The massive structure in the distant universe challenges our understanding of how the universe evolved.
In light that traveled 6.9 billion years to reach us, astronomers have discovered a giant, nearly perfect galactic ring, about 1.3 billion light-years in diameter. It does not match any known structure or formation mechanism.
The Big Ring, as its structure is called, may mean that we need to modify the Standard Model of cosmology.
This discovery was led by astronomer Alexia Lopez from the University of Central Lancashire. Submitted At the 243rd Meeting of the American Astronomical Society.
It is the second giant structure that Lopez and her colleagues have discovered. The first, called Giant Sagittarius, is actually in the same part of the sky, At the same distance. When the discovery of Sagittarius was announced in 2021, it baffled astronomers. The big ring only deepens the mystery.
“Neither of these supermassive structures is easy to explain in our current understanding of the universe.” Lopez says. “Their extremely large sizes, distinctive shapes and cosmic proximity certainly tell us something important – but what exactly?”
The direct link appears to be the so-called Baryon Acoustic Oscillation (BAO). These are giant circular arrangements of galaxies found throughout space. They're actually spheres, fossils of sound waves that spread across the early universe, then froze when space became so that propagating sound waves could no longer travel.
The big ring is not BAO. The BAOs are all of constant size with a diameter of about a billion light-years. Close examination of the large ring shows that it resembles the shape of a key that has been aligned in such a way that it looks like a ring.
Which leaves the question unanswered: What the hell is this? What does this mean for the cosmological principle, which states that in all directions, any given patch of space should look very similar to all other patches of space?
“We expect matter to be evenly distributed everywhere in space when we look at the universe on a large scale, so there should not be any noticeable irregularities above a certain size.” Lopez explains.
“Cosmologists calculate the current theoretical maximum for the structures is 1.2 billion light-years, yet both of these structures are much larger – the giant arc is approximately three times larger and the circumference of the large ring is similar to the length of the giant arc.”
But size is just one of the problems. The other is what cosmology means, that is, the study of the evolution of the universe. The current model is the model that currently fits best 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 address these features. Under one such model, Roger Penrose Conformal periodic cosmologyas the universe goes through the endless expansion cycles of the Big Bang, ring structures are expected – although it is worth noting that a corresponding periodic cosmology may Big problems of their own.
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Another possibility is that the structures are a type of topological defect in the fabric of space-time known as cosmic strings. These are thought to resemble the broad proton wrinkles that appeared in the early universe when spacetime expanded, then froze in place. We haven't found much physical evidence for cosmic strings, but the theoretical evidence is very promising.
Right now, no one knows for sure what the big ring and giant bow mean. They could just be chance arrangements of galaxies orbiting across the sky, although the likelihood of that seems very small.
The best hope is to find more of these arrangements of galaxies scattered throughout the universe, hiding in plain sight.
“From current cosmological theories, we did not think structures on this scale were possible.” Lopez says. “We can expect perhaps one very large structure in all of our observable universe. However, the Big Ring and the Giant Arc are two massive structures, and they are even cosmically adjacent, which is quite remarkable.”
The research was presented at the 243rd meeting of the committee American Astronomical Society.