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  • richardmitnick 3:18 pm on September 24, 2014 Permalink | Reply
    Tags: , , , Cosmic Rays, , Physics arXiv Blog   

    From Xb: “How Astrophysicists Are Turning The Entire Moon Into A Cosmic Ray Detector” 

    Xb Physics Archive Blog
    The Physics arXiv Blog

    The $1.5 billion plan breaks ground in 2018 and should be complete by 2025

    One of the great mysteries in astrophysics surrounds the origin of the highest energy particles ever observed. These particles, called ultra-high energy cosmic rays, come from space and smash into the Earth with so much energy that physicists have struggled to believe, let alone explain, it.

    An ultra-high energy cosmic ray can have an energy of 10^20 electron volts. To put that in context, that’s a single proton with the same energy as a baseball flying at 100 kilometres per hour.

    It might come as some relief to know that these particles are extremely rare. Physicists detect them on Earth at a rate of less than one particle per square kilometre per century. And that makes them difficult to study.

    So physicists want to study more of these particles to work out where they come from and how they might form. The obvious approach is to build bigger detectors. The largest on Earth is the Pierre Auger Observatory in Argentina that covers an area of 3000 square kilometres, about the size of Rhode Island or Luxembourg.

    Clearly, finding a significantly larger area of the Earth for a bigger detector is no easy task. So scientists are turning their attention to the heavens.

    moon
    Their idea is to exploit an exotic physical effect that turns the entire Moon into a detector for ultra-high energy cosmic rays. Today, Justin Bray at the University of Southampton and a few pals outline the plan.

    This is no pie in the sky project. Their plans are already drawn up and the €1.5 billion budget is in place. They plan to start construction of the necessary equipment in 2018 and be in full operation by 2025.

    So what’s the big deal about ultra-high energy cosmic rays? The biggest mystery is how a single particle can have such high energy.

    Physicists think there are essentially two possible mechanisms. The first is that the particles are accelerated in an electric or magnetic field. But nobody is sure where such extreme fields exist or how they might trap a particle long enough to accelerate it to these energies.

    The second possibility is that the ultrahigh energy particles are created by the decay of a hypothetical supermassive exotic particle, perhaps dark matter or perhaps produced by topological defects early in the universe.

    One way to pinpoint this mechanism is to discover the source of these particles, by finding where in the sky they come from. That is easier said than done because cosmic rays are charged and are therefore bent by magnetic fields as they travel. So the direction of arrival does not necessarily indicate the source.

    Having said that, there is another effect that ought to prevent the highest energy cosmic rays reaching us at all. High-energy particles should interact with the cosmic microwave background radiation as they travel through space and this should cause them to lose energy. That suggests the highest energy particles were probably created within our galaxy since they could not have travelled intergalactic distances and remained so energetic.

    So where does the Moon come into all this? On Earth, physicists detect these high-energy particles when they smash into the upper atmosphere triggering a cascade of other particles that rain down on the surface. This is how the Pierre Auger Observatory works— by detecting the daughter particles created in the cascade.

    grpah
    These cascades also generate another signal. The rapid acceleration and deceleration of charged particles produces radio waves. So another signature of the impact of an ultra-high energy cosmic ray is a brief burst of radio waves, known as the Askaryan effect after Gurgen Askaryan the Soviet-American physicist who proposed it in the early 1960s.

    It is this signal that astronomers hope to pick up from the Moon. The idea is that ultrahigh energy cosmic rays should smash into the lunar surface generating a cascade of other particles and a short burst of radio waves less than a nanosecond long.

    This effect is complicated by the fact that radio pulses are projected forward in a cone and cannot travel far through the lunar surface before being absorbed.

    That means that astronomers will only be able to see the radio pulses from ultrahigh energy cosmic rays that graze the edge of the Moon coming our way.

    So the gear they need to detect the signal is a highly sensitive radio telescope on Earth. These signals are so short and faint that the current generation of radio telescopes cannot pick them up.

    But astronomers are about to start work on a much bigger and more sensitive radio telescope called the Square Kilometre Array, which will be built in South Africa and Australia at a cost of about €1.5 billion. This will give them access to more data about ultrahigh energy cosmic rays than they have ever had.

    array
    Unnamed portion of SKA

    Although there are limitations on the lunar detector, it is still sizeable. Bray and co estimate that it will be equivalent to a ground array of 33,0000 square kilometres or about the size of Maryland or Belgium. That is more than 10 times larger than the Pierre Auger Observatory. And they say the Array should detect around 165 ultra-high energy cosmic rays a year from the Moon compared to the 15-a-year currently observed.

    That suggests an exciting time ahead for radio astronomers and for the astrophysicists attempting to understand the origin of these mysterious particles. With any luck, they should soon be able to tease apart the extraordinary events that somehow create the most energetic particles ever observed.

    Ref: arxiv.org/abs/1408.6069 : Lunar Detection Of Ultra-High-Energy Cosmic Rays And Neutrinos

    See the full article here.

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  • richardmitnick 2:28 pm on July 16, 2014 Permalink | Reply
    Tags: , , , Cosmic Rays, , Telescope Array Project   

    From The Christian Science Monitor: “Where do cosmic rays come from? The answer could be in the Big Dipper.” 

    ChristianScienceMonitor

    July 9, 2014
    Nola Taylor Redd, Space.com

    Researchers discovered a hotspot of high-energy particles that could offer clues about origin of cosmic rays.

    A hotspot of powerful, ultrahigh-energy particles streams toward Earth from beneath the handle of the Big Dipper constellation. This collection of cosmic rays may help scientists nail down the origin point of the powerful particles, a century-old mystery.

    “This puts us closer to finding out the sources — but no cigar yet,” Gordon Thomson, of the University of Utah, said in a statement. Thomson is the co-principle investigator for the Telescope Array cosmic ray observatory in southern Utah, which discovered the hotspot, and one of the 125 researchers on the project.

    ta

    “All we see is a blob in the sky, and inside this blob there is all sorts of stuff — various types of objects — that could be the source,” he added. “Now we know where to look.”

    A hundred-year-old mystery

    Gordon worked with an international team of scientists to capture 72 ultrahigh-energy cosmic rays with the Telescope Array over a period of five years. If powerful cosmic ray sources spread evenly across the sky, the resulting waves should also be evenly distributed. Instead, 19 of the detected signals came from a 40-degree circle that makes up only six percent of the sky. The hot spot lies in the constellation Ursa Major, home of the Big Dipper.

    “We have a quarter of our events in that circle instead of 6 percent,” collaborator Charlie Jui, also from the University of Utah, said in the same statement.

    Jui describes the hotspot’s location as “a couple of hand widths below the Big Dipper’s handle.” The region would appear like any other region of the sky to regular optical telescopes.

    According to the researchers, the odds that the hotspot is a statistical fluke rather than real are only 1.4 in 10,000.

    The hotspot region of the sky lies near the supergalactic plane, which contains local galaxy clusters such as the Ursa Major cluster, the Coma cluster and the Virgo cluster.

    The research, which is an international collaboration of over 100 scientists, was recently accepted for publication in the Astrophysical Journal Letters.

    Discovered in 1912, cosmic rays are thought to consist of the bare protons of hydrogen nuclei, or the centers of heavier elements. The powerful particles stream in from various regions of the sky, with energies reaching as high as 300 billion billion electron volts. Cosmic rays are classified as “ultrahigh-energy” if they carry the energy of 1 billion billion electron volts, comparable to a fast-pitch baseball.

    While low-energy cosmic rays come from stars like the sun over the course of their life or explosive deaths, the origins of more energetic rays remain a mystery.

    Suggested progenitors for the more powerful cosmic rays include Active Galactic Nuclei (AGN), where material is sucked into supermassive black holes at the center of galaxies, or gamma-ray bursts from the explosive supernova death of massive stars. Other potential causes include shockwaves from noisy radio galaxies and colliding galaxies. More exotic possibilities include the decay of “cosmic strings,” hypothetical one-dimensional defects proposed by string theory.

    Ultrahigh-energy cosmic rays stem from outside the Milky Way, but are weakened by interactions with the cosmic microwave background radiation — the leftover fingerprint from the Big Bang that kicked off the universe.

    Cosmic Background Radiation Planck
    Cosmic background Radiation from ESA/Planck

    As a result, 90 percent of the detected ultrahigh-energy cosmic rays originate within 300 million light-years of Earth.

    According to Jui, a separate study currently in progress suggests that the distribution of ultrahigh-energy cosmic rays in the northern sky is related to concentrations of large-scale structures like clusters and superclusters of galaxies.

    super
    A map of the Superclusters and voids nearest to Earth

    “It tells us there is at least a good chance these are coming from matter we can see, as opposed to a different class of mechanisms where you are producing these particles with exotic processes,” Jui said.

    The Telescope Array houses 523 detectors spread over 300 square miles of desert. Physicists hope to make the observatory more sensitive by doubling the number of detectors and quadrupling the area they cover, which should capture more cosmic rays.

    “With more events, we are more likely to see structure in that hotspot blob, and that may point us toward the real sources,” Jui said.

    A preprint of the article may be found online at arXiv.org

    See the full article here.


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  • richardmitnick 8:50 am on July 8, 2014 Permalink | Reply
    Tags: , , , cosmic, Cosmic Rays, ,   

    From space.com 

    space-dot-com logo

    July 08, 2014
    Nola Taylor Redd

    A hotspot of powerful, ultrahigh-energy particles streams toward Earth from beneath the handle of the Big Dipper constellation. This collection of cosmic rays may help scientists nail down the origin point of the powerful particles, a century-old mystery.

    bd

    “This puts us closer to finding out the sources — but no cigar yet,” Gordon Thomson, of the University of Utah, said in a statement. Thomson is the co-principle investigator for the Telescope Array cosmic ray observatory in southern Utah, which discovered the hotspot, and one of the 125 researchers on the project.

    tel
    One telescope in the array

    “All we see is a blob in the sky, and inside this blob there is all sorts of stuff — various types of objects — that could be the source,” he added. “Now we know where to look.” [8 Baffling Astronomy Mysteries]

    A hundred-year-old mystery

    Gordon worked with an international team of scientists to capture 72 ultarhigh-energy cosmic rays with the Telescope Array over a period of five years. If powerful cosmic ray sources spread evenly across the sky, the resulting waves should also be evenly distributed. Instead, 19 of the detected signals came from a 40-degree circle that makes up only six percent of the sky. The hot spot lies in the constellation Ursa Major, home of the Big Dipper.

    “We have a quarter of our events in that circle instead of 6 percent,” collaborator Charlie Jui, also from the University of Utah, said in the same statement.

    Jui describes the hotspot’s location as “a couple of hand widths below the Big Dipper’s handle.” The region would appear like any other region of the sky to regular optical telescopes.

    According to the researchers, the odds that the hotspot is a statistical fluke rather than real are only 1.4 in 10,000.

    The hotspot region of the sky lies near the supergalactic plane, which contains local galaxy clusters such as the Ursa Major cluster, the Coma cluster and the Virgo cluster.

    The research, which is an international collaboration of over 100 scientists, was recently accepted for publication in the Astrophysical Journal Letters.

    Discovered in 1912, cosmic rays are thought to consist of the bare protons of hydrogen nuclei, or the centers of heavier elements. The powerful particles stream in from various regions of the sky, with energies reaching as high as 300 billion billion electron volts. Cosmic rays are classified as “ultrahigh-energy” if they carry the energy of 1 billion billion electron volts, comparable to a fast-pitch baseball.

    While low-energy cosmic rays come from stars like the sun over the course of their life or explosive deaths, the origins of more energetic rays remain a mystery.

    Suggested progenitors for the more powerful cosmic rays include Active Galactic Nuclei (AGN), where material is sucked into supermassive black holes at the center of galaxies, or gamma-ray bursts from the explosive supernova death of massive stars. Other potential causes include shockwaves from noisy radio galaxies and colliding galaxies. More exotic possibilities include the decay of “cosmic strings,” hypothetical one-dimensional defect proposed by string theory.

    Ultrahigh-energy cosmic rays stem from outside the Milky Way, but are weakened by interactions with the cosmic microwave background radiation — the leftover fingerprint from the Big Bang that kicked off the universe. As a result, 90 percent of the detected ultrahigh-energy cosmic rays originate within 300 million light-years of Earth.

    Cosmic Background Radiation Planck
    CMB via ESA/Planck

    According to Jui, a separate study currently in progress suggests that the distribution of ultrahigh-energy cosmic rays in the northern sky is related to concentrations of large-scale structures like clusters and superclusters of galaxies.

    map
    Map of voids and superclusters within 500 million light years from Milky May

    “It tells us there is at least a good chance these are coming from matter we can see, as opposed to a different class of mechanisms where you are producing these particles with exotic processes,” Jui said.

    The Telescope Array houses 523 detectors spread over 300 square miles of desert. Physicists hope to make the observatory more sensitive by doubling the number of detectors and quadrupling the area they cover, which should capture more cosmic rays.

    “With more events, we are more likely to see structure in that hotspot blob, and that may point us toward the real sources,” Jui said.

    A preprint of the article may be found online at arXiv.org

    See the full article here.


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  • richardmitnick 3:09 pm on February 14, 2013 Permalink | Reply
    Tags: , , , Cosmic Rays, , , ,   

    From NASA Goddard: More on Cosmic Rays 

    A neat little video courtesy of NASA’s Goddard Space Flight Center.


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  • richardmitnick 2:52 pm on February 14, 2013 Permalink | Reply
    Tags: , , , Cosmic Rays, , ,   

    From ESO: “Clues to the Mysterious Origin of Cosmic Rays” 

    VLT probes remains of medieval supernova

    Contacts

    Sladjana Nikolić
    Max Planck Institute for Astronomy
    Heidelberg, Germany
    Tel: +49 6221 528 438
    Email: nikolic@mpia.de

    Glenn van de Ven
    Max Planck Institute for Astronomy
    Heidelberg, Germany
    Tel: +49 6221 528 275
    Email: glenn@mpia.de

    Richard Hook
    ESO, La Silla, Paranal, E-ELT & Survey Telescopes Press Officer
    Garching bei München, Germany
    Tel: +49 89 3200 6655
    Cell: +49 151 1537 3591
    Email: rhook@eso.org

    Very detailed new observations with ESO’s Very Large Telescope (VLT) of the remains of a thousand-year-old supernova have revealed clues to the origins of cosmic rays. For the first time the observations suggest the presence of fast-moving particles in the supernova remnant that could be the precursors of such cosmic rays. The results are appearing in the 14 February 2013 issue of the journal Science.

    four cells
    VLT/VIMOS observations of the shock front in the remnant of SN1006

    In the year 1006 a new star was seen in the southern skies and widely recorded around the world. It was many times brighter than the planet Venus and may even have rivaled the brightness of the Moon. It was so bright at maximum that it cast shadows and it was visible during the day. More recently astronomers have identified the site of this supernova and named it SN 1006. They have also found a glowing and expanding ring of material in the southern constellation of Lupus (The Wolf) that constitutes the remains of the vast explosion.

    It has long been suspected that such supernova remnants may also be where some cosmic rays — very high energy particles originating outside the Solar System and travelling at close to the speed of light — are formed. But until now the details of how this might happen have been a long-standing mystery.

    A team of astronomers led by Sladjana Nikolić (Max Planck Institute for Astronomy, Heidelberg, Germany [1]) has now used the VIMOS instrument on the VLT to look at the one-thousand-year-old SN 1006 remnant in more detail than ever before.

    vimos
    VIMOS – VIsible MultiObject Spectrograph

    They wanted to study what is happening where high-speed material ejected by the supernova is ploughing into the stationary interstellar matter — the shock front. This expanding high-velocity shock front is similar to the sonic boom produced by an aircraft going supersonic and is a natural candidate for a cosmic particle accelerator.

    sf
    Schlieren photograph of an attached shock on a sharp-nosed supersonic body.

    For the first time the team has not just obtained information about the shock material at one point, but also built up a map of the properties of the gas, and how these properties change across the shock front. This has provided vital clues to the mystery.

    The results were a surprise — they suggest that there were many very rapidly moving protons in the gas in the shock region. While these are not the sought-for high-energy cosmic rays themselves, they could be the necessary seed particles, which then go on to interact with the shock front material to reach the extremely high energies required and fly off into space as cosmic rays.”

    See the full article with complete scholarly apparatus here.

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