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  • richardmitnick 9:45 pm on July 31, 2014 Permalink | Reply
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    From SLAC Lab: “Despite Extensive Analysis, Fermi Bubbles Defy Explanation” 


    SLAC Lab

    July 31, 2014

    Scientists from Stanford and the Department of Energy’s SLAC National Accelerator Laboratory have analyzed more than four years of data from NASA’s Fermi Gamma-ray Space Telescope, along with data from other experiments, to create the most detailed portrait yet of two towering bubbles that stretch tens of thousands of light-years above and below our galaxy.

    https://www6.slac.stanford.edu/sites/www6.slac.stanford.edu/files/styles/lightbox_large_image/public/images/Fermi_bubbles-ST.jpg
    This artist’s representation shows the Fermi bubbles towering above and below the galaxy. (NASA’s Goddard Space Flight Center)

    NASA Fermi Telescope
    NASA/Fermi

    The bubbles, which shine most brightly in energetic gamma rays, were discovered almost four years ago by a team of Harvard astrophysicists led by Douglas Finkbeiner who combed through data from Fermi’s main instrument, the Large Area Telescope.

    NASA Fermi LAT Large Area Telescope
    NASA/Fermi LAT

    The new portrait, described in a paper that has been accepted for publication in The Astrophysical Journal, reveals several puzzling features, said Dmitry Malyshev, a postdoctoral researcher at the Kavli Institute for Particle Astrophysics and Cosmology who co-led on the analysis.

    For example, the outlines of the bubbles are quite sharp, and the bubbles themselves glow in nearly uniform gamma rays over their colossal surfaces, like two 30,000-light-year-tall incandescent bulbs screwed into the center of the galaxy.

    Their size is another puzzle. The farthest reaches of the Fermi bubbles boast some of the highest energy gamma rays, but there’s no discernable cause for them that far from the galaxy.

    Finally, although the parts of the bubbles closest to the galactic plane shine in microwaves as well as gamma rays, about two-thirds of the way out the microwaves fade and only gamma rays are detectable. Not only is this different from other galactic bubbles, but it makes the researchers’ work that much more challenging, said Malyshev’s co-lead, KIPAC postdoctoral researcher Anna Franckowiak.

    two
    KIPAC researchers Dmitry Malyshev (left) and Anna Franckowiak with the magazine issues that contain the articles about the Fermi bubbles they co-authored for the general public. Malyshev’s is in the July 2014 issue of Scientific American, while Franckowiak’s article is in the July 2014 issue of Physics Today. (SLAC National Accelerator Laboratory)

    “Since the Fermi bubbles have no known counterparts in other wavelengths in areas high above the galactic plane, all we have to go on for clues are the gamma rays themselves,” she said.

    What Blew The Bubbles?

    Soon after the initial discovery theorists jumped in, offering several explanations for the bubbles’ origins. For example, they could have been created by huge jets of accelerated matter blasting out from the supermassive black hole at the center of our galaxy. Or they could have been formed by a population of giant stars, born from the plentiful gas surrounding the black hole, all exploding as supernovae at roughly the same time.

    “There are several models that explain them, but none of the models is perfect,” Malyshev said. “The bubbles are rather mysterious.”

    Creating the portrait wasn’t easy.

    “It’s very tricky to model,” said Franckowiak. “We had to remove all the foreground gamma-ray emissions from the data before we could clearly see the bubbles.”

    From the vantage point of most Earth-bound telescopes, all but the highest-energy gamma rays are completely screened out by our atmosphere. It wasn’t until the era of orbiting gamma-ray observatories like Fermi that scientists discovered how common extra-terrestrial gamma rays really are. Pulsars, supermassive black holes in other galaxies and supernovae are all gamma rays point sources, like distant stars are point sources of visible light, and all those gamma rays had to be scrubbed from the Fermi data. Hardest to remove were the galactic diffuse emissions, a gamma ray fog that fills the galaxy from cosmic rays interacting with interstellar particles.

    “Subtracting all those contributions didn’t subtract the bubbles,” Franckowiak said. “The bubbles do exist and their properties are robust.” In other words, the bubbles don’t disappear when other gamma-ray sources are pulled out of the Fermi data – in fact, they stand out quite clearly.

    Franckowiak says more data is necessary before they can narrow down the origin of the bubbles any further.

    “What would be very interesting would be to get a better view of them closer to the galactic center,” she said, “but the galactic gamma ray emissions are so bright we’d need to get a lot better at being able to subtract them.”

    Fermi is continuing to gather the data Franckowiak wants, but for now, both researchers said, there are a lot of open questions.

    See the full article here.

    SLAC Campus
    SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.
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  • richardmitnick 4:59 pm on July 31, 2014 Permalink | Reply
    Tags: Seth Shostak,   

    From Seth Shostak at SETI Institute: “Why the Aliens Want Earth” 


    SETI Institute

    July 31, 2014
    SETI Seth Shostak
    Seth Shostak, Senior Astronomer, Director of SETI Research

    Expedia’s galaxy-wide website must be offering Earth at a major discount. In one movie after another, aliens decide to pass up competing Milky Way attractions — including neutron stars, antimatter clouds, hot Jupiters, and a 4 billion-trillion-trillion-ton central black hole — in favor of our planet. The small speck of rock we inhabit is more popular with tourists than Disneyland.

    Even an abbreviated laundry list of invasion films will give you the idea: Independence Day, War of the Worlds, Superman II, Mars Attacks, The Day the Earth Stood Still, Killer Clowns from Outer Space … They all share a common premise, namely that Earth is the bee’s knees, cosmically speaking.

    But really, you’ve got to wonder what would motivate creatures from other worlds to suffer a journey of hundreds of trillions of miles to visit our planet? It’s a trip so relentlessly devoid of scenery, their spacecraft wouldn’t need windows. Why bother?

    I’ve been asked this question at least a half-dozen times by Hollywood writers, and the best answer I can muster is “I don’t know.”

    My impoverished reply is clearly disappointing, and the usual response by the filmmakers is to resort to two hackneyed incentives to rope in the aliens, namely (1) a quest for natural resources, and (2) breeding experiments.

    Frankly, and not to rain on anyone’s parade, neither makes sense.

    Consider the idea that the extraterrestrials want materials for their industrial needs. It’s nice to imagine that Earth is valuable as a mining claim, but what do we have that they don’t?

    A frequent suggestion is water. But that’s silly: The universe is awash in water, thanks to the abundance of its two atomic ingredients, hydrogen and oxygen. Like Kimye and Kanye, these two elements are everywhere. Heck, there’s more water on some of the moons of Jupiter than on Earth, and no one’s going to get ruffled if you opt to remove it. But really, you can save the tanker costs by finding water in your own solar system. There’s bound to be plenty.

    Digging up other minerals and metals is similarly unnecessary and inconvenient. The entire cosmos is made of the same elements (and more or less in the same proportions) as is our local neighborhood. You don’t need to import this stuff from light-years away.

    Maybe they just need farmland? Like Captain Bligh, perhaps aliens are hoping to find a place to grow breadfruit, or whatever the galactic equivalent might be. Again, this is the kind of incentive that might work if you don’t first need to traverse interstellar space. If you do, consider building orbiting greenhouses at home. They’ll be cheaper, and the produce will be fresher. And honestly, if Earth’s countryside is that attractive, why didn’t someone plant a flag (or Klingon breadfruit) millions or billions of years ago? It seems that terrestrial real estate is a dog on the market.

    Breeding experiments are even less plausible, even if many movie-goers feel like participating. Anyone who’s made it through tenth-grade biology will recognize that breeding with other species here on Earth — all of whom are card-carrying members of the DNA club, and therefore closely related to you — is not only difficult, it’s guaranteed to be fruitless. And possibly illegal.

    Trendy scenarists will often invoke the social concern du jour, and suggest that the extraterrestrials are here to save us from ourselves. Aside from the obvious fact that they don’t know of such contemporary problems as climate change or nuclear proliferation (our newscasts haven’t reached them yet), why would they be interested? I bet the dinosaurs would have wished for a bit of alien help in giving an asteroid a nudge 66 million years ago, but it seems the extraterrestrials couldn’t be bothered. Are we that much more deserving?

    No, the bottom line is that the only truly special things about Earth are likely to be our biota and our culture. They could learn a lot about either one by merely analyzing the spectral signature of our atmosphere or tuning in to our TV broadcasts, and they would save a king’s ransom on fuel by avoiding actual travel.

    Despite the dramas played out at the local cineplex, real aliens won’t be itching to visit. What we’ve got, they’ve already seen, and the doorbell won’t ring. We’re not on their bucket list.

    See the full article here.

    SETI Institute – 189 Bernardo Ave., Suite 100
    Mountain View, CA 94043
    Phone 650.961.6633 – Fax 650-961-7099
    Privacy PolicyQuestions and Comments


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  • richardmitnick 4:45 pm on July 31, 2014 Permalink | Reply
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    From SPACE.com: “Weird Supernova May Blow Away Star Explosion Theories” 

    space-dot-com logo

    SPACE.com

    July 31, 2014
    Jesse Emspak

    Light from a radioactive metal forged inside a supernova blast could prompt a rethink of how some star explosions occur.

    image
    This image from NASA’s Swift space telescope, taken on Jan. 22, 2014, shows the supernova SN 2014J as seen in three different exposures by the space observatory. Scientists suspect the weird supernova’s progenitor star may have had a helium belt. Credit: NASA/Swift/P. Brown, TAMU

    The supernova SN 2014J is located 11.4 million light-years from Earth in the galaxy M82. Astronomers used the European Space Agency’s International Gamma-Ray Astrophysics Laboratory (INTEGRAL) spacecraft to examine the star explosion’s light spectrum in the gamma-ray bands and saw elements that shouldn’t have been there — suggesting that widely accepted models of how such events happen might be incomplete.

    ESA Integral
    ESA/INTEGRAL

    m82.
    To celebrate the Hubble Space Telescope’s 16 years of success, the two space agencies involved in the project, NASA and the European Space Agency (ESA), are releasing this image of the magnificent starburst galaxy, Messier 82 (M82). This mosaic image is the sharpest wide-angle view ever obtained of M82. The galaxy is remarkable for its bright blue disk, webs of shredded clouds, and fiery-looking plumes of glowing hydrogen blasting out of its central regions.

    Throughout the galaxy’s center, young stars are being born 10 times faster than they are inside our entire Milky Way Galaxy. The resulting huge concentration of young stars carved into the gas and dust at the galaxy’s center. The fierce galactic superwind generated from these stars compresses enough gas to make millions of more stars.

    In M82, young stars are crammed into tiny but massive star clusters. These, in turn, congregate by the dozens to make the bright patches, or “starburst clumps,” in the central parts of M82. The clusters in the clumps can only be distinguished in the sharp Hubble images. Most of the pale, white objects sprinkled around the body of M82 that look like fuzzy stars are actually individual star clusters about 20 light-years across and contain up to a million stars.

    The rapid rate of star formation in this galaxy eventually will be self-limiting. When star formation becomes too vigorous, it will consume or destroy the material needed to make more stars. The starburst then will subside, probably in a few tens of millions of years.

    Located 12 million light-years away, M82 appears high in the northern spring sky in the direction of the constellation Ursa Major, the Great Bear. It is also called the “Cigar Galaxy” because of the elliptical shape produced by the oblique tilt of its starry disk relative to our line of sight.

    The observation was made in March 2006, with the Advanced Camera for Surveys’ Wide Field Channel. Astronomers assembled this six-image composite mosaic by combining exposures taken with four colored filters that capture starlight from visible and infrared wavelengths as well as the light from the glowing hydrogen filaments.

    Scientists with the Max Planck Institute for Extraterrestrial Physics in Germany made the supernova discovery.

    A strange supernova

    SN 2014J is a type Ia supernova. Type Ia supernovas occur in binary systems with two stars in orbits so close that the stars exchange mass. As the more massive star of the pair ages it evolves into a white dwarf, a star that is the size of Earth but has up to 1.4 times the mass of the sun. The companion star’s outer envelope gets pulled to the tiny, but very dense, dwarf’s surface.

    Over time, the gas piles up on the white dwarf until enough pressure and heat build up and ignite fusion reactions. The hydrogen becomes helium, and then the helium goes through the “triple alpha” process, fusing into carbon and oxygen. Since the fusion is happening very quickly and the gravity of the white dwarf is so large, there’s not enough time for the gas to expand and the stuff on the white dwarf surface explodes. The explosion is so powerful that it disrupts the white dwarf’s interior, obliterating it and seeding the rest of the universe with heavy elements.

    What the Max Planck team saw was a gamma-ray signature of nickel-56, a radioactive isotope of the metal that emits gamma rays as it decays into cobalt-56. It has a half-life of only about six days, but the gamma rays were still visible 15 days after the supernova blew up.

    “We were observing it and after about three weeks most of nickel-56 would have decayed,” said Roland Diehl, lead author of the study. “The nickel-56 would be cobalt. But we saw the gamma-ray line… Some of our colleagues said that can’t be true.”

    A helium belt?

    The spectral line was also narrow and sharp, when it should have been wider and more diffuse – the result of moving toward the observers along the line of sight in the wake of the explosion. The blast should have also been relatively symmetrical. But it wasn’t.

    That led Diehl and his colleagues to think there had to be a “belt” of helium around the white dwarf’s equator, which would account for the supernova’s shape. Seeing the nickel could be explained if the view was pole-on, so that the helium fusing into other elements such as carbon and oxygen wouldn’t block the light from the nickel.

    The hypotheses in Diehl’s study also depend on the accretion of mass being relatively fast. Too slow and the white dwarf turns into either a more massive dwarf or a neutron star. On top of that, any gas that reaches the surface of a white dwarf tends to “flatten out” and cover the surface evenly because the gravity is so strong.

    The next question is where the helium came from. There are two possible sources. One is a companion star, but most stars don’t have a lot of helium in their outer envelopes unless they are rather massive to begin with.

    “Usually stars with bigger [helium] cores evolve faster, so the star with the bigger core should die first,” said Alexander Heger, a professor of physics at Monash University in Australia, in an email to Space.com. “The only way out would be to have a system with more than one phase of mass transfer, i.e., the star that is now the less massive white dwarf initially was the more massive star but by the time it died it had transferred a lot of mass to the companion. Such models and details of mass transfer and ejection from the system are still quite uncertain.”

    Alternate theories

    The other possibility is a helium white dwarf, orbiting close enough to a companion white dwarf that it nearly grazes it.

    Helium white dwarfs are hard to create because a star that could become one on its own would have a low mass, on the order of 0.6 times the mass of Earth’s sun, said Enrico Ramirez-Ruiz, a professor of astronomy at the University of California, Santa Cruz. Such stars would take so long to become white dwarfs that the universe hasn’t been around long enough for them to form.

    Ramirez-Ruiz, who was not involved in Diehl’s research, said that’s why the traditional model of type Ia supernovas needs tweaking. To get the helium there is probably some kind of mass exchange between the two stars in a binary system as well as between the remaining aged star and white dwarf, and even between two white dwarf stars.

    Diehl’s observations, he said, are the first time anyone has seen clear evidence of that kind of supernova, as well as the nickel.

    The nickel is important, because it shows the disruption at the center of the white dwarf, evidence for a “double detonation” model. In that scenario, the explosive fusion of the helium on the white dwarf surface produces a kind of focused shockwave that triggers yet other fusion reactions inside the dwarf, leading to the production of radioactive nickel.

    “It’s really forced us to revisit the old models,” Ramirez-Ruiz said.

    Their research is detailed in the Aug. 1 issue of the journal Science.

    See the full article here.


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  • richardmitnick 4:10 pm on July 31, 2014 Permalink | Reply
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    From NASA/Fermi: “NASA’s Fermi Space Telescope Reveals New Source of Gamma Rays” 

    NASA Fermi

    July 31, 2014
    No Writer Credit

    Observations by NASA’s Fermi Gamma-ray Space Telescope of several stellar eruptions, called novae, firmly establish these relatively common outbursts almost always produce gamma rays, the most energetic form of light.

    novae
    These images show Fermi data centered on each of the four gamma-ray novae observed by the LAT. Colors indicate the number of detected gamma rays with energies greater than 100 million electron volts (blue indicates lowest, yellow highest). Image Credit: NASA/DOE/Fermi LAT Collaboration

    “There’s a saying that one is a fluke, two is a coincidence, and three is a class, and we’re now at four novae and counting with Fermi,” said Teddy Cheung, an astrophysicist at the Naval Research Laboratory in Washington, and the lead author of a paper reporting the findings in the Aug. 1 edition of the journal Science.

    A nova is a sudden, short-lived brightening of an otherwise inconspicuous star caused by a thermonuclear explosion on the surface of a white dwarf, a compact star not much larger than Earth. Each nova explosion releases up to 100,000 times the annual energy output of our sun. Prior to Fermi, no one suspected these outbursts were capable of producing high-energy gamma rays, emission with energy levels millions of times greater than visible light and usually associated with far more powerful cosmic blasts.

    Fermi’s Large Area Telescope (LAT) scored its first nova detection, dubbed V407 Cygni, in March 2010. The outburst came from a rare type of star system in which a white dwarf interacts with a red giant, a star more than a hundred times the size of our sun. Other members of the same unusual class of stellar system have been observed “going nova” every few decades.

    NASA Fermi LAT Large Area Telescope
    NASA/Fermi LAT

    image
    The white dwarf star in V407 Cygni, shown here in an artist’s concept, went nova in 2010. Scientists think the outburst primarily emitted gamma rays (magenta) as the blast wave plowed through the gas-rich environment near the system’s red giant star. Image Credit: NASA’s Goddard Space Flight Center/S. Wiessinger

    In 2012 and 2013, the LAT detected three so-called classical novae which occur in more common binaries where a white dwarf and a sun-like star orbit each other every few hours.

    “We initially thought of V407 Cygni as a special case because the red giant’s atmosphere is essentially leaking into space, producing a gaseous environment that interacts with the explosion’s blast wave,” said co-author Steven Shore, a professor of astrophysics at the University of Pisa in Italy. “But this can’t explain more recent Fermi detections because none of those systems possess red giants.”

    Fermi detected the classical novae V339 Delphini in August 2013 and V1324 Scorpii in June 2012, following their discovery in visible light. In addition, on June 22, 2012, the LAT discovered a transient gamma-ray source about 20 degrees from the sun. More than a month later, when the sun had moved farther away, astronomers looking in visible light discovered a fading nova from V959 Monocerotis at the same position.

    Astronomers estimate that between 20 and 50 novae occur each year in our galaxy. Most go undetected, their visible light obscured by intervening dust and their gamma rays dimmed by distance. All of the gamma-ray novae found so far lie between 9,000 and 15,000 light-years away, relatively nearby given the size of our galaxy.

    Novae occur because a stream of gas flowing from the companion star piles up into a layer on the white dwarf’s surface. Over time — tens of thousands of years, in the case of classical novae, and several decades for a system like V407 Cygni — this deepening layer reaches a flash point. Its hydrogen begins to undergo nuclear fusion, triggering a runaway reaction that detonates the accumulated gas. The white dwarf itself remains intact.

    shock
    Novae typically originate in binary systems containing sun-like stars, as shown in this artist’s rendering. A nova in a system like this likely produces gamma rays (magenta) through collisions among multiple shock waves in the rapidly expanding shell of debris. Image Credit: NASA’s Goddard Space Flight Center/S. Wiessinger

    One explanation for the gamma-ray emission is that the blast creates multiple shock waves that expand into space at slightly different speeds. Faster shocks could interact with slower ones, accelerating particles to near the speed of light. These particles ultimately could produce gamma rays.

    “This colliding-shock process must also have been at work in V407 Cygni, but there is no clear evidence for it,” said co-author Pierre Jean, a professor of astrophysics at the University of Toulouse in France. This is likely because gamma rays emitted through this process were overwhelmed by those produced as the shock wave interacted with the red giant and its surroundings, the scientists conclude.

    See the full article here.

    The Fermi Gamma-ray Space Telescope , formerly referred to as the Gamma-ray Large Area Space Telescope (GLAST), is a space observatory being used to perform gamma-ray astronomy observations from low Earth orbit. Its main instrument is the Large Area Telescope (LAT), with which astronomers mostly intend to perform an all-sky survey studying astrophysical and cosmological phenomena such as active galactic nuclei, pulsars, other high-energy sources and dark matter. Another instrument aboard Fermi, the Gamma-ray Burst Monitor (GBM; formerly GLAST Burst Monitor), is being used to study gamma-ray bursts. The mission is a joint venture of NASA, the United States Department of Energy, and government agencies in France, Germany, Italy, Japan, and Sweden.


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  • richardmitnick 3:28 pm on July 31, 2014 Permalink | Reply
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    From physicsworld.com: A SKA For Astronomy 

    physicsworld
    physicsworld.com

    Jul 31, 2014

    The Square Kilometre Array (SKA) promises to usher in a new era in radio astronomy. Astronomers will use the telescope to probe the early universe by looking as far back in time as the first 100 million years after the Big Bang. It will also be employed to search for life and planets, as well as to study the nature of dark energy. [The] video [in this article] takes you on a tour of the sites in Australia and southern Africa that will host the SKA, featuring artists’ impressions of the impressive telescope equipment. The film will also transport you to the headquarters of the SKA Organisation in the UK, where scientists and engineers describe the challenges and opportunities that lie ahead.

    vla
    The Very Large Array, a radio interferometer in New Mexico, USA

    When completed, the SKA will be the world’s largest radio telescope, with a total collecting area of one million square metres. Construction of the first phase is scheduled to begin in 2018. This will see an array of 254 dishes being built in South Africa’s Karoo region covering the bulk of the high and mid-frequencies of the radio spectrum. Meanwhile, the Murchison region in Western Australia will host the low-frequency section of the array with 96 dishes accompanied by approximately 250,000 individual dipole antennas.

    Engineers involved in the SKA project are full of impressive facts about the scale of the technology infrastructure. For instance, they say that the number of data being collected by the array will be equivalent to 10 times the global Internet traffic. And given its processing capabilities, the array will be able to survey the sky 10,000 times faster than any existing radio telescope and at a sensitivity that is 50 times greater. To put the latter figure in perspective, it means that the SKA would be able to detect an airport radar signal on a planet tens of light-years away.

    “I think it’s fair to say that the SKA really represents the next step in the evolution of low-frequency radio astronomy,” says Jeff Wagg, a SKA project scientist featured in the film. “Observing the universe at low radio frequency not only tells us about the evolution of gas in our own galaxy and other galaxies, but also tells us about the evolution of star formation in the universe.”

    In addition, the film takes a look at some of the precursor telescope arrays that are being developed in both host nations as a means of testing some of the SKA technologies. South Africa has the MeerKAT array, which is currently under construction in the Karoo and had the first of its 64 antenna inaugurated in March. Meanwhile, Australia has the Murchison Widefield Array (MWA), which is already up and running. It also has the Australian Square Kilometre Array Pathfinder (ASKAP), which astronomers are currently commissioning and testing.

    SKA MeerKAT Array
    Elements of the MeerKAT Array

    SKA Murchison Widefield Array
    Murchison Widefield Array

    Australian Square Kilometer Array Pathfinder Project
    Australian Square Kilometre Array Pathfinder

    “There are some really exciting images coming out of those instruments right now,” says SKA engineer Roshene McCool, referring to developments at ASKAP and MeerKAT. McCool says that as well as being important scientific instruments in their own right, the SKA precursor projects will also return a lot of practical information about building telescope arrays in these environments. “The design and the construction of those telescopes has built both infrastructure and also human capital in those areas so that we have skilled people who understand what is actually quite a specialized area,” she says.

    See the full article, with video, here.

    [I see no mention in this article of interferometry. Are we just supposed to assume that tey can pull this off? For this reder, thi is a missing piece.]

    PhysicsWorld is a publication of the Institute of Physics. The Institute of Physics is a leading scientific society. We are a charitable organisation with a worldwide membership of more than 50,000, working together to advance physics education, research and application.

    We engage with policymakers and the general public to develop awareness and understanding of the value of physics and, through IOP Publishing, we are world leaders in professional scientific communications.
    IOP Institute of Physics


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  • richardmitnick 2:53 pm on July 31, 2014 Permalink | Reply
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    From Don Lincoln of Fermilab: The Origin of Mass, a Really Cool Video 


    Fermilab is an enduring source of strength for the US contribution to scientific research world wide.

    Don Lincoln at his best.

    Learn and enjoy

    Fermilab Campus

    Fermi National Accelerator Laboratory (Fermilab), located just outside Batavia, Illinois, near Chicago, is a US Department of Energy national laboratory specializing in high-energy particle physics.


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  • richardmitnick 2:42 pm on July 31, 2014 Permalink | Reply
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    From ScienceDaily: “Mercury’s bizzare magnetic field tells scientists how its interior is different from Earth’s” 

    Science Daily Icon

    July 30, 2014
    No Writer Credit

    Earth and Mercury are both rocky planets with iron cores, but Mercury’s interior differs from Earth’s in a way that explains why the planet has such a bizarre magnetic field, UCLA planetary physicists and colleagues report.

    MERCURY

    Measurements from NASA’s Messenger spacecraft have revealed that Mercury’s magnetic field is approximately three times stronger at its northern hemisphere than its southern one. In the current research, scientists led by Hao Cao, a UCLA postdoctoral scholar working in the laboratory of Christopher T. Russell, created a model to show how the dynamics of Mercury’s core contribute to this unusual phenomenon.

    NASA Messenger satellite
    NASA Messenger satellite

    The magnetic fields that surround and shield many planets from the sun’s energy-charged particles differ widely in strength. While Earth’s is powerful, Jupiter’s is more than 12 times stronger, and Mercury has a rather weak magnetic field. Venus likely has none at all. The magnetic fields of Earth, Jupiter and Saturn show very little difference between the planets’ two hemispheres.

    Within Earth’s core, iron turns from a liquid to a solid at the inner boundary of the planet’s liquid outer core; this results in a solid inner part and liquid outer part. The solid inner core is growing, and this growth provides the energy that generates Earth’s magnetic field. Many assumed, incorrectly, that Mercury would be similar.

    “Hao’s breakthrough is in understanding how Mercury is different from the Earth so we could understand Mercury’s strongly hemispherical magnetic field,” said Russell, a co-author of the research and a professor in the UCLA College’s department of Earth, planetary and space sciences. “We had figured out how the Earth works, and Mercury is another terrestrial, rocky planet with an iron core, so we thought it would work the same way. But it’s not working the same way.”

    Mercury’s peculiar magnetic field provides evidence that iron turns from a liquid to a solid at the core’s outer boundary, say the scientists, whose research currently appears online in the journal Geophysical Research Letters and will be published in an upcoming print edition.

    “It’s like a snow storm in which the snow formed at the top of the cloud and middle of the cloud and the bottom of the cloud too,” said Russell. “Our study of Mercury’s magnetic field indicates iron is snowing throughout this fluid that is powering Mercury’s magnetic field.”

    The research implies that planets have multiple ways of generating a magnetic field.

    Hao and his colleagues conducted mathematical modeling of the processes that generate Mercury’s magnetic field. In creating the model, Hao considered many factors, including how fast Mercury rotates and the chemistry and complex motion of fluid inside the planet.

    The cores of both Mercury and Earth contain light elements such as sulfur, in addition to iron; the presence of these light elements keeps the cores from being completely solid and “powers the active magnetic field-generation processes,” Hao said.

    Hao’s model is consistent with data from Messenger and other research on Mercury and explains Mercury’s asymmetric magnetic field in its hemispheres. He said the first important step was to “abandon assumptions” that other scientists make.

    “Planets are different from one another,” said Hao, whose research is funded by a NASA fellowship. “They all have their individual character.”

    Co-authors include Jonathan Aurnou, professor of planetary science and geophysics in UCLA’s Department of Earth, Planetary and Space Sciences, and Johannes Wicht, a research scientist at Germany’s Max Planck Institute for Solar System Research.

     
  • richardmitnick 2:27 pm on July 31, 2014 Permalink | Reply
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    From Science Daily: “Weighing the Milky Way: Researchers devise precise method for calculating the mass of galaxies” 

    ScienceDaily Icon

    Science Daily

    Does the Milky Way look fat in this picture? Has Andromeda been taking skinny selfies? It turns out the way some astrophysicists have been studying our galaxy made it appear that the Milky Way might be more massive than it’s neighbor down the street, Andromeda.

    andro
    The Andromeda Galaxy is a spiral galaxy approximately 2.5 million light-years away in the constellation Andromeda. The image also shows Messier Objects 32 and 110, as well as NGC 206 (a bright star cloud in the Andromeda Galaxy) and the star Nu Andromedae. This image was taken using a hydrogen-alpha filter.

    Not true, says a study published in the journal Monthly Notices of the Royal Astronomical Society by an international group of researchers, including Matthew Walker of Carnegie Mellon University‘s McWilliams Center for Cosmology. In the paper, they demonstrate a new, more accurate method for measuring the mass of galaxies. Using this method, the researchers have shown that the Milky Way has only about half the mass of its neighbor, the Andromeda Galaxy.

    In previous studies, researchers were only able to estimate the mass of the Milky Way and Andromeda based on observations made using their smaller satellite dwarf galaxies. In the new study, researchers culled previously published data that contained information about the distances between the Milky Way, Andromeda and other close-by galaxies — including those that weren’t satellites — that reside in and right outside an area referred to as the Local Group.

    lg
    Local Group which includes both Andromeda and the Milky Way

    Galaxies in the Local Group are bound together by their collective gravity. As a result, while most galaxies, including those on the outskirts of the Local Group, are moving farther apart due to expansion [dark energy?], the galaxies in the Local Group are moving closer together because of gravity. For the first time, researchers were able to combine the available information about gravity and expansion to complete precise calculations of the masses of both the Milky Way and Andromeda.

    “Historically, estimations of the Milky Way’s mass have been all over the map,” said Walker, an assistant professor of physics at Carnegie Mellon. “By studying two massive galaxies that are close to each other and the galaxies that surround them, we can take what we know about gravity and pair that with what we know about expansion to get an accurate account of the mass contained in each galaxy. This is the first time we’ve been able to measure these two things simultaneously.”

    By studying both the galaxies in and immediately outside the Local Group, Walker was able to pinpoint the group’s center. The researchers then calculated the mass of both the ordinary, visible matter and the invisible dark matter throughout both galaxies based on each galaxy’s present location within the Local Group. Andromeda had twice as much mass as the Milky Way, and in both galaxies 90 percent of the mass was made up of dark matter.

    The study was supported by the UK’s Science and Technology Facilities Council and led by Jorge Peñarrubia of the University of Edinburgh’s School of Physics and Astronomy. Co-authors include Yin-Zhe Ma of the University of British Columbia and Alan McConnachie of the NRC Herzberg Institute of Astrophysics.

    See the full article here.

    ScienceDaily is one of the Internet’s most popular science news web sites. Since starting in 1995, the award-winning site has earned the loyalty of students, researchers, healthcare professionals, government agencies, educators and the general public around the world. Now with more than 3 million monthly visitors, ScienceDaily generates nearly 15 million page views a month and is steadily growing in its global audience.


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  • richardmitnick 12:11 pm on July 31, 2014 Permalink | Reply
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    From NASA/ESA Hubble: “Hubble Shows Farthest Lensing Galaxy Yields Clues to Early Universe” 

    NASA Hubble Telescope

    Hubble

    July 31, 2014

    Astronomers using NASA’s Hubble Space Telescope have unexpectedly discovered the most distant galaxy that acts as a cosmic magnifying glass. Seen here as it looked 9.6 billion years ago, this monster elliptical galaxy breaks the previous record-holder by 200 million years.

    two
    The farthest cosmic lens yet found, a massive elliptical galaxy, is shown in the inset image at left. The galaxy existed 9.6 billion years ago and belongs to the galaxy cluster, IRC 0218. Image Credit: NASA and ESA

    These lensing galaxies are so massive that their gravity bends, magnifies, and distorts light from objects behind it, a phenomenon called gravitational lensing. Finding one in such a small area of the sky is so rare that you would normally have to survey a region hundreds of times larger to find just one.

    The object behind the cosmic lens is a tiny spiral galaxy undergoing a rapid burst of star formation. Its light has taken 10.7 billion years to arrive here and seeing this chance alignment at such a great distance from Earth is a rare find. Locating more of these distant lensing galaxies will offer insight into how young galaxies in the early universe build themselves up into the massive dark-matter-dominated galaxies of today. Dark matter cannot be seen, but it accounts for the bulk of the universe’s matter.

    “When you look more than 9 billion years ago in the early universe, you don’t expect to find this type of galaxy lensing at all,” explained lead researcher Kim-Vy Tran of Texas A&M University in College Station. “It’s very difficult to see an alignment between two galaxies in the early universe. Imagine holding a magnifying glass close to you and then moving it much farther away. When you look through a magnifying glass held at arm’s length, the chances that you will see an enlarged object are high. But if you move the magnifying glass across the room, your chances of seeing the magnifying glass nearly perfectly aligned with another object beyond it diminishes.”

    Team members Kenneth Wong and Sherry Suyu of Academia Sinica Institute of Astronomy & Astrophysics (ASIAA) in Taipei, Taiwan, used the gravitational lensing from the chance alignment to measure the giant galaxy’s total mass, including the amount of dark matter, by gauging the intensity of its lensing effects on the background galaxy’s light. The giant foreground galaxy weighs 180 billion times more than our sun and is a massive galaxy for its time. It is also one of the brightest members of a distant cluster of galaxies, called IRC 0218.

    “There are hundreds of lens galaxies that we know about, but almost all of them are relatively nearby, in cosmic terms,” said Wong, first author on the team’s science paper. “To find a lens as far away as this one is a very special discovery because we can learn about the dark-matter content of galaxies in the distant past. By comparing our analysis of this lens galaxy to the more nearby lenses, we can start to understand how that dark-matter content has evolved over time.”

    The team suspects the lensing galaxy continued to grow over the past 9 billion years, gaining stars and dark matter by cannibalizing neighboring galaxies. Tran explained that recent studies suggest these massive galaxies gain more dark matter than stars as they continue to grow. Astronomers had assumed dark matter and normal matter build up equally in a galaxy over time, but now know the ratio of dark matter to normal matter changes with time. The newly discovered distant lensing galaxy will eventually become much more massive than the Milky Way and will have more dark matter, too.

    Tran and her team were studying star formation in two distant galaxy clusters, including IRC 0218, when they stumbled upon the gravitational lens. While analyzing spectrographic data from the W.M. Keck Observatory in Hawaii, Tran spotted a strong detection of hot hydrogen gas that appeared to arise from a giant elliptical galaxy. The detection was surprising because hot hydrogen gas is a clear signature of star birth. Previous observations showed that the giant elliptical, residing in the galaxy cluster IRC 0218, was an old, sedate galaxy that had stopped making stars a long time ago. Another puzzling discovery was that the young stars were at a much farther distance than the elliptical galaxy. Tran was very surprised, worried and thought her team made a major mistake with their observations.

    The astronomer soon realized she hadn’t made a mistake when she looked at the Hubble images taken in blue wavelengths, which revealed the glow of fledgling stars. The images, taken by Hubble’s Advanced Camera for Surveys and the Wide Field Camera 3, revealed a blue, eyebrow-shaped object next to a smeared blue dot around the massive elliptical. Tran recognized the unusual features as the distorted, magnified images of a more distant galaxy behind the elliptical galaxy, the signature of a gravitational lens.

    NASA Hubble ACS
    Hubble’s ACS

    NASA Hubble WFC3
    Hubble’s WFC3

    To confirm her gravitational-lens hypothesis, Tran’s team analyzed Hubble archival data from two observing programs, the 3D-HST survey, a near-infrared spectroscopic survey taken with the Wide Field Camera 3, and the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey, a large Hubble deep-sky program. The data turned up another fingerprint of hot gas connected to the more distant galaxy.

    The distant galaxy is too small and far away for Hubble to determine its structure. So, team members analyzed the distribution of light in the object to infer its spiral shape. In addition, spiral galaxies are more plentiful during those early times. The Hubble images also revealed at least one bright compact region near the center. The team suspects the bright region is due to a flurry of star formation and is most likely composed of hot hydrogen gas heated by massive young stars. As Tran continues her star-formation study in galaxy clusters, she will be hunting for more signatures of gravitational lensing.

    The team’s results appeared in the July 10 issue of The Astrophysical Journal Letters.

    See the full article here.

    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.

    ESA50 Logo large

    AURA Icon


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  • richardmitnick 11:47 am on July 31, 2014 Permalink | Reply
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    From Fermilab- “Frontier Science Result: DZero Which Higgs? 


    Fermilab is an enduring source of strength for the US contribution to scientific research world wide.

    Thursday, July 31, 2014
    Leo Bellantoni

    With all the discussion about “the Higgs,” it is worth remembering that what Peter Higgs (and Robert Brout, François Englert, Gerald Guralnik, Carl Hagen and Tom Kibble) gave us was not at first a particle. Originally, it was a trick.

    Specifically, it was a mathematical trick to solve a particular physics problem — the problem of how to retain a lovely property called gauge invariance and still allow massive particles in the theory. The trick is to add mathematical expressions to the theory that have what are called doublets.

    Now, that trick can be played more than one way. If the trick is played in the simplest way, by adding one doublet, the existence of one and only one new particle is predicted; that is the particle that we usually call “the Higgs.” But there is no particular reason to believe that the simplest way is how nature is playing with us. The next simplest play has two of these doublets and predicts both three new neutral particles and a pair of charged particles. There are many other ways in which nature might be playing its cards.

    One way to figure out what is in this hand of cards is to measure the spin and parity of the Higgs that has been found. The spin of a particle is its intrinsic angular momentum; the parity has to do with how the particle’s interactions will appear if they are viewed in a mirror.

    If there is only one doublet and there is only one Higgs boson, then the spin must be zero and the parity must be even. If there are two doublets and if we have found one of those three neutral particles, then the particle we have found must have a spin of zero but it might not have even parity. It could have an odd parity or be a mixture of even and odd parity. Because the found Higgs decays into a pair of photons, it can not have a spin of one; but a spin of two and a positive parity is possible in some theories with extra dimensions.

    Although the spin and parity are properties of the particle itself and do not depend on what the particle decays into, it is valuable to check that one obtains the same result regardless of what the particle decays into. For this reason, DZero has leveraged the comparative advantage of the Tevatron to set constraints on the spin and parity of the Higgs that has been found in the case where it decays into a pair of bottom quarks.

    Fermilab DZero
    DZero at Fermilab

    Fermilab Tevatron
    Tevatron Campus at Fermilab

    The DZero result suggests that nature is playing the simplest hand — the single-doublet scenario. Comparing odd to even parities for the spin zero case, the odd parity hypothesis is disfavored with 97.6 percent confidence. Comparing spin zero to spin two for the even parity case, the spin two hypothesis is disfavored with 99.0 percent confidence. However, this does not quite prove that there is only one doublet. It is possible to get the same result with two doublets. We shall have to see a few more cards before we know exactly what is in that hand!

    See the full article here.

    Fermilab Campus

    Fermi National Accelerator Laboratory (Fermilab), located just outside Batavia, Illinois, near Chicago, is a US Department of Energy national laboratory specializing in high-energy particle physics.


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