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gamma ray bursts...

Discussion in 'General Discussion' started by Tango3, Dec 29, 2006.

  1. Tango3

    Tango3 Aimless wanderer

    Wow not only is the history channel doing "armageddon" week and covering teotewaki events.tonight even the scifi channel is runninng teotwaki stuff. Keep your eyes open for Gamma ray burst info,seems theywere discovered in the 70's while our satelites were watching the soviets for nuke tests and classified for decades the information is just entering the astronomical communtity now., the deep space bursts (the result of a collapsing or colliding star were triggering the military satelites once a day, from all corners of the universe. They are the most massive and violent releases of energy since the "bigbang". A burst in our own galaxy directed towards the earth would strip off the atmoshere and melt crust.
    YOU'll probably be hearing more about these: http://imagine.gsfc.nasa.gov/docs/ask_astro/grb.html
    The Answer

    If a gamma-ray burst occurred near to us, it would be Bad.
    For a description of what a mere supernova could do, see http://stupendous.rit.edu/richmond/answers/snrisks.txt
    The gamma-rays from 990123 had 1000 times the energy flux of the optical light, so at 2000 light years the gammas would deposit 2000 times as much energy as the Sun (in addition to twice as much visible light). Furthermore, this gamma-ray energy would interact in the upper atmosphere, producing nitrogen oxides that would rapidly catalyze the destruction of the ozone layer.
    And then, a few centuries later, it gets worse, if current models are correct. A storm of cosmic rays would pretty much wipe out everything that wasn't beneath a few hundred meters of rock.
    See Sky and Telescope for February 1998 (in most good libraries) for more details.
    In answer to your EMP question, I believe that the typical scenarios involve a a big bomb, call it 10 megatons, at a high altitude, call it 1000 km. 10 megatons is 4.2 x 10<sup>23</sup> ergs. 990123 produced about 4 x <sup>54</sup> ergs of gamma-rays, so it produced 1 x 10<sup>31</sup> times as much, and would be as vicious at 3 x 10<sup>15</sup> times the distance. 3 x 10<sup>15</sup> x 1000 km is about 300,000 light years.
    So by this analysis, from anywhere in our Galaxy, the gamma rays would cause a massive EMP event and smite all of the electronics on that side of the planet. (And maybe on the other side as well, I don't know how EMP propagates over the horizon.)
    However, there are probably mitigating effects. A bomb produces a very fast release of gamma-rays (microseconds to milliseconds) causing a fast rise in electric field, the same amount of energy over a shorter time means more power in the pulse. The slower GRB 990123 (lasting about a minute) would probably cause a corresponding decrease in the EMP. There are, however, GRBs with rise times of less than a millisecond.
    David Palmer and Samar Safi-Harb
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