Emission-pressure degeneracy of a brightness temperature
= Emission-pressure degeneracy of a brightness temperature
A <brightness temperature> equates a measured intensity with a <Planck function>; it does not determine its contribution pressure. In <hydrostatic equilibrium>, $\tau_\lambda(P)=\int_0^P\kappa_\lambda\,dP'/g$. Estimating $P\sim g/\kappa_\lambda$ therefore needs gravity and <opacity>, as well as a model of the contribution function. Different pressures can produce the same band brightness.