By the Planck Law, all heated objects emit a characteristic spectrum of electromagnetic radiation, and this spectrum is concentrated in higher wavelengths for cooler bodies. The adjacent table summarizes the blackbody temperatures necessary to give a peak for emitted radiation in various regions of the spectrum.
Blackbody radiation corresponds to radiation from bodies in thermal equilibrium. We will consider later the emission of non-thermal radiation, which doesn't follow a blackbody law. Such radiation is often produced by violent collisions rather than equilibrium heating. For example, in astrophysical environments radiation at the long and short wavelength ends of the above table is more likely to be produced by non-thermal processes.