Scientists have discovered an inconceivably massive hole 1.8 billion light years across in deep space. They say the ‘Supervoid’ is the largest known structure in the Universe. Shaped like a spherical blob, it is distinguished by its mysterious emptiness.
Astronomers examining a map of the cosmic microwave background or CMB (radiation leftover from the Big Bang) discovered the Cold Spot, a very large and unusually cold area of the sky.
According to theories surrounding the Big Bang, the infant universe had warmer and cooler spots of various sizes. However, a spot this large and so cold was unexpected.
The ‘Cold Spot’ area is located in the constellation Eridanus in the southern galactic hemisphere. (Credit: ESA Planck Collaboration)
Now, Dr. Istvan Szapudi, of the Institute for Astronomy at the University of Hawaii at Manoa, and colleagues believe they can explain the existence of the Cold Spot.
The astronomers wrote about their findings in the academic journal Monthly Notices of the Royal Astronomical Society (citation below).
If the Cold Spot or Supervoid originated from the Big Bang itself, it might be a rare sign of exotic physics that the Big Bang theory and related physics fails to explain.
Rare ultra-large structure
If, on the other hand, it is caused by a foreground structure between the CMB and us, it would be a sign that there is a very rare, incredibly large structure in the mass distribution of the universe.
Dr. Szapudi and team found that the density of the galaxies in this supervoid is much lower than usual in the known universe after analyzing data from the WISE (Wide Field Survey Explorer) satellite and Hawaii’s PS1 (Pan-STARRS1) telescope.
The supervoid was found by combining observations taken by WISE at infrared wavelengths with PS1’s optical wavelength observations to estimate the distance to and positon of each galaxy in that part of the sky.
Previous studies, also carried out in Hawaii, spotted a much smaller area in the direction of the Cold Spot, but the researchers could establish only that no very distant structure is in that part of the sky.
Harder to detect larger structures
Funnily enough, detecting nearby large structures is more difficult than finding faraway ones, since we must map larger portions of the sky to see the nearer structures. The large 3-D sky maps created from WISE and PS1 by Dr. András Kovács, who works at Eötvös Loránd University, Budapest, Hungary, were thus vital for this study.
The supervoid is about 3 billion light years from Earth, which the authors say is a relatively short distance “in the cosmic scheme of things.”
“Imagine there is a huge void with very little matter between you (the observer) and the CMB. Now think of the void as a hill. As the light enters the void, it must climb this hill. If the universe were not undergoing accelerating expansion, then the void would not evolve significantly, and light would descend the hill and regain the energy it lost as it exits the void.”
“But with the accelerating expansion, the hill is measurably stretched as the light is traveling over it. By the time the light descends the hill, the hill has gotten flatter than when the light entered, so the light cannot pick up all the energy it lost upon entering the void. The light exits the void with less energy, and therefore at a longer wavelength, which corresponds to a colder temperature.”
It can take millions of years to get through the supervoid, even at light speed, so this measurable effect, known as ISW (Integrated Sachs-Wolfe), may provide the first explanation for one of the most significant abnormalities found so far in the CMB, first by the WMAP (Wilkinson Microwave Anisotropy Probe), a NASA satellite, and more recently, by the Planck European Space Agency satellite.
The authors wrote:
“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.”
Citation: “Detection of a supervoid aligned with the cold spot of the cosmic microwave background,” István Szapudi, András Kovács, Benjamin R. Granett, Zsolt Frei, Joseph Silk, Will Burgett, Shaun Cole, Peter W. Draper, Daniel J. Farrow, Nicholas Kaiser, Eugene A. Magnier, Nigel Metcalfe, Jeffrey S. Morgan, Paul Price, John Tonry and Richard Wainscoat. Monthly Notices of the Royal Astronomical Society. First published online 19 April, 2015. DOI: 10.1093/mnras/stv488.