Updated March 29, 2026
- A 1.3-billion-light-year ring of galaxies exceeds the theoretical size limit
- Alexia Lopez detected it using quasar absorption lines in survey data
- Seven ultra-large structures now challenge the cosmological principle
Alexia Lopez was mapping quasar light when she found a ring of galaxies too large for the Big Ring to exist under current cosmological theory.
Lopez, then a PhD student at the University of Central Lancashire's Jeremiah Horrocks Institute, had been using distant quasars as cosmic backlights. Their spectra carried absorption fingerprints from galaxies lying between Earth and the quasars.
She catalogued those fingerprints, specifically magnesium II absorption lines in Sloan Digital Sky Survey data. That let her plot the positions of galaxies that no telescope could image directly.
The technique works, as Lopez put it, "kind of like looking at bright spotlights in a dark room, so the spotlights are highlighting to us where all these galaxies and galaxy clusters are."
The spotlights traced something remarkable. A ring of galaxies 1.3 billion light-years across, sitting 9.2 billion light-years from Earth near the constellation Bootes.
It was, by any reasonable standard, too big to be there.
She announced the discovery in January 2024 at the American Astronomical Society's 243rd meeting. Her supervisor Roger Clowes at UCLan and Gerard Williger at the University of Louisville were co-investigators.
Key figure
1.3 billion light-years
The diameter of the Big Ring, exceeding the theoretical size limit for cosmic structures
A Ceiling the Universe Keeps Breaking
The cosmological principle is one of the oldest assumptions in modern cosmology. On large enough scales, it says, matter in the universe should look evenly spread in every direction. No lumps, no patterns, no preferred positions.
What is the cosmological principle?
The foundational assumption that the universe, viewed at large enough scales, is homogeneous (the same everywhere) and isotropic (the same in every direction). It sets a theoretical upper limit of roughly 1.2 billion light-years on cosmic structures.
That smoothness implies a ceiling. Structures larger than roughly 1.2 billion light-years should not form, because at that scale the universe has no obvious reason to clump. The limit is a theoretical expectation, not a measured physical constant.
The Big Ring exceeds it. Its circumference stretches approximately four billion light-years.
And it is not alone. The Big Ring is the seventh ultra-large structure found to breach that theoretical ceiling. Intriguingly, Lopez had already found one of the other six: the Giant Arc, a crescent of galaxies she identified in 2021, also near Bootes.
Two Structures, One Patch of Sky
Finding one oversized structure could be a statistical accident. Finding two in the same region of sky, using the same method, is harder to dismiss.
Lopez has the quiet confidence of someone whose data keeps proving her right. She and her collaborators considered whether the Big Ring might be a baryon acoustic oscillation, a relic ripple from the early universe. They ruled it out. The ring's shape and size do not match the expected BAO signature.
We need to start thinking about if we should be using alternative models of cosmology... seriously be questioning whether our standard model can hold if the basic assumptions are proving to be challenged.
Alexia Lopez, UCLan
What could account for the ring? Two alternative frameworks offer possibilities.
Conformal cyclic cosmology, the model proposed by Nobel laureate Roger Penrose, predicts large circular features in the sky. These would be remnants of a previous cosmic cycle.
Cosmic strings, hypothetical defects in spacetime from the early universe, could theoretically seed structure on scales that the standard model cannot explain.
Neither explanation is confirmed. Both predict features that conventional cosmology does not.
The Limit on Large Scale Structure May Need Replacing
In February 2025, Till Sawala at the University of Helsinki published simulations testing whether the standard cosmological model can stretch far enough. His work focused on the Giant Arc rather than the Big Ring specifically, and the results suggest the standard model may accommodate some anomalously large structures.
That finding cuts both ways. It may extend the model's credibility, or it may simply confirm that cosmologists keep needing to stretch it further.
The debate has noticeably shifted. A growing number of cosmologists now accept that these ultra-large structures are real. The open question is whether the theoretical ceiling still holds.
By January 2026, Lopez had found an even larger ring, this one spanning 3.3 billion light-years, nearly three times the supposed maximum.
Lopez, who stumbles on these structures while looking for something else entirely, seems characteristically unfazed. "We stumble across these discoveries accidentally," she has said, "so it's so fun to be able to write up analysis on these kind of discoveries."
Seven structures now exceed the limit. The list keeps growing. At some point, the exceptions become the evidence, and the ceiling becomes the thing that needs explaining.
Sources
- Primary: Galaxy ring discovery challenges thinking on universe (BBC News)
- Additional Context:
- Big Ring (Wikipedia)
- Cosmic ring challenges the cosmological principle (Science News, Jan 2026)
- PhD student discovers large-scale structure (UCLan press release)
- Sky & Telescope coverage
Fact Check: Claim-by-Claim Verification Verified
All 15 claims verified against multiple sources. Minor hedging added to cosmological principle limit and cosmic strings claim. No factual errors found in final draft.
Sources used for verification
- Galaxy ring discovery challenges thinking on universe - BBC News
- Big Ring - Wikipedia
- Cosmic ring challenges the cosmological principle - Science News
- PhD student discovers large-scale structure - UCLan
