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  • richardmitnick 9:44 am on August 19, 2018 Permalink | Reply
    Tags: "Discovery of a structurally ‘inside-out’ planetary nebula, , , , , , NOAO WIYN 3.5 meter telescope at Kitt Peak AZ USA, Planetary nebula HuBi   

    From Astrobiology Magazine: “Discovery of a structurally ‘inside-out’ planetary nebula” 

    Astrobiology Magazine

    From Astrobiology Magazine

    Aug 18, 2018

    Planetary nebula HuBi 1 (left) and another planetary nebula Abell39 (right, 6800 light years away from our solar system). (HuBi 1 image adopted from Guerrero, Fang, Miller Bertolami, et al., 2018, Nature Astronomy, tmp, 112. Image credit for Abell39: The 3.5m WIYN Telescope, National Optical Astronomical Observatory, NSF.)

    NOAO WIYN 3.5 meter telescope interior

    NOAO WIYN 3.5 meter telescope at Kitt Peak, AZ, USA, Altitude 2,096 m (6,877 ft)

    The Instituto de Astrofísica de Andalucía (IAA-CSIC) in Spain, the Laboratory for Space Research (LSR) of the University of Hong Kong (HKU), and an International team comprising scientists from Argentina, Mexico and Germany have discovered the unusual evolution of the central star of a planetary nebula in our Milky Way. This extraordinary discovery sheds light on the future evolution, and more importantly, the ultimate fate of the Sun.

    The discovery of a structurally ‘inside-out’ planetary nebula — the ionized material that surrounds a white dwarf — was just reported online in Nature Astronomy. This is also the eighth research paper produced by HKU LSR with its international collaborators in the Nature journals since 2017.

    The research team believes this inverted ionization structure of the nebula is resulted from the central star undergoing a ‘born-again’ event, ejecting material from its surface and creating a shock that excites the nebular material.

    Planetary nebulae are ionized clouds of gas formed by the hydrogen-rich envelopes of low- and intermediate-mass stars ejected at late evolutionary stages. As these stars age, they typically strip their outer layers, forming a ‘wind’. As the star transitions from its red giant phase to become a white dwarf, it becomes hotter, and starts ionizing the material in the surrounding wind. This causes the gaseous material closer to the star to become highly ionized, while the gas material further out is less so.

    Studying the planetary nebula HuBi 1 (17,000 light years away and nearly 5 billion years ahead of our solar system in evolution), however, Dr Martín Guerrero et al. found the reverse: HuBi 1’s inner regions are less ionized, while the outer regions more so. Analysing the central star, with the participation of top theoretical astrophysicists, the authors found that it is surprisingly cool and metal-rich, and is evolved from a low-mass progenitor star which has a mass 1.1 times of the Sun.

    The authors suggest that the inner nebula was excited by the passage of a shockwave caused by the star ejecting matter unusually late in its evolution. The stellar material cooled to form circumstellar dust, obscuring the star; this well explains why the central star’s optical brightness has diminished rapidly over the past 50 years. In the absence of ionizing photons from the central star, the outer nebula has begun recombining — becoming neutral. The authors conclude that, as HuBi 1 was roughly the same mass as the Sun, this finding provides a glimpse of a potential future for our solar system.

    Dr Xuan Fang, co-author of the paper and a postdoctoral fellow at the HKU LSR and Department of Physics, said the extraordinary discovery resolves a long-lasting question regarding the evolutionary path of metal-rich central stars of planetary nebulae. Dr Fang has been observing the evolution of HuBi 1 early since 2014 using the Spanish flagship telescope Nordic Optical Telescope and was among the first astrophysicists to discover its inverted ionization structure.

    Nordic Optical telescope, at Roque de los Muchachos Observatory, La Palma in the Canary Islands, Spain, Altitude 2,396 m (7,861 ft)

    He said: “After noting HuBi 1’s inverted ionization structure and the unusual nature of its central star, we looked closer to find the reasons in collaboration with top theoretical astrophysicists in the world. We then came to realize that we had caught HuBi 1 at the exact moment when its central star underwent a brief ‘born-again’ process to become a hydrogen-poor [WC] and metal-rich star, which is very rare in white dwarf stars evolution.”

    Dr Fang, however, said the discovery would not alter the fate of the Earth. He remarked: “Our findings suggest that the Sun may also experience a ‘born-again’ process while it is dying out in about 5 billion years from now; but way before that event, our earth will be engulfed by the Sun when it turns into a superhot red giant and nothing living will survive.”

    HKU LSR Acting Director Professor Quentin Parker is exceptionally pleased with the findings of this international collaboration. He said: “I am delighted by this latest important contribution by Dr Xuan Fang who played a key role in this very unusual discovery of the international project. This exciting result in the area of evolved stars adds to several other impressive findings that members of the LSR have been producing over the last two years in astrophysics and planetary science research. It demonstrates yet again that the universe still has surprises for us. The LSR has an excellent and growing reputation in late-stage stellar evolution, high energy astrophysics, and planetary sciences and I expect this to continue.”

    See the full article here .

    Please help promote STEM in your local schools.

    Stem Education Coalition

  • richardmitnick 5:05 pm on June 4, 2018 Permalink | Reply
    Tags: , , , Can Exoplanets Form in a Binary Star System?, , , NOAO WIYN 3.5 meter telescope at Kitt Peak AZ USA   

    From Gemini Observatory: “Can Exoplanets Form in a Binary Star System?” 


    Gemini Observatory
    From Gemini Observatory

    May 31, 2018

    Artist interpretation of a close binary star system in which several planets orbit the brighter star. The fainter companion star looms brightly in the sky (upper right). A recent investigation confirms that the presence of a stellar pair does not interfere in planet formation. The study finds that approximately half of the stars harboring exoplanets are binary. Image credit: Robin Dienel, courtesy of the Carnegie Institution for Science.

    A new study using Gemini data reveals that the ratio of binary stars in Kepler’s K2 exoplanet host stars is similar to that found elsewhere in our neighborhood of the Milky Way. According to lead author Dr. Rachel Matson of NASA’s Ames Research Center, “While we have known that about 50% of all stars are binary, to confirm a similar ratio in exoplanet host stars helps set some important constraints on the formation of potential exoplanets seen by Kepler.”

    Until recently, astronomers generally focused on single exoplanet host stars, believing that planets form primarily around lone stars like our Sun. However, the research led by Matson, who’s team observed 206 star systems, demonstrates that the influence of a neighboring star does not appear to deter planet formation. The presence of a very close neighboring star produces enormous collateral effects on a planetary system, possibly ejecting planets into interstellar space, or gravitationally interfering with their formation and orbits.

    “In our sample we did not find evidence that the proximity of a companion star suppresses the formation of exoplanets, even at distances as small as 50 Astronomical Units, which is similar to the distance between the Sun and the edge of the Kuiper belt,” explained Matson.

    Dr. Steve Howell, Space Science & Astrobiology Division Chief at NASA Ames Research Center, a co-author of the study and leader of the Gemini Observatory high-resolution imaging effort, said, “We now have found that about half of the stars that host exoplanets are binary, both in the Kepler sample and now in the K2 sample, telling us we cannot ignore such systems and need to take them into account in our exoplanet studies.“

    The researchers used observations from the Gemini North and South telescopes, and the WIYN telescope using the Differential Speckle Survey Instrument (DSSI), for the high-resolution imaging of the K2 stars.

    NOAO WIYN telescope DSSI Differential Speckle Survey Instrument

    NOAO WIYN 3.5 meter telescope at Kitt Peak, AZ, USA, Altitude 2,096 m (6,877 ft)

    The paper is accepted for publication in The Astrophysical Journal.

    A preprint of the paper can be found here.

    See the full article here .

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Gemini/North telescope at Maunakea, Hawaii, USA,4,207 m (13,802 ft) above sea level

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

    AURA Icon

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

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

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

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