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  • richardmitnick 9:24 am on April 20, 2015 Permalink | Reply
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    From Don Lincoln at FNAL: “Complex Dark Matter” 

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    Fermilab is an enduring source of strength for the US contribution to scientific research world wide.

    FNAL Don Lincoln
    Don Lincoln

    After a century of study, scientists have come to the realization that the ordinary matter made of atoms is a minority in the universe. In order to explain observations, it appears that there exists a new and undiscovered kind of matter, called dark matter, that is five times more prevalent than ordinary matter. The evidence for this new matter’s existence is very strong, but scientists know only a little about its nature. In today’s video, Fermilab’s Dr. Don Lincoln talks about an exciting and unconventional idea, specifically that dark matter might have a very complex set of structures and interactions. While this idea is entirely speculative, it is an interesting hypothesis and one that scientists are investigating.

    See the full article here.

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    Fermilab Campus

    Fermi National Accelerator Laboratory (Fermilab), located just outside Batavia, Illinois, near Chicago, is a US Department of Energy national laboratory specializing in high-energy particle physics. Fermilab is America’s premier laboratory for particle physics and accelerator research, funded by the U.S. Department of Energy. Thousands of scientists from universities and laboratories around the world
    collaborate at Fermilab on experiments at the frontiers of discovery.

     
  • richardmitnick 8:42 am on April 14, 2015 Permalink | Reply
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    From FNAL: “Mapping the cosmos: Dark Energy Survey creates detailed guide to spotting dark matter” 

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    Fermilab is an enduring source of strength for the US contribution to scientific research world wide.

    Media contacts:

    Andre Salles, Fermilab Office of Communication, 630-840-3351, media@fnal.gov

    Science contacts:

    Josh Frieman, director of the Dark Energy Survey, 847-274-0429, frieman@fnal.gov
    Chihway Chang, ETH Zurich, +41-798101425, chihway.chang@phys.ethz.ch
    Bhuvnesh Jain, University of Pennsylvania, 267-973-7063, bjain@physics.upenn.edu
    Gary Bernstein, University of Pennsylvania, 215-573-6252, garyb@physics.upenn.edu

    Analysis will help scientists understand the role that dark matter plays in galaxy formation

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    This is the first Dark Energy Survey map to trace the detailed distribution of dark matter across a large area of sky. The color scale represents projected mass density: red and yellow represent regions with more dense matter. The dark matter maps reflect the current picture of mass distribution in the universe where large filaments of matter align with galaxies and clusters of galaxies. Clusters of galaxies are represented by gray dots on the map – bigger dots represent larger clusters. This map covers three percent of the area of sky that DES will eventually document over its five-year mission. Image: Dark Energy Survey

    Dark Energy Survey
    Dark Energy Camera
    CTIO Victor M Blanco 4m Telescope
    CTIO Victor M Blanco 4m Telescope interior
    Dark Energy Survey; Camera, built at FNAL; and CTIO Victor M Blanco 4 meter telescope which houses the DECam Camera

    Scientists on the Dark Energy Survey have released the first in a series of dark matter maps of the cosmos. These maps, created with one of the world’s most powerful digital cameras, are the largest contiguous maps created at this level of detail and will improve our understanding of dark matter’s role in the formation of galaxies. Analysis of the clumpiness of the dark matter in the maps will also allow scientists to probe the nature of the mysterious dark energy, believed to be causing the expansion of the universe to speed up.

    The new maps were released today at the April meeting of the American Physical Society in Baltimore, Maryland. They were created using data captured by the Dark Energy Camera, a 570-megapixel imaging device that is the primary instrument for the Dark Energy Survey (DES).

    Dark matter, the mysterious substance that makes up roughly a quarter of the universe, is invisible to even the most sensitive astronomical instruments because it does not emit or block light. But its effects can be seen by studying a phenomenon called gravitational lensing – the distortion that occurs when the gravitational pull of dark matter bends light around distant galaxies. Understanding the role of dark matter is part of the research program to quantify the role of dark energy, which is the ultimate goal of the survey.

    This analysis was led by Vinu Vikram of Argonne National Laboratory (then at the University of Pennsylvania) and Chihway Chang of ETH Zurich. Vikram, Chang and their collaborators at Penn, ETH Zurich, the University of Portsmouth, the University of Manchester and other DES institutions worked for more than a year to carefully validate the lensing maps.

    “We measured the barely perceptible distortions in the shapes of about 2 million galaxies to construct these new maps,” Vikram said. “They are a testament not only to the sensitivity of the Dark Energy Camera, but also to the rigorous work by our lensing team to understand its sensitivity so well that we can get exacting results from it.”

    The camera was constructed and tested at the U.S. Department of Energy’s Fermi National Accelerator Laboratory and is now mounted on the 4-meter Victor M. Blanco telescope at the National Optical Astronomy Observatory’s Cerro Tololo Inter-American Observatory in Chile. The data were processed at the National Center for Supercomputing Applications at the University of Illinois in Urbana-Champaign.

    The dark matter map released today makes use of early DES observations and covers only about three percent of the area of sky DES will document over its five-year mission. The survey has just completed its second year. As scientists expand their search, they will be able to better test current cosmological theories by comparing the amounts of dark and visible matter.

    Those theories suggest that, since there is much more dark matter in the universe than visible matter, galaxies will form where large concentrations of dark matter (and hence stronger gravity) are present. So far, the DES analysis backs this up: The maps show large filaments of matter along which visible galaxies and galaxy clusters lie and cosmic voids where very few galaxies reside. Follow-up studies of some of the enormous filaments and voids, and the enormous volume of data, collected throughout the survey will reveal more about this interplay of mass and light.

    “Our analysis so far is in line with what the current picture of the universe predicts,” Chang said. “Zooming into the maps, we have measured how dark matter envelops galaxies of different types and how together they evolve over cosmic time. We are eager to use the new data coming in to make much stricter tests of theoretical models.”

    View the Dark Energy Survey analysis.

    The Dark Energy Survey is a collaboration of more than 300 scientists from 25 institutions in six countries. Its primary instrument, the Dark Energy Camera, is mounted on the 4-meter Blanco telescope at the National Optical Astronomy Observatory’s Cerro Tololo Inter-American Observatory in Chile, and its data is processed at the National Center for Supercomputing Applications at the University of Illinois at Urbana-Champaign.

    Funding for the DES Projects has been provided by the U.S. Department of Energy Office of Science, the U.S. National Science Foundation, the Ministry of Science and Education of Spain, the Science and Technology Facilities Council of the United Kingdom, the Higher Education Funding Council for England, ETH Zurich for Switzerland, the National Center for Supercomputing Applications at the University of Illinois at Urbana-Champaign, the Kavli Institute of Cosmological Physics at the University of Chicago, Financiadora de Estudos e Projetos, Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro, Conselho Nacional de Desenvolvimento Científico e Tecnológico and the Ministério da Ciência e Tecnologia, the Deutsche Forschungsgemeinschaft and the collaborating institutions in the Dark Energy Survey. The DES participants from Spanish institutions are partially supported by MINECO under grants AYA2012-39559, ESP2013-48274, FPA2013-47986 and Centro de Excelencia Severo Ochoa SEV-2012-0234, some of which include ERDF funds from the European Union.

    Fermilab is America’s premier national laboratory for particle physics and accelerator research. A U.S. Department of Energy Office of Science laboratory, Fermilab is located near Chicago, Illinois, and operated under contract by the Fermi Research Alliance, LLC. Visit Fermilab’s website at http://www.fnal.gov and follow us on Twitter at @Fermilab.

    The DOE Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov.

    See the full article here.

    Please help promote STEM in your local schools.

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    Fermilab Campus

    Fermi National Accelerator Laboratory (Fermilab), located just outside Batavia, Illinois, near Chicago, is a US Department of Energy national laboratory specializing in high-energy particle physics. Fermilab is America’s premier laboratory for particle physics and accelerator research, funded by the U.S. Department of Energy. Thousands of scientists from universities and laboratories around the world
    collaborate at Fermilab on experiments at the frontiers of discovery.

     
  • richardmitnick 12:48 pm on April 13, 2015 Permalink | Reply
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    From New Scientist: “Looking into the voids could help explain dark energy” 

    NewScientist

    New Scientist

    10 April 2015
    Anil Ananthaswamy

    1
    A complex web (Image: Volker Springle/Max Planck Institute for Astrophysics/SP)

    HOLES in the universe could help explain why it’s ripping apart. The number and size of cosmic voids could shed light on the mysterious dark energy that is causing the universe to grow at an ever-increasing pace.

    In the late 1990s, astronomers realised that the expansion of the universe was accelerating and attributed this to the inherent “dark energy” of space-time.

    But we understand little about dark energy. Each unit of space-time contains some, but if this energy density changes with time, it implies different fates for our universe. If it is constant, as current observations suggest, then the universe will expand forever. But if it changes, we could be heading for a more dramatic end, like a big rip or a big crunch.

    One way to understand whether dark energy changes with time is to observe its effect on the large-scale structure of the universe. Just instants after the big bang, quantum fluctuations in the fabric of space-time led to regions that had more matter than their neighbours. As the universe expanded, the denser regions evolved to form clusters of galaxies. The less dense regions became voids – regions of space-time almost empty of matter, which can stretch from 30 million to 150 million light years across.

    While most efforts at deciphering dark energy involve studying its effect on clusters of galaxies, Alice Pisani and colleagues at the Paris Institute of Astrophysics decided to see if dark energy influenced the number of voids in the universe. “Voids are just an unavoidable part of the distribution of matter in the universe,” says team member Benjamin Wandelt.

    It turns out that there was a time in the evolution of the universe when the effects of dark energy kicked in and stopped the formation of new large-scale structures, whether clusters or voids. The properties of dark energy influenced when this happened and therefore the distribution of these structures.

    Pisani and colleagues considered three scenarios, all of which can explain the observed rate of expansion today. One was that dark energy is a cosmological constant [Λ]; in the other scenarios, dark energy changed with time. The second caused the expansion to accelerate later but faster than the cosmological constant would have, and in the third, it was earlier but slower.

    “Depending exactly on when the universe started accelerating, you have more or less voids of various sizes,” says Wandelt. The team’s analysis shows that with later but faster acceleration, there should be more big voids but fewer smaller ones compared with the cosmological constant. The opposite would be the case for acceleration that began earlier but was slower (arxiv.org/abs/1503.07690).

    Observations are not yet good enough to differentiate between the three scenarios but the European Space Agency’s Euclid mission, due for launch in 2020, will study more voids than ever before. The Paris team says its analysis could be applied to the Euclid data to elucidate dark energy, alongside studies investigating clusters.

    ESA Euclid spacecraft
    ESA/Euclid

    See the full article here.

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  • richardmitnick 3:25 pm on April 3, 2015 Permalink | Reply
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    From FNAL: “Frontier Science Result – PICO Seeing dark matter 

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    Fermilab is an enduring source of strength for the US contribution to scientific research world wide.

    April 3, 2015
    Alan Robinson, University of Chicago

    1
    A calibration event from PICO-2L shows boiling from multiple recoiling atomic nuclei. PICO-2L is designed to see a recoiling nucleus a from dark matter interaction.

    We are not yet seeing dark matter, but we could.

    Dark matter is all around us. There is six times more dark matter in our universe than there is the ordinary matter that we experience every day. Like neutrinos, dark matter can pass right through us and the Earth without being noticed. Moreover, dark matter does not interact with light, so we cannot see it, except perhaps in a bubble chamber.

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    Fermilab’s disused 15-foot bubble chamber

    Temp 0
    A bubble chamber

    Bubble chambers, including Fermilab’s 15-foot bubble chamber, were among the largest and most important particle detectors of the 1960s and 1970s investigating the physics of the weak force. In operation, bubble chambers are filled with liquid held above its boiling point temperature at the bubble chamber’s expansion pressure. The liquid boils if a nucleation site, such as a dust grain or a surface scratch, is available. In their absence, ionizing radiation (that is, particle tracks) can create bubbles. The exploding line of bubbles formed along a track lets physicists “see” the particle and photograph it.

    The PICO collaboration, of which Fermilab is a member (formed from the merger of PICASSO and COUPP), has revisited bubble chamber technology in order to look for dark matter particles. While dark matter particles pass through the Earth, they may very occasionally bounce off an atomic nucleus. PICO bubble chambers can see these nuclear recoils. They do not see most other types of ionizing radiation that can emulate dark matter in other detector technologies. PICO can also see bubbles from alpha radiation, but these are distinguishable as they sound different from those made by dark matter. As a bubble rapidly grows, PICO uses ultrasonic acoustic sensors to measure the sound of this small explosion and to reject the louder bubbles created by alpha radiation.

    The PICO-2L bubble chamber operated in 2013 and 2014 at SNOLAB, 6,800 feet underground in a Canadian nickel mine. Using 2 liters of perfluoropropane, C3F8, PICO-2L has set the world’s strongest proton spin-dependent dark matter search limits. Fluorine provides the most sensitive target nucleus to detect a spin-dependent dark matter interaction, which means future large bubble chambers may see, and hear, dark matter interactions that other detectors can not.

    3
    PICO-2L bubble chamber

    See the full article here.

    Please help promote STEM in your local schools.

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    Fermilab Campus

    Fermi National Accelerator Laboratory (Fermilab), located just outside Batavia, Illinois, near Chicago, is a US Department of Energy national laboratory specializing in high-energy particle physics. Fermilab is America’s premier laboratory for particle physics and accelerator research, funded by the U.S. Department of Energy. Thousands of scientists from universities and laboratories around the world
    collaborate at Fermilab on experiments at the frontiers of discovery.

     
  • richardmitnick 10:42 am on March 25, 2015 Permalink | Reply
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    From FNAL: “From the Center for Particle Astrophysics – Building a dark matter radio” 

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    Fermilab is an enduring source of strength for the US contribution to scientific research world wide.

    1
    Craig Hogan, head of the Center for Particle Astrophysics, wrote this column.

    You may have heard lately that the famous cosmic dark matter — the mysterious new kind of stuff that makes up most of the gravitational mass of the universe — may not, in fact, be completely dark, but may actually emit small amounts of light. That would be very exciting, because we might detect the light and use it to help figure out what the stuff is made of.

    For example, the Fermi Gamma-Ray Space Telescope detects light, in the form of photons from the center of our galaxy, that may be caused by massive dark matter particles annihilating each other.

    NASA Fermi Telescope
    NASA/Fermi

    Such high-energy photons can be created if the individual dark matter particles themselves are massive— much more massive than any known stable particle.

    But it’s also possible that the dark matter particles have extraordinarily low mass — even smaller than the tiny masses associated with neutrinos. In that case, the light emitted by dark matter, if any, would not show up as high-energy gamma rays; instead, it would show up as radio waves. Indeed, even the dark matter itself acts more like a coherent oscillating wave field than a collection of individual particles. In this situation, the best way to search for them may not be a traditional particle detector but a receiver more like a radio.

    A leading candidate for this kind of dark matter is called an axion. The existence of such a field was predicted long ago, not from a need for dark matter, but as a way to explain why strong interactions (the quantum chromodynamics of the Standard Model that control the structure of atomic nuclei) do not appear to distinguish the past from the future as the other interactions do.

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    Standard Model of Particle Physics. The diagram shows the elementary particles of the Standard Model (the Higgs boson, the three generations of quarks and leptons, and the gauge bosons), including their names, masses, spins, charges, chiralities, and interactions with the strong, weak and electromagnetic forces. It also depicts the crucial role of the Higgs boson in electroweak symmetry breaking, and shows how the properties of the various particles differ in the (high-energy) symmetric phase (top) and the (low-energy) broken-symmetry phase (bottom).

    In standard cosmology, if such a particle has a low mass, roughly in the microwave range of radio frequencies, it could be produced in sufficient abundance to be some, or even all, of the cosmic dark matter.

    If so, we might find them in the laboratory. It turns out that if cosmic axions from our galaxy pass through a strong magnet, they give off a small amount of radio light at exactly the frequency corresponding to their tiny mass. To detect them, we want to build a radio tuned to that mass. The radio in this case uses a highly resonant cavity, similar to those that Fermilab uses all the time to accelerate particles. We don’t know the mass of the axion exactly, so to search for the axion, we have to tune the radio — the cavity — until we get a signal.

    The Axion Dark Matter Experiment has started a search like this at the University of Washington.

    ADMX Axion Dark Matter Experiment
    AXION DME
    Axion Dark Matter Experiment, U Washington

    (Because the experiment is not sensitive to cosmic rays, the actual apparatus does not have to be deep underground, but is on campus.) The tuning starts at low frequencies, searching for axions of relatively low mass, where it can use relatively large cavities. But there is a long way to go: Theory provides only a rough guess about the mass of the axion, and nobody yet knows exactly how to build smaller cavities that can efficiently search for higher-mass axions.

    Fermilab scientists and engineers are planning to make unique contributions to state-of-the-art higher-frequency cavity designs for the higher-mass search, drawing on their years of experience with radio-frequency cavities in accelerators. This unique fusion of accelerator science and dark matter science is an exciting example of the synergy that happens at Fermilab.

    See the full article here.

    Please help promote STEM in your local schools.

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    Fermilab Campus

    Fermi National Accelerator Laboratory (Fermilab), located just outside Batavia, Illinois, near Chicago, is a US Department of Energy national laboratory specializing in high-energy particle physics. Fermilab is America’s premier laboratory for particle physics and accelerator research, funded by the U.S. Department of Energy. Thousands of scientists from universities and laboratories around the world
    collaborate at Fermilab on experiments at the frontiers of discovery.

     
  • richardmitnick 1:18 pm on March 21, 2015 Permalink | Reply
    Tags: , , Dark Energy/Dark Matter, U Notre Dame   

    From Notre Dame: “New paper explains methods that may lead to new insights about dark matter” 

    Notre Dame bloc

    Notre Dame University

    2
    This is Henize 2-10, a blob-shaped dwarf galaxy 30 million light-years away. The tiny galaxy has a colossal black hole at its center and could be a transition between young, small galaxies and massive spirals like our Milky Way, suggesting that galaxies form around central black holes, not the other way around. Astronomers suggest think that Henize 2-10 could be a nearby example of some of the first galaxies ever formed in the universe. Image is from NASA/Chandra, NASA/ESA Hubble NRAO/VLA January 10, 2011

    NASA Chandra Telescope
    NASA/Chandra

    NASA Hubble Telescope
    NASA/ESA Hubble

    NRAO VLA
    NRAO/VLA

    1
    Illustration of dark matter falling into a neutron star, forming a black hole and radiating out (Courtesy of NASA)

    A new paper, co-authored by University of Notre Dame astrophysicist Joseph Bramante, discusses how detecting imploding pulsars may lead to insights about the properties of dark matter. The paper, Detecting Dark Matter with Imploding Pulsars in the Galactic Center, was recently published in Physical Review Letters, the flagship journal for the American Physical Society.

    Pulsars, or pulsating stars, are rotating neutron stars that emit pulses of light visible to astronomers on Earth. Pulsars are created from the collapsing cores of supermassive stars that have exploded into supernovae. These supermassive stars, 10 to 40 times the mass of the sun, have been found at the center of the galaxy, leading astronomers to predict a certain number of pulsars should also reside there, but that predicted number of pulsars has not yet been observed.

    “In 2013, the first pulsar at the galactic center was detected, and this observation has deepened the mystery of these stellar objects,” explained Bramante, a postdoctoral associate in the lab of Christopher Kolda. “Prior to this detection, it was thought that pulsars at the galactic center might simply be shielded from observation by dense material in the center of the galaxy.”

    In the paper, Bramante and his colleague at the University of Chicago, Tim Linden, discuss how dark matter could explain the absence of pulsars in the galactic center. Dark matter, which makes up approximately 25 percent of the matter in the universe, is a very dense type of matter that does not emit a significant amount of light. A particular kind of dark matter could destroy pulsars at the galactic center by falling into the pulsars and forming black holes that swallow them.

    “Observations of pulsars imploding into black holes could provide important clues to the properties of dark matter, specifically indicating it is asymmetric, just like visible matter,” said Bramante.

    The paper also explains how the researchers showed that the presently unknown mass and quantum couplings of dark matter could be found by determining the age at which a pulsar is swallowed by a dark matter black hole. One predictor of this pulsar-collapsing dark matter is a maximum age for pulsars, which gets higher the further away from the galactic center the pulsars are because there is less dark matter away from the center.

    The next steps in this work for Bramante and his collaborators includes building and testing a model of dark matter to ensure the model meets all other cosmological and astrophysical dark matter observations.

    See the full article here.

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    Notre Dame Campus

    The University of Notre Dame du Lac (or simply Notre Dame /ˌnoʊtərˈdeɪm/ NOH-tər-DAYM) is a Catholic research university located near South Bend, Indiana, in the United States. In French, Notre Dame du Lac means “Our Lady of the Lake” and refers to the university’s patron saint, the Virgin Mary.

    The school was founded by Father Edward Sorin, CSC, who was also its first president. Today, many Holy Cross priests continue to work for the university, including as its president. It was established as an all-male institution on November 26, 1842, on land donated by the Bishop of Vincennes. The university first enrolled women undergraduates in 1972. As of 2013 about 48 percent of the student body was female.[6] Notre Dame’s Catholic character is reflected in its explicit commitment to the Catholic faith, numerous ministries funded by the school, and the architecture around campus. The university is consistently ranked one of the top universities in the United States and as a major global university.

    The university today is organized into five colleges and one professional school, and its graduate program has 15 master’s and 26 doctoral degree programs.[7][8] Over 80% of the university’s 8,000 undergraduates live on campus in one of 29 single-sex residence halls, each of which fields teams for more than a dozen intramural sports, and the university counts approximately 120,000 alumni.[9]

    The university is globally recognized for its Notre Dame School of Architecture, a faculty that teaches (pre-modernist) traditional and classical architecture and urban planning (e.g. following the principles of New Urbanism and New Classical Architecture).[10] It also awards the renowned annual Driehaus Architecture Prize.

     
  • richardmitnick 10:43 am on March 12, 2015 Permalink | Reply
    Tags: , , , Dark Energy/Dark Matter   

    From DES: “The best of the best” Old but Worth it 

    Dark Energy Icon
    The Dark Energy Survey

    1

    Det. Josh Frieman [Fermilab and the University of Chicago]

    The clearest skies give the best images and provide the best clues to cosmic expansion

    Scroll down through Dark Energy Detectives case files, and you’ll see beautiful images of galaxies taken with the Dark Energy Camera.

    Dark Energy Camera
    DECam, built at FNAL

    CTIO Victor M Blanco 4m Telescope
    CTIO Victor M Blanco telescope in Chile houses the DECam

    While they come in different shapes, sizes, and colors, these galaxies all have one thing in common: they’re all speeding away from our own Milky Way, at speeds of tens to hundreds of millions of miles per hour. The Universe is expanding, something we’ve known for nearly 90 years.

    If we could track the speeds of each of these galaxies over time, what would we find: would they stay the same, speed up, or slow down? Since the Milky Way’s gravity tugs on them, [Sir]Isaac Newton would have told us they would slow down over time, just as an apple thrown straight up in the air slows down (and eventually falls) due to the pull of Earth’s gravity. But Isaac would have been wrong, the galaxies are getting faster, not slower. The expansion of the Universe is speeding up, something we’ve known for only 17 years. The 300 detectives of the Dark Energy Survey (DES) are embarked on a five-year mission to understand why this is happening. In this quest, they’re carrying out the largest survey of the cosmos ever undertaken.

    While these goals sound lofty and profound (and they are), at its core DES is really about taking pictures. Lots of them. On a typical night, DES detectives snap about 250 photos of the sky. After five years, we’ll have over 80,000 photos in our album. For each snapshot, the camera shutter is kept open for about a minute and a half to let in enough light from distant galaxies. On each image, you can count about 80,000 galaxies. When we put them all together, and accounting for the fact that we’ll snap each part of the sky about 50 times, that adds up to pictures of about 200 million galaxies, give or take.

    One of the ways we’ll learn about dark energy—the putative stuff causing the universe to speed up—is by measuring the shapes of those 200 million galaxies very precisely and comparing them to each other. Imagine taking photos of 200 million people, roughly one out of every 35 people on Earth, to learn about the diversity of the human race. To gain the most information about our species, you will want all of your photos to be taken by a professional photographer under identical conditions conducive to getting the best image: good lighting, camera perfectly in focus, no jiggling of the camera or movement of your human subject during the exposure, etc. But inevitably, with 200 million photos, given the vagaries of people and circumstance, some photos will come out better than others. In some, the subject may be a bit blurred. In others, there may be too much or too little background light to see the person clearly.

    In the Dark Energy Survey, we’re striving to get the best, clearest snapshots of these 200 million galaxies that we can. As professional photographers of the night sky (a.k.a. astronomers), we’re using the best equipment there is—the Dark Energy Camera, which we built ourselves—to do the job. The camera has 570 Megapixels and 5 large lenses. It has a sophisticated auto-focus mechanism to always give us the crispest images possible.

    No need for a flash, since galaxies burn with the light of billions of suns.

    But as with human photography, Nature doesn’t always cooperate. The Dark Energy Camera is mounted on the Blanco telescope, located at Cerro Tololo in the Chilean Andes. This site has mostly very clear nights, but occasionally, clouds roll by. Turbulence in the atmosphere, which makes stars twinkle, leads to a slight blurring of the images of stars and galaxies, even if the camera is in perfect focus. The camera works by taking pictures of all the light that reflects off the 4-meter-diameter mirror of the telescope. If a cold front moves through, making the air in the telescope dome cooler than the 15-ton mirror, plumes of hot air rising off the mirror lead to blurry images. The sharpest images are those taken straight overhead—the further away from straight up that we point the telescope, the more atmosphere the light has to pass through, again increasing the blurring; since our survey covers a large swath of the sky, we cannot always point straight up. Strong wind blowing in through the open slit of the dome can cause the telescope to sway slightly during an exposure, also blurring the picture. Since the Earth rotates around its axis, during an exposure the massive telescope must compensate by continuously, very smoothly moving to stay precisely locked on to its target; any deviation in its motion will—you guessed it—blur the image.

    For all these reasons and others, the quality of the DES images varies. On some nights, conditions conspire to give us very crisp images. On others, the images are a bit more blurred than we’d like, making it harder to measure the shapes of those distant galaxies. If an image is too blurred, we don’t include it in the album: we’ll come back another night to take a photo of those particular galaxies. So far, about 80% of the photos we’ve taken have been good enough to keep.

    Most nights during our observing season, we have three detectives operating the camera; each of us is there for about a week, and in the course of a season about 50 detectives rotate through, taking their “shifts.” On the night of January 27, 2015, I was in the middle of my week-long observing shift at the telescope with two fellow detectives, Yuanyuan Zhang from the University of Michigan and Andrew Nadolski from the University of Illinois at Urbana-Champaign. That night, Andrew was manning the camera, I was checking the quality of the images as they were taken, and Yuanyuan was our boss.

    The conditions that night were outstanding. Although it was a bit humid, the atmosphere was extremely smooth and stable. We were mainly taking pictures using filters that let in only very red or near-infrared light. This was because the moon was up, and the moon is actually quite blue: red filters block most of the moonlight that scatters off the atmosphere from entering the camera, enabling us to see red galaxies against the dark night sky. In his famous photograph “Monolith, the Face of Half Dome” taken in Yosemite National Park, Ansel Adams used a red (but not infrared) filter to darken the blue daytime sky to dramatic effect.

    At 12:28 am local time, we snapped exposure number 403841, using a near-infrared filter called the z-band. The z-band is so red that it’s beyond the visible spectrum that can be seen by the human eye, but digital cameras, and the Dark Energy Camera in particular, are very sensitive to near-infrared light. Computers at the telescope analyze each image right after it’s taken and display the results on a bank of monitors, so we can tell whether we’re taking data that passes muster for our cosmic album. When 403841 came out, the screen showed that it was an exceptionally sharp image. Further analysis convinced us that it was in fact the sharpest image of the roughly 35,000 snapshots that DES has taken so far, going back two years to the beginning of the survey.

    The image was so sharp that the light from each star was spread out over only about 0.6 seconds of arc or about 0.00017 degrees. For comparison, that’s how big a crater a kilometer across on the surface of the moon looks from Earth. It’s also the angular size of a typical human hair seen at a distance of about 100 feet.

    A small portion of the 403841 image is shown above in false color, showing a great spiral galaxy plus a number of smaller, fainter galaxies and a few bright stars in our own Milky Way. The star inside the red circle at the lower right of the image has its light spread out over only 0.6 arc seconds. While not as pretty as the color images of galaxies in other DED case files, this is closer to what a raw image directly from the camera looks like. The raw DES digital images are sent for processing to the National Center for Supercomputing Applications in Urbana-Champaign, Illinois (if you’re under 40, ask your parents if they remember sending film out for processing), to make them science-ready for our fellow DES detectives.

    In DES, we keep a “bragging rights” web page of the sharpest images we have taken in each of the five filters we use. Our friend 403841 is now prominently displayed there—the best of the best. But the best thing about records is that they’re made to be broken.

    See the full article here.

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    Dark Energy Camera

    The Dark Energy Survey (DES) is designed to probe the origin of the accelerating universe and help uncover the nature of dark energy by measuring the 14-billion-year history of cosmic expansion with high precision. More than 120 scientists from 23 institutions in the United States, Spain, the United Kingdom, Brazil, and Germany are working on the project. This collaboration [has built] an extremely sensitive 570-Megapixel digital camera, DECam, and [has mounted] it on the Blanco 4-meter telescope at Cerro Tololo Inter-American Observatory high in the Chilean Andes. Started in Sept. 2012 and continuing for five years, DES will survey a large swath of the southern sky out to vast distances in order to provide new clues to this most fundamental of questions.

     
  • richardmitnick 4:11 am on March 12, 2015 Permalink | Reply
    Tags: , Dark Energy/Dark Matter,   

    From NYT: “Gamma Rays May Be Clue on Dark Matter” 

    New York Times

    The New York Times

    MARCH 10, 2015
    DENNIS OVERBYE

    NYT Dennis Overbye Older

    1
    Bright areas indicate gamma rays coming from the direction of the galaxy about 100,000 light-years away. Credit Geringer-Sameth & Walker/Carnegie Mellon University

    A small, newly discovered galaxy orbiting the Milky Way is emitting a surprising amount of electromagnetic radiation in the form of gamma rays, astronomers reported Tuesday. The finding may be the latest in a long string of cosmic false alarms, they said, or it might be that the mysterious dark matter that permeates the universe is finally showing its face.

    If confirmed, the results could mean that most of the matter of the universe is in the form of as-yet-unidentified elementary particles, 20 to 100 times as heavy as a proton, that have been drifting and clumping like fog in space ever since the Big Bang.

    But while the gamma-ray signal is “tantalizing,” in the words of Alex Geringer-Sameth of Carnegie Mellon University and colleagues from Brown and Cambridge Universities, “it would be premature to conclude it has a dark matter origin.” Their analysis appears in a paper submitted to the journal Physical Review Letters.

    The group used data from NASA’s Fermi Large Area Telescope, which orbits the Earth, to search for gamma rays from a loose-looking accumulation of stars known as Reticulum-2, in the southern constellation of the same name. It is one of a rare breed known as dwarf galaxies, which can have fewer than a hundred stars and are only a billionth as luminous and a millionth as massive as the Milky Way.

    NASA Fermi Large Area Telescope
    NASA Fermi Telescope
    NASA/Fermi and LAT

    Because dwarf galaxies have so little atomic matter, astronomers see them as happy hunting grounds for dark matter. That mysterious stuff has led scientists on a merry chase ever since Fritz Zwicky in the 1930s and Vera Rubin and her colleagues in the 1970s discerned that galaxies move under the gravitational influence of massive clouds of invisible matter.

    Cosmologists now agree that dark matter is 80 percent of the matter in the universe and that it is not the ordinary atomic matter that planets and people are made of, nor anything else predicted by the Standard Model that rules particle physics today.

    What is it?

    Lately physicists have speculated that it consists of exotic particles left over from the Big Bang known colloquially as Wimps — for weakly interacting massive particles. So far particle accelerators like CERN’s Large Hadron Collider have been unable to make them, although looking for them will be a major priority when that machine starts running again this spring.

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

    Meanwhile, there is the sky.

    In the centers of galaxies, where dark matter is densest, the Wimp particles would collide and annihilate one another in a telltale flash of gamma rays, the thinking goes. Some support for this notion has come from the Fermi telescope’s observations of excess gamma rays, the most energetic form of electromagnetic radiation, coming from the center of the Milky Way. But astronomers cannot rule out the possibility that pulsars, black holes and other astrophysical phenomena are creating the gamma rays in our own galaxy.

    Still, dwarf galaxies typically appear to have nothing going on in them at all.

    “They are very quiet systems, just containing some old stars and a lot of dark matter,” Dr. Geringer-Sameth said in an email. “If you see any excess gamma rays coming from them, something intriguing is going on.”

    Neal Weiner, a dark matter theorist at New York University, agreed, saying, “If you see gamma rays in a dwarf galaxy, it would be a good way to make a case that you are seeing dark matter.”

    Lately astronomers have been discovering these dwarfs in droves, thanks to new tools like the Sloan Digital Sky Survey. Reticulum-2 is one of several such clumpings of stars recently discovered in data compiled by another effort, the Dark Energy Survey.

    Sloan Digital Sky Survey Telescope
    SDSS telescope at Apache Point Observatoryin New Mexico

    Dark Energy Survey
    Dark Energy Camera
    Dark Energy Survey and DECam, built at FNAL

    CTIO Victor M Blanco 4m Telescope
    CTIO Victor M Blanco Telescope in Chile which houses the DECam

    The Reticulum galaxy is one of the closest dwarfs to our own galaxy, about 100,000 light-years away. So far it is the only one in which gamma rays have been observed.

    And that observation is not unanimous. A group from Cambridge University found the galaxy in the Dark Energy Survey data and shared the information with Dr. Geringer-Sameth’s group, which searched the Fermi Large Area Telescope data and saw evidence for gamma rays from the galaxy. Another team, led by Alex Drlica-Wagner of the Fermi National Accelerator Laboratory in Illinois and the Dark Energy Survey as well as the Fermi telescope collaboration, independently found the galaxy and looked for gamma rays, but did not see them.

    So goes life in what they call the dark sector. “This is the question to get to the bottom of, from our perspective,” Dr. Geringer-Sameth said. “What is causing the two analyses to reach different conclusions?”

    Dr. Weiner said it was far too soon to make any assumptions. “We don’t know what dark matter looks like,” he said. “We will need patience. But the payoff is going to be huge.”

    See the full article here.

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  • richardmitnick 3:16 pm on March 10, 2015 Permalink | Reply
    Tags: , , Dark Energy/Dark Matter,   

    From FNAL: “Scientists find rare dwarf satellite galaxy candidates in Dark Energy Survey data” 

    FNAL Home


    Fermilab is an enduring source of strength for the US contribution to scientific research world wide.

    March 10, 2015
    Media contacts:

    Andre Salles, Fermilab Office of Communication, media@fnal.gov, 630-840-3351 (office), 630-940-8239 (cell)
    Sarah Collins, Office of Communications, University of Cambridge, sarah.collins@admin.cam.ac.uk, +44 (0)1223 765542 (office), +44 (0)7525 337458 (cell)

    Science contacts:

    Josh Frieman, Fermilab, director of the Dark Energy Survey, frieman@fnal.gov, 847-274-0429 (cell)
    Alex Drlica-Wagner, David N. Schramm fellow, Fermilab, kadrlicka@fnal.gov
    Keith Bechtol, KICP fellow, Kavli Institute for Cosmological Physics at the University of Chicago, bechtol@kicp.uchicago.edu
    Vasily Belokurov, University of Cambridge, vasily@ast.cam.ac.uk
    1
    These two images allow you to see how difficult it is to spot these dwarf galaxy candidates in the Dark Energy Camera’s images. The first image is a snapshot of DES J0335.6-5403, a celestial object found with the Dark Energy Camera. It is the most likely of the newly discovered candidates to be a galaxy, according to DES scientists. This object sits roughly 100,000 light-years from Earth, and contains very few stars – only about 300 could be detected with DES data. The second image shows the detectable stars that likely belong to this object, with all other visible matter blacked out. Dwarf satellite galaxies are so faint that it takes an extremely sensitive instrument like the Dark Energy Camera to find them. More analysis is required to confirm if any of the newly discovered objects are in fact galaxies. Image: Fermilab/Dark Energy Survey

    Scientists on two continents have independently discovered a set of celestial objects that seem to belong to the rare category of dwarf satellite galaxies orbiting our home galaxy, the Milky Way.

    Dwarf galaxies are the smallest known galaxies, and they could hold the key to understanding dark matter and the process by which larger galaxies form.

    A team of researchers with the Dark Energy Survey, headquartered at the U.S. Department of Energy’s Fermi National Accelerator Laboratory, and an independent group from the University of Cambridge jointly announced their findings today. Both teams used data taken during the first year of the Dark Energy Survey, all of which is publicly available, to carry out their analysis.

    Dark Energy Survey
    DECam
    Dark Energy Survey, DECam Dark Energy Camera built at FNAL

    CTIO Victor M Blanco 4m Telescope
    CTIO Victor M Blanco Telescope which houses the DECam

    “The large dark matter content of Milky Way satellite galaxies makes this a significant result for both astronomy and physics,” said Alex Drlica-Wagner of Fermilab, one of the leaders of the Dark Energy Survey analysis.

    Satellite galaxies are small celestial objects that orbit larger galaxies, such as our own Milky Way. Dwarf galaxies can be found with fewer than 100 stars and are remarkably faint and difficult to spot. (By contrast, the Milky Way, an average-sized galaxy, contains billions of stars.)

    These newly discovered objects are a billion times dimmer than the Milky Way and a million times less massive. The closest of them is about 100,000 light-years away.

    “The discovery of so many satellites in such a small area of the sky was completely unexpected,” said Cambridge’s Institute of Astronomy’s Sergey Koposov, the Cambridge study’s lead author. “I could not believe my eyes.”

    Scientists have previously found more than two dozen of these satellite galaxies around our Milky Way. About half of them were discovered in 2005 and 2006 by the Sloan Digital Sky Survey, the precursor to the Dark Energy Survey. After that initial explosion of discoveries, the rate fell to a trickle and dropped off entirely over the past five years.

    Sloan Digital Sky Survey Telescope
    SDSS Telescope at Apache Point Observatory

    The Dark Energy Survey is looking at a new portion of the southern hemisphere, covering a different area of sky than the Sloan Digital Sky Survey. The galaxies announced today were discovered in a search of only the first of the planned five years of Dark Energy Survey data, covering roughly one-third of the portion of sky that DES will study. Scientists expect that the full Dark Energy Survey will find up to 30 of these satellite galaxies within its area of study.

    2
    This illustration maps out the previously discovered dwarf satellite galaxies (in blue) and the newly discovered candidates (in red) as they sit outside the Milky Way. Image: Yao-Yuan Mao, Ralf Kaehler, Risa Wechsler (KIPAC/SLAC).

    Atlas image obtained as part of the Two Micron All Sky Survey (2MASS), a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation.

    2MASS Telescope
    2MASS telescope interior
    2MASS telescopes. 2MASS was carried out by a pair of identical, fully dedicated, 1.3 meter cassegrain equatorial telescopes and cameras that were located at the Whipple Observatory on Mt. Hopkins south of Tucson, AZ, and at the Cerro Tololo Inter-American Observatory near La Serena, Chile.

    While more analysis is required to confirm any of the observed celestial objects as satellite galaxies, researchers note their size, low surface brightness and significant distance from the center of the Milky Way as evidence that they are excellent candidates. Further tests are ongoing, and data collected during the second year of the Dark Energy Survey could yield more of these potential dwarf galaxies to study.

    Newly discovered galaxies would also present scientists with more opportunities to search for signatures of dark matter. Dwarf satellite galaxies are dark matter-dominated, meaning they have much more mass in unseen matter than in stars. The nature of this dark matter remains unknown but might consist of particles that annihilate each other and release gamma rays. Because dwarf galaxies do not host other gamma ray sources, they make ideal laboratories to search for signs of dark matter annihilation. Scientists are confident that further study of these objects will lead to even more sensitive searches for dark matter.

    In a separate result also announced today, the Large Area Telescope Collaboration for NASA’s Fermi Gamma-Ray Telescope mission reported that they did not see any significant excess of gamma ray emission associated with the new Dark Energy Survey objects. This result demonstrates that new discoveries from optical telescopes can be quickly translated into tests of fundamental physics.

    NASA Fermi Telescope
    Fermi

    “We did not detect significant emission with the LAT, but the dwarf galaxies that DES has and will discover are extremely important targets for the dark matter search,” said Peter Michelson, spokesperson for the LAT collaboration. “If not leading to an identification of particle dark matter, they will certainly be useful to constrain its properties.”

    The Dark Energy Survey is a five-year effort to photograph a large portion of the southern sky in unprecedented detail. Its primary instrument is the Dark Energy Camera, which – at 570 megapixels – is the most powerful digital camera in the world, able to see galaxies up to 8 billion light-years from Earth. Built and tested at Fermilab, the camera is now mounted on the 4-meter Victor M. Blanco telescope at the Cerro Tololo Inter-American Observatory in the Andes Mountains in Chile.

    The survey’s five-year mission is to discover clues about the nature of dark energy, the mysterious force that makes up about 70 percent of all matter and energy in the universe. Scientists believe that dark energy may be the key to understanding why the expansion of the universe is accelerating.

    “The Dark Energy Camera is a perfect instrument for discovering small satellite galaxies,” said Keith Bechtol of the Kavli Institute for Cosmological Physics at the University of Chicago, who helped lead the Dark Energy Survey analysis. “It has a very large field of view to quickly map the sky and great sensitivity, enabling us to look at very faint stars. These results show just how powerful the camera is and how significant the data it collects will be for many years to come.”

    The Dark Energy Survey analysis is available here. The University of Cambridge analysis is available here.

    The Dark Energy Survey is a collaboration of more than 300 scientists from 25 institutions in six countries. For more information about the survey, please visit the experiment’s website.

    Funding for the DES Projects has been provided by the U.S. Department of Energy, the U.S. National Science Foundation, the Ministry of Science and Education of Spain, the Science and Technology Facilities Council of the United Kingdom, the Higher Education Funding Council for England, the National Center for Supercomputing Applications at the University of Illinois at Urbana-Champaign, the Kavli Institute of Cosmological Physics at the University of Chicago, Financiadora de Estudos e Projetos, Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro, Conselho Nacional de Desenvolvimento Científico e Tecnológico and the Ministério da Ciência e Tecnologia, the Deutsche Forschungsgemeinschaft and the collaborating institutions in the Dark Energy Survey. The DES participants from Spanish institutions are partially supported by MINECO under grants AYA2012-39559, ESP2013-48274, FPA2013-47986 and Centro de Excelencia Severo Ochoa SEV-2012-0234, some of which include ERDF funds from the European Union.

    Fermilab is America’s premier national laboratory for particle physics and accelerator research. A U.S. Department of Energy Office of Science laboratory, Fermilab is located near Chicago, Illinois, and operated under contract by the Fermi Research Alliance, LLC. Visit Fermilab’s website at http://www.fnal.gov and follow us on Twitter at @Fermilab.

    The DOE Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov .

    The mission of the University of Cambridge is to contribute to society through the pursuit of education, learning and research at the highest international levels of excellence. To date, 90 affiliates of the university have won the Nobel Prize. Founded in 1209, the university comprises 31 autonomous colleges, which admit undergraduates and provide small-group tuition, and 150 departments, faculties and institutions. Cambridge is a global university. Its 19,000 student body includes 3,700 international students from 120 countries. Cambridge researchers collaborate with colleagues worldwide, and the university has established larger-scale partnerships in Asia, Africa and America. The university sits at the heart of one of the world’s largest technology clusters. The ‘Cambridge Phenomenon’ has created 1,500 hi-tech companies, 14 of them valued at over US$1 billion and two at over US$10 billion. Cambridge promotes the interface between academia and business and has a global reputation for innovation. http://www.cam.ac.uk .

    See the full article here.

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    Fermilab Campus

    Fermi National Accelerator Laboratory (Fermilab), located just outside Batavia, Illinois, near Chicago, is a US Department of Energy national laboratory specializing in high-energy particle physics.

     
  • richardmitnick 6:46 am on March 7, 2015 Permalink | Reply
    Tags: , , , Dark Energy/Dark Matter,   

    From ScienceNews: “Sam Ting tries to expose dark matter’s mysteries” 

    ScienceNews bloc

    ScienceNews

    March 6, 2015
    Andrew Grant

    Physics Nobel laureate’s space-based detector is analyzing billions of cosmic rays

    1
    EYES ON THE INVISIBLE PRIZE Designed to detect cosmic rays, the Alpha Magnetic Spectrometer cruises above Earth on the International Space Station.

    AMS-02
    AMS-02

    In the near vacuum of outer space, each rare morsel of matter tells a story. A speedy proton may have been propelled by the shock wave of an exploding star. A stray electron may have teetered on the precipice of a black hole, only to be flung away in a powerful jet of searing gas.

    Since 2011, the International Space Station has housed an experiment that aims to decipher those origin stories. The Alpha Magnetic Spectrometer has already cataloged more than 60 billion protons, electrons and other spaceborne subatomic particles, known as cosmic rays, as they zip by.

    Other experiments sample the shower of particles produced when cosmic rays strike atoms and molecules in Earth’s atmosphere. But the spectrometer scrutinizes pristine cosmic rays — some of which have traveled undisturbed over millions of light-years — from its perch some 400 kilometers above Earth. The Alpha Magnetic Spectrometer is by far the most sensitive cosmic ray detector ever to fly in space, and with a price tag of about $2 billion, it’s also the most expensive.

    The detector’s unprecedented particle census could unmask the identity of dark matter, the mysterious, invisible substance that is five times as abundant in the universe as ordinary matter. Some of the cosmic rays snatched by the instrument may have been produced by particles of dark matter colliding and annihilating each other in the center of the galaxy.

    The spectrometer could also help scientists determine why planets, stars and other structures in the universe are made of matter rather than antimatter. Particles of antimatter have the opposite charge as their matter counterparts but are identical in nearly every other way. It’s uncertain why most of the antimatter particles disappeared just after the Big Bang 13.8 billion years ago. Physicists would love to discover primordial antimatter to test their theories on what hastened its demise.

    2
    Sam Ting

    Nearly four years into the mission, the Alpha Magnetic Spectrometer is delivering precise data and arguably providing a few hints about the nature of dark matter. But it’s unclear whether the mission will ever deliver on its ambitious goals. Cosmic rays are charged particles that get whipped around by magnetic fields, so they don’t travel in straight lines and cannot be traced back to their source. To pin the origin of particular cosmic rays to dark matter, scientists will have to rule out every other possible explanation. Critics say the chances of identifying dark matter are very slim. And finding primordial antimatter, they say, is nearly impossible.

    Such criticism barely registers with the mission’s leader, particle physicist Samuel Ting. The 79-year-old Nobel laureate has made a career of designing elegant experiments and, despite frequent opposition, successfully lobbying to get them built. Then he has patiently collected and analyzed data, meticulous to the extreme, before revealing the often-impressive findings. Though results may come later than most scientists would prefer, Ting is confident that conducting a powerful particle physics experiment in space will expand scientists’ understanding of the cosmos.

    Full focus

    Ting’s home base these days is at CERN, the European physics laboratory outside Geneva that partially funds the Alpha Magnetic Spectrometer and is home to the mission’s command center. But on one afternoon in December, Ting is at MIT, where he still runs a lab. His office is housed in a building marked with a capital J that honors his Nobel Prize–winning discovery, the J particle. The alleged reason for Ting’s U.S. visit was to meet with a contractor to discuss renovating his Cambridge, Mass., home. But the contractor confab was brief. For Ting, matters outside of physics take a backseat.

    “You really can’t get into this field without thinking this is the most important thing in your life,” Ting says.

    Two high-definition monitors on his office wall reinforce his obsession. One shows a live feed from the space station, a grainy black-and-white image capturing the spectrometer and our imperceptibly spinning planet below. The other screen plays a computer reconstruction of the instrument in action. In nearly real time, cosmic rays pass through its magnet, triggering a slate of sensors that determine the particles’ identity, energy and trajectory.

    Ting doesn’t have a background in astrophysics, but he has plenty of experience sorting through a glut of particles to find really cool stuff.

    He pulls up a 1965 New York Times article on his computer. The article describes Ting’s first major discovery, when he, Leon Lederman (who won the 1988 Nobel Prize in physics) and colleagues produced and detected antimatter nuclei for the first time. (A team at CERN made a similar discovery soon after.) It’s difficult enough to observe single particles of antimatter because they disappear in a burst of energy when they encounter ordinary matter. Ting and Lederman managed to observe bound pairs of antimatter particles, called antideuterons, in a particle accelerator at Brookhaven National Laboratory in Upton, N.Y.

    Ting’s childlike curiosity quickly comes across as he describes the possibility that antideuterons and other large chunks of antimatter, relics of the first moments after the Big Bang, could be drifting in the cosmos, waiting to be found. But beneath the inquisitiveness is also an extreme confidence, even an arrogance, that he alone knows the way to probe the big questions.

    Those qualities were on display in the early 1970s when Ting became interested in quarks, tiny parcels that compose such particles as protons and neutrons. Physicists had proposed and discovered evidence for three kinds of quarks. But Ting, eager to unravel every detail about matter’s makeup, joined a group of physicists who wondered whether there were other quark varieties. He proposed colliding particles at high energies, which would create short-lived matter that ultimately decayed into electrons and their antimatter counterparts, positrons. By analyzing the electrons and positrons, he could determine the composition of the intermediate particles.

    Ting says many physicists scoffed at his proposal; they believed that the three quarks could explain all the more complex particles in physics. Multiple labs turned him down before Brookhaven let him give it a try.

    In the summer of 1974, Ting and his team saw convincing signs of a new subatomic particle with an unusual composition. But Ting refused to release the data until he was sure everything was correct. He split his team into two groups that independently analyzed the data again and again. Only in November of that year, when a colleague at a meeting told Ting that particle physicist Burton Richter had seen the same signal at the Stanford Linear Accelerator Center, did Ting share his finding. The confirmation of a fourth quark, the charm, embedded in a particle that Ting called J and Richter called Psi earned Ting a share (with Richter) of the 1976 Nobel Prize in physics. Ting’s experimental design skill, combined with large doses of meticulousness, smarts and stubbornness, had netted him the ultimate physics honor. He was 40 years old.

    From there, Ting kept pursuing big projects. In the late 1980s, he organized a team to design a detector for the multibillion-dollar Superconducting  Super Collider, an 87-kilometer-around particle accelerator slated for construction near Waxahachie, Texas. Ting wanted to build a $750 million instrument; the U.S. Department of Energy said the detector should not cost more than $500 million. So Ting quit. “He was very determined to do it his way,” says Gary Sanders, a high-energy physicist and former Ting graduate student who was part of that team.

    In 1993, Congress dealt American physicists a devastating blow by canceling the Super Collider. Ting, however, had moved on. In 1994, he pitched perhaps the most ambitious project of his career.

    Like his first major experiment, it would hunt for antideuterons and other antimatter nuclei. And similar to his Nobel-winning research, it would use electrons and positrons as probes to identify undiscovered parent particles. Except instead of sorting through shrapnel created in carefully orchestrated particle collisions, he wanted to go after particles produced naturally in the universe. The Alpha Magnetic Spectrometer experiment would collect and analyze particles in space.

    Both NASA and the Department of Energy, the same agency that rejected Ting’s plan for the detector in Texas, pledged their support.

    From lab to liftoff

    Scientists have studied cosmic rays for a century in hope of learning about the objects that produce them. But Ting’s proposal offered the rare chance to create a robust census of cosmic rays from well above Earth’s meddlesome atmosphere. Most previous experiments took place on balloons, which fly only briefly and don’t leave the atmosphere, or on the ground, forcing scientists to analyze cascading showers of particles triggered by cosmic rays striking atoms in the atmosphere.

    Those past experiments still delivered some tantalizing results. In 1997, the High-Energy Antimatter Telescope, or HEAT, a cosmic ray detector tethered to a high-altitude balloon, revealed an unexpectedly high concentration of positrons in space. At the time, physicists didn’t know of many processes in the universe that could produce positrons, so theorists quickly came up with some ideas. The most intriguing possibility was that the positrons were created by particles of dark matter in the galaxy. Though the dark matter particles would be invisible, they would occasionally collide and annihilate each other to produce gamma radiation and detectable particles, including electrons and positrons. If these dark matter theories were correct, then a precise measurement of cosmic ray positrons would enable physicists to pin down the nature and mass of dark matter particles.

    But dark matter wasn’t the only explanation. Other theorists proposed positron-forming mechanisms that have far less relevance for deciphering the universe. Atop the list were pulsars — dense, rapidly spinning cores left over after massive stars explode. A pulsar’s rapid rotational speed generates an intense electromagnetic field strong enough to rip electrons from its surface. Those electrons interact with photons and create pairs of electrons and positrons. Calculations suggested that just one or two pulsars, which are difficult to detect, within hundreds of light-years of the solar system would be enough to litter Earth with positrons.

    Despite the intriguing quandary exposed by HEAT, some scientists doubted that the Alpha Magnetic Spectrometer could add much to the positron origin debate or resolve any big physics mysteries. But Ting was determined to see his project fly. He assembled a 16-country collaboration to divide the work and the ballooning costs. When the 2003 explosion of the space shuttle Columbia led NASA to rescind its offer of a ride to the space station, Ting lobbied members of Congress, teasing at the wonders that could be hidden in cosmic rays and stressing the International Space Station’s not-so-stellar reputation for housing serious science.

    “If you told Sam that to get what he wanted he had to win the Indy 500, he’d become the world’s best race car driver,” says Richard Milner, the director of MIT’s Laboratory for Nuclear Science, who oversees Ting’s group. Ting wouldn’t let up on government officials in Washington, even as many of his collaborators focused on other projects.

    He was very persuasive, says Kay Bailey Hutchison, at the time a U.S. Senator from Texas. She says Ting convinced her and others that the mission was worth the cost and safety concerns of extending the beleaguered shuttle program. “He’s such a visionary,” she says. She was inspired enough to switch appropriations subcommittees to find funding for the project. In October 2008, President George W. Bush signed a bill adding shuttle flights so that the Alpha Magnetic Spectrometer would hitch a ride on one of them. “Without [Ting’s] absolute unwillingness to give up, we would not have gotten it,” Hutchison says.

    By the time Ting’s brainchild reached the space station in May 2011, a couple of space-based cosmic ray experiments had beaten his spectrometer to the punch. In 2008, PAMELA, a cosmic ray detector attached to a Russian reconnaissance satellite, revealed the same positron excess hinted at by HEAT. NASA’s Fermi Gamma-ray Space Telescope, which also carries a cosmic ray detector, came up with similar results in 2011. Neither probe discerned the source of the positrons, however.

    PAMELA Cosmic Ray Detector
    PAMELA

    NASA Fermi Telescope
    NASA’s Fermi Gamma-ray Space Telescope

    4
    POSITRON PUZZLE The positron measurements (as a fraction of the total number of positrons and electrons) made by the Alpha Magnetic Spectrometer (AMS) are shown with solid red circles in this graph. Measurements made by previous instruments (see legend) had much larger margins of error, as indicated by the lines above and below each data point. [Source: L. Accardo et al/Phys. Rev. Lett. 2014]

    Ting’s instrument began its cosmic ray survey almost immediately after installation, collecting as much data in one day as PAMELA did in 50. It sifted through positively charged particles, most of which are protons, and picked out the more valuable positrons. Ting, true to form, took his time before releasing the first results. “I doubt in the next 20 years anyone will be able to repeat the experiment,” he says. “There’s nobody to check us. It’s of the utmost importance to get it correct.”

    Ting broke his silence with a news conference at CERN in April 2013. After again employing two separate teams to comb through the data, he confirmed the positron excess detected by HEAT, PAMELA and Fermi (SN: 5/4/13, p. 14). Analyzing the properties of 6.8 million positrons and electrons, Ting’s team found that the number of positrons keeps rising as the particle energies increase. The clear excess of positrons, Ting said, reinforces that something relatively nearby must be producing them. He pushed the dark matter explanation but admitted it was not the only possibility.

    Ting returned for another news conference in September. This time, after poring over 10.9 million positrons and electrons, Ting’s team pinpointed the energy, about 275 billion electron volts, at which the concentration of positrons stops increasing (see graph above). That’s an interesting number, says Peter McIntyre, a high-energy physicist at Texas A&M University in College Station, because it indicates that the mass of hypothetical dark matter particles limits the energy of the positrons they can produce. Theorists could use the peak positron energy to estimate dark matter’s mass. But again, the experiment did not come close to proving that dark matter actually produced the positrons.

    ___________________________________________________________________________________________________

    5
    X-ray: NASA/CXC/Univ. of Toronto/M. Durant et al; Optical: DSS/Davide De Martin

    Pulsars, like the Vela pulsar located about 1,000 light-years away, are rapidly spinning dense cores of former stars. Nearby pulsars may produce the unexplained excess of positrons detected by the Alpha Magnetic Spectrometer and other experiments.
    What is it?

    Dark matter A form of matter that accounts for most of the mass in a galaxy but does not consist of the ordinary kind of matter found on Earth.

    Pulsar A dense, rapidly spinning remnant of a star that was initially much more massive than the sun.
    How would it produce positrons?

    Dark matter In theory, two dark matter particles can collide and annihilate each other to produce electrons and positrons.

    Pulsar The collision of photons with speedy electrons ripped from a pulsar’s surface by intense electromagnetic fields produces electrons and positrons.

    What are the implications?

    Dark matter Finding positrons from dark matter would help scientists to determine the type and mass of dark matter particles, resolving a decades-long mystery.

    Pulsar Positrons from pulsars would reveal something about particles that pulsars create. But it would not lead to big-picture understanding of the universe.
    ________________________________________________________________________________________________________

    In fact, some physicists argue that the Alpha Magnetic Spectrometer, despite its unmatched particle-detecting prowess, can never definitively distinguish between dark matter annihilation, pulsars or a yet-to-be-discovered process that might be producing those surplus shards of antimatter.

    “A pulsar could explain any observation that AMS could ever make,” says Gregory Tarlé, a particle astrophysicist at the University of Michigan in Ann Arbor. No matter what the positron data, physicists will not be able to definitively isolate the alleged signal of dark matter, he argues.

    Katherine Freese, a theoretical astrophysicist at the Nordic Institute for Theoretical Physics in Stockholm, agrees that conclusively proving dark matter from positrons will be very difficult. “My bet is on pulsars,” she says.

    Other experiments also suggest that AMS has a slim chance of making a compelling case for dark matter. In a study posted online in January at arXiv.org, physicists pored over Fermi telescope measurements to look for gamma radiation, which should also be produced when dark matter particles annihilate each other. The data ruled out most dark matter collision mechanisms proposed by theorists. And in December, scientists with the Planck satellite announced that their survey of the universe’s most ancient light revealed no signs of detritus from colliding dark matter, which if self-annihilating now also should have been when the cosmos was young (SN: 12/27/14, p. 11).

    ESA Planck
    ESA/Planck

    Ting says he pays about as much attention to other experiments as he does to his critics. He monitors the scientific literature, but doesn’t put much stock in blanket conclusions based on one set of data. “I learned a long time ago: Only look at your own experiment,” he says.

    He expects to learn more by studying positrons at higher energies. If the mass of a dark matter particle is, say, one trillion electron volts, then it probably wouldn’t produce positrons with more than a quarter of that energy. So if the positron concentration falls off a cliff after the newly identified peak, Ting says, that would suggest a dark matter origin. Pulsars, on the other hand, should produce positrons with a spectrum of energies that wouldn’t drop so precipitously.

    Within the next year or two, the AMS team will release its first analysis of antiprotons, antimatter particles that Ting says are too heavy to be manufactured by pulsars but should be produced in dark matter collisions. Ting calls the preliminary results “intriguing.” But of course, he won’t offer more until all the cross-checks are complete.

    He’s confident that future measurements will allow him to definitively pin down the origin of positrons, whether from dark matter or something else.

    Even if the dark matter picture remains muddled, there is a possibility that AMS will detect primordial antimatter. One of the biggest mysteries in physics is why matter won out in a universe that presumably began with equal parts of matter and antimatter. Ting hopes to find complex antimatter — perhaps antihelium (two antiprotons and two antineutrons) or antideuterons — that was forged just after the Big Bang. Tarlé and other scientists say the chances of detecting these antinuclei are extremely low because the antimatter would have to navigate through the matter-rich galaxy and solar system without being destroyed.

    Ting is undeterred. Gathering insights about the cosmos takes time. Anticipating that funding will run as long as the space station operates, Ting simply wants to see what nature throws at him. “If you don’t look,” he says, “you do not know.”

    See the full article here.

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