Distribution of CLASSIX clusters and 2MASS galaxies in the z = 0.03–0.06 shell. Supercluster members are color-coded—red (Quipu), blue (Shapley), green (Serpens-Corona Borealis), purple (Hercules), beige (Sculptor-Pegasus)—and outlined with a black ring if within range. Clusters outside superclusters appear as gray circles (open in the Zone of Avoidance). Dotted blue lines indicate |b| < 20° and solid blue lines enclose regions with nₕ > 2.5×10²¹ cm⁻². From the arXiv preprint.
Astronomers have identified what appears to be the largest confirmed filament in the universe, a structure named “Quipu,” using a combination of X-ray surveys and redshift analysis. It measures about 1.3 billion light-years across and holds the mass of roughly 200 quadrillion suns. Quipu’s filamentary path emerged through X-ray detections of hot intracluster gas—markers of galaxy clusters—and precise redshift measurements that map each cluster’s distance.
The discovery of Quipu, highlighted in a preprint, underscores how powerful wide-field X-ray surveys and data-driven algorithms are for unveiling the cosmic web’s grandest scales, providing a test for current cosmological models.
The tech toolkit that helped reveal Quipu
X-ray vision: The CLASSIX Survey and ROSAT
Galaxy clusters shine brightly in X-rays owing to intracluster gas heated to millions of degrees, making X-ray emission a candidate for detecting clusters. CLASSIX – built on data from the ROSAT satellite — covers about 86% of the sky, cataloging thousands of X-ray–emitting clusters. These clusters serve as signposts for tracing how matter is distributed on the largest scales.
Redshift measurements and ESO: The CLASSIX survey, supplemented by spectroscopic data at facilities like the European Southern Observatory (ESO), assigned precise distances (redshifts) to each cluster. This nearly all-sky coverage enabled researchers to map Quipu’s reach, revealing a filament that appears to stretch for more than a billion light-years.
The “Friends-of-Friends” algorithm: Identifying a connected filament meant linking clusters lying within a specific “linking length.” In Quipu’s case, dozens of clusters formed a continuous chain so pronounced that it stood out visually in 3D maps, even before algorithms confirmed it.
More than just large numbers
Along its 1.3-billion-light-year spine, Quipu’s concentration of galaxy clusters surpasses other well-documented structures like the Shapley Supercluster. It also approaches the scale of the hypothesized Hercules–Corona Borealis Great Wall, although that remains controversial.
Matter concentration and the cosmic web: Researchers report that Quipu, plus four similar super-filaments, encloses about 45% of the galaxy clusters and ~25% of the matter in the local survey volume—yet occupies only ~13% of the space. Such uneven “lumpiness” is a hallmark of the cosmic web, and studying Quipu shows how filaments might shape galaxy formation on extreme scales.
Impact on cosmological observations
- Integrated Sachs–Wolfe (ISW) effect: Gigantic mass concentrations like Quipu can imprint foreground signals onto the cosmic microwave background.
- Bulk flows and Hubble constant: The sheer mass of these filaments can tug on neighboring galaxies, introducing peculiar velocities that affect local Hubble measurements.
- Gravitational lensing: Quipu’s potential to bend background light means deep-sky surveys must correct for lensing distortions caused by super-filaments.
These effects, already modeled in the standard Lambda–CDM paradigm, show how Quipu can refine our understanding of dark matter and dark energy. Its confirmed presence matches large-scale simulations yet reveals just how extensive filamentary structures can become, guiding future work to confirm or adjust cosmological parameters.
The minds behind the map
Led by Hans Böhringer (Max Planck Institute for Extraterrestrial Physics), the Quipu study involves the University of Cape Town, Ludwig-Maximilians-Universität Munich, and ESA. Decades of experience in X-ray cluster surveys made this all-sky large-scale mapping feasible.
As new telescopes—like eROSITA—conduct deeper all-sky X-ray surveys, astronomers expect to reveal even more extensive structures. Overlapping radio and infrared data can also pierce the Milky Way’s obscuration to see whether Quipu extends farther. Knowing the location and mass of these filaments helps cosmologists correct for their gravitational influence on key observations (CMB data, galaxy bulk flows) and move toward more precise measures of the universe’s composition and expansion.
Quipu’s discovery also opens new opportunities to study galaxy evolution in dense filamentary corridors. Future targeted observations of galaxies embedded in Quipu will test how superstructure environments might accelerate galaxy mergers, quench star formation, or feed supermassive black holes. Finally, detailed comparisons of Quipu’s properties with simulations could help validate or fine-tune cosmological models — showing how synergy between X-ray surveys and advanced data analysis can continue to unveil the grand design of the cosmos.
