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00:00:00 --> 00:00:02 Anna: Hello and welcome to Astronomy daily.
00:00:02 --> 00:00:05 It's Saturday 12th September,
00:00:05 --> 00:00:08 2026. This is series five,
00:00:08 --> 00:00:10 episode 192.
00:00:11 --> 00:00:13 And this is the weekend wrap. I'm
00:00:13 --> 00:00:14 Anna.
00:00:14 --> 00:00:17 Avery: And I'm Avery. Anna. Uh, our lead
00:00:17 --> 00:00:20 today is a planet getting smaller, which is
00:00:20 --> 00:00:22 not a sentence I expected to say this week.
00:00:23 --> 00:00:26 Anna: Mercury. And not smaller as in a revised
00:00:26 --> 00:00:29 measurement of what it is now. Smaller as in
00:00:29 --> 00:00:31 how much it has physically lost since it
00:00:31 --> 00:00:33 form. The planet has been contracting for
00:00:33 --> 00:00:36 four and a half billion years as its
00:00:36 --> 00:00:39 interior cools and it writes the evidence on
00:00:39 --> 00:00:42 its own surface. A new paper says we've been
00:00:42 --> 00:00:44 reading that evidence wrong in one very
00:00:44 --> 00:00:46 specific and rather beautiful way.
00:00:47 --> 00:00:48 Avery: Wrong by how much?
00:00:48 --> 00:00:51 Anna: By up to 30%. The old figure
00:00:51 --> 00:00:54 for how much Mercury's diameter has shrunk
00:00:54 --> 00:00:56 was something like 4 to 16 kilometres.
00:00:57 --> 00:01:00 The new one goes as high as 23. And
00:01:00 --> 00:01:02 the reason we missed it is that the thing
00:01:02 --> 00:01:04 doing the hiding is the same thing that has
00:01:04 --> 00:01:07 been resurfacing Mercury for 4 billion years.
00:01:08 --> 00:01:09 Avery: Craters.
00:01:09 --> 00:01:12 Anna: Craters. We'll take it properly because the
00:01:12 --> 00:01:14 method is as interesting as the number and
00:01:14 --> 00:01:16 because there's a spacecraft arriving at
00:01:16 --> 00:01:18 Mercury in about 10 weeks built to settle it.
00:01:19 --> 00:01:21 Avery: Then the week that was, and it was full.
00:01:22 --> 00:01:25 A rocket reaching orbit from Western European
00:01:25 --> 00:01:27 soil for the first time. The moon
00:01:28 --> 00:01:30 possibly assembled in five hours.
00:01:31 --> 00:01:33 27 new worlds beyond Neptune.
00:01:34 --> 00:01:36 A hundred and nine radio bursts weighing the
00:01:36 --> 00:01:39 universe's missing gas and magnetars,
00:01:39 --> 00:01:42 turning out to be half of everything, rather
00:01:42 --> 00:01:44 than one in a hundred plus one
00:01:44 --> 00:01:46 Anna: we didn't get to during the week. New
00:01:46 --> 00:01:49 evidence that our own sun is capable of a
00:01:49 --> 00:01:52 super flare. And two fresh developments
00:01:52 --> 00:01:54 from the last 48 hours. Rocket Lab
00:01:54 --> 00:01:56 has gone to the Government Accountability
00:01:56 --> 00:01:59 Office over that $700 million Mars
00:01:59 --> 00:02:02 contract. And Starship's first orbital
00:02:02 --> 00:02:03 flight has moved again.
00:02:03 --> 00:02:06 Avery: And the sky for both hemispheres, which this
00:02:06 --> 00:02:09 week has a supernova in it, you can go and
00:02:09 --> 00:02:11 find yourself. Let's get into it.
00:02:12 --> 00:02:14 Anna: Let's kick things off with Mercury, shall we?
00:02:14 --> 00:02:16 Avery: Start me with the basic physics.
00:02:16 --> 00:02:18 Why would a planet shrink at all?
00:02:19 --> 00:02:20 Anna: Because it was born hot and it has been
00:02:20 --> 00:02:23 losing that heat ever since. Mercury is
00:02:23 --> 00:02:26 a small planet with an enormous iron core,
00:02:26 --> 00:02:29 around 85% of the planet's radius, which
00:02:29 --> 00:02:31 is wildly out of proportion compared with,
00:02:31 --> 00:02:34 uh, Earth. Hot rock and hot metal
00:02:34 --> 00:02:36 occupy more volume than cold rock and cold
00:02:36 --> 00:02:39 metal. So as the interior cools,
00:02:39 --> 00:02:42 the inside of the planet contracts and the
00:02:42 --> 00:02:44 rigid outer shell has to accommodate a
00:02:44 --> 00:02:45 smaller interior.
00:02:45 --> 00:02:48 Avery: And a solid shell can't just deflate
00:02:48 --> 00:02:48 smoothly.
00:02:48 --> 00:02:51 Anna: It can't. It has to go
00:02:51 --> 00:02:54 somewhere. And it does that by breaking.
00:02:54 --> 00:02:57 The crust gets pushed together, thrust
00:02:57 --> 00:03:00 faults form and one slab of crust
00:03:00 --> 00:03:02 rides up over another on the surface that
00:03:02 --> 00:03:05 shows up as a cliff. Long sinuous
00:03:05 --> 00:03:08 lobe fronted, sometimes a kilometre or two
00:03:08 --> 00:03:11 high and hundreds of kilometres long. They're
00:03:11 --> 00:03:13 called lobate scarps. There are wrinkle
00:03:13 --> 00:03:16 ridges and high relief ridges too. And the
00:03:16 --> 00:03:18 whole family goes by a wonderfully plain
00:03:18 --> 00:03:21 shortening structures because they record
00:03:21 --> 00:03:24 Avery: the surface getting shorter. And
00:03:24 --> 00:03:26 Mercury's the textbook case for the solar
00:03:26 --> 00:03:29 system. We've known since Mariner 10
00:03:29 --> 00:03:32 flew past in 1974 and
00:03:32 --> 00:03:34 came back with images of these things
00:03:34 --> 00:03:36 everywhere. Discovery Roops is the
00:03:36 --> 00:03:39 famous one. A scarp 500
00:03:39 --> 00:03:41 kilometres long, cutting straight through
00:03:41 --> 00:03:43 craters and offsetting their rims.
00:03:44 --> 00:03:46 So how do you turn cliffs into a number?
00:03:47 --> 00:03:49 Anna: Very directly, every thrust fault has taken
00:03:49 --> 00:03:52 up a certain amount of horizontal shortening
00:03:52 --> 00:03:54 and you can estimate it from the height of
00:03:54 --> 00:03:56 the scarp and the angle the fault dips at.
00:03:57 --> 00:03:59 Map every shortening structure on the planet.
00:04:00 --> 00:04:02 Add up all the shortening and that tells you
00:04:02 --> 00:04:04 how much the circumference has reduced.
00:04:04 --> 00:04:06 Divide through and you get the change in
00:04:06 --> 00:04:07 diameter.
00:04:07 --> 00:04:10 Avery: And that's where the old number came from.
00:04:10 --> 00:04:13 Anna: Roughly 4 to 16 kilometres off the
00:04:13 --> 00:04:16 diameter. And it had a problem everybody in
00:04:16 --> 00:04:18 the field knew about. It was lower than the
00:04:18 --> 00:04:21 physics wanted model. Mercury's thermal
00:04:21 --> 00:04:22 history and the models predict more
00:04:22 --> 00:04:25 contraction than the surface appears to show.
00:04:25 --> 00:04:28 A mismatch with the surface on the small
00:04:28 --> 00:04:28 side.
00:04:29 --> 00:04:31 Avery: Which usually means one of two things.
00:04:32 --> 00:04:34 Anna: Either the model is wrong or you're not
00:04:34 --> 00:04:37 seeing all the evidence. This new work argues
00:04:37 --> 00:04:39 it's the second for a reason that's almost
00:04:39 --> 00:04:41 embarrassingly simple once somebody says it
00:04:41 --> 00:04:44 out loud. This is Gaku Nishiyama,
00:04:44 --> 00:04:47 a planetary scientist at the German Aerospace
00:04:47 --> 00:04:49 Centre in Berlin with colleagues in Japan,
00:04:49 --> 00:04:52 published in Geophysical Research Letters and
00:04:52 --> 00:04:55 released by the American Geophysical Union on
00:04:55 --> 00:04:58 Thursday the 10th. And the simple reason is
00:04:58 --> 00:05:01 impact craters bury the cliffs. Impact
00:05:01 --> 00:05:04 every asteroid that has hit mercury over 4
00:05:04 --> 00:05:06 billion years has thrown out a blanket of
00:05:06 --> 00:05:09 pulverised rock and that debris drapes over
00:05:09 --> 00:05:12 whatever was there before. A sharp kilometre
00:05:12 --> 00:05:14 high cliff gets softened, partly filled,
00:05:15 --> 00:05:18 buried at one end, broken into pieces that no
00:05:18 --> 00:05:20 longer read as one continuous structure.
00:05:20 --> 00:05:23 And then you, sitting at a desk mapping
00:05:23 --> 00:05:26 images, either don't see it or map it as
00:05:26 --> 00:05:27 something smaller than it was.
00:05:27 --> 00:05:30 Avery: Is that a hunch or did they measure it?
00:05:30 --> 00:05:32 Anna: They measured it. And that's what makes the
00:05:32 --> 00:05:34 paper convincing rather than merely
00:05:34 --> 00:05:37 plausible. They used Messenger,
00:05:37 --> 00:05:39 NASA's Mercury orbiter, which went round the
00:05:39 --> 00:05:42 planet 4 times
00:05:42 --> 00:05:45 between 2011 and 2015 before
00:05:45 --> 00:05:47 being deliberately crashed into the surface.
00:05:48 --> 00:05:50 It carried a laser altimeter and a dual
00:05:50 --> 00:05:53 imaging system. The team did two things with
00:05:53 --> 00:05:56 that. First, stereophotogrammetry.
00:05:56 --> 00:05:58 Take two images of the same ground from
00:05:58 --> 00:06:00 different angles and the parallax gives you
00:06:00 --> 00:06:03 topography. It's the trick your two eyes play
00:06:03 --> 00:06:05 to give you depth perception applied to a
00:06:05 --> 00:06:06 planet.
00:06:07 --> 00:06:09 Avery: So three dimensional terrain where before
00:06:09 --> 00:06:10 there
00:06:10 --> 00:06:12 Anna: were flat pictures at much better
00:06:12 --> 00:06:15 resolution than the altimeter alone. And
00:06:15 --> 00:06:17 across parts of the planet the altimeter
00:06:17 --> 00:06:20 never properly covered. And second,
00:06:20 --> 00:06:22 the clever bit, they measured surface
00:06:22 --> 00:06:25 roughness independently and asked a question.
00:06:25 --> 00:06:28 Does the density of shortening structures you
00:06:28 --> 00:06:30 can see depend on how rough the surrounding
00:06:30 --> 00:06:31 terrain is?
00:06:32 --> 00:06:33 Avery: And it does.
00:06:33 --> 00:06:36 Anna: Strongly. The rougher the terrain, which
00:06:36 --> 00:06:38 is to say, the more heavily battered by
00:06:38 --> 00:06:41 impacts, the fewer shortening structures you
00:06:41 --> 00:06:44 find per unit area. Now, there's
00:06:44 --> 00:06:46 no physical reason the interior should have
00:06:46 --> 00:06:48 contracted less under under rough ground than
00:06:48 --> 00:06:51 under smooth ground. The faults don't know
00:06:51 --> 00:06:53 what the surface looks like. So that
00:06:53 --> 00:06:56 correlation isn't geology, it's a detection
00:06:56 --> 00:06:58 limit. It's the signature of evidence being
00:06:58 --> 00:07:01 erased. And you can use the strength of the
00:07:01 --> 00:07:03 correlation to estimate how much has been
00:07:03 --> 00:07:04 erased.
00:07:04 --> 00:07:07 Avery: I like that. The bias announces itself.
00:07:08 --> 00:07:10 Anna: It does indeed. Which is the best thing a
00:07:10 --> 00:07:13 bias can do. Nishiyama's own analogy
00:07:13 --> 00:07:15 is freshly laid gravel hiding the ruts in a
00:07:15 --> 00:07:18 road. The ruts are still there, you just
00:07:18 --> 00:07:20 can't see them from a moving car.
00:07:20 --> 00:07:22 Avery: So what's the corrected number?
00:07:23 --> 00:07:26 Anna: Between 10 and 30% more contraction
00:07:26 --> 00:07:29 than previously estimated. In round figures,
00:07:29 --> 00:07:31 the total loss of diameter goes from a range
00:07:31 --> 00:07:34 topping out around 16 kilometres to as much
00:07:34 --> 00:07:37 as 23, about 14 and a half miles.
00:07:37 --> 00:07:39 Call it an extra seven kilometres that was
00:07:39 --> 00:07:40 hiding under rubble.
00:07:41 --> 00:07:43 Avery: Which doesn't sound enormous for a whole
00:07:43 --> 00:07:44 planet.
00:07:44 --> 00:07:47 Anna: It doesn't. And Mercury is about 4
00:07:47 --> 00:07:50 kilometres across, so we're talking a
00:07:50 --> 00:07:52 fraction of a percent. But the number isn't
00:07:52 --> 00:07:54 interesting because it's big. It's
00:07:54 --> 00:07:57 interesting because of what it constrains.
00:07:57 --> 00:08:00 Nishiyama's line on that is the one to hold
00:08:00 --> 00:08:03 onto. He says more shrinking means
00:08:03 --> 00:08:05 mercury could have a larger metal core or
00:08:05 --> 00:08:08 fewer light elements like silicon mixed into
00:08:08 --> 00:08:10 that core, or a higher starting temperature.
00:08:11 --> 00:08:14 Avery: Unpack that. Why does total contraction
00:08:14 --> 00:08:15 tell you about the core?
00:08:15 --> 00:08:18 Anna: Because the amount a planet shrinks is a
00:08:18 --> 00:08:21 thermometer reading integrated over its whole
00:08:21 --> 00:08:23 history. Iron contracts as it
00:08:23 --> 00:08:26 cools and contracts again when it
00:08:26 --> 00:08:29 solidifies. So if mercury lost
00:08:29 --> 00:08:31 more volume than we thought, either there was
00:08:31 --> 00:08:34 more iron to lose it from. Or the core was
00:08:34 --> 00:08:37 purer. Light elements like silicon or
00:08:37 --> 00:08:39 sulphur change how iron behaves as it
00:08:39 --> 00:08:42 freezes. Or the planet simply started hotter
00:08:42 --> 00:08:45 and had further to fall. And the mismatch
00:08:45 --> 00:08:47 with the thermal models closes, which is the
00:08:47 --> 00:08:50 quietly satisfying part. Nishiyama says
00:08:50 --> 00:08:52 the corrected amount actually makes sense to
00:08:52 --> 00:08:54 him, meaning the surface record and the
00:08:54 --> 00:08:57 predictions now agree rather than pulling
00:08:57 --> 00:08:57 against each other.
00:08:58 --> 00:09:00 Avery: There's a pattern here I want to name,
00:09:00 --> 00:09:02 because we hit it twice already this week.
00:09:03 --> 00:09:05 Wednesday, The Galaxy M M74
00:09:06 --> 00:09:08 found to be more than twice its catalogue
00:09:08 --> 00:09:11 size, because the catalogue size was really
00:09:11 --> 00:09:14 a statement about how deep the survey went.
00:09:14 --> 00:09:17 And yesterday, magnetars turning out to be
00:09:17 --> 00:09:20 half of all neutron stars, because the
00:09:20 --> 00:09:23 catalogue counted how long each kind stays
00:09:23 --> 00:09:25 visible, rather than how many are born.
00:09:25 --> 00:09:27 Anna: And today, a planet that's shrunk by more
00:09:27 --> 00:09:30 than the map says, because the map is drawn
00:09:30 --> 00:09:32 on a surface that's been partly erasing
00:09:32 --> 00:09:34 itself for 4 billion years. Same
00:09:34 --> 00:09:37 lesson three times in one week. And it's the
00:09:37 --> 00:09:39 most useful habit of mind in the field.
00:09:39 --> 00:09:41 Before you ask what the universe is doing,
00:09:42 --> 00:09:44 ask what your instrument and your sample are
00:09:44 --> 00:09:45 letting you see.
00:09:45 --> 00:09:47 Avery: Which brings us to the spacecraft that's
00:09:47 --> 00:09:49 about to do it again properly
00:09:50 --> 00:09:51 Bepicolombo.
00:09:51 --> 00:09:54 Anna: And the timing is genuinely lovely. The joint
00:09:54 --> 00:09:56 European and Japanese mission has been flying
00:09:56 --> 00:09:59 since 2018, and after nine planetary
00:09:59 --> 00:10:02 flybys, it's now in the arrival phase.
00:10:02 --> 00:10:05 It separated its big electric transfer module
00:10:05 --> 00:10:07 on 3rd September, which we covered at the
00:10:07 --> 00:10:10 time. Gravity capture at Mercury is 21st
00:10:10 --> 00:10:13 November, so about 10 weeks away. The
00:10:13 --> 00:10:16 Japanese orbiter is released around the
00:10:16 --> 00:10:19 9th or 10th of December. The European
00:10:19 --> 00:10:21 orbiter reaches its final science orbit on
00:10:21 --> 00:10:24 the 10th of March, and routine science begins
00:10:24 --> 00:10:25 on the 6th of April.
00:10:25 --> 00:10:27 Avery: And what does it bring to this specific
00:10:27 --> 00:10:28 problem?
00:10:29 --> 00:10:31 Anna: Two things messenger could not the laser
00:10:31 --> 00:10:34 altimeter is substantially more
00:10:34 --> 00:10:36 capable, with vertical precision quoted down
00:10:36 --> 00:10:39 to the tens of centimetres, and orbit
00:10:39 --> 00:10:41 geometry, which matters just as much and gets
00:10:41 --> 00:10:44 mentioned less. MESSENGER flew a highly
00:10:44 --> 00:10:47 eccentric orbit, so it had superb
00:10:47 --> 00:10:49 resolution over the northern Hemisphere and
00:10:49 --> 00:10:52 much poorer coverage of the South. Bepi
00:10:52 --> 00:10:55 Colombo's European orbiter sits on a far less
00:10:55 --> 00:10:57 eccentric polar orbit. Even coverage of the
00:10:57 --> 00:10:59 whole planet at consistent resolution.
00:11:00 --> 00:11:02 Avery: So the small structures that were being
00:11:02 --> 00:11:05 Anna: missed get counted, and that's a proper
00:11:05 --> 00:11:07 falsifiable prediction out of this paper,
00:11:08 --> 00:11:10 which is what you want. If the shortfall
00:11:10 --> 00:11:12 really is buried small structures,
00:11:13 --> 00:11:15 BepiColombo should find a population of
00:11:15 --> 00:11:18 modest scarps and ridges in exactly
00:11:18 --> 00:11:20 the rough terrain where current maps look
00:11:20 --> 00:11:23 suspiciously empty. If it looks at that
00:11:23 --> 00:11:26 ground at 20 centimetre precision and finds
00:11:26 --> 00:11:26 nothing.
00:11:26 --> 00:11:29 The correction is wrong and the thermo models
00:11:29 --> 00:11:31 have a real problem. Either way we'll know
00:11:31 --> 00:11:32 within a couple of years.
00:11:33 --> 00:11:35 Avery: And there's an Australian threat in this one.
00:11:35 --> 00:11:38 Anna: There is, and it's infrastructure rather than
00:11:38 --> 00:11:40 science, which I think makes it better rather
00:11:40 --> 00:11:43 than worse. Everything BepiColombo does at
00:11:43 --> 00:11:46 Mercury has to come home through a dish. And
00:11:46 --> 00:11:48 one of the dishes is in Western Australia.
00:11:49 --> 00:11:51 ESA's new Norcia station, about 140
00:11:51 --> 00:11:53 kilometres north of Perth and run in
00:11:53 --> 00:11:56 partnership with CSIRO, is where Europe's
00:11:56 --> 00:11:59 Deep Space Network began. The 35
00:11:59 --> 00:12:01 metre antenna there was the agency's first.
00:12:02 --> 00:12:04 There's Now a second 35 metre dish at the
00:12:04 --> 00:12:06 site built for the current generation of
00:12:06 --> 00:12:09 missions with BepiColombo named among those
00:12:09 --> 00:12:10 it supports.
00:12:11 --> 00:12:13 Avery: Same reason the Canberra complex exists,
00:12:14 --> 00:12:14 same
00:12:14 --> 00:12:17 Anna: reason and its simple geometry. A
00:12:17 --> 00:12:19 spacecraft is only visible from part of the
00:12:19 --> 00:12:22 earth at a time, so continuous contact needs
00:12:22 --> 00:12:24 dishes spread around the planet in longitude,
00:12:24 --> 00:12:27 which means southern stations and is also why
00:12:27 --> 00:12:30 ESA built one at Malargue in Argentina.
00:12:30 --> 00:12:32 The southern hemisphere isn't a, uh, nice to
00:12:32 --> 00:12:35 have in deep space communications, it's load
00:12:35 --> 00:12:37 bearing. When the first detailed topography
00:12:37 --> 00:12:39 of Mercury's southern hemisphere comes down
00:12:39 --> 00:12:42 next year, some of it will have arrived via a
00:12:42 --> 00:12:43 paddock in Western Australia.
00:12:44 --> 00:12:47 Avery: One last thing, Mercury is actually
00:12:47 --> 00:12:49 in the sky this week.
00:12:49 --> 00:12:52 Anna: Barely very low in the western Twilight,
00:12:52 --> 00:12:55 setting inside 40 minutes of the sun and a
00:12:55 --> 00:12:57 difficult catch for everybody. We'll come
00:12:57 --> 00:13:00 back to it, but I like the symmetry. The
00:13:00 --> 00:13:03 hardest planet to see is also the one whose
00:13:03 --> 00:13:05 surface has been hardest to read. And for the
00:13:05 --> 00:13:08 same underlying reason, something keeps
00:13:08 --> 00:13:09 getting in the way.
00:13:09 --> 00:13:12 Avery: Right, let's move on to the week that was
00:13:13 --> 00:13:15 five storeys from the weekday run in the
00:13:15 --> 00:13:16 order they happened.
00:13:16 --> 00:13:19 One we didn't get to and two fresh
00:13:19 --> 00:13:21 developments from the last day or so.
00:13:21 --> 00:13:24 Anna: And the theme of the week, if it had one, was
00:13:24 --> 00:13:27 honest revision. Almost everything on this
00:13:27 --> 00:13:29 list is somebody finding out that a number we
00:13:29 --> 00:13:31 were comfortable with was wrong.
00:13:31 --> 00:13:33 Avery: Let's start at the beginning of the week,
00:13:34 --> 00:13:36 Monday and the launch storey of the week.
00:13:37 --> 00:13:40 On Friday the 5th, at 12 minutes past
00:13:40 --> 00:13:42 10 in the evening local time, a rocket
00:13:42 --> 00:13:45 called Spectrum lifted off from Andoya
00:13:45 --> 00:13:48 spaceport in Northern Norway and reached
00:13:48 --> 00:13:51 orbit. Built by a, um, Munich company,
00:13:51 --> 00:13:54 Isar Aerospace, and it's the first
00:13:54 --> 00:13:56 vehicle ever to reach orbit from Western
00:13:56 --> 00:13:57 European soil
00:13:58 --> 00:14:00 Anna: with a real payload, not a mass simulator.
00:14:01 --> 00:14:03 Avery: Five university cubesats, Berlin,
00:14:04 --> 00:14:07 Trondheim, Maribor, Vienna and the
00:14:07 --> 00:14:09 Bulgarian company Endurosat,
00:14:09 --> 00:14:12 plus a fixed experiment from D Cubed
00:14:12 --> 00:14:15 it went into a stretched orbit and
00:14:15 --> 00:14:17 circularised on a second stage restart,
00:14:17 --> 00:14:20 which is non trivial on your second ever
00:14:20 --> 00:14:23 flight, the first in March last
00:14:23 --> 00:14:26 year, failed about 30 seconds in on a vent
00:14:26 --> 00:14:26 valve.
00:14:27 --> 00:14:30 Anna: And the thing to watch now is cadence, not
00:14:30 --> 00:14:32 the milestone exactly.
00:14:33 --> 00:14:35 Avery: Vehicles three through seven are in
00:14:35 --> 00:14:37 production and the Munich factory is built
00:14:37 --> 00:14:39 for more than 30 a year.
00:14:40 --> 00:14:42 Reaching orbit once is a headline.
00:14:42 --> 00:14:45 Reaching it on schedule is a launch industry.
00:14:46 --> 00:14:48 We paired it with Gilmour Space in Queensland
00:14:48 --> 00:14:51 as the Southern hemisphere version of the
00:14:51 --> 00:14:53 same ambition. And Eris flew 14
00:14:53 --> 00:14:56 seconds from Bowen last year. And test
00:14:56 --> 00:14:59 flight two is now listed for early
00:14:59 --> 00:15:00 2027.
00:15:01 --> 00:15:03 Anna: Next up was our big moon storey for the week
00:15:03 --> 00:15:04 Tuesday.
00:15:04 --> 00:15:07 Avery: And the headline everybody else ran was that
00:15:07 --> 00:15:09 the Moon formed in five hours,
00:15:10 --> 00:15:13 which isn't quite what the paper said and the
00:15:13 --> 00:15:14 difference matters.
00:15:14 --> 00:15:16 Anna: It's a sensitivity result.
00:15:16 --> 00:15:19 Avery: It's a sensitivity result. Kagan
00:15:19 --> 00:15:22 Denton and Robin Canup at the Southwest
00:15:22 --> 00:15:24 Research Institute with Eric Asfog in
00:15:24 --> 00:15:27 Arizona in Astrophysical Journal
00:15:27 --> 00:15:30 Letters. The canonical storey is a
00:15:30 --> 00:15:33 Mars sized body called Theia hitting the
00:15:33 --> 00:15:36 proto Earth, throwing a disc of debris
00:15:36 --> 00:15:38 into orbit and the Moon slowly accreting, uh,
00:15:39 --> 00:15:41 out of it. What this group added was
00:15:41 --> 00:15:44 something nobody had properly included,
00:15:44 --> 00:15:45 rather rock strength that
00:15:45 --> 00:15:48 Anna: changes with temperature because previous
00:15:48 --> 00:15:49 simulations treated
00:15:49 --> 00:15:52 Avery: the rock as a fluid essentially
00:15:52 --> 00:15:55 an rock isn't a fluid, it has strength
00:15:55 --> 00:15:57 and that strength collapses as it heats.
00:15:58 --> 00:16:01 Put it in and for some impact conditions
00:16:01 --> 00:16:04 you skip the disc entirely. The
00:16:04 --> 00:16:06 collision directly produces a single
00:16:06 --> 00:16:09 intact satellite in about five hours.
00:16:10 --> 00:16:13 Not always. A hot young Thea
00:16:13 --> 00:16:15 under 60 million years old gives the
00:16:15 --> 00:16:18 immediate moon. A cooler older
00:16:18 --> 00:16:21 one gives the classical slow disc.
00:16:21 --> 00:16:23 Anna: So the finding is that the outcome is
00:16:23 --> 00:16:25 sensitive to a parameter we'd been ignoring.
00:16:26 --> 00:16:29 Avery: A genuinely important result and a
00:16:29 --> 00:16:31 much less exciting sentence. Follow
00:16:31 --> 00:16:34 ups uh, are the full parameter survey and
00:16:34 --> 00:16:37 deep lunar samples. The two routes
00:16:37 --> 00:16:39 give different interiors. So there's a test.
00:16:40 --> 00:16:43 We closed it on the Jack Hills zircons in
00:16:43 --> 00:16:46 Western Australia, the oldest bits of Earth
00:16:46 --> 00:16:47 anybody has held.
00:16:47 --> 00:16:50 Anna: Moving on to Wednesday, 27 new
00:16:50 --> 00:16:52 worlds past Neptune.
00:16:52 --> 00:16:55 Avery: Wednesday's lead was Hubble and Webb working
00:16:55 --> 00:16:58 the same patch of sky together and pulling
00:16:58 --> 00:17:01 out 27 previously unknown trans
00:17:01 --> 00:17:04 Neptunian objects, the faintest
00:17:04 --> 00:17:07 ever directly detected. The smallest around
00:17:07 --> 00:17:09 five kilometres across, five
00:17:09 --> 00:17:12 times below what ground based surveys reach.
00:17:13 --> 00:17:15 Anna: And the surprise wasn't the number, it was
00:17:15 --> 00:17:16 the colours.
00:17:16 --> 00:17:19 Avery: Two papers in the Astronomical Journal on the
00:17:19 --> 00:17:19 8th.
00:17:19 --> 00:17:22 Morgan at Northern Arizona on colour,
00:17:22 --> 00:17:25 Eduardo at Victoria on the size distribution.
00:17:26 --> 00:17:29 The expectation was that small objects are
00:17:29 --> 00:17:31 collision fragments. So, so they should look
00:17:31 --> 00:17:33 like rubble. Mixed homogenised
00:17:33 --> 00:17:36 no memory of origin. Instead, the
00:17:36 --> 00:17:39 small ones keep the same colour relationship
00:17:39 --> 00:17:41 as the large ones in both the dynamically
00:17:41 --> 00:17:43 cold population and the hot one.
00:17:44 --> 00:17:46 David Trilling's line was that the hot
00:17:46 --> 00:17:48 objects retain a signature of where they
00:17:48 --> 00:17:51 Anna: were born, which points back to
00:17:51 --> 00:17:54 how planetesimals formed in the first place.
00:17:54 --> 00:17:57 Avery: It supports rapid formation directly at large
00:17:57 --> 00:18:00 sizes rather than slow grinding up from
00:18:00 --> 00:18:02 dust form, with Arrokoth as the type
00:18:02 --> 00:18:05 specimen. And the next act is Ruben
00:18:05 --> 00:18:08 at Cerro Pachon in Chile, which will
00:18:08 --> 00:18:11 find these in bulk plus occultation
00:18:11 --> 00:18:13 chasing from Australia and New Zealand.
00:18:14 --> 00:18:16 Anna: Now I know this next one is a favourite of
00:18:16 --> 00:18:19 yours from Thursday. Weighing the
00:18:19 --> 00:18:21 universe with radio bursts
00:18:22 --> 00:18:22 Thursday.
00:18:22 --> 00:18:25 Avery: And yes, it is indeed one of my favourites of
00:18:25 --> 00:18:28 the year. 109 localised
00:18:28 --> 00:18:31 fast radio bursts, mostly from the Deep
00:18:31 --> 00:18:33 Synoptic Array at Owens Valley, used to
00:18:33 --> 00:18:35 measure something nobody could pin down
00:18:35 --> 00:18:38 properly before how far galactic
00:18:38 --> 00:18:41 feedback has pushed gas out of galaxies and
00:18:41 --> 00:18:43 smoothed the clumpiness of matter in the
00:18:43 --> 00:18:44 universe.
00:18:44 --> 00:18:46 Anna: And the mechanism is the nicest thing about
00:18:46 --> 00:18:47 it.
00:18:47 --> 00:18:50 Avery: A fast radio burst is a millisecond
00:18:50 --> 00:18:53 flash and every free electron between
00:18:53 --> 00:18:55 us. And it slows the low frequencies
00:18:55 --> 00:18:58 slightly more than the high ones. So the
00:18:58 --> 00:19:01 burst arrives smeared a, uh, chirp
00:19:01 --> 00:19:03 and the size of the smear counts the
00:19:03 --> 00:19:06 electrons along the line of sight. Kriti
00:19:06 --> 00:19:09 Sharma, Vikram Ravi, Elizabeth Kraus
00:19:09 --> 00:19:11 and colleagues. Nature astronomy on the
00:19:11 --> 00:19:14 8th, a prism made out of the entire
00:19:14 --> 00:19:15 intervening universe.
00:19:16 --> 00:19:17 Anna: And the result?
00:19:19 --> 00:19:21 Avery: Gas fractions in big halos running about
00:19:21 --> 00:19:24 1.9-sigma above stacked
00:19:24 --> 00:19:26 Erosita X ray measurements. The
00:19:26 --> 00:19:29 bursts count cool gas, the X rays miss
00:19:29 --> 00:19:32 and clustering variants cut by something like
00:19:32 --> 00:19:34 a factor of eight at the scales where
00:19:34 --> 00:19:37 feedback bites, which bears directly on the
00:19:37 --> 00:19:40 S8 tension. The Southern spine of that
00:19:40 --> 00:19:43 storey is long. The first fast radio
00:19:43 --> 00:19:45 burst came out of Parkes Murrayang in
00:19:45 --> 00:19:48 2007 and the McQuart relation came
00:19:48 --> 00:19:50 from ASCAP in Western Australia.
00:19:51 --> 00:19:54 Anna: Moving on to Friday's episode. Magnetars are
00:19:54 --> 00:19:57 half of everything yesterday, the
00:19:57 --> 00:19:59 Avery: one that still feels too big.
00:20:00 --> 00:20:03 Magnetars, neutron stars with magnetic
00:20:03 --> 00:20:05 fields around a hundred trillion times
00:20:05 --> 00:20:07 Earth's, have always been the exotics.
00:20:08 --> 00:20:10 About 30 confirmed against several thousand
00:20:10 --> 00:20:13 radio pulsars. One in a hundred,
00:20:13 --> 00:20:14 give or take.
00:20:15 --> 00:20:17 Anna: And the new number is one in two.
00:20:17 --> 00:20:19 Avery: Roughly one in two at birth.
00:20:20 --> 00:20:23 Celsa Pardo Araujo and Nanda Rea, uh,
00:20:23 --> 00:20:26 in Barcelona with Michelle Ronqui and Vanessa
00:20:26 --> 00:20:29 Graeber. Nature astronomy on the 10th,
00:20:29 --> 00:20:32 a population synthesis modelling every
00:20:32 --> 00:20:35 class of isolated neutron star as one
00:20:35 --> 00:20:37 family evolving spin down,
00:20:37 --> 00:20:40 magnetic and thermal decay and galactic
00:20:40 --> 00:20:42 dynamics together among the
00:20:42 --> 00:20:45 24 known neutron stars younger than
00:20:45 --> 00:20:48 2000 years. Magnetars and central
00:20:48 --> 00:20:51 compact objects are about 59%.
00:20:53 --> 00:20:56 Anna: And the catalogue was never counting
00:20:56 --> 00:20:56 births.
00:20:57 --> 00:21:00 Avery: It was counting visibility. A uh radio
00:21:00 --> 00:21:03 pulsar beams for tens of millions of years.
00:21:03 --> 00:21:06 A uh, magnetar burns bright and fades
00:21:06 --> 00:21:08 fast. Count sightings and you count
00:21:08 --> 00:21:10 lifetimes, not births.
00:21:12 --> 00:21:15 The galactic supernova rate has to go up to
00:21:15 --> 00:21:18 about 2 per century, double the long
00:21:18 --> 00:21:20 standing figure and magnetar central
00:21:20 --> 00:21:23 engine models for super luminous supernovae,
00:21:23 --> 00:21:26 gamma ray burst plateaus and fast
00:21:26 --> 00:21:29 radio bursts suddenly become affordable
00:21:29 --> 00:21:31 because there are enough engines to go round,
00:21:32 --> 00:21:33 which is a
00:21:33 --> 00:21:35 Anna: direct handshake with Thursday's lead.
00:21:35 --> 00:21:38 Avery: Within a day of each other from opposite ends
00:21:38 --> 00:21:41 and the southern thread is foundational. The
00:21:41 --> 00:21:43 whole field starts with SGR
00:21:44 --> 00:21:46 05261 minus 66
00:21:47 --> 00:21:49 in the Large Magellanic Cloud in
00:21:49 --> 00:21:52 1979. And the modern end
00:21:52 --> 00:21:55 runs through the Murchison Wide Field Array
00:21:55 --> 00:21:56 in Western Australia.
00:21:57 --> 00:21:59 Anna: Now I believe you also have a storey that we
00:21:59 --> 00:22:01 ran out of time to run during the week.
00:22:02 --> 00:22:05 Avery: Indeed the one we didn't run during the week.
00:22:05 --> 00:22:08 And it's a proper storey. On Thursday,
00:22:08 --> 00:22:11 the Max Planck Institute for Solar System
00:22:11 --> 00:22:13 Research with the University of Colorado
00:22:14 --> 00:22:16 published new evidence that our sun is
00:22:16 --> 00:22:18 capable of a super flare.
00:22:18 --> 00:22:21 Anna: Define superflare because the word gets
00:22:21 --> 00:22:21 thrown
00:22:21 --> 00:22:24 Avery: around a flare an order of
00:22:24 --> 00:22:26 magnitude or more beyond the biggest. Our
00:22:26 --> 00:22:29 instruments have recorded the kind of energy
00:22:29 --> 00:22:31 release that makes the carrington event of
00:22:31 --> 00:22:34 1859 look like a warm up.
00:22:34 --> 00:22:37 Two years ago the same institute surveyed
00:22:37 --> 00:22:40 more than 56 sun like stars in
00:22:40 --> 00:22:43 Kepler data and found stars like ours
00:22:43 --> 00:22:46 appear to produce superflares roughly once a
00:22:46 --> 00:22:49 century each. Which was uncomfortable
00:22:49 --> 00:22:51 because we have four centuries of sunspot
00:22:51 --> 00:22:54 records and no superflare in them.
00:22:55 --> 00:22:57 Anna: So either we're unusual or we're
00:22:57 --> 00:23:00 overdue, or the uh, comparison is wrong
00:23:01 --> 00:23:01 and
00:23:01 --> 00:23:03 Avery: this paper goes at it from our own star
00:23:03 --> 00:23:06 rather than from other stars. Natalie
00:23:06 --> 00:23:09 Krivova and colleagues took the 300
00:23:09 --> 00:23:11 strongest solar flares recorded between
00:23:11 --> 00:23:14 2010 and 2016 and
00:23:14 --> 00:23:17 correlated the energy released in each with
00:23:17 --> 00:23:19 the size of the active region it came from.
00:23:20 --> 00:23:23 You get a scaling relation, bigger magnetic
00:23:23 --> 00:23:26 region, more available energy, and
00:23:26 --> 00:23:26 then you
00:23:26 --> 00:23:28 Anna: extrapolate it to the biggest spot we've
00:23:28 --> 00:23:31 Avery: ever seen, a sunspot group from
00:23:31 --> 00:23:33 1947, the largest in
00:23:33 --> 00:23:36 400 years of systematic observation,
00:23:36 --> 00:23:39 covering about 6/10 of 1%
00:23:39 --> 00:23:42 of the solar disc. Run it through the
00:23:42 --> 00:23:44 relation and a region that size holds
00:23:44 --> 00:23:47 enough stored magnetic energy to power a
00:23:47 --> 00:23:50 superflare. Krivova's line is
00:23:50 --> 00:23:53 blunt. Our sun has superflare potential,
00:23:53 --> 00:23:56 it can produce massive sunspots. And
00:23:56 --> 00:23:58 those can serve as the starting point for the
00:23:58 --> 00:24:01 most extreme bursts of radiation.
00:24:02 --> 00:24:03 Anna: Caveats, please.
00:24:03 --> 00:24:05 This is the kind of result that gets a
00:24:05 --> 00:24:06 terrible headline.
00:24:07 --> 00:24:10 Avery: Three and they matter. An
00:24:10 --> 00:24:12 extrapolated scaling relation is not a
00:24:12 --> 00:24:15 prediction. It says the energy budget is
00:24:15 --> 00:24:17 there, not that the sun will spend it.
00:24:18 --> 00:24:20 1947 produced large flares,
00:24:20 --> 00:24:23 but nothing like a superflare. So having the
00:24:23 --> 00:24:26 potential is demonstrably not the same as
00:24:26 --> 00:24:29 using it. And the spot coverage on the
00:24:29 --> 00:24:32 genuinely super flaring Kepler stars is still
00:24:32 --> 00:24:34 well beyond anything our sun has shown.
00:24:35 --> 00:24:37 Anna: What's the independent evidence it has ever
00:24:37 --> 00:24:37 happened?
00:24:38 --> 00:24:41 Avery: That comes from Earth. And it's rather
00:24:41 --> 00:24:43 wonderful. Tree rings and polar
00:24:43 --> 00:24:46 ice record sudden spikes in cosmogenic
00:24:46 --> 00:24:49 isotopes. Carbon 14 in wood,
00:24:49 --> 00:24:52 beryllium 10 in ice. And there are
00:24:52 --> 00:24:55 several sharp events in the record. The best
00:24:55 --> 00:24:58 known around 774 of the Common
00:24:58 --> 00:24:59 Era and another around
00:25:00 --> 00:25:02 993. Almost
00:25:03 --> 00:25:05 certainly extreme solar particle events
00:25:06 --> 00:25:08 far larger than anything in the instrumental
00:25:08 --> 00:25:09 era.
00:25:09 --> 00:25:12 So the geological answer is yes. It
00:25:12 --> 00:25:14 happens on roughly millennial
00:25:14 --> 00:25:15 timescales.
00:25:16 --> 00:25:18 Anna: And the practical read, not
00:25:18 --> 00:25:19 alarm.
00:25:19 --> 00:25:22 Avery: Infrastructure. A, uh, Carrington class event
00:25:22 --> 00:25:24 today is a grid and satellite problem.
00:25:24 --> 00:25:27 And that's exactly what space weather
00:25:27 --> 00:25:28 forecasting exists for.
00:25:29 --> 00:25:32 Australia's own Space Weather Forecasting
00:25:32 --> 00:25:34 Centre sits inside the Bureau of Meteorology
00:25:35 --> 00:25:38 and issues the warnings airlines, power
00:25:38 --> 00:25:40 operators and satellite fleets act on.
00:25:41 --> 00:25:44 It's also the reason the Aurora Australis
00:25:44 --> 00:25:46 gets spectacular. The same particles,
00:25:47 --> 00:25:48 a, um, much smaller dose.
00:25:48 --> 00:25:50 Anna: And before we get into Skywatch,
00:25:51 --> 00:25:53 I believe you have a couple of storey updates
00:25:53 --> 00:25:54 for us.
00:25:54 --> 00:25:56 Avery: Two quick developments from the last couple
00:25:56 --> 00:25:59 of days. The first is a sequel to
00:25:59 --> 00:26:01 a storey we opened on the third.
00:26:02 --> 00:26:05 NASA awarded Blue Origin a firm
00:26:05 --> 00:26:07 fixed price contract worth about $700
00:26:07 --> 00:26:10 million to build the Mars
00:26:10 --> 00:26:12 telecommunications network. A relay
00:26:12 --> 00:26:15 orbiter on a Blue Ring bus launching
00:26:15 --> 00:26:18 on New Glenn, delivered by the end of
00:26:18 --> 00:26:21 2028 and operational at Mars
00:26:21 --> 00:26:24 by 2030. Rocket Lab was the
00:26:24 --> 00:26:25 losing bidder.
00:26:25 --> 00:26:27 Anna: And Rocket Lab has now protested
00:26:28 --> 00:26:29 filed
00:26:29 --> 00:26:31 Avery: with the Government Accountability Office on
00:26:31 --> 00:26:34 Friday the 11th two grounds
00:26:34 --> 00:26:36 that the award appears inconsistent with the
00:26:36 --> 00:26:39 eligibility criteria Congress mandated
00:26:39 --> 00:26:42 for the procurement and that NASA's Technical
00:26:42 --> 00:26:45 Review of Rocket Lab's proposal contained
00:26:45 --> 00:26:48 what the company calls incorrect assertions
00:26:48 --> 00:26:50 and conclusions. Their framing is
00:26:50 --> 00:26:53 that procurement standards exist to ensure
00:26:53 --> 00:26:56 fair competition and and protect public
00:26:56 --> 00:26:56 investment.
00:26:57 --> 00:26:58 Anna: How do these usually go?
00:26:58 --> 00:27:01 Avery: Historically, not well for the protester.
00:27:01 --> 00:27:03 And there's a neat irony in the precedent.
00:27:04 --> 00:27:06 When Blue Origin protested NASA's Lunar
00:27:06 --> 00:27:09 Lander Award in 2021, the
00:27:09 --> 00:27:11 GAO denied it. That July, Blue
00:27:11 --> 00:27:14 Origin sued And lost in November. And
00:27:14 --> 00:27:17 NASA awarded Blue origin a, uh, second lander
00:27:17 --> 00:27:19 contract anyway in 2023.
00:27:20 --> 00:27:23 The GAO works to a statutory hundred day
00:27:23 --> 00:27:25 clock, which puts a decision around mid
00:27:25 --> 00:27:26 December.
00:27:27 --> 00:27:29 Anna: And we should say plainly that neither NASA
00:27:29 --> 00:27:32 nor Blue Origin has responded publicly, as we
00:27:32 --> 00:27:34 record they haven't.
00:27:34 --> 00:27:36 Avery: And we're not going to guess at the merits.
00:27:37 --> 00:27:39 This is a procurement dispute between two
00:27:39 --> 00:27:42 serious companies. And we'll report what the
00:27:42 --> 00:27:44 GAO finds. And the second
00:27:44 --> 00:27:47 update, Starship Flight 14,
00:27:47 --> 00:27:50 which we've tracked since Booster 21's static
00:27:50 --> 00:27:53 fire cleared at the end of August, has moved
00:27:53 --> 00:27:55 again. It was no earlier than the
00:27:55 --> 00:27:58 15th of September. As of Thursday the
00:27:58 --> 00:28:01 10th, it's no earlier than the 18th.
00:28:01 --> 00:28:04 Same vehicles, Booster 21 and
00:28:04 --> 00:28:07 Ship 41, both flying for the first
00:28:07 --> 00:28:10 time. Both block 3 from Pad
00:28:10 --> 00:28:13 2 at Starbase. Third flight of
00:28:13 --> 00:28:14 Starship version 3.
00:28:15 --> 00:28:18 And the headline objectives are big. The
00:28:18 --> 00:28:20 first attempt at an actual orbital trajectory
00:28:20 --> 00:28:23 and the first deployment of real satellites.
00:28:23 --> 00:28:26 Around 20 operational Starlink V3
00:28:26 --> 00:28:27 spacecraft.
00:28:28 --> 00:28:30 Anna: And I want to correct something we said on
00:28:30 --> 00:28:31 air earlier in the month.
00:28:31 --> 00:28:34 Avery: You do, and I'm glad you're doing it. When
00:28:34 --> 00:28:37 we first previewed this flight, we described
00:28:37 --> 00:28:39 it as including the first attempt to catch
00:28:39 --> 00:28:41 the ship itself with the tower arms.
00:28:42 --> 00:28:44 The current public flight plan has that catch
00:28:44 --> 00:28:47 deferred to a later mission. The booster is
00:28:47 --> 00:28:50 targeting a water landing in the Gulf, and
00:28:50 --> 00:28:52 the ship a, uh, splashdown in the Indian
00:28:52 --> 00:28:53 Ocean.
00:28:53 --> 00:28:56 Anna: So orbital trajectory, starlink
00:28:56 --> 00:28:59 deployment, water recoveries. No tower
00:28:59 --> 00:29:00 catch of the ship on this one.
00:29:00 --> 00:29:01 As things stand.
00:29:02 --> 00:29:05 Avery: As things stand. And SpaceX has a
00:29:05 --> 00:29:08 habit of changing the profile late, so we'll
00:29:08 --> 00:29:11 take it as it comes, no earlier than the
00:29:11 --> 00:29:13 Anna: 18th and to the sky for the week
00:29:13 --> 00:29:16 ahead. A good one because the Moon stays out
00:29:16 --> 00:29:19 of the way. New Moon was yesterday afternoon,
00:29:19 --> 00:29:21 so we're into thin evening crescents,
00:29:21 --> 00:29:24 building to first quarter on Friday the 18th,
00:29:24 --> 00:29:26 and dark mornings all week.
00:29:26 --> 00:29:29 Southern hemisphere first from
00:29:29 --> 00:29:31 Sydney and similar latitudes. Venus rewards
00:29:31 --> 00:29:34 being prompt, low in the west after
00:29:34 --> 00:29:36 sunset, unmissable at magnitude
00:29:36 --> 00:29:39 -4.8, heading for greatest
00:29:39 --> 00:29:42 brilliancy on Friday the 18th. Note
00:29:42 --> 00:29:44 that date some listings give the 22nd
00:29:45 --> 00:29:47 from a different definition of the peak. We
00:29:47 --> 00:29:49 use the 18th and there's a
00:29:49 --> 00:29:51 Avery: conjunction right on top of us.
00:29:51 --> 00:29:54 Anna: Tomorrow and Monday evening a very
00:29:54 --> 00:29:57 thin crescent sweeps past Venus half
00:29:57 --> 00:30:00 a degree apart at closest, a moon's
00:30:00 --> 00:30:02 width in front of Spica uh, in Virgo,
00:30:03 --> 00:30:05 one of the lovely naked eye sights of the
00:30:05 --> 00:30:07 year. And southern observers get the better
00:30:07 --> 00:30:10 geometry. The pair sits higher at the same
00:30:10 --> 00:30:13 stage of twilight than from North America, if
00:30:13 --> 00:30:16 you own a camera and a tripod, Sunday evening
00:30:16 --> 00:30:16 is the one.
00:30:17 --> 00:30:20 Avery: And Mercury, since we spent 10 minutes
00:30:20 --> 00:30:22 Anna: on it, worth trying. And be realistic.
00:30:23 --> 00:30:26 Magnitude minus 0.5, which is
00:30:26 --> 00:30:28 bright but only 2 degrees up 20 minutes after
00:30:28 --> 00:30:31 sunset. You need a flat western horizon,
00:30:32 --> 00:30:34 clean air and binoculars to find it before
00:30:34 --> 00:30:37 your eye does a, uh, tick the box observation
00:30:37 --> 00:30:39 rather than a spectacle. But there's
00:30:39 --> 00:30:40 something to be said for looking at the
00:30:40 --> 00:30:41 planet.
00:30:41 --> 00:30:43 We've just spent, uh, a segment taking apart
00:30:43 --> 00:30:46 Saturn, the week's reliable telescope target
00:30:46 --> 00:30:49 for everybody, building towards opposition on
00:30:49 --> 00:30:51 the 4th of October. With the rings about 7
00:30:51 --> 00:30:54 degrees open from the south, it rises in the
00:30:54 --> 00:30:56 east in the evening and rides high through
00:30:56 --> 00:30:59 the middle of the night. Rings plus Titan
00:30:59 --> 00:31:02 is a five minute look that never gets old.
00:31:02 --> 00:31:04 Avery: North America, your turn.
00:31:04 --> 00:31:07 Anna: Saturn's the same target, different timing,
00:31:07 --> 00:31:10 up around midnight and about 50 degrees high
00:31:10 --> 00:31:12 by 2 in the morning, which is superb altitude
00:31:12 --> 00:31:15 for detail. Two satellite events in the small
00:31:15 --> 00:31:18 hours for telescope owners. Dione transits
00:31:18 --> 00:31:21 Saturn's north polar region from about 2:55
00:31:21 --> 00:31:23 Eastern for roughly 40 minutes. And
00:31:23 --> 00:31:26 Tethys slides into Saturn's shadow around 10
00:31:26 --> 00:31:29 past 2. And Mars is your predawn
00:31:29 --> 00:31:31 object, up about half past one and working
00:31:31 --> 00:31:34 through Gemini on the 18th, it passes 6
00:31:34 --> 00:31:37 degrees south of Pollux. An easy colour
00:31:37 --> 00:31:39 comparison of orange planet against orange
00:31:39 --> 00:31:40 giant.
00:31:40 --> 00:31:43 Avery: Now the one I'm most pleased about. The
00:31:43 --> 00:31:44 supernova.
00:31:44 --> 00:31:46 Anna: This is the week's observing gift. There's a
00:31:46 --> 00:31:49 type 1A supernova going off in the galaxy
00:31:49 --> 00:31:52 NGC 7331 in
00:31:52 --> 00:31:53 Pegasus.
00:31:53 --> 00:31:56 SN2026AAIV,
00:31:56 --> 00:31:59 picked up by the Atlas survey at the start of
00:31:59 --> 00:32:01 the month and sitting around magnitude 12,
00:32:02 --> 00:32:04 peaking near the 10th. That's comfortably
00:32:04 --> 00:32:06 within reach of an 8 inch telescope under a
00:32:06 --> 00:32:09 decent sky and well within reach of a modest
00:32:09 --> 00:32:12 camera on a tracking mount. The galaxy's a
00:32:12 --> 00:32:14 lovely target in its own right. A bright
00:32:14 --> 00:32:17 spiral about 40 million light years off,
00:32:17 --> 00:32:20 often called the Deneb Galaxy. With the Deer
00:32:20 --> 00:32:23 lit group in the same field. Sources differ
00:32:23 --> 00:32:25 on the distance anywhere from 30 to 45
00:32:25 --> 00:32:28 million light years. So treat 40 as a round
00:32:28 --> 00:32:29 figure.
00:32:29 --> 00:32:30 Avery: Hemisphere split.
00:32:30 --> 00:32:33 Anna: North America has the clear advantage.
00:32:33 --> 00:32:36 Pegasus is high overhead in your evening,
00:32:36 --> 00:32:39 close to ideal from Sydney, it's a
00:32:39 --> 00:32:42 real challenge. The galaxy sits at about
00:32:42 --> 00:32:45 34 degrees north declination, so from
00:32:45 --> 00:32:48 34 degrees south it only reaches around 22
00:32:48 --> 00:32:50 degrees above the northern horizon through a
00:32:50 --> 00:32:53 lot of atmosphere and usually a lot of city
00:32:53 --> 00:32:53 light.
00:32:53 --> 00:32:56 Doable from a dark site with a clear northern
00:32:56 --> 00:32:59 aspect around 10 to 11 in the evening.
00:32:59 --> 00:33:02 Avery: And why it's worth the trouble because
00:33:02 --> 00:33:05 Anna: a, uh, type 1A is the standard candle. The
00:33:05 --> 00:33:07 entire accelerating universe result is built
00:33:07 --> 00:33:10 on the thing three Nobel laureates were
00:33:10 --> 00:33:13 defending at the end of August. And three
00:33:13 --> 00:33:15 days ago we covered Chandra, finding 84
00:33:15 --> 00:33:18 hypersoft X ray sources that may be
00:33:18 --> 00:33:21 the progenitor system's producing exactly
00:33:21 --> 00:33:23 this kind of explosion. So when you put an
00:33:23 --> 00:33:26 eyepiece on that faint dot in Pegasus, you're
00:33:26 --> 00:33:28 looking at one member of the population that
00:33:28 --> 00:33:31 measures the expansion of the universe. Not a
00:33:31 --> 00:33:34 bad Saturday night zodiacal light as
00:33:34 --> 00:33:37 well. And the equinox rule applies, so
00:33:37 --> 00:33:38 it's uh, a both hemispheres item with
00:33:38 --> 00:33:41 opposite instructions. We're inside two weeks
00:33:41 --> 00:33:44 of the equinox on the 22nd and the
00:33:44 --> 00:33:47 ecliptic stands steeply to the horizon, which
00:33:47 --> 00:33:49 is what makes this faint cone of dust
00:33:49 --> 00:33:52 scattered sunlight visible at all. From the
00:33:52 --> 00:33:54 south it's an evening object west after
00:33:54 --> 00:33:57 full darkness, a tall faint wedge
00:33:57 --> 00:33:59 rising from where the sun set.
00:33:59 --> 00:34:02 The false dusk. From the north it's the
00:34:02 --> 00:34:05 mirror image pre dawn. In the east, the
00:34:05 --> 00:34:08 false dawn. Either way, dark sight,
00:34:08 --> 00:34:11 no moon patience. This new moon
00:34:11 --> 00:34:12 window is the best chance until early
00:34:12 --> 00:34:13 October.
00:34:13 --> 00:34:15 Avery: Safety passage.
00:34:15 --> 00:34:18 Anna: Yes, and it's in every episode for a reason.
00:34:19 --> 00:34:21 With Venus this bright, some of you will try
00:34:21 --> 00:34:23 to find it in daylight and it is a real
00:34:23 --> 00:34:25 observation. Venus at Ah
00:34:25 --> 00:34:28 -4.8 is visible in a blue sky. If you
00:34:28 --> 00:34:31 know exactly where to look, do not sweep the
00:34:31 --> 00:34:33 sky near the sun with binoculars or a
00:34:33 --> 00:34:34 telescope to hunt for it.
00:34:34 --> 00:34:37 And do not try for Mercury in twilight with
00:34:37 --> 00:34:39 the sun still up. Concentrated sunlight
00:34:39 --> 00:34:42 through any optic causes permanent retinal
00:34:42 --> 00:34:44 damage in a fraction of a second with no
00:34:44 --> 00:34:47 pain. To warn you if you're ever looking at
00:34:47 --> 00:34:50 or near the sun, use a filter certified to
00:34:50 --> 00:34:53 ISO 123122,
00:34:53 --> 00:34:55 fit it over the front of the instrument,
00:34:55 --> 00:34:58 never at the eyepiece end and inspect it for
00:34:58 --> 00:35:00 scratches or pinholes every single time
00:35:00 --> 00:35:03 before it goes near your eye looking further
00:35:03 --> 00:35:05 ahead. Two for the diary. Saturn at
00:35:05 --> 00:35:07 opposition on the 4th of October.
00:35:08 --> 00:35:10 And on the 6th of October a pre dawn
00:35:10 --> 00:35:13 lunar occultation of Jupiter,
00:35:13 --> 00:35:16 the moon passing directly in front of the
00:35:16 --> 00:35:18 planet. Billed as the year's spectacular
00:35:18 --> 00:35:21 event. We'll build a proper curtain raiser
00:35:21 --> 00:35:24 nearer the time. And that's the weekend wrap
00:35:24 --> 00:35:27 for Saturday 12th September. Mercury has
00:35:27 --> 00:35:29 lost more of itself than we thought, as much
00:35:29 --> 00:35:32 as 23 kilometres off its diameter. And
00:35:32 --> 00:35:34 we missed it because 4 billion years of
00:35:34 --> 00:35:36 impacts have been quietly burying the
00:35:36 --> 00:35:39 evidence. BepiColombo arrives in about
00:35:39 --> 00:35:41 10 weeks with the instrument to cheque.
00:35:41 --> 00:35:44 Avery: Looking back on the week a rocket reached
00:35:44 --> 00:35:46 orbit from western European soil for the
00:35:46 --> 00:35:49 first time. The moon may have assembled in
00:35:49 --> 00:35:52 five hours rather than centuries. Hubble and
00:35:52 --> 00:35:55 Webb found 27 new worlds beyond
00:35:55 --> 00:35:57 Neptune. 109 radio
00:35:57 --> 00:36:00 bursts weighed the universe's missing gas
00:36:00 --> 00:36:03 and magnetars turned out to be half of all
00:36:03 --> 00:36:04 neutron stars.
00:36:05 --> 00:36:07 Anna: Plus new evidence our own sun has the
00:36:07 --> 00:36:09 magnetic energy budget for a super flare
00:36:09 --> 00:36:12 rocket. Lab has taken NASA to the GAO over
00:36:12 --> 00:36:15 the Mars relay contract and Starship's
00:36:15 --> 00:36:17 first orbital attempt is now no earlier than
00:36:17 --> 00:36:18 the 18th.
00:36:19 --> 00:36:21 Avery: Everything we covered with links to every
00:36:21 --> 00:36:24 paper and source release is in the show
00:36:24 --> 00:36:24 notes
00:36:24 --> 00:36:27 and@astronomydaily.IO
00:36:27 --> 00:36:28 and the contact form
00:36:28 --> 00:36:31 Anna: on the site is real and we do read it more
00:36:31 --> 00:36:32 than one storey.
00:36:32 --> 00:36:34 This fortnight started as a listener
00:36:34 --> 00:36:36 question. If there's something you want us to
00:36:36 --> 00:36:38 take apart properly, tell us.
00:36:38 --> 00:36:41 Avery: We're back on Monday with the weekday run.
00:36:41 --> 00:36:42 Anna: I'm Anna.
00:36:42 --> 00:36:43 Avery: And I'm Avery.
00:36:44 --> 00:36:46 Clear Skies. And if you're in the southern
00:36:46 --> 00:36:49 hemisphere, go out tomorrow evening and look
00:36:49 --> 00:36:51 west. The Moon and Venus half a
00:36:51 --> 00:36:54 degree apart in front of Spica. You won't
00:36:54 --> 00:36:57 need a telescope and you won't forget it.