Other sources I have read (e.g. Britannica) say the rapid ejection of matter from a type 2 supernova is due to a shockwave caused by the rapidly contracting outer layers rebounding off the solid iron/neutron core, and nearly all the neutrinos escape without interacting. Is this wrong? Great video series. Thanks!
"When iron core exceeds 1.4 solar mass, the core will collapse & the star will start the supernova process" I think 1.4 solar mass limit is valid for carbon core... Is it valid for iron also? I think for iron it will be lower than 1.4 solar mass. What do u think sir?
By the time the core fills with iron, it will result in a type 2 supernova. The core remnants of such a supernova is typically a neutron start and sometimes a black hole. Only super sized stars with end up with a iron core and a type 2 supernova. The remnants typically will be well over 1.4 solar masses.
Sir, I have seen your many videos. Especially the whole astronomy part. You are one of the best teacher in the whole world. You have cleared my 99% doubts on this topic. I have a small request. I have a very small youtube channel on astronomy. Is it possible to promote my channel on your RUclips page? If possible, if you don't have any problems, then I will send you the link of the channel. If not possible then also thank you sir for this knowledge. Thanks a lot for cleaning my each and every doubt. Sir, Please reply.
The model currently used to describe what happens during a type 2 supernoca (iron core collapse), accounts for about 10% mass/energy loss due to photodisintegration. The vast majority of the energy is used to fuse heavier than iron elements.
NON-DEGENERATE case: (1) Iron core loses energy due to neutrino emission, slowly contracts and heats up (see Kelvin-Helmholtz contraction). Gravitational energy is being spent on both neutrino emission and on heating up. The gamma photons mentioned are in thermal equilibrium with the core, so it is thermal radiation, its energy increases as the core shrinks. (2) When the temperature of the core and of the radiation reaches levels that can destroy iron nuclei, the iron core photo-disintegrates into alpha-particles, loses its adiabatic stability and begins to implode. (Adiabatic index becomes less than 4/3) The temperature rises some more and alpha particles are also proto-disintegrated into nucleons, this further destabilizes the core. Electron gas energy follows the gamma radiation energy and also rises. (3) When electron energy is higher than neutron - proton rest masses, electron capture on protons begins and further destabilizes the core. All in all photodisintegration of iron into helium, photodisintegration of helium into free nucleons, electron capture on protons happen in quick succession and allow the core to rapidly implode. The core implodes, reaches and temporarily exceeds nuclear densities until both neutron degeneracy pressure and strong nuclear repulsion abruptly stops the compression. DEGENERATE case: If the star is a bit lighter, the iron core is produced slower, neutrinos have more time to cool it down so that stage (1) contraction can be paused by degeneracy pressure of the electrons. Degenerate gas is much more tough (or rigid) than Boltzmann gas so that contraction due to neutrino cooling stops and only small contraction from core mass increase is possible. Iron core grows slowly due to Silicon burning layer around it and degenerate gas becomes increasingly more relativistic-degenerate. When the cores mass exceeds ~1.3 M-Solar election capture happens, possibly with or without photodisintegrations of iron and of helium. The core implodes as electron gas disappears from it.
@@MichelvanBiezen i had my exam on this this morning. unfortunately there weren't any questions on this part but it still helped how come you explain this in so much detail but not making it boring :0
I have a question UYscuti as far as we know the larest star in the galexy how big would the syper nova be because the core is so big would it be able to make coalbolt
If the iron core is endothermic, that is, absorbing energy, then wouldn't the core become hotter, rather than cooler? Likewise, if the other layers of fusion are releasing energy, wouldn't they cool the star down?
I wouldn't use the term "endothermic" and "exothermic", which is a term used more for chemical reactions and implies that the heat escapes or enters the reaction very quickly. The heat that is generated in the core of a star stays in the core for a very long time and heats up the core. Consequently when the core begins to fuse iron into the next element, heat is no longer generated but rather heat is absorbed which must come from the core since there is no other place it could come from.
Okay now I'm beginning to see. Now: is heat absorbed rather than generated ONLY because of the excessive heat in the core at that time (when iron is trying to fuse),...or because the nature of fusing iron is in-and-of-itself "endothermic,"...or a combination?
When an element lighter than iron is fused into a heavier element, mass is lost and converted to energy. (E = m c^2). But when iron (or any element heavier than iron) is fused into a heavier element, mass is gained which requires energy (E = m c^2).
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.
Iron is heavier than carbon; why should the Chandrasekar limit for electron degeneracy pressure be the same for both a carbon white dwarf and a SNII iron core?
Chandrasekar limit depends on "Ye" ~ A/Z of the material. Ye ~ 0.5 for Helium, Carbon, Oxygen Ye ~0.4 for Iron and Nickel Chandrasekar limits are ~1.39 M-Solar and ~1.34 M-Solar respectively
Betelgeuse is still a red giant. You can see it every night (when there are no clouds) in the sky as part of the constellation Orion. It still looks very red.
@@MichelvanBiezen ty as well I have been self teaching heliophysics for ten years now just tryin to recover from legionaires to pursue my dream sorry if too enthusiastic
Both are correct. When the white dwarf exceeds the Chandrasakhar limit, the white dwarf collapses. The resulting explosion appears to leave no remnant.
3 hours exam-able lecture summarised well in just less than 10 minutes. THANK YOU SO MUCH!
Fantastic explanation. Thanks!
This is my favorite of this series. Nicely explained.
You're a great lecturer, thorough explanation
Thank you for your comment.
Brilliant!! I finally understand! Thank you so much!
best lecture on type 2 supernova!!! love it
Best of best and simple! Thank you!
I really like your lectures sir! Student from India😇
It's our pleasure
Very clearly explained, thanks :)
Other sources I have read (e.g. Britannica) say the rapid ejection of matter from a type 2 supernova is due to a shockwave caused by the rapidly contracting outer layers rebounding off the solid iron/neutron core, and nearly all the neutrinos escape without interacting. Is this wrong?
Great video series. Thanks!
It is one of the theorized aspects of a type 2 supernova. Neutrinos do escape without interacting.
This is not wrong. The exact mechanism is still up for debate.
Very Wonderful explanation
Excelent lecture.
Fantastic...THANK YOU SO MUCH!
much respect prof
Thank you. Glad you like our videos. 🙂
Excellent explanation.
great video, great lecture
"When iron core exceeds 1.4 solar mass, the core will collapse & the star will start the supernova process"
I think 1.4 solar mass limit is valid for carbon core... Is it valid for iron also?
I think for iron it will be lower than 1.4 solar mass.
What do u think sir?
By the time the core fills with iron, it will result in a type 2 supernova. The core remnants of such a supernova is typically a neutron start and sometimes a black hole. Only super sized stars with end up with a iron core and a type 2 supernova. The remnants typically will be well over 1.4 solar masses.
Sir, I have seen your many videos. Especially the whole astronomy part. You are one of the best teacher in the whole world. You have cleared my 99% doubts on this topic. I have a small request. I have a very small youtube channel on astronomy. Is it possible to promote my channel on your RUclips page?
If possible, if you don't have any problems, then I will send you the link of the channel.
If not possible then also thank you sir for this knowledge. Thanks a lot for cleaning my each and every doubt.
Sir, Please reply.
very good disciption wow good job
Does break down of the electron degeneracy pressure lead to generation of gamma photons and initiationof photodisintegration of iron core?
The model currently used to describe what happens during a type 2 supernoca (iron core collapse), accounts for about 10% mass/energy loss due to photodisintegration. The vast majority of the energy is used to fuse heavier than iron elements.
NON-DEGENERATE case:
(1) Iron core loses energy due to neutrino emission, slowly contracts and heats up (see Kelvin-Helmholtz contraction). Gravitational energy is being spent on both neutrino emission and on heating up.
The gamma photons mentioned are in thermal equilibrium with the core, so it is thermal radiation, its energy increases as the core shrinks.
(2) When the temperature of the core and of the radiation reaches levels that can destroy iron nuclei, the iron core photo-disintegrates into alpha-particles, loses its adiabatic stability and begins to implode. (Adiabatic index becomes less than 4/3)
The temperature rises some more and alpha particles are also proto-disintegrated into nucleons, this further destabilizes the core.
Electron gas energy follows the gamma radiation energy and also rises.
(3) When electron energy is higher than neutron - proton rest masses, electron capture on protons begins and further destabilizes the core.
All in all photodisintegration of iron into helium, photodisintegration of helium into free nucleons, electron capture on protons happen in quick succession and allow the core to rapidly implode.
The core implodes, reaches and temporarily exceeds nuclear densities until both neutron degeneracy pressure and strong nuclear repulsion abruptly stops the compression.
DEGENERATE case:
If the star is a bit lighter, the iron core is produced slower, neutrinos have more time to cool it down so that stage (1) contraction can be paused by degeneracy pressure of the electrons.
Degenerate gas is much more tough (or rigid) than Boltzmann gas so that contraction due to neutrino cooling stops and only small contraction from core mass increase is possible.
Iron core grows slowly due to Silicon burning layer around it and degenerate gas becomes increasingly more relativistic-degenerate.
When the cores mass exceeds ~1.3 M-Solar election capture happens, possibly with or without photodisintegrations of iron and of helium.
The core implodes as electron gas disappears from it.
thank you so much
You're welcome!
@@MichelvanBiezen i had my exam on this this morning. unfortunately there weren't any questions on this part but it still helped how come you explain this in so much detail but not making it boring :0
I have a question UYscuti as far as we know the larest star in the galexy how big would the syper nova be because the core is so big would it be able to make coalbolt
If the iron core is endothermic, that is, absorbing energy, then wouldn't the core become hotter, rather than cooler? Likewise, if the other layers of fusion are releasing energy, wouldn't they cool the star down?
I wouldn't use the term "endothermic" and "exothermic", which is a term used more for chemical reactions and implies that the heat escapes or enters the reaction very quickly. The heat that is generated in the core of a star stays in the core for a very long time and heats up the core. Consequently when the core begins to fuse iron into the next element, heat is no longer generated but rather heat is absorbed which must come from the core since there is no other place it could come from.
Okay now I'm beginning to see. Now: is heat absorbed rather than generated ONLY because of the excessive heat in the core at that time (when iron is trying to fuse),...or because the nature of fusing iron is in-and-of-itself "endothermic,"...or a combination?
When an element lighter than iron is fused into a heavier element, mass is lost and converted to energy. (E = m c^2). But when iron (or any element heavier than iron) is fused into a heavier element, mass is gained which requires energy (E = m c^2).
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.
Iron is heavier than carbon; why should the Chandrasekar limit for electron degeneracy pressure be the same for both a carbon white dwarf and a SNII iron core?
Iron is more dense. The Chandrasekar limit doesn't depend on density, but on the total mass
@@MichelvanBiezen yes, nevermind...I was thinking number density not mass...the number density Is less for iron...
Chandrasekar limit depends on "Ye" ~ A/Z of the material. Ye ~ 0.5 for Helium, Carbon, Oxygen Ye ~0.4 for Iron and Nickel
Chandrasekar limits are ~1.39 M-Solar and ~1.34 M-Solar respectively
So if a red star turns blue what’s that mean
Res starts cannot turn blue. A blue star is a VERY large main sequence star. A red star is either a very small main sequence star or a red giant.
@@MichelvanBiezen well Betelgeuse spelled it wrong but the star that pose to go nova turnt blue
Betelgeuse is still a red giant. You can see it every night (when there are no clouds) in the sky as part of the constellation Orion. It still looks very red.
@@MichelvanBiezen so just a imagery phenomena Ty was verifying some dude has a video of it saying it went supernova is all
@@MichelvanBiezen ty as well I have been self teaching heliophysics for ten years now just tryin to recover from legionaires to pursue my dream sorry if too enthusiastic
My professor took 100 slides to explain it and it wasn't nearly as clear as you said it
Thank you. Glad you found our videos. 🙂
In previous video you said white dwarf explodes WITHOUT core remnant....now you say it collapses inside. Where is the truths ?
Both are correct. When the white dwarf exceeds the Chandrasakhar limit, the white dwarf collapses. The resulting explosion appears to leave no remnant.
@@MichelvanBiezen ok. so, what are conditions for dwarf explosion without core remnant?
When the mass of the white dwarf exceeds 1.4 x mass of the Sun.
shmidereens