Density dependence of the average neutrino opacity (13)for selected weak processes, comparing NN (thin blue lines) and NN^∗ (thick brown lines); see text for definitions. The corresponding conditions are shown in Fig. 4. Short vertical black lines at the top of graphs a)–c) mark the locations of the averaged neutrinospheres of last absorption labelled “abs.” (dash-dotted lines) and last elastic scattering labelled “scat.” (solid lines). The grey shaded region in between represents the scattering atmosphere.