Credit & Copyright: Tony Hallas Explanation: These are galaxies of theHerculesCluster, an archipelago ofisland universes a mere500 million light-years away.Also known asAbell 2151,this cluster is loaded with gas and dust rich,star-forming spiral galaxiesbut has relatively few elliptical galaxies,which lack gas and dust and the associated newborn stars.The colors inthis remarkablydeep composite imageclearly show the star forming galaxies with a blue tint andgalaxies with older stellar populations with a yellowish cast.The sharp picture spans about 3/4 degree across thecluster center, corresponding to over 6 million light-years at thecluster's estimated distance.In the cosmic vista many galaxies seem to becolliding ormergingwhile others seemdistorted - clear evidence thatcluster galaxiescommonly interact.In fact, the Hercules Cluster itself may be seen as the result ofongoing mergers of smaller galaxy clusters and is thought to besimilar to young galaxy clusters inthe much more distant,early Universe.
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