of Stellar Structure
PETER P EGGLETON
Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, CA 94551-0808, USA
Abstract. For me, and for many astrophysicists of my generation, Chandrasekhar’s book An Introduction
to the Study of Stellar Structure was very important. I could not have done my PhD
(1962–1965) without it. Much more recently (1998) I realized that I could not have written my
lecture course on thermodynamics and statistical mechanics without much of it, particularly the first
chapter. I shall present anecdotal evidence that the influence of his discussion on the second law of
thermodynamics has been important not just for astrophysics but for a much wider range of physics.
Chandrasekhar’s discussion of polytropes was masterly. Even today polytropes play an important
role as an aid for understanding stellar structure. I believe that to the list of analytic solutions of the
polytrope only one more has to be added: a curious n = 5 model of Srivastava (1962).
Stellar structure is nowadays a very computationally intensive subject. I shall illustrate this with
a couple of topics from my experience with Djehuty, a supercomputer code for modelling stars in
3D. Nevertheless it remains true, I believe, that analytical mathematical entities like polytropes are
fundamental as aids for understanding what the computers churn out.
How close are we to seeing a book with the title ‘The LastWord on the Study of Stellar Structure’?
Not very, although much has been learned in 70 years. I shall discuss a few of the aspects of stellar
evolution that are problematic today.
I shall discuss a couple of aspects where I believe analysis of ‘piecewise polytropic’ structures
sheds light on the question ‘Why do stars become red giants?’
Keywords. S Chandrasekhar; stellar structure; thermodynamics.
PACS Nos 97.10.Cv; 64.70.qd; 67.30.ef