Discovered in 2004, this strange feature etched into the primordial echo of the Big Bang has been the focus of many hypotheses.Despite some theories that the feature may actually be an error caused by our statistical analysis methods, it was generally thought that the CMB Cold Spot was real.
By constructing a 3-D map of galaxies, the researchers discovered a vast region, only 3 billion light-years away, that has a lower density of galaxies than the rest of the known universe. This supervoid is huge, measuring about 1.8 billion light-years wide. This vast supervoid could therefore be the largest structure ever identified by humanity.
As the CMB radiation encountered the supervoid, the Integrated Sachs-Wolfe (ISW) effect may have altered the characteristics of any radiation traveling through it. As the universe is expanding, the radiation traveling through the supervoid will lose more energy than radiation traveling through ‘normal’ space, manifesting itself as a huge Cold Spot.