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

A second ultra-large structure found in the distant cosmos has further upended some of the fundamental cosmological presumptions.

It is 9.2 billion light-years from Earth to the Big Ring in the Sky. Its radius is approximately 4 billion light-years, while its diameter is around 1.3 billion light-years. The circumference of the Big Ring would require around fifteen full moons to completely cover it, if we could go outside and observe it.

Ph.D. candidate Alexia Lopez of the University of Central Lancashire (UCLan) has found this second ultra-large structure; two years prior, she had also found the Giant Arc in the Sky. Surprisingly, the 3.3 billion light-year-wide Giant Arc and the Big Ring are located in the same cosmological neighborhood; they are separated in the sky by only 12 degrees and may be observed at the same distance and cosmic time.

"With our current understanding of the universe, neither of these two ultra-large structures is easy to explain," Alexia said. Furthermore, something significant must be being revealed to us by their extraordinarily massive sizes, unique forms, and cosmic closeness. But what exactly?

One theory is that baryonic acoustic oscillations, or BAOs, are connected to the Big Ring. BAOs originate from oscillations in the early cosmos and should manifest as spherical shells in the galaxy arrangement today, at least statistically. Detailed examination of the Big Ring, however, showed that it is not truly consistent with the BAO theory since it is not spherical and is far too big."

It may be necessary to provide additional explanations, ones that deviate from what is usually accepted as the accepted knowledge of cosmology. An alternative hypothesis, Conformal Cyclic Cosmology (CCC), put out by Nobel laureate Sir Roger Penrose, might be one option. It is possible that rings throughout the cosmos indicate CCC.

A further possibility is the impact of cosmic strings moving through. Cosmic strings are large-scale filamentary "topological defects" that may have originated in the early cosmos. Jim Peebles, another Nobel laureate, has proposed that cosmic strings may play a part in the genesis of certain additional oddities in the large-scale galaxy distribution.

In addition, the Big Ring contradicts the Cosmological Principle, just as the Giant Arc did earlier. Furthermore, the argument against the Cosmological Principle gains strength if the Big Ring and the Giant Arc combine to produce an even bigger structure.

These massive formations, along with others discovered by other cosmologists, put our conception of what constitutes a "average" region of space to the test. They are potentially problematic for the Cosmological Principle since they are larger than what is thought to be theoretically feasible.

"The Cosmological Principle presumes that the portion of the universe that is visible to us is considered to be a 'fair sample' of what we anticipate the remainder of the universe to be like," Alexia said. When we look at the cosmos from a big enough scale, we anticipate matter to be uniformly dispersed throughout space, therefore anything larger than a certain size shouldn't show any obvious abnormalities.

The Big Ring's circumference is equivalent to that of the Giant Arc, and the Giant Arc itself is nearly three times larger than the theoretical size limit of structures now estimated by cosmologists to be 1.2 billion light-years.

According to accepted cosmological theories, structures of this size are not thought to be feasible. In the entire observable cosmos, we may anticipate seeing only one really massive structure. Nonetheless, it is really remarkable that the Big Ring and the Giant Arc are two enormous structures that are even cosmic neighbors."

The Big Ring is seen as an almost perfect ring in the sky, but upon closer inspection, Alexia discovers that it is actually more of a corkscrew-shaped coil that is directly aligned with Earth. In the distant cosmos, the Giant Arc appears as a massive, fairly symmetrical crescent of galaxies. Its radius is about 1/15th that of the visible universe. Its size is double that of the remarkable Sloan Great Wall of galaxies and clusters observed in the comparatively close cosmos.

"The Big Ring and Giant Arc are the same distance from us, near the constellation of Bo├Âtes the Herdsman, meaning they existed at the same cosmic time when the universe was only half of its present age" said Alexia. "When looking up at the night sky, they are also in the same area of the sky, separated by just 12 degrees.

"Identifying two extraordinary ultra-large structures in such close configuration raises the possibility that together they form an even more extraordinary cosmological system."This data comes from a time when the universe was around 1.8 times smaller than it is now, and it has traveled so far to reach us that it has taken half the life of the universe to do it. In our quest to comprehend the universe and its evolution, the Big Ring and the Giant Arc provide a significant cosmic puzzle, both alone and collectively."

The novel structure was found by Alexia, collaborator Gerard Williger from the University of Louisville, U.S., mentor Dr. Roger Clowes from the Jeremiah Horrocks Institute at UCLan, and by examining absorption lines in the spectra of quasars from the Sloan Digital Sky Survey (SDSS).

They discovered the intervening Magnesium-II (or MgII; the term refers to the atom having lost an electron) absorption systems back-lit by quasars, which are distant super-luminous galaxies, using the same technique that resulted in the discovery of the Giant Arc. These quasars, which are extremely far away and extremely brilliant, function like enormous lamps that shine a spotlight through much fainter, farther-off intervening galaxies that would not otherwise be visible.

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

Provided by University of Central Lancashire