There never was a hole in outer space

May 15, 2008 07:50 GMT  ·  By
False color microwave image of the giant cold spot found by the WMAP spacecraft last year
   False color microwave image of the giant cold spot found by the WMAP spacecraft last year

In November last year astronomers reported having discovered a large cold spot in the CMB radiation, coinciding with a void about one billion light years across in the Eridanus constellation, the biggest void in cosmos, or the hole in outer space as some named it. According to calculations, the respective volume of space presents about 20 to 45 percent less matter than the surrounding areas and could be either a texture or evidence of the existence of a parallel universe.

However, what was there only a couple of months ago seems to have disappeared now and it might have been nothing more than the result of a statistical error. Said "hole in outer space" was discovered with the help of the Wilkinson Microwave Anisotropy Probe by Lawrence Rudnick from the University of Minnesota. The WMAP spacecraft discovered the giant cold spot while making measurements on the cosmic microwave background, the radiation left behind by the Big Bang event that created the universe. The cold spot was then corroborated to a large void in the Eridanus constellation with the help of the VLA.

Kendrick Smith from the University of Cambridge believes that Rudnick's interpretation that the cold spot in the CMB is devoid of any matter is erroneous. Along with Dragan Huterer from the University of Michigan, Smith showed that the huge void can be considered as a statistical fluke because it had stars both in front of and behind it.

For example, the cold spot in the CMB and the void seen by Rudnick with the help of the Very Large Array telescope may not coincide and could have different centers as well. Furthermore, in order to find the void the Minnesota team would have had to choose an area of space in the cold spot with the fewest galaxies and consider only the ones having certain luminosities.

If the luminosity cut-offs are considered and the research is concentrated on another location of the cold spot, then the void disappears. Smith says that this statistical mistake could in fact have the same signature as a region of space with a high concentration of galaxies.

"I think Smith and Huterer have made a good case that there is no void in the radio data at this location", said theorist David Spergel from the Princeton University, WMAP. The paper produced by Rudnick describing the void, does indeed say that statistical uncertainties have not been accounted for.