Also found in: Acronyms, Wikipedia.
brightness temperatureIn radio astronomy, a source of surface brightness (i.e., flux density per unit solid angle) B has a brightness temperature of T B = B λ2/(2k ), where λ is the observing wavelength and k is the Boltzmann constant. If the source of that radiation is a black body, and the observing wavelength sufficiently long, the brightness temperature will equal the temperature of the black body. In the case of an interstellar cloud, it may equal the physical temperature of the cloud if the radiation is by thermal emission and the cloud is optically thick (see optical depth). If the cloud is optically thin, the brightness temperature is reduced.
brightness temperature[′brīt·nəs ‚tem·prə·chər]