Old star offers sneak preview of the future

Discussion in 'Astronomy, Exobiology, & Cosmology' started by paddoboy, Dec 16, 2016.

  1. paddoboy Valued Senior Member

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    Will Earth still exist 5 billion years from now? Old star offers sneak preview of the future
    December 8, 2016

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    Composite view of L2 Puppis in visible light (from the VLT/SPHERE instrument, blue colors) and ALMA continuum (orange colors). The central star light has been subtracted from the ALMA image to better show the companion object. Credit: © P. Kervella et al. (CNRS / U. de Chile / Observatoire de Paris / LESIA / ESO / ALMA)
    What will happen to Earth when, in a few billion years' time, the sun is a hundred times bigger than it is today? Using the most powerful radio telescope in the world, an international team of astronomers has set out to look for answers in the star L2 Puppis. Five billion years ago, this star was very similar to the sun as it is today.

    "Five billion years from now, the sun will have grown into a red giant star, more than a hundred times larger than its current size," says Professor Leen Decin from the KU Leuven Institute of Astronomy. "It will also experience an intense mass loss through a very strong stellar wind. The end product of its evolution, 7 billion years from now, will be a tiny white dwarf star. This will be about the size of the Earth, but much heavier: one tea spoon of white dwarf material weighs about 5 tons."




    Read more at: http://phys.org/news/2016-12-earth-billion-years-star-preview.html#jCp
     
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  3. paddoboy Valued Senior Member

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    http://www.aanda.org/articles/aa/abs/2016/12/aa29877-16/aa29877-16.html

    ALMA observations of the nearby AGB star L2 Puppis
    I. Mass of the central star and detection of a candidate planet:

    Abstract

    Six billion years from now, while evolving on the asymptotic giant branch (AGB), the Sun will metamorphose from a red giant into a beautiful planetary nebula. This spectacular evolution will impact the solar system planets, but observational confirmations of the predictions of evolution models are still elusive as no planet orbiting an AGB star has yet been discovered. The nearby AGB red giant L2 Puppis (d = 64 pc) is surrounded by an almost edge-on circumstellar dust disk. We report new observations with ALMA at very high angular resolution (18 × 15 mas) in band 7 (ν ≈ 350 GHz) that allow us to resolve the velocity profile of the molecular disk. We establish that the gas velocity profile is Keplerian within the central cavity of the dust disk, allowing us to derive the mass of the central star L2 Pup A, mA = 0.659 ± 0.011 ± 0.041 M⊙ (± 6.6%). From evolutionary models, we determine that L2 Pup A had a near-solar main-sequence mass, and is therefore a close analog of the future Sun in 5 to 6 Gyr. The continuum map reveals a secondary source (B) at a radius of 2 AU contributing fB/fA = 1.3 ± 0.1% of the flux of the AGB star. L2 Pup B is also detected in CO emission lines at a radial velocity of vB = 12.2 ± 1.0 km s-1. The close coincidence of the center of rotation of the gaseous disk with the position of the continuum emission from the AGB star allows us to constrain the mass of the companion to mB = 12 ± 16MJup. L2 Pup B is most likely a planet or low-mass brown dwarf with an orbital period of about five years. Its continuum brightness and molecular emission suggest that it may be surrounded by an extended molecular atmosphere or an accretion disk. L2 Pup therefore emerges as a promising vantage point on the distant future of our solar system.
     
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