Gamma-ray bursts (http://www.aas.org/publications/baas/v30n2/aas192/abs/S043014.html)! (at least, this is one theory of what some gamma-ray bursts are) Which may not be entirely safe (http://universe.gsfc.nasa.gov/press/images/GRB/).
I've heard that theory too. Using the figure quoted (http://www.aas.org/publications/baas/v30n2/aas192/abs/S043014.html) of 1051 erg, I get 1018 Jm-2 at this distance. We're toast.
I was trying to work out how you were out by a factor of 1014. Duh, I should have realised when I saw the 107 that that was probably it.
It's still scary. At that level, it might not wipe out all life, but it'd be pretty nasty and might well cause a mass extinction, depending on how long that energy blast is spread over.
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(no subject)
Date: 2004-01-10 04:28 am (UTC)Which may not be entirely safe (http://universe.gsfc.nasa.gov/press/images/GRB/).
(no subject)
Date: 2004-01-10 04:59 am (UTC)(no subject)
Date: 2004-01-10 01:57 pm (UTC)Still toast, but not quite so toasty.
(1051 ergs is 1044J. 1 LY =~ 1016m. Area of sphere radius 2000 LY is therefore roughly 5 x 1039 m2. 1044J/5 x 1039 m2 -> 2 x 104 Jm-2)
(no subject)
Date: 2004-01-10 05:55 pm (UTC)I must have got erg->joule the wrong way round. Oops...
We were wondering tonight how you'd stop them colliding.
(no subject)
Date: 2004-01-10 06:05 pm (UTC)It's still scary. At that level, it might not wipe out all life, but it'd be pretty nasty and might well cause a mass extinction, depending on how long that energy blast is spread over.
(no subject)
Date: 2004-01-11 04:35 am (UTC)(no subject)
Date: 2004-01-10 11:31 am (UTC)Yes; for at least two millennia.
(no subject)
Date: 2004-01-10 01:11 pm (UTC)... but it's not due for about 85 million years, anyway, and by then we might have a little more ability to stave off the consequences.