Evrim Yazgin
Cosmos science journalist
About 9.2 billion light-years from Earth is a colossal structure which has confounded astronomers.
The discovery might upend current cosmological theories.
What they’ve found is a 1.3-billion-light-year-across, almost perfect ring of galaxies. No such structure has been seen before. And it doesn’t match any known formation mechanism. It has been dubbed the “Big Ring.”
The discovery was presented at the 243rd meeting of the American Astronomical Society and is detailed in a pre-print paper available on arXiv.
It is the second giant structure found by teams led by Alexia Lopez, an astronomer at the University of Central Lancashire in the UK. The first, a giant arc of galaxies, was unveiled in 2022. That structure is 3.3 billion light-years across and appears in the same region of sky at the same distance from Earth as the Big Ring.
“Neither of these two ultra-large structures is easy to explain in our current understanding of the universe,” Lopez says. “And their ultra-large sizes, distinctive shapes, and cosmological proximity must surely be telling us something important – but what exactly?”
A possible explanation for the Big Ring, according to Lopez, is “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.”
Another possibility is the structures are remnants of “defects” in the early universe called cosmic strings.
The structures challenge the so-called “Cosmological Principle.”
“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,” Lopez explains. “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.”
“Cosmologists calculate the current theoretical size limit of structures to be 1.2 billion light-years, yet both of these structures are much larger,” Lopez adds.
“From current cosmological theories we didn’t 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,” Lopez says.
