The radiation flux density of the starry sky far from cosmic bodies is about 2 μW / m2. How can the temperature

The radiation flux density of the starry sky far from cosmic bodies is about 2 μW / m2. How can the temperature of interstellar dust be estimated from this value?

Under conditions of thermodynamic equilibrium, all the energy received by the particle must be re-emitted. An estimate of the particle temperature can be made based on the Stefan – Boltzmann law. Assuming a speck of dust to be an absolutely black body, which is a good approximation, its temperature under these conditions will be 2.4 K.