WEBVTT - What happens when stars collide? 0:00:08.480 --> 0:00:13.440 Hail. Hey, have you ever seen two stars collide? Well, 0:00:13.560 --> 0:00:16.880 I live near Hollywood, so it does happen sometimes. What 0:00:16.920 --> 0:00:19.720 do you mean, you know, like Brad Pitt and Angelina Julie, 0:00:19.720 --> 0:00:22.760 they're like binary star system. I get it. And when 0:00:22.800 --> 0:00:26.360 they collided, it sent out paparazzi waves or something. Yeah, 0:00:26.360 --> 0:00:29.160 it sends out ripples in the fabric of the entertainment 0:00:29.200 --> 0:00:33.479 space time. Well, I hope that's somewhere. Alien physicists have 0:00:33.520 --> 0:00:36.000 built a device to measure those ripples and are wondering 0:00:36.320 --> 0:00:40.199 what it is they're looking at. Probably two attractive human beings, hope, 0:00:40.200 --> 0:00:57.360 only they're not thinking how delicious they look. Ye Hi 0:00:57.440 --> 0:01:00.520 am Or Hammock cartoonists and the creator of pH D comment, Hi, 0:01:00.600 --> 0:01:03.160 I'm Daniel. I'm a particle physicist, and I live in 0:01:03.200 --> 0:01:07.039 southern California. But I've never accidentally bumped into a celebrity. 0:01:07.720 --> 0:01:10.360 How about on purpose? Have you bumped into one on purpose? No? 0:01:10.480 --> 0:01:13.360 Their bodyguards keep me away. It's so frustrating. Really, you 0:01:13.400 --> 0:01:15.920 live down here and you've never had a celebrity sighting. 0:01:16.280 --> 0:01:18.559 I've seen them from afar, but always imagine I would 0:01:18.560 --> 0:01:21.120 bump into one at the grocery store or something m 0:01:21.560 --> 0:01:23.360 I see. Well, sort of you're sort of becoming a 0:01:23.400 --> 0:01:26.200 star yourself, Daniel, And at least in the Physics Podcast 0:01:26.280 --> 0:01:29.040 universe whatever, I can walk around you see Irvine and 0:01:29.040 --> 0:01:31.959 people think I'm just some homeless person or a professor, 0:01:31.959 --> 0:01:34.920 one of those you need to confuse sometimes. How would 0:01:34.959 --> 0:01:36.920 you have you had any good celebrity sightings and all 0:01:37.000 --> 0:01:40.479 your years in Hollywood? Sure? Yeah, yeah, I've I've had severally. Yeah, 0:01:40.840 --> 0:01:43.360 sometimes you or you can't get away from them sometimes. 0:01:44.200 --> 0:01:46.480 But welcome to a podcast. Daniel and Jorge explain the 0:01:46.560 --> 0:01:49.600 university production of I Heart Radio, in which we collide 0:01:49.600 --> 0:01:53.400 your brain and the universe. We take all the incredible, 0:01:53.480 --> 0:01:56.280 all the amazing, all the bonkers, all the wild stuff 0:01:56.280 --> 0:01:58.840 that's out there, and we squish it all into your 0:01:58.880 --> 0:02:02.400 head because we think that the entire universe should be 0:02:02.520 --> 0:02:06.480 understandable and should be explainable to everyone. Yeah, because it 0:02:06.800 --> 0:02:09.160 is sort of a wild universe. It's a lot happening 0:02:09.240 --> 0:02:12.960 in it. There's obviously stars burning bright out there, and 0:02:13.080 --> 0:02:16.760 planets orbiting them and asteroids flying around. But sometimes we 0:02:16.840 --> 0:02:21.040 get some pretty interesting events happening. That's right, while you 0:02:21.080 --> 0:02:23.120 look out into the sky and it seems sort of 0:02:23.160 --> 0:02:25.520 like static. It seems like, hey, it's just sort of 0:02:25.560 --> 0:02:28.400 hanging out, it's not really doing anything. If you watch 0:02:28.480 --> 0:02:32.000 the universe in fast forward, it would seem like a crazy, 0:02:32.120 --> 0:02:35.120 chaotic place. It would seem like a drink that somebody 0:02:35.200 --> 0:02:37.400 is shaking really really fast. It would seem like the 0:02:37.440 --> 0:02:40.160 mosh pit at a crazy concert. What's the music that 0:02:40.200 --> 0:02:43.280 the universe is dancing to? Is it like punk rock 0:02:43.360 --> 0:02:46.800 but it's super slow motion? Exactly? The universe is a 0:02:46.840 --> 0:02:50.000 super slow mo punk rock concert. But it is interesting 0:02:50.040 --> 0:02:51.880 to think about all the things that could be happening 0:02:51.880 --> 0:02:54.600 out there, and all of the near misses and all 0:02:54.639 --> 0:02:56.560 of the things sort of flying by each other, and 0:02:56.639 --> 0:03:00.160 sometimes things sort of inevitably collide out there in the 0:03:00.240 --> 0:03:03.160 universe because there's a lot of space out there in space, 0:03:03.400 --> 0:03:06.840 but also a big universe, So eventually everything's going to 0:03:06.880 --> 0:03:09.480 happen at some point exactly. And we're not unfamiliar with 0:03:09.520 --> 0:03:12.560 the idea of collisions. After all, we know that sometimes 0:03:12.680 --> 0:03:15.960 asteroids hit planets, right. We see craters all over the 0:03:16.000 --> 0:03:18.960 surfaces of everything in the Solar System. We even see 0:03:19.000 --> 0:03:22.040 comets smashing the planets, like Shoemaker Levy did a few 0:03:22.040 --> 0:03:25.399 decades ago. But what about bigger collisions? Is it possible 0:03:25.440 --> 0:03:28.640 for even larger things to smash into each other? Yeah? 0:03:28.720 --> 0:03:31.360 Isn't the prevailing theory about our moon is that it 0:03:31.440 --> 0:03:34.720 came from a big collision of the Earth with an asteroid, Right, 0:03:34.760 --> 0:03:37.520 That's how the moon was born. Yeah, maybe not even 0:03:37.560 --> 0:03:41.680 an asteroid. Maybe two proto planets collided merged in the 0:03:41.680 --> 0:03:44.200 Earth on the Moon are like weird mixtures of those 0:03:44.240 --> 0:03:48.720 two planets. It's an awesome titanic collision. Yeah, but you're 0:03:48.720 --> 0:03:53.160 thinking even bigger than planets or proto planets colliding. You're 0:03:53.160 --> 0:03:57.480 thinking maybe stars colliding. That's right, Why not always think bigger? Right? 0:03:57.760 --> 0:03:59.800 These collisions are boring. Now when we go to the 0:03:59.800 --> 0:04:02.080 next level, it's like fast and furious. They gotta get 0:04:02.120 --> 0:04:05.840 even crazier. Yeah, what happens when vin diesel collides with 0:04:05.920 --> 0:04:09.960 the rock. Everyone knows about that. Exactly what happens is 0:04:09.960 --> 0:04:12.680 they each get their own movie franchise because they handworked. 0:04:13.040 --> 0:04:16.640 That's the only way that it can go on. So yeah, 0:04:16.640 --> 0:04:18.800 so that was an elastic collision because they both seem 0:04:18.839 --> 0:04:21.479 to have survived it with their careers intact. But is 0:04:21.520 --> 0:04:24.960 it always so clean? What happens when bigger things smash 0:04:25.000 --> 0:04:27.440 into each other. Does that ever happen? Has it happened 0:04:27.440 --> 0:04:29.560 to our son? These are the kind of questions that 0:04:29.720 --> 0:04:32.080 keep me up at night. Yeah, so today we'll be 0:04:32.120 --> 0:04:35.320 looking into some stellar events, and in particular, we'll be 0:04:35.360 --> 0:04:44.400 asking the question what happens when stars collide? And are 0:04:44.440 --> 0:04:50.120 their children as good looking as they are? Usually? Not? Right? Oh, 0:04:50.200 --> 0:04:53.560 are you throwing shade on the children of stars right now? 0:04:53.600 --> 0:04:56.320 Showley Jolie or whatever her name is. I thought you 0:04:56.320 --> 0:05:00.599 were still talking about stars, like real stars. Put it 0:05:00.640 --> 0:05:04.600 on me, like stellar objects. I think all stellar objects 0:05:04.600 --> 0:05:09.000 are beautiful, even the ones that might inevitably come for us. 0:05:09.240 --> 0:05:11.400 But yeah, it is pretty interesting. I guess that there 0:05:11.400 --> 0:05:13.400 are so many stars out there in the galaxy and 0:05:13.440 --> 0:05:16.280 the universe that eventually some of them might run into 0:05:16.279 --> 0:05:18.440 each other, right, they might crash into each other. It 0:05:18.440 --> 0:05:20.440 turns out to be quite interesting. In some parts of 0:05:20.440 --> 0:05:23.880 the universe, stellar collisions are quite common, and in other 0:05:23.920 --> 0:05:26.800 places they're very rare. So, as usually, we were wondering 0:05:26.839 --> 0:05:30.000 how many people out there had thought about these stellar collisions, 0:05:30.000 --> 0:05:33.280 these stars colliding, and what would happened, And so Daniel 0:05:33.279 --> 0:05:35.719 went out there to ask people on the Internet. What 0:05:35.880 --> 0:05:39.080 do you think happens when stars collide? That's right and 0:05:39.120 --> 0:05:42.560 as usual. I'm grateful to our Internet volunteers for answering 0:05:42.640 --> 0:05:45.280 random physics questions. If it sounds fun to you to 0:05:45.360 --> 0:05:48.320 get four random physics questions and your inbox that you 0:05:48.360 --> 0:05:51.520 have to answer without any preparation, please just write us 0:05:51.520 --> 0:05:54.600 an email two questions at Daniel and Jorge dot com. 0:05:54.760 --> 0:05:56.360 So think about it for a second. What do you think? 0:05:56.400 --> 0:05:58.240 What do you see in your head when you imagine 0:05:58.279 --> 0:06:02.000 two stars colliding. Here's what people have to say, Well, 0:06:02.040 --> 0:06:08.880 I don't think they usually collide because um having this 0:06:09.200 --> 0:06:13.920 um fusion inside them and all the energy coming out 0:06:14.000 --> 0:06:20.800 of the sun. I think actually it's not usually for 0:06:20.960 --> 0:06:26.040 the stars to collide. Yes, and very often, because there's 0:06:26.080 --> 0:06:28.960 so many stars out in the universe. It seems like 0:06:29.000 --> 0:06:32.880 a trick question, like everyone would say, yeah, they collide, 0:06:32.960 --> 0:06:36.039 that's how they form mergers and stuff. But it's probably 0:06:36.720 --> 0:06:40.920 really unlikely that two stars would hit each other smack 0:06:41.000 --> 0:06:44.760 on on the first pass. They would pass close to 0:06:44.800 --> 0:06:49.479 each other and lock into orbit around each other. Maybe 0:06:49.480 --> 0:06:51.599 once they're locked in orbit around each other, either that's 0:06:51.600 --> 0:06:55.000 stable or one of them is way bigger and it 0:06:55.240 --> 0:06:57.680 sucks the matter out of the other one. Well, I 0:06:57.839 --> 0:07:01.200 definitely think they do. And some terms, whole galaxies can 0:07:01.240 --> 0:07:06.440 actually collide post each other's past and just became one. Um. 0:07:06.480 --> 0:07:08.599 I could imagine that it would probably happen with a 0:07:08.680 --> 0:07:11.680 huge explosion or just I don't know, depending on their 0:07:11.760 --> 0:07:15.440 mass and like what gases are burning in them. And 0:07:15.560 --> 0:07:18.400 for example, if there's like a Jewel star star system 0:07:18.680 --> 0:07:21.200 and they just don't know, like really close to each 0:07:21.240 --> 0:07:24.720 other and orbiting each other or just being really close 0:07:24.760 --> 0:07:27.720 to each other, they can also exchange matter maybe just 0:07:27.800 --> 0:07:30.960 get closer and closer to each other by gravitational pool 0:07:31.040 --> 0:07:33.480 and at one point they can just get so close 0:07:33.560 --> 0:07:37.600 that they actually collide. They do. They circle around one 0:07:37.640 --> 0:07:41.320 another and then eventually collide into one another or fall 0:07:41.400 --> 0:07:43.800 into one another. I think yes and no. I think 0:07:43.800 --> 0:07:45.720 it is possible for things to crash into each other. 0:07:45.760 --> 0:07:48.600 Things with master fall into each other, just like how 0:07:48.640 --> 0:07:51.840 they discover gravity waves too, black holes crash into each other. 0:07:52.320 --> 0:07:55.320 But also I think space is very spacey and for 0:07:55.520 --> 0:07:57.560 things to death spiral into each other has to be 0:07:57.640 --> 0:08:02.120 special uh circumstances. Because I think when objects roach each 0:08:02.160 --> 0:08:04.440 other around each other, like say stars are rotating around 0:08:04.440 --> 0:08:06.960 each other. I think they it's possible to have stable orbits, 0:08:06.960 --> 0:08:10.560 so there has to be some special math where if 0:08:10.600 --> 0:08:14.040 they fall over a certain criteria, then then yes, objects 0:08:14.080 --> 0:08:16.920 in space like stars with mass will crash into each other. 0:08:17.480 --> 0:08:22.240 I would say, very very rarely nowadays. Maybe it was 0:08:22.480 --> 0:08:26.440 more common in the very early universe when the what 0:08:26.600 --> 0:08:30.040 is it third generation of stars was firstborn. Maybe those 0:08:30.080 --> 0:08:33.720 collided from time to time, but nowadays it's very rare. 0:08:34.080 --> 0:08:37.679 All right. I'm seeing where it's like huge explosion crashes. 0:08:38.880 --> 0:08:42.280 Some pretty exciting times here, also some very technical answers, 0:08:42.320 --> 0:08:45.200 like space is very spacey. It's a good point. It 0:08:45.280 --> 0:08:48.080 is pretty spacey. There's it's a roomy too. There's a 0:08:48.080 --> 0:08:50.520 lot of room in the space of rooms. That's right. 0:08:50.559 --> 0:08:54.480 It's very minimally appointed in the universe. It's not overcrowded. Yeah. Well, 0:08:54.480 --> 0:08:56.320 I like the person who thought it was a trick question, 0:08:56.400 --> 0:09:00.679 like maybe stars never collided, but is that possible? Maybe 0:09:00.720 --> 0:09:04.160 they just bump into each other at the supermarket by 0:09:04.320 --> 0:09:07.120 quote accident unquote. Hey, I was reaching for that box 0:09:07.120 --> 0:09:09.320 of cookies exactly, and up in a tug of war 0:09:09.400 --> 0:09:11.320 with Brad Pitt over a box of cookies. That's my 0:09:11.360 --> 0:09:14.040 Southern California dream. There you go. I'm guessing Brad Pitt 0:09:14.160 --> 0:09:18.720 will will win no offense. He's pretty strong. But yeah, 0:09:18.760 --> 0:09:21.320 it seems like some people didn't think they would actually collide, 0:09:21.320 --> 0:09:24.000 and some people thought that it happens, I mean, binary 0:09:24.040 --> 0:09:26.880 star systems. There's a wide range of answers here, and 0:09:26.920 --> 0:09:29.280 that maybe this is an interesting one. People thought that 0:09:29.400 --> 0:09:33.080 maybe it happens more often in the early universe than 0:09:33.120 --> 0:09:36.080 in the older universe. Yeah, really fascinating stuff. I like 0:09:36.160 --> 0:09:38.240 the people are using their physics brains to think about 0:09:38.320 --> 0:09:41.080 what would make this happen. Yeah, because I guess in 0:09:41.160 --> 0:09:44.120 the early universe things were more crowded, right, technically, Well, 0:09:44.160 --> 0:09:46.160 we'll get into it. It's quite interesting. You know, in 0:09:46.200 --> 0:09:48.840 the early universe the stars had just formed and so 0:09:48.960 --> 0:09:52.360 galaxies hadn't formed yet, so in some sense, things were 0:09:52.440 --> 0:09:55.240 less dense. All right, well, let's jump into it, Daniel. 0:09:55.559 --> 0:09:59.240 What happens when stars collide? How common are these star collisions? 0:09:59.280 --> 0:10:02.720 It depends on lot on where you are, because star 0:10:02.880 --> 0:10:05.960 densities vary a lot from place to place. Like in 0:10:06.000 --> 0:10:09.000 the center of the galaxy, things are much denser. The 0:10:09.120 --> 0:10:13.320 distances between stars are much smaller than they are out 0:10:13.360 --> 0:10:16.160 here where we are where like twenty thousand light years 0:10:16.200 --> 0:10:18.280 from the center of the galaxy, sort of like out 0:10:18.320 --> 0:10:21.200 in the suburbs. Out here, there's like three or four 0:10:21.360 --> 0:10:24.920 light years between stars, and so it's much less likely 0:10:25.200 --> 0:10:28.280 for stars to collide. Like the closest star to us 0:10:28.400 --> 0:10:32.200 is Proximus Centauri, just under four light years away. In 0:10:32.320 --> 0:10:35.240 terms of the width of our Sun, that's like one 0:10:35.360 --> 0:10:38.600 hundred million sun width. Like if you try to fill 0:10:38.679 --> 0:10:40.680 up the space between our Sun and the next star, 0:10:40.920 --> 0:10:43.520 you'd have to stack it with a hundred million copies 0:10:43.640 --> 0:10:45.600 of our Sun. That gives you a sense for like 0:10:45.679 --> 0:10:49.079 how far apart stars are in our neighborhood. M M, 0:10:49.360 --> 0:10:51.560 that's interesting. What about closer to the center of the 0:10:51.559 --> 0:10:54.679 galaxy or stars more crunched together, Like what are the 0:10:54.760 --> 0:10:57.480 relative distances there? So in the center of the galaxy 0:10:57.480 --> 0:10:59.959 it can get much much denser in the stars average 0:11:00.080 --> 0:11:02.480 less than a light year apart, but it grows very 0:11:02.600 --> 0:11:05.440 very quickly as you get closer to that black hole, 0:11:05.559 --> 0:11:07.760 things get very very dense. And it's not just the 0:11:07.760 --> 0:11:10.560 center of the galaxy where things are denser. Our galaxy 0:11:10.600 --> 0:11:14.520 has these things called globular clusters, which are collections of 0:11:14.600 --> 0:11:17.360 stars we think formed all at the same time or 0:11:17.559 --> 0:11:20.560 might even be like many dwarf for galaxies that got 0:11:20.600 --> 0:11:23.360 eaten by the Milky Way. But these are much much 0:11:23.400 --> 0:11:25.920 denser than the rest of the galaxy. So you're saying 0:11:25.960 --> 0:11:28.520 that even in the outer parts of the galaxy there 0:11:28.600 --> 0:11:31.160 might be sort of like dense clusters where there could 0:11:31.160 --> 0:11:33.680 be a lot of stars running into each other. Yeah, 0:11:33.679 --> 0:11:36.480 these globular clusters, they're fascinating. We did a whole podcast 0:11:36.480 --> 0:11:39.000 episode about them last year. Some of them are sort 0:11:39.040 --> 0:11:41.200 of embedded in the Milky Way, and some of them 0:11:41.200 --> 0:11:43.920 are sort of like in close orbit around the Milky Way, 0:11:43.920 --> 0:11:46.000 but people consider it all to be part of the 0:11:46.040 --> 0:11:48.719 Milky Way. So in the center of the galaxy and 0:11:48.840 --> 0:11:53.040 in globular clusters, there are better conditions for having collisions. 0:11:53.040 --> 0:11:55.440 Like out here where we are, for the Sun to 0:11:55.520 --> 0:11:59.040 get into a collision is very very unlikely. Somebody actually 0:11:59.120 --> 0:12:02.120 did a calculation and they estimate that the Sun should 0:12:02.120 --> 0:12:06.559 collide with another star every ten to the twenty eight years. 0:12:07.040 --> 0:12:09.240 Like that's a hard number to think about. Just remember 0:12:09.280 --> 0:12:12.600 that the universe is ten to the ten years old, 0:12:12.800 --> 0:12:14.960 so it would take a lot lot longer than the 0:12:15.000 --> 0:12:17.640 age of the universe, so far before we expect the 0:12:17.720 --> 0:12:21.320 Sun to collide with anything interesting, So it seems like 0:12:21.480 --> 0:12:23.840 pretty unlikely, although I wonder if it's like, you know, 0:12:24.120 --> 0:12:25.800 like in in the center of a downtown, there's a 0:12:25.840 --> 0:12:28.760 lot more traffic, but people are going slower maybe, but 0:12:28.880 --> 0:12:31.480 out in the submers where you have these empty highways 0:12:31.520 --> 0:12:33.640 that maybe people are going faster, And so wonder of 0:12:33.720 --> 0:12:36.800 that increases the likelihood of a crash. Things are actually 0:12:36.800 --> 0:12:39.520 moving really rapidly in the center of the galaxy because 0:12:39.559 --> 0:12:42.280 things are closer to the source of gravity. Right, there's 0:12:42.280 --> 0:12:44.920 a huge black hole there, and when a star, for example, 0:12:45.000 --> 0:12:47.200 swings around the back of that black hole, it picks 0:12:47.280 --> 0:12:49.560 up a lot of speed. These stars can get up 0:12:49.559 --> 0:12:51.480 to like half of the speed of light when the 0:12:51.520 --> 0:12:53.840 whizz around the back of that black hole. So things 0:12:53.840 --> 0:12:56.520 are moving pretty rapidly in the center of the galaxy. 0:12:56.679 --> 0:12:59.880 They estimate that in globular clusters there's a stellar coll 0:13:00.040 --> 0:13:03.719 vision every ten thousand years. Well it's a lot, right, 0:13:03.920 --> 0:13:06.040 I mean, in terms of the age of the universe, 0:13:06.120 --> 0:13:08.760 that's like crash every other day. That's a lot of 0:13:08.800 --> 0:13:12.680 collisions exactly. And if you estimate how many globular clusters 0:13:12.720 --> 0:13:15.400 there are in all of the galaxies out there. The 0:13:15.480 --> 0:13:18.200 current estimate is about a trillion or so, you know, 0:13:18.440 --> 0:13:20.400 give or take to a factor of ten. But if 0:13:20.400 --> 0:13:23.200 you assume that there are a trillion globular clusters in 0:13:23.240 --> 0:13:26.360 the observable universe, then that estimate tells you that there 0:13:26.400 --> 0:13:30.320 are a thousand pairs of stars colliding at every moment, 0:13:30.559 --> 0:13:33.880 Like right now, a thousand stars are colliding with a 0:13:33.920 --> 0:13:38.160 thousand other stars. Wow, that's amazing to think about, for sure. Yeah, 0:13:38.480 --> 0:13:41.880 like right now, boom or a thousand booms stars colliding 0:13:43.400 --> 0:13:46.319 a thousand booms exactly. And these are not stars that 0:13:46.360 --> 0:13:49.640 are colliding like in neighborhoods similar to our son. These 0:13:49.640 --> 0:13:51.679 are stars colliding in the center of the galaxy or 0:13:51.720 --> 0:13:55.240 again in these globular clusters that these pockets of density 0:13:55.360 --> 0:13:58.199 elsewhere in the galaxy. But we're not near any one 0:13:58.200 --> 0:14:00.400 of these globular clusters, right, I mean, we have them 0:14:00.400 --> 0:14:02.480 in the Milky Way, but are we near one. We 0:14:02.520 --> 0:14:05.440 aren't near any globular clusters, not near enough to be 0:14:05.520 --> 0:14:08.040 worried about it or like to be sucked in or anything. 0:14:08.320 --> 0:14:11.080 So these collisions are happening in other places, But globular 0:14:11.080 --> 0:14:14.440 clusters are really fascinating scientifically and help us probe really 0:14:14.440 --> 0:14:17.600 interesting questions about the formations of stars. And there's still 0:14:17.640 --> 0:14:21.320 a lot of things that we don't understand about globular clusters. Yeah, 0:14:21.360 --> 0:14:24.120 they're sort of almost sort of where people call them 0:14:24.160 --> 0:14:26.080 like the cradle of stars, right like sort of, or 0:14:26.240 --> 0:14:28.640 nursery star nurseries they call them, right, Yeah, And these 0:14:28.680 --> 0:14:31.160 things are typically really really old, like they think they 0:14:31.240 --> 0:14:34.720 might mostly be population two stars. So these things were 0:14:34.720 --> 0:14:37.680 formed billions and billions of years ago in the second 0:14:37.720 --> 0:14:40.520 generation of stars, after the first ones blew up, the 0:14:40.560 --> 0:14:43.800 second generation formed, and these sort of low metalisity. They 0:14:43.800 --> 0:14:46.480 don't have as many heavy elements in them as our 0:14:46.560 --> 0:14:50.200 stars do because the universe hadn't made as much heavy metals, 0:14:50.440 --> 0:14:52.360 but they were all born about the same time. And 0:14:52.400 --> 0:14:54.760 so when you look at the globular cluster, you're seeing 0:14:54.760 --> 0:14:57.760 a lot of really old stars, or at least we thought. 0:14:58.280 --> 0:15:00.960 And they found a bunch of stars inside these globular 0:15:01.000 --> 0:15:04.400 clusters that look sort of unusually young, like they're really 0:15:04.440 --> 0:15:08.040 really blue stars, which means that glow really really brightly 0:15:08.440 --> 0:15:11.320 and really bright glowing stars tend to not live very long, 0:15:11.360 --> 0:15:13.760 they like burn out really fast. So there are these 0:15:13.760 --> 0:15:16.840 stars in these globular clusters that look really blue, look 0:15:16.880 --> 0:15:19.200 really young when the rest of the globular cluster is 0:15:19.240 --> 0:15:21.760 really old. So they imagine that what might be happening 0:15:21.840 --> 0:15:23.480 is that you could be getting like a bunch of 0:15:23.480 --> 0:15:26.040 stars that collide. They're like on their way at the 0:15:26.160 --> 0:15:27.840 end of their life, and then they collide to form 0:15:27.880 --> 0:15:30.880 a new huge star which then burns brightly. So these 0:15:30.880 --> 0:15:34.400 are called blue stragglers. They are currently a mystery in astronomy, 0:15:34.400 --> 0:15:37.840 but that's one possible explanation for them. Interesting. So they're 0:15:37.880 --> 0:15:40.640 old and so maybe they're not as heavy metals, so 0:15:40.640 --> 0:15:44.080 maybe they're listening to music under parties. It's sort of 0:15:44.120 --> 0:15:46.520 like two stars at the end of their career decide, hey, 0:15:46.680 --> 0:15:49.720 let's have kids and they can carry on burning brightly 0:15:49.760 --> 0:15:52.400 and earning money to support us in retirement. So that's 0:15:52.440 --> 0:15:55.240 sort of our chances of running into another star or 0:15:55.640 --> 0:15:58.440 star colliining nero us doesn't seem very likely. But let's 0:15:58.440 --> 0:16:00.920 talk about maybe what would happen if our star did 0:16:00.960 --> 0:16:03.600 collide with another star, or generally what happens when stars 0:16:03.640 --> 0:16:06.360 collide with each other. Yeah, it can be pretty dramatic, 0:16:06.360 --> 0:16:09.680 But it also depends on exactly how fast the collision 0:16:09.720 --> 0:16:12.920 happens and whether there's actually a collision or just sort 0:16:12.920 --> 0:16:15.160 of a near miss. You might feel a little bit 0:16:15.160 --> 0:16:17.120 relieved to think, well, our son is not going to 0:16:17.200 --> 0:16:19.360 hit any other stars for another you know, ten to 0:16:19.400 --> 0:16:22.840 the eighteen years, so I can relax. But our Solar 0:16:22.880 --> 0:16:26.040 system might be seriously impacted. Even if just another star 0:16:26.160 --> 0:16:29.040 comes somewhere near us. You could have a real impact 0:16:29.080 --> 0:16:31.280 on our lives. Right, Like, they don't have to actually 0:16:31.320 --> 0:16:33.880 touch each other for there to be a disaster, right yeah, 0:16:33.920 --> 0:16:37.160 because those stars are huge sources of gravity and they're 0:16:37.200 --> 0:16:39.800 already sort of tugging on each other a little bit. 0:16:40.080 --> 0:16:42.760 Remember that our Solar system doesn't just have a star 0:16:42.840 --> 0:16:45.560 and a bunch of planets. It's surrounded by this vast 0:16:45.720 --> 0:16:49.160 cloud of trillions of icy objects. We call this the 0:16:49.320 --> 0:16:51.800 ort cloud, and we think that's where comments come from. 0:16:51.880 --> 0:16:54.720 And so if another star passes anywhere near our Solar system, 0:16:54.760 --> 0:16:56.880 it can perturb some of those and then they can 0:16:57.000 --> 0:17:00.240 fall into the gravitational well of our Solar system, picking 0:17:00.280 --> 0:17:02.840 up a huge amount of speed and energy as they 0:17:02.880 --> 0:17:06.119 fall in zooming down through the inner Solar System and 0:17:06.200 --> 0:17:08.600 right past the planets, and these comments, if they hit 0:17:08.640 --> 0:17:11.880 the Earth, for example, they could wipe out humanity. It's 0:17:11.880 --> 0:17:14.639 an incredible source of energy in a real danger. So 0:17:14.680 --> 0:17:17.720 if a star comes nearby, they could disturb one of those, 0:17:17.760 --> 0:17:19.720 and if they come even closer, they could even like 0:17:19.880 --> 0:17:22.879 toss a planet out of the Solar system. Wow, you 0:17:22.920 --> 0:17:25.880 could get booted off the island or the Solar system. Yeah, 0:17:25.880 --> 0:17:28.679 because our orbits are fairly fragile. We have to be 0:17:28.720 --> 0:17:31.840 going in the right direction, at the right velocity and 0:17:31.960 --> 0:17:35.439 at the right radius for everything to balance. So orbits 0:17:35.480 --> 0:17:37.639 are not that hard to perturb and they're sort of 0:17:37.720 --> 0:17:40.360 hard to recover. And so you're saying that even if 0:17:40.480 --> 0:17:43.879 our star doesn't collide with another star, just having a 0:17:43.920 --> 0:17:46.960 near miss could be potentially fatal to us. It could 0:17:47.000 --> 0:17:49.479 be fatally Earth could get tossed out of our Solar 0:17:49.480 --> 0:17:52.520 system into the galaxy itself without a star, or we 0:17:52.520 --> 0:17:55.440 could get hit by a comment that gets perturbed by 0:17:55.440 --> 0:17:58.320 a passing star. So how close do we need to 0:17:58.440 --> 0:18:01.720 come to another star for it to be sort of dangerous? 0:18:01.800 --> 0:18:03.639 In order for the Earth to get like tossed out 0:18:03.680 --> 0:18:05.800 of orbit, the star would need to come sort of 0:18:05.960 --> 0:18:08.480 within a few au of our star in order to 0:18:08.560 --> 0:18:11.000 have like the gravity to really perturb the orbit, in 0:18:11.080 --> 0:18:14.040 order to perturb the Org cloud. Well, we don't really know. 0:18:14.119 --> 0:18:16.879 And there's actually a lot of really interesting theories that 0:18:16.960 --> 0:18:19.400 suggests that there might be another star out there. It's 0:18:19.400 --> 0:18:23.000 called the Nemesis that every like thirty million years swoops 0:18:23.040 --> 0:18:26.440 around near our Sun and perturbs all those objects in 0:18:26.480 --> 0:18:29.359 the Org cloud and rains down comments on us. People 0:18:29.359 --> 0:18:32.760 look back at the history of commentary impacts on Earth 0:18:33.000 --> 0:18:35.000 and they think they might see like a pattern, like 0:18:35.040 --> 0:18:38.160 a thirty million years cycle, and that suggests there could 0:18:38.200 --> 0:18:41.200 be something out there doing this regularly every thirty million years. 0:18:41.320 --> 0:18:43.120 Maybe that's how we got our water. It was one 0:18:43.160 --> 0:18:46.120 of these commage howers, right, Yeah, it could be exactly 0:18:46.119 --> 0:18:48.560 a lot of the water on Earth came from comets, 0:18:48.640 --> 0:18:51.639 and so maybe you know, fed us, nurtured us, and 0:18:51.640 --> 0:18:54.040 then it's going to come back and kill us. Well, 0:18:54.040 --> 0:18:56.680 we just have to get umbrellas to fend off all 0:18:56.680 --> 0:19:01.080 that water rain and down giant ice block. So you're saying, 0:19:01.119 --> 0:19:03.040 if another star comes within a few a U s, 0:19:03.080 --> 0:19:05.920 and a U is sort of the distance between the 0:19:05.960 --> 0:19:08.440 Sun and the Earth, right, So if it comes within 0:19:08.480 --> 0:19:10.719 a few distances of Earth and the Sun, then it 0:19:10.720 --> 0:19:13.800 could be big trouble. But if it comes far away, 0:19:13.840 --> 0:19:17.320 it could still cause some trouble by raining comments on us. Yeah, 0:19:17.320 --> 0:19:19.359 anything less than like a light year or so, it 0:19:19.359 --> 0:19:22.199 could be serious problems. What about a direct hit? What 0:19:22.200 --> 0:19:24.560 would happen when two stars sort of directly hit each other, 0:19:24.880 --> 0:19:27.879 So this is much more exciting. If another star comes 0:19:27.920 --> 0:19:30.919 in sort of at high speed, then basically what's going 0:19:30.960 --> 0:19:33.479 to happen is the Sun would be destroyed. If you imagine, 0:19:33.520 --> 0:19:36.600 for example, like a white dwarf, which is a solar remnant, 0:19:36.640 --> 0:19:39.359 like a big hot chunk of metal, and it plows 0:19:39.440 --> 0:19:42.360 into the Sun, and people actually have done simulations about this, 0:19:42.520 --> 0:19:45.240 it would trigger the whole Sun to start burning. Currently, 0:19:45.280 --> 0:19:47.560 fusion is happening, but mostly at the heart of the Sun. 0:19:47.760 --> 0:19:50.159 If a white dwarf comes in, it would increase the 0:19:50.160 --> 0:19:52.919 pressure and the temperature of the Sun so dramatically that 0:19:53.000 --> 0:19:55.560 it would release as much energy through fusion in an 0:19:55.600 --> 0:19:59.280 hour as it would have otherwise in a hundred million years. 0:20:00.200 --> 0:20:02.240 You mean, like just from the impact. It would sort 0:20:02.240 --> 0:20:05.320 of as it's impacting or crashing into the Sun, it 0:20:05.320 --> 0:20:09.159 would actually cause fusion on its way in exactly, it 0:20:09.160 --> 0:20:11.680 would increase the temperature, and so the rate of fusion 0:20:11.880 --> 0:20:14.680 depends on the temperature. So basically the Sun would just 0:20:14.720 --> 0:20:17.560 like burn up super duper fast as this thing passes 0:20:17.560 --> 0:20:20.520 through it. But then it would also explode like that 0:20:20.600 --> 0:20:23.600 much fusion would blow the star out, and so a 0:20:23.720 --> 0:20:26.639 huge chunk of the Sun's energy would be burned up 0:20:26.840 --> 0:20:29.160 in this rapid fusion. A lot of it would get 0:20:29.160 --> 0:20:31.960 blown out because of the radiation from this fusion. And 0:20:32.000 --> 0:20:34.560 then also the Sun might lose its cohesion, like it 0:20:34.640 --> 0:20:37.080 might get sprayed out, like you know, an egg yolk 0:20:37.320 --> 0:20:41.280 or something against the wall sprayed out into the galaxy. Whoa, 0:20:42.000 --> 0:20:44.479 and there goes plans for an over easy solar system. 0:20:45.280 --> 0:20:47.000