When astronomers started studying a map of the cosmic microwave background radiation (CMB or CMBR), the residue of the earliest stages of the universe, they found what was called the Cold Spot. That’s a huge area colder than expected which could be the largest single cosmic structure never identified. According to an international team of scientists consists of a cosmic supervoid which about 1.8 billion light years across.

The Cold Spot was identified thanks to the map created usind data from NASA’s space probe WMAP (Wilkinson Microwave Anisotropy Probe) and from the beginning the discussion started about its nature. The most accurate map created later thanks to the Planck Surveyor satellite confirmed its existence, proving that it wasn’t a mistake due to problems in the WMAP probe or in analysis models used with the data it collected.

Now the results of a research on the Cold Spot were published in the journal “Monthly Notices of the Royal Astronomical Society”. An international team led by Dr. István Szapudi of the University of Hawaii at Manoa used the data obtained with Hawaii’s Pan-STARRS1 (PS1) telescope located on Haleakala, Maui, and NASA’s WISE satellite to identify a cosmic supervoid.

This supervoid is about 3 billion light years from Earth. This is a relatively small distance for the standard of this type of astronomical research and this makes its observation more difficult. This may sound strange but that’s due to the fact that maps of larger areas of the sky are needed to to examine closer structures.

This study of the Cold Spot used huge three-dimensional maps made using data from PS1 and WISE by Andràs Kovàcs of Eötvös Loránd University in Budapest, Hungary. In that enormous area the density of galaxies is much lower than the average of the universe.

This ​​anomalous area of the cosmos has an effect on the cosmic microwave background radiation, precisely the slightly lower temperature. Technically it’s called the integrated Sachs-Wolfe effect. To understand it you can use a comparison with a hill that the light climbs and then descend on the other side.

If the expansion of the universe wasn’t accelerating, the supervoid wouldn’t evolve significantly so the light would descend gaining the energy lost during its climb. Hosever, because the expansion accelerates, the hill gets stretched as the light passes through it becoming flatter. The consequence is that the light can’t regain the energy lost when it entered the supervoid. It comes out from the supervoid with less energy, which means with a wavelength longer corresponding to a lower temperature.

The explanation of the Cold Spot isn’t yet complete but the presence of the supervoid and its effects on the cosmic microwave background radiation in the same area of ​​the universe would be a really incredible coincidence. The team of scientists will continue the research using new data collected in the meantime, also from the Dark Energy Survey, including another big void near the constellation Draco.

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