(lambda) * T  = 0.0029 m K  (Wien's displacement law for thermal radiation)

  F = (sigma) * T^4           (Stefan-Boltzmann law for thermal flux)

For any heat source with temperature T, Wien's displacement law gives
the wavelength where the peak of its thermal radiation (also called "black 
body radiation") is emitted.  The flux of thermal radiation at the surface
of that heat source is given by the Stefan-Boltzmann law, where sigma is
a constant, 5.67 * 10^(-5) erg cm^(-2) deg^(-4) s^(-1).  What's noteworthy
is that the surface flux is proportional to the fourth power of the source
temperature; so a small change in temperature means a big change in flux.