In 1990, NASA’s Cosmic Background Explorer (COBE) satellite found that light from the CMB had the telltale spectrum of a system in equilibrium, known as a blackbody—exactly what was expected ...

However, the degree of narrowing was limited to about half of the blackbody spectrum, and it is important for a number of applications to realize an even narrower emission bandwidth while also ...

and interaction of photons and electrons leads inevitably to an equilibrium (blackbody) spectrum. The shape of the equilibrium spectrum is preserved during the subsequent expansion and cooling ...

The shape of the spectrum of this kind of radiation has a special form known as blackbody radiation. When it was emitted the temperature of the Universe was almost 3,000 degrees Centigrade.