Giant Structure Found Lurking in Deep Space

 Mysterious Giant Structure Challenges Our Understanding of the Universe

A colossal structure in the distant Universe is defying our understanding of how the Universe evolved.  Scientist discovered a mysterious ultra-large structure in space may challenge our understanding of the cosmos. The structure dubbed the "Big Ring on the Sky" lies around 9.2 billion light-years away from Earth and presents a mystery to astronomers, as such large structures are supposed to be too big for the "average region" of space. It was discovered by PhD student Alexia Lopez at the University of Central Lancashire in the UK. Lopez also discovered the Giant Arc on the Sky, another large structure from 2 years ago. In light that has travelled for 6.9 billion years to reach us, astronomers have found a giant, almost perfect ring of galaxies, some 1.3 billion light-years in diameter. It doesn't match any known structure or formation mechanism.

The Big Ring, as the structure has been named, could mean that we need to amend the standard model of cosmology. The Big Ring is about 1.3 billion light-years in diameter, with a circumference of about four billion light-years. Both of these large structures are in the same cosmological neighborhood, a summary of the findings said. They were also seen in the same cosmic time, which presents many questions for astronomers. There are several possible explanations for the mysterious new structure, though none are confirmed. It's the second giant structure discovered by Lopez and her colleagues. The first, called the Giant Arc, is actually in the same part of the sky, at the same distance away. When the arc's discovery was announced in 2021, it puzzled astronomers. The Big Ring only deepens the mystery.

"Neither of these two ultra-large structures is easy to explain in our current understanding of the universe. And their ultra-large sizes, distinctive shapes, and cosmological proximity must surely be telling us something important – but what exactly?" Lopez said in the findings. "One possibility is that the Big Ring could be related to Baryonic Acoustic Oscillations (BAOs). BAOs arise from oscillations in the early universe and today should appear, statistically at least, as spherical shells in the arrangement of galaxies. However, detailed analysis of the Big Ring revealed it is not really compatible with the BAO explanation: the Big Ring is too large and is not spherical."

The most immediate link seems to be with something called a Baryon Acoustic Oscillation (BAO). These are giant, circular arrangements of galaxies found all throughout space. They're actually spheres, the fossils of acoustic waves that propagated through the early Universe, and then froze when space became so diffuse acoustic waves could no longer travel. The Big Ring is not a BAO. BAOs are all a fixed size of around 1 billion light-years in diameter. Thorough inspection of the Big Ring shows that it is more like a corkscrew shape which is aligned in such a way that it looks like a ring. Which leaves the very unanswered question: What the heck is it? And what does it mean for the Cosmological Principle, which states that, in all directions, any given patch of space should look pretty much the same as all other patches of space?

These structures present many questions for scientists. The Big Ring appeared to be a perfect circle in the sky at first. However, Lopez later found that it is actually more of a coil shape when it is observed from Earth. This ring could also be a signal of Conformal Cyclic Cosmology. This theory was developed by physicists Roger Penrose and Vahe Gurzadyan and proposes that the universe goes through infinite cycles. The idea is that each one begins with a huge event, such as the Big Bang. The ring could also be the result of the passing of cosmic strings, which are "topological defects" created in the early days of the universe. The Big Ring and the previously discovered Giant Arc present real challenges against the Cosmological Principle, which itself remains a great mystery in physics. The Cosmological Principle questions whether the universe is homogeneous or inhomogeneous.

"We expect matter to be evenly distributed everywhere in space when we view the universe on a large scale, so there should be no noticeable irregularities above a certain size," Lopez explains. "Cosmologists calculate the current theoretical size limit of structures to be 1.2 billion light-years, yet both of these structures are much larger – the Giant Arc is almost three times bigger and the Big Ring's circumference is comparable to the Giant Arc's length." But the size is just one of the problems. The other is what it means for cosmology, the study of the evolution of the Universe. The current model is the one that currently fits the best with what we observe, but there are some features which are challenging to explain under its framework. There are other models which have been put forward to address these features. Under one such model, Roger Penrose's conformal cyclic cosmology, in which the Universe goes through endless Big Bang expansion cycles, ring structures are expected – although it's worth noting that conformal cyclic cosmology has significant problems of its own. "The Cosmological Principle assumes that the part of the universe we can see is viewed as a 'fair sample' of what we expect the rest of the universe to be like. We expect matter to be evenly distributed everywhere in space when we view the universe on a large scale, so there should be no noticeable irregularities above a certain size," Lopez said. 

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 be like proton-wide wrinkles that emerged in the early Universe as space-time stretched, then froze into place. We've not found much physical evidence of cosmic strings, but the theoretical evidence is pretty promising. At the moment, nobody knows for sure what the Big Ring and the Giant Arc signify. They could just be chance arrangements of galaxies twirling across the sky, although the likelihood of that seems pretty small. The best hope would be to find more such arrangements of galaxies, scattered throughout the Universe, hiding in plain sight. "From current cosmological theories we didn't think structures on this scale were possible," Lopez said from current cosmological theories, astronomers did not think "structures on this scale were possible. We could expect maybe one exceedingly large structure in all our observable universe. Yet, the Big Ring and the Giant Arc are two huge structures and are even cosmological neighbours, which is extraordinarily fascinating."