The Evolving Enigma of Dark Energy and the Sun's Mysterious Past

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Anna: Three decades of exploding stars

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pulled apart and rebuilt from the ground up

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into a single consistent picture,

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2,884 of them.

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And when an Australian led team stepped back

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to look at what that picture was saying about

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dark energy, it wasn't saying what the

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textbook says.

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Avery: We've also got a study asking whether our,

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uh, own sun once swallowed a planet and

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whether the evidence for it is still sitting

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inside the star right now, waiting to be

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ready.

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Anna: Plus why the quietest stretch of the solar

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cycle is the one that matters most.

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If you spend your working life at

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Avery: 35,000ft, and the James Webb

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Space Telescope has just run the most

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sensitive search for a moon around another

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planet that anyone has ever attempted,

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it found nothing at all. That is the good

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news.

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Anna: This is Astronomy AstroDailyPod. I'm Anna.

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Avery: And I'm avery.

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It's Monday 14th September

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2026 and we're coming to you as always,

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from Syd. You, let's get into it.

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Anna: We're starting today with a result that has

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been quietly sitting in the open for about a

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week and I think it deserves a great deal

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more attention than it has had. An

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international team led out of the University

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of Queensland has published what is now the

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largest and most internally consistent

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catalogue of type 1A supernovae ever

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assembled,

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2,884 of them.

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And it adds fresh weight to a very awkward

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idea that dark energy might not be

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constant, which would be a

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Avery: problem because the word constant is doing

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enormous structural work.

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Anna: In modern cosmology, it is the load bearing

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wall. So let's build this up properly because

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the method here matters as much as the

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answer. A, uh, type 1A supernova is what

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happens when a white dwarf star, the dense,

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burnt out core left behind by a star like our

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sun, gathers too much material and detonates.

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The crucial thing is that these explosions

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are close to identical. They go off at

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roughly the same intrinsic brightness every

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time. So if you measure how bright one looks

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from here, you can work out how far away it

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is. Astronomers call them standard

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candles.

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Avery: And that's the technique that won the Nobel

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Prize in 2011.

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Anna: It is. And this is where Australia enters the

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storey early, because one of the three

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laureates, Brian Schmidt, was working at the

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Australian National University when that

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discovery was made. Two teams in

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1998 independently found that distant

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supernovae were fainter than they should have

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been, which meant they were further away than

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expected, which meant the expansion of the

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universe is not slowing down under gravity,

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as everyone assumed, it's speeding up.

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And the thing doing the Speeding up, got the

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placeholder name dark Energy, because nobody

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knew, and to be completely honest, nobody

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still knows what it actually is.

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Avery: So where does the new work come in?

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Anna: Here's the difficulty.

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In the 28 years since, we have collected

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supernovae from dozens of different surveys

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on dozens of different telescopes with

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different detectors, different filters,

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different calibrations observed across

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decades, in which our understanding of these

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explosions changed substantially.

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You cannot simply pour all of that into one

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bucket and start doing cosmology with it.

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The systematic errors will eat you alive.

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Avery: So somebody had to do the unglamorous work.

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Anna: Somebody had to do the unglamorous work. And

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that somebody is ryan Camilleri, a

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PhD candidate at the University of

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Queensland's School of Mathematics and

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Physics, working with Professor Tamara M.

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Davis and a long list of collaborators across

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Australia, the United States, the United

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Kingdom, South Africa, Spain and

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France. What they've done is take Pantheon

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plus, which is the big historical compilation

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of supernovae going back roughly 30 years,

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and combine it with the Dark energy survey's

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full five year sample, which added around

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1500 new high redshift supernovae

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of its own. And rather than stapling the two

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together, they rebuilt both from the same

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starting assumptions in one framework

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with one set of calibrations.

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Avery: Camilleri's own description of it is the

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cleanest summary I've read. Quote,

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we've rebuilt three decades of astronomical

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observations into a single consistent

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framework.

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And he makes the point that this isn't just

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tidying up, it's reanalysis.

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Over the years, we've learned a lot more

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about how supernovae behave. So we've

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been able to go back and apply that improved

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understanding to older data.

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Anna: That improved understanding is doing real

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work here. Two of the biggest headaches in

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supernova cosmology are, uh, dust, cosmic

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dust between us and the explosion reddens and

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dims the light in ways that mimic distance

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and the mass of the galaxy. The supernova

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went off in which turns out to correlate with

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the supernova's brightness in a way we still

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don't fully understand. Both had to be

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handled consistently across the whole sample.

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The team cared about that second problem

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enough that they published a companion paper

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on host galaxy masses alongside the main

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one.

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Avery: Alright, so what does the rebuilt catalogue

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actually say?

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Anna: Two things, and the first one is reassuring.

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If you take the supernovae on their own and

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assume the standard model, a flat universe

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with a genuinely constant dark energy, you

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get a matter density of 0.310

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that is bang in line with everything else we

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Know, the catalogue is not broken, it's

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behaving.

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Avery: And the second thing is the interesting one.

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Anna: The second thing is what happens when you

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fold in the other two great pillars of

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cosmology. The cosmic microwave

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background, the leftover glow of the Big

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Bang, and baryon acoustic

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oscillations, which are frozen sound waves

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from the early universe that act as a cosmic

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ruler. Do that, and under the standard

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constant dark energy model, the three

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datasets start pulling against each other.

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There's a tension, and here's the pointed

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bit, that tension eases if you allow

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dark energy to change with time. The team

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find a preference for evolving dark energy

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over the standard model at between

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2.5 and 3.1-sigma,

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depending on exactly which combination you

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use.

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Avery: Let's be careful with sigma, because we've

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had this conversation before on this show.

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Anna: We have, and we should be careful. Back when

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we covered the LZ dark matter flash, we

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spent a while on this.

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Three Sigma is roughly a, uh, 1 in 700 chance

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of the data looking like this. If the

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standard model is right, that is interesting.

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That is worth chasing. It is emphatically

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not a discovery. Particle physics won't call

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anything discovered below five sigma. And

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cosmology has been burned by three sigma

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results before. Nobody on this paper is

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claiming otherwise.

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Avery: But it's the second independent line of

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evidence pointing the same way, which is a

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different kind of argument.

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Anna: That's exactly the argument Professor Davis

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makes, and it's the heart of why this

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matters. Her words quote

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our Supernova data from DES in

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2024 first showed hints that dark energy

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may be time varying. And this new compilation

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also sees a deviation from the standard

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model. And then. So

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two completely independent measurements have

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found hints of time variation in dark energy

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challenging the standard model. That dark

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energy doesn't change.

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Avery: And this sits alongside what DESSI the,

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the Dark Energy Spectroscopic instrument

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has been reporting from an entirely different

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direction, using those baryon

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acoustic oscillations rather than

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supernovae.

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Anna: Right. Three separate methodologies with

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separate systematics, separate failure modes

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and separate teams. And they keep producing

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the same faint smell of something wrong.

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The other number worth flagging is precision.

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This compilation tightens the uncertainties

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on the dark energy parameters by about

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30% compared with what came before.

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Which means the next round of data won't just

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add noise. It'll actually be able to settle

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this.

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Avery: So spell out the stakes. What changes if

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dark energy really is

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Anna: evolving almost everything downstream?

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A constant dark energy is the simplest

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possible thing. Einstein's cosmological

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constant, a fixed energy density baked into

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empty space itself. If instead it's a field

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that changes strength over cosmic time, then

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it's not a constant. It's a dynamic thing

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with a history and possibly a future.

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It changes how the universe ends.

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And Professor Davis takes it further than

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that. Her line is that all of this quote

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may also hold the clue to explain how gravity

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and quantum physics fit together. That's the

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biggest unfinished problem in physics. And

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dark energy is one of the very few places

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where the two are forced into the same room.

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Avery: Now, I want to note where this was published

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because it's not incidental.

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Anna: No, it isn't. This is in publications of

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the Astronomical Society of Australia,

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Australia's own journal, led from the

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University of Queensland with the Australian

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National University and Swinburne on the

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author list and South African colleagues

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alongside. And the Dark energy survey data at

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the core of it came off the Blanco 4 metre

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telescope at Cerro Tololo in Chile. A

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southern telescope looking at a southern sky.

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From the Nobel winning work at Matt Stromlo

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through to this, the question of what dark

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energy is has been a southern hemisphere

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argument for a very long time.

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Avery: And there's a lovely thread back through our

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own recent episodes here.

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Anna: There really is. Back in episode 181,

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we covered a rebuttal from Nobel laureates,

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including Schmidt and Adam Reese, pushing

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back hard on a claim that the universe's

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acceleration was slowing and confirming the

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acceleration is real. That still stands.

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This is a different question, not whether

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dark energy exists, but whether it holds

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still. On Thursday of last week, we talked

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about fast radio bursts being used to weigh

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the missing gas in the cosmic web, and how

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that bears on the S8 tension. And on

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Saturday, our Skywatch feature was

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SN2026AAIV,

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uh, a type 1A going off in NGC

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7331. One single example

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of exactly the kind of explosion that fills

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this catalogue. Bright enough to chase with a

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backyard telescope.

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Avery: 2,883 more of

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those and you've got a cosmology

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that's the whole trick.

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Anna: And what happens next is that the sample size

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goes up by an order of magnitude. The Vera

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Rubin Observatory in Chile is about to start

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finding these things in industrial

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quantities. And the Nancy Grace Roman Space

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Telescope, which we watched launch a

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fortnight ago and which powered up its

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00:10:58.580 --> 00:11:01.260
coronagraph earlier this month, was designed

270
00:11:01.260 --> 00:11:03.220
in large part to nail exactly this

271
00:11:03.220 --> 00:11:05.860
measurement. If dark energy is changing,

272
00:11:06.020 --> 00:11:08.459
we are going to know within a few years. If

273
00:11:08.459 --> 00:11:11.100
it isn't, we'll know that too. And this will

274
00:11:11.100 --> 00:11:13.420
go down as A very well built catalogue that

275
00:11:13.420 --> 00:11:14.900
briefly made everybody nervous.

276
00:11:15.460 --> 00:11:18.420
Avery: Either way, somebody had to do 30 years

277
00:11:18.420 --> 00:11:19.540
of homework first.

278
00:11:20.450 --> 00:11:23.010
Anna: Somebody did. His name's on the paper.

279
00:11:23.410 --> 00:11:25.970
Avery: Here's a question you don't often hear asked

280
00:11:25.970 --> 00:11:27.010
of our own star.

281
00:11:27.490 --> 00:11:29.170
Did the sun eat a planet?

282
00:11:29.490 --> 00:11:31.650
Anna: We ask that about other stars all the time,

283
00:11:32.130 --> 00:11:33.010
Constantly.

284
00:11:33.410 --> 00:11:36.370
Avery: It's one of the standard results in exoplanet

285
00:11:36.370 --> 00:11:39.290
science. You find a star with an oddly high

286
00:11:39.290 --> 00:11:42.050
abundance of the heavy rock forming elements.

287
00:11:42.130 --> 00:11:44.970
And the neat explanation is that it swallowed

288
00:11:44.970 --> 00:11:47.460
one of its own planets and and the debris is

289
00:11:47.460 --> 00:11:50.180
still floating in its outer layers. New

290
00:11:50.180 --> 00:11:52.780
work published in Monthly Notices of the

291
00:11:52.780 --> 00:11:55.540
Royal Astronomical Society turns that

292
00:11:55.540 --> 00:11:58.420
telescope around and points it at us. It's

293
00:11:58.420 --> 00:12:01.220
by Professor Mutlu Yildiz at Egg University

294
00:12:01.460 --> 00:12:04.300
in Turkey. And the Royal Astronomical

295
00:12:04.300 --> 00:12:06.900
Society put it out on the 10th of September.

296
00:12:07.300 --> 00:12:10.180
Anna: And the argument is that the sun has form.

297
00:12:10.740 --> 00:12:13.420
Avery: The argument is that the sun has two long

298
00:12:13.420 --> 00:12:15.460
standing unexplained quirks.

299
00:12:15.460 --> 00:12:15.770
Anna: And.

300
00:12:15.840 --> 00:12:18.800
Avery: And one event could account for both. Quirk

301
00:12:18.800 --> 00:12:21.520
1 is a genuine embarrassment in solar

302
00:12:21.520 --> 00:12:24.320
physics. We can measure the inside of the

303
00:12:24.320 --> 00:12:27.200
sun, not model it. Measure it using

304
00:12:27.200 --> 00:12:29.880
helioseismology. Sound waves

305
00:12:29.880 --> 00:12:32.680
ring through the solar interior. We watch the

306
00:12:32.680 --> 00:12:35.200
surface vibrate and from that we can

307
00:12:35.200 --> 00:12:37.440
reconstruct the speed of sound at different

308
00:12:37.440 --> 00:12:40.080
depths with real precision. And the

309
00:12:40.080 --> 00:12:42.440
standard solar models don't quite match what

310
00:12:42.440 --> 00:12:45.090
we measure. They've never quite matched.

311
00:12:45.490 --> 00:12:47.530
Anna: That's been an open soar for a couple of

312
00:12:47.530 --> 00:12:48.130
decades.

313
00:12:48.770 --> 00:12:51.730
Avery: It has. Quirk two is lithium.

314
00:12:52.130 --> 00:12:54.730
The sun has far less lithium than it ought

315
00:12:54.730 --> 00:12:57.610
to. It's depleted by a factor of well over

316
00:12:57.610 --> 00:12:59.890
a hundred compared with the material it

317
00:12:59.890 --> 00:13:02.810
formed from. And Yildiz's proposal is that

318
00:13:02.810 --> 00:13:05.250
if the young sun swallowed a super Earth,

319
00:13:05.650 --> 00:13:08.290
something in the range of 5 to 10 times the

320
00:13:08.290 --> 00:13:10.490
mass of our planet, the chemical

321
00:13:10.490 --> 00:13:12.730
rearrangement that follows can push the

322
00:13:12.730 --> 00:13:14.970
models toward the measurements and take the

323
00:13:14.970 --> 00:13:16.850
lithium down at the same time.

324
00:13:17.410 --> 00:13:19.730
Anna: How does eating a planet lower your lithium?

325
00:13:20.290 --> 00:13:22.970
Avery: Broadly by changing the structure and the

326
00:13:22.970 --> 00:13:25.490
mixing near the base of the convective zone,

327
00:13:25.890 --> 00:13:28.250
the boundary where the churning outer layers

328
00:13:28.250 --> 00:13:31.210
meet the still interior. That boundary is

329
00:13:31.210 --> 00:13:33.410
where lithium gets dragged down deep enough

330
00:13:33.490 --> 00:13:35.730
to be destroyed by nuclear reactions.

331
00:13:36.450 --> 00:13:38.650
Adjust the composition and the temperature

332
00:13:38.650 --> 00:13:41.450
gradient there and you change how efficiently

333
00:13:41.450 --> 00:13:43.570
the sun burns its own lithium away.

334
00:13:44.050 --> 00:13:46.130
Yildiz's framing is careful.

335
00:13:47.410 --> 00:13:50.050
A planet several times more massive than

336
00:13:50.050 --> 00:13:52.970
Earth may have fallen into the young sun and

337
00:13:52.970 --> 00:13:55.290
left a uh, lasting chemical imprint deep

338
00:13:55.290 --> 00:13:58.050
inside it. And the

339
00:13:58.050 --> 00:14:00.730
ingestion of a super Earth could help explain

340
00:14:00.730 --> 00:14:03.170
long standing differences between standard

341
00:14:03.170 --> 00:14:05.010
solar models and observations.

342
00:14:05.910 --> 00:14:08.750
Anna: May could. Those are Load bearing

343
00:14:08.750 --> 00:14:10.470
words they are,

344
00:14:10.550 --> 00:14:13.350
Avery: and I want to keep them. This is a

345
00:14:13.350 --> 00:14:15.510
modelling result offering a candidate

346
00:14:15.510 --> 00:14:18.510
solution to a modelling discrepancy. It

347
00:14:18.510 --> 00:14:21.309
is not a fossil. Nobody has dug up the

348
00:14:21.309 --> 00:14:23.430
planet. And there are other live

349
00:14:23.510 --> 00:14:26.230
explanations for the solar abundance problem.

350
00:14:26.710 --> 00:14:29.310
Revisions to the measured composition of the

351
00:14:29.310 --> 00:14:32.090
solar photosphere. For one that don't

352
00:14:32.090 --> 00:14:34.970
require eating anything. What makes this

353
00:14:34.970 --> 00:14:37.930
one attractive is economy. One event,

354
00:14:38.250 --> 00:14:39.290
two problems.

355
00:14:40.090 --> 00:14:41.850
Anna: And there's something faintly unsettling

356
00:14:41.850 --> 00:14:44.210
about it, given what it implies about the

357
00:14:44.210 --> 00:14:45.530
early inner solar system.

358
00:14:46.330 --> 00:14:48.090
Avery: That's the part that stays with me.

359
00:14:48.490 --> 00:14:51.330
Super Earths are the single most common class

360
00:14:51.330 --> 00:14:54.010
of planet we find around other stars.

361
00:14:54.250 --> 00:14:57.130
And our solar system conspicuously lacks

362
00:14:57.130 --> 00:14:59.950
one. If the answer is that we had one

363
00:14:59.950 --> 00:15:02.910
and the sun ate it, that makes us a lot

364
00:15:02.910 --> 00:15:05.590
less unusual and makes the ground under

365
00:15:05.670 --> 00:15:08.590
Mercury's orbit feel a good deal less stable

366
00:15:08.590 --> 00:15:10.710
than it looks now.

367
00:15:11.030 --> 00:15:12.910
Anna: A storey about the sun from the opposite

368
00:15:12.910 --> 00:15:15.710
direction and one with a very practical

369
00:15:15.710 --> 00:15:18.510
edge, particularly for anyone listening from

370
00:15:18.510 --> 00:15:21.310
a crew rest seat. New research in the Journal

371
00:15:21.310 --> 00:15:23.670
of Geophysical Research Atmospheres

372
00:15:24.220 --> 00:15:26.340
finds that cosmic radiation at cruising

373
00:15:26.340 --> 00:15:29.020
altitude gets worse when the sun goes

374
00:15:29.020 --> 00:15:29.420
quiet.

375
00:15:29.900 --> 00:15:32.260
Avery: Which is backwards from how most people would

376
00:15:32.260 --> 00:15:32.780
guess it.

377
00:15:33.260 --> 00:15:35.940
Anna: Completely backwards. And the logic is worth

378
00:15:35.940 --> 00:15:38.860
a minute. The work is by Dr. Roy Yaniv

379
00:15:38.860 --> 00:15:41.660
with Professor Yoav Yair and Professor

380
00:15:41.660 --> 00:15:44.500
Colin Price across the Hebrew University of

381
00:15:44.500 --> 00:15:47.340
Jerusalem, Reichman University and Tel

382
00:15:47.340 --> 00:15:49.740
Aviv University. They flew six

383
00:15:49.740 --> 00:15:51.900
instrumented balloons from southern Israel,

384
00:15:52.400 --> 00:15:55.240
each climbing to around 35 kilometres and

385
00:15:55.240 --> 00:15:57.320
measured the radiation environment the whole

386
00:15:57.320 --> 00:15:57.840
way up.

387
00:15:58.480 --> 00:16:00.400
Avery: So what's the profile look like?

388
00:16:00.720 --> 00:16:03.600
Anna: It peaks higher than you fly. The maximum

389
00:16:03.600 --> 00:16:06.000
sits between 17 and 20 kilometres.

390
00:16:06.320 --> 00:16:08.360
That's a known feature called the Regener

391
00:16:08.360 --> 00:16:11.320
Fotzer maximum, where incoming cosmic rays

392
00:16:11.320 --> 00:16:13.680
have smashed into enough atmosphere to

393
00:16:13.680 --> 00:16:16.080
produce a full shower of secondary particles.

394
00:16:16.480 --> 00:16:18.640
But the shower hasn't yet been absorbed.

395
00:16:19.430 --> 00:16:22.390
Below that, it tails off at a typical

396
00:16:22.390 --> 00:16:24.510
airliner cruising altitude of around 10

397
00:16:24.510 --> 00:16:27.390
kilometres. They measure roughly 0.9

398
00:16:27.390 --> 00:16:29.830
to 1.3 microsieverts per hour.

399
00:16:30.310 --> 00:16:32.750
Avery: And um, the solar connection, the sun's

400
00:16:32.750 --> 00:16:35.350
Anna: magnetic field carried out on the solar wind,

401
00:16:35.750 --> 00:16:38.310
acts as a shield for the entire solar system.

402
00:16:38.790 --> 00:16:41.710
It deflects galactic cosmic rays, the

403
00:16:41.710 --> 00:16:43.590
high energy particles arriving from

404
00:16:43.590 --> 00:16:45.710
supernovae and other violence out in the

405
00:16:45.710 --> 00:16:46.230
galaxy.

406
00:16:46.840 --> 00:16:49.400
When the sun is active, that shield is strong

407
00:16:49.400 --> 00:16:51.480
and fewer of those particles get through.

408
00:16:51.800 --> 00:16:54.440
When the sun goes quiet, the shield weakens

409
00:16:54.440 --> 00:16:57.040
and more of them arrive. The team measure

410
00:16:57.040 --> 00:16:59.800
that anti correlation directly at minus

411
00:16:59.800 --> 00:17:02.800
0.71 and the size of the swing is the

412
00:17:02.800 --> 00:17:05.800
headline. At solar minimum, the dose rate

413
00:17:05.800 --> 00:17:08.520
runs something like 40 to 60% higher

414
00:17:08.760 --> 00:17:09.040
than

415
00:17:09.040 --> 00:17:12.040
Avery: at solar maximum 40 to 60%

416
00:17:12.200 --> 00:17:14.520
is not a rounding error. It isn't.

417
00:17:14.760 --> 00:17:16.640
Anna: They also break down what's actually hitting

418
00:17:16.640 --> 00:17:19.080
you. Neutrons are about 40 to

419
00:17:19.080 --> 00:17:22.080
45% of the dose. With electromagnetic

420
00:17:22.080 --> 00:17:24.520
radiation, another 35 to 40

421
00:17:25.160 --> 00:17:27.280
neutrons matter because they're difficult to

422
00:17:27.280 --> 00:17:29.120
shield against and they're weighted heavily

423
00:17:29.120 --> 00:17:30.440
for biological damage.

424
00:17:31.400 --> 00:17:34.160
Avery: Now, proportion before anyone cancels a

425
00:17:34.160 --> 00:17:34.600
holiday.

426
00:17:35.160 --> 00:17:37.960
Anna: Yes, proportion. A, uh, micro sievert

427
00:17:37.960 --> 00:17:40.890
is a millionth of a sievert. A a long haul

428
00:17:40.890 --> 00:17:43.290
flight puts a few tens of micro sieverts on

429
00:17:43.290 --> 00:17:45.690
you, which is in the same broad territory as

430
00:17:45.690 --> 00:17:48.490
a chest X ray for a passenger. This is not

431
00:17:48.490 --> 00:17:51.210
something to lose sleep over for aircrew who

432
00:17:51.210 --> 00:17:53.690
are occupationally exposed and monitored as

433
00:17:53.690 --> 00:17:56.610
radiation workers in many jurisdictions and

434
00:17:56.610 --> 00:17:59.170
for frequent flyers on the very long, very

435
00:17:59.170 --> 00:18:01.890
high, high latitude routes. And

436
00:18:01.890 --> 00:18:03.850
Australia runs some of the longest sectors on

437
00:18:03.850 --> 00:18:06.530
the planet. A, uh, 40 to 60%

438
00:18:06.610 --> 00:18:09.390
seasonal swing driven by where we sit in the

439
00:18:09.390 --> 00:18:12.310
solar cycle is a real input into how you

440
00:18:12.310 --> 00:18:13.590
calculate annual dose.

441
00:18:14.310 --> 00:18:16.710
Avery: And it dovetails with what we talked about on

442
00:18:16.710 --> 00:18:18.470
Saturday from the other end.

443
00:18:18.950 --> 00:18:21.670
Anna: It's the same dial on the weekend we covered

444
00:18:21.670 --> 00:18:24.110
the Max Planck work on the sun's capacity for

445
00:18:24.110 --> 00:18:27.030
a superflare. The danger of the sun at its

446
00:18:27.030 --> 00:18:29.870
loudest, this is the danger of the sun at

447
00:18:29.870 --> 00:18:32.790
its quietest. An active sun can fire

448
00:18:32.790 --> 00:18:35.690
a particle storm at you. A quiet sun simply

449
00:18:35.690 --> 00:18:37.770
stops holding the galaxy's particles at the

450
00:18:37.770 --> 00:18:40.770
door. Two different risks, opposite ends

451
00:18:40.770 --> 00:18:43.090
of the same cycle. And both of them show up

452
00:18:43.090 --> 00:18:44.130
at altitude first.

453
00:18:44.850 --> 00:18:47.090
Avery: Our last storey before we look up is a, uh,

454
00:18:47.130 --> 00:18:49.770
null result. And I want to argue that it's

455
00:18:49.770 --> 00:18:51.810
one of the better pieces of news this week.

456
00:18:52.130 --> 00:18:54.690
The James Webb Space Telescope has just

457
00:18:54.690 --> 00:18:56.890
carried out the most sensitive search for a

458
00:18:56.890 --> 00:18:59.570
moon around another planet ever attempted.

459
00:18:59.980 --> 00:19:02.500
It didn't find one. What matters is how

460
00:19:02.500 --> 00:19:04.220
thoroughly it didn't find one.

461
00:19:04.700 --> 00:19:06.900
Anna: Exomoons have been the great near miss

462
00:19:06.900 --> 00:19:09.420
Avery: of the field for 15 years.

463
00:19:09.900 --> 00:19:12.620
We have close to 6,000 confirmed planets

464
00:19:12.620 --> 00:19:15.380
around other stars and not one confirmed

465
00:19:15.380 --> 00:19:18.260
moon, which is faintly ridiculous given that

466
00:19:18.260 --> 00:19:21.260
our own solar system has hundreds. The new

467
00:19:21.260 --> 00:19:23.820
work is by David Kipping, who has effectively

468
00:19:23.900 --> 00:19:26.790
made exomoon hunting his life's work. And

469
00:19:26.790 --> 00:19:29.228
it went up on the preprint server on 4

470
00:19:29.352 --> 00:19:29.910
September.

471
00:19:30.390 --> 00:19:31.990
Anna: Which planet did he point it at?

472
00:19:32.390 --> 00:19:35.030
Avery: LP899C,

473
00:19:35.430 --> 00:19:37.870
a rocky planet in the temperate zone of a

474
00:19:37.870 --> 00:19:39.910
very cool, very faint star.

475
00:19:40.310 --> 00:19:43.110
Kipping used 12 separate JWST

476
00:19:43.350 --> 00:19:46.270
transits, 12 passes of the planet in front

477
00:19:46.270 --> 00:19:48.910
of its star and stacked them. And the

478
00:19:48.910 --> 00:19:51.350
sensitivity he gets out of that is the storey

479
00:19:51.750 --> 00:19:54.510
he can exclude Moons down to one tenth of

480
00:19:54.510 --> 00:19:57.120
Earth's radius and at 95%

481
00:19:57.200 --> 00:19:59.960
confidence across the planet's entire hill

482
00:19:59.960 --> 00:20:02.800
sphere. That's the whole region where a moon

483
00:20:02.800 --> 00:20:04.640
could gravitationally hang on.

484
00:20:05.200 --> 00:20:07.960
Anna: One tenth of Earth's Radius is about 650

485
00:20:07.960 --> 00:20:10.880
kilometres which rules out the entire

486
00:20:10.880 --> 00:20:13.600
Avery: mid tier of our own solar system's moons.

487
00:20:14.000 --> 00:20:16.560
Europa's gone. Rhea's gone.

488
00:20:16.800 --> 00:20:18.640
Umbriel's gone. If

489
00:20:18.640 --> 00:20:21.280
LP899C

490
00:20:21.520 --> 00:20:23.980
had anything like those or Webb would have

491
00:20:23.980 --> 00:20:24.420
seen it.

492
00:20:24.580 --> 00:20:26.580
Anna: So why is the absence good news?

493
00:20:27.300 --> 00:20:30.180
Avery: Two reasons. First, because it was always

494
00:20:30.260 --> 00:20:32.900
possible that we'd found no exomoons,

495
00:20:32.900 --> 00:20:35.700
simply because we can't see them. That the

496
00:20:35.700 --> 00:20:38.300
whole search was hopeless and we were wasting

497
00:20:38.300 --> 00:20:40.900
our time. This demonstrates the

498
00:20:40.900 --> 00:20:43.780
opposite. Webb can find astonishingly

499
00:20:43.780 --> 00:20:46.700
small moons and stacking transits buys

500
00:20:46.700 --> 00:20:49.220
you far more sensitivity than a single one.

501
00:20:49.950 --> 00:20:52.950
That's a capability result and it applies to

502
00:20:52.950 --> 00:20:55.910
every other target. Second, this

503
00:20:55.910 --> 00:20:58.270
particular non detection is physically

504
00:20:58.270 --> 00:21:00.870
expected. The planet orbits at Ah, just

505
00:21:00.870 --> 00:21:03.790
0.04 astronomical units,

506
00:21:04.030 --> 00:21:07.030
extremely close in and at that distance

507
00:21:07.030 --> 00:21:09.710
tidal forces would strip a large moon away

508
00:21:09.790 --> 00:21:12.390
over time anyway. So the theory

509
00:21:12.390 --> 00:21:15.150
predicted an empty hill sphere and the

510
00:21:15.150 --> 00:21:16.990
observation delivered an empty

511
00:21:16.990 --> 00:21:19.650
Anna: hill sphere Theory and observation

512
00:21:19.650 --> 00:21:22.170
agreeing is not the most thrilling headline

513
00:21:22.490 --> 00:21:24.650
but it's how you know the instrument is

514
00:21:24.650 --> 00:21:25.210
honest.

515
00:21:25.930 --> 00:21:28.610
Avery: Exactly right. And a small Southern

516
00:21:28.610 --> 00:21:29.650
footnote. The

517
00:21:29.650 --> 00:21:32.650
LP899 system was

518
00:21:32.650 --> 00:21:35.330
found by Speculus, a survey hunting

519
00:21:35.330 --> 00:21:37.890
planets around the coolest stars whose

520
00:21:37.890 --> 00:21:40.410
southern station sits at Paranal in Chile

521
00:21:40.730 --> 00:21:43.330
under the same skies as the telescopes that

522
00:21:43.330 --> 00:21:44.970
keep turning up in this programme.

523
00:21:45.130 --> 00:21:47.920
Anna: Quick update before the skywatch on a storey

524
00:21:47.920 --> 00:21:49.840
we left open a couple of weeks back.

525
00:21:50.400 --> 00:21:52.800
NASA's Crew 13 mission to the International

526
00:21:52.960 --> 00:21:55.920
Space Station is now targeting no earlier

527
00:21:55.920 --> 00:21:57.120
than late September.

528
00:21:57.520 --> 00:21:59.600
Avery: That's the flight that was supposed to go on

529
00:21:59.600 --> 00:22:00.160
the 12th.

530
00:22:00.320 --> 00:22:02.720
Anna: It was on the 29th of August.

531
00:22:02.720 --> 00:22:05.560
NASA and SpaceX stood the mission down after

532
00:22:05.560 --> 00:22:07.920
teams found an oxidizer leak in the Dragon

533
00:22:07.920 --> 00:22:10.200
spacecraft's propulsion system during

534
00:22:10.200 --> 00:22:13.080
standard pre launch processing. At the time

535
00:22:13.080 --> 00:22:14.800
the statement was simply that a new target

536
00:22:14.800 --> 00:22:17.300
date would be announced once available and

537
00:22:17.300 --> 00:22:19.740
that joint teams would complete any necessary

538
00:22:19.740 --> 00:22:22.420
rework before flight. The Canadian Space

539
00:22:22.420 --> 00:22:24.340
Agency has now confirmed the mission is

540
00:22:24.340 --> 00:22:26.460
aiming for no earlier than late September.

541
00:22:26.860 --> 00:22:29.580
Though as we record, NASA hasn't published

542
00:22:29.580 --> 00:22:31.700
Avery: a specific date and the crew is an

543
00:22:31.700 --> 00:22:32.460
interesting one.

544
00:22:32.540 --> 00:22:35.420
Anna: It is Commander Jessica Watkins and

545
00:22:35.420 --> 00:22:38.300
pilot Luke Delaney for NASA with mission

546
00:22:38.300 --> 00:22:40.820
specialist Joshua Kutryk of the Canadian

547
00:22:40.820 --> 00:22:42.910
Space Agency and and Sergey

548
00:22:42.910 --> 00:22:45.870
Teteryatnikov of Roscosmos. They'll

549
00:22:45.870 --> 00:22:48.310
fly on a Falcon 9 from Space Launch Complex

550
00:22:48.310 --> 00:22:51.150
40 at Cape Canaveral. The same pad that

551
00:22:51.150 --> 00:22:53.550
quietly notched its 400th orbital flight

552
00:22:53.550 --> 00:22:54.070
yesterday.

553
00:22:54.710 --> 00:22:56.350
We'll bring you the date the moment it's

554
00:22:56.350 --> 00:22:56.710
firm.

555
00:22:56.710 --> 00:22:59.230
Avery: Right, let's get you outside. And there's

556
00:22:59.230 --> 00:23:02.110
something live happening tonight. A large

557
00:23:02.110 --> 00:23:05.030
coronal hole on the sun has rotated around

558
00:23:05.030 --> 00:23:07.590
into a geo effective position and

559
00:23:07.670 --> 00:23:10.310
forecasters expect the fast solar wind

560
00:23:10.390 --> 00:23:12.950
streaming out of it to to reach Earth today.

561
00:23:13.510 --> 00:23:16.150
That means active geomagnetic conditions,

562
00:23:16.630 --> 00:23:17.150
which means

563
00:23:17.150 --> 00:23:19.950
Anna: aurora watching is on at both ends of the

564
00:23:19.950 --> 00:23:20.390
planet.

565
00:23:20.470 --> 00:23:22.790
Avery: It does for our southern hemisphere

566
00:23:22.790 --> 00:23:25.310
listeners. That's Aurora australis

567
00:23:25.310 --> 00:23:28.310
territory Tasmania first and best,

568
00:23:28.470 --> 00:23:31.230
with a genuine chance from southern Victoria

569
00:23:31.230 --> 00:23:33.950
and the far south of New Zealand. If it holds

570
00:23:33.950 --> 00:23:36.790
up, look south, get away from town

571
00:23:36.790 --> 00:23:39.740
lights and be patient. Keep cameras will pick

572
00:23:39.740 --> 00:23:42.580
up colour your eyes won't. For, uh, our

573
00:23:42.580 --> 00:23:44.660
North American listeners, you're looking

574
00:23:44.660 --> 00:23:47.300
north and the northern tier states and

575
00:23:47.300 --> 00:23:50.020
Canada are in play. This is a

576
00:23:50.020 --> 00:23:52.940
coronal hole stream rather than a big flare

577
00:23:52.940 --> 00:23:55.780
event. So think a steady moderate

578
00:23:55.780 --> 00:23:58.460
glow rather than a spectacular overhead

579
00:23:58.460 --> 00:24:01.020
display. But it's free and it's

580
00:24:01.020 --> 00:24:02.380
tonight and

581
00:24:02.380 --> 00:24:04.500
Anna: the moon is out of the way for it.

582
00:24:05.280 --> 00:24:08.120
Avery: Beautifully out of the way. New Moon was last

583
00:24:08.120 --> 00:24:10.920
Friday, so we're in a young crescent evening

584
00:24:10.920 --> 00:24:13.680
sky and the deep sky is still yours.

585
00:24:14.080 --> 00:24:16.920
Over the next week, the Moon climbs back into

586
00:24:16.920 --> 00:24:19.760
the evening and walks past two landmarks

587
00:24:19.760 --> 00:24:22.600
worth Antares, the Red

588
00:24:22.600 --> 00:24:25.320
Heart of Scorpius and the Teapot of

589
00:24:25.320 --> 00:24:28.200
Sagittarius. Use the Moon to find

590
00:24:28.200 --> 00:24:31.160
them between now and the 20th. And from

591
00:24:31.160 --> 00:24:34.000
Sydney, the centre of the Milky Way is still

592
00:24:34.000 --> 00:24:36.280
riding high overhead after dark.

593
00:24:36.760 --> 00:24:39.120
That dense textured band through the

594
00:24:39.120 --> 00:24:42.000
teapot is the galactic core and

595
00:24:42.000 --> 00:24:44.480
it is one of the genuine privileges of

596
00:24:44.480 --> 00:24:47.400
southern observing. From mid northern

597
00:24:47.400 --> 00:24:50.400
latitudes, it's much lower in the south, so

598
00:24:50.400 --> 00:24:52.520
northern listeners should hunt for a clear

599
00:24:52.600 --> 00:24:55.320
southern horizon while the season lasts.

600
00:24:56.210 --> 00:24:58.850
Anna: Planets. Venus is the headline.

601
00:24:59.490 --> 00:25:02.330
Avery: Venus is the headline and Thursday is the

602
00:25:02.330 --> 00:25:02.690
date.

603
00:25:03.090 --> 00:25:06.050
On the 18th of September, Venus reaches

604
00:25:06.050 --> 00:25:07.970
greatest brilliancy for this evening

605
00:25:07.970 --> 00:25:10.210
apparition. At magnitude

606
00:25:10.210 --> 00:25:12.850
-4.8. That is

607
00:25:12.850 --> 00:25:15.770
spectacularly bright. Bright enough to cast

608
00:25:15.770 --> 00:25:18.490
a shadow from a dark sight. Bright enough

609
00:25:18.490 --> 00:25:21.370
that you'll field phone calls about it. Look

610
00:25:21.370 --> 00:25:24.200
west shortly after sunset. You'll notice

611
00:25:24.200 --> 00:25:26.360
some listings give a different date for this.

612
00:25:26.840 --> 00:25:29.200
We're going with the 18th, which is the

613
00:25:29.200 --> 00:25:32.080
correct one for the standard definition. And

614
00:25:32.080 --> 00:25:35.080
this apparition favours the south. From

615
00:25:35.080 --> 00:25:38.000
Sydney, Venus sits higher and lingers

616
00:25:38.000 --> 00:25:40.800
longer in a darker sky than it does from most

617
00:25:40.800 --> 00:25:43.320
of the United States, where it's a lower,

618
00:25:43.320 --> 00:25:45.320
briefer object in the twilight.

619
00:25:45.720 --> 00:25:48.680
Anna: Take the win m. Anything else worth chasing?

620
00:25:49.560 --> 00:25:52.240
Avery: Three things Mercury is low in the

621
00:25:52.240 --> 00:25:55.080
western twilight, tricky but doable with

622
00:25:55.080 --> 00:25:58.040
a clear horizon. Mars is in the

623
00:25:58.040 --> 00:26:00.960
morning sky and passes about 6 degrees

624
00:26:00.960 --> 00:26:03.800
south of Pollux, the brighter of the Gemini

625
00:26:03.800 --> 00:26:06.040
twins, also on the 18th.

626
00:26:06.600 --> 00:26:09.480
That one's a northern favourite view. And

627
00:26:09.560 --> 00:26:12.160
Saturn is building towards opposition on the

628
00:26:12.160 --> 00:26:15.000
4th of October, with the rings about 7

629
00:26:15.000 --> 00:26:17.850
degree open. So it is well placed

630
00:26:17.850 --> 00:26:20.730
all night and getting better. The Harvest

631
00:26:20.730 --> 00:26:23.690
Moon rides past it on the 26th with

632
00:26:23.690 --> 00:26:25.930
Neptune nearby. For anyone with

633
00:26:25.930 --> 00:26:27.610
binoculars or a scope,

634
00:26:28.090 --> 00:26:30.010
Anna: there's also a date for the diary. Next

635
00:26:30.010 --> 00:26:31.770
Saturday there is.

636
00:26:32.090 --> 00:26:34.330
Avery: 19th September is international

637
00:26:34.810 --> 00:26:37.250
observe the Moon night, which is one of the

638
00:26:37.250 --> 00:26:39.730
few global astronomy events that works

639
00:26:39.730 --> 00:26:42.170
equally well from either hemisphere. With no

640
00:26:42.170 --> 00:26:45.000
equipment at all, the Moon will be a fat

641
00:26:45.000 --> 00:26:47.520
crescent in the evening sky, which is

642
00:26:47.520 --> 00:26:50.200
genuinely the best phase for it because the

643
00:26:50.200 --> 00:26:52.360
shadows along the terminator throw the

644
00:26:52.360 --> 00:26:55.320
craters and mountains into relief. If you've

645
00:26:55.320 --> 00:26:57.600
got a pair of binoculars, that's all you

646
00:26:57.600 --> 00:26:59.880
need. If you've got a telescope and a

647
00:26:59.880 --> 00:27:01.360
neighbour, that's even better.

648
00:27:02.000 --> 00:27:04.480
Anna: And the equinox is coming, the

649
00:27:04.480 --> 00:27:05.120
22nd

650
00:27:05.600 --> 00:27:08.040
Avery: spring here, autumn for our northern

651
00:27:08.040 --> 00:27:10.560
listeners. And it brings the zodiacal light

652
00:27:10.560 --> 00:27:13.260
with it. That's sunlight scattering off

653
00:27:13.260 --> 00:27:15.940
dust in the plane of the solar system and

654
00:27:15.940 --> 00:27:18.500
around the equinox. It's an evening object

655
00:27:18.580 --> 00:27:21.060
low in the west from the southern hemisphere,

656
00:27:21.380 --> 00:27:24.380
a false dusk and a pre dawn object

657
00:27:24.380 --> 00:27:27.139
in the east from the northern hemisphere. A

658
00:27:27.139 --> 00:27:30.060
faint tapering cone of light, dark

659
00:27:30.060 --> 00:27:32.580
skies, no moon and patience.

660
00:27:33.220 --> 00:27:35.660
Anna: And the safety note, which is not optional on

661
00:27:35.660 --> 00:27:36.180
this programme.

662
00:27:36.990 --> 00:27:39.670
Avery: Never optional. With Venus at its most

663
00:27:39.670 --> 00:27:41.990
brilliant, some of you will be tempted to

664
00:27:41.990 --> 00:27:44.790
hunt it in daylight and it is genuinely

665
00:27:44.790 --> 00:27:47.590
findable. But that means aiming optics

666
00:27:47.590 --> 00:27:49.790
near the sun and that is how people

667
00:27:49.870 --> 00:27:52.590
permanently damage their eyes. If you are

668
00:27:52.590 --> 00:27:55.350
going to look anywhere near the sun, use a

669
00:27:55.350 --> 00:27:57.430
filter Certified to the ISO

670
00:27:57.430 --> 00:28:00.350
123122 standard

671
00:28:00.590 --> 00:28:02.430
fitted over the front of the instrument,

672
00:28:03.000 --> 00:28:04.280
never at the eyepiece.

673
00:28:04.520 --> 00:28:06.920
Cheque it for scratches and pinholes before

674
00:28:06.920 --> 00:28:09.160
every use. Sunglasses,

675
00:28:09.320 --> 00:28:11.840
exposed film, smoked glass and

676
00:28:11.840 --> 00:28:14.840
welding glass below shade 14 are

677
00:28:14.840 --> 00:28:17.400
not safe and never were. And

678
00:28:17.400 --> 00:28:19.640
supervise children the entire time.

679
00:28:20.280 --> 00:28:22.080
Anna: And that's Astronomy daily for Monday

680
00:28:22.080 --> 00:28:24.816
14th September

681
00:28:25.104 --> 00:28:27.320
2884. Supernovae

682
00:28:27.560 --> 00:28:30.080
rebuilt from three decades of observations by

683
00:28:30.080 --> 00:28:33.050
an Australian led team quietly making the

684
00:28:33.050 --> 00:28:35.410
case that dark energy might not hold still.

685
00:28:35.890 --> 00:28:38.690
Avery: A sun that may have eaten a super earth and

686
00:28:38.690 --> 00:28:41.530
still carries the receipt. A reminder that

687
00:28:41.530 --> 00:28:44.010
the sun's quiet years are the ones that let

688
00:28:44.010 --> 00:28:46.770
the galaxy's particles through. And the most

689
00:28:46.770 --> 00:28:49.330
sensitive exomoon search ever attempted,

690
00:28:49.650 --> 00:28:52.210
finding precisely nothing in the most

691
00:28:52.210 --> 00:28:53.730
useful possible way.

692
00:28:54.290 --> 00:28:56.650
Anna: All of Today's storeys with links to the

693
00:28:56.650 --> 00:28:58.910
papers and the press releases are are at

694
00:28:58.910 --> 00:29:01.830
astronomydaily IO you'll find the

695
00:29:01.830 --> 00:29:04.390
full back catalogue there too, along with our

696
00:29:04.390 --> 00:29:06.230
news feed and the newsletter. If you'd like

697
00:29:06.230 --> 00:29:07.230
this in your inbox

698
00:29:07.630 --> 00:29:09.710
Avery: and we do read the contact form.

699
00:29:10.030 --> 00:29:12.990
Questions, corrections and storey tips all

700
00:29:12.990 --> 00:29:15.430
land with us, and they have shaped more than

701
00:29:15.430 --> 00:29:18.190
one segment lately. You can also find us

702
00:29:18.190 --> 00:29:19.070
on socials.

703
00:29:19.150 --> 00:29:22.030
Anna: Astrodaily pod astronomy daily

704
00:29:22.030 --> 00:29:24.430
is part of the bytes.com podcast network.

705
00:29:24.920 --> 00:29:25.560
I'm Anna.

706
00:29:25.640 --> 00:29:28.280
Avery: And I'm Avery. Clear skies

707
00:29:28.280 --> 00:29:29.560
wherever you're standing.