Astronomers find oldest cluster of galaxies ever discovered

Astronomers find oldest cluster of galaxies ever discovered


Astronomers claim to have discovered a cluster of 12 galaxies formed 13 billion years ago, 700 million years after the Big Bang. The details of the study are published in The Astrophysical Journal.

A year ago, researchers announced the detection of a cluster of galaxies 11.1 billion light-years from Earth. The oldest at the time. But the record has just fallen. Astronomers from the National Observatory of Japan and the University of Tokyo have indeed detected a small cluster even older. This object evolved 13 billion years ago when the Universe was only 6% of its current age. An incredible discovery made possible by three of the most powerful telescopes in the world: Subaru, Keck, and Gemini.

One of the galaxies – named Himiko – had already been discovered 10 years ago by the same researchers. What we learn from this study is that this massive object was actually located on the periphery of a very old cluster – or protocluster – containing at least 11 other galaxies. To give you an idea of the size of this galactic cluster, Himiko is about 500 million light-years away from the center.

Understanding the evolution of galactic clusters
Most galaxies – including the Milky Way – are now evolving into clusters with other congeners. It is important to understand these galactic populations since the density of galaxies within each cluster can affect their behavior. A cluster filled with galaxies does not behave in the same way as a cluster containing a few scattered objects. And these behaviors seem to evolve over time.

It has indeed been noticed that the recent clusters very dense in galaxies form much fewer stars than the more dispersed clusters. As if these formations had “aged” faster than the others, giving up in the end to the creation of new stars. On the other hand, we observe the opposite in the primitive universe. High-density clusters seem to form many more stars than less dense clusters.

This galactic evolution is still poorly understood. This is why the discovery of such an ancient object is important. It will allow researchers to evaluate how these clusters, still small at the time, have become over time the real behemoths observed today. Some may contain thousands of galaxies.