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  • richardmitnick 7:56 am on October 9, 2015 Permalink | Reply
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    From Daily Galaxy- “Image of the Day: Is the Milky Way’s Red Giant Betelgeuse the Next Nearby Supernova? 

    Daily Galaxy
    The Daily Galaxy

    October 08, 2015
    No Writer Credit

    1

    While there is, on average, only one supernova per galaxy per century, there is something on the order of 100 billion galaxies in the observable Universe. Taking 10 billion years for the age of the Universe (it’s actually 13.7 billion, but stars didn’t form for the first few hundred million), Dr. Richard Mushotzky of the NASA Goddard Space Flight Center, derived a figure of 1 billion supernovae per year, or 30 supernovae per second in the observable Universe! Could the Milky Way’s red giant star, Betelgeuse be the next?

    Betelgeuse, one of the brightest stars in the sky, could burst into its supernova phase and become as bright as a full moon — and last for as long as a year.

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    The pink arrow at the star on left labeled α indicates Betelgeuse in Orion.

    The massive star, visible in the winter sky over most of the world as a bright, reddish star, could explode as a supernova anytime within the next 100,000 years.

    Most astronomers today believe that one of the plausible reasons we have yet to detect intelligent life in the universe is due to the deadly effects of local supernova explosions that wipe out all life in a given region of a galaxy.

    The red giant Betelgeuse, once so large it would reach out to Jupiter’s orbit if placed in our own solar system, has shrunk by 15 percent over the past decade in a half, although it’s just as bright as it’s ever been.

    Betelgeuse, whose name derives from Arabic, is easily visible in the constellation Orion. It gave Michael Keaton’s character his name in the movie Beetlejuice and was the home system of Galactic President Zaphod Beeblebrox in The Hitchhiker’s Guide to the Galaxy.

    Red giant stars are thought to have short, complicated and violent lifespans. Lasting at most a few million years, they quickly burn out their hydrogen fuel and then switch to helium, carbon and other elements in a series of partial collapses, refuelings and restarts.

    Betelgeuse, which is thought to be reaching the end of its lifespan, may be experiencing one of those collapses as it switches from one element to another as nuclear-fusion fuel.

    “We do not know why the star is shrinking,” said Townes’ Berkeley colleague Edward Wishnow. “Considering all that we know about galaxies and the distant Universe, there are still lots of things we don’t know about stars, including what happens as red giants near the ends of their lives.”

    If Betelgeuse goes nova, it could offer Earth’s astronomers an up close look at how supernovae evolve and the physics that governs how they work. The problem is that it is not clear when that will happen. While stories have been circulating that the star could explode in 2012, the odds of that are actually quite small. Betelgeuse may explode tomorrow night, or it may not go nova until the year 100,000 A.D. It’s impossible to know.

    Betelgeuse is beyond the death beam distance — somewhere within 30 light years range — where it could do ultimate damage to Earth. The explosion won’t do the Earth any harm, as a star has to be relatively close — on the order of 25 light years — to do that. Betelgeuse is about 600 light years distant.

    Betelgeuse, one of the most luminous stars known and ten times the size of the Sun, is thought to be only 10 million years old. The more massive a star is the shorter its lifespan, which is why astronomers think it has an outside chance of exploding relatively soon.

    Late in 2009, astronomers witnessed the largest explosion ever recorded: a super giant star two hundred times bigger than the sun utterly obliterated by runaway thermonuclear reactions triggered by gamma ray-driven antimatter production. The resulting blast was visible for months because it unleashed a cloud of radioactive material over fifty times the size of our own star, giving off a nuclear fission glow visible from galaxies away.

    The super-supernova SN2007bi is an example of a pair-instability breakdown, and that’s like calling an atomic bomb a “plutonium-pressing” device. At sizes of around four megayottagrams (that’s thirty-two zeros) giant stars are supported against gravitational collapse by gamma ray pressure. The hotter the core, the higher the energy of these gamma rays — but if they get too energetic, these gamma rays can begin pair production: creating an electron-positron matter-antimatter pair out of pure energy as they pass an atom. Yes, this does mean that the entire stellar core acts as a gigantic particle accelerator.

    The antimatter annihilates with its opposite, as antimatter is wont to do, but the problem is that the speed of antimatter explosion — which is pretty damn fast — is still a critical delay in the gamma-pressure holding up the star. The outer layers sag in, compressing the core more, raising the temperature, making more energetic gamma rays even more likely to make antimatter, and suddenly the whole star is a runaway nuclear reactor beyond the scale of the imagination. The entire thermonuclear core detonates at once, an atomic warhead that’s not just bigger than the Sun — it’s bigger than the Sun plus the mass of another ten close-by stars.

    The entire star explodes. No neutron star, no black hole, nothing left behind but an expanding cloud of newly radioactive material and empty space where once was the most massive item you can actually have without ripping space. The explosion alone triggers alchemy on a suprasolar scale, converting stars’ worth of matter into new radioactive elements.

    Certain rare stars –real killers, type 11 stars — are core-collapse hypernova that generate deadly gamma ray bursts (GRBs). These long burst objects release 1000 times the non-neutrino energy release of an ordinary core-collapse supernova. Concrete proof of the core-collapse GRB model came in 2003.

    It was made possible in part to a fortuitously “nearby” burst whose location was distributed to astronomers by the Gamma-ray Burst Coordinates Network (GCN). On March 29, 2003, a burst went off close enough that the follow-up observations were decisive in solving the gamma-ray burst mystery. The optical spectrum of the afterglow was nearly identical to that of supernova SN1998bw. In addition, observations from x-ray satellites showed the same characteristic signature of “shocked” and “heated” oxygen that’s also present in supernovae. Thus, astronomers were able to determine the “afterglow” light of a relatively close gamma-ray burst (located “just” 2 billion light years away) resembled a supernova.

    It isn’t known if every hypernova is associated with a GRB. However, astronomers estimate only about one out of 100,000 supernovae produce a hypernova. This works out to about one gamma-ray burst per day, which is in fact what is observed.

    What is almost certain is that the core of the star involved in a given hypernova is massive enough to collapse into a black hole (rather than a neutron star). So every GRB detected is also the “birth cry” of a new black hole.

    Scientists agree that new observations of T Pyxidis in the constellation Pyxis (the compass) using the International Ultraviolet Explorer satellite, indicate the white dwarf is part of a close binary system with a sun, and the pair are 3,260 light-years from Earth and much closer than the previous estimate of 6,000 light-years.

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    T Pyxidis
    Hubble telescope picture of T Pyxidis, from a compilation of data taken on Feb. 26, 1994, and June 16, Oct. 7, and Nov. 10, 1995, by the Wide Field and Planetary Camera 2 [WFPC2].

    NASA Hubble Telescope
    NASA/ESA Hubble

    NASA Hubble WFPC2
    NASA Hubble WFPC2

    The white dwarf in the T Pyxidis system is a recurrent nova, which means it undergoes nova (thermonuclear) eruptions around every 20 years. The most recent known events were in 1967, 1944, 1920, 1902, and 1890. These explosions are nova rather than supernova events, and do not destroy the star, and have no effect on Earth. The astronomers do not know why the there has been a longer than usual interval since the last nova eruption.

    Astronomers believe the nova explosions are the result of an increase of mass as the dwarf siphons off hydrogen-rich gases from its stellar companion. When the mass reaches a certain limit a nova is triggered. It is unknown whether there is a net gain or loss of mass during the siphoning/explosion cycle, but if the mass does build up the so-called Chandrasekhar Limit could be reached, and the dwarf would then become a Type 1a supernova.

    In this event the dwarf would collapse and detonate a massive explosion resulting in its total destruction. This type of supernova releases 10 million times the energy of a nova.

    Observations of the white dwarf during the nova eruptions suggest its mass is increasing, and pictures from the Hubble telescope of shells of material expelled during the previous explosions support the view. Models estimate the white dwarf’s mass could reach the Chandrasekhar Limit in around 10 million years or less.

    According to the scientists the supernova would result in gamma radiation with an energy equivalent to 1,000 solar flares simultaneously — enough to threaten Earth by production of nitrous oxides that would damage and perhaps destroy the ozone layer. The supernova would be as bright as all the other stars in the Milky Way put together. One of the astronomers, Dr. Edward Sion, from Villanova University, said the supernova could occur “soon” on the timescales familiar to astronomers and geologists, but this is a long time in the future, in human terms.

    Astronomers think supernova explosions closer than 100 light years from Earth would be catastrophic, but the effects of events further away are unclear and would depend on how powerful the supernova is. The research team postulate it could be close enough and powerful enough to damage Earth, possibly severely, although other researchers, such as Alex Filippenko at UC Berkeley, who specializes in supernovae, active galaxies, black holes, gamma-ray bursts, and the expansion of the universe, disagree with the calculations and believe the supernova, if it occurred, would be unlikely to damage the planet.

    See the full article here .

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  • richardmitnick 12:06 pm on March 31, 2015 Permalink | Reply
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    From Daily Galaxy: “Mystery of Extreme Continent Building Solved –A Key to Life on Earth and Beyond” 

    Daily Galaxy
    The Daily Galaxy

    March 31, 2015
    No Writer Credit

    1

    “We’ve revealed a major unknown in the evolution of our planet,” says Esteban Gazel, an assistant professor of geology with Virginia Tech. An international research team, led geoscientist Gazel, has revealed information about how continents were generated on Earth more than 2.5 billion years ago — and how those processes have continued within the last 70 million years to profoundly affect the planet’s life and climate.

    Published online today in Nature Geoscience, the study details how relatively recent geologic events — volcanic activity 10 million years ago in what is now Panama and Costa Rica — hold the secrets of the extreme continent-building that took place billions of years earlier.

    The discovery provides new understanding about the formation of the Earth’s continental crust — masses of buoyant rock rich with silica, a compound that combines silicon and oxygen.

    “Without continental crust, the whole planet would be covered with water,” said Gazrl. “Most terrestrial planets in the solar system have basaltic crusts similar to Earth’s oceanic crust, but the continental masses — areas of buoyant, thick silicic crust — are a unique characteristic of Earth.”

    The continental mass of the planet formed in the Archaean Eon, about 2.5 billion years ago. The Earth was three times hotter, volcanic activity was considerably higher, and life was probably very limited.

    Many scientists think that all of the planet’s continental crust was generated during this time in Earth’s history, and the material continually recycles through collisions of tectonic plates on the outermost shell of the planet.

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    The tectonic plates of the world were mapped in the second half of the 20th century.

    But the new research shows “juvenile” continental crust has been produced throughout Earth’s history.

    “Whether the Earth has been recycling all of its continental crust has always been the big mystery,” Gazel said. “We were able to use the formation of the Central America land bridge as a natural laboratory to understand how continents formed, and we discovered while the massive production of continental crust that took place during the Archaean is no longer the norm, there are exceptions that produce ‘juvenile’ continental crust.”

    The researchers used geochemical and geophysical data to reconstruct the evolution what is now Costa Rica and Panama, which was generated when two oceanic plates collided and melted iron- and magnesium-rich oceanic crust over the past 70 million years, Gazel said.

    Melting of the oceanic crust originally produced what today are the Galapagos islands, reproducing Achaean-like conditions to provide the “missing ingredient” in the generation of continental crust.

    The researchers discovered the geochemical signature of erupted lavas reached continental crust-like composition about 10 million years ago. They tested the material and observed seismic waves traveling through the crust at velocities closer to the ones observed in continental crust worldwide.

    Additionally, the researchers provided a global survey of volcanoes from oceanic arcs, where two oceanic plates interact. The western Aleutian Islands and the Iwo-Jima segment of the Izu-Bonin islands of are some other examples of juvenile continental crust that has formed recently, the researchers said.

    The study raises questions about the global impact newly generated continental crust has had over the ages, and the role it has played in the evolution of not just continents, but life itself.

    “This is an interesting paper that makes the case that andesitic melts inferred to derive ultimately by melting of subducted slabs in some modern arcs are a good match for the composition of the average continental crust,” said Roberta L. Rudnick, a Distinguished University Professor and chair of the Department of Geology at the University of Maryland, who was not involved in conducting the research. “The authors focus primarily on Central America, but incorporate global data to strengthen their case that slab melting is important in unusual conditions of modern continent generation — and probably in the past.”

    For example, the formation of the Central American land bridge resulted in the closure of the seaway, which changed how the ocean circulated, separated marine species, and had a powerful impact on the climate on the planet.

    See the full article here.

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  • richardmitnick 2:23 pm on March 1, 2015 Permalink | Reply
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    From Daily Galaxy: “Our Observed Universe is a Tiny Corner of an Enormous Cosmos –‘Ruled by Dark Energy'” 

    Daily Galaxy
    The Daily Galaxy

    March 01, 2015
    No Writer Credit

    1

    “This new concept is, potentially, as drastic an enlargement of our cosmic perspective as the shift from pre-Copernican ideas to the realization that the Earth is orbiting a typical star on the edge of the Milky Way.” Sir Martin Rees, physicist, Cambridge University, Astronomer Royal of Great Britain.

    Is our universe merely a part of an enormous universe containing diverse regions each with the right amount of the dark energy and each larger than the observed universe, according to Raphael Bousso, Professor of Theoretical Physics, U of California/Berkeley and Leonard Susskind, Felix Bloch Professor of Physics, Stanford University. The two theorize that information can leak from our causal patch into others, allowing our part of the universe to “decohere” into one state or another, resulting in the universe that we observe.

    The many worlds interpretation of quantum mechanics is the idea that all possible alternate histories of the universe actually exist. At every point in time, the universe splits into a multitude of existences in which every possible outcome of each quantum process actually happens.The reason many physicists love the many worlds idea is that it explains away all the strange paradoxes of quantum mechanics.

    Putting the many world interpretation aside for a moment, another strange idea in modern physics is the idea that our universe was born along with a large, possibly infinite, number of other universes. So our cosmos is just one tiny corner of a much larger multiverse.

    Susskind and Bousso have put forward the idea that the multiverse and the many worlds interpretation of quantum mechanics are formally equivalent, but if both quantum mechanics and the multiverse take special forms.

    Let’s take quantum mechanics first. Susskind and Bousso propose that it is possible to verify the predictions of quantum mechanics. In theory, it could be done if an observer could perform an infinite number of experiments and observe the outcome of them all, which is known as the supersymmetric multiverse with vanishing cosmological constant.

    If the universe takes this form, then it is possible to carry out an infinite number of experiments within the causal horizon of each other. At each instant in time, an infinite (or very large) number of experiments take place within the causal horizon of each other. As observers, we are capable of seeing the outcome of any of these experiments but we actually follow only one.

    Bousso and Susskind argue that since the many worlds interpretation is possible only in their supersymmetric multiverse, they must be equivalent. “We argue that the global multiverse is a representation of the many-worlds in a single geometry,” they say, calling this new idea the multiverse interpretation of quantum mechanics.

    But we have now entered the realm of what mathematical physicist Peter Woit of Columbia calls “Not Even Wrong, because the theory lacks is a testable prediction that would help physicists distinguish it experimentally from other theories of the universe. And without this crucial element, the multiverse interpretation of quantum mechanics is little more than philosophy, according to Woit.

    What this new supersymmetric multiverse interpretation does have is a simplicity– it’s neat and elegant that the many worlds and the multiverse are equivalent. Ockham’s Razor is fulfilled and no doubt, many quantum physicists delight in what appears to be an exciting. plausible interpretation of ultimate if currently untestable, reality.

    Ref: arxiv.org/abs/1105.3796: The Multiverse Interpretation of Quantum Mechanics

    The Daily Galaxy via technologyreview.com

    Image credit: hellstormde.deviantart.com

    See the full article here.

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  • richardmitnick 4:10 pm on January 5, 2015 Permalink | Reply
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    From Daily Galaxy: “A Living Fossil from Early Universe –Gigantic S-Shaped Dwarf Galaxy” 

    Daily Galaxy
    The Daily Galaxy

    January 05, 2015
    No Writer Credit

    i

    In 2013, a UCLA team used a unique telescope to discover a previously unknown companion to the nearby galaxy NGC 4449 (image above), which is some 12.5 million light years from Earth. The newly discovered dwarf galaxy had escaped even the illuminating eyes of the Hubble Space Telescope.

    NASA Hubble Telescope
    Hubble

    NGC 4449B is stretched into a gigantic “S” so large that if one end were placed at the center of the Milky Way, the other end would reach all the way to the sun’s position. In fact, NGC 4449B is the largest dwarf galaxy known in the “local group” that also includes the Milky Way and the Andromeda galaxy.

    Local Grp II
    Local Group

    a
    Andromeda

    The larger, host galaxy, NGC 4449, may be “something of a living fossil,” representing what most galaxies probably looked like shortly after the Big Bang, [Michael] Rich said. The galaxy is forming stars “so furiously” that it has giant clusters of young stars and even appears bluish — a sign of a young galaxy — to the eye in large amateur telescopes.”

    NGC 4449 has a nucleus that may someday host a black hole and an irregular structure, lacking the spiral arms characteristic of many galaxies, he said. It is surrounded by a huge complex of hydrogen gas that spans approximately 300,000 light years, which may be fueling its burst of star formation.

    UCLA research astronomer Michael Rich collaborated with Francis Longstaff, a professor of finance at the UCLA Anderson School of Management and an amateur astronomer, in acquiring and using a specialized telescope designed to take images of wide fields of the sky. Known as the Centurion 28 (the diameter of the mirror is 28 inches), the telescope, and the observatory the astronomers used, are located at the Polaris Observatory Association.

    c
    Centurion 28

    With the C28 telescope, the astronomers discovered the companion dwarf galaxy, which has “evidently experienced a close encounter with the nucleus of NGC 4449,” Rich said. Dubbed NGC 4449B, the dwarf galaxy has been stretched into a comet-like shape by this gravitational encounter.

    NGC 4449B had remained undetected because it is more than 10 times fainter than the natural brightness of the night sky and some 1,000 times fainter than our own Milky Way galaxy. The dwarf galaxy is in a “transient stage,” Rich said, and will soon — by astronomical standards — be dissolved. The Milky Way has a similar companion, known as the Sagittarius Dwarf galaxy, which has been wrapped around our galaxy as it orbits and which loses its stars to the Milky Way’s gravitational tug.

    With the help of the wide field of the C28 telescope and special image processing conducted by Christine Black, a UCLA research assistant, and David Reitzel of the Griffith Observatory, the astronomers were able to subtract the light of the sky and that of the outer parts of NGC 4449 to reveal the new galaxy.

    The deep images of the larger NGC 4449 revealed other surprises as well: a strange arc of stars that might be an ingested galaxy, and a “remarkable halo” of old stars that appears to consist of two parts; the outermost part of this “halo” population was unexpected, and makes NGC 4449 equivalent in size to the Milky Way.

    The origin of these old stars is not known, but they may have been acquired when galaxies similar to NGC 4449B fell into NGC 4449 and were shredded, Rich said.

    “Our own galaxy, the Milky Way, has a host of smaller galaxies which orbit around it, ” added Andrew Benson, a co-author and a senior research fellow in theoretical cosmology at the California Institute of Technology. “On much larger scales, we see groups and clusters of galaxies which orbit under the pull of their mutual gravitational attraction. Gravity has no preferred length scale, so we’d expect that dark matter (which interacts only through gravity) should behave in more or less the same way on all scales. For a galaxy like NGC4449, that means it should have its own system of small dark-matter satellites orbiting around it — assuming that dark matter works the way we think it does.”

    Original UCLA article is here.

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  • richardmitnick 6:35 pm on December 14, 2014 Permalink | Reply
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    From Daily Galaxy: “The Messier 67 Mystery’ –Is Our Solar System an Orphan from a Distant Star Cluster?” 

    Daily Galaxy
    The Daily Galaxy

    December 14, 2014
    via ESO

    Astronomers over the decades have been searching for star clusters that could have shared our original region of the galaxy that come close to matching the composition and age of our Sun. The prime suspect so far One is a collective known as Messier 67, some 2,700 light-years distant that contains more than a hundred stars that bear a striking resemblance to the Sun. This cluster lies about 2500 light-years away in the constellation of Cancer (The Crab) and contains about 500 stars. Many of the cluster stars are fainter than those normally targeted for exoplanet searches and trying to detect the weak signal from possible planets pushed HARPS to the limit.

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    M67

    ESO HARPS
    ESO HARPS

    This past January, astronomers used the ESO’s HARPS planet hunter in Chile, along with other telescopes around the world, to discover three planets orbiting stars in Messier 67. Although more than one thousand planets outside the Solar System are now confirmed, only a handful have been found in star clusters. Remarkably one of these new exoplanets is orbiting a star that is a rare solar twin — a star that is almost identical to the Sun in all respects.

    Up to now, very few planets have been found inside star clusters. This is particularly odd as it is known that most stars are born in such clusters. Astronomers have wondered if there might be something different about planet formation in star clusters to explain this strange paucity.

    Star clusters come in two main types. Open clusters are groups of stars that have formed together from a single cloud of gas and dust in the recent past. They are mostly found in the spiral arms of a galaxy like the Milky Way. On the other hand globular clusters are much bigger spherical collections of much older stars that orbit around the centre of a galaxy. Despite careful searches, no planets have been found in a globular cluster and less than six in open clusters. Exoplanets have also been found in the past two years in the clusters NGC 6811 and Messier 44, and even more recently one has also been detected in the bright and nearby Hyades cluster.

    Anna Brucalassi (Max Planck Institute for Extraterrestrial Physics, Garching, Germany), lead author of the new study, and her team wanted to find out more. “In the Messier 67 star cluster the stars are all about the same age and composition as the Sun. This makes it a perfect laboratory to study how many planets form in such a crowded environment, and whether they form mostly around more massive or less massive stars.”

    The team used the HARPS planet-finding instrument on ESO’s 3.6-metre telescope at the La Silla Observatory. These results were supplemented with observations from several other observatories around the world. They carefully monitored 88 selected stars in Messier 67 over a period of six years to look for the tiny telltale motions of the stars towards and away from Earth that reveal the presence of orbiting planets.

    ESO 3.6m telescope & HARPS at LaSilla
    ESO/3.6 Meter Telescope and HARPS

    ESO LaSilla Long View
    ESO La Silla

    Three planets were discovered, two orbiting stars similar to the Sun and one orbiting a more massive and evolved red giant star. The first two planets both have about one third the mass of Jupiter and orbit their host stars in seven and five days respectively. The third planet takes 122 days to orbit its host and is more massive than Jupiter.

    The first of these planets proved to be orbiting a remarkable star — it is one of the most similar solar twins identified so far and is almost identical to the Sun (eso1337 – http://www.eso.org/public/news/eso1337/) . It is the first solar twin in a cluster that has been found to have a planet. Solar twins, solar analogues and solar-type stars are categories of stars according to their similarity to the Sun. Solar twins are the most similar to the Sun, as they have very similar masses, temperatures, and chemical abundances. Solar twins are very rare, but the other classes, where the similarity is less precise, are much more common.

    Two of the three planets are “hot Jupiters” — planets comparable to Jupiter in size, but much closer to their parent stars and hence much hotter. All three are closer to their host stars than the habitable zone where liquid water could exist.

    “These new results show that planets in open star clusters are about as common as they are around isolated stars — but they are not easy to detect,” adds Luca Pasquini (ESO, Garching, Germany), co-author of the new paper. “The new results are in contrast to earlier work that failed to find cluster planets, but agrees with some other more recent observations. We are continuing to observe this cluster to find how stars with and without planets differ in mass and chemical makeup.

    But is our Sun actually an orphan, ejected billions of years ago from Messier 67? Recent computer simulations of the motions of stars in the cluster and have projected the path that our solar system would have had to take if it were ejected and concluded that it doesn’t seem highly probable. It would require a very rare alignment of no less than two or three massive stars in Messier 67 to provide the gravitational slingshot to throw our solar system out to where we are today, not to mention that the gravitational forces would likely have torn our infant solar system to shreds.

    The scientific community is still in hot debate over our galactic origins, but there is little doubt that, one way or the other, we have been orphaned from somewhere in the outer regions of the Milky Way.

    See the full article here.

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  • richardmitnick 4:38 pm on December 5, 2014 Permalink | Reply
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    From Daily Galaxy: “Discovery of a Pulsar and Supermassive Black Hole Pairing Could Help Unlock the Enigma of Gravity” 

    Daily Galaxy
    The Daily Galaxy

    Last year, the very rare presence of a pulsar (named SGR J1745-2900) was also detected in the proximity of a supermassive black hole (Sgr A**, made up of millions of solar masses), but there is a combination that is still yet to be discovered: that of a pulsar orbiting a ‘normal’ black hole; that is, one with a similar mass to that of stars.

    b

    sgr

    Supermassive Black Hole Sagittarius A*

    The center of the Milky Way galaxy, with the supermassive black hole Sagittarius A* (Sgr A*), located in the middle, is revealed in these images. As described in our press release, astronomers have used NASA’s Chandra X-ray Observatory to take a major step in understanding why material around Sgr A* is extraordinarily faint in X-rays.

    NASA Chandra Telescope
    NASA/Chandra

    The large image contains X-rays from Chandra in blue and infrared emission from the Hubble Space Telescope in red and yellow. The inset shows a close-up view of Sgr A* in X-rays only, covering a region half a light year wide. The diffuse X-ray emission is from hot gas captured by the black hole and being pulled inwards. This hot gas originates from winds produced by a disk-shaped distribution of young massive stars observed in infrared observations.

    NASA Hubble Telescope
    NASA/ESA Hubble

    These new findings are the result of one of the biggest observing campaigns ever performed by Chandra. During 2012, Chandra collected about five weeks worth of observations to capture unprecedented X-ray images and energy signatures of multi-million degree gas swirling around Sgr A*, a black hole with about 4 million times the mass of the Sun. At just 26,000 light years from Earth, Sgr A* is one of very few black holes in the universe where we can actually witness the flow of matter nearby.

    The authors infer that less than 1% of the material initially within the black hole’s gravitational influence reaches the event horizon, or point of no return, because much of it is ejected. Consequently, the X-ray emission from material near Sgr A* is remarkably faint, like that of most of the giant black holes in galaxies in the nearby Universe.

    The captured material needs to lose heat and angular momentum before being able to plunge into the black hole. The ejection of matter allows this loss to occur.

    This work should impact efforts using radio telescopes to observe and understand the “shadow” cast by the event horizon of Sgr A* against the background of surrounding, glowing matter. It will also be useful for understanding the impact that orbiting stars and gas clouds might make with the matter flowing towards and away from the black hole.

    The paper is available online and is published in the journal Science. The first author is Q.Daniel Wang from University of Massachusetts at Amherst, MA; and the co-authors are Michael Nowak from Massachusetts Institute of Technology (MIT) in Cambridge, MA; Sera Markoff from University of Amsterdam in The Netherlands, Fred Baganoff from MIT; Sergei Nayakshin from University of Leicester in the UK; Feng Yuan from Shanghai Astronomical Observatory in China; Jorge Cuadra from Pontificia Universidad de Catolica de Chile in Chile; John Davis from MIT; Jason Dexter from University of California, Berkeley, CA; Andrew Fabian from University of Cambridge in the UK; Nicolas Grosso from Universite de Strasbourg in France; Daryl Haggard from Northwestern University in Evanston, IL; John Houck from MIT; Li Ji from Purple Mountain Observatory in Nanjing, China; Zhiyuan Li from Nanjing University in China; Joseph Neilsen from Boston University in Boston, MA; Delphine Porquet from Universite de Strasbourg in France; Frank Ripple from University of Massachusetts at Amherst, MA and Roman Shcherbakov from University of Maryland, in College Park, MD. Image credit: X-ray: NASA/UMass/D.Wang et al., IR: NASA/STScI

    k.
    This image was taken with NASA’s Chandra X-Ray Observatory.

    The intermittent light emitted by pulsars, the most precise timekeepers in the universe, allows scientists to verify Einstein’s theory of relativity, especially when these objects are paired up with another neutron star or white dwarf that interferes with their gravity. However, this theory could be analysed much more effectively if a pulsar with a black hole were found, except in two particular cases, according to researchers from Spain and India.

    Pulsars are very dense neutron stars that are the size of a city (their radius approaches ten kilometres), which, like lighthouses for the universe, emit gamma radiation beams or X-rays when they rotate up to hundreds of times per second. These characteristics make them ideal for testing the validity of the theory of general relativity, published by Einstein between 1915 and 1916.

    “Pulsars act as very precise timekeepers, such that any deviation in their pulses can be detected,” Diego F. Torres, ICREA researcher from the Institute of Space Sciences (IEEC-CSIC), explains to SINC. “If we compare the actual measurements with the corrections to the model that we have to use in order for the predictions to be correct, we can set limits or directly detect the deviation from the base theory.”

    These deviations can occur if there is a massive object close to the pulsar, such as another neutron star or a white dwarf. A white dwarf can be defined as the stellar remnant left when stars such as our Sun use up all of their nuclear fuel. The binary systems, comprised of a pulsar and a neutron star (including double pulsar systems) or a white dwarf, have been very successfully used to verify the theory of gravity.

    Until now scientists had considered the strange pulsar/black hole pairing to be an authentic ‘holy grail’ for examining gravity, but there exist at least two cases where other pairings can be more effective. This is what is stated in the study that Torres and the physicist Manjari Bagchi, from the International Centre of Theoretical Sciences (India) and now postdoc at the IEEC-CSIC, have published in the Journal of Cosmology and Astroparticle Physics. The work also received an Honourable Mention in the 2014 Essays of Gravitation prize.

    The first case occurs when the so-called principle of strong equivalence is violated. This principle of the theory of relativity indicates that the gravitational movement of a body that we test only depends on its position in space-time and not on what it is made up of, which means that the result of any experiment in a free fall laboratory is independent of the speed of the laboratory and where it is found in space and time.

    The other possibility is if one considers a potential variation in the gravitational constant that determines the intensity of the gravitational pull between bodies. Its value is G = 6.67384(80) x 10-11 N m2/kg2. Despite it being a constant, it is one of those that is known with the least accuracy, with a precision of only one in 10,000.

    In these two specific cases, the pulsar-black hole combination would not be the perfect ‘holy grail’, but in any case scientists are anxious to find this pair, because it could be used to analyse the majority of deviations. In fact, it is one of the desired objectives of X-ray and gamma ray space telescopes (such as Chandra, NuStar or Swift), as well as that of large radio telescopes that are currently being built, such as the enormous ‘Square Kilometre Array’ (SKA) in Australia and South Africa.

    NASA NuSTAR
    NASA/Nu-STAR

    NASA SWIFT Telescope
    NASA/Swift

    SKA Square Kilometer Array

    The image at the top of the page shows dynamic rings, wisps and jets of matter and antimatter around the pulsar in the Crab Nebula as observed in X-ray light by Chandra Space Observatory in 2001.

    Manjari Bagchi y Diego F. Torres. “In what sense a neutron star−black hole binary is the holy grail for testing gravity?”. Journal of Cosmology and Astroparticle Physics, 2014. Doi:10.1088/1475-7516/2014/08/055.

    See the full article here.

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  • richardmitnick 12:16 pm on November 30, 2014 Permalink | Reply
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    From Daily Galaxy: “DNA’s Ability to Survive Extreme Conditions of Space –‘Has Implications in Search for Extraterrestrial Life'” 

    Daily Galaxy
    The Daily Galaxy

    November 30, 2014
    via University of Zurich

    DNA can survive a flight through space and re-entry into Earth’s atmosphere — and still pass on genetic information. A team of scientists from the University of Zurich obtained these astonishing results during an experiment on the TEXUS-49 research rocket mission. Various scientists believe that DNA could certainly reach us from outer space as Earth is not insulated: in extraterrestrial material made of dust and meteorites, for instance, around 100 tons of which hits our planet every day.
    “This study provides experimental evidence that the DNA’s genetic information is essentially capable of surviving the extreme conditions of space and the re-entry into Earth’s dense atmosphere,” says study head Oliver Ullrich from the University of Zurich’s Institute of Anatomy.

    dna
    No image credit

    This extraordinary stability of DNA under space conditions also needs to be factored into the interpretion of results in the search for extraterrestrial life: “The results show that it is by no means unlikely that, despite all the safety precautions, space ships could also carry terrestrial DNA to their landing site. We need to have this under control in the search for extraterrestrial life,” points out Ullrich.

    Applied to the outer shell of the payload section of a rocket using pipettes, small, double-stranded DNA molecules flew into space from Earth and back again. After the launch, space flight, re-entry into Earth’s atmosphere and landing, the so-called plasmid DNA molecules were still found on all the application points on the rocket from the TEXUS-49 mission. And this was not the only surprise: For the most part, the DNA salvaged was even still able to transfer genetic information to bacterial and connective tissue cells.

    The experiment called DARE (DNA atmospheric re-entry experiment) resulted from a spontaneous idea: UZH scientists Dr. Cora Thiel and Ullrich were conducting experiments on the TEXUS-49 mission to study the role of gravity in the regulation of gene expression in human cells using remote-controlled hardware inside the rocket’s payload. During the mission preparations, they began to wonder whether the outer structure of the rocket might also be suitable for stability tests on so-called biosignatures.

    “Biosignatures are molecules that can prove the existence of past or present extraterrestrial life,” explains Dr. Thiel. And so the two UZH researchers launched a small second mission at the European rocket station Esrange in Kiruna, north of the Arctic Circle.

    The quickly conceived additional experiment was originally supposed to be a pretest to check the stability of biomarkers during spaceflight and re-entry into the atmosphere. Dr. Thiel did not expect the results it produced: “We were completely surprised to find so much intact and functionally active DNA.” The study reveals that genetic information from the DNA can essentially withstand the most extreme conditions..

    Two types of biomolecules serve as the genetic information carriers for all Earthly biota. RNA on its own suffices for the business of life for simpler creatures, such as some viruses. Complex life, like humans, however, relies on DNA as its genetic carrier. Extremophiles have been discovered in recent decades thriving in strongly acidic hot springs, within liquid asphalt, and in other eyebrow-raising niches. Salt-tolerant bacteria and archaea, like H. volcanii, have been found to survive in deserts, and simulated Mars conditions. We should not be surprised, perhaps, if life has managed to take hold on formidable worlds.

    See the full article here.

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  • richardmitnick 2:14 pm on November 29, 2014 Permalink | Reply
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    From Daily Galaxy: “The Hunt for Colossal “Quark” Stars –Do They Exist?” 

    Daily Galaxy
    The Daily Galaxy

    November 29, 2014

    No Writer Credit

    “We haven’t found strange stars yet,” explains Prashanth Jaikumar from the Argonne National Laboratory. “But that doesn’t mean they don’t exist. Maybe we have found them. Maybe some of these neutron stars are really strange stars. According to our theory, it would be very difficult to tell a strange star from a neutron star.”

    Recent research suggests that neutron stars may gradually transform into ‘strange’ stars – i.e. in stars made up primarily from the ‘strange’ quark. The conventional wisdom is that the electric field of a such a hypothetical strange star (made up from strange matter) at its surface would be so huge and its luminosity so big that it would be impossible to confuse it with anything else.

    However, Jaikumar and his fellow researchers from the Argonne National Laboratory, and two colleagues from Los Alamos National Laboratory in New Mexico, have challenged that. The team developed a theory about what a strange star would look like.

    One of the most interesting aspects of neutron stars is that they are not gaseous like usual stars, but they are so closely packed that they are liquid. Strange stars should also be liquid with a surface that is solid.

    However, Jaikumar and his colleagues challenge that. Strange stars are usually assumed to exhibit huge electric fields on their surface precisely because they are assumed to have a smooth surface. But according to the scientists neither neutron stars nor strange stars have such a smooth solid-like surface.

    “It’s like taking water,” Jaikumar says, “with a flat surface. Add detergent and it reduces surface tension, allowing bubbles to form. In a strange star, the bubbles are made of strange quark matter, and float in a sea of electrons. Consequently, the star’s surface may be crusty, not smooth. The effect of surface tension had been overlooked before.”

    One consequence is that a strange star wouldn’t have large electrical field at surface or be super-luminous. It also allows for a strange star to be less dense than originally thought, although such stars are definitely unusually dense compared to regular stars.

    Much of the matter in our Universe may be made of a type of dark matter called weakly interacting massive particles, also known as WIMPs, . Although some scientists predict that these hypothetical particles possess many of the necessary properties to account for dark matter, until recently scientists have not been able to make any definite predictions of their mass. In a new study, physicists have derived a limit on the WIMP mass by calculating how these dark matter particles can transform neutron stars into stars made of strange quark matter, or “strange” stars.

    h

    WIMPs are thought to be largely located in the halos of galaxies. Although galaxy halos (image above) are not visible, they contain most of a galaxy’s mass in the form of the heavy WIMPs.

    Dr. M. Angeles Perez-Garcia from the University of Salamanca in Salamanca, Spain, along with Dr. Joseph Silk of the University of Oxford and Dr. Jirina R. Stone of the University of Oxford and the University of Tennessee showed that, when a neutron star gravitationally captures nearby WIMPs, the WIMPs may trigger the conversion of the neutron star into a strange star.

    One important issue is whether at high density ‘strange’ quark matter is more stable than regular matter (which is comprised of ‘up’ and ‘down’ quarks). Jaikumar and colleagues think that as a neutron star spins down and its core density increases, it may convert into the more stable state of strange quark matter, forming a strange star.

    Theorists cannot say with absolute certainty whether or not a neutron star gradually converts into a strange star. The conversion occurs, according to new research, as a result of the WIMPs seeding the neutron stars with long-lived lumps of strange quark matter, or strangelets. WIMPs captured in the neutron star’s core self-annihilate, releasing energy in the process.

    According to Jaikumar, making the distinction is rather tricky: “There might be a slight difference. You’d look at surface temperature and see how stars are cooling in time. If it is quark matter, the emission rates are different, so the strange star may cool a little faster.”

    It’s the astronomers’ job to discover whether strange stars exist or not. Either discovery will have important implications for the theory of Quantum Chromodynamics (QCD) — which is the fundamental theory of quarks. “Finding a strange star would improve our understanding of QCD, the fundamental theory of the nuclear force. And it would also be the first solid evidence of stable quark matter”, Jaikumar said.

    Elsewhere, Kwong-Sang Cheng of the University of Hong Kong, China, and colleagues have presented evidence that a quark star formed in a bright supernova called SN 1987A (above), which is among the nearest supernovae to have been observed.

    Observing a quark star could shed light on what happened just after the Big Bang, because at this time, the Universe was filled with a dense sea of quark matter superheated to a trillion °C. While some groups have claimed to have found candidate quark stars, no discovery has yet been confirmed.

    Now Kwong-Sang Cheng of the University of Hong Kong, China, and colleagues have presented evidence that a quark star formed in a bright supernova called SN 1987A (pictured), which is among the nearest supernovae to have been observed.

    The birth of a neutron star is known to be accompanied by a single burst of neutrinos. But when the team examined data from two neutrino detectors – Kamiokande II in Japan and Irvine-Michigan-Brookhaven in the US – they found that SN 1987A gave off two separate bursts.

    “There is a significant time delay between [the bursts recorded by] these two detectors,” says Cheng. They believe the first burst was released when a neutron star formed, while the second was triggered seconds later by its collapse into a quark star. The results appeared in The Astrophysical Journal (http://www.arxiv.org/abs/0902.0653v1).

    “This model is intriguing and reasonable,” says Yong-Feng Huang of Nanjing University, China. “It can explain many key features of SN 1987A.” However, Edward Witten of the Institute for Advanced Study in Princeton, New Jersey, is not convinced. “I hope they’re right,” he says. “My first reaction, though, is that this is a bit of a long shot.”

    High-resolution X-ray observatories, due to fly in space in the next decade, may have the final say. Neutron stars and quark stars should look very different at X-ray wavelengths, says Cheng.

    The image of SN 1987A at top of the page combines data from NASA’s orbiting Chandra X-ray Observatory and the 8-meter Gemini South infrared telescope in Chile, which is funded primarily by the National Science Foundation.

    The X-ray light detected by Chandra is colored blue. The infrared light detected by Gemini South is shown as green and red, marking regions of slightly higher and lower-energy infrared, respectively. The core remains of the star that exploded in 1987 is not visible here. The ring is produced by hot gas (largely the X-ray light) and cold dust (largely the infrared light) from the exploded star interacting with the interstellar region. Credit: Gemini/NASA

    “Supernova 1987A is changing right before our eyes,” said Dr. Eli Dwek, a cosmic dust expert at NASA Goddard Space Flight Center in Greenbelt, Md. For several years Dwek has been following this supernova, named 1987A for the year it was discovered in the Large Magellanic Cloud, a neighboring dwarf galaxy. “What we are seeing now is a milestone in the evolution of a supernova.”

    See the full article here.

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  • richardmitnick 8:49 am on November 18, 2014 Permalink | Reply
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    From Daily Galaxy: “Ancient Antarctica Lake Provides Clues to One of the Unsolved Mysteries of Early Earth” 

    Daily Galaxy
    The Daily Galaxy

    November 17, 2014
    via astrobiology.com and Woods Hole Oceanographic Institution

    While the extinction of the dinosaurs has largely been explained by the impact of a large meteorite, the crash of the stromatolites remains unsolved. “It’s one of the major questions in Earth history,” says Woods Hole Oceanographic Institution microbial ecologist Virginia Edgcomb.

    l

    The Antarctic discovery in an ancient lake in April of 2011 helped scientists better understand the conditions under which the Earth’s primitive life-forms thrived. “It’s like going back to early Earth,” said Dawn Sumner, a geobiologist at the University of California, Davis, describing her explorations of the eerie depths of East Antarctica’s Lake Untersee where Sumner and her colleagues, led by Dale Andersen of the SETI Institute in Mountain View, Calif., discovered otherworldly mounds of Photosynthetic microbial stromatolites.

    lake

    “The weather looks to be pretty good tomorrow, with clear skies and low winds, at least for Novo. Monday and Tuesday the weather may go down with 45 kt winds so we need to get the camp up as soon as possible….at least a few tents anyway. It will be great to get back to the lake, and everyone is pretty excited now.” Reports Dale Andersen of the SETI Institute in Mountain View, Calif in his Field Report from Lake Untersee, Antarctica 15 November 2014.

    The stromatolites, built layer by layer by bacteria on the lake bottom, resemble similar structures that first appeared billions of years ago and remain in fossil form as one of the oldest widespread records of ancient life dating from 3 billion years ago or more, to understand how life got a foothold on Earth.

    more

    Lake Untersee is located at 71°20’S, 13°45’E in the Otto-von-Gruber-Gebirge (Gruber Mountains) of central Dronning Maud Land.The lake is 563 meters above sea level, with an area of 11.4 square kilometers and is the largest surface lake in East Antarctica.

    The purple-bluish mounds are composed of long, stringy cyanobacteria, ancient photosynthetic organisms. Similar to coral reef organisms, the bacteria takes decades to build each layer in Untersee’s icy waters, Sumner said, so the mounds may have taken thousands of years to accumulate.

    Today, stromatolites are found in only a few spots in the ocean, including off the western coast of Australia and in the Bahamas. They they have also been found thriving in freshwater environments, such as super-salty lakes high in the Andes and in a few of Antarctica’s other freshwater lakes.

    But scientists were stunned by the size and shape of the purplish stromatolite mounds built by Phormidium bacteria in Untersee’s extremely alkaline waters and high concentrations of dissolved methane, are unique reaching up to half a meter high, dotting the lake floor. “It totally blew us away,” Andersen said. “We had never seen anything like that.” The stromatolite mounds were found adjacent to smaller, pinnacle-shaped lumps made of another bacterial group, Leptolyngbya.

    “Everywhere else that we’ve looked you have a gradation between the structures,” like in bacterial mats sprawling around Yellowstone’s hot springs, she said. “There’s something very special about this particular example that’s allowing these large conical stromatolites to form.”

    The widespread disappearance of stromatolites, the earliest visible manifestation of life on Earth, may have been driven by single-celled organisms called foraminifera. Stromatolites (“layered rocks”) are structures made of calcium carbonate and shaped by the actions of photosynthetic cyanobacteria and other microbes that trapped and bound grains of coastal sediment into fine layers. They showed up in great abundance along shorelines all over the world about 3.5 billion years ago.

    “Stromatolites were one of the earliest examples of the intimate connection between biology—living things—and geology—the structure of the Earth itself,” said Woods Hole Oceanographic Institution (WHOI) geobiologist Joan Bernhard.

    The growing bacterial community secreted sticky compounds that bound the sediment grains around themselves, creating a mineral “microfabric” that accumulated to become massive formations. Stromatolites dominated the scene for more than two billion years, until late in the Proterozoic Eon.

    “Then, around 1 billion years ago, their diversity and their fossil abundance begin to take a nosedive,” said Bernhard. All over the globe, over a period of millions of years, the layered formations that had been so abundant and diverse began to disappear. To paleontologists, their loss was almost as dramatic as the extinction of the dinosaurs millions of years later, although not as complete: Living stromatolites can still be found today, in limited and widely scattered locales, as if a few velociraptors still roamed in remote valleys.

    Just as puzzling is the sudden appearance in the fossil record of different formations called thrombolites (“clotted stones”). Like stromatolites, thrombolites are produced through the action of microbes on sediment and minerals. Unlike stromatolites, they are clumpy, rather than finely layered.

    It’s not known whether stromatolites became thrombolites, or whether thrombolites arose independently of the decline in strombolites. Hypotheses proposed to explain both include changes in ocean chemistry and the appearance of multicellular life forms that might have preyed on the microbes responsible for their structure.

    Bernhard and Edgcomb thought foraminifera might have played a role. Foraminifera (or “forams,” for short) are protists, the kingdom that includes amoeba, ciliates, and other groups formerly referred to as “protozoa.” They are abundant in modern-day oceanic sediments, where they use numerous slender projections called pseudopods to engulf prey, to move, and to continually explore their immediate environment. Despite their known ability to disturb modern sediments, their possible role in the loss of stromatolites and appearance of thrombolites had never been considered.

    The Woods Hole researchers examined modern stromatolites and thrombolites from Highborne Cay in the Bahamas for the presence of foraminifera. Using microscopic and rRNA sequencing techniques, they found forams in both kinds of structures. Thrombolites were home to a greater diversity of foraminifera and were especially rich in forams that secrete an organic sheath around themselves. These “thecate” foraminifera were probably the first kinds of forams to evolve, not long (in geologic terms) before stromatolites began to decline.

    “The timing of their appearance corresponds with the decline of layered stromatolites and the appearance of thrombolites in the fossil record,” said Edgcomb. “That lends support to the idea that it could have been forams that drove their evolution.”

    Next, Bernhard, Edgcomb, and postdoctoral investigator Anna McIntyre-Wressnig created an experimental scenario that mimicked what might have happened a billion years ago.

    “No one will ever be able to re-create the Proterozoic exactly, because life has evolved since then, but you do the best you can,” Edgcomb said.

    They started with chunks of modern-day stromatolites collected at Highborne Cay, and seeded them with foraminifera found in modern-day thrombolites. Then they waited to see what effect, if any, the added forams had on the stromatolites. After about six months, the finely layered arrangement characteristic of stromatolites had changed to a jumbled arrangement more like that of thrombolites. Even their fine structure, as revealed by CAT scans, resembled that of thrombolites collected from the wild. “The forams obliterated the microfabric,” said Bernhard.

    That result was intriguing, but it did not prove that the changes in the structure were due to the activities of the foraminifera. Just being brought into the lab might have caused the changes. But the researchers included a control in their experiment: They seeded foraminifera onto freshly-collected stromatolites as before, but also treated them with colchicine, a drug that prevented them from sending out pseudopods. “They’re held hostage,” said Bernhard. “They’re in there, but they can’t eat, they can’t move.”

    After about six months, the foraminifera were still present and alive—but the rock’s structure had not become more clotted like a thrombolite. It was still layered. The researchers concluded that active foraminifera can reshape the fabric of stromatolites and could have instigated the loss of those formations and the appearance of thrombolites.

    The findings, by scientists at Woods Hole Oceanographic Institution (WHOI); Massachusetts Institute of Technology; the University of Connecticut; Harvard Medical School; and Beth Israel Deaconess Medical Center, Boston, were published online in the Proceedings of the National Academy of Sciences.

    The Woods Hole Oceanographic Institution is a private, non-profit organization on Cape Cod, Mass., dedicated to marine research, engineering, and higher education. Established in 1930 on a recommendation from the National Academy of Sciences, its primary mission is to understand the oceans and their interaction with the Earth as a whole, and to communicate a basic understanding of the oceans’ role in the changing global environment.

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  • richardmitnick 5:02 pm on November 14, 2014 Permalink | Reply
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    From DG: “‘The Supermassive Shadow’ –Imaging the Glow of Milky Way’s Central Black Hole 

    Daily Galaxy
    The Daily Galaxy

    November 14, 2014
    via Daniel Stolte/University of Arizona

    With the sci-fi movie Interstellar — hitting theaters last week — with its computer-generated views of one of most enigmatic and fascinating phenomena in the universe, University of Arizona astrophysicists are likely to nod appreciatively and say something like, “Meh, that looks nice, but check out what we’ve got.”

    “We want to know what happens near extremely compact objects such as black holes and neutron stars,” said Dimitrios Psaltis, a professor of astronomy and physics in the UA’s Department of Astronomy and Steward Observatory. “We want to watch as matter fed onto a black hole crosses the event horizon, the point of no return, and disappears.”

    Steward Observatory
    Steward Observatory interior
    Steward Observtory

    To find answers, the group created a monster in the basement of the UA’s high-performance computing facility. Harnessing the power of the UA’s new supercomputer — nicknamed El Gato — the researchers combined knowledge from mathematical equations and astronomical observations to generate visualizations of an object known by astronomers as Sagittarius A* (“Sagittarius A star”), a supermassive black hole comprising the mass of 4.3 million suns.

    sa
    sa2
    two images of Sagittarius A* from NASA/Chandra

    NASA Chandra Telescope
    NASA Chandra schematic
    NASA/Chandra

    Located 26,000 light-years from Earth at the center of our galaxy, Sagittarius A* is tiny to the eyes of astronomers. Smaller than Mercury’s orbit around the sun, it appears about the same size as a grapefruit on the moon.

    The team just published the first major science results obtained using El Gato’s unique, massive, parallel-computing capabilities to create visualizations of what a space traveler might see upon approaching SgrA**. The results, published in two reports in the Astrophysical Journal — one focusing on the imaging and the other on the computing — provide some of the groundwork for the Event Horizon Telescope, or EHT, a huge undertaking involving scientists and observatories around the world to take the first-ever picture of SgrA*.

    Event Horizon Telescope
    EHT

    The film Interstellar, starring Matthew McConaughey and Anne Hathaway, prominently features a black hole, touted as the first visual depictions based on the actual science and mathematics of [Albert]Einstein’s Theory of General Relativity. On some of the renderings, a special-effects team of about 30 experts reportedly spent up to 100 hours of running calculations to create each frame.

    Our team of four here at the UA can produce visuals of a black hole that are more scientifically accurate in a few seconds,” said Feryal Ozel, also a professor of astronomy and physics at Steward Observatory. “It’s a bit like gaming on steroids,” she explained. “El Gato uses a massively parallel architecture of hundreds of graphic processors working side by side, with each node functioning as a renderer in real time.”

    As part of a collaboration that includes the papers’ first author, postdoctoral fellow Chi-kwan Chan, and researchers at Harvard University and MIT, the husband-and-wife research team of Psaltis and Ozel developed software algorithms capable of calculating the paths of millions of individual photons in mere seconds as they shoot toward the black hole.

    Funded by the National Science Foundation and NASA, the computer simulations are a crucial step before astronomers can start to look for the black hole using the EHT, functioning as a sort of field ID guide of what astronomers should look for once the EHT is up and running.

    The EHT will combine radio telescopes across the globe to create a virtual telescope the size of the Earth. These include the UA’s Arizona Radio Observatory as well as the South Pole Telescope, outfitted with new receivers built by a group led by UA assistant professor of astronomy Daniel Marrone.

    Arizona Radio Observatory
    Arizona Radio Observatory

    South Pole Telescope
    South Pole Telescope

    “We wouldn’t be able to observe a black hole against a black sky,” Ozel said. “Therefore, we look for other telltale signatures telling us about the presence of a black hole.”

    The gravitational field around a black hole is so immense that it swallows everything in its reach. Not even light can escape its grip. For that reason, black holes are just that: They emit no light whatsoever, and their “nothingness” blends into the black void of the universe.

    As matter comes under the black hole’s spell of extreme gravity, a cosmic traffic jam ensues, in which gas swirls around it like water circling a drain. As matter compresses, the resulting friction turns it into plasma heated to a billion degrees or more, causing it to “glow” — and radiate energy that astronomers can detect here on Earth.

    “Our visualizations show there is a place where photons linger and form a ring outlining the shadow of the black hole,” Psaltis said. “That ring of light makes the black hole easier to find than if we were looking for complete blackness. These simulations also help us find ways to distinguish this signature from all this swirling plasma around the black hole.”

    By imaging the glow of matter swirling around the black hole before it goes over the edge and plunges into the abyss of space and time, scientists can see only the outline of the black hole, also called its shadow.

    In addition to providing groundwork for the EHT, the simulations will support NICER, a new NASA mission involving an instrument that will be attached to the International Space Station, to help scientists better understand neutron stars and to test navigation methods for future spacecraft using neutron stars as extremely accurate clocks.

    NASA NICER
    NASA NICER

    Until EHT is ready to take the first images of what lurks at the center of our Milky Way, astrophysicists will have to get by with gaming on steroids — or going to the movies.

    See the full article here.

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