Could a Nearby Supernova WIPE OUT All Life on Earth?

Added: 2026-05-05

[00:00:00]Right now, somewhere in our very own galaxy, a star is dying. And I don't mean peacefully fading away, but actually preparing for the most violent explosion the universe can actually produce. And when it does detonate, it will release more energy in a few seconds than our sun will produce in its entire 10 billionyear lifetime. It's called a supernova. And the real question isn't whether it's dangerous.

[00:00:31]It's whether we're far enough away to survive the next one. And so today, I'd like to talk about one of the most spectacular and terrifying phenomena in the entire universe. Could a supernova actually end all life on Earth?

[00:01:03]Now, first things first. A supernova is what happens when some stars reach the end of their life cycle and they explode with catastrophic force. But not every star gets to go out this way. Your star needs to meet very specific criteria.

[00:01:20]You see, for most of a stars life, it's a constant battle. Gravity is trying to crush everything inward while the nuclear fusion happening in the core pushes everything outward. Eventually though, the star runs out of fuel. And when that happens, gravity wins suddenly and violently. You know, when we look up in the daytime sky and we see the sun, we always know it's there. Uh, and it looks just so calm and peaceful and always there. But when we send spacecraft up there or look through telescopes, we see the sun is this boiling, roing just uh very unstable thing that's just always shooting plasma out from its surface and very very nonstable I guess is what I would try to say. It looks very peaceful, but it's very very dynamic when you really study it. Right? So what's going on inside of every star is this constant battle. You see, they started nuclear fusion to make all the heat and the light because of gravity. Because when the solar system forms and makes a star, um the gravity pulls the gas together. It clumps together and when you get more and more and more and more of it, then gravity can squeeze it enough so that the repulsion of the atoms is overcome, right? Because remember, you have atoms, let's call it uh, you know, hydrogen atoms. Let's say most of the elements in in the universe is hydrogen. And so you have an electron around there and they're repelling an adjacent hydrogen atom, right?

[00:02:43]Uh, and if you have molecular hydrogen, the the temperature goes up and it makes atomic hydrogen and they are repelling each other, right? Then when the temperature gets high enough, the electrons are stripped away entirely and so you have these naked protons and naked electrons there. The protons are repelling, right? They're positive and so they're repelling each other. Well, when when the star gets massive enough, well, let me back up. When a body of gas is not quite mass enough, you you get something like Jupiter, lots of gravity, lots of, you know, uh uh gravity pushing together the gas inside the hydrogen for instance, but not enough to overcome the repulsion. So, you just get a giant gas giant star, but no fusion going on. So when the mass of the body of gas gets bigger and bigger and bigger, more and more gravity squeezing it, eventually the gravitational force can overcome that electric repulsion between for instance the protons. And when he gets them inside of a certain distance to each other, the strong nuclear force takes over and and basically causes them to crash together and form a new element. The two hydrogen separate uh nuclei, hydrogen nuclei which are protons. uh well then they can become a helium nuclei and so you have fusion and you have energy released. Why? Because as you get them close enough together past a certain point when they're uh close enough where the strong nuclear force can take over it'll cause them to crash into each other that creates a lot of heat, right? And that and and light and so on. And that's where the energy of the fusion's coming from. It's overcoming with the strong nuclear force. So there's a lot of inward pressure due to gravity is the point.

[00:04:20]But once the fusion starts, there's a lot of energy released in the core of the star from this crashing in of the nuclei forming helium. Right now, that heat is causing all of the things in there to agitate and basically try to expand like a gas. So, it's trying to push outward because of the energy released in the center of the star. So, when I say there's a battle in a star, the fancy word is the star is in equilibrium. But really, it's a battle.

[00:04:50]I think it's a better word. Gravity's trying to crush it. And then the fusion is causing energy to be released, which is trying to push it out. And the shape of the star that we see, the boundary and all the things, the size of the star and everything is a balancing act between the crushing and the outward pressure from the fusion. So this fusion goes on and on and on and on, turning hydrogen to helium and helium into something else, and so on and so on. But eventually you get to a point in the periodic table where it's not energetically favorable to fuse things into higher elements, right? Into heavier and heavier elements. You run out of fuel, in other words. So what happens, do you think, when you have uh very strong gravity pulling something in and there's an outward pressure balancing it from the inside, but then you run out of fuel and that out inward pre the pressure pushing from the outside suddenly goes down. Well, the gravity is going to take over and the thing is going to become unstable for a period of millions of years depending on the type of star. And depending on the mass of the star that you have, you can get a supernova, which is what we're talking about here. But for a different mass class of star, you might actually get a black hole. Gravity might be able to pull it into a singularity. Uh, and you don't get a supernova. In some of those cases, you get a black hole. But what we're talking about today is what happens when a supernova happens. The energy released from that instability causing an explosion spews out into space. Could it harm Earth? So that's what I would call the big picture. Now let's dive into a few more details.

[00:06:23]There are two main paths to becoming a supernova. The first one is when a massive star is at least eight times more massive than our sun burns through its nuclear fuel. So these stellar giants fuse the hydrogen into helium and the helium gets fused and goes into carbon and the carbon fuses to oxygen and it keeps going up and up and up the periodic table producing iron in their core. But here's the problem. Fusing iron, as I mentioned a minute ago, it's not energetically favorable. It doesn't release energy. It actually takes energy to cause that to happen. It consumes energy. And so the moment a star starts making iron, it's basically signed its death warrant within hours or even minutes in some cases. Again, it mostly depends on the mass of the star that we're talking about. The core actually collapses and then it rebounds in a catastrophic explosion. It's almost like it comes in c collapse and then rebounds. Boom. We call this a core collapse supernova. Now the other way a supernova can happen is in a binary star system. Uh that's two stars orbiting each other, right? Where a white dwarf star, which is the dead remnant of a sunlike star, steals material from the companion star that it's orbiting with.

[00:07:40]And so when the white dwarf accumulates enough mass to hit about 1.4 times the mass of our sun, it triggers a runaway nuclear reaction that completely obliterates the star. This is called a type 1A supernova. And it's actually more predictable and uniform than the core collapse variety. Now, before you worry about our own sun, it's actually safe. Our sun doesn't have nearly enough mass to go supernova. In about 5 billion years, what will actually happen is it will begin to swell into a red giant, possibly swallowing up the Earth, literally consuming the inner planets and swallowing up the Earth. So when I say swell, I mean it gets way bigger than it is today. And then what'll actually happen is it will gently shed its outer layers. Not an explosion, gently shedding them, fading into what's called a white dwarf. We mentioned that a second ago. Not really pleasant for us because it will incinerate the Earth, but definitely not a supernova. Let me just take an aside and tell you something fascinating. I mentioned that in nuclear fusion in stars, it goes up and up and up the periodic table making heavier and heavier elements because you're fusing protons into heavier and heavier elements, nuclei into heavier and heavier elements, but it stops at iron. It's not energetically favorable.

[00:08:59]In other words, it doesn't release more energy when you fuse things to make uh when you fuse iron together, right? You can make iron in a star and it releases some energy, but not enough to continue to push the uh iron nuclei together.

[00:09:12]Why? Because iron has a lot of protons and so it has a a very strong electric repulsion and the amount of energy released gets slightly less. So it's not enough to to cause the the core to have enough energy to push those uh iron nuclei together to fuse into something heavier. Iron is actually element number 26. What about all the elements after that? What about gold? You've heard of gold. That didn't get made in a star.

[00:09:37]Where'd it come from? What about silver?

[00:09:40]What about platinum? You've heard of that. What about copper? All of our wiring has copper. Copper wiring. What about tungsten in the light bulbs?

[00:09:47]Anyway, if you look in the periodic table, there's elements way beyond element of iron. Element number 26.

[00:09:53]Where do they come from? Well, they come from supernova. So, the fusion process in a star um fuses he to get heavier and heavier elements up to iron, but iron will not fuse inside of a star to make something heavier. So, anything heavier than iron comes from when one of these supernovas happen. And during the supernova process, that violent explosion was releasing so much energy, it confused that iron into heavier and heavier things. And that's where all of the gold and the silver and all of the other things that we think of as heavy heavy elements come from. Now, some of those elements are in your body. Some of those elements heavier than iron are necessary. They're in your in your body and and and and forming up your chemical processes. So when some astronomers say something like you're really made of star stuff, that's literally true. Some of the elements in your body were once inside of a star that went supernova.

[00:10:47]Though that means there must have been a star system here before our sun that went supernova, maybe several of them that recoales and some of those heavy elements made the the inner rocky planets, right? And then we came from there. So when you really sit and think about it one day, it's crazy where we come from that some of the elements in our body came from not our sun, but from some other star that existed and is long gone before our sun. All right, now let's take a second and just talk about how powerful these explosions really are when we have a supernova because powerful doesn't really even begin to cover it. So when a supernova goes undergoes this instability and finally detonates, it releases about 10 to the 44th power of jewels of energy. That number is so absurdly large it's almost meaningless to a human brain. For me, it's totally incomprehensible. 10 raised to the power of 44. Right? So let me put it another way. In the first 10 seconds of a supernova, 10 seconds, the dying star releases more energy than our sun will produce, our sun in the sky right there, over its entire 10 billiony year lifetime. Think about what I'm saying.

[00:12:05]These supernova explosions are so energetic that in the first 10 seconds, they actually release enough energy to dwarf the energy output of our sun over its whole life. Now, if you could somehow harness a supernova's energy, you would have enough power to run every device humanity has ever built for trillions upon trillions of years. It's basically incomprehensible to me how much energy that is. Now, get this. The explosion itself, when it actually happens, it expands at speeds up to 10% of the speed of light. That's something like 30,000 kilometers per second.

[00:12:46]That's what the blast wave is that we're talking about here. And as that blast wave propagates through space, it heats materials up to hundreds of millions of degrees. It creates a shell of superheated gas and debris that expands outward for years, even decades, even up to centuries. We can see this expanding shock wave of gas from a supernova. Now, here is where the scale of all this stuff gets really mind-boggling. The explosion itself, the actual detonation is relatively compact on cosmic scales.

[00:13:21]The blast doesn't directly extend all the way out to Mars or Jupiter for instance. Instead, what happens is the star actually ejects its outer layers like concentric ejection at tremendous speed as we mentioned like something like 10% of the speed of light. It creates that hot bubble of gas and radiation. Now, that expanding bubble of gas and radiation has a name. We call it a supernova remnant and it can eventually grow to dozens of light years across. So enormous in our night sky over thousands of years. The Crabia Nebula, which is one of these that we'll talk about in just a few minutes, is about 11 light years across now, nearly a thousand years after the explosion that created it. And we can see that very easily with telescopes in the night sky today. Now, these supernova don't just threaten you with an explosion.

[00:14:11]They bombard everything around them with multiple types of deadly radiation. So, let's start with the basics of that so we know what's spewing out of a supernova. We have something called alpha radiation. That's basically a helium nuclei. It's two protons and two neutrons bound together as a unit.

[00:14:29]That's called an alpha particle. So, these particles are relatively heavy and they're relatively slow. They really can't even penetrate a sheet of paper.

[00:14:38]Literally notebook paper. They can't usually go through that very easily. So, they can't penetrate your skin either.

[00:14:44]They're only dangerous if you like eat them or drink them uh accidentally. So, they're inside of your body uh or if you ingest them or even inhale them into your lungs, they can hurt you from the inside. Then, we have what's called beta radiation. That's made of high-speed electrons or posetrons. Remember, a posetron is the antimatter particle to an electron. So, these can penetrate the skin, but they're stopped by thin sheets of metal or plastic. They're more dangerous than alpha particles, but they're still manageable with pretty basic shielding. Then there's your friendly neighborhood gamma radiation.

[00:15:19]You may have heard of this one from The Incredible Hulk if you're a comic book fan. Uh, this is where things get serious. Gamma rays are extremely high energy photons. So they're just like light, but way higher energy per photon than the visible light that you see, right? Millions of times more energy. In fact, they can blast right through most materials. You need thick layers of lead or several feet of concrete. So very, very thick concrete, lead, or even water to attempt to stop them. Gamma rays can break apart DNA. They can disrupt the chemical bonds in the DNA, destroy cells, cause radiation poisoning and cancer. Now, all of these things are made in supernova, and they also produce X-rays. And I know you've heard of X-rays from getting your dental X-rays.

[00:16:07]Uh, but they're also electromagnetic radiation, photons of light with an energy lower than gamma rays and higher than the visible light. Basically, high energy uh photons. There's also something called cosmic rays. These are just high energy particles, mostly protons, traveling very, very close to the speed of light. And when they hit you, they can cause a lot of damage.

[00:16:29]Now, a supernova unleashes all of this stuff, everything that we've listed. And the initial explosion produces an intense flash of gamma rays and X-rays.

[00:16:39]And for days and weeks after the blast, the expanding debris continues to emit high energy radiation as radioactive elements created in that explosion begin to decay. And the shock wave accelerates particles to create cosmic rays that can persist for thousands of years. And all this stuff is going out in all directions after a supernova explosion.

[00:17:02]Now, here is the crucial thing to understand. A supernova doesn't actually need to hit the Earth with debris in order to hurt us. The real danger comes from radiation, particularly the gamma rays. When gamma rays from a supernova hit the Earth, they don't kill organisms directly in the way that you probably think. Instead, what happens is they attack our atmosphere, which we absolutely need to survive.

[00:17:27]Specifically, what they do is they break apart molecules in the ozone layer.

[00:17:32]Ozone is oxygen, but instead of O2, which is oxygen gas in the atmosphere, it's 03. Three oxygen atoms bonded together. And it's what protects the Earth from the sun's ultraviolet radiation. The sun's trying to kill us all the time. Fortunately, we have a magnetic field and we also have an atmosphere. And so what gets happens is that ozone layer gets disrupted. If a supernova stripped away a significant portion of our ozone layer, then the sun's ultraviolet radiation would become lethal. we wouldn't be able to survive that. What would happen would be that the phytolankton in the oceans which are the foundation of marine food chain right and a major oxygen producer and if you don't recall we need oxygen to live they would die off plants on land would suffer severe damage animals including humans that are eating all of these plants they would have problems face dramatic in increases in cancer rates wouldn't be able to get any food get cancer at higher rates and other radiation related illnesses the entire ecosystem would basically ally collapse.

[00:18:34]But wait, there's more. The gamma radiation would also ionize nitrogen and oxygen in the upper atmosphere. And what that would do is it would create nitrogen oxides that produce reddish brown haze. This haze could hang in the atmosphere and basically persist for years and that reduces visible sunlight from reaching the surface and also could potentially trigger a period of global cooling. Some scientists actually think that supernova might have contributed to past mass extinctions on Earth, although the evidence is still debated. We don't know if that happened, but it absolutely could have contributed to some of the ancient extinction events that we know existed on Earth. Then there's also this cosmic ray component. So, we kind of skipped over that a little bit. We'll talk about that a little bit now. After the initial gammaray burst, a nearby supernova would actually bathe our solar system in high energy cosmic rays.

[00:19:29]Remember, these are basically protons traveling near or very close to the speed of light. And so for thousands of years, they're traveling, interacting with our solar system, increasing radiation exposure for all life on Earth. When one of those particles hits you, it literally microscopically rips through the atoms in your DNA and your cells. And just imagine a bullet going through tissue paper. It just rips you apart microscopically from the inside.

[00:19:55]So the big question is how close would a supernova need to be to cause Earth real problems? And the scientific consensus places the danger zone somewhere between 25 to 50 lighty years away from Earth.

[00:20:10]And within this range, a supernova could significantly deplete the ozone layer of our atmosphere, causing all kinds of disruption that we just discussed a second ago. Now for perspective, the nearest star to us is Proxima Centauri.

[00:20:24]It's only about four light years away.

[00:20:26]Four point, you know, just just some change. Just a little bit over four lighty years away. Uh but it's too far too small to ever actually become a supernova itself. Now, the good news is that there aren't any supernova candidates within this bubble of what we call a danger zone to Earth. Astronomers have cataloged the nearby massive stars, and the closest one that could potentially go supernova is actually called Beetlejuice. It's a red super giant that forms in the shoulder of the constellation Orion. If you ever look up at the night sky and see Orion is one of the biggest constellations we have in the northern hemisphere, uh the the big red star there, that one is is a possibility. But Beetlejuice is 650 light years away. It's well outside what we think is the danger zone. But don't forget, this is all based on calculations. We've never seen this happen, so we're not totally sure. And when that star explodes, Beetlejuice, it it could actually do it any day now or a 100,000 years from now. We don't really know. It'll be spectacular to observe, but hopefully harmless because it's outside of that boundary. Now, Spya is another really massive star. It's about 250 light-years away. IK Pegasy is a binary system with a white dwarf that could theoretically trigger a type 1A supernova. That one's about 150 lighty years away. So luckily, we're basically in a safe neighborhood. But let me just put a thought in your mind. Maybe we're not just lucky to be in a safe neighborhood. Maybe all of the stars that have planets around them near the center of the galaxy are in all in unsafe neighborhoods. In other words, as you get closer to the center of the galaxy, it might be that there's just too many supernovas going off within their bubble of danger so that you don't really get life forming on planets or at least not complex life forming on planets closer to the center where the star density is higher. It reminds me of one time I was driving down the freeway and there was this tire that I guess came off of a car or got shredded or something and the debris from the tire was in the freeway and it would have absolutely caused a wreck. But the tire debris was right on the line, you know, dot dot dot all the dashes on the freeway, it was it was right on the line. So, all of the cars were in their lanes and they were just passing on left and right hand side of this of this debris of tire. Uh, and if you accidentally change lanes and hit the tire, you'd wreck your car. But all the cars were pretty much going straight.

[00:22:57]And as they as I was passing this tire, I was thinking to myself, man, how lucky are we that that tire landed right in the middle of the road? Isn't that amazing that I'm so lucky that I didn't have that tire right in the middle of my lane? But then as I was thinking about it more, I was like, well, probably what happened probably is that tire shredded.

[00:23:17]it landed somewhere and a few cars hit it until finally it landed in a place where the cars were not likely to hit it anymore. So, it wasn't so much that I was lucky. It was that the physics of the situation eventually knocked it around enough and so it appeared that I was just so incredibly lucky, but actually it just ended up landing in a place that didn't harm me or any of the cars anymore. And so it might turn out that there's tons of life in the galaxy, but near the center of the galaxy, the life gets wiped out by supernova every 100 million years or so and never can get to enough time to evolve into complex life. So that could be part of the Fermy paradox. Why don't we see intelligent life everywhere in the universe? It might turn out that the only place you can have intelligent life in the universe is in the suburbs of the galaxy near the edge like where the Earth is. But here's an interesting thing to think about. Over Earth's long history, we've probably wandered through less safe neighborhoods from supernova.

[00:24:21]That is our solar system orbits the center of the galaxy. that happens over hundreds of millions of years. And we pass through different regions of space with different stellar populations all the time. And when I say all the time, I mean over hundreds of millions of years as we orbit the center of the galaxy. So it's statistically likely that Earth has been within that 25 to 50 lightyear danger zone at some point in the past.

[00:24:47]So, some researchers have suggested that certain minor extinction events in our past have been related to supernova, but not supernova that we can really see in our local neighborhood now. Maybe things that have happened in our distant past that we can no longer see. So, if a supernova did actually explode nearby, say if Beetlejuice in Orion literally exploded tomorrow, and by the way, it's a very unstable star, so it could explode at any time, right? What would it look like? So, a supernova in Beetlejuice distance in Orion would be extraordinarily bright. For several weeks, it would actually outshine every object in the night sky except for the moon. And if you've ever looked at the full moon, the moon is really, really bright. So, it would be second in brightness right behind the moon. At its peak, it might even be visible during the day, appearing as a bright star, like a point next to the sun. Ancient records actually describe this exact phenomena. So, get this. In 1054 AD, Chinese and Arab astronomers actually recorded what they called a guest star that appeared in the constellation Taurus. It was actually visible during the day for 23 days. That's almost a whole month. And it remained visible at night for nearly 2 years. This was a supernova. And what's left of it is called the Crab Nebula. One of the most studied objects in astronomy. The Crab Nebula is about 6,500 light years from Earth. It's far too distant to have caused any damage to us.

[00:26:25]All we got was the light show. The supernova that created it was bright enough to read by at night. Think about that. Actually, at night, you could pull out a book and read because of the light of that thing in the sky. Remember that the actual explosion happened 6,500 years ago before humans actually saw it because it takes that long for the light to travel here. Historical records actually describe other supernova as well. Tao supernova in 1572 and Kepler supernova in6004 were both visible to the naked eye and they appeared about as bright as Venus.

[00:27:02]Venus is extremely bright in the night sky. Most people think it's a star, but of course it's a planet in our solar system. So really, really bright. Both of these were thousands of light years away, well outside of the danger zone to eradicate life on Earth. I want you to think about that for a second. You know, we know what these things are now, but pretend that you're just a farmer or somebody in ancient times a thousand years ago or something, and suddenly during the day, you see a star in the sky, but you don't know it's a star. You don't know what any of this stuff is.

[00:27:32]You just see a bright dot that's appearing next to the sun and you can see it during the day. And when the sun goes down, you can still see that thing in the sky. And it's so bright, it's not as bright as the moon, but it's so bright that you could pull out a book and actually read by the light of this thing. And during the day, it's present in the sky for I don't know, almost a whole month. And at night time, you can actually see it with the naked eye and read by it for like two years. And if you don't know what any of this stuff is, that honestly must have been terrifying. And so it makes sense to me that they would have made up stories about, you know, this thing being caused by the gods or whatever because they're trying to explain it and they have no idea what they're looking at. It's just this thing that appears out of nowhere and it looks pretty mean and pretty menacing. And also keep in mind that the uh the Crab Nebula that we see today in the telescopes, which is a supernova remnant remnant, 6,500 light-years away and it was still that bright to see it during the day and read by it at night.

[00:28:32]Beetlejuice is only hundreds of light years away. So think about something 10 times closer, what that would look like if it actually went off in our lifetime.

[00:28:41]So as we wrap it up today, I just want to say the universe is capable of violence uh that we can barely imagine.

[00:28:48]and supernova are really one of the most spectacular demonstrations of the power in the universe. The energy released, the radiation produced that goes everywhere. The sheer scale of destruction, it's really almost beyond comprehension. But yet, here we are, little old humans on a tiny little rock orbiting our averagesized star, relatively safe in our little quiet corner in the backwoods on the edge of our average size galaxy. We don't have any stellar time bombs ticking nearby as far as we can tell. Um, perhaps a requirement for advanced civilizations to evolve is for them to always be on the outskirts of the galaxy, far away from where the stars are on average much closer together near the center of the galaxy. And that's what I want to leave you with today. We mentioned it before, but it's worth saying again. Maybe other life forms took a foothold on their planets, but they were periodically wiped out by a nearby star exploding. Uh maybe near the center of the galaxy when this happens more often. And they never got a chance to grow up, look into a camera, and shoot videos to ponder all this stuff. And as you think about that, as you look up in the night sky and wonder what's going to happen next, always remember to stay curious. Learn anything at math andcience.com.