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  • richardmitnick 9:45 am on July 6, 2019 Permalink | Reply
    Tags: , , , , , From UCSC "All the Gold in the Unverse", , , Neutron star collisions   

    From COSMOS Magazine: “We are stardust. And Big Bang dust.” 

    Cosmos Magazine bloc

    From COSMOS Magazine

    06 July 2019
    Katie Mack

    Neutron star collisions appear to be essential to our chemical origin story.

    Artist’s now iconic conception shows two merging black holes similar to those detected by LIGO in 2017.
    LIGO/Caltech/MIT/Sonoma State (Aurore Simonnet)

    When, in 2017, the LIGO experiment detected gravitational waves from two neutron stars colliding, it sent electromagnetic and gravitational ripples through the universe and the astronomical community.

    This remarkable event, hotly anticipated but never before seen in this way, did more than give us a few new data points about the deaths of stars – it fundamentally changed our understanding of where we and our constituent atoms come from.

    You may have heard before that “we are stardust”. This isn’t wrong. But it’s not the whole story, either.

    A star is, fundamentally, an alchemy machine. It starts as a giant ball of mostly hydrogen gas, slowly crushing its central regions with the pressure of its own gravity. The core of a star eventually gets so hot and dense that it becomes a nuclear reactor, fusing hydrogen into helium.

    In the core of our own sun, this process is converting hundreds of millions of tons of hydrogen into helium every second; what we receive as sunlight is essentially just the waste heat from the reaction.

    This is how the vast majority of stars spend their lives: steadily burning themselves up, turning hydrogen into helium for billions of years. In their final death throes, as they become red giants ready to expel their outer layers, the fusion flares up in bursts, making lithium, carbon and nitrogen, and a smattering of heavier elements.

    To fill in the rest of the periodic table, though, we need stars much more massive than our own. A star more than about eight times as massive as the sun contains at its centre a nuclear furnace that’s burning unimaginably hot.

    After it tears through its supply of hydrogen in the core, it climbs up the list of elements, burning helium, carbon, neon, oxygen and silicon, until after only a few million years the centre of the star is iron and the fusion radiation that had been puffing the star up finally runs out.

    At that point, nothing can stop the star from collapsing on itself, resulting in a spectacular supernova explosion. In the end, at the centre of the debris field will be either a super-dense neutron star or a black hole.

    It’s this final explosion itself, rather than the interior burning, that creates the star’s ultimate chemical legacy. For a brief moment, a shock wave explodes through the layers of the star, creating heat and pressure so intense that a blast front of nuclear fusion carries a radioactive shell of new elements out into interstellar space.

    The universe is seeded with stardust, ready to coalesce into new stars, new planets, new life. For years, it was thought that these stellar deaths were the main mechanisms by which the universe was enriched with metals and other heavy elements.

    But evidence has been mounting that for heavy metals like gold, platinum and uranium, the supernova is just the beginning. It’s the tiny, dense, neutron star that carries within it the potential to explode across the rest of the periodic table.

    Which brings us back to the LIGO detection. When the signal was first seen, astronomers around the world trained their telescopes on the same part of the sky. The resulting observations showed a clear sign in the brief flash that the stars had created enough gold to outweigh the Earth several times over.


    Please access this huge project on the 2017 find

    Tim Stephens
    Nick Gonzales
    Carolyn Lagattuta
    Header image:
    Illustration by Robin Dienel courtesy of the Carnegie Institution for Science
    Design and development:
    Rob Knight
    Project managers:
    Sherry Main, Scott Hernandez-Jason, Tim Stephens

    Neutron star collisions appear to be essential to our chemical origin story. We are born of unimaginable violence in the stellar generations that came before our own. But there’s more to the story.

    Most of the atoms in our bodies didn’t come from stars at all. They are, in fact, much more ancient. If you count up all the atoms in your body, more than 60% will be hydrogen, and the majority of the hydrogen in the universe has never been in a star at all.

    Hydrogen, or, specifically, the protons that would later join with electrons to make neutral hydrogen atoms, was created in the primordial fire of the Big Bang itself.

    In the first moments of the universe, every part of space was filled with a kind of prenuclear plasma hotter and denser than the centre of even the most massive star.

    As this fire expanded and cooled, protons and neutrons, the building blocks of atomic nuclei, first came into being.

    Hydrogen appeared in the form of solitary protons, along with small amounts of helium and lithium. These nuclei have persisted for the 13.8 billion years since those first moments, coming together in stars and, eventually, us.

    So, yes, you are stardust. But you are also the ashes of the Big Bang: ancient atomic alchemy brought together by the inexorable flow of gravity and time.

    See the full article here .

    Please help promote STEM in your local schools.

    Stem Education Coalition

  • richardmitnick 1:27 pm on October 17, 2018 Permalink | Reply
    Tags: , , , , , from Euclid to LIGO, From UCSC "All the Gold in the Unverse", , The Australian International Gravitational Research Centre   

    From The Australian International Gravitational Research Centre via COSMOS: “A short [?] history of spacetime from Euclid to LIGO” 

    From The Australian International Gravitational Research Centre



    17 October 2018
    David Blair

    A year ago today, the world learned that a huge team of scientists around the world had confirmed the existence of gravitational waves, the long history of discovery that led to breakthrough.

    The discovery of gravitational waves marked an important step on a never-ending journey of discovery regarding the nature of the universe.
    sakkmesterke/Getty Images

    In 2015 we first heard the whooping sound made by a pair of colliding black holes. Two years later it was the unique chirp made by a pair of colliding neutron stars. Our newfound ability to eavesdrop on cataclysmic events at the far reaches of the universe is thanks to a new generation of gravitational wave detectors. The gravitational sound show is just beginning, and it promises to reveal the nature of spacetime as never before.

    The quest to understand space

    What is space? We know thinkers have pondered that question at least for as long as there are recorded texts. The clay tablets left by Ancient Babylonians show they were toying with the nature of triangles.

    But, 2300 years ago, the Greek mathematician Euclid revolutionised the science of geometry with systematic thinking that captured the descriptive work of the past and elevated it to the level of universal truths or axioms.

    His 13-volume treatise Elements uncovered the perfection of lines and shapes and put it all together in the most influential science book of all time, in print for 2000 years and published in 1000 editions. It is still taught in schools today.

    But are Euclid’s axioms truly universal?

    In the early 1800s, German mathematician and physicist Carl Gauss was the first to challenge Euclid’s laws of geometry, especially his fifth axiom, which states that parallel lines can never meet.

    Gauss observed that on curved surfaces, parallel lines – such as longitude lines at the earth’s equator – intersect at the poles. He also realised that space could have shape, and his Egregium Theorem showed that you could measure its shape if you measured distances and angles.

    Imagine you’re an ant living on a balloon; your world would seem flat. But an ant familiar with the Egregium Theorem would stretch strings and draw triangles. If the angles of the triangle added up to more than 180 degrees, the ant would know it’s living on curved space.

    Egregium, by the way, is Latin for “exceptional”.

    Gauss’ determination to put Euclid’s theorems to the test set the scene for Einstein.

    By 1905, he had already come up with his theory of Special Relativity. This was the theory that gave us E=Mc2, which means that energy has mass and mass has energy.

    In 1907 Einstein had another revelation that he later described as “the happiest thought of my life”. He realised that gravity is indistinguishable from acceleration. If you’re riding an elevator with your bathroom scales, you’ll find you’re lighter as the elevator accelerates down and heavier when it decelerates. So, Einstein realised, gravity is the force you feel when you prevent free fall.

    It took eight more years and help from his friends for him to combine this happy thought with Gauss’s thinking about the shape of space, to create his final theory of gravity: General Relativity. Published in 1915, it was based on the revolutionary idea that mass and energy deform space and time, and that deformed spacetime itself has energy. In a certain sense spacetime is an elastic material: immensely stiff but deformable – like a trampoline.

    Einstein’s publication gave rise to a succession of remarkable discoveries.

    Within months, while serving in the German army, physicist and astronomer Karl Schwarzschild solved Einstein’s equations to reveal how the curvature of space and the warping of time depends on distance from a central mass. The closer the distance and the larger the mass, the more warping there is, and at a certain distance from a central point mass space and time actually come to an end.

    He was of course imagining a ‘black hole’, but it would take 50 years before the term was coined.

    A few months later, in 1916, Einstein found a solution to his own equations. It predicted the existence of gravitational waves, ripples in spacetime that would travel at the speed of light.

    And in the following years, discoveries provided support for the notion that space was a deformable elastic medium – one that could propagate gravitational waves.

    In 1919, English physicist Sir Arthur Eddington’s observation of an eclipse from the island of Principe near West Africa proved that space is curved by the Sun. In 1922 Russian scientist Alexander Friedmann showed that Einstein’s equations predicted a dynamic universe in which space itself must either expand or contract. And in 1929 American astronomer Edwin Hubble discovered that the universe was in fact expanding.

    When Einstein predicted gravitational waves in 1916 he realised that they could be generated by pair of stars circling each other. He came up with a formula that describes how gravitational wave power depends on their masses, the speeds and the spacing – all measurable numbers.

    But there was a catch: in his formula, the wave power was divided by an enormous number, a crazy number, that I call Einstein’s number. Algebraically, Einstein’s number is c5/G – the speed of light multiplied by itself five times, divided by G, the tiny number that tells us the weakness of gravity.

    Put together, c5/G is more than 1054. If you divide anything by a number this vast, you get next to nothing. Einstein realised this. Nothing he could conceive of could possibly produce measurable gravitational waves. The waves were of academic interest only, he concluded.

    What Einstein hadn’t been aware of was that Schwarzschild, who died of an auto-immune disease in 1916, had left him a hidden treasure. The trouble was that Schwarzschild’s solution, which described a singularity where space and time cease to exist, was viewed by Einstein and others as a mathematical oddity, not a description of anything that could possibly be real.

    But 50 years on, black holes – as these singularities were later dubbed – were the best hypothesis to explain a strange x-ray emitting star called Cygnus X-1.

    A tiny object with vast gravity was needed to explain this powerful erratic x-ray emission. People began to think that black holes might be real.

    Then someone took Einstein’s 1916 equation for wave power, and substituted in Schwarzschild’s black hole formula. A school kid could have done it. The result was miraculous!

    With Schwarzschild’s formula, the division by Einstein’s number that made gravitational waves merely academic is transformed into a multiplication by the same number. Suddenly the wave power for a pair of black holes circling each other up-close becomes almost as big as Einstein’s number itself.

    This is roughly the power of all the stars in the visible universe! The catch is it lasts for only an instant. This was Schwarzschild’s hidden treasure.

    Schwarzschild’s work tells us that when black holes collide they create a pure gravitational explosion, more powerful than a supernova or a gamma ray burst. Nothing beats it except the Big Bang itself.

    However, as an explosion of rippling space, it would pass freely through you. Even if it happened as nearby to Earth as the Sun, you would feel no more than a tiniest shudder. Yet each such gravitational explosion would in principle be detectable across the entire universe.

    Harnessing inertia to build a gravitational wave detector

    I was inspired to join the quest to detect colliding black holes by the eccentric pioneer of gravitational wave astronomy, American physicist Joseph Weber. Back then, we reasoned that explosions so vast must be detectable. We thought that if we worked hard at inventing a gravitational detector, we might pick up a signal by Christmas! That was in 1973.

    Our ability to detect gravitational waves relies on the concept of inertia – the tendency of matter to continue in its state of motion unless acted on by an external force.

    Scientists have been relying on inertia to detect relative motion for nearly 2000 years. In 132 AD, Chinese scientist Zhang Heng harnessed inertia to build the first seismometer.

    Inside a big bronze urn he suspended a mass so that it could swing freely in the horizontal plane. If the ground moved, so would the urn, but the mass, anchored to space by the law of inertia, would stay in place.

    Inside, the movement dislodged a ball from the mouth of one of eight dragons that marked the cardinal directions. The ball rolled out and was caught in the mouth of a bronze toad. This way he detected an earthquake hundreds of kilometres away.

    Heng’s seismometer allowed him to detect the motion of the earth against unchanging space. But what if space suddenly stretches? You won’t feel a thing, and nor will a seismometer, just as you do not feel the universe expanding. But, you might notice that a distant object has just moved away from you. It did this because inertia caused it to follow expanding space.

    Modern day gravitational wave detectors like the Laser Interferometer Gravitational-Wave Observatory (LIGO) in the US detect the stretching and shrinking of space caused by a passing wave by suspending two 40 kilogram masses four kilometres apart.

    These masses are coated with near-perfect mirrors, so changes in the distance between them can be measured by using a beam of laser light as a ruler. The catch is the minuscule size of the change. Like ripples in a pond, gravitational waves diminish as they expand away from the source.

    Even though LIGO was aiming to measure the space distortion created by colliding black holes – the biggest dynamic distortion possible – the ripples they create reduce to half every time you double the distance.

    By the time the wave reaches the Earth from a black hole collision a billion light years away, the stretching and shrinking of space in a LIGO detector has reduced to a hundredth of a billionth of a billionth of a metre – much smaller than the size of a proton.

    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

    ESA/eLISA the future of gravitational wave research

    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)

    A dream fulfilled

    It took more than 40 years and several generations of detectors, before, finally, the pair of advanced LIGO detectors were ready to begin listening for the sounds of gravitational waves. The new detectors were three times more sensitive than previous ones, but still three times below their ultimate design specification. We were hopeful but not optimistic.

    On September 14, 2015, a few days before the official start date, the first signal came in. Was it a hoax? Was it accidental? A short rapidly rising pitch, from two octaves below to middle-C made a brief whoop sound. It was heard in two detectors 3000 kilometres apart and had a time delay just right for a wave travelling at the speed of light. After months of investigation there was no doubt that it was real.

    All our dreams were finally fulfilled on February 11, 2016, when gravitational wave astronomers announced in a Washington press conference, that they had indeed detected a pair of black holes spiralling together and merging into a single black hole.

    And since that first detection, more whoops from other colliding black holes have followed.

    You might think that detecting the collision of a pair black holes would be a hard act to follow. Yet a year and a half after that announcement, the world was again thrilling to the news of another type of cosmic cataclysm.

    We had not been optimistic about detecting colliding black holes because we had very little idea how many pairs of black holes might exist. Instead we had placed our hopes on something we knew much more about: neutron stars.

    Neutron stars are one step away from becoming a black hole. Many exist as pulsars: rapidly spinning remnants of supernova explosions that emit powerful flickering beams of radio waves. They have a dimeter of about 20 kilometres, are composed of neutrons, and are denser than an atomic nucleus.

    Thousands of them are known in the Milky Way, and the predictions were that out in the distant universe we might be able to detect one or two of them merging every year.

    Little did we know that we were already detecting those events.

    During the 1980s astronomers were puzzling over vast bursts of gamma rays being detected by orbiting gamma ray telescopes, on average one every day.

    In 1989 a paper published in Nature by Hebrew University physicist Tsvi Piran proposed these bursts were created by merging neutron stars, spiralling together at 10% of light speed, and flinging some of their nearly pure neutron matter out into space. Here it would go off like an enormous nuclear fission bomb, giving off bursts of gamma rays. The process would also be a forge for heavy elements in the universe like platinum and gold.

    Since the advanced LIGO detectors started working in 2015, our 1000-strong team comprising researchers based at more than 80 universities around the world were hoping for all of this: a long slow chirp of gravitational waves as a pair of neutron stars spiralled together, a burst of gamma rays produced when they collided, and an atomic explosion where we might see the signature of gold production.

    Most of us thought the chances of all of this was very small. The gamma ray beam might miss the earth. The explosion, called a macronova or kilonova, is much weaker than a supernova and would be hard to detect.

    However, more than 100 telescopes around the world had already signed up to receive alerts from the LIGO detectors on either side of the US, and the European Virgo detector in Pisa, Italy, in the event of a gravitational wave signal.

    On August 17, 2017, all of our Christmases came at once.

    It was exactly what we had dreamed of. The gravitational wave signal was loud and clear in the two LIGO detectors in the US, but very weak in the European Virgo detector because of its orientation.

    The non-detection by Virgo told us roughly where to look in the sky. The Fermi gamma ray observatory out in space detected a burst of gamma rays 1.7 seconds later, coming from the same region of sky. A few hours later the Swope telescope in Chile detected the fading glow of a vast explosion, in that same region, at the edge of a known galaxy, 130 million light years away.

    Before long 100 telescopes across the southern hemisphere were watching it. The colours in the light indicated the presence of heavy elements like gold and platinum.

    The future

    We called this the birth of multi-messenger astronomy: the gravity wave messenger and the electromagnetic messenger worked in unison. This discovery was a stupendous example of scientific prediction. It confirmed Einstein’s 102 year-old prediction that gravity waves travel at the speed of light, and Piran’s 28 year-old prediction that gamma ray bursts were the signature of colliding neutron stars, and that gold and platinum were formed in this explosion.

    Think about this: that gold on your finger is a fossil from the collision of two neutron stars.

    From these recent discoveries we can predict what lies ahead. As sensitivity improves, we’ll exponentially increase our reach into the universe. Increase the sensitivity by two and you’re reaching into a volume 23 times larger, which means eight times as many signals.

    In the next few years the world’s existing three detectors, plus two more under construction in Japan and India, should be tuning in to the sounds of hundreds of black hole and neutron stars collisions every year.

    More detectors will help to pinpoint the source of the signals, but the biggest pay-off comes from increasing sensitivity. Just a four-fold increase in sensitivity would expand our horizon to more than half of the visible universe. A 10-fold improvement would give us the whole universe! Detectors with this capability have been suggested for Australia, China, Europe and the USA.

    The legacy of Einstein, the recent Nobel Prize winners and the huge international LIGO and Virgo team, will be the ability to listen to the symphony of the universe. It will be in a minor key because the truth is that our universe is winding down as black holes form, grow and gobble up each other.

    But I can’t end on a melancholy note. Rather I want to sing in celebration of gravitational waves as humanity’s new set of ears. We are no longer deaf to the sounds of space. And we can be pretty certain that our cosmic ears will give us deeper understanding of the nature of space.

    We are still groping to understand its microstructure and its reason for being. Is it a quantum foam inhabited by strings, or is it something else?

    Stay tuned for surprises, unforeseen revelations, and an avalanche of discoveries as our remarkable new technology develops.

    An extra treat https://sciencesprings.wordpress.com/2017/10/20/from-ucsc-neutron-stars-gravitational-waves-and-all-the-gold-in-the-universe/

    See the full article here .


    Please help promote STEM in your local schools.

    Stem Education Coalition

    The Australian International Gravitational Observatory (AIGO) Located at Gingin

    Welcome to the Australian International Gravitational Research Centre. The Australian International Gravitational Research Centre is based in the School of physics of the University of Western Australia (UWA) and is part of the Australian Consortium for Interferometric Gravitational Astronomy (ACIGA). It was established in 1990 to enable a cooperative research centre providing a national focus in a major frontier in physics: the detection of gravitational waves and the development of gravitational astronomy. Through strong national and international participation, the research centre concentrates on the development of advanced technologies driven by the goal of the next generation large scale gravitational observatory construction.

  • richardmitnick 6:19 am on August 24, 2018 Permalink | Reply
    Tags: , , From UCSC "All the Gold in the Unverse", , , ,   

    From The Conversation: “We’re going to get a better detector: time for upgrades in the search for gravitational waves” 

    From The Conversation

    August 16, 2018
    Robert Ward

    It’s been a year since ripples in space-time from a colliding pair of dead stars tickled the gravitational wave detectors of the Advanced LIGO and Advanced Virgo facilities.

    Soon after, astronomers around the world began a campaign to observe the afterglow of the collision of a binary neutron star merger in radio waves, microwaves, visible light, x-rays and more.

    See https://sciencesprings.wordpress.com/2017/10/16/from-ucsc-a-uc-santa-cruz-special-report-neutron-stars-gravitational-waves-and-all-the-gold-in-the-universe/

    This was the dawn of multi-messenger astronomy: a new era in astronomy, where events in the universe are observed with more than just a single type of radiation. In this case, the messengers were gravitational waves and electromagnetic radiation.

    What we’ve learned (so far)

    From this single event, we learned an incredible amount. Last October, on the day the detection was made public, 84 scientific papers were published (or the preprints made available).

    We learned that gravity and light travel at the same speed, neutron star mergers are a source of short gamma-ray bursts, and that kilonovae – the explosion from a neutron star merger – are where our gold comes from.

    This rich science came from the fact that we were able to combine our observatories to witness this single event from multiple astronomical “windows”. The gravitational waves arrived first, followed 1.7 seconds later by gamma-rays. That is a pretty small delay, considering the waves had been travelling for 130 million years.

    Over the next few weeks, visible light and radio waves began to be observed and then slowly faded.

    It seemed like the news about gravitational waves was coming fast and furious, with the first detection announced in 2016, a Nobel prize in 2017, and the announcement of the binary neutron star merger just weeks after the Nobel prize.

    Time for upgrades

    On this first anniversary of the neutron star merger, the gravitational wave detectors are offline for upgrades. They actually went offline shortly after the detection and will come back online some time early in 2019.

    The work of making gravitational wave detectors function requires extraordinary patience and dedication. These are exquisite experiments – it took more than 40 years of technological development by a community of more than a thousand scientists to get to the point of detecting the first signal.

    Naturally, improving on this work is not easy. So what does it actually take?

    We really do listen to gravitational waves, and our detectors act more like microphones than telescopes or cameras.

    Quiet please!

    To detect gravitational waves, we need to do more than just turn off the dishwasher. We need to build the quietest, best-isolated thing on Earth.

    Unfortunately, the laws of quantum mechanics and thermodynamics both prevent us from eliminating the noise entirely. Nonetheless, we strive to do the best that these fundamental limits permit. This involves, among many other extraordinary things, hanging our mirrors on glass threads .

    Before sealing up the chamber and pumping the vacuum system down, a LIGO optics technician inspects one of LIGO’s core optics (mirrors) by illuminating its surface with light at a glancing angle. Matt Heintze/Caltech/MIT/LIGO Lab

    Our mirrors weight 40kg each and are suspended from four of these glass threads, which are less than a half-millimetre in diameter and exquisitely crafted.

    The threads are under enormous stress, and the slightest imperfection (or the slightest touch) can cause them to explode.

    Just such an explosion happened earlier this year while installing a new mirror. Fortunately, the precious mirror fell into a cradle designed for just such a possibility, and was not damaged.

    Nonetheless, the delicate, intricate work of creating the glass threads, attaching them to the mirror, hanging the mirror and then installing it all needed to be redone.

    Improvements to the detector

    This was a heartbreaking setback for the team, but the added delay was not entirely in vain. In parallel with remaking the glass threads and rehanging the new mirror, we made some other improvements to the detector, for which we otherwise would not have had enough time.

    One of the goals of this upgrade period is to install something called a quantum squeezed light source into the gravitational wave detectors.

    As mentioned earlier, quantum mechanics mandates a certain minimum amount of noise in any measurement. We can’t arbitrarily reduce this quantum noise, but we can move it around and change its shape by squeezing it.

    This is a bit like sweeping dust under the rug. It’s not really gone, but it might not bother you so much anymore. The quantum squeezed light source does just this.

    Australian National University scientists Nutsinee Kijbunchoo and Terry McCrae build components for a quantum squeezed light source at LIGO Hanford Observatory in Washington, US. Nutsinee Kijbunchoo

    A gravitational wave detector is already a very complex system, and a squeezed light source is another complex system, so putting them together can be a challenge.

    Despite the complexity of this challenge, when the squeezed light source was activated for the first time at the LIGO detector in Livingston, Louisiana, US, in February this year there was an immediate improvement in the quantum noise: the gravitational wave detector output got just a bit quieter.

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

    See the full article here .


    Please help promote STEM in your local schools.

    Stem Education Coalition

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

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