Spinning dust emission is microwave emission from dust particles that carry a dipole electric 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 window on the location and constitution of dust, and they present a problem regarding the study of other microwave radiation such as the cosmic microwave background: to measure either, you have to figure out how to disentangle the signals.
The signal seen is from within the Milky Way. The dipole field stems from the fact that the particles have two portions that relative to each other are positive and negative. The movement of the localized charge produces the microwaves, producing a frequency corresponding to the rotation rate. The signal is polarized, giving clues to the rotation direction and alignment and the local magnetic field. Dust made of polycyclic aromatic hydrocarbons is considered a likely source and presumed in some models of the emission mechanism.