Protogalaxy Cluster Discovered When the Cosmic Fog Was Beginning to Clear, When the Universe Was Simply 750 Million Years Outdated

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

Origin stories are the focus of many astronomical studies. Planet formation, solar system formation, and even galaxy formation have long been studied to understand how the universe got where it is today. Now a team of scientists from Lyman Alpha Galaxies in the Consortium of the Epoch of Reionization (LAGER) has found an extremely early “protogalaxy” that was formed around 750 million years after the Big Bang. Studies can provide insights into this early type of galaxy formation and everything that comes after.

750 million years ago was the end of the period in the history of the universe known as “reionization”. During this epoch, which lasted approximately 370 million years, the first galaxies and large-scale structures began to form in the universe. The protocluster (a high-density cluster of galaxies) that Jorge González-López, a postdoc member of the LAGER team, found around this era. It is the most widely discovered protocluster discovered to date.

ALMA image of 14 galaxies forming a protocluster known as SPT2349-56. These galaxies are just merging and will eventually form the core of a really massive galaxy cluster. Credit: ALMA (ESO / NAOJ / NRAO); B. Saxton (NRAO / AUI / NSF)

Finding such a distant object required a great deal of observation time on a variety of instruments. The team originally used 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 in Chile. Las Campanas has the added benefit of having an extra “seeing” that ground-based telescopes can capture very faint objects, such as this new protocluster, that may not be seen in the skies of other parts of the world.

The protocluster is weak, but certainly not physically small. The LAGER team estimated the amount of mass that was most likely present in the detected protocluster. Proceed with today’s sizing and there is a high probability that it is a supercluster, the size of which is similar to that of Coma Group.

UT video describing how galaxies, including those shown in the LAGER study, move.

As of yet, the protocluster hasn’t been given a similar name, but it might be worth calling it the most distant ever seen. The LAGER group continues 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. That and the important thing is to differentiate each discovery with a name as part of its own origin story.

Learn more:
Carnegie Science: Large proto-cluster of galaxies discovered in the middle of the clearing of the cosmic nebula
S&T: Astronomers discover galaxies that collect in the early universe
UT: Hubble finds a distant proto-cluster of galaxies

Mission statement:
Graphic with the locations of the galaxies found by LAGER.
Photo credit: Carnegie Institution for Science

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