For 10 points, name this ideal radiator, named for its color.
A spectrum associated with these objects has a denominator proportional to the exponential of quantity H C over lambda T minus one. A relic of cosmological recombination has the form of one of these objects with a relevant value of two point seven K. The problem of its spectrum was solved by Max Planck, resolving the ultraviolet catastrophe, and the total power radiated by these objects is proportional to the fourth power of the temperature according to a law named for Stefan and Boltzmann. The emissivity of these objects is equal to one, so they absorb all incident radiation leading to their most distinctive feature. For 10 points, name this ideal radiator, named for its color.
A spectrum associated with these objects has a denominator proportional to the exponential of quantity H C over lambda T minus one.
{Blackbody} [prompt on "perfect absorber"]