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  • richardmitnick 12:17 pm on February 11, 2021 Permalink | Reply
    Tags: "A brief history: what we know so far about fast radio bursts across the universe", Arecibo Radio Observatory, , , , , Caltech STARE2 Radio telescope at Owens Valley Radio Observatory, , Fast radio bursts are one of the great mysteries of the universe., , Radio interferometry, , The first FRB was discovered in 2007 by a team led by British-American astronomer Duncan Lorimer using Murriyang-the traditional Indigenous name for the iconic Parkes Radio Telescope., The Lorimer burst had travelled through far too much gas to have originated in our galaxy., The NASA Neil Gehrels Swift Observatory captured X-rays from a very magnetic and erratic neutron star in our own Milky Way., We need to detect an FRB with a radio interferometer-an array of antennas spread out over at least a few kilometres.   

    From The Conversation (AU): “A brief history: what we know so far about fast radio bursts across the universe” 

    From The Conversation (AU)

    February 10, 2021
    Ryan Shannon
    Associate Professor, Swinburne University of Technology (AU)

    Keith Bannister
    Astronomer, CSIRO (AU)

    1
    CSIRO/Parkes Observatory [ Murriyang, the traditional Indigenous name] , located 20 kilometres north of the town of Parkes, New South Wales, Australia, 414.80m above sea level.

    Fast radio bursts are one of the great mysteries of the universe. Since their discovery, we have learned a great deal about these intense millisecond-duration pulses.

    But we still have much to learn, such as what causes them.

    We know the intense bursts originate in galaxies billions of light years away. We have also used these bursts (called FRBs) to find missing matter that couldn’t be found otherwise.

    With teams of astronomers around the world racing to understand their enigma, how did we get to where we are now?

    The first burst

    The first FRB was discovered in 2007 by a team led by British-American astronomer Duncan Lorimer using Murriyang, the traditional Indigenous name for the iconic Parkes radio telescope.

    The team found an incredibly bright pulse — so bright that many astronomers did not believe it to be real. But there was yet more intrigue.

    Radio pulses provide a tremendous gift to astronomers. By measuring when a burst arrives at the telescope at different frequencies, astronomers can tell the total amount of gas that it passed through on its journey to Earth.

    2
    A typical Fast Radio Burst. The burst arrives first at high frequencies and is delayed by as much as several seconds at the lower frequencies. This tell-tale curve is what astronomers are looking for. Credit:Ryan Shannon and Vikram Ravi.

    The Lorimer burst had travelled through far too much gas to have originated in our galaxy, the Milky Way. The team concluded it came from a galaxy billions of light years away.

    To be visible from so far away, whatever produced it must have released an enormous amount of energy. In just a millisecond it released as much energy as our Sun would in 80 years.

    Lorimer’s team could only guess which galaxy their FRB had come from. Murriyang can’t pinpoint FRB locations very accurately. It would take several years for another team to make the breakthrough.

    Locating FRBs

    To pinpoint a burst location, we need to detect an FRB with a radio interferometer — an array of antennas spread out over at least a few kilometres.

    When signals from the telescopes are combined, they produce an image of an FRB with enough detail not only to see in which galaxy the burst originated, but in some cases to tell where within the galaxy it was produced.

    The first FRB localised was from a source that emitted many bursts. The first burst was discovered in 2012 with the giant Arecibo telescope in Puerto Rico.


    NAIC Arecibo Observatory operated by University of Central Florida, Yang Enterprises and UMET, Altitude 497 m (1,631 ft), which has now collapsed.

    Subsequent bursts were detected by the Very Large Array, in New Mexico, and found to be coming from a tiny galaxy about 3 billion light years away.

    NRAO Karl G Jansky Very Large Array, located in central New Mexico on the Plains of San Agustin, between the towns of Magdalena and Datil, ~50 miles (80 km) west of Socorro. The VLA comprises twenty-eight 25-meter radio telescopes.

    In 2018, using the Australian Square Kilometre Array Pathfinder Telescope (ASKAP) in Western Australia, our team identified the second FRB host galaxy.

    Australian Square Kilometre Array Pathfinder (ASKAP) is a radio telescope array located at Murchison Radio-astronomy Observatory (MRO) in the Australian Mid West on the traditional lands of the Wajarri peoples. ASKAP consists of 36 identical parabolic antennas, each 12 metres in diameter, working together as a single instrument with a total collecting area of approximately 4,000 square metres.

    In stark contrast to the previous galaxy, this galaxy was very ordinary. But our published discovery was this month awarded the 2020 AAAS Newcomb Cleveland Prize by the American Association for the Advancement of Science.

    Teams including ours have now localised roughly a dozen more bursts from a wide range of galaxies, large and small, young and old. The fact FRBs can come from such a wide range of galaxies remains a puzzle.

    A burst from close to home

    On April 28, 2020, a flurry of X-rays suddenly bashed into the Swift telescope orbiting Earth.

    NASA Neil Gehrels Swift Observatory.

    The satellite telescope dutifully noted the rays had come from a very magnetic and erratic neutron star in our own Milky Way. This star has form: it goes into fits every few years.

    Two telescopes, CHIME in Canada and the STARE2 array in the United States, detected a very bright radio burst within milliseconds of the X-rays and in the direction of that star.

    CHIME Canadian Hydrogen Intensity Mapping Experiment -A partnership between the University of British Columbia (CA), the University of Toronto (CA), McGill University (CA), Yale and the National Research Council in British Columbia (CA), at the Dominion Radio Astrophysical Observatory in Penticton, British Columbia, (CA) Altitude 545 m (1,788 ft).

    Caltech STARE2 Radio telescope at Owens Valley Radio Observatory, located near Big Pine, California (US) in Owens Valley. It lies east of the Sierra Nevada, approximately 350 kilometers (220 mi) north of Los Angeles and 20 kilometers (12 mi) southeast of Bishop. It was established in 1956, and is owned and operated by the California Institute of Technology (Caltech), Altitude 1,222 m (4,009 ft).

    Caltech Owens Valley Radio Observatory, Owens Valley, California, Altitude 1,222 m (4,009 ft).

    This demonstrated such neutron stars could be a source of the FRBs we see in galaxies far away.

    The simultaneous release of X-rays and radio waves gave astrophysicists important clues to how nature can produce such bright bursts. But we still don’t know for certain if this is the cause of FRBs.

    So what’s next?

    While 2020 was the year of the local FRB, we expect 2021 will be the year of the the far-flung FRB, even further than already observed.

    The CHIME telescope has collected by far the largest sample of bursts and is compiling a meticulous catalogue that should be available to other astronomers soon.

    A team at Caltech is building an array specifically dedicated to finding FRBs.

    Caltech Deep Synoptic Array being built at Owens Valley Radio Observatory Owens Valley, California, Altitude 1,222 m (4,009 ft)

    There’s plenty of action in Australia too. We are developing a new burst-detection supercomputer for ASKAP that will find FRBs at a faster rate and find more distant sources.

    It will effectively turn ASKAP into a high-speed, high-definition video camera, and make a movie of the universe at 40 trillion pixels per second.

    By finding more bursts, and more distant bursts, we will be able to better study and understand what causes these mysteriously intense bursts of energy.


    Fast Radio Burst Research Earns AAAS Newcomb Cleveland Prize

    See the full article here .

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    Please help promote STEM in your local schools.

    Stem Education Coalition

    The Conversation (AU) launched as a pilot project in October 2014. It is an independent source of news and views from the academic and research community, delivered direct to the public.
    Our team of professional editors work with university and research institute experts to unlock their knowledge for use by the wider public.
    Access to independent, high quality, authenticated, explanatory journalism underpins a functioning democracy. Our aim is to promote better understanding of current affairs and complex issues. And hopefully allow for a better quality of public discourse and conversation.

     
  • richardmitnick 1:45 pm on June 25, 2018 Permalink | Reply
    Tags: , , , , , Galaxy OJ 287, , , , Radio interferometry, Super-mass-rich black hole   

    From MPG: “Close-up of a galaxy nucleus” 

    MPG bloc

    From Max Planck Gesellschaft

    June 25, 2018

    Dr. Norbert Junkes
    Press and public relations
    Max Planck Institute for Radio Astronomy, Bonn
    +49 2 28525-399
    njunkes@mpifr-bonn.mpg.de

    Dr. Silke Britzen
    Max Planck Institute for Radio Astronomy, Bonn
    +49 228 525-280 sbritzen
    @mpifr-bonn.mpg.de

    Dr. Christian Fendt
    Max Planck Institute for Astronomy, Heidelberg
    +49 6221 528-387
    fendt@mpia-hd.mpg.de

    Max Planck Institute for Radio Astronomy Bonn Germany

    Max Planck Institute for Astronomy campus Heidelberg, Baden-Württemberg, Germany

    In the centre of the galaxy OJ 287, there is one active, super-mass-rich black hole. An international research team led by Silke Britzen of the Max Planck Institute for Radio Astronomy has now discovered that the active nucleus of this galaxy generates a jet that staggers like a spinning top on a time jet on a timescale of about 22 years. With this movement called ‘precession’, the fluctuation of the radiation of OJ 287 can be explained. The discovery thus provides the key to understanding the variability in active galaxy nuclei.

    1
    Zoom into the heart of a galaxy: artist’s impression of the central region of the active galaxy OJ 287 with a preceding jet. The precession could either be caused by a binary black hole (Inset A) or by a mis-aligned accretion disk (Inset B).
    © Axel Quetz / MPIA Heidelberg

    It took a long time to decipher the Egyptian hieroglyphs, the inscriptions of the pyramids. It finally succeeded with the help of the so-called Rosetta Stone found in 1799. This stele was inscribed with three versions of the same text – one in Ancient Egyptian using hieroglyphic script, one in Demotic script, and the bottom one in Ancient Greek. Realizing that it is the same text, the enigmatic hieroglyphs could be deciphered and translated with the help of the ancient Greek language. This discovery opened up a whole new window to understand the ancient Egyptian culture. A research team now has deciphered the jet of a galaxy which has been named the Rosetta Stone of blazars. Blazars are active galactic nuclei where a central supermassive black hole is being fed.

    The well-known galaxy OJ 287 at a distance of about 3.5 billion light years harbors at least one supermassive black hole weighing Millions to Billions of solar masses. The supermassive black hole is active and produces a jet – a plasma stream which originates in the central nuclear region of galaxies in the vicinity of the central black hole. This jet is observable at radio wavelengths. The galaxy is also a well-known target to optical astronomers. The brightness fluctuations of this galaxy in the optical regime are legendary and have been observed since the late 19th century, providing one of the longest light-curves in astronomy.

    However, despite decades of radio observations of many jet sources and many sophisticated studies, jets remained enigmatic. Traditionally, the origin of the jet brightness variations observed at radio wavelengths was attributed to the jet feeding mechanism by the central black hole system. On the other hand, the observed moving features in the jets – called knots – were attributed to shocks traveling in the jet. Researchers looked for a connection between both phenomena but this could not be done consistently so far.

    The research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy (MPIfR) in Bonn used a clever observational technique to monitor the jet of OJ 287 close to its launching site near the central black hole in precious detail. The technique of radio interferometry involves radio telescopes around the globe in order to construct a virtual monster telescope of earth size diameter that is able to zoom into the very centers of galaxies and to observe jets close to the central black hole with unprecedented resolution.

    By considering a large data set spanning a long period of time, the team has now found strong indication that both phenomena have the same origin: both types of observations can be explained by the motion of the jet only. The jet itself is precessing. Michal Zajacek, also from the MPIfR, who has done the modeling of the precession model: “The brightness variations result from the jet precession that induces a variation of the Doppler boosting when the viewing angle of the jet changes. It was really surprising when we found that not only does the jet precess, it also seems to follow a smaller nutation-like motion. The combined precession-nutation motion leads to the radio variability and can also explain some of the light flares.“

    “We realized that it is the same physical process that explains both the jet wandering in the sky and the brightness variations of the galaxy – that is the change of motion of the jet. It’s all geometry and deterministic. No magic involved, so far”, adds Silke Britzen. “This offers a unique opportunity to understand the jets and their potential origin in the immediate vicinity of the black hole. This jet really serves as Rosetta stone for us and will allow to understand jets and their active black holes much more fundamentally.”Britzen and her team are convinced that the precession-scenario can also explain the 130 years of optical flaring of this source but, as always, more data and more work is required for a final confirmation.

    A pressing question remains about the origin of the jet precession. Precession is a physical process well-known from spinning tops or the Earth itself. The rotational axis of our planet is not stable but orbiting in space with a period of 26,000 years due to the tidal influence of the Sun and the moon. For the jet precession in OJ 287 the team has indicated two possible scenarios. “We either have a system of two supermassive black holes with the disk-ejecting jet forced to wobble by tidal effects of the secondary black hole or a single black hole that is tidaly interacting with a misaligned accretion disk,” concludes Christian Fendt from the Max Planck Institute for Astronomy (MPIA) in Heidelberg.Either way, the jet of the active galaxy OJ 287 is one of the best understood jets so far and will certainly be used to decipher other extragalactic jets as well. It might even help to further unravel the enigmatic activity of supermassive black holes.

    Science papers:
    OJ287: Deciphering the “Rosetta stone of blazars”, MNRAS
    Jet precession in binary black holes Nature

    See the full article here .


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    Please help promote STEM in your local schools.

    Stem Education Coalition

    MPG campus

    The Max Planck Society for the Advancement of Science (German: Max-Planck-Gesellschaft zur Förderung der Wissenschaften e. V.; abbreviated MPG) is a formally independent non-governmental and non-profit association of German research institutes founded in 1911 as the Kaiser Wilhelm Society and renamed the Max Planck Society in 1948 in honor of its former president, theoretical physicist Max Planck. The society is funded by the federal and state governments of Germany as well as other sources.

    According to its primary goal, the Max Planck Society supports fundamental research in the natural, life and social sciences, the arts and humanities in its 83 (as of January 2014)[2] Max Planck Institutes. The society has a total staff of approximately 17,000 permanent employees, including 5,470 scientists, plus around 4,600 non-tenured scientists and guests. Society budget for 2015 was about €1.7 billion.

    The Max Planck Institutes focus on excellence in research. The Max Planck Society has a world-leading reputation as a science and technology research organization, with 33 Nobel Prizes awarded to their scientists, and is generally regarded as the foremost basic research organization in Europe and the world. In 2013, the Nature Publishing Index placed the Max Planck institutes fifth worldwide in terms of research published in Nature journals (after Harvard, MIT, Stanford and the US NIH). In terms of total research volume (unweighted by citations or impact), the Max Planck Society is only outranked by the Chinese Academy of Sciences, the Russian Academy of Sciences and Harvard University. The Thomson Reuters-Science Watch website placed the Max Planck Society as the second leading research organization worldwide following Harvard University, in terms of the impact of the produced research over science fields.

     
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