The Galactic H ii region RCW 120 in the mid-IR from Spitzer 8 μm (left), and 24 μm (right). The white circle shows the location of the ionizing star CD −38°11 636 that drives the nebula’s expansion. The coordinates are in units of RA (J2000) and Dec (J2000) on the horizontal and vertical scales, respectively. The outer ring, clearest at 8 μm, is the H ii region boundary and the inner arc seen at 24 μm may show the edge of the stellar wind bubble.