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

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Three decades of exploding stars pulled


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apart and rebuilt from the ground up


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into a single consistent picture. 2,884


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of them. And when an Australian le team


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stepped back to look at what that


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picture was saying about dark energy, it


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wasn't saying what the textbook says.


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>> We've also got a study asking whether


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our own sun once swallowed a planet and


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whether the evidence for it is still


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sitting inside the star right now


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waiting to be read. Plus, why the


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quietest stretch of the solar cycle is


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the one that matters most if you spend


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your working life at 35,000 ft.


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>> And the James Web Space Telescope has


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just run the most sensitive search for a


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moon around another planet that anyone


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has ever attempted. It found nothing at


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all. That is the good news.


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>> This is Astronomy Daily. I'm Anna.


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>> And I'm Avery. It's Monday, the 14th of


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September, 2026, and we're coming to you


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as always from Sydney, Australia. Let's


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get into it.


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>> We're starting today with a result that


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has been quietly sitting in the open for


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about a week, and I think it deserves a


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great deal more attention than it has


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had. An international team led out of


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the University of Queensland has


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published what is now the largest and


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most internally consistent catalog of


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type 1A supernova ever assembled. 2,884


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of them. And it adds fresh weight to a


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very awkward idea. That dark energy


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might not be constant.


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>> Which would be a problem because the


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word constant is doing enormous


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structural work in modern cosmology.


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>> It is the loadbearing wall. So, let's


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build this up properly because the


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method here matters as much as the


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answer. A type 1A supernova is what


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happens when a white dwarf star, the


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dense, burnt out core left behind by a


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star like our sun, gathers too much


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material and detonates. The crucial


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thing is that these explosions are close


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to identical. They go off at roughly the


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same intrinsic brightness every time.


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So, if you measure how bright one looks


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from here, you can work out how far away


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it is. Astronomers call them standard


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candles.


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>> And that's the technique that won the


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Nobel Prize in 2011.


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>> It is. And this is where Australia


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enters the story early because one of


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the three laurates, Brian Schmidt, was


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working at the Australian National


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University when that discovery was made.


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Two teams in 1998 independently found


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that distant supernovi were fainter than


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they should have been which meant they


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were further away than expected which


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meant the expansion of the universe is


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not slowing down under gravity as


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everyone assumed. It's speeding up and


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the thing doing the speeding up got the


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placeholder name dark energy because


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nobody knew and to be completely honest


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nobody still knows what it actually is.


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>> So where does the new work come in?


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Here's the difficulty. In the 28 years


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since, we have collected supernova from


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dozens of different surveys on dozens of


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different telescopes with different


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detectors, different filters, different


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calibrations, observed across decades in


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which our understanding of these


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explosions changed substantially. You


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cannot simply pour all of that into one


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bucket and start doing cosmology with


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it. The systematic errors will eat you


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alive. So, somebody had to do the


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unglamorous work.


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>> Somebody had to do the unglamorous work.


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And that somebody is Ryan Cameli, a PhD


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candidate at the University of


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Queensland's School of Mathematics and


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Physics, working with Professor Tamara


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Davis, and a long list of collaborators


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across Australia, the United States, the


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United Kingdom, South Africa, Spain, and


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France. What they've done is take


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Pantheon Plus, which is the big


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historical compilation of supernova


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going back roughly 30 years, and combine


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it with the dark energy surveys full


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5-year sample, which added around 1,500


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new high red shift supernova of its own.


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And rather than stapling the two


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together, they rebuilt both from the


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same starting assumptions in one


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framework with one set of calibrations.


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Cameli'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


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astronomical observations into a single


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consistent framework." And he makes the


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point that this isn't just tidying up,


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it's reanalysis. Quote, "Over the years,


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we've learned a lot more about how


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supernovi behave. So, we've been able to


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go back and apply that improved


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understanding to older data." That


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improved understanding is doing real


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work here. Two of the biggest headaches


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in supernova cosmology are dust. Cosmic


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dust between us and the explosion reens


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and dims the light in ways that mimic


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distance and the mass of the galaxy the


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supernova went off in, which turns out


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to correlate with the supernova's


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brightness in a way we still don't fully


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understand. Both had to be handled


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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


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paper on host galaxy masses alongside


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the main one.


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>> All right, so what does the rebuilt


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catalog actually say?


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>> Two things. And the first one is


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reassuring. If you take the supernova on


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their own and assume the standard model,


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a flat universe with a genuinely


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constant dark energy, you get a matter


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density of 0.310.


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That is bang in line with everything


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else we know. The catalog is not broken.


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It's behaving.


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>> And the second thing is the interesting


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one.


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>> The second thing is what happens when


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you fold in the other two great pillars


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of cosmology. The cosmic microwave


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background, the leftover glow of the big


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bang and baron acoustic oscillations,


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which are frozen sound waves from the


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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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data sets start pulling against each


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other. There's a tension. And here's the


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pointed bit. That tension eases if you


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allow dark energy to change with time.


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The team find a preference for evolving


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dark energy over the standard model at


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between 2.5 and 3.1 sigma depending on


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exactly which combination you use. Let's


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be careful with Sigma because we've had


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this conversation before on this show.


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>> We have and we should be careful. Back


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when we covered the LZ dark matter


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flash, we spent a while on this. Three


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sigma is roughly a 1 in700 chance of the


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data looking like this if the standard


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model is right. That is interesting.


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That is worth chasing. It is


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emphatically not a discovery. Particle


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physics won't call anything discovered


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below five sigma. and cosmology has been


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burned by three sigma results before.


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Nobody on this paper is claiming


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otherwise.


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>> But it's the second independent line of


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evidence pointing the same way, which is


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a different kind of argument.


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>> That's exactly the argument Professor


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Davis makes. And it's the heart of why


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this matters. Her words, quote, "Our


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supernova data from dees in 2024 first


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showed hints that dark energy may be


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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 two completely


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independent measurements have found


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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. And this sits


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alongside what DESIE, the dark energy


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spectroscopic instrument, has been


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reporting from an entirely different


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direction using those barri acoustic


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oscillations rather than supernovi.


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>> Right? Three separate methodologies with


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separate systematics, separate failure


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modes, and separate teams. And they keep


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producing the same faint smell of


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something wrong. The other number worth


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flagging is precision. This compilation


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tightens the uncertainties on the dark


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energy parameters by about 30% compared


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with what came before. Which means the


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next round of data won't just add noise.


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It'll actually be able to settle this.


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>> So spell out the stakes. What changes if


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dark energy really is evolving?


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>> Almost everything downstream. A constant


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dark energy is the simplest possible


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thing. Einstein's cosmological constant,


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a fixed energy density baked into empty


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space itself. If instead it's a field


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that changes strength over cosmic time,


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then it's not a constant, it's a dynamic


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thing with a history and possibly a


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future. It changes how the universe


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ends. And Professor Davis takes it


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further than that. Her line is that all


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of this quote may also hold the clue to


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explain how gravity and quantum physics


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fit together. That's the biggest


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unfinished problem in physics. and dark


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energy is one of the very few places


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where the two are forced into the same


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room.


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>> Now, I want to note where this was


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published because it's not incidental.


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>> 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


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Australian National University and


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Swinburn on the author list and South


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African colleagues alongside and the


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dark energy survey data at the core of


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it came off the Blanco 4meter telescope


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at Sarotolo in Chile, a southern


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telescope looking at a southern sky.


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From the Nobel work at Mount Stromllo


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through to this, the question of what


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dark energy is has been a southern


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hemisphere argument for a very long


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time.


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>> And there's a lovely thread back through


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our own recent episodes here.


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>> There really is. Back in episode 181, we


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covered a rebuttal from Nobel laureates


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including Schmidt and Adam Ree pushing


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back hard on a claim that the universe's


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acceleration was slowing and confirming


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the acceleration is real. That still


00:10:02.880 --> 00:10:05.269
stands. This is a different question.


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Not whether dark energy exists, but


00:10:07.519 --> 00:10:10.150
whether it holds still. On Thursday of


00:10:10.160 --> 00:10:12.150
last week, we talked about fast radio


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bursts being used to weigh the missing


00:10:13.920 --> 00:10:16.710
gas in the cosmic web and how that bears


00:10:16.720 --> 00:10:19.509
on the S8 tension. And on Saturday, our


00:10:19.519 --> 00:10:23.750
skywatch feature was SN 2026 A AIV, a


00:10:23.760 --> 00:10:27.990
type 1A going off in NGC 7331.


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One single example of exactly the kind


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of explosion that fills this catalog.


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bright enough to chase with a backyard


00:10:34.000 --> 00:10:35.430
telescope.


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>> 2,883


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more of those and you've got a


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cosmology.


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>> That's the whole trick. And what happens


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next is that the sample size goes up by


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an order of magnitude. The Vera Rubin


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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


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Space Telescope, which we watched launch


00:10:56.240 --> 00:10:58.630
a fortnight ago and which powered up its


00:10:58.640 --> 00:11:00.870
coronagraph earlier this month, was


00:11:00.880 --> 00:11:03.030
designed in large part to nail exactly


00:11:03.040 --> 00:11:05.509
this measurement. If dark energy is


00:11:05.519 --> 00:11:07.430
changing, we are going to know within a


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few years. If it isn't, we'll know that,


00:11:09.920 --> 00:11:12.230
too. And this will go down as a very


00:11:12.240 --> 00:11:14.069
well-built catalog that briefly made


00:11:14.079 --> 00:11:15.590
everybody nervous.


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>> Either way, somebody had to do 30 years


00:11:18.480 --> 00:11:20.389
of homework first.


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>> Somebody did. His name's on the paper.


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>> Here's a question you don't often hear


00:11:25.680 --> 00:11:28.790
asked of our own star. Did the sun eat a


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planet?


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>> We ask that about other stars all the


00:11:31.440 --> 00:11:32.230
time


00:11:32.240 --> 00:11:34.790
>> constantly. It's one of the standard


00:11:34.800 --> 00:11:37.829
results in exoplanet science. You find a


00:11:37.839 --> 00:11:40.389
star with an oddly high abundance of the


00:11:40.399 --> 00:11:42.790
heavy rock forming elements. And the


00:11:42.800 --> 00:11:44.949
neat explanation is that it swallowed


00:11:44.959 --> 00:11:47.509
one of its own planets and the debris is


00:11:47.519 --> 00:11:50.230
still floating in its outer layers. New


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work published in monthly notices of the


00:11:52.800 --> 00:11:55.590
Royal Astronomical Society turns that


00:11:55.600 --> 00:11:58.150
telescope around and points it at us.


00:11:58.160 --> 00:12:00.949
It's by Professor Mutlu Yildes at Egg


00:12:00.959 --> 00:12:03.509
University in Turkey and the Royal


00:12:03.519 --> 00:12:05.829
Astronomical Society put it out on the


00:12:05.839 --> 00:12:07.430
10th of September.


00:12:07.440 --> 00:12:09.829
>> And the argument is that the sun has


00:12:09.839 --> 00:12:10.870
form.


00:12:10.880 --> 00:12:13.190
>> The argument is that the sun has two


00:12:13.200 --> 00:12:16.230
longstanding unexplained quirks and one


00:12:16.240 --> 00:12:19.110
event could account for both. Quirk one


00:12:19.120 --> 00:12:21.590
is a genuine embarrassment in solar


00:12:21.600 --> 00:12:24.150
physics. We can measure the inside of


00:12:24.160 --> 00:12:27.269
the sun, not model it, measure it. Using


00:12:27.279 --> 00:12:29.190
heliocismology,


00:12:29.200 --> 00:12:31.110
sound waves ring through the solar


00:12:31.120 --> 00:12:33.990
interior. We watch the surface vibrate.


00:12:34.000 --> 00:12:36.150
And from that, we can reconstruct the


00:12:36.160 --> 00:12:38.389
speed of sound at different depths with


00:12:38.399 --> 00:12:40.949
real precision. And the standard solar


00:12:40.959 --> 00:12:42.710
models don't quite match what we


00:12:42.720 --> 00:12:45.590
measure. They've never quite matched.


00:12:45.600 --> 00:12:47.590
That's been an open sore for a couple of


00:12:47.600 --> 00:12:48.870
decades.


00:12:48.880 --> 00:12:52.790
>> It has. Quirk two is lithium. The sun


00:12:52.800 --> 00:12:55.509
has far less lithium than it ought to.


00:12:55.519 --> 00:12:57.829
It's depleted by a factor of well over a


00:12:57.839 --> 00:13:00.230
100 compared with the material it formed


00:13:00.240 --> 00:13:03.030
from. And yield's proposal is that if


00:13:03.040 --> 00:13:05.750
the young sun swallowed a super earth,


00:13:05.760 --> 00:13:07.750
something in the range of five to 10


00:13:07.760 --> 00:13:10.069
times the mass of our planet, the


00:13:10.079 --> 00:13:12.310
chemical rearrangement that follows can


00:13:12.320 --> 00:13:14.310
push the models toward the measurements


00:13:14.320 --> 00:13:16.470
and take the lithium down at the same


00:13:16.480 --> 00:13:17.430
time.


00:13:17.440 --> 00:13:19.269
>> How does eating a planet lower your


00:13:19.279 --> 00:13:20.310
lithium?


00:13:20.320 --> 00:13:22.790
>> Broadly, by changing the structure and


00:13:22.800 --> 00:13:24.550
the mixing near the base of the


00:13:24.560 --> 00:13:27.030
convective zone, the boundary where the


00:13:27.040 --> 00:13:29.190
churning outer layers meet the still


00:13:29.200 --> 00:13:31.910
interior. That boundary is where lithium


00:13:31.920 --> 00:13:33.910
gets dragged down deep enough to be


00:13:33.920 --> 00:13:36.870
destroyed by nuclear reactions. Adjust


00:13:36.880 --> 00:13:38.710
the composition and the temperature


00:13:38.720 --> 00:13:40.870
gradient there and you change how


00:13:40.880 --> 00:13:42.870
efficiently the sun burns its own


00:13:42.880 --> 00:13:45.670
lithium away. Yield's framing is


00:13:45.680 --> 00:13:49.110
careful. Quote, "A planet several times


00:13:49.120 --> 00:13:51.509
more massive than Earth may have fallen


00:13:51.519 --> 00:13:53.990
into the young sun and left a lasting


00:13:54.000 --> 00:13:57.110
chemical imprint deep inside it." and


00:13:57.120 --> 00:13:59.670
quote, "The ingestion of a super Earth


00:13:59.680 --> 00:14:01.590
could help explain long-standing


00:14:01.600 --> 00:14:03.590
differences between standard solar


00:14:03.600 --> 00:14:07.670
models and observations." May, could


00:14:07.680 --> 00:14:09.910
those are loadbearing words.


00:14:09.920 --> 00:14:13.030
>> They are, and I want to keep them. This


00:14:13.040 --> 00:14:15.030
is a modeling result offering a


00:14:15.040 --> 00:14:16.949
candidate solution to a modeling


00:14:16.959 --> 00:14:20.470
discrepancy. It is not a fossil. Nobody


00:14:20.480 --> 00:14:22.870
has dug up the planet. And there are


00:14:22.880 --> 00:14:25.269
other live explanations for the solar


00:14:25.279 --> 00:14:27.829
abundance problem. Revisions to the


00:14:27.839 --> 00:14:29.750
measured composition of the solar


00:14:29.760 --> 00:14:32.629
photosphere for one that don't require


00:14:32.639 --> 00:14:35.269
eating anything. What makes this one


00:14:35.279 --> 00:14:38.710
attractive is economy. One event, two


00:14:38.720 --> 00:14:40.150
problems.


00:14:40.160 --> 00:14:41.910
>> And there's something faintly unsettling


00:14:41.920 --> 00:14:44.230
about it given what it implies about the


00:14:44.240 --> 00:14:46.389
early inner solar system.


00:14:46.399 --> 00:14:48.629
>> That's the part that stays with me.


00:14:48.639 --> 00:14:51.030
Super Earths are the single most common


00:14:51.040 --> 00:14:53.430
class of planet we find around other


00:14:53.440 --> 00:14:56.790
stars and our solar system conspicuously


00:14:56.800 --> 00:14:59.750
lacks one. If the answer is that we had


00:14:59.760 --> 00:15:02.790
one and the sun ate it, that makes us a


00:15:02.800 --> 00:15:05.430
lot less unusual and makes the ground


00:15:05.440 --> 00:15:07.910
under Mercury's orbit feel a good deal


00:15:07.920 --> 00:15:11.590
less stable than it looks. Now, a story


00:15:11.600 --> 00:15:12.949
about the sun from the opposite


00:15:12.959 --> 00:15:15.750
direction and one with a very practical


00:15:15.760 --> 00:15:18.310
edge, particularly for anyone listening


00:15:18.320 --> 00:15:20.949
from a crew rest seat. New research in


00:15:20.959 --> 00:15:22.949
the journal of geoysical research


00:15:22.959 --> 00:15:25.750
atmospheres finds that cosmic radiation


00:15:25.760 --> 00:15:28.470
at cruising altitude gets worse when the


00:15:28.480 --> 00:15:30.069
sun goes quiet,


00:15:30.079 --> 00:15:32.069
>> which is backwards from how most people


00:15:32.079 --> 00:15:33.350
would guess it.


00:15:33.360 --> 00:15:35.750
>> Completely backwards, and the logic is


00:15:35.760 --> 00:15:38.389
worth a minute. The work is by Dr. Roy


00:15:38.399 --> 00:15:41.269
Yaniv with Professor Yoav Yaer and


00:15:41.279 --> 00:15:43.990
Professor Colin Price across the Hebrew


00:15:44.000 --> 00:15:46.150
University of Jerusalem, Reichman


00:15:46.160 --> 00:15:48.790
University, and Tel Aviv University.


00:15:48.800 --> 00:15:51.110
They flew six instrumented balloons from


00:15:51.120 --> 00:15:53.590
southern Israel, each climbing to around


00:15:53.600 --> 00:15:56.389
35 km and measured the radiation


00:15:56.399 --> 00:15:58.470
environment the whole way up.


00:15:58.480 --> 00:16:00.870
>> So, what's the profile look like?


00:16:00.880 --> 00:16:03.110
>> It peaks higher than you fly. The


00:16:03.120 --> 00:16:06.389
maximum sits between 17 and 20 km.


00:16:06.399 --> 00:16:07.829
That's a known feature called the


00:16:07.839 --> 00:16:10.629
Regener Fzer maximum where incoming


00:16:10.639 --> 00:16:12.629
cosmic rays have smashed into enough


00:16:12.639 --> 00:16:15.189
atmosphere to produce a full shower of


00:16:15.199 --> 00:16:17.350
secondary particles, but the shower


00:16:17.360 --> 00:16:20.470
hasn't yet been absorbed. Below that, it


00:16:20.480 --> 00:16:22.949
tails off. At a typical airliner


00:16:22.959 --> 00:16:25.749
cruising altitude of around 10 km, they


00:16:25.759 --> 00:16:29.350
measure roughly 0.9 to 1.3 microverts


00:16:29.360 --> 00:16:32.150
per hour. And the solar connection,


00:16:32.160 --> 00:16:34.550
>> the sun's magnetic field carried out on


00:16:34.560 --> 00:16:37.189
the solar wind acts as a shield for the


00:16:37.199 --> 00:16:39.670
entire solar system. It deflects


00:16:39.680 --> 00:16:42.389
galactic cosmic rays. The high energy


00:16:42.399 --> 00:16:44.629
particles arriving from supernovi and


00:16:44.639 --> 00:16:46.949
other violence out in the galaxy. When


00:16:46.959 --> 00:16:49.509
the sun is active, that shield is strong


00:16:49.519 --> 00:16:51.189
and fewer of those particles get


00:16:51.199 --> 00:16:53.670
through. When the sun goes quiet, the


00:16:53.680 --> 00:16:56.150
shield weakens and more of them arrive.


00:16:56.160 --> 00:16:58.230
The team measure that anti-correlation


00:16:58.240 --> 00:17:01.350
directly at minus0.71


00:17:01.360 --> 00:17:02.790
and the size of the swing is the


00:17:02.800 --> 00:17:05.590
headline. At solar minimum, the dose


00:17:05.600 --> 00:17:08.150
rate runs something like 40 to 60%


00:17:08.160 --> 00:17:10.789
higher than at solar maximum.


00:17:10.799 --> 00:17:14.069
>> 40 to 60% is not a rounding error.


00:17:14.079 --> 00:17:15.990
>> It isn't. They also break down what's


00:17:16.000 --> 00:17:18.630
actually hitting you. Neutrons are about


00:17:18.640 --> 00:17:21.270
40 to 45% of the dose. with


00:17:21.280 --> 00:17:24.230
electromagnetic radiation another 35 to


00:17:24.240 --> 00:17:26.789
40. Neutrons matter because they're


00:17:26.799 --> 00:17:28.390
difficult to shield against and they're


00:17:28.400 --> 00:17:31.350
weighted heavily for biological damage.


00:17:31.360 --> 00:17:34.230
Now, proportion before anyone cancels a


00:17:34.240 --> 00:17:35.350
holiday.


00:17:35.360 --> 00:17:38.390
>> Yes, proportion. A micro sever is a


00:17:38.400 --> 00:17:40.870
millionth of a seavert. A long haul


00:17:40.880 --> 00:17:43.110
flight puts a few tens of micro severts


00:17:43.120 --> 00:17:45.029
on you, which is in the same broad


00:17:45.039 --> 00:17:47.430
territory as a chest x-ray. For a


00:17:47.440 --> 00:17:49.110
passenger, this is not something to lose


00:17:49.120 --> 00:17:51.430
sleep over. for air crew who are


00:17:51.440 --> 00:17:53.750
occupationally exposed and monitored as


00:17:53.760 --> 00:17:56.310
radiation workers in many jurisdictions


00:17:56.320 --> 00:17:58.870
and for frequent flyers on the very long


00:17:58.880 --> 00:18:02.390
very high latitude routes and Australia


00:18:02.400 --> 00:18:04.150
runs some of the longest sectors on the


00:18:04.160 --> 00:18:07.909
planet. A 40 to 60% seasonal swing


00:18:07.919 --> 00:18:09.750
driven by where we sit in the solar


00:18:09.760 --> 00:18:12.390
cycle is a real input into how you


00:18:12.400 --> 00:18:14.390
calculate annual dose


00:18:14.400 --> 00:18:16.310
>> and it dovetales with what we talked


00:18:16.320 --> 00:18:19.029
about on Saturday from the other end.


00:18:19.039 --> 00:18:21.430
It's the same dial. On the weekend, we


00:18:21.440 --> 00:18:23.510
covered the max plank work on the sun's


00:18:23.520 --> 00:18:25.990
capacity for a super flare. The danger


00:18:26.000 --> 00:18:28.789
of the sun at its loudest. This is the


00:18:28.799 --> 00:18:31.669
danger of the sun at its quietest. An


00:18:31.679 --> 00:18:33.830
active sun can fire a particle storm at


00:18:33.840 --> 00:18:36.310
you. A quiet sun simply stops holding


00:18:36.320 --> 00:18:39.029
the galaxy's particles at the door. Two


00:18:39.039 --> 00:18:41.110
different risks, opposite ends of the


00:18:41.120 --> 00:18:43.190
same cycle, and both of them show up at


00:18:43.200 --> 00:18:44.950
altitude first.


00:18:44.960 --> 00:18:47.110
>> Our last story before we look up is a


00:18:47.120 --> 00:18:49.590
null result. And I want to argue that


00:18:49.600 --> 00:18:51.270
it's one of the better pieces of news


00:18:51.280 --> 00:18:54.230
this week. The James Web Space Telescope


00:18:54.240 --> 00:18:56.230
has just carried out the most sensitive


00:18:56.240 --> 00:18:58.710
search for a moon around another planet


00:18:58.720 --> 00:19:01.669
ever attempted. It didn't find one. What


00:19:01.679 --> 00:19:03.990
matters is how thoroughly it didn't find


00:19:04.000 --> 00:19:04.789
one.


00:19:04.799 --> 00:19:06.950
>> Exomoons have been the great near miss


00:19:06.960 --> 00:19:10.390
of the field. For 15 years, we have


00:19:10.400 --> 00:19:13.029
close to 6,000 confirmed planets around


00:19:13.039 --> 00:19:16.230
other stars and not one confirmed moon,


00:19:16.240 --> 00:19:18.310
which is faintly ridiculous given that


00:19:18.320 --> 00:19:21.029
our own solar system has hundreds. The


00:19:21.039 --> 00:19:23.430
new work is by David Kipping, who has


00:19:23.440 --> 00:19:25.669
effectively made exomoon hunting his


00:19:25.679 --> 00:19:27.590
life's work, and it went up on the


00:19:27.600 --> 00:19:30.470
preprint server on the 4th of September.


00:19:30.480 --> 00:19:32.549
>> Which planet did he point it at?


00:19:32.559 --> 00:19:35.510
LP890-9C,


00:19:35.520 --> 00:19:37.909
a rocky planet in the tempered zone of a


00:19:37.919 --> 00:19:41.350
very cool, very faint star. Kipping used


00:19:41.360 --> 00:19:45.430
12 separate JWST transits, 12 passes of


00:19:45.440 --> 00:19:47.510
the planet in front of its star and


00:19:47.520 --> 00:19:50.070
stack them. And the sensitivity he gets


00:19:50.080 --> 00:19:52.789
out of that is the story. He can exclude


00:19:52.799 --> 00:19:56.150
moons down to oneth of Earth's radius at


00:19:56.160 --> 00:19:59.270
95% confidence across the planet's


00:19:59.280 --> 00:20:01.830
entire hillphere. That's the whole


00:20:01.840 --> 00:20:03.110
region where a moon could


00:20:03.120 --> 00:20:05.350
gravitationally hang on.


00:20:05.360 --> 00:20:08.070
>> 1/10enth of Earth's radius is about 650


00:20:08.080 --> 00:20:09.430
km,


00:20:09.440 --> 00:20:11.750
>> which rules out the entire mid tier of


00:20:11.760 --> 00:20:14.870
our own solar systems moons. Europa's


00:20:14.880 --> 00:20:18.710
gone, Ria's gone, Umbreel's gone. If


00:20:18.720 --> 00:20:21.590
LP890-9C


00:20:21.600 --> 00:20:23.990
had anything like those, Web would have


00:20:24.000 --> 00:20:24.630
seen it.


00:20:24.640 --> 00:20:27.350
>> So why is the absence good news?


00:20:27.360 --> 00:20:30.310
>> Two reasons. first because it was always


00:20:30.320 --> 00:20:32.950
possible that we'd found no exomoons


00:20:32.960 --> 00:20:35.510
simply because we can't see them. That


00:20:35.520 --> 00:20:37.750
the whole search was hopeless and we


00:20:37.760 --> 00:20:40.710
were wasting our time. This demonstrates


00:20:40.720 --> 00:20:43.830
the opposite. Web can find astonishingly


00:20:43.840 --> 00:20:46.710
small moons and stacking transits buys


00:20:46.720 --> 00:20:48.950
you far more sensitivity than a single


00:20:48.960 --> 00:20:52.230
one. That's a capability result and it


00:20:52.240 --> 00:20:55.669
applies to every other target. Second,


00:20:55.679 --> 00:20:57.750
this particular non-detection is


00:20:57.760 --> 00:21:00.470
physically expected. The planet orbits


00:21:00.480 --> 00:21:04.070
at just 0.04 astronomical units,


00:21:04.080 --> 00:21:06.630
extremely close in. And at that


00:21:06.640 --> 00:21:08.870
distance, tidal forces would strip a


00:21:08.880 --> 00:21:11.830
large moon away over time. Anyway, so


00:21:11.840 --> 00:21:13.990
the theory predicted an empty hill


00:21:14.000 --> 00:21:16.710
sphere, and the observation delivered an


00:21:16.720 --> 00:21:19.029
empty hill sphere. Theory and


00:21:19.039 --> 00:21:21.270
observation agreeing is not the most


00:21:21.280 --> 00:21:23.510
thrilling headline, but it's how you


00:21:23.520 --> 00:21:25.990
know the instrument is honest.


00:21:26.000 --> 00:21:28.630
>> Exactly right. And a small southern


00:21:28.640 --> 00:21:31.990
footnote, the LP890-9


00:21:32.000 --> 00:21:34.950
system was found by Speculus, a survey


00:21:34.960 --> 00:21:36.789
hunting planets around the coolest


00:21:36.799 --> 00:21:39.190
stars, whose southern station sits at


00:21:39.200 --> 00:21:42.310
Paranol in Chile under the same skies as


00:21:42.320 --> 00:21:44.470
the telescopes that keep turning up in


00:21:44.480 --> 00:21:46.310
this program. Quick update before the


00:21:46.320 --> 00:21:48.950
skywatch on a story we left open a


00:21:48.960 --> 00:21:51.830
couple of weeks back. NASA's Crew 13


00:21:51.840 --> 00:21:53.430
mission to the International Space


00:21:53.440 --> 00:21:56.310
Station is now targeting no earlier than


00:21:56.320 --> 00:21:57.590
late September.


00:21:57.600 --> 00:21:59.270
>> That's the flight that was supposed to


00:21:59.280 --> 00:22:00.390
go on the 12th.


00:22:00.400 --> 00:22:03.590
>> It was on the 29th of August. NASA and


00:22:03.600 --> 00:22:05.590
SpaceX stood the mission down after


00:22:05.600 --> 00:22:07.510
teams found an oxidizer leak in the


00:22:07.520 --> 00:22:09.909
Dragon spacecraft's propulsion system


00:22:09.919 --> 00:22:12.549
during standard pre-launch processing.


00:22:12.559 --> 00:22:14.070
At the time, the statement was simply


00:22:14.080 --> 00:22:15.430
that a new target date would be


00:22:15.440 --> 00:22:17.830
announced once available and that joint


00:22:17.840 --> 00:22:19.830
teams would complete any necessary


00:22:19.840 --> 00:22:22.470
rework before flight. The Canadian Space


00:22:22.480 --> 00:22:24.390
Agency has now confirmed the mission is


00:22:24.400 --> 00:22:25.990
aiming for no earlier than late


00:22:26.000 --> 00:22:28.950
September. Though, as we record, NASA


00:22:28.960 --> 00:22:30.549
hasn't published a specific date,


00:22:30.559 --> 00:22:32.710
>> and the crew is an interesting one.


00:22:32.720 --> 00:22:35.430
>> It is. Commander Jessica Watkins and


00:22:35.440 --> 00:22:38.310
pilot Luke Delaney for NASA with mission


00:22:38.320 --> 00:22:40.390
specialist Joshua Kutrich of the


00:22:40.400 --> 00:22:42.870
Canadian Space Agency and Sergey


00:22:42.880 --> 00:22:46.070
Teteratnikov of Ross Cosmos. They'll fly


00:22:46.080 --> 00:22:48.390
on a Falcon 9 from Space Launch Complex


00:22:48.400 --> 00:22:51.110
40 at Cape Canaveral, the same pad that


00:22:51.120 --> 00:22:53.590
quietly notched its 400th orbital flight


00:22:53.600 --> 00:22:55.909
yesterday. We'll bring you the date the


00:22:55.919 --> 00:22:56.870
moment it's firm.


00:22:56.880 --> 00:22:58.950
>> Right, let's get you outside. And


00:22:58.960 --> 00:23:00.549
there's something live happening


00:23:00.559 --> 00:23:03.909
tonight. A large coronal hole on the sun


00:23:03.919 --> 00:23:06.630
has rotated around into a geoeffective


00:23:06.640 --> 00:23:09.669
position and forecasters expect the fast


00:23:09.679 --> 00:23:12.230
solar wind streaming out of it to reach


00:23:12.240 --> 00:23:14.710
earth today. That means active


00:23:14.720 --> 00:23:16.710
geomagnetic conditions


00:23:16.720 --> 00:23:19.270
>> which means aurora watching is on at


00:23:19.280 --> 00:23:20.549
both ends of the planet.


00:23:20.559 --> 00:23:22.789
>> It does for our southern hemisphere


00:23:22.799 --> 00:23:25.350
listeners. That's Aurora Australas


00:23:25.360 --> 00:23:28.870
territory. Tasmania first and best with


00:23:28.880 --> 00:23:31.350
a genuine chance from southern Victoria


00:23:31.360 --> 00:23:33.669
and the far south of New Zealand if it


00:23:33.679 --> 00:23:36.870
holds up. Look south, get away from town


00:23:36.880 --> 00:23:39.590
lights, and be patient. Cameras will


00:23:39.600 --> 00:23:42.630
pick up color your eyes won't. For our


00:23:42.640 --> 00:23:44.789
North American listeners, you're looking


00:23:44.799 --> 00:23:47.430
north and the northern tier states and


00:23:47.440 --> 00:23:50.710
Canada are in play. This is a coronal


00:23:50.720 --> 00:23:53.029
hole stream rather than a big flare


00:23:53.039 --> 00:23:56.390
event. So, think a steady, moderate glow


00:23:56.400 --> 00:23:58.549
rather than a spectacular overhead


00:23:58.559 --> 00:24:02.230
display. But it's free and it's tonight.


00:24:02.240 --> 00:24:05.270
>> And the moon is out of the way for it.


00:24:05.280 --> 00:24:07.830
>> Beautifully out of the way. New moon was


00:24:07.840 --> 00:24:09.909
last Friday. So, we're in a young


00:24:09.919 --> 00:24:12.870
crescent evening sky and the deep sky is


00:24:12.880 --> 00:24:15.669
still yours. Over the next week, the


00:24:15.679 --> 00:24:18.070
moon climbs back into the evening and


00:24:18.080 --> 00:24:21.190
walks past two landmarks worth knowing.


00:24:21.200 --> 00:24:24.149
and Taries, the red heart of Scorpius,


00:24:24.159 --> 00:24:26.950
and the teapot of Sagittarius.


00:24:26.960 --> 00:24:29.269
Use the moon to find them between now


00:24:29.279 --> 00:24:32.230
and the 20th. And from Sydney, the


00:24:32.240 --> 00:24:34.549
center of the Milky Way is still riding


00:24:34.559 --> 00:24:37.830
high overhead after dark. That dense


00:24:37.840 --> 00:24:40.390
textured band through the teapot is the


00:24:40.400 --> 00:24:43.029
galactic core, and it is one of the


00:24:43.039 --> 00:24:45.029
genuine privileges of southern


00:24:45.039 --> 00:24:47.430
observing. From mid-n northern


00:24:47.440 --> 00:24:50.149
latitudes, it's much lower in the south.


00:24:50.159 --> 00:24:52.390
So, northern listeners should hunt for a


00:24:52.400 --> 00:24:54.789
clear southern horizon while the season


00:24:54.799 --> 00:24:56.149
lasts.


00:24:56.159 --> 00:24:59.590
>> Planets. Venus is the headline.


00:24:59.600 --> 00:25:02.149
>> Venus is the headline and Thursday is


00:25:02.159 --> 00:25:05.110
the date. On the 18th of September,


00:25:05.120 --> 00:25:07.350
Venus reaches greatest brilliancancy for


00:25:07.360 --> 00:25:10.789
this evening apparition at magnitude


00:25:10.799 --> 00:25:12.390
4.8.


00:25:12.400 --> 00:25:15.110
That is spectacularly bright. Bright


00:25:15.120 --> 00:25:17.110
enough to cast a shadow from a dark


00:25:17.120 --> 00:25:19.430
sight. bright enough that you'll field


00:25:19.440 --> 00:25:22.230
phone calls about it. Look west shortly


00:25:22.240 --> 00:25:24.470
after sunset. You'll notice some


00:25:24.480 --> 00:25:26.950
listings give a different date for this.


00:25:26.960 --> 00:25:29.269
We're going with the 18th, which is the


00:25:29.279 --> 00:25:31.990
correct one for the standard definition.


00:25:32.000 --> 00:25:34.789
And this apparition favors the south.


00:25:34.799 --> 00:25:37.510
From Sydney, Venus sits higher and


00:25:37.520 --> 00:25:40.070
lingers longer in a darker sky than it


00:25:40.080 --> 00:25:42.310
does from most of the United States,


00:25:42.320 --> 00:25:44.549
where it's a lower, briefer object in


00:25:44.559 --> 00:25:47.830
the twilight. Take the win. Anything


00:25:47.840 --> 00:25:49.510
else worth chasing?


00:25:49.520 --> 00:25:52.310
>> Three things. Mercury is low in the


00:25:52.320 --> 00:25:54.950
western twilight. Tricky, but doable


00:25:54.960 --> 00:25:58.070
with a clear horizon. Mars is in the


00:25:58.080 --> 00:26:01.590
morning sky and passes about 6° south of


00:26:01.600 --> 00:26:03.830
Pollock, the brighter of the Gemini


00:26:03.840 --> 00:26:07.430
twins, also on the 18th. That one's a


00:26:07.440 --> 00:26:10.390
northern favored view. And Saturn is


00:26:10.400 --> 00:26:12.470
building towards opposition on the 4th


00:26:12.480 --> 00:26:16.470
of October with the rings about 7° open.


00:26:16.480 --> 00:26:18.789
So, it is well placed all night and


00:26:18.799 --> 00:26:21.590
getting better. The harvest moon rides


00:26:21.600 --> 00:26:25.029
past it on the 26th with Neptune nearby


00:26:25.039 --> 00:26:28.230
for anyone with binoculars or a scope.


00:26:28.240 --> 00:26:30.070
>> There's also a date for the diary next


00:26:30.080 --> 00:26:31.269
Saturday.


00:26:31.279 --> 00:26:34.070
>> There is the 19th of September is


00:26:34.080 --> 00:26:36.470
International Observe the Moon night,


00:26:36.480 --> 00:26:38.789
which is one of the few global astronomy


00:26:38.799 --> 00:26:40.789
events that works equally well from


00:26:40.799 --> 00:26:42.950
either hemisphere with no equipment at


00:26:42.960 --> 00:26:45.750
all. The moon will be a fat crescent in


00:26:45.760 --> 00:26:48.470
the evening sky, which is genuinely the


00:26:48.480 --> 00:26:50.710
best phase for it because the shadows


00:26:50.720 --> 00:26:52.870
along the terminator throw the craters


00:26:52.880 --> 00:26:55.430
and mountains into relief. If you've got


00:26:55.440 --> 00:26:57.669
a pair of binoculars, that's all you


00:26:57.679 --> 00:26:59.990
need. If you've got a telescope and a


00:27:00.000 --> 00:27:02.070
neighbor, that's even better.


00:27:02.080 --> 00:27:04.230
>> And the equinox is coming.


00:27:04.240 --> 00:27:07.669
>> The 22nd, spring here, autumn for our


00:27:07.679 --> 00:27:09.669
northern listeners, and it brings the


00:27:09.679 --> 00:27:12.549
zodiacal light with it. That's sunlight


00:27:12.559 --> 00:27:14.630
scattering off dust in the plane of the


00:27:14.640 --> 00:27:17.190
solar system. And around the equinox,


00:27:17.200 --> 00:27:19.669
it's an evening object low in the west


00:27:19.679 --> 00:27:22.149
from the southern hemisphere, a false


00:27:22.159 --> 00:27:25.110
dusk, and a pre-dawn object in the east


00:27:25.120 --> 00:27:27.669
from the northern hemisphere. A faint


00:27:27.679 --> 00:27:31.269
tapering cone of light, dark skies, no


00:27:31.279 --> 00:27:33.269
moon, and patience.


00:27:33.279 --> 00:27:35.110
>> And the safety note, which is not


00:27:35.120 --> 00:27:36.950
optional on this program,


00:27:36.960 --> 00:27:39.750
>> never optional. With Venus at its most


00:27:39.760 --> 00:27:41.830
brilliant, some of you will be tempted


00:27:41.840 --> 00:27:44.230
to hunt it in daylight and it is


00:27:44.240 --> 00:27:46.630
genuinely findable. But that means


00:27:46.640 --> 00:27:49.350
aiming optics near the sun and that is


00:27:49.360 --> 00:27:51.269
how people permanently damage their


00:27:51.279 --> 00:27:53.750
eyes. If you are going to look anywhere


00:27:53.760 --> 00:27:56.549
near the sun, use a filter certified to


00:27:56.559 --> 00:27:59.830
the ISO 12312-2


00:27:59.840 --> 00:28:01.990
standard fitted over the front of the


00:28:02.000 --> 00:28:04.870
instrument, never at the eyepiece. Check


00:28:04.880 --> 00:28:07.029
it for scratches and pin holes before


00:28:07.039 --> 00:28:10.789
every use. Sunglasses, exposed film,


00:28:10.799 --> 00:28:13.190
smoked glass, and welding glass below


00:28:13.200 --> 00:28:17.510
shade 14 are not safe and never were and


00:28:17.520 --> 00:28:20.310
supervised children the entire time.


00:28:20.320 --> 00:28:22.230
>> And that's Astronomy Daily for Monday


00:28:22.240 --> 00:28:26.470
the 14th of September. 2,884


00:28:26.480 --> 00:28:29.190
supernova rebuilt from three decades of


00:28:29.200 --> 00:28:32.070
observations by an Australian-led team


00:28:32.080 --> 00:28:34.389
quietly making the case that dark energy


00:28:34.399 --> 00:28:35.990
might not hold still.


00:28:36.000 --> 00:28:38.470
>> A sun that may have eaten a super Earth


00:28:38.480 --> 00:28:40.950
and still carries the receipt. A


00:28:40.960 --> 00:28:43.190
reminder that the sun's quiet years are


00:28:43.200 --> 00:28:45.350
the ones that let the galaxy's particles


00:28:45.360 --> 00:28:48.070
through. and the most sensitive exomoon


00:28:48.080 --> 00:28:50.950
search ever attempted, finding precisely


00:28:50.960 --> 00:28:54.310
nothing in the most useful possible way.


00:28:54.320 --> 00:28:56.630
>> All of today's stories with links to the


00:28:56.640 --> 00:28:58.870
papers and the press releases are at


00:28:58.880 --> 00:29:01.269
astronomyaily.io.


00:29:01.279 --> 00:29:03.190
You'll find the full back catalog there,


00:29:03.200 --> 00:29:05.269
too, along with our news feed and the


00:29:05.279 --> 00:29:06.789
newsletter if you'd like this in your


00:29:06.799 --> 00:29:07.750
inbox.


00:29:07.760 --> 00:29:10.149
>> And we do read the contact form.


00:29:10.159 --> 00:29:12.789
questions, corrections, and story tips


00:29:12.799 --> 00:29:15.029
all land with us, and they have shaped


00:29:15.039 --> 00:29:17.510
more than one segment lately. You can


00:29:17.520 --> 00:29:20.310
also find us on socials at Astro Daily


00:29:20.320 --> 00:29:21.190
Pod.


00:29:21.200 --> 00:29:23.590
>> Astronomy Daily is part of the bytes.com


00:29:23.600 --> 00:29:25.830
podcast network. I'm Anna


00:29:25.840 --> 00:29:28.870
>> and I'm Avery. Clear skies wherever


00:29:28.880 --> 00:29:41.029
you're standing.


00:29:41.039 --> 00:29:44.840
Stories told.