PHAS 3135: The Physics of Stars

The exam is at 10:00 on 17/5/2012, in venue 'EXAMCSH',

The exam paper has the standard "Part A/Part B" structure. You will be expected to attempt all six questions from Part A, and any two of the four questions in Part B. The first three questions in Part A, and the first two questions in Part B, have been set by Dr Zane, and the remainder by Prof Howarth. Remaining comments relate to 'Part II' of the course, as taught by Ian Howarth (although some may also apply to Dr Zane's material).

[Note the distinction between 'Part I' and 'Part II' of the course, and 'Part A' and 'Part B' of the exam paper. Part A of the exam will contain three questions from Part I of the course, and three questions from Part II; Part B of the exam will contain two questions from Part I of the course, and two questions from Part II.]

Most of the material in Part II of the course (and much from Part I) is based on the previous course PHAS3134; the main difference in 2011/12 is that I was not able to spend as much time on qualitative descriptions of 'stellar evolution' as used to be the case (this topic taking up between a third and a half of PHAS3134, but only about 20 per cent of PHAS3135).

Old exam papers from PHAS3134 will therefore provide students with clear guidance on expected 'Part II' content for PHAS3135 papers. In particular, to ease the transition from 3134, Part II questions in the 2012 PHAS3135 exam paper will be familiar, in general terms, to anyone who has worked through old PHAS3134 papers. General questions on stellar evolution are fair game for the PHAS3135 exam, but if they're asked, they won't require answers as detailed as were expected for old PHAS3134 questions, for the reasons given above.

Another important difference is that 'standard' equations (e.g., hydrostatic equilibrium) were often given in PHAS3134 papers, along with values for physical and astrophysical constants; no such equations are provided this year (though [astro]physical constants will be, of course).

As a guide, here's a list of selected questions from old PHAS3134 papers that I'd say might reasonably be asked as 'Part II' questions this year (where number in brackets indicate questions that contain some material no longer examinable, or where my notes use different nomenclature/derivations – as in the case of convection & mixing-length theory, for example):

Several people have emailed me with concerns when attempting Q8 of the 2009 PHAS3134 paper.

The lecturer for 3134 used a different notation to that which I adopted when discussing convection (I don't think that I used the term 'superadiabatic', for example), and covered somewhat different aspects.

As far as 3135 is concerned, I'd expect students to be able to derive the condition for convection to occur (the Schwarzschild criterion), but I would ask for it using the notation delivered in the PHAS3135 course (and not the notation used in the 2009 paper).

We didn't cover the material in the second part of the question (worth 5 marks) – so it wouldn't be examined this year

For the 15-mark derivation, there are again differences in notation. Students wouldn't be asked to derive the convective flux in the form given in the 2009 paper; if it were to appear this year, I'd be working with eqtn 2.43 in my notes.

The last part of the question can be attempted by noting that
F [=F_conv] = L/4πR²
(since "all the energy transport is convective"). Use this to calculate F_conv, the convective flux; then substitute back into the big equation given in Q8 to get the superadiabatic temperature gradient, ∇-∇_ad.

3135 Lecture Notes (pdf, including supplementary PHAS2112 Notes). N.B.: these notes don't yet include 'stellar evolution' material.

Problem sheet II:1; and notes for answers

Problem sheet II:2; and notes for answers

This is the course proposal to DTC (pdf)