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 --> 00:00:26.839 slumber under the night sky. 7 00:00:27.000 --> 00:00:30.160 So if you look up at the night sky tonight, 8 00:00:30.640 --> 00:00:33.280 the light hitting your eye is well, it's basically a 9 00:00:33.320 --> 00:00:33.799 time machine. 10 00:00:33.880 --> 00:00:35.000 Yeah, that's exactly what it is. 11 00:00:35.039 --> 00:00:37.520 I mean, the glow from the Andromeda galaxy alone took 12 00:00:37.560 --> 00:00:39.240 like two and a half million years to reach you. 13 00:00:39.600 --> 00:00:41.640 But it makes you wonder, you know what did the 14 00:00:41.759 --> 00:00:44.119 very first light in the universe actually look like? 15 00:00:44.280 --> 00:00:47.240 Right, the absolute first starlight exactly. 16 00:00:47.520 --> 00:00:50.799 And for decades the universe's original stars were just these 17 00:00:51.840 --> 00:00:55.439 these ghosts, like the math told us they had to exist, 18 00:00:55.479 --> 00:00:57.359 but telescopes saw absolutely nothing. 19 00:00:58.359 --> 00:01:01.520 But today, in this deep dive, we are finally crossing 20 00:01:01.520 --> 00:01:05.560 that threshold from mathematical theory to concrete reality. We have 21 00:01:05.640 --> 00:01:07.680 actually found the first starlight. 22 00:01:08.120 --> 00:01:11.079 It's honestly a monumental shift in astrophysics, Like we are 23 00:01:11.120 --> 00:01:13.599 no longer just guessing about the conditions of the early 24 00:01:13.640 --> 00:01:17.040 cosmos based on computer simulations. 25 00:01:16.439 --> 00:01:18.040 Which is what we've been doing for years. 26 00:01:18.239 --> 00:01:21.400 Right now, we're talking about the direct observation of a tiny, 27 00:01:21.680 --> 00:01:27.000 incredibly ancient cosmic object, something that existed just four hundred 28 00:01:27.079 --> 00:01:28.599 million years after the Big Bang. 29 00:01:28.640 --> 00:01:31.319 Wow, four hundred million years. That sounds like a long time, 30 00:01:31.319 --> 00:01:34.760 but on a cosmic scale, it's nothing. To put that 31 00:01:34.840 --> 00:01:37.879 in perspective for you. If the universe is current thirteen 32 00:01:37.920 --> 00:01:41.159 point eight billion year lifespan was scaled down to a 33 00:01:41.200 --> 00:01:44.200 single calendar year, we're looking at something that happened in 34 00:01:44.239 --> 00:01:45.319 the first week of January. 35 00:01:45.439 --> 00:01:45.920 Oh wow. 36 00:01:46.280 --> 00:01:49.280 Yeah, the universe was barely a toddler, and yet it 37 00:01:49.319 --> 00:01:52.760 was already constructing things of just unimaginable scale. 38 00:01:53.120 --> 00:01:55.560 I want to focus on that phrase you use, direct observation, 39 00:01:56.079 --> 00:02:00.519 because for anyone who has just casually followed astronomy, the 40 00:02:00.640 --> 00:02:03.040 narrative has always been that the first generation of stars 41 00:02:03.120 --> 00:02:04.359 is fundamentally out of reach. 42 00:02:04.519 --> 00:02:06.799 Yeah, that they burned out billions of years ago and 43 00:02:06.799 --> 00:02:07.640 we'd never see them. 44 00:02:07.799 --> 00:02:10.639 Right. So the idea that we can now point a 45 00:02:10.680 --> 00:02:14.479 telescope at a patch of seemingly empty space and capture 46 00:02:14.520 --> 00:02:18.719 the actual light emitted by these primordial giants is staggering. 47 00:02:19.439 --> 00:02:21.639 So today we're going to explore this origin story. We'll 48 00:02:21.680 --> 00:02:25.240 break down how astronomers capture this ancient light, what these 49 00:02:25.240 --> 00:02:29.240 colossal structures were actually made of, and how they basically 50 00:02:29.280 --> 00:02:32.240 set the chemical stage for absolutely everything that exists today. 51 00:02:32.719 --> 00:02:35.599 And to really appreciate the sheer scale of this breakthrough, 52 00:02:35.879 --> 00:02:38.719 we need to completely discard our modern understanding of what 53 00:02:38.759 --> 00:02:39.960 a star actually is. 54 00:02:40.240 --> 00:02:43.400 Okay, let's unpack this. Discard it how well. 55 00:02:43.240 --> 00:02:46.159 If you look at our sun, we're serious or batel juice, 56 00:02:46.560 --> 00:02:52.000 You're looking at a highly evolved, chemically complex object. Astronomers 57 00:02:52.039 --> 00:02:55.759 categorize stars into different populations based on their chemical. 58 00:02:55.400 --> 00:02:56.599 Makeup, right, I've heard of this. 59 00:02:56.800 --> 00:02:59.919 So our Sun is a Population I star. It's relatively young, 60 00:03:00.560 --> 00:03:03.319 and it's rich and heavier elements. If you look at 61 00:03:03.319 --> 00:03:05.639 the older stars orbiting in the outer halo of the 62 00:03:05.639 --> 00:03:09.199 Milky Way, those are population two stars. They have fewer 63 00:03:09.240 --> 00:03:10.800 heavy elements, but they still have. 64 00:03:10.719 --> 00:03:12.919 Some, which means there has to be a population three 65 00:03:13.039 --> 00:03:13.800 right there is. 66 00:03:14.000 --> 00:03:18.639 Conceptually, population three stars are the universe's absolute first generation 67 00:03:18.719 --> 00:03:21.800 of stars, and they operate under a completely different set 68 00:03:21.800 --> 00:03:24.520 of physical laws than anything burning in the sky today 69 00:03:24.560 --> 00:03:26.919 because of what they're made of exactly. It all comes 70 00:03:26.960 --> 00:03:29.919 down to the chemical inventory of the universe immediately following 71 00:03:29.960 --> 00:03:30.520 the Big Bang. 72 00:03:30.680 --> 00:03:34.159 Let's dive into that inventory, because when the universe first 73 00:03:34.439 --> 00:03:38.039 cooled enough for matter to form, it wasn't exactly a 74 00:03:38.080 --> 00:03:40.120 diverse chemical playground, was it. 75 00:03:40.000 --> 00:03:43.280 Not at all? It was profoundly simple. Our modern sun 76 00:03:43.360 --> 00:03:46.759 has trace amounts of carbon, oxygen, nitrogen, iron. 77 00:03:46.680 --> 00:03:48.560 All just churning inside of it, right. 78 00:03:48.560 --> 00:03:51.680 But population third stars had absolutely none of that. They 79 00:03:51.719 --> 00:03:56.919 formed from sprawling clouds of essentially pure hydrogen and helium. 80 00:03:57.120 --> 00:04:00.520 So heavier elements like carbon and iron simple did not 81 00:04:00.639 --> 00:04:02.479 exist anywhere in the cosmosne you know. 82 00:04:02.479 --> 00:04:05.520 They had literally never been forged. The timeline of that 83 00:04:05.599 --> 00:04:09.199 early chemistry is really fascinating. During the first three minutes 84 00:04:09.199 --> 00:04:13.680 after the Big Bang, the universe was essentially an unfathomably hot, 85 00:04:14.120 --> 00:04:16.199 dense nuclear reactor. 86 00:04:16.000 --> 00:04:18.680 Just protons and neutrons slamming into each other. 87 00:04:18.600 --> 00:04:21.800 Exactly fusing to create the first atomic nuclei. But the 88 00:04:21.920 --> 00:04:25.199 universe was expanding and cooling so rapidly that this cosmic 89 00:04:25.199 --> 00:04:27.639 reactor shut down incredibly. 90 00:04:27.040 --> 00:04:28.959 Fast, So the window just closed, slam. 91 00:04:28.800 --> 00:04:30.839 Shut by the time the universe was cool enough for 92 00:04:30.879 --> 00:04:34.160 stable atoms to form, that brief window for nuclear fusion 93 00:04:34.279 --> 00:04:37.639 was gone. The final tally was roughly seventy five percent hydrogen, 94 00:04:37.839 --> 00:04:41.720 twenty five percent helium, and a tiny, almost negligible trace 95 00:04:41.800 --> 00:04:44.519 of lithium. That was the entire periodic table. 96 00:04:44.759 --> 00:04:47.639 Okay, So just to clarify the terminology here, because I 97 00:04:47.680 --> 00:04:51.160 know the astrophysics community has a very specific, almost strained 98 00:04:51.199 --> 00:04:54.399 way of talking about elements. To a normal person, a 99 00:04:54.439 --> 00:04:58.040 metal is something shiny, you know, like gold, silver, iron. 100 00:04:58.319 --> 00:05:01.879 Yeah, but in astronomy the definition is drastically simplified. A 101 00:05:01.920 --> 00:05:05.240 metal is literally any element heavier than helium. 102 00:05:05.519 --> 00:05:07.759 So wait, oxygen is a metal, Yes. 103 00:05:08.319 --> 00:05:12.759 Carbon, nitrogen, neons, silicon. Astronomers call all of them metals. 104 00:05:13.079 --> 00:05:14.160 It is so weird. 105 00:05:14.480 --> 00:05:17.319 It's a quirky terminology, sure, but the reason for it 106 00:05:17.360 --> 00:05:20.319 is that hydrogen and helium are the primordial building blocks. 107 00:05:20.319 --> 00:05:23.120 They're the default state of the universe. Everything else was 108 00:05:23.120 --> 00:05:25.839 manufactured later inside the cores of stars. 109 00:05:26.279 --> 00:05:29.120 So when we talk about the environment that birth these 110 00:05:29.160 --> 00:05:32.959 population third stars, we describe it as metal free, right. 111 00:05:33.079 --> 00:05:35.879 They were born out of massive collapse in clouds of 112 00:05:36.000 --> 00:05:37.759 absolutely pristine gas. 113 00:05:38.000 --> 00:05:40.879 Okay, but if there are no metals, wouldn't the gas 114 00:05:40.920 --> 00:05:43.920 cloud just stay a cloud. I'm trying to visualize the 115 00:05:43.959 --> 00:05:46.879 mechanics here, like, how does a cloud of pure hydrogen 116 00:05:46.920 --> 00:05:50.360 and helium actually condense into a functioning star? Because I 117 00:05:50.360 --> 00:05:53.120 imagine a giant cloud of gas floating in space is 118 00:05:53.120 --> 00:05:56.000 going to get incredibly hot as starts to get squeezed 119 00:05:56.000 --> 00:05:57.839 by gravity, and heat wants to expand. 120 00:05:57.920 --> 00:06:00.920 Right, You've hit on the central physics crisis of the 121 00:06:00.959 --> 00:06:04.079 early universe. The formation of a star is fundamentally a 122 00:06:04.120 --> 00:06:07.639 battle between gravity and thermal pressure. Gravity wants to pull 123 00:06:07.720 --> 00:06:11.279 all that gas inward, crushing it down into a dense core. 124 00:06:11.560 --> 00:06:13.680 But as you can press gas, it heats. 125 00:06:13.480 --> 00:06:16.800 Up exactly and that thermal energy creates an outward pressure 126 00:06:16.879 --> 00:06:19.600 fighting the gravity. So in order for gravity to actually 127 00:06:19.639 --> 00:06:21.920 win the battle and collapse the cloud into a star, 128 00:06:22.360 --> 00:06:24.399 the cloud must have a way to cool down, has 129 00:06:24.439 --> 00:06:26.160 to bleed off that heat into space. 130 00:06:26.720 --> 00:06:29.920 Well, in modern star forming regions, like say the Orion nebula, 131 00:06:30.480 --> 00:06:32.160 how does the gas cool down today? 132 00:06:32.560 --> 00:06:35.199 It uses those heavy elements, the metals we just talked about, 133 00:06:35.560 --> 00:06:39.000 carbon and oxygen. Atoms are fantastic at radiating away heat. 134 00:06:39.279 --> 00:06:41.800 When atoms in a gas cloud collide, they excite the 135 00:06:41.839 --> 00:06:45.279 electrons and the carbon and oxygen atoms, and then what happens, Well, 136 00:06:45.399 --> 00:06:48.160 those electrons quickly drop back down to their normal state, 137 00:06:48.560 --> 00:06:51.600 and in the process they emit a photon, a particle 138 00:06:51.639 --> 00:06:56.240 of light. That photon escapes the cloud, carrying away a 139 00:06:56.279 --> 00:07:00.680 tiny bit of thermal energy oh I see sollions upon 140 00:07:00.759 --> 00:07:04.680 trillions of these escaping photons effectively act as a cosmic 141 00:07:04.720 --> 00:07:09.120 cooling system. Because the gas cloud can efficiently radiate heat 142 00:07:09.120 --> 00:07:13.759 away into space, it cools down, loses its internal thermal pressure, 143 00:07:14.079 --> 00:07:16.720 and fragments into many smaller clumps, and. 144 00:07:16.680 --> 00:07:21.240 Those clumps then collapse easily to form relatively small, stable 145 00:07:21.279 --> 00:07:23.839 stars like our sun. Exactly so, the heavy metals are 146 00:07:23.879 --> 00:07:27.040 essentially a car's radiator system. They let the heat escape 147 00:07:27.240 --> 00:07:28.879 so the engine doesn't blow itself apart. 148 00:07:28.959 --> 00:07:30.399 That's a perfect way to look at it. 149 00:07:30.480 --> 00:07:33.519 But the primordial clouds in the early universe didn't have radiators. 150 00:07:33.879 --> 00:07:35.800 They had no carbon or oxygen, right. 151 00:07:35.879 --> 00:07:38.639 Pure hydrogen and helium are terrible at cooling down at 152 00:07:38.680 --> 00:07:41.879 the temperatures required for star formation. Their atomic structures just 153 00:07:41.920 --> 00:07:45.360 don't allow them to emit photons efficiently. Under those specific conditions. 154 00:07:45.680 --> 00:07:48.120 So you basically have a massive cloud of gas being 155 00:07:48.120 --> 00:07:51.399 pulled inward by gravity, heating up fiercely, and it has 156 00:07:51.600 --> 00:07:54.360 absolutely no way to vent that heat none. 157 00:07:54.680 --> 00:07:57.560 The thermal pressure pushing outward becomes immense. 158 00:07:57.800 --> 00:08:00.600 So if the cloud is basically an engine running incredibly 159 00:08:00.600 --> 00:08:03.160 hot with no radiator, the only way to keep it 160 00:08:03.160 --> 00:08:06.000 from blowing apart is to build the engine block out 161 00:08:06.000 --> 00:08:10.240 of thicker, heavier, massive amounts of steel. And in this 162 00:08:10.360 --> 00:08:14.480 cosmic scenario, that steel is sheer gravitational force. 163 00:08:15.040 --> 00:08:18.879 That is a brilliant analogy. To overcome that immense trapped 164 00:08:18.920 --> 00:08:22.959 thermal pressure, gravity had to win through brute force. A 165 00:08:23.000 --> 00:08:26.360 small clump of primordial gas simply didn't have enough gravitational 166 00:08:26.399 --> 00:08:28.480 pull to crush itself into a star. 167 00:08:28.879 --> 00:08:30.680 It just couldn't overcome the heat, right. 168 00:08:30.800 --> 00:08:34.519 The cloud had to accumulate a staggering, almost incomprehensible amount 169 00:08:34.559 --> 00:08:37.399 of mass before the inward pull of gravity could finally 170 00:08:37.440 --> 00:08:40.720 overpower the outward push up the trapped heat. The result 171 00:08:40.919 --> 00:08:43.799 was inevitable. The stars that form from these clouds had 172 00:08:43.840 --> 00:08:47.879 to be extremely massive. We are talking about stellar behemoths. 173 00:08:47.440 --> 00:08:49.399 And because they were so massive, the pressure at their 174 00:08:49.440 --> 00:08:51.840 cores must have been off the charts, which I'm guessing 175 00:08:51.879 --> 00:08:52.799 dictates how they burn. 176 00:08:53.080 --> 00:08:56.960 The core temperatures and pressures were unfathomably high. And here's 177 00:08:57.000 --> 00:09:00.720 the brutal irony of stellar physics. I'd assume that a 178 00:09:00.759 --> 00:09:04.039 massive star, having collected so much fuel, would live a 179 00:09:04.120 --> 00:09:06.679 very long time. Like it has a massive gas tank, right. 180 00:09:06.639 --> 00:09:08.320 Yeah, you'd think it would burn for eons. 181 00:09:08.519 --> 00:09:11.639 But because gravity is squeezing that core so intensely, the 182 00:09:11.720 --> 00:09:16.240 nuclear fusion reactions happen at a furious, runaway pace. It's 183 00:09:16.360 --> 00:09:20.320 literally a cosmic bonfire burning out of control. While a 184 00:09:20.399 --> 00:09:23.519 smaller star like our Sun SIPs its fuel and will 185 00:09:23.559 --> 00:09:27.240 happily burn for about ten billion years, these massive population 186 00:09:27.320 --> 00:09:31.320 third stars just guzzled their hydrogen. Wow, they burned through 187 00:09:31.360 --> 00:09:34.200 their entire fuel supply in just a few million years. 188 00:09:34.679 --> 00:09:38.000 On a cosmological timescale, a few million years is a 189 00:09:38.039 --> 00:09:39.679 mere blip. It's the blink of an eye. 190 00:09:39.720 --> 00:09:42.480 So they lived on fast forward. But what happens when 191 00:09:42.480 --> 00:09:45.960 that massive gas tank hits empty? Because a star that 192 00:09:46.159 --> 00:09:49.120 huge doesn't just quietly fade away or puff out its 193 00:09:49.159 --> 00:09:49.840 outer layers. 194 00:09:49.919 --> 00:09:52.799 Oh no. The end of a population third star's life 195 00:09:52.840 --> 00:09:55.399 was among the most violent events since the Big Bang itself. 196 00:09:55.799 --> 00:09:58.159 When the hydrogen and helium fuel in the core finally 197 00:09:58.240 --> 00:10:02.039 runs out, the outward pressure generated by nuclear fusion suddenly stops, 198 00:10:02.320 --> 00:10:06.440 just instantly, basically, and in that instant, gravity which has 199 00:10:06.480 --> 00:10:10.080 been waiting patiently for millions of years, takes over completely. 200 00:10:10.480 --> 00:10:13.799 The entire immense mass of the star collapses inward in 201 00:10:13.840 --> 00:10:14.919 a fraction of a second. 202 00:10:15.000 --> 00:10:16.039 That is terrifying. 203 00:10:16.159 --> 00:10:20.480 The core is crushed to an unimaginable density, temperatures spike 204 00:10:20.559 --> 00:10:23.840 into the billions of degrees, and the star violently rebounds 205 00:10:23.879 --> 00:10:28.200 in a colossal explosion. A supernova, yes, but given the 206 00:10:28.200 --> 00:10:30.559 sheer mass of these stars, we are talking about a 207 00:10:30.559 --> 00:10:35.759 completely different scale of explosion. Astrophysicists believe many of these 208 00:10:35.759 --> 00:10:38.399 stars ended their lives in what is called a pair 209 00:10:38.639 --> 00:10:40.360 instability supernova. 210 00:10:40.600 --> 00:10:41.519 Okay, what does that mean. 211 00:10:41.639 --> 00:10:44.720 It's a catastrophic event where the core becomes so incredibly 212 00:10:44.759 --> 00:10:47.559 hot that the high energy photon so the light itself 213 00:10:47.919 --> 00:10:52.480 actually spontaneously convert into pairs of matter and antimatter particles, 214 00:10:52.840 --> 00:10:55.240 specifically electrons and positrons. 215 00:10:55.240 --> 00:10:57.200 Oh wait, wait, the light inside the star gets so 216 00:10:57.279 --> 00:11:00.840 intense it literally turns into solid matter and anti yeah. 217 00:11:00.639 --> 00:11:03.759 It's the energy mass equivalence E equals MC squared in 218 00:11:03.799 --> 00:11:08.679 spectacular action. But here's the thing. Photons exert pressure. Particles 219 00:11:08.720 --> 00:11:10.480 do not exert the same kind of pressure. 220 00:11:10.720 --> 00:11:11.960 Oh, I see where this is going. 221 00:11:12.039 --> 00:11:14.799 So the moment the light turns into matter and anti matter, 222 00:11:15.159 --> 00:11:19.240 the internal pressure holding the star up suddenly plummets. It's 223 00:11:19.279 --> 00:11:22.600 like pulling the supporting pillars out from under a skyscraper. 224 00:11:22.840 --> 00:11:23.639 It just falls. 225 00:11:23.879 --> 00:11:29.039 The star experiences a catastrophic collapse, triggering a runaway thermonuclear 226 00:11:29.120 --> 00:11:33.200 explosion that completely obliterates the star. There is no black 227 00:11:33.200 --> 00:11:37.000 hole left behind, no neutron star. The entire star is 228 00:11:37.080 --> 00:11:39.120 blown apart into the surrounding universe. 229 00:11:39.320 --> 00:11:42.600 And that explosion is the crucial mechanism for the rest 230 00:11:42.639 --> 00:11:46.600 of the universe's history because during their short, furious lives 231 00:11:46.960 --> 00:11:50.879 inside those blistering cores, these population third stars were doing 232 00:11:50.960 --> 00:11:52.679 something unprecedented exactly. 233 00:11:52.720 --> 00:11:55.240 They were taking that pure hydrogen and helium and fusing 234 00:11:55.279 --> 00:11:58.279 it into heavier elements. They were forging the first carbon, 235 00:11:58.360 --> 00:12:01.320 the first oxygen, the first silicon, the first iron, And 236 00:12:01.360 --> 00:12:04.559 when they detonated, they blasted all of those newly forged 237 00:12:04.600 --> 00:12:05.440 elements outward. 238 00:12:05.559 --> 00:12:07.480 They polluted the pristine universe. 239 00:12:07.879 --> 00:12:11.600 Yes, they seated the surrounding clouds of hydrogen and helium 240 00:12:11.720 --> 00:12:15.440 with those crucial heavy elements, and that changed the mechanics 241 00:12:15.480 --> 00:12:18.679 of the cosmos forever. The gas clouds that formed in 242 00:12:18.679 --> 00:12:22.440 the aftermath of these explosions now had those radiators. 243 00:12:22.600 --> 00:12:26.039 They had the carbon and oxygen needed to cool down efficiently. 244 00:12:25.679 --> 00:12:29.159 Right, which meant those subsequent clouds could fragment, allowing for 245 00:12:29.200 --> 00:12:32.679 the formation of the smaller, longer lived stars we see today, 246 00:12:33.039 --> 00:12:35.440 the Population two and Population I stars. 247 00:12:35.559 --> 00:12:37.200 You know, think about this next time you drink a 248 00:12:37.200 --> 00:12:40.639 glass of water. It's a wild thought experiment. The hydrogen 249 00:12:40.679 --> 00:12:43.399 atoms in that glass of water are thirteen point eight 250 00:12:43.519 --> 00:12:47.559 billion years old. They were forged in the chaotic aftermath 251 00:12:47.600 --> 00:12:48.600 of the Big Bang itself. 252 00:12:48.639 --> 00:12:50.120 Yeah, it's amazing to think about. 253 00:12:50.360 --> 00:12:54.120 But the oxygen atom they're bonded to, that oxygen didn't 254 00:12:54.120 --> 00:12:56.679 exist at the beginning of time. It was forged in 255 00:12:56.720 --> 00:13:00.279 the explosive death of a population third star. When you 256 00:13:00.279 --> 00:13:02.519 take a sip of water, you are basically consuming a 257 00:13:02.600 --> 00:13:05.639 mixture of the beginning of time and the catastrophic death 258 00:13:05.679 --> 00:13:06.919 of a primordial giant. 259 00:13:07.000 --> 00:13:08.639 It's deeply poetic. 260 00:13:08.519 --> 00:13:12.159 Right, Every atom of calcium in your bones, the iron 261 00:13:12.200 --> 00:13:16.279 carrying oxygen in your blood was exclusively made possible because 262 00:13:16.320 --> 00:13:20.240 these massive first stars lived fast and died spectacularly. 263 00:13:20.480 --> 00:13:24.159 Without population third stars acting as the universe's first foundaries, 264 00:13:24.639 --> 00:13:28.600 planets like Earth could never have formed the chemistry required 265 00:13:28.639 --> 00:13:32.080 for biology. It would be totally impossible. The universe would 266 00:13:32.080 --> 00:13:35.159 have remained just a sterile, monotonous expanse of hydrogen and 267 00:13:35.240 --> 00:13:36.879 helium gas forever. 268 00:13:37.480 --> 00:13:40.559 So finding evidence of these stars isn't just about filling 269 00:13:40.600 --> 00:13:43.679 in a blank spot in an astronomical textbook, not at all. 270 00:13:43.759 --> 00:13:46.200 It's confirming the very first link in the chain of 271 00:13:46.240 --> 00:13:49.240 cosmic events that ultimately led to biological life. 272 00:13:49.279 --> 00:13:51.720 I mean, I understand the theory, and the stakes obviously 273 00:13:51.720 --> 00:13:55.080 couldn't be higher. But moving from theory to observation presents 274 00:13:55.120 --> 00:13:59.080 an obvious physical problem. If these stars lived incredibly short 275 00:13:59.120 --> 00:14:02.320 lives and blew themselves to pieces thirteen billion years ago, 276 00:14:02.639 --> 00:14:04.399 how do we actually find them. We can't just go 277 00:14:04.399 --> 00:14:06.840 looking for their ashes. We want to see the stars themselves. 278 00:14:07.000 --> 00:14:07.200 Well. 279 00:14:07.279 --> 00:14:09.360 The only way to see a star that lived and 280 00:14:09.399 --> 00:14:13.320 died thirteen billion years ago is to look thirteen billion 281 00:14:13.440 --> 00:14:17.720 light years away, because light takes time. To travel through space. 282 00:14:18.200 --> 00:14:20.720 Telescopes act as literal time machines. 283 00:14:20.879 --> 00:14:22.960 Right the further away we look, the further back. 284 00:14:22.759 --> 00:14:25.159 In time we see exactly if we look deep enough 285 00:14:25.200 --> 00:14:28.159 into the cosmos, we aren't seeing the universe as it 286 00:14:28.240 --> 00:14:30.519 is today. We are seeing it as it was when 287 00:14:30.600 --> 00:14:33.879 that light first began its journey. So to find population 288 00:14:34.039 --> 00:14:37.600 third stars, we have to look incredibly far away, targeting 289 00:14:37.600 --> 00:14:40.000 an arrow when the universe was only a few hundred 290 00:14:40.080 --> 00:14:42.960 million years old. We have to catch them while they 291 00:14:42.960 --> 00:14:45.080 are still actively forming and burning. 292 00:14:45.480 --> 00:14:48.600 Which brings us to the physical location of this major discovery, 293 00:14:49.120 --> 00:14:52.159 because we're zooming in on a very specific cosmic neighborhood. 294 00:14:52.720 --> 00:14:56.200 It involves a galaxy known as GNZ eleven. Now, in 295 00:14:56.200 --> 00:14:59.360 the world of astrophysics, GNZ eleven is already kind of famous, 296 00:14:59.399 --> 00:14:59.679 isn't it. 297 00:14:59.720 --> 00:14:59.879 Oh? 298 00:15:00.000 --> 00:15:02.840 Absolutely, It's one of the most distant, oldest and brightest 299 00:15:02.879 --> 00:15:05.039 known galaxies in the very early universe. 300 00:15:05.320 --> 00:15:08.200 But the focus of this breakthrough isn't the galaxy itself. 301 00:15:08.720 --> 00:15:12.919 It's a faint, seemingly insignificant companion object located right next 302 00:15:12.919 --> 00:15:15.840 to it, which drama is called hebe right Hebee. 303 00:15:15.919 --> 00:15:18.440 It's situated in what we call the halo of the galaxy. 304 00:15:18.639 --> 00:15:21.919 It's located just three kiloparsecs away from the luminous core 305 00:15:21.960 --> 00:15:22.919 of GNZ eleven. 306 00:15:22.960 --> 00:15:26.360 Okay, three kiloparsex. Let's translate the spatial geography for a second. 307 00:15:26.480 --> 00:15:29.240 A kilopartech is about three thousand, two hundred and sixty 308 00:15:29.320 --> 00:15:32.480 light years, So three killoparsex is roughly ten thousand light 309 00:15:32.559 --> 00:15:35.919 years away to a human walking on Earth. Ten thousand 310 00:15:35.960 --> 00:15:39.679 light years is a vast, unimaginable distance. But on a 311 00:15:39.720 --> 00:15:42.600 cosmic scale, if we look at massive structures like galaxies, 312 00:15:43.000 --> 00:15:45.159 is he Be basically just sitting in the immediate suburbs 313 00:15:45.159 --> 00:15:46.799 of gnzlel Oh, Yeah. 314 00:15:46.679 --> 00:15:49.840 Three kiloparsex is practically right next door. In galactic terms. 315 00:15:50.159 --> 00:15:52.399 To give you some spatial context, the bright disc of 316 00:15:52.440 --> 00:15:55.039 our own Milky Way galaxy is roughly one hundred thousand 317 00:15:55.120 --> 00:15:57.919 light years across, so Hebe is sitting well within the 318 00:15:57.919 --> 00:16:01.799 gravitational sphere of influence the halo GZ eleven. It's deeply 319 00:16:01.960 --> 00:16:03.519 entwined with the galaxy's environment. 320 00:16:03.720 --> 00:16:07.440 But wait, that raises a massive observational red flag for me. 321 00:16:08.480 --> 00:16:10.279 If he Be is that close to one of the 322 00:16:10.279 --> 00:16:14.200 brightest galaxies in the early universe, shouldn't the sheer, blinding 323 00:16:14.240 --> 00:16:18.120 brightness of GenZ eleven completely wash out our ability to 324 00:16:18.159 --> 00:16:21.440 see a tiny, faint companion. It sounds like trying to 325 00:16:21.480 --> 00:16:24.879 spot a firefly fluttering right next to a military grade searchlight. 326 00:16:25.000 --> 00:16:27.120 I mean, the glare alone should make it invisible. 327 00:16:27.240 --> 00:16:31.080 The glare is an astronomical nightmare. You're right. Telescopes suffer 328 00:16:31.120 --> 00:16:34.159 from diffraction, which is the way light bends and scatters 329 00:16:34.159 --> 00:16:37.720 when it enters the optics. A brilliantly bright object like 330 00:16:37.799 --> 00:16:41.360 GNZ eleven will naturally spill light into the surrounding pixels 331 00:16:41.399 --> 00:16:44.679 on a detector, potentially drowning out anything faint nearby. 332 00:16:45.000 --> 00:16:46.360 So how do we even see it? 333 00:16:46.759 --> 00:16:51.000 Well? Overcoming that glare requires incredible optical precision and sophisticated 334 00:16:51.039 --> 00:16:54.120 data processing to subtract the light of the host galaxy 335 00:16:54.159 --> 00:16:56.840 and isolate the faint signal of the companion. But what's 336 00:16:56.879 --> 00:16:59.720 fascinating here is that proximity, the very thing making it 337 00:16:59.720 --> 00:17:03.000 differicult to observe, is also exactly why hebe is the 338 00:17:03.080 --> 00:17:05.319 key to this whole mystery. Wait, how does. 339 00:17:05.200 --> 00:17:08.480 Being next to a blazing galaxy actually help the situation? Yeah, 340 00:17:08.519 --> 00:17:10.880 if G and Z eleven is so active, shouldn't it 341 00:17:10.920 --> 00:17:13.240 have already polluted its suburbs with heavy metals. 342 00:17:13.880 --> 00:17:17.160 The timeline of cosmic pollution is the critical factor here. 343 00:17:17.640 --> 00:17:20.680 Remember we are observing this system as it existed just 344 00:17:20.799 --> 00:17:24.559 four hundred million years after the Big Bang. GNZ eleven 345 00:17:24.599 --> 00:17:29.200 is indeed a bustling, intensely luminous galaxy experiencing a massive 346 00:17:29.240 --> 00:17:30.240 burst of star. 347 00:17:30.079 --> 00:17:32.920 Formation, So there is supernovae happening there constantly. 348 00:17:33.680 --> 00:17:37.480 The stars in its dense core are living, dying, and exploding, 349 00:17:37.799 --> 00:17:40.799 which means the very center of GNZ eleven is already 350 00:17:40.799 --> 00:17:44.880 becoming enriched with heavier elements. The core is polluted, but 351 00:17:44.960 --> 00:17:48.759 the universe is still incredibly young. The vast space surrounding 352 00:17:48.759 --> 00:17:51.920 the galaxy, the extended halo, hasn't been completely mixed yet. 353 00:17:52.079 --> 00:17:54.680 The supernoble winds haven't had enough time to push those 354 00:17:54.720 --> 00:17:58.240 heavy elements out to a distance of three kiloparsex. 355 00:17:57.640 --> 00:18:00.640 Ah, so this smog hasn't reached the suburbs precisely. 356 00:18:01.160 --> 00:18:03.519 The fact that hebeas sitting on the outskirts means it 357 00:18:03.559 --> 00:18:07.799 is still a pristine, uncontaminated pocket of primordial gas. It 358 00:18:07.839 --> 00:18:11.839 is a massive cloud of pure hydrogen and helium. Finding 359 00:18:11.920 --> 00:18:15.559 an uncontaminated area is rare enough, but finding one so 360 00:18:15.839 --> 00:18:19.079 close to a bright, intensely active galaxy is what makes 361 00:18:19.119 --> 00:18:21.559 he Be the perfect laboratory because. 362 00:18:21.319 --> 00:18:24.400 The intense radiation pouring out of GNZ eleven is essentially 363 00:18:24.440 --> 00:18:27.880 acting as a massive backlight. It's illuminating this pristine gas cloud, 364 00:18:28.039 --> 00:18:30.559 giving us a clear view of it without physically dumping 365 00:18:30.559 --> 00:18:31.519 heavy metals into it. 366 00:18:31.599 --> 00:18:34.759 Exactly. It provides the energetic context to make the cloud visible. 367 00:18:34.799 --> 00:18:36.960 And because the chemical makeup of Hebe is still pure, 368 00:18:37.000 --> 00:18:39.920 it's the exact type of raw, unpolluted environment where the 369 00:18:39.960 --> 00:18:44.160 massive metal free population through stars can still actively form. 370 00:18:44.759 --> 00:18:47.240 Okay, so we had our setting. We're staring deep into 371 00:18:47.279 --> 00:18:51.799 the halo of GNZ eleven, focusing on this tiny, uncontaminated 372 00:18:51.839 --> 00:18:55.319 suburb called Hebe, four hundred million years after the birth 373 00:18:55.359 --> 00:18:58.839 of time. But when astronomers say they observed Hebe, they 374 00:18:58.839 --> 00:19:01.079 didn't just get a high resolute suh polaroid picture of 375 00:19:01.119 --> 00:19:03.400 a giant star, right. I mean, they can't see the 376 00:19:03.400 --> 00:19:06.480 physical shape of a star from thirteen point four billion 377 00:19:06.559 --> 00:19:09.200 light years away. Everything is just a smudge of light. 378 00:19:09.720 --> 00:19:12.720 So what are they actually looking at to determine what's 379 00:19:12.839 --> 00:19:14.119 inside that smudge. 380 00:19:14.200 --> 00:19:18.920 You're absolutely right. At these extreme cosmological distances, spatial resolution, 381 00:19:19.119 --> 00:19:22.440 the ability to see physical details, is largely impossible for 382 00:19:22.519 --> 00:19:25.319 individual stars. Instead of looking at the shape of the light, 383 00:19:25.359 --> 00:19:28.480 astronomers analyze the behavior of the light. They rely on. 384 00:19:28.440 --> 00:19:31.000 Spectroscopy, breaking the light apart to see what it's made of. 385 00:19:31.279 --> 00:19:34.880 Spectroscopy is arguably the most powerful tool in all of astronomy. 386 00:19:35.200 --> 00:19:38.200 Imagine taking the faint light captured from hebee and passing 387 00:19:38.200 --> 00:19:41.559 it through a highly advanced prism or more accurately, a 388 00:19:41.599 --> 00:19:46.160 complex diffraction grating. This splits the light into its component wavelengths, 389 00:19:46.319 --> 00:19:48.720 spreading it out into a spectrum, much like a rainbow. 390 00:19:49.079 --> 00:19:50.839 And why is a rainbow of light useful? 391 00:19:51.119 --> 00:19:54.839 Because of quantum mechanics, every chemical element in the universe 392 00:19:54.880 --> 00:19:57.720 interacts with light in a unique way. An atom of 393 00:19:57.720 --> 00:20:02.039 oxygen will absorb and emit light at very specific exact wavelengths. 394 00:20:02.240 --> 00:20:05.039 An atom of carbon will do the same at different wavelengths. 395 00:20:05.359 --> 00:20:08.720 Lisa Mark exactly when we look at the spectrum of 396 00:20:08.839 --> 00:20:11.519 a distant object, we see dark lines where light has 397 00:20:11.559 --> 00:20:14.559 been absorbed by certain elements, and bright lines where light 398 00:20:14.640 --> 00:20:19.359 is being intensely emitted. That spectrum is a literal chemical barcode. 399 00:20:19.839 --> 00:20:21.960 By reading the barcode, we don't have to guess what 400 00:20:22.000 --> 00:20:24.680 an object is made of. The laws of quantum physics 401 00:20:24.720 --> 00:20:27.319