Protogalaxy Cluster Found When the Cosmic Fog Was Starting to Clear, When the Universe Was Just 750 Million Years Old

Origin stories are a focus of many astronomical studies.  Planetary formation, solar system formation, and even galaxy formation have long been studied in order to understand how the universe came to be where it is today.  Now, a team of scientists from the Lyman Alpha Galaxies in the Epoch of Reionization (LAGER) consortium have found an extremely early “protogalaxy” that was formed approximately 750 million years after the big bang.  Studying it can provide insights into that early type of galaxy formation and everything that comes after.

750 million years ago was near the end of the period in the history of the universe called “reionization”.  During this epoch, which lasted approximately 370 million years, the first galaxies and large scale structures in the universe began forming.  The protocluster (a high density cluster of galaxies) that Jorge González-López, a postdoc member of the LAGER team, found was created around this epoch.  It is the furthest protocluster discovered so far. 

Image of an early protogalaxy found by ALMA.
ALMA image of 14 galaxies forming a protocluster known as SPT2349-56. These galaxies are in the process of merging and will eventually form the core of a truly massive galaxy cluster. Credit: ALMA (ESO/NAOJ/NRAO); B. Saxton (NRAO/AUI/NSF)

To find such a distant object required a lot of observational time on a variety of instruments. The team originally leveraged the Dark Energy Camera attached to the Victor M. Blanco Telescope and then performed follow-up observations with the Magellan telescope in Las Campanas, both located in Chile.  Las Campanas has the added advantage of extra “seeing”, which allows ground-based telescopes to capture very faint objects, such as this new protocluster, which might be unobservable in the sky of other parts of the world.

While the protocluster might be faint, it is certainly not physically small.  The LAGER team estimated the amount of mass that was most likely present in the detected protocluster.  Push forward to modern day sizing, and there is a high likelihood that it would be a supercluster similar in size to the Coma Group.

UT video describing how galaxies, including the ones seen in the LAGER study, move.

So far, the protocluster has not yet received a similar name, but it might be worthwhile to distinguish it as the farthest ever seen.  The LAGER group is continuing to search for early stage galaxy formations in similar areas of the universe.  The more they find, the more we will understand about our early universe.  The and the important it is to distinguish each discovery with a name as part of its own origin story.

Learn More:
Carnegie Science: Large Proto-Cluster Of Galaxies Discovered In The Midst Of Clearing The Cosmic Fog
S&T : Astronomers Spot Galaxies Clustering in Early Universe
UT: Hubble Finds a Distant Proto-Cluster of Galaxies

Lead Image:
Graphic depicting the locations of the galaxies LAGER found.
Credit: Carnegie Institution for Science

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