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  • richardmitnick 11:03 am on March 19, 2019 Permalink | Reply
    Tags: "Quantum tunnelling is instantaneous researchers find", Cosmos Magazine, , Griffiths’ Australian Attosecond Science Facility,   

    From Griffith University via COSMOS Magazine: “Quantum tunnelling is instantaneous, researchers find” 

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    From Griffith University

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    COSMOS Magazine

    19 March 2019
    Alan Duffy

    Physicists establish that electrons waste no time bashing through a barrier.

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    A diagrammatic representation of quantum tunnelling. Normaals/Getty Images

    Researchers have found that electrons passing through solid matter in a quantum process known as “tunnelling” do so instantaneously.

    The finding, led by scientists from Australia’s Griffith University, contradicts previous experiments [Nature] that suggested a degree of time elapses between the start and finish of a tunnelling event.

    The work is detailed in a paper in the journal Nature.

    Quantum tunnelling is one of the more bizarre differences between our everyday, classical world and the surprising realm of quantum mechanics.

    “If you lean on a wall, that wall pushes back in force so that you don’t go through it,” co-author Robert Sang says.

    “But when you go down to the microscopic level, things behave quite differently. This is where the laws of physics change from classical to quantum.”

    A particle in the quantum world actually can pass through that wall. The experimental question was, how long does it take to transition through a given obstacle – in this case, the electric barrier potential of a hydrogen atom.

    “We use the simplest atom, atomic hydrogen, and we’ve found that there’s no delay in what we can measure,” says Sang.

    The Nature paper is the culmination of a three-year international project, in which the team shot a hydrogen atom and its lone electron with an enormously powerful, ultra-fast laser contained in Griffiths’ Australian Attosecond Science Facility. The laser was circularly polarised, meaning that it imparted a rotation to an emitted electron.

    That resulting rotation in the electron’s “phase” could then be measured as if it were a clock hand ticking around – or in this case, more precisely, an atto-clock.

    “There’s a well-defined point where we can start that interaction, and there’s a point where we know where that electron should come out if it’s instantaneous,” explains Sang.

    “So anything that varies from that time we know that it’s taken that long to go through the barrier. That’s how we can measure how long it takes.

    “It came out to agree with the theory within experimental uncertainty being consistent with instantaneous tunnelling.”

    The precision of the clock to measure the tunnelling event was driven by the ultra-fast pulse of light in the attosecond laser – just a billionth of a billionth of a second long. The energy emitted by the laser during such a tiny amount of time is greater than that of the entire US power grid.

    Sang notes about the attosecond timescale that “it’s hard to appreciate how short that is, but it takes an electron about a hundred attoseconds to orbit a nucleus in an atom”.

    Tunnelling may be an unfamiliar effect in our everyday lives, yet common devices from electron microscopes to computer transistors rely on it.

    “One limitation you might think of is how fast can I make a transistor work – the ultimate limit will be partly about how quickly quantum particles can tunnel,” says Sang.

    “For a classical computer, it implies a limit as to how quickly you can switch a transistor.”

    As we explore the realms, and limits, of these strange quantum mechanical processes, there may be a speed boost for personal computers, too.

    Griffith University Australian Attosecond Science Facility laser

    Griffith University a breakthrough ‘speed test’ in quantum tunnelling

    The researchers have demonstrated that the electron spends no measurable time “under the potential” as it tunnels through the barrier, but noted that these events “are only as ‘instantaneous’ as the electron wave-function collapse that orthodox interpretations of quantum mechanics” predicts.

    This, Sang adds, offers a tantalising possibility of future zeptosecond lasers – which would operate for a period of time a thousand times shorter than an attosecond – “obtaining information on the dynamics of the wave-function collapse itself”. Such a measurement would explore that most fundamental difference of the quantum to the classical world, where common sense expectations break down in the face of wave-functions describing particles.

    See the full article here .

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    Griffith U Campus

    In 1971, Griffith was created to be a new kind of university—one that offered new degrees in progressive fields such as Asian studies and environmental science. At the time, these study areas were revolutionary—today, they’re more important than ever.

    Since then, we’ve grown into a comprehensive, research-intensive university, ranking in the top 5% of universities worldwide. Our teaching and research spans five campuses in South East Queensland and all disciplines, while our network of more than 120,000 graduates extends around the world.

    Griffith continues the progressive traditions of its namesake, Sir Samuel Walker Griffith, who was twice the Premier of Queensland, the first Chief Justice of the High Court of Australia, and the principal author of the Australian Constitution.

     
  • richardmitnick 11:29 am on February 28, 2019 Permalink | Reply
    Tags: "Dark matter detection may involve a pinch of salt", Cosmos Magazine, ,   

    From Stockholm University via COSMOS Magazine: “Dark matter detection may involve a pinch of salt” 

    Stockholm University

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    COSMOS Magazine

    28 February 2019
    Alan Duffy

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    Billion-year-old salt crystals, physicists suggest, could contain conclusive evidence of the existence of dark matter. Allison Achauer/Getty Images.

    Tiny pieces of billion-year-old salt could reveal the existence of dark matter, researchers claim.

    Dark matter is thought to comprise as much as 85% of the universe, but to date billions of dollars spent on high-tech facilities designed to verify its existence have failed to produce unambiguous results.

    Now, a team of physicists headed by Andrzej Drukier from Stockholm University in Sweden suggest a radically different approach.

    Dark matter is thought to be made of subatomic entities known as Weakly Interacting Massive Particles, or, delightfully, WIMPs.

    Current experiments designed to detect them rely on installing huge “target masses”, comprising, for example, 100 tonnes of noble gas, in remote and shielded environments, such as a cave or mine shaft. The targets are then monitored using detectors sensitive enough to pick up the recoil of a nucleus when a WIMP smacks into it.

    Inside the ADMX experiment hall at the University of Washington Credit Mark Stone U. of Washington

    LBNL LZ project at SURF, Lead, SD, USA

    The targets are large in order to maximise the chances of a nucleus-WIMP collision – an event that particle physicists agree happens only very rarely because dark matter and visible, or baryonic, matter don’t often interact. They also have to be shielded because many other subatomic phenomena, such as radioactive decay and the impact of cosmic rays, are so much more common by comparison that dark matter is drowned out by the noise.

    Drukier and colleagues advocate a very, very different approach. In a paper published in the journal Physical Review D, they suggest looking closely at 100-milligram mineral crystals in order to find scars from past collisions.

    “We propose to examine ancient minerals for traces of WIMP-nucleus interactions recorded over timescales as large as [one billion years],” they write.

    The logic is compelling. A 100-tonne mass of noble gas monitored for 10 years might record a given number of dark matter collisions. A mineral speck buried in appropriate circumstances for a billion years may well have recorded more.

    To ensure that dark matter interactions aren’t overwritten by natural radioactive decay or even particles from space, Drukier and colleagues propose using salt crystals that formed deep underwater, called marine evaporites.

    “Such minerals have significantly lower concentrations of radioactive contaminants … than typical minerals found in the Earth’s crust,” they say.

    Dark matter is therefore the only source of these interactions, the physicists say, that can leave scars – nanometre-scale marks – on the crystals that can be detected by state-of-the-art technology.

    “Recoiling nuclei leave damage tracks in certain classes of minerals, so-called solid state track detectors,” they write.

    They propose two methods to identify these scars, depending on the size of dark matter particles – a matter which itself is a matter of considerable debate [Journal of Cosmology and Astroparticle Physics].

    Drukier and colleagues say that the damage left by dark matter particles with a mass equivalent to 10 protons or less could be detected using a technique called helium-ion beam microscopy.

    The scars inflicted by larger dark matter candidate particles, with a mass greater than 10 protons, could be detected by using another approach, known as Small-Angle X-ray scattering.

    The idea that ancient minerals could be a path to verifiable dark matter detection is not new. It was first proposed [Physical Review Letters] by another group of physicists in 1995, using a mineral known as muscovite mica.

    That experiment, however, was limited by the measuring technologies then available – a matter readily admitted by the researchers.

    “We argue that a background may not appear until we have pushed our current limits down by several orders of magnitude,” they concluded.

    More than 20 years later, things have changed.

    Drukier’s team call their proposed set-ups “paleo-detectors”. They concede that, as yet, the idea remains largely theoretical, but propose a next step using minerals obtained from close to the surface and subjecting them to approximated WIMP interactions to demonstrate the feasibility of the approach.

    Indeed, they add that their experiments may in time reveal far more about the universe than just the verification of dark matter.

    “The sensitivity and exposure time also makes paleo-detector interesting for a host of applications beyond WIMP dark matter searches,” they write.

    “Examples include studying the time-variability of the fluxes of cosmic rays, or of neutrinos from the Sun or supernovae. Another example would be the study of proton decay facilitated by the large exposure.”

    See the full article here .


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  • richardmitnick 11:21 am on February 19, 2019 Permalink | Reply
    Tags: 24 radio telescopes from the Low Frequency Array (LOFAR), , , , , , Cosmos Magazine, University of Helsinki   

    From University of Helsinki via COSMOS: “Observations reveal new ‘shape’ for coronal mass ejections” 

    From University of Helsinki

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    COSMOS Magazine

    19 February 2019
    Phil Dooley

    Radiation signatures produced by giant solar storms more complex than previously thought.

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    An artist’s impression of a coronal mass ejection. LV4260/Getty Images

    Astronomers using one of the most sensitive arrays of radio telescopes in the world have caught a huge storm erupting on the sun and observed material flung from it at more than 3000 kilometres a second, a massive shockwave and phenomena known as herringbones.

    In the journal Nature Astronomy, Diana Morosan from the University of Helsinki in Finland and her colleagues report detailed observations of the huge storm, a magnetic eruption known as a coronal mass ejection (CME).

    Unlike the herringbones a biologist might find while dissecting, well, a herring, the team found a data-based version while dissecting the radio waves emitted during the violent event.

    The shape of the fish skeleton emerged when they plotted the frequencies of radio waves as the CME evolved. The spine is a band of emission at a constant frequency, while the vertical offshoot “bones” on either side were sudden short bursts of radiation at a much wider range of frequencies.

    Herringbones have been found in the sun’s radio-wave entrails before, but this is the first time that such a sensitive array of radio telescopes has recorded them. The detailed data enabled Morosan and colleagues for the first time to pin down the origin of the radiation bursts.

    To their surprise, the bones were being created in three different locations, on the sides of the CME.

    “I was very excited when I first saw the results, I didn’t know what to make of them,” Morosan says.

    As the CME erupted, the astronomers were already monitoring the sun, using 24 radio telescopes from the Low Frequency Array (LOFAR) distributed around an area of about 320 hectares near the village of Exloo in The Netherlands.

    ASTRON LOFAR Radio Antenna Bank, Netherlands

    SKA LOFAR core (“superterp”) near Exloo, Netherlands

    “We had seen this really complicated active region – really big ugly sunspots, that had already produced three X-class flares, so we thought we should point LOFAR at it and see if it produces any other eruptions,” explains Morosan.

    A last minute request to the LOFAR director was rewarded with an eight-hour slot on the following Sunday, during which the active region erupted again, emitting X-rays so intense that it was classified as an X-class flare, the most extreme category.

    Flares are caused by turbulence in the plasma that makes up the sun. Plasma is gas that is so hot that the electrons begin to be stripped from the atoms, forming a mixture of charged particles. As it swirls around in the sun the charged particles create magnetic fields. When the turbulence rises the magnetic field lines can get contorted and unstable, a little like a tightly coiled and tangled spring.

    Sometimes the tangled magnetic field suddenly rearranges itself in a violent event called magnetic reconnection, a bit like a coiled spring breaking and thus releasing a lot of trapped energy. It is this energy that powers the flare and propels the plasma out into space to form the CME.

    “The CME is still connected to the solar atmosphere via the magnetic field, so it looks like a giant bubble expanding out,” Morosan says.

    The extreme energy in the CME – the second largest during the sun’s most recent 11-year cycle – accelerated matter away from the sun’s surface to over 3000 kilometres per second, or 1% of the speed of light.

    Because it was so fast the CME formed a shockwave as it travelled through the heliosphere – the atmosphere around the sun. Similar to the sonic boom created by a supersonic aircraft, the shockwave accelerated electrons to extreme speeds and caused them to emit radio waves that Morosan and her colleagues recorded.

    The exact frequency of the radio waves emitted by the electrons depends on the density of their environment. Close to the sun the photosphere density is higher, which creates higher frequency radio waves. The further the electrons are from the sun the lower the frequency of the radio emission.

    So the shape of the herringbones as a plot of frequencies shows where the accelerated electrons are in the sun’s atmosphere.

    The spine represents a constant frequency emission originating from electrons trapped in the shockwave. These escape in bursts from the shock and get funneled along the magnetic field lines on the surface of the CME bubble.

    Some bursts of electrons are funneled back towards the sun. These are the herringbone offshoots to higher frequency, while the ones that get funneled the other way, out into space, create offshoots to lower frequency.

    The sensitivity of the array of radio telescopes allowed the team to clearly identify three sources of herringbone radiation, all of them on the flanks of the CME, not at the front of it, as had been proposed.

    However, the success of the observation was cut short because the timeslot on the LOFAR array came to its end, while the CME was still in full swing.

    “We don’t know what happened after the flare peaked,” Morosan notes. “So we were lucky, and unlucky!”

    See the full article here .

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    U Helsinki main building

    University of Helsinki, Viikki campus focusing on biological sciences

    The University of Helsinki (Finnish: Helsingin yliopisto, Swedish: Helsingfors universitet, Latin: Universitas Helsingiensis, abbreviated UH) is a university located in Helsinki, Finland since 1829, but was founded in the city of Turku (in Swedish Åbo) in 1640 as the Royal Academy of Åbo, at that time part of the Swedish Empire. It is the oldest and largest university in Finland with the widest range of disciplines available. Around 36,500 students are currently enrolled in the degree programs of the university spread across 11 faculties and 11 research institutes.

    As of 1 August 2005, the university complies with the harmonized structure of the Europe-wide Bologna Process and offers Bachelor, Master, Licenciate, and Doctoral degrees. Admission to degree programmes is usually determined by entrance examinations, in the case of bachelor’s degrees, and by prior degree results, in the case of master and postgraduate degrees. Entrance is particularly selective (circa 15% of the yearly applicants are admitted). It has been ranked a top 100 university in the world according to the 2016 ARWU, QS and THE rankings.

    The university is bilingual, with teaching by law provided both in Finnish and Swedish. Since Swedish, albeit an official language of Finland, is a minority language, Finnish is by far the dominating language at the university. Teaching in English is extensive throughout the university at Master, Licentiate, and Doctoral levels, making it a de facto third language of instruction.

    Remaining true to its traditionally strong Humboldtian ethos, the University of Helsinki places heavy emphasis on high-quality teaching and research of a top international standard. It is a member of various prominent international university networks, such as Europaeum, UNICA, the Utrecht Network, and is a founding member of the League of European Research Universities.

     
  • richardmitnick 10:32 am on December 4, 2018 Permalink | Reply
    Tags: , , , , Cosmos Magazine, , First stars may have been in massive dark matter halos, Institute for Advanced Study in Princeton New Jersey US, New observations challenge universe model   

    From COSMOS Magazine: “New observations challenge universe model” 

    Cosmos Magazine bloc

    From COSMOS Magazine

    04 December 2018
    Lauren Fuge

    First stars may have been in massive dark matter halos.

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    The cosmic microwave background, captured by NASA’s Wilkinson Microwave Anistropy Probe. NASA

    Observations of the very first stars to form might change accepted models of the dawn of the universe.

    A team of astronomers led by Alexander Kaurov of the Institute for Advanced Study in New Jersey, US, says these observations may indicate that the majority of the first stellar generation were located in rare and massive dark matter halos.

    First, though, a quick cosmology refresher.

    Current models tell us that for almost 400,000 years after the Big Bang, the universe was so hot that atoms couldn’t form yet. All that existed was a searing soup of plasma, with photons trapped within it like a fog. But when the universe finally cooled enough for protons and electrons to combine into hydrogen atoms, those photons escaped.

    Today, this jailbreak radiation is known as the cosmic microwave background (CMB). It’s like the universe’s baby photo, and by studying it and the tiny fluctuations within it, we can learn about the system’s infancy and how stars and galaxies began to form.

    The first generation of stars appear so faint and distant that they’re difficult to detect directly. However, astronomers theorised that these stars emitted ultraviolet radiation that heated up the gas around them, which in turn absorbed some of CMB – at radio wavelengths of 21 centimetres, to be specific.

    In March 2018, the Experiment to Detect the Global Epoch of Reionization Signature (EDGES) detected this signal as a small distortion in the CMB, like a fingerprint of the first stars.

    EDGES telescope in a radio quiet zone at the Murchison Radio-astronomy Observatory in Western Australia.

    But upon analysis, the EDGES team realised that the signal’s shape was much deeper than predicted, with sharper boundaries.

    Any number of studies have since attempted to explain the unexpected depth, using new physics or astrophysics. Now, Kaurov’s team at the US Institute for Advanced Study has tackled the signal’s sharp boundaries.

    In a study published in The Astrophysical Journal Letters, he and co-authors argue that this feature indicates that as the first stars lit up, ultraviolet photons flooded the universe much more quickly than expected. The team’s computer simulations showed that this suddenness would occur naturally if the first stars were concentrated in the most massive and rarest dark matter halos – rather than distributed evenly throughout the universe as previously thought.

    These halos, weighing over a billion times more than our Sun, exploded in number in the universe’s infancy and could have easily produced the huge influx of ultraviolet photons necessary to explain the EDGES signal.

    If this scenario is correct, then these rare halos might be bright enough to be observed by the James Webb Space Telescope, which will launch in 2021.

    Time, thus, in more ways than one, will tell.

    See the full article here .


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  • richardmitnick 12:20 pm on November 7, 2018 Permalink | Reply
    Tags: , , , , Cosmos Magazine, Demonstrated that there is an upper limit – now called the Chandrasekhar limit – to the mass of a white dwarf star, ,   

    From COSMOS Magazine: “Science history: The astrophysicist who defined how stars behave” Subrahmanyan Chandrasekhar 

    Cosmos Magazine bloc

    From COSMOS Magazine

    07 November 2018
    Jeff Glorfeld

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    Subrahmanyan Chandrasekhar meets the press in 1983, shortly after winning the Nobel Prize. Bettmann / Contributor / Getty Images

    Subrahmanyan Chandrasekhar was so influential, NASA honoured him by naming an orbiting observatory after him.

    NASA/Chandra X-ray Telescope

    The NASA webpage devoted to astrophysicist Subrahmanyan Chandrasekhar says he “was known to the world as Chandra. The word chandra means ‘moon’ or ‘luminous’ in Sanskrit.”

    Subrahmanyan Chandrasekhar was born on October 19, 1910, in Lahore, Pakistan, which at the time was part of British India. NASA says that he was “one of the foremost astrophysicists of the 20th century. He was one of the first scientists to couple the study of physics with the study of astronomy.”

    The Encyclopaedia Britannica adds that, with William A. Fowler, he won the 1983 Nobel Prize for physics, “for key discoveries that led to the currently accepted theory on the later evolutionary stages of massive stars”.

    According to an entry on the website of the Harvard-Smithsonian Centre for Astrophysics, early in his career, between 1931 and 1935, he demonstrated that there is an upper limit – now called the Chandrasekhar limit – to the mass of a white dwarf star.

    “This discovery is basic to much of modern astrophysics, since it shows that stars much more massive than the Sun must either explode or form black holes,” the article explains.

    When he first proposed his theory, however, it was opposed by many, including Albert Einstein, “who refused to believe that Chandrasekhar’s findings could result in a star collapsing down to a point”.

    Writing for the Nobel Prize committee, Chandra described how he approached a project.

    “My scientific work has followed a certain pattern, motivated, principally, by a quest after perspectives,” he wrote.

    “In practice, this quest has consisted in my choosing (after some trials and tribulations) a certain area which appears amenable to cultivation and compatible with my taste, abilities, and temperament. And when, after some years of study, I feel that I have accumulated a sufficient body of knowledge and achieved a view of my own, I have the urge to present my point of view, ab initio, in a coherent account with order, form, and structure.

    “There have been seven such periods in my life: stellar structure, including the theory of white dwarfs (1929-1939); stellar dynamics, including the theory of Brownian motion (1938-1943); the theory of radiative transfer, including the theory of stellar atmospheres and the quantum theory of the negative ion of hydrogen and the theory of planetary atmospheres, including the theory of the illumination and the polarisation of the sunlit sky (1943-1950); hydrodynamic and hydromagnetic stability, including the theory of the Rayleigh-Benard convection (1952-1961); the equilibrium and the stability of ellipsoidal figures of equilibrium, partly in collaboration with Norman R. Lebovitz (1961-1968); the general theory of relativity and relativistic astrophysics (1962-1971); and the mathematical theory of black holes (1974- 1983).”

    In 1999, four years after his death on August 21, 1995, NASA launched an x-ray observatory named Chandra, in his honour. The observatory studies the universe in the x-ray portion of the electromagnetic spectrum.

    See the full article here .


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  • richardmitnick 12:55 pm on September 24, 2018 Permalink | Reply
    Tags: , , , , Cosmos Magazine, , ,   

    From COSMOS Magazine: “A galactic near-miss set stars on an unexpected path around the Milky Way” 

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    From COSMOS Magazine

    24 September 2018
    Ben Lewis

    A close pass from the Sagittarius dwarf galaxy sent ripples through the Milky Way that are still visible today.

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    Image Credit: R. Ibata (UBC), R. Wyse (JHU), R. Sword (IoA)

    Milky Way NASA/JPL-Caltech /ESO R. Hurt

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    Tiny galaxy; big trouble. Gaia imaging shows the Sagittarius galaxy, circled in red. ESA/Gaia/DPAC

    ESA/GAIA satellite

    Between 300 and 900-million years ago the Sagittarius dwarf galaxy made a close pass by the Milky Way, setting millions of stars in motion, like ripples on a pond. The after-effects of that galactic near miss are still visible today, according to newly published findings.

    The unique pattern of stars left over from the event was detected by the European Space Agency’s star mapping mission, Gaia. The details are contained in a paper written by Teresa Antoja and colleagues from the Universitat de Barcelona in Spain, and published in the journal Nature.

    The movements of over six million stars in the Milky Way were tracked by Gaia to reveal that groups of them follow different courses as they orbit the galactic centre.

    In particular, the researchers found a pattern that resembled a snail shell in a graph that plotted star altitudes above or below the plane of the galaxy, measured against their velocity in the same direction. This is not to say that the stars themselves are moving in a spiral, but rather that the roughly circular orbits correlate with up-and-down motion in a pattern that has never been seen before.

    While some perturbations in densities and velocities had been seen previously, it was generally assumed that the movement of the disk’s stars is largely in dynamic equilibrium and symmetry about the galactic plane. Instead, Antoja’s team discovered something had knocked the disk askew.

    “It is a bit like throwing a stone in a pond, which displaces the water as ripples and waves,” she explains.

    Whereas water will eventually settle out after being disturbed, a star’s motion carries signatures from the change in movement. While the ripples in the distribution caused by Sagittarius passing by has evened out, the motion of the stars themselves still carry the pattern.

    “At the beginning the features were very weird to us,” says Antoja. “I was a bit shocked and I thought there could be a problem with the data because the shapes are so clear.”

    The new revelations came about because of a huge increase in quality of the Gaia data, compared to what had been captured previously. The new information provided, for the first time, a measurement of three-dimensional speeds for the stars. This allowed the study of stellar motion using the combination of position and velocity, known as “phase space”.

    “It looks like suddenly you have put the right glasses on and you see all the things that were not possible to see before,” says Antoja.

    Computer models suggest the disturbance occurred between 300 and 900 million years ago – a point in time when it’s known the Sagittarius galaxy came near ours.

    In cosmic terms, that’s not very long ago, which also came as a surprise. It was known that the Milky Way had endured some much earlier collisions – smashing into a dwarf galaxy some 10 billion years ago, for instance – but until now more recent events had not been suspected. The Gaia results have changed that view.

    See the full article here .


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  • richardmitnick 8:39 am on September 18, 2018 Permalink | Reply
    Tags: , Cosmos Magazine, , , , , Super-Kamioka Neutrino Detection Experiment at Kamioka Observatory Tokyo Japan   

    From COSMOS Magazine: “Hints of a fourth type of neutrino create more confusion” 

    Cosmos Magazine bloc

    From COSMOS Magazine

    18 September 2018
    Katie Mack

    Anomalous experimental results hint at the possibility of a fourth kind of neutrino, but more data only makes the situation more confusing.

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    Inside the Super-Kamioka Neutrino Detection Experiment at Kamioka Observatory, Tokyo, Japan. Credit: Kamioka Observatory, ICRR (Institute for Cosmic Ray Research), The University of Tokyo

    It was a balmy summer in 1998 when I first became aware of the confounding weirdness of neutrinos. I have vivid memories of that day, as an embarrassingly young student researcher, walking along a river in Japan, listening to a graduate student tell me about her own research project: an attempt to solve a frustrating neutrino–related mystery. We were both visiting a giant detector experiment called Super-Kamiokande, in the heady days right after it released data that forever altered the Standard Model of Particle Physics.

    The Standard Model of elementary particles (more schematic depiction), with the three generations of matter, gauge bosons in the fourth column, and the Higgs boson in the fifth.


    Standard Model of Particle Physics from Symmetry Magazine

    What Super-K found was that neutrinos – ghostly, elusive particles that are produced in the hearts of stars and can pass through the whole Earth with only a miniscule chance of interacting with anything – have mass.

    A particle having mass might not sound like a big deal, but the original version of the otherwise fantastically successful Standard Model described neutrinos as massless – just like photons, the particles that carry light and other electromagnetic waves. Unlike photons, however, neutrinos come in three ‘flavours’: electron, muon, and tau.

    Super-K’s discovery was that neutrinos could change from one flavour to another as they travelled, in a process called oscillation. This can only happen if the three flavours have different masses from one another, which means they can’t be massless.

    The finding suggested there must be a fourth neutrino, one invisible in experiments.

    This discovery was a big deal, but it wasn’t the mystery the grad student was working to solve. A few years before, an experiment called the Liquid Scintillator Neutrino Detector (LSND), based in the US, had seen tantalising evidence that neutrinos were oscillating in a way that made no sense at all with the results of other experiments, including Super-K. The LSND finding indirectly suggested there had to be a fourth neutrino in the picture that the other neutrinos were sometimes oscillating into. This fourth neutrino would be invisible in experiments, lacking the kind of interactions that made the others detectable, which gave it the name ‘sterile neutrino’. And it would have to be much more massive than the other three.

    As I learned that day by the river, the result had persisted, unexplained, for years. Most people assumed something had gone wrong with the experiment, but no one knew what.

    In 2007, the plot thickened. An experiment called MiniBooNE, designed primarily to figure out what the heck happened with LSND, didn’t find the distribution of neutrinos it should have seen to confirm the LSND result.

    FNAL/MiniBooNE

    But some extra neutrinos did show up in MiniBooNE in a different energy range. They were inconsistent with LSND and every other experiment, perhaps suggesting the existence of even more flavours of neutrino.

    Meanwhile, experiments looking at neutrinos produced by nuclear reactors were seeing numbers that also couldn’t easily be explained without a sterile neutrino, though some physicists wrote these off as possibly due to calibration errors.

    And now the plot has grown even thicker.

    In May, MiniBooNE announced new results that seem more consistent with LSND, but even less palatable in the context of other experiments. MiniBooNE works by creating a beam of muon neutrinos and shooting them through the dirt at an underground detector 450 m away. The detector, meanwhile, is monitoring the arrival of electron neutrinos, in case any muon neutrinos are shape-shifting. More of these electron neutrinos turn up than standard neutrino models predict, which implies that some muon neutrinos transform by oscillating into sterile neutrinos too. (Technically, all neutrinos would be swapping around with all others, but this beam only makes sense if there’s an extra, massive one in the mix.)

    But there are several reasons this explanation is facing resistance. One is that experiments just looking for muon neutrinos disappearing (becoming sterile neutrinos or anything else) don’t find a consistent picture. Secondly, if sterile neutrinos at the proposed mass exist, they should have been around in the very early universe, and measurements we have from the cosmic microwave background of the number of neutrino types kicking around then strongly suggest it was just the normal three.

    So, as usual, there’s more work to be done. A MiniBooNE follow-up called MicroBooNE is currently taking data and might make the picture clearer, and other experiments are on the way.

    FNAL/MicroBooNE

    It seems very likely that something strange is happening in the neutrino sector. It just remains to be seen exactly what, and how, over the next 20 years of constant neutrino bombardment, it will change our understanding of everything else.

    See the full article here .


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  • richardmitnick 8:19 am on September 18, 2018 Permalink | Reply
    Tags: , Cosmos Magazine, , Earth’s most volcanic places   

    From COSMOS Magazine: “Earth’s most volcanic places” 

    Cosmos Magazine bloc

    From COSMOS Magazine

    18 September 2018
    Vhairi Mackintosh

    Some countries are famous for images of spewing lava and mountainous destruction. However, appearances can be deceiving. Not all volcanoes are the same.

    1
    Credit Stocktrek Images / Getty Images

    Volcanic activity. It’s the reason why the town of El Rodeo in Guatemala is currently uninhabitable, why the Big Island of Hawaii gained 1.5 kilometres of new coastline in June, and why Denpasar airport in Bali has closed twice this year.

    But these eruptions should not be seen as destructive attacks on certain places or the people that live in them. They have nothing to do with even the country that hosts them. They occur in specific regions because of much larger-scale processes originating deep within the Earth.

    According to the United States Geological Survey (USGS), approximately 1,500 potentially active volcanoes exist on land around the globe. Here’s a look at four of the world’s most volcanically active spots, and the different processes responsible for their eruptions. As you’ll see, there is no one-size-fits-all volcano.

    ICELAND

    Most volcanic eruptions go unnoticed. That’s because they happen continuously on the ocean floor where cracks in the Earth’s outer layer, the lithosphere (comprising the crust and solid upper mantle), form at so-called divergent plate boundaries. These margins form due to convection in the underlying mantle, which causes hot, less dense molten material, called magma, to rise to the surface. As it forces its way through the lithospheric plate, magma breaks the outer shell. Lava, the surface-equivalent of magma, fills the crack and pushes the broken pieces in opposite directions.

    Volcanism from this activity created Iceland. The country is located on the Mid-Atlantic Ridge, which forms the seam between the Eurasian and North American plates. Iceland is one of the few places where this type of spreading centre pops above sea level.

    However, volcanism on Iceland also happens because of its location over a hot spot. These spots develop above abnormally hot, deep regions of the mantle known as plumes.

    Each plume melts the overlying material and buoyant magma rises through the lithosphere – picture a lava lamp – to erupt at the surface.

    This volcanic double whammy produces both gentle fissure eruptions of basaltic lava as well as stratovolcanoes that are characterised by periodic non-explosive lava flows and explosive, pyroclastic eruptions, which produce clouds of ash, gas and debris.

    In 2010, the two-month eruption of the ice-capped Eyjafjallajökull stratovolcano – the one that no one outside Iceland can pronounce – attracted a lot of media attention because the resulting ash cloud grounded thousands of flights across Europe.

    3
    Eruption at Fimmvörðuháls at dusk. Boaworm

    In fact, it was a relatively small eruption. It is believed that a major eruption in Iceland is long overdue. Four other volcanoes are all showing signs of increased activity, including the country’s most feared one, called Katla.

    3
    Credit: Westend61 / Getty Images

    4
    Photograph of Katla volcano erupting through Mýrdalsjökull ice cap in 1918. ICELANDIC GLACIAL LANDSCAPES
    Author Public Domain

    INDONESIA

    More than 197 million Indonesians live within 100 km of a volcano, with nearly nine million of those within 10 km. Indonesia has more volcanoes than any other country in the world. The 1815 eruption of its Mount Tambora still holds the record for the largest in recent history.

    Indonesia is one of many places located within the world’s most volcanically, and seismically, active zone, known as the Pacific Ring of Fire. This 40,000 km horseshoe-shaped region, bordering the Pacific Ocean, is where many tectonic plates bang into each other.

    In this so-called convergent plate boundary setting, the process of subduction generates volcanism. Subduction occurs because when two plates collide, the higher density plate containing oceanic crust sinks beneath another less dense plate, which contains either continental crust or younger, hotter and therefore less dense oceanic crust. As the plate descends into the mantle, it releases fluids that trigger melting of the overriding plate, thus producing magma. This then rises and erupts at the surface to form an arc-shaped chain of volcanoes, inward of, but parallel to, the subducting plate margin.

    Indonesia marks the junction between many converging plates and, thus, the subduction processes and volcanism are complex. Most of Indonesia’s volcanoes, however, are part of the Sundra Arc, an island volcanic range caused by the subduction of the Indo-Australian Plate beneath the Eurasian Plate. Volcanism in eastern Indonesia is mainly caused by the subduction of the Pacific Plate under the Eurasian Plate.

    The stratovolcanoes that form in convergent plate boundary settings are the most dangerous because they are characterised by incredibly fast, highly explosive pyroclastic flows. One of Indonesia’s stratovolcanoes, Mount Agung, erupted on 29 June for the second time in a year, spewing ash more than two km into the air and grounding hundreds of flights to the popular tourist destination, Bali.

    5
    Mount Agung, November 2017 eruption – 27 Nov 2017. Michael W. Ishak (http://www.myreefsdiary.com)

    6
    Credit: shayes17 / Getty Images

    GUATEMALA

    The June 3 eruption of the Guatemalan stratovolcano, Volcan de Fuego (Volcano of Fire), devastated Guatemalans, and the rest of the world, as horrifying images and videos of people trying to escape the quick-moving pyroclastic flow filled the news.

    Like Indonesia, Guatemala’s location within the Ring of Fire and the subduction-related processes that go along with its location are responsible for the volcanoes found here. Located on the other side of the Pacific Ocean, volcanism is caused by the subduction of the much smaller Cocos Plate beneath the North American-Caribbean Plate.

    Unlike Indonesia, however, the convergent boundary between these two plates occurs on land instead of within the ocean. Therefore, the Guatemalan arc does not form islands but a northwest-southeast trending chain of onshore volcanoes.

    The same process is responsible for the formation of the Andes – the world’s longest continental mountain range – further south along the western coast of South America. In this case, subduction of the Nazca-Antarctic Plate beneath the South American Plate causes volcanism in countries such as Chile and Peru.

    7
    October 1974 eruption of Volcán de Fuego — seen from Antigua Guatemala, Guatemala. Paul Newton, Smithsonian Institution

    7
    Credit: ShaneMyersPhoto / Getty Images

    HAWAII

    When someone mentions Hawaii, it’s hard not to picture a volcano. But Hawaii’s volcanoes are actually not typical. That’s because they are not found on a plate boundary. In fact, Hawaii is slap-bang in the middle of the Pacific Plate – the world’s largest.

    Like Iceland, Hawaii is also underlain by a hot spot. However, because the Pacific Plate is moving to the northwest over this relatively fixed mantle anomaly, the resulting volcanism creates a linear chain of islands within the Pacific Ocean. A volcano forming over the hot spot will be carried away, over millions of years, by the moving tectonic plate. As a new volcano begins to form, the older one becomes extinct, cools and sinks to form a submarine mountain. Through this process, the islands of Hawaii have been forming for the past 70 million years.

    The typical shield volcanoes that form in this geological setting are produced from gentle eruptions of basaltic lava and are rarely explosive. The youngest Hawaiian shield volcano, Kilauea, erupted intensely on 3 May of this year, and 1,170 degree Celsius lava has been flowing over the island and into the ocean ever since. Kilauea, which has been continuously oozing since 1983, is regarded as one of the world’s most active volcanoes, if not the most.

    9
    Looking up the slope of Kilauea, a shield volcano on the island of Hawaii. In the foreground, the Puu Oo vent has erupted fluid lava to the left. The Halemaumau crater is at the peak of Kilauea, visible here as a rising vapor column in the background. The peak behind the vapor column is Mauna Loa, a volcano that is separate from Kilauea. USGS

    9
    An aerial view of the erupting Pu’u ‘O’o crater on Hawaii’s Kilauea volcano taken at dusk on June 29, 1983.
    Credit: G.E. Ulrich, USGS

    AND THE WORLD’S LEAST VOLCANIC PLACE?

    It may be surprising to hear that despite the Himalayas, like the Andes, being located on a very active convergent plate boundary, they are not volcanically active. In fact, there are barely any volcanoes at all within the mountain range.

    This is because the two colliding plates that are responsible for the formation of the Himalayas contain continental crust at the convergent plate boundary, distinct from the oceanic-continental or oceanic-oceanic crustal boundaries in the Guatemalan and Indonesian cases, respectively.

    As the two colliding plates have similar compositions, and therefore densities, and both their densities are much lower than the underlying mantle, neither plate is subducted. It’s a bit like wood floating on water. As subduction causes the lithospheric partial melting that generates the magma in convergent plate boundary settings, volcanism is not common in continent-continent collisions.

    Unfortunately, Himalayan people don’t get off that easily though, because devastating earthquakes go hand-in-hand with this sort of setting.

    See the full article here .


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  • richardmitnick 8:48 am on August 20, 2018 Permalink | Reply
    Tags: , , , , Cosmos Magazine, , KELT-9b   

    From IAC via COSMOS: “The planet KELT-9b literally has an iron sky” 

    IAC

    From Instituto de Astrofísica de Canarias – IAC

    via

    COSMOS

    20 August 2018
    Ben Lewis

    1
    The Gran Telescopio Canarias on Las Palma in the Canary Islands was instrumental in determining the constituents of the exoplanet’s atmosphere. Dominic Dähncke/Getty Images

    KELT-9b, one of the most unlikely planets ever discovered, has surprised astronomers yet again with the discovery that its atmosphere contains the metals iron and titanium, according to research published in the journal Nature.

    2
    NASA/JPL-Caltech

    The planet is truly like no other. Located around 620 light-years away from Earth in the constellation Cygnus, it is known as a Hot Jupiter – which gives a hint to its nature. Nearly three times the size of Jupiter, its surface temperature tops 3780 degrees Celsius – the hottest exoplanet ever discovered. It is even hotter than the surface of some stars. In some ways it straddles the line between a star and a gas-giant exoplanet.

    And it’s that super-hot temperature, created by a very close orbit to its host star, that allows the metals to become gaseous and fill the atmosphere, say the findings from a team led by Jens Hoeijmakers of the University of Geneva in Switzerland.

    On the night of 31 July 2017, as KELT-9b passed across the face of its star, the HARPS-North spectrograph attached to the Telescopio Nazionale Galileo, located the Spanish Canary Island of La Palma, began watching. The telescope recorded changes in colour in the planet’s atmosphere, the result of chemicals with different light-filtering properties.

    Telescopio Nazionale Galileo – Harps North


    Telescopio Nazionale Galileo a 3.58-meter Italian telescope, located at the Roque de los Muchachos Observatory on the island of La Palma in the Canary Islands, Spain, Altitude 2,396 m (7,861 ft)

    By subtracting the plain starlight from the light that had passed through the atmosphere, the team were left with a spectrograph of its chemical make-up.

    They then homed in on titanium and iron, because the relative abundances of uncharged and charged atoms tend to change dramatically at the temperatures seen on KELT-9b. After a complex process of analysis and cross-correlation of results, they saw dramatic peaks in the ionised forms of both metals.

    It has been long suspected that iron and titanium exist on some exoplanets, but to date they have been difficult to detect. Somewhat like Earth, where the two elements are mostly found in solid form, the cooler conditions of most exoplanets means that the iron and titanium atoms are generally “trapped in other molecules,” as co-author Kevin Heng from the University of Bern in Switzerland recently told Space.com.

    However, the permanent heatwave on KELT-9b means the metals are floating in the atmosphere as individual charged atoms, unable to condense or form compounds.

    While this is the first time iron has been detected in an exoplanet’s atmosphere, titanium has previously been detected in the form of titanium dioxide on Kepler 13Ab, another Hot Jupiter. The discovery on KELT-9b however, is the first detection of elemental titanium in an atmosphere.

    KELT-9b’s atmosphere is also known to contain hydrogen, which was easily identifiable without requiring the type of complex analysis needed to identify iron and titanium. However, a study in July [Nature Astronomy] found that the hydrogen is literally boiling off the planet, leading to the hypothesis that its escape could also be dragging the metals higher into the atmosphere, making their detection easier.

    Further studies into KELT-9b’s atmosphere are continuing, with suggestions that announcements of other metals could be forthcoming. In addition, the complex analysis required in this study could be useful for identifying obscure components in the atmospheres of other planets.

    See the full article here.


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    Please help promote STEM in your local schools.


    Stem Education Coalition

    The Instituto de Astrofísica de Canarias(IAC) is an international research centre in Spain which comprises:

    The Instituto de Astrofísica, the headquarters, which is in La Laguna (Tenerife).
    The Centro de Astrofísica en La Palma (CALP)
    The Observatorio del Teide (OT), in Izaña (Tenerife).
    The Observatorio del Roque de los Muchachos (ORM), in Garafía (La Palma).

    Roque de los Muchachos Observatory is an astronomical observatory located in the municipality of Garafía on the island of La Palma in the Canary Islands, at an altitude of 2,396 m (7,861 ft)

    These centres, with all the facilities they bring together, make up the European Northern Observatory(ENO).

    The IAC is constituted administratively as a Public Consortium, created by statute in 1982, with involvement from the Spanish Government, the Government of the Canary Islands, the University of La Laguna and Spain’s Science Research Council (CSIC).

    The International Scientific Committee (CCI) manages participation in the observatories by institutions from other countries. A Time Allocation Committee (CAT) allocates the observing time reserved for Spain at the telescopes in the IAC’s observatories.

    The exceptional quality of the sky over the Canaries for astronomical observations is protected by law. The IAC’s Sky Quality Protection Office (OTPC) regulates the application of the law and its Sky Quality Group continuously monitors the parameters that define observing quality at the IAC Observatories.

    The IAC’s research programme includes astrophysical research and technological development projects.

    The IAC is also involved in researcher training, university teaching and outreachactivities.

    The IAC has devoted much energy to developing technology for the design and construction of a large 10.4 metre diameter telescope, the ( Gran Telescopio CANARIAS, GTC), which is sited at the Observatorio del Roque de los Muchachos.



    Gran Telescopio Canarias at the Roque de los Muchachos Observatory on the island of La Palma, in the Canaries, SpainGran Telescopio CANARIAS, GTC

     
  • richardmitnick 10:23 am on August 17, 2018 Permalink | Reply
    Tags: A step closer to a theory of quantum gravity, Cosmos Magazine   

    From COSMOS Magazine: “A step closer to a theory of quantum gravity” 

    Cosmos Magazine bloc

    From COSMOS Magazine

    17 August 2018
    Phil Dooley

    1
    Resolving differences between the theory of general relativity and the predictions of quantum physics remains a huge challenge. Credit: diuno / Getty Images

    A new approach to combining Einstein’s General Theory of Relativity with quantum physics could come out of a paper published in the journal Nature Physics. The insights could help build a successful theory of quantum gravity, something that has so far eluded physicists.

    Magdalena Zych from University of Queensland in Australia and Caslav Brukner from University of Vienna in Austria have devised a set of principles that compare the way objects behave as predicted by Einstein’s theory with their behaviour predicted by quantum theory.

    Quantum physics has very successfully described the behaviour of tiny particles such as atoms and electrons, while relativity is very accurate for forces at cosmic scales. However, in some cases, notably gravity, the two theories produce incompatible results.

    Einstein’s theory revolutionised the concept of the gravity, by showing that it was caused by curves in spacetime rather than by a force. In contrast, quantum theory has successfully shown other forces, such as magnetism, are the result of fleeting particles being exchanged between interacting objects.

    The difference between the two cases throws up a surprising question: do objects attracted by electrical or magnetic forces behave the same way as when attracted by the gravity of a nearby planet?

    In physics language, an object’s inertial mass and its gravitational mass are held to be the same, a property known as the Einstein equivalence principle. But, given that the two theories are so different, it is not clear that the idea still holds at the quantum level.

    Zych and Brukner combined two principles to formulate the problem. From relativity they took the equation E=MC2, which holds that when objects gain more energy they become heavier. This even applies to an atom moving from a low energy level to a more excited state.

    To this they added the principle of quantum superposition, which holds that particles can be smeared into more than one state at once. And since the different energy levels have different masses, then the total mass gets smeared across a range of values, too.

    This prediction allowed the pair to propose tests that would tease out the quantum behaviour of gravitational acceleration.

    “For example, for an object in freefall in a superposition of accelerations, quantum correlations – entanglement – would develop between the internal states of the particle and their position,” Zych explains.

    “So, the particle would actually smear across space as it falls, which would violate the equivalence principle.”

    As most current theories of quantum gravity predict that the equivalence principle will indeed be violated, the tests proposed by Zych and Brukner could help evaluate whether these approaches are on the right track.

    Zych was inspired to tackle the problem when thinking about a variant of Einstein’s “twin paradox”. This arises as a consequence of relativity, and says that one twin travelling at high speed will age more slowly than the other, who remains stationary.

    Instead, Zych imagined kind of quantum conjoined twins, built from the quantum superposition of two different energy states – and therefore two superposed masses.

    “It was surprising to find these corners of quantum physics that have not been explored before,” Zych says.

    She estimates the difference caused by the quantum behaviour of an atom interacting with a visible wavelength laser would be around one part in 10^11.

    An Italian group has already begun work on such experiments and found no deviation from the equivalence principle up to one part in 109.

    If Einstein’s work does turn out to be violated, it could have consequences for the use of quantum systems as very precise atomic clocks.

    “If the Einstein principle was violated only as allowed in classical physics, clocks could fail to be time-dilated, as predicted by relativity,” says Zych.

    “But if it is violated as allowed in quantum theory, clocks would generically cease to be clocks at all.”

    See the full article here .


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