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  • richardmitnick 4:34 pm on June 20, 2018 Permalink | Reply
    Tags: , Astronomy, , , , Exploring Jets from a Supermassive Black Hole   

    From AAS NOVA: “Exploring Jets from a Supermassive Black Hole” 

    AASNOVA

    From AAS NOVA

    1
    The double-sided jets of the active galaxy NGC 4261, shown here in this composite optical (white) and radio (orange) image, span around 88,000 light-years across. A new study explores the structure and properties of these jets. [HST/NASA/ESA/NRAO]

    What are the feeding — and burping — habits of the supermassive black holes peppering the universe? In a new study, observations of one such monster reveal more about the behavior of its powerful jets.

    Beams from Behemoths

    Across the universe, supermassive black holes of millions to billions of solar masses lie at the centers of galaxies, gobbling up surrounding material. But not all of the gas and dust that spirals in toward a black hole is ultimately swallowed! A large fraction of it can instead be flung out into space again, in the form of enormous, powerful jets that extend for thousands or even millions of light-years in opposite directions.

    2
    Messier 87, shown in this Hubble image, is a classic example of a nearby (55 million light-years distant) supermassive black hole with a visible, collimated jet. Its counter-jet isn’t seen because relativistic effects make the receding jet appear less bright. [The Hubble Heritage Team (STScI/AURA) and NASA/ESA]

    What causes these outflows to be tightly beamed — collimated — in the form of jets, rather than sprayed out in all directions? Does the pressure of the ambient medium — the surrounding gas and dust that the jet is injected into — play an important role? In what regions do these jets accelerate and decelerate? There are many open questions that scientists hope to understand by studying some of the active black holes with jets that live closest to us.

    Eyes on a Nearby Giant

    In a new study led by Satomi Nakahara (The Graduate University for Advanced Studies in Japan), a team of scientists has used multifrequency Very Long Baseline Array (VLBA) and Very Large Array (VLA) images to explore jets emitted from a galaxy just 100 million light-years away: NGC 4261.

    NRAO/VLBA

    NRAO/Karl V Jansky VLA, on the Plains of San Agustin fifty miles west of Socorro, NM, USA, at an elevation of 6970 ft (2124 m)

    This galaxy’s (relatively) close distance — as well as the fact that we’re viewing it largely from the side, so we can clearly see both of its polar jets — allows us to observe in detail the structure and intensity of its jets as a function of their distance from the black hole. Nakahara and collaborators’ observations span the enormous radial distance of a thousand to a billion times the radius of the black hole, or about 54 light-days to more than a million light-years.

    3
    The width of the jet as a function of radial distance from the black hole, for NGC 4261 (red) compared to the few other jets from nearby supermassive black holes that we’ve measured. NGC 4261’s jets transition from parabolic to conical at around 10,000 times the radius of the black hole (RS). [Nakahara et al. 2018]

    Scale for Change

    The authors’ observations of NGC 4261’s jets indicate that a transition occurs at ~10,000 times the radius of the black hole (that’s a little over a light-year from the black hole). At this point, the jets’ structures change from parabolic (becoming more tightly beamed) to conical (expanding freely). Around the same location, Nakahara and collaborators also see the radiation profile of one of the jets change, suggesting the physical conditions in the jets transition here as well.

    This is the first time we’ve been able to examine jet width this closely for both of the jets emitted from a supermassive black hole. The fact that the structure changes at the same distance for both jets indicates that the shape of these powerful streams is likely governed by global properties of the environment surrounding the galaxy’s nucleus, or properties of the jets themselves, rather than by a local condition.

    The authors next hope to pin down velocities inside NGC 4261’s jets to determine where the jets accelerate and decelerate. This nearby powerhouse is clearly going to be a useful laboratory in the future, helping to unveil the secrets of more distant, feeding monsters.

    Bonus

    Curious what these hungry supermassive black holes look like? Check out this artist’s imagining of NGC 4261, which shows how it feeds from a large, swirling accretion disk and emits fast-moving, collimated jets. [Original video credit to Dana Berry, Space Telescope Science Institute]

    Citation

    Satomi Nakahara et al 2018 ApJ 854 148. http://iopscience.iop.org/article/10.3847/1538-4357/aaa45e/meta The Astrophysical Journal

    Related journal articles
    _________________________________________________
    See the full article for further references with links.

    See the full article here .


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    Please help promote STEM in your local schools.

    Stem Education Coalition

    1

    AAS Mission and Vision Statement

    The mission of the American Astronomical Society is to enhance and share humanity’s scientific understanding of the Universe.

    The Society, through its publications, disseminates and archives the results of astronomical research. The Society also communicates and explains our understanding of the universe to the public.
    The Society facilitates and strengthens the interactions among members through professional meetings and other means. The Society supports member divisions representing specialized research and astronomical interests.
    The Society represents the goals of its community of members to the nation and the world. The Society also works with other scientific and educational societies to promote the advancement of science.
    The Society, through its members, trains, mentors and supports the next generation of astronomers. The Society supports and promotes increased participation of historically underrepresented groups in astronomy.
    The Society assists its members to develop their skills in the fields of education and public outreach at all levels. The Society promotes broad interest in astronomy, which enhances science literacy and leads many to careers in science and engineering.

    Adopted June 7, 2009

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  • richardmitnick 2:19 pm on June 20, 2018 Permalink | Reply
    Tags: Astronomy, , , , , The Surprising Reason Why Neutron Stars Don’t All Collapse To Form Black Holes   

    From Ethan Siegel: “The Surprising Reason Why Neutron Stars Don’t All Collapse To Form Black Holes” 

    From Ethan Siegel
    June 20, 2018

    1
    In the aftermath of the creation of a neutron star, it can have a variety of masses, many of which are far in excess of the most massive white dwarf. But there is a limit to how massive they can get before becoming a black hole, and a simple nuclear physics experiment on a single proton may have just discovered why. (NASA)

    There’s something very special inside a proton and neutron that holds the key.

    There are few things in the Universe that are as easy to form, in theory, as black holes are. Bring enough mass into a compact volume and it gets more and more difficult to gravitationally escape from it. If you were to gather enough matter in a single spot and let gravitation do its thing, you’d eventually pass a critical threshold, where the speed you’d need to gravitationally escape would exceed the speed of light. Reach that point, and you’ll create a black hole.

    But real, normal matter will very much resist getting there. Hydrogen, the most common element in the Universe, will fuse in a chain reaction at high temperatures and densities to create a star, rather than a black hole. Burned out stellar cores, like white dwarfs and neutron stars, can also resist gravitational collapse and stave off becoming a black hole. But while white dwarfs can reach only 1.4 times the mass of the Sun, neutron stars can get twice as massive. At long last, we finally understand why [Nature].

    2
    Sirius A and B, a normal (Sun-like) star and a white dwarf star. Even though the white dwarf is much lower in mass, its tiny, Earth-like size ensures its escape velocity is many times larger. For a neutron stars, masses can be even larger, with physical sizes in the tens of kilometers. (NASA, ESA and G. Bacon (STScI))

    In our Universe, the matter-based objects we know of are all made of just a few simple ingredients: protons, neutrons, and electrons. Each proton and neutron is made up of three quarks, with a proton containing two up and one down quark, and a neutron containing one up and two downs. On the other hand, electrons themselves are fundamental particles. Although particles come in two classes — fermions and bosons — both quarks and electrons are fermions.

    3
    The Standard Model of particle physics accounts for three of the four forces (excepting gravity), the full suite of discovered particles, and all of their interactions. Quarks and leptons are fermions, which have a host of unique properties that the other (bosons) particles do not possess. (Contemporary Physics Education Project / DOE / NSF / LBNL)

    Standard Model of Particle Physics from Symmetry Magazine

    Why should you care? It turns out that these classification properties are vitally important when it comes to the question of black hole formation. Fermions have a few properties that bosons don’t, including:

    they have half-integer (e.g., ±1/2, ±3/2, ±5/2, etc.) spins as opposed to integer (0, ±1, ±2, etc.) spins,
    they have antiparticle counterparts; there are no anti-bosons,
    and they obey the Pauli Exclusion Principle, whereas bosons don’t.

    That last property is the key to staving off collapse into a black hole.

    4
    The energy levels and electron wavefunctions that correspond to different states within a hydrogen atom. Because of the spin = 1/2 nature of the electron, only two (+1/2 and -1/2 states) electrons can be in any given state at once. (PoorLeno / Wikimedia Commons)

    The Pauli exclusion principle, which only applies to fermions, not bosons, states, explicitly, that in any quantum system, no two fermions can occupy the same quantum state. It means that if you take, say, an electron and put it in a particular location, it will have a set of properties in that state: energy levels, angular momentum, etc.

    If you take a second electron and add it to your system, however, in the same location, it is forbidden from having those same quantum numbers. It must either occupy a different energy level, have a different spin (+1/2 if the first was -1/2, for example), or occupy a different location in space. This principle explains why the periodic table is arranged as it is.

    This is why atoms have different properties, why they bind together in the intricate combinations that they do, and why each element in the periodic table is unique: because the electron configuration of each type of atom is unlike any other.

    Periodic table Sept 2017. Wikipedia

    5
    The three valence quarks of a proton contribute to its spin, but so do the gluons, sea quarks and antiquarks, and orbital angular momentum as well. The electrostatic repulsion and the attractive strong nuclear force, in tandem, are what give the proton its size.(APS/Alan Stonebraker)

    Protons and neutrons are similar. Despite being composite particles, made up of three quarks apiece, they behave as single, individual fermions themselves. They, too, obey the Pauli Exclusion Principle, and no two protons or neutrons can occupy the same quantum state. The fact that electrons are fermions is what keeps white dwarf stars from collapsing under their own gravity; the fact that neutrons are fermions prevents neutron stars from collapsing further. The Pauli exclusion principle responsible for atomic structure is responsible for keeping the densest physical objects of all from becoming black holes.

    6
    A white dwarf, a neutron star or even a strange quark star are all still made of fermions. The Pauli degeneracy pressure helps hold up the stellar remnant against gravitational collapse, preventing a black hole from forming. (CXC/M. Weiss)

    And yet, when you look at the white dwarf stars we have in the Universe, they cap out at around 1.4 solar masses: the Chandrasekhar mass limit. The quantum degeneracy pressure arising from the fact that no two electrons can occupy the same quantum state is what prevents black holes from forming until that threshold is crossed.

    In neutron stars, there should be a similar mass limit: the Tolman-Oppenheimer-Volkoff limit. Initially, it was anticipated that this would be about the same as the Chandrasekhar mass limit, since the underlying physics is the same. Sure, it’s not specifically electrons that are providing the quantum degeneracy pressure, but the principle (and the equations) are pretty much the same. But we now know, from our observations, that there are neutron stars much more massive than 1.4 solar masses, perhaps rising as high as 2.3 or 2.5 times the mass of our Sun.

    7
    A neutron star is one of the densest collections of matter in the Universe, but there is an upper limit to their mass. Exceed it, and the neutron star will further collapse to form a black hole. (ESO/Luís Calçada)

    And yet, there are reasons for the differences. In neutron stars, the strong nuclear force plays a role, causing a larger effective repulsion than for a simple model of degenerate, cold gases of fermions (which is what’s relevant for electrons). For the past 20+ years, calculations of the theoretical mass limit for neutron stars have varied tremendously: from about 1.5 to 3.0 solar masses. The reason for the uncertainty has been the unknowns surrounding the behavior of extremely dense matter, like the densities you’ll find inside an atomic nucleus, are not well known.

    Or rather, these unknowns plagued us for a long time, until a new paper last month changed all of that. With the publication of their new paper in Nature, The pressure distribution inside the proton, coauthors V. D. Burkert, L. Elouadrhiri, and F. X. Girod may have just achieved the key advance needed to understand what’s happening inside neutron stars.

    8
    A better understanding of the internal structure of a proton, including how the “sea” quarks and gluons are distributed, has been achieved through both experimental improvements and new theoretical developments in tandem. These results apply to neutrons as well. (Brookhaven National Laboratory)

    Our models of nucleons like protons and neutrons have improved tremendously over the past few decades, coincident with improvements in both computational and experimental techniques. The latest research uses an old technique known as Compton scattering, where electrons are fired at the internal structure of a proton to probe its structure. When an electron interacts (electromagnetically) with a quark, it emits a high-energy photon, along with a scattered electron and leads to nuclear recoil. By measuring all three products, you can calculate the pressure distribution experienced by the quarks inside the atomic nucleus. In a shocking find, the average peak pressure, near the center of the proton, comes out to 10³⁵ pascals: a greater pressure than neutron stars experience anywhere.

    9
    At large distances, quarks are confined within a nucleon. But at short distances, there’s a repulsive pressure that prevents other quarks-and-nuclei from getting too close to each individual proton (or, by extension, neutron). (The quark-confinement-induced pressure distribution in the proton by V.D. Burkert, L. Elouadrhiri, and F.X. Girod)

    In other words, by understanding how the pressure distribution inside an individual nucleon works, we can calculate when and under what conditions that pressure can be overcome. Although the experiment was only done for protons, the results should be analogous for neutrons, too, meaning that, in the future, we should be able to calculate a more exact limit for the masses of neutron stars.

    10
    The masses of stellar remnants are measured in many different ways. This graphic shows the masses for black holes detected through electromagnetic observations (purple); the black holes measured by gravitational-wave observations (blue); neutron stars measured with electromagnetic observations (yellow); and the masses of the neutron stars that merged in an event called GW170817, which were detected in gravitational waves (orange). The result of the merger was a neutron star, briefly, that swiftly became a black hole. (LIGO-Virgo/Frank Elavsky/Northwestern)

    The measurements of the enormous pressure inside the proton, as well as the distribution of that pressure, show us what’s responsible for preventing the collapse of neutron stars. It’s the internal pressure inside each proton and neutron, arising from the strong force, that holds up neutron stars when white dwarfs have long given out. Determining exactly where that mass threshold is just got a great boost. Rather than solely relying on astrophysical observations, the experimental side of nuclear physics may provide the guidepost we need to theoretically understand where the limits of neutron stars actually lie.

    See the full article here .


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    Please help promote STEM in your local schools.

    Stem Education Coalition

    “Starts With A Bang! is a blog/video blog about cosmology, physics, astronomy, and anything else I find interesting enough to write about. I am a firm believer that the highest good in life is learning, and the greatest evil is willful ignorance. The goal of everything on this site is to help inform you about our world, how we came to be here, and to understand how it all works. As I write these pages for you, I hope to not only explain to you what we know, think, and believe, but how we know it, and why we draw the conclusions we do. It is my hope that you find this interesting, informative, and accessible,” says Ethan

     
  • richardmitnick 12:35 pm on June 20, 2018 Permalink | Reply
    Tags: Astronomy, , , , , XMM-Newton Finds Missing Intergalactic Material   

    From Harvard-Smithsonian Center for Astrophysics: “XMM-Newton Finds Missing Intergalactic Material” 

    Harvard Smithsonian Center for Astrophysics


    From Harvard-Smithsonian Center for Astrophysics

    June 20, 2018
    Megan Watzke
    Harvard-Smithsonian Center for Astrophysics
    +1 617-496-7998
    mwatzke@cfa.harvard.edu

    Peter Edmonds
    Harvard-Smithsonian Center for Astrophysics
    +1 617-571-7279
    pedmonds@cfa.harvard.edu

    ESA/XMM Newton

    1
    This figure shows the filamentary structure of the hot gas that represents part of the warm-hot intergalactic medium (WHIM). It is based on a simulation extending over more than 200 million light years. The red and orange regions have the highest densities & the green regions have lower densities. Princeton University/Renyue Cen

    2
    Astronomers have used ESA’s XMM-Newton space observatory (lower right) to detect the WHIM. The white box encloses the filamentary structure of the hot gas that represents part of the WHIM. It is based on a cosmological simulation extending over more than 200 million light years. The red and orange regions have the highest densities & the green regions have lower densities. The discovery was made using observations of a distant quasar – a supermassive black hole that is actively devouring matter and shining brightly from X-rays to radio waves (upper left). The team found the signature of oxygen in the WHIM lying between the observatory and the quasar, at two different locations along the line of sight (shown in the spectrum in the lower left with green and magenta arrows). The blue arrows are signatures of nitrogen in our Milky Way galaxy.
    Illustrations and composition: ESA / ATG medialab; data: ESA / XMM-Newton / F. Nicastro et al. 2018; cosmological simulation: Princeton University/Renyue Cen

    3
    The mysterious dark matter and dark energy make up about 25 and 70 percent of our cosmos respectively, and ordinary matter, which makes up everything we see, including galaxies, stars and planets – amounts to only about five percent. However, stars in galaxies across the Universe only make up about seven percent of all ordinary matter and the cold and hot interstellar gas that permeates galaxies and galaxy clusters together accounts for only about 11 percent. Most of the Universe’s ordinary matter, or baryons, lurks in the cosmic web, the filamentary distribution of both dark and ordinary matter that extends throughout the Universe. In the past astronomers were able to locate a good chunk of the cool and warm parts of this intergalactic material (about 43 percent of all baryons in total). Astronomers have now used ESA’s XMM-Newton space observatory to detect the hot component of this intergalactic material along the line of sight to a quasar. The amount of hot intergalactic gas detected in these observations amounts up to 40 percent of all baryons in the Universe, closing the gap in the overall budget of ordinary matter in the cosmos. ESA

    After a nearly twenty-year long game of cosmic hide-and-seek, astronomers using ESA’s XMM-Newton space observatory have finally found evidence of hot, diffuse gas permeating the cosmos, closing a puzzling gap in the overall budget of ‘normal’ matter in the Universe.

    While the mysterious dark matter and dark energy make up about 25 and 70 percent of our cosmos respectively, the ordinary matter that makes up everything we see – from stars and galaxies to planets and people – amounts to only about five percent.

    But even this five percent turns out to be hard to track down.

    The total amount of ordinary matter, which astronomers refer to as baryons, can be estimated from observations of the Cosmic Microwave Background [CMB], which is the most ancient light in the history of the Universe, dating back to only about 380,000 years after the Big Bang.

    CMB per ESA/Planck

    ESA/Planck 2009 to 2013

    Observations of very distant galaxies allow astronomers to follow the evolution of this matter throughout the Universe’s first couple of billions of years. After that, however, more than half of it seemed to have gone missing.

    “The missing baryons represent one of the biggest mysteries in modern astrophysics,” explains Fabrizio Nicastro, lead author of the paper presenting a solution to the mystery, published today in Nature. Nicastro is from the INAF-Osservatorio Astronomico di Roma, Italy, and the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Mass.

    “We know this matter must be out there, we see it in the early Universe, but then we can no longer get hold of it. Where did it go?”

    Counting the population of stars in galaxies across the Universe, plus the interstellar gas that permeates galaxies – the raw material to create stars – only gets as far as a mere ten percent of all ordinary matter. Adding up the hot, diffuse gas in the haloes that encompass galaxies and the even hotter gas that fills galaxy clusters, which are the largest cosmic structures held together by gravity, raises the inventory to less than twenty percent.

    This is not surprising: stars, galaxies and galaxy clusters form in the densest knots of the cosmic web, the filamentary distribution of both dark and ordinary matter that extends throughout the Universe. While these sites are dense, they are also rare, so not the best spots to look for the majority of cosmic matter.

    Astronomers suspected that the ‘missing’ baryons must be lurking in the ubiquitous filaments of this cosmic web, where matter is, however, less dense and therefore more challenging to observe. Using different techniques over the years, they were able to locate a good chunk of this intergalactic material – mainly its cool and warm components – bringing up the total budget to a respectable 60 percent, but leaving the overall mystery still unsolved.

    Nicastro and many other astronomers around the world have been on the tracks of the remaining baryons for almost two decades, ever since X-ray observatories such as ESA’s XMM-Newton and NASA’s Chandra X-ray Observatory became available to the scientific community.

    Observing in this portion of the electromagnetic spectrum, they can detect hot intergalactic gas, with temperatures around a million degrees or more, that is blocking the X-rays emitted by even more distant sources.

    For this project, Nicastro and his collaborators used XMM-Newton to look at a quasar – a massive galaxy with a supermassive black hole at its center that is actively devouring matter and shining brightly from X-rays to radio waves. They observed this quasar, whose light takes more than four billion years to reach us, for a total of 18 days, split between 2015 and 2017, in the longest X-ray observation ever performed of such a source.

    “After combing through the data, we succeeded at finding the signature of oxygen in the hot intergalactic gas between us and the distant quasar, at two different locations along the line of sight,” says Nicastro.

    “This is happening because there are huge reservoirs of material – including oxygen – lying there, and just in the amount we were expecting, so we finally can close the gap in the baryon budget of the Universe.”

    This extraordinary result is the beginning of a new quest. Observations of different sources across the sky are needed to confirm whether these findings are truly universal, and to further investigate the physical state of this long-sought-for matter.

    Fabrizio and his colleagues are planning to study more quasars with XMM-Newton and Chandra in the coming years. To fully explore the distribution and properties of this so-called warm-hot intergalactic medium, however, more sensitive instruments will be needed, like ESA’s Athena, the Advanced Telescope for High-Energy Astrophysics, scheduled for launch in 2028.

    ESA/Athena spacecraft depiction

    “The discovery of the missing baryons with XMM-Newton is the exciting first step to fully characterize the circumstances and structures in which these baryons are found,” says co-author Jelle Kaastra from the Netherlands Institute for Space Research.

    “For the next steps, we will need the much higher sensitivity of Athena, which has the study of the warm-hot intergalactic medium as one of its main goals, to improve our understanding of how structures grow in the history of the Universe.”

    “It makes us very proud that XMM-Newton was able to discover the weak signal of this long elusive material, hidden in a million-degree hot fog that extends through intergalactic space for hundreds of thousands of light years,” says Norbert Schartel, XMM-Newton project scientist at ESA.

    “Now that we know these baryons are no longer missing, we can’t wait to study them in greater detail.”

    See the full article here .


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    Please help promote STEM in your local schools.

    Stem Education Coalition

    The Center for Astrophysics combines the resources and research facilities of the Harvard College Observatory and the Smithsonian Astrophysical Observatory under a single director to pursue studies of those basic physical processes that determine the nature and evolution of the universe. The Smithsonian Astrophysical Observatory (SAO) is a bureau of the Smithsonian Institution, founded in 1890. The Harvard College Observatory (HCO), founded in 1839, is a research institution of the Faculty of Arts and Sciences, Harvard University, and provides facilities and substantial other support for teaching activities of the Department of Astronomy.

     
  • richardmitnick 10:14 am on June 20, 2018 Permalink | Reply
    Tags: Astronomy, , , , Dark fusion?, , ,   

    From Science News: “If real, dark fusion could help demystify this physics puzzle” 


    From Science News

    June 6, 2018
    Emily Conover

    1
    DARK CLOUDS Galaxies and galaxy clusters are surrounded by dark matter (illustrated in blue over an image of the cluster Abell 2744; red indicates gas). Dark matter particles may undergo a process called dark fusion, one scientist suggests. XMM-Newton/ESA, WFI/ESO, NASA, CFHT

    Fusion may have a dark side. A shadowy hypothetical process called “dark fusion” could be occurring throughout the cosmos, a new study suggests.

    The standard type of fusion occurs when two atomic nuclei unite to form a new element, releasing energy in the process. “This is why the sun shines,” says physicist Sam McDermott of Fermilab in Batavia, Ill. A similar process — dark fusion — could occur with particles of dark matter, McDermott suggests in a paper published in the June 1, 2018 in Physical Review Letters.

    If the idea is correct, the proposed phenomenon may help physicists resolve a puzzle related to dark matter — a poorly understood substance believed to bulk up the mass of galaxies. Without dark matter, scientists can’t explain how galaxies’ stars move the way they do. But some of the quirks of how dark matter is distributed within galaxy centers remain a mystery.

    Dark matter is thought to be composed of reclusive particles that don’t interact much with ordinary matter — the stuff that makes up stars, planets and living creatures. That introverted nature is what makes the enigmatic particles so hard to detect. But dark matter may not be totally antisocial (SN: 3/3/18, p. 8). “Why wouldn’t the dark matter particles interact with each other? There’s really no good reason to say they wouldn’t,” says physicist Manoj Kaplinghat of the University of California, Irvine.

    Scientists have suggested that dark matter particles might ricochet off one another. But the new study goes a step further, proposing that pairs of dark matter particles could fuse, forming other unknown types of dark matter particles in the process.

    Such dark fusion could help explain why dark matter near the centers of galaxies is more evenly distributed than expected. In computer simulations of galaxy formation, the density of dark matter rises sharply toward a cusp in the center of a galaxy. But in reality, galaxies have a core evenly filled with dark matter.

    Those simulations assume dark matter particles don’t interact with one another. But dark fusion could change how the particles behave, giving them energy that would provide the oomph necessary to escape entrapment in a galaxy’s dense cusp, thereby producing an evenly filled core.

    “You can kick [particles] around through this interaction, so that’s kind of cool,” says physicist Annika Peter of the Ohio State University in Columbus. But, she says, dark fusion might end up kicking the particles out of the galaxy entirely, which wouldn’t mesh with expectations: The particles could escape the halo of dark matter that scientists believe surrounds each galaxy.

    For now, if fusion does have an alter ego, scientists remain in the dark.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

     
  • richardmitnick 10:21 pm on June 19, 2018 Permalink | Reply
    Tags: Astronomy, , , , , , NASA's Next Flagship Mission May Be A Crushing Disappointment For Astrophysics   

    From Ethan Siegel: “NASA’s Next Flagship Mission May Be A Crushing Disappointment For Astrophysics” 

    From Ethan Siegel
    Jun 19, 2018

    1
    Various long-exposure campaigns, like the Hubble eXtreme Deep Field (XDF) shown here, have revealed thousands of galaxies in a volume of the Universe that represents a fraction of a millionth of the sky. Ambitious, flagship-class observatories are needed to take the next great leap forward for science. NASA, ESA, H. Teplitz and M. Rafelski (IPAC/Caltech), A. Koekemoer (STScI), R. Windhorst (Arizona State University), and Z. Levay (STScI)

    Every ten years, the field of astronomy and astrophysics undergoes a Decadal Survey. This charts out the path that NASA’s astrophysics division will follow for the next decade, including what types of questions they’ll investigate, which missions will be funded, and what won’t be chosen. The greatest scientific advances of all come when we invest a large amount of resources in a single, ultra-powerful, multi-purpose observatory, such as the Hubble Space Telescope.

    NASA/ESA Hubble Telescope

    These are high-risk, high-reward propositions. If the mission succeeds, we can learn an unprecedented amount about the Universe as never before.

    2
    Star birth in the Carina Nebula, in the optical (top) and the infrared (bottom). Our willingness to invest in fundamental science is directly related to how much we can learn about the Universe. NASA, ESA and the Hubble SM4 ERO Team

    Even though the mission proposals go through NASA, its the National Research Council and the National Academy of Sciences that ultimately make the recommendations. Since the inception of NASA in the 1960s, these Decadal Surveys have shaped the field of astronomy and astrophysics research. They brought us our greatest ground-based and space-based observatories. On the ground, radio arrays like the Very Large Array and the Very Long Baseline Array, as well as the Atacama Large Millimeter Array, owe their origins to the decadal surveys.

    NRAO/Karl V Jansky VLA, on the Plains of San Agustin fifty miles west of Socorro, NM, USA, at an elevation of 6970 ft (2124 m)

    NRAO VLBA

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

    Space-based missions include NASA’s great observatories: the Hubble Space Telescope, the Chandra X-ray observatory, the Spitzer Space Telescope, and the Compton Gamma-Ray Observatory Even though the mission proposals go through NASA, its the National Research Council and the National Academy of Sciences that ultimately make the recommendations. Since the inception of NASA in the 1960s, these Decadal Surveys have shaped the field of astronomy and astrophysics research. They brought us our greatest ground-based and space-based observatories. On the ground, radio arrays like the Very Large Array and the Very Long Baseline Array, as well as the Atacama Large Millimeter Array, owe their origins to the decadal surveys. Space-based missions include NASA’s great observatories: the Hubble Space Telescope, the Chandra X-ray observatory, the Spitzer Space Telescope, and the Compton Gamma-Ray Observatory in the 1990s and early 2000s.

    NASA/Chandra X-ray Telescope


    NASA/Spitzer Infrared Telescope

    NASA Compton Gamma Ray Observatory

    4
    NASA’s Fermi Satellite has constructed the highest resolution, high-energy map of the Universe ever created. Without space-based observatories such as this one, we could never learn all that we have about the Universe. NASA/DOE/Fermi LAT Collaboration

    NASA/Fermi LAT


    NASA/Fermi Gamma Ray Space Telescope

    More recent Decadal Surveys, conducted this millennium, will bring us the James Webb Space Telescope, the WFIRST observatory designed to probe dark energy and exoplanets, and the Large Synoptic Survey Telescope (LSST), among others.

    NASA/ESA/CSA Webb Telescope annotated

    NASA/WFIRST

    LSST


    LSST Camera, built at SLAC



    LSST telescope, currently under construction on the El Peñón peak at Cerro Pachón Chile, a 2,682-meter-high mountain in Coquimbo Region, in northern Chile, alongside the existing Gemini South and Southern Astrophysical Research Telescopes.

    They’ve identified the major, most important science goals of astronomy and astrophysics, including dark energy, exoplanets, supernovae, mergers of extreme objects, and the formation of the first stars and the large-scale structure of the Universe. But there was a warning issued in 2001’s report that hasn’t been heeded, and now it’s creating an enormous problem.

    5
    The 2010 NASA mission timeline doesn’t just show a planned James Webb, but an enormous suite of missions that require ongoing funding. Without a commensurate increase in funds, that means fewer resources available for new missions. NASA Astrophysics Division.

    While a robust astronomy program has many benefits for the nation and the world, it’s vital to have a diverse portfolio of missions and observatories. Prior Decadal Surveys have simultaneously stressed the importance of the large flagship missions that drive the field forward like no other type of mission can, while warning against investing too much in these flagships at the expense of other small and medium-sized missions.

    They’ve also stressed the importance of providing additional funding or securing external funding to support ongoing missions, facilities, and observatories. Without it, the development of new missions is hamstrung by the need to continually fund the existing ones.

    6
    As a percentage of the federal budget, investment in NASA is at a 58 year low; at only 0.4% of the budget, you have to go back to 1959 to find a year where we invested a smaller percentage in our nation’s space agency. Office of Management & Budget.

    Many austerity proponents and budget-hawks — both in politics and among the general public — will often point to the large cost of these flagship missions, which can balloon if unexpected problems arise. The far greater problem, however, would arise if one of these flagship missions failed.

    When Hubble launched with its flawed mirror, unable to properly focus the light it gathered, fixing it became mandatory [Soon after Hubble began sending images from space, scientists discovered that the telescope’s primary mirror had a flaw called spherical aberration. The outer edge of the mirror was ground too flat by a depth of 4 microns (roughly equal to one-fiftieth the thickness of a human hair). The flaw resulted in images that were fuzzy because some of the light from the objects being studied was being scattered.After this discovery, scientists and engineers developed COSTAR, corrective optics that functioned like eyeglasses to restore Hubble’s vision. By placing small and carefully designed mirrors in front of the original Hubble instruments, COSTAR –installed during the 1993 First Servicing Mission — successfully improved their vision to their original design goals (Thank you, Sandy Faber)]. Yes, it was expensive, but the far greater cost — to science, to society, and to humanity — would have been not to fix it. Our choice to invest in repairing (and upgrading) Hubble directly led to some of our greatest discoveries of all-time.

    James Webb, similarly, is now over budget, and will require additional funds to complete. But the small, additional cost to get it right enormously outweighs the cost we’d all bear if we cheated ourselves and didn’t finish this incredible investment. [Also, here, we have commitments from CSA and ESA]

    7
    The science instruments aboard the ISIM module being lowered and installed into the main assembly of JWST in 2016. The telescope must be folded and properly stowed in order to fit aboard the Ariane 5 rocket which will launch it, and all its components must work together, correctly, to deliver a successful mission outcome. NASA / Chris Gunn.

    Now, the 2020 Decadal Survey approaches. The future course of astronomy and astrophysics will be charted, and one flagship mission will be selected as the top priority for a premiere mission of the 2030s. (James Webb was that mission for the 2010s; WFIRST will be it for the 2020s.) Unfortunately, a memorandum was just released by the astronomy & astrophysics director, Paul Hertz, of NASA’s Science Mission Directorate. In it, each of the four finalist teams were instructed to develop a second architechture: a lower-cost, scientifically-inferior option.

    8
    This figure shows the real stars in the sky for which a planet in the habitable zone can be observed. The color coding shows the probability of observing an exoEarth candidate if it’s present around that star (green is a high probability, red is a low one). Note how the size of your telescope/observatory in space impacts what you can see. C. Stark and J. Tumlinson, STScI.

    It flies in the face of what a flagship mission actually is. Speaking at this year’s big American Astronomical Society meeting, NASA Associate Administrator Thomas Zurbuchen said,

    “What we learn from these flagship missions is why we study the Universe. This is civilization-scale science… If we don’t do this, we aren’t NASA.”

    8
    A simulated view of the same part of the sky, with the same observing time, with both Hubble (L) and the initial architecture of LUVOIR (R). The difference is breathtaking, and represents what civilization-scale science can deliver. G. Snyder, STScI /M. Postman, STScI.

    And yet, these scaled-down architectures are by definition not as ambitious. It’s an indication from NASA that, unless the budget is increased to accommodate the actual costs of doing civilization-scale science, we won’t be doing it. Each of the four finalists has been instructed to propose an option with a total cost of below $5 billion, which will severely curtail the capabilities of such an observatory.

    9
    The concept design of the LUVOIR space telescope would place it at the L2 Lagrange point, where a 15.1-meter primary mirror would unfold and begin observing the Universe, bringing us untold scientific and astronomical riches. NASA / LUVOIR concept team; Serge Brunier (background)

    As an example, one of the proposals, LUVOIR, was designed to be the ultimate successor to Hubble: 40 times as powerful with a diameter of up to ~15 meters. It was designed to tackle problems in our Solar System, measure molecular biosignatures on exoplanets, to perform a cosmic census of stars in every type of galaxy in the Universe, to achieve the sensitivity capable of seeing every galaxy in the Universe, to directly image and map the gas in galaxies everywhere, and to measure the rotation of galaxies (and better understand dark matter) for every galaxy in the Universe.

    But the new architecture would be only half the diameter, half the resolution, and with a quarter of the light-gathering power of the original design. It would basically be an optical version of the James Webb Space Telescope. The sweeping ambition of the original project, with the potential to revolutionize our view of the Universe, would be lost.

    9
    A simulated image of what Hubble would see for a distant, star-forming galaxy (L), versus what a 10-15 meter class telescope would see for the same galaxy (R). With a telescope of half the size, the resolution would be halved, and the light-gathering time would need to be four times as great to create that inferior image. NASA / Greg Snyder / LUVOIR-HDST concept team.

    The other three proposals are more easily scaled-down, but again lose their power. HabEx, designed to directly image Earth-like planets around other stars, loses 87.5% of the interesting planets it can survey if its size is reduced in half. It might not offer much more than the other suites of missions that will fly, like WFIRST (especially if WFIRST gets a starshade), to justify being the flagship mission with such a reduction. LYNX, designed to be a next-generation X-ray observatory that’s vastly superior to Chandra and XMM-Newton, might not be much superior to the ESA’s upcoming Athena mission on such a budget. Its spatial and energy resolution were supposed to be its big selling points; on a reduced budget, it’s hard to see how it will achieve those.

    10
    An artist’s concept of the Origins Space Telescope, with the (architecture 1) 9.1 meter primary mirror. At lower resolutions and sizes, it still offers a tremendous improvement over current-and-previous far-IR observatories. NASA/GSFC

    The best bet might be OST: the Origins Space Telescope, which would represent a huge upgrade over Spitzer: the only other far-infrared observatory NASA’s ever sent to space. Its 9.1 meter design is likely impossible at that price point, but a reduction in size is less devastating to this mission. At a lower price tag, it can still teach us a huge amount about space, from our Solar System to exoplanets to black holes to distant, early galaxies. There is no NASA or European counterpart to compete with, and unlike the optical part of the spectrum, it’s notoriously challenging to attempt astronomy in this wavelength from the ground. The closest we have is the airplane-borne SOFIA, which is fantastic, but has a number of limitations.

    11
    NASA’s Stratospheric Observatory for Infrared Astronomy (SOFIA) with open telescope doors. This joint partnership between NASA and the German organization DLR enables us to take a state-of-the-art infrared telescope to any location on Earth’s surface, allowing us to observe events wherever they occur. NASA / Carla Thomas

    This is NASA. This is the pre-eminent space agency in the world. This is where science, research, development, discovery, and innovation all come together. The spinoff technologies alone justify the investment, but that’s not why we do it. We are here to discover the Universe. We are here to learn all that we can about the cosmos and our place within it. We are here to find out what the Universe looks like and how it came to be the way it is today.

    It’s time for the United States government to step up to the plate and invest in fundamental science in a way the world hasn’t seen in decades. It’s time to stop asking the scientific community to do more with less, and give them a realistic but ambitious goal: to do more with more. If we can afford an ill-thought-out space force, perhaps we can afford to learn about the greatest unexplored natural resource of all. The Universe, and the vast unknowns hiding in the great cosmic ocean.

    See the full article here .


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    Please help promote STEM in your local schools.

    Stem Education Coalition

    “Starts With A Bang! is a blog/video blog about cosmology, physics, astronomy, and anything else I find interesting enough to write about. I am a firm believer that the highest good in life is learning, and the greatest evil is willful ignorance. The goal of everything on this site is to help inform you about our world, how we came to be here, and to understand how it all works. As I write these pages for you, I hope to not only explain to you what we know, think, and believe, but how we know it, and why we draw the conclusions we do. It is my hope that you find this interesting, informative, and accessible,” says Ethan

     
  • richardmitnick 2:42 pm on June 19, 2018 Permalink | Reply
    Tags: ASKAP, Astronomy, , , , Meerkat, , ,   

    From AAAS: “New radio telescope in South Africa will study galaxy formation” 

    AAAS

    From AAAS

    Jun. 19, 2018
    Daniel Clery

    SKA Meerkat telescope, 90 km outside the small Northern Cape town of Carnarvon, SA

    Today, the Square Kilometre Array (SKA), a continent-spanning radio astronomy project, announced that Spain has come on board as the collaboration’s 11th member. That boost will help the sometimes-troubled project as, over the next year or so, it forms an international treaty organization and negotiates funding to start construction. Meanwhile, on the wide-open plains of the Karoo, a semiarid desert northeast of Cape Town, South Africa, part of the telescope is already in place in the shape of the newly completed MeerKAT, the largest and most powerful radio telescope in the Southern Hemisphere.

    The last of 64 13.5-meter dishes was installed late last year, and next month South African President Cyril Ramaphosa will officially open the facility. Spread across 8 kilometers, the dishes have a collecting area similar to that of the great workhorse of astrophysics, the Karl G. Jansky Very Large Array (VLA) near Socorro, New Mexico.

    NRAO/Karl V Jansky VLA, on the Plains of San Agustin fifty miles west of Socorro, NM, USA, at an elevation of 6970 ft (2124 m)

    But with new hardware designs and a powerful supercomputer to process data, the newcomer could have an edge on its 40-year-old northern cousin.

    “For certain studies, it will be the best” in the world, says Fernando Camilo, chief scientist of the South African Radio Astronomy Observatory in Cape Town, which operates MeerKAT. Sensitive across a wide swath of the radio spectrum, MeerKAT can study how hydrogen gas moves into galaxies to fuel star formation. With little experience, South Africa has “a major fantastic achievement,” says Heino Falcke of Radboud University in Nijmegen, the Netherlands.

    MeerKAT, which stands for Karoo Array Telescope along with the Afrikaans word for “more,” is one of several precursor instruments for the SKA. . The first phase of the SKA could begin in 2020 at a cost of €798 million. It would add another 133 dishes to MeerKAT, extending it across 150 kilometers, and place 130,000 smaller radio antennas across Australia—but only if member governments agree to fully fund the work. Months of delicate negotiations lie ahead. “In every country, people are having that discussion on what funding is available,” Falcke says.

    With MeerKAT’s 64 dishes now in place, engineers are learning how to process the data they gather. In a technique called interferometry, computers correlate the signals from pairs of dishes to build a much sharper image than a single dish could produce. For early science campaigns last year, 16 dishes were correlated. In March, the new supercomputer came online, and the team hopes to be fully operational by early next year. “It’s going to be a challenge,” Camilo says.

    MeerKAT’s dishes are smaller than the VLA’s, but having more of them puts it in “a sweet spot of sensitivity and resolution,” Camilo says. Its dishes are split into a densely packed core, which boosts sensitivity, and widely dispersed arms, which increase resolution. The VLA can opt for sensitivity or resolution, but not both at once—and only after the slow process of moving its 27 dishes into a different configuration.

    The combination makes MeerKAT ideal for mapping hydrogen, the fuel of star and galaxy formation. Because of a spontaneous transition in the atoms of neutral hydrogen, the gas constantly emits microwaves with a wavelength of 21 centimeters. Stretched to radio frequencies by the expansion of the universe, these photons land in the telescope’s main frequency band. It should have the sensitivity to map the faint signal to greater distances than before, and the resolution to see the gas moving in and around galaxies.

    MeerKAT will also watch for pulsars, dense and rapidly spinning stellar remnants. Their metronomic radio wave pulses serve as precise clocks that help astronomers study gravity in extreme conditions. “By finding new and exotic pulsars, MeerKAT can provide tests of physics,” says Philip Best of the University of Edinburgh. Falcke wants to get a better look at a highly magnetized pulsar discovered in 2013. He hopes it will shed light on the gravitational effects of the leviathan it orbits: the supermassive black hole at the center of the Milky Way.

    Other SKA precursors are taking shape. The Australian SKA Pathfinder (ASKAP) at the Murchison Radio-astronomy Observatory in Western Australia is testing a novel survey technology with its 36 12-meter dishes that could be used in a future phase of the SKA.

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

    Whereas a conventional radio dish has a single-element detector—the equivalent of a single pixel—the ASKAP’s detectors have 188 elements, which should help it quickly map galaxies across large areas of the sky.

    Nearby is the Murchison Widefield Array (MWA), an array of 2048 antennas, each about a meter across, that look like metallic spiders.

    SKA Murchison Widefield Array, Boolardy station in outback Western Australia, at the Murchison Radio-astronomy Observatory (MRO)

    Sensitive to lower frequencies than MeerKAT, the MWA can pick up the neutral hydrogen signal from as far back as 500 million years after the big bang, when the first stars and galaxies were lighting up the universe. Astronomers have been chasing the faint signal for years, and earlier this year, one group reported a tentative detection. “We’re really curious to see if it can be replicated,” says MWA Director Melanie Johnston-Hollitt of Curtin University in Perth, Australia.

    If the MWA doesn’t deliver a verdict, the SKA, with 130,000 similar antennas, almost certainly will. Although the MWA may detect the universe lighting up, the SKA intends to map out where it happened.

    The American Association for the Advancement of Science is an international non-profit organization dedicated to advancing science for the benefit of all people.

    See the full article here .


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    Please help promote STEM in your local schools.


    Stem Education Coalition

     
  • richardmitnick 2:14 pm on June 19, 2018 Permalink | Reply
    Tags: Astronomy, , , , ,   

    From Science News: “Magnetic fields may be propping up the Pillars of Creation” 


    From Science News

    June 15, 2018
    Emily Conover

    The structure’s internal magnetism could mean the columns of gas and dust will be long-lived.

    1
    PILLAR OF STRENGTH Columns of cosmic gas and dust dubbed the Pillars of Creation (shown in this image from the Hubble Space Telescope) may be propped up by an internal magnetic field. NASA, ESA, Hubble Heritage Team/STScI and AURA

    The Pillars of Creation may keep standing tall due to the magnetic field within the star-forming region.

    For the first time, scientists have made a detailed map of the magnetic field inside the pillars, made famous by an iconic 1995 Hubble Space Telescope image (SN Online: 1/6/15). The data reveal that the field runs along the length of each pillar, perpendicular to the magnetic field outside. This configuration may be slowing the destruction of the columns of gas and dust, astronomer Kate Pattle and colleagues suggest in the June 10 Astrophysical Journal Letters.

    Hot ionized gas called plasma surrounds the pillars, located within the Eagle Nebula about 7,000 light-years from Earth. The pressure from that plasma could cause the pillars to pinch in at the middle like an hourglass before breaking up. However, the researchers suggest, the organization of the magnetic field within the pillars could be providing an outward force that resists the plasma’s onslaught, preventing the columns from disintegrating.

    The Pillars of Creation may keep standing tall due to the magnetic field within the star-forming region.

    For the first time, scientists have made a detailed map of the magnetic field inside the pillars, made famous by an iconic 1995 Hubble Space Telescope image (SN Online: 1/6/15). The data reveal that the field runs along the length of each pillar, perpendicular to the magnetic field outside. This configuration may be slowing the destruction of the columns of gas and dust, astronomer Kate Pattle and colleagues suggest in the June 10 Astrophysical Journal Letters.

    2
    FIELD OF DREAMS A map of the magnetic field within the Pillars of Creation reveals that the orientation of the field runs roughly parallel to each skinny column. White bars indicate the field’s orientation in that location. K. Pattle et al/Astrophysical Journal Letters 2018

    Hot ionized gas called plasma surrounds the pillars, located within the Eagle Nebula about 7,000 light-years from Earth. The pressure from that plasma could cause the pillars to pinch in at the middle like an hourglass before breaking up. However, the researchers suggest, the organization of the magnetic field within the pillars could be providing an outward force that resists the plasma’s onslaught, preventing the columns from disintegrating.

    Eagle Nebula NASA/ESA Hubble Public Domain

    The team studied light emitted from the pillars, measuring its polarization — the direction of the wiggling of the light’s electromagnetic waves — using the James Clerk Maxwell Telescope in Hawaii. Dust grains within the pillars are aligned with each other due to the magnetic field. These aligned particles emit polarized light, allowing the researchers to trace the direction of the magnetic field at various spots.

    “There are few clear measurements of the magnetic fields in objects like pillars,” says Koji Sugitani of Nagoya City University in Japan. To fully understand the formation of such objects, more observations are needed, he says.

    Studying objects where stars are born, such as the pillars, could help scientists better understand the role that magnetic fields may play in star formation (SN: 6/9/18, p. 12). “This is really one of the big unanswered questions,” says Pattle, of National Tsing Hua University in Hsinchu, Taiwan. “We just don’t have a very good idea of whether magnetic fields are important and, if they are, what they are doing.”

    See the full article here .


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    Please help promote STEM in your local schools.

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  • richardmitnick 12:56 pm on June 19, 2018 Permalink | Reply
    Tags: , Astronomy, , , , , The paleo-detector   

    From astrobites: “A Paleo-Detector for Dark Matter: How Ancient Rocks Could Help Unravel the Mystery” 

    Astrobites bloc

    From astrobites

    Title: Searching for Dark Matter with Paleo-Detectors
    Authors: S. Baum, A. K. Drukier, K. Freese, M. Górski, & P. Stengel
    First Author’s Institution: The Oskar Klein Centre for Cosmoparticle Physics, Department of Physics, Stockholm University, Sweden
    1
    Status: Pre-print available [open access on arXiv]

    Dark matter is, by its very nature, elusive. Though we can detect its presence by observing its gravitational influence, dark matter remains invisible because it doesn’t interact electromagnetically. The most widely accepted explanation for dark matter is the existence of weakly interacting massive particles (WIMPs). WIMPs, if eventually observed, would constitute a new, massive kind of elementary particle. Their discovery would be revolutionary for particle physics and cosmology; therefore, countless direct (in labs) and indirect (observing their annihilation or decay) detection experiments are being conducted to identify them. Today’s astrobite discusses a novel proposal for direct dark matter detection that seems more fit for scientists in Jurassic Park than for particle physicists: the paleo-detector.

    The authors of today’s featured paper theorize that ancient rocks could contain evidence of interactions between WIMPS and nuclei in the minerals, forming a completely natural “detector” that would allow scientists to search for evidence of the massive particles using excavated rocks. This experiment varies significantly from other direct detection efforts, as those look for evidence of WIMPs hitting Earth-based detectors in real time. The paleo-detector would instead trace nanometers-long “tracks” of chemical and physical change in the rocks as the result of WIMP-induced nuclear recoil that occurred long ago.

    See the full article here .


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    Please help promote STEM in your local schools.

    Stem Education Coalition

    What do we do?

    Astrobites is a daily astrophysical literature journal written by graduate students in astronomy. Our goal is to present one interesting paper per day in a brief format that is accessible to undergraduate students in the physical sciences who are interested in active research.
    Why read Astrobites?

    Reading a technical paper from an unfamiliar subfield is intimidating. It may not be obvious how the techniques used by the researchers really work or what role the new research plays in answering the bigger questions motivating that field, not to mention the obscure jargon! For most people, it takes years for scientific papers to become meaningful.
    Our goal is to solve this problem, one paper at a time. In 5 minutes a day reading Astrobites, you should not only learn about one interesting piece of current work, but also get a peek at the broader picture of research in a new area of astronomy.

     
  • richardmitnick 4:12 pm on June 18, 2018 Permalink | Reply
    Tags: Astronomy, , , , , Star Shredded by Rare Breed of Black Hole, The galaxy is named 6dFGS gJ215022.2-055059, X-ray source inferred to contain the IMBH is named 3XMM J215022.4−055108   

    From NASA Chandra: “Star Shredded by Rare Breed of Black Hole” 

    NASA Chandra Banner

    NASA/Chandra Telescope


    From NASA Chandra

    June 18, 2018
    Media contacts:
    Megan Watzke
    Chandra X-ray Center, Cambridge, Mass.
    617-496-7998
    mwatzke@cfa.harvard.edu

    1
    Credit: X-ray: NASA/CXC/UNH/D.Lin et al, Optical: NASA/ESA/STScI

    ESA’s XMM-Newton observatory has discovered the best-ever candidate for a very rare and elusive type of cosmic phenomenon: a medium-weight black hole in the process of tearing apart and feasting on a nearby star.

    ESA/XMM Newton

    There are various types of black holes lurking throughout the Universe: massive stars create stellar-mass black holes when they die, while galaxies host supermassive black holes at their centers, with masses equivalent to millions or billions of Suns.

    Lying between these extremes is a more retiring member of the black hole family: intermediate-mass black holes. Thought to be seeds that will eventually grow to become supermassive, these black holes are especially elusive, and thus very few robust candidates have ever been found.

    Now, a team of researchers using data from ESA’s XMM-Newton X-ray space observatory, NASA’s Chandra X-ray Observatory and NASA’s Swift X-ray Telescope, has found a rare telltale sign of activity.

    NASA Neil Gehrels Swift Observatory

    They detected an enormous flare of radiation in the outskirts of a distant galaxy, thrown off as a star passed too close to a black hole and was subsequently torn apart and partly devoured.

    “This is incredibly exciting: this type of black hole hasn’t been spotted so clearly before,” says lead scientist Dacheng Lin of the University of New Hampshire, USA. “A few candidates have been found, but on the whole they’re extremely rare and very sought after. This is the best intermediate black hole candidate observed so far.”

    This breed of black hole is thought to form in various ways. One formation scenario is the runaway merger of massive stars lying within dense star clusters, making the centres of these clusters one of the best places to hunt for them. However, by the time such black holes have formed, these sites tend to be devoid of gas, leaving the black holes with no material to consume and thus little radiation to emit — which in turn makes them extremely difficult to spot.

    “One of the few methods we can use to try to find an intermediate black hole is to wait for a star to pass close to it and become disrupted — this essentially ‘activates’ the black hole’s appetite again and prompts it to emit a flare that we can observe,” adds Lin.

    “This kind of event has only been clearly seen at the center of a galaxy before, not at the outer edges.”

    Lin and colleagues sifted through data from XMM-Newton to find the candidate. They identified it in observations of a large galaxy some 740 million light-years away, taken in 2006 and 2009 as part of a galaxy survey, and in additional data from Chandra (2006 and 2016) and Swift (2014).

    2
    Credit: ESA/XMM-Newton/D.Lin et al.

    “We also looked at images of the galaxy taken by a whole host of other telescopes, to see what the emission looked like optically,” says co-author Jay Strader of Michigan State University, USA.

    “We spotted the source flaring in brightness in two images from 2005 — it appeared far bluer and brighter than it had just a few years previously.

    “By comparing all the data we determined that the unfortunate star was likely disrupted in October 2003 in our time, and produced a burst of energy that decayed over the following 10 years or so.”

    The scientists believe that the star was disrupted and torn apart by a black hole with a mass of around fifty thousand times that of the Sun.

    Such star-triggered outbursts are expected to only happen rarely from this type of black hole, so this discovery suggests that there could be many more lurking in a dormant state in galaxy peripheries across the local Universe.

    “This candidate was discovered via an intensive search of XMM-Newton’s X-ray Source Catalogue, which is filled with high-quality data covering large areas of sky, essential for determining how large the black hole was and what happened to cause the observed burst of radiation,” says Norbert Schartel, ESA Project Scientist for XMM-Newton.

    “The XMM-Newton X-ray Source Catalogue is presently the largest catalogue of this type, containing more than half a million sources: exotic objects like the one discovered in our study are still hidden there and waiting to be discovered through intensive data mining,” adds co-author Natalie Webb, director of the XMM-Newton Survey Science Center at the Research Institute in Astrophysics and Planetology (IRAP) in Toulouse, France.

    “Learning more about these objects and associated phenomena is key to our understanding of black holes. Our models are currently akin to a scenario in which an alien civilization observes Earth and spots grandparents dropping their grandchildren at pre-school: they might assume that there’s something intermediate to fit their model of a human lifespan, but without observing that link, there’s no way to know for sure,” said Schartel. “This finding is incredibly important, and shows that the discovery method employed here is a good one to use.”

    The study used data from ESA’s XMM-Newton X-ray space observatory, NASA’s Chandra X-Ray Observatory, and NASA’s Swift X-Ray Telescope, and additional images from the Canada-France-Hawaii Telescope, the NASA/ESA Hubble Space Telescope, NAOJ’s Subaru Telescope, the Southern Astrophysical Research (SOAR) Telescope, and the Gemini Observatory.



    CFHT Telescope, Maunakea, Hawaii, USA, at Maunakea, Hawaii, USA,4,207 m (13,802 ft) above sea level

    NASA/ESA Hubble Telescope


    NAOJ/Subaru Telescope at Mauna Kea Hawaii, USA,4,207 m (13,802 ft) above sea level

    South African Large Telescope, close to the town of Sutherland in the semi-desert region of the Karoo, South Africa, Altitude 1,798 m (5,899 ft)


    Gemini South telescope, Cerro Tololo Inter-American Observatory (CTIO) campus near La Serena, Chile, at an altitude of 7200 feet

    Added from ESA:

    Dacheng Lin
    University of New Hampshire, USA
    Email: dacheng.lin@unh.edu
    Tel: +1-603-862-4379

    Jay Strader
    Michigan State University, USA
    Email: strader@pa.msu.edu

    Natalie Webb
    XMM-Newton Survey Science Center
    Research Institute in Astrophysics and Planetology (IRAP)
    Toulouse, France
    Email: Natalie.Webb@irap.omp.eu

    Norbert Schartel
    XMM-Newton Project Scientist
    European Space Agency
    Email: norbert.schartel@esa.int

    Markus Bauer








    ESA Science Communication Officer









    Tel: +31 71 565 6799









    Mob: +31 61 594 3 954









    Email: markus.bauer@esa.int

    “A luminous X-ray outburst from an intermediate-mass black hole in an off-centre star cluster”, by D. Lin et al, is published in Nature Astronomy.

    The study used data from ESA’s XMM-Newton X-ray space observatory, NASA’s Chandra X-Ray Observatory, and NASA’s Swift X-Ray Telescope, and additional images from the Canada-France-Hawaii Telescope, the NASA/ESA Hubble Space Telescope, NAOJ’s SubaruTelescope, the Southern Astrophysical Research (SOAR) Telescope, and the Gemini Observatory.

    The galaxy is named 6dFGS gJ215022.2-055059, while the X-ray source inferred to contain the IMBH is named 3XMM J215022.4−055108.

    See the full article here .


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    Please help promote STEM in your local schools.

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    NASA’s Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program for NASA’s Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory controls Chandra’s science and flight operations from Cambridge, Mass.

     
  • richardmitnick 9:23 am on June 18, 2018 Permalink | Reply
    Tags: , Astronomy, , ,   

    From astrobites: “The Planets in the Gaps” 

    Astrobites bloc

    From astrobites

    Title: A Kinematical Detection of Two Embedded Jupiter Mass Planets in HD 163296
    Authors: Richard Teague (University of Michigan), Jaehan Bae, Edwin Bergin, Tilman Birnstiel, Daniel Foreman-Mackey

    Status: Accepted to ApJL, 2018 [open access]

    Planets form. (We know this, occupying, as we do, a planet.) And planets form out of the disks of gas and dust that surround young stars. (We know this because we see these disks around young stars, and we cannot explain where the stuff of planets comes from otherwise.) And planets form in these disks quite quickly. (We know this because the disks only last a few million years–a blink of an eye, astronomically speaking.) And planets form in these disks easily. (We know this because planets are everywhere! On average, there’s at least one planet per star.)

    Planet formation, then: it’s quick, easy, commonplace, and completely mysterious. How does a sphere the size of Jupiter coalesce from a bunch of grains of dust swimming in hydrogen gas? Or a snowball like Pluto (planet, dwarf planet, don’t @ me), for that matter, or a rock like Earth?

    1
    Figure 1. The big q

    See the full article here .


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    Please help promote STEM in your local schools.

    Stem Education Coalition

    What do we do?

    Astrobites is a daily astrophysical literature journal written by graduate students in astronomy. Our goal is to present one interesting paper per day in a brief format that is accessible to undergraduate students in the physical sciences who are interested in active research.
    Why read Astrobites?

    Reading a technical paper from an unfamiliar subfield is intimidating. It may not be obvious how the techniques used by the researchers really work or what role the new research plays in answering the bigger questions motivating that field, not to mention the obscure jargon! For most people, it takes years for scientific papers to become meaningful.
    Our goal is to solve this problem, one paper at a time. In 5 minutes a day reading Astrobites, you should not only learn about one interesting piece of current work, but also get a peek at the broader picture of research in a new area of astronomy.

     
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