An Etymological Dictionary of Astronomy and Astrophysics

Thermal emission in infrared from interstellar → dust grains
receiving photons. Dust grains absorb ultraviolet and visible light emitted by nearby stars and re-radiate in the infrared wavelengths. Since the infrared light is of lower energy than the ultraviolet/visible light, the difference goes into heating the dust grain. Typical temperatures for interstellar grains are tens of degrees Kelvin.

See also: → dust; → emission.