From our balcony on Earth, the universe appears sparkling with stars and galaxies. But if our gaze were to move away, we would see a scene full of monotony in all directions, deep darkness, in which the galaxies dwindle and become pale dots, and the matter appears identical from every aspect.
But the hypothesis that the universe is equally distributed in matter and appears identical to the eyes of observers, known as the cosmological principle, has become a matter of dispute. Last week, a doctoral student in England revealed her discovery of a giant necklace of galaxies, extending across 1.3 billion light-years.
The so-called “Large Ring” of galaxies and galaxy clusters joins an expanding group of massive structures that defy scientific expectations. Taken together with other confusing observations, this suggests that the Standard Model of the Universe, in which the cosmological principle plays a supporting role, may not be the final say in how the Universe we know today took shape.
As amazing as the discovery itself was, the reactions among cosmology experts were just as exciting.
“A lot of people are excited,” Alexia Lopez, the student at the University of Central Lancashire who discovered the Big Ring, told me, “but if you say that, you are getting this resistance reaction in cosmology that you don’t get in any other branch of science.” She continued: “Good science should be about testing our basic assumptions, but clearly there are people who always want to protect the standard model.”
This is perhaps because there is no more fundamental question in science than “how the universe began,” and anything that upsets our understanding leaves a scientific and philosophical question mark over our very existence.
The discovery of the large ring came during Lopez’s analysis of gas absorption in light measured from distant quasars, some of the brightest objects in the universe. A certain gas, a form of ionized magnesium known as MgII, is associated with galaxies and galaxy clusters. “It’s a really clear and detectable feature in quasar spectra,” Lopez says, when talking about magnesium absorption, indicating the possibility that this method could allow the detection of distant galaxies that would otherwise be unobservable.
Just as a cut-out piece of cardboard would reflect a silhouette onto a backlit object, the large ring appeared as ionized magnesium absorbed some of the bright light from the quasars behind it. If it were visible from Earth, the diameter of the ring would extend to the equivalent of 15 moons.
Lopez presented her discoveries, in which Roger Claus, her colleague at the University of Central Lancashire, and Gerard Williger from the University of Louisville in Kentucky, participated, during a meeting of the American Astronomical Society in New Orleans last week.
Lopez is currently writing her findings into a scientific paper, which will undergo appropriate peer review. In 2021, Lopez discovered a massive galaxy, called Sagittarius Giant, in the same way. This sickle-shaped curve of galaxies is larger than the Great Ring, and extends for more than 3 billion light-years from beginning to end.
These dimensions are important, because the size of the two galaxies exceeds 1.2 billion light-years, and is sometimes referred to as the homogeneity scale. Lopez explained the matter in detail, explaining that it is related to the minimum distance at which the entire universe must appear homogeneous. But that is no longer the case now. The Great Ring and the Giant Arc join other massive objects in the Standard Model orbit, including the Great Walls galaxy cluster.
The largest of them, the Great Polar Corona Wall of Hercules-Borealis, is 10 billion light-years away from us and extends 10 billion light-years in length. But is this measure of homogeneity too small? Even if it expanded, Lopez points out, it would leave a mystery about how such vast galactic structures formed so quickly in the early universe.
Large, improbable galaxies, which some researchers believe might emerge as a result of statistical coincidence, are not the only deviation from the standard model. Another anomaly is the sudden fluctuation of the Hubble Law, a number associated with the expansion of the universe. As these anomalies increased, the standard model began to look substandard.
Cosmic strings, which according to some theories are imperfections in the fabric of space-time, have been proposed as one possible solution. They can be considered “cracks” that opened during the early formation of the universe, and are thus similar to the cracks that appear on ice as water freezes.
These marks would allow such oddities, like large galactic walls, to take shape. As for the large ring, it is like a vortex that cosmologists have difficulty explaining.
