Jul 15

Huge New Survey to Shine Light on Dark Matter

Source: ESO Organisation Release eso1528

eso1528aImage credits: Kilo-Degree Survey Collaboration/A. Tudorica & C. Heymans/ESO.

The first results have been released from a major new dark matter survey of the southern skies using ESO’s VLT Survey Telescope (VST) at the Paranal Observatory in Chile. The VST KiDS survey will allow astronomers to make precise measurements of dark matter, the structure of galaxy halos, and the evolution of galaxies and clusters. The first KiDS results show how the characteristics of the observed galaxies are determined by the invisible vast clumps of dark matter surrounding them.(learn more)

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Jul 14

Mystery in the Perseus Cluster

Source: NASA Science News

A mysterious X-ray signal from the Perseus cluster of galaxies, which researchers say cannot be explained by known physics, could be a key clue to the nature of Dark Matter.(learn more)

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Oct 12

Dark Matter Filament Studied in 3D for the First Time Inbox x

Source: ESA/Hubble heic1215

Hubble image of MACS J0717 with mass overlay.
Image credits: NASA, ESA, Harald Ebeling (University of Hawaii at Manoa) & Jean-Paul Kneib (LAM)

Astronomers using the NASA/ESA Hubble Space Telescope have studied a giant filament of dark matter in 3D for the first time. Extending 60 million light-years from one of the most massive galaxy clusters known, the filament is part of the cosmic web that constitutes the large-scale structure of the Universe, and is a leftover of the very first moments after the Big Bang. If the high mass measured for the filament is representative of the rest of the Universe, then these structures may contain more than half of all the mass in the Universe. (read more)

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Jul 12

Dark Galaxies of the Early Universe Spotted for the First Time

Source: ESO Science Release eso1228

Dark galaxies spotted for the first time.
Image credits: ESO, Digitized Sky Survey 2 and S. Cantalupo (UCSC)

For the first time, dark galaxies — an early phase of galaxy formation, predicted by theory but unobserved until now — may have been spotted. These objects are essentially gas-rich galaxies without stars. Using ESO’s Very Large Telescope, an international team thinks they have detected these elusive objects by observing them glowing as they are illuminated by a quasar.(read more)

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Jun 12

Dark Universe mission blueprint complete

Source: ESA

Artist’s impression of Euclid.
Credits: ESA - C. Carreau.

ESA’s Euclid mission to explore the hidden side of the Universe – dark energy and dark matter – reached an important milestone today that will see it head towards full construction. (read more)

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Jun 11

Dark galaxies dominate the Universe

Source: Chandra@University of Texas

Fornax Galaxy.
Image credit: David Malin/ Anglo-Australian Observatory

Astronomical observations show that everything that we have ever seen, including stars and planets, is a small fraction of what there is in the Universe. At least 90% of the Universe is made of something else - of dark matter (DM). We know that it exists only because its gravity pulls on the things we see. But it emits no known form of radiation, so we do not know what it is made of. Many possibilities have been proposed, including elementary particles left over from the Big Bang, underluminous or dead stars, and million-solar-mass black holes. The problem of DM - what it is and how it affects galaxy formation and evolution - is one of the most fundamental puzzles of astronomy.

Smaller galaxies are observed to be more dominated by dark matter. The smallest galaxies known are at least 99 % dark. These galaxies look incredibly gossamer, but they are really like cannonballs: they contain a much higher density of dark matter than do giant galaxies. These galaxies did not know when they formed that we would be able to discover them 10 billion years later only if they managed to hold onto 1 % of their mass in stars. Instead, when their first stars died in supernova explosions, they may in many cases have blown away so much of the remaining gas that too few stars were ever formed for us to find the empty halos that are left.

Smaller galaxies are also more numerous; tiny dSph galaxies outnumber large galaxies like our Milky Way. More of them continue to be discovered; clearly we have not found all of them. Since almost-dark galaxies are the most common ones known, darker galaxies may be more common still. (read source)


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Jun 11

Dark Matter researchers in the dark

Source: University of Chicago

A dark-matter experiment deep in the Soudan mine of Minnesota now has detected a seasonal signal variation similar to one an Italian experiment has been reporting for more than a decade.

The new seasonal variation, recorded by the Coherent Germanium Neutrino Technology (CoGeNT) experiment, is exactly what theoreticians had predicted if dark matter turned out to be what physicists call Weakly Interacting Massive Particles (WIMPs). (read more)

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May 11

New 3-D map of Universe is the best one yet

Source: SPACE.com

Astronomers have created the most complete 3-D map of our local universe, revealing new details about our place in the cosmos. The map shows all visible structures out to about 380 million light-years, which includes about 45,000 of our neighboring galaxies (the diameter of the Milky Way is about 100,000 light-years across).(read more)

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Feb 11

Herschel finds less dark matter but more stars

Source: ESA

This animation shows the distribution of the dark matter, obtained
from a numerical simulation, at a redshift z~2, or when the Universe
was about 3 billion years old.
Credits: The Virgo Consortium/Alexandre Amblard/ESA

ESA’s Herschel space observatory has discovered a population of dust-enshrouded galaxies that do not need as much dark matter as previously thought to collect gas and burst into star formation.(read more)

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Nov 10

Detailed Dark Matter Map Yields Clues to Galaxy Cluster Growth

Credit:Hubble Site News Release STScI-2010-37

Hubble Helps Astronomers Map Dark Matter in Abell 1689. Image credit: HST

Astronomers using NASA's Hubble Space Telescope received a boost from a cosmic magnifying glass to construct one of the sharpest maps of dark matter in the universe. They used Hubble's Advanced Camera for Surveys to chart the invisible matter in the massive galaxy cluster Abell 1689, located 2.2 billion light-years away. The cluster contains about 1,000 galaxies and trillions of stars. Dark matter is an invisible form of matter that accounts for most of the universe's mass. Hubble cannot see the dark matter directly. Astronomers inferred its location by analyzing the effect of gravitational lensing, where light from galaxies behind Abell 1689 is distorted by intervening matter within the cluster.

Researchers used the observed positions of 135 lensed images of 42 background galaxies to calculate the location and amount of dark matter in the cluster. They superimposed a map of these inferred dark matter concentrations, tinted blue, on a Hubble image of the cluster. The new dark matter observations may yield new insights into the role of dark energy in the universe's early formative years. (read more)

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May 10

X-ray Discovery Points to Location of Missing Matter

Source: Chandra X-ray Observatory for NASA by SAO

Credit: Illustration: NASA/CXC/M.Weiss; Spectrum: NASA/CXC/Univ. of California Irvine/T. Fang et al.

Scientists have used NASA's Chandra X-ray Observatory and ESA's XMM-Newton to detect a vast reservoir of gas lying along a wall-shaped structure of galaxies about 400 million light years from Earth. In this artist's impression, a close-up view of the so-called Sculptor Wall is depicted. Spiral and elliptical galaxies are shown in the wall along with the newly detected intergalactic gas, part of the so-called Warm Hot Intergalactic Medium (WHIM), shown in blue. This discovery is the strongest evidence yet that the "missing matter" in the nearby Universe is located in an enormous web of hot, diffuse gas.

The X-ray emission from WHIM in this wall is too faint to be detected, so instead a search was made for absorption of light from a bright background source by the WHIM, using deep observations with Chandra and XMM. This background source is a rapidly growing supermassive black hole located far beyond the wall at a distance of about two billion light years. This is shown in the illustration as a star-like source, with light traveling through the Sculptor Wall towards the Earth. The relative location of the background source, the Sculptor Wall, and the Milky Way galaxy are shown in a separate plot, where the view instead looks down on the source and the Wall from above.

An X-ray spectrum of the background source is given in the inset, where the yellow points show the Chandra data and the red line shows the best model for the spectrum after including all of the Chandra and XMM data. The dip in X-rays towards the right side of the spectrum corresponds to absorption by oxygen atoms in the WHIM contained in the Sculptor Wall. The characteristics of the absorption are consistent with the distance of the Sculptor Wall as well as the predicted temperature and density of the WHIM. This result gives scientists confidence that the WHIM will also be found in other large-scale structures.

This result supports predictions that about half of the normal matter in the local Universe is found in a web of hot, diffuse gas composed of the WHIM. Normal matter — which is different from dark matter -- is composed of the particles, such as protons and electrons, that are found on the Earth, in stars, gas, and so on. A variety of measurements have provided a good estimate of the amount of this "normal matter" present when the Universe was only a few billion years old. However, an inventory of the nearby Universe has turned up only about half as much normal matter, an embarrassingly large shortfall. (read more)

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Mar 10

Seeking Dark Matter on a Desktop

Source: Space Daily

Desktop experiments could point the way to dark matter discovery, complementing grand astronomical searches and deep underground observations. According to recent theoretical results, small blocks of matter on a tabletop could reveal elusive properties of the as-yet-unidentified dark matter particles that make up a quarter of the universe, potentially making future large-scale searches easier.(read more)

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Mar 10

Dark Matter still in the darkness

Source: University of Florida

Physicists may have glimpsed a particle that is a leading candidate for mysterious dark matter but say conclusive evidence remains elusive.

A 9-year search from a unique observatory in an old iron mine 2,000 feet underground has yielded two possible detections of weakly interacting massive particles, or WIMPs. But physicists, who include two University of Florida researchers, say there is about a one in four chance that the detections were merely background noise — meaning that a worldwide hunt involving at least two dozen different observatories and hundreds of scientists will continue. (read more)

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Feb 10

XMM-Newton traces dark matter in faint, distant galaxy groups

Source: ESA

X-ray emission in the COSMOS field. Credit: ESA

Observations of faint and distant galaxy groups made with the European Space Agency's XMM-Newton observatory have been used to probe the evolution of dark matter. The results of the study are reported in the 20 January issue of The Astrophysical Journal. (read more)

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Jan 10

Neutralino dark matter stars can not exist

Source: arXiv

Dark matter "clumping" together over time confirming  theories
of how structure formed in our evolving universe.
Credit: NASA, ESA, CalTech

Recent observational data gives an indication that the universe contains a significant fraction (22%) of dark matter whose origin is still unclear. A possible solution to this problem comes from supersymmetric (SUSY) models in the form of neutralino. Neutralino is the lightest supersymmetric partner in SUSY, with the mass of about 100GeV, and is stable. It interacts with the gravitational and weak interactions only, which indicates that it is ”dark”. Weak interactions and neutralino mass are sufficient to satisfy the relic density needed to explain the observed portion of the dark matter in the universe.

Recently a group of astronomers has obtained a detailed distribution of dark matter as a function of the redshift in a part of our universe. Their observations indicate that dark matter plays a role of a scaffolding upon which ordinary matter builds structures. However, the observations show that large pockets with only dark matter (and no ordinary matter) also exist.

De-Chang Dai and Dejan Stojkovic of HEPCOS, Department of Physics, SUNY at Buffalo, have researched the question that arises from the existence of these large pockets of dark matter that is whether compact objects like planets, stars or maybe even large may or not exist.
They concluded that, a stable neutralino star can not exist and also estimated that a stable star can not contain more than a few percents of neutralinos. This information has been published in  the Journal of High Energy Physics (JHEP)(read more)

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