1 00:00:00,160 --> 00:00:02,919 Speaker 1: Welcome to the deep dive. We are going to start 2 00:00:02,960 --> 00:00:06,200 today with something that should really make the hair stand 3 00:00:06,280 --> 00:00:07,240 up in the back of your neck. 4 00:00:07,639 --> 00:00:08,759 Speaker 2: Oh, go on. 5 00:00:09,439 --> 00:00:13,480 Speaker 1: It's this idea, this premise that for the first time, 6 00:00:13,560 --> 00:00:17,239 maybe in human history, something genuinely alien, I mean, something 7 00:00:17,239 --> 00:00:21,199 from way outside our solar system has actually actively communicated 8 00:00:21,239 --> 00:00:21,600 with us. 9 00:00:21,760 --> 00:00:24,600 Speaker 2: Wow. Okay, yeah, that's the classic sci fi opening, isn't 10 00:00:24,640 --> 00:00:27,399 it straight out of a movie exactly? And our sources, well, 11 00:00:27,440 --> 00:00:30,839 they do kick off with this really electrifying though, let's 12 00:00:30,879 --> 00:00:36,079 be clear, completely unsubstantiated claim. A signal supposedly an active 13 00:00:36,119 --> 00:00:38,640 response from an interstellar. 14 00:00:38,000 --> 00:00:40,880 Speaker 1: Object detected where somewhere dramatic. 15 00:00:40,560 --> 00:00:43,439 Speaker 2: I bet deep beneath Switzerland apparently, you know, maybe near 16 00:00:43,479 --> 00:00:46,719 Cern in those super shielded tunnels. The implication, if it 17 00:00:46,719 --> 00:00:50,119 were true, is just massive a visitor, maybe from some 18 00:00:50,320 --> 00:00:52,079 galactic alliance heading our way. 19 00:00:52,359 --> 00:00:54,799 Speaker 1: It's a fantastic hook, you have to admit. But while 20 00:00:54,799 --> 00:00:57,119 that idea of you know, et phony home grebs the 21 00:00:57,119 --> 00:00:59,200 headlines the real story here. 22 00:00:59,159 --> 00:01:00,560 Speaker 2: The actual science. 23 00:01:00,920 --> 00:01:03,600 Speaker 1: Yeah, the actual science is just as thrilling. I think 24 00:01:03,679 --> 00:01:09,799 it's rigorous, incredibly challenging, and honestly pretty revolutionary. High precision 25 00:01:09,840 --> 00:01:12,079 work tracking this object and. 26 00:01:11,959 --> 00:01:17,000 Speaker 2: Totally grounded in real observations, cross planetary stuff, astronomical grit as. 27 00:01:17,000 --> 00:01:20,000 Speaker 1: You say, absolutely, So we're focusing today on three IA lists. 28 00:01:20,000 --> 00:01:23,000 That's the third interstellar traveler we've confirmed, right. 29 00:01:23,040 --> 00:01:26,319 Speaker 2: It recently zipped past Mars through the Inner Solar System. 30 00:01:26,480 --> 00:01:28,799 Speaker 1: So our mission for this deep dive is to kind 31 00:01:28,799 --> 00:01:32,560 of peel back that dramatic fiction, the sensationalism, and really 32 00:01:32,599 --> 00:01:35,200 dig into the science. How did we track this thing, 33 00:01:35,480 --> 00:01:38,280 How did we push our best instruments way past what 34 00:01:38,319 --> 00:01:38,959 they were built for. 35 00:01:39,120 --> 00:01:41,200 Speaker 2: What did they find, what could they figure out about 36 00:01:41,200 --> 00:01:44,879 its chemistry from just a faint bit of light? And crucially, 37 00:01:44,959 --> 00:01:47,879 what does this third visitor tell us about? Well, everything 38 00:01:47,879 --> 00:01:51,519 else out there the galaxy is inventory, so to speak. 39 00:01:51,680 --> 00:01:54,319 Speaker 1: We've got sources covering everything from like high ris stereo 40 00:01:54,400 --> 00:01:55,519 cameras orbiting. 41 00:01:55,239 --> 00:01:58,200 Speaker 2: Mars cameras designed to look down at Mars, not up 42 00:01:58,280 --> 00:01:59,719 at faint fast. 43 00:01:59,480 --> 00:02:04,719 Speaker 1: Things exactly all the way to ground based spectroscopy trying 44 00:02:04,760 --> 00:02:08,360 to decipher this signal, and the object itself was moving 45 00:02:08,400 --> 00:02:10,840 faster than our satellites could even track properly. 46 00:02:10,919 --> 00:02:13,039 Speaker 2: It really wasn't standard astronomy at all. It was more 47 00:02:13,120 --> 00:02:16,400 like scientific improvisation under huge pressure. 48 00:02:16,599 --> 00:02:18,479 Speaker 1: Yeah, so we're going to find out how they managed 49 00:02:18,479 --> 00:02:21,479 to confirm something that was barely there, like a whisper 50 00:02:21,520 --> 00:02:23,439 of light just above the background noise. 51 00:02:23,560 --> 00:02:27,960 Speaker 2: Precisely. The technical constraints basically define this discovery. It's a 52 00:02:27,960 --> 00:02:29,120 story about limits. 53 00:02:29,400 --> 00:02:33,560 Speaker 1: Okay, let's unpack this then. What exactly were scientists chasing 54 00:02:33,840 --> 00:02:36,159 and what did they actually find when they pushed their 55 00:02:36,199 --> 00:02:40,000 instruments right to the absolute edge. 56 00:02:40,639 --> 00:02:40,960 Speaker 2: Hmm. 57 00:02:41,840 --> 00:02:43,719 Speaker 1: So the first big thing that jumps out from the 58 00:02:43,759 --> 00:02:48,240 sources is just how incredibly difficult, how technically improbable tracking 59 00:02:48,280 --> 00:02:49,759 three ieals actually was. 60 00:02:49,919 --> 00:02:51,599 Speaker 2: Oh definitely, this whole. 61 00:02:51,400 --> 00:02:55,879 Speaker 1: Story seems to be about compromise, astronomically speaking, using hardware 62 00:02:55,919 --> 00:02:58,560 for a job it was never ever designed for. 63 00:02:58,680 --> 00:03:00,360 Speaker 2: It's kind of astonishing when you dig in to it. 64 00:03:00,439 --> 00:03:03,159 The main instrument that gave us that crucial early data 65 00:03:03,280 --> 00:03:06,400 was the cassi's camera. It's on the Trace gas orbiter 66 00:03:06,800 --> 00:03:10,800 and CASSIS. Yeah. Well, it's basically the exact opposite of 67 00:03:10,840 --> 00:03:14,759 what you'd want for chasing a fast, faint interstellar object. 68 00:03:15,199 --> 00:03:18,719 It was built to be a map maker, a very careful, 69 00:03:18,960 --> 00:03:21,080 meticulous cartographer. 70 00:03:20,439 --> 00:03:23,680 Speaker 1: Designed to look down to Mars right map the surface exactly. 71 00:03:23,759 --> 00:03:27,080 Speaker 2: Its whole purpose was mapping the Martian surface in color 72 00:03:27,199 --> 00:03:30,639 in stereo, drawing these super precise topographic lines. 73 00:03:30,840 --> 00:03:32,479 Speaker 1: So I was looking for features on the ground. 74 00:03:32,560 --> 00:03:37,080 Speaker 2: Yeah. It's filters were tuned for things like iron oxides, silicates, 75 00:03:37,520 --> 00:03:41,560 you know, rocks, things that sit still, and maybe more importantly, 76 00:03:41,800 --> 00:03:44,680 its sensors were designed for long exposures. 77 00:03:44,319 --> 00:03:46,360 Speaker 1: To get good detail on the terrain, right, to. 78 00:03:46,319 --> 00:03:49,400 Speaker 2: Get a high signal to noise ratio for stationary stuff, 79 00:03:49,560 --> 00:03:52,039 low contrast ground features. It wasn't built for speed. 80 00:03:52,560 --> 00:03:54,879 Speaker 1: Okay. So you have this finely tuned instrument, perfect for 81 00:03:54,919 --> 00:03:57,520 mapping rocks, and then someone says, right, forget the rocks 82 00:03:57,560 --> 00:03:59,840 for a minute. Point that thing up out in this base. 83 00:04:00,080 --> 00:04:03,680 Try to catch this tiny, incredibly fast blur that's coming 84 00:04:03,680 --> 00:04:05,000 from another star system. 85 00:04:05,080 --> 00:04:05,879 Speaker 2: Yeah, pretty much. 86 00:04:06,039 --> 00:04:08,000 Speaker 1: The difficulty must have been a man. Just the speed 87 00:04:08,039 --> 00:04:09,280 of three eyallis alone. 88 00:04:09,400 --> 00:04:13,319 Speaker 2: The speed was absolutely this central problem. Three ils was 89 00:04:13,360 --> 00:04:17,639 moving incredibly rapidly, and on top of that, the trace 90 00:04:17,759 --> 00:04:21,680 gas orbiter itself is whipping around Mars at high speed. 91 00:04:21,959 --> 00:04:24,959 Speaker 1: So everything's moving relative to everything else constantly. 92 00:04:24,480 --> 00:04:31,680 Speaker 2: Constant orbital corrections, constant motion relative to the background stars, no. 93 00:04:32,000 --> 00:04:34,680 Speaker 1: Use, what's called rate tracking, with the camera locks onto 94 00:04:34,720 --> 00:04:36,680 the target and follows it smoothly exactly. 95 00:04:36,720 --> 00:04:39,680 Speaker 2: It keeps the image sharp by matching the target's movement. 96 00:04:40,040 --> 00:04:43,560 Speaker 1: But the sources say that just was impossible here. Why not? 97 00:04:44,240 --> 00:04:46,000 Was it the motors, the software? 98 00:04:46,120 --> 00:04:49,319 Speaker 2: It was a mix of things, mechanical limits, computational limits. 99 00:04:49,720 --> 00:04:52,480 Cassie's just wasn't built with the kind of fast response 100 00:04:52,600 --> 00:04:55,920 gyros or the high speed processing power you'd need for 101 00:04:55,959 --> 00:04:57,879 those tiny subsecond corrections. 102 00:04:58,000 --> 00:05:01,480 Speaker 1: It was designed for stability, for locking onto fixed points. 103 00:05:01,560 --> 00:05:04,439 Speaker 2: Precisely, if they'd tried standard rate tracking, the system just 104 00:05:04,480 --> 00:05:07,319 couldn't have kept up with the object hitting speeds near 105 00:05:07,439 --> 00:05:09,519 seventy kilometers per second relative to the. 106 00:05:09,480 --> 00:05:11,279 Speaker 1: Sun seventy kilometers a second. 107 00:05:11,439 --> 00:05:13,560 Speaker 2: Yeah, the image would have just been a useless smear. 108 00:05:13,800 --> 00:05:17,439 Speaker 1: Okay, that sounds well, it sounds pretty hopeless. Then how 109 00:05:17,519 --> 00:05:20,319 on earth did they get any usable picture? How did 110 00:05:20,360 --> 00:05:21,560 they work around those limits? 111 00:05:22,000 --> 00:05:26,959 Speaker 2: They had to fall back on this technique that feels like, well, 112 00:05:27,040 --> 00:05:30,000 like applied trigonometry mixed with a healthy dose of faith. 113 00:05:30,079 --> 00:05:30,920 It's called step and. 114 00:05:30,920 --> 00:05:32,519 Speaker 1: Stare imaging stiff and stare. 115 00:05:32,920 --> 00:05:36,240 Speaker 2: So the orbiter wasn't actively tracking the object in real time. 116 00:05:36,279 --> 00:05:39,759 It was anticipating it. The flight dynamics team had to 117 00:05:39,800 --> 00:05:44,480 calculate the object's orbit with extreme precision from ground observations 118 00:05:44,519 --> 00:05:47,439 first Wow, Then they had to project exactly where it 119 00:05:47,439 --> 00:05:50,360 would be against the Martian sky, second by second, so. 120 00:05:50,240 --> 00:05:52,800 Speaker 1: They weren't following the object itself. They were following the 121 00:05:52,839 --> 00:05:54,639 mass the prediction of where it should be. 122 00:05:54,800 --> 00:05:57,959 Speaker 2: That's exactly it. The orbiter would tilt the camera slightly 123 00:05:58,000 --> 00:06:00,439 ahead of where they predicted three I Alice would. Then 124 00:06:00,480 --> 00:06:03,160 it would take a fairly long exposure, like five seconds. 125 00:06:03,160 --> 00:06:06,040 Speaker 1: Five seconds is long for something moving that fast it is. 126 00:06:06,519 --> 00:06:09,639 Speaker 2: Then it would quickly tilt again to the next predicted spot, 127 00:06:09,680 --> 00:06:12,759 take another five second shot, and just repeat that sequence 128 00:06:12,839 --> 00:06:16,079 over and over, dozens of times, each shot perfectly timed 129 00:06:16,439 --> 00:06:19,680 down to the microsecond. If their timing was off or 130 00:06:19,720 --> 00:06:22,759 their angle calculation was off by even a tiny fraction 131 00:06:22,839 --> 00:06:25,319 of a degree, the object just wouldn't be in the 132 00:06:25,319 --> 00:06:27,000 frame during that brief window. 133 00:06:27,279 --> 00:06:30,720 Speaker 1: I'm picturing the raw data just being a complete mess. 134 00:06:31,000 --> 00:06:34,720 Five second exposures the object moving tens of kilometers in 135 00:06:34,720 --> 00:06:37,040 that time, plus the orbiter's own movement. 136 00:06:37,199 --> 00:06:40,439 Speaker 2: Oh, the raw images were almost unusable, just full of noise, 137 00:06:40,480 --> 00:06:44,199 you'd have faint streaks from distant background stars drifting across 138 00:06:44,759 --> 00:06:48,720 hot pixels on the detector, cosmic rays hitting it constantly. 139 00:06:49,319 --> 00:06:51,360 Speaker 1: So how did they pull the actual signal out of 140 00:06:51,360 --> 00:06:52,040 all that chunk? 141 00:06:52,240 --> 00:06:55,120 Speaker 2: Okay, this is the clever bit. The background stars were 142 00:06:55,160 --> 00:06:58,480 drifting in one predictable direction, right, That was just due 143 00:06:58,480 --> 00:07:02,720 to the orbiter's own motion around. But the interstellar object 144 00:07:02,800 --> 00:07:05,920 three I eight less because of its unique hyperbolic trajectory, 145 00:07:06,279 --> 00:07:09,079 it was streaking across the background in a slightly different direction. 146 00:07:09,240 --> 00:07:11,800 Speaker 1: Ah, the geometry was different, the angle. 147 00:07:11,519 --> 00:07:15,040 Speaker 2: Of the streak exactly. That difference in the motion vectors. 148 00:07:15,199 --> 00:07:17,800 That was the key. They couldn't just stack the images 149 00:07:17,839 --> 00:07:20,839 based on the stars. They had to mathematically align all 150 00:07:20,879 --> 00:07:24,680 those dozens of frames along the very precise predicted motion 151 00:07:24,839 --> 00:07:27,600 vector of three iless Wow. Okay, And only when they 152 00:07:27,680 --> 00:07:30,680 did that, aligning along the expected path of the object, 153 00:07:30,879 --> 00:07:35,079 did this faint, persistent pattern finally emerge, A faint streak 154 00:07:35,279 --> 00:07:37,759 getting slightly brighter right where the leading edge of three 155 00:07:37,800 --> 00:07:38,920 iyelis was supposed to be. 156 00:07:39,199 --> 00:07:42,519 Speaker 1: So not a shirt picture, more like a composite ghost. 157 00:07:42,680 --> 00:07:44,959 Speaker 2: A ghost like composite is a great way to put it. 158 00:07:45,480 --> 00:07:49,000 But Crucially, its direction and its apparent speed matched the 159 00:07:49,120 --> 00:07:51,839 orbital model perfectly. It was conformation. 160 00:07:52,120 --> 00:07:55,839 Speaker 1: They literally pulled a verified signal out of geometric noise. 161 00:07:56,680 --> 00:07:59,040 That data processing must have taken ages. 162 00:07:58,920 --> 00:08:01,959 Speaker 2: Months of incredibly careful work, and the effort didn't stop 163 00:08:02,040 --> 00:08:05,199 with just Kassis. The sources mention another orbiter getting involved, 164 00:08:05,279 --> 00:08:07,800 Mars Express, using its HRSC camera. 165 00:08:07,680 --> 00:08:11,000 Speaker 1: Right, the high resolution stereo camera. Did that help clarify things? 166 00:08:11,079 --> 00:08:14,519 Speaker 2: Well, yes and no, it presented an even steeper technical challenge. Actually, 167 00:08:14,639 --> 00:08:18,800 so HRSC is designed for maximum sharpness of the Martian surface. 168 00:08:19,519 --> 00:08:23,360 That means it uses extremely short exposure times. Its maximum 169 00:08:23,399 --> 00:08:24,839 is only half a second. 170 00:08:24,519 --> 00:08:26,879 Speaker 1: Half a second for something this faint and fast. 171 00:08:27,160 --> 00:08:31,079 Speaker 2: Exactly. It's designed to freeze the terrain below prevent blurring, 172 00:08:31,600 --> 00:08:33,559 which is great for maps, but it meant three i 173 00:08:33,679 --> 00:08:38,159 at lass was practically invisible in any single HRSC frame. 174 00:08:38,679 --> 00:08:41,519 It's like trying to photograph lightning with a slow shutter speed. 175 00:08:41,559 --> 00:08:42,480 You get almost nothing. 176 00:08:42,799 --> 00:08:44,559 Speaker 1: So how did they use HRSC data? 177 00:08:44,600 --> 00:08:48,000 Speaker 2: Then they had to resort to what's called extreme deep snacking, 178 00:08:48,399 --> 00:08:51,840 piling up hundreds, literally hundreds of these half second exposures. 179 00:08:51,919 --> 00:08:52,399 Speaker 1: Oh wow. 180 00:08:52,480 --> 00:08:55,840 Speaker 2: And again they had to precisely offset each frame, accounting 181 00:08:55,879 --> 00:08:58,440 not just for the object's predicted motion, but also for 182 00:08:58,480 --> 00:09:01,279 the drift of the background stars and even tiny thermal 183 00:09:01,360 --> 00:09:04,879 variations in the camera detector itself that could create false signals. 184 00:09:05,000 --> 00:09:06,759 Speaker 1: That sounds incredibly sensitive. 185 00:09:06,600 --> 00:09:09,879 Speaker 2: Usually sensitive. But eventually, after all that stacking and cleaning, 186 00:09:09,919 --> 00:09:13,159 this faint composite image emerged from HRC too, and it 187 00:09:13,200 --> 00:09:15,879 confirmed the track derived from CASSIS. It gave them that 188 00:09:16,000 --> 00:09:18,039 crucial cross planetary conformation. 189 00:09:18,679 --> 00:09:22,519 Speaker 1: So CASSIES gave the longer blurs showing the path, HRC 190 00:09:22,559 --> 00:09:25,919 gave hundreds of tiny snapshots confirming the same path, a 191 00:09:26,039 --> 00:09:29,759 kind of rough triangulation from two different orbits around Mars. 192 00:09:29,639 --> 00:09:33,279 Speaker 2: Exactly, and that allowed them to really nail down the 193 00:09:33,320 --> 00:09:36,519 object's incredible speed and its motion relative to the Sun 194 00:09:36,840 --> 00:09:40,279 and what they saw in those faint composite images. While 195 00:09:40,320 --> 00:09:44,559 that completely changed the game regarding what we thought interstellar visitors. 196 00:09:44,159 --> 00:09:46,200 Speaker 1: Should look like, Okay, so they managed to see it 197 00:09:46,279 --> 00:09:48,879 against all odds. But what they saw is the next 198 00:09:48,879 --> 00:09:52,039 big mystery. The sources call it the anatomy of restraint. 199 00:09:52,200 --> 00:09:53,879 Speaker 2: That's a great phrase for it. 200 00:09:53,840 --> 00:09:56,399 Speaker 1: Because the images showed that three I at lasts seemed 201 00:09:56,399 --> 00:10:00,919 to be well, exhaling light. As they put it, it 202 00:10:00,960 --> 00:10:01,960 was definitely. 203 00:10:01,559 --> 00:10:03,840 Speaker 2: Active, right, There was clearly something coming. 204 00:10:03,559 --> 00:10:07,240 Speaker 1: Off it, but completely failed to form a proper comet tail, 205 00:10:07,840 --> 00:10:10,639 which is weird. Right, If it's active, shouldn't it have 206 00:10:10,679 --> 00:10:11,080 a tail. 207 00:10:11,279 --> 00:10:14,840 Speaker 2: That's the textbook definition. Usually a comet has a coma, 208 00:10:14,919 --> 00:10:17,679 the fuzzy head and a tail that dramatic plume. But 209 00:10:17,720 --> 00:10:22,120 when the scientists painstakingly analyze these stacked images from cassies 210 00:10:22,159 --> 00:10:24,720 and hrse, what did they see? They couldn't resolve the 211 00:10:24,759 --> 00:10:27,799 surface itself, the solid nucleus, it was too small or 212 00:10:27,840 --> 00:10:32,399 too far. All they saw was this diffuse, slightly asymmetrical glow, 213 00:10:32,600 --> 00:10:35,559 a glow like a haze around it exactly. It was 214 00:10:35,600 --> 00:10:37,879 thicker near the front, the direction of travel, and then 215 00:10:37,919 --> 00:10:41,240 it just smoothly fell away behind it. It suggested a coma, 216 00:10:41,480 --> 00:10:45,639 definitely a cloud of dust and gas, maybe thousands of kilometers. 217 00:10:45,039 --> 00:10:47,519 Speaker 1: Wide, but no distinct tail structure, no long. 218 00:10:47,360 --> 00:10:50,600 Speaker 2: Streamer, none at all, just the smooth gradient, which led 219 00:10:50,600 --> 00:10:55,759 to that description breath, not body. It was active, but 220 00:10:55,919 --> 00:10:58,080 subtly muted. 221 00:10:58,360 --> 00:11:01,279 Speaker 1: Okay, so it's an anomaly, a comet that's sort of 222 00:11:01,840 --> 00:11:04,519 refusing to act like a comet. What physics could be 223 00:11:04,559 --> 00:11:07,679 causing that, especially considering it was out near Mars's orbit. 224 00:11:07,559 --> 00:11:10,120 Speaker 2: Right, the environment matters. It was about one point five 225 00:11:10,240 --> 00:11:12,679 astronomical units from the Sun when they observed it. That's 226 00:11:12,720 --> 00:11:15,000 one and a half times Earth's distance, So the sunlight 227 00:11:15,039 --> 00:11:17,360 is weaker there, about half the intensity we get here 228 00:11:17,399 --> 00:11:20,360 on Earth, but still strong enough that sunlight was hitting 229 00:11:20,399 --> 00:11:24,039 volatile grains, probably ices near the object's surface, causing. 230 00:11:23,840 --> 00:11:26,200 Speaker 1: Them to sublimate turned directly into. 231 00:11:26,039 --> 00:11:30,519 Speaker 2: Gas, exactly sublimation, and that escaping gas would drag fine 232 00:11:30,600 --> 00:11:33,399 dust particles off the surface with it, forming that coma 233 00:11:33,440 --> 00:11:37,080 cloud they observed. So activity was definitely happening. 234 00:11:37,120 --> 00:11:40,159 Speaker 1: Okay, But how did they prove the light they were 235 00:11:40,240 --> 00:11:44,240 seeing was from active sublimation? Yeah, and not just you know, 236 00:11:44,360 --> 00:11:47,000 sunlight reflecting off a dull, rocky asteroid. 237 00:11:47,159 --> 00:11:50,120 Speaker 2: Ah, that's a key question. They looked at how the 238 00:11:50,159 --> 00:11:53,080 brightness fell off across that fuzzy glow the coma. 239 00:11:53,120 --> 00:11:54,480 Speaker 1: The brightness profile. 240 00:11:54,480 --> 00:11:58,120 Speaker 2: Precisely simple reflection off a solid body would cause the 241 00:11:58,120 --> 00:12:01,159 brightness to decay in a fairly prediction bull weigh mostly 242 00:12:01,200 --> 00:12:03,559 tied to the inverse square of the distance from the Sun. 243 00:12:03,960 --> 00:12:06,679 A gentle, smooth fall off okay, but what they saw 244 00:12:06,879 --> 00:12:09,879 was different. The brightness dropped off really sharply, following a 245 00:12:09,879 --> 00:12:13,240 distinct exponential curve. It faded very rapidly within just a 246 00:12:13,240 --> 00:12:15,519 few arcseconds of the central brightest point. 247 00:12:15,559 --> 00:12:19,600 Speaker 1: And that exponential curve is a smoking gun for for sublimation. 248 00:12:19,799 --> 00:12:22,679 Speaker 2: It's the physical signature you expect when gas and dust 249 00:12:22,720 --> 00:12:25,879 are actively being released from a relatively small central source 250 00:12:26,320 --> 00:12:29,720 and then expanding outwards into space. And there was another 251 00:12:29,799 --> 00:12:34,600 clue that elongated glow, the faint breath. It wasn't pointing 252 00:12:34,600 --> 00:12:37,519 directly away from the sun. It was tilted slightly, maybe 253 00:12:37,639 --> 00:12:38,840 eight to ten degrees off. 254 00:12:39,320 --> 00:12:41,240 Speaker 1: Why is that significant because that's. 255 00:12:41,080 --> 00:12:44,600 Speaker 2: Exactly where you'd expect solar radiation pressure, the push from 256 00:12:44,600 --> 00:12:49,039 sunlight itself to nudge the lightest, most recently released dust grains. 257 00:12:49,600 --> 00:12:53,039 It confirmed the material was being actively pushed, not just 258 00:12:53,080 --> 00:12:54,080 passively reflecting. 259 00:12:54,440 --> 00:12:57,360 Speaker 1: Okay, so they had solid proof of activity gas and 260 00:12:57,440 --> 00:12:59,399 dust coming off it. But that brings us back to 261 00:12:59,440 --> 00:13:04,159 the big question. If it's actively shedding stuff, why no tail, 262 00:13:04,519 --> 00:13:05,440 why the restraint? 263 00:13:05,559 --> 00:13:08,240 Speaker 2: And that's where the single most defining characteristic of three 264 00:13:08,279 --> 00:13:12,159 I at last comes back into play. It's absolutely incredible speed. 265 00:13:12,240 --> 00:13:14,080 Speaker 1: The seventy kilometers per second. 266 00:13:13,840 --> 00:13:16,679 Speaker 2: Nearly seventy kilometers per second relative to the Sun around 267 00:13:16,679 --> 00:13:20,279 the time of these observations. That hypervelocity, the sources argue, 268 00:13:20,320 --> 00:13:23,240 is the definitive reason the tail failed to form. Properly. 269 00:13:23,919 --> 00:13:26,480 Speaker 1: Break that down for you. Why does speed stop a 270 00:13:26,559 --> 00:13:30,240 tail from forming? Doesn't the Sun push the material away? Regardless? 271 00:13:30,600 --> 00:13:34,440 Speaker 2: It does, But forming a visible tail takes time. Solar 272 00:13:34,519 --> 00:13:39,039 radiation pressure isn't instantaneous. It needs time to accelerate those 273 00:13:39,080 --> 00:13:42,600 tiny dust grains and gas molecules to push them back 274 00:13:42,639 --> 00:13:46,240 and shape them into that recognizable structure, that trailing filament 275 00:13:46,360 --> 00:13:47,759 or detached arc. We see. 276 00:13:47,840 --> 00:13:49,759 Speaker 1: How much time are we talking about, Well. 277 00:13:49,519 --> 00:13:51,519 Speaker 2: It depends on the size of the dust grains, but 278 00:13:51,600 --> 00:13:55,200 it can take anywhere from minutes for the very smallest particles, 279 00:13:55,320 --> 00:13:58,840 up to hours or even days for a larger micron 280 00:13:58,960 --> 00:14:03,080 sized dust to be pushed significantly far back to form 281 00:14:03,120 --> 00:14:04,159 a distinct tail. 282 00:14:04,559 --> 00:14:07,279 Speaker 1: Okay, minutes to hours, But in that time. 283 00:14:07,080 --> 00:14:10,360 Speaker 2: In that time, three i atlas traveling at nearly seventy 284 00:14:10,440 --> 00:14:14,559 kilometers had moved an enormous distance tens of thousands, even 285 00:14:14,639 --> 00:14:17,200 hundreds of thousands of kilometers further along its path. 286 00:14:17,240 --> 00:14:19,879 Speaker 1: So it was literally out running its own exhaust. Material 287 00:14:19,919 --> 00:14:22,759 couldn't get pushed back fast enough to form a coherent 288 00:14:22,799 --> 00:14:23,639 stream behind it. 289 00:14:23,879 --> 00:14:27,480 Speaker 2: That's exactly the idea. The material was escaping the nucleus. Sure, 290 00:14:27,559 --> 00:14:29,840 maybe at speeds of meters per second relative to the 291 00:14:29,879 --> 00:14:33,559 object itself, but the whole system object plus freshly released 292 00:14:33,600 --> 00:14:36,799 gas and dust was hurtling forward at seventy kilometers per second. 293 00:14:37,120 --> 00:14:40,480 The material just dispersed too rapidly onto the vastness of space. 294 00:14:40,919 --> 00:14:43,279 What should have become a visible plume got spread out 295 00:14:43,320 --> 00:14:46,080 so thinly, so quickly over such a huge distance that 296 00:14:46,120 --> 00:14:49,519 it just blended into the background sky. The Sun's pressure 297 00:14:49,559 --> 00:14:52,000 didn't have enough time to organize it before it was gone. 298 00:14:52,440 --> 00:14:55,639 The velocity essentially diluted the tail before it could form. 299 00:14:55,759 --> 00:14:59,320 Speaker 1: That is, that's a really stunning constraint. The lack of 300 00:14:59,320 --> 00:15:01,919 a tail, which you'd normally think means an object as 301 00:15:01,919 --> 00:15:05,600 inactive here means the exact opposite. It was active, but 302 00:15:05,799 --> 00:15:08,120 just moving too darn fast for the Sun to sculpt 303 00:15:08,120 --> 00:15:09,399 its debris precisely. 304 00:15:09,440 --> 00:15:11,679 Speaker 2: And the thermal data we got kind of backs this up. 305 00:15:11,720 --> 00:15:14,960 They estimated the surface equilibrium temperature around one point five 306 00:15:15,039 --> 00:15:18,679 AU was near two hundred kelvin, which is cold, very cold, 307 00:15:18,879 --> 00:15:22,279 minus seventy three celsius. Roughly, that's way too cold for 308 00:15:22,320 --> 00:15:24,879 water ice to sublimate vigorously like we see in comets 309 00:15:24,879 --> 00:15:27,440 closer to the Sun in our own solar system. Ah okay, 310 00:15:27,519 --> 00:15:29,960 but it is warm enough for more volatile things like 311 00:15:30,039 --> 00:15:33,919 frozen carbon dioxide CO two to sublimate slowly. So the 312 00:15:33,960 --> 00:15:37,279 picture that emerges is one of slow, steady leakage of 313 00:15:37,440 --> 00:15:40,919 trace gases maybe CO two, percolating through a kind of 314 00:15:40,919 --> 00:15:41,919 protective crust on. 315 00:15:41,879 --> 00:15:44,600 Speaker 1: The surface, a crust formed over its long. 316 00:15:44,480 --> 00:15:47,519 Speaker 2: Journey, likely hardened and processed by millions of years of 317 00:15:47,600 --> 00:15:53,080 interstellar travel and radiation. So you have this minimal, steady outgassing, 318 00:15:53,200 --> 00:15:56,120 no big jets or flares like you see on fresh comets, 319 00:15:56,320 --> 00:15:59,759 combined with that phenomenal speed, and that combination created this 320 00:15:59,879 --> 00:16:03,879 u nique restrained appearance, a coma without a tail. 321 00:16:04,519 --> 00:16:09,200 Speaker 1: So three iadalys's identity, its appearance is really defined by 322 00:16:09,200 --> 00:16:12,679 its refusal to behave like a familiar native commet, and 323 00:16:12,720 --> 00:16:15,480 that refusal is purely down to its incredible speed and 324 00:16:15,519 --> 00:16:19,080 probably its very old process surface. Right, Okay, So they 325 00:16:19,080 --> 00:16:21,480 figured out why it looked weird. The speed basically smeared 326 00:16:21,480 --> 00:16:23,759 out its tail. The next step was trying to figure 327 00:16:23,759 --> 00:16:26,679 out what it was made of, it's chemical identity, right. 328 00:16:26,559 --> 00:16:28,759 Speaker 2: Moving from geometry and motion to chemistry, and. 329 00:16:28,759 --> 00:16:31,320 Speaker 1: The sources really emphasize just how difficult this was too. 330 00:16:31,559 --> 00:16:34,000 It sounds like three iadols was right at the absolute 331 00:16:34,120 --> 00:16:37,240 ragged edge of what our instruments could even measure, like 332 00:16:37,320 --> 00:16:39,440 trying to analyze a whisper in a noisy room. 333 00:16:39,639 --> 00:16:42,919 Speaker 2: That's a perfect analogy. Every instrument seemed to hit its 334 00:16:42,919 --> 00:16:47,480 limit almost immediately. The object's light footprint was incredibly faint, 335 00:16:48,039 --> 00:16:51,279 just barely registering only a few counts above the detector's 336 00:16:51,279 --> 00:16:51,840 own background. 337 00:16:51,919 --> 00:16:54,120 Speaker 1: Noise real but just barely. 338 00:16:53,919 --> 00:16:59,720 Speaker 2: Exactly real, but profoundly ambiguous, and that faintness, that fragility, 339 00:17:00,120 --> 00:17:04,319 the camera simply couldn't resolve the solid body itself the nucleus. 340 00:17:03,840 --> 00:17:07,160 Speaker 1: Which leads that frustrating problem you mentioned earlier, the ambiguous size. 341 00:17:07,200 --> 00:17:10,000 If you can't see the surface directly, you can't tell 342 00:17:10,039 --> 00:17:12,359 how big it is unless you know how reflective it is. 343 00:17:12,400 --> 00:17:15,559 Speaker 2: It's albedo precisely, and we didn't know the albedo, so 344 00:17:15,599 --> 00:17:19,519 we end up with these two wildly different possibilities based 345 00:17:19,559 --> 00:17:21,599 on the same faint smudge of lights. 346 00:17:21,680 --> 00:17:22,440 Speaker 1: Scenario one. 347 00:17:22,480 --> 00:17:26,200 Speaker 2: Scenario one, if the nucleus was relatively bright, maybe reflecting 348 00:17:26,200 --> 00:17:28,240 about twenty percent of the sunlight hitting it, kind of 349 00:17:28,279 --> 00:17:31,200 like a typical comet's nucleus, maybe with some fresh ice patches, 350 00:17:31,279 --> 00:17:32,599 then it would be Then it would have to be 351 00:17:32,759 --> 00:17:35,880 quite small to match the observed brightness, maybe only fifty 352 00:17:35,880 --> 00:17:38,359 meters across, like a large building. 353 00:17:38,119 --> 00:17:39,799 Speaker 1: Okay, fifty meters scenario two. 354 00:17:40,119 --> 00:17:44,559 Speaker 2: Scenario two, If the nucleus was really dark, like charcoal 355 00:17:44,640 --> 00:17:49,880 or asphalt coated and complex radiation processed organics, reflecting only 356 00:17:49,920 --> 00:17:50,559 maybe five. 357 00:17:50,400 --> 00:17:53,680 Speaker 1: Percent of the light, then to produce that same faint smudge, it. 358 00:17:53,599 --> 00:17:56,240 Speaker 2: Would have to be much much larger, perhaps five hundred 359 00:17:56,319 --> 00:17:58,599 meters across, ten times bigger. 360 00:17:58,759 --> 00:18:02,599 Speaker 1: Wow of ten differents in size fifty meters versus five 361 00:18:02,680 --> 00:18:06,039 hundred meters, And yet the light signature looks identical within 362 00:18:06,079 --> 00:18:08,960 the limits of detection. That's a huge uncertain. 363 00:18:08,680 --> 00:18:10,319 Speaker 2: Way is a massive range. 364 00:18:10,400 --> 00:18:12,680 Speaker 1: Now, you might think, with modern astronomy, couldn't they use 365 00:18:12,720 --> 00:18:15,960 other methods like ground based radar, or maybe watch how 366 00:18:16,000 --> 00:18:18,400 its brightness changes as it rotates to get a sense 367 00:18:18,440 --> 00:18:19,400 of shape and size. 368 00:18:19,440 --> 00:18:21,799 Speaker 2: That's a great question, and it really highlights the unique 369 00:18:21,880 --> 00:18:25,079 challenges here. Radar was pretty much out. The object was 370 00:18:25,119 --> 00:18:27,920 too far away past Mars's orbit and moving too fast 371 00:18:28,000 --> 00:18:29,640 across the sky relative to Earth. 372 00:18:29,839 --> 00:18:32,039 Speaker 1: Radar knees a strong return signal and time to. 373 00:18:32,000 --> 00:18:34,720 Speaker 2: Integrate exactly the signal would have been far too weak, 374 00:18:34,880 --> 00:18:37,559 and its position relative to Earth was changing too rapidly. 375 00:18:37,839 --> 00:18:40,720 And as for optical phase functions watching for brightness dips 376 00:18:40,720 --> 00:18:43,599 as it spins, again, the object was just too faint. 377 00:18:43,359 --> 00:18:45,920 Speaker 1: Overall, couldn't get a stable enough measurement over time. 378 00:18:46,079 --> 00:18:50,720 Speaker 2: Correct. You need long stable observations to reliably detect those 379 00:18:50,759 --> 00:18:55,640 small rotational brightness variations. But the light profile we saw 380 00:18:55,839 --> 00:18:59,240 was dominated by the fuzzy coma, not the tiny nucleus 381 00:18:59,319 --> 00:19:01,759 hidden inside, So they literally couldn't tell if it was 382 00:19:01,799 --> 00:19:04,839 a small bright thing or a big dark thing. The 383 00:19:04,920 --> 00:19:06,200 data just wasn't there. 384 00:19:06,359 --> 00:19:09,480 Speaker 1: Okay, So direct measurement of the nucus was impossible. They 385 00:19:09,480 --> 00:19:12,240 had to rely purely on the quality of that faint 386 00:19:12,319 --> 00:19:17,519 light they did receive, using spectroscopy to look for chemical fingerprints. 387 00:19:17,039 --> 00:19:20,079 Speaker 2: Exactly analyzing the light itself. And this is where as 388 00:19:20,079 --> 00:19:22,480 you said, the identity starts to get written in the 389 00:19:22,519 --> 00:19:24,200 missing lines in what wasn't there? 390 00:19:24,640 --> 00:19:26,119 Speaker 1: What did the initial spectra show? 391 00:19:26,279 --> 00:19:29,200 Speaker 2: Well, the first results were, in themselves a huge clue. 392 00:19:29,559 --> 00:19:34,079 The spectrum was almost entirely featureless, blank, what astronomers call 393 00:19:34,200 --> 00:19:35,960 a sooty spectrum. 394 00:19:35,559 --> 00:19:39,319 Speaker 1: Sooty meaning dark and boring. 395 00:19:39,359 --> 00:19:43,400 Speaker 2: Dark and spectrally neutral. Essentially, it was flat from the 396 00:19:43,440 --> 00:19:45,480 red end of the visible spectrum all the way through 397 00:19:45,519 --> 00:19:50,359 the near infrared. Critically, it lacked that characteristic upward slope 398 00:19:50,359 --> 00:19:52,480 towards the blue end that you'd expect if there was 399 00:19:52,519 --> 00:19:56,359 a lot of reflective water, ice, or even fine silica dust. 400 00:19:56,920 --> 00:19:59,559 Speaker 1: Okay, so what does that spectral flatness tell us about 401 00:19:59,599 --> 00:20:01,039 the material in the coma? 402 00:20:01,079 --> 00:20:06,079 Speaker 2: It strongly suggests the coma was dominated by carbon dust, dark, neutral, colored, 403 00:20:06,160 --> 00:20:10,039 ancient carbon dust. This is the classic signature of material 404 00:20:10,119 --> 00:20:12,960 that's been floating between the stars for potentially millions or 405 00:20:13,000 --> 00:20:13,519 billions of. 406 00:20:13,559 --> 00:20:18,039 Speaker 1: Years, processed by cosmic rays and stellar radiation, exactly. 407 00:20:17,920 --> 00:20:22,279 Speaker 2: Coded in complex, heavily modified organic compounds than cosmic tar 408 00:20:22,599 --> 00:20:25,480 or soot. There was no sign of a fresh, bright, 409 00:20:25,759 --> 00:20:28,880 icy surface reflecting sunlight. The light was just scattering neutrally 410 00:20:28,880 --> 00:20:31,519 off these old dark dust grains. That had been released. 411 00:20:31,599 --> 00:20:35,799 Speaker 1: Okay, so mostly dark ancient dust. But within that general 412 00:20:35,839 --> 00:20:39,519 flatness did they detect any specific chemical signatures, even faint ones? 413 00:20:39,599 --> 00:20:43,559 Speaker 2: They did, but it required incredible instrument precision and patience. 414 00:20:43,599 --> 00:20:47,000 There was a whisper, a hint of carbon dioxide CO two. 415 00:20:47,039 --> 00:20:47,960 Speaker 1: How did they spot that? 416 00:20:48,319 --> 00:20:51,039 Speaker 2: They used another instrument on the trace gas orbiter, the 417 00:20:51,119 --> 00:20:54,839 Nomad spectrometer. They pointed it precisely at the coordinates where 418 00:20:54,880 --> 00:20:57,880 the imager CASSIS had tracked the object's. 419 00:20:57,480 --> 00:21:00,920 Speaker 1: Movement, aiming the spectrometer through the predicted pats of the coma. 420 00:21:01,079 --> 00:21:05,880 Speaker 2: Yes, Nomad took very long, difficult observations staring at that spot, 421 00:21:06,119 --> 00:21:09,640 and eventually a very faint absorption feature started to emerge 422 00:21:09,720 --> 00:21:13,599 near the four point three micron wavelength in the infrared. 423 00:21:13,359 --> 00:21:17,319 Speaker 1: Four point three microns? Why is that particular wavelength important 424 00:21:17,359 --> 00:21:21,079 for CO two? For listeners less familiar with molecular. 425 00:21:20,559 --> 00:21:24,680 Speaker 2: Physics, good point that specific wavelength four point three microns 426 00:21:24,920 --> 00:21:28,599 corresponds to a very strong vibration within the carbon dioxide molecule. 427 00:21:28,640 --> 00:21:32,160 Technically its asymmetrical stretching and bending mode. It's the most 428 00:21:32,160 --> 00:21:35,640 prominent absorption signature for CO two gas, especially at their 429 00:21:35,720 --> 00:21:37,920 relatively cold temperatures they were dealing. 430 00:21:37,759 --> 00:21:41,480 Speaker 1: With, so detecting that dip, however faint, was strong evidence 431 00:21:41,519 --> 00:21:43,440 for CO two gas being present in the coma. 432 00:21:43,599 --> 00:21:47,200 Speaker 2: Yes, it confirmed that the steady out gassing they inferred 433 00:21:47,200 --> 00:21:50,680 from the coma's shape wasn't just dust being pushed off passively. 434 00:21:51,039 --> 00:21:54,240 There was specific volatile gas being released through sublimation. 435 00:21:54,599 --> 00:21:57,759 Speaker 1: Okay, CO two was there faintly, But the elephant in 436 00:21:57,799 --> 00:22:00,480 the room for any comet discussion is water. H two. 437 00:22:00,519 --> 00:22:02,039 Oh did they see any water? 438 00:22:02,279 --> 00:22:04,960 Speaker 2: That was the crucial emission? The signal for CO two 439 00:22:05,200 --> 00:22:08,319 was right there at the very edge of detection, extremely faint, 440 00:22:08,759 --> 00:22:12,000 and crucially, no water signatures, which have their own specific 441 00:22:12,119 --> 00:22:14,160 spectral fingerprints, were detected at all. 442 00:22:14,400 --> 00:22:16,880 Speaker 1: So does that mean three eyed ass definitely had no 443 00:22:17,000 --> 00:22:20,680 water ice or just that it wasn't active enough to detect. 444 00:22:20,880 --> 00:22:23,599 Speaker 2: It's likely a combination of instrument limits and the physics. 445 00:22:23,680 --> 00:22:27,240 Remember that two hundred kelvin temperature. That's warm enough for 446 00:22:27,319 --> 00:22:30,720 CO two ice to sublimate slowly, but it's still generally 447 00:22:30,759 --> 00:22:34,039 too cold for water ice to sublimate strongly and produce 448 00:22:34,079 --> 00:22:36,799 a detectable gas signature, especially from a distance. 449 00:22:37,079 --> 00:22:40,759 Speaker 1: Ah right, water needs more warmth to really get going exactly. 450 00:22:41,079 --> 00:22:43,960 Speaker 2: So the leading interpretation is that three is does contain 451 00:22:44,039 --> 00:22:46,759 water ice, and it probably does deep down based on 452 00:22:46,799 --> 00:22:49,119 how we think these things form. It must be buried 453 00:22:49,119 --> 00:22:51,759 beneath that thick insulating crust we talked about. 454 00:22:51,680 --> 00:22:53,440 Speaker 1: The crust hardened by interstellar travel. 455 00:22:53,759 --> 00:22:58,680 Speaker 2: Yeah, an opaque, maybe meter thick layer of processed organics 456 00:22:58,759 --> 00:23:01,960 and dust that prevented the deeper water ice from being 457 00:23:02,039 --> 00:23:05,160 heated enough by the Sun to sublimate significantly during its 458 00:23:05,160 --> 00:23:08,880 brief pass through the inner Solar system. The activity they 459 00:23:08,920 --> 00:23:11,400 saw was just the slow bleed off of the most 460 00:23:11,519 --> 00:23:14,400 volatile stuff, the CO two that managed to make its 461 00:23:14,400 --> 00:23:15,200 way to the surface. 462 00:23:15,720 --> 00:23:18,000 Speaker 1: Okay, so the chemistry paints this picture of an object 463 00:23:18,039 --> 00:23:22,160 that's profoundly aged. Its surface composition is dominated by ancient 464 00:23:22,200 --> 00:23:25,559 carbon dust, maybe with a saint whiff of CO two escaping. 465 00:23:26,039 --> 00:23:29,200 But any primordial water ice is locked away deep inside, 466 00:23:29,720 --> 00:23:32,519 its identity shaped by its long history between the stars, 467 00:23:32,880 --> 00:23:35,920 preserved by its speed, resulting in just that steady, quiet 468 00:23:35,920 --> 00:23:38,440 exhale from a crusted body, not the bright eruption you 469 00:23:38,519 --> 00:23:41,240 see from a fresh comet from our own backyard. So 470 00:23:41,319 --> 00:23:42,680 now we can kind of take a step back and 471 00:23:42,720 --> 00:23:45,119 put three ilis into the bigger picture. Wasn't the first 472 00:23:45,119 --> 00:23:46,279 interstellar visitor. 473 00:23:46,039 --> 00:23:48,599 Speaker 2: We've seen now, it was the third confirmed one. 474 00:23:48,400 --> 00:23:51,319 Speaker 1: Right, So we now have this trio Omoa, Moa, Borsov 475 00:23:51,400 --> 00:23:54,640 and now three iolists, and together the sources suggest they 476 00:23:54,680 --> 00:23:56,640 start to map out the spectrum of what the galaxy 477 00:23:56,680 --> 00:23:58,640 actually sends our way. It is like the beginning of 478 00:23:58,680 --> 00:23:59,640 the interstellar archive. 479 00:24:00,039 --> 00:24:02,279 Speaker 2: That's a great way to think about it. This growing 480 00:24:02,359 --> 00:24:06,799 register is incredibly important because remember, before twenty seventeen, the 481 00:24:06,839 --> 00:24:10,200 whole idea of detecting interstellar objects was purely theoretical. We 482 00:24:10,240 --> 00:24:12,400 assumed they were out there, but we'd never actually seen one. 483 00:24:12,559 --> 00:24:16,000 Speaker 1: And now we have three distinct data points, three different 484 00:24:16,000 --> 00:24:18,839 examples of material from other star systems. 485 00:24:18,599 --> 00:24:20,160 Speaker 2: Each telling a slightly distant story. 486 00:24:20,160 --> 00:24:22,920 Speaker 1: Okay, let's quickly recap the first two. Umum woah. That 487 00:24:23,039 --> 00:24:25,720 was the first one back in twenty seventeen, and it 488 00:24:25,759 --> 00:24:27,920 was just weird from the start, wasn't it. 489 00:24:28,079 --> 00:24:33,079 Speaker 2: Umam wah was an enigma, small, apparently silent, no detectable 490 00:24:33,119 --> 00:24:36,960 gas or dust coming off it, and it was tumbling erratically. 491 00:24:37,359 --> 00:24:42,039 Speaker 1: Its brightness changed dramatically, suggesting a really elongated or irregular shape. 492 00:24:42,119 --> 00:24:44,599 Speaker 2: Yeah, it's brightness swung by a factor of ten every 493 00:24:44,640 --> 00:24:48,359 eight hours or so, which implied a very strange, perhaps 494 00:24:48,440 --> 00:24:52,079 cigar like or pancake like shape, And critically, no coma, 495 00:24:52,279 --> 00:24:56,680 no gas confirmed, just this weird solid object behaving oddly. 496 00:24:56,839 --> 00:24:58,920 Speaker 1: And the big debate around umam woah was that non 497 00:24:58,920 --> 00:25:02,200 gravitational acceleration, right, somethings needed to be pushing it gently 498 00:25:02,440 --> 00:25:04,720 other than the Sun's gravity, but we couldn't see any 499 00:25:04,720 --> 00:25:06,599 outgassing to explain the push. 500 00:25:06,680 --> 00:25:09,359 Speaker 2: That was the mystery. So its lesson maybe was about 501 00:25:09,359 --> 00:25:13,799 the survival of structure. It proved that solid, intact objects, 502 00:25:13,880 --> 00:25:18,720 even really strangely shaped ones, can actually survive that incredibly long, 503 00:25:18,880 --> 00:25:20,960 harsh journey between the stars, and. 504 00:25:20,880 --> 00:25:23,440 Speaker 1: It forced us to get better at measuring tiny forces. 505 00:25:23,680 --> 00:25:27,799 Speaker 2: Absolutely. It pushed instrument teams worldwide to develop new techniques 506 00:25:27,839 --> 00:25:33,559 to measure those incredibly subtle non gravitational accelerations with unprecedented precision. 507 00:25:34,160 --> 00:25:36,359 It showed us the interstellar medium wasn't empty. 508 00:25:36,519 --> 00:25:40,720 Speaker 1: Okay. Then visitor number two arrived in twenty nineteen, Comet Borisov, 509 00:25:41,240 --> 00:25:45,000 and then that one felt almost like an astronomical sigh 510 00:25:45,039 --> 00:25:45,599 of relief. 511 00:25:45,839 --> 00:25:49,599 Speaker 2: Huh Yeah, in a way. Borisov was the perfect counterpoint 512 00:25:49,640 --> 00:25:53,759 to Umumu's strangeness, because Borisov looked and acted exactly like 513 00:25:53,799 --> 00:25:55,319 a comet from our own solar system. 514 00:25:55,400 --> 00:25:57,400 Speaker 1: Should it had a tail, Oh yeah, bright. 515 00:25:57,279 --> 00:26:01,119 Speaker 2: Nucleus, long, beautiful cyan colored tail. Spectrus gopic analysis showed 516 00:26:01,160 --> 00:26:04,160 strong signatures of water, carbon monoxide, the usual suspects for 517 00:26:04,200 --> 00:26:07,000 a comet. Its activity levels were completely normal for its 518 00:26:07,160 --> 00:26:08,000 distance from the Sun. 519 00:26:08,079 --> 00:26:11,200 Speaker 1: So Boresov's lesson was more about universality. Things are similar 520 00:26:11,200 --> 00:26:11,880 out there. 521 00:26:11,960 --> 00:26:17,359 Speaker 2: Exactly the survival of composition. Borisov proved that interstellar space 522 00:26:17,400 --> 00:26:22,359 can transport fully active, chemically normal commets. Its composition was 523 00:26:22,440 --> 00:26:25,599 remarkably similar to commets from our own piper Belt. 524 00:26:25,359 --> 00:26:28,680 Speaker 1: Or Ort Cloud, suggesting the basic ingredients and processes for 525 00:26:28,759 --> 00:26:32,559 making icy bodies are probably quite common across different star systems. 526 00:26:32,640 --> 00:26:35,440 Speaker 2: That's the strong implication planetary formation, or at least the 527 00:26:35,440 --> 00:26:39,680 formation of these icy planetesimals, might follow fairly universal rules. 528 00:26:39,759 --> 00:26:44,279 Speaker 1: Okay, so Umoha showed structure survives, Borsov showed composition survives. 529 00:26:44,720 --> 00:26:47,279 Now we add three il ass to the mix. Where 530 00:26:47,279 --> 00:26:49,599 does it fit? It seems kind of in the middle. 531 00:26:49,799 --> 00:26:51,200 Speaker 2: I think that's a good way to put it. Three 532 00:26:51,279 --> 00:26:53,759 ils sort of bridges the gap. It shows the effects 533 00:26:53,759 --> 00:26:58,240 of time and interstellar erosion on composition and activity. How so, well, 534 00:26:58,279 --> 00:27:01,599 like Borisov, it was active coma. It was releasing gas 535 00:27:01,599 --> 00:27:05,279 and dust, but unlike Borsov, its activity was really muted, 536 00:27:05,519 --> 00:27:06,039 very faint. 537 00:27:06,200 --> 00:27:09,079 Speaker 1: The breath not body thing exactly. 538 00:27:08,920 --> 00:27:13,039 Speaker 2: And its spectrum was dominated by that ancient processed carbon dust, 539 00:27:13,359 --> 00:27:16,039 suggesting it was volatile poor near the surface. Unlike the 540 00:27:16,039 --> 00:27:19,880 seemingly fresher Borisov. That coma without a tail puts it 541 00:27:19,920 --> 00:27:24,079 somewhere between the highly active Borisov and the completely silent Umama. 542 00:27:24,160 --> 00:27:25,519 Speaker 1: So its lesson is about. 543 00:27:25,440 --> 00:27:28,279 Speaker 2: Maybe the survival of motion itself, or perhaps the evidence 544 00:27:28,319 --> 00:27:31,160 of survival. Its incredible speed is what allowed it to 545 00:27:31,200 --> 00:27:33,839 get here. But its appearance tells a story of aging. 546 00:27:34,599 --> 00:27:38,400 It reveals how fragile that cometary activity becomes after potentially 547 00:27:38,440 --> 00:27:42,319 millions of years drifting between stars, being bombarded by radiation. 548 00:27:42,559 --> 00:27:45,279 Speaker 1: It marks a surface that's been profoundly shaped, not just 549 00:27:45,319 --> 00:27:48,720 by its birth environment, but by the long, slow grind 550 00:27:48,759 --> 00:27:50,240 of intertellar space itself. 551 00:27:50,359 --> 00:27:53,000 Speaker 2: Precisely, it's a surface evolved by exposure. 552 00:27:53,079 --> 00:27:56,559 Speaker 1: So if you look at the three together Borsov, three Iolass. 553 00:27:56,680 --> 00:27:58,920 They almost map out a kind of decay process for 554 00:27:59,000 --> 00:28:00,279 matter between the stars. 555 00:28:00,519 --> 00:28:03,039 Speaker 2: That's one way to interpret it. Umu Mua showed that 556 00:28:03,119 --> 00:28:06,640 solid structure can make it, Norsov showed that relatively fresh, 557 00:28:06,759 --> 00:28:10,279 volatile rich composition can make it. And three I Atlas 558 00:28:10,279 --> 00:28:13,200 shows how even if the composition is there deep down, 559 00:28:13,319 --> 00:28:16,440 the surface activity can be severely muted by age and 560 00:28:16,480 --> 00:28:19,720 the journey itself, with speed being the key factor defining 561 00:28:19,759 --> 00:28:20,880 its observable behavior. 562 00:28:21,559 --> 00:28:25,039 Speaker 1: And looking at the three collectively, does a statistical patterns 563 00:28:25,079 --> 00:28:27,160 start to emerge in terms of how they arrived. 564 00:28:27,359 --> 00:28:31,519 Speaker 2: Yes, and this is potentially very significant. When you chart 565 00:28:31,680 --> 00:28:34,920 the orbits of all three, they share some striking geometrical 566 00:28:34,920 --> 00:28:39,279 features like what Well, For one, all three arrived inbound 567 00:28:39,319 --> 00:28:41,759 from roughly the same direction in the sky near the 568 00:28:41,759 --> 00:28:45,680 constellation Hoociles, which is the direction our entire solar system 569 00:28:45,759 --> 00:28:49,119 is moving through the local interstellar medium, the so called 570 00:28:49,400 --> 00:28:50,359 solar apex. 571 00:28:50,519 --> 00:28:53,039 Speaker 1: Interesting, they came from the direction we're heading towards. 572 00:28:52,960 --> 00:28:56,079 Speaker 2: Roughly, Yes, and all three cross the plane of our 573 00:28:56,079 --> 00:28:59,240 solar system the ecliptic at quite steep angles. They weren't 574 00:28:59,319 --> 00:29:01,160 orbiting nicely with the planets. 575 00:29:00,759 --> 00:29:02,359 Speaker 1: They were diving in from above or. 576 00:29:02,279 --> 00:29:07,240 Speaker 2: Below exactly, and most importantly, mathematically speaking, all three displayed 577 00:29:07,279 --> 00:29:11,440 a hyperbolic trajectory. Their orbital eccentricity was greater than. 578 00:29:11,359 --> 00:29:15,160 Speaker 1: One, and eccentricity greater than one is the absolute mathematical 579 00:29:15,200 --> 00:29:18,519 proof that they're not bound to our Sun right, They're 580 00:29:18,559 --> 00:29:19,359 just passing through. 581 00:29:19,599 --> 00:29:23,440 Speaker 2: It's the definitive stamp. Our Sun's gravity could bend their paths, 582 00:29:23,480 --> 00:29:26,200 but it couldn't capture them. They came in fast, swung 583 00:29:26,240 --> 00:29:29,319 around the Sun, and are heading back out into interstellar space, 584 00:29:29,640 --> 00:29:30,400 never to return. 585 00:29:31,599 --> 00:29:34,640 Speaker 1: So this first trio, this initial data set from the 586 00:29:34,680 --> 00:29:38,319 interstellar Archive, it starts to give us the first real 587 00:29:38,400 --> 00:29:40,880 clues about what interstellar traffic actually looks like. 588 00:29:41,119 --> 00:29:44,359 Speaker 2: It does. It seems to be faint, generally fast, arriving 589 00:29:44,400 --> 00:29:48,319 from preferred directions, perhaps often at steep angles, and consisting 590 00:29:48,359 --> 00:29:50,440 of bodies that tell their story as much through their 591 00:29:50,480 --> 00:29:53,759 motion and what they lack, like a tail or bright features, 592 00:29:54,039 --> 00:29:55,640 as through what they actively display. 593 00:29:56,039 --> 00:29:58,359 Speaker 1: It really shifts our view of the Solar System, doesn't it, 594 00:29:58,359 --> 00:30:01,240 from thinking of it as this isolation island to more 595 00:30:01,359 --> 00:30:04,759 like well, an open coalgate on an ancient cosmic highway. 596 00:30:04,839 --> 00:30:08,079 Speaker 2: That's a very apt analogy, a checkpoint in a much larger, 597 00:30:08,160 --> 00:30:09,279 older system. 598 00:30:09,400 --> 00:30:12,839 Speaker 1: Okay, so this idea of the Solar System being a checkpoint, 599 00:30:12,920 --> 00:30:16,119 a toll gate, naturally leads us to think about the future. 600 00:30:16,680 --> 00:30:19,279 What comes next? What have we learned from these first 601 00:30:19,359 --> 00:30:22,799 three visitors that helps us prepare for the fourth, the fifth, 602 00:30:22,880 --> 00:30:25,319 the tenth. This is the future watchboard. 603 00:30:25,559 --> 00:30:29,359 Speaker 2: Exactly how do we improve our detection and characterization in 604 00:30:29,400 --> 00:30:30,039 that alignment? 605 00:30:30,079 --> 00:30:32,920 Speaker 1: You mentioned all three coming from roughly the same direction 606 00:30:33,599 --> 00:30:36,920 near the Solar apex. That seems like the most provocative 607 00:30:36,960 --> 00:30:39,119 finding for future searches, doesn't it. 608 00:30:39,119 --> 00:30:42,599 Speaker 2: It really is. Now, three objects isn't a huge statistical sample. 609 00:30:42,680 --> 00:30:45,640 Let's be clear. It could be coincidence, sure, but the 610 00:30:45,640 --> 00:30:48,720 fact that all three inbound paths originated from that same 611 00:30:48,839 --> 00:30:52,839 general patch of sky is suggestive. The sources float the 612 00:30:52,880 --> 00:30:55,759 idea of a potential corridor of approach. 613 00:30:55,480 --> 00:30:59,079 Speaker 1: A corridor like a preferred lane for interstellar traffic entering 614 00:30:59,079 --> 00:30:59,559 our system. 615 00:31:00,440 --> 00:31:03,319 Speaker 2: It could be that simple random chance brought these three 616 00:31:03,359 --> 00:31:06,720 from that direction, or it could hint at something more structural, 617 00:31:06,759 --> 00:31:10,240 maybe a stream or drift of interstellar debris related to 618 00:31:10,279 --> 00:31:13,160 the Solar System's motion. Through the local part of the galaxy, 619 00:31:13,440 --> 00:31:15,319 the local interstellar cloud, a. 620 00:31:15,400 --> 00:31:18,400 Speaker 1: Sort of interstellar headwind carrying this stuff towards us. 621 00:31:18,559 --> 00:31:21,200 Speaker 2: That's the hypothesis that needs testing. If it is a 622 00:31:21,240 --> 00:31:25,160 genuine structural feature, a drift channel, then future detections are 623 00:31:25,240 --> 00:31:27,400 much more likely to come from that same direction. It 624 00:31:27,440 --> 00:31:29,440 tells us where to look more closely. 625 00:31:29,200 --> 00:31:32,240 Speaker 1: And preparing to look more closely to catch these future visitors. 626 00:31:32,599 --> 00:31:35,440 That brings us to the next generation of instruments, the 627 00:31:35,559 --> 00:31:40,400 ultimate interstellar traffic cop you might say, the Vera Rubin Observatory. 628 00:31:40,559 --> 00:31:45,160 Speaker 2: Ah. Yes, Vera Rubin formerly known as LSST, the Large 629 00:31:45,160 --> 00:31:49,839 Synoptic Survey Telescope. It's really poised to revolutionize this feel, 630 00:31:50,200 --> 00:31:54,480 to dramatically expand that watchboard capacity beyond anything we've ever had. 631 00:31:54,599 --> 00:31:56,160 Speaker 1: It's coming online soon right. 632 00:31:56,079 --> 00:32:00,160 Speaker 2: Nearing full operation, and its sheer scale and speed are 633 00:32:00,200 --> 00:32:03,359 just perfect for finding these faint, fast moving objects. 634 00:32:03,480 --> 00:32:05,880 Speaker 1: How is it so much better suited for this specific 635 00:32:05,960 --> 00:32:09,079 task than previous sky surveys. 636 00:32:08,720 --> 00:32:11,880 Speaker 2: Well, its fundamental mission is different. It's designed to scan 637 00:32:11,960 --> 00:32:15,200 the entire visible southern sky every few nights down to 638 00:32:15,359 --> 00:32:20,160 incredibly faint magnitudes. That constant deep wide coverage. 639 00:32:19,720 --> 00:32:23,200 Speaker 1: Is key, catching things that change or move quickly exactly. 640 00:32:23,359 --> 00:32:26,319 Speaker 2: But the critical difference is also in the software, the 641 00:32:26,440 --> 00:32:30,319 data processing pipeline. The algorithms are being specifically tuned to 642 00:32:30,440 --> 00:32:33,480 flag objects whose motion doesn't fit the pattern of normal 643 00:32:33,519 --> 00:32:37,359 Solar System bodies, asteroids, comets, Kuiper Belt objects. 644 00:32:37,440 --> 00:32:40,519 Speaker 1: So it's actively looking for the outliers, the ones moving 645 00:32:40,519 --> 00:32:42,920 too fast or at too steep an angle, or that 646 00:32:43,000 --> 00:32:44,960 are just too faint for where they should be if 647 00:32:45,000 --> 00:32:45,640 they were native. 648 00:32:45,960 --> 00:32:48,880 Speaker 2: That's precisely the strategy. It's like setting up a speed 649 00:32:48,920 --> 00:32:52,559 trap on the cosmic highway. It's looking for the statistical speeders, 650 00:32:52,559 --> 00:32:55,200 the ones cutting across lanes at weird angles, and any 651 00:32:55,279 --> 00:32:59,160 candidata flags will immediately be cross referenced against the profile 652 00:32:59,200 --> 00:33:02,720 we're building from Ouma, Borisov and especially three I eight lists. 653 00:33:03,160 --> 00:33:06,519 Does it have that extreme velocity, the steep inclination. Does 654 00:33:06,519 --> 00:33:10,279 it maybe show that flat, reddish, sooty spectral color that 655 00:33:10,359 --> 00:33:14,000 seems characteristic of these age interstellar surfaces we're building the 656 00:33:14,079 --> 00:33:14,599 rule book. 657 00:33:14,799 --> 00:33:18,160 Speaker 1: It's incredible, really, after millennia of humans looking at the sky, 658 00:33:18,599 --> 00:33:21,519 we're only just now figuring out the identifying features of 659 00:33:21,599 --> 00:33:24,400 visitors from other stars. We know what to look for now, 660 00:33:24,480 --> 00:33:26,920 even if it's just a faint smudge exhaling a bit 661 00:33:26,960 --> 00:33:28,519 of CO two and missing its tail. 662 00:33:29,359 --> 00:33:32,680 Speaker 2: We've learned that the game isn't always about bright, flashy displays. 663 00:33:33,039 --> 00:33:36,519 Sometimes it's about speed, geometry and survival against the odds. 664 00:33:37,200 --> 00:33:40,519 And speaking of survival, what about three ilis itself? Where 665 00:33:40,559 --> 00:33:41,079 is it now? 666 00:33:41,319 --> 00:33:45,039 Speaker 1: Yeah, it's story as something we can actually observe is over, 667 00:33:45,160 --> 00:33:45,480 isn't it? 668 00:33:45,519 --> 00:33:48,000 Speaker 2: Pretty much? The last observations caught it right at the 669 00:33:48,079 --> 00:33:50,880 very margin of detectability. It was fading rapidly as it 670 00:33:50,920 --> 00:33:53,000 moved further from the Sun, just as. 671 00:33:52,880 --> 00:33:55,720 Speaker 1: Expected, So it's crossed that line from being a physical 672 00:33:55,720 --> 00:34:01,160 object we can image, however faintly, to being purely mathematical. 673 00:34:01,319 --> 00:34:03,680 Speaker 2: That's a good way to put it. Our orbital extrapolations 674 00:34:03,680 --> 00:34:06,759 place it well beyond Jupiter's orbit by now, still accelerating 675 00:34:06,759 --> 00:34:10,440 away on that hyperbolic trajectory, no telescope on Earth or 676 00:34:10,480 --> 00:34:13,760 in space can realistically follow it further. The light is 677 00:34:13,800 --> 00:34:16,440 simply gone lost in the background. 678 00:34:16,000 --> 00:34:19,360 Speaker 1: So the mat just carries its position forward silently through 679 00:34:19,400 --> 00:34:21,000 empty coordinates on a chart. 680 00:34:20,960 --> 00:34:24,480 Speaker 2: Until it eventually leaves our Sun's gravitational influence entirely and 681 00:34:24,599 --> 00:34:28,280 drifts back into the interstellar void. Our watchboard now has 682 00:34:28,320 --> 00:34:33,519 those three entries, more boresov, three idealists, three lines on 683 00:34:33,559 --> 00:34:36,280 the ledger, and a huge amount of blank space waiting 684 00:34:36,320 --> 00:34:37,280 for the next arrivals. 685 00:34:37,559 --> 00:34:40,280 Speaker 1: And that really hammers home the perspective shift, doesn't it. 686 00:34:40,480 --> 00:34:44,239 Our solar system isn't this closed, isolated bubble. It's just 687 00:34:44,360 --> 00:34:48,400 one stop, one checkpoint in this immense cosmic traffic system 688 00:34:48,440 --> 00:34:51,360 that's way older than our own planets. Absolutely so, the 689 00:34:51,360 --> 00:34:54,280 next time an interstellar object is detected and with vera Rubin, 690 00:34:54,320 --> 00:34:57,079 it feels like when, not if, it will be such 691 00:34:57,079 --> 00:34:59,480 a shock. Thanks to the lessons learned from this first 692 00:34:59,480 --> 00:35:02,639 trio is, especially the incredibly difficult technical chase for three idolists, 693 00:35:02,920 --> 00:35:06,800 It'll feel more like confirmation, like seeing another predicted data 694 00:35:06,840 --> 00:35:07,360 point arrive. 695 00:35:07,719 --> 00:35:11,480 Speaker 2: It's confirmation that interstellar space is dynamic, it's restless, it's 696 00:35:11,480 --> 00:35:15,280 constantly exchanging material between star systems. We learn from three 697 00:35:15,280 --> 00:35:18,360 iat lists that these ancient travelers often speak to us 698 00:35:18,400 --> 00:35:21,519 through their geometry, that hyperbolic path, the angle of approach, 699 00:35:21,639 --> 00:35:23,880 long after the internal forces that might have once made 700 00:35:23,920 --> 00:35:27,119 them shine brightly like abundant surface ies reacting to a 701 00:35:27,159 --> 00:35:29,559 strong sun have significantly decayed. 702 00:35:29,880 --> 00:35:33,119 Speaker 1: That flat, sooty spectrum we talked about, that faint whisper 703 00:35:33,119 --> 00:35:36,360 of CO two, the complete lack of a tail despite 704 00:35:36,400 --> 00:35:39,920 being active. These are the new characteristics, new rules you 705 00:35:40,039 --> 00:35:43,559 now know about intertellar visitors and their composition after potentially 706 00:35:43,599 --> 00:35:46,440 EON's adrift. You're now well informed on what it takes 707 00:35:46,480 --> 00:35:49,639 for matter to survive that journey, defined largely by speed 708 00:35:49,679 --> 00:35:51,280 in the resulting erosion or crusting. 709 00:35:51,519 --> 00:35:54,800 Speaker 2: And it really leaves us with a fascinating, provocative thought 710 00:35:54,880 --> 00:35:57,800 to chew on, doesn't it if three IAT lists revealed 711 00:35:57,800 --> 00:36:01,320 its unique aged identity mohostly through what it failed to 712 00:36:01,400 --> 00:36:04,719 show us the lack of strong water activity, the missing tail, 713 00:36:04,840 --> 00:36:07,840 the ambiguous size because it was so faint. What other 714 00:36:07,880 --> 00:36:10,519 crucial secrets about the interstellar medium, about the history of 715 00:36:10,559 --> 00:36:13,880 material in our galaxy are currently hidden within the statistics 716 00:36:13,880 --> 00:36:18,039 of objects that appear quiet or unremarkable, objects just waiting 717 00:36:18,079 --> 00:36:21,280 for powerful new eyes like the ver Reuben Observatory to 718 00:36:21,360 --> 00:36:25,519 finally detect their subtle signatures and reveal their true, deeply aged, 719 00:36:25,679 --> 00:36:26,440 muted nature. 720 00:36:26,840 --> 00:36:29,199 Speaker 1: What else is out there defined by its silence? Something 721 00:36:29,199 --> 00:36:31,599 profound to mull Over. Indeed, as we keep watching for 722 00:36:31,639 --> 00:36:33,880 the next interstellar speed or hitting our way, we'll see 723 00:36:33,880 --> 00:36:34,800 you for the next deep dive.