A vast hole in the universe has only just been spotted by astronomers – despite the fact that it is nearly a billion light years wide. The cosmic chasm is completely empty of stars, galaxies, dust and even that mysterious, invisible stuff called dark matter.
The hole is so vast that a ray of light, travelling at 186,300 miles per second, would take nearly a billion years to cross it.
American astronomers found the empty patch by studying images produced by radio telescopes in a survey of the entire sky. The pictures indicated a remarkable drop in the number of galaxies within the constellation of Eridanus, the River.
Co-discoverer Lawrence Rudnick, of the University of Minnesota, said: “Not only has no one ever found a void this big, but we never even expected to find one this size.”
Colleague Liliya Williams said: “What we’ve found is not normal, based on either observational studies or on computer simulations of the large-scale evolution of the Universe.”
The astronomers’ attention was first drawn to the region because it was dubbed a “cold spot” in a previous mapping of radiation left over from the Big Bang that created the universe.
This map of the Cosmic Wave Background was produced by Nasa’s Wilkinson Microwave Anisotopy Probe satellite, launched in 2001. The cold spot, with temperature differences of only millionths of a degree, was noticed in 2004.
Now observations have shown that the coldness is due to it being completely empty of stars and galaxies.
Rudnick said: “The slightly colder temperature of the CMB in this region appears to be caused by a huge hole devoid of nearly all matter roughly six to ten billion light-years from Earth.”
The survey used by the team was made by the Very Large Array of radio telescopes which mapped 82 per cent of the sky from New Mexico. The discovery will be reported in the Astrophysical Journal.
The rather inventive illustration shows the hole left as the cosmic radiation expends, plus the satellite and radio telescopes used to make the discovery. Credit: Bill Saxton, NRAO/AUI/NSF, Nasa.
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