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  • richardmitnick 2:33 pm on January 17, 2019 Permalink | Reply
    Tags: , , , , , prototype Schwarzschild-Couder Telescope (pSCT), , Whipple Observatory in Arizona   

    From UC Santa Cruz: “Scientists to inaugurate a new type of gamma ray telescope at Whipple Observatory” 

    UC Santa Cruz

    From UC Santa Cruz

    January 16, 2019
    Tim Stephens

    The prototype Schwarzschild-Couder Telescope (pSCT) is a novel type of gamma-ray telescope designed for the Čerenkov Telescope Array (CTA). (Photo by Amy Oliver, Fred Lawrence Whipple Observatory, Center for Astrophysics, Harvard & Smithsonian)

    A new type of gamma-ray telescope will be unveiled January 17 in an inauguration event at the Fred Lawrence Whipple Observatory in Amado, Arizona. Expected to see first light in early 2019, the telescope is a prototype Schwarzschild-Couder Telescope (pSCT) designed for the Čerenkov Telescope Array (CTA), the next generation ground-based observatory for gamma-ray astronomy at very high energies.

    David Williams, adjunct professor of physics at UC Santa Cruz, chairs the CTA-US Consortium.

    “The inauguration of the pSCT is an exciting moment for the institutions involved in its development and construction,” Williams said. “The first of its kind in the history of gamma-ray telescopes, the SCT design is expected to boost CTA performance towards the theoretical limit of the technology.”

    The CTA Observatory, for which construction will begin in 2019, will be the world’s largest and most sensitive high-energy gamma-ray observatory, with more than 100 telescopes located in the northern and southern hemispheres.

    The 9.7-meter aperture pSCT is a pathfinder telescope for use in the CTA and exploits a novel optical design. Its complex dual-mirror optical system improves on the single-mirror designs traditionally used in gamma-ray telescopes by dramatically enhancing the optical quality of their focused light over a large region of the sky, and by enabling the use of compact, highly-efficient photo-sensors in the telescope camera.

    “Ultimately, the SCT is designed to improve CTA’s ability to detect very-high-energy gamma-ray sources, which may also be sources of neutrinos and gravitational waves,” said Vladimir Vassiliev, principal investigator of the pSCT. “Once the SCT technology is demonstrated at FLWO, it is hoped that SCTs will become a part of at least one of the two CTA arrays, located in each of the northern and southern hemispheres.”

    The CTA Observatory (CTAO) will consist of 118 telescopes of three different sizes and is expected to detect sources of gamma rays in the energy range 20 GeV to 300 TeV, with about ten times increased sensitivity compared to any current observatory. Notable for providing improved gamma-ray angular resolution and its very-high-resolution camera (more than 11,000 pixels), the SCT is proposed for the medium-sized CTA telescopes and will primarily contribute to the middle of CTA’s energy range (80 GeV to 50 TeV).

    “The SCT and other telescopes at CTA will greatly improve upon current gamma-ray research being conducted at HAWC, HESS, MAGIC, and VERITAS, the last of which is located at the Fred Lawrence Whipple Observatory,” said VERITAS Director Wystan Benbow.

    HAWC High Altitude Čerenkov Experiment, located on the flanks of the Sierra Negra volcano in the Mexican state of Puebla at an altitude of 4100 meters(13,500ft), at WikiMiniAtlas 18°59′41″N 97°18′30.6″W. searches for cosmic rays

    HESS Čerenkov Telescope Array, located on the Cranz family farm, Göllschau, in Namibia, near the Gamsberg searches for cosmic rays, altitude, 1,800 m (5,900 ft)

    MAGIC Cherenkov telescopes at the Observatorio del Roque de los Muchachos (Garfia, La Palma, Spain))

    CfA/VERITAS, a major ground-based gamma-ray observatory with an array of four 12m optical reflectors for gamma-ray astronomy in the GeV – TeV energy range. Located at Fred Lawrence Whipple Observatory,Mount Hopkins, Arizona, US in AZ, USA, Altitude 2,606 m (8,550 ft)

    “Gamma-ray observatories like VERITAS have been operating for 12 to 16 years, and their many successes have brought very-high-energy gamma-ray astronomy into the mainstream, and have made many exciting discoveries. We hope CTA will supersede VERITAS around 2023, and it will be used to continue to build upon the 50 years of gamma-ray research at the Whipple Observatory and elsewhere.”

    The Whipple Observatory is operated by the Harvard-Smithsonian Center for Astrophysics.

    The SCT optical design was first conceptualized by U.S. members of CTA in 2006, and the construction of the pSCT was funded in 2012. Preparation of the pSCT site at the base of Mt. Hopkins in Amado, AZ, began in late 2014, and the steel structure was assembled on site in 2016. The installation of pSCT’s 9.7-meter primary mirror surface, consisting of 48 aspheric mirror panels, occurred in early 2018, and was followed by the camera installation in June 2018 and the 5.4-meter secondary mirror surface installation, consisting of 24 aspheric mirror panels, in August 2018.

    Leading up to the inauguration and in preparation for first light, scientists opened the telescope’s optical surfaces in January 2019. The SCT is based on a 114-year-old dual-mirror optical system first proposed by Karl Schwarzschild in 1905. It became possible to construct only recently as a result of critical research and development progress made at both the Brera Astronomical Observatory and Media Lario Technologies Incorporated in Italy.

    The pSCT was made possible by funding through the U.S. National Science Foundation Major Research Instrumentation program and by the contributions of thirty institutions and five critical industrial partners across the United States, Italy, Germany, Japan, and Mexico.

    More information about the pSCT is available online at http://www.cta-observatory.org/project/technology/sct.

    See the full article here .


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    UCSC Lick Observatory, Mt Hamilton, in San Jose, California, Altitude 1,283 m (4,209 ft)


    UCO Lick Shane Telescope
    UCO Lick Shane Telescope interior
    Shane Telescope at UCO Lick Observatory, UCSC

    Lick Automated Planet Finder telescope, Mount Hamilton, CA, USA

    Lick Automated Planet Finder telescope, Mount Hamilton, CA, USA

    UC Santa Cruz campus
    The University of California, Santa Cruz, opened in 1965 and grew, one college at a time, to its current (2008-09) enrollment of more than 16,000 students. Undergraduates pursue more than 60 majors supervised by divisional deans of humanities, physical & biological sciences, social sciences, and arts. Graduate students work toward graduate certificates, master’s degrees, or doctoral degrees in more than 30 academic fields under the supervision of the divisional and graduate deans. The dean of the Jack Baskin School of Engineering oversees the campus’s undergraduate and graduate engineering programs.

    UCSC is the home base for the Lick Observatory.

    Lick Observatory's Great Lick 91-centimeter (36-inch) telescope housed in the South (large) Dome of main building
    Lick Observatory’s Great Lick 91-centimeter (36-inch) telescope housed in the South (large) Dome of main building

    Search for extraterrestrial intelligence expands at Lick Observatory
    New instrument scans the sky for pulses of infrared light
    March 23, 2015
    By Hilary Lebow
    The NIROSETI instrument saw first light on the Nickel 1-meter Telescope at Lick Observatory on March 15, 2015. (Photo by Laurie Hatch) UCSC Lick Nickel telescope

    Astronomers are expanding the search for extraterrestrial intelligence into a new realm with detectors tuned to infrared light at UC’s Lick Observatory. A new instrument, called NIROSETI, will soon scour the sky for messages from other worlds.

    “Infrared light would be an excellent means of interstellar communication,” said Shelley Wright, an assistant professor of physics at UC San Diego who led the development of the new instrument while at the University of Toronto’s Dunlap Institute for Astronomy & Astrophysics.

    Wright worked on an earlier SETI project at Lick Observatory as a UC Santa Cruz undergraduate, when she built an optical instrument designed by UC Berkeley researchers. The infrared project takes advantage of new technology not available for that first optical search.

    Infrared light would be a good way for extraterrestrials to get our attention here on Earth, since pulses from a powerful infrared laser could outshine a star, if only for a billionth of a second. Interstellar gas and dust is almost transparent to near infrared, so these signals can be seen from great distances. It also takes less energy to send information using infrared signals than with visible light.

    Frank Drake, professor emeritus of astronomy and astrophysics at UC Santa Cruz and director emeritus of the SETI Institute, said there are several additional advantages to a search in the infrared realm.

    “The signals are so strong that we only need a small telescope to receive them. Smaller telescopes can offer more observational time, and that is good because we need to search many stars for a chance of success,” said Drake.

    The only downside is that extraterrestrials would need to be transmitting their signals in our direction, Drake said, though he sees this as a positive side to that limitation. “If we get a signal from someone who’s aiming for us, it could mean there’s altruism in the universe. I like that idea. If they want to be friendly, that’s who we will find.”

    Scientists have searched the skies for radio signals for more than 50 years and expanded their search into the optical realm more than a decade ago. The idea of searching in the infrared is not a new one, but instruments capable of capturing pulses of infrared light only recently became available.

    “We had to wait,” Wright said. “I spent eight years waiting and watching as new technology emerged.”

    Now that technology has caught up, the search will extend to stars thousands of light years away, rather than just hundreds. NIROSETI, or Near-Infrared Optical Search for Extraterrestrial Intelligence, could also uncover new information about the physical universe.

    “This is the first time Earthlings have looked at the universe at infrared wavelengths with nanosecond time scales,” said Dan Werthimer, UC Berkeley SETI Project Director. “The instrument could discover new astrophysical phenomena, or perhaps answer the question of whether we are alone.”

    NIROSETI will also gather more information than previous optical detectors by recording levels of light over time so that patterns can be analyzed for potential signs of other civilizations.

    “Searching for intelligent life in the universe is both thrilling and somewhat unorthodox,” said Claire Max, director of UC Observatories and professor of astronomy and astrophysics at UC Santa Cruz. “Lick Observatory has already been the site of several previous SETI searches, so this is a very exciting addition to the current research taking place.”

    NIROSETI will be fully operational by early summer and will scan the skies several times a week on the Nickel 1-meter telescope at Lick Observatory, located on Mt. Hamilton east of San Jose.

    The NIROSETI team also includes Geoffrey Marcy and Andrew Siemion from UC Berkeley; Patrick Dorval, a Dunlap undergraduate, and Elliot Meyer, a Dunlap graduate student; and Richard Treffers of Starman Systems. Funding for the project comes from the generous support of Bill and Susan Bloomfield.

  • richardmitnick 5:03 pm on April 14, 2017 Permalink | Reply
    Tags: and HESS, , , , , , , , Extensive air shower, Ground-based gamma-ray astrophysics, , TeV gamma rays, TeV gamma-ray astronomy, , Whipple Observatory in Arizona   

    From astrobites: “The birth of a new field” 

    Astrobites bloc


    Apr 14, 2017
    Kelly Malone

    Title: Observation of TeV gamma rays from the Crab Nebula using the Atmospheric Cerenkov Imaging technique
    Authors: Weekes et. al
    First Author’s Institution: Harvard-Smithsonian Center of Astrophysics

    Status: Published in The Astrophysical Journal (1989), [open access]

    Today’s paper is historical in nature rather than a current summary – it describes the 1989 paper that essentially birthed the field of ground-based gamma-ray astrophysics by making the first > 5 sigma detection of a TeV gamma-ray source!

    A brief history of TeV gamma-ray astronomy

    Gamma rays lie on the highest-frequency end of the electromagnetic spectrum and have been observed spanning a few orders of magnitude in energy, starting from a few hundred keV, going through the MeV range, the GeV range, and beyond. The most energetic gamma rays observed to date have been in the TeV range, which is roughly the same energy the proton collisions at the Large Hadron Collider take place at. TeVCat currently lists 198 known TeV gamma-ray sources.


    They are associated with some of the most energetic and violent things in our universe, including supernova explosions and active galactic nuclei.

    TeV gamma-ray sources are of particular interest because of their ability to probe phenomena associated with some of the big unsolved problems in astroparticle physics – they are associated with the acceleration sites of charged cosmic rays, but are somewhat easier to study since gamma rays are electrically neutral and don’t curve in magnetic fields on their way to us. This means that they point directly back to their sources. The origins and acceleration sites of charged cosmic rays are still open questions – we know a large portion of the galactic cosmic rays originate in supernova explosions, but don’t know a whole lot else. They can also be used for other science; for example, many current gamma-ray observatories are involved in finding electromagnetic counterparts to gravitational waves.

    The Whipple 10 m telescope used to make the observations described in this Astrobite. (Source: Michael Richmond, used under a Creative Commons license)

    CfA Whipple Observatory, near Amado, Arizona on the slopes of Mount Hopkins

    When a gamma ray hits the Earth’s atmosphere, it interacts with the air molecules and creates what is known as an extensive air shower. This means that it is not possible to directly observe the gamma ray from the Earth and its indirect products must be studied instead. The extensive air shower consists of many electrons and positrons, some of which are traveling faster than the phase velocity of light in air. This leads to the emission of a type of radiation known as Cherenkov radiation. Detecting this radiation is one of the ways that we can indirectly detect gamma rays on the Earth, and many currently running experiments (such as VERITAS, MAGIC, and HESS) have used this technique to great success.


    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

    A few decades ago, the prospects for detecting gamma rays from the Earth was not so rosy. Techniques to separate the showers caused by gamma rays from those caused by the very large background caused by hadrons were still in their infancy. Experiments were publishing only weak detections (~3 sigma) and contradictory results. Statistical tests that we use today to check the validity of results were not widely used yet. An overview of the field from 1988 stresses that it is likely that some of the “sources” in their list will likely be removed as techniques are refined. (For more information about this time period, see section 2.2 of this history of gamma-ray astronomy, written in 2012.)

    A pioneering observation

    The spectrum of the Crab Nebula. The “W” is the measurement from this paper, the others are results from earlier experiments, which were less significant detections. The lines are the predicted spectrum for two different values of the magnetic field.

    In 1989, everything changed for the field of ground-based gamma-ray astrophysics. That was the year that scientists published a 9 sigma detection of TeV gamma rays from the Crab Nebula, the first unambiguous detection of gamma rays (from any source) at TeV energies.

    Supernova remnant Crab nebula. NASA/ESA Hubble

    The data was collected at the Whipple Observatory in Arizona, which had a 10 m reflector outfitted with a 37 pixel camera to detect the Cherenkov radiation described in the preceding section. The 37 phototubes were arranged in a hexagonal pattern and were capable of tracking sources across the sky.

    It was the improved gamma/background discrimination that led to the unambiguous detection. After each observation, the data was calibrated, the observed showers parameterized, and then candidate gamma rays were selected. Monte Carlo simulations were used to predict how the camera would respond to gamma-ray initiated showers and hadron-initiated background showers. When the analysis was finished, the Crab Nebula was seen with a significance of 9 sigma above an energy threshold of 0.7 TeV. No variability was observed over the months or years the data was taken over, and it was established that the emission was likely coming from the hard Compton synchrotron spectrum in the Nebula.

    The authors close the paper by noting that observing a steady source such as the Crab Nebula is important for the field of TeV gamma ray astronomy, since such a source can be used as a standard candle in calibrating new detectors. In fact, this is still true today. Nearly every gamma-ray experiment starts off their life by publishing a paper with their observations of the Crab Nebula, as it is still the most significant source in the gamma ray sky!

    See the full article here .

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    What do we do?

    Astrobites is a daily astrophysical literature journal written by graduate students in astronomy. Our goal is to present one interesting paper per day in a brief format that is accessible to undergraduate students in the physical sciences who are interested in active research.
    Why read Astrobites?

    Reading a technical paper from an unfamiliar subfield is intimidating. It may not be obvious how the techniques used by the researchers really work or what role the new research plays in answering the bigger questions motivating that field, not to mention the obscure jargon! For most people, it takes years for scientific papers to become meaningful.
    Our goal is to solve this problem, one paper at a time. In 5 minutes a day reading Astrobites, you should not only learn about one interesting piece of current work, but also get a peek at the broader picture of research in a new area of astronomy.

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