Supernova warnings?

[steve]

Just reading in the Audubon series of books, this one on astronomy. It was reported that the star, Sirius, in older times was coppery colored or red. In modern times it's now blue.

When Sanduleak in the GMC went supernova in 1987, many astrophysicists were surprised that a blue-white giant would go supernova. It was then stated that before it had done so, it had some thousands of years before gone thru a red giant stage (As betelgeuse and Antares are now doing), shed its outter layers, revealing the inner heavy element burning core and then went on to supernova.

Are there ANY percursor signs, neon burning, silicon burning or other spectral findings which might indicate if Sirius or other blue giants are reaching, or have reached the stage in which Sanduleak was just a few decades ago?

In other words if Sirius has indeed gone thru the red giant phase, shed its outter layers, it being 9 light years away and plenty close to cause some real damage to earth from a supernova, how would we have any warning of it?

[timeshifter]

very little.

the fact that the shock wave would travel at very fast speeds would mean that the only clue we would have is that the subject in question suddenly got a lot bigger. when we notice that, we would have about half an hour to an hour to evacuate earth to a place where the shock wave would have dissipated enough to not cause any damage.

problem: no place to live. in which case, it would be easier to just stay on earth and be torn to itty bitty pieces from the shock wave and get it over with than to try and escape from our own solar system and beyond for safety.

if we did, we would have to worry about life support, artificial gravity, and a place to live when the chaos was over. when all of this ends, earth will be a few large hunks of rock in space, but the shock wave from the star going nova would trigger a more catastrophic event.

an explosion of that magnitude would no doubt trigger our own sun to go nova, and that would extend the shock wave's range to another half a light year. assuming that the shock wave didn't trigger another star to go nova, the chain would keep going and going.

in that event, almost nothing in the galaxy would be safe from a catastrophe of this magnatude. fortunately, the nearest star is oh say 19 or 20 light years away, so even if one did go nova, the chances of it hitting the milky way in a strong enough force to do damage is very small.

something else to think about... if another galaxy had that event. the chances of such a thing happening are small, but if it did, it would trigger a shock wave so massive, it might reach earth with more than enough force to totally destroy our solar system, and the chain reaction would continue.

how i come to this conclusion is simple- for every star that goes nova, the shock wave will trigger at least two more. add it up over the coarse of billions of stars and you have one heck of a shock wave on your hands.

[budcamp]

If Sirius blows the shock wave would be at best 80% of the speed of light. That means when we see the light, sirius being 9 light years away, gives us 20% of 9 Years befor the shock wave gets to us.

Almost two years.

[steve]

Interesting. So while & after we've been fried by the heavy radiation from the Sirian supernova, we can expect the shock wave to blow us out of orbit about 2 years later.
I'm moving to E Eridani. Don't bother forwarding E-mail. (Grin)

But will we get any warnings before the star goes supernova?

[budcamp]

Some stars seem to give us signs that something is happening with them (eta Carinae being a good example), but so far none of these stars have blown. The one star that has blown in our time did not give any observed warning. It was a star that no one paid any attention to. Untill afterwords, that is.

Only stars within a thousand light years are a problem and probable not even most of them.

Don't worry you are safe for a few months no mater what blows

[Steve Langford]

Although blue giants can go supernovae, we can take some comfort in the relatively low mass of Sirius A, about 2.14 solar masses. Stars of less than 5-8 solar masses are expected to eject the great majority of their mass toward the end of their lives and are not expected to supernova. This is apparently what happened to Sirius B, which must have originally been more massive than Sirius A, as it made the transition to white dwarf before Sirius A. Another possible route to supernova in the Sirius system is where Sirius B accretes enough mass to exceed the Chandrasekhar limit. This is unlikely because of the large distance between Sirius A and Sirius B (23 AU). The expansion of Sirius A in its red giant phase (expect maybe 3 AU) will probably not be enough to transfer the required 0.4 solar masses. Call me an optimist. (Some of this information is taken from NASA’s "Ask the Space Scientist Archive.")

Recent references on supernovae include:

S. E. Woosley, A. Heger, and T. A. Weaver, "The evolution and explosion of massive stars," Review of Modern Physics 74(4), 1015-1071 (2003).

J. Craig Wheeler, "Resource Letter: OTS-1: Observations and theory of supernovae," American Journal of Physics 71(1), 11-22 (2003).

[irizarry]

Prior to a supernova there is a rise in the neutrino flux (number of neutrinos/solid angle at the observers location) as discovered during SN1987. The shock wave follows the increase in neutrino density. I recall from SN1987 astronomers reporting this event as a few days later. Since the universal speed limit is c (the speed of light) and the shock wave is not to far behind the neutrino increase our best-case scenario would be a few days. Most of this theory is based on a single observed supernova. I don’t know if all supernovas act basically the same. There is hope however! There might be an obstruction between Sirius and us, say a low-density cloud of dust. This might be enough to change the shape of the expanding surface wave. Put us in a node so to speak. Fat chance maybe? I wouldn’t bet the family farm on it though. This is great nightmare!

Irizarry

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[timeshifter]

Great nightmare?
Yes.
Very little warning?
Yes.
A very potential danger?
Yes.

I don't know if I am the only one here that thinks so, but I think that even if Sirius A went supernova, that good ol' trigger I talked about earlier would come into play.

So what? We have two years' warning. Again, where would we go? Even if we got off the planet and out of the danger zone for Sirius A, our own star would go nova as a result of the immense shock wave from a star of that size. Now, I know they do get much bigger, but with Sirius A being more than twice the mass of our star, then I think that the triggered nova from our star would be just as catastrophic as Sirius A but on a much smaller scale.

[timeshifter]

Great nightmare?
Yes.
Very little warning?
Yes.
A very potential danger?
Yes.

I don't know if I am the only one here that thinks so, but I think that even if Sirius A went supernova, that good ol' trigger I talked about earlier would come into play.

So what? We have two years' warning. Again, where would we go? Even if we got off the planet and out of the danger zone for Sirius A, our own star would go nova as a result of the immense shock wave from a star of that size. Now, I know they do get much bigger, but with Sirius A being more than twice the mass of our star, then I think that the triggered nova from our star would be just as catastrophic as Sirius A but on a much smaller scale.

[timeshifter]

Great nightmare?
Yes.
Very little warning?
Yes.
A very potential danger?
Yes.

I don't know if I am the only one here that thinks so, but I think that even if Sirius A went supernova, that good ol' trigger I talked about earlier would come into play.

So what? We have two years' warning. Again, where would we go? Even if we got off the planet and out of the danger zone for Sirius A, our own star would go nova as a result of the immense shock wave from a star of that size. Now, I know they do get much bigger, but with Sirius A being more than twice the mass of our star, then I think that the triggered nova from our star would be just as catastrophic as Sirius A but on a much smaller scale.

[nickzed]

Great nightmare?
Yes.
Very little warning?
Yes.
A very potential danger?
Yes.

I don't know if I am the only one here that thinks so, but I think that even if Sirius A went supernova, that good ol' trigger I talked about earlier would come into play.

So what? We have two years' warning. Again, where would we go? Even if we got off the planet and out of the danger zone for Sirius A, our own star would go nova as a result of the immense shock wave from a star of that size. Now, I know they do get much bigger, but with Sirius A being more than twice the mass of our star, then I think that the triggered nova from our star would be just as catastrophic as Sirius A but on a much smaller scale.


you watch too many sci-fi movies/shows and read too many sci-fi books.

not every star novas. they need a large enough mass. sirius likely wont even nova. you're basing all your statements off personal speculation and not actual fact.

[Martha Adams]

I think this is an interesting topic, but it's not all alone in this reality so it wants a context. An academic context might be, all that stuff about "shock waves" and etc, is so far totally free of detail and magnitude. It's a bogeyman, if an interesting one. Has anyone done plausible estimates using numbers? That would be interesting.

Another context is, how about all the other disaster and extinction risks we face, here on Terra? The supervolcano at Yellowstone comes to mind, and from what I've heard of it, I'm much more inclined to think about possibilities at Yellowstone than around Sirius.

Another context is, what can we reasonably expect of Sirius and how would we go about surviving it? On Mars; on Luna: how many meters under the surface? Here on Terra, how deep a mine, how would you respond realistically to the needs of a *few billion* people who would like to see their lives and cultures survive a Sirius explosion? ??

Cheers -- Martha Adams [2007 Oct 27]

[budcamp]

One thing to concider is that although the shock wave from a Super Nova moves at a very high percentage of the speed of light, it does not continue at that speed. As it moves away from its source, it looses energy and decreases in speed. Light, however, continues at the same speed, so we see the light from the explosion well before any other effects can reach earth. Also if we are going to worry about a Super Nove we should worry about Betelgeuse. It is about a million times the mass of Sirus and is close enough to give earth some real problems, and we know it is getting ready to blow (or perhaps has already blown).

I agree with Martha that the YellowStone and Mammoth Lake (California) Super Volcanos are a lot more dangerous to us than a Super Nova explosion.

[greatcountysky]

I always wondered what it would be like for the sun to go nova. I mean, just look up at the sky and suddenly it's blood red and on the verge of exploding. Not that I WANT that to happen. Now, I never considered what it would be like of a nearby star went nova and the shockwave just suddenly destroyed us with no warning whatsoever. Yikes!:eek: Just goes to show you that we should live our life like any day the Earth could blow up!:rolleyes:

~GreatCountySky~
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