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  • richardmitnick 2:08 pm on December 2, 2016 Permalink | Reply
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    From Symmetry: “Viewing our turbulent universe” 

    Symmetry Mag

    Liz Kruesi

    Construction has begun for the Cherenkov Telescope Array [CTA], a discovery machine that will study the highest energy objects and events across the entire sky.

    Daniel Mazinkn, CTA Observatory

    Billions of light-years away, a supermassive black hole is spewing high-energy radiation, launching it far outside of the confines of its galaxy. Some of the gamma rays released by that turbulent neighborhood travel unimpeded across the universe, untouched by the magnetic fields threading the cosmos, toward our small, rocky, blue planet.

    We have space-based devices, such as the Fermi Gamma-ray Space Telescope, that can detect those messengers, allowing us to see into the black hole’s extreme environment or search for evidence of dark matter.

    NASA/Fermi Telescope
    NASA/Fermi Telescope

    But Earth’s atmosphere blocks gamma rays. When they meet the atmosphere, sequences of interactions with gas molecules break them into a shower of fast-moving secondary particles. Some of those generated particles—which could be, for example, fast-moving electrons and their antiparticles, positrons—speed through the atmosphere so quickly that they generate a faint flash of blue light, called Cherenkov radiation.

    A special type of telescope—large mirrors fitted with small reflective cones to funnel the faint light—can detect this blue flash in the atmosphere. Three observatories equipped with Cherenkov telescopes look at the sky during moonless hours of the night: VERITAS in Arizona has an array of four; MAGIC in La Palma, Spain, has two; and HESS in Namibia, Africa, has an array of five.


    MAGIC Cherenkov gamma ray telescope  on the Canary island of La Palma, Spain
    MAGIC Cherenkov gamma ray telescope on the Canary island of La Palma, Spain

    HESS Cherenko Array, located on the Cranz family farm, Göllschau, in Namibia, near the Gamsberg
    HESS Cherenko Array, located on the Cranz family farm, Göllschau, in Namibia, near the Gamsberg

    All three observatories have operated for at least 10 years, revealing a gamma-ray sky to astrophysicists.

    “Those telescopes really have helped to open the window, if you like, on this particular region of the electromagnetic spectrum,” says Paula Chadwick, a gamma-ray astronomer at Durham University in the United Kingdom. But that new window has also hinted at how much more there is to learn.

    “It became pretty clear that what we needed was a much bigger instrument to give us much better sensitivity,” she says. And so gamma-ray scientists have been working since 2005 to develop the next-generation Cherenkov observatory: “a discovery machine,” as Stefan Funk of Germany’s Erlangen Centre for Astroparticle Physics calls it, that will reveal the highest energy objects and events across the entire sky. This is the Cherenkov Telescope Array (CTA), and construction has begun.

    Ironing out the details

    As of now, nearly 1400 researchers and engineers from 32 countries are members of the CTA collaboration, and membership continues to grow. “If we look at the number of CTA members as a function of time, it’s essentially a linear increase,” says CTA spokesperson Werner Hofmann.

    Technology is being developed in laboratories spread across the globe: in Germany, Italy, the United Kingdom, Japan, the United States (supported by the NSF—given the primarily astrophysics science mission of the CTA, it is not a part of the Department of Energy High Energy Physics program), and others. Those nearly 1400 researchers are collaborating and working together to gain a better understanding of how our universe works. “It’s the science that’s got everybody together, got everybody excited, and devoting so much of their time and energy to this,” Chadwick says.

    G. Pérez, IAC, SMM

    The CTA will be split between two locations, with one array in the Northern Hemisphere and a larger one in the Southern Hemisphere. The dual location enables a view of the entire sky.

    CTA’s northern site will host four large telescopes (23 meters wide) and 15 medium telescopes (12 meters wide). The southern site will also host four large telescopes, plus 25 medium and 70 small telescopes (4 meters) that will use three different designs. The small telescopes are equipped to capture the highest energy gamma rays, which emanate, for example, from the center of our galaxy. That high-energy source is visible only from the Southern Hemisphere.

    In July 2015, the CTA Observatory (CTAO) council—the official governing body that acts on behalf of the observatory—chose their top locations in each hemisphere. And in 2016, the council has worked to make those preferences official. On September 19 the council and the Instituto de Astrofísica de Canarias signed an agreement stating that the Roque de los Muchachos Observatory on the Canary Island of La Palma would host the northern array and its 19 constituent telescopes. This same site hosts the current-generation Cherenkov array MAGIC.


    Construction of the foundation is progressing at the La Palma site to prepare for a prototype of the large telescope. The telescope itself is expected to be complete in late 2017.

    “It’s an incredibly aggressive schedule,” Hofmann says. “With a bit of luck we’ll have the first of these big telescopes operational at La Palma a year from now.”

    While the large telescope prototype is being built on the La Palma site, the medium and small prototype telescopes are being built in laboratories across the globe and installed at observatories similarly scattered. The prototypes’ optical designs and camera technologies need to be tested in a variety of environments. For example, the team working on one of the small telescope designs has a prototype on the slope of Mount Etna in Sicily. There, volcanic ash sometimes batters the mirrors and attached camera, providing a test to ensure CTA telescopes and instruments can withstand the environment. Unlike optical telescopes, which sit in protective domes, Cherenkov telescopes are exposed to the open air.

    The CTAO council expects to complete negotiations with the European Southern Observatory before the end of 2016 to finalize plans for the southern array. The current plan is to build 99 telescopes in Chile.

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    This year, the council also chose the location of the CTA Science Management Center, which will be the central point of data processing, software updates and science coordination. This building, which will be located at Deutsches Elektronen-Synchrotron (also known as DESY) outside of Berlin, has not yet been built, but Hofmann says that should happen in 2018.


    The observatory is on track for the first trial observations (essentially, testing) in 2021 and the first regular observations beginning in 2022. How close the project’s construction stays to this outlined schedule depends on funding from nations across the globe. But if the finances remain on track, then in 2024, the full observatory should be complete, and its 118 telescopes will then look for bright flashes of Cherenkov light signaling a violent event or object in the universe.

    See the full article here .

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    Symmetry is a joint Fermilab/SLAC publication.

  • richardmitnick 3:27 pm on December 11, 2015 Permalink | Reply
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    From Symmetry: “The next gamma-ray eye on the sky” 


    Liz Kruesi

    Scientists have successfully tested the first prototype camera for the Cherenkov Telescope Array.

    DESY/Milde Science Comm./Exozet

    Telescope arrays VERITAS, HESS and MAGIC have spied active supermassive black holes, the remnants of the explosions of massive stars, binary star systems, and galaxies actively churning out new stars.

    Veritas Telescope

    HESS Cherenko Array
    HESS Cherenko Array

    MAGIC Telescope

    This is possible thanks to what all of these cosmic objects have in common: They are all sources of high-energy gamma rays. VERITAS, HESS and MAGIC all look for the optical light produced when those gamma rays interact with Earth’s atmosphere.

    One gamma-ray source that continues to elude these powerful telescopes is the brightest electromagnetic event known to occur in the universe: a gamma-ray burst. But a new telescope array currently under development might be able to catch one.

    The Cherenkov Telescope Array, or CTA, will cover a substantially larger area on the ground, making it an enormous “bucket” to collect incoming gamma-ray-produced radiation.

    Cherenkov Telescope Array

    It will also be able to collect data during almost twice as many hours per year as current arrays.

    The array will study the entire range of gamma-ray sources. It also has the capability to detect the annihilation signature of dark matter particles.

    “We’re really hoping to find something new, some new type of high-energy astrophysical phenomenon,” says Rene Ong, the CTA consortium co-spokesperson.

    Scientists successfully operated the first CTA prototype camera in late November. The full array is scheduled to start running in the 2020s.

    The usefulness of gamma rays

    Gamma rays are almost ideal messengers of high-energy particle astrophysics. They are created in the most energetic processes in the universe. And, like all other forms of light, they are electrically neutral and thus aren’t buffeted by galactic magnetic fields as they travel through space. This means scientists can use them to point back to their sources.

    The drawback is that these messengers can’t make it through Earth’s atmosphere. Instead, they interact and produce a shower of lower-energy particles.

    If some of those are traveling at a velocity faster than the speed of light in the gaseous medium of the atmosphere, they will create flashes of light peaking between blue and ultraviolet, akin to a sonic boom following a supersonic jet. This light is called Cherenkov radiation, and it’s what ground-based high-energy gamma-ray telescopes actually detect.

    VERITAS in Arizona, HESS in Namibia, and MAGIC on the Canary island of La Palma are arrays of optical telescopes that have been detecting this light for about a decade. VERITAS contains four of these scopes, HESS has five, and MAGIC has two. The weak light reflects off each segmented primary mirror and is funneled to a “camera.” Each telescope’s camera is made of hundreds to thousands of photomultiplier tubes which convert the incoming photons into electrical signals.

    With the next-generation CTA, scientists hope to catch a gamma-ray burst with a ground-based telescope array for the first time. They want to know the underlying physics of these blasts, the sources of which are thought to be located millions to billions of light-years away.

    Scientists have seen gamma-ray bursts with space-based instruments, such as the Fermi Gamma-Ray Space Telescope and Swift.

    NASA Fermi Telescope

    NASA SWIFT Telescope

    But only a ground-based array could detect their highest-energy gamma rays, those above 100 billion electronvolts. And a large ground-based array such as the CTA, which will cover 10 square kilometers in the south and 1 square kilometer in the north, would be able to capture much more information.
    Building the CTA

    An international consortium of nearly 1300 researchers from 31 countries is working toward building the CTA. The array will focus on a wider gamma ray energy range than the currently operating instruments—seeing between 20 billion electronvolts and 300 trillion electronvolts—and will do so with 10 times the sensitivity.

    The CTA will consist of two detection sites on Earth, one in each hemisphere. At Cerro Paranal in Chile’s Atacama Desert, approximately 100 telescopes spread across an area of about 10 square kilometers will scan the Southern sky. On the Spanish island of La Palma, some 19 telescopes will watch the Northern sky. The CTA Observatory is in the final negotiations with representatives from both locations to finalize the agreements to host the arrays.

    Both the northern and southern arrays will each have four large telescopes, each 23 meters wide and spaced about 100 meters apart from one another, clustered toward the center of the array. Moving outward will be telescopes in the 10 to 12 meters range. The northern array will have 15 of these medium-sized telescopes, while the southern array will have 25. The Cerro Paranal location additionally will host approximately 70 4-meter-wide telescopes, farther out from the array’s center.

    The 70 small telescopes will use new detectors made of silicon. These have several advantages over the current design, says University of Oxford graduate student Andrea De Franco, “but the most sexy for us is they can resist bright night-sky background.”

    That means they can detect Cherenkov light even in bright moonlight, something VERITAS, HESS and MAGIC cannot do. This new technology will let the CTA observatory operate for about 16 to 17 percent of the hours in a year; current arrays can observe during only about 10 percent.

    Work in progress

    CTA is in the development phase right now, meaning the consortium members are developing and testing the hardware, verifying how to deploy and operate the instruments, and simulating the best layout of those telescopes at each site.

    In October, the CTA project began constructing the large telescope prototype at La Palma.

    Two medium-sized telescope prototypes are also under construction: A two-mirror design with a 10-meter primary mirror is being built in southern Arizona; a prototype of a single-mirror, 12-meter-wide design is in testing in Berlin, and its camera is nearly complete.

    All three small-sized prototypes are well underway. A single-mirror, 4-meter design has been constructed in Krakow, Poland; a two-mirror, 4-meter design is operational near Mount Etna, Italy; and another two-mirror, 4-meter design was just inaugurated December 1 outside of Paris.

    De Franco has spent the last two years building and testing the camera for the Paris-based prototype in addition to helping commission it before the inauguration. On November 26, he and his colleagues proved the design was working—even with the City of Light nearby. The camera recorded Cherenkov light, making it the first CTA prototype fully working and observing.

    De Franco says it’s more likely that the light was part of a particle shower caused by an incoming cosmic ray rather than a gamma ray. But even if it was, this detection marked yet another step forward along the path to build science’s next gamma-ray eye scouring the sky.

    The next step will be to construct and deploy the pre-production telescopes at the actual array sites.

    “Ideally, [each of these] is identical to the final production telescope,” says CTA Project Manager Christopher Townsley. “It’s just that we will always learn something from putting it in the desert.”

    Members of the CTA project expect to begin this phase in spring 2017, depending on the availability of funding.

    Once the pre-production telescopes are operational, data collection can begin, though it won’t be anywhere near the quality expected from the full observatory. According to the current timeline, most of the telescopes at both arrays will be complete in 2020 or 2021.

    At that point, the data will surpass what today’s best gamma-ray instruments can obtain. And CTA will only get better from there.

    See the full article here .

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    Symmetry is a joint Fermilab/SLAC publication.

  • richardmitnick 3:13 pm on July 16, 2015 Permalink | Reply
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    From ESO: “Paranal Observatory First Choice to Host World’s Largest Array of Gamma-ray Telescopes” 

    European Southern Observatory

    16 July 2015
    Richard Hook
    ESO Public Information Officer
    Garching bei München, Germany
    Tel: +49 89 3200 6655
    Cell: +49 151 1537 3591
    Email: rhook@eso.org

    Temp 0

    On 15 and 16 July 2015, the Cherenkov Telescope Array (CTA) Resource Board decided to enter into detailed contract negotiations for hosting the CTA’s southern hemisphere array within the grounds of the Paranal Observatory, one of ESO’s sites in Chile. Similar negotiations for a northern site on La Palma are also starting.

    CTA Array

    The CTA project is an initiative to build the next generation of ground-based instruments designed for the detection of very high energy gamma-rays. Gamma rays are emitted by the hottest and most powerful objects in the Universe — such as supermassive black holes, supernovae and possibly remnants of the Big Bang. The array will provide valuable deeper insights into the high-energy Universe.

    Although gamma rays don’t make it to the Earth’s surface, the CTA’s mirrors and high-speed cameras will capture short-lived flashes of the characteristic eerie blue Cherenkov radiation that is produced when the gamma rays interact with the Earth’s atmosphere. Pinpointing the source of this radiation will allow each gamma ray to be traced back to its cosmic source.

    The CTA Resource Board is composed of representatives of ministries and funding agencies from Austria, Brazil, the Czech Republic, France, Germany, Italy, Namibia, the Netherlands, Japan, Poland, South Africa, Spain, Switzerland and the and the United Kingdom. After months of negotiations and careful consideration of extensive studies of the environmental conditions, simulations of the science performance and assessments of construction and operation costs the Board has decided to start contract negotiations with ESO. The Namibian and Mexican sites will be kept as viable alternatives.

    In order for the CTA to maximise its coverage of the night sky, the array will consist of about 100 telescopes on the Chile site in the southern hemisphere and about 20 telescopes at the northern site.

    The Chile site for the CTA is less than ten kilometres southeast of the location of the Very Large Telescope, within the grounds of ESO’s Paranal Observatory in the Atacama Desert. This is considered one of the driest and most isolated regions on Earth — an astronomical paradise. In addition to the ideal conditions for year-round observation, installing the CTA at the Paranal Observatory offers the CTA the opportunity to take advantage of the existing infrastructure (roads, accommodation, water, electricity, etc.) and access to established facilities and processes for the construction and operation of the telescope array.

    Currently in its pre-construction phase, determination of the array sites is a critical factor in the CTA construction project.

    More Information

    The CTA aims to build the world’s largest and most sensitive high-energy gamma-ray telescope array. Over 1000 scientists and engineers from five continents, 31 countries (Argentina, Armenia, Australia, Austria, Brazil, Bulgaria, Canada, Chile, Croatia, the Czech Republic, Finland, France, Germany, Greece, India, Ireland, Italy, Japan, Mexico, Namibia, the Netherlands, Norway, Poland, Slovenia, South Africa, Spain, Sweden, Switzerland, the United Kingdom, the United States of America and Ukraine) and over 170 research institutes participate in the CTA project. The CTA will serve as an open facility to a wide astrophysics community and provide a deep insight into the non-thermal, high-energy Universe. The CTA will detect high-energy radiation with unprecedented accuracy and approximately ten times the sensitivity of current instruments, providing novel insights into some of the most extreme and violent events in the Universe.

    See the full article here.

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

    ESO LaSilla

    ESO VLT Interferometer

    ESO Vista Telescope

    ESO VLT Survey telescope
    VLT Survey Telescope

    ALMA Array


    Atacama Pathfinder Experiment (APEX) Telescope

  • richardmitnick 8:30 am on March 27, 2015 Permalink | Reply
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    From DESY: “Negotiations for CTA northern site to start” 


    No Writer Credit

    Cherenkov Telescope Array
    Proposed Cherenkov Telescope Array for hunting Gamma Rays

    On 26 March 2015, the partner countries of Cherenkov Telescope Array (CTA) have decided to start negotiations for the location of the telescope array in the northern hemisphere. At a meeting in Heidelberg representatives of ministries and funding agencies have decided to begin negotiations with Spain for a possible location on La Palma and Mexico for one in San Pedro Mártir. Another candidate site in Arizona (USA) is considered as a possible back-up site.

    “I appreciate that we have successfully chosen the northern candidate sites with whom we would like to start negotiations as soon as possible,” said Beatrix Vierkorn-Rudolph from the German Federal Ministry of Research and Education, chair of the CTA Resource Board, after the decision of the voting members representing Argentina, Austria, Brazil, Czech Republic, France, Germany, Italy, Japan, Poland, South Africa, Spain, Switzerland and the UK. After negotiations, the Board will select the final site in November 2015. In regards to the southern hemisphere site, negotiations with the candidates Namibia and Chile are progressing and are expected to end in August 2015. Christian Stegmann from DESY added: “I’m very much looking forward to the final site decisions later this year; scientists worldwide are eager to see CTA advancing towards implementation.”

    Currently in its pre-construction phase, determining the northern and southern hemisphere sites will be a critical step towards the realization of the Cherenkov Telescope Array. “I’m looking forward to converging on final designs for the telescope arrays now that negotiations will start with specific locations in mind,” said Christopher Townsley, CTA project manager. Following the site selection, the project will move forward with construction of the first telescopes on site planned for 2016.

    See the full article here.

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    DESY is one of the world’s leading accelerator centres. Researchers use the large-scale facilities at DESY to explore the microcosm in all its variety – from the interactions of tiny elementary particles and the behaviour of new types of nanomaterials to biomolecular processes that are essential to life. The accelerators and detectors that DESY develops and builds are unique research tools. The facilities generate the world’s most intense X-ray light, accelerate particles to record energies and open completely new windows onto the universe. 
That makes DESY not only a magnet for more than 3000 guest researchers from over 40 countries every year, but also a coveted partner for national and international cooperations. Committed young researchers find an exciting interdisciplinary setting at DESY. The research centre offers specialized training for a large number of professions. DESY cooperates with industry and business to promote new technologies that will benefit society and encourage innovations. This also benefits the metropolitan regions of the two DESY locations, Hamburg and Zeuthen near Berlin.

  • richardmitnick 12:45 pm on January 23, 2015 Permalink | Reply
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    From phys.org: “Three extremely luminous gamma-ray sources discovered in Milky Way’s satellite galaxy” 


    Jan 23, 2015
    Thomas Zoufal

    Optical image of the Milky Way and a multi-wavelength (optical, Hα) zoom into the Large Magellanic Cloud with superimposed H.E.S.S. sky maps. Credit: Milky Way image: © H.E.S.S. Collaboration, optical: SkyView, A. Mellinger

    Once again, the High Energy Stereoscopic System, H.E.S.S., has demonstrated its excellent capabilities. In the Large Magellanic Cloud, it discovered most luminous very high-energy gamma-ray sources: three objects of different type, namely the most powerful pulsar wind nebula, the most powerful supernova remnant, and a shell of 270 light years in diameter blown by multiple stars, and supernovae – a so-called superbubble.

    High Energy Stereoscopic System

    The Large Magellanic Cloud

    This is the first time that stellar-type gamma-ray sources are detected in an external galaxy, at these gamma-ray energies. The superbubble represents a new source class in very high-energy gamma rays.

    Very high-energy gamma rays are the best tracers of cosmic accelerators such as supernova remnants and pulsar wind nebulae – end-products of massive stars. There, charged particles are accelerated to extreme velocities. When these particles encounter light or gas in and around the cosmic accelerators, they emit gamma rays. Very high-energy gamma rays can be measured on Earth by observing the Cherenkov light emitted from the particle showers produced by incident gamma rays high up in the atmosphere using large telescopes with fast cameras.

    The Large Magellanic Cloud (LMC) is a dwarf satellite galaxy of our Milky Way, located about 170.000 light years away and showing us its face. New, massive stars are formed at a high rate in the LMC, and it harbors numerous massive stellar clusters. The LMC’s supernova rate relative to its stellar mass is five times that of our Galaxy. The youngest supernova remnant in the local group of galaxies, SN 1987A, is also a member of the LMC. Therefore, the H.E.S.S. scientists dedicated significant observation to searching for very high-energy gamma rays from this cosmic object.

    Local Group

    SN1987a before and after by David Malin Anglo-Australian Telescope

    For a total of 210 hours, the High Energy Stereoscopic System (H.E.S.S.) has observed the largest star-forming region within the LMC called Tarantula Nebula. For the first time in a galaxy outside the Milky Way, individual sources of very high-energy gamma rays could be resolved: three extremely energetic objects of different type.

    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.

    The so-called superbubble 30 Dor C is the largest known X-ray-emitting shell and appears to have been created by several supernovae and strong stellar winds. Superbubbles are broadly discussed as (complementary or alternative to individual supernova remnants) factories where the galactic cosmic rays are produced. The H.E.S.S. results demonstrate that the bubble is a source of, and filled by, highly energetic particles. The superbubble represents a new class of sources in the very high-energy regime.

    Pulsars are highly magnetized, fast rotating neutron stars that emit a wind of ultra-relativistic particles forming a nebula. The most famous one is the Crab Nebula, one of the brightest sources in the high-energy gamma-ray sky.

    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.

    NASA Hubble Telescope
    NASA/ESA Hubble

    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 William Parsons, 3rd Earl of 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.

    ESO VLT Interferometer
    ESO/ VLT

    The newly composed image was assembled from 24 individual Wide Field and Planetary Camera 23 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 WFPC2
    WFPC2 (no longer in service)

    The pulsar PSR J0537−6910 driving the wind nebula N 157B discovered by the H.E.S.S. telescopes in the LMC is in many respects a twin of the very powerful Crab pulsar in our own Galaxy. However, its pulsar wind nebula N 157B outshines the Crab Nebula by an order of magnitude, in very high-energy gamma rays. Reasons are the lower magnetic field in N 157B and the intense starlight from neighboring star-forming regions, which both promote the generation of high-energy gamma rays.

    The supernova remnant N 132D, known as a bright object in the radio and infrared bands, appears to be one of the oldest – and strongest – supernova remnants still glowing in very high-energy gamma rays. Between 2500 and 6000 years old – an age where models predict that the supernova explosion front has slowed down and it ought no longer be efficiently accelerating particles – it still outshines the strongest supernova remnants in our Galaxy. The observations confirm suspicions raised by other H.E.S.S. observations, that supernova remnants can be much more luminous than thought before.

    Observed at the limits of detectability, and partially overlapping with each other, these new sources challenged the H.E.S.S. scientists. The discoveries were only possible due to the development of advanced methods of interpreting the Cherenkov images captured by the telescopes, improving in particular the precision with which gamma-ray directions can be determined.

    “Both the pulsar wind nebula and the supernova remnant, detected in the Large Magellanic Cloud by H.E.S.S., are more energetic than their most powerful relatives in the Milky Way. Obviously, the high star formation rate of the LMC causes it to breed very extreme objects”, summarizes Chia Chun Lu, a student who analyzed the LMC data as her thesis project. “Surprisingly, however, the young supernova remnant SN 1987A did not show up, in contrast to theoretical predictions. But we’ll continue the search for it,” adds her advisor Werner Hofmann, director at the MPI for Nuclear Physics in Heidelberg and for many years H.E.S.S. spokesperson.

    Indeed, the new H.E.S.S. II 28 m telescope will boost performance of the H.E.S.S. telescope system, and in the more distant future the planned Cherenkov Telescope Array (CTA) will provide even deeper and higher-resolution gamma-ray images of the LMC – in the plans for science with CTA, the satellite galaxy is already identified as a “Key Science Project” deserving special attention.

    Cherenkov Telescope Array

    The H.E.S.S. Telescopes

    The collaboration: The High Energy Stereoscopic System (H.E.S.S.) team consists of scientists from Germany, France, the United Kingdom, Namibia, South Africa, Ireland, Armenia, Poland, Australia, Austria, the Netherlands and Sweden, supported by their respective funding agencies and institutions.

    The instrument: The results were obtained using the High Energy Stereoscopic System (H.E.S.S.) telescopes in Namibia, in South-West Africa. This system of four 13 m diameter telescopes – recently complemented with the huge 28 m H.E.S.S. II telescope – is one of the most sensitive detectors of very high-energy gamma rays. These are absorbed in the atmosphere, where they create a short-lived shower of particles. The H.E.S.S. telescopes detect the faint, short flashes of bluish light which these particles emit (named Cherenkov light, lasting a few billionths of a second), collecting the light with big mirrors which reflect onto extremely sensitive cameras. Each image gives the position on the sky of a single gamma-ray photon, and the amount of light collected gives the energy of the initial gamma ray. Building up the images photon by photon allows H.E.S.S. to create maps of astronomical objects as they appear in gamma rays.

    The H.E.S.S. telescopes have been operating since late 2002; in September 2012 H.E.S.S. celebrated the first decade of operation, by which time the telescopes had recorded 9415 hours of observations, and detected 6361 million air shower events. H.E.S.S. has discovered the majority of the about 150 known cosmic objects emitting very high-energy gamma rays. In 2006, the H.E.S.S. team was awarded the Descartes Prize of the European Commission, in 2010 the Rossi Prize of the American Astronomical Society. A study performed in 2009 listed H.E.S.S. among the top 10 observatories worldwide.

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  • richardmitnick 3:18 pm on October 28, 2014 Permalink | Reply
    Tags: , , , Cherenkov Telescope Array, ,   

    From Symmetry: “Scientists mull potential gamma-ray study sites” 


    October 28, 2014
    Kelen Tuttle

    An international panel is working to determine the two locations from which the Cherenkov Telescope Array will observe the gamma-ray sky.

    Cherenkov Telescope Array
    Cherenkov Telescope Array

    Somewhere in the Southern Hemisphere, about 100 state-of-the-art telescopes will dot the otherwise empty landscape for half a kilometer in every direction. Meanwhile, in the Northern Hemisphere, a swath of land a little over a third the size will house about 20 additional telescopes, every one of them pointing toward the heavens each night for a full-sky view of the most energetic—and enigmatic—processes in the universe.

    This is the plan for the Cherenkov Telescope Array Observatory, the world’s largest and most sensitive gamma-ray detector. The first of the two arrays is scheduled to begin taking data in 2016, with the other coming online in by 2020. At that point, CTA’s telescopes will observe gamma rays produced in some of the universe’s most violent events—everything from supernovas to supermassive black holes.

    Yet where exactly the telescopes will be built remains to be seen.

    Scientists representing the 29-country CTA consortium met last week to discuss the next steps toward narrowing down potential sites in the Northern Hemisphere: two in the United States (both in Arizona) and two others in Mexico and the Canary Islands. Although details from that meeting remain confidential, the CTA resource board is expected to begin negotiations with the potential host countries within the next few months. That will be the final step before the board makes its decision, says Rene Ong, co-spokesperson of CTA and a professor of physics and astronomy at UCLA.

    “Whichever site it goes to, it will be very important in that country,” Ong says. “It’s a major facility, and it will bring with it a huge amount of intellectual capital.”

    Site selection for the Southern Hemisphere is a bit further along. Last April, the CTA resource board narrowed down that list to two potential sites: one in Southern Namibia and one in Northern Chile. The board is now in the process of choosing between the sites based on factors including weather, operating costs, existing infrastructure like roads and utilities, and host country contributions. A final decision is expected soon.

    Artwork by: Sandbox Studio, Chicago

    “The consortium went through an exhaustive 3-year process of examining the potential sites, and all of the sites now being considered will deliver on the science,” says CTA Project Scientist Jim Hinton, a professor of physics and astronomy at the University of Leicester. “We’re happy that we have so many really good potential sites. If we reach an impasse with one, we can still keep moving forward with the others.”

    Scientists do not completely understand how high-energy gamma rays are created. Previous studies suggest that they stream from jets of plasma pouring out of enormous black holes, supernovae and other extreme environments, but the processes that create the rays—as well as the harsh environments where they are produced—remain mysterious.

    To reach its goal of better understanding high-energy gamma rays, CTA needs to select two sites—one in the Northern Hemisphere and one in the Southern Hemisphere—to see the widest possible swath of sky. In addition, the view from the two sites will overlap just enough to allow experimenters to better calibrate their instruments, reducing error and ensuring accurate measurements.

    With 10 times the sensitivity of previous experiments, CTA will fill in the many blank regions in our gamma-ray map of the universe. Gamma-rays with energies up to 100 gigaelectronvolts have already been mapped by the Fermi Gamma-ray Space Telescope and others; CTA will cover energies up to 100,000 gigaelectronvolts. It will survey more of the sky than any previous such experiment and be significantly better at determining the origin of each gamma ray, allowing researchers to finally understand the astrophysical processes that produce these energetic rays.

    NASA Fermi Telescope

    CTA may also offer insight into dark matter. If a dark matter particle were to naturally decay or interact with its antimatter partner to release a flash of energy, the telescope array could theoretically detect that flash. In fact, CTA is one of very few instruments that could see such flashes with energies above 100 gigaelectronvolts.

    “I’m optimistic that we’ll see something totally new and unexpected,” Ong says. “Obviously I can’t tell you what it will be—otherwise it wouldn’t be unexpected—but history tells us that when you make a big step forward in capability, you tend to see something totally new. And that’s just what we’re doing here.”

    See the full article here.

    Symmetry is a joint Fermilab/SLAC publication.

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  • richardmitnick 12:04 pm on April 15, 2014 Permalink | Reply
    Tags: , , , Cherenkov Telescope Array, ,   

    From ESO: “ESO Site Shortlisted for Cherenkov Telescope Array” 

    European Southern Observatory

    15 April 2014

    Lars Lindberg Christensen
    Head of ESO ePOD
    ESO ePOD, Garching, Germany
    Tel: +49 89 3200 6761
    Cellular: +49 173 3872 621
    E-mail: lars@eso.org

    ESO’s Paranal–Armazones site in Chile has been shortlisted as one of two potential sites in the southern hemisphere for the international Cherenkov Telescope Array (CTA) — a large array for ground-based gamma-ray astronomy. This is an important step towards the realisation of the project and if the site is selected, this will open up a new frontier for ESO.


    On 10 April 2014 Government representatives from the 12 of the countries involved in the Cherenkov Telescope Array (CTA) project met in Munich and decided to start negotiations with the two sites — Aar in Namibia and ESO’s Paranal–Armazones site in Chile — keeping Leoncito in Argentina as a third option.

    The CTA project is an initiative to build the next generation of ground-based, very high energy gamma-ray instruments. The CTA project aims to use detection of high-energy gamma-rays to provide a deeper insight into the high-energy Universe.

    The representatives received consultation from an international Site Selection Committee as well as the CTA consortium’s extensive input on the merits of the proposed sites. The Consortium expects to close the site selection by the end of 2014.

    The spokesperson of the CTA Consortium, Professor Werner Hofmann said: “The site choice is on the critical path towards implementing CTA; this decision represents a major step forward and we appreciate very much the engagement and support of the funding agencies and the country delegates involved in the decision.”

    Gamma-rays are emitted by the hottest and most powerful objects in our Universe — such as supermassive black holes, supernovae and possibly remnants of the Big Bang. When a high-energy gamma photon hits the Earth’s atmosphere, it may produce a cascade of secondary particles and cause emission of what is known as Cherenkov radiation — a characteristic faint blue visible-light flash. This flash may last only a few billionths of a second so must be imaged with super-fast and sensitive cameras and with telescopes of enormous light gathering power.

    The Cherenkov Telescope Array is a multinational, world-wide project with which 1000 scientists and engineers from 28 countries and over 170 research institutes are involved. The CTA will provide an order-of-magnitude jump in sensitivity over current instruments, providing novel insights into some of the most extreme processes in the Universe. Most systems measuring Cherenkov radiation use only a handful of telescopes, but the CTA will consist of about 100 Cherenkov telescopes of 23-metre, 12-metre and 4-metre dish sizes located in the southern hemisphere, plus a smaller site in the northern hemisphere. An array of this size will increase the number of detected flashes, it will also cover the full energy range [3] and improve drastically upon the angular resolution [4], allowing for identification of the emitting objects at other wavelengths.

    “Although formal discussions have not yet started, the shortlisting of Paranal-Armazones as a potential site for CTA illustrates the excellence of the site and the infrastructure for the Very Large Telescope and European Extremely Large Telescope. If chosen, CTA would take advantage of ESO’s great expertise in ground-based astronomy.” said ESO’s Director General, Tim de Zeeuw. “We look forward to the discussions with CTA.”

    See the full article, with notes here.

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  • richardmitnick 11:07 am on June 27, 2012 Permalink | Reply
    Tags: , , , Cherenkov Telescope Array,   

    From ISGTW: “The grand vision of the Cherenkov Telescope Array” 

    June 27, 2012
    Adrian Giordani

    The Cherenkov Telescope Array (CTA) will consist of two arrays of telescopes in two different hemispheres, allowing full coverage of the sky. The south CTA will cover about one square kilometer (0.39 square miles) of land with around 60 telescopes that will monitor all the energy ranges in the center of the Milky Way’s galactic plane. The north CTA will cover three square kilometers (1.16 square miles) and be composed of 30 telescopes. These telescopes will be targeted at extragalactic astronomy.

    An artist’s impression of the final constructed Cherenkov Telescope Array. Image courtesy G. Perez, SMM, IAC.

    ‘CTA opens a new window of essentially unexplored photon energies,’ said Giovanni Bignami, president of the Italian National Institute for Astrophysics (INAF). ‘Its potential impact is enormous: part of it, we imagine, will consist in discovering thousands of new [very-high-energy photon] sources, and part of it will be surprises. It’s the surprises we like best, and it’s the surprises that will most appeal to the public at large.’

    The project represents a major global effort with research groups from Africa, Argentina, Brazil, India, Japan, Mexico, and the US. There are currently more than 27 countries, and over 1,000 scientists involved.

    What is the goal of the CTA?

    The project will be composed of a collection of Cherenkov telescopes that will scan the universe at very-high-energy gamma-rays from 100 giga-electronvolts to about 100 tera-electronvolts; energies which are one hundred billion to one hundred trillion times higher than of visible light.The CTA will also investigate cosmic processes that create particles travelling close to the speed of light.

    The CTA combines the fields of astronomy, astrophysics, and fundamental physics research. Studies will include the origin of cosmic rays and their impact on other bodies within the universe. Researchers will investigate galactic particle accelerators, black holes, extragalactic gamma rays, dark matter, and the effects of quantum gravity.”

    See the full article here.

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