Researchers relying on the Gran Telescopio Canarias announce that they have isolated the most densely populated cluster of galaxies in formation in the early universe. Their work is published in the Monthly Notices of the Royal Astronomical Society.
Galaxy clusters are associations of several galaxies bound together by gravitation. These gigantic structures can have several thousand entities each. The Virgo cluster, which sits at the center of the supercluster that bears the same name and which includes the Milky Way, has, for example, more than 2,000 visible galaxies .
To understand the evolution of these "galactic cities", scientists search for structures forming in the early universe. One of these clusters has just been spotted more than 12.5 billion light-years away of the Earth.
In 2012, a team of astronomers had precisely determined the distance of the galaxy HDF850.1. It is one of the objects with the highest rate of star formation in the observable universe. To their surprise, the researchers then discovered that this galaxy was part of a group of a dozen protogalaxies formed during the first billion years of cosmic history.
In a recent study, researchers from the Institute of Astrophysics of the Canary Islands relied on the OSIRIS instrument, installed on the Gran Telescopio Canarias, to analyze the physical properties of this system. According to this work, it would indeed be the most massive cluster ever detected in the early universe .
Structurally, astronomers have also made a discovery. "Surprisingly, we found that all of the cluster members studied so far, about two dozen, are normal star-forming galaxies and that the Central Galaxy appears to dominate star production in this structure “, indeed explains Rosa Calvi, formerly postdoctoral researcher at the IAC and main author of the article.
Astronomers predict that this structure, a true " city under construction", will gradually change until it becomes a cluster of galaxies similar to that of Virgo.
Note that while this cluster appears very massive to us, it is not the oldest ever isolated. In 2019, a team of astronomers had indeed detected a cluster formed 13 billion years ago , when the Universe was only 6% of its current age . This incredible discovery was made possible thanks to three of the most powerful telescopes in the world:Subaru, Keck and Gemini.
