Astronomers discover youngest-ever galaxy cluster

BBC : Most of the galaxies in the universe are found in groups or clusters that assembled, according to current thinking, after the galaxies themselves formed. Caltech’s Peter Capak and his collaborators announced today that they had found the youngest-ever cluster. Dubbed Cosmos-Aztec3, the cluster is so far away that the light reaching Earth today was emitted when the cluster was just 1 billion years old. Consistent with the idea that clusters grow through mergers, Cosmos-Aztek3 is smaller than older, closer clusters.