At first glance, M64 seems to be a fairly normal spiral galaxy. As in the majority of galaxies, all of the stars in M64 are orbiting in the same direction, clockwise as seen in the Hubble image.
However, recent detailed studies have led to the remarkable discovery that the interstellar gas in the outer regions of M64 rotates in the opposite direction from the gas and stars in the inner regions. The inner region has a radius of only approximately 3,000 light-years, while the outer section extends another 40,000 light-years. This pattern is believed to trigger the creation of many new stars around the boundary separating the two regions.
A collision of two galaxies has left a merged star system with an unusual appearance as well as bizarre internal motions. Astronomers believe that the oppositely rotating gas arose when M64 absorbed a satellite galaxy that collided with it, perhaps more than one billion years ago. Active formation of new stars is occurring in the shear region where the oppositely rotating gases collide, are compressed, and contract.