EXPLAINING THE COSMIC MEGASTRUCTURES
What mechanism could be behind their formation?
distribution. But Lopez explains that the BAOs should appear as spherical shells in the arrangement of galaxies, and this isn’t what is happening. As a statement from UCLan states: “Alexia’s detailed analysis of her discovery is not really compatible with the BAO explanation. The Big Ring is too large and is not spherical.”
Another potential explanation involves conformal cyclic cosmology (CCC). This general relativity-based theory was proposed by the 2020 Nobel Prize-winning English physicist Roger Penrose as a model for a cyclical universe. It challenges the Big Bang by stating there was no theoretical beginning, saying instead that the region of the universe we observe is merely an aeon within an infinitely larger space-time. As time goes on, our aeon eventually becomes smooth, but expands and births a new larger scale aeon. It means the Big Bang was one of a series of cyclical big bangs.
“Rings in the universe could conceivably be a signal of CCC,” the UCLan statement affirms. Equally, however, the two structures may be the effect of cosmic strings passing through. These are hypothetical one-dimensional topological defects that may have formed in the early universe. Introduced by theoretical physicist Tom Kibble in the late 1970s, they are similar to vortex lines in liquid helium, and they could have triggered the formation of large-scale structures such as galaxies. CanadianAmerican astrophysicist Jim Peebles, currently the Albert Einstein professor in science, emeritus, at Princeton University, says cosmic strings may play a part in the large-scale distribution of galaxies.
Until any hypothesis can be confirmed, however, the presence of these gigantic structures will remain something of a mystery. Yet clearing up the matter is important because of the repercussions for our accepted understanding of the universe, which is why astronomers are hard at work coming up with potential explanations.
The standard cosmological model has also been revisited for other reasons, not least in 2022 when studies of a million galaxies showed asymmetrical distribution. But does this mean the cosmological principle ought to be consigned to the history books? There’s a lot at stake.
When Lopez presented her observations at the 243rd meeting of the American Astronomical Society in New Orleans earlier this year, it certainly got scientists talking. Some have suggested that the large structures could be made up of smaller ones, which would continue to sit well within the cosmological principle. It’s also
Baryon acoustic oscillations
Baryon acoustic oscillations are spherical ripples in the distribution of galaxies across the universe. Created by the equivalent of sound waves in the early universe, they formed when particles began to be pulled together by gravity. According to Lopez, they should appear “statistically, at least, as spherical shells in the arrangement of galaxies”. But the Big Ring is not spherical, and it’s too large.
The Apache Point Observatory is home to the telescope used for the Sloan Digital Sky Survey
Conformal cyclic cosmology
This intriguing cosmological model proposed by theoretical physicist Roger Penrose is an alternative to the Big Bang theory. It suggests that stars and galaxies die out, matter disperses and supermassive black holes evaporate, creating a smooth aeon in a larger space-time, only to continue expanding and giving birth to a new aeon on a larger scale. The Big Ring could be a signal of CCC.
important that the data used is robust and proves beyond doubt that these structures exist as described and are not simply a random yet patterned arrangement of stars. As it stands, the Giant Arc’s statistical significance is 4.5 sigma; the gold standard is five.
But that’s the very nature of scientific research, and with more data in the future, it could well mean that even more megastructures are uncovered.
The European Space Agency, for example, launched the Euclid wide-angle space telescope last year, boasting a 600-megapixel camera to record visible light. The spacecraft also has a nearinfrared
Cosmic strings
There is also a possibility that the gigantic structures are a cosmic string – a hypothetical clumping of matter created in the early universe. There is a suggestion that cosmic strings could play a part in galaxy distribution, but much work will now need to be carried out. There is a possibility that an entirely new theory, different to these three, may be needed in order to get to the bottom of this particular mystery.
spectrometer and photometer to determine the redshift of detected galaxies. As astronomers explore the data it gathers, they could make further breakthroughs and continue to challenge the cosmological principle. Who knows how big some of these structures may be?