In the galaxy called M31 or Andromeda two groups of stars have been found that appear to be the result of an intergalactic shock. The Hubble Space Telescope has shown in the center of the galaxy two nuclei of stars.
These two cores are located at five light years and knowing that the diameter of the galaxy is about 160,000 light years, the distance is small. The darkest area is in the very center of the Andromeda galaxy and the brightest area can be the footprint of another galaxy “food” by Andromeda.