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EvilEye
2007-Oct-27, 12:48 PM
What is the possibility of a Gamma Ray burst being close enough to kill us all?

Jens
2007-Oct-27, 01:02 PM
1.256 x e-6

Ronald Brak
2007-Oct-27, 01:05 PM
As I understand it the odds are our galaxy hasn't experienced a single gamma ray burst in its entire existance. And if one did go off it we would have to be unlucky enough to be sitting in the way of its twin death rays (unless it was really close.) So all up not really worth losing sleep over. (Unlike the red robots of death. Because that's when they come for you, you know. At night.)

antoniseb
2007-Oct-27, 01:19 PM
As I understand it the odds are our galaxy hasn't experienced a single gamma ray burst in its entire existance.
Where did you get that stat? I haven't worked the numbers, but I think the Milky way has produced many. Your note about the likelihood of being in the beam is correct, and it seems unlikely that the Earth has been in the beam of one in the last half billion years, simply because the surface hasn't been sterilized since then or before.

If no one gets a real estimate as to the number from the Milky way, I'll try to find one in a few days.

Ronald Brak
2007-Oct-27, 01:21 PM
Where did you get that stat?

I read it somewhere. I'll have a quick look and see if I can find it again.

Okay, here's an article:

http://physicsworld.com/cws/article/news/24692

antoniseb
2007-Oct-27, 07:31 PM
Okay, here's an article:
Ah, that doesn't say never happened, but rather that it never will again... but it really isn't clear. Further, this is only speaking of the Hypernova GRBs. There is a pair of close orbiting pulsars in our galaxy which IIRC, will merge in 50 million years or so (the blink of an eye cosmologically speaking). This is most likely the cause of the short burst GRBs, so there will be GRBs in our galaxy, and perhaps quite a few.

KaiYeves
2007-Oct-28, 12:08 AM
So all up not really worth losing sleep over. (Unlike the red robots of death. Because that's when they come for you, you know. At night.)
But... it's night here right now! Uh oh...
You don't have to worry about a gamma burst killing en masse, but if one happened to transform a lot of people into Hulks and they trashed everything... then you would be right to worry. ;-D

Ronald Brak
2007-Oct-28, 01:30 AM
Ah, that doesn't say never happened, but rather that it never will again... but it really isn't clear. Further, this is only speaking of the Hypernova GRBs. There is a pair of close orbiting pulsars in our galaxy which IIRC, will merge in 50 million years or so (the blink of an eye cosmologically speaking). This is most likely the cause of the short burst GRBs, so there will be GRBs in our galaxy, and perhaps quite a few.

It's not a very good article. Less than a 0.15% chance? Ever? Per day? And why does high metalicity protect us? How long has high metalicity protected us? If they don't know it should make it clear that we don't know. What effect do they have on the red robots of death? It's not the original article I read, but it's probably very similar.

Van Rijn
2007-Oct-28, 03:29 AM
Here's the original article (note, this is a pdf):

http://arxiv.org/PS_cache/astro-ph/pdf/0604/0604113v4.pdf

They say they have evidence that long GRBs are associated with metal poor galaxies. Near the end of the article is discussion of the collapsar long GRB model. Apparently, some of the theoretical work suggests that only metal poor stars are good candidates for the events creating long GRBs. Since these stars would have to be extremely massive, and therefore would have very short lifespans, they would have to be formed out of material available today (with, in this galaxy, too high a metallicity). So, according to this argument, there could be no stars still existing in our galaxy that could cause long GRBs.

They also mention short GRBs, which they argue are less common than long GRBs, tend to be relatively weak and not tightly beamed.

As for myself, I'll just say that I'm not so sure that these issues are that well nailed down yet.

Ronald Brak
2007-Oct-28, 03:39 AM
Here's the original article (note, this is a pdf):

Thanx.

astromark
2007-Oct-28, 04:08 AM
This is great news. It gives me hope and great wealth. wealth will be mine and need note concern myself about the great red robots of whatever it was they are said to be or do.... I am going to rush off and start a construction company on Monday next. With all this destruction pending I can not miss..... Great stuff. thank you all. I knew coming in here was a great idea. Mark rushes outside to watch for singes of impending GRB and red robots.... what is it I might see? what ya mean at night... No way, its dark. what am I gonna see in the dark?

NB:) You would do better to concern yourself with safe driving practice and better food intake habits.... These things will kill you just the once.

EvilEye
2007-Oct-28, 12:54 PM
This is great news. It gives me hope and great wealth. wealth will be mine and need note concern myself about the great red robots of whatever it was they are said to be or do.... I am going to rush off and start a construction company on Monday next. With all this destruction pending I can not miss..... Great stuff. thank you all. I knew coming in here was a great idea. Mark rushes outside to watch for singes of impending GRB and red robots.... what is it I might see? what ya mean at night... No way, its dark. what am I gonna see in the dark?

NB:) You would do better to concern yourself with safe driving practice and better food intake habits.... These things will kill you just the once.

I asked the question because a friend watched doom & gloom show on the History channel about GRBs. Others here are better qualified to answer the question than was I.

No need to be pithy.