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In the National Geographic article: it is suggested that a gamma ray burst likely caused a mass extinction in earth's history. How severe is the threat of a gamma ray burst to life on earth? It would be nice to see a chart that considers the threat within the next hundred years as follows (I have no idea what the actual numbers are, hence I am asking):

Severity - Likelihood in 100 years:

  • Global extinction - 0.0000001%
  • Major impact - 0.001%
  • Moderate impact - 0.1%
  • Minor impact (e.g. deplete ozone layer by 0.01%) - 10%
  • Observable - 100% ("minor" gamma ray bursts are frequently detected)

Follow up questions are:

Something else I found to be shocking is that the Bible appears to predict such an event. I would rate the predicted event on the major impact level. I asked about this in the Christian Stack Exchange here:

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For all of those question I can answer to one of them: we may have some preview a few hours before receiving the gamma ray burst in form of a high increase of neutrino detection since neutrinos are always emitted first in theses cases. – Joan.bdm May 30 '14 at 11:43
There's no evidence of any dangerous GRB in historic time. It can never have been described by any human account. The mere proportions of space and time explains this very obiously, for those who care to try to understand, anyway. There's no potentially dangerous GRB source in our neighborhood during the rest of human existance either. It'll take at least more than 10^7 years until the Sun has moved into a potential danger area. That's a thousand times all of historic age. – LocalFluff May 30 '14 at 15:45
you might find interesting – samcarter Jun 30 '14 at 17:22
@Jonathan, I know you only made it a very minor point, but the Bible claim has no backing to it. And WR104 is considered a "potential threat" only because it is a Wolf-Rayet star with an axis pointed in the general vicinity of our solar system. The National Geographic article says that the star would have to be pointed pretty much exactly at Earth. WR-104 is off by 16 degrees - too much for it to be "threat". – HDE 226868 Aug 9 '14 at 19:54

1 Answer 1

up vote 2 down vote accepted

I'll address WR104 first. The National Geographic article calls it a "potential threat." Yet that potential may be low. There are a slew of articles quoting astronomer Grant Hill on the subject. Hill studied the star and found that it looks like it isn't pointing straight at us. Its axis might be up to 45 degrees in another direction, meaning that we'd be fine if it underwent a burst.

From here:

It would appear the original Keck imagry may not have been as straight-forward as it seemed. Spectroscopic emission lines from the binary pair strongly suggest the system is in fact inclined 30°-40° (possibly as much as 45°) away from us.

So, Earth doesn’t appear to be in the firing line of WR 104 after all…

Here and here Hill is quoted as saying that the star looks like it could be pointed at us - which goes against the evidence he found! Finally, this is another example of Hill's cautious attitude: The evidence says we're good, but he's not making any assumptions.

Sabre Tooth, I know you said that you didn't want Wikipedia, but my primary goal here isn't to collect the bounty, so I'm going to reference it in this section. I hope you're okay with that. I may withdraw it, though, if Jonathan indicates that he doesn't want it.

Okay, back to the topic at hand. Wikipedia, of course, has a short tidbit on the frequency of gamma-ray bursts effecting Earth:

Estimating the exact rate at which GRBs occur is difficult, but for a galaxy of approximately the same size as the Milky Way, the expected rate (for long-duration GRBs) is about one burst every 100,000 to 1,000,000 years. Only a small percentage of these would be beamed towards Earth. Estimates of rate of occurrence of short-duration GRBs are even more uncertain because of the unknown degree of collimation, but are probably comparable.

'A small percentage' isn't too specific. The BBC article that is cited in this passage says the following:

Observations of deep space suggest that gamma ray-bursts are rare. They are thought to happen at the most every 10,000 years per galaxy, and at the least every million years per galaxy.

However, the 'small percentage' is never elaborated on.

That's all I have for this edit; more to come later. By the way, this Physics.SE question may interest anyone reading this. . .

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