Back at the dawn of the Universe, astronomers found a lot of cosmic proportions. At least 21 galaxies, which form stars with extraordinary speed, come together in the early stages of forming a group of galaxies. And it all happens 13 billion light-years away – just 770 million years from the Big Bang itself.
This is the oldest protocluster discovered so far, called LAGER-z7OD1, and today it probably evolved into a group of galaxies 3.7 billion times larger than the Sun’s mass.
Such a great protocol, so early in the Universe – just a cosmic blink, since the curtain was lifted on life, the Universe and everyone – could contain some vital clues as to how the primordial smoke cleared and the lights lit, sending light freely through space.
Our universe is a massively interconnected place. Galaxies may appear relatively independent, but more than half of galaxies are gravitationally linked together in groups or groups, huge structures of hundreds to thousands of galaxies.
The beginnings of such clusters are not unknown in the early universe. Protocols were found almost up to LAGER-z7OD1, some even larger, suggesting that clusters could begin assembly much faster than previously thought possible.
But LAGER-z7OD1, according to a team of researchers led by astronomer Weida Hu of China’s University of Science and Technology, is special. It may reveal clues about one of the most mysterious stages in the history of the Universe: the Age of Reionization.
“The total volume of ionized bubbles generated by its member galaxies proves to be comparable to the volume of the protocluster itself, indicating that we are witnessing the fusion of individual bubbles and that the intergalactic environment in the protocol is almost completely ionized,” they wrote in their newspaper.
“LAGER-z7OD1 thus provides a unique natural laboratory to investigate the reionization process.”
You see, space has not always been the wonderful and transparent place it is today. In the first 370 million years or so, it was filled with a hot cloud of hot ionized gas. The light could not travel freely through this fog; it scattered free electrons and that was it.
Once the universe cooled enough, protons and electrons began to recombine into neutral hydrogen atoms. This meant that light – not that it was much, though – could finally travel through space.
As the first stars and galaxies began to form, their ultraviolet light reionized the neutral hydrogen ubiquitous throughout the Universe: first into bubbles located around ultraviolet sources and then into larger and larger areas as the bubbles ionized. they connected and overlapped, allowing the entire spectrum of electromagnetic radiation to flow freely.
About 1 billion years after the Big Bang, the universe was completely reionized. This means that it is more difficult to research beyond this point (about 12.8 light-years away), but it also means that the reionization process itself is difficult to understand.
Ideally, you need really bright objects whose ionizing radiation could cut off neutral hydrogen, and that’s what Hu and his team with the Alpha Lyman Galaxies in the Epoch of Reionization investigation were looking for. These are small galaxies in the early universe that form stars with insane speed, which means that they can be detected at fairly long distances, even within the Reionization Age. This makes them useful probes of the period.
In their search, researchers discovered LAGER-z7OD1, an over-dense region of galaxies in a three-dimensional volume of space measuring 215 million by 98 million by 85 million light-years. This volume contained two distinct sub-protocols merging together into a larger one, with at least 21 galaxies, of which 16 were confirmed.
The total volume of ionized space around galaxies was slightly larger than the volume of LAGER-z7OD1.
“This demonstrates substantial overlaps between individual bubbles, indicating that the individual bubbles are in the act of merging into one or two huge bubbles,” the researchers wrote.
So the protocol not only represents an excellent example of this kind, providing a new data point for studying how these structures form and appear, as well as star formation in the early Universe, but also provides a unique window into the formation and combination of ionized bubbles in the middle of the Reionization Age.
However, what will appear is not yet discovered. As the researchers note, this will be the work of future more powerful telescopes, which will be able to better observe the finer details of the reionization process.
The team ‘s research was published in Nature Astronomy.