DWB-111, the Propeller Nebula, is an emission nebula in the
constellation Cygnus. Astronomers seem to have more questions than
answers, regarding this nebula. The origin of the peculiar structure
is still completely unknown. The nebula's distance and source of
excitation are also undetermined. DWB-111 mass is believed to be
quite low, probably less than 50 solar masses. Obscuring dust is
closely associated with the nebula, but seems to occur mostly in
front of it.