$\gamma$-Radiation of thermalized Quark-Gluon-Plasma

Long time ago, photon production was proposed as a probe and a thermometer for Quark-Gluon Plasma (QGP). However, only recently has the complete ${\alpha }_s$ order photon spectrum been obtained. In this paper we give a brief review of the problematic as well as discuss the $\mathcal{O}({\alpha }_s)$ result.