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  • richardmitnick 6:19 am on August 24, 2018 Permalink | Reply
    Tags: , , , , , , The Conversation   

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

    Conversation
    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 .

    2
    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.

    3
    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 .

    five-ways-keep-your-child-safe-school-shootings

    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.

     
  • richardmitnick 12:08 pm on August 21, 2018 Permalink | Reply
    Tags: , , , , deaths and collisions of stars through 1 million snapshots in UV, , Swift’s telescope reveals birth, The Conversation   

    From The Conversation: “Swift’s telescope reveals birth, deaths and collisions of stars through 1 million snapshots in UV” 

    Conversation
    From The Conversation

    1

    Imagine if the color camera had never been invented and all our images were in black and white. The world would still look beautiful, but incomplete. For thousands of years, that was how humans saw the universe. On Earth, we can only see part of the light that stars emit.

    Much of what we can’t see – in the infrared, the ultraviolet, the X-ray and the gamma ray wavelengths – is blocked by the Earth’s atmosphere. For the most part, this is a good thing. The atmosphere traps infrared light keeping the Earth warm at night and blocks high-energy ultraviolet light, X-rays and gamma rays, keeping us safe from deadly cosmic radiation, while letting in visible portions of the spectrum of light. For astronomers, however, this has a drawback: We look at the universe with one eye shut, unable to receive all of the information the universe is sending to us.

    2
    Visible light is just a tiny part of the electromagnetic spectrum. NASA

    Launched on November 20, 2004, and orbiting an altitude of 340 miles, NASA’s Neil Gehrels Swift Observatory has three telescopes that monitor the universe using wavelengths of light that are blocked by Earth’s atmosphere.

    NASA Neil Gehrels Swift Observatory

    These included the X-Ray Telescope, the gamma-ray-sensitive Burst-Alert Telescope and the Ultraviolet Optical Telescope (UVOT). The UVOT recently delivered its 1 millionth image – data that astrophysicists like me use to gain insights into everything from the origins of the universe to the chemical composition of nearby comets.

    Watching the birth of black holes

    Swift’s primary mission is to study the afterglow of gamma ray bursts (GRBs) – which document the birth of black holes. Black holes are forged in the most violent explosions in the universe – the explosion of a massive star or the merging of two neutron stars (the shriveled husks left over from past stellar explosions). These explosions are so powerful – producing tens to hundreds of billions of times more energy than the sun – that even though they occur billions of light years away from Earth, they can still be detected by instruments like Swift. In fact, the first GRBs were detected by the Vela satellites, which were built to detect the explosions of nuclear weapons.

    Over nearly 14 years, Swift has studied over a thousand GRBs. In doing so, it has revealed what powers them and given us glimpses into the furthest reaches of the cosmos, to the time when the first stars were being formed after the Big Bang.

    However, one of the things you learn working on a space telescope mission is that if you build it, they will come. The mission provides capabilities to the community of astrophysicists – simultaneous X-ray/UV imaging and a rapid response to requests to observe and photograph specific sections of the sky – which are only available to Swift. We can focus our telescopes on an object of interest within hours of a “Target of Opportunity” request through our website, something no other mission can do. UVOT also fills an important niche by observing larger areas of the sky than can be observed with the more powerful UV instruments aboard the Hubble Space Telescope. These capabilities have proved a boon to the community and enabled study all sorts of objects and phenomenon beyond GRBs.

    Swift’s ultraviolet-aided discoveries

    Nearby galaxies are full of activity with new stars being formed. Swift is able to capture panoramic ultraviolet images that highlight the youngest, most massive stars in these galaxies. This gives us insight into what the universe has been doing over the last few hundred million years. My research team’s work has focused on nearby galaxies – like Andromeda and the Magellanic Clouds – to reveal what processes drive their past and ongoing star formation.

    Andromeda Galaxy Messier 31 with Messier32 -a satellite galaxy copyright Terry Hancock.

    Magellanic Clouds ESO S. Brunier

    With UVOT, we get a much better view of supernova explosions. These can occur when a white dwarf, the remnant of a star like the sun, explodes, or during the final death throes of a massive star, more than eight times the mass of the sun. These events generate enormous amounts of ultraviolet light, and Swift has a unique ability to observe them within hours of discovery.

    3
    On the left is an ultraviolet composite made from several images of the Whirpool Galaxy (M51) taken between 2005-2007. The image on the right was made in June 2011, shortly after astronomers detected the explosion of a massive star in one of the galaxy’s outer spiral arms. The object is marked by the red circle. NASA/Swift/E. Hoversten, PSU, CC BY-ND

    Comets sweep through our solar system, transforming from a frozen solid ball to a vapor as they approach the sun and creating magnificent tails of ionized particles. Swift studies these comets, and analyzes their chemical composition by breaking the light they emit into different wavelengths. Swift also allows scientists to measure a comet’s rotation by seeing how the light changes over time. This has revealed that violent eruptions on the comet surface can dramatically alter a comet’s path.

    5
    This image of Comet Lulin was taken by Swift on January 28, 2009. It shows data obtained by Swift’s Ultraviolet/Optical Telescope (blue and green) and X-Ray Telescope (red). The image of the star field (white) was acquired by the Digital Sky Survey. At the time of the observation, comet Lulin was 99.5 million miles from Earth and 115.3 million miles from the sun. The ultraviolet light comes from hydroxyl molecules and shows that, at this time, Lulin was shedding 800 gallons of water every second. D. Bodewits/Swift/NASA, CC BY-ND

    One of the most exciting discoveries that Swift made was connected with the recent discovery of gravitational waves by the Laser Interferometer Gravitational-Wave Observatory (LIGO).


    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)

    Gravitational waves are distortions in the fabric of spacetime created by the motions of extremely massive objects. In August of 2017, two neutrons stars collided in a distant galaxy, creating gravitational waves powerful enough to be detected on Earth. Swift was one of an army of telescopes that looked for the source of the gravitational waves. The mad scramble over those few days led to one of the most exciting discoveries of the last decade – a luminous afterglow from the source of the gravitational waves. This has opened up new branches of science by connecting a new way of studying the universe – through gravitational waves – to the traditional way – through light.

    See also 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/

    UVOT has been taking snapshots of the universe since 2004 and finally piled up its millionth image. Its success is a testament to the international team of engineers, scientists and staff at the three institutions that support it – the Pennsylvania State University; Mullard Space Science Laboratory in Surrey, England; and NASA’s Goddard Space Flight Center in Greenbelt, Maryland. It has been my privilege to be a part of this team for the last nine years. What does the future hold for UVOT? We hope to find more sources of gravitational waves, survey nearby galaxies, study even more supernovae, and monitor how objects in the universe change over time.

    Here’s to the next million images.

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    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.

     
  • richardmitnick 9:43 am on August 21, 2018 Permalink | Reply
    Tags: , , , , , The Conversation   

    From The Conversation and EarthSky: “What are rare earths, crucial elements in modern technology? 4 questions answered” 

    1

    EarthSky

    Conversation
    From The Conversation

    August 16, 2018
    Stanley Mertzman

    1
    A handful of europium. Image via Alchemist-hp

    Most Americans use rare earth elements every day – without knowing it, or knowing anything about what they do. That could change, as these unusual materials are becoming a focal point in the escalating trade war between the U.S. and China.

    1. What are rare earth elements?

    Strictly speaking, they are elements like others on the periodic table – such as carbon, hydrogen and oxygen – with atomic numbers 57 to 71. There are two others with similar properties that are sometimes grouped with them, but the main rare earth elements are those 15. To make the first one, lanthanum, start with a barium atom and add one proton and one electron. Each successive rare earth element adds one more proton and one more electron.

    2
    An electron diagram of a barium element, the last element before the lanthanide rare earth elements. Greg Robson and Pumbaa, CC BY-SA

    3
    An electron diagram of a lanthanum atom, with one more electron in its fifth orbital than barium. Greg Robson and Pumbaa, CC BY-SA

    4
    Cerium has one more electron in its fifth orbital and one more in its fourth than barium. Greg Robson and Pumbaa, CC BY-SA

    It’s significant that there are 15 rare earth elements: Chemistry students may recall that when electrons are added to an atom, they collect in groups or layers, called orbitals, which are like concentric circles of a target around the bull’s-eye of the nucleus.

    The innermost target circle of any atom can contain two electrons; adding a third electron means adding one in the second target circle. That’s where the next seven electrons go, too – after which electrons must go to the third target circle, which can hold 18. The next 18 electrons go into the fourth target circle.

    Then things start to get a bit odd. Though there is still room for electrons in the fourth target circle, the next eight electrons go into the fifth target circle. And despite more room in the fifth, the next two electrons after that go into the sixth target circle.

    That’s when the atom becomes barium, atomic number 56, and those empty spaces in earlier target circles start to fill. Adding one more electron – to make lanthanum, the first in the series of rare earth elements – puts that electron in the fifth circle. Adding another, to make cerium, atomic number 58, adds an electron to the fourth circle. Making the next element, praseodymium, actually moves the newest electron in the fifth circle to the fourth, and adds one more. From there, additional electrons fill up the fourth circle.

    In all elements, the electrons in the outermost circle largely influence the element’s chemical properties. Because the rare earths have identical outermost electron configurations, their properties are quite similar.

    2. Are rare earth elements really rare?

    No. They’re much more abundant in the Earth’s crust than many other valuable elements. Even the rarest rare earth, thulium, with atomic number 69, is 125 times more common than gold. And the least-rare rare earth, cerium, with atomic number 58, is 15,000 times more abundant than gold.

    5
    The rarest rare earth element, thulium. Jurii, CC BY

    They are rare in one sense, though – mineralogists would call them “dispersed,” meaning they’re mostly sprinkled across the planet in relatively low concentrations. Rare earths are often found in rare igneous rocks called carbonatites – nothing so common as basalt from Hawaii or Iceland, or andesite from Mount St. Helens or Guatemala’s Volcano Fuego.

    There are a few regions that are have lots of rare earths – and they’re mostly in China, which produces more than 80 percent of the global annual total of 130,000 metric tons. Australia has a few areas too, as do some other countries. The U.S. has a little bit of area with lots of rare earths, but the last American source for them, California’s Mountain Pass Quarry, closed in 2015.

    3. If they’re not rare, are they very expensive?

    Yes, quite. In 2018, the cost for an oxide of neodymium, atomic number 60, is US$107,000 per metric ton. The price is expected to climb to $150,000 by 2025.

    Europium is even more costly – about $712,000 per metric ton.

    Part of the reason is that rare earth elements can be chemically difficult to separate from each other to get a pure substance.

    4. What are rare earth elements useful for?

    In the last half of the 20th century, europium, with atomic number 63, came in to wide demand for its role as a color-producing phosphor in video screens, including computer monitors and plasma
    TVs. It’s also useful for absorbing neutrons in nuclear reactors’ control rods.

    6
    A cube of small neodymium magnets. XRDoDRX, CC BY-SA

    Other rare earths are also commonly used in electronic devices today. Neodymium, atomic number 60, for instance, is a powerful magnet, useful in smartphones, televisions, lasers, rechargeable batteries and hard drives. An upcoming version of Tesla’s electric car motor is also expected to use neodymium.

    Demand for rare earths has risen steadily since the middle of the 20th century, and there are no real alternative materials to replace them. As important as rare earths are to a modern technology-based society, and as difficult as they are to mine and use, the tariff battle may put the U.S. in a very bad place, turning both the country and rare earth elements themselves into pawns in this game of economic chess.

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    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.

    Deborah Byrd created the EarthSky radio series in 1991 and founded EarthSky.org in 1994. Today, she serves as Editor-in-Chief of this website. She has won a galaxy of awards from the broadcasting and science communities, including having an asteroid named 3505 Byrd in her honor. A science communicator and educator since 1976, Byrd believes in science as a force for good in the world and a vital tool for the 21st century. “Being an EarthSky editor is like hosting a big global party for cool nature-lovers,” she says.

     
  • richardmitnick 9:59 am on June 11, 2018 Permalink | Reply
    Tags: , , , , How we discovered 840 minor planets beyond Neptune – and what they can tell us, , The Conversation   

    From Queens University, Belfast via The Conversation: “How we discovered 840 minor planets beyond Neptune – and what they can tell us” 

    Queens University, Belfast

    The Conversation

    May 25, 2018
    Michele Bannister

    Our solar system is a tiny but wonderfully familiar corner of the vast, dark universe – we have even been able to land spacecraft on our celestial neighbours. Yet its outer reaches are still remarkably unmapped. Now we have discovered 840 small worlds in the distant and hard-to-explore region beyond Neptune. This is the largest set of discoveries ever made, increasing the number of distant objects with well known paths around the sun by 50%.

    These little icy worlds are important as they help us tell the solar system’s history. They can also help us test the idea that there’s a yet unseen planet lurking in the outer solar system.

    Our planetary system as we see it today is not as it formed. When the sun was newborn, it was surrounded by a massive disk of material. Encounters with tiny, growing planets – including some of the worlds we’ve just discovered – moved the giant planets outward from the sun until they settled into their present locations. The growing planets, on the other hand, went everywhere, scattering both inward and outward.

    Planetary migration also happened in far away systems around many other stars. Fortunately, the celestial bodies in our own planetary system are comparatively close by, making it the only place where we can see the intricate details of how migration happened. Mapping the minor planet populations that are left over from the disk lets us reconstruct the history of how the big planets were pushed into place.

    Mapping the sky

    The new discoveries were made as part of a five year project called the Outer Solar System Origins Survey (OSSOS). The observations, conducted in 2013-2017, used the [MegaCam] imaging camera of one of the world’s major telescopes – the Canada-France-Hawaii Telescope on Maunakea in Hawaii.



    CFHT Telescope, Maunakea, Hawaii, USA, at Maunakea, Hawaii, USA,4,207 m (13,802 ft) above sea level


    CFHT MegaCam

    The survey looked for faint, slow-moving points of light within eight big patches of sky near the plane of the planets and away from the dense star fields of the Milky Way.

    With 840 discoveries made at distances between six and 83 astronomical units (au) – one such unit is the distance between the sun and the Earth – the survey gives us a very good overview of the many sorts of orbits these “trans-Neptunian objects” have.

    Earlier surveys have suffered from losing some of their distant discoveries – when too few observations occur, the predicted path of a minor planet in the sky will be so uncertain that a telescope can’t spot it again, and it is considered “lost”. This happens more to objects with highly tilted and elongated orbits, producing a bias in what’s currently known about these populations.

    Our new survey successfully tracked all its distant discoveries. The frequent snapshots we made of the 840 objects over several years meant that each little world’s orbit could be determined very precisely. In total, more than 37,000 hand-checked measurements of the hundreds of discoveries precisely pinned down their arcs across the sky.

    We also created an accompanying software “simulator” (a computer model), which provides a powerful tool for testing the inventory and history of our solar system. This lets theorists test out their models of how the solar system came to be in the shape we see it today, comparing them with our real discoveries.

    Strange new worlds

    The new icy and rocky objects fall into two main groups. One includes those that reside on roundish orbits in the Kuiper belt, which extends from 37au to approximately 50au from the sun.

    Kuiper Belt. Minor Planet Center

    The other consists of worlds that orbit in a careful dance of avoidance with Neptune as it travels around the sun. These “resonant” trans-Neptunian objects, which include Pluto, were pushed into their current elongated orbits during Neptune’s migration outwards.

    In the Kuiper belt, we found 436 small worlds. Their orbits confirm that a concentrated “kernel” of the population nestles on almost perfectly round, flat orbits at 43 to 45au. These quiet orbits may have been undisturbed since the dawn of the solar system, a leftover fraction of the original disk. Soon, we will see a member of this group up close: the New Horizons spacecraft, which visited Pluto in 2015, will be flying by a world that’s about the size of London on New Year’s Day 2019.

    NASA/New Horizons spacecraft

    3
    The dwarf planet candidate 2015 RR245 is on an exceptionally distant orbit, but is one of the few dwarf planets that could one day be reached by a spacecraft mission. Alex Parker/OSSOS, CC BY-SA

    We found 313 resonant trans-Neptunian objects, with the survey showing that they exist as far out as an incredible 130au – and are far more abundant than previously thought. Among these discoveries is the dwarf planet 2015 RR245, which is about half the size of Britain. It may have hopped onto its current orbit at 82au after an encounter with Neptune hundreds of millions of years ago. It was once among the 90,000 scattered objects of smaller size that we estimate currently exist.

    Are there more planets?

    Among the most unusual of the discoveries are nine little worlds on incredibly distant orbits, never coming closer to the sun than Neptune’s orbit, and taking as long as 20,000 years to travel around our star. Their existence implies an unseen population of hundreds of thousands of trans-Neptunian objects on similar orbits.

    5
    Artist’s concept of Planet Nine. NASA/JPL-Caltech/Robert Hurt, CC BY-SA

    How these objects got on their present paths is unclear — some orbit so far out that, even at their closest approach, they are barely tugged by Neptune’s gravity. One explanation that has been put forward is that a yet unseen large planet, sometimes called “Planet Nine”, could be causing them to cluster in space. However, our nine minor planets all seem to be spread out smoothly, rather than clustering. Perhaps the shepherding of such a large planet is more subtle – or these orbits instead formed in a different way.

    The history of our solar system is just beginning to be told. We hope this new set of discoveries will help piece together the story.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

    Queen’s University Belfast (informally Queen’s or QUB) is a public research university in Belfast, Northern Ireland. The university was chartered in 1845, and opened in 1849 as “Queen’s College, Belfast”.

    The university forms the focal point of the Queen’s Quarter area of the city, one of Belfast’s six cultural districts. It offers academic degrees at various levels and across a broad subject range, with over 300 degree programmes available. Its acting President and Vice-Chancellor is James McElnay, and its Chancellor is Thomas Moran. The annual income of the institution for 2016–17 was £337.6 million of which £79.6 million was from research grants and contracts, with an expenditure of £325.1 million.

    Queen’s is a member of the Russell Group of leading research intensive universities, the Association of Commonwealth Universities, the European University Association, Universities Ireland and Universities UK. The university is associated with two Nobel laureates and one Turing Award laureate.

     
  • richardmitnick 3:17 pm on May 14, 2018 Permalink | Reply
    Tags: , , , , , , The Conversation, The next big discovery in astronomy? Scientists probably found it years ago – but they don’t know it yet   

    From The Conversation: “The next big discovery in astronomy? Scientists probably found it years ago – but they don’t know it yet” 

    Conversation
    From The Conversation

    May 14, 2018
    Eileen Meyer

    1
    An artist’s illustration of a black hole “eating” a star. NASA/JPL-Caltech

    Earlier this year, astronomers stumbled upon a fascinating finding: Thousands of black holes likely exist near the center of our galaxy.

    1
    Hundreds — Perhaps Thousands — of Black Holes Occupy the Center of the Milky Way

    The X-ray images that enabled this discovery weren’t from some state-of-the-art new telescope. Nor were they even recently taken – some of the data was collected nearly 20 years ago.

    No, the researchers discovered the black holes by digging through old, long-archived data.

    Discoveries like this will only become more common, as the era of “big data” changes how science is done. Astronomers are gathering an exponentially greater amount of data every day – so much that it will take years to uncover all the hidden signals buried in the archives.

    The evolution of astronomy

    Sixty years ago, the typical astronomer worked largely alone or in a small team. They likely had access to a respectably large ground-based optical telescope at their home institution.

    Their observations were largely confined to optical wavelengths – more or less what the eye can see. That meant they missed signals from a host of astrophysical sources, which can emit non-visible radiation from very low-frequency radio all the way up to high-energy gamma rays. For the most part, if you wanted to do astronomy, you had to be an academic or eccentric rich person with access to a good telescope.

    Old data was stored in the form of photographic plates or published catalogs. But accessing archives from other observatories could be difficult – and it was virtually impossible for amateur astronomers.

    Today, there are observatories that cover the entire electromagnetic spectrum. No longer operated by single institutions, these state-of-the-art observatories are usually launched by space agencies and are often joint efforts involving many countries.

    With the coming of the digital age, almost all data are publicly available shortly after they are obtained. This makes astronomy very democratic – anyone who wants to can reanalyze almost any data set that makes the news. (You too can look at the Chandra data that led to the discovery of thousands of black holes!)

    These observatories generate a staggering amount of data. For example, the Hubble Space Telescope, operating since 1990, has made over 1.3 million observations and transmits around 20 GB of raw data every week, which is impressive for a telescope first designed in the 1970s.

    NASA/ESA Hubble Telescope

    The Atacama Large Millimeter Array in Chile now anticipates adding 2 TB of data to its archives every day.

    ESO/NRAO/NAOJ ALMA Array in Chile in the Atacama at Chajnantor plateau, at 5,000 metres

    Data firehose

    The archives of astronomical data are already impressively large. But things are about to explode.

    Each generation of observatories are usually at least 10 times more sensitive than the previous, either because of improved technology or because the mission is simply larger. Depending on how long a new mission runs, it can detect hundreds of times more astronomical sources than previous missions at that wavelength.

    For example, compare the early EGRET gamma ray observatory, which flew in the 1990s, to NASA’s flagship mission Fermi, which turns 10 this year. EGRET detected only about 190 gamma ray sources in the sky. Fermi has seen over 5,000.

    NASA/Fermi LAT


    NASA/Fermi Gamma Ray Space Telescope

    The Large Synoptic Survey Telescope, an optical telescope currently under construction in Chile, will image the entire sky every few nights. It will be so sensitive that it will generate 10 million alerts per night on new or transient sources, leading to a catalog of over 15 petabytes after 10 years.

    LSST

    LSST Camera, built at SLAC



    LSST telescope, currently under construction on the El Peñón peak at Cerro Pachón Chile, a 2,682-meter-high mountain in Coquimbo Region, in northern Chile, alongside the existing Gemini South and Southern Astrophysical Research Telescopes.

    The Square Kilometre Array , when completed in 2020, will be the most sensitive telescope in the world, capable of detecting airport radar stations of alien civilizations up to 50 light-years away. In just one year of activity, it will generate more data than the entire internet.


    SKA/ASKAP radio telescope at the Murchison Radio-astronomy Observatory (MRO) in Mid West region of Western Australia


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


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


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


    These ambitious projects will test scientists’ ability to handle data. Images will need to be automatically processed – meaning that the data will need to be reduced down to a manageable size or transformed into a finished product. The new observatories are pushing the envelope of computational power, requiring facilities capable of processing hundreds of terabytes per day.

    The resulting archives – all publicly searchable – will contain 1 million times more information that what can be stored on your typical 1 TB backup disk.

    Unlocking new science

    The data deluge will make astronomy become a more collaborative and open science than ever before. Thanks to internet archives, robust learning communities and new outreach initiatives, citizens can now participate in science. For example, with the computer program Einstein@Home, anyone can use their computer’s idle time to help search for gravitational waves from colliding black holes.

    It’s an exciting time for scientists, too. Astronomers like myself often study physical phenomena on timescales so wildly beyond the typical human lifetime that watching them in real-time just isn’t going to happen. Events like a typical galaxy merger – which is exactly what it sounds like – can take hundreds of millions of years. All we can capture is a snapshot, like a single still frame from a video of a car accident.

    However, there are some phenomena that occur on shorter timescales, taking just a few decades, years or even seconds. That’s how scientists discovered those thousands of black holes in the new study. It’s also how they recently realized that the X-ray emission from the center of a nearby dwarf galaxy has been fading since first detected in the 1990s. These new discoveries suggest that more will be found in archival data spanning decades.

    In my own work, I use Hubble archives to make movies of “jets,” high-speed plasma ejected in beams from black holes. I used over 400 raw images spanning 13 years to make a movie of the jet in nearby galaxy M87. That movie showed, for the first time, the twisting motions of the plasma, suggesting that the jet has a helical structure.

    This kind of work was only possible because other observers, for other purposes, just happened to capture images of the source I was interested in, back when I was in kindergarten. As astronomical images become larger, higher resolution and ever more sensitive, this kind of research will become the norm.

    See the full article here .

    Please help promote STEM in your local schools.

    stem

    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.

     
  • richardmitnick 12:02 pm on April 8, 2018 Permalink | Reply
    Tags: , , , , The Conversation   

    Liverpool John Moores University via The Conversation: “Our study suggests the elusive ‘neutrino’ could make up a significant part of dark matter” 


    Liverpool John Moores University

    The Conversation

    April 5, 2018
    Ian G. McCarthy*

    Physicists trying to understand the fundamental structure of nature rely on consistent theoretical frameworks that can explain what we see and simultaneously make predictions that we can test. On the smallest scale of elementary particles, the standard model of particle physics provides the basis of our understanding.

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


    Standard Model of Particle Physics from Symmetry Magazine

    On the scale of the cosmos, much of our understanding is based on “standard model of cosmology”. Informed by Einstein’s theory of general relativity, it posits that the most of the mass and energy in the universe is made up of mysterious, invisible substances known as dark matter (making up 80% of the matter in the universe) and dark energy.
    1
    James Childs, CC BY

    Lambda-Cold Dark Matter, Accelerated Expansion of the Universe, Big Bang-Inflation (timeline of the universe) Date 2010 Credit: Alex Mittelmann Cold creation

    Over the past few decades, this model has been remarkably successful at explaining a wide range of observations of our universe. Yet we still don’t know what makes up dark matter – we only know it exists because of the gravitational pull it has on galaxy clusters and other structures. A number of particles have been proposed as candidates, but we can’t say for sure which one or several particles make up dark matter.

    Now our new study [MNRAS] – which hints that extremely light particles called neutrinos are likely to make up some of the dark matter – challenges our current understanding of its composition.

    Hot versus cold

    The standard model holds that dark matter is “cold”. That means it consists of relatively heavy particles that initially had sluggish motions. As a consequence, it is very easy for neighbouring particles to get together to form objects bound by gravity. The model therefore predicts that the universe should be filled with small dark matter “haloes”, some of which will merge and form progressively more massive systems – making the cosmos “lumpy”.

    However, it is not impossible that at least some dark matter is “hot”. This would comprise relatively light particles that have quite high velocities – meaning the particles could easily escape from dense regions such as galaxies. This would slow the accumulation of new matter and lead to a universe where the formation of structure is suppressed (less lumpy).

    3

    Neutrinos, which whizz around at extremely high velocities, are a good candidate for hot dark matter. In particular, they do not emit or absorb light – making them appear “dark”. It was long assumed that neutrinos, which come in three different species, don’t have mass. But experiments have demonstrated that they can change (oscillate) from one species to another. Importantly, scientists have shown that this changing requires them to have mass – making them a legitimate candidate for hot dark matter.

    Over the past few decades, however, both particle physics experiments and various astrophysical lines of argument have ruled out neutrinos as making up most of the dark matter in the universe. What’s more, the standard model assumes that neutrinos (and hot dark matter in general) have so little mass that their contribution to dark matter can be ignored completely (in most cases assumed to be 0%). And, until very recently, this model has reproduced a wide variety of cosmological observations quite well.

    Changing picture

    In the past few years, the quantity and quality of cosmological observations has shot up enormously. One of the most prominent examples of this has been the emergence of “gravitational lensing observations”. General relativity tells us that matter curves spacetime so that light from distant galaxies can be deflected by massive objects that lie between us and the galaxies. Astronomers can measure such deflection to estimate the growth of structure (the “lumpiness”) in the universe over cosmic time.

    These new data sets have presented cosmologists with a number of ways to test in detail the predictions of the standard model. A picture that is beginning to emerge from these comparisons is that the mass distribution in the universe appears to be less lumpy than it ought to be if the dark matter is entirely cold.

    However, making comparisons between the standard model and the new data sets may not be as straightforward as first thought. In particular, researchers have shown that the apparent lumpiness of the universe is not just affected by dark matter, but also by complex processes that affect normal matter (protons and neutrons). Previous comparisons assumed that normal matter, which “feels” both gravity and pressure forces, is distributed like dark matter, which only feels gravity.

    4

    Now our new study has produced the largest suite of cosmological computer simulations of normal and dark matter to date (called BAHAMAS). We have also made careful comparisons with a wide range of recent observations. We conclude that the discrepancy between the new observational data sets and the standard cold dark matter model is even larger than previously claimed.

    We looked at the effects of neutrinos and their motions in great detail. As expected, when neutrinos were included in the model, the structure formation in the cosmos was washed out, making the universe less lumpy. Our results suggest that neutrinos make up between 3% and 5% of the total dark matter mass. This is sufficient to consistently reproduce a wide variety of observations – including the new gravitational lensing measurements. If a larger fraction of the dark matter is “hot”, the growth of structure in the universe is suppressed too much.

    The research may also help us solve the mystery of what the mass of an individual neutrino is. From various experiments, particle physicists have calculated that the the sum of the three neutrino species should be at least 0.06 electron Volts (a unit of energy, similar to joules). You can convert this into an estimate of the total neutrino contribution to dark matter, and it works out to be 0.5%. Given that we have found it is actually six to ten times larger than this, we can deduce that the neutrino mass should be about 0.3-0.5 eV instead.

    This is tantalisingly close to values that can actually be measured by upcoming particle physics experiments. If these measurements corroborate the masses we found in our simulations, this would be very reassuring – giving us a consistent picture of the role of neutrinos as dark matter from the largest cosmological scales to the tiniest particle physics realm.

    *Disclosure statement

    Ian G. McCarthy works for Liverpool John Moores University. He receives funding from the Science and Technology Facilities Council (STFC) and the European Research Council (ERC).

    See the full article here .

    Please help promote STEM in your local schools.

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    3

    Liverpool John Moores University is a public research university[6] in the city of Liverpool, England. It has 21,875 students, of which 18,375 are undergraduate students and 3,500 are postgraduate, making it the 33rd largest university in the UK by total student population.

    The university can trace its origins to the Liverpool Mechanics’ School of Arts, established in 1823 making it a contestant as the third-oldest university in England; this later merged to become Liverpool Polytechnic. In 1992, following an Act of Parliament the Liverpool Polytechnic became what is now Liverpool John Moores University.

    It is a member of the University Alliance, a mission group of British universities which was established in 2007.[9] and the European University Association.

     
  • richardmitnick 4:50 pm on March 8, 2018 Permalink | Reply
    Tags: , , Bias in the publishing pipeline, Holding journals accountable, Publish or Perish, The Conversation, Women in all scientific fields experience gender bias,   

    From The Conversation: Women in STEM – “Perish not publish? New study quantifies the lack of female authors in scientific journals” 

    Conversation
    The Conversation

    March 8, 2018
    Ione Fine, Professor of Psychology, University of Washington
    Alicia Shen, Ph.D Candidate in Psychology, University of Washington

    [IMPORTANT NOTE: WHILE THESE WRITERS ARE DESCRIBING WHAT GOES ON IN NEUROSICENCE, KNOW FOR A FACT THAT IT GOES ON IN EVERY FIELD OF SCIENCE.]

    1
    Author lists in journals should reflect who is doing science today and not the ‘old, white men’ of yore. Giammarco Boscaro on Unsplash, CC BY

    “Publish or perish” is tattooed on the mind of every academic. Like it or loathe it, publishing in high-profile journals is the fast track to positions in prestigious universities with illustrious colleagues and lavish resources, celebrated awards and plentiful grant funding. Yet somehow, in the search to understand why women’s scientific careers often fail to thrive, the role of high-impact journals has received little scrutiny.

    One reason is that these journals don’t even collect data about the gender or ethnic background of their authors. To examine the representation of women within these journals, with our colleagues Jason Webster and Yuichi Shoda, we delved into MEDLINE, the online repository that contains records of almost every published peer-reviewed neuroscience article. We used the Genderize.io database to predict the gender of first and last authors on over 166,000 articles published between 2005 and 2017 in high-profile journals that include neuroscience, our own scientific discipline. The results were dispiriting.

    Female scientists underrepresented

    We began by looking at first authors – the place in the author list that traditionally is held by the junior researcher who does the hands-on research. We expected over 40 percent to be women, similar to the percentage of women postdocs in neuroscience in the U.S. and Europe. Instead, fewer than 25 percent first authors in the journals Nature and Science were women.

    Our findings were similar for last authors, the place typically held by the laboratory leader. We expected the numbers to match large National Institutes of Health grants, which are a similarly rigorous measure of significance, scientific sophistication and productivity; 30 percent are awarded to women – comparable to the proportion of women tenure-track faculty in neuroscience. The proportion of women last authors was half what we expected – just over 15 percent of last authors in Science and Nature were women.

    “Publish or perish” is tattooed on the mind of every academic. Like it or loathe it, publishing in high-profile journals is the fast track to positions in prestigious universities with illustrious colleagues and lavish resources, celebrated awards and plentiful grant funding. Yet somehow, in the search to understand why women’s scientific careers often fail to thrive, the role of high-impact journals has received little scrutiny.

    One reason is that these journals don’t even collect data about the gender or ethnic background of their authors. To examine the representation of women within these journals, with our colleagues Jason Webster and Yuichi Shoda, we delved into MEDLINE, the online repository that contains records of almost every published peer-reviewed neuroscience article. We used the Genderize.io database to predict the gender of first and last authors on over 166,000 articles published between 2005 and 2017 in high-profile journals that include neuroscience, our own scientific discipline. The results were dispiriting.
    Female scientists underrepresented

    We began by looking at first authors – the place in the author list that traditionally is held by the junior researcher who does the hands-on research. We expected over 40 percent to be women, similar to the percentage of women postdocs in neuroscience in the U.S. and Europe. Instead, fewer than 25 percent first authors in the journals Nature and Science were women.

    Our findings were similar for last authors, the place typically held by the laboratory leader. We expected the numbers to match large National Institutes of Health grants, which are a similarly rigorous measure of significance, scientific sophistication and productivity; 30 percent are awarded to women – comparable to the proportion of women tenure-track faculty in neuroscience. The proportion of women last authors was half what we expected – just over 15 percent of last authors in Science and Nature were women.

    Our study, published online [BioRxiv] and highlighted in a letter printed in the journal Nature, focused on neuroscience. We made our code accessible, and we’re thrilled that students in other fields are already beginning to examine the gender breakdown of bylines in their own disciplines.

    One thing our data mining study doesn’t reveal is why women are so seriously underrepresented. But a large literature suggests that gender bias almost certainly plays a role.

    Bias in the publishing pipeline

    One place bias occurs is when scientists themselves undervalue the scientific contributions of women. One analysis found that women are more likely to be the person performing experiments. Despite this, they are more likely to be in the less prestigious “middle” author position. Anecdotally, many laboratory leaders have observed that male students tend to be more proactive about negotiating their position in the author list than women.

    Bias can also influence the reviewing process. Researchers at the Ohio State University found that, when reviewers are randomly assigned to evaluate scientific work ostensibly submitted by a female or a male author, they rated the work written by male authors as having higher rigor. An analysis of peer-review scores for postdoctoral fellowship applications in Sweden revealed a system that was “riddled with prejudice” – women were given lower competence ratings than men who had less than half their publication impact. Bias may be particularly strong when expectations are high – qualities like “brilliance” are far more likely to be attributed to men. This may be why we found the proportion of women authors was negatively correlated with journal “impact factor.”

    Finally, bias occurs within the editorial process. Nature, in a series of editorials spanning more than a decade, has observed that its editors are less likely to ask women to write commissioned pieces.

    Do women fail to “lean in”? Female authors may be less likely to submit to high-profile journals. Success rates for elite journals are low – for instance, in Nature, less than 10 percent of submissions make it into print. In many fields, the publication delay associated with a failed submission means there’s a high risk of being scooped by another research team. If a female scientist estimates her chance of success more conservatively than a man, for whatever reason, she will be more likely to play it safe.

    Holding journals accountable

    Scientific publishing is staggeringly profitable: In 2017, Elsevier reported profits of over US$1.2 billion. These companies rely heavily on the scientific community, both as authors of the journal content they are selling and as reviewers. Given the profit they make and the outsized influence they wield over scientific careers, it seems obvious that journals have a moral and perhaps even a legal responsibility to make sure the process is equable.

    We believe journals need to take full responsibility for ensuring social equity across the publishing pipeline: encouraging women to submit, ensuring that women receive fair reviews, and enforcing equity in the editorial process.

    There are some obvious first steps. The scientific community should demand that journals collect data about gender and ethnicity for article submissions and acceptances, and these data should be publicly available. That way researchers can choose to avoid (or even boycott) journals with a poor track record. Researchers should insist that reviewers be given more specific review criteria – such as requirements to explain their ratings of significance and impact, as well as their assessment of scientific quality, as is done at the NIH and the National Science Foundation. Finally, it is past time for journals to adopt mandatory double-blind reviewing.

    While the representation of women authors may not have changed over the last decade or so, the attitude of the scientific community has transformed. When I (Ione Fine) was an undergraduate at Oxford, I was told casually by a professor that “women don’t run with the ball intellectually” – even though I was interviewing him for a feminist magazine! (For 20 years, I have wondered whether this reflected extraordinary arrogance combined with a singular lack of tact or sheer idiocy.) But the only thing that made the comment surprising was the context – his attitude was commonplace.

    These days there is an overwhelming consensus in our scientific community that scientific talent is not gendered. Universities, funding agencies, conference organizers and individual laboratory leaders around the world are all working to resolve this problem. It is time for the journals to “lean in.”

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    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.

     
  • richardmitnick 1:58 pm on January 16, 2018 Permalink | Reply
    Tags: , , , , , , , , , , , , The Conversation   

    From QUB via The Conversation: “How we created a mini ‘gamma ray burst’ in the lab for the first time” 

    QUB bloc

    Queens University Belfast (QUB)

    The Conversation

    January 15, 2018
    GIANLUCA SARRI

    Gamma ray bursts, intense explosions of light, are the brightest events ever observed in the universe – lasting no longer than seconds or minutes. Some are so luminous that they can be observed with the naked eye, such as the burst “GRB 080319B” discovered by NASA’s Swift GRB Explorer mission on March 19, 2008.

    NASA Neil Gehrels Swift Observatory

    But despite the fact that they are so intense, scientists don’t really know what causes gamma ray bursts. There are even people who believe some of them might be messages sent from advanced alien civilisations. Now we have for the first time managed to recreate a mini version of a gamma ray burst in the laboratory – opening up a whole new way to investigate their properties. Our research is published in Physical Review Letters.

    One idea for the origin of gamma ray bursts [Science] is that they are somehow emitted during the emission of jets of particles released by massive astrophysical objects, such as black holes. This makes gamma ray bursts extremely interesting to astrophysicists – their detailed study can unveil some key properties of the black holes they originate from.

    The beams released by the black holes would be mostly composed of electrons and their “antimatter” companions, the positrons – all particle have antimatter counterparts that are exactly identical to themselves, only with opposite charge. These beams must have strong, self-generated magnetic fields. The rotation of these particles around the fields give off powerful bursts of gamma ray radiation. Or, at least, this is what our theories predict [MNRAS]. But we don’t actually know how the fields would be generated.

    Unfortunately, there are a couple of problems in studying these bursts. Not only do they last for short periods of time but, most problematically, they are originated in distant galaxies, sometimes even billion light years from Earth (imagine a one followed by 25 zeroes – this is basically what one billion light years is in metres).

    That means you rely on looking at something unbelievably far away that happens at random, and lasts only for few seconds. It is a bit like understanding what a candle is made of, by only having glimpses of candles being lit up from time to time thousands of kilometres from you.

    World’s most powerful laser

    It has been recently proposed that the best way to work out how gamma ray bursts are produced would be by mimicking them in small-scale reproductions in the laboratory – reproducing a little source of these electron-positron beams and look at how they evolve when left on their own. Our group and our collaborators from the US, France, UK, and Sweden, recently succeeded in creating the first small-scale replica of this phenomenon by using one of the most intense lasers on Earth, the Gemini laser, hosted by the Rutherford Appleton Laboratory in the UK.

    1
    The Gemini laser, hosted by the Rutherford Appleton Laboratory in the UK.

    How intense is the most intense laser on Earth? Take all the solar power that hits the whole Earth and squeeze it into a few microns (basically the thickness of a human hair) and you have got the intensity of a typical laser shot in Gemini. Shooting this laser onto a complex target, we were able to release ultra-fast and dense copies of these astrophysical jets and make ultra-fast movies of how they behave. The scaling down of these experiments is dramatic: take a real jet that extends even for thousands of light years and compress it down to a few millimetres.

    In our experiment, we were able to observe, for the first time, some of the key phenomena that play a major role in the generation of gamma ray bursts, such as the self-generation of magnetic fields that lasted for a long time. These were able to confirm some major theoretical predictions of the strength and distribution of these fields. In short, our experiment independently confirms that the models currently used to understand gamma ray bursts are on the right track.

    The experiment is not only important for studying gamma ray bursts. Matter made only of electrons and positrons is an extremely peculiar state of matter. Normal matter on Earth is predominantly made of atoms: a heavy positive nucleus surrounded by clouds of light and negative electrons.

    2
    Artist impression of gamma ray burst. NASA [no additional credit for which facility or which artist].

    Due to the incredible difference in weight between these two components (the lightest nucleus weighs 1836 times the electron) almost all the phenomena we experience in our everyday life comes from the dynamics of electrons, which are much quicker in responding to any external input (light, other particles, magnetic fields, you name it) than nuclei. But in an electron-positron beam, both particles have exactly the same mass, meaning that this disparity in reaction times is completely obliterated. This brings to a quantity of fascinating consequences. For example, sound would not exist in an electron-positron world.

    So far so good, but why should we care so much about events that are so distant? There are multiple reasons indeed. First, understanding how gamma ray bursts are formed will allow us to understand a lot more about black holes and thus open a big window on how our universe was born and how it will evolve.

    But there is a more subtle reason. SETI – Search for Extra-Terrestrial Intelligence – looks for messages from alien civilisations by trying to capture electromagnetic signals from space that cannot be explained naturally (it focuses mainly on radio waves, but gamma ray bursts are associated with such radiation too).

    Breakthrough Listen Project

    1

    Lick Automated Planet Finder telescope, Mount Hamilton, CA, USA



    GBO radio telescope, Green Bank, West Virginia, USA


    CSIRO/Parkes Observatory, located 20 kilometres north of the town of Parkes, New South Wales, Australia

    U Manchester Jodrell Bank Lovell Telescope


    SETI@home, BOINC project at UC Berkeley Space Science Lab

    Laser SETI, the future of SETI Institute research

    Of course, if you put your detector to look for emissions from space, you do get an awful lot of different signals. If you really want to isolate intelligent transmissions, you first need to make sure all the natural emissions are perfectly known so that they can excluded. Our study helps towards understanding black hole and pulsar emissions, so that, whenever we detect anything similar, we know that it is not coming from an alien civilisation.

    See the full article here .

    Please help promote STEM in your local schools.

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    QUB campus

    An international institution

    Queen’s is in the top one per cent of global universities.

    With more than 23,000 students and 3,700 staff, it is a dynamic and diverse institution, a magnet for inward investment, a major employer and investor, a patron of the arts and a global player in areas ranging from cancer studies to sustainability, and from pharmaceuticals to creative writing.
    World-leading research

    Queen’s is a member of the Russell Group of 24 leading UK research-intensive universities, alongside Oxford, Cambridge and Imperial College London.

    In the UK top ten for research intensity

    The Research Excellence Framework (REF) 2014 results placed Queen’s joint 8th in the UK for research intensity, with over 75 per cent of Queen’s researchers undertaking world-class or internationally leading research.

    The University also has 14 subject areas ranked within the UK’s top 20 and 76 per cent of its research classified in the top two categories of world leading and internationally excellent.

    This validates Queen’s as a University with world-class researchers carrying out world-class or internationally leading research.

    Globally recognised education

    The University has won the Queen’s Anniversary Prize for Higher and Further Education on five occasions – for Northern Ireland’s Comprehensive Cancer Services programme and for world-class achievement in green chemistry, environmental research, palaeoecology and law.

     
  • richardmitnick 5:09 pm on January 8, 2018 Permalink | Reply
    Tags: , , , , Piercing the mystery of the cosmic origins of gold, The Conversation,   

    From The Conversation: “Piercing the mystery of the cosmic origins of gold” 

    Conversation
    The Conversation

    December 17, 2017
    Jérôme Margueron

    Where does gold, the precious metal coveted by mortals through the ages, come from? How, where and when was it produced? Last August, a single astrophysical observation finally gave us the key to answer these questions. The results of this research were published on October 16, 2017 [Physical Review Letters , The Astrophysical Letters and Nature].

    Gold pre-exists the formation of Earth: this is what differentiates it from, for example, diamond. However valuable it may be, this precious stone is born out of mere carbon, whose atomic structure is modified by enormous pressure from the earth’s crust. Gold is totally different – the strongest forces in the earth’s mantle are unable to change the composition of its atomic nucleus. Too bad for the alchemists who dreamed of transforming lead into gold.

    Yet there is gold on Earth, both in its deep core, where it has migrated together with heavy elements such as lead or silver, and in the planet’s crust, which is where we extract this precious metal. While the gold in the core was already there at the formation of our planet, that in the crust is mostly extraterrestrial and arrived after the formation of Earth. It was brought by a gigantic meteor shower that bombarded the Earth (and the Moon) about 3.8 billion years ago.

    Formation of heavy elements

    How gold is produced in the universe? The elements heavier than iron, including gold, are partially produced by the s process during the ultimate evolution phases of the stars. It is a slow process (s stands for slow) that operates in the core of what are referred to as AGB stars – those of low and intermediate mass (less than 10 solar masses) that can produce chemical elements up to polonium. The other half of the heavy elements is produced by the r process (r stands for rapid). But the site where this nucleo-synthesis process takes place has long remained a mystery.

    To understand the discovery enabled by the August 17, 2017, observation, we need to understand the scientific status quo that existed beforehand. For about 50 years, the dominant assumption among the scientific community was that the r process took place during the final explosion of massive stars (specialists speak of a core collapse supernova). Indeed, the formation of light elements (those up to iron) implies nuclear reactions that ensure the stability of the stars by counteracting contraction induced by gravity. For heavier elements – those from iron and beyond – it is necessary to add energy or to take very specific paths, such as the s and r processes. Researchers believed that the r process could occur in ejected matter from the explosion of massive stars, capturing a part of the released energy and participating to the dissemination of material in the interstellar medium.

    Despite the simplicity of this explanation, numerical modelling of supernovae has proved extremely complicated. After 50 years of efforts, researchers have just begun to understand its mechanism. Most of these simulations do unfortunately not provide the physical conditions for the r process.

    These conditions are however quite simple: you need a lot of neutrons and a really warm environment.

    Fusion of neutron stars

    In the last decade or so, some researchers have begun to seriously investigate an alternative scenario of the heavy-element production site. They focused their attention on neutron stars. As befits their name, they constitute a gigantic reservoir of neutrons, which are released occasionally. The strongest of these releases occurs during their merging, in a binary system, also called kilonova. There are several signatures of this phenomenon that luckily were seen on August 17: a gravitational-wave emission culminating a fraction of a second before the final fusion of the stars and a burst of highly energetic light (known as a gamma-ray burst) emitted by a jet of matter approaching the speed of light. Although these bursts have been observed regularly for several decades, it is only since 2015 that gravitational waves have been detectable on Earth thanks to the Virgo and LIGO interferometers.

    August 17 will remain a major date for the scientific community. Indeed, it marks the first simultaneous detection of the arrival of gravitational waves – whose origin in the sky was fairly well identified – and a gamma-ray burst, whose origin was also fairly well localized and coincided with the first one. Gamma-ray burst emissions are focused in a narrow cone, and the astronomers’ lucky break was that this one was emitted in the Earth’s direction.

    In the following days, telescopes continuously analysed the light from this kilonova and found confirmation of the production of elements heavier than iron. They were also able to estimate the frequency of the phenomenon and the amount of material ejected. These estimates are consistent with the average abundance of the elements observed in our galaxy.

    From UCSC:

    UC Santa Cruz

    UC Santa Cruz

    14

    A UC Santa Cruz special report

    Tim Stephens

    Astronomer Ryan Foley says “observing the explosion of two colliding neutron stars” [see https://sciencesprings.wordpress.com/2017/10/17/from-ucsc-first-observations-of-merging-neutron-stars-mark-a-new-era-in-astronomy ]–the first visible event ever linked to gravitational waves–is probably the biggest discovery he’ll make in his lifetime. That’s saying a lot for a young assistant professor who presumably has a long career still ahead of him.

    2
    The first optical image of a gravitational wave source was taken by a team led by Ryan Foley of UC Santa Cruz using the Swope Telescope at the Carnegie Institution’s Las Campanas Observatory in Chile. This image of Swope Supernova Survey 2017a (SSS17a, indicated by arrow) shows the light emitted from the cataclysmic merger of two neutron stars. (Image credit: 1M2H Team/UC Santa Cruz & Carnegie Observatories/Ryan Foley)

    Carnegie Institution Swope telescope at Las Campanas, Chile, 100 kilometres (62 mi) northeast of the city of La Serena. near the north end of a 7 km (4.3 mi) long mountain ridge. Cerro Las Campanas, near the southern end and over 2,500 m (8,200 ft) high, at Las Campanas, Chile

    A neutron star forms when a massive star runs out of fuel and explodes as a supernova, throwing off its outer layers and leaving behind a collapsed core composed almost entirely of neutrons. Neutrons are the uncharged particles in the nucleus of an atom, where they are bound together with positively charged protons. In a neutron star, they are packed together just as densely as in the nucleus of an atom, resulting in an object with one to three times the mass of our sun but only about 12 miles wide.

    “Basically, a neutron star is a gigantic atom with the mass of the sun and the size of a city like San Francisco or Manhattan,” said Foley, an assistant professor of astronomy and astrophysics at UC Santa Cruz.

    These objects are so dense, a cup of neutron star material would weigh as much as Mount Everest, and a teaspoon would weigh a billion tons. It’s as dense as matter can get without collapsing into a black hole.

    THE MERGER

    Like other stars, neutron stars sometimes occur in pairs, orbiting each other and gradually spiraling inward. Eventually, they come together in a catastrophic merger that distorts space and time (creating gravitational waves) and emits a brilliant flare of electromagnetic radiation, including visible, infrared, and ultraviolet light, x-rays, gamma rays, and radio waves. Merging black holes also create gravitational waves, but there’s nothing to be seen because no light can escape from a black hole.

    Foley’s team was the first to observe the light from a neutron star merger that took place on August 17, 2017, and was detected by the Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO).


    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)

    Now, for the first time, scientists can study both the gravitational waves (ripples in the fabric of space-time), and the radiation emitted from the violent merger of the densest objects in the universe.

    3
    The UC Santa Cruz team found SSS17a by comparing a new image of the galaxy N4993 (right) with images taken four months earlier by the Hubble Space Telescope (left). The arrows indicate where SSS17a was absent from the Hubble image and visible in the new image from the Swope Telescope. (Image credits: Left, Hubble/STScI; Right, 1M2H Team/UC Santa Cruz & Carnegie Observatories/Ryan Foley)

    It’s that combination of data, and all that can be learned from it, that has astronomers and physicists so excited. The observations of this one event are keeping hundreds of scientists busy exploring its implications for everything from fundamental physics and cosmology to the origins of gold and other heavy elements.


    A small team of UC Santa Cruz astronomers were the first team to observe light from two neutron stars merging in August. The implications are huge.

    ALL THE GOLD IN THE UNIVERSE

    It turns out that the origins of the heaviest elements, such as gold, platinum, uranium—pretty much everything heavier than iron—has been an enduring conundrum. All the lighter elements have well-explained origins in the nuclear fusion reactions that make stars shine or in the explosions of stars (supernovae). Initially, astrophysicists thought supernovae could account for the heavy elements, too, but there have always been problems with that theory, says Enrico Ramirez-Ruiz, professor and chair of astronomy and astrophysics at UC Santa Cruz.

    4
    The violent merger of two neutron stars is thought to involve three main energy-transfer processes, shown in this diagram, that give rise to the different types of radiation seen by astronomers, including a gamma-ray burst and a kilonova explosion seen in visible light. (Image credit: Murguia-Berthier et al., Science)

    A theoretical astrophysicist, Ramirez-Ruiz has been a leading proponent of the idea that neutron star mergers are the source of the heavy elements. Building a heavy atomic nucleus means adding a lot of neutrons to it. This process is called rapid neutron capture, or the r-process, and it requires some of the most extreme conditions in the universe: extreme temperatures, extreme densities, and a massive flow of neutrons. A neutron star merger fits the bill.

    Ramirez-Ruiz and other theoretical astrophysicists use supercomputers to simulate the physics of extreme events like supernovae and neutron star mergers. This work always goes hand in hand with observational astronomy. Theoretical predictions tell observers what signatures to look for to identify these events, and observations tell theorists if they got the physics right or if they need to tweak their models. The observations by Foley and others of the neutron star merger now known as SSS17a are giving theorists, for the first time, a full set of observational data to compare with their theoretical models.

    According to Ramirez-Ruiz, the observations support the theory that neutron star mergers can account for all the gold in the universe, as well as about half of all the other elements heavier than iron.

    RIPPLES IN THE FABRIC OF SPACE-TIME

    Einstein predicted the existence of gravitational waves in 1916 in his general theory of relativity, but until recently they were impossible to observe. LIGO’s extraordinarily sensitive detectors achieved the first direct detection of gravitational waves, from the collision of two black holes, in 2015. Gravitational waves are created by any massive accelerating object, but the strongest waves (and the only ones we have any chance of detecting) are produced by the most extreme phenomena.

    Two massive compact objects—such as black holes, neutron stars, or white dwarfs—orbiting around each other faster and faster as they draw closer together are just the kind of system that should radiate strong gravitational waves. Like ripples spreading in a pond, the waves get smaller as they spread outward from the source. By the time they reached Earth, the ripples detected by LIGO caused distortions of space-time thousands of times smaller than the nucleus of an atom.

    The rarefied signals recorded by LIGO’s detectors not only prove the existence of gravitational waves, they also provide crucial information about the events that produced them. Combined with the telescope observations of the neutron star merger, it’s an incredibly rich set of data.

    LIGO can tell scientists the masses of the merging objects and the mass of the new object created in the merger, which reveals whether the merger produced another neutron star or a more massive object that collapsed into a black hole. To calculate how much mass was ejected in the explosion, and how much mass was converted to energy, scientists also need the optical observations from telescopes. That’s especially important for quantifying the nucleosynthesis of heavy elements during the merger.

    LIGO can also provide a measure of the distance to the merging neutron stars, which can now be compared with the distance measurement based on the light from the merger. That’s important to cosmologists studying the expansion of the universe, because the two measurements are based on different fundamental forces (gravity and electromagnetism), giving completely independent results.

    “This is a huge step forward in astronomy,” Foley said. “Having done it once, we now know we can do it again, and it opens up a whole new world of what we call ‘multi-messenger’ astronomy, viewing the universe through different fundamental forces.”

    IN THIS REPORT

    Neutron stars
    A team from UC Santa Cruz was the first to observe the light from a neutron star merger that took place on August 17, 2017 and was detected by the Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO)

    5
    Graduate students and post-doctoral scholars at UC Santa Cruz played key roles in the dramatic discovery and analysis of colliding neutron stars.Astronomer Ryan Foley leads a team of young graduate students and postdoctoral scholars who have pulled off an extraordinary coup. Following up on the detection of gravitational waves from the violent merger of two neutron stars, Foley’s team was the first to find the source with a telescope and take images of the light from this cataclysmic event. In so doing, they beat much larger and more senior teams with much more powerful telescopes at their disposal.

    “We’re sort of the scrappy young upstarts who worked hard and got the job done,” said Foley, an untenured assistant professor of astronomy and astrophysics at UC Santa Cruz.

    7
    David Coulter, graduate student

    The discovery on August 17, 2017, has been a scientific bonanza, yielding over 100 scientific papers from numerous teams investigating the new observations. Foley’s team is publishing seven papers, each of which has a graduate student or postdoc as the first author.

    “I think it speaks to Ryan’s generosity and how seriously he takes his role as a mentor that he is not putting himself front and center, but has gone out of his way to highlight the roles played by his students and postdocs,” said Enrico Ramirez-Ruiz, professor and chair of astronomy and astrophysics at UC Santa Cruz and the most senior member of Foley’s team.

    “Our team is by far the youngest and most diverse of all of the teams involved in the follow-up observations of this neutron star merger,” Ramirez-Ruiz added.

    8
    Charles Kilpatrick, postdoctoral scholar

    Charles Kilpatrick, a 29-year-old postdoctoral scholar, was the first person in the world to see an image of the light from colliding neutron stars. He was sitting in an office at UC Santa Cruz, working with first-year graduate student Cesar Rojas-Bravo to process image data as it came in from the Swope Telescope in Chile. To see if the Swope images showed anything new, he had also downloaded “template” images taken in the past of the same galaxies the team was searching.

    9
    Ariadna Murguia-Berthier, graduate student

    “In one image I saw something there that was not in the template image,” Kilpatrick said. “It took me a while to realize the ramifications of what I was seeing. This opens up so much new science, it really marks the beginning of something that will continue to be studied for years down the road.”

    At the time, Foley and most of the others in his team were at a meeting in Copenhagen. When they found out about the gravitational wave detection, they quickly got together to plan their search strategy. From Copenhagen, the team sent instructions to the telescope operators in Chile telling them where to point the telescope. Graduate student David Coulter played a key role in prioritizing the galaxies they would search to find the source, and he is the first author of the discovery paper published in Science.

    10
    Matthew Siebert, graduate student

    “It’s still a little unreal when I think about what we’ve accomplished,” Coulter said. “For me, despite the euphoria of recognizing what we were seeing at the moment, we were all incredibly focused on the task at hand. Only afterward did the significance really sink in.”

    Just as Coulter finished writing his paper about the discovery, his wife went into labor, giving birth to a baby girl on September 30. “I was doing revisions to the paper at the hospital,” he said.

    It’s been a wild ride for the whole team, first in the rush to find the source, and then under pressure to quickly analyze the data and write up their findings for publication. “It was really an all-hands-on-deck moment when we all had to pull together and work quickly to exploit this opportunity,” said Kilpatrick, who is first author of a paper comparing the observations with theoretical models.

    11
    César Rojas Bravo, graduate student

    Graduate student Matthew Siebert led a paper analyzing the unusual properties of the light emitted by the merger. Astronomers have observed thousands of supernovae (exploding stars) and other “transients” that appear suddenly in the sky and then fade away, but never before have they observed anything that looks like this neutron star merger. Siebert’s paper concluded that there is only a one in 100,000 chance that the transient they observed is not related to the gravitational waves.

    Ariadna Murguia-Berthier, a graduate student working with Ramirez-Ruiz, is first author of a paper synthesizing data from a range of sources to provide a coherent theoretical framework for understanding the observations.

    Another aspect of the discovery of great interest to astronomers is the nature of the galaxy and the galactic environment in which the merger occurred. Postdoctoral scholar Yen-Chen Pan led a paper analyzing the properties of the host galaxy. Enia Xhakaj, a new graduate student who had just joined the group in August, got the opportunity to help with the analysis and be a coauthor on the paper.

    12
    Yen-Chen Pan, postdoctoral scholar

    “There are so many interesting things to learn from this,” Foley said. “It’s a great experience for all of us to be part of such an important discovery.”

    13
    Enia Xhakaj, graduate student

    IN THIS REPORT

    Scientific Papers from the 1M2H Collaboration

    Coulter et al., Science, Swope Supernova Survey 2017a (SSS17a), the Optical Counterpart to a Gravitational Wave Source

    Drout et al., Science, Light Curves of the Neutron Star Merger GW170817/SSS17a: Implications for R-Process Nucleosynthesis

    Shappee et al., Science, Early Spectra of the Gravitational Wave Source GW170817: Evolution of a Neutron Star Merger

    Kilpatrick et al., Science, Electromagnetic Evidence that SSS17a is the Result of a Binary Neutron Star Merger

    Siebert et al., ApJL, The Unprecedented Properties of the First Electromagnetic Counterpart to a Gravitational-wave Source

    Pan et al., ApJL, The Old Host-galaxy Environment of SSS17a, the First Electromagnetic Counterpart to a Gravitational-wave Source

    Murguia-Berthier et al., ApJL, A Neutron Star Binary Merger Model for GW170817/GRB170817a/SSS17a

    Kasen et al., Nature, Origin of the heavy elements in binary neutron star mergers from a gravitational wave event

    Abbott et al., Nature, A gravitational-wave standard siren measurement of the Hubble constant (The LIGO Scientific Collaboration and The Virgo Collaboration, The 1M2H Collaboration, The Dark Energy Camera GW-EM Collaboration and the DES Collaboration, The DLT40 Collaboration, The Las Cumbres Observatory Collaboration, The VINROUGE Collaboration & The MASTER Collaboration)

    Abbott et al., ApJL, Multi-messenger Observations of a Binary Neutron Star Merger

    PRESS RELEASES AND MEDIA COVERAGE


    Watch Ryan Foley tell the story of how his team found the neutron star merger in the video below. 2.5 HOURS.

    Press releases:

    UC Santa Cruz Press Release

    UC Berkeley Press Release

    Carnegie Institution of Science Press Release

    LIGO Collaboration Press Release

    National Science Foundation Press Release

    Media coverage:

    The Atlantic – The Slack Chat That Changed Astronomy

    Washington Post – Scientists detect gravitational waves from a new kind of nova, sparking a new era in astronomy

    New York Times – LIGO Detects Fierce Collision of Neutron Stars for the First Time

    Science – Merging neutron stars generate gravitational waves and a celestial light show

    CBS News – Gravitational waves – and light – seen in neutron star collision

    CBC News – Astronomers see source of gravitational waves for 1st time

    San Jose Mercury News – A bright light seen across the universe, proving Einstein right

    Popular Science – Gravitational waves just showed us something even cooler than black holes

    Scientific American – Gravitational Wave Astronomers Hit Mother Lode

    Nature – Colliding stars spark rush to solve cosmic mysteries

    National Geographic – In a First, Gravitational Waves Linked to Neutron Star Crash

    Associated Press – Astronomers witness huge cosmic crash, find origins of gold

    Science News – Neutron star collision showers the universe with a wealth of discoveries

    UCSC press release
    First observations of merging neutron stars mark a new era in astronomy

    Credits

    Writing: Tim Stephens
    Video: Nick Gonzales
    Photos: 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

    Dark Energy Survey


    Dark Energy Camera [DECam], built at FNAL


    NOAO/CTIO Victor M Blanco 4m Telescope which houses the DECam at Cerro Tololo, Chile, housing DECam at an altitude of 7200 feet

    Gemini South telescope, Cerro Tololo Inter-American Observatory (CTIO) campus near La Serena, Chile, at an altitude of 7200 feet

    Noted in the vdeo but not in te article:

    NASA/Chandra Telescope

    NASA/SWIFT Telescope

    NRAO/Karl V Jansky VLA, on the Plains of San Agustin fifty miles west of Socorro, NM, USA

    Prompt telescope CTIO Chile

    NASA NuSTAR X-ray telescope

    See the full article here

    In a single observation, the hypothesis that prevailed until now – of a r process occurring exclusively during supernovae – is now seriously under question and it is now certain that the r process also takes place in kilonovae. The respective contribution of supernovae and kilonovae for the heavy elements’ nucleo-synthesis remains to be determined, and it will be done with the accumulation of datum related to the next observations. The August 17 observation alone has already allowed a great scientific advance for the global understanding of the origin of heavy elements, including gold.


    This NASA animation is an artist’s view and accelerated version of the first nine days of a kilonova (the merging of two neutron stars) similar to that observed on August 17, 2017 (GW170817). In the approach phase of the two stars, the gravitational waves emitted are coloured pale blue, then after the fusion a jet near the speed of light is emitted (in orange) generating itself a gamma burst (in magenta). The material ejected from the kilonova produces an initially ultraviolet light (violet), then white in the optics, and finally infra-red (red). The jet continues its expansion by emitting light in the X-ray range (blue)

    A new window on the Universe

    A new window to the universe has just been opened, like the day that Galileo focused the first telescope on the sky. The Virgo and LIGO interferometers now make it possible to “hear” the most violent phenomena of the universe, and immense perspectives have opened up for astronomers, astrophysicists, particle physicists and nuclear physicists. This scientific achievement was only possible thanks to the fruitful collaboration between highly supportive nations, in particular the United States, Germany, France and Italy. As an example, there is only one laboratory in the world capable of reaching the required precision for the mirrors reflecting lasers, LMA in Lyon, France. New interferometers are under development in Japan and Indian, and this list will surely soon become longer given huge discoveries expected for the future.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    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.

     
  • richardmitnick 3:49 pm on October 26, 2017 Permalink | Reply
    Tags: , , , , , , , The Conversation   

    From The Conversation: “Dark matter: The mystery substance physics still can’t identify that makes up the majority of our universe” 

    FNAL II photo

    Fermilab

    Conversation
    The Conversation

    10.25.17
    Dan Hooper

    1
    Astronomers map dark matter indirectly, via its gravitational pull on other objects. NASA, ESA, and D. Coe (NASA JPL/Caltech and STScI), CC BY

    The past few decades have ushered in an amazing era in the science of cosmology. A diverse array of high-precision measurements has allowed us to reconstruct our universe’s history in remarkable detail.

    And when we compare different measurements – of the expansion rate of the universe, the patterns of light released in the formation of the first atoms, the distributions in space of galaxies and galaxy clusters and the abundances of various chemical species – we find that they all tell the same story, and all support the same series of events.

    This line of research has, frankly, been more successful than I think we had any right to have hoped. We know more about the origin and history of our universe today than almost anyone a few decades ago would have guessed that we would learn in such a short time.

    But despite these very considerable successes, there remains much more to be learned. And in some ways, the discoveries made in recent decades have raised as many new questions as they have answered.

    One of the most vexing gets at the heart of what our universe is actually made of. Cosmological observations have determined the average density of matter in our universe to very high precision. But this density turns out to be much greater than can be accounted for with ordinary atoms.

    After decades of measurements and debate, we are now confident that the overwhelming majority of our universe’s matter – about 84 percent – is not made up of atoms, or of any other known substance. Although we can feel the gravitational pull of this other matter, and clearly tell that it’s there, we simply do not know what it is. This mysterious stuff is invisible, or at least nearly so. For lack of a better name, we call it “dark matter.” But naming something is very different from understanding it.

    For almost as long as we’ve known that dark matter exists, physicists and astronomers have been devising ways to try to learn what it’s made of. They’ve built ultra-sensitive detectors, deployed in deep underground mines, in an effort to measure the gentle impacts of individual dark matter particles colliding with atoms.

    They’ve built exotic telescopes – sensitive not to optical light but to less familiar gamma rays, cosmic rays and neutrinos – to search for the high-energy radiation that is thought to be generated through the interactions of dark matter particles.

    And we have searched for signs of dark matter using incredible machines which accelerate beams of particles – typically protons or electrons – up to the highest speeds possible, and then smash them into one another in an effort to convert their energy into matter. The idea is these collisions could create new and exotic substances, perhaps including the kinds of particles that make up the dark matter of our universe.

    As recently as a decade ago, most cosmologists – including myself – were reasonably confident that we would soon begin to solve the puzzle of dark matter. After all, there was an ambitious experimental program on the horizon, which we anticipated would enable us to identify the nature of this substance and to begin to measure its properties. This program included the world’s most powerful particle accelerator – the Large Hadron Collider – as well as an array of other new experiments and powerful telescopes.

    LHC

    CERN/LHC Map

    CERN LHC Tunnel

    CERN LHC particles

    2
    Experiments at CERN are trying to zero in on dark matter – but so far no dice. CERN, CC BY-ND

    But things did not play out the way that we expected them to. Although these experiments and observations have been carried out as well as or better than we could have hoped, the discoveries did not come.

    Over the past 15 years, for example, experiments designed to detect individual particles of dark matter have become a million times more sensitive, and yet no signs of these elusive particles have appeared. And although the Large Hadron Collider has by all technical standards performed beautifully, with the exception of the Higgs boson, no new particles or other phenomena have been discovered.

    3
    At Fermilab, the Cryogenic Dark Matter Search uses towers of disks made from silicon and germanium to search for particle interactions from dark matter. Reidar Hahn/Fermilab, CC BY

    The stubborn elusiveness of dark matter has left many scientists both surprised and confused. We had what seemed like very good reasons to expect particles of dark matter to be discovered by now. And yet the hunt continues, and the mystery deepens.

    In many ways, we have only more open questions now than we did a decade or two ago. And at times, it can seem that the more precisely we measure our universe, the less we understand it. Throughout the second half of the 20th century, theoretical particle physicists were often very successful at predicting the kinds of particles that would be discovered as accelerators became increasingly powerful. It was a truly impressive run.

    But our prescience seems to have come to an end – the long-predicted particles associated with our favorite and most well-motivated theories have stubbornly refused to appear. Perhaps the discoveries of such particles are right around the corner, and our confidence will soon be restored. But right now, there seems to be little support for such optimism.

    In response, droves of physicists are going back to their chalkboards, revisiting and revising their assumptions. With bruised egos and a bit more humility, we are desperately attempting to find a new way to make sense of our world.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    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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