Similar to Figs. 2, 5, B.1, and B.3, but for simulation E, which combines a 5 μG  magnetic field with a warm, low density medium. The bubble expands very quickly and becomes much larger than for the previous simulations. (Note the different scale: the left panel is 160 by 160 pc, the centre and right panels are 290 by 290 pc.) This allows the red supergiant and Wolf-Rayet shells to form unimpaired by the aspherical shape of the bubble.