Radiation of a neutral polarizable particle moving uniformly through a thermal radiation field

We discuss the properties of thermal electromagnetic radiation produced by a neutral polarizable nanoparticle moving with an arbitrary relativistic velocity in a heated vacuum background with a fixed temperature. We show that the particle in its own rest frame acquires the radiation temperature of a vacuum multiplied by a velocity-dependent factor, and then it emits thermal photons predominantly in a forward direction. The intensity of the radiation for a moving particle proves to be much higher than that for a particle at rest. For metal particles with high energy, the ratio of emitted and absorbed radiation power is proportional to the Lorentz factor squared.