What's the biggest star in the Universe?

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Speaker 1: Hey, Daniel, what's the biggest number you can hold in your head? I can think about infinity, I guess, can you do have an infinite number of neurons? No, but it feels like I've eaten an infinite number of cookies during this pandemic. It does feel like it's dragging onto infinity. But you know, even if you ate a hundred cookies a day, that's not even a million cookies a year. Although that's a good goal to happen, you're right, And honestly, it's hard to visualize a number bigger than like a hundred or a thousand anything else. In my head. Frankly, it's just like a lot, a bunch, a zillion. So then how do you think about how big things are out in space, like Jupiter or the Sun or the galaxy? Like, how do you conceive or think about the mass of such huge objects? I just use the unit of cookies. Jupiter is a whole lot of cookies. It's a pandemic bard fool of cookies. It's the biggest cookie jar in the universe. That's my goal in this pandemic. To eat one Jupiter's worth of cookies. Then you look like Jupiter I think we just wrote Jupiter's formation story for the comic book series. I am more hammade cartoonists and the creator of PhD comments. Hi. I'm Daniel. I'm a particle physicist, but I have strong opinions about cookies. Do you really like a positive or negative like you're never ambivalent about cookies. I'm never ambivalent about cookies and very specific taste for what makes a good cookie really according to you? Or do you think you have some sort of universal standard of cookie goodness. I would not want to be the cookie spokesperson for humanity, but I have strong reactions to cookies. Yes, really, What do you think about hips of hoyies? Those are not cookies, My god, those are cardboards simulcrums of cookies. Man, Well, welcome to our podcast. Daniel and Jorge explain the universe of cookies, just the regular universe, the other universe, A production of I Heart Radio, in which we take our cookie fueled brains on a tour of everything in the universe, how it works, how big it is, how small it is. Nothing on this podcast is too vast, too incredibly huge for us to try to wrap our minds around. Nor is it too small for us to try to penetrate with our intellect and get a grasp of what's going on down at the tiniest level. Yeah, because it's pretty hard sometimes to hold the hold universe in your head. I mean, you have to hold not just the tiny microscopic particles that everything is made out of, but you also have to hold the ginormous structures that are out there in space, those huge suns and stars and galaxies and solar systems and clusters of galaxies. It's a big universe. It is a big universe, and often we just rely on math as like a mental scaffolding to take us where our minds have a hard time going. We talk about these numbers, but it's good to understand that these things are real. When we talk about these objects that are out there, they're real. They're out there. There's actually enormous, vast burning plasma balls in the sky. This is not a joke, This is not just notation. It's reality. Yeah, they're giant cookies as well, the size of Jupiter. You know. I always say we shouldn't be surprised by anything we discover in the universe. But if hubble turns up enormous planet sized cookies. I would be surprised and delighted. Depends on what's in the cookie, man, and if they're Jupiter sized chips of hoys, I'm out well. In today's podcast, will be tackling another one of our Extreme Universe series, in which we talk about the biggest things in the universe, the hottest, the coldest, the emptiest bass in the universe. We like to talk about extreme things, Yeah, because the extremes tell us what's a limit are. That's what reveals what the rules are. When you push the universe to the edges of what he can do, you understand why you can do something and why it can't. So the Extreme Universe series is not just fun because it blows your mind, but also it teaches us something about the way the universe works. Yeah, it's extremely educational as well. So on today's podcast will be tackling one of these extreme things in the universe, and we're doing something a little different today. That's right. Today we have a guest who will be asking the question of the episode for us. Yeah, he's kind of a bit of a celebrity online, right, Yeah. Absolutely, he's definitely the youngest host of a science podcast that I'm aware of. Yeah, so here is our special guest to introduce the question. Hello, with my pleasure to welcome to the program. Today's special guest question asker Tie Pool. Hi, say hello to everyone. Hi, I'm really excited to be here. I'm a little bit nervous, but mostly excited. Well, welcome to the program. Why don't you tell us a little bit about yourself and your podcast? Well, I'm fourteen, just started high school. I'm here in Toronto, and I host a CBC podcast called tie Asks Why the Journey of a kid just asking questions because you know, my curiosity got the better of me. You asked so many questions that they decided you should host a podcast about it. Yeah, pretty much. And what kind of topics does your podcast ask about or answer? Well, we have a wide range of stuff. You know, it can get kind of silly stuff like why do we dance? Or how do songs get stuck in your head? But we also deal with deeper ones like what is love and what is death? And then of course we get to some really crazy ones like the end of the universe and a pretty topical one about viruses. Awesome, it sounds like a lot of fun here on the program. We are definitely big fans of curiosity for folks or even down to nine years old. And I've listened to a bunch of episodes of your podcast. It's a lot of fun. So congrats, thanks, I'm really honored. I recently listened to your episode about John von Newman, and I think it's really cool because he's a really cool guy. He just is in the background of a lot of science things, but he did a lot. Yeah, he definitely was a curious person. All right, So then let's dig into today's episode. We have you on to be our guest question asker, So why don't you introduce for our listeners what today's episode is about. Well, I got another question and I decided to be a good idea to ask you guys. So the question for this episode is what is the biggest star in the universe? Awesome? I love that question. But tell me first, what tickles you about that question? What makes you curious about the size of stars? Well, it's just kind of thinking about the sun, and it's a strange thing to think about. It seems like really big and scale of our planets and stuff. But I kind of learned and realized that our son is not very big in comparison to other stars. So it kind of just got me thinking, like how big could we reallyly go? You know, can we get something that's like twice the size of our stunt? Is that the biggest or like a million times we go like really really big? Awesome? Well, I love your expectation that the universe will surprise you, will shock you, because I think there's a lot of examples in history where we learned something about the universe and we are totally surprised at the size of things, about the scale of the crazy stuff that's going on out there in the universe. Yeah, I kind of just was in the mood to get my mind blown. You know, I'm excited to hear the number. It's gonna be crazy. It's gonna be like a billion or something. All right, Well, thanks very much. We'll hope to blow your mind. All right. That was Tie Pool, host of TI ask why, and like him, I think we're all ready to get our mind bloom. That's right. It's a lot of pressure though, right, he's really expecting a big number. Yeah, yeah, because you know, I bet there are huge stars out there in the universe. There are huge stars out there in the universe, and Ty was reaching for what he thought was like a vast number of star, a million times bigger than our son. But actually we're going to deliver something much much bigger than that, bigger than a million times the size of our son. That's right. We're gonna make our son look like a tiny dust spec, a shiny, tiny dustpec. Al right, Well, as usual, you also went out there into the wilds of the Internet to ask regular listeners what they thought of this question. That's right, So thank you to everybody who stretched their minds and tried to imagine an enormous star out there in the universe. And if you would like to respond to tough questions from a physicist without any reference materials, please write to me two questions at Daniel and Jorge dot com. So think about it for a second. If someone asked you what you thought was the biggest star in the universe, what would you say. Here's what people had to say. I think that a big factor for determining how big a star can get. I think it's gravity. Well, one thing for sure, it's they always discovered something that is bigger than they thought it would be. That stars can get much more massive than our own son. I do not know how big a star can get, but I know that at a certain point it, when it passes a certain threshold, it will collapse on itself and from a black hole. All right, Well, the answer seemed to be all over the place, big answers and small answers. Yeah, exactly, definitely. People are prepared to have their minds blown and to be surprised. I think one thing we've learned in our exploration of the universe is that what we expect is very rarely what's actually out there. Yeah. Well, I think maybe to start us off, maybe we should settle this technical question, which is I think is important. What do we mean by biggest star? Do we mean the biggest in volume, like the one that occupies the most space, or the dancest or most massive star. What are we talking about here? Most paparazzi following them around taking pictures? Maybe, yeah, most Instagram followers, biggest box office. That's right, that's what it take to be massive on social media. Though it's a fair question that you can make an argument in either direction. Mass is really important in determining the life cycle of a star, and what it means. But volume is also a big deal. Really in the end, maybe what we're talking about is like the physical size of these things. Yeah, because when you see it, when you're in front of it at this point, you would think about when you think about the word big, like, oh, wow, that's big. But if it was small and dense, you've been impressed, but you wouldn't say, wow, that's big. Yeah. Well it's a big deal, right. It makes a big dent in the structure of the universe. It's like a large gravitational well, I mean, black holes are not a tiny thing to be ignored. And I think initially I would have voted for the mass of the star because that really does tell you about the nature of the star and also like its fate. The entire fate of the star is determined by how much stuff it has. If it has a certain amount of stuff, it's going to end up as a white dwarf that has more, it's gonna become a neutron star or eventually a black hole. All of that is determined by the mass of the star. It's a really important way to categorize stars. And I guess it doesn't change because the volume of a star changes, right, Like stars go through a life cycle and they grow and they shrank and they end up small at the end. Right, it's a varying quantity. But the math doesn't really change, does it. It doesn't change that much. I mean, the end cycle of a star, it does blow off some of its outer layers. So, for example, our sun is going to end up as a white dwarf, and it won't have all the mass that it had in it's early part of its life because it's going to blow out a huge amount of that into like a planetary nebula. So it does sort of change. But you know, you might say that by the time our sun becomes a white dwarf, it's no longer a star, right because it has no more fusion going on inside of it. To see list celebrity now exactly can't even get into the hottest restaurants in l A anymore. It's in dancing with the stars, exactly. But volume, you're right, it's variable. Star can grow a lot during its life cycle. So if we just look out into space and compare two stars, we might be comparing two stars that eventually would have the same size. If you sort of lined them up. But one of them is like a grandpa star that's really big at the end of his life. The other one it's like a baby star that's more condensed. Okay, so then we're really talking about the mass of the star then, like what's the most massive star? Yeah, I don't know. I'm honestly on the fence about it, because the mass of the star is also important for other reasons, Like it tells you about the history of the universe. You know, the very early universe stars were much bigger and hotter and burned faster because there weren't these pockets of metal to collapse smaller stars, and later on the stars that were formed are smaller and lasts longer, So that's really important. On the other hand, what I think about what is the biggest star in the universe, I definitely am thinking about volume. I want my mind blown by the sheer amount of space that this thing takes up. Right, it's a tough call. So why don't we do both? All Right, We're gonna hand out two awards, right, We're just gonna like dilute the value of our prizes by giving out two of them. Make two categories, you know, like the Peace Nobel Prize and the actual Nobel Prizes. You mean the one in chemistry, right, That's exactly what I was thinking. Yes, all right, so let's talk about most massive star and also most I don't know, voluminous star, biggest man, it is just biggest, most volume is just the biggest. All right, so let's jump into it. I guess what we talk about when we talk about mass. Yeah, well, we had a fun podcast a week or so ago about how massive stars can get, how big they can get, how small they can get. And we also talked recently about like where's the threshold between a planet and a star? And really the definition of something that's a star is something that confuse hydrogen, and in order for that to happen, you just have to have enough mass, just like a minimum mass threshold. You don't have enough stuff enough like hydrogen gathered together and then compressed down, then you can't get fusion going. And the minimum threshold there is something like about a hundred times the mass of Jupiter. Doesn't have to be hydrogen though, right, some stars confuse other elements. Yeah, the heavier stuff like helium or carbon or neon or oxygen. That takes even more mass in order to get that started. But you're right, there is like a special category of star called a brown dwarf that doesn't fuse hydrogen itself. Iffuses an isotope of hydrogen called deuterium. So if you have like fifty Jupiter masses or actually anything between about like fifteen to eighty, you can get a form of fusion going. It's called deuterium fusion. It's not like as bright and as hot as normal hydrogen fusion. And so this is I think a disagreement about whether or not you would call this a star. Doesn't have regular hydrogen fusion, so it's called a brown dwarf, also sometimes called a failed star. And so the smallest thing you would really call a star is about hundred times the mass of Jupiter, and it can really fuse hydrogen, and you call these red dwarfs. It's actually the most common kind of star in the universe, these red dwarfs. They're everywhere, meaning like if you take a hundred jupiters and you put them on the same place, they will become a star. Yes, if you took a to jupiters and put them all in the same place, they would collapse and they would start fusion. The interesting thing is that they actually wouldn't be much bigger than Jupiter because there'd be so much gravity would pull it together. So a red dwarf is not actually bigger than Jupiter. It's just much more dense that has a hundred times the mass, and that's enough to get hydrogen fusion going. And what would they look like if you saw them, Like, would they look as bright as Arthen? No, they're not nearly as bright because there's a very strong relationship between the mass of a star and its brightness, and as the mass goes up, the brightness increases by the power of four. So a star that has like a tenth the mass of the Sun has much much less brightness. It's like one ten thousands of the brightness of the Sun. And in fact, the closest red dwarf to Earth is called Bernard's Star, is too dim to see by I even though it's pretty close. Mmmmm, all right, So you take a hundred jupiters, you put in together, you start fusing in the middle. And is it basically like a more like a simmering ball of fire, or is it only happening in the core for example, it's definitely a ball of or like if you were near you would get fried. It's still very hot, it's just not nearly as bright as a larger star, all right. So that's the minimum star. That's the minimum star. And the amazing thing about the minimum star is that remember that big stars burn hotter, and so they burn faster. These small stars they're just sitting there like glowing embers, and they're gonna last a long long time. Like these red dwarves, they could last for ten trillion years, ten trillion years and would never run out of fuel or anything. Yeah, because they're just very slowly burning their fuel. They're much cooler than our sun, which is why they're much less bright, and so they're sort of like conserving our fuel. The biggest, brightest stars will only last like a few million years. The smaller stars that are not as big and not as hot, they can go on for trillions of years, much much longer than the age of our universe so far. They're like those TV actors that get work forever on TV, but they're they're not as they don't shine as brightly on the big screen. That's right, Christopher Walking, for example, No, my Colcaine, that guy is still working, all right. Well, so that's the minimum star, and so let's crank up the mass style and get into more massive stars and then we'll get to the actual biggest stars. But first let's take a quick break, all right, Daniel, we're on the hunt for the most massive stars in the universe, and also the biggest stars in the universe, physical stars, like the shiny kind that's out in space as through physical stars, unless you're suggesting that Hollywood celebrities are non physical, that they're like supernatural. They're very ithereal they transcend physcality, that's right. So the next thing up after red dwarfs are stars like our Sun, would you call a yellow dwarf? And our son Like it's not nearly the biggest or most massive star in the universe, but it's huge, you know, compared to the size of the Earth, which already is like staggeringly large, the Sun is enormous. It's like three hundred thousand times the massive the Earth, and you could fit more than a million earths inside of it. Mm hmmmm. And that one is also fusion, right, definitely, this fusion happening at the core of the Sun. Mm hmmm. Yeah, and it's sort of just right for us though, right, Like, if it was brighter, maybe we wouldn't be a lot were dimmer. Yeah, exactly. If it was a lot brighter than the surface of the Earth would be a lot toastier, and maybe Mars would be a better neighborhood to live in. So it's like three hundred times brighter than those red dwarfs that are nearby, but it's only gonna last about ten billion years. So we're halfway through the life of the Sun. Oh wow, So it's about three hundred times bigger than the red dwarf but will last much much less. Yeah, so it's only about ten times the mass, but it's gonna last a lot less time because if you crank up the temperature, fusion really takes off and starts burning a lot faster. It's very nonlinear. You double the mass, you get much hotter temperatures, and you burn through that mass much faster. So here in our solar system, that means we're sort of on the low end of the massive sun scale, right, our sun is relatively small compared to what's out there. Yes, absolutely, our sun is not impressive compared to the most massive stars that are out there. It's not in the population of the smallest stars, the red dwarfs that are very, very common. But it's not an impressive star at all. We still like it though. It's still our favorite star. It's perfect for us, all right. So let's crack up the mass even more. What happens if you get into thousands of times the mass of our Sun? Well you can't. Actually, it turns out that the biggest stars that are out there are only like a hundred hundred fifty up to maybe about two hundred times the mass of the Sun. I see, because what happens after that. What happens after that is that the Sun gets really big and really hot, and it starts to burn really strongly is core, and that fusion generates a lot of radiation, and so it blows out the outer layers of the star. So there's sort of an upper limit to how much mass you can cram into a star and how it still be stable. Remember, a star is sort of a balance between gravity that's trying to compact it and fusion that's pushing out the glowing the hot energy that's keeping it from compacting. I see. So if you gather more than two hundred times the mass of our Sun together in like a giant hydrogen cloud, it wouldn't all crunch together in the middle because by the time it starts to crunch, the middle starts exploding, and then that blows everything away. Yeah, and first of all, if you have such a huge cloud, it probably wouldn't collapse into just one star. It's more likely to collapse into several smaller stars. But if you somehow arranged like a bunch of really big stars to combine themselves together into something which was two or three hundred times the mass of the Sun, it would blow itself apart because the fusion at its core would be so powerful. All right, well, let's take the next step. Then, what's next step? After our star? After our star? This serious which is actually the brightest star in night sky, and it has two times the mass of our Sun, so it's like two scoops of suns, and it's much bigger actually than our son. It's like eight times the volume. And even though it's only twice the mass, it's like twenty five times brighter than our sun. That's a general thing, or is it just this one star? Now? In general? As you crank up the mass, the brightness goes up much much faster. This is the mass luminosity relationship we talked about in another podcast episode. That's what we use actually to measure the massive stars. We look at their brightness because, as we said before, as you add mass, the temperature increases, and it increases really dramatically, which tips off nuclear fusion, which makes things even brighter. M Yeah. In fact, the brightest star in our night sky is one of these two suns. Starts. Yeah, exactly, that's serious. Are you serious? Surely you're joking and stop calling me Shirlett. Alright, So a star that's two times the massive our sun would only live two and a half billion years. Yeah, wow, it's burned through his fuel, all right, what's the next step? Next step up is Beta Centauri. This thing is twelve times the mass of the Sun and it's about a thousand times as big. So you could take our son and fitted into this star a thousand times. It's hard to hold that idea in your mind. Wow, it's only like ten times more massive, but it creates such a crazy condition of explosions that that sun basically flows up right, It's like a big fire exactly. It's a huge fire, and that's why it's twenty thousand times brighter than our sun. Twenty thousand times. Wow, that's like taking twenty sons and shining it on us. Imagine having twenty thousand sons in the sky like that's a hot day. Yeah, we need twenty thousand SPF at least. And this is a super awesome star because it's only going to live for twenty million years. These things, they are fiery, they're impressive, but they do not stick around. What happens after twenty million years. After twenty million years, it goes into its super giant is. It actually gets much much bigger and then eventually collapses and it's going to form either a neutron star or a black hole, depending exactly on how much mass it has. Wow, don't you mean in years is not a lot of time astronomically speaking, right, you wouldn't have enough time to develop life for really, you know, get all your grocery shopping done. No, you wouldn't. And the other interesting thing is that this is part of a star system that has three stars. You've heard of a binary star system. We have two stars orbiting each other. This one's part of a triple system. So there are two other stars there that are much smaller that will last longer, and you might develop life around one of those, but only if it can survive the cataclysmic end of Bitta Centaur. How common are these types of stars? Are we getting too more rare kinds of stars? These are definitely much more rare. As the mass goes up, the frequency that you'll find these stars drops, not just because it's harder to get a large blob of mass, it's just less likely for it to happen, but also because they don't last very long. Like these red dwarfs, they're gonna be around basically for ever, right, trillions of years. The yellow doors we're talking about billions of years about the lifetime of the universe. Here, we're just talking about millions of years, which astronomically speaking, is like a blink. So these things, when they do happen, they don't stick around very long, and that of course contributes to their rareness. M All right, let's get into the King of all or queen of all massive stars. There is one that you can crown as the most massive star there is, though there is some disagreement. You know, it's hard to measure these things, as we talked about, especially on the very upper edge, and so different astronomers might say that different stars are the most massive. But there's a couple that are like right at the edge. And the one I think that's super cool is this one called are one three six A one. This one's two hundred and fifteen times the mass of the Sun, two hundred and fifteen serving scoops all put together into one star. Wow, And I imagine that's really bright. Yeah, this thing is as bright as nine million sons nine millions Sun's shining all at once. Yeah. And it's so close to this limit at how big a star can be that it's just not going to last very long. It's radiating out so much energy that the fusion happening at its core is pushing out the edges of the star. It's losing mass constantly. It's an explosion. It's falling apart mm because at some point it like pushes things out so far that they just escaped the gravity. Yeah, exactly. The fusion pressure at the surface is greater than the gravitational hold though. Things are getting pushed away from the star like you imagine these really really massive objects in space are going to suck you in. Right, this is the star that pushes you away. The solar wind from this star is so strong that it's actually pushing its own skin off. Wow. That's disgusting but also pretty impressive. Don't be judgmental, man, That's just the way the stars are. And when you say pushing you, you really mean more like frying you, right, Like, if you're there being pushed by the star, it's not like it's pushing you, it's like it's throwing fire at you. Well, both, Like, it's a lot of energy for you to remember, the solar wind has momentum. That's how we talk about like solar sails, right. They can really capture the momentum of the solar wind, and that's why these things are expanding. That's why they're literally blowing up because the solar wind is literally pushing, not just frying and cooking. There's a lot of momentum that's being imparted anything that comes close to this thing, and actually the outer layers, so it's tearing itself apart. Right. I guess what I mean is it wouldn't feel good to be pushed by that much radiation. No, it would not feel good. I don't recommend going like solar surfing or anything sailing. The incredible thing is that this is just one part of an enormous cluster. Like this is maybe the most massive star in the universe, nine million times brighter than the Sun. But actually only recently we figured out that it's one star because it's part of this big blob of stars that together, this huge cluster is called R one three six, is ten thousand times brighter than just this star. Oh wow, this most massive star is really like the minor player in an orchestra of stars. Yeah, it's the biggest one. It's just a huge collection of stars, and this is like the big grand Pappy. But together all those stars outshine this one by ten. So it's a crazy object out there. Is that about as massive as stars can get. What if I have a star that massive and I pumped more hydrogen into it, what would happen? It would blow itself up. As you get it more massive, it's going to increase the temperature and that's going to increase the rate of fusion, which is an increase the radiation and pressure, and so it's going to tear itself apart. It's gonna blow up, It's gonna blow up. Yeah. Somebody actually wrote to me and asked me, like, if you wanted to blow up a star, what would be your go to strategy? And you know, as usual, I thought, is this a supervillain making a plan asking me for physics consulting? But the answer I gave him I thought was pretty impractical, which was, like, just add a lot of mass to the star. That will blow it up. So if he's somehow capable of injecting five times more mass into our sun, for example, that would spell its doom. Right. Well, I mean, obviously it's a lot, but it doesn't sound like a lot. You don't need millions of suns to blow it up. You can just gather a few hundred. Yeah, And it's fascinating. That's why these extremes are really interesting. It tells you that you can't have an arbitrarily sized star, right, You can't just have an enormous galaxy size star. That's why galaxies are filled with stars instead of us having galaxy sized stars, because there's an upper limit. Because stars are not just like blobs of gas floating out in space. There's this push and pull. Gravity squeezing them down, fusion is pushing them out, And there's only certain regimes in which those two things are close enough to being balanced that the thing can exist for very long at all. Right, But I guess also that's only in the star category. You can have objects that are more massive than two or three hundred masses of the Sun, right, Yeah, for example, a black hole. Right, you may have black holes that are billion times the mass of the Sun. And we talked about what's the biggest planet you can have to Yeah, exactly though that's definitional, right, as far as we know, though, there's no physical upper limit on the mass of a black hole. The only limit there is how do you get so much stuff near a black hole so that he can eat it? And how does it actually fall in within the lifetime of the universe, which is why we think the biggest black holes out there are like five, ten, maybe fifteen billion times in the mass of the Sun. We don't see an the outh that there are a trillion times the mass of the Sun, though theoretically there's nothing preventing that from happening. But here, even theoretically, you can't build a star that has five dred times the mass of the Sun and expect it to last more than a few hundred thousand years. Right, What if I take like a harrier element? Can I take five hundred times the mass of the Sun in helium and put that together? Would that give me a star? No, because that would also trigger fusion, and that fusion would be even hotter and more energetic, and so you would also just spell the death of the star. But the elements would be heavier, wouldn't it, wouldn't there be more gravitational pressure. Yeah, And more gravitational pressure is exactly what's driving the fusion. Right. More gravitational pressure means higher temperatures, which means faster fusion, which means more fusion radiation, which means the death of your star. All right, so there's a limit to start them. There is a limit to start them. Exactly about Tom Cruise. You can't get any bigger than that, Tom Hanks, Tom Cruise, Nicole Kidman, that's it. You collapse into an egotistical black hole after that black hole of paparazzis and and tabloids. Exactly. All right, Well that's the most massive stars. Now let's get to the question of what's the biggest star, Like, if you're standing in front of it, what would be the biggest star that you can see or be in the presence of. So let's get into that, but first let's take a quick break. All right, we're talking about the biggest star in the universe, not just here on Earth as a movie star, but in the astronomical sense. What's the largest right, that's what we're talking about now, largest star that you can have, Like, if you're standing in front of it, what's the biggest thing that you could be looking at? What takes up the most space in our universe? I like to imagine, you know, taking a spaceship and going up to the surface of the Sun. It would seem like it filled up your whole horizon, right, It would be so vast, like an ocean of burning plasma. And then it's awesome to think about like that being dwarfed by something even larger, right right, all right, So then let's talk about volume, like what determines the volume of a star. This is a little bit tricky, right, Like how you measure the volume of the star and how you even define it is a little bit tricky. Don't suns have a surface that you can measure off of, like our sons has a surface, right, pictures of it looked like it has an edge. Yeah, but it's sort of like the Earth, like where it is the atmosphere end. It's not a hard cut off. It's sort of like drifts off gradually. So you can say, obviously we have a surface on the Earth, but the Sun doesn't have a rigid surface the same way the Earth does. It sort of has a gradual draw off in density. Then you get to the outer layers, and so it's hard to know exactly where to define the size of the star. Right, It's a little fuzzy, but still I feel like, you know, if you look at a picture of the Sun that they've taken, it does seem to have like a surface of molten something or the surface of fire, after which it's not as defined, or you see the blackness of space behind it. And you can also think about, like what is the part of the star that's actually glowing, that's giving off light. Maybe you could define the edge of it that way, And that's actually useful because that's connected to how we know the size of these stars. Like we're gonna talk about some really big stars that are super far away, and you might wonder, like, well, how do we know this thing is so big and we can't measure it exactly? Only for like really close up stars, can we actually resolve the left side of it and the right side of it make a measurement directly of how big it is. It only works for stars that are very very close to us, where we can use like parallax. Beyond that, we have to have models that say, if the star is this temperature and has this brightness, and that tells us it must have a certain surface area in order to emit that much light, and from that we can deduce the volume of the star. You have to basically sort of guests based on your knowledge of how sounds work. Yeah, we have a model who is not exactly a guess. It's called nuclear physics. But we have a model for what's going on inside the star that connects the brightness of the star with the mass of the star and the temperature of the star, and from all that we can estimate what the radius of the star must be. I feel like I just insulted you. Then you not just me It's okay, It's just a whole field of physics. You mean, a hypothesis without proof is not a guess. It's not without proof. We develop these models and we test them. We look at in the universe and we see do the stars behave the way we expect? And we can only test them in some cases for closer up stars, And the rest of it is extrapolation. But it's not just like, I don't know, let's pick a number. So there are stars that we can measure the size of from here. Yeah, there's stars that are close enough that we can use parallax to directly measure their size, but not very many. Al right. Well, the other tricky thing is that the size of a star changes over its life. You know, it grows and then it shrinks. Yeah, exactly. The star for most of its life is about the same size. It burns happily, it's in that's happy place where fusion and gravity are like in balance with each other. But eventually fusion makes really heavy metals which collected the core of the star and increase the gravity, and then eventually the fusion starts happening sort of more on the outer edges of the star. You only have hydrogen near the outer edges of the star now, and so that's where most of the hydrogen fusion is happening, and that creates more pressure to blow out the star, makes it get much much bigger. Our Sun, for example, is going to get to two hundred times its current volume when it goes into its red super giant phase. Mmm. Right. It gets so hot that it burns brighter and bigger. Basically the flame gets bigger, yeah, exactly, and so it gets really big and fluffy. And like where the Earth is right now is probably gonna be pretty close to the radius of the Sun when it gets near the end of its life cycle. That's in about five billion years, so you still got time to do a lot of stuff. But that's going to happen to our star and to almost every star out there, all right, So I guess maybe we're really talking about what's the peak volume of stars right like at their biggest what's the biggest they can get exactly? Or like when we look out there currently in the universe, what are the biggest stars that are around right now? Some of the most of the ones that are really big are going to be the ones that are about to die because they're in this last stage where they're blowing themselves up before they collapse. Mm hmmm. Al right, well, let's go down the list. What are some of the ones that are huge, you know, just to get a sense of scale. There's a star, for example, called gay Crux, which is like the nearest giant star to the Sun, and it's got only one and a half times the mass the Sun, but the radius of this thing is a hundred and twenty times the radius of the Sun, which makes it much much bigger. And is it a start one point five times the massive arson it's it's a pretty similar kind of star. Then it's a pretty similar kind of star exactly. And it's in the Southern Cross actually, so it's sort of famous. But you know, it's much bigger. It's only got like another fifty percent of the mass, but the volume is like ten thousand times bigger. M m. Yeah, that's huge. But is it just because it's in a different stage than our Sun? Because our son is gonna get that big, right, our stage is also going to get that big. So yeah, this one is, like all the ones on our Biggest Stars list, is near the end of its life. Oh I see that these are like peak peak size. Yeah, exactly. This is when their stars are really reaching, like the peak of their career, you know, when they are the biggest they're ever going to be, right, And so the one we can see right now is this one called gay Crux, which is a hundred times the size of our son. That's huge. Yeah. It's radius is about a hundred times, right, which means the volume is a hundred cubed right, right, So it's huge. Arson was sitting next to it, it would look like one percent. That's big, yeah, exactly. The ratio between the Earth and our Sun is about the same as our sun and this star, So this thing is just enormous alright. So you can see that in the nice sky. If you go out at nine and look up, you can see this, yeah, exactly. If you're in the southern hemisphere and you can see the Southern Cross, then yes, you can see this enormous star. All right. Well, what's the next one on the list? Next one on the list is the Pistol Star. This one is twenty five times the mass the really substantially bigger, but it's got three hundred times the radius, right, And remember the volume goes up by radius cubed, so you double the radius, you're going up in volume by a factor eight. And so this one's like three times the radius of gack Rux, which means it's like almost thirty times the volume of that previous star. Wow, at that size, would that fit, for example, in our solar system or would it take up the whole solar system? That would not fit in our solar system very comfortably, right, it would go out past the radius of the Earth. I think Jupiter Saturn would still survive, but it would not be good for us, Like, you would not want to put this star in our solar system. Too big, it's too big. And you can't even see this star by e super big. It's super bright, but it's actually close to the center of the galaxy where there's a lot of gas and dust going on, so you can't actually see it with the naked eye. It's hidden. Yeah, it's hidden from us by all this interstellar dust. And what to call it? Blue hyper giant? What does that mean? Well, blue just tells you the kind of light that it's emitting, and a hypergiant is just the stage of life that it's in. All these stars when they're done with the main sequence and they're about to blow themselves out. They become giants or supergiants or hypergiants, depending on you know, the radius. All right, well, what else do we know is out there? What's the next biggest star? The next one is Roe Cassiopeia. It's a yellow hypergiant. This one is five hundred times the radius of the Sun. Wow. So this is kind of what would happen to our star. But like a little bigger star, eventually it would grow to this big. This one is forty times the mass of our Sun. Our star is never gonna get this big. And because it's so massive, it also makes it more rare. Like, we don't know very many of these yellow hyper giant stars in the whole galaxy. The only like fifteen of them that have ever been seen. Wow. And this one is definitely bigger than our solar system. This one would definitely like eat Earth and Mars, but actually wouldn't even get out to Jupiter. Jupiter is much further out than all the other planets because the asteroid belt in between. But still that's huge, right, It's huge. I mean, that's it's like fire front of times the radis of our Sun. Yeah. I mean, if you look at the Solar system, for example, zoomed out so you can see all the planets. Even the huge Sun looks really really small. Now replace that with an enormous star that's like the size of the radius of Mars. The whole Solar system would look totally different, right right, And from here on Earth, our Sun was five hundred times bigger, you know, we would see it take up the entire sky and then eventually eat does up. Yeah, that would be really crazy. Imagine living on a planet where the Sun took up the entire sky toast all right, Now, what's the next biggest star that we can see? Next? Is one that's pretty famous. It's actually Beetle Juice. Beetle Juice is about a thousand times the radius of the Sun. Like, it just totally dwarfs our entire solar system. This one would even eat of Jupiter if you put it in the center of the solar system. Interesting, And so again it's a star that's kind of at its peak. It's like it's burning really brightly right now. Yeah, And actually this one is quite interesting recently because it's been dimming. Like remember, Beetle Juice got dim all of a sudden in a way nobody understood, and people thought, it is gonna go supernova? Is it about to blow? And then people thought, maybe it's just a big blob of dust the past in front of beetle Juice, and other people thought, maybe it's an alien superstructure. We really didn't understand it. Maybe this is like a variable star that's like compressing and then glowing, compressing and glowing. We didn't really understand it. But this is definitely a much bigger star than our son. Wow, a thousand times the size for Sun that would be huge. Yeah, if you're sitting in front of it. Yeah, and so a thousand times the radius of the Sun, right means a thousand cubed of the volume, And so that's a billion times the volume of the Sun. Remember, TI was like, I wonder if there are stars out there that are like a million times the volume of the Sun. We're like, here's one that fits a billion sons inside of it. Yeah, that's that's why. Well, I hope we blew your mind. Tie all right, So then let's maybe skip a little bit ahead to what is the biggest star that we know about, like in terms of size that you can see in the night sky. What is the biggest one that you can see, the biggest one out there right now. The current champion is one called Stevenson to eighteen. This one has more than two thousand times the radius of our sun. Wow, two thousand times bigger, which means it's like, you know, a bazillion times more volume. It's yeah, exactly, It's like more than sixteen billion sons could fit inside this thing. If you dropped the sun into this thing, you wouldn't even notice it. Wow. And how much brighter is it? It's a half million times brighter. So you put half a million sons together and you get the brightness of this thing. Five thousand sons in one place. That's crazy in one place. Yeah, it's just it's taking up so much space. It's incredible. Like if you try to fly around this thing in a spaceship, it would take you like nine hours at light speed just to do one orbit around this star. Wow, that's crazy. It takes hours for the light just to leave this star exactly. If you're a photon generated at the heart of this thing, you're not getting out there for a while, all right. So that's that is the biggest star that we can see. It's thousands of times bigger than our sun. Bazillion times bazillion is at the technical term bigger and volume than our star, and it's half a million times brighter. It's really impressive. It definitely deserves some kind of prize. And you can see it in the night sky. Is out there in the night sky. It's near this cluster called Stephenson two, which is why it's called Stevenson two eighteen. And you can't see it by eyes. Actually discovered in around by astronomers using infrared telescopes. Wow, that's wild. That's huge. So you can't see it because it's so far away. Yeah, this thing is like twenty thousand light years from Earth. So remember the brightness of a star falls with like the distance squared, and so if you're twice as far away, it's a quarter of the brightness. And so this one, we're twenty thousand light years away, which is why it's apparently so dim to the naked eye. But I guess if you have a telescope, you can see it and you can sort of model its size. You can model its size by understanding its luminosity and its temperature, and then we can do these calculations but we definitely can't measure directly, and that's a shame, because man, I would love to see this thing close up, Like, what is the surface of this thing look like? Yeah, what would it look like? Is it a different color or is it just a big bright yellow ball. Well, it's a red super giant, so probably would be mostly red. But yeah, you know, if you look at pictures of the sun close up, you notice that there are a lot of like hot spots and cold spots. It's like a lot of stuff going on. So I think you'd see the same thing. But we've never seen one of these things super close up. It would be an awesome opportunity to learn more about how a star gets really big and what it looks like at the end of its life cycle if we could. But you know, it's so far away, right, And what kind of star is this? Is it like our star but you put more hydrogen into it or is it something fundamentally different. No, it's just like a bigger serving of hydrogen. It's just got a lot more mass than our star. Like, we don't have a precise number for how much mass it has. It's not always easy to measure for these really really big, very bright stars. But it just started out with a bigger helping and that's why I ended up a much bigger star. And then you wait sort of for the end of its life cycle. It's like a really massive star also at the peak of its size. Wow, it's hot stuff. It's hot stuff, exactly alright. So we covered the most voluminous star and also the most massive star. So the most massive star is our one three six A one, which is two hundred times the massive our Sun, and the most voluminous the biggest star is about two thousand times the size war Sun. Yeah, two thousand times of radius and then billions of times the volume, all right, and that basically makes me feel small, Daniel. That was the goal of the podcast exactly to think about the size of the stuff that's out there in the universe. And remember that we're pretty tiny compared to the enormous, powerful forces creating these objects out there. Yeah, because they make our star look tiny, and we're super tiny compared to our Sun. Yeah, we're even super tiny compared to our Earth, which is super tiny compared to our Sun, which turns out to be a pip squeak in the universe. Well, It's pretty amazing to sort of think about, because the recipe for all these stars is the same. You know, it's just ad hydrogen, but you know, you get all this huge variation in like what's happening in the processes and the volume and the mass. It's a pretty complex and impressive universe. Yeah. I do like the idea of a star having a recipe which is one ingredient and one step right, but no more right, Like, if you get it off by a little bit, it becomes a totally different star. That's true. If you get it off by a factor of five hundred, then you no longer get a star. But that's also true of cookies. You know, you put in five times too much sugar, they're not really cookies anymore, right, Or five hundred times more chocolate chips, you just get a chocolate chip exactly. That's just a recipe for a chocolate chip. It sounds like a star of a recipe. I have strong opinions, but I would taste it. You would just taste chocolate. It's like, oh, yeah, that's an interesting recipe. Chunk of chocolate with little tiny cookies ambitted in it. A cookie chip. Yeah, all right, Well, We hope you enjoyed that and made you think about the brightness and the amazing things that are shining out during the night sky. And remember that however big you think things are, they're actually much more vast than you could ever possibly imagine. All Right, we hope you enjoyed that. Thanks for joining us, see you next time. Thanks for listening, and remember that Daniel and Jorge Explain the Universe is a production of I Heart Radio. Or more podcast from my heart Radio visit the I heart Radio app, Apple Podcasts, or wherever you listen to your favorite shows. H