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  • richardmitnick 2:45 pm on February 16, 2018 Permalink | Reply
    Tags: , , , CfA, , Magnetic Reconnection in the Sun   

    From CfA: “Magnetic Reconnection in the Sun” 

    Harvard Smithsonian Center for Astrophysics


    Center For Astrophysics

    February 16, 2018

    1

    An ultraviolet picture of the sun’s chromosphere, the thin layer of solar atmosphere sandwiched between the visible surface, the photosphere, and the corona. Astronomers have developed a simulation to address magnetic reconnection in the chromosphere. The image was taken by the Hinode spacecraft.

    JAXA/NASA HINODE spacecraft


    JAXA/NASA

    The Sun glows with a surface temperature of about 5500 degrees Celsius. On the other hand its hot outer layer, the corona, has a temperature of over a million degrees and ejects a wind of charged particles at a rate equivalent to about one-millionth of the moon’s mass each year. Some of these particles bombard the Earth, producing auroral glows and occasionally disrupting global communications. In between these two regions of the Sun is the chromosphere. Within this complex interface zone, only a few thousand kilometers deep, the density of the gas drops with height by a factor of about one million and the temperature increases. Almost all of the mechanical energy that drives solar activity is converted into heat and radiation within this interface zone.

    Charged particles are produced by the high temperatures of the gas, and their motions produce powerful, dynamic magnetic fields. Those field lines can sometimes break apart forcefully, but movement of the underlying charged particles often leads them to reconnect. There are two important, longstanding, and related questions about the hot solar wind: how is it heated, and how does the corona produce the wind? Astronomers suspect that magnetic reconnection in the chromosphere plays a key role.

    CfA astronomer Nicholas Murphy and his three colleagues have completed complex new simulations of magnetic reconnection in hot ionized gas like that present in the solar chromosphere. (The lead author on the study, Lei Ni, was a visitor to the CfA.) The scientists include for the first time the effects of incompletely ionized gas in lower temperature regions, certain particle-particle effects, and other details of the neutral and ionized gas interactions. They find that the neutral and ionized gas is well-coupled throughout the reconnection region, and conclude that reconnection can often occur in the cooler portions of the zone. They also note that new, high-resolution solar telescopes are capable of studying smaller and smaller regions of low ionization for which their results are particularly applicable.

    Science paper:
    Magnetic Reconnection in Strongly Magnetized Regions of the Low Solar Chromosphere, The Astrophysical Journal

    See the full article here .

    Please help promote STEM in your local schools.

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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.

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  • richardmitnick 12:21 pm on February 15, 2018 Permalink | Reply
    Tags: , , , , CfA,   

    From CfA: “The Extreme Nucleus of the Galaxy Arp220” 

    Harvard Smithsonian Center for Astrophysics


    Center For Astrophysics

    1
    Arp 220 – two collided spiral galaxies. NASA/ESA Hubble

    NASA/ESA Hubble Telescope

    2
    The compound view shows a new ALMA Band 5 image of the colliding galaxy system Arp 220 (in red) on top of an image from the NASA/ESA Hubble Space Telescope (blue/green). With the newly installed Band 5 receivers, ALMA has now opened its eyes to a whole new section of this radio spectrum, creating exciting new observational possibilities and improving the telescope’s ability to search for water in the Universe.

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

    In the Hubble image, most of the light from this dramatic merging galaxy pair is hidden behind dark clouds of dust. ALMA’s observations in Band 5 show a completely different view. Here, Arp 220’s famous double nucleus, invisible for Hubble, is by far the brightest feature in the whole galaxy complex. In this dense, double centre, the bright emission from water and other molecules revealed by the new Band 5 receivers will give astronomers new insights into star formation and other processes in this extreme environment.
    This image is one of the first taken using Band 5 and was intended to verify the scientific capability of the new receivers. The ALMA image includes data recording emission from water, CS and HCN in the galaxies.
    Date 21 December 2016
    ALMA(ESO/NAOJ/NRAO)/NASA/ESA and The Hubble Heritage Team (STScI/AURA)

    4
    A Chandra X-ray image of the ultraluminous merging galaxy Arp 220. Astronomers studying the X-ray emission have concluded that accretion onto the supermassive black hole nuclei contributes only a modest amount, compared with star formation, to the galaxy’s luminosity. NASA/SAO/CXC/J.McDowell

    The galaxy Arp 220 is ultraluminous (defined as having more than about 300 times the luminosity of our own galaxy) and, at a distance of only about 260 million light-years, is the closest ultraluminous galaxy to our Milky Way. Even more dramatic galaxies can have luminosities as much as ten times brighter, and astronomers are still piecing together the reasons for these huge energy outputs. The two primary suspects for the energetics are bursts of star formation that produce many hot young stars, or the accretion of material onto the supermassive black hole at a galaxy’s nucleus – an active galactic nucleus (AGN). As the closest example, Arp 220 is one of the best places to probe these different scenarios; however, observations are difficult because whatever is powering the activity in Arp220 is heavily shrouded in dust and the nuclear region is invisible at optical wavelengths.

    The starburst explanation should produce many hot young stars with abundant ultraviolet light and supernovae resulting from the deaths of the most massive and short-lived stars. The AGN explanation will produce hotter gas with more X-ray emission and characteristic spectral features. So far signs of both processes have been detected. Astronomers generally have concluded that stars are being made at a rate of about ten thousand solar-masses per year, dominating the luminosity, and that the AGN contributes only modestly to the output, less than 25%.

    Adding to the appeal and mystery of Arp 220, however, is the fact that it is a merger of two galaxies and its two constituent galactic nuclei are approaching coalescence, currently being only about one thousand light-years apart. This makes the relatively small AGN output puzzling: Simulations of galaxy mergers suggest that as the nuclei get close together their accretion soars and their luminosity dominates the emission, even exceeding 80% of the total. Moreover, observations of supermassive black hole nuclei in general find that they are systematically larger in larger galaxies, something that would be expected if, as galaxies grow in a merger, their black holes also grow from accreting matter and radiate as they do so.

    CfA astronomers Alessandro Paggi, Giuseppina Fabbiano, Guido Risaliti, Margarita Karovska, Martin Elvis, W. Peter Maksym, and Jonathan McDowell and two colleagues obtained new data using the Chandra X-ray Observatory which, combined with archival Chandra data, allowed them to identify in X-rays two locations of extremely hot atomic iron and potassium emission that coincide with the two nuclei. The lines can be produced either in supernovae (a consequence of star formation) or by an AGN. The scientists analyze these and related data to conclude that supernovae are most likely the primary source of the emission, and that, in agreement with earlier results, the AGN contribution is only modest. They also estimate the masses of the two black holes as being relatively modest, only about ten thousand solar-masses each. One implication of this paper is that the merger has not yet progressed to the stage in which active accretion onto the black hole lights up the galaxy.

    Science paper:
    X-Ray Emission from the Nuclear Region of Arp 220

    See the full article here .

    Please help promote STEM in your local schools.

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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 7:28 am on February 7, 2018 Permalink | Reply
    Tags: , , , CfA, , ,   

    From CfA: “Massive Galaxies in the Early Universe” 

    Harvard Smithsonian Center for Astrophysics


    Center For Astrophysics

    February 2, 2018

    The South Pole Telescope (SPT) is a 10-meter-diameter telescope in the Antarctic that has been operating at millimeter- and submillimeter-waves for a decade; the CfA is an institutional member of the collaboration.

    South Pole Telescope SPTPOL. The SPT collaboration is made up of over a dozen (mostly North American) institutions, including the University of Chicago, the University of California, Berkeley, Case Western Reserve University, Harvard/Smithsonian Astrophysical Observatory, the University of Colorado Boulder, McGill University, The University of Illinois at Urbana-Champaign, University of California, Davis, Ludwig Maximilian University of Munich, Argonne National Laboratory, and the National Institute for Standards and Technology. It is funded by the National Science Foundation.

    For the past six years it has been surveying the sky in a search for galaxies in the first few billion years of cosmic history; they are thought to be preferentially detectable at these wavelengths because their dust has been heated by the ultraviolet light of young stars. One of SPT discoveries, the galaxy SPT0311–58, has upon further investigation turned out to date from an epoch a mere 780 million years after the big bang. It is the most distant known case of this postulated but previously undetected population of optically dim but infrared luminous clusters.

    CfA astronomers Chris Hayward, Matt Ashby and Tony Stark are members of the SPT team that made the discovery and then followed up with the Spitzer Space Telescope, the ALMA array, the Hubble Space Telescope, and the Gemini optical/infrared telescope.

    NASA/Spitzer Infrared Telescope

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

    NASA/ESA Hubble Telescope

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

    The scientists were able to determine the cluster’s distance and epoch from the redshift of its spectral features, including a line of ionized carbon, and to characterize the overall emission properties across a wider range of wavelengths. The Spitzer and Hubble images of the source revealed the presence of a foreground galaxy that is acting as a gravitational lens to magnify SPT0311-58 and thus greatly facilitated its detection. The ALMA measurements at high spatial resolution found that the original source is actually two galaxies less than twenty-five thousand light-years apart. The implication is that these two galaxies are in the midst of colliding.

    The masses of the two galaxies are nearly one hundred billion and ten billion solar masses, respectively. The larger one is more massive than any other known galaxy at this early time in cosmic evolution, a period during which many galaxies are thought to be just forming, and is very bright, making new stars at a rate of about 2900 solar masses per year (thousands of times faster than the Milky Way). Although current models of cosmic evolution do not preclude such giant systems from existing at such early times, the observation does push the models to its limits. The results also imply that there should be a dark-matter halo present with more than 400 billion solar masses, among the rarest dark-matter haloes that should exist in the early universe.

    Reference(s):

    Galaxy Growth in a Massive Halo in the First Billion Years of Cosmic History, D. P. Marrone, J. S. Spilker, C. C. Hayward, J. D. Vieira, M. Aravena, M. L. N. Ashby, M. B. Bayliss, M. B’ethermin, M. Brodwin, M. S. Bothwell, J. E. Carlstrom, S. C. Chapman, Chian-Chou Chen, T. M. Crawford;, D. J. M. Cunningham, C. De Breuck, C. D. Fassnacht, A. H. Gonzalez, T. R. Greve, Y. D. Hezaveh, K. Lacaille, K. C. Litke, S. Lower, J. Ma, M. Malkan, T. B. Miller, W. R. Morningstar, E. J. Murphy, D. Narayanan, K. A. Phadke, K. M. Rotermund, J. Sreevani, B. Stalder, A. A. Stark, M. L. Strandet, M. Tang, & A. Weiß, Nature, 553, 51, 2018.

    3
    a, Emission in the 157.74-μm fine-structure line of ionized carbon ([C ii]) as measured at 240.57 GHz with ALMA, integrated over 1,500 km s−1 of velocity, is shown with the colour scale. The range in flux per synthesized beam (the 0.25″ × 0.30″ beam is shown in the lower left) is provided at right. The rest-frame 160-μm continuum emission that was measured simultaneously is overlaid, with contours at 8, 16, 32 and 64 times the noise level of 34 μJy per beam. SPT0311−58 E and SPT0311−58 W are labelled. b, The continuum-subtracted, source-integrated [C ii] (red) and [O iii] (blue) spectra. The upper spectra are as observed (‘apparent’) with no correction for lensing, whereas the lensing-corrected (‘intrinsic’) [C ii] spectrum is shown at the bottom. SPT0311−58 E and SPT0311−58 W separate almost completely at a velocity of 500 km s−1. c, The source-plane structure after removing the effect of gravitational lensing. The image is coloured according to the flux-weighted mean velocity, showing that the two objects are physically associated but separated by roughly 700 km s−1 in velocity and 8 kpc (projected) in space. The reconstructed 160-μm continuum emission is shown as contours. The scale bar represents the angular size of 5 kpc in the source plane. d, The line-to-continuum ratio at the 158-μm wavelength of [C ii], normalized to the map peak. The [C ii] emission from SPT0311−58 E is much brighter relative to its continuum than for SPT0311−58 W. e, Velocity-integrated emission in the 88.36-μm fine-structure line of doubly ionized oxygen ([O iii]) as measured at 429.49 GHz with ALMA (colour scale). The data have an intrinsic angular resolution of 0.2″ × 0.3″, but have been tapered to 0.5″ owing to the lower signal-to-noise ratio of these data. f, The luminosity ratio between the [O iii] and [C ii] lines. As for the [C ii] line-to-continuum ratio, a large disparity is seen between SPT0311−58 E and SPT0311−58 W. The sky coordinates and contours for rest-frame 160-μm continuum emission in d–f are the same as in a.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

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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 3:41 pm on January 22, 2018 Permalink | Reply
    Tags: , , , , CfA, , , ,   

    From CfA: “A New Bound on Axions” 

    Harvard Smithsonian Center for Astrophysics


    Center For Astrophysics

    January 19, 2018

    1
    A composite image of M87 in the X-ray from Chandra (blue) and in radio emission from the Very Large Array (red-orange). Astronomers used the X-ray emission from M87 to constrain the properties of axions, putative particles suggested as dark matter candidates. X-ray NASA/CXC/KIPAC/N. Werner, E. Million et al.; Radio NRAO/AUI/NSF/F. Owen.

    NASA/Chandra Telescope

    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)

    An axion is a hypothetical elementary particle whose existence was postulated in order to explain why certain subatomic reactions appear to violate basic symmetry constraints, in particular symmetry in time. The 1980 Nobel Prize in Physics went for the discovery of time-asymmetric reactions. Meanwhile, during the following decades, astronomers studying the motions of galaxies and the character of the cosmic microwave background [CMB] radiation came to realize that most of the matter in the universe was not visible.

    CMB per ESA/Planck

    Cosmic Background Radiation per Planck

    ESA/Planck

    It was dubbed dark matter, and today’s best measurements find that about 84% of matter in the cosmos is dark. This component is dark not only because it does not emit light — it is not composed of atoms or their usual constituents, like electrons and protons, and its nature is mysterious. Axions have been suggested as one possible solution. Particle physicists, however, have so far not been able to detect directly axions, leaving their existence in doubt and reinvigorating the puzzles they were supposed to resolve.

    CfA astronomer Paul Nulsen and his colleagues used a novel method to investigate the nature of axions. Quantum mechanics constrain axions, if they exist, to interact with light in the presence of a magnetic field. As they propagate along a strong field, axions and photons should transmute from one to the other other in an oscillatory manner. Because the strength of any possible effect depends in part on the energy of the photons, the astronomers used the Chandra X-ray Observatory to monitor bright X-ray emission from galaxies. They observed X-rays from the nucleus of the galaxy Messier 87, which is known to have strong magnetic fields, and which (at a distance of only fifty-three million light-years) is close enough to enable precise measurements of variations in the X-ray flux. Moreover, Me3ssier 87 lies in a cluster of galaxies, the Virgo cluster, which should insure the magnetic fields extend over very large scales and also facilitate the interpretation. Not least, Messier 87 has been carefully studied for decades and its properties are relatively well known.

    The search did not find the signature of axions. It does, however, set an important new limit on the strength of the coupling between axions and photons, and is able to rule out a substantial fraction of the possible future experiments that might be undertaken to detect axions. The scientists note that their research highlights the power of X-ray astronomy to probe some basic issues in particle physics, and point to complementary research activities that can be undertaken on other bright X-ray emitting galaxies.

    Science paper:
    A New Bound on Axion-Like Particles, Journal of Cosmology and Astroparticle Physics.

    See the full article here .

    Please help promote STEM in your local schools.

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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 6:32 pm on January 11, 2018 Permalink | Reply
    Tags: , , , Benzonitrile, CfA, , , , GBT Detection Unlocks Exploration of 'Aromatic' Interstellar Chemistry, PAHs-polycyclic aromatic hydrocarbons,   

    From CfA: “GBT Detection Unlocks Exploration of ‘Aromatic’ Interstellar Chemistry” 

    Harvard Smithsonian Center for Astrophysics


    Center For Astrophysics

    January 11, 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

    1
    The aromatic molecule benzonitrile was detected by the GBT in the Taurus Molecular Cloud 1 (TMC-1). B. McGuire, B. Saxton (NRAO/AUI/NSF).

    Astronomers had a mystery on their hands. No matter where they looked, from inside the Milky Way to distant galaxies, they observed a puzzling glow of infrared light. This faint cosmic light, which presents itself as a series of spikes in the infrared spectrum, had no easily identifiable source. It seemed unrelated to any recognizable cosmic feature, like giant interstellar clouds, star-forming regions, or supernova remnants. It was ubiquitous and a bit baffling.

    The likely culprit, scientists eventually deduced, was the intrinsic infrared emission from a class of organic molecules known as polycyclic aromatic hydrocarbons (PAHs), which, scientists would later discover, are amazingly plentiful; nearly 10 percent of all the carbon in the universe is tied up in PAHs.

    Even though, as a group, PAHs seemed to be the answer to this mystery, none of the hundreds of PAH molecules known to exist had ever been conclusively detected in interstellar space.

    New data from the Green Bank Telescope (GBT) show, for the first time, the convincing radio fingerprints of a close cousin and chemical precursor to PAHs, the molecule benzonitrile (C₆H₅CN).



    GBO radio telescope, Green Bank, West Virginia, USA

    This detection may finally provide the “smoking gun” that PAHs are indeed spread throughout interstellar space and account for the mysterious infrared light astronomers had been observing.

    The results of this study are presented today at the 231st meeting of the American Astronomical Society (AAS) in Washington, D.C., and published in the journal Science.

    The science team, led by chemist Brett McGuire from the National Radio Astronomy Observatory (NRAO) in Charlottesville, Virginia and the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Massachusetts, detected this molecule’s telltale radio signature coming from a nearby star-forming nebula known as the Taurus Molecular Cloud 1 (TCM-1), which is about 430 light-years from Earth.

    “These new radio observations have given us more insights than infrared observations can provide,” said McGuire. “Though we haven’t yet observed polycyclic aromatic hydrocarbons directly, we understand their chemistry quite well. We can now follow the chemical breadcrumbs from simple molecules like benzonitrile to these larger PAHs.”

    Though benzonitrile is one of the simplest so-called aromatic molecules, it is in fact the largest molecule ever seen by radio astronomy. It also is the first 6-atom aromatic ring (a hexagonal array of carbon atoms bristling with hydrogen atoms) molecule ever detected with a radio telescope. A

    While aromatic rings are commonplace in molecules seen here on Earth (they are found in everything from food to medicine), but one of this type had not previously been this is the first such ring molecule ever observed in space with radio telescopes. Its unique structure enabled the scientists to tease out its distinctive radio signature, which is the “gold standard” when confirming the presence of molecules in space.

    As molecules tumble in the near vacuum of interstellar space, they give off a distinctive signature, a series of telltale spikes that appear in the radio spectrum. Larger and more complex molecules have a correspondingly more-complex signature, making them harder to detect. PAHs and other aromatic molecules are even more difficult to detect because they typically form with very symmetrical structures.

    To produce a clear radio fingerprint, molecules must be somewhat asymmetrical. Molecules with more uniform structures, like many PAHs, can have very weak signatures or no signature at all..

    “The evidence that the GBT allowed us to amass for this detection is incredible,” said McGuire. “As we look for yet larger and more interesting molecules, we will need the sensitivity of the GBT, which has unique capabilities as a cosmic molecule detector.”

    Benzonitrile’s lopsided chemical arrangement produces strong signals as the molecule rotates, but the pattern of these signals needed to be measured very precisely here on Earth first, so that the team could match the pattern with radio observations. McGuire worked in the laboratory of Michael McCarthy at the CfA to determine the spectra fingerprint unique to benzonitrile, which then allowed the team to identify nine distinct spikes in the radio spectrum that correspond to the molecule. They also could observe the additional effects of nitrogen atom nuclei on the radio signature.

    “This discovery is another beautifully illustrates the importance and power of closely coordinating radio observations with precise measurements in the laboratory; by doing so scientists can greatly increase the speed and confidence with which we can understand the exquisite chemical richness of space,” added McCarthy.

    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 3:43 pm on December 27, 2017 Permalink | Reply
    Tags: , , , CfA, , , , , , Toothbrush Cluster   

    From CfA: “The Toothbrush Cluster” 

    Harvard Smithsonian Center for Astrophysics


    Center For Astrophysics

    1
    A multiwavelength false-color image of the “Toothbrush” cluster of galaxies, 1RXS J0603.3+4214. The intensity in red shows the radio emission, blue is X -ray, and the background color composite is optical emission. Astronomers studying the cluster with new radio observations combined with other wavelengths have been able to confirm the galaxy merger scenario and estimate the magnetic field strength in the shocks. van Weeren et al.

    Most galaxies lie in clusters containing from a few to thousands of objects. Our Milky Way, for example, belongs to a cluster of about fifty galaxies called the Local Group whose other large member is the Andromeda galaxy about 2.3 million light-years away.

    Local Group. Andrew Z. Colvin 3 March 2011

    Andromeda Galaxy Adam Evans

    Clusters are the most massive gravitationally bound objects in the universe and form (according to current ideas) in a “bottoms-up” fashion with smaller structures developing first and larger groupings assembling later in cosmic history. Dark matter plays an important role in this growth process.

    Dark matter cosmic web and the large-scale structure it forms The Millenium Simulation, V. Springel et al

    Caterpillar Project A Milky-Way-size dark-matter halo and its subhalos circled, an enormous suite of simulations . Griffen et al. 2016

    Dark matter halo Image credit: Virgo consortium / A. Amblard / ESA

    Exactly how they grow, however, appears to depend on several competing physical processes including the behavior of the intracluster gas. There is more mass in this gas than there is in all the stars of a cluster’s galaxies, and the gas can have a temperature of ten million kelvin or even higher. As a result, the gas plays an important role in the cluster’s evolution. The hot intracluster gas contains rapidly moving charged particles that radiate strongly at radio wavelengths, sometimes revealing long filamentary structures.

    The “Toothbrush” galaxy cluster, 1RXS J0603.3+4214, hosts three of these radio structures as well as a large halo. The most prominent radio feature extends over more than six million light years, with three distinct components that resemble the brush and handle of a toothbrush. The handle is particularly enigmatic because, besides being large and very straight, it is off center from the axis of the cluster. The halo is thought to result from turbulence produced by the merger of galaxies, although some other possibilities have been suggested.

    CfA astronomers Reinout van Weeren, Bill Forman, Felipe Andrade-Santos, Ralph Kraft, and Christine Jones and their colleagues used the Very Large Array (VLA) facility to observe the relativistic particles in the cluster with precise, sensitive radio imaging, which they compared with Chandra X-ray and other datasets.

    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)

    NASA/Chandra Telescope

    In the radio, the Toothbrush has a very narrow ridge, created by a huge shock resulting from the merger, and at least thirty-two previously undetected compact sources. The halo’s radio and X-ray morphologies are very similar and lend support to the merger scenario. Astronomers are also able to estimate the strength of the magnetic field, and combined with other results, use it to conclude that the merger scenario is most suitable.

    Reference(s):

    Deep VLA Observations of the Cluster 1RXS J0603.3+4214 in the Frequency Range 1-2 GHz, K. Rajpurohit, M. Hoeft, R. J. van Weeren, L. Rudnick, H. J. A. R ottgering, W. R. Forman, M. Bruggen, J. H. Croston, F. Andrade-Santos, W. A. Dawson, H. T. Intema, R. P. Kraft, C. Jones, and M. James Jee, http://lanl.arxiv.org/abs/1712.01327

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    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 4:49 pm on December 20, 2017 Permalink | Reply
    Tags: A snake-like structure lurking near our galaxy’s supermassive black hole is the latest discovery to tantalize astronomers, , , , CfA, , ,   

    From CfA: “Cosmic Filament Probes Our Galaxy’s Giant Black Hole” 

    Harvard Smithsonian Center for Astrophysics


    Center For Astrophysics

    December 20, 2017
    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

    1
    A radio image from the NSF’s Karl G. Jansky Very Large Array showing the center of our galaxy. The mysterious radio filament is the curved line located near the center of the image, & the supermassive black hole Sagittarius A* (Sgr A*), is shown by the bright source near the bottom of the image. NSF/VLA/UCLA/M. Morris et al.

    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)

    The center of our Galaxy has been intensely studied for many years, but it still harbors surprises for scientists. A snake-like structure lurking near our galaxy’s supermassive black hole is the latest discovery to tantalize astronomers.

    In 2016, Farhad Yusef-Zadeh of Northwestern University reported the discovery of an unusual filament near the center of the Milky Way Galaxy using the NSF’s Karl G. Jansky Very Large Array (VLA). The filament is about 2.3 light years long and curves around to point at the supermassive black hole, called Sagittarius A* (Sgr A*), located in the Galactic center.

    Now, another team of astronomers has employed a pioneering technique to produce the highest-quality image yet obtained of this curved object.

    “With our improved image, we can now follow this filament much closer to the Galaxy’s central black hole, and it is now close enough to indicate to us that it must originate there,” said Mark Morris of the University of California, Los Angeles, who led the study. “However, we still have more work to do to find out what the true nature of this filament is.”

    The researchers have considered three main explanations for the filament. The first is that it is caused by high-speed particles kicked away from the supermassive black hole. A spinning black hole coupled with gas spiraling inwards can produce a rotating, vertical tower of magnetic field that approaches or even threads the event horizon, the point of no return for infalling matter. Within this tower, particles would be sped up and produce radio emission as they spiral around magnetic field lines and stream away from the black hole.

    The second, more fantastic, possibility is that the filament is a cosmic string, theoretical, as-yet undetected objects that are long, extremely thin objects that carry mass and electric currents. Previously, theorists had predicted that cosmic strings, if they exist, would migrate to the centers of galaxies. If the string moves close enough to the central black hole it might be captured once a portion of the string crosses the event horizon.

    The final option is that the position and the direction of the filament aligning with the black hole are merely coincidental superpositions, and there is no real association between the two. This would imply it is like dozens of other known filaments found farther away from the center of the Galaxy. However, such a coincidence is quite unlikely to happen by chance.

    “Part of the thrill of science is stumbling across a mystery that is not easy to solve,” said co-author Jun-Hui Zhao of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. “While we don’t have the answer yet, the path to finding it is fascinating. This result is motivating astronomers to build next generation radio telescopes with cutting edge technology.”

    Each of the scenarios being investigated would provide intriguing insight if proven true. For example, if the filament is caused by particles being ejected by Sgr A*, this would reveal important information about the magnetic field in this special environment, showing that it is smooth and orderly rather than chaotic.

    The second option, the cosmic string, would provide the first evidence for a highly speculative idea with profound implications for understanding gravity, space-time and the Universe itself.

    Evidence for the idea that particles are being magnetically kicked away from the black hole would come from observing that particles further away from Sgr A* are less energetic than those close in. A test for the cosmic string idea will capitalize on the prediction by theorists that the string should move at a high fraction of the speed of light. Follow-up observations with the VLA should be able to detect the corresponding shift in position of the filament.

    Even if the filament is not physically tied to Sgr A*, the bend in the shape of this filament is still unusual. The bend coincides with, and could be caused by, a shock wave, akin to a sonic boom, where the blast wave from an exploded star is colliding with the powerful winds blowing away from massive stars surrounding the central black hole.

    “We will keep hunting until we have a solid explanation for this object,” said co-author Miller Goss, from the National Radio Astronomy Observatory in Socorro, New Mexico. “And we are aiming to next produce even better, more revealing images.”

    A paper describing these results appeared in the December 1st, 2017 issue of The Astrophysical Journal Letters.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    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 2:55 pm on December 19, 2017 Permalink | Reply
    Tags: , , , CfA, , Greenland Telescope achieves “first light”,   

    From NSF: “Greenland Telescope achieves ‘first light'” 

    nsf
    National Science Foundation

    Greenland Telescope achieves “first light”

    1

    Using an artificial light source on South Mountain at the Thule Air Base, Greenland, the Greenland Telescope has proved its operational effectiveness and achieved a significant milestone toward being an operational telescope.

    The optical telescope, attached to the telescope’s 12-meter radio dish, with its focus set just shy of infinity, captured the lights on South Mountain. This is a significant milestone and step toward an operating telescope!

    The telescope’s science team will spend the coming weeks fine-tuning and pointing the telescope at known astronomical sources to help calibrate the instrument. They plan to participate with other telescopes in a springtime Very-Long-Baseline Interferometry (VLBI) -observation campaign. The Greenland Telescope is also set to observe as part of the Event Horizon Telescope campaign in April. Event Horizon is a project to create a large telescope array consisting of a global network of radio telescopes and combining data from several very-long-baseline interferometry (VLBI) stations around the Earth. The aim is to observe the immediate environment of the Milky Way’s supermassive black hole.

    Originally a North America Prototype Antenna for the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, assembly of the telescope was completed in July 2017. OPP’s Arctic Research Support & Logistics program has provided guidance and planning support to the Smithsonian Astrophysical Observatory (SAO) throughout the effort to install the telescope in Greenland. The Greenland Telescope project is a joint effort between SAO and ASIAA in Taiwan.

    See the full article here .

    Please help promote STEM in your local schools.
    STEM Icon

    Stem Education Coalition

    The National Science Foundation (NSF) is an independent federal agency created by Congress in 1950 “to promote the progress of science; to advance the national health, prosperity, and welfare; to secure the national defense…we are the funding source for approximately 24 percent of all federally supported basic research conducted by America’s colleges and universities. In many fields such as mathematics, computer science and the social sciences, NSF is the major source of federal backing.

     
  • richardmitnick 12:37 pm on October 16, 2017 Permalink | Reply
    Tags: , , , , CfA, , ,   

    From CfA: “CfA Scientists Weigh in on Historic Gravitational Wave Discovery” and the Press Release 

    Harvard Smithsonian Center for Astrophysics


    Center For Astrophysics

    October 16, 2017

    Scientists have detected gravitational waves and electromagnetic radiation, or light, from the same event for the first time, as described in our latest press release [see below].

    Thousands of scientists around the world have worked on this result, with researchers at the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Mass., playing a pivotal role. A series of eight papers led by CfA astronomers and their colleagues detail the complete story of the aftermath of this event and reveal clues about its origin.

    We conducted interviews with four CfA scientists about their work on this discovery: Professor Edo Berger, who led the work, postdoctoral fellow Matt Nicholl, and graduate students Kate Alexander and Philip Cowperthwaite. Here they describe their reactions to the exciting news that Advanced LIGO had detected gravitational waves from a neutron star merger, and they discuss unanswered questions and prospects for future work.

    How did you hear about LIGO’s detection of a neutron star merger and what were your first thoughts?

    Kate Alexander:

    I saw the e-mail from the LIGO collaboration when I woke up in the morning, and no one was expecting it because LIGO was a week away from shutting down from its current observing run. We all just kind of went “Wow. Oh my goodness! This is actually happening.” Edo called a meeting and we all rushed into his office to prepare our plans for following it up.


    VIRGO Gravitational Wave interferometer, near Pisa, Italy

    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

    1
    Skymap showing how adding Virgo to LIGO helps in reducing the size of the source-likely region in the sky. (Credit: Giuseppe Greco (Virgo Urbino group)

    Edo Berger:

    So, we first got an alert from LIGO on the morning of August 17th. I was actually in the middle of a boring committee meeting. My office phone started ringing, and I ignored it. Then my cell phone started ringing and I ignored it. Then text messages started coming in. At that point I knew that I couldn’t ignore it anymore, so I kicked everybody out of the office and started catching up on this new alert that came from the LIGO observatory saying that they detected the first merger of a neutron star binary system.

    Matt Nicholl:

    As soon as we started observing the sky in Chile we were transferring these images back to computers at Harvard as soon as they came in and we all frantically brought them up on our computer screens and looked for new sources that appeared. Really what we expected was that we wouldn’t find anything in real time and that we’d spend the whole day next day processing these images trying to find some sort of faint little detections of possible candidates. But what actually happened was that one of the first giant galaxies we looked had an obvious new source popping right out at us. This was an incredible moment. I think one of my collaborators saw it first and sent an email that I can’t quite repeat but I will never forget. After that our email inboxes exploded. Every team in the world was looking at this thing and trying to compete to say things first. It was a night unlike any other I’ve had in my career.

    Phil Cowperthwaite:

    I actually heard about it through a very informal email from a colleague. I just woke up that morning and it was there on my phone: “Oh we have a binary neutron star in LIGO with a coincident Fermi detection. It’s insane. It took a moment to process – it didn’t seem real because that was the goal we never expected to happen.”

    What are some unanswered questions and the prospects for future work?

    Kate Alexander:

    The VLA has been invaluable to the science so far.

    NRAO/Karl V Jansky VLA, on the Plains of San Agustin fifty miles west of Socorro, NM, USA

    This is going to continue to be a very interesting target for radio observations going forward. The radio emission that we’re observing is likely to continue to be observable with the VLA for the next several weeks to months, and we’ll be very eager to monitor the radio emission we’ve seen as it slowly fades away. We also predict that several years from now the source should brighten in the radio again as all of the slower moving material that produced the optical light eventually starts producing a shock wave [akin to a sonic boom] with the surrounding medium. Then we’ll have a completely independent second chance to figure out all of these properties of the environment around the neutron star. We don’t know exactly when this will happen, but we certainly will continue to look at it with the VLA for years to come.

    Edo Berger:

    In studying both the gravitational wave signal and the electromagnetic signal what we hope to do is understand the detailed composition of neutron stars. What are they exactly made of? What do they look like on the inside? The only way we get to see the inside of a neutron star is when it collides with another neutron star and then material from the inside spills out. This is what we see in our observations. We also want to understand how pairs of neutron stars actually come into being. How are they actually formed? How are these systems born? How was their life before they ended it in that final catastrophic collision?

    One of the particularly exciting aspects of studying the collisions of neutron stars in both gravitational waves and electromagnetic radiation is that it gives us a completely new way of measuring the Hubble Constant, which is the measurement of how fast the Universe is expanding. So far, we’ve been studying the Hubble Constant using different techniques: supernova explosions or the cosmic microwave background [leftover radiation from the Big Bang].

    CMB per ESA/Planck

    ESA/Planck

    But here, for the first time, we have a completely independent new way of measuring the Hubble Constant. We can measure the distance to the object from the gravitational wave signal and we can then measure the amount of redshifting which tells us how fast the universe is expanding from the electromagnetic signal. And by combining these two measurements we can directly measure the Hubble Constant.

    Matt Nicholl:

    I think the big outstanding questions now are first of all how typical was this event of the general population of neutron star mergers? Maybe we got lucky and we found a very bright one. Maybe the others aren’t going to be so great. But we’ll find this out in the next few years as LIGO detects more and more of these sources. By detecting more sources we can also measure the rate at which they occur. The combination of those two things is very powerful. If we know how diverse they are and how often they occur we can work out the total production of heavy elements in the universe. If we compare this production of heavy elements to the abundances that we measure in our local environment we can show definitively whether all heavy elements come from neutron star mergers.

    Phil Cowperthwaite:

    You can do all kinds of science that you could not do with just a gravitational wave detection. The gravitational wave detection is great for telling you about the binary, the objects that merged and their properties, but it can’t do other things. For instance, LIGO can’t give you a precise location on the sky. It can do very well, especially with Virgo, but once you have an optical counterpart you know exactly where that event occurred. And then you can do all kinds of other exciting science. We can associate the source with a galaxy. We can learn about where these objects come from. What are their homes like? Understanding all this information will help us understand the behavior of the merger: how much material is produced, which is important for understanding whether or not these events can truly be the source of heavy element production. So, it really is necessary to maximize the science goals.

    Press release:
    Astronomers See Light Show Associated With Gravitational Waves
    October 16, 2017
    Megan Watzke
    Harvard-Smithsonian Center for Astrophysics
    +1 617-496-7998
    mwatzke@cfa.harvard.edu

    Marking the beginning of a new era in astrophysics, scientists have detected gravitational waves and electromagnetic radiation, or light, from the same event for the first time. This historic discovery reveals the merger of two neutron stars, the dense cores of dead stars, and resolves the debate about how the heaviest elements such as platinum and gold were created in the Universe.

    To achieve this remarkable result, thousands of scientists around the world have worked feverishly using data from telescopes on the ground and in space. Researchers at the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Mass., have played a pivotal role. A series of eight papers led by CfA astronomers and their colleagues detail the complete story of the aftermath of this event and examine clues about its origin.

    “It’s hard to describe our sense of excitement and historical purpose over the past couple of months,” said the leader of the team, CfA’s Edo Berger. “This is a once in a career moment — we have fulfilled a dream of scientists that has existed for decades.”

    Gravitational waves are ripples in space-time caused by the accelerated motion of massive celestial objects. They were first predicted by Einstein’s General Theory of Relativity. The Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO) made the first direct detection of gravitational waves in September 2015, when the merger of two stellar-mass black holes was discovered.

    On 8:41 am EDT August 17, 2017, LIGO detected a new gravitational wave source, dubbed GW170817 to mark its discovery date. Just two seconds later NASA’s Fermi satellite detected a weak pulse of gamma rays from the same location of the sky. Later that morning, LIGO scientists announced that two merging neutron stars produced the gravitational waves from GW170817.

    “Imagine that gravitational waves are like thunder. We’ve heard this thunder before, but this is the first time we’ve also been able to see the lightning that goes with it,” said Philip Cowperthwaite of the CfA. “The difference is that in this cosmic thunderstorm, we hear the thunder first and then get the light show afterwards.”

    A few hours after the announcement, as night set in Chile, Berger’s team used the powerful Dark Energy Camera on the Blanco telescope to search the region of sky from which the gravitational waves emanated. In less than an hour they located a new source of visible light in the galaxy NGC 4993 at a distance of about 130 million light years.

    “One of the first giant galaxies we looked at had an obvious new source of light popping right out at us, and this was an incredible moment,” said Matt Nicholl of the CfA. “We thought it would take days to locate the source but this was like X marks the spot.”

    The CfA team and collaborators then launched a series of observations that spanned the electromagnetic spectrum from X-rays to radio waves to study the aftermath of the neutron star merger.

    In their set of papers, the CfA scientists report their studies of the brightness and spectrum of the optical and infrared light and how it changed over time. They show that the light is caused by the radioactive glow when heavy elements in the material ejected by the neutron star merger are produced in a process called a kilonova.

    “We’ve shown that the heaviest elements in the periodic table, whose origin was shrouded in mystery until today are made in the mergers of neutron stars,” said Edo Berger. “Each merger can produce more than an Earth’s mass of precious metals like gold and platinum and many of the rare elements found in our cellphones.”

    The material observed in the kilonova is moving at high speeds, suggesting that it was expelled during the head-on collision of two neutron stars. This information, independent of the gravitational wave signature, suggests that two neutron stars were involved in GW170817, rather than a black hole and a neutron star.

    Radio observations with the Very Large Array in New Mexico helped confirm that the merger of the two neutron stars triggered a short gamma ray burst (GRB), a brief burst of gamma rays in a jet of high-energy particles. The properties match those predicted by theoretical models of a short GRB that was viewed with the jet initially pointing at a large angle away from Earth. Combining the radio data with observations from NASA’s Chandra X-ray Observatory shows that the jet pointed about 30 degrees away from us.

    “This object looks far more like the theories than we had any right to expect,” said the CfA’s Kate Alexander who led the teams’ VLA observations. “We will continue to track the radio emission for years to come as the material ejected from the collision slams into the surrounding medium,” she continued.

    An analysis of the host galaxy, NGC 4993, and the environment of the cataclysmic merger shows that the neutron star binary most likely formed more than 11 billion years ago.

    “The two neutron stars formed in supernova explosions when the universe was only two billion years old, and have spent the rest of cosmic history getting closer and closer to each other until they finally smashed together,” said Peter Blanchard of the CfA.

    A long list of observatories were used to study the kilonova, including the SOAR and Magellan telescopes, the Hubble Space Telescope, the Dark Energy Camera on the Blanco, and the Gemini-South telescope.

    The series of eight papers describing these results appeared in the Astrophysical Journal Letters on October 16th. The four papers with first authors from CfA are led by Philip Cowperthwaite about the changes with time of light from the kilonova, one led by Matt Nicholl about the changes with time of the kilonova’s spectrum, another led by Kate Alexander about the VLA observations, and another led by Peter Blanchard about how long the merger took to unfold and the properties of the host galaxy.

    Completing the series of eight papers, Marcelle Soares-Santos from Brandeis University in Waltham MA led a paper about the discovery of the optical counterpart; Ryan Chornock from Ohio University in Athens, OH, led a paper about the kilonova’s infrared spectra, Raffaella Margutti from Northwestern University in Evanston, IL, led a paper about the Chandra observations of the jet, and Wen-fai Fong also from Northwestern led a paper about the comparison between GW170817 and previous short GRBs.

    Graphics and other additional information on this result can be found at http://www.kilonova.org.

    Headquartered in Cambridge, Mass., the Harvard-Smithsonian Center for Astrophysics (CfA) is a collaboration between the Smithsonian Astrophysical Observatory and the Harvard College Observatory. CfA scientists, organized into six research divisions, study the origin, evolution and ultimate fate of the universe.

    See the full main article here .
    See the press release here .

    Please help promote STEM in your local schools.

    STEM Icon

    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 3:51 pm on October 12, 2017 Permalink | Reply
    Tags: , , , CfA, , , NRAO/VLBA - Very Long Baseline Array, The far side of the Milky Way   

    From Max Planck Institute for Radio Astronomy and CfA : “The far side of the Milky Way” 


    Max Planck Institute for Radio Astronomy

    CfA

    October 12, 2017
    Contact
    Dr. Alberto Sanna
    Max Planck Institute for Radio Astronomy, Bonn
    Phone:+49 228 525-304
    asanna@mpifr-bonn.mpg.de

    Prof. Dr. Karl M. Menten
    Max Planck Institute for Radio Astronomy, Bonn
    Phone:+49 228 525-297
    Fax:+49 228 525-435
    kmenten@mpifr-bonn.mpg.de

    Dr. Norbert Junkes
    Max Planck Institute for Radio Astronomy, Bonn
    Phone:+49 228 525-399
    njunkes@mpifr.de

    Astronomers achieve record measurement for an improved picture of our home galaxy.

    Astronomers from the Max Planck Institute for Radio Astronomy in Bonn, Germany, and the Harvard-Smithsonian Center for Astrophysics, using the Very Long Baseline Array, have directly measured a distance of more than 66,000 light-years to a star-forming region. This region, known as G007.47+00.05, is on the opposite side of our Milky Way Galaxy from the Sun. The researchers’ achievement reaches deep into the Milky Way’s terra incognita and nearly doubles the previous record for distance measurement within our Galaxy.

    NRAO VLBA


    NRAO/VLBA


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

    Distance measurements are crucial for an understanding of the structure of the Milky Way. Most of our Galaxy’s material, consisting principally of stars, gas, and dust, lies within a flattened disk, in which our Solar System is embedded. Because we cannot see our Galaxy face-on, its structure, including the shape of its spiral arms, can only be mapped by measuring distances to objects elsewhere in the Galaxy.

    The astronomers used a technique called trigonometric parallax, first applied by Friedrich Wilhelm Bessel in 1838 to measure the distance to the star 61 Cygni in the constellation of the Swan. This technique measures the apparent shift in the sky position of a celestial object as seen from opposite sides of the Earth’s orbit around the Sun. This effect can be demonstrated by holding a finger in front of one’s nose and alternately closing each eye — the finger appears to jump from side to side.

    Measuring the angle of an object’s apparent shift in position this way allows astronomers to use simple trigonometry to directly calculate the distance to that object. The smaller the measured angle, the greater the distance is. In the framework of the Bar and Spiral Structure Legacy (BeSSeL) Survey, it is now possible to measure parallaxes a thousand times more accurate than Friedrich Bessel. The Very Long Baseline Array (VLBA), a continent-wide radio telescope system, with ten dish antennas distributed across North America, Hawaii, and the Caribbean, can measure the minuscule angles associated with great distances. In this case, the measurement was roughly equal to the angular size of a baseball on the Moon.

    “Using the VLBA, we now can accurately map the whole extent of our Galaxy,” says Alberto Sanna, of the Max Planck Institute for Radio Astronomy in Germany (MPIfR).

    The new VLBA observations, made in 2014 and 2015, measured a distance of more than 66,000 light-years to the star-forming region G007.47+00.05 on the opposite side of the Milky Way from the Sun, well past the Galaxy’s center in a distance of 27,000 light-years. The previous record for a parallax measurement was about 36,000 light-years.

    2

    Highly complex observations: The calculation of distances is principally simple, but requires highly accurate measurements of the angle of apparent shifts in an object’s position – only the VLBA has the capability to deliver such measurements.
    © Bill Saxton, NRAO/AUI/NSF; Robert Hurt, NASA.

    “Most of the stars and gas in our Galaxy are within this newly-measured distance from the Sun. With the VLBA, we now have the capability to measure enough distances to accurately trace the Galaxy’s spiral arms and learn their true shapes,” Sanna explains.

    The VLBA observations measured the distance to a region where new stars are being formed.

    Such regions include areas where molecules of water and methanol act as natural amplifiers of radio signals — masers, the radio-wave equivalent of lasers for light waves. This effect makes the radio signals bright and readily observable with radio telescopes.

    The Milky Way has hundreds of such star-forming regions that include masers. “So we have plenty of ‘mileposts’ to use for our mapping project. But this one is special: Looking all the way through the Milky Way, past its center, way out into the other side”, says the MPIfR’s Karl Menten.

    The astronomers’ goal is to finally reveal what our own Galaxy looks like if we could leave it, travel outward perhaps a million light-years, and view it face-on, rather than along the plane of its disk. This task will require many more observations and much painstaking work, but, the scientists say, the tools for the job now are in hand. How long will it take?

    “Within the next 10 years, we should have a fairly complete picture,” predicts Mark Reid of the Harvard-Smithsonian Center for Astrophysics.

    Science paper:
    Mapping Spiral Structure on the far side of the Milky Way, Science

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    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.



    MPIFR/Effelsberg Radio Telescope, Germany

    The Max Planck Institute for Radio Astronomy (German: Max-Planck-Institut für Radioastronomie) is located in Bonn, Germany. It is one of 80 institutes in the Max Planck Society (German: Max-Planck-Gesellschaft).

    By combining the already existing radio astronomy faculty of the University of Bonn led by Otto Hachenberg with the new Max Planck institute the Max Planck Institute for Radio Astronomy was formed. In 1972 the 100-m radio telescope in Effelsberg was opened. The institute building was enlarged in 1983 and 2002.

    The institute was founded in 1966 by the Max-Planck-Gesellschaft as the “Max-Planck-Institut für Radioastronomie” (MPIfR).

    The foundation of the institute was closely linked to plans in the German astronomical community to construct a competitive large radio telescope in (then) West Germany. In 1964, Professors Friedrich Becker, Wolfgang Priester and Otto Hachenberg of the Astronomische Institute der Universität Bonn submitted a proposal to the Stiftung Volkswagenwerk for the construction of a large fully steerable radio telescope.

    In the same year the Stiftung Volkswagenwerk approved the funding of the telescope project but with the condition that an organization should be found, which would guarantee the operations. It was clear that the operation of such a large instrument was well beyond the possibilities of a single university institute.

    Already in 1965 the Max-Planck-Gesellschaft (MPG) decided in principle to found the Max-Planck-Institut für Radioastronomie. Eventually, after a series of discussions, the institute was officially founded in 1966.

    The Max Planck Society for the Advancement of Science (German: Max-Planck-Gesellschaft zur Förderung der Wissenschaften e. V.; abbreviated MPG) is a formally independent non-governmental and non-profit association of German research institutes founded in 1911 as the Kaiser Wilhelm Society and renamed the Max Planck Society in 1948 in honor of its former president, theoretical physicist Max Planck. The society is funded by the federal and state governments of Germany as well as other sources.

    According to its primary goal, the Max Planck Society supports fundamental research in the natural, life and social sciences, the arts and humanities in its 83 (as of January 2014)[2] Max Planck Institutes. The society has a total staff of approximately 17,000 permanent employees, including 5,470 scientists, plus around 4,600 non-tenured scientists and guests. Society budget for 2015 was about €1.7 billion.

    The Max Planck Institutes focus on excellence in research. The Max Planck Society has a world-leading reputation as a science and technology research organization, with 33 Nobel Prizes awarded to their scientists, and is generally regarded as the foremost basic research organization in Europe and the world. In 2013, the Nature Publishing Index placed the Max Planck institutes fifth worldwide in terms of research published in Nature journals (after Harvard, MIT, Stanford and the US NIH). In terms of total research volume (unweighted by citations or impact), the Max Planck Society is only outranked by the Chinese Academy of Sciences, the Russian Academy of Sciences and Harvard University. The Thomson Reuters-Science Watch website placed the Max Planck Society as the second leading research organization worldwide following Harvard University, in terms of the impact of the produced research over science fields.

     
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