Curious about why the ring was in the cluster and how it had formed, Jee found previous research that suggested the cluster had collided with another cluster 1 to 2 billion years ago. The research, published in 2002 by Oliver Czoske of the Argelander-Institute for Astronomy at the University of Bonn, was based on
spectroscopic observations of the cluster's three-dimensional structure. The study revealed two distinct groupings of galaxies clusters, indicating a collision between two clusters.
Astronomers have a head-on view of the collision because it occurred along Earth's line of sight. From this perspective, the dark-matter structure looks like a ring.