WEBVTT 1 00:00:03.399 --> 00:00:07.719 Welcome to Bedtime Astronomy. Explore the wonders of the cosmos 2 00:00:07.759 --> 00:00:12.279 with our soothing Bedtime Astronomie podcast. Each episode offers a 3 00:00:12.359 --> 00:00:16.320 gentle journey through the stars, planets, and beyond, perfect for 4 00:00:16.399 --> 00:00:20.239 unwinding after a long day. Let's travel through the mysteries 5 00:00:20.239 --> 00:00:22.440 of the universe as you drift off into a peaceful 6 00:00:22.480 --> 00:00:23.800 slumber under the night sky. 7 00:00:26.879 --> 00:00:29.120 I want you to try a little mental experiment with me. 8 00:00:29.399 --> 00:00:30.199 Okay, im game. 9 00:00:30.640 --> 00:00:34.320 Picture a clock, and not a digital display on your phone, 10 00:00:34.439 --> 00:00:38.679 but an old school, high precision mechanical. 11 00:00:38.200 --> 00:00:41.039 Watch, right, like a really finely tuned gear system. 12 00:00:41.079 --> 00:00:44.479 Exactly. You can hear it ticking, tick tick tick. It 13 00:00:44.520 --> 00:00:46.880 has a perfect rhythm, unshakable. 14 00:00:47.039 --> 00:00:50.119 I am visualizing it reliable and steady. 15 00:00:50.719 --> 00:00:53.399 Now, take that watch and throw it into the middle 16 00:00:53.439 --> 00:00:55.799 of a hurricane, well that escalated quickly, and not just 17 00:00:55.840 --> 00:00:58.399 a regular hurricane. Throw it into a jet engine that 18 00:00:58.479 --> 00:01:03.399 is somehow inside herane. The noise is completely. 19 00:01:02.880 --> 00:01:04.519 Definitely just absolute chaos. 20 00:01:04.599 --> 00:01:08.879 The pressure is crushing, the turbulence is ripping literally everything apart. 21 00:01:09.040 --> 00:01:11.640 And I assume my job in this experiment is to 22 00:01:11.719 --> 00:01:12.959 still hear the ticking. 23 00:01:13.159 --> 00:01:15.359 Your job is to hear the ticking. But it is 24 00:01:15.400 --> 00:01:17.799 actually more than that. You need to measure the gap 25 00:01:17.840 --> 00:01:20.959 between the ticks to the nanosecond. Oh wow, because if 26 00:01:20.959 --> 00:01:22.840 that watch skips a beat, I mean even by a 27 00:01:22.879 --> 00:01:24.719 fraction of a fraction of a second, it tells you 28 00:01:24.760 --> 00:01:26.319 something about the wind and the pressure. 29 00:01:26.400 --> 00:01:28.719 It tells you about the very fabric of the reality 30 00:01:28.760 --> 00:01:32.239 it is floating in. That is a terrifying level of precision. 31 00:01:32.840 --> 00:01:34.599 But I know exactly where you were going with this. 32 00:01:34.680 --> 00:01:36.120 You were talking about the galactic center. 33 00:01:36.280 --> 00:01:38.719 I totally am We're talking about a needle in the 34 00:01:38.799 --> 00:01:40.400 ultimate haystack. 35 00:01:39.879 --> 00:01:41.519 Today, the biggest haystack we know of. 36 00:01:41.719 --> 00:01:44.480 Right, we are looking at a discovery announced just days 37 00:01:44.480 --> 00:01:48.480 ago in February twenty twenty six, a team of astronomers, 38 00:01:48.560 --> 00:01:52.120 using data meant to hunt for aliens, has potentially found 39 00:01:52.120 --> 00:01:54.079 the holy Grail of astrophysics. 40 00:01:54.280 --> 00:01:56.079 The Holy Grail. It really is. 41 00:01:56.120 --> 00:01:59.840 A cosmic clock spinning hundreds of times a second, hidden 42 00:01:59.799 --> 00:02:03.400 in the darkest, loudest, most dangerous neighborhood in the Milky Way. 43 00:02:03.359 --> 00:02:07.920 Right next to the supermassive black hole Sagittarius a star. 44 00:02:08.319 --> 00:02:11.319 And holy Grail is not hyperbole here. Scientists have been 45 00:02:11.360 --> 00:02:13.879 chasing this specific setup for decades. 46 00:02:14.080 --> 00:02:16.960 Yeah, finding a pulsar orbiting a black hole is the dream. 47 00:02:17.479 --> 00:02:20.319 It is the one test of Einstein's general relativity that 48 00:02:20.360 --> 00:02:22.120 we just have not been able to run. 49 00:02:22.080 --> 00:02:24.680 Yet exactly if this thing is real, And we really 50 00:02:24.680 --> 00:02:27.199 need to stress early on that it is a candidate, right, it. 51 00:02:27.199 --> 00:02:28.520 Is not fully confirmed yet. 52 00:02:28.599 --> 00:02:30.719 But if it is real, it is not just a 53 00:02:30.719 --> 00:02:33.120 new star. It is a laboratory. It is a way 54 00:02:33.159 --> 00:02:35.800 to break physics or prove it right once and for all. 55 00:02:36.120 --> 00:02:37.400 It is a massive deal. 56 00:02:37.680 --> 00:02:40.599 So today we are exploring a brand new paper. The 57 00:02:40.680 --> 00:02:45.400 title is on the Deepest Search for Galactic Center Pulsars. 58 00:02:45.280 --> 00:02:47.240 Published in the Astrophysical Journal. 59 00:02:47.159 --> 00:02:51.240 Exactly on February twenty one, twenty twenty six. We are 60 00:02:51.240 --> 00:02:53.360 going to look at the machine they used to find it. 61 00:02:53.840 --> 00:02:56.879 We will look at the monster black hole it is orbiting. 62 00:02:56.919 --> 00:03:01.039 And why this tiny, spinning city sized mag It might 63 00:03:01.080 --> 00:03:03.759 hold the key to understanding gravity itself. 64 00:03:03.879 --> 00:03:05.840 It is a heavy topic today. 65 00:03:05.639 --> 00:03:07.360 Literally the heaviest topic in the galaxy. 66 00:03:07.360 --> 00:03:10.319 So let us start with the headline. This is fresh 67 00:03:10.360 --> 00:03:14.280 news and it is a really interesting collaboration between Columbia 68 00:03:14.360 --> 00:03:16.400 University and Breakthrough Listen. 69 00:03:16.639 --> 00:03:19.360 Yeah, the Breakthrough Listen part is fascinating. 70 00:03:18.879 --> 00:03:21.199 Because when I hear breakthrough listen, I usually think of 71 00:03:21.280 --> 00:03:23.879 giant satellite dishes listening for little green men. 72 00:03:24.159 --> 00:03:27.000 Right, the search for extraterrestrial intelligence isn't. 73 00:03:26.800 --> 00:03:30.319 That their whole mandate, looking for alien civilizations, It is. 74 00:03:30.599 --> 00:03:33.680 That is their primary mission. They scan the skies for 75 00:03:33.800 --> 00:03:35.439 techno signatures. 76 00:03:35.039 --> 00:03:38.199 Meaning signals that look engineered by someone rather than just 77 00:03:38.319 --> 00:03:39.400 natural space noise. 78 00:03:39.840 --> 00:03:42.759 Exactly. But here is the thing about hunting for aliens. 79 00:03:43.599 --> 00:03:47.560 To do it right, you need incredibly sensitive equipment. 80 00:03:47.240 --> 00:03:50.039 Because space is big and signals are faint. 81 00:03:49.879 --> 00:03:52.560 And you need to process a staggering amount of data. 82 00:03:53.080 --> 00:03:56.199 You are looking for narrow band signals in an ocean 83 00:03:56.240 --> 00:03:57.319 of cosmic static. 84 00:03:57.439 --> 00:04:01.280 So essentially they build a massive vacuum clean for radio waves. 85 00:04:01.479 --> 00:04:05.039 That is a brilliant way to put it. A giant vacuum. 86 00:04:05.560 --> 00:04:08.479 And when you turn on a vacuum that powerful, you 87 00:04:08.560 --> 00:04:11.080 do not just suck up the specific dust bunny you 88 00:04:11.080 --> 00:04:11.599 are looking for. 89 00:04:11.759 --> 00:04:13.039 You get everything else on the floor too. 90 00:04:13.159 --> 00:04:15.919 You get the background noise, you get interference from satellites. Yeah, 91 00:04:15.919 --> 00:04:17.879 and you get rare natural phenomena. 92 00:04:18.199 --> 00:04:20.480 It is almost ironic. They were listening for a call 93 00:04:20.480 --> 00:04:23.600 from ET and instead they picked up the heartbeat of 94 00:04:23.639 --> 00:04:24.319 a dead star. 95 00:04:24.680 --> 00:04:28.120 Well, in astrophysics, one person's noise is another person's data. 96 00:04:28.160 --> 00:04:30.879 Breakthrough Listens has been surveying the Galactic Center for a while. 97 00:04:30.959 --> 00:04:33.560 Why there, though, Why look for aliens in the middle 98 00:04:33.560 --> 00:04:34.839 of a hurricane. 99 00:04:34.720 --> 00:04:38.519 Because hypothetically, if you were in an advanced civilization, that 100 00:04:38.680 --> 00:04:40.600 is a great place to put a beacon. It is 101 00:04:40.680 --> 00:04:42.480 the town square of the galaxy. 102 00:04:42.639 --> 00:04:45.240 High visibility. Anyone looking inward would. 103 00:04:45.079 --> 00:04:48.079 See it exactly. So they're staring at the Galactic Center 104 00:04:48.360 --> 00:04:50.279 with the Green Bank telescope. 105 00:04:49.920 --> 00:04:54.079 Which is this massive one hundred meter dish in West Virginia, right. 106 00:04:54.160 --> 00:04:57.519 Huge dish, And because of that they are collecting some 107 00:04:57.560 --> 00:05:01.399 of the highest resolution radio data have ever seen of 108 00:05:01.399 --> 00:05:02.399 that specific region. 109 00:05:02.560 --> 00:05:05.680 So the research team basically saw this data sitting there 110 00:05:05.720 --> 00:05:08.800 and said, hey, while you are sifting through that, hey 111 00:05:09.120 --> 00:05:13.240 looking for alien needles? Mind if we look for pulsar needles. 112 00:05:12.920 --> 00:05:15.720 And they found one, or well they think they found one. 113 00:05:15.759 --> 00:05:19.360 They found an eight point one to nine millisecond pulsar candidate. 114 00:05:19.439 --> 00:05:22.480 Yes, a candidate. That is a very careful scientific word. 115 00:05:22.560 --> 00:05:25.279 It means do not pop the champagne quite yet, right right. 116 00:05:25.399 --> 00:05:27.279 It means we see a signal. It looks like a duck. 117 00:05:27.360 --> 00:05:29.839 It quacts like a duck, but the pond is so 118 00:05:29.959 --> 00:05:31.959 foggy we cannot quite see the feathers yet. 119 00:05:32.000 --> 00:05:33.759 We will definitely get into why it is so hard 120 00:05:33.759 --> 00:05:35.879 to confirm later. I know the galactic center is a 121 00:05:35.920 --> 00:05:36.519 total mess. 122 00:05:36.519 --> 00:05:38.639 Oh is a chaotic mess. But yes, they have a 123 00:05:38.720 --> 00:05:42.000 very strong signal repeating every eight point one to nine millisecond. 124 00:05:42.240 --> 00:05:44.439 Let us pause on the object itself for a second. 125 00:05:44.839 --> 00:05:48.399 An eight point one nine millisecond pulsar. I feel like 126 00:05:48.439 --> 00:05:50.439 we toss the word pulsar around a lot in sci 127 00:05:50.439 --> 00:05:52.920 fi movies. We do. It sounds cool, but let us 128 00:05:52.920 --> 00:05:55.360 ground this for you listening. We are not talking about 129 00:05:55.360 --> 00:05:57.079 a normal star like our son. 130 00:05:57.040 --> 00:05:59.720 No, not at all. A pulsar is what you get 131 00:05:59.759 --> 00:06:03.959 when a massive star dies, a star much bigger than 132 00:06:03.959 --> 00:06:04.360 our Sun. 133 00:06:04.600 --> 00:06:06.040 It runs out of fuel, right, It. 134 00:06:06.079 --> 00:06:08.399 Runs out of fuel and collapses under its own gravity. 135 00:06:08.560 --> 00:06:12.199 Then it explodes into supernova. Big boom, the biggest boom. 136 00:06:12.360 --> 00:06:16.040 The outer layers get blasted off into space, but the core, 137 00:06:16.360 --> 00:06:17.920 the core gets crushed. 138 00:06:17.680 --> 00:06:20.160 Crushed how much exactly? Give me a sense of the 139 00:06:20.199 --> 00:06:20.800 scale here. 140 00:06:21.000 --> 00:06:23.399 Imagine taking the mass of the Sun, all that gas 141 00:06:23.439 --> 00:06:26.600 all that fire and compressing it into a ball the 142 00:06:26.639 --> 00:06:28.040 size of Manhattan. 143 00:06:27.560 --> 00:06:29.399 A ball twelve miles across. 144 00:06:29.199 --> 00:06:30.279 Rubb twelve miles across. 145 00:06:30.319 --> 00:06:32.439 Yes, that is just insanely dense. 146 00:06:32.560 --> 00:06:35.879 It's inconceivable. A single tea spoon of this material would 147 00:06:35.879 --> 00:06:37.600 weigh a billion tons on Earth. 148 00:06:37.680 --> 00:06:38.720 A billion tons. 149 00:06:38.839 --> 00:06:42.839 Yes, the atoms themselves are crushed so hard that the 150 00:06:42.839 --> 00:06:45.920 electrons and protons merge together to form neutrons. 151 00:06:46.000 --> 00:06:47.800 Oh, so that is why we call it a neutron star. 152 00:06:48.000 --> 00:06:51.839 Exactly, it is basically one giant atomic nucleus the size 153 00:06:51.839 --> 00:06:52.319 of a city. 154 00:06:52.560 --> 00:06:56.600 Okay, so we have a city sized zombie star corpse. 155 00:06:57.120 --> 00:06:59.360 But why does it pulse? Why is it acting like 156 00:06:59.399 --> 00:06:59.839 a clock? 157 00:07:00.439 --> 00:07:03.480 Two things happen during that collapse. First, the magnetic field 158 00:07:03.480 --> 00:07:05.959 gets compressed and it amplifies. 159 00:07:05.439 --> 00:07:07.480 So it becomes super magnetic. 160 00:07:07.040 --> 00:07:10.759 Trillions of times stronger than Earth's magnetic field. And second, 161 00:07:10.879 --> 00:07:12.879 conservation of angular momentum. 162 00:07:12.560 --> 00:07:14.680 Kicks in the figure skaterect exactly. 163 00:07:14.839 --> 00:07:16.959 You know when a figure skater pulls their arms in 164 00:07:17.040 --> 00:07:18.680 and they suddenly spin way. 165 00:07:18.439 --> 00:07:20.040 Faster, Yeah, they become a blur. 166 00:07:20.439 --> 00:07:23.120 Well, imagine a star that was a million miles wide 167 00:07:23.600 --> 00:07:27.959 suddenly shrinking to ten miles wide. It spins insanely. 168 00:07:27.319 --> 00:07:30.759 Fast, and it has that crazy magnetic field right. 169 00:07:30.800 --> 00:07:33.879 Because of the magnetic field, it beams out radio waves 170 00:07:33.959 --> 00:07:35.319 from its magnetic. 171 00:07:34.879 --> 00:07:36.160 Poles like a lighthouse. 172 00:07:36.480 --> 00:07:38.839 That is a perfect analogy. The beam is always on, 173 00:07:38.959 --> 00:07:41.279 but the star is spinning. So if Earth happens to 174 00:07:41.279 --> 00:07:43.360 be in the path of that sweeping beam, we see 175 00:07:43.399 --> 00:07:46.879 a flash, flash, flash, exactly, and that flash is the 176 00:07:46.879 --> 00:07:47.680 tick of our clock. 177 00:07:47.800 --> 00:07:50.600 Okay, So for normal pulsars, that tick is fast, right, 178 00:07:50.680 --> 00:07:51.879 maybe once a second. 179 00:07:51.639 --> 00:07:54.120 Yes, a typical pulsar might spin once a second or so. 180 00:07:54.399 --> 00:07:58.319 But this object, this candidate, it is not a normal pulsar. 181 00:07:58.240 --> 00:08:01.879 Because it is a millisecond pulsar or MSP. 182 00:08:02.319 --> 00:08:06.000 Yes, it is ticking every eight point one to nine milliseconds. 183 00:08:06.000 --> 00:08:08.800 Do the math for me. How fast is that star spinning? 184 00:08:09.279 --> 00:08:12.120 That is roughly one hundred and twenty two rotations every 185 00:08:12.160 --> 00:08:13.160 single second. 186 00:08:12.879 --> 00:08:16.360 One hundred and twenty two times a second a city 187 00:08:16.399 --> 00:08:17.720 size ball of neutrons. 188 00:08:17.800 --> 00:08:21.079 Yes, the surface velocity is a significant fraction of the 189 00:08:21.079 --> 00:08:23.399 speed of light. It is mind boggling. 190 00:08:23.560 --> 00:08:25.639 And here is the crucial part for our story today. 191 00:08:25.759 --> 00:08:29.800 Millisecond pulsars do not just spin fast. They spin with 192 00:08:30.000 --> 00:08:31.319 terrifying regularity. 193 00:08:31.480 --> 00:08:33.960 They rival our best atomic clocks. They are some of 194 00:08:34.039 --> 00:08:36.919 the most stable timekeepers in the entire physical universe. 195 00:08:37.000 --> 00:08:38.200 How regular are we talking? 196 00:08:38.240 --> 00:08:40.679 A normal pulsar is like a cheap courtz watch. It 197 00:08:40.759 --> 00:08:42.759 might drift a little bit over a few years as 198 00:08:42.759 --> 00:08:46.240 it loses energy, but an MSP will keep perfect time 199 00:08:46.279 --> 00:08:48.559 to within a microsecond over billions of years. 200 00:08:48.679 --> 00:08:51.799 So nature essentially accidentally built a perfect chronometer. 201 00:08:51.919 --> 00:08:54.200 Actually, accidentally might be the wrong word for an MSP. 202 00:08:54.360 --> 00:08:56.120 There is a whole backstory to these speed demaons. 203 00:08:56.279 --> 00:08:57.960 Really, they do not just start out that fast. 204 00:08:58.000 --> 00:09:00.039 Usually when a pulser is born, it spins fast, but 205 00:09:00.120 --> 00:09:03.039 then it gradually slows down over time that loses energy 206 00:09:03.039 --> 00:09:04.039 to the surrounding space. 207 00:09:04.519 --> 00:09:07.279 So to get an old pulsar to spin one hundred 208 00:09:07.320 --> 00:09:09.759 and twenty two times a second, he usually. 209 00:09:09.440 --> 00:09:11.679 Needs a partner. We call him recycled. 210 00:09:11.279 --> 00:09:14.480 Pulsars recycled like it gets a second life exactly. 211 00:09:14.879 --> 00:09:17.519 The neutron star is in a binary orbit with another 212 00:09:17.600 --> 00:09:21.279 regular star. It's gravity is so intense it starts stripping 213 00:09:21.320 --> 00:09:22.399 gas off its neighbor. 214 00:09:22.559 --> 00:09:23.960 It eats its companion star. 215 00:09:24.120 --> 00:09:26.759 It siphons the gas off, and as that gas falls 216 00:09:26.759 --> 00:09:30.320 onto the neutron star, it spirals in and transfers its 217 00:09:30.320 --> 00:09:31.240 angular momentum. 218 00:09:31.279 --> 00:09:33.639 Oh so it physically spins up the dead star. 219 00:09:33.840 --> 00:09:36.120 Yes, it is like hitting a spinning top with a 220 00:09:36.200 --> 00:09:38.919 leaf blower. You are adding energy back into the system. 221 00:09:38.960 --> 00:09:42.240 That makes total sense. So finding an MSP usually implies 222 00:09:42.240 --> 00:09:46.480 a pretty complex history a binary star system gas swapping. 223 00:09:46.200 --> 00:09:50.240 Right, But finding one here, specifically in the galactic center, 224 00:09:50.559 --> 00:09:51.399 that is the real. 225 00:09:51.240 --> 00:09:54.440 Headline which brings us to the location. Because having a 226 00:09:54.440 --> 00:09:55.639 perfect plock. 227 00:09:55.600 --> 00:09:58.159 Is useful, very useful for astronomy. 228 00:09:57.679 --> 00:09:59.440 But having a perfect clock sitting on the edge of 229 00:09:59.480 --> 00:10:01.519 a press of pit is a whole different ballgame. 230 00:10:01.600 --> 00:10:04.960 It transforms the discovery from a cool astronomical object into 231 00:10:04.960 --> 00:10:06.240 a fundamental physics test. 232 00:10:06.600 --> 00:10:10.000 Let us talk about that neighborhood. The research describes this 233 00:10:10.080 --> 00:10:13.559 candidate as being close to Sagittarius a star. 234 00:10:13.720 --> 00:10:18.720 Sgr a star, the supermassive black hole at the absolute 235 00:10:18.720 --> 00:10:19.919 center of our Milky Way. 236 00:10:20.080 --> 00:10:22.200 I feel like we often visualize the center of the 237 00:10:22.200 --> 00:10:27.879 galaxy as this glowing, beautiful, peaceful orb of light, but physically, 238 00:10:28.159 --> 00:10:29.799 what is it actually like there? 239 00:10:29.879 --> 00:10:32.679 It is the most hostile environment you can imagine. It 240 00:10:32.799 --> 00:10:34.679 is a cosmic moshpit. 241 00:10:34.399 --> 00:10:35.120 Oh wash pit. 242 00:10:35.240 --> 00:10:37.600 Yeah, in our neighborhood. Out here in the spiral arms, 243 00:10:37.960 --> 00:10:40.600 stars are pretty far apart. If the Sun were a 244 00:10:40.600 --> 00:10:43.440 great fruit in New York, the next nearest star is 245 00:10:43.480 --> 00:10:44.720 a great fruit in California. 246 00:10:44.840 --> 00:10:46.440 Lots of personal space exactly. 247 00:10:46.799 --> 00:10:49.600 But in the galactic center, the stars are packed in tight. 248 00:10:50.000 --> 00:10:52.000 The radiation is just intense. 249 00:10:51.600 --> 00:10:53.440 And there's debris everywhere. 250 00:10:53.039 --> 00:10:57.879 Right, massive magnetic filaments, clouds of super hot gas, shockwaves 251 00:10:57.879 --> 00:11:00.000 from old supernova explosions, bouncing around. 252 00:11:00.279 --> 00:11:02.440 And sitting right in the middle of this total chaos 253 00:11:02.600 --> 00:11:03.720 is the monster. 254 00:11:03.720 --> 00:11:06.879 Four million solar masses of black hole. It dominates everything 255 00:11:06.919 --> 00:11:08.000 in its vicinity. 256 00:11:07.639 --> 00:11:10.200 Its gravity anchors the entire galaxy, and. 257 00:11:10.120 --> 00:11:13.639 This pulsar candidate is apparently deep within its fhere of influence. 258 00:11:14.000 --> 00:11:15.960 Now I have a question about that. If this place 259 00:11:16.000 --> 00:11:18.960 is so crowded, and if there are so many stars 260 00:11:19.000 --> 00:11:22.559 living and dying there, shouldn't the galactic center just be 261 00:11:22.759 --> 00:11:26.080 full of pulsars? You would think, so, why is finding 262 00:11:26.080 --> 00:11:27.200 one such a big deal? 263 00:11:27.679 --> 00:11:31.399 That is actually known as the missing pulsar problem. It 264 00:11:31.480 --> 00:11:34.279 is one of the nagging mysteries of astrophysics. 265 00:11:34.360 --> 00:11:37.919 Right now, Wait, there is an official missing pulsar problem 266 00:11:38.000 --> 00:11:38.879 a huge one. 267 00:11:39.240 --> 00:11:41.919 Based on the sheer number of massive stars we see 268 00:11:42.000 --> 00:11:45.759 dying in the center, there should be thousands of pulsars there, 269 00:11:45.960 --> 00:11:47.120 maybe tens. 270 00:11:46.799 --> 00:11:48.799 Of thousands, but until recently we. 271 00:11:48.799 --> 00:11:50.320 Had found basically none. 272 00:11:50.440 --> 00:11:52.039 Why are they hiding from us? 273 00:11:52.120 --> 00:11:54.879 They are not hiding, They're being camouflaged. This goes back 274 00:11:54.879 --> 00:11:57.120 to our vacuum cleaner analogy from earlier. 275 00:11:56.799 --> 00:11:58.320 Wait listening for the radio click. 276 00:11:58.440 --> 00:12:00.440 To find a pulsar, you have to hear the radio 277 00:12:00.480 --> 00:12:03.840 clicks sweeping past Earth. But the galactic center is filled 278 00:12:03.879 --> 00:12:06.039 with ionized plasma hot. 279 00:12:05.840 --> 00:12:09.480 Charged gas, and radio waves do not play nicely with plasma. 280 00:12:09.519 --> 00:12:13.440 They absolutely hated. It causes two mathi of problems for astronomers, 281 00:12:13.759 --> 00:12:15.039 dispersion and scattering. 282 00:12:15.159 --> 00:12:17.399 Break those two down for me. Start with dispersion. 283 00:12:17.799 --> 00:12:21.240 Dispersion means the high frequency parts of the pulsar's signal 284 00:12:21.279 --> 00:12:24.919 travel faster through the plasma than the low frequency parts. 285 00:12:24.840 --> 00:12:26.519 So the signal gets stretched. 286 00:12:26.120 --> 00:12:29.480 Out exactly the sharp click gets smeared out into a 287 00:12:29.600 --> 00:12:33.000 long slide whistle sound. We can correct for that mathematically 288 00:12:33.039 --> 00:12:33.960 if we are smart about it. 289 00:12:34.000 --> 00:12:34.200 Though. 290 00:12:34.279 --> 00:12:38.519 Okay, so dispersion is annoying but fixable. What about scattering? 291 00:12:38.759 --> 00:12:42.960 Scattering is way worse. Imagine shining a crisp laser pointer 292 00:12:43.120 --> 00:12:44.759 through a pane of frosted glass. 293 00:12:44.919 --> 00:12:46.960 The beam spreads down, gets all fuzzy. 294 00:12:46.720 --> 00:12:49.000 Right, The sharp click of the pulsar gets blurred into 295 00:12:49.039 --> 00:12:52.279 a long, mushy hiss, and if the scattering is too strong, 296 00:12:52.600 --> 00:12:55.440 the pulse just disappears entirely into the background noise. 297 00:12:55.519 --> 00:12:58.679 So the pulsars are there, they are screaming into the void, 298 00:12:59.240 --> 00:13:01.440 but the fog is just too thick for us to 299 00:13:01.440 --> 00:13:02.639 see the lighthouse beam. 300 00:13:02.759 --> 00:13:05.320 That is exactly it, and that is why this specific 301 00:13:05.320 --> 00:13:08.480 discovery is so incredibly impressive. They did not just point 302 00:13:08.519 --> 00:13:09.679 a telescope and get lucky. 303 00:13:09.759 --> 00:13:10.759 What did they do differently? 304 00:13:10.960 --> 00:13:14.039 They use high frequency observations up around four to eight 305 00:13:14.039 --> 00:13:18.519 gigahertz because high frequencies punched through that plasma fog much 306 00:13:18.559 --> 00:13:19.879 better than lower frequencies. 307 00:13:20.120 --> 00:13:23.000 Ah, So they essentially change the channel to a frequency 308 00:13:23.000 --> 00:13:24.639 that the fog does not block as much. 309 00:13:24.840 --> 00:13:28.200 Right, But that comes with a major trade off. Pulsars 310 00:13:28.200 --> 00:13:30.320 are usually much dimmer at high frequencies. 311 00:13:30.399 --> 00:13:33.679 Oh so you were trading blurriness for faintness exactly. 312 00:13:33.919 --> 00:13:38.840 It is an incredibly difficult balance to strike. Finding This 313 00:13:38.960 --> 00:13:42.240 eight point one to nine millisecond signal is a huge 314 00:13:42.279 --> 00:13:44.480 testament to the sensitivity of the Green Bank. 315 00:13:44.320 --> 00:13:47.919 Telescope and to the processing algorithms the team used to 316 00:13:47.960 --> 00:13:48.799 clean up the data. 317 00:13:49.159 --> 00:13:52.759 Absolutely, the computing power required to sift through that is immense. 318 00:13:52.960 --> 00:13:55.240 So we have a miracle detection of a perfect clock 319 00:13:55.519 --> 00:13:59.159 sitting in a thick fog bank orbiting a super massive 320 00:13:59.200 --> 00:13:59.799 black hole. 321 00:14:00.080 --> 00:14:02.039 And that proximity to the black hole is the key 322 00:14:02.080 --> 00:14:03.639 to everything, because when you have a clock next to 323 00:14:03.720 --> 00:14:07.000 a massive gravity, well, things get weird. 324 00:14:07.080 --> 00:14:09.919 Einstein weird, very Einstein weird. This is the part I 325 00:14:09.919 --> 00:14:13.360 have been waiting for, the holy grail. Why does Einstein's 326 00:14:13.360 --> 00:14:15.600 ghosts care so much about this dead spinning star? 327 00:14:15.720 --> 00:14:17.919 Okay, let us talk about general relativity. It is our 328 00:14:17.960 --> 00:14:20.720 absolute best working theory of gravity. 329 00:14:20.320 --> 00:14:23.480 The core idea being that matter tells space how to curve. 330 00:14:23.360 --> 00:14:25.120 And space tells matter how to move. 331 00:14:25.360 --> 00:14:28.600 Yes, the classic bowling ball in the trampoline analogy. 332 00:14:28.240 --> 00:14:32.679 Right, Sagittarius star is a very heavy bowling ball. It 333 00:14:32.720 --> 00:14:36.759 creates a deep, deep dent in the fabric of space time, a. 334 00:14:36.840 --> 00:14:39.240 Four million solar mass dent. 335 00:14:39.440 --> 00:14:42.080 Now we have tested general relativity a lot here on 336 00:14:42.120 --> 00:14:45.799 Earth and throughout the Solar System, and it works beautifully. 337 00:14:45.799 --> 00:14:47.600 But those are weak gravity environments. 338 00:14:47.720 --> 00:14:50.320 Earth is a tiny pebble compared to a super massive 339 00:14:50.360 --> 00:14:50.879 black hole. 340 00:14:51.080 --> 00:14:53.279 So we want to know does the theory hold up 341 00:14:53.279 --> 00:14:55.080 in the strongest possible gravity. 342 00:14:55.279 --> 00:14:57.960 Exactly does the math break down at the very edge 343 00:14:57.960 --> 00:15:01.000 of the abyss. That is what physicist are desperate to 344 00:15:01.000 --> 00:15:01.679 find out. 345 00:15:01.639 --> 00:15:03.080 And the pulsar helps us do that. 346 00:15:03.320 --> 00:15:07.039 How exactly because it is a clock. Imagine the pulsar 347 00:15:07.200 --> 00:15:09.679 is orbiting the black hole. As it goes behind the 348 00:15:09.720 --> 00:15:12.960 black hole. From our perspective, the radio waves have to 349 00:15:13.000 --> 00:15:15.000 travel past the black hole to get to Earth. 350 00:15:15.159 --> 00:15:17.399 The ticks of the clog have to skim the edge 351 00:15:17.399 --> 00:15:17.919 of the crater. 352 00:15:18.120 --> 00:15:22.480 Yes, and because space is severely curved, the path the 353 00:15:22.559 --> 00:15:24.679 light has to take is longer. It is not a 354 00:15:24.720 --> 00:15:27.679 straight line anymore. Space itself is warped, so it has. 355 00:15:27.519 --> 00:15:30.159 To travel further, which causes a delay. 356 00:15:30.240 --> 00:15:31.799 It is called the Shapiro delay. 357 00:15:32.039 --> 00:15:35.279 The Shapiro delay. So the ticks should literally arrive late. 358 00:15:35.799 --> 00:15:41.600 Yes, if we time the ticks, remember they are incredibly precise, 359 00:15:42.279 --> 00:15:45.080 and we see them arriving slightly later than they should. 360 00:15:45.279 --> 00:15:46.840 When the star is behind the black hole. 361 00:15:46.919 --> 00:15:48.639 We can measure the delay, We. 362 00:15:48.600 --> 00:15:51.840 Can measure the exact curvature of space time. We can 363 00:15:51.879 --> 00:15:53.840 map the pothole using a stopwatch. 364 00:15:53.960 --> 00:15:56.240 That is incredible. You are using the delay of a 365 00:15:56.320 --> 00:15:59.960 tiny radio wave to map the invisible geometry of the universe. 366 00:16:00.039 --> 00:16:02.919 And it gets even cooler than that. There's another relativistic 367 00:16:02.919 --> 00:16:06.440 effect called frame dragging, sometimes called the lens thiring. 368 00:16:06.200 --> 00:16:09.639 Effect frame dragging that sounds like a video game graphics glitch. 369 00:16:09.799 --> 00:16:12.519 It is much trippier than a glitch. Since the black 370 00:16:12.519 --> 00:16:16.159 hole is spinning, it literally drags space time along with 371 00:16:16.240 --> 00:16:17.399 it as it turns. 372 00:16:17.360 --> 00:16:19.639 Like a spoon twisting in a jar of honey. 373 00:16:19.759 --> 00:16:22.679 Exactly, space itself is twisting around the black hole. 374 00:16:22.759 --> 00:16:25.240 So the pulsar is not just orbiting in a static 375 00:16:25.320 --> 00:16:28.399 dip on the trampoline. It is orbiting in a whirlpool 376 00:16:28.440 --> 00:16:29.519 of twisting space. 377 00:16:29.720 --> 00:16:33.519 Yes, and that twisting should make the pulsar's orbit wobble 378 00:16:33.600 --> 00:16:35.480 in a very specific mathematical way. 379 00:16:35.559 --> 00:16:37.639 And because it is a perfect clock, we can measure 380 00:16:37.679 --> 00:16:38.240 that wobble. 381 00:16:38.519 --> 00:16:41.600 If we can track this eight point one to nine 382 00:16:41.600 --> 00:16:46.000 millisecond signal for a few years, we could potentially detect 383 00:16:46.080 --> 00:16:47.279 that precise. 384 00:16:46.840 --> 00:16:49.799 Wobble, and if the wobble matches Einstein's. 385 00:16:49.120 --> 00:16:52.840 Math, then he is right again. General relativity holds up 386 00:16:52.840 --> 00:16:53.919 in the extreme limit. 387 00:16:54.000 --> 00:16:55.480 And what if it doesn't match. 388 00:16:55.399 --> 00:16:58.399 Then someone wins a Nobel prize. Because we have found 389 00:16:58.399 --> 00:17:02.480 a crack in general relativity, we would need new physics. 390 00:17:02.840 --> 00:17:04.839 That is why we call this the Holy grail. It 391 00:17:04.920 --> 00:17:07.160 is the ultimate stress test for physics. 392 00:17:07.480 --> 00:17:10.039 There is no better laboratory in the universe for this 393 00:17:10.480 --> 00:17:13.440 than a pulsar near a supermassive black hole. 394 00:17:13.599 --> 00:17:16.559 But and there's always a butt in astrophysics. We are 395 00:17:16.599 --> 00:17:19.359 not quite ready to hand out Nobel prizes yet, No, 396 00:17:19.480 --> 00:17:22.119 definitely not, which brings us to the uncertainty. We have 397 00:17:22.160 --> 00:17:24.559 to be very careful with our language here. Today the 398 00:17:24.640 --> 00:17:29.440 research describes this as an intriguing millisecond pulsar candidate. 399 00:17:29.119 --> 00:17:31.079 Candidate being the operative word. 400 00:17:31.039 --> 00:17:33.359 Meaning they haven't officially hired it yet to do the 401 00:17:33.359 --> 00:17:34.200