A region of the cosmic microwave background emission around the region of the WMAP cold spot (circled). The colours represent very small variations around the average temperature of 2.7 degrees above absolute zero, with blue colours being colder. Photograph: Rudnick/NRAO/AUI/NSF, Nasa
Astronomers have found a disturbing gap in the sky. Well, not disturbing perhaps, just mysterious. Nearly a billion light years across and around 6-10bn light years from Earth, it seems devoid of not only the normal matter that makes up stars and planets, it lacks the unseen "dark matter" too.
"Not only has no one ever found a void this big, but we never even expected to find one this size," said Lawrence Rudnick of the University of Minnesota. His paper describing the findings have been accepted for publication in the Astrophysical Journal.
On the large scale of the universe, astronomers know that there are voids that are empty of all matter - but all those located so far have been much smaller than the one found by Prof Rudnick. The mega-void has been named the "WMAP cold spot", after it stood out in a map of the universe made by the Wilkinson Microwave Anisotropy Probe. This satellite measured the temperature differences in the cosmic microwave background, a remnant of the Big Bang which shows how the universe might have looked, temperature-wise, in its earliest days.
"What we've found is not normal, based on either observational studies or on computer simulations of the large-scale evolution of the Universe," said Liliya Williams, also of the University of Minnesota.
Question is, what caused the void? Any speculation - scientific or spurious - welcome...
