What is Hercules–Corona Borealis Great Wall?
[[File:Hubble image of MACS J0717 with mass overlay.jpg|thumb|right|A massive galaxy cluster named MACS J0717.5+3745, which may be similar to the Hercules–Corona Borealis Great Wall.]] The '''Hercules–Corona Borealis Great Wall''' is the largest known superstructure in the [[universe]]. It is a huge group of galaxies forming a giant sheet-like pattern which is about 10 [[billion]] light-years long, 7.2 billion light-years wide, and almost 1 billion light-years thick. It is about 10 billion light-years away in the [[constellation]]s of [[Hercules (constellation)|Hercules]] and [[Corona Borealis]], hence its name. It was discovered in November 2013 by mapping [[gamma-ray bursts]].<ref>Clowes, Roger ''et al'' 2012. A structure in the early Universe at z ∼ 1.3 that exceeds the homogeneity scale of the R-W concordance cosmology. ''Monthly Notices of the Royal Astronomical Society''. '''1211''' (4): 6256. [http://mnras.oxfordjournals.org/content/early/2013/01/07/mnras.sts497.full]</ref> They are very luminous explosions of distant, massive stars, the most powerful explosions in the universe. A typical burst releases more energy in less than a tenth of a second than the [[Sun]] will in its whole life of 10 billion years. Gamma-ray bursts are very rare: only one happens in a typical galaxy every few million years. The stars which cause these explosions are very massive, so the material required for them to be formed must be in great amounts. So, these explosions can be used to track down if there is a galaxy in that direction, or there is a large group of [[matter]] in there. Between the years of 1997 to 2012, astronomers mapped these bursts in the sky, with the help of the robotic satellites Swift and Fermi which look for gamma-ray bursts and measure their redshifts. In the map they produced, they noticed something interesting; 14 gamma-ray bursts have very similar redshifts and are very close to each other. This means that there is a very large group of galaxies and matter in the region. They say, measuring th