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Current time:0:00Total duration:11:58

Video transcript

where we left off in the last video we had a mature massive star a star that had started forming a core of iron it has enormous pressure enormous inward pressure on this core because as we form heavier and heavier elements in the core the core gets denser and denser and denser and so we keep we keep we keep fusing more and more elements into iron this iron core becomes more and more massive more and more dense it's squeezing in on itself and so and it's it's not fusing that is not exothermic anymore if iron were to fuse it would not even be an exothermic process it would require energy so it wouldn't be even something that could be helped to fend off this squeezing to fend off this increasing density of the core so we have this iron here and it just gets more and more massive more and more dense and so at some mass already a reasonably high mass the only thing that's keeping this from just completely collapsing is we could call it electron degeneracy pressure so let me write this here electron electron degeneracy pressure degeneracy and all this means is we have all of these iron atoms we have all of these iron atoms you know are getting really really really close to each other and the only thing that keeps it from collapsing at this earlier stage the only thing that keeps it collapsing altogether is that they have these electrons you have these electrons and these are being squeezed together now I mean we're talking about unbelievably unbelievably dense states of matter and electron degeneracy pressure is essentially what it it it's saying these electrons don't want to be in the same place at the same time I won't go into the quantum mechanics of it but they cannot be squeezed into each other anymore so that at least temporarily holds this thing holds this thing from keep from collapsing even further and in the case of a less massive star in the case of a white dwarf that hot that's how a white dwarf actually maintains its shape because of the electron degeneracy pressure but as as this iron core gets even more massive more dense and we get more and more gravitational pressure so this is our core now even more gravitational pressure eventually even this electron degeneracy I guess we could call it force or pressure this outward pressure this thing that keeps it from collapsing even that gives in even that gives it and then we have something called electron capture electron capture which is essentially which is essentially the electrons get captured by protons in the nucleus they start collapsing into the nucleuses it's kind of the the it's kind of the opposite of beta negative beta negative decay where you have the electrons get captured protons get turned into neutrons you have neutrinos being released but you can imagine an enormous amount of energy is also being released so this is kind of a tempering and all of a sudden this collapses this collapse is even more until all you have and all the protons are turning into neutrons because they're capturing electrons so then you what you would eventually have this this entire core is collapsing into a dense ball of neutrons so dense dense neutrons you can you can kind of view them as just one really really really really really massive atom because it's just a dense ball of neutrons at the same time when this collapse happens when this collapse happens you have an enormous amount of energy being released in the form of in the form of neutrinos in the form of neutrinos as I say that neutrons are being released no no no the electrons are being captured by the protons protons turning into neutrons this dense ball of neutrons right here and in the process neutrinos get released these fundamental particles we won't go into the details here but it's enormous amount of energy enormous amount of energy and this actually is not really really well understood of all of the dynamics here because at the same time that this iron core is undergoing through this you know it first kind of pauses due to the electron degeneracy pressure and then it finally gives it and because it's so massive and then it collapses and into the this dense ball of neutrons but when it does it all of this energy it's not clear how because it has to be a lot of energy because remember this is a massive star so you have a lot of mass in this area over here but it's so much energy that it causes the rest of the star to explode outward causes the rest of the star to explode outward and unbelievable in an unbelievable I guess unbelievable ly bright or energetic explosion and that's called a supernova that's called a supernova super super nova and the reason why it's called nova comes from I believe I'm not an expert here Latin for knew and the first time people observed a nova they thought it was a new star because all of a sudden something they didn't see before all of a sudden looks like a star appeared because maybe it wasn't bright enough for us to observe it before but then when it when the Nova occurred it did become bright enough so it comes from the idea of new but a supernova is when you have a pretty massive stars core collapsing and that energy is being released to explode the rest of the star out of unbelievable velocities and just to just to kind of fathom the amount of energy that's being released in a supernova it can temporarily outshine an entire galaxy and in a galaxy we're talking about hundreds of billions of stars or another way to think about it in that very short period of time it can release as much energy as the Sun will in its entire lifetime so these are unbelievably energetic events and so you actually have the material on the front that's not in the core being shot out of the star at appreciable percentages of the actual speed of light so we're talking about things being shot out it you know up to 10% 10% the speed of light 10% the speed of light on that's 30,000 kilometers per second that's almost circumnavigating the earth every second so that's I mean these this is unbelievably energetic events that we're talking about here and so if the star if the original star was and these are rough estimates people don't have kind of a hard limit here if the original star original star if the original star what as nine is nine to twenty I should say approximately nine to twenty the Matt times the mass of the Sun then it will supernova and the core will turn into what's called a neutron star this is a neutron neutron star which you can imagine it's just this dense ball it's this dense ball of neutrons and just to give you a sense of it it'll be something you know about maybe two times the mass of the Sun give or take one and a half to three times the mass of the Sun so this is one and a half to three times the mass the mass of the Sun in in a volume that has a diameter of about Technium you know on the order of tens of kilometers so it was roughly the size of a city in the in a diameter of a city so this is unbelievably dense diameter of a city I mean we know how much larger the Sun is relative to the earth and we know how much larger the earth is relative to a city but this is the something large more mass than the Sun being squeezed into the density or than to the size of C so unbelievably dense now if the if the original star is even more massive if it's more than 20 times the Sun so let me write it over here let me scroll up if it's if it's greater than 20 times the Sun then even the neutron degeneracy pressure even the pressure even even even the neutrons inability to squeeze further will give up and will turn into a black hole and that's okay I can do many videos on that and that's actually an open area of research still on exactly what's going on inside of a black hole but then you turn into a black hole where essentially all of the mass gets condensed into an infinitely small and dense point so something unbelievably hard to imagine and just to give you a sense of it so this this will be more mass than even three times the mass of the Sun so we're talking about an incredibly high amount of mass so let's just kind of visualize things here is actually a remnant of a supernova this is the Crab Nebula this is right here is the Crab Nebula Crab Nebula and it's about 60 500 light-years away lightyears so it's still you know from Galactica if you think of our galaxy as being a hundred thousand light-years in diameter it's still not too far from us and on both skills which is an enormous distance the closest star to us is four light-years away and it would take Voyager traveling at 60,000 kilometers an hour 80,000 years to get there so this is a very very that's only four light years that is sixty-five hundred light years but this supernova it's believed happened a thousand years ago right at the center and so at the center here we should be we should have a neutron star and this this cloud the shockwave that you see here this is from this is this is still the material traveling outward from that supernova over a thousand years this the shockwave or the diameter of the sphere of a material is six light years so we could say this distance right here is six light years so this is an enormous Liebig shockwave cloud and actually we believe that the the our our solar system started to form it started to condense because of a shock wave created by a supernova relatively near to us and and just to answer another question that was kind of jumping up probably in the last video and this is still not really really well understood we talked about how elements up to iron or maybe nickel can be formed inside of the cores of massive stars so you can imagine when the star explodes a lot of that material is released into the universe and so that's why we have a lot of these materials in our own bodies in fact we could not exist we could not exist if if our if these heavier elements were not formed inside of the cores of primitive stars stars that have supernovae long time ago now the question is how do these heavier elements form how do we get all of this other stuff on the periodic table how do we get all these other heavier elements and mate they're formed during the supernova itself it's so energetic you have all sorts of particles streaming out and streaming in be streaming out because of the force of the shockwave streaming in because of the gravity that you have all sorts of kind of mishmash of elements forming and that's actually where you have you're heavier elements forming and because and I'll talk more about this in future videos most of the uranium ore actually all of the uranium on earth right now it must have been formed in some type of a supernova explosion at least based on our current understanding and it looks to be about 4.6 billion years old so given that it looks to be about 4.6 billion years old based on how fast it's decayed and I'll do a whole video on that that's why we think that earth that earth was probably that that our solar system was first formed from some type of supernova explosion because that that that uranium would have been formed right at about the birth of our solar system anyway hopefully you found that interesting is a fascinating picture and if you go to Wikipedia and look up the Crab Nebula keep clicking on the image and eventually you'll get a zoomed in picture and that's just kind of even more mind-blowing because you could see all the intricacy in actual photo