Temperature vs. time for the cooling (red line) and heating (blue line) processes. In all the plots, the initial temperature for the heating process is 4000 K and the final temperature is 9000 K, while in the cooling process, the initial and final temperatures are 9000 K and 4000 K, respectively. Furthermore, from now on, in all the plots optically thin radiation has been considered as well as the same constant density value, ρ = 5 × 10^-11 kg m^-3.