WEBVTT 0 00:00:00.000 --> 00:00:02.720 Anna: The side of the Moon we never see has been 1 00:00:02.720 --> 00:00:04.800 quietly keeping a secret about our own 2 00:00:04.800 --> 00:00:06.960 planet. And this week, two very different 3 00:00:06.960 --> 00:00:09.200 groups of scientists arrived at the same 4 00:00:09.200 --> 00:00:10.960 place from opposite directions. 5 00:00:11.280 --> 00:00:13.440 Avery: One group read it out of the dirt. The other 6 00:00:13.440 --> 00:00:15.120 argued about who gets to own it. 7 00:00:15.200 --> 00:00:17.800 Anna: Meanwhile, a rocket sits on a pad in South 8 00:00:17.800 --> 00:00:19.760 Texas waiting for a second chance. 9 00:00:20.000 --> 00:00:22.040 Avery: And a star that vanished behind its own 10 00:00:22.040 --> 00:00:24.760 wreckage 25 years ago has finally 11 00:00:24.760 --> 00:00:26.000 stepped back into the light. 12 00:00:26.520 --> 00:00:29.080 Anna: Welcome to Astronomy Daily. I'm Ana. 13 00:00:29.160 --> 00:00:31.548 Avery: And I'm, um. Avery. It's Thursday 23rd 14 00:00:31.705 --> 00:00:34.360 July 2026, and this is episode 15 00:00:34.360 --> 00:00:35.560 148. 16 00:00:35.880 --> 00:00:38.720 Anna: Coming up, Starship gets another go with 17 00:00:38.720 --> 00:00:41.440 a caveat. What the far side of the Moon knows 18 00:00:41.440 --> 00:00:43.640 about Earth's magnetic field, whether that 19 00:00:43.640 --> 00:00:46.240 far side should be off limits to industry. A 20 00:00:46.240 --> 00:00:48.880 one of a kind stellar explosion finally 21 00:00:48.880 --> 00:00:51.360 identified. And the possibility that our 22 00:00:51.360 --> 00:00:53.720 entire galaxy once turned over. 23 00:00:54.080 --> 00:00:56.090 Avery: Uh, plus a skywatch closer with some 24 00:00:56.090 --> 00:00:58.410 genuinely useful advice about the Delta 25 00:00:58.410 --> 00:01:01.250 Aquarids, which is to not wait for the peak. 26 00:01:01.410 --> 00:01:02.370 Anna: Let's get into it. 27 00:01:02.450 --> 00:01:05.210 Avery: We start at Starbase, because today is meant 28 00:01:05.210 --> 00:01:05.970 to be the day. 29 00:01:06.210 --> 00:01:08.930 Anna: SpaceX is targeting Flight 13 of 30 00:01:08.930 --> 00:01:11.370 Starship with a 90 minute launch window that 31 00:01:11.370 --> 00:01:14.290 opens at 6:45 in the evening Eastern 32 00:01:14.290 --> 00:01:16.930 Time. That's 5:45 Central and 33 00:01:16.930 --> 00:01:19.730 3:45 in the afternoon on the Pacific coast. 34 00:01:20.080 --> 00:01:22.000 For those of us on this side of the world, 35 00:01:22.000 --> 00:01:24.560 that lands at a quarter to nine on Friday 36 00:01:24.560 --> 00:01:27.320 morning Australian Eastern Time and a quarter 37 00:01:27.320 --> 00:01:29.680 to 11 Friday morning in New Zealand. 38 00:01:30.000 --> 00:01:32.360 Avery: So North America gets it over dinner and we 39 00:01:32.360 --> 00:01:35.000 get it over breakfast for once, nobody has to 40 00:01:35.000 --> 00:01:37.280 set an alarm for three in the morning for 41 00:01:37.280 --> 00:01:37.600 once. 42 00:01:37.680 --> 00:01:40.200 Anna: Although, and this is the part I want to be 43 00:01:40.200 --> 00:01:43.200 upfront about, that schedule is not locked. 44 00:01:43.360 --> 00:01:45.840 Meaning? Meaning the public schedule says 45 00:01:45.840 --> 00:01:48.080 today, but the road and beach closure 46 00:01:48.080 --> 00:01:50.480 notifications around Starbase suggest 47 00:01:50.560 --> 00:01:52.260 additional testing is happening happening on 48 00:01:52.260 --> 00:01:54.940 Pad 2. Those closure notices are one of the 49 00:01:54.940 --> 00:01:57.340 more reliable tells in this business because 50 00:01:57.340 --> 00:01:59.300 they have to be filed in advance and they 51 00:01:59.300 --> 00:02:01.420 tend to reflect what's actually planned 52 00:02:01.420 --> 00:02:03.580 rather than what's been announced. So there 53 00:02:03.580 --> 00:02:05.260 is a realistic chance this 54 00:02:05.260 --> 00:02:07.460 Avery: slides again, which would make it the third 55 00:02:07.460 --> 00:02:08.700 date for Flight 13. 56 00:02:09.180 --> 00:02:11.980 Anna: It would. Let's recap how we got here because 57 00:02:11.980 --> 00:02:14.940 the arc matters. Flight 13 was first set 58 00:02:14.940 --> 00:02:17.860 for Thursday 16th July. The countdown went 59 00:02:17.860 --> 00:02:20.310 all the way to zero and then stopped. The 60 00:02:20.310 --> 00:02:22.710 flight software triggered an automatic abort 61 00:02:22.710 --> 00:02:25.670 right at T0 because four of the 33 62 00:02:25.670 --> 00:02:27.950 Raptor engines on the Super Heavy booster 63 00:02:28.030 --> 00:02:29.870 failed to reach acceptable starting 64 00:02:29.870 --> 00:02:30.510 parameters. 65 00:02:30.670 --> 00:02:32.790 Avery: And um, the threshold is 3, so 66 00:02:32.790 --> 00:02:35.670 Anna: it missed by exactly one engine. That's the 67 00:02:35.670 --> 00:02:38.150 system working as designed and it protected 68 00:02:38.150 --> 00:02:41.150 both the vehicle and the pad. Elon Musk said 69 00:02:41.150 --> 00:02:43.350 afterwards that two Raptors would be pulled 70 00:02:43.350 --> 00:02:45.230 and replaced before the next attempt. 71 00:02:45.470 --> 00:02:47.750 Avery: That's a remarkably narrow margin between a 72 00:02:47.750 --> 00:02:48.750 scrub and a launch. 73 00:02:49.330 --> 00:02:51.850 Anna: It is, and it's deliberate. The vehicle was 74 00:02:51.850 --> 00:02:53.930 cleared to fly in the first place because the 75 00:02:53.930 --> 00:02:56.810 SAA closed out its mishap investigation into 76 00:02:56.810 --> 00:02:59.530 Flight 12 on 13 July. And the 77 00:02:59.530 --> 00:03:02.130 booster had already completed a full duration 78 00:03:02.130 --> 00:03:04.890 static fire of all 33 engines back on the 79 00:03:04.890 --> 00:03:05.329 10th. 80 00:03:05.570 --> 00:03:07.490 Avery: So the hardware had been through its paces. 81 00:03:07.490 --> 00:03:08.930 It just didn't like the moment. 82 00:03:09.250 --> 00:03:11.490 Anna: That's about the size of it. Here's what 83 00:03:11.490 --> 00:03:13.490 makes this flight worth paying attention to. 84 00:03:13.490 --> 00:03:16.270 Beyond the launch itself, Blight 13 is 85 00:03:16.270 --> 00:03:19.030 carrying 20 V3 Starlink satellites, 86 00:03:19.030 --> 00:03:21.630 the next generation of the Constellation, and 87 00:03:21.630 --> 00:03:23.710 the first time Starship has ever deployed 88 00:03:23.710 --> 00:03:23.950 them. 89 00:03:24.190 --> 00:03:25.710 Avery: That's the whole point of the vehicle 90 00:03:25.710 --> 00:03:28.110 eventually. Not the spectacle, the payload. 91 00:03:28.350 --> 00:03:30.870 Anna: Right up to now, these have been test flights 92 00:03:30.870 --> 00:03:33.590 carrying simulators and mass models. This is 93 00:03:33.590 --> 00:03:35.750 the first time the thing does the job it was 94 00:03:35.750 --> 00:03:38.350 built for. Even on a suborbital trajectory 95 00:03:38.510 --> 00:03:41.190 and the flight profile. Oster and ship 96 00:03:41.190 --> 00:03:43.920 separate as usual. Super Heavy steers 97 00:03:43.920 --> 00:03:46.600 itself to a controlled splashdown in the Gulf 98 00:03:46.600 --> 00:03:49.400 about seven minutes after liftoff. No 99 00:03:49.400 --> 00:03:51.560 catch attempt with the chopstick arms on this 100 00:03:51.560 --> 00:03:53.840 one. The ship continues on, 101 00:03:54.080 --> 00:03:56.560 deploys the satellites and then comes down 102 00:03:56.560 --> 00:03:59.120 for its own splashdown in the Indian Ocean 103 00:03:59.120 --> 00:04:01.760 off the coast of Western Australia at around 104 00:04:01.920 --> 00:04:02.520 65 105 00:04:02.520 --> 00:04:04.640 Avery: minutes, which is worth flagging for our, uh, 106 00:04:04.680 --> 00:04:07.240 listeners in Perth and along that coast. You 107 00:04:07.240 --> 00:04:09.440 are not going to see it from the beach. It's 108 00:04:09.440 --> 00:04:11.860 a long way offshore, but it is your patch of 109 00:04:11.860 --> 00:04:12.300 ocean. 110 00:04:12.460 --> 00:04:15.220 Anna: It is. And for anyone in North America 111 00:04:15.220 --> 00:04:17.940 hoping to catch the launch itself, it's a 112 00:04:17.940 --> 00:04:20.500 star based departure. So the viewing sites 113 00:04:20.500 --> 00:04:23.380 around Boca Chica and South Padre island are 114 00:04:23.380 --> 00:04:24.140 the ones that matter. 115 00:04:24.620 --> 00:04:26.140 Avery: So assuming it goes. 116 00:04:26.620 --> 00:04:29.540 Anna: Assuming it goes. If you're listening to this 117 00:04:29.540 --> 00:04:32.220 on Thursday, check before you commit your 118 00:04:32.220 --> 00:04:34.380 evening. If you're listening later, you 119 00:04:34.380 --> 00:04:36.500 already know how it turned out and we'll pick 120 00:04:36.500 --> 00:04:38.420 up the result in the next episode. Either 121 00:04:38.420 --> 00:04:41.290 way, this ark has taught us not to get ahead 122 00:04:41.290 --> 00:04:41.930 of ourselves. 123 00:04:42.490 --> 00:04:44.850 Avery: Now, to the moon and to something I find 124 00:04:44.850 --> 00:04:46.890 genuinely lovely about this next result, 125 00:04:47.290 --> 00:04:49.970 which is that it turns lunar soil into a 126 00:04:49.970 --> 00:04:50.890 record of Earth. 127 00:04:51.210 --> 00:04:51.850 Anna: Go on. 128 00:04:52.090 --> 00:04:54.970 Avery: The sun blows a continuous stream of charged 129 00:04:55.050 --> 00:04:57.450 particles out across a solar system. The 130 00:04:57.450 --> 00:05:00.370 solar wind. The moon has no atmosphere and 131 00:05:00.370 --> 00:05:03.250 no global magnetic field to speak of. So 132 00:05:03.250 --> 00:05:05.730 those particles hit the surface directly and 133 00:05:05.730 --> 00:05:08.660 bury themselves in the soil over billions of 134 00:05:08.660 --> 00:05:11.340 years. The regolith becomes an archive of 135 00:05:11.340 --> 00:05:12.580 everything that struck it. 136 00:05:12.660 --> 00:05:15.300 Anna: And noble gases are the good bookkeepers. 137 00:05:15.780 --> 00:05:18.660 Avery: Exactly. Helium, neon, argon, 138 00:05:18.660 --> 00:05:21.340 krypton, xenon. They don't react with 139 00:05:21.340 --> 00:05:23.940 anything. So whatever went in stays in. 140 00:05:24.100 --> 00:05:26.780 And how deep it went tells you how fast it 141 00:05:26.780 --> 00:05:28.100 was traveling when it arrived. 142 00:05:28.660 --> 00:05:29.860 Anna: So what did they find? 143 00:05:30.180 --> 00:05:32.900 Avery: A team at the Chinese Academy of Sciences, 144 00:05:32.900 --> 00:05:35.820 Institute of Geology and Physics analyzed 145 00:05:35.820 --> 00:05:38.290 samples from Chang' E6. The mission that 146 00:05:38.290 --> 00:05:41.050 returned material from the far side from the 147 00:05:41.050 --> 00:05:43.410 south pole aitken Basin. That's 148 00:05:43.410 --> 00:05:46.330 1,935 grams of soil, 149 00:05:46.730 --> 00:05:48.410 just under 2 kilograms. 150 00:05:48.730 --> 00:05:51.530 Anna: And that's the first far side material anyone 151 00:05:51.530 --> 00:05:53.130 has ever had in a laboratory. 152 00:05:53.610 --> 00:05:56.610 Avery: Every previous return sample, Apollo, Luna, 153 00:05:56.610 --> 00:05:59.570 Chang' e5 came from the near side. So this 154 00:05:59.570 --> 00:06:01.690 is the first time anyone could directly 155 00:06:01.690 --> 00:06:03.990 compare the two hemispheres. They worked 156 00:06:03.990 --> 00:06:06.430 through seven portions using stepwise heating 157 00:06:06.430 --> 00:06:09.270 and laser extraction, measuring the isotopes 158 00:06:09.270 --> 00:06:12.270 of all five noble gases. And the far side 159 00:06:12.270 --> 00:06:15.110 soil is measurably different. The solar 160 00:06:15.110 --> 00:06:17.470 wind went in faster and went in deeper. 161 00:06:17.870 --> 00:06:19.630 Anna: Deeper, meaning higher energy. 162 00:06:19.950 --> 00:06:22.710 Avery: Higher energy, yes. The clearest signal was 163 00:06:22.710 --> 00:06:25.510 in neon. The ratio of Neon 20 to 164 00:06:25.510 --> 00:06:28.110 Neon 22 in the Cheng' E6 material 165 00:06:28.270 --> 00:06:30.870 sits below anything recorded in any near 166 00:06:30.870 --> 00:06:33.270 sight sample, which points to stronger 167 00:06:33.270 --> 00:06:35.790 processing on the way in. And the heavier 168 00:06:35.790 --> 00:06:38.710 gases krypton and xenon come out of the 169 00:06:38.710 --> 00:06:40.750 sample at different temperatures than they do 170 00:06:40.750 --> 00:06:43.350 from Chang' E5 material, which is another way 171 00:06:43.350 --> 00:06:44.990 of reading implantation depth. 172 00:06:45.310 --> 00:06:48.110 Anna: So why would the far side get hit harder? 173 00:06:48.430 --> 00:06:50.100 Avery: Because we're in the way. M 174 00:06:50.990 --> 00:06:53.670 Earth magnetosphere. As the moon 175 00:06:53.670 --> 00:06:56.150 travels around its orbit, it spends part of 176 00:06:56.150 --> 00:06:58.950 each month downstream of Earth, inside the 177 00:06:58.950 --> 00:07:01.430 long magnetic tail our planet trails behind 178 00:07:01.430 --> 00:07:04.240 it. And in that region, the solar wind 179 00:07:04.240 --> 00:07:06.440 gets slowed down before it reaches the lunar 180 00:07:06.440 --> 00:07:09.200 surface. But it's the near side that's facing 181 00:07:09.200 --> 00:07:11.680 us. So the near side is the one that catches 182 00:07:11.680 --> 00:07:14.280 at the celerated wind. The far side is 183 00:07:14.280 --> 00:07:16.560 permanently turned away and takes the full 184 00:07:16.640 --> 00:07:17.920 unmoderated stream. 185 00:07:18.240 --> 00:07:20.200 Anna: Earth has been sheltering the side of the 186 00:07:20.200 --> 00:07:22.800 moon that looks at us for 4 billion 187 00:07:22.880 --> 00:07:23.280 years. 188 00:07:23.680 --> 00:07:26.680 Avery: For 4 billion years. And the team put 189 00:07:26.680 --> 00:07:29.100 a number on it. Roughly a quarter of the 190 00:07:29.100 --> 00:07:31.500 total solar wind exposure at the Chang' e 5 191 00:07:31.500 --> 00:07:34.300 landing site involved that slowed down flow. 192 00:07:34.540 --> 00:07:36.940 At the Chang' e 6 site on the far side, 193 00:07:37.100 --> 00:07:38.940 there's no sign of it at all. 194 00:07:39.180 --> 00:07:42.020 Anna: That's a beautiful result. And I assume it 195 00:07:42.020 --> 00:07:43.260 cuts the other way as well. 196 00:07:43.580 --> 00:07:45.980 Avery: That's the part that excites me most. If the 197 00:07:45.980 --> 00:07:48.700 near site soil records how much shielding 198 00:07:48.700 --> 00:07:51.500 Earth was providing, then heavy noble gases 199 00:07:51.500 --> 00:07:54.260 in lunar Regolith become a fossil record of 200 00:07:54.260 --> 00:07:57.000 our own magnetosphere. Combine that with the 201 00:07:57.000 --> 00:07:59.640 rock magnetism record on Earth, and you have 202 00:07:59.640 --> 00:08:02.400 a completely new way of reconstructing how 203 00:08:02.400 --> 00:08:04.920 our magnetic field has changed over deep 204 00:08:04.920 --> 00:08:05.200 time. 205 00:08:05.280 --> 00:08:07.160 Anna: Which is not a small thing, given the 206 00:08:07.160 --> 00:08:09.320 magnetosphere is the reason we still have an 207 00:08:09.320 --> 00:08:09.920 atmosphere. 208 00:08:10.000 --> 00:08:12.200 Avery: Not a small thing at all. The Moon has been 209 00:08:12.200 --> 00:08:14.600 keeping notes on us, and it turns out the far 210 00:08:14.600 --> 00:08:17.480 side has the cleaner copy. Which, as 211 00:08:17.480 --> 00:08:20.160 it happens, is exactly why a room full of 212 00:08:20.160 --> 00:08:22.520 astronomers spent Tuesday evening arguing 213 00:08:22.520 --> 00:08:24.320 about what we're allowed to do out there. 214 00:08:24.480 --> 00:08:26.360 Anna: So this was at the Royal Astronomical 215 00:08:26.360 --> 00:08:28.580 Society's National Astronomy Meeting, which 216 00:08:28.580 --> 00:08:30.100 is running this week at the University of 217 00:08:30.100 --> 00:08:32.660 Birmingham. On Tuesday evening, they staged a 218 00:08:32.660 --> 00:08:35.060 formal debate on a single proposition, that 219 00:08:35.060 --> 00:08:37.020 the far side of the Moon should be preserved 220 00:08:37.100 --> 00:08:38.620 solely for scientific endeavors. 221 00:08:38.780 --> 00:08:41.340 Avery: And the answer is presumably not obvious or 222 00:08:41.340 --> 00:08:42.420 there'd be no debate. 223 00:08:42.420 --> 00:08:45.340 Anna: It's genuinely not. Arguing in favor were 224 00:08:45.340 --> 00:08:47.740 Joe Silk of Johns Hopkins and Jonathan 225 00:08:47.740 --> 00:08:49.860 McDowell, who most of our listeners will know 226 00:08:49.860 --> 00:08:52.140 from Jonathan's space report and who is now 227 00:08:52.140 --> 00:08:54.180 an honorary professor at Durham Space 228 00:08:54.180 --> 00:08:56.460 Research Center. After decades at the Harvard 229 00:08:56.460 --> 00:08:58.840 Smithsonian center for Astrophysica, um, and 230 00:08:58.840 --> 00:09:01.480 against M. Nikita Chu, also at Durham, who 231 00:09:01.480 --> 00:09:03.720 works on space technology governance, and 232 00:09:03.720 --> 00:09:06.400 manuel Salvoldi, an Aram space engineer with 233 00:09:06.400 --> 00:09:08.880 25 years across industry and academia. 234 00:09:09.120 --> 00:09:11.600 Barton Ward convened it. The case for 235 00:09:11.600 --> 00:09:14.359 protection rests on one physical fact. The 236 00:09:14.359 --> 00:09:17.000 far side is the only radio quiet real 237 00:09:17.000 --> 00:09:18.760 estate anywhere near Earth. 238 00:09:18.760 --> 00:09:21.160 Avery: The Moon is tidally locked, so the same 239 00:09:21.160 --> 00:09:24.080 hemisphere always faces us, which means the 240 00:09:24.080 --> 00:09:26.840 far side is permanently shielded from every 241 00:09:26.840 --> 00:09:29.720 transmitter, every radar, every broadcast on 242 00:09:29.720 --> 00:09:31.740 this planet. And that matters because. 243 00:09:32.220 --> 00:09:34.340 Anna: Because there are signals we want to detect 244 00:09:34.340 --> 00:09:36.900 that are drowned out everywhere else. The 245 00:09:36.900 --> 00:09:39.260 cosmic dark ages, the stretch of time after 246 00:09:39.260 --> 00:09:41.420 the Big Bang before the first star switched 247 00:09:41.420 --> 00:09:44.180 on. The radio emission from that era is faint 248 00:09:44.180 --> 00:09:47.020 and it's low frequency. And Earth is far too 249 00:09:47.020 --> 00:09:49.700 noisy a place to hear it. A far side radio 250 00:09:49.700 --> 00:09:52.340 telescope is arguably the only way we ever 251 00:09:52.340 --> 00:09:52.620 will. 252 00:09:52.620 --> 00:09:54.570 Avery: That's a fairly specific and, um, 253 00:09:54.580 --> 00:09:56.620 irreplaceable thing to be arguing about. 254 00:09:56.620 --> 00:09:58.860 Anna: It is, and Cilk's framing was essentially 255 00:09:58.860 --> 00:10:01.180 generational, that we should protect these 256 00:10:01.180 --> 00:10:03.560 conditions for science. That won't be done 257 00:10:03.560 --> 00:10:05.920 for decades, because the questions at stake 258 00:10:05.920 --> 00:10:08.520 are whether we're alone and how the universe 259 00:10:08.520 --> 00:10:08.920 began. 260 00:10:09.000 --> 00:10:10.960 Avery: And, um, the physical case doesn't stop at 261 00:10:10.960 --> 00:10:11.400 radio. 262 00:10:11.480 --> 00:10:13.880 Anna: No. They also argued the far side would be an 263 00:10:13.880 --> 00:10:16.040 exceptional site for gravitational wave 264 00:10:16.040 --> 00:10:19.000 detection. No atmosphere, no weather, very 265 00:10:19.000 --> 00:10:21.080 little seismic activity compared with Earth, 266 00:10:21.320 --> 00:10:23.600 and no artificial light, which is becoming a 267 00:10:23.600 --> 00:10:25.880 real problem for optical astronomy down here. 268 00:10:25.880 --> 00:10:28.640 Avery: So what's the counterargument, because leave 269 00:10:28.640 --> 00:10:30.040 it alone is easy to say. 270 00:10:30.120 --> 00:10:32.280 Anna: The counterargument is about sustainability, 271 00:10:32.360 --> 00:10:34.110 and I thought it was stronger than people 272 00:10:34.340 --> 00:10:36.740 might expect. Few's position was that this 273 00:10:36.740 --> 00:10:38.580 isn't a challenge to the value of the 274 00:10:38.580 --> 00:10:40.740 science, it's a question of how you keep 275 00:10:40.740 --> 00:10:43.580 going back at all. Lunar exploration that 276 00:10:43.580 --> 00:10:46.020 depends entirely on government funding is 277 00:10:46.020 --> 00:10:48.460 fragile. Commercial investment is what makes 278 00:10:48.460 --> 00:10:50.940 it resilient. And her argument was that you 279 00:10:50.940 --> 00:10:53.420 can have both under proper governance, that 280 00:10:53.420 --> 00:10:55.900 an inclusive CIS lunar economy on the far 281 00:10:55.900 --> 00:10:57.980 side doesn't have to turn into a free for 282 00:10:57.980 --> 00:10:58.260 all. 283 00:10:58.340 --> 00:11:01.010 Avery: Which is a fair point. A protected region 284 00:11:01.170 --> 00:11:04.010 nobody can afford to reach is protected in a 285 00:11:04.010 --> 00:11:05.170 fairly useless way. 286 00:11:05.250 --> 00:11:08.250 Anna: That's the tension. Exactly. And McDowell's 287 00:11:08.250 --> 00:11:09.970 put the stakes in the broadest possible 288 00:11:09.970 --> 00:11:12.770 terms. His line was is the whole solar system 289 00:11:12.770 --> 00:11:15.650 up for grabs or do we set aside reserves? 290 00:11:15.889 --> 00:11:18.090 Avery: That's the real question, isn't it? Not the 291 00:11:18.090 --> 00:11:18.930 Moon specifically. 292 00:11:19.010 --> 00:11:21.210 Anna: Not the Moon specifically. His argument was 293 00:11:21.210 --> 00:11:23.330 that whatever we decide in the next few years 294 00:11:23.330 --> 00:11:25.650 becomes the precedent for everything after 295 00:11:26.220 --> 00:11:28.060 Mars, the asteroids, all of it. 296 00:11:28.140 --> 00:11:29.220 Avery: Did they take a vote? 297 00:11:29.220 --> 00:11:31.980 Anna: They did. Before and after. By QR code. 298 00:11:32.060 --> 00:11:34.700 Support for the motion went from 68% 299 00:11:34.780 --> 00:11:37.500 to 76%, though the room moved 300 00:11:37.500 --> 00:11:39.260 towards protection, which, given the 301 00:11:39.260 --> 00:11:41.540 audience, isn't a shock. But an eight point 302 00:11:41.540 --> 00:11:43.900 swing after hearing both sides is a real 303 00:11:43.900 --> 00:11:46.620 result rather than a formality. And it fed 304 00:11:46.620 --> 00:11:49.060 into a full session the next day on lunar 305 00:11:49.060 --> 00:11:49.980 governance and regulation. 306 00:11:50.300 --> 00:11:52.780 Avery: And in the meantime, Chang' E6 has just 307 00:11:52.780 --> 00:11:54.660 demonstrated that the far side is 308 00:11:54.660 --> 00:11:57.060 scientifically valuable in ways nobody had 309 00:11:57.060 --> 00:11:58.920 directly measured measured until this month, 310 00:11:58.920 --> 00:11:59.760 which rather 311 00:11:59.760 --> 00:12:02.080 Anna: sharpens the argument staying at the National 312 00:12:02.080 --> 00:12:04.160 Avery: Astronomy Meeting because there is a 313 00:12:04.160 --> 00:12:06.560 genuinely extraordinary object I want to talk 314 00:12:06.560 --> 00:12:08.680 about, and it lives in our skies. 315 00:12:08.920 --> 00:12:11.400 Southern skies Puppis, which for our 316 00:12:11.400 --> 00:12:13.720 Australian and New Zealand listeners is well 317 00:12:13.720 --> 00:12:16.040 placed for a good chunk of the year, and for 318 00:12:16.040 --> 00:12:18.680 northern listeners sits low on the south. The 319 00:12:18.680 --> 00:12:21.400 object is V445 Puppis, 320 00:12:21.400 --> 00:12:24.280 and it is the only confirmed helium nova in 321 00:12:24.280 --> 00:12:24.920 the Milky Way. 322 00:12:24.920 --> 00:12:26.840 Anna: Define helium nova. 323 00:12:27.000 --> 00:12:29.630 Avery: So a nova, an ordinary nova, 324 00:12:30.020 --> 00:12:32.740 is a white dwarf in a binary system stealing 325 00:12:32.740 --> 00:12:35.700 gas off its companion. That gas piles 326 00:12:35.700 --> 00:12:37.860 up on the surface, pressure and temperature 327 00:12:37.860 --> 00:12:40.260 climb, and eventually you get a runaway 328 00:12:40.260 --> 00:12:42.900 thermonuclear explosion. It doesn't 329 00:12:42.900 --> 00:12:44.940 destroy the star, it just blows the 330 00:12:44.940 --> 00:12:47.700 accumulated layer off. And in virtually 331 00:12:47.700 --> 00:12:50.180 every case, that stolen material is 332 00:12:50.180 --> 00:12:53.180 hydrogen rich, because hydrogen is what stars 333 00:12:53.180 --> 00:12:54.260 are mostly made of. 334 00:12:54.260 --> 00:12:55.620 Anna: And this one isn't. 335 00:12:55.960 --> 00:12:58.680 Avery: This one has essentially no hydrogen at all, 336 00:12:58.840 --> 00:13:01.200 which is a very strange thing for a stellar 337 00:13:01.200 --> 00:13:03.520 explosion to be missing, given hydrogen is 338 00:13:03.520 --> 00:13:06.480 the most abundant element in the universe. So 339 00:13:06.480 --> 00:13:08.920 the obvious question is what is it stealing 340 00:13:08.920 --> 00:13:09.160 from? 341 00:13:09.240 --> 00:13:10.760 Anna: And nobody could see. 342 00:13:10.920 --> 00:13:13.134 Avery: Nobody could see. V445 343 00:13:13.306 --> 00:13:16.240 puppys erupted in late 2000, and it 344 00:13:16.240 --> 00:13:19.240 threw out an enormous bipolar outflow. Two 345 00:13:19.240 --> 00:13:21.600 lobes of material streaming in opposite 346 00:13:21.600 --> 00:13:23.640 directions, more than a trillion miles 347 00:13:23.640 --> 00:13:26.590 across. But the eruption also created a thick 348 00:13:26.590 --> 00:13:29.190 disk of dust that completely swallowed the 349 00:13:29.190 --> 00:13:32.190 system. For more than 20 years, astronomers 350 00:13:32.190 --> 00:13:34.510 could watch the debris expanding, but they 351 00:13:34.510 --> 00:13:36.830 could not see what was inside it. The dust 352 00:13:36.830 --> 00:13:39.590 has now thinned enough. John Mills, a 353 00:13:39.590 --> 00:13:41.910 researcher and PhD student at the University 354 00:13:41.910 --> 00:13:44.350 of Warwick, put together observations 355 00:13:44.350 --> 00:13:47.190 spanning two decades to finally see through 356 00:13:47.270 --> 00:13:49.270 using what a stack of instruments. 357 00:13:49.670 --> 00:13:51.870 Infrared from the Very Large Telescope in 358 00:13:51.870 --> 00:13:54.450 Chile, Optical imaging from Hubble, 359 00:13:54.690 --> 00:13:56.930 Long term spectroscopy from the Southern 360 00:13:56.930 --> 00:13:59.650 African Large Telescope and photometry from 361 00:13:59.650 --> 00:14:02.530 tess. And the answer is a white dwarf 362 00:14:02.530 --> 00:14:04.130 feeding off a helium star. 363 00:14:04.290 --> 00:14:07.050 Anna: And a helium star is a star 364 00:14:07.050 --> 00:14:09.170 Avery: that has been stripped of its outer hydrogen 365 00:14:09.170 --> 00:14:11.610 envelope, most likely by the companion it's 366 00:14:11.610 --> 00:14:14.290 now feeding. They are genuinely rare. 367 00:14:14.530 --> 00:14:16.570 The estimate is a few thousand stripped 368 00:14:16.570 --> 00:14:18.850 helium stars among the hundreds of billions 369 00:14:18.850 --> 00:14:20.770 of stars in the entire galaxy. 370 00:14:21.010 --> 00:14:23.770 Anna: So one of the rarest kinds of stars in the 371 00:14:23.770 --> 00:14:26.270 only known example of one of the rarest kinds 372 00:14:26.270 --> 00:14:26.990 of explosions. 373 00:14:27.070 --> 00:14:29.870 Avery: And it's already loading the gun again. The 374 00:14:29.870 --> 00:14:32.430 system is actively transferring material once 375 00:14:32.510 --> 00:14:35.150 more. The two stars orbit each other every 376 00:14:35.150 --> 00:14:38.070 3.7 days, which is around twice as 377 00:14:38.070 --> 00:14:39.790 long as anyone previously thought. 378 00:14:39.790 --> 00:14:41.150 Anna: You said there was a mystery. 379 00:14:41.150 --> 00:14:43.590 Avery: The bullets. The bullets embedded in the 380 00:14:43.590 --> 00:14:46.590 outflowing debris are discrete clumps of gas, 381 00:14:46.830 --> 00:14:49.310 possibly oxygen rich, though the composition 382 00:14:49.310 --> 00:14:51.870 isn't nailed down. Moving at up to 20 383 00:14:51.950 --> 00:14:54.340 million miles an hour, that's roughly 384 00:14:54.340 --> 00:14:57.100 9,000 kilometers per second, around 385 00:14:57.100 --> 00:14:58.780 3% of the speed of light. 386 00:14:59.020 --> 00:15:00.740 Anna: And nothing like that has been seen 387 00:15:00.740 --> 00:15:01.180 elsewhere. 388 00:15:01.420 --> 00:15:04.060 Avery: Nothing like it in any other nova anywhere. 389 00:15:04.300 --> 00:15:06.860 Mills suspects they formed after the outburst 390 00:15:06.860 --> 00:15:09.060 rather than during it. But as he put it, 391 00:15:09.060 --> 00:15:10.700 their origin is a mystery. 392 00:15:10.700 --> 00:15:12.940 Anna: Which is the honest answer. And I appreciate 393 00:15:12.940 --> 00:15:13.660 that he said it. 394 00:15:13.660 --> 00:15:16.540 Avery: So do I. Now, the reason this matters. Beyond 395 00:15:16.540 --> 00:15:19.180 its own strangeness, Astronomers suspect that 396 00:15:19.180 --> 00:15:21.500 repeated helium rich eruptions on a white 397 00:15:21.500 --> 00:15:23.700 dwarf might be one of the pathways that 398 00:15:23.700 --> 00:15:26.640 eventually produces a type 1A supernova. 399 00:15:26.640 --> 00:15:29.080 Anna: And type IAs are the standard candles. 400 00:15:29.400 --> 00:15:31.800 Avery: They are. They explode with remarkably 401 00:15:31.800 --> 00:15:33.600 consistent brightness, which is what makes 402 00:15:33.600 --> 00:15:35.680 them useful as distance markers across the 403 00:15:35.680 --> 00:15:38.040 universe. They're how we measured cosmic 404 00:15:38.040 --> 00:15:40.360 expansion. The work that won the Nobel Prize 405 00:15:40.360 --> 00:15:42.320 for the discovery that the expansion is 406 00:15:42.320 --> 00:15:42.920 accelerating. 407 00:15:43.320 --> 00:15:45.800 Anna: So the ruler we use to measure the universe 408 00:15:45.800 --> 00:15:48.160 depends on understanding how these things 409 00:15:48.160 --> 00:15:48.840 detonate. 410 00:15:49.000 --> 00:15:51.800 Avery: It does. And whether helium novae actually 411 00:15:51.800 --> 00:15:54.320 get there is still an open question. But 412 00:15:54.320 --> 00:15:56.960 V445 Puppis is now the clearest 413 00:15:56.960 --> 00:15:59.880 laboratory anyone has for testing it. And it 414 00:15:59.880 --> 00:16:02.240 took 25 years of dust clearing to get the 415 00:16:02.240 --> 00:16:02.720 door open. 416 00:16:03.120 --> 00:16:05.440 Anna: Last story before we look up. And it's the 417 00:16:05.440 --> 00:16:08.000 biggest one in terms of sheer scale. There's 418 00:16:08.000 --> 00:16:10.480 a case being made that the entire Milky Way 419 00:16:10.480 --> 00:16:11.600 once flipped over. 420 00:16:12.000 --> 00:16:14.640 Avery: Flipped over how exactly? Because a galaxy 421 00:16:14.640 --> 00:16:15.920 doesn't have a right way up. 422 00:16:16.080 --> 00:16:18.320 Anna: It doesn't. And that's the right instinct. 423 00:16:18.480 --> 00:16:20.640 What's being proposed is a change of 424 00:16:20.640 --> 00:16:23.200 orientation. That the disk of our galaxy 425 00:16:23.200 --> 00:16:25.670 reoriented itself by more than 90 degrees 426 00:16:26.140 --> 00:16:28.460 relative to the halo of old stars around it. 427 00:16:28.780 --> 00:16:30.620 Avery: And what put that idea on the table? 428 00:16:30.860 --> 00:16:32.620 Anna: A puzzle that's been sitting there since 429 00:16:32.620 --> 00:16:35.500 Gaia. Our galaxy has a flat disk where 430 00:16:35.500 --> 00:16:37.980 most of the stars live. And around that a 431 00:16:37.980 --> 00:16:40.860 much larger, much sparser stellar halo. 432 00:16:41.020 --> 00:16:43.420 Mostly stars that formed in smaller galaxies 433 00:16:43.420 --> 00:16:45.460 and got absorbed when those galaxies were 434 00:16:45.460 --> 00:16:47.740 Avery: pulled in debris from past meals. 435 00:16:47.980 --> 00:16:50.740 Anna: Essentially. And Gaia showed that the halo 436 00:16:50.740 --> 00:16:53.660 barely rotates. It creeps around at something 437 00:16:53.660 --> 00:16:56.540 like 10 to 20 kilometers per second. The 438 00:16:56.540 --> 00:16:58.660 disk by comparison is moving at about 439 00:16:58.660 --> 00:16:59.580 220. 440 00:17:00.140 --> 00:17:02.300 Avery: That is a very large discrepancy. 441 00:17:02.540 --> 00:17:04.820 Anna: It is. And nobody had a satisfying 442 00:17:04.820 --> 00:17:07.580 explanation. So Kirill Botrikov at 443 00:17:07.580 --> 00:17:10.060 Durham went looking for one in simulations. 444 00:17:10.060 --> 00:17:13.060 The Auriga Suite, which models Milky Way like 445 00:17:13.060 --> 00:17:15.900 galaxies in detail. He took 25 of them 446 00:17:15.980 --> 00:17:18.300 and followed their evolution across roughly 447 00:17:18.300 --> 00:17:21.130 11 billion years. And the 448 00:17:21.130 --> 00:17:23.770 galaxies that ended up with the most slowly 449 00:17:23.770 --> 00:17:26.410 rotating halos had two things in common. 450 00:17:26.410 --> 00:17:29.210 They'd experienced a major head on merger 451 00:17:29.530 --> 00:17:32.250 and their disks had reoriented by more than 452 00:17:32.250 --> 00:17:33.050 90 degrees. 453 00:17:33.450 --> 00:17:35.690 Avery: And we know we had a major head on merger. 454 00:17:35.850 --> 00:17:38.850 Anna: We do. Gaia Sausage, Enceladus. The 455 00:17:38.850 --> 00:17:41.170 collision roughly 10 billion years ago that 456 00:17:41.170 --> 00:17:43.610 dumped an enormous quantity of stars into our 457 00:17:43.610 --> 00:17:46.130 halo and is the reason the halo looks the way 458 00:17:46.130 --> 00:17:46.570 it does. 459 00:17:47.060 --> 00:17:49.140 Avery: So the proposal is that the same collision 460 00:17:49.140 --> 00:17:51.820 exerted a gravitational torque on our disk 461 00:17:51.820 --> 00:17:54.060 and slowly turned it over inside the 462 00:17:54.060 --> 00:17:55.700 surrounding dark matter halo. 463 00:17:56.020 --> 00:17:58.820 Anna: Slowly meaning over hundreds of 464 00:17:58.820 --> 00:18:00.980 millions of years. Nothing about this was 465 00:18:00.980 --> 00:18:03.220 sudden, but the end state is that the plane 466 00:18:03.220 --> 00:18:05.620 the sun orbits in today may bear no 467 00:18:05.620 --> 00:18:07.860 relationship to the plane stars were orbiting 468 00:18:07.860 --> 00:18:09.220 in before the collision. 469 00:18:09.540 --> 00:18:11.620 Avery: That does something odd to my sense of place. 470 00:18:11.860 --> 00:18:14.500 Anna: It does mine too. And I want to be careful 471 00:18:14.500 --> 00:18:16.780 here because Botcherkov himself is careful. 472 00:18:16.940 --> 00:18:19.580 His position is that a disk flip is a likely 473 00:18:19.660 --> 00:18:22.540 explanation given how slowly the halo turns, 474 00:18:22.620 --> 00:18:24.780 but that it's too early to claim it with full 475 00:18:24.780 --> 00:18:27.420 confidence. What he wants is independent 476 00:18:27.420 --> 00:18:30.260 signatures, other scars that a reorientation 477 00:18:30.260 --> 00:18:31.980 on that Scale should have left behind. 478 00:18:32.380 --> 00:18:34.060 Avery: Is there anything pointing the same way 479 00:18:34.060 --> 00:18:34.380 already? 480 00:18:34.700 --> 00:18:37.060 Anna: There is, and it's suggestive rather than 481 00:18:37.060 --> 00:18:39.660 conclusive. Separate work this year led by 482 00:18:39.660 --> 00:18:42.300 Ling Xu used the motions of more than 483 00:18:42.300 --> 00:18:45.090 600,000 giant stars from Gaia and the 484 00:18:45.240 --> 00:18:47.960 LAMOST survey to reconstruct the shape of our 485 00:18:47.960 --> 00:18:50.800 dark matter halo. And the outer halo appears 486 00:18:50.800 --> 00:18:52.690 to be oriented almost vertically relative, 487 00:18:52.690 --> 00:18:53.520 uh, to the 488 00:18:53.520 --> 00:18:56.080 Avery: stellar disk, which is what you'd expect if 489 00:18:56.080 --> 00:18:58.200 the inner part tilted and the outer part 490 00:18:58.200 --> 00:18:58.680 didn't. 491 00:18:58.920 --> 00:19:01.520 Anna: That's the reading. The outer halo kept the 492 00:19:01.520 --> 00:19:04.160 old orientation. The disk and inner halo 493 00:19:04.160 --> 00:19:06.800 swung round. Two independent lines of 494 00:19:06.800 --> 00:19:09.160 evidence converging on the same story from 495 00:19:09.160 --> 00:19:12.050 completely different data. Not proof, 496 00:19:12.370 --> 00:19:14.410 but it's the kind of thing that turns a 497 00:19:14.410 --> 00:19:17.410 curiosity into a research program. And 498 00:19:17.410 --> 00:19:19.690 I rather like that. The biggest structural 499 00:19:19.690 --> 00:19:22.490 question about our own galaxy is one we can 500 00:19:22.490 --> 00:19:25.170 only answer by looking at it from the inside. 501 00:19:25.570 --> 00:19:27.050 Avery: Right, Time to look up. 502 00:19:27.050 --> 00:19:29.410 And Anna, uh, we have actual advice today 503 00:19:29.410 --> 00:19:30.610 rather than a countdown. 504 00:19:30.930 --> 00:19:33.850 Anna: We do. And the advice is don't wait for the 505 00:19:33.850 --> 00:19:34.210 peak. 506 00:19:34.530 --> 00:19:35.170 Avery: Explain. 507 00:19:35.410 --> 00:19:38.130 Anna: The southern Delta Aquarids are running now. 508 00:19:38.520 --> 00:19:41.000 The shower is already active and it stays 509 00:19:41.000 --> 00:19:43.880 active into late August. The American Meteor 510 00:19:43.880 --> 00:19:46.680 Society puts maximum activity around the 511 00:19:46.680 --> 00:19:47.560 30th of July. 512 00:19:48.040 --> 00:19:50.520 Avery: And the problem with the 30th is the moon. 513 00:19:50.680 --> 00:19:53.400 Anna: The moon is the problem. Full moon falls on 514 00:19:53.400 --> 00:19:56.320 the 29th of July. So on peak night, you're 515 00:19:56.320 --> 00:19:59.080 looking at a sky that is something like 98% 516 00:19:59.160 --> 00:20:01.680 illuminated. That will wash out most of the 517 00:20:01.680 --> 00:20:04.560 shower. Because Delta Aquariad meteors tend 518 00:20:04.560 --> 00:20:07.400 towards long, graceful trails rather than 519 00:20:07.400 --> 00:20:09.980 bright fireballs. They're exactly the kind 520 00:20:09.980 --> 00:20:11.300 that moonlight erases. 521 00:20:11.780 --> 00:20:13.780 Avery: So the peak is the worst night of the run. 522 00:20:14.180 --> 00:20:16.900 Anna: Close to it. But here's the good news. This 523 00:20:16.900 --> 00:20:19.420 shower has no sharp maximum. It 524 00:20:19.420 --> 00:20:21.980 rambles. Rates build slowly and stay 525 00:20:21.980 --> 00:20:24.740 roughly level for well over a week. Which 526 00:20:24.740 --> 00:20:27.140 means the mornings between now and about the 527 00:20:27.140 --> 00:20:29.980 27th are better than peak night because the 528 00:20:29.980 --> 00:20:32.700 waxing gibbous moon still sets before the 529 00:20:32.700 --> 00:20:33.700 radiant gets high. 530 00:20:34.350 --> 00:20:36.630 Avery: So the window is after moonset, before 531 00:20:36.630 --> 00:20:39.550 Anna: dawn, after moonset, before dawn. That's 532 00:20:39.550 --> 00:20:41.790 your window. And it applies wherever you are. 533 00:20:41.950 --> 00:20:44.550 Where do we look? The radiant sits near the 534 00:20:44.550 --> 00:20:47.390 star Skat in Aquarius. The easiest way 535 00:20:47.390 --> 00:20:50.069 in is to find Fomalhaut bright and 536 00:20:50.069 --> 00:20:52.950 noticeably alone in a fairly empty patch of 537 00:20:52.950 --> 00:20:55.790 sky. And work from there. The Great Square of 538 00:20:55.790 --> 00:20:57.230 Pegasus helps as well. 539 00:20:57.390 --> 00:20:59.070 Avery: And, um, that's a very different experience 540 00:20:59.230 --> 00:21:01.150 depending on which hemisphere you're in. 541 00:21:01.780 --> 00:21:04.260 Anna: Completely different from Australia and New 542 00:21:04.260 --> 00:21:06.820 Zealand. The radiant climbs close to overhead 543 00:21:06.820 --> 00:21:09.620 in the pre dawn hours. This is genuinely 544 00:21:09.620 --> 00:21:11.900 our Shower. The southern part of the world 545 00:21:11.900 --> 00:21:14.820 gets the best of it every year from Sydney or 546 00:21:14.820 --> 00:21:17.219 Auckland, anywhere from about 2 in the 547 00:21:17.219 --> 00:21:18.660 morning until first light. 548 00:21:18.980 --> 00:21:21.140 Avery: And for our North American listeners, who are 549 00:21:21.140 --> 00:21:22.660 the largest part of this audience, 550 00:21:22.980 --> 00:21:25.300 Anna: you still get a good showing, but the 551 00:21:25.300 --> 00:21:27.940 radiance stays lower in the southern sky, so 552 00:21:27.940 --> 00:21:29.980 you'll see fewer of them and they'll come in 553 00:21:29.980 --> 00:21:32.580 at shallower angles. And the upside of a low 554 00:21:32.580 --> 00:21:35.460 radiant is Earth grazers, meteors that 555 00:21:35.460 --> 00:21:37.900 skim along the atmosphere and leave much 556 00:21:37.900 --> 00:21:40.620 longer trails than usual. The best hours are 557 00:21:40.620 --> 00:21:43.300 the same from around 2 in the morning local 558 00:21:43.300 --> 00:21:46.110 time, uh, until dawn. So 2 to 5am, um, 559 00:21:46.110 --> 00:21:48.500 eastern and the equivalent across Central 560 00:21:48.660 --> 00:21:49.940 Mountain and Pacific. 561 00:21:50.340 --> 00:21:52.340 Avery: And get south facing and dark. 562 00:21:52.500 --> 00:21:55.260 Anna: Get south facing, get away from lights and 563 00:21:55.260 --> 00:21:57.980 give your eyes 20 minutes to adapt before you 564 00:21:57.980 --> 00:21:58.980 judge whether it's working. 565 00:21:59.640 --> 00:22:01.640 Avery: One more thing. And, um, this one is a watch 566 00:22:01.720 --> 00:22:03.880 this space rather than a forecast. 567 00:22:04.200 --> 00:22:05.720 Anna: The sun has woken up. 568 00:22:06.120 --> 00:22:07.880 Avery: Sunspot 4493. 569 00:22:08.120 --> 00:22:10.400 Anna: That one. It appeared essentially from 570 00:22:10.400 --> 00:22:12.520 nothing over the space of a couple of days 571 00:22:12.520 --> 00:22:15.480 and grew fast. And it now has what's called 572 00:22:15.480 --> 00:22:17.800 a beta gamma delta magnetic 573 00:22:17.800 --> 00:22:20.240 classification, which is the most complex 574 00:22:20.240 --> 00:22:22.800 classification there is. Regions like that 575 00:22:22.800 --> 00:22:24.680 are, uh, where the big flares come from. 576 00:22:25.110 --> 00:22:27.600 Avery: And it's already produced some 3M M 577 00:22:27.670 --> 00:22:30.150 Anna: class flares inside a single day. The 578 00:22:30.150 --> 00:22:33.150 Strongest an M M3.4, each of 579 00:22:33.150 --> 00:22:35.710 them causing brief minor radio blackouts 580 00:22:35.710 --> 00:22:37.270 across different parts of the world. 581 00:22:37.590 --> 00:22:39.670 Forecasters have been putting the odds of 582 00:22:39.670 --> 00:22:42.150 further M M class activity at better than 583 00:22:42.150 --> 00:22:44.590 even with a smaller chance of an X class 584 00:22:44.590 --> 00:22:44.950 event. 585 00:22:45.350 --> 00:22:47.310 Avery: So it's worth keeping an eye on the aurora 586 00:22:47.310 --> 00:22:48.630 alerts it is. 587 00:22:48.950 --> 00:22:51.630 Anna: Earlier this week, a fast solar wind stream 588 00:22:51.630 --> 00:22:53.910 from a coronal hole pushed conditions to 589 00:22:53.910 --> 00:22:56.620 minor storm level, with aurora possible as 590 00:22:56.850 --> 00:22:59.530 far equatorward as Hobart in the south and 591 00:22:59.530 --> 00:23:02.210 Seattle and Edinburgh in the north. That 592 00:23:02.210 --> 00:23:04.850 particular stream is easing now. But with a 593 00:23:04.850 --> 00:23:07.490 region that complex facing us, the situation 594 00:23:07.570 --> 00:23:08.690 can change quickly. 595 00:23:09.010 --> 00:23:11.010 Avery: And Southern hemisphere observers have the 596 00:23:11.010 --> 00:23:13.009 advantage of long winter nights right now, 597 00:23:13.170 --> 00:23:15.970 while northern observers are fighting short 598 00:23:15.970 --> 00:23:18.210 summer ones. Swings and 599 00:23:18.210 --> 00:23:19.250 roundabouts. 600 00:23:19.490 --> 00:23:22.370 Anna: That's episode 148, Starship waiting 601 00:23:22.370 --> 00:23:25.260 on a window that may or may not hold, a far 602 00:23:25.260 --> 00:23:27.260 side that's been quietly recording our 603 00:23:27.260 --> 00:23:29.860 magnetic field and an argument about whether 604 00:23:29.860 --> 00:23:30.820 we should leave it alone. 605 00:23:30.900 --> 00:23:33.740 Avery: Plus a star that spent 25 years behind a 606 00:23:33.740 --> 00:23:36.180 curtain and the galaxy that may have rolled 607 00:23:36.180 --> 00:23:37.220 over in its sleep. 608 00:23:37.220 --> 00:23:39.500 Anna: Show notes, sources and everything else are 609 00:23:39.500 --> 00:23:41.820 at astronomydaily, IO or 610 00:23:41.820 --> 00:23:44.340 astrodaily Pod, wherever you like to find us. 611 00:23:44.420 --> 00:23:46.500 Avery: If you're up before dawn this week chasing 612 00:23:46.500 --> 00:23:49.260 Delta Aquariids, we'd love to see what you 613 00:23:49.260 --> 00:23:49.620 catch. 614 00:23:49.620 --> 00:23:50.660 Anna: We'll be back tomorrow. 615 00:23:50.660 --> 00:23:52.200 Avery: Until then, clear skies.