The clustering of gamma-ray bursts in the Hercules–Corona Borealis Great Wall: the largest structure in the Universe?

Abstract

The Hercules–Corona Borealis Great Wall is a statistically significant clustering of gamma-ray bursts (GRBs) around redshift 2. Motivated by recent theoretical results indicating that a maximal Universal structure size may indeed coincide with its estimated size (2–3 Gpc), we reexamine the question of this Great Wall’s existence from both observational and theoretical perspectives. Our statistical analyses confirm the clustering’s presence in the most reliable data set currently available, and we present a video showing what this data set looks like in 3D. Cosmological explanations (i.e. having to do with the distribution of gravitating matter) and astrophysical explanations (i.e. having to do with the rate of star formation over cosmic time and space) regarding the origin of such a structure are presented and briefly discussed and the role of observational bias is also discussed at length. This, together with the scientific importance of using GRBs as unique cosmological probes, emphasises the need for future missions such as the THESEUS satellite, which will provide us with unprecedentedly homogeneous data of GRBs with measured redshifts. We conclude from all this that the Hercules–Corona Borealis Great Wall may indeed be the largest structure in the Universe – but to be able to decide conclusively whether it actually exists, we need THESEUS.