Joining forces with ground-based telescopes, NASA's Chandra and Spitzer space telescopes have uncovered the most distant galaxy cluster yet at 10.2 billion light years, beating the previous record holder by one billion light years.

Galaxy clusters are the largest gravitationally bound objects in the Universe and the new contender, JKCS041, puts theories on how structure evolved in the early Universe to the test. Forming at the boundary of when scientists believe galaxy clusters can assemble, JKCS041's vital statistics – composition, mass and temperature – will reveal more about how the Universe evolved.

“This object is close to the distance limit expected for a galaxy cluster,” says Stefano Andreon of the National Institute for Astrophysics (INAF) in Italy. “We don’t think gravity can work fast enough to make galaxy clusters much earlier.”

JKCS041 was first identified in 2006 by the United Kingdom Infrared Telescope (UKIRT), revealing component galaxies dominated by old red stars. It's record-breaking distance was determined from optical and infrared measurements by the UKIRT, the Canada-France-Hawaii Telescope in Hawaii, and NASA’s Spitzer Space Telescope. Chandra added the final piece of evidence – hot gas detected between the galaxies – proving that JKCS041 is indeed a true cluster, and not one that is still forming.

The observations also ruled out the possibility of the galaxies distributed along the same line of sight, and the extent and shape of the X-ray emission, combined with the lack of a central radio source, argue against the possibility that the X-ray emission is caused by scattering of cosmic microwave background light by particles emitting radio waves.

“This discovery is exciting because it is like finding a Tyrannosaurus Rex fossil that is much older than any other known,” says Ben Maughan from the UK's University of Bristol. “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.”

The hunt is now on for similar distant clusters. Previous record holder XMMXCS J2215.9-1738 was discovered by ESA's XMM-Newton space telescope in 2006 at 9.2 billion light years, but astronomers need more case studies to thoroughly test cosmological models, such as the nature and prevalence of dark matter and the destiny of our Universe.

The results of the research will appear in a forthcoming edition of the journal Astronomy & Astrophysics.