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 Supernova... how close is too close?

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mm5agm

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PostSubject: Supernova... how close is too close?   Tue Aug 23, 2011 3:47 pm

Ok, from what I have been able to gather around the web... or rather, from the lack of what I have been able to gather, it looks as though our knowledge and understanding of Supernova's is pretty limited.

That being said, I figured I would pose some itching questions to the community and see what I can turn up.

I am not even sure if the questions are good, but maybe the answers I get will allow for better questions.

So...

Supernova... how close is too close? What is the general range of Supernova from smallest to biggest? What would be the affects on a colony 5 ly away, 10, 20, 50, 100? How close is the "your dead no matter what" range, the "you better be under a mountain, thats under the ocean" range, the "bubble city with reasonably good shielding... your kids may have 12 fingers" range... etc...

The nebula/remnant that comes after... how large do these generally get? How fast do they expand? How long do they last? Is there a simple guestimate I can use to determine these variables in relation to the scale of the supernova itself?

If a black hole was left behind how would this affect the nebula/remnant?

I know this is a tough one... any info at all would be really helpful though. Thanks Smile
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scopeman

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PostSubject: Re: Supernova... how close is too close?   Tue Aug 23, 2011 3:49 pm

Read an article about this recently. Some scientists think those once a century bursts wipe out whole sections of the galaxy. Depends on how big they are. Neighbouring star systems can be sterilised though.
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starhopper

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PostSubject: Re: Supernova... how close is too close?   Tue Aug 23, 2011 3:49 pm

We are in one. The Local Bubble is the nebula of Geminga supernova, 300 000 years ago.
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scopeman

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PostSubject: Re: Supernova... how close is too close?   Tue Aug 23, 2011 3:50 pm

starhopper wrote:
We are in one. The Local Bubble is the nebula of Geminga supernova, 300 000 years ago.

true we are in one, but the Local Bubble appears to be the result of multiple supernovae from progenitors from the Centaurus-Sco Association over the course of several million years. these giant stars have repeatedly created explosions which swept out the Local Bubble from our neighborhood of the Milky Way. Geminga is a close pulsar at ~ 400 light-years, but not the closest which at present is PSR J0108-1431 @ ~ 280 light-years. Either could have been the latest one and the exact extent of the Local Bubble in all directions remains an area of active research, and some controversy. If the last close supernova went off in an already swept volume, sya by a predecessor within a few million years,most of the periphery of the local Bubble we now see could have been established in the last two thousand years, as the maximum velocity for an ejecta cloud runs just under a tenth the speed of light (A.Fllipenko...re: SN1987a).
There is at least some evidence for a Sne in that range of time from the marine sediment deposits of Fe-60 seen in mud cores. (Brian Fields et. al )
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mm5agm

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PostSubject: Re: Supernova... how close is too close?   Tue Aug 23, 2011 3:51 pm

Soooo.... we are in a nebula, but a very old one, I gather. What about the fantastic images I have seen of the crab nebula, or the horse head nebula, or the eagle nebula (if thats the right name)... Those come from supernova? Or regular nova? If I were in a ship traveling through these nebula would the view be as spectacular as the images we see or are those beautiful pictures the result of the type of photography used or some other effect?
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Astrotones



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PostSubject: Re: Supernova... how close is too close?   Tue Aug 23, 2011 3:52 pm

mm5agm wrote:
Soooo.... we are in a nebula, but a very old one, I gather. What about the fantastic images I have seen of the crab nebula, or the horse head nebula, or the eagle nebula (if thats the right name)... Those come from supernova? Or regular nova? If I were in a ship traveling through these nebula would the view be as spectacular as the images we see or are those beautiful pictures the result of the type of photography used or some other effect?

Not very old geologically speaking. The hominids living 300,000 years wouldn't have been surprisingly similar to modern day man.
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astro_alan

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PostSubject: Re: Supernova... how close is too close?   Tue Aug 23, 2011 3:52 pm

Novas can be quite puny, but Super nova are big, possibly very big, if the once per century theory is correct. Assurance has been given that only minor damage occurs for supernova more than 30 light years away, but perhaps the once per century is destructive to hundreds of light years. People off Earth would receive a larger dose than allowed for occupational purposes, which would shorten their life expectancy at least slightly. Near sea level, us Earthlings are well protected by the magnetic field and our rather thick atmosphere with green house gases. The fact that many of us live indoors, 98% of our life (average) gives us at least a bit more protection. At present (and for the next million years) none of the stars closer than a few hundred light years are capable of supernova = they will eventually become red giants which are dangerous only closer than one light year. Reliable numbers are hard to find, so please correct my guesstimates.
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