Using a combination of space and ground-based telescopes, astronomers have spotted the most distant, and hence earliest, cluster of galaxies ever seen. The cluster dates to a time when the Universe was just a quarter of its current age of 13.7 billion years, yet, surprisingly, it looks more like nearby, modern galaxy clusters than the star-forming proto-clusters found so far at the same epoch.

Raphael Gobat of the Laboratory for Astrophysics Instrumentation and Modelling in Gif-sur-Yvette, France, and his colleagues say that more observations should show whether the cluster is a fluke, or whether theories of cluster formation need to be revised.

Astron. Astrophys. 526, A133 (2011)