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

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

    Cosmos Magazine bloc

    COSMOS Magazine

    05 December 2017
    Lauren Fuge

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

    NASA/ESA Hubble Telescope

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

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

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

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

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

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

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

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

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

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

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

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

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

    See the full article here .

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  • richardmitnick 1:45 pm on December 7, 2017 Permalink | Reply
    Tags: , COSMOS, Each volcano like each individual person has its own unique “personality.”, , Mount Agung in Bali - when will it blow?, ,   

    From COSMOS: “Each volcano has unique warning signs that eruption is imminent” 

    Cosmos Magazine bloc

    COSMOS Magazine

    07 December 2017
    Tracy K. P. Gregg

    1
    Mount Agung in Bali. Just a burp, or indication of coming disaster? AP Photo/Firdia Lisnawati..

    Mount Agung in Bali has been thrusting ash thousands of feet into the sky for almost two weeks. Lava is burbling at the volcano’s peak. Indonesian authorities have ordered evacuations around Agung, while tourists are stranded at the closed airport. The volcano’s flanks are bulging from magma trying to push its way out, and earthquake frequency has been increasing. Heat from the magma has melted snow and ice at Agung’s summit, causing volcanic mudflows called lahars. It’s looking like an eruption is imminent… but how do volcanologists know for sure what’s to come?

    Each volcano, like each individual person, has its own unique “personality.” You may know, for example, that you can tease your brother mercilessly – up until the point where his eyebrows crease together because that means he’s going to blow his top. But do you know what it means if my eyebrows crease together? (It’s a surefire sign I’m thinking really hard.)

    Similarly, one volcano might reveal an imminent eruption by a sudden increase in the frequency and strength of earthquakes located directly below it. A different volcano might not show an increase in earthquake strength but instead display an increase in elevation as magma swells beneath its surface – just as air filling a balloon causes it to increase in size.

    2
    This fall showed a spike in number and magnitude of earthquakes around Agung. MAGMA Indonesia.

    The best way scientists can determine whether a volcano is about to erupt is to study its past behavior: How did this volcano act before it erupted last time? Our ability to predict eruptions is directly related to the amount of historic data we have for a given volcano.

    For most of Earth’s active volcanoes, though, we don’t have detailed information. The last time Agung volcano erupted, for example, was in 1963. And that was before it was closely monitored with seismometers. Satellite observations of volcanoes were not commonplace then, as they are now. We therefore don’t know what specific type, frequency or size of volcanic precursors – that is, events that precede an eruption – to look for with Agung volcano.

    Mount Pinatubo, Philippines, for example, erupted catastrophically in 1991; before that, its most recent eruption was around 500 years earlier. Precursors at Mount Pinatubo included ash explosions at the summit, increases in the number of vents spewing hot gas, changes in the volcano’s shape and increases in both the frequency and size of earthquakes. Two months of increasing activity preceded the 1991 paroxysmal eruption.

    In contrast, Mount St. Helens volcano in the U.S. is probably the most closely watched volcano on the planet. Decades of detailed observations allow geologists to make fairly precise predictions about Mount St. Helens: a specific pattern of earthquakes, for example, means that new lava will erupt within two weeks.

    We don’t yet know if Agung volcano is currently giving us two weeks, two months or two years (or more) of warning because we don’t know precisely what it did before its 1963 eruption.

    3
    GPS measurements provide models of the direction and rate (length of arrow) of deformation at the summit of Mauna Loa, a potential eruption precursor. USGS

    As technology advances, volcanologists and experts in collecting and interpreting satellite data (including remote-sensing scientists and geodesists) are improving our ability to predict eruptions. Now we can collect important information about volcano shape, temperature and changes in those parameters using satellites that provide the view from space. Satellites give volcanologists a good overall view of the volcano, but can’t supply human-scale details. Satellite orbits typically allow them to pass over a given volcano only once every week or two. We still require seismometers on the ground to detect and report earthquakes caused by magma moving beneath the volcano, but seismometers are too expensive to deploy and maintain everywhere.

    Accurate predictions of volcanic eruptions – particularly the size of the eruption and whether the volcano will explode or generate lava flows – are essential for local authorities to make life-and-death decisions about people in the vicinity of an active volcano. If an evacuation is ordered and a volcano explodes, lives are saved. This happened in the 1991 Pinatubo eruption. If an evacuation is ordered and the volcano doesn’t explode, economic losses and human suffering can be catastrophic. This scenario played out in Mammoth Mountain, California, in 1984, where the local community lost millions of tourist dollars – and there was no eruption.

    To predict eruptions on the scale of hours, days or weeks, we need detailed information about each potentially threatening volcano. Without that, we are forced to make comparisons: will Agung volcano behave more like Mount St Helens or Mount Pinatubo, for example? In other words, do creased eyebrows on someone you’ve just met (or, for example, increased seismicity at Agung volcano) mean that person is about to blow its top (like Mount Pinatubo did in 1991) or is just thinking really hard? More data, from more volcanoes, make for better comparisons, but nothing beats really getting to know the behavior of an individual volcano.

    See the full article here .

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  • richardmitnick 1:25 pm on December 7, 2017 Permalink | Reply
    Tags: , , COSMOS, Gertrude Belle Elion, , Nobel Prize in Medicine in 1988, Three honorary doctorate degrees from George Washington University Brown University and the University of Michigan,   

    From COSMOS: Women in STEM – “Gertrude Belle Elion’s journey from mayonnaise to medicine” 

    Cosmos Magazine bloc

    COSMOS Magazine

    07 December 2017
    No writer credit

    4
    Gertrude Belle Elion

    1
    The life and times of chemist, cancer researcher and Nobel Laureate in medicine Gertrude Belle Elion. Jeffrey Phillips.

    Think of leukaemia and the subject of mayonnaise doesn’t immediately spring to mind. Yet had fate not intervened, one of the most important researchers into the nature and treatment of blood cancer might today be known – if at all – as simply a master of mayo.

    Gertrude Belle Elion was born in New York City in 1918. Her father had been a child immigrant from Lithuania, and her mother had arrived, aged 14, from Russia in 1914.

    When Gertrude was born her parents were comfortably off, mainly because her father, Robert, had built up a healthy dental practice. “My first seven years were spent in a large apartment in Manhattan where my father had his dental office, with our living quarters adjoining it,” she later recalled.

    In 1929, however, life for the Elion family took a big turn for the worse when they lost most of their money in the Wall Street Crash. This limited Gertrude’s options for further education after high school, but fortunately she gained admission, at age 15, to a nearby free college on the back of her good grades. Her grandfather’s death from cancer spurred her choice to major in chemistry.

    After graduating from college, she had no means to pay to attend graduate school and her employment prospects were bleak. Work was scarce for everyone during the Great Depression, and many potential employers could not accept the idea a woman could be a good chemist. She scored several stints of unpaid and temporary work as a lab assistant, then switched to relief high school teaching while also studying at nights in her quest for a Master’s degree in chemistry.

    Then World War II broke out and suddenly – with men joining the fighting forces en masse – many more jobs became available to women. Elion gave up the world of freelance science teaching and took a job with food manufacturer Quaker Maid. Her responsibilities included testing the acidity of pickles and making sure egg yolk going into mayonnaise was the right colour.

    There she might have remained, had not her ever-curious mind driven her to seek new challenges. In 1944 she found a position as a biochemist at the research laboratories of Burroughs Wellcome, which would later become GlaxoSmithKline pharmaceutical company.

    She would remain with the company, even after officially retiring in 1983, until her death in 1999 at the age of 81.

    Along the way, she would win the Nobel Prize in Medicine in 1988. The prize, shared with colleagues James Black and George Hitchings, was awarded in recognition of research that, to quote the citation, “demonstrated differences in nucleic acid metabolism between normal human cells, cancer cells, protozoa, bacteria and virus”.

    The trio’s discoveries went far further than simply establishing the ways in which different cells operate. They put their findings to work and created several critically important drugs saving millions of lives.

    Elion played a central role in the development of thioguanine and 6-mercaptopurine, used to treat leukaemia. Thioguanine is still on the World Health Organisation’s List of Essential Medicines.

    Her team also developed pyrimethamine, a malaria treatment, and allopurinol, used to treat gout. Another of Elion’s drugs, azathioprine, works to stop the immune system from rejecting new organs – without it, there could be no transplant surgery. If that wasn’t enough, in 1977 her team’s discoveries were adapted to create acyclovir, the first effective treatment against the herpes virus.

    At one stage in her early years at Wellcome, Elion was faced with a very tough choice: she was told that if she wanted to complete her PhD she would have to quit work and study full-time. She opted to drop her studies and stay at the lab – a difficult decision at a time when female scientists were often considered inferior to male ones.

    “Years later, when I received three honorary doctorate degrees from George Washington University, Brown University and the University of Michigan, I decided that perhaps that decision had been the right one after all,” she observed wryly at the time of accepting her Nobel Prize.

    See the full article here .

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  • richardmitnick 2:21 pm on December 4, 2017 Permalink | Reply
    Tags: , , , , , COSMOS, ,   

    From ANU: “Astronomers create most detailed radio image of nearby dwarf galaxy” 

    ANU Australian National University Bloc

    Australian National University

    28 November 2017

    Will Wright
    +61 2 6125 7979
    media@anu.edu.au

    New imaging hints at a violent past and a fatal future for the Small Magellanic cloud. COSMOS

    1
    The new radio image of the Small Magellanic Cloud. ANU/CSIRO

    Astronomers at ANU have created the most detailed radio image of nearby dwarf galaxy, the Small Magellanic Cloud, revealing secrets of how it formed and how it is likely to evolve.

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

    This image was taken by CSIRO’s powerful new radio telescope, the Australian Square Kilometre Array Pathfinder (ASKAP), and its innovative radio camera technology, known as phased array feeds.

    SKA ASKAP Phased Array

    The Small Magellanic Cloud, which is a tiny fraction of the size and mass of the Milky Way, is one of our nearest galactic neighbours and visible to the naked eye in the southern sky.

    Small Magellanic Cloud. NASA/ESA Hubble and ESO/Digitized Sky Survey 2

    Co-lead researcher Professor Naomi McClure-Griffiths said the complex structure of the dwarf galaxy likely resulted, in part, from interactions with its companion, the Large Magellanic Cloud, and the Milky Way.

    Large Magellanic Cloud. Adrian Pingstone December 2003

    “The new image captured by CSIRO’s Australian Square Kilometre Array Pathfinder telescope reveals more gas around the edges of the galaxy, indicating a very dynamic past for the Small Magellanic Cloud,” said Professor McClure-Griffiths from the ANU Research School of Astronomy and Astrophysics.

    “These features are more than three times smaller than we were able to see before and allow us to probe the detailed interaction of the small galaxy and its environment.”

    Professor McClure-Griffiths said distortions to the Small Magellanic Cloud occurred because of its interactions with the larger galaxies and because of its own star explosions that push gas out of the galaxy.

    “The outlook for this dwarf galaxy is not good, as it’s likely to eventually be gobbled up by our Milky Way,” she said.

    “Together, the Magellanic Clouds are characterised by their distorted structures, a bridge of material that connects them, and an enormous stream of hydrogen gas that trails behind their orbit – a bit like a comet.”

    Magellanic Bridge ESA_Gaia satellite. Image credit V. Belokurov D. Erkal A. Mellinger.

    The Small Magellanic Cloud has been studied extensively in the past few years by infrared telescopes such as NASA’s Spitzer Space Telescope and ESA’s Herschel telescope, which study the dust and stars within the galaxy.

    NASA/Spitzer Infrared Telescope

    ESA/Herschel spacecraft

    “The new radio image finally reaches the same level of detail as those infrared images, but on a very different component of the galaxy’s make-up: its hydrogen gas,” Professor McClure-Griffiths said.

    “Hydrogen is the fundamental building block of all galaxies and shows off the more extended structure of a galaxy than its stars and dust.”

    CSIRO spokesperson, Dr Philip Edwards, said: “This stunning image showcases the wide field of view of the ASKAP telescope, and augurs well for when the full array will come on-line next year.”

    See the full article here .

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    ANU Campus

    ANU is a world-leading university in Australia’s capital city, Canberra. Our location points to our unique history, ties to the Australian Government and special standing as a resource for the Australian people.

    Our focus on research as an asset, and an approach to education, ensures our graduates are in demand the world-over for their abilities to understand, and apply vision and creativity to addressing complex contemporary challenges.

     
  • richardmitnick 3:29 pm on December 1, 2017 Permalink | Reply
    Tags: André Maeder, , COSMOS, , , , Katie Mack, , The strongest evidence for dark matter comes not from the motions of stars and galaxies “but from the behavior of matter on cosmological scales as measured by signatures in the cosmic microwave back   

    From COSMOS: “Radical dark matter theory prompts robust rebuttals” 

    Cosmos Magazine bloc

    COSMOS Magazine

    01 December 2017
    Richard A Lovett

    1
    Most cosmologists invoke dark energy to explain the accelerating expansion of the universe. A few are not so certain. Mina De La O / Getty
    Images

    In 1887, physicists Alfred Michelson and Edward Morley set up an array of prisms and mirrors in an elegant attempt to measure the passage of the Earth through what was then known as “luminiferous ether” – a mysterious substance through which light waves were believed to propagate, like sound waves through air.

    The experiment should have worked, but in one of the most famous results of Nineteenth Century physics no ether movement was detected. That was a head-scratcher until 1905, when Albert Einstein took the results at face value and used them as a cornerstone in developing his theory of relativity.

    Today, physicists are hunting for two equally mysterious commodities: dark matter and dark energy. And maybe, suggests a recent line of research from astrophysicist André Maeder at the University of Geneva, Switzerland, they too don’t exist, and scientists need to again revise their theories, this time to look for ways to explain the universe without the need for either of them.

    Dark matter was first proposed all the way back in 1933, when astrophysicists realised there wasn’t enough visible matter to explain the motions of stars and galaxies. Instead, there appeared to be a hidden component contributing to the gravitational forces affecting their motion. It is now believed that even though we still have not successfully observed it, dark matter is five times more prevalent in the universe than normal matter.

    Dark energy came into the picture more recently, when astrophysicists realised that the expansion of the universe could not be explained without the existence of some kind of energy that provides a repulsive force that steadily accelerates the rate at which galaxies are flying away from each other. Dark energy is believed to be even more prevalent than dark matter, comprising a full 70% of the universe’s total mass-energy.

    Maeder’s argument, published in a series of papers this year in The Astrophysical Journal is that maybe we don’t need dark matter and dark energy to explain these effects. Maybe it’s our concept of Einsteinian space-time that’s wrong.

    His argument begins with the conventional cosmological understanding that the universe started with a Big Bang, about 13.8 billion years ago, followed by continual expansion. But in this mode, there is a possibility that hasn’t been taken into account, he says: “By that I mean the scale invariance of empty space; in other words the empty space and its properties do not change following a dilation or contraction.”

    If so, that would affect our entire understanding of gravity and the evolution of the universe.

    Based on this hypothesis, Maeder found that with the right parameters he could explain the expansion of the universe without dark energy. He could also explain the motion of stars and galaxies without the need for dark matter.

    To say that Maeder’s ideas are controversial is an understatement. Katie Mack, an astrophysicist at the University of Melbourne on Australia, calls them “massively overhyped.” And physicist and blogger Sabine Hossenfelder of the Frankfurt Institute for Advanced Studies, Germany, wrote that while Maeder “clearly knows his stuff,” he does not yet have “a consistent theory.”

    Specifically, Mack notes that the strongest evidence for dark matter comes not from the motions of stars and galaxies, “but from the behavior of matter on cosmological scales, as measured by signatures in the cosmic microwave background [CMB] and the distribution of galaxies.” Gravitational lensing of distant objects by nearer galaxies also reveals the existence of dark matter, she says.

    CMB per ESA/Planck

    ESA/Planck

    Gravitational Lensing NASA/ESA

    Also, she notes that while there are a “whole heap” of ways to modify Einstein’s theories, these are “nothing new and not especially interesting.”

    The challenge, she says, is to reproduce everything, including “dark matter and dark energy’s biggest successes.” Until a new theory can produce “precise agreement” with measurements of a wide range of cosmic variables, she says, there’s no reason “at all” to throw out the existing theory.

    Dark matter researcher Benjamin Roberts, at the University of Reno, Nevada, US, agrees. “The evidence for dark matter is very substantial and comes from a large number of sources,” he says. “Until a single theory can explain all of these observations, there is no reason to doubt the existence of dark matter.”

    That said, this doesn’t mean that “new physics” theories such as Maeder’s should be ignored. “They should be, and are, taken seriously,” he says.

    Or as Maeder puts it, “Nothing can ever be taken for granted.”

    See the full article here .

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  • richardmitnick 9:35 am on November 27, 2017 Permalink | Reply
    Tags: , , , , COSMOS, Nuke blasts reveal true size of neutron stars   

    From COSMOS: “Nuke blasts reveal true size of neutron stars” 

    Cosmos Magazine bloc

    COSMOS Magazine

    27 November 2017
    Andrew Masterson

    Satellite data and new modelling find neutron stars are less than 25 kilometres wide.

    1
    Thermonuclear blasts on a neutron star give away its size and mass.
    JULIAN BAUM/NEW SCIENTIST/SCIENCE PHOTO LIBRARY

    New modelling of the thermonuclear blasts happening on the surface of a neutron star means that astrophysicists have now determined the size of the super-dense bodies to within an astonishing 400 metres.

    Neutron stars are the core remnants of large stars that explode as supernovae. In October this year, teams of scientists announced the first ever recording of two of them colliding, producing a rarely detected gravitational wave.

    It has been known for years that neutron stars are very small, with a radius of between 10 to 20 kilometres. They are also extremely dense. A cubic centimetre of one is estimated to weigh in the region of 100 million tonnes.

    The ongoing quest to better understand the properties, shape and behaviour of the gravitational wave recently detected is highly influenced by knowing the size and density of the neutron stars that set it in motion when they smacked into each other 130 million light years away.

    For this reason, work led by Joonas Nättilä of the University of Turku in Finland has already been closely scrutinised by physicists from both the LIGO and Virgo detectors at the centre of the research.


    Nättilä and his colleagues set about refining estimates for the size of neutron stars by calculating the x-ray radiation previously recorded from a low-mass binary neutron star dubbed 4U 1702-429. The radiation is produced by intense atomic explosions taking place on the surface of the star.

    Using five x-ray bursts detected by the Rossi X-ray Timing Explorer, a NASA satellite launched in 1995, the scientists compared the data to state-of-the-art neutron star models and tracked the difference between real and predicted outcomes.

    NASA/ROSSI

    The result revealed that the radius of a neutron star is 12.4 kilometres, with a margin of error of only another 400 metres, plus or minus. This means the stars are at the lower end of earlier estimates.

    The research also found that 4U 1702-429, and likely therefore all other similar stars, had a gravitational mass of 1.9 times that of the sun, with a margin of 0.3 masses. The scientists caution, however, that mass calculations using available models are the “hardest to constrain”.

    With the Finnish study adding unprecedented accuracy to earlier research, work is already underway to use its findings to better investigate the complex and delicate physics of gravitational waves.

    The research is published in the journal Astronomy and Astrophysics, and a full version is available on the pre-print server arXiv.

    See the full article here .

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  • richardmitnick 9:15 am on November 20, 2017 Permalink | Reply
    Tags: , , , , COSMOS, Exoplanet HD76920b   

    From COSMOS: “We’ve found an exo-planet with an extraordinarily eccentric orbit” 

    Cosmos Magazine bloc

    COSMOS Magazine

    18 November 2017
    Jonti Horner
    Vice Chancellor’s Senior Research Fellow, University of Southern Queensland

    Jake Clark
    PhD Student, University of Southern Queensland

    Rob Wittenmyer
    Associate Professor (Astrophysics), University of Southern Queensland

    Stephen Kane
    Associate Professor, University of California, Riverside

    A newly discovered world could expand our understanding of planet formation.

    1
    An artist’s impression of the exoplanet in close orbit to a star.
    ESA, NASA, G. Tinetti (University College London, UK & ESA) and M. Kornmesser (NASA/ESA Hubble)

    The discovery of a planet with a highly elliptical orbit around an ancient star could help us understand more about how planetary systems form and evolve over time.

    The new planet, HD76920b, is four times the mass of Jupiter, and can be found some 587 light years away in the southern constellation Volans, the Flying Fish. At its furthest, it orbits almost twice as far from its star as Earth does from the Sun.

    1
    Superimposing HD76920b’s orbit on the Solar system shows how peculiar it is. Its orbit is more like that of the asteroid Phaethon than any of the Solar system’s planets. Jake Clark

    Details of the planet and its discovery are published today [Accepted for publication in AJ]. So how does this fit into the planet formation narrative, and are planets like it common in the cosmos?

    The Solar system

    Before the first exoplanet discovery, our understanding of how planetary systems formed came from the only example we had at the time: our Solar system.

    Close to the Sun orbit four rocky planets – Mercury, Venus, Earth and Mars. Further out are four giants – Jupiter, Saturn, Uranus and Neptune.

    Scattered in their midst we have debris – comets, asteroids and the dwarf planets.

    The eight planets move in almost circular orbits, close to the same plane. The bulk of the debris also lies close to that plane, although on orbits that are somewhat more eccentric and inclined.

    How did this system form? The idea was that it coalesced from a disk of material surrounding the embyronic Sun. The colder outer reaches were rich in ices, while the hotter inner regions contained just dust and gas.

    2
    The Solar system formed from a protoplanetary disk, surrounding the young Sun. NASA/JPL-Caltech

    Over millions of years, the tiny particles of dust and ice collided with one another, slowly building ever larger objects. In the icy depths of space, the giant planets grew rapidly. In the hot, rocky interior, growth was slower.

    Eventually, the Sun blew away the gas and dust leaving a (relatively) orderly system – roughly co-planar planets, moving on near-circular orbits.

    The exoplanet era

    The first exoplanets, discovered in the 1990s, shattered this simple model of planet formation. We quickly learned that they are far more diverse than we could have possibly imagined.

    Some systems feature giant planets, larger than Jupiter, orbiting incredibly close to their star. Others host eccentric, solitary worlds, with no companions to call their own.

    3
    Artist’s impression of the Hot Jupiter HD209458b – a planet so close to its star that its atmosphere is evaporating to space.
    European Space Agency, A.Vidal-Madjar (Institut d’Astrophysique de Paris, CNRS, France) and NASA

    This wealth of data reveals one thing – planet formation and evolution is more complicated and diverse than we ever imagined.

    Core accretion vs dynamical instability


    Massive protoplanetary disks can become unstable, rapidly giving birth to giant planets. No video credit.

    Both models can explain some, but not all, of the newly discovered planets. Depending on the initial conditions around the star, it seems that both processes can occur.

    Each theory offers potential to explain eccentric worlds in somewhat different ways.

    How do you get an eccentric planet?

    In the dynamical instability model you can easily get several clumps forming and interacting, slinging one another around until their orbits are both tilted and eccentric.

    Under the core accretion model things are a bit harder, as this method naturally creates co-planar, ordered planetary systems. But over time those systems can become unstable.

    One possible outcome is for one planet to eject the others through a series of chaotic encounters. That would naturally leave it as a solitary body, following a highly elongated orbit.

    4
    Chaotic planetary systems can eject planets entirely, leading to lonely rogue planets. NASA/JPL-Caltech.

    But there is another option. Many stars in our galaxy are binary – they have stellar companions. The interactions between a planet and its host star’s sibling could readily stir it up and eventually eject it, or place it on an extreme orbit.

    An eccentric planet

    This brings us to our newly discovered world, HD76920b. A handful of similarly eccentric worlds have been found before, but HD76920b is unique. It orbits an ancient star, more than two billion years older than the Sun.

    The orbit HD76920b is following is not tenable in the long-term. As it swings close to its host star, it will experience dramatic tides.

    A gaseous planet, HD76920b will change shape as it swings past its star, stretched by its enormous gravity. Those tides will be far greater than any we experience on Earth.

    That tidal interaction will act over time to circularise the planet’s orbit. The point of closest approach to the star will remain unchanged, but the most distant point will gradually be dragged closer in, driving the orbit towards circularity.

    All of this suggests that HD76920b cannot have occupied its current orbit since its birth. If that were the case, the orbit would have circularised aeons ago.

    5
    Extremely eccentric planets have been discovered before, but this is the first around such an ancient star. Goddard Space Flight Center/NASA.

    Perhaps what we’re seeing is evidence of a planetary system gone rogue. A system that once contained several planets on circular (or near circular) orbits.

    Over time, those planets nudged one another around, eventually hitting a chaotic architecture as their star evolved. The result – chaos – with most planets scattered and flung to the depths of space leaving just one – HD76920b.

    The truth is, we just don’t know – yet. As is always the case in astronomy, more observations are needed to truly understand the life story of this peculiar planet.

    One thing we do know is the story is coming to a fiery end. In the next few million years, the star will swell, devouring its final planet. Then, HD76920b will be no more.

    See the full article here .

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  • richardmitnick 8:50 am on November 20, 2017 Permalink | Reply
    Tags: , , , , , COSMOS, Dying star blows aluminium, , , silicon into space, The silicon is there but remains as silicon oxide gas rather than condensing into dust particles, W-Hydrae   

    From COSMOS: “Dying star blows aluminium, silicon into space” 

    Cosmos Magazine bloc

    COSMOS Magazine

    20 November 2017
    Richard A Lovett

    Research adds clues to how old stars supply the building blocks for new planets.

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


    ALMA’s telescopes are watching as a dying star flings aluminium into space. ESO/NRAO/NAOJ

    Astronomers using a giant telescope array on high in the Chilean desert are mapping how solar winds blowing off a dying star distribute important planet-forming materials into space, adding a new layer to our understanding of how the death of old stars helps fuel the birth of planets such as ours.

    The star in question, called W-Hydrae, is a large red one 254 light years away in the constellation Hydrae. It is slightly too dim to be seen with the naked eye.

    Nearing the end of its life, W-Hydrae is in a phase of stellar evolution during which stars are known to eject significant quantities of elements heavier than hydrogen and helium into space. This process enriches the gas and dust clouds from which new stars and planetary systems will later form.

    “Some of the ejected materials form the next generation of stars and planets,” says Aki Takigawa, an astromineralogist at Kyoto University, Japan.

    Using a collection of 66 radio telescopes known as the Atacama Large Millimetre/submillimetre Array (ALMA), Takigawa’s team was able to zoom in on this star so closely that they could see features as small as 0.035 arc-seconds, or one-one-thousandth of a degree. At that distance, Takigawa says, it is possible to see features smaller than the star itself, although the star is so huge that it would fill our entire solar system well out into the Asteroid Belt.

    These molecules included aluminium monoxide (AlO), which condenses into aluminium-containing grains as it cools, and silicon oxide (SiO), which condenses into rock-like silicate dust. They escape the star not just because they are blasted off its surface at high speeds, but because radiation pressure from the star’s light creates a stellar wind that steadily accelerates them and sweeps them off toward interstellar space.

    One of the mysteries of this process, however, has been that while silicon is much more common in the galaxy as a whole than aluminium, the regions around stars such as W-Hydrae appear to be unexpectedly rich in aluminium oxide particles.

    The new research, published earlier this month in Science Advances, found that this might be due to a combination of factors. One is that aluminium oxide particles condense from vapour at a higher temperature than silicate particles. That means that they form closer to the star than the silicates.

    Once formed and accumulated to sufficient quantities, the particles are subject to radiation pressure, which accelerates them outward, carrying other gases with them. The result is that the later-to-condense silicon oxide molecules are picked up in the maelstrom and blown away from the star so fast that by the time they have cooled enough to condense they are too dispersed to do so.

    In other words, the silicon is there, but remains as silicon oxide gas, rather than condensing into dust particles.

    “Our estimation showed that more than 70% of SiO molecules remain in the gas phase,” Takigawa says.

    All of this is important, she adds, because planetary scientists studying our own solar system have found “pre-solar” aluminium oxide and silicate grains in primitive meteorites — grains that were formed before the solar system and have remained unaltered over the ensuing billions of years.

    The stars that formed these grains died more than 4.6 billion years ago, she says, “but we can now study similar stars with telescopes”.

    Brad Tucker, an astrophysicist and cosmologist at Australian National University, agrees. Finding large amounts of aluminum oxide dust, he adds, is quite interesting because some of the first exoplanet atmospheres that have been measured contain another metal oxide, titanium oxide.

    “I bring this up because the dust and gas that leaves [stars like W-Hydrae] will eventually form new star systems and planets,” he says, “and some of the new planets we are finding are weird.

    “A big question has always been to try to understand where all the gas and dust in the universe comes from, because eventually that will help tell us how new things are formed.”

    An important next step, he notes, will be to use ALMA to take images of exploding stars. “The dust involved in supernova explosions has lots of questions that need to be solved,” he says.

    See the full article here .

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  • richardmitnick 10:51 am on November 16, 2017 Permalink | Reply
    Tags: , , , , COSMOS, The Cosmic Snake   

    From COSMOS: “Probing the mysteries of the Cosmic Snake” 

    Cosmos Magazine bloc

    COSMOS Magazine

    16 November 2017
    Richard A Lovett

    1
    The Cosmic Snake. Cava/University of Geneva.

    In a study, the subject matter of which sounds like a topic for a New Age journal, astronomers using the Hubble Space Telescope (HST) are probing the anatomy of a galactic feature known as the “Cosmic Snake”, hoping to understand star-formation processes that occurred billions of years ago.

    Too faint to have an official name, the Cosmic Snake is a galaxy that indeed looks like a giant worm. It appears to be winding its way through a cluster of galaxies known as MACS1206.2-0847. But instead of being part of the cluster, it is a more distant galaxy that happens to lie in the same line of sight.

    That distant galaxy isn’t really snake-shaped. Instead, its image has been stretched, fragmented, and pieced back together again by an effect known as gravitational lensing, which occurs as its light passes through the cluster.

    “The mass of the cluster is able to warp space-time,” says Antonio Cava, an astrophysicist at the University of Geneva, Switzerland. “The light coming from the background galaxy can follow different paths, producing multiple deformed images.”

    That which we see as a snake, he says, really consists of four separate images of the galaxy, twisted and lying end to end. A fifth image, which he calls the “counter-image,” lies off to the side.

    The Cosmic Snake would be interesting enough if it were simply an exotic optical effect. But in addition to distorting and multiplying images, gravitational lensing also magnifies them.

    In a study published this week in Nature Astronomy, an international team led by Cava used this magnification to study the background galaxy in unprecedented detail. In particular, they looked for bright regions known as clumps, in which massive numbers of stars are caught in the process of forming.

    Prior studies of distant galaxies had shown these clumps to be enormous — as large as 3000 light years across. That makes them a thousand times larger than similar clumps in nearby galaxies, in which star formation is also occurring.

    This difference in scale has been a conundrum for astrophysicists, who could not explain why the more distant galaxies had such dramatically larger clumps. One partial explanation was that that the light from those more distant galaxies has been traveling for so long that by looking at them we are, in effect, peering billions of years back into the youth of the universe.

    Could star formation process back then have been somehow different than now? If so, astrophysicists couldn’t figure out why.

    What Cava’s team learned from the Cosmic Snake’s giant “natural telescope” is that without the help of gravitational lensing, even our best telescopes are simply not powerful enough to see the clumps in sufficient detail.

    Gravitational Lensing NASA/ESA

    To prove it, they took advantage of the fact that different parts of the Cosmic Snake are magnified by different amounts.

    The counter-image, for example, is only magnified by a factor of five by the lensing effect. It shows a small number of large clumps, similar to those been seen for other galaxies.

    But the snake itself is magnified by as much as a factor of 100, Cava says, allowing the HST to see details 100 times smaller than could otherwise be detected.

    That revealed that instead of having a relatively small number of giant clumps, the distant galaxy actually had numerous smaller ones, not all that different from those seen in nearby galaxies.

    “We have reduced the differences between what we observe in the nearby universe and in distant galaxies from a factor of 1000 to a factor of 10,” says Daniel Schaerer, a professor at Geneva Observatory who was also part of the study team.

    Ryo Ando, an astronomer from the University of Tokyo whose own study of star-forming clumps in a nearby galaxy was published recently in The Astrophysical Journal, calls the new study ingenious.

    Astronomers studying nearby galaxies, he says, had previously realised that looking at them without sufficient resolution might produce an “averaged view” in which numerous smaller clumps merged to look bigger than they really are. The new study proves that this clump-merging effect is real, he says: “It demonstrates the importance of high-resolution observations. It is really intriguing.”

    See the full article here .

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  • richardmitnick 1:27 pm on November 10, 2017 Permalink | Reply
    Tags: , , , , COSMOS, GPS satellites 'the largest dark matter detector ever built'   

    From COSMOS: “GPS satellites ‘the largest dark matter detector ever built’ “ 

    Cosmos Magazine bloc

    COSMOS Magazine

    10 November 2017
    Richard A. Lovett

    1
    GPS satellites comprise the largest dark matter detector ever constructed. And they can find you a coffee shop. What’s not to like?
    Bernhard Classen/Getty Images

    In an effort to solve one of modern physics’ deepest mysteries, scientists have found a way to use GPS satellites as an exquisitely sensitive dark-matter observatory.

    Dark matter is an enigmatic form that, with its cousin dark energy, may be the largest building block of the universe. “[Normal matter] is five per cent of what is out there,” says Andrei Derevianko, a quantum physicist at the University of Reno, Nevada, US. “The rest is dark matter and dark energy.”

    Astrophysicists are convinced it exists because they can see its gravitational effects on distant galaxies. And there should be enough of it in our own galaxy that the Earth should be encountering it often.

    But so far, it’s eluded detection because its very nature makes it extremely hard to find. Derevianko compares it to trying to prove the existence of cell phone signals without a phone. “I’m talking on the phone, and you are understanding me,” he says. “[But] you would not be able to understand me without this special device.”

    Traditional searches have used special particle detectors designed to recognise rare interactions between normal matter and particles of dark matter passing through the Earth. Because the interactions are likely to be extremely rare, the detectors need to be heavily shielded from interference by other forms of radiation — as is done with Australia’s SABRE dark matter detector in the depths of an abandoned gold mine in Victoria.

    1
    Australia’s SABRE dark matter detector in the depths of an abandoned gold mine in Victoria, AU.

    Derevianko’s brainwave was to realise it might not be necessary to spend millions of dollars on specialty detectors. Perhaps dark matter could be found via its interaction with atomic clocks.

    The clocks, which measure time based on the quantum properties of atoms, are the most precise instruments ever built, Derevianko says.

    They are so accurate that they wouldn’t gain or lose more than a single second over the age of the universe. Dark matter passing through them, however, should affect the atomic processes on which they are based, throwing them off ever so slightly.

    “The electrons and the nucleus ‘feel’ the effect of the dark matter, and this can change their properties temporarily,” says Benjamin Roberts, an Australian postdoctoral researcher working with Derevianko in Reno.

    “For example, the dark matter might make the electrons in the atom attracted to the nucleus slightly more (or less) strongly. Another way to say it is that the dark matter field may speed up or slow down the electrons (very slightly and only for a few seconds).”

    Furthermore, the Earth is surrounded by an entire network of atomic clocks. They are carried by satellites in the global positioning system network, which uses them to send out the hyper-accurate timing signals that make GPS work.

    Over all, 32 satellites form a halo of instruments around the planet, spanning a sphere 50,000 kilometres wide. That’s enough that even though dark matter is expected to be reaching the Earth at speeds in the order of 300 kilometres per second, it would still take three minutes to cross the entire cloud of GPS satellites. Rippling glitches in their time signals could thus be used to detect sheets of passing dark matter, as long as they are large and dense enough.

    “The GPS system is acting as a truly huge detector,” says Roberts. “At 50,000 kilometres in diameter, one could say that this is the largest detector ever built.”

    Furthermore, it’s a detector that has been in place for years, not only allowing cell phones to guide caffeine junkies to the nearest Starbucks, but also allowing scientists to measure the precise shape of the Earth, monitor movement of tectonic plates, and track the effect of ocean currents and weather on sea-surface levels.

    Based on this, Derevianko teamed up with geophysicist Geoff Blewitt, also of the University of Nevada, Reno, to pore through 16 years of GPS records, looking for anomalies.

    So far, like conventional endeavours to detect dark matter, the search hasn’t found anything. But that, in itself, is useful, because the known laws of physics allow dark matter to take many forms, referred to by physicists as ‘models’.

    “We are one step closer,” Derevianko says. “The range of models is huge, and what we are trying to do is rule out some models in a cheap way. Basically, we only paid to do the search; there’s no huge investment in the instrument.”

    Alan Duffy, an astronomer at Australia’s Swinburne University of Technology, who was not part of the study team, adds that the new work ruled out theories of dark matter compositions that would produce the type of sheets of it that Derevianko’s team was specifically looking for.

    “[This is] fascinating work…” Duffy says, “a use of GPS data its creators, I suspect, would never have envisaged.”

    “We re-purposed existing technology that we all use every day to do fundamental physics research,” adds Roberts.

    The work was published earlier this month in Nature Communications.

    See the full article here .

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