Biggest void in space is 1 billion light years across
by Anil Ananthaswamy
24 August 2007 - Radio astronomers have found the biggest hole ever seen in the universe. The void, which is nearly a billion light years across, is empty of both normal matter and dark matter. The finding challenges theories of large-scale structure formation in the universe.
Lawrence Rudnick and colleagues of the University of Minnesota in Minneapolis, US, stumbled upon the void by accident. Rudnick’s team had been studying data from a survey carried out by the Very Large Array radio telescope in New Mexico, also in the US. “One morning I was a little bored, and said, ‘why don’t I look in the direction of the WMAP cold spot’,” says Rudnick.
The cold spot in question is an unexplained anomaly in the map of the cosmic microwave background (CMB) created by NASA’s WMAP satellite. The photons of the CMB coming from a region of the sky in the direction of the constellation Eridanus are colder than expected.
Rudnick’s team started looking for radio sources such as radio galaxies and quasars in the direction of the cold spot. “Radio sources track the distribution of mass in the universe,” says Rudnick. “They are the signposts for galaxies, clusters of galaxies and dark matter.”…