I didn’t really see this point addressed yet, and feel it’s an essential part of the OP’s question. When fusion starts you do get outwards pressure stopping further gravitational contraction, but this doesn’t equal lower pressure in the core. The radiation from the fusion processes isn’t pushing only outwards, it’s pushing in all directions, so in the core the pressure you lose from having a slightly larger star is compensated by the pressure from having fusion.
Thanks for all the replies!
CanTak3 is thinking my thoughts. O Manuel’s Iron Sun says that our Sol has ordered elements, and an iron core. He postulates our sun had a collapse which shows in the ring around our solar system recently discovered. I agree that the iron collection would continue until all the core is solid iron and then? Seems to me that a strong magnetic field such as discovered in space would be able to restrain an explosion – isnt that what a hydrogen bomb does? Uses a plutonium cover to force the explosion inward? In Sol’s case the energy went all to iron.
See Chandra’s new Cass A picture of ordered elements still layered 300 y after the iron womb birthed the white dwarf now rapidly losing heat. We find new interpretations every day.
The Iron Sun model is, to put it as simply as possible, flat-out completely wrong. Next question?
Personally, I myself do not know enough on this subject, but am a very quick study. As such, it is coming to my attention that everyone whom has posted on this matter is ultimately more correct than I, but the question that lead me here is. What starts the gravitational pull and what is in the very core of a star? These are things that got me thinking, and please correct me if I’m wrong, what if at the very center of a stars core is already is a black hole pulling all the particles together. And while while these particles are being pulled into the black hole they compact side by side fusing together forming a barrier right along the event horizon preventing matter from entering until such matter is too compacted at which point the compacted matter reaches its breaking point and at that very moment caving in on itself. But reading back on what I have just wrote i failed to mention what was going on with the energy emitted by the fusion, so to further that thought, is that it is acting a a relatively weak but potent shaped charge prolonging the amount of time it takes to reach its maximum stress point, or breaking point as earlier stated.
Like I have previously stated, and as my horrendous grammar suggests, everyone on here has gone through more education than I have having only just having been graduated from high school and looking to further my knowledge in science. And I didn’t know what I was supposed to do with the title so if there was something I was supposed to put there I apologize in advance.
It’s an interesting idea. But your shell would have to be rigid and perfectly balanced around the black hole. Can you imagine that happening naturally?
Think of an igloo, which has half a self supporting shell. It stays up because the blocks have flat sides that press against each other, preventing them from sliding. Now replace all the blocks with beach balls. Make the beach balls frictionless. And have them repel each other.
Can you imagine that being stable?
If you now go “Aha! But the forces on the shell I’m thinking of are not like the downward force on the igloo.”, then try thinking of just the top of the igloo, where the downward force is almost exactly the same as an inward force, and then replace the beach balls with ping pong balls, marbles, pinheads, and you’re still billions of billions of spheres away from the number of atoms you need to stack perfectly in your shell, even if it was stable when stacked perfectly.
This. Let me just add that the energy released by fusion gets less and less as the atomic number increases, becoming negative after iron. So an ordinary star cannot continue to generated energy from fusion once the core becomes iron. Moreover, there is so little energy gained in fusing to iron that it all happens quickly, in a day or so. What happens next depends on the mass of the star. A sufficiently massive star will go supernova, a somewhat less massive one will collapse to a neutron star, while an ordinary star will just gradually cool to a dead star.
Important notice! The center of a star consists of zombies. No other replies necessary at this point.
Maybe this was covered, but it seems the one piece of information missing in this discussion is that fusing two hydrogen atoms into a single helium atom releases energy above and beyond the energy from gravitational collapse. This extra energy quickly caused two more fusion reactions, which in turn cause four reactions and we have a chain reaction. As mentioned up-thread we achieve an equilibrium state where gravity is collapsing the star which is balanced by the radiation trying to blow the star up.
Our own sun has a core of helium, surrounded by a shell of hydrogen being converted to helium and then just hydrogen outside that.
Eventually temperatures and pressures build up at the center so that the helium begins to fuse into either carbon or oxygen*, which also releases energy causing a chain reaction. Now we have a carbon/oxygen core surrounded by a shell of helium fusing, a layer of helium, a shell of hydrogen fusing and then just hydrogen …
… layers, like an ogre …
I may be wrong, but I believe this is as far as our own sun will go, as the fuels get used up the sun will become a white dwarf. There’s not enough mass to create the pressures required to start fusing carbon and oxygen into heavier elements.
So, for stars with enough mass, these fusion chain reaction continue in layers until we start making iron. When iron forms the reaction absorbs energy. That’s a very bad thing for the star. We still have the inward pressing gravity, but now we’ve cut the outward radiation pressure, that outbound energy is now being locked up in the iron atoms.
Gravity takes over and the star collapse into itself with such violence we get quite literally all the atoms all fusing all at once becoming a supernova.
Thus to Chronos’ quote, an iron star is not possible as iron is the very seed of destruction for a star.
- = I don’t know exactly why two helium atoms don’t form a beryllium atom, but apparently they don’t. Three helium form carbon, four helium form oxygen.
Naita, thank you for clarifying that for me. I didn’t think of how the atoms had to stack together to do that and the igloo made perfect sense in that regard. But then how is a black hole formed from an exploding star? Is it caused due to it imploding?
And i agree, the sun has zombies in the center and when it becomes a red giant there will be enough space for them to squeeze there way out onto the earth thus every Call of Duty gamer will try to be Rick Grimes. Sadly though I play Call of Duty in my spare time.
I don’t think this is the case. The Sun is currently more homogenous than that, and the core is where the fusion occurs, not a shell around it. You may be describing the structure of a sun-like star that has left the main sequence, such as an orange subgiant like Arcturus.
Yes. It’s not that the explosion creates the black hole, but that both are the result of everything collapsing rapidly inwards. The bits that just keep falling into the middle, and contract so hard gravity overcomes everything become the black hole. The bits that are just suddenly squeezed a smidgen less than that release a lot of energy. (Grossly simplified and possibly not entirely correct.)
I agree fusion occurs throughout the core of our sun, I was simplifying to a large degree trying to get to the good parts …
Sometimes spell-check has a mind of its own? 
Spelting is overratted.
It’s a reference to Shrek. At one point, Shrek tells Donkey that ogres have layers, like an onion (Donkey’s suggestion to instead be like a chocolate cake, which also has layers, is not well-received).
Perhaps I should have said " … layers … like parfait … "
Fascinating.
I even wiki-ed “ogre” to make sure part of their legend wasn’t that ogres really do come in layers & I would just be demonstrating my ignorance by suggesting watchwolf49 meant “onions” but got spell-checked.
I guess instead I’ve demonstrated that I haven’t seen Shrek. Which I haven’t. :smack: