DescriptionDescription

Hercules Corona Borealis Great Wall. The Hercules Corona Borealis Great Wall is like a dragon. The Hercules–Corona Borealis Great Wall (HCB) or simply the Great Wall is a galaxy filament that is the largest known structure in the observable universe, measuring approximately 10 billion light-years in length (the observable universe is about 93 billion light-years in diameter). This massive superstructure is a region of the sky seen in the data set mapping of gamma-ray bursts (GRBs) that has been found to have a concentration of similarly distanced GRBs that is unusually higher than the expected average distribution. It was discovered in early November 2013 by a team of American and Hungarian astronomers led by István Horváth, Jon Hakkila and Zsolt Bagoly while analyzing data from the Swift Gamma-Ray Burst Mission, together with other data from ground-based telescopes. It is the largest known formation in the universe, exceeding the size of the Huge-LQG by about a factor of two. The overdensity lies at the Second, Third and Fourth Galactic Quadrants (NGQ2, NGQ3 and NGQ4) of the sky. Thus, it lies in the Northern Hemisphere, centered on the border of the constellations Draco and Hercules. The entire clustering consists of around 19 GRBs with the redshift ranges between 1.6 and 2.1. Typically, the distribution of GRBs in the universe appears in the sets of less than the 2σ distribution, or with less than two GRBs in the average data of the point-radius system.[clarification needed] One possible explanation of this concentration is the Hercules–Corona Borealis Great Wall. The wall has a mean size in excess of 2 billion to 3 billion parsecs (6 to 10 billion light-years). Such a supercluster can explain the significant distribution of GRBs because of its tie to star formation. Doubt has been placed on the existence of the structure in other studies, positing that the structure was found through biases in certain statistical tests, without considering the full effects of extinction. A 2020 paper (by the original group of discoverers and others) says that their analysis of the most reliable current dataset supports the structure's existence, but that the THESEUS satellite will be needed to decide the question conclusively.

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