Where does a nova get the h2 to form a star?

[SmartAlex]

Pardon my ignorance but how on Earth, er… well… in the universe do supernovae reform into new stars? We know that our sun was formed from a supernova because we have heavier elements. Without a supernova, there can not be heavy elements.

 

It is my understanding that we have heavier elements on Earth (and throughout the solar system) because a previously existing star in the vicinity of our solar system went nova. I am also to understand that a star goes nova when it runs out of Hydrogen, then helium, carbon, nitrogen, oxygen, etc until it reaches iron and cannot fuse any more. Then the force of gravity causes the core to collapse and the star explodes. And the life of the solar system begins anew. In the explosion, heavier elements are created. Okay this is all fine and good for creating heavier elements. I can buy that these star bits and pieces over millions or billions of years coalesce into planets. But now we have a problem. Well two actually. If our goal is to create a new solar system with this cloud, we need a new star. But when a star goes nova, it forms a neutron star, right? So we have to get rid of that nasty neutron star. It’s totally useless. How can you have a sustained fusion reaction with just neutrons? You can’t. So how do we get rid of it? Or do we actually have to? Can we use it to create a new star? Does it form the core of the new hydrogen burning star? I’ve never heard any scientist suggest this.

 

I know that it is possible that a different kind of supernova can create a supernova remnant without a neutron star. http://antwrp.gsfc.nasa.gov/apod/ap020912.html is just such a supernova. So, let’s move on and assume that this is what happened. Or just for kicks lets just say that the giant xcartulons in the scortmilpharrx galaxy shoot their marble and knock the neutron star out of the way and we have a plain ole starless cloud of exploded star stuff. Now we are in the clear to create a new solar system. Or are we? We still need a star, a hydrogen burning one. Hmm… How to create a star? We need hydrogen. This is the second problem. Where does the hydrogen for the new sun come from? The early star burned it all up. The supernova creates heavy elements with fusion. Can it also create lighter elements with fission? I can’t imagine this being possible. It takes energy to split helium into hydrogen. More energy to split other elements into helium. And the star would have to split the elements all the way from iron down to hydrogen. I can imagine some of it happening, but not enough to form a new star. Even the power of a supernova can’t create the kind of energy necessary to reform enough hydrogen necessary for a new star. If the hydrogen doesn’t come from the supernova, then where DOES it come from? Does another cloud of hydrogen enter the area and mix with the supernova remnant? If that’s true, then why didn’t that cloud of hydrogen create a star all on its own like the rest of the clouds of hydrogen?

 

So that is where I am stuck. I’ve heard teachers and scientists explain how stars form and how they die. But they have never explained how they REFORM. I am totally at a loss to understand how a star can burn something up, explode, then reform into that new already burned up stuff?

[Martin]

Pardon my ignorance but how on Earth' date=' er… well… in the universe do supernovae [b']reform[/b] into new stars? We know that our sun was formed from a supernova because we have heavier elements. Without a supernova, there can not be heavy elements.

 

 

there are these star-forming regions of the galaxy which have vast clouds of gas and dust

 

in a star-forming region, there may be 100 stars forming at any one time

 

they gradually condense out of the cloud by their own gravity pulling them together

 

 

in one of those regions, if a bigger than usual star forms and goes thru the stages you describe (til the core is iron) and explodes supernova----then that massive star does not RE-FORM into a solar system

 

that supernova blows off the outer part of the star (which has lighter elements up to iron in an onion like) all to hell and gone

 

that stuff that it blows off into space, that is never coming back

it ENRICHES THE VAST CLOUDS OF GAS AND DUST IN THE STARFORMING REGION

 

one supernova may ENRICH HUNDREDS OF STARS with the heavier elements that it has cooked prior to explosion.

 

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if you think about it, maybe you do not have a problem. your problem was probably caused by your thinking that the supernova had to reform into a solar system in a one-to-one way

 

it doesnt. the remnant is a neutron star all right. and it is useless from our standpoint, and it stays a neutron star----but meanwhile the supernova explosion has blown all these goodies out into the larger surrounding region where normal-size stars can form out of it

 

and the gas in the region is always mostly hydrogen----so there is never a problem of where do you get enough hydrogen

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good question. dont take anything on faith, think about it and keep asking until it really makes sense-----pleasure responding to someone who does that. cheers

[[Tycho?]]

When a star goes supernova it means its core has run out of fusionable elements (ie its trying to fuse iron). But that doesn't mean that all of the hydrogen in the star has been consumed, only the hydrogen near enough the core to be exposed to the high temperatures and pressures. I'm not too sure about this, but I would think most of the stars outer layers would still be lighter elements when the star goes supernova.

[insane_alien]

A star after supernova (after the fusion stops) is still about about 99% hydrogen. its only a very small volume of the core(relatively, for the sun its about the size of the earth i believe) has the right conditions for fusion.

[[Tycho?]]

A star after supernova (after the fusion stops) is still about about 99% hydrogen. its only a very small volume of the core(relatively, for the sun its about the size of the earth i believe) has the right conditions for fusion.

 

Good, I wasn't just making it up.