 Hello everyone, it's been nice to be here and thank you for coming. So, this star is your favorite guy, right? So, I was casting out of my excitement memories and I came across this scene from the Miami movie. Now, at some point in the film with friends, Limon, Umba and Simba lay down on the graph and they're getting into the stars. Wherever there's Limon, there's Umba. And we're going to have these two guys together. There's gonna be some time. Now, Limon, looking at the stars, insists that they're fireflies. Which is quite interesting in a theory of it. But Umba seems to be a little bit more educated apparently and he believes that time was worth a gasp. So, who do you think is wrong and who is right? Before we answer that, let's take a moment and think how do we see stars? Right? I mean, we see the day. First, in the day we see our sun. Big, yellow, very, very bright. It makes our day. And plus, it gives us a time during summer. In a cool and nice summer night, we see thousands of close stars on the sky. For example, the day. If you don't know him, trust me, he's out there. Now, we see them never, they're small, they're far away, right? I mean, sometimes they flicker, they flicker, right? And if you take close attention, you can actually distinguish some colors. The thing is that when we look at the stars, all of the air is out there. What are they made of? Or we'll be there forever, right? We don't know that. We don't know that. Who outriders the stars look exactly the same every day and every night. And I think now that this is not the case, stars will change. And together through this code, we're going to explore the lives of stars. The life of a star on a diagram, it will look something like that. So how about these magnificent things, like red diamonds, and planetary light, and supernovae, black holes, mutual stars. I mean, these are fascinating things. And together we're going to learn what are these and why they're so important for a star. Before we go on, I want you to know something. Stars are, let's say, divided into two glasses. We have small stars, or low stars, and high stars, or large stars. Now, low stars live for up to billions of years. They're smaller, they're dimmer, and they likely conclude their lives in more subtle ways, let's say. On the other hand, we have the large stars. These are massive. They tend to live sort of, for a certain time, millions of years, very short. They're brighter, they're bigger, and they end their lives in glorious explosions. And believe me, they want everybody to know about them. So, let's start now. Let's answer two questions. First, what is a star? And two, where is a star for? Now, stars are big balls of burning hydrogen, boom-bang, right? Gigantic clouds, hydrogen clouds in outer space. In these clouds, gravity, which is an attractive force, piles up hydrogen atoms together to form a larger mass and produce what we call a proto-star. Now, proto-stars are nothing more than big balls of hydrogen in high-end reserves, which is called the vanishing process. Now, be careful here, because a proto-star is not yet a star. As a sigma, it's still in the mother of its baby. So, it's like an embryo star. Something is missing here from the actual star we've got. Let's see what this is. The proto-star is more and more mass, and it's squeezing hydrogen atoms in its core. The temperature rises extremely. Those are the millions of degrees. And suddenly, the hydrogen atoms are so close together, but they are actually merged. They combine to form helium and produce energy. That's exactly what we were missing. Now, a star is born. Hydrogen atoms, and they merge, and people produce helium and energy. This is a process that we call fusion. And this is why stars live, they burn, and this is why we see neighboring spores on the sky. It's simply a simple process, right? Well, I guarantee you, the birth of a star is hundreds of thousands of years. I mean, if you think about it, this is about a hundred times more than the age of Egyptian pyramids. So, a person, even if they want to, they won't be able to witness something so amazing. Now, we know that a star is born. We can imagine it as the birth of any animal species, or in this case, the birth of Simba. Then, people go on and on, and then there comes a point where Simba has faced the force of the star and the hyenas into the age of non-pasadence. In a very similar way, the life of a star is imagined, but not with hyenas. It's about the interpretation of forces and thermal forces. So, what does this mean? What are these forces? We're going to see now. On hand, we have the interpretation of forces. These forces drive fusion. They put more and more hydrogen into the core, and that's strictly the star. But on the other hand, when human is produced, and for it, energy is produced and it wants to be released away from the star. So, the star is expanding. Thermal forces expand the star. Okay? And this also because when we look at the release of energy, the temperature of the star is going down a little bit. Now, when these two forces are in balance with each other throughout the whole star, our star is in what we say equilibrium, or the animal kingdom, is now at peace. This process goes on for millions or even billions of years. But unfortunately, there comes a time where actually hydrogen reserves in the core do run low, right? in the fuel. The hydrogen now forms a cell around what is now a helium core. In the cell, hydrogen can still fuse, produce energy and so the star is expanding because of the thermal forces remaining, right? But at the inner part of the star the helium atoms do really start to combine to produce energy for the star to go on. And of course, it's wind and it's freezing in the core. The star now becomes so, so big through this continuous fusion of hydrogen in the cell that we can't go back for a long time. Now, these are amazing stars. These stars are like they're amazing. So, let's see what happens. I can prove it, I can prove it. We say that we use the giant because through the continuous fusion of the stars we use the word red because the star is releasing energy and so it lowers the temperature and cools down. Now, this is why they are amazing. They can become so big as the inner part of our solar system. If this were to be our sun and wind at some point but no pressure in the world it's about five billion years from now to the world. The sun will swallow any planet in its path if my inner swallow earth. Now, let's go in the center of the star because something is standing there. As we said, grant is meaning in the core and so it squeezes helium atoms so hard together that it actually don't mind and they are now proposed energy and form carbon atoms and the star continues to live. Think that the ashes of hydrogen burning have actually become the fuel for a new period of the star and so the star will be used to live. This one has forever. There comes a point where the star will not be able to produce any more energy. Now this depends entirely on the mass of the star. Right? Let's first see what will happen to a low mass star. Now, a low mass star cannot produce any more energy at this point and the gravitational forces will be in the core. The gravity shrinks and shrinks the core so much that the core becomes unstable, and suddenly the thermal forces in the core produce a soft wave that goes throughout the star. Now the soft wave drives all the layers of the star into outer space. It produces a magnificent colourful cloud which we call the planetary nebula as we see here. Now let's go to the center of the nebula because something is still there. The core of the star has actually survived the layers feeding and is what we call the white lord. Now these stars are small like they are the size of the Earth and it's smaller. And here's the fun fact about this base. We have carbon. We have high temperatures and high pressures. After many years temperatures will go down what we have. We make diamond. The holes are crystallized. So at some point after many many many years our sun will become the Earth in space. This concludes the life of a small star. Let's see what happens now in the large star. Large stars produce more energy because they have more mass and gravity is stronger. Gravity rides usually and more and more elements are formed and energy is produced. I mean look how many elements are here. We can think of the star now as an element factor. This usually goes on until the core is made entirely out of iron. At this point the star cannot produce any more energy. No matter how big it is no more energy is produced. And so it comes to its death. Gravity forces win the core but they are so strong this time. They squeeze the core with enormous pressures. The core becomes unstable again but now produces a much much more violent star throughout the star. And this star when it explodes the whole star into outer space into what we call a supernova. Now supernovas are these they are so violent and so so bright as billions of stars put together. Still about. There is a good chance that even if there is a star on the star which you cannot see with your bare eyes after it explodes into a supernova you will be able to see. There is a good chance. Let's go down to the center of the supernova because again something is happening over there. The core of the star does not survive the explosion per se. Something else happens. The core goes something more like a transformation. It can turn into what we call a nuclear star and these galaxies are starling and turning out of nuclear. They are very very small they have the sizes of seas that are extremely small. So we go from something which is like half of the solar system that looks something like the size of the city. But they do not scare you but they dare you to go. Go close, take a teaspoon and scale it. You will find out that a teaspoon of those stars weighs more than amount of air. So a lot. Now before the star is even larger the core will transform into something more dark. A black hole. Now black holes are these and it's so big holes. Because the addition is so strong that they can trap anything in their proximity, even light. So please don't worry about that. It's a no zone. We see now the key characteristic of a star is its mass. I mean whatever the star turns into nuclear star like all white dwarf it's entirely on its mass. And this is amazing because if we know the mass of the star at the very beginning of its life we can predict its whole life. That concludes my presentation and I just want to finish with this amazing demonstration of a supernova and the final moments of a large star. And say one more time that stars do have lives. They are born, they live and they die. And what is most amazing is that this is the cycle. So after the day of the star through the hours of the star more and more stars will be born again and again. Thank you very much. That was your presentation and now we have 5 minutes of time for your questions. So initially I don't know if you have a fancy microphone. Okay, and it works? Cool. So that there is a question here to the left. Yes, so you just throw the spoon, right? Yes. So how do you measure the mass of the star? I don't know if you have a question so how do you measure the mass of a star? Okay. So there are two main ways. One way is usually stars go in pairs or real or whatever. So they like to have some kind of. So if you observe these two or three stars for the system it's easy to use some basic gravitational laws to find the mass. Another way is very, very interesting. You can get the mass of the star by only knowing its temperature and how much light you get from the star. And so you can do that. So it's always easier to observe stars in big groups because then you can start to work with them and then you can form a relationship to that. Okay. So what determines that a supernova will turn into a new star or a backhoe? So what determines how the supernova will behave? Will it go to a mother star or will it die? Okay. So the supernova as I said whether the star will will the core of the star will turn into a new star where a black hole remains entirely its mass. So the more mass of the star is it will turn into a black hole. If it's a little bit less massive it will turn into a new star. And if it's even less massive it will turn into a white hole. So the mass here is the key. Okay. Here's one. So so because iron is the the highest binding energy so then it will need extra energy input energy for it to form two other elements. Right? So if you don't have extra energy you cannot produce any more energy. This will be the final element of the star. Okay. Do we have time for one more final question? Let's consider the beginning of the star light. So the question was what is considered as the beginning of the light of the star? It's the proto-star. But when fusion starts fusion is the key here. When fusion starts the star is actually born. So that's why I said that a proto-star is like an embryo star it's still trying to form within the cloud. So the moment fusion hits in the form then the star is born. So basically it does coming together close to this ball of iron and the rest. Alright. Thank you very much George.