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Most distant gammaray blast detected

  1. Sep 12, 2005 #1

    marcus

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    http://news.bbc.co.uk/2/hi/science/nature/4237800.stm

    Most distant cosmic blast sighted

    "Astronomers have witnessed the most distant cosmic explosion on record: a gamma-ray burst that has come from the edge of the visible Universe.
    Gamma-ray bursts are intense flares of high-energy radiation that appear without warning from across the cosmos.

    They can release as much energy in a few minutes as our Sun will emit in its expected 10-billion-year lifetime.

    The blast was observed by the Swift space telescope and by a number of ground-based observatories.

    The latest, record gamma-ray burst was detected on 4 September, 2005, and lasted about three minutes. It probably marked the death of a massive star as it collapsed into a black hole.

    It has a so-called redshift of 6.29, which translates to a distance of about 13 billion light-years from Earth.

    Used by astronomers to measure cosmic distances, redshift refers to the extent to which light is shifted towards the red part of the electromagnetic spectrum during its long journey across the Universe. The greater the distance, the higher the redshift.

    Record distance

    "This burst smashes the old distance record by 500 million light-years," said Dr Daniel Reichart, of the University of North Carolina, US, who has been leading the measurement of its distance..."

    have to look out for technical reports on this by Daniel Reichart,
    or Keith Mason, or Nial Tanvir.
     
    Last edited: Sep 13, 2005
  2. jcsd
  3. Sep 13, 2005 #2

    marcus

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    I found the raw observation reports in a thread from various observatories and places where the astrometric calculations were in progress that day

    http://gcn.gsfc.nasa.gov/other/050904.gcn3

    the name of the GRB was GRB050904
    which is just the date 2005 September 04
    Dan Reichart, who was mentioned by the BBC as providing the redshift figure, generated many of the observation reports on this thread, so one can see him gradually narrowing down his estimate of the z
    and reporting step by step as he goes.

    all the stuff on the thread is dated that same day, as the afterglow of the burst was being observed
     
  4. Sep 13, 2005 #3

    marcus

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    here is extra goodies
    http://www.swift.ac.uk/grb.shtml

    this has movies of a neutron star merger, such as might result in a GRB as they spiral together and form a black hole.

    http://www.ukaff.ac.uk/movies/nsmerger/

    the merger takes about 8 milliseconds, according to the moviemakers,
    and produces temperatures as high as 100 thousand million kelvin

    the core of the sun is about 15 million kelvin, so this is about 10 thousand times hotter than the core of the sun.

    the suncore is so hot it glows Xray light (which fortunately for us we cant see because it is muffled by the surrounding material)
    but this GRB was originally 10 thousand times shorter wavelength even than that.

    nice movies

    Darn! I see that Clifford found that observation report before I did. I did a google search with some of the names of the people mentioned by BBC.
    Hats off to Clifford.
     
    Last edited: Sep 13, 2005
  5. Sep 13, 2005 #4

    Garth

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    The age of the universe at 6.29 was 894 Myr. (Ned Wright's calculator standard flat universe.)

    How long does it take for neutron stars to form and then coalesce?

    Garth
     
  6. Sep 13, 2005 #5

    marcus

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    I think if you read the BBC article they indicate it was a massive star collapse-----like 40 solar masses

    I dont have time to check this. just with my rough knowledge I reckon there are two GRB mechanisms, one is two neutron stars merge and the other is a massive star collapses, like a supernova only worse, and makes a black hole.

    in learning about GRB one wants to think about both, so that is what the movies help with

    but THIS PARTICULAR GRB was probably not that merger kind.

    about the time intervals you want, I cant tell Garth. it is bedtime for me, but if you find the answer why dont you post it?
     
  7. Sep 13, 2005 #6
    i'm pretty sure you could use the jean's criterion more accurately this time, Garth. Although it may be difficult to account for fragmentation of the original gas cloud (assuming it was a merger which caused the GRB).
     
  8. Sep 13, 2005 #7

    Chronos

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    Why is 894 Myr a problem, Garth?
     
  9. Sep 13, 2005 #8

    Garth

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    It's not necessarily, however it is a constraint that might rule out the 'coalescing neutron stars' scenario.

    Free fall time for a mass at the time of Surface Last Scattering ~ 150 Myrs.
    Later the time increases according to inverse square root of the density, so collapse takes longer the later the object forms.
    The PopIII star hyper-nova is my favourite option here.

    Garth
     
    Last edited: Sep 13, 2005
  10. Sep 13, 2005 #9

    SpaceTiger

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    Those are the two most popular theories, though to my knowledge, the latter is the only one with strong observational support. Of course, it's possible that both mechanisms would give a GRB.
     
  11. Sep 13, 2005 #10
    Marcus, I know this is a stupid question, but the date states:DATE: 05/09/04

    which according to us here in the UK = 5th Sept 2004?

    I know it is here:http://news.bbc.co.uk/2/hi/science/nature/4237800.stm

    and it clearly states:4 September, 2005

    Which is it? :yuck: :surprised convention is for date difference:

    UK Date today = 13th Sept 05/13-9-05

    Normally the US Date format would = 9 13TH 05/9th=month-13th=day 05 =yr

    I know we are both right, and conversely would have to agree to disagree that we are both incorrect!

    Whereas under normal definitions we just reverse the day/month, the linked paper author appears to be reversing the year? :eek:
     
    Last edited: Sep 13, 2005
  12. Sep 13, 2005 #11

    marcus

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    Spacetiger would be able to answer more generally concerning the various date-abbreviation conventions used by various groups of astronomers.

    I will just say that as far as I know AT LEAST IN THE MATTER OF NAMING GAMMA RAY BURSTS the way they do it is year-month-day

    so if something blasted from the sky on 4 Sept 2005, then that thing is going to be catalogued
    GRB050904
    that is just how it is, at least in that branch of the astronomy profession.

    Each group of professionals that observes and catalogues HAS to decide for themselves what is a convenient practice for their purposes and then TRY to use it consistently

    In the world at large there is no consistent set of date-abbreviation conventions as far as I know.

    =========================
    just as a cultural anthropology note
    :smile: what we see here is a permanent stumbling block that will never go away.

    the GRB catalogrr will always want numerical order to correspond to chronological----so if you tell the computer to sort a list numerically it will come out in chrono order. so those guys will always write the year first

    but ordinary PEOPLE will always want the year at the end SO THEY CAN LEAVE IT OFF if it is clear from context. when it is obvious what the year is then you only want to say "4 September" or "September 4" whichever you like best. So for most people the year always comes after the other info, often with a comma, like September 4, 2005.

    No idealistic reformer is ever going to be able to get ordinary people and astronomers to use the same date-conventions. the PRACTICAL NEEDS are too different.
     
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