Monday, 27 August 2007
‘Space,is big. Really big. You just won't believe how vastly hugely mindboggingly big it is. I mean you may think it's a long way down the road to the chemist, but that's just peanuts to space.’
(You probably know this already but the distance travelled by light in one year is calculated as being about 5,878,625,373,184 miles)
From the Astrophysical Journal via the BBC
Astronomers have found an enormous void in space that measures nearly a billion light-years across. It is located in the direction of the Eridanus constellation and has been identified in data from a survey of the sky made at radio wavelengths.
Previous sky surveys that have traced the large-scale structure of the nearby Universe have long shown, for example, how the clustering of galaxies is strung into vast filaments and sheets that are separated by great gaps.
But the void discovered by a University of Minnesota team is about 1,000 times the volume of what would be expected in typical cosmic gaps.
"It's hard even for astronomers to picture how big these things are," conceded Minnesota's Professor Lawrence Rudnick.
"If you were to travel at the speed of light, it would take you several years to get to the nearest stars in our own Milky Way galaxy; but if you were to go to this hole and enter one side, you'd have to travel for a billion years before you would get to the other side," he explained.
The void is roughly 6-10 billion light-years away and takes a sizeable chunk out of the visible Universe in its direction.
The finding is said to fit neatly with observations of the Universe's "oldest light" - the Cosmic Microwave Background (CMB) radiation. This is the radiation that comes from just 380,000 years after the Big Bang when the Universe had cooled to such a degree that hydrogen atoms could exist. Before that time, it is believed that the Universe would have been so hot that matter and light would have been "coupled" and that the cosmos would have been opaque.
Today, this light shines at microwave wavelengths of -270C; and observations of the CMB show a particular "cold spot" in the direction of the newly identified void.
The explanation for this may lie with the "dark energy" which is said to be accelerating the expansion of the Universe.
Light particles passing through the void would be expected to lose a little more energy than those passing through space cluttered with matter - if dark energy is stretching the Universe apart at a faster and faster rate.
Scientists refer to this as the Integrated Sachs-Wolfe Effect and a corresponding "warm spot" in the CMB associated with an area of space dominated by a supercluster of galaxies was identified some years ago.
"In essence, this latest study gives us a very elegant demonstration of the existence of dark energy in a way which is very convincing," commented Professor Carlos Frenk, the director of the Institute for Computational Cosmology at Durham University, UK.
"We keep getting evidence for dark energy, this component of the Universe which is so dominant, and yet we still have only a tiny glimmer of what it could be."
The reasons why the void exists are not known.