Abell 370: Galaxy Cluster Gravitational Lens

Explanation: What are those strange arcs? While imaging the cluster of galaxies Abell 370, astronomers noticed an unusual arc. The arc wasn't understood right away -- not until better images showed that the arc was a previously unseen type of astrophysical artifact of a gravitational lens , where the lens was the center of an entire cluster of galaxies . Today, we know that this arc , the brightest arc in the cluster, actually consists of two distorted images of a fairly normal galaxy that happens to lie far in the distance. Abell 370's gravity caused the background galaxies' light -- and others -- to spread out and come to the observer along multiple paths , not unlike a distant light appears through the stem of a wine glass . Almost all of the yellow images featured here are galaxies in the Abell 370 cluster. An astute eye can pick up many strange arcs and distorted arclets , however, that are actually gravitationally lensed images of distant normal galaxies . Studying Abell 370 and its images gives astronomers a unique window into the distribution of normal and dark matter in galaxy clusters and the universe.