Could a gamma ray burst destroy life on Earth?

[Avalancheon]

Anders Sandberg looked at this question a few years ago.
http://aleph.se/andart2/tag/gamma-ray-burst/
His rather basic analysis of the problem indicates that there is a risk, but it is fare from uniform all over the galaxy, and isn't even 100% in the galactic centre.

Mapping this onto the densities of stars in the galaxy shows that there is a cluster of (probably) unaffected stars in the Galactic Habitable Zone near the plane, which is where we are.

This does mean that any civilisation near the Galactic Hub probably migrated there, or it must somehow have evolved to be highly resistant to radiation events.

Interesting article. The Galactic hub is still not a promising spot for life, though. The Milky Way used to have an active nucleus that spewed radiation in all directions. It only went inactive a couple billion years ago.

Random GRBs can sterilise large swaths of the Galaxy, but not all of it. Even so, it would tend to explain why we don't observe alien civilisations. Lets say that in the lifetime of our Galaxy, there were 2000 biospheres that managed to evolve to pass the eukaryotic filter. If they were randomly distributed across the Milky Way, a large number of them would be exterminated by GRBs.

The few eukaryotic biospheres remaining would then face the 'porous filters' of cephalisation and civilisation. That would cut down the number of sentient races to a tiny number that includes us (at least for now).