1 00:00:00,000 --> 00:00:02,120 Welcome back to Cosmos in a Pod, Space, 2 00:00:02,120 --> 00:00:04,760 and Astronomy series, episode six. 3 00:00:04,760 --> 00:00:06,080 Episode six already. 4 00:00:06,080 --> 00:00:09,120 Time flies when you're having fun exploring the universe. 5 00:00:09,120 --> 00:00:10,360 Doesn't it though? 6 00:00:10,360 --> 00:00:12,840 Today we're taking a deep dive into something 7 00:00:13,800 --> 00:00:16,380 pretty spectacular, the life cycle of stars. 8 00:00:16,380 --> 00:00:19,660 It's a story of, well, cosmic proportions really. 9 00:00:19,660 --> 00:00:22,920 It is, from their birth in these vast nebulae. 10 00:00:22,920 --> 00:00:25,600 Some of their dramatic deaths, some of them at least. 11 00:00:25,600 --> 00:00:27,600 Yeah, you know, when you look up at the night sky, 12 00:00:27,600 --> 00:00:30,600 it's easy to think of stars as just these static points 13 00:00:30,600 --> 00:00:31,440 of light, but. 14 00:00:31,440 --> 00:00:33,200 But there's so much more going on. 15 00:00:33,200 --> 00:00:34,040 There is. 16 00:00:34,040 --> 00:00:37,480 Each one of those twinkling dots is a giant ball of plasma 17 00:00:37,480 --> 00:00:40,160 undergoing, well, incredible transformations 18 00:00:40,160 --> 00:00:43,040 over millions, billions, even trillions of years. 19 00:00:43,040 --> 00:00:44,080 So let's start at the beginning. 20 00:00:44,080 --> 00:00:44,920 Okay. 21 00:00:44,920 --> 00:00:46,320 Where do stars come from? 22 00:00:46,320 --> 00:00:48,040 I know they're born in these massive clouds 23 00:00:48,040 --> 00:00:50,520 of gas and dust called nebulae, 24 00:00:50,520 --> 00:00:52,240 but what's happening in those clouds 25 00:00:52,240 --> 00:00:54,400 to actually spark a star into existence? 26 00:00:54,400 --> 00:00:57,520 Well, imagine a nebula as this cosmic nursery. 27 00:00:57,520 --> 00:00:58,360 Okay. 28 00:00:58,360 --> 00:00:59,440 Filled with hydrogen and helium, 29 00:00:59,440 --> 00:01:01,600 along with trace amounts of heavier elements. 30 00:01:01,600 --> 00:01:03,320 It's all pretty spread out at first, 31 00:01:03,320 --> 00:01:05,120 but then gravity comes into play. 32 00:01:05,120 --> 00:01:07,640 Right, gravity, the ultimate sculptor of the cosmos. 33 00:01:07,640 --> 00:01:10,840 Exactly, gravity starts pulling these particles together, 34 00:01:10,840 --> 00:01:14,160 and as they get closer, the clouds' own gravity 35 00:01:14,160 --> 00:01:17,240 gets stronger, pulling in even more material. 36 00:01:17,240 --> 00:01:21,040 It's like a runaway train gathering momentum as it goes. 37 00:01:21,040 --> 00:01:22,760 And eventually all that gas and dust 38 00:01:22,760 --> 00:01:24,640 gets squeezed into a tight little ball. 39 00:01:24,640 --> 00:01:25,680 That's right. 40 00:01:25,680 --> 00:01:29,480 It forms a dense hot core called a protostar. 41 00:01:29,480 --> 00:01:31,640 Think of it as a star in the making. 42 00:01:31,640 --> 00:01:34,240 It's still gathering material and heating up. 43 00:01:34,240 --> 00:01:36,240 So at this point, it's not quite a star yet. 44 00:01:36,240 --> 00:01:37,080 Not yet. 45 00:01:37,080 --> 00:01:38,880 It's still growing, still evolving. 46 00:01:38,880 --> 00:01:42,120 As the protostar continues to pull in material, 47 00:01:42,120 --> 00:01:44,600 the pressure and temperature in its core, 48 00:01:44,600 --> 00:01:45,640 they just keep rising. 49 00:01:45,640 --> 00:01:46,880 So things are getting pretty intense 50 00:01:46,880 --> 00:01:47,720 down there in the core. 51 00:01:47,720 --> 00:01:49,800 Oh, incredibly intense. 52 00:01:49,800 --> 00:01:52,000 The temperature at the core of a protostar 53 00:01:52,000 --> 00:01:54,640 can reach millions of degrees Celsius. 54 00:01:54,640 --> 00:01:57,040 And eventually, something amazing happens. 55 00:01:57,040 --> 00:01:57,560 OK. 56 00:01:57,560 --> 00:01:59,280 When the core hits a critical temperature 57 00:01:59,280 --> 00:02:02,440 of about 10 million degrees Celsius, 58 00:02:02,440 --> 00:02:04,440 nuclear fusion ignites. 59 00:02:04,440 --> 00:02:06,680 Nuclear fusion, that's the real game changer, right? 60 00:02:06,680 --> 00:02:07,360 Absolutely. 61 00:02:07,360 --> 00:02:10,920 It's what separates a wannabe star from a true star. 62 00:02:10,920 --> 00:02:11,960 It is. 63 00:02:11,960 --> 00:02:15,520 Nuclear fusion is the powerhouse of a star. 64 00:02:15,520 --> 00:02:18,360 It's the process where hydrogen atoms fuse together 65 00:02:18,360 --> 00:02:21,560 to form helium, releasing an incredible amount of energy 66 00:02:21,560 --> 00:02:22,360 in the process. 67 00:02:22,360 --> 00:02:24,440 And that energy is what makes the star shine. 68 00:02:24,440 --> 00:02:25,360 Precisely. 69 00:02:25,360 --> 00:02:29,400 That energy radiates outward, creating the light and heat 70 00:02:29,400 --> 00:02:31,640 that we see and feel from stars. 71 00:02:31,640 --> 00:02:33,880 So it's like a giant nuclear reactor in space. 72 00:02:33,880 --> 00:02:35,400 That's a great way to put it. 73 00:02:35,400 --> 00:02:38,440 And this outward pressure from nuclear fusion, 74 00:02:38,440 --> 00:02:41,440 that's what counteracts the inward pull of gravity, 75 00:02:41,440 --> 00:02:44,600 creates a delicate balance that allows the star to exist. 76 00:02:44,600 --> 00:02:46,440 So it's like a cosmic tug of war. 77 00:02:46,440 --> 00:02:47,520 Exactly. 78 00:02:47,520 --> 00:02:49,400 And once that balance is achieved, 79 00:02:49,400 --> 00:02:52,680 the protostar officially becomes a main sequence star. 80 00:02:52,680 --> 00:02:54,560 Our sun is a main sequence star, right? 81 00:02:54,560 --> 00:02:55,040 That's right. 82 00:02:55,040 --> 00:02:58,040 Our sun is a pretty average star, about halfway 83 00:02:58,040 --> 00:02:59,840 through its main sequence lifespan. 84 00:02:59,840 --> 00:03:02,640 And how long does a star stay in this main sequence phase? 85 00:03:02,640 --> 00:03:04,320 Well, it depends on the star's mass. 86 00:03:04,320 --> 00:03:07,280 The bigger the star, the faster it burns through its fuel. 87 00:03:07,280 --> 00:03:08,120 So it's like a car. 88 00:03:08,120 --> 00:03:10,360 The bigger the engine, the more gas it guzzles. 89 00:03:10,360 --> 00:03:11,760 A perfect analogy. 90 00:03:11,760 --> 00:03:15,520 Massive stars live fast and die young, cosmically speaking. 91 00:03:15,520 --> 00:03:17,400 They might only last a few million years. 92 00:03:17,400 --> 00:03:19,960 While smaller stars, like our sun, 93 00:03:19,960 --> 00:03:21,680 can live for billions of years. 94 00:03:21,680 --> 00:03:22,360 Exactly. 95 00:03:22,360 --> 00:03:25,680 Our sun is expected to have a total lifespan of about 10 96 00:03:25,680 --> 00:03:26,360 billion years. 97 00:03:26,360 --> 00:03:28,880 So it's still got about 5 billion years to go. 98 00:03:28,880 --> 00:03:29,880 OK, good to know. 99 00:03:29,880 --> 00:03:31,640 But eventually, even our sun will run out 100 00:03:31,640 --> 00:03:33,120 of hydrogen fuel, right? 101 00:03:33,120 --> 00:03:33,800 That's right. 102 00:03:33,800 --> 00:03:35,520 And when that happens, things start 103 00:03:35,520 --> 00:03:37,320 to change dramatically for a star, 104 00:03:37,320 --> 00:03:39,640 leading to its next phase of life. 105 00:03:39,640 --> 00:03:42,920 So what happens when a star starts to run low on fuel? 106 00:03:42,920 --> 00:03:44,160 That's a great question. 107 00:03:44,160 --> 00:03:46,680 That's where we'll pick up in the next part of our deep dive. 108 00:03:46,680 --> 00:03:47,760 Sounds good. 109 00:03:47,760 --> 00:03:50,680 So we left off with our star happily chugging along, 110 00:03:50,680 --> 00:03:53,400 you know, fusing hydrogen into helium, 111 00:03:53,400 --> 00:03:55,000 radiating light and heat. 112 00:03:55,000 --> 00:03:56,280 Keeping things nice and stable. 113 00:03:56,280 --> 00:03:58,360 Right, like a giant cosmic campfire 114 00:03:58,360 --> 00:03:59,680 keeping the universe warm. 115 00:03:59,680 --> 00:04:01,320 Very apt analogy. 116 00:04:01,320 --> 00:04:05,800 But as with any fire, eventually you start to run low on fuel. 117 00:04:05,800 --> 00:04:06,400 Right. 118 00:04:06,400 --> 00:04:09,760 In a star's case, that fuel is hydrogen in its core. 119 00:04:09,760 --> 00:04:12,840 OK, so what happens when that hydrogen starts to run out? 120 00:04:12,840 --> 00:04:14,760 Does the star just sort of fizzle out? 121 00:04:14,760 --> 00:04:15,600 Not exactly. 122 00:04:15,600 --> 00:04:19,520 It's more like a dramatic transformation. 123 00:04:19,520 --> 00:04:22,120 You see, when the core runs out of hydrogen, 124 00:04:22,120 --> 00:04:24,240 the outward pressure from fusion weakens. 125 00:04:24,240 --> 00:04:26,520 And gravity, always lurking in the background, 126 00:04:26,520 --> 00:04:28,000 starts to gain the upper hand. 127 00:04:28,000 --> 00:04:29,280 Precisely. 128 00:04:29,280 --> 00:04:31,520 Gravity starts to compress the core, 129 00:04:31,520 --> 00:04:33,840 causing it to heat up even more. 130 00:04:33,840 --> 00:04:36,360 Now this intense heat triggers fusion 131 00:04:36,360 --> 00:04:38,520 in a shell around the core, where there's still 132 00:04:38,520 --> 00:04:39,760 some hydrogen left. 133 00:04:39,760 --> 00:04:42,000 So it's like a backup generator kicking in. 134 00:04:42,000 --> 00:04:42,960 In a way, yes. 135 00:04:42,960 --> 00:04:45,560 But this backup generator has some side effects. 136 00:04:45,560 --> 00:04:46,080 OK. 137 00:04:46,080 --> 00:04:49,200 The energy from the shell fusion causes the outer layers 138 00:04:49,200 --> 00:04:51,440 of the star to expand dramatically. 139 00:04:51,440 --> 00:04:52,480 The star gets bigger. 140 00:04:52,480 --> 00:04:53,280 Much bigger. 141 00:04:53,280 --> 00:04:55,800 It swells up into what we call a red giant. 142 00:04:55,800 --> 00:04:57,760 Red giant, that sounds pretty ominous. 143 00:04:57,760 --> 00:04:58,600 They are impressive. 144 00:04:58,600 --> 00:05:02,240 Imagine our sun swelling up to engulf Mercury, Venus, 145 00:05:02,240 --> 00:05:03,360 and maybe even Earth. 146 00:05:03,360 --> 00:05:04,480 Whoa. 147 00:05:04,480 --> 00:05:05,480 That's a sobering thought. 148 00:05:05,480 --> 00:05:05,960 Yeah. 149 00:05:05,960 --> 00:05:08,080 So Earth becomes a crispy cinder. 150 00:05:08,080 --> 00:05:09,240 No chance of survival. 151 00:05:09,240 --> 00:05:11,160 Well, it's not a definite outcome, 152 00:05:11,160 --> 00:05:13,040 but it's certainly a possibility. 153 00:05:13,040 --> 00:05:16,360 The good news is this red giant phase is still billions 154 00:05:16,360 --> 00:05:17,680 of years away for our sun. 155 00:05:17,680 --> 00:05:21,280 OK, phew, got some time to figure out a plan B. 156 00:05:21,280 --> 00:05:22,360 But I'm curious. 157 00:05:22,360 --> 00:05:26,440 What happens to the star itself during this red giant phase? 158 00:05:26,440 --> 00:05:29,000 The core continues to contract and heat up, 159 00:05:29,000 --> 00:05:30,400 and eventually it gets hot enough 160 00:05:30,400 --> 00:05:33,200 to trigger a new kind of fusion, helium fusion. 161 00:05:33,200 --> 00:05:35,080 So it's like upgrading to a new fuel source. 162 00:05:35,080 --> 00:05:36,000 Exactly. 163 00:05:36,000 --> 00:05:38,880 Helium atoms fuse to form carbon and oxygen, 164 00:05:38,880 --> 00:05:40,800 releasing even more energy. 165 00:05:40,800 --> 00:05:43,000 And this keeps the star going for a while longer. 166 00:05:43,000 --> 00:05:44,880 For a time, yes. 167 00:05:44,880 --> 00:05:47,840 But eventually, even the helium runs out. 168 00:05:47,840 --> 00:05:48,440 Right. 169 00:05:48,440 --> 00:05:50,080 And for a star like our sun, this 170 00:05:50,080 --> 00:05:52,360 is where the story takes a dramatic turn. 171 00:05:52,360 --> 00:05:54,400 A dramatic turn, I'm on the edge of my seat. 172 00:05:54,400 --> 00:05:55,280 OK. 173 00:05:55,280 --> 00:05:56,280 What happens next? 174 00:05:56,280 --> 00:06:00,160 The outer layers of the star are no longer supported by fusion, 175 00:06:00,160 --> 00:06:03,120 drift off into space, forming this, well, 176 00:06:03,120 --> 00:06:05,160 it's really beautiful, actually, this glowing 177 00:06:05,160 --> 00:06:06,920 cloud of gas and dust. 178 00:06:06,920 --> 00:06:08,240 That sounds stunning. 179 00:06:08,240 --> 00:06:09,440 What do we call those clouds? 180 00:06:09,440 --> 00:06:11,160 Planetary nebulae. 181 00:06:11,160 --> 00:06:13,160 And at the center of this nebula lies 182 00:06:13,160 --> 00:06:17,560 the exposed core of the star, a white, hot, incredibly dense 183 00:06:17,560 --> 00:06:19,240 object about the size of Earth. 184 00:06:19,240 --> 00:06:21,400 So it's like the star has shed its skin 185 00:06:21,400 --> 00:06:22,800 and revealed its inner core. 186 00:06:22,800 --> 00:06:24,360 That's a great way to visualize it. 187 00:06:24,360 --> 00:06:27,360 And this exposed core is what we call a white dwarf. 188 00:06:27,360 --> 00:06:28,480 White dwarfs, I've heard of those. 189 00:06:28,480 --> 00:06:30,000 They're like the remnants of a dead star. 190 00:06:30,000 --> 00:06:30,200 Right. 191 00:06:30,200 --> 00:06:31,080 Exactly. 192 00:06:31,080 --> 00:06:33,440 They're no longer generating energy through fusion, 193 00:06:33,440 --> 00:06:37,160 but they're still incredibly hot and radiating heat, 194 00:06:37,160 --> 00:06:40,440 slowly cooling down over billions of years. 195 00:06:40,440 --> 00:06:42,120 Just like the embers of a dying fire. 196 00:06:42,120 --> 00:06:43,720 A perfect analogy. 197 00:06:43,720 --> 00:06:46,480 But for stars much more massive than our sun, 198 00:06:46,480 --> 00:06:48,760 the end game is even more spectacular. 199 00:06:48,760 --> 00:06:49,280 OK. 200 00:06:49,280 --> 00:06:51,400 Instead of gently fading away as white dwarfs, 201 00:06:51,400 --> 00:06:52,920 they go out with a bang. 202 00:06:52,920 --> 00:06:53,440 Uh-huh. 203 00:06:53,440 --> 00:06:54,200 Supernova. 204 00:06:54,200 --> 00:06:55,040 Supernova. 205 00:06:55,040 --> 00:06:57,320 Those are the most powerful explosions in the universe, 206 00:06:57,320 --> 00:06:57,800 right? 207 00:06:57,800 --> 00:06:58,520 Absolutely. 208 00:06:58,520 --> 00:07:00,400 When a massive star runs out of fuel, 209 00:07:00,400 --> 00:07:02,920 its core collapses under its own gravity, 210 00:07:02,920 --> 00:07:05,120 triggering this catastrophic explosion that 211 00:07:05,120 --> 00:07:07,040 can outshine an entire galaxy. 212 00:07:07,040 --> 00:07:08,400 Wow. 213 00:07:08,400 --> 00:07:10,200 That's mind blowing. 214 00:07:10,200 --> 00:07:12,120 So what happens to the star during a supernova? 215 00:07:12,120 --> 00:07:13,520 Is there anything left? 216 00:07:13,520 --> 00:07:16,200 The outer layers of the star are blasted into space, 217 00:07:16,200 --> 00:07:18,160 seeding the cosmos with heavy elements 218 00:07:18,160 --> 00:07:21,080 like gold, silver, uranium, and the core. 219 00:07:21,080 --> 00:07:23,200 Well, it depends on how massive the star was. 220 00:07:23,200 --> 00:07:23,560 OK. 221 00:07:23,560 --> 00:07:25,080 So different sizes, different outcomes. 222 00:07:25,080 --> 00:07:25,760 Exactly. 223 00:07:25,760 --> 00:07:27,520 If the core is massive enough, it 224 00:07:27,520 --> 00:07:29,920 collapses further, squeezing itself 225 00:07:29,920 --> 00:07:33,640 into this incredibly dense object called a neutron star. 226 00:07:33,640 --> 00:07:34,480 Neutron star. 227 00:07:34,480 --> 00:07:35,760 I remember reading about those. 228 00:07:35,760 --> 00:07:37,560 They're incredibly dense, right? 229 00:07:37,560 --> 00:07:40,960 Like a teaspoon full would weigh billions of tons. 230 00:07:40,960 --> 00:07:41,880 That's right. 231 00:07:41,880 --> 00:07:45,160 Neutron stars are mind bogglingly dense, 232 00:07:45,160 --> 00:07:48,040 spinning rapidly and emitting these powerful beams 233 00:07:48,040 --> 00:07:49,720 of radiation. 234 00:07:49,720 --> 00:07:52,560 They're like cosmic lighthouses sweeping their beams 235 00:07:52,560 --> 00:07:53,640 across the universe. 236 00:07:53,640 --> 00:07:56,080 So neutron stars are pretty extreme. 237 00:07:56,080 --> 00:07:58,760 But what happens if the core is even more massive? 238 00:07:58,760 --> 00:08:01,240 Is there anything denser than a neutron star? 239 00:08:01,240 --> 00:08:03,400 That's where things get really mysterious. 240 00:08:03,400 --> 00:08:05,560 For the most massive stars, the core 241 00:08:05,560 --> 00:08:08,040 collapses beyond the neutron star stage, 242 00:08:08,040 --> 00:08:10,880 forming something even more extreme, a black hole. 243 00:08:10,880 --> 00:08:11,720 Black holes. 244 00:08:11,720 --> 00:08:13,280 The ultimate cosmic enigmas. 245 00:08:13,280 --> 00:08:15,040 I've always been fascinated by them. 246 00:08:15,040 --> 00:08:17,400 Tell me more about what happens when a black hole forms. 247 00:08:17,400 --> 00:08:19,800 Well, when the core collapses to form a black hole, 248 00:08:19,800 --> 00:08:23,160 its gravity becomes so strong that nothing, not even light, 249 00:08:23,160 --> 00:08:24,400 can escape its pull. 250 00:08:24,400 --> 00:08:26,440 So it's like a cosmic vacuum cleaner sucking up 251 00:08:26,440 --> 00:08:27,360 everything around it. 252 00:08:27,360 --> 00:08:28,520 In a way, yes. 253 00:08:28,520 --> 00:08:30,320 Anything that crosses the event horizon, 254 00:08:30,320 --> 00:08:33,080 the point of no return, is trapped forever. 255 00:08:33,080 --> 00:08:34,760 That's both terrifying and fascinating. 256 00:08:34,760 --> 00:08:35,320 It is. 257 00:08:35,320 --> 00:08:37,120 So black holes are invisible to us, right? 258 00:08:37,120 --> 00:08:39,000 Because no light can escape. 259 00:08:39,000 --> 00:08:40,000 That's right. 260 00:08:40,000 --> 00:08:42,800 But we can detect their presence by their effects 261 00:08:42,800 --> 00:08:43,840 on nearby matter. 262 00:08:43,840 --> 00:08:46,480 For example, if a black hole is pulling in gas 263 00:08:46,480 --> 00:08:50,320 from a nearby star, that gas heats up and emits x-rays 264 00:08:50,320 --> 00:08:51,360 that we can detect. 265 00:08:51,360 --> 00:08:54,600 So black holes are these invisible monsters lurking 266 00:08:54,600 --> 00:08:58,240 out there in the universe, warping space and time 267 00:08:58,240 --> 00:09:00,680 and gobbling up anything that gets too close. 268 00:09:00,680 --> 00:09:02,200 That's one way to think about them. 269 00:09:02,200 --> 00:09:04,280 They're certainly some of the most extreme objects 270 00:09:04,280 --> 00:09:05,160 in the cosmos. 271 00:09:05,160 --> 00:09:07,120 And they're formed from the deaths 272 00:09:07,120 --> 00:09:08,600 of the most massive stars. 273 00:09:08,600 --> 00:09:09,280 Exactly. 274 00:09:09,280 --> 00:09:11,360 It's a reminder that even in death, 275 00:09:11,360 --> 00:09:14,240 stars can create some of the most fascinating objects 276 00:09:14,240 --> 00:09:15,120 in the universe. 277 00:09:15,120 --> 00:09:17,800 So we've talked about white dwarfs, neutron stars, 278 00:09:17,800 --> 00:09:18,840 and black holes. 279 00:09:18,840 --> 00:09:21,160 Three very different fates for stars. 280 00:09:21,160 --> 00:09:23,760 And each of these outcomes has a profound impact 281 00:09:23,760 --> 00:09:26,640 on the universe, contributing to this cosmic cycle 282 00:09:26,640 --> 00:09:27,800 of life and death. 283 00:09:27,800 --> 00:09:30,400 And that's what we'll explore in the next part of our deep dive. 284 00:09:30,400 --> 00:09:32,840 We'll delve into the concept of cosmic recycling 285 00:09:32,840 --> 00:09:35,600 and how the deaths of stars seed the universe 286 00:09:35,600 --> 00:09:40,280 with the ingredients for new stars, planets, and even life. 287 00:09:40,280 --> 00:09:42,520 So we've been talking about the spectacular ways 288 00:09:42,520 --> 00:09:44,200 that stars can die. 289 00:09:44,200 --> 00:09:47,000 Going out in a blaze of glory as supernovae 290 00:09:47,000 --> 00:09:49,760 or collapsing into these incredibly dense objects 291 00:09:49,760 --> 00:09:52,000 like neutron stars and black holes. 292 00:09:52,000 --> 00:09:54,520 It's a pretty dramatic end to a star's life. 293 00:09:54,520 --> 00:09:57,880 But it's not really the end of the story, is it? 294 00:09:57,880 --> 00:09:58,640 That's right. 295 00:09:58,640 --> 00:10:01,560 It's kind of like the circle of life, but on a cosmic scale. 296 00:10:01,560 --> 00:10:02,320 Exactly. 297 00:10:02,320 --> 00:10:05,080 And that's where the concept of cosmic recycling comes in. 298 00:10:05,080 --> 00:10:06,280 OK, cosmic recycling. 299 00:10:06,280 --> 00:10:07,360 Tell me more about that. 300 00:10:07,360 --> 00:10:09,920 Well, when a star dies, it doesn't just disappear. 301 00:10:09,920 --> 00:10:12,440 It releases this tremendous amount of material 302 00:10:12,440 --> 00:10:13,600 back into space. 303 00:10:13,600 --> 00:10:16,040 Right, we were talking about the outer layers of a star 304 00:10:16,040 --> 00:10:18,000 being blasted off during a supernova 305 00:10:18,000 --> 00:10:20,680 and forming those beautiful planetary nebulae. 306 00:10:20,680 --> 00:10:21,360 Exactly. 307 00:10:21,360 --> 00:10:23,480 And those planetary nebulae, along with the material 308 00:10:23,480 --> 00:10:27,120 ejected during, well, stellar winds throughout a star's life, 309 00:10:27,120 --> 00:10:28,680 contain all sorts of elements that 310 00:10:28,680 --> 00:10:30,720 were forged in the star's core. 311 00:10:30,720 --> 00:10:33,680 So it's like the star is returning all those elements 312 00:10:33,680 --> 00:10:34,800 back to the universe. 313 00:10:34,800 --> 00:10:35,800 Precisely. 314 00:10:35,800 --> 00:10:39,520 And these elements, including carbon, oxygen, nitrogen, 315 00:10:39,520 --> 00:10:42,320 and even heavier elements like iron and gold, 316 00:10:42,320 --> 00:10:45,840 become the building blocks for new stars, planets, and even 317 00:10:45,840 --> 00:10:46,760 life. 318 00:10:46,760 --> 00:10:49,840 Wait, so the stuff that makes up our bodies, the air we breathe, 319 00:10:49,840 --> 00:10:52,480 the ground we walk on it, all came from stars. 320 00:10:52,480 --> 00:10:53,200 That's right. 321 00:10:53,200 --> 00:10:55,760 Every atom in your body, except for the hydrogen, 322 00:10:55,760 --> 00:10:58,560 was created inside a star billions of years ago. 323 00:10:58,560 --> 00:10:59,440 That's incredible. 324 00:10:59,440 --> 00:11:01,840 I mean, it's kind of mind blowing 325 00:11:01,840 --> 00:11:03,680 to think that we're all made of stardust. 326 00:11:03,680 --> 00:11:05,280 It really is a profound thought. 327 00:11:05,280 --> 00:11:08,160 We are, well, we are literally connected to the universe 328 00:11:08,160 --> 00:11:09,600 in a very tangible way. 329 00:11:09,600 --> 00:11:12,600 And it makes you realize that the death of a star 330 00:11:12,600 --> 00:11:14,200 isn't just an ending. 331 00:11:14,200 --> 00:11:15,360 It's also a beginning. 332 00:11:15,360 --> 00:11:16,480 Absolutely. 333 00:11:16,480 --> 00:11:19,640 The death of one star can seed the birth of countless others, 334 00:11:19,640 --> 00:11:22,680 along with planetary systems and potentially even life. 335 00:11:22,680 --> 00:11:24,480 It's a beautiful cycle, really. 336 00:11:24,480 --> 00:11:26,080 And it makes me wonder, what will 337 00:11:26,080 --> 00:11:28,200 happen to all the material that our sun will 338 00:11:28,200 --> 00:11:30,240 eject when it reaches the end of its life? 339 00:11:30,240 --> 00:11:32,120 Well, in about 5 billion years, when 340 00:11:32,120 --> 00:11:35,000 our sun becomes a red giant, it will shed its outer layers, 341 00:11:35,000 --> 00:11:36,560 forming a planetary nebula. 342 00:11:36,560 --> 00:11:37,040 Right. 343 00:11:37,040 --> 00:11:39,480 And that material will eventually drift off into space. 344 00:11:39,480 --> 00:11:40,520 Exactly. 345 00:11:40,520 --> 00:11:43,320 And it might eventually become part of a new nebula, 346 00:11:43,320 --> 00:11:45,440 where gravity will start to pull it together, 347 00:11:45,440 --> 00:11:47,760 and the whole process will begin again. 348 00:11:47,760 --> 00:11:50,200 So the atoms that make up our bodies 349 00:11:50,200 --> 00:11:54,000 might one day be part of a new star or a new planet, 350 00:11:54,000 --> 00:11:55,480 or maybe even a new life form? 351 00:11:55,480 --> 00:11:56,760 It's certainly a possibility. 352 00:11:56,760 --> 00:11:59,080 It's all part of this grand cosmic cycle 353 00:11:59,080 --> 00:12:01,360 of creation and destruction, a cycle that's been 354 00:12:01,360 --> 00:12:03,160 going on for billions of years. 355 00:12:03,160 --> 00:12:05,000 And who knows what the future holds? 356 00:12:05,000 --> 00:12:07,880 Maybe one day, billions of years from now, 357 00:12:07,880 --> 00:12:09,960 there will be intelligent beings on a planet 358 00:12:09,960 --> 00:12:11,640 orbiting a distant star. 359 00:12:11,640 --> 00:12:13,360 And they'll look up at the night sky 360 00:12:13,360 --> 00:12:15,880 and wonder about the stars, just like we do. 361 00:12:15,880 --> 00:12:17,680 And maybe they'll even realize that they, too, 362 00:12:17,680 --> 00:12:19,680 are made of stardust, just like us. 363 00:12:19,680 --> 00:12:21,720 Well, I think we've covered a lot of ground today. 364 00:12:21,720 --> 00:12:25,280 We've journeyed from the birth of stars in these vast nebulae 365 00:12:25,280 --> 00:12:27,680 to their dramatic deaths as supernovae 366 00:12:27,680 --> 00:12:30,120 or their quiet fading as white dwarfs. 367 00:12:30,120 --> 00:12:32,760 We've explored the mind-boggling concepts 368 00:12:32,760 --> 00:12:34,920 of neutron stars and black holes. 369 00:12:34,920 --> 00:12:36,920 And we've delved into the profound idea 370 00:12:36,920 --> 00:12:40,000 of cosmic recycling, how the death of one star 371 00:12:40,000 --> 00:12:42,200 can seed the birth of countless others. 372 00:12:42,200 --> 00:12:44,320 It's been quite a cosmic adventure. 373 00:12:44,320 --> 00:12:46,160 And I hope our listeners have enjoyed 374 00:12:46,160 --> 00:12:49,040 joining us on this deep dive into the fascinating world 375 00:12:49,040 --> 00:12:49,800 of stars. 376 00:12:49,800 --> 00:12:50,680 I'm sure they have. 377 00:12:50,680 --> 00:12:54,080 It's a topic that never fails to inspire awe and wonder. 378 00:12:54,080 --> 00:12:56,360 So the next time you look up at the night sky, 379 00:12:56,360 --> 00:13:00,000 remember the incredible story unfolding above you. 380 00:13:00,000 --> 00:13:02,160 Each one of those twinkling points of light 381 00:13:02,160 --> 00:13:06,880 has its own unique tale to tell, a tale of birth, life, death, 382 00:13:06,880 --> 00:13:07,760 and rebirth. 383 00:13:07,760 --> 00:13:10,640 And remember that you are a part of that story connected 384 00:13:10,640 --> 00:13:13,840 to the universe in a way that is both profound and beautiful. 385 00:13:13,840 --> 00:13:15,760 And if you want to keep exploring the mysteries 386 00:13:15,760 --> 00:13:18,680 of the cosmos with us, be sure to follow and subscribe 387 00:13:18,680 --> 00:13:19,920 to Cosmos in a Pod. 388 00:13:19,920 --> 00:13:22,840 We'll be back soon with more deep dives into the universe. 389 00:13:22,840 --> 00:13:26,440 Until then, keep looking up and keep wondering.