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Spinning dust emission is microwave emission from dust particles that carry a dipole electric field and are spinning. This mechanism is considered a source of some anomalous microwave emission (AME). Aside from interest in their own right, they provide a means of detecting the location and constitution of dust, and they present a problem regarding the study of other microwave radiation such as the cosmic microwave background (CMB): to measure either, you have to figure out how to disentangle the signals.
The observed signal is from within the Milky Way. The dipole field stems from the fact that the particles have two portions that are positive and negative relative to each other. The movement of the localized charges produce the microwaves, producing a frequency corresponding to the rotation rate (electric dipole radiation). The signal is polarized, giving clues regarding the rotation direction and alignment and regarding the local magnetic field. Dust made of polycyclic aromatic hydrocarbons (PAHs) is considered a likely source and is presumed in some models of the emission mechanism.