Plenty of Room to Stretch -The Universe's "Great Void"

Feeling claustrophobic? You have to share this planet with over seven billion people and a far larger number of insects. It's almost as tight in the rest of the solar system, home to ten planets (still clinging to Pluto) and a moon tally that seems to grow annually. By extension, our star has millions of companions in the Milky Way... finally, the Milky Way is just one of the millions of galaxies scattered about the universe. Uncountable asteroids and occasional comets occupy 'empty' spaces in our own system; matter in various forms makes its presence known, on a grand scale, out there in the 'dark reaches of space', as well.

So, is there ever... nothing? In the classic, self-deprecating episodes of Seinfeld wherein Jerry and George create a new show for NBC, they pitch the concept as being about 'nothing'. But the screen wasn't blank, was it? An even better example of harvesting something from nothing is Nicholson Baker's 1995 novel, Room Temperature.

Nothing has just been discovered. A whole lot of nothing.

University of Minnesota astronomers have found an enormous hole in the Universe, nearly a billion light-years across, empty of both normal matter such as stars, galaxies and gas, as well as the mysterious, unseen “dark matter.” While earlier studies have shown holes, or voids, in the large-scale structure of the Universe, this new discovery dwarfs them all.

“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 astronomy professor.

Astronomers have known for years that, on large scales, the Universe has voids largely empty of matter. However, most of these voids are much smaller than the one found by Rudnick and his colleagues. In addition, the number of discovered voids decreases as the size increases.

What they found is not normal, based on either observational studies or on computer simulations of the large-scale evolution of the Universe. Their study of the NVSS data showed a remarkable drop in the number of galaxies in a region of sky in the constellation Eridanus, southwest of Orion.

“We already knew there was something different about this spot in the sky,” Rudnick said. The region had been dubbed the “WMAP Cold Spot,” because it stood out in a map of the Cosmic Microwave Background (CMB) radiation made by the Wilkinson Microwave Anisotopy Probe (WMAP) satellite, launched by NASA in 2001.

The CMB, faint radio waves that are the remnant radiation from the Big Bang, is the earliest “baby picture” available of the Universe. Irregularities in the CMB show structures that existed only a few hundred thousand years after the Big Bang.

The WMAP satellite measured temperature differences in the CMB that are only millionths of a degree. The cold region in Eridanus was discovered in 2004.

Astronomers wondered if the cold spot was intrinsic to the CMB, and thus indicated some structure in the very early Universe, or whether it could be caused by something more nearby through which the CMB had to pass on its way to Earth. Finding the dearth of galaxies in that region by studying NVSS data resolved that question.

“Although our surprising results need independent confirmation, the slightly lower temperature of the CMB in this region appears to be caused by a huge hole devoid of nearly all matter roughly 6-10 billion light-years from Earth,” Rudnick said.

How does a lack of matter cause a lower temperature in the Big Bang’s remnant radiation as seen from Earth.

The answer lies in dark energy, which became a dominant force in the Universe very recently, when the Universe was already three-quarters of the size it is today. Dark energy works opposite gravity and is speeding up the expansion of the Universe. Thanks to dark energy, CMB photons that pass through a large void just before arriving at Earth have less energy than those that pass through an area with a normal distribution of matter in the last leg of their journey.

In a simple expansion of the universe, without dark energy, photons approaching a large mass -- such as a supercluster of galaxies -- pick up energy from its gravity. As they pull away, the gravity saps their energy, and they wind up with the same energy as when they started.

The physical properties of dark energy are unknown, though it is by far the most abundant form of energy in the Universe today. Learning its nature is one of the most fundamental current problems in astrophysics.

You're probably a lot like me, cruising back alleys on the astrophysics side of town, looking for the latest dark energy fix. Word on the street? Nothing is not always what it seems to be. To not be. Is it apples-and-oranges to compare this finding to non-coding DNA, commonly referred to as 'junk DNA'? Things can be detected long before they're solved; things can exist long before they're detectable by present methods.

Besides, even true desolation isn't desolate forever: rumor has it a Starbucks will open soon near the edge of the Eridanus Constellation, just a few hundred light years from something.

Rudnick, along with grad student Shea Brown and associate professor Liliya Williams, also of the University of Minnesota, reported their findings in a paper accepted for publication in the Astrophysical Journal.

by Eric Duby with Casey Kazan. Adapted from a University of Minnesota release.

link:
www.discovermagazine.com

Comments

[jczubach]

you mention 'Dark Energy' as if it is an ' as plain as the nose on your face' fact. restrain yourselves, puhlease! I, for one, am not entirely convinced of this 'fact', as are others. Right up there with String Theory, and other unprovable phenomena. Please preface your comments/opinions appropriately as not to misguide the unwashed masses. Godspeed...

[mindscape]

I have an idea.... What if the void was created by the death of a single galactic core. I bet if you punched in all the numbers into an equation of how much space is crunched and distorted by one galaxy that amount of space would be equal to an amount of space it takes to create a great void.

[mindscape]

I have an idea.... What if the void was created by the death of a single galactic core. I bet if you punched in all the numbers into an equation of how much space is crunched and distorted by one galaxy that amount of space would be equal to an amount of space it takes to create a great void.

[mindscape]

I have an idea.... What if the void was created by the death of a single galactic core. I bet if you punched in all the numbers into an equation of how much space is crunched and distorted by one galaxy that amount of space would be equal to an amount of space it takes to create a great void.