The absorption and emission spectra of benzo[g,h,i]perylene, a six ring polycyclic aromatic hydrocarbon molecule (C22H12), embedded in a rare gas matrix are reported. Time dependent emission shows that this molecule exhibits sharp phosphorescence in the red. Supporting theoretical calculations using the recently developed time-dependent density-functional response theory formalism (TD-DFRT) allow a tentative assignment for the observed transitions. The astrochemical significance of the results is briefly discussed.