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Dark Matter Mystery May Soon Be Solved

The hiding spots for the particles making up dark matter are narrowing, and the answer to this cosmic mystery could come within the next three or four years, scientists say.

Image: Astronomers using the W. M. Keck Observatory, the Hubble Space Telescope, and other telescopes on Mauna Kea have studied a giant filament of dark matter in 3D for the first time. Image released Oct. 17. 2012. Credit: Image by ESA; additional elements by K. Teramura, Univ. Hawaii Institute for Astronomy.

Dark matter is an elusive substance that is invisible and almost never detected, except by its gravitational pull. Yet astronomers say it likely makes up a quarter of the entire universe and dwarfs the amount of normal matter (galaxies, stars and planets) out there in space.

Just last week, particle physics discovery from the Large Hadron Collider in Switzerland cast doubt on a theory called supersymmetry, which predicts the existence of particles that are among the leading candidates for dark matter. That finding limited the types of supersymmetric particles that can exist, but didn’t take the supersymmetry explanation off the table completely.

And supersymmetric particles are just one of a number of theorized particles that might account for dark matter. Searches for these and other undiscovered particles have been underway for decades, though none have been detected so far.

“I think we’re looking in enough different ways that unless it’s something that we just haven’t thought of at all yet, it seems to me we’re very likely to find it within the next decade,” said Dan Bauer, a physicist at the Fermi National Accelerator Laboratory in Illinois working on one of the experiments, called CDMS.

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Mystery Glow of Dark Matter Halos Fueled by Extragalactic Stars

Stars ripped from their home galaxies as they collide with other galaxies can get slung into giant invisible cocoons of dark matter, researchers say, which might explain mysterious radiation pervading the sky.

Image: New research from scientists using NASA’s Spitzer Space Telescope suggests that a mysterious infrared glow across our whole sky is coming from stray stars torn from galaxies. This artwork is adapted, in part, from galaxy images obtained from the NASA/ESA Hubble Space Telescope. Credit: NASA/JPL-Caltech

These findings suggest the halos of dark matter surrounding galaxies are not completely dark after all, but contain a small number of stars, investigators added.

In recent decades, satellite telescopes have detected more infrared light emanating from the sky than known galaxies could account for. Scientists had suggested this strange glow might come from sources too dim for observatories to see directly — for instance, the earliest, most distant galaxies. If such primordial galaxies were responsible for this radiation, that might suggest far more of them existed than before thought, potentially radically altering notions of how the cosmos evolved.

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Giant Strand of Elusive Dark Matter Seen in 3D

Astronomers have taken their first 3D look at a gigantic filament of dark matter, an invisible cosmic structure that can only be detected by its gravitational effects it has on its surroundings.

Image: This enormous image shows Hubble’s view of massive galaxy cluster MACS J0717. The large field of view is a combination of 18 separate Hubble images. The location of the dark matter is revealed in a map of the mass in the cluster and surrounding region, shown here in blue. The filament visibly extends out and to the left of the cluster core. Credit: NASA, ESA, Harald Ebeling (University of Hawaii at Manoa) & Jean-Paul Kneib (LAM)

The universe is thought to be structured like a tangled web, with long strings of mostly dark matter intersecting at giant galaxy clusters. Since dark matter cannot be seen directly, these filaments are difficult to observe. But using the Hubble Space Telescope, astronomers have managed to probe one of the elusive cosmic strands in 3D.

The researchers sought out a 60 million light-year strand of dark matter around the massive galaxy cluster MACS J0717. The galaxy cluster is one of the largest yet seen and is about 5.4 billion light-years from Earth.

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Invisible Dark Matter Likely Bountiful Near Sun

The area around our sun is probably rife with dark matter, the pervasive invisible stuff that populates the universe, a new study suggests.

Dark matter is thought to be all around us, making up a large fraction of the mass in the universe. Yet whatever particles compose dark matter interact so rarely with normal matter that we cannot shine light on it nor detect it through any means other than gravity.

While scientists have been fairly sure for decades that dark matter is common in galaxies and clusters of galaxies, experts have been unclear on just how prevalent it is in our immediate cosmic neighborhood.

Some past measurements have suggested the vicinity of our sun is chock-full of dark matter, while a 2011 study with new data predicted a relative dearth of the stuff near us.

Now astronomers have used a new mass-measuring technique to tackle the problem. To test their method, the researchers tried it first on a simulation of our whole galaxy. The results suggested that this and other past methods have been undercounting dark matter, so the team adjusted their technique to correct for the bias.

They then applied their measurement algorithm to real data, using the known positions and velocities of thousands of orange K dwarf stars near the sun to estimate the density of invisible matter nearby.

The new calculation suggests that dark matter almost definitely exists around the sun, and there’s a 90 percent chance it is more abundant than thought.

“If future data confirms this high value, the implications are exciting,” study leader Silvia Garbari of the University of Zurich in Switzerland said in a statement. “It could be the first evidence for a ‘disc’ of dark matter in our galaxy, as recently predicted by theory and numerical simulations of galaxy formation. Or it could be that the dark matter halo of our galaxy is squashed, boosting the local dark matter density.”

The mystery of dark matter could become clear if scientists could finally capture just a tiny bit of it. A number of detectors buried deep underground, in order to shield out all other particles, aim to catch dark matter on the extremely rare occasions dark particles might bump into normal matter particles. One such experiment, called XENON, is buried in Italy, while another, CDMS, is in Minnesota. So far, neither has found a reliable signal of dark matter.

“If dark matter is a fundamental particle, billions of these particles will have passed through your body by the time your finish reading this article,” said the University of Zurich’s George Lake. “Experimental physicists hope to capture just a few of these particles each year in experiments like XENON and CDMS currently in operation. Knowing the local properties of dark matter is the key to revealing just what kind of particle it consists of.”

jtotheizzoe:

Dark Matter and the Phantom Filaments

Sounds like a good band name, eh?

Simulations of how we think the universe is organized, astrophysically speaking, show patterns resembling nodes of clustered galaxies connected by filaments of dense matter. We’ve found plenty of the galaxy clusters, but the filaments have been harder to actually observe. That’s because they are likely made of dark matter, which neither emits or absorbs light (and is therefore invisible to we mere humans).

But scientists may have witnessed the effect of one of these filaments recently, marking the first time that dark matter has been observed connecting galaxy clusters. As Matthew Francis reports:

The researchers used archival data from the 8.2 meter Subaru telescope in Hawaii, which includes visible and infrared observations of the supercluster. These were scanned to look for subtle changes in the light from objects behind the clusters. These can be signs of weak gravitational lensing, which would reveal the distribution of dark matter near the clusters.

Gravitational lensing basically means that something invisible with mass, like dark matter, is bending the light from the cluster of galaxies. So although we can’t see the dark matter, we can see it affecting the light’s path and take a pretty good guess it is there.

I bet these guys wish they hadn’t announced this in the same week as the Higgs boson, but hey … can’t win ‘em all. It gives support to the idea that our universe could be built on enormous webs of dark matter, and where these filaments and strands intersect, there is where gravity pulls galaxies together to form the clusters of stars and visible matter that we see every time we look up at night.

(↬ Ars Technica)

DNA Transforms into Dark Matter Detector

Image: A supercomputer simulation of the Milky Way-size dark matter halo.

Underground experiments costing millions of dollars have still failed to find definite proof of the dark matter that supposedly makes up 90 percent of our Milky Way galaxy. But a much cheaper detector made of DNA could finally come up with the “smoking gun” for dark matter’s existence.

The smoking gun would come from finding both daily and annual changes in the detection of suspected dark matter particles called weakly interacting massive particles (WIMPs) — pattern changes that would fit leading theories about dark matter. Scientists have figured out how thousands of DNA strands can show the direction of incoming WIMPs for the first time, so that they can detect the proposed pattern changes.

“The devil is always in the details and pilot experiments need to be done, but it is possible detectors could be built cost-effectively using known mature DNA manipulation and detection methods,” said Charles Cantor, chief scientific officer of Sequenom, Inc. and co-author of a new paper describing the dark matter detector.

New Research Confirms The Existence of Dark Matter

Image: Don Dixon

Fans of dark matter can rest easy. A study published last month raised eyebrows by suggesting that our cosmic neighbourhood is empty of the extra mass needed to hold the galaxy together. But a re-analysis shows that the dark matter was there all along.

Dark matter is the mysterious, invisible stuff that makes up 83 per cent of the matter in the universe. It is responsible for keeping galaxies from flying apart despite their high spinning speeds, and has aided our understanding of how structures in the universe formed.

The most popular theories say that dark matter is a hitherto undetected particle called a WIMP (weakly interacting massive particle) that is shy of interacting with ordinary matter through any force except gravity.

But several underground detectors waiting for WIMPs have come up empty, or with conflicting results. If the galaxy is so full of dark matter, why hasn’t it shown up yet?

In April, a team led by Christian Moni-Bidin of the University of Concepcion in Chile thought they had a solution: the WIMPs aren’t actually there.

The team tracked the motions of more than 400 stars within 13,000 light years of Earth to estimate the mass of matter – visible and dark – in the sun’s local neighbourhood. They concluded that the mass they found could be explained by the visible matter alone, with no need for dark matter.

But the team made a subtle error, say Jo Bovy and Scott Tremaine of the Institute for Advanced Study in Princeton, New Jersey.

Moni-Bidin and colleagues considered stars whose orbits take them far above or below the Milky Way’s main bright disc, and used the speed at which they orbit the centre of the galaxy to figure out how much of a pull they feel from the nearby mass of stars and dark matter. They assumed that the stars’ speeds would be the same no matter how far they were from the galactic centre. Observations of dust clumps have shown that this assumption is true for young stars orbiting in the galactic disc, which mostly move in a near-perfect circle.

But the stars that orbit high above or far below the disc can’t have circular orbits, Bovy says. The only stars that reach such great heights have been kicked away from the disc by matter in the galaxy’s spiral arms, which sent them on highly elliptical orbits.

Full Article: Crisis averted: Dark matter was there all along

Has Our Galaxy’s Dark Matter Gone Missing?

If a new study is true, then the search for dark matter just got a lot weirder. Our little corner of the Milky Way contains no observable concentration of the mysterious stuff whose gravity binds the galaxy, claims one team of astronomers.

That finding would present a major problem for models of how galaxies form and may undermine the whole notion of dark matter, the researchers claim. But some scientists doubt the reliability of the team’s method for measuring the elusive substance.

“This is not just some piddling little detail,” says Frederic Hessman, an astronomer at the University of Göttingen in Germany who was not involved in the work. “If this is right, it turns everything totally upside-down.” But that’s a big if, says Julio Navarro, an astrophysicist at the University of Victoria in Canada: “The argument is provocative, but it remains inconclusive, in my opinion.”

According to standard cosmology, we should be swimming in dark matter. Measurements of the afterglow of the big bang—the so-called cosmic microwave background—and of the distribution of the galaxies suggest that 85% of all matter in the universe is dark matter. What’s more, decades of astronomical observations show that the stars within galaxies swirl about faster than they could if only the gravity of the others stars were holding them in. In fact, the speed with which the sun goes around the center of our galaxy suggests that dark matter ought to be about as abundant as ordinary matter at our distance from the galactic center, about 27,000 light-years.

But that’s not what Christian Moni Bidin, an astronomer at the University of Concepción in Chile, and colleagues find. Using data gathered with several telescopes, they studied old stars called red giants in a cylindrical region a couple of light-years wide and extending 13,000 light-years above the plane of the galaxy.

Treating the stars a bit like atoms in a gas, researchers assumed that they were trapped in the gravitational “well” of the galaxy. So by studying distributions of the stars’ speeds in three dimensions, they could deduce the well’s shape and hence the total distribution of mass from both dark and ordinary matter along the cylinder. Subtracting the distribution of ordinary matter as determined from star counts would then reveal the distribution of dark matter.

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Galactic Pile-Up Leaves Behind Mysterious Dark Matter Core

Astronomers have found an enormous and strange clump of dark matter left behind following a violent collision of galaxy clusters.

The clump is located in the Abell 520 cluster, a diffuse collection of galaxies located 2.4 billion light-years away in the constellation Orion. The celestial object, sometimes called the Train Wreck cluster, is thought to be the remnant of a chaotic crash between several galaxy clusters.

Galaxy clusters are massive collections containing tens or even thousands of galaxies gravitationally bound together. They contain large amounts of dark matter — a strange form of matter that interacts through gravity but gives off no light — which is thought to provide an anchor attracting visible matter to a specific spot.

A 2007 study of Abell 520 showed that it was mostly typical: Wherever astronomers saw visible matter, they found a large clump of dark matter. But there was one gigantic and perplexing “dark core” that should have attracted large amounts of visible matter yet contained almost no galaxies.

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The Cosmic Web

Image: Miguel A. Aragon Calvo/Julieta Aguilera/Mark SubbaRao/AAAS/Science

Dark matter outweighs visible matter more than 6 to 1, making it a crucial yet invisible galaxy component.

To visualize dark matter’s influence, artists visualized a 240-million-light-year-wide zone of space and depicted the universe’s structure from the Big Bang (left) to the present (right). (The full image is too big to fit in this space, so be sure to view the high-resolution version.)

Orange strings of dark matter coalesce along the edges of 10-million-light-year-wide cosmic voids, giving rise to the filamentous web of galaxies seen in space today. The image won first place in informational graphics.

El Gordo: Massive Galaxy Cluster Caught in Midst of Violent Merger

Tipping the scales at two quadrillion times the mass of the sun, the El Gordo galaxy cluster is the largest, hottest, and most energetic cluster ever seen.

Officially called ACT-CL J0102-4915, astronomers nicknamed the cluster “El Gordo” — meaning the fat one — due to its heft. A large portion of its mass is in the form of dark matter, an invisible material that pervades the universe.

Galaxy clusters are the largest known objects in the universe, occurring when hundreds or even thousands of galaxies come together.

El Gordo is located more than 7 billion light years from Earth. At this distance, the universe was only half its current age, presenting a puzzle for researchers. Could such a massive cluster have formed so early in the universe?

“Although El Gordo is a very rare object, it’s not inconsistent with current formation theories,” said astronomer Jack Hughes of Rutgers University, who presented the giant object Jan. 10 at the [American Astronomical Society](http://aas.org/meetings/aas219) meeting.

Part of the reason for the cluster’s enormous size is that it is was once two separate clusters that are now undergoing a collision. El Gordo has two density peaks, corresponding to the centers of the fuzzy purple blobs in the image above, indicating the locations of the two clusters.

The bluish feature in the center of the picture is a large gas and dust pocket caught at the point of the crash. The wake of this violent impact appears as a hazy tail streaming toward the upper right in the image.

Because dark matter hardly interacts, even with itself, the dark matter halos of the clusters are thought to be essentially collisionless, said Hughes. “They stream through each other,” he said.

It is only the gas and dust of the clusters and interacts, producing tremendous shocks and releasing large amounts of energy.

rhamphotheca:

What is Dark Matter?

by NASA staff

By fitting a theoretical model of the composition of the Universe to the combined set of cosmological observations, scientists have come up with the composition that we described above, ~70% dark energy, ~25% dark matter, ~5% normal matter. What is dark matter?

We are much more certain what dark matter is not than we are what it is. First, it is dark, meaning that it is not in the form of stars and planets that we see. Observations show that there is far too little visible matter in the Universe to make up the 25% required by the observations. Second, it is not in the form of dark clouds of normal matter, matter made up of particles called baryons. We know this because we would be able to detect baryonic clouds by their absorption of radiation passing through them. Third, dark matter is not antimatter, because we do not see the unique gamma rays that are produced when antimatter annihilates with matter. Finally, we can rule out large galaxy-sized black holes on the basis of how many gravitational lenses we see…

(read more: NASA Astrophysics)   

(image: X-ray: NASA/CXC/ITA/INAF/J.Merten et al, Lensing: NASA/STScI; NAOJ/Subaru; ESO/VLT, Optical: NASA/STScI/R.Dupke)

discoverynews:

Vast Web of Dark Matter Mapped

Astronomers have created a vast cosmic map revealing an intricate web of dark matter and galaxies spanning a distance of one billion light-years.

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