A polar-ring galaxy is a relatively rare type of galaxy, with only around 100 examples known. The best known polar-ring galaxy is NGC 4650A. It is theorized that the structure of these galaxies result from the collision of two galaxies. The collision results in a structure composed of two rings of material rotating at an approximate right angle to each other.
It is theorized that the structure of these galaxies result from the collision of two galaxies. The collision results in a structure composed of two rings of material rotating at an approximate right angle to each other. It is important to understand that the collision happens so slow that over even a lifetime, the movement is almost imperceptible. Also important is that once what is left of the interacting galaxy has gone on after the collision, the remaining static galaxy does not simply stop moving. The stars in the galaxy will continue on their new paths until they are dispersed and it is no longer a galaxy. What one sees when they look at a polar-ring galaxy is a freeze-frame of a former galaxy spilling out around itself, its stars destined to disperse over many light-years.
