WISE color–color diagram for WISE 3.4, 4.6, and 12 μm bands showing the different contamination cuts described in Section 3.2. All 14,814 sources extracted from the AllWISE catalog using a spatial search around CTB 102 are plotted. Sources categorized as shock objects, star-forming galaxies, and PAH emission are found within the boundaries of the black lines on the plot. Source color refers to the WISE 4.6 μm band magnitude.