One Flash in the Xenon: The Dark Matter Event Nobody Can Explain

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Language: en

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Welcome back [music] to Astronomy Daily.


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It's Friday, September 4th, 2026. I'm


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Anna and this is series 5, episode 185.


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>> And I'm Avery. [music] Anna, I want to


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start today with a number 2.6.


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>> 2.6 sigma, which [music] is not a


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discovery.


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>> You said that very fast.


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>> I said it fast because [music] it's the


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most important sentence in the story.


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But here's the rest of it. A dark matter


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detector a mile underground in South


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Dakota recorded a single flash of light


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in exactly the place a dark matter


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particle was supposed to show up. And


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the collaboration spent months trying to


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make that flash go away and could not do


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it.


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>> One event.


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>> One event. That's our lead. Including


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why we can't explain it and we found


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dark matter are very different


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sentences.


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Then India has put its first imaging


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satellite into geostationary orbit. A


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real first and a capability nobody else


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in the region has.


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>> The first private mission to Venus has


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been grounded, not by Venus, but by a


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rocket that hasn't flown yet.


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>> And a lovely piece of physics out of


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Syracuse. Why a star that keeps getting


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torn apart by a black hole puts on a


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fainter show every time.


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>> Plus the sky this weekend. both


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hemispheres and a new sunspot worth


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knowing about.


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>> Let's get into it. Start me at the


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beginning. Who announced what and where?


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>> The LZ collaboration, Lux Zeppelin,


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presented a result this week at Tev


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Particle Astrophysics 2026 in Chiba,


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Japan, which wraps up today. Brown


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University released it on Tuesday. The


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US Department of Energy has published


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its own account and the paper has gone


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to physical review letters.


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>> And LZ is the big xenon one.


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>> LZ is the big xenon one. 10 tons of


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ultra pure liquid xenon in a tank at the


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Sanford underground research facility in


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Leed, South Dakota. That's the old


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homestate gold mine. And the detector


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sits about a mile down, roughly 1480 m


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of rock overhead.


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>> Why underground?


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Because the enemy isn't darkness, it's


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noise. At the surface, you're rained on


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constantly by cosmic rays. A mile of


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rock filters nearly all of that out.


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Then they wrap the xenon in a water tank


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and a veto detector for stray neutrons


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and build it all from materials screened


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for radioactivity to absurd levels. The


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art of this field is subtraction. You


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spend 20 years removing every signal you


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can explain. Then look at what's left.


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>> And what are they hoping is left? A


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WIMP, weekly interacting massive


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particle, the leading dark matter


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candidate for about 40 years. A heavy


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particle left over from the early


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universe that has mass. So, it pulls on


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galaxies gravitationally, but ignores


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light and ignores ordinary matter almost


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all of the time.


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>> Almost all of the time being the


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operative phrase.


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>> That's the whole bet. If a wimp


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occasionally bumps into an atomic


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nucleus, a big enough tub of xenon


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sitting quietly for long enough should


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eventually record one. The nucleus


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recoils and you get two flashes. A


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prompt one, then a second from electrons


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drifting up through the liquid.


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Together, they tell you where in the


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tank it happened and whether you hit a


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nucleus or just knocked an electron


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loose.


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>> Okay, tell me about the event. It's in


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data taken between March 2023 and April


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2024.


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220 live days. That data set has been


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analyzed before. LZ published


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worldleading limits from it. What's new


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is that a team went back and searched a


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much wider range of possible


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interactions than the standard analysis


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covers, including higher energies. And


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one event turned up. A nuclear recoil in


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a region where the expected background


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is very close to zero.


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>> Higher energy. Is that where you'd


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expect dark matter?


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>> No. And that's the first genuinely odd


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thing. The simplest WIMP models put your


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first signal at low energies. This is up


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the other end. Taken at face value, it


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points to a particle of at least 200 gig


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electron volts, more than 200 times the


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mass of a proton interacting in a way


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the simplest models don't predict.


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>> So, it's not the wimp anyone ordered.


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>> It is not the wimp anyone ordered, which


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cuts both ways, and we'll come back to


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that.


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>> Give me the statistics honestly.


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>> 2.6 sigma globally, 3.4 four sigma


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locally and the difference between those


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two numbers is the most useful thing I


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can teach anyone today.


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>> Go on.


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>> Local significance asks at this exact


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energy for this exact mass how


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surprising is this event? Fairly


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surprising. Global significance asks the


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fairer question. I searched a whole


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range of masses and energies. So how


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surprising is it that somewhere in that


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range I found one odd thing? account for


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the haystack and the surprise drops.


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That's the look elsewhere effect. Honest


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experiments quote both and LZ did.


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>> And 2.6 sigma means what in plain terms?


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>> Roughly a half a% chance known


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backgrounds produced it, which sounds


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compelling until you remember the bar.


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Particle physics calls something a


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discovery at 5 sigma. About 1 in 3 and


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12 million. 2.6 is nowhere near it. And


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physicists have watched three sigma


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results evaporate for decades.


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>> Did they try to kill it?


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>> For months. Cosmic rays, neutrons from


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the rock, radioactivity in the detector


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materials, instrumental artifacts, all


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modeled. Aaron Manalise at Berkeley Lab,


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who chairs LZ's institutional board,


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said it's the first example in any


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experiment he's worked on of an outlier


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that appears valid in every way. That's


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a striking thing for an experimentalist


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to say out loud.


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>> What does the spokesperson say?


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>> Rick Gateskull at Brown is the


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spokesperson and he's been about as


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disciplined as you can be. His line,


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with only one event, we don't want to


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get ahead of ourselves. We are not


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claiming to have seen dark matter. And


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separately, we're very intrigued to see


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this event in the data in the region


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where we expect dark matter to show up


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and the competing backgrounds are very


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low. Both things at once.


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>> Both things at once. And that's the


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correct posture. Sam Ericson at Bristol


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led the analysis and made the point that


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matters. Dark matter events are expected


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to be so rare that only a handful could


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mark the first detection. You can't


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dismiss one event for being single. But


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you can't build a discovery on it


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either.


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>> Is there a UK end to this?


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>> A significant one. Imperial College


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London did much of the work


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characterizing the event. and Henrique


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Araho there put it beautifully. We need


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to analyze more data to be sure, but


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these are certainly interesting times.


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>> Now, you promised the caveat about it


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not being the expected wimp.


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>> Two ways to read an unexpected signal.


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The generous one, nature isn't obliged


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to be simple, and 40 years of not


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finding dark matter may be exactly


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because we searched the tidiest places


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first. The unkind one. When a result


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lands where no model predicted, an


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unmodled background is a very live


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explanation. The reason you haven't


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modeled it is that you didn't know it


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was there.


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>> Has this field been burned before?


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>> Repeatedly, DAMA in Italy has claimed an


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annual dark matter signal for over 20


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years that nobody else can reproduce.


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Xenon 1T reported an excess in 2020 that


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caused enormous excitement and was most


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likely tridium contamination, a hydrogen


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isotope at a level almost too small to


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measure. That's the standard to hear


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this week against. To LZ's credit,


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they've published this as an anomaly,


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not a discovery.


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>> So, what settles it?


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>> More xenon and more time. LZ has already


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banked substantially more data than went


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into this analysis and is running toward


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a thousand live days. If it's real, the


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rate is set by physics and more events


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follow. The significance climbs. If it's


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a fluke, it decays as exposure grows and


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a proposed successor XLZD would hold 10


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times the xenon. This resolves itself in


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data, not argument. southern hemisphere


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angle because dark matter feels like a


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northern hemisphere sport.


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>> It has been and that's changing for a


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genuinely clever reason. There's now an


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underground lab in Australia, SUPL, the


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Stalwell Underground Physics Laboratory,


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a kilometer down a working gold mine in


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Western Victoria. It's the first


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underground physics lab in the Southern


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Hemisphere. built by the University of


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Melbourne with the Ark Center of


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Excellence for Dark Matter Particle


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Physics and ANSTOW and its first


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experiment Saber South moves in late


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this year.


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>> And why does the hemisphere matter for


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dark matter of all things?


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>> Because of damma. Its claim is that the


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signal rises and falls once a year as


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Earth's motion around the sun adds to


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and subtracts from the solar systems


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motion through the galaxy's dark matter


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halo. The trouble is that plenty of


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ordinary things cycle annually, too.


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Temperature, radon, cosmic ray rates.


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And in Italy, they all peak in summer


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alongside the claimed signal.


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>> And in Victoria, the seasons are


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flipped.


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>> The seasons are flipped and the dark


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matter signal isn't. run a near


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identical detector in the southern


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hemisphere and a real galactic signal


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peaks in the same calendar month it does


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in Italy while a seasonal artifact peaks


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six months out. Elegant piece of


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experiment design and the only place on


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Earth you can do it is the one we happen


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to broadcast from.


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>> So what should people take away from


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today?


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>> Three things. LZ has found something it


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cannot explain in the right place and


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said so honestly. One event is one event


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and 2.6 6 sigma is a long way from a


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discovery and the answer is already


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being collected. The detector is running


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right now. The honest headline is dark


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matter hunters find something they can't


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explain and refuse to overlim it. A good


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day for science even if it isn't the


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day.


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>> On to our second story today and this


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one is a genuine national first.


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Overnight our time 2:55 in the morning


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Indian standard time on the 4th which


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was 5:25 yesterday evening US Eastern


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ISRO launched EOS05 on a GSLV Mark II


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out of Shrihari Kota


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>> and it's the orbit that's the story not


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the rocket


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>> exactly EOS05 is India's first dedicated


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imaging satellite headed for


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geocynchronous orbit Everything India


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has flown for Earth observation until


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now has been in low orbit a few hundred


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km up.


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>> Spell out the difference for people.


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>> A low orbit imaging satellite is a


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sprinter. It races around the planet in


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90 minutes and gives you a superb, very


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highresolution snapshot of a strip of


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ground and then it's gone and you wait.


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Depending on the orbit, you might get


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another look in a day or several days.


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Whereas geostationary is a stair.


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>> Geostationary is a stair 36,000 km up


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matching Earth's rotation. So from the


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ground, the satellite appears to hang


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motionless over the same piece of the


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planet permanently. You don't get a


00:12:01.920 --> 00:12:04.630
revisit time because you never leave


00:12:04.640 --> 00:12:07.190
>> and that changes what you can use it for


00:12:07.200 --> 00:12:11.269
>> completely. ISRO's framing is persistent


00:12:11.279 --> 00:12:13.670
coverage of the subcontinent and the


00:12:13.680 --> 00:12:15.829
applications are obvious once you say it


00:12:15.839 --> 00:12:18.389
that way. A cyclone forming in the Bay


00:12:18.399 --> 00:12:20.949
of Bengal. You watch it develop


00:12:20.959 --> 00:12:22.870
continuously instead of getting one


00:12:22.880 --> 00:12:26.310
frame a day. A flood, you see the water


00:12:26.320 --> 00:12:29.509
advance, a firefront, a landslide, a


00:12:29.519 --> 00:12:32.629
border. It's a dual use satellite, civil


00:12:32.639 --> 00:12:35.350
and military. And India hasn't been shy


00:12:35.360 --> 00:12:36.389
about that.


00:12:36.399 --> 00:12:37.990
>> There's a trade-off though. Surely


00:12:38.000 --> 00:12:40.310
>> there is and it's worth being honest


00:12:40.320 --> 00:12:43.030
about it. You are imagining from a 100


00:12:43.040 --> 00:12:45.350
times further away than a low orbit


00:12:45.360 --> 00:12:47.509
satellite. So the resolution is


00:12:47.519 --> 00:12:50.310
inevitably coarser. You are not reading


00:12:50.320 --> 00:12:53.430
number plates from geostationary orbit.


00:12:53.440 --> 00:12:56.550
What you're buying is time, not detail.


00:12:56.560 --> 00:12:59.030
And for disaster response, time is


00:12:59.040 --> 00:13:01.350
usually the thing you're short of.


00:13:01.360 --> 00:13:03.190
>> How did the launch go?


00:13:03.200 --> 00:13:07.990
>> Clean. The spacecraft is about 2,367


00:13:08.000 --> 00:13:12.230
kg and ISRO chairman V. Nurionan said it


00:13:12.240 --> 00:13:14.389
was successfully and precisely injected


00:13:14.399 --> 00:13:18.790
into its planned orbit. From here, EOS05


00:13:18.800 --> 00:13:21.030
works its way up to its final station


00:13:21.040 --> 00:13:22.870
over the coming days.


00:13:22.880 --> 00:13:25.829
>> And the GSLV has had a mixed history.


00:13:25.839 --> 00:13:27.990
>> It has, which is part of why this


00:13:28.000 --> 00:13:32.310
matters to ISRO. The GSLV Mark II has


00:13:32.320 --> 00:13:35.670
now flown 12 times for 10 successes.


00:13:35.680 --> 00:13:37.350
That's a vehicle that has visibly


00:13:37.360 --> 00:13:39.430
matured and it's the one carrying


00:13:39.440 --> 00:13:42.550
India's heavier missions to high orbit.


00:13:42.560 --> 00:13:44.710
>> Small country club. This


00:13:44.720 --> 00:13:47.670
>> very small dedicated highresolution


00:13:47.680 --> 00:13:50.710
imaging from geostationary orbit is a


00:13:50.720 --> 00:13:53.030
capability only a handful of nations


00:13:53.040 --> 00:13:55.990
have ever fielded. India has just joined


00:13:56.000 --> 00:13:58.230
that list and it did it with its own


00:13:58.240 --> 00:14:00.870
rocket from its own spaceport.


00:14:00.880 --> 00:14:03.750
>> Third story and it's a frustrating one.


00:14:03.760 --> 00:14:05.829
The first privately funded mission to


00:14:05.839 --> 00:14:08.230
another planet is still on the ground


00:14:08.240 --> 00:14:09.990
and it's going to stay there for a while


00:14:10.000 --> 00:14:11.110
yet.


00:14:11.120 --> 00:14:13.990
>> This is the Venus Lifeinder.


00:14:14.000 --> 00:14:17.269
>> That's it. It's an MIT mission driven by


00:14:17.279 --> 00:14:19.590
Sarah Seager flying in partnership with


00:14:19.600 --> 00:14:21.910
Rocket Lab. And it is beautifully,


00:14:21.920 --> 00:14:24.710
almost aggressively simple. A small


00:14:24.720 --> 00:14:27.590
probe, one instrument, a few minutes of


00:14:27.600 --> 00:14:29.189
useful life.


00:14:29.199 --> 00:14:31.670
>> One instrument, that's it.


00:14:31.680 --> 00:14:33.509
>> One instrument. It's called an


00:14:33.519 --> 00:14:36.150
autofllororescent nylometer, which is a


00:14:36.160 --> 00:14:38.949
mouthful for a fairly elegant idea. You


00:14:38.959 --> 00:14:41.189
fire an ultraviolet laser into the cloud


00:14:41.199 --> 00:14:43.189
droplets as you fall through them.


00:14:43.199 --> 00:14:45.189
Certain organic molecules absorb


00:14:45.199 --> 00:14:47.189
ultraviolet light and remit it at a


00:14:47.199 --> 00:14:49.990
different wavelength. They flues. So,


00:14:50.000 --> 00:14:51.509
the instrument is looking for a glow


00:14:51.519 --> 00:14:53.910
that ordinary sulfuric acid chemistry


00:14:53.920 --> 00:14:55.590
shouldn't produce.


00:14:55.600 --> 00:14:58.230
>> And why the clouds specifically?


00:14:58.240 --> 00:15:00.230
>> Because the surface of Venus is out of


00:15:00.240 --> 00:15:04.310
the question. 460 odd degrees, 90


00:15:04.320 --> 00:15:07.829
atmospheres, but between about 45 and 60


00:15:07.839 --> 00:15:10.629
km up, the temperature and pressure are


00:15:10.639 --> 00:15:12.550
close to conditions at sea level on


00:15:12.560 --> 00:15:15.509
Earth. Extremely acidic, but not


00:15:15.519 --> 00:15:18.150
thermodynamically hopeless. That's the


00:15:18.160 --> 00:15:20.310
only plausible habitable niche on the


00:15:20.320 --> 00:15:22.870
planet and it's what the 2020 phosphine


00:15:22.880 --> 00:15:25.189
claim put back on the table. A result


00:15:25.199 --> 00:15:27.430
that is still genuinely disputed and


00:15:27.440 --> 00:15:29.189
which this mission is designed to go and


00:15:29.199 --> 00:15:31.670
settle rather than argue about.


00:15:31.680 --> 00:15:34.230
>> So why isn't it flying?


00:15:34.240 --> 00:15:36.870
>> Neutron. The mission moved onto Rocket


00:15:36.880 --> 00:15:39.670
Lab's new medium lift rocket and Neutron


00:15:39.680 --> 00:15:41.829
hasn't flown yet. It was originally


00:15:41.839 --> 00:15:45.590
talked about for 2024, slipped to 2026,


00:15:45.600 --> 00:15:47.990
and it's still in qualification. The


00:15:48.000 --> 00:15:50.069
launch date on Rocket Lab's own website


00:15:50.079 --> 00:15:52.949
now simply says to be confirmed.


00:15:52.959 --> 00:15:54.550
>> How is Seagar taking it?


00:15:54.560 --> 00:15:57.509
>> With more grace than I would. Her line


00:15:57.519 --> 00:16:00.150
was, "We are awaiting neutron


00:16:00.160 --> 00:16:02.629
readiness." And she went on to say she


00:16:02.639 --> 00:16:04.389
continues to have high hopes for the


00:16:04.399 --> 00:16:06.310
mission and for its role in


00:16:06.320 --> 00:16:08.230
demonstrating what private enterprise


00:16:08.240 --> 00:16:10.790
can do in space exploration.


00:16:10.800 --> 00:16:13.189
There's an irony in there somewhere.


00:16:13.199 --> 00:16:15.430
>> There's a real one. The whole pitch of


00:16:15.440 --> 00:16:18.069
this mission was speed. That a small,


00:16:18.079 --> 00:16:20.870
focused, privately funded probe could go


00:16:20.880 --> 00:16:23.269
and answer one sharp question years


00:16:23.279 --> 00:16:24.870
before an agency flight could be


00:16:24.880 --> 00:16:28.069
approved, built, and launched. And it's


00:16:28.079 --> 00:16:30.389
now waiting on launch capacity, which is


00:16:30.399 --> 00:16:31.910
the one part of the problem private


00:16:31.920 --> 00:16:34.150
industry was supposed to have solved.


00:16:34.160 --> 00:16:36.870
>> Meanwhile, Venus is getting crowded.


00:16:36.880 --> 00:16:40.310
>> It is. NASA's Da Vinci and Veraritoss


00:16:40.320 --> 00:16:42.470
and Europe's Envision are all in the


00:16:42.480 --> 00:16:44.069
pipeline for around the end of this


00:16:44.079 --> 00:16:46.629
decade. The Venus Lifefinder was meant


00:16:46.639 --> 00:16:48.310
to be the scrappy one that got there


00:16:48.320 --> 00:16:50.710
first, and that lead is quietly


00:16:50.720 --> 00:16:53.590
evaporating on a launchpad in Virginia.


00:16:53.600 --> 00:16:55.829
Last news story and it's pure


00:16:55.839 --> 00:16:57.509
astrophysics


00:16:57.519 --> 00:16:59.590
published in the astrophysical journal


00:16:59.600 --> 00:17:03.509
on Tuesday led by Ana Bondopadi a


00:17:03.519 --> 00:17:06.150
doctoral student at Syracuse University


00:17:06.160 --> 00:17:08.949
with Benjamin Amend and Eric Coughlin


00:17:08.959 --> 00:17:12.390
plus collaborators at Leeds MIT and the


00:17:12.400 --> 00:17:14.949
Space Telescope Science Institute.


00:17:14.959 --> 00:17:17.110
>> And the puzzle is about stars that


00:17:17.120 --> 00:17:19.270
survive being eaten.


00:17:19.280 --> 00:17:22.230
>> Partly eaten. When a star wanders too


00:17:22.240 --> 00:17:24.630
close to a super massive black hole and


00:17:24.640 --> 00:17:27.429
is ripped apart entirely, that's a tidal


00:17:27.439 --> 00:17:30.630
disruption event. One enormous flare and


00:17:30.640 --> 00:17:33.350
it's over. But there's a smaller class


00:17:33.360 --> 00:17:35.510
where the star is only partly stripped


00:17:35.520 --> 00:17:38.390
on each pass, survives, and comes back


00:17:38.400 --> 00:17:39.350
around.


00:17:39.360 --> 00:17:41.909
>> So, it flares over and over,


00:17:41.919 --> 00:17:45.590
>> over and over on a schedule. The famous


00:17:45.600 --> 00:17:49.350
one is Assassin 14 KO, which flares


00:17:49.360 --> 00:17:52.950
roughly every 114 days and has done so


00:17:52.960 --> 00:17:55.830
for years. There are now something like


00:17:55.840 --> 00:17:58.070
seven or eight of these known.


00:17:58.080 --> 00:17:59.750
>> And what's the problem?


00:17:59.760 --> 00:18:02.549
>> The flares get dimmer each time, which


00:18:02.559 --> 00:18:05.190
sounds intuitive. Less star left to


00:18:05.200 --> 00:18:07.510
strip. Except the simulations kept


00:18:07.520 --> 00:18:10.230
saying the opposite. Strip material from


00:18:10.240 --> 00:18:13.190
a star and it puffs up. And a puffier


00:18:13.200 --> 00:18:16.470
star is easier to strip next time round.


00:18:16.480 --> 00:18:18.549
Models kept producing flares that got


00:18:18.559 --> 00:18:20.950
brighter and the sky kept producing


00:18:20.960 --> 00:18:22.789
flares that got fainter.


00:18:22.799 --> 00:18:24.950
>> So, what's the missing ingredient?


00:18:24.960 --> 00:18:28.150
>> Spin. This team ran hydrodnamic


00:18:28.160 --> 00:18:30.710
simulations of a highmass main sequence


00:18:30.720 --> 00:18:33.430
star being repeatedly disrupted by a


00:18:33.440 --> 00:18:35.510
black hole of about a million solar


00:18:35.520 --> 00:18:38.390
masses. And the key move was giving the


00:18:38.400 --> 00:18:40.710
star a fast rotation before the first


00:18:40.720 --> 00:18:42.870
encounter. spinning in the same


00:18:42.880 --> 00:18:44.950
direction as its orbit.


00:18:44.960 --> 00:18:46.630
>> Why does that change the outcome?


00:18:46.640 --> 00:18:49.029
>> Because ordinarily, the encounter itself


00:18:49.039 --> 00:18:51.830
spins the star up. And that spin up is


00:18:51.840 --> 00:18:54.070
part of what makes the next pass more


00:18:54.080 --> 00:18:56.710
violent. If the star arrives already


00:18:56.720 --> 00:18:58.789
rotating at a decent fraction of its


00:18:58.799 --> 00:19:01.350
breakup speed, there's very little extra


00:19:01.360 --> 00:19:03.909
spin to give it. The debris then falls


00:19:03.919 --> 00:19:06.150
back to the black hole spread over a


00:19:06.160 --> 00:19:08.230
longer stretch of time instead of


00:19:08.240 --> 00:19:10.630
arriving in one lump. And the same


00:19:10.640 --> 00:19:13.190
material dribbling in over longer makes


00:19:13.200 --> 00:19:16.150
a fainter, more drawn out flare.


00:19:16.160 --> 00:19:17.909
>> Spread the fuel out and the fire is


00:19:17.919 --> 00:19:18.870
lower.


00:19:18.880 --> 00:19:21.510
>> That's it exactly. And with tens of


00:19:21.520 --> 00:19:24.390
percent of breakup rotation prograde,


00:19:24.400 --> 00:19:26.789
the simulations reproduce the dimming


00:19:26.799 --> 00:19:28.789
that's actually observed.


00:19:28.799 --> 00:19:30.630
>> Does it tell us anything about how the


00:19:30.640 --> 00:19:32.789
star got there in the first place?


00:19:32.799 --> 00:19:35.909
>> It does, and that's the bonus. A fast


00:19:35.919 --> 00:19:38.390
spinning star on a tight orbit around a


00:19:38.400 --> 00:19:41.110
super massive black hole fits the hills


00:19:41.120 --> 00:19:44.070
mechanism. A binary pair strays too


00:19:44.080 --> 00:19:47.190
close. The black hole keeps one star and


00:19:47.200 --> 00:19:50.230
flings the other away at enormous speed.


00:19:50.240 --> 00:19:52.630
The captured one lands exactly where you


00:19:52.640 --> 00:19:55.510
need it. So the spin isn't an arbitrary


00:19:55.520 --> 00:19:57.990
knob. It's a fingerprint of how these


00:19:58.000 --> 00:19:59.669
systems get built.


00:19:59.679 --> 00:20:01.909
>> Right. Let's get you outside. And the


00:20:01.919 --> 00:20:04.390
moon is doing us a favor this weekend.


00:20:04.400 --> 00:20:06.310
Last quarter today.


00:20:06.320 --> 00:20:09.029
>> Last quarter today, September 4th, which


00:20:09.039 --> 00:20:10.549
means it doesn't rise until around


00:20:10.559 --> 00:20:12.549
midnight. So, the entire evening is


00:20:12.559 --> 00:20:14.710
dark. If you have been waiting for a


00:20:14.720 --> 00:20:16.070
night to actually look at something


00:20:16.080 --> 00:20:18.310
faint, this is the weekend.


00:20:18.320 --> 00:20:20.310
>> Southern hemisphere first.


00:20:20.320 --> 00:20:22.390
>> Southern hemisphere first because we get


00:20:22.400 --> 00:20:24.549
the best of it. From Sydney, the sun


00:20:24.559 --> 00:20:26.950
sets about 20 to 6 now. And once it's


00:20:26.960 --> 00:20:28.630
properly dark, the center of the Milky


00:20:28.640 --> 00:20:31.590
Way is high overhead. Sagittarius and


00:20:31.600 --> 00:20:34.230
Scorpius almost directly above you. From


00:20:34.240 --> 00:20:36.149
mid-southern latitudes, the galactic


00:20:36.159 --> 00:20:38.470
core passes near the zenith, so you're


00:20:38.480 --> 00:20:39.990
looking through the least possible


00:20:40.000 --> 00:20:42.470
atmosphere. Northern listeners get the


00:20:42.480 --> 00:20:44.630
same object low and murky above the


00:20:44.640 --> 00:20:47.029
southern horizon. It's the one thing we


00:20:47.039 --> 00:20:49.430
can be smug about. And September is the


00:20:49.440 --> 00:20:50.950
last good month before it sinks


00:20:50.960 --> 00:20:51.830
westward.


00:20:51.840 --> 00:20:53.990
>> What do you actually look at?


00:20:54.000 --> 00:20:56.149
>> Find the teapot of Sagittarius with the


00:20:56.159 --> 00:20:58.950
naked eye and let your eye drift up out


00:20:58.960 --> 00:21:01.909
of the spout. That steam is the galactic


00:21:01.919 --> 00:21:04.470
center. Binoculars turn it into star


00:21:04.480 --> 00:21:06.870
clouds and dark lanes. And the Lagoon


00:21:06.880 --> 00:21:09.430
Nebula is sitting right there along with


00:21:09.440 --> 00:21:11.669
a dozen globular clusters.


00:21:11.679 --> 00:21:12.789
>> Planets.


00:21:12.799 --> 00:21:14.950
>> Venus in the west after sunset.


00:21:14.960 --> 00:21:17.590
Brilliant, unmistakable, low, and


00:21:17.600 --> 00:21:19.350
building toward greatest brilliancancy


00:21:19.360 --> 00:21:22.230
on the 18th. Saturn is up most of the


00:21:22.240 --> 00:21:24.230
night in Aquarius, climbing toward


00:21:24.240 --> 00:21:26.630
opposition on October 4th. And from


00:21:26.640 --> 00:21:29.029
here, it passes far higher overhead than


00:21:29.039 --> 00:21:30.950
it does for northern observers.


00:21:30.960 --> 00:21:32.310
Pre-dawn.


00:21:32.320 --> 00:21:35.029
>> Jupiter is the pre-dawn showpiece well


00:21:35.039 --> 00:21:37.750
up in the east before sunrise. And on


00:21:37.760 --> 00:21:40.789
Sunday morning the 6th, Mars sits just a


00:21:40.799 --> 00:21:43.270
few degrees below a thin waning crescent


00:21:43.280 --> 00:21:45.510
moon. That's a lovely one for a phone


00:21:45.520 --> 00:21:47.270
camera if you're up early.


00:21:47.280 --> 00:21:49.590
>> Now, North America because there's a


00:21:49.600 --> 00:21:50.950
proper event coming.


00:21:50.960 --> 00:21:53.590
>> On Tuesday the 8th, the moon occults


00:21:53.600 --> 00:21:56.310
Jupiter. The planet passes behind the


00:21:56.320 --> 00:21:58.870
lunar disc. The footprint favors


00:21:58.880 --> 00:22:01.110
northeastern Asia where it happens in


00:22:01.120 --> 00:22:04.390
the dawn sky and eastern North America


00:22:04.400 --> 00:22:06.789
where it happens after sunrise in broad


00:22:06.799 --> 00:22:08.070
daylight.


00:22:08.080 --> 00:22:09.350
>> Daylight.


00:22:09.360 --> 00:22:11.669
>> Daylight which brings us to the standing


00:22:11.679 --> 00:22:14.470
reminder and it applies directly here.


00:22:14.480 --> 00:22:16.390
If you are observing anywhere near the


00:22:16.400 --> 00:22:18.549
sun, hunting for Jupiter in a bright


00:22:18.559 --> 00:22:20.950
sky, or looking at the sunspot I'm about


00:22:20.960 --> 00:22:23.430
to mention, any filter you use for


00:22:23.440 --> 00:22:25.990
direct solar viewing must be certified


00:22:26.000 --> 00:22:29.510
to the ISO12312-2


00:22:29.520 --> 00:22:32.149
standard. Not sunglasses, not welding


00:22:32.159 --> 00:22:34.149
glass of unknown grade, not smoked


00:22:34.159 --> 00:22:39.669
glass, not a phone screen. ISO12312-2


00:22:39.679 --> 00:22:42.070
and check the certification is real.


00:22:42.080 --> 00:22:43.990
Sweeping binoculars or a telescope


00:22:44.000 --> 00:22:46.390
across a daylight sky is exactly the


00:22:46.400 --> 00:22:48.149
situation where people injure themselves


00:22:48.159 --> 00:22:50.310
permanently. And it takes a fraction of


00:22:50.320 --> 00:22:51.430
a second.


00:22:51.440 --> 00:22:54.390
>> And the day after, there's one for us.


00:22:54.400 --> 00:22:57.350
>> The 9th, the moon occults Regulus, the


00:22:57.360 --> 00:22:59.350
brightest star in Leo. And that


00:22:59.360 --> 00:23:01.909
footprint runs across the South Pacific,


00:23:01.919 --> 00:23:04.870
New Calonia, best placed. Not Australia,


00:23:04.880 --> 00:23:06.390
unfortunately. But if you're in that


00:23:06.400 --> 00:23:09.110
track, a first magnitude star vanishing


00:23:09.120 --> 00:23:11.190
off the edge of the moon is one of the


00:23:11.200 --> 00:23:13.270
sharpest things you'll ever see.


00:23:13.280 --> 00:23:14.870
Instantaneous.


00:23:14.880 --> 00:23:16.789
>> You mentioned a sunspot.


00:23:16.799 --> 00:23:20.470
>> A new one, active region 4524,


00:23:20.480 --> 00:23:22.230
which rotated into view over the


00:23:22.240 --> 00:23:24.230
northeastern limb this week and has been


00:23:24.240 --> 00:23:27.510
busy. It fired an M3 flare peaking at


00:23:27.520 --> 00:23:30.230
1920 universal time on Wednesday the


00:23:30.240 --> 00:23:33.350
2nd, plus a stack of smaller ones. The


00:23:33.360 --> 00:23:35.190
coronal mass ejection from that flare


00:23:35.200 --> 00:23:37.350
isn't aimed at us, but a filament


00:23:37.360 --> 00:23:39.190
eruption the same day threw out material


00:23:39.200 --> 00:23:41.270
that may deliver a glancing blow around


00:23:41.280 --> 00:23:42.789
Monday the 7th.


00:23:42.799 --> 00:23:44.470
>> Aurora chances


00:23:44.480 --> 00:23:47.029
>> modest and honest quiet conditions


00:23:47.039 --> 00:23:48.630
through the weekend. So nothing to


00:23:48.640 --> 00:23:50.870
promise tonight or Saturday. Monday is


00:23:50.880 --> 00:23:52.870
the one to watch. And if anything comes


00:23:52.880 --> 00:23:54.390
of it, the people with a shot are


00:23:54.400 --> 00:23:56.390
Tasmania and southern New Zealand down


00:23:56.400 --> 00:23:58.789
here and the northern tier of the US,


00:23:58.799 --> 00:24:01.270
Canada, and Scotland up there. Watch the


00:24:01.280 --> 00:24:02.870
space weather feeds rather than the


00:24:02.880 --> 00:24:03.990
headlines.


00:24:04.000 --> 00:24:05.990
>> And one for northern observers with


00:24:06.000 --> 00:24:07.270
binoculars.


00:24:07.280 --> 00:24:09.990
>> The double cluster in Perseus. Two open


00:24:10.000 --> 00:24:11.990
clusters side by side in the same


00:24:12.000 --> 00:24:14.549
binocular field. Naked eye, it's a


00:24:14.559 --> 00:24:16.950
smudge. In binoculars, it's one of the


00:24:16.960 --> 00:24:19.269
best sights in the sky. And a moonless


00:24:19.279 --> 00:24:21.750
evening is exactly when to try it.


00:24:21.760 --> 00:24:25.750
>> And that's episode 185. A dark matter


00:24:25.760 --> 00:24:28.710
detector a mile underground has recorded


00:24:28.720 --> 00:24:31.669
one flash of light it cannot explain and


00:24:31.679 --> 00:24:33.990
has been admirably careful about what


00:24:34.000 --> 00:24:36.470
that does and doesn't mean.


00:24:36.480 --> 00:24:38.310
>> India has put its first imaging


00:24:38.320 --> 00:24:39.909
satellite on station over the


00:24:39.919 --> 00:24:42.230
subcontinent. The first private mission


00:24:42.240 --> 00:24:44.149
to Venus is stuck waiting on a rocket


00:24:44.159 --> 00:24:46.549
that hasn't flown. And a star that keeps


00:24:46.559 --> 00:24:48.549
surviving a black hole shines a little


00:24:48.559 --> 00:24:51.110
fainter each time because of how fast it


00:24:51.120 --> 00:24:53.830
was already spinning. Full show notes,


00:24:53.840 --> 00:24:56.390
links to every primary source, and the


00:24:56.400 --> 00:24:58.070
whole back catalog are at


00:24:58.080 --> 00:25:00.230
astronomyaily.io.


00:25:00.240 --> 00:25:02.710
>> You can find us on X, Instagram, and Tik


00:25:02.720 --> 00:25:05.990
Tok at astroaily pod. And if you've got


00:25:06.000 --> 00:25:08.789
a question or a correction, we genuinely


00:25:08.799 --> 00:25:10.870
want it. There's a contact form on the


00:25:10.880 --> 00:25:12.149
website.


00:25:12.159 --> 00:25:14.630
>> And if today's episode was useful, the


00:25:14.640 --> 00:25:16.789
single most helpful thing you can do is


00:25:16.799 --> 00:25:19.350
send it to one person who'd enjoy it.


00:25:19.360 --> 00:25:21.510
>> It's the weekend. Get outside and look


00:25:21.520 --> 00:25:23.269
up while the moon's out of the way.


00:25:23.279 --> 00:25:25.190
Until tomorrow, clear skies.


00:25:25.200 --> 00:25:29.430
>> Clear skies. [music]


00:25:29.440 --> 00:25:32.707
>> Stories told


00:25:32.717 --> 00:25:37.430
[music]


00:25:37.440 --> 00:25:45.807
stories [music] told.


00:25:45.817 --> 00:25:47.837
[singing]