In 2004, astronomers examining a map of the radiation leftover from the Big Bang (the cosmic microwave background, or CMB) 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.
A mysterious large structure
Now, a team of astronomers led by Astronomer István Szapudi of the Institute for Astronomy at the University of Hawaiʻi at Mānoa may have found an explanation for the existence of the Cold Spot, which Szapudi says may be “the largest individual structure ever identified by humanity.”
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 Earth and the CMB, it would be a sign that there is an extremely rare large-scale structure in the mass distribution of the universe.
Using data from Hawaiʻi’s Pan-STARRS1 (PS1) telescope located on Haleakalā, Maui, and NASA’s Wide Field Survey Explorer (WISE) satellite, 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.
Not a coincidence
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 team will continue its work using improved data from PS1 and from the Dark Energy Survey being conducted with a telescope in Chile to study the Cold Spot and supervoid, as well as another large void located near the constellation Draco.
The study is being published online on April 20 in Monthly Notices of the Royal Astronomical Society by the Oxford University Press. In addition to Szapudi, researchers who contributed to this study include András Kovács, (Eötvös Loránd University, Hungary), UH Mānoa alumnus Benjamin Granett (now at the National Institute for Astrophysics, Italy), Zsolt Frei (Eötvös Loránd University) and Joseph Silk (Johns Hopkins).
—By Louise Good