August 19, 1998: A Space Telescope Science Institute astronomer has found the equivalent of the proverbial 900-pound gorilla in deep space. The "gorilla" is an extremely massive cluster of galaxies — the weight of several thousand of our Milky Ways — that existed when the universe was half its present age.
Paradoxically, the unexpected discovery of this ancient, heavyweight cluster is one of the strongest pieces of evidence yet that we live in a lightweight universe, one that doesn't have enough bulk to provide the gravity necessary to halt the expansion of space. Using X-ray satellites and ground-based telescopes to probe the remote regions of space, the Institute astronomer discovered MS1054-0321, a hefty galaxy cluster containing thousands of galaxies and many trillions of stars. The image on the left, taken by ground-based and X-ray observatories, shows the entire galaxy cluster surrounded by background and foreground galaxies. The image on the right, taken by Hubble's visible-light camera, provides a clearer view of the galaxies in the heart of the cluster.See the rest: