Log of gas density (left-hand panels) and gas temperature (right-hand panels) for a 3D simulation of an expanding WR nebula. In both panels, a slice through the x–z plane at y = 0 is shown, with the star at the origin. The axes show the domain in parsecs. The first row shows the CSM 10 000 yr after the RSG→WR transition; the second row after 20 000 yr; the third after 30 000 yr.