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  • richardmitnick 1:59 pm on May 21, 2020 Permalink | Reply
    Tags: "New gravitational-wave model can bring neutron stars into even sharper focus", , , , phys.org,   

    From University of Birmingham UK via phys.org: “New gravitational-wave model can bring neutron stars into even sharper focus” 

    From University of Birmingham UK

    via


    phys.org

    May 21, 2020

    1
    The results from a numerical relativity simulation of two merging neutron stars similar to GW170817. Credit: University of Birmingham

    Gravitational-wave researchers at the University of Birmingham have developed a new model that promises to yield fresh insights into the structure and composition of neutron stars.

    The model shows that vibrations, or oscillations, inside the stars can be directly measured from the gravitational-wave signal alone. This is because neutron stars will become deformed under the influence of tidal forces, causing them to oscillate at characteristic frequencies, and these encode unique information about the star in the gravitational-wave signal.

    This makes asteroseismology—the study of stellar oscillations—with gravitational waves from colliding neutron stars a promising new tool to probe the elusive nature of extremely dense nuclear matter.

    Neutron stars are the ultradense remnants of collapsed massive stars. They have been observed in the thousands in the electromagnetic spectrum and yet little is known about their nature. Unique information can be gleaned through measuring the gravitational waves emitted when two neutron stars meet and form a binary system. First predicted by Albert Einstein, these ripples in spacetime were first detected by the Advanced Laser Interferometer Gravitational Wave Observatory (LIGO) in 2015.

    By utilising the gravitational wave signal to measure the oscillations of the neutron stars, researchers will be able to discover new insights into the interior of these stars. The study is published in Nature Communications.

    Dr. Geraint Pratten, of the University of Birmingham’s Gravitational Wave Institute, is lead author of the study. He explained: “As the two stars spiral around each other, their shapes become distorted by the gravitational force exerted by their companion. This becomes more and more pronounced and leaves a unique imprint in the gravitational wave signal.

    “The tidal forces acting on the neutron stars excite oscillations inside the star giving us insight into their internal structure. By measuring these oscillations from the gravitational-wave signal, we can extract information about the fundamental nature and composition of these mysterious objects that would otherwise be inaccessible.”

    The model developed by the team enables the frequency of these oscillations to be determined directly from gravitational-wave measurements for the first time. The researchers used their model on the first observed gravitational-wave signal from a binary neutron star merger—GW170817.

    Co-lead author, Dr. Patricia Schmidt, added: “Almost three years after the first gravitational-waves from a binary neutron star were observed, we are still finding new ways to extract more information about them from the signals. The more information we can gather by developing ever more sophisticated theoretical models, the closer we will get to revealing the true nature of neutron stars.”

    Next generation gravitational wave observatories planned for the 2030s, will be capable of detecting far more binary neutron stars and observing them in much greater detail than is currently possible. The model produced by the Birmingham team will make a significant contribution to this science.

    “The information from this initial event was limited as there was quite a lot of background noise that made the signal difficult to isolate,” says Dr. Pratten. “With more sophisticated instruments we can measure the frequencies of these oscillations much more precisely and this should start to yield some really interesting insights.”

    See the full article here .

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  • richardmitnick 11:07 am on May 19, 2020 Permalink | Reply
    Tags: "Binary-driven hypernova model gains observational support", , , , , , ICRA-ICRANet-INAF, phys.org   

    From phys.org: “Binary-driven hypernova model gains observational support” 


    From phys.org

    May 19, 2020
    by ICRANet

    1
    Fig. 1 Taken from 2020ApJ…893..148R. Schematic evolutionary path of a massive binary up to the emission of a BdHN. (a) Binary system composed of two main-sequence stars, say 15 and 12 solar masses, respectively. (b) At a given time, the more massive star undergoes the core-collapse SN and forms a NS (which might have a magnetic field B~1013 G). (c) The system enters the X-ray binary phase. (d) The core of the remaining evolved star, rich in carbon and oxygen, for short CO star, is left exposed since the hydrogen and helium envelope have been striped by binary interactions and possibly multiple common-envelope phases (not shown in this diagram). The system is, at this stage, a CO-NS binary, which is taken as the initial configuration of the BdHN model [2]. (e) The CO star explodes as SN when the binary period is of the order of few minutes, the SN ejecta of a few solar masses start to expand and a fast rotating, newborn NS, for short vNS, is left in the center. (f) The SN ejecta accrete onto the NS companion, forming a massive NS (BdHN II) or a BH (BdHN I; this example), depending on the initial NS mass and the binary separation. Conservation of magnetic flux and possibly additional MHD processes amplify the magnetic field from the NS value to B~1014 G around the newborn BH. At this stage the system is a vNS-BH binary surrounded by ionized matter of the expanding ejecta. (g) The accretion, the formation and the activities of the BH contribute to the GRB prompt gamma-ray emission and GeV emission. Credit: ICRANet

    The change of paradigm in gamma-ray burst (GRBs) physics and astrophysics introduced by the binary driven hypernova (BdHN) model, proposed and applied by the ICRA-ICRANet-INAF members in collaboration with the University of Ferrara and the University of Côte d’Azur, has gained further observational support from the X-ray emission in long GRBs. These novel results are presented in the new article, published on April 20, 2020, in The Astrophysical Journal, co-authored by J. A. Rueda, Remo Ruffini, Mile Karlica, Rahim Moradi, and Yu Wang.

    The GRB emission is composed by episodes: from the hard X-ray trigger and the gamma-ray prompt emission, to the high-energy emission in GeV, recently observed also in TeV energies in GRB 190114C, to the X-ray afterglow. The traditional model of GRBs attempts to explain the entire GRB emissions from a single-component progenitor, i.e., from the emission of a relativistic jet originating from a rotating black hole (BH). Differently, the BdHN scenario proposes GRBs originate from a cataclysmic event in the last evolutionary stage of a binary system composed of a carbon-oxygen (CO) star and a neutron star (NS) companion in close orbit. The gravitational collapse of the iron core of the CO star produces a supernova (SN) explosion ejecting the outermost layers of the star, and at the same time, a newborn NS (vNS) at its center. The SN ejecta trigger a hypercritical accretion process onto the NS companion and onto the vNS. Depending on the size of the orbit, the NS may reach, in the case of short orbital periods of the order of minutes, the critical mass for gravitational collapse, hence forming a newborn BH. These systems where a BH is formed are called BdHN of type I. For longer periods, the NS gets more massive but it does not form a BH. These systems are BdHNe II. Three-dimensional simulations of all this process showing the feasibility of its occurrence, from the SN explosion to the formation of the BH, has been recently made possible by the collaboration between ICRANet and the group of Los Alamos National Laboratory (LANL) guided by Prof. C. L. Fryer (see Figure 1).

    The role of the BH for the formation of the high-energy GeV emission has been recently presented in The Astrophysical Journal. There, the “inner engine” composed of a Kerr BH, with a magnetic field aligned with the BH rotation axis immersed in a low-density ionized plasma, gives origin, by synchrotron radiation, to the beamed emission in the MeV, GeV, and TeV, currently observed only in some BdHN I, by the Fermi-LAT and MAGIC instruments. In the new publication, the ICRA-ICRANet team addresses the interaction of the vNS with the SN due to hypercritical accretion and pulsar-like emission. They show that the fingerprint of the vNS appears in the X-ray afterglow of long GRBs observed by the XRT detector on board the Niels Gehrels Swift observatory. Therefore, the vNS and the BH have well distinct and different roles in the long GRB observed emission.

    3
    Fig. 2 :Model evolution of synchrotron spectral luminosity at various times compared with measurements in various spectral bands for GRB 160625B.

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    Fig. 3 The brown, deep blue, orange, green and bright blue points correspond to the bolometric (about 5 times brighter than the soft X-ray observed by Swift-XRT data) light-curves of GRB 160625B, 160509A, 130427A, 190114C and 180728A, respectively. The solid lines are theoretical light-curves obtained from the rotational energy loss of the vNS powering the late afterglow (t>5000 s, white background), while in the earlier times (300300 s, where data are more available. At earlier times, only GRB 130427A and GRB 190114C in this same have available data. Credit: ICRANet

    The emission from the magnetized vNS and the hypercritical accretion of the SN ejecta into it, gives origin to the afterglow observed in all BdHN I and II subclasses. The early (~few hours) X-ray emission during the afterglow phase is explained by the injection of ultra-relativistic electrons from the vNS into the expanding ejecta, producing synchrotron radiation (see Figure 2). The magnetic field inferred from the synchrotron analysis agrees with the expected toroidal/longitudinal magnetic field component of the vNS. Furthermore, from the analysis of the XRT data of these GRBs at times t>10^4 s, it has been shown that the power-law decaying luminosity is powered by the vNS rotational energy loss by the torque acted upon it by its dipole+quadrupole magnetic. From this, it has been inferred that the vNS possesses a magnetic field of strength ~ 10^12 to 10^13 G, and a rotation period of the order of a millisecond (see Figure 3). It is shown that the inferred millisecond rotation period of the vNS agrees with the conservation of angular momentum in the gravitational collapse of the iron core of the CO star which the vNS came from.

    The inferred structure of the magnetic field of the “inner engine” agrees with a scenario in which, along the rotational axis of the BH, it is rooted in the magnetosphere left by the NS that collapsed into a BH.

    On the equatorial plane, the field is magnified by magnetic flux conservation.

    See the full article here .

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    About Science X in 100 words
    Science X™ is a leading web-based science, research and technology news service which covers a full range of topics. These include physics, earth science, medicine, nanotechnology, electronics, space, biology, chemistry, computer sciences, engineering, mathematics and other sciences and technologies. Launched in 2004 (Physorg.com), Science X’s readership has grown steadily to include 5 million scientists, researchers, and engineers every month. Science X publishes approximately 200 quality articles every day, offering some of the most comprehensive coverage of sci-tech developments world-wide. Science X community members enjoy access to many personalized features such as social networking, a personal home page set-up, article comments and ranking, the ability to save favorite articles, a daily newsletter, and other options.
    Mission 12 reasons for reading daily news on Science X Organization Key editors and writersinclude 1.75 million scientists, researchers, and engineers every month. Phys.org publishes approximately 100 quality articles every day, offering some of the most comprehensive coverage of sci-tech developments world-wide. Quancast 2009 includes Phys.org in its list of the Global Top 2,000 Websites. Phys.org community members enjoy access to many personalized features such as social networking, a personal home page set-up, RSS/XML feeds, article comments and ranking, the ability to save favorite articles, a daily newsletter, and other options.

     
  • richardmitnick 9:52 am on May 19, 2020 Permalink | Reply
    Tags: "Longstanding mystery of matter and antimatter may be solved", , , , phys.org, , University of the West of Scotland   

    From phys.org: “Longstanding mystery of matter and antimatter may be solved” 


    May 19, 2020

    1
    Thorium-228. Credit: University of the West of Scotland

    An element which could hold the key to the long-standing mystery around why there is much more matter than antimatter in our Universe has been discovered by a University of the West of Scotland (UWS)-led team of physicists.

    The UWS and University of Strathclyde academics have discovered, in research published in the journal Nature Physics, that one of the isotopes of the element thorium possesses the most pear-shaped nucleus yet to be discovered. Nuclei similar to thorium-228 may now be able to be used to perform new tests to try find the answer to the mystery surrounding matter and antimatter.

    UWS’s Dr. David O’Donnell, who led the project, said: “Our research shows that, with good ideas, world-leading nuclear physics experiments can be performed in university laboratories.

    “This work augments the experiments which nuclear physicists at UWS are leading at large experimental facilities around the world. Being able to perform experiments like this one provides excellent training for our students.”

    Physics explains that the Universe is composed of fundamental particles such as the electrons which are found in every atom. The Standard Model, the best theory physicists have to describe the sub-atomic properties of all the matter in the Universe, predicts that each fundamental particle can have a similar antiparticle.

    2
    If we allow X and Y particles to decay into the quarks and lepton combinations shown, their… [+] E. Siegel / Beyond The Galaxy

    Collectively the antiparticles, which are almost identical to their matter counterparts except they carry opposite charge, are known as antimatter.

    According to the Standard Model, matter and antimatter should have been created in equal quantities at the time of the Big Bang—yet our Universe is made almost entirely of matter.

    In theory, an electric dipole moment (EDM) could allow matter and antimatter to decay at different rates, providing an explanation for the asymmetry in matter and antimatter in our universe.

    Pear-shaped nuclei have been proposed as ideal physical systems in which to look for the existence of an EDM in a fundamental particle such as an electron. The pear shape means that the nucleus generates an EDM by having the protons and neutrons distributed non-uniformly throughout the nuclear volume.

    Through experiments conducted in laboratories at UWS’s Paisley Campus, researchers have found that the nuclei in thorium-228 atoms have the most pronounced pear shape to be discovered so far. As a result, nuclei like thorium-228 have been identified as ideal candidates to search for the existence of an EDM.

    The research team was made up of Dr. O’Donnell, Dr. Michael Bowry, Dr. Bondili Sreenivasa Nara Singh, Professor Marcus Scheck, Professor John F Smith and Dr. Pietro Spagnoletti from UWS’s School of Computing, Engineering and Physical Sciences; and the University of Strathclyde’s Professor Dino Jaroszynski, and Ph.D. students Majid Chishti and Giorgio Battaglia.

    Professor Dino Jaroszynski, Director of the Scottish Centre for the Application of Plasma-based Accelerators (SCAPA) at the University of Strathclyde, said: “This collaborative effort, which draws on the expertise of a diverse group of scientists, is an excellent example of how working together can lead to a major breakthrough. It highlights the collaborative spirit within the Scottish physics community fostered by the Scottish University Physics Alliance (SUPA) and lays the groundwork for our collaborative experiments at SCAPA.”

    The experiments began with a sample of thorium-232, which has a half-life of 14 billion years, meaning it decays very slowly. The decay chain of this nucleus creates excited quantum mechanical states of the nucleus thorium-228. Such states decay within nanoseconds of being created, by emitting gamma rays.

    Dr. O’Donnell and his team used highly sensitive state-of-the-art scintillator detectors to detect these ultra-rare and fast decays. With careful configuration of detectors and signal-processing electronics, the research team have been able to precisely measure the lifetime of the excited quantum states, with an accuracy of two trillionths of a second. The shorter the lifetime of the quantum state the more pronounced the pear shape of the thorium-228 nucleus—giving researchers a better chance of finding an EDM.

    See the full article here .

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    About Science X in 100 words
    Science X™ is a leading web-based science, research and technology news service which covers a full range of topics. These include physics, earth science, medicine, nanotechnology, electronics, space, biology, chemistry, computer sciences, engineering, mathematics and other sciences and technologies. Launched in 2004 (Physorg.com), Science X’s readership has grown steadily to include 5 million scientists, researchers, and engineers every month. Science X publishes approximately 200 quality articles every day, offering some of the most comprehensive coverage of sci-tech developments world-wide. Science X community members enjoy access to many personalized features such as social networking, a personal home page set-up, article comments and ranking, the ability to save favorite articles, a daily newsletter, and other options.
    Mission 12 reasons for reading daily news on Science X Organization Key editors and writersinclude 1.75 million scientists, researchers, and engineers every month. Phys.org publishes approximately 100 quality articles every day, offering some of the most comprehensive coverage of sci-tech developments world-wide. Quancast 2009 includes Phys.org in its list of the Global Top 2,000 Websites. Phys.org community members enjoy access to many personalized features such as social networking, a personal home page set-up, RSS/XML feeds, article comments and ranking, the ability to save favorite articles, a daily newsletter, and other options.

     
  • richardmitnick 11:52 am on May 18, 2020 Permalink | Reply
    Tags: "Take a peek inside a giant star right before it dies", , , , , phys.org   

    From phys.org: “Take a peek inside a giant star right before it dies” 


    From phys.org

    May 18, 2020
    Paul M. Sutter

    1
    The interior of a giant star right before it’s about to blow. Layers of elements all piled up on each other, all fusing, all crazy. Credit: R. J. Hall

    The biggest stars in the universe are some of the most fascinatingly complex objects to inhabit the cosmos. Indeed, giant stars have defied full explanation for decades, especially when they’re near the end of their lives.

    Stars power themselves through nuclear fusion, from the smashing together of lighter elements into heavier ones. This process leaves behind a little bit of extra energy. It’s not much, but when those fusion reactions occur at millions or billions of times every single second, it’s enough to keep a star powered for millions or billions of years.

    Like ashes at the bottom of a fire, the leftovers from the nuclear reactions sink to the core of the star, building up and preventing new reactions from taking place in that region, forcing the fusion to happen in a shell surrounding it.

    At the beginning, stars fuse the lightest element, hydrogen, into helium, with the helium building up in the core and the hydrogen fusion moving out into a shell. But once temperatures and pressures reach a critical density, the star is able to burn helium, turning that into carbon and oxygen in the core, with helium fusion surrounding that, and a hydrogen-burning layer surrounding that.

    Toward the end of their lives, stars form a gigantic plasma onion, with a core of iron, surrounded by layers of fusion of silicon, magnesium, carbon, oxygen, helium and hydrogen.

    The stars are unable to fuse iron into anything heavier without losing energy, so that’s where the train stops. And once it does, the star turns that onion layer inside out and dies in a spectacular supernova explosion.

    That complex onion layer situation is brief—after millions of years of life, that structure will only appear for about 15 eventful minutes.

    See the full article here .

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    Science X™ is a leading web-based science, research and technology news service which covers a full range of topics. These include physics, earth science, medicine, nanotechnology, electronics, space, biology, chemistry, computer sciences, engineering, mathematics and other sciences and technologies. Launched in 2004 (Physorg.com), Science X’s readership has grown steadily to include 5 million scientists, researchers, and engineers every month. Science X publishes approximately 200 quality articles every day, offering some of the most comprehensive coverage of sci-tech developments world-wide. Science X community members enjoy access to many personalized features such as social networking, a personal home page set-up, article comments and ranking, the ability to save favorite articles, a daily newsletter, and other options.
    Mission 12 reasons for reading daily news on Science X Organization Key editors and writersinclude 1.75 million scientists, researchers, and engineers every month. Phys.org publishes approximately 100 quality articles every day, offering some of the most comprehensive coverage of sci-tech developments world-wide. Quancast 2009 includes Phys.org in its list of the Global Top 2,000 Websites. Phys.org community members enjoy access to many personalized features such as social networking, a personal home page set-up, RSS/XML feeds, article comments and ranking, the ability to save favorite articles, a daily newsletter, and other options.

     
  • richardmitnick 11:25 am on May 18, 2020 Permalink | Reply
    Tags: , , , , , phys.org, Scientists puzzle over massive never-before-seen star system in the Milky Way   

    From ARC Centres of Excellence for Gravitational Wave Discovery via phys.org: “Scientists puzzle over massive, never-before-seen star system in the Milky Way” 

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    From ARC Centres of Excellence for Gravitational Wave Discovery

    via


    From phys.org

    May 18, 2020

    1
    Artist impression of galaxy. Credit: Pixabay

    Earlier this year, an international team of scientists announced the second detection of a gravitational-wave signal from the collision of two neutron stars. The event, called GW190425, is puzzling: The combined mass of the two neutron stars is greater than any other observed binary neutron star system. The combined mass is 3.4 times the mass of our sun.

    A neutron star binary this massive has never been seen in our galaxy, and scientists have been mystified by how it could have formed—until now. A team of astrophysicists from the ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav) think they might have the answer.

    Binary neutron stars emit gravitational waves—ripples in space-time— as they orbit each other, and scientists can detect these waves when the neutron stars merge. The gravitational waves contain information about the neutron stars, including their masses.

    The gravitational waves from cosmic event GW190425 tell of a neutron star binary more massive than any neutron star binary previously observed, either through radio-wave or gravitational-wave astronomy. A recent study [MNRAS ] led by OzGrav Ph.D. student Isobel Romero-Shaw from Monash University proposes a formation channel that explains both the high mass of this binary and the fact that similar systems aren’t observed with traditional radio astronomy techniques .

    Romero-Shaw says, “We propose that GW190425 formed through a process called ‘unstable case BB mass transfer,” a procedure that was originally defined in 1981. It starts with a neutron star that has a stellar partner: a helium (He) star with a carbon-oxygen (CO) core. If the helium part of the star expands far enough to engulf the neutron star, this helium cloud ends up pushing the binary closer together before it dissipates. The carbon-oxygen core of the star then explodes in a supernova and collapses to a neutron star.”

    2
    Credit: Carl Knox, ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav)

    Binary neutron stars that form in this way can be significantly more massive than those observed through radio waves. They also merge very fast following the supernova explosion, making them unlikely to be captured in radio astronomy surveys.

    “Our study points out that the process of unstable case BB mass transfer could be how the massive star system formed,” says Romero-Shaw.

    The OzGrav researchers also used a recently-developed technique to measure the eccentricity of the binary—how much the star system’s orbital shape deviates from a circle. Their findings are consistent with unstable case BB mass transfer.

    Current ground-based gravitational-wave detectors aren’t sensitive enough to precisely measure the eccentricity; however, future detectors—like space-based detector LISA, due for launch in 2034—will allow scientists to make more accurate conclusions.

    ESA/NASA eLISA


    ESA/NASA eLISA space based, the future of gravitational wave research

    See the full article here .

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    OzGrav

    THE ARC CENTRE of excellence FOR GRAVITATIONAL WAVE DISCOVERY
    A new window of discovery.
    A new age of gravitational wave astronomy.
    One hundred years ago, Albert Einstein produced one of the greatest intellectual achievements in physics, the theory of general relativity. In general relativity, spacetime is dynamic. It can be warped into a black hole. Accelerating masses create ripples in spacetime known as gravitational waves (GWs) that carry energy away from the source. Recent advances in detector sensitivity led to the first direct detection of gravitational waves in 2015. This was a landmark achievement in human discovery and heralded the birth of the new field of gravitational wave astronomy. This was followed in 2017 by the first observations of the collision of two neutron-stars. The accompanying explosion was subsequently seen in follow-up observations by telescopes across the globe, and ushered in a new era of multi-messenger astronomy.

    The mission of the ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav) is to capitalise on the historic first detections of gravitational waves to understand the extreme physics of black holes and warped spacetime, and to inspire the next generation of Australian scientists and engineers through this new window on the Universe.

    OzGrav is funded by the Australian Government through the Australian Research Council Centres of Excellence funding scheme, and is a partnership between Swinburne University (host of OzGrav headquarters), the Australian National University, Monash University, University of Adelaide, University of Melbourne, and University of Western Australia, along with other collaborating organisations in Australia and overseas.

    ________________________________________________________

    The objectives for the ARC Centres of Excellence are to to:

    undertake highly innovative and potentially transformational research that aims to achieve international standing in the fields of research envisaged and leads to a significant advancement of capabilities and knowledge
    link existing Australian research strengths and build critical mass with new capacity for interdisciplinary, collaborative approaches to address the most challenging and significant research problems
    develope relationships and build new networks with major national and international centres and research programs to help strengthen research, achieve global competitiveness and gain recognition for Australian research
    build Australia’s human capacity in a range of research areas by attracting and retaining, from within Australia and abroad, researchers of high international standing as well as the most promising research students
    provide high-quality postgraduate and postdoctoral training environments for the next generation of researchers
    offer Australian researchers opportunities to work on large-scale problems over long periods of time
    establish Centres that have an impact on the wider community through interaction with higher education institutes, governments, industry and the private and non-profit sector.

     
  • richardmitnick 10:57 am on May 18, 2020 Permalink | Reply
    Tags: "A theoretical boost to nano-scale devices", , , phys.org, The Korea Advanced Institute of Science and Technology (KAIST)   

    From The Korea Advanced Institute of Science and Technology (KAIST) via phys.org: “A theoretical boost to nano-scale devices” 

    1

    From The Korea Advanced Institute of Science and Technology (KAIST)

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    From phys.org

    1
    The newly developed formalism and QFL splitting analysis led to new ways of characterizing extremely scaled-down semiconductor devices and the technology computer-aided design (TCAD) of next- generation nano-electronic/energy/bio devices. Credit: Yong-Hoon Kim, KAIST

    Semiconductor companies are struggling to develop devices that are mere nanometers in size, and much of the challenge lies in being able to more accurately describe the underlying physics at that nano-scale. But a new computational approach that has been in the works for a decade could break down these barriers.

    Devices using semiconductors, from computers to solar cells, have enjoyed tremendous efficiency improvements in the last few decades. Famously, one of the co-founders of Intel, Gordon Moore, observed that the number of transistors in an integrated circuit doubles about every two years—and this ‘Moore’s law’ held true for some time.

    In recent years, however, such gains have slowed as firms that attempt to engineer nano-scale transistors hit the limits of miniaturization at the atomic level.

    Researchers with the School of Electrical Engineering at KAIST have developed a new approach to the underlying physics of semiconductors.

    “With open quantum systems as the main research target of our lab, we were revisiting concepts that had been taken for granted and even appear in standard semiconductor physics textbooks such as the voltage drop in operating semiconductor devices,” said the lead researcher Professor Yong-Hoon Kim. “Questioning how all these concepts could be understood and possibly revised at the nano-scale, it was clear that there was something incomplete about our current understanding.”

    “And as the semiconductor chips are being scaled down to the atomic level, coming up with a better theory to describe semiconductor devices has become an urgent task.”

    The current understanding states that semiconductors are materials that act like half-way houses between conductors, like copper or steel, and insulators, like rubber or Styrofoam. They sometimes conduct electricity, but not always. This makes them a great material for intentionally controlling the flow of current, which in turn is useful for constructing the simple on/off switches—transistors—that are the foundation of memory and logic devices in computers.

    In order to ‘switch on’ a semiconductor, a current or light source is applied, exciting an electron in an atom to jump from what is called a ‘valence band,’ which is filled with electrons, up to the ‘conduction band,’ which is originally unfilled or only partially filled with electrons. Electrons that have jumped up to the conduction band thanks to external stimuli and the remaining ‘holes’ are now able to move about and act as charge carriers to flow electric current.

    The physical concept that describes the populations of the electrons in the conduction band and the holes in the valence band and the energy required to make this jump is formulated in terms of the so-called ‘Fermi level.’ For example, you need to know the Fermi levels of the electrons and holes in order to know what amount of energy you are going to get out of a solar cell, including losses.

    But the Fermi level concept is only straightforwardly defined so long as a semiconductor device is at equilibrium—sitting on a shelf doing nothing—and the whole point of semiconductor devices is not to leave them on the shelf.

    Some 70 years ago, William Shockley, the Nobel Prize-winning co-inventor of the transistor at the Bell Labs, came up with a bit of a theoretical fudge, the ‘quasi-Fermi level,’ or QFL, enabling rough prediction and measurement of the interaction between valence band holes and conduction band electrons, and this has worked pretty well until now.

    “But when you are working at the scale of just a few nanometers, the methods to theoretically calculate or experimentally measure the splitting of QFLs were just not available,” said Professor Kim.

    This means that at this scale, issues such as errors relating to voltage drop take on much greater significance.

    Kim’s team worked for nearly ten years on developing a novel theoretical description of nano-scale quantum electron transport that can replace the standard method—and the software that allows them to put it to use. This involved the further development of a bit of math known as the Density Functional Theory that simplifies the equations describing the interactions of electrons, and which has been very useful in other fields such as high-throughput computational materials discovery.

    For the first time, they were able to calculate the QFL splitting, offering a new understanding of the relationship between voltage drop and quantum electron transport in atomic scale devices.

    In addition to looking into various interesting non-equilibrium quantum phenomena with their novel methodology, the team is now further developing their software into a computer-aided design tool to be used by semiconductor companies for developing and fabricating advanced semiconductor devices.

    Science paper:
    https://www.pnas.org/content/117/19/10142
    PNAS

    See the full article here .

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    About Science X in 100 words
    Science X™ is a leading web-based science, research and technology news service which covers a full range of topics. These include physics, earth science, medicine, nanotechnology, electronics, space, biology, chemistry, computer sciences, engineering, mathematics and other sciences and technologies. Launched in 2004 (Physorg.com), Science X’s readership has grown steadily to include 5 million scientists, researchers, and engineers every month. Science X publishes approximately 200 quality articles every day, offering some of the most comprehensive coverage of sci-tech developments world-wide. Science X community members enjoy access to many personalized features such as social networking, a personal home page set-up, article comments and ranking, the ability to save favorite articles, a daily newsletter, and other options.
    Mission 12 reasons for reading daily news on Science X Organization Key editors and writersinclude 1.75 million scientists, researchers, and engineers every month. Phys.org publishes approximately 100 quality articles every day, offering some of the most comprehensive coverage of sci-tech developments world-wide. Quancast 2009 includes Phys.org in its list of the Global Top 2,000 Websites. Phys.org community members enjoy access to many personalized features such as social networking, a personal home page set-up, RSS/XML feeds, article comments and ranking, the ability to save favorite articles, a daily newsletter, and other options.

     
  • richardmitnick 12:48 pm on May 15, 2020 Permalink | Reply
    Tags: "Black holes and neutron stars merge unseen in dense star clusters", , , , , Heidelburg University, phys.org   

    From phys.org: “Black holes and neutron stars merge unseen in dense star clusters” 


    From phys.org

    [Source: Heidelburg University]

    1
    Invisible black hole-neutron star mergers, i.e. fusions without the emission of electromagnetic radiation, take place in dense stellar environments like in the globular cluster NGC 3201 seen here. Credit: European Southern Observatory (ESO)

    Mergers between black holes and neutron stars in dense star clusters are quite unlike those that form in isolated regions where stars are few. Their associated features could be crucial to the study of gravitational waves and their source. Dr. Manuel Arca Sedda of the Institute for Astronomical Computing at Heidelberg University came to this conclusion in a study that used computer simulations. The research may offer critical insights into the fusion of two massive stellar objects that astronomers observed in 2019. The findings were published in the journal Communications Physics.

    Stars much more massive than our sun usually end their lives as a neutron star or black hole. Neutron stars emit regular pulses of radiation that allow their detection. In August 2017, for example, when the first double neutron star merger was observed, scientists all around the globe detected light from the explosion with their telescopes. Black holes, on the other hand, usually remain hidden because their gravitational attraction is so strong that even light cannot escape, making them invisible to electromagnetic detectors.

    If two black holes merge, the event may be invisible but is nonetheless detectable from ripples in space-time in the form of so-called gravitational waves. Certain detectors, like the “Laser Interferometer Gravitational Waves Observatory” (LIGO) in the USA, are able to detect these waves. The first successful direct observation was made in 2015. The signal was generated by the fusion of two black holes. But this event may not be the only source of gravitational waves, which could also come from the merger of two neutron stars or a black hole with a neutron star. Discovering the differences is one of the major challenges in observing these events, according to Dr. Arca Sedda.

    In his study, the Heidelberg researcher analysed the fusion of pairs of black holes and neutron stars. He used detailed computer simulations to study the interactions between a system made up of a star and a compact object, such as a black hole, and a third massive roaming object that is required for a fusion. The results indicate that such three-body interactions can in fact contribute to black hole-neutron star mergers in dense stellar regions like globular star clusters. “A special family of dynamic mergers that is distinctly different from mergers in isolated areas can be defined,” explains Manuel Arca Sedda.

    The fusion of a black hole with a neutron star was first observed by gravitational wave observatories in August 2019. Yet optical observatories around the world were unable to locate an electromagnetic counterpart in the region from which the gravitational wave signal originated, suggesting that the black hole had completely devoured the neutron star without first destroying it. If confirmed, this could be the first observed black hole-neutron star merger detected in a dense stellar environment, as described by Dr. Arca Sedda.

    See the full article here .

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    Please help promote STEM in your local schools.

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    About Science X in 100 words
    Science X™ is a leading web-based science, research and technology news service which covers a full range of topics. These include physics, earth science, medicine, nanotechnology, electronics, space, biology, chemistry, computer sciences, engineering, mathematics and other sciences and technologies. Launched in 2004 (Physorg.com), Science X’s readership has grown steadily to include 5 million scientists, researchers, and engineers every month. Science X publishes approximately 200 quality articles every day, offering some of the most comprehensive coverage of sci-tech developments world-wide. Science X community members enjoy access to many personalized features such as social networking, a personal home page set-up, article comments and ranking, the ability to save favorite articles, a daily newsletter, and other options.
    Mission 12 reasons for reading daily news on Science X Organization Key editors and writersinclude 1.75 million scientists, researchers, and engineers every month. Phys.org publishes approximately 100 quality articles every day, offering some of the most comprehensive coverage of sci-tech developments world-wide. Quancast 2009 includes Phys.org in its list of the Global Top 2,000 Websites. Phys.org community members enjoy access to many personalized features such as social networking, a personal home page set-up, RSS/XML feeds, article comments and ranking, the ability to save favorite articles, a daily newsletter, and other options.

     
  • richardmitnick 10:06 am on May 14, 2020 Permalink | Reply
    Tags: , , phys.org   

    From Moscow Institute of Physics and Technology via phys.org: “Where neutrinos come from” 

    1

    From Moscow Institute of Physics and Technology

    via


    phys.org

    May 13, 2020

    1
    The Russian RATAN-600 telescope helps to understand the origin of cosmic neutrinos Credit: Daria Sokol/MIPT

    3
    RATAN-600 ~ The World’s Largest Radio Telescope in Russia

    Russian astrophysicists have come close to determining the origin of high-energy neutrinos from space. The team compared data on the elusive particles gathered by the Antarctic neutrino observatory IceCube and on long electromagnetic waves measured by radio telescopes. Cosmic neutrinos turned out to be linked to flares at the centers of distant active galaxies, which are believed to host supermassive black holes. As matter falls toward the black hole, some of it is accelerated and ejected into space, giving rise to neutrinos that then coast along through the universe at nearly the speed of light.

    The study is published in The Astrophysical Journal.

    Neutrinos are mysterious particles so tiny that researchers do not even know their mass. They pass effortlessly through objects, people and even entire planets. High-energy neutrinos are created when protons accelerate to nearly the speed of light.

    The Russian astrophysicists focused on the origins of ultra-high-energy neutrinos at 200 trillion electron volts or more. The team compared the measurements of the IceCube facility, buried in the Antarctic ice, with a large number of radio observations. The elusive particles were found to emerge during radio frequency flares at the centers of quasars.

    Quasars are sources of radiation at the centers of some galaxies. They consist of a massive black hole that consumes matter floating in a disk around it and spews out extremely powerful jets of ultrahot gas.

    “Our findings indicate that high-energy neutrinos are born in active galactic nuclei, particularly during radio flares. Since both the neutrinos and the radio waves travel at the speed of light, they reach the Earth simultaneously,” said the study’s first author Alexander Plavin.

    Plavin is a Ph.D. student at Lebedev Physical Institute of the Russian Academy of Sciences (RAS) and the Moscow Institute of Physics and Technology. As such, he is one of the few young researchers to obtain results of that caliber at the outset of their scientific career.

    Neutrinos come from where no one had expected

    After analyzing around 50 neutrino events detected by IceCube, the team showed that these particles come from bright quasars seen by a network of radio telescopes around the planet.

    U Wisconsin ICECUBE neutrino detector at the South Pole

    The network uses the most precise method of observing distant objects in the radio band: very long baseline interferometry. This method in essence creates a giant telescope by placing many antennas around the globe. Among the largest elements of this network is the 100-meter telescope of the Max Planck Society in Effelsberg.

    MPIFR/Effelsberg Radio Telescope, in the Ahrgebirge (part of the Eifel) in Bad Münstereifel, Germany

    Additionally, the team hypothesized that the neutrinos emerged during radio flares. To test this idea, the physicists studied the data of the Russian RATAN-600 radio telescope in the North Caucasus. The hypothesis proved highly plausible despite the common assumption that high-energy neutrinos are supposed to originate together with gamma rays.

    “Previous research on high-energy neutrino origins had sought their source right ‘under the spotlight.” We thought we would test an unconventional idea, though with little hope of success. But we got lucky,” says Yuri Kovalev from Lebedev Institute, MIPT, and the Max Planck Institute for Radio Astronomy. “The data from years of observations on international radio telescope arrays enabled that very exciting finding, and the radio band turned out to be crucial in pinning down neutrino origins.”

    “At first, the results seemed too good to be true, but after carefully reanalyzing the data, we confirmed that the neutrino events were clearly associated with the signals picked up by radio telescopes,” Sergey Troitsky from the Institute for Nuclear Research of RAS added. “We checked that association based on the data of years-long observations of the RATAN telescope of the RAS Special Astrophysical Observatory, and the probability of the results being random is only 0.2%. This is quite a success for neutrino astrophysics, and our discovery now calls for theoretical explanations.”

    The team intends to recheck the findings and figure out the mechanism behind the neutrino origins in quasars using the data from Baikal-GVD, an underwater neutrino detector in Lake Baikal, which is in the final stages of construction and already partly operational. The so-called Cherenkov detectors, used to spot neutrinos—including IceCube and Baikal-GVD—rely on a large mass of water or ice as a means of both maximizing the number of neutrino events and preventing the sensors from accidental firing. Of course, continued observations of distant galaxies with radio telescopes are equally crucial to this task.

    See the full article here.

     
  • richardmitnick 11:25 am on May 11, 2020 Permalink | Reply
    Tags: "A tale of two kinds of volcanoes", Aegina, Methana and Poros Islands, phys.org, Santorini Island, Some minerals only form at greater depths., Underneath all these volcanoes at Aegina; Methana; Poros; and Santorini something else is going on in deep inside the crust of planet Earth.   

    From phys.org: “A tale of two kinds of volcanoes” 


    From phys.org

    May 11, 2020
    University of Johannesburg
    1

    2
    Why a big volcanic blow-up at the popular travel destimation Santorini 3200 years ago, but just a few hundred kilometers away, no drama at the volcanoes on Aegina , Methana and Poros islands? Thin sections of the lavas from these four volcanoes yield some of the reasons why. Some minerals only form at greater depths – and the hornblende in the lava from Aegina island indicates that the magma chambers there are deeper than the those underneath the Santorini caldera. But plate tectonics add another, hidden reason also, found research from the University of Johannesburg. Credit: Prof Marlina A. Elburg, University of Johannesburg.

    At an idyllic island in the Mediterranean Sea, ocean covers up the site of a vast volcanic explosion from 3200 years ago. A few hundred kilometers north-west, three other islands still have their volcanic histories from a few million years ago mostly intact. No explosions there. So why the differences between the Santorini caldera and the Aegina, Methana and Poros lava domes? Researchers used volcanic “fingerprints’ and plate tectonics research to find out why.

    The end of a civilisation

    A big volcano blew up about 3200 years ago, right next to where Santorini island is in Greece today. During that eruption, liquid molten rock under the ground (magma) built up immense pressure, and then erupted into a lava explosion. The impact was so intense that the volcano collapsed into a huge basin called a caldera.

    What had been an island-volcano, was then overrun by ocean, an event considered partially responsible for the demise of the Minoan civilisation.

    Santorini Island became a popular travel destination with big ocean-going ships sailing over the caldera. The village of Phira perches on the cliff-edge of the remains of the volcano.

    As idyllic as it looks, the Santorini volcano underneath the ocean still constitutes the biggest volcanic hazard for Europe, together with the Vesuvius volcano in Italy.

    Toothpaste rather than fireworks

    A few hundred kilometers north-west of Santorini, in Greece’s Saronic Gulf, much closer to Athens, a completely different kind of “volcano” looks much less dramatic.

    The small islands of Aegina, Methana and Poros sport rounded hills with roads winding uphill in hairpin bends. These hills have volcanic ancestry too—but they are nothing like Santorini.

    Here, liquid lava didn’t explode in a big eruption.

    “There is no evidence that that large dramatic events ever took place at these islands,” says Prof Marlina A. Elburg, a Geology researcher at the University of Johannesburg.

    “Thick blocky lava oozed out of magma chambers under the ground at these islands between 5.3 to 2.6 million years ago, during the Pliocene. The lava was so thick, it was more like toothpaste or putty than liquid. It formed lava domes rather than lava volcanoes.

    “After a few million years’ worth of weathering, they’re well camouflaged hills, but they are still considered volcanically active,” she says.

    How is it possible that volcanoes so close in geological time and space can behave to differently? The researchers used several techniques to find out.

    Finding volcanic ‘fingerprints’

    Elburg and co-author Ingrid Smet, a Ph.D. candidate at the time, analysed samples of the lavas in new whole rock analyses, in research published in Lithos.

    The study followed on their previous research on the lavas at Methana, also published in Lithos.

    They looked for the ratios of very specific elements in the samples, called isotope signatures. Isotope signatures work similar to ‘fingerprints’ for lavas—they help researchers figure out what the lavas were made of, where, and when they were formed.

    “Mostly the isotope signatures matched what one would expect from where the islands are located in the Aegean volcanic arc,” says Elburg.

    But there were surprises too.

    4
    Why a big volcanic blow-up at the popular travel destimation Santorini 3200 years ago, but just a few hundred kilometers away, no drama at the volcanoes on Aegina , Methana and Poros islands? These islands sit on the edge of the same tectonic plate, so one could expect similar volcanic behaviour. But they have individual histories. Research from the University of Johannesburg delves into the lava mix ingredients and plate tectonics to figure out the differences. Credit: Ms Therese van Wyk, University of Johannesburg.

    Subterranean recycling machine

    Underneath all these volcanoes at Aegina, Methana, Poros and Santorini, something else is going on in deep inside the crust of planet Earth. Running roughly east to west underneath the Mediterranean Sea is the Aegean volcanic arc. This arc is where the African tectonic plate ‘dives under’ the Aegean microplate.

    The ‘diving under’ process is called subduction by geologists. It means that one part of the cool outer crust of Earth starts moving underneath another part of the crust, getting ‘recycled’ inside the hot liquid rock of the Earth’s mantle.

    The islands of Aegina, Methana, Poros and Santorini are not just islands with volcanoes. All of them are an integral part of Earth’s ‘recycling machine’ that keeps renewing the crust underneath the planet’s oceans.

    This raises the question: Why do these islands have such different ‘lava histories’, even though all of them are on the edge of the Aegean plate?

    Some of the answers have to do with what goes into the lava “mixes” for the volcanoes.

    Variable lava mix recipes

    The African plate ‘dives under’ the Aegean plate in an oceanic trench in the Mediterranean Sea. This happens very slowly at a few centimeters per year. Which means the pristine cold basalt of the down-going African plate’s crust has been soaking in ocean water for millions of years before it enters the much warmer magma underneath the over-riding Aegean plate.

    “The crust of the down-going plate now consists of altered rocks, containing minerals with water in them. These minerals become unstable during subduction because of the increasing pressure and temperature, and release their water,” says Elburg.

    “This water lowers the melting point of the mantle, similar to what happens when adding salt to ice. That is why the mantle under the over-riding starts to melt. It is this molten material, or magma, that flows/oozes out of volcanoes/lava domes as lava.”

    Another possible ingredient of the differing lavas is sediments in the oceanic trench at the subduction zone. At the Aegean Arc the down-going plate is covered by a very thick pile of ocean sediments. Some of the sediment is former continental crust.

    A lot of this sediment is ‘scraped off’ when the plate subducts and forms an accretionary (or build-up) wedge. However, some of it is also going down into the mantle and getting mixed with the melting mantle wedge, she says.

    Same plate, different lavas

    Since Aegina, Methana, Poros and Santorini volcanoes are all part of the same subduction zone, the different volcanic activity raises several big questions. One of these is:

    Why the thick blocky lava at the western volcanic centres Aegina, Methana and Poros 2.5 to 2 million years ago, but liquid lava at Santorini 3,200 years ago?

    The answers to this creates other questions about the recycling behaviour of the planet we live on.

    But subduction zones are tricky to study. It’s not possible to go to one of those and come back with some sample materials. Scientists still need more understanding of what role the overriding plate plays; how much interaction there is between ascending magmas and the crust they ascend through; and whether subduction-related magmas obtain their geochemical signature from the sediment that is recycled back into the earth, says Elburg.

    “The answers to these questions can help us understand to what extent the melting processes that started at more than 100 kilometers deep in the mantle, continue when the magma is closer to the surface of the earth,” she says.

    “This process of ‘crustal contamination’ is yet another ‘Earth recycling machine’, which may also influence the potential for ore deposits—like in the Andes, where major copper deposits are found, and where this ‘intracrustal recycling’ is thought to play an important role”.

    5
    Why a big volcanic blow-up at the popular travel destimation Santorini 3200 years ago, but just a few hundred kilometers away, no drama at the volcanoes on Aegina , Methana and Poros islands? At Santorini, the explosion was so intense, the volcano collapsed into a caldera and filled up with ocean. But the other islands have had no such drama. How can volcanoes so close in geological time and space behave so differently? Research from the University of Johannesburg uses lava ‘fingerprints’ and more to find out why. Credit: Prof Marlina A. Elburg, University of Johannesburg.

    Deeper vs shallower

    One way of studying lavas is to put thin slices (called thin sections) under a microscope and identify the minerals. Because minerals need different conditions to form, their presence can say a lot about where and how magmas were mixed.

    In this study the minerals indicated that Santorini lavas were more liquid because they formed at inside shallower magma chambers, while the western volcanic centre lavas were thicker and more blocky because they formed in deeper magma chambers.

    “The thin sections of the Santorini lavas display pyroxenes and significant plagioclase. This indicates that the magma from which the crystals formed was located at shallow depths in the earth,” says Elburg.

    And there is an invisible reason the magma was at shallower depths at Santorini.

    “The tectonic plate above Santorini’s magma chambers is being pulled apart. In geology terms, it is under localised extension. And because the plate is being stretched out and Santorini is in the middle of it, Santorini happens to be at the thinnest part of the plate.

    “With a magma chamber at a shallower depth, the roof will cave in when the chamber starts emptying itself during an eruption. This makes the eruption even worse and creates a caldera, as at Santorini,” she adds.

    No explosions

    In contrast, when they looked at the thin sections of the thick blocky lavas from Aegina and Methana, they found hornblende. The mineral was absent in the Santorini lavas.

    Hornblende can only form if the magma is deep enough in the Earth. This indicates that the magma chambers on Aegina and Methana should be located deeper than on Santorini.

    “With the magma chambers at greater depths for the western Aegina- Methana-Poros volcanoes, that makes for changes in the lava. There the magma chambers underneath the lava domes did not cave in. Additionally, the crystallization of the amphibole mineral group that includes hornblende, makes magma more viscous, or sticky. So it is more difficult for the magma to come to the surface in the first place.

    Over-riding plate vs sediment

    To figure out whether the over-riding plate or the ocean sediments were the bigger factor in creating thick blocky lavas, the researchers analysed specific ‘lava fingerprints’. These radiogenic isotope ratios gave them the best indication on which materials were mixed into the underground magmas for those lavas.

    “We compared Santorini with Aegina-Poros-Methana lavas in terms of their geochemistry on 87Sr/86Sr, 143Nd/144Nd and 208Pb/204Pb. They were distinctly different. Then by combining the radiogenic isotope signature of the lavas with trace element ratios, we managed to pinpoint the down-going sediment as the biggest influence creating thick blocky lavas, not the overriding plate.

    No one lava size

    “We found that Aegina and Methana-Poros have their own individual volcanic histories, even though they’re part of the Aegean arc.

    “This means that a simple one-size-fits-all explanation, based on crustal contamination history, for the difference in eruptive style compared to Santorini does not work.

    “Modern subduction zones are not all alike. Even in one volcanic arc, more than one eruptive style points to differences in subduction processes,” concludes Elburg.

    See the full article here .

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    About Science X in 100 words
    Science X™ is a leading web-based science, research and technology news service which covers a full range of topics. These include physics, earth science, medicine, nanotechnology, electronics, space, biology, chemistry, computer sciences, engineering, mathematics and other sciences and technologies. Launched in 2004 (Physorg.com), Science X’s readership has grown steadily to include 5 million scientists, researchers, and engineers every month. Science X publishes approximately 200 quality articles every day, offering some of the most comprehensive coverage of sci-tech developments world-wide. Science X community members enjoy access to many personalized features such as social networking, a personal home page set-up, article comments and ranking, the ability to save favorite articles, a daily newsletter, and other options.
    Mission 12 reasons for reading daily news on Science X Organization Key editors and writersinclude 1.75 million scientists, researchers, and engineers every month. Phys.org publishes approximately 100 quality articles every day, offering some of the most comprehensive coverage of sci-tech developments world-wide. Quancast 2009 includes Phys.org in its list of the Global Top 2,000 Websites. Phys.org community members enjoy access to many personalized features such as social networking, a personal home page set-up, RSS/XML feeds, article comments and ranking, the ability to save favorite articles, a daily newsletter, and other options.

     
  • richardmitnick 1:35 pm on May 8, 2020 Permalink | Reply
    Tags: "South Africa's MeerKAT solves mystery of 'X-galaxies'", , , , , MeerKAT telescope, phys.org, , The galaxy PKS 2014-55 located 800 million light years from Earth is classified as ‘X-shaped’ because of its appearance in previous relatively blurry images.   

    From SKA South Africa via phys.org: “South Africa’s MeerKAT solves mystery of ‘X-galaxies'” 

    SKA South Africa


    From SKA South Africa

    via


    From phys.org

    May 8, 2020

    1
    The galaxy PKS 2014-55, located 800 million light years from Earth, is classified as ‘X-shaped’ because of its appearance in previous relatively blurry images. The detail provided in this radio image obtained with the MeerKAT telescope indicates that its shape is best described as a ‘double boomerang’. Two powerful jets of radio waves, indicated in blue color, each extend 2.5 million light years into space (comparable to the distance between the Milky Way and the Andromeda galaxy, our nearest major neighbour). Eventually, they are ‘turned back’ by the pressure of tenuous intergalactic gas. As they flow back towards the central galaxy, they are deflected by its relatively high gas pressure into the shorter, horizontal, arms of the boomerang. The background image shows visible light from myriad galaxies in the distant universe. Adapted from W Cotton et al, MNRAS (2020). Credit: NRAO/AUI/NSF; SARAO; DES

    Many galaxies far more active than the Milky Way have enormous twin jets of radio waves extending far into intergalactic space. Normally these go in opposite directions, coming from a massive black hole at the centre of the galaxy. However, a few are more complicated and appear to have four jets forming an ‘X’ on the sky.

    Several possible explanations have been proposed to understand this phenomenon. These include changes in the direction of spin of the black hole at the center of the galaxy, and associated jets, over millions of years; two black holes each associated with a pair of jets; and material falling back into the galaxy being deflected into different directions forming the other two arms of the X.

    Exquisite new MeerKAT observations of one such galaxy, PKS 2014-55, strongly favor the latter explanation as they show material “turning the corner” as it flows back towards the host galaxy; the results have just been accepted for publication in the journal Monthly Notices of the Royal Astronomical Society.

    This work was carried out by a team from the South African Radio Astronomy Observatory (SARAO), the (US) National Radio Astronomy Observatory (NRAO), the University of Pretoria, and Rhodes University.

    Previous studies of these unusual galaxies lacked the high quality imaging provided by the recently completed MeerKAT telescope.

    SKA SARAO Meerkat telescope(s), 90 km outside the small Northern Cape town of Carnarvon, SA

    This telescope array consists of 64 radio dishes located in the Karoo semi-desert in the Northern Cape province of South Africa. Computers combined the data from these antennas into a telescope 8 km in diameter, and provided images in the radio band of unprecedented quality for PKS 2014-55 which enabled solving the mystery of its shape.

    3
    Annotated image showing X-shaped giant radio galaxy PKS 2014-55, observed with the South African Radio Astronomy Observatory’s MeerKAT telescope, indicating the old X-shaped radio jets, the younger jets closer to the central black hole, and the region of influence dominated by the central galaxy’s stars and gas. The curved arrows denote the direction of the backflow that forms the horizontal components of the X. Credit: UP; NRAO/AUI/NSF; SARAO; DES

    Bernie Fanaroff, former director of the SKA South Africa project that built MeerKAT, and a co-author of the study, notes that “MeerKAT was designed to be the best of its kind in the world. It’s wonderful to see how its unique capabilities are contributing to resolving longstanding questions related to the evolution of galaxies.”

    Lead author William Cotton of the NRAO says, “MeerKAT is one of a new generation of instruments whose power solves old puzzles even as it finds new ones—this galaxy shows features never seen before in this detail which are not fully understood.” Further research into these open questions is already underway.

    See the full article here .

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    Please help promote STEM in your local schools.

    Stem Education Coalition

    Australian Square Kilometre Array Pathfinder (ASKAP) is a radio telescope array located at Murchison Radio-astronomy Observatory (MRO) in the Australian Mid West. 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.


    SKA Meerkat telescope, 90 km outside the small Northern Cape town of Carnarvon, SA

    Murchison Widefield Array,SKA Murchison Widefield Array, Boolardy station in outback Western Australia, at the Murchison Radio-astronomy Observatory (MRO)


    SKA Murchison Wide Field Array

    SKA Hera at SKA South Africa

    SKA Pathfinder – LOFAR location at Potsdam via Google Images

    About SKA South Africa

    MeerKAT, originally the Karoo Array Telescope, is a radio telescope consisting of 64 antennas in the Northern Cape of South Africa. In 2003, South Africa submitted an expression of interest to host the Square Kilometre Array (SKA) Radio Telescope in Africa, and the locally designed and built MeerKAT was incorporated into the first phase of the SKA.

    About SKA

    The Square Kilometre Arraywill be the world’s largest and most sensitive radio telescope. The total collecting area will be approximately one square kilometre giving 50 times the sensitivity, and 10 000 times the survey speed, of the best current-day telescopes. The SKA will be built in Southern Africa and in Australia. Thousands of receptors will extend to distances of 3 000 km from the central regions. The SKA will address fundamental unanswered questions about our Universe including how the first stars and galaxies formed after the Big Bang, how dark energy is accelerating the expansion of the Universe, the role of magnetism in the cosmos, the nature of gravity, and the search for life beyond Earth. Construction of phase one of the SKA is scheduled to start in 2016. The SKA Organisation, with its headquarters at Jodrell Bank Observatory, near Manchester, UK, was established in December 2011 as a not-for-profit company in order to formalise relationships between the international partners and centralise the leadership of the project.

    The Square Kilometre Array (SKA) project is an international effort to build the world’s largest radio telescope, led by SKA Organisation. The SKA will conduct transformational science to improve our understanding of the Universe and the laws of fundamental physics, monitoring the sky in unprecedented detail and mapping it hundreds of times faster than any current facility.

    Already supported by 10 member countries – Australia, Canada, China, India, Italy, New Zealand, South Africa, Sweden, The Netherlands and the United Kingdom – SKA Organisation has brought together some of the world’s finest scientists, engineers and policy makers and more than 100 companies and research institutions across 20 countries in the design and development of the telescope. Construction of the SKA is set to start in 2018, with early science observations in 2020.

     
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