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  • richardmitnick 6:25 pm on July 27, 2015 Permalink | Reply
    Tags: , Dark Energy/Dark Matter, , Pions   

    From livescience: “Dark Pion Particles May Explain Universe’s Invisible Matter” 


    July 25, 2015
    Jesse Emspak

    Researchers propose that dark matter is a kind of invisible, intangible version of a pion, or a type of meson — a category of particles made up of quarks and antiquarks.
    Credit: MichaelTaylor

    Dark matter is the mysterious stuff that cosmologists think makes up some 85 percent of all the matter in the universe. A new theory says dark matter might resemble a known particle. If true, that would open up a window onto an invisible, dark matter version of physics.

    The only way dark matter interacts with anything else is via gravity. If you poured dark matter into a bucket, it would go right through it because it doesn’t react to electromagnetism (one reason you can stand on the ground is because the atoms in your feet are repelled by the atoms in the Earth). Nor does dark matter reflect or absorb light. It’s therefore invisible and intangible.

    Scientists were clued into its existence by the way galaxies behaved. The mass of the galaxies calculated from the visible stuff they contained wasn’t enough to keep them bound to each other. Later, observations of gravitational lensing, in which light bends in the presence of gravity fields, showed there was something that made galaxy clusters more massive that couldn’t be seen.

    Invisible pions

    Now, a team of five physicists has proposed that dark matter might be a kind of invisible, intangible version of a pion, a particle that was originally discovered in the 1930s. A pion is a type of meson — a category of particles made up of quarks and antiquarks; neutral pions travel between protons and neutrons and bind them together into atomic nuclei.

    Most proposals about dark matter assume it is made up of particles that don’t interact with each other much — they pass through each other, only gently touching. The name for such particles is weakly interacting massive particles, or WIMPs. Another idea is that dark matter is made up of axions, hypothetical particles that could solve some unanswered questions about the Standard Model of particle physics.

    The Standard Model of elementary particles (more schematic depiction), with the three generations of matter, gauge bosons in the fourth column, and the Higgs boson in the fifth.

    Axions wouldn’t interact strongly with each other, either.

    The new proposal assumes that the dark matter pions interact much more strongly with each other. When the particles touch, they partially annihilate and turn into normal matter. “It’s a SIMP [strongly interacting massive particle],” said Yonit Hochberg, a postdoctoral researcher at Berkeley and lead author on the study. “Strongly interacting with itself.”

    To annihilate into normal matter, the particles must collide in a “three-to-two” pattern, in which three dark matter particles meet. Some of the dark matter “quarks” that make up the particles annihilate and turn into normal matter, leaving some dark matter behind. With this ratio, the result would leave the right proportion of dark matter to normal matter in the current universe.

    This new explanation suggests that in the early universe the dark pions would have collided with each other, reducing the amount of dark matter. But as the universe expanded the particles would collide less and less often, until now, when they are spread so thinly they hardly ever meet at all.

    The interaction bears a close resemblance to what happens to charged pions in nature. These particles consist of an up quark and an anti-down quark. (Quarks come in six flavors, or types: up, down, top, bottom, charm and strange.) When three pions meet, they partially annihilate and become two pions.

    “[The theory] is based on something similar — something that already happens in nature,” said Eric Kuflik, a postdoctoral researcher at Cornell University in New York and a co-author of the study.

    Different kind of pion

    For the new explanation to work, the dark matter pions would have to be made of something different from normal matter. That’s because anything made of normal quarks simply wouldn’t behave the way dark matter does, at least not in the group’s calculations. (There are theories that strange quarks could make up dark matter).

    Charged pions are made up of an up quark and an anti-down quark, or a down and anti-up quark, while neutral pions are made of an up quark plus an anti-up or a down quark plus an anti-down.

    In the new hypothesis, dark matter pions are made up of dark matter quarks that are held together by dark matter gluons. (Ordinary quarks are held together by normal gluons.) The dark quarks wouldn’t be like the familiar six types, and the dark gluon would, unlike ordinary gluons, have mass, according to the mathematics.

    Dark pions and dwarf galaxies

    Another co-author on the paper, Hitoshi Murayama, professor of physics at the University of California, Berkeley, said the new hypothesis would help explain the density of certain kinds of dwarf galaxies. Computer simulations show dwarf galaxies with very dense center regions, but that isn’t what astronomers see in the sky. “If SIMPs are spread out, the distribution is flatter — it works better,” he said.

    Dan Hooper, a staff scientist at Fermi National Accelerator Laboratory in Illinois, said he isn’t quite convinced that this model of dark matter is necessary to explain the dwarf galaxy conundrum. “There’s a handful of people who say dwarfs don’t look like we expect,” he said. “But do you need some other property to solve that? People have showed it could be the heating of gas.” That is, gas heated at the center of a dwarf galaxy would be less dense.

    The Large Hadron Collider might soon offer some insight into which camp is correct; that strange new “dark pions” are dark matter or that they aren’t and there’s something else. Particle accelerators work by taking atomic nuclei — usually hydrogen but sometimes heavier elements like lead —and smashing them together at nearly the speed of light. The resulting explosion scatters new particles, born of the energy of the collision. In that sense the particles are the “shrapnel.”

    Kuflik said that if there’s “missing” mass (more precisely, mass-energy) from the collision of particles that’s a strong pointer to the kind of dark matter that the researchers are looking for. This is because mass and energy are conserved; if the products of a collision don’t tally up to the same amount of mass and energy you started with, that means there might be a previously unknown particle that escaped detection somewhere.

    Such measurements are hard to do, though, so it will take a lot of sifting through data to see if that happens and what the explanation is.

    Another way to track down dark matter particles might be in a detector made with liquid xenon or germanium, in which electrons would occasionally get knocked off an atom by a passing dark matter particle. There’s already an experiment like that, though, the Large Underground Xenon (LUX) project in South Dakota. It didn’t find anything yet, but it was focused on WIMPs (though it was able to rule out some types). A newer version of the experiment is planned; it might detect other kinds of dark matter particle.

    The team is currently working on a paper outlining the kinds of observations that would detect this kind of dark matter. “We’re currently working on writing up explicit ways these dark pions can interact with ordinary matter,” Hochberg said.

    The study appears in the July 10 issue of the journal Physical Review Letters.

    [The article does not include any deatil as to what sort of equipment was used in this work.]

    See the full article here.

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  • richardmitnick 7:18 am on July 24, 2015 Permalink | Reply
    Tags: , , , Dark Energy/Dark Matter   

    From CAASTRO: “Dark matter halo of dwarf galaxies shaped by supernova feedback” 

    CAASTRO bloc

    CAASTRO ARC Centre of Excellence for All Sky Astrophysics

    21 July 2015
    No Writer Credit


    The Cold Dark Matter (CDM) model has proven very successful, however there exists a long standing problem of ubiquitous ‘cusps’ of dark matter halos, i.e. the dark matter distribution sharply increases to a high value at a central point. Significant improvements in the understanding of detailed physical processes of dark and luminous matter on galactic scales have been achieved by observational data from several galaxy surveys in tandem with advances in cosmological hydrodynamic simulations. These have only been tested in a small number of field galaxies though, owing to the lack of high-quality multi-wavelength data and of standardised analysis tools. In order to provide robust observational constraints to dark matter models, we need to extend the investigation to a larger number of galaxies in a more systematic and consistent manner.

    In a new publication, CAASTRO researcher Dr Se-Heon Oh (ICRAR – University of Western Australia) and colleagues present high-resolution (20-300 pc) mass models of 26 dwarf galaxies and discuss the dark matter distributions near their centres, as part of the LITTLE THINGS survey. This is a high-resolution (~6″ angular; < 2.6 km/s velocity resolution) HI 21cm survey of nearby (< 11 Mpc) gas-rich dwarf galaxies undertaken with the NRAO Very Large Array (VLA) in the northern sky.


    In their publication, the team quantified the degree of the central dark matter concentration of the sample galaxies by measuring the logarithmic inner slopes of their dark matter density profiles. The mean value of the inner slopes (-0.32) indicates a mass distribution with a sizeable constant density-core towards the centres of the galaxies. Comparing these observations with latest Lambda CDM simulations of galaxies where realistic baryonic feedback is included, the dark matter cusps of the halos in both samples can effectively be accounted for by supernova (SN) driven gas outflows.

    Some LITTLE THINGS sample galaxies, however, such as DDO 210, DDO 101 and Haro 29, have relatively steeper inner density slopes. According to the latest hydrodynamic simulations, SN feedback in low mass dwarf galaxies of less than 106 solar masses is not sufficient to disrupt the central cusps, largely due to low star formation efficiencies in these systems. Dr Oh and his team have submitted a Gemini observing proposal for spectroscopy of DDO 210’s inner dark matter halo density profile where simulations have predicted primordial CDM cusps to have survived. This will be a fundamental test for the presence or absence of a signature of the central cusp in low mass halos, and whatever the outcome, will inform the debate on the formation process of low-mass galaxies in particular, as well as provide a crucial test to the LCDM.

    See the full article here.

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    Astronomy is entering a golden age, in which we seek to understand the complete evolution of the Universe and its constituents. But the key unsolved questions in astronomy demand entirely new approaches that require enormous data sets covering the entire sky.

    In the last few years, Australia has invested more than $400 million both in innovative wide-field telescopes and in the powerful computers needed to process the resulting torrents of data. Using these new tools, Australia now has the chance to establish itself at the vanguard of the upcoming information revolution centred on all-sky astrophysics.

    CAASTRO has assembled the world-class team who will now lead the flagship scientific experiments on these new wide-field facilities. We will deliver transformational new science by bringing together unique expertise in radio astronomy, optical astronomy, theoretical astrophysics and computation and by coupling all these capabilities to the powerful technology in which Australia has recently invested.


    The University of Sydney
    The University of Western Australia
    The University of Melbourne
    Swinburne University of Technology
    The Australian National University
    Curtin University
    University of Queensland

  • richardmitnick 7:06 am on July 24, 2015 Permalink | Reply
    Tags: , , , Dark Energy/Dark Matter, Shear   

    From CAASTRO: “New trick uses velocity maps to measure weak lensing directly” 

    CAASTRO bloc

    CAASTRO ARC Centre of Excellence for All Sky Astrophysics

    23 July 2015
    No Writer Credit


    Despite dark matter dominating the Universe with 84% of the mass compared to 16% of baryonic matter, it is non-interacting and cannot be measured directly. There are techniques to measure the fraction of the two types of matter but weak gravitational lensing is the only tool available to measure the spatial distribution of dark matter relative to its baryonic counterpart in galaxies, clusters and other structures. Understanding the matter distribution in galaxies is vital for constraining our models of cosmology and for forming a complete picture of galaxy formation and evolution. Current weak lensing techniques require hundreds of galaxies for a single weak lensing measurement, they are insensitive to the shape of the dark matter halo and they are useless for analyses that require individual, direct measurements of the weak lensing distortion, called ‘shear’.

    Our PhD student Catherine de Burgh-Day and her three CAASTRO co-authors from the University of Melbourne and the Australian Astronomical Observatory (AAO) have now developed a technique to directly measure the shear around galaxies with individual measurements: Direct Shear Mapping (DSM). DSM uses velocity maps to measure shear. A velocity map shows the velocity of each part of a galaxy relative to the motion of the centre of the galaxy (which in the galaxy’s frame or reference is stationary). DSM is based on the assumption that a galaxy’s velocity map is symmetrical about the axis of no rotation (i.e. the axis about which the galaxy is rotating) and the axis of maximal rotation. The distortions imposed by weak lensing destroy these symmetries. DSM uses a Markov-Chain-Monte-Carlo Maximum-Likelihood method to fit for the shear in the velocity maps of spiral and elliptical galaxies by attempting to restore symmetries. The researchers find that in simulated data DSM can measure shears to with an error of +\-0.01, and have obtained observational data for the first DSM measurement.

    DSM is the first weak lensing technique which measures shear directly. This opens up exciting new possibilities for studying dark matter, with the ability to make direct measurements that are not possible with traditional weak lensing methods. For example, the team is currently working on a sample of simulated DSM measurements in a galaxy population to measure the scatter in the stellar mass-halo mass relation. With multiple DSM measurements around a single galaxy, it will be possible to measure not just the mass of the galaxy’s dark matter halo, but also the shape. This has previously only been possible with stacked weak lensing measurements.

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    Astronomy is entering a golden age, in which we seek to understand the complete evolution of the Universe and its constituents. But the key unsolved questions in astronomy demand entirely new approaches that require enormous data sets covering the entire sky.

    In the last few years, Australia has invested more than $400 million both in innovative wide-field telescopes and in the powerful computers needed to process the resulting torrents of data. Using these new tools, Australia now has the chance to establish itself at the vanguard of the upcoming information revolution centred on all-sky astrophysics.

    CAASTRO has assembled the world-class team who will now lead the flagship scientific experiments on these new wide-field facilities. We will deliver transformational new science by bringing together unique expertise in radio astronomy, optical astronomy, theoretical astrophysics and computation and by coupling all these capabilities to the powerful technology in which Australia has recently invested.


    The University of Sydney
    The University of Western Australia
    The University of Melbourne
    Swinburne University of Technology
    The Australian National University
    Curtin University
    University of Queensland

  • richardmitnick 10:54 am on July 18, 2015 Permalink | Reply
    Tags: , , Dark Energy/Dark Matter,   

    From phys.org: “A dark matter bridge in our cosmic neighborhood” 


    July 14, 2015
    No Writer Credit

    The figure shows the current stream of galaxies – the flow along in the cosmic super-highway and on the bridge to Virgo, in the region around the Milky Way, Andromeda and Centaurus A.

    By using the best available data to monitor galactic traffic in our neighborhood, Noam Libeskind from the Leibniz Institute for Astrophysics Potsdam (AIP) and his collaborators have built a detailed map of how nearby galaxies move. In it they have discovered a bridge of dark matter stretching from our Local Group all the way to the Virgo cluster—a huge mass of some 2,000 galaxies roughly 50 million light-years away, that is bound on either side by vast bubbles completely devoid of galaxies. This bridge and these voids help us understand a 40 year old problem regarding the curious distribution of dwarf galaxies.

    The Local Group of galaxies. The Milky Way and Andromeda are the most massive galaxies by far.

    This deep image of the Virgo Cluster obtained by Chris Mihos and his colleagues using the Burrell Schmidt telescope shows the diffuse light between the galaxies belonging to the cluster. North is up, east to the left. The dark spots indicate where bright foreground stars were removed from the image. Messier 87 is the largest galaxy in the picture (lower left).

    These dwarf galaxies are often found swarming around larger hosts like our own Milky Way. Since they are dim they are hard to detect, and are thus found almost exclusively in our cosmic neighborhood. A particularly fascinating aspect of their existence is that near the Milky Way and at least two of our closest neighbors—the Andromeda and Centaurus A galaxies—these satellites don’t just fly around randomly, but are instead compressed on to vast, flat, possibly spinning, planes. Such structures are not a naive outcome of the cold dark matter model that most cosmologists believe is responsible for how the universe forms galaxies. These structures are thus a challenge to the current doctrine.

    Andromeda_Galaxy – Adam Evans

    ESO/WFI (Optical); MPIfR/ESO/APEX/A.Weiss et al. (Submillimetre); NASA/CXC/CfA/R.Kraft et al. (X-ray)

    One possibility is that these small galaxies echo the geometry of structure on much greater scales. “This is the first time we have had observational verification that large filamentary super highways are channeling dwarf galaxies across the cosmos along magnificent bridges of dark matter,” Libeskind says. This cosmic “super highway” gives the speeding satellites an off ramp along which they can be beamed towards the Milky Way, Andromeda and Centaurus A. “The fact that this galactic bridge can affect the dwarf galaxies around us is impressive, given the difference in scale between the two: the planes of dwarfs are around 1 percent of the size of the galactic bridge to Virgo.”

    Current stream of galaxies (detailed).

    See the full article here.

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    About Phys.org in 100 Words

    Phys.org™ (formerly Physorg.com) is a leading web-based science, research and technology news service which covers a full range of topics. These include physics, earth science, medicine, nanotechnology, electronics, space, biology, chemistry, computer sciences, engineering, mathematics and other sciences and technologies. Launched in 2004, Phys.org’s readership has grown steadily to include 1.75 million scientists, researchers, and engineers every month. Phys.org publishes approximately 100 quality articles every day, offering some of the most comprehensive coverage of sci-tech developments world-wide. Quancast 2009 includes Phys.org in its list of the Global Top 2,000 Websites. Phys.org community members enjoy access to many personalized features such as social networking, a personal home page set-up, RSS/XML feeds, article comments and ranking, the ability to save favorite articles, a daily newsletter, and other options.

  • richardmitnick 2:09 pm on July 15, 2015 Permalink | Reply
    Tags: , Dark Energy/Dark Matter, ,   

    From Symmetry: “Miraculous WIMPs” 


    July 15, 2015
    Manuel Gnida

    Artwork by Sandbox Studio, Chicago with Ana Kova

    What are WIMPs, and what makes them such popular dark matter candidates?

    Invisible dark matter accounts for 85 percent of all matter in the universe, affecting the motion of galaxies, bending the path of light and influencing the structure of the entire cosmos. Yet we don’t know much for certain about its nature.

    Most dark matter experiments are searching for a type of particles called WIMPs, or weakly interacting massive particles.

    “Weakly interacting” means that WIMPs barely ever “talk” to regular matter. They don’t often bump into other matter and also don’t emit light—properties that could explain why researchers haven’t been able to detect them yet.

    Created in the early universe, they would be heavy (“massive”) and slow-moving enough to gravitationally clump together and form structures observed in today’s universe.

    Scientists predict that dark matter is made of particles. But that assumption is based on what they know about the nature of regular matter, which makes up only about 4 percent of the universe.

    WIMPs advanced in popularity in the late 1970s and early 1980s when scientists realized that particles that naturally pop out in models of Supersymmetry could potentially explain the seemingly unrelated cosmic mystery of dark matter.

    Supersymmetry, developed to fill gaps in our understanding of known particles and forces, postulates that each fundamental particle has a yet-to-be-discovered superpartner. It turns out that the lightest one of the bunch has properties that make it a top contender for dark matter.

    Supersymmetry standard model
    Standard Model of Supersymmetry

    “The lightest supersymmetric WIMP is stable and is not allowed to decay into other particles,” says theoretical physicist Tim Tait of the University of California, Irvine. “Once created in the big bang, many of these WIMPs would therefore still be around today and could have gone unnoticed because they rarely produce a detectable signal.”

    When researchers use the properties of the lightest supersymmetric particle to calculate how many of them would still be around today, they end up with a number that matches closely the amount of dark matter experimentally observed—a link referred to as the “WIMP miracle.” Many researchers believe it could be more than coincidence.

    “But WIMPs are also popular because we know how to look for them,” says dark matter hunter Thomas Shutt of Stanford University and SLAC National Accelerator Laboratory. “After years of developments, we finally know how to build detectors that have a chance of catching a glimpse of them.”


    Shutt is co-founder of the LUX experiment and one of the key figures in the development of the next-generation LUX-ZEPLIN experiment. He is one member of the group of scientists trying to detect WIMPs as they traverse large, underground detectors.

    Lux Dark Matter 2

    Lux Zeplin project

    Other scientists hope to create them in powerful particle collisions at CERN’s Large Hadron Collider.

    CERN LHC Map
    CERN LHC Grand Tunnel
    CERN LHC particles
    LHC at CERN

    “Most supersymmetric theories estimate the mass of the lightest WIMP to be somewhere above 100 gigaelectronvolts, which is well within LHC’s energy regime,” Tait says. “I myself and others are very excited about the recent LHC restart. There is a lot of hope to create dark matter in the lab.”


    A third way of searching for WIMPs is to look for revealing signals reaching Earth from space. Although individual WIMPs are stable, they decay into other particles when two of them collide and annihilate each other. This process should leave behind detectable amounts of radiation. Researchers therefore point their instruments at astronomical objects rich in dark matter such as dwarf satellite galaxies orbiting our Milky Way or the center of the Milky Way itself.


    “Dark matter interacts with regular matter through gravitation, impacting structure formation in the universe,” says Risa Wechsler, a researcher at Stanford and SLAC. “If dark matter is made of WIMPs, our predictions of the distribution of dark matter based on this assumption must also match our observations.”

    Wechsler and others calculate, for example, how many dwarf galaxies our Milky Way should have and participate in research efforts under way to determine if everything predicted can also be found experimentally.

    So how would researchers know for sure that dark matter is made of WIMPs? “We would need to see conclusive evidence for WIMPs in more than one experiment, ideally using all three ways of detection,” Wechsler says.

    In the light of today’s mature detection methods, dark matter hunters should be able to find WIMPs in the next five to 10 years, Shutt, Tait and Wechsler say. Time will tell if scientists have the right idea about the nature of dark matter.

    See the full article here.

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    Symmetry is a joint Fermilab/SLAC publication.

  • richardmitnick 11:12 am on July 9, 2015 Permalink | Reply
    Tags: , Dark Energy/Dark Matter,   

    From ESO: “Huge New Survey to Shine Light on Dark Matter” 

    European Southern Observatory

    9 July 2015
    Koen Kuijken
    Leiden Observatory
    Leiden, The Netherlands
    Email: kuijken@strw.leidenuniv.nl

    Massimo Viola
    Leiden Observatory
    Leiden, The Netherlands
    Email: viola@strw.leidenuniv.nl

    Lars Lindberg Christensen
    Head of ESO ePOD
    Garching bei München, Germany
    Tel: +49 89 3200 6761
    Cell: +49 173 3872 621
    Email: lars@eso.org


    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.

    Around 85% of the matter in the Universe is dark [1], and of a type not understood by physicists. Although it doesn’t shine or absorb light, astronomers can detect this dark matter through its effect on stars and galaxies, specifically from its gravitational pull. A major project using ESO’s powerful survey telescopes is now showing more clearly than ever before the relationships between this mysterious dark matter and the shining galaxies that we can observe directly [2].

    The project, known as the Kilo-Degree Survey (KiDS), uses imaging from the VLT Survey Telescope and its huge camera, OmegaCAM.

    ESO Omegacam on VST

    Sited at ESO’s Paranal Observatory in Chile, this telescope is dedicated to surveying the night sky in visible light — and it is complemented by the infrared survey telescope VISTA. One of the major goals of the VST is to map out dark matter and to use these maps to understand the mysterious dark energy that is causing our Universe’s expansion to accelerate.

    The best way to work out where the dark matter lies is through gravitational lensing — the distortion of the Universe’s fabric by gravity, which deflects the light coming from distant galaxies far beyond the dark matter. By studying this effect it is possible to map out the places where gravity is strongest, and hence where the matter, including dark matter, resides.

    As part of the first cache of papers, the international KiDS team of researchers, led by Koen Kuijken at the Leiden Observatory in the Netherlands [3], has used this approach to analyse images of over two million galaxies, typically 5.5 billion light-years away [4]. They studied the distortion of light emitted from these galaxies, which bends as it passes massive clumps of dark matter during its journey to Earth.

    The first results come from only 7% of the final survey area and concentrate on mapping the distribution of dark matter in groups of galaxies. Most galaxies live in groups — including our own Milky Way, which is part of the Local Group — and understanding how much dark matter they contain is a key test of the whole theory of how galaxies form in the cosmic web.

    Local Group

    From the gravitational lensing effect, these groups turn out to contain around 30 times more dark than visible matter.

    “Interestingly, the brightest galaxy nearly always sits in the middle of the dark matter clump,” says Massimo Viola (Leiden Observatory, the Netherlands) lead author of one of the first KiDS papers.

    “This prediction of galaxy formation theory, in which galaxies continue to be sucked into groups and pile up in the centre, has never been demonstrated so clearly before by observations,” adds Koen Kuijken.

    The findings are just the start of a major programme to exploit the immense datasets coming from the survey telescopes and the data are now being made available to scientists worldwide through the ESO archive.

    The KiDS survey will help to further expand our understanding of dark matter. Being able to explain dark matter and its effects would represent a major breakthrough in physics.

    [1] Astronomers have found that the total mass/energy content of the Universe is split in the proportions 68% dark energy, 27% dark matter and 5% “normal” matter. So the 85% figure relates to the fraction of “matter” that is dark.

    [2] Supercomputer calculations show how a Universe filled with dark matter will evolve: over time dark matter will clump into a huge cosmic web structure, and galaxies and stars form where gas is sucked into the densest concentrations of dark matter.

    [3] The international KiDS team of researchers includes scientists from the Netherlands, the UK, Germany, Italy and Canada.

    [4] This work made use of the 3D map of galaxy groups, provided by the Galaxy And Mass Assembly project (GAMA), following extensive observations on the Anglo-Australian Telescope.

    Anglo Australian Telescope Exterior
    Anglo Australian Telescope Interior
    Anglo-Australian Telescope

    More information

    This research was presented in a series of papers submitted to several leading journals. A list can be found here.

    See the full article here.

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    ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre European Extremely Large Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

    ESO LaSilla

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    Atacama Pathfinder Experiment (APEX) Telescope

  • richardmitnick 2:06 pm on July 7, 2015 Permalink | Reply
    Tags: , , Dark Energy/Dark Matter,   

    From Symmetry: “What is dark energy?” 


    From NASA/ WFIRST*

    July 07, 2015
    Diana Kwon

    It’s everywhere. It will determine the fate of our universe. And we still have no idea what it is.

    Looking up at the night sky reveals a small piece of the cosmos—patches of stars speckled across a dark, black void. Though the universe appears stationary to the naked eye, it is expanding at an increasing rate, with the distance between galaxies doubling every 10 billion years. Scientists attribute this phenomenon to dark energy, which makes up 70 percent of our universe—and will determine its eventual fate.

    A changing universe

    In the early 1900s, when Albert Einstein formulated the theory of general relativity, scientists believed in a static universe. This posed a problem for Einstein. According to his calculations, space was dynamic—either contracting or expanding. To resolve this discrepancy in his equations, he added the cosmological constant (usually denoted by the Greek capital letter lambda: Λ), a factor to counter the force of gravity. But when news broke that the universe was expanding, Einstein dropped the term, reportedly calling it his biggest blunder.

    Fast-forward to 1998. Scientists observing supernovae, the extremely bright, explosive deaths of stars, made an unexpected discovery. By comparing the observed to expected brightness of these explosions, they found that the universe’s expansion was accelerating.

    Why this was happening was a mystery. Michael Turner, a theoretical cosmologist at the University of Chicago, coined the term “dark energy” to describe the unknown cause of this accelerating expansion.

    For almost two decades, physicists have been developing theories about what dark energy could be. Some propose dark energy is static, others say it changes over time. Some even suggest that it might not exist.

    “We’re at the very beginning of a very profound puzzle,” Turner says.

    Filling the void

    Dark energy is an additional “thing” in the universe besides regular and dark matter. Two leading theories describe what it might be: a cosmological constant or something called quintessence.

    The cosmological constant is considered a strong contender. Named after Einstein’s correction, it suggests that dark energy is the energy associated with the vacuum of space and has remained unchanged over the 14 billion years of the universe’s history.

    Unchanging and uniformly distributed through space, it will continue to drive cosmic acceleration at a constant pace until the universe becomes a cold, lonely place where galaxies become too far apart to see.

    Scientists favor the cosmological constant for its simplicity and because existing experimental evidence points to it. Despite its popularity, a major conceptual problem exists—it’s way smaller than it should be.

    “The simplest quantum mechanical estimate would give you a number that’s enormous compared to the actual size of the cosmological constant if it’s dark energy,” describes Aaron Roodman, an experimental physicist at SLAC National Accelerator Laboratory. “How you end up with something that’s non-zero and really tiny is very mysterious.”

    Some physicists suggest that the value is zero and that dark energy is something other than a cosmological constant. One possibility is that a field generates the energy driving cosmic acceleration; this is called quintessence, or the “fifth stuff.” Unlike the cosmological constant, it does not remain unchanging over time.

    This model has subsets that differently predict how exactly dark energy changes. One example is called phantom dark energy, where not only is expansion accelerating, but the acceleration is also increasing over time. This leads to a scenario called the Big Rip, where expansion becomes infinitely fast, tearing galaxies, atoms and the fabric of space-time itself apart.

    A new take on gravity

    It’s also possible that dark energy doesn’t exist and something strange is going on with gravity.

    Modifying gravity allows for all sorts of weird possibilities. One theory incorporates a higher dimension that gravity can extend to but we can’t directly access. This dimension can influence ours, and interactions can produce effects like cosmic acceleration.

    Revising gravity is no easy task. Einstein’s theory of general relatively has proven to be incredibly accurate, and attempts to rewrite his equations have been largely unsuccessful. Trying to fit cosmic acceleration into these equations makes them unable to explain well understood phenomena, such as how the moon revolves around the earth.

    Scientists have extensively tested Einstein’s theory, but they are just beginning to investigate it at the enormous intergalactic scales of dark energy’s effects. If scientists find inconsistencies, they will have uncovered signs of new physics.

    “If the only way we could interpret the discrepancy was that something strange is going on with gravity, we’d be pointed in a whole new direction in fundamental physics,” says astrophysicist Josh Frieman, director of the Dark Energy Survey, an experiment aimed at finding the cause of cosmic acceleration.

    Because modified gravity models fall into uncharted territory, they make the fate of the universe more difficult to predict. To do so, scientists will first need to better understand how it works.

    Surveying the skies

    In the quest to understand dark energy, the initial tasks are to determine whether it actually exists and to test whether it fits with the idea of the cosmological constant.

    To do this, scientists are studying the history of the universe’s expansion as well as the growth of galaxies and other structures. Gravity and the cosmological constant make very specific predictions about what they should see, so finding discrepancies can help rule out some of these theories.

    However, eliminating possibilities doesn’t necessarily mean an answer is near.

    “We need more experimental data. We need another clue. Nothing that exists is very compelling,” Turner says. “But the next clue could come in weeks, months or years with the currently running and future experiments.”
    The verdict

    If you ask a physicist to bet on which theory they thought was most likely, most will put their money on the cosmological constant.

    But many, including Scott Dodelson, a Fermilab astrophysicist studying dark energy, think it’s conceivable that none of these theories are correct.

    “It’s possible that we’re very wrong in the way we’re thinking about this and that we need to rethink our interpretations of the observations completely,” Dodelson says.

    The ultimate fate of our universe is a question humans have been pondering since the earliest civilizations. The answer might not be around the corner, but we’re certainly closer than we’ve ever been before.

    *This is not the image presented with the article.
    See the full article here.

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    Symmetry is a joint Fermilab/SLAC publication.

  • richardmitnick 10:17 am on July 4, 2015 Permalink | Reply
    Tags: , , Dark Energy/Dark Matter,   

    From Alex Millar at Quantum Diaries: “Why Dark Matter Exists: Believing Without Seeing” 

    Alex Millar, University of Melbourne

    The Milky Way rises over the Cerro Tololo Inter-American Observatory in northern Chile. The Dark Energy Survey operates from the largest telescope at the observatory, the 4-meter Victor M. Blanco Telescope (left). Photo courtesy of Andreas Papadopoulos

    CTIO Victor M Blanco 4m Telescope
    CTIO Victor M Blanco 4m Telescope interior
    CTIO Victor M Blanco 4 meter Telescope

    Dark Energy Survey

    DECam, built at FNAL, at Victor M. Blanco Telescope

    For decades physicists have been convinced that most of our universe is invisible, but how do we know that if we can’t see it? I want to explain the thought process that leads one to believe in a theory via indirect evidence. For those who want to see a nice summary of the evidence, check 81 Comments out. So this post isn’t 3000 words, I will simply say that either our theories of gravity are wrong, or the vast majority of the matter in our universe is invisible. That most of the matter in the universe is invisible, or “dark”, is actually well supported. Dark matter as a theory fits the data much better than modifications to gravity (with a couple of possible exceptions like mimetic dark matter). This isn’t necessarily surprising; frankly it would be a bit arrogant to assume that only matter similar to us exists. Particle physicists have known for a long time that not all particles are affected by all the fundamental forces. For example, the neutrino is invisible as it doesn’t interact with the electromagnetic force (or strong force, for that matter). So the neutrino is actually a form of dark matter, though it is much too quick and light to make up most of what we see.

    The standard cosmological model, the ΛCDM, has had tremendous success explaining the evolution of our universe. This is what most people refer to when they think of dark matter: the CDM stands for “cold dark matter”, and it is this consistency that allows us to explain observations from almost every cosmological epoch that is so compelling about dark matter. We see the effect of dark matter across the sky in the CMB, in the helium formed in primordial nucleosynthesis, in the very structure of the galaxies. We see dark matter a minute after the big bang, a million years, a billion years, and even today. Simply put, when you add in dark matter (and dark energy) almost the entirety of cosmological history makes sense. While there some elements that seem to be lacking in the ΛCDM model (small scale structure formation, core vs cusp, etc), these are all relatively small details that seem to have solutions in either simulating normal matter more accurately, or small changes to the exact nature of dark matter.

    Dark matter is essentially like a bank robber: the money is gone, but no-one saw the theft. Not knowing exactly who stole the money doesn’t mean that someone isn’t living it up in the Bahamas right now. The ΛCDM model doesn’t really care about the fine details of dark matter: things like its mass, exact interactions and formation are mostly irrelevant. To the astrophysicist, there are really two features that they require: dark matter cannot have strong interactions with normal matter (electromagnetic or strong forces), and dark matter must be moving relatively slowly (or “cold”). Anything that has these properties is called a dark matter “candidate” as it could potentially be the main constituent of dark matter. Particle physicists try to come up with these candidates, and hopefully find ways to test them. Ruling out a candidate is not the same as ruling out the idea of dark matter itself, it is just removing one of a hundred suspects.

    Being hard to find is a crucial property of dark matter. We know dark matter must be a slippery bastard, as it doesn’t interact via the electromagnetic or strong forces. In one sense, assuming we can discover dark matter in our lifetime is presumptuous: we are assuming that it has interactions beyond gravity. This is one of a cosmologist’s fondest hopes as without additional interactions we are screwed. This is because gravity is by far the weakest force. You can test this yourself – go to the fridge, and get a magnet. With a simple fridge magnet, weighing only a few grams, you can pick up a paperclip, overpowering the 6*10^24 kg of gravitational mass the earth possesses. Trying to get a single particle, weighing about the same as an atom, to show an appreciable effect only through gravity is ludicrous. That being said, the vast quantities of dark matter strewn throughout our universe have had a huge and very detectable gravitational impact. This gravitational impact has led to very successful and accurate predictions. As there are so many possibilities for dark matter, we try to focus on the theories that link into other unsolved problems in physics to kill two birds with one stone. While this would be great, and is well motivated, nature doesn’t have to take pity on us.

    So what do we look for in indirect evidence? Essentially, you want an observation that is predicted by your theory, but is very hard to explain without it. If you see an elephant shaped hole in your wall, and elephant shaped foot prints leading outside, and all your peanuts gone, you are pretty well justified in thinking that an elephant ate your peanuts. A great example of this is the acoustic oscillations in the CMB. These are huge sound waves, the echo of theCMB big bang in the primordial plasma.


    The exact frequency of this is related to the amount of matter in the universe, and how this matter interacts. Dark matter makes very specific predictions about these frequencies, which have been confirmed by measurements of the CMB. This is a key observation that modified gravity theories tend to have trouble explaining.

    The combination of the strong indirect evidence for dark matter, the relative simplicity of the theory and the lack of serious alternatives means that research into dark matter theories is the most logical path. That is not to say that alternatives should not be looked into, but to disregard the successes of dark matter is simply foolish. Any alternative must match the predictive power and observational success of dark matter, and preferably have a compelling reason for being ‘simpler’ or philosophically nicer then dark matter. While I spoke about dark matter, this is actually something that occurs all the time in science: natural selection, atomic theory and the quark model are all theories that have all been in the same position at one time or another. A direct discovery of dark matter would be fantastic, but is not necessary to form a serious scientific consensus. Dark matter is certainly mysterious, but ultimately not a particularly strange idea.

    Disclaimer: In writing this for a general audience, of course I have to make sacrifices. Technical details like the model dependent nature of cosmological observations are important, but really require an entire blog post to themselves to answer fully.

    See the full article here.

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  • richardmitnick 1:45 pm on June 25, 2015 Permalink | Reply
    Tags: , , Dark Energy/Dark Matter,   

    From Symmetry: “Exploring dark energy with robots” 


    June 25, 2015
    Glenn Roberts Jr.

    The Dark Energy Spectroscopic Instrument will produce a 3-D space map using a ‘hive’ of robots.

    Courtesy of NOAO

    Five thousand pencil-shaped robots, densely nested in a metal hive, whir to life with a precise, dizzying choreography. Small U-shaped heads swivel into a new arrangement in a matter of seconds.

    This preprogrammed routine will play out about four times per hour every night at the Dark Energy Spectroscopic Instrument. The robots of DESI will be used to produce a 3-D map of one-third of the sky. This will help DESI fulfill its primary mission of investigating dark energy, a mysterious force thought to be causing the acceleration of the expansion of the universe.

    DESI Dark Energy Spectroscopic Instrument

    The tiny robots will be arranged in 10 wedge-shaped metal “petals” that together form a cylinder about 2.6 feet across. They will maneuver the ends of fiber-optic cables to point at sets of galaxies and other bright objects in the universe. DESI will determine their distance from Earth based on the light they emit.

    DESI’s robots are in development at Lawrence Berkeley National Laboratory, the lead in the DESI collaboration, and at the University of Michigan.

    Courtesy of: DESI collaboration

    The robots—each about 8 millimeters wide in their main section and 8 inches long—will be custom-built around commercially available motors measuring just 4 millimeters in diameter. This type of precision motor, at this size, became commercially available in 2013 and is now manufactured by three companies. The motors have found use in medical devices such as insulin pumps, surgical robots and diagnostic tools.

    At DESI, the robots will automate what was formerly a painstaking manual process used at previous experiments. At the Baryon Oscillation Spectroscopic Survey, or BOSS, which began in 2009, technicians must plug 1000 fibers by hand several times each day into drilled metal plates, like operators plugging cables into old-fashioned telephone switchboards.

    “DESI is exciting because all of that work will be done robotically,” says Risa Wechsler, a co-spokesperson for DESI and an associate professor of the Kavli Institute for Particle Astrophysics and Cosmology, a joint institute of Stanford University and SLAC National Accelerator Laboratory. Using the robots, DESI will be able to redirect all of its 5000 fibers in an elaborate dance in less than 30 seconds (see video).

    “DESI definitely represents a new era,” Wechsler says.

    In addition to precisely measuring the color of light emitted by space objects, DESI will also measure how the clustering of galaxies and quasars, which are very distant and bright objects, has evolved over time. It will calculate the distance for up to 25 million space objects, compared to the fewer than 2 million objects examined by BOSS.

    The robots are designed to both collect and transmit light. After each repositioning of fibers, a special camera measures the alignment of each robot’s fiber-optic cable within thousandths of a millimeter. If the robots are misaligned, they are automatically individually repositioned to correct the error.

    Each robot has its own electronics board and can shut off and turn on independently, says Joe Silber, an engineer at Berkeley Lab who manages the system that includes the robotic array.

    In seven successive generations of prototype designs, Silber has worked to streamline and simplify the robots, trimming down their design from 60 parts to just 18. “It took a long time to really understand how to make these things as cheap and simple as possible,” he says. “We were trying not to get too clever with them.”

    The plan is for DESI to begin a 5-year run at Kitt Peak National Observatory near Tucson, Arizona, in 2019. Berkeley and Michigan scientists plan to build a test batch of 500 robots early next year, and to build the rest in 2017 and 2018.

    See the full article here.

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    Symmetry is a joint Fermilab/SLAC publication.

  • richardmitnick 10:59 am on May 7, 2015 Permalink | Reply
    Tags: , Dark Energy/Dark Matter, ,   

    From Sanford via KDLT: “Unlocking Mysteries of Dark Matter & Neutrinos in South Dakota” 

    Sanford Underground Research facility

    Sanford Underground levels

    Sanford Underground Research facility


    May 06, 2015
    Tom Hanson, KDLT News Anchor

    The former Homestake Gold Mine in Lead closed in 2002. It is now the Sanford Underground Research Facility Funded by the state of South Dakota, the U.S. Department of Energy and a donation from T. Denny Sanford the lab is drawing some of the sharpest minds in science to South Dakota.

    The search for dark matter and the study of neutrinos are at the heart of two of the underground labs biggest projects. The equipment used in this research is so sensitive it has to be shielded from cosmic rays on the earth’s surface.

    Located almost a mile underground the LUX is a dark matter detector.

    Lux Dark Matter 2
    LUX Dark matter

    The two men behind the project Simon Fiorucci (left) and Harry Nelson are hunting something so rare, no one has ever seen it, in fact no one really knows exactly what it is.

    “We are trying to detect a new form of matter which we are absolutely sure constitutes about 85 percent of the matter in the universe,” said Nelson. “And the fabulous thing is no one knows what it is. So there are a bunch of conjectures and so the gadget behind us is dedicated to the most popular conjecture of what this dark matter of the universe is.”

    The gadget is the Large Underground Xenon Detector or LUX, a phone booth sized container holding liquid xenon, cooled to -160 degrees F and surrounded by thousands of gallons of specially treated water. And according to Sanford Underground Lab officials the LUX has the reputation as the most sensitive detector ever built. Nelson has a nack for taking a very complicated process and simplifying it.

    “Our detector occasionally should see a little touch of the dark matter and it will make the atoms in our detector recoil and emit a little bit of light and also make a little bit of electric charge, that’s what we are trying to do here,” said Nelson.

    But according to Fiorucci so far that hasn’t happened.

    “We’ve seen nothing at all, which at first glance you might think well that’s not great, actually what that means is we’ve eliminated quite a number of possibilities, said Fiorucci.


    Possibilities surround the other big project currently underway at the Sanford lab. The Majorana Demonstrator is looking at neutrinos.

    Majorano Demonstrator Experiment

    Particles so small there are billions of them passing through your body as you read this story. Professor John Wilkerson and his team are searching for a rare form of radioactive decay.

    “If we see this rare decay it would actually tell us that neutrinos can be their own anti particle and it might explain why we exist, why there’s so much matter and why there’s not anti-matter in the universe,” said Wilkerson.

    The vast majority of the observable universe from our planet seems to be made of matter and not antimatter. Why? Is one of the most interesting questions facing scientists.

    Building on the success of the LUX and Majorana Demonstrator, the next generations of projects are coming to the underground facility.
    The LZ project will continue the search for dark matter and will be 30 times larger than the LUX.

    LZ project
    LZ Project

    However the Deep Underground Neutrino Experiment or DUNE will be the biggest of all.


    The $1.5 billion project will try to find out how neutrinos change from point A to point B. It involves shooting neutrinos through the earth from Fermilab in Illinois to a huge detector at the Sanford Underground Lab.

    The man in charge of the facility, executive director Brookings native Mike Headley says they are excited to be a part of the project.

    “This will really be a big deal”, said Headley. “It’s an international collaboration that has close to 150 institutions worldwide and over 700 collaborators. The Long Base Neutrino Experiment (also called DUNE) is basically a $1.5 billion project. It is 1/3 funded international 2/3 funded in U.S. About 300 million of that $1.5 Billion will be facility construction here in South Dakota, so it’s going to be one of the biggest construction projects we’ve ever had in the state.”

    Construction on DUNE will begin next year. Scientists behind the project say neutrinos could hold clues about how the universe began and why matter greatly outnumbers antimatter, allowing us to exist.

    See the full article here.

    Please help promote STEM in your local schools.
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    About us.
    The Sanford Underground Research Facility in Lead, South Dakota, advances our understanding of the universe by providing laboratory space deep underground, where sensitive physics experiments can be shielded from cosmic radiation. Researchers at the Sanford Lab explore some of the most challenging questions facing 21st century physics, such as the origin of matter, the nature of dark matter and the properties of neutrinos. The facility also hosts experiments in other disciplines—including geology, biology and engineering.

    The Sanford Lab is located at the former Homestake gold mine, which was a physics landmark long before being converted into a dedicated science facility. Nuclear chemist Ray Davis earned a share of the Nobel Prize for Physics in 2002 for a solar neutrino experiment he installed 4,850 feet underground in the mine.

    Homestake closed in 2003, but the company donated the property to South Dakota in 2006 for use as an underground laboratory. That same year, philanthropist T. Denny Sanford donated $70 million to the project. The South Dakota Legislature also created the South Dakota Science and Technology Authority to operate the lab. The state Legislature has committed more than $40 million in state funds to the project, and South Dakota also obtained a $10 million Community Development Block Grant to help rehabilitate the facility.

    In 2007, after the National Science Foundation named Homestake as the preferred site for a proposed national Deep Underground Science and Engineering Laboratory (DUSEL), the South Dakota Science and Technology Authority (SDSTA) began reopening the former gold mine.

    In December 2010, the National Science Board decided not to fund further design of DUSEL. However, in 2011 the Department of Energy, through the Lawrence Berkeley National Laboratory, agreed to support ongoing science operations at Sanford Lab, while investigating how to use the underground research facility for other longer-term experiments. The SDSTA, which owns Sanford Lab, continues to operate the facility under that agreement with Berkeley Lab.

    The first two major physics experiments at the Sanford Lab are 4,850 feet underground in an area called the Davis Campus, named for the late Ray Davis. The Large Underground Xenon (LUX) experiment is housed in the same cavern excavated for Ray Davis’s experiment in the 1960s. In October 2013, after an initial run of 80 days, LUX was determined to be the most sensitive detector yet to search for dark matter—a mysterious, yet-to-be-detected substance thought to be the most prevalent matter in the universe. The Majorana Demonstrator experiment, also on the 4850 Level, is searching for a rare phenomenon called “neutrinoless double-beta decay” that could reveal whether subatomic particles called neutrinos can be their own antiparticle. Detection of neutrinoless double-beta decay could help determine why matter prevailed over antimatter. The Majorana Demonstrator experiment is adjacent to the original Davis cavern.

    Another major experiment, the Long Baseline Neutrino Experiment (LBNE) [being replaced by DUNE]—a collaboration with Fermi National Accelerator Laboratory (Fermilab) and Sanford Lab, is in the preliminary design stages. The project got a major boost last year when Congress approved and the president signed an Omnibus Appropriations bill that will fund LBNE operations through FY 2014. Called the “next frontier of particle physics,” LBNE [DUNE] will follow neutrinos as they travel 800 miles through the earth, from FermiLab in Batavia, Ill., to Sanford Lab.

    Fermilab LBNE

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