great lecture, I'd like to say a few things for you to think about. When you say a star runs out of fuel that's not entirely true. What happens is the core of hydrogen fusion grows outward into a shell as the heavier helium falls into a new core as this happens the core of helium gets larger and the shell of hydrogen fusion expands. In the process of a new helium core being formed it steals heat and energy from the hydrogen shell causing the star itself to expand into a red giant. So as the helium core gets larger the shell of hydrogen fusion expands until the helium core gathers enough density to begin fusion again. When this happens the star stops expanding because now the helium atoms are now sinking into a newly formed core of carbon. So when the helium core stops growing its size and begins falling inward again creating a newly dense core of carbon the expansion of the red giant stops and the star becomes stable again. The same process happens again with each newly formed core of new elements in very high mass stars and like you stated they do this all the way to the element of Iron. This is the point where the heat and energy that the iron core steals from the fusion shells of the lighter elements does not stop even if the iron core gets dense enough to fuse into a heavier element, that fusion process has the same effect it steals energy from the outer shells and as the iron core does this the shells of lighter elements get burned up by the process of the iron core stealing energy from them. If the stars are massive enough they can cause the iron to fuse into more heavier elements but sense this process steals energy from its outer shells they begin to fall inward. So when heat and energy is absorbed by the iron core that in turn makes the stars expansion process from the fusion in the stars shells to weaken so the star begins to shrink. The Super Nova explosion happens from the parts of the iron core fusing into heavier elements like gold and such but as this process happens it constantly is stealing heat and energy from its outer fusion shells causing them to collapse inward tell they are fully absorbed by the fusion of the iron core into heavier elements until there's nothing left of the lighter elements to collapse inward then all that remains is the outer explosion of the iron fusion into heavier elements. It is only the expansion effect of iron fusing into heavier elements that remains and there is nothing left in the outer shells to collapse then inward movement stops and only outward expansion movement remains. This is when the super nova occurs when the core of the star absorbs outer shells and the fusion of the iron into heavier elements is thrown out into space along with any new elements the iron core fused in its short time it had to absorb its outer shells heat and energy until they are completely absorbed then there's nothing that can collapses anymore and all that's left is the outer explosion/expansion of the iron core fusing into these heavier elements. This causes the material to have no where else to go other then outward into space as a super nova explosion. So I believe for a brief moment a star has an iron core and absorbs its outer shells and fuses iron into heavier elements then after all outer shells are absorbed then the fusion explosion of iron into gold and such causes the iron core to explode into a super nova. This is why after a super nova there is no left over dense core that remains after because the brief fusion process of iron into the heavier elements absorbs all of the energy of the stars outer shells tell there's nothing to absorb and hold back the explosion effect from the iron fusion and then creates the super nova. So it makes sense that a stars Iron core can become dense enough to make newly dense heavier element cores within it but because that process absorbs energy these denser cores from iron fusion only last a very brief and short period of time. So I think its not the rebound effect that causes the super nova its the fusion of iron into heavier elements that steals energy from its outer shells until they are fully absorbed and all that remains is the outer explosion of the iron fusion remains that causes the super nova. If there was a rebound effect that we are told happens then there would be some sort of core that would remain that the material thrown out would have bounced off of but after a super nova there is no left over core. This is what makes me believe that this process I explained happens and not the rebound effect we are told that happens. Of course this is all just good guess work and that's all anyone can really speculate on because there is no way to test or experiment a super nova in a lab and all super nova's are so far away that observational evidence is impossible to collect. So this is my best guess on what happens to a star when it becomes a super nova and that's what I wanted to share. I hope this wasn't too long for you to read and I look forward to watching more of your videos. Thanks again!
This is one of the best explanations of this process. Now, can you do a video on the concept of " dredge up" in stars during the asymptotic branch in particular?😃👍
Why don't slightly endothermic Ni(p,γ)Cu or Ni(α,γ)Zn processes happen in heavy stars anytime during Si burn but before core collapse begins? Assume stellar core has gravitational energy to spend, there is more than enough energy to convert significant portion of Fe/Ni core into Cu/Zn. Why this does not happen ? Skip talking abut: - stellar evolution - supernovae - s-,r- processes - Cu & Zn real origin, skip Discovery channel talk, focus on the topic at hand. University level explanation is expected, that uses binding energy, photodissociation rates, Saha equation, nuclear statistical equilibrium e.t.c The core might initially be either degenerate or non-degenerate, address both states.
You stated that the plutonium used in reactors was all created in supernovas but I have always understood that the plutonium that we use is produced in uranium reactors.
Thank you, this video has effectively given me the answers I was looking for the past few days. One thing, though. In the video it is stated that ALL main sequence stars become red giants. Aren't there some low-mass dwarf stars that are fully convective and therefore do not develop a degenerate helium core, meaning they do not become red giants?
They don't. Instead, I think amateur astonomers and automated surveys monitoring for changes first notice the change in brightness, and then astronomers quickly point their big main telescopes at that spot after someone or some automated survey has noticed it. Also, I think sometimes neutrino detectors get a first indication that a supernova happened and about where, and other astronomers go looking for it.
It will become a white dwarf. Our Sun isn't massive enough to become a supernova. I think stars that are over 8 times more massive than the Sun will go supernova :)
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great lecture, I'd like to say a few things for you to think about. When you say a star runs out of fuel that's not entirely true. What happens is the core of hydrogen fusion grows outward into a shell as the heavier helium falls into a new core as this happens the core of helium gets larger and the shell of hydrogen fusion expands. In the process of a new helium core being formed it steals heat and energy from the hydrogen shell causing the star itself to expand into a red giant. So as the helium core gets larger the shell of hydrogen fusion expands until the helium core gathers enough density to begin fusion again. When this happens the star stops expanding because now the helium atoms are now sinking into a newly formed core of carbon. So when the helium core stops growing its size and begins falling inward again creating a newly dense core of carbon the expansion of the red giant stops and the star becomes stable again. The same process happens again with each newly formed core of new elements in very high mass stars and like you stated they do this all the way to the element of Iron. This is the point where the heat and energy that the iron core steals from the fusion shells of the lighter elements does not stop even if the iron core gets dense enough to fuse into a heavier element, that fusion process has the same effect it steals energy from the outer shells and as the iron core does this the shells of lighter elements get burned up by the process of the iron core stealing energy from them. If the stars are massive enough they can cause the iron to fuse into more heavier elements but sense this process steals energy from its outer shells they begin to fall inward. So when heat and energy is absorbed by the iron core that in turn makes the stars expansion process from the fusion in the stars shells to weaken so the star begins to shrink. The Super Nova explosion happens from the parts of the iron core fusing into heavier elements like gold and such but as this process happens it constantly is stealing heat and energy from its outer fusion shells causing them to collapse inward tell they are fully absorbed by the fusion of the iron core into heavier elements until there's nothing left of the lighter elements to collapse inward then all that remains is the outer explosion of the iron fusion into heavier elements. It is only the expansion effect of iron fusing into heavier elements that remains and there is nothing left in the outer shells to collapse then inward movement stops and only outward expansion movement remains. This is when the super nova occurs when the core of the star absorbs outer shells and the fusion of the iron into heavier elements is thrown out into space along with any new elements the iron core fused in its short time it had to absorb its outer shells heat and energy until they are completely absorbed then there's nothing that can collapses anymore and all that's left is the outer explosion/expansion of the iron core fusing into these heavier elements. This causes the material to have no where else to go other then outward into space as a super nova explosion. So I believe for a brief moment a star has an iron core and absorbs its outer shells and fuses iron into heavier elements then after all outer shells are absorbed then the fusion explosion of iron into gold and such causes the iron core to explode into a super nova. This is why after a super nova there is no left over dense core that remains after because the brief fusion process of iron into the heavier elements absorbs all of the energy of the stars outer shells tell there's nothing to absorb and hold back the explosion effect from the iron fusion and then creates the super nova. So it makes sense that a stars Iron core can become dense enough to make newly dense heavier element cores within it but because that process absorbs energy these denser cores from iron fusion only last a very brief and short period of time. So I think its not the rebound effect that causes the super nova its the fusion of iron into heavier elements that steals energy from its outer shells until they are fully absorbed and all that remains is the outer explosion of the iron fusion remains that causes the super nova. If there was a rebound effect that we are told happens then there would be some sort of core that would remain that the material thrown out would have bounced off of but after a super nova there is no left over core. This is what makes me believe that this process I explained happens and not the rebound effect we are told that happens. Of course this is all just good guess work and that's all anyone can really speculate on because there is no way to test or experiment a super nova in a lab and all super nova's are so far away that observational evidence is impossible to collect. So this is my best guess on what happens to a star when it becomes a super nova and that's what I wanted to share. I hope this wasn't too long for you to read and I look forward to watching more of your videos. Thanks again!
This is one of the best explanations of this process. Now, can you do a video on the concept of " dredge up" in stars during the asymptotic branch in particular?😃👍
Why don't slightly endothermic Ni(p,γ)Cu or Ni(α,γ)Zn processes happen in heavy stars anytime during Si burn but before core collapse begins?
Assume stellar core has gravitational energy to spend, there is more than enough energy to convert significant portion of Fe/Ni core into Cu/Zn. Why this does not happen ?
Skip talking abut:
- stellar evolution
- supernovae
- s-,r- processes
- Cu & Zn real origin,
skip Discovery channel talk, focus on the topic at hand.
University level explanation is expected, that uses binding energy, photodissociation rates, Saha equation, nuclear statistical equilibrium e.t.c
The core might initially be either degenerate or non-degenerate, address both states.
You stated that the plutonium used in reactors was all created in supernovas but I have always understood that the plutonium that we use is produced in uranium reactors.
Plutonium is man made and does not occur in nature - everything above Uranium 92 is the same.
Wonderfully explained Madam .Thank You.
Excellent lecture! I hate to be picky, but I'm pretty sure that's the Helix Nebula pictured, not the Ring Nebula.
great video. thanks!
Wait...why low mass stars expands...😅
Great explanation.
Thank you, this video has effectively given me the answers I was looking for the past few days. One thing, though. In the video it is stated that ALL main sequence stars become red giants. Aren't there some low-mass dwarf stars that are fully convective and therefore do not develop a degenerate helium core, meaning they do not become red giants?
+Mathias Claessen yes i think below 0.4 Msun stars just keep on burning for a trillion years and never end up becoming giants
@@TheFloydios
Stars don't "burn".
Burning is an oxidative process.
Introductory lecture. Many details are left out.
Supernovae probably cannot be predicted, but how do astronomers know when and where to look for them?
They don't. Instead, I think amateur astonomers and automated surveys monitoring for changes first notice the change in brightness, and then astronomers quickly point their big main telescopes at that spot after someone or some automated survey has noticed it. Also, I think sometimes neutrino detectors get a first indication that a supernova happened and about where, and other astronomers go looking for it.
What will happen to the Sun when its' time is up? Will it die like any other star or evolve? Has it happened before?
Thank you
astrophysics without the math - how awesome is that?
not that awesome sadly
Does the mass of the star decrease during planetary nebula because the outer layers are ejected or because the core contracts?
who else is here for SEES?
Gonzalez Mary Harris Nancy Thomas Brenda
does this lecture cover the lane-emden equation?
Will our sun become a white dwarf or a supernova? Why? -Steven
It will become a white dwarf. Our Sun isn't massive enough to become a supernova. I think stars that are over 8 times more massive than the Sun will go supernova :)
have we seen a star similar to the sun become a white dwarf?
+Iron Osiris Sirius B
- via YTPak(.com)
yes
What is the most common type of star?
+Iron Osiris Brown dwarves aren't as common as yellow dwarves.
+Ojas Nain I was under the impression that the number of brown dwarves isn't agreed upon at the moment because they're so difficult to detect.
OK. Thanks for replying :)
The most common stars are low mass stars with masses