brightness temperature

A measure of the amount of radiation being emitted from a source. It is defined as the temperature a black body replacing the source would need to be at in order to produce the level of radiation actually observed. Brightness temperature is frequently used by radio astronomers as a measure of the intensity of radiation being received. It is a useful concept, since it indicates whether the source is emitting thermal radiation, in which case the source's brightness temperature will be measured in hundreds or thousands of degrees, or synchrotron radiation, when the brightness temperature will be billions of degrees.