What is a superluminous supernova?

00:00:08
Speaker 1: Hey, Jorge, do you think that our culture might be devaluing the word super?

00:00:14
Speaker 2: I think our culture is sadly devaluing a lot of things. I hadn't really thought about the word super though.

00:00:19
Speaker 1: You know, you hear it super often. It's kind of like super everywhere, and after a while you super start to not even notice it.

00:00:25
Speaker 2: Yeah, I guess you're right. Are superheroes, super villains, super califragilistic, xpialidoses? It's used a lot.

00:00:32
Speaker 1: Maybe we should like limit how much we use it before it loses all of its power.

00:00:36
Speaker 2: Do you think we're gonna run out of words?

00:00:38
Speaker 1: We're gonna have to go to super duper, super extra duper. It's gonna get exhausting, or we're.

00:00:42
Speaker 2: Going to go to super conducting super colliders.

00:00:46
Speaker 1: All right, I admit scientists are guilty of this as well, but that's super duper not my fault.

00:00:51
Speaker 2: That's not a super excuse.

00:00:52
Speaker 1: There.

00:01:08
Speaker 2: I am hooreham May, cartoonists and the creator of PhD comics.

00:01:11
Speaker 1: Hi, I'm Daniel. I'm a particle physicist and a professor at UC Irvine, and I super duper love science.

00:01:18
Speaker 2: But what does that mean? I mean you love it in a super way, or you love it a lot.

00:01:24
Speaker 1: I guess it also means I kind of love super science. I love those projects that are big and grandiose that just put you at awe at what humans can do, what their minds can imagine, and what their hands can build.

00:01:36
Speaker 2: Well, the problem is you never know who those projects really are. You know, by day they're just mild mannered physics projects, but by night they take off their glasses, they put under cows and become superphysics.

00:01:48
Speaker 1: So the super conducting super Collider by day was just the normal, everyday conducting collider.

00:01:53
Speaker 2: And then it had a physics accident. I guess which gave it superpowers. That makes no sense. You superphysics become super heroid.

00:02:02
Speaker 1: Maybe you just put glasses on your normal, everyday conducting collider and it becomes a super collider.

00:02:07
Speaker 2: Oh no, no, the glass that makes you every day an every day person.

00:02:10
Speaker 1: Oh right, right, that's right. Take the glasses off the collider.

00:02:14
Speaker 2: Yeah, that's the issue, that's right, the fake glasses. We know lenses in them.

00:02:18
Speaker 1: Well, if we take all the lenses out of the large Hadron collider, I'm not convinced it's going to become a super large Hadron Collider.

00:02:25
Speaker 2: It's going to be super fun, though. What's going to happen? It's going to leap over tall buildings and or destroy tall buildings.

00:02:32
Speaker 1: Discover new particles in a single bound.

00:02:34
Speaker 2: But anyways, welcome to our podcast Daniel and Jorge Explain the Universe, a production of iHeartRadio.

00:02:39
Speaker 1: In which we delve into the super fascinating mysteries of the universe. How does it all work? Is it possible to make sense of this incredible dizzy and cosmos, all of its wonderful tiny particles and enormous swirling black holes, This incredible project that humans have been on for thousands of years to try to digest this incredible universe and translate it into a story that we can tell ourselves and explain to our children and make sense of.

00:03:07
Speaker 2: Yeah, because it is a pretty super universe, full of amazing demonstrations of power and abilities, and incredible particles and incredible stars and objects out there in space.

00:03:18
Speaker 1: And we want to understand all of it. Sometimes the answers to deep questions about the universe are right under our feet in the everyday physics that's going on around us. But other times we can find clues to how the universe works from the most dramatic, the most amazing, the most explosive situations out there.

00:03:36
Speaker 2: I fail. You're trying to find out what the real identity of the universe is. So do you think the universe wants its privacy, it's trying to protect its secrets.

00:03:44
Speaker 1: I do not believe in the privacy of the universe. Basically, physics is trying to unveil or undress the universe.

00:03:51
Speaker 2: Boy, you make it's some kind of RACYO super racy.

00:03:54
Speaker 1: Depends what's underneath that veil. I suppose if it's just equations, then it's very safe for work.

00:04:00
Speaker 2: It sounds like work. Actually that crazy at all.

00:04:04
Speaker 1: Actually, that's literally my job is to try to reveal the safer work equations that underpin the whole workings of the universe. Everything that's happening out there, we imagine can be described with mathematical formula and scientific thinking, or at least so far that's always worked.

00:04:22
Speaker 2: Yeah, because there is a lot to discover and a lot that we have seen about the universe out there. There are a lot of bright things out there for us to see and to study and to kind of parse the light to figure out what's going on out there.

00:04:33
Speaker 1: And we'd like to understand the whole universe, not just the part that's here under our feet, also the things that are very far out there in space. But those things present a special challenge, of course, because they're not right here for us to study. Instead, all we can do is examine the messages that they send us, the particles that be in clues to us from those distant objects.

00:04:53
Speaker 2: Yeah, and thank goodness that they are sending a signals through light, because otherwise we'd be living in a dark universe and have no idea what's going on out there beyond our Solar system.

00:05:02
Speaker 1: And in fact, we are probably living in a dark universe. Most of the stuff that's out there in the universe isn't sending us photons or any other kind of particles to give us clues about what it is and what it's doing. The dark matter that's out there holding galaxies together is stubbornly invisible to all of our senses and all of our telescopes is sending us messages, and those are not very subtle. It is screaming messages at us. It is blinding us with the incredible power of the photons that it creates.

00:05:31
Speaker 2: You make it sound like the universe is not a superhero, but maybe it's a super villain.

00:05:35
Speaker 1: Mm exactly. Maybe that's why it's evading our ability to understand it so far.

00:05:40
Speaker 2: It's a dark universe. It's a dark superuniverse.

00:05:43
Speaker 1: Well, you know, the story of science would be a lot more boring if the universe was more helpful. If it was just like, all right, look, humans, sit down for an hour. I'm gonna explain all this to you, then we would have been done thousands of years ago.

00:05:54
Speaker 2: Right, that sounds like a great story. I would be like, what why say universe being helpful? That's going on?

00:06:01
Speaker 1: It's a much more interesting story when there are twists and turns in dramatic revelations like a thousand years in Right, We're like on season five thousand of Science and we are still discovering incredible plot twists. Right, So, like no writer's room could have invented that.

00:06:15
Speaker 2: It's like a new genre of Netflix shows. P dramas, not K dramas or T dramas. It's physics dramas.

00:06:22
Speaker 1: The universe is the greatest story ever told, But.

00:06:25
Speaker 2: There are a lot of interesting signals coming to us from the universe out there. As you said, some of them are really bright. Some of them are super bright.

00:06:31
Speaker 1: And you know about stars and galaxies and black holes and even very bright events like supernova. But there are some things in the universe that are even brighter than your typical supernova. So today on the podcast, we'll be tackling the question what is a super luminous supernova. I'm guessing it's super but is it super duper only when it takes off its glasses? But this is what I was wondering about, Like, this thing has two supers in its name. It's not just a luminous nova. It's not just a luminous supernova. It's not a super luminous nova. It's a super luminous supernova. Oh my gosh.

00:07:11
Speaker 2: It's almost like you're making things up as you go along, like a three year old.

00:07:17
Speaker 1: Almost like we need somebody to tell us how to organize the naming of things in the universe.

00:07:21
Speaker 2: It's almost like physicis nitith thesaurus perhaps to look up synonyms for super I mean, I think there are a couple out there that you could have used that basically say the same thing.

00:07:31
Speaker 1: Mmmm, the super luminous extra nova, the hyper luminous supernova, those kind of things.

00:07:37
Speaker 2: Yeah, the uber luminous supernova, the extremely luminous sounds like you need a superhero called mister Thesaurus to rescue the day at the university there.

00:07:48
Speaker 1: The super thesaurus supernova.

00:07:50
Speaker 2: You're right. It is sort of like like there was a nova, and then there was a supernova, and then there was a luminous supernova, and then they found something even brighter. I'm guessing that they had to call a superluminous supernovas.

00:08:02
Speaker 1: Where are they going to go next? Right? The double superluminous supernova.

00:08:06
Speaker 2: Well, I guess you would have to find some other property of it, like maybe size, like supersize superluminous supernova.

00:08:15
Speaker 1: That sounds like you're ordering a second helping of fries, you know, Can I supersize my supernova? Please?

00:08:20
Speaker 3: No?

00:08:21
Speaker 2: Can I supersize my superluminous supernova? They're like, what do you think this is? Burger king? Get out of here.

00:08:27
Speaker 1: Only two supers per order, please, sir.

00:08:29
Speaker 2: But yeah, I'm guessing it is like an upgraded supernova. That's what I'm guessing what it is.

00:08:33
Speaker 1: It is something like that, and yet it contains deep mysteries that we do not yet understand well.

00:08:38
Speaker 2: As usual, we were wondering how many people out there had thought about what a superluminous supernova is or have any idea what it is.

00:08:44
Speaker 1: So thanks very much to everybody who answers these questions for our fun segment of the podcast, which used to be Person on the Street and is now a random person on the Internet. If you are a person on the Internet and you would like to participate in the future, please write to me too, question at Danielandjorge dot com.

00:09:02
Speaker 2: So think about it for a second. What do you think is a superluminous supernova? He would beeple had to say.

00:09:09
Speaker 4: My best guess would be that it's a supernova that, for some reason, perhaps do to excess energy input or some initial conditions that are extraordinary, produces way more electromagnetic radiation than a normal supernova.

00:09:22
Speaker 3: A super luminous supernova is probably a supernova that is extremely bright past the normal brightness that a supernova has. That would mean it would be an extremely bright supernova because the regular ones are already pretty bright.

00:09:40
Speaker 5: Superluminous supernova must be a supernova that just has high visual magnitude. Super super bright. Maybe we use it to measure distances.

00:09:52
Speaker 1: Well. The name seems to suggest that it's a supernova that emits more radiation than a regular super nova. Why that might be the case, I have no idea.

00:10:03
Speaker 6: I guess a super illuminous super and iva is in the name and that it's extra bright. But I thought a supernova I would say standard candle that people judge distances by. So maybe I'm being too simplistic.

00:10:16
Speaker 2: I think it's super illuminous supernova would be a supernova brighter than usual.

00:10:21
Speaker 1: Supernova's probably connected to the mouse.

00:10:24
Speaker 2: All right, I like the person who said it's in the name.

00:10:29
Speaker 1: You might almost say it's well named because it's communicated effectively what it is.

00:10:34
Speaker 2: I'm sure it's well named and that it communicates what it is. But you know, sometimes thesaurus comes in handy. For example, the same person said it means it extra bright. You could have just called it an extra bright supernova and then it wouldn't sound so sinsy.

00:10:51
Speaker 1: I don't know, it makes it sound more hollywoody. Maybe that's what they were going for, a.

00:10:54
Speaker 2: Little bit of glam super luminous supernova.

00:10:56
Speaker 1: Hmmm, it does have a certain ring to it.

00:10:58
Speaker 2: Well, step us through this interesting thing coming on, and let's start with the beginning. What is a supernova? Is it like a Noah that's super.

00:11:06
Speaker 1: It's like a nova that took off it's glasses.

00:11:09
Speaker 2: It's like a nova that's not an older Yeah.

00:11:11
Speaker 1: Actually the name comes from Kikobraje who wrote this book De Nova Stella, from which the word nova comes from nova there and means new as a new star because an observation of the changes in the sky. And so the supernova are one of these really cool astronomical objects because they happen sort of on human time scales. I mean, we're used to thinking about like stars forming and burning over millions and billions of years, and galaxies swarming for billions of years in the universe expanding over billions of years. Everything sort of happens on these really long time scales that we don't get to watch. We just have to like imagine and fast forward or in reverse. But supernova are really awesome because they're dramatic and they happen on human timescales, Like you can see this thing appear in the sky and then burn for a few weeks or months and then fade out. So the sky changes at a rate that we can actually see, which is why supernova are some of the oldest astronomical observations that we have. People have been seeing them and wondering what they were for literally thousands of years. And now we know, of course that supernova represent the endpoint of certain kinds of stars. Most stars don't end this way, but some stars end with this very dramatic collapse, this implosion, which then leads to very dramatic explosion and a huge release of energy.

00:12:28
Speaker 2: Wait, so you're saying it's the end point of a star, like the death of a star, and yet it's called the super nova, like a super new Well.

00:12:37
Speaker 1: It gets a little bit into what you mean by a star. But yeah, you have stars which are born and then burned and have fusion going on at their core, and there's this usual struggle between gravity that's compressing it and trying to make it more and more dense, and the fusion and the radiation that's puffing it out and keeping it from collapsing. But in the case of some supernova, eventually gravity wins, and we can walk through some of the mechanism for this, and you get this collapse where this shock wave propagates in very very fast crushes the star and then burns all of its fuel very very quickly and explodes. And so in a sense, that's the end point of the star and the birth of something new because you no longer have fusion happening.

00:13:18
Speaker 2: It sounds like a very political answer there.

00:13:21
Speaker 1: Well, you know, every death leads to a rebirth of some kind.

00:13:24
Speaker 2: All right, Well, it's like you said it, and it all starts with the collapse of a star. I think that's something that a lot of people don't know. Like, you know, we usually say a supernowa is the explosion of a star, But before the star explodes, it actually collapses, right.

00:13:38
Speaker 1: Yeah, And there's two ways that this can happen. The sort of classic way that we call core collapse is basically the end point of your standard solar fusion. You know, when a star starts out, it's mostly hydrogen. Sometimes it's a little bit of metal leftover from previous star burning. But you know, in the early universe it was all hydrogen. That hydrogen gas clumps together and falls together because of gravity, pushes it together, squeezes it together, gets it hot enough to have fusion, and then that fusion makes heavier stuff turns hydrogen into helium, and then helium into carbon, and carbon into oxygen and nitrogen and silicon. You get heavier and heavier stuff, until eventually it's made stuff that's so heavy, so massive that the gravity from its inner ashes, the product of its fusion, causes it to collapse. It can no longer hold off gravity, and so gravity eventually overcomes the outward pressure from fusion and the star collapses.

00:14:31
Speaker 2: Yeah. It's almost sort of like a phase transition, right, Like all of a sudden, the molecules inside of the Sun can't take the pressure, so they sort of collapse into a different arrangement, right, Like they're maybe staying apart from each other or staying at a certain density because of some forces. But then at some point those verses get overcome and the whole thing just kind of rearranges into a more compact form, right, something like that happens.

00:14:55
Speaker 1: Yeah, And it's very sudden. Right. Once it falls over the threshold is a runaway effect because gravit squeezes it and you get this shockwave inwards towards the core, which then bounces back out right. Because when the shockwave happens, now you've compressed the core. It's super duper high temperature, and now very quickly it does kinds of fusion that couldn't do before. It didn't used to be hot enough to make the heaviest of metals. But now in those brief moments during that shockwave, the conditions are right to make some of the really heavy metals, the ones you don't get during normal burning of the star. And then that fusion creates an incredible amount of radiation. So now the radiation wins. So it's sort of like a tug of war where it was balanced and then gravity starts to win. But then that creates the conditions for the pressure to take over again, and gravity loses and the star explodes.

00:15:42
Speaker 2: Yeah, it's sort of like a building collapsing. But then once the building collapses, that pressure of all that stuff being crushed together somehow unleashes other kinds of energy, right, and then the whole thing explodes. What's being unleashed is basically fusion energy, right.

00:15:56
Speaker 1: Yeah, what's being unleashed there is fusion energy exactly off and in kinds of fusion that you can't get during normal burning. And so that's one way that the universe makes super duper heavy metals like gold or uranium. Other methods are like collisions of neutron stars or other kinds of shock waves. It's very very hard to make those heavy elements because they require energy rather than producing it.

00:16:18
Speaker 2: That's kind of why they say some of these heavy elements like gold and some of the more complex elements are made in the heart of a dying star.

00:16:25
Speaker 1: Yeah, exactly, and so that's method number one. Basically for supernovas to form, it's actually called a type two supernova. This core collapse the other way similar, but it happens via a different path. Like you start out with a star that doesn't naturally have core collapse. It burns, it becomes a red giant as it puffs out and the hydrogen, helium and its atmosphere start to burn, a really big star. But then it doesn't turn into a supernova. Instead, it turns into a white dwarf, which is basically just leaving the hot core of the star, the metals that form during the initial burning. Everything else puffs out and the hot is left behind this white dwarf, And normally that white dwarf would just hang out for a long time and eventually over maybe like trillions of years would cool into a black dwarf. But if somebody comes along, like another star that's nearby, or it's part of a binary star system, it can eat a little bit more of that other star, which pushes it over the threshold for gravity to win and to cause a supernova. So it's sort of like a second act for this star. It gets enough fuel to cause this collapse and this supernova sort of later in the game.

00:17:31
Speaker 2: Right, that happens in like binary star systems, right, like a star system with two sons in them. But I guess my question is why do you need that extra step, Like why does it need to go in this particular way? Like why does one need to go into a white dwarf? And then the own has to get sucked in? What happens If the Sun's merged before that happens, would they still go supernova?

00:17:49
Speaker 1: If they merged before that happened, then they probably have enough mass. It's all about having enough mass. If you were big enough to begin with, then probably you would have ended up in a supernova. If you weren't big enough to begin with, if you were sort of a smaller star like our star, you just would have ended up with a white dwarf. And really it's all about the mass, because having more mass means having more gravity. Having less mass means having less gravity and not having enough force to overcome the structure of the star. I mean, to have this sort of collapse to have gravity trigger the supernova, you need enough gravity and resisting that is the structure of the star. A white dwarf has chemical bonds that are pushing out against this gravitational collapse. It's already a very dense object, but it's able to withstand the gravitational pressure. So you need an extra scoop, an extra helping of gravity to come over that threshold.

00:18:37
Speaker 2: I see. So it's really kind of mostly about just how much mass is out there or in that neighborhood.

00:18:42
Speaker 1: And type two supernova means you had enough mass originally to go supernova. Type one means you didn't and then you got an extra serving later which brought you over that threshold.

00:18:51
Speaker 2: Now, is it the case that any star that's bigger than this threshold is going to go supernova? Or at some point to do stars get too big to go supernova?

00:18:59
Speaker 1: Stars never get too big to go supernova. Basically, anything that's over like eight times the mass of the Sun is going to go red super giant and then type two supernova. Absolutely, there's really no way around that. That's just the fate of all these stars. But those stars are pretty rare, Like most of the stars in the universe are not that big. Even our star, which of course has one solar mass, is an unusually large and bright star in the universe. Most of the stars in the universe are smaller and cooler than our star. They are red dwarfs. So the number of stars in the universe that will go supernova is a small fraction. It's like a rare thing to happen.

00:19:36
Speaker 2: How rare is it? Like, is it super rare or just mild mannered rare.

00:19:41
Speaker 1: It's not something we know very accurately because we don't understand this initial mass function in the universe, the thing that determines like how much mass the stars get. But some calculations estimate it's like a few in a million stars. So you have a population of like a million stars, four or five of them might go supernova.

00:19:59
Speaker 2: Oh, only four, four or five are bigger than eight solar masses exactly.

00:20:03
Speaker 1: Yeah, it's really very dramatically dominated by the lower mass stars.

00:20:07
Speaker 2: And also I resented you said most stars are cooler than our son. I think our son is pretty cool.

00:20:12
Speaker 1: I think our son's pretty hot.

00:20:13
Speaker 2: Actually exactly, yeah, right, is.

00:20:16
Speaker 1: Our son hot or not? Yes, it's definitely hot.

00:20:21
Speaker 2: The answer is yes.

00:20:22
Speaker 1: That's a safer work answer.

00:20:23
Speaker 2: All right, Well, that's a super nova, and so let's dig into why they're hard to study, how we have studied them in the past, and then finally, what exactly is a super luminous supernova? So super stay with us, we'll be right back. All right, we're talking about superluminous supernova in a super way.

00:20:54
Speaker 1: And even a normal, non super luminous supernova is super nuper. It can be hard to appreciate, like how dramatic these events are, but a single supernova when it goes, can be brighter than the rest of the galaxy that it's in. These galaxies contain, you know, often hundreds of billions of stars. Now you have a single object brighter than hundreds of billions of stars. It's really an incredible event. And we're just talking about your ordinary garden variety supernova.

00:21:26
Speaker 2: Yeah, I know we've mentioned that before. Like when a star goes supernova's brighter than the galaxy. And but that sounds kind of crazy, like what does that mean. It means that it's outputting more light than all of the stars, the hundreds of billions of stars in that galaxy in that moment.

00:21:40
Speaker 1: Yeah, that's exactly what it means, and that's why we can see them. Right, Most of the supernova we have seen are in other galaxies. The Milky Way is kind of weirdly quiet in supernova. We haven't seen one in our galaxy in several centuries. So most of the supernova that we have seen are in other galaxies, and we can see them because they are brighter then the entire galaxy that they're in.

00:22:02
Speaker 2: Wait, you said that we haven't seen one in the Milky Way, but so we have seen super nova that have come from the Milky Way.

00:22:08
Speaker 1: We have seen supernova in the Milky Way. But the last person to do it was Kepler, like sixteen oh four, Kepler, he's got like the last paper on supernova's in the Milky Way. We haven't seen one from our own galaxy in four hundred years.

00:22:23
Speaker 2: But how did Kepler knowa was within our galaxy?

00:22:25
Speaker 1: Well, Kepler didn't really know because He didn't really understand the idea of galaxies. We didn't even know like that there were other galaxies back then. But we can now look at the thing he was studying, and we understand what he was looking at, and we know that it's in our galaxy.

00:22:38
Speaker 2: How do we know what he was looking at? Did he leave like a star map?

00:22:41
Speaker 1: Kepler was pretty good at taking records. That's why he and Tiko Brahe were one of the first ones to really understand stellar motion and planetary motion. They were pretty nerdy about it.

00:22:52
Speaker 2: M So, I guess, how do we know he looked at one in our milk way? Because it brightness or what?

00:22:57
Speaker 1: Again? We know which object he was looking at. He told us where it was in the sky. He has pretty detailed records of what he was looking at, so we can now look at that object like, what was that? Oh, look, it's a remnant from a supernova.

00:23:10
Speaker 2: Oh, we can see the remnant of it now.

00:23:12
Speaker 1: Yeah, And that's actually really valuable because we'd love to study these things over many centuries or many thousands of years to understand like what happens after supernova? How does the cloud disperse? It gives you a lot of clues about what was going on inside of it, something we still don't really understand. So studying something hundreds of years later is really valuable. And so having like ancient astronomical records that say, oh, there was a supernova here five hundred years ago or two thousand years ago is actually really relevant and powerful to astronomy today.

00:23:42
Speaker 2: Now, if a supernova has as much energy as the whole galaxy, wouldn't that just fry everything in the galaxy or at least in like the half of the galaxy it's in.

00:23:51
Speaker 1: Yes, supernova are very dangerous and very damaging potentially to life. So we should be glad that there haven't been like a whole rash of supernova in our neighborhood, because we might not be. Here's an enormous amount of radiation released in supernova, and it's very dramatic in the visible spectrum and the high energy photons like gamma rays, et cetera, which would be extraordinarily damaging to life on Earth. It turns out, though, actually most of the energy from a supernova isn't even in the visible light, like they're already as bright as the rest of the galaxy. But that's one percent of the energy released by the supernova, most of it is actually released in new trinos.

00:24:29
Speaker 2: Yeah, that's amazing. I think we've talked about that before. But why neutrinos, Like, why would it put all of its energy into something that can barely be felt.

00:24:39
Speaker 1: Well, I don't think there's like a committee there deciding, like how much do we budget in neutrinos versus photons. It's just sort of what the physics does. And for a long time we didn't understand how important neutrinos were because it feels like they're sort of irrelevant. Once energy turns into neutrinos, it feels like it can't really participate in physics anymore because most of the universe ignores neutrinos. Neutrinos are these particles that only feel the weak interaction, and they can fly through like a light year of lead without interacting with anything. So people thought for a long time, well, if you're dumping the energy into neutrinos, that's basically just lost. But more recent simulations of supernovas have discovered that those neutrinos actually do interact with the rest of the material. Rest of the material that's collapsing is so dense that it actually can absorb some of that heat back from neutrinos. So there's an amazing effect in supernova's called neutrino heating, where the neutrinos from the supernova actually reheat the material. And if you don't have this effect, then the explosion doesn't happen. So why is it produced. It's just because in fusion you get a lot of these nuclear processes. A lot of them just result in photons and neutrinos, but it turns out those neutrinos are really important for making the explosion happen.

00:25:49
Speaker 2: But somehow they're like the main product of whatever's happening in the supernova.

00:25:54
Speaker 1: Yeah, and it's not just supernovas, right, Stars in their normal course of business produce an enormal number of neutrinos. Like here on Earth there's one hundred billion neutrinos per square centimeter per second. Like you hold your hands out and there's a trillion neutrinos going through your fingernails every second. And we're really far away from the Sun, right, So imagine like how many neutrinos are produced in the Sun itself, And now supernova's produce like ten to the fifty eight neutrinos during their supernova explosion. So it's really an incredible amount of energy in neutrinos. So, yeah, supernovas are super duper bright and luminous, and that's a tiny fraction of the sort of true brightness of these incredible events.

00:26:40
Speaker 2: It's almost like it's a good thing it's making so many neutrinos. But it's a good thing it's putting all its energy into neutrinos, because if it put it into something that we would feel like every galaxy everywhere would be toast all the time.

00:26:50
Speaker 1: Right, Yeah, yeah, that's exactly right. We're lucky that they're exploding in this sort of safe way. And even still, they're very dangerous. If there were a super nova in our backyard, it would fry half of the Earth, or if it lasted long enough for the Earth to rotate, who basically fry the whole Earth.

00:27:07
Speaker 2: How far would a supernova need to be to be at a safe distance from us.

00:27:11
Speaker 1: That's a good question, and it depends a little bit on the brightness of the supernova. The type one supernova's the ones that start with binary stars there are st like ten times brighter than the core collapse supernovas because they're more dramatic, So it depends a little bit on the type. Anything in our stellar neighborhood at all would really fry us. So supernova's on the other side of the galaxy, no big deals. Supernova's on our side of the galaxy, you start to get a little bit nervous. Supernova's within a few tens of light years, we're toasted.

00:27:39
Speaker 2: Okay, so we're sort of safe. But I feel like you said that supernovas happen like a few every couple of million stars, and the milk Away has several hundred billion stars, right, so there should be, you know, thousands and thousands of them sprinkled all over the Milky Way potentially about to go off.

00:27:54
Speaker 1: There should be, and we don't understand it. And we did a whole podcast episode about the mystery of the missing Milky Way supernova. Go check that out. It's a really fun question about whether supernova's are happening in our galaxy but we can't see them because they're obscured by the center of the galaxy, or maybe there's something weird about our galaxy. Also, the supernova that had happened in the Milky way tend to be sort of weirdly distributed. They're not really in the place where most of the stars are, and so there's a lot of mysteries about why we haven't had more supernova in our galaxy. Check out that episode.

00:28:27
Speaker 2: Maybe it was Superman who pushed all those supernova away, or maybe another superhero or Superwoman.

00:28:34
Speaker 1: Yeah, it's really fun to read the sort of historical record here of like Chinese astronomers talking about guest stars that appear in the night sky. Hilariously, they describe them as some having pleasurable colors and others not having pleasurable colors.

00:28:47
Speaker 2: Way, there were so many happening somebody supernova happening that they could compare the colors.

00:28:53
Speaker 1: They just commented on them, because these things evolve over time, you know, they change in color. I thought it was just hilarious that they note not only did this incredible thing happen in the sky, but some of us didn't think it was very pretty.

00:29:04
Speaker 2: Some of us didn't think it was pretty, very super there were more kind of a met.

00:29:07
Speaker 1: Nova, or maybe they were just recording, you know, their anxiety about it, like, wow, this is a crazy thing to be happening in our sky. You don't usually see a lot of things changing. Eclipses and comets and supernova are like pretty dramatic events in the sky. It's fascinating to think about what it must have been like to be somebody seeing that happen and not understand it at all. It must have seemed very mystical.

00:29:31
Speaker 2: Well, you said, it's very rare to see a supernova, like, how many have we seen since recorded history?

00:29:36
Speaker 1: Well, we've only seen a handful in our galaxy. But because we now have incredible telescopes, we've seen hundreds and hundreds of supernova in other galaxy. But still it's limited to you know, like numbers like hundreds. We don't have thousands and thousands of these examples.

00:29:52
Speaker 2: Is it likely that I would see a supernoa go off? You know, first of all, I would have to be a whig all night, which I guess I am. But I'm looking at the sky. I am, Like, would I notice but supernova went off to light up the whole sky? Would it just kind of appear like, oh, there's a new pinpoint of light there.

00:30:07
Speaker 1: Well, a new supernova in our galaxy you could see with the naked eye. It would be like a new event in the sky, and it could be brighter than many other starts depending on how close it is. It could definitely brighten up the night sky. For sure. Most of the supernova we have observed are in other galaxies, and so they are brighter or as bright as that galaxy, which is still pretty dim to the naked eye, so easy to spot with telescopes. Not that easy to see with the naked eye, but potentially somebody could point you to one and say that's a supernova. That little dot. There is a distant galaxy with a supernova in it.

00:30:40
Speaker 2: I guess what I mean is like, you would have to know what this night sky looked like before the supernova in order to be like, oh, that's something new there that you couldn't see before with the telescope.

00:30:49
Speaker 1: Yeah, exactly. And that's basically what we do is we scan the sky and we look for changes or always on the lookout for these supernova because they're hard to predict. We can't very easily look at a bunch of stars and say that one's going to go supernova, and that one's going to do supernova tomorrow or Tuesday. We have to just catch them happening. So we're constantly scanning the sky, comparing it to what the sky looked like yesterday and last week, looking for changes, and as soon as somebody spots one, then a bunch of telescopes get trained on it to track it in great detail to understand its light curve. Because remember that's like really valuable information for understanding how far away is that galaxy, which tells us things about like the expansion of the universe. Really incredible scientific discoveries are pinned on capturing these supernova inaction.

00:31:32
Speaker 2: Wonder if that's stressful for astrophysicists, you know, like I can't go to the bathroom, go get coffee, because what if supernova comes up just as I'm leaving my desk.

00:31:41
Speaker 1: It is sometimes very dramatic.

00:31:43
Speaker 3: You know.

00:31:43
Speaker 1: We have automated systems that scan for these things, but once you see one, then they get communicated to other telescopes around the world which might have been busy doing something else, and then decide, you know what, this is more important. We're going to change our observation plan. We're going to turn around and look at this crazy thing that's happening because it might only last for a few days.

00:32:00
Speaker 2: And you said they're sort of unpredictable. I guess they're not unpredictable in the sense that I mean, you can tell if a star is going to go supernova at some point, right, you said all stars above us certain size, do you just don't know when it's going to happen.

00:32:12
Speaker 1: Yeah, I think that's true. We can't look at a star and say this is about to go supernova, or that's about to go supernova. And some stars don't actually explode, like they collapse. They have the first part of it, but then they don't bounce back and have an explosion. And there's all sorts of different kinds of ways that these stars can collapse, and sometimes there's a black hole that's created at the heart and sometimes not, and so they can look very different from collapse to collapse. So while all these stars that are big enough will eventually burn out their fuel and collapse, they don't all trigger exactly the same kind of supernova. Some of them kind of whiff out, some of them get very bright. And that's a lot of what we don't understand. And the reason we don't understand it is that it's very complicated physics. You have a lot of things going on here. You have general relativity that describes the gravitational pull, and you have very complicated fluid dynamics to describe like how the pressure is propagated through this thing. Plus you have fusion happening, so you have radiation coming outwards. You have neutrinos, which turn out to be important. So it's one of these scenarios. We have to get a lot of the details right in order to make the prediction accurate. And we're just very recently able to even like simulate these things and see supernova happen on the computers.

00:33:21
Speaker 2: Sounds like you need another category for them, like super confusing, super lubinus supernovas. Maybe we just need supercomputers, yeah, or maybe you need Superman to come in and do some physics. I think I need a super grand to understand supernovas with a super big pile of money. It sounds like you're getting super greedy. They're super villain.

00:33:42
Speaker 1: I just want to understand the universe. Is that so greedy?

00:33:44
Speaker 2: Well, all supervillains think they're doing the right thing. All right. It's a deep dive into how we study supernovas. Let's get into what a super luminous supernova is and whether or not it is super or not. But first, let's take a quick break. All right, we're talking about super luminous supernovas, which I guess means just the super bright supernovas.

00:34:18
Speaker 1: It does mean super bright supernovas, though we sort of run out of modifiers here because already supernovas are super bright events and super rare events. They're like very dramatic moments in this story of the universe. But then we saw some supernova that were so ridiculously bright even by the standards of supernova, that they had to come up with another category for them. So super luminous supernova are supernova that are at least ten times brighter than your normal, run of the mill incredibly bright supernova.

00:34:49
Speaker 2: Whoa first of all, ten times brighter, that's amazing. And second, see you just used another word, incredibly bright. You don't have to use super again.

00:34:58
Speaker 1: You're right, we should call them incredibly bright.

00:35:00
Speaker 2: It's supernova amazingly bright, extra right.

00:35:05
Speaker 1: Overwhelmingly bright supernova.

00:35:06
Speaker 2: Now let's go with super luminous. That sounds cooler or hotter.

00:35:10
Speaker 1: But there's something else going on here, which is this astronomical need to like categorize, because in one sense like you make a distribution of all the supernova some are brighter, some are dimmer. Whatever you expect them to not all be the same, and so why can't you just say, well, look, here's supernova summer brighter, some are dimmer. But this need to name this extra bright category comes out of this like feeling like something different is happening. It's not just that there's a distribution and these are the ones on the tail. They feel like they see this cluster, this collection of supernova that are different from the other ones. It's like this grouping on the very high side where they think maybe something different is happening.

00:35:48
Speaker 2: Oh, that's interesting. So there's a range of brightness for supernovas, and typically I thought all supernovas, we're all sort of the same. That's how they use as standard markers in the universe.

00:35:58
Speaker 1: So the type one A supernova, the ones that are super bright already, they're not all the same brightness. Actually, they have all the same shape of their light curve, which means how they get bright and then how they dim which then you can calibrate to how bright they are actually at their source through a few steps. So it's not quite as simple as all these supernovas are exactly the same brightness always. It's that you can deduce how bright they are by how quickly they ramp up and how quickly they ramp down. It's sort of like remember the cephids, those variable stars, the ones that get brighter and dimmer and brighter and dimmer. It's not that they're all the same brightness, it's that from the period of their pulsation, you can deduce how bright they are. It's sort of that way for type one A supernova. They're not all the same brightness, but you can figure out how bright they are from their curve.

00:36:45
Speaker 2: So you have these super or extra brightnd supernovas that are ten times brighter than regular supernovas, But then you have some that are ten times even brighter than that exactly.

00:36:55
Speaker 1: So you got the type twos the sort of like normal supernovas, and then type one A are ten times brighter than that.

00:37:02
Speaker 2: So they're super luminous supernova.

00:37:04
Speaker 1: And then and then the extra right supernova extralous supernova. These are ten times brighter than even those.

00:37:13
Speaker 2: You might as well say super super humanous.

00:37:16
Speaker 1: Super squared supernova. And these things are super nuper right, and they're also really rare, like one in ten thousand supernova, which is already like, you know, five out of a million stars, So now we're talking about like five out of ten billion stars are going to be super luminous supernova. These are incredibly rare. Wow.

00:37:37
Speaker 2: So that means that their brightness is ten times brighter than the galaxy they're in over regular galaxy.

00:37:42
Speaker 1: Yeah, they can outshine their galaxy by huge amount, and not just because they're extra bright, but weirdly, for reasons we don't understand, they tend to be found in smaller, dimmer galaxies. So we talked recently on the podcast about these things called dwarf galaxies, galaxies with a small or a number of stars in them, and how they're fascinating laboratory for understanding maybe the formation of the universe and how galaxies form and dark matter. But these superluminous supernova tend to be found only in these dwarf galaxies, which is like a weird clue maybe about why they happen and what makes them super luminous, But it also means that they're extra bright compared to their galaxies, which tend to be extra dimm That.

00:38:24
Speaker 2: Is a weird clue, right. A dwarf galaxy, as we talked about before, is just kind of a small galaxy, but it's also sort of made up of different kinds of stars too.

00:38:31
Speaker 1: Yeah, dwarf galaxy just means a smaller blob of stars. It can be like thousands to just a few billion stars. It's a pretty big range. Remember that our galaxy is like one hundred billion or two hundred billion stars, So dwarf galaxy is a much much smaller galaxy. But there's a really wide range of these things. Some of them are like mostly dark matter and have just a few sprinkling of stars. Others have had their dark matter stripped out of them. Some of them are like early progenitor galaxies. We think that the big galaxies came from the combination of a bunch of dwarf galaxies. So some of these dwarf galaxies might be sort of like primordial and as you say, could have like older stars from the earlier part of the universe.

00:39:11
Speaker 2: All right, So then what's making these super super superluminous supernovas.

00:39:16
Speaker 1: We don't know. It's a mystery something we see in the universe but do not yet understand. We have like no model that tells us why this can be happening. I remember, we just barely understand why supernovas go boom and what's going on inside of them and how all that radiation happens. You know, when we write down all of our physics and code it in the computer, we can barely get it to happen in simulation, and maybe in those simulations line up with what we see in the universe. But there are a few ideas for what might make it happen, and they come from noticing how these are different from the other supernoas, not just in their brightness, but in other characteristics.

00:39:50
Speaker 2: Well, I guess, first of all, do we know why some supernovas are brighter than others? Is it just about how much size they have, how much mass was there when they collapse?

00:39:59
Speaker 1: We don't really understand. It has to do with all the internal dynamics and how much energy is devoted to photons and whether the object itself is transparent enough to release those photons or if it's going to be opaque and reabsorb those photons. So it's a complicated thing that we do not understand very well right now, and.

00:40:16
Speaker 2: It doesn't have to do with the size, like I would imagine like a bigger star if it collapses, would make a bigger explosion than a small star that collapses.

00:40:24
Speaker 1: It's definitely part of the equation, right, The more energy you have, the more energy you can convert into radiation. It's definitely part of that equation. But it's not quite so simple, right. It's not just like bigger star, brighter supernova. But you might be on the right track because one suspicion is that these superluminous supernova come from stars that are unusually large stars that have more than forty times our Sun's mass when they start out, and that's very unusually large for a star. So that's one suspicion is that maybe they come from the heaviest of heavy stars.

00:40:55
Speaker 2: And what makes us think that just from the idea that bigger is brighter.

00:40:58
Speaker 1: It's just like one of the things. It's just like one explanation, as you say, more mass means you have more energy that you can convert into light. So it's just like a starting point. There are a few other interesting clues that point in that same direction, like the light from these stars is a little bit different from light from other supernova. They don't seem to have a lot of helium or hydrogen in their outer atmosphere. Remember, you can tell what's in a star by looking at the light that it emits, because helium and hydrogen and all the elements have their own characteristic ladder of energy levels that the electrons are allowed to be around them, which means when the electrons jump down an energy level or release a photon, you can kind of tell which kind of atom it came from by looking at the energy of that photon, which has to line up with the spacing of the energy levels of that atom. So you can look at the spectrum from a star and you say, oh, look, there's a peak here that means there was hydrogen, or there's a dip here that means there was helium that was absorbing that light. So from the peaks and the dips in the emission of the star specs you can tell what it's made out of. What they've noticed is that these stars when they go tend to have almost no hydrogen a no helium in them, which is pretty unusual. Most stars when they go supernova still have helium and hydrogen like in the outer layer that hasn't been burnt yet.

00:42:16
Speaker 2: But these don't put that mean that they're older stars maybe or more mature stars.

00:42:21
Speaker 1: It could be, or it could be that something else is going on nearby that's like strip them of their atmosphere. Maybe there's a very strong solar wind, or there's a binary star that's been gobbling up their atmosphere, or maybe they're one of these weird kind of stars called a wolf rayet star that do tend to have very little hydrogen and helium in them because as you say, they've burned it already. That feels like an important clue. That's one thing that makes these things different. But we don't understand why not having hydrogen and not having helium would make the explosion brighter. Like if you take a star and you remove it's hydrogen helium, why would that give you a brighter supernova? We don't understand, or maybe that's not the answer. Maybe there's some other reason that generates a bright supernova and happens to also remove the hydrogen and helium from the star. It's just like a clue we have found. We don't understand it yet.

00:43:11
Speaker 2: Now have we seen any Are there any special superluminous supernova that we've seen that are sort of interesting to talk about.

00:43:17
Speaker 1: The most dramatic one is really incredible. It's this supernova called ASASSN, which is the name of the telescope fifteen LH and it's about four billion light years away. But when we saw it in twenty fifteen using these twin telescopes in Chile, it was the most luminous supernova ever observed. It was almost a trillion times brighter than our sun.

00:43:42
Speaker 2: A trillion times brighter than the Sun. Yeah, that's wild. It's a good thing. It wasn't in our doubts.

00:43:49
Speaker 1: Yeah, there's this astronomer from Ohio State University, christof Stenek said if it was in our own galaxy, it would shine brighter than the full moon. There would re no night it would be easily seen during the day. Like, this thing was a monster. It's more than two times brighter than any other superluminous supernova.

00:44:10
Speaker 5: Whoa.

00:44:10
Speaker 2: And it was sort of a kind of luck that we caught it right.

00:44:13
Speaker 1: Absolutely, it's lucky. We just like happened to be pointing telescopes in the right direction at the right time, and that's why we saw it. But it's also sort of hard to miss. Like, this thing is twenty times brighter than our higher galaxy. It's really amazing. So this was definitely the brightest supernova ever.

00:44:28
Speaker 2: But it's also kind of far away. That's why it's easy to miss.

00:44:31
Speaker 1: Yeah, it's four billion light years away, otherwise it might have fried us.

00:44:35
Speaker 2: It's like a tensive the way to the end of the universe.

00:44:37
Speaker 1: Yeah, exactly, So pack some snacks if you're going to go visit.

00:44:40
Speaker 2: But it's cool. We could see it from here, right, and it's so bright even for me so far away.

00:44:44
Speaker 1: It is really cool, and it offers an opportunity to like think about what's going on and understand how supernova's form.

00:44:52
Speaker 3: You know.

00:44:52
Speaker 1: One idea about what makes these things so bright is that they're just like super big versions of stars that make super luminous supernova. Maybe they're just bigger and they're more massive and that's what's happening. But there are also other theories, like maybe these are other kinds of events, they're not just bigger versions of supernova. Like maybe there's an interplay between these stars and black holes that are nearby that are triggering a different kind of collapse.

00:45:16
Speaker 2: Yeah, Like if you see something bright in the sky doesn't necessarily have to be a supernova, right, it could be something else exploding, or maybe like a quasar or something like that.

00:45:25
Speaker 1: Yeah, although these things have the sort of pretty characteristic light curve of a supernova and they appear briefly and then disappear, which quasars don't. But black holes might be contributing. Like maybe you have a star that was going to go supernova anyway, and the tidal forces from a nearby black hole add to the collapse and like make that collapse more powerful. Right, if you're near like a supermassive black hole in the center of your galaxy, it could be that the tidal forces from that trigger the collapse in a way that wouldn't have happened otherwise you get like a special version or an unusual version of the collapse.

00:45:58
Speaker 2: Wait, so this would be a super massive black holes supercharged, superluminous supernova. Is that what you're telling me? It would be pretty incredible, extra extra bright exactly.

00:46:12
Speaker 1: That's one alternative idea. Another really cool idea that's reading about is that it could be magnetars losing their energy. Right, maybe it's not a supernova at all. A magnetar is a neutron star, which is another potential endpoint for a star that's spinning really really fast and has a huge magnetic field and all sorts of incredible energy, But they're dumping a lot of that energy out into space. They're converting their rotational energy into this beam. And so the idea is maybe one of these magnetars has a dramatic spin down effect where it's transforming its rotational energy very suddenly into a bunch of radiation, which creates these huge jets and produces enough energy to look like a superluminous supernova. But people have tried to do calculations to make that happen, and they don't think that those things could be bright enough to explain what we've seen. So it's still sort of a wild West of ideas out there, people wondering like, maybe it's this, maybe it's that. Maybe it's these two things combined that makes this crazy event.

00:47:12
Speaker 2: I guess if it's something so bright and so explosive, wouldn't we sort of see evidence of that explosion affecting the whole galaxy it's in, or a lot of the stars it's in. You know, maybe that way you could tell if it's an explosion after all or not, it is.

00:47:24
Speaker 1: Actually really cool to track these explosions. You feel like it's going to affect the whole galaxy. But remember that galaxies are really big, and so for information to get across the galaxy takes a long time. So these explosions look sort of like they're happening in slow motion because the distances are just so vast, Which is one reason why it's really cool to look at old supernova to see how has the supernova affected stuff nearby, Like when the supernova radiation slams into nearby gas, what happens. Do you generate new stars? Do you heat it up? Do you blow it out? That's one reason why it's really cool to look at these sort of old supernovas from the past.

00:47:59
Speaker 2: Yeah, like I would maybe imagine like at the side of where there was a supernova, maybe like all the stars around it got snuffed out or something re a least pushed out of the way or something. At least that's how it looks like in movies. In superhero movies, well you do.

00:48:13
Speaker 1: Get this very dramatic and I think very pleasing to the eye clouds of gas and shock waves that come out of supernova. Some of the prettiest nebula that are out there, like the crab Nebula, actually did come from ancient supernova. It was in the nineteen forties we realized that the crab nebula is the remnant of a supernova that the Chinese saw about a thousand years ago. So we get to watch like a thousand years of slow mo explosion playing out in the sky.

00:48:40
Speaker 2: So we're not even true if it is a supernova. These super luminous events, yeah.

00:48:44
Speaker 1: That's true. There's still a bunch of different theories about what could be causing them, and eventually we might even give them a different name. We might even drop the super.

00:48:52
Speaker 2: Yeah, or maybe a super luminous supernova might try it to be just a mild mannered black hole explosion or.

00:48:57
Speaker 1: Something like that. You never know what happens when they take off their glasses.

00:49:01
Speaker 2: All right, Well, another amazing excuse to look at the night sky each night. If you're looking at the night sky and you look up at the start, maybe you'll catch a supernova one day. Right, It's totally possible, isn't it.

00:49:12
Speaker 1: It's totally possible, And here's hoping that supernova is not so close that it super fries your super eyeballs.

00:49:19
Speaker 2: Yeah, it might be the last thing you see unfortunately in the night sky.

00:49:22
Speaker 1: And for everything that we have learned already about the universe, remember that we are still learning new things. It was only a couple of decades ago that we first identified super luminous supernova, these very incredibly rare things. So there could be things happening out there in the universe that are so rare. We just haven't seen one yet. And maybe somebody out there will be the first person to see this new super event.

00:49:44
Speaker 2: Yeah, and then you can give it a good name, an incredible name, an amazing name, an extra special name, a hyper name, while avoiding hyperbole of course, exactly. All right, Well, we hope you enjoyed that. Thanks for joining us, See you next time.

00:50:09
Speaker 1: Thanks for listening, and remember that Daniel and Jorge Explain the Universe is a production of iHeartRadio. For more podcasts from iHeartRadio, visit the iHeartRadio app, Apple Podcasts, or wherever you listen to your favorite shows.