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  • richardmitnick 10:52 am on March 25, 2019 Permalink | Reply
    Tags: , , , Cosmology, , , ExaLearn, , , , ,   

    From insideHPC: “ExaLearn Project to bring Machine Learning to Exascale” 

    From insideHPC

    March 24, 2019

    As supercomputers become ever more capable in their march toward exascale levels of performance, scientists can run increasingly detailed and accurate simulations to study problems ranging from cleaner combustion to the nature of the universe. Enter ExaLearn, a new machine learning project supported by DOE’s Exascale Computing Project (ECP), aims to develop new tools to help scientists overcome this challenge by applying machine learning to very large experimental datasets and simulations.

    The first research area for ExaLearn’s surrogate models will be in cosmology to support projects such a the LSST (Large Synoptic Survey Telescope) now under construction in Chile and shown here in an artist’s rendering. (Todd Mason, Mason Productions Inc. / LSST Corporation)

    “The challenge is that these powerful simulations require lots of computer time. That is, they are “computationally expensive,” consuming 10 to 50 million CPU hours for a single simulation. For example, running a 50-million-hour simulation on all 658,784 compute cores on the Cori supercomputer NERSC would take more than three days.


    NERSC Cray Cori II supercomputer at NERSC at LBNL, named after Gerty Cori, the first American woman to win a Nobel Prize in science

    NERSC Hopper Cray XE6 supercomputer

    LBL NERSC Cray XC30 Edison supercomputer

    The Genepool system is a cluster dedicated to the DOE Joint Genome Institute’s computing needs. Denovo is a smaller test system for Genepool that is primarily used by NERSC staff to test new system configurations and software.


    PDSF is a networked distributed computing cluster designed primarily to meet the detector simulation and data analysis requirements of physics, astrophysics and nuclear science collaborations.


    Cray Shasta Perlmutter SC18 AMD Epyc Nvidia pre-exascale supeercomputer

    Running thousands of these simulations, which are needed to explore wide ranges in parameter space, would be intractable.

    One of the areas ExaLearn is focusing on is surrogate models. Surrogate models, often known as emulators, are built to provide rapid approximations of more expensive simulations. This allows a scientist to generate additional simulations more cheaply – running much faster on many fewer processors. To do this, the team will need to run thousands of computationally expensive simulations over a wide parameter space to train the computer to recognize patterns in the simulation data. This then allows the computer to create a computationally cheap model, easily interpolating between the parameters it was initially trained on to fill in the blanks between the results of the more expensive models.

    “Training can also take a long time, but then we expect these models to generate new simulations in just seconds,” said Peter Nugent, deputy director for science engagement in the Computational Research Division at LBNL.

    From Cosmology to Combustion

    Nugent is leading the effort to develop the so-called surrogate models as part of ExaLearn. The first research area will be cosmology, followed by combustion. But the team expects the tools to benefit a wide range of disciplines.

    “Many DOE simulation efforts could benefit from having realistic surrogate models in place of computationally expensive simulations,” ExaLearn Principal Investigator Frank Alexander of Brookhaven National Lab said at the recent ECP Annual Meeting.

    “These can be used to quickly flesh out parameter space, help with real-time decision making and experimental design, and determine the best areas to perform additional simulations.”

    The surrogate models and related simulations will aid in cosmological analyses to reduce systematic uncertainties in observations by telescopes and satellites. Such observations generate massive datasets that are currently limited by systematic uncertainties. Since we only have a single universe to observe, the only way to address these uncertainties is through simulations, so creating cheap but realistic and unbiased simulations greatly speeds up the analysis of these observational datasets. A typical cosmology experiment now requires sub-percent level control of statistical and systematic uncertainties. This then requires the generation of thousands to hundreds of thousands of computationally expensive simulations to beat down the uncertainties.

    These parameters are critical in light of two upcoming programs:

    The Dark Energy Spectroscopic Instrument, or DESI, is an advanced instrument on a telescope located in Arizona that is expected to begin surveying the universe this year.

    LBNL/DESI Dark Energy Spectroscopic Instrument for the Nicholas U. Mayall 4-meter telescope at Kitt Peak National Observatory near Tucson, Ariz, USA

    NOAO/Mayall 4 m telescope at Kitt Peak, Arizona, USA, Altitude 2,120 m (6,960 ft)

    DESI seeks to map the large-scale structure of the universe over an enormous volume and a wide range of look-back times (based on “redshift,” or the shift in the light of distant objects toward redder wavelengths of light). Targeting about 30 million pre-selected galaxies across one-third of the night sky, scientists will use DESI’s redshifts data to construct 3D maps of the universe. There will be about 10 terabytes (TB) of raw data per year transferred from the observatory to NERSC. After running the data through the pipelines at NERSC (using millions of CPU hours), about 100 TB per year of data products will be made available as data releases approximately once a year throughout DESI’s five years of operations.

    The Large Synoptic Survey Telescope, or LSST, is currently being built on a mountaintop in Chile.


    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.

    LSST Data Journey, Illustration by Sandbox Studio, Chicago with Ana Kova

    When completed in 2021, the LSST will take more than 800 panoramic images each night with its 3.2 billion-pixel camera, recording the entire visible sky twice each week. Each patch of sky it images will be visited 1,000 times during the survey, and each of its 30-second observations will be able to detect objects 10 million times fainter than visible with the human eye. A powerful data system will compare new with previous images to detect changes in brightness and position of objects as big as far-distant galaxy clusters and as small as nearby asteroids.

    For these programs, the ExaLearn team will first target large-scale structure simulations of the universe since the field is more developed than others and the scale of the problem size can easily be ramped up to an exascale machine learning challenge.

    As an example of how ExaLearn will advance the field, Nugent said a researcher could run a suite of simulations with the parameters of the universe consisting of 30 percent dark energy and 70 percent dark matter, then a second simulation with 25 percent and 75 percent, respectively. Each of these simulations generates three-dimensional maps of tens of billions of galaxies in the universe and how the cluster and spread apart as time goes by. Using a surrogate model trained on these simulations, the researcher could then quickly run another surrogate model that would generate the output of a simulation in between these values, at 27.5 and 72.5 percent, without needing to run a new, costly simulation — that too would show the evolution of the galaxies in the universe as a function of time. The goal of the ExaLearn software suite is that such results, and their uncertainties and biases, would be a byproduct of the training so that one would know the generated models are consistent with a full simulation.

    Toward this end, Nugent’s team will build on two projects already underway at Berkeley Lab: CosmoFlow and CosmoGAN. CosmoFlow is a deep learning 3D convolutional neural network that can predict cosmological parameters with unprecedented accuracy using the Cori supercomputer at NERSC. CosmoGAN is exploring the use of generative adversarial networks to create cosmological weak lensing convergence maps — maps of the matter density of the universe as would be observed from Earth — at lower computational costs.

    See the full article here .


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    Founded on December 28, 2006, insideHPC is a blog that distills news and events in the world of HPC and presents them in bite-sized nuggets of helpfulness as a resource for supercomputing professionals. As one reader said, we’re sifting through all the news so you don’t have to!

    If you would like to contact me with suggestions, comments, corrections, errors or new company announcements, please send me an email at rich@insidehpc.com. Or you can send me mail at:

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  • richardmitnick 12:12 pm on March 23, 2019 Permalink | Reply
    Tags: "This Is Why The Multiverse Must Exist", , , , , Cosmology,   

    From Ethan Siegel: “This Is Why The Multiverse Must Exist” 

    From Ethan Siegel
    Mar 22, 2019

    The multiverse idea states that there are an arbitrarily large number of Universes like our own out there, embedded in our Multiverse. It’s possible, but not necessary, for other pockets within the Multiverse to exist where the laws of physics are different.

    If you accept cosmic inflation and quantum physics, there’s no way out. The Multiverse is real.

    Look out at the Universe all you want, with arbitrarily powerful technology, and you’ll never find an edge. Space goes on as far as we can see, and everywhere we look we see the same things: matter and radiation. In all directions, we find the same telltale signs of an expanding Universe: the leftover radiation from a hot, dense state; galaxies that evolve in size, mass, and number; elements that change abundances as stars live and die.

    But what lies beyond our observable Universe? Is there an abyss of nothingness beyond the light signals that could possibly reach us since the Big Bang? Is there just more Universe like our own, out there past our observational limits? Or is there a Multiverse, mysterious in nature and forever unable to be seen?

    Unless there’s something seriously wrong with our understanding of the Universe, the Multiverse must be the answer. Here’s why.

    Artist’s logarithmic scale conception of the observable universe. Note that we’re limited in how far we can see back by the amount of time that’s occurred since the hot Big Bang: 13.8 billion years, or (including the expansion of the Universe) 46 billion light years. Anyone living in our Universe, at any location, would see almost exactly the same thing from their vantage point. (WIKIPEDIA USER PABLO CARLOS BUDASSI)

    The Multiverse is an extremely controversial idea, but at its core it’s a very simple concept. Just as the Earth doesn’t occupy a special position in the Universe, nor does the Sun, the Milky Way, or any other location, the Multiverse goes a step farther and claims that there’s nothing special about the entire visible Universe.

    The Multiverse is the idea that our Universe, and all that’s contained within it, is just one small part of a larger structure. This larger entity encapsulates our observable Universe as a small part of a larger Universe that extends beyond the limits of our observations. That entire structure — the unobservable Universe — may itself be part of a larger spacetime that includes many other, disconnected Universes, which may or may not be similar to the Universe we inhabit.

    If this is the idea of the Multiverse, I can understand your skepticism at the notion that we could somehow know whether it does or doesn’t exist. After all, physics and astronomy are sciences that rely on measurable, experimental, or otherwise observational confirmation. If we are looking for evidence of something that exists outside of our visible Universe and leaves no trace within it, it seems that the idea of a Multiverse is fundamentally untestable.

    But there are all sorts of things that we cannot observe that we know must be true. Decades before we directly detected gravitational waves, we knew that they must exist, because we observed their effects.

    Gravitational waves. Credit: MPI for Gravitational Physics/Werner Benger

    Binary pulsars — spinning neutron stars orbiting around one another — were observed to have their revolutionary periods shorten. Something must be carrying energy away, and that thing was consistent with the predictions of gravitational waves.

    Binary pulsars via Universe Today

    The rate of orbital decay of a binary pulsar is highly dependent on the speed of gravity and the orbital parameters of the binary system. We have used binary pulsar data to constrain the speed of gravity to be equal to the speed of light to a precision of 99.8%, and to infer the existence of gravitational waves decades before LIGO and Virgo detected them. (NASA (L), MAX PLANCK INSTITUTE FOR RADIO ASTRONOMY / MICHAEL KRAMER (R))

    While we certainly welcomed the confirmation that LIGO and Virgo provided for gravitational waves via direct detection, we already knew that they needed to exist because of this indirect evidence.

    Caltech/MIT Advanced aLigo Hanford, WA, USA installation

    Caltech/MIT Advanced aLigo detector installation Livingston, LA, USA

    Cornell SXS, the Simulating eXtreme Spacetimes (SXS) project

    Gravitational waves. Credit: MPI for Gravitational Physics/W.Benger-Zib

    ESA/eLISA the future of gravitational wave research

    Those who would argue that indirect evidence is no indicator of gravitational waves might still be unconvinced that binary pulsars emit them; LIGO and Virgo didn’t see the gravitational waves that came from the binary pulsars we’ve observed.

    So if we cannot observe the Multiverse directly, what indirect evidence do we have for its existence? How do we know that there’s more unobservable Universe beyond the part we can observe, and how do we know that what we call our Universe is likely just one of many embedded in the Multiverse?

    We look to the Universe itself, and draw conclusions about its nature based on what observations about it reveal.

    The light from the cosmic microwave background and the pattern of fluctuations from it gives us one way to measure the Universe’s curvature. To the best of our measurements, to within 1 part in about 400, the Universe is perfectly spatially flat. (SMOOT COSMOLOGY GROUP / LAWRENCE BERKELEY LABS)

    When we look out to the edge of the observable Universe, we find that the light rays emitted from the earliest times — from the Cosmic Microwave Background [CMB] — make particular patterns on the sky.

    CMB per ESA/Planck

    Gravitational Wave Background from BICEP 2 which ultimately failed to be correct. The Planck team determined that the culprit was cosmic dust.

    ESA/Planck 2009 to 2013

    These patterns not only reveal the density and temperature fluctuations that the Universe was born with, as well as the matter and energy composition of the Universe, but also the geometry of space itself.

    We can conclude from this that space isn’t positively curved (like a sphere) or negatively curved (like a saddle), but rather spatially flat, indicating that the unobservable Universe likely extends far beyond the part we can access. It never curves back on itself, it never repeats, and it has no empty gaps in it. If it is curved, it has a diameter that’s hundreds of times greater than the part we can see.

    With every second that ticks by, more Universe, just like our own, is revealed to us, consistent with this picture.

    The observable Universe might be 46 billion light years in all directions from our point of view, but there’s certainly more, unobservable Universe, perhaps even an infinite amount, just like ours beyond that. Over time, we’ll be able to see more of it, eventually revealing approximately 2.3 times as much matter as we can presently view. (FRÉDÉRIC MICHEL AND ANDREW Z. COLVIN, ANNOTATED BY E. SIEGEL)

    That might indicate that there’s more unobservable Universe beyond the part of our Universe we can access, but it doesn’t prove it, and it doesn’t provide evidence for a Multiverse. There are, however, two concepts in physics that have been established far beyond a reasonable doubt: cosmic inflation and quantum physics.


    Alan Guth, from Highland Park High School and M.I.T., who first proposed cosmic inflation

    HPHS Owls

    Lambda-Cold Dark Matter, Accelerated Expansion of the Universe, Big Bang-Inflation (timeline of the universe) Date 2010 Credit: Alex MittelmannColdcreation

    Alan Guth’s notes:

    Cosmic inflation is the theory that gave rise to the hot Big Bang. Rather than beginning with a singularity, there’s a physical limit to how hot and how dense the initial, early stages of our expanding Universe could have reached. If we had achieved arbitrarily high temperatures in the past, there would be clear signatures that aren’t there:

    large-amplitude temperature fluctuations early on,
    seed density fluctuations limited by the scale of the cosmic horizon,
    and leftover, high-energy relics from early times, like magnetic monopoles.

    Inflation causes space to expand exponentially, which can very quickly result in any pre-existing curved or non-smooth space appearing flat. If the Universe is curved, it has a radius of curvature that is at minimum hundreds of times larger than what we can observe. (E. SIEGEL (L); NED WRIGHT’S COSMOLOGY TUTORIAL (R))

    These signatures are all missing. The temperature fluctuations are at the 0.003% level; the density fluctuations exceed the scale of the cosmic horizon; the limits on monopoles and other relics are incredibly stringent. The fact that these signatures aren’t there have an enormous implication to them: the Universe never reached those arbitrarily high temperatures. Something else came before the hot Big Bang to set it up.

    That’s where cosmic inflation comes in. Theorized in the early 1980s [above], it was designed to solve a number of puzzles with the Big Bang, but did what you’d hope for any new physical theory: it made measurable, testable predictions for observable signatures that would appear within our Universe.

    We see the predicted lack of spatial curvature; we see an adiabatic nature to the fluctuations the Universe was born with; we’ve detected a spectrum and magnitude of initial fluctuations that jibe with inflation’s predictions; we’ve seen the superhorizon fluctuations that inflation predicts must arise.

    Fluctuations in spacetime itself at the quantum scale get stretched across the Universe during inflation, giving rise to imperfections in both density and gravitational waves. Whether inflation arose from an eventual singularity or not is unknown, but the signatures of whether it occurred are accessible in our observable Universe. (E. SIEGEL, WITH IMAGES DERIVED FROM ESA/PLANCK AND THE DOE/NASA/ NSF INTERAGENCY TASK FORCE ON CMB RESEARCH)

    We may not know everything about inflation, but we do have a very strong suite of evidence that supports a period in the early Universe where it occurred. It set up and gave rise to the Big Bang, and predicts a set and spectrum of fluctuations that gave rise to the seeds of structure that grew into the cosmic web we observe today. Only inflation, as far as we know, gives us predictions for our Universe that match what we observe.

    “So, big deal,” you might say. “You took a small region of space, you allowed inflation to expand it to some very large volume, and our observable, visible Universe is contained within that volume. Even if this is all right, this only tells us that our unobservable Universe extends far beyond the visible part. You haven’t established the Multiverse at all.”

    And all of that would be correct. But remember, there’s one more ingredient we need to add in: quantum physics.

    (Illustration: Getty Images)

    An illustration between the inherent uncertainty between position and momentum at the quantum level. There is a limit to how well you can measure these two quantities simultaneously, and uncertainty shows up in places where people often least expect it. (E. SIEGEL / WIKIMEDIA COMMONS USER MASCHEN)

    Inflation is treated as a field, like all the quanta we know of in the Universe, obeying the rules of quantum field theory. In the quantum Universe, there are many counterintuitive rules that are obeyed, but the most relevant one for our purposes is the rule governing quantum uncertainty.

    While we conventionally view uncertainty as mutually occurring between two variables — momentum and position, energy and time, angular momentum of mutually perpendicular directions, etc. — there’s also an inherent uncertainty in the value of a quantum field. As time marches forward, a field value that was definitive at an earlier time now has a less certain value; you can only ascribe probabilities to it.

    In other words, the value of any quantum field spreads out over time.

    As time goes on, even for a simple, single particle, its quantum wavefunction that describes its position will spread out, spontaneously, over time. This happens for all quantum particles for a myriad of properties beyond position, such as the field value. (HANS DE VRIES / PHYSICS QUEST)

    Now, let’s combine this: we have an inflating Universe, on one hand, and quantum physics on the other. We can picture inflation as a ball rolling very slowly on top of a flat hill. So long as the ball remains atop the hill, inflation continues. When the ball reaches the end of the flat part, however, it rolls down into the valley below, which converts the energy from the inflationary field itself into matter and energy.

    This conversion signifies the end of cosmic inflation through a process known as reheating, and it gives rise to the hot Big Bang we’re all familiar with. But here’s the thing: when your Universe inflates, the value of the field changes slowly. In different inflating regions, the field value spreads out by randomly different amounts and in different directions. In some regions, inflation ends quickly; in others, it ends more slowly.

    The quantum nature of inflation means that it ends in some “pockets” of the Universe and continues in others. It needs to roll down the metaphorical hill and into the valley, but if it’s a quantum field, the spreading-out means it will end in some regions while continuing in others. (E. SIEGEL / BEYOND THE GALAXY)

    This is the key point that tells us why a Multiverse is inevitable! Where inflation ends right away, we get a hot Big Bang and a large Universe, where a small part of it might be similar to our own observable Universe. But there are other regions, outside of the region where it ends, where inflation continues for longer.

    Where the quantum spreading occurs in just the right fashion, inflation might end there, too, giving rise to a hot Big Bang and an even larger Universe, where a small portion might be similar to our observable Universe.

    But the other regions aren’t still just inflating, they’re also growing. You can calculate the rate at which the inflating regions grow and compare them to the rate at which new Universes form and hot Big Bangs occur. In all cases where inflation gives you predictions that match the observed Universe, we grow new Universes and newly inflating regions faster than inflation can come to an end.

    Wherever inflation occurs (blue cubes), it gives rise to exponentially more regions of space with each step forward in time. Even if there are many cubes where inflation ends (red Xs), there are far more regions where inflation will continue on into the future. The fact that this never comes to an end is what makes inflation ‘eternal’ once it begins, and what gives rise to our modern notion of a Multiverse. (E. SIEGEL / BEYOND THE GALAXY)

    This picture, of huge Universes, far bigger than the meager part that’s observable to us, constantly being created across this exponentially inflating space, is what the Multiverse is all about. It’s not a new, testable scientific prediction, but rather a theoretical consequence that’s unavoidable, based on the laws of physics as they’re understood today. Whether the laws of physics are identical to our own in those other Universes is unknown.

    If you have an inflationary Universe that’s governed by quantum physics, a Multiverse is unavoidable. As always, we are collecting as much new, compelling evidence as we can on a continuous basis to better understand the entire cosmos. It may turn out that inflation is wrong, that quantum physics is wrong, or that applying these rules the way we do has some fundamental flaw. But so far, everything adds up. Unless we’ve got something wrong, the Multiverse is inevitable, and the Universe we inhabit is just a minuscule part of it.

    See the full article here .


    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 10:25 am on March 23, 2019 Permalink | Reply
    Tags: , , , , Cosmology, Solar Flares Waves Jets and Ejections,   

    From AAS NOVA: “Flares, Waves, Jets, and Ejections” 


    From AAS NOVA

    22 March 2019
    Susanna Kohler

    Solar Dynamics Observatory images at 171 Å of a blowout jet erupting in the solar corona on 9 Mar 2011. The dashed white line shows the direction of jet eruption. [SDO/Miao et al. 2018]


    Our Sun often exhibits a roiling surface full of activity. But how do the different types of eruptions and disturbances we see relate to one another? Observations of one explosive jet are helping us to piece together the puzzle.

    Looking for Connections

    A coronal blowout jet captured by the Solar Dynamics Observatory on 9 Mar 2011. [Miao et al. 2018]

    Energy travels through and from the Sun via dozens of different phenomena. We see ultraviolet waves that propagate across the disk, loops and flares of plasma stretching into space, enormous coronal mass ejections that expel material through the solar system, and jets of all different sizes extending from the Sun’s surface and atmospheric layers. A longstanding mission for solar physicists has been to relate these phenomena into a broader picture explaining how energy is released from our closest star.

    Positions of the two STEREO satellites relative to the Sun and the Earth. SDO orbits the Earth. The green arrow shows the eruption direction of the blowout jet. [Miao et al. 2018]

    An Enlightening Explosion

    On 9 March 2011, a coronal blowout jet erupted from the Sun’s surface. Three spacecraft were on hand to watch: the Solar Dynamics Observatory, STEREO Ahead, and STEREO Behind.

    NASA/STEREO spacecraft

    These observatories were each located roughly 90° from each other, providing a view of the Sun’s surface from multiple angles at the moment of the explosion.

    What did they these observatories see?

    The flare
    The eruption of the blowout jet — which lasted ~21 minutes — was accompanied by a class 9.4 solar flare.
    The wave
    Shortly after the jet launch, an arc-shaped extreme ultraviolet (EUV) wave appeared on the southeastern side of the jet. This wave lasted ~4 minutes and propagated away from the site of the jet.
    The jet
    The jet itself contains both bright and dark material. The dark material appears to be due to a mini-filament — a thread of cool, dense gas suspended above the Sun’s surface by magnetic fields — that erupted in the jet base.
    The coronal mass ejection
    The two STEREO spacecraft captured what happened on large scales in the outer corona of the Sun, revealing an explosive coronal mass ejection spewing matter into space. The ejection consisted of two structures: a jet-like component and a bubble-like component.

    Causal Ties?

    STEREO Ahead (left) and Behind (right) images of the coronal mass ejection in the outer corona. Both a jet-like and a bubble-like component can be seen. [Miao et al. 2018]

    These observations provide an unprecedented look at multiple types of solar activity all occurring simultaneously — and they suggest causal ties between the different phenomena.

    In particular, the authors propose a relation in which the EUV wave was a fast-mode magnetohydrodynamic wave driven by the blowout jet eruption. They also suggest that the jet-like component of the coronal mass ejection is the outer-corona extension of the hot part of the blowout jet body, while the bubble-like component might be associated with the eruption of the mini-filament at the jet base.

    More observations like those of this event are needed to draw definitive conclusions, but this explosion has provided some definite clues about the relationship between different phenomena as the Sun lashes out into its surroundings.


    Watch the propagation of the EUV wave (top video), the eruption of the blowout jet (middle video), and the coronal mass ejections (bottom video) in the clips below. Videos can not be
    Copied and presented here. You can view them at the full article.


    “A Blowout Jet Associated with One Obvious Extreme-ultraviolet Wave and One Complicated Coronal Mass Ejection Event,” Y. Miao et al 2018 ApJ 869 39.

    See the full article here .


    Please help promote STEM in your local schools.

    Stem Education Coalition


    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.

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  • richardmitnick 4:10 pm on March 22, 2019 Permalink | Reply
    Tags: , , , Cosmology, , VVV-WIT-07, WIT-"What Is This" star   

    From ESOblog: “What Is This?” 

    ESO 50 Large

    From ESOblog

    22 March 2019

    Astronomers discover mysterious star displaying never-seen-before behaviour.

    Many, if not most, stars vary in brightness, typically by just a little and very predictably. These changes occur on timescales from minutes to years, and can tell us about the internal structure of stars in a way that no other observations can. But recently, a team of astronomers used ESO facilities to discover an extreme variable star named VVV-WIT-07, with WIT being short for “What is this?”. Seen from Earth, this strange star suddenly and irregularly reduces in brightness by 30–40%. In one extraordinary case it even dimmed by about 80%. But “normal” stars just don’t do that. The research was led by Roberto Saito from the Universidade Federal de Santa Catarina. ESO astronomer Valentin Ivanov was involved in the research and tells us more.

    We made this discovery whilst searching for extreme variable stars in the innermost parts of the Milky Way using ESO’s VISTA survey telescope.

    The Milky Way arcing over VISTA, the Visible and Infrared Survey Telescope for Astronomy, used to discover VVV-WIT-07. Credit: ESO/Y. Beletsky

    This was part of a survey of the Milky Way — named VISTA Variables in Via Lactea, or VVV for short — that we have been working on for many years. The survey is the first to image the most crowded and obscured regions of our home galaxy with high angular resolution at infrared wavelengths. The high angular resolution helps to separate the billions of stars that are superimposed close together on the sky and observing at infrared wavelengths makes it easier to see through the dust that — just like fog hides magnificent views on Earth — blocks our view of the most interesting parts of the Milky Way.

    VVV-WIT-07 in the centre of a star field. Credit: Saito et al.

    A key word that could be used to describe our finding is extreme. In every aspect. Extreme objects are always the most interesting, because they push the limits of our knowledge beyond the well-known and well-understood comfort zone. The extreme places are where new discoveries await. And surveys like VVV are a great way to identify such objects because they scan a lot of the sky many times over.

    Whilst we have found a number of extreme objects through the VVV survey so far, possibly the most mysterious is the highly varying VVV-WIT-07, which doesn’t fit with any known class of variable star. Over eight years, we observed this star 85 times through the VVV survey. The first observations showed nothing strange — simply a mild scatter in the brightness measurements, consistent with the observational uncertainties. However, in August–September 2011, just before the end of the observing season, the star dimmed by a factor of almost two! By June 2012, when we began re-observing it, the star’s brightness was nearly back to normal. But by mid-July, it had dimmed by almost 80%! Then it was back to its usual self in about a week. The data taken since then contain hints of additional drops in brightness, but nothing so dramatic.

    Our first reaction was “this can not be” — this is just a healthy pessimism, common among scientists. But once we inspected the images and checked the observations, it was clear that we had come across something very strange.

    By June 2012, when we began re-observing it, the star’s brightness was nearly back to normal. But by mid-July, it had dimmed by almost 80%!

    Since making this discovery, we have been asking ourselves why this star varies so much in brightness, but that’s not a simple question to answer. One relatively likely possibility is that an object (or even multiple objects!) is orbiting VVV-WIT-07, passing between us and its host star, blocking some of the light. Given the drastic light loss, this object could a ringed exoplanet, but with extreme, giant rings, far larger than those of Saturn. Or it could be a family of comet-like objects that occasionally block up to 80% of the starlight.

    Lightcurve of VVV-WIT-07 showing how it varied in brightness between 2010 and 2018. The insert shows an expanded view of the particularly dramatic dimming event that occurred in July 2012. Credit: Saito et al.

    Another possibility is that VVV-WIT-07 may be surrounded by a clumpy or warped disc, oriented nearly edge-on from our point of view, and the dips in brightness are caused by the clumps, or the warp, crossing the star and blocking its light.

    All these options involve extremely rare classes of objects. So far astronomers know of only one case each for a passing Saturn-like planet and comet family, and just a handful of cases of edge-on clumpy or warped discs. And the host stars in those cases don’t resemble VVV-WIT-07 at all.

    Indeed, VVV-WIT-07 is a strange object, fully justifying the “What Is This” in its name.

    SPHERE image of dust rings around a nearby star. The disc is clumpy — something astronomers currently have no explanation for. It´s possible that this phenomenon is caused by the presence of planets. Credit: ESO/Perrot

    ESO SPHERE extreme adaptive optics system and coronagraphic facility on the extreme adaptive optics system and coronagraphic facility on the VLT MELIPAL UT3, Cerro Paranal, Chile, with an elevation of 2,635 metres (8,645 ft) above sea level

    The possibility of finding new worlds is always fascinating, but we have identified a system that challenges the imagination even more than usual, because it is so unlike our own planetary system. The unusual dips in the observed brightness of VVV-WIT-07 remind us of the famous Boyajian’s Star, that dims as much as 22% — still a feeble amount compared to our star’s brightness reduction of 80%.

    Huge variations in brightness are common for stars in binary systems with two stars of near-equal mass, when one passes in front of the other. But through our observations we see clearly that VVV-WIT-07 is not a binary star. The only previously discovered non-binary star to dim by a comparable amount is Mamajek’s Object, which is the previously-mentioned star shadowed by a passing planet with a gigantic ring system.

    Further observations are needed before we will be able to draw a firm conclusion about what causes this phenomenon. We are continuing to monitor it, hoping to catch it in the act: during a dip. Then we will attempt to obtain new types of observations that should help us to find out what causes this strange behavior.

    See the full article here .


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    ESO Bloc Icon

    ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre European Extremely Large Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

    ESO VLT at Cerro Paranal in the Atacama Desert, •ANTU (UT1; The Sun ),
    •KUEYEN (UT2; The Moon ),
    •MELIPAL (UT3; The Southern Cross ), and
    •YEPUN (UT4; Venus – as evening star).
    elevation 2,635 m (8,645 ft) from above Credit J.L. Dauvergne & G. Hüdepohl atacama photo,

    ESO LaSilla
    ESO/Cerro LaSilla 600 km north of Santiago de Chile at an altitude of 2400 metres.

    ESO VLT 4 lasers on Yepun

    ESO Vista Telescope
    ESO/Vista Telescope at Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level.

    ESO/NTT at Cerro LaSilla 600 km north of Santiago de Chile at an altitude of 2400 metres.

    ESO VLT Survey telescope
    VLT Survey Telescope at Cerro Paranal with an elevation of 2,635 metres (8,645 ft) above sea level.

    ALMA Array
    ALMA on the Chajnantor plateau at 5,000 metres.

    ESO/E-ELT,to be on top of Cerro Armazones in the Atacama Desert of northern Chile. located at the summit of the mountain at an altitude of 3,060 metres (10,040 ft).

    APEX Atacama Pathfinder 5,100 meters above sea level, at the Llano de Chajnantor Observatory in the Atacama desert.

    Leiden MASCARA instrument, La Silla, located in the southern Atacama Desert 600 kilometres (370 mi) north of Santiago de Chile at an altitude of 2,400 metres (7,900 ft)

    Leiden MASCARA cabinet at ESO Cerro la Silla located in the southern Atacama Desert 600 kilometres (370 mi) north of Santiago de Chile at an altitude of 2,400 metres (7,900 ft)

    ESO Next Generation Transit Survey at Cerro Paranel, 2,635 metres (8,645 ft) above sea level

    ESO Speculoos telescopes four 1m-diameter robotic telescopes at ESO Paranal Observatory 2635 metres 8645 ft above sea level

    ESO TAROT telescope at Paranal, 2,635 metres (8,645 ft) above sea level

    ESO ExTrA telescopes at Cerro LaSilla at an altitude of 2400 metres

  • richardmitnick 2:46 pm on March 22, 2019 Permalink | Reply
    Tags: "What Ionized the Universe?", , , , , Cosmology, , Reionization era and first stars- Caltech   

    From Harvard-Smithsonian Center for Astrophysics: “What Ionized the Universe?” 

    Harvard Smithsonian Center for Astrophysics

    From Harvard-Smithsonian Center for Astrophysics

    A NASA/ESA Hubble Space Telescope image of the rapidly fading visible-light fireball from a gamma-ray burst (GRB) in a distant galaxy. A new study used the spectra of 140 GRB afterglows to estimate the amount of ionizing radiation from massive stars that escapes from galaxies to ionize the intergalactic medium, and finds the surprising result that it is very small. Andrew Fruchter (STScI) and NASA/ESA

    The sparsely distributed hot gas that exists in the space between galaxies, the intergalactic medium, is ionized. The question is, how? Astronomers know that once the early universe expanded and cooled enough, hydrogen (its main constituent) recombined into neutral atoms. Then, once newly formed massive stars began to shine in the so-called “era of reionization,” their extreme ultraviolet radiation presumably ionized the gas in processes that continue today.

    Reionization era and first stars, Caltech

    One of the key steps, however, is not well understood, namely the extent to which the stellar ionizing radiation escapes from the galaxies into the IGM. Only if the fraction escaping was high enough during the era of reionization could starlight have done the job, otherwise some other significant source of ionizing radiation is required. That might imply the existence of an important population of more exotic objects like faint quasars, X-ray binary stars, or perhaps even decaying/annihilating particles.

    Direct studies of extreme ultraviolet light are difficult because the neutral gas absorbs it very strongly. Because the universe is expanding, the spectrum absorbed covers more and more of the optical range with distance until optical observations of cosmologically remote galaxies are essentially impossible. CfA astronomer Edo Berger joined a large team of colleagues to estimate the amount of absorbing gas by looking at the spectra of gamma-ray burst (GRB) afterglows. GRBs are very bright bursts of radiation produced when the core of a massive star collapses. They are bright enough that when their radiation is absorbed in narrow spectral features by gas along the line-of sight, those features can be measured and used to calculate the amount of absorbing atomic hydrogen. That number can then be directly converted into an escape fraction for the ultraviolet light of the associated galaxy. Although a single observation of a GRB in one galaxy does not provide a robust measure, a sample of GRBs is thought to be able to provide a representative measure across all sightlines to massive stars.

    The astronomers carefully measured the spectra of 140 GRB afterglows in galaxies ranging as far away as epochs slightly less than one billion years after the big bang. They find a remarkably small escape fraction – less than about 1% of the ionizing photons make it out into the intergalactic medium. The dramatic result finds that stars provide only a small contribution to the ionizing radiation budget in the universe from that early period until today, not even in galaxies actively making new stars. The authors discuss possible reasons why GRBs might not provide an accurate measure of the absorption, although none is particularly convincing. The result needs confirmation and additional measurements, but suggests that a serious reconsideration of the ionizing budget of the intergalactic medium of the universe is needed.

    Science paper:
    “The Fraction of Ionizing Radiation from Massive Stars That Escapes to the Intergalactic Medium,” N. R. Tanvir et al.

    See the full article here .

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    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 9:18 am on March 22, 2019 Permalink | Reply
    Tags: , , , Cosmology, , , , HP 1   

    From Gemini Observatory: “Ultra-sharp Images Make Old Stars Look Absolutely Marvelous! “ 


    Gemini Observatory
    From Gemini Observatory

    March 21, 2019

    Media Contact:

    Peter Michaud
    Public Information and Outreach manager
    Gemini Observatory
    Email: pmichaud”at”gemini.edu
    Desk: 808-974-2510
    Cell: 808-936-6643

    Science Contacts:

    Leandro Kerber
    Universidade Estadual de Santa Cruz, Brazil
    Email: lokerber”at”uesc.br
    Cell: +55 11 94724-6073
    Desk: +55 73 3680-5167

    Figure 1. Color composite GSAOI+GeMS image of HP 1 obtained using the Gemini South telescope in Chile. North is up and East to the left. Composite image produced by Mattia Libralato of the Space Telescope Science Institute. Credit: Gemini Observatory/AURA/NSF.

    GSAOI+GeMS color composite image of HP 1 (right image) shown relative to the full field of the cluster obtained by the Visible and Infrared Survey Telescope for Astronomy (left). Credit: Gemini Observatory/NSF/AURA/VISTA/Aladin/CDS.

    Part of ESO’s Paranal Observatory, the VLT Survey Telescope (VISTA) observes the brilliantly clear skies above the Atacama Desert of Chile. It is the largest survey telescope in the world in visible light.
    Credit: ESO/Y. Beletsky, with an elevation of 2,635 metres (8,645 ft) above sea level

    Using high-resolution adaptive optics imaging from the Gemini Observatory, astronomers have uncovered one of the oldest star clusters in the Milky Way Galaxy. The remarkably sharp image looks back into the early history of our Universe and sheds new insights on how our Galaxy formed.

    Just as high-definition imaging is transforming home entertainment, it is also advancing the way astronomers study the Universe.

    “Ultra-sharp adaptive optics images from the Gemini Observatory allowed us to determine the ages of some of the oldest stars in our Galaxy,” said Leandro Kerber of the Universidade de São Paulo and Universidade Estadual de Santa Cruz, Brazil. Kerber led a large international research team that published their results in the April 2019 issue of the Monthly Notices of the Royal Astronomical Society.

    Gemini Observatory Adaptie Optics-Gemini South on the summit of Cerro Pachón in Chile (left) and Gemini North on the summit of Mauna Kea in Hawai’i, USA (right). Image credit Gemini/NSF/AURA

    Using advanced adaptive optics technology at the Gemini South telescope in Chile, the researchers zoomed in on a cluster of stars known as HP 1. “Removing our atmosphere’s distortions to starlight with adaptive optics reveals tremendous details in the objects we study,” added Kerber. “Because we captured these stars in such great detail, we were able to determine their advanced age and piece together a very compelling story.”

    That story begins just as the Universe was reaching its one-billionth birthday.

    “This star cluster is like an ancient fossil buried deep in our Galaxy’s bulge, and now we’ve been able to date it to a far-off time when the Universe was very young,” said Stefano Souza, a PhD student at the Universidade de São Paulo, Brazil, who worked with Kerber as part of the research team. The team’s results date the cluster at about 12.8 billion years, making these stars among the oldest ever found in our Galaxy. “These are also some of the oldest stars we’ve seen anywhere,” added Souza.

    “HP 1 is one of the surviving members of the fundamental building blocks that assembled our Galaxy’s inner bulge,” said Kerber. Until a few years ago, astronomers believed that the oldest globular star clusters — spherical swarms of up to a million stars — were only located in the outer parts of the Milky Way, while the younger ones resided in the innermost Galactic regions. However, Kerber’s study, as well as other recent work based on data from the Gemini Observatory and the Hubble Space Telescope (HST), have revealed that ancient star clusters are also found within the Galactic bulge and relatively close to the Galactic center.

    Globular clusters tell us much about the formation and evolution of the Milky Way. Most of these ancient and massive stellar systems are thought to have coalesced out of the primordial gas cloud that later collapsed to form the spiral disk of our Galaxy, while others appear to be the cores of dwarf galaxies consumed by our Milky Way. Of the roughly 160 globular clusters known in our Galaxy, about a quarter are located within the greatly obscured and tightly packed central bulge region of the Milky Way. This spherical mass of stars some 10,000 light years across forms the central hub of the Milky Way (the yolk if you will) which is made primarily of old stars, gas, and dust. Among the clusters within the bulge, those that are the most metal-poor (lacking in heavier elements) – which includes HP 1 – have long been suspected of being the oldest. HP 1 then is pivotal, as it serves as an excellent tracer of our Galaxy’s early chemical evolution.

    “HP 1 is playing a critical role in our understanding of how the Milky Way formed,” Kerber said. “It is helping us to bridge the gap in our understanding between our Galaxy’s past and its present.”

    Kerber and his international team used the exquisitely deep high-resolution adaptive optics images from Gemini Observatory as well as archival optical images from the HST to identify faint cluster members, which are essential for age determination. With this rich data set they confirmed that HP 1 is a fossil relic born less than a billion years after the Big Bang, when the Universe was in its infancy.

    “These results crown an effort of more than two decades with some of the world’s premier telescopes aimed at determining accurate chemical abundances with high-resolution spectroscopy,” said Beatriz Barbuy of the Universidade de São Paulo, coauthor of this paper and a world-renowned expert in this field. “These Gemini images are the best ground-based photometric data we have. They are at the same level of HST data, allowing us to recover a missing piece in our puzzle: the age of HP 1. From the existence of such old objects, we can attest to the short star formation timescale in the Galactic bulge, as well as its fast chemical enrichment.”

    To determine the cluster’s distance, the team used archival ground-based data to identify 11 RR Lyrae variable stars (a type of “standard candle” used to measure cosmic distances) within HP 1. The observed brightness of these RR Lyrae stars indicate that HP 1 is at a distance of about 21,500 light years, placing it approximately 6,000 light years from the Galactic center, well within the Galaxy’s central bulge region.

    Kerber and his team also used the Gemini data, as well HST, Very Large Telescope, and Gaia mission data, to refine the orbit of HP 1 within our Galaxy. This analysis shows that during HP 1’s history, the cluster came as close as about 400 light years from the Galactic center – less than one-tenth of its current distance.

    NASA/ESA Hubble Telescope

    ESO VLT at Cerro Paranal in the Atacama Desert, •ANTU (UT1; The Sun ),
    •KUEYEN (UT2; The Moon ),
    •MELIPAL (UT3; The Southern Cross ), and
    •YEPUN (UT4; Venus – as evening star).
    elevation 2,635 m (8,645 ft) from above Credit J.L. Dauvergne & G. Hüdepohl atacama photo,

    ESA/GAIA satellite

    “The combination of high angular resolution and near-infrared sensitivity makes GeMS/GSAOI an extremely powerful tool for studying these compact, highly dust-enshrouded stellar clusters,” added Mattia Libralato of the Space Telescope Science Institute, a coauthor on the study. “Careful characterization of these ancient systems, as we’ve done here, is paramount to refine our knowledge of our Galaxy’s formation.”

    Chris Davis, Program Officer at the National Science Foundation (NSF) for Gemini, commented, “These fabulous results demonstrate why the development of wide-field, high-resolution imaging at Gemini is key to the Observatory’s future. The recent NSF award to support the development of a similar system at Gemini North will make routine super-sharp imaging from both hemispheres a reality. These are certainly exciting times for the Observatory.”

    The Gemini observations resolve stars to about 0.1 arcsecond which is one 36 thousandths of a degree and comparable to separating two automobile headlamps from approximately 1,500 miles, or 2,500 kilometers, away (the distance from Manaus to Sao Paulo in Brazil, or from San Francisco to Dallas in the USA). This resolution was obtained using the Gemini South Adaptive Optics Imager (GSAOI) – a near-infrared adaptive optics camera used with the Gemini Multi-conjugate adaptive optics System (GeMS). GeMS is an advanced adaptive optics system utilizing three deformable mirrors to correct for distortions imparted on starlight by turbulence in layers of our atmosphere.

    See the full article here .

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    NOAO Gemini North on MaunaKea, Hawaii, USA, Altitude 4,213 m (13,822 ft)

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

    AURA Icon

    Gemini’s mission is to advance our knowledge of the Universe by providing the international Gemini Community with forefront access to the entire sky.

    The Gemini Observatory is an international collaboration with two identical 8-meter telescopes. The Frederick C. Gillett Gemini Telescope is located on Mauna Kea, Hawai’i (Gemini North) and the other telescope on Cerro Pachón in central Chile (Gemini South); together the twin telescopes provide full coverage over both hemispheres of the sky. The telescopes incorporate technologies that allow large, relatively thin mirrors, under active control, to collect and focus both visible and infrared radiation from space.

    The Gemini Observatory provides the astronomical communities in six partner countries with state-of-the-art astronomical facilities that allocate observing time in proportion to each country’s contribution. In addition to financial support, each country also contributes significant scientific and technical resources. The national research agencies that form the Gemini partnership include: the US National Science Foundation (NSF), the Canadian National Research Council (NRC), the Chilean Comisión Nacional de Investigación Cientifica y Tecnológica (CONICYT), the Australian Research Council (ARC), the Argentinean Ministerio de Ciencia, Tecnología e Innovación Productiva, and the Brazilian Ministério da Ciência, Tecnologia e Inovação. The observatory is managed by the Association of Universities for Research in Astronomy, Inc. (AURA) under a cooperative agreement with the NSF. The NSF also serves as the executive agency for the international partnership.

  • richardmitnick 2:35 pm on March 21, 2019 Permalink | Reply
    Tags: "The Milky Way Contains the Mass of 1.5 Trillion Suns", , , , , Cosmology, , Milkdromeda   

    From Sky & Telescope: “The Milky Way Contains the Mass of 1.5 Trillion Suns” 

    SKY&Telescope bloc

    From Sky & Telescope

    March 18, 2019
    Monica Young

    Astronomers are using Gaia and the Hubble Space Telescope to make the most precise measure of the Milky Way’s mass to date. The new result puts our galaxy on par with — if not more massive than — Andromeda Galaxy.

    ESA/GAIA satellite

    NASA/ESA Hubble Telescope

    The mass of the Milky Way has long been debated, to the point that we don’t even know where it stands in the Local Group of galaxies.

    Local Group. Andrew Z. Colvin 3 March 2011

    Is it the heavyweight champion, or does our sister galaxy, Andromeda, outweigh us?

    Andromeda Galaxy Adam Evans

    Laura Watkins (Space Telescope Science Institute) and colleagues have used data recently released by the European Space Agency’s Gaia satellite, as well as roughly ten years of Hubble Space Telescope observations, to peg the motions of 46 tightly packed bunches of stars. Known as globular clusters, their orbits help pin down the Milky Way’s mass.

    This artist’s impression shows a computer generated model of the Milky Way and the accurate positions of the globular clusters used in this study surrounding it.
    ESA / Hubble, NASA / L. Calçada

    Milky Way NASA/JPL-Caltech /ESO R. Hurt

    Our galaxy’s gravitational pull determines the clusters’ movements, explains coauthor N. Wyn Evans (University of Cambridge, UK). If our galaxy is more massive, the clusters will move faster under the stronger pull of its gravity. The key is to understand exactly how fast the clusters are moving.

    Many previous measurements have measured the speed at which a cluster is approaching or receding from Earth. “However,” Evans says, “we were able to also measure the sideways motion of the clusters, from which the total velocity, and consequently the galactic mass, can be calculated.”

    The team finds a mass equivalent to 1.5 trillion Suns. The results appear in The Astrophysical Journal.

    The Milky Way’s disk of stars (labeled here as “thin disk”) are relatively insignificant to the galaxy’s massive dark matter halo.
    NASA / ESA / A. Feild

    Milky Way Dark Matter Halo. Jürg Diemand, UCSC/UCO/ Lick

    A Tricky Scale

    Astronomers have been fussing over the mass of the Milky Way the way parents fuss over their newborns. Understandably so: Just as a baby’s weight serves as an indicator of more important things, like their growth and well-being, the heft of our galaxy affects everything from our understanding of its formation to the nature of dark matter.

    But while the pediatrician will usually tell you your baby’s weight to within a percent (equivalent to a tenth of an ounce if you’re in the U.S.), the Milky Way’s mass is known only to within a factor of two. Imagine putting your newborn on the scale, only to have the needle waver between 5 and 10 — is baby failing to thrive? Or doing just fine? The uncertainty would render the result meaningless.

    On the galactic scale, of course, there are a few more zeroes involved: Over the years, astronomers have found that the Milky Way’s mass is somewhere between 0.5 trillion and 3 trillion Suns. There are plenty of reasons for the large range. First, studying our galaxy is difficult because we’re inside of it; things like dust or the galactic plane of stars can block our view. Second, even when astronomers trace the orbits of objects — such as globular clusters — measuring their motion across the sky is trickier. It takes many years of observations to nail down their so-called proper motions. That’s what Watkins and her colleagues have done, using dedicated Hubble programs that have monitored stellar motions over roughly 10 years, as well as the second data release from the Gaia mission that has been monitoring stars since 2014.

    By far the trickiest part of the problem, though, is that much of the mass astronomers are trying to measure can’t be seen. The bulk of the Milky Way is in dark matter, not stars. Moreover, the Milky Way’s dark matter halo may extend 1 million light-years out from the galaxy’s center. Even if astronomers follow the orbit of a globular cluster around the galaxy, it will only reveal the mass inside its orbit. The farthest globular cluster in Watkins’s study is out at 130,000 light-years. To measure the mass beyond that distance, the astronomers must make some assumptions about the nature and shape of the dark matter halo.

    A More Exact Mass

    The globular cluster NGC 4147 is about 60,000 light-years from Earth.
    ESA / Hubble / NASA / T. Sohn et al.

    Nevertheless, the new measurement is so precise that it has helped narrow things down. “Together with another analysis of similar data by Posti & Helmi, this [Astronomy and Astrophysics] has tipped the scale towards a heavier Milky Way,” says Ana Bonaca (Harvard-Smithsonian Center for Astrophysics), who was not involved in the study. “Thanks to these studies, we now know that a very low value for the mass of the Milky Way is unlikely.”

    For astronomers, this new mass estimate will be most relevant for understanding the Milky Way’s swarm of satellite galaxies. For the rest of us: Phew — we’re not smaller than Andromeda after all!

    There’s still work to be done, though. The ideal tracer would be in the outer halo, Bonaca notes, out beyond 300,000 light-years. The trick is finding something that far out that we can still see, such as globular clusters, dwarf galaxies, or even streams of stars that the Milky Way’s gravity has torn from an infalling cluster or dwarf. Watkins and colleagues for their part think it’s likely that Gaia will continue to estimate the motions of many more globular clusters. No doubt, researchers will continue to narrow down the Milky Way’s mass using this and other methods for some time to come.

    Milkdromeda -Andromeda on the left-Earth’s night sky in 3.75 billion years-NASA

    See the full article here .


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    Sky & Telescope magazine, founded in 1941 by Charles A. Federer Jr. and Helen Spence Federer, has the largest, most experienced staff of any astronomy magazine in the world. Its editors are virtually all amateur or professional astronomers, and every one has built a telescope, written a book, done original research, developed a new product, or otherwise distinguished him or herself.

    Sky & Telescope magazine, now in its eighth decade, came about because of some happy accidents. Its earliest known ancestor was a four-page bulletin called The Amateur Astronomer, which was begun in 1929 by the Amateur Astronomers Association in New York City. Then, in 1935, the American Museum of Natural History opened its Hayden Planetarium and began to issue a monthly bulletin that became a full-size magazine called The Sky within a year. Under the editorship of Hans Christian Adamson, The Sky featured large illustrations and articles from astronomers all over the globe. It immediately absorbed The Amateur Astronomer.

    Despite initial success, by 1939 the planetarium found itself unable to continue financial support of The Sky. Charles A. Federer, who would become the dominant force behind Sky & Telescope, was then working as a lecturer at the planetarium. He was asked to take over publishing The Sky. Federer agreed and started an independent publishing corporation in New York.

    “Our first issue came out in January 1940,” he noted. “We dropped from 32 to 24 pages, used cheaper quality paper…but editorially we further defined the departments and tried to squeeze as much information as possible between the covers.” Federer was The Sky’s editor, and his wife, Helen, served as managing editor. In that January 1940 issue, they stated their goal: “We shall try to make the magazine meet the needs of amateur astronomy, so that amateur astronomers will come to regard it as essential to their pursuit, and professionals to consider it a worthwhile medium in which to bring their work before the public.”

  • richardmitnick 10:02 am on March 21, 2019 Permalink | Reply
    Tags: "Looking for Life? Try Around K Dwarfs", , , , , Cosmology   

    From AAS NOVA: “Looking for Life? Try Around K Dwarfs” 


    From AAS NOVA

    20 March 2019
    Susanna Kohler

    Artist’s impression of a planet orbiting a K-dwarf star. These stars may make the best targets for identifying signs of life in their planets’ atmospheres. [ESO/L. Calçada/Nick Risinger]

    Signs of life in planetary atmospheres are hard to spot! A new study suggests that the best strategy for discovering them may be to look at planets orbiting K-dwarf stars.

    The Hunt for Fingerprints

    Is there life beyond Earth? This remains one of the most profound scientific questions astronomers are currently poised to address, and development of ever more powerful telescopes continues to bring us closer to an answer.

    One way we can hope to use these telescopes to identify the presence of life on distant exoplanets is by detecting atmospheric biosignatures. Left alone, a planet’s atmosphere ought to be in chemical equilibrium. But when life is present, the atmosphere accumulates excess gases produced by the life — telltale fingerprints that we can hope to spot.

    The spectra of various types of stars used by the author in models, including the Sun (a G2V dwarf) and three types of K dwarfs. K dwarfs produce less radiation in the 200–350 nm range. [Adapted from Arney 2019]

    Signatures in Methane

    A good example of these fingerprints is the simultaneous presence of oxygen and methane in a planet’s atmosphere — something that shouldn’t occur if life isn’t there. The hunt for this biosignature is complicated by the fact that methane in the presence of oxygen is destroyed via chemical reactions driven by stellar light; if too much of the methane is removed by these photochemical reactions, we won’t be able to detect it.

    There’s hope, though: some planets may be more likely to maintain life-produced methane in their atmospheres than others. Stellar light in the 200–350 nm range triggers this reaction — so the less light a planet’s host star produces in this range, the longer methane can survive in the planet’s atmosphere. This means that the type of host star matters: G dwarfs like the Sun will destroy the methane in their planets’ atmospheres faster than smaller and cooler M dwarfs.

    Spectra from two of the author’s modeled quasi-modern planets: one around the Sun, and one around a K6V star. Orange lines show the spectra with methane removed, making the methane absorption features easier to see. The absorption features are much more evident in the planet around the K dwarf. [Adapted from Arney 2019]

    Unfortunately, M dwarfs have other complications hindering the potential for life — including high levels of stellar activity that drive atmospheric loss from their planets. For this reason, scientist Giada Arney (NASA Goddard SFC and NASA NExSS Virtual Planetary Laboratory) has explored the advantages of a different type of star: K dwarfs.

    The K-Dwarf Advantage

    K dwarfs fall between G and M dwarfs in size and temperature, and they are more abundant than G dwarfs. Dimmer than G dwarfs, K dwarfs provide better planet-to-star contrast ratios that make it easier to observe potential habitable worlds. And they are are less active than M dwarfs, providing a more hospitable environment for their planets.

    In addition to these benefits, K dwarfs also produce less radiation in the 200–350 nm range than G dwarfs do. By using a one-dimensional photochemical climate model to simulate a variety of planetary atmospheres, Arney demonstrates that a planet orbiting a K6V star can support roughly an order of magnitude more methane in the presence of oxygen relative to an equivalent planet around a G2V dwarf like the Sun.

    But is this enough to produce signatures we can soon detect? Arney uses synthesized spectra to show that, with the technologies proposed for potential future missions like LUVOIR or HabEx, we have a decent chance of spotting the simultaneous methane and oxygen signatures in planets orbiting nearby mid-late K-dwarf stars.

    NASA Large UV Optical Infrared Surveyor (LUVOIR)

    NASA Habitable Exoplanet Imaging Mission (HabEx) The Planet Hunter

    Thus the “K-dwarf advantage” gives us a great list of promising targets for the next major space missions!


    “The K Dwarf Advantage for Biosignatures on Directly Imaged Exoplanets,” Giada N. Arney 2019 ApJL 873 L7.

    See the full article here .


    Please help promote STEM in your local schools.

    Stem Education Coalition


    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

  • richardmitnick 2:30 pm on March 20, 2019 Permalink | Reply
    Tags: "X-ray ‘chimneys’ connect the Milky Way to mysterious gamma-ray bubbles", , , , Cosmology,   

    From Science News: “X-ray ‘chimneys’ connect the Milky Way to mysterious gamma-ray bubbles” 

    From Science News

    March 20, 2019
    Emily Conover

    Two glowing columns hundreds of light-years long extend from the center of the galaxy.

    DOUBLE BUBBLE Two enormous bubbles sandwich the Milky Way and emit gamma rays (illustrated). Two chimneys that glow in X-rays seem to connect these bubbles to the galaxy’s center, scientists report. NASA Goddard Space Flight Center.

    Two towering “chimneys” glowing with X-rays extend from the center of the Milky Way. The newly discovered structures could help explain the source of two even larger features: giant bubbles that emit gamma rays, or high-energy light, found above and below the plane of the galaxy.

    Stretching hundreds of light-years, the X-ray chimneys seem to connect the gamma-ray bubbles to the center of the galaxy, scientists report in the March 21 Nature. “This is really interesting, and it could potentially tell us quite a lot about the origin of the gamma-ray bubbles,” says astrophysicist Tracy Slatyer of MIT. Slatyer was part of the team that discovered the bubbles but was not involved in the new study.

    New observations with the European Space Agency’s XMM-Newton satellite uncovered the chimneys.

    ESA/XMM Newton

    The researchers “have done a fantastic job to demonstrate these very distinct features,” says astronomer Daniel Wang of the University of Massachusetts Amherst. Previously, hints of such structures have been found using Japan’s Suzaku X-ray satellite, he says.

    JAXA/Suzaku satellite

    The chimneys, which are each about 300 light-years wide, could be funneling energy from the galaxy’s center to the gamma-ray bubbles, says astronomer Mark Morris of UCLA, a coauthor of the new study. “One way of looking at it is they are exhaust vents,” through which energy escapes.

    Colossal chimneys
    Two large gamma-ray bubbles (left) are linked to the galaxy’s heart by chimneys, each hundreds of light-years long (illustrated, center; in X-ray image, right).

    Left two: NASA Goddard from M. Chernyakova/Nature 2019; Right: G. Ponti et al/Nature 2019

    Each gamma-ray bubble is itself the size of a small galaxy, and the source of the spheres’ energetic light has been a mystery since their discovery in 2010 (SN: 12/4/10, p. 18). Producing gamma rays requires highly energetic particles, which could be belched out by exploding stars, for example, or by the supermassive black hole at the heart of the galaxy as it slurps up matter and rips apart stars.

    The discovery of the chimneys doesn’t definitively pinpoint such a source. But it draws a clearer connection between the galaxy’s center and the bubbles, says astrophysicist Jun-Hui Zhao of the Harvard-Smithsonian Center for Astrophysics. “This is very important to find this piece of the puzzle,” he says.

    See the full article here .


    Please help promote STEM in your local schools.

    Stem Education Coalition

  • richardmitnick 8:34 am on March 20, 2019 Permalink | Reply
    Tags: , , , Cosmology, , ,   

    From ALMA: “Spiraling giants: witnessing the birth of a massive binary star system” 

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

    From ALMA

    18 March, 2019

    Nicolás Lira
    Education and Public Outreach Coordinator
    Joint ALMA Observatory, Santiago – Chile
    Phone: +56 2 2467 6519
    Cell phone: +56 9 9445 7726
    Email: nicolas.lira@alma.cl

    Jens Wilkinson
    RIKEN Global Communications
    Phone: +81-(0)48-462-1225
    Email: pr@riken.jp

    Masaaki Hiramatsu
    Education and Public Outreach Officer, NAOJ Chile
, Tokyo – Japan
    Phone: +81 422 34 3630
    Email: hiramatsu.masaaki@nao.ac.jp

    Calum Turner
    ESO Assistant Public Information Officer
    Garching bei München, Germany
    Phone: +49 89 3200 6670
    Email: calum.turner@eso.org

    Charles E. Blue
    Public Information Officer
    National Radio Astronomy Observatory Charlottesville, Virginia – USA
    Phone: +1 434 296 0314
    Cell phone: +1 202 236 6324
    Email: cblue@nrao.edu


    ALMA’s view of the IRAS-07299 star-forming region and the massive binary system at its center. The background image shows dense, dusty streams of gas (shown in green) that appear to be flowing towards the center. Gas motions, as traced by the methanol molecule, that are towards us are shown in blue; motions away from us in red. The inset image shows a zoom-in view of the massive forming binary, with the brighter, primary protostar moving toward us is shown in blue and the fainter, secondary protostar moving away from us shown in red. The blue and red dotted lines show an example of orbits of the primary and secondary spiraling around their center of mass (marked by the cross).

    Movie composed of images taken by ALMA showing the gas streams, as traced by the methanol molecule, with different line-of-sight color-coded velocities, around the massive binary protostar system. The grey background image shows the overall distribution, from all velocities, of dust emission from the dense gas streams.

    Scientists from the RIKEN Cluster for Pioneering Research in Japan,the Chalmers University of Technology in Sweden,and the University of Virginia in the USA and collaborators used the Atacama Large Millimeter/submillimeter Array (ALMA) to observe a molecular cloud that is collapsing to form two massive protostars that will eventually become a binary star system.

    While it is known that most massive stars possess orbiting stellar companions it has been unclear how this comes about – for example, are the stars born together from a common spiraling gas disk at the center of a collapsing cloud, or do they pair up later by chance encounters in a crowded star cluster.

    Understanding the dynamics of forming binaries has been difficult because the protostars in these systems are still enveloped in a thick cloud of gas and dust that prevents most light from escaping. Fortunately, it is possible to see them using radio waves, as long as they can be imaged with sufficiently high spatial resolution.

    In the current research, published in Nature Astronomy, the researchers led by Yichen Zhang of the RIKEN Cluster for Pioneering Research and Jonathan C. Tan at the Chalmers University,and the University of Virginia, used ALMA to observe, at high spatial resolution, a star-forming region known as IRAS07299-1651, which is located 1.68 kiloparsecs, or about 5,500 light years, away.

    The observations showed that already at this early stage, the cloud contains two objects, a massive “primary” central star and another “secondary” forming star, also of high mass. For the first time, the research team was able to use these observations to deduce the dynamics of the system. The observations showed that the two forming stars are separated by a distance of about 180 astronomical units—a unit approximately the distance from the earth to the sun. Hence, they are quite far apart. They are currently orbiting each other with a period of at most 600 years and have a total mass at least 18 times that of our Sun.

    According to Zhang, “This is an exciting finding because we have long been perplexed by the question of whether stars form into binaries during the initial collapse of the star-forming cloud or whether they are created during later stages. Our observations clearly show that the division into binary stars takes place early on, while they are still in their infancy.”

    Another finding of the study was that the binary stars are being nurtured from a common disk fed by the collapsing cloud and favoring a scenario in which the secondary star of the binary formed as a result of fragmentation of the disk originally around the primary. This allows the initially smaller secondary protostar to “steal” infalling matter from its sibling and eventually they should emerge as quite similar “twins”.

    Tan adds, “This is an important result for understanding the birth of massive stars. Such stars are important throughout the universe, not least for producing, at the ends of their lives, the heavy elements that make up our Earth and are in our bodies.”

    Zhang concludes, “What is important now is to look at other examples to see whether this is a unique situation or something that is common for the birth of all massive stars.”

    Additional Information

    RIKEN is Japan’s largest research institute for basic and applied research. Over 2500 papers by RIKEN researchers are published every year in leading scientific and technology journals covering a broad spectrum of disciplines including physics, chemistry, biology, engineering, and medical science. RIKEN’s research environment and a strong emphasis on interdisciplinary collaboration and globalization have earned a worldwide reputation for scientific excellence.

    At the RIKEN Pioneering Research Cluster, outstanding researchers with rich research achievements and strong leadership abilities serve as leaders of Chief Scientist Laboratories, from where they carry out innovative fundamental research, pioneer new research fields, and carry on research that crosses disciplinary and organizational barriers.

    See the full article here .


    Please help promote STEM in your local schools.

    Stem Education Coalition

    The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of Europe, North America and East Asia in cooperation with the Republic of Chile. ALMA is funded in Europe by the European Organization for Astronomical Research in the Southern Hemisphere (ESO), in North America by the U.S. National Science Foundation (NSF) in cooperation with the National Research Council of Canada (NRC) and the National Science Council of Taiwan (NSC) and in East Asia by the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Academia Sinica (AS) in Taiwan.

    ALMA construction and operations are led on behalf of Europe by ESO, on behalf of North America by the National Radio Astronomy Observatory (NRAO), which is managed by Associated Universities, Inc. (AUI) and on behalf of East Asia by the National Astronomical Observatory of Japan (NAOJ). The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.

    NRAO Small
    ESO 50 Large

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