The emission can be from black-body radiation or any other radiative mechanism. Since all materials emit black-body radiation (unless they are totally reflective or at absolute zero), this source for radiation pressure is ubiquitous but usually tiny. However, because black-body radiation increases rapidly with temperature (as the fourth power of temperature, given by the Stefan–Boltzmann law), radiation pressure due to the temperature of a very hot object (or due to incoming black-body radiation from similarly hot surroundings) can become significant. This is important in stellar interiors.
the emission can be from black-body radiation or any other radiative mechanism since all materials emit black-body radiation (unless they are totally reflective or at absolute zero) this source for radiation pressure is ubiquitous but usually tiny however because black-body radiation increases rapidly with temperature (as the fourth power of temperature given by the stefan–boltzmann law) radiation pressure due to the temperature of a very hot object (or due to incoming black-body radiation from similarly hot surroundings) can become significant this is important in stellar interiors