Another fun fact, polycyclic aromatic hydrocarbons (PAHs or "paws") are commonly observed in interstellar space and a substantial reservoir of carbon overall!

Another fun fact, polycyclic aromatic hydrocarbons (PAHs or "paws") are commonly observed in interstellar space and a substantial reservoir of carbon overall! The 3.6 micron band from the IRAC camera on the Spitzer space telescope has a strong PAH flourescence feature in the band (absorbs UV, emits vibrational mode IR). The 3.6 micron wavelength is commonly colored green in composites, so if you see lots of green nebulosity in images from Spitzer, those are likely mainly PAHS.