Plenty of nothing - August 24, 2007
A “giant hole” in the universe has been discovered by astronomers from Minnesota. Investigating an area of the sky known as the WMAP Cold Spot, Lawrence Rudnick and colleagues found a void empty of stars, gas and even dark matter (press release). As AP’s widely circulating report notes, the hole is big: an “expanse of nearly 6 billion trillion miles of emptiness” (AP, and the same version with a much better headline from the San Diego Union Tribune). "Not only has no one ever found a void this big, but we never even expected to find one this size," said Rudnick.
Astronomers have long known that there are big voids in the universe, and think they can explain them with their theories as to how large scale structures first formed. But those theories are hard put to describe a void quite this big. Either it’s a statistical fluke or something is wrong with our current understanding. "What we've found is not normal, based on either observational studies or on computer simulations of the large-scale evolution of the Universe," Williams said (Reuters and the press release).
Using data that imaged the entire sky visible to the Very Large Array radio telescope Rudnick found a drop in the number of galaxies in one region. The region was already thought to be a bit odd because of the way it stands out as a hole in a map of background radiation left over from the Big Bang. This new study shows that this "WMAP cold spot" is not just intrinsic to this background radiation. "Although our surprising results need independent confirmation, the slightly colder temperature of the CMB in this region appears to be caused by a huge hole devoid of nearly all matter roughly 6-10 billion light-years from Earth," Rudnick said in the press release.
Image: Cold spot in Cosmic Microwave Background (left) and reduction in emission from radio galaxies (right) / Rudnick et al., NRAO/AUI/NSF, NASA
