Illusion and Evolution
What's happening to the galaxies of cluster Abell 2667? On the upper left, a galaxy appears to be breaking up into small pieces, while on the far right, another galaxy appears to be stretched like taffy in this image from the Hubble Telescope.
To start, most of the yellowish objects are galactic members of a massive cluster of galaxies known as Abell 2667. The distortion of the galaxy on the upper left is real. As the galaxy plows through the intercluster medium, gas is stripped out and condenses to form bright new knots of stars. This detailed image of ram pressure stripping helps astronomers understand why so many galaxies today have so little gas. The distortion of the galaxy on the far right, however, is an illusion. This nearly normal galaxy is actually far behind the massive galaxy cluster. Light from this galaxy is gravitationally lensed by Abell 2667, appearing much like a distant person would appear through a wine glass. Each distorted galaxy gives important clues about how galaxies and clusters of galaxies evolve.
Image Credit: NASA, ESA, Jean-Paul Kneib (Laboratoire d’Astrophysique de Marseille) et al.