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 00:00:27.000 --> 00:00:29.199 Imagine looking up at the night sky and seeing a 8 00:00:29.239 --> 00:00:34.159 star just erupt right. For centuries, that's what astronomers saw. 9 00:00:34.320 --> 00:00:37.159 A nova would flare up, and we'd log it as 10 00:00:37.200 --> 00:00:40.880 this sudden, intense flash of light would get incredibly bright 11 00:00:40.960 --> 00:00:43.719 and then, you know, slowly and predictably fade away. 12 00:00:43.840 --> 00:00:47.799 That was the entire story. A simple impulsive explosion. That 13 00:00:48.000 --> 00:00:48.560 was the model. 14 00:00:48.679 --> 00:00:52.479 But the actual moment, the blast itself, the shape of 15 00:00:52.479 --> 00:00:55.880 it unfolding in real time, that was always hitting from us. 16 00:00:55.920 --> 00:00:58.719 It was just a frustratingly blurry point of light. 17 00:00:58.840 --> 00:01:01.399 It was a fundamental imitation. I mean, we could measure 18 00:01:01.439 --> 00:01:04.879 the total light output perfectly, we could analyze the energy, 19 00:01:05.000 --> 00:01:07.239 we could clock the timing down to the second, all 20 00:01:07.280 --> 00:01:11.359 the numbers, all the numbers, but the actual physical movement 21 00:01:11.400 --> 00:01:14.159 of the material, the way it was flowing, whether there 22 00:01:14.200 --> 00:01:17.280 were lumps, how things were interacting. That was all just 23 00:01:17.319 --> 00:01:20.359 an inference. It was a guess based on computer models. 24 00:01:20.400 --> 00:01:22.159 We just didn't have a telescope big enough to see 25 00:01:22.159 --> 00:01:23.200 the details exactly. 26 00:01:23.560 --> 00:01:26.159 We lack the resolving power to confirm the mechanics of 27 00:01:26.200 --> 00:01:27.319 the detonation itself. 28 00:01:27.599 --> 00:01:31.560 Well, that era of inference is officially over, and for you, 29 00:01:31.719 --> 00:01:34.640 the curious learner, our mission today is to get right 30 00:01:34.719 --> 00:01:40.040 into this extraordinary scientific breakthrough, the first high definition images 31 00:01:40.159 --> 00:01:41.519 of stellar explosion. 32 00:01:41.680 --> 00:01:42.760 Yeah, this is huge. 33 00:01:42.840 --> 00:01:44.840 We're going to break down the recent findings from a 34 00:01:44.879 --> 00:01:47.840 major study in Nature Astronomy and look at exactly how 35 00:01:47.879 --> 00:01:52.239 scientists managed to capture these stellar eruptions, these novy in 36 00:01:52.760 --> 00:01:54.519 really unprecedented details. 37 00:01:54.519 --> 00:01:57.959 And these images they don't just tweak the old models, 38 00:01:58.239 --> 00:02:02.000 they completely overturned in the decades old assumption that a 39 00:02:02.079 --> 00:02:05.879 nova is this single symmetrical puff of material. 40 00:02:05.959 --> 00:02:08.159 It's not a simple balloon inflating. 41 00:02:07.719 --> 00:02:09.599 Not at all. We now have visual proof of these 42 00:02:09.599 --> 00:02:13.159 incredibly complex, non uniform shakes. We're talking multidirectional jets, we're 43 00:02:13.159 --> 00:02:16.439 talking about dramatically delayed injections. It's a whole new ballgame. 44 00:02:16.520 --> 00:02:19.360 Okay, let's really unpack this because to appreciate just how 45 00:02:19.400 --> 00:02:21.280 big of a loop this is, we need to understand 46 00:02:21.319 --> 00:02:23.560 the baseline. We need to get into the physics of 47 00:02:23.560 --> 00:02:25.479 what's actually exploding here. 48 00:02:25.520 --> 00:02:27.439 All right, So we are focusing on nova, and it's 49 00:02:27.439 --> 00:02:30.639 so important to distinguish a nova from his more famous cousin, the. 50 00:02:30.599 --> 00:02:34.360 Supernova, right, not the same thing at all, not even close. 51 00:02:34.639 --> 00:02:39.800 A supernova is the final catastrophic death of a massive star. 52 00:02:40.360 --> 00:02:43.280 It's a one time event that completely destroys the star. 53 00:02:43.439 --> 00:02:45.520 The nova, on the other hand, is a cyclical thing. 54 00:02:45.560 --> 00:02:49.479 It happens on a star that's well, technically it's already dead, right, 55 00:02:49.599 --> 00:02:50.120 that's the key. 56 00:02:50.159 --> 00:02:53.039 It's a surface level explosion on a dead star that's 57 00:02:53.120 --> 00:02:56.719 locked into this fatal cosmic dance with the companion. 58 00:02:57.240 --> 00:02:59.199 So if the star is already dead, what does that 59 00:02:59.240 --> 00:03:01.599 actually mean and what kind of dead star are we 60 00:03:01.639 --> 00:03:02.240 talking about here? 61 00:03:02.280 --> 00:03:04.599 We're talking about a white dwarf. This is the remnant 62 00:03:04.599 --> 00:03:07.199 of a star like our own Sun. After it exhausts 63 00:03:07.199 --> 00:03:10.199 its main nuclear fuel, it sheds its outer layers and 64 00:03:10.240 --> 00:03:15.159 the core collapses down into this incredibly dense, super hot object. 65 00:03:15.240 --> 00:03:17.680 So you've got something with the mass of the Sun 66 00:03:17.800 --> 00:03:21.039 squeeze into the size of what the Earth. 67 00:03:20.800 --> 00:03:22.360 About the size of the Earth. Yeah, it can have 68 00:03:22.479 --> 00:03:24.479 up to one point four times the mass of the 69 00:03:24.520 --> 00:03:28.080 Sun crammed into that tiny volume, and that density, that 70 00:03:28.120 --> 00:03:31.919 concentration of mass is what gives it this immense gravitational pull. 71 00:03:32.039 --> 00:03:34.199 And it's not held up by normal pressure like a 72 00:03:34.240 --> 00:03:37.080 regular star. It's something else, something exotics precisely. 73 00:03:37.680 --> 00:03:41.439 Its structure is maintained by something called electron degeneracy pressure. 74 00:03:41.680 --> 00:03:44.400 It's a quantum mechanical effect. The electrons are packed in 75 00:03:44.520 --> 00:03:47.919 so tightly that they physically resist being compressed any further. 76 00:03:48.039 --> 00:03:51.360 So it's stable. It's basically an inert stellar core just 77 00:03:51.400 --> 00:03:51.960 sitting there. 78 00:03:52.080 --> 00:03:55.240 It is. It's stable and inert, but its immense gravity 79 00:03:55.319 --> 00:03:58.199 is still very very active, and that's what sets the 80 00:03:58.240 --> 00:03:59.240 stage to the explosion. 81 00:03:59.560 --> 00:04:02.639 It needs trigger, and that trigger comes from its let's say, 82 00:04:03.000 --> 00:04:04.599 unfortunate companion star. 83 00:04:04.840 --> 00:04:07.759 Exactly. This white dwarf is almost always part of a 84 00:04:07.800 --> 00:04:11.039 close binary system, and it acts like a cosmic thief, 85 00:04:11.400 --> 00:04:15.840 just pulling material, mostly hydrogen and helium, off its companion. 86 00:04:15.960 --> 00:04:17.959 It's literally stealing fuel it is. 87 00:04:18.600 --> 00:04:21.959 This stolen material forms a turbulent, swirling cloud around the 88 00:04:22.000 --> 00:04:24.720 white dwarf called an accretion disc, and from there it 89 00:04:24.759 --> 00:04:28.519 spirals down and piles up, forming this shallow, super dense 90 00:04:28.600 --> 00:04:29.959 layer on the white dwarf's surface. 91 00:04:30.079 --> 00:04:32.800 Okay, so you have this dead quantum supported core and 92 00:04:32.839 --> 00:04:36.040 it's now covered in a fresh layer of highly compressed hydrogen. 93 00:04:36.560 --> 00:04:39.480 What flips the switch? What turns that into a city 94 00:04:39.519 --> 00:04:40.720 sized hydrogen bomb. 95 00:04:40.920 --> 00:04:43.839 Well, this is where the specific physics gets really interesting. 96 00:04:44.399 --> 00:04:48.160 As that hydrogen layer piles up, the immense gravity from 97 00:04:48.199 --> 00:04:51.519 the white dwarf creates incredible pressure and heat at the 98 00:04:51.519 --> 00:04:54.199 bottom of that layer. It's being crushed, crushed, and cooked. 99 00:04:54.560 --> 00:04:57.439 The white dwarf itself is extremely hot, maybe one hundred 100 00:04:57.439 --> 00:05:00.959 million kelvin, So the base of this new hydrogen envelope 101 00:05:01.120 --> 00:05:02.360 heats up very quickly. 102 00:05:02.439 --> 00:05:04.879 But the core itself isn't doing any hugion anymore. It's 103 00:05:04.959 --> 00:05:06.319 just a hot rock essentially. 104 00:05:06.480 --> 00:05:09.600 That's right, The core is inert. But here's the key 105 00:05:09.639 --> 00:05:13.720 to the explosion. That hydrogen layer is supported by the 106 00:05:13.759 --> 00:05:18.480 same degeneracy pressure as the core, and degenerate matter has 107 00:05:18.519 --> 00:05:21.959 this weird property where its temperature can skyrocket without its 108 00:05:22.000 --> 00:05:23.879 pressure immediately increasing to match. 109 00:05:24.240 --> 00:05:26.560 So in a normal gas, if you heat it up 110 00:05:26.600 --> 00:05:27.839 it expands and cools. 111 00:05:27.959 --> 00:05:30.120 Right, it's a natural thermostet. 112 00:05:29.680 --> 00:05:30.800 But that doesn't happen here. 113 00:05:30.879 --> 00:05:33.480 It doesn't happen here. The temperature just keeps climbing and climbing. 114 00:05:33.480 --> 00:05:36.040 It's a runaway heating process. And when it hits the 115 00:05:36.040 --> 00:05:39.279 critical threshold some are around ten to twenty million kelvin, 116 00:05:39.720 --> 00:05:41.319 that hydrogen suddenly ignites. 117 00:05:41.720 --> 00:05:43.319 And we're not talking about a slow burn. 118 00:05:43.600 --> 00:05:48.680 Oh no, it's a catastrophic, runaway thermonuclear reaction. The CNO 119 00:05:48.839 --> 00:05:53.480 cycle carbon nitrogen oxygen fusion kicks in, violently, releasing a 120 00:05:53.519 --> 00:05:56.920 massive amount of energy that finally overcomes the star's gravity. 121 00:05:57.279 --> 00:06:01.519 It blasts that entire accumulated layer into space at thousands 122 00:06:01.560 --> 00:06:02.720 of kilometers per second. 123 00:06:02.839 --> 00:06:05.240 And that's the flash. That's the nova we see, that's 124 00:06:05.279 --> 00:06:05.720 the nova. 125 00:06:06.079 --> 00:06:09.399 The star temporarily brightens by many, many orders of magnitude. 126 00:06:09.519 --> 00:06:12.600 An incredible blast, and yet for all of history we 127 00:06:12.639 --> 00:06:15.839 could only interpret it. The material expands so fast that 128 00:06:15.879 --> 00:06:19.600 even our best single telescopes just saw it as that single, smooth, 129 00:06:19.839 --> 00:06:21.199 unresolved point of light. 130 00:06:21.360 --> 00:06:23.959 That was the historical observation challenge. Yeah, because they're so 131 00:06:24.040 --> 00:06:27.439 far away, even something expanding in say five thousand kilometers 132 00:06:27.480 --> 00:06:30.079 per second still looks like a tiny, slowly growing blob. 133 00:06:30.800 --> 00:06:33.240 We knew mass was being ejected, but we couldn't resolve 134 00:06:33.279 --> 00:06:34.360 the geometry. 135 00:06:33.959 --> 00:06:37.240 The shape, the direction, whether there were jets or clumps. 136 00:06:37.399 --> 00:06:39.879 All that was hidden in those crucial first few hours 137 00:06:39.959 --> 00:06:40.399 and days. 138 00:06:40.519 --> 00:06:42.800 So because the geometry was hidden, the physics of the 139 00:06:42.879 --> 00:06:45.199 explosion was well. It was based on the assumption that 140 00:06:45.240 --> 00:06:48.079 it was symmetrical, right, like a perfectly inflated balloon. 141 00:06:48.160 --> 00:06:52.079 Exactly, and that created a huge knowledge gap, I mean understanding. 142 00:06:52.079 --> 00:06:55.240 The geometry is everything because it dictates how the ejected 143 00:06:55.279 --> 00:06:56.759 material interacts with itself. 144 00:06:56.839 --> 00:06:59.920 If it's a smooth sphere, the physics is pretty. 145 00:06:59.639 --> 00:07:04.160 Straight, relatively simple, yes, But if you have multiple outflows 146 00:07:04.360 --> 00:07:07.959 or lumpy bits or directed jets, then they're going to crash. 147 00:07:07.720 --> 00:07:09.839 Into each other and that's where things get interesting. 148 00:07:09.920 --> 00:07:13.079 That's where you get intense shockwaves, and those shockwaves are 149 00:07:13.079 --> 00:07:16.720 where the highest energy physics, the particle acceleration, takes place. 150 00:07:17.399 --> 00:07:20.680 Before this study, the true complexity of those shock powered 151 00:07:20.720 --> 00:07:24.680 processes was a complete mystery. We were modeling simple physics 152 00:07:24.680 --> 00:07:27.240 because we couldn't see the complex reality. 153 00:07:27.360 --> 00:07:31.079 So, given this massive barrier, this fundamental limit of distance 154 00:07:31.120 --> 00:07:34.480 and resolution, what was the breakthrough? How did we finally 155 00:07:34.519 --> 00:07:35.879 see the physics as it happened. 156 00:07:36.040 --> 00:07:39.480 The answer is a really advanced technique called long baseline 157 00:07:39.519 --> 00:07:40.800 optical inoferometry. 158 00:07:40.839 --> 00:07:44.160 It sounds incredibly complex, but the basic idea is a 159 00:07:44.160 --> 00:07:47.040 clever way to shoot the system right, to get around 160 00:07:47.040 --> 00:07:49.759 the problem of building impossibly large telescopes. 161 00:07:49.959 --> 00:07:52.199 That's a perfect way to describe it. Look, if you 162 00:07:52.240 --> 00:07:56.800 want higher resolution, the ability to see finer details, you 163 00:07:56.879 --> 00:07:59.399 just need a bigger mirror, a bigger aperture. 164 00:07:59.680 --> 00:08:02.920 Building a single mirror beyond what eight or ten meters 165 00:08:02.920 --> 00:08:05.879 in diameter is just an immense engineering challenge. 166 00:08:05.519 --> 00:08:09.519 Immensely complex and incredibly expensive. Yeah. So interferometry solves this 167 00:08:09.639 --> 00:08:13.560 by combining the light waves from multiple physically separate telescopes. 168 00:08:13.800 --> 00:08:16.920 So instead of one giant, one hundred meters mirror, you 169 00:08:16.959 --> 00:08:19.560 can have, say, a handful of smaller mirrors spread out 170 00:08:19.560 --> 00:08:20.399 over one hundred. 171 00:08:20.160 --> 00:08:23.839 Meters exactly, and the combined system acts as if it 172 00:08:23.879 --> 00:08:27.360 were a single giant telescope whose diameter is equal to 173 00:08:27.360 --> 00:08:29.920 the maximum distance between any two of the smaller ones. 174 00:08:30.000 --> 00:08:31.920 It creates a synthetic aperture. 175 00:08:31.839 --> 00:08:34.519 That's the term. The resolution you get is dictated by 176 00:08:34.559 --> 00:08:37.600 that longest baseline, not the size of the individual mirrors, 177 00:08:37.759 --> 00:08:41.159 and this lets astronomers achieve resolutions equivalent to a mirror 178 00:08:42.240 --> 00:08:44.679 hundreds of meters across. It's just phenomenal. 179 00:08:44.720 --> 00:08:47.879 And we should stress this isn't some brand new, untested idea. 180 00:08:48.039 --> 00:08:50.480 This is the same powerful technique that was crucial for 181 00:08:50.559 --> 00:08:52.440 the Event Horizon telescope project, the. 182 00:08:52.480 --> 00:08:54.279 One that gave is the first ever image of a 183 00:08:54.320 --> 00:08:55.279 black hole shadow. 184 00:08:55.559 --> 00:08:58.519 Right, So when we're talking about resolving power, this is 185 00:08:58.559 --> 00:09:00.200 the absolute cutting edge. 186 00:09:00.120 --> 00:09:03.799 It really is. And the specific facility that pulled off 187 00:09:03.879 --> 00:09:08.360 this nova breakthrough is the Center for High Angular Resolution Astronomy. 188 00:09:08.639 --> 00:09:10.679 The Chair Array app in California. 189 00:09:10.799 --> 00:09:13.000 Tell us about that setup because it's at a really 190 00:09:13.120 --> 00:09:15.960 historic site, but the tech itself is I mean, it's 191 00:09:16.000 --> 00:09:17.120 borderline science fiction. 192 00:09:17.279 --> 00:09:20.039 It's a wonderful marriage of history in the future. The 193 00:09:20.120 --> 00:09:22.639 Chair Array is at the Mount Wilson Observatory in the 194 00:09:22.679 --> 00:09:25.840 San Gabriel Mountains, which is famous for Edwin Hubble's work 195 00:09:26.320 --> 00:09:27.919 discovering the expansion. 196 00:09:27.559 --> 00:09:30.279 Of the universe, a legendary place in astronomy. 197 00:09:29.759 --> 00:09:34.440 Absolutely, and the array itself consists of six one meter telescopes. 198 00:09:35.120 --> 00:09:38.679 These six telescopes are arranged very precisely along three arms 199 00:09:39.000 --> 00:09:42.080 in a big y shape. The longest distance between any 200 00:09:42.080 --> 00:09:44.159 two of them is three hundred and thirty meters, so. 201 00:09:44.120 --> 00:09:46.039 You're getting the resolving power of a three hundred and 202 00:09:46.080 --> 00:09:50.120 thirty meter telescope. That's just it's mind boggling. But it 203 00:09:50.159 --> 00:09:53.600 requires this almost impossible feat of engineering. You have to 204 00:09:53.600 --> 00:09:56.240 get the light from all six separate telescopes to arrive 205 00:09:56.279 --> 00:09:58.559 at the central lab at the exact same time. 206 00:09:58.519 --> 00:10:00.320 Down to fractions of a wavelength light. 207 00:10:00.519 --> 00:10:01.879 How do you even do that? 208 00:10:01.879 --> 00:10:05.759 That is the core technical challenge. It's called maintaining coherence. 209 00:10:06.440 --> 00:10:08.960 Light travels at a finite speed, so you have to 210 00:10:09.000 --> 00:10:13.320 compensate for the different distances. Chera uses these incredibly precise 211 00:10:13.360 --> 00:10:18.039 systems of movable mirrors on railway tracks. They're called delay lines. 212 00:10:18.200 --> 00:10:21.360 And they're all inside sealed vacuum pipes right to keep 213 00:10:21.399 --> 00:10:22.919 the atmosphere from messing. 214 00:10:22.639 --> 00:10:25.440 With the light correct The light from eachy telescope is 215 00:10:25.480 --> 00:10:28.799 beamed into these vacuum pipes, and these delay lines physically 216 00:10:28.840 --> 00:10:31.480 move back and forth, constantly adjusting the path length of 217 00:10:31.519 --> 00:10:33.960 the light to make sure all six beams are perfectly 218 00:10:34.000 --> 00:10:36.759 synchronized when they meet and interfere in the central lab. 219 00:10:36.879 --> 00:10:39.159 The precision must be on the order of nanometers. 220 00:10:39.559 --> 00:10:42.039 It is. They have to align the light paths with 221 00:10:42.200 --> 00:10:46.360 unbelievable accuracy to track the interference pattern the fringes and 222 00:10:46.440 --> 00:10:49.120 build up a coherent image. And it's all happening in 223 00:10:49.159 --> 00:10:51.960 real time. Because the Earth is rotating, the object is 224 00:10:52.000 --> 00:10:55.519 moving across the sky, those pathlengths are constantly changing. 225 00:10:55.679 --> 00:10:58.399 That level of coordination is already a huge feed. But 226 00:10:58.480 --> 00:11:00.360 for something like a nova, I mean, you can plan 227 00:11:00.519 --> 00:11:03.360 for years to image a static target like a black hole. 228 00:11:03.639 --> 00:11:04.919 A nova just appears. 229 00:11:05.200 --> 00:11:08.600 And that's what makes this so impressive. It requires immense 230 00:11:08.679 --> 00:11:13.000 operational flexibility. A nova can brighten dramatically in less than 231 00:11:13.039 --> 00:11:16.080 a day. The team has to be able to drop everything, 232 00:11:16.600 --> 00:11:20.440 pivot the entire array, all six telescopes, all the optics, 233 00:11:20.440 --> 00:11:23.840 all the synchronization, and lock onto this new target immediately. 234 00:11:23.919 --> 00:11:26.399 It's high stakes, rapid response science. 235 00:11:26.120 --> 00:11:29.799 It really is. But the visual data from Shira, as 236 00:11:29.840 --> 00:11:33.200 powerful as it was, was only half the picture. They 237 00:11:33.279 --> 00:11:36.559 used a really smart, complimentary approach to double. 238 00:11:36.320 --> 00:11:38.399 Check their work, so they weren't just relying on the 239 00:11:38.440 --> 00:11:39.240 images alone. 240 00:11:39.480 --> 00:11:42.559 No, the sharp images from the interferometry told them the 241 00:11:42.600 --> 00:11:46.039 shape and the structure, but they complimented that data with 242 00:11:46.159 --> 00:11:49.440 spectra gathered from major observatories like Gemini. 243 00:11:49.159 --> 00:11:51.799 And the spectra that's like the chemical fingerprint of the 244 00:11:51.840 --> 00:11:52.759 guests exactly. 245 00:11:52.879 --> 00:11:55.399 Yeah. It tells you it's velocity, its density, it's temperature, 246 00:11:55.399 --> 00:11:57.879 it's chemical composition, all the physics. 247 00:11:58.000 --> 00:12:00.320 So you have the geometry from one instrument and the 248 00:12:00.360 --> 00:12:02.200 physics from another, and you can marry them up. 249 00:12:02.399 --> 00:12:05.759 And this is where their confidence just soared. The study 250 00:12:05.799 --> 00:12:09.519 found what they called a powerful one to one confirmation. 251 00:12:10.279 --> 00:12:13.600 As soon as a new high velocity feature appeared in the. 252 00:12:13.519 --> 00:12:16.480 Spectra, meaning a burst of fast moving gas or a 253 00:12:16.480 --> 00:12:17.840 strong collision. 254 00:12:17.799 --> 00:12:21.639 That spectroscopic signal lined up perfectly with a new structure, 255 00:12:21.720 --> 00:12:24.720 a new lump or jet that simultaneously appeared in the 256 00:12:24.799 --> 00:12:26.200 interferometric images. 257 00:12:26.360 --> 00:12:29.360 That's the smoking gun. It proves you're not just seeing 258 00:12:29.399 --> 00:12:33.600 some kind of optical artifact, you're visually confirming the physics. 259 00:12:33.879 --> 00:12:37.360 It validated the entire process. One of the co authors 260 00:12:37.360 --> 00:12:40.559 called it an extraordinary leap forward, and he's not wrong. 261 00:12:41.240 --> 00:12:44.120 We are now literally watching the material as it's blasted 262 00:12:44.120 --> 00:12:46.639 into space and connecting that directly to the physics of 263 00:12:46.679 --> 00:12:49.960 how it's happening. We've gone from theorizing about how shockwaves 264 00:12:49.960 --> 00:12:52.120 form to directly observing them form. 265 00:12:52.240 --> 00:12:54.720 And what that new window immediately showed was that the 266 00:12:54.759 --> 00:12:58.840 simple spherical model of a nova is well, it's just wrong. 267 00:12:58.919 --> 00:12:59.960 It's completely insfie. 268 00:13:00.559 --> 00:13:03.120 The team managed to image two novae that erupted in 269 00:13:03.159 --> 00:13:05.720 twenty twenty one, and they couldn't have been more different 270 00:13:05.720 --> 00:13:08.639 from each other. That variability is really the heart of 271 00:13:08.679 --> 00:13:09.639 this whole discovery. 272 00:13:09.879 --> 00:13:13.440 Absolutely, the contrast between these two novae, V one seventy 273 00:13:13.440 --> 00:13:17.360 before hercules and V fourteen oh five cassiopa is the 274 00:13:17.399 --> 00:13:20.639 direct evidence that's forcing us to rewrite the textbooks. We're 275 00:13:20.679 --> 00:13:24.159 seeing this incredible variety of ejection pathways. 276 00:13:23.919 --> 00:13:26.559 Which proves that the final shape isn't just about the 277 00:13:26.639 --> 00:13:28.039 energy of the blast, right, it. 278 00:13:28.080 --> 00:13:30.440 Must be highly dependent on other factors, like the white 279 00:13:30.519 --> 00:13:33.279 dwarf's rotation, or its magnetic field, or the shape of 280 00:13:33.279 --> 00:13:34.320 the material it's stealing. 281 00:13:34.360 --> 00:13:37.600 Okay, let's get into the first case, nova V one 282 00:13:37.679 --> 00:13:41.399 sits seventy four hercules. The sources described this one as 283 00:13:41.440 --> 00:13:44.720 one of the fastest stellar explosions ever recorded. What do 284 00:13:44.759 --> 00:13:46.000 we mean by fast. 285 00:13:45.879 --> 00:13:49.720 We mean blindingly fast. V one cs seventy four hercules 286 00:13:49.919 --> 00:13:52.159 peaked in brightness and then faded away in just a 287 00:13:52.159 --> 00:13:54.960 few days, just days, just a few days. A more 288 00:13:55.000 --> 00:13:57.440 typical nova might take weeks or even months to go 289 00:13:57.519 --> 00:14:00.679 through its whole cycle. So this rapid elevilution meant that 290 00:14:00.720 --> 00:14:04.639 the crucial early stages, the initial ejection of material, were 291 00:14:04.679 --> 00:14:07.759 all compressed into this tiny observational. 292 00:14:07.159 --> 00:14:09.440 Window, which makes the fact that they caught it with 293 00:14:09.559 --> 00:14:11.279 Chara even more incredible. 294 00:14:11.320 --> 00:14:13.360 It's a huge achievement. And what they saw in this 295 00:14:13.399 --> 00:14:16.879 first couple of days, I mean, the geometry is stunningly asymmetrical, 296 00:14:16.960 --> 00:14:19.919 not a sphere, not even close to his sphere. The 297 00:14:19.960 --> 00:14:22.559 images taken just two point two and three point two 298 00:14:22.679 --> 00:14:26.519 days after the explosion revealed the immediate formation of two 299 00:14:26.639 --> 00:14:29.240 distinct perpendicular outflows of gas. 300 00:14:29.320 --> 00:14:32.720 Perpendicular, so not just two jets shooting out from the poles, 301 00:14:33.120 --> 00:14:35.759 but two sets of jets at right angles to each other. 302 00:14:35.879 --> 00:14:38.200 That's what the data shows. We're talking about high speed 303 00:14:38.279 --> 00:14:41.200 jets of material shooting out almost at right angles. It's 304 00:14:41.240 --> 00:14:43.639 an incredibly complex shape to form so quickly. 305 00:14:43.759 --> 00:14:46.639 That implies the explosion's engine isn't uniform at all. What 306 00:14:46.720 --> 00:14:49.960 kind of physics could possibly drive flows like that. 307 00:14:49.960 --> 00:14:53.320 That's the million dollar question now, and it's probably tied 308 00:14:53.360 --> 00:14:57.039 to the system's rotation and magnetic fields. A rapidly spinning 309 00:14:57.080 --> 00:15:00.440 white dwarf can easily form a bipolar outflow, you know, 310 00:15:00.480 --> 00:15:02.159 two jets shooting from the poles. 311 00:15:01.919 --> 00:15:04.679 Right, That makes sense the path of least resistance. 312 00:15:04.480 --> 00:15:08.159 But perpendicular flows suggests something even more complex is going on, 313 00:15:08.559 --> 00:15:11.279 maybe a pre existing structure that the blast is hitting, 314 00:15:11.639 --> 00:15:14.759 or perhaps a rapidly tumbling or tilted magnetic field that's 315 00:15:14.840 --> 00:15:17.399 channeling the plasma in multiple directions at once. 316 00:15:17.759 --> 00:15:21.440 So this is direct visual evidence of multiple interacting ejections, 317 00:15:21.759 --> 00:15:23.200 not one single puff. 318 00:15:23.399 --> 00:15:26.679 That's the takeaway. And what's critical is that this complex 319 00:15:26.720 --> 00:15:30.440 geometry immediately explained the high energy data they were seeing 320 00:15:30.440 --> 00:15:31.039 at the same. 321 00:15:30.879 --> 00:15:32.159 Time, the gamma rays. 322 00:15:32.279 --> 00:15:35.279 The gamma rays the images from Shara showed these fast 323 00:15:35.320 --> 00:15:38.919 moving jets colliding with slower moving gas that was probably 324 00:15:38.960 --> 00:15:42.000 ejected just a little bit earlier. This violent collision is 325 00:15:42.039 --> 00:15:45.279 the perfect setup for generating intense shockwaves, and. 326 00:15:45.240 --> 00:15:47.480 We now know those shockwaves are the source of the 327 00:15:47.519 --> 00:15:50.320 gamma rays that NASA's Fermi Space telescope saw. 328 00:15:50.600 --> 00:15:54.919 It was direct, irrefutable proof the geometric complexity is driving 329 00:15:54.919 --> 00:15:55.960 the high energy physics. 330 00:15:56.000 --> 00:15:58.720 Okay, so that's one star that just rushed through its 331 00:15:58.720 --> 00:16:02.519 explosion with this specta tacular jet driven chaos. But then 332 00:16:02.559 --> 00:16:04.799 we look at the other one, nova V fourteen oh 333 00:16:04.879 --> 00:16:07.559 five Cassiopa, and it seems to be operating on a 334 00:16:07.600 --> 00:16:08.799 totally different schedule. 335 00:16:09.000 --> 00:16:11.879 V fourteen oh five Cassiopa was the polar opposite in 336 00:16:11.960 --> 00:16:15.480 many ways. It evolved much more slowly, which isn't unheard of. 337 00:16:16.159 --> 00:16:20.799 But the central surprise here was a clear, dramatic physical delay. 338 00:16:20.919 --> 00:16:25.000 This nova showed the first clear evidence of a delayed expulsion. 339 00:16:24.559 --> 00:16:27.600 A delay. What does that mean? The explosion happened, but 340 00:16:27.639 --> 00:16:28.759 the material didn't leave. 341 00:16:29.120 --> 00:16:33.480 Essentially, yes, the star held onto its outer layer's material 342 00:16:33.799 --> 00:16:35.080 for more than fifty days. 343 00:16:35.720 --> 00:16:39.240 Fifty so for almost two months. The thermonuclear runaway had 344 00:16:39.240 --> 00:16:41.519 already happened on the surface, but the material was just 345 00:16:41.720 --> 00:16:42.320 stuck there. 346 00:16:42.440 --> 00:16:45.679 That's right. The energy was generated, but the stellar envelope 347 00:16:45.720 --> 00:16:49.080 didn't fully disperse. It was contained somehow. 348 00:16:49.279 --> 00:16:52.240 That's incredible. I mean, the pressure from a runaway thermal 349 00:16:52.279 --> 00:16:56.639 pulse should be enormous and immediate. What could possibly hold 350 00:16:56.720 --> 00:16:58.240 it in for fifty days? 351 00:16:58.440 --> 00:17:02.279 It suggests there was some power full confining mechanism, perhaps 352 00:17:02.279 --> 00:17:05.960 an incredibly strong and compressed magnetic field acting like a 353 00:17:06.000 --> 00:17:10.000 cage trapping the plasma, or maybe an unusually dense initial 354 00:17:10.079 --> 00:17:13.079 envelope that needed a lot more sustained energy to finally 355 00:17:13.119 --> 00:17:14.440 overcome the star's gravity. 356 00:17:14.559 --> 00:17:17.680 Whatever the cause, the consequences when that containment finally failed 357 00:17:17.799 --> 00:17:19.039 must have been spectacular. 358 00:17:19.200 --> 00:17:22.160 They were. When the material was finally expelled after that 359 00:17:22.200 --> 00:17:27.279 fifty day confinement, it erupted violently. This triggered new incredibly 360 00:17:27.279 --> 00:17:29.960 intense shocks, like a spring that's been compressed for two 361 00:17:30.000 --> 00:17:31.720 months and is suddenly released. 362 00:17:31.839 --> 00:17:34.519 And I'm guessing fermisaw a burst of gamma rays from 363 00:17:34.519 --> 00:17:36.400 this one too, a huge. 364 00:17:36.039 --> 00:17:39.559 Burst of gamma rays, Yeah, which provided even more support 365 00:17:39.839 --> 00:17:42.720 for this shock driven model of high energy emission. 366 00:17:42.799 --> 00:17:46.279 So what's fascinating here is the sheer variability. You look 367 00:17:46.279 --> 00:17:49.160 at just two events and you get one that's immediate 368 00:17:49.279 --> 00:17:53.480 perpendicular jets and another that's a fifty day magnetic cage scenario. 369 00:17:54.000 --> 00:17:57.839 It completely shatters the idea of a standard nova. It 370 00:17:57.880 --> 00:18:01.160 tells us that the local environment, the white dwarf's magnetic field, 371 00:18:01.200 --> 00:18:04.279 it's spin, the density of the material, it's stealing all 372 00:18:04.319 --> 00:18:07.240 of that dictates the outcome. The geometry is everything, and 373 00:18:07.240 --> 00:18:08.960 the geometry is wildly diverse. 374 00:18:09.119 --> 00:18:11.440 So we have the visual proof of the geometry, We 375 00:18:11.480 --> 00:18:13.440 have the timeline of the ejection. Now we have to 376 00:18:13.440 --> 00:18:17.680 connect the docks. Why does seeing these structural details, the 377 00:18:17.680 --> 00:18:20.920 perpendicular jets, the fifty day delay, why does that matter 378 00:18:21.000 --> 00:18:24.799 so much to the broader field of high energy astrophysics. 379 00:18:24.039 --> 00:18:26.920 Because it directly solves a major puzzle from the last decade, 380 00:18:26.920 --> 00:18:29.240 which is where are all these high energy gamma rays 381 00:18:29.279 --> 00:18:30.400 in our galaxy coming from? 382 00:18:30.440 --> 00:18:32.400 We knew novae were one of the sources. 383 00:18:32.759 --> 00:18:38.640 Right before Shara, NASA's FIRMI Large Area Telescope had detected 384 00:18:38.799 --> 00:18:42.640 JIV emission that's gig electron BOLG gamma rays from more 385 00:18:42.680 --> 00:18:46.640 than twenty novae. This established them as significant galactic gamma 386 00:18:46.680 --> 00:18:47.400 ray factories. 387 00:18:47.519 --> 00:18:50.359 We knew the factory existed, but we didn't know how 388 00:18:50.400 --> 00:18:53.799 the machinery inside actually worked. We assumed it with shockwaves, 389 00:18:53.960 --> 00:18:55.400 but that was just a theory. 390 00:18:55.519 --> 00:18:57.440 It was a very strong theory, but it was still 391 00:18:57.480 --> 00:19:02.039 a theory. These new images provide the direct proof. They 392 00:19:02.079 --> 00:19:05.000 allow us to definitively tie the gamma rays seen by 393 00:19:05.079 --> 00:19:08.400 Fermi not to the initial flash, but directly to those 394 00:19:08.440 --> 00:19:09.440 colliding outflows. 395 00:19:09.680 --> 00:19:12.559 The visual structures are the engines creating the high energy 396 00:19:12.640 --> 00:19:13.759 radiation precisely. 397 00:19:14.039 --> 00:19:18.000 It's a remarkable piece of validation. If novae were truly spherical, 398 00:19:18.480 --> 00:19:22.480 those shockwaves would dissipate quickly and symmetrically. You probably wouldn't 399 00:19:22.480 --> 00:19:24.640 get such intense gamma rays. It's the fact that the 400 00:19:24.640 --> 00:19:27.839 ejecta are lumpy and messy and colliding that creates the 401 00:19:27.839 --> 00:19:29.759