... Credit: W.N. Colley and E. Turner ( Princeton University ), J.A. Tyson ( AT Bell Labs , Lucent Technologies ), Hubble Space Telescope , and NASA Explanation: What are those strange blue objects? Many are images of a single, unusual, beaded, blue, ring-like galaxy which just happens to line-up behind a giant cluster of galaxies. Cluster galaxies here appear yellow and -- together with the cluster's dark matter -- act as a gravitational lens . ... Giant Cluster Bends, Breaks Images . ...