Detection of anisotropic cosmic structures on a gigaparsec scale

Galaxy redshift surveys map the cosmic web and provide a key observational test of whether the Universe becomes statistically homogeneous and isotropic on sufficiently large scales, as assumed by the cosmological principle underpinning the standard cosmological model¹. In this framework, beyond the nonlinear regime of structure formation, inhomogeneous and anisotropic features are expected to fade rapidly, reflecting the near-isotropic primordial density field and its subsequent gravitational evolution. Although supported by the small amplitude of cosmic microwave background anisotropies², this view is increasingly challenged by the complex network of large-scale structures and voids in the galaxy distribution^3-6, as well as by independent probes reporting possible large-scale deviations from statistical homogeneity⁷ and isotropy^8,9. Here we show that the galaxy distribution exhibits persistent anisotropic structures extending to scales on the order of one gigaparsec. Using the Angular Distribution of Pairwise Distances (ADPD)¹⁰, a parameter-free statistic that measures directional correlations, we detect anisotropy signals exceeding those in isotropic controls and geometry-matched ΛCDM mock catalogues with conservative significance greater than 3σ. These results provide direct evidence that directional coherence persists to larger scales than predicted in the standard framework, challenging the assumption of large-scale isotropy. They call for a reassessment of how homogeneity and isotropy are realized in the observed Universe and motivate new tests of cosmological models based on directional statistics.