WISE mid-IR view of the region surrounding the Orion OB association at 12 μm. The different sub-groups of the Orion OB association are overplotted for stars of spectral type B2 and earlier (Brown et al. 1994), where the oversized symbols represent σ Ori (diamond) and ϵ Ori (inverted triangle), respectively. The 12 μm emission reveal the edges of the Orion molecular clouds as they are being illuminated by the ionizing flux of members of the Orion OB association. Also shown are several prominent structures in the image: the L1630 molecular cloud, the emission nebula NGC  2024, and the Orion Nebular cloud (ONC). Of particular interest here is the bubble centered at (l,b) = (206.1, –17.5), which is the IR counterpart of the GS206-17+13 HI shell (Ehlerová & Palouš 2005) and encircles the members of Orion OB1b (dashed outline). Overplotted in solid lines are the space motions of the stars, tracing back the motion of the stars in the plane of the sky during 1 Myr. For σ Ori, this trajectory has been extended to 3 Myr, where the open diamond symbols mark 1 Myr, 2 Myr, and 3 Myr.