The sun has sunspots, which are concentrations of the magnetic field that inhibit convection, resulting in reduced surface temperature compared to the surrounding photosphere. Apparently, there is a similar spot within the universe which is about 1.8 billion light years across and is located around three billion light years away from our solar system.
Currently, this is the largest structure we have found in the universe. Little energy emanates from this circular area, which contains about 10,000 fewer galaxies than in other areas of the universe. In effect, it has about 20 percent less matter inside it. This cold spot within our universe has perplexed scientists since 2004, when it was discovered as an anomaly in the otherwise homogenous cosmic microwave background radiation. This cosmic microwave background which can be traced back to the Big Bang is spread evenly throughout our universe except this area, which is about 2.7 degrees K cooler than the average temperature in the universe.
The Milky Way is included in a cluster of galaxies called Laniakea. Due to the uneven distribution of matter just after the Big Bang, the universe has lots of filaments and voids, but this giant void completely dwarfs the scale of all known threads or filaments scientists have seen.
This is an anomaly in the model of an expanding homogenous universe. Scientists followed up with a new survey using the Pan-STARRS telescope to count galaxies in the area and they found a void in the same location where the Planck satellite detected the cold spot.
Scientists at the University of Hawaii at Manoa used several telescopes to create a three-dimensional map of galaxies that were located less than three billion light years away from the spot. This survey located a gigantic void with about 10,000 fewer galaxies than expected. There are other voids in the universe, but this is the largest one discovered to date. This giant void could explain the colder temperature because as light travels across it, it should lose energy. This could also explain why less energy is emanating from that area.
But we still do not know why there are so few galaxies in this area. One theory is that this is the origin of the Big Bang. The Big Bang explosion was so powerful that it blew most of the matter, out of the original entry point, leaving a void. It also may support the theory that the universe is shrinking since it may show a boundary between the expansion of the universe after the Big Bang and the contraction of the universe which followed when matter passed the cold spot boundary.