A massive structure discovered in the distant universe challenges our understanding of how the universe evolved.
In 2024, astronomers discovered a giant, nearly perfect ring of galaxies about 1.3 billion light-years across.
Yes, you read that right. BILLIONS of light years.
It does not match any known structure or formation mechanism.
The discovery, led by astronomer Alexia Lopez of the University of Central Lancashire, was presented at the 243rd meeting of the American Astronomical Society in 2024 and was published in the Journal of Cosmology and Astroparticle Physics.
The signal was captured in light that had traveled 6.9 billion years to reach us.
The existence of the “Big Ring“, as the structure has been called, could mean we need to change the standard model of cosmology.
This is the second giant structure discovered by Lopez and her colleagues. The first, called the Giant Arc, is actually located in the same part of the sky, at the same distance. When the discovery of the rainbow was announced in 2021, it puzzled astronomers. The large ring only deepens the mystery.
“Neither of these two ultra-large structures is easy to explain in our current understanding of the universe,“ Lopez said in January 2024.
“And their ultra-large size, distinctive shapes, and cosmological proximity certainly tell us something important – but what exactly?”
The most immediate connection seems to be to something called Baryon Acoustic Oscillations (BAOs). These are giant, circular arrangements of galaxies found throughout space. They are actually spheres, fossils of acoustic waves that propagated through the early universe and then froze when space became so diffuse that acoustic waves could no longer propagate.
The Great Ring is not a BAO. BAOs are a fixed size of about 1 billion light-years in diameter. And a close inspection of the Great Ring shows that it is more like a corkscrew, aligned in such a way that it looks like a ring.
Which leaves the question unanswered: What the hell is this? And what does this mean for the Cosmological Principle, which states that in all directions any given patch of space should look pretty much the same as every other patch of space?
“We expect matter to be evenly distributed throughout space when we look at the universe on a large scale, so there shouldn't be any noticeable irregularities above a certain size,“ Lopez explained.
“Cosmologists calculate the current theoretical limit on the size of the structures at 1.2 billion light-years, but both structures are much larger - the Giant Arc is almost three times as large, and the circumference of the Great Ring is comparable to the length of the Giant Arc.“
But size is only one issue. The other is what this means for cosmology, the study of the evolution of the universe. The current model is the one that currently best fits what we observe, but there are some features that are difficult to explain within its framework.
There are other models that have been proposed to deal with these features. According to one such model, Roger Penrose's conformal cyclic cosmology, in which the universe goes through infinite cycles of expansion during the Big Bang, ring-like structures are expected - although it is worth noting that conformal cyclic cosmology has its own significant problems.
Another possibility is that the structures are a type of topological defect in the fabric of space-time known as cosmic strings. They are thought to be like wrinkles the width of a proton that appeared in the early Universe when space-time stretched and then froze in place.
We haven't found much physical evidence for cosmic strings, but the theoretical evidence is quite promising.
At the moment, no one knows for sure what the Great Ring and the Giant Arc mean. They could simply be random arrangements of galaxies spinning across the sky, although the likelihood of that seems quite small.
The best hope would be to find more such arrangements of galaxies scattered throughout the universe, hidden in plain sight.
“From current cosmological theories, we didn't think structures of this scale were possible,“ Lopez said.
“We might expect perhaps one extremely large structure in our entire observable universe.“ Still, the Great Ring and the Giant Arc are two enormous structures, and they are even cosmological neighbors, which is extremely fascinating.
The findings are published in the Journal of Cosmology and Astroparticle Physics.
Source: sciencealert.com