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  • richardmitnick 8:54 pm on May 23, 2022 Permalink | Reply
    Tags: "Planets of binary stars as possible homes for alien life", , Binary star systems, Bursts may influence the structure of the later planetary system., , , , , , , The binary star systems studied in this work-NGC 1333-IRAS2A-is surrounded by a disc consisting of gas and dust., , The team has complemented the observations with computer simulations reaching both backwards and forwards in time., The two stars encircle each other and at given intervals their joint gravity will affect the surrounding gas and dust disc in a way which causes huge amounts of material to fall towards the star.   

    From The Niels Bohr Institute [Niels Bohr Institutet] (DK): “Planets of binary stars as possible homes for alien life” 

    Niels Bohr Institute bloc

    From The Niels Bohr Institute [Niels Bohr Institutet] (DK)

    at

    University of Copenhagen [Københavns Universitet] [UCPH] (DK)

    23 May 2022

    Contacts:

    Jes Kristian Jørgensen
    Professor
    Astrophysics and Planetary Science
    Niels Bohr Institute
    University of Copenhagen
    jeskj@nbi.ku.dk
    +45 35 32 41 86

    Rajika L. Kuruwita
    Postdoc
    Astrophysics and Planetary Science
    Niels Bohr Institute
    University of Copenhagen
    rajika.kuruwita@nbi.ku.dk
    +45 35 32 79 98

    Maria Hornbek
    Journalist
    Faculty of Science
    University of Copenhagen
    maho@science.ku.dk
    +45 22 95 42 83

    Nearly half of Sun-size stars are binary. According to University of Copenhagen research, planetary systems around binary stars may be very different from those around single stars. This points to new targets in the search for extraterrestrial life forms.

    Since the only known planet with life, the Earth, orbits the Sun, planetary systems around stars of similar size are obvious targets for astronomers trying to locate extraterrestrial life. Nearly every second star in that category is a binary star. A new result from research at University of Copenhagen indicate that planetary systems are formed in a very different way around binary stars than around single stars such as the Sun.

    “The result is exciting since the search for extraterrestrial life will be equipped with several new, extremely powerful instruments within the coming years. This enhances the significance of understanding how planets are formed around different types of stars. Such results may pinpoint places which would be especially interesting to probe for the existence of life,” says Professor Jes Kristian Jørgensen, Niels Bohr Institute, University of Copenhagen, heading the project.

    The results from the project, which also has participation of astronomers from Taiwan and USA, are published in the distinguished journal Nature.

    Bursts shape the planetary system

    The new discovery has been made based on observations made by the ALMA telescopes in Chile of a young binary star about 1,000 lightyears from Earth.

    The binary star system, NGC 1333-IRAS2A, is surrounded by a disc consisting of gas and dust. The observations can only provide researchers with a snapshot from a point in the evolution of the binary star system. However, the team has complemented the observations with computer simulations reaching both backwards and forwards in time.

    “The observations allow us to zoom in on the stars and study how dust and gas move towards the disc. The simulations will tell us which physics are at play, and how the stars have evolved up till the snapshot we observe, and their future evolution,” explains Postdoc Rajika L. Kuruwita, Niels Bohr Institute, second author of the Nature article.

    2
    Simulation of binary star (from the scientific article by Jørgensen, Kuruwita et al.)

    Notably, the movement of gas and dust does not follow a continuous pattern. At some points in time – typically for relatively shorts periods of ten to one hundred years every thousand years – the movement becomes very strong. The binary star becomes ten to one hundred times brighter, until it returns to its regular state.

    Presumably, the cyclic pattern can be explained by the duality of the binary star. The two stars encircle each other, and at given intervals their joint gravity will affect the surrounding gas and dust disc in a way which causes huge amounts of material to fall towards the star.

    “The falling material will trigger a significant heating. The heat will make the star much brighter than usual,” says Rajika L. Kuruwita, adding:

    “These bursts will tear the gas and dust disc apart. While the disc will build up again, the bursts may still influence the structure of the later planetary system.”

    Comets carry building blocks for life.

    The observed stellar system is still too young for planets to have formed. The team hopes to obtain more observational time at ALMA, allowing to investigate the formation of planetary systems.

    Not only planets but also comets will be in focus:

    “Comets are likely to play a key role in creating possibilities for life to evolve. Comets often have a high content of ice with presence of organic molecules. It can well be imagined that the organic molecules are preserved in comets during epochs where a planet is barren, and that later comet impacts will introduce the molecules to the planet’s surface,” says Jes Kristian Jørgensen.

    Understanding the role of the bursts is important in this context:

    “The heating caused by the bursts will trigger evaporation of dust grains and the ice surrounding them. This may alter the chemical composition of the material from which planets are formed.”

    Thus, chemistry is a part of the research scope:

    “The wavelengths covered by ALMA allow us to see quite complex organic molecules, so molecules with 9-12 atoms and containing carbon. Such molecules can be building blocks for more complex molecules which are key to life as we know it. For example, amino acids which have been found in comets.”

    Powerful tools join the search for life in space

    ALMA (Atacama Large Millimeter/submillimeter Array) is not a single instrument but 66 telescopes operating in coordination. This allows for a much better resolution than could have been obtained by a single telescope.

    Very soon the new James Webb Space Telescope (JWST) will join the search for extraterrestrial life.

    Near the end of the decade, JWST will be complemented by the ELT (European Large Telescope) and the extremely powerful SKA (Square Kilometer Array) both planned to begin observing in 2027.

    The ELT will with its 39-meter mirror be the biggest optical telescope in the world and will be poised to observe the atmospheric conditions of exoplanets (planets outside the Solar System, ed.). SKA will consist of thousands of telescopes in South Africa and in Australia working in coordination and will have longer wavelengths than ALMA.

    ”The SKA will allow for observing large organic molecules directly. The James Webb Space Telescope operates in the infrared which is especially well suited for observing molecules in ice. Finally, we continue to have ALMA which is especially well suited for observing molecules in gas form. Combining the different sources will provide a wealth of exciting results,” Jes Kristian Jørgensen concludes.

    See the full article here .


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    Stem Education Coalition

    Niels Bohr Institute Campus

    The Niels Bohr Institutet (DK) is a research institute of the Københavns Universitet [UCPH] (DK). The research of the institute spans astronomy, geophysics, nanotechnology, particle physics, quantum mechanics and biophysics.

    The Institute was founded in 1921, as the Institute for Theoretical Physics of the Københavns Universitet [UCPH] (DK), by the Danish theoretical physicist Niels Bohr, who had been on the staff of the University of Copenhagen since 1914, and who had been lobbying for its creation since his appointment as professor in 1916. On the 80th anniversary of Niels Bohr’s birth – October 7, 1965 – the Institute officially became The Niels Bohr Institutet (DK). Much of its original funding came from the charitable foundation of the Carlsberg brewery, and later from the Rockefeller Foundation.

    During the 1920s, and 1930s, the Institute was the centre of the developing disciplines of atomic physics and quantum physics. Physicists from across Europe (and sometimes further abroad) often visited the Institute to confer with Bohr on new theories and discoveries. The Copenhagen interpretation of quantum mechanics is named after work done at the Institute during this time.

    On January 1, 1993 the institute was fused with the Astronomic Observatory, the Ørsted Laboratory and the Geophysical Institute. The new resulting institute retained the name Niels Bohr Institutet (DK).

    Københavns Universitet (UCPH) (DK) is the oldest university and research institution in Denmark. Founded in 1479 as a studium generale, it is the second oldest institution for higher education in Scandinavia after Uppsala University (1477). The university has 23,473 undergraduate students, 17,398 postgraduate students, 2,968 doctoral students and over 9,000 employees. The university has four campuses located in and around Copenhagen, with the headquarters located in central Copenhagen. Most courses are taught in Danish; however, many courses are also offered in English and a few in German. The university has several thousands of foreign students, about half of whom come from Nordic countries.

    The university is a member of the International Alliance of Research Universities (IARU), along with University of Cambridge (UK), Yale University , The Australian National University (AU), and University of California-Berkeley , amongst others. The 2016 Academic Ranking of World Universities ranks the University of Copenhagen as the best university in Scandinavia and 30th in the world, the 2016-2017 Times Higher Education World University Rankings as 120th in the world, and the 2016-2017 QS World University Rankings as 68th in the world. The university has had 9 alumni become Nobel laureates and has produced one Turing Award recipient.

     
  • richardmitnick 2:07 pm on January 12, 2022 Permalink | Reply
    Tags: "Cosmic 'Spider' Found to Be Source of Powerful Gamma-Rays", About 80 extremely low-mass white dwarfs are known but this is the first precursor to an extremely low-mass white dwarf found that is likely orbiting a neutron star., Binary star systems, Gamma ray source called 4FGL J1120.0-2204, , , Most millisecond pulsars emit gamma rays and X-rays., , , Vhite dwarf stars   

    From The National Science Foundation (US)’ NOIRLab (National Optical-Infrared Astronomy Research Laboratory) (US): “Cosmic ‘Spider’ Found to Be Source of Powerful Gamma-Rays” 

    From The National Science Foundation (US)’ NOIRLab (National Optical-Infrared Astronomy Research Laboratory) (US)

    12 January 2022

    Contacts:
    Samuel Swihart
    National Research Council Research Associate
    The National Academy of Sciences (US), resident at The Naval Research Laboratory (US)
    +1 269 944 9282
    samuel.swihart.ctr@nrl.navy.mil

    Amanda Kocz
    NSF’s NOIRLab Communications
    +1 520 318 8591
    amanda.kocz@noirlab.edu

    Investigated by the SOAR Telescope [below] operated by NOIRLab , the binary system is the first to be found at the penultimate stage of its evolution.

    1
    Using the 4.1-meter SOAR Telescope in Chile, astronomers have discovered the first example of a binary system where a star in the process of becoming a white dwarf is orbiting a neutron star that has just finished turning into a rapidly spinning pulsar. The pair, originally detected by the Fermi Gamma-ray Space Telescope, is a “missing link” in the evolution of such binary systems.

    National Aeronautics and Space Administration(US) Fermi Large Area Telescope.
    National Aeronautics and Space Administration(US)/Fermi Gamma Ray Space Telescope.

    A bright, mysterious source of gamma rays has been found to be a rapidly spinning neutron star — dubbed a millisecond pulsar — that is orbiting a star in the process of evolving into an extremely-low-mass white dwarf. These types of binary systems are referred to by astronomers as “spiders” because the pulsar tends to “eat” the outer parts of the companion star as it turns into a white dwarf.

    The duo was detected by astronomers using the 4.1-meter SOAR Telescope on Cerro Pachón in Chile, part of Cerro Tololo Inter-American Observatory (CTIO)[below], a Program of NSF’s NOIRLab.

    NASA’s Fermi Gamma-ray Space Telescope [above] has been cataloging objects in the Universe that produce copious gamma rays since its launch in 2008, but not all of the sources of gamma rays that it detects have been classified. One such source, called 4FGL J1120.0-2204 by astronomers, was the second brightest gamma-ray source in the entire sky that had gone unidentified, until now.

    Astronomers from the United States and Canada, led by Samuel Swihart of the US Naval Research Laboratory in Washington, D.C., used the Goodman Spectrograph on the SOAR Telescope to determine the true identity of 4FGL J1120.0-2204.

    3
    Goodman High Throughput Spectrograph. Credit: NOIRLab.

    The gamma-ray source, which also emits X-rays, as observed by NASA’s Swift and ESA’s XMM-Newton space telescopes, has been shown to be a binary system consisting of a “millisecond pulsar” that spins hundreds of times per second, and the precursor to an extremely-low-mass white dwarf. The pair are located over 2600 light-years away.

    National Aeronautics and Space Administration(US) Neil Gehrels Swift Observatory.

    European Space Agency [Agence spatiale européenne][Europäische Weltraumorganisation](EU) XMM Newton X-ray telescope. http://sci.esa.int/xmm-newton/

    The Michigan State University (US)’s dedicated time on the SOAR Telescope, its location in the southern hemisphere and the precision and stability of the Goodman spectrograph, were all important aspects of this discovery,” says Swihart.

    “This is a great example of how mid-sized telescopes in general, and SOAR in particular, can be used to help characterize unusual discoveries made with other ground and space-based facilities”, notes Chris Davis, NOIRLab Program Director at The National Science Foundation (US). “We anticipate that SOAR will play a crucial role in the follow-up of many other time-variable and multi-messenger sources over the coming decade.”

    The optical spectrum of the binary system measured by the Goodman spectrograph showed that light from the proto-white dwarf companion is Doppler shifted — alternately shifted to the red and the blue — indicating that it orbits a compact, massive neutron star every 15 hours.

    Doppler method – The European Southern Observatory [Observatoire européen austral][Europäische Südsternwarte](EU)(CL).

    “The spectra also allowed us to constrain the approximate temperature and surface gravity of the companion star,” says Swihart, whose team was able to take these properties and apply them to models describing how binary star systems evolve. This allowed them to determine that the companion is the precursor to an extremely-low-mass white dwarf, with a surface temperature of 8200 °C (15,000 °F), and a mass of just 17% that of the Sun.

    When a star with a mass similar to that of the Sun or less reaches the end of its life, it will run out of the hydrogen used to fuel the nuclear fusion processes in its core. For a time, helium takes over and powers the star, causing it to contract and heat up, and prompting its expansion and evolution into a red giant that is hundreds of millions of kilometers in size. Eventually, the outer layers of this swollen star can be accreted onto a binary companion and nuclear fusion halts, leaving behind a white dwarf about the size of Earth and sizzling at temperatures exceeding 100,000 °C (180,000 °F).

    The proto-white dwarf in the 4FGL J1120.0-2204 system hasn’t finished evolving yet. “Currently it’s bloated, and is about five times larger in radius than normal white dwarfs with similar masses,” says Swihart. “It will continue cooling and contracting and, in about two billion years, it will look identical to many of the extremely low mass white dwarfs that we already know about.”

    Millisecond pulsars twirl hundreds of times every second. They are spun up by accreting matter from a companion, in this case from the star that became the white dwarf. Most millisecond pulsars emit gamma rays and X-rays, often when the pulsar wind, which is a stream of charged particles emanating from the rotating neutron star, collides with material emitted from a companion star.

    About 80 extremely low-mass white dwarfs are known, but “this is the first precursor to an extremely low-mass white dwarf found that is likely orbiting a neutron star,” says Swihart. Consequently, 4FGL J1120.0-2204 is a unique look at the tail-end of this spin-up process. All the other white dwarf–pulsar binaries that have been discovered are well past the spinning-up stage.

    “Follow-up spectroscopy with the SOAR Telescope, targeting unassociated Fermi gamma-ray sources, allowed us to see that the companion was orbiting something,” says Swihart. “Without those observations, we couldn’t have found this exciting system.”

    Science paper:
    The Astrophysical Journal

    See the full article here.

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    Stem Education Coalition

    What is NOIRLab?

    NSF’s NOIRLab (National Optical-Infrared Astronomy Research Laboratory) (US), the US center for ground-based optical-infrared astronomy, operates the international Gemini Observatory (US) (a facility of National Science Foundation (US), NRC–Canada, ANID–Chile, MCTIC–Brazil, MINCyT–Argentina, and Korea Astronomy and Space Science Institute [한국천문연구원] (KR)), NOAO Kitt Peak National Observatory(US) (KPNO), Cerro Tololo Inter-American Observatory(CL) (CTIO), the Community Science and Data Center (CSDC), and Vera C. Rubin Observatory (in cooperation with DOE’s SLAC National Accelerator Laboratory (US)). It is managed by the Association of Universities for Research in Astronomy (AURA) (US) under a cooperative agreement with NSF and is headquartered in Tucson, Arizona. The astronomical community is honored to have the opportunity to conduct astronomical research on Iolkam Du’ag (Kitt Peak) in Arizona, on Maunakea in Hawaiʻi, and on Cerro Tololo and Cerro Pachón in Chile. We recognize and acknowledge the very significant cultural role and reverence that these sites have to the Tohono O’odham Nation, to the Native Hawaiian community, and to the local communities in Chile, respectively.

    National Science Foundation(US) NOIRLab’s Gemini North Frederick C Gillett telescope at Mauna Kea Observatory Hawai’i (US) Altitude 4,213 m (13,822 ft)

    NSF NOIRLab(US) NOAO(US) Gemini South telescope (US) on the summit of Cerro Pachón at an altitude of 7200 feet. There are currently two telescopes commissioned on Cerro Pachón, Gemini South and the Southern Astrophysical Research Telescope. A third, the Vera C. Rubin Observatory, is under construction.

    NSF (US) NOIRLab (US) NOAO (US) Vera C. Rubin Observatory [LSST] Telescope currently under construction on the El Peñón peak at Cerro Pachón Chile, a 2,682-meter-high mountain in Coquimbo Region, in northern Chile, alongside the existing NSF (US) NOIRLab (US) NOAO (US) AURA (US) Gemini South Telescope and Southern Astrophysical Research Telescope.

    Carnegie Institution for Science (US)’s Las Campanas Observatory on Cerro Pachón in the southern Atacama Desert of Chile in the Atacama Region approximately 100 kilometres (62 mi) northeast of the city of La Serena,near the southern end and over 2,500 m (8,200 ft) high.

    National Science Foundation(US) NOIRLab (US) NOAO (US) Kitt Peak National Observatory (US) on Kitt Peak of the Quinlan Mountains in the Arizona-Sonoran Desert on the Tohono O’odham Nation, 88 kilometers (55 mi) west-southwest of Tucson, Arizona, Altitude 2,096 m (6,877 ft). annotated.

    NSF NOIRLab NOAO (US) Cerro Tololo Inter-American Observatory(CL) approximately 80 km to the East of La Serena, Chile, at an altitude of 2200 meters.

    The NOAO-Community Science and Data Center(US)

    The NSF NOIRLab Vera C. Rubin Observatory. It is managed by the Association of Universities for Research in Astronomy(US) under a cooperative agreement with NSF and is headquartered in Tucson, Arizona. The astronomical community is honored to have the opportunity to conduct astronomical research on Iolkam Du’ag (Kitt Peak) in Arizona, on Maunakea in Hawaiʻi, and on Cerro Tololo and Cerro Pachón in Chile. We recognize and acknowledge the very significant cultural role and reverence that these sites have to the Tohono O’odham Nation, to the Native Hawaiian community, and to the local communities in Chile, respectively.

    This work is supported in part by The Department of Energy (US) Office of Science (US). The Dark Energy Survey is a collaboration of more than 400 scientists from 26 institutions in seven countries. Funding for the DES Projects has been provided by the US Department of Energy Office of Science, The National Science Foundation (US), Ministry of Science and Education of Spain, The Science and Technology Facilities Council (UK), The Higher Education Funding Council for England (UK), The Swiss Federal Institute of Technology ETH Zürich [Eidgenössische Technische Hochschule Zürich)](CH), The National Center for Supercomputing Applications (US) at The University of Illinois at Urbana-Champaign (US), The Kavli Institute of Cosmological Physics (US) at The University of Chicago (US), Center for Cosmology and AstroParticle Physics at The Ohio State University (US), Mitchell Institute for Fundamental Physics and Astronomy at The Texas A&M University (US), Brazil Funding Authority for Studies and Projects for Scientific and Technological Development [Financiadora de Estudos e Projetos ] (BR) , Carlos Chagas Filho Foundation for Research Support of the State of Rio de Janeiro [Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro](BR), The Ministry of Science and Technology [Conselho Nacional de Desenvolvimento Científico e Tecnológico and Ministério da Ciência e Tecnologia(BR), German Research Foundation [Deutsche Forschungsgemeinschaft](DE), and the collaborating institutions in the Dark Energy Survey.

    The National Center for Supercomputing Applications(US) at the University of Illinois at Urbana-Champaign provides supercomputing and advanced digital resources for the nation’s science enterprise. At NCSA, The University of Illinois (US) faculty, staff, students, and collaborators from around the globe use advanced digital resources to address research grand challenges for the benefit of science and society. NCSA has been advancing one-third of the Fortune 50® for more than 30 years by bringing industry, researchers, and students together to solve grand challenges at rapid speed and scale.

    DOE’s Fermi National Accelerator Laboratory (US) is America’s premier national laboratory for particle physics and accelerator research. A Department of Energy (US) Office of Science laboratory, Fermilab is located near Chicago, Illinois, and operated under contract by the Fermi Research Alliance LLC, a joint partnership between The University of Chicago (US) and The Universities Research Association, Inc (US).

    The DOE Office of Science (US) is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time.

     
  • richardmitnick 9:37 pm on February 16, 2021 Permalink | Reply
    Tags: "A backward-spinning star with two coplanar orbiting planets in a multi-stellar system", , , , , , Binary star systems, , , The protoplanetary disk in which the two planets formed is tilted by the second star in this system.   

    From Aarhus University [Aarhus Universitet] (DK) via phys.org: “A backward-spinning star with two coplanar orbiting planets in a multi-stellar system” 

    From Aarhus University [Aarhus Universitet] (DK)

    1
    Backwards planets in double star system. Credit: Christoffer Grønne.

    In a recent paper in the PNAS a group of researchers led by Maria Hjorth and Simon Albrecht from the Stellar Astrophysics Centre, Aarhus University [Aarhus Universitet] (DK), have published the discovery of a special exoplanetary system in which two exoplanets are orbiting backward around their star. This surprising orbital architecture was caused by the protoplanetary disk in which the two planets formed being tilted by the second star in this system.

    Maria Hjorth says, “We found a very intriguing planetary system. There are two planets that orbit around the star in nearly the opposite direction as the star rotates around its own axis. This is unlike our own solar system, where all the planets are revolving in the same direction as the sun’s rotation.”

    Joshua Winn from Princeton University (US) says, “This isn’t the first known case of a ‘backwards’ planetary system—the first ones were sighted more than 10 years ago. But this is a rare case in which we think we know what caused the drastic misalignment, and the explanation is different from what researchers have assumed might have happened in the other systems.”

    Co-author Rebekah Dawson of Pennsylvania State University (US) says, “In any planetary system, the planets are thought to form in a spinning, circular disk of material that swirls around a young star for a few million years after the star itself is born, the so-called protoplanetary disk. Usually, the disk and the star are spinning the same way. However, if there is a neighboring star (where ‘neighboring’ in astronomy means within a light-year or so), the gravitational force from the neighboring star might tilt the disk.”

    2
    A protoplanetary disc has been twisted almost 180° before planet formation. Credit: Christoffer Grønne.

    John Zannazzi from University of Toronto (CA) continues: ” The underlying physics is connected to the behavior a spinning top displays, when its rotation slows down and the axis itself starts to rotate in a cone.”

    The scenario was first theorized in 2012, and now this research team has found the first system in which this process has played out. Teruyuki Hirano of the Tokyo Institute of Technology [東京工業大学; Tōkyō Kōgyō Daigaku] (JP) says, “After we discovered the K2-290 system, we realized this system is ideally suited to test this theory, as it is not only orbited by two planets but also contains two stars. So logically, the next step would be to study the system in finer detail, and indeed we have hit the jackpot.”

    Ph.D. student Emil Knudstrup from Aarhus University [Aarhus Universitet] (DK) says, “The idea that planets travel on wildly misaligned orbits has fascinated me throughout my graduate study. It is one thing to predict the existence of these crazy orbits, so very different from what we see in the solar system. It is quite another thing to participate in actually finding them! Also fascinating is the idea that a structure as enormous as a protoplanetary disk is governed by similar physics as a spinning top.”

    One implication of the discovery is that astronomers can no longer assume that the initial conditions of planet formation exhibit alignment between stellar rotation and planetary orbits. Importantly, while other theories that aim at explaining misalignments in exoplanet systems tend to work best on large, Jupiter-like planets in short period orbits, the disk-tilting mechanism applies to planets of any size. There may be another Earth-like world, for example, that travels over the north and south poles of its home star.

    “I find our results encouraging as it means that we have found another aspect of system architecture where planetary systems show a fascinating variety of configurations,” Simon Albrecht from the Stellar Astrophysics Centre, Aarhus rounds up. “How would astronomy here on Earth have developed if the situation here had been similar to K2-290—then, Galileo would have seen sunspots moving in the opposite direction of the orbit of the Earth around the sun. One just wonders what his explanation would have been to that?”

    See the full article here.

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    Stem Education Coalition

    Aarhus Universitet DK campus.

    Aarhus University [Aarhus Universitet] (DK), abbreviated AU) is the largest and second oldest research university in Denmark. The university belongs to the Coimbra Group, the Guild, and Utrecht Network of European universities and is a member of the European University Association.

    The university was founded in Aarhus, Denmark, in 1928 and comprises five faculties in Arts, Natural Sciences, Technical Sciences, Health, and Business and Social Sciences and has a total of twenty-seven departments. It is home to over thirty internationally recognised research centres, including fifteen Centres of Excellence funded by the Danish National Research Foundation. The university is ranked among the top 100 world’s best universities. The business school within Aarhus University, called Aarhus BSS, holds the EFMD (European Foundation for Management Development) Equis accreditation, the Association to Advance Collegiate Schools of Business (AACSB) and the Association of MBAs (AMBA). This makes the business school of Aarhus University one of the few in the world to hold the so-called Triple Crown accreditation. Times Higher Education ranks Aarhus University in the top 10 of the most beautiful universities in Europe (2018).

    The university’s alumni include Bjarne Stroustrup, the inventor of programming language C++, Queen Margrethe II of Denmark, Crown Prince Frederik of Denmark, and Anders Fogh Rasmussen, former Prime Minister of Denmark and a Secretary General of NATO.

    Nobel Laureate Jens Christian Skou (Chemistry, 1997), conducted his groundbreaking work on the Na/K-ATPase in Aarhus and remained employed at the university until his retirement. Two other nobel laureates: Trygve Haavelmo (Economics, 1989) and Dale T. Mortensen (Economics, 2010). were affiliated with the university.

     
  • richardmitnick 2:28 pm on January 12, 2019 Permalink | Reply
    Tags: Astronomers find signatures of a ‘messy’ star that made its companion go supernova, , , , Binary star systems, , It takes many astronomers and a wide variety of types of telescopes working together to understand transient cosmic phenomena, , SN 2015cp, , ,   

    From University of Washington: “Astronomers find signatures of a ‘messy’ star that made its companion go supernova” 

    U Washington

    From University of Washington

    January 10, 2019
    James Urton

    1
    An X-ray/infrared composite image of G299, a Type Ia supernova remnant in the Milky Way Galaxy approximately 16,000 light years away.NASA/Chandra X-ray Observatory/University of Texas/2MASS/University of Massachusetts/Caltech/NSF

    NASA/Chandra X-ray Telescope


    Caltech 2MASS Telescopes, a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center (IPAC) at Caltech, at the Whipple Observatory on Mt. Hopkins south of Tucson, AZ, Altitude 2,606 m (8,550 ft) and at the Cerro Tololo Inter-American Observatory at an altitude of 2200 meters near La Serena, Chile.

    Many stars explode as luminous supernovae when, swollen with age, they run out of fuel for nuclear fusion. But some stars can go supernova simply because they have a close and pesky companion star that, one day, perturbs its partner so much that it explodes.

    These latter events can happen in binary star systems, where two stars attempt to share dominion. While the exploding star gives off lots of evidence about its identity, astronomers must engage in detective work to learn about the errant companion that triggered the explosion.

    On Jan. 10 at the 2019 American Astronomical Society meeting in Seattle, an international team of astronomers announced that they have identified the type of companion star that made its partner in a binary system, a carbon-oxygen white dwarf star, explode. Through repeated observations of SN 2015cp, a supernova 545 million light years away, the team detected hydrogen-rich debris that the companion star had shed prior to the explosion.

    “The presence of debris means that the companion was either a red giant star or similar star that, prior to making its companion go supernova, had shed large amounts of material,” said University of Washington astronomer Melissa Graham, who presented the discovery and is lead author on the accompanying paper accepted for publication in The Astrophysical Journal.

    The supernova material smacked into this stellar litter at 10 percent the speed of light, causing it to glow with ultraviolet light that was detected by the Hubble Space Telescope and other observatories nearly two years after the initial explosion. By looking for evidence of debris impacts months or years after a supernova in a binary star system, the team believes that astronomers could determine whether the companion had been a messy red giant or a relatively neat and tidy star.

    The team made this discovery as part of a wider study of a particular type of supernova known as a Type Ia supernova. These occur when a carbon-oxygen white dwarf star explodes suddenly due to activity of a binary companion. Carbon-oxygen white dwarfs are small, dense and — for stars — quite stable. They form from the collapsed cores of larger stars and, if left undisturbed, can persist for billions of years.

    Type Ia supernovae have been used for cosmological studies because their consistent luminosity makes them ideal “cosmic lighthouses,” according to Graham. They’ve been used to estimate the expansion rate of the universe and served as indirect evidence for the existence of dark energy.

    2
    An image of SN 1994D (lower left), a Type Ia supernova detected in 1994 at the edge of galaxy NGC 4526 (center).NASA/ESA/The Hubble Key Project Team/The High-Z Supernova Search Team.

    NASA/ESA Hubble Telescope

    Yet scientists are not certain what kinds of companion stars could trigger a Type Ia event. Plenty of evidence indicates that, for most Type Ia supernovae, the companion was likely another carbon-oxygen white dwarf, which would leave no hydrogen-rich debris in the aftermath. Yet theoretical models have shown that stars like red giants could also trigger a Type Ia supernova, which could leave hydrogen-rich debris that would be hit by the explosion. Out of the thousands of Type Ia supernovae studied to date, only a small fraction were later observed impacting hydrogen-rich material shed by a companion star. Prior observations of at least two Type Ia supernovae detected glowing debris months after the explosion. But scientists weren’t sure if those events were isolated occurrences, or signs that Type Ia supernovae could have many different kinds of companion stars.

    “All of the science to date that has been done using Type Ia supernovae, including research on dark energy and the expansion of the universe, rests on the assumption that we know reasonably well what these ‘cosmic lighthouses’ are and how they work,” said Graham. “It is very important to understand how these events are triggered, and whether only a subset of Type Ia events should be used for certain cosmology studies.”

    The team used Hubble Space Telescope observations to look for ultraviolet emissions from 70 Type Ia supernovae approximately one to three years following the initial explosion.

    “By looking years after the initial event, we were searching for signs of shocked material that contained hydrogen, which would indicate that the companion was something other than another carbon-oxygen white dwarf,” said Graham.

    In the case of SN 2015cp, a supernova first detected in 2015, the scientists found what they were searching for. In 2017, 686 days after the supernova exploded, Hubble picked up an ultraviolet glow of debris. This debris was far from the supernova source — at least 100 billion kilometers, or 62 billion miles, away. For reference, Pluto’s orbit takes it a maximum of 7.4 billion kilometers from our sun.

    3
    In 2017, 686 days after the initial explosion, the Hubble Space Telescope recorded an ultraviolet emission (blue circle) from SN 2015cp, which was caused by supernova material impacting hydrogen-rich material previously shed by a companion star. Yellow circles indicate cosmic ray strikes, which are unrelated to the supernova. NASA/Hubble Space Telescope/Graham et al. 2019.

    By comparing SN 2015cp to the other Type Ia supernovae in their survey, the researchers estimate that no more than 6 percent of Type Ia supernovae have such a litterbug companion. Repeated, detailed observations of other Type Ia events would help cement these estimates, Graham said.

    The Hubble Space Telescope was essential for detecting the ultraviolet signature of the companion star’s debris for SN 2015cp. In the fall of 2017, the researchers arranged for additional observations of SN 2015cp by the W.M. Keck Observatory in Hawaii, the Karl G. Jansky Very Large Array in New Mexico, the European Southern Observatory’s Very Large Telescope and NASA’s Neil Gehrels Swift Observatory, among others. These data proved crucial in confirming the presence of hydrogen and are presented in a companion paper lead by Chelsea Harris, a research associate at Michigan State University.

    Keck Observatory, Maunakea, Hawaii, USA.4,207 m (13,802 ft), above sea level,

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

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

    NASA Neil Gehrels Swift Observatory

    “The discovery and follow-up of SN 2015cp’s emission really demonstrates how it takes many astronomers, and a wide variety of types of telescopes, working together to understand transient cosmic phenomena,” said Graham. “It is also a perfect example of the role of serendipity in astronomical studies: If Hubble had looked at SN 2015cp just a month or two later, we wouldn’t have seen anything.”

    Graham is also a senior fellow with the UW’s DIRAC Institute and a science analyst with the Large Synoptic Survey Telescope, or LSST.

    LSST telescope, currently under construction at Cerro Pachón Chile, a 2,682-meter-high mountain in Coquimbo Region, in northern Chile, alongside the existing Gemini South and Southern Astrophysical Research Telescopes, altitude 2,663 m (8,737 ft),

    “In the future, as a part of its regularly scheduled observations, the LSST will automatically detect optical emissions similar to SN 2015cp — from hydrogen impacted by material from Type Ia supernovae,” said Graham said. “It’s going to make my job so much easier!”

    Co-authors are Harris; Peter Nugent at the University of California, Berkeley and the Lawrence Berkeley National Laboratory; Kate Maguire at Queen’s University Belfast; Mark Sullivan and Mathew Smith at the University of Southampton; Stefano Valenti at the University of California, Davis; Ariel Goobar at Stockholm University; Ori Fox at the Space Telescope Science Institute; Ken Shen, Tom Brink and Alex Filippenko at the University of California, Berkeley; Patrick Kelly at the University of Minnesota; and Curtis McCully at the University of California, Santa Barbara and the Las Cumbres Observatory. The research was funded by the National Science Foundation, NASA, the European Research Council and the U.K.’s Science and Technology Facilities Council.

    See the full article here .


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    Please help promote STEM in your local schools.

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    So what defines us —the students, faculty and community members at the University of Washington? Above all, it’s our belief in possibility and our unshakable optimism. It’s a connection to others, both near and far. It’s a hunger that pushes us to tackle challenges and pursue progress. It’s the conviction that together we can create a world of good. Join us on the journey.

     
  • richardmitnick 2:08 pm on November 23, 2016 Permalink | Reply
    Tags: , , , Binary star systems, Pop III stars, X-Ray Background from Early Binaries   

    From AAS NOVA: “X-Ray Background from Early Binaries” 

    AASNOVA

    American Astronomical Society

    23 November 2016
    Susanna Kohler

    1
    Artist’s impression of Population III stars, the first generation of stars believed to have formed more than 13 billion years ago. [NASA]

    What impact did X-rays from the first binary star systems have on the universe around them? A new study suggests this radiation may have played an important role during the reionization of our universe.

    Ionizing the Universe

    During the period of reionization, the universe reverted from being neutral (as it was during recombination, the previous period) to once again being ionized plasma — a state it has remained in since then. This transition, which occurred between 150 million and one billion years after the Big Bang (redshift of 6 < z < 20), was caused by the formation of the first objects energetic enough to reionize the universe’s neutral hydrogen.

    2
    ROSAT image of the soft X-ray background throughout the universe. The different colors represent different energy bands: 0.25 keV (red), 0.75 keV (green), 1.5 keV (blue). [NASA/ROSAT Project]

    Understanding this time period — in particular, determining what sources caused the reionization, and what the properties were of the gas strewn throughout the universe during this time — is necessary for us to be able to correctly interpret cosmological observations.

    Conveniently, the universe has provided us with an interesting clue: the large-scale, diffuse X-ray background we observe all around us. What produced these X-rays, and what impact did this radiation have on the intergalactic medium long ago?

    The First Binaries

    A team of scientists led by Hao Xu (UC San Diego) has suggested that the very first generation of stars might be an important contributor to these X-rays.

    This hypothetical first generation, Population III stars, are thought to have formed before and during reionization from large clouds of gas containing virtually no metals. Studies suggest that a large fraction of Pop III stars formed in binaries — and when those stars ended their lives as black holes, ensuing accretion from their companions could produce X-ray radiation.

    3
    The evolution with redshift of the mean X-ray background intensities. Each curve represents a different observed X-ray energy (and the total X-ray background is given by the sum of the curves). The two panels show results from two different calculation methods. [Xu et al. 2016]

    Xu and collaborators have now attempted to model to the impact of this X-ray production from Pop III binaries on the intergalactic medium and determine how much it could have contributed to reionization and the diffuse X-ray background we observe today.

    Generating a Background

    The authors estimated the X-ray luminosities from Pop III binaries using the results of a series of galaxy-formation simulations, beginning at a redshift of z ~ 25 and evolving up to z = 7.6. They then used these luminosities to calculate the resulting X-ray background.

    Xu and collaborators find that Pop III binaries can produce significant X-ray radiation throughout the period of reionization, and this radiation builds up gradually into an X-ray background. The team shows that X-rays from Pop III binaries might actually dominate more commonly assumed sources of the X-ray background at high redshifts (such as active galactic nuclei), and this radiation is strong enough to heat the intergalactic medium to 1000K and ionize a few percent of the neutral hydrogen.

    If Pop III binaries are indeed this large of a contributor to the X-ray background and to the local and global heating of the intergalactic medium, then it’s important that we follow up with more detailed modeling to understand what this means for our interpretation of cosmological observations.

    Citation

    Hao Xu et al 2016 ApJL 832 L5. doi:10.3847/2041-8205/832/1/L5

    See the full article here .

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    STEM Icon

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