On a more specific note, often Astronomy courses will require you to make observations of celestial phenomena. Obtaining observational data from another student or by accessing an electronic resource and then representing those data as your own observations are a violation of academic integrity. Academic dishonesty will be taken seriously. Please don’t put either of us in the position where we have to deal with this section of the syllabus.

DISABILITY ASSISTANCEIf you require disability-related accommodations to meet the course objectives, please contact the Coordinator of Disability Resources located in the Student Development and Advising area in the University Centre building. For more information about Disability Resources or academic accommodations, please visit the website at: http://web.ubc.ca/okanagan/students/disres/welcome.html

Physics 321 • Stellar Astrophysics • Prof. Rosolowsky • Course Outline • p. 4

© Dr. Erik Rosolowsky, 2011-2012, All Rights Reserved

Course GoalsPHYS 321: Stellar Astrophysics

This is a list of course goals that I would like you to achieve by the end of the course. By definition goals are obtainable and assessable. I have constructed the course to address each of these goals. If you feel like you have not met one of the course goals after we have covered the material in the course, feel free to ask around for advice from your peers or me.

By the end of Physics 321, students should be able to:1. Estimate the properties of the Sun (including mass, radius, luminosity, surface and core

temperatures, energy source, internal pressures, and lifetimes) from simple observations and minimal assumptions.

2. Convert between SI and the units typically used in astronomy (e.g. parsecs and solar masses) without a referring to a table.

3. Motivate the basic assumptions about the properties of stars.4. Construct theoretical and observational Hertzsprung-Russell diagrams and indicate the

approximate loci of the main sequence, white dwarfs, helium-burning sequence, zone of instability, protostars, red giants, and asymptotic giant branch stars.

5. Explain the observational methods used to establish the distance, mass, luminosity, radius, surface temperature and composition of other stars and be able to make simple calculations of these properties from observed data.

6. Be able to use the magnitude system with sufficient facility to quantitatively compare the relative brightness of objects.

7. Relate observational color bands (e.g. b, g) to spectra.8. Discuss why the magnitude system is archaic and actually kind of dumb.9. Construct and interpret schematic spectra of different astronomical objects including line and

continuum features.10. Derive the four basic equations of stellar structure and list the three constituative

relationships required to close the system.11. Give the boundary conditions for the four differential equations of stellar structure.12. Derive and apply approximate forms of the equations of stellar structure to estimate stellar

properties.13. Derive and apply the equation of radiative transfer in one-dimension and solve simple

problems in radiative transfer.14. Estimate the timescales for stellar evolution and apply the appropriate timescales to estimate

the duration of various physical events (e.g. how long would it take for the sun to collapse in the absence of hydrostatic support?).

15. Discuss different sources of pressure in stars (gas, radiation, degeneracy) and derive their behavior as a function of density, temperature and composition.

16. Discuss the physical conditions that lead to degeneracy pressure being significant for electrons and neutrons.

17. Derive and apply the equations of state for relativistic and non-relativistic electron degeneracy pressure.

18. Identify the physical conditions under which various forms of pressure will contribute.19. Derive the equation of radiative diffusion for stars and motivate the assumptions in the

derivation.

Physics 321 • Stellar Astrophysics • Prof. Rosolowsky • Course Outline • p. 5

© Dr. Erik Rosolowsky, 2011-2012, All Rights Reserved

20. List the various sources of opacity in stars, and describe how their contributions vary with composition, density and temperature.

21. Derive the conditions for convective instability in stars. Describe where convection is important in solar-type stars as well as more and less massive objects.

22. Discuss the influence of convection on the Sun.23. Explain the dominant physical processes in thermonuclear fusion.24. Outline the primary nucleosynthetic pathways by which stars produce energy including the

pp-chain, the CNO cycle and the triple-αC/ process.25. Describe how the rate of thermonuclear fusion varies with density and temperature for the

three pathways given above. Outline how this influences the structure and evolution of stars of different masses.

26. Explain why main sequence stars are stable.27. Discuss how a real stellar model is constructed and why that is not a goal for this class.28. Discuss the derivation and utility of polytropic density models.29. Use numerical techniques to construct a partial solar model. 30. Use scalings to estimate the mass-luminosity relationships for all stars.31. Describe what sets the upper and lower mass limits on stars.32. Estimate the main sequence lifetimes of a star with masses between 0.1 and 100 M☉. 33. Outline why stars become red giants after they deplete their core hydrogen.34. Discuss the internal structure and lifetime of stars on the horizontal branch.35. Compare the long term evolution of stars with masses between 0.1 and 100 M☉, with

particular attention to the physical mechanisms that divide the evolution by time and by mass.

36. Contrast the internal structure of main sequence stars, red giant stars, horizontal branch stars, asymptotic giant branch stars, and white dwarfs.

37. Describe the internal structure of a white dwarf.38. Explain why white dwarfs are close to isothermal.39. Derive cooling curves for white dwarfs.40. Describe neutron stars and black holes qualitatively and outline their basic properties.41. Discuss why pulsars “pulse” and evaluate how long a typical pulsar will take to spin down. 42. Quantitatively describe the initial conditions of star formation and outline some of the

physical impediments to creating a star. 43. Describe some current limitations in our understanding of star and planet formation and

avenues of current research.44. Define the initial mass function (IMF) and use the IMF to calculate average properties of

stellar populations (e.g., typical stellar mass).

Physics 321 • Stellar Astrophysics • Prof. Rosolowsky • Course Outline • p. 6

© Dr. Erik Rosolowsky, 2011-2012, All Rights Reserved

Initial Version of Course Schedule

This is the first draft of the course schedule. Always use the version linked off Vista for up-to-date reading assignments. You can access the link at http://goo.gl/ifQNd

Physics 321 • Stellar Astrophysics • Prof. Rosolowsky • Course Outline • p. 7

Date Topic Hwk Quiz Reading Assignment1/5/2012 Properties of the Sun

1/10/2012 Thermal Spectral, Magnitudes, Colours Carroll and Ostlie, Chapter 3 (all)

1/12/2012 Spectroscopy 1 Carroll and Ostlie, Chapter 5 (all)1/17/2012 Binary Stars 1 Carroll and Ostlie, Chapter 7 (all)1/19/2012 Boltzmann and Saha Carroll and Ostlie, 8.11/24/2012 Boltzmann and Saha 31/26/2012 The HR Diagram Carroll and Ostlie 8.21/31/2012 Radiation Fields 2 Carroll and Ostlie 9.12/2/2012 Radiative Transfer 4 Carroll and Ostlie, 9.2 (to page 244)

2/7/2012 Radiative Transfer Carroll and Ostlie, 9.2 (244 onward) and 9.3

2/9/2012 Hydrostatic Equilibrium, Mass Continuity 5 Carroll and Ostlie, 10.1, Schwarzschild,

Section 5 (p. 30-37)2/14/2012 Pressure 3 Carroll and Ostlie, 10.22/16/2012 Pressure Scwarzschild, Section 8 (p. 52-62)2/21/2012 Reading Break2/23/2012 Reading Break2/28/2012 Nuclear Fusion Carroll and Ostlie, 10.33/1/2012 Nuclear Fusion 6 Clayton 4-1 to 4-3, p. 283-3093/6/2012 Guest lecture 4

3/8/2012 Energy Transport 7 Carroll and Ostlie 10.4, Schwarzschild Section 7 (p. 44-52)

3/13/2012 Stellar Models Carroll and Ostlie 10.53/15/2012 Stellar Models 8 Carroll and Ostlie 11.13/20/2012 Star Formation 5 Carroll and Ostlie 12.2, 12.33/22/2012 Stellar Evolution (low mass) 9 Carroll and Ostlie 13.1, 13.23/27/2012 Stellar Evolution (high mass) Carroll and Ostlie Ch. 15 (all)3/29/2012 White Dwarfs 10 Carroll and Ostlie 16.1 - 16.44/3/2012 Neutron Stars 6 Carroll and Ostlie 16.5 - 16.74/5/2012 Summary

© Dr. Erik Rosolowsky, 2011-2012, All Rights Reserved