Scientists have identified a cluster of galaxies further from earth than anything else that has ever been detected in the skies.
The cluster now known as JKCS041 is so far away that it has taken three quarters of the lifetime of the universe for its light to reach earth. Its distance, 10.2 billion light years away, beats the previous record by about a billion light years.
It is also of almost unimaginable size, containing hundreds of galaxies, though at such a distance it cannot be seen directly even through the most powerful telescope. Its existence has been deduced from data obtained with optical and infra red telescopes by Nasa's Chandra X-Ray Observatory.
JKCS041 was first detected in 2006 by the United Kingdom Infrared Telescope, in Hawaii. Originally, scientists were not sure that it was a true galaxy cluster, rather than one caught in the process of forming when the universe was still comparatively young.
It was also impossible to tell simply from telescope observations how far away it was.
Dr Ben Maughan, from the University of Bristol, carried out a long-term analysis of the Chandra X-ray data which has finally proved JKCS041 was a fully-formed cluster, less than four billion years after Big Bang.
At that distance, the cluster could add to what scientists know about the origin of the universe. Ten billion years ago is reckoned to be right at the beginning of the epoch when star clusters, the largest gravitationally-bound objects in the universe, first started to form. Studying its composition, mass and temperature should therefore reveal something about how the universe was formed.
The search is on for other galaxies at extreme distances. Before JKCS041, the most distant one known to science was XMMXCS J2215.9-1738, discovered in 2006 by the European Space Agency's X-ray satellite observatory, XMM-Newton. It was 9.2 billion light years away, beating the previous record by 0.1 billion light years.
Dr Maughan said: "This discovery is exciting because it is like finding a Tyrannosaurus Rex fossil that is much older than any other known.
"One fossil might just fit in with our understanding of dinosaurs, but if you found many more you would have to start rethinking how dinosaurs evolved. The same is true for galaxy clusters and our understanding of cosmology."
Stefano Andreon of the National Institute for Astrophysics (INAF) in Milan, Italy, said: "This object is close to the distance limit expected for a galaxy cluster. We don't think gravity can work fast enough to make galaxy clusters much earlier.
"What's exciting about this discovery is the astrophysics that can be done with detailed follow-up studies."
The discovery is another coup for the Chandra observatory, which has just passed its tenth anniversary. It was launched into orbit aboard a space shuttle in July 1999, ushering in what scientists say has been an unprecedented decade for discovering the high energy universe. Chandra has an unrivalled capacity to create high resolution X ray images, which have advanced the study of phenomena as diverse as comets, black holes, dark matter and dark energy.