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  • richardmitnick 12:49 pm on February 3, 2016 Permalink | Reply
    Tags: , , , NASA Fermi   

    From AAS NOVA: “Upgrading Fermi Without Traveling to Space” 

    AASNOVA

    Amercan Astronomical Society

    3 February 2016
    Susanna Kohler

    NASA Fermi Telescope
    NASA Fermi

    Fermi Lat sky image
    This image, constructed from 6+ years of observations by NASA’s Fermi Gamma-ray Space Telescope, is the first to show how the entire sky appears at energies between 50 GeV and 2 TeV. A recent improvement to Fermi-LAT’s data analysis software has significantly increased the instrument’s sensitivity, resulting in this spectacular high-energy sky map. [NASA/DOE/Fermi LAT Collaboration]

    The Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope has received an upgrade that increased its sensitivity by a whopping 40% — and nobody had to travel to space to make it happen!

    NASA Fermi LAT
    Fermi LAT

    The difference instead stems from remarkable improvement to the software used to analyze Fermi-LAT’s data, and it has resulted in a new high-energy map of our sky.

    Pass 8

    Fermi-LAT has been surveying the whole sky since August 2008. It detects gamma-ray photons by converting them into electron-positron pairs and tracking the paths of these charged particles. But differentiating this signal from the charged cosmic rays that also pass through the detector — with a flux that can be 10,000 times larger! — is a challenging process. Making this distinction and rebuilding the path of the original gamma ray relies on complex analysis software.

    Pass 8” is a complete reprocessing of all data collected by Fermi-LAT. The software has gone through many revisions before now, but this is the first revision that has taken into account all of the experience that the Fermi team has gained operating the LAT in its orbital environment.

    The improvements made in Pass 8 include better background rejection of misclassified charged particles, improvements to the point spread function and effective area of the detector, and an extension of the effective energy range from below 100 MeV to beyond a few hundred GeV. The changes made in Pass 8 have increased the sensitivity of Fermi-LAT by an astonishing 40%.

    Map of the High-Energy Sky

    The first result from the improvements of Pass 8 is 2FHL, the second catalog of high-energy Fermi sources, constructed from 80 months of data from Fermi-LAT. The 2FHL catalog contains 360 sources from across the sky in the 50 GeV–2TeV range. Here are just a few details:

    47 of the sources are new — they have not previously been detected by Fermi or ground-based gamma-ray detectors.
    86% of the sources can be associated with counterparts at other wavelengths. This includes
    75% that are active galactic nuclei, and
    11% that originate in our galaxy, the majority of which are associated with objects at the final stage of stellar evolution, such as pulsar wind nebulae. and supernova remnants.

    Because the quality of Fermi-LAT’s observations is limited by the number of photons collected, longer observing time will only serve to improve the detections in this catalog. And since only 22% of the 2FHL sources have been observed by ground-based gamma-ray detectors (which have much more limited fields of view), this catalog provides an excellent list of candidates that these detectors can now follow up at very high energies.

    Bonus

    Want to learn more about Pass 8? Check out this video, created by the Fermi team. [NASA’s Goddard Space Flight Center]


    download mp4 video here .

    Citation

    M. Ackermann et al 2016 ApJS 222 5. doi:10.3847/0067-0049/222/1/5

    See the full article here .

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  • richardmitnick 6:08 pm on January 7, 2016 Permalink | Reply
    Tags: , , , , NASA Fermi   

    From NASA Fermi: “NASA’s Fermi Satellite Kicks Off a Blazar-detecting Bonanza” 


    Fermi

    Dec. 15, 2015
    Francis Reddy
    NASA’s Goddard Space Flight Center, Greenbelt, Maryland

    A long time ago in a galaxy half the universe away, a flood of high-energy gamma rays began its journey to Earth. When they arrived in April, NASA’s Fermi Gamma-ray Space Telescope caught the outburst, which helped two ground-based gamma-ray observatories detect some of the highest-energy light ever seen from a galaxy so distant. The observations provide a surprising look into the environment near a supermassive black hole at the galaxy’s center and offer a glimpse into the state of the cosmos 7 billion years ago.


    download mp4 video here .
    Explore how gamma-ray telescopes in space and on Earth captured an outburst of high-energy light from PKS 1441+25, a black-hole-powered galaxy more than halfway across the universe. Credits: NASA’s Goddard Space Flight Center

    “When we looked at all the data from this event, from gamma rays to radio, we realized the measurements told us something we didn’t expect about how the black hole produced this energy,” said Jonathan Biteau at the Nuclear Physics Institute of Orsay, France. He led the study of results from the Very Energetic Radiation Imaging Telescope Array System (VERITAS), a gamma-ray telescope in Arizona.

    Veritas Telescope
    VERITAS

    Astronomers had assumed that light at different energies came from regions at different distances from the black hole. Gamma rays, the highest-energy form of light, were thought to be produced closest to the black hole.

    “Instead, the multiwavelength picture suggests that light at all wavelengths came from a single region located far away from the power source,” Biteau explained. The observations place the area roughly five light-years from the black hole, which is greater than the distance between our sun and the nearest star.

    The gamma rays came from a galaxy known as PKS 1441+25, a type of active galaxy called a blazar. Located toward the constellation Boötes, the galaxy is so far away its light takes 7.6 billion years to reach us. At its heart lies a monster black hole with a mass estimated at 70 million times the sun’s and a surrounding disk of hot gas and dust. If placed at the center of our solar system, the black hole’s event horizon — the point beyond which nothing can escape — would extend almost to the orbit of Mars.

    As material in the disk falls toward the black hole, some of it forms dual particle jets that blast out of the disk in opposite directions at nearly the speed of light. Blazars are so bright in gamma rays because one jet points almost directly toward us, giving astronomers a view straight into the black hole’s dynamic and poorly understood realm.

    Temp 1
    Black-hole-powered galaxies called blazars are the most common sources detected by NASA’s Fermi Gamma-ray Space Telescope. As matter falls toward the supermassive black hole at the galaxy’s center, some of it is accelerated outward at nearly the speed of light along jets pointed in opposite directions. When one of the jets happens to be aimed in the direction of Earth, as illustrated here, the galaxy appears especially bright and is classified as a blazar.Credits: M. Weiss/CfA

    In April, PKS 1441+25 underwent a major eruption. Luigi Pacciani at the Italian National Institute for Astrophysics in Rome was leading a project to catch blazar flares in their earliest stages in collaboration with the Major Atmospheric Gamma-ray Imaging Cerenkov experiment (MAGIC), located on La Palma in the Canary Islands.

    MAGIC Cherenkov gamma ray telescope
    MAGIC telescope

    Using public Fermi data, Pacciani discovered the outburst and immediately alerted the astronomical community. Fermi’s Large Area Telescope revealed gamma rays up to 33 billion electron volts (GeV), reaching into the highest-energy part of the instrument’s detection range. For comparison, visible light has energies between about 2 and 3 electron volts.

    NASA Fermi LAT
    NASA/Fermi LAT

    “Detecting these very energetic gamma rays with Fermi, as well as seeing flaring at optical and X-ray energies with NASA’s Swift satellite, made it clear that PKS 1441+25 had become a good target for MAGIC,” Pacciani said.

    NASA SWIFT Telescope
    NASA/Swift

    Following up on the Fermi alert, the MAGIC team turned to the blazar and detected gamma rays with energies ranging from 40 to 250 GeV. “Because this galaxy is so far away, we didn’t have a strong expectation of detecting gamma rays with energies this high,” said Josefa Becerra Gonzalez, a researcher at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, who analyzed Fermi LAT data as part of the MAGIC study. “There are fewer and fewer gamma rays at progressively higher energies, and fewer still from very distant sources.”

    The reason distance matters for gamma rays is that they convert into particles when they collide with lower-energy light. The visible and ultraviolet light from stars shining throughout the history of the universe forms a remnant glow called the extragalactic background light (EBL). For gamma rays, this is a cosmic gauntlet they must pass through to be detected at Earth. When a gamma ray encounters starlight, it transforms into an electron and a positron and is lost to astronomers. The farther away the blazar is, the less likely its highest-energy gamma rays will survive to be detected.

    Temp 2
    More distant blazars show a loss of higher-energy gamma rays thanks to the extragalactic background light (EBL), a “cosmic fog” of visible and ultraviolet starlight that permeates the universe. From studies of nearby blazars, scientists know how many gamma rays should be emitted at different energies. If a gamma ray on its way to Earth collides with lower-energy light in the EBL, it converts into a pair of particles and is lost to astronomers. As shown by the graphs at left in this illustration, the more distant the blazar, the fewer high-energy gamma rays we can detect. During the April 2015 outburst of PKS 1441+25, MAGIC and VERITAS saw rare gamma rays exceeding 100 GeV that managed to survive a journey of 7.6 billion light-years. Credits: NASA’s Goddard Space Flight Center

    Following the MAGIC discovery, VERITAS also detected gamma rays with energies approaching 200 GeV. Findings from both teams are detailed in papers published Dec. 15 in The Astrophysical Journal Letters.

    PKS 1441+25 is one of only two such distant sources for which gamma rays with energies above 100 GeV have been observed. Its dramatic flare provides a powerful glimpse into the intensity of the EBL from near-infrared to near-ultraviolet wavelengths and suggests that galaxy surveys have identified most of the sources responsible for it.

    NASA’s Fermi Gamma-ray Space Telescope is an astrophysics and particle physics partnership, developed in collaboration with the U.S. Department of Energy and with important contributions from academic institutions and partners in France, Germany, Italy, Japan, Sweden and the United States.

    For more information about NASA’s Fermi, visit:

    http://www.nasa.gov/fermi

    See the full article here .

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  • richardmitnick 5:30 pm on January 7, 2016 Permalink | Reply
    Tags: , , , NASA Fermi   

    From NASA Fermi: “NASA’s Fermi Space Telescope Sharpens its High-energy Vision” 


    Fermi

    Jan. 7, 2016
    Francis Reddy
    NASA’s Goddard Space Flight Center, Greenbelt, Maryland

    Major improvements to methods used to process observations from NASA’s Fermi Gamma-ray Space Telescope have yielded an expanded, higher-quality set of data that allows astronomers to produce the most detailed census of the sky yet made at extreme energies. A new sky map reveals hundreds of these sources, including 12 that produce gamma rays with energies exceeding a trillion times the energy of visible light. The survey also discovered four dozen new sources that remain undetected at any other wavelength.

    Temp 1
    This image, constructed from more than six years of observations by NASA’s Fermi Gamma-ray Space Telescope, is the first to show how the entire sky appears at energies between 50 billion (GeV) and 2 trillion electron volts (TeV). For comparison, the energy of visible light falls between about 2 and 3 electron volts. A diffuse glow fills the sky and is brightest in the middle of the map, along the central plane of our galaxy. The famous Fermi Bubbles, first detected in 2010, appear as red extensions north and south of the galactic center and are much more pronounced at these energies.

    Temp 2
    Gamma-Ray bubbles at the center of the Milky Way. Credit: NASA’s Goddard Space Flight Center

    Discrete gamma-ray sources include pulsar wind nebulae and supernova remnants within our galaxy, as well as distant galaxies called blazars powered by supermassive black holes. Labels show the highest-energy sources, all located within our galaxy and emitting gamma rays exceeding 1 TeV.
    Credits: NASA/DOE/Fermi LAT Collaboration

    “What made this advance possible was a complete reanalysis, which we call Pass 8, of all data acquired by Fermi’s Large Area Telescope (LAT),” said Marco Ajello, a Fermi team member at Clemson University in South Carolina. “The end result is effectively a complete instrument upgrade without our ever having to leave the ground.”

    By carefully reexamining every gamma-ray and particle detection by the LAT since Fermi’s 2008 launch, scientists improved their knowledge of the detector’s response to each event and to the background environment in which it was measured. This enabled the Fermi team to find many gamma rays that previously had been missed while simultaneously improving the LAT’s ability to determine the directions of incoming gamma rays. These improvements effectively sharpen the LAT’s view while also significantly widening its useful energy range.


    download mp4 video here .
    Watch Fermi scientists explain why they’re so excited about Pass 8, a complete reprocessing of all data collected by the mission’s Large Area Telescope. This analysis increased the LAT’s sensitivity, widened its energy range, and effectively sharpened its view through improved backtracking of incoming gamma rays. Credits: NASA’s Goddard Space Flight Center

    Using 61,000 Pass 8 gamma rays collected over 80 months, Ajello and his colleagues constructed a map of the entire sky at energies ranging from 50 billion (GeV) to 2 trillion electron volts (TeV). For comparison, the energy of visible light ranges from about 2 to 3 electron volts.


    download mp4 video here .
    Tour the best view of the high-energy gamma-ray sky yet seen. This video highlights the plane of our galaxy and identifies objects producing gamma rays with energies greater than 1 TeV. Credits: NASA’s Goddard Space Flight Center

    “Of the 360 sources we cataloged, about 75 percent are blazars, which are distant galaxies sporting jets powered by supermassive black holes,” said co-investigator Alberto Domínguez at the Complutense University in Madrid. “The highest-energy sources, all located in our galaxy, are mostly remnants of supernova explosions and pulsar wind nebulae, places where rapidly rotating neutron stars accelerate particles to near the speed of light.” One famous example, the Crab Nebula, tops the list of the highest-energy Fermi sources, producing a steady drizzle of gamma rays exceeding 1 TeV.

    Astronomers think these very high-energy gamma rays are produced when lower-energy light collides with accelerated particles. This results in a small energy loss for the particle and a big gain for the light, transforming it into a gamma ray.


    download mp4 video here.
    Gamma-ray emission from the highest-energy sources detected by Fermi is likely produced by what scientists call the inverse Compton process. When an electron moving near the speed of light strikes a low-energy photon, the collision slightly slows the electron and boosts the light’s energy into the gamma-ray regime. Credits: NASA’s Goddard Space Flight Center

    For the first time, Fermi data now extend to energies previously seen only by ground-based detectors. Because ground-based telescopes have much smaller fields of view than the LAT, which scans the whole sky every three hours, they have detected only about a quarter of the objects in the catalog. This study provides ground facilities with more than 280 new targets for follow-up observations.

    “An exciting aspect of this catalog is that we find many new sources that emit gamma rays over a comparatively large patch of the sky,” explained Jamie Cohen, a University of Maryland graduate student working with the Fermi team at NASA’s Goddard Space Flight Center in Greenbelt. “Finding more of these objects enables us to probe their structures as well as better understand mechanisms that accelerate the subatomic particles that ultimately produce gamma-ray emission.” The new catalog identifies 25 of these extended objects, including three new pulsar wind nebulae and two new supernova remnants.

    Ajello presented the findings Thursday at the 227th meeting of the American Astronomical Society in Kissimmee, Florida. A paper describing the catalog has been accepted for publication in The Astrophysical Journal Supplement.

    NASA’s Fermi Gamma-ray Space Telescope is an astrophysics and particle physics partnership, developed in collaboration with the U.S. Department of Energy and with important contributions from academic institutions and partners in France, Germany, Italy, Japan, Sweden and the United States.

    For more information about NASA’s Fermi, visit:

    http://www.nasa.gov/fermi

    See the full article here .

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  • richardmitnick 1:31 pm on December 25, 2015 Permalink | Reply
    Tags: , , Gama rays, NASA Fermi   

    From NASA Fermi: “NASA’s Fermi Telescope Finds Giant Structure in our Galaxy” 2010 b ut Very Interesting 

    NASA Fermi

    Nov. 9, 2010 [Just found this in a search]
    Trent Perrotto
    Headquarters, Washington
    202-358-0321
    trent.j.perrotto@nasa.gov

    Lynn Chandler
    Goddard Space Flight Center, Greenbelt, Md.
    301-286-2806
    lynn.chandler-1@nasa.gov


    Using data from NASA’s Fermi Gamma-ray Space Telescope, scientists have recently discovered a gigantic, mysterious structure in our galaxy. This feature looks like a pair of bubbles extending above and below our galaxy’s center. Each lobe is 25,000 light-years tall and the whole structure may be only a few million years old.
    Credits: NASA’s Goddard Space Flight Center
    download mp4 video here.

    1
    From end to end, the newly discovered gamma-ray bubbles extend 50,000 light-years, or roughly half of the Milky Way’s diameter, as shown in this illustration. Hints of the bubbles’ edges were first observed in X-rays (blue) by ROSAT, a Germany-led mission operating in the 1990s. The gamma rays mapped by Fermi (magenta) extend much farther from the galaxy’s plane.Credits: NASA’s Goddard Space Flight Center

    Temp 1
    When an electron moving near the speed of light strikes a low-energy photon, the collision slightly slows the electron and boosts the photon’s energy to the gamma-ray regime. Credits: NASA’s Goddard Space Flight Center

    Temp 1
    The bubbles display a spectrum with higher peak energies than the diffuse gamma-ray glow seen throughout the sky. In addition, the bubbles display sharp edges in Fermi LAT data. Both of these qualities suggest that the structure arose in a sudden, impulsive event. Credits: NASA/DOE/Fermi LAT/D. Finkbeiner et al.

    NASA’s Fermi Gamma-ray Space Telescope has unveiled a previously unseen structure centered in the Milky Way. The feature spans 50,000 light-years and may be the remnant of an eruption from a supersized black hole at the center of our galaxy.

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

    “What we see are two gamma-ray-emitting bubbles that extend 25,000 light-years north and south of the galactic center,” said Doug Finkbeiner, an astronomer at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., who first recognized the feature. “We don’t fully understand their nature or origin.”

    The structure spans more than half of the visible sky, from the constellation Virgo to the constellation Grus, and it may be millions of years old. A paper about the findings has been accepted for publication in The Astrophysical Journal.

    Finkbeiner and his team discovered the bubbles by processing publicly available data from Fermi’s Large Area Telescope (LAT).

    NASA Fermi LAT
    NASA Fermi LAT

    The LAT is the most sensitive and highest-resolution gamma-ray detector ever launched. Gamma rays are the highest-energy form of light.

    Other astronomers studying gamma rays hadn’t detected the bubbles partly because of a fog of gamma rays that appears throughout the sky. The fog happens when particles moving near the speed of light interact with light and interstellar gas in the Milky Way. The LAT team constantly refines models to uncover new gamma-ray sources obscured by this so-called diffuse emission. By using various estimates of the fog, Finkbeiner and his colleagues were able to isolate it from the LAT data and unveil the giant bubbles.

    Scientists now are conducting more analyses to better understand how the never-before-seen structure was formed. The bubble emissions are much more energetic than the gamma-ray fog seen elsewhere in the Milky Way. The bubbles also appear to have well-defined edges. The structure’s shape and emissions suggest it was formed as a result of a large and relatively rapid energy release – the source of which remains a mystery.

    One possibility includes a particle jet from the supermassive black hole at the galactic center. In many other galaxies, astronomers see fast particle jets powered by matter falling toward a central black hole. While there is no evidence the Milky Way’s black hole has such a jet today, it may have in the past. The bubbles also may have formed as a result of gas outflows from a burst of star formation, perhaps the one that produced many massive star clusters in the Milky Way’s center several million years ago.

    “In other galaxies, we see that starbursts can drive enormous gas outflows,” said David Spergel, a scientist at Princeton University in New Jersey. “Whatever the energy source behind these huge bubbles may be, it is connected to many deep questions in astrophysics.”

    Hints of the bubbles appear in earlier spacecraft data. X-ray observations from the German-led Roentgen Satellite suggested subtle evidence for bubble edges close to the galactic center, or in the same orientation as the Milky Way.

    NASA ROSAT staellite
    Roentgen Satellite

    NASA’s Wilkinson Microwave Anisotropy Probe detected an excess of radio signals at the position of the gamma-ray bubbles.

    WMAP
    NASA/WMAP

    The Fermi LAT team also revealed Tuesday the instrument’s best picture of the gamma-ray sky, the result of two years of data collection.

    “Fermi scans the entire sky every three hours, and as the mission continues and our exposure deepens, we see the extreme universe in progressively greater detail,” said Julie McEnery, Fermi project scientist at NASA’s Goddard Space Flight Center in Greenbelt, Md.

    “Since its launch in June 2008, Fermi repeatedly has proven itself to be a frontier facility, giving us new insights ranging from the nature of space-time to the first observations of a gamma-ray nova,” said Jon Morse, Astrophysics Division director at NASA Headquarters in Washington. “These latest discoveries continue to demonstrate Fermi’s outstanding performance.”

    For more information about Fermi, visit:

    http://www.nasa.gov/fermi

    See the full article here .

    Please help promote STEM in your local schools.

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    The Fermi Gamma-ray Space Telescope , formerly referred to as the Gamma-ray Large Area Space Telescope (GLAST), is a space observatory being used to perform gamma-ray astronomy observations from low Earth orbit. Its main instrument is the Large Area Telescope (LAT), with which astronomers mostly intend to perform an all-sky survey studying astrophysical and cosmological phenomena such as active galactic nuclei, pulsars, other high-energy sources and dark matter. Another instrument aboard Fermi, the Gamma-ray Burst Monitor (GBM; formerly GLAST Burst Monitor), is being used to study gamma-ray bursts. The mission is a joint venture of NASA, the United States Department of Energy, and government agencies in France, Germany, Italy, Japan, and Sweden.

     
  • richardmitnick 11:26 am on November 14, 2015 Permalink | Reply
    Tags: , , INFOWARS, NASA Fermi   

    From NASA Fermi via INFOWARS: “NASA’s Fermi Mission Finds Hints of Gamma-ray Cycle in an Active Galaxy” 


    Fermi

    1
    INFOWARS

    November 13, 2015

    1

    Astronomers using data from NASA’s Fermi Gamma-ray Space Telescope have detected hints of periodic changes in the brightness of a so-called “active” galaxy, whose emissions are powered by a supersized black hole.

    If confirmed, the discovery would mark the first years-long cyclic gamma-ray emission ever detected from any galaxy, which could provide new insights into physical processes near the black hole.

    “Looking at many years of data from Fermi’s Large Area Telescope (LAT), we picked up indications of a roughly two-year-long variation of gamma rays from a galaxy known as PG 1553+113,” said Stefano Ciprini, who coordinates the Fermi team at the Italian Space Agency’s Science Data Center (ASDC) in Rome. “This signal is subtle and has been seen over less than four cycles, so while this is tantalizing we need more observations.”

    Supermassive black holes weighing millions of times the sun’s mass lie at the hearts of most large galaxies, including our own Milky Way. In about 1 percent of these galaxies, the monster black hole radiates billions of times as much energy as the sun, emission that can vary unpredictably on timescales ranging from minutes to years. Astronomers refer to these as active galaxies.

    More than half of the gamma-ray sources seen by Fermi’s LAT are active galaxies called blazars, like PG 1553+113. As matter falls toward its supermassive black hole, some subatomic particles escape at nearly the speed of light along a pair of jets pointed in opposite directions. What makes a blazar so bright is that one of these particle jets happens to be aimed almost directly toward us.

    “In essence, we are looking down the throat of the jet, so how it varies in brightness becomes our primary tool for understanding the structure of the jet and the environment near the black hole,” said Sara Cutini, an astrophysicist at ASDC.

    Motivated by the possibility of regular gamma-ray changes, the researchers examined a decade of multiwavelength data. These included long-term optical observations from Tuorla Observatory in Finland, Lick Observatory in California, and the Catalina Sky Survey near Tucson, Arizona, as well as optical and X-ray data from NASA’s Swift spacecraft.

    Tuorla Observatory  1 meter telescope
    Tuorla Observatory 1 meter telescope interior
    Tuorla Observatory 1 meter telescope

    UCO Lick Shane Telescope
    UCO Lick Shane Telescope interior
    UCO Lick Shane telescope

    U Arizona Catalina Sky Survey
    U Arizona Catalina Sky Survey

    NASA SWIFT Telescope
    NASA/Swift

    The team also studied observations from the Owens Valley Radio Observatory near Bishop, California, which has observed PG 1553+113 every few weeks since 2008 as part of an ongoing blazar monitoring program in support of the Fermi mission.

    Caltech Owens Valley Radio Observatory
    Caltech Owens Valley Radio Observatory

    “The cyclic variations in visible light and radio waves are similar to what we see in high-energy gamma-rays from Fermi,” said Stefan Larsson, a researcher at the Royal Institute of Technology in Stockholm and a long-time collaborator with the ASDC team. “The fact that the pattern is so consistent across such a wide range of wavelengths is an indication that the periodicity is real and not just a fluctuation seen in the gamma-ray data.”

    Ciprini, Cutini, Larsson and their colleagues published the findings in the Nov. 10 edition of The Astrophysical Journal Letters. If the gamma-ray cycle of PG 1553+113 is in fact real, they predict it will peak again in 2017 and 2019, well within Fermi’s expected operational lifetime.

    The scientists identified several scenarios that could drive periodic emission, including different mechanisms that could produce a years-long wobble in the jet of high-energy particles emanating from the black hole. The most exciting scenario involves the presence of a second supermassive black hole closely orbiting the one producing the jet we observe. The gravitational pull of the neighboring black hole would periodically tilt the inner part of its companion’s accretion disk, where gas falling toward the black hole accumulates and heats up. The result would be a slow oscillation of the jet much like that of a lawn sprinkler, which could produce the cyclic gamma-ray changes we observe.

    PG 1553+113 lies in the direction of the constellation Serpens, and its light takes about 5 billion years to reach Earth.

    NASA’s Fermi Gamma-ray Space Telescope was launched in June 2008. The mission is an astrophysics and particle physics partnership, developed in collaboration with the U.S. Department of Energy and with important contributions from academic institutions and partners in France, Germany, Italy, Japan, Sweden and the United States.

    See the full article here .

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  • richardmitnick 9:53 pm on November 12, 2015 Permalink | Reply
    Tags: , , NASA Fermi,   

    From NASA Goddard: “NASA’s Fermi Satellite Detects First Gamma-ray Pulsar in Another Galaxy” 

    NASA Goddard Banner
    Goddard Space Flight Center

    Nov. 12, 2015
    Francis Reddy
    NASA’s Goddard Space Flight Center, Greenbelt, Maryland


    Explore Fermi’s discovery of the first gamma-ray pulsar detected in a galaxy other than our own. Credits: NASA’s Goddard Space Flight Center
    download mp4 video here.

    The pulsar lies in the outskirts of the Tarantula Nebula in the Large Magellanic Cloud, a small galaxy that orbits our Milky Way and is located 163,000 light-years away.

    2
    This first light image of the TRAPPIST national telescope at La Silla shows the Tarantula Nebula, located in the Large Magellanic Cloud (LMC) — one of the galaxies closest to us. Also known as 30 Doradus or NGC 2070, the nebula owes its name to the arrangement of bright patches that somewhat resembles the legs of a tarantula. Taking the name of one of the biggest spiders on Earth is very fitting in view of the gigantic proportions of this celestial nebula — it measures nearly 1000 light-years across! Its proximity, the favourable inclination of the LMC, and the absence of intervening dust make this nebula one of the best laboratories to help understand the formation of massive stars better. The image was made from data obtained through three filters (B, V and R) and the field of view is about 20 arcminutes across.

    ESO TRAPPIST telescope
    ESO/Trappist telescope

    2
    LMC

    The Tarantula Nebula is the largest, most active and most complex star-formation region in our galactic neighborhood. It was identified as a bright source of gamma rays, the highest-energy form of light, early in the Fermi mission. Astronomers initially attributed this glow to collisions of subatomic particles accelerated in the shock waves produced by supernova explosions.

    “It’s now clear that a single pulsar, PSR J0540-6919, is responsible for roughly half of the gamma-ray brightness we originally thought came from the nebula,” said lead scientist Pierrick Martin, an astrophysicist at the National Center for Scientific Research (CNRS) and the Research Institute in Astrophysics and Planetology in Toulouse, France. “That is a genuine surprise.”

    1
    NASA’s Fermi Gamma-ray Space Telescope has detected the first extragalactic gamma-ray pulsar, PSR J0540-6919, near the Tarantula Nebula (top center) star-forming region in the Large Magellanic Cloud, a satellite galaxy that orbits our own Milky Way. Fermi detects a second pulsar (right) as well but not its pulses. PSR J0540-6919 now holds the record as the highest-luminosity gamma-ray pulsar. The angular distance between the pulsars corresponds to about half the apparent size of a full moon. Background: An image of the Tarantula Nebula and its surroundings in visible light. Credits: NASA’s Goddard Space Flight Center; background: ESO/R. Fosbury (ST-ECF)

    2
    A gamma-ray view of the same region shown above in visible wavelengths. Lighter colors indicate greater numbers of gamma rays with energies between 2 and 200 billion electron volts. For comparison, visible light ranges between 2 and 3 electron volts. The two pulsars, PSR J0540−6919 (left) and PSR J0537−6910, clearly stand out. Credits: NASA/DOE/Fermi LAT Collaboration

    When a massive star explodes as a supernova, the star’s core may survive as a neutron star, where the mass of half a million Earths is crushed into a magnetized ball no larger than Washington, D.C. A young isolated neutron star spins tens of times each second, and its rapidly spinning magnetic field powers beams of radio waves, visible light, X-rays and gamma rays. If the beams sweep past Earth, astronomers observe a regular pulse of emission and the object is classified as a pulsar.

    The Tarantula Nebula was known to host two pulsars, PSR J0540-6919 (J0540 for short) and PSR J0537−6910 (J0537), which were discovered with the help of NASA’s Einstein and Rossi X-ray Timing Explorer (RXTE) satellites, respectively. J0540 spins just under 20 times a second, while J0537 whirls at nearly 62 times a second — the fastest-known rotation period for a young pulsar.

    Nevertheless, it took more than six years of observations by Fermi’s Large Area Telescope (LAT), as well as a complete reanalysis of all LAT data in a process called Pass 8, to detect gamma-ray pulsations from J0540. The Fermi data establish upper limits for gamma-ray pulses from J0537 but do not yet detect them.

    Martin and his colleagues present these findings in a paper to be published in the Nov. 13 edition of the journal Science.

    “The gamma-ray pulses from J0540 have 20 times the intensity of the previous record-holder, the pulsar in the famous Crab Nebula, yet they have roughly similar levels of radio, optical and X-ray emission,” said coauthor Lucas Guillemot, at the Laboratory for Physics and Chemistry of Environment and Space, operated by CNRS and the University of Orléans in France.

    4
    This is a mosaic image, one of the largest ever taken by NASA’s Hubble Space Telescope of the Crab Nebula, a six-light-year-wide expanding remnant of a star’s supernova explosion. Japanese and Chinese astronomers recorded this violent event nearly 1,000 years ago in 1054, as did, almost certainly, Native Americans. The orange filaments are the tattered remains of the star and consist mostly of hydrogen. The rapidly spinning neutron star embedded in the center of the nebula is the dynamo powering the nebula’s eerie interior bluish glow. The blue light comes from electrons whirling at nearly the speed of light around magnetic field lines from the neutron star. The neutron star, like a lighthouse, ejects twin beams of radiation that appear to pulse 30 times a second due to the neutron star’s rotation. A neutron star is the crushed ultra-dense core of the exploded star. The Crab Nebula derived its name from its appearance in a drawing made by Irish astronomer Lord Rosse in 1844, using a 36-inch telescope. When viewed by Hubble, as well as by large ground-based telescopes such as the European Southern Observatory’s Very Large Telescope, the Crab Nebula takes on a more detailed appearance that yields clues into the spectacular demise of a star, 6,500 light-years away. The newly composed image was assembled from 24 individual Wide Field and Planetary Camera 2 exposures taken in October 1999, January 2000, and December 2000. The colors in the image indicate the different elements that were expelled during the explosion. Blue in the filaments in the outer part of the nebula represents neutral oxygen, green is singly-ionized sulfur, and red indicates doubly-ionized oxygen.

    NASA Hubble Telescope
    NASA/ESA Hubble

    “Accounting for these differences will guide us to a better understanding of the extreme physics at work in young pulsars.”

    J0540 is a rare find, with an age of roughly 1,700 years, about twice that of the Crab Nebula pulsar. By contrast, most of the more than 2,500 known pulsars are from 10,000 to hundreds of millions of years old.

    Despite J0540’s luminosity, too few gamma rays reach the LAT to detect pulsations without knowing the period in advance. This information comes from a long-term X-ray monitoring campaign using RXTE, which recorded both pulsars from the start of the Fermi mission to the end of 2011, when RXTE operations ceased.

    “This campaign began as a search for a pulsar created by SN 1987A, the closest supernova seen since the invention of the telescope,” said co-author Francis Marshall, an astrophysicist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “That search failed, but it discovered J0537.”

    Prior to the launch of Fermi in 2008, only seven gamma-ray pulsars were known. To date, the mission has found more than 160.

    NASA’s Fermi Gamma-ray Space Telescope is an astrophysics and particle physics partnership, developed in collaboration with the U.S. Department of Energy and with important contributions from academic institutions and partners in France, Germany, Italy, Japan, Sweden and the United States.

    See the full article here .

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    NASA’s Goddard Space Flight Center is home to the nation’s largest organization of combined scientists, engineers and technologists that build spacecraft, instruments and new technology to study the Earth, the sun, our solar system, and the universe.

    Named for American rocketry pioneer Dr. Robert H. Goddard, the center was established in 1959 as NASA’s first space flight complex. Goddard and its several facilities are critical in carrying out NASA’s missions of space exploration and scientific discovery.

    NASA Goddard Campus
    NASA/Goddard Campus
    NASA

     
  • richardmitnick 8:47 pm on July 13, 2015 Permalink | Reply
    Tags: , , , NASA Fermi   

    From NASA Fermi: “NASA’s Fermi Sees Record Flare from a Black Hole in a Distant Galaxy” 


    Fermi

    July 10, 2015
    Francis Reddy
    NASA’s Goddard Space Flight Center

    Five billion years ago, a great disturbance rocked a region near the monster black hole at the center of galaxy 3C 279.

    1
    3C 279
    EGRET team, Compton Observatory, NASA
    26 December 1998

    On June 14, the pulse of high-energy light produced by this event finally arrived at Earth, setting off detectors aboard NASA’s Fermi Gamma-ray Space Telescope and other satellites. Astronomers around the world turned instruments toward the galaxy to observe this brief but record-setting flare in greater detail.

    “One day 3C 279 was just one of many active galaxies we see, and the next day it was the brightest thing in the gamma-ray sky,” said Sara Cutini, a Fermi Large Area Telescope scientist at the Italian Space Agency’s Science Data Center in Rome.

    1
    Blazar 3C 279’s historic gamma-ray flare can be seen in this image from the Large Area Telescope (LAT) on NASA’s Fermi satellite. Gamma rays with energies from 100 million to 100 billion electron volts (eV) are shown; for comparison, visible light has energies between 2 and 3 eV. The image spans 150°, is shown in a stereographic projection, and represents an exposure from June 11 at 00:28 UT to June 17 at 08:17 UT. The scale bar at left shows an angular distance of 10°, which is about the width of a clenched fist at arm’s length. During the flare, the blazar outshone the Vela pulsar, usually the brightest object in the gamma-ray sky. NASA/DOE/Fermi LAT Collaboration

    3C 279 is a famous blazar, a galaxy whose high-energy activity is powered by a central supermassive black hole weighing up to a billion times the sun’s mass and roughly the size of our planetary system. As matter falls toward the black hole, some particles race away at nearly the speed of light along a pair of jets pointed in opposite directions. What makes a blazar so bright is that one of these particle jets happens to be aimed almost straight at us.

    “This flare is the most dynamic outburst Fermi has seen in its seven years of operation, becoming 10 times brighter overnight,” said Elizabeth Hays, a Fermi deputy project scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. Astronomers think some change within the jet is likely responsible for the flare, but they don’t know what it is.

    The brightest persistent source in the gamma-ray sky is the Vela pulsar, which is about 1,000 light-years away.

    2
    The Vela Pulsar and its surrounding pulsar wind nebula
    NASA/CXC/PSU/G.Pavlov et al.
    6 July 2003

    3C 279 is millions of times farther off, but during this flare it became four times brighter than Vela. This corresponds to a tremendous energy release, and one that cannot be sustained for long. The galaxy dimmed to normal gamma-ray levels by June 18.

    The rapid fading is why astronomers rush to collect data as soon as they detect a blazar flare. “Our priority is to make observations while the object is still bright,” said Masaaki Hayashida, a Fermi team member at the University of Tokyo’s Institute for Cosmic Ray Research. “Once it’s over, we can start trying to understand the mechanisms powering it.”

    The Italian Space Agency’s AGILE gamma-ray satellite first reported the flare, followed by Fermi.
    Rapid follow-up observations were made by NASA’s Swift satellite and the European Space Agency’s INTEGRAL spacecraft, which just happened to be looking in the right direction, along with optical and radio telescopes on the ground.

    Italian Space Agency AGILE Spacecraft
    ISA AGILE

    NASA SWIFT Telescope
    NASA/Swift

    ESA Integral
    ESA/Integral

    3C 279 holds a special place in the history of gamma-ray astronomy. During a flare in 1991 detected by the EGRET instrument on NASA’s then recently launched Compton Gamma Ray Observatory (CGRO), which operated until 2000, the galaxy set the record for the most distant and luminous gamma-ray source known at the time. “Although we didn’t expect to find the galaxy so bright, we soon had a much greater surprise,” recalled Robert Hartman, who led the first gamma-ray study of 3C 279 with CGRO and is now a member of the Fermi team at Goddard. “Its brightness varied substantially, becoming four times brighter within 10 days.”

    The June 14 outburst rapidly brightened in less than a day and peaked on June 16, producing a gamma-ray flare 10 times brighter than the 1991 event. These rapid variations convey information about the size of the emitting region, which cannot be larger than the distance light can travel during the flare.

    Mid-June proved to be an intense period for the Fermi team. As the satellite’s Large Area Telescope studied 3C 279, its Gamma-ray Burst Monitor became the busiest it has ever been since the start of the mission. The instrument picked up a series of eruptions on the sun, which is unusual in itself, as well as multiple outbursts from V404 Cygni, a binary system containing a black hole that erupts every few decades.

    NASA’s Fermi Gamma-ray Space Telescope is an astrophysics and particle physics partnership mission, developed in collaboration with the U.S. Department of Energy and important contributions from academic institutions and partners in France, Germany, Italy, Japan, Sweden and the United States.

    See the full article here.

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  • richardmitnick 3:18 pm on June 24, 2015 Permalink | Reply
    Tags: , , , NASA Fermi,   

    From Symmetry: “Seeing in gamma rays” 

    Symmetry

    June 24, 2015
    Glenn Roberts Jr.

    1
    Courtesy of Fermi LAT collaboration

    The Fermi Gamma-ray Space Telescope creates maps of the gamma-ray sky.

    Maps from the Fermi Gamma-ray Space Telescope literally show the universe in a different light.

    NASA Fermi Telescope
    Fermi

    Fermi’s Large Area Telescope (LAT) has been watching the universe at a broad range of gamma-ray energies for more than seven years.

    Gamma rays are the highest-energy form of light in the cosmos. They come from jets of high-energy particles accelerated near supermassive black holes at the centers of galaxies, shock waves around exploded stars, and the intense magnetic fields of fast-spinning collapsed stars. On Earth, gamma rays are produced by nuclear reactors, lightning and the decay of radioactive elements.

    From low-Earth orbit, the Fermi Gamma-ray Space Telescope scans the entire sky for gamma rays every three hours. It captures new and recurring sources of gamma rays at different energies, and it can be diverted from its usual course to fix on explosive events known as gamma-ray bursts.

    Combining data collected over years, the LAT collaboration periodically creates gamma-ray maps of the universe. These colored maps plot the universe’s most extreme events and high-energy objects.

    The all-sky maps typically portray the universe as an ellipse that shows the entire sky at once, as viewed from Earth. On the maps, the brightest gamma-ray light is shown in yellow and progressively dimmer gamma-ray light is shown in red, blue, and black. These are false colors, though; gamma-rays are invisible.

    The maps are oriented with the center of the Milky Way at their center and the plane of our galaxy oriented horizontally across the middle. The plane of the Milky Way is bright in gamma rays. Above and below the bright band, much of the gamma-ray light comes from outside of our galaxy.

    “What you see in gamma rays is not so predictable,” says Elliott Bloom, a SLAC National Accelerator Laboratory professor and member of the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC) who is part of a scientific collaboration supporting Fermi’s principal instrument, the Large Area Telescope.

    Teams of researchers have identified mysterious, massive “bubbles” blooming 30,000 light-years outward from our galaxy’s center, for example, with most features appearing only at gamma-ray wavelengths.

    Scientists create several versions of the Fermi sky maps. Some of them focus only on a specific energy range, says Eric Charles, another member of the Fermi collaboration who is also a KIPAC scientist.

    “You learn a lot by correlating things in different energy ‘bins,’” he says. “If you look at another map and see completely different things, then there may be these different processes. What becomes useful is at different wavelengths you can make comparisons and correlate things.”

    But sometimes what you need is the big picture, says Seth Digel, a SLAC senior staff scientist and a member of KIPAC and the Fermi team. “There are some aspects you can only study with maps, such as looking at the extended gamma-ray emissions—not just the point sources, but regions of the sky that are glowing in gamma rays for different reasons.”

    See the full article here.

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    Symmetry is a joint Fermilab/SLAC publication.


     
  • richardmitnick 9:23 am on June 12, 2015 Permalink | Reply
    Tags: , , , , NASA Fermi   

    From FNAL- “Frontier Science Result: Fermi Gamma-Ray Space Telescope” 

    FNAL Home

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

    June 12, 2015
    Dan Hooper

    NASA Fermi Telescope
    Fermi Gamma Ray Telescope

    2
    A team of astrophysicists is looking for dark matter in the form of subhalos. These clumps of dark matter within the Milky Way are predicted to produce a distinctive gamma-ray signal. Image courtesy of The Aquarius Project

    In addition to teaching us about pulsars, cosmic rays and supermassive black holes, the Fermi Gamma Ray Space Telescope is one of the world’s premier dark matter experiments. In many models, the interactions of dark matter particles can create energetic photons, known as gamma rays. Fermi provides us with our most sensitive view of the gamma-ray sky and is able to test many of our most promising theories of dark matter.

    Over the past several years, my collaborators and I have published a series of papers describing an excess of gamma rays from the region surrounding the center of the Milky Way. After many long discussions, arguments and debates, the majority of the gamma-ray astrophysics community seems to have reached a consensus that this excess is real and is in need of an explanation. One exciting possibility is that these gamma rays could be produced by dark matter particles. But even though this signal looks very much like what we expected from dark matter, we can’t entirely rule out other explanations, such as a series of recent outbursts of cosmic rays or some unknown population of faint gamma-ray sources.

    One way to potentially confirm a dark matter origin for this excess would be to observe the same spectrum of gamma rays from otherwise invisible clumps of dark matter — known as subhalos — elsewhere in the sky. In fact, if the gamma rays from the Galactic Center do come from dark matter particles, we estimate that Fermi should be able to detect a handful of these subhalos as bright gamma-ray sources. The challenge is that Fermi has detected hundreds of bright, unidentified sources, the vast majority of which are not related to dark matter. This large haystack of sources makes it hard to find the dark matter subhalos that are the needles we are looking for.

    But in one important respect, dark matter subhalos should look different from other kinds of gamma-ray sources: They should be slightly extended or “puffy.” My collaborators (Bridget Bertoni of the University of Washington and Tim Linden of the University of Chicago) and I have recently found evidence that some of Fermi’s unidentified sources are in fact extended, making them seem more likely to be dark matter subhalos. We continue to scrutinize the data, and although we’re not prepared to claim discovery yet, we are very excited that this new information might make it possible to independently test — and maybe even confirm — a dark matter origin for Fermi’s Galactic Center gamma-ray excess.

    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 8:17 am on May 14, 2015 Permalink | Reply
    Tags: , , NASA Fermi,   

    From New Scientist: “Found: giant spirals in space that could explain our existence” 

    NewScientist

    New Scientist

    14 May 2015
    Michael Slezak

    Giant magnetic spirals in the sky could explain why there is something rather than nothing in the universe, according to an analysis of data from NASA’s Fermi space telescope.

    NASA Fermi Telescope

    Our best theories of physics imply we shouldn’t be here. The Big Bang ought to have produced equal amounts of matter and antimatter particles, which would almost immediately annihilate each other, leaving nothing but light.

    So the reality that we are here – and there seems to be very little antimatter around – is one of the biggest unsolved mysteries in physics.

    Monopole monopoly

    In 2001, Tanmay Vachaspati from Arizona State University offered a purely theoretical solution. Even if matter and antimatter were created in equal amounts, he suggested that as they annihilated each other, they would have briefly created monopoles and antimonopoles, hypothetical particles with just one magnetic pole, north or south.

    As the monopoles and antimonopoles in turn annihilated each other, they would produce matter and antimatter. But because of a quirk in nature called CP violation, that process would be biased towards matter, leaving the matter-filled world we see today.

    If that happened, Vachaspati showed that there should be a sign of it today: twisted magnetic fields permeating the universe – a fossil of the magnetic monopoles that briefly dominated. And he showed they should look like left-handed screws rather than right-handed screws.

    So Vachaspati and his colleagues went looking for them in data from NASA’s Fermi Gamma ray Space Telescope. As gamma rays shoot through the cosmos, they should be bent by any magnetic field they pass through, so if there are helical magnetic fields permeating the universe, that should leave a visible mark on those gamma rays.

    All of a twist

    Lo and behold, that’s just what they found – well, maybe. “What we found is consistent with them all being left-handed,” says Vachaspati. “But we can’t be sure.” He says there’s less than a one per cent chance that what they see in the Fermi data happened by chance. “That’s being conservative,” he says.

    They also found that the twists in the field are a bit bigger than they predicted. “So there is some mystery there,” says Vachaspati. He says more data from Fermi, which is expected this year, will help narrow down the odds.

    Nicole Bell from the University of Melbourne in Australia warns that magnetic fields could have been caused in other ways, including from inflation. What’s more, for CP-violation to provide enough matter in the universe you usually need “new physics” – stuff beyond the standard model of particle physics – which hasn’t been confirmed experimentally yet. “But it is a very interesting idea,” she says.

    Journal reference: Monthly Notices of the Royal Astronomical Society, DOI: 10.1093/mnras/stv308

    See the full article here.

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