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'Wonders' question


Robthevegetable
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Im curious.

If a Star at birth has X mass over the life of that star that mass is going to reduce due to Burning the fuel which could be called Y

so X-Y is all that is left when it goes boom, and that Boom process is so powerful must also convert a % of that mass in to energy also call this Z

So the Nebula would be X-Y-Z = B

New stars are formed from B

these stars much be much smaller than the original X star?

Edited by Earl
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I like that I've got people thinking, although I think it's clear (without any disrespect) that none of us really know...

Erm, I do have a degree in Astronomy and Astrophysics and the post I put a bit earlier is the actual reason! :o

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Surely then they must only be A) a tiny %age of the mass of the original, and :o burn for a tiny %age of time... Bearing in mind they have to be a certain size before fusion can even take place, then surely their lifetime can only be a fraction of the original?!

Edited by Robthevegetable
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If a Star at birth has X mass over the life of that star that mass is going to reduce due to Burning the fuel which could be called Y

so X-Y is all that is left when it goes boom, and that Boom process is so powerful must also convert a % of that mass in to energy also call this Z

So the Nebula would be X-Y-Z = B

I don't think fusion is the conversion of mass into energy - I think it's the joining of lighter elements to form heavier elements and energy is released by the rearrangement of the bonds within the nucleus of the atoms being fused.

My understanding is that mass is lost from the star when it's blown off by the stellar wind and during the red giant / super nova stages, but that "blown off" mass goes back into space to make up the ISM.

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Surely then they must only be A) a tiny %age of the mass of the original, and :o burn for a tiny %age of time... Bearing in mind they have to be a certain size before fusion can even take place, then surely their lifetime can only be a fraction of the original?!

It depends. If here are several stars that go supernova and create a nebula there is no reason why a huge star could not be formed. Generally though stars would get smaller through succesive generations but by doing so would actually burn for a lot longer. Super massive stars have a very short lifespan, usually only a few 100 million years where as red dwarfs would last for billions of years.

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Although it doesn't directly answer these questions, have a look at http://en.wikipedia.org/wiki/Star_formation especially on cloud collapse and protostars.

I'm no expert but I've a feeling the prof's description of the process was a little simplified, a stella remnant probably doesn't have enough matter to form a region of star formation on its own. But it'll clump and attract ISM over time (thanks to gravity) and when dense enough that the cloud collapses, then bingo! :o

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It depends. If here are several stars that go supernova and create a nebula there is no reason why a huge star could not be formed. Generally though stars would get smaller through succesive generations but by doing so would actually burn for a lot longer. Super massive stars have a very short lifespan, usually only a few 100 million years where as red dwarfs would last for billions of years.

That makes sense. So the smaller the star, generally, the longer it will last because it doesn't burn its fuel as quickly as a super giant.

Using Betelgeuse as an example then - Would be a young star,but because it's so massive it's used it's Hydrogen supply much quicker than a smaller star?

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I don't think fusion is the conversion of mass into energy - I think it's the joining of lighter elements to form heavier elements and energy is released by the rearrangement of the bonds within the nucleus of the atoms being fused.

My understanding is that mass is lost from the star when it's blown off by the stellar wind and during the red giant / super nova stages, but that "blown off" mass goes back into space to make up the ISM.

This was something that wasn't explained well in the WOTU programme. when fusion takes place and forms a helium atom from hydrogen the final atom has less mass than the 'ingrediants'. this lost mass is converted into energy (using Einstein's e=mc2). This carries on up untill iron after which elements are actually heavier than their ingrediants and requires energy input to continue fusion. When the star goes supernova it gives it this extra energy and allows heavier elements to be created.

Edited by zcapp96
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This was something that wasn't explained well in the WOTU programme. when fusion takes place and forms a helium atom from hydrogen the final atom has less mass than the 'ingrediants'. this lost mass is converted into energy (using Einstein's e=mc2). This carries on up untill iron which actually is heavier than it's ingrediants and requires energy input to continue fusion. When the star goes supernova it gives it this extra energy and allows heavier elements to be created.

I've heard that before, brings back memories from my Physics A-level, memories it's taken me years to repress :o

Yup

Steve

Woohoo! I'll be an Astrophysics... Guy... Thing before you know it!

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Now, if the star used all of its basic fuel (Hydrogen and Helium) during the 'first life', how can new stars form from the nebula cloud formed from the supernova? Although the cloud will have some Hydrogen present, how can there be enough to form new stars from the ashes of only a single star?

The key point here is that stars do NOT burn ALL of their Hydrogen during their lifetimes, in fact only a small fraction of it (though I can't remember the numbers just now). Most of the material goes through the stellar life cycle completely unprocessed.

The 'metals' (everything other than H & He) produced in stars only make up a tiny fraction of interstellar gas; about 2% percent by mass -- and even less than that by number, because metals are relatively heavy. It's not a bad model to think of Supernova (another soruces of metal such as red giants) as going around 'polluting' hydrogen clouds with their dirty metals :o

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Speaking of Betelgeuse:

The show said that when it dies it will leave a black void in space where it used to be. It will simply vanish after a while (but will be a bright SN in the day light sky). I was expecting it to go SN and then leave a lovely nebula behind.

So how come some stars go SN and vanish while others leave a nebula (planetary) behind?

Size? if thats the case i'd expect the larger stars like beetlejuice to leave a neb behind while smaller stars fizzle out.

OR

is it a case that larger stars like Betelgeuse burn off MOST their fuel and when they do die there is not very much left over to form a nebula.........whereas smaller stars have a lot more fuel left over when they explode and this is how the neb forms.?

Edited by LukeSkywatcher
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Let's just hope it goes up in our winter - it would be a shame if we were on the wrong side of the sun and missed it! :o

That hadn't even entered my mind... That literally is a once in a lifetime thing isn't it, Orion disappears for the Summer, and comes back in the Winter after being on a diet and loosing a squillion kg's and a limb!

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i'd expect the larger stars like beetlejuice to leave a neb behind

Let's hope so - our "problem" is that if we see Betelgeuse go supernova, the light will have come to us at the speed of light - but the debris which would form the nebula would move outwards at much slower speed and so would take a long time to become something spectacular.

There's a thread somewhere on SGL calculating how quickly the nebula would grow - I'll see if I can find it

Steve

Edited by Steve 1962
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Speaking of Betelgeuse:

The show said that when it dies it will leave a black void in space where it used to be. It will simply vanish after a while (but will be a bright SN in the day light sky). I was expecting it to go SN and then leave a lovely nebula behind.

So how come some stars go SN and vanish while others leave a nebula (planetary) behind?

Size? if thats the case i'd expect the larger stars like beetlejuice to leave a neb behind while smaller stars fizzle out.

OR

is it a case that larger stars like Betelgeuse burn off MOST their fuel and when they do die there is not very much left over to form a nebula.........whereas smaller stars have a lot more fuel left over when they explode and this is how the neb forms.?

All stars will leave a nebula eventually but not for a while as they would need to have expanded to a few AU's across before they could be seen from the earth. Betelgeuse will form something like the crab nebula. star under 1.4 times the mass of the sun will not go supernova and will just shed their outer layers and form planetary nebulas like M57.

Edited by zcapp96
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Had a look on Wiky, even if its not always too reliable but any how thought it may explain something about the reason why we get certain type's of Nebula :o

Planetary nebula - Wikipedia, the free encyclopedia

Stars more massive than 8 solar masses (M⊙) will likely end their lives in a dramatic supernova explosion.[14] Planetary nebula may result from the death of intermediate and low mass stars down to 0.8 M⊙.[14]

Thanks.

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