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  • richardmitnick 8:29 am on July 30, 2014 Permalink | Reply
    Tags: , , , , Gamma Ray Detection,   

    From SPACE.com: “NASA’s Top 10 Gamma-Ray Sources in the Universe” 

    SpacedotcomHeader
    SPACE.com

    December 06, 2011
    SPACE.com Staff and NASA

    Gamma-rays are the highest-energy form of light in the universe. Some are generated by transient events, such as solar flares and the huge star explosions known as supernovas. Others are produced by steady sources like the supermassive black holes at the hearts of galaxies.

    NASA’s Fermi Gamma-ray Space Telescope has been mapping out the high-energy sky since its June 2008 launch. Earlier this year, the Fermi team released its second catalog of sources detected by the instrument’s Large Area Telescope (LAT), producing an inventory of 1,873 objects shining in gamma-ray light.

    NASA Fermi Telescope
    NASA/Fermi

    Fermi scientists recently compiled a “top 10 list” to mark the occasion, and to highlight the diversity of gamma-ray sources. Five of the sources on the list are found within our own Milky Way, while the other five reside in distant galaxies.

    Fermi’s top five sources within our galaxy are:

    1. The Crab Nebula: The famous Crab Nebula, located in the constellation Taurus, is the wreckage of an exploded star whose light reached Earth in 1054. Located 6,500 light-years away, the Crab is one of the most-studied objects in the sky.

    crab
    Crab Nebula

    At the heart of an expanding gas cloud lies what’s left of the original star’s core, a super-dense neutron star (also called a pulsar) that spins 30 times per second. Until recently, all of the Crab’s high-energy emissions were thought to be the result of physical processes near the pulsar that tapped into this rapid spin.

    For decades, most astronomers regarded the Crab Nebula as a super-steady beacon at X-ray energies. But data from several orbiting instruments — including Fermi’s Gamma-ray Burst Monitor — now show unexpected variations. Astronomers have demonstrated that since 2008, the nebula has faded by 7 percent at high energies, a reduction likely tied to the environment around its central neutron star.

    Since 2007, Fermi and the Italian Space Agency’s AGILE satellite have detected several short-lived gamma-ray flares at energies hundreds of times higher than the nebula’s observed X-ray variations. In April, the satellites detected two of the most powerful gamma-ray flares yet recorded.

    To account for these “superflares,” scientists say that electrons near the pulsar must be accelerated to energies a thousand trillion times greater than that of visible light. That’s far beyond what can be achieved by the Large Hadron Collider near Geneva, Switzerland, now the most powerful particle accelerator on Earth.

    2. W44:Another interesting supernova remnant detected by Fermi is W44. Thought to be about 20,000 years old — middle-aged for a such a structure — W44 is located 9,800 light-years away in the constellation Aquila.

    W44

    The LAT not only detects this W44, it actually reveals super-energetic gamma-rays coming from places where the remnant’s expanding shock wave is known to be interacting with cold, dense gas clouds.

    Such observations are important in solving a long-standing problem in astrophysics: the origin of cosmic rays. Cosmic rays are particles, primarily protons, that move through space at nearly the speed of light. Magnetic fields deflect the particles as they race across the galaxy, and this interaction scrambles their path and masks their origins.

    Scientists can’t say for sure where the highest-energy cosmic rays come from, but they regard supernova remnants as perhaps their likliest origin.

    In 1949, the Fermi telescope’s namesake, physicist Enrico Fermi, suggested that the highest-energy cosmic rays were accelerated in the magnetic fields of gas clouds. In the decades that followed, astronomers showed that the magnetic fields in the expanding shock wave of a supernova remnant are just about the best location for this process to work.

    So far, LAT observations of W44 and several other remnants strongly suggest that the gamma-ray emission arises from accelerated protons as they collide with gas atoms.

    3. V407 Cygni: V407 Cygni is a so-called symbiotic binary system — one that contains a compact white dwarf and a red giant star that has swollen to about 500 times the size of the sun.

    v407
    V407 Cygni

    V407 Cyni lies about 9,000 light-years away in the constellation Cygnus. The system occasionally flares up when gas from the red giant accumulates on the dwarf’s surface and eventually explodes. This event is sometimes called a nova (after a Latin term meaning “new star”).

    When the system’s most recent eruption occurred in March 2010, Fermi’s LAT surprised many scientists by detecting the nova as a brilliant source. Scientists didn’t expect that this type of outburst had the power to produce high-energy gamma-rays.

    4. Pulsar PSR J0101-6422: Pulsars — rapidly rotating neutron stars — constitute about 6 percent of the new catalog. In some cases the LAT can detect gamma-ray pulses directly, but in many cases pulses were first found at radio wavelengths based on suspicions that a faint LAT source might be a pulsar.

    image
    image of a pulsar

    PSR J0101-6422 is located in the southern constellation of Tucana, its quirky name reflecting its position in the sky.

    The Fermi team originally took notice of the object as a fairly bright but unidentified gamma-ray source in an earlier LAT catalog. Because the distribution of gamma-ray energies in the source resembled what is normally seen in pulsars, radio astronomers in Australia took a look at it using their Parkes radio telescope.

    Pulsars are neutron stars, compact objects packing more mass than the sun’s into a sphere roughly the size of Washington, D.C. Lighthouse-like beams of radiation powered by the pulsar’s rapid rotation and strong magnetic field sweep across the sky with every spin, and astronomers can detect these beams if they happen to sweep toward Earth.

    The Parkes study found radio signals from a pulsar rotating at nearly 400 times a second — comparable to the spin of a kitchen blender — at the same position as the unknown Fermi source. With this information, the LAT team was able to discover that PSR J0101-6422 also blinks in gamma-rays at the same incredible rate.

    5. 2FGL J0359.5+5410: Fermi scientists don’t know what to make of this source, which is located in the constellation Camelopardalis. It resides near the populous midplane of our galaxy, which increases the chance that it’s actually an object in the Milky Way.

    While its gamma-ray spectrum resembles that of a pulsar, pulsations have not been detected, and it isn’t associated with a known object at other wavelengths.

    The top five sources beyond the Milky Way are:

    Centaurs A Galaxy

    Cent A

    1. Centaurus A:The giant elliptical galaxy NGC 5128 is located 12 million light-years away in the southern constellation Centaurus. One of the closest active galaxies, it hosts the bright radio source designated Cen A. Much of the radio emission arises from lobes of gas a million light-years wide, which have been hurled out by the supermassive black hole at the galaxy’s center. [Photos: Black Holes of the Universe]

    Fermi’s LAT detects high-energy gamma-rays from an extended region around the galaxy that corresponds to the radio-emitting lobes. The radio emission comes from fast-moving particles. When a lower-energy photon collides with one of these particles, the photon receives a kick that boosts its energy into the gamma-ray regime.

    It’s a process that sounds more like billiards than astrophysics, but Fermi’s LAT shows that it’s happening in Cen A.
    Our neighboring galaxy, Andromeda, also goes by the names Messier 31 or M31. Here, it is captured in full in this new image by WISE.
    [Pin It] Our neighboring galaxy, Andromeda, also goes by the names Messier 31 or M31. Here, it is captured in full in this new image by WISE.
    Credit: NASA/JPL-Caltech/UCLA
    View full size image

    2. The Andromeda Galaxy (M31): At a distance of 2.5 million light-years, the Andromeda Galaxy is the nearest spiral galaxy to us, one of similar size and structure as our own Milky Way. Easily visible to the naked eye in a dark sky, it’s also a favorite target of sky gazers.

    andro
    Andromeda

    The LAT team expected to detect M31 because it’s so similar to our own galaxy, which sports a bright band of diffuse emission that creates the most prominent feature in the gamma-ray sky. These gamma-rays are mostly produced when high-energy cosmic rays smash into the gas between stars.

    “It took two years of LAT observations to detect M31,” Jürgen Knödlseder at the Research Institute for Astrophysics and Planetology in Toulouse, France, said in a statement. Currently a visiting scientist at the SLAC National Accelerator Laboratory in California, he worked on the M31 study.

    “We concluded that the Andromeda Galaxy has fewer cosmic rays than our own Milky Way, probably because M31 forms stars — including those that die as supernovae, which help produce cosmic rays —more slowly than our galaxy,” Knödlseder added.

    Hubble M82 Galaxy

    m82

    3. The Cigar Galaxy (M82): What works for the Andromeda Galaxy works even better for M82, a so-called starburst galaxy that is also a favorite of amateur astronomers. M82 is located 12 million light-years away in the constellation Ursa Major.

    M82’s central region forms young stars at a rate some 10 times higher than the Milky Way does, activity that also guarantees a high rate of supernovae as the most short-lived stars come to explosive ends.

    Eventually, M82’s superpowered star formation will subside as the gas needed to make new stars is consumed, but that may be tens of millions of years in the future. For now, it’s a bright source of gamma-rays for Fermi.

    4. Blazar PKS 0537-286:

    blazar
    A blazar

    At the core of an active galaxy is a massive black hole that drives jets of particles moving near the speed of light. Astronomers call the galaxy a blazar when one of these jets is pointed our way — the best view for seeing dramatic flares as conditions change within the jet.

    PKS 0537-286 is a variable blazar in the constellation Leo and the second most distant LAT object. Astronomers have determined that the galaxy lies more than 11.7 billion light-years away.

    The blazar is the farthest active galaxy in the Fermi catalog to show variability. Astronomers are witnessing changes in the jet powered by this galaxy’s supermassive black hole that occurred when the universe was just 2 billion years old (it is now about 13.7 billion years old).

    5. 2FGL J1305.0+1152: The last item is another mystery object, one located in the constellation Virgo and high above our galaxy’s midplane. It remains faint even after two years of LAT observations.

    One clue to classifying these objects lies in their gamma-ray spectrum — that is, the relative number of gamma-rays seen at different energies. At some energy, the spectra of many objects display what astronomers call a “spectral break,” a greater-than-expected drop-off in the number of gamma-rays seen at increasing energies.

    If this object were a pulsar, it would show a fast cutoff at higher energies. Many blazars exhibit much more gradual cutoffs. But 2FGL J1305.0+1152 shows no evidence of a spectral break at all, leaving its nature a true mystery — for now, anyway.

    See the full article here.


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  • richardmitnick 1:47 pm on April 18, 2014 Permalink | Reply
    Tags: , , Gamma Ray Detection,   

    From Brookhaven Lab: “The Science of Detecting and Defeating Radiological Threats” 

    Brookhaven Lab

    April 18, 2014
    Kay Cordtz

    If you were at the Super Bowl in New Jersey in February, or at the concurrent “NFL Experience” in Manhattan, you may have spotted some elite Brookhaven Lab employees. Not cheering in the stands or even inside the stadium, these members of the Lab’s Radiological Assistance Program (RAP) team were working on Super Bowl Sunday and for several weeks beforehand to monitor the metropolitan area for potential radiological threats.

    The RAP team, one of the National Nuclear Security Administration’s (NNSA) radiological emergency response assets, is comprised of a few permanent staff, augmented by highly trained volunteers from many Lab disciplines. Together, they work to stay ahead of any such threats using a palette of detection tools that have become increasingly sophisticated and user-friendly, driven by the evolving mission of the program.

    “The whole profile of the team has changed,” said Kathleen McIntyre, who is the contractor operations manager for RAP Region 1, which covers the East Coast from Maine to Maryland and inland to the Pennsylvania-Ohio border. “We used to investigate questionable material found in grandpa’s basement, but since 9/11 the focus has been on search-and-detect missions.”

    Working with first responder partners like the Federal Bureau of Investigation, police and fire departments, hazmat units, Weapons of Mass Destruction Civil Support Teams (Air and Army National Guard), and others, the RAP team offers radiological assistance efforts upon the request of federal, state, tribal, and local governments and private groups and individuals for incidents involving radiological materials. In addition to prominent sporting events, the RAP team supports security efforts for high-profile events like the United Nations General Assembly, New Year’s Eve activities in one or multiple locations, the holiday tree lighting ceremony, the Democratic and Republican national conventions, and even Presidential inaugurations.

    During a deployment, researchers and technicians with backgrounds in various aspects of radiological controls and analysis conduct field monitoring and environmental sampling, assessment, and documentation activities to help decision makers choose appropriate protective actions for the safety of both the public and first responders. Between deployments, the team examines issues of coordination between agencies, plans, and procedures, and trains and evaluates the proficiency of individuals using the equipment. Initially, all RAP team members are required to take a specialized course in Albuquerque, NM, and then attend training sessions at least quarterly. Team members are periodically evaluated through their participation in drills and exercises. Occasionally a “No Notice Exercise” is conducted by NNSA that tests the team’s readiness to respond.
    Advances in equipment

    Although some of the equipment now being used is commercially developed, other instruments are developed specifically for the use of DOE assets such as RAP teams, with the expertise of scientists and engineers from the DOE and NNSA complexes. Lab staff has participated in the development, testing, and functional evaluation of numerous pieces of equipment in this category. The evolution of this equipment conforms to the change in the program’s mission.

    Historically the RAP mission was “consequence management” — events and situations along the lines of responding to a spill from a truck carrying medical radioisotopes, for example. But as the profile of terrorism has been raised across the country and around the world, the need for a more preemptive approach in radiological screening was recognized, and RAP has been increasingly called upon to support law enforcement groups conducting directed or random screening for illicit movement of radiological materials.

    “That screening tends to be correlated with the potential for radiological material to be used to threaten a large mass gathering or other high-profile event,” said Chuck Finfrock, principal engineer for RAP team science. “To assist us in doing what we call low-profile missions, we need to be able to blend into crowds and collect radiological data in the field. Some of the equipment that we originally had was extremely bulky, so scientists have been working on equipment that is easier and less cumbersome to use and allows us to do a quicker assessment of our environment.”

    One of the techniques now being applied to the search and crisis response missions is gamma ray spectroscopy (GRS), largely a laboratory technique used for more than 40 years to identify radiological material. Like a fingerprint, a particular radiological material has a particular gamma ray spectrum that is unique to that radioisotope. As a result, this technique can be used to not only detect the radioactivity of a sample, but also to give information identifying that particular material. The instruments can be very large and are delicate items that need very stable temperature control and a constant supply of liquid nitrogen to cool them.

    grs
    One example of a Gamma Ray Sectroscope

    grs1
    Example of a GRS lab room

    As the RAP program moves to emergency response, more portable equipment allows the team to conduct a search operation with greater focus. For example, a construction site may report a missing soil density gauge – a commercial product containing some radioactive material that’s used to measure the density of compacted soil. With a spectroscopic system, the team knows in advance what isotope they’re seeking and can use GRS to search in a more specific way. Also, while the older GRS systems always required a human to take, calibrate, and analyze the data, computer software can now automate some analysis of that gamma ray spectral information.

    “The instruments are also, in effect, becoming ‘smarter’ and better able to help first responder partners with limited knowledge collect the initial on-scene information. This improves the quality of the data collected, which in turn helps a team scientist to understand the event more quickly,” said McIntyre. “Another important technological change that’s taking place is that instruments are being equipped with the ability to communicate by cell phone, satellite or Wi-Fi, allowing us to send data from the field back to a command center in near real time. Operators in the field working in multiple locations can send data back to the command center to be analyzed by one specialist at the command center.”

    grs3
    Portable GRS Unit

    Other new, more sophisticated algorithms can generate data products, such as maps, at different stages of an event, so technical information can be conveyed to decision makers at a glance.
    Training, teamwork critical

    But McIntyre warns that as sophisticated and user friendly that this gear has become, “we cannot emphasize enough how important it is to have an individual who has proficiency in the equipment that is being deployed in the field. Some of the first responders wear many hats, and while they do receive training, they don’t have the kind of in-depth knowledge and access to scientific expertise that members of the RAP team have. There are still important issues related to the fact that we live in a sea of radiation from rocks and soil. Also, we live in a community where radiological materials are used in many medical applications. As an example, we often encounter people who have had a thallium stress test or other medical administration. That person will measure as radioactive for days or weeks.”

    “Construction materials can also offer challenges,” she added. “On the streets of New York City, you’ll see great changes in the background radiation levels as you go from avenue to avenue and street to street. Our team has been trained to be cognizant of those changes and those contributing factors as well as being on high alert for something that might contribute additional information that might be of interest.”

    The context surrounding a measurement needs to be evaluated by someone with some understanding of the world’s background radiation footprint. The DOE community also has a capability called TRIAGE, where highly trained specialists from the NNSA nuclear weapons laboratories provide a scientific confirmation of the measurements made in the field. Advances in equipment communication allow that information to be communicated to specialists who can analyze field measurements that may look ambiguous.

    “The evolution of our capabilities is a combination of advancements in different areas,” Finfrock said “The advancements in detector engineering have caused them to become more field-usable. The advances in communications electronics and computers have enabled the detectors to more easily send data to the right people quickly. Most detectors now have global positioning tagged in with the radiological data, so not only are we getting back radiological measurements but we also know very precisely where that measurement was taken. We can correlate multiple measurements in multiple locations to be able to anticipate situations because we have geospatial awareness as well as radiological awareness.”

    As the radiological landscape continues to evolve, both in this country and abroad, the RAP team and others will continue to refine their search and detection techniques, and scientists at Brookhaven Lab and elsewhere will be working to stay ahead of the technology curve.

    See the full article here.

    One of ten national laboratories overseen and primarily funded by the Office of Science of the U.S. Department of Energy (DOE), Brookhaven National Laboratory conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies and national security. Brookhaven Lab also builds and operates major scientific facilities available to university, industry and government researchers. The Laboratory’s almost 3,000 scientists, engineers, and support staff are joined each year by more than 5,000 visiting researchers from around the world.Brookhaven is operated and managed for DOE’s Office of Science by Brookhaven Science Associates, a limited-liability company founded by Stony Brook University, the largest academic user of Laboratory facilities, and Battelle, a nonprofit, applied science and technology organization.
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