Questions about the Formation of the Sun
- Thread starter JimBowie1958
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Fort Fun Indiana
Diamond Member
- Mar 10, 2017
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Yep, in a nutshell. The pressure (thus, energy of fusing hydrogen with hydrogen is lower, so those reactions will all occur first.
That is still a mystery.
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Fort Fun Indiana
Diamond Member
- Mar 10, 2017
- 110,250
- 99,375
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No. If a neutron star were surrounded by matter, matter would fall into it until either there was no more matter to fall into it, or the neutron star collapsed into a black hole. Fusion could not be reignited in a neutron star, as there is nothing to fuse. The entire star is as dense as an atomic nucleus and does not contain any atoms.
toobfreak
Tungsten/Glass Member
RUBBISH.
toobfreak
Tungsten/Glass Member
No. Let me try to explain a bit. As the heat and pressure at the center of the Sun reach the point of hydrogen fusion, helium is produced. Some of the helium there may be from other, older stars as well. But the Sun does not start to burn the helium until the hydrogen runs out and then the outward pressure drops, the Sun contracts and builds up even greater pressure and heat until it reaches the point of fusing helium. This goes on for several iterations until the star reaches an element it has manufactured where it lacks sufficient heat and pressure to fuse farther.
In the case of a dwarf star like the Sun, it eventually evolves into a red giant, throws off its outer layers as a planetary nebula then cools as a white dwarf.
If the star is massive enough (much bigger than the Sun), as a supergiant, the process continues until iron is reached. No star can burn iron. Iron is so heavy, it takes as much energy to fuse it to heavier elements as the star would get out of it in burning it. At that point all nuclear fusion stops and the star falls in on itself, no longer having the outward radiant pressure to hold itself up.
When that happens, the titanic impact of the giant star collapsing in creates such heat and pressure, there is a supernova explosion and all elements heavier than iron are created there in various quantities and thrown out into space. What is left behind, depending omn the conditions, may be a neutron star, a pulsar, or even a Black Hole.
If anyone really wants to understand it better, you can try reading some of this:
Nucleosynthesis - Wikipedia
Stellar nucleosynthesis - Wikipedia
Stellar evolution - Wikipedia
ReinyDays
Gold Member
No. Let me try to explain a bit. As the heat and pressure at the center of the Sun reach the point of hydrogen fusion, helium is produced. Some of the helium there may be from other, older stars as well. But the Sun does not start to burn the helium until the hydrogen runs out and then the outward pressure drops, the Sun contracts and builds up even greater pressure and heat until it reaches the point of fusing helium. This goes on for several iterations until the star reaches an element it has manufactured where it lacks sufficient heat and pressure to fuse farther.
In the case of a dwarf star like the Sun, it eventually evolves into a red giant, throws off its outer layers as a planetary nebula then cools as a white dwarf.
If the star is massive enough (much bigger than the Sun), as a supergiant, the process continues until iron is reached. No star can burn iron. Iron is so heavy, it takes as much energy to fuse it to heavier elements as the star would get out of it in burning it. At that point all nuclear fusion stops and the star falls in on itself, no longer having the outward radiant pressure to hold itself up.
When that happens, the titanic impact of the giant star collapsing in creates such heat and pressure, there is a supernova explosion and all elements heavier than iron are created there in various quantities and thrown out into space. What is left behind, depending omn the conditions, may be a neutron star, a pulsar, or even a Black Hole.
If anyone really wants to understand it better, you can try reading some of this:
Nucleosynthesis - Wikipedia
en.wikipedia.org
Stellar nucleosynthesis - Wikipedia
Stellar evolution - Wikipedia
Just a quick clarification of toobfreak's excellent explanation ... our own Sun isn't massive enough to create the temperatures and pressures for Helium to fuse into larger nuclei ... once the Hydrogen is gone, our Sun will just collapse into a white dwarf ... and very very slowly cool down ...
toobfreak
Tungsten/Glass Member
No. Let me try to explain a bit. As the heat and pressure at the center of the Sun reach the point of hydrogen fusion, helium is produced. Some of the helium there may be from other, older stars as well. But the Sun does not start to burn the helium until the hydrogen runs out and then the outward pressure drops, the Sun contracts and builds up even greater pressure and heat until it reaches the point of fusing helium. This goes on for several iterations until the star reaches an element it has manufactured where it lacks sufficient heat and pressure to fuse farther.
In the case of a dwarf star like the Sun, it eventually evolves into a red giant, throws off its outer layers as a planetary nebula then cools as a white dwarf.
If the star is massive enough (much bigger than the Sun), as a supergiant, the process continues until iron is reached. No star can burn iron. Iron is so heavy, it takes as much energy to fuse it to heavier elements as the star would get out of it in burning it. At that point all nuclear fusion stops and the star falls in on itself, no longer having the outward radiant pressure to hold itself up.
When that happens, the titanic impact of the giant star collapsing in creates such heat and pressure, there is a supernova explosion and all elements heavier than iron are created there in various quantities and thrown out into space. What is left behind, depending omn the conditions, may be a neutron star, a pulsar, or even a Black Hole.
If anyone really wants to understand it better, you can try reading some of this:
Nucleosynthesis - Wikipedia
Stellar nucleosynthesis - Wikipedia
Stellar evolution - Wikipedia
Just a quick clarification of toobfreak's excellent explanation ... our own Sun isn't massive enough to create the temperatures and pressures for Helium to fuse into larger nuclei ... once the Hydrogen is gone, our Sun will just collapse into a white dwarf ... and very very slowly cool down ...
Well, now you're going into a very complicated area I hoped to avoid as this crap is too deep for social media chat (and boring as hell to most people). Let's just say that for a star below about 40% less mass of the Sun they never reach the heat necessary to go past fusing hydrogen--- that's a red dwarf. These are the most common stars in the universe, very small, very faint and very long lived. They just kind of smolder along like a dull cinder for trillions of years. They are so dim that we don't even see them in the sky, you have to be very close to them.
But once you go over that threshold, heavier elements may occur through various processes. Direct fusion of helium into carbon through the triple-alpha process (lithium, beryllium and boron are skipped over as these are not produced inside stars), via a brief helium flashover of intense heat, onward up to probably the carbon-oxygen reaction in the Sun's case at some point, but also some heavier elements as well up to possibly polonium as an isotope of lead through some r-process and s-process nucleosynthesis. But these reactions are forever changing and evolving like waves on the ocean due to the various rates of complex enrichment and decay.
But even with the burning of helium in the core, hydrogen will still likely remain the predominant source of energy in a layer surrounding the core because helium burning produces so much less energy than does hydrogen.
But in either regard, RD, none of us will live to see any of it happen.
And for us, that's a very GOOD thing. 
ReinyDays
Gold Member
No. Let me try to explain a bit. As the heat and pressure at the center of the Sun reach the point of hydrogen fusion, helium is produced. Some of the helium there may be from other, older stars as well. But the Sun does not start to burn the helium until the hydrogen runs out and then the outward pressure drops, the Sun contracts and builds up even greater pressure and heat until it reaches the point of fusing helium. This goes on for several iterations until the star reaches an element it has manufactured where it lacks sufficient heat and pressure to fuse farther.
In the case of a dwarf star like the Sun, it eventually evolves into a red giant, throws off its outer layers as a planetary nebula then cools as a white dwarf.
If the star is massive enough (much bigger than the Sun), as a supergiant, the process continues until iron is reached. No star can burn iron. Iron is so heavy, it takes as much energy to fuse it to heavier elements as the star would get out of it in burning it. At that point all nuclear fusion stops and the star falls in on itself, no longer having the outward radiant pressure to hold itself up.
When that happens, the titanic impact of the giant star collapsing in creates such heat and pressure, there is a supernova explosion and all elements heavier than iron are created there in various quantities and thrown out into space. What is left behind, depending omn the conditions, may be a neutron star, a pulsar, or even a Black Hole.
If anyone really wants to understand it better, you can try reading some of this:
Nucleosynthesis - Wikipedia
Stellar nucleosynthesis - Wikipedia
Stellar evolution - Wikipedia
Just a quick clarification of toobfreak's excellent explanation ... our own Sun isn't massive enough to create the temperatures and pressures for Helium to fuse into larger nuclei ... once the Hydrogen is gone, our Sun will just collapse into a white dwarf ... and very very slowly cool down ...
Well, now you're going into a very complicated area I hoped to avoid as this crap is too deep for social media chat (and boring as hell to most people). Let's just say that for a star below about 40% less mass of the Sun they never reach the heat necessary to go past fusing hydrogen--- that's a red dwarf. These are the most common stars in the universe, very small, very faint and very long lived. They just kind of smolder along like a dull cinder for trillions of years. They are so dim that we don't even see them in the sky, you have to be very close to them.
But once you go over that threshold, heavier elements may occur through various processes. Direct fusion of helium into carbon through the triple-alpha process (lithium, beryllium and boron are skipped over as these are not produced inside stars), via a brief helium flashover of intense heat, onward up to probably the carbon-oxygen reaction in the Sun's case at some point, but also some heavier elements as well up to possibly polonium as an isotope of lead through some r-process and s-process nucleosynthesis. But these reactions are forever changing and evolving like waves on the ocean due to the various rates of complex enrichment and decay.
But even with the burning of helium in the core, hydrogen will still likely remain the predominant source of energy in a layer surrounding the core because helium burning produces so much less energy than does hydrogen.
But in either regard, RD, none of us will live to see any of it happen.
Interesting, thanks for the clarification ... we've two billion years yet, let the insects figure it out ...
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