Rayleigh–Jeans approximation in the infrared range of thermal radiation of stars

The paper provides a quantitative assessment of the effectiveness of the Rayleigh–Jeans approximation for the thermal radiation of stars in the infrared region of the spectrum. For a number of fixed temperatures, the relative deviations of the Rayleigh – Jeans spectral density from the Planck one at the edges of the NIR, MIR and FIR ranges are calculated. For the same ranges, the relative deviations of emissivities, luminosities and fluxes are also determined. The efficiency of the approximation for some stars is assessed as well.