WEBVTT 1 00:00:03.399 --> 00:00:07.719 Welcome to Bedtime Astronomy. Explore the wonders of the cosmos 2 00:00:07.759 --> 00:00:12.279 with our soothing Bedtime Astronomie podcast. Each episode offers a 3 00:00:12.359 --> 00:00:16.320 gentle journey through the stars, planets, and beyond, perfect for 4 00:00:16.399 --> 00:00:20.239 unwinding after a long day. Let's travel through the mysteries 5 00:00:20.239 --> 00:00:22.440 of the universe as you drift off into a peaceful 6 00:00:22.480 --> 00:00:23.800 slumber under the night sky. 7 00:00:26.960 --> 00:00:29.199 So I want you to imagine, just for a second, 8 00:00:29.280 --> 00:00:31.679 that you are an archaeologist. Okay, I'm with you, but 9 00:00:31.800 --> 00:00:34.640 you aren't, you know, hacking your way through a dense, 10 00:00:34.719 --> 00:00:38.079 uncharted jumble somewhere. And you're definitely not sifting through the 11 00:00:38.079 --> 00:00:39.719 remote sands of Egypt. 12 00:00:39.439 --> 00:00:41.719 Right, none of the Indiana Jones stuff exactly. 13 00:00:41.960 --> 00:00:45.159 Instead, you are standing right in the middle of a bustling, 14 00:00:45.439 --> 00:00:50.159 hyper modern, neonlit metropolis. I mean, cars are just zooming by, 15 00:00:50.359 --> 00:00:54.240 massive skyscrapers are towering overhead, and there are millions of 16 00:00:54.320 --> 00:00:58.719 people rushing around in this well, this chaotic symphony of modern. 17 00:00:58.399 --> 00:01:01.320 Life sounds pretty overwhelming, honestly it is. 18 00:01:01.640 --> 00:01:05.200 But then right there, sitting completely unnoticed in the middle 19 00:01:05.200 --> 00:01:08.480 of a twelve lane super highway, you spot something that 20 00:01:08.599 --> 00:01:10.239 is just flat out impossible. 21 00:01:10.319 --> 00:01:11.400 An agent artifact. 22 00:01:11.560 --> 00:01:17.319 Yes, an absolutely pristine, untouched mint condition model T four, 23 00:01:17.599 --> 00:01:20.519 just you know, idling in the fast lane. Right. It's 24 00:01:20.640 --> 00:01:23.840 completely out of place among all the electric vehicles and 25 00:01:23.879 --> 00:01:27.000 the hyper modern infrastructure. It really shouldn't be there at all. 26 00:01:27.040 --> 00:01:30.200 It belongs to an entirely different era. But there it is, 27 00:01:30.239 --> 00:01:32.519 just hiding in plain sight. And if you pop the hood, 28 00:01:33.079 --> 00:01:36.439 the engine block actually holds the very engineering secrets of 29 00:01:36.519 --> 00:01:38.560 how the first factories were ever built. 30 00:01:38.879 --> 00:01:42.799 That visual the whole anachronism of it. It maps perfectly 31 00:01:42.840 --> 00:01:46.040 onto the reality of what we were looking at in 32 00:01:46.040 --> 00:01:48.719 this deep dive today. Yeah, because we're dealing with an 33 00:01:48.719 --> 00:01:52.760 object that frankly fundamentally breaks the timeline of its surroundings. 34 00:01:52.840 --> 00:01:53.519 It really does. 35 00:01:53.760 --> 00:01:56.359 Yeah, it's a relic from the absolute beginning of history. 36 00:01:56.599 --> 00:01:59.439 It's preserving a state of the universe that's supposedly vanished 37 00:02:00.200 --> 00:02:01.760 over thirteen billion years ago. 38 00:02:01.879 --> 00:02:05.439 Thirteen billion years. It's staggering. We are tracking down the 39 00:02:05.519 --> 00:02:09.240 ultimate cosmic relic today, the most pristine star ever found 40 00:02:09.319 --> 00:02:10.319 in the known universe. 41 00:02:10.360 --> 00:02:12.039 And it has a very catchy name too, right. 42 00:02:12.080 --> 00:02:15.199 Oh, the catchiest. It has a deeply unglamorous catalog name 43 00:02:15.400 --> 00:02:19.599 SDSSJ zero seven. One, five, seven three three four. But 44 00:02:19.680 --> 00:02:23.159 the single faint point of light is that exact model 45 00:02:23.199 --> 00:02:25.759 t Ford on the Galactic super Highway, hiding and plain 46 00:02:25.879 --> 00:02:29.280 sight exactly. So today we're going to explore the mechanics 47 00:02:29.319 --> 00:02:32.479 of what actually makes a star truly pristine. You know, 48 00:02:32.960 --> 00:02:37.120 we'll get into the massive automated technological ecosystem that was 49 00:02:37.159 --> 00:02:38.919 required to even locate it. 50 00:02:39.000 --> 00:02:40.800 It's a story itself, huge. 51 00:02:40.520 --> 00:02:45.120 Story, and maybe my favorite part the incredible human element, 52 00:02:45.439 --> 00:02:49.120 the undergraduate students who actually cracked its chemical code while 53 00:02:49.120 --> 00:02:50.439 on a spring break field trip. 54 00:02:50.560 --> 00:02:52.680 It's just such a great narrative, it really. 55 00:02:52.479 --> 00:02:54.520 Is, because when you step outside and look up at 56 00:02:54.560 --> 00:02:57.719 the night sky, you aren't just seeing lights. You are 57 00:02:57.759 --> 00:03:01.919 looking at a multi generational family tree of stellar evolution. 58 00:03:02.120 --> 00:03:06.319 You've got you know, parents, grandparents, highly complex descendants up there, 59 00:03:06.759 --> 00:03:09.360 and today we are meeting the ultimate ancestor. 60 00:03:09.639 --> 00:03:13.719 To really grasp the mechanical improbability of STSSG zero seven 61 00:03:13.800 --> 00:03:16.560 one five, seven, three three four surviving all the way 62 00:03:16.560 --> 00:03:18.479 to the present day, we kind of have to rewind 63 00:03:18.520 --> 00:03:20.520 the clock all the way back, right all the way 64 00:03:20.520 --> 00:03:23.800 back to the era immediately following the Big Bank, Specifically 65 00:03:24.080 --> 00:03:26.199 this period we call the epoch of recombination. 66 00:03:26.319 --> 00:03:28.000 Okay, so set the scene for us. What does that 67 00:03:28.039 --> 00:03:28.400 look like. 68 00:03:28.680 --> 00:03:31.520 So we're talking about a period roughly three hundred and 69 00:03:31.560 --> 00:03:35.719 eighty thousand years after the initial expansion. That is when 70 00:03:35.759 --> 00:03:39.439 the universe finally cooled down enough for the ambient radiation 71 00:03:39.919 --> 00:03:43.800 to drop below the ionization threshold of hydrogen. 72 00:03:43.840 --> 00:03:45.520 That's the moment the fog finally lifted. 73 00:03:45.719 --> 00:03:49.639 Exactly the fog lifted, because before that point the universe 74 00:03:49.719 --> 00:03:54.199 was essentially this opaque plasma. Protons and electrons were just 75 00:03:54.319 --> 00:03:56.879 zipping around with so much kinetic energy that they couldn't 76 00:03:56.960 --> 00:03:57.919 bind together. 77 00:03:57.800 --> 00:03:59.080 Like a hyperactive mosh pit. 78 00:03:59.199 --> 00:04:01.879 That's a good way to pickture, and any photon of 79 00:04:01.960 --> 00:04:04.159 light that tried to travel through that mess would just 80 00:04:04.240 --> 00:04:07.960 instantly scatter off a free electron. The universe was effectively 81 00:04:08.000 --> 00:04:09.639 this blinding, superheated soup. 82 00:04:09.879 --> 00:04:12.400 You couldn't see anything even if you were there, right. 83 00:04:12.719 --> 00:04:16.319 But as space expanded, the thermal energy of those particles 84 00:04:16.319 --> 00:04:19.480 began to drop, and once the temperature dipped below about 85 00:04:19.480 --> 00:04:22.240 three thousand kelvin, something crucial happened. 86 00:04:22.240 --> 00:04:24.480 They slowed down enough to stick exactly. 87 00:04:25.000 --> 00:04:28.600 The electrostatic attraction between the protons and electrons. Finally overcame 88 00:04:28.639 --> 00:04:31.800 all that kinetic energy. They snapped together and they formed 89 00:04:31.800 --> 00:04:33.240 the very first neutral atoms. 90 00:04:33.439 --> 00:04:36.759 And those first atoms were incredibly basic. 91 00:04:36.439 --> 00:04:39.959 Right, extremely basic. They were almost exclusively hydrogen, with you know, 92 00:04:40.040 --> 00:04:44.279 a smattering of helium and just a negligible trace of lithium. 93 00:04:44.319 --> 00:04:46.439 And that was it. That was the entire periodic table 94 00:04:46.480 --> 00:04:47.040 at that moment. 95 00:04:47.160 --> 00:04:50.639 No carbon, no oxygen, no iron, nothing. 96 00:04:50.680 --> 00:04:55.560 Just a vast cooling ocean of neutral gas slowly settling 97 00:04:55.600 --> 00:04:58.000 into what we call the cosmic dark ages. 98 00:04:57.759 --> 00:05:01.199 Which sounds ominous, but it's really just the stage being set. 99 00:05:01.279 --> 00:05:05.120 Because out of that pristine, incredibly simple gas, gravity had 100 00:05:05.160 --> 00:05:07.560 to somehow figure out a way to build the first 101 00:05:07.600 --> 00:05:11.759 generation of stars what your astronomers call population three. 102 00:05:11.560 --> 00:05:15.720 Stars, right, population three, And the thermodynamics of that building 103 00:05:15.759 --> 00:05:18.480 process are incredibly hostile to star formation. 104 00:05:19.040 --> 00:05:19.600 Why is that. 105 00:05:20.120 --> 00:05:22.639 Well, for a cloud of gas to collapse into a star, 106 00:05:23.040 --> 00:05:25.519 gravity basically has to win a tug of war against 107 00:05:25.560 --> 00:05:28.279 thermal pressure. When you can press gas, it heats up. 108 00:05:28.319 --> 00:05:29.040 Everybody knows that. 109 00:05:29.040 --> 00:05:30.959 Right, right, Like pumping up a bicycle tire, the pump 110 00:05:30.959 --> 00:05:32.199 gets hot exactly. 111 00:05:32.319 --> 00:05:34.920 So if that gas cloud can't radiate that newly generated 112 00:05:34.959 --> 00:05:38.560 heat away into space. The thermal pressure pushes back against gravity, 113 00:05:38.759 --> 00:05:41.079 and the collapse just halts. It stops dead. 114 00:05:41.319 --> 00:05:44.240 So it needs a way to cool down while it's collapsing. 115 00:05:44.439 --> 00:05:51.199 Yes, in the modern universe, gas clouds contain heavier elements carbon, oxygen, silicon, 116 00:05:51.720 --> 00:05:54.279 and these elements are fantastic cool ones. 117 00:05:54.360 --> 00:05:56.920 How do they cool things down in the vacuum of space. 118 00:05:57.480 --> 00:06:00.519 Their atomic structures are complex, so they they allow them 119 00:06:00.519 --> 00:06:04.079 to easily absorb kinetic energy from all the particles colliding 120 00:06:04.120 --> 00:06:06.920 around them, and then they radiate that energy away as 121 00:06:07.000 --> 00:06:07.720 infrared light. 122 00:06:07.920 --> 00:06:12.120 Okay, so they act like thermal exhaust vents for the 123 00:06:12.120 --> 00:06:15.759 gas cloud. They let it cool down, lose that outward pressure, 124 00:06:16.040 --> 00:06:18.040 and then gravity can keep crushing it together. 125 00:06:18.399 --> 00:06:21.240 That is a perfect analogy thermal exhaust vents. But here's 126 00:06:21.240 --> 00:06:26.079 the problem. Those first population three stars, they didn't have heavy. 127 00:06:25.839 --> 00:06:28.120 Elements, right because nothing had made them yet. They only 128 00:06:28.120 --> 00:06:30.279 had hydrogen and helium exactly. 129 00:06:29.879 --> 00:06:33.360 And molecular hydrogen is an incredibly inefficient coolant. It's terrible 130 00:06:33.360 --> 00:06:36.319 at it. So the only way gravity could overcome the 131 00:06:36.360 --> 00:06:41.120 fierce thermal pressure that pristine gas was through sheer overwhelming mass. 132 00:06:41.160 --> 00:06:42.800 It just had to brute force the collapse. 133 00:06:43.240 --> 00:06:47.920 Yes, the physics essentially required these first generation stars to 134 00:06:47.959 --> 00:06:52.800 be absolute behemoths. We are talking hundreds, perhaps even a thousand, 135 00:06:52.839 --> 00:06:56.120 times the mass of our modern sun. That was the 136 00:06:56.160 --> 00:07:00.079 only way to force the gas to collapse enough to 137 00:07:00.160 --> 00:07:01.600 ignite nuclear fusion. 138 00:07:01.800 --> 00:07:04.480 So the gravitational crush just had to be immense to 139 00:07:04.519 --> 00:07:07.480 trigger that ignition. And because they were so massive, their 140 00:07:07.480 --> 00:07:11.120 core temperatures would have been unimaginably high off the. 141 00:07:11.120 --> 00:07:14.319 Charts, and a star's lifespan is entirely dictated by the 142 00:07:14.319 --> 00:07:17.120 temperature of its core. A massive star doesn't just burn 143 00:07:17.199 --> 00:07:20.879 its fuel linearly faster than a small star. It burns 144 00:07:20.879 --> 00:07:22.040 it exponentially faster. 145 00:07:22.199 --> 00:07:25.360 It's like a gas guzzling supercar compared to an economy sedan. 146 00:07:25.519 --> 00:07:28.120 Exactly the extreme pressure in a population the third star 147 00:07:28.160 --> 00:07:30.759 would have forced its hydrogen fusion process to just run 148 00:07:30.800 --> 00:07:33.600 at maximum capacity constantly. It had to do that just 149 00:07:33.600 --> 00:07:35.480 to maintain hydrostatic equilibrium. 150 00:07:35.560 --> 00:07:38.839 Hydrostatic equilibrium being the balance between gravity crushing it and 151 00:07:38.920 --> 00:07:40.279 fusion pushing out right. 152 00:07:40.319 --> 00:07:43.319 So to maintain that balance, they burned incredibly fast. They 153 00:07:43.360 --> 00:07:47.199 lived incredibly brief, violently energetic lives, and they exhausted their 154 00:07:47.240 --> 00:07:48.959 fuel in just a few million years. 155 00:07:48.959 --> 00:07:51.600 Which in the lifespan of the universe is a cosmic 156 00:07:51.680 --> 00:07:52.079 blink of. 157 00:07:52.079 --> 00:07:54.879 An eye, not even a blink. And when they ran 158 00:07:54.920 --> 00:07:58.120 out of fuel, that outward pressure from the fusion just stopped. 159 00:07:58.879 --> 00:08:01.480 Gravity won the tug of war instantly, and the core. 160 00:08:01.319 --> 00:08:03.519 Collapsed, resulting in supernova right core. 161 00:08:03.399 --> 00:08:06.759 Collapse supernovaes or even parents stability supernova, which are so 162 00:08:06.839 --> 00:08:11.120 violent they completely obliterate the star without leaving even a 163 00:08:11.160 --> 00:08:13.000 black hole behind. Just total destruction. 164 00:08:13.160 --> 00:08:15.160 Wow, total obliteration. 165 00:08:15.480 --> 00:08:19.519 But the really crucial mechanic here for our story is 166 00:08:19.560 --> 00:08:21.959 what happened in the moments leading up to and during 167 00:08:22.000 --> 00:08:23.240 those massive explosions. 168 00:08:23.279 --> 00:08:24.279 The alchemy part of it. 169 00:08:24.439 --> 00:08:28.680 Yes, the intense pressures and temperatures inside these dying bohemos 170 00:08:29.040 --> 00:08:33.440 acted as stellar forges through a process called nucleosynthesis. They 171 00:08:33.519 --> 00:08:36.399 smashed helium atoms together to make carbon okay, and then 172 00:08:36.399 --> 00:08:39.919 they fused carbon to make oxygen, then neon silicon all 173 00:08:39.919 --> 00:08:42.440 the way up to the periodic table to iron. And 174 00:08:42.559 --> 00:08:47.159 then the explosion itself synthesized even heavier elements and blasted 175 00:08:47.200 --> 00:08:51.159 all this newly forged material out into the pristine cosmic ocean. 176 00:08:51.159 --> 00:08:55.320 So they essentially seated the universe with the very first 177 00:08:55.639 --> 00:08:59.799 heavy elements, the first pollution basically, and actually this brings 178 00:08:59.879 --> 00:09:02.200 up that's that terminology quirk we should probably address because 179 00:09:02.200 --> 00:09:04.519 it definitely changes how we have to read the data 180 00:09:04.600 --> 00:09:04.960 later on. 181 00:09:05.360 --> 00:09:07.200 Yes, the astronomer's definition. 182 00:09:06.840 --> 00:09:10.200 Of metals, right, because in astrophysics, the periodic table is 183 00:09:10.200 --> 00:09:15.360 basically divided into three distinct things hydrogen, helium, and everything else, 184 00:09:15.559 --> 00:09:19.799 and everything else gets grouped into one single word metals. 185 00:09:19.879 --> 00:09:24.279 Yeah, two in astronomer Literally, anything heavier than helium is a. 186 00:09:24.240 --> 00:09:27.440 Metal, which is so confusing for the rest of us. 187 00:09:27.480 --> 00:09:30.120 I know, I know, oxygen is a metal, carbon is 188 00:09:30.159 --> 00:09:32.679 a metal, neon is a metal. It's well, it's an 189 00:09:32.759 --> 00:09:35.840 archaic naming convention from the early days of spectroscopy, honestly, 190 00:09:36.480 --> 00:09:39.440 but it still serves a very practical mathematical purpose for us. 191 00:09:39.759 --> 00:09:44.039 So it allows astrophysicists to define a star's composition using 192 00:09:44.159 --> 00:09:47.600 just one single parameter, metallicity. 193 00:09:47.120 --> 00:09:47.600 Got it. 194 00:09:47.679 --> 00:09:50.840 So those Population three stars we just discussed, they were 195 00:09:50.879 --> 00:09:54.559 completely metal free, zero metallicity. It manufactured the first metals 196 00:09:54.720 --> 00:09:56.200 and then scattered them. 197 00:09:56.000 --> 00:09:59.080 Which then sets the stage for the second generation of stars. 198 00:09:59.200 --> 00:10:02.519 Population two stars. They form from gas clouds that have 199 00:10:02.559 --> 00:10:06.000 been slightly polluted by the shrapnel of those first supernovae, 200 00:10:06.559 --> 00:10:09.639 And that brings us to our star sdss J zero 201 00:10:09.759 --> 00:10:11.519 seven one five seven three three four. 202 00:10:11.720 --> 00:10:13.759 Exactly. It is a second generation star. 203 00:10:14.039 --> 00:10:16.480 It formed right out of the immediate wreckage of those 204 00:10:16.519 --> 00:10:20.000 first massive explosions, which makes it what over thirteen billion 205 00:10:20.080 --> 00:10:22.360 years old right around there? Yes, okay, wait, I'm doing 206 00:10:22.360 --> 00:10:24.240 the math in my head here, and I'm seeing a 207 00:10:24.360 --> 00:10:26.919 gaping structural contradiction in what we just talked about. 208 00:10:27.039 --> 00:10:28.039 Oh, laid on me. 209 00:10:28.279 --> 00:10:31.120 You just laid out the physics. A star forming from 210 00:10:31.600 --> 00:10:35.320 metal free or nearly metal free gas has to be 211 00:10:35.360 --> 00:10:38.720 incredibly massive to overcome thermal pressure because it doesn't have 212 00:10:38.759 --> 00:10:41.879 the thermal exhaust fence correct and because it's massive, it 213 00:10:41.919 --> 00:10:44.679 burns extremely hot and blows up in a few million years. 214 00:10:44.840 --> 00:10:48.159 So if sdss J zero seven one five seven three 215 00:10:48.240 --> 00:10:51.480 three four formed in an environment with almost no metals, 216 00:10:51.679 --> 00:10:54.519 why didn't it blow up twelve point nine billion years ago? 217 00:10:54.919 --> 00:10:57.279 How is a thirteen billion year old low metal star 218 00:10:57.440 --> 00:11:01.200 still sitting there quietly fused and hydrogen today? It shouldn't exist. 219 00:11:01.519 --> 00:11:05.440 That paradox right there, That is exactly why this store 220 00:11:05.639 --> 00:11:08.120 is considered a holy grail in astrophysics. You've hit the 221 00:11:08.200 --> 00:11:11.240 nail on the head. Its mere existence challenges the standard 222 00:11:11.320 --> 00:11:13.000 models of early star formation. 223 00:11:13.440 --> 00:11:15.639 So what's the workaround? How did it survive? 224 00:11:16.240 --> 00:11:21.039 The answer lies in the highly localized mechanics those first supernovae. 225 00:11:21.200 --> 00:11:24.720 When a massive population third star exploded, it didn't just 226 00:11:24.799 --> 00:11:28.440 passively scatter metals. It generated massive, violent. 227 00:11:28.200 --> 00:11:30.320 Shockwaves, okay, shock waves. 228 00:11:30.000 --> 00:11:33.960 And these shockwaves slammed into surrounding uncollapsed clouds of that 229 00:11:34.039 --> 00:11:38.399 pristine gas. The mechanical compression from the shockwave forced the 230 00:11:38.440 --> 00:11:41.879 gas together so rapidly that it basically bypassed the Thumble 231 00:11:41.960 --> 00:11:43.360 pressure bottleneck entirely. 232 00:11:43.559 --> 00:11:46.360 Oh wow. So the shockwave did the work that gravity 233 00:11:46.399 --> 00:11:47.240 couldn't do alone. 234 00:11:47.399 --> 00:11:49.960 Exactly, It forced the gas to fragment into much smaller 235 00:11:50.000 --> 00:11:53.039 clumps before it ignited, and this allowed the second generation 236 00:11:53.080 --> 00:11:56.639 of stars to form with significantly lower masses, even without 237 00:11:56.679 --> 00:11:58.679 the cooling benefits of those heavy metals. 238 00:11:58.759 --> 00:12:00.720 That is wild incredible. 239 00:12:00.960 --> 00:12:04.200 So sdss J zero seven one five seven three three 240 00:12:04.279 --> 00:12:07.639 four is a low mass star. It's actually likely less 241 00:12:07.639 --> 00:12:10.200 massive than our own Sun. And because it has such 242 00:12:10.279 --> 00:12:14.320 low mass, its core is under far less gravitational pressure. 243 00:12:14.240 --> 00:12:16.480 So it doesn't have to burn hot to fight back. 244 00:12:16.399 --> 00:12:19.039 Right the nuclear engine add its core only have to 245 00:12:19.279 --> 00:12:22.639 like idle to push back against gravity. It just SIPs 246 00:12:22.679 --> 00:12:24.919 its hydrogen fuel at an incredibly slow rate. 247 00:12:25.120 --> 00:12:28.879 So while its massive first generation parents redline their engines 248 00:12:28.919 --> 00:12:32.720 and exploded in millions of years, this tiny low mass 249 00:12:32.759 --> 00:12:36.399 descendant has just been quietly simmering on low heat for 250 00:12:36.480 --> 00:12:38.240 the entire history of the universe. 251 00:12:38.320 --> 00:12:41.799 Simmering, yes, and preserving the exact chemical fingerprint of the 252 00:12:41.840 --> 00:12:44.039 gas cloud it was born from. That's the case. 253 00:12:44.240 --> 00:12:46.240 How does it preserve It doesn't the fusion in the 254 00:12:46.279 --> 00:12:47.759 core mess up the chemistry. 255 00:12:48.240 --> 00:12:50.600 You'd think so, but no, the outer envelope of a 256 00:12:50.600 --> 00:12:53.159 low mass star doesn't actually mix deeply with the nuclear 257 00:12:53.200 --> 00:12:55.919 furnace down at its core. The surface layers were made 258 00:12:55.919 --> 00:12:59.360 of pristine, unadulterated sample of the environment present just moments 259 00:12:59.399 --> 00:12:59.960 after the first. 260 00:13:00.639 --> 00:13:03.080 So it really is a true cosmic fossil. 261 00:13:02.720 --> 00:13:04.200 Record, perfect time capsule. 262 00:13:04.399 --> 00:13:06.679 Well, let's get into the actual anatomy of this fossil, 263 00:13:06.840 --> 00:13:10.679 because the measurements of sdss J zero seven one five 264 00:13:10.759 --> 00:13:13.879 seven three three four are pretty mind bending. When we 265 00:13:13.919 --> 00:13:16.639 say the star is pristine. We are talking about a 266 00:13:16.679 --> 00:13:20.720 fractional trace of metals that borders on undetectable. 267 00:13:20.039 --> 00:13:22.200 Right, yes, extremely minute quantities. 268 00:13:22.320 --> 00:13:25.159 It has less than point zero zero five percent of 269 00:13:25.200 --> 00:13:27.600 the metal content found in our modern sun. Less than 270 00:13:27.600 --> 00:13:29.120 point zero zero zero five percent. 271 00:13:29.159 --> 00:13:30.000 It's almost nothing. 272 00:13:30.159 --> 00:13:33.080 It is twice as metal pore as the previous record holder. 273 00:13:33.480 --> 00:13:35.639 But the most important metric, the one that really blew 274 00:13:35.639 --> 00:13:39.480 people away, is its iron content. It is a staggering 275 00:13:39.759 --> 00:13:43.080 forty times more iron pore than the most pristine star 276 00:13:43.240 --> 00:13:46.679 previously documented in astronomical catalogs. Forty times. 277 00:13:46.759 --> 00:13:50.399 Yeah, that iron scarcity is the defining metric here. Why iron, specifically, 278 00:13:50.480 --> 00:13:54.120 because iron is the absolute endpoint of standard stellar nucleosynthesis. 279 00:13:54.440 --> 00:13:57.360 A star confuse lighter elements together to release energy right 280 00:13:57.480 --> 00:14:00.399 the alium in to carbon carbon into oxygen fuse. Iron 281 00:14:00.440 --> 00:14:02.879 actually consumes more energy than it produces. 282 00:14:02.519 --> 00:14:03.919 Which is a fatal flaw for a star. 283 00:14:04.279 --> 00:14:07.679 Exactly when a star tries to fuse iron, the energy 284 00:14:07.679 --> 00:14:11.360 output drops, gravity winds, and that is what triggers the 285 00:14:11.360 --> 00:14:15.200 core collapse. Because iron is produced in such vast quantities 286 00:14:15.240 --> 00:14:19.000 by the supernovae, its abundance in a star's atmosphere acts 287 00:14:19.039 --> 00:14:21.679 as a highly reliable clock for cosmic. 288 00:14:21.279 --> 00:14:24.600 Evolution, like counting tree rings almost sort of. 289 00:14:24.679 --> 00:14:28.000 Yeah, the more iron a star has, the more generations 290 00:14:28.000 --> 00:14:31.960 of supernovae preceded its birth. It's a measure of how polluted. 291 00:14:31.480 --> 00:14:33.600 The gas was, which makes sense. I mean, our modern 292 00:14:33.639 --> 00:14:36.200 sun formed roughly four point six billion years ago, right, 293 00:14:36.240 --> 00:14:38.000 so it was born from a nebula that had been 294 00:14:38.080 --> 00:14:42.000 heavily enriched by thousands, maybe millions of supernova cycles over 295 00:14:42.080 --> 00:14:46.440 billions of years. It's a highly complex chemical stew, very complex. 296 00:14:46.639 --> 00:14:48.720 So to find a star with an iron content forty 297 00:14:48.759 --> 00:14:51.120 times lower than the previous extreme, yeah, I mean it 298 00:14:51.159 --> 00:14:54.360 means stss JAY zero seven one five seven three three 299 00:14:54.399 --> 00:14:57.000 four formed from a pocket of gas that was almost 300 00:14:57.120 --> 00:14:58.759 entirely isolated. 301 00:14:58.360 --> 00:15:00.000 Like a completely untouched bubble. 302 00:15:00.200 --> 00:15:02.840 Exactly. It was touched by the ejecta of perhaps one 303 00:15:02.919 --> 00:15:06.919 single specific population three supernova, just one, and then the 304 00:15:06.919 --> 00:15:09.120 star lock that material away and hasn't changed since. 305 00:15:09.360 --> 00:15:13.039 That's incredible. But there is another crucial chemical marker here 306 00:15:13.080 --> 00:15:16.120 that makes this discovery unprecedented. Isn't there carbon? 307 00:15:16.480 --> 00:15:18.559 Yes? The carbon anomaly is huge. 308 00:15:18.759 --> 00:15:22.519 Let's dig into that, because usually when astronomers find extremely 309 00:15:22.600 --> 00:15:26.759 metal poor stars, they are weirdly rich in carbon. Is 310 00:15:26.799 --> 00:15:27.159 that right? 311 00:15:27.480 --> 00:15:30.559 You're exactly right. We call them carbon enhanced metal poor stars, 312 00:15:30.639 --> 00:15:34.679 or CEMP stars. Most of the ancient iron pore stars 313 00:15:34.720 --> 00:15:37.919 we find have these surprisingly high ratios of carbon in them. 314 00:15:37.960 --> 00:15:39.879 Why would they have so much carbon if everything else 315 00:15:39.960 --> 00:15:40.440 is missing? 316 00:15:40.559 --> 00:15:44.080 Well, this led astrophysicists to hypothesize that early in the universe, 317 00:15:44.200 --> 00:15:48.039 carbon fine structure line emission, basically carbon radiating heat away, 318 00:15:48.559 --> 00:15:51.440 was the primary cooling mechanism that allowed these low mass 319 00:15:51.480 --> 00:15:54.840 stars to form. The prevailing theory was that you absolutely 320 00:15:54.879 --> 00:15:58.159 needed an overabundance of carbon to cool the gas enough 321 00:15:58.200 --> 00:15:59.960 to make a small star like this one. 322 00:16:00.159 --> 00:16:03.200 But stss J zero seven one, five seven through three 323 00:16:03.279 --> 00:16:05.679 four shatters that model entirely, doesn't. 324 00:16:05.679 --> 00:16:08.720 It completely shatters it. It is exceptionally low abundances of 325 00:16:08.720 --> 00:16:11.639 both iron and carbon. According to the carbon cooling theory, 326 00:16:11.759 --> 00:16:13.799 this star physically should not exist. 327 00:16:13.879 --> 00:16:15.279 So what does that mean for the science? 328 00:16:15.639 --> 00:16:19.399 Its mere existence forces theorists right back to the drawing board. 329 00:16:20.360 --> 00:16:24.080 It proves that other mechanisms, like that mechanical shockwave compression 330 00:16:24.120 --> 00:16:27.919 we discussed earlier, or perhaps dust driven cooling pathways, we're 331 00:16:27.960 --> 00:16:31.320 capable of forming low mass stars. In the very earliest 332 00:16:31.279 --> 00:16:35.519 step box without needing high carbon. It's tangible proof exactly. 333 00:16:35.679 --> 00:16:39.759 You know, we rely on these incredibly complex supercomputer hydrodynamic 334 00:16:39.799 --> 00:16:43.519 simulations to model the early universe. We input all the physics, 335 00:16:43.600 --> 00:16:46.360 we hit play, and we see what the simulation predicts 336 00:16:46.360 --> 00:16:49.639 a first generation supernova should produce. But finding a physical 337 00:16:49.679 --> 00:16:52.720 star like this, it takes those models out of the 338 00:16:52.759 --> 00:16:53.840 realm of pure theory. 339 00:16:53.919 --> 00:16:55.039 You can actually check the math. 340 00:16:55.200 --> 00:16:57.279 We can look at the precise chemical ratios in its 341 00:16:57.279 --> 00:17:01.200 atmosphere and say with confidence, this the exact distribution of 342 00:17:01.240 --> 00:17:05.480 elements matches the nucleosynthetic yield of an asymmetrical explosion of 343 00:17:05.519 --> 00:17:09.480 a sixty solar mass population three star. It is empirical 344 00:17:09.519 --> 00:17:10.400 ground truth. 345 00:17:10.400 --> 00:17:14.039 Which really highlights the monumental challenge of actually finding empirical 346 00:17:14.079 --> 00:17:15.920 ground truth in the first place. I mean, let's talk 347 00:17:15.960 --> 00:17:18.759 about the logistics of this. The Milky Way galaxy contains 348 00:17:18.799 --> 00:17:22.160 somewhere between what one hundred and four hundred billion. 349 00:17:21.920 --> 00:17:23.480 Stars that's the current estimate. 350 00:17:23.559 --> 00:17:27.000 Yeah, and the vast overwhelming majority of them are modern, 351 00:17:27.160 --> 00:17:30.160 highly metallic stars like our sun. They are noisy, they 352 00:17:30.160 --> 00:17:32.880 are bright, and they are everywhere. So how do you 353 00:17:33.000 --> 00:17:37.319 find one single faint, low mass star with a zero 354 00:17:37.480 --> 00:17:40.920 point zero five percent metal content hiding in a sea 355 00:17:40.960 --> 00:17:43.799 of hundreds of billions of heavy metal descendants. 356 00:17:43.839 --> 00:17:45.359 Well, I can tell you you definitely don't do it 357 00:17:45.400 --> 00:17:47.359 by peering through an eyepiece on your back porch and 358 00:17:47.440 --> 00:17:48.160 just getting lucky. 359 00:17:48.319 --> 00:17:50.519 Right. It's a bit more involved than that, just a bit. 360 00:17:50.599 --> 00:17:54.599 You do it with industrial scale, highly automated stellar demographics. 361 00:17:54.960 --> 00:17:57.799 The methodology here is amazing. It relies on an interconnected 362 00:17:57.839 --> 00:18:01.920 ecosystem of observatories operating in tandem and the primary net 363 00:18:01.960 --> 00:18:04.920 the big sweep is cast by the Sloan Digital Sky 364 00:18:05.039 --> 00:18:08.680 Survey V, which is currently directed by the astrophysicist Juna 365 00:18:08.720 --> 00:18:10.880 Colemeyer right SDSSV. 366 00:18:11.240 --> 00:18:14.319 And it's important to note this isn't taking pretty full 367 00:18:14.359 --> 00:18:17.759 color pictures of nebulae for desktop background. No, it's a 368 00:18:17.880 --> 00:18:22.000 massive spectroscopic survey. They are taking the optical and infrared 369 00:18:22.000 --> 00:18:26.759 spectra of millions of stars simultaneously using these robotic fiber positioners. 370 00:18:26.440 --> 00:18:30.200 Which is a monumental engineering feat in itself. But we 371 00:18:30.240 --> 00:18:34.359 need to explain how high resolution spectroscopy actually extracts this 372 00:18:34.440 --> 00:18:38.240 information because it's not intuitive, Okay, laid out for us obviously, 373 00:18:38.279 --> 00:18:41.240 We can't send a probe eighty thousand light years away 374 00:18:41.319 --> 00:18:43.119 to scoop up some plasma in a jar and bring 375 00:18:43.160 --> 00:18:45.160 it back to a lab. We have to decode the 376 00:18:45.200 --> 00:18:49.759 starlight itself. When the light from sdss JAY zero seven 377 00:18:49.880 --> 00:18:53.000 one five seven three three four finally reaches Earth, it 378 00:18:53.079 --> 00:18:56.319 is a composite of every single wavelength emitted by its hot. 379 00:18:56.160 --> 00:18:57.880 Surface, a full rainbow of light. 380 00:18:58.160 --> 00:19:00.960 Right. But as that light pass asses through the star's 381 00:19:01.039 --> 00:19:04.200 cooler outer atmosphere on its way out, the atoms in 382 00:19:04.200 --> 00:19:07.240 that atmosphere absorb very specific frequencies. 383 00:19:06.720 --> 00:19:09.319 Of light, depending on the element, Right, Like an electron 384 00:19:09.400 --> 00:19:11.799 in an iron atom will absorb a photon of a 385 00:19:11.920 --> 00:19:14.759 very specific wavelength to jump to a higher energy state. 386 00:19:14.880 --> 00:19:18.359 Precisely, the physics of quantum mechanics dictates that an atom 387 00:19:18.400 --> 00:19:21.880 can only absorb exact, discrete packets of energy. So when 388 00:19:21.920 --> 00:19:24.279 you take that incoming starlight and run it through a spectrograph, 389 00:19:24.480 --> 00:19:27.559 you spread it out into a continuum a rainbow. But 390 00:19:27.640 --> 00:19:30.279 wherever an atom in the star's atmosphere absorbed a photon, 391 00:19:30.720 --> 00:19:32.680 there is a dark gap in the spectrum. 392 00:19:32.319 --> 00:19:34.720 An absorption line or a frontoffer line. 393 00:19:34.839 --> 00:19:38.400 Yes, and when you look at it It literally looks 394 00:19:38.440 --> 00:19:41.359 like a highly complex bar code. The depth and the 395 00:19:41.359 --> 00:19:43.440 width of those dark lines in the bar code tell 396 00:19:43.480 --> 00:19:46.559 you exactly how much of a specific element is present 397 00:19:46.599 --> 00:19:47.880 in that star's atmosphere. 398 00:19:48.240 --> 00:19:51.720 But capturing a high resolution spectrum where you can measure 399 00:19:51.759 --> 00:19:54.519 the width of an absorption line down to like fractions 400 00:19:54.519 --> 00:19:57.480 of an angstrum just to detect a point zero zero 401 00:19:57.640 --> 00:20:01.799