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This episode includes AI-generated content.
00:00:00 --> 00:00:02 Anna: Hi everyone. Welcome back. It is
00:00:02 --> 00:00:05 a Tuesday morning in Sydney, a um, Monday
00:00:05 --> 00:00:08 afternoon in New York and somewhere
00:00:08 --> 00:00:11 off the southern tip of Japan a
00:00:11 --> 00:00:13 rocket has just tried to carry a spacecraft
00:00:13 --> 00:00:15 towards the moons of Mars.
00:00:16 --> 00:00:18 Avery: And uh, this one is planning to come back
00:00:18 --> 00:00:21 with a handful of Phobos in its pocket
00:00:21 --> 00:00:24 and a landing in South Australia pencilled in
00:00:24 --> 00:00:25 for 2031.
00:00:26 --> 00:00:28 Anna: Welcome to Astronomy AstroDailyPod.
00:00:28 --> 00:00:29 I'm Anna.
00:00:29 --> 00:00:32 Avery: And I'm Avery. Today, Japan's Martian
00:00:32 --> 00:00:35 moons exploration mission mmx and the
00:00:35 --> 00:00:38 question it was built to answer then more
00:00:38 --> 00:00:40 than half of the biggest telescope mirror
00:00:40 --> 00:00:43 ever made has now reached Chile. A year
00:00:43 --> 00:00:45 old preprint finally becomes a paper with an
00:00:45 --> 00:00:48 awkward message for anyone modelling the dawn
00:00:48 --> 00:00:50 of the universe. And a musical looking radial
00:00:50 --> 00:00:53 source hiding behind the Milky Way turns out
00:00:53 --> 00:00:55 to be a uh, cosmic phoenix.
00:00:55 --> 00:00:58 Anna: Plus Hera's breaking burn, the Orionid
00:00:58 --> 00:01:01 meteors and the last week of Venus in the
00:01:01 --> 00:01:03 evening sky. Let's go.
00:01:04 --> 00:01:05 Avery: Ready when you are.
00:01:05 --> 00:01:08 Anna: Okay. Mars has two moons
00:01:08 --> 00:01:10 and nobody's quite sure where either of them
00:01:10 --> 00:01:13 came from. Phobos is about
00:01:13 --> 00:01:16 27 kilometres across at its longest,
00:01:16 --> 00:01:19 lumpy, dark and so close to
00:01:19 --> 00:01:21 Mars that it goes around three times a day.
00:01:22 --> 00:01:24 Deimos is smaller and further out.
00:01:25 --> 00:01:28 They look a lot like asteroids. That
00:01:28 --> 00:01:29 is half the puzzle.
00:01:29 --> 00:01:32 Avery: They were found in 1877 by Asaph
00:01:32 --> 00:01:35 hall at the U.S. naval Observatory and named
00:01:35 --> 00:01:37 for the attendance of the God of Phobos.
00:01:38 --> 00:01:40 Fear and Deimos dread.
00:01:40 --> 00:01:43 Phobos orbits only about 6 kilometres
00:01:43 --> 00:01:46 above the Martian surface, closer than any
00:01:46 --> 00:01:48 other moon to its planet in the solar system.
00:01:48 --> 00:01:51 And it's slowly spiralling inwards. In
00:01:51 --> 00:01:53 something like 30 to 50 million years, it's
00:01:53 --> 00:01:56 expected to be torn apart or crash into Mars.
00:01:56 --> 00:01:59 Anna: So it's a moon with a deadline.
00:01:59 --> 00:02:02 It's also scarred by a crater called
00:02:02 --> 00:02:05 Stickney, about nine kilometres wide
00:02:05 --> 00:02:07 on a body only 27 kilometres
00:02:07 --> 00:02:10 long. Whatever made that came
00:02:11 --> 00:02:13 very close to breaking Phobos apart.
00:02:13 --> 00:02:15 Avery: And the other half of the puzzle is that
00:02:15 --> 00:02:18 their orbits don't look like asteroid orbits.
00:02:18 --> 00:02:21 Captured asteroids should end up on tilted
00:02:21 --> 00:02:24 stretched paths. Phobos and Deimos
00:02:24 --> 00:02:27 sit almost in Mars equatorial plane
00:02:27 --> 00:02:29 on nearly circular orbits.
00:02:29 --> 00:02:31 That's what you'd expect if they formed from
00:02:31 --> 00:02:34 a disc of debris around Mars itself thrown
00:02:34 --> 00:02:37 up by a giant impact. Two good
00:02:37 --> 00:02:39 stories. And um, they predict different
00:02:39 --> 00:02:41 rocks, which
00:02:41 --> 00:02:43 Anna: is exactly why you go and get some.
00:02:44 --> 00:02:47 That is the job of mmx, the Martian
00:02:47 --> 00:02:49 Moons exploration mission led by
00:02:49 --> 00:02:52 jaxa, the Japan Aerospace Exploration
00:02:52 --> 00:02:55 Agency, with NASA, the French Space
00:02:55 --> 00:02:58 Agency sines, the German Aerospace
00:02:58 --> 00:03:00 Centre DLR and the European Space Agency
00:03:00 --> 00:03:01 as Partners.
00:03:02 --> 00:03:03 Avery: So what happened?
00:03:04 --> 00:03:07 Anna: It went. JAXA has confirmed
00:03:07 --> 00:03:10 that the H3 lifted off and that MMX has
00:03:10 --> 00:03:12 separated from the rocket and is on its way.
00:03:13 --> 00:03:16 The spacecraft weighed about 4 1/2 tons at uh
00:03:16 --> 00:03:19 launch, which tells you how much fuel a round
00:03:19 --> 00:03:20 trip to Mars takes.
00:03:20 --> 00:03:23 Avery: Worth saying, because H3 has not had an
00:03:23 --> 00:03:26 easy life. Its very first flight was
00:03:26 --> 00:03:29 lost in 2023. A clean launch
00:03:29 --> 00:03:32 carrying a flagship planetary mission matters
00:03:32 --> 00:03:33 for the vehicle as much as for the
00:03:33 --> 00:03:34 spacecraft.
00:03:34 --> 00:03:37 Anna: The cruise to Mars takes about a year.
00:03:37 --> 00:03:40 ESA's timeline has MMX entering orbit around
00:03:40 --> 00:03:43 Mars in August 2027
00:03:43 --> 00:03:45 and moving onto what's called a quasi
00:03:45 --> 00:03:48 satellite orbit around Phobos from September
00:03:48 --> 00:03:51 2027. Phobos is too small to
00:03:51 --> 00:03:53 orbit in the ordinary way, so the
00:03:53 --> 00:03:56 spacecraft flies a loop around it while both
00:03:56 --> 00:03:57 go round Mars together.
00:03:58 --> 00:04:00 Avery: Then comes a long, careful survey.
00:04:01 --> 00:04:04 MMX carries 11 science instruments in all,
00:04:04 --> 00:04:07 seven on the main spacecraft and four on a
00:04:07 --> 00:04:09 small rover. One of those seven is
00:04:09 --> 00:04:12 NASA's contribution, a gamma ray and neutron
00:04:12 --> 00:04:15 spectrometer called Megan, which reads the
00:04:15 --> 00:04:18 elements in Phobos surface from orbit. That's
00:04:18 --> 00:04:19 how the team chooses where to land.
00:04:19 --> 00:04:22 Anna: The rover is called Edifics, built by
00:04:22 --> 00:04:25 CNES and DLR. It weighs about
00:04:25 --> 00:04:28 25 kilogrammes on earth. On
00:04:28 --> 00:04:30 Phobos, ESA says it will weigh about
00:04:30 --> 00:04:33 15 grammes. 15 grammes?
00:04:34 --> 00:04:35 You could knock it off the surface with a
00:04:35 --> 00:04:38 sneeze, which is why the rover's first job is
00:04:38 --> 00:04:41 to find out how Phobos surface actually
00:04:41 --> 00:04:43 behaves before the main spacecraft commits to
00:04:43 --> 00:04:44 touching it.
00:04:44 --> 00:04:47 Avery: Edifics is due to be released in early
00:04:47 --> 00:04:48 2029.
00:04:48 --> 00:04:51 The landing and sampling follow in 2030, and
00:04:51 --> 00:04:53 the return module heads home with at least 10
00:04:53 --> 00:04:56 grammes of Phobos. MMX carries
00:04:56 --> 00:04:58 two separate sampling devices, so it isn't
00:04:58 --> 00:05:01 relying on a single grab. It will also study
00:05:01 --> 00:05:03 Deimos from a distance and fly past it and
00:05:03 --> 00:05:04 Mars on the way out.
00:05:05 --> 00:05:08 Anna: For scale, Hayabusa2 brought back about
00:05:08 --> 00:05:10 five and a half grammes from asteroid Ryugu,
00:05:10 --> 00:05:13 and that tiny amount has fed hundreds of
00:05:13 --> 00:05:15 studies. GAXA has done sample return
00:05:15 --> 00:05:16 twice before.
00:05:17 --> 00:05:19 This is the first time anyone has tried it in
00:05:19 --> 00:05:21 the Mars system, and it sits alongside
00:05:21 --> 00:05:24 Europe's plans, too. ESA's Mars Express,
00:05:25 --> 00:05:27 now confirmed to operate until at least 2029,
00:05:28 --> 00:05:30 may support MMX's observations. And the
00:05:30 --> 00:05:33 ExoMars Rothland Franklin rover is meant to
00:05:33 --> 00:05:35 complement it by drilling beneath the Martian
00:05:35 --> 00:05:38 surface. 10 grammes sounds
00:05:38 --> 00:05:41 tiny, and it's worth explaining why the
00:05:41 --> 00:05:43 people who built this are so excited about
00:05:43 --> 00:05:45 it. A captured asteroid and a chunk of
00:05:45 --> 00:05:48 Mars thrown into orbit would carry very
00:05:48 --> 00:05:50 different chemical fingerprints in their
00:05:50 --> 00:05:53 minerals, in their water, in the ratios of
00:05:53 --> 00:05:55 isotopes that labs on Earth can measure to
00:05:55 --> 00:05:56 astonishing precision.
00:05:57 --> 00:06:00 Orbiters can hint at those differences. A
00:06:00 --> 00:06:01 sample settles them.
00:06:01 --> 00:06:04 Avery: And there's a bonus. Phobos has spent
00:06:04 --> 00:06:07 billions of years sitting right next to Mars
00:06:07 --> 00:06:09 collecting material blasted off the Martian
00:06:09 --> 00:06:12 surface by impacts. So a, uh, Phobos
00:06:12 --> 00:06:14 sample may well contain little grains of
00:06:14 --> 00:06:17 Mars itself, delivered without anyone having
00:06:17 --> 00:06:19 to land on Mars and fly back up.
00:06:19 --> 00:06:22 Anna: This also connects to a story we covered back
00:06:22 --> 00:06:25 in episode 181, the study
00:06:25 --> 00:06:27 suggesting Deimos may have formed from a
00:06:27 --> 00:06:30 single impact on Mars. MMX is
00:06:30 --> 00:06:33 the test. If the moons are Martian debris,
00:06:33 --> 00:06:33 the
00:06:33 --> 00:06:36 Avery: rocks will say so here's the southern
00:06:36 --> 00:06:38 hemisphere bit, and, um, it's a good one.
00:06:38 --> 00:06:41 When MMX comes home in 2031,
00:06:41 --> 00:06:43 the capsule is expected to land in South
00:06:43 --> 00:06:44 Australia.
00:06:44 --> 00:06:47 The Australian Space Agency and JAXA
00:06:47 --> 00:06:49 formalise their cooperation on the mission in
00:06:49 --> 00:06:50 2023.
00:06:51 --> 00:06:53 Anna: And this is a path well worn.
00:06:53 --> 00:06:56 JAXA's Hayabusa capsule came down at Woomera
00:06:56 --> 00:06:58 in 2010 with grains from asteroid
00:06:58 --> 00:07:01 Itokawa. And Hayabusa2's capsule
00:07:01 --> 00:07:04 landed there in December 2020 with material
00:07:04 --> 00:07:07 from Ryugu. One honest
00:07:07 --> 00:07:10 caveat. The agency's own page says
00:07:10 --> 00:07:12 South Australia, rather than naming a site
00:07:12 --> 00:07:15 for mmx. So we're not going to name one for
00:07:15 --> 00:07:18 them. But if a third Japanese sample
00:07:18 --> 00:07:20 capsule streaks across an outback night sky
00:07:20 --> 00:07:23 in 2031, nobody will be surprised.
00:07:23 --> 00:07:26 Avery: ESA's project scientist Elliot Sefton Nash
00:07:26 --> 00:07:29 calls returned samples the gift that keeps on
00:07:29 --> 00:07:32 giving. The Apollo rocks are still producing
00:07:32 --> 00:07:34 papers more than 50 years on.
00:07:35 --> 00:07:38 If this works, Phobos will be on lab benches
00:07:38 --> 00:07:40 long after everyone who built MMX has
00:07:40 --> 00:07:41 retired.
00:07:41 --> 00:07:44 Anna: An ambiguous project indeed. And here's
00:07:44 --> 00:07:45 wishing them every success.
00:07:46 --> 00:07:48 Avery: Staying in the south. The The European
00:07:48 --> 00:07:51 Southern Observatory says more than half of
00:07:51 --> 00:07:53 the main mirror of its Extremely Large
00:07:53 --> 00:07:55 Telescope has now arrived in Chile.
00:07:55 --> 00:07:58 Anna: That mirror is 39 metres across.
00:07:58 --> 00:08:00 You can't cast a single piece of glass that
00:08:00 --> 00:08:02 size, so it's built from
00:08:02 --> 00:08:05 798 hexagonal segments that act
00:08:05 --> 00:08:07 together as one surface. And because the
00:08:07 --> 00:08:10 reflective coating wears out, ESO has made
00:08:10 --> 00:08:12 133 spares as well,
00:08:13 --> 00:08:16 931 segments in total, so
00:08:16 --> 00:08:18 that once the telescope is running, two
00:08:18 --> 00:08:20 segments a day can be swapped out for
00:08:20 --> 00:08:22 recoding without ever leaving a hole.
00:08:23 --> 00:08:26 Avery: Two a day, every day for the
00:08:26 --> 00:08:28 life of the telescope. That's a job
00:08:28 --> 00:08:31 description. And these aren't dinner plates.
00:08:31 --> 00:08:34 Each hexagon is roughly one and a half metres
00:08:34 --> 00:08:37 across and only a few centimetres thick.
00:08:37 --> 00:08:40 And ESO's spec is that the surface is smooth
00:08:40 --> 00:08:43 to better than 10nm, like less than
00:08:43 --> 00:08:45 a thousandth of the width of a human hair.
00:08:46 --> 00:08:49 Anna: Nearly 500 segments are now sitting at the
00:08:49 --> 00:08:51 ELT technical facility at Paranal.
00:08:52 --> 00:08:55 The journey is a genuinely European one.
00:08:55 --> 00:08:58 Blanks of a glass ceramic called Zerodur,
00:08:58 --> 00:09:01 cast by Schott in Germany, polished
00:09:01 --> 00:09:04 near Poitiers in France by Saffron Riosque,
00:09:05 --> 00:09:08 mounted on supports designed and made by two
00:09:08 --> 00:09:10 Dutch companies, fitted with sensors and
00:09:10 --> 00:09:13 actuators from France and Germany, and
00:09:13 --> 00:09:16 then shipped 10 kilometres to the
00:09:16 --> 00:09:19 Atacama by Danish logistics firm DSV.
00:09:19 --> 00:09:22 Avery: And the pace has changed. The first segments
00:09:22 --> 00:09:24 only reached chile in early 2024.
00:09:25 --> 00:09:27 Safran Riosque is now finishing a segment a
00:09:27 --> 00:09:30 day, and the very last one has entered
00:09:30 --> 00:09:33 production. ESO expects all of them to be in
00:09:33 --> 00:09:36 Chile within months now, one number
00:09:36 --> 00:09:38 Anna: to be careful with. ESO says the
00:09:38 --> 00:09:41 ELT project as a whole is more than
00:09:41 --> 00:09:44 75% complete and that the first
00:09:44 --> 00:09:46 observations with scientific instruments are
00:09:46 --> 00:09:49 planned for late 2030. If you've
00:09:49 --> 00:09:52 seen 2028, quoted for the ELT's first
00:09:52 --> 00:09:55 light in older material, those aren't quite
00:09:55 --> 00:09:57 the same milestone. But it's fair to say the
00:09:57 --> 00:10:00 science dates it's later than many people had
00:10:00 --> 00:10:00 in their heads.
00:10:01 --> 00:10:03 Avery: And the science, when it comes, is the reason
00:10:03 --> 00:10:04 to wait.
00:10:04 --> 00:10:07 The atmospheres of rocky planets around other
00:10:07 --> 00:10:10 stars, the first galaxies, and
00:10:10 --> 00:10:12 even whether the constants of physics have
00:10:12 --> 00:10:15 drifted over cosmic time. It sits on
00:10:15 --> 00:10:18 cerro armasones, about 20 kilometres from the
00:10:18 --> 00:10:21 Very Large Telescope at Parnal, under some
00:10:21 --> 00:10:24 of the darkest skies on Earth. And
00:10:24 --> 00:10:27 Australia, as an ESO strategic partner,
00:10:27 --> 00:10:29 has a seat at that table.
00:10:29 --> 00:10:32 Anna: Now a story about the first billion years of
00:10:32 --> 00:10:35 the universe told using galaxies in our
00:10:35 --> 00:10:36 own backyard.
00:10:37 --> 00:10:40 Avery: Quick background after the Big Bang cooled,
00:10:40 --> 00:10:42 the universe filled with neutral hydrogen
00:10:42 --> 00:10:44 gas, which soaks up the high energy
00:10:44 --> 00:10:47 ultraviolet light that can ionise it.
00:10:47 --> 00:10:49 Astronomers call that light the Lyman
00:10:49 --> 00:10:52 continuum. At some point, the first stars
00:10:52 --> 00:10:54 and galaxies produce enough of it to strip
00:10:54 --> 00:10:56 the electrons back off almost all that
00:10:56 --> 00:10:58 hydrogen. That's reionization.
00:10:59 --> 00:11:02 The big open question is which galaxies
00:11:02 --> 00:11:04 did the work and how the light got out?
00:11:05 --> 00:11:07 Anna: Because getting out is the hard part.
00:11:08 --> 00:11:10 A young galaxy is wrapped in its own gas.
00:11:11 --> 00:11:14 For years, a lot of simulations have assumed
00:11:14 --> 00:11:16 the escape route is blasted open by
00:11:16 --> 00:11:19 supernovae. Massive stars explode,
00:11:19 --> 00:11:22 drive a wind, clear the gas and the
00:11:22 --> 00:11:23 ultraviolet light pours out.
00:11:24 --> 00:11:26 Avery: A paper published in Nature Astronomy last
00:11:26 --> 00:11:29 week suggests it may be close to the other
00:11:29 --> 00:11:31 way round. Cody Carr and Ren
00:11:31 --> 00:11:34 Yitzen of Zhejiang University and 26
00:11:34 --> 00:11:37 co authors used the Hubble Space Telescope to
00:11:37 --> 00:11:39 look at six nearly identical compact
00:11:40 --> 00:11:42 star forming galaxies whose light left them
00:11:42 --> 00:11:45 roughly 3 to 4 billion years ago.
00:11:45 --> 00:11:48 Same chemistry, same size, same star
00:11:48 --> 00:11:51 formation rate. The main thing that differs
00:11:51 --> 00:11:53 is the age of their latest burst of stars.
00:11:53 --> 00:11:56 Anna: Why nearby galaxies? Because you
00:11:56 --> 00:11:58 can't measure this directly. In the early
00:11:58 --> 00:12:01 universe, any ionising light
00:12:01 --> 00:12:04 escaping a galaxy at that time gets soaked
00:12:04 --> 00:12:07 up by neutral gas between the galaxies long
00:12:07 --> 00:12:08 before it reaches us.
00:12:08 --> 00:12:11 So astronomers use local lookalikes from the
00:12:11 --> 00:12:14 low redshift Lyman Continuum Survey, where
00:12:14 --> 00:12:17 Hubble's Cosmic Origins Spectrograph can
00:12:17 --> 00:12:19 catch the escaping ultraviolet itself.
00:12:20 --> 00:12:22 Avery: And the pattern is striking. The youngest
00:12:22 --> 00:12:25 burst, at a mean stellar age of about
00:12:25 --> 00:12:27 2.7 million years, leaks the most.
00:12:28 --> 00:12:30 About 21% of its ionising light
00:12:30 --> 00:12:33 escapes and its wind is slow, around
00:12:33 --> 00:12:36 135 kilometres a second. The
00:12:36 --> 00:12:39 oldest bursts a little past 5 million years,
00:12:39 --> 00:12:42 leak almost nothing under half a percent.
00:12:42 --> 00:12:45 And their winds are running at 600 kilometres
00:12:45 --> 00:12:46 a second or more.
00:12:46 --> 00:12:49 Anna: That age matters because the most massive
00:12:49 --> 00:12:52 stars start going supernova at around 3
00:12:52 --> 00:12:55 million years. So the window opens
00:12:55 --> 00:12:57 early, while the light is being pushed out by
00:12:57 --> 00:13:00 radiation and stellar winds. And the
00:13:00 --> 00:13:02 supernovae, the thing many models were
00:13:02 --> 00:13:05 counting on to open the door, load the wind
00:13:05 --> 00:13:07 with neutral gas and close it.
00:13:07 --> 00:13:10 Avery: If you were listening in episode 199,
00:13:10 --> 00:13:13 when Andromeda's um, super bubbles turned out
00:13:13 --> 00:13:15 to be enough to keep a whole galaxy churning,
00:13:16 --> 00:13:19 or episode 194 and feedback that
00:13:19 --> 00:13:21 builds as well as breaks, this is
00:13:21 --> 00:13:23 another face of the same idea.
00:13:24 --> 00:13:26 Feedback is not one switch.
00:13:27 --> 00:13:29 Anna: Timing matters now, the honest
00:13:29 --> 00:13:32 bits. It's six galaxies. The
00:13:32 --> 00:13:34 stellar ages carry large uncertainties and
00:13:34 --> 00:13:37 the authors say so the hottest phase of the
00:13:37 --> 00:13:40 wind isn't measured. And these are nearby
00:13:40 --> 00:13:42 stand ins, not reionization era galaxies
00:13:42 --> 00:13:43 themselves.
00:13:44 --> 00:13:47 Also a disclosure from us. The preprint first
00:13:47 --> 00:13:49 appeared in October last year, so this is
00:13:49 --> 00:13:52 published this month rather than brand new.
00:13:52 --> 00:13:55 But the implication is clear enough to state
00:13:55 --> 00:13:58 simulations that only let the light out after
00:13:58 --> 00:14:00 the supernovae may need to let it out
00:14:00 --> 00:14:01 earlier.
00:14:01 --> 00:14:04 Avery: Last story before the quick hits.
00:14:04 --> 00:14:07 A radial source that looks like a, uh, treble
00:14:07 --> 00:14:07 clef.
00:14:08 --> 00:14:10 Anna: It goes by VLSS
00:14:10 --> 00:14:13 J03 18
00:14:13 --> 00:14:16 9.57.55, which is why everyone
00:14:16 --> 00:14:19 calls it the treble clef. It sits
00:14:19 --> 00:14:21 almost exactly behind the plane of the Milky
00:14:21 --> 00:14:24 Way in what astronomers call the zone of
00:14:24 --> 00:14:27 avoidance, where our own galaxy's dust and
00:14:27 --> 00:14:29 gas hide most of the universe behind it.
00:14:29 --> 00:14:32 It's been known for years, and at One point
00:14:32 --> 00:14:33 was thought to be a pulsar.
00:14:34 --> 00:14:36 Avery: A team led by Andrea Botellon UM of
00:14:36 --> 00:14:39 Italy's National Institute for Astrophysics
00:14:39 --> 00:14:42 combined X rays from NASA's Chandra and the
00:14:42 --> 00:14:44 Erosita survey with radio maps from the
00:14:44 --> 00:14:47 LOFAR network and India's upgraded GMRT
00:14:48 --> 00:14:50 plus infrared from the UK Infrared telescope.
00:14:51 --> 00:14:53 They found it sits in a massive galaxy
00:14:53 --> 00:14:54 cluster.
00:14:54 --> 00:14:57 In fact two clusters that collided a few
00:14:57 --> 00:14:59 hundred million years ago and are now moving
00:14:59 --> 00:15:00 apart.
00:15:00 --> 00:15:03 Anna: And the radio source itself is what's called
00:15:03 --> 00:15:06 a radio phoenix. Long ago,
00:15:06 --> 00:15:08 the supermassive black hole at the heart of
00:15:08 --> 00:15:11 the cluster blew out a cloud of fast
00:15:11 --> 00:15:14 particles and magnetic fields that glowed
00:15:14 --> 00:15:17 in radio, then faded. Then the
00:15:17 --> 00:15:19 cluster collision squeezed the old cloud and
00:15:19 --> 00:15:20 lit it back up.
00:15:21 --> 00:15:23 Avery: The giveaway is the colour. In
00:15:23 --> 00:15:26 radio terms, its brightness drops off
00:15:26 --> 00:15:28 incredibly steeply with frequency.
00:15:29 --> 00:15:32 The paper puts the spectral index above 4
00:15:32 --> 00:15:34 between 400 and 650
00:15:35 --> 00:15:37 MHz, which is extreme.
00:15:37 --> 00:15:40 That's the signature of old electrons that
00:15:40 --> 00:15:43 have lost most of their energy. The team
00:15:43 --> 00:15:45 estimates the filament electrons are around
00:15:45 --> 00:15:48 190 to 200 million years
00:15:48 --> 00:15:48 old.
00:15:48 --> 00:15:51 Anna: The cluster gas around it is hot, around
00:15:51 --> 00:15:54 6 kiloelectron volts in X ray terms,
00:15:54 --> 00:15:56 which is about 70 million degrees.
00:15:57 --> 00:15:59 And there's a nice detail in the author list.
00:16:00 --> 00:16:03 Rashid Sunyayev of the Sunyayev Zeldovich
00:16:03 --> 00:16:05 effect and Eugene Churasov are both on it.
00:16:06 --> 00:16:08 These are people who have spent careers
00:16:08 --> 00:16:09 reading hot cluster gas.
00:16:11 --> 00:16:14 Avery: As for the shape, NASA is careful to say the
00:16:14 --> 00:16:16 resemblance to a treble clef is pareidolia.
00:16:17 --> 00:16:19 Our brains finding a pattern.
00:16:19 --> 00:16:22 The real shape is probably sculpted by gas
00:16:22 --> 00:16:24 sloshing around inside the cluster.
00:16:24 --> 00:16:27 Anna: The thing is roughly 760
00:16:27 --> 00:16:30 kiloparsecs across, about two and a
00:16:30 --> 00:16:33 half million light years in a cluster
00:16:33 --> 00:16:36 weighing around half a million billion
00:16:36 --> 00:16:39 suns. Seen as it was about
00:16:39 --> 00:16:40 1 1/2
00:16:40 --> 00:16:43 Avery: billion years ago, the
00:16:43 --> 00:16:46 preprint dates from July. So this is a,
00:16:46 --> 00:16:48 uh, NASA release this month about a paper
00:16:48 --> 00:16:50 that's been circulating for three months
00:16:51 --> 00:16:53 and no Australian telescope in this one.
00:16:53 --> 00:16:56 It's a northern sky object, but
00:16:56 --> 00:16:59 steep spectrum, low frequency radio sources
00:16:59 --> 00:17:02 are exactly the kind of thing Ska Lo
00:17:02 --> 00:17:04 in Western Australia is being built to find.
00:17:05 --> 00:17:07 So Expect more Phoenixes.
00:17:07 --> 00:17:09 Anna: Three quick ones first.
00:17:10 --> 00:17:12 HERA ESA's asteroid mission
00:17:12 --> 00:17:14 completed its first braking manoeuvre on
00:17:14 --> 00:17:17 Thursday. Three thrusters firing together for
00:17:17 --> 00:17:18 93 minutes.
00:17:18 --> 00:17:21 ESA confirmed on Friday that it performed
00:17:21 --> 00:17:23 within the required parameters. The follow up
00:17:23 --> 00:17:26 burn is scheduled for this Thursday, 22nd
00:17:26 --> 00:17:29 October, and arrival at the Didymos asteroid
00:17:29 --> 00:17:32 system is due In November, HERA is going
00:17:32 --> 00:17:34 to measure what NASA's DART impact did to the
00:17:34 --> 00:17:37 little moonlit dimorphos in 2022,
00:17:37 --> 00:17:39 the first real test of whether we could nudge
00:17:39 --> 00:17:41 a, uh, dangerous asteroid.
00:17:41 --> 00:17:44 Avery: Second, the satellite that rode up with Flex
00:17:44 --> 00:17:46 In September, Copernicus Sentinel 3C
00:17:47 --> 00:17:49 has sent back its first images. And
00:17:50 --> 00:17:53 the Caribbean, Italy from southern Germany to
00:17:53 --> 00:17:56 Sicily and the Canadian Arctic, plus
00:17:56 --> 00:17:57 sea surface heights and the height of the
00:17:57 --> 00:18:00 Greenland ice sheet from its radar altimeter.
00:18:00 --> 00:18:03 ESA says commissioning has about five months
00:18:03 --> 00:18:05 Anna: to run and third, Swift
00:18:06 --> 00:18:09 DASA has still not published a re entry date
00:18:09 --> 00:18:11 for the observatory after the failed Boost
00:18:11 --> 00:18:13 mission and recent press coverage points to
00:18:13 --> 00:18:16 early November. That thread began with your
00:18:16 --> 00:18:18 questions through the contact form, so we'll
00:18:18 --> 00:18:20 bring you NASA's confirmation when it comes
00:18:21 --> 00:18:22 time to look up.
00:18:23 --> 00:18:25 Avery: This week belongs to the Moon, the
00:18:25 --> 00:18:28 Orionids and a planet saying goodbye.
00:18:28 --> 00:18:31 Anna: The Moon reached first quarter early on
00:18:31 --> 00:18:34 Monday Sydney time, and it's growing towards
00:18:34 --> 00:18:34 full on
00:18:34 --> 00:18:37 26-10-0411
00:18:37 --> 00:18:40 Universal Time, which is 3:11 Monday
00:18:40 --> 00:18:43 afternoon in Sydney, just after midnight on
00:18:43 --> 00:18:46 the 26th in New York and 9:11
00:18:46 --> 00:18:48 on the evening of the 25th in Los Angeles.
00:18:49 --> 00:18:52 In the north, that's the Hunter's Moon, and
00:18:52 --> 00:18:53 like the harvest Moon we talked about in
00:18:53 --> 00:18:56 episode 199, its short gap
00:18:56 --> 00:18:59 between successive moonrises is a northern
00:18:59 --> 00:19:01 effect from the south.
00:19:01 --> 00:19:04 The anti Harvest Moon rule still applies,
00:19:04 --> 00:19:07 Avery: which matters because the Orionid, uh, meteor
00:19:07 --> 00:19:09 shower peaks on the nights of the 21st and
00:19:09 --> 00:19:12 22nd. The Orionids are debris from
00:19:12 --> 00:19:14 Hallie's Comet, the same dust that gives us
00:19:14 --> 00:19:17 the Eta Aquarids in May, and they hit
00:19:17 --> 00:19:20 our atmosphere at around 66 kilometres
00:19:20 --> 00:19:23 a second. So they're quick and the
00:19:23 --> 00:19:25 brightest can leave glowing trails that hang
00:19:25 --> 00:19:28 for a second or two. And the moon is about
00:19:28 --> 00:19:30 80% lit, so the evening is no good.
00:19:31 --> 00:19:32 The trick is to go late.
00:19:33 --> 00:19:35 Anna: We ran the numbers for the morning of
00:19:35 --> 00:19:38 Thursday the 22nd. The moon sets at
00:19:38 --> 00:19:40 3.38am in Sydney,
00:19:40 --> 00:19:43 322 in Los Angeles, 312
00:19:43 --> 00:19:46 in New York and 249 in London.
00:19:47 --> 00:19:49 That gives you a dark window of about 90
00:19:49 --> 00:19:52 minutes in Sydney and roughly three hours in
00:19:52 --> 00:19:54 the north before dawn starts to brighten.
00:19:55 --> 00:19:57 Avery: And here the north has the better of it.
00:19:57 --> 00:20:00 By nautical dawn, the radiant up near
00:20:00 --> 00:20:02 Orion's raised club stands about
00:20:02 --> 00:20:04 68 degrees high from Los Angeles,
00:20:05 --> 00:20:07 62 from New York and 52 from
00:20:07 --> 00:20:10 London against about 40 degrees from
00:20:10 --> 00:20:12 Sydney. The higher the radiant, the more
00:20:12 --> 00:20:15 meteors you see. Expect modest
00:20:15 --> 00:20:18 rates at best, Perhaps up to 20 an hour
00:20:18 --> 00:20:21 under ideal dark skies and fewer from
00:20:21 --> 00:20:24 town. Lie back, look about
00:20:24 --> 00:20:26 halfway up and give your eyes 20 minutes.
00:20:27 --> 00:20:29 Anna: The south gets the evening Planet
00:20:29 --> 00:20:32 Mercury had its best evening showing of the
00:20:32 --> 00:20:35 season around the 12th of October, and it's
00:20:35 --> 00:20:38 still holding on at the end of civil
00:20:38 --> 00:20:39 twilight on Wednesday the 21st.
00:20:39 --> 00:20:42 It's about 17 degrees up from Sydney
00:20:42 --> 00:20:45 in the west, setting just after 9 from
00:20:45 --> 00:20:48 Los Angeles it's 4 degrees up from New
00:20:48 --> 00:20:51 York 2 and from London it has already
00:20:51 --> 00:20:54 set. Southern listeners, this one's
00:20:54 --> 00:20:57 yours. Look low in the west about
00:20:57 --> 00:21:00 half an hour after sunset and only bring out
00:21:00 --> 00:21:02 binoculars once the sun is completely down.
00:21:03 --> 00:21:05 Avery: Venus meanwhile, is leaving. It
00:21:05 --> 00:21:08 reaches inferior conjunction passing between
00:21:08 --> 00:21:11 us and the sun around the 24th of
00:21:11 --> 00:21:14 October and drops out of sight. It'll
00:21:14 --> 00:21:16 reappear in the morning sky in November. If
00:21:16 --> 00:21:18 you've been enjoying it in the west since
00:21:18 --> 00:21:20 September, this is the goodbye week.
00:21:21 --> 00:21:24 Anna: Saturn is well placed in the evening just
00:21:24 --> 00:21:27 past opposition and the waxing moon
00:21:27 --> 00:21:29 passes about 6 degrees from it around the
00:21:29 --> 00:21:32 24th, a good pairing for both
00:21:32 --> 00:21:34 hemispheres and for early risers.
00:21:34 --> 00:21:36 Avery: Mars and Jupiter keep closing in the pre dawn
00:21:36 --> 00:21:39 sky about 11 degrees apart on the 19th,
00:21:39 --> 00:21:42 eight by the 26th on their way to a close
00:21:42 --> 00:21:45 pass in mid November, again a northern treat
00:21:45 --> 00:21:48 at nautical dawn on Tuesday, Mars is 61
00:21:48 --> 00:21:50 degrees up from Los Angeles and 58 from New
00:21:50 --> 00:21:53 York against 24 from Sydney with Jupiter
00:21:53 --> 00:21:54 not far below.
00:21:55 --> 00:21:56 Anna: And the safety line?
00:21:56 --> 00:21:59 As always, never look at the sun directly
00:21:59 --> 00:22:02 or through binoculars or a telescope without
00:22:02 --> 00:22:05 certified solar filters meeting the ISO
00:22:05 --> 00:22:07 12322 standard.
00:22:07 --> 00:22:10 Ordinary sunglasses are not safe for solar
00:22:10 --> 00:22:10 viewing.
00:22:11 --> 00:22:13 Avery: So north the Orionids and the morning
00:22:13 --> 00:22:16 planets South Mercury and the higher
00:22:16 --> 00:22:19 evening Moon. Both of you Saturn. Some
00:22:19 --> 00:22:20 weeks it runs the other way.
00:22:20 --> 00:22:22 Anna: That's Astronomy AstroDailyPod for today.
00:22:23 --> 00:22:26 To recap, MMX um and its round trip to
00:22:26 --> 00:22:28 Phobos with a capsule bound for South
00:22:28 --> 00:22:31 Australia, more than half of the
00:22:31 --> 00:22:34 ELT's giant mirror now in Chile,
00:22:35 --> 00:22:37 Supernovae closing the window on early
00:22:37 --> 00:22:40 starlight and the treble clef
00:22:40 --> 00:22:42 rising from the radio dead.
00:22:42 --> 00:22:45 Avery: Show notes, sources and all our episodes are
00:22:45 --> 00:22:48 at astronomydaily IO and you can find us
00:22:48 --> 00:22:50 on social astrodaily Pod
00:22:51 --> 00:22:52 if you've got a question about anything we
00:22:52 --> 00:22:55 covered the contact form on the website comes
00:22:55 --> 00:22:57 straight to the team. That's how the Swift
00:22:57 --> 00:22:57 story started.
00:22:58 --> 00:23:00 Anna: We'll keep a close eye on MMX and on
00:23:00 --> 00:23:02 Harrah's second breaking burn on Thursday.
00:23:03 --> 00:23:05 And if you do get up for the Orionids, tell
00:23:05 --> 00:23:07 us what you saw and where you saw it from
00:23:08 --> 00:23:10 north or south? We'd love to compare
00:23:11 --> 00:23:11 until next time.
00:23:11 --> 00:23:12 Avery: I'm Avery.
00:23:13 --> 00:23:15 Anna: And I'm Anna. Clear skies.