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.
