Star Clusters Formed 460 Million Years After Big Bang Discovered By James Webb Telescope

Astronomers have discovered five young star clusters, potentially among the oldest ever, dating back to the Universe's infancy. These gravitationally-bound massive clusters could provide vital clues about the reionization era of the Universe, according to an international team led by Stockholm University, with collaborators from select European countries, the US, and Japan.

"This is the first discovery of star clusters in an infant galaxy less than 500 million years after the Big Bang," said a statement released by the European Space Agency (ESA) on Monday.

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The Cosmic Gems arc was initially discovered in NASA/ESA Hubble Space Telescope images obtained by the RELICS (Reionization Lensing Cluster Survey) programme of the lensing galaxy cluster SPT-CL J0615-5746, NASA said in a release. 

"These galaxies are thought to be a prime source of the intense radiation that reionised the early Universe," shared lead author Angela Adamo of Stockholm University and the Oskar Klein Centre in Sweden. "What is special about the Cosmic Gems arc is that thanks to gravitational lensing we can actually resolve the galaxy down to parsec scales!"

Astronomers can now see where stars formed and how they are distributed, in a similar way to how the Hubble Space Telescope is used to study local galaxies. Webb's view provides a unique opportunity to study star formation and the inner workings of infant galaxies at such an unprecedented distance.

"Webb's incredible sensitivity and angular resolution at near-infrared wavelengths, combined with gravitational lensing provided by the massive foreground galaxy cluster, enabled this discovery," explained Larry Bradley of the Space Telescope Science Institute and PI of the Webb observing programme that captured these data."No other telescope could have made this discovery."

"The surprise and astonishment was incredible when we opened the Webb images for the first time," added Adamo. "We saw a little chain of bright dots, mirrored from one side to the other - these cosmic gems are star clusters! Without Webb, we would not have known we were looking at star clusters in such a young galaxy!" 

In our galaxy, the Milky Way, there are many ancient globular clusters of stars bound by gravity that have survived for billions of years. These clusters are relics of intense star formation in the early Universe, but their exact origins and formation times are not well understood.

The detection of massive young star clusters in this arc has the potential to initiate a series of studies on the early stages of the star formation process and the subsequent development into globular clusters. This discovery is crucial, as it will enable scientists to better understand how and where infant galaxies were born.

"These galaxies are thought to be a prime source of the intense radiation that re-ionised the early Universe," said Angela Adamo, Stockholm University, and the lead author of the paper published in the journal Nature.

This discovery could also serve as direct evidence of proto-globular clusters forming in faint galaxies during the reionization phase of the Universe, reinforcing the understanding that galaxies played a key role in reionizing the Universe.