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Current time:0:00Total duration:9:28

Video transcript

in the videos on on massive stars and on black holes we learned that if the remnant of a star of a massive star is massive enough the gravitational contraction the gravitational force will be stronger than even the electron degeneracy pressure even stronger than the neutron degeneracy pressure even stronger than the quark degeneracy pressure and everything would collapse into a point into a point and we called these points black holes black holes and we learned there's an event horizon around these black holes and if anything gets closer or goes within the boundary of that event horizon there's no way that can ever escape from the black hole all it can do is get closer and closer to the black hole and that includes light and that's why it's called a black hole so even though all of the mass is at the central point this entire area or the entire surface of the event horizon this entire surface of the event horizon I'll do it in purple because it's supposed to be black this entire thing will appear black it will emit it will emit no light now though these type of black holes that we describe would call those stellar black holes stellar stellar black holes and that's because they're formed from collapsing massive stars and the largest stellar black holes that we've observed are on the order of 33 solar masses give or take 33 solar masses so very massive to begin with let's just be clear and this is what the remnant of the star has to be so a lot more of the original stars mass might have been pushed off in supernovae I'm Laura love supernova now there's another class of black holes here and these are somewhat mysterious and they're called supermassive black holes super supermassive black holes and to some degree the word super isn't big enough supermassive black holes because they're just they're not just a little bit more massive than stellar stellar black holes there are a lot more massive they're on the order of hundreds of thousands hundreds of thousands to billions to billions billions of solar masses a hundred thousands to billions times the mass of our Sun solar masses and what's interesting about these other than the fact that they are super huge is that there doesn't seem to be black holes in between or at least we haven't observed black holes in between weave up the largest stellar black holes 33 solar masses and then there are these supermassive black holes that we think exists and that we think they mean ly exist in the Centers of galaxies and we think most if not all centers of galaxies actually have one of these supermassive black holes but it's kind of an interesting question if all black holes were formed from collapsing stars wouldn't we see things in between so one theory of how these really massive black holes form is that you have a regular stellar black hole in an area that has a lot of matter that it can accrete around it so let's imagine you have a regular so I'll draw thee this is the event horizon around it the actual black hole is going to be in the center of a toward the mass of the black hole will be in the center of it and then over time you just have you have just more and more mass just falling into this black hole just more and more stuff just keeps falling into this black hole and then it just keeps growing and then it just keeps growing and so this could be a plausible reason or at least the mass in the center keeps growing until the event horizon will also keep growing in radius now this is a plausible explanation based on our current understanding but the reason why this one doesn't gel that well is you would if this was the explanation for supermassive black holes you would explain you expect to see more black holes in between maybe black holes with a hundred solar masses or a thousand solar masses or ten thousand solar masses but we're not seeing those right now we just see the stellar black holes and we see the supermassive black holes so another possible explanation this is where my my inclinations lean towards this one because it kind of explains the gap is that these supermassive black holes actually formed shortly after the Big Bang that these are primordial black holes these are very these started near the beginning of our universe primordial primordial black hole now remember what do you need to have a black hole you need to have an amazingly dense amount of matter or a dense amount of mass if you have a lot of mass in a very small volume then their gravitational pull will pull them closer and closer to closer together and they'll able to bill be able to overcome all of the the electron degeneracy pressure is and the neutron degeneracy pressures and the court degenerative pressures to really cool to really collapse into what we think is a single point I want to be clear here too we don't know it's a single point we've never gone into the center of a black hole just the mathematics of the black holes or at least as we understand it right now have everything colliding into a single point where the math starts to break down so we're really not sure what happens at that at that very small center point but needless to say it will be an unbelievably may be infinite may be almost infinitely dense point in space or dense amount of matter and the reason why I kind of favored this primordial black hole and why this would make sense is right after the formation of the universe all of the matter was in the universe was in a much denser space because the universe was smaller so let's say that this is right after the Big Bang some period of time after the Big Bang now what we've talked about before when we talked about cosmic background radiation is at that point the universe was relatively uniform it was super super dense but it was relatively uniform so you know a universe like this there's no reason why anything would collapse into black holes because if you look at a point here sure there's a ton of mass very close to it but it's very close to it in every direction so it would be pulled the gravitational force would be the same in every direction if it was completely uniform but if you go shortly after the Big Bang maybe because of slight quantum fluctuation effects it becomes slightly non-uniform so let's say it become slightly non-uniform but it still is unbelievably dense so let's say it looks something like this where you have areas that are denser and but it's it's slightly slightly non-uniform but extremely dense extremely dense so here all of a sudden you have the type of densities necessary for a black hole and where you have where you have higher densities where it's less uniform here all of a sudden you will have inward force the the gravitational pull from things outside of this area we're going to be less than the gravitational pull towards those area and the more things and the more things get pulled towards it the more the less uniform it's going to get so you can imagine in that primordial universe at very shortly after the Big Bang when things were very dense and closely packed together you we may we may have had the conditions where these supermassive black holes could have formed where we had so much mass in such a small volume and it was just not uniform enough so that you can kind of have the snowballing effect so that more and more mass would collect would collect into into these supermassive the supermassive black holes that are hundreds of thousands to billions of times the mass of the Sun and this is maybe didn't even more interesting part those black holes would become the Centers of future galaxies so things that so you have these black holes forming these supermassive black holes forming and then as not everything would go into a black hole only if it didn't have a lot of if it didn't have a lot of angular velocity then it might go into the black hole but if it's going past it fast enough it'll just start going in orbit around the black hole and so you could imagine that this is how the early galaxies or even our galaxies formed and so you might be wondering well what about the galaxies at the center of the Milky Way or so what about the black hole at the center of the Milky Way and we think there is one we think there is one because we've observed stars orbiting very quickly around something at the center of at the center of the universe I start at the center of our Milky Way want to be very clear not at the center of the universe and the only plausible explanation for it it it orbiting so quickly around something is that it has to have a density of either a black hole or something that will eventually turn into a black hole and when you do the math for the middle of our galaxy the center of the Milky Way our supermassive black hole is on the order of four million times the mass times the mass of the Sun so hopefully that gives you a little bit of food for thought there aren't just only stellar collapse coal's or maybe there are and somehow they grow into supermassive black holes and that everything in between we just can't observe or that they really are a different class of black holes or actually form different ways maybe they formed near the beginning of the actual universe when things just the the density of things was a little on uniform things condensed into each other we're going to talk about in the next video is how these supermassive black holes can generate can help generate unbelievable sources of radiation even though the black holes themselves aren't emitting them and those are going to be quasars