The unique structure of M64, also known as the Black Eye Galaxy, is primarily attributed to a major collision involving two distinct types of progenitor systems. Astronomers hypothesize that the counter-rotating gas disk was formed when a smaller, gas-rich satellite galaxy was ingested by the larger, more massive lenticular galaxy.
In this merger scenario, the incoming satellite galaxy entered the main system on an orbit that was nearly opposite to the rotation of the host galaxy's existing stars. As the smaller galaxy was torn apart by tidal forces, its gas was deposited into a disk that rotates in the opposite direction to the stellar component of M64. This event explains why the gas moves one way while the majority of the stars move another way.
This specific type of interaction is a classic example of how galactic mergers can fundamentally alter the internal kinematics of a galaxy. Such collisions are essential processes in galactic evolution, often leading to new patterns of star formation and changing the physical characteristics of the involved galaxies over billions of years.
