Hey, welcome to sign Stuff, a production of iHeartRadio. I'm Horhea Cham and today we are asking what is the worst place to live in the galaxy. We live in a nice, cozy place in the Milky Way, but is there a spot where you definitely don't want your planet to be. We think we have the answer, and it came up during a conversation I had with Randall Munroe. Randall's the number one New York Times best selling creator of XKCD comics and the what If books and YouTube channel. If you are in designs, chances are you've seen his comics and videos featuring stick figures and nerdy humor. Randall had questions for me about exoplanets, which are planets outside of our solar system, and he specifically wondered what it would be like to live in a particular location in our galaxy. So get ready to travel to the worst place to live in the Milky Way galaxy. Here's my conversation with Randall Munroe. Hey everyone, Okay, I started off by asking my friend Randall, what if I so interesting about exoplanets, which are planets outside of our Solar system.

Hey, welcome to sign Stuff, a production of iHeartRadio. I'm Horhea Cham and today we are asking what is the worst place to live in the galaxy. We live in a nice, cozy place in the Milky Way, but is there a spot where you definitely don't want your planet to be. We think we have the answer, and it came up during a conversation I had with Randall Munroe. Randall's the number one New York Times best selling creator of XKCD comics and the what If books and YouTube channel. If you are in designs, chances are you've seen his comics and videos featuring stick figures and nerdy humor. Randall had questions for me about exoplanets, which are planets outside of our solar system, and he specifically wondered what it would be like to live in a particular location in our galaxy. So get ready to travel to the worst place to live in the Milky Way galaxy. Here's my conversation with Randall Munroe. Hey everyone, Okay, I started off by asking my friend Randall, what if I so interesting about exoplanets, which are planets outside of our Solar system.

Here's what he said, I don't really know I feel like it's as close to like intrinsically interesting as something can be. It's like, did you know there's other worlds out there? And we have never taken a picture of one of them where it's more than a pixel, But we just learned they're out there. And I think it's the novelty of it, like the newness of it, that is really exciting for me. Like when I was born, we had not confirmed the existence of any exoplanets. It was all entirely speculative, and then all of a sudden in my lifetime it's like, oh, hey, we spotted one of them, and then we spotted another one, and then more, and now we know about like thousands and thousands of exoplanets. So it's like, Okay, I want to see them. I want to know what they're like.

Here's what he said, I don't really know I feel like it's as close to like intrinsically interesting as something can be. It's like, did you know there's other worlds out there? And we have never taken a picture of one of them where it's more than a pixel, But we just learned they're out there. And I think it's the novelty of it, like the newness of it, that is really exciting for me. Like when I was born, we had not confirmed the existence of any exoplanets. It was all entirely speculative, and then all of a sudden in my lifetime it's like, oh, hey, we spotted one of them, and then we spotted another one, and then more, and now we know about like thousands and thousands of exoplanets. So it's like, Okay, I want to see them. I want to know what they're like.

Would you want to go there?

Would you want to go there?

I feel like physics means that I don't really have to make that decision. Oh right. I think any kind of space travel such a big commitment. I could see wanting to travel in the Solar System, but something where it's one of those one way across the universe, I mean that sounds cool. I don't know that I personally would opt for it, but I figure I'll worry about that once the tickets become available.

I feel like physics means that I don't really have to make that decision. Oh right. I think any kind of space travel such a big commitment. I could see wanting to travel in the Solar System, but something where it's one of those one way across the universe, I mean that sounds cool. I don't know that I personally would opt for it, but I figure I'll worry about that once the tickets become available.

Right right, you wouldn't be a tour as you'd be a migrant.

Right right, you wouldn't be a tour as you'd be a migrant.

Yeah, Like getting to another star one way is already such a big lift, because just getting there is going to be so hard, But I think I would put like huge amounts of work into just like seeing them, even if we just get a telescope that gives us a handful of pixels or some kind of detailed atmospheric breakdown clouds, anything that gives us a sense of like what this place is like. I love that, you know.

Yeah, Like getting to another star one way is already such a big lift, because just getting there is going to be so hard, But I think I would put like huge amounts of work into just like seeing them, even if we just get a telescope that gives us a handful of pixels or some kind of detailed atmospheric breakdown clouds, anything that gives us a sense of like what this place is like. I love that, you know.

Awesome, So you had some questions for me. What's the first question?

Awesome, So you had some questions for me. What's the first question?

I know, I've heard that there are these stars that are orbiting the Milky Way super massive black hole, and that's part of how we know that there's a black hole there. We see these stars orbiting really close to something that we can't see that seems to be really heavy. And it just occurred to me, what would it be like if you were on a planet around those stars? Is it possible for there to be a planet around the star? Would you notice you were around a black hole?

I know, I've heard that there are these stars that are orbiting the Milky Way super massive black hole, and that's part of how we know that there's a black hole there. We see these stars orbiting really close to something that we can't see that seems to be really heavy. And it just occurred to me, what would it be like if you were on a planet around those stars? Is it possible for there to be a planet around the star? Would you notice you were around a black hole?

Okay, what Randall is asking here? Is what would it be like to live in a planet near the super massive black hole at the center of our galaxy. It turns out that most galaxies out there, including ours, has a super massive black hole at their center. These are huge black holes. For example, the one at the center of our galaxy is called Sagittarius, a star, and it has a mass that is about four million times heavier than our sun. We recently took a picture of it, but the main reason we knew it was there was that we could see stars in clouds of gas circling a spot that looked empty, which was a sign that there was something really heavy there. Okay, back to Randall's.

Okay, what Randall is asking here? Is what would it be like to live in a planet near the super massive black hole at the center of our galaxy. It turns out that most galaxies out there, including ours, has a super massive black hole at their center. These are huge black holes. For example, the one at the center of our galaxy is called Sagittarius, a star, and it has a mass that is about four million times heavier than our sun. We recently took a picture of it, but the main reason we knew it was there was that we could see stars in clouds of gas circling a spot that looked empty, which was a sign that there was something really heavy there. Okay, back to Randall's.

Question, would you be affected in any way? Is there like a weird radiation environment?

Question, would you be affected in any way? Is there like a weird radiation environment?

Like?

Like?

What's it like there? Is it just like anywhere else in the galaxy. It's just you happen to be near a black hole? Or is it a bad place to be? Yeah?

What's it like there? Is it just like anywhere else in the galaxy. It's just you happen to be near a black hole? Or is it a bad place to be? Yeah?

Excellent question. Did you up with this while trying to figure out places to move to? No?

Excellent question. Did you up with this while trying to figure out places to move to? No?

I mean that's like fifty thousand light years something like that, So I feel like if you're paying for a moving van by the mile, that's going to get pretty expensive. But I think I'm I'm going to keep black holes at a healthy distance until I've talked to someone about whether or not it's a good place to be.

I mean that's like fifty thousand light years something like that, So I feel like if you're paying for a moving van by the mile, that's going to get pretty expensive. But I think I'm I'm going to keep black holes at a healthy distance until I've talked to someone about whether or not it's a good place to be.

Yeah. Super amazing question. And by the way, I should mention Randall that everyone I talked to, all the experts I've talked to, they're all huge fans of yours.

Yeah. Super amazing question. And by the way, I should mention Randall that everyone I talked to, all the experts I've talked to, they're all huge fans of yours.

Oh, thank you.

Oh, thank you.

So for this question, I reached out to Professor Anne Marie Madigan. Okay, I'm always excited when I find the right person to talk to about a question, and in this case, I found the perfect person. Anne Marie Madigan is a professor of astrophysics and planetary sciences at the University of Colorado at Boulder, and she happens to study how stars and clouds of gases move around super massive black holes like the one at the center of our galaxy. Now, the first thing she wanted to do in her answer was to paint us a picture of what space is like at the center of our galaxy? Is it like the space around us? Right now? Here's what she said.

So for this question, I reached out to Professor Anne Marie Madigan. Okay, I'm always excited when I find the right person to talk to about a question, and in this case, I found the perfect person. Anne Marie Madigan is a professor of astrophysics and planetary sciences at the University of Colorado at Boulder, and she happens to study how stars and clouds of gases move around super massive black holes like the one at the center of our galaxy. Now, the first thing she wanted to do in her answer was to paint us a picture of what space is like at the center of our galaxy? Is it like the space around us? Right now? Here's what she said.

Okay, so this is a really fun question. So I'm going to perform this little thought experiment. We're going to make a bubble around the Sun that has a radius of four light years. Okay, so got this sphere around the Sun, and we're going to think how much stuff is in here. We've left the Sun of one solar mass that makes sense, and the next biggest thing is Jupiter and that's a thousandth the mass of the Sun, and everything else has just changed. There's you know, Saturn, Mars. Nothing really matters here. It's just one star.

Okay, so this is a really fun question. So I'm going to perform this little thought experiment. We're going to make a bubble around the Sun that has a radius of four light years. Okay, so got this sphere around the Sun, and we're going to think how much stuff is in here. We've left the Sun of one solar mass that makes sense, and the next biggest thing is Jupiter and that's a thousandth the mass of the Sun, and everything else has just changed. There's you know, Saturn, Mars. Nothing really matters here. It's just one star.

All right.

All right.

Imagine a bubble around us right now. That's four light years or twenty four trillion miles in all directions. The only thing you'd find in that bubble is our solar system, meaning that there's four light years of empty space all around us. Now, what happens if you draw that same bubble in the center of our galaxy.

Imagine a bubble around us right now. That's four light years or twenty four trillion miles in all directions. The only thing you'd find in that bubble is our solar system, meaning that there's four light years of empty space all around us. Now, what happens if you draw that same bubble in the center of our galaxy.

I'm going to take this bubble. We're going to put it in the center of our galaxy, centered on the supermassive black hole, and ask the same question, what's inside this bubble. First of all, you've got the supermass black hole, and it's four million times the mass of the Sun. And then you've got about ten million stars.

I'm going to take this bubble. We're going to put it in the center of our galaxy, centered on the supermassive black hole, and ask the same question, what's inside this bubble. First of all, you've got the supermass black hole, and it's four million times the mass of the Sun. And then you've got about ten million stars.

Ten million stars.

Ten million stars.

We can see some red giant stars. They're like absolutely huge stars. Just like pumping out a lot of radiation. But we also think there's a lot of stellar mass black holes, neutron stars, white dwarfs, so like the remnants of stars that have already died, and they're all just swimming around the black hole. And that's a big problem for planets.

We can see some red giant stars. They're like absolutely huge stars. Just like pumping out a lot of radiation. But we also think there's a lot of stellar mass black holes, neutron stars, white dwarfs, so like the remnants of stars that have already died, and they're all just swimming around the black hole. And that's a big problem for planets.

Whoa, yes, it's pretty busy in the center of the galaxy.

Whoa, yes, it's pretty busy in the center of the galaxy.

Wait a minute, so a four light year bubble around the Solar System. The nearest stars are a little over four light years from us. So yeah, in that bubble there are no stars. And I think of that as like, that's how normal space is. But did she say ten million stars? That is more than I would have guessed.

Wait a minute, so a four light year bubble around the Solar System. The nearest stars are a little over four light years from us. So yeah, in that bubble there are no stars. And I think of that as like, that's how normal space is. But did she say ten million stars? That is more than I would have guessed.

Yeah. If you take that same bubble you put it in the center of our galaxy, you not only have this super massive black hole, which is four million times the mass of our Sun, but you also have ten million stars, which is ten million times more than what we have around us.

Yeah. If you take that same bubble you put it in the center of our galaxy, you not only have this super massive black hole, which is four million times the mass of our Sun, but you also have ten million stars, which is ten million times more than what we have around us.

I am suddenly feeling less good about the possibility of having planets. I'm a little concerned because I've seen diagrams of the super massive black hole and like some of the nearby star orbits, but they only showed one or two. They didn't show millions or billions. I'm getting very nervous here about my plans to move to one of these.

I am suddenly feeling less good about the possibility of having planets. I'm a little concerned because I've seen diagrams of the super massive black hole and like some of the nearby star orbits, but they only showed one or two. They didn't show millions or billions. I'm getting very nervous here about my plans to move to one of these.

Yeah, the center of our galaxy is a busy place. There's about ten million more stars there than what's around us right now. It's like we live in the equivalent of a farmhouse in a field in the middle of nowhere, and the center of the galaxy is Times Square in New York City. Now you might think, well, that's exciting. I want to live in Times Square in New York City. But when space is that busy, there are a lot of bad things that can happen. Here's how doctor Madigan describes it.

Yeah, the center of our galaxy is a busy place. There's about ten million more stars there than what's around us right now. It's like we live in the equivalent of a farmhouse in a field in the middle of nowhere, and the center of the galaxy is Times Square in New York City. Now you might think, well, that's exciting. I want to live in Times Square in New York City. But when space is that busy, there are a lot of bad things that can happen. Here's how doctor Madigan describes it.

So let's say you're a planet in orbit around a star that's in orbit. It's all for end the supermassive black hole. The problem is that average density in that region is so much higher that your closest star is going to be, on average, about three hundred times closer than our closest star is to us. And so there's just stars whizzing past all the time, and you can just be ripped off your orbit, completely ripped away from your host star.

So let's say you're a planet in orbit around a star that's in orbit. It's all for end the supermassive black hole. The problem is that average density in that region is so much higher that your closest star is going to be, on average, about three hundred times closer than our closest star is to us. And so there's just stars whizzing past all the time, and you can just be ripped off your orbit, completely ripped away from your host star.

Okay, what can happen is if another star flies too close to you. It's gravity can actually pull you away from the star that you're orbiting, Like if another star flew close to our Solar system right now, it might pull away Neptune or Saturn or even Us.

Okay, what can happen is if another star flies too close to you. It's gravity can actually pull you away from the star that you're orbiting, Like if another star flew close to our Solar system right now, it might pull away Neptune or Saturn or even Us.

And this is kind of fun. So you could actually start orbiting that star that ripped you away, so you can incinded this like interstellar hopping of planets, which is exciting but terrible for stability for obvious reasons. Or you could just be ripped off your host star and you'll be freely floating in this sea around the black hole and indeed directly just orbit the black hole itself. Again, very cool, bad for stability.

And this is kind of fun. So you could actually start orbiting that star that ripped you away, so you can incinded this like interstellar hopping of planets, which is exciting but terrible for stability for obvious reasons. Or you could just be ripped off your host star and you'll be freely floating in this sea around the black hole and indeed directly just orbit the black hole itself. Again, very cool, bad for stability.

Being bad for like whatever might be alive there.

Being bad for like whatever might be alive there.

Yeah, it's very unpredictable. You'd have to evolve to really deal with not just like hostile environment, but changing you're changing circumstances, and that seems like a tall order.

Yeah, it's very unpredictable. You'd have to evolve to really deal with not just like hostile environment, but changing you're changing circumstances, and that seems like a tall order.

So yeah, it's pretty dangerous at the center of the galaxy. And if you think that's bad, just wait a little bit and you'll see it's going to get a lot worse. And it involves deadly solar flares and explosive super novas.

So yeah, it's pretty dangerous at the center of the galaxy. And if you think that's bad, just wait a little bit and you'll see it's going to get a lot worse. And it involves deadly solar flares and explosive super novas.

We'll dig into those stay with us. We'll be right back, and we're back.

We'll dig into those stay with us. We'll be right back, and we're back.

Okay. That is a sort of more exciting answer than I was expecting. Ah yeah, that's man. That is a lot of stars in a very small space. So okay, you get ripped free from your host star. You know, if you say the Sun falls into this zone for some reason, all the planets get gravitationally yanked away from the Sun and either up orbiting this other star or just kind of freely orbiting the black hole, you know, with this many stars around, maybe and here's me being optimistic in hey, maybe we'll just always be near enough to one of them that it's like nice weather. We got like enough sunlight to keep the earth warm but not too much.

Okay. That is a sort of more exciting answer than I was expecting. Ah yeah, that's man. That is a lot of stars in a very small space. So okay, you get ripped free from your host star. You know, if you say the Sun falls into this zone for some reason, all the planets get gravitationally yanked away from the Sun and either up orbiting this other star or just kind of freely orbiting the black hole, you know, with this many stars around, maybe and here's me being optimistic in hey, maybe we'll just always be near enough to one of them that it's like nice weather. We got like enough sunlight to keep the earth warm but not too much.

Uh huh.

Uh huh.

I wonder how long we could keep that going, like stay in the habitable zone by sheer luck of just like going between the stars far enough away that they're not toasting us, but close enough that it's keeping the surface warm and the water liquid. I wonder how long we could keep that up?

I wonder how long we could keep that going, like stay in the habitable zone by sheer luck of just like going between the stars far enough away that they're not toasting us, but close enough that it's keeping the surface warm and the water liquid. I wonder how long we could keep that up?

You mean, like, how long can we keep couch surfing hopping from star to star or flying around between stars?

You mean, like, how long can we keep couch surfing hopping from star to star or flying around between stars?

Yeah, yeah, you know, I'm just like, maybe we could like nudge the Earth and like, look at all the stars swarming around and be like, there's a path where if we go plunge between those two stars. It's like setting up a complicated pool shot, Like we can ricochet near this one and then over to that one and around to that one, and hopefully we can get a trajectory that keeps the Earth habitable, you know, for the next I don't know, let's say a hundred years, so at least in all of our lifetimes, and then after that, that's a problem for the next generation to solve.

Yeah, yeah, you know, I'm just like, maybe we could like nudge the Earth and like, look at all the stars swarming around and be like, there's a path where if we go plunge between those two stars. It's like setting up a complicated pool shot, Like we can ricochet near this one and then over to that one and around to that one, and hopefully we can get a trajectory that keeps the Earth habitable, you know, for the next I don't know, let's say a hundred years, so at least in all of our lifetimes, and then after that, that's a problem for the next generation to solve.

Well, Randald, that's just one problem. Oh okay, So you not only have to worry about a star coming near your solar system and maybe affecting your orbit and getting you thrown out of your solar system or sucking you into their solar system. You also have to worry about the black hole itself.

Well, Randald, that's just one problem. Oh okay, So you not only have to worry about a star coming near your solar system and maybe affecting your orbit and getting you thrown out of your solar system or sucking you into their solar system. You also have to worry about the black hole itself.

Okay, I was afraid of that.

Okay, I was afraid of that.

There's another thing that I need to bring up as well. It's not just the stellar density, it's the black hole. As your host star moves around, it will change the shape of your orbit.

There's another thing that I need to bring up as well. It's not just the stellar density, it's the black hole. As your host star moves around, it will change the shape of your orbit.

Ah.

Ah.

The dynamics are actually the gorgeous, it's fascinating. Okay, we're going to have a star, and we're going to have a planet, an orbiter and the star, and the star isn't orbiting the super massive black hole. So we got those three bodies. And if there's any tilt but respect to each other, they actually torque each other. Does that make sense.

The dynamics are actually the gorgeous, it's fascinating. Okay, we're going to have a star, and we're going to have a planet, an orbiter and the star, and the star isn't orbiting the super massive black hole. So we got those three bodies. And if there's any tilt but respect to each other, they actually torque each other. Does that make sense.

They try to make each other a ligne.

They try to make each other a ligne.

That's exactly right. They try and make each other a line because they're just like massive gravitating rings. It's a conservation of angular momentum iss you and in doing so, you have to change the shape of the planetary orbit.

That's exactly right. They try and make each other a line because they're just like massive gravitating rings. It's a conservation of angular momentum iss you and in doing so, you have to change the shape of the planetary orbit.

What doctor Matigan is saying is that if you're orbiting a star that's orbiting a black hole, the black hole is going to change how you orbit around your star. So if you were moving around in a nice circle around your star, the gravity from that black hole nearby, it's going to squish your orbit so it's thinner and more stretched out, eventually making it almost like a straight line, which means sometimes you're going to be super close to your star and sometimes you're going to be super far.

What doctor Matigan is saying is that if you're orbiting a star that's orbiting a black hole, the black hole is going to change how you orbit around your star. So if you were moving around in a nice circle around your star, the gravity from that black hole nearby, it's going to squish your orbit so it's thinner and more stretched out, eventually making it almost like a straight line, which means sometimes you're going to be super close to your star and sometimes you're going to be super far.

Okay, and you might be like, that's not so bad. But if you can think about going from a near circular orbit that the Earth has as a moves round the Sun to going much more elongated, eccentric to almost a straight line. You see, the problem is that your closest approach to your star, you're going to get lots of different levels of radiation. That could be a problem for life. But if you even just thinking of stability, you can actually go so close to your host star that you just smash into it. There's a lot of pathways to destruction.

Okay, and you might be like, that's not so bad. But if you can think about going from a near circular orbit that the Earth has as a moves round the Sun to going much more elongated, eccentric to almost a straight line. You see, the problem is that your closest approach to your star, you're going to get lots of different levels of radiation. That could be a problem for life. But if you even just thinking of stability, you can actually go so close to your host star that you just smash into it. There's a lot of pathways to destruction.

Why does the orbit change shape because of the black hole?

Why does the orbit change shape because of the black hole?

Is it called Kosi leadoff oscillations? Orbit shape would be changing as a function of time.

Is it called Kosi leadoff oscillations? Orbit shape would be changing as a function of time.

Yeah, so you not only have to worry about stars affecting your orbit, the black hole itself that your star is orbiting will change your orbit over time. And these are what she calls Kosei leadoff oscillations that I may have you've heard of these before.

Yeah, so you not only have to worry about stars affecting your orbit, the black hole itself that your star is orbiting will change your orbit over time. And these are what she calls Kosei leadoff oscillations that I may have you've heard of these before.

I think I've heard of them, but I didn't know that they would apply to a star orbiting a black hole. So what you're saying is that even if we were riding in toward the black hole on the Sun, that we have, due to a series of bad decisions, somehow steered toward the center of the gallicy And even if we managed to like plot a course that avoids all of those stars, our orbit would be getting more and more eccentric, so the Earth would be frozen, you know, on the outer part of its orbit, assuming it's not getting toasted by nearby stars, and then we would crash into the Sun. Which I'm pretty optimistic, but I feel like it's hard to come up with a version of that that's good for us. Crashing into the Sun is definitely bad.

I think I've heard of them, but I didn't know that they would apply to a star orbiting a black hole. So what you're saying is that even if we were riding in toward the black hole on the Sun, that we have, due to a series of bad decisions, somehow steered toward the center of the gallicy And even if we managed to like plot a course that avoids all of those stars, our orbit would be getting more and more eccentric, so the Earth would be frozen, you know, on the outer part of its orbit, assuming it's not getting toasted by nearby stars, and then we would crash into the Sun. Which I'm pretty optimistic, but I feel like it's hard to come up with a version of that that's good for us. Crashing into the Sun is definitely bad.

Yeah, imagine here on Earth we have pretty extreme winters, hot summers, cold winters, We've had ice ages, and it's still our orbit. It's pretty much a circle, right, Yeah, So imagine because you're going close to the black hole, it's going to change the shape of that orbit. It's going to make it more narrow and longer, and so you're going to just get super extreme seasons.

Yeah, imagine here on Earth we have pretty extreme winters, hot summers, cold winters, We've had ice ages, and it's still our orbit. It's pretty much a circle, right, Yeah, So imagine because you're going close to the black hole, it's going to change the shape of that orbit. It's going to make it more narrow and longer, and so you're going to just get super extreme seasons.

Well, okay, I can see this is a bad idea.

Well, okay, I can see this is a bad idea.

Okay, we're talking about the worst place to live in the galaxy, and it seems to be the center of it. It's so busy and crowded there that it's a pretty dangerous place. There is a way to have a stable orbit around a star there, but as you'll hear later, on. It might not help you very much. It is kind of a bad idea, but Professor Madigan does think it's still possible to survive in that environment.

Okay, we're talking about the worst place to live in the galaxy, and it seems to be the center of it. It's so busy and crowded there that it's a pretty dangerous place. There is a way to have a stable orbit around a star there, but as you'll hear later, on. It might not help you very much. It is kind of a bad idea, but Professor Madigan does think it's still possible to survive in that environment.

Okay, you need to get out to a few light years from the black hole for the stellar density to drop enough that this isn't going to be completely catastrophic for your stability, and that closer you were a bit your host star, the better.

Okay, you need to get out to a few light years from the black hole for the stellar density to drop enough that this isn't going to be completely catastrophic for your stability, and that closer you were a bit your host star, the better.

Okay.

Okay.

Kind of like to keep in tight within the orbit of mercury, so passing stars don't grab you as easily. Oh yeah, if you're a neptune or something, you're a gunner.

Kind of like to keep in tight within the orbit of mercury, so passing stars don't grab you as easily. Oh yeah, if you're a neptune or something, you're a gunner.

M's just no hope.

M's just no hope.

A few light years away from the black hole is where the stellar density drops sufficiently that if you're orbiting very close to your host star, you might be okay.

A few light years away from the black hole is where the stellar density drops sufficiently that if you're orbiting very close to your host star, you might be okay.

Yeah, so there's a little bit of hope. So this super density of stars around black holes is not even throughout that four light year bubble that she mentioned. It's denser in the center. So she did some math on this for us, and she figured out that at about two light years away you kind of stand the chance that the density is not so high that maybe you could survive maybe a few billion years without some star passing too close to you to disrupt you.

Yeah, so there's a little bit of hope. So this super density of stars around black holes is not even throughout that four light year bubble that she mentioned. It's denser in the center. So she did some math on this for us, and she figured out that at about two light years away you kind of stand the chance that the density is not so high that maybe you could survive maybe a few billion years without some star passing too close to you to disrupt you.

Okay, but you have to be orbiting really close to the star. If you have to be orbit closer than mercury, suddenly those little tiny stars, those aren't looking so bad.

Okay, but you have to be orbiting really close to the star. If you have to be orbit closer than mercury, suddenly those little tiny stars, those aren't looking so bad.

According to doctor Madigan, one way to protect yourself in the center of the galaxy is to live in a planet that orbits really close to its sun, as close as mercury circles our Sun. But of course being that close to a sun would roast you, so you need to circle what are called M dwarf stars. Yeah. So it turns out that about three quarters of all the stars that we know about are these M dwarfs type of stars, and they're smaller and they're cooler than the sun, our sun.

According to doctor Madigan, one way to protect yourself in the center of the galaxy is to live in a planet that orbits really close to its sun, as close as mercury circles our Sun. But of course being that close to a sun would roast you, so you need to circle what are called M dwarf stars. Yeah. So it turns out that about three quarters of all the stars that we know about are these M dwarfs type of stars, and they're smaller and they're cooler than the sun, our sun.

So our sun is it's really like a bigger than average star, Like these are normal stars and we have a really big one.

So our sun is it's really like a bigger than average star, Like these are normal stars and we have a really big one.

Yeah. That is exactly what she said, is that our only hope for living in this environment is to find an M dwarf type of star, small, not super hot, so that we can be really close to it so that our orbit is really tight until we don't get as influenced by the black hole or stars passing by.

Yeah. That is exactly what she said, is that our only hope for living in this environment is to find an M dwarf type of star, small, not super hot, so that we can be really close to it so that our orbit is really tight until we don't get as influenced by the black hole or stars passing by.

I like that she's brought up challenges and problems with these ideas that are so big.

I like that she's brought up challenges and problems with these ideas that are so big.

Okay, Now, let's say that we happen to be orbiting an M dwarf type of star. We're close to the star, we have a tight orbit that's stable on a rocky planet with an atmosphere. You're still not home safe.

Okay, Now, let's say that we happen to be orbiting an M dwarf type of star. We're close to the star, we have a tight orbit that's stable on a rocky planet with an atmosphere. You're still not home safe.

Okay.

Okay.

Yeah, And this kind of gets to your second question, which is how habitable would these planets be? Like, if such a planet was possible and you're stable for billions of years, would it be habitable? And the answer is probably not.

Yeah, And this kind of gets to your second question, which is how habitable would these planets be? Like, if such a planet was possible and you're stable for billions of years, would it be habitable? And the answer is probably not.

There are problems. One problem is that these types of stars flare intensely. So Proximus century, again, this is our nearest star to our Sun. It is a low mass red dwarf stars by an eighth the mass of the Sun, so it's not producing as much radiation, it's much less luminous. It actually has a planet in its habitable zone, which is really exciting. But a few years ago, in a monitoring campaign, astronomers saw Proximus Andury flare by a factor of ten thousand in ultraviolet radiation. Whoa, and you can imagine if the Sun did that, like all of a sudden not a factor of two brighter and UV, but a factor of ten thousand. Yeah.

There are problems. One problem is that these types of stars flare intensely. So Proximus century, again, this is our nearest star to our Sun. It is a low mass red dwarf stars by an eighth the mass of the Sun, so it's not producing as much radiation, it's much less luminous. It actually has a planet in its habitable zone, which is really exciting. But a few years ago, in a monitoring campaign, astronomers saw Proximus Andury flare by a factor of ten thousand in ultraviolet radiation. Whoa, and you can imagine if the Sun did that, like all of a sudden not a factor of two brighter and UV, but a factor of ten thousand. Yeah.

I don't think they make ten thousand spf sunblocks exactly.

I don't think they make ten thousand spf sunblocks exactly.

You'd really have to have a really good thick atmosphere to withstand that bombardment.

You'd really have to have a really good thick atmosphere to withstand that bombardment.

You know. I always heard if the littler stars live longer because they're not burning through their fuel as it's like, really big stars might burn out in a few billion, a few million years. Even the Sun lasts maybe twelve billion years, but those little stars can last for way longer. And so I thought of them as being more chill and quiet. But boy, they're really not seeming chill.

You know. I always heard if the littler stars live longer because they're not burning through their fuel as it's like, really big stars might burn out in a few billion, a few million years. Even the Sun lasts maybe twelve billion years, but those little stars can last for way longer. And so I thought of them as being more chill and quiet. But boy, they're really not seeming chill.

They're small and angry. Yeah, yeah, you know, and something flares ten thousand times brighter than normal that will fry anything. Yeah, So the planet to orbit a small nuts a bright star so you can have a super tight black hole and steel proof orbit in the center of the galaxy just went out the window. These small stars are crazy. They flare up, burning everything on the surface of your planet. And that's not the only thing you have to worry about burning you to a crisp. There are two other big sources of radiation. So when we come back. We'll talk about those two sources, how they definitely make the center of the galaxy the worst place to have your planet. Will be right back, and we're back. But these solar flares are not the only thing you would have to worry about. So if you are around one of these stars near the galactic center, there's other things you also have to worry about. One of them are sort of brief quasars that happen near the black hole.

They're small and angry. Yeah, yeah, you know, and something flares ten thousand times brighter than normal that will fry anything. Yeah, So the planet to orbit a small nuts a bright star so you can have a super tight black hole and steel proof orbit in the center of the galaxy just went out the window. These small stars are crazy. They flare up, burning everything on the surface of your planet. And that's not the only thing you have to worry about burning you to a crisp. There are two other big sources of radiation. So when we come back. We'll talk about those two sources, how they definitely make the center of the galaxy the worst place to have your planet. Will be right back, and we're back. But these solar flares are not the only thing you would have to worry about. So if you are around one of these stars near the galactic center, there's other things you also have to worry about. One of them are sort of brief quasars that happen near the black hole.

Okay, I'm going to tell you two more issues.

Okay, I'm going to tell you two more issues.

Okay, so let's.

Okay, so let's.

Say you're a planet in the habit of plisode. You're close to this en dwarf star, but you've got a nice atmosphere, you're doing just fine. There are two very explosive events that could be dangerous for you. One they're called tidal disruption events. These are wonderful, it's a little destructive. This happens when a star gets shoved down to an orbit that brings it so close to a supermassive black hole that it gets ripped apart. And in essence, what's happening is the gravity acting on one side of the star is so much greater than the gravity acting on the other side of the star that actually overcomes the gravity that binds the star together, so it just rips it apart. It's half of the star. It gets slunk shot out of the system, which is kind of fun. But the other half forms an accretion disc. So this is a disc of ionized plasma made up of the star that's been ripped apart and forms like a mini quasar. It lights up the whole region and at peak, this title disruption event can actually produce so much energy per second it can I shine the galaxy what just for a split second, And we see this happening in external galaxies, and our estimates are that this should happen once every ten thousand years.

Say you're a planet in the habit of plisode. You're close to this en dwarf star, but you've got a nice atmosphere, you're doing just fine. There are two very explosive events that could be dangerous for you. One they're called tidal disruption events. These are wonderful, it's a little destructive. This happens when a star gets shoved down to an orbit that brings it so close to a supermassive black hole that it gets ripped apart. And in essence, what's happening is the gravity acting on one side of the star is so much greater than the gravity acting on the other side of the star that actually overcomes the gravity that binds the star together, so it just rips it apart. It's half of the star. It gets slunk shot out of the system, which is kind of fun. But the other half forms an accretion disc. So this is a disc of ionized plasma made up of the star that's been ripped apart and forms like a mini quasar. It lights up the whole region and at peak, this title disruption event can actually produce so much energy per second it can I shine the galaxy what just for a split second, And we see this happening in external galaxies, and our estimates are that this should happen once every ten thousand years.

Oh, I see, you're saying. We might be stable, but around you these things might be popping.

Oh, I see, you're saying. We might be stable, but around you these things might be popping.

Off exactly and it's like, all of a sudden, you've got a galaxy's worth of luminosity just blasting from the very center at the galaxy. So if you're host to that, that two could be really bad for your atmosphere.

Off exactly and it's like, all of a sudden, you've got a galaxy's worth of luminosity just blasting from the very center at the galaxy. So if you're host to that, that two could be really bad for your atmosphere.

That does seem bad now, And then we see a flash of light from across the universe. There will be like a star that something goes very wrong and they explode and it's so bright that we can see it from all the way across the visible observable universe. And I always think like, well, luckily those seem to be rare enough that we don't have to worry about one happening in our galaxy, because that seems like that could be bad being right next to it, even when a one or two light years away. Yeah, okay, that does sound worrying.

That does seem bad now, And then we see a flash of light from across the universe. There will be like a star that something goes very wrong and they explode and it's so bright that we can see it from all the way across the visible observable universe. And I always think like, well, luckily those seem to be rare enough that we don't have to worry about one happening in our galaxy, because that seems like that could be bad being right next to it, even when a one or two light years away. Yeah, okay, that does sound worrying.

Yeah, and it's not just these quasars. You also have to worry about supernovas. You said, that's number two, number two.

Yeah, and it's not just these quasars. You also have to worry about supernovas. You said, that's number two, number two.

There's a third one, and that is a supernova, which I'm sure a lot of people have heard of. There are a lot of very massive stars in orbit about the super musbuckle at the center of our galaxy. We actually think that massive stars are forming in the center of the galaxy kind of like in a disk, just like planets form a right, stars, massive stars are forming in a disk around the black hole, exciting. But when they run out of fuel, which they do quickly, their cores collapse. You know, if they don't have enough fuel to keep up thermonuclear fusion, they don't have that pressure support, so gravity just like catastrophically collapses. The core. But the outer layers of the star just go bananas. And it's not a technical term, but they just explode. And that too is very energetic, very exciting. But yes, you're going to have explosions in your sky if you're in that region, and that can also, i'm afraid, just really damage your atmosphere.

There's a third one, and that is a supernova, which I'm sure a lot of people have heard of. There are a lot of very massive stars in orbit about the super musbuckle at the center of our galaxy. We actually think that massive stars are forming in the center of the galaxy kind of like in a disk, just like planets form a right, stars, massive stars are forming in a disk around the black hole, exciting. But when they run out of fuel, which they do quickly, their cores collapse. You know, if they don't have enough fuel to keep up thermonuclear fusion, they don't have that pressure support, so gravity just like catastrophically collapses. The core. But the outer layers of the star just go bananas. And it's not a technical term, but they just explode. And that too is very energetic, very exciting. But yes, you're going to have explosions in your sky if you're in that region, and that can also, i'm afraid, just really damage your atmosphere.

In other words, if you're living on a planet near the center of the galaxy, you're going to have front row seeds to stars getting ripped apart and first thing super brightly and two giant stars collapsing and going supernova all around you every few thousand years.

In other words, if you're living on a planet near the center of the galaxy, you're going to have front row seeds to stars getting ripped apart and first thing super brightly and two giant stars collapsing and going supernova all around you every few thousand years.

Yeah, that also seems not ideal. I heard the rule of thumb is like, if you're trying to estimate anything involving a supernova, whatever your intuition says, it's bigger than that. So like, what's the safe distance from a supernova? Like farther than you think?

Yeah, that also seems not ideal. I heard the rule of thumb is like, if you're trying to estimate anything involving a supernova, whatever your intuition says, it's bigger than that. So like, what's the safe distance from a supernova? Like farther than you think?

Two light years doesn't seem enough, especially because she estimates that these quasar events and also these supernova events probably happen in near the galactic center around every ten thousand years.

Two light years doesn't seem enough, especially because she estimates that these quasar events and also these supernova events probably happen in near the galactic center around every ten thousand years.

Okay, that is about as long as the Neolithic Revolution, as long as humans have been farming and building cities. Yeah, we'd have one of those happened sometime in there.

Okay, that is about as long as the Neolithic Revolution, as long as humans have been farming and building cities. Yeah, we'd have one of those happened sometime in there.

Yeah. If you're trying to evolve in this planet and trying to be intelligent things, you'd have to contend with every ten thousand years, basically your whole planet getting fried.

Yeah. If you're trying to evolve in this planet and trying to be intelligent things, you'd have to contend with every ten thousand years, basically your whole planet getting fried.

Yeah, that seems bad. Hey, look at least now the flaring and dwarf started and seems so bad. You know, astronomers talking to astronomers, it's always great for a perspective. They're like, there's this horrible thing, but don't worry. It's actually very small compared to this other even worse thing.

Yeah, that seems bad. Hey, look at least now the flaring and dwarf started and seems so bad. You know, astronomers talking to astronomers, it's always great for a perspective. They're like, there's this horrible thing, but don't worry. It's actually very small compared to this other even worse thing.

It could be worse. Yeah, but we did come up with sort of a solution together.

It could be worse. Yeah, but we did come up with sort of a solution together.

Oh okay, I'm listening.

Oh okay, I'm listening.

And the solution is that it might be possible for life to be there and for us to live in that place. If you're living in an icy planet. Okay, okay, but.

And the solution is that it might be possible for life to be there and for us to live in that place. If you're living in an icy planet. Okay, okay, but.

But I do I do have I do have a thought. Okay, this is this is very like Earth centric and thinking, like you want a rocky planet with a thin atmosphere and you want humans walking around all over it with plants and stuff. Maybe if you're a planet near the galactic center and your atmosphere is just getting destroyed continuously. Maybe you just evolved to not really need that thing, you know, so.

But I do I do have I do have a thought. Okay, this is this is very like Earth centric and thinking, like you want a rocky planet with a thin atmosphere and you want humans walking around all over it with plants and stuff. Maybe if you're a planet near the galactic center and your atmosphere is just getting destroyed continuously. Maybe you just evolved to not really need that thing, you know, so.

You could still have water. Is that what you're saying. Maybe the water is underground.

You could still have water. Is that what you're saying. Maybe the water is underground.

Yeah, let's let's go with that. Maybe you're an icy planet, so maybe not too This is good. We're like doing science in real time. Let's say you're you're not in the habitable zone of your M dwarf stars, so we'll put you a little bit further away. So you're icy, but you've got liquid water under that surface, the surface ice, and you know, your your atmosphere can come and go and that's fine. But you're just living in the ocean.

Yeah, let's let's go with that. Maybe you're an icy planet, so maybe not too This is good. We're like doing science in real time. Let's say you're you're not in the habitable zone of your M dwarf stars, so we'll put you a little bit further away. So you're icy, but you've got liquid water under that surface, the surface ice, and you know, your your atmosphere can come and go and that's fine. But you're just living in the ocean.

And you have that ice to kind of shield you maybe from all this.

And you have that ice to kind of shield you maybe from all this.

Yeah, yeah, exactly. Yeah, maybe it's a little like little tardy grades, just like floating around these little mass piglets in water or oct octopus people. Was the next thing I was going to.

Yeah, yeah, exactly. Yeah, maybe it's a little like little tardy grades, just like floating around these little mass piglets in water or oct octopus people. Was the next thing I was going to.

Say, Yeah, meaning it wouldn't be habitable for something like us. But you know, if we expand our definition of what is habitable, or if we just imagine something that doesn't need an atmosphere, it could be habitable.

Say, Yeah, meaning it wouldn't be habitable for something like us. But you know, if we expand our definition of what is habitable, or if we just imagine something that doesn't need an atmosphere, it could be habitable.

Yeah.

Yeah.

Yeah, wow, Well you said there's a ton of stars there, right.

Yeah, wow, Well you said there's a ton of stars there, right.

Yeah, so you know there's about ten million stars just the bubble of four light years in radius from the supermass black hole. There's a lot of stars.

Yeah, so you know there's about ten million stars just the bubble of four light years in radius from the supermass black hole. There's a lot of stars.

There may be millions of planets potentially, right.

There may be millions of planets potentially, right.

Yeah, and then there's no reason planets couldn't form about a light year out from the black hole. You know, you see stars forming in that region, and it could be discs around these stars out of which planets form. So there could be a little planet formation there.

Yeah, and then there's no reason planets couldn't form about a light year out from the black hole. You know, you see stars forming in that region, and it could be discs around these stars out of which planets form. So there could be a little planet formation there.

For sure.

For sure.

There's life in the center of our galaxy and conclusion.

There's life in the center of our galaxy and conclusion.

So yeah, it might be possible for there to be life in the center of the galaxy.

So yeah, it might be possible for there to be life in the center of the galaxy.

Okay, so you just got to hide under an ice sheet. It's almost like a planet sized a glue surrounding you, just for protection against the Sun. I guess that would at least be Yeah, what's the SPF of Europa's icy shell?

Okay, so you just got to hide under an ice sheet. It's almost like a planet sized a glue surrounding you, just for protection against the Sun. I guess that would at least be Yeah, what's the SPF of Europa's icy shell?

Good question.

Good question.

Yeah, yeah, we should figure out the SPF and then for posing as emission to land on Europa and put the label there saying what SPF Europa is.

Yeah, yeah, we should figure out the SPF and then for posing as emission to land on Europa and put the label there saying what SPF Europa is.

So, like, if there is life out there, maybe it would have to be sort of like octopus people or octopus type of beings or underwater type of beans.

So, like, if there is life out there, maybe it would have to be sort of like octopus people or octopus type of beings or underwater type of beans.

They sound nice.

They sound nice.

Yeah, all right, Well I think that answers all of your questions. Randall.

Yeah, all right, Well I think that answers all of your questions. Randall.

Hey, thanks so much to you and all the experts for answering these questions. That was so much more than I could have imagined. I feel like whenever I ask scientists things, I always think like, oh, this question is too silly for them to want to spend time on. And then it's always so cool to see how excited they are to talk about the thing. Yeah, space is too big to fit in the inside our heads. It's really cool.

Hey, thanks so much to you and all the experts for answering these questions. That was so much more than I could have imagined. I feel like whenever I ask scientists things, I always think like, oh, this question is too silly for them to want to spend time on. And then it's always so cool to see how excited they are to talk about the thing. Yeah, space is too big to fit in the inside our heads. It's really cool.

Yeah all right.

Yeah all right.

So to recap, the center of the galaxy is definitely the worst place to live in the galaxy. If you manage to avoid something crashing into your planet, another star might steal or kick your planet off its orbit, or maybe the gravity of the super massive black hole at the will cause you to crash into your star, or movie stars getting ripped apart by the black hole or stars exploding near you might fry you. It would be extremely chaotic, but there could still be life near the center, maybe a few light years away, in underground oceans, in icy planets, around angry red dwarf stars. So if you're thinking of moving there, just remember to bearing a scuba suit and some toe warmers. Or maybe we should just stay where we are and be glad live in a peaceful neighborhood in the Milky Way Galaxy. Thanks for joining us, see you next time, and thanks to Randall Monroe and Professor and Marie Madigan for being on the show. Check out Randall's work at xkcd dot com. You've been listening to Science Stuff production of iHeartRadio, written and produced by me or Cham, edited by Rose Seguda, executive producer Jerry Rowland, and audio engineer and mixer Ksey Peckrom And you can follow me on social media. Just search for PhD Comics and the name of your favorite platform. Be sure to subscribe to Sign Stuff on the iHeartRadio app, Apple Podcasts, or wherever you get your podcasts. Please tell your friends we'll be back next Wednesday with another episode.

So to recap, the center of the galaxy is definitely the worst place to live in the galaxy. If you manage to avoid something crashing into your planet, another star might steal or kick your planet off its orbit, or maybe the gravity of the super massive black hole at the will cause you to crash into your star, or movie stars getting ripped apart by the black hole or stars exploding near you might fry you. It would be extremely chaotic, but there could still be life near the center, maybe a few light years away, in underground oceans, in icy planets, around angry red dwarf stars. So if you're thinking of moving there, just remember to bearing a scuba suit and some toe warmers. Or maybe we should just stay where we are and be glad live in a peaceful neighborhood in the Milky Way Galaxy. Thanks for joining us, see you next time, and thanks to Randall Monroe and Professor and Marie Madigan for being on the show. Check out Randall's work at xkcd dot com. You've been listening to Science Stuff production of iHeartRadio, written and produced by me or Cham, edited by Rose Seguda, executive producer Jerry Rowland, and audio engineer and mixer Ksey Peckrom And you can follow me on social media. Just search for PhD Comics and the name of your favorite platform. Be sure to subscribe to Sign Stuff on the iHeartRadio app, Apple Podcasts, or wherever you get your podcasts. Please tell your friends we'll be back next Wednesday with another episode.