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  • richardmitnick 9:16 am on January 15, 2018 Permalink | Reply
    Tags: , , , Citizen Science Exoplanet Explorers, , COSMOS, K2-138, Music of the spheres: chain of planets rotates at “perfect fifth” intervals, Zooniverse   

    From COSMOS Magazine: “Music of the spheres: chain of planets rotates at “perfect fifth” intervals” 

    Cosmos Magazine bloc

    COSMOS Magazine

    15 January 2018
    Richard A Lovett

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    In 1619 Johannes Kepler calculated the “divine” musical scales of the planets in the solar system. Now citizen science has found a strong musical equivalence in a chain of newly discovered exoplanets. Photo 12/UIG via Getty Images.

    With the help of citizen scientists, exoplanet hunters have made one of their most unusual discoveries yet: a system called K2-138 that contains five planets orbiting in near-perfect resonances so close to their star that all five orbits are less than 13 days.

    Orbital resonances occur when planetary orbits are spaced so that they circle their star in numerically related patterns. In the case of K2-138, this resonance is close to 3:2, which means that each planet makes three circuits of the star in the time it takes the next one out to make two. That is, the outer planet’s orbit is 50% longer than the inner one’s.

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    Artist’s concept of a top-down view of the K2-138 system discovered by citizen scientists, showing the orbits and relative sizes of the five known planets. Orbital periods of the five planets, shown to scale, fall close to a series of 3:2 mean motion resonances. This indicates that the planets orbiting K2-138, which likely formed much farther away from the star, migrated inward slowly and smoothly.
    Credit: NASA/JPL-Caltech/R. Hurt (IPAC)

    Such resonances are common in the planetary systems discovered by NASA’s Kepler space telescope (which seeks exoplanets by looking for dips in the brightness of distant stars that occur when planets cross in front of them, blocking part of their light). That’s because Kepler has discovered a great many compact planetary systems, in which planets would gravitationally interfere with each other if their orbits were not somehow synchronised.

    But K2-138 is the most dramatic example of this yet, with five planets — all between 1.6 and 3.3 times the size of the Earth — moving like clockwork in a succession of 3:2 resonances. Specifically, their orbits are 2.35, 3.56, 5.40, 8.26, and 12.76 days, forming an unbroken chain of close-to-3:2 resonances — the longest such chain ever discovered. Moreover, there are hints of a sixth planet, which, if it exists, would orbit in about 42 days.

    That’s particularly interesting, says Jessie Christiansen, an astronomer from California Institute of Technology, Pasadena, US, who presented her findings last week at a meeting of the American Astronomical Society in National Harbor, Maryland, because 42 days falls into the same resonance chain.

    That raises the possibility that there might be as-yet unobserved planets in the gaps between 12.76 days and 42. “If you continue the chain it would be 19, 27, and 42,” she says. “So it could be that the longest chain could get longer yet.”

    It’s an exciting discovery, says Steve Bryson, an exoplanet-hunting astronomer at NASA Ames Research Centre at Mountain View in California, who was not a member of Christiansen’s team. “It gives us a deeper understanding of how planetary systems form.”

    Christiansen agrees. The fact that the planets wound up in such a smooth arrangement, she says, suggests that they migrated inward to their present positions very sedately, rather than via chaotic gravitational interactions. “They had no fights,” she says.

    It’s also intriguing because the 3:2 interval between these planets’ orbits is what musicians call a perfect fifth. “You can find them everywhere in music,” Christiansen says, citing the first two notes of Twinkle, Twinkle, Little Star as an example.

    Even more interestingly, the orbits aren’t quite perfect fifths, but are just ever so slightly off, she says. That is, instead of having orbital resonances that are exactly in a 3:2 ratio (or 1.5 to 1), they are 1.513, 1.518, 1.528, and 1.544. That’s intriguing, she says, because musicians actually tune their instruments to be just slightly off from perfect-fifth intervals to avoid the irritating “beat” phenomena that happens when tuning is too perfect.

    Possibly, she says, K2-138’s planets may have wound up in orbits just slightly off from perfect in order to avoid being destabilised by a similar phenomena due to too-perfect synchronisation.

    But even more exciting than the science, says Bryson, is the way in which the find was made. It came via a project called Exoplanet Explorers carried out on a website called zooniverse.org.

    The goal of that project, says Christiansen, is to recruit volunteers to examine any data in which the computer found a blip that might be a planet.

    “They’re doing the vetting,” she says. “Looking through and saying, ‘This is junk; this is real.’

    “It’s really hard to tell the computer to find everything that looks like a blip, but not ‘that’ kind of blip or ‘that’ kind of blip or ‘that’ kind of blip. So we just tell the computer to find all the blips and we’ll check.”

    But with thousands of stars involved, and a desire to have at least 10 people look at everything that might be interesting, that involves a tremendous amount of person-power.

    “We just uploaded 55,000 new potential planetary signals,” Christiansen says. “We would never be able to get through all of the signals we have without our volunteers.”

    Meg Schwamb, an astronomer at the Gemini Observatory in Hilo, Hawaii, agrees.

    “In our Internet age, online citizen science is enabling scientists to enlist the help of the general public from around the globe to perform data sorting and analysis tasks that are impossible to automate, or would be insurmountable for a single person or small group to undertake,” she says.

    “With so many eyes looking at the data, these projects can find hidden gems that may have gone missed in today’s large datasets.”

    “One of the things I love about astronomy,” adds Bryson, “is that it’s the one science where everyone can relate to it. Everyone knows what it’s like to look up at the stars.”

    Caltech article is posted here:
    https://sciencesprings.wordpress.com/2018/01/12/from-caltech-citizen-scientists-discover-five-planet-system/

    Christiansen’s study is in the online edition of The Astronomical Journal.

    See the full article here .

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  • richardmitnick 9:54 am on January 5, 2018 Permalink | Reply
    Tags: , Coral bleaching, COSMOS, , Widespread coral bleaching in Australia's Great Barrier Reef   

    From COSMOS Magazine: “Worldwide coral bleaching has sped up dramatically in 30 years” 

    Cosmos Magazine bloc

    COSMOS Magazine

    05 January 2018
    Tanya Loos

    International data predicts annual reef bleaching is a real possibility.

    1
    Bleaching events have sped up significantly since the 1980s. Reinhard Dirscherl/ullstein bild via Getty Images

    2
    Global Coral Bleaching. http://www.globalcoralbleaching.org .

    The time between coral bleaching events at multiple reef locations has decreased five-fold in the past four decades, new research has found.

    A study in the journal Science reports that time elapsed between bleaching events in the tropics has contracted from 25-to-30 years in the early 1980s to just six years by 2010.

    “Before the 1980s, mass bleaching of corals was unheard of, even during strong El Niño conditions, but now repeated bouts of regional-scale bleaching and mass mortality of corals have become the new normal around the world as temperatures continue to rise,” says lead author Terry Hughes of the ARC Centre of Excellence for Coral Reef Studies based at James Cook University in Queensland, Australia.

    Using data from 100 reef sites around the world, Hughes and colleagues from Australia, Saudi Arabia, Canada and the US demonstrate that tropical sea temperatures are warmer today during cooler-than-average La Niña conditions than they were 40 years ago during El Niño periods.

    They find that the frequency of the bleaching events is having dire consequences for the complex ecosystems of coral reefs, because six years is insufficient time for the mature assemblages of the reef to recover. Even the fastest growing coral communities take approximately 10 to 15 years to recover after a bleaching event.

    The researchers fear that annual bleaching could soon occur.

    “Reefs have entered a distinctive human-dominated era – the Anthropocene,” says co-author Mark Eakin of the US National Oceanic & Atmospheric Administration.

    “The climate has warmed rapidly in the past 50 years, first making El Niños dangerous for corals, and now we’re seeing the emergence of bleaching in every hot summer.”

    The timing and severity of mass bleaching events has varied across geographic regions. In the 1980s, the Western Atlantic and Pacific regions were at highest risk. More recently, bleaching risk has increased only slowly in the Western Atlantic, at an intermediate rate in the Pacific and very strongly in the Middle East and Australasian regions.

    The study highlights the Great Barrier Reef, which has bleached four times since 1998, including unprecedented back-to-back events in 2016 and 2017.

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    Widespread coral bleaching in Australia’s Great Barrier Reef. http://www.slate.com .

    The researchers conclude that the future conditions of reefs, and the ecosystem services they provide to people, will depend critically on the trajectory of global emissions.

    “We hope our stark results will help spur on the stronger action needed to reduce greenhouse gases in Australia, the United States and elsewhere,” says Hughes.

    See the full article here .

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  • richardmitnick 9:29 am on January 5, 2018 Permalink | Reply
    Tags: 30 Doradus (also known as the Tarantula Nebula), , , , , COSMOS, ,   

    From COSMOS: “Unlike Hollywood, the universe is full of big stars” 

    Cosmos Magazine bloc

    COSMOS Magazine

    05 January 2018
    Richard A Lovett

    Research finds massive star numbers have been underestimated – affecting calculations for black holes, neutron stars and gravitational waves.

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    This composite of 30 Doradus, aka the Tarantula Nebula, contains data from Chandra, Hubble, and Spitzer. Located in the Large Magellanic Cloud, the Tarantula Nebula is one of the largest star-forming regions close to the Milky Way. Universal History Archive / Contributor / Getty Images

    NASA/Chandra Telescope

    NASA/ESA Hubble Telescope

    NASA/Spitzer Infrared Telescope

    2
    Large Magellanic Cloud, NASA/ESA Hubble

    Giant stars hundreds of times more massive than the sun may have been much more common in the early universe than previously believed, astronomers say.

    The find, published in the journal Science, used the European Southern Observatory’s Very Large Telescope in Chile to examine about 800 stars in a “starburst” region called 30 Doradus (also known as the Tarantula Nebula) in the Large Magellanic Cloud, a galaxy about 160,000 light years away from the Milky Way.

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    30 Doradus, aka the Tarantula Nebula, ESO/VLT

    ESO/VLT at Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level

    Using a spectrometer so sensitive it could pick out individual stars only 1.2 arcseconds apart (about 1/1500 the width of the full moon), the researchers counted substantially more high-mass stars – ranging from 30 to 200 times the mass of the sun – than predicted by long-standing models of star formation. Furthermore, the discrepancy was particularly large for the largest stars.

    Historically, astronomers have believed that the vast majority of stellar matter is in the form of myriad small stars, with only a fraction of it in giants of the type observed in 30 Doradus. (In fact, it was only recently that astronomers realized that the largest of these gigantic stars even existed.)

    But the new research appears to have stood the traditional notion on its head. “Our results suggest that a significant fraction [of the mass] is in high-mass stars,” says one of the authors, Chris Evans of the UK’s Astronomy Technology Centre, in Edinburgh, Scotland.

    That’s important, adds the study’s lead author, Fabian Schneider, an astrophysicist from the University of Oxford, because a star 100 times the mass of our sun isn’t equivalent to 100 suns.

    “These are extremely bright,” he says. “A 100 solar-mass star would be a million times brighter than our sun. You need only a handful of these to outshine all the others.”

    Such bright stars, he adds, are “cosmic engines” that blast out not only light but ionising radiation and strong stellar winds. They burn bright, but also die young in massive explosions that not only create black holes and neutron stars, but disperse the elements of planets — and life — into space: carbon, oxygen, silicon, iron, and many others.

    In the earliest universe, after it had cooled down from the initial fury of the Big Bang, there was nothing but hydrogen and helium, cold and dark, Schneider says. But about 150 million years later, astrophysicists believe that the infant universe’s “dark age” ended with the coalescing of these materials into the first stars and galaxies.

    The resulting burst of radiation not only brought light back to the universe, but produced a series of other important effects, including the production of ionising radiation, stellar winds, and supernovae. In combination, these shaped galaxies and slowed the rate of star formation enough to keep the first generation of stars from gobbling up all of the available matter.

    The result, Schneider says, was to “regulate” the star forming process “so that you [still] see stars forming today. Otherwise, it would have stopped early on.”

    In today’s universe, giant star-forming regions such as 30 Doradus are relatively rare. Ancient regions can still be studied by peering at distant galaxies, whose light has been traveling for billions of years, but these are far away and difficult to observe in detail.

    Having one nearby, where we can study it closely, is therefore a perfect opportunity, especially because 30 Doradus is so close and large that it is easily visible in a small telescope.

    And it is so bright that if it were in our own galaxy at the distance of the Orion Nebula’s star-forming cluster (easily visible to the naked eye) it would span an area 60 times larger than the full moon and cast visible shadows on cloudless nights, Schneider says.

    And while it doesn’t constitute a perfect laboratory – it has too many heavier elements, for example, to be a perfect analogy to star-forming regions in the earliest galaxies – the fact it contains so many super-massive stars has major ramifications for our understanding of our universe’s history.

    “There might [have been] 70% more supernovae, a tripling of the chemical yields and towards four times the ionising radiation from massive star populations,” says Schneider.

    “Also, the formation rate of black holes might be increased by 180%, directly translating into a corresponding increase of binary black hole mergers that have recently been detected via their gravitational wave signals.”

    Brad Tucker, an astrophysicist and cosmologist at Australian National University, calls the new study “a very good paper” with “wide-reaching impact.”

    Its authors, he adds comprise a “who’s who” of experts in the field.

    “[It] suggests we should expect more core-collapse supernovae, and thus more metals, in the early Universe,” he says. There should also be more black hole mergers to be detected in the future by the gravitational waves they produced.

    “Simply put,” he says, “more larger stars equals a more exciting universe.”

    See the full article here .

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  • richardmitnick 1:06 pm on January 2, 2018 Permalink | Reply
    Tags: , Artificial Intelligence (AI), BDI, Computers don’t have any common sense. They don’t know that a glass of water when dropped will fall- likely break- and surely wet the carpet, COSMOS, IBM's Watson which in 2011 beat human champions at the TV quiz Jeopardy can now diagnose pneumonia better than radiologists, Moravec’s paradox   

    From COSMOS: “Dark intentions: should we fear AI with purpose?” 

    Cosmos Magazine bloc

    COSMOS Magazine

    02 January 2018
    Toby Walsh

    1
    Will robots ever develop minds of their own? Only if we tell them to. GERARD JULIEN/AFP/Getty Images.

    It’s hard to ignore dystopian pronouncements about how Artificial Intelligence (AI) is going to take over our lives, especially when they come from luminaries in tech. Entrepreneur Elon Musk, for instance, says “If you’re not concerned about AI safety, you should be. Vastly more risk than North Korea.” And IT maven Erik Brnyojolfsson, at MIT, has quoted Vladimir Putin’s claim that “The one who be-comes leader in this sphere will be ruler of the world.”

    I understand the angst. AI is chalking up victories over human intelligence at an alarming rate. In 2016 AlphaGo, training itself on millions of human moves, beat the world Go champion, Lee Sedol. In 2017 the upgrade – AlphaGo Zero – trained itself to champion level in three days, without studying human moves.

    Watson, which in 2011 beat human champions at the TV quiz Jeopardy, can now diagnose pneumonia better than radiologists. And Kalashnikov are training neural networks to fire machine guns. What’s not to fear?

    3

    4

    The real danger would be AIs with bad intentions and the competence to act upon them outside their normally closed and narrow worlds. AI is a long way from having either.

    AlphaGo Zero isn’t going to wake up tomorrow, decide humans are no good at playing board games — not compared to AlphaZero, at least — and make some money beating us at online poker.

    And it’s certainly not going to wake up and decide to take over the world. That’s not in its code. It will never do anything but play the games we train it for. Indeed, it doesn’t even know it is playing board games. It will only ever do one thing: maxim-ise its estimate of the probability that it will win the current game. Other than that, it has no intentions of its own.

    However, some machines already exist that do have broader intentions. But don’t panic. Those intentions are very modest and still are played out in a closed world. For instance, punch a destination into the screen of an autonomous car and its in-tent is to get you from A to B. How it does that is up to the car.

    Deep Space 1, the first fully autonomous spacecraft, also has limited human-given goals. These include things like adjusting the trajectory to get a better look at a passing asteroid. The spacecraft works out precisely how to achieve such goals for itself.

    There’s even a now rather old branch of robot programming based on beliefs, desires & intentions that goes by the acronym BDI.

    In BDI, the robot has “beliefs” about the state of the world, some of which are programmed and others derived from its sensors. The robot might be given the “desire” of returning a book to the library. The robot’s “intentions” are the plan to execute this desire. So, based on its beliefs that the book is on my desk and my desk is in my office, the robot goes to my office, picks up the book, and drives it down the corridor to the library. We’ve been building robots that can achieve such simple goals now for decades.

    So, some machines already do have simple intentions. But there’s no reason to go sending out alarmed tweets. These intentions are always human-given and of rather limited extent.

    Am I being too complacent? Suppose for a moment we foolishly gave some evil intents to a machine. Perhaps robots were given the goal of invading some country. The first flight of stairs or closed door would likely defeat their evil plans.

    One of the more frustrating aspects of working on AI is that what seems hard is often easy and what seems easy is often hard. Playing chess, for instance, is hard for humans, but we can get machines to do it easily. On the other hand, picking up the chess pieces is child’s play for us but machines struggle. No robot has anything close to the dexterity of a three-year-old.

    This is known as Moravec’s paradox, after Carnegie Mellon University roboticist Hans Moravec. Steven Pinker has said that he considers Moravec’s paradox to be the main lesson uncovered by AI research in 35 years.

    I don’t entirely agree. I would hope that my colleagues and I have done more than just uncover Moravec’s paradox. Ask Siri a question. Or jump in a Tesla and press AutoPilot. Or get Amazon to recommend a book. These are all impressive exam-ples of AI in action today.

    But Moravec’s paradox does certainly highlight that we have a long way to go in getting machines to match, let alone exceed, our capabilities.

    Computers don’t have any common sense. They don’t know that a glass of water when dropped will fall, likely break, and surely wet the carpet. Computers don’t understand language with any real depth. Google Translate will finding nothing strange with translating “he was pregnant”. Computers are brittle and lack our adaptability to work on new problems. Computers have limited social and emotion-al intelligence. And computers certainly have no consciousness or sentience.

    One day, I expect, we will build computers that match humans. And, sometime after, computers that exceed humans. They’ll have intents. Just like our children (for they will be our children), we won’t want to spell out in painful detail all that they should do. We have, I predict, a century or so to ensure we give them good intents.

    See the full article here .

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  • richardmitnick 11:20 am on December 27, 2017 Permalink | Reply
    Tags: COSMOS, , If there’s any consensus among geologists it is that something changed about 2.7 billion years ago to kick tectonic plates in action,   

    From COSMOS: “Plate tectonics: the hidden key to life on Earth” 

    Cosmos Magazine bloc

    COSMOS Magazine

    27 December 2017
    Richard A. Lovett

    Earth’s constantly moving crust helps keep the climate habitable. If circumstances had been only a little different, we could have ended up a barren hothouse like Venus or a frozen snowball like Mars. How did we get so lucky?

    1
    Vitalij Cerepok / Getty Images

    “Look again at that dot. That’s here. That’s home. That’s us.” Carl Sagan was moved to lyricism by the pale blue dot that Voyager 1 photographed as it exited the solar system 27 years ago. The pale blue dot is precious, and lucky.

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    Earth from Voyager 1

    NASA/Voyager 1

    Not only does Earth lie in the ‘Goldilocks zone’ that allows water to exist in the liquid form that life requires. It is also the only rocky planet we know of that constantly renovates its surface as its tectonic plates dive into the mantle in some places and re-emerge as molten lava in others.

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    The Earth’s rigid tectonic plates float on a playdoh-like mantle in slow, constant motion. Without this movement, the planet might well have ended up with a ‘stagnant lid’ no more conducive to sustaining life than Mars or Venus

    Many astrobiologists now think this constant renewal is just as important as liquid water for the flourishing of life as we know it.

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    A slice through the earth. The crust and upper mantle form the brittle lithosphere which cracks into tectonic plates. No image credit.

    The theory, explains planetary scientist Adrian Lenardic of Rice University in Houston, Texas, is that the Earth’s climate has been buffered by the recycling of carbon dioxide (CO2) from the atmosphere into the planet’s interior via mineral sequestration and then out again via volcanoes. This has kept the climate temperate even as the Sun’s heat has increased in intensity by about a third since the planet’s birth. Without this buffering, Earth might have heated so much that all the water in its oceans boiled away and huge quantities of CO2 accumulated in the atmosphere, much like Venus which has an average temperature of 462°C. Or it might never have recovered from being a snowball, remaining permanently frozen.

    Among the rocky worlds we know, Earth’s tectonics are unique. Venus and Mercury have no similar geological activity. Mars might have once, but not for billions of years. So why are we so lucky?

    According to geophysicist David Bercovici, of Yale University, models show the Earth sits right on the cusp between being a world with plate tectonics and one with a ‘stagnant lid’, like modern-day Mars or Venus. Something must have kicked it in the direction that produced a geologically active world that eventually gave birth to us. Bizarrely, even as astronomers probe planets hundreds of light-years distant, geologists still can’t precisely explain what triggered the events taking place beneath our feet.

    Tectonics derives from the Greek word ‘tektonikos’, meaning to build. It points to what we do understand about the way Earth’s surface is constantly remodelled. Our planet has a rigid shell called the lithosphere that comprises the crust and a hardened upper slice of an otherwise playdoh-like mantle (see diagram). That shell is cracked into seven large plates and a number of smaller ones that float on the mantle in slow, constant motion.

    The first inkling that continents moved dates back to the 1500s, when Flemish mapmaker Abraham Ortelius noted that the eastern and western coastlines of the Atlantic Ocean looked as if they might have once fitted together like pieces from a jigsaw puzzle.

    In 1912 German geophysicist Alfred Wegener coined the term ‘continental drift’ to describe how the lands on each side of the Atlantic had become so strangely sundered, but it wasn’t until 1963 that British marine geologists Fred Vine and Drummond Matthews provided the explanation (see Cosmos 54, p48). They realised the interior of the Earth is in motion. The rock of the mantle is slightly plastic – enough so that it can rise and fall in slow, roiling motions called convection currents: hot rock rises from the depths, cools, become denser and then descends. The best analogy is a lava lamp, which uses heat from a light bulb to induce the circulation of coloured wax in liquid. While the lava lamp’s convection currents are fast enough to produce mesmerising changes of colour, the rock of the mantle moves “about as fast as your fingernails grow”, says Bercovici – at a speed of less than 10 cm a year.

    When rising currents hit the underside of the solid lithosphere, they deflect sideways, exerting drag. If that drag is strong enough, it can rip the lithosphere apart, creating new plates and making old ones move, upwelling magma filling in the gaps. When this happens at the bottom of the ocean, the result is ‘sea floor spreading’ – which is what Vine and Matthews observed. This is occurring today in places such as the Mid-Atlantic Ridge and the Red Sea Rift between Africa and Arabia.

    As the spreading crust cools, it grows denser. Eventually the leading edge furthest from the magma flow starts sinking back into the mantle, pulling the rest of the slab behind it – a process called subduction – and so completing the convection cycle. Like the wax in the lava lamp, the cycle of rising, spreading, falling and rising again is the engine that moves the plates, and with them the continents, which ride atop like rafts.

    Though these motions occur at a rate of only a few centimetres per year, that is rapid enough to make even the oldest seafloor in the world startlingly young – less than 200 million years old. Continental crust, the buoyant crud that froths to the surface as ocean crust subducts, is much older.

    The plates do not move in the same direction or at the same speed. This causes some plates to crash into each other, driving up mountain ranges, such as the Himalayas at the collision of the Indian and Eurasian plates. They can also grind past one another, as along California’s famed San Andreas Fault. Or one can dive beneath another, as occurs at the Pacific ‘Ring of Fire’ that circles the Pacific Ocean in a belt of earthquake-prone regions and volcanic activity.

    In this process, continents tend to remain on the surface. They are too buoyant to be easily subducted into the depths. But they still play an important role via a process known as ‘weathering’, which provides a vital thermostat that has helped keep the Earth temperate for billions of years.
    Tectonic thermostat: continental weathering removes 300 million tonnes from the atmosphere each year. It’s a vital part of the carbon cycle that has kept the Earth temperate.

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    Tectonic thermostat: continental weathering removes 300 million tonnes from the atmosphere each year. It’s a vital part of the carbon cycle that has kept the Earth temperate.

    It begins when CO2 from the atmosphere dissolves in rainwater to form carbonic acid. This breaks down minerals in continental rocks, producing calcium and bicarbonate ions that wash into the sea. Marine organisms take them up to form calcium carbonate, the building block for their shells and skeletons, which ultimately settle to the seafloor and become limestone.

    Each year the process removes about 300 million tonnes of CO2 from the atmosphere. But the carbon isn’t sequestered forever, because some of that limestone is subducted along with the seabed. It heats, melts and is incorporated into magma for carbon dioxide-spewing volcanoes to release. This also produces fresh rock for the next weathering cycle.

    What makes this process function like a thermostat is that the more CO2 there is in the atmosphere, the more carbonic acid there is in rain (and the more rapidly weathering occurs). This removes CO2 from the atmosphere more swiftly, keeping the Earth from transforming into a Venusian runaway greenhouse. Conversely, if atmospheric CO2 levels fall,weathering slows, allowing volcanic CO2 to slowly build back up. It’s a slow, self-correcting process that for billions of years has kept the Earth’s temperature within a zone that is hospitable to life.

    So what got Earth’s plate tectonics going, rather than the planet ending up with a largely inert ‘stagnant lid’ like Mars and Venus?

    The earliest Earth was all magma ocean with no solid surface to form plates, let alone plates that drift around and collide with one another. At a minimum, plate tectonics couldn’t have begun until after the Earth’s surface solidified, somewhere about 4.5 to 4 billion years ago. Just when the plate tectonics kicked in, though, still has geologists squabbling.

    If you’re seeking the earliest traces of plate tectonics, a good place to look is the Jack Hills in Western Australia.

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    Low and smoothed by erosion, the Jack Hills aren’t too impressive as a mountain range. But mineral crystals have weathered out of the Jack Hills and washed into streams, and these crystals tell a fascinating story about how far back in Earth’s past the oceans might have formed. (NASA image by Robert Simmon, based on Landsat data provided by the Global Land Cover Facility)
    Source http://earthobservatory.nasa.gov/Study/Zircon/
    Author Robert Simmon, NASA

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    At the Jack Hills. U Mass Lowell.

    To the casual traveller this range of low mountains about 800 km north of Perth is not hugely impressive. But to geologists the hills are of towering significance, containing time capsules of the world’s oldest rocks in tiny crystals of zirconium silicate (ZrSiO4).

    Zircons formed in cooling magma. Three things make them geological gems. First, they carry a date stamp of formation, based on the decay of traces of uranium trapped within them. Second, they are extremely durable; the ancient volcanic rocks that gave birth to them eroded long ago and were reconstituted into sedimentary rocks in the Jack Hills’ outcrops. Third, they bear trace elements like titanium and aluminium, which reveal the conditions of their birth.

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    Time capsule: Jack Hills zircon. Born 4 billion years ago, it shows earth was already churning. John Valley, University Wisconsin.

    So far these zircon time capsules have telegraphed an extraordinary message: 4.2 billion years ago they were born kilometres below, crystallising as they rose to Earth’s surface. This tells us the mantle was starting to churn at that time.

    But were these upwellings the same as those that drive modern plate tectonics? Craig O’Neill thinks not. He’s a cheery geodynamicist at Sydney’s Macquarie University who has been studying Jack Hills zircons for many years. In his view, the zircons could have been formed by localised upwellings similar to those occurring today in places like Hawaii and Yellowstone. In other words, not an Earth-wide tectonic churning but a local percolation.

    Vicki Hansen, a planetary geologist at the University of Minnesota, Duluth, has come to the same conclusion based on “greenstone terranes” found in Greenland, South Africa, Canada and Scandinavia.

    These rock assemblages, which measure a few hundred kilometres across, date back to the Archaean Eon, 4 to 2.5 billion years ago. They are interesting because the greenish granites that give them their name are mixed up higgledy-piggledy with seabed sediments in ways we never see in more recent volcanic provinces. If modern-day rocks are like the vegetables displayed at the supermarket, the greenstone rocks are like stir-fry. This, Hansen says, indicates that whatever was going on in the Achaean involved processes “fundamentally different” to those today.

    More evidence that modern plate tectonics had not geared into action until relatively recently comes from the study of the history of continental drift.

    _____________________________________________________________
    If there’s any consensus among geologists, it is that something changed about 2.7 billion years ago to kick tectonic plates in action.
    _____________________________________________________________

    Supercontinents are formed when the plate-tectonic engine drives the Earth’s land masses to merge into one gigantic block. The closest we now have to a supercontinent is Eurasia. But some remarkable detective work – using the age of rocks and magnetic signatures that mark the latitudes where they first formed – reveals at least four granddaddy supercontinents that make Eurasia look tiny.

    The most recent is Pangaea, which formed about 335 million years ago and lasted through much of the age of the dinosaurs.

    It was preceded by Rodinia (1 billion to 750 million years ago), then by Nuna (2 to 1.8 billion years ago). The earliest detectable supercontinent is Kenorland (2.7 to 2.4 billion years ago), relics of which are scattered across Western Australia, North America, Greenland, Scandinavia and the Kalahari Desert.

    8
    http://www.the-dialogue.com/en/en33-earths-supercontinents/

    The fact we can’t find a supercontinent older than Kenorland may simply mean the surviving bits are too scattered for geologists to piece back together. It’s like trying to figure out the history of a vase that has been broken and reassembled several times.

    But with supercontinent formation and break-up requiring modern-style plate tectonics, the fact we haven’t found one before Kenorland might instead be telling us that for the Earth’s first 1.8 billion years the lava lamp was not strong enough to produce anything other than localised percolations, not the continent-driving process we have today.

    9
    Iceland’s lava fields: evidence of the rift between the North American and Eurasian tectonic plates. Picture Press / Getty Images

    If there’s any consensus amongst geologists, it is that something changed about 2.7 billion years ago to kick tectonic plates into action. “There appears to have been a major event,” says Kent Condie, a geochronologist at the New Mexico Institute of Mining and Technology in Socorro.

    But what could that have been? Theories range from the mundane to the dramatic, but all require the Earth to have overcome the same basic hurdles. Either the power of the lava lamp that makes mantle currents rise and swirl must have increased or the Earth’s crust must have weakened, allowing it to break into plates; or perhaps both occurred simultaneously.

    One view, favoured by Matt Welller of Rice University, is that feedback loops in magma currents gradually built up to a level strong enough to produce self-sustaining plate tectonics via what engineers call a ‘hysteresis loop’. A hysteresis loop occurs when there is a lag between cause and effect. It is analogous to an out-of-tune automobile engine. When you press down on the accelerator, at first the engine barely reacts, then it lurches forward.

    Suppose the deep convection currents driving the Earth’s plate tectonics were to suddenly shut down. That would reduce the amount of heat that can escape, causing mantle rocks to heat up and become more plastic. Softer rocks can support more vigorous convection, so the lava-lamp effect intensifies, carrying heat more rapidly from the interior –until enough has escaped, the mantle cools and its currents slow again.

    “You can shift back and forth as you heat up and cool down, heat up and cool down,” says Julian Lowman, a geodynamicist from the University of Toronto. According to this view, the juvenile Earth experienced these on-and-off episodes on a small scale, producing the localised tectonics suggested by the Jack Hills zircons and the greenstone terrains. Then, about 2.7 billion years ago, these shifts became locked into a self-sustaining Earth-wide convection cycle.

    Hansen, on the other hand, opts for a more dramatic scenario. The event that kicked off the tectonic plates might literally have been a kick – in the form of an asteroid or comet strike. Not as big as the one that formed the Moon, but far larger than the one that killed the dinosaurs.

    She first described her theory in 2007 in the journal Geology, arguing such an object would have punched right through the crust, heating the mantle and setting currents in motion, dragging the plates along with them and starting tectonic movements. Once plates began colliding and sinking, the process expanded until it spread across the planet. “Subduction is like a virus,” the paper states. “Once begun it can easily spread.”

    Alternatively, the dramatic event might have come from below. In a 2015 paper in Nature, a team led by Teras Gerya, of the Swiss Federal Institute of Technology in Zurich, argued that hot spots on the Earth’s core could have caused plumes of hot mantle to rise beneath a continent. Under the right circumstances, they calculated, this could break up the continent and cause pieces to sink, creating a self-sustaining cycle that became plate tectonics.

    __________________________________________________
    Even the strongest mantle currents wouldn’t have triggered tectonic activity if the Earth’s crust was too strong to break into plates.
    __________________________________________________

    Yet another possibility is that something changed the distribution of heat deep within the Earth. That heat comes from two sources: the long-lived radioactive decay of atoms such as uranium and thorium trapped in the mantle; and from the core, which contains a vast reservoir of heat remaining from the formation of the Earth. Both are slowly declining as the Earth ages.

    One might think a cooling Earth would have weaker tectonics. But it’s not that simple. “There are lines of research,” Lowman says, “suggesting that plate tectonics has a better chance of manifesting itself as a planet cools.” That’s because the lava-lamp engine that drives plate tectonics depends less on how hot the Earth’s interior is as on how rapidly it can transfer heat to the surface. The faster heat is transferred, the stronger the engine, and the stronger the mantle currents that drive tectonics.

    It has been known since the 1930s that the Earth’s core has two layers: an outer one composed of molten metal, and an inner one made of solid metal. As the Earth cools, the inner core grows. In the process it releases heat energy – equal to the amount it took to melt all that material in the first place. That energy rises through the core, increasing the rate at which it heats the mantle and, ultimately, rises to the surface.

    Supporting the theory that the cooling core may power the tectonic engine, a 2015 study by Condie and colleagues in the journal Precambrian Research traced the motions of continents over the past 2 billion years. They concluded that plate tectonics have been slowly speeding up, with average plate speed nearly doubling over that time.

    But even the strongest mantle currents would not have triggered tectonic activity if the Earth’s crust was too strong to break into plates. As it was, apparently, on Mars. For Berkovici, the key factor for the emergence of plate tectonics was therefore the weakening of Earth’s crust. It might have started gradually, beginning with the type of plume tectonics reflected in ancient greenstone terranes. Each of these magma breakthroughs would have created fault lines along which rocks slipped against each other, just as they do in today’s earthquakes. These motions would have produced weak spots that might have become focal points for later breakthroughs. Bercovici compares it to repeatedly bending a paper clip. “It gets softer,” he says. “Eventually you can bend it easily.”

    Gradually these weak zones would have spread until they merged into plate boundaries similar to today’s, and the process went from local and intermittent to global and continuous. “A meteor might have gotten it started,” Bercovici says in a nod to Hansen, “but it needs these feedbacks to keep going.”

    It is easy to try to fold all of this into a nice, coherent story. It would begin with a magma ocean, followed by weak, intermittent plume-style tectonics. These would eventually reach some tipping point that shifted the process to its present state, either due to changes in the core, an asteroid impact, the accumulation of Bercovici’s weak spots, or some combination of all three. But the plethora of options suggests caution.

    We may not yet have all the pieces to the puzzle. Lindy Elkins-Tanton, director of the School of Earth and Space Exploration at Arizona State University in Tempe, remembers being a graduate student at a conference, wondering what made scientists who disagreed with her own presentation so sure of themselves.

    “I sat there thinking perhaps I just didn’t know enough yet,” she recalls. “But now, 15 years later, I see that none of us know enough. We can only make small incremental progress in this very complicated problem.”

    See the full article here .

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  • richardmitnick 12:16 pm on December 25, 2017 Permalink | Reply
    Tags: , , , , , COSMOS, From UCSC "All the gold in the universe", , Waves of joy: why astronomers are ecstatic about colliding neutron stars   

    From COSMOS: “Waves of joy: why astronomers are ecstatic about colliding neutron stars” 

    Cosmos Magazine bloc

    COSMOS Magazine

    22 December 2017
    Lauren Fuge

    1
    An artist’s impression of colliding neutron stars. MARK GARLICK/UNIVERSITY OF WARWICK.

    Every few years, a discovery is announced that makes scientists so excited they could explode – consider the rockstar coverage that greeted the discovery of the Higgs boson in 2012, or the triumphant global cheer when Curiosity landed safely on Mars in the same year.

    CERN CMS Higgs Event

    CERN ATLAS Higgs Event

    NASA/Mars Curiosity Rover

    On 16 October 2017 the announcement of another science spectacle swept the world: for the first time, astronomers had been treated to the cosmic fireworks of colliding neutron stars. They could both listen – thanks to gravitational waves – and watch – thanks to electromagnetic waves. Astronomers the world over were catapulted into a frenzy.


    VIRGO Gravitational Wave interferometer, near Pisa, Italy

    Caltech/MIT Advanced aLigo Hanford, WA, USA installation


    Caltech/MIT Advanced aLigo detector installation Livingston, LA, USA

    Cornell SXS, the Simulating eXtreme Spacetimes (SXS) project

    Gravitational waves. Credit: MPI for Gravitational Physics/W.Benger-Zib

    ESA/eLISA the future of gravitational wave research

    1
    Skymap showing how adding Virgo to LIGO helps in reducing the size of the source-likely region in the sky. (Credit: Giuseppe Greco (Virgo Urbino group)

    Here are five reasons why.

    1. Their life’s work was just validated.

    The reality of science – and especially physics and astronomy – is that, sometimes, scientists end up studying phenomena that they’re not 100% sure actually exist. For some researchers, this discovery confirmed that they haven’t wasted their careers.

    Anna Heffernan, Marie Curie Fellow at the University of Florida and the University College Dublin, summed up the sentiment: “I’ve spent my life looking at gravitational waves – at least, the last 11 or 12 years – and to actually find that they really do exist and I haven’t dedicated 12 years to nonsense was a very good feeling.”

    David Blair, from the University of Western Australia, spent even longer in the dark. “I started working on the first high sensitivity gravitational wave detectors in the USA in 1973,” he said. “I expected to spend a year or two detecting Einstein’s waves and then move on to something else … Forty-four years later we have found the holy grail!”

    2
    Image: CSIRO

    2. Astronomers have reached a goal they have chased for decades.

    This discovery not only validated many scientists’ entire careers but also marked the triumphant achievement of a long-held and dearly desired goal: “That is,” said National Science Foundation director France Córdova, “to simultaneously observe rare cosmic events using both traditional as well as gravitational-wave observatories.”

    3
    Cataclysmic Collision Artist’s illustration of two merging neutron stars. The rippling space-time grid represents gravitational waves that travel out from the collision, while the narrow beams show the bursts of gamma rays that are shot out just seconds after the gravitational waves. Swirling clouds of material ejected from the merging stars are also depicted. The clouds glow with visible and other wavelengths of light. Image credit: NSF/LIGO/Sonoma State University/A. Simonnet

    It is “very, very exciting” that it worked out in the end, said Rainer Weiss, LIGO co-founder and winner of the 2017 Nobel Prize in Physics: “For as long as 40 years, people have been thinking about this, trying to make a detection, sometimes failing in the early days, and then slowly but surely getting the technology together to be able to do it.”

    Scientists persisted for so long, explained Tamara Davis from the ARC Centre of Excellence for All-Sky Astrophysics (CAASTRO) and the University of Queensland, because hearing this faint sound and momentary burst of light confirmed a suite of predictions – “such as how the heavy elements were created, what happens when neutron stars collide, and how fast is the universe expanding.”

    Ju Li, of the University of Western Australia, agreed: “It is extraordinary that with one faint sound, the faintest sound ever detected, we have created one giant leap in our understanding of the universe.”

    Blair adds: “This is the most amazing vindication of all of Einstein’s theories.”

    3. The discovery involved a massive, unprecedented global collaboration.

    After the initial gravitational waves alert on August 17, hundreds of astronomers around the world leapt into action to try and spot electromagnetic radiation from the source.

    Stefano Covino, at INAF–Osservatorio Astronomico di Brera in Italy, says the effort was frankly impressive. “The days were filled with frenetic and exciting activity,” he remembers. “You had the precise feeling that something historic was happening.”

    According to Dave Reitze, executive director of LIGO, these mass-scale follow-up observations allowed astronomers to obtain “a full picture of one of the most violent, cataclysmic events in the universe. This is the most intense observational campaign there has ever been.”

    Matthew Bailes, the Director of the ARC Centre of Excellence for Gravitational Wave Discovery, agrees that the “avalanche of science was virtually unparalleled in modern astrophysics.”

    As a result, dozens of research papers went online on October 16, the day of the official announcement. One paper in particular [The Astrophysical Journal] demonstrates the mind-blowing scale of the collaboration – it’s co-authored by almost 4000 astronomers from more than 900 institutions: about a third of all astronomers in the world.

    4. It marks the beginning of a new era of multi-messenger astronomy.

    “Probably the most exciting thing of all is really that it’s the beginning,” says Richard O’Shaughnessy at the Rochester Institute of Technology’s Center for Computational Relativity and Gravitation. “This is a transformation in the way that we’re going to do astronomy.”

    His sentiment was echoed by almost every astronomers who spoke about the event. If there’s one thing scientists get universally excited about, it’s doing more science.

    Jeff Cooke from Swinburne University is among the enthusiastic horde: “Before this event, it was like we were sitting in an IMAX theatre with blindfolds on. The gravitational wave detectors let us ‘hear’ the movies of black hole collisions, but we couldn’t see anything. This event lifted the blindfolds and, wow, what an amazing show!”

    Neil Tanvir from Leicester University explains further: “This discovery has opened up a new approach to astronomical research, where we combine information from both electromagnetic light and from gravitational waves. We call this multi-messenger astronomy – but until now it has just been a dream.”

    Some astronomers, like Edward van den Heuvel from the University of Amsterdam, are already getting pumped for what the next few decades hold.

    “Within 20 years or so, gravitational-wave measurements may be just as routine as X-ray observations have become over the past 40 years,” he says. “It’s really beyond my wildest dreams.”

    5. It’s just plain cool.

    There’s just no getting around the fact that measuring miniscule fluctuations in the fabric of spacetime from a titanic clash of ultra-dense stars 130 million years ago – and in the process, finding that our predictions were spot on – is just amazingly cool.

    Covino is particularly excited because the data coming in so far “are an amazingly close match to theory. It is a triumph for the theorists, a confirmation that the LIGO–VIRGO events are absolutely real.”

    Stephen Smartt of Queen’s University Belfast agrees wholeheartedly: “It’s quite amazing that these physical models predated the discovery by years, but ended up being very similar to the data that we actually saw!”

    According to David Coward from the University of Western Australia, he and his team “knew on day one, when the event happened, that this was something big. This is like gold for scientists.”

    For some astronomers, the discovery is so awesome that words just aren’t enough.

    “Superlatives fail,” says O’Shaughnessy.

    See the full article here .

    See further from UCSC, https://sciencesprings.wordpress.com/2017/10/20/from-ucsc-neutron-stars-gravitational-waves-and-all-the-gold-in-the-universe/ for the full story including the optical astronomy involved in this event.

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  • richardmitnick 11:36 am on December 25, 2017 Permalink | Reply
    Tags: , Amyloid plaques, , COSMOS, Inflammasome, , The AD-afflicted brain is like a crime scene. The victims are masses of dead neurons that leave many parts of the brain shrunken.   

    From COSMOS: “Brain inflammation sows the seeds of Alzheimer’s” 

    Cosmos Magazine bloc

    COSMOS Magazine

    21 December 2017
    Elizabeth Finkel

    1
    Amyloid plaques can be seen gumming up the spaces between neurons in this illustration. Juan Gaertner / Science Photo Library.

    When it comes to the perpetrator of Alzheimer’s disease (AD), the finger of blame has long pointed to hard deposits of protein in the brain known as amyloid plaques. But smouldering signs of inflammation are also clearly evident in the background.

    Now a paper in Nature reveals how the two processes connive. During inflammation, specks of a protein called ASC are released. Like the grit inside a pearl, they seed the deposition of amyloid. The authors – Carmen Venegas at the University of Bonn, Germany and colleagues – showed that in mice, removing the specks prevented the formation of amyloid and slowed progression of the disease.

    “The paper bridges different camps and puts inflammation front and centre as a potential cause of AD,” says Bryce Vissel, an AD researcher at the University of Technology, Sydney.

    The finding also suggests that anti-inflammatory drugs, particularly those that target the formation of the ASC specks, offer a new therapeutic way forward.

    “This is an extremely important paper for the Alzheimer’s field and is likely to greatly influence the way researchers think about potential Alzheimer’s treatment strategies going forward,” adds Vissel.

    The AD-afflicted brain is like a crime scene. The victims are masses of dead neurons that leave many parts of the brain shrunken. The suspects are many: alongside amyloid plaques, tangles of tau proteins inside the neurons have also been interrogated, and investigators find signs of riled-up immune cells called microglia everywhere they look.

    But amyloid plaques have been at the top of the list. That’s because people who inherit rare genetic forms of the disease also inherit abnormal genes that cause excessive production of sticky forms of amyloid protein that are more likely to aggregate into plaques. Assuming that the plaques were also the cause of neuron death in more common forms of AD, researchers have for the last three decades been developing plaque-busting drugs. But while some, like the promising antibody aducanumab, have scrubbed away plaque, so far they do not appear to have halted the disease.

    Given the dead end, many researchers have turned their interest to other suspects. An irritable brain has become a hot favourite. Those agitated microglia and the mobilizing chemicals factors they secrete are found all over the brains of AD sufferers. General signs of body inflammation in middle age also appear to correlate with an increased risk of AD in later life.

    The Venegas team decided to piece together the chain of events that occurs after microglia become irritated. A key occurrence is the formation of a protein complex inside them called an inflammasome. Like a smouldering fire, it continues to release inflammatory signals which mobilize other microglia.

    One of the other things the inflammasome does is to release tiny specks of aggregated ASC protein. The researchers had a hunch that ASC specks might be affecting the course of the disease. Not only are they visible in the brain tissue of people with AD, but mice studies had shown that when the formation of the inflammasome was impaired, the mice were protected from their version of the disease.

    To test if the specks played some role, the researchers carried out experiments in mice that are genetically engineered to overproduce amyloid plaque. Some of the mice were also engineered not to produce the ASC protein.

    For starters, the researchers found that mice lacking ASC produced less amyloid plaque and their disease appeared less severe: they performed better at memorizing mazes, for instance. When brain extracts from plaque-ridden mice were injected into young mice, they seeded the development of new amyloid plaques.

    But strikingly, if antibodies to ASC were injected at the same time, it interfered with the seeding.

    If the recipient animals lacked ASC altogether, no spreading was seen. ASC did indeed appear to be acting as the grit that seeded the plaque deposits.

    The findings show how inflammation and amyloid may collude in a vicious cycle to cause the disease. Amyloid deposits cause inflammation; inflammation releases ASC; ASC seeds the deposition of more amyloid plaque.

    What this means, explains senior author Michael Heneka, is that minor insults to the brain – perhaps a virus or mild injury – could snowball into a major inflammatory cascade that kills off neurons.

    So what’s to be done?

    Heneka points out that population studies already show the use of anti-inflammatory drugs like ibuprofen allay the onset of AD. But he says these drugs are too non-specific. Many drug companies are now focussed on finding drugs that inhibit the function of the inflammasome in a particular tissue. “This is all under way,” he says.

    See the full article here .

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  • richardmitnick 1:24 pm on December 13, 2017 Permalink | Reply
    Tags: , , , , COSMOS, Extragalactic jets and why they collapse, Extragalactic jets are powerful streams of particles blasted from feeding supermassive black holes, The research was conducted mathematically using 3D computer simulations to study how instabilities and turbulence develop, , Usually at the hearts of active galaxies such as quasars and radio galaxies, Weak points in the structure of extragalactic jets may be what causes them to collapse into enormous plumes   

    From U Leeds via COSMOS: “Extragalactic jets, and why they collapse” 

    U Leeds bloc

    University of Leeds

    COSMOS

    13 December 2017
    Lauren Fuge

    Mathematics shed light on a powerful but poorly understood astronomical phenomenon.

    1
    An artist’s impression of an extragalactic jet. MARK GARLICK/SCIENCE PHOTO LIBRARY.

    Weak points in the structure of extragalactic jets may be what causes them to collapse into enormous plumes, according to researchers at the University of Leeds, UK.

    First observed in 1918 zooming out from the massive galaxy Messier 87, extragalactic jets are powerful streams of particles blasted from feeding supermassive black holes, usually at the hearts of active galaxies such as quasars and radio galaxies. They are remarkably energetic and stretch out for millions of light-years.

    Scientists still don’t know much about these powerful phenomena. Even their composition is uncertain. Two popular models suggest they are made up of either positron-electron plasma or a mix of electrons, positrons, and atomic nuclei. It is well-known, however, that although they mostly remain stable, sometimes these monstrous streamers disintegrate into huge plume-like structures.

    The study, published in Nature Astronomy, discovered that this disintegration is likely caused by unexpected weak points, causing instabilities similar to those that can develop in water flowing through a curved pipe.

    According to lead author Kostas Gourgouliatos, the weak points are created by their narrow oval shape, which gives them a curved boundary.

    “Instability starts at the curved boundary, travels upstream on the jet and then converges at one point,” explains Gourgouliatos. “Below this point the jet stays tidy and tight but everything above will be destroyed and creates a large cosmic plume.”

    The research was conducted mathematically, using 3D computer simulations to study how instabilities and turbulence develop. But the collapse can also be observed.

    “When the jet disintegrates into a plume it releases heat, making them easier to spot on telescopes,” Gourgouliatos says. “The jets and their plumes are so bright that sometimes they outshine their host galaxies and are always more easily spotted than black holes, which are inferred indirectly.”

    The formation and evolution of these highly complex phenomena are still open areas of research. It is thought that as a black hole devours gas and dust from its accretion disc, particles can be accelerated to immense speeds and form two narrow but highly energetic beams, like giant party poppers in space.

    “The observed instability exhibited some rather unexpected features,” adds co-author Serguei Komissarov. The stability seems to be related to the centrifugal force acting on the fluid elements that zoom out along curved streamlines. According to Komissarov, nobody expected such centrifugal instability to be important in jet dynamics.

    See the full article here.

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    U Leeds Campus

    The University, established in 1904, is one of the largest higher education institutions in the UK. We are a world top 100 university and are renowned globally for the quality of our teaching and research. The strength of our academic expertise combined with the breadth of disciplines we cover, provides a wealth of opportunities and has real impact on the world in cultural, economic and societal ways. The University strives to achieve academic excellence within an ethical framework informed by our values of integrity, equality and inclusion, community and professionalism.

     
  • richardmitnick 11:19 am on December 11, 2017 Permalink | Reply
    Tags: According to the second law of thermodynamics the universe can only become more disordered and random over time – in other words the total entropy must increase, , , , Clusters of stars and galaxies are tight groups of celestial bodies shackled together by gravity, , COSMOS, Entropy is a measure of disorder, the formation of star and galaxy clusters is flawed and misrepresents the nature of time, The problem is that Vlasov’s equation assumes constant entropy in the system, Vlasov equation   

    From COSMOS Magazine: “Models of star and galaxy cluster formation incorrect” 

    Cosmos Magazine bloc

    COSMOS Magazine

    05 December 2017
    Lauren Fuge

    1
    A twin star cluster called NGC 1850, recorded by the Hubble Telescope in 2001. Normal rules of entropy and time apply.
    NASA/Getty Images

    NASA/ESA Hubble Telescope

    The dominant explanation of the formation of star and galaxy clusters is flawed and misrepresents the nature of time, a team of Brazilian researchers claim, in a new study that uses simulations to explain a long-standing paradox in a process called ‘violent relaxation’.

    Clusters of stars and galaxies are tight groups of celestial bodies shackled together by gravity. Star clusters contain up to one million stars with a common origin and are up to 30 light-years across, while collections of galaxies are among the largest structures in the Universe, composed of up to 1000 galaxies with a mass of a quadrillion Suns.

    In the study, published in The Astrophysical Journal, the researchers report the results of complex computer simulations of the puzzling gravitational dance of these massive objects.

    Such groups form in a maelstrom followed by a calming-down process called violent relaxation, when the celestial bodies settle into their new arrangements and reach a state of equilibrium.

    Violent relaxation has always been understood through the lens of the Vlasov equation, which was developed by Russian theoretical physicist Anatoly Vlasov in 1938 to describe the changing distribution of particles in plasma. It was applied to this phenomenon to approximate how thousands of stars and galaxies interact and rearrange their positions over time.

    The new study, however, questions whether this understanding is valid.

    “The problem is that Vlasov’s equation assumes constant entropy in the system,” explains Laerte Sodré Júnior, an author in the study and professor at the University of São Paulo’s Institute of Astronomy, Geophysics & Atmospheric Sciences (IAG-USP).

    Entropy is a measure of disorder. According to the second law of thermodynamics, the universe can only become more disordered and random over time – in other words, the total entropy must increase.

    But Vlasov’s equation assumes that entropy stays the same. This suggests that time is ‘reversible’, which clearly cannot be the case – a puff of smoke does not turn back into unburnt wood, and a star cluster does not spontaneously fly apart. The tension between Vlasov’s equation and the one-way nature of violent relaxation is referred to as “the fundamental paradox of stellar dynamics”.

    “It was clear to us that something was wrong, and our suspicion was confirmed by the study,” Sodré says. “The Vlasov equation simply doesn’t apply to this case.”

    The team relied on powerful computational resources to investigate the gravitational interactions between celestial bodies. For a two-body system this is a cinch, but in a system containing millions of bodies each interacting with every other body, the team needed to conduct complex numerical simulations, each of which took several days of computer time.

    The simulations showed that the overall entropy does increase. But the team also found that at the beginning of the relaxation period, the entropy of the system actually fluctuates, sometimes increasing and sometimes decreasing.

    “No other types of system display entropy oscillations that I know of, bar one: chemical reactions in which the compound produced serves as a catalyst for the inverse reaction,” Sodré said. “As a result, the reaction switches to and fro, and entropy in the system oscillates.”

    See the full article here .

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