Astronomers solve 'Cold Spot' mystery

Astronomers may have found an explanation for the existence of the "Cold Spot" which may be "the largest individual structure ever identified by humanity".

In 2004, astronomers examining a map of the radiation leftover from the Big Bang discovered the "Cold Spot" -- a larger-than-expected unusually cold area of the sky.

The physics surrounding the Big Bang theory predicts warmer and cooler spots of various sizes in the infant universe, but a spot this large and this cold was unexpected.

Now, a team of astronomers led by Istvan Szapudi of the institute for astronomy at the University of Hawaii, Manoa, have discovered what might be the largest known structure in the universe that leaves its imprint on cosmic microwave background (CMB) radiation.

If the Cold Spot originated from the Big Bang itself, it could be a rare sign of exotic physics that the standard cosmology (basically, the Big Bang theory and related physics) does not explain.

"If, however, it is caused by a foreground structure between us and the CMB, it would be a sign that there is an extremely rare large-scale structure in the mass distribution of the universe," Szapudi added.

Szapudi's team discovered a large supervoid, a vast region 1.8 billion light-years across, in which the density of galaxies is much lower than usual in the known universe.

The supervoid is only about three billion light-years away from us, a relatively short distance in the cosmic scheme of things.

"While the existence of the supervoid and its expected effect on the CMB do not fully explain the Cold Spot, it is very unlikely that the supervoid and the Cold Spot at the same location are a coincidence," the authors noted.

The team will continue its work using improved data to study the Cold Spot and supervoid.

The study was published in the journal Monthly Notices of the Royal Astronomical Society.