Discovery of second ultra-large structure in deep space further challenges our understanding of the universe

The discovery of a second ultra-large structure in the distant universe has further called into question some fundamental assumptions about cosmology.

The Great Ring in the Sky is 9.2 billion light years from Earth. It has a diameter of about 1.3 billion light years and a circumference of about 4 billion light years. If we could go out and see it directly, the diameter of the Great Ring would need about 15 full moons to cover it.

It is the second ultra-large structure discovered by the University of Central Lancashire (UCLan) PhD. student Alexia Lopez who, two years ago, also discovered the Giant Arc in the Sky. Remarkably, the Great Ring and the Giant Arc, which measures 3.3 billion light-years, are in the same cosmological neighborhood: they are seen at the same distance, at the same cosmic time, and are only 12 degrees in the sky.

Alexia said: “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 tell us something important, but what exactly?

“One possibility is that the Great Ring could be linked to baryonic acoustic oscillations (BAO). BAOs originate from oscillations in the early universe and today should appear, at least statistically, as spherical shells in the arrangement of galaxies However, detailed analysis of the Big Ring revealed that it is not really compatible with BAO’s explanation: the Big Ring is too large and is not spherical.

Other explanations may be needed, explanations that deviate from what is generally considered the standard understanding in cosmology. One possibility could be a different theory – conformal cyclic cosmology (CCC) – proposed by Nobel laureate Sir Roger Penrose. Rings in the universe could possibly be a signal of CCC.

Another explanation could be the effect of the passage of cosmic strings. Cosmic strings are large filamentous “topological defects”, which could have been created at the very beginning of the universe. Another Nobel laureate, Jim Peebles, recently speculated that cosmic strings might play a role in causing some other features of the large-scale distribution of galaxies.

Additionally, the Great Ring challenges the Cosmological Principle, just like the Giant Arc did before. And if the Great Ring and the Giant Arc together form an even greater structure, then the challenge to the Cosmological Principle becomes even more compelling.

Structures this large – and other cosmologists have discovered others – challenge our idea of ​​what an “average” region of space looks like. They exceed the size limit of what is considered theoretically viable and pose potential challenges to cosmological principle.

Alexia said: “The cosmological principle assumes that the part of the universe we can see is considered a ‘fair sample’ of what we expect the rest of the universe to look like. We expect matter to be distributed evenly everywhere in space when we view the universe on a large scale, so there should be no noticeable irregularities above a certain size.

“Cosmologists calculate that the current theoretical size limit for structures is 1.2 billion light years, but these two structures are much larger: the Giant Arc is almost three times larger and the circumference of the Great Ring is comparable to the length of the Giant Arc.

“Based on current cosmological theories, we didn’t think structures on this scale were possible. We would expect that there might be one extremely large structure throughout our observable universe. Yet the Great Ring and the Giant Arc are two enormous structures and are even cosmological neighbors, which is extraordinarily fascinating.

The Great Ring appears as a near-perfect ring in the sky, but Alexia’s closer analysis reveals that it is instead shaped like a coil, like a corkscrew, aligned facing Earth. The giant arc, which is about 1/15th the radius of the observable universe, appears as an enormous, nearly symmetrical crescent of galaxies in the distant universe. It is twice as large as the impressive Sloan Great Wall of galaxies and clusters seen in the relatively nearby universe.

“The Great Ring and the Giant Arc are at the same distance from us, near the constellation Boötes the Shepherd, which means that they existed in the same cosmic epoch, when the universe was only half the size his current age,” commented Alexia. “They are also in the same region of the sky, just 12 degrees apart when looking at the night sky.

“The identification of two extraordinary ultra-large structures in such a close configuration raises the possibility that together they form an even more extraordinary cosmological system.

“The data we’re looking at is so far away that it took half the lifetime of the universe to reach us, so at a time when the universe was about 1.8 times smaller than it is today. The Great Ring and the Giant Arc, both individually and together, reveal to us a great cosmological mystery as we work to understand the universe and its development.”

Alexia, along with advisor Dr Roger Clowes, both from the Jeremiah Horrocks Institute at UCLan, and collaborator Gerard Williger from the University of Louisville, US, discovered the new structure by examining lines of absorption in quasar spectra from the Sloan Digital Sky Survey (SDSS).

Using the same method that led to the discovery of the Giant Arc, they observed the intermediate absorption systems of Magnesium-II (or MgII – this means the atom has lost an electron) backlit by quasars, which are distant super-luminous galaxies. These very distant and very bright quasars act as giant lamps that illuminate distant, but much fainter, intervening galaxies that would otherwise remain invisible.

Alexia presented her findings on the Big Ring at the 243rd meeting of the American Astronomical Society (AAS) on January 10.