A pre-main-sequence star of sits on the Hayashi track at

PHYSICS · Subjective · Fermi University Physics · Astrophysics & Cosmology · Stellar structure, energy generation and evolution · Stellar structure, energy generation and evolution

Stars from the Inside, Ch Stellar evolution: from the Hayashi track to the iron core, and the ages of clusters

Problem

A pre-main-sequence star of

1\,M_\odot

sits on the Hayashi track at

(T_{\rm eff}, L) = (4000\,\mathrm{K}, 3\,L_\odot)

. Two proposed states, one million years later, are: State A at

(3900\,\mathrm{K}, 0.5\,L_\odot)

, and State B at

(3500\,\mathrm{K}, 3\,L_\odot)

(the same luminosity as before, but cooler). Predict which of these two states, if either, is forbidden for a star in hydrostatic equilibrium, and explain the argument, based on the interior's structure, that rules it out.

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