revealed that much of the light is polarized. When H alpha light is generated in clouds of hot ionized gas, it is unpolarized; it can only become polarized if it reflects off other material. According to one theory, the H alpha light in the filaments is actually reflected from the galaxyΓÇÖs bright center by a dust cloud through which the galaxy is moving. If this were so, the apparent velocity of the gas would simply be the motion of the galaxy as it moves through the dust. The origin of this intergalactic dust is another mystery. Perhaps it remains from an earlier interaction with the nearby galaxy M81.