What was the brightest explosion ever seen?

00:00:07
Speaker 1: Hey, Orge, you work with a lot of scientists. Who is the brightest one you've ever interviewed?

00:00:13
Speaker 2: Well, I have made a lot of Nobel Prize winners. They're all pretty humble, but yeah, generally they're pretty sharp at that level, you know, beams of light or shooting out of their eyes. They have an ore of genius.

00:00:26
Speaker 1: So do you think when you're talking to a scientists you can predict if they're going to be a future Nobel Prize winner?

00:00:30
Speaker 2: If I could, that would be awesome. I could probably make a lot of money that way. Aren't there betting pools for Nobel Prize winners?

00:00:38
Speaker 1: If there are, you probably qualify as insider information.

00:00:41
Speaker 2: Well, good thing, I'm not a betting person. Hi am Jorhem Makartudas and the author of All of Great Big Universe.

00:01:01
Speaker 1: Hi. I'm Daniel. I'm a particle physicist, a professor at U c Irvine, and I actually do have a tiny slice of a Nobel Prize.

00:01:07
Speaker 2: Ooh, what does that mean, Like they shaved off a piece of the metal or something.

00:01:12
Speaker 1: No, I'm one of a large group of collective winners of the Nobel Prize. Oh. Several years ago they gave the Nobel Peace Prize to the European Union, and that's back when Britain was a member, and I'm a citizen of the UK, so I'm not sure if I lost it during Brexit, but I was briefly one five hundred millionth of a Nobel Prize winner.

00:01:34
Speaker 2: Oh, I see you and all Europeans have won the Nobel Prize. Well technically you're not part of Europe, so yeah, I think you did lose it.

00:01:42
Speaker 1: I used to round that up to one Nobel Prize. Now I guess I got to round it down to zero to zero.

00:01:48
Speaker 2: I think you could have rounded it down to zero before you know, one fortieth million probably maybe count to zero.

00:01:58
Speaker 1: Well to me, one five hundred billion was pretty different from zero, but I take your point.

00:02:03
Speaker 2: But anyways, Welcome to our podcast Daniel and Jora Explain the Universe, a production of iHeartRadio.

00:02:07
Speaker 1: In which we think everybody deserves a prize for their curiosity about the universe. We're here to stimulate that curiosity, to encourage it, and to go with you on the journey of exploration of understanding the universe. We think, we hope, we believe that the universe out there can be understood and deserves to be understood, and that everything that scientists have figured out so far and that they're puzzling over currently deserves to be explained to you.

00:02:34
Speaker 2: That's right. We're here to illuminate the darkest corners of science and take you on a trip to the bright future of our understanding of how things work and why things are the way they are.

00:02:43
Speaker 1: We want to understand everything here on Earth, how water flows, how mountains form the history of life, but we also want to understand our vast cosmos, what's happening in the dark deep reaches of space. How did the universe get to look the way that it does. One of the most powerful forces operating on galaxies and stars and galactic clusters out there, shaping the entire structure of space, time and the universe. And to do that we have to look out into the night sky and gather messages that are coming here from the rest of the universe.

00:03:16
Speaker 2: Yeah, because the cosmos is vast and mostly dark, with lots of empty space, but there are some bright spots out there making the universe visible to us and giving us information about what's out there in the farthest reaches of existence.

00:03:30
Speaker 1: Though very few humans have actually left the surface of the Earth for significant periods of time and entered even our space neighborhood. We have a pretty good understanding of what's going on in the rest of our galaxy, the structure of galaxies beyond that, and all of that comes from gathering that information that's beamed to us from the rest of the universe. Imagine if instead the universe was totally dark, we would have no idea what was out there. We're grateful that at least some little fraction of it is shown brightly and letting us know what it's up to.

00:04:03
Speaker 2: Yeah, there are things happening all over the universe creating light, blasting it out into the universe, but some of them are maybe a little bit stronger than others.

00:04:13
Speaker 1: That's right. We have a whole series of episodes about the darkest things in the universe, dark matter, and the mysteries of the missing gravity. But today in the podcast, we're going to go in exactly the opposite direction.

00:04:24
Speaker 2: So to On the podcast, we'll be tackling the question what was the brightest explosion ever seen?

00:04:35
Speaker 1: And was it that moment when Jorge finally understood particle physics? Boom mind a blown as it happened. I'm anticipating it. Man, we're building up to it.

00:04:45
Speaker 2: Has that even happened for you?

00:04:49
Speaker 1: You know, there's that old quote, if you think you understand quantum field theory, then you don't understand quantum field theory. So it's a matter of degrees.

00:04:55
Speaker 2: I think, yeah, yeah, it's a dimmer setting the light bulb of quantum physics. But yeah, there are explosions happening all over the universe, and some of them are incredibly bright, and some of them are less bright. But maybe we haven't seen all of them. Maybe there are some that we have managed to see out there.

00:05:13
Speaker 1: Something that's wonderful about exploring the universe is being shocked by the scale of it. Learning how deep the history of time is, not thousands of years, not millions of years, but billions of years, Learning how large the universe is, how many billions of light years across stuff has spread out. These enormous scales that shock our understanding also serve to give us a better context for our existence. Turns out, the Earth and the Milky Way are a tiny little speck of dust in the vast cosmos, But there are other dimensions to be shocked in the sun you think is quite bright, it turns out the universe gets much much much brighter than that.

00:05:52
Speaker 2: Yeah, the universe never sees us to make us all feel tiny and insignificant and short lived compared to the scale of the cost and its existence. But as you said, there are things that maybe would even shock of physicists about how bright they are.

00:06:07
Speaker 1: Absolutely, and today we're going to be learning about the brightest of all time what physicists called the boat the boat boat.

00:06:15
Speaker 2: The biggest of all time, the brightest of all time.

00:06:18
Speaker 1: Not the banana East of all time, the amazing.

00:06:27
Speaker 2: Of all time. So, as usual, we were wondering how many people out there had thought about this question about what is the brightest explosion ever seen in the universe. So Daniel went out there as usual to ask people this question.

00:06:40
Speaker 1: Thanks very much to everybody who plays for this segment of the podcast, and if you'd like to hear your voice for future episodes, please don't be shy. We would love to add you to our group. Write to me two questions at Daniel and Jorge dot com to volunteer, or send me questions or send me ideas or pictures of your cats, whatever, we love to hear from listeners.

00:06:59
Speaker 2: And today, Daniel, what are our players playing for?

00:07:03
Speaker 1: They're playing for the recognition of having their voice on the podcast. Their friends and relatives will all be jealous.

00:07:11
Speaker 2: They'll be brightly jealous.

00:07:14
Speaker 1: They're playing for the biggest banana of all time.

00:07:17
Speaker 2: So think about it for a second. What do you think is the brightest explosion ever seen? Here's what people had to say.

00:07:24
Speaker 3: I am going to say that is a supernova explosion, either that or the source of whatever gamma ray bursts are.

00:07:36
Speaker 4: The biggest explosion ever seen would have to be the Big Bang, although there was nobody around to see it. We can still see the cosmic microwave background radiation, so we still can see it. But that's not.

00:07:50
Speaker 1: Really bright anymore. So I don't know.

00:07:53
Speaker 4: This is You got me in a quandary here, So it's probably a supernova.

00:07:58
Speaker 5: I would imagine the Big Bang was pretty bright, and then maybe gamma ray burse but maybe something to do with merging black holes or merging neutron stars. I guess bright doesn't necessarily have to be in our visible spectrum.

00:08:15
Speaker 2: All right. A couple of answers, kind of a trick answers here the Big Bang was maybe the biggest explosion. You can't argue with that.

00:08:23
Speaker 1: You can't actually argue with that. I don't think of the Big Bang as an explosion. I think of it as an expansion.

00:08:29
Speaker 2: Oh, I see, you're gonna use grammar to disqualify their answer.

00:08:33
Speaker 1: I know, words meanings, words having meanings are so annoying.

00:08:38
Speaker 2: I know it did just all be bath right, But I mean, you do call it the Big Bang? I mean, yourself are saying it's a bang.

00:08:48
Speaker 1: Well, you know, there's that famous story about how the Big Bang was not named by anybody who actually believed in the Big Bang, but by proponents of the steady state theory.

00:08:58
Speaker 2: Physicistal call it the Big Bang?

00:08:59
Speaker 1: Right, who still call it the Big Bang? Yes?

00:09:02
Speaker 2: Absolutely, they don't call it the Big Stretch or the Big Expansion.

00:09:06
Speaker 1: I think we should call it the Big Stretch. I think that's a much better name. Absolutely.

00:09:10
Speaker 2: Maybe we should amend the title of this episode to what was the biggest explosion besides the Big Bang?

00:09:20
Speaker 1: The brightest explosion? Though? Yeah, good question. I'm not sure how you measure the brightness of the Big Bang.

00:09:27
Speaker 2: Now, the way we phrased this question, what was the brightest explosion ever seen. Are we only counting the ones that we've seen or that we think happened, or is that the same, Well, we're.

00:09:36
Speaker 1: Only going to talk about the ones that we've seen. But as soon as you've seen something extraordinarily bright, it means that there's something out there capable of making very very bright explosions, and it's very unlikely you've seen the brightest one. So it's like discovering a unicorn. You figure, ooh, there are probably other unicorns in the forest, maybe even with longer horns. So we could only talk about the brightest. That suggests that there are very likely even brighter explosions out there we haven't seen.

00:10:05
Speaker 2: But that's an assumption, right, I mean, there could just be one unicorn out there in the universe.

00:10:09
Speaker 1: Oh absolutely, it's a statistical statement. But yes, as soon as you discover one unicorn, you figure, like, well, probably had parents, maybe it had siblings. You know, there are probably other unicorns out there, but it could be the sole unicorn, you know, created by a random collection of quantum fluctuations. That's also a possibility, even.

00:10:27
Speaker 2: If it's unlikely, it could be the unicorn of unicorn spottings.

00:10:32
Speaker 1: Yeah, we could sell it for a billion dollars. That should be our startup. My startup idea is give me a billion dollars. I will make you a unicorn, and then it'll be a unicorn startup.

00:10:40
Speaker 2: You would only make one unicorn, otherwise it's not worth much.

00:10:46
Speaker 1: Yeah, but if you only have one, you can set the price, right. I mean, I'm not an economist, but.

00:10:49
Speaker 2: I think that's how economy worries. Sure, well that's our problem.

00:10:54
Speaker 1: We're selling shares in our unicorns, folks, unicorns singular.

00:10:58
Speaker 2: But anyways, it's an interesting question. The brightest explosion ever seen? And so Daniel steps through, what are some things that can cause explosions in the universe?

00:11:08
Speaker 1: Well, first, I think it's useful to think about brightness, Like what do we mean by brightness? Obviously you're very bright, All of our listeners are very bright, our children are very bright. But when we talk about brightness in an astronomical setting, what we mean is like how many photons are arriving from it to Earth. And it used to be that astronomy only really dealt with photons. We had telescopes that could see photons. We used our eyeballs. These days, though, we have other devices like particle detectors and gravitational wave detectors that can see other kinds of messengers from astronomical events.

00:11:43
Speaker 2: Now, would brightness and photons be the best way to measure the energy of an explosion? Like, could there be an explosion that maybe you know, throws up part other kinds of particles more than photons or neutrinos or something like that that might have more energy but be less bright or there's like a pretty good indication of the energy.

00:12:03
Speaker 1: No, different astronomical events have a different fraction. They are energy produced in photons, in neutrinos, or in gravitational waves. So the best way to do astronomy they call these days multi messenger astronomy, where you're looking for photons and you're looking for particles, and you're looking for gravitational waves. It's the best way to get a handle on what happened. For example, when we look at neutrons star collisions, you can sometimes see a gravitational wave and also see light from the collision. But sometimes like supernova, can release huge amounts of energy just in neutrinos, because when the neutrinos are produced in the supernova, they're not reabsorbed, they just fly right out because the supernova itself, though it's super dense, is also transparent to those neutrinos, whereas photons get reabsorbed. So definitely there are things that are brighter in neutrinos than in photons. So that makes it very, very complicated. I think today, let's just focus on the photons.

00:12:57
Speaker 2: Okay, let's just focus on the photons, because my eyeballs can neutrinos.

00:13:00
Speaker 1: Yet, you'd have to have eyeballs the size of swimming pools.

00:13:06
Speaker 2: Oh, Daniel, that's very flattering. Thank you you saying my eyes are endless pools of.

00:13:13
Speaker 1: Of chlorinated water.

00:13:14
Speaker 2: Yeah, of physics detection technology.

00:13:17
Speaker 1: Yes, you're like an anime character with big eyes.

00:13:19
Speaker 2: Yeah, yeah, there you go.

00:13:21
Speaker 1: And the other issue with brightness is that it depends a little bit on where you are, Like you could have a really bright source, but it's really really far away and so its appears quite dim. Like when quasars were first discovered, they were quite bright in the sky, and then we discovered, oh my gosh, they're also super dup far away, which means at their source they're extraordinarily bright. So what astronomers typically do is define brightness by how bright something would seem if you were one AU away from it. If you were, like the distance the Earth is from the Sun away from that object, how bright would it be.

00:13:54
Speaker 2: That's what an AU is, right, It's like an earth distance from the Sun.

00:13:57
Speaker 1: Yeah, exactly, all right.

00:13:59
Speaker 2: So step us through, like how bright are things in the night sky?

00:14:02
Speaker 1: Yeah? So if you define the Sun as brightness of one, then you can look at things like some of the biggest stars that are out there, Like the biggest brightest star ever discovered. It's three hundred and fifteen solar masses. It's got the amazing name of R one three six a one, and it's eight point three million times brighter than the Sun. Like, if you took that star. What, Yeah, you took that star and put it in our solar system and looked up at the sky, it would be eight point three million times as intense as the Sun.

00:14:35
Speaker 2: Wow, you would need eight point three layers of sunblock just to walk out into the Sun.

00:14:40
Speaker 1: Eight point three million, Yes, it's million, yes, exactly. So that's the brightest star in the universe. And already that gives you a sense of like, wow, this stuff in our neighborhood not really that bright when we're talking about like Hall of Fame brightness.

00:14:56
Speaker 2: Wouldn't this star be huge or is it still a small star?

00:15:00
Speaker 1: So it's very large. It's right up on the edge of the biggest star you can have around three hundred and fifteen solar masses. Because bigger stars have a higher temperature at their core, so they burn hotter and faster. They don't last very long typically, and they also produce an enormous amount of radiation which pulls the star apart. Stars are actually a delicate balance between the radiation pressure from fusion and the gravitational pressure inwards from all of that mass. So it's sort of incredible that so many stars are stable for millions and billions of years. These guys essentially tear themselves apart. Anything bigger than that can't really last very long. So this is the brightest star I ever seen.

00:15:39
Speaker 2: Could you even stand at one AU away from the star, would you be inside the star?

00:15:43
Speaker 1: You wouldn't be inside the actual edge of the star. Its radius is like forty three times the radius of the Sun, so it's much much denser than our Sun. But it's nowhere near an AU for example.

00:15:57
Speaker 2: And why is it brighter. Is it just the more dense so there's more fusion going on.

00:16:02
Speaker 1: Yeah, fusion is very nonlinear, and so because you have so much more mass and it's more dense, then it's much hotter. The pressure and temperature at the core is much greater. And remember that while there's fusion happening at the core of our star, it's still pretty inefficient, Like most of the hydrogen in the star is not fusing, because fusion is a hard thing to make happen. You got these two protons, you're trying to squeeze them together. There are electromagnetic forces are trying to push them apart. Most of the time in the Sun, protons don't fuse. But the higher the temperature and the higher the pressure, the more often you do get fusion happening. And so the fusion is just much more efficient at the heart of this star, which keats the whole thing up and makes it brighter.

00:16:41
Speaker 2: WHOA, but you said they don't last pretty long.

00:16:44
Speaker 1: Yeah, these stars last for like millions of years, whereas smaller stars like hours less billions and red dwarfs can last even longer, maybe even up to trillions of years. We're not sure because the universe is kind of young compared to the expected lifetime of some of these stars.

00:17:01
Speaker 2: Now, is that as bridess it gets out there in space.

00:17:03
Speaker 1: That's not even close to how bright things get. That's the brightest star we've seen. But stars are not bright compared to like the radiation emission at the hearts of galaxies. Big galaxies have big black holes at their centers, and their enormous gravity creates a lot of high temperature and high pressure in the accretion disk around the black hole. So the black hole, of course is black. Maybe this hawking radiation, but that would be very, very dim. But because it has so much gravitational energy, there's a big swirling mass of stuff around the black hole, and that is so hot it's emitting a lot of radiation. That radiation then gets guided by the magnetic field of the black hole up and down the poles, sort of the same way that like the Aurora Borealis guides charged particles to the north pole and the south pole. Here, the magnetic field of the quasar creates two beams of particles when shooting up the north pole and when shooting down the south pole, and that's what a quasar is that's also called an active galactic nucleus WHOA.

00:18:03
Speaker 2: So it creates a jet of particles or light for both.

00:18:07
Speaker 1: If you look at pictures of galaxies with jets, these jets can be enormous. They can be even much longer than the galaxy itself. The power of the hearts of these galaxies is really incredible. And there's an enormous amount of photons also emitted here because this is just like hot particles, and hot particles emit photons.

00:18:24
Speaker 2: Because I guess it can't guide the photons to the North pole and South poles, but it guides other particles and in those particles are what emit the brightness the light.

00:18:32
Speaker 1: Yeah, exactly. And anytime you have charge particles changing direction, like an electron flies to a magnetic field and bends, how does it bend. It has to bend by emitting a photon. So you have accelerating charged particles, you're going to get lots and lots of photons, like in the particle colliders like the Large Hadron Collider or the Large Electron positron Collider. One of the biggest challenges is that these particles are bending with magnets and constantly losing energy to radiation, and so that's why you get so many photons.

00:19:00
Speaker 2: H all right, I have more questions about this quasar and about maybe what could be even brighter than a quasar. So let's set the dimmer too high on those questions. But first let's take a quick break. All Right, we're talking about the brightest explosion ever seen, and Daniel, you were saying, a quasar has many times more brightness than the brightest star that we know about.

00:19:33
Speaker 1: Yeah, quasars in the sky are like bafflingly bright. It was a huge mystery for a long time before we even knew that there were black holes in the hearts of galaxies. People saw these sources in the sky and they calculated the distance and then they were like, oh my gosh, it's already brightened the sky and it's super duper far away. Because quasars tend to be formed in the early universe and not recently, so all the quasars we see are like really far across the universe. And so you do that calculation, you discover that like, wow, quasars are trillions of times brighter than the sun. Trillions trillions. Yeah, there's one called three C two seven three is the brightest quasar we know officially, and it's four trillion times brighter than the sun. Like, if you were one AU away from it, it would be equivalent to having four trillion suns.

00:20:21
Speaker 2: But only if you're one AU at the north or south poles.

00:20:24
Speaker 1: Right, Yes, exactly, if you're at the horizontal or you're a little bit tilted away from it, then it's less bright.

00:20:30
Speaker 2: Now does that technically count as an explosion?

00:20:32
Speaker 3: Though?

00:20:32
Speaker 1: I don't think it counts as an explosion because it's constant, but it is super duper bright, and.

00:20:37
Speaker 2: It's super directed too, right, Like you said, it's not like it's not an explosion going in all directions. It's more like a laser.

00:20:44
Speaker 1: Yeah, it's more like a laser like a pencil beam, which is actually really useful, and we can use these quasars not just to understand the early universe, but also to understand what's between us and the quasars. There's lots of studies where people examine the light from quasars and they use it as a probe of all the the material between us and the quasar, for example, the dark matter density and the gravitational lensing that happens along the way. They're really useful. Sometimes a quasar can get even brighter due to relativistic effects. These quasars are called blazars. If the quasar is moving towards us, then its light is enhanced by relativistic effects and it can seem even brighter than a quasar.

00:21:23
Speaker 2: Wait, a blazar is a quasar that's moving towards us. It's not just a quasar with a nice jacket on. Is that what you mean, Like, it's a quasar moving towards us.

00:21:33
Speaker 1: Well, a blazar is a quasar. It's not. It doesn't have to be just moving towards us, but it's pointed like directly at the Earth. We can see these quasars even if they're not directly at us, because we can see their jets and the light emitted. But if they are actually pointed directly at us, then we call them a blazar.

00:21:48
Speaker 2: Wait, that's the only difference is that it's pointing at us.

00:21:51
Speaker 1: Yeah, blazars are quasars that are basically pointing right at the Earth.

00:21:55
Speaker 2: And you need a whole new name for that.

00:21:57
Speaker 1: Well, you know, it's historical. People see the things in the sky. They don't always understand the connections between them. It's like, why do we even have constellations? You could say, hey, now we know that like stars and constellations, some of them are super close and some of them are across the galaxy. Why do we group them together? It's historical? You know, people have called that ursa minor for a long time, so we're gonna keep doing it.

00:22:17
Speaker 2: M So, blazar, then, is a quasar that's pointing at us? Now, is it brighter than four trillion times brighter than the sun.

00:22:25
Speaker 1: Yeah, the brightest blazar is three hundred trillion times brighter than the sun. So we're talking about a factor of one hundred boost when a quasar is pointed right at us.

00:22:35
Speaker 2: So this is if we're one au at the north and south pole of a quasar, Yeah, three hundred trillion times more than brighter than the sun. But if we're not in the north and south pole, you're saying it's more like four trillion times.

00:22:46
Speaker 1: Yeah, exactly, And so not recommended to do any sunbathing on the north or south pole of a blazar.

00:22:53
Speaker 2: Well, as you have three hundred trillion layers of some.

00:22:56
Speaker 1: Block also known as like three light years of lead still might not be enough.

00:23:01
Speaker 2: Now, that sounds pretty intense. But if we're counting beams, I wonder like, is it brighter than the brightest laser we've made here on Earth.

00:23:08
Speaker 1: It's much brighter than the brightest laser. Yes, I mean, if you were one AU from the brightest laser, you would not think it's very bright. Even a laser is pretty colimated. It's going to spread out, and an AU is a large distance.

00:23:20
Speaker 2: But in terms of intensity per you know, area, is it as intense or more intense?

00:23:26
Speaker 1: These blazers are much more intense than any source on Earth at one au. Yes, but these are constant things, right. Blazer is key pumping out, so I don't know if it really counts as explosions. And the brightest thing in the universe is actually not something that's constant.

00:23:41
Speaker 2: So then we are disqualifying quasars and blazers from being the boats.

00:23:46
Speaker 1: We don't even need to disqualify them. They don't even qualify.

00:23:49
Speaker 2: We're seeking their chances of being the boat.

00:23:52
Speaker 1: Yeah, we're going to torpedo them, but even if we didn't, they still wouldn't qualify because the brightest thing in the universe isn't explo and it's also much brighter than the most constant thing in the universe, which are blazers.

00:24:05
Speaker 2: WHOA all right, what are these things that are brighter than a blazer? Is it a dinner jacket?

00:24:10
Speaker 1: Are I don't know if it's white tie or black time?

00:24:14
Speaker 3: Right?

00:24:14
Speaker 2: Which is brighter? It's a glittery on the disco jacket.

00:24:18
Speaker 1: Oh, sparkle tie. Yeah. The brightest explosion in the universe, and also the brightest thing we've ever seen, is a gamma ray burst. These are sort of mysterious and enormous bursts of gamma rays. Gamma rays are just very high energy photons that we see sometimes in the night sky.

00:24:37
Speaker 2: Well, meaning like we have gamma ray antenna and gamma rays are just a kind of light, right, like it's a high frequency light.

00:24:43
Speaker 1: Yeah, Gamma rays are very very high energy.

00:24:46
Speaker 3: You know.

00:24:46
Speaker 1: Photons exist all across the electromagnetic spectrum. Some of them we call in the visible range. Some are very long wavelength and infrared or radio waves. But these are just artificial divisions above the visible We have ultraviolet and then X rays and the gamma rays. But again these are just like historic dotted lines we've put on the electromagnetic spectrum. There's nothing above gamma rays. So gamma rays include everything above X rays and then out to infinite energy.

00:25:12
Speaker 2: Whoa, So we have these antennas out there on Earth like in the tech gamma rays, and sometimes we get these burds coming from space, like these huge kind of waves of gamma rays.

00:25:22
Speaker 1: Yeah, exactly. And it's fascinating history because this is something that really benefits from the Cold War. Like in the second half of last century, the United States military was really curious whether the Soviet Union was doing atmospheric nuclear testings before it was ruled out. So they built satellites and all sorts of technologies to try to detect nuclear testing. And sure they found some, I guess, but they also spotted these weird bursts in the sky of gamma rays that they didn't understand that were not coming from below, they were coming from above. That's how gamma ray bursts were first discovered. I love when we spend money on the military, we accidentally end up doing science.

00:26:00
Speaker 2: Are you making a case for more military spending.

00:26:05
Speaker 1: I don't think military spending is a very efficient way to do science. I'm just grateful when sometimes that money turns out to be useful for science as well.

00:26:13
Speaker 2: Hey, I see, it's a win. It's a win for everyone.

00:26:16
Speaker 1: Yeah, I'll take it. I mean, the military budget totally dwarfs the science budget. But anyway, that's a topic for another time.

00:26:23
Speaker 2: How bright are these gammay bursts?

00:26:25
Speaker 1: Some of them are crazy, crazy bright. Like we've seen gamma ray bursts that are a million trillion times brighter than the sun, like a quadrillion times brighter than the sun.

00:26:37
Speaker 2: So yeah, in terms of how bright we think they are at the source, you're on Earth. We don't get a million trillion times more gamma rays than the sun.

00:26:46
Speaker 1: Yes, that's right. We were all killed several years ago due to the gamma ray burst. We're just now catching up. No, this is at the source absolutely. Fortunately for us, they're quite distant, so when they get here on Earth, there's a few very high energy gamma rays, but we're not all fried.

00:27:02
Speaker 2: But so, how do we know how far they are? Like we're just getting a blip on our antennas, Like, how do we know like how far away they came from?

00:27:09
Speaker 1: Yeah, it's a good question. We're not exactly sure because for many of them, you look in the night sky where they came from and there's like nothing there. It's not like you can point to and say, oh, it came from this star that went supernova, or it came from that galaxy. Like you look at the sky, you're like, oh, here's a huge source of gamma rays. There's nothing in the night sky there that we can see. It must mean that there's something extraordinarily distant. So there's a lot of uncertainty on the inherent brightness of these things.

00:27:34
Speaker 2: A huge amount of uncertainty, right, Like, it could be something closed that's dim, or it could be something really far that's super duper bright. How do you tell the difference, Well.

00:27:41
Speaker 1: It's definitely not something close and dim. Right. If it was something close, we would see it, because these things are very very bright. It could be something close that's dim most of the time and occasionally bright. But yet there is uncertainty on the distance to these.

00:27:54
Speaker 2: Things, meaning like the range goes from sixty what to a million trillion times brighter than the sun.

00:28:00
Speaker 1: Yeah, we don't know exactly how far they are. All of the gamma ray bursts we've seen have originated from outside the Milky Way galaxy, which means that they're very far away, but there's a huge range there, right, they could be a neighboring galaxy, that could be a very very distant galaxy at the edge of the universe.

00:28:17
Speaker 2: And we think they came from outside the Milky Way because when we pinpoint where they came from, we don't see anything that we think is in the Milky Way.

00:28:23
Speaker 1: Yeah, exactly. And we think these things are extraordinarily bright. And any gamma ray burst in the Milky Way that's actually pointed towards Earth would probably fry the Earth. And there are some theories about how, like some mass extinctions might have occurred due to gamma ray bursts in the Milky Way, for example. But yeah, these things we think are extraordinarily bright. I mean, it's hard to get your mind around these numbers. It's easier if you express it, like in terms of how much energy the Sun puts out. So for example, our Sun in its entire lifetime will put out as much energy as is in one of these gamma ray bursts for one second, So like a second of gamma ray bursts is ten billion years of the Sun. WHOA, we think, Yeah, we think there is definitely a lot of uncertainty here.

00:29:06
Speaker 2: I mean, it sounds like a huge amount of absurdity, right, How do we know how far away it is?

00:29:09
Speaker 1: Yeah, we don't know. We can say sort of like lower limits because we know the nearest neighborhood and we can tell that there's nothing there that's generating these things. You know, there's a lot of fuzziness in some general arguments there. But yet take these numbers definitely with a big grain of salt.

00:29:24
Speaker 2: And you said it was a mystery for a long time, meaning that we still don't know what makes these bursts.

00:29:30
Speaker 1: We still don't really understand it. Yeah, we have some theories. It turns out the gamma ray bursts come in two categories, is like shorter ones and longer ones. The shorter ones last for like seconds or tens of seconds, and the longer ones last for like minutes. So that seems like probably there are two different things going on there, and there are theories. The leading theory is that short gamma ray bursts might come from merging neutron stars like we talked about. You know, neutron stars are these very dense objects that the end of life of large stars not so big that they become a black hole and not so small they become a white dwarf, but having enough mass to become very dense neutron stars, and often these stars are in binary systems and then at the end of their life they're orbiting and eventually they collapse and fall into each other. And these are incredibly powerful events. They generate gravitational waves, they generate the conditions needed to make like gold and platinum and all the heavy nuclei in the universe, just like supernova, and also generate very high energy gamma rays.

00:30:29
Speaker 2: Would they also generate regular light like visible light or would they maybe only generate gamma rays, and that's why we don't see them with the naked eye.

00:30:39
Speaker 1: Yeah, we definitely see neutron star collisions, and we've seen some. We've also correlated some with gravitational waves. But you know, there's lots of different varieties of these things, different masses of neutron stars, and the collision themselves can happen in lots of different ways. So we've seen neutron star collisions that haven't caused huge gamma ray bursts, but there's a speculation that sometimes neutrons our collisions might cause these incredibly bright gamma ray bursts. But it's not something we understand very well. Even the heart of a single neutron star is not something we understand. Like, what is the state of matter under these incredible densities? Is it a quark, gluon plasma? Is it some other state of matter? Is it nuclear pasta? We have a whole episode about this question. We're really just the very beginning of the ability to think about these things coherently. And then take two neutron stars that are swirling around each other, and the dynamics of that and the relativity. It's really just sort of beyond our ability to calculate in a robust manner. And so there's a lot of sort of theoretical questions about whether those even could cause gamma.

00:31:38
Speaker 2: Ray bursts, meaning they might not even be bright enough, or they might not be enough to generate the kinds of bursts we think we're seeing.

00:31:46
Speaker 1: Yeah, it's the leading theory, but it's definitely far from proven.

00:31:49
Speaker 2: All right, let's begin more into what could be causing these gamma ray bursts, and then we'll get to the boat the brightest of all time. But first let's take another quick break. All right, we're hopping on a boat here, Daniel trying to find the brightest of all time, the brightest explosion of.

00:32:18
Speaker 1: All time, right, yes, exactly.

00:32:21
Speaker 2: It's the biggest exploding boat.

00:32:25
Speaker 1: Yeah, and it's really wonderful. I love the experience of just being overwhelmed by stuff that happens in the universe. Really stretches your mind to even try to conceive of these incredible events. You know, it makes everything that happens here on Earth just seem inconsequential. Yeah.

00:32:39
Speaker 2: I mean for it to have been so bright that even though it's super duper duper far away, we're still seeing it here on Earth. It's pretty amazing, right, I mean, I'm sure the rest of the universe is also seen it.

00:32:50
Speaker 1: Yeah, exactly. And unless this is the unicorn of unicorns, it means that's probably even brighter stuff out there that we're missing.

00:32:57
Speaker 2: Oh, maybe it is the unicorn making this.

00:33:00
Speaker 1: Yeah. Maybe it's the collision of two unicorns when they cross their horns. Maybe that's what happens.

00:33:06
Speaker 2: Yeah, yeah, Or it's a unicorn farting.

00:33:09
Speaker 1: Let's keep it clean for the families out there.

00:33:13
Speaker 2: It's something wrong with farts. Everybody farts, even unicorns.

00:33:17
Speaker 1: This is not a fart podcast. Folks, we're talking about bright explosions, not stinky ones.

00:33:23
Speaker 2: But you did say these things are really fart away.

00:33:26
Speaker 1: They are. They are mind blowingly far away exactly. So we have the short gamma ray bursts that are probably emerging neutron stars, and then we have these longer gamma ray bursts, which just means that we see photons for longer, like a last four minutes instead of seconds. And the leading theory here is supernova collapse. That when supernova's collapse sometimes they create these very bright bursts of photons. Not always like we see supernovas that don't cause gamma ray bursts, but sometimes we think like there's a jet of matter ejected from the supernova, Like the collapse isn't completely symmetric, and this jet of matter sort of like a blazar or a quasar, can accelerate particles and generate enormous bursts of very very intense light.

00:34:11
Speaker 3: Hm.

00:34:12
Speaker 2: Does that mean we have to disqualify supernova from our category here because a burst is not sort of going in all directions.

00:34:19
Speaker 1: No, I think it's fine. I don't think there's a reason to disqualify it just because it's focused, you know, I think it's still it's bright and it's an explosion, so yeah, I think it qualifies as one of the brightest explosions.

00:34:31
Speaker 2: M it's more of a float, like the focused, focusedly bright of all time. All right, So those are leading theories, but we're not sure. It seems you're saying maybe even a supernova emerging neutron stars might not be powerful enough to generate the kinds of gamma ray burst we're seeing.

00:34:51
Speaker 1: Yeah, exactly. And you know, this is the exciting edge of astronomy when we see stuff in the night sky we can't quite explain. We're not sure if it's like a weird, extreme version of something we've already seen, or if it's something totally new kind of thing out there in the universe we've never considered. And that's definitely happened, right. I think about the first time we discovered supernova or black holes or quasars. All these things were discoveries of something new out there in the universe, a whole new category of things the universe can do. So we don't really know if gamma ray bursts represent that, or if they represent like the extreme edge of some kind of thing we're familiar with.

00:35:29
Speaker 2: Yeah, it's pretty exciting. So is that then the brightest thing we've seen explode out there in the universe.

00:35:35
Speaker 1: So the brightest thing we've ever seen in the universe is a gamma ray burst, and it's one that just happened last year. Like the record was set in October twenty twenty three.

00:35:45
Speaker 2: Ooh, was there a celebration, was Thinkinness World Record official there at the telescope.

00:35:53
Speaker 1: I think that everybody was too stunned, Like this is something just crazy bright, brighter than anything we've ever seen by like a big factor. This is one hundred times brighter than any other gamma ray burst we've ever seen, which remember is already like quadrillions of times brighter than the sun.

00:36:11
Speaker 2: Wow, that's incredible. But then do we know how far away this one was? Like maybe it was dimmer than the ones before, it was just closer.

00:36:19
Speaker 1: They think this one might just be closer. They actually have a candidate to where it might have come from, which is a galaxy only two and a half billion light years from Earth, and so it might be why it seemed brighter here and it seemed like the jet might be like pointed right at us. That's sort of one theory for why this one was so bright. But you know, we have this telescope orbiting Earth. It's called the Fermi LAT and it's excellent finding gamma rays, really high energy photons. It's kind of like a particle detector in space. So I think it's pretty cool. Like photons enter the telescope and it's not like a telescope like Hubble where you have lenses and optics. Instead, it converts the photon into electron and positron then attract those particles, so it's sort of like a very high energy particle detector. And this thing was totally overwhelmed, Like it was just flooded with higher energy photons than it had ever seen before.

00:37:11
Speaker 2: Wow, Like it maxed out the sensor.

00:37:13
Speaker 1: Yes, exactly, it saturated that eyeball in space. It was totally overwhelmed, and not just our sensors, like the ionosphere, this part of the atmosphere of the Earth. The whole thing swelled up for several hours. This is the kind of thing that happens when like we got a big solar flare, like when the Sun burps out an enormous number of particles towards the Earth at the ionosphere response, but this is something that happened like billions of light years away and it still made the Earth like a little swollen and inflamed.

00:37:43
Speaker 2: WHOA, Now, how do we know where it came from?

00:37:45
Speaker 1: We don't know exactly, but there's sort of a candidate galaxy in that direction to people think maybe it came from there. But you know, this is all very speculative. You can't really tell me, like.

00:37:54
Speaker 2: How do we triangulate where it came from?

00:37:56
Speaker 1: Oh, we can measure the direction of these photons, Like for me, lat is a detector, and so we can see the trajectory of the particles that come from the photon. So we can reconstruct the direction of these photons.

00:38:08
Speaker 2: What do you mean we can see the direction? How do we do that?

00:38:10
Speaker 1: Well, the photon turns into an electron and positron pair, and those carry the momentum of the original photon. And then we have layers of detector. So we have like ten or one hundred layers that detect the motion of the particles that come from the photon, and then we can reconstruct that track and it points back to where it came from.

00:38:28
Speaker 2: Oh, I see, it's like a sort of like a cake, you know, like if you stick your finger in a cake, you can sort of trace which direction the finger was poking.

00:38:36
Speaker 1: Yeah, imagine like a hundred layer cake and you like shoot a bullet through it, and then you'll take slices of that cake and you traced where that bullet hole was. You could figure out what direction the bullet came from.

00:38:47
Speaker 2: Yeah, there you go. Just don't eat the bullet.

00:38:50
Speaker 1: I was going to go with a JFK analogy, but I decided to go with cakes.

00:38:57
Speaker 2: GOTFK, We got the boat.

00:39:00
Speaker 1: The mystery gamma ray burst came from the direction of the Texas school Book Depository. It's all a big conspiracy theory.

00:39:06
Speaker 2: Yeah, yeah, it's a cosmic conspiracy theory. All right. So this was detected just last year and who detected it?

00:39:13
Speaker 1: So it was detected all over the Earth. It was seen by Fermi Laugh which is a big collaboration of scientists from across the world. It was also seen by the Large High Altitude Air Shower Observatory in China, and then there was a Russian facility that saw it also. And this observatory in China is only for very very high energy photons and they only ever seen a few photons very high energy, and this time they saw five thousand photons just from this one gamma ray burst. It's like ten times as many as they've ever seen in the entire history of the entire detector. They saw in this one day. This one period lasted about seven minutes long.

00:39:54
Speaker 2: Wait weaning that it was visible to the naked eye, or you could only see it in gammorrays.

00:39:58
Speaker 1: You could only see it in gammorys. You cannot see gamma rays with the naked eye. They're way too high energy. And one of the most interesting and weird things about this gamma raburse if not just the intensity, like the number of photons, but the energy of each individual photon. So this thing also set a record as sending the highest energy photon ever seen. This one photon had eighteen terra electron bolts, which is like much more energy than protons have the Large Hadron collider. And yes, it means it's a very very high frequency, very short wavelength. This is the highest energy photon ever seen by a factor of four. So like, this thing is really far out there on the tails.

00:40:37
Speaker 2: We wouldn't it mean that it's really close, right, because then don't photons kind of get stretched out as they go further out in space.

00:40:44
Speaker 1: Absolutely, it's very weird for a super high energy photon to come from really far away for two reasons. One is you're right, if it's coming from really far away, then as the universe expands, those photons get stretched out, they get red shifted right, so they get lower energy, which means originally had even more energy. The other reason is that the universe is actually not very transparent to super high energy photons. As particles get really really high energy, they start to interact with the cosmic microwave background radiation like protons and other cosmic ray particles. If they're super high energy, they'll collide with the photons from the cosmic microwave background the remnants of the Big Bang, and interact and disappear. The same thing is true with super duper high energy photons interact with those photons from the CMB. So we shouldn't be able to see photons from really really far away because they should get absorbed by the universe. So here we're seeing a super high energy photon from what seems like really really far away. It's very weird.

00:41:44
Speaker 2: So we can trace where the burths came from and when we look in that direction, we see some galaxy where maybe it came from. That's why you think it came from that gux.

00:41:54
Speaker 1: But that's very speculative. It's like, yeah, it's in the same direction in the sky, right, and that's the first thing we see there. That doesn't mean it came from that. I could have come from behind that. There could be something else between us and there. All right, we're really limited by our vantage point.

00:42:08
Speaker 2: Like it could be an alien in between us and this galaxy with like a laser pointer that shoots lighting the gama right direction and they're just messing with us.

00:42:17
Speaker 1: Yeah. Absolutely, it could be or you know, it could be that it just came from something else and it happened to land here on Earth. This one special photon happened to land here on Earth at the same time as this gamma ray burst, right.

00:42:28
Speaker 2: That could have been random, or maybe it's not random. What if it's like a phone.

00:42:32
Speaker 1: Call, it's like a voicemail. It's like in your hotel room when you ignore that blipp you're like, it's an emoji.

00:42:42
Speaker 2: It's a text message that says you up.

00:42:44
Speaker 1: Wow, It's a late night booty call from aliens.

00:42:49
Speaker 2: Hopefully not a booty call ye, hopefully to science call family friendly.

00:42:53
Speaker 1: But you know, there's a lot of really interesting science that could be done with this, because again, people don't understand how a photon with that much energy could travel that far across space. One fun paper I read suggests that maybe it wasn't a photon the whole time. Maybe it converted to this weird theoretical particle called an axion. There's this idea that maybe axion particles are the dark matter, and they couple a little bit to photons, and so photons can sometimes turn into axions. There's a set of experiments called light shining through walls where people look for photons penetrating stuff that photons shouldn't be able to penetrate by turning briefly or for a while into axions and then converting back into photons when they come near the Earth, for example, and hit our magnetic field. So some people argue that this might be evidence that this photon turned into an axion, flew across the universe, and then came back into photon modes so we could see it.

00:43:46
Speaker 2: WHOA, that's a little too convenient, though, isn't it.

00:43:50
Speaker 1: It's just hard to explain that we have no actual explanation for this photon. There is no way we should see. It's like an impossible photon. I mean, the most boring explanation for the crazy photon is that it's a mistake that we don't know how to measure the energy of particles with super duper high energy, because remember, we're always reconstructing these things. This is an air shower observatory, which means you're not seeing the original photon. You're seeing the particles that turned into when it's slammed into the atmosphere and created this cascade of particles that are shining and flashing light.

00:44:23
Speaker 2: Meaning it could have been something else, not a photon.

00:44:25
Speaker 1: It could have been something else not a photon, or it could have been something with lower energy. You know, the uncertainty on this resolution is significant. We should also say the Russian observatory reported an even higher energy photon two hundred and fifty terra electron bolts, like more than ten times the energy of this one scene in China. But the truth is nobody believes them. They're like, yeah, no, you guys messed up.

00:44:48
Speaker 2: Let me get this straight. We don't know what cost this burst. We don't know where it is exactly. We don't even know if it is a burst.

00:44:56
Speaker 1: We know it's a gamma y burst. It was very, very intense, but it has a special photons in it that really raise some questions. Maybe we've mismeasured them, or maybe they're evidence of axion, dark matter, or something else happening. But there's a lot of uncertainty in these things, and you know, the frustrating thing in astronomy is you can't control these experiments, Like if this was something you were doing in your lab, in your basement, or even if a large hadron collider, so you could say, let's do it again and check. But these are just things we're lucky or unlucky enough to see in the sky and have to wait for it to happen again before we can convince ourselves it's real.

00:45:30
Speaker 2: I wonder then we should maybe retitle the episode, because really we're just talking about the brightest flash we've ever seen. We don't even know if it came from an explosion or an alien laser or an alien phone call.

00:45:43
Speaker 1: Right, yeah, or space unicorn farts.

00:45:46
Speaker 2: Yeah, absolutely, yeah, a very focused space unicorn part.

00:45:51
Speaker 1: Maybe they are the aliens woo, I'm unifying the theories.

00:45:54
Speaker 2: That's how they make phone calls to their fart network, in which case it is sort of technically a booty call.

00:46:02
Speaker 1: People are doing a lot of work to try to understand this better. They're trying to see, like was there a jet of material that was emitted. By looking at the spectrum of light that comes in the gamma ray burst, they can try to get a sense for like what was in that jet? Was it wide, was it narrow? Did they have the kind of material we expect from a collapsing star? What can we learn about the origin star? Maybe there was something weird about the star that collapsed that generated this incredibly bright source of light. And so there's a lot of sort of conflicting studies still about this. Some people say the jet was really really narrow, that's why I was bright. Another study said no, actually the jet looks like it was wider. But you know, there's a lot of questions. This is early days in understanding this. But unless we're lucky enough to see a brighter one, this is going to be a boat for a while.

00:46:47
Speaker 2: Is it possible also that maybe it was like focus somehow right, because isn't there a sort of lensing out there by dark matter or maybe other things? Could something have lensed this light to make it seem more intense.

00:46:59
Speaker 1: Mm hm, that's certainly a possibility. There's some really cool studies to try to understand how much dark matter there is between us and any point in the sky by looking for evidence of lensing. We don't see lensing evidence in this distribution, but it's certainly possible. We don't have a great map of where the dark matter is in the universe, and you know, that's a fundamental limitation to looking at the universe only from the surface of one planet. Anytime you get a photon, you don't exactly know where it came from, what happened to it along the way. You have to try to untangle all of these mysteries simultaneously, right, how much dust is there between us and there? How much dark matter is there? How much is the universe stretching? Is that even? Is that isotropic? Because there are other weird stuff going on simultaneously. We have to try to unravel these mysteries to explain this incredible mosaic we see in the night sky.

00:47:47
Speaker 2: Amazing, but I guess maybe the overall message is that we've seen something that is brighter than what we thought was possible, and it's pretty incredible that we're still doing that, right, We're seeing things we didn't think could exist before.

00:48:00
Speaker 1: Yeah, and it's stunned astronomers. I mean, astronomers are used to big numbers about the universe, but even this one sort of like you can tell, it rocked them back on their heels. Well.

00:48:11
Speaker 2: Wait, it is shocked, even the bright ones exactly.

00:48:14
Speaker 1: Eric Urns is an astronomer who studies this kind of stuff, said, quote, the energy of this thing is so extreme that if you took the entire Sun and you converted all of it into pure energy, it still wouldn't match this event. There's just nothing comparable.

00:48:29
Speaker 2: Yeah, that's incredible. Yeah, unless you consider farting unicorns in this case, anything's possible. All right. Well, it's an interesting exploration of a new universal or at least local world record of the brightest flash we've seen and its mysteries.

00:48:45
Speaker 1: And one thing we do know is that the universe contains enduring mysteries. And the more we look out there in the universe, the more we understand and the more we are shocked by what's out there?

00:48:54
Speaker 2: Yeah, and the more that we need bright people like maybe you out there to figure out.

00:49:00
Speaker 1: Mister he's talking to you, folks, guys, not to me.

00:49:03
Speaker 2: We hope you enjoyed that. Thanks for joining us, See you next time.

00:49:10
Speaker 1: For more science and curiosity, come find us on social media where we answer questions and post videos. We're on Twitter, Discorg, Insta, and now TikTok. 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.