Heavy elements ?

[Dart15]

Hi All,

 

I am new to this forum - so, be gentle with me.

 

My question is this : I am told/read that all the heavy elements, that is all above Hydrogen and Helium have been created in large stars with enough heat and pressure or/and by Supernovae.

These heavy elements require temperatures in a Supanovae above somewhere above 10^9 Kelvin.

 

These temperatures occured in the very early stages of expansion of the universe - around 100 - 1000 seconds. So, why do we not think the heavy elements were created then ?

 

George

[Realitycheck]

Heavy elements are generally believed to have been created more recently in Population 1 and 2 stars because in the first generation or Population 3, there was mostly only Hydrogen and Helium, and most of the stars were very big and red, grew very fast and exploded, providing heavier gases for successively heavier stars, which were more metallic. IIRC, I'm pretty sure the life cycle of Population 3 stars were substantially different than later populations. It wouldn't surprise me, however, if this was incorrect. Just because there were hardly any metals created in the BB doesn't necessarily mean that a star(correction: supernova) shouldn't be able to fuse Hydrogen into successively heavier elements all the way down to Iron, without exploding first.

Edited October 13, 2011 by Realitycheck

[Dart15]

Heavy elements are generally believed to have been created more recently in Population 1 and 2 stars because in the first generation or Population 3, there was mostly only Hydrogen and Helium, and most of the stars were very big and red, grew very fast and exploded, providing heavier gases for successively heavier stars, which were more metallic. IIRC, I'm pretty sure the life cycle of Population 3 stars were substantially different than later populations. It wouldn't surprise me, however, if this was incorrect. Just because there were hardly any metals created in the BB doesn't necessarily mean that a star shouldn't be able to fuse Hydrogen into successively heavier elements all the way down to Iron, without exploding first.

 

Hi,

 

I agree with all you have said. However, what I do not understand is why there is no consideration for any elements heavier than Helium being created in the BB when the conditions are similar and all the component parts are present in abundance ?

 

G

[Moontanman]

Hi,

 

I agree with all you have said. However, what I do not understand is why there is no consideration for any elements heavier than Helium being created in the BB when the conditions are similar and all the component parts are present in abundance ?

 

G

 

 

Actually there was some lithium made then or it is thought to have been made but not much, only a tiny amount but during the beginning of the "big bang" atoms could not exist and by the time atoms could exist the density dropped off too fast for heavy elements to form or at least that's my understanding of it. then there is the fact that older stars have few metals, the oldest we know of having almost none which agrees with theory quite well.

[Realitycheck]

But, alas, we can observe that many of the oldest stars have little metal content which fits in with original model pretty well. Also, looking around a bit, there appears to be a bit of disagreement on the specifics of some metallic formation in stars, but that the heaviest elements are formed in the biggest supernovae, which means that Population 3 supernovae seemingly could have burnt up fast and formed iron.

 

To answer your question, right after the BB, the small universe was filled with very hot matter like what is termed quark-gluon plasma. When it cools, it automatically forms the two lightest elements. There is no mechanism for it to form into heavier, more complicated elements.

[Moontanman]

You said it better than i did realitycheck, good answer...

[Realitycheck]

Also, to correct you, while those temperatures were present just after the BB, like I said, only the simplest of elements were formed in it. Only in supernovae are there temperatures necessary to form the heavier metals out of successively lighter elements. There has to be a method for the metals to form. There is no way for them to form after the BB out of quark-gluon plasma, only in supernovae. Sorry for beating around the bush.

[baric]

Hi All,

 

I am new to this forum - so, be gentle with me.

 

My question is this : I am told/read that all the heavy elements, that is all above Hydrogen and Helium have been created in large stars with enough heat and pressure or/and by Supernovae.

These heavy elements require temperatures in a Supanovae above somewhere above 10^9 Kelvin.

 

These temperatures occured in the very early stages of expansion of the universe - around 100 - 1000 seconds. So, why do we not think the heavy elements were created then ?

 

George

 

It requires high temperature and pressure (i.e. lots of nuclei to fuse).

 

The big bang was TOO hot initially for matter to exist. By the time the universe cooled sufficiently for matter to form, material density was too low to initiate fusion.

[Genius13]

elements to iron r made in massive stars and the rest of the heacy elements were made in the high speed colisions in the supernova explosions when the star stuff exploded outward and colided with the matter that headed to the star