Ay 101
Physics of Stars
(Fall Term 2013)

Left: by Mark A. Hicks [licensed from the Clip Art Gallery on DiscoverySchool.com ]
Right: Omega Cen [from STScI]

Class Logistics

Professor: Lynne Hillenbrand (lah@astro)
Graduate Teaching Assistant: Katie Kaufman (kkaufman@astro)

Purpose: This is the advanced undergraduate "stars" class at Caltech. Our other junior/senior level course is "ism" or insterstellar medium. Armed with these two courses plus your physics background, you are equipped for our graduate classes.

Lectures: MWF 11am -12n
On Mondays and Wednesdays will meet in Cahill 219 while on Fridays class will be held in 273 (along the back hallway of the building towards the eastern side).

Problem Sets: To develop your understanding of course material, roughly weekly you will be asked to do analytic work and/or plot and analyze stellar structure / atmosphere / evolution data using your favorite coding language.

Exams: The mid-term assessment will be an evaluation of conceptual understanding rather than problem solving ability. The final exam will be open note, closed book, and held during finals period. It will test both problem solving and conceptual understanding.


The material in this course naturally divides itself into three main topics: stellar interiors, stellar atmospheres, and stellar evolution. We will cover them in a logical sequence, incorporating a range of physics areas (nuclear, atomic/molecular, thermal, radiative transfer) in our discussions of the physics of stars.

Problem sets are a critical means of learning the material, not just "busy work." Collaboration on problem sets is permitted in the conceptual phase of completing an assigment, though students are expected to work out the final solutions themselves. Several of the problem sets will require use of computers for calculations and plotting of results. Exams are not collaborative but handwritten notes such as class notes may be permitted.

Grading will be based on the weekly assignments (~55%), the mid-term exam (~15%), and the final exam (~30%).

If you have either constructive feedback or complaints about this course, please come see me. You may also use the (anonymous if you like) feedback form to provide input.


Ay 101 syllabus and reading assignments

Beyond your course reading/studying and class attendance, a quick (daily) visit to the Astronomy Picture of the Day might broaden your astronomical horizons.



It is recommended that you review the relevant chapters in Carroll & Ostlie (Ay20 text) as a refresher on the basics. Specifically, the chapters on Stellar Atmospheres, The Interiors of Stars, and The Sun are useful review as are the chapters covering star formation and stellar evolution. We will build upon and expand on this simple version of the material in the Ay 101 course.

The recommended text is appropriate for an upper level undergraduate course. Please acquire a copy of:

  • LeBlanc, An Introduction to Stellar Astrophysics, 2010
    with a small set of errata available; i found that my copy printed in 2011, September had all of these corrections accounted for.

    There is an e-book version available through the Caltech library that can be read by one student at a time.

    If you are looking for supplemental material, there are many many books on stellar physics, some of them even good ones. See the list below. A few at about the right level for this course are the Bohm-Vitense series, Prialnik, and also Philipps due to their emphasis on explanations of the physical phenomena; but they don't quite reach the needed depth and/or breadth for use as Ay101 course texts. Graduate level texts are those by Hansen/Kawaler/Trimble, Collins, Gray, or Rutten, some of which we have actually used in this course in past years.

  • Bohm-Vitense, Stellar Astrophysics Vol. 2: Stellar Atmospheres, 1989
  • Bohm-Vitense, Stellar Astrophysics Vol. 3: Stellar Structure and Evolution, 1989
  • Prialnik, An Introduction to the Theory of Stellar Structure and Evolution, 2000
  • Phillips, The Physics of Stars, 1999
  • Bowers & Deeming, Astrophysics Vol. 1: Stars, 1984
  • Collins, Fundamentals of Stellar Astrophysics, 1989
  • Hansen, Kawaler, & Trimble, Stellar Interiors, 2004 (2nd edition)
  • Rutten, Radiative Transfer in Stellar Atmospheres, 2003
  • Gray, The Observation and Analysis of Stellar Photospheres, 2005 (3rd edition)

    The above are on reserve for this course. The location in the past has been the astrophysics library though for this year it may be that all Caltech course reserves will be in SFL.

    On-Line (note that these are arranged from less to more sophisticated user experience)

  • X, Y, Z Calculator from detailed element abundances
  • Post-Main Sequence HR Diagram Simulator
  • Hydrogen Fusion Simulator
  • Helium Fusion Simulator
  • Polytropes applet
  • Main Sequence Interiors Applet Applet
  • Stellar Interiors via the "Starcode" Model
  • "EZ" Stellar Evolution input/output details and movies
  • MESA - A high level code/interface covering everything we need to know, but somewhat complex to install!

    Class Slides

  • part 1 -- review/overview and basic physics
  • part 2 -- star formation
  • part 3_1 -- stellar atmospheres - first set
  • part 3_2 -- stellar atmospheres - second set
  • part 4 -- stellar interiors
  • part 5 -- stellar nucleosynthesis and evolution

    Problem Sets

    Please please please get your sets in on time. It is easiest on everyone (the professor, the TA, and - especially - your fellow students) if all homeworks are turned in by the due date/time so that they can be graded together and turned back to you with solutions in a timely manner.

    Please write next to your name on submitted work how long it took *you* to do the set.

  • ps1 due 8 October

  • ps2 due 15 October

  • ps3 due 22 October

  • ps4 due 29 October

  • ps5 due 6 November and needed text file falc.dat

  • "ps6" due ASAP - this is the midterm review that you are to conduct on your own, i.e. there is no "test"

  • ps7 due 19 November -- note there is an error in the equation associated with problem #2, which needs a negative sign in the rightmost portion.

  • ps8 due 26 November

  • ps9 due 10 December

    Left: Experimental convection moving top-to-bottom [from http://www.solarviews.com/eng/edu/convect.htm]
    Right: Oberved convection moving bottom-to-top [viewed from my office during the 2009 Station Fire]

    Last Revised: 13 September 2013 by LAH