<p>I'll address WR104 first. The National Geographic article calls it a &quot;potential threat.&quot; 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.</p>
<p>From <a href="http://www.universetoday.com/23342/wr-104-wont-kill-us-after-all/" rel="nofollow noreferrer">here</a>:</p>
<blockquote>
<p>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.</p>
<p>So, Earth doesn’t appear to be in the firing line of WR 104 after all…</p>
</blockquote>
<p><a href="http://www.foxnews.com/science/2013/05/28/gamma-ray-burst-from-star-wr-104/" rel="nofollow noreferrer">Here</a> and <a href="http://www.news.com.au/technology/science/lethal-gamma-ray-burst-from-star-wr-104-could-reach-earth/story-fn5fsgyc-1226651950006" rel="nofollow noreferrer">here</a> Hill is quoted as saying that the star <em>looks</em> like it could be pointed at us - which goes against the evidence he found! Finally, <a href="http://www.forbes.com/sites/brucedorminey/2013/05/27/earth-may-still-lie-in-path-of-potential-gamma-ray-burst-grb-say-astronomers/" rel="nofollow noreferrer">this</a> is another example of Hill's cautious attitude: The evidence says we're good, but he's not making any assumptions.</p>
<hr />
<p>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.</p>
<p>Okay, back to the topic at hand. Wikipedia, of course, has a short tidbit on the frequency of gamma-ray bursts effecting Earth:</p>
<blockquote>
<p>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.</p>
</blockquote>
<p>'A small percentage' isn't too specific. <a href="http://www.bbc.com/news/science-environment-21082617" rel="nofollow noreferrer">The BBC article</a> that is cited in this passage says the following:</p>
<blockquote>
<p>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.</p>
</blockquote>
<p>However, the 'small percentage' is never elaborated on.</p>
<hr />
<p>That's all I have for this edit; more to come later. By the way, <a href="https://physics.stackexchange.com/questions/26580/what-will-happen-if-a-gamma-ray-burst-hits-the-earth">this</a> Physics.SE question may interest anyone reading this. . .</p>

CC BY-SA 3.0
2014-11-23T22:25:31.880Z
2014-11-26T20:31:57.780Z
2020-06-17T09:47:40.653Z
HDE 226868
<p>In the National Geographic article: <a href="http://news.nationalgeographic.com/news/2009/04/090403-gamma-ray-extinction_2.html" rel="nofollow noreferrer">http://news.nationalgeographic.com/news/2009/04/090403-gamma-ray-extinction_2.html</a> 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):</p>

<p>Severity - Likelihood in 100 years:</p>

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

<p>Follow up questions are: </p>

<ul>
<li>Would there be any warning of an impending severe gamma ray burst?</li>
<li>Could we survive in gamma ray burst shelters? (it would appear being underground may be sufficient according to: <a href="http://en.wikipedia.org/wiki/Radiation_protection#Shielding_design" rel="nofollow noreferrer">http://en.wikipedia.org/wiki/Radiation_protection#Shielding_design</a> and <a href="http://2013.org/showthread.php/188-How-does-one-prepare-sufficiently-for-gamma-radiation-in-a-shelter-etc" rel="nofollow noreferrer">http://2013.org/showthread.php/188-How-does-one-prepare-sufficiently-for-gamma-radiation-in-a-shelter-etc</a>)</li>
</ul>

<p>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:
<a href="https://hermeneutics.stackexchange.com/questions/9324/interpretations-of-revelation-168-11/9335#9335">https://hermeneutics.stackexchange.com/questions/9324/interpretations-of-revelation-168-11/9335#9335</a></p>

CC BY-SA 3.0
2014-05-30T11:43:42.267Z
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
CC BY-SA 3.0
2014-05-30T15:45:11.447Z
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
CC BY-SA 3.0
2014-05-30T19:51:24.903Z
@LocalFluff: The National Geographic article I quoted above, in the first page states: "Currently WR104, a massive star 8,000 light-years away in the constellation Sagittarius, is in position to be a potential threat, Thomas noted."
Jonathan
CC BY-SA 3.0
2014-05-30T20:50:07.667Z
As the question appears to be about probability, not severity, perhaps the headline and question body should be rephrased to not use 'severity' ?
Jeremy
CC BY-SA 3.0
2014-06-30T17:22:51.017Z
you might find http://arxiv.org/abs/1211.3962 interesting
samcarter_is_at_topanswers.xyz
CC BY-SA 3.0
2014-08-09T19:54:17.467Z
@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
CC BY-SA 3.0
2014-11-24T20:44:13.300Z
http://news.bbc.co.uk/2/hi/sci/tech/1975354.stm
Count Iblis
CC BY-SA 3.0
2014-11-30T21:07:28.460Z
@SabreTooth - I've never been interested in this bounty; the only reason I answered was because the bounty reminded me that I had meant to answer it long ago. I'm fine with not getting the bounty because I used Wikipedia, and I completely understand if it isn't awarded. And there's still 36 minutes for another answer to appear. . .
HDE 226868
CC BY-SA 3.0
2014-11-30T21:34:46.627Z
@SabreTooth I don't think that answers posted within the grace period count, though.
HDE 226868
CC BY-SA 3.0
2014-11-30T21:36:43.413Z
I might be wrong, though.
HDE 226868
<earth><cosmology><life><surface><gamma-ray-bursts>
How likely and severe is the threat of a gamma ray burst to earth?
Jonathan
# How likely and severe is the threat of a gamma ray burst to earth?

(Asked by: username_0 on 2014-05-30)

In the National Geographic article: <http://news.nationalgeographic.com/news/2009/04/090403-gamma-ray-extinction_2.html> 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:

* Would there be any warning of an impending severe gamma ray burst?
* Could we survive in gamma ray burst shelters? (it would appear being underground may be sufficient according to: <http://en.wikipedia.org/wiki/Radiation_protection#Shielding_design> and <http://2013.org/showthread.php/188-How-does-one-prepare-sufficiently-for-gamma-radiation-in-a-shelter-etc>)

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:
<https://hermeneutics.stackexchange.com/questions/9324/interpretations-of-revelation-168-11/9335#9335>

**Tags:** earth, cosmology, life, surface, gamma-ray-bursts

> **Comments:**
> **username_1**: 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.  
> **username_2**: 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.  
> **username_0**: @username_2: The National Geographic article I quoted above, in the first page states: "Currently WR104, a massive star 8,000 light-years away in the constellation Sagittarius, is in position to be a potential threat, Thomas noted."  
> **username_3**: As the question appears to be about probability, not severity, perhaps the headline and question body should be rephrased to not use 'severity' ?  
> **username_4**: you might find http://arxiv.org/abs/1211.3962 interesting  
> **username_5**: @username_0, 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".  
> **username_6**: http://news.bbc.co.uk/2/hi/sci/tech/1975354.stm  
> **username_5**: @SabreTooth - I've never been interested in this bounty; the only reason I answered was because the bounty reminded me that I had meant to answer it long ago. I'm fine with not getting the bounty because I used Wikipedia, and I completely understand if it isn't awarded. And there's still 36 minutes for another answer to appear. . .  
> **username_5**: @SabreTooth I don't think that answers posted within the grace period count, though.  
> **username_5**: I might be wrong, though.  

---

## 1 answers

### Answer by username_5 on 2014-11-23. Score: 4 | Accepted answer

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](http://www.universetoday.com/23342/wr-104-wont-kill-us-after-all/):

> 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](http://www.foxnews.com/science/2013/05/28/gamma-ray-burst-from-star-wr-104/) and [here](http://www.news.com.au/technology/science/lethal-gamma-ray-burst-from-star-wr-104-could-reach-earth/story-fn5fsgyc-1226651950006) 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](http://www.forbes.com/sites/brucedorminey/2013/05/27/earth-may-still-lie-in-path-of-potential-gamma-ray-burst-grb-say-astronomers/) 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 username_0 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](http://www.bbc.com/news/science-environment-21082617) 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](https://physics.stackexchange.com/questions/26580/what-will-happen-if-a-gamma-ray-burst-hits-the-earth) Physics.SE question may interest anyone reading this. . .


---

