WEBVTT 0 00:00:00.480 --> 00:00:03.120 Avery: Welcome to Astronomy Daily, the podcast that 1 00:00:03.120 --> 00:00:05.760 brings you the universe, one story at a time. 2 00:00:05.920 --> 00:00:06.800 I'm Avery. 3 00:00:06.880 --> 00:00:09.720 Anna: And I'm Anna. Today we're journeying 4 00:00:09.720 --> 00:00:12.440 from our own cosmic backyard to the 5 00:00:12.440 --> 00:00:14.400 vast structures of our galaxy. 6 00:00:14.480 --> 00:00:16.720 Avery: That's right. We'll be looking at surprising 7 00:00:16.720 --> 00:00:19.400 new data from the Moon's far side. A 8 00:00:19.400 --> 00:00:21.640 colossal wave of stars discovered in the 9 00:00:21.640 --> 00:00:24.600 Milky Way, and an update on SpaceX's next 10 00:00:24.600 --> 00:00:25.200 big launch. 11 00:00:25.600 --> 00:00:27.800 Anna: And we'll wrap up with a look at the 12 00:00:27.800 --> 00:00:30.360 invisible asteroids lurking closer to the 13 00:00:30.360 --> 00:00:32.980 Sun. A potential threat yet we're only just 14 00:00:32.980 --> 00:00:35.420 beginning to understand. Let's get started. 15 00:00:35.740 --> 00:00:37.540 Avery: First up, Anna, uh, let's talk about the 16 00:00:37.540 --> 00:00:40.460 Moon. We tend to think of it as this static, 17 00:00:40.460 --> 00:00:42.980 unchanging rock. But China's Chang' 18 00:00:42.980 --> 00:00:45.420 E6 mission is telling us a different story. 19 00:00:45.660 --> 00:00:48.620 Anna: It certainly is. The rock and soil samples 20 00:00:48.620 --> 00:00:50.940 returned from the far side are revealing a 21 00:00:50.940 --> 00:00:53.700 fascinating thermal asymmetry. In 22 00:00:53.700 --> 00:00:56.420 simple terms, the interior of the Moon's far 23 00:00:56.420 --> 00:00:59.300 side, the side we never see from Earth, is 24 00:00:59.300 --> 00:01:01.740 significantly cooler than the near side. 25 00:01:02.170 --> 00:01:04.090 Avery: Cooler. How much cooler are we talking? 26 00:01:04.490 --> 00:01:07.370 Anna: Around 180 degrees Fahrenheit 27 00:01:07.370 --> 00:01:10.290 or 100 degrees Celsius cooler? That 28 00:01:10.290 --> 00:01:12.290 might not sound like a huge number on a 29 00:01:12.290 --> 00:01:14.850 planetary scale, but it's enough to explain 30 00:01:14.850 --> 00:01:17.250 some long standing mysteries about the Moon's 31 00:01:17.250 --> 00:01:17.930 two faces. 32 00:01:18.250 --> 00:01:20.450 Avery: Like why the near side is covered in those 33 00:01:20.450 --> 00:01:23.250 dark volcanic plains, the maria. While 34 00:01:23.250 --> 00:01:25.610 the far side is so much more rugged and 35 00:01:25.610 --> 00:01:26.250 cratered. 36 00:01:26.330 --> 00:01:29.290 Anna: Exactly. A hotter nearside mantle would 37 00:01:29.290 --> 00:01:31.450 have been more molten, leading to more 38 00:01:31.450 --> 00:01:33.840 widespread and prolonged volcanic activity. 39 00:01:34.230 --> 00:01:36.230 This heat also explains why the near side 40 00:01:36.230 --> 00:01:39.150 crust is thinner. The cooler far side mantle 41 00:01:39.150 --> 00:01:41.630 solidified earlier, resulting in a thicker 42 00:01:41.630 --> 00:01:43.510 crust and far less volcanism. 43 00:01:43.990 --> 00:01:46.870 Avery: So the big question is why? Why 44 00:01:46.870 --> 00:01:49.150 would one side be so much hotter than the 45 00:01:49.150 --> 00:01:49.430 other? 46 00:01:49.590 --> 00:01:51.870 Anna: That's the billion dollar question. The 47 00:01:51.870 --> 00:01:54.550 leading hypothesis is an uneven distribution 48 00:01:54.550 --> 00:01:57.190 of heat producing radioactive elements like 49 00:01:57.270 --> 00:01:59.830 uranium and thorium. For some reason, 50 00:02:00.070 --> 00:02:02.550 these elements were concentrated on the near 51 00:02:02.550 --> 00:02:04.070 side when the Moon was forming. 52 00:02:04.460 --> 00:02:05.740 Avery: And how would that have happened? 53 00:02:05.740 --> 00:02:07.900 Anna: There are a couple of compelling theories. 54 00:02:08.060 --> 00:02:10.700 One suggests that a massive ancient impact 55 00:02:10.780 --> 00:02:12.860 could have essentially splattered these 56 00:02:12.860 --> 00:02:15.580 elements across one hemisphere. Another, 57 00:02:15.740 --> 00:02:18.660 more dramatic theory posits that early in its 58 00:02:18.660 --> 00:02:21.500 history, Earth had two moons and a 59 00:02:21.500 --> 00:02:24.260 smaller companion moon had a slow motion 60 00:02:24.260 --> 00:02:27.100 collision with the larger one, depositing its 61 00:02:27.100 --> 00:02:29.740 element rich material onto what is now the 62 00:02:29.740 --> 00:02:30.460 MIR side. 63 00:02:30.820 --> 00:02:33.180 Avery: Wow. So the face of the Moon we see every 64 00:02:33.180 --> 00:02:35.300 night might actually be the result of a 65 00:02:35.300 --> 00:02:37.980 cosmic fender bender. It really highlights 66 00:02:37.980 --> 00:02:40.620 how dynamic and violent the early solar 67 00:02:40.620 --> 00:02:41.220 system was. 68 00:02:41.460 --> 00:02:43.900 A truly incredible discovery from the Chang' 69 00:02:43.900 --> 00:02:44.820 E6 mission. 70 00:02:45.140 --> 00:02:47.780 Anna: From our closest neighbor to the grand scale 71 00:02:47.780 --> 00:02:50.780 of our entire galaxy. Avery. Data 72 00:02:50.780 --> 00:02:53.340 from the European Space Agency's Gaia space 73 00:02:53.340 --> 00:02:55.780 telescope has revealed something truly 74 00:02:55.780 --> 00:02:56.500 monumental. 75 00:02:57.040 --> 00:02:59.360 Avery: Gaia is always turning up amazing things. 76 00:02:59.600 --> 00:03:00.880 What has it found this time? 77 00:03:01.040 --> 00:03:03.760 Anna: It's been described as a great wave of 78 00:03:03.760 --> 00:03:06.400 stars. A colossal ripple moving 79 00:03:06.400 --> 00:03:08.560 outwards from the center of the Milky Way. 80 00:03:08.640 --> 00:03:10.640 We're talking about a structure that spans 81 00:03:10.640 --> 00:03:12.560 tens of thousands of light years. 82 00:03:12.720 --> 00:03:15.520 Avery: A wave of stars. What does that even 83 00:03:15.520 --> 00:03:18.120 look like? Are the stars themselves moving in 84 00:03:18.120 --> 00:03:19.680 a wave pattern, like water? 85 00:03:19.920 --> 00:03:22.800 Anna: In a way, yes. This isn't a wave of light, 86 00:03:22.960 --> 00:03:25.720 but a literal wave of motion. The 87 00:03:25.720 --> 00:03:27.800 collective positions and velocities of 88 00:03:27.800 --> 00:03:29.980 millions of stars. Stars are perturbed, 89 00:03:30.060 --> 00:03:32.300 causing them to move up and down as this 90 00:03:32.300 --> 00:03:34.780 ripple propagates through the galactic disk. 91 00:03:34.860 --> 00:03:37.580 It's a subtle effect, but on a galactic 92 00:03:37.580 --> 00:03:39.180 scale, it's enormous. 93 00:03:39.340 --> 00:03:42.220 Avery: That's mind boggling. A wave that's tens 94 00:03:42.220 --> 00:03:44.660 of thousands of light years across. What 95 00:03:44.660 --> 00:03:46.940 could possibly cause something that huge? 96 00:03:47.260 --> 00:03:50.140 Anna: The most likely culprit is a collision. Not a 97 00:03:50.140 --> 00:03:52.100 recent one, but an event that happened 98 00:03:52.100 --> 00:03:54.860 perhaps a few billion years ago. The thinking 99 00:03:54.860 --> 00:03:57.620 is that a dwarf galaxy plunged through 100 00:03:57.620 --> 00:03:59.020 the center of the Milky. 101 00:03:59.020 --> 00:04:01.800 Avery: Way's disk like drop a stone into a pond. 102 00:04:01.800 --> 00:04:04.680 But the pond is our galaxy, and the stone 103 00:04:04.680 --> 00:04:06.200 is another, smaller galaxy. 104 00:04:06.520 --> 00:04:09.400 Anna: That's the perfect analogy. The dwarf 105 00:04:09.400 --> 00:04:11.800 galaxy's gravity would have punched through 106 00:04:11.800 --> 00:04:14.560 the disk, setting off these ripples that 107 00:04:14.560 --> 00:04:16.840 are still expanding outwards today. 108 00:04:17.480 --> 00:04:20.200 It's a testament to the power of big data 109 00:04:20.280 --> 00:04:23.280 in astronomy. By mapping out the 3D 110 00:04:23.280 --> 00:04:26.160 motion of billions of stars, we can 111 00:04:26.160 --> 00:04:28.200 uncover these hidden dynamics. 112 00:04:28.810 --> 00:04:31.250 Avery: And does this wave affect us here in our 113 00:04:31.250 --> 00:04:31.930 solar system? 114 00:04:32.410 --> 00:04:35.410 Anna: That's a great question. We are likely caught 115 00:04:35.410 --> 00:04:37.810 up in this wave, just like all the other 116 00:04:37.810 --> 00:04:40.810 stars in our neighborhood. The effect on our 117 00:04:40.810 --> 00:04:43.770 solar system's orbit is probably very small, 118 00:04:44.249 --> 00:04:46.970 but it's a powerful reminder that we are part 119 00:04:46.970 --> 00:04:49.530 of a much larger dynamic system 120 00:04:50.010 --> 00:04:52.730 shaped by events that took place long before 121 00:04:52.730 --> 00:04:54.170 the Earth even formed. 122 00:04:54.590 --> 00:04:55.990 Avery: All right, let's bring it back a little 123 00:04:55.990 --> 00:04:58.420 closer to home. It's time for an update from, 124 00:04:58.420 --> 00:05:01.350 uh, SpaceX. Mark your calendars because they 125 00:05:01.350 --> 00:05:04.110 are targeting October 13th for the 126 00:05:04.110 --> 00:05:06.830 11th flight of the Starship Mega 127 00:05:06.830 --> 00:05:08.830 Rocket Flight 11. 128 00:05:09.390 --> 00:05:11.950 Anna: They are certainly keeping a rapid pace. 129 00:05:12.270 --> 00:05:14.910 This will be another crucial test for the 130 00:05:14.910 --> 00:05:17.830 most powerful rocket ever built. What are 131 00:05:17.830 --> 00:05:20.060 the main objectives for this flight? Avery? 132 00:05:20.450 --> 00:05:22.650 Avery: The mission profile will look very similar to 133 00:05:22.650 --> 00:05:25.530 the successful Flight 10. The main goal is to 134 00:05:25.530 --> 00:05:27.190 demonstrate reliability and reusability. Uh, 135 00:05:28.370 --> 00:05:30.850 they'll launch the super heavy booster, will 136 00:05:30.850 --> 00:05:33.250 separate and perform a boostback burn, aiming 137 00:05:33.250 --> 00:05:34.730 For a soft splashdown in the. 138 00:05:34.730 --> 00:05:37.650 Anna: Gulf of Mexico and the starship upper 139 00:05:37.650 --> 00:05:38.050 stage. 140 00:05:38.610 --> 00:05:40.850 Avery: The ship will continue on a suborbital 141 00:05:40.850 --> 00:05:43.810 trajectory, Coasting for about an hour before 142 00:05:43.810 --> 00:05:46.250 performing its own re entry and attempting a 143 00:05:46.250 --> 00:05:48.610 controlled splashdown in the Indian Ocean. 144 00:05:48.930 --> 00:05:51.090 They'll also be testing the payload bay door 145 00:05:51.090 --> 00:05:53.390 again, this time by deploying some mock 146 00:05:53.470 --> 00:05:54.830 Starlink satellites. 147 00:05:55.230 --> 00:05:57.710 Anna: Deploying mach satellites is an important 148 00:05:57.870 --> 00:06:00.350 step towards the vehicle becoming operational 149 00:06:00.510 --> 00:06:03.310 for its primary mission. Launching the 150 00:06:03.310 --> 00:06:05.070 next generation of Starlink. 151 00:06:05.470 --> 00:06:07.590 Avery: Exactly. It's also worth noting that this 152 00:06:07.590 --> 00:06:09.870 will be the final flight for the current 153 00:06:09.950 --> 00:06:12.910 version 2 of the Starship vehicle. 154 00:06:12.910 --> 00:06:14.750 The next flights will feature significant 155 00:06:15.070 --> 00:06:17.710 upgrades aimed at even faster turnaround 156 00:06:17.710 --> 00:06:19.710 times and greater reliability. 157 00:06:20.520 --> 00:06:22.760 Anna: So it's both a validation of the current 158 00:06:22.840 --> 00:06:25.720 design and a, uh, final farewell before 159 00:06:25.720 --> 00:06:28.280 we see the next evolution of starship. 160 00:06:28.840 --> 00:06:31.040 Each of these flights, even when they seem 161 00:06:31.040 --> 00:06:33.800 repetitive, gathers an immense amount of 162 00:06:33.800 --> 00:06:36.600 data that feeds directly into those future 163 00:06:36.680 --> 00:06:37.400 improvements. 164 00:06:37.880 --> 00:06:40.840 Avery: That's the key iteration we'll be watching on 165 00:06:40.840 --> 00:06:43.360 October 13th to see if they can stick the 166 00:06:43.360 --> 00:06:45.480 landing or at least to splashdown. 167 00:06:46.160 --> 00:06:48.280 Anna: For our final story, we're looking at 168 00:06:48.280 --> 00:06:50.920 something that's, um, a bit unsettling. The 169 00:06:50.920 --> 00:06:53.760 idea of hitting dangers in our own solar 170 00:06:53.760 --> 00:06:56.400 system. Astronomers are suggesting there 171 00:06:56.400 --> 00:06:59.360 could be a large undiscovered population of 172 00:06:59.360 --> 00:07:02.080 asteroids lurking near the orbit of 173 00:07:02.080 --> 00:07:02.640 Venus. 174 00:07:03.120 --> 00:07:05.360 Avery: Undiscovered asteroids are always a concern. 175 00:07:05.920 --> 00:07:08.480 Why are these ones particularly hard to spot? 176 00:07:08.720 --> 00:07:11.120 Are they very small or very dark? 177 00:07:11.670 --> 00:07:14.110 Anna: It's neither of those actually. It's a 178 00:07:14.110 --> 00:07:16.910 problem of location. These asteroids are 179 00:07:16.910 --> 00:07:18.990 believed to be orbiting the sun in a 180 00:07:18.990 --> 00:07:21.870 resonance with Venus. From our viewpoint 181 00:07:21.870 --> 00:07:24.790 on Earth, this means they spend almost all 182 00:07:24.790 --> 00:07:26.950 their time in the direction of the Sun. 183 00:07:27.430 --> 00:07:30.190 Avery: Ah, uh, so they're lost in the glare. You 184 00:07:30.190 --> 00:07:32.030 can't really point a telescope at the sun to 185 00:07:32.030 --> 00:07:33.190 look for faint objects. 186 00:07:33.510 --> 00:07:36.150 Anna: Precisely. It's like trying to spot a 187 00:07:36.150 --> 00:07:38.790 firefly next to a searchlight. You ground 188 00:07:38.790 --> 00:07:41.310 based telescopes are limited to searching the 189 00:07:41.310 --> 00:07:44.150 sky at twilight, just after sunset 190 00:07:44.150 --> 00:07:47.070 or before sunrise, which gives them a very 191 00:07:47.070 --> 00:07:49.350 narrow window to hunt in that direction. 192 00:07:49.750 --> 00:07:52.470 This creates a huge observational blind 193 00:07:52.470 --> 00:07:52.950 spot. 194 00:07:53.190 --> 00:07:55.790 Avery: So we have this potential swarm of asteroids 195 00:07:55.790 --> 00:07:58.510 nearby, and we can barely see them. Should we 196 00:07:58.510 --> 00:08:01.190 be worried? Do they pose a threat to Earth? 197 00:08:01.510 --> 00:08:04.390 Anna: The potential is there. The models show 198 00:08:04.390 --> 00:08:06.870 that the gravitational pull of Venus can 199 00:08:06.870 --> 00:08:09.870 nudge these asteroids into chaotic orbits 200 00:08:09.870 --> 00:08:12.530 over millions of years. Some of those 201 00:08:12.530 --> 00:08:15.370 chaotic orbits could eventually intersect 202 00:08:15.370 --> 00:08:18.290 with Earth's orbit, creating a collision risk 203 00:08:18.370 --> 00:08:19.090 down the line. 204 00:08:19.730 --> 00:08:22.210 Avery: So this isn't an immediate threat, but a long 205 00:08:22.210 --> 00:08:24.770 term hazard we need to map out. Is there any 206 00:08:24.770 --> 00:08:25.810 hope in finding them? 207 00:08:26.290 --> 00:08:28.970 Anna: Yes, there is. Upcoming missions 208 00:08:28.970 --> 00:08:31.370 are specifically designed to tackle this 209 00:08:31.370 --> 00:08:34.330 problem. The Vera Rubin Observatory, with 210 00:08:34.330 --> 00:08:37.210 its massive field of view, will be able to 211 00:08:37.210 --> 00:08:39.850 survey the sky much more rapidly during 212 00:08:39.850 --> 00:08:41.890 twilight. And even better, 213 00:08:42.430 --> 00:08:45.250 NASA's NEO Surveyor mission will be a, ah, 214 00:08:45.310 --> 00:08:47.550 space based infrared telescope. 215 00:08:48.190 --> 00:08:50.950 Avery: A space telescope wouldn't be hampered by the 216 00:08:50.950 --> 00:08:52.910 sun's glare in the same way, right? 217 00:08:53.390 --> 00:08:56.030 Anna: Exactly. By operating in space 218 00:08:56.030 --> 00:08:59.030 and observing in the infrared where asteroids 219 00:08:59.030 --> 00:09:01.590 glow from the Sun's heat, NEO 220 00:09:01.590 --> 00:09:04.270 Surveyor will be able to find these elusive 221 00:09:04.270 --> 00:09:06.790 objects regardless of their position in the 222 00:09:06.790 --> 00:09:09.790 sky. It's designed to fill in these dangerous 223 00:09:09.790 --> 00:09:12.190 blind spots in our planetary defense network. 224 00:09:12.950 --> 00:09:15.390 Avery: That's reassuring. It's a good reminder that 225 00:09:15.390 --> 00:09:18.190 the sky isn't empty and we need to keep our 226 00:09:18.190 --> 00:09:20.910 eyes open even in the places that are hardest 227 00:09:20.910 --> 00:09:21.350 to look. 228 00:09:21.830 --> 00:09:24.070 And that's all the time we have for today on 229 00:09:24.070 --> 00:09:26.630 Astronomy Daily. We've journeyed from our two 230 00:09:26.630 --> 00:09:29.510 face Moon to a great wave in the Milky Way, 231 00:09:29.670 --> 00:09:31.950 checked in on Starship, and peered into the 232 00:09:31.950 --> 00:09:33.830 Sun's glare for hidden asteroids. 233 00:09:34.550 --> 00:09:36.910 Anna: It's a constant reminder that there are 234 00:09:36.910 --> 00:09:39.630 always new discoveries to be made, both near 235 00:09:39.630 --> 00:09:42.150 and far. Thanks so much for joining us. 236 00:09:43.000 --> 00:09:45.360 Avery: You can find Astronomy Daily wherever you get 237 00:09:45.360 --> 00:09:47.880 your podcasts or simply visit our website at 238 00:09:47.880 --> 00:09:50.800 astronomydaily IO Be sure 239 00:09:50.800 --> 00:09:52.840 to subscribe so you don't miss an episode. 240 00:09:52.920 --> 00:09:55.440 Until next time, keep looking up and keep 241 00:09:55.440 --> 00:09:55.960 wondering.