A galaxy is bound by laws of nature.
 The speed in which a galaxy rotates is thought to correlate with the flatness of the disc as some spiral galaxies have thick bulges, while others are thin and dense
 These structures are thought to develop when a larger galaxy absorbs a smaller companion galaxythat as the two galaxy centers approach, they start to oscillate around a center point, and the oscillation creates gravitational ripples forming the shells of stars, similar to ripples spreading on water

