Most-distant known galaxy cluster discovered

In a breakthrough, astrophysicists have discovered the most-distant known galaxy cluster that would give them a unique opportunity to study old galaxies in detail and better understand their origins.

"Our observations make this galaxy cluster one of the best-studied structures from the early universe," said lead author Andrew Newman from Carnegie Mellon University.

Named JKCS 041, the unusually distant galaxy cluster was discovered using the Hubble Space Telescope.

It captured sharp images of the distant cluster and split the starlight from the galaxies into its constituent colours, a technique known as spectroscopy.

The team found 19 galaxies at precisely the same great distance of 9.9 billion light years, the tell-tale sign of an early galaxy cluster.

A previous study using the Chandra X-ray Observatory discovered X-ray emissions in the location of JKCS 041.

"These X-rays likely originate from hot gas in JKCS 041, which has been heated to a temperature of about 80 million degrees by the gravity of the massive cluster," said Stefano Andreon from the Osservatorio Astronomico di Brera (Brera Astronomical Observatory) in Milan, Italy.

Today the largest and oldest galaxies are found in clusters, but there is a mystery about when and why these giant galaxies stopped forming new stars and became dormant, or quiescent.

Peering back to a time when the galaxies in JKCS 041 were only one billion years old - or 10 percent of their present age - the team found that most had already entered their quiescent phase.

Once massive galaxies enter their quiescent phase, they continue expanding in overall size.

This is thought to occur as galaxies collide with one another and evolve into a new, larger galaxy, said the study published in the Astrophysical Journal.