The Rosette Nebula, its molecular cloud Mon OB2, and their surrounding medium as seen by Planck at 353 GHz. The dotted lines give the approximate outer radii of the Rosette H ii region and the Mon Loop supernova remnant (described in Sect. 2). The northern Monoceros cloud Mon OB1 is above the Galactic plane; part of the dust ring of λ Ori is visible at the bottom right corner of the map; the northern end of Orion B is seen at (l,b) = (204°, −12°) (Dame et al. 2001).