Newly discovered galaxy cluster is by far the most ancient ever detected

Newly discovered galaxy cluste...
Composite image of the galaxy cluster CL J1001+0220
Composite image of the galaxy cluster CL J1001+0220
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Composite image of the galaxy cluster CL J1001+0220
Composite image of the galaxy cluster CL J1001+0220

Astronomers have detected themost distant galaxy cluster ever discovered lurking some 11.1 billion light-years away from Earth. Named CLJ1001+0220 (CL J1001), the new find indicates that galaxy clusters were formed around 700million years earlier than previously thought.

Galaxy clusters are thought to be thelargest structures in the universe bound together by the force ofgravity. The clusters can be comprised of anything from a handful, tohundreds of thousands of galaxies, and have been observed to varygreatly in terms of characteristics and galaxy distributions.

Priorto the new discovery, which was made using a host of ground and spacebased telescopes including Hubble, Chandra, and the ESO's Very Large Telescope,only loose protoclusters hadbeen found so far away.

Astronomyis like cosmic archaeology, in that we never observe a heavenlybody as it actually exists in the present day. Instead, we see it asit appeared when the light left its source. In the case of CLJ1001, we are seeingthe galaxy cluster as it was roughly 11.1 billion years ago.

Theteam behind the discovery believe that the light from CL J1001 leftits source soon after it made the transition from a loose gatheringof galaxies to a fully formed cluster, with a core consisting of 11massive elliptical galaxies. This stage of evolution has never beenseen before, and so could prove instrumental in updating modelsregarding the early evolutionary paths taken by galaxy clusters.

Ananalysis of the data showed that nine of the galaxies forming thecore of CL J1001's were undergoing an impressive bout of starformation, with the equivalent of 3,400 Suns being created each year.

"This galaxy cluster isn't just remarkable for its distance, it's also going through an amazing growth spurt unlike any we've ever seen," says Tao Wang of the French Alternative Energies and Atomic Energy Commission (CEA) who led the study.

After comparing their data with advanced computer simulationsdesigned to model the formation of galaxy clusters, the teamdiscovered that CL J1001 was carrying a surprising amount of mass inthe form of stars contained within the core galaxies.

Thiscould suggest that current models are wrong regarding the rate ofstar birth in newly formed galaxy clusters, or that CL J1001represents a rare form of cluster seldom seen, and therefore notaccounted for in present theories.

Thelevels of star-birth could indicate that elliptical galaxies thatform the cores of clusters experience bouts of star formation thatare more intense, but also significantly more short-lived than thoseundertaken by their cousins existing outside of a cluster. Theresults also cast doubt on the prevailing theory that star birth ingalaxies forming the core of a cluster takes place before the galaxyjoins with the larger structure.

Movingforward, astronomers will attempt to discover further examples ofclusters with characteristics similar to CL J1001, which will helpdetermine whether these traits were common in the early universe, orsome kind of cosmic fluke.

A paper describing the results is published in The Astrophysical Journal.


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