Texas A&M University scientists who led the study said the group of approximately 60 galaxies is nearly 10 billion years old, born just 4 billion years after the Big Bang.
But Assistant Professor Casey Papovich said the amazing part of the discovery is neither the size nor age of the cluster, but rather its surprisingly modern appearance -- a huge, red collection of galaxies previously thought typical of only present-day galaxies.
"It's like we dug an archaeological site in Rome and found pieces of modern Rome amongst the ruins," Papovich said.
He said the newly discovered cluster has enormous red galaxies at its center containing nearly 10 times as many stars as the Milky Way. He said before now, such a finding would have been considered highly unlikely.
"The predictions are that these things should be very rare when the universe was 4 billion years old, and yet, we found them," Papovich said.
The research that included astronomers from NASA's Jet Propulsion Laboratory and the Carnegie Observatories is to be published in the Astrophysical Journal.