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 Astronomy 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 00:00:26.920 --> 00:00:30.519 I want you to just picture the total energy output 8 00:00:30.640 --> 00:00:33.759 of our sun. Oh wow, starting big, right, but I 9 00:00:33.799 --> 00:00:36.240 mean really picture it. Not just you know that the 10 00:00:36.280 --> 00:00:38.520 warmth you feel on your face on a summer afternoon. 11 00:00:38.600 --> 00:00:40.600 Yeah, that's just a tiny fracture exactly. 12 00:00:40.679 --> 00:00:46.359 I'm talking about the sheer, just incomprehensible fusion reaction that's 13 00:00:46.399 --> 00:00:50.200 required to heat an entire solar system constantly, right, constantly, 14 00:00:50.280 --> 00:00:52.799 every single second. I mean, the Sun has been burning 15 00:00:52.799 --> 00:00:55.719 steadily for what about four and a half billion years. 16 00:00:55.679 --> 00:00:59.679 Yeah, give or take a few hundred million, and. 17 00:00:59.640 --> 00:01:02.479 It has an fuel to keep going for roughly another 18 00:01:02.560 --> 00:01:06.599 five billion years, right yeah, okay, So imagine taking every 19 00:01:06.680 --> 00:01:10.200 last drop of that energy, the absolute sum total of 20 00:01:10.239 --> 00:01:12.480 a ten billion year stellar. 21 00:01:12.120 --> 00:01:14.799 Lifespan, the entire tank of gas, yes. 22 00:01:14.680 --> 00:01:17.680 And then detonating it all at once in a fraction 23 00:01:17.760 --> 00:01:18.560 of a single second. 24 00:01:18.840 --> 00:01:21.920 It's it's almost impossible to actually visualize that. 25 00:01:21.920 --> 00:01:24.760 It really is. But today we were launching into an 26 00:01:24.799 --> 00:01:28.439 exploration of exactly that. One of the most violent anomalies 27 00:01:28.519 --> 00:01:29.640 ever recorded in space. 28 00:01:29.760 --> 00:01:30.560 It's a wild one. 29 00:01:30.599 --> 00:01:33.680 We're going to figure out why an explosion that basically 30 00:01:33.680 --> 00:01:38.560 broke every law of stellar physics has astronomers completely, you know, 31 00:01:39.040 --> 00:01:40.680 rethinking the cosmic food chain. 32 00:01:41.079 --> 00:01:43.000 It really threw everyone for a loop, it did. 33 00:01:43.400 --> 00:01:46.040 So our mission today is to tear apart the data 34 00:01:46.079 --> 00:01:49.959 behind an event called ERB two five seven zero two 35 00:01:50.079 --> 00:01:53.920 B and we're going to hunt down a prime suspect 36 00:01:54.400 --> 00:01:57.439 that has eluded astrophysicists for half a century. 37 00:01:57.519 --> 00:02:00.079 And when we talk about this scale of violence, I 38 00:02:00.120 --> 00:02:03.200 mean it really challenges the limits of our mathematical mind. 39 00:02:03.280 --> 00:02:05.799 It's off the charts totally. When we talk about a 40 00:02:05.840 --> 00:02:08.560 gamma ray burst or you know at GRB, we are 41 00:02:08.639 --> 00:02:11.560 not just talking about a big explosion. We're talking about 42 00:02:11.560 --> 00:02:15.919 these single most energetic luminous electromagnetic events occurring in the 43 00:02:15.960 --> 00:02:17.360 universe since the Big Bang. 44 00:02:17.159 --> 00:02:19.680 Itself, like nothing else comes close nothing. 45 00:02:20.000 --> 00:02:22.919 And the fundamental foundational rule of a gamma ray burst 46 00:02:22.919 --> 00:02:25.560 a rule we've relied on since well since the very 47 00:02:25.560 --> 00:02:28.479 first ones were detected by those old Villa military satellites 48 00:02:28.520 --> 00:02:29.479 back in the late sixties. 49 00:02:29.560 --> 00:02:31.319 Right, the ones looking for nuclear. 50 00:02:31.000 --> 00:02:34.879 Tests exactly, But the foundational rule they established is brevity. 51 00:02:35.400 --> 00:02:36.280 They are fleeting. 52 00:02:36.520 --> 00:02:39.800 They are the ultimate one and done cosmic events. 53 00:02:39.960 --> 00:02:43.719 Yes, out of the roughly fifteen thousand bursts we have 54 00:02:43.800 --> 00:02:47.120 cataloged over the last fifty years, the vast majority are 55 00:02:47.159 --> 00:02:49.800 over before you can even consciously register them, like a 56 00:02:49.840 --> 00:02:53.159 blink of an eye faster. Actually, a short burst might 57 00:02:53.240 --> 00:02:56.120 last a few milliseconds wow. And even a long burst, 58 00:02:56.159 --> 00:02:58.439 which is driven by what we call the collapse or model, 59 00:02:58.719 --> 00:03:01.879 that might last a couple of minutes at the absolute extreme, but. 60 00:03:01.800 --> 00:03:04.599 The fuel source is exhausted almost instant. 61 00:03:04.360 --> 00:03:07.280 Always the engine turns on, burns everything, and dies. 62 00:03:07.639 --> 00:03:11.479 But that entire framework completely collapsed. On July two, twenty 63 00:03:11.520 --> 00:03:12.280 twenty five. 64 00:03:12.159 --> 00:03:12.800 It really did. 65 00:03:13.280 --> 00:03:17.080 NASA's Fermi gamma RaSE based telescope triggers an alert for 66 00:03:17.120 --> 00:03:20.400 this GRB two five zero two B, and instead of 67 00:03:20.400 --> 00:03:23.560 flashing and fading into the background radiation like it's supposed to, 68 00:03:23.919 --> 00:03:25.280 the alarm just kept ringing. 69 00:03:25.560 --> 00:03:26.280 He didn't stop. 70 00:03:26.400 --> 00:03:28.240 It didn't stop for seven hours. 71 00:03:28.080 --> 00:03:31.080 Which is just I mean, the duration alone sent shockwaves 72 00:03:31.120 --> 00:03:33.960 through the astrophysics community. To have a burst persist for 73 00:03:34.000 --> 00:03:37.840 seven hours is statistically off the charge impossible, right, But 74 00:03:37.879 --> 00:03:40.639 the continuous duration wasn't even the most baffling part of 75 00:03:40.680 --> 00:03:44.400 the telemetry. Oh yeah, the light curve data exactly. The 76 00:03:44.520 --> 00:03:48.719 data showed that this event fired off three completely distinct 77 00:03:48.919 --> 00:03:52.639 massive bursts of gamma radiation spread out across an entire 78 00:03:52.680 --> 00:03:54.000 twenty four hour period. 79 00:03:53.759 --> 00:03:55.840 Which is just insane to think about. 80 00:03:56.039 --> 00:03:59.400 And when the high energy emission finally ceased, it left 81 00:03:59.400 --> 00:04:03.360 behind this multi wavelength after glow. 82 00:04:03.240 --> 00:04:05.840 Like visible in X ray, optical and radio bands. 83 00:04:05.879 --> 00:04:08.400 Right, yeah, all of them, and that lingering after glow 84 00:04:08.479 --> 00:04:09.319 lasted for months. 85 00:04:09.400 --> 00:04:12.159 Okay, let's unpack this because the contrast here is the 86 00:04:12.199 --> 00:04:15.319 crux of the entire mystery. If your standard gamma ray 87 00:04:15.360 --> 00:04:18.560 burst is like a single devastating camera flash going off 88 00:04:18.600 --> 00:04:21.920 in a pitch black stadium, then GRB two five ZHO 89 00:04:21.959 --> 00:04:24.800 seven oh two B was like someone firing up a 90 00:04:24.839 --> 00:04:28.040 massive industrial strobe light, leaving it running all day long, 91 00:04:28.279 --> 00:04:31.040 and like burning the bulb permanently into your retina. 92 00:04:31.199 --> 00:04:33.680 That is actually a terrifyingly accurate analogy. 93 00:04:33.800 --> 00:04:36.920 It sounds horrifying. And to really grasp why those three 94 00:04:37.000 --> 00:04:39.920 distinct pulses over twenty four hours through the whole astronomical 95 00:04:39.959 --> 00:04:42.360 community into chaos, we have to look at the engines 96 00:04:42.360 --> 00:04:43.519 that normally drive these. 97 00:04:43.360 --> 00:04:44.680 Bursts, right, the usual set. 98 00:04:44.959 --> 00:04:48.639 Historically we rely on two primary mechanisms. I'll take the 99 00:04:48.680 --> 00:04:51.399 first one, which is neutron star mergers. 100 00:04:51.560 --> 00:04:52.199 Okay, go for it. 101 00:04:52.600 --> 00:04:56.000 So when two neutron stars in a binary system lose 102 00:04:56.120 --> 00:05:01.360 orbital energy via gravitational ways, they viral inward. 103 00:05:01.040 --> 00:05:03.319 Toward each other, being closer and closer, and. 104 00:05:03.279 --> 00:05:06.199 When they finally cross the threshold and collide, the sheer 105 00:05:06.319 --> 00:05:09.959 kinetic and gravitational energy of that merger powers a massive, 106 00:05:10.079 --> 00:05:13.120 short lived, relativistic jet. 107 00:05:13.040 --> 00:05:16.920 Yeah, often resulting in an object that breaches the Tolmenopenheimer 108 00:05:17.000 --> 00:05:19.319 Volkoff limit and collapses into a black hole. 109 00:05:19.439 --> 00:05:21.199 Right. So that's engine number one, and. 110 00:05:21.160 --> 00:05:23.879 The second established engine is the collaps or model. This 111 00:05:24.000 --> 00:05:25.879 is the one that drives the longer. 112 00:05:25.560 --> 00:05:28.040 Burst, the ones that last a couple of minutes exactly. 113 00:05:28.439 --> 00:05:32.759 This requires a massive, rapidly rotating wolf ray star, a 114 00:05:32.920 --> 00:05:36.639 huge star huge when its core exhausts its nuclear fuel, 115 00:05:37.000 --> 00:05:41.000 electron degeneracy, pressure fails and the core instantly collapses into 116 00:05:41.040 --> 00:05:41.600 a black hole. 117 00:05:41.800 --> 00:05:43.279 Boom falls inward right. 118 00:05:43.519 --> 00:05:45.720 The outer layers of the star then free fall inward, 119 00:05:46.120 --> 00:05:50.079 creating a dense, superheated accretion disk around that new black hole. 120 00:05:50.360 --> 00:05:52.600 And that disc is what powers the jet. 121 00:05:52.959 --> 00:05:57.040 Yes, the intense magnetic fields channel a fraction of that 122 00:05:57.120 --> 00:06:01.040 infalling material into twin jets that just punched their way 123 00:06:01.079 --> 00:06:03.879 out through the stars outer envelope at near light speed. 124 00:06:04.000 --> 00:06:07.000 But and here is the massive problem. Both the merger 125 00:06:07.040 --> 00:06:11.160 model and the collapser model share a glaring limitation when 126 00:06:11.199 --> 00:06:13.839 you try to apply them to this July twenty. 127 00:06:13.560 --> 00:06:15.480 Twenty five event, a huge limitation. 128 00:06:15.639 --> 00:06:20.040 They are terminal, absolute, irreversible endings. You can't merge the 129 00:06:20.079 --> 00:06:23.920 same two neutron stars twice alone, three times exactly, let 130 00:06:23.920 --> 00:06:27.839 alone three times. And once a massive star undergoes core collapse, 131 00:06:28.120 --> 00:06:32.040 you can't magically reinflate the stellar envelope just to crush 132 00:06:32.079 --> 00:06:33.560 it again a few hours later. 133 00:06:33.639 --> 00:06:36.399 You really can't. The physics of a terminal event simply 134 00:06:36.399 --> 00:06:39.120 cannot support a twenty four hour stuttering explosion. 135 00:06:39.199 --> 00:06:40.360 It's one and done right. 136 00:06:40.399 --> 00:06:43.279 The structural integrity of the progenitor is permanently destroyed in 137 00:06:43.319 --> 00:06:45.920 milliseconds in both of those scenarios. 138 00:06:45.360 --> 00:06:47.639 So the scientists must have been losing their minds. 139 00:06:47.279 --> 00:06:50.279 Oh they were. When the Fermi data was published, the 140 00:06:50.319 --> 00:06:54.720 immediate reaction among theoreticians was this weird mix of intense 141 00:06:54.759 --> 00:06:56.560 fascination and complete. 142 00:06:56.240 --> 00:06:59.240 Bewilderment, like, what are we even looking at exactly? 143 00:06:59.279 --> 00:07:01.759 I mean, one of the lead investigators on the detection 144 00:07:01.879 --> 00:07:05.800 team flatly stated, and I quote, this is certainly an 145 00:07:05.839 --> 00:07:09.000 outburst unlike any other we've seen in the past fifty years. 146 00:07:09.560 --> 00:07:12.000 That's a huge statement from an astronomer. 147 00:07:12.079 --> 00:07:15.720 It is because it implied an engine that could generate 148 00:07:15.839 --> 00:07:19.920 apocalyptic amounts of energy, shut down and turn back on 149 00:07:20.000 --> 00:07:22.720 again with terrifying regularity. 150 00:07:22.120 --> 00:07:26.000 Which means the traditional standard candles and stellar death models 151 00:07:26.000 --> 00:07:28.759 had to be thrown completely out the window for this 152 00:07:29.199 --> 00:07:33.439 specific event into the trash. Astronomers had to start searching 153 00:07:33.439 --> 00:07:36.040 for an engine capable of tearing an immense amount of 154 00:07:36.079 --> 00:07:39.839 matter apart systematically, piece by piece, rather than destroying it 155 00:07:39.879 --> 00:07:41.800 all in a single terminal. 156 00:07:41.360 --> 00:07:44.199 Cataclos yes, a totally different kind of machine, and that. 157 00:07:44.160 --> 00:07:47.600 Search leads us to the primary suspect, a suspect that 158 00:07:47.639 --> 00:07:51.279 addresses a glaring, almost uncomfortable void in our mapping of 159 00:07:51.319 --> 00:07:51.959 the universe. 160 00:07:52.120 --> 00:07:54.759 And what's fascinating here is how the physical evidence from 161 00:07:54.759 --> 00:07:59.160 this unprecedented burst aligns perfectly with the theoretical object we 162 00:07:59.240 --> 00:08:02.839 have been hunting for decades. To really contextualize this suspect, 163 00:08:03.439 --> 00:08:05.800 we need to take a step back and look at 164 00:08:05.800 --> 00:08:07.639 the mass distribution of black. 165 00:08:07.360 --> 00:08:09.120 Holes the black hole scale. 166 00:08:09.279 --> 00:08:11.600 Right, at the lower end of the mass spectrum, we 167 00:08:11.720 --> 00:08:13.360 have stellar mass black holes. 168 00:08:13.480 --> 00:08:14.839 These are the common ones, right. 169 00:08:14.720 --> 00:08:17.879 Relatively speaking. Yeah, these are the direct remnants of the 170 00:08:17.920 --> 00:08:19.759 mass of star collapses we just discussed. 171 00:08:19.879 --> 00:08:20.120 Okay. 172 00:08:20.319 --> 00:08:24.240 They typically range from about three to perhaps fifty times 173 00:08:24.360 --> 00:08:27.639 the mass of our Sun, and they populate the galactic 174 00:08:27.680 --> 00:08:30.160 disc in the millions. 175 00:08:29.839 --> 00:08:32.519 Millions of them millions. Okay, So that's the small end. 176 00:08:32.759 --> 00:08:36.120 And at the absolute opposite extreme, we have the super. 177 00:08:35.840 --> 00:08:38.200 Massive black holes, the real monsters. 178 00:08:37.840 --> 00:08:41.720 The gravitational titans, anchoring the centers of virtually every large 179 00:08:41.720 --> 00:08:42.360 galaxy in. 180 00:08:42.320 --> 00:08:45.639 The universe, including Sagittarius, a star in our own Milky Way. 181 00:08:45.840 --> 00:08:49.480 Right, And here we are talking about singularities that pack 182 00:08:49.559 --> 00:08:52.679 the mass of millions or even tens of billions of 183 00:08:52.759 --> 00:08:56.159 suns into a space smaller than our solar system. 184 00:08:56.240 --> 00:08:58.200 It's hard to even wrap your head around that density, 185 00:08:58.279 --> 00:08:58.679 it really is. 186 00:08:58.720 --> 00:09:00.440 So you have the small ones and you have the 187 00:09:00.480 --> 00:09:01.360 super massive ones. 188 00:09:01.399 --> 00:09:05.240 But between those two extremes lies the missing population. 189 00:09:05.039 --> 00:09:07.000 The gap in the data, exactly. 190 00:09:06.759 --> 00:09:13.320 Intermediate mass black holes or imbhs. Mathematically, they absolutely must exist. 191 00:09:13.080 --> 00:09:15.159 Because the big ones had to come from somewhere. 192 00:09:14.919 --> 00:09:20.039 Right Precisely, the hierarchical merging models of galaxy formation suggest 193 00:09:20.159 --> 00:09:24.840 that supermassive black holes didn't just spring into existence fully. 194 00:09:24.600 --> 00:09:25.679 Formed, had to grow. 195 00:09:25.799 --> 00:09:30.120 They had to grow by consuming smaller black holes. So imbhs, 196 00:09:30.240 --> 00:09:33.360 which range from a few hundred to one hundred thousand 197 00:09:33.440 --> 00:09:36.960 solar masses, are the required evolutionary stepping stones. 198 00:09:37.000 --> 00:09:38.919 They're the missing link exactly. 199 00:09:39.440 --> 00:09:43.320 Furthermore, models of the early universe suggest that massive pristine 200 00:09:43.360 --> 00:09:48.120 gas clouds could have undergone direct collapse into imbh seeds, so. 201 00:09:48.080 --> 00:09:52.279 The math actually demands their existence. We should theoretically be 202 00:09:52.360 --> 00:09:54.720 tripping over these things in certain galactic environments. 203 00:09:54.799 --> 00:09:55.480 We really should. 204 00:09:55.679 --> 00:10:00.000 Yet observational astronomy has a notoriously difficult time finding them. 205 00:10:00.120 --> 00:10:01.679 It's been incredibly frustrating. 206 00:10:01.759 --> 00:10:05.200 I mean, it's the equivalent of paleontologists finding fossil evidence 207 00:10:05.240 --> 00:10:09.399 of millions of housecats and thousands of giant t rexes, 208 00:10:10.039 --> 00:10:12.639 but never finding a single skeleton of a wolf or 209 00:10:12.679 --> 00:10:13.000 a bear. 210 00:10:13.559 --> 00:10:14.840 That is a perfect way to put it. 211 00:10:14.960 --> 00:10:19.000 The entire middle of the mass distribution is essentially a ghost. 212 00:10:18.639 --> 00:10:20.120 Town, just completely empty. 213 00:10:20.399 --> 00:10:23.600 Why I mean, why is an object weighing fifty thousand 214 00:10:23.639 --> 00:10:25.960 suns so incredibly difficult to detect? 215 00:10:26.080 --> 00:10:28.919 It comes down to their environment and their accretion rates. 216 00:10:29.000 --> 00:10:30.480 Okay, break that down for us. 217 00:10:30.639 --> 00:10:34.480 So a black hole is by definition a region of 218 00:10:34.519 --> 00:10:37.919 space time where gravity prevents light from escaping. 219 00:10:37.840 --> 00:10:40.080 So they are inherently invisible right. 220 00:10:40.600 --> 00:10:43.080 The only way we ever detect them is through their 221 00:10:43.159 --> 00:10:45.000 interaction with surrounding. 222 00:10:44.519 --> 00:10:46.919 Matter, specifically when they feed. 223 00:10:47.320 --> 00:10:50.039 Exactly when they eat, they get messy, and we can 224 00:10:50.039 --> 00:10:53.639 see the mess Supermassive black holes sit in the dense, 225 00:10:53.720 --> 00:10:56.679 chaotic environment of a galactic core well lots of food, 226 00:10:56.679 --> 00:10:59.919 there a near infinite buffet of interstellar gas and wanderings. 227 00:11:00.759 --> 00:11:06.440 This creates massive, brilliantly luminous accretion discs and active galactic nuclei. 228 00:11:06.240 --> 00:11:08.600 So they shine incredibly bright because of all the friction. 229 00:11:08.840 --> 00:11:11.720 Yes, and on the other end, stellar mass black holes 230 00:11:11.720 --> 00:11:13.879 are often found in tight binary. 231 00:11:13.440 --> 00:11:16.039 Systems with a partner star, right. 232 00:11:15.919 --> 00:11:19.960 And they are continuously siphoning plasma off that companion star, 233 00:11:20.399 --> 00:11:23.480 which generates a steady stream of detectable X rays. 234 00:11:23.559 --> 00:11:27.519 So they're messy eaters in crowded rooms, which makes them visible. 235 00:11:27.720 --> 00:11:28.879 That's a great way to put it. 236 00:11:28.960 --> 00:11:32.240 But an intermediate mass black hole doesn't have those advantages, 237 00:11:32.279 --> 00:11:33.519 it really doesn't. 238 00:11:33.919 --> 00:11:38.039 They are too massive to maintain a tight, stable binary 239 00:11:38.200 --> 00:11:42.200 orbit with the standard star without just completely disrupting it. 240 00:11:42.240 --> 00:11:42.919 They're too bulky. 241 00:11:43.240 --> 00:11:46.840 Yeah, and dynamic friction models suggests many of them actually 242 00:11:46.840 --> 00:11:49.360 get kicked out of the galactic core during early merger. 243 00:11:49.240 --> 00:11:51.120 Events out like ejected. 244 00:11:51.240 --> 00:11:54.840 Yeah, Gravitational sling shots basically fling them outward, so they 245 00:11:54.840 --> 00:11:59.120 are relegated to the galacticalo or the outer disc, the suburbs. 246 00:11:59.120 --> 00:12:02.120 They're wandering through the vast empty suburbs of the galaxy. 247 00:12:02.120 --> 00:12:06.519 There's nothing to eat, exactly. The ambient interstellar gas density 248 00:12:06.519 --> 00:12:10.960 in these regions is incredibly low, so they're just starving basically. Yeah. 249 00:12:11.039 --> 00:12:11.200 Yeah. 250 00:12:11.279 --> 00:12:14.480 If you look at the Bondy Hoil Littleton accretion rate, 251 00:12:14.559 --> 00:12:17.279 which is what exactly, it's the formula that dictates how 252 00:12:17.360 --> 00:12:20.639 much ambient gas a black hole can passively sweep up 253 00:12:21.120 --> 00:12:24.360 just as it moves through space. Okay, according to that rate, 254 00:12:24.639 --> 00:12:28.679 and IMBH in the galactic suburbs is capturing almost nothing. Wow, 255 00:12:28.960 --> 00:12:31.759 it has no accretion disc it emits no X rays. 256 00:12:32.120 --> 00:12:37.200 It is just a silent, invisible gravitational sinkhole drifting through. 257 00:12:37.080 --> 00:12:41.440 The dark, drifting until its trajectory intersects with something massive 258 00:12:41.519 --> 00:12:42.720 enough to light up that dark. 259 00:12:42.879 --> 00:12:45.080 Precisely so, an intermediate. 260 00:12:44.679 --> 00:12:48.039 Mass black hole solves the problem of why the suspect 261 00:12:48.080 --> 00:12:49.480 was hiding from our telescopes. 262 00:12:49.639 --> 00:12:50.600 It fits the profile. 263 00:12:50.679 --> 00:12:55.360 But a quiet, starving black hole doesn't spontaneously generate a 264 00:12:55.480 --> 00:12:58.279 seven hour multi stage gamma ray burst. 265 00:12:58.559 --> 00:12:59.279 No it doesn't. 266 00:12:59.320 --> 00:13:02.320 It required it required a victim to cross its path. 267 00:13:02.519 --> 00:13:03.120 Yes it did. 268 00:13:03.440 --> 00:13:06.039 And that brings us to the specific mechanics proposed by 269 00:13:06.039 --> 00:13:09.200 these researchers. They didn't just point a finger at an IMBH. 270 00:13:09.440 --> 00:13:11.480 They modeled the exact crime scene. 271 00:13:11.519 --> 00:13:14.039 They really did. They introduced this concept called the Milli 272 00:13:14.080 --> 00:13:15.840 titled disruption event model. 273 00:13:15.679 --> 00:13:18.279 MILLI title disruption event Techi Right. 274 00:13:18.600 --> 00:13:22.679 And in this highly specific scenario, the catalyst the victim 275 00:13:23.120 --> 00:13:24.879 was a main sequence star, so. 276 00:13:24.879 --> 00:13:28.240 Just a regular stable hydrogen burning star, very much like 277 00:13:28.320 --> 00:13:29.360 our own son just. 278 00:13:29.320 --> 00:13:32.639 An ordinary star minding its own business, but through sheer 279 00:13:32.799 --> 00:13:36.919 cosmic bad luck, the dynamic orbital interactions within its local 280 00:13:36.960 --> 00:13:39.759 star cluster perturbed its trajectory. 281 00:13:39.840 --> 00:13:40.639 It got nudged. 282 00:13:40.799 --> 00:13:42.919 It got nudged, sending it on a path that brushed 283 00:13:42.960 --> 00:13:46.279 dangerously close to the gravitational sphere of influence of a 284 00:13:46.320 --> 00:13:48.279 lurking intermediate mass black hole. 285 00:13:48.519 --> 00:13:51.000 Now, when a star encounters a black hole, we often 286 00:13:51.039 --> 00:13:54.559 hear the term spagetification, which is, you know, a fun 287 00:13:54.559 --> 00:13:57.000 word for a truly horrifying. 288 00:13:56.480 --> 00:13:58.679 Process, very sunword, terrible way to go right. 289 00:13:58.759 --> 00:14:02.440 But to understand how this specific event generated gamma rays, 290 00:14:02.960 --> 00:14:05.200 we need to go beyond the basic definition of getting 291 00:14:05.200 --> 00:14:08.159 stretched out. We need to look at the gravitational gradient 292 00:14:08.240 --> 00:14:09.720 and something called the Roche limit. 293 00:14:09.960 --> 00:14:13.000 Ah, Yes, the Roche limit. So this is the critical 294 00:14:13.039 --> 00:14:15.360 distance at which the tidal force is exerted by a 295 00:14:15.399 --> 00:14:18.519 massive body. In this case, the black hole right exceed 296 00:14:18.559 --> 00:14:21.840 the gravitational forces holding the smaller body, the star together. 297 00:14:22.200 --> 00:14:24.480 So it's the point of no return for the star's 298 00:14:24.519 --> 00:14:25.679 structural integrity. 299 00:14:26.039 --> 00:14:30.320 Exactly as the star approaches the black hole, the gravitational 300 00:14:30.399 --> 00:14:33.879 pull on the star's leading hemisphere, the side facing the 301 00:14:33.879 --> 00:14:37.679 black hole is significantly stronger than the pole on its 302 00:14:37.720 --> 00:14:39.399 trailing hemisphere. 303 00:14:38.799 --> 00:14:42.279 Because gravity gets exponentially stronger the closer you get. 304 00:14:42.440 --> 00:14:44.440 Right, so the front is being pulled so much faster 305 00:14:44.559 --> 00:14:47.080 than the back. The star is literally stretched apart. 306 00:14:47.120 --> 00:14:50.000 Wait, hold on, here's where it gets really interesting, and 307 00:14:50.039 --> 00:14:53.440 where I have to just interrupt the standard tidal disruption model. 308 00:14:53.559 --> 00:14:53.960 Go for it. 309 00:14:54.240 --> 00:14:57.240 If the star crosses the Roche limit and the title 310 00:14:57.360 --> 00:15:01.240 sheer forces overcome its self gravity, the star is ripped 311 00:15:01.240 --> 00:15:05.600 apart into a stream of superheated plasma. Half of that 312 00:15:05.679 --> 00:15:08.720 material gets ejected out into the interstellar medium, and the 313 00:15:08.799 --> 00:15:13.000 other half circularizes into an accretion disk around the black hole. 314 00:15:13.120 --> 00:15:14.840 The buffet opens right. 315 00:15:14.679 --> 00:15:19.360 The black hole feeds, and through the Blanford's nagic process, 316 00:15:19.600 --> 00:15:23.360 the twisting of magnetic field lines in the ergosphere acts 317 00:15:23.360 --> 00:15:25.840 as an immense particle accelerator. 318 00:15:25.360 --> 00:15:27.919 Blasting a relativistic jet toward Earth. 319 00:15:28.120 --> 00:15:32.120 Okay, so that perfectly explains a massive burst of energy. 320 00:15:32.279 --> 00:15:35.240 It does, But you just said the stars ripped apart. 321 00:15:35.399 --> 00:15:35.840 I did. 322 00:15:36.200 --> 00:15:39.679 If the progenitor is shredded into a plasma stream, how 323 00:15:39.720 --> 00:15:44.120 does the Fermi telescope register three distinct bursts over twenty 324 00:15:44.120 --> 00:15:47.200 four hours. The math just doesn't add up. 325 00:15:47.320 --> 00:15:48.320 It really doesn't seem to. 326 00:15:48.639 --> 00:15:52.200 You cannot cross the roche limit and suffer complete structural 327 00:15:52.200 --> 00:15:53.639 failure three times. 328 00:15:53.720 --> 00:15:56.399 You are absolutely correct. And that is the exact physical 329 00:15:56.399 --> 00:15:58.840 contradiction that the team had to solve. 330 00:15:58.799 --> 00:16:01.279 Because you can eat the same star three times, right. 331 00:16:02.000 --> 00:16:06.200 A standard tidal disruption event or TDE, involves a deep 332 00:16:06.240 --> 00:16:09.159 plunge where the periapsis, which is the closest point of 333 00:16:09.200 --> 00:16:11.639 the orbit, is well inside the roach limit, so. 334 00:16:11.639 --> 00:16:13.720 It dives deep into the danger zone. 335 00:16:13.519 --> 00:16:17.360 Deep bin and in that standard scenario, total disruption is instantaneous. 336 00:16:17.639 --> 00:16:20.679 The engine turns on once, feeds until the accretion disc 337 00:16:20.799 --> 00:16:22.519 is depleted, and then turns off. 338 00:16:22.600 --> 00:16:23.360 Well then done. 339 00:16:23.399 --> 00:16:26.480 To get three distinct bursts, the team had to calculate 340 00:16:26.519 --> 00:16:30.000 a scenario where the victim actually survives the initial encounter, 341 00:16:30.159 --> 00:16:32.399 surviving the first bite. Surviving the first bite. 342 00:16:32.440 --> 00:16:35.480 This completely shifts the mechanics of the whole event. It 343 00:16:35.519 --> 00:16:39.000 requires an incredibly precise orbital trajectory, doesn't it. 344 00:16:39.039 --> 00:16:43.159 Oh, precision is staggering. It requires a grazing encounter, grazing intown. 345 00:16:43.519 --> 00:16:49.519 The researchers modeled a highly elliptical near parabolic orbit. So 346 00:16:49.600 --> 00:16:53.200 the star's periapsis didn't plunge deep into the roach limit. 347 00:16:53.960 --> 00:16:55.919 It just barely skimmed the edge of it. 348 00:16:55.960 --> 00:16:58.440 Think of it like skipping a stone across the surface 349 00:16:58.480 --> 00:17:01.480 of a pond. Yes, the stone doesn't just plunge straight 350 00:17:01.559 --> 00:17:04.359 down to the bottom. On the first impact, it hits 351 00:17:04.400 --> 00:17:08.799 the dense surface of the water, experiences intense drag, loses 352 00:17:08.799 --> 00:17:11.400 a fraction of its kinetic energy, and bounces back up 353 00:17:11.440 --> 00:17:14.440 into the air exactly, But because it lost energy, its 354 00:17:14.480 --> 00:17:17.240 next arc is shorter, bringing it back down for a second, 355 00:17:17.559 --> 00:17:18.839 more damaging impact. 356 00:17:19.119 --> 00:17:23.240 That mechanical analogy maps perfectly onto the hydrodynamics of this event. 357 00:17:23.519 --> 00:17:24.920 So how does that look for the star? 358 00:17:25.200 --> 00:17:29.079 On the star's first close approach, the tidal sheer forces 359 00:17:29.359 --> 00:17:32.079 were only strong enough to strip away the outermost layers 360 00:17:32.119 --> 00:17:33.519 of the star's gaseous. 361 00:17:33.160 --> 00:17:35.039 Envelope, just skimming off the surface. 362 00:17:35.519 --> 00:17:40.119 Right The dense stellar core, where the self gravity is strongest, 363 00:17:40.599 --> 00:17:42.200 remained entirely intact. 364 00:17:42.519 --> 00:17:45.039 So the black hole shears off a massive chunk of 365 00:17:45.119 --> 00:17:49.400 hydrogen plasma. Yes, that stolen material falls into the gravitational well, 366 00:17:49.680 --> 00:17:53.799 circularizes and triggers a violent accretion episode. The first meal, 367 00:17:54.039 --> 00:17:58.160 the magnetic fields wind up, the relativistic jet punches outward, 368 00:17:58.480 --> 00:18:00.119 and Fermi's detectors light up with. 369 00:18:00.160 --> 00:18:02.519 The first burst Boom burst number one. 370 00:18:02.680 --> 00:18:05.079 But the black hole hasn't destroyed the engine. It has 371 00:18:05.119 --> 00:18:06.480 only taken a surface layer. 372 00:18:06.640 --> 00:18:10.960 Precisely after that first grazing pass, the surviving stellar core 373 00:18:11.480 --> 00:18:14.960 swings back out to the equalcess of its elliptical. 374 00:18:14.519 --> 00:18:16.160 Orbit, flying back out into space. 375 00:18:16.279 --> 00:18:19.759 But just like you're skipping stone, the encounter robbed the 376 00:18:19.799 --> 00:18:23.000 star of critical orbital energy and angular momentum. 377 00:18:23.000 --> 00:18:23.759 Its slowing down. 378 00:18:23.880 --> 00:18:26.640 It cannot escape the black hole's gravity. Its orbit is 379 00:18:26.680 --> 00:18:27.680 decaying rapidly. 380 00:18:27.759 --> 00:18:30.039 The star is bleeding out, and it's being pulled back 381 00:18:30.079 --> 00:18:31.279 in for a second pass. 382 00:18:31.400 --> 00:18:35.640 It is several hours later, dictated purely by Kyplerian orbital mechanics. 383 00:18:35.880 --> 00:18:39.279 The damaged star swings back down to periapses. 384 00:18:38.720 --> 00:18:39.279 For round two. 385 00:18:39.480 --> 00:18:43.000 Because it's orbit decayed, This second pass takes it slightly 386 00:18:43.079 --> 00:18:46.440 deeper into the Roche limit. Oh no, the tidal forces 387 00:18:46.480 --> 00:18:49.440 are even stronger this time. A much larger fraction of 388 00:18:49.480 --> 00:18:51.400 the scar's mass is violently torn. 389 00:18:51.240 --> 00:18:53.839 Away, so the second massive chunk of plasma hits the 390 00:18:53.880 --> 00:18:57.240 accretion disk exactly the temperature and magnetic flux spike again. 391 00:18:57.720 --> 00:19:01.599 The black hole fires a second relativistic and Fermi records 392 00:19:01.640 --> 00:19:03.440 burst number two, and. 393 00:19:03.400 --> 00:19:07.400 The star, now critically deformed and lacking the mass to 394 00:19:07.440 --> 00:19:11.240 maintain its structural integrity at all, swings out one final 395 00:19:11.319 --> 00:19:13.319 time on a drastically shortened orbit. 396 00:19:13.599 --> 00:19:16.839 It's barely holding together when it returns for the third pass. 397 00:19:17.000 --> 00:19:20.200 It finally plunges deeply enough into the roch limit that 398 00:19:20.319 --> 00:19:21.519 total disruption occurs. 399 00:19:21.599 --> 00:19:22.279 The final blow. 400 00:19:22.400 --> 00:19:25.960 The remaining core is entirely shredded. The black hole consumes 401 00:19:25.960 --> 00:19:28.839