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  • richardmitnick 8:57 am on October 18, 2017 Permalink | Reply
    Tags: , , COSMOS, DAMA LIBRA Dark Matter Experiment, , , , , NIST PROSPECT detector, U Washington ADMX, , ,   

    From COSMOS: “Closing in on dark matter” 

    Cosmos Magazine bloc

    COSMOS Magazine

    18 October 2017
    Cathal O’Connell

    1
    Dark matter can’t be detected but it glues galaxies together. It outweighs ordinary matter by five to one. Maltaguy1/Getty Images

    One Saturday I hired a metal detector and drove four hours to the historic gold-rush town of Bright in Victoria, Australia, where my wedding ring lies lost, somewhere on the bed of the Ovens River. I spent the evening wading through the icy waters in gumboots, uncovering such treasures as a bottle cap, a fisher’s lead weight and a bracelet caked in rust. I did not uncover the ring. But that doesn’t mean the ring is not there.

    Like me, physicists around the world are in the midst of an important search that has so far proven fruitless. Their quarry is nothing less than most of the matter in the universe, so-called “dark matter”.

    So far their most sensitive detectors have found – to be pithy – nada. Despite the lack of results, scientists aren’t giving up. “The frequency with which articles show up in the popular press saying ‘maybe dark matter isn’t real’ massively exceeds the frequency with which physicists or astronomers find any reason to re-examine that question,” says Katie Mack, a theoretical astrophysicist at the University of Melbourne.

    In many respects, the quest for dark matter has only just begun. We can expect quite a few more null results before the real treasure turns up. So here is where we stand, and what we can expect from the next few years.

    Imagine a toddler sitting on one end of a seesaw and launching her father, at the other end, high into the air. It’s a weird and unsettling image, yet we regularly observe this kind of ‘impossible’ behaviour in the universe at large. Like the little girl on the seesaw, galaxies behave as if they have four or five times the mass we can see.

    Our first inkling of this discrepancy came in the 1930s, when the Swiss astronomer Fritz Zwicky noticed odd movements among the Coma cluster of galaxies.

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    Fritz Zwicky: The Father of Dark Matter. https://www.youtube.com/watch?v=TV0c1EFIKy4

    Zwicky’s anomaly was largely ignored until the 1970s, when astrophysicist Vera Rubin, based at the Carnegie Institute in Washington, noticed that the way galaxies spin did not tally with the laws of physics.

    3
    Astronomer Vera Rubin in 1974, with her “measuring engine” used to examine photographic plates. Credit: Courtesy of Carnegie Institution of Washington

    The meticulous observations by Rubin (who passed away in December 2016) convinced most of the astronomical community something was amiss. There were two possible answers to the problem: either galaxies were a lot heavier than they appeared, or our theory of gravity was kaput when it came to galaxy-scale movements.

    From the outset, astronomers preferred the first explanation. At first they thought the missing matter was probably nothing too weird – just regular astronomical objects (like planets, black holes and stars) too dim for us to see. But as we surveyed the sky with ever bigger telescopes, these so-called ‘massive compact halo objects’ (or MACHOs) never turned up in the numbers needed to explain all the extra mass.

    Other astrophysicists, such as the Mordehai Milgrom at Israel’s Weizmann Institute, explored models where gravity behaved differently at cosmic scales. [See https://sciencesprings.wordpress.com/2017/05/18/from-nautilus-the-physicist-who-denies-dark-matter/%5D

    5
    Mordehai Milgrom. Cosmos on Nautilus

    They were not successful.

    Slowly astronomers realised they had something radically different on their hands – a new kind of stuff they called ‘dark matter’, which must outweigh the universe’s regular matter by about five to one. “Certainly, when all the evidence is taken together,” Mack says, “there’s no competing idea right now that comes anywhere close to explaining it as well.”

    We know four main facts about dark matter. First, it has gravity. Second, it doesn’t emit, absorb or reflect light. Third, it moves slowly. Fourth, it doesn’t seem to interact with anything, even itself.

    Like detectives in a TV murder mystery, physicists have compiled a list of suspects. Topping the list are three hypothetical particles already wanted on other charges: axions, sterile neutrinos and WIMPs. Besides nailing dark matter, each would help explain a grand mystery of their own.

    The axion is a particle proposed by Roberto Peccei and Helen Quinn back in 1977 to explain a quirk of the strong force (namely, why it can’t distinguish left from right, the way the weak force does). Thirty years on, axions are still our best explanation for that puzzle.

    Axions could have any mass, but if – and it is a big ‘if’ – they have a mass about 100 billion times lighter than an electron, theorists have calculated they would have been created in the Big Bang in such vast numbers that they could account for the universe’s dark matter. Like detectives with a dragnet, physicists are searching through different possible masses in an attempt to close in from both ends and corner the axion.

    The Axion Dark Matter eXperiment (ADMX), based at the University of Washington, is dragging the lightest end of the range.

    U Washington ADMX


    U Washington ADMX Axion Dark Matter Experiment

    Since 2010 the project has been trying to catch axions by turning them into photons using strong magnetic fields. So far ADMX has ruled out the featherweight mass range between 150 to 270 billion times lighter than the electron.

    The CERN Axion Solar Telescope (CAST) is dragging the heavyweight end of the range looking for axions that are a few tens of millions to about a million times lighter than the electron.

    CERN CAST Axion Solar Telescope

    The theorised source of these hefty axions is the Sun, where they might be created by X-rays in the presence of strong electric fields. In an example of recycling at its big-science best, CAST was assembled from a piece of the Large Hadron Collider -– a giant test magnet. It aims to detect solar axions by turning them back into X-rays. It has been running since 2003. The search goes on.

    4
    Hypothetical particles known as axions could explain dark matter. Physicists at CERN have taken a giant magnet from the Large Hadron Collider and turned it into an axion detector, the CERN Axion Solar Telescope. Howard Cunningham/Getty Images

    Sterile neutrinos are the hypothetical heavier, lazier brothers of neutrinos – the ghostly, fast-moving particles created in nuclear reactions and in the centre of the Sun. They are called ‘sterile’ or ‘inactive’ because they only interact via gravity.

    Besides being a dark-matter candidate, sterile neutrinos would plug a number of holes in the Standard Model,

    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.

    which, like a subatomic version of the periodic table, has had great success in predicting the properties of the fundamental building blocks of the universe. For instance, sterile neutrinos could explain why neutrinos are so light, and why every neutrino we’ve ever seen has a ‘left-handed’ spin; sterile neutrinos would be the missing ‘right-handed’ partners.

    Physicists are trying to detect sterile neutrinos in different ways, including searching deep space for the X-rays emitted when they decay. NASA’s Chandra X-ray telescope has picked up an excess of X-rays from the Perseus cluster of galaxies, which is so far unexplained.

    NASA/Chandra Telescope

    6
    Perseus cluster. NASA

    Meanwhile, regular neutrino detectors based at nuclear reactors, such as Daya Bay in China, have noticed anomalies that might be explained by sterile neutrinos.

    Daya Bay, approximately 52 kilometers northeast of Hong Kong and 45 kilometers east of Shenzhen, China

    “Like Elvis, people see hints of the sterile neutrino everywhere,” quipped Francis Halzen in August 2016, when he and his colleagues at the IceCube Neutrino Observatory announced the disappointing results of their own search.


    U Wisconsin ICECUBE neutrino detector at the South Pole

    Their detector, buried up to 2.5 km deep in ice near the South Pole, found no evidence of the elusive sterile neutrino – a result that seems to rule out the Daya Bay reactor sightings. For a conclusive answer, we’ll need to wait for the next neutrino searches, such as the Precision Reactor Antineutrino Oscillation and Spectrum Measurement (PROSPECT) under construction at the US National Institute of Standards and Technology (NIST) in Maryland.

    8
    The PROSPECT detector will consist of an 11 x 14 array of long skinny cells filled with liquid scintillator, which is designed to sense antineutrinos emanating from the reactor core. If a sterile neutrino flavor exists, then PROSPECT will see waves of antineutrinos that appear and disappear with a period determined by their energy. Composition not drawn to scale. NIST.

    The third and most popular suspect is WIMPs – weakly interacting massive particles. The name covers a broad range of hypothetical particles that would interact via the weak force. They pop naturally out of the ideas of supersymmetry, an extension proposed to tidy up the loose ends of the Standard Model.

    Physicists calculate that the simplest possible WIMP, with a mass of about 100 billion electron volts, would have been created in the Big Bang at just the right numbers to explain dark matter: the so-called ‘WIMP miracle’.

    WIMP detectors are typically deep underground, watching for a telltale flash given out when a particle of dark matter bumps into an atomic nucleus.

    The most sensitive WIMP experiment yet is LUX, a bathtub-sized vat holding 370 kg of liquid xenon at the Sanford Underground Research Facility [SURF] in South Dakota. In 2016, the LUX team announced it had discovered no dark matter signals during its first 20-month-long search. Undeterred, the LUX team plan to upgrade to a 7,000-kg vat, LUX-ZEPLIN, by 2020.

    LBNL Lux Zeplin project at SURF

    The most intriguing dark matter result so far comes from the DAMA/LIBRA experiment in Italy. Using a detector made of highly purified sodium-iodide crystals, 1.5 km beneath Italy’s Gran Sasso mountain, scientists believe they have seen evidence of dark matter every year for the past 14 years (see Cosmos 65, p60). Their evidence comes in an annual rise and fall in background detections. Such a pattern might reflect the Earth’s relative speed through the dark-matter cloud that surrounds the Milky Way; while our planet moves around the Sun at 30 km/s, the Solar System as a whole is travelling at 230 km/s around the centre of the Milky Way.

    DAMA LIBRA Dark Matter Experiment, 1.5 km beneath Italy’s Gran Sasso mountain

    Gran Sasso LABORATORI NAZIONALI del GRAN SASSO, located in L’Aquila, Italy

    For half of the year the Earth’s orbital speed would add to the speed of the Solar System, increasing the rate of dark-matter interactions. For the other half, the speeds would subtract and the rate of interactions decrease. The problem is that lots of other things change with the seasons too, such as the thickness of the atmosphere. To rule out terrestrial effects, astronomers are setting up two identical detectors, called SABRE, in opposite hemispheres – so that one is collecting data in winter and the other in summer.

    One detector will be based at Gran Sasso, the other in Australia, in an abandoned gold mine near Stawell, Victoria. Each detector will be made of 50 kg of sodium iodide, and have noise levels 10 times lower than DAMA/LIBRA. Construction on each is under way, and could be finished this year.

    Rather than detecting dark matter, others are trying to make it. The closest we can get to the conditions of the Big Bang – where dark matter was presumably created – is in the collision chambers of the Large Hadron Collider, CERN’s 27-km long particle smasher. These chambers are ringed by sensors that can pick up the energies of millions of particles generated in each smash-up, and tally this against the known collision energy. If some energy is missing, it might indicate the creation of a particle that could not be detected by any sensors: dark matter.

    So far, notwithstanding a brief, hallucinatory blip in late 2015, the LHC has not discovered anything that might constitute a dark matter particle such as a WIMP. But the LHC has only collected about 1% of the data it is due to produce before it is retired in 2025. So it is too early to throw in the towel on producing dark matter yet. Plans are afoot for the LHC’s successor, which will be able to probe far higher energies.

    Snowmelt from the Alpine ranges had swelled the Ovens River. I had to hug the shore with my metal detector, where the water was shallow and easy to sweep. I searched those parts that I could search as thoroughly as possible. If I did not find my prize, I wanted to at least be able to point to the map and say with confidence where the ring was not.

    The map that physicists search has coordinates of energy levels and interaction strengths. Each new search sweeps out a new territory, so even a null result is valuable information. So far, in our search for the three primary candidates – axions, sterile neutrinos and WIMPs – we have only probed the most shallow, accessible waters. “There’s nothing really that says they have to be easy to detect,” Mack says. “It may just be that their interactions with our detectors are smaller than expected.”

    It took almost 50 years for the Higgs boson to be discovered. Gravitational waves took almost a century. Let’s not give up on dark matter just yet.

    I certainly won’t be giving up my own search. Next summer, when the Ovens dries, I will return to Bright and sweep the next unprobed area of the riverbed. I’d say wish me luck, but the point is to be so rigorous that luck has nothing to do with it.

    See the full article here .

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  • richardmitnick 8:00 am on October 11, 2017 Permalink | Reply
    Tags: , , , Confirmed: cosmic rays blast from supernovae, Cosmic rays – high energy subatomic particles – are produced within at least one supernova, COSMOS, GHaFaS,   

    From Weizmann via COSMOS: “Confirmed: cosmic rays blast from supernovae” 

    Weizmann Institute of Science logo

    Weizmann Institute of Science

    COSMOS
    11 October 2017
    Andrew Masterson

    An exploded star first seen by 500 years ago helps astrophysicists to solve a cosmic conundrum.

    1

    Left. Composite image of the remnant of Tycho Brahe’s supernova (1572) using data from the Chandra x-ray satellite observatory (yellow, green, blue (credits NASA/SAO), from the Spitzer infrared satellite observatory (red, credits, NASA/JPL-Caltech), and from the Calar Alto observatory (stars white, credit, Krause et al.). The transparent magenta box shows the field of the ACAM instrument at the Cassegrain focus of the William Herschel Telescope (WHT, ORM, La Palma). Centre, a zoom-in on the ACAM field with a green box showing the size of the field of the 2d spectrograph GHaFaS (WHT, ORM). Right. The reduced and integrated image of GHaFaS in the emission from ionized hydrogen (Ha). NASA/SAO, NASA/JPL-Caltech

    Ending an astronomical mystery, scientists have confirmed that cosmic rays – high energy subatomic particles – are produced within at least one supernova.

    The rays, which consist primarily of protons and atomic nuclei, continuously bombard the Earth’s atmosphere. It’s been known for decades that they originate from outside the solar system, even perhaps outside the galaxy, but how and where they are created has until now remained obscure.

    Now research published in The Astrophysical Journal finds that an as yet unknown mechanism within exploding stars is the likely source. The mechanism acts as an accelerator, producing an unexpectedly wide range of particle velocities that cannot be accounted for by the mass and temperature of the gases involved.

    The discovery was made by a team led by astrophysicist Sladjana Knežević of the Weizmann Institute of Science in Israel, using as instrument known as GHaFaS, mounted on the 4.2m William Herschel Telescope at the Roque de los Muchachos Observatory in the Canary Islands.


    ING 4 meter William Herschel Telescope at Roque de los Muchachos Observatory on La Palma in the Canary Islands, 2,396 m (7,861 ft)

    The team focussed the instrument’s attention on a supernova known formally as SN 1572, but more commonly as Tycho’s supernova, after the pioneering astronomer Tycho Brahe who first recorded its existence in in 1572.

    3
    Remnant of SN 1572 as seen in X-ray light from the Chandra X-ray Observatory

    NASA/Chandra Telescope

    The supernova – more correctly, a supernova remnant – has been studied several times in recent years, including by British radio-astronomers in the 1950s, and observers at the California’s Mount Palomar Observatory a decade later. NASA’s orbiting Chandra X-ray Observatory imaged it in 2002

    Caltech Palomar Observatory, located in San Diego County, California, US, at 1,712 m (5,617 ft)

    None of these investigations, however, had sufficient resolution to test the hypothesis that supernovae may be the source of cosmic rays.

    Using the Canary Islands facility, Knežević and his colleagues mapped a section of the dissipating cloud that surrounds the Tycho remnant, including a bright, visible filament. Measuring two levels of hydrogen emission spread, the team found that the results only made sense if somewhere in the remnant an accelerator was producing high energy particles.

    The finding is the first time evidence for such a mechanism has been found, and appears to confirm supernovae as the source of cosmic rays.

    The data has important implications for both astrophysics and particle physics.

    The researchers now intend to combine their results with other measurements of Tycho’s supernova already taken by another facility on the Canary Islands, the larger Gran Telescopio Canariasto, to gain a clearer picture of cosmic ray acceleration.


    Gran Telescopio Canarias at the Roque de los Muchachos Observatory on the island of La Palma, in the Canaries, Spain, sited on a volcanic peak 2,267 metres (7,438 ft) above sea level

    See the full article here .

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    Weizmann Institute Campus

    The Weizmann Institute of Science is one of the world’s leading multidisciplinary research institutions. Hundreds of scientists, laboratory technicians and research students working on its lushly landscaped campus embark daily on fascinating journeys into the unknown, seeking to improve our understanding of nature and our place within it.

    Guiding these scientists is the spirit of inquiry so characteristic of the human race. It is this spirit that propelled humans upward along the evolutionary ladder, helping them reach their utmost heights. It prompted humankind to pursue agriculture, learn to build lodgings, invent writing, harness electricity to power emerging technologies, observe distant galaxies, design drugs to combat various diseases, develop new materials and decipher the genetic code embedded in all the plants and animals on Earth.

    The quest to maintain this increasing momentum compels Weizmann Institute scientists to seek out places that have not yet been reached by the human mind. What awaits us in these places? No one has the answer to this question. But one thing is certain – the journey fired by curiosity will lead onward to a better future.

     
  • richardmitnick 12:27 pm on October 10, 2017 Permalink | Reply
    Tags: , COSMOS, , Volcanologists lose their lives in pursuit of knowledge   

    From U Bristol via COSMOS: “Volcanologists lose their lives in pursuit of knowledge” 

    University of Bristol

    COSMOS

    10 October 2017
    Andrew Masterson

    Death records show scientists and tourists at risk of death in eruptions.

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    A village destroyed by pyroclastic density currents in the 2010 eruption of Merapi, Indonesia. Over 350 people lost their lives, but successful evacuations saved many thousands. Susanna Jenkins.

    Scientists are among the groups of people most likely to be killed in a volcanic eruption, new research has shown.

    A team led by Sarah Brown of the School of Earth Sciences at the UK’s University of Bristol tracked down and compiled some 635 documents spanning the years 1500 CE to 2017, which collectively catalogued 278,368 volcano-linked fatalities. The death records, drawn from academic papers and press reports, included deaths caused by lava, projectiles flung from erupting volcanoes, pyroclastic flows, mudslides and ash clouds.

    Brown’s team also combed the reports for information relating to how far away from the volcano each fatality occurred, and, where available, the occupation of the person concerned. Previously existing records contained location data for only 5% of recorded deaths; the latest work, published in Journal of Applied Volcanology, ups that to 72%.

    The team found that almost half of all eruption-related deaths happened within 10km of a volcano, but at least one was recorded 170km away.

    Volcano ballistics – rocks flung into the air – were the most common cause of death within five kilometres of a summit, with pyroclastic flows accounting for most of those occurring between five and 15 kilometres away. Ash clouds were responsible for the majority of deaths further away.

    Most victims across the centuries, not surprisingly, were people who lived on or near volcanoes. Specific types of non-residents, however, stood out for being at greatest risk, namely tourists, emergency service personnel, journalists and scientists.
    A total of 561 tourists were killed, mostly within a five kilometre radius, and predominantly by flying rocks. These occurred mainly as a result of very sudden eruptions, affecting visitors who thought the volcano was inactive.

    The next most common group of fatalities were scientists – mainly volcanologists who were standing within one kilometre of a crater, doing research at the time. Brown’s group found 67 such death records, compared to 57 for first responders and 30 for media.

    Brown hopes the data will lead to improved management strategies around volcanoes, which could save lives.

    “While volcanologists and emergency response personnel might have valid reasons for their approach into hazardous zones, the benefits and risks must be carefully weighed,” she says.

    “The media and tourists should observe exclusion zones and follow direction from the authorities and volcano observatories.”

    “Tourist fatalities could be reduced with appropriate access restrictions, warnings and education.”

    See the full article here .

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    Bristol is one of the most popular and successful universities in the UK and was ranked within the top 50 universities in the world in the QS World University Rankings 2018.

    The University of Bristol is at the cutting edge of global research. We have made innovations in areas ranging from cot death prevention to nanotechnology.

    The University has had a reputation for innovation since its founding in 1876. Our research tackles some of the world’s most pressing issues in areas as diverse as infection and immunity, human rights, climate change, and cryptography and information security.

    The University currently has 40 Fellows of the Royal Society and 15 of the British Academy – a remarkable achievement for a relatively small institution.

    We aim to bring together the best minds in individual fields, and encourage researchers from different disciplines and institutions to work together to find lasting solutions to society’s pressing problems.

    We are involved in numerous international research collaborations and integrate practical experience in our curriculum, so that students work on real-life projects in partnership with business, government and community sectors.

     
  • richardmitnick 7:29 am on October 9, 2017 Permalink | Reply
    Tags: Back in 1905 Einstein had helped pioneer quantum theory with his revolutionary discovery that light has the characteristics of both a wave and a particle, Bohr found a flaw in Einstein’s logic, But does this also mean “spooky action at a distance” is real?, COSMOS, Einstein and Bohr continued to debate the issue for the rest of their lives, , Einstein was the first to publicly support de Broglie’s bold hypothesis, Einstein-Podolsky-Rosen paradox, Einstein: “God does not play dice with the universe”, Einstein’s hopes of finding hidden variables that would take the uncertainty out of quantum theory were dashed, Erwin Schrödinger, Fifth Solvay Congress in Brussels, Instant action violated Einstein’s theory of relativity: nothing can travel faster than the speed of light, Louis de Broglie, , , , The Copenhagen theory held that subatomic particles were ruled by chance   

    From COSMOS: “Einstein, Bohr and the origins of entanglement” Wonderful article on this debate between Einstein and Bohr 

    Cosmos Magazine bloc

    COSMOS Magazine

    06 October 2017
    Robyn Arianrhod

    Two of history’s greatest physicists argued for decades over one of the deepest mysteries of quantum mechanics. Today, their successors are opening new fronts in the battle to understand ‘spooky action at a distance’.

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    Niels Bohr and Albert Einstein at the Fifth Solvay Congress. American Institute Of Physics / Getty Images

    It all began in October 1927, at the Fifth Solvay Congress in Brussels. It was Louis de Broglie’s first congress, and he had been “full of pleasure and curiosity” at the prospect of meeting Einstein, his teenage idol. Now 35, de Broglie happily reported: “I was particularly struck by his mild and thoughtful expression, by his general kindness, by his simplicity, and by his friendliness.”

    Back in 1905, Einstein had helped pioneer quantum theory with his revolutionary discovery that light has the characteristics of both a wave and a particle. Niels Bohr later explained this as “complementarity”: depending on how you observe light, you will see either wave or particle behaviour. As for de Broglie, he had taken Einstein’s idea into even stranger territory in his 1924 PhD thesis: if light waves could behave like particles, then perhaps particles of matter could also behave like waves! After all, Einstein had shown that energy and matter were interchangeable, via E = mc2.

    Einstein was the first to publicly support de Broglie’s bold hypothesis. By 1926, Erwin Schrödinger had developed a mathematical formula to describe such “matter waves”, which he pictured as some kind of rippling sea of smeared-out particles. But Max Born showed that Schrödinger’s waves are, in effect, “waves of probability”. They encode the statistical likelihood that a particle will show up at a given place and time based on the behaviour of many such particles in repeated experiments. When the particle is observed, something strange appears to happen. The wave-function “collapses” to a single point, allowing us to see the particle at a particular position.

    Born’s probability wave also fitted neatly with Werner Heisenberg’s recently proposed “uncertainty principle”. Heisenberg had concluded that in the quantum world it is not possible to obtain exact information about both the position and the momentum of a particle at the same time. He imagined the very act of measuring a quantum particle’s position, say by shining a light on it, gave it a jolt that changed its momentum, so the two could never be precisely measured at once.

    When the world’s leading physicists gathered in Brussels in 1927, this was the strange state of quantum physics.

    The official photograph of the participants shows 28 besuited, sober-looking men, and one equally serious woman, Marie Curie. But fellow physicist Paul Ehrenfest’s private photo of intellectual adversaries Bohr and Einstein captures the spirit of the conference: Bohr looks intensely thoughtful, hand on his chin, while Einstein is leaning back looking relaxed and dreamy. This gentle, contemplative picture belies the depth of the famous clash between these two intellectual titans – a clash that hinged on the extraordinary concept of quantum entanglement.

    At the congress, Bohr presented his view of quantum mechanics for the first time. Dubbed the Copenhagen interpretation, in honour of Bohr’s home city, it combined his own idea of particle-wave complementarity with Born’s probability waves and Heisenberg’s uncertainty principle.

    Most of the attendees readily accepted this view, but Einstein was perturbed. It was one thing for groups of particles to be ruled by chance; indeed Einstein had explained the jittery motion of pollen in apparently still water (dubbed Brownian motion) by invoking the random group behaviour of water molecules. Individual molecules, though, would still be ruled by Newton’s laws of motion; their exact movements could in principle be calculated.

    By contrast, the Copenhagen theory held that subatomic particles were ruled by chance.

    Einstein began his attack in the time-honoured tradition of reductio ad absurdum – arguing that the logical extension of quantum theory would lead to an absurd outcome.

    After several sleepless nights, Bohr found a flaw in Einstein’s logic. Einstein did not retreat: he was sure he could convince Bohr of the absurdity of this strange new theory. Their debate flowed over into the Sixth Solvay Congress in 1930, and on until Einstein felt he finally had the pieces in place to checkmate Bohr at the seventh congress in 1933. Two weeks before that, however, Nazi persecution forced Einstein to flee to the United States. The planned checkmate would have to wait.

    When it came, it was deceptively simple. In 1935 at Princeton, Einstein and two collaborators, Boris Podolsky and Nathan Rosen, published what became known as the Einstein-Podolsky-Rosen paradox [Physical Review Journals Archive], or EPR for short. Podolsky wrote up the thought experiment in a mathematical form, but let me illustrate it with jellybeans.

    Suppose you have a red and a green jellybean in a box. The box seals off the jellybeans from all others: technically speaking, the pair form an “isolated system”, and they are “entangled” in the sense that the colour of one jellybean gives information about the other. You can see this by asking a friend to close her eyes and pick a jellybean at random. If she picks red, you know the remaining sweet is green.

    This is key to EPR: by knowing the colour of your friend’s jellybean, you can know the colour of your own without “disturbing” it by looking at it. But in trying to bypass the supposed observer-effect in this way, EPR had also inadvertently uncovered the strange idea of “entanglement”. The term was coined by Schrödinger after he read the EPR paper .

    So now apply this technique to two electrons. Instead of a colour, each one has an intrinsic property called “spin”. Imagine something like the spin axis of a gyroscope. If two electrons are prepared together in the lab so that they have zero total spin, then the principle of conservation of angular momentum means that if one of the electrons has its spin axis up, the other electron’s axis must be down. The electrons are entangled, just as the jellybeans were.

    2

    With jellybeans, the colour of your friend’s chosen sweet is fixed, whether or not she actually observes it. With electrons, by contrast, until your friend makes her observation, quantum theory simply says there is a 50% chance its spin is up, and 50% it is down.

    The EPR attempt to strike at the heart of quantum theory now goes like this. Perhaps the spin of your friend’s electron was in fact determined before she picked it out. However, like a watermark that can’t be detected until a special light is shone on it, the spin state is only revealed when she looks at it. Quantum spin, then, involves a “hidden variable”, yet to be described by quantum theory. Alternatively, if quantum mechanics is correct and complete, then the theory defies common sense – because as soon as your friend checks the spin of her electron, your electron appears to respond instantly, because if hers is “up” then yours will be “down”.

    This is because the correlation between the two spins was built into the experiment when the electrons were first entangled, just as putting the two jellybeans in a box ensures the colour of your jellybean will be “opposite” that of your friend’s. The implications are profound. Even if your friend moved to the other side of the galaxy, your electron would “know” that it must manifest the opposite spin in the instant she makes her observation.

    Of course, instant action violated Einstein’s theory of relativity: nothing can travel faster than the speed of light. Hence Einstein dubbed this absurd proposition “spooky action at a distance”.

    But there was more. Spin is not the only property your friend could have chosen to observe. What EPR showed, then, is that the physical nature of your electron seems to have no identity of its own. Rather, it depends on how your friend chooses to observe her electron. As Einstein put it: “Do you really believe the Moon is there only when you look at it?” The EPR paper concluded: “No reasonable definition of reality could be expected to permit this.” Ergo, the authors believed, quantum theory had some serious problems.

    Bohr was stumped by EPR. He ditched the idea that the act of measurement jolted the state of the particle. (Indeed, later experiments would show that uncertainty is not solely the result of an interfering observer; it is an inherent characteristic of particles.)

    But he did not abandon the uncertainty at the heart of quantum mechanics. Instead of trying to wrestle with the real world implications, he concluded [Physical Review Journals Archive] that we can only speak of what we observe – at the beginning of the experiment and the end when your friend’s electron is definitely “up”, say. We cannot speak about what happens in between.

    Einstein and Bohr continued to debate the issue for the rest of their lives. What they really disagreed about was the nature of reality. Bohr believed that nature was fundamentally random. Einstein did not. “God does not play dice with the universe,” he declared.

    Nevertheless, Einstein knew that quantum theory accurately described the results of real as opposed to thought experiments. So most physicists considered that Bohr had won. They focused on applying quantum theory, and questions about the EPR paradox and entanglement became a niche interest.

    In 1950, Chien-Shiung Wu and Irving Shaknov [Physical Review Journals Archive] found oddly linked behaviour in pairs of photons. They didn’t know it at the time but it was the first real-world observation of quantum entanglement.

    ___________________________________________________________________________
    Some suggest that something like a ‘wormhole’ – a tunnel in spacetime between two widely separated black holes, a consequence of general relativity theory first deduced by Einstein and Rosen – may be the mechanism underlying entanglement.
    ___________________________________________________________________________

    Later, David Bohm realised [Physical Review Journals Archive] Wu and Shaknov’s discovery was an opportunity to take entanglement out of the realm of thought experiments and into the lab. Following Bohm, in 1964 John Bell translated the two EPR alternatives into a mathematical relationship that could be tested. But it was left to other experimenters – most famously Alain Aspect in 1981 [Physical Review Letters] – to carry out the tests.

    Einstein’s hopes of finding hidden variables that would take the uncertainty out of quantum theory were dashed. There seemed no escaping the bizarre consequences of EPR and the reality of entanglement.

    But does this also mean “spooky action at a distance” is real? Entanglement in electrons has been demonstrated at distances of a kilometre or two. But so far that’s too short a distance to know if faster-than-light interactions between them were involved. Things may soon become clearer: at the time of writing, Chinese scientists have just announced the successful transmission of entangled photons [Science] from an orbiting satellite over distances of more than 1,200 km.

    On the other hand, some physicists have recently taken up Einstein’s side of the argument. For instance, in 2016 Bengt Nordén, of Chalmers University in Sweden, published a paper [Cambridge Quarterly Reviews of Biophysics] entitled, Quantum entanglement: facts and fiction – how wrong was Einstein after all? Against Bohr’s better judgement, such physicists are once again asking about the meaning of reality, and wondering what is causing the weird phenomenon of entanglement.

    Some even suggest that something like a “wormhole” – a tunnel in spacetime between two widely separated black holes, a consequence of general relativity theory first deduced by Einstein and Rosen – may be the mechanism underlying entanglement. The mythical faster-than-light tachyon is another possible contender.

    But nearly everyone agrees that whatever is going on between entangled particles, experimenters can only communicate their observations of entangled particles at light speed or less.

    Entanglement is no longer a philosophical curio: not only are physicists using it to encrypt information and relying on it to underpin the design of tomorrow’s quantum computers, they are once again grappling with the hard questions about the nature of reality that entanglement raises.

    Ninety years after the Fifth Solvay Congress, Einstein’s thought experiments continue to drive science onwards.

    See the full article here .

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  • richardmitnick 12:56 pm on October 5, 2017 Permalink | Reply
    Tags: , , , , COSMOS, , The Calabash Nebula a.k.a. the Rotten Egg Nebula because it contains a lot of sulphur   

    From Hubble via COSMOS: “Death of a star” 

    NASA Hubble Banner

    NASA/ESA Hubble Telescope

    NASA/ESA Hubble Telescope

    COSMOS

    05 October 2017

    A star caught while transforming from a red giant to a planetary nebula.

    2
    The Calabash Nebula. NASA/ESA Hubble, Judy Schmidt

    The Calabash Nebula, pictured here — which has the technical name OH 231.8+04.2 — is a spectacular example of the death of a low-mass star like the sun.

    This image taken by the Hubble Space Telescope shows the star going through a rapid transformation from a red giant to a planetary nebula, during which it blows its outer layers of gas and dust out into the surrounding space. The recently ejected material is spat out in opposite directions with immense speed — the gas shown in yellow is moving close to one million kilometers per hour.

    Astronomers rarely capture a star in this phase of its evolution because it occurs within the blink of an eye — in astronomical terms. Over the next thousand years the nebula is expected to evolve into a fully-fledged planetary nebula.

    The nebula is also known as the Rotten Egg Nebula because it contains a lot of sulphur, an element that, when combined with other elements, smells like a rotten egg — but luckily, it resides over 5,000 light-years away in the constellation of Puppis.

    See the full article here .

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    The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA’s Goddard Space Flight Center manages the telescope. The Space Telescope Science Institute (STScI), is a free-standing science center, located on the campus of The Johns Hopkins University and operated by the Association of Universities for Research in Astronomy (AURA) for NASA, conducts Hubble science operations.

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  • richardmitnick 12:37 pm on October 5, 2017 Permalink | Reply
    Tags: COSMOS, Magma plumes on Mars, , Mars has the largest and oldest volcanoes known in the solar system, Nakhilite meteorite, , Plumes of molten rock - Hawaii, Without plate tectonics Martian volcanoes grew huge   

    From COSMOS: “Meteorite clues to giant volcanoes on Mars” 

    Cosmos Magazine bloc

    COSMOS Magazine

    05 October 2017
    Andrew Masterson

    Without plate tectonics, Martian volcanoes grew huge. New research explains why.

    1
    An image of a piece of nakhilite meteorite about 1 mm across, taken in cross-polarised light. Different colours represent different volcanic minerals. Benjamin Cohen.

    Mars endured a much more volcanically active past than previously thought, but its volcanoes grew at a rate 1000 times slower than those on Earth, new research shows.

    The fresh estimate for volcanic activity, published in the journal Nature Communications, is derived from an analysis of the composition of a group of meteorites known as the nakhilites, which are all thought to be the products of a single, long-lived Martian volcano.

    Most volcanoes on Earth arise because of the pressures exerted by tectonics, with hotspots arising where the plates comprising the planet’s crust either collide or diverge.

    A few, however, are caused by a different process, wherein a magma “plume” is pushed directly up from deep in the Earth’s mantle. This is especially the case with the Hawaiian island chain, which were (and are still being) created by a plume of molten rock.

    The Hawaiian chain, however, is also influenced by plate tectonics. Research shows that as a volcano forms, the Pacific plate moves it inexorably away from the plume that is pushing it from below. Volcanoes in the Hawaiian chain grow older as they move away from the source plume.

    In geologic time, too, the entire Hawaiian chain is remarkably young. A study published last year estimated the initial plate movement that uncovered the plume occurred only around three million years ago.

    Mars, in stark contrast, does not have plate tectonic movements that influence the landscape. Instead the planet has a “stagnant lid”, an outer crust that never changes position.

    It does, however, have magma plumes. This means that when such a plume ruptures the crust and erupts, depositing lava and other ejecta and thus catalysing the creation of a volcanic mountain, the rupture and the above-ground result will always stay in the same relationship to each other – for billions of years.

    As a result, Mars has the largest and oldest volcanoes known in the solar system. Just how old and just how fast these grew has until now remained poorly understood.

    To try to shed light on the matter, a team led by Benjamin Cohen of the Scottish Universities Environmental Research Centre in the UK, turned to meteorites.

    The nakhilites are a group of 18 meteorites that over a period of time landed on Earth after a single large object slammed into a Martian volcano about 10.7 million years ago.

    The meteorites comprise mostly basalt, interlaced with other minerals including clinopyroxene, olivine, feldspar and volcanic glass. They are all similar to each other but, crucially, not identical.

    These small differences allowed Cohen and his colleagues to estimate when each was created, using a combination of laser step-heating and argon-based dating.

    “The data show that the nakhilites were not all formed during a single cooling event, but instead reveal a protracted volcanic eruption history on Mars,” the scientists report.

    Using the results, the team found that the volcano was the result of four discrete eruptions over a period of 93 million years. The volcano itself, they calculated, grew at a rate of only 400 to 700 millimetres every million years – orders of magnitude slower than plume-driven volcano growth on Earth.

    See the full article here .

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  • richardmitnick 11:49 am on September 22, 2017 Permalink | Reply
    Tags: A phonon is a collective movement of particles vibrating together, A photon (a quantum of light), At the microscopic quantum level a phonon behaves even more like a particle, COSMOS, Hanbury Brown and Twiss interferometry, Optomechanical crystal, Photons and phonons combine for quantum solution, Vibrations in crystals can obey the laws of quantum mechanics and might be used to store information in quantum computers   

    From COSMOS: “Photons and phonons combine for quantum solution” 

    Cosmos Magazine bloc

    COSMOS Magazine

    22 September 2017
    Michael Lucy

    1
    A conceptual illustration showing the crystal (middle), a phonon (top) and the quantum probability distribution (bottom). Moritz Forsch / TU Delft

    Vibrations in crystals can obey the laws of quantum mechanics and might be used to store information in quantum computers, according to new research published in the journal Science.

    The new development, achieved by Sungkun Hong at the University of Vienna in Austria and colleagues, revolves around the idea of the phonon. Not to be confused with a photon (a quantum of light), a phonon is a collective movement of particles vibrating together.

    For an analogue at the macroscopic scale, think of a single wave moving through the ocean – after the wave passes, the water molecules that made it go back to where they began, but the wave itself moves on.

    At the microscopic, quantum level, a phonon behaves even more like a particle, to the point where it is often referred to as a “quasiparticle”. Physicists think phonons may provide a useful bridge between quantum and classical worlds, and the interactions between light and vibrations are a very active area of research.

    Hong’s team analysed phonons using an optomechanical crystal – described as a “microfabricated silicon nanobeam” – that is designed to vibrate in a specific way when struck by a photon.

    The researchers fired photons at the device, creating phonons within it. They then fired photons of a different frequency, which were reflected back after interacting with those phonons.

    They then analysed the reflected photons via a process called Hanbury Brown and Twiss interferometry, which lets them gain information about the quantum state of the phonons. Using this technique, they proved that a single phonon in the crystal obeys the laws of quantum mechanics rather than classical physics.

    Because of this quantum property, and the ability manipulate them with light, phonons in crystals could be “an ideal candidate for storage of quantum information”, the authors say.

    See the full article here .

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  • richardmitnick 12:23 pm on September 12, 2017 Permalink | Reply
    Tags: 3D view helps us to understand how galaxies formed and evolved, , , , , COSMOS   

    From COSMOS: “3D view helps us to understand how galaxies formed and evolved” 

    Cosmos Magazine bloc

    COSMOS Magazine

    12 September 2017
    Caroline Foster, ASTRO3D Fellow
    University of Sydney

    Richard McDermid, ARC Future Fellow
    Senior Lecturer
    Macquarie University

    Huge numbers of observations combined with computational modelling are finally giving astronomers a realistic idea of the three-dimensional shape of galaxies.

    1
    So many galaxies viewed by the Hubble Space Telescope: but what’s their real shape in 3D? NASA, ESA, and J. Lotz and the HFF Team (STScI)

    There are billions of galaxies in our universe – more than 10 times the previous estimate of 200 billion – but we know surprisingly little about what they really look like in three dimensions.

    Unlike Solar System objects, which are within physical reach of humanity’s technology such as the Cassini and Voyager probes, galaxies are so distant that they are only ever viewed in projection onto the celestial sphere.

    While we may have images of many of the galaxies, these images are two-dimensional, and deducing the galaxies’ true shape is a bit like trying to work out the shape of an object that creates a shadow puppet.

    2
    Much like shadow puppetry, astronomers see galaxies as projected on the sky. This pictogram illustrates how galaxies with vastly different 3D shapes can project identically on the sky, making them visually indistinguishable when viewed from Earth. Myriam Rodrigues (Observatore de Paris), Author provided

    As different shapes can project identically on a two-dimensional surface, measuring the three-dimensional shape of galaxies is a challenging problem that has daunted scientists for almost a century.

    But our research, published today in the Monthly Notices of the Royal Astronomical Society, sheds new light on how to determine the 3D shape of a galaxy.

    Shape points to formation

    Galaxies may be flat like a pancake, squashed like a sea urchin, elongated like a rugby ball, or anything in between.

    It’s theorised [MNRAS]that the 3D shape of a galaxy may give some idea on how it formed and evolved.

    For example, models suggest [MNRAS] that galaxy-on-galaxy encounters lead to more spherical systems as the stars get puffed up through these cosmic collisions.

    When gas falls into a galaxy to form new stars, it usually settles onto a disc, leading to a flatter structure [ApJ].

    So accessing the shape information of a galaxy can provide a new angle for studying its formation.

    4
    A stunning image of NGC 6050, a system of interacting galaxies. Violent encounters of galactic proportions are thought to significantly alter the 3D shape of galaxies by mixing the stellar orbits. NASA, ESA, the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration, and K. Noll (STScI)

    The first galaxies were probably formed by gravity pulling vast clouds of matter together. For the same reason that figure skaters spin faster when their arms are closer to their body than when they are extended, the collapse of matter leads to an increase in spin of the galaxy.

    The possible subsequent aggregation of surrounding matter also speeds up the spin of galaxies.

    On the other hand, galaxy interactions mix the stellar orbits, causing galaxies to lose their preferred sense of rotation.

    Most previous studies have used images to estimate the 3D shape of galaxies, but images provide little leverage on the third dimension, yielding multiple possible solutions.

    The extra dimension

    But with the Sydney-Australian-Astronomical-Observatory Multi-object Integral (SAMI) field unit instrument on the 4-metre Anglo-Australian Telescope, astronomers can obtain detailed information about the movement of gas and stars inside galaxies.

    5
    SAMI


    AAO Anglo Australian Telescope near Siding Spring, New South Wales, Australia

    Analysing the movement of stars around galaxies together with their image on the sky is key to unlocking the third dimension.

    Measuring the motion of stars around galaxies is not exactly the same as measuring their position in 3D. In order to infer the 3D shape of galaxies from their stellar motions, large samples are required.

    The novel SAMI instrument can observe 13 galaxies at a time, enabling the collection of data on thousands of galaxies in a relatively short period.

    6
    A selection of SAMI galaxies imaged with the Hyper Suprime Camera on the Subaru Telescope in Hawaii. National Astronomical Observatory of Japan (NAOJ), Caroline Foster (The University of Sydney) and Dan Taranu (University of Western Australia)

    NAOJ Subaru Hyper Suprime Camera


    NAOJ/Subaru Telescope at Mauna Kea Hawaii, USA

    With more than three times more data than the largest previous study, astronomers are now beginning to understand the processes that shape galaxies.


    This video shows various projections of the inferred 3D shape of the fast spinning galaxies in our study. This animation highlights that galaxies can look very different depending on how they project on the sky. No credit.

    Conversely, galaxies that do not rotate, or rotate very little, have more varied shapes ranging from oblate spheroids (like sea urchins, or squashed beach balls) to triaxial ellipsoids (more like potatoes, or squashed rugby balls), consistent with having experienced a history of significant interaction.


    Similar to the previous animation, but this time showing various projections of the likely 3D shape of low spin galaxies in our study. No credit.

    The 3D shape of galaxies reveals that low-spin galaxies have undergone a complex history of interaction, while high-spin galaxies probably lead a quieter lifestyle and/or have engulfed significant amounts of gas from their surroundings.

    7
    The giant elliptical galaxy M60 (left) and smaller spiral galaxy NGC 4647 (right) located in the constellation Virgo. From our vantage point both galaxies look round but they have different shapes with the latter being flatter. NASA, ESA, and the Hubble Heritage (STScI/AURA)–ESA/Hubble Collaboration., Author provided

    The shape of things to come

    Detailed computer simulations of galaxy formation suggest that galaxy shapes can also be influenced by the so-called halo of invisible dark matter that surrounds them.

    In future studies, by comparing this newly observed shape information with other observed galaxy properties (such as their location in the universe, how much gas they have, and the ages and chemistry of their stars), astronomers will now have a new tool for testing these theoretical predictions.

    The ConversationIn this way, by measuring the 3D shape of the visible parts of galaxies, we will also learn about the invisible parts.

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  • richardmitnick 7:44 am on September 11, 2017 Permalink | Reply
    Tags: , COSMOS, , , Zirconium   

    From COSMOS: “Zircons: How tiny crystals open a window into the early history of Earth” 

    Cosmos Magazine bloc

    COSMOS Magazine

    11 September 2017
    Richard A. Lovett

    1
    These microscopic zircons collected from Mount Narryer in Western Australia have been dated at more than 4.1 billion years old. Auscape / Getty

    Zirconium is the eighteenth most common element in the Earth’s crust – more common than such well-known substances as zinc, copper, nickel, and chromium. But most people have never heard of it, unless in the form of imitation diamonds known as cubic zirconia.

    In nature, zirconium forms another type of crystal called zircons. To geophysicists, these are the true gems, because they provide vital time capsules from the Earth’s deepest past.

    Chemically, zircons are nothing fancy. They are tiny lumps of zirconium silicate (ZrSiO4) that are ubiquitous in volcanic rocks. But they’re typically only 0.1 mm to 0.3 mm across, making them hard to spot without a magnifying glass. Not exactly the type of thing most of us would notice, let alone care about.

    But they have two important traits.

    One is that they are incredibly durable. The rocks in which they initially formed may weather away, but the zircons survive as tiny grains of sand that may later be incorporated into the next generation of rocks.

    “We have no rocks that are older than 4 billion years,” says John Valley, a geochemist at the University of Wisconsin, Madison. (The Earth itself is 4.543 billion years old.) “[Zircons] are what we study if we want to analyze things that formed that far back.”

    Their other trait is that they aren’t pure zirconium silicate. They contain trace amounts of other elements, most importantly uranium, trapped within them as they crystalize. Over the eons, that uranium slowly decays to lead. By comparing the amounts of uranium and lead, scientists can determine the date at which the crystal formed.

    Another element, oxygen (the “O” in ZrSiO4), helps tell the conditions under which each zircon formed. That’s because oxygen has two well-known stable isotopes, 16O and 18O, either of which can be incorporated into the crystal as it grows.

    Typically, these come from water (H2O), which can contain either 16O or 18O (or a more rare stable isotope called 17O). All these forms of water are chemically identical, but 18O-containing water is about ten percent heavier than 16O-containing water. That causes the two types of water to (very slightly) separate — and to do so by different amounts under different conditions.

    Geologists once thought the early Earth was far too hot for its surface to be anything but an ocean of magma, let alone to have liquid water. In fact, the earliest period in the Earth’s history, from its formation to 4 billion years ago, is called the Hadean because it was widely believed to resemble hell, or Hades.That meant zircons from the Hadean period should have oxygen isotope ratios comparable to that of water molecules in the Earth’s mantle. But geologists studying the Jack Hills region of Western Australia, which has yielded the oldest zircons ever found, have been unearthing zircons from as far back as 4.375 billion years ago whose oxygen isotope ratios show they may have formed from magma that incorporated liquid water.

    Other zircon research has suggested that life too may date back a lot further than we once thought. This research involves the ratio of non-radioactive carbon isotopes (12C and 13C) in tiny diamonds incorporated in the zircon structure. These diamonds have carbon isotope signatures suggesting the carbon from which they were formed may have included organic material from living organisms.

    “This implies that there was life in the Hadean,” says Craig O’Neill, a geodynamicist at Macquarie University. Though, he notes, there are other explanations involving purely geologic processes. “It’s hard to be sure,” he says.

    Still more studies have used hyper-sensitive magnets to look for trace magnetic fields carried by magnetic impurities in ancient zircons, in the hope of determining the strength of the Earth’s magnetic field at the time these zircons formed. “The analysis takes about a week,” says John Tarduno, a geophysicist at the University of Rochester, New York. Such studies, he says, indicate that the Earth’s magnetic field might be as old as its zircons.

    And that’s just the beginning. In a 2017 study in Science Advances, geophysicists used zircons in Moon rocks brought back by Apollo astronauts to determine that the Moon’s crust solidified 4.51 billion years ago, only 60 million years after the formation of the first protoplanets. And zircons in meteorites blasted off the surface of Mars are being studied to peer nearly as far back into the Red Planet’s early history.

    So who cares if copper, zinc, nickel, and chromium are vastly more valuable to the modern economy? Lowly zirconium may be what helps us unravel the greatest of all mysteries: who we are and where we came from.

    See the full article here .

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  • richardmitnick 7:29 am on September 11, 2017 Permalink | Reply
    Tags: , , , , COSMOS, , , Super-Earths a juicy target for new space telescope   

    From SAO via Cosmos: “Super-Earths a juicy target for new space telescope” 

    Smithsonian Astrophysical Observatory
    Smithsonian Astrophysical Observatory

    COSMOS

    11 September 2017
    Andrew Masterson

    NASA/ESA/CSA Webb Telescope annotated

    The discovery of three “super-Earth” planets orbiting a dwarf star roughly 97 light years away provides a juicy target for the James Webb Space Telescope to be launched later this year, say US astronomers.

    In a paper posted on the pre-print science platform arXiv, a team of scientists led by Joseph Rodriguez from the Harvard-Smithsonian Centre for Astrophysics in Massachusetts, US, say the discovery affords a rare opportunity to investigate the dividing line between smaller rocky planets and larger gaseous ones.

    The planets, dubbed GJ 9827-b, -c, and –d, all orbit a K-type dwarf star, and do so rapidly, with orbits that range between 1.2 and 6.2 Earth-days. The frequency of their orbit means that the new space telescope – a joint venture between NASA and the European and Canadian space agencies – will be able to monitor them many times as they move in front of their host star, potentially revealing a wide array of valuable information.

    Rodriguez and colleagues are particularly excited about the discovery because two of them fall within a size range that so far seems rare – or at least elusive.

    To date, more than 3000 exoplanets have been identified, with the Kepler mission adding at least another 4500 candidates to the list.

    The California Kepler Survey, operated by NASA, has so far logged precise radii for 2000 identified planets and produced a surprising result. Almost all of them fall in a range that tops out at one-and-a-half times the radius of Earth, or starts at two.

    This has led to the observation that so far all exoplanets seem to be either super-Earths or mini-Neptunes.

    2
    PLANETARY COUSINS Planets may be lumped into two groups: smaller and rocky like Kepler-452b (left), or bigger and gassy like Kepler-22b (right). W. Stenzel/NASA Ames. Science News.

    The key difference, of course, is that those on the Earth-side of the divide are rocky, and those on the Neptune side are gaseous.

    One theory for the puzzling lack of intermediates is that the rocky “sub-Neptune” planets recorded so far orbit comparatively close to their host stars. This may mean that solar radiation burns off the thick gaseous envelopes that cloak their more distant neighbours, leaving only small rocky cores.

    GJ 9827-b, at 1.64 Earth radii, and GJ 9827-d, at 2.08, fall between the two divisions, potentially affording strong opportunities to study the transitional zone between rocky Earths and gassy Neptunes. GJ 9827-c has a radius of 1.29 Earth equivalents, and should therefore be simply rocky.

    The short orbit periods of the three planets, the researchers note, will enable repeated observations over a limited timespan.

    “The planets span the transition from rocky to gaseous planets, so the characteristics of their atmospheres and interior structures may illuminate how the structure and composition of small planets change with radius,” the scientists write.

    See the full article here .

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    About CfA

    The Center for Astrophysics combines the resources and research facilities of the Harvard College Observatory and the Smithsonian Astrophysical Observatory under a single director to pursue studies of those basic physical processes that determine the nature and evolution of the universe. The Smithsonian Astrophysical Observatory (SAO) is a bureau of the Smithsonian Institution, founded in 1890. The Harvard College Observatory (HCO), founded in 1839, is a research institution of the Faculty of Arts and Sciences, Harvard University, and provides facilities and substantial other support for teaching activities of the Department of Astronomy. The long relationship between the two organizations, which began when the SAO moved its headquarters to Cambridge in 1955, was formalized by the establishment of a joint center in 1973. The CfA’s history of accomplishments in astronomy and astrophysics is reflected in a wide range of awards and prizes received by individual CfA scientists.

    Today, some 300 Smithsonian and Harvard scientists cooperate in broad programs of astrophysical research supported by Federal appropriations and University funds as well as contracts and grants from government agencies. These scientific investigations, touching on almost all major topics in astronomy, are organized into the following divisions, scientific departments and service groups.

     
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