Washington, May 15 : The re-examination of a giant hole in the cosmos that shocked astrophysicists last year has indicated that the hole might not exist after all.
Lawrence Rudnick and colleagues at the University of Minnesota in Minneapolis first spotted the apparent void after detecting a cold spot in the cosmic microwave background measured by the WMAP (Wilkinson Microwave Anisotropy Probe) spacecraft.
Rudnick used data from the Very Large Array telescope at the National Radio Astronomy Observatory near Socorro, New Mexico, to study the area and concluded that the cold spot coincided with a void almost 1 billion light years across, the largest anyone had ever seen.
The story grabbed headlines and it was determined that if the void were real, astronomers would need to rewrite their theories of structure formation in the universe.
Some astrophysicists had even claimed it was the unmistakable imprint of another universe.
But, a new analysis by Kendrick Smith, an astronomer at the University of Cambridge, and Dragan Huterer of the University of Michigan, casts doubt on Rudnick's conclusion.
According to them, the 'void', which supposedly contained far fewer stars and galaxies than expected, could be nothing but a statistical artefact.
Because there will always be some stars in front of it and behind it, a void cannot be seen with the naked eye, so must be inferred statistically, they said.
Smith and Huterer raise doubts about the statistics on two fronts.
First, they say the cold spot and the alleged void don't coincide exactly but have different centres. Second, according to Smith, the Minnesota group had to make a particular set of choices to "see" the void - they focused on the portion of the cold spot with the fewest galaxies and counted only galaxies above a certain luminosity.
"Make equally valid though different choices regarding the luminosity cut-off and the portion of the cold spot to concentrate on, and the void disappears entirely," said Smith. "It is even possible to find a region with an overabundance of galaxies within the cold spot with the same degree of statistical significance," he added.
According to WMAP theorist David Spergel of Princeton University, "I think Smith and Huterer have made a good case that there is no void in the radio data at this location."