I've been WRONG about Supernovas my Entire Career

Massive stars end their existence in a blaze of glory called a supernova. What are those last moments like? And why does it end in a supernova?
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TIME CODES
00:00 Intro
00:29 Which stars end with a supernova?
02:08 Stellar Core Structure
03:50 Nuclear Binding Energy
05:55 Exothermic vs Endothermic Fusion
06:26 The Final Moments
07:36 Photodisintegration
08:16 Why a supernova though?
09:36 Supporter Shoutouts
09:54 Featured Comment
10:13 Surprise Surprise!

[@LetsTakeWalk]

When a star goes supernova, most of the energy released goes into neutrinos. In normal circumstances, neutrinos just pass through everything without influence. But the amount of neutrinos produced during supernova is so large, that the tiny influence neutrinos have does add up. This means if there is a planet orbiting the star, it would vaporize BEFORE the light of supernova hits it, because neutrinos get a head start (the neutrino shockwave bounces off the created neutron star and phases through all the layers of the star, unlike the light, that gets trapped in the star until the explosion finally disintegrates the star).

[@ScienceAsylum]

Devastatingly accurate.

[@hurmzz]

So, you wouldn’t actually be able to see the sun going supernova as a final moment? That’s a sad detail..

[@b.s.7693]

These freakin neutrinos...

[@LetsTakeWalk]

@@hurmzzEven if there was no neutrino shockwave, the light shockwave would instantly vaporize you as well, so you would never see it coming in either case.

[@Andy__A]

Didn't JWST find planets orbiting what seems like post-supernova stars? These planets might have been far enough (I think it was described like a Jupiter orbit) for ultra dense neutrinos stream to dissipate, however, still mindboggling

[@AlexBesogonov]

Another couple of facts: 1. When the core begins to collapse, apparently for a few seconds there's enough pressure from _neutrinos_ to stop the upper layers from falling in. It's a literal Willy E Coyote moment, where the star needs a couple of seconds to understand that it's collapsing. 2. The main energy source for the explosion is good old gravitational potential energy, released when the core (itself the size of a small star) collapses into a ball just 2-4 kilometers in diameter.

[@hanifarroisimukhlis5989]

🤔Can it be used to measure neutrino mass?

[@phdnk]

I agree on the second and disagree on the first.

[@MichaelGrundler]

Yeah, I was waiting for the second part to be mentioned in the video. As far as I remember when the core collapses all the outer layers fall down, collide with the core, bounce back and collide with the subsequent layers that come rushing in. That collision ramps up fusion again with enough energy to create all (or most) of the heavier elements and distribute them throughout the interstellar medium. I might be wrong about some of the details, though. It's been almost 20 years since the first time I learned about this.

[@denysvlasenko1865]

The core is ~10000km in diameter. It collapses to ~20km diameter. It takes approximately one second. The released potential gravitational energy is about 20% of rest mass of the collapsed core and it heats the core to insane temperatures in excess of 100 BILLION kelvins. With temperatures like this, the collapsed core shines with about 10 billion solar luminosities ... per square meter. The core is transparent to neutrinos. Only after collapse, and only central, the densest region of newly born proto-neutron star, is not transparent to them (and to anything else). Neutrinos still have the longest, by far, free mean path, and therefore they are the main mechanism of energy transfer in the interior, up to the layer (still inside PNS) where density falls to "low" enough values where neutrino mean free path is larger than the star radius, and neutrinos escape. This surface is called "neutrinosphere", analogous with photosphere of a star, where photons escape because the star above them is transparent to photons. The layers of the star above the ~10000km core region mostly don't have any time to noticeably react to what just happened under them. Then, a shockwave from the PNS arrives and sends the upper layers of the star flying outwards. At this temperatures, shockwaves are so strong that they not only make plasma they traverse through heat up and glow (stronger than it was glowing before), no - *most* of shock energy is not in kinetic energy of motion of plasma particles, but in the "light", in the generated photons from plasma heating. (Such strong shocks are called Marshak waves). Since we know from observations that supernova's light is fueled by radioactive decays of Fe/Ni isotopes in ejecta, it means that shockwave is strong enough to heat the star material to ~ 7 billion kelvins, at which temperature the thermonuclear burn mostly converts all lighter elements to iron group nuclei.

[@phdnk]

@@denysvlasenko1865I heard that that Marshak wave photodisintegrates all heavy nuclei in its path and thus loses energy and stalls.

[@OmateYayami]

08:54 "to make matters worse" used in the context of matter transmutation and gravity collapse was phenomenally puntastic!

[@grumpypurplesloth7950]

That one went totally over my head. That...was really good lol

[@Wise4HarvestTime]

It takes someone who thinks in puns all day to notice his statement was a pun

[@OmateYayami]

​@@Wise4HarvestTimeguilty as charged

[@1TakoyakiStore]

I find it hilarious that as soon as a star's fusion goes from the thousand year carbon fusion to the 1 year Neon fusion the products are literally "O, Mg." 😂

[@renezirkel]

So many interesting graphs within the video. I had to stop serveral times, just to appreciate the graphs. But thanks, never seen of these graphs before. Great video.

[@ScienceAsylum]

Thanks! I recently learned how to import massive amounts of data into After Effects and took advantage.

[@tradtke101]

I always try to plug Jason Kendall's channel. He's an astronomy professor and has an incredible lecture series that deserves more recognition. I specifically recall seeing this binding energy graph on his videos on stellar life cycles. Check him out if you'd like more on this subject! And Nick, I think you'd like his stuff too. He is currently re-tooling his channel/lecture series to be more YT/algorithm friendly. But I think his lectures are one of the best hidden gems on the platform.

[@richardlandrum1966]

"Some stars burn out and die, bigger stars burnout and die with PASSION" -Bill Wurtz

[@coloripple]

_Even Crayyyzier space dust_

[@AmateurTP]

Guy sensei

[@IroAppe]

"Brown dwarfs, failed stars that are a HUGE disappointment to their moms." - Kurzgesagt

[@IroAppe]

"But we want to talk about stars, not failed wannabe stars, so let's move on." - Kurzgesagt

[@SpenceReam]

We call these stars “anthropomorphic stars”…🧐

[@evanbasnaw]

Great explanation of those stages in a simple enough way for the casual science enthusiast.

[@Jackiee_Chann]

Always glad to see another awesome video from you! Thanks for all the work you put into your videos

[@ScienceAsylum]

Glad you like them and thanks for the support!

[@john_michael_white]

I love seeing a video about something I very well understand....and find that I didn't understand it as well as I thought I did! Great work!

[@Ikbeneengeit]

These videos look simple but they are always still correct and not oversimplified. Great one.

[@ScienceAsylum]

Thanks for appreciating the research and planning that goes into these videos.

[@victormendoza_6]

The more videos from you I watch, the more I enjoy the way you make them❤

[@ScienceAsylum]

Thanks! I'm glad I'm growing on you 🤓

[@johannaverplank4858]

I’ve always found it interesting that we speak of stars living and dying, as if they’re alive. I prefer to think of them as changing into something else. It’s how we are here. It’s quite beautiful. As always, you help me understand complicated topics in a new way. Thanks!

[@ScienceAsylum]

We do that a lot with inanimate objects. Our phones are a good example. I'm not sure what the commonality is between all the examples of it.

[@WisdomShark]

@@ScienceAsylum My guess is that there's a significant drop in the apparently continuous activity in its previous state versus the new state. Fires, phones, and stars are all said to "die" when they look like they've "stopped." The same could be said for something like waterfalls when they dry up, but that process is too gradual of a change for it to register the same way for most people.

[@marcoasturias8520]

Life is a system that tries to not reach equilibrium, so life is a natural metaphor for other systems like it.

[@tradtke101]

Paging Mufasa for a heavy-handed metaphor about antelope and grass.

[@XL-5117]

Hmm, never thought about a phone as a living thing 🧐 I can see a star as living because of the processes it generates to stay ‘alive’ and that it generates heat, like living things (that in turn get their life force from the star).

[@AvangionQ]

Having to unlearn and relearn advances our understanding.

[@nigeldepledge3790]

Perhaps the best science channel on KZbin. Your explanations are always clear and concise, even when dealing with mind-boggling stuff like quantum mechanics or supernovae.

[@florian2442]

"I was trying to give you the day off" 😂😂 I love how you present your videos

[@Adrian-yz7oe]

Man!! This channel's quality is skyrocketing!!!

[@macronencer]

I love it that seconds after talking about good band names you showed us the star's sequence doing a "Nickel-back".

[@DezzieYT]

I enjoy watching your channel and PBS Space Time. You compliment each other giving both depth and easier to wrap my brain around analogies to these topics.

[@rtt1961]

The more chill presentation is greatly appreciated.

[@AhhZrulz]

I always heard it stops at iron. I am going to have to look into it more.

[@RedRocket4000]

The process that starts breaking atoms apart I think is what was missed when we came up with the Iron part as little of the higher stuff survives instead decaying lower. But this just the heaviest fused elements Iron still has it's role as not contributing any energy to help the Star not collapse so there is no significant Iron Fusioning period in the star Collapse the Star Collapses when it would start doing Iron if that were possible. So Iron not causing the collapse but neither is it helping prevent it.

[@angelcarriazoventura1270]

thank you Nick. never stop making videos

[@IndranilBiswas_]

Great video! Many videos talk about stellar nucleosynthesis but this video did awesome! I found out that the transition from collapsing star to neutron star is quick. Good for the poor dying star.

[@techjunky82]

I have been telling a lie for so long. I can’t believe FE isn’t the end. 😭

[@ScienceAsylum]

The iron thing is a very ingrained misconception that keeps being taught over and over again across generations.

[@markkettlewell7441]

@@ScienceAsylumBut why is it still being taught Nick? It’s annoying that we were taught this. When I was taught this I asked ‘why’ is iron the star killer. I was told simply that it was.

[@fir3w4lk3r]

1. Please tell the story of a new born star. What happens when the fusion starts for the first time. Is it violent? 2. Isn't a supernova explosion the rebound of the outer layers to the core due to gravity winning?

[@Eoraph]

I am too still confused about the actual mechanism of the boom. The lead up was excellently explained though.

[@davidcroft95]

Yes, the outer layers after collapsing they rebound on the (almost) impenetrable nucleus. Fun fact: some stars (the nucleus actually) are so massive that they dissipate all the energy of the oncoming layers and collapse in black hole w\out the supernova The first nuclear fusion is not quite violent, it changes the internal structure but nothing really happened on the outside (in fact at that stage the star is not considered born yet, they will wipe out the pre-stellar cloud "only" a few milions of years later)

[@snowthemegaabsol6819]

When the stellar core becomes so crushed that the electrons and protons combine, this forms neutrons and neutrinos. The neutrons stay put, but the high energy neutrinos are so light that they get flung away at an extremely high fraction of the speed of light. The sheer amount of them flying against the outer layers of the stellar core create a titanic shockwave that pushes those layers outward

[@macronencer]

It's outrageous that you don't have a million subs yet. I love your videos :) Very educational... and yes, I was under that same misapprehension about iron. Interesting!

[@hurmzz]

So to be clear; the ‘onion’ model showes the different layer of fusion, not elements in the star. As the Silicium at the core is still fusing with Helium, Helium (and all the other elements present too?) are still flowing through the whole star, right?

[@ScienceAsylum]

*"The ‘onion’ model shows the different layers of fusion, not elements in the star."* Yes, that's correct. The labels are the type of fusion occurring in those regions. The elements are all over the place. *"Helium (and all the other elements present too?) are still flowing through the whole star, right?"* Correct. There are higher _concentrations_ of the fusion products in those onion layers than in the rest of the star, but the elements are generally everywhere.

[@bpz8175]

@@ScienceAsylum The elements might be everywhere, but I'm pretty sure there isn't a significant outflow of fusion products to the whole star (ie outer layers). That would mean any star can cycle fuel from the outer layers into the core, which IIRC only low-mass red dwarf stars are capable of (contributing to their extreme lifespans).

[@shanent5793]

The silicon is burnt through a combination of photo-disintegration and alpha capture. The alpha (or helium) particles present in the core come from photo-disintegration, helium does not get exchanged with the envelope (outside the core). Once carbon burning starts, there's only a couple thousand years left so there isn't enough time for the heavier elements to mix with the rest of the star so the core becomes disconnected and evolves on its own. The layers in the onion represent layers of elements. The fusion generally only continues when lower layers deplete their fuel for that stage which allows the core to contract and reignite fusion between the layers and at the center. Depending on the initial mass and composition of the star a layer can convect but generally the elements aren't mixing except at the burning interfaces

[@ScienceAsylum]

@@bpz8175 Yes, stars _can_ cycle material, but only if there's a convection zone near the core. Some stars have radiation zone near the core instead, which prevents them from cycling material.

[@MurderMostFowl]

The “creation” of elements as products of fusion has always fascinated me. If I’m not mistaken, this is where all these elements come from. So that our entire planet ( and all planets ) is a byproduct of billions of years of super novae.

[@RedRocket4000]

Not exactly that an old theory shot down by Supernova not generating anywhere close to what we expected they would do. Then we actually got to monitor a collision of two Neutron Stars, I think from gravity wave detectors to point everything else right way. This collision produced massive amounts of everything on the higher part of the table. So it now Neutron Star collisions considered the biggest source of heavy elements.

[@stevengeorges9046]

This is the best explanation on this subject I've ever seen. Nice job!!! 👍🏼👍🏼

[@ScienceAsylum]

Thanks!!

[@HugoFilho.]

I think that stars don't make significant amounts of Fe56 and elements heavier than that before the supernova is because adding He4 to Si28 will only create nuclei with equal and even number of protons and neutrons, and out of those nuclei Ni56 is the most stable.

[@davidgroll-cook7125]

Very cool, thanks for sharing this, learned something new today Love your channel

[@FewVidsJustComments]

Thank you for informing me why fusion is forced to stop when fusion reaches its limit. I had learned that it was because "Iron absorbs energy" or whatever, but that answer wasnt satisfying enough for me. Hearing you explain that "electrons are breaking atoms apart instead of supporting the star" is much better. You should really consider becoming a science teacher someday, I'm sure your students would love learning from you. I know I certianly would! :D

[@carlosvigil1868]

5:15 "stelar cores are hot... xD" hahaha this episode should be called: "the dark secrets of a supernova... the glory core" xD haha great video!!! Keep going!!!

[@simonrobbins815]

This is an excellent video, so much packed into a short video and really well explained. Thanks!

[@ScienceAsylum]

Glad you enjoyed it! 🤓

[@GWAIHIRKV]

What a great explanation. Thanks.

[@PieterPatrick]

I still learn from your channel. Thanks.

[@KeithCooper-Albuquerque]

Excellent video, NIck!

[@SiddharthSingh-hx1bp]

Nice analogy with the ditch animation. Your content is amazing, as always 👏🏻👌🏻✨️

[@ScienceAsylum]

Thank you so much for the support!

[@hexramdass2644]

thank you, wonderful to learn the details of giant explosions

[@MarcoRoepers]

Thank you very much for this more detailed explanation.

[@ScienceAsylum]

You're welcome! It was so much work.

[@eroraf8637]

Funny thing is, this still doesn’t even scratch the surface of how complex supernovae actually are, or how hard it was to actually figure out how to make a star explode in a 3D model. There’s whole graduate courses worth of history and nitty-gritty details you could dive into if you have a few years to spare.

[@SlimThrull]

6:00 Thank you! I'd been confused on how this process works for years. It made no sense that it just "stopped at iron". But now it makes complete sense. (Or nickel as it turns out.)

[@TheLonemango]

Another great video! I would love to see one where you compare and contrast nova verse supernova.

[@davidcroft95]

List of fun fact incoming! (astrophysics student approved) -- in the later stages the nucleus evolves so fast that outer layers can't adjust in time, so they actually freeze their structure and observable quantity (like luminosity, color, etc) -- nickel-56 decades in iron-52 via a "double beta decadement" (it emits 2 electrons at the same time instead of 1, nuclear energy reasons) -- (a lil bit technical one) the photo-disintegration happens when a photon of energy about 215 kEv (kilo electronvolt) hit a iron nucleus and destroys it in 13 alpha particles and 4 neutrons -- neutrinos are really important for the thermodynamic of the star, especially in the stages where nuclear fusions are not active (red giant & asymptotic giant phases) when they remove so much energy from the core it actually cools down! -- neutrinos interact weakly with mass, but in the last stages the densities are so high that they form an atmosphere around (inside?) the nucleus! (but it dissipates quickly tho) -- (now the best one) some stars are so massive they actually collapse in BH w\out going supernova! (if I remember correctly it is when M>200 in solar masses)

[@mkardigen]

This is a great video! Thanks Nick!

[@ScienceAsylum]

You're welcome! Glad you liked it.

[@stefaniasmanio5857]

Thank you so much!!❤❤❤❤

[@Waccoon]

I've always been facilitated with the concept of supernovae, and for a while was searching for visual computer simulations of the collapse. One thing that's never been made clear is just how fast/sudden the process is. Does the star collapse within a matter of hours, minutes, or seconds? Most articles talk in astronomical time scales, and thus may say something like, "Fusion takes place over millions of years, and the star explodes almost in an instant." It's hard to understand if that's meant to be taken literally or not! Anyway, once again, I'd like to say that your channel is probably my favorite science fix on KZbin. Thank you! 8)

[@shanent5793]

The inner core collapses on the order of ten milliseconds. The outer core falling inwards can trap neutrinos for three to ten seconds. The resulting shock wave then takes hours or days to reach the surface of the star and create the first visible and X-ray pulse. Note that the entire star does not collapse, only the core does so.

[@olampros321]

You stoped early. Can you explain what exactly happens in the last milliseconds and why or how could a star emit so much energy? Great video by the way! Is the best I have seen for supernova. Please do a part II.

[@LtShifty]

Thank you for your hard work👏

[@JAYMOAP]

Keep up the good work

[@xoiyoub]

Your videos have improved in quality over time, I like them.a lot now

[@ScienceAsylum]

Thanks! Glad you like them. They're a labor of love.

[@TheGamePhilter]

I love that this man is still making these excellent videos.

[@ScienceAsylum]

I love that I'm making them too 😉

[@SSMLivingPictures]

New SA and Im HERE for it!!!!!!

[@turingmachine4617]

Literally a millisecond before you said it, I thought, “wow, cool band name”

[@ScienceAsylum]

🤘

[@notillusion193]

Great Videos. Love your channel. Can you make one about how larger Atoms that are further down the Periodic Table are created?

[@ScienceAsylum]

Already on the list 👍

[@mikebauer6917]

Loved this one in particular.

[@ScienceAsylum]

Thanks! I'm glad you liked it. It was so much more work than I thought it would be.

[@sirjaroid4725]

i've always wondered what exactly happens

[@artificercreator]

Oh thanks so much for the cool video! It is a blast to learn science!

[@simo9445tsns]

Great video, thanks

[@HaraldMacGerhard]

wow Nick, again you made landmark video, and thanks for showing off that onion layer model of different layered fusion processes, way cool! 🤩 Just one thing I never understood, is there any way from the outside to understand in which stage of fusion a star is? Ref: Betelguise I reckon the answer is no 😥

[@takashitamagawa5881]

Excellent video describing the processes that create a Type II supernova. There are also the famous Type Ia supernovae which occur when carbon-rich white dwarf stars undergo a fusion detonation under circumstances that are not yet fully determined and which leave behind no core remnant.

[@ScienceAsylum]

Type 1a's are a _whole_ different video.

[@adb012]

@@ScienceAsylum ... Type 1a is a totally different kind of supernova. Altogether. (And don't call me Shirley)

[@AroundUsGreenWorld]

Great explanation. Thanks

[@ScienceAsylum]

You're welcome!

[@BuzzBizzYou]

After watching, still had a sense of incompleteness because there seems to be an abrupt transition from "Shapeshifting" to "Kaboom'. Spent 3 minutes of extensive and indepth research to understand :) Correct me if I am wrong, I am not a physicist 1. Larger and heavier cores are being formed due to fusion 2. The core maintains it's "size" due to continuous energy production /fusion 3. If the core becomes too large, it "gives up", and gravity overpowers 4. Core collapsed, meaning it just rapidly starts shrinking in size. 5. Just like in cartoons, the "earth" under the outer layers disappears, so everything starts rushing to the center at up to 0.25c. outer layer material is now speeding up towards the core 6. At some point some of the outer layer material bounces back, and some of it starts fusing producing even more energy 7. "Kaboom" outwards Did I understand it right? Again, not a physicist, but really curious

[@LendriMujina]

It's little wonder why supernovas are one of the only things that can create a black hole; even a little bit of the outward force is enough to destroy planets effortlessly, and every action has an equal and opposite reaction. The amount of _inward_ force - and all of it in one place, not just catching a small portion while the rest escapes elsewhere like with the explosion - is simply unimaginable.

[@csdn4483]

One note on the binding energy curve, it's a bit more pronounced than what was shown. The overall binding energy curve is what is used also for predicting the amount of energy release in fission. With Hydrogen and Helium fusion, you get 5 to 10 MeV per interaction whereas with Uranium fission, you get around 200 MeV per interaction. However, the thing to realize is you have a lot more fusion reactions going on from fission reactions which leads to fusion being able to produce more energy on the whole. Another aspect that is missed here is that fusion in a star does not go directly from hydrogen to helium, it first has to go through the intermediary stages of isotope production. First two protons (protium) will fuse and one of the protons will decay into a neutron and the whole then becomes deuterium (still hydrogen). It is once you have the deuterium that you will see the hydrogen then fuse into helium 3 or helium 4 depending on if you have a protium and deuterium fuse or two deuterium fuse.

[@AnarchoReptiloidUa]

Great educating video👍 A comment to support this video and channel. ❤❤❤

[@ScienceAsylum]

Thanks for the engagement!

[@wedot1]

I feel like this video needs to be a little longer. I enjoyed it

[@kobrakalle6930]

Where can I get those eye brows that make a sound when I raise 'em? ;) Great video once again. Thank you so much ❤ Oh and is cherenkov radiation actually also emitted within stars? If so, what's the share of all energy that is emitted?

[@kobrakalle6930]

I just thought if it happens in very dense mediums like water it could also be the case in less dense mediums such as plasma but probably at smaller scale.

[@CT-pi2gl]

What would be super cool is finishing off the long hill/ditch illustration with an incredibly deep ditch with steep mountains on each side, representing the transition to neutron matter.

[@petergreen5337]

❤thank you very much ESPECIALLY about IRON

[@lechatrelou6393]

"These massive stars begin their libes calm, but end in a panic." I never thought I would relate to 8 or more solar masses stars

[@nugboy420]

4:42 out of contexts seems like it hurts

[@AlleyKatt]

I love having to unlearn stuff. Call me crazy but it feels like the best form of learning. Excellent video, as always. Glad you & Awesome Em took the time to get it right.

[@danfg7215]

8:13 "Catastrophic failure is imminent", oh what a wasted opportunity for a klaxon and some red lights 🚨🚨

[@ScienceAsylum]

Yep. Dang it.

[@danfg7215]

🤣🤣 btw the classic callbacks are hilarious, love your content!

[@SmogandBlack]

Fantastic video 😊.

[@ScienceAsylum]

Thanks!

[@74jparralel38]

Yay new video

[@eritronc]

Thank you nick!!!

[@ScienceAsylum]

You're welcome!

[@MediaWML]

Thank you for clearing some things up. I have always been fascinated by stellar evolution but watching videos about the end of massive stars has always been a little confusing. Some videos seem to state that a star is doomed once iron is formed (e.g. silicon burning), whereas some state that it is when iron itself is fused and most videos are simply ambiguous. Even reading papers on the subject (admittedly only free to access ones) has not always been clear. A lot of literature uses ambiguous terms (at least in my opinion) such as "This fusion cycle continues until you get to iron". But what does that mean?? Great video as always. Thank you.

[@jamesleatherwood5125]

yay!!!! NEW VIDEO!!!!!

[@_ninthRing_]

I've often wondered why an igniting proto-star often blasts away so much of the gaseous part of the proto-planetary disc (which later condenses, becoming the Oort cloud) when it ignites & now you've supplied me with the answer. It's because the star hasn't yet accumulated sufficient mass to counter the outward force from the initial fusion pressure, and this only stops when Hydrostatic Equilibrium is reached.

[@claude_in_Cincinnati]

Yooooo, Nick is actually a really great actor. 1:03, check out his reaction to his clone (who you know is also him, so you know he was reacting to a tennis ball or nothing). I honestly had to pause and say how much I like this guy. Been watching for years. Thank you Nick!

[@frodobolson213]

Hi :D, could you made another video explaining the hole supernova step by step? Thank you ☺️☺️

[@Primeagen]

Whenever I watch this channel, I want to watch all day. And my seniors in computer science department says how anybody could have "hobby" watching physics videos on youtube

[@stapler942]

I love how the fusion products of Neon are "O, Mg" and part of the list for Silicon is one more S away from spelling out "Sarcastic" (S, Ar, Ca, Ti, Cr, Fe, Ni).

[@frederf3227]

I've always wondered how much fusion can/does happen even when below the typical masses for such temperatures. Since temperature is a distribution of velocities and not an every-particle-exactly-at-average there must be some fusion events for sub fusion mass stars. Of course on average the events don't go critical like a supercritical mass star but with the Boltzman high energy tail plus probabilistic quantum tunneling it must be non zero. Do these events have any practical meaning or is the changeover at certain masses so "sharp" that you can treat it like a binary threshold?

[@dibenp]

Enjoyed this on Nebula, but I came here to leave this comment because it’s OK to be a little crazy. 😂

[@denischarette-de3te]

Interesting video as usual. I just became aware that the fusion, layer after layer, is always with helium nuclei. I look forward to a possible video explaining what happens after the formation of nickel, the explosion and the formation of neutrons. I see the explosion as a repulsion caused by the electromagnetic interaction between the nuclei, up to uranium, formed by the fusion of the nuclei of all the layers during the collapse.

[@phdnk]

please get an expert review so that there would be no misinformation

[@NotKnafo]

i have an unrelated question about the cmb how do we know its the oldest light in the universe and not just light emitted from interstellar mass?

[@astrophyz]

Hey! Would you mind if I used some of your imagery and animations in my outreach for a talk on star lives?

[@ScienceAsylum]

Email me at [e-mail] so I can get more info 🙂

[@TerranIV]

Very cool info! That is really interesting that it is actually Ni56 not Fe56 that is the end of the line!!!

[@allannirvana]

Nick, have you played mass effect trilogy before? You should try it. It has one mission where you investigate a sun that goes into the supernova stage early and you have to dodge the sunlight. Fascinating stuff.

[@morryDad]

Do a video on how the other elements are made next please

[@soumajitsen1395]

Awesome video as always, Nick! Just a question, why does the nuclear binding energy curve go up after helium nuclei formation? Is it because Helium's a bit too stable? Sorry, I don't know much beyond early high school science.

[@ScienceAsylum]

That random spike after Helium is Lithium. Stars basically skip over it.

[@sarbanisarkar8748]

Just like the sun will be a red giant twice(RGB and AGB), higher mass stars can be a red (super)giant 3-4 times, with the last few phases happening too quickly for the star to contract.

[@quangobaud]

I've learnt a lot from this video and from the commenters. Didn't know about nickel being one end point. Didn't know about the neutrino shock wave (as mentioned by a commenter (whose comment I have liked)). I'm going to have to re-research and re-write a few things.

[@Primeagen]

I was repeating hot-hot before you and you are doing this 5:14.

[@AwTickStick]

It’s always great to learn something new. I thought Iron was the end of the road but it turns out it’s a bit more complicated than I previously thought.

[@ScienceAsylum]

"But it turns out it’s a bit more complicated than I previously thought" is a pretty common thing to say in science education (especially physics) 👍

[@Eoraph]

I wish you went more into detail about between the star stopping to be able to generate energy and going boom. That one sentence about photons was too rushed for me. How does it turn into the neutron star and why the shockwave? On the other hand all the information before i already knew for the most part. Hence i am somewhat disappointed that for another time, the part about supernovas that I don't understand well enough for my liking gets once again glanced over. The video title made me believe that i finally get to close that gap in my knowledge. Elsewise the video was as always informative and fun to watch. Thanks for making it. Edit: added questions after rewatching

[@ScienceAsylum]

*"How does it turn into the neutron star?"* That's a whole other video with some quantum physics. *"And why the shockwave?"* Once the neutron star surface forms, it prevents further collapse. The in-falling material rebounds. *"That one sentence about photons was too rushed for me."* You mean the photodisintegration? Most of the fusion reaction that have been happening inside the star it's entire life (especially the later ones) have been releasing photons. Near the end, there just happen to be so many photons that they're immediately undoing all the work the fusion is doing. That leave no photons left over to support the star.

[@zen1647]

Would love a deep dive in this topic.

[@0-by-1_Publishing_LLC]

"What happens in existence stays in existence."

[@ScienceAsylum]

If only that were true 😞

[@WeedPatch71]

Thanks!

[@ScienceAsylum]

Thanks for the support!

[@tanmayshukla7339]

2:46 I thought, he'll say, "Is it faster bcz it's hotter or is it hotter bcz it's faster" 😂😂😂😂