A recently unearthed crescent of galaxies, spanning a length of 3.3 billion light-years, has perplexed astronomers with its enormous size, challenging some of the most fundamental concepts about the universe.
The Giant Arc is a colossal assemblage of galaxies, galaxy clusters, and copious amounts of gas and dust. Encompassing roughly 1/15th of the observable universe, this structure is situated 9.2 billion light-years from Earth.
The discovery was serendipitous, according to Alexia Lopez, a doctoral candidate in cosmology at the University of Central Lancashire (UCLan) in the UK. Lopez was utilizing light from over 120,000 quasars, which are bright centers of galaxies located far away where supermassive black holes consume matter, to map objects in the night sky.
As light travels from these quasars to us, it passes through matter and is absorbed by various elements, leaving behind distinct signatures that can be useful for researchers. Lopez specifically used the markings of magnesium to measure the distance to the intervening gas and dust, as well as its composition.
Huge Arc. Gray areas, which represent the dispersion of galaxies and galaxy clusters, are used to identify regions where magnification is occurring. The “lue dots” are background quasars, commonly known as spotlights. (Image provided by Alexia Lopez/UCLan.)
The quasars, in Lopez’s words, “work like spotlights in a dark room, lighting this interesting material.” During the span of cosmic ages, a structure began to form. There was “sort of a hint of an arc,” according to Lopez. I can still see myself going up to Roger Clowes and pointing something out.
Her PhD advisor at UCLan, Clowes, recommended additional investigation to make sure it wasn’t a mistake or a data trick. Two distinct statistical tests were conducted by the researchers, and they determined that there was less than a 0.0003% that the Great Arc was a fabrication. At the 238th virtual meeting of the American Astronomical Society, they presented their research.
The Giant Arc’s structure is represented in grey, while nearby quasars are superimposed in blue, showing a potential relationship between the two datasets. (Image credit: Alexia Lopez/UCLan).
However, this discovery poses a challenge to one of the fundamental beliefs about the universe and ranks among the most significant cosmic discoveries. The cosmological principle, which suggests that matter is distributed evenly throughout space on the largest scales, has been a cornerstone of astronomy.
The Sloan Great Wall and the South Pole Wall, both of which are smaller than the Giant Arc, are dwarfed by even larger cosmic structures. Over time, astronomers have identified various large-scale structures that seem to defy the cosmological principle due to their massive size, as noted by Clowes in an interview with Live Science.
The fact that such massive entities have congregated in specific areas of the universe implies that matter may not have been distributed uniformly across the universe. However, Lopez noted that the current standard model of the cosmos is based on the cosmological principle.
“If we find that it is not true, maybe we need to consider a different set of theories or rules,” she added.
Although she doesn’t know what those theories would entail, Lopez suggested the possibility of modifying how gravity functions on the largest scales, an idea that has gained popularity among a small but vocal group of scientists in recent years.
Daniel Pomarède, a cosmographer at Paris-Saclay University in France and the founder of the South Pole Wall, agreed that the cosmological principle should limit the theoretical size of cosmic objects.
According to some study, structures should grow to a specific size before becoming immobile, Pomarède told Lié Science. Instead, we continue to discover these igger structures.
Yet, he hasn’t completely decided to abandon the cosmological principle, which has been applied to univariate methods for around a century.
“To say that it will be replaced by something else would be quite dated,” he remarked.
Soucre: news.sci-nature.com