A Cluster and a Sea of Galaxies

A new wide-field image released today by ESO displays many thousands of distant galaxies, and more particularly a large group belonging to the massive galaxy cluster known as Abell 315. As crowded as it may appear, this assembly of galaxies is only the proverbial “tip of the iceberg”, as Abell 315 — like most galaxy clusters — is dominated by dark matter. The huge mass of this cluster deflects light from background galaxies, distorting their observed shapes slightly.