[ExI] Fermi Paradox and GRB bursts

BillK pharos at gmail.com
Mon Oct 6 10:22:23 UTC 2014


On Mon, Oct 6, 2014 at 2:30 AM, Anders Sandberg wrote:
> I did some simulations:
> http://aleph.se/andart2/space/galactic-duck-and-cover/
>
> If one takes directionality into account the risk does not seem to be as
> dramatic as in the paper. Or rather, the variance goes way up: stars near
> the galactic centre are at risk, but there is a fair fraction that are never
> hit.
>

Beam angle is important and there appears to be quite a wide
variation, though mostly seem to be concentrated around 4 degrees.
Some GRBs may even be spherical in dispersion. The wider spread beams
would catch more nearby systems, but the gamma ray density would
dwindle earlier with less effect on farther away stars. So being near
the galaxy centre or in a crowded star region would be a disadvantage.

Another point is that narrower, more concentrated GRB beams can go
right across the galaxy, so they could hit more than one star system.
(As could beams in crowded star regions).

BillK



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