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  • richardmitnick 3:20 pm on October 19, 2018 Permalink | Reply
    Tags: , , , Blazar PG 1553+113, Blazars, ,   

    From Discover Magazine: “In a First, Astronomers Find a Blazar That Cycles Every Two Years” 

    DiscoverMag

    From Discover Magazine

    October 19, 2018
    Chelsea Gohd

    1
    A visualization of the blazar being observed while emitting gamma rays. (Credit: Stefano Ciprini)

    Blazar Brightness

    After 10 years of observations, scientists have confirmed a two-year cycle in the gamma-ray brightness of a blazar, or a galaxy with supermassive black holes that consume mass and produce high-energy jets as a result. Blazars are the most energetic and luminous objects that we have identified so far in the known universe.

    “This is the first time that a gamma-ray period has been confirmed in an active galaxy,” Stefano Ciprini, a researcher at the INFN Tor Vergata division of the Italian Space Agency’s Space Science Data Center in Rome, said in a press statement. Gamma rays are some of the most energetic electromagnetic emissions, and powerful objects like blazars produce them in large quantities.

    Finding that the emissions increase and decrease in a predictable cycle, though, hints to researchers that there might be more than one supermassive black hole at the center of this galaxy.

    The confirmation, the first of its kind, could help to support new investigations and provide new insight into what really happens close to supermassive black holes.

    2
    An animation of emissions from the blazar showing how they vary predictably. (Credit: NASA)

    Exploring Black Holes

    One of the most exciting things about this work and this blazar, named PG 1553+113, is that scientists think that the galaxy may have a pair of supermassive black holes in its center, instead of just one. This could explain the cyclical nature of the blazar, the researchers say. One black hole would be emitting a jet of gamma rays and other material, and the other might be interfering with the stream as it orbits, causing the jet to wobble.

    In 2015, this research team found hints of this gamma-ray cycle inPG 1553+113. They suspected that this distant blazar might be producing the first observed years-long gamma-ray emission cycle. And, after a few more years of observations, the team has confirmed these previous inklings.

    “This result has been achieved after 10 years of continuous monitoring by Fermi’s Large Area Telescope (LAT),” Sara Cutini, a researcher at the Italian Institute for Nuclear Physics (INFN) in Perugia, said in the statement.

    A paper detailing this analysis and conclusions is in the works and the findings were announced yesterday (Oct. 17) at the Eighth International Fermi Symposium meeting in Baltimore.

    See the full article here .

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  • richardmitnick 2:40 pm on July 15, 2018 Permalink | Reply
    Tags: , , , Blazars, , , , , ,   

    From Spaceflight Insider: “Fermi Telescope discovers neutrino’s origin as supermassive black hole” 

    1

    From Spaceflight Insider

    NASA/Fermi LAT


    NASA/Fermi Gamma Ray Space Telescope

    A cosmic neutrino detected by NASA’s Fermi Gamma-ray Space Telescope was found to have originated in a gamma ray emitted by a supermassive black hole 3.7 billion light years away at the center of a galaxy in the constellation Orion.

    The discovery, made by an international team of scientists, marks the first time a high-energy neutrino from beyond the Milky Way has been traced to its place of origin as well as the furthest any neutrino has been known to travel.

    Neutrinos are high-energy, hard-to-catch particles likely produced in powerful cosmic events, such as supermassive black holes actively devouring matter and galaxy mergers. Because they travel at nearly the speed of light and do not interact with other matter, they are capable of traversing billions of light years.

    By studying neutrinos, scientists gain insight into the processes that drive powerful cosmic events, including supernovae and black holes.

    Gamma rays are the brightest and most energetic form of light, which is why scientists use them to trace the sources of neutrinos and cosmic rays.

    “The most extreme cosmic explosions produce gravitational waves, and the most extreme cosmic accelerators produce high-energy neutrinos and cosmic rays,” explained Regina Caputo of NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and analysis coordinator for the Fermi Large Area Telescope Collaboration. “Through Fermi, gamma rays are providing a bridge to each of these new cosmic signals.”

    Scientists found this particular neutrino on September 22, 2017, using the National Science Foundation‘s (NSF) IceCube Neutrino Observatory at the Amundsen-Scott South Pole Station. They then traced the neutrino to its origin in a gamma ray blast within the distant supermassive black hole using Fermi.[ https://sciencesprings.wordpress.com/2018/07/13/the-great-neutrino-catch-a-bunch-of-articles/ ]

    “Again, Fermi has helped make another giant leap in a growing field we call multimessenger astronomy. Neutrinos and gravitational waves deliver new kinds of information about the most extreme environments in the universe. But to understand what they’re telling us, we need to connect them to the ‘messenger’ astronomers know best–light,” emphasized Paul Hertz, director of NASA’s Astrophysics Division in Washington, DC.

    IceCube tracked the neutrino, which hit Antarctica with 300 trillion electron volts. Its extremely high energy level meant it likely came from beyond our solar system. Its galaxy of origin, with which scientists are familiar, is a blazar, a galaxy with an extremely bright and active central supermassive black hole that blasts out jets of particles in opposite directions at nearly the speed of light.

    Blazars have several million to several billion times the mass of our Sun. Scientists find them when one of the jets they emit travels in the direction of Earth.

    Yasuyuki Tanaka of Japan’s Hiroshima University was the first scientist to link the neutrino to a specific blazar known as TXS 0506+056, which has recently shown increased activity. Fermi keeps track of approximately 2,000 blazars.

    Followup observations of TXS 0506 were conducted with the Major Atmospheric Gamma Imaging Cherenkov Telescopes (MAGIC) NASA’s Neil Gehrels Swift Observatory, and various other observatories.[See above link to previous post Bunch of Articles]

    Two papers on the discovery have been published here and here in the journal Science.

    See the full article here .

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    SpaceFlight Insider reports on events taking place within the aerospace industry. With our team of writers and photographers, we provide an “insider’s” view of all aspects of space exploration efforts. We go so far as to take their questions directly to those officials within NASA and other space-related organizations. At SpaceFlight Insider, the “insider” is not anyone on our team, but our readers.

    Our team has decades of experience covering the space program and we are focused on providing you with the absolute latest on all things space. SpaceFlight Insider is comprised of individuals located in the United States, Europe, South America and Canada. Most of them are volunteers, hard-working space enthusiasts who freely give their time to share the thrill of space exploration with the world.

     
  • richardmitnick 1:13 pm on July 14, 2018 Permalink | Reply
    Tags: Blazars, , , ,   

    From U Hawaii via Eureka Alert: Late to the Party, but “Hawaii telescopes help unravel long-standing cosmic mystery” 

    U Hawaii

    From University of Hawaii Manoa

    via

    EurekAlert!

    12-Jul-2018

    Astronomers and physicists around the world, including in Hawaii, have begun to unravel a long-standing cosmic mystery. Using a vast array of telescopes in space and on Earth, they have identified a source of cosmic rays.

    Artist’s impression of a blazar emitting neutrinos and gamma rays via IceCube and NASA

    Blazar. NASA Fermi Gamma ray Space Telescope. Credits M. Weiss/ CfA

    NASA/Fermi LAT

    NASA/Fermi Gamma Ray Space Telescope

    Astronomers and physicists around the world, including in Hawaii, have begun to unravel a long-standing cosmic mystery. Using a vast array of telescopes in space and on Earth, they have identified a source of cosmic rays–highly energetic particles that continuously rain down on Earth from space.

    In a paper published this week in the journal Science, scientists have, for the first time, provided evidence for a known blazar, designated TXS 0506+056, as a source of high-energy neutrinos. At 8:54 p.m. on September 22, 2017, the National Science Foundation-supported IceCube neutrino observatory at the South Pole detected a high energy neutrino from a direction near the constellation Orion. Just 44 seconds later an alert went out to the entire astronomical community.

    U Wisconsin ICECUBE neutrino detector at the South Pole

    IceCube employs more than 5000 detectors lowered on 86 strings into almost 100 holes in the Antarctic ice NSF B. Gudbjartsson, IceCube Collaboration

    Lunar Icecube

    IceCube DeepCore annotated

    IceCube PINGU annotated


    DM-Ice II at IceCube annotated

    The All Sky Automated Survey for SuperNovae team (ASAS-SN), an international collaboration headquartered at Ohio State University, immediately jumped into action. ASAS-SN uses a network of 20 small, 14-centimeter telescopes in Hawaii, Texas, Chile and South Africa to scan the visible sky every 20 hours looking for very bright supernovae. It is the only all-sky, real-time variability survey in existence.

    ASAS-SN Brutus at lcogt site Hawaii

    LCOGT Las Cumbres Observatory Global Telescope Network, Haleakala Hawaii, USA, Elevation 10,023 ft (3,055 m)

    “When ASAS-SN receives an alert from IceCube, we automatically find the first available ASAS-SN telescope that can see that area of the sky and observe it as quickly as possible,” said Benjamin Shappee, an astronomer at the University of Hawaii’s Institute for Astronomy and an ASAS-SN core member.

    On September 23, only 13 hours after the initial alert, the recently commissioned ASAS-SN unit at McDonald Observatory in Texas [image of exas unit N/A] mapped the sky in the area of the neutrino detection. Those observations and the more than 800 images of the same part of the sky taken since October 2012 by the first ASAS-SN unit, located on Maui’s Haleakala, showed that TXS 0506+056 had entered its highest state since 2012.

    “The IceCube detection and the ASAS-SN detection combined with gamma-ray detections from NASA’s Fermi gamma-ray space telescope and the MAGIC telescopes that show TXS 0506+056 was undergoing the strongest gamma-ray flare in a decade, indicate that this could be the first identified source of high-energy neutrinos, and thus a cosmic-ray source,” said Anna Franckowiak, ASAS-SN and IceCube team member, Helmholtz Young Investigator, and staff scientist at DESY in Germany.

    MAGIC Cherenkov telescope array at the Roque de los Muchachos Observatory on the island of La Palma, in the Canaries, Spain, sited on a volcanic peak 2,267 metres (7,438 ft) above sea level

    Since they were first detected more than one hundred years ago, cosmic rays have posed an enduring mystery: What creates and launches these particles across such vast distances? Where do they come from?

    One of the best suspects have been quasars, supermassive black holes at the centers of galaxies that are actively consuming gas and dust.

    Quasar. ESO/M. Kornmesser

    Quasars are among the most energetic phenomena in the universe and can form relativistic jets where elementary particles are accelerate and launched at nearly the speed of light. If that jet happens to be pointed toward Earth, the light from the jet outshines all other emission from the host galaxy and the highly accelerated particles are launched toward the Milky Way. This specific type of quasar is called a blazar [above].

    However, because cosmic rays are charged particles, their paths cannot be traced directly back to their places of origin. Due to the powerful magnetic fields that fill space, they don’t travel along a straight path. Luckily, the powerful cosmic accelerators that produce them also emit neutrinos, which are uncharged and unaffected by even the most powerful magnetic fields. Because they rarely interact with matter and have almost no mass, these “ghost particles” travel nearly undisturbed from their cosmic accelerators, giving scientists an almost direct pointer to their source.

    “Crucially, the presence of neutrinos also differentiates between two types of gamma-ray sources: those that accelerate only cosmic-ray electrons, which do not produce neutrinos, and those that accelerate cosmic-ray protons, which do,” said John Beacom, an astrophysicist at the Ohio State University and an ASAS-SN member.

    Detecting the highest energy neutrinos requires a massive particle detector, and the National Science Foundation-supported IceCube observatory [above] is the world’s largest. The detector is composed of more than 5,000 light sensors arranged in a grid, buried in a cubic kilometer of deep, pristine ice a mile beneath the surface at the South Pole. When a neutrino interacts with an atomic nucleus, it creates a secondary charged particle, which, in turn, produces a characteristic cone of blue light that is detected by IceCube’s grid of photomultiplier tubes. Because the charged particle and the light it creates stay essentially true to the neutrino’s original direction, they give scientists a path to follow back to the source.

    About 20 observatories on Earth and in space have also participated in this discovery. This includes the 8.4-meter Subaru Telescope on Maunakea, which was used to observe the host galaxy of TXS 0506+056 in an attempt to measure its distance, and thus determine the intrinsic luminosity, or energy output, of the blazar.


    NAOJ/Subaru Telescope at Mauna Kea Hawaii, USA,4,207 m (13,802 ft) above sea level

    These observations are difficult, because the blazar jet is much brighter than the host galaxy. Disentangling the jet and the host requires the largest telescopes in the world, like those on Maunakea.

    “This discovery demonstrates how the many different telescopes and detectors around and above the world can come together to tell us something amazing about our Universe. This also emphasizes the critical role that telescopes in Hawaii play in that community,” said Shappee.

    See the full article here .


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    System Overview

    The University of Hawai‘i System includes 10 campuses and dozens of educational, training and research centers across the Hawaiian Islands. As the public system of higher education in Hawai‘i, UH offers opportunities as unique and diverse as our Island home.

    The 10 UH campuses and educational centers on six Hawaiian Islands provide unique opportunities for both learning and recreation.

    UH is the State’s leading engine for economic growth and diversification, stimulating the local economy with jobs, research and skilled workers.

     
  • richardmitnick 1:37 pm on July 13, 2018 Permalink | Reply
    Tags: , , , Biggest neutrino event ever from IceCube, Blazars, , IceCube-170922A, , ,   

    The Great Neutrino Catch: A Bunch of Articles 

    IceCube

    U Wisconsin ICECUBE neutrino detector at the South Pole

    IceCube employs more than 5000 detectors lowered on 86 strings into almost 100 holes in the Antarctic ice NSF B. Gudbjartsson, IceCube Collaboration

    Lunar Icecube

    IceCube DeepCore annotated

    IceCube PINGU annotated


    DM-Ice II at IceCube annotated

    ARTICLES

    From Nature Magazine Single subatomic particle illuminates mysterious origins of cosmic rays

    When a subatomic particle from space streaked through Antarctica last September, astrophysicists raced to find the source.

    13 July 2018
    Davide Castelvecchi

    A single subatomic particle detected at the South Pole last September is helping to solve a major cosmic mystery: what creates electrically charged cosmic rays, the most energetic particles in nature.

    Follow-up studies by more than a dozen observatories suggest that researchers have, for the first time, identified a distant galaxy as a source of high-energy neutrinos

    This discovery could, in turn, help scientists pin down the still mysterious source of protons and atomic nuclei that arrive to Earth from outer space, collectively called cosmic rays. The same mechanisms that produce cosmic rays should also make high-energy neutrinos.

    Multiple teams of researchers from around the world describe the neutrino’s source in at least seven papers released on 12 July.

    “Everything points to this as the ultra-bright, energetic source — a gorgeous source,” says Elisa Resconi, an astroparticle physicist at the Technical University of Munich in Germany.

    Astrophysicists have proposed a number of scenarios for astrophysical phenomena that could produce both high-energy neutrinos and their electrically charged counterparts: protons and atomic nuclei collectively called cosmic rays. But until now, they had not managed to unambiguously trace any of these particles back to their source. This is especially difficult with cosmic rays, whose electric charges make their paths curve on their way to Earth, whereas neutrinos travel in straight lines.

    The finding also underscores the promise of ‘multi-messenger’ astronomy, a nascent field that combines signals from different types of observatory to pin down details of celestial events.

    Muon alert

    The story began on 22 September 2017, when an electrically charged particle called a muon streaked through the Antarctic ice cap at close to the speed of light. IceCube — an array of more than 5,000 sensors buried in a cubic kilometre’s worth of ice — detected flashes of light that the muon produced in its wake. The particle appeared to emerge from below the detector — an orientation that indicated that it was the decay product of a neutrino that had come from below the horizon. Muons can only travel so far inside matter, whereas neutrinos often pass through the entire planet unimpeded; most of the ones that IceCube detects have crashed with a particle inside Earth to produce a muon (see ‘Neutrino observatory’).

    Within seconds, a computer cluster at the US National Science Foundation’s Amundsen–Scott South Pole Station, which sits atop Earth’s southernmost point, had reconstructed the precise path of the particle and recognized that the muon had come from a highly energetic neutrino; 43 seconds after the event, the station sent an automated alert to a network of astronomers via a satellite link. It tagged the neutrino as IceCube-170922A.

    After receiving the alert, Derek Fox, an astrophysicist at Pennsylvania State University in University Park, quickly secured observing time on the X-ray observatory Swift, which orbits Earth.

    NASA Neil Gehrels Swift Observatory

    Fox had created the automated alert system two years before, precisely in the hope that researchers could follow up on events such as this one.

    He and his team found nine sources of high-energy X-rays close to where the neutrino had come from. Among them was an object called TXS 0506+056. This was a blazar, a galaxy with a supermassive black hole at the centre and a known source of γ-rays. In a blazar, the black hole stirs gas up to temperatures of millions of degrees and shoots it out of its poles in two highly collimated jets, one of which points in the direction of the Solar System. Fox’s team announced its findings to the astronomical community the next day after.

    1

    Flare up

    In the following days, another team inspected data from the Large Area Telescope (LAT) aboard NASA’s Fermi Gamma-ray Space Telescope.

    NASA/Fermi LAT


    NASA/Fermi Gamma Ray Space Telescope

    LAT constantly sweeps the sky, and among other things monitors about 2,000 blazars. These objects go through periods of increased activity that can last weeks or months, during which they become unusually bright. “When we looked at the region that IceCube said the neutrino came from, we noticed that this blazar had been flaring more than ever before,” says Regina Caputo, an astrophysicist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, who is Fermi-LAT’s analysis coordinator.

    On 28 September, the Fermi-LAT team sent out an alert to reveal this finding. It was at that point that other astronomers got very excited. IceCube has detected about a dozen such high-energy neutrinos each year since it started operating in 2010, but none had been associated with a particular source in the sky. “That’s what made the hair stand at the back of the neck,” Fox says.

    Still, the association between the neutrino and the TXS blazar flare could have been a coincidence. To make the case stronger, researchers from both IceCube and Fermi-LAT calculated the odds that the flare and the neutrino were related, rather than coming from the same direction in the sky by chance.

    “We had to calculate the chance that random neutrinos in the sky come from one of the known gamma-ray sources, and the likelihood that it was flaring at that time,” says Anna Franckowiak, an astroparticle physicist at the German Electron Synchrotron (DESY) in Zeuthen who is a member of both IceCube and Fermi-LAT. She and her collaborators found that likelihood to be good, though not at the level of statistical significance required for claiming a discovery in physics.

    Evidence hunt

    Finding more neutrinos and gamma rays detected during a previous flare from the same blazar would boost the evidence for TXS 0506+056 being the source. In November, IceCube researchers found that the observatory had recorded an excess of neutrinos coming from the same direction in the sky between late 2014 and 2015.

    Resconi, who is a senior member of IceCube, got so excited by the discovery that she got lost while driving to a Nick Cave concert after work. “I ended up in the open countryside. My colleagues now tease me that next time we see a neutrino source, who knows where I will end up.”

    Soon though, the researchers realized that this apparent flare did not seem to show up in Fermi-LAT data. “That news came as a wet blanket,” Resconi says. But in a separate study, she and her collaborators found hints of a TXS flare during that period, but with gamma rays of energies that were mostly too high for Fermi-LAT to detect.

    A major missing piece of information was the blazar’s distance from Earth, says Simona Paiano of the Astronomical Observatory of Padua in Italy. To measure it, she and her team booked 15 hours of observing time on the world’s largest optical telescope, the 10.4-metre Gran Telescopio Canarias on La Palma, one of Spain’s Canary Islands.

    Gran Telescopio Canarias at the Roque de los Muchachos Observatory on the island of La Palma, in the Canaries, Spain, sited on a volcanic peak 2,267 metres (7,438 ft) above sea level

    They found it to be around 1.15 billion parsecs (3.78 billion light years) away.

    Together, the data pinpoint the likely source, says Kyle Cranmer, a particle physics and data-analysis expert at New York University, but “the observation isn’t unambiguous”, he says. “More follow-up is needed to conclusively establish blazars as a source of high-energy neutrinos.

    Researchers hope that this is only the first of many multi-messenger events of this kind.They are especially looking forward to detecting neutrinos together with gravitational waves. The celebrated collision of two neutron stars that was discovered using gravitational waves in August 2017 should have produced neutrinos as well, but IceCube did not detect any. But if the TXS blazar flares up again, it might be possible to detect more high-energy neutrinos and other kinds of radiation coming from it.

    From Astronomy Magazine

    July 12, 2018
    Michelle Hampson

    The rare detection of a high-energy neutrino hints at how these strange particles are created.

    Four billion years ago, an immense galaxy with a black hole at its heart spewed forth a jet of particles at nearly the speed of light. One of those particles, a neutrino that is just a fraction of the size of a regular atom, traversed across the universe on a collision course for Earth, finally striking the ice sheet of Antarctica last September. Coincidentally, a neutrino detector planted by scientists within the ice recorded the neutrino’s charged interaction with the ice, which resulted in a blue flash of light lasting just a moment. The results are published today in the journal Science.

    This detection marks the second time in history that scientists have pinpointed the origins of a neutrino from outside of our solar system. And it’s the first time they’ve confirmed that neutrinos are created in the supermassive black holes at the centers of galaxies — a somewhat unexpected source.

    Neutrinos are highly energetic particles that rarely ever interact with matter, passing through it as though it weren’t even there. Determining the type of cosmological events that create these particles is critical for understanding the nature of the universe. But the only confirmed source of neutrinos, other than our Sun, is a supernova that was recorded in 1987.

    Physicists have a number of theories about what sort of astronomical events may create neutrinos, with some suggesting that blazars could be a source. Blazars are massive galaxies with black holes at their center, trying to suck in too much matter at once, causing jets of particles to be ejected outward at incredible speeds. Acting like the giant counterparts to terrestrial particle accelerators, blazar jets are believed to produce cosmic rays that can in turn create neutrinos.

    “This [detection] in particular is a chance of nature,” says Darren Grant, a lead scientist of the team that first discovered the high-energy neutrino, as part of the neutrino detection project IceCube. “There’s a blazar there that just happened to turn on at the right time and we happened to capture it. It’s one of those eureka moments. You hope to experience those a few times in your career and this was one of them, where everything aligned.”

    4
    Blazars are active supermassive black holes sucking in immense amounts of material, which form swirling accretion disks and generate high-powered particle jets that churn out particles that astronomers have believed eventually result in neutrinos. DESY, Science Communication Lab

    A cosmic messenger

    On September 22, 2017, the neutrino reached the Antarctica ice sheet, passing by an ice crystal at just the right angle to cause a subatomic particle (called a muon) to be created from the interaction. The resulting blue flash was recorded by one of IceCube’s 5,160 detectors, embedded within the ice. Grant was in the office when the detection occurred. This neutrino was about 300 million times more energetic than those that are emitted by the Sun.

    Grant and his colleague briefly admired the excellent image depicting the trajectory of the muon, which provides basic information necessary to begin tracing back the neutrino’s origin. However, they weren’t overly excited quite yet. His team observes about 10 to 20 high-energy neutrinos each year, but the right combination of events — in space, time and energy, for example — is required to precisely pinpoint the source of the neutrino. Such an alignment had eluded scientists so far. As Grant’s team began their analysis, though, they began to narrow in on a region: an exceptionally bright blazar called TXS 0506+056.

    Upon the detection, an automatic alert was sent to other astronomy teams around the world, which monitor various incoming cosmic signals, such as radio and gamma rays. A few days later a team of scientists using the MAGIC telescope in the Canary Islands responded with some exciting news: the arrival of the neutrino had coincided with a burst of gamma rays – which are extremely energetic photons – also coming from the direction of TXS 0506+056.

    MAGIC Cherenkov telescope array at the Roque de los Muchachos Observatory on the island of La Palma, in the Canaries, Spain, sited on a volcanic peak 2,267 metres (7,438 ft) above sea level

    Other teams analyzing the region following the initial detection observed changes in X-ray emissions and radio signals too. Collectively, the data is a huge step forward for physicists in understanding blazars, and high-energy cosmological events in general.

    John Learned of University of Hawaii, Manoa, who was not involved in the study, says that the data linking the blazar as the source is “overwhelmingly convincing” and he emphasizes the importance of this finding. “This is the realization of many long-standing scientific dreams. Neutrinos at high energies can tell us about the guts of these extremely luminous objects … The implications of the finding are that we are now finally … [able] to see inside the most dense and luminous objects, and to further our grasp of the ‘deus ex machina’ which drives them and powers these awesome phenomena.”

    For example, this detection also provides the first evidence that a blazar can produce the high-energy protons needed to generate neutrinos such as the one IceCube saw. Sources of high-energy protons also remain largely a mystery, so the identification of one such source is another big step forward for astronomers. “It’s really quite convincing that we’ve unlocked one piece of that puzzle,” says Grant.

    Gems from the past

    And it gets even better. “We looked back at [archival] data [that had been collected since 2010], in the direction of this particular blazar source, and what we discovered was really quite remarkable,” Grant says. A barrage of high-energy neutrinos and gamma rays from TXS 0506+056 reached Earth in late 2014 and early 2015. At the time, IceCube’s real-time alert system was not fully functioning, so other scientific teams were not aware of the detection. But now these previous neutrinos are on scientists’ radar, providing a more long-term glimpse into the life of a blazar.

    “That was really icing on the cake, because what [the archived data indicated] was that the source had been active in neutrinos in the past, and then again, with this very high-energy neutrino in September — those are the pieces that really start to come together, to make a picture of what’s happening there,” explains Grant.

    6
    The alert IceCube sent once the neutrino’s interaction with the ice was detected resulted in follow-up observations from about 20 Earth- and space-based observatories. This immense effort resulted in the clear identification of a distant blazar as the source of the neutrino — as well as gamma rays, X-rays, radio emission, and optical light.
    Nicolle R. Fuller/NSF/IceCube

    Previous coverage https://sciencesprings.wordpress.com/2018/07/12/from-nrao-via-newswise-vla-gives-tantalizing-clues-about-source-of-energetic-cosmic-neutrino/

    The data also reveal that radio emissions from TXS 0506+056 gradually increased in the 18 months leading up to the September neutrino detection. Greg Sivakoff, an associate professor at the University of Alberta who helped analyze the data, says one possibility is that the black hole began to consume surrounding matter much faster during this time, causing the jet of particles being emitted to speed up. He says, “If the jet gets too fast too quickly, it might run into some of its own material, creating what astronomers call a shock. Shocks have long been used in astronomy to explain how particles are accelerated to high energies. We are not sure that this is the answer yet, but this may be part of the story.”

    Scientists are continuing to monitor TXS 0506+056, hoping to learn more about this colossal event. One team conducted a detailed analysis to determine how far away the blazar is from us, astounded to discover that it is a whopping four billion light years away. While TXS 0506+056 was always considered a bright object in the sky, this luminosity at such a distance makes it one of the brightest objects in the universe. No doubt future studies of this powerful blazar will yield valuable insights into the most energetic events to occur in our universe.

    Learned says, “We are just opening a new door and I would love to be able to say what we shall find beyond. But I guarantee that initiating this new means of observing the universe will bring surprises and new insights. In an extreme analogy it is like asking Galileo what his new astronomical telescope will reveal.”

    From UCSC: VERITAS supplies critical piece to neutrino discovery puzzle

    July 12, 2018
    Megan Watzke, CfA

    Potential connection between blazar and neutrino detection by IceCube observatory marks a new advance in multi-messenger astrophysics

    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)

    7
    One of the telescopes in the Very Energetic Radiation Imaging Telescope Array System (VERITAS), Located at Fred Lawrence Whipple Observatory, Mount Hopkins, Arizona, US in AZ, USA. VERITAS is operated and managed by the Smithsonian Astrophysical Observatory. (Photo by Wystan Benbow)

    The VERITAS array has confirmed the detection of gamma rays from the vicinity of a supermassive black hole. While these detections are relatively common for VERITAS, this black hole is potentially the first known astrophysical source of high-energy cosmic neutrinos, a type of ghostly subatomic particle.

    On September 22, 2017, the IceCube Neutrino Observatory, a cubic-kilometer neutrino telescope located at the South Pole, detected a high-energy neutrino of potential astrophysical origin. However, the observation of a single neutrino by itself is not enough for IceCube to claim the detection of a source. For that, scientists needed more information.

    Very quickly after the detection by IceCube was announced, telescopes around the world including VERITAS (which stands for the “Very Energetic Radiation Imaging Telescope Array System”) swung into action to identify the source. The VERITAS, MAGIC [above], and H.E.S.S. gamma-ray observatories all looked at the neutrino position.

    HESS Cherenkov 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)

    In addition, two gamma-ray observatories that monitor much of the sky at lower and higher energies also provided coverage.

    These follow-up observations of the rough IceCube neutrino position suggest that the source of the neutrino is a blazar, which is a supermassive black hole with powerful outflowing jets that can change dramatically in brightness over time. This blazar, known as TXS 0506+056, is located at the center of a galaxy about 4 billion light years from Earth.

    “We know that the blazar jet is accelerating particles to very high energies, but it is difficult to tell from gamma rays alone if it is accelerating just electrons or also protons and heavier nuclei,” said David Williams, adjunct professor of physics at UC Santa Cruz and the Santa Cruz Institute for Particle Physics (SCIPP) and a member of the VERITAS collaboration. “If the blazar is a neutrino source, that’s a smoking gun for protons, because high-energy protons colliding with gas produce pions, which decay into neutrinos,” he said.

    Initially, NASA’s Fermi Gamma-ray Space Telescope [above] observed that TXS 0506+056 was several times brighter than usually seen in its all-sky monitoring. Eventually, the MAGIC observatory made a detection of much higher-energy gamma rays within two weeks of the neutrino detection, while VERITAS, H.E.S.S., and HAWC did not see the blazar in any of their observations during the two weeks following the alert.

    Given the importance of higher-energy gamma-ray detections in identifying the possible source of the neutrino, VERITAS continued to observe TXS 0506+056 over the following months, through February 2018, and revealed the source but at a dimmer state than what was detected by MAGIC.

    “The VERITAS detection shows us that the gamma-ray brightness of the source changes, which is a signature of a blazar,” said Wystan Benbow of the Smithsonian Astrophysical Observatory (SAO), which operates and manages VERITAS. “Finding a link between an astrophysical source and a neutrino event could open yet another window of exploration to the extreme universe.”

    Cosmic rays

    The detection of gamma rays coincident with neutrinos is tantalizing, since both particles must be produced in the generation of cosmic rays. Since they were first detected over 100 years ago, cosmic rays—highly energetic particles that continuously rain down on Earth from space—have posed an enduring mystery. What creates and launches these particles across such vast distances? Where do they come from?

    “The potential connection between the neutrino event and TXS 0506+056 would shed new light on the acceleration mechanisms that take place at the core of these galaxies and provide clues on the century-old question of the origin of cosmic rays,” said coauthor and VERITAS spokesperson Reshmi Mukherjee of Barnard College, Columbia University in New York.

    “Astrophysics is entering an exciting new era of multi-messenger observations, in which celestial sources are being studied through the detection of the electromagnetic radiation they emit across the spectrum, from radio waves to high-energy gamma rays, in combination with non-electromagnetic means, such as gravitational waves and high-energy neutrinos,” said coauthor Marcos Santander of the University of Alabama in Tuscaloosa, who led the study.

    A paper describing the deep VERITAS observations of TXS 0506+056 (“VERITAS Observations of the BL Lac Object TXS 0506+056”) has been accepted for publication in The Astrophysical Journal Letters and appears online on July 12, 2018. A paper on the IceCube and initial gamma-ray observations, including VERITAS’s, appears in the latest issue of the journal Science.

    “This is a terrific step forward in multi-messenger astrophysics,” said Williams, who worked on the analysis of the VERITAS data and coordinated the VERITAS contributions to the Science paper.

    VERITAS is a ground-based facility located at the SAO’s Fred Lawrence Whipple Observatory in southern Arizona. It consists of an array of four 12-meter optical telescopes that can detect gamma rays via the extremely brief flashes of blue “Cherenkov” light created when gamma rays are absorbed in the Earth’s atmosphere. The VERITAS Collaboration consists of about 80 scientists from 20 institutions in the United States, Canada, Germany and Ireland.

    The Fermi-LAT Collaboration [above], which also played an important role in this research, includes researchers at the Santa Cruz Institute for Particle Physics at UC Santa Cruz.

    From ESA INTEGRAL joins multi-messenger campaign to study high-energy neutrino source

    12 July 2018
    Erik Kuulkers
    ESA INTEGRAL Project Scientist
    European Space Agency
    Tel: +31 6 30249526
    Email: Erik.Kuulkers@esa.int

    Carlo Ferrigno
    INTEGRAL Science Data Centre
    University of Geneva, Switzerland
    Email: Carlo.Ferrigno@unige.ch

    Volodymyr Savchenko
    INTEGRAL Science Data Centre
    University of Geneva, Switzerland
    Email: Volodymyr.Savchenko@unige.ch

    Francis Halzen
    IceCube Principal Investigator
    University of Wisconsin–Madison, USA
    Email: francis.halzen@icecube.wisc.edu

    Sílvia Bravo Gallart
    IceCube Press Office
    University of Wisconsin–Madison, USA
    Email: silvia.bravo@icecube.wisc.edu

    Markus Bauer
    ESA Science Communication Officer
    Tel: +31 71 565 6799
    Mob: +31 61 594 3 954
    Email: markus.bauer@esa.int

    An international team of scientists has found first evidence of a source of high-energy neutrinos: a flaring active galaxy, or blazar, 4 billion light years from Earth. Following a detection by the IceCube Neutrino Observatory on 22 September 2017, ESA’s INTEGRAL satellite joined a collaboration of observatories in space and on the ground that kept an eye on the neutrino source, heralding the thrilling future of multi-messenger astronomy.

    ESA/Integral

    Neutrinos are nearly massless, ‘ghostly’ particles that travel essentially unhindered through space at close to the speed of light [1]. Despite being some of the most abundant particles in the Universe – 100 000 billion pass through our bodies every second – these electrically neutral, subatomic particles are notoriously difficult to detect because they interact with matter incredibly rarely.

    While primordial neutrinos were created during the Big Bang, more of these elusive particles are routinely produced in nuclear reactions across the cosmos. The majority of neutrinos arriving at Earth derive from the Sun, but those that reach us with the highest energies are thought to stem from the same sources as cosmic rays – highly energetic particles originating from exotic sources outside the Solar System.

    Unlike neutrinos, cosmic rays are charged particles and so their path is bent by magnetic fields, even weak ones. The neutral charge of neutrinos instead means they are unaffected by magnetic fields, and because they pass almost entirely through matter they can be used to trace a straight path all the way back to their source.

    Acting as ‘messengers’, neutrinos directly carry astronomical information from the far reaches of the Universe. Over the past decades, several instruments have been built on Earth and in space to decode their messages, though detecting these particles is no easy feat. In particular, the source of high-energy neutrinos has, until now, remained unproven.

    On 22 September 2017, one of these high-energy neutrinos arrived at the IceCube Neutrino Observatory at the South Pole [2]. The event was named IceCube-170922A.

    The IceCube observatory, which encompasses a cubic kilometre of deep, pristine ice, detects neutrinos through their secondary particles, muons. These muons are produced on the rare occasion that a neutrino interacts with matter in the vicinity of the detector, and they create tracks, kilometres in length, as they pass through layers of Antarctic ice. Their long paths mean their position can be well defined, and the source of the parent neutrino can be pinned down in the sky.

    During the 22 September event, a traversing muon deposited 22 TeV of energy in the IceCube detector. From this, scientists estimated the energy of the parent neutrino to be around 290 TeV, indicating a 50 percent chance that it had an astrophysical origin beyond the Solar System.

    When the origin of a neutrino cannot be robustly identified by IceCube, like in this case, multi-wavelength observations are required to investigate its source. So, following the detection, IceCube scientists circulated the coordinates in the sky of the neutrino’s origin, inferred from their observations, to a worldwide network of ground and space-based observatories working across the full electromagnetic spectrum.

    These included NASA’s Fermi gamma-ray space telescope [above] and the Major Atmospheric Gamma-Ray Imaging Cherenkov (MAGIC) [above] on La Palma, in the Canary Islands, which looked to this portion of the sky and found the known blazar, TXS 0506+056, in a ‘flaring’ state – a period of intense high-energy emission – at the same time the neutrino was detected at the South Pole.

    Blazars are the central cores of giant galaxies that host an actively accreting supermassive black-hole at their heart, where matter spiralling in forms a hot, rotating disc that generates enormous amounts of energy, along with a pair of relativistic jets.

    These jets are colossal columns that funnel radiation, photons and particles – including neutrinos and cosmic rays – tens of light years away from the central black hole at speeds very close to the speed of light. A specific feature of blazars is that one of these jets happens to point towards Earth, making its emission appear exceptionally bright.

    Scientists around the world began observing this blazar – the likely source of the neutrino detected by IceCube – in a variety of wavelengths, from radio waves to high-energy gamma rays. ESA’s INTEGRAL gamma-ray observatory was part of this international collaboration [3].

    “This is a very important milestone to understanding how high-energy neutrinos are produced,” says Carlo Ferrigno from the INTEGRAL Science Data Centre at the University of Geneva, Switzerland.

    “There have been previous claims that blazar flares were associated with the production of neutrinos, but this, the first confirmation, is absolutely fundamental. This is an exciting period for astrophysics,” he adds.

    INTEGRAL, which surveys the sky in hard X-rays and soft gamma rays, is also sensitive to transient high-energy sources across the whole sky. At the time the neutrino was detected, it did not record any burst of gamma rays from the location of the blazar, so scientists were able to rule out prompt emissions from certain sources, such as a gamma-ray burst.

    After the neutrino alert from IceCube, INTEGRAL pointed to this area of the sky on various occasions between 30 September and 24 October 2017 with its wide-field instruments, and it did not observe the blazar to be in a flaring state in the hard X-ray or soft gamma-ray range.

    The fact that INTEGRAL could not detect the source in the follow-up observations provided significant information about this blazar, allowing scientists to place a useful upper limit on its energy output during this period.

    “INTEGRAL was important in constraining the properties of this blazar, but also in allowing scientists to exclude other neutrino sources such as gamma-ray bursts,” explains Volodymyr Savchenko from the INTEGRAL Science Data Centre, who led the analysis of the INTEGRAL data.

    With facilities spread across the globe and in space, scientists now have the capability to detect a plethora of ‘cosmic messengers’ travelling vast distances at extremely high speeds, in the form of light, neutrinos, cosmic rays, and even gravitational waves.

    “The ability to globally marshal telescopes to make a discovery using a variety of wavelengths in cooperation with a neutrino detector like IceCube marks a milestone in what scientists call multi-messenger astronomy,” says Francis Halzen from the University of Wisconsin–Madison, USA, lead scientist for the IceCube Neutrino Observatory.

    By combining the information gathered by each of these sophisticated instruments to investigate a wide range of cosmic processes, the era of multi-messenger astronomy has truly entered the phase of scientific exploitation.

    ESA’s high-energy space telescopes are fully integrated into this network of large multi-messenger collaborations, as demonstrated during the recent detection of gravitational waves with a corresponding gamma-ray burst – the latter detected by INTEGRAL – released by the collision of two neutron stars, and in the subsequent follow-up campaign, with contributions by INTEGRAL as well as the XMM-Newton X-ray observatory.

    ESA/XMM Newton

    Pooling resources from these and other observatories is key for the future of astrophysics, fostering our ability to decode the messages that reach us from across the Universe.

    “INTEGRAL is the only observatory available in the hard X-ray and soft gamma-ray domain that has the ability to perform dedicated imaging and spectroscopy, as well as having an instantaneous all-sky view at any time,” notes Erik Kuulkers, INTEGRAL project scientist at ESA.

    “After more than 15 years of operations, INTEGRAL is still at the forefront of high-energy astrophysics.”
    Notes

    [1] Described by Frederick Reines, one of the scientists who made the first neutrino detection, as “… the most tiny quantity of reality ever imagined by a human being,” one neutrino is estimated to contain one millionth of the mass of an electron.

    [2] The IceCube Collaboration is funded primarily by the National Science Foundation and is operated by a team headquartered at the University of Wisconsin–Madison, USA. The research efforts, including critical contributions to the detector operation, are supported by funding agencies in Australia, Belgium, Canada, Denmark, Germany, Japan, New Zealand, Republic of Korea, Sweden, Switzerland, the United Kingdom, and the USA.

    [3] These results are detailed in the paper Multimessenger observations of a flaring blazar coincident with high-energy neutrino IceCube-170922A by The IceCube, Fermi-LAT, MAGIC, AGILE, ASAS-SN, HAWC, H.E.S.S, INTEGRAL, Kanata, Kiso, Kapteyn, Liverpool telescope, Subaru, Swift/NuSTAR, VERITAS, and VLA/17B-403 teams, published in Science. DOI:10.1126/science.aat1378

     
  • richardmitnick 3:07 pm on July 12, 2018 Permalink | Reply
    Tags: Blazar, Blazars, , , , , , ,   

    From NRAO via newswise: “VLA Gives Tantalizing Clues About Source of Energetic Cosmic Neutrino” 

    NRAO Icon
    From National Radio Astronomy Observatory

    NRAO Banner

    via

    2

    newswise

    1
    Supermassive black hole at core of galaxy accelerates particles in jets moving outward at nearly the speed of light. In a Blazar, one of these jets is pointed nearly straight at Earth. Credit: Sophia Dagnello, NRAO/AUI/NSF

    A single, ghostly subatomic particle that traveled some 4 billion light-years before reaching Earth has helped astronomers pinpoint a likely source of high-energy cosmic rays for the first time. Subsequent observations with the National Science Foundation’s (NSF) Karl G. Jansky Very Large Array (VLA) [depicted below] have given the scientists some tantalizing clues about how such energetic cosmic rays may be formed at the cores of distant galaxies.

    On September 22, 2017, an observatory called IceCube, made up of sensors distributed through a square kilometer of ice under the South Pole, recorded the effects of a high-energy neutrino coming from far beyond our Milky Way Galaxy.

    U Wisconsin ICECUBE neutrino detector at the South Pole

    Lunar Icecube

    IceCube DeepCore annotated

    IceCube PINGU annotated


    DM-Ice II at IceCube annotated

    Neutrinos are subatomic particles with no electrical charge and very little mass. Since they interact only very rarely with ordinary matter, neutrinos can travel unimpeded for great distances through space.

    Follow-up observations with orbiting and ground-based telescopes from around the world soon showed that the neutrino likely was coming from the location of a known cosmic object — a blazar called TXS 0506+056, about 4 billion light-years from Earth.

    3

    Like most galaxies, blazars contain supermassive black holes at their cores. The powerful gravity of the black hole draws in material that forms a hot rotating disk. Jets of particles traveling at nearly the speed of light are ejected perpendicular to the disk. Blazars are a special class of galaxies, because in a blazar, one of the jets is pointed almost directly at Earth.

    Theorists had suggested that these powerful jets could greatly accelerate protons, electrons, or atomic nuclei, turning them into the most energetic particles known in the Universe, called ultra-high energy cosmic rays. The cosmic rays then could interact with material near the jet and produce high-energy photons and neutrinos, such as the neutrino detected by IceCube.

    Cosmic rays were discovered in 1912 by physicist Victor Hess, who carried instruments in a balloon flight. Subsequent research showed that cosmic rays are either protons, electrons, or atomic nuclei that have been accelerated to speeds approaching that of light, giving some of them energies much greater than those of even the most energetic electromagnetic waves. In addition to the active cores of galaxies, supernova explosions are probable sites where cosmic rays are formed. The galactic black-hole engines, however, have been the prime candidate for the source of the highest-energy cosmic rays, and thus of the high-energy neutrinos resulting from their interactions with other matter.

    “Tracking that high-energy neutrino detected by IceCube back to TXS 0506+056 makes this the first time we’ve been able to identify a specific object as the probable source of such a high-energy neutrino,” said Gregory Sivakoff, of the University of Alberta in Canada.

    Following the IceCube detection, astronomers looked at TXS 0506+056 with numerous telescopes and found that it had brightened at wavelengths including gamma rays, X-rays, and visible light. The blazar was observed with the VLA six times between October 5 and November 21, 2017.

    “The VLA data show that the radio emission from this blazar was varying greatly at the time of the neutrino detection and for two months afterward. The radio frequency with the brightest radio emission also was changing,” Sivakoff said.

    TXS 0506+056 has been monitored over a number of years with the NSF’s Very Long Baseline Array (VLBA), a continent-wide radio telescope system that produces extremely detailed images. The high-resolution VLBA images have shown bright knots of radio emission that travel outward within the jets at speeds nearly that of light. The knots presumably are caused by denser material ejected sporadically through the jet.

    “The behavior we saw with the VLA is consistent with the emission of at least one of these knots. It’s an intriguing possibility that such knots may be associated with generating high-energy cosmic rays and thus the kind of high-energy neutrino that IceCube found,” Sivakoff said.

    The scientists continue to study TXS 0506+056. “There are a lot of exciting phenomena going on in this object,” Sivakoff concluded.

    “The era of multi-messenger astrophysics is here,” said NSF Director France Córdova. “Each messenger — from electromagnetic radiation, gravitational waves and now neutrinos — gives us a more complete understanding of the Universe, and important new insights into the most powerful objects and events in the sky. Such breakthroughs are only possible through a long-term commitment to fundamental research and investment in superb research facilities.”

    Sivakoff and numerous colleagues from institutions around the world are reporting their findings in the journal Science.

    See the full article here .


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    NRAO/Karl V Jansky VLA, on the Plains of San Agustin fifty miles west of Socorro, NM, USA

    The NRAO operates a complementary, state-of-the-art suite of radio telescope facilities for use by the scientific community, regardless of institutional or national affiliation: the Very Large Array (VLA), and the Very Long Baseline Array (VLBA)*.

    ESO/NRAO/NAOJ ALMA Array in Chile in the Atacama at Chajnantor plateau, at 5,000 metres

    Access to ALMA observing time by the North American astronomical community will be through the North American ALMA Science Center (NAASC).

    NRAO VLBA

    NRAO VLBA

    *The Very Long Baseline Array (VLBA) comprises ten radio telescopes spanning 5,351 miles. It’s the world’s largest, sharpest, dedicated telescope array. With an eye this sharp, you could be in Los Angeles and clearly read a street sign in New York City!

    Astronomers use the continent-sized VLBA to zoom in on objects that shine brightly in radio waves, long-wavelength light that’s well below infrared on the spectrum. They observe blazars, quasars, black holes, and stars in every stage of the stellar life cycle. They plot pulsars, exoplanets, and masers, and track asteroids and planets.

    And the future Expanded Very Large Array (EVLA).

     
  • richardmitnick 11:53 am on July 12, 2018 Permalink | Reply
    Tags: A cosmic particle spewed from a distant galaxy strikes Earth, , , , Blazars, , , , , , ,   

    From Astronomy Magazine: “A cosmic particle spewed from a distant galaxy strikes Earth” 

    Astronomy magazine

    From Astronomy Magazine

    July 12, 2018
    Michelle Hampson

    The rare detection of a high-energy neutrino hints at how these strange particles are created.

    U Wisconsin ICECUBE neutrino detector at the South Pole



    IceCube Gen-2 DeepCore PINGU annotated

    Four billion years ago, an immense galaxy with a black hole at its heart spewed forth a jet of particles at nearly the speed of light. One of those particles, a neutrino that is just a fraction of the size of a regular atom, traversed across the universe on a collision course for Earth, finally striking the ice sheet of Antarctica last September. Coincidentally, a neutrino detector planted by scientists within the ice recorded the neutrino’s charged interaction with the ice, which resulted in a blue flash of light lasting just a moment. The results are published today in the journal Science.

    This detection marks the second time in history that scientists have pinpointed the origins of a neutrino from outside of our solar system. And it’s the first time they’ve confirmed that neutrinos are created in the supermassive black holes at the centers of galaxies — a somewhat unexpected source.

    Neutrinos are highly energetic particles that rarely ever interact with matter, passing through it as though it weren’t even there. Determining the type of cosmological events that create these particles is critical for understanding the nature of the universe. But the only confirmed source of neutrinos, other than our Sun, is a supernova that was recorded in 1987.

    2
    The most recent Hubble image of SN 1987A, taken in January 2017, captures the glow of hydrogen gas around the supernova remnant.
    NASA, ESA, and R. Kirshner (Harvard-Smithsonian Center for Astrophysics and Gordon and Betty Moore Foundation) and P. Challis (Harvard-Smithsonian Center for Astrophysics)

    Physicists have a number of theories about what sort of astronomical events may create neutrinos, with some suggesting that blazars could be a source. Blazars are massive galaxies with black holes at their center, trying to suck in too much matter at once, causing jets of particles to be ejected outward at incredible speeds. Acting like the giant counterparts to terrestrial particle accelerators, blazar jets are believed to produce cosmic rays that can in turn create neutrinos.

    “This [detection] in particular is a chance of nature,” says Darren Grant, a lead scientist of the team that first discovered the high-energy neutrino, as part of the neutrino detection project IceCube. “There’s a blazar there that just happened to turn on at the right time and we happened to capture it. It’s one of those eureka moments. You hope to experience those a few times in your career and this was one of them, where everything aligned.”

    A cosmic messenger

    On September 22, 2017, the neutrino reached the Antarctica ice sheet, passing by an ice crystal at just the right angle to cause a subatomic particle (called a muon) to be created from the interaction. The resulting blue flash was recorded by one of IceCube’s 5,160 detectors, embedded within the ice. Grant was in the office when the detection occurred. This neutrino was about 300 million times more energetic than those that are emitted by the Sun.

    Grant and his colleague briefly admired the excellent image depicting the trajectory of the muon, which provides basic information necessary to begin tracing back the neutrino’s origin. However, they weren’t overly excited quite yet. His team observes about 10 to 20 high-energy neutrinos each year, but the right combination of events — in space, time and energy, for example — is required to precisely pinpoint the source of the neutrino. Such an alignment had eluded scientists so far. As Grant’s team began their analysis, though, they began to narrow in on a region: an exceptionally bright blazar called TXS 0506+056.

    3
    IceCube employs more than 5,000 detectors lowered on 86 strings into almost 100 holes in the Antarctic ice.
    NSF / B. Gudbjartsson, IceCube Collaboration

    Upon the detection, an automatic alert was sent to other astronomy teams around the world, which monitor various incoming cosmic signals, such as radio and gamma rays. A few days later a team of scientists using the MAGIC telescope in the Canary Islands responded with some exciting news: the arrival of the neutrino had coincided with a burst of gamma rays – which are extremely energetic photons – also coming from the direction of TXS 0506+056.

    MAGIC Cherenkov gamma ray telescope on the Canary island of La Palma, Spain, Altitude 2,200 m (7,200 ft)

    Other teams analyzing the region following the initial detection observed changes in X-ray emissions and radio signals too. Collectively, the data is a huge step forward for physicists in understanding blazars, and high-energy cosmological events in general.

    John Learned of University of Hawaii, Manoa, who was not involved in the study, says that the data linking the blazar as the source is “overwhelmingly convincing” and he emphasizes the importance of this finding. “This is the realization of many long-standing scientific dreams. Neutrinos at high energies can tell us about the guts of these extremely luminous objects … The implications of the finding are that we are now finally … [able] to see inside the most dense and luminous objects, and to further our grasp of the ‘deus ex machina’ which drives them and powers these awesome phenomena.”

    For example, this detection also provides the first evidence that a blazar can produce the high-energy protons needed to generate neutrinos such as the one IceCube saw.

    4
    Blazars are active supermassive black holes sucking in immense amounts of material, which form swirling accretion disks and generate high-powered particle jets that churn out particles that astronomers have believed eventually result in neutrinos. DESY, Science Communication Lab

    Sources of high-energy protons also remain largely a mystery, so the identification of one such source is another big step forward for astronomers. “It’s really quite convincing that we’ve unlocked one piece of that puzzle,” says Grant.

    Gems from the past

    And it gets even better. “We looked back at [archival] data [that had been collected since 2010], in the direction of this particular blazar source, and what we discovered was really quite remarkable,” Grant says. A barrage of high-energy neutrinos and gamma rays from TXS 0506+056 reached Earth in late 2014 and early 2015. At the time, IceCube’s real-time alert system was not fully functioning, so other scientific teams were not aware of the detection. But now these previous neutrinos are on scientists’ radar, providing a more long-term glimpse into the life of a blazar.

    “That was really icing on the cake, because what [the archived data indicated] was that the source had been active in neutrinos in the past, and then again, with this very high-energy neutrino in September — those are the pieces that really start to come together, to make a picture of what’s happening there,” explains Grant.

    6
    The alert IceCube sent once the neutrino’s interaction with the ice was detected resulted in follow-up observations from about 20 Earth- and space-based observatories. This immense effort resulted in the clear identification of a distant blazar as the source of the neutrino — as well as gamma rays, X-rays, radio emission, and optical light.
    Nicolle R. Fuller/NSF/IceCube

    The data also reveal that radio emissions from TXS 0506+056 gradually increased in the 18 months leading up to the September neutrino detection. Greg Sivakoff, an associate professor at the University of Alberta who helped analyze the data, says one possibility is that the black hole began to consume surrounding matter much faster during this time, causing the jet of particles being emitted to speed up. He says, “If the jet gets too fast too quickly, it might run into some of its own material, creating what astronomers call a shock. Shocks have long been used in astronomy to explain how particles are accelerated to high energies. We are not sure that this is the answer yet, but this may be part of the story.”

    Scientists are continuing to monitor TXS 0506+056, hoping to learn more about this colossal event. One team conducted a detailed analysis to determine how far away the blazar is from us, astounded to discover that it is a whopping four billion light years away. While TXS 0506+056 was always considered a bright object in the sky, this luminosity at such a distance makes it one of the brightest objects in the universe. No doubt future studies of this powerful blazar will yield valuable insights into the most energetic events to occur in our universe.

    Learned says, “We are just opening a new door and I would love to be able to say what we shall find beyond. But I guarantee that initiating this new means of observing the universe will bring surprises and new insights. In an extreme analogy it is like asking Galileo what his new astronomical telescope will reveal.”

    See the full article here .
    See also From CfA: VERITAS Supplies Critical Piece to Neutrino Discovery Puzzle


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  • richardmitnick 12:33 pm on August 24, 2016 Permalink | Reply
    Tags: Blazars, , Gamma-ray objects, , NASA's WISE and Fermi Missions Reveal a Surprising Blazar Connection   

    From JPL-Caltech: “NASA’s WISE, Fermi Missions Reveal a Surprising Blazar Connection” 

    NASA JPL Banner

    JPL-Caltech

    August 24, 2016
    Elizabeth Landau
    Jet Propulsion Laboratory, Pasadena, Calif.
    818-354-6425
    elizabeth.landau@jpl.nasa.gov

    Written by Francis Reddy
    NASA’s Goddard Space Flight Center, Greenbelt, Maryland

    1
    Credit: M. Weiss/CfA
    2
    Credit: NASA’s Goddard Space Flight Center/Francesco Massaro, Univ. of Turin

    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.

    An analysis of blazar properties observed by the Wide-field Infrared Survey Explorer (WISE) and Fermi’s Large Area Telescope (LAT) reveal a correlation in emissions from the mid-infrared to gamma rays (see Figure 1). The relationship allows astronomers to identify potential new gamma-ray blazars by studying WISE infrared data.

    NASA/WISE Telescope
    NASA/WISE Telescope

    NASA/Fermi LAT
    NASA/Fermi LAT

    More information is online at http://www.nasa.gov/wise and http://wise.astro.ucla.edu and http://www.jpl.nasa.gov/wise.

    Astronomers studying distant galaxies powered by monster black holes have uncovered an unexpected link between two very different wavelengths of the light they emit, the mid-infrared and gamma rays. The discovery, which was accomplished by comparing data from NASA’s Wide-field Infrared Survey Explorer (WISE) and Fermi Gamma-ray Space Telescope, has enabled the researchers to uncover dozens of new blazar candidates.

    Francesco Massaro at the University of Turin in Italy and Raffaele D’Abrusco at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, show for the first time that the mid-infrared colors of blazars in WISE data correlate to an equivalent measurement of their gamma-ray output.

    “This connection links two vastly different forms of light over an energy range spanning a factor of 10 billion,” said Massaro. “Ultimately, it will help us decipher how supermassive black holes in these galaxies manage to convert the matter around them into vast amounts of energy.”

    Blazars constitute more than half of the discrete gamma-ray sources seen by Fermi’s Large Area Telescope (LAT). At the heart of a blazar lies a supersized black hole with millions of times the sun’s mass surrounded by a disk of hot gas and dust. As material in the disk falls toward the black hole, some of it forms dual jets that blast subatomic particles straight out of the disk in opposite directions at nearly the speed of light. A blazar appears bright to Fermi for two reasons. Its jets produce many gamma rays, the highest-energy form of light, and we happen to be viewing the galaxy face on, which means one of its jets is pointing in our direction.

    From January to August 2010, NASA’s WISE mapped the entire sky in four infrared wavelengths, cataloging more than half a billion sources. In 2011, Massaro, D’Abrusco and their colleagues began using WISE data to investigate Fermi blazars.

    “WISE made it possible to explore the mid-infrared colors of known gamma-ray blazars,” said D’Abrusco. “We found that when we plotted Fermi blazars by their WISE colors in a particular way, they occupied a distinctly different part of the plot than other extragalactic gamma-ray sources.”

    The scientists detail new aspects of the infrared/gamma-ray connection in a paper published in The Astrophysical Journal on Aug. 9. They say the electrons, protons and other particles accelerated in blazar jets leave a specific “fingerprint” in the infrared light they emit. This same pattern is also clearly evident in their gamma rays. The relationship effectively connects the dots for blazars across an enormous swath of the electromagnetic spectrum.

    About 1,000 Fermi sources remain unassociated with known objects at any other wavelength. Astronomers suspect many of these are blazars, but there isn’t enough information to classify them. The infrared/gamma-ray connection led the authors to search for new blazar candidates among WISE infrared sources located within the positional uncertainties of Fermi’s unidentified gamma-ray objects. When the researchers applied this relationship to Fermi’s unknown sources, they quickly found 130 potential blazars. Efforts are now underway to confirm the nature of these objects through follow-up studies and to search for additional candidates using the WISE connection.

    “About a third of the gamma-ray objects seen by Fermi remained unknown in the most recent catalog, and this result represents an important advance in understanding their natures,” said David Thompson, a Fermi deputy project scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.

    NASA’s Jet Propulsion Laboratory in Pasadena, California, manages and operates WISE for NASA’s Science Mission Directorate in Washington. The spacecraft was put into hibernation mode in 2011 after twice scanning the entire sky, thereby completing its main objectives. In September 2013, WISE was reactivated, renamed NEOWISE and assigned a new mission to assist NASA’s efforts to identify potentially hazardous near-Earth objects.

    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 on Fermi, visit:

    http://www.nasa.gov/fermi

    For more information on WISE, visit:

    http://www.nasa.gov/wise

    See the full article here .

    Please help promote STEM in your local schools.

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    NASA JPL Campus

    Jet Propulsion Laboratory (JPL) is a federally funded research and development center and NASA field center located in the San Gabriel Valley area of Los Angeles County, California, United States. Although the facility has a Pasadena postal address, it is actually headquartered in the city of La Cañada Flintridge [1], on the northwest border of Pasadena. JPL is managed by the nearby California Institute of Technology (Caltech) for the National Aeronautics and Space Administration. The Laboratory’s primary function is the construction and operation of robotic planetary spacecraft, though it also conducts Earth-orbit and astronomy missions. It is also responsible for operating NASA’s Deep Space Network.

    Caltech Logo

    jpl

    NASA image

     
  • richardmitnick 2:57 pm on May 1, 2016 Permalink | Reply
    Tags: , , Blazars, , ,   

    From Science Alert: “Astronomers might have finally detected where mysterious, extragalactic neutrinos are coming from” 

    ScienceAlert

    Science Alert

    29 APR 2016
    FIONA MACDONALD

    3
    NASA/DOE/LAT Collaboration

    Just over three years ago, physicists working in Antarctica announced they’d detected the first evidence of mysterious subatomic particles, known as neutrinos, coming from outside our galaxy. It was a huge moment for astrophysics, but since then, no one’s quite been able to figure out where those particles are coming from, and what’s sending them hurtling our way.

    Until now, that is – a team of astronomers has just identified the possible source of one these extragalactic visitors, and it appears that it started its journey to us nearly 10 billion years ago, when a massive explosion erupted in a galaxy far, far away (seriously, George Lucas couldn’t make this stuff up).

    Let’s step back for a second here though and explain why this is a big deal. Neutrinos are arguably the weirdest of the fundamental subatomic particles. They don’t have any mass, they’re incredibly fast, and they’re pretty much invisible, because they hardly ever interact with matter. Like tiny ghosts, billions of neutrinos per second are constantly flowing through us, and we never even know about it.

    In order to detect them, researchers have step up extravagant labs, like the IceCube Neutrino Observatory at the South Pole, where they wait patiently to capture glimpses of neutrinos streaking through the planet, and measure how energetic they are, to try to work out where they came from.

    U Wisconsin ICECUBE neutrino detector
    IceCube neutrino detector interior
    U Wisconsin ICECUBE neutrino detector

    Usually that source is radioactive decay here on Earth or inside the Sun, or maybe from the black hole at the centre of our galaxy. But in 2013, the IceCube researchers announced they’d detected a couple of neutrinos so unimaginably energetic, they knew they must have come from outside our galaxy.

    These neutrinos were named ‘Bert’ and ‘Ernie’ (seriously) and they were the first evidence of extragalactic neutrinos. Their discovery was followed by the detection of a couple of dozen more, slightly less energetic, extragalactic neutrinos over the coming months.

    Then at the end of 2012, they spotted ‘Big Bird’. At the time it was the most energetic neutrino ever detected, with energy exceeding 2 quadrillion electron volts – that’s more than a million million times greater than the energy of a dental X-ray. Not bad for a massless ghost particle.

    Since then, teams across the world have been working to figure out where the hell this anomaly had come from. And now we might finally have a suspect.

    “It’s like a crime scene investigation,” said lead researcher Matthias Kadler from the University of Würzburg in Germany, “The case involves an explosion, a suspect, and various pieces of circumstantial evidence.”

    Using that circumstantial evidence, the best astronomers could do at the time was narrow the source down to a patch of the southern sky about 32 degrees across – roughly the size of 64 full moons.

    That sounds pretty specific, but an area that size in the night sky covers a whole lot of galaxies, and researchers had the tough job of sifting through all that data to figure out what happened in one of those galaxies to send Big Bird to us.

    They now think they have their answer – a huge explosion known as a blazar, which occurred in a galaxy called PKS B1424-418 around 10 billion years ago, but was only detected by our telescopes between 2011 and 2013 because of how far away it is.

    Blazar NASA Fermi Gamma ray Space Telescope Credits M. Weiss CfA
    Blazar. NASA Fermi Gamma ray Space Telescope. Credits M. Weiss/CfA

    A blazar is one of the most energetic events in the known Universe, and it occurs when a galaxy’s material falls towards the supermassive black hole at its centre, and some of that material ends up being blasted in huge jets directly towards Earth.

    Publishing* in Nature Physics, the team has now calculated that there’s only a 5 percent chance that Big Bird and the blazar at PKS B1424-418 coincidentally hit Earth at the same time, but weren’t linked.

    “Taking into account all of the observations, the blazar seems to have had means, motive and opportunity to fire off the Big Bird neutrino, which makes it our prime suspect,” said Kadler.

    The fact that these two individually fascinating events are associated is pretty exciting in itself.

    “There was a moment of wonder and awe when we realised that the most dramatic outburst we had ever seen in a blazar happened in just the right place at just the right time,” said co-author Felicia Krauß, from the University of Erlangen-Nürnberg.

    This hypothesis now needs to be independently verified before we can say for sure where Big Bird, and potentially other extragalactic neutrinos, come from. But it’s pretty exciting that we might finally, finally be getting close to understanding more about these enigmatic subatomic particles.

    Francis Halzen, who’s the principal investigator of IceCube, and wasn’t involved in this study, thinks the research heralds in an exciting new time in neutrino research.

    “IceCube is about to send out real-time alerts when it records a neutrino that can be localised to an area a little more than half a degree across, or slightly larger than the apparent size of a full moon,” he explains. “We’re slowly opening a neutrino window onto the cosmos.” Bring it on.

    *Science paper:
    Coincidence of a high-fluence blazar outburst with a PeV-energy neutrino event

    See the full article here .

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

    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 .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

     
  • richardmitnick 1:43 pm on November 24, 2015 Permalink | Reply
    Tags: , , Blazars,   

    From Sky and Telescope: “Mystery Signal from a Black Hole-Powered Jet” 

    SKY&Telescope bloc

    Sky & Telescope

    November 23, 2015
    Monica Young

    1
    This artist’s concept shows a supermassive black hole shooting out a jet of plasma headed almost straight for Earth. In the telescope, though, this object would appear as a (usually) randomly flickering point of light. NASA / JPL-Caltech

    Observing a blazar is a little like standing beneath a relativistic waterfall. Look up: that flickering point of light is a head-on view of the powerful plasma jet shooting out from a supermassive black hole.

    The free-flying electrons within that mess of plasma twirl at almost light speed around magnetic fields, and they radiate across the electromagnetic spectrum, often drowning out any other forms of emission. We might even see a sudden outburst when turbulence, a sudden influx of plasma, or some other force roils the jet.

    But when Markus Ackermann (DESY, Germany) and colleagues pored through almost seven years of data collected with the Fermi Gamma-Ray Space Telescope, they saw something completely unexpected: a regular signal coming from a blazar. Gamma rays from PG 1553+113 seem to brighten roughly every 2.2 years, with three complete cycles captured so far.

    NASA Fermi Telescope
    NASA/Fermi

    Moreover, other wavelengths seem to echo this cycle. Inspired by the gamma-ray find, Ackermann’s team sought out radio and optical measurements from blazar-monitoring campaigns — and both wavelengths show hints of the same periodic signal. The team also looked at X-ray data collected over the years by the Swift and Rossi X-ray Timing Explorer spacecraft, but there weren’t enough data points for a proper analysis.

    NASA SWIFT Telescope
    NASA/Swift

    NASA ROSSI
    NASA/ROSSI

    The results are published in the November 10th Astrophysical Journal Letters. (Click here for full text).

    2
    This light curve shows how the brightness of blazar PG 1553+113 varies for gamma rays with more than 100 million electron volts of energy. The plot, which includes data from August 4, 2008, to July 19, 2015, displays three complete cycles of an apparently regular, 2-year cycle. M. Ackermann & others / Astrophysics Journal Letters

    If this signal is real, it has to come from the black hole-powered jet, and the authors explore a number of explanations.

    For example, the jet might be precessing or rotating, sweeping its beam past Earth every 2 years or so. Or perhaps a strong magnetic field chokes the flow of gas toward the black hole, creating instabilities that then regularly flood the jet with material. The most intriguing prospect is another supermassive black hole in the system, its presence affecting gas flow and jet alignment.

    At this point, though, the authors admit they don’t have enough data to distinguish between these possibilities. Further monitoring might remedy that.
    Keep Watching

    “I am always skeptical about claims of periodicity based on only 2 to 3 cycles,” says Alan Marscher (Boston University), a blazar expert not involved in the study. Even completely random processes, he adds, can create apparently regular signals over short periods of time.

    3
    These light curves compare how the blazar varies in X-rays (top panel), optical (middle), and radio waves (bottom). Though there aren’t enough X-rays to track the regular variation seen in gamma rays, the optical and radio data seem to echo the gamma-ray cycle, which is shown as a dotted line in the middle panel. M. Ackermann & others / Astrophysics Journal Letters

    And Ackermann’s team is frank about the data’s limits. After all, blazars are known to flare randomly and, due to the length of the suspected cycle, only three complete periods have been captured so far. The authors estimate a few percent probability that this signal is indeed a chance alignment of random flares.

    Still, the fact that the signal is observed across radio, optical, and gamma rays strengthens the case. “Seeing such well-correlated oscillations across the different wavebands isn’t as common as simple models would expect,” Marscher notes.

    “It’s worth keeping an eye on this object.”

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

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

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

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

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

     
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