Ring shatters hypothesis that universe appears uniform on large scales
PHOENIX – An abnormally huge cosmic structure has put a ring on it – and that bling could threaten a fundamental hypothesis of cosmology.
A ring of dense matter spans more than 3.3 billion light yearscosmologist Alexia Lopez reported on January 6 at a meeting of the American Astronomical Society. If real, this structure could pose a problem to the cosmological principle, according to which the universe looks the same in all directions on a large scale.
The principle is “the second most fundamental hypothesis in the field,” after Einstein’s theory of general relativity, says mathematical physicist Eoin ÓColgáin of the Atlantic University of Technology in Ireland, who studies challenges to the cosmological principle but was not involved in the new work. Every theoretical model of the universe assumes that matter is uniformly distributed when considering sufficiently large volumes of space. Without this assumption, says ÓColgáin, “all hell would break loose.”
The giant ring joins a growing list of enormous structures that should not exist if this hypothesis is true. This is apparently an extension of a previously reported ” “.giant bow“, and encircles a smaller – but still huge – “big ring» of matter.
“They now seem to present more of a challenge to the cosmological principle,” says Lopez, of the University of Central Lancashire in Preston, England. “Can we explain something like a ring and an arc together? »
Lopez and his colleagues spotted the structures in the light of distant quasars – bright disks of matter surrounding supermassive black holes – captured by the Sloan Digital Sky Survey in New Mexico. As light from quasars passes through the universe, some of it may be absorbed and modified by atoms in and around galaxies in the intervening space. Studying changes in the light of quasars allows astronomers to map this question.
Lopez first noticed the “giant arc” of galaxies in 2021. All the galaxies in the arc appeared to be at the same cosmic distance, sending their signals from when the universe was half its current age, nearly 7 billion years ago. In 2024, she added the “great ring”, an apparent circle of galaxies located at the same distance hovering above the arc like a cyclops eye above a smile.
Then Lopez noticed a thin filament forming an arc above the large ring. “It almost looked like it could be a continuation of the giant arc,” she says. Or it could have been a coincidence, his eye picking up shapes that didn’t really exist. To rule out this possibility, she performed statistical tests and found that it was unlikely that the ring had formed by accident. Because a homogeneous universe should not contain such immense structures, they challenge current models of cosmology, she says.
Other researchers disagree. ÓColgáin believes that large structures alone are not enough to overturn the cosmological principle, although this hypothesis faces other challenges. And some say the current model of the universe has no difficulty forming such immense features. In a paper published on arXiv.org in February 2025, theoretical astrophysicist Till Sawala of the University of Helsinki and his colleagues reported computer simulations of universes. which include both the cosmological principle and structures like the giant arc (the giant ring was not included as it had not yet been presented). Lopez counters that the analog arcs found by this group were different from his, so the studies are not comparable.
“We can discuss this forever,” says astrophysicist Subir Sarkar of the University of Oxford. “But I think the rings completely change the game. It’s not something you would expect to come across… It seems quite extraordinary.”
Sarkar notes that Lopez’s work has not yet been published in a peer-reviewed journal, so he cannot verify his calculations. But larger sky surveys, such as those carried out with the Dark Energy Spectroscopic Instrument in Arizona or the Vera C. Rubin Observatory in Chile, should uncover larger-scale structures, if they actually exist.
“We don’t need to argue until the end of time whether this structure is real or accidental or whatever,” Sarkar says. “We should just get more data, and more things should show up.”
