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  • richardmitnick 2:02 pm on November 1, 2017 Permalink | Reply
    Tags: , Dark Energy Survey, Jennifer Marshall, Texas A&M Astronomer Jennifer Marshall Witnesses Cosmic History in Chile, ,   

    From Texas A&M: Women in STEM – “Texas A&M Astronomer Jennifer Marshall Witnesses Cosmic History in Chile” 

    Texas A&M logo

    Texas A&M

    1

    Marshall (above and below), operating the Dark Energy Camera on the Blanco Telescope at the Cerro Tololo Inter-American Observatory in August 2017. The image displayed on the monitor is the gravitational wave event GW170817, the source just to the top left of the larger galaxy NGC 4993 in the center of the screen. (Credit: Erika Cook, Texas A&M University.)

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    “It was truly amazing. I felt so fortunate to be in the right place at the right time to help make perhaps one of the most significant observations of my career.”
    Dr. Jennifer Marshall, Texas A&M astronomer

    Dark Energy Survey


    Dark Energy Camera [DECam], built at FNAL


    NOAO/CTIO Victor M Blanco 4m Telescope which houses the DECam at Cerro Tololo, Chile, housing DECam at an altitude of 7200 feet

    August 17 dawned as the first day in an otherwise ordinary observing run for Texas A&M University astronomer Jennifer Marshall. She had arrived in Chile a few days earlier as part of another routine visit to the National Optical Astronomy Observatory’s (CTIO), distinguished solely by the fact that it happened to kick off the fifth and final year of the Dark Energy Survey (DES), a five-year international project led by the U.S. Department of Energy’s Fermi National Accelerator Laboratory to map one-eighth of the sky in unprecedented detail.

    CTIO Cerro Tololo Inter-American Observatory, CTIO Cerro Tololo Inter-American Observatory,approximately 80 km to the East of La Serena, Chile, at an altitude of 2200 meters

    However, just as swiftly as day turned to night and darkness descended over the Andes Mountains, Marshall found herself at the fateful crossroads of proximity and cosmic history, courtesy of one universally significant target of opportunity observation.

    By virtue of being in the right place at the right time, Marshall got to witness firsthand the fiery aftermath of a recently detected burst of gravitational waves, personally recording some of the initial images of the first confirmed explosion from two colliding neutron stars ever seen by astronomers.

    The discovery, historic because it marks the first cosmic event observed in both gravitational waves and light, was made using the U.S.-based Laser Interferometer Gravitational-Wave Observatory (LIGO); the Europe-based Virgo detector in Italy; and more than 60 ground- and space-based telescopes.


    VIRGO Gravitational Wave interferometer, near Pisa, Italy

    Caltech/MIT Advanced aLigo Hanford, WA, USA installation


    Caltech/MIT Advanced aLigo detector installation Livingston, LA, USA

    Cornell SXS, the Simulating eXtreme Spacetimes (SXS) project

    Gravitational waves. Credit: MPI for Gravitational Physics/W.Benger-Zib

    ESA/eLISA the future of gravitational wave research

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    Skymap showing how adding Virgo to LIGO helps in reducing the size of the source-likely region in the sky. (Credit: Giuseppe Greco (Virgo Urbino group)

    During the course of seven days in Chile, Marshall watched the extraordinary event play out in real time through two telescopes — the 4-meter Victor M. Blanco Telescope at CTIO, then moving on to the 6.5-meter Magellan Telescope at nearby Las Campanas Observatory. She was the only astronomer present and observing for DES at Blanco during the unprecedented occurrence.

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    The Twin Magellan telescope domes on Cerro Manqui at 8370 feet (2450 m) above sea level. Each dome houses a 6.5-meter class telescope, with the Landon Clay telescope in the left dome and
    Walter Baade telescope in the right dome. The building connecting the two domes serves as a storage area for various instruments and a maintenance facility for realuminizing the mirrors.
    Note the tall, slender silo next to the domes. This is a differential image motion monitor (DIMM) telescope used to measure atmospheric seeing.

    “It is my observation that every telescope in Chile, including the two I was using, was pointed at this thing for the entire week,” Marshall said. “It was definitely the most important science I have ever had the opportunity to be involved in.”

    Images taken by Marshall using the 570-megapixel Dark Energy Camera (DECam) captured the flaring up and fading over time of a kilonova — an explosion similar to a supernova but on a smaller scale — that occurs when collapsed stars, called neutron stars, crash into each other, theoretically creating heavy radioactive elements.

    This particular violent merger, which occurred 130 million years ago in a galaxy (NGC 4993) relatively near our own Milky Way galaxy, is the source of the gravitational waves detected by the LIGO and the Virgo collaborations on Aug. 17. Although this is the fifth source of gravitational waves to be detected, it is unique because it is the first one with a visible electromagnetic counterpart observable by optical telescopes — the glowing aftermath of the collision of two neutron stars — as opposed to binary black holes, which are not expected to produce a remnant that can be seen through telescopes.

    Capitalizing on a Target of Opportunity

    When DES officials at Fermilab learned along with dozens of LIGO-affiliated collaborations and observatories around the world that a strong gravitational signal, named GW170817, had been detected at 7:41 a.m. CDT by two of LIGO’s three detectors — a find further corroborated by a gamma-ray burst detected by NASA’s Fermi Gamma-ray Space Telescope at roughly the same time — they sent out a target of opportunity observation notice that Marshall quickly seized upon.

    As she was observing at Blanco, Marshall was simultaneously collaborating via Skype with fellow DES scientists Marcelle Soares-Santos (Fermilab/Brandeis University), the DES principal investigator in charge of gravitational wave observations, and Daniel Holtz (University of Chicago), who is a member of both LIGO and DES. Coincidentally, Marshall also was sharing some of those nights via remote with Ting Li ’16, who earned her doctorate in astronomy at Texas A&M in 2016 working with Marshall and currently is a Lederman Fellow in Experimental Physics at Fermilab.

    “LIGO tells you the equivalent of, ‘If you look in this area of the sky, there might be something,'” Marshall explained. “Virgo helped narrow that area down to the extent that, instead of 100 square degrees, it was only 30. DECam has a large field of view of three square degrees, so we only had to look at 30 telescope pointings. I was there with Erika Cook, our Munnerlyn Astronomical Laboratory control systems engineer, and Marcus Sauseda, an undergraduate aerospace engineering major here at Texas A&M, and we took some quick, short exposures — a total of roughly one hour. I sent the data off, then went to bed. I woke up to an ecstatic email from Edo Berger at Harvard, who happens to be a longtime colleague from our postdoc days at The Observatories of the Carnegie Institution of Washington.”

    Armed with the crystal-clear images from DECam, for which Texas A&M astronomer Darren DePoy served as project scientist, Berger’s team went to work analyzing the phenomenon using several different resources, including NASA’s Hubble Space Telescope and Chandra X-ray Observatory. For her part, Marshall continued imaging the galaxy for five more nights at CTIO, watching the event fade rapidly and change in color from blue to red as the explosion quickly cooled down. She then spent a seventh night at Las Campanas, doing follow-up observation with the Magellan telescope, using a different spectrometer to enable more detailed study of the event in collaboration with Carnegie Observatories scientists Maria Drout and Ben Shappee.

    Jennifer Marshall may have been one of many astronomers observing GW170817 from both ground- and space-based telescopes on Aug. 17, but she likely was the only one who happened to have a film crew in tow. Check out this video produced by NOVA PBS, present at CTIO at the time, shooting footage for an upcoming segment on the Dark Energy Survey. Catch Marshall at the 0:45, 1:10 and 1:42 marks!

    Byproducts of a Binary Star Merger

    Understandable excitement aside, Marshall says this event is particularly interesting to her because it is directly related her research on r-process elements — the heavy elements that exist on Earth and are produced in theory as the byproducts of neutron star collisions and mergers. These observations show that the theory is accurate, providing the final piece of the puzzle regarding the origin of r-process elements.

    “This was the first time anyone has ever watched such an event play out from beginning to end, all thanks to LIGO,” Marshall said. “It was truly amazing. Watching science happen in real time is not something most astronomers get to experience. With the exception of supernovae and exoplanet studies, most things we work on take billions of years to play out. I felt so fortunate to be in the right place at the right time to help make perhaps one of the most significant observations of my career.”

    Marshall said one indication of just how well LIGO/Virgo is working is the amount of event follow-up requests, which are so numerous as a result of its second and most recent observing run since being upgraded via a program called Advanced LIGO that astronomers have been forced to prioritize.

    “There were actually several binary black hole mergers that same week that we didn’t bother to look at because the neutron star source was so much more important,” Marshall said. “We had absolutely no idea this was going to happen. Everyone was shocked, and understandably so, because it was truly unbelievable.”

    In addition to Marshall and DePoy, fellow Texas A&M astronomers and Mitchell Institute members Lucas Macri, Casey Papovich, Nicholas Suntzeff and Louis Strigari are full members of the 400-plus-member international DES collaboration that spans 26 institutions and seven countries as well as the gamut of science and engineering in the search for answers regarding the universe’s accelerated expansion. Texas A&M statistician James Long and Mitchell Institute Postdoctoral Fellow Peter Brown also are external collaborators.

    Publications Aplenty

    The LIGO-Virgo results are published today in the journal Physical Review Letters, while additional papers from the LIGO and Virgo collaborations and the astronomical community either have been submitted or accepted for publication in various journals.

    Six papers relating to the DECam discovery of the optical counterpart are planned for publication in The Astrophysical Journal. Preprints of all papers are available online.

    Marshall’s observations made during that fateful August week in Chile appear in a total of nine publications making their debut today, including the mega paper from LIGO that includes citations for 75 associated papers, in addition to two DES-related papers appearing in The Astrophysical Journal as well as two papers in the journal Science featuring the Las Campanas spectra and images. Beyond those, she is an author on three additional DES papers, including one that uses the binary neutron star merger event to derive the Hubble constant. DePoy and Li join her as co-authors on several of those papers by virtue of their status as fellow DES Builders. Finally, she is an author on the Transient Optical Robotic Observatory of the South (TOROS) Collaboration paper in The Astrophysical Journal Letters.

    “The August 17 binary neutron star merger event occurred in nearby galaxy NGC 4993, located at a distance of 39.5 megaparsecs from the Milky Way,” Marshall said. “This event will surely usher in a new field of science, the direct observational study of the formation of r-process elements starting now and being fueled by future discovery of similar events by LIGO and follow-up study by astronomers.”

    Read more on today’s announcement and its broader significance in the official press releases from LIGO/Virgo , DES/Fermilab, which include additional images along with animations and videos and from From UCSC: “Neutron stars, gravitational waves, and all the gold in the universe”, which tells the optical astronomy part of the story. This last, written by Tim Stephens is quite a production, complete with a 2.5 hour video of the press conference is not to be missed.

    Learn more about the Texas A&M Astronomy Group’s broader role in the imaging and analyses.

    For more information about Texas A&M astronomy, visit http://astronomy.tamu.edu.

    See the full article here .

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    Holds membership in the prestigious Association of American Universities, one of only 62 institutions with this distinction.
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  • richardmitnick 3:28 pm on October 16, 2017 Permalink | Reply
    Tags: , , , , Dark Energy Survey, ,   

    From Symmetry: “Scientists observe first verified neutron-star collision” 


    Symmetry

    10/16/17
    Sarah Charley

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    Fermilab

    Today scientists announced the first verified observation of a neutron star collision. LIGO detected gravitational waves radiating from two neutron stars as they circled and merged, triggering 50 additional observational groups to jump into action and find the glimmer of this ancient explosion.


    VIRGO Gravitational Wave interferometer, near Pisa, Italy

    Caltech/MIT Advanced aLigo Hanford, WA, USA installation


    Caltech/MIT Advanced aLigo detector installation Livingston, LA, USA

    Cornell SXS, the Simulating eXtreme Spacetimes (SXS) project

    Gravitational waves. Credit: MPI for Gravitational Physics/W.Benger-Zib

    ESA/eLISA the future of gravitational wave research

    1
    Skymap showing how adding Virgo to LIGO helps in reducing the size of the source-likely region in the sky. (Credit: Giuseppe Greco (Virgo Urbino group)

    This observation represents the first time experiments have seen both light and gravitational waves from a single celestial crash, unlocking a new era of multi-messenger astronomy.

    On August 17 at 7:41 a.m. Eastern Time, NASA astronomer Julie McEnery had just returned from an early morning row on the Anacostia River when her experiment, the Fermi Gamma Ray Space Telescope, sent out an automatic alert that it had just recorded a burst of gamma rays coming from the southern constellation Hydra.

    NASA/Fermi Telescope


    NASA/Fermi LAT

    By itself, this wasn’t novel; the Gamma-ray Burst Monitor instrument on Fermi has seen approximately 2 gamma-ray outbursts per day since its launch in 2008.

    “Forty minutes later, I got an email from a colleague at LIGO saying that our trigger has a friend and that we should buckle up,” McEnery says.

    Most astronomy experiments, including the Fermi Gamma Ray Space Telescope, watch for light or other particles emanating from distant stars and galaxies. The LIGO experiment, on the other hand, listens for gravitational waves. Gravitational waves are the equivalent of cosmic tremors, but instead of rippling through layers of rock and dirt, they stretch and compress space-time itself.

    Exactly 1.7 seconds before Fermi noticed the gamma ray burst, a set of extremely loud gravitational waves had shaken LIGO’s dual detectors.

    “The sky positions overlapped, strongly suggesting the two signals were coming from the same astronomical event,” says Daniel Holz, a professor at the University of Chicago and member of LIGO collaboration and the Dark Energy Survey Gravitational Wave group.

    Dark Energy Survey


    Dark Energy Camera [DECam], built at FNAL


    NOAO/CTIO Victor M Blanco 4m Telescope which houses the DECam at Cerro Tololo, Chile, housing DECam

    LIGO reconstructed the location and distance of the event and sent an alert to their allied astronomers. About 12 hours later, right after sunset, multiple astronomical surveys found a glowing blue dot just above the horizon in the area LIGO predicted.

    “It lasted for two weeks, and we observed it for about an hour every night,” says Jim Annis, a researcher at the US Department of Energy’s Fermi National Accelerator Laboratory, the lead institution on the Dark Energy Survey. “We used telescopes that could see everything from low-energy radio waves all the way to high-energy X-rays, giving us a detailed image of what happened immediately after the initial collision.”

    Neutron stars are roughly the size of the island of Nantucket but have more mass than the sun. They have such a strong gravitational pull that all their matter has been squeezed and transformed into a single, giant atomic nucleus consisting entirely of neutrons.

    “Right before two neutron stars collide, they circle each other about 100 times a second,” Annis says. “As they collide, huge electromagnetic tornados erupt at the poles and material is sprayed out in all directions at close to the speed of light.”

    As they merge, neutron stars release a quick burst of gamma radiation and then a spray of decompressing neutron star matter. Exotic heavy elements form and decay, dumping enough energy that the surface reaches temperatures of 20,000 degrees Kelvin. That’s almost four times hotter than the surface of the sun and much brighter. Scientists theorize that a good portion of the heavy elements in our universe, such as gold, originated in neutron star collisions and other massively energetic events.

    Since coming online in September 2015, the US-based LIGO collaboration and their Italy-based partners, the Virgo collaboration, have reported detecting five bursts of gravitational waves. Up until now, each of these observations has come from a collision of black holes.

    “When two black holes collide, they emit gravitational waves but no light,” Holz says. “But this event released an enormous amount of light and numerous astronomical surveys saw it. Hearing and seeing the event provides a goldmine of information, and we will be mining the data for years to come.”

    This is a Rosetta Stone-type discovery, Holz says. “We’ve learned about the processes that neutron stars are undergoing as they fling out matter and how this matter synthesizes into some of the elements we find on Earth, such as gold and platinum,” he says. “In addition to teaching us about mysterious gamma-ray bursts, we can use this event to calculate the expansion rate of the universe. We will be able to estimate the age and composition of the universe in an entirely new way.”

    For McEnery, the discovery ushers in a new age of cooperation between gravitational-wave experiments and experiments like her own.

    “The light and gravitational waves from this collision raced each other across the cosmos for 130 million years and hit earth 1.7 seconds apart,” she says. “This shows that both are moving at the speed of light, as predicted by Einstein. This is what we’ve been hoping to see.”

    Editor’s note: See LIGO scientific publications here.

    See the full article here .

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    Symmetry is a joint Fermilab/SLAC publication.


     
  • richardmitnick 9:38 am on August 3, 2017 Permalink | Reply
    Tags: , , , , Dark Energy Survey, ,   

    From U Chicago: “Dark Energy Survey reveals most precise measure of universe’s structure” 

    U Chicago bloc

    University of Chicago

    August 3, 2017

    Dark Energy Survey


    Dark Energy Camera [DECam], built at FNAL


    NOAO/CTIO Victor M Blanco 4m Telescope which houses the DECam at Cerro Tololo, Chile, housing DECam at an altitude of 7200 feet


    The Dark Energy Survey’s primary instrument, the 570-megapixel Dark Energy Camera, is mounted on the Blanco Telescope in Chile. UChicago, Argonne and Fermilab scientists are members of international Dark Energy Survey collaboration.

    Imagine planting a single seed and, with great precision, being able to predict the exact height of the tree that grows from it. Now imagine traveling to the future and snapping photographic proof that you were right.

    If you think of the seed as the early universe, and the tree as the universe the way it looks now, you have an idea of what the international Dark Energy Survey collaboration has just done. Scientists unveiled their most accurate measurement of the present large-scale structure of the universe at a meeting Aug. 3 at the University of Chicago-affiliated Fermi National Accelerator Laboratory. UChicago, Argonne and Fermilab scientists are members of international Dark Energy Survey collaboration.

    These measurements of the amount and “clumpiness” (or distribution) of dark matter in the present-day cosmos were made with a precision that, for the first time, rivals that of inferences from the early universe by the European Space Agency’s orbiting Planck observatory. The new Dark Energy Survey result (the tree, in the above metaphor) is close to “forecasts” made from the Planck measurements of the distant past (the seed), allowing scientists to understand more about the ways the universe has evolved over 14 billion years.

    “This result is beyond exciting,” said Fermilab’s Scott Dodelson, a professor in the Department of Astronomy and Astrophysics at UChicago and one of the lead scientists on this result, which was announced at the American Physical Society Division of Particles and Fields meeting. “For the first time, we’re able to see the current structure of the universe with the same clarity that we can see its infancy, and we can follow the threads from one to the other, confirming many predictions along the way.”

    Most notably, this result supports the theory that 26 percent of the universe is in the form of mysterious dark matter and that space is filled with an also-unseen dark energy, which makes up 70 percent and is causing the accelerating expansion of the universe.

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    A map of dark matter covering about one-thirtieth of the entire sky and spanning several billion light years—red regions have more dark matter than average, blue regions less dark matter. (Courtesy of Chihway Chang, the DES collaboration)

    Paradoxically, it is easier to measure the large-scale clumpiness of the universe in the distant past than it is to measure it today. In the first 400,000 years following the Big Bang, the universe was filled with a glowing gas, the light from which survives to this day. The Planck observatory’s map of this cosmic microwave background radiation gives us a snapshot of the universe at that very early time. Since then, the gravity of dark matter has pulled mass together and made the universe clumpier over time. But dark energy has been fighting back, pushing matter apart. Using the Planck map as a start, cosmologists can calculate precisely how this battle plays out over 14 billion years.

    “These first major cosmology results are a tribute to the many people who have worked on the project since it began 14 years ago,” said Dark Energy Survey Director Josh Frieman, a scientist at Fermilab and a professor in the Department of Astronomy and Astrophysics at UChicago. “It was an exciting moment when we unveiled the results to ourselves just last month, after carrying out a ‘blind’ analysis to avoid being influenced by our prejudices.”

    The Dark Energy Survey is a collaboration of more than 400 scientists from 26 institutions in seven countries. Its primary instrument is the 570-megapixel Dark Energy Camera, one of the most powerful in existence, which is able to capture digital images of light from galaxies eight billion light years from Earth. The camera was built and tested at Fermilab, the lead laboratory on the Dark Energy Survey, and is mounted on the National Science Foundation’s four-meter Blanco telescope, part of the Cerro Tololo Inter-American Observatory in Chile. The DES data are processed at the National Center for Supercomputing Applications at the University of Illinois at Urbana-Champaign.

    Scientists are using the camera to map an eighth of the sky in unprecedented detail over five years. The fifth year of observation will begin this month. The new results draw only from data collected during the survey’s first year, which covers one-thirtieth of the sky.

    Scientists used two methods to measure dark matter. First, they created maps of galaxy positions as tracers, and second, they precisely measured the shapes of 26 million galaxies to directly map the patterns of dark matter over billions of light years, using a technique called gravitational lensing.

    Gravitational Lensing NASA/ESA

    To make these ultra-precise measurements, the team developed new ways to detect the tiny lensing distortions of galaxy images—an effect not even visible to the eye, enabling revolutionary advances in understanding these cosmic signals. In the process, they created the largest guide to spotting dark matter in the cosmos ever drawn. The new dark matter map is ten times the size of the one that the Dark Energy Survey released in 2015 and will eventually be three times larger than it is now.

    “The Dark Energy Survey has already delivered some remarkable discoveries and measurements, and they have barely scratched the surface of their data,” said Fermilab Director Nigel Lockyer. “Today’s world-leading results point forward to the great strides DES will make toward understanding dark energy in the coming years.”

    See the full article here .

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  • richardmitnick 2:16 pm on June 10, 2017 Permalink | Reply
    Tags: , , , , , Dark Energy Survey, , The largest virtual Universe ever simulated, U Zürich   

    From U Zürich: “The largest virtual Universe ever simulated.” 

    University of Zürich

    9 June 2017
    Contact
    Prof. Dr. Romain Teyssier
    romain.teyssier@uzh.ch
    Institute for Computational Science
    University of Zurich
    +41 44 635 60 20

    Dr. Joachim Stadel
    stadel@physik.uzh.ch
    Institute for Computational Science
    University of Zurich
    Phone: +41 44 635 58 16

    Researchers from the University of Zürich have simulated the formation of our entire Universe with a large supercomputer. A gigantic catalogue of about 25 billion virtual galaxies has been generated from 2 trillion digital particles. This catalogue is being used to calibrate the experiments on board the Euclid satellite, that will be launched in 2020 with the objective of investigating the nature of dark matter and dark energy.

    ESA/Euclid spacecraft

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    The Cosmic Web: A section of the virtual universe, a billion light years across, showing how dark matter is distributed in space, with dark matter halos the yellow clumps, interconnected by dark filaments. Cosmic void, shown as the white areas, are the lowest density regions in the Universe. (Image: Joachim Stadel, UZH)

    Over a period of three years, a group of astrophysicists from the University of Zürich has developed and optimised a revolutionary code to describe with unprecedented accuracy the dynamics of dark matter and the formation of large-scale structures in the Universe. As Joachim Stadel, Douglas Potter and Romain Teyssier report in their recently published paper [Computational Astrophysics and Cosmology], the code (called PKDGRAV3) has been designed to use optimally the available memory and processing power of modern supercomputing architectures, such as the “Piz Daint” supercomputer of the Swiss National Computing Center (CSCS). The code was executed on this world-leading machine for only 80 hours, and generated a virtual universe of two trillion (i.e., two thousand billion or 2 x 1012) macro-particles representing the dark matter fluid, from which a catalogue of 25 billion virtual galaxies was extracted.

    Cray Piz Daint supercomputer of the Swiss National Supercomputing Center (CSCS)

    Studying the composition of the dark universe

    Thanks to the high precision of their calculation, featuring a dark matter fluid evolving under its own gravity, the researchers have simulated the formation of small concentration of matter, called dark matter halos, in which we believe galaxies like the Milky Way form.

    Caterpillar Project A Milky-Way-size dark-matter halo and its subhalos circled, an enormous suite of simulations . Griffen et al. 2016

    The challenge of this simulation was to model galaxies as small as one tenth of the Milky Way, in a volume as large as our entire observable Universe. This was the requirement set by the European Euclid mission, whose main objective is to explore the dark side of the Universe.

    Measuring subtle distortions

    Indeed, about 95 percent of the Universe is dark. The cosmos consists of 23 percent of dark matter and 72 percent of dark energy. “The nature of dark energy remains one of the main unsolved puzzles in modern science,” says Romain Teyssier, UZH professor for computational astrophysics.

    Earthbound science of Dark Energy

    Dark Energy Camera [DECam], built at FNAL


    NOAO/CTIO Victor M Blanco 4m Telescope which houses the DECam at Cerro Tololo, Chile, housing DECam

    A puzzle that can be cracked only through indirect observation: When the Euclid satellite will capture the light of billions of galaxies in large areas of the sky, astronomers will measure very subtle distortions that arise from the deflection of light of these background galaxies by a foreground, invisible distribution of mass – dark matter. “That is comparable to the distortion of light by a somewhat uneven glass pane,” says Joachim Stadel from the Institute for Computational Science of the UZH.

    Optimizing observation strategies of the satellite

    This new virtual galaxy catalogue will help optimize the observational strategy of the Euclid experiment and minimize various sources of error, before the satellite embarks on its six-year data collecting mission in 2020. “Euclid will perform a tomographic map of our Universe, tracing back in time more than 10-billion-year of evolution in the cosmos,” Stadel says. From the Euclid data, researchers will obtain new information on the nature of this mysterious dark energy, but also hope to discover new physics beyond the standard model, such as a modified version of general relativity or a new type of particle.

    See the full article here .

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    The University of Zürich (UZH, German: Universität Zürich), located in the city of Zürich, is the largest university in Switzerland, with over 26,000 students. It was founded in 1833 from the existing colleges of theology, law, medicine and a new faculty of philosophy.

    Currently, the university has seven faculties: Philosophy, Human Medicine, Economic Sciences, Law, Mathematics and Natural Sciences, Theology and Veterinary Medicine. The university offers the widest range of subjects and courses of any Swiss higher education institutions.

     
  • richardmitnick 9:59 pm on June 6, 2017 Permalink | Reply
    Tags: , , , , Dark Energy Survey, ,   

    From FNAL: “Scientists close in on dark matter using Dark Energy Survey data” 

    FNAL II photo

    FNAL Art Image
    FNAL Art Image by Angela Gonzales

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

    June 6, 2017
    Troy Rummler

    Scientists exploring data collected by the Fermilab-constructed, Chilean-based Dark Energy Camera (DECam) discovered 20 satellite galaxies of the Milky Way, nearly doubling the number previously known and adding to those identified by the earlier Sloan Digital Sky Survey, another project where Fermilab played a key role. These tiny satellite galaxies can contain hundreds of times more dark matter than normal matter. Whether the mysterious dark matter turns out to be axions, weakly interacting massive particles or something else, DECam has proven itself to be a powerful new tool for the dark matter community.


    Dark Energy Camera [DECam], built at FNAL


    NOAO/CTIO Victor M Blanco 4m Telescope which houses the DECam at Cerro Tololo, Chile, housing DECam

    See the full article here .

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    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 9:16 am on February 22, 2017 Permalink | Reply
    Tags: , , , , Dark Energy Survey, Paul Sutter,   

    From CBS: “When the lights went out in the universe” 

    CBS News

    CBS News

    February 21, 2017
    Paul Sutter

    1
    Astronomers think that the expansion of the universe is regulated by both the force of gravity, and a mysterious dark energy. In this artist’s conception, dark energy is represented by the purple grid above, and gravity by the green grid below.
    NASA/JPL-Caltech

    About 5 billion years ago, everything changed. The expansion of the universe, which had been gradually decelerating for billions of years, reversed course and entered into a period of unbridled acceleration. (It was sort of like a car that switches from decelerating to accelerating, but is still moving forward the whole time.) The unhurried, deliberate process of structure formation — the gradual buildup of ever-larger assemblies of matter from galaxies to groups to clusters — froze and began to undo itself.

    Map of voids and superclusters within 500 million light years from Milky Way 8/11/09 http://www.atlasoftheuniverse.com/nearsc.html  Richard Powell
    Map of voids and superclusters within 500 million light years from Milky Way 8/11/09 http://www.atlasoftheuniverse.com/nearsc.html Richard Powell

    Five billion years ago, a mysterious force overtook the universe. Hidden in the shadows, it lay dormant, buried underneath fields of matter and radiation. But once it uncovered itself, it worked quickly, bending the entire cosmos to its will.

    Five billion years ago, dark energy awoke.

    The guts of the universe

    To explain what’s going on in this overly dramatic telling of the emergence of dark energy, we need to talk about what the universe is made of and how that affects its expansion.

    Let’s start with the mantra of general relativity: mass and energy tell space-time how to bend, and the bending of space-time tells objects how to move. Usually, we think of this as a local interaction, used to explain the orbits of particular planets or the unusual properties of a black hole.

    But those same mathematics of relativity — which provide the needed accuracy for GPS satellites to tell you how close you are to your coffee fix — also serve as the foundation for understanding the growth and evolution of the entire universe. I mean, it is “general” relativity after all.

    The universe is made of all sorts of stuff, and the properties of that stuff influence the overall curvature of the entire cosmos, which impacts its expansion. It’s the mantra of relativity writ large: the mass and energy of the entire universe is bending the spacetime of the entire universe, which is telling the entire universe how to move.

    If the total density of all the stuff is greater than a very specific value — called “the critical density” and equal to about 4 hydrogen atoms per cubic meter — then the universe’s expansion will slow down, stop and reverse in a Big Crunch. If the universe’s density is less than this critical value, the universe will expand forever. And if it’s exactly equal to the critical value, then the universe will expand forever, but at an ever-diminishing rate.

    Measurements suggest that we live in a contradictory universe, where the total density exactly equals the critical density — but the universe’s expansion is still accelerating as if the density was too low.

    What in Hubble’s ghost is going on?

    An empty argument

    What’s going on is dark energy. Totaling 69.2 percent of the energy density of the universe, it simply behaves … strangely. Dark energy’s most important property is that its density is constant. Its second most important property is that it appears to be tied to the vacuum of empty space.

    Dark Energy Icon
    Dark Energy Camera. Built at FNAL
    Dark Energy Camera. Built at FNAL
    NOAO/CTIO Victor M Blanco 4m Telescope which houses the DECam at Cerro Tololo, Chile
    NOAO/CTIO Victor M Blanco 4m Telescope which houses the DECam at Cerro Tololo, Chile

    Take a box, and empty out everything, removing all the matter (regular and dark), neutrinos, radiation … everything. If you did it right, you’ll have a box of pure, unadulterated vacuum — which means you’ll have a box of pure dark energy. Double the size of the box, and you’ll have double the dark energy.

    This behavior is the total opposite of the behavior of matter and radiation. If you have a box (or, say, a universe) with a fixed amount of matter and you double that container’s volume, the density of matter is cut in half. Radiation’s energy density goes down even further: Not only does the expansion of the universe dilute radiation, it also stretches out its wavelength.

    But as the universe expands, we continually get more empty space (vacuum) in it, so we continually get more dark energy. If you’re worried that this violates some sort of principle of conservation of energy, you can rest easy tonight: The universe is a dynamic system, and the form of the conservation laws taught in Physics 101 only apply to static systems. The universe is a dynamic place, and the concept of “conservation of energy” still holds but in a more complex, noninuitive way. But that’s an article for another day.

    You may also be wondering how I can talk so confidently about the nature of dark energy, since we don’t seem to understand it at all. You’re right: We don’t understand dark energy. At all. We know it exists, because we directly observe the accelerated expansion of the universe, and a half-dozen other lines of evidence all point to its existence.

    And while we don’t know what’s creating the accelerated expansion, we do know that we can model it as a property of the vacuum of space that has a constant density, so that’s good enough for now.

    A vacuum and an empty place

    The fact that dark energy has constant density means that in the distant past, it simply didn’t matter — because of matter. All the stuff in the universe was crammed into a smaller volume, which means regular and dark matter had very high densities. This high density meant that for a long time, the expansion of the universe was slowing down.


    The day Dark Energy switched on – Ask a Spaceman! by Paul M. Sutter on YouTube

    But as expansion continued, the matter and radiation in the universe became more and more dilute, and they got less and less dense. Eventually, about 5 billion years ago, the density of matter dropped beneath that of dark energy, which had been holding constant all that time. And once dark energy took over, the game changed completely. Because of the constant nature of its density, compared to the lowering density of matter, expansion not only continued but also accelerated. And that accelerated expansion halted the process of structure formation: Galaxies would love to continue gluing onto each other to form larger structures like clusters and superclusters, but the intervening empty space is inexorably pulling them apart.

    Some chance mergers will continue to happen, of course, but the universe’s days of building larger structures are long over.

    A cosmic coincidence

    The emergence of dark energy leaves us with a little puzzle. In the distant past, when matter densities were incredibly high in a compact universe, dark energy didn’t matter at all. In the distant future, matter will be spread so thin — like too little butter over too much bread — that its density will be ridiculously, hilariously, pathetically small compared to dark energy’s.

    Dark energy depiction. Image: Volker Springle/Max Planck Institute for Astrophysics/SP)
    Dark energy depiction. Image: Volker Springle/Max Planck Institute for Astrophysics/SP


    The surprising coincidence between dark matter and dark energy – Ask a Spaceman! by Paul M. Sutter on YouTube

    Right now, we live in the in-between epoch, where dark energy is roughly three-quarters of the total mass-energy of the universe and dark matter is about one-quarter (regular matter is a negligible amount). This seems a bit … coincidental. Considering the grand history of the universe, we just happen to observe it in the tiny slice of time when matter and dark energy are trading places.

    Did we just happen to get lucky? To arise to consciousness and observe the universe where both dark matter and dark energy are of roughly equal strength? Or is the universe telling us something more? Maybe it’s not a coincidence at all. Maybe dark matter and dark energy “talk” to each other and keep in balance via additional forces of nature; forces that simply don’t manifest in Earthly laboratories. Maybe they’re connected and related.

    Or maybe not. We simply don’t know. It’s a little too dark out there to tell.

    Paul Sutter is an astrophysicist at The Ohio State University and the chief scientist at COSI Science Center. Sutter is also host of Ask a Spaceman, RealSpace and COSI Science Now.

    See the full article here .

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  • richardmitnick 4:07 pm on February 8, 2017 Permalink | Reply
    Tags: , Dark Energy Survey, , Lambda-The Cosmological Constant, What is Dark Energy?   

    From the Dark Energy Survey: “Science” A Monster of an Article and a Must Read 

    Dark Energy Icon

    The Dark Energy Survey

    2.8.17
    No writer credit

    Today marks the 100th anniversary of Einstein’s cosmological constant! Read more about how his “biggest blunder” may actually explain dark energy in the following article.

    The accelerated expansion of the universe is thought to be caused by a new phenomenon, dark energy, or perhaps requires a modification in our theory of gravity. We know little about the fundamental nature of dark energy: is it constant, or does it change in time? DES will observe thousands of supernovae and hundreds of millions of galaxies to measure or constrain changes in dark energy over cosmic time.

    The Universe is getting away from us

    For over 13 billion years, the universe has been expanding. The earliest evidence for expansion came from the work of Edwin Hubble, Vesto Slipher, and others in the 1920’s, who studied the distances to and the motions of galaxies a few million light-years distant. They found that the farther away galaxies are, the faster they recede from us, with recession speed proportional to distance. This Hubble Law of recession is universal: all galaxies across the universe are speeding away from each other with speed proportional to distance; that is, the universe is expanding.

    The expansion can be visualized by imagining a rubber sheet with a square grid imprinted on it, with galaxies occupying points on the grid. As the sheet stretches with the expansion, the size of the grid squares grows. As a result, any two points fixed on the grid move away from each other with a relative speed that’s proportional to the distance between them. With time, there is more and more space between the galaxies.

    Another visualization is presented in Figure 1, which shows the entire history of the universe, from the moment of the Big Bang (left) to today (right): when we look out at the universe, we look (leftward) into its past. The vertical size of the cone provides a scale for relative size of the observable universe from our vantage point on the right.

    1
    Figure 1: Timeline of the cosmos; Photo credit: NASA/WMAP Science Team

    While cosmic expansion increases the distances between galaxies, they and their constituents still feel gravitational attraction: they are pulled toward each other whilst the expansion takes place. Galaxies and groups of galaxies can therefore remain gravitationally bound objects despite the overall expansion. Figure 1 also shows how stars, gas, dust, and dark matter eventually agglomerated into galaxies and galaxies into larger structures of the cosmic web (see Figure 3, which should be renamed Fig. 4).

    2
    Figure 2: The fabric of space-time is warped by any object with mass; the greater the mass, the larger the resulting curvature of space-time. No image credit.

    In the early 20th century, Albert Einstein set the stage for modern cosmology by formulating his theory of gravity, General Relativity: curved space-time tells mass and energy (including light and particles of matter) how to move, while mass and energy tell space-time how to curve. This means that any thing that has mass (or energy) will warp space-time, even if slightly; and, in turn, that warped space-time will change the trajectories of particles traveling through it.

    Applied to the universe as a whole, Einstein’s theory relates the rate of cosmic expansion to the mass-energy of all the stuff in the universe. Since galaxies feel the gravitational tug of their neighbors, we would expect them to slow down over time: the expansion should be decelerating. If there were enough matter in the universe, the curvature of space-time would be strong enough to eventually reverse the expansion, leading to a big crunch in which everything collapses to an infinitely dense point. Throughout the 20th century, cosmologists attempted to measure the density of matter in the universe and the rate of slowing of the expansion, in order to answer the question of whether the universe would expand forever or recollapse.

    This picture changed in 1998, with the discovery by two teams of astronomers studying distant supernovae–exploding stars–that the expansion is not slowing down but speeding up. A particular kind of supernova, called a type Ia, reaches its maximum brightness (comparable to the brightness of an entire galaxy) two to three weeks after exploding and then fades over a few months. Type Ia supernovae have the remarkable property that, after accounting for differences in their colors and the rates at which they fade, they all have nearly the same intrinsic maximum brightness. For such “standardizable candles”, measuring how bright they appear to us tells us how far away they are and thus roughly how long it has taken their light to reach us. The two teams of astronomers found that supernovae that exploded when the universe was about two-thirds its present size appeared about 25% fainter than would be expected if the expansion were decelerating (see Fig. 4). This discovery of cosmic acceleration was awarded the Nobel Prize in physics in 2011.

    3
    Figure 3: Supernova Hubble Diagram shows brightnesses of supernovae (vertical axis) vs. the size of the universe (horizontal axis). The blue region shows universes that accelerate, and the pink region shows universes in which the expansion slows down. The supernovae measured in the late 1990’s were fainter (and thus farther away) than expected for a universe that is decelerating, i.e., without dark energy. No image credit.

    Since ordinary matter would cause the expansion to slow down, cosmic acceleration requires us to posit a new, unseen form of energy in the universe–now called dark energy–that would have the strange property of giving rise to gravitational repulsion instead of attraction. Our picture is that, for much of cosmic history, matter dominated over dark energy and the expansion indeed slowed, enabling galaxies and large-scale structures to form as indicated above in Fig. 1. But several billion years ago, matter became sufficiently dilute due to expansion that dark energy became the dominant component of the universe, and the expansion hit the gas pedal.

    Around the turn of the millennium, this picture was bolstered by maps of the large-scale spatial distribution of galaxies, as shown in Fig. 4, and observations of the Cosmic Microwave Background (CMB) radiation.

    CMB per ESA/Planck
    CMB per ESA/Planck

    The CMB measurements showed that the spatial geometry of the universe is flat or Euclidean–two light rays emitted in parallel will always remain parallel, which is not the case if the geometry is curved–and this determines the total energy density of the universe. By contrast, the galaxy maps indicated that the density of matter in the universe is only about 30% of this total, so there must be another, unseen component that makes up the remaining 70%. That deficit fits perfectly with how much dark energy should be there according to the supernova observations.

    4
    Figure 4: Two-dimensional map of the large-scale galaxy distribution observed by the Sloan Digital Sky Survey (SDSS). The Milky Way (our galaxy) is at the center. Regions with redder color have a higher density of galaxies; regions of a greener color have lower galaxy densities, and black regions have no galaxies. The filamentary structure evident in the map is known as the “cosmic web.” Image Credit: Sloan Digital Sky Survey

    SDSS Telescope at Apache Point Observatory, NM, USA
    SDSS Telescope at Apache Point Observatory, NM, USA

    5
    Figure 5: Cosmic Energy Budget; Image Credit: Wikipedia

    Most of the mass in the universe comes from “dark matter,” which does not interact directly with light; dark matter interacts through gravity and at most weakly with other particles. The total cosmic energy budget is made up of about 25% dark matter, 5% “baryonic” or “ordinary” matter that is made of atoms, and about 70% dark energy (see Figure 5).

    We don’t yet know what makes up most of the energy in the universe. This makes dark energy one of the greatest mysteries in cosmology (perhaps all of science) as well as the focus of many experiments and surveys, possibly for years to come.

    lambda
    Figure 6: The cosmological constant, “lambda.”

    What might dark energy be?

    One explanation is that dark energy is the intrinsic energy of empty space or of the vacuum. Scientists often refer to this as the “cosmological constant” — represented by the Greek letter, Λ (“lambda”), which is the same constant proposed by Einstein a century ago! In this theory, the vacuum energy behaves as a source of negative pressure that accelerates cosmic expansion. The vacuum energy would be constant throughout space and time.

    However, what if the density of dark energy changes over time? This is the question that many modern cosmology experiments and surveys, such as DES, are working to answer.

    One possibility for dark energy that changes in time is a new field that permeates the universe and that is in essence a much, much lighter cousin of the Higgs boson discovered in 2012 (this idea is sometimes dubbed “quintessence”). In these models, the density of dark energy would be slowly decreasing with time. A more exotic possibility would be if the density of dark energy grows over time; this would eventually result in a “Big Rip,” in which the gravitational repulsion of dark energy would grow so strong as to rip apart galaxies, stars and even atoms (see Figure 7).

    7
    Figure 7: The consequences of different dark energy models. Where does this come from? Image credit: NASA

    How is DES suited for this study, and the probes?

    Dark Energy Camera [DECam],  built at FNAL
    Dark Energy Camera [DECam], built at FNAL

    NOAO/CTIO Victor M Blanco 4m Telescope which houses the DECam at Cerro Tololo, Chile
    NOAO/CTIO Victor M Blanco 4m Telescope which houses the DECam at Cerro Tololo, Chile

    The Dark Energy Survey is using four probes, all observed with a single instrument, to study cosmic acceleration with unprecedented accuracy and precision.

    The late 20th century gave us the era of ‘precision’ cosmology, in which we sought larger numbers of celestial objects (stars, galaxies, supernovae, etc.) for our measurements and analysis. The 21st century is now bringing the era of ‘accurate’ cosmology, in which our measurements are becoming increasingly exact. That is, we are performing our observations and analyses with greater and greater specificity, reducing the effect of systematic (measurement) uncertainties on our measurements.

    To learn that dark energy existed, we measured the structures within the universe (e.g., galaxies and galaxy clusters), the geometry of the universe (e.g., the Cosmic Microwave Background) and the expansion rate of the universe (with supernovae). In the Dark Energy Survey, we measure different versions of all of these phenomena.

    DES will use four probes of these phenomena to measure the effects of dark energy on the expansion history of the universe and on the growth of structure. We will observe thousands of supernovae, more than any other single survey in history: this reveals the expansion history of the universe. Using weak gravitational lensing and galaxy clusters, we will learn about the formation of structure and the amount of matter in the universe. Finally, we measure the distribution of galaxies across the cosmos through a technique called Baryon Acoustic Oscillations (BAO): this is similar to the measurements made of cosmic geometry with the CMB, but DES will use galaxies.

    © 2017 The Dark Energy Survey

    See the full article here .

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    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. 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 4:39 pm on January 18, 2017 Permalink | Reply
    Tags: , , , , Dark Energy Survey, ,   

    From Dark Energy Survey via Inside Science: “Computer Science Technique Helps Astronomers Explore the Universe” 

    Dark Energy Icon

    The Dark Energy Survey

    1

    Inside Science

    “Deep learning” finds telltale arcs of light that indicate massive objects.

    2
    Image credits: Abigail Malate, Staff Illustrator

    January 13, 2017
    Ramin Skibba

    Google uses “deep learning” to generate captions for images, Facebook uses it to recognize faces and Tesla uses it to train self-driving cars. Now astronomers have caught on to deep learning, a form of machine learning in which a computer can be trained to identify or classify particular objects in images.

    The newest telescopes, such as the Dark Energy Survey, which uses a 4-meter telescope in northern Chile and covers about one quarter of the southern sky, take millions of images of a variety of celestial objects. These often include visual distortions, cosmic rays and satellite trails that make them difficult to interpret. Deep learning could help process this deluge of data quickly.

    “Astronomy is the next frontier to take it on,” said Brian Nord, an astrophysicist at Fermilab [FNAL] in Batavia, Illinois.

    Nord is one of a group of astrophysicists who search for rare gravitational lenses with signs of curved slivers of light or duplicated images that indicate the presence of massive objects skewing light rays.

    Gravitational Lensing NASA/ESA
    Gravitational Lensing NASA/ESA
    Gravitational microlensing, S. Liebes, Physical Review B, 133 (1964): 835
    Gravitational microlensing, S. Liebes, Physical Review B, 133 (1964): 835

    The scientists often have to sift through numerous images by eye, one at a time. But now they have a potentially game-changing technique at their disposal.

    Massive objects in space — like clusters of galaxies combined with dark matter hidden from view — distort the light we see from faraway galaxies and quasars, deflecting and warping the light rays around them. Distant galaxies look like magnified arcs, as if seen through the edge of a cosmic magnifying glass.

    Scientists have found hundreds of such lenses so far, confirming predictions of general relativity theory by Albert Einstein and others in the 1930s. With newly developed deep learning tools, astronomers expect to find at least 2,000 more with the Dark Energy Survey, according to research presented by Nord at the American Astronomical Society meeting in Grapevine, Texas on Jan. 4. A big catalog of gravitational lenses would help astronomers learn more about the nature of dark matter and how it holds galaxies together.

    Finding gravitational lenses is like finding needles in haystacks far away, when no two needles or haystacks are alike. “Deep learning is a way for us to create a model of a complicated system,” Nord said.

    To make complex classifications, astronomers have long used statistical machine learning techniques like neural networks, which are programmed systems with layered nodes connected in a web, much like neurons in the human brain. Deep learning just involves more interconnected layers or steps in the computation, including “hidden” ones of increasing complexity as the algorithm proceeds from input to output.

    For example, with facial recognition software, someone feeds in an image, and the system first detects edges, lines and curves. Intermediate layers then put together higher-level features, like eyes or a mouth, and eventually a face. For gravitational lenses, the software would gradually recognize a big galaxy surrounded by arcs, indicating lensed background objects.

    After it’s been trained with many lens images, such an algorithm can then find new lenses in images it has never encountered before. The current state-of-the-art algorithms can correctly identify these lenses all but a few percent of the time, when they mistake a particularly messy image for the real thing.

    “If it works but is 97 percent accurate, you could be vastly swamped by false positives,” said Colin Jacobs, who along with Karl Glazebrook at Swinburne University of Technology in Melbourne, Australia, is also working on the problem. “Ideally, it should be more accurate than what you’d need for computer vision or facial recognition,” he added.

    To address this challenge, Nord and Jacobs and their colleagues could design the algorithm to be strict, ensuring that it finds the cream of the crop, the clearest lenses in a survey. But this risks missing many lenses. Alternatively, they are trying to be more lenient in their search criteria, knowing it would mean later weeding out by hand some images that happen to look a bit like lenses.

    Over the past couple years, astronomers have begun to apply deep learning in other areas as well, mostly for deciphering images in other ways. They have used the techniques to distinguish between distant galaxies and stars in the Milky Way, to estimate the distance to faraway objects and to categorize the structures of galaxies, which can take on a variety of spiral and elliptical shapes.

    Others have utilized citizen science, recruiting people around the world to help sort through images. A project called Galaxy Zoo, for example, has classified the structures of hundreds of thousands of galaxies, while another, called Space Warps, has discovered dozens of candidate gravitational lenses missed by others.

    Nord applauds these efforts, but if his software works as well as advertised, “deep learning has the potential to be much faster,” he said.

    See the full article here .

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    DECam, built at FNAL
    DECam, built at FNAL
    CTIO Victor M Blanco 4m Telescope
    CTIO Victor M Blanco 4m Telescope interior
    CTIO Victor M Blanco Telescope at Cerro Tololo which houses the DECAm

    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 10:19 pm on December 12, 2016 Permalink | Reply
    Tags: , , Dark Energy Survey, , , TNO 2014 UZ224 a.k.a. DeeDee   

    From FNAL: “Dark Energy Survey discovers potential new dwarf planet” 

    FNAL II photo

    FNAL Art Image
    FNAL Art Image by Angela Gonzales

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

    December 12, 2016
    Ricarda Laasch

    Thanks to scientists on the Dark Energy Survey (DES), the solar system just got another member.

    Dark Energy Icon

    DES scientists recently reported the discovery of a potential dwarf planet located 92 times farther from the sun than the Earth is, more than twice as distant as Pluto. The new dwarf planet was discovered using the Dark Energy Camera [DECam], a scientific instrument built at Fermilab to probe the mystery of dark energy.

    Dark Energy Camera [DECam],  built at FNAL
    Dark Energy Camera [DECam], built at FNAL

    NOAO/CTIO Victor M Blanco 4m Telescope which houses the DECam at Cerro Tololo, Chile
    NOAO/CTIO Victor M Blanco 4m Telescope which houses the DECam at Cerro Tololo, Chile

    But as scientists on the DES collaboration can attest, DECam turns out to be a powerful tool for astronomy as well as cosmology.

    The newly discovered object, which the team has nicknamed DeeDee (for “distant dwarf”), is for now known as 2014 UZ224. DeeDee takes more than 1,100 years to complete one orbit around our sun and is currently the second-most distant known object in the solar system. Light from DeeDee takes 12-and-a-half hours to reach us.

    DeeDee is one of many small icy worlds that lie beyond the most distant planet in the solar system, Neptune. Such celestial bodies are called trans-Neptunian objects, or TNOs, the most famous of which is the dwarf planet Pluto. TNOs are “cosmic leftovers” from the formation 4 billion years ago of the giant planets, such as Jupiter and Neptune, and scientists study them to learn more about the history of our solar system.

    David Gerdes and his students at the University of Michigan first spotted DeeDee as a moving spot of light that appeared in just 14 of the tens of thousands of pictures taken by the Dark Energy Survey.

    The DES collaboration uses the state-of-the-art Dark Energy Camera on a telescope in Chile to map distant galaxies, to find supernovae and to search for patterns in the cosmic structure. DES began observing the sky in 2013 with the goal of shining light on dark energy, the mysterious substance that is accelerating the expansion of the universe, and collaboration scientists are primarily engaged in that task. Trans-Neptunian objects are not part of DES’ main science interests since they don’t tell us about the universe’s expansion.

    The DES supernova search, which takes pictures of the same part of the sky every week, sparked a bright idea in Gerdes: Instead of searching for spots that change their brightness over time, his students would search for spots whose positions change over time. Although DES looks at faraway galaxies, the backyard that is our own solar system is part of every picture the telescope takes. A dwarf planet could be captured in the DES data — one just had to look for it in the right way.

    “I wanted a self-contained project for my summer students that would be fun and achievable in 10 weeks,” Gerdes said. “Most topics using DES data are parts of long and complex analyses that are not manageable in such a short time frame.”

    Gerdes and his collaborators Masao Sako and Gary Bernstein at the University of Pennsylvania employed a technique developed for DES supernova searches and adjusted it to find slow-moving objects.

    “So far we’ve discovered over 50 new TNOs in our data,” Gerdes said. “DeeDee is the largest and most distant one.”

    2
    David Gerdes and his students at the University of Michigan discovered DeeDee, a potential dwarf planet at the edge of our solar system, in the Dark Energy Survey data. Photo courtesy of David Gerdes

    For DeeDee to be a dwarf planet, it has to fulfill four criteria: First, it must orbit the sun. Second, it cannot be a planet’s satellite, such as our moon. Third, it can’t have attracted other objects along its orbit to become its satellites, nor can it have forced their orbits out of its way. This is the major difference between a dwarf planet and a full-fledged planet. Since Pluto’s orbit is tied to Neptune’s, by this criterion Pluto was demoted to dwarf planet status.

    And last but not least, it has to have enough mass so that its own gravitational force compacts it into a spherical shape. DeeDee easily checks the first three qualifications, but its shape is not yet confirmed.

    The team speculates that DeeDee is round because it has a diameter of about 350 miles, which means that it likely has enough mass, and therefore enough gravitational force, to be spherical. Gerdes and his team are currently analyzing additional data from a radio telescope to determine its size.

    So far DeeDee’s chances of joining the elite group of dwarf planets are good. It might even earn its own mythological name, such as the dwarf planets Eris and Haumea, named after the ancient Greek goddess of discord and strife and the Hawaiian goddess of childbirth and fertility, respectively.

    Scouting for more

    DES uses the Dark Energy Camera to take its awe-inspiring pictures of the cosmos. The camera is mounted on the Victor M. Blanco 4-meter Telescope at the Cerro Tololo Inter-American Observatory in the Chilean Andes mountains. Fermilab, with the support of DOE’s Office of Science, led its construction and plays a major role in the DES data analysis, with a focus on illuminating the dark universe.

    “The DES data set is a very rich astronomical data set, and one critical step toward its discoveries is the calibration of the data,” said William Wester, Fermilab scientist involved in DES analysis. “The calibration helps determine the brightness of an object. In DeeDee’s case, this hints to its size.”

    Not every bright dot is actually a star or a galaxy, or even a TNO. It could also be an artifact or a reflection of light created by the camera.

    “You need to know what you are searching for, then you can formulate your question correctly for the data at hand and pull out from the multitude a sensible and manageable number of candidates,” said Jim Annis, Fermilab senior scientist.

    The number of possible objects in the DES data set easily approaches a billion, so thorough and reliable data sorting is critical to find promising candidates. Wester and Annis are well-practiced in similar exercises, having been involved in many different searches across the DES collaboration.

    DeeDee’s discovery is more than just that — it is another step on the way to a greater possible discovery: Planet 9. Planet 9 is a hypothetical ninth planet at the edge of our solar system with 10 times the mass of Earth. Otherwise unexplained patterns in the orbits of the largest-orbit TNOs hint at its existence. This opens the possibility that Planet 9 itself could be captured in the DES data, as in DeeDee’s case.

    The scientists of the DES collaboration, both at Fermilab and at its other 24 partner institutions, continue to mine the three years’ worth of data they’ve already collected and will gather more data through its conclusion in 2018. DeeDee is just one more of many discoveries to come.

    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 11:32 am on October 12, 2016 Permalink | Reply
    Tags: , , Dark Energy Survey, , New Object Vies for Kuiper Belt Record, Object 2014 UZ224,   

    From Sky & Telescope: “New Object Vies for Kuiper Belt Record” 

    SKY&Telescope bloc

    Sky & Telescope

    October 11, 2016
    Kelly Beatty

    1
    Based on observations over the past three years, astronomers know that the Kuiper Belt object known as 2014 UZ224 has a highly elliptical, 1,140-year-long orbit that stretches nearly four times farther from the Sun than Pluto can ever be. NASA / JPL / Horizons

    Kuiper Belt. Minor Planet Center
    Kuiper Belt. Minor Planet Center

    Right now 2014 UZ224 lies nearly 14 billion kilometers away, ranking it third among the most distant objects known in the Kuiper Belt.

    Early today the IAU’s Minor Planet Center announced that astronomers in Chile have discovered a Kuiper Belt object, designated 2014 UZ224, that’s currently 91.6 astronomical units from the Sun. This corresponds to 13.7 billion kilometers (8.5 billion miles), nearly three times farther out than Pluto is at the moment. Only two other known KBOs are more distant: Eris (96.2 a.u.) and V774104 (103 a.u.) to…[?]

    In fact, 2014 UZ224 is closer to the Sun than average right now and headed inbound. Its 1,140-year-long orbit is quite eccentric, swinging as close as 38 a.u. (think “Pluto’s orbit”) and as far away as 179.8 a.u. Technically, astronomers don’t consider it part of the classical Kuiper Belt but instead a “scattered disk object” whose orbits have been perturbed outward due to encounters with Neptune.

    A team led by David Gerdes (University of Michigan) first spotted this object in August 2014, and then several times again in 2015 and 2016, using the 4-m Victor Blanco reflector at Cerro Tololo Inter-American Observatory in Chile. Thanks to CTIO’s Dark Energy Camera, which Gerdes helped develop for the Dark Energy Survey (DES), 2014 UZ224 stood out clearly in images despite its apparent magnitude of only 23½.

    Dark Energy Icon
    Dark Energy Camera. Built at FNAL
    Dark Energy Camera. Built at FNAL
    NOAO/CTIO Victor M Blanco 4m Telescope which houses the DECam at Cerro Tololo, Chile
    NOAO/CTIO Victor M Blanco 4m Telescope which houses the DECam at Cerro Tololo, Chile

    “The same combination of survey area and depth that makes DES a state-of-the-art cosmological survey also makes it a great tool for making discoveries in our own cosmic backyard,” Gerdes explains. “Our search for trans-Neptunian objects is a serendipitous by-product of the survey data.” The effort has yielded dozens of Kuiper Belt objects so far, even though the team has examined only a fraction of the amassed observations. “I hope 2014 UZ224 is not the most interesting thing we eventually find!” Gerdes adds.

    For now, his team knows little more about their distant discovery other than its orbit and apparent brightness. Given its distance, however, the object should be sizable — anywhere from 400 km across (if its surface is bright and 50% reflective) to 1,200 km (if very dark and 5% reflective). If its true size edges toward the larger end of this range, then 2014 UZ224 would likely qualify for dwarf-planet status.

    Fortunately, we should have a much better estimate of the object’s size very soon. Gerdes has used the ALMA radio-telescope array to measure the heat radiating from 2014 UZ224, which can be combined with the optical measurements to yield its size and albedo.

    “The Blanco telescope is decades old, but DECam is a state-of-the-art instrument that has revitalized it in several ways,” Gerdes explains. “First, the focal plane is huge, so the telescope now has a 3°-square field of view. And second, the DECam’s CCDs are extremely sensitive in the red and near-infrared light, which makes it particularly good at detecting high-redshift objects.”

    See the full article here .

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    Sky & Telescope magazine, founded in 1941 by Charles A. Federer Jr. and Helen Spence Federer, has the largest, most experienced staff of any astronomy magazine in the world. Its editors are virtually all amateur or professional astronomers, and every one has built a telescope, written a book, done original research, developed a new product, or otherwise distinguished him or herself.

    Sky & Telescope magazine, now in its eighth decade, came about because of some happy accidents. Its earliest known ancestor was a four-page bulletin called The Amateur Astronomer, which was begun in 1929 by the Amateur Astronomers Association in New York City. Then, in 1935, the American Museum of Natural History opened its Hayden Planetarium and began to issue a monthly bulletin that became a full-size magazine called The Sky within a year. Under the editorship of Hans Christian Adamson, The Sky featured large illustrations and articles from astronomers all over the globe. It immediately absorbed The Amateur Astronomer.

    Despite initial success, by 1939 the planetarium found itself unable to continue financial support of The Sky. Charles A. Federer, who would become the dominant force behind Sky & Telescope, was then working as a lecturer at the planetarium. He was asked to take over publishing The Sky. Federer agreed and started an independent publishing corporation in New York.

    “Our first issue came out in January 1940,” he noted. “We dropped from 32 to 24 pages, used cheaper quality paper…but editorially we further defined the departments and tried to squeeze as much information as possible between the covers.” Federer was The Sky’s editor, and his wife, Helen, served as managing editor. In that January 1940 issue, they stated their goal: “We shall try to make the magazine meet the needs of amateur astronomy, so that amateur astronomers will come to regard it as essential to their pursuit, and professionals to consider it a worthwhile medium in which to bring their work before the public.”

     
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