The Planet That Keeps Shrinking plus the Weekend Wrap

WEBVTT

0
00:00:00.000 --> 00:00:02.560
Anna: Hello and welcome to Astronomy daily.

1
00:00:02.880 --> 00:00:05.381
It's Saturday 12th September,

2
00:00:05.552 --> 00:00:08.480
2026. This is series five,

3
00:00:08.560 --> 00:00:10.640
episode 192.

4
00:00:11.280 --> 00:00:13.960
And this is the weekend wrap. I'm

5
00:00:13.960 --> 00:00:14.480
Anna.

6
00:00:14.800 --> 00:00:17.560
Avery: And I'm Avery. Anna. Uh, our lead

7
00:00:17.560 --> 00:00:20.480
today is a planet getting smaller, which is

8
00:00:20.480 --> 00:00:22.960
not a sentence I expected to say this week.

9
00:00:23.360 --> 00:00:26.360
Anna: Mercury. And not smaller as in a revised

10
00:00:26.360 --> 00:00:29.200
measurement of what it is now. Smaller as in

11
00:00:29.200 --> 00:00:31.400
how much it has physically lost since it

12
00:00:31.400 --> 00:00:33.900
form. The planet has been contracting for

13
00:00:33.900 --> 00:00:36.460
four and a half billion years as its

14
00:00:36.460 --> 00:00:39.340
interior cools and it writes the evidence on

15
00:00:39.340 --> 00:00:42.340
its own surface. A new paper says we've been

16
00:00:42.340 --> 00:00:44.780
reading that evidence wrong in one very

17
00:00:44.780 --> 00:00:46.780
specific and rather beautiful way.

18
00:00:47.180 --> 00:00:48.380
Avery: Wrong by how much?

19
00:00:48.780 --> 00:00:51.700
Anna: By up to 30%. The old figure

20
00:00:51.700 --> 00:00:54.140
for how much Mercury's diameter has shrunk

21
00:00:54.300 --> 00:00:56.860
was something like 4 to 16 kilometres.

22
00:00:57.260 --> 00:01:00.150
The new one goes as high as 23. And

23
00:01:00.150 --> 00:01:02.110
the reason we missed it is that the thing

24
00:01:02.110 --> 00:01:04.830
doing the hiding is the same thing that has

25
00:01:04.830 --> 00:01:07.670
been resurfacing Mercury for 4 billion years.

26
00:01:08.310 --> 00:01:09.110
Avery: Craters.

27
00:01:09.510 --> 00:01:12.030
Anna: Craters. We'll take it properly because the

28
00:01:12.030 --> 00:01:14.550
method is as interesting as the number and

29
00:01:14.550 --> 00:01:16.350
because there's a spacecraft arriving at

30
00:01:16.350 --> 00:01:18.870
Mercury in about 10 weeks built to settle it.

31
00:01:19.270 --> 00:01:21.910
Avery: Then the week that was, and it was full.

32
00:01:22.550 --> 00:01:25.310
A rocket reaching orbit from Western European

33
00:01:25.310 --> 00:01:27.930
soil for the first time. The moon

34
00:01:28.250 --> 00:01:30.410
possibly assembled in five hours.

35
00:01:31.210 --> 00:01:33.850
27 new worlds beyond Neptune.

36
00:01:34.170 --> 00:01:36.850
A hundred and nine radio bursts weighing the

37
00:01:36.850 --> 00:01:39.850
universe's missing gas and magnetars,

38
00:01:39.930 --> 00:01:42.330
turning out to be half of everything, rather

39
00:01:42.330 --> 00:01:44.690
than one in a hundred plus one

40
00:01:44.690 --> 00:01:46.730
Anna: we didn't get to during the week. New

41
00:01:46.730 --> 00:01:49.090
evidence that our own sun is capable of a

42
00:01:49.090 --> 00:01:52.010
super flare. And two fresh developments

43
00:01:52.010 --> 00:01:54.950
from the last 48 hours. Rocket Lab

44
00:01:54.950 --> 00:01:56.430
has gone to the Government Accountability

45
00:01:56.590 --> 00:01:59.270
Office over that $700 million Mars

46
00:01:59.270 --> 00:02:02.030
contract. And Starship's first orbital

47
00:02:02.030 --> 00:02:03.310
flight has moved again.

48
00:02:03.870 --> 00:02:06.830
Avery: And the sky for both hemispheres, which this

49
00:02:06.830 --> 00:02:09.350
week has a supernova in it, you can go and

50
00:02:09.350 --> 00:02:11.870
find yourself. Let's get into it.

51
00:02:12.190 --> 00:02:14.190
Anna: Let's kick things off with Mercury, shall we?

52
00:02:14.590 --> 00:02:16.350
Avery: Start me with the basic physics.

53
00:02:16.750 --> 00:02:18.670
Why would a planet shrink at all?

54
00:02:19.070 --> 00:02:20.950
Anna: Because it was born hot and it has been

55
00:02:20.950 --> 00:02:23.800
losing that heat ever since. Mercury is

56
00:02:23.800 --> 00:02:26.400
a small planet with an enormous iron core,

57
00:02:26.720 --> 00:02:29.680
around 85% of the planet's radius, which

58
00:02:29.680 --> 00:02:31.760
is wildly out of proportion compared with,

59
00:02:31.760 --> 00:02:34.280
uh, Earth. Hot rock and hot metal

60
00:02:34.280 --> 00:02:36.880
occupy more volume than cold rock and cold

61
00:02:36.880 --> 00:02:39.600
metal. So as the interior cools,

62
00:02:39.680 --> 00:02:42.360
the inside of the planet contracts and the

63
00:02:42.360 --> 00:02:44.360
rigid outer shell has to accommodate a

64
00:02:44.360 --> 00:02:45.280
smaller interior.

65
00:02:45.760 --> 00:02:48.160
Avery: And a solid shell can't just deflate

66
00:02:48.160 --> 00:02:48.720
smoothly.

67
00:02:48.720 --> 00:02:51.170
Anna: It can't. It has to go

68
00:02:51.170 --> 00:02:54.010
somewhere. And it does that by breaking.

69
00:02:54.570 --> 00:02:57.210
The crust gets pushed together, thrust

70
00:02:57.210 --> 00:03:00.170
faults form and one slab of crust

71
00:03:00.170 --> 00:03:02.890
rides up over another on the surface that

72
00:03:02.890 --> 00:03:05.609
shows up as a cliff. Long sinuous

73
00:03:05.609 --> 00:03:08.330
lobe fronted, sometimes a kilometre or two

74
00:03:08.330 --> 00:03:11.170
high and hundreds of kilometres long. They're

75
00:03:11.170 --> 00:03:13.690
called lobate scarps. There are wrinkle

76
00:03:13.690 --> 00:03:16.300
ridges and high relief ridges too. And the

77
00:03:16.300 --> 00:03:18.300
whole family goes by a wonderfully plain

78
00:03:18.780 --> 00:03:21.500
shortening structures because they record

79
00:03:21.500 --> 00:03:24.020
Avery: the surface getting shorter. And

80
00:03:24.020 --> 00:03:26.500
Mercury's the textbook case for the solar

81
00:03:26.500 --> 00:03:29.260
system. We've known since Mariner 10

82
00:03:29.260 --> 00:03:32.060
flew past in 1974 and

83
00:03:32.060 --> 00:03:34.140
came back with images of these things

84
00:03:34.220 --> 00:03:36.980
everywhere. Discovery Roops is the

85
00:03:36.980 --> 00:03:39.340
famous one. A scarp 500

86
00:03:39.340 --> 00:03:41.620
kilometres long, cutting straight through

87
00:03:41.620 --> 00:03:43.820
craters and offsetting their rims.

88
00:03:44.560 --> 00:03:46.560
So how do you turn cliffs into a number?

89
00:03:47.040 --> 00:03:49.960
Anna: Very directly, every thrust fault has taken

90
00:03:49.960 --> 00:03:52.320
up a certain amount of horizontal shortening

91
00:03:52.320 --> 00:03:54.240
and you can estimate it from the height of

92
00:03:54.240 --> 00:03:56.880
the scarp and the angle the fault dips at.

93
00:03:57.520 --> 00:03:59.840
Map every shortening structure on the planet.

94
00:04:00.080 --> 00:04:02.680
Add up all the shortening and that tells you

95
00:04:02.680 --> 00:04:04.480
how much the circumference has reduced.

96
00:04:04.880 --> 00:04:06.840
Divide through and you get the change in

97
00:04:06.840 --> 00:04:07.440
diameter.

98
00:04:07.920 --> 00:04:10.160
Avery: And that's where the old number came from.

99
00:04:10.800 --> 00:04:13.400
Anna: Roughly 4 to 16 kilometres off the

100
00:04:13.400 --> 00:04:16.080
diameter. And it had a problem everybody in

101
00:04:16.080 --> 00:04:18.520
the field knew about. It was lower than the

102
00:04:18.520 --> 00:04:21.160
physics wanted model. Mercury's thermal

103
00:04:21.160 --> 00:04:22.880
history and the models predict more

104
00:04:22.880 --> 00:04:25.360
contraction than the surface appears to show.

105
00:04:25.920 --> 00:04:28.520
A mismatch with the surface on the small

106
00:04:28.520 --> 00:04:28.880
side.

107
00:04:29.280 --> 00:04:31.520
Avery: Which usually means one of two things.

108
00:04:32.000 --> 00:04:34.280
Anna: Either the model is wrong or you're not

109
00:04:34.280 --> 00:04:37.250
seeing all the evidence. This new work argues

110
00:04:37.250 --> 00:04:39.650
it's the second for a reason that's almost

111
00:04:39.650 --> 00:04:41.810
embarrassingly simple once somebody says it

112
00:04:41.810 --> 00:04:44.330
out loud. This is Gaku Nishiyama,

113
00:04:44.570 --> 00:04:47.170
a planetary scientist at the German Aerospace

114
00:04:47.170 --> 00:04:49.690
Centre in Berlin with colleagues in Japan,

115
00:04:49.930 --> 00:04:52.690
published in Geophysical Research Letters and

116
00:04:52.690 --> 00:04:55.210
released by the American Geophysical Union on

117
00:04:55.210 --> 00:04:58.170
Thursday the 10th. And the simple reason is

118
00:04:58.570 --> 00:05:01.550
impact craters bury the cliffs. Impact

119
00:05:01.780 --> 00:05:04.100
every asteroid that has hit mercury over 4

120
00:05:04.100 --> 00:05:06.500
billion years has thrown out a blanket of

121
00:05:06.500 --> 00:05:09.420
pulverised rock and that debris drapes over

122
00:05:09.420 --> 00:05:12.300
whatever was there before. A sharp kilometre

123
00:05:12.300 --> 00:05:14.980
high cliff gets softened, partly filled,

124
00:05:15.220 --> 00:05:18.220
buried at one end, broken into pieces that no

125
00:05:18.220 --> 00:05:20.580
longer read as one continuous structure.

126
00:05:20.980 --> 00:05:23.020
And then you, sitting at a desk mapping

127
00:05:23.020 --> 00:05:26.020
images, either don't see it or map it as

128
00:05:26.020 --> 00:05:27.300
something smaller than it was.

129
00:05:27.990 --> 00:05:30.310
Avery: Is that a hunch or did they measure it?

130
00:05:30.390 --> 00:05:32.830
Anna: They measured it. And that's what makes the

131
00:05:32.830 --> 00:05:34.710
paper convincing rather than merely

132
00:05:34.710 --> 00:05:37.030
plausible. They used Messenger,

133
00:05:37.350 --> 00:05:39.790
NASA's Mercury orbiter, which went round the

134
00:05:39.790 --> 00:05:42.590
planet 4,105 times

135
00:05:42.590 --> 00:05:45.510
between 2011 and 2015 before

136
00:05:45.510 --> 00:05:47.750
being deliberately crashed into the surface.

137
00:05:48.230 --> 00:05:50.750
It carried a laser altimeter and a dual

138
00:05:50.750 --> 00:05:53.510
imaging system. The team did two things with

139
00:05:53.510 --> 00:05:56.320
that. First, stereophotogrammetry.

140
00:05:56.560 --> 00:05:58.600
Take two images of the same ground from

141
00:05:58.600 --> 00:06:00.600
different angles and the parallax gives you

142
00:06:00.600 --> 00:06:03.360
topography. It's the trick your two eyes play

143
00:06:03.360 --> 00:06:05.880
to give you depth perception applied to a

144
00:06:05.880 --> 00:06:06.320
planet.

145
00:06:07.040 --> 00:06:09.520
Avery: So three dimensional terrain where before

146
00:06:09.680 --> 00:06:10.000
there

147
00:06:10.000 --> 00:06:12.680
Anna: were flat pictures at much better

148
00:06:12.680 --> 00:06:15.200
resolution than the altimeter alone. And

149
00:06:15.200 --> 00:06:17.320
across parts of the planet the altimeter

150
00:06:17.320 --> 00:06:20.010
never properly covered. And second,

151
00:06:20.330 --> 00:06:22.730
the clever bit, they measured surface

152
00:06:22.730 --> 00:06:25.210
roughness independently and asked a question.

153
00:06:25.850 --> 00:06:28.210
Does the density of shortening structures you

154
00:06:28.210 --> 00:06:30.890
can see depend on how rough the surrounding

155
00:06:30.890 --> 00:06:31.530
terrain is?

156
00:06:32.170 --> 00:06:33.050
Avery: And it does.

157
00:06:33.690 --> 00:06:36.610
Anna: Strongly. The rougher the terrain, which

158
00:06:36.610 --> 00:06:38.530
is to say, the more heavily battered by

159
00:06:38.530 --> 00:06:41.330
impacts, the fewer shortening structures you

160
00:06:41.330 --> 00:06:44.210
find per unit area. Now, there's

161
00:06:44.210 --> 00:06:46.290
no physical reason the interior should have

162
00:06:46.290 --> 00:06:48.730
contracted less under under rough ground than

163
00:06:48.730 --> 00:06:51.370
under smooth ground. The faults don't know

164
00:06:51.370 --> 00:06:53.410
what the surface looks like. So that

165
00:06:53.410 --> 00:06:56.210
correlation isn't geology, it's a detection

166
00:06:56.210 --> 00:06:58.970
limit. It's the signature of evidence being

167
00:06:58.970 --> 00:07:01.490
erased. And you can use the strength of the

168
00:07:01.490 --> 00:07:03.610
correlation to estimate how much has been

169
00:07:03.610 --> 00:07:04.170
erased.

170
00:07:04.570 --> 00:07:07.530
Avery: I like that. The bias announces itself.

171
00:07:08.010 --> 00:07:10.370
Anna: It does indeed. Which is the best thing a

172
00:07:10.370 --> 00:07:13.250
bias can do. Nishiyama's own analogy

173
00:07:13.250 --> 00:07:15.890
is freshly laid gravel hiding the ruts in a

174
00:07:15.890 --> 00:07:18.530
road. The ruts are still there, you just

175
00:07:18.530 --> 00:07:20.010
can't see them from a moving car.

176
00:07:20.730 --> 00:07:22.490
Avery: So what's the corrected number?

177
00:07:23.130 --> 00:07:26.050
Anna: Between 10 and 30% more contraction

178
00:07:26.050 --> 00:07:29.050
than previously estimated. In round figures,

179
00:07:29.050 --> 00:07:31.370
the total loss of diameter goes from a range

180
00:07:31.370 --> 00:07:34.370
topping out around 16 kilometres to as much

181
00:07:34.370 --> 00:07:37.290
as 23, about 14 and a half miles.

182
00:07:37.690 --> 00:07:39.810
Call it an extra seven kilometres that was

183
00:07:39.810 --> 00:07:40.810
hiding under rubble.

184
00:07:41.210 --> 00:07:43.610
Avery: Which doesn't sound enormous for a whole

185
00:07:43.610 --> 00:07:44.090
planet.

186
00:07:44.640 --> 00:07:47.640
Anna: It doesn't. And Mercury is about 4,900

187
00:07:47.640 --> 00:07:50.080
kilometres across, so we're talking a

188
00:07:50.080 --> 00:07:52.800
fraction of a percent. But the number isn't

189
00:07:52.800 --> 00:07:54.920
interesting because it's big. It's

190
00:07:54.920 --> 00:07:57.040
interesting because of what it constrains.

191
00:07:57.760 --> 00:08:00.040
Nishiyama's line on that is the one to hold

192
00:08:00.040 --> 00:08:03.040
onto. He says more shrinking means

193
00:08:03.040 --> 00:08:05.680
mercury could have a larger metal core or

194
00:08:05.680 --> 00:08:08.080
fewer light elements like silicon mixed into

195
00:08:08.080 --> 00:08:10.640
that core, or a higher starting temperature.

196
00:08:11.340 --> 00:08:14.100
Avery: Unpack that. Why does total contraction

197
00:08:14.100 --> 00:08:15.340
tell you about the core?

198
00:08:15.500 --> 00:08:18.140
Anna: Because the amount a planet shrinks is a

199
00:08:18.140 --> 00:08:21.020
thermometer reading integrated over its whole

200
00:08:21.020 --> 00:08:23.780
history. Iron contracts as it

201
00:08:23.780 --> 00:08:26.260
cools and contracts again when it

202
00:08:26.260 --> 00:08:29.180
solidifies. So if mercury lost

203
00:08:29.180 --> 00:08:31.740
more volume than we thought, either there was

204
00:08:31.740 --> 00:08:34.500
more iron to lose it from. Or the core was

205
00:08:34.500 --> 00:08:37.300
purer. Light elements like silicon or

206
00:08:37.300 --> 00:08:39.840
sulphur change how iron behaves as it

207
00:08:39.840 --> 00:08:42.800
freezes. Or the planet simply started hotter

208
00:08:42.800 --> 00:08:45.360
and had further to fall. And the mismatch

209
00:08:45.360 --> 00:08:47.840
with the thermal models closes, which is the

210
00:08:47.840 --> 00:08:50.840
quietly satisfying part. Nishiyama says

211
00:08:50.840 --> 00:08:52.800
the corrected amount actually makes sense to

212
00:08:52.800 --> 00:08:54.960
him, meaning the surface record and the

213
00:08:54.960 --> 00:08:57.120
predictions now agree rather than pulling

214
00:08:57.120 --> 00:08:57.880
against each other.

215
00:08:58.360 --> 00:09:00.280
Avery: There's a pattern here I want to name,

216
00:09:00.440 --> 00:09:02.840
because we hit it twice already this week.

217
00:09:03.320 --> 00:09:05.960
Wednesday, The Galaxy M M74

218
00:09:06.360 --> 00:09:08.800
found to be more than twice its catalogue

219
00:09:08.800 --> 00:09:11.730
size, because the catalogue size was really

220
00:09:11.730 --> 00:09:14.290
a statement about how deep the survey went.

221
00:09:14.770 --> 00:09:17.730
And yesterday, magnetars turning out to be

222
00:09:17.730 --> 00:09:20.450
half of all neutron stars, because the

223
00:09:20.450 --> 00:09:23.210
catalogue counted how long each kind stays

224
00:09:23.210 --> 00:09:25.410
visible, rather than how many are born.

225
00:09:25.890 --> 00:09:27.770
Anna: And today, a planet that's shrunk by more

226
00:09:27.770 --> 00:09:30.210
than the map says, because the map is drawn

227
00:09:30.210 --> 00:09:32.050
on a surface that's been partly erasing

228
00:09:32.050 --> 00:09:34.690
itself for 4 billion years. Same

229
00:09:34.690 --> 00:09:37.220
lesson three times in one week. And it's the

230
00:09:37.220 --> 00:09:39.100
most useful habit of mind in the field.

231
00:09:39.660 --> 00:09:41.660
Before you ask what the universe is doing,

232
00:09:42.060 --> 00:09:44.260
ask what your instrument and your sample are

233
00:09:44.260 --> 00:09:45.100
letting you see.

234
00:09:45.580 --> 00:09:47.860
Avery: Which brings us to the spacecraft that's

235
00:09:47.860 --> 00:09:49.980
about to do it again properly

236
00:09:50.220 --> 00:09:51.340
Bepicolombo.

237
00:09:51.580 --> 00:09:54.380
Anna: And the timing is genuinely lovely. The joint

238
00:09:54.380 --> 00:09:56.740
European and Japanese mission has been flying

239
00:09:56.740 --> 00:09:59.620
since 2018, and after nine planetary

240
00:09:59.620 --> 00:10:02.060
flybys, it's now in the arrival phase.

241
00:10:02.730 --> 00:10:05.170
It separated its big electric transfer module

242
00:10:05.170 --> 00:10:07.690
on 3rd September, which we covered at the

243
00:10:07.690 --> 00:10:10.658
time. Gravity capture at Mercury is 21st

244
00:10:10.802 --> 00:10:13.650
November, so about 10 weeks away. The

245
00:10:13.650 --> 00:10:16.610
Japanese orbiter is released around the

246
00:10:16.610 --> 00:10:19.210
9th or 10th of December. The European

247
00:10:19.210 --> 00:10:21.490
orbiter reaches its final science orbit on

248
00:10:21.490 --> 00:10:24.290
the 10th of March, and routine science begins

249
00:10:24.290 --> 00:10:25.370
on the 6th of April.

250
00:10:25.770 --> 00:10:27.890
Avery: And what does it bring to this specific

251
00:10:27.890 --> 00:10:28.250
problem?

252
00:10:29.050 --> 00:10:31.730
Anna: Two things messenger could not the laser

253
00:10:31.730 --> 00:10:34.290
altimeter is substantially more

254
00:10:34.290 --> 00:10:36.890
capable, with vertical precision quoted down

255
00:10:36.890 --> 00:10:39.490
to the tens of centimetres, and orbit

256
00:10:39.490 --> 00:10:41.890
geometry, which matters just as much and gets

257
00:10:41.890 --> 00:10:44.889
mentioned less. MESSENGER flew a highly

258
00:10:44.889 --> 00:10:47.290
eccentric orbit, so it had superb

259
00:10:47.290 --> 00:10:49.770
resolution over the northern Hemisphere and

260
00:10:49.770 --> 00:10:52.570
much poorer coverage of the South. Bepi

261
00:10:52.570 --> 00:10:55.050
Colombo's European orbiter sits on a far less

262
00:10:55.050 --> 00:10:57.930
eccentric polar orbit. Even coverage of the

263
00:10:57.930 --> 00:10:59.810
whole planet at consistent resolution.

264
00:11:00.450 --> 00:11:02.330
Avery: So the small structures that were being

265
00:11:02.330 --> 00:11:05.330
Anna: missed get counted, and that's a proper

266
00:11:05.490 --> 00:11:07.890
falsifiable prediction out of this paper,

267
00:11:08.290 --> 00:11:10.850
which is what you want. If the shortfall

268
00:11:10.850 --> 00:11:12.530
really is buried small structures,

269
00:11:13.010 --> 00:11:15.770
BepiColombo should find a population of

270
00:11:15.770 --> 00:11:18.770
modest scarps and ridges in exactly

271
00:11:18.770 --> 00:11:20.890
the rough terrain where current maps look

272
00:11:20.890 --> 00:11:23.740
suspiciously empty. If it looks at that

273
00:11:23.740 --> 00:11:26.020
ground at 20 centimetre precision and finds

274
00:11:26.020 --> 00:11:26.460
nothing.

275
00:11:26.860 --> 00:11:29.100
The correction is wrong and the thermo models

276
00:11:29.100 --> 00:11:31.380
have a real problem. Either way we'll know

277
00:11:31.380 --> 00:11:32.460
within a couple of years.

278
00:11:33.100 --> 00:11:35.580
Avery: And there's an Australian threat in this one.

279
00:11:35.980 --> 00:11:38.219
Anna: There is, and it's infrastructure rather than

280
00:11:38.219 --> 00:11:40.900
science, which I think makes it better rather

281
00:11:40.900 --> 00:11:43.620
than worse. Everything BepiColombo does at

282
00:11:43.620 --> 00:11:46.420
Mercury has to come home through a dish. And

283
00:11:46.420 --> 00:11:48.300
one of the dishes is in Western Australia.

284
00:11:49.160 --> 00:11:51.800
ESA's new Norcia station, about 140

285
00:11:51.800 --> 00:11:53.760
kilometres north of Perth and run in

286
00:11:53.760 --> 00:11:56.680
partnership with CSIRO, is where Europe's

287
00:11:56.680 --> 00:11:59.320
Deep Space Network began. The 35

288
00:11:59.320 --> 00:12:01.720
metre antenna there was the agency's first.

289
00:12:02.200 --> 00:12:04.600
There's Now a second 35 metre dish at the

290
00:12:04.600 --> 00:12:06.880
site built for the current generation of

291
00:12:06.880 --> 00:12:09.560
missions with BepiColombo named among those

292
00:12:09.560 --> 00:12:10.360
it supports.

293
00:12:11.160 --> 00:12:13.640
Avery: Same reason the Canberra complex exists,

294
00:12:14.610 --> 00:12:14.770
same

295
00:12:14.770 --> 00:12:17.370
Anna: reason and its simple geometry. A

296
00:12:17.370 --> 00:12:19.530
spacecraft is only visible from part of the

297
00:12:19.530 --> 00:12:22.330
earth at a time, so continuous contact needs

298
00:12:22.330 --> 00:12:24.770
dishes spread around the planet in longitude,

299
00:12:24.930 --> 00:12:27.730
which means southern stations and is also why

300
00:12:27.730 --> 00:12:30.210
ESA built one at Malargue in Argentina.

301
00:12:30.770 --> 00:12:32.810
The southern hemisphere isn't a, uh, nice to

302
00:12:32.810 --> 00:12:35.330
have in deep space communications, it's load

303
00:12:35.330 --> 00:12:37.730
bearing. When the first detailed topography

304
00:12:37.730 --> 00:12:39.650
of Mercury's southern hemisphere comes down

305
00:12:39.650 --> 00:12:42.380
next year, some of it will have arrived via a

306
00:12:42.380 --> 00:12:43.700
paddock in Western Australia.

307
00:12:44.660 --> 00:12:47.620
Avery: One last thing, Mercury is actually

308
00:12:47.780 --> 00:12:49.300
in the sky this week.

309
00:12:49.780 --> 00:12:52.420
Anna: Barely very low in the western Twilight,

310
00:12:52.660 --> 00:12:55.420
setting inside 40 minutes of the sun and a

311
00:12:55.420 --> 00:12:57.740
difficult catch for everybody. We'll come

312
00:12:57.740 --> 00:13:00.740
back to it, but I like the symmetry. The

313
00:13:00.740 --> 00:13:03.180
hardest planet to see is also the one whose

314
00:13:03.180 --> 00:13:05.740
surface has been hardest to read. And for the

315
00:13:05.740 --> 00:13:08.410
same underlying reason, something keeps

316
00:13:08.410 --> 00:13:09.170
getting in the way.

317
00:13:09.810 --> 00:13:12.530
Avery: Right, let's move on to the week that was

318
00:13:13.330 --> 00:13:15.650
five storeys from the weekday run in the

319
00:13:15.650 --> 00:13:16.690
order they happened.

320
00:13:16.930 --> 00:13:19.530
One we didn't get to and two fresh

321
00:13:19.530 --> 00:13:21.490
developments from the last day or so.

322
00:13:21.890 --> 00:13:24.730
Anna: And the theme of the week, if it had one, was

323
00:13:24.730 --> 00:13:27.570
honest revision. Almost everything on this

324
00:13:27.570 --> 00:13:29.690
list is somebody finding out that a number we

325
00:13:29.690 --> 00:13:31.090
were comfortable with was wrong.

326
00:13:31.650 --> 00:13:33.330
Avery: Let's start at the beginning of the week,

327
00:13:34.250 --> 00:13:36.730
Monday and the launch storey of the week.

328
00:13:37.210 --> 00:13:40.090
On Friday the 5th, at 12 minutes past

329
00:13:40.090 --> 00:13:42.850
10 in the evening local time, a rocket

330
00:13:42.850 --> 00:13:45.770
called Spectrum lifted off from Andoya

331
00:13:45.770 --> 00:13:48.410
spaceport in Northern Norway and reached

332
00:13:48.410 --> 00:13:51.050
orbit. Built by a, um, Munich company,

333
00:13:51.450 --> 00:13:54.210
Isar Aerospace, and it's the first

334
00:13:54.210 --> 00:13:56.490
vehicle ever to reach orbit from Western

335
00:13:56.490 --> 00:13:57.530
European soil

336
00:13:58.090 --> 00:14:00.650
Anna: with a real payload, not a mass simulator.

337
00:14:01.260 --> 00:14:03.900
Avery: Five university cubesats, Berlin,

338
00:14:04.060 --> 00:14:07.020
Trondheim, Maribor, Vienna and the

339
00:14:07.020 --> 00:14:09.340
Bulgarian company Endurosat,

340
00:14:09.740 --> 00:14:12.380
plus a fixed experiment from D Cubed

341
00:14:12.860 --> 00:14:15.020
it went into a stretched orbit and

342
00:14:15.020 --> 00:14:17.740
circularised on a second stage restart,

343
00:14:17.820 --> 00:14:20.420
which is non trivial on your second ever

344
00:14:20.420 --> 00:14:23.140
flight, the first in March last

345
00:14:23.140 --> 00:14:26.140
year, failed about 30 seconds in on a vent

346
00:14:26.140 --> 00:14:26.620
valve.

347
00:14:27.390 --> 00:14:30.190
Anna: And the thing to watch now is cadence, not

348
00:14:30.190 --> 00:14:32.430
the milestone exactly.

349
00:14:33.070 --> 00:14:35.150
Avery: Vehicles three through seven are in

350
00:14:35.150 --> 00:14:37.790
production and the Munich factory is built

351
00:14:37.790 --> 00:14:39.390
for more than 30 a year.

352
00:14:40.110 --> 00:14:42.510
Reaching orbit once is a headline.

353
00:14:42.749 --> 00:14:45.230
Reaching it on schedule is a launch industry.

354
00:14:46.110 --> 00:14:48.830
We paired it with Gilmour Space in Queensland

355
00:14:48.910 --> 00:14:51.150
as the Southern hemisphere version of the

356
00:14:51.150 --> 00:14:53.770
same ambition. And Eris flew 14

357
00:14:53.930 --> 00:14:56.570
seconds from Bowen last year. And test

358
00:14:56.570 --> 00:14:59.050
flight two is now listed for early

359
00:14:59.130 --> 00:15:00.170
2027.

360
00:15:01.050 --> 00:15:03.370
Anna: Next up was our big moon storey for the week

361
00:15:03.850 --> 00:15:04.250
Tuesday.

362
00:15:04.570 --> 00:15:07.330
Avery: And the headline everybody else ran was that

363
00:15:07.330 --> 00:15:09.530
the Moon formed in five hours,

364
00:15:10.330 --> 00:15:13.010
which isn't quite what the paper said and the

365
00:15:13.010 --> 00:15:14.090
difference matters.

366
00:15:14.650 --> 00:15:16.090
Anna: It's a sensitivity result.

367
00:15:16.570 --> 00:15:19.560
Avery: It's a sensitivity result. Kagan

368
00:15:19.560 --> 00:15:22.240
Denton and Robin Canup at the Southwest

369
00:15:22.240 --> 00:15:24.760
Research Institute with Eric Asfog in

370
00:15:24.760 --> 00:15:27.520
Arizona in Astrophysical Journal

371
00:15:27.600 --> 00:15:30.360
Letters. The canonical storey is a

372
00:15:30.360 --> 00:15:33.240
Mars sized body called Theia hitting the

373
00:15:33.240 --> 00:15:36.040
proto Earth, throwing a disc of debris

374
00:15:36.040 --> 00:15:38.630
into orbit and the Moon slowly accreting, uh,

375
00:15:39.160 --> 00:15:41.760
out of it. What this group added was

376
00:15:41.760 --> 00:15:44.000
something nobody had properly included,

377
00:15:44.290 --> 00:15:45.600
rather rock strength that

378
00:15:45.600 --> 00:15:48.280
Anna: changes with temperature because previous

379
00:15:48.360 --> 00:15:49.440
simulations treated

380
00:15:49.440 --> 00:15:52.040
Avery: the rock as a fluid essentially

381
00:15:52.360 --> 00:15:55.160
an rock isn't a fluid, it has strength

382
00:15:55.400 --> 00:15:57.960
and that strength collapses as it heats.

383
00:15:58.600 --> 00:16:01.240
Put it in and for some impact conditions

384
00:16:01.400 --> 00:16:04.240
you skip the disc entirely. The

385
00:16:04.240 --> 00:16:06.760
collision directly produces a single

386
00:16:06.760 --> 00:16:09.240
intact satellite in about five hours.

387
00:16:10.370 --> 00:16:13.010
Not always. A hot young Thea

388
00:16:13.010 --> 00:16:15.690
under 60 million years old gives the

389
00:16:15.690 --> 00:16:18.570
immediate moon. A cooler older

390
00:16:18.570 --> 00:16:21.010
one gives the classical slow disc.

391
00:16:21.810 --> 00:16:23.570
Anna: So the finding is that the outcome is

392
00:16:23.570 --> 00:16:25.810
sensitive to a parameter we'd been ignoring.

393
00:16:26.370 --> 00:16:29.250
Avery: A genuinely important result and a

394
00:16:29.250 --> 00:16:31.890
much less exciting sentence. Follow

395
00:16:31.890 --> 00:16:34.410
ups uh, are the full parameter survey and

396
00:16:34.410 --> 00:16:37.290
deep lunar samples. The two routes

397
00:16:37.290 --> 00:16:39.890
give different interiors. So there's a test.

398
00:16:40.530 --> 00:16:43.290
We closed it on the Jack Hills zircons in

399
00:16:43.290 --> 00:16:46.210
Western Australia, the oldest bits of Earth

400
00:16:46.210 --> 00:16:47.330
anybody has held.

401
00:16:47.970 --> 00:16:50.690
Anna: Moving on to Wednesday, 27 new

402
00:16:50.690 --> 00:16:52.050
worlds past Neptune.

403
00:16:52.690 --> 00:16:55.530
Avery: Wednesday's lead was Hubble and Webb working

404
00:16:55.530 --> 00:16:58.490
the same patch of sky together and pulling

405
00:16:58.490 --> 00:17:01.290
out 27 previously unknown trans

406
00:17:01.290 --> 00:17:04.040
Neptunian objects, the faintest

407
00:17:04.040 --> 00:17:07.000
ever directly detected. The smallest around

408
00:17:07.080 --> 00:17:09.880
five kilometres across, five

409
00:17:09.880 --> 00:17:12.600
times below what ground based surveys reach.

410
00:17:13.240 --> 00:17:15.520
Anna: And the surprise wasn't the number, it was

411
00:17:15.520 --> 00:17:16.200
the colours.

412
00:17:16.520 --> 00:17:19.280
Avery: Two papers in the Astronomical Journal on the

413
00:17:19.280 --> 00:17:19.720
8th.

414
00:17:19.880 --> 00:17:22.520
Morgan at Northern Arizona on colour,

415
00:17:22.600 --> 00:17:25.560
Eduardo at Victoria on the size distribution.

416
00:17:26.280 --> 00:17:29.000
The expectation was that small objects are

417
00:17:29.000 --> 00:17:31.090
collision fragments. So, so they should look

418
00:17:31.090 --> 00:17:33.570
like rubble. Mixed homogenised

419
00:17:33.810 --> 00:17:36.770
no memory of origin. Instead, the

420
00:17:36.770 --> 00:17:39.130
small ones keep the same colour relationship

421
00:17:39.130 --> 00:17:41.730
as the large ones in both the dynamically

422
00:17:41.730 --> 00:17:43.890
cold population and the hot one.

423
00:17:44.370 --> 00:17:46.489
David Trilling's line was that the hot

424
00:17:46.489 --> 00:17:48.810
objects retain a signature of where they

425
00:17:48.810 --> 00:17:51.690
Anna: were born, which points back to

426
00:17:51.690 --> 00:17:54.130
how planetesimals formed in the first place.

427
00:17:54.850 --> 00:17:57.730
Avery: It supports rapid formation directly at large

428
00:17:57.730 --> 00:18:00.450
sizes rather than slow grinding up from

429
00:18:00.450 --> 00:18:02.640
dust form, with Arrokoth as the type

430
00:18:02.640 --> 00:18:05.640
specimen. And the next act is Ruben

431
00:18:05.640 --> 00:18:08.520
at Cerro Pachon in Chile, which will

432
00:18:08.520 --> 00:18:11.120
find these in bulk plus occultation

433
00:18:11.120 --> 00:18:13.320
chasing from Australia and New Zealand.

434
00:18:14.200 --> 00:18:16.480
Anna: Now I know this next one is a favourite of

435
00:18:16.480 --> 00:18:19.360
yours from Thursday. Weighing the

436
00:18:19.360 --> 00:18:21.400
universe with radio bursts

437
00:18:22.040 --> 00:18:22.440
Thursday.

438
00:18:22.840 --> 00:18:25.720
Avery: And yes, it is indeed one of my favourites of

439
00:18:25.720 --> 00:18:28.370
the year. 109 localised

440
00:18:28.370 --> 00:18:31.090
fast radio bursts, mostly from the Deep

441
00:18:31.090 --> 00:18:33.890
Synoptic Array at Owens Valley, used to

442
00:18:33.890 --> 00:18:35.650
measure something nobody could pin down

443
00:18:35.650 --> 00:18:38.450
properly before how far galactic

444
00:18:38.450 --> 00:18:41.410
feedback has pushed gas out of galaxies and

445
00:18:41.410 --> 00:18:43.570
smoothed the clumpiness of matter in the

446
00:18:43.570 --> 00:18:44.130
universe.

447
00:18:44.770 --> 00:18:46.930
Anna: And the mechanism is the nicest thing about

448
00:18:46.930 --> 00:18:47.250
it.

449
00:18:47.810 --> 00:18:50.250
Avery: A fast radio burst is a millisecond

450
00:18:50.250 --> 00:18:53.010
flash and every free electron between

451
00:18:53.090 --> 00:18:55.950
us. And it slows the low frequencies

452
00:18:55.950 --> 00:18:58.710
slightly more than the high ones. So the

453
00:18:58.710 --> 00:19:01.390
burst arrives smeared a, uh, chirp

454
00:19:01.390 --> 00:19:03.590
and the size of the smear counts the

455
00:19:03.590 --> 00:19:06.470
electrons along the line of sight. Kriti

456
00:19:06.470 --> 00:19:09.230
Sharma, Vikram Ravi, Elizabeth Kraus

457
00:19:09.230 --> 00:19:11.910
and colleagues. Nature astronomy on the

458
00:19:11.910 --> 00:19:14.550
8th, a prism made out of the entire

459
00:19:14.550 --> 00:19:15.870
intervening universe.

460
00:19:16.830 --> 00:19:17.950
Anna: And the result?

461
00:19:19.070 --> 00:19:21.870
Avery: Gas fractions in big halos running about

462
00:19:21.870 --> 00:19:24.270
1.9-sigma above stacked

463
00:19:24.270 --> 00:19:26.850
Erosita X ray measurements. The

464
00:19:26.850 --> 00:19:29.450
bursts count cool gas, the X rays miss

465
00:19:29.930 --> 00:19:32.450
and clustering variants cut by something like

466
00:19:32.450 --> 00:19:34.570
a factor of eight at the scales where

467
00:19:34.570 --> 00:19:37.530
feedback bites, which bears directly on the

468
00:19:37.530 --> 00:19:40.490
S8 tension. The Southern spine of that

469
00:19:40.490 --> 00:19:43.290
storey is long. The first fast radio

470
00:19:43.290 --> 00:19:45.850
burst came out of Parkes Murrayang in

471
00:19:45.850 --> 00:19:48.770
2007 and the McQuart relation came

472
00:19:48.770 --> 00:19:50.730
from ASCAP in Western Australia.

473
00:19:51.940 --> 00:19:54.940
Anna: Moving on to Friday's episode. Magnetars are

474
00:19:54.940 --> 00:19:57.900
half of everything yesterday, the

475
00:19:57.900 --> 00:19:59.620
Avery: one that still feels too big.

476
00:20:00.340 --> 00:20:03.340
Magnetars, neutron stars with magnetic

477
00:20:03.340 --> 00:20:05.340
fields around a hundred trillion times

478
00:20:05.340 --> 00:20:07.859
Earth's, have always been the exotics.

479
00:20:08.420 --> 00:20:10.820
About 30 confirmed against several thousand

480
00:20:10.820 --> 00:20:13.460
radio pulsars. One in a hundred,

481
00:20:13.620 --> 00:20:14.420
give or take.

482
00:20:15.300 --> 00:20:17.700
Anna: And the new number is one in two.

483
00:20:17.860 --> 00:20:19.780
Avery: Roughly one in two at birth.

484
00:20:20.510 --> 00:20:23.310
Celsa Pardo Araujo and Nanda Rea, uh,

485
00:20:23.310 --> 00:20:26.310
in Barcelona with Michelle Ronqui and Vanessa

486
00:20:26.310 --> 00:20:29.150
Graeber. Nature astronomy on the 10th,

487
00:20:29.390 --> 00:20:32.110
a population synthesis modelling every

488
00:20:32.110 --> 00:20:35.070
class of isolated neutron star as one

489
00:20:35.070 --> 00:20:37.390
family evolving spin down,

490
00:20:37.550 --> 00:20:40.350
magnetic and thermal decay and galactic

491
00:20:40.350 --> 00:20:42.910
dynamics together among the

492
00:20:42.910 --> 00:20:45.750
24 known neutron stars younger than

493
00:20:45.750 --> 00:20:48.740
2000 years. Magnetars and central

494
00:20:48.900 --> 00:20:51.700
compact objects are about 59%.

495
00:20:53.700 --> 00:20:56.020
Anna: And the catalogue was never counting

496
00:20:56.260 --> 00:20:56.980
births.

497
00:20:57.460 --> 00:21:00.300
Avery: It was counting visibility. A uh radio

498
00:21:00.300 --> 00:21:03.060
pulsar beams for tens of millions of years.

499
00:21:03.540 --> 00:21:06.220
A uh, magnetar burns bright and fades

500
00:21:06.220 --> 00:21:08.940
fast. Count sightings and you count

501
00:21:08.940 --> 00:21:10.900
lifetimes, not births.

502
00:21:12.740 --> 00:21:15.460
The galactic supernova rate has to go up to

503
00:21:15.460 --> 00:21:18.060
about 2 per century, double the long

504
00:21:18.060 --> 00:21:20.820
standing figure and magnetar central

505
00:21:20.820 --> 00:21:23.700
engine models for super luminous supernovae,

506
00:21:23.860 --> 00:21:26.380
gamma ray burst plateaus and fast

507
00:21:26.380 --> 00:21:29.140
radio bursts suddenly become affordable

508
00:21:29.460 --> 00:21:31.780
because there are enough engines to go round,

509
00:21:32.660 --> 00:21:33.420
which is a

510
00:21:33.420 --> 00:21:35.460
Anna: direct handshake with Thursday's lead.

511
00:21:35.940 --> 00:21:38.660
Avery: Within a day of each other from opposite ends

512
00:21:38.820 --> 00:21:41.780
and the southern thread is foundational. The

513
00:21:41.780 --> 00:21:43.700
whole field starts with SGR

514
00:21:44.020 --> 00:21:46.990
05261 minus 66

515
00:21:47.230 --> 00:21:49.590
in the Large Magellanic Cloud in

516
00:21:49.590 --> 00:21:52.510
1979. And the modern end

517
00:21:52.510 --> 00:21:55.110
runs through the Murchison Wide Field Array

518
00:21:55.110 --> 00:21:56.190
in Western Australia.

519
00:21:57.310 --> 00:21:59.630
Anna: Now I believe you also have a storey that we

520
00:21:59.630 --> 00:22:01.630
ran out of time to run during the week.

521
00:22:02.350 --> 00:22:05.310
Avery: Indeed the one we didn't run during the week.

522
00:22:05.310 --> 00:22:08.190
And it's a proper storey. On Thursday,

523
00:22:08.430 --> 00:22:11.150
the Max Planck Institute for Solar System

524
00:22:11.150 --> 00:22:13.770
Research with the University of Colorado

525
00:22:14.010 --> 00:22:16.570
published new evidence that our sun is

526
00:22:16.570 --> 00:22:18.250
capable of a super flare.

527
00:22:18.970 --> 00:22:21.210
Anna: Define superflare because the word gets

528
00:22:21.210 --> 00:22:21.530
thrown

529
00:22:21.530 --> 00:22:24.090
Avery: around a flare an order of

530
00:22:24.090 --> 00:22:26.810
magnitude or more beyond the biggest. Our

531
00:22:26.810 --> 00:22:29.290
instruments have recorded the kind of energy

532
00:22:29.370 --> 00:22:31.690
release that makes the carrington event of

533
00:22:31.690 --> 00:22:34.330
1859 look like a warm up.

534
00:22:34.730 --> 00:22:37.530
Two years ago the same institute surveyed

535
00:22:37.530 --> 00:22:40.450
more than 56,000 sun like stars in

536
00:22:40.450 --> 00:22:43.300
Kepler data and found stars like ours

537
00:22:43.300 --> 00:22:46.180
appear to produce superflares roughly once a

538
00:22:46.180 --> 00:22:49.020
century each. Which was uncomfortable

539
00:22:49.340 --> 00:22:51.740
because we have four centuries of sunspot

540
00:22:51.740 --> 00:22:54.380
records and no superflare in them.

541
00:22:55.020 --> 00:22:57.780
Anna: So either we're unusual or we're

542
00:22:57.780 --> 00:23:00.700
overdue, or the uh, comparison is wrong

543
00:23:01.100 --> 00:23:01.380
and

544
00:23:01.380 --> 00:23:03.660
Avery: this paper goes at it from our own star

545
00:23:03.900 --> 00:23:06.700
rather than from other stars. Natalie

546
00:23:06.700 --> 00:23:09.260
Krivova and colleagues took the 300

547
00:23:09.420 --> 00:23:11.900
strongest solar flares recorded between

548
00:23:11.980 --> 00:23:14.560
2010 and 2016 and

549
00:23:14.560 --> 00:23:17.280
correlated the energy released in each with

550
00:23:17.280 --> 00:23:19.720
the size of the active region it came from.

551
00:23:20.200 --> 00:23:23.160
You get a scaling relation, bigger magnetic

552
00:23:23.160 --> 00:23:26.080
region, more available energy, and

553
00:23:26.080 --> 00:23:26.400
then you

554
00:23:26.400 --> 00:23:28.800
Anna: extrapolate it to the biggest spot we've

555
00:23:28.800 --> 00:23:31.040
Avery: ever seen, a sunspot group from

556
00:23:31.040 --> 00:23:33.600
1947, the largest in

557
00:23:33.600 --> 00:23:36.440
400 years of systematic observation,

558
00:23:36.680 --> 00:23:39.400
covering about 6/10 of 1%

559
00:23:39.560 --> 00:23:42.160
of the solar disc. Run it through the

560
00:23:42.160 --> 00:23:44.960
relation and a region that size holds

561
00:23:44.960 --> 00:23:47.720
enough stored magnetic energy to power a

562
00:23:47.720 --> 00:23:50.440
superflare. Krivova's line is

563
00:23:50.440 --> 00:23:53.400
blunt. Our sun has superflare potential,

564
00:23:53.640 --> 00:23:56.400
it can produce massive sunspots. And

565
00:23:56.400 --> 00:23:58.920
those can serve as the starting point for the

566
00:23:58.920 --> 00:24:01.480
most extreme bursts of radiation.

567
00:24:02.200 --> 00:24:03.320
Anna: Caveats, please.

568
00:24:03.960 --> 00:24:05.680
This is the kind of result that gets a

569
00:24:05.680 --> 00:24:06.760
terrible headline.

570
00:24:07.680 --> 00:24:10.000
Avery: Three and they matter. An

571
00:24:10.000 --> 00:24:12.520
extrapolated scaling relation is not a

572
00:24:12.520 --> 00:24:15.000
prediction. It says the energy budget is

573
00:24:15.000 --> 00:24:17.360
there, not that the sun will spend it.

574
00:24:18.000 --> 00:24:20.920
1947 produced large flares,

575
00:24:20.920 --> 00:24:23.880
but nothing like a superflare. So having the

576
00:24:23.880 --> 00:24:26.560
potential is demonstrably not the same as

577
00:24:26.560 --> 00:24:29.240
using it. And the spot coverage on the

578
00:24:29.240 --> 00:24:32.240
genuinely super flaring Kepler stars is still

579
00:24:32.240 --> 00:24:34.800
well beyond anything our sun has shown.

580
00:24:35.720 --> 00:24:37.440
Anna: What's the independent evidence it has ever

581
00:24:37.440 --> 00:24:37.960
happened?

582
00:24:38.600 --> 00:24:41.000
Avery: That comes from Earth. And it's rather

583
00:24:41.000 --> 00:24:43.760
wonderful. Tree rings and polar

584
00:24:43.760 --> 00:24:46.720
ice record sudden spikes in cosmogenic

585
00:24:46.720 --> 00:24:49.560
isotopes. Carbon 14 in wood,

586
00:24:49.720 --> 00:24:52.600
beryllium 10 in ice. And there are

587
00:24:52.600 --> 00:24:55.440
several sharp events in the record. The best

588
00:24:55.440 --> 00:24:58.280
known around 774 of the Common

589
00:24:58.280 --> 00:24:59.960
Era and another around

590
00:25:00.120 --> 00:25:02.950
993. Almost

591
00:25:03.030 --> 00:25:05.830
certainly extreme solar particle events

592
00:25:06.070 --> 00:25:08.750
far larger than anything in the instrumental

593
00:25:08.750 --> 00:25:09.110
era.

594
00:25:09.670 --> 00:25:12.390
So the geological answer is yes. It

595
00:25:12.390 --> 00:25:14.510
happens on roughly millennial

596
00:25:14.510 --> 00:25:15.430
timescales.

597
00:25:16.070 --> 00:25:18.470
Anna: And the practical read, not

598
00:25:18.470 --> 00:25:19.110
alarm.

599
00:25:19.270 --> 00:25:22.150
Avery: Infrastructure. A, uh, Carrington class event

600
00:25:22.150 --> 00:25:24.630
today is a grid and satellite problem.

601
00:25:24.870 --> 00:25:27.150
And that's exactly what space weather

602
00:25:27.150 --> 00:25:28.790
forecasting exists for.

603
00:25:29.590 --> 00:25:32.030
Australia's own Space Weather Forecasting

604
00:25:32.030 --> 00:25:34.870
Centre sits inside the Bureau of Meteorology

605
00:25:35.190 --> 00:25:38.030
and issues the warnings airlines, power

606
00:25:38.030 --> 00:25:40.870
operators and satellite fleets act on.

607
00:25:41.270 --> 00:25:44.110
It's also the reason the Aurora Australis

608
00:25:44.110 --> 00:25:46.870
gets spectacular. The same particles,

609
00:25:47.030 --> 00:25:48.550
a, um, much smaller dose.

610
00:25:48.710 --> 00:25:50.630
Anna: And before we get into Skywatch,

611
00:25:51.590 --> 00:25:53.750
I believe you have a couple of storey updates

612
00:25:53.750 --> 00:25:54.230
for us.

613
00:25:54.390 --> 00:25:56.750
Avery: Two quick developments from the last couple

614
00:25:56.750 --> 00:25:59.720
of days. The first is a sequel to

615
00:25:59.720 --> 00:26:01.600
a storey we opened on the third.

616
00:26:02.320 --> 00:26:05.000
NASA awarded Blue Origin a firm

617
00:26:05.000 --> 00:26:07.840
fixed price contract worth about $700

618
00:26:07.920 --> 00:26:10.120
million to build the Mars

619
00:26:10.120 --> 00:26:12.800
telecommunications network. A relay

620
00:26:12.800 --> 00:26:15.680
orbiter on a Blue Ring bus launching

621
00:26:15.680 --> 00:26:18.320
on New Glenn, delivered by the end of

622
00:26:18.320 --> 00:26:21.160
2028 and operational at Mars

623
00:26:21.160 --> 00:26:24.120
by 2030. Rocket Lab was the

624
00:26:24.120 --> 00:26:25.040
losing bidder.

625
00:26:25.750 --> 00:26:27.910
Anna: And Rocket Lab has now protested

626
00:26:28.630 --> 00:26:29.030
filed

627
00:26:29.030 --> 00:26:31.310
Avery: with the Government Accountability Office on

628
00:26:31.310 --> 00:26:34.070
Friday the 11th two grounds

629
00:26:34.230 --> 00:26:36.910
that the award appears inconsistent with the

630
00:26:36.910 --> 00:26:39.710
eligibility criteria Congress mandated

631
00:26:39.710 --> 00:26:42.590
for the procurement and that NASA's Technical

632
00:26:42.590 --> 00:26:45.390
Review of Rocket Lab's proposal contained

633
00:26:45.390 --> 00:26:48.110
what the company calls incorrect assertions

634
00:26:48.110 --> 00:26:50.950
and conclusions. Their framing is

635
00:26:50.950 --> 00:26:53.430
that procurement standards exist to ensure

636
00:26:53.510 --> 00:26:56.070
fair competition and and protect public

637
00:26:56.070 --> 00:26:56.470
investment.

638
00:26:57.350 --> 00:26:58.630
Anna: How do these usually go?

639
00:26:58.710 --> 00:27:01.110
Avery: Historically, not well for the protester.

640
00:27:01.350 --> 00:27:03.750
And there's a neat irony in the precedent.

641
00:27:04.070 --> 00:27:06.790
When Blue Origin protested NASA's Lunar

642
00:27:06.790 --> 00:27:09.190
Lander Award in 2021, the

643
00:27:09.190 --> 00:27:11.950
GAO denied it. That July, Blue

644
00:27:11.950 --> 00:27:14.950
Origin sued And lost in November. And

645
00:27:14.950 --> 00:27:17.830
NASA awarded Blue origin a, uh, second lander

646
00:27:17.830 --> 00:27:19.990
contract anyway in 2023.

647
00:27:20.720 --> 00:27:23.600
The GAO works to a statutory hundred day

648
00:27:23.600 --> 00:27:25.960
clock, which puts a decision around mid

649
00:27:25.960 --> 00:27:26.480
December.

650
00:27:27.120 --> 00:27:29.840
Anna: And we should say plainly that neither NASA

651
00:27:29.840 --> 00:27:32.560
nor Blue Origin has responded publicly, as we

652
00:27:32.560 --> 00:27:34.480
record they haven't.

653
00:27:34.480 --> 00:27:36.720
Avery: And we're not going to guess at the merits.

654
00:27:37.120 --> 00:27:39.560
This is a procurement dispute between two

655
00:27:39.560 --> 00:27:42.160
serious companies. And we'll report what the

656
00:27:42.160 --> 00:27:44.680
GAO finds. And the second

657
00:27:44.680 --> 00:27:47.120
update, Starship Flight 14,

658
00:27:47.520 --> 00:27:50.480
which we've tracked since Booster 21's static

659
00:27:50.480 --> 00:27:53.260
fire cleared at the end of August, has moved

660
00:27:53.260 --> 00:27:55.820
again. It was no earlier than the

661
00:27:55.820 --> 00:27:58.660
15th of September. As of Thursday the

662
00:27:58.660 --> 00:28:01.260
10th, it's no earlier than the 18th.

663
00:28:01.980 --> 00:28:04.900
Same vehicles, Booster 21 and

664
00:28:04.900 --> 00:28:07.860
Ship 41, both flying for the first

665
00:28:07.860 --> 00:28:10.620
time. Both block 3 from Pad

666
00:28:10.620 --> 00:28:13.420
2 at Starbase. Third flight of

667
00:28:13.420 --> 00:28:14.860
Starship version 3.

668
00:28:15.180 --> 00:28:18.110
And the headline objectives are big. The

669
00:28:18.110 --> 00:28:20.790
first attempt at an actual orbital trajectory

670
00:28:20.950 --> 00:28:23.750
and the first deployment of real satellites.

671
00:28:23.990 --> 00:28:26.870
Around 20 operational Starlink V3

672
00:28:26.870 --> 00:28:27.670
spacecraft.

673
00:28:28.310 --> 00:28:30.110
Anna: And I want to correct something we said on

674
00:28:30.110 --> 00:28:31.350
air earlier in the month.

675
00:28:31.830 --> 00:28:34.830
Avery: You do, and I'm glad you're doing it. When

676
00:28:34.830 --> 00:28:37.430
we first previewed this flight, we described

677
00:28:37.430 --> 00:28:39.630
it as including the first attempt to catch

678
00:28:39.630 --> 00:28:41.830
the ship itself with the tower arms.

679
00:28:42.390 --> 00:28:44.990
The current public flight plan has that catch

680
00:28:44.990 --> 00:28:47.980
deferred to a later mission. The booster is

681
00:28:47.980 --> 00:28:50.380
targeting a water landing in the Gulf, and

682
00:28:50.380 --> 00:28:52.500
the ship a, uh, splashdown in the Indian

683
00:28:52.580 --> 00:28:53.140
Ocean.

684
00:28:53.940 --> 00:28:56.700
Anna: So orbital trajectory, starlink

685
00:28:56.700 --> 00:28:59.660
deployment, water recoveries. No tower

686
00:28:59.660 --> 00:29:00.980
catch of the ship on this one.

687
00:29:00.980 --> 00:29:01.860
As things stand.

688
00:29:02.579 --> 00:29:05.460
Avery: As things stand. And SpaceX has a

689
00:29:05.460 --> 00:29:08.140
habit of changing the profile late, so we'll

690
00:29:08.140 --> 00:29:11.100
take it as it comes, no earlier than the

691
00:29:11.100 --> 00:29:13.790
Anna: 18th and to the sky for the week

692
00:29:13.790 --> 00:29:16.710
ahead. A good one because the Moon stays out

693
00:29:16.710 --> 00:29:19.470
of the way. New Moon was yesterday afternoon,

694
00:29:19.470 --> 00:29:21.510
so we're into thin evening crescents,

695
00:29:21.510 --> 00:29:24.110
building to first quarter on Friday the 18th,

696
00:29:24.270 --> 00:29:26.110
and dark mornings all week.

697
00:29:26.830 --> 00:29:29.390
Southern hemisphere first from

698
00:29:29.390 --> 00:29:31.790
Sydney and similar latitudes. Venus rewards

699
00:29:31.790 --> 00:29:34.190
being prompt, low in the west after

700
00:29:34.190 --> 00:29:36.750
sunset, unmissable at magnitude

701
00:29:36.750 --> 00:29:39.160
-4.8, heading for greatest

702
00:29:39.160 --> 00:29:42.080
brilliancy on Friday the 18th. Note

703
00:29:42.080 --> 00:29:44.760
that date some listings give the 22nd

704
00:29:45.000 --> 00:29:47.520
from a different definition of the peak. We

705
00:29:47.520 --> 00:29:49.640
use the 18th and there's a

706
00:29:49.640 --> 00:29:51.400
Avery: conjunction right on top of us.

707
00:29:51.560 --> 00:29:54.480
Anna: Tomorrow and Monday evening a very

708
00:29:54.480 --> 00:29:57.400
thin crescent sweeps past Venus half

709
00:29:57.400 --> 00:30:00.160
a degree apart at closest, a moon's

710
00:30:00.160 --> 00:30:02.760
width in front of Spica uh, in Virgo,

711
00:30:03.320 --> 00:30:05.440
one of the lovely naked eye sights of the

712
00:30:05.440 --> 00:30:07.730
year. And southern observers get the better

713
00:30:07.730 --> 00:30:10.450
geometry. The pair sits higher at the same

714
00:30:10.450 --> 00:30:13.210
stage of twilight than from North America, if

715
00:30:13.210 --> 00:30:16.010
you own a camera and a tripod, Sunday evening

716
00:30:16.010 --> 00:30:16.610
is the one.

717
00:30:17.250 --> 00:30:20.010
Avery: And Mercury, since we spent 10 minutes

718
00:30:20.010 --> 00:30:22.770
Anna: on it, worth trying. And be realistic.

719
00:30:23.250 --> 00:30:26.010
Magnitude minus 0.5, which is

720
00:30:26.010 --> 00:30:28.770
bright but only 2 degrees up 20 minutes after

721
00:30:28.770 --> 00:30:31.650
sunset. You need a flat western horizon,

722
00:30:32.110 --> 00:30:34.110
clean air and binoculars to find it before

723
00:30:34.110 --> 00:30:37.070
your eye does a, uh, tick the box observation

724
00:30:37.070 --> 00:30:39.230
rather than a spectacle. But there's

725
00:30:39.230 --> 00:30:40.710
something to be said for looking at the

726
00:30:40.710 --> 00:30:41.070
planet.

727
00:30:41.070 --> 00:30:43.150
We've just spent, uh, a segment taking apart

728
00:30:43.550 --> 00:30:46.550
Saturn, the week's reliable telescope target

729
00:30:46.550 --> 00:30:49.190
for everybody, building towards opposition on

730
00:30:49.190 --> 00:30:51.470
the 4th of October. With the rings about 7

731
00:30:51.470 --> 00:30:54.470
degrees open from the south, it rises in the

732
00:30:54.470 --> 00:30:56.950
east in the evening and rides high through

733
00:30:56.950 --> 00:30:59.860
the middle of the night. Rings plus Titan

734
00:30:59.860 --> 00:31:02.100
is a five minute look that never gets old.

735
00:31:02.660 --> 00:31:04.420
Avery: North America, your turn.

736
00:31:04.900 --> 00:31:07.300
Anna: Saturn's the same target, different timing,

737
00:31:07.540 --> 00:31:10.020
up around midnight and about 50 degrees high

738
00:31:10.020 --> 00:31:12.780
by 2 in the morning, which is superb altitude

739
00:31:12.780 --> 00:31:15.500
for detail. Two satellite events in the small

740
00:31:15.500 --> 00:31:18.420
hours for telescope owners. Dione transits

741
00:31:18.420 --> 00:31:21.340
Saturn's north polar region from about 2:55

742
00:31:21.340 --> 00:31:23.870
Eastern for roughly 40 minutes. And

743
00:31:23.870 --> 00:31:26.630
Tethys slides into Saturn's shadow around 10

744
00:31:26.630 --> 00:31:29.350
past 2. And Mars is your predawn

745
00:31:29.350 --> 00:31:31.790
object, up about half past one and working

746
00:31:31.790 --> 00:31:34.710
through Gemini on the 18th, it passes 6

747
00:31:34.710 --> 00:31:37.390
degrees south of Pollux. An easy colour

748
00:31:37.390 --> 00:31:39.630
comparison of orange planet against orange

749
00:31:39.630 --> 00:31:40.190
giant.

750
00:31:40.590 --> 00:31:43.110
Avery: Now the one I'm most pleased about. The

751
00:31:43.110 --> 00:31:44.110
supernova.

752
00:31:44.430 --> 00:31:46.950
Anna: This is the week's observing gift. There's a

753
00:31:46.950 --> 00:31:49.910
type 1A supernova going off in the galaxy

754
00:31:49.910 --> 00:31:52.750
NGC 7331 in

755
00:31:52.750 --> 00:31:53.470
Pegasus.

756
00:31:53.870 --> 00:31:56.590
SN2026AAIV,

757
00:31:56.990 --> 00:31:59.070
picked up by the Atlas survey at the start of

758
00:31:59.070 --> 00:32:01.710
the month and sitting around magnitude 12,

759
00:32:02.110 --> 00:32:04.670
peaking near the 10th. That's comfortably

760
00:32:04.670 --> 00:32:06.870
within reach of an 8 inch telescope under a

761
00:32:06.870 --> 00:32:09.790
decent sky and well within reach of a modest

762
00:32:09.790 --> 00:32:12.510
camera on a tracking mount. The galaxy's a

763
00:32:12.510 --> 00:32:14.910
lovely target in its own right. A bright

764
00:32:14.910 --> 00:32:17.310
spiral about 40 million light years off,

765
00:32:17.630 --> 00:32:20.350
often called the Deneb Galaxy. With the Deer

766
00:32:20.350 --> 00:32:23.230
lit group in the same field. Sources differ

767
00:32:23.230 --> 00:32:25.870
on the distance anywhere from 30 to 45

768
00:32:25.870 --> 00:32:28.670
million light years. So treat 40 as a round

769
00:32:28.670 --> 00:32:29.110
figure.

770
00:32:29.590 --> 00:32:30.790
Avery: Hemisphere split.

771
00:32:30.790 --> 00:32:33.030
Anna: North America has the clear advantage.

772
00:32:33.590 --> 00:32:36.470
Pegasus is high overhead in your evening,

773
00:32:36.630 --> 00:32:39.590
close to ideal from Sydney, it's a

774
00:32:39.590 --> 00:32:42.270
real challenge. The galaxy sits at about

775
00:32:42.270 --> 00:32:45.190
34 degrees north declination, so from

776
00:32:45.190 --> 00:32:48.070
34 degrees south it only reaches around 22

777
00:32:48.070 --> 00:32:50.720
degrees above the northern horizon through a

778
00:32:50.720 --> 00:32:53.000
lot of atmosphere and usually a lot of city

779
00:32:53.000 --> 00:32:53.360
light.

780
00:32:53.920 --> 00:32:56.480
Doable from a dark site with a clear northern

781
00:32:56.480 --> 00:32:59.200
aspect around 10 to 11 in the evening.

782
00:32:59.760 --> 00:33:02.320
Avery: And why it's worth the trouble because

783
00:33:02.320 --> 00:33:05.120
Anna: a, uh, type 1A is the standard candle. The

784
00:33:05.120 --> 00:33:07.720
entire accelerating universe result is built

785
00:33:07.720 --> 00:33:10.360
on the thing three Nobel laureates were

786
00:33:10.360 --> 00:33:13.040
defending at the end of August. And three

787
00:33:13.040 --> 00:33:15.680
days ago we covered Chandra, finding 84

788
00:33:15.680 --> 00:33:18.600
hypersoft X ray sources that may be

789
00:33:18.600 --> 00:33:21.080
the progenitor system's producing exactly

790
00:33:21.080 --> 00:33:23.720
this kind of explosion. So when you put an

791
00:33:23.720 --> 00:33:26.520
eyepiece on that faint dot in Pegasus, you're

792
00:33:26.520 --> 00:33:28.600
looking at one member of the population that

793
00:33:28.600 --> 00:33:31.440
measures the expansion of the universe. Not a

794
00:33:31.440 --> 00:33:34.240
bad Saturday night zodiacal light as

795
00:33:34.240 --> 00:33:37.160
well. And the equinox rule applies, so

796
00:33:37.160 --> 00:33:38.840
it's uh, a both hemispheres item with

797
00:33:38.840 --> 00:33:41.720
opposite instructions. We're inside two weeks

798
00:33:41.720 --> 00:33:44.260
of the equinox on the 22nd and the

799
00:33:44.260 --> 00:33:47.020
ecliptic stands steeply to the horizon, which

800
00:33:47.020 --> 00:33:49.100
is what makes this faint cone of dust

801
00:33:49.100 --> 00:33:52.020
scattered sunlight visible at all. From the

802
00:33:52.020 --> 00:33:54.940
south it's an evening object west after

803
00:33:54.940 --> 00:33:57.540
full darkness, a tall faint wedge

804
00:33:57.540 --> 00:33:59.100
rising from where the sun set.

805
00:33:59.579 --> 00:34:02.380
The false dusk. From the north it's the

806
00:34:02.380 --> 00:34:05.220
mirror image pre dawn. In the east, the

807
00:34:05.220 --> 00:34:08.060
false dawn. Either way, dark sight,

808
00:34:08.140 --> 00:34:11.020
no moon patience. This new moon

809
00:34:11.020 --> 00:34:12.860
window is the best chance until early

810
00:34:12.860 --> 00:34:13.420
October.

811
00:34:13.980 --> 00:34:15.180
Avery: Safety passage.

812
00:34:15.660 --> 00:34:18.380
Anna: Yes, and it's in every episode for a reason.

813
00:34:19.020 --> 00:34:21.100
With Venus this bright, some of you will try

814
00:34:21.100 --> 00:34:23.340
to find it in daylight and it is a real

815
00:34:23.340 --> 00:34:25.420
observation. Venus at Ah

816
00:34:25.460 --> 00:34:28.420
-4.8 is visible in a blue sky. If you

817
00:34:28.420 --> 00:34:31.300
know exactly where to look, do not sweep the

818
00:34:31.300 --> 00:34:33.180
sky near the sun with binoculars or a

819
00:34:33.180 --> 00:34:34.540
telescope to hunt for it.

820
00:34:34.860 --> 00:34:37.300
And do not try for Mercury in twilight with

821
00:34:37.300 --> 00:34:39.810
the sun still up. Concentrated sunlight

822
00:34:39.810 --> 00:34:42.090
through any optic causes permanent retinal

823
00:34:42.090 --> 00:34:44.530
damage in a fraction of a second with no

824
00:34:44.530 --> 00:34:47.210
pain. To warn you if you're ever looking at

825
00:34:47.210 --> 00:34:50.210
or near the sun, use a filter certified to

826
00:34:50.210 --> 00:34:53.130
ISO 123122,

827
00:34:53.530 --> 00:34:55.210
fit it over the front of the instrument,

828
00:34:55.290 --> 00:34:58.050
never at the eyepiece end and inspect it for

829
00:34:58.050 --> 00:35:00.410
scratches or pinholes every single time

830
00:35:00.410 --> 00:35:03.010
before it goes near your eye looking further

831
00:35:03.010 --> 00:35:05.890
ahead. Two for the diary. Saturn at

832
00:35:05.890 --> 00:35:07.770
opposition on the 4th of October.

833
00:35:08.090 --> 00:35:10.890
And on the 6th of October a pre dawn

834
00:35:10.970 --> 00:35:13.210
lunar occultation of Jupiter,

835
00:35:13.690 --> 00:35:16.170
the moon passing directly in front of the

836
00:35:16.170 --> 00:35:18.850
planet. Billed as the year's spectacular

837
00:35:18.850 --> 00:35:21.490
event. We'll build a proper curtain raiser

838
00:35:21.490 --> 00:35:24.050
nearer the time. And that's the weekend wrap

839
00:35:24.050 --> 00:35:27.010
for Saturday 12th September. Mercury has

840
00:35:27.010 --> 00:35:29.250
lost more of itself than we thought, as much

841
00:35:29.250 --> 00:35:32.250
as 23 kilometres off its diameter. And

842
00:35:32.250 --> 00:35:34.490
we missed it because 4 billion years of

843
00:35:34.490 --> 00:35:36.370
impacts have been quietly burying the

844
00:35:36.370 --> 00:35:39.210
evidence. BepiColombo arrives in about

845
00:35:39.210 --> 00:35:41.130
10 weeks with the instrument to cheque.

846
00:35:41.770 --> 00:35:44.370
Avery: Looking back on the week a rocket reached

847
00:35:44.370 --> 00:35:46.770
orbit from western European soil for the

848
00:35:46.770 --> 00:35:49.570
first time. The moon may have assembled in

849
00:35:49.570 --> 00:35:52.530
five hours rather than centuries. Hubble and

850
00:35:52.530 --> 00:35:55.330
Webb found 27 new worlds beyond

851
00:35:55.330 --> 00:35:57.930
Neptune. 109 radio

852
00:35:57.930 --> 00:36:00.410
bursts weighed the universe's missing gas

853
00:36:00.840 --> 00:36:03.680
and magnetars turned out to be half of all

854
00:36:03.680 --> 00:36:04.840
neutron stars.

855
00:36:05.240 --> 00:36:07.280
Anna: Plus new evidence our own sun has the

856
00:36:07.280 --> 00:36:09.480
magnetic energy budget for a super flare

857
00:36:09.800 --> 00:36:12.480
rocket. Lab has taken NASA to the GAO over

858
00:36:12.480 --> 00:36:15.360
the Mars relay contract and Starship's

859
00:36:15.360 --> 00:36:17.680
first orbital attempt is now no earlier than

860
00:36:17.680 --> 00:36:18.440
the 18th.

861
00:36:19.000 --> 00:36:21.560
Avery: Everything we covered with links to every

862
00:36:21.560 --> 00:36:24.160
paper and source release is in the show

863
00:36:24.160 --> 00:36:24.640
notes

864
00:36:24.640 --> 00:36:27.240
and@astronomydaily.IO

865
00:36:27.800 --> 00:36:28.840
and the contact form

866
00:36:28.840 --> 00:36:31.640
Anna: on the site is real and we do read it more

867
00:36:31.640 --> 00:36:32.360
than one storey.

868
00:36:32.360 --> 00:36:34.160
This fortnight started as a listener

869
00:36:34.160 --> 00:36:36.400
question. If there's something you want us to

870
00:36:36.400 --> 00:36:38.280
take apart properly, tell us.

871
00:36:38.760 --> 00:36:41.080
Avery: We're back on Monday with the weekday run.

872
00:36:41.400 --> 00:36:42.280
Anna: I'm Anna.

873
00:36:42.440 --> 00:36:43.720
Avery: And I'm Avery.

874
00:36:44.040 --> 00:36:46.480
Clear Skies. And if you're in the southern

875
00:36:46.480 --> 00:36:49.040
hemisphere, go out tomorrow evening and look

876
00:36:49.040 --> 00:36:51.960
west. The Moon and Venus half a

877
00:36:51.960 --> 00:36:54.940
degree apart in front of Spica. You won't

878
00:36:54.940 --> 00:36:57.380
need a telescope and you won't forget it.