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00:00:00 --> 00:00:03 Anna: Welcome back to Astronomy daily. It's Friday,
00:00:03 --> 00:00:06 September 4th, 2026. I'm
00:00:06 --> 00:00:09 Anna and this is series five, episode
00:00:09 --> 00:00:10 185.
00:00:11 --> 00:00:13 Avery: And I'm Avery. Anna.
00:00:13 --> 00:00:15 I want to start today with a number.
00:00:16 --> 00:00:17 2.6.
00:00:17 --> 00:00:20 Anna: 2.6 Sigma, which is not a
00:00:20 --> 00:00:21 discovery.
00:00:21 --> 00:00:23 Avery: M. You said that very fast.
00:00:24 --> 00:00:26 Anna: I said it fast because it's the most
00:00:26 --> 00:00:29 important sentence in the storey. But here's
00:00:29 --> 00:00:32 the rest of it. A dark matter detector a mile
00:00:32 --> 00:00:34 underground in South Dakota recorded a single
00:00:34 --> 00:00:37 flash of light in exactly the place a dark
00:00:37 --> 00:00:40 matter particle was supposed to show up. And
00:00:40 --> 00:00:42 the collaboration spent months trying to make
00:00:42 --> 00:00:45 that flash go away and could not do it.
00:00:46 --> 00:00:46 Avery: One event.
00:00:47 --> 00:00:49 Anna: One event. That's our lead.
00:00:50 --> 00:00:52 Including why we can't explain it. And
00:00:52 --> 00:00:55 we found dark matter are very different
00:00:55 --> 00:00:56 sentences.
00:00:57 --> 00:00:59 Avery: Then India has put its first imaging
00:00:59 --> 00:01:02 satellite into geostationary orbit. A,
00:01:02 --> 00:01:05 uh, real first and a capability nobody
00:01:05 --> 00:01:06 else in the region has.
00:01:07 --> 00:01:09 Anna: The first private mission to Venus has been
00:01:09 --> 00:01:12 grounded. Not by Venus, but by a
00:01:12 --> 00:01:14 rocket that hasn't flown yet.
00:01:14 --> 00:01:17 Avery: And a lovely piece of physics out of
00:01:17 --> 00:01:19 Syracuse. Why a star that keeps getting
00:01:19 --> 00:01:22 torn apart by a black hole puts on a fainter
00:01:22 --> 00:01:23 show every time.
00:01:24 --> 00:01:27 Anna: Plus the sky this weekend, both hemispheres
00:01:27 --> 00:01:29 and a new sunspot worth knowing about.
00:01:30 --> 00:01:31 Avery: Let's get into it.
00:01:32 --> 00:01:34 Start me at the beginning. Who announced what
00:01:35 --> 00:01:35 and where?
00:01:36 --> 00:01:39 Anna: The LZ collaboration, Lux Zeppelin,
00:01:39 --> 00:01:42 presented a result this week at TEV Particle
00:01:42 --> 00:01:45 Astrophysics 2026 in Chiba, Japan, which
00:01:45 --> 00:01:47 wraps up today. Brown University released it
00:01:47 --> 00:01:50 on Tuesday. The U.S. department of Energy has
00:01:50 --> 00:01:52 published its own account. And. And the paper
00:01:52 --> 00:01:54 has gone to Physical Review Letters.
00:01:55 --> 00:01:58 Avery: And LZ is the big Xenon one.
00:01:58 --> 00:02:01 Anna: LZ is the big Xenon one. 10
00:02:01 --> 00:02:04 tonnes of ultra pure liquid xenon in a tank
00:02:04 --> 00:02:06 at the Sanford Underground Research facility
00:02:06 --> 00:02:08 in Lead, South Dakota. That's the old home
00:02:08 --> 00:02:11 state gold mine. And the detector sits about
00:02:11 --> 00:02:14 a mile down, roughly 1480
00:02:14 --> 00:02:15 metres of rock overhead.
00:02:16 --> 00:02:17 Avery: Why underground?
00:02:18 --> 00:02:20 Anna: Because the enemy isn't darkness. It's noise.
00:02:21 --> 00:02:23 At the surface, you're rained on constantly
00:02:23 --> 00:02:26 by cosmic rays. A mile of rock filters
00:02:26 --> 00:02:28 nearly all of that out. Then they wrap the
00:02:28 --> 00:02:31 xenon in a water tank and a veto detector for
00:02:31 --> 00:02:33 stray neutrons and build it all from
00:02:33 --> 00:02:35 materials screened for radioactivity to
00:02:35 --> 00:02:38 absurd levels. The art of this field
00:02:38 --> 00:02:41 is subtraction. You spend 20 years
00:02:41 --> 00:02:43 removing every signal you can explain, then
00:02:43 --> 00:02:44 look at what's left.
00:02:45 --> 00:02:47 Avery: And what are they hoping is left?
00:02:47 --> 00:02:50 Anna: A, uh, wimp, weakly interacting massive
00:02:50 --> 00:02:53 particle. The leading dark matter candidate
00:02:53 --> 00:02:56 for about 40 years. A heavy particle left
00:02:56 --> 00:02:58 over from the early universe. That has mass,
00:02:58 --> 00:03:01 so it pulls on galaxies gravitationally, but
00:03:01 --> 00:03:03 ignores light and ignores ordinary matter.
00:03:03 --> 00:03:04 Almost all of the time.
00:03:05 --> 00:03:08 Avery: Almost all of the time being the operative
00:03:08 --> 00:03:08 phrase.
00:03:08 --> 00:03:11 Anna: That's the whole bet. If a WIMP occasionally
00:03:11 --> 00:03:14 bumps into an atomic nucleus, a big enough
00:03:14 --> 00:03:17 tub of xenon sitting quietly for long enough
00:03:17 --> 00:03:20 should eventually record one. The nucleus
00:03:20 --> 00:03:23 recoils and you get two flashes. A
00:03:23 --> 00:03:25 prompt one, then a second, from electrons
00:03:25 --> 00:03:28 drifting up through the liquid. Together they
00:03:28 --> 00:03:30 tell you where in the tank it happened and
00:03:30 --> 00:03:33 whether you hit a nucleus or just knocked an
00:03:33 --> 00:03:33 electron loose.
00:03:34 --> 00:03:36 Avery: Okay, tell me about the event.
00:03:37 --> 00:03:40 Anna: It's in data taken between March 2023
00:03:40 --> 00:03:42 and April 2024.
00:03:43 --> 00:03:45 220 live days. That
00:03:45 --> 00:03:48 dataset has been analysed before. LZ
00:03:48 --> 00:03:50 published world leading limits from it.
00:03:51 --> 00:03:53 What's new is that a team went back and
00:03:53 --> 00:03:55 searched a much wider range of possible
00:03:55 --> 00:03:58 interactions than the standard analysis
00:03:58 --> 00:04:00 covers, including higher energies.
00:04:00 --> 00:04:03 And one event turned up, uh, a nuclear
00:04:03 --> 00:04:05 recoil in a region where the expected
00:04:05 --> 00:04:07 background is very close to zero.
00:04:08 --> 00:04:10 Avery: Higher energy. Is that where you'd expect
00:04:10 --> 00:04:11 dark matter?
00:04:12 --> 00:04:15 Anna: No. And that's the first genuinely odd
00:04:15 --> 00:04:17 thing. The simplest WIMP models put your
00:04:17 --> 00:04:20 first signal at low energies. This is up the
00:04:20 --> 00:04:22 other end. Taken at face value, it points to
00:04:22 --> 00:04:25 a particle of at least 200 giga electron
00:04:25 --> 00:04:28 volts, more than 200 times the mass of a
00:04:28 --> 00:04:31 proton, interacting in a way the simplest
00:04:31 --> 00:04:32 models don't predict.
00:04:33 --> 00:04:35 Avery: So it's not the WIMP anyone ordered.
00:04:35 --> 00:04:38 Anna: It is not the WIMP anyone ordered.
00:04:38 --> 00:04:40 Which cuts both ways. And we'll come back to
00:04:40 --> 00:04:40 that.
00:04:41 --> 00:04:43 Avery: Give me the statistics. Honestly.
00:04:43 --> 00:04:46 Anna: 2.6- Sigma globally, 3.4-
00:04:46 --> 00:04:49 Sigma locally. And the difference between
00:04:49 --> 00:04:51 those two numbers is the most useful thing I
00:04:51 --> 00:04:52 can teach anyone today.
00:04:53 --> 00:04:54 Avery: Go on.
00:04:54 --> 00:04:57 Anna: LocalSignificants asks at this
00:04:57 --> 00:04:59 exact energy for this exact mass,
00:05:00 --> 00:05:02 how surprising is this event? Fairly
00:05:02 --> 00:05:05 surprising. Global significance asks the
00:05:05 --> 00:05:08 fairer question. I searched a whole range of
00:05:08 --> 00:05:11 masses and energies. So how surprising is it
00:05:11 --> 00:05:13 that somewhere in that range I found one odd
00:05:13 --> 00:05:16 thing? Account for the haystack and the
00:05:16 --> 00:05:19 surprise drops. That's the look elsewhere
00:05:19 --> 00:05:21 effect. Honest experiments quote both
00:05:22 --> 00:05:23 and LZ did
00:05:23 --> 00:05:26 Avery: M and 2.6 Sigma means what? In
00:05:26 --> 00:05:27 plain terms?
00:05:28 --> 00:05:30 Anna: Roughly a half a percent chance known
00:05:30 --> 00:05:32 backgrounds produced it. Which sounds
00:05:32 --> 00:05:34 compelling until you remember the bar.
00:05:35 --> 00:05:37 Particle physics calls something a discovery
00:05:37 --> 00:05:40 at five sigma, about one in three and
00:05:40 --> 00:05:43 a half million. 2.6 is nowhere near
00:05:43 --> 00:05:45 it. And physicists have watched three sigma
00:05:45 --> 00:05:47 results evaporate for decades.
00:05:48 --> 00:05:50 Avery: Did they try to kill it for months?
00:05:51 --> 00:05:54 Anna: Cosmic rays, neutrons from the rock,
00:05:54 --> 00:05:56 radioactivity in the detector materials,
00:05:57 --> 00:05:59 instrumental artefacts all modelled.
00:06:00 --> 00:06:02 Aaron Manalaise at Berkeley Lab, who chairs
00:06:02 --> 00:06:05 LZ's institutional board, said it's the first
00:06:05 --> 00:06:08 example in any experiment he's worked on of
00:06:08 --> 00:06:10 an outlier that appears valid in every way.
00:06:11 --> 00:06:12 That's a striking thing for an
00:06:12 --> 00:06:14 experimentalist to say out loud.
00:06:14 --> 00:06:16 Avery: What does the spokesperson say?
00:06:16 --> 00:06:18 Anna: Rick Gates, skull at Brown, is the
00:06:18 --> 00:06:20 spokesperson and he's been about as
00:06:20 --> 00:06:23 disciplined as you can be. His. His line
00:06:23 --> 00:06:25 with only one event. We don't want to get
00:06:25 --> 00:06:28 ahead of ourselves. We are not claiming to
00:06:28 --> 00:06:30 have seen dark matter and separately
00:06:30 --> 00:06:33 we're very intrigued to see this event in the
00:06:33 --> 00:06:35 data in the region where we expect dark
00:06:35 --> 00:06:37 matter to show up and the competing
00:06:37 --> 00:06:39 backgrounds are very low.
00:06:40 --> 00:06:41 Avery: Both things at once.
00:06:41 --> 00:06:43 Anna: Both things at once. And that's the correct
00:06:43 --> 00:06:46 posture. Sam Erickson at Bristol led the
00:06:46 --> 00:06:48 analysis and made the point that matters.
00:06:49 --> 00:06:51 Dark matter events are expected to be so rare
00:06:51 --> 00:06:53 that only a handful could mark the first
00:06:53 --> 00:06:56 detection. You can't dismiss one event for
00:06:56 --> 00:06:59 being single, but you can't build a discovery
00:06:59 --> 00:06:59 on it either.
00:07:00 --> 00:07:02 Avery: Is there a UK end um, to this?
00:07:02 --> 00:07:05 Anna: A significant one. Imperial College
00:07:05 --> 00:07:07 London did much of the work characterising
00:07:07 --> 00:07:10 the event and Henrique Araujo there put
00:07:10 --> 00:07:13 it beautifully. We need to analyse more data
00:07:13 --> 00:07:15 to be sure, but. But these are certainly
00:07:15 --> 00:07:16 interesting times.
00:07:16 --> 00:07:19 Avery: Now you promised the caveat about it not
00:07:19 --> 00:07:21 being the expected wimp.
00:07:21 --> 00:07:24 Anna: Two ways to read an unexpected signal.
00:07:24 --> 00:07:27 The generous one. Nature isn't obliged to
00:07:27 --> 00:07:30 be simple and 40 years of not finding dark
00:07:30 --> 00:07:32 matter may be exactly because we searched the
00:07:32 --> 00:07:35 tidiest places first. The unkind one,
00:07:36 --> 00:07:38 when a result lands where no model predicted,
00:07:38 --> 00:07:41 an unmodeled background is a very live
00:07:41 --> 00:07:44 explanation. The reason you haven't modelled
00:07:44 --> 00:07:45 it is that you didn't know it was there.
00:07:46 --> 00:07:48 Avery: Has this field been burned before?
00:07:49 --> 00:07:51 Anna: Repeatedly. DAMA in Italy has claimed an
00:07:51 --> 00:07:54 annual dark matter signal for over 20 years
00:07:54 --> 00:07:56 that nobody else can reproduce.
00:07:56 --> 00:07:59 Xenon1T reported an excess in 2020
00:07:59 --> 00:08:02 that caused enormous excitement and was most
00:08:02 --> 00:08:05 likely tritium contamination. A hydrogen
00:08:05 --> 00:08:07 isotope at a level almost too small to
00:08:07 --> 00:08:09 measure. That's the standard to hear this
00:08:09 --> 00:08:12 week against. To LZ's credit, they've
00:08:12 --> 00:08:14 published this as an anomaly, not a
00:08:14 --> 00:08:15 discovery.
00:08:15 --> 00:08:17 Avery: So what settles it?
00:08:17 --> 00:08:20 Anna: More xenon and more time. LZ has
00:08:20 --> 00:08:22 already banked substantially more data than
00:08:22 --> 00:08:25 went into this analysis and is running toward
00:08:25 --> 00:08:27 a thousand live days. If it's real,
00:08:27 --> 00:08:30 the rate is set by physics and more events
00:08:30 --> 00:08:33 follow. The significance climbs. If it's
00:08:33 --> 00:08:35 a fluke, it decays as exposure grows
00:08:35 --> 00:08:38 and A proposed successor, XLZD,
00:08:38 --> 00:08:41 would hold 10 times the xenon. This
00:08:41 --> 00:08:43 resolves itself in data, not argument.
00:08:44 --> 00:08:47 Avery: Southern hemisphere angle. Because dark
00:08:47 --> 00:08:49 matter feels like a Northern Hemisphere
00:08:49 --> 00:08:49 sport.
00:08:50 --> 00:08:52 Anna: It has been. And that's changing for a
00:08:52 --> 00:08:54 genuinely clever reason. There's now an
00:08:54 --> 00:08:57 underground lab in Australia, supl.
00:08:57 --> 00:09:00 The Stawell Underground Physics Laboratory, a
00:09:00 --> 00:09:02 kilometre down. A working gold mine in
00:09:02 --> 00:09:05 western Victoria. It's the first underground
00:09:05 --> 00:09:07 physics lab in the Southern hemisphere, built
00:09:07 --> 00:09:09 by the University of Melbourne with the ARC
00:09:09 --> 00:09:11 Centre of Excellence for Dark Matter Particle
00:09:11 --> 00:09:14 Physics and Ansto. And its first
00:09:14 --> 00:09:17 experiment, Sabre south, moves in late
00:09:17 --> 00:09:17 this year.
00:09:18 --> 00:09:20 Avery: And why does the hemisphere matter for dark
00:09:20 --> 00:09:21 matter of all things?
00:09:22 --> 00:09:25 Anna: Because of dama. Its claim is
00:09:25 --> 00:09:27 that the signal rises and falls once a year
00:09:28 --> 00:09:31 as Earth's motion around the sun adds to and
00:09:31 --> 00:09:33 subtracts from the solar system's motion
00:09:33 --> 00:09:36 through the galaxy's dark matter halo. The
00:09:36 --> 00:09:39 trouble is that plenty of ordinary things
00:09:39 --> 00:09:41 cycle annually too. Temperature,
00:09:41 --> 00:09:44 radon, cosmic ray rates. And
00:09:44 --> 00:09:47 in Italy they all peak in summer alongside
00:09:47 --> 00:09:48 the claimed signal.
00:09:48 --> 00:09:51 Avery: And in Victoria, the seasons are flipped.
00:09:51 --> 00:09:53 Anna: The seasons are flipped and the dark matter
00:09:53 --> 00:09:56 signal isn't. Run a near identical
00:09:56 --> 00:09:58 detector in the Southern hemisphere and a
00:09:58 --> 00:10:01 real galactic signal peaks in the same
00:10:01 --> 00:10:03 calendar month it does in Italy, while a
00:10:03 --> 00:10:05 seasonal artefact peaks six months out.
00:10:06 --> 00:10:08 Elegant piece of experiment design. And the
00:10:08 --> 00:10:10 only place on Earth you can do it is the one
00:10:10 --> 00:10:12 we happen to broadcast from.
00:10:13 --> 00:10:15 Avery: So what should people take away from today?
00:10:15 --> 00:10:18 Anna: Three things. LZ has found something it
00:10:18 --> 00:10:21 cannot explain in the right place and
00:10:21 --> 00:10:24 said so honestly. One event is one event and
00:10:24 --> 00:10:26 2.6 Sigma is a long way from a discovery.
00:10:27 --> 00:10:29 And the answer is already being collected.
00:10:29 --> 00:10:32 The detector is running right now. The honest
00:10:32 --> 00:10:34 headline is dark matter hunters find
00:10:34 --> 00:10:36 something they can't explain and refuse to
00:10:36 --> 00:10:39 overclaim it a good day for science, even if
00:10:39 --> 00:10:40 it isn't the day.
00:10:41 --> 00:10:43 Avery: On to our second storey today and this one
00:10:43 --> 00:10:45 is a genuine national first.
00:10:46 --> 00:10:49 Overnight, our time, 2:55 in the
00:10:49 --> 00:10:51 morning, Indian Standard Time on the 4th,
00:10:52 --> 00:10:54 which was 5:25 yesterday evening,
00:10:54 --> 00:10:57 US Eastern ISRO
00:10:57 --> 00:10:59 launched EOS05 on a
00:10:59 --> 00:11:02 GSLV Mark 2 out of Srihari
00:11:02 --> 00:11:03 Kota.
00:11:03 --> 00:11:06 Anna: And it's the orbit that's the storey, not the
00:11:06 --> 00:11:06 rocket.
00:11:07 --> 00:11:10 Avery: Exactly. EOS05
00:11:10 --> 00:11:12 is India's first dedicated imaging
00:11:12 --> 00:11:15 satellite headed for geosynchronous orbit.
00:11:16 --> 00:11:18 Everything India has flown for Earth
00:11:18 --> 00:11:20 observation until now has been in low
00:11:20 --> 00:11:23 orbit a few hundred kilometres up.
00:11:23 --> 00:11:25 Anna: Spell out the difference for people, a,
00:11:25 --> 00:11:28 Avery: uh, low orbit imaging satellite is a
00:11:28 --> 00:11:30 sprinter. It races around the planet in
00:11:30 --> 00:11:33 90 minutes and gives you a superb,
00:11:33 --> 00:11:36 very high resolution snapshot of a strip of
00:11:36 --> 00:11:39 ground and then it's gone. And you wait.
00:11:40 --> 00:11:42 Depending on the orbit, you might get another
00:11:42 --> 00:11:44 look in a day or, or several days.
00:11:45 --> 00:11:47 Anna: Whereas geostationary is a stair.
00:11:48 --> 00:11:49 Avery: Geostationary is a stair
00:11:50 --> 00:11:53 36 kilometres up, matching
00:11:53 --> 00:11:56 Earth's rotation. So from the ground, the
00:11:56 --> 00:11:58 satellite appears to hang motionless over the
00:11:58 --> 00:12:01 same piece of the planet permanently. You
00:12:01 --> 00:12:03 don't get a revisit time because you never
00:12:03 --> 00:12:04 leave.
00:12:04 --> 00:12:06 Anna: And that changes what you can use it for
00:12:06 --> 00:12:07 completely.
00:12:08 --> 00:12:11 Avery: Isro's framing is persistent
00:12:11 --> 00:12:13 coverage of the subcontinent and the
00:12:13 --> 00:12:15 applications are obvious once you say it that
00:12:15 --> 00:12:18 way. A, uh, cyclone forming in the Bay of
00:12:18 --> 00:12:20 Bengal. You watch it develop
00:12:20 --> 00:12:23 continuously instead of getting one frame a
00:12:23 --> 00:12:26 day. A flood, you see the water
00:12:26 --> 00:12:29 advance, a fire front, a landslide,
00:12:29 --> 00:12:31 a border. It's a dual use satellite,
00:12:32 --> 00:12:34 civil and military, and India hasn't been
00:12:34 --> 00:12:35 shy about that.
00:12:36 --> 00:12:38 Anna: There's a trade off though, surely there
00:12:38 --> 00:12:40 Avery: is, and it's worth being honest about it.
00:12:41 --> 00:12:43 You are imagining from a hundred times
00:12:43 --> 00:12:45 further away than a low orbit satellite,
00:12:46 --> 00:12:48 so the resolution is inevitably coarser.
00:12:49 --> 00:12:51 You are not reading number plates from
00:12:51 --> 00:12:53 geostationary orbit. What you're
00:12:53 --> 00:12:56 buying is time, not detail. And
00:12:56 --> 00:12:59 for disaster response, time is usually the
00:12:59 --> 00:13:00 thing you're short of.
00:13:01 --> 00:13:03 Anna: How did the launch go clean?
00:13:04 --> 00:13:05 Avery: The Spacecraft is about
00:13:05 --> 00:13:07 2
00:13:07 --> 00:13:10 kilogrammes, and ISRO chairman V
00:13:10 --> 00:13:13 Narayanan said it was successfully and
00:13:13 --> 00:13:15 precisely injected into its planned orbit.
00:13:16 --> 00:13:19 From here, EOS05 works
00:13:19 --> 00:13:21 its way up to its final station over the
00:13:21 --> 00:13:21 coming days.
00:13:22 --> 00:13:24 Anna: And the GSLV has had a mixed history.
00:13:25 --> 00:13:28 Avery: It has, which is part of why this matters to
00:13:28 --> 00:13:31 ISRO. The GSLV
00:13:31 --> 00:13:33 MK2 has now flown 12 times for
00:13:33 --> 00:13:36 10 successes. That's a vehicle that has
00:13:36 --> 00:13:39 visibly matured and it's the one carrying
00:13:39 --> 00:13:41 India's heavier missions to high orbit.
00:13:42 --> 00:13:43 Anna: Small country club.
00:13:43 --> 00:13:45 Avery: This very small,
00:13:45 --> 00:13:48 dedicated, high resolution imaging from
00:13:48 --> 00:13:50 geostationary orbit is a capability
00:13:51 --> 00:13:54 only a handful of nations have ever fielded.
00:13:54 --> 00:13:57 India has just joined that list and it did
00:13:57 --> 00:13:59 it with its own rocket from its own
00:13:59 --> 00:13:59 spaceport.
00:14:00 --> 00:14:03 Anna: Third storey, and it's a frustrating one. The
00:14:03 --> 00:14:05 first privately funded mission to another
00:14:06 --> 00:14:08 planet is still on the ground and it's going
00:14:08 --> 00:14:10 to stay there for a while yet.
00:14:10 --> 00:14:13 Avery: This is the Venus Life Finder.
00:14:13 --> 00:14:16 Anna: That's it. It's an MIT led mission
00:14:16 --> 00:14:19 driven by Sarah Seager, flying in partnership
00:14:19 --> 00:14:21 with Rocket Lab, and it is beautifully,
00:14:21 --> 00:14:24 almost aggressively simple. A small
00:14:24 --> 00:14:27 probe, one instrument, a few minutes of
00:14:27 --> 00:14:28 useful life.
00:14:29 --> 00:14:30 Avery: One instrument. That's it.
00:14:31 --> 00:14:33 Anna: One instrument. It's called an
00:14:33 --> 00:14:36 autofluorescence nifalometer, which is a
00:14:36 --> 00:14:38 mouthful for a fairly elegant idea. You
00:14:38 --> 00:14:40 fire an ultraviolet laser into the cloud
00:14:40 --> 00:14:43 droplets. As you fall through them, certain
00:14:43 --> 00:14:45 organic molecules absorb ultraviolet light
00:14:45 --> 00:14:47 and re emit it at a different wavelength.
00:14:48 --> 00:14:50 They fluoresce. So the instrument is looking
00:14:50 --> 00:14:53 for a glow that ordinary sulfuric acid
00:14:53 --> 00:14:54 chemistry shouldn't produce.
00:14:55 --> 00:14:57 Avery: And why the clouds, specifically?
00:14:58 --> 00:15:00 Anna: Because the surface of Venus is out of the
00:15:00 --> 00:15:02 question. 460 odd
00:15:02 --> 00:15:05 degrees, 90 atmospheres, but
00:15:05 --> 00:15:08 between about 45 and 60 kilometres up,
00:15:08 --> 00:15:10 the temperature and pressure are, uh, close
00:15:10 --> 00:15:12 to conditions at sea level on Earth.
00:15:13 --> 00:15:16 Extremely acidic, but not thermodynamically
00:15:16 --> 00:15:18 hopeless. That's the only plausible
00:15:18 --> 00:15:21 habitable niche on the planet. And it's what
00:15:21 --> 00:15:23 the 2020 phosphine claim put back on the
00:15:23 --> 00:15:26 table. A result that is still genuinely
00:15:26 --> 00:15:28 disputed and which this mission is designed
00:15:28 --> 00:15:30 to go and settle rather than argue about.
00:15:31 --> 00:15:33 Avery: So why isn't it flying?
00:15:34 --> 00:15:36 Anna: Neutron. The mission moved onto Rocket
00:15:36 --> 00:15:39 Lab's new medium lift rocket and Neutron
00:15:39 --> 00:15:42 hasn't flown yet. It was originally talked
00:15:42 --> 00:15:44 about for 2024, slipped to
00:15:44 --> 00:15:46 2026 and it's still in qualification.
00:15:47 --> 00:15:49 The launch date on Rocket Lab's own website
00:15:49 --> 00:15:51 now simply says to be confirmed.
00:15:52 --> 00:15:54 Avery: How is Seeger taking it?
00:15:54 --> 00:15:57 Anna: With more grace than I would. Her
00:15:57 --> 00:16:00 line was, we are awaiting neutron
00:16:00 --> 00:16:02 readiness. And she went on to say she
00:16:02 --> 00:16:04 continues to have high hopes for the mission
00:16:04 --> 00:16:07 and for its role in demonstrating what
00:16:07 --> 00:16:08 private enterprise can do in space
00:16:08 --> 00:16:09 exploration.
00:16:10 --> 00:16:12 Avery: There's an irony in there somewhere.
00:16:13 --> 00:16:15 Anna: There's a real one. The whole pitch of this
00:16:15 --> 00:16:17 mission was speed. That a small,
00:16:17 --> 00:16:20 focused, privately funded probe could go
00:16:20 --> 00:16:23 and answer one sharp question years before an
00:16:23 --> 00:16:26 agency flight could be approved, built and
00:16:26 --> 00:16:28 launched. And it's now waiting on launch
00:16:28 --> 00:16:31 capacity, which is the one part of the
00:16:31 --> 00:16:32 problem private industry was supposed to have
00:16:32 --> 00:16:33 solved.
00:16:33 --> 00:16:36 Avery: Meanwhile, Venus is getting crowded.
00:16:36 --> 00:16:39 Anna: It is. NASA's DaVinci and
00:16:39 --> 00:16:42 Veritas and Europe's Envision are all in
00:16:42 --> 00:16:43 the pipeline. For around the end of this
00:16:43 --> 00:16:46 decade, the Venus Life Finder was meant to be
00:16:46 --> 00:16:49 the scrappy one that got there first. And
00:16:49 --> 00:16:51 that lead is quietly evaporating on a launch
00:16:51 --> 00:16:52 pad in Virginia.
00:16:53 --> 00:16:55 Avery: Last news storey and it's pure
00:16:55 --> 00:16:58 astrophysics, published in the
00:16:58 --> 00:17:01 Astrophysical Journal on Tuesday, led by
00:17:01 --> 00:17:03 Ananya Bandopadhyay, a doctoral
00:17:03 --> 00:17:06 student at Syracuse University with Benjamin
00:17:06 --> 00:17:09 Amend and Eric Coughlin, plus collaborators
00:17:09 --> 00:17:12 at Leeds MIT and the Space
00:17:12 --> 00:17:14 Telescope Science Institute.
00:17:14 --> 00:17:17 Anna: And the puzzle is about stars that survive
00:17:17 --> 00:17:18 being eaten.
00:17:19 --> 00:17:22 Avery: Partly eaten. When a star wanders too
00:17:22 --> 00:17:24 close to a supermassive black hole and is
00:17:24 --> 00:17:27 ripped apart entirely, that's a tidal
00:17:27 --> 00:17:30 disruption event. One enormous flare
00:17:30 --> 00:17:32 and it's over. But there's a smaller
00:17:32 --> 00:17:35 class where the star is only partly stripped
00:17:35 --> 00:17:38 on each pass, survives and comes back
00:17:38 --> 00:17:38 around.
00:17:39 --> 00:17:42 Anna: So it flares over and over, over
00:17:42 --> 00:17:45 Avery: and over on a schedule. The
00:17:45 --> 00:17:48 Famous one is Assassin 14 Ko,
00:17:48 --> 00:17:51 which flares roughly every 114
00:17:51 --> 00:17:53 days and has done so for years.
00:17:54 --> 00:17:56 There are now something like seven or eight
00:17:56 --> 00:17:57 of these known.
00:17:58 --> 00:17:58 Anna: And what's the problem?
00:17:59 --> 00:18:02 Avery: The flares get dimmer each time. Which
00:18:02 --> 00:18:05 sounds intuitive. Less star left to strip.
00:18:05 --> 00:18:07 Except the simulations kept saying the
00:18:07 --> 00:18:10 opposite. Strip material from a star and
00:18:10 --> 00:18:13 it puffs up. And a puffier star is
00:18:13 --> 00:18:15 easier to strip next time round.
00:18:16 --> 00:18:18 Models kept producing flares that got
00:18:18 --> 00:18:21 brighter and the sky kept producing flares
00:18:21 --> 00:18:22 that got fainter.
00:18:22 --> 00:18:24 Anna: So what's the missing ingredient?
00:18:24 --> 00:18:27 Avery: Spin. This team ran
00:18:27 --> 00:18:29 hydrodynamic simulations of a high mass
00:18:29 --> 00:18:32 main sequence star being repeatedly
00:18:32 --> 00:18:34 disrupted by a black hole of about a million
00:18:34 --> 00:18:37 solar masses. And the key move was
00:18:37 --> 00:18:40 giving the star a fast rotation before the
00:18:40 --> 00:18:42 first encounter, spinning in the same
00:18:42 --> 00:18:44 direction as its orbit.
00:18:44 --> 00:18:46 Anna: Why does that change the outcome?
00:18:46 --> 00:18:48 Avery: Because ordinarily, the encounter itself
00:18:48 --> 00:18:51 spins the star up. And that spin up is
00:18:51 --> 00:18:53 part of what makes the next pass more
00:18:53 --> 00:18:56 violent. If the star arrives already
00:18:56 --> 00:18:59 rotating at a decent fraction of its breakup
00:18:59 --> 00:19:01 speed, there's very little extra spin to give
00:19:01 --> 00:19:04 it. The debris then falls back to the black
00:19:04 --> 00:19:07 hole, spread over a longer stretch of time
00:19:07 --> 00:19:10 instead of arriving in one lump. And the same
00:19:10 --> 00:19:13 material dribbling in over longer makes a
00:19:13 --> 00:19:15 fainter, more drawn out flare.
00:19:16 --> 00:19:18 Anna: Spread the fuel out and the fire is lower.
00:19:18 --> 00:19:21 Avery: That's it exactly. And with tens of
00:19:21 --> 00:19:23 percent of breakup rotation prograde,
00:19:24 --> 00:19:27 the simulations reproduce the dimming that's
00:19:27 --> 00:19:28 actually observed.
00:19:28 --> 00:19:30 Anna: Does it tell us anything about how the star
00:19:30 --> 00:19:31 got there in the first place?
00:19:32 --> 00:19:35 Avery: It does. And that's the bonus. A
00:19:35 --> 00:19:38 fast spinning star on a tight orbit around a
00:19:38 --> 00:19:40 supermassive black hole fits the Hill's
00:19:40 --> 00:19:43 mechanism. A, uh, binary pair strays too
00:19:43 --> 00:19:46 close. The black hole keeps one star
00:19:46 --> 00:19:49 and flings the other away at enormous speed.
00:19:50 --> 00:19:52 The captured one lands exactly where you need
00:19:52 --> 00:19:55 it. So the spin isn't an arbitrary
00:19:55 --> 00:19:58 knob. It's a fingerprint of how these systems
00:19:58 --> 00:19:58 get built.
00:19:59 --> 00:20:02 Anna: Right, let's get you outside. And the Moon is
00:20:02 --> 00:20:03 doing us a favour this weekend.
00:20:04 --> 00:20:05 Avery: Last quarter today.
00:20:06 --> 00:20:08 Anna: Last quarter today. September 4th. Which
00:20:08 --> 00:20:10 means it doesn't rise until around midnight.
00:20:10 --> 00:20:13 So. So the entire evening is dark. If you
00:20:13 --> 00:20:15 have been waiting for a night to actually
00:20:15 --> 00:20:17 look at something faint, this is the weekend.
00:20:18 --> 00:20:19 Avery: Southern hemisphere first.
00:20:20 --> 00:20:22 Anna: Southern hemisphere first because we get the
00:20:22 --> 00:20:25 best of it from Sydney. The sun sets about 20
00:20:25 --> 00:20:27 to 6 now, and once it's properly Dark. The
00:20:27 --> 00:20:29 centre of the Milky Way is high overhead.
00:20:30 --> 00:20:32 Sagittarius and Scorpius almost directly
00:20:32 --> 00:20:35 above you. From mid southern latitudes, the
00:20:35 --> 00:20:38 galactic core passes near the zenith, so
00:20:38 --> 00:20:39 you're looking through the least possible
00:20:39 --> 00:20:42 atmosphere. Northern listeners get the same
00:20:42 --> 00:20:44 object low and murky above the southern
00:20:44 --> 00:20:47 horizon. It's the one thing we can be smug
00:20:47 --> 00:20:50 about. And September is the last good month
00:20:50 --> 00:20:51 before it sinks westward.
00:20:51 --> 00:20:53 Avery: What do you actually look at?
00:20:53 --> 00:20:56 Anna: Find the teapot of Sagittarius with the naked
00:20:56 --> 00:20:59 eye and let your eye drift up out of the
00:20:59 --> 00:21:01 spout. That steam is the galactic
00:21:01 --> 00:21:04 centre. Binoculars turn it into star clouds
00:21:04 --> 00:21:07 and dark lanes. And the Lagoon Nebula is
00:21:07 --> 00:21:09 sitting right there, along with a dozen
00:21:09 --> 00:21:10 globular clusters.
00:21:11 --> 00:21:12 Avery: Planets.
00:21:12 --> 00:21:15 Anna: Venus in the west after sunset. Brilliant,
00:21:15 --> 00:21:18 unmistakable. Low and building toward
00:21:18 --> 00:21:20 greatest Brilliancy on the 18th.
00:21:20 --> 00:21:23 Saturn is up most of the night in Aquarius,
00:21:23 --> 00:21:25 climbing toward opposition on October 4th.
00:21:25 --> 00:21:28 And from here it passes far higher overhead
00:21:28 --> 00:21:30 than it does for northern observers.
00:21:30 --> 00:21:31 Avery: Pre dawn.
00:21:32 --> 00:21:35 Anna: Jupiter is the predawn showpiece, well up in
00:21:35 --> 00:21:37 the east before sunrise. And on Sunday
00:21:37 --> 00:21:40 morning the 6th, Mars sits just a few
00:21:40 --> 00:21:43 degrees below a thin, waning crescent Moon.
00:21:43 --> 00:21:45 That's a lovely one for a phone camera if
00:21:45 --> 00:21:46 you're up early.
00:21:47 --> 00:21:49 Avery: Now North America, because there's a proper
00:21:49 --> 00:21:50 event coming.
00:21:50 --> 00:21:53 Anna: On Tuesday the 8th, the moon occults
00:21:53 --> 00:21:56 Jupiter. The planet passes behind the
00:21:56 --> 00:21:58 lunar disc. The footprint favours
00:21:58 --> 00:22:01 northeastern Asia, where it happens in the
00:22:01 --> 00:22:04 dawn sky, and eastern North America
00:22:04 --> 00:22:06 where it happens after sunrise in broad
00:22:06 --> 00:22:08 daylight. Daylight,
00:22:09 --> 00:22:11 daylight. Which brings us to the standing
00:22:11 --> 00:22:13 reminder. And it applies directly here.
00:22:14 --> 00:22:16 If you are observing anywhere near the sun,
00:22:16 --> 00:22:19 hunting for Jupiter in a bright sky or
00:22:19 --> 00:22:21 looking at the sunspot. I'm about to mention
00:22:21 --> 00:22:24 any filter you use for direct solar viewing
00:22:25 --> 00:22:26 must be certified to the ISO
00:22:26 --> 00:22:29 123122 standard.
00:22:30 --> 00:22:32 Not sunglasses, not welding glass of unknown
00:22:32 --> 00:22:35 grade, not smoked glass, not a phone screen.
00:22:35 --> 00:22:36 ISO
00:22:36 --> 00:22:39
00:22:39 --> 00:22:41 and cheque. The certification is real.
00:22:41 --> 00:22:44 Sweeping binoculars or a telescope across a
00:22:44 --> 00:22:46 daylight sky is exactly the situation where
00:22:46 --> 00:22:49 people injure themselves permanently and it
00:22:49 --> 00:22:50 takes a fraction of a second.
00:22:51 --> 00:22:53 Avery: And the day after there's one for us.
00:22:53 --> 00:22:56 Anna: M the ninth, the Moon occults
00:22:56 --> 00:22:59 Regulus, the brightest star in Leo. And
00:22:59 --> 00:23:01 that footprint runs across the South Pacific.
00:23:01 --> 00:23:04 New Caledonia, best placed. Not Australia,
00:23:04 --> 00:23:07 unfortunately. But if you're in that track, a
00:23:07 --> 00:23:09 first magnitude star vanishing off the edge
00:23:09 --> 00:23:11 of the Moon is one of the sharpest things
00:23:11 --> 00:23:14 you'll ever see. Instantaneous.
00:23:14 --> 00:23:17 Avery: You mentioned a Sunspot, a new one,
00:23:17 --> 00:23:20 Anna: Active Region 4524, which
00:23:20 --> 00:23:23 rotated into view over the northeastern limb
00:23:23 --> 00:23:25 this week and has been busy. It fired an M
00:23:25 --> 00:23:28 M3 flare peaking at 19:20 Universal
00:23:28 --> 00:23:31 Time on Wednesday the 2nd, plus a stack of
00:23:31 --> 00:23:34 smaller ones. The coronal mass ejection from
00:23:34 --> 00:23:37 that flare isn't aimed at us, but a filament
00:23:37 --> 00:23:39 eruption the same day threw out material that
00:23:39 --> 00:23:41 may deliver a glancing blow around Monday the
00:23:41 --> 00:23:43 7th. Aurora chances
00:23:44 --> 00:23:47 modest and honest quiet conditions through
00:23:47 --> 00:23:49 the weekend, so nothing to promise tonight or
00:23:49 --> 00:23:52 Saturday. Monday is the one to watch. And if
00:23:52 --> 00:23:54 anything comes of it, the people with a shot
00:23:54 --> 00:23:56 are Tasmania and southern New Zealand down
00:23:56 --> 00:23:58 here and the northern tier of the us, Canada
00:23:58 --> 00:24:01 and Scotland up there. Watch the space
00:24:01 --> 00:24:03 weather feeds rather than the headlines.
00:24:03 --> 00:24:05 Avery: And one for northern observers with
00:24:05 --> 00:24:06 binoculars.
00:24:07 --> 00:24:09 Anna: The Double Cluster in Perseus. Two open
00:24:09 --> 00:24:12 clusters side by side in the same binocular
00:24:12 --> 00:24:15 field. Naked eye. It's a smudge in
00:24:15 --> 00:24:17 binoculars. It's one of the best sights in
00:24:17 --> 00:24:20 the sky and a moonless evening is exactly
00:24:20 --> 00:24:21 when to try it.
00:24:21 --> 00:24:24 Avery: And that's episode 185.
00:24:24 --> 00:24:27 A dark matter detector a mile underground
00:24:27 --> 00:24:30 has recorded one flash of light it cannot
00:24:30 --> 00:24:33 explain and has been admirably careful
00:24:33 --> 00:24:35 about what that does and and doesn't mean.
00:24:36 --> 00:24:38 Anna: India has put its first imaging satellite on
00:24:38 --> 00:24:41 station over the subcontinent. The first
00:24:41 --> 00:24:43 private mission to Venus is stuck waiting on
00:24:43 --> 00:24:46 a rocket that hasn't flown. And a star that
00:24:46 --> 00:24:48 keeps surviving a black hole shines a little
00:24:48 --> 00:24:51 fainter each time because of how fast it was
00:24:51 --> 00:24:51 already spinning.
00:24:52 --> 00:24:55 Avery: Full show notes, links to every primary
00:24:55 --> 00:24:57 source and the whole back catalogue are, uh,
00:24:57 --> 00:24:59 @astronomydaily.IO.
00:25:00 --> 00:25:02 Anna: you can find us on X Instagram and
00:25:02 --> 00:25:04 TikTok Strodaily pod.
00:25:05 --> 00:25:07 And if you've got a question or a correction,
00:25:07 --> 00:25:10 we genuinely want it. There's a contact form
00:25:10 --> 00:25:10 on the website.
00:25:12 --> 00:25:14 Avery: And if today's episode was useful, the single
00:25:14 --> 00:25:17 most helpful thing you can do is send it to
00:25:17 --> 00:25:18 one person who'd enjoy it.
00:25:19 --> 00:25:21 Anna: It's the weekend. Get outside and look up
00:25:21 --> 00:25:22 while the Moon's out of the way.
00:25:23 --> 00:25:24 Until tomorrow. Clear skies.
00:25:24 --> 00:25:25 Avery: Clear skies.
00:25:26 --> 00:25:27 Anna: Astronomy Day
00:25:29 --> 00:25:30 storeys
00:25:32 --> 00:25:32 the.
00:25:37 --> 00:25:37 Storey.