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Topic: Biggest void in space is 1 billion light years across. (Read 981 times) |
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Fox
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Biggest void in space is 1 billion light years across.
« on: 2007-09-14 17:17:39 » |
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I thought this was worth posting, as I'm curious to see whether this could really challange our current and accepted ways of thinking on universal formation. After all, this is one hell of a huge void!
Biggest void in space is 1 billion light years across
Source: NewScientistSpace
Author: Anil Ananthaswamy
Date: 24 August 2007
The biggest known hole in the universe has left a cold-spot in the cosmic microwave radiation (Illustration: Bill Saxton, NRAO/AUI/NSF, NASA)
Radio astronomers have found the biggest hole ever seen in the universe. The void, which is nearly a billion light years across, is empty of both normal matter and dark matter. The finding challenges theories of large-scale structure formation in the universe.
Lawrence Rudnick and colleagues of the University of Minnesota in Minneapolis, US, stumbled upon the void by accident. Rudnick’s team had been studying data from a survey carried out by the Very Large Array radio telescope in New Mexico, also in the US. "One morning I was a little bored, and said, 'why don’t I look in the direction of the WMAP cold spot’," says Rudnick.
The cold spot in question is an unexplained anomaly in the map of the cosmic microwave background (CMB) created by NASA’s WMAP satellite. The photons of the CMB coming from a region of the sky in the direction of the constellation Eridanus are colder than expected.
Rudnick’s team started looking for radio sources such as radio galaxies and quasars in the direction of the cold spot. "Radio sources track the distribution of mass in the universe," says Rudnick. "They are the signposts for galaxies, clusters of galaxies and dark matter."
Unexpected size
The team was in for a surprise. They saw little or no radio sources in a volume that is about 280 megaparsecs or nearly a billion light years in diameter. The lack of radio sources means that there are no galaxies or clusters in that volume, and the fact that the CMB is cold there suggests the region lacks dark matter, too.
The void, which is about 6 billion to 10 billion light years away, is considerably larger than any found before. Until now, optical surveys have found no voids larger than 80 megaparsecs wide – making the new hole 40 times larger in volume than the previous record holder.
Rudnick says that these optical surveys could easily miss the void his team found simply because they don’t study large enough volumes.
He thinks that the void is a confirmation that dark energy is at work in the universe. Normally, when the CMB photons pass through a gravitational well, created say, by a supercluster of galaxies, they first gain energy as they fall into the well, then lose energy as they climb out.
Problem poser
If the expansion of the universe is accelerating due to dark energy, then by the time the photons climb out, the supercluster has expanded, and its gravity is a little less strong. So the photons exit relatively easily and with more energy than they had when they entered the gravitational well.
But photons going through a void actually lose energy, ending up colder than if they had been flying through a series of superclusters. Rudnick thinks that the discovery of the void ties in neatly with the WMAP cold spot and the existence of dark energy. "What the community says remains to be seen," he told New Scientist. "People will take shots at it now."
Because the CMB is leftover radiation from the big bang, some cosmologists have said that the cold spot is a problem for the theories of the early universe. But Rudnick says that the void could have been created billions of years after the big bang. "We have taken the problem away from the very early universe and put the problem in the time of structure formation," he says.
Computer simulations that recreate the formation of clusters and super-clusters have never seen voids of this size. That could be because modellers have not simulated large enough volumes to see such a void, says Rudnick. If they did, maybe a void would emerge. "It is an open question whether this will create problems for structure formation," he says.
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Walter Watts
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Just when I thought I was out-they pull me back in
 
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Re:Biggest void in space is 1 billion light years across.
« Reply #1 on: 2007-09-14 20:49:59 » |
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I did a bit of Googling around and this looks like a good place to start for an
explanation of that rather large empty spot.
http://tinyurl.com/26xjpa
If the abstract in the above link looks relevant to our "quest", the entire treatise can be found at:
http://arxiv.org/abs/hep-th/0306071
Also, several questions should be asked first:
1) Is it really relatively devoid of both normal and dark matter?
2) Is it a statistically significant void relative to the CMB radiation profile of the immediate region if it in fact "looks" relatively void?
3) Are there large areas of particularly high density (multiple galaxies and/or black holes) in neighboring regions that might balance the void on larger scales?
4) etc., etc.
Walter
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Walter Watts
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No one gets to see the Wizard! Not nobody! Not no how!
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Blunderov
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"We think in generalities, we live in details"
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Re:Biggest void in space is 1 billion light years across.
« Reply #2 on: 2007-10-26 02:43:16 » |
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[Blunderov] It seems even the bits that look empty are "ontologically active"  And aren't phase transitions interesting...?
http://www.sciencedaily.com/releases/2007/10/071025143314.htm
Possible Cosmic Defect, Remnant From Big Bang, Discovered
ScienceDaily (Oct. 26, 2007) — Scientists from the Institute of Physics of Cantabria (IFCA) and the University of Cambridge may have discovered an example of a cosmic defect, a remnant from the Big Bang called a texture. If confirmed, their discovery, reported in Science, will provide dramatic new insight into how the universe evolved following the Big Bang.
Textures are defects in the structure of the vacuum left over from the hot early universe. Professor Neil Turok of Cambridge's Department of Applied Mathematics and Theoretical Physics first showed how textures form in the 1990s, highlighting that some would survive from the Big Bang and should be visible in today's universe. Textures can be observed by the hot and cold spots they create in the cosmic microwave background radiation (CMB) which fills the universe and was released in the Big Bang 14 billion years ago.
The Big Bang theory proposes that the cosmos began in a very high density, high temperature state, cooling as it expands. In the early hot universe, physicists believe that the different types of elementary particle (particles such as a quark from which larger particles are created) behaved identically. As the universe cooled, the vacuum changed and the symmetry between the particles was broken, in a phase transition analogous to the freezing of water. During this kind of phase transition, quarks become distinct from electrons and neutrinos, for example.
Just as misalignments in the crystalline structure of ice lead to defects, misalignments in the symmetry-breaking pattern form cosmic defects. Textures, such as the one which may have been discovered, are one type of defect.
Professor Turok provides the following analogy: "Imagine a large crowd of people with everyone standing. To any person in it, the crowd looks roughly the same in all directions. Now tell them all to lie down. People would tend to lie in the same direction as their neighbours, but over large distances the direction chosen would vary. In some places, people would be unable to decide which was the best direction to lie in: if everyone lies down pointing directly away from you, you are forced to stand. You are now a defect in the symmetry, a texture."
It is believed that textures collapse and unwind on progressively larger scales, creating intense energy as well as gravitational potential. This unwinding also creates areas of extreme cold or hot, such as the very cold spot in the South Galactic Hemisphere discovered by the IFCA team in 2004.
Marcos Cruz and his colleagues, Dr. Patricio Vielva and Professor Enrique Martínez-González with the IFCA, pursued numerous possibilities for the existence of the cold spot. In particular, they thoroughly explored the possibility of being due to systematic effects, foreground contamination from our own galaxy or due to the scattering of cosmic microwave background radiation by large galaxy clusters.
Each time they came to the same conclusion: there were not any convincing arguments for any of these possibilities. They also hypothesised that it could be a texture and with the assistance of Dr Mike Hobson, a member of the Astrophysics Group at Cambridge's Cavendish Laboratory, and Professor Neil Turok, they were able to examine this possibility in detail.
Professor Turok performed large scale simulations using the COSMOS supercomputer at Cambridge to more accurately compare the theory with the event. Dr Hobson ranked the relative probabilities that the cold spot is due to a texture rather than just an extreme statistical fluctuation. The researchers concluded that the texture hypothesis is the most plausible explanation for the cold spot but acknowledge that additional tests are necessary.
"The possibility that this is a texture is very exciting," said Professor Turok. "If it is, it will revolutionise our understanding of how the fundamental symmetries between the particles and forces were broken as the universe emerged from the big bang. The current data is suggestive but not yet compelling. There are a number of follow-up tests which can be made with future data. It's a very testable hypothesis and we will know the answer within the next decade."
Dr Hobson said: "The prominent cold spot in the image of the cosmic microwave background taken by the WMAP satellite is a very puzzling feature that has attracted a lot of attention in the cosmological community, but has not as yet been convincingly explained.
"Our work investigates the exciting possibility that the cold spot is due to the presence of a cosmic texture; some current particle physics theories predict textures to be produced as the universe evolves, but they had never been observed. Somewhat to our surprise, we found that the cold spot, and in fact the cosmic microwave background radiation over the whole sky, is indeed consistent with such a texture model. Although the current data are not yet compelling, we suggest future observations that should be able to test our hypothesis definitively. If the cold spot is indeed proven to be a texture it will completely change our view of how the universe evolved following the Big Bang."
Reference: "A Feature in the Cosmic Background Radiation Consistent with a Cosmic Texture," by M. Cruz, P. Vielva and E. Martínez-González of the Instituto de Física de Cantabria (CSIC, Univ. Cantabria) , in Santander, Spain; N. Turok of the University of Cambridge in Cambridge, UK; and M. Hobson of Cavendish Laboratory in Cambridge, UK, Science, October 25, 2007. This research was supported by the Spanish National Research Council (CSIC) and the Ministerio de Educación y Ciencia.
Adapted from materials provided by University of Cambridge
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