It was discovered by Penzias and Wilson and studied by COBE [CO-bee] and WMAP.  
Theoretical estimates of the temperature of this phenomenon were undertaken by Robert Herman and Robert Dicke, but Andrew McKellar was its first observer, having noted a typical bolometric temperature of the interstellar medium in his search for interstellar absorption lines. This phenomenon and galactic emission lines were observed by a polarizing Michelson interferometer called FIRAS. The "yin-yang" pattern in this phenomenon results from the sun's orbital motion. A primary source of its large-scale anisotropy is due to time-dependent density perturbations, which cause gravitational redshift, specifically the Integrated Sachs-Wolfe Effect, the angular scale of which suggests a flat universe. Its perceived source is called the surface of last scattering.  Inverse Compton Scattering of this phenomenon is also called the Sunyaev-Zel'dovich Effect. It was discovered by Penzias and Wilson and studied by COBE [CO-bee] and WMAP.  For 10 points, name this nearly uniform, 2.8-Kelvin radiation source.
Theoretical estimates of the temperature of this phenomenon were undertaken by Robert Herman and Robert Dicke, but Andrew McKellar was its first observer, having noted a typical bolometric temperature of the interstellar medium in his search for interstellar absorption lines.
Cosmic Microwave Background Radiation [or relic radiation]