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Gavitational Lensing by Galaxy Cluster CL 0024+17

Many of the bright-blue images are of a single, unusual, beaded, blue, ring-like galaxy which just happens to line-up behind a giant cluster of galaxies. Cluster galaxies here typically appear yellow and—together with the cluster's dark matter—act as a gravitational lens. A gravitational lens can create several images of background galaxies, analogous to the many points of light one would see while looking through a wine glass at a distant street light. The distinctive shape of this background galaxy—which is probably just forming—has allowed astronomers to deduce that it has separate images at 4, 10, 11, and 12 o'clock, from the center of the cluster. A blue smudge near the cluster center is likely another image of the same background galaxy. In all, a recent analysis postulated that at least 33 images of 11 separate background galaxies are discernable. This image of galaxy cluster CL0024+17 from the Hubble Space Telescope was taken in November 2004.

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