= Geometrical thickness of a white-dwarf radiative envelope
{title2=$s/R=q/(1+q),\quad q=17\mathcal RT_cR/(4GM)$}
Integrating the <hydrostatic pressure support equation> with the <radiative-zero white-dwarf envelope> law yields $T=4GM(1/r-1/R)/(17\mathcal R)$. Matching $T=T_c$ at $r_b$ gives $s=R-r_b$ as displayed. A strongly degenerate bulk core has thermal energy small compared with its <Fermi energy>, making $q\ll1$ and hence $s\ll R$. The inequality $T_c\gg T_{\rm eff}$ alone does not establish geometrical thinness.
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