Hole in space thought to be a billion light years wide
Tom Spears, CanWest News ServicePublished: Saturday, August 25, 2007
OTTAWA -- Astronomers think they have found the biggest empty hole ever, a region of the universe a billion light-years wide where everything -- stars, dust, even dark matter -- is simply missing.
It's a discovery that lends itself to jokes about your favourite suburb, but Lawrence Rudnick, a University of Minnesota astronomy professor, is serious.
If someone crossed this area in a spacecraft, "travelling at the speed of light it would take about a billion years and there wouldn't be much to see. A pretty boring journey," he said.
Astronomers have known for years there are empty places in the universe, but they never expected one so big.
In our own neighbourhood, there would be hundreds of galaxies in a region this size, each of them holding a few hundred billion stars, as well as immense clouds of dust and gas.
There would also be dark matter -- mysterious stuff we can't see that still has mass, and exerts a gravitational pull.
Signals would be zooming all over the place -- X-rays, visible light, ultraviolet, infrared, all sorts of radio waves.
But when the Minnesota team looked for radio signals coming from this area south of the constellation Orion, there was just a lot of missing signal. As well, there's a spot where the "background" of microwaves from the very early universe is unusually cold, another indication that matter is missing.
He can't say the region is absolutely empty. Matter in this void may be like water in a desert: It's there, but very, very scarce.
But why is the empty space there -- or not there, if you look at it that way?
Through gravity, the astronomer says.
In the very young universe, matter was distributed very evenly all over, he says. "If the universe had stayed that way we wouldn't be here because you wouldn't have stars [or] galaxies if you didn't have clumping of material."
"Gravity makes things clump. But what that means is, it leaves holes behind."
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