Meteorite Myths, Daylight Fireballs & the Secrets of Ultra-Faint Galaxies

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Andrew Dunkley: Hi there. Thanks for joining us on Space Nuts

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where we talk astronomy and space science. My

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name is Andrew Dunkley and hope, uh, you're.

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Well, coming up in this episode we are going

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to, uh, look at, oh, there's a whole bunch of

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stuff. We might not fit it all in. We'll do

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our very best. Uh, a meteorite versus a

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windscreen. Did it happen the way people

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think? We'll tell you. And over the

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weekend, uh, there was a fireball seen over,

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uh, southeastern states, uh, Victoria, New

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South Wales. The act. We'll talk about that.

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Uh, there's been a bit of chatter on social

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media, including the Space nuts podcast group

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about 3i Atlas. So we'll have

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an update on that. And time permitting, we

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will be looking at a huge black hole and a

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tiny galaxy. I mean tiny as in

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maybe only hundreds or thousands of stars. It

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sounds unusual, doesn't it? And life

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after an asteroid impact. That's all coming

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up on this episode of Space Nuts.

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15 seconds. Guidance is internal.

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10, 9, ignition

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sequence time.

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Jonti Horner: Uh, Space Nuts. 5, 4, 3, 2.

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Andrew Dunkley: 1, 2, 3, 4, 5, 5, 4, 3,

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2, 1. Space Nuts astronauts report

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it feels good.

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And with Fred still away, we are, uh,

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thrilled to welcome again Jonti Horner,

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professor of astrophysics at the University

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of Southern Queensland. Hello, Jonny.

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Jonti Horner: Good morning. How are you going?

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Andrew Dunkley: I am well. Good to see you. Nice backdrop

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too, by the way. What do you got there?

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Jonti Horner: Um, so another of the picks I've been playing

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around with with the telescope I bought about

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12 months ago. This is supplied ease I can

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slap out of shot.

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Andrew Dunkley: Um, very nice.

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Jonti Horner: My chair immediately interferes. The chair

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caption. Human being.

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Andrew Dunkley: But that was the, that was the Chair Nebula.

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Jonti Horner: Absolutely. But yes, I get the angle of the

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chair just right. The AI doesn't recognize it

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as a human being and we get to see it. Yeah,

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pretty good. But I'm going to have to have

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another go at that site. It doesn't quite

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feel right. It looks a little uncanny valley

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to me. So I may have to take some more photos

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later in the ah, year if the wonderful

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thunderstorms we're getting at the minute

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kind of stop because we've had some

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interesting weather appear again over the

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last few days. Um, there was a possible

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tornado within 30km of my house, which is

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cool. And some places got 10 centimeter

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diameter hail and lots of damage and

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yeah, tasty stuff going on and we might get a

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little bit more today and tomorrow. So it's

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another of those events which is spectacular

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and fun to watch. But you also sympathise

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with those who are directly in the thyroid

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line.

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Andrew Dunkley: Yeah, I saw those, uh, tornado

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forecasts pop up. And, uh,

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the bureau does not often go that far,

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uh, with their forecasting, but they were

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pretty confident. So, yeah, we get a few of

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those down our way too.

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Jonti Horner: It is an interesting one. I mean, growing up

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in the uk, I grew up in the country or one of

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the few countries that has the most tornadoes

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per year, which shocks everybody. But they're

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really, really itty bitty diddy ones that are

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associated with frontal systems. And I think

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a lot of Americans say, oh, no, they're not

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tornadoes, they're just gusnados or something

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like that. But in terms of the really

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damaging thunderstorms around the world,

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you've got the Great Plains in the US and

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then you've got the kind of area around

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Bangladesh, I think. But after that kind of

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Southeast Queensland, northeast New South

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Wales is the New South Wales is the third

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best place in the world for these kind of

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storms. And we get fewer tornadoes than

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the Great Plains because we get less wind

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shear at high altitudes. But we get

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equivalent amounts of mega hail and guerrilla

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hail is what they're calling it nowadays when

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you're bigger than giant hail. So we do get

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some really tasty and interesting stuff. And

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I did have one day not long after we built

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this house and moved in where the garage was

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still full of boxes, um, which is always a

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good thing. And this thunderstorm came in and

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suddenly there's the roaring of a freight

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train kind of noise, which was so weird, and

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hailstones, hailstones as my fist started

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coming down and I had to run out with

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blankets and a doona, uh, to cover the

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windscreen of my car to prevent it getting

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damaged. And unfortunately it didn't. Well,

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fortunately it didn't get much worse than

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that. But it was an interesting experience

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for someone who grew up in the uk, where the

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worst weather gets a bit of drizzle and a lot

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of wind.

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Andrew Dunkley: Yeah, yeah, it can get pretty volatile, uh,

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in Australia, and especially in the eastern

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parts.

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Uh, speaking of volatile, our first story

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is about, um,

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what people thought was a meteorite hitting

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the windscreen of a car. And when you see the

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photo, it's. It's one heck of a crack. It's,

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um, it's come in hard, whatever it was. Uh,

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what is the story here?

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Jonti Horner: It's a slightly weird one. Um, there's a

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guy driving along. Um, he's a vet down

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in South Australia, goes by the name of

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Melville Smith. It's his name, Andrew M.

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Melville Smith. Driving along in his

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Tesla. And the Tesla part is important to the

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story. Apparently about 40km out from

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a place called Port Garmin, when suddenly

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there's a really loud smash on his

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windscreen. Um, him and his partner in the

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front seats get showered with glass from this

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shattered windscreen and there's an impact

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crater on the windscreen. Um, and

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obviously the car just kept on driving

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because it's a Tesla and they don't seem to

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notice when they hit things, they just carry

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on. Um, all is good

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now. He thought it was weird, so he reached

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out to the museum in South Australia with

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the idea that this could have been a

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meteorite hitting a car. And that would be

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very unusual. Now we've had occasions in the

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past, um, most famously the Peekskill

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meteorite, and I think it was 1994, where

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meteorites have hit parked cars and done a

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lot of damage. And I think in the case of the

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Peekskill meteorite, it was a fairly hefty

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iron ore, stony iron meteorite that basically

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wrote off the rear end of the car. And the

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person who owned the car was very upset until

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a museum bought the car for a six figure sum,

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which kind of the blow. This, um,

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case, part of the reason that they thought it

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was a meteorite was that there was melting of

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the windscreen as well as just shattering of

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the windscreen. And this, the people at South

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Australia Museum basically came out with a

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fairly neutral statement and said, we're

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going to investigate this. It sounds really

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weird. The melting sounds odd. We're not sure

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what's going on. To me as an

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astronomer though, it speaks to one of the

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kind of really big Hollywood movie driven

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myths, I think, about meteorites.

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There's this idea that if a meteorite falls

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through the atmosphere and you pick it up

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immediately, it'll burn your hands, it'll be

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super, super hot. And that just really

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isn't the case now. I mean, it would be the

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case if something like the dinosaur killing

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asteroid hit the Earth. Uh, that'd get really

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hot, but you wouldn't be picking it up

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because you'd be vaporized and dead. Right.

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Um, for the smaller things that hit the, uh,

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Earth but can make it to the ground intact,

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they typically are slowed down by the

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atmosphere such that by the time they're 10

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or 20 kilometers above the ground, they've

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slowed down to below the speed of sound. And

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so that's why when you see the fireball for

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these things, that fireball terminates still

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quite high in the atmosphere. And while it

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might look like it was just over the next

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hill from you. The thing was still 20 or 30

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kilometers up. That's because the air

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resistance has been enough to slow them down.

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And at that point, they're falling at just a

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couple of hundred kilometers per hour at

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terminal velocity. Now, that's still pretty

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fast. And I mean, I wouldn't want to fall at

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200km an hour into the ground. No, but it

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means that from a height of 20 or 30 km, it

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takes a few minutes to reach the ground.

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What that means is that there's time for the

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rock to equilibrate to get

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the temperature equalized across this entire

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object. Now, the object's been held in space

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in cold storage for millions of years. Years.

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So the interior of the rock is bitterly,

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bitterly, bitterly cold. And, um, they've got

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rocky asteroids, rocky meteorites have a

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fairly high thermal inertia. They're not very

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conductive. And so what

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happens is that the thin outer layer gets

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super hot when it's coming through the

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atmosphere and it's luminous and that's

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getting ablated away. But very little

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of that heat actually is conducted to the

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interior. Once this thing slows down,

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it just keeps falling. And you've got a huge

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amount of cold material and a very, very tiny

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thin layer of hot material. So by the time it

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reaches the ground, meteorites are typically

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cold to the touch. And you're more likely to

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see frost forming on them or water vapor

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condensing on them. It's a bit like maybe

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deep fried ice cream. You deep fry the ice

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cream, you get a hot layer on the outside,

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but the ice cream in the middle stays cold.

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Same kind of idea. The one caveat to that

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is if you get an iron meteorite, a metal

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meteorite, that'll have a much higher thermal

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conductivity. So that can be quite warm when

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it reaches the ground. But rather than being

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super hot like the atmosphere, it's probably

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going to be nearer to room temperature.

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That's fine. What was pointed out to me,

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um, famous astronomer called Rob McNaught got

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in touch with me after he heard me on the

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radio talking about this one. Because I got

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called out, I got cold about this while I was

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driving back from the airport, having picked

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up colleague talked about it and Rob got

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in touch and pointed out that space junk,

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because it comes in at a much shallower

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angle, it actually ablates in the atmosphere

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for much, much, much longer. And it's usually

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much more conductive material. So you put

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those two things together and if a bit of

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space junk were to reach the Ground,

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there is a good chance that would be hot to

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the touch at the time you get to it. So one

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of the. Another thing that you could possibly

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use to differentiate, uh, between whether

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this is a meteorite or a bit of SpaceX

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material. All of that put together

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means that the melting of the windscreen and

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this rock being hot to me, actually kind of

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rules out it being a meteorite.

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Andrew Dunkley: Yeah.

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Jonti Horner: What adds to my argument that it's almost

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certainly not a meteorite is it was a

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nighttime event, the skies were clear in the

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area, nobody saw a fireball. There are no

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00:09:34.810 --> 00:09:37.650
reports of a bright fireball, added to

255
00:09:37.650 --> 00:09:40.570
which are also no reports of sonic events

256
00:09:40.570 --> 00:09:42.580
or tremors, you know, things that would show

257
00:09:42.580 --> 00:09:44.660
up in the seismograph. So I think we can

258
00:09:44.660 --> 00:09:47.420
fairly definitively rule out a meteorite as

259
00:09:47.420 --> 00:09:49.180
the source of this impact on this car.

260
00:09:50.540 --> 00:09:52.580
Um, there is the amusing option that it could

261
00:09:52.580 --> 00:09:54.740
have been a SpaceX on Tesla impact, which

262
00:09:54.740 --> 00:09:56.060
would have been very entertaining. You know,

263
00:09:56.060 --> 00:09:57.660
it could have been a bit of space debris

264
00:09:58.140 --> 00:10:00.180
falling through the atmosphere and almost be

265
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friendly fire. But again, that would have

266
00:10:02.340 --> 00:10:04.060
created a very bright fireball that people

267
00:10:04.060 --> 00:10:05.660
would have seen. So I think we can rule that

268
00:10:05.660 --> 00:10:07.580
out as well. And the thing that to me

269
00:10:08.590 --> 00:10:11.310
tells the story here and will point me in a

270
00:10:11.310 --> 00:10:12.910
direction of investigation is in his

271
00:10:12.910 --> 00:10:15.750
interview, um, Dr. Melville Smith

272
00:10:15.750 --> 00:10:18.310
says a truck went past. Five or ten seconds

273
00:10:18.310 --> 00:10:20.670
later, there was an enormous explosion. Now,

274
00:10:20.670 --> 00:10:22.390
I've been hit by bits of gravel falling off

275
00:10:22.390 --> 00:10:24.270
trucks before and had my windscreen damaged.

276
00:10:24.270 --> 00:10:26.790
Yep. Quite possible that this was a rock that

277
00:10:26.790 --> 00:10:29.270
fell off that truck that went past, or that

278
00:10:29.270 --> 00:10:31.350
the truck kicked up a bit of rock from the

279
00:10:31.350 --> 00:10:32.990
surface of the road that bounced along the

280
00:10:32.990 --> 00:10:35.760
road and hit the windscreen. I still

281
00:10:35.760 --> 00:10:38.160
find it hard to see how that would have

282
00:10:38.160 --> 00:10:40.680
generated heat from the thing that hit the

283
00:10:40.680 --> 00:10:42.360
windscreen that will cause a bit of melting.

284
00:10:42.920 --> 00:10:44.720
Even though it's been really hot there, the

285
00:10:44.720 --> 00:10:46.880
road surface could have been hot. You still

286
00:10:46.880 --> 00:10:48.600
don't expect the surface of the road to be

287
00:10:48.600 --> 00:10:51.000
hot enough to melt glass. But the

288
00:10:51.080 --> 00:10:53.400
kinetic energy of an impact, if you've got a

289
00:10:53.400 --> 00:10:55.800
more massive impactor coming in a bit more

290
00:10:55.800 --> 00:10:57.880
slowly, you still can put a lot of energy in.

291
00:10:57.960 --> 00:10:59.840
And it may well just be that what they're

292
00:10:59.840 --> 00:11:02.250
mistaking for melting is actually this

293
00:11:02.250 --> 00:11:04.570
deformation, this crater in the windscreen,

294
00:11:04.970 --> 00:11:06.690
with all of the material in the windscreen

295
00:11:06.690 --> 00:11:08.370
that is designed to stop your windscreen

296
00:11:08.370 --> 00:11:10.450
shattering. And that's done a really good

297
00:11:10.450 --> 00:11:11.890
job. I know when I've had cracks in my

298
00:11:11.890 --> 00:11:13.610
windscreen, I'm always surprised how you get

299
00:11:13.610 --> 00:11:15.970
a break but it doesn't shatter, doesn't

300
00:11:15.970 --> 00:11:18.970
create a whole windscreen. Modern windscreens

301
00:11:18.970 --> 00:11:20.410
are designed to be like this multi layer

302
00:11:20.410 --> 00:11:22.970
thing that stops them doing that. And I'm

303
00:11:22.970 --> 00:11:25.530
wondering if what they think looked as signs

304
00:11:25.530 --> 00:11:27.290
of melting was actually the structure of the

305
00:11:27.290 --> 00:11:29.590
wind windscreen behaving as it's expected to,

306
00:11:29.590 --> 00:11:32.190
with a bigger impact. And um, because this is

307
00:11:32.350 --> 00:11:33.950
substantial, I mean it's bigger than some of

308
00:11:33.950 --> 00:11:35.790
the pictures of hail damage I saw over the

309
00:11:35.790 --> 00:11:37.670
weekend, for example. And it's bigger than

310
00:11:37.670 --> 00:11:39.550
the usual chip you see kicked up off the

311
00:11:39.550 --> 00:11:42.270
road. It's at a size that people might not

312
00:11:42.270 --> 00:11:44.790
expect it to look like that. So my take on

313
00:11:44.790 --> 00:11:47.510
this one is very confident it's not a rock

314
00:11:47.510 --> 00:11:48.950
from space, but it might have been a rock

315
00:11:48.950 --> 00:11:49.550
from truck.

316
00:11:49.710 --> 00:11:52.670
Andrew Dunkley: Yes, well, the timing sounds about right. And

317
00:11:52.770 --> 00:11:55.110
um, yeah, good picture of you on the ABC

318
00:11:55.110 --> 00:11:56.990
story on the website too, by the way.

319
00:11:57.230 --> 00:11:59.730
Jonti Horner: Yeah, back when I was younger and slimmer.

320
00:11:59.730 --> 00:12:01.970
Andrew Dunkley: Yeah, they generally use those photos for us.

321
00:12:01.970 --> 00:12:04.810
It's very nice. But yeah, it

322
00:12:04.810 --> 00:12:07.290
reminds me once when um, we, we had a brand

323
00:12:07.290 --> 00:12:09.650
new car and we decided to take it for a run

324
00:12:09.650 --> 00:12:12.610
and we were approaching roadworks and we were

325
00:12:12.610 --> 00:12:14.690
teaching our son to drive at the time. So

326
00:12:14.690 --> 00:12:17.690
he's hammering along at the minimum,

327
00:12:17.690 --> 00:12:20.530
you know, maximum, minimum speed of a, ah, a

328
00:12:20.530 --> 00:12:23.490
learner. And I told him to hit the brakes

329
00:12:23.490 --> 00:12:25.740
because I didn't want to hit that road work

330
00:12:25.820 --> 00:12:27.980
when a truck approached and that's exactly

331
00:12:27.980 --> 00:12:30.140
what happened. We got showered in gravel.

332
00:12:30.460 --> 00:12:33.020
That brand new car had so much,

333
00:12:33.740 --> 00:12:35.500
you know, chipping on the front. We were

334
00:12:35.500 --> 00:12:36.540
very, very upset.

335
00:12:37.180 --> 00:12:39.660
Jonti Horner: To say it's shocking. I mean, one of the good

336
00:12:39.660 --> 00:12:41.580
things is, and it's not often that you can

337
00:12:41.900 --> 00:12:44.700
readily praise insurance companies, but I got

338
00:12:44.700 --> 00:12:47.500
a big chip on my windscreen at the turn of

339
00:12:47.500 --> 00:12:50.260
the year last year and um, got in touch with

340
00:12:50.260 --> 00:12:52.690
my insurance company and they soldered a

341
00:12:52.690 --> 00:12:55.130
windscreen replacement free of charge without

342
00:12:55.130 --> 00:12:57.130
it impacting my excess or anything like that.

343
00:12:57.130 --> 00:12:58.570
Now, well, I guess it's not free of charge

344
00:12:58.570 --> 00:13:00.130
because I'm paying the insurance premiums.

345
00:13:00.370 --> 00:13:02.850
But you know, it didn't impact my insurance

346
00:13:02.850 --> 00:13:05.170
rates, it didn't cause an excess. And I'm

347
00:13:05.170 --> 00:13:06.770
guessing that's because if you don't fix

348
00:13:06.770 --> 00:13:08.409
that, uh, it can become a much bigger problem

349
00:13:08.409 --> 00:13:10.410
and cause them a much bigger accident. So

350
00:13:10.410 --> 00:13:11.890
from their point of view, it's a very

351
00:13:11.890 --> 00:13:14.050
valuable investment. But it does mean that

352
00:13:14.050 --> 00:13:16.290
when we get these kind of events, we can get

353
00:13:16.290 --> 00:13:18.210
our windscreens fixed fairly easily and

354
00:13:18.990 --> 00:13:20.190
probably means that the trucks that are

355
00:13:20.190 --> 00:13:21.950
driving around shedding their loads get off A

356
00:13:21.950 --> 00:13:23.790
little bit scot free compared to having

357
00:13:23.790 --> 00:13:25.790
people chasing them down to pay for repairs.

358
00:13:25.870 --> 00:13:28.510
Andrew Dunkley: Yes, yes indeed. Okay,

359
00:13:28.510 --> 00:13:31.430
so probably not a meteorite, but probably

360
00:13:31.430 --> 00:13:32.920
a rock. Um.

361
00:13:35.230 --> 00:13:36.990
Jonti Horner: Roger, you're allowed to clear also.

362
00:13:37.070 --> 00:13:40.020
Andrew Dunkley: Space nuts to another event that uh,

363
00:13:40.020 --> 00:13:42.990
happened over uh, Victoria, New South Wales

364
00:13:43.390 --> 00:13:46.350
and the act, which, which are next door

365
00:13:46.350 --> 00:13:48.910
to each other, a fireball, um,

366
00:13:49.150 --> 00:13:51.870
as recently as yesterday as we

367
00:13:51.870 --> 00:13:52.270
speak.

368
00:13:52.830 --> 00:13:55.190
Jonti Horner: Yes. So this is very much breaking news. So

369
00:13:55.190 --> 00:13:57.710
I'm aware this doesn't air immediately. So

370
00:13:57.710 --> 00:13:59.390
this was a fireball that was seen on Sunday

371
00:13:59.870 --> 00:14:02.790
2nd November, which as we're recording at

372
00:14:02.790 --> 00:14:04.830
the minute, this was actually about 18 hours

373
00:14:04.830 --> 00:14:07.590
ago from now, roughly. And so that means

374
00:14:07.590 --> 00:14:10.560
information's still coming in. It was at uh,

375
00:14:10.740 --> 00:14:13.380
just about 20 to 5 in the evening,

376
00:14:13.700 --> 00:14:16.460
which means it was broad daylight. So this is

377
00:14:16.460 --> 00:14:18.500
a daylight fireball. And to me that's always

378
00:14:18.900 --> 00:14:21.620
a really exciting flag that this could be a

379
00:14:21.620 --> 00:14:23.220
bigger event because to be bright enough to

380
00:14:23.220 --> 00:14:25.540
be seen in broad daylight, and particularly

381
00:14:25.540 --> 00:14:27.460
to be bright enough to be seen widely in

382
00:14:27.460 --> 00:14:29.660
broad daylight by the general public means

383
00:14:29.660 --> 00:14:31.380
that this was a fairly substantial thing

384
00:14:31.380 --> 00:14:33.260
coming into the atmosphere. There are

385
00:14:33.260 --> 00:14:35.420
observations of this in New South Wales, in

386
00:14:35.420 --> 00:14:38.020
the act, the Australian Capital Territory

387
00:14:38.360 --> 00:14:41.000
and down into Victoria. Um, it's also

388
00:14:41.480 --> 00:14:43.680
a sonic boom and rumbles have been heard

389
00:14:43.680 --> 00:14:46.200
across Victoria recorded on seismograph

390
00:14:46.520 --> 00:14:49.320
in Nurbuchen in eastern Victoria.

391
00:14:50.040 --> 00:14:52.720
So it kind of sounds really promising from

392
00:14:52.720 --> 00:14:54.319
the point of view of something that is big

393
00:14:54.319 --> 00:14:56.280
enough to potentially drop a meteorite.

394
00:14:56.600 --> 00:14:58.920
There's a lot of good footage popping up on

395
00:14:58.920 --> 00:15:00.760
Facebook groups like the Australian Meteor

396
00:15:00.760 --> 00:15:03.600
Reports Facebook group. And the

397
00:15:03.600 --> 00:15:05.040
one thing that gives me a little bit of

398
00:15:05.040 --> 00:15:06.880
caution about something making it to the

399
00:15:06.880 --> 00:15:09.320
ground here is on some of those videos I've

400
00:15:09.320 --> 00:15:11.020
seen, this single looks like it was a very

401
00:15:11.020 --> 00:15:13.540
fast moving object. Now

402
00:15:13.700 --> 00:15:16.580
typically really fast moving things

403
00:15:16.580 --> 00:15:18.300
coming into the atmosphere have a lower

404
00:15:18.300 --> 00:15:20.220
likelihood of leaving anything to make it to

405
00:15:20.220 --> 00:15:22.740
the ground. Couple of reasons for that.

406
00:15:22.900 --> 00:15:25.340
Firstly, they tend to detonate higher up in

407
00:15:25.340 --> 00:15:27.700
the atmosphere and ah, more things get

408
00:15:27.700 --> 00:15:29.900
destroyed. But the other thing which I think

409
00:15:29.900 --> 00:15:31.980
is more to the point is things that come in

410
00:15:31.980 --> 00:15:34.580
really, really fast are typically moving on

411
00:15:34.580 --> 00:15:36.740
more comet like orbits and asteroid like

412
00:15:36.740 --> 00:15:39.020
orbits and therefore are more likely to be

413
00:15:39.020 --> 00:15:41.460
cometary material than asteroidal material,

414
00:15:41.810 --> 00:15:43.050
which means they're likely to be more

415
00:15:43.050 --> 00:15:45.850
friable, more fragile, more dust and

416
00:15:45.850 --> 00:15:48.530
ice rather than rock and metal. And that

417
00:15:48.530 --> 00:15:50.130
means that uh, when you see something coming

418
00:15:50.130 --> 00:15:51.970
in at really high speed, like some of these

419
00:15:51.970 --> 00:15:54.650
videos seem to show, that possibly

420
00:15:54.650 --> 00:15:56.650
means that there is a lower chance of

421
00:15:56.650 --> 00:15:59.410
something surviving to the surface. Doesn't

422
00:15:59.410 --> 00:16:02.130
mean that there won't be a meteorite found

423
00:16:02.130 --> 00:16:04.770
from this. Particularly because this, like I

424
00:16:04.770 --> 00:16:06.250
said, was bright enough to see in broad

425
00:16:06.250 --> 00:16:08.490
daylight and bright enough to be quite widely

426
00:16:08.490 --> 00:16:11.050
observed. The fact that the explosion, the

427
00:16:11.050 --> 00:16:13.650
terminal detonation, the air burst happened

428
00:16:13.650 --> 00:16:15.450
low enough for people to hear the sonic booms

429
00:16:15.450 --> 00:16:17.930
and for it to pick up on seismographs, all of

430
00:16:17.930 --> 00:16:19.570
these things are kind of things that we'd

431
00:16:19.570 --> 00:16:21.850
look for to say this is a promising event.

432
00:16:22.250 --> 00:16:23.930
The one thing that's giving me some caution

433
00:16:23.930 --> 00:16:26.850
is a very high speed. So this is very much a

434
00:16:26.850 --> 00:16:28.770
developing story. It might be that by the

435
00:16:28.770 --> 00:16:31.250
time people listen to this episode, they can

436
00:16:31.250 --> 00:16:32.690
go online and have a look and there'll be

437
00:16:32.690 --> 00:16:35.050
more information available. I'm honestly

438
00:16:35.050 --> 00:16:36.490
quite surprised that there's not been more

439
00:16:36.490 --> 00:16:38.850
media interest in this this morning. Usually

440
00:16:38.850 --> 00:16:40.250
when there's a bright event like this,

441
00:16:40.650 --> 00:16:42.450
journalists are ringing up and saying, what

442
00:16:42.450 --> 00:16:44.490
do you think? And what's happened? Yeah, so

443
00:16:44.490 --> 00:16:46.610
it may be a little bit of a slow burn, but

444
00:16:46.610 --> 00:16:48.250
it'll be interesting to see what develops on

445
00:16:48.250 --> 00:16:50.130
this in the next week or two. Maybe that

446
00:16:50.130 --> 00:16:52.250
nothing had always found, but it could be yet

447
00:16:52.250 --> 00:16:53.770
another rock dropping to the surface of

448
00:16:53.770 --> 00:16:55.250
Australia to give us something to study.

449
00:16:55.490 --> 00:16:58.370
Andrew Dunkley: Yeah, indeed. Yeah, yeah. Um, I've never

450
00:16:58.370 --> 00:17:00.690
seen one myself, but we've, we've had a few

451
00:17:00.690 --> 00:17:03.450
over the years, um, crossing the. The

452
00:17:03.450 --> 00:17:06.410
sky in Dubbo. One particular daytime

453
00:17:06.410 --> 00:17:09.370
one that someone filmed many, many years ago.

454
00:17:09.370 --> 00:17:11.170
And, uh, yeah, quite spectacular.

455
00:17:12.180 --> 00:17:14.940
Okay, uh, this is Space Nuts with

456
00:17:14.940 --> 00:17:17.220
Andrew Dunkley and John de Horner.

457
00:17:21.540 --> 00:17:22.580
Jonti Horner: Space Nuts.

458
00:17:22.800 --> 00:17:25.740
Andrew Dunkley: Uh, now this next story takes, um,

459
00:17:26.020 --> 00:17:28.990
us back to 3I Atlas, the, um,

460
00:17:29.140 --> 00:17:31.740
exo comet, I

461
00:17:31.740 --> 00:17:34.380
suppose, um, that's currently moving through

462
00:17:34.380 --> 00:17:37.340
our solar system. Uh, the reason it's

463
00:17:37.340 --> 00:17:39.760
sort of gained more traction is because

464
00:17:39.840 --> 00:17:42.600
things have changed and it's

465
00:17:42.600 --> 00:17:44.600
doing weird things. And of course, that's

466
00:17:44.600 --> 00:17:46.680
brought out the popular press and a few of

467
00:17:46.680 --> 00:17:48.080
those other comments that we're not going to

468
00:17:48.080 --> 00:17:50.080
talk about, but, um, bit of chatter on

469
00:17:50.080 --> 00:17:52.560
Facebook through the Space Nuts podcast

470
00:17:52.560 --> 00:17:55.240
group. Uh, what's happening with 3i

471
00:17:55.240 --> 00:17:55.840
Atlas?

472
00:17:57.120 --> 00:18:00.000
Jonti Horner: Well, the latest update is that it got a lot

473
00:18:00.000 --> 00:18:02.400
of coverage last week. Not really because

474
00:18:02.400 --> 00:18:04.160
anything special was happening, but because

475
00:18:04.160 --> 00:18:06.280
last week was the point at which Comet Atlas

476
00:18:06.280 --> 00:18:08.350
went through perihelion. Yeah, so that was

477
00:18:08.350 --> 00:18:09.750
the time it was closest to the sun.

478
00:18:09.750 --> 00:18:11.990
Perihelion was on about 30 October,

479
00:18:12.790 --> 00:18:15.430
so people are obviously interested. Um, I see

480
00:18:15.430 --> 00:18:17.550
the astronomer who Shall Not Be Named and

481
00:18:17.550 --> 00:18:19.870
they'll call him Voldemort for now, has come

482
00:18:19.870 --> 00:18:21.550
out with new stories saying that this Thing

483
00:18:21.550 --> 00:18:23.549
is changing direction and the aliens are

484
00:18:23.549 --> 00:18:25.550
definitely invading and rocket engines have

485
00:18:25.550 --> 00:18:28.070
kicked off. And, um, all this stuff,

486
00:18:28.370 --> 00:18:30.190
um, and it clearly isn't, you know, we are

487
00:18:30.190 --> 00:18:31.630
safe, we're not going to be invaded by

488
00:18:31.630 --> 00:18:33.670
aliens. You don't have to worry and protect

489
00:18:33.670 --> 00:18:35.790
yourself and buy some wine, Cokes or whatever

490
00:18:35.790 --> 00:18:38.240
you need to do. Um, does open up the question

491
00:18:38.240 --> 00:18:40.800
at what point this guy lost his credibility

492
00:18:40.800 --> 00:18:42.560
with the scientific community. The best part

493
00:18:42.560 --> 00:18:44.600
of a decade ago. But I wonder at what point

494
00:18:45.240 --> 00:18:47.360
the Boy who Cried Wolf syndrome will kick in

495
00:18:47.360 --> 00:18:49.360
to such an extent to overwhelm the Harvard

496
00:18:49.360 --> 00:18:52.320
affiliation and that the stories this

497
00:18:52.320 --> 00:18:54.280
guy puts out will stop getting oxygen. That's

498
00:18:54.280 --> 00:18:56.840
going to be an interesting study in the,

499
00:18:57.300 --> 00:18:59.240
um, I guess the scientific literacy of

500
00:18:59.240 --> 00:19:01.280
journalists at the lowest common denominator

501
00:19:01.280 --> 00:19:03.160
publications. That might be the way I put it,

502
00:19:04.010 --> 00:19:05.890
but it is definitely not aliens. But what is

503
00:19:05.890 --> 00:19:08.770
happening with Comet 3i Atlas is it's giving

504
00:19:08.770 --> 00:19:11.050
us this unprecedented window into the

505
00:19:11.050 --> 00:19:12.690
behavior of a comet that formed around

506
00:19:12.690 --> 00:19:15.410
another star. It's also a comet that's coming

507
00:19:15.410 --> 00:19:17.170
in and traveling through the solar system at

508
00:19:17.170 --> 00:19:19.409
a higher speed than typical comets do. And

509
00:19:19.409 --> 00:19:20.770
that's of course, how we know it's from

510
00:19:20.770 --> 00:19:23.330
another star. What that means, though, is

511
00:19:23.330 --> 00:19:26.210
that, uh, the typical process by which

512
00:19:26.210 --> 00:19:29.090
comets do their thing will happen

513
00:19:29.090 --> 00:19:30.850
in a slightly different way for this object,

514
00:19:30.850 --> 00:19:32.250
naturally, because it's coming through

515
00:19:32.250 --> 00:19:34.730
quicker. So things happen at an accelerated

516
00:19:34.730 --> 00:19:37.350
rate. And that might be what's happening.

517
00:19:37.350 --> 00:19:39.470
That ties into a paper that's just been

518
00:19:39.470 --> 00:19:41.470
published that you can read on the archive,

519
00:19:41.470 --> 00:19:43.870
the preprint server that we as astronomers

520
00:19:43.870 --> 00:19:46.110
use to spread the word of our work and

521
00:19:46.110 --> 00:19:48.870
circumvent the exorbitant prices that

522
00:19:48.870 --> 00:19:50.670
journals charge for you to read. Then we put

523
00:19:50.670 --> 00:19:52.470
all our papers on Arxiv as well and say,

524
00:19:52.870 --> 00:19:54.790
don't pay the journal, read it for free here,

525
00:19:54.790 --> 00:19:57.430
because we're nice like that. Um, this paper

526
00:19:57.430 --> 00:20:00.070
has been looking at the light curve of this

527
00:20:00.070 --> 00:20:02.320
comet, so how it's brightening over time.

528
00:20:02.960 --> 00:20:05.760
And what it's found is that, ah3i Atlas has

529
00:20:05.760 --> 00:20:08.480
been brightening faster than typical OC cloud

530
00:20:08.480 --> 00:20:10.880
comets do at this distance from the sun.

531
00:20:11.360 --> 00:20:13.080
So when you've got a comet coming in from the

532
00:20:13.080 --> 00:20:16.000
sun, it brightens in

533
00:20:16.000 --> 00:20:18.880
a slightly predictable rate. And the reason I

534
00:20:18.880 --> 00:20:21.480
say slightly predictable rate is, uh, there's

535
00:20:21.480 --> 00:20:23.800
a famous quote from a comet astronomer called

536
00:20:23.800 --> 00:20:25.840
David Levy that says comets are like cats.

537
00:20:26.080 --> 00:20:28.000
They have tails and they do whatever the hell

538
00:20:28.000 --> 00:20:30.960
they want. And there's a truth in that. So

539
00:20:30.960 --> 00:20:33.030
what we tend to do is when we first find a

540
00:20:33.180 --> 00:20:36.060
comet, we can work out Fairly quickly, what

541
00:20:36.060 --> 00:20:39.020
orbit it's moving on around the sun to some

542
00:20:39.020 --> 00:20:41.260
degree, how far away it is from the sun and

543
00:20:41.260 --> 00:20:43.300
how quickly it's moving. And, um, by knowing

544
00:20:43.300 --> 00:20:45.260
how far away it is and how bright it is, when

545
00:20:45.260 --> 00:20:47.580
we find it, we can work out

546
00:20:48.939 --> 00:20:50.820
an absolute magnitude for it, which is a

547
00:20:50.820 --> 00:20:52.700
quantity that characterizes whether it's a

548
00:20:52.700 --> 00:20:54.780
big, bright comet or a small, faint comet.

549
00:20:55.180 --> 00:20:57.060
And we can use that and, um, the orbit it's

550
00:20:57.060 --> 00:20:59.180
going around the sun to make a first

551
00:20:59.180 --> 00:21:00.980
prediction of how the comet will brighten or

552
00:21:00.980 --> 00:21:03.820
fade. Then, as we observe it over a little

553
00:21:03.820 --> 00:21:06.460
bit of time, we can characterize how its

554
00:21:06.460 --> 00:21:08.900
activity is changing and work out not only

555
00:21:08.900 --> 00:21:10.740
whether it's a big comet or a small comet,

556
00:21:10.740 --> 00:21:12.500
but whether it's an active comet or whether

557
00:21:12.500 --> 00:21:15.180
it's a very quiescent comet. So whether it's

558
00:21:15.260 --> 00:21:18.100
brightening rapidly or brightening slowly

559
00:21:18.100 --> 00:21:20.780
for a comet of that size. And over time, this

560
00:21:20.780 --> 00:21:22.940
allows people to predict the brightness of

561
00:21:22.940 --> 00:21:25.460
the comet going forward. And assuming the

562
00:21:25.460 --> 00:21:27.460
comet doesn't do anything unusual, like

563
00:21:27.460 --> 00:21:29.740
fragmenting or having an outburst or

564
00:21:29.740 --> 00:21:32.470
something like this, we can get a fairly good

565
00:21:32.470 --> 00:21:35.390
handle several months ahead of time, of how

566
00:21:35.390 --> 00:21:37.990
bright the comet's going to be with a certain

567
00:21:37.990 --> 00:21:39.950
degree of uncertainty. And so we've got a

568
00:21:39.950 --> 00:21:42.470
fairly good feeling for how a comet coming in

569
00:21:42.470 --> 00:21:44.510
from the Oort Cloud that is about the size of

570
00:21:44.510 --> 00:21:46.390
Comet ATLAS should brighten.

571
00:21:47.350 --> 00:21:48.910
Now, some comets brighten a bit quicker

572
00:21:48.910 --> 00:21:50.390
because they're more active. Some brighten a

573
00:21:50.390 --> 00:21:53.070
bit slower. What's happened with Comet ATLAS

574
00:21:53.070 --> 00:21:55.630
is it started to brighten significantly

575
00:21:55.630 --> 00:21:58.190
quicker than we'd expect a typical Oort cloud

576
00:21:58.190 --> 00:22:00.190
comet to brighten at the same distance from

577
00:22:00.190 --> 00:22:02.290
the Sun. And that's what this paper's all

578
00:22:02.290 --> 00:22:04.010
about. Basically, the comet's brightening

579
00:22:04.010 --> 00:22:06.930
unusually quickly. Now, there's a

580
00:22:06.930 --> 00:22:08.890
variety of possible explanations for that,

581
00:22:08.890 --> 00:22:11.090
and we won't know which answer is true until

582
00:22:11.090 --> 00:22:13.890
we do more study. The most common reason

583
00:22:13.890 --> 00:22:16.490
for a comet to brighten unusually quickly

584
00:22:16.810 --> 00:22:18.730
is often linked to the comet's head becoming

585
00:22:18.730 --> 00:22:20.570
a bit more diffuse because it's a comet

586
00:22:20.570 --> 00:22:23.130
fragmentation event. So the comet's

587
00:22:23.210 --> 00:22:25.970
falling apart. You release a lot of

588
00:22:25.970 --> 00:22:27.930
dust as the comet falls apart, but you also

589
00:22:27.930 --> 00:22:29.730
increase the surface area exposed to

590
00:22:29.730 --> 00:22:31.170
sunlight, which means you increase the

591
00:22:31.170 --> 00:22:33.880
activity. And the analogy here will be the

592
00:22:33.880 --> 00:22:34.960
difference. If you've ever had the

593
00:22:34.960 --> 00:22:36.960
effervescent tablets you put in water and you

594
00:22:36.960 --> 00:22:39.720
let them dissolve. If you get two of them and

595
00:22:39.720 --> 00:22:41.720
you put one in a glass of water fully intact,

596
00:22:41.720 --> 00:22:43.360
and you crumble the other one up and drop in

597
00:22:43.360 --> 00:22:45.680
the crumbled one, the crumbled one reacts

598
00:22:45.680 --> 00:22:47.800
much quicker, and it foams up really quickly.

599
00:22:48.120 --> 00:22:49.880
The solid one takes a while to go.

600
00:22:51.160 --> 00:22:53.040
That could be the case. We'll only know if we

601
00:22:53.040 --> 00:22:54.400
observe for a little bit of time. And that

602
00:22:54.400 --> 00:22:56.240
wouldn't necessarily be that unsurprising.

603
00:22:56.240 --> 00:22:58.770
There is a suspicion that this comet, 3i

604
00:22:58.770 --> 00:23:01.170
atlas never actually got close enough to its

605
00:23:01.170 --> 00:23:03.210
parent star to be active as a comet. So it

606
00:23:03.210 --> 00:23:05.210
will be more equivalent to what we call the

607
00:23:05.450 --> 00:23:07.330
new Oort cloud comets coming through for the

608
00:23:07.330 --> 00:23:09.690
very first time, rather than one that's had

609
00:23:09.690 --> 00:23:12.250
multiple perihelion passages. And, um, we do

610
00:23:12.250 --> 00:23:14.130
know that new comets have a tendency to

611
00:23:14.130 --> 00:23:16.370
fragment more often than older comets that

612
00:23:16.370 --> 00:23:18.370
have been more baked in, essentially. So

613
00:23:18.370 --> 00:23:19.890
that's one possible explanation.

614
00:23:19.890 --> 00:23:21.770
But I think another one that's really

615
00:23:21.770 --> 00:23:23.850
interesting and would probably fit quite well

616
00:23:23.850 --> 00:23:26.750
is that our models of cometary

617
00:23:26.750 --> 00:23:29.680
activity have built within them. Though, uh,

618
00:23:29.710 --> 00:23:31.790
we don't normally think about it, the time at

619
00:23:31.790 --> 00:23:34.390
which activity driven by different ices

620
00:23:34.470 --> 00:23:36.830
kicks in. So as the comet gets closer to the

621
00:23:36.830 --> 00:23:39.750
sun and it gets hotter, different ices on

622
00:23:39.750 --> 00:23:41.390
the surface will reach the temperature where

623
00:23:41.390 --> 00:23:43.310
they can no longer be ices, and they turn

624
00:23:43.310 --> 00:23:45.350
from ice to gas in a process called

625
00:23:45.350 --> 00:23:46.950
sublimation. And that's what drives the

626
00:23:46.950 --> 00:23:49.310
activity of the comet. And as a comet heats

627
00:23:49.310 --> 00:23:51.430
up, different ices turn on, effectively.

628
00:23:52.810 --> 00:23:55.010
Now, when you're far from the sun, water ice

629
00:23:55.010 --> 00:23:57.730
is really cold and stays as water ice. But

630
00:23:57.730 --> 00:24:00.090
other volatile materials like carbon monoxide

631
00:24:00.090 --> 00:24:02.290
and carbon dioxide are, uh, what drive the

632
00:24:02.290 --> 00:24:04.370
activity of a comet when it's further from

633
00:24:04.370 --> 00:24:07.250
the Sun. Now, as it comes in closer, it

634
00:24:07.250 --> 00:24:09.850
heats up and water turns on. And certainly

635
00:24:09.930 --> 00:24:11.810
within a few astronomical units of the sun.

636
00:24:11.810 --> 00:24:13.930
Water is usually the dominant driving factor

637
00:24:13.930 --> 00:24:16.530
of comet reactivity. With Comet

638
00:24:16.530 --> 00:24:19.110
atlas, this brightening is happening

639
00:24:19.590 --> 00:24:21.710
interior to the distance where most comets

640
00:24:21.710 --> 00:24:23.270
would have turned on their water emission.

641
00:24:23.750 --> 00:24:26.590
But Comet ATLAS is coming in quicker, and

642
00:24:26.590 --> 00:24:29.110
so therefore, it is heating up

643
00:24:29.350 --> 00:24:31.710
due to the radiation from the Sun. But as

644
00:24:31.710 --> 00:24:34.190
it's coming in quicker, maybe it was closer

645
00:24:34.190 --> 00:24:36.630
to the sun by the time that the heat from the

646
00:24:36.630 --> 00:24:39.190
sun got to be enough to penetrate the surface

647
00:24:39.190 --> 00:24:41.190
material and start kicking on the water

648
00:24:41.190 --> 00:24:43.630
activity. But then that heating is happening

649
00:24:43.630 --> 00:24:45.740
really quickly because the distance to the

650
00:24:45.740 --> 00:24:48.340
sun is dropping quite fast. And so therefore,

651
00:24:48.340 --> 00:24:49.940
you've had this spike in temperature and

652
00:24:49.940 --> 00:24:52.740
therefore a spike in activity as the water

653
00:24:52.740 --> 00:24:55.100
activity is turned on, not so much as a

654
00:24:55.100 --> 00:24:57.460
trickle, but as a flood. And that ties in

655
00:24:57.460 --> 00:24:59.020
actually quite nicely to some of the recent

656
00:24:59.020 --> 00:25:01.260
stories in the last few weeks about the water

657
00:25:01.660 --> 00:25:03.420
vapor, uh, and the water being emitted from

658
00:25:03.420 --> 00:25:06.420
the comet I saw some article about the comet

659
00:25:06.420 --> 00:25:09.100
emitting a jet of water like a firehose. So

660
00:25:09.100 --> 00:25:11.060
this is one of those narratives that seems to

661
00:25:11.060 --> 00:25:13.200
fit together really, really well. And it

662
00:25:13.200 --> 00:25:14.680
could just be that the high speed of the

663
00:25:14.680 --> 00:25:16.720
comet means that it got closer in before the

664
00:25:16.720 --> 00:25:19.080
water turned on. And now it's catching up for

665
00:25:19.080 --> 00:25:22.040
lost time. What this means for the future is

666
00:25:22.040 --> 00:25:24.560
that, in all honesty, we are

667
00:25:24.720 --> 00:25:26.960
less confident in predicting the future

668
00:25:26.960 --> 00:25:28.679
brightness of the comet than we normally

669
00:25:28.679 --> 00:25:30.720
would be. Because it's all this cometary

670
00:25:30.720 --> 00:25:32.480
activity going on. It's effectively having a

671
00:25:32.480 --> 00:25:35.320
bit of an outburst. When we were talking

672
00:25:35.320 --> 00:25:36.920
about it months ago, we always said it would

673
00:25:36.920 --> 00:25:38.680
never get brighter than about magnitude 11,

674
00:25:38.680 --> 00:25:41.450
magnitude 12. There's a chance it might get a

675
00:25:41.450 --> 00:25:42.970
little bit brighter than that now. But it's

676
00:25:42.970 --> 00:25:44.770
really hard to model. We don't know whether

677
00:25:45.010 --> 00:25:46.850
the comet will brighten further than

678
00:25:46.850 --> 00:25:49.850
expected, brighten really rapidly, go back to

679
00:25:49.850 --> 00:25:52.450
behaving as normal. It might fade away

680
00:25:52.690 --> 00:25:54.610
because suddenly it's had this outburst. It's

681
00:25:54.610 --> 00:25:56.930
clogged itself up. It might even go out

682
00:25:56.930 --> 00:25:58.650
relatively quickly like a bit of a snuff

683
00:25:58.650 --> 00:26:00.650
torch if it has fully fragmented and

684
00:26:00.650 --> 00:26:03.370
disintegrated. And we saw that with the great

685
00:26:03.370 --> 00:26:06.100
comet earlier this year, Comet Atlas, which

686
00:26:06.100 --> 00:26:07.980
was really bright and spectacular. And then

687
00:26:07.980 --> 00:26:09.860
became the headless comet because its head

688
00:26:09.860 --> 00:26:12.540
just totally disintegrated. And all you were

689
00:26:12.540 --> 00:26:14.580
left was this tail gradually drifting through

690
00:26:14.580 --> 00:26:17.340
space with no comet to call its own. Yeah, so

691
00:26:17.340 --> 00:26:19.620
we just, honestly, we just don't, um, know

692
00:26:19.620 --> 00:26:22.220
There's a lot more to learn. And, yeah, this

693
00:26:22.220 --> 00:26:24.580
is getting a lot of hyperbolic stories

694
00:26:25.140 --> 00:26:27.180
about it and people arguing that it's

695
00:26:27.180 --> 00:26:29.220
actually the mass driver engine that's turned

696
00:26:29.220 --> 00:26:31.100
on as it will reroute itself to the Earth.

697
00:26:31.100 --> 00:26:33.760
Courtesy Harvard astronomer of doom.

698
00:26:34.240 --> 00:26:36.600
But in reality, this is why these objects are

699
00:26:36.600 --> 00:26:38.440
so exciting, because they give us a window

700
00:26:38.440 --> 00:26:40.560
into comets with different compositions that

701
00:26:40.560 --> 00:26:42.440
formed around different stars. And also how

702
00:26:42.440 --> 00:26:44.400
comets behave at higher speed. You know,

703
00:26:45.360 --> 00:26:46.560
this is why it's cool.

704
00:26:46.720 --> 00:26:49.640
Andrew Dunkley: Yeah. Uh, I must say I'm surprised that this

705
00:26:49.640 --> 00:26:52.120
one's receiving so much attention. But I

706
00:26:52.120 --> 00:26:54.120
shouldn't be surprised because it is a little

707
00:26:54.120 --> 00:26:56.640
bit different to most.

708
00:26:56.960 --> 00:26:59.910
And, um, being an ex. Extra, um,

709
00:27:00.420 --> 00:27:03.170
solar comet, um,

710
00:27:03.420 --> 00:27:05.180
it just, Just makes it that much more

711
00:27:05.180 --> 00:27:07.980
interesting. So, yeah, um, lots to learn,

712
00:27:07.980 --> 00:27:10.900
really. Uh, so, yeah, this one, uh, will no

713
00:27:10.900 --> 00:27:13.420
doubt, uh, be getting some attention for some

714
00:27:13.420 --> 00:27:16.220
time to come. Um, would be a pity if

715
00:27:16.220 --> 00:27:17.900
it kind of, you know,

716
00:27:19.020 --> 00:27:21.940
lost itself in our solar

717
00:27:21.940 --> 00:27:24.220
system. But, um, that's just the way it goes

718
00:27:24.220 --> 00:27:24.700
sometimes.

719
00:27:26.510 --> 00:27:26.990
Jonti Horner: Absolutely.

720
00:27:26.990 --> 00:27:27.950
Andrew Dunkley: Well, there it is.

721
00:27:28.270 --> 00:27:28.750
Jonti Horner: Yeah.

722
00:27:29.790 --> 00:27:31.190
I was going to say, while we're on the topic

723
00:27:31.190 --> 00:27:32.830
of comets, I should just flag up to everyone,

724
00:27:32.830 --> 00:27:34.630
particularly the Northern Hemisphere people,

725
00:27:34.630 --> 00:27:37.430
but also us in the Southern Hemisphere, a

726
00:27:37.430 --> 00:27:39.510
tiny little bit. Comet Lemon, which is

727
00:27:39.510 --> 00:27:41.550
getting a lot of media coverage, is at its

728
00:27:41.550 --> 00:27:44.030
brightest pretty much bang at the minute.

729
00:27:44.030 --> 00:27:46.230
It's about magnitude 4.3, which means

730
00:27:46.230 --> 00:27:47.990
technically it's visible to the naked eye.

731
00:27:47.990 --> 00:27:50.550
But in reality, because comets are diffuse

732
00:27:50.550 --> 00:27:52.390
objects, it'll be a very hard spot unless

733
00:27:52.390 --> 00:27:54.610
you're somewhere incredibly dark. But it is

734
00:27:54.610 --> 00:27:57.050
very photogenic comet. It is most visible to

735
00:27:57.050 --> 00:27:59.530
people in the Northern Hemisphere. For those

736
00:27:59.530 --> 00:28:02.130
of us in Australia, it's basically lost in

737
00:28:02.130 --> 00:28:04.290
the glare of twilight, even though it's at a

738
00:28:04.290 --> 00:28:06.250
declination where it could be visible if it

739
00:28:06.250 --> 00:28:08.010
was in a dark sky. It's too near the sun in

740
00:28:08.010 --> 00:28:10.890
the sky. But these few days around now,

741
00:28:10.890 --> 00:28:12.570
the next week or so, it's the best chance

742
00:28:12.570 --> 00:28:15.050
we'll get to see it from Australia while it's

743
00:28:15.050 --> 00:28:17.330
bright. And, um, that'll be very low in the

744
00:28:17.330 --> 00:28:20.010
west after sunset, um, as the sky

745
00:28:20.010 --> 00:28:22.090
gets darker. Have a look on

746
00:28:22.410 --> 00:28:24.930
planetarium programs like Stellarium to find

747
00:28:24.930 --> 00:28:27.250
the location. But my memory is that, uh, the

748
00:28:27.250 --> 00:28:29.170
planet Mercury is going to be visible low to

749
00:28:29.170 --> 00:28:30.850
the west after sunset. And if you can find

750
00:28:30.850 --> 00:28:33.610
Mercury and you go to the right of Mercury,

751
00:28:33.610 --> 00:28:35.730
it's about the same height as Mercury on the

752
00:28:35.730 --> 00:28:38.490
7th or 8th of November. So worth

753
00:28:38.490 --> 00:28:41.250
looking at. It is not the best comet of the

754
00:28:41.250 --> 00:28:42.730
year. We already have that back in January,

755
00:28:42.810 --> 00:28:44.370
despite what some of the articles said. But

756
00:28:44.370 --> 00:28:45.770
if you do want to see a comet that's

757
00:28:46.020 --> 00:28:47.660
borderline bright enough to see the naked

758
00:28:47.660 --> 00:28:49.500
eye, that's your one. It should be quite good

759
00:28:49.500 --> 00:28:52.100
in binoculars and certainly for people doing

760
00:28:52.100 --> 00:28:54.100
astrophotography. Have a look online. Some of

761
00:28:54.100 --> 00:28:55.420
the photos of this thing are really

762
00:28:55.420 --> 00:28:57.210
spectacular. There's people who've done, um,

763
00:28:57.620 --> 00:28:59.660
yeah, pretty clever things imaging it with

764
00:28:59.660 --> 00:29:02.179
lovely foreground views like lakes or rocks

765
00:29:02.179 --> 00:29:04.620
or castles or whatever. So there's lovely

766
00:29:04.620 --> 00:29:07.060
images of this comet out there if you want to

767
00:29:07.060 --> 00:29:08.540
feast your eyes on what people who are

768
00:29:08.540 --> 00:29:09.860
talented photographers can do.

769
00:29:10.420 --> 00:29:13.420
Andrew Dunkley: Yes, very good. Uh, that's Three Eye, Three

770
00:29:13.420 --> 00:29:15.750
Eye Atlas. Uh, now, um,

771
00:29:16.620 --> 00:29:18.580
oh, and you can, you can read, uh, about

772
00:29:18.580 --> 00:29:21.420
that, uh, on, um, the archive website,

773
00:29:21.420 --> 00:29:22.860
as Jonti mentioned.

774
00:29:25.100 --> 00:29:25.540
Jonti Horner: Okay.

775
00:29:25.540 --> 00:29:27.820
Andrew Dunkley: We checked all four systems and being with a

776
00:29:27.820 --> 00:29:30.580
girl, space nats, uh, let's move on to

777
00:29:30.580 --> 00:29:33.340
this really interesting story. An enormous

778
00:29:33.900 --> 00:29:36.460
black hole has been found. But what's really

779
00:29:36.460 --> 00:29:39.340
interesting is the galaxy that it's in is

780
00:29:39.820 --> 00:29:42.340
tiny. And when I, when I read into the

781
00:29:42.340 --> 00:29:45.270
details of this Story. We're talking about a

782
00:29:45.270 --> 00:29:47.470
galaxy with very few stars,

783
00:29:48.030 --> 00:29:49.710
surprisingly few stars.

784
00:29:50.670 --> 00:29:52.750
Jonti Horner: And, um, this fascinated me reading it now. I

785
00:29:52.750 --> 00:29:54.150
always say, particularly when we're doing the

786
00:29:54.150 --> 00:29:56.150
questions, and we get lots of cosmology type

787
00:29:56.150 --> 00:29:58.630
questions. I'm not a cosmologist, I'm not a

788
00:29:58.630 --> 00:30:01.590
galactic type astronomer. Uh, my expertise

789
00:30:01.590 --> 00:30:03.150
and my focus is very much on the things

790
00:30:03.150 --> 00:30:05.550
closer to home. So I tend to try and pick

791
00:30:05.550 --> 00:30:07.630
stories where I can talk from a position of

792
00:30:07.630 --> 00:30:09.750
some authority rather than no authority, if

793
00:30:09.750 --> 00:30:12.060
that makes sense. But this story was so cool,

794
00:30:12.060 --> 00:30:14.480
I thought we had to include it, even if, um,

795
00:30:14.500 --> 00:30:16.100
it might be a little bit of the blind leading

796
00:30:16.100 --> 00:30:17.900
the blind in a way. But this is one of the

797
00:30:17.900 --> 00:30:19.860
Milky Way's satellite galaxies. And our

798
00:30:19.860 --> 00:30:22.740
galaxy has many, many satellites, from the

799
00:30:22.900 --> 00:30:24.980
incredibly large and bright, large and Small

800
00:30:24.980 --> 00:30:27.340
Magellanic Clouds, which we can see here in

801
00:30:27.340 --> 00:30:28.860
the Southern Hemisphere, really high in the

802
00:30:28.860 --> 00:30:31.580
sky at the minute, really spectacular, down

803
00:30:31.580 --> 00:30:33.860
to really, really tiny satellite galaxies

804
00:30:33.860 --> 00:30:36.100
that almost push our understanding of what it

805
00:30:36.100 --> 00:30:39.070
means to be a galaxy. And this galaxy

806
00:30:39.070 --> 00:30:41.590
is one such galaxy. It's what's described as

807
00:30:41.590 --> 00:30:44.430
an ultra faint dwarf galaxy. And there are

808
00:30:44.430 --> 00:30:47.030
likely an enormous number of these in space

809
00:30:47.030 --> 00:30:49.790
that we just don't find. I guess the analogy

810
00:30:49.790 --> 00:30:51.430
I'd use here is that if you go out and look

811
00:30:51.430 --> 00:30:53.990
at the stars in the night sky, the stars that

812
00:30:53.990 --> 00:30:55.670
you're seeing are very much the superstars of

813
00:30:55.670 --> 00:30:57.350
our galaxy. They're stars that are much more

814
00:30:57.350 --> 00:30:59.590
massive than the sun that we're seeing from

815
00:30:59.590 --> 00:31:02.510
great distances. The most common stars in

816
00:31:02.510 --> 00:31:05.030
the galaxy are the dim little red dwarfs like

817
00:31:05.030 --> 00:31:07.980
Proxima Centauri. And Proxima is fairly

818
00:31:07.980 --> 00:31:10.180
massive and fairly luminous for a red dwarf.

819
00:31:10.500 --> 00:31:12.420
It is the closest star to the solar system,

820
00:31:12.420 --> 00:31:14.340
and it's too fancy with the naked eye by a

821
00:31:14.340 --> 00:31:17.140
factor of 100 times. So there's lots and lots

822
00:31:17.140 --> 00:31:19.980
of very small, faint things that until we

823
00:31:19.980 --> 00:31:21.780
have telescopes, we couldn't find at all.

824
00:31:21.780 --> 00:31:23.700
There are always more small things than big

825
00:31:23.700 --> 00:31:26.040
things. So it seems likely that there are,

826
00:31:26.040 --> 00:31:28.820
uh, many, many, many faint,

827
00:31:28.820 --> 00:31:31.020
ultra faint dwarf galaxies that have simply

828
00:31:31.020 --> 00:31:33.380
not been discovered even in our local area,

829
00:31:33.380 --> 00:31:36.040
never mind at the far parts of the cosmos.

830
00:31:36.040 --> 00:31:38.560
When we talk about galaxies that are many

831
00:31:38.560 --> 00:31:40.160
hundreds of millions of light years away,

832
00:31:40.160 --> 00:31:41.800
we're only seeing the superstars. We're not

833
00:31:41.800 --> 00:31:44.440
seeing the little baby ones like this. The

834
00:31:44.440 --> 00:31:47.440
galaxy in the story here is called Segue one.

835
00:31:47.520 --> 00:31:50.040
And I must admit that I don't think I'd ever

836
00:31:50.040 --> 00:31:51.560
heard of this, or I'd only ever heard of it

837
00:31:51.560 --> 00:31:54.480
in passing before this story came out. It is

838
00:31:54.480 --> 00:31:57.040
really tiny and very Anonymous. It's about

839
00:31:57.040 --> 00:31:59.440
75,000 light years from the Earth.

840
00:32:00.250 --> 00:32:01.570
Like I say, it's one of our satellite

841
00:32:01.570 --> 00:32:03.130
galaxies. And, uh, our, uh, best

842
00:32:03.130 --> 00:32:05.090
observations. There's a photograph in the

843
00:32:05.090 --> 00:32:07.250
Space.com article which is fabulous. It says,

844
00:32:07.250 --> 00:32:09.650
you know, here's this dwarf galaxy with only

845
00:32:09.650 --> 00:32:11.330
a handful of stars, and I'm not sure where

846
00:32:11.330 --> 00:32:13.370
the galaxy is because there's so little in

847
00:32:13.370 --> 00:32:15.850
the photograph. That's what it's like. And so

848
00:32:15.850 --> 00:32:17.730
you're talking here of just a few hundred or

849
00:32:17.730 --> 00:32:20.090
a few thousand stars held together.

850
00:32:21.050 --> 00:32:23.370
Now, that's been a puzzle for galaxy

851
00:32:23.370 --> 00:32:25.490
astronomers for a long time, because so few

852
00:32:25.490 --> 00:32:28.160
stars have so little mass that the

853
00:32:28.160 --> 00:32:30.640
galaxy shouldn't hold itself together. The

854
00:32:30.640 --> 00:32:33.440
galaxy should have dispersed over time. And

855
00:32:33.440 --> 00:32:35.640
for a long time, the best explanation people

856
00:32:35.640 --> 00:32:37.720
have had for this is that these are kind of

857
00:32:37.720 --> 00:32:40.000
dark matter galaxies, that they've got a

858
00:32:40.000 --> 00:32:42.439
massive dark matter agglomerated as a big

859
00:32:42.439 --> 00:32:45.080
dark matter halo, giving you enough mass

860
00:32:45.080 --> 00:32:47.560
there that we can't see to provide enough

861
00:32:47.560 --> 00:32:49.640
gravity to hold this very small number of

862
00:32:49.640 --> 00:32:51.960
stars together to keep them kind of whizzing

863
00:32:51.960 --> 00:32:54.240
around one another. And that kind of makes

864
00:32:54.240 --> 00:32:57.000
sense. We know that a lot of galaxies have

865
00:32:57.000 --> 00:32:58.640
big amounts of dark matter. In fact, all

866
00:32:58.640 --> 00:33:01.280
galaxies do. So you could almost have dark

867
00:33:01.280 --> 00:33:02.800
matter galaxies where you've got a clump of

868
00:33:02.800 --> 00:33:04.760
dark matter with very few stars. That kind of

869
00:33:04.760 --> 00:33:07.640
made sense. But the new story

870
00:33:08.200 --> 00:33:10.560
comes from improved observations of this

871
00:33:10.560 --> 00:33:12.440
galaxy, coupled with some computational

872
00:33:12.440 --> 00:33:14.960
numerical orbital modeling. And what they've

873
00:33:14.960 --> 00:33:16.960
found is that the stars near the middle of

874
00:33:16.960 --> 00:33:19.240
Segue one are, uh, going round the middle

875
00:33:19.240 --> 00:33:21.620
really, really quickly. Now, that allows us

876
00:33:21.620 --> 00:33:24.420
to take a measurement of the mass that is

877
00:33:24.420 --> 00:33:26.620
closer to the middle of the galaxy than those

878
00:33:26.620 --> 00:33:29.620
stars are. So anything feels

879
00:33:29.620 --> 00:33:31.500
gravity from the things closer to the middle

880
00:33:31.500 --> 00:33:34.180
than they do fundamentally. So what this

881
00:33:34.180 --> 00:33:36.820
means is by observing those stars that are in

882
00:33:36.820 --> 00:33:38.660
the middle of this galaxy, seeing them move,

883
00:33:38.980 --> 00:33:41.620
we can weigh the very innermost parts of that

884
00:33:41.620 --> 00:33:44.060
galaxy. And, um, what that tells us is that

885
00:33:44.060 --> 00:33:46.860
there is about 450,000 times

886
00:33:46.860 --> 00:33:48.540
more mass in the middle of that galaxy than

887
00:33:48.540 --> 00:33:51.120
the mass of our sun that we cannot see.

888
00:33:51.280 --> 00:33:51.760
Andrew Dunkley: Yeah.

889
00:33:51.760 --> 00:33:54.600
Jonti Horner: Which makes this a black hole, and it makes

890
00:33:54.600 --> 00:33:57.600
this a supermassive black hole, albeit a

891
00:33:57.600 --> 00:33:59.640
relatively low mass supermassive black hole

892
00:33:59.640 --> 00:34:01.240
compared to the one in the middle of Milky

893
00:34:01.240 --> 00:34:04.040
Way. Now, that in itself is not hugely

894
00:34:04.040 --> 00:34:06.640
unexpected. Pretty much all big galaxies have

895
00:34:06.640 --> 00:34:08.920
supermassive black holes, but we've not

896
00:34:08.920 --> 00:34:10.480
really seen them in teeny, tiny little

897
00:34:10.480 --> 00:34:13.440
galaxies like this before. Even

898
00:34:13.520 --> 00:34:16.200
more so, we've not really seen cases where

899
00:34:16.200 --> 00:34:18.749
there are galaxies whose black hole is, is

900
00:34:18.749 --> 00:34:20.429
more than 10 times the mass of all of the

901
00:34:20.429 --> 00:34:23.069
stars we can see in that galaxy. Feels like a

902
00:34:23.069 --> 00:34:25.229
really kind of weird imbalance. The black

903
00:34:25.229 --> 00:34:27.229
hole is more massive than the galaxy around

904
00:34:27.229 --> 00:34:29.389
it seems to suggest there would have been

905
00:34:29.389 --> 00:34:31.749
enough material for. But it's

906
00:34:32.149 --> 00:34:34.428
really weird from a few reasons, but really

907
00:34:34.428 --> 00:34:36.269
cool in the same way in that it's suggesting

908
00:34:36.269 --> 00:34:38.389
that this galaxy is not held together by dark

909
00:34:38.389 --> 00:34:40.469
matter, it's held together by this

910
00:34:40.469 --> 00:34:43.109
supermassive black hole at the middle. That

911
00:34:43.109 --> 00:34:45.710
maybe gives us an insight into how other

912
00:34:45.710 --> 00:34:48.630
ultra faint dwarf galaxies behave. This is

913
00:34:48.630 --> 00:34:50.550
probably not alone suggesting that there

914
00:34:50.550 --> 00:34:52.310
could be a lot more of these supermassive

915
00:34:52.310 --> 00:34:54.150
black holes out there in the cosmos than we

916
00:34:54.150 --> 00:34:56.990
thought. It also possibly is a bit of a

917
00:34:56.990 --> 00:34:59.110
hint that segue one was once a more massive

918
00:34:59.110 --> 00:35:01.990
galaxy. You know, if you think about the

919
00:35:01.990 --> 00:35:03.710
idea of the mass of this supermassive black

920
00:35:03.710 --> 00:35:05.950
hole and think, well, what kind of galaxy

921
00:35:05.950 --> 00:35:08.830
would normally expect to have a mass massive

922
00:35:08.830 --> 00:35:10.710
black hole like that in its center? How many

923
00:35:10.710 --> 00:35:13.310
stars should it have had? Maybe Segue one was

924
00:35:13.310 --> 00:35:15.950
like that in the past, but because it's so

925
00:35:15.950 --> 00:35:18.190
close to the Milky Way, it has been

926
00:35:18.190 --> 00:35:20.830
continually stripped and denuded of its stars

927
00:35:20.830 --> 00:35:23.310
from the outside inwards by our galaxy,

928
00:35:23.310 --> 00:35:25.190
essentially playing Pac man and gobbling it

929
00:35:25.190 --> 00:35:27.550
up going nom nom, nom, essentially, which is

930
00:35:27.550 --> 00:35:29.510
how galaxies grow. Galaxies grow through

931
00:35:29.510 --> 00:35:31.550
cannibalizing their neighbors. And we see

932
00:35:31.550 --> 00:35:33.150
that to an extent even with our largest

933
00:35:33.150 --> 00:35:35.150
satellite galaxies which have been disrupted

934
00:35:35.150 --> 00:35:37.110
and devoured a bit by the Milky Way and will

935
00:35:37.110 --> 00:35:39.710
eventually be gone. So there's a lot in this,

936
00:35:39.710 --> 00:35:42.550
it is a really fascinating story, albeit one,

937
00:35:42.550 --> 00:35:44.790
like I say, where I'm much further from being

938
00:35:44.790 --> 00:35:46.470
an expert than a lot of the other stuff that

939
00:35:46.470 --> 00:35:48.710
we talk about. Um, but you can find more

940
00:35:48.710 --> 00:35:50.990
about it online. And it is just a really cool

941
00:35:50.990 --> 00:35:53.230
little story, you know, it may well totally

942
00:35:53.230 --> 00:35:54.910
revolutionize our understanding of how the

943
00:35:54.910 --> 00:35:56.110
smallest galaxies work.

944
00:35:56.590 --> 00:35:59.590
Andrew Dunkley: Yes, indeed. Um, I, I, you kind of took the

945
00:35:59.590 --> 00:36:01.350
question out of my mouth, but I wasn't

946
00:36:01.350 --> 00:36:03.670
thinking of a neighboring galaxy stripping

947
00:36:03.670 --> 00:36:06.030
the, the stars away from segue. I was

948
00:36:06.030 --> 00:36:08.310
thinking the black hole might be devouring

949
00:36:08.310 --> 00:36:10.730
the stars within galaxy, but.

950
00:36:11.340 --> 00:36:13.170
Jonti Horner: Uh, you'd probably get a bit of that as well

951
00:36:13.170 --> 00:36:16.090
because the thing with the black hole is

952
00:36:16.090 --> 00:36:18.170
that uh, its gravitational pull is exactly

953
00:36:18.170 --> 00:36:20.850
the same as, ah, a group of objects of the

954
00:36:20.850 --> 00:36:23.130
same mass would have. Um, so it doesn't

955
00:36:23.130 --> 00:36:24.810
really pull things in any harder than the

956
00:36:24.810 --> 00:36:27.250
material that was there beforehand. But if

957
00:36:27.250 --> 00:36:28.970
you've got a neighboring galaxy like the

958
00:36:28.970 --> 00:36:31.970
Milky Way stirring up and um, numbing

959
00:36:31.970 --> 00:36:33.890
on this galaxy. It will also stir up the

960
00:36:33.890 --> 00:36:36.300
orbits of the stars in that galaxy, making

961
00:36:36.300 --> 00:36:38.340
some of them sufficiently elongated that they

962
00:36:38.340 --> 00:36:40.740
could fall onto that central black hole. So

963
00:36:40.740 --> 00:36:42.540
it's likely that the process of the Milky Way

964
00:36:42.540 --> 00:36:45.220
eating this galaxy has also led to the black

965
00:36:45.220 --> 00:36:47.340
hole in the middle of it getting a bit of a

966
00:36:47.340 --> 00:36:50.340
feed as well. A bit like the, um, white dwarf

967
00:36:50.340 --> 00:36:52.180
we were talking about last week, getting fed

968
00:36:52.180 --> 00:36:54.060
asteroids by the planets going around it.

969
00:36:54.060 --> 00:36:54.980
Same kind of idea.

970
00:36:55.140 --> 00:36:57.380
Andrew Dunkley: Yeah. It sounds like these stars, uh, in

971
00:36:57.380 --> 00:36:59.380
segue, are like a school of fish being

972
00:36:59.380 --> 00:37:02.140
attacked from all sides by predators, and

973
00:37:02.140 --> 00:37:05.000
eventually they'll just all be gone. Uh,

974
00:37:05.060 --> 00:37:07.340
yeah, you can read all about that@space.com

975
00:37:07.340 --> 00:37:10.040
or, or you can look at the paper that was

976
00:37:10.040 --> 00:37:12.880
published in astrophysical journal letters.

977
00:37:15.840 --> 00:37:18.080
3, 2, 1.

978
00:37:18.640 --> 00:37:19.920
Space nuts.

979
00:37:20.720 --> 00:37:22.920
I think we've got time for one more quick

980
00:37:22.920 --> 00:37:25.840
yarn, Jonti. And this is a story

981
00:37:25.920 --> 00:37:28.880
that I find fascinating, uh, and certainly

982
00:37:28.880 --> 00:37:31.280
relates to, um, the history of Earth in many

983
00:37:31.280 --> 00:37:33.920
ways. Uh, life after an

984
00:37:33.920 --> 00:37:36.320
asteroid impact. Now, a big

985
00:37:36.320 --> 00:37:39.270
asteroid conking the Earth, uh, can

986
00:37:39.270 --> 00:37:41.430
have cataclysmic effects, as

987
00:37:41.750 --> 00:37:44.630
we've seen in our history. And the,

988
00:37:44.700 --> 00:37:47.030
um, geology certainly backs that up.

989
00:37:47.590 --> 00:37:50.590
But, um, you know, fast forward a few

990
00:37:50.590 --> 00:37:53.350
gazillion years or whatever the number is,

991
00:37:53.420 --> 00:37:56.120
uh, and life does return. Um,

992
00:37:57.430 --> 00:37:59.070
they've been looking into this effect,

993
00:37:59.070 --> 00:37:59.750
haven't they?

994
00:38:00.310 --> 00:38:02.750
Jonti Horner: Now, this is some lovely research that's come

995
00:38:02.750 --> 00:38:05.670
out of Finland, where there's a beautiful

996
00:38:05.670 --> 00:38:07.270
impact crater. And I will apologize for

997
00:38:07.270 --> 00:38:08.950
anybody listening who speaks a beautiful

998
00:38:08.950 --> 00:38:11.070
Finnish language. Um, but there's a beautiful

999
00:38:11.070 --> 00:38:13.990
impact crater, uh, in Finland called Lake

1000
00:38:13.990 --> 00:38:16.990
Lapijavi, which is an impact

1001
00:38:16.990 --> 00:38:19.710
basin about 23 kilometers across that was

1002
00:38:19.710 --> 00:38:22.470
formed 78 million years ago. It's a

1003
00:38:22.470 --> 00:38:24.350
fairly hefty impact. It's the kind of thing

1004
00:38:24.350 --> 00:38:26.270
that would be a bit of a drama if you lived

1005
00:38:26.270 --> 00:38:28.510
in that part of the world, but not large

1006
00:38:28.510 --> 00:38:30.230
enough to cause a global mass extinction

1007
00:38:30.230 --> 00:38:32.150
event. So this is nothing like the one that

1008
00:38:32.150 --> 00:38:35.140
killed the dinosaurs 65, 66 million

1009
00:38:35.140 --> 00:38:37.660
years ago. This is a bit smaller, a bit more

1010
00:38:37.660 --> 00:38:40.620
run of the mill. Now, there's a vague rough

1011
00:38:40.620 --> 00:38:43.260
rule of thumb for impacts that if an impact

1012
00:38:43.260 --> 00:38:45.500
happens, the size of the crater is about 19

1013
00:38:45.580 --> 00:38:48.100
times the diameter of the impactor. So that

1014
00:38:48.100 --> 00:38:50.900
tells me that the rock that hit to create

1015
00:38:50.900 --> 00:38:53.580
this crater was probably a bit more than a

1016
00:38:53.580 --> 00:38:56.300
kilometer across. So it's fairly substantial.

1017
00:38:56.620 --> 00:38:59.060
That's the kind of impact that statisticians

1018
00:38:59.060 --> 00:39:00.900
would argue would kill about a quarter of the

1019
00:39:00.900 --> 00:39:03.100
world's human population. So not an

1020
00:39:03.100 --> 00:39:05.140
extinction event, but a very bad day.

1021
00:39:06.100 --> 00:39:09.060
The Team that have looked into this were

1022
00:39:09.060 --> 00:39:11.900
really interested in how quickly

1023
00:39:11.900 --> 00:39:14.700
life can reestablish itself in the

1024
00:39:14.700 --> 00:39:16.860
rocks left behind from an impact. Because you

1025
00:39:16.860 --> 00:39:19.740
have an impact happen, it superheats

1026
00:39:19.740 --> 00:39:21.460
and sterilize the rocks. This would have

1027
00:39:21.620 --> 00:39:23.980
sterilized the rocks in the impact site by

1028
00:39:23.980 --> 00:39:25.940
heating them to more than 2,000 degrees C.

1029
00:39:25.940 --> 00:39:28.420
That's 3,600 Fahrenheit for the American.

1030
00:39:29.600 --> 00:39:31.440
Enough to kind of really sterilize the place

1031
00:39:31.440 --> 00:39:34.160
it hit. It would have also, though, caused

1032
00:39:34.480 --> 00:39:36.360
huge temperature gradients. It would have

1033
00:39:36.360 --> 00:39:38.480
shattered the rocks, and it would have driven

1034
00:39:38.480 --> 00:39:40.800
some interesting chemistry. So that means

1035
00:39:40.800 --> 00:39:43.000
that, uh, once the clouds clear and there's

1036
00:39:43.000 --> 00:39:45.800
time for things to settle down, you have a

1037
00:39:45.800 --> 00:39:48.600
site here that is similar to the kind of

1038
00:39:48.600 --> 00:39:50.680
conditions at, uh, locations where people

1039
00:39:50.680 --> 00:39:52.320
think the first life on Earth may have got

1040
00:39:52.320 --> 00:39:54.480
started. So there's some interesting

1041
00:39:55.180 --> 00:39:58.100
what happened after. So to study that,

1042
00:39:58.100 --> 00:40:01.030
this team have gone to the, um,

1043
00:40:01.180 --> 00:40:03.740
store of drill cores that they can get to in

1044
00:40:03.740 --> 00:40:06.460
Finland, where there are, uh, results,

1045
00:40:06.860 --> 00:40:08.820
resources left behind from drilling

1046
00:40:08.820 --> 00:40:11.220
expeditions that dug into this crater lake

1047
00:40:11.220 --> 00:40:14.140
back in the 1980s, 1990s. Now this is a

1048
00:40:14.140 --> 00:40:15.820
really good example, incidentally, of how

1049
00:40:16.380 --> 00:40:19.300
legacy materials continue to have

1050
00:40:19.300 --> 00:40:20.940
worth. And we've talked about that with the

1051
00:40:21.020 --> 00:40:22.780
rocks from the Apollo missions, where they

1052
00:40:22.780 --> 00:40:24.790
put a lot of them and preserve them for

1053
00:40:24.790 --> 00:40:27.590
future use, because our technology improves

1054
00:40:27.590 --> 00:40:29.270
all the time. So we can go back and look at

1055
00:40:29.270 --> 00:40:30.950
things that were collected in the past and

1056
00:40:30.950 --> 00:40:33.790
get new insights. So the team

1057
00:40:33.790 --> 00:40:35.870
went back to these rocks that, uh, were dug

1058
00:40:35.870 --> 00:40:38.830
up back in the 80s and 90s from drill

1059
00:40:38.830 --> 00:40:41.110
cores that dug down all the way into this

1060
00:40:41.110 --> 00:40:43.430
crater lake, into the floor of it. And they

1061
00:40:43.430 --> 00:40:45.910
got 33 different drill core samples from

1062
00:40:45.910 --> 00:40:48.070
different locations, looked at them

1063
00:40:48.070 --> 00:40:49.830
essentially with a microscope and a pair of

1064
00:40:49.830 --> 00:40:52.710
tweezers, and, um, plucked out a number of

1065
00:40:52.710 --> 00:40:55.680
crystals of calcite and. And

1066
00:40:55.680 --> 00:40:56.920
what was the other rock? There were a couple

1067
00:40:56.920 --> 00:40:59.240
of things, calcite and pyrite, these rocks.

1068
00:40:59.560 --> 00:41:01.760
And they use these for chemical analyses. And

1069
00:41:01.760 --> 00:41:03.760
what they were interested in doing was

1070
00:41:03.760 --> 00:41:06.080
getting a chronology of what happened in the

1071
00:41:06.080 --> 00:41:09.080
years after this crater was formed.

1072
00:41:09.480 --> 00:41:11.680
Now, similar work has been done before for

1073
00:41:11.680 --> 00:41:13.800
the Rhys Crater in Germany and the Horton

1074
00:41:13.800 --> 00:41:16.760
Crater in Canada, which suggested for those

1075
00:41:16.760 --> 00:41:19.120
craters, the material under and around the

1076
00:41:19.120 --> 00:41:21.850
crater cooled fairly quickly in geological

1077
00:41:21.850 --> 00:41:24.290
times. For those craters, it cooled to about

1078
00:41:24.290 --> 00:41:26.890
50 degrees C within a quarter of a million

1079
00:41:26.890 --> 00:41:28.810
years. For the Reese Crater and for the

1080
00:41:28.810 --> 00:41:30.930
Horton Crater in Canada for about 50,000

1081
00:41:30.930 --> 00:41:32.850
years. So that cooled down fairly quickly.

1082
00:41:33.170 --> 00:41:35.970
But this Finnish team, looking at these

1083
00:41:35.970 --> 00:41:38.850
crystals from, um, this beautiful Lake

1084
00:41:38.850 --> 00:41:41.810
Lapiavi, found that it took about 4 million

1085
00:41:41.890 --> 00:41:44.370
years for the rocks to cool to 50 degrees C,

1086
00:41:44.370 --> 00:41:47.090
which to me is astonishingly long time.

1087
00:41:47.090 --> 00:41:49.530
That's very slow cool. And they're saying, we

1088
00:41:49.530 --> 00:41:51.370
don't really understand why it took so long,

1089
00:41:51.370 --> 00:41:52.680
but it's probably to do with the kind of

1090
00:41:52.830 --> 00:41:54.150
rocks that were around and the kind of

1091
00:41:54.150 --> 00:41:57.150
insulating properties. But what they did

1092
00:41:57.150 --> 00:41:59.190
then was that they looked at the chemistry of

1093
00:41:59.190 --> 00:42:01.390
these samples. They used mass spectrometry

1094
00:42:01.950 --> 00:42:04.270
to look at basically the different isotopes

1095
00:42:04.270 --> 00:42:07.150
of oxygen, carbon and sulfur in the rock.

1096
00:42:07.470 --> 00:42:09.550
And they were doing that because microbes

1097
00:42:09.550 --> 00:42:12.550
tend to process oxygen, carbon and sulfur and

1098
00:42:12.550 --> 00:42:14.550
preferentially use one isotope over the

1099
00:42:14.550 --> 00:42:16.710
other. So they can put this very distinctive

1100
00:42:16.710 --> 00:42:19.230
chemical signature in to what's left behind.

1101
00:42:19.890 --> 00:42:22.650
So the team were very much looking for, in

1102
00:42:22.650 --> 00:42:25.410
addition to this cooling data, uh, the point

1103
00:42:25.410 --> 00:42:27.170
at which you started to get the fingerprints

1104
00:42:27.170 --> 00:42:29.730
of microbial life once again. And what they

1105
00:42:29.730 --> 00:42:31.930
found was that, uh, 4 million year point when

1106
00:42:31.930 --> 00:42:34.410
it cooled to about 50 degrees C. That was

1107
00:42:34.410 --> 00:42:36.730
when you started to get life there again. And

1108
00:42:36.730 --> 00:42:38.450
you started to get life that was turning

1109
00:42:38.450 --> 00:42:41.170
sulfates into sulfides. I think that was

1110
00:42:41.410 --> 00:42:43.170
the chemical terminology there.

1111
00:42:44.210 --> 00:42:47.100
So there were processing materials and

1112
00:42:47.260 --> 00:42:50.180
life had recolonized effectively, yes,

1113
00:42:50.180 --> 00:42:53.100
sulfate into sulfide. That was after 4

1114
00:42:53.100 --> 00:42:55.340
million years. 10 million years after that,

1115
00:42:55.340 --> 00:42:57.300
the temperature dropped to about 30 degrees

1116
00:42:57.300 --> 00:42:59.740
C. And you got the kind of microbes that make

1117
00:42:59.740 --> 00:43:02.540
methane recolonize there. So you've now got

1118
00:43:02.540 --> 00:43:04.780
this really nice chronological timeline of

1119
00:43:04.780 --> 00:43:07.250
the recolonization of this site. And, um,

1120
00:43:07.580 --> 00:43:09.700
they talk about this being a surprisingly

1121
00:43:09.700 --> 00:43:12.060
quick time. To me, this is surprisingly slow

1122
00:43:12.790 --> 00:43:14.750
given how much life we've got around on the

1123
00:43:14.750 --> 00:43:17.550
Earth. So obviously they are more expert than

1124
00:43:17.550 --> 00:43:20.150
I am, and I'm happy to take their

1125
00:43:20.470 --> 00:43:21.830
word that this is a very quick

1126
00:43:21.830 --> 00:43:24.630
recolonisation. But to me, it's interesting

1127
00:43:24.630 --> 00:43:26.830
that it took it so long to cool down and for

1128
00:43:26.830 --> 00:43:29.470
life to get going again afterwards. That's

1129
00:43:29.470 --> 00:43:30.990
maybe telling us something about the kind of

1130
00:43:30.990 --> 00:43:33.110
rocks the impact happened in. I don't know

1131
00:43:33.110 --> 00:43:34.590
whether it could also be telling us something

1132
00:43:34.590 --> 00:43:36.910
about the underlying geology of the area at

1133
00:43:36.910 --> 00:43:39.480
the time. I'm just not expert enough. But

1134
00:43:39.480 --> 00:43:42.320
it's a really fascinating study and it's a

1135
00:43:42.320 --> 00:43:45.320
really good example of how the science of

1136
00:43:45.320 --> 00:43:47.200
astrobiology, which is the science of the

1137
00:43:47.200 --> 00:43:49.400
search for life elsewhere and the science of

1138
00:43:49.400 --> 00:43:51.120
the question of how we learn in the universe

1139
00:43:51.120 --> 00:43:53.160
and of how did life get started on Earth, all

1140
00:43:53.160 --> 00:43:56.040
those really thorny questions. That's not a

1141
00:43:56.040 --> 00:43:57.680
science that can be answered by just one

1142
00:43:57.680 --> 00:44:00.040
discipline within astronomy. It's a really

1143
00:44:00.040 --> 00:44:02.240
multidisciplinary area where you need people

1144
00:44:02.240 --> 00:44:04.960
from an incredibly wide and diverse

1145
00:44:06.410 --> 00:44:08.330
variety of areas in the sciences to come

1146
00:44:08.330 --> 00:44:10.450
together because no one area has the

1147
00:44:10.450 --> 00:44:11.890
knowledge and the skill set and the

1148
00:44:11.890 --> 00:44:14.370
methodology and the samples to provide an

1149
00:44:14.370 --> 00:44:17.130
answer on their own. It's why conference

1150
00:44:17.130 --> 00:44:19.370
on this kind of topic are so, uh, fascinating

1151
00:44:19.370 --> 00:44:21.489
to me because you go to talks from biology

1152
00:44:21.489 --> 00:44:24.170
and chemistry and geophysics rather than just

1153
00:44:24.170 --> 00:44:26.210
a lot of talks from astronomers on astronomy

1154
00:44:26.210 --> 00:44:29.090
things. And um, this is the kind of study no

1155
00:44:29.090 --> 00:44:30.930
one I work with directly would have been able

1156
00:44:30.930 --> 00:44:33.260
to do. But these people have been able to

1157
00:44:33.260 --> 00:44:35.540
drill down, do this awesome work and get some

1158
00:44:35.540 --> 00:44:38.340
really fascinating results. So I'm looking

1159
00:44:38.340 --> 00:44:40.340
forward to hearing more about this. And to be

1160
00:44:40.340 --> 00:44:41.980
honest, this would almost set the scene for

1161
00:44:41.980 --> 00:44:43.340
groups elsewhere in the world to start

1162
00:44:43.340 --> 00:44:45.220
drilling down into other creators to see if

1163
00:44:45.220 --> 00:44:47.900
we can get a feel for. Is this unusual? Is

1164
00:44:47.900 --> 00:44:50.100
this common? And, um, the other two unusual,

1165
00:44:50.660 --> 00:44:52.020
essentially, what's going on?

1166
00:44:52.100 --> 00:44:54.860
Andrew Dunkley: Yeah, yeah. And uh, as you said, it's just

1167
00:44:54.860 --> 00:44:57.300
great that historical studies,

1168
00:44:57.730 --> 00:45:00.460
uh, being dredged back up and

1169
00:45:00.940 --> 00:45:03.400
reused with modern, um,

1170
00:45:03.580 --> 00:45:06.020
techniques and technology to, to uh, find out

1171
00:45:06.020 --> 00:45:08.830
more. I think that's amazing. And uh,

1172
00:45:08.830 --> 00:45:11.260
keeping rocks for future reference,

1173
00:45:11.790 --> 00:45:14.740
um, when we can do things even

1174
00:45:14.740 --> 00:45:17.660
better, um, may reveal more answers.

1175
00:45:17.660 --> 00:45:19.820
So, ah, that's. That. That in itself is a

1176
00:45:19.820 --> 00:45:22.060
terrific part of that particular story.

1177
00:45:22.860 --> 00:45:25.020
Uh, and I was just wondering about the Tim

1178
00:45:25.020 --> 00:45:28.000
Horton, the uh, Horton crater. It couldn't

1179
00:45:28.000 --> 00:45:30.080
be named after Tim Horton the famous ice

1180
00:45:30.080 --> 00:45:31.200
hockey player, could it?

1181
00:45:32.320 --> 00:45:34.200
Jonti Horner: Ice hockey player. Are there not some famous

1182
00:45:34.200 --> 00:45:37.040
pancakes? Uh, Tim Hortons.

1183
00:45:37.200 --> 00:45:37.520
Andrew Dunkley: Yeah.

1184
00:45:37.520 --> 00:45:38.600
Jonti Horner: Well, that's. Yeah.

1185
00:45:38.600 --> 00:45:40.600
Andrew Dunkley: I mean you can't go to Canada and not go to

1186
00:45:40.600 --> 00:45:41.360
Tim Hortons.

1187
00:45:41.760 --> 00:45:43.399
Jonti Horner: Um, I think the spelling may be different.

1188
00:45:43.399 --> 00:45:46.360
This is Horton. H, A, U, G, H. Right.

1189
00:45:46.360 --> 00:45:48.000
So probably a distant relative.

1190
00:45:48.400 --> 00:45:51.200
Andrew Dunkley: You never know. Uh, okay, that brings us to

1191
00:45:51.200 --> 00:45:52.720
the end. Johnny, thank you so much.

1192
00:45:53.370 --> 00:45:54.810
Jonti Horner: Matt, it's an absolute pleasure. Thank you.

1193
00:45:55.450 --> 00:45:57.370
Andrew Dunkley: Good, uh, to see you. Jonti Horner, professor

1194
00:45:57.370 --> 00:45:59.890
of Astrophysics at the University of Southern

1195
00:45:59.890 --> 00:46:02.050
Queensland, joining us. Don't forget to visit

1196
00:46:02.050 --> 00:46:05.010
us online, uh, at our website and check

1197
00:46:05.010 --> 00:46:06.890
everything out. You can, uh, send us

1198
00:46:06.890 --> 00:46:09.370
questions via the uh, website as well and

1199
00:46:09.370 --> 00:46:11.970
check out the shop and maybe, uh, sign up to

1200
00:46:11.970 --> 00:46:14.450
become a supporter. Whatever floats your

1201
00:46:14.450 --> 00:46:16.221
boat. Uh, it's@Space

1202
00:46:16.488 --> 00:46:19.210
Nutspodcast.com uh, and

1203
00:46:19.210 --> 00:46:21.250
thanks to Huw in the studio who couldn't be

1204
00:46:21.250 --> 00:46:22.930
with us today. I don't know if you know this

1205
00:46:22.930 --> 00:46:25.550
about Huw, but he's a bit old. He doesn't use

1206
00:46:25.550 --> 00:46:27.550
satnav, but he heard about this great new

1207
00:46:27.550 --> 00:46:29.430
book and he's gone to a bookshop to try and

1208
00:46:29.430 --> 00:46:32.350
get it today. Uh, it's, um. It's the

1209
00:46:32.350 --> 00:46:33.910
Three Eye Atlas book.

1210
00:46:35.120 --> 00:46:38.030
Um, I'm not going to tell him. And from me,

1211
00:46:38.030 --> 00:46:39.430
Andrew Dunkley, thanks for your company.

1212
00:46:39.430 --> 00:46:41.110
We'll see you on the next episode of Space

1213
00:46:41.110 --> 00:46:43.830
Nuts. Bye. Bye. You'll be

1214
00:46:43.830 --> 00:46:45.390
listening to the Space Nuts.

1215
00:46:45.390 --> 00:46:48.390
Jonti Horner: Podcast, available at

1216
00:46:48.390 --> 00:46:50.310
Apple Podcasts, Spotify,

1217
00:46:50.720 --> 00:46:53.680
iHeartRadio or your favorite podcast player.

1218
00:46:53.760 --> 00:46:56.670
You can also stream on demand@bytes.com M.

1219
00:46:57.040 --> 00:46:59.120
Andrew Dunkley: This has been another quality podcast

1220
00:46:59.120 --> 00:47:01.200
production from bytes.com.