by Scientists have discovered a gargantuan ring structure – about 1.3 billion light-years in diameter – that they say is so big it challenges our understanding of the universe.
Called the Great Ring, this ultra-large structure – with a circumference of about four billion light years – was observed in the distant universe, about 9.2 billion light years away.
Composed of galaxies and galaxy clusters, the Great Ring appears to be about 15 times the diameter of the Moon in the night sky as seen from Earth.
It is the second cosmic structure of that size to be identified by Alexia Lopez, a PhD student at the University of Central Lancashire (UCLan) who also discovered the Great Arc – which spans 3.3 billion light-years of space – around three years ago.
She said: “Either of these two ultra-massive structures are not easy to explain in our current understanding of the universe.
“And their ultra-large sizes, distinctive shapes, and cosmological proximity certainly tell us something important—but what exactly?”
Ms Lopez’s findings – presented at the 243rd meeting of the American Astronomical Society (AAS) – appear to challenge the cosmological principle, which states that the universe should look roughly the same everywhere on a large scale.
The general consensus is that large structures in the universe are formed by a process called gravitational instability but this has a size limit of about 1.2 billion light years.
Anything more than that would not have enough time to form.
Miss Lopez said: “The cosmological principle assumes that the part of the universe we see is considered a ‘fair example’ of what we expect the rest of the universe to look like.
“We expect matter to be evenly distributed everywhere in space when we look at the universe on a large scale, so there shouldn’t be any noticeable irregularities above a certain size.
“Cosmologists estimate that the current theoretical limit on the size of the structures is 1.2 billion light-years, but these two structures are much larger – the Arc Giant is almost three times larger and the circumference of the Great Ring is comparable to the length of the Arc Giant.
“From current cosmological theories we didn’t think structures on this scale were possible.”
Other cosmologists have discovered similarly large structures – such as Sloan’s Great Wall, which is about 1.5 billion light-years long, and the South Hole Wall, which stretches 1.4 billion light-years across.
But the largest single entity known to scientists is a massive galaxy cluster called the Great Wall of Hercules-Corona Borealis, which is about 10 billion light-years across.
For comparison, the diameter of the observable universe is about 93 billion light years.
Both the Great Ring and the Giant Arc appear in the same vicinity, Ms. Lopez said, near the constellation Bootes the Herdsman.
Although the Great Ring appears as an almost perfect ring on the sky, Ms Lopez’s analysis suggests that it has more of a coil shape – like a corkscrew – with its face aligned with Earth.
Miss Lopez said: “This data we’re looking at is so far away that it took half a lifetime to get to us – from a time when the universe was about 1.8 times smaller than it is now.
“The Great Ring and the Great Arc, individually and together, provide us with a great cosmological mystery as we work to understand the universe and its development.”
Miss Lopez, along with her adviser Dr Roger Clowes, also from UCLan, and her collaborator Gerard Williger from the University of Louisville, USA, used a technique called magnesium II (MgII) to make the discoveries.
It involves turning quasars – extremely energetic and luminous celestial objects found at the center of some galaxies – into giant lamps for observing otherwise invisible cosmic matter and galaxies in the universe.
Referring to the research, Professor Don Pollacco, from the Department of Physics at the University of Warwick, said that much more research is needed to be sure of finding these ultra-large structures.
He said: “The likelihood of this happening is very low so the authors speculate that the two objects are related and that they are an even larger structure.
“So the question is how do you make structures that big?
“It is extremely difficult to conceive of any mechanism that could produce these structures so the authors argue that we are seeing a remnant from the early universe of waves of high-density and low-density matter ‘frozen’ into an extragalactic medium.”
