Comet (or gamma ray burst) killed N. Americans 13,000 y/a?

[silylene old]

<i>A GRB from anywhere in our galaxy pointed directly at us would be potentially devastating. </i><br /><br />DISCLAIMER: I have no knowledge that Vega would every become a GRB or a nova. Please don't get overexcited, and let me indulge in some speculation.<br /><br />What we know, and my speculation.....<br />Vega is a type A01 star 25 light years away with a mass 2.3x the sun, and about 500M years old. It is very rapidly rotating, so its shape is an oblate spheroid. In fact, it rotates so fast it is very close (93%) to the rotation speed which would cause disruption due to centrifugal effects. Vega is known to be surrounded by a disc of dust, presumed rocks, and perhaps planets which are slowly infalling.<br /><br />OK, so what makes Vega interesting? <font color="yellow">Vega's polar rotational axis is coincidently<i> aimed directly at the earth</i></font> I read about this last month in an interesting article in the journal <i>Nature</i>, and immediately thought...what if some inflalling planet or planettoid broke apart and fell into Vega? Couldn't that cause a huge jet of plasma to be ejected right at the Earth?<br /><br />The <i>Nature</i> article doesn't claim this happened, it just describes recent research on this very interesting and close star. It is entirely my speculation that Vega could be the smoking gun. I am curious what others think. If this is absurd, my apologies, I do not have deep knowledge of the mechanisms which can cause huge polar jet emissions and bursts from stars. <div class="Discussion_UserSignature"> <div class="Discussion_UserSignature" align="center"><em><font color="#0000ff">- - - - - - - - - - - - - - - - - - - - - -</font></em> </div><div class="Discussion_UserSignature" align="center"><font color="#0000ff"><em>I really, really, really miss the "first unread post" function.</em></font> </div> </div>

 

[docm]

IMO you've presented a plausible candidate, but it would be nice if we could confirm that Vega could produce such a jet. Back to my collection of papers & research links <img src="/images/icons/wink.gif" /> <div class="Discussion_UserSignature"> </div>

 

[derekmcd]

Vega isn't nearly large enough to become a supernova, nor when it achieves it's white dwarf stage will it have a companion to feed off of and become a supernova. An infalling planet wouldn't even remotely come close to creating enough energy. <br /><br />Edit: GRB bursts are generally associated with supernovae, though not all supernovae produce GRBs. <div class="Discussion_UserSignature"> <div> </div><br /><div><span style="color:#0000ff" class="Apple-style-span">"If something's hard to do, then it's not worth doing." - Homer Simpson</span></div> </div>

 

[docm]

Doesn't look like size is an issue when it comes to expelling polar jets. This one isn't very energetic, but it does make one wonder what kind of jet a dynamo like Vega could muster given the right circumstances.<br /><br />Link....<br /><br /><blockquote><font class="small">In reply to:</font><hr /><p><b>A brown dwarf joins the jet-set</b><br /><br /><b><i>Jets of matter have been discovered around a very low mass 'failed star', mimicking a process seen in young stars. This suggests that these 'brown dwarfs' form in a similar manner to normal stars but also that outflows are driven out by objects as massive as hundreds of millions of solar masses down to Jupiter-sized objects.</i></b><br /><br /> Brown dwarfs are objects whose masses are below those of normal stars - the borderline is believed to be about 8% of the mass of our Sun - but larger than those of planets. Unlike normal stars, brown dwarfs are unable to sustain stable nuclear fusion of hydrogen.<br /><br />The brown dwarf with the name 2MASS1207-3932 is full of surprises. Its companion, a 5 Jupiter-mass giant, was the first confirmed exoplanet for which astronomers could obtain an image, thereby opening a new field of research - the direct detection of alien worlds. It was then later found that the brown dwarf has a disc surrounding it, not unlike very young stars.<br /><br />Now, astronomers using ESO's Very Large Telescope (VLT) have found that the young brown dwarf is also spewing jets, a behaviour again quite similar to young stars.<br /><br />The mass of the brown dwarf is only 24 Jupiter-masses. Hence, it is by far the smallest object known to drive an outflow. "This leads us to the tantalizing prospect that young giant planets could also be associated with outflows," says Emma Whelan, the lead-author of the paper reporting the results.<br /> /><br /> /><br />Source: European Southern Observatory<p><hr /></p></p></blockquote> <br /><br />Maybe this kind of c <div class="Discussion_UserSignature"> </div>

 

[derekmcd]

Interesting but not suprising. It would appear that given the right circumstances, any object capable of sustaining an accretion disk could produce these outflows at some level. GRBs, though, are orders of magnitude more energetic than stellar outflows. <div class="Discussion_UserSignature"> <div> </div><br /><div><span style="color:#0000ff" class="Apple-style-span">"If something's hard to do, then it's not worth doing." - Homer Simpson</span></div> </div>

 

[robnissen]

Agreed. I doubt any brown dwarf outflow more than at most a few tens of LYs from earth would be cause for much concern.

 

[dragon04]

<font color="yellow">And this explains the high radiation event how?</font><br /><br />It doesn't. Nor does the radiation hypothesis explain how on a planet that spins on an axis would only be sterilized on one specific portion of the planet rather than the whole world. I find it exceedingly difficult to believe that such a thing would be a regional event.<br /><br />Of course, that's what makes it intriguing. Would an ozone hole be a factor? If so, I'd have more confidence in its plausibility.<br /><br /><br /><br /> <div class="Discussion_UserSignature"> <em>"2012.. Year of the Dragon!! Get on the Dragon Wagon!".</em> </div>

 

[silylene old]

Regardless, having Vega (hyper-rotating, with a large accretion disk) having its pole pointed directly at Earth is a somewhat scary prospect. This is what I thought the moment I read the <i>Nature</i> paper. I wondered at the time if any event on Vega may have coincided with an extinction event. Recall that Vega is but 500M years old, and the early history of any forming star is quit energetic. (Of course, Vega may have been further away from the Sun earlier, or perhaps it was closer, I simply don't know) <div class="Discussion_UserSignature"> <div class="Discussion_UserSignature" align="center"><em><font color="#0000ff">- - - - - - - - - - - - - - - - - - - - - -</font></em> </div><div class="Discussion_UserSignature" align="center"><font color="#0000ff"><em>I really, really, really miss the "first unread post" function.</em></font> </div> </div>

 

[silylene old]

I looked it up.<br /><br />The Sun and Vega are rapidly approaching each other, and the closest approach will be about 250,000 years from now, with a minimum separation of 10.4 light years. At this time, Vega will become the brightest star in earth's sky. Hmmmm..........<br /><br />Vega <div class="Discussion_UserSignature"> <div class="Discussion_UserSignature" align="center"><em><font color="#0000ff">- - - - - - - - - - - - - - - - - - - - - -</font></em> </div><div class="Discussion_UserSignature" align="center"><font color="#0000ff"><em>I really, really, really miss the "first unread post" function.</em></font> </div> </div>

 

[docm]

<font color="yellow">....very high energy electrons would be emitted, colliding with the atoms and molecules forming the atmosphere..... thus emitting gamma rays -and potentially a very intense burst.</font><br /><br />Answering my own question after reflection;<br /><br />Another approach that would produce a neutron flux would be if the comet had high levels of deuterium and pressures rose to the point of fusion, in which case several percent of the energy would be neutrons. Add photofission and that would explain a lot of the transmutations. <div class="Discussion_UserSignature"> </div>

 

[dragon04]

I don't mean to belabor the point, and honestly, I'm not trying to be difficult, but rather trying to understand things with the hope that one of you vastly more knowledgable guys can help me out.<br /><br />How could a GRB produce only a regional extinction event? Certainly a "jet" of massively energetic particles would have a cross section far greater than the diameter of the Earth, right?<br /><br />And if so, how would only an area a thousand or so kilometers in diameter be affected?<br /><br />That would seem to be a very peculiar event requiring a very extraordinary explanation. But I'm saying that from a position of ignorance to be honest. <div class="Discussion_UserSignature"> <em>"2012.. Year of the Dragon!! Get on the Dragon Wagon!".</em> </div>

 

[docm]

The portion of Earth directly facing the event would get the highest dose because the atmosphere would be at its relative thinnest. <br /><br />All other facing points have increasing incidence angles and therefore more atmospheric filtration; basically the same effect that causes winter when the sun is low in the sky, plus some might get reflected/refracted. Yes, gamma's can do that if the incidence angle is acute enough. <br /><br />All points on the opposite side of Earth would be protected from direct exposure but not atmosphereic side effects, if any. <div class="Discussion_UserSignature"> </div>

 

[dragon04]

Fair enough, and thanks for the explanation. I was (mistakenly) assuming that if a GRB was close or powerful enough to make contact with Earth's surface, that no part of the atmosphere would be thick enough to prevent a global or hemispheric event. <div class="Discussion_UserSignature"> <em>"2012.. Year of the Dragon!! Get on the Dragon Wagon!".</em> </div>

 

[docm]

Depends on the intensity of the burst. If it were <i>just right</i> then it could be lethal dead-on but less lethal as the incidence angle increases and the atmosphere "thickens". On the other hand a very strong burst would turn the atmosphere into a plasma torch. <div class="Discussion_UserSignature"> </div>

 

[dragon04]

That would seem to be an unusual event, indeed. Maybe in the future, there will be supportive evidence uncovered at even higher latitudes.<br /><br />Using the Aurorae as an example, there should be prodigious evidence to the north of the anomaly, no? <div class="Discussion_UserSignature"> <em>"2012.. Year of the Dragon!! Get on the Dragon Wagon!".</em> </div>