Supernovae

Saiph · Jan 30, 2009

Over in another thread the question was raised as to what the concentration of elements in a Supernova was.  The answer...is complicated.  And in order to avoid taking that threads discussion off topic for such a possibly involved tangent, I decided to make a new thread.  SDC tidbit...I think this makes the 7th thread I've ever started here...in nearly 9 years

Supernova explosions are the powerhouse generators of nearly every heavy element in universe.  Let me elaborate on what I mean by 'heavy element'.  By that, I mean 'metals' as an astronomer means it, and a metal is every element that is NOT Hydrogen (H) and Helium (He).  Thats right, and here's a link for an illustration of what I mean... http://lasp.colorado.edu/~bagenal/3750/ClassNotes/Class6/PeriodicTable.jpg  They occur in super massive stars, many times the size of our sun, when the core of the star has fused hydrogen into helium, helium into carbon/nitrogen/oxygen, and on until the end result is Iron.  Why Iron?  Because fusing iron requires more energy than it releases, which halts the chain reaction required to power a star.  When this chain reaction halts, the core of a star is like a layered onion.  The core is Iron, with a shell around it of ever lighter elements (which may still be fusing) until you get to H and He...which blend into the envelope of the star (you could consider this the 'mantle' for a geologic analogy).When the inert iron core gets to large...when it steals to much energy from the surrounding environment in what little iron is fused into still heavier elements, the star dies, and the core collapses.  It shrinks, into either an Neutron Star, or even further, into a Black hole!  All the iron in the core is essentially lost as it's converted into neutrons, or swallowed by the growing black hole.This core collapse removes the support out from the rest of the star, which begins to fall inwards...and compresses, and heats and...triggers massive fusion, not in the shrinking core, but shell of still viable nuclear fuel (i.e. not iron) around it.  This fusion event causes the shell to expand...and slams right into the rest of the star still falling inwards.  This creates a massive traveling, self-reinforcing, shockwave of fusion that swells out from the inner shells.  It's a massive amount of fusion, in an uncontrolled chain reaction as the rest of the star is still falling inwards (due to inertia) feeding the swelling inferno.Now, you'd think that all the heavy elements we get, are created in the inner shells of this explosion, the shells that were heavy elements around the core before the entire catastrophe, and are spewed out into space...but you'd be wrong!  The inner regions of the supernova are so intense, so energetic that the atoms undergo photo-dissociation.  The photons created, the collisions endured, are so energetic as to actually smash the heavy elements apart, leaving only hydrogen (and a little helium) in it's wake.  The heavy elements actually come from the outer edges of that massive fusion shockwave, where all that excess energy is used to fuse elements. Even the heavy elements beyond iron are fused and created here..there is a lot of energy here, even for inefficient fusion.  And yet these outer regions are 'cool' enough that these fusion events are immediately destroyed in a wash of insanely powerful photons.And since they are on the outer edge of this expanding shockwave, a wave traveling at relativistic velocities, they get a massive boost into space, to be scattered into new dust clouds, into new planetary regions, to form the next generation of stars and planets. So, talking about the concentration of metals in a supernova is a bit complicated.  What region? At what point in time? <div class="Discussion_UserSignature"> --------------------SaiphMOD@gmail.com -------------------"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- The Tenth Doctor, "Blink" </div>

BoJangles · Jan 30, 2009

Thanks Saiph for you detailed reply, and a good post it was; It was probably the most enlightening description of a supernova event I’ve ever read, and just about answered all my questions in one fell swoop. I suppose my question was focusing on the end of a supernova explosion when it’s seeding space with metals (the stuff we call earth). Basically I was curious as to how much interaction/mixing supernovas had to with the primordial cloud that collapsed to create the solar system, as obviously they had some role, the evidence is the computer I'm typing on and just about everything else on earth. Quite interesting stuff.So I guess knowing that the sun has only a low metallicity of 0.01% or so and knowing the ratio between H, He and metals, I was trying to get my head around how much of a potential role supernovae had in the composition of our solar system. If the ratio is low, then the answer would be only a small component of our solar system was the result of supernovae, though if the ratio is high, the answer would be a lot more complicated to figure out ( on a theoretical level, without observation ). Thats to say there may have been many more generations of stars that resulted in our own.I guess if I had to dig deeper into my original train of thought, I`m wondered how much of the solar system was due H, He left over from the big bang  (going around it the long way, and trying to get mental picture of what was happening in the early days of the solar system/galaxy).    <div class="Discussion_UserSignature"> -------------- Let me start out with the standard disclaimer ... I am an idiot, I know almost nothing, I haven’t taken calculus, I don’t work for NASA, and I am one-quarter Bulgarian sheep dog. With that out of the way, I have several stupid questions... *** A few months blogging can save a few hours in research *** </div>

Saiph · Jan 30, 2009

Replying to: <DIV CLASS='Discussion_PostQuote'>Thanks Saiph for you detailed reply, and a good post it was; It was probably the most enlightening description of a supernova event I’ve ever read, and just about answered all my questions in one fell swoop. I suppose my question was focusing on the end of a supernova explosion when it’s seeding space with metals (the stuff we call earth). Basically I was curious as to how much interaction/mixing supernovas had to with the primordial cloud that collapsed to create the solar system, as obviously they had some role, the evidence is the computer I'm typing on and just about everything else on earth. Quite interesting stuff.So I guess knowing that the sun has only a low metallicity of 0.01% or so and knowing the ratio between H, He and metals, I was trying to get my head around how much of a potential role supernovae had in the composition of our solar system. If the ratio is low, then the answer would be only a small component of our solar system was the result of supernovae, though if the ratio is high, the answer would be a lot more complicated to figure out ( on a theoretical level, without observation ). Thats to say there may have been many more generations of stars that resulted in our own.I guess if I had to dig deeper into my original train of thought, I`m wondered how much of the solar system was due H, He left over from the big bang  (going around it the long way, and trying to get mental picture of what was happening in the early days of the solar system/galaxy).    Posted by BoJangles</DIV> Good questions!  First, let me amend my original figure of metals in the sun, I shifted a decimal place in my memory, it's ~0.1%, not 0.01%.  And of that 0.1%, 90% is carbon/nitrogen/oxygen, leaving only ~0.01% are metals heavier than those.As for how many generations of supermassive stars going supernova are required to seed that much metal into our sun...I don't know off hand.  It is important to know that our sun is considered 'metal rich', not metal poor.  Also, with the exception of hydrogen that is 're-created' in the supernova as I describe above, all hydrogen is from the BB (and almost all He for that matter).In order to help grasp how many supernova are required to create the 'metals' we see in our solar system I'd like to point out that our sun is ~5 billion years old.  So the universe had been around for ~8 billion years before it formed.  The stars that are large enough to undergo the supernova explosions have lifetimes measured in millions of years, not billions.  So there are many, many generations of stars that help seed our system with heavy metals.  While any single supernova might create enough metals to account for a singificant portion of the metals in our system (or all, I'm sorta winging it here) they do explode, and seed all that matter out into the vastness that is interstellar space.  It takes a lot of supernova to raise the average composition levels of a large portion of space, that measures thousands of ly across, that is the typical stellar nursery. Let alone the fact that they seed everything else too, not just star forming regions. <div class="Discussion_UserSignature"> --------------------SaiphMOD@gmail.com -------------------"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- The Tenth Doctor, "Blink" </div>

michaelmozina · Jan 30, 2009

Replying to: <DIV CLASS='Discussion_PostQuote'>Now, you'd think that all the heavy elements we get, are created in the inner shells of this explosion, the shells that were heavy elements around the core before the entire catastrophe, and are spewed out into space...but you'd be wrong!  The inner regions of the supernova are so intense, so energetic that the atoms undergo photo-dissociation.  The photons created, the collisions endured, are so energetic as to actually smash the heavy elements apart, leaving only hydrogen (and a little helium) in it's wake. Posted by Saiph</DIV>I'm a bit confused.  It was my understanding that a neutron star or a black hole could form from such events. I had always assumed that the heavier elements were created near and around the core due to compression in the core.  If the core is likely to undergo photo-dissociation and revert to hydrogen and helium, is it a "size" issue then that determines what's left in the core after the event?  In other words, what determines whether a neutron core forms from such events? <div class="Discussion_UserSignature"> It seems to be a natural consequence of our points of view to assume that the whole of space is filled with electrons and flying electric ions of all kinds. - Kristian Birkeland </div>

Saiph · Jan 30, 2009

The main determination between the creation of a neutron star or a BH is size.  If the collapsing core is small enough, the neutron degeneracy pressure can halt the collapse...and that's it.  If it isn't, the core continues to collapse into a BH (the event horizon of which starts in the center, and grows outwards as the core continues to shrink).The reason not everything falls into the BH btw, is the fusing shell/shockwave acts as a shield upon which the rest of the star rebounds.Part of the determination of neutron star formation is the explosion itself.  It is possible for the explosion to compress the core enough to tip it into the BH...or perhaps cause it to shed enough mass to stay a neutron star.  But the mass of the star is the primary factor.As for the metals forming around the core, that is a very common misconception, as people treat the supernova like your everyday explosion, and the core is just shrapnel/debris to be spread around. <div class="Discussion_UserSignature"> --------------------SaiphMOD@gmail.com -------------------"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- The Tenth Doctor, "Blink" </div>

michaelmozina · Jan 30, 2009

Replying to: <DIV CLASS='Discussion_PostQuote'>The main determination between the creation of a neutron star or a BH is size.  If the collapsing core is small enough, the neutron degeneracy pressure can halt the collapse...and that's it.  If it isn't, the core continues to collapse into a BH (the event horizon of which starts in the center, and grows outwards as the core continues to shrink).The reason not everything falls into the BH btw, is the fusing shell/shockwave acts as a shield upon which the rest of the star rebounds.Part of the determination of neutron star formation is the explosion itself.  It is possible for the explosion to compress the core enough to tip it into the BH...or perhaps cause it to shed enough mass to stay a neutron star.  But the mass of the star is the primary factor.As for the metals forming around the core, that is a very common misconception, as people treat the supernova like your everyday explosion, and the core is just shrapnel/debris to be spread around. Posted by Saiph</DIV>Thanks for the clarification.  I believe I've seen a number of supernova explosions where the iron seems to be concentrated around the edges rather than the core, so your comments make a lot of sense. <div class="Discussion_UserSignature"> It seems to be a natural consequence of our points of view to assume that the whole of space is filled with electrons and flying electric ions of all kinds. - Kristian Birkeland </div>

michaelmozina · Jan 30, 2009

http://chandra.harvard.edu/photo/1999/casajph/ <div class="Discussion_UserSignature"> It seems to be a natural consequence of our points of view to assume that the whole of space is filled with electrons and flying electric ions of all kinds. - Kristian Birkeland </div>

BoJangles · Feb 1, 2009

Thanks Saiph.I have a lot more questions but ill do a little more research before i inundate you with the speculative.  <div class="Discussion_UserSignature"> -------------- Let me start out with the standard disclaimer ... I am an idiot, I know almost nothing, I haven’t taken calculus, I don’t work for NASA, and I am one-quarter Bulgarian sheep dog. With that out of the way, I have several stupid questions... *** A few months blogging can save a few hours in research *** </div>

kg · Feb 1, 2009

Replying to: <DIV CLASS='Discussion_PostQuote'>...  And yet these outer regions are 'cool' enough that these fusion events are immediately destroyed in a wash of insanely powerful photons. Posted by Saiph</DIV> I think you should mention something about neutrinos here.  http://en.wikipedia.org/wiki/Nutrino#Supernova  Even though a supernova can be brighter that the entire galaxy it's located in in visible light most of the energy produced is in the form of neutrinos!  I think I've read somewhere that much of the heaver elements formed in the exploding star are destroyed by neutrinos.

emperor_of_localgroup · Feb 4, 2009

Replying to: <DIV CLASS='Discussion_PostQuote'>So, talking about the concentration of metals in a supernova is a bit complicated.  What region? At what point in time? Posted by Saiph</DIV>Please educate me. I have a couple of questions about supernova and solar system. I'm a total ignorant when it comes to our solar system.Our current theory says explosion of a supernova  was the origin of our solar system. Which means our solar system is just a small or a big part of the original supernova. Have anyone  made any estimation of our 'mother' supernova?  This supernova must be much larger than the mass of our entire solar system. What happened to the remaining parts of this supernova? Can those parts go as far as where our nearest stars are? A Supernova is in fact a star (correct me if I have said something stupid). Shouldn't a star that size collapse into a black-hole? Are there any stars in the sky like our 'mother' supernova (star)?A curious mind wants to know.  <div class="Discussion_UserSignature"> Earth is Boring </div>

UFmbutler · Feb 4, 2009

It's believed the formation of our solar system was triggered by a supernova, meaning that a nearby star exploded and presumably shocked the surrounding nebula enough to cause parts of it to collapse into stars.  If you look at dying stars you will see a very large nebula surrounding them, which is the result of mass loss during the giant branch phase of the star's life.  This can extend very far from the parent star.  Presumably the other gas in the nebula went into forming other stars, or just diffused into the interstellar medium.  It's hard to say what kind of supernova remnant was left behind(neutron star, black hole, neither) since we don't know exactly when or where it occured, we just know that based on the composition of material in the solar system, one or more had to have occurred nearby. <div class="Discussion_UserSignature"> </div>

emperor_of_localgroup · Feb 4, 2009

Replying to: <DIV CLASS='Discussion_PostQuote'>It's believed the formation of our solar system was triggered by a supernova, meaning that a nearby star exploded and presumably shocked the surrounding nebula enough to cause parts of it to collapse into stars.  If you look at dying stars you will see a very large nebula surrounding them, which is the result of mass loss during the giant branch phase of the star's life.  This can extend very far from the parent star.  Presumably the other gas in the nebula went into forming other stars, or just diffused into the interstellar medium.  It's hard to say what kind of supernova remnant was left behind(neutron star, black hole, neither) since we don't know exactly when or where it occured, we just know that based on the composition of material in the solar system, one or more had to have occurred nearby. Posted by UFmbutler</DIV>Thanks for the post. The nebula thing never occurred to me before. The supernova indirectly created our solar system, not even from its own materials but from the materials of a nebula. Have astronomers visually noticed in the sky this type of events involving a supernova and nearby nebula? Or is this a theory so far? Note that there are so many million/billion stars (supernova) in the sky, I have a thought, the stages through which our solar system and even life evolved, there are examples of these stages scattered throughout the sky.That nebula theory also cast a shadow on another thing about the universe, its age. Considering the pace at which astronomical events occur, my guess is  this 13 or 15 billion years time are too short for all this to happen  and  make such intelligent life as ourselves. I mean forming a star, turning into supernova, affecting a nebula, forming another solar system, creating life, then intelligent life, all these may take much longer than 13-15B years.   <div class="Discussion_UserSignature"> Earth is Boring </div>

MeteorWayne · Feb 4, 2009

Replying to: <DIV CLASS='Discussion_PostQuote'>Thanks for the post. The nebula thing never occurred to me before. The supernova indirectly created our solar system, not even from its own materials but from the materials of a nebula. </DIV>Well, really a combination of the local nebula and some elements from the supernova that compressed the gas. Replying to: <DIV CLASS='Discussion_PostQuote'>Have astronomers visually noticed in the sky this type of events involving a supernova and nearby nebula? Or is this a theory so far? </DIV>Yes, from what I know that is fairly common, and is one reason that it is theorized as part of the formation of our solar system Replying to: <DIV CLASS='Discussion_PostQuote'>Note that there are so many million/billion stars (supernova) in the sky, I have a thought, the stages through which our solar system and even life evolved, there are examples of these stages scattered throughout the sky.</DIV>That is correct; in fact since these events occur over periods of time much longer that our observing histsory, this is the means by which we understand as much as we do. We have hundreds or thousands of snapshots of the development of galaxies and stars...by looking at them all we can try and understand how one system might develop over time. Replying to: <DIV CLASS='Discussion_PostQuote'>That nebula theory also cast a shadow on another thing about the universe, its age. Considering the pace at which astronomical events occur, my guess is  this 13 or 15 billion years time are too short for all this to happen  and  make such intelligent life as ourselves. I mean forming a star, turning into supernova, affecting a nebula, forming another solar system, creating life, then intelligent life, all these may take much longer than 13-15B years.   Posted by emperor_of_localgroup</DIV>Well, the 13.5 BY age of the Universe is pretty well constrained. One thing you should realize is that massive stars have much shorter lifetimes than the sun. The sun (a yellow dwarf) lasts 10+ billion years. The most massive stars have lifetimes measured in hundreds of thousands of years. From what I understand, the first stars were exttremely massive, so consumed their fuel very quickly. Don't have any hard numbers here, that's more up the alley of some other posters. On the other hand tiny red dwarf stars have lifetimes as long as the Universe, so will never burn out until the end...whatever that turns out to be.MW <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

Saiph · Feb 4, 2009

We have many snapshots of various stages of proto-stellar evolution that corroborate with the theory.  Supernova , or even just the wake of large stars/clusters will help trigger the cold dark nebulae to collapse.  Most star formation is on the 'leading edge' of the spiral arm, as the stars sweep past the generally slower moving gas clouds (who's motion is slowed because of obeying the requirements of a balanced pressure system).If anybody is curious how we can study and understand events and lifecycles that take millions of years to complete, consider how you would consider the lifecycle of a human being.  You have two ways of doing it, the first is to pick a baby, and follow it itensively throughout it's life, until it dies of old age.  This, obviously, is a lot of work and takes a very long time.  It also is heavily influenced by individual, unique factors that may not be applicable to every human.  The alternative is to take a look at many people, all at different stages.  Grab a group of 50 toddles, 50 children, 50 unruly teenagers, 50...etc and take a look at what aspects define them all, and what they all share in common across the groups too.  This can, in a much shorter time period, provide a robust analysis of the entire species.  Same with stars, we see one star forming, another dying, another in it's middle age duldrums...and just look at more and more in each stage. As for star formation throwing the age of the universe question a curve ball...that's highly unlikely.  Once star formation is triggered, it only takes a few tens of millions of years to become a true star.  Massive stars (say 5x our sun) don't live for billions of years, they actually burn for only hundreds of millions of years (or even less with the supergiants!) As the universe is believed to be 13 Billion years...you can easily fit in countless generations of massive stars with no problem. <div class="Discussion_UserSignature"> --------------------SaiphMOD@gmail.com -------------------"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- The Tenth Doctor, "Blink" </div>

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