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Solved: source of gammas from Milky Way centre

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  1. Mar 18, 2004 #1

    Nereid

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    ESA's Integral solves 30-year old gamma-ray mystery. Regular readers will recall that we've several times discussed this gamma glow seen in the direction of the Milky Way centre; some PF members have posted links to papers which propose mechanisms for it, some have put forward their own ideas.

    Well, what Integral found was that ~90% of the gammas come from discrete sources, many of which seem to also be discreet - they're not readily visible at other wavelengths, and may be a new class of astronomical object (or three).

    "The first clues about a new class of gamma-ray objects came last October, when Integral discovered an intriguing gamma-ray source, known as IGRJ16318-4848. The data from Integral and ESA's other high-energy observatory XMM-Newton suggested that this object is a binary system, probably including a black hole or neutron star, embedded in a thick cocoon of cold gas and dust. When gas from the companion star is accelerated and swallowed by the black hole, energy is released at all wavelengths, mostly in the gamma rays."

    Sensibly, Lebrun (lead author of a Nature paper reporting the finding of 91 'point sources') feels it's premature to say whether most, or even many, of the new sources are also BH-NS binaries in a thick cocoon of cold gas and dust.

    It's also unclear, at this stage, how widespread these new point-source gamma objects are, beyong the direction to the MW centre.
     
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  3. Mar 18, 2004 #2

    wolram

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    embedded in a thick cocoon of cold gas and dust.

    this is a part of what i dont understand, why is it that
    galactic centers can be rich in gas dust, intuitively
    galaxy centers would be first to be swept clean by
    gravity. or is this dust gas detritus from earlier cataclysms?
     
  4. Mar 18, 2004 #3

    Nereid

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    You may be jumping to conclusions ... The 'centre' imaged by Integral is ~>20o wide. Radio images, like this 4x4 degree one, clearly show lots and lots of gas. Further, the Quintuplet star cluster, which contains the Pistol Star (the most massive star yet observed?) is only ~100 light-years from Sag A* (<1o), and clearly contains lots of gas and dust. This part of the galaxy is also home to the Arches cluster (as seen by the Hubble Space Telescope
     
  5. Mar 18, 2004 #4

    wolram

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    NEREID what is the "new class of object" ?
     
  6. Mar 18, 2004 #5

    Nereid

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    Here is the PR announcing the elucidation of the nature of IGRJ16318-4848.

    Some quotes from this PR:
    "These are binary systems, probably including a black hole or a neutron star, embedded in a thick cocoon of cold gas."

    "XMM-Newton detected this object last February [2002? 2003?], as well as the existence of a dense 'cocoon' of cold gas with a diameter of similar size to that of the Earth's orbit around the Sun.

    This obscuring material forming the cocoon is probably 'stellar wind', namely gas ejected by the supermassive companion star. Astronomers think that this gas may be accreted by the compact black hole, forming a dense shell around it. This obscuring cloud traps most of the energy produced inside it."
     
  7. Mar 19, 2004 #6

    wolram

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    the universe and discoveries about it get more fascinating every
    day.
     
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