The ring-like structure is evident in the blue map of the cluster's dark matter distribution. The map is superimposed on a Hubble image of the cluster. The ring is one of the strongest pieces of evidence to date for the existence of dark matter, an unknown substance that pervades the universe.

Astronomers suggest that the dark-matter ring was produced from a collision between two gigantic clusters.

Dark matter makes up the bulk of the universe's material and is believed to make up the underlying structure of the cosmos.

The Hubble observations were taken in November 2004 by the Advanced Camera for Surveys. Thanks its exquisite resolution, astronomers saw the detailed cobweb tracery of gravitational lensing in the cluster.

Credits: NASA, ESA, M. Jee and H. Ford (Johns Hopkins University)

The image displays faint faraway background galaxies that had their light bent by the cluster's strong gravitational field. By mapping the distorted light and using it to deduce how dark matter is distributed in the cluster, astronomers spotted the ring of dark matter.

One of the background galaxies is located about two times further away than the yellow cluster galaxies in the foreground, and has been multiple-imaged into five separate arc-shaped components, seen in blue.

Credits: NASA, ESA, M. Jee and H. Ford (Johns Hopkins University)

The image is a colour composite from Digitised Sky Survey 2 (DSS2) images. The field of view is 3.0 degrees. The cluster of galaxies is in the centre of the image.

Credits: Davide De Martin (ESA/Hubble), the ESA/ESO/NASA Photoshop FITS Liberator & Digitised Sky Survey 2