  Examination of equilibrium radiation in plasma media shows that the spectral
energy distribution of such radiation is different from the Planck equilibrium
radiation. Using the approach of quantum electrodynamics the general relation
for the spectral energy density of equilibrium radiation in a system of charged
particles is found. The obtained result takes into account the influence of
plasma on equilibrium radiation through the explicit transverse dielectric
permittivity which takes into account spatial and frequency dispersion, as well
as the finite collisional damping. For the limiting case of an infinitesimal
damping the result coincides with the known expression.
