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  • richardmitnick 1:25 pm on July 6, 2020 Permalink | Reply
    Tags: "Dying stars breathe life into Earth: study", ,   

    From Johns Hopkins University via phys.org: “Dying stars breathe life into Earth: study” 

    From Johns Hopkins University

    via


    phys.org

    July 6, 2020

    1
    NGC 7789, also known as Caroline’s Rose, is an old open star cluster of the Milky Way, which lies about 8,000 light-years away toward the constellation Cassiopeia. It hosts a few White Dwarfs of unusually high mass, analyzed in this study. Credit: Guillaume Seigneuret and NASA

    As dying stars take their final few breaths of life, they gently sprinkle their ashes into the cosmos through the magnificent planetary nebulae. These ashes, spread via stellar winds, are enriched with many different chemical elements, including carbon.

    Findings from a study published today in Nature Astronomy show that the final breaths of these dying stars, called white dwarfs, shed light on carbon’s origin in the Milky Way.

    “The findings pose new, stringent constraints on how and when carbon was produced by stars of our galaxy, ending up within the raw material from which the Sun and its planetary system were formed 4.6 billion years ago,” says Jeffrey Cummings, an Associate Research Scientist in the Johns Hopkins University’s Department of Physics & Astronomy and an author on the paper.

    The origin of carbon, an element essential to life on Earth, in the Milky Way galaxy is still debated among astrophysicists: some are in favor of low-mass stars that blew off their carbon-rich envelopes by stellar winds became white dwarfs, and others place the major site of carbon’s synthesis in the winds of massive stars that eventually exploded as supernovae.

    Using data from the Keck Observatory near the summit of Mauna Kea volcano in Hawaii collected between August and September 2018, the researchers analyzed white dwarfs belonging to the Milky Way’s open star clusters. Open star clusters are groups of up to a few thousand stars held together by mutual gravitational attraction.

    From this analysis, the research team measured the white dwarfs’ masses, and using the theory of stellar evolution, also calculated their masses at birth.

    The connection between the birth masses to the final white dwarf masses is called the initial-final mass relation, a fundamental diagnostic in astrophysics that contains the entire life cycles of stars. Previous research always found an increasing linear relationship: the more massive the star at birth, the more massive the white dwarf left at its death.

    But when Cummings and his colleagues calculated the initial-final mass relation, they were shocked to find that the white dwarfs from this group of open clusters had larger masses than astrophysicists previously believed. This discovery, they realized, broke the linear trend other studies always found. In other words, stars born roughly 1 billion years ago in the Milky Way didn’t produce white dwarfs of about 0.60-0.65 solar masses, as it was commonly thought, but they died leaving behind more massive remnants of about 0.7—0.75 solar masses.

    The researchers say that this kink in the trend explains how carbon from low-mass stars made its way into the Milky Way. In the last phases of their lives, stars twice as massive as the Milky Way’s Sun produced new carbon atoms in their hot interiors, transported them to the surface and finally spread them into the surrounding interstellar environment through gentle stellar winds. The research team’s stellar models indicate that the stripping of the carbon-rich outer mantle occurred slowly enough to allow the central cores of these stars, the future white dwarfs, to grow considerably in mass.

    The team calculated that stars had to be at least 1.5 solar masses to spread its carbon-rich ashes upon death.

    The findings, according to Paola Marigo, a Professor of Physics and Astronomy at the University of Padova and the study’s first author, helps scientists understand the properties of galaxies in the universe. By combining the theories of cosmology and stellar evolution, the researchers expect that bright carbon-rich stars close to their death, like the progenitors of the white dwarfs analyzed in this study, are presently contributing to the light emitted by very distant galaxies. This light, which carries the signature of newly produced carbon, is routinely collected by the large telescopes from space and Earth to probe the evolution of cosmic structures. Therefore, this new understanding of how carbon is synthesized in stars also means having a more reliable interpreter of the light from the far universe.

    See the full article here .

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    The Johns Hopkins University opened in 1876, with the inauguration of its first president, Daniel Coit Gilman. “What are we aiming at?” Gilman asked in his installation address. “The encouragement of research … and the advancement of individual scholars, who by their excellence will advance the sciences they pursue, and the society where they dwell.”

    The mission laid out by Gilman remains the university’s mission today, summed up in a simple but powerful restatement of Gilman’s own words: “Knowledge for the world.”

    What Gilman created was a research university, dedicated to advancing both students’ knowledge and the state of human knowledge through research and scholarship. Gilman believed that teaching and research are interdependent, that success in one depends on success in the other. A modern university, he believed, must do both well. The realization of Gilman’s philosophy at Johns Hopkins, and at other institutions that later attracted Johns Hopkins-trained scholars, revolutionized higher education in America, leading to the research university system as it exists today.

     
  • richardmitnick 12:54 pm on July 6, 2020 Permalink | Reply
    Tags: "Herschel and Planck views of star formation", , , , ,   

    From European Space Agency – United space in Europe: “Herschel and Planck views of star formation” 

    ESA Space For Europe Banner

    From European Space Agency – United space in Europe

    From United Space in Europe

    06/07/2020

    A collection of intriguing images based on data from ESA’s Herschel and Planck space telescopes show the influence of magnetic fields on the clouds of gas and dust where stars are forming.

    ESA/Herschel spacecraft active from 2009 to 2013

    ESA/Planck 2009 to 2013

    The images are part of a study by astronomer Juan D. Soler of the Max Planck Institute for Astronomy in Heidelberg, Germany, who used data gathered during Planck’s all-sky observations and Herschel’s ‘Gould Belt Survey’. Both Herschel and Planck were instrumental in exploring the cool Universe, and shed light on the many complexities of the interstellar medium – the mix of gas and dust that fills the space between the stars in a galaxy. Both telescopes ended their operational lifetime in 2013, but new discoveries continue to be made from their treasure trove of data.

    Herschel revealed in unprecedented detail the filaments of dense material in molecular clouds across our Milky Way galaxy, and their key role in the process of star formation. Filaments can fragment into clumps which eventually collapse into stars. The results from Herschel show a close link between filament structure and the presence of dense clumps.

    Herschel observed the sky in far-infrared and sub-millimetre wavelengths, and the data is seen in these images as a mixture of different colours, with light emitted by interstellar dust grains mixed within the gas. The texture of faint grey bands stretching across the images like a drapery pattern, is based on Planck’s measurements of the direction of the polarised light emitted by the dust and show the orientation of the magnetic field.

    The study explored several nearby molecular clouds all within 1500 light years from the Sun including Taurus, Ophiuchus, Lupus, Corona Australis, Chamaeleon-Musca, Aquila Rift, Perseus, and Orion.

    In this study, published last year in Astronomy & Astrophysics, the Herschel data were used to calculate the density of the molecular clouds along our line of sight to investigate how the interstellar medium interacts with surrounding magnetic fields.

    Astronomers have long thought magnetic fields play a role in star formation, along with other factors such as gas pressure, turbulence, and gravity. However, observations of the magnetic fields in and around nearby star-forming clouds have been limited until the advent of Planck.

    The paper builds upon previous studies by the Planck collaboration to investigate how interstellar matter is likely coupled to these magnetic field lines, moving along them until multiple ‘conveyor belts’ of matter converge to form an area of high density. This can be seen in some images in the form of ‘striations’, which is material that appears perpendicular to the filament. These regions continue to receive matter along the magnetic lines until they collapse under their own gravity, becoming cooler and dense enough to create stellar newborns.

    While the magnetic field is preferentially orientated perpendicular to the densest filaments, it appears that the orientation of the magnetic field changes from parallel to perpendicular with increasing density. However, there appears to be no correlation between the star formation rate and the orientation between filaments and magnetic fields, although the study also finds a correlation between the distribution of projected densities.

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    Corona Australis molecular cloud viewed by Herschel and Planck

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    Taurus Molecular Cloud viewed by Herschel and Planck

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    Rho Ophiuchi cloud complex viewed by Herschel and Planck

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    Lupus cloud complex viewed by Herschel and Planck

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    The Aquila Rift star-forming complex viewed by Herschel and Planck

    Many more at the full article.

    See the full article here .


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    The European Space Agency (ESA), established in 1975, is an intergovernmental organization dedicated to the exploration of space, currently with 19 member states. Headquartered in Paris, ESA has a staff of more than 2,000. ESA’s space flight program includes human spaceflight, mainly through the participation in the International Space Station program, the launch and operations of unmanned exploration missions to other planets and the Moon, Earth observation, science, telecommunication as well as maintaining a major spaceport, the Guiana Space Centre at Kourou, French Guiana, and designing launch vehicles. ESA science missions are based at ESTEC in Noordwijk, Netherlands, Earth Observation missions at ESRIN in Frascati, Italy, ESA Mission Control (ESOC) is in Darmstadt, Germany, the European Astronaut Centre (EAC) that trains astronauts for future missions is situated in Cologne, Germany, and the European Space Astronomy Centre is located in Villanueva de la Cañada, Spain.

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  • richardmitnick 12:05 pm on July 6, 2020 Permalink | Reply
    Tags: "Star-forming region IRAS 12272-6240 probed in infrared", According to the paper the results confirm that IRAS 12272-6240 is a giant young complex one million years old and still active at its nucleus., , , , ,   

    From phys.org: “Star-forming region IRAS 12272-6240 probed in infrared” 


    From phys.org

    July 6, 2020
    Tomasz Nowakowski

    1
    Mid- and far-infrared composite colour images of the region centred on IRAS 12272-6240. Credit: Tapia et al., 2020.

    Astronomers have conducted spectroscopic observations of a star-forming region known as IRAS 12272-6240. Results of this observational campaign shed more light on the nature of this massive and complex region. The study was detailed in a paper published in MNRAS.

    Star-forming regions are essential for astronomers to better understand the processes of star formation and stellar evolution. Observations of such regions have the potential to expand the list of known stars, protostars, young stellar objects and clumps, which could be then be studied comprehensively in various wavelengths in order to get more insights into initial stages of the stellar life cycle.

    Located some 30,300 light years away, at the far end of the Carina-Sagittarius arm of the Milky Way galaxy, IRAS 12272-6240 is a complex star-forming region with a compact massive dense clump and several associated masers.

    A team of astronomers led by Mauricio Tapia of the National Autonomous University of Mexico took a closer look at IRAS 12272-6240. Using the Baade/Magellan telescope in Chile, they performed near-infrared imaging and low-resolution spectroscopy of this region.

    Carnegie 6.5 meter Magellan Baade and Clay Telescopes located at Carnegie’s Las Campanas Observatory, Chile. over 2,500 m (8,200 ft) high.

    The study was complemented by data from the Herschel Infrared GALactic Plane survey (Hi-GAL) and from NASA’s two spacecraft: Spitzer and Wide-field Infrared Survey Explorer (WISE).

    NASA/Spitzer Infrared Telescope. No longer in service.

    NASA/WISE NEOWISE Telescope

    “In this work, we present new sub-arcsec broad- and narrowband near-IR imaging of a 120 x 120 square arcsec area centered on the massive star-forming region IRAS 12272-6240. We supplemented these data with HI-GAL/Herschel far-IR images combined with archive IRAC/Spitzer and WISE mid-IR observations,” the astronomers wrote in the paper.

    The observations found that IRAS 12272-6240 has a compact massive (around 13,100 solar masses) dense dust clump containing two young stellar objects (YSOs) of Class I, designated Irs-1N and Irs-1S, and associated methanol, hydroxide as well as water masers. The two YSOs probably form a binary system that is about 21,000 AU wide.

    The data suggest that the central star of IRAS 12272-6240 is most likely of spectral type O9V, has an effective temperature of about 33,500 K and is about 23 times more massive than our sun. The central star seems to have a pre-planetary disc with a mass of 0.01 solar masses at an inclination angle of 32 degrees.

    The astronomers were able to distinguish two embedded clusters in IRAS 12272-6240 differing in age, spatial distribution and physical characteristics. The older and more extended of these two is about 1 million years old, contains more than 50 stars in its nucleus and a halo of some 80 fainter stars extending to a radius of about 4.24 light years. The second one, consisting of at least 35 identified members, is estimated to be significantly younger than 1 million years and appears to be more deeply embedded.

    According to the paper, the results confirm that IRAS 12272-6240 is a giant young complex located where massive star formation processes started some one million years ago and is still active at its nucleus.

    See the full article here .

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    About Science X in 100 words
    Science X™ is a leading web-based science, research and technology news service which covers a full range of topics. These include physics, earth science, medicine, nanotechnology, electronics, space, biology, chemistry, computer sciences, engineering, mathematics and other sciences and technologies. Launched in 2004 (Physorg.com), Science X’s readership has grown steadily to include 5 million scientists, researchers, and engineers every month. Science X publishes approximately 200 quality articles every day, offering some of the most comprehensive coverage of sci-tech developments world-wide. Science X community members enjoy access to many personalized features such as social networking, a personal home page set-up, article comments and ranking, the ability to save favorite articles, a daily newsletter, and other options.
    Mission 12 reasons for reading daily news on Science X Organization Key editors and writersinclude 1.75 million scientists, researchers, and engineers every month. Phys.org publishes approximately 100 quality articles every day, offering some of the most comprehensive coverage of sci-tech developments world-wide. Quancast 2009 includes Phys.org in its list of the Global Top 2,000 Websites. Phys.org community members enjoy access to many personalized features such as social networking, a personal home page set-up, RSS/XML feeds, article comments and ranking, the ability to save favorite articles, a daily newsletter, and other options.

     
  • richardmitnick 11:38 am on July 6, 2020 Permalink | Reply
    Tags: "New insights into van der Waals materials found", Layered van der Waals materials are of high interest for electronic and photonic applications according to researchers at Penn State and SLAC National Accelerator Laboratory., , , Two-dimensional van der Waals materials are composed of strongly bonded layers of molecules with weak bonding between the layers.   

    From Pennsylvania State University and SLAC National Accelerator Lab: “New insights into van der Waals materials found” 

    Penn State Bloc

    From Pennsylvania State University

    and

    SLAC National Accelerator Lab

    July 03, 2020
    Walt Mills

    1
    The lattice dynamics of monoclinic gallium telluride (GaTe) is studied by ultrafast electro diffraction (UED). This study provides a generalized understanding of Friedel’s law and a comprehensive explanation of the lattice dynamics. Image: Qingkai Qian, Penn State.

    Layered van der Waals materials are of high interest for electronic and photonic applications, according to researchers at Penn State and SLAC National Accelerator Laboratory, in California, who provide new insights into the interactions of layered materials with laser and electron beams.

    Two-dimensional van der Waals materials are composed of strongly bonded layers of molecules with weak bonding between the layers.

    The researchers used a combination of ultrafast pulses of laser light that excite the atoms in a material lattice of gallium telluride, followed by exposing the lattice to an ultrafast pulse of an electron beam. This shows the lattice vibrations in real time using electron diffraction and could lead to a better understanding of these materials.

    “This is a quite unique technique,” said Shengxi Huang, assistant professor of electrical engineering and corresponding author of a paper in ACS Nano that describes their work. “The purpose is to understand fully the lattice vibrations, including in-plane and out-of-plane.”

    One of the interesting observations in their work is the breaking of a law that applies to all material systems. Friedel’s Law posits that in the diffraction pattern, the pairs of centrosymmetric Bragg peaks should be symmetric, directly resulting from Fourier transformation. In this case, however, the pairs of Bragg peaks show opposite oscillating patterns. They call this phenomenon the dynamic breaking of Friedel’s Law. It is a very rare if not unprecedented observation in the interactions between the beams and these materials.

    “Why do we see the breaking of Friedel’s Law?” she said. “It is because of the lattice structure of this material. In layered 2D materials, the atoms in each layer typically align very well in the vertical direction. In gallium telluride, the atomic alignment is a little bit off.”

    When the laser beam shines onto the material, the heating generates the lowest-order longitudinal acoustic phonon mode, which creates a wobbling effect for the lattice. This can affect the way electrons diffract in the lattice, leading to the unique dynamic breaking of Friedel’s law.

    This technique is also useful for studying phase change materials, which absorb or radiate heat during phase change. Such materials can generate the electrocaloric effect in solid-state refrigerators. This technique will also be interesting to people who study oddly structured crystals and the general 2D materials community.

    The lead author on the article, titled “Coherent Lattice Wobbling and Out-of-Phase Intensity Oscillations of Friedel Pairs Observed by Ultrafast Electron Diffraction” is Huang’s postdoctoral scholar Qingkai Qian. Additional Penn State authors in her group are graduate students Kunyan Zhang and Lanxin Jia, and research scholar Yu Zhou. Xijie Wang led the ten-member SLAC team.

    The National Science Foundation supported this work. The Department of Energy supports SLAC.

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    SLAC National Accelerator Lab


    SLAC/LCLS


    SLAC/LCLS II projected view


    SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.

    SSRL and LCLS are DOE Office of Science user facilities.

    Penn State Campus

    About Penn State

    WHAT WE DO BEST

    We teach students that the real measure of success is what you do to improve the lives of others, and they learn to be hard-working leaders with a global perspective. We conduct research to improve lives. We add millions to the economy through projects in our state and beyond. We help communities by sharing our faculty expertise and research.

    Penn State lives close by no matter where you are. Our campuses are located from one side of Pennsylvania to the other. Through Penn State World Campus, students can take courses and work toward degrees online from anywhere on the globe that has Internet service.

    We support students in many ways, including advising and counseling services for school and life; diversity and inclusion services; social media sites; safety services; and emergency assistance.

    Our network of more than a half-million alumni is accessible to students when they want advice and to learn about job networking and mentor opportunities as well as what to expect in the future. Through our alumni, Penn State lives all over the world.

    The best part of Penn State is our people. Our students, faculty, staff, alumni, and friends in communities near our campuses and across the globe are dedicated to education and fostering a diverse and inclusive environment.

    See the full article here .

     
  • richardmitnick 11:02 am on July 6, 2020 Permalink | Reply
    Tags: , , , "A 'breath of nothing' provides a new perspective on superconductivity", Josephson oscillations   

    From U Hamburg via phys.org: “A ‘breath of nothing’ provides a new perspective on superconductivity” 

    1
    From U Hamburg

    via


    phys.org

    July 6, 2020

    1
    Credit: CC0 Public Domain

    Zero electrical resistance at room temperature? A material with this property, i.e. a room temperature superconductor, could revolutionize power distribution. But so far, the origin of superconductivity at high temperature is only incompletely understood. Scientists from Universität Hamburg and the Cluster of Excellence “CUI: Advanced Imaging of Matter” have succeeded in observing strong evidence of superfluidity in a central model system, a two-dimensional gas cloud for the first time. The scientists report on their experiments in the journal Science, which allow to investigate key issues of high-temperature superconductivity in a very well-controlled model system.

    There are things that aren’t supposed to happen. For example, water cannot flow from one glass to another through the glass wall. Surprisingly, quantum mechanics allows this, provided the barrier between the two liquids is thin enough. Due to the quantum mechanical tunneling effect, particles can penetrate the barrier, even if the barrier is higher than the level of the liquids. Even more remarkably, this current can even flow when the level on both sides is the same or the current must flow slightly uphill. For this, however, the fluids on both sides must be superfluids, i.e. they must be able to flow around obstacles without friction.

    This striking phenomenon was predicted by Brian Josephson during his doctoral thesis, and it is of such fundamental importance that he was awarded the Nobel Prize for it. The current is driven only by the wave nature of the superfluids and can, among other things, ensure that the superfluid begins to oscillate back and forth between the two sides—a phenomenon known as Josephson oscillations.

    The Josephson effect was first observed in 1962 between two superconductors. In the experiment—in direct analogy to the water flow without level difference—an electric current could flow through a tunnel contact without an applied voltage. With this discovery, an impressive proof had been provided that the wave nature of matter in superconductors can be observed even at the macroscopic level.

    Now, for the first time, the scientists in Prof. Henning Moritz’s group have succeeded in observing Josephson oscillations in a two-dimensional (2-D) Fermi gas. These Fermi gases consist of a “breath of nothing,” namely a gas cloud of only a few thousand atoms. If they are cooled to a few millionth of a degree above absolute zero, they become superfluid. They can now be used to study superfluids in which the particles interact strongly with each other and live in only two dimensions—a combination that seems to be central to high-temperature superconductivity, but which is still only incompletely understood.

    “We were amazed at how clearly the Josephson oscillations were visible in our experiment. This is clear evidence of phase coherence in our ultracold 2-D Fermi gas,” says first author Niclas Luick. “The high degree of control we have over our system has also allowed us to measure the critical current above which the superfluidity breaks down.”

    “This breakthrough opens up many new opportunities for us to gain insights into the nature of strongly correlated 2-D superfluids,” says Prof. Moritz, “These are of outstanding importance in modern physics, but very difficult to simulate theoretically. We are pleased to contribute to a better understanding of these quantum systems with our experiment.”

    See the full article here .

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    2

    U Hamburg is the largest institution for research and education in northern Germany. As one of the country’s largest universities, we offer a diverse range of degree programs and excellent research opportunities. The University boasts numerous interdisciplinary projects in a broad range of fields and an extensive partner network of leading regional, national, and international higher education and research institutions.
    Sustainable science and scholarship

    Universität Hamburg is committed to sustainability. All our faculties have taken great strides towards sustainability in both research and teaching.
    Excellent research

    As part of the Excellence Strategy of the Federal and State Governments, Universität Hamburg has been granted clusters of excellence for 4 core research areas: Advanced Imaging of Matter (photon and nanosciences), Climate, Climatic Change, and Society (CliCCS) (climate research), Understanding Written Artefacts (manuscript research) and Quantum Universe (mathematics, particle physics, astrophysics, and cosmology).

    An equally important core research area is Infection Research, in which researchers investigate the structure, dynamics, and mechanisms of infection processes to promote the development of new treatment methods and therapies.
    Outstanding variety: over 170 degree programs

    Universität Hamburg offers approximately 170 degree programs within its eight faculties:

    Faculty of Law
    Faculty of Business, Economics and Social Sciences
    Faculty of Medicine
    Faculty of Education
    Faculty of Mathematics, Informatics and Natural Sciences
    Faculty of Psychology and Human Movement Science
    Faculty of Business Administration (Hamburg Business School).

    Universität Hamburg is also home to several museums and collections, such as the Zoological Museum, the Herbarium Hamburgense, the Geological-Paleontological Museum, the Loki Schmidt Garden, and the Hamburg Observatory.
    History

    Universität Hamburg was founded in 1919 by local citizens. Important founding figures include Senator Werner von Melle and the merchant Edmund Siemers. Nobel Prize winners such as the physicists Otto Stern, Wolfgang Pauli, and Isidor Rabi taught and researched at the University. Many other distinguished scholars, such as Ernst Cassirer, Erwin Panofsky, Aby Warburg, William Stern, Agathe Lasch, Magdalene Schoch, Emil Artin, Ralf Dahrendorf, and Carl Friedrich von Weizsäcker, also worked here.

     
  • richardmitnick 10:35 am on July 6, 2020 Permalink | Reply
    Tags: "White dwarfs reveal new insights into the origin of carbon in the universe", 1.5 solar masses represents the minimum mass for a star to spread carbon-enriched ashes upon its death., , Astrophysicists still debate which types of stars are the primary source of the carbon in our own galaxy., , , Carbon in our own galaxy, , Every carbon atom in the universe was created by stars through the fusion of three helium nuclei.,   

    From UC Santa Cruz: “White dwarfs reveal new insights into the origin of carbon in the universe” 

    From UC Santa Cruz

    July 06, 2020
    Tim Stephens
    stephens@ucsc.edu

    1
    NGC 7789, also known as Caroline’s Rose, is an old open star cluster of the Milky Way, which lies about 8,000 light-years away toward the constellation Cassiopeia. It hosts a few white dwarfs of unusually high mass that were analyzed in this study. (Image credit: Guillaume Seigneuret and NASA)

    A new analysis of white dwarf stars supports their role as a key source of carbon, an element crucial to all life, in the Milky Way and other galaxies.

    1
    White dwarf star in the process of solidifying. Credit: University of Warwick/Mark Garlick

    Approximately 90 percent of all stars end their lives as white dwarfs, very dense stellar remnants that gradually cool and dim over billions of years. With their final few breaths before they collapse, however, these stars leave an important legacy, spreading their ashes into the surrounding space through stellar winds enriched with chemical elements, including carbon, newly synthesized in the star’s deep interior during the last stages before its death.

    Every carbon atom in the universe was created by stars, through the fusion of three helium nuclei. But astrophysicists still debate which types of stars are the primary source of the carbon in our own galaxy, the Milky Way. Some studies favor low-mass stars that blew off their envelopes in stellar winds and became white dwarfs, while others favor massive stars that eventually exploded as supernovae.

    In the new study, published July 6 in Nature Astronomy, an international team of astronomers discovered and analyzed white dwarfs in open star clusters in the Milky Way, and their findings help shed light on the origin of the carbon in our galaxy. Open star clusters are groups of up to a few thousand stars, formed from the same giant molecular cloud and roughly the same age, and held together by mutual gravitational attraction. The study was based on astronomical observations conducted in 2018 at the W. M. Keck Observatory in Hawaii and led by coauthor Enrico Ramirez-Ruiz, professor of astronomy and astrophysics at UC Santa Cruz.

    Keck Observatory, operated by Caltech and the University of California, Maunakea Hawaii USA, 4,207 m (13,802 ft)

    “From the analysis of the observed Keck spectra, it was possible to measure the masses of the white dwarfs. Using the theory of stellar evolution, we were able to trace back to the progenitor stars and derive their masses at birth,” explained Ramirez-Ruiz, who also holds a Niels Bohr Professorship at the University of Copenhagen.

    The relationship between the initial masses of stars and their final masses as white dwarfs is known as the initial-final mass relation, a fundamental diagnostic in astrophysics that integrates information from the entire life cycles of stars, linking birth to death. In general, the more massive the star at birth, the more massive the white dwarf left at its death, and this trend has been supported on both observational and theoretical grounds.

    But analysis of the newly discovered white dwarfs in old open clusters gave a surprising result: the masses of these white dwarfs were notably larger than expected, putting a “kink” in the initial-final mass relation for stars with initial masses in a certain range.

    “Our study interprets this kink in the initial-final mass relationship as the signature of the synthesis of carbon made by low-mass stars in the Milky Way,” said lead author Paola Marigo at the University of Padua in Italy.

    In the last phases of their lives, stars twice as massive as our Sun produced new carbon atoms in their hot interiors, transported them to the surface, and finally spread them into the interstellar medium through gentle stellar winds. The team’s detailed stellar models indicate that the stripping of the carbon-rich outer mantle occurred slowly enough to allow the central cores of these stars, the future white dwarfs, to grow appreciably in mass.

    Analyzing the initial-final mass relation around the kink, the researchers concluded that stars bigger than 2 solar masses also contributed to the galactic enrichment of carbon, while stars of less than 1.5 solar masses did not. In other words, 1.5 solar masses represents the minimum mass for a star to spread carbon-enriched ashes upon its death.

    These findings place stringent constraints on how and when carbon, the element essential to life on Earth, was produced by the stars of our galaxy, eventually ending up trapped in the raw material from which the Sun and its planetary system were formed 4.6 billion years ago.

    “Now we know that the carbon came from stars with a birth mass of not less than roughly 1.5 solar masses,” said Marigo.

    Coauthor Pier-Emmanuel Tremblay at University of Warwick said, “One of most exciting aspects of this research is that it impacts the age of known white dwarfs, which are essential cosmic probes to understand the formation history of the Milky Way. The initial-to-final mass relation is also what sets the lower mass limit for supernovae, the gigantic explosions seen at large distances and that are really important to understand the nature of the universe.”

    By combining the theories of cosmology and stellar evolution, the researchers concluded that bright carbon-rich stars close to their death, quite similar to the progenitors of the white dwarfs analyzed in this study, are presently contributing to a vast amount of the light emitted by very distant galaxies. This light, carrying the signature of newly produced carbon, is routinely collected by large telescopes to probe the evolution of cosmic structures. A reliable interpretation of this light depends on understanding the synthesis of carbon in stars.

    In addition to Marigo, Tremblay, and Ramirez-Ruiz, the coauthors of the paper include scientists at Johns Hopkins University, American Museum of Natural History in New York, Columbia University, Space Telescope Science Institute, University of Warwick, University of Montreal, University of Uppsala, International School for Advanced Studies in Trieste, Italian National Institute for Astrophysics, and the University of Geneva. This research was supported by the European Union through an ERC Consolidator Grant and the DNRF through a Niels Bohr Professorship.

    See the full article here .


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    The University of California, Santa Cruz, opened in 1965 and grew, one college at a time, to its current (2008-09) enrollment of more than 16,000 students. Undergraduates pursue more than 60 majors supervised by divisional deans of humanities, physical & biological sciences, social sciences, and arts. Graduate students work toward graduate certificates, master’s degrees, or doctoral degrees in more than 30 academic fields under the supervision of the divisional and graduate deans. The dean of the Jack Baskin School of Engineering oversees the campus’s undergraduate and graduate engineering programs.

    UCSC Lick Observatory, Mt Hamilton, in San Jose, California, Altitude 1,283 m (4,209 ft)

    .

    UC Observatories Lick Autmated Planet Finder, fully robotic 2.4-meter optical telescope at Lick Observatory, situated on the summit of Mount Hamilton, east of San Jose, California, USA

    The UCO Lick C. Donald Shane telescope is a 120-inch (3.0-meter) reflecting telescope located at the Lick Observatory, Mt Hamilton, in San Jose, California, Altitude 1,283 m (4,209 ft)

    UC Santa Cruz campus

    UCSC is the home base for the Lick Observatory.

    Lick Observatory's Great Lick 91-centimeter (36-inch) telescope housed in the South (large) Dome of main building
    Lick Observatory’s Great Lick 91-centimeter (36-inch) telescope housed in the South (large) Dome of main building

     
  • richardmitnick 9:40 am on July 6, 2020 Permalink | Reply
    Tags: "The supersizing of quantum physics", , , , , , Squeezer table   

    From Australian National University via COSMOS: “The supersizing of quantum physics” 

    ANU Australian National University Bloc

    From Australian National University

    via

    Cosmos Magazine bloc

    COSMOS

    3 July 2020
    Phil Dooley

    Quantum physics is the realm of tiny particles no longer. Scientists at the giant gravitational wave detector LIGO in the US are now measuring the quantum effects of 40-kilogram mirrors used to detect gravitational waves.


    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

    While physicists routinely observe quantum effects in nanometre-scale experiments, LIGO team member Robert Ward says this new level of sensitivity was unmatched in other experiments.

    1
    ANU’s Nutsinee Kijbunchoo (left) and Terry McRae building a squeezer table at LIGO Hanford. Credit: ANU.

    “There’s nowhere else close, nothing like it. That’s as big as my kids!” says Ward, who is part of the OzGrav Research Centre based at the Australian National University (ANU).

    “The reality that we can measure to this level of precision on an instrument that is so large is incredible,” adds his ANU colleague Terry McRae, who recently spent a year installing new componentry at the Livingston site in Louisiana, US.

    Livingston is one of two linked gravitational wave detectors run by the LIGO organisation. Each detector is made of two high-powered laser beams at right angles, bouncing between mirrors four kilometres apart. The second is in Washington State, 3000 kilometres to the northwest.

    The LIGO team has published results in the journal Nature that accurately show quantum correlations between the 40-kilogram mirrors and the laser beam, which at 200 kilowatts is about 2000 times more powerful than a laser cutter.

    For the purpose of detecting gravitational waves, it has used the correlations and manipulated the quantum properties of the system, to reduce noise and make it more sensitive, a technique called quantum squeezing.

    The sensitivity of LIGO is crucial. Although black hole collisions are the most violent events known to humans, the gravitational waves from them reach earth as tiny flickers in space and time. In the triumphant first detections of gravitational waves, LIGO’s mirrors moved about a billionth of the diameter of the atoms making up the mirrors.

    The two-decade story of LIGO is one of tirelessly removing one noise source after another, says ANU’s Nutsinee Kijbunchoo.

    “We’re always trying to do better: sensitivity less than the width of a hair? Not good enough, we have to keep improving,” she says.

    Kijbunchoo worked with McRae on the recent upgrade at Livingston and was amazed to see people banging on parts of the apparatus to try to induce noise, characterise it precisely and work out how to cut it out.

    A recent paper [Physics]announced the new sensitivity levels reached, thanks to the new quantum squeezing system that Kijbunchoo and McRae were involved in installing. The paper estimated that the improvement would lead to a 50% jump in the rate of gravitational wave detections.

    This new paper takes a step back, however, and discusses the significance of the LIGO’s sensitivity, saying in its conclusions that “the measurements presented here represent long-awaited milestones in verifying the role of quantum mechanics in limiting the measurement of small displacements…”.

    Rob Ward says this moment has been a long time coming, citing Russian scientist Braginsky as one of the first to begin thinking [Reviews of Modern Physics] about the quantum limits of measurement in 1996.

    “Now we’ve crossed that threshold, and now we have to start thinking about the quantum mechanics of our test masses (mirrors). We’re being forced to grapple with the quantum mechanics of a human-sized objects,” Ward says.

    The quantum noise has been revealed after an intricate system of suspension wires, feedback systems, laser stabiliser and cooling systems have stabilised the experiment – removing the so-called classical noise.

    3
    Credit: Nutsinee Kijbunchoo ANU.

    You would think all of these vibrations and wobbles could be cut out completely, but quantum noise is a fundamental property of a system, first expressed by Heisenberg in the famous Uncertainty Principle, which lays out that measurements have limits to their precision, beyond which you cannot pass, no matter how cold, stable or isolated your experiment is.

    But there is a loophole: these measurements come in pairs, and the uncertainty is distributed between the pairs, and can be shifted from one quantity to the other.

    Imagine cleaning the house, which you could measure by how fast it was done, or how clean the house ends up. The quicker the clean-up, the lower the final standard of cleanliness. Or, an exhaustive spring clean could take well past tea time.

    It’s this kind of trade-off that the squeezing system uses – in this case playing off the radiation pressure against the randomness in the arrival time of the photons. The trick is the photons need to be paired – correlated – which enables the quantum link to be leveraged.

    These play into the overall noise differently for different signals, so the LIGO scientists constrain the value of one that will make the experiment most sensitive, say to a neutron star merger, and let the other be a little less certain.

    This is how the LIGO detector achieves sensitivity that is better than non-quantum physics could have imagined – a limit known as the standard quantum limit (SQL).

    These quantum tricks can only be used if the overall noise is infinitesimal, otherwise the pairings become smeared out, and quantum effects can’t be seen.

    This is the case in our everyday world. But now, says Ward, with this exquisite instrument we’re in a realm we’ve never seen before.

    “We never normally see quantum effects of big objects, and we don’t exactly know why, but now we’re getting to that level of precision,” he says. “We’re exploring fundamental questions about reality.”

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    ANU Campus

    ANU is a world-leading university in Australia’s capital city, Canberra. Our location points to our unique history, ties to the Australian Government and special standing as a resource for the Australian people.

    Our focus on research as an asset, and an approach to education, ensures our graduates are in demand the world-over for their abilities to understand, and apply vision and creativity to addressing complex contemporary challenges.

     
  • richardmitnick 9:11 am on July 6, 2020 Permalink | Reply
    Tags: "U.K. buys stake in satellite company that could spoil astronomy", , , “It’s the stuff at 1000 kilometers that is the real killer for astronomy” says Mark McCaughrean of the European Space Agency., “Megaconstellations” of satellites, , , OneWeb filed for bankruptcy protection in March 2020, , The U.K. government said in a statement today that its acquisition of OneWeb will “contribute to the government’s plan to join the first rank of space nations.”, U.K. government and the Indian cellphone operator Bharti Global have successfully bid to rescue OneWeb with a $1 billion investment.   

    From Science Magazine: “U.K. buys stake in satellite company that could spoil astronomy” 

    From Science Magazine

    Jul. 3, 2020
    Daniel Clery

    1
    OneWeb plans to launch as many as 42,000 satellites to an orbit that could harm astronomy. Credit: NASA/Kim Shiflett

    When OneWeb filed for bankruptcy protection in March, astronomers breathed a sigh of relief. The company planned to launch thousands of internet-providing satellites into low-Earth orbit, where their reflections could disrupt the observations of ground-based telescopes. But now, the company has risen from the grave with the announcement today that the U.K. government and the Indian cellphone operator Bharti Global have successfully bid to rescue OneWeb with a $1 billion investment.

    The revived company now plans an even larger constellation of up to 42,000 satellites, at an altitude of 1200 kilometers—the worst possible outcome for astronomers. At that altitude, satellites will leave bright trails across telescope images all through the night, effectively ruining the observations of survey telescopes such as the 8-meter Vera C. Rubin Observatory, under construction in Chile. “It’s the stuff at 1000 kilometers that is the real killer for astronomy,” says Mark McCaughrean of the European Space Agency, speaking at a briefing organized by the European Astronomical Society (EAS). “Engagement [with astronomers] has to happen and it has to happen now.”

    Astronomers first became concerned about such “megaconstellations” last year, when the launch company SpaceX lofted the first batch of its Starlink satellites. The aim of the project is to provide internet access in areas hard to reach with fiber-optic cables. The satellites, launched 60 at a time in a single rocket, proved to be highly visible in the sky, to the alarm of astronomers. The company has now launched 540 Starlink satellites—part of an initial goal of 1584—and aims to provide a service in the United States and Canada before the end of the year.

    Early on, astronomers began working with SpaceX to mitigate the impact of its satellites. In a January launch, one satellite was covered with an antireflective coating (dubbed Darksat), and in June, one satellite carried a sunshade to stop reflections (Visorsat). Although Darksat partially reduced the satellite’s visibility, it wasn’t enough to satisfy astronomers. Visorsat has yet to reach its operational altitude so, Olivier Hainaut of the European Southern Observatory told the EAS briefing, “we don’t know yet” how bright it will appear. But McCaughrean says Starlink’s next launch will be populated entirely with Visorsats.

    OneWeb is one of several other companies chasing Starlink with similar goals. Astronomers had only limited interactions with the company before it filed for Chapter 11 protection in March with 74 satellites launched toward an initial goal of 650. While new owners were being sought, OneWeb applied for permission to expand its constellation to 42,000.

    The U.K. government said in a statement today that its acquisition of OneWeb will “contribute to the government’s plan to join the first rank of space nations.” Initial reports suggested the government wanted to transform the constellation into a navigation system akin to GPS, because with Brexit, the United Kingdom will no longer be a governing member of Europe’s Galileo navigation system. But there is no mention of navigation plans in today’s statement.

    The rescue of OneWeb still has political and legal hurdles to overcome, but Robert Massey of the Royal Astronomical Society told the EAS briefing: “I would hope the government uses its leverage to ensure OneWeb are a good partner and engages with the scientific community.” He adds, “It’s hard to believe they didn’t know.”

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

     
  • richardmitnick 9:47 am on July 5, 2020 Permalink | Reply
    Tags: "Astronomers Are Uncovering the Magnetic Soul of the Universe", , , , , , ,   

    From Quanta Magazine via WIRED: “Astronomers Are Uncovering the Magnetic Soul of the Universe” 

    From Quanta Magazine

    via


    WIRED

    07.05.2020
    Natalie Wolchover

    Researchers are discovering that magnetic fields permeate much of the cosmos. If these fields date back to the Big Bang, they could solve a cosmological mystery.

    1
    Hidden magnetic field lines stretch millions of light years across the universe.Illustration: Pauline Voß/Quanta Magazine.

    Anytime astronomers figure out a new way of looking for magnetic fields in ever more remote regions of the cosmos, inexplicably, they find them.

    These force fields—the same entities that emanate from fridge magnets—surround Earth, the sun, and all galaxies. Twenty years ago, astronomers started to detect magnetism permeating entire galaxy clusters, including the space between one galaxy and the next. Invisible field lines swoop through intergalactic space like the grooves of a fingerprint.

    Last year, astronomers finally managed to examine a far sparser region of space—the expanse between galaxy clusters. There, they discovered the largest magnetic field yet: 10 million light-years of magnetized space spanning the entire length of this “filament” of the cosmic web [Science]. A second magnetized filament has already been spotted elsewhere in the cosmos by means of the same techniques. “We are just looking at the tip of the iceberg, probably,” said Federica Govoni of the National Institute for Astrophysics in Cagliari, Italy, who led the first detection.

    The question is: Where did these enormous magnetic fields come from?

    “It clearly cannot be related to the activity of single galaxies or single explosions or, I don’t know, winds from supernovae,” said Franco Vazza, an astrophysicist at the University of Bologna who makes state-of-the-art computer simulations of cosmic magnetic fields. “This goes much beyond that.”

    One possibility is that cosmic magnetism is primordial, tracing all the way back to the birth of the universe. In that case, weak magnetism should exist everywhere, even in the “voids” of the cosmic web—the very darkest, emptiest regions of the universe. The omnipresent magnetism would have seeded the stronger fields that blossomed in galaxies and clusters.

    2
    The cosmic web, shown here in a computer simulation, is the large-scale structure of the universe. Dense regions are filled with galaxies and galaxy clusters. Thin filaments connect these clumps. Voids are nearly empty regions of space.Illustration: Springel & others/Virgo Consortium.

    Primordial magnetism might also help resolve another cosmological conundrum known as the Hubble tension—probably the hottest topic in cosmology.

    The problem at the heart of the Hubble tension is that the universe seems to be expanding significantly faster than expected based on its known ingredients. In a paper posted online in April and under review with Physical Review Letters, the cosmologists Karsten Jedamzik and Levon Pogosian argue that weak magnetic fields in the early universe would lead to the faster cosmic expansion rate seen today.

    Primordial magnetism relieves the Hubble tension so simply that Jedamzik and Pogosian’s paper has drawn swift attention. “This is an excellent paper and idea,” said Marc Kamionkowski, a theoretical cosmologist at Johns Hopkins University who has proposed other solutions to the Hubble tension.

    Kamionkowski and others say more checks are needed to ensure that the early magnetism doesn’t throw off other cosmological calculations. And even if the idea works on paper, researchers will need to find conclusive evidence of primordial magnetism to be sure it’s the missing agent that shaped the universe.

    Still, in all the years of talk about the Hubble tension, it’s perhaps strange that no one considered magnetism before. According to Pogosian, who is a professor at Simon Fraser University in Canada, most cosmologists hardly think about magnetism. “Everyone knows it’s one of those big puzzles,” he said. But for decades, there was no way to tell whether magnetism is truly ubiquitous and thus a primordial component of the cosmos, so cosmologists largely stopped paying attention.

    Meanwhile, astrophysicists kept collecting data. The weight of evidence has led most of them to suspect that magnetism is indeed everywhere.

    The Magnetic Soul of the Universe

    In the year 1600, the English scientist William Gilbert’s studies of lodestones—naturally magnetized rocks that people had been fashioning into compasses for thousands of years—led him to opine that their magnetic force “imitates a soul.” He correctly surmised that Earth itself is a “great magnet,” and that lodestones “look toward the poles of the Earth.”

    Magnetic fields arise anytime electric charge flows. Earth’s field, for instance, emanates from its inner “dynamo,” the current of liquid iron churning in its core. The fields of fridge magnets and lodestones come from electrons spinning around their constituent atoms.


    Cosmological simulations illustrate two possible explanations for how magnetic fields came to permeate galaxy clusters. At left, the fields grow from uniform “seed” fields that filled the cosmos in the moments after the Big Bang. At right, astrophysical processes such as star formation and the flow of matter into supermassive black holes create magnetized winds that spill out from galaxies.Video: F. Vazza.

    However, once a “seed” magnetic field arises from charged particles in motion, it can become bigger and stronger by aligning weaker fields with it. Magnetism “is a little bit like a living organism,” said Torsten Enßlin, a theoretical astrophysicist at the Max Planck Institute for Astrophysics in Garching, Germany, “because magnetic fields tap into every free energy source they can hold onto and grow. They can spread and affect other areas with their presence, where they grow as well.”

    Ruth Durrer, a theoretical cosmologist at the University of Geneva, explained that magnetism is the only force apart from gravity that can shape the large-scale structure of the cosmos, because only magnetism and gravity can “reach out to you” across vast distances. Electricity, by contrast, is local and short-lived, since the positive and negative charge in any region will neutralize overall. But you can’t cancel out magnetic fields; they tend to add up and survive.

    Yet for all their power, these force fields keep low profiles. They are immaterial, perceptible only when acting upon other things. “You can’t just take a picture of a magnetic field; it doesn’t work like that,” said Reinout van Weeren, an astronomer at Leiden University who was involved in the recent detections of magnetized filaments.

    In their paper last year, van Weeren and 28 coauthors inferred the presence of a magnetic field in the filament between galaxy clusters Abell 399 and Abell 401 from the way the field redirects high-speed electrons and other charged particles passing through it. As their paths twist in the field, these charged particles release faint “synchrotron radiation.”

    The synchrotron signal is strongest at low radio frequencies, making it ripe for detection by LOFAR, an array of 20,000 low-frequency radio antennas spread across Europe.

    ASTRON LOFAR European Map

    The team actually gathered data from the filament back in 2014 during a single eight-hour stretch, but the data sat waiting as the radio astronomy community spent years figuring out how to improve the calibration of LOFAR’s measurements. Earth’s atmosphere refracts radio waves that pass through it, so LOFAR views the cosmos as if from the bottom of a swimming pool. The researchers solved the problem by tracking the wobble of “beacons” in the sky—radio emitters with precisely known locations—and correcting for this wobble to deblur all the data. When they applied the deblurring algorithm to data from the filament, they saw the glow of synchrotron emissions right away.

    3
    LOFAR consists of 20,000 individual radio antennas spread across Europe.Photograph: ASTRON.

    The filament looks magnetized throughout, not just near the galaxy clusters that are moving toward each other from either end. The researchers hope that a 50-hour data set they’re analyzing now will reveal more detail. Additional observations have recently uncovered magnetic fields extending throughout a second filament. Researchers plan to publish this work soon.

    The presence of enormous magnetic fields in at least these two filaments provides important new information. “It has spurred quite some activity,” van Weeren said, “because now we know that magnetic fields are relatively strong.”

    A Light Through the Voids

    If these magnetic fields arose in the infant universe, the question becomes: how? “People have been thinking about this problem for a long time,” said Tanmay Vachaspati of Arizona State University.

    In 1991, Vachaspati proposed that magnetic fields might have arisen during the electroweak phase transition—the moment, a split second after the Big Bang, when the electromagnetic and weak nuclear forces became distinct. Others have suggested that magnetism materialized microseconds later, when protons formed. Or soon after that: The late astrophysicist Ted Harrison argued in the earliest primordial magnetogenesis theory in 1973 that the turbulent plasma of protons and electrons might have spun up the first magnetic fields. Still others have proposed that space became magnetized before all this, during cosmic inflation—the explosive expansion of space that purportedly jump-started the Big Bang itself. It’s also possible that it didn’t happen until the growth of structures a billion years later.

    The way to test theories of magnetogenesis is to study the pattern of magnetic fields in the most pristine patches of intergalactic space, such as the quiet parts of filaments and the even emptier voids. Certain details—such as whether the field lines are smooth, helical, or “curved every which way, like a ball of yarn or something” (per Vachaspati), and how the pattern changes in different places and on different scales—carry rich information that can be compared to theory and simulations. For example, if the magnetic fields arose during the electroweak phase transition, as Vachaspati proposed, then the resulting field lines should be helical, “like a corkscrew,” he said.

    The hitch is that it’s difficult to detect force fields that have nothing to push on.

    One method, pioneered by the English scientist Michael Faraday back in 1845, detects a magnetic field from the way it rotates the polarization direction of light passing through it. The amount of “Faraday rotation” depends on the strength of the magnetic field and the frequency of the light. So by measuring the polarization at different frequencies, you can infer the strength of magnetism along the line of sight. “If you do it from different places, you can make a 3D map,” said Enßlin.

    4
    Illustration: Samuel Velasco/Quanta Magazine.

    Researchers have started to make [MNRAS] rough Faraday rotation measurements using LOFAR, but the telescope has trouble picking out the extremely faint signal. Valentina Vacca, an astronomer and a colleague of Govoni’s at the National Institute for Astrophysics, devised an algorithm a few years ago for teasing out subtle Faraday rotation signals statistically, by stacking together many measurements of empty places. “In principle, this can be used for voids,” Vacca said.

    But the Faraday technique will really take off when the next-generation radio telescope, a gargantuan international project called the Square Kilometer Array, starts up in 2027. “SKA should produce a fantastic Faraday grid,” Enßlin said.

    For now, the only evidence of magnetism in the voids is what observers don’t see when they look at objects called blazars located behind voids.

    Blazars are bright beams of gamma rays and other energetic light and matter powered by supermassive black holes. As the gamma rays travel through space, they sometimes collide with ancient microwaves, morphing into an electron and a positron as a result. These particles then fizzle and turn into lower-energy gamma rays.

    But if the blazar’s light passes through a magnetized void, the lower-energy gamma rays will appear to be missing, reasoned Andrii Neronov and Ievgen Vovk of the Geneva Observatory in 2010. The magnetic field will deflect the electrons and positrons out of the line of sight. When they decay into lower-energy gamma rays, those gamma rays won’t be pointed at us.

    5
    Illustration: Samuel Velasco/Quanta Magazine.

    Indeed, when Neronov and Vovk analyzed data from a suitably located blazar, they saw its high-energy gamma rays, but not the low-energy gamma-ray signal. “It’s the absence of a signal that is a signal,” Vachaspati said.

    A nonsignal is hardly a smoking gun, and alternative explanations for the missing gamma rays have been suggested. However, follow-up observations have increasingly pointed to Neronov and Vovk’s hypothesis that voids are magnetized. “It’s the majority view,” Durrer said. Most convincingly, in 2015, one team overlaid many measurements of blazars behind voids and managed to tease [Physical Review Letters] out a faint halo of low-energy gamma rays around the blazars. The effect is exactly what would be expected if the particles were being scattered by faint magnetic fields—measuring only about a millionth of a trillionth as strong as a fridge magnet’s.

    Cosmology’s Biggest Mystery

    Strikingly, this exact amount of primordial magnetism may be just what’s needed to resolve the Hubble tension—the problem of the universe’s curiously fast expansion.

    That’s what Pogosian realized when he saw recent computer simulations [Physical Review Letters] by Karsten Jedamzik of the University of Montpellier in France and a collaborator. The researchers added weak magnetic fields to a simulated, plasma-filled young universe and found that protons and electrons in the plasma flew along the magnetic field lines and accumulated in the regions of weakest field strength. This clumping effect made the protons and electrons combine into hydrogen—an early phase change known as recombination—earlier than they would have otherwise.

    Pogosian, reading Jedamzik’s paper, saw that this could address the Hubble tension. Cosmologists calculate how fast space should be expanding today by observing ancient light emitted during recombination. The light shows a young universe studded with blobs that formed from sound waves sloshing around in the primordial plasma. If recombination happened earlier than supposed due to the clumping effect of magnetic fields, then sound waves couldn’t have propagated as far beforehand, and the resulting blobs would be smaller. That means the blobs we see in the sky from the time of recombination must be closer to us than researchers supposed. The light coming from the blobs must have traveled a shorter distance to reach us, meaning the light must have been traversing faster-expanding space. “It’s like trying to run on an expanding surface; you cover less distance,” Pogosian said.

    The upshot is that smaller blobs mean a higher inferred cosmic expansion rate—bringing the inferred rate much closer to measurements of how fast supernovas and other astronomical objects actually seem to be flying apart.

    “I thought, wow,” Pogosian said, “this could be pointing us to [magnetic fields’] actual presence. So I wrote Karsten immediately.” The two got together in Montpellier in February, just before the lockdown. Their calculations indicated that, indeed, the amount of primordial magnetism needed to address the Hubble tension also agrees with the blazar observations and the estimated size of initial fields needed to grow the enormous magnetic fields spanning galaxy clusters and filaments. “So it all sort of comes together,” Pogosian said, “if this turns out to be right.”

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

     
  • richardmitnick 10:00 am on July 4, 2020 Permalink | Reply
    Tags: "Peering under galactic dust study reveals radiation at center of Milky Way", (WHAM)-Wisconsin H-Alpha Mapper telescope, , , , , LINER-type galaxy,   

    From University of Wisconsin Madison: “Peering under galactic dust, study reveals radiation at center of Milky Way” 

    From University of Wisconsin Madison

    July 3, 2020
    Eric Hamilton
    eshamilton@wisc.edu

    Thanks to 20 years of homegrown galactic data, astronomers at the University of Wisconsin–Madison, UW–Whitewater and Embry-Riddle Aeronautical University have finally figured out just how much energy permeates the center of the Milky Way.

    Milky Way NASA/JPL-Caltech /ESO R. Hurt. The bar is visible in this image

    The researchers say it could one day help astronomers track down where all that energy comes from. Understanding the source of the radiation could help explain not only the nature of the Milky Way, but the countless others that resemble it.

    Writing in the journal Science Advances on July 3, UW–Madison astronomy graduate student Dhanesh Krishnarao, UW–Whitewater Professor of Astronomy Bob Benjamin and Embry-Riddle Professor of Astronomy Matt Haffner report that the Milky Way’s center occupies a middle ground of galactic radiation levels known as a LINER-type galaxy.

    1
    The researchers used the Wisconsin H-alpha Mapper, or WHAM, telescope to measure the emission of visible light from hydrogen in a disk-shaped region tilted beneath the plane of the Milky Way, highlighted in red. Dhanesh Krishnarao/Milky Way image by Axel Mellinger.

    In many ways, the Milky Way is among the most mysterious galaxies. Although we call it home, our view of the galaxy’s dense and active center is blocked by immense clouds of dust. However, working with the Wisconsin H-Alpha Mapper telescope, (WHAM), the researchers recently stumbled onto a fortuitous path toward understanding more about the energy at the center of the Milky Way.

    1
    U Wisconsin WHAM Wisconsin Alpha Mapper telescope

    A few years ago, Benjamin was reviewing two decades worth of information gathered by WHAM about ionized hydrogen gas across the entire galaxy. Gas that’s ionized has absorbed enough energy to strip it of its electrons, and it gives off a red hue that telescopes can capture.

    He noticed an anomaly. In a bubble protruding beneath the dark dust toward the center of the galaxy, some of the gas was heading in the direction of Earth when that shouldn’t have been possible.

    “That didn’t make any sense because galactic rotation can’t produce that,” says Benjamin.

    The errant gas not only begged to be explained, but also offered an opportunity to understand the energy permeating the galactic center. Because the bubble of gas extended away from the heaviest clouds of dust, it allowed the researchers to see further toward the galactic center than is normally possible. Measuring how much of the gas was ionized would tell them how much radiation existed in the galactic center.

    So, Krishnarao set WHAM’s sights squarely on this protruding bubble to gather additional information on the ionized nitrogen, oxygen and hydrogen that resided there. He then turned his attention to a 40-year-old model of galactic gas that might help him explain his data.

    The model attempted to explain the extent of the neutral, or non-ionized, gas within the protruding bubble. Krishnarao first refined the model’s prediction of the shape of the gas, and then he adapted it to account for ionized gas as well.

    By combining the raw data from WHAM with the updated model, the astronomers were able to estimate the three-dimensional size, location and composition of ionized gas. The results showed that there was a large amount of ionized gas permeating the center of the Milky Way, which had never been seen before.

    “It was surprising to us because we’d only known about the neutral gas before,” Benjamin says. “But compared to other galaxies we’ve observed, the amount of ionized gas looked pretty normal.”

    Krishnarao’s team also noticed that the composition of the ionized gas — and thus the nature of the radiation that produces it — changes as you move away from the center of the galaxy.

    “That’s telling us that what’s happening at the very nucleus of our galaxy, really close to that central supermassive black hole, is different than what’s happening a little bit farther away,” says Krishnarao.


    Study reveals radiation at center of Milky Way
    Working with the Wisconsin H-Alpha Mapper telescope, (WHAM), the researchers recently stumbled onto a fortuitous path toward understanding more about the energy at the center of the Milky Way.

    The overall radiation at the galactic center places it into a category known as LINER. About one-third of all galaxies we can see are LINERs. It’s a catch-all term for galaxies with more radiation at the center relative to galaxies dominated by star formation, but less radiation than that produced by the galactic engines of mass-eating supermassive black holes known as active galactic nuclei. Not too much, and not too little, the Milky Way plays the role of the Goldilocks of galactic radiation.

    The researchers were also able to explain the gas’s unusual trajectory. The three-dimensional location of the gas showed that it was on an orbit headed toward Earth due to the elliptical rotation of the bar of the Milky Way.

    However, the source of radiation in LINER galaxies remains a mystery. Now that it’s known the Milky Way falls into that category, it offers a chance for up-close observations of radiation sources to try and pin down just what creates all that energy.

    Krishnarao is now studying whether barred spiral galaxies like our own are prone to being LINERs, and what could explain that association. The answers will help make sense of the Milky Way’s sister spiral galaxies, spread throughout the universe, and give us a deeper understanding of our galactic home.

    This work was supported in part by the National Science Foundation for WHAM development, operations and science activities including grants AST-0607512, AST-1108911, and AST-1714472/1715623; NASA grant NNX17AJ27G; and IDEX Paris-Saclay grant ANR-11-IDEX-0003-02.

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    In achievement and prestige, the University of Wisconsin–Madison has long been recognized as one of America’s great universities. A public, land-grant institution, UW–Madison offers a complete spectrum of liberal arts studies, professional programs and student activities. Spanning 936 acres along the southern shore of Lake Mendota, the campus is located in the city of Madison.

     
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