Comets, Meteors & Celestial Wonders : A Cosmic Special

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Andrew Dunkley: Hello again. Thank you for joining us on

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another episode of Space Nuts. My name is

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Andrew Dunkley, your host. It's great to have

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your company. As I mentioned last episode,

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Fred is away for a few weeks or

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a couple of years. Now it's a few weeks. And,

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uh, in his stead, we'll be joined by

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Professor Jonti Horner, who you know and love

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because he's been with us before and uh, he's

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a part of the team. So, uh, we will be

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doing over the next, uh, several episodes,

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um, taking a different approach. Uh, we're

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going to, to uh, focus on specific topics

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within each of the episodes. Uh,

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we could call them specials if you like. And

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today our focus will be on

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comets and meteors. Stick around.

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We're doing all of that on this episode of

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space nuts. 15 seconds. Guidance

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is internal. 10, 9,

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ignition sequence start.

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Jonti Horner: 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.

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Jonti Horner: Space nuts.

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Andrew Dunkley: Astronauts. Feels good and

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it's great to have him back. Professor Jonti

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Horner, professor of Astrophysics at the

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University of Southern Queensland. Jonti,

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hello.

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Jonti Horner: Ah, uh, hey, how are you going? Good.

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Andrew Dunkley: Great to see you again.

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Jonti Horner: Well, it's good to be back. It's something

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nice to keep me entertained while I'm having

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a little bit of a restful couple of weeks.

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I'm, you know, I've got a bit of leave, so

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I'm recovering from a minor surgery and

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therefore I can give my entire forecast to.

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Talking about fun things rather than doing

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admin effectively means I get to see a little

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bit of the life Fred gets to live.

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Andrew Dunkley: Yeah, maybe. Yes. Although he doesn't seem to

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slow down much. Um, in fact, I think

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the worst thing you can do when you retire is

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slow down because the brain matter decides to

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give up the ghost and that's when it's all

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over. Red Rover. But, uh, no, he, he's going,

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going great guns.

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And um, you didn't mention that you're having

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a little bit of a recuperation. Are

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you in a position to talk about that or

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too embarrassing?

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Jonti Horner: Well, it's one of those things that when I,

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when I first had this pointed out, I a bit

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embarrassed about it, but I don't think as

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bloats we ever talk about health that much

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until it's worth muscling past a little bit

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of embarrassment. So I'm in my late 40s and

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I went to the doctor about a year ago

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because, had a little bit of bleeding when I

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was sitting down and stuff like this and

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nothing dramatic. Um, But I found out two

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things. Firstly, in Australia, and I don't

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know about the rest of the world, you should

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look this up. But when you're in your 40s,

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the Medicare system here affords the

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opportunity for you to get health checks.

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Yep. Which is brilliant. So you basically get

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what in the UK they'd call an MOT for a car.

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You get everything run over and you get your

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blood pressure done and your heart rate done

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and everything else. And then you go back

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every three months and do it again and again

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and again, and it's basically you're at an

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edge where things start to break. Let's get

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on top of it early so that you can enjoy the

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rest of your life in peace, effectively. I

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think it's a really good idea and I suspect

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from a government point of view, makes a lot

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of sense, because if you find things easy

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earlier, they're easier and quicker and

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cheaper to solve. Um, what it turned out from

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that was I spent about two months going back

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and forth with a doctor who thought I had one

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thing wrong, which is not what it was. And

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then I got. Got sent to this specialist who

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said, you've got something called a fistula

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down near your backside, which, not life

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threatening, not the end of the world, not

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doomed, but it's uncomfortable. Um, and, you

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know, it's been slightly embarrassing in that

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I've had to learn more about sanitary pads

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and, you know, um, you would have expected,

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you know, which the women in the audience are

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going, about bloody time a man learned about

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this. Um, but it's a weird

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one because it's not life threatening. It's

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nothing of a problem, something 10 or 20% of

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guys apparently get them, but they contain

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multiple surgeries to fix. And when I went in

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for the first surgery in January, there was

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another guy there who was on surgery number

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seven.

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Andrew Dunkley: Wow.

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Jonti Horner: Which he had deep and joyous, um, kind of day

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surgery. But you get a full general and you

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go under and Dr. Does snippy, snippy things

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and you get a couple of weeks off work, which

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is where I am now. So I've just had surgery

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number two and the doctor is hopeful,

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confident, whatever, that surgery number

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three will be the final fix. And it's one of

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these weird things because people say, what's

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wrong with you? And if it's a sore arm, you

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just say, I've hurt my arm, or you've broken

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your arm or something. Or in Australia, a

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really common one, a melanoma. People have

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been in the sun too much going into hospital.

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What do you get, I've, ah, got a melanoma

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taken off. But as soon as it's anywhere

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between about your belly button and your

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knee, people are bashful about talking about

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it. And I first few months I was mortified

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and like, wouldn't talk about it. And

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realization is that if you don't talk about

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it, people don't get checked. And we as

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men are terrible for that. And so, yeah,

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worth talking about. I'm a bit embarrassed

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about it, but I shouldn't be. And it's good,

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it's going to tune up. And it means that in

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40 years time I'll still be up and kicking

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and having a lot of fun rather than in

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discomfort and grumbling about a problem I

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could have got fixed.

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Andrew Dunkley: Yeah, yeah. And, um, I think you're

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right. I think men do tend to keep things to

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themselves. Uh, a lot of them go into denial

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or they just think, well, no, that won't

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happen to me, so no problem. But,

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uh, when I was diagnosed with prostate

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cancer, it was like a bolt from the blue. And

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I didn't, I never expected

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to get it because there was next to no

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history of it in my family. So, um, that was

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a bit of a shock. And this is. How long is

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it now? Three years. Three years. And I'm

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still working my way through it. So,

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um, but the latest scans are all good.

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So fingers crossed that we've, you know,

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reached a good position. But, um, it's

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just an ongoing thing in your life. You just

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got to get used to it. But you. My

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advice to men is go and get checked. If

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you're over 50, go and get a

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prostate exam, go and get your PSA tests

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done. Because if you don't and

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then they find it, it might be too far along.

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Um, and then the treatment becomes more

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dramatic. So anyway, um, it's a good

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thing to bring up.

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Jonti Horner: It is. And it goes for the mental health

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stuff as well. I have a former partner of

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mine, kind of 20 years ago, who was very

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severely bipolar, had a lot of challenges

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and she was continually frustrated by

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people's responses to that in public, in that

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it's a hidden illness there. She's getting

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treatment. But what she always said is, it's

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really frustrating. If I, if I had a broken

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leg or I had an injury to my arm and people

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could see it, they'd be supportive. But with

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mental health, she got a hell of a lot of,

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I'll just get over it, uh, or toughen up or.

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Andrew Dunkley: Yep. Yeah.

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Jonti Horner: And, yeah, and, you know, she was female,

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so she's more likely to go to the doctor and

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talk about it. Statistically, men with mental

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health challenges tend to avoid that even

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more than they'll go to the doctor with

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physical health challenges. And it's

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something I'd like to change. I come from a

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working class background in Yorkshire where

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men m. Don't talk about anything. You know,

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you're meant to be stoic and the only, the

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only expression of emotion you're allowed is

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rage or a single manly tear. You know, it's,

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it's really creative the way we're

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conditioned. And even though I'm, you know, I

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went to uni, I've had a life, I've grown up.

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All this stuff still there at the back of

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your head and you've got to fight against it

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because the instinct is, ah, there's nothing

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wrong. I won't bother, you know. Yeah.

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Andrew Dunkley: And, um, yeah, you see it way too often.

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Um, I know it's a departure from what this

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podcast is all about, but I,

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when given the opportunity, will

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openly, um, say to men, um, you know,

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don't, don't hesitate to go to the

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doctor. Not, not when you think something's

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wrong. Just preemptively go and get. Once a

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year, go and get checked and make sure

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everything's where it's supposed to be or

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whatever. Um, we do it, do it for

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Jonti Horner: our cars, we do it for our pets.

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Andrew Dunkley: Yeah.

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Jonti Horner: Do it for yourself as well.

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Andrew Dunkley: Yeah, exactly.

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Jonti Horner: And yeah, I think it's probably a record for

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the quickest we've ever got off topic. And

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possibly we shouldn't have a trigger warning

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at the front of it and all the rest of it,

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but no good way to start even though it is

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off topic.

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Andrew Dunkley: It's okay, we'll get on to topic right now

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because, uh, uh, as I mentioned, these,

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these, uh, next, uh, several, uh,

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episodes are going to be dedicated to

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singular topics each. And today

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it's, uh, well, related topics. Comets and

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meteors. Uh, this is a, this is pet

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topic of yours, I imagine.

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Jonti Horner: It is. I, I've always been a bit more into

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the nearby stuff than the more distant stuff.

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So it always tickles me a little bit that

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when questions come in when I'm on the show,

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we get all the Big bang and cosmology ones.

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And I'm sure if you've got uh, someone like

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the wonderful Tamara Davis on to talk

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cosmology, she get all the planets questions.

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It's always the way it goes. Yeah, but comets

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and meteors are a big part of what hooked me

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into astronomy as A kid. And, um, my thinking

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behind this is that we're recording in

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advance. You know, um, obviously Fred

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is away, but you've got recordings with Fred

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already. And so the news that we would

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normally talk about hasn't happened yet. So

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I, I have many talents, but seeing into the

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future isn't one of them to that degree. And

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so I thought it better to have a discussion

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about the general stuff in a bit more depth

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than go into particular news topics. And

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it's. It could almost be a bit of an

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explainer, a bit of the background, and

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hopefully at least gives my insight into why

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a given topic's interesting, but also what

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people can look out for in the future and how

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they can get more into and more out

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of that particular topic, if that makes

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sense. Yeah, Um, a little bit different, I

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understand. For some listeners it might be a

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bit of an abrupt departure and a change. So

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it'll be interesting to see what feedback you

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get. But hopefully people like it as a little

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bit of a change in a breath of fresh air. And

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if they don't, well, there's only a couple of

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episodes and Fred's back anyway, so you'll

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have to deal with it and we'll see.

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Andrew Dunkley: I'm sure it'll be fine.

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Uh, comets and meteors are a very popular,

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uh, topic. So, um, uh, where do we

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start? Maybe, maybe look at a bit of the

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history of this.

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Jonti Horner: Yeah, I think that is always a good place.

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It sets the context of where we are now. And,

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um, for both comets and meteors, there's a

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kind of global connection societally that

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really predates by a long, long way

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our scientific knowledge. Essentially the

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modern scientific viewpoint and the

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scientific method. All cultures across the

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world, from our wonderful, uh, traditional

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owners here in Australia to the peoples of

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every continent and every land, um, both

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current and past, historically had a

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really firm connection to the night sky. They

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knew the night sky better than most people

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these days do because it wasn't light

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pollution, there weren't TVs and Xboxes.

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So the sky was something people much more

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exposed to. A lot of cultures have

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this kind of idea of as above, so below, as

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below, so above. So they were very firmly of

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the idea that major events on the Earth were

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reflected in the sky. And, uh, major events

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in the sky would have their counterparts on

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the Earth. And that's where astrology

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was born. And for a long time, astrology and

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astronomy were one and the same. You know,

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people doing astronomy studies were doing it

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because they wanted to understand the events

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that would influence what's on the Earth. And

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there are good examples of this in terms of

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the nominally fixed stars, uh, things like

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the ancient Egyptians using the rising of

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Sirius in the dawn sky after it disappeared

297
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in the evenings as a predictor of the

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flooding of the Nile, for example, the use of

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the night sky as a calendar, lots of stuff

300
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like that. But because people are so aware of

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the night sky, anything that was ephemeral,

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anything that was transitory, that appeared

303
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and then disappeared, that was unexpected,

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was often seen as kind of a portent or an

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omen, something that was an

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indication either of major change and

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upheaval currently happening or one soon to

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come. And really bright comets and, um,

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spectacular meteor showers kind of often fill

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this role. And you can go back through

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ancient history where we have the records and

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see good examples of this. I've got, in one

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of my talks, talks about a

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00:11:41.530 --> 00:11:43.770
guy called, uh, Mithridates,

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um, Jupiter 6, I think his name was. He was

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one of the great enemies of the Roman Empire.

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And there are quotes ascribed to him saying

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things like, um, even the heavens predicted

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the greatness of this man. For in the year in

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which he was born and the year in which he

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came to reign, a comet shone through Both

322
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periods for 70 days as

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bright as the sun. Um, each rising and

324
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setting took four hours each. And that's kind

325
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of hyperbolic, but it gives this idea that

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people saw something in the sky that was

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unusual and tied it to events on Earth.

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Another good example would be the alleged

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comet called Caesar's Comet in 44 BC

330
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43-43, which

331
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is recorded in Roman writings from

332
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a century or two later, talking

333
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about after the death of Caesar, a comet

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blazed in the sky for seven days that was

335
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spectacularly bright, then disappeared and

336
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was never seen again. Now, that comet is a

337
00:12:38.960 --> 00:12:40.600
really good example of the challenge people

338
00:12:40.600 --> 00:12:42.960
have with historical records,

339
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because on the one hand you've got these

340
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clear reports from the Roman Empire, none of

341
00:12:48.160 --> 00:12:50.240
them at the time, though, all of them a bit

342
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later on. But that comet is not recorded from

343
00:12:52.920 --> 00:12:54.360
anywhere else on the planet. And there were

344
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cultures around the globe leaving records

345
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like ancient China and ancient Korea, who

346
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would have seen it. So was that comet real,

347
00:13:02.000 --> 00:13:04.520
or was it a case of after the event, people

348
00:13:04.520 --> 00:13:07.520
inventing a night sky phenomena to tie

349
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with the soul of the emperor rising to

350
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heaven? It's one of the challenges people in

351
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the kind of cultural astronomy space face, I

352
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think, in terms of disentangling the

353
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narrative from the events that prompted it,

354
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if that kind of makes sense. Yeah, but what's

355
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certainly true is, uh, for as long as we've

356
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looked at the sky, really bright comets and,

357
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um, unusually powerful meteor showers

358
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were things that people took note of. And

359
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recently there was a lot of media, media

360
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coverage of the April Lyrid meteor shower,

361
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which is not one of the strongest of the

362
00:13:37.560 --> 00:13:40.080
year, but one of the reasonable, moderate

363
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ones. It's kind of one that if you're a

364
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meteor enthusiast, you'll go out and watch,

365
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but isn't worth going out if you're not that

366
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interested because there's too few.

367
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I had to grumble about some of the coverage

368
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here in Australia because it's not a great

369
00:13:51.020 --> 00:13:53.620
shower for us. But that meteor shower

370
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was recognized by the traditional owners in

371
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Australia. And there are stories from

372
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Victoria, from, I think, the Burong people,

373
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although I stand to be corrected on that,

374
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that associate this meteor shower with the

375
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Mallee Fowl, one of the big ground nesting

376
00:14:05.820 --> 00:14:08.220
birds in Australia, which nests around that

377
00:14:08.220 --> 00:14:10.940
time of year. The meteors seen shrieking from

378
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low in the northern sky were viewed as being

379
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the dust being kicked up by the nesting bird

380
00:14:15.870 --> 00:14:17.630
celestially. So they recorded this meteor

381
00:14:17.630 --> 00:14:19.030
shower, even though it isn't a particularly

382
00:14:19.030 --> 00:14:21.390
strong one. But our oldest

383
00:14:22.270 --> 00:14:24.710
written record of any meteor shower is the

384
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April Lyrids, and it's dated back to

385
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something like 687 BCE, when

386
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stars fell like rain, when there was a major

387
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storm from the Lyrids, and it was significant

388
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enough for people to record. So comets

389
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and meteors, way before the modern

390
00:14:39.190 --> 00:14:41.920
scientific understanding of them really had

391
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this important cultural role,

392
00:14:44.880 --> 00:14:46.720
um, even in the Battle of Hastings. If you

393
00:14:46.720 --> 00:14:48.840
ever go to see the Bayer Tapestry, this

394
00:14:48.840 --> 00:14:50.960
wonderful woven record of the Battle of

395
00:14:50.960 --> 00:14:52.600
Hastings and the invasion of William the

396
00:14:52.600 --> 00:14:55.000
Conqueror, Comet Hallie features prominently

397
00:14:55.000 --> 00:14:57.080
on that, because in 1066,

398
00:14:58.040 --> 00:15:00.160
you had the second best apparition of Comet

399
00:15:00.160 --> 00:15:02.320
Hallie in the last 2,000 years. Arguably, it

400
00:15:02.320 --> 00:15:04.400
was very spectacular in the sky at the time

401
00:15:04.400 --> 00:15:06.480
the conquest was going on. And, um, that was

402
00:15:06.480 --> 00:15:09.060
considered important enough to be recorded in

403
00:15:09.060 --> 00:15:12.020
the tapestry that was woven at the time. You

404
00:15:12.020 --> 00:15:14.980
know, it's amazing that you've got this panel

405
00:15:14.980 --> 00:15:16.660
where there's all the peasants pointing up at

406
00:15:16.660 --> 00:15:18.780
this thing in the sky and somebody whispering

407
00:15:18.780 --> 00:15:20.820
in King Harold's ear about the comet that's

408
00:15:20.820 --> 00:15:23.620
visible. So, yeah, don't know whether the

409
00:15:23.620 --> 00:15:25.500
invading forces took it as a good sign or a

410
00:15:25.500 --> 00:15:26.940
bad sign, but they thought it was important

411
00:15:27.020 --> 00:15:29.860
enough to include. So that in

412
00:15:29.860 --> 00:15:31.700
itself is fairly breathtaking. And so when we

413
00:15:31.700 --> 00:15:33.620
see these objects, it's a lovely connection

414
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to thousands of years of our heritage of

415
00:15:36.710 --> 00:15:39.710
people looking at the night sky in wonder I

416
00:15:39.710 --> 00:15:42.390
think the first step we had really,

417
00:15:43.430 --> 00:15:46.070
in moving from cultural

418
00:15:46.470 --> 00:15:48.630
cometary astronomy to modern scientific

419
00:15:48.630 --> 00:15:51.150
astronomy, in a way, came with the Great

420
00:15:51.150 --> 00:15:54.150
Comet of 1577, which was

421
00:15:54.390 --> 00:15:56.710
another of the really amazing, spectacular,

422
00:15:56.710 --> 00:15:59.390
bright comets that was widely

423
00:15:59.390 --> 00:16:02.100
observed, hence why it's a great comet.

424
00:16:02.180 --> 00:16:04.460
But it was observed by the great astronomer

425
00:16:04.460 --> 00:16:07.180
Tycho Brahe. And, um, I'm sure Brahe is

426
00:16:07.180 --> 00:16:09.220
featured on the podcast many times before,

427
00:16:09.220 --> 00:16:11.260
but the quirky individual he was, it's well

428
00:16:11.260 --> 00:16:14.100
worth looking up. His Wikipedia record is

429
00:16:14.500 --> 00:16:17.140
this wealthy nobleman with a silver

430
00:16:17.140 --> 00:16:19.500
replacement nose after he lost half his nose

431
00:16:19.500 --> 00:16:22.140
in a duel. He's that guy. Yes,

432
00:16:22.140 --> 00:16:24.620
yes. Um, he had a pet moose that died when it

433
00:16:24.620 --> 00:16:26.420
fell down the steps because it got drunk at a

434
00:16:26.420 --> 00:16:29.360
banquet. He really odd, odd

435
00:16:29.360 --> 00:16:32.000
man. Um, but probably viewed as being

436
00:16:32.400 --> 00:16:35.040
the last great pre telescope astronaut,

437
00:16:35.040 --> 00:16:36.720
astronomical observer, if that makes sense.

438
00:16:36.720 --> 00:16:39.360
Naked eye observer. Now, at this time,

439
00:16:39.520 --> 00:16:41.640
comets were kind of thought to be probably

440
00:16:41.640 --> 00:16:44.200
atmospheric phenomenon. They were nearby,

441
00:16:44.200 --> 00:16:47.200
high in the atmosphere, and so

442
00:16:47.360 --> 00:16:49.640
that was what was going on. People had that

443
00:16:49.640 --> 00:16:52.480
kind of idea. He realized that if that were

444
00:16:52.480 --> 00:16:55.080
true, these things would display a noticeable

445
00:16:55.080 --> 00:16:57.300
parallax if people observe them from

446
00:16:57.300 --> 00:16:59.620
different locations. Uh-huh. So in other

447
00:16:59.620 --> 00:17:01.420
words, people looking from different

448
00:17:01.420 --> 00:17:03.980
locations would see the comet in a different

449
00:17:04.060 --> 00:17:06.100
place in the sky because it was in the

450
00:17:06.100 --> 00:17:08.340
foreground. It's the same technique we use to

451
00:17:08.340 --> 00:17:10.180
measure the distance to the nearest stars. If

452
00:17:10.180 --> 00:17:12.540
you put your finger in front of your face and

453
00:17:12.540 --> 00:17:13.940
look at it through one eye and then look

454
00:17:13.940 --> 00:17:15.820
through the other, you'll see your finger

455
00:17:15.820 --> 00:17:18.100
blinking side to side. And the further away

456
00:17:18.100 --> 00:17:20.740
your finger is, the less it moves. We use

457
00:17:20.740 --> 00:17:22.420
that to measure the distance to stars by

458
00:17:22.420 --> 00:17:24.180
observing from one side of the Earth's orbit,

459
00:17:24.180 --> 00:17:26.360
then the other. But what Brahe did was

460
00:17:26.360 --> 00:17:28.920
collect observations from around Europe of

461
00:17:28.920 --> 00:17:31.760
where the comet was in the sky. With those

462
00:17:31.760 --> 00:17:33.960
observations, he would have been able to

463
00:17:33.960 --> 00:17:36.680
detect a parallax for the comet if it were

464
00:17:36.680 --> 00:17:39.040
closer than the orbit of the Moon. So if it

465
00:17:39.040 --> 00:17:40.920
was atmospheric, absolutely, definitely would

466
00:17:40.920 --> 00:17:43.600
do. But no measurable parallax was found

467
00:17:44.000 --> 00:17:45.840
which showed the comet had to be at least a

468
00:17:45.840 --> 00:17:47.400
couple of million kilometers away. And in

469
00:17:47.400 --> 00:17:49.400
fact, it was probably several tens of

470
00:17:49.400 --> 00:17:52.130
millions of kilometers distant. He got this

471
00:17:52.130 --> 00:17:54.330
beautiful figure, and I've. I use this in my

472
00:17:54.330 --> 00:17:57.090
talks occasionally. That is his drawing of

473
00:17:57.090 --> 00:17:59.170
the motion of the comet. And it's fascinating

474
00:17:59.170 --> 00:18:01.370
from a cultural point of view because it's

475
00:18:01.370 --> 00:18:03.090
clearly at the time when you still have the

476
00:18:03.090 --> 00:18:05.010
geocentric model, the Earth was the center of

477
00:18:05.010 --> 00:18:06.930
the universe. So you've got the Earth in the

478
00:18:06.930 --> 00:18:09.130
middle, the sun going around the Earth but

479
00:18:09.130 --> 00:18:11.010
then Mercury, Venus and the moon going around

480
00:18:11.010 --> 00:18:13.650
the sun. This kind of weird hybrid thing.

481
00:18:13.650 --> 00:18:15.330
Yeah, but you've got the path of the comet

482
00:18:15.330 --> 00:18:17.090
moving through there that he's determined.

483
00:18:17.580 --> 00:18:19.940
And what's really interesting to me, what's

484
00:18:19.940 --> 00:18:22.260
really fascinating is he's got the tails

485
00:18:22.260 --> 00:18:24.620
pointing away from the sun all the time. So

486
00:18:24.620 --> 00:18:26.580
he's got the phenomenology of where the comet

487
00:18:26.580 --> 00:18:28.700
is in the solar system. Modular.

488
00:18:30.060 --> 00:18:32.100
The sun's going around the Earth and the

489
00:18:32.100 --> 00:18:34.820
tails pointing the right way as it moves.

490
00:18:34.820 --> 00:18:36.900
Tails of comets always pointing away from the

491
00:18:36.900 --> 00:18:39.700
sun. And to me that kind of marks the

492
00:18:39.700 --> 00:18:42.700
dawn of the modern scientific view

493
00:18:42.700 --> 00:18:45.690
of comets from the cultural. We don't

494
00:18:45.690 --> 00:18:48.130
know what they are, but they are important.

495
00:18:50.210 --> 00:18:52.210
That's a real kind of boundary point for me.

496
00:18:52.450 --> 00:18:53.810
Andrew Dunkley: Yeah, yeah, fascinating.

497
00:18:53.810 --> 00:18:55.630
I was actually going to ask you about the uh,

498
00:18:55.630 --> 00:18:57.610
you know, the point in time where we went

499
00:18:57.610 --> 00:18:59.890
from the mythology m to the

500
00:19:00.610 --> 00:19:03.010
understanding that this, this was something

501
00:19:03.010 --> 00:19:05.410
else. And yeah, you covered that beautifully.

502
00:19:05.730 --> 00:19:08.630
Gonna just take a breath on space nuts. Uh,

503
00:19:08.630 --> 00:19:10.450
you're with Andrew Dunkley and Professor

504
00:19:10.450 --> 00:19:11.490
Jonti Horner.

505
00:19:14.180 --> 00:19:17.060
Jonti Horner: 0G and I feel fine. Space nuts.

506
00:19:17.140 --> 00:19:18.660
Andrew Dunkley: I did say a breath. That was quick.

507
00:19:18.830 --> 00:19:21.180
Um, let's continue talking about, uh, comets

508
00:19:21.180 --> 00:19:24.060
and meteors. There have been a lot of them in

509
00:19:24.060 --> 00:19:26.940
the news of late. Um, Comet

510
00:19:26.940 --> 00:19:29.540
Pan Stars is, um, you know, it was very,

511
00:19:29.620 --> 00:19:32.460
very popular, uh, late

512
00:19:32.460 --> 00:19:35.160
April. Uh, and uh,

513
00:19:35.620 --> 00:19:38.620
we've seen in recent times, um, a

514
00:19:38.620 --> 00:19:40.420
new kind of comet. And those are the ones

515
00:19:40.420 --> 00:19:43.220
that are coming from other systems, uh,

516
00:19:43.500 --> 00:19:45.420
not the ones that are

517
00:19:45.820 --> 00:19:48.660
continually rotating through our own solar

518
00:19:48.660 --> 00:19:51.660
system. We've had these exo comets that have

519
00:19:52.140 --> 00:19:54.970
been quite intriguing and um,

520
00:19:54.970 --> 00:19:56.980
opening up all sorts of new ideas and

521
00:19:56.980 --> 00:19:59.900
questions about, uh, comets and other

522
00:19:59.900 --> 00:20:02.620
parts of the universe and what we could learn

523
00:20:02.620 --> 00:20:05.420
from them. Um, and

524
00:20:05.740 --> 00:20:07.660
new comets are being discovered all the time.

525
00:20:08.060 --> 00:20:09.500
That doesn't mean they haven't been here

526
00:20:09.500 --> 00:20:12.230
before, but it does mean that they've got

527
00:20:12.310 --> 00:20:15.190
very longitudinal travel times.

528
00:20:15.430 --> 00:20:18.110
So, um, you know, some we won't ever see

529
00:20:18.110 --> 00:20:20.350
because we'll have been and gone before they

530
00:20:20.350 --> 00:20:22.630
get here and others we'll

531
00:20:23.190 --> 00:20:25.590
maybe see several times during our lifetimes.

532
00:20:26.310 --> 00:20:29.190
Jonti Horner: Absolutely. Now historically, people broke

533
00:20:29.350 --> 00:20:31.670
the comets we found down into two categories.

534
00:20:31.670 --> 00:20:34.150
We had short period comets, which are

535
00:20:34.150 --> 00:20:36.710
comets. The definition when I was a kid was

536
00:20:36.710 --> 00:20:38.670
comets whose orbital periods were less than

537
00:20:38.670 --> 00:20:41.160
200 years shorter than that and you were a

538
00:20:41.160 --> 00:20:42.760
short period comet, longer than that and you

539
00:20:42.760 --> 00:20:44.280
were a long period comet. Now there are

540
00:20:44.440 --> 00:20:46.520
subtleties within that, within the short

541
00:20:46.520 --> 00:20:48.240
period comets. We have comets like Comet

542
00:20:48.240 --> 00:20:49.680
Hallie, which are called the Hallie type

543
00:20:49.680 --> 00:20:52.200
comets which come round with a period

544
00:20:52.200 --> 00:20:54.000
comparable to a human lifetime or a bit

545
00:20:54.000 --> 00:20:56.040
longer. The two brightest and most famous of

546
00:20:56.040 --> 00:20:57.520
those are Comet Hallie and Comet Swift

547
00:20:57.520 --> 00:20:59.880
Tuttle. You then have the Jupiter family

548
00:20:59.880 --> 00:21:01.520
comets, which are comets whose orbits, uh,

549
00:21:01.520 --> 00:21:04.000
are just a few years and are typically under

550
00:21:04.000 --> 00:21:06.410
Jupiter's control. And when I was a kid,

551
00:21:06.410 --> 00:21:08.690
anything longer than 200 years was considered

552
00:21:08.690 --> 00:21:11.210
long period. Now that kind of got smashed

553
00:21:11.210 --> 00:21:13.250
into the ground a bit in the early 2000s when

554
00:21:13.250 --> 00:21:16.130
Comet IKEA Jang was sighted, because Comet

555
00:21:16.130 --> 00:21:19.090
Ikea Zhang was very well observed,

556
00:21:19.090 --> 00:21:20.690
its orbit was well calculated and it was

557
00:21:20.690 --> 00:21:23.450
found to have a period of 366 years, I think

558
00:21:23.450 --> 00:21:26.210
it is. And that allowed people to identify

559
00:21:26.210 --> 00:21:28.330
the previous observations of that comet from

560
00:21:28.330 --> 00:21:30.890
the last time it was around. So that's

561
00:21:30.890 --> 00:21:33.370
currently the record holder where we're

562
00:21:33.370 --> 00:21:36.080
absolutely certain that it's been seen on

563
00:21:36.080 --> 00:21:38.440
multiple occasions and it has a

564
00:21:38.680 --> 00:21:41.160
periodic comet designation now. Now a

565
00:21:41.160 --> 00:21:43.600
subtlety to that is we do have the Kreutz sun

566
00:21:43.600 --> 00:21:45.480
grazing comets. I can talk more about them a

567
00:21:45.480 --> 00:21:47.760
little later where we have a strong

568
00:21:47.760 --> 00:21:50.639
identification between an observation of

569
00:21:50.639 --> 00:21:52.720
the comet, say with comedy kaya Seki in

570
00:21:52.720 --> 00:21:55.160
1965 and um, a previous

571
00:21:55.160 --> 00:21:58.080
apparition in the 1100s, which is about

572
00:21:58.080 --> 00:22:00.760
an 800 year return. Yeah, that's a bit

573
00:22:00.760 --> 00:22:03.400
woolier because the comets we observe now are

574
00:22:03.400 --> 00:22:06.260
fragments of one comet back then, and

575
00:22:06.260 --> 00:22:08.060
so therefore several comets tied to that

576
00:22:08.060 --> 00:22:09.500
initial apparition. So there's all that

577
00:22:09.500 --> 00:22:12.060
complexity there. We then have the long

578
00:22:12.060 --> 00:22:14.820
period comets, which, like I say were

579
00:22:14.820 --> 00:22:17.820
200 years or more. It still kind

580
00:22:17.820 --> 00:22:19.980
of is. But with those objects that are both

581
00:22:19.980 --> 00:22:22.140
long period and short period thanksgiang,

582
00:22:22.140 --> 00:22:23.540
you've got these objects whose orbital

583
00:22:23.540 --> 00:22:26.100
periods are so long that they are markedly

584
00:22:26.100 --> 00:22:28.860
longer than a human lifetime, even if they're

585
00:22:28.860 --> 00:22:30.340
comets that have been through before. So a

586
00:22:30.340 --> 00:22:32.880
good example of a really bright comet that is

587
00:22:32.880 --> 00:22:35.280
considered long period but has been through

588
00:22:35.520 --> 00:22:38.000
many times before is Comet Hale Bopp. Yes,

589
00:22:38.480 --> 00:22:41.320
was spectacular in 96, 97. It was visible

590
00:22:41.320 --> 00:22:43.320
with a naked eye for 18 months, shattering

591
00:22:43.320 --> 00:22:45.880
all the records. It will be back in about the

592
00:22:45.880 --> 00:22:47.840
year 4400. It was the last round when the

593
00:22:47.840 --> 00:22:50.720
Egyptians were building pyramids. And that is

594
00:22:50.720 --> 00:22:53.280
perversely a long period comet with a

595
00:22:53.280 --> 00:22:55.320
relatively short period orbit for a long

596
00:22:55.320 --> 00:22:58.280
period of comet. And so scientifically we'd

597
00:22:58.280 --> 00:23:01.250
call that dynamically old or not a

598
00:23:01.250 --> 00:23:02.970
new comet because it's been around a number

599
00:23:02.970 --> 00:23:05.930
of times at the very long period

600
00:23:05.930 --> 00:23:07.650
end of the long period comets, you get things

601
00:23:07.650 --> 00:23:09.770
that are coming in from halfway to the

602
00:23:09.770 --> 00:23:12.010
nearest star from a region we describe as the

603
00:23:12.010 --> 00:23:14.970
Oort Cloud or the Opic Oort cloud. And

604
00:23:14.970 --> 00:23:17.490
those things on their way in have

605
00:23:17.490 --> 00:23:20.090
calculated orbital periods of hundreds of

606
00:23:20.090 --> 00:23:23.050
thousands or even millions of years. And many

607
00:23:23.050 --> 00:23:25.010
of those actually only come through once. And

608
00:23:25.010 --> 00:23:27.130
then they get nudged and ejected from the

609
00:23:27.130 --> 00:23:29.780
solar system, never to return, going out to

610
00:23:29.780 --> 00:23:32.220
wander among the stars. And it's objects like

611
00:23:32.220 --> 00:23:34.260
that that will become the interstellar comets

612
00:23:34.260 --> 00:23:37.180
for other stars, in the same way that

613
00:23:37.180 --> 00:23:38.900
this third group of comets that you alluded

614
00:23:38.900 --> 00:23:41.580
to that we found recently are interstellar

615
00:23:41.580 --> 00:23:43.140
comets in our system. So these are the

616
00:23:43.140 --> 00:23:45.100
objects coming through so quickly that they

617
00:23:45.100 --> 00:23:47.620
are not gravitationally bound to the sun,

618
00:23:47.860 --> 00:23:49.900
but also so quickly that there is no

619
00:23:49.900 --> 00:23:52.260
possibility that they ever were. They've been

620
00:23:52.260 --> 00:23:54.740
flung in so quickly that they must come from

621
00:23:55.460 --> 00:23:58.100
another place. The most recent one was Three

622
00:23:58.100 --> 00:24:00.740
Eye Atlas, which got talked about a huge

623
00:24:00.740 --> 00:24:03.220
amount. Yes. Was definitely not an alien

624
00:24:03.220 --> 00:24:05.780
spaceship. And to avoid getting too

625
00:24:05.780 --> 00:24:07.780
political, just a very brief comment on that

626
00:24:07.780 --> 00:24:09.740
because it needs to be stated and restated,

627
00:24:09.740 --> 00:24:12.620
which is, uh, the arguments of that being an

628
00:24:12.620 --> 00:24:14.900
alien spaceship were the work of one person.

629
00:24:15.620 --> 00:24:17.740
One person who is not a solar system

630
00:24:17.740 --> 00:24:19.820
astronomer historically, but has reached that

631
00:24:19.820 --> 00:24:22.180
age and level of senility that they believe

632
00:24:22.180 --> 00:24:24.350
they can be an expert in things that they are

633
00:24:24.350 --> 00:24:27.270
not and has a certain financial interest in

634
00:24:27.430 --> 00:24:29.430
keeping people interested in aliens because

635
00:24:29.430 --> 00:24:31.030
they buy his book.

636
00:24:31.350 --> 00:24:31.830
Andrew Dunkley: Click.

637
00:24:32.950 --> 00:24:35.310
Jonti Horner: The community of astronomers has been very

638
00:24:35.310 --> 00:24:37.110
upset and very Shrek about that because it

639
00:24:37.110 --> 00:24:39.190
diverts attention from what is a really

640
00:24:39.190 --> 00:24:41.510
fascinating object on the fact that it's

641
00:24:41.510 --> 00:24:44.030
really fascinating, but also breeds a certain

642
00:24:44.030 --> 00:24:45.670
amount of fear. And I genuinely had people

643
00:24:45.670 --> 00:24:48.630
reaching out to me when he was pushing

644
00:24:48.630 --> 00:24:50.430
this narrative of it being aliens that were

645
00:24:50.430 --> 00:24:51.830
going to invade because they were frightened,

646
00:24:51.900 --> 00:24:54.020
heightened, they were genuinely worried

647
00:24:54.020 --> 00:24:55.820
because a Harvard astronomer was saying

648
00:24:55.820 --> 00:24:58.380
aliens were going to come and beat us all up.

649
00:24:58.700 --> 00:24:59.100
Andrew Dunkley: Yeah.

650
00:24:59.100 --> 00:25:01.220
Jonti Horner: And it's problematic because it hides the

651
00:25:01.220 --> 00:25:03.460
science, but it's also more widely

652
00:25:03.460 --> 00:25:06.220
problematic at a time when we have lowering

653
00:25:06.220 --> 00:25:09.180
levels of engagement with science and very

654
00:25:09.180 --> 00:25:11.540
much lowering levels of trust in science and

655
00:25:11.540 --> 00:25:14.140
scientists. It's very bad to have someone

656
00:25:14.140 --> 00:25:17.060
acting disingenuously, telling lies

657
00:25:17.060 --> 00:25:19.670
on muddying the water. Um, and then

658
00:25:19.670 --> 00:25:21.870
arguing that everybody else is wrong and mean

659
00:25:21.870 --> 00:25:23.750
to me and I'm the only one telling the truth.

660
00:25:23.750 --> 00:25:26.310
And it's part of that whole fake news thing

661
00:25:26.310 --> 00:25:29.070
that I think is dangerous and damaging.

662
00:25:29.150 --> 00:25:32.150
You know, we need people to have trust and

663
00:25:32.150 --> 00:25:33.950
faith in science because it's so integral to

664
00:25:33.950 --> 00:25:36.230
our lives. And it's good to question. But

665
00:25:36.230 --> 00:25:38.670
it's bad when people say things that they

666
00:25:38.670 --> 00:25:40.590
fundamentally know are not true just to get

667
00:25:40.590 --> 00:25:42.750
hits or clicks or money. Yeah.

668
00:25:43.710 --> 00:25:46.580
Andrew Dunkley: And it's important to debunk that

669
00:25:46.580 --> 00:25:49.260
kind of, uh, approach because

670
00:25:49.420 --> 00:25:51.660
I've had people come up to me very recently

671
00:25:51.740 --> 00:25:54.560
who know I do this podcast, uh,

672
00:25:54.560 --> 00:25:56.020
who've said to me, oh, what do you think of

673
00:25:56.020 --> 00:25:58.620
that alien spaceship? And I go, it's,

674
00:25:59.180 --> 00:26:01.499
it's, that's what I think

675
00:26:01.980 --> 00:26:04.020
because it's, it's somebody trying to get

676
00:26:04.020 --> 00:26:05.940
media attention. It's got nothing. It's a

677
00:26:05.940 --> 00:26:08.540
rock. It's actually, it's, it's a, it's an

678
00:26:08.540 --> 00:26:10.940
ice conglomerate. It's, it's not a, it's not

679
00:26:10.940 --> 00:26:13.790
a spaceship at all. It's not behaving like a

680
00:26:13.790 --> 00:26:15.830
spaceship would. It's behaving like something

681
00:26:15.830 --> 00:26:17.270
passing through our solar system.

682
00:26:18.190 --> 00:26:21.190
Um, and people, people. The thing is,

683
00:26:21.190 --> 00:26:22.390
Jonti, people are buying

684
00:26:22.390 --> 00:26:25.270
Jonti Horner: this rubbish, but there's an old saying

685
00:26:25.270 --> 00:26:28.270
that you know, like, and run around the

686
00:26:28.270 --> 00:26:30.310
world before the truth has got its boots on,

687
00:26:30.710 --> 00:26:32.470
especially when it's an attractive light.

688
00:26:32.550 --> 00:26:35.350
It's, I mean, again, digging into my

689
00:26:35.350 --> 00:26:36.830
memories of Terry Pratchett stuff which

690
00:26:36.830 --> 00:26:39.150
happens a lot. It's the old quote when

691
00:26:39.150 --> 00:26:41.430
they're talking about newspapers and nobody

692
00:26:41.430 --> 00:26:43.310
really ever wants to hear a story about dog

693
00:26:43.310 --> 00:26:44.910
bites mum because it happens all the time.

694
00:26:44.910 --> 00:26:46.710
But if you've got a story that says Mum bites

695
00:26:46.710 --> 00:26:48.230
dog, everybody's fascinated.

696
00:26:48.230 --> 00:26:48.710
Andrew Dunkley: Yeah.

697
00:26:48.790 --> 00:26:51.190
Jonti Horner: And this story has all the elements. It's so

698
00:26:51.190 --> 00:26:53.670
salacious that it gets coverage and people

699
00:26:53.670 --> 00:26:56.390
who don't normally read or digest science

700
00:26:56.390 --> 00:26:58.470
are not interested, will see this and hook

701
00:26:58.470 --> 00:27:00.830
into it. And when the byline is Harvard

702
00:27:00.830 --> 00:27:03.310
astronomer, that gives it a huge amount of

703
00:27:03.310 --> 00:27:03.830
credence.

704
00:27:03.830 --> 00:27:04.230
Andrew Dunkley: It does.

705
00:27:04.230 --> 00:27:06.230
Jonti Horner: Uh, and nobody hears the rebuttals. It's

706
00:27:07.510 --> 00:27:09.070
a bit like, you know, when there are claims

707
00:27:09.070 --> 00:27:10.670
of life on a planet around another star.

708
00:27:10.670 --> 00:27:13.550
Nobody remembers the, the follow

709
00:27:13.550 --> 00:27:15.830
ups that say actually it wasn't. They just

710
00:27:15.830 --> 00:27:17.910
remember, oh, we found aliens and we haven't.

711
00:27:18.390 --> 00:27:20.790
I mean, I think that story that,

712
00:27:20.970 --> 00:27:23.110
Andrew Dunkley: uh, the most recent story

713
00:27:23.830 --> 00:27:26.510
that I recall where that, that claim was made

714
00:27:26.510 --> 00:27:29.350
was um, the one about the

715
00:27:29.350 --> 00:27:31.670
something they. What was it they found in

716
00:27:31.670 --> 00:27:33.430
the, in the atmosphere of Venus. It was

717
00:27:34.380 --> 00:27:34.900
phosphine.

718
00:27:34.900 --> 00:27:37.140
Jonti Horner: Yes. I can go on a little bit of a side rant

719
00:27:37.140 --> 00:27:39.980
about that. My heart broke. Um, the

720
00:27:39.980 --> 00:27:42.380
lead author on that study was Jane Greaves in

721
00:27:42.380 --> 00:27:44.380
the uk, who's someone I knew very well when I

722
00:27:44.380 --> 00:27:46.140
was in the uk and she's a fabulous science

723
00:27:46.140 --> 00:27:49.060
and just all around wonderful individual. And

724
00:27:49.060 --> 00:27:51.820
the story was led by a UK team

725
00:27:52.380 --> 00:27:54.980
who, if you actually read the paper, don't

726
00:27:54.980 --> 00:27:57.700
say anything that is, this is life. What they

727
00:27:57.700 --> 00:28:00.550
say is we found a very weak signal of

728
00:28:00.550 --> 00:28:02.790
this gas in Venus's atmosphere. It's right

729
00:28:02.790 --> 00:28:04.750
down in the noise. So there is a chance it's

730
00:28:04.750 --> 00:28:07.110
a false positive anyway, so there needs to be

731
00:28:07.110 --> 00:28:09.790
a bit of extra work done. It's a little bit

732
00:28:09.790 --> 00:28:12.150
interesting because on the Earth, the only

733
00:28:12.150 --> 00:28:15.110
processes that produce this peculiar gas

734
00:28:15.830 --> 00:28:18.710
are, uh, technology and industry or life.

735
00:28:19.110 --> 00:28:20.630
Yeah. We don't know of any other way that

736
00:28:20.630 --> 00:28:22.270
it's made, but that doesn't mean that there

737
00:28:22.270 --> 00:28:23.590
aren't other ways that it's made.

738
00:28:23.670 --> 00:28:25.830
Andrew Dunkley: Isn't that a tasty morsel for the popular

739
00:28:25.830 --> 00:28:26.150
press?

740
00:28:26.310 --> 00:28:26.950
Jonti Horner: Absolutely.

741
00:28:26.950 --> 00:28:28.870
But what happened then was that there is an

742
00:28:29.460 --> 00:28:32.020
American outreach journal,

743
00:28:32.310 --> 00:28:34.820
um, science communication journal, that broke

744
00:28:34.820 --> 00:28:37.580
embargo on this story, didn't talk to Jane

745
00:28:37.580 --> 00:28:39.780
and her colleagues, but instead ran a story

746
00:28:39.780 --> 00:28:41.660
saying British scientists found life on

747
00:28:41.660 --> 00:28:43.540
Venus. Which is not what they'd said at all.

748
00:28:43.700 --> 00:28:45.940
No, that's what started the absolute bum

749
00:28:45.940 --> 00:28:48.780
fight. And the vitriol on the hair and the

750
00:28:48.780 --> 00:28:50.900
death threats, believe it or not, that Jane

751
00:28:50.900 --> 00:28:53.060
Grieves got because of this were

752
00:28:53.060 --> 00:28:55.820
astonishing. It was absolutely terrible. And

753
00:28:55.820 --> 00:28:58.350
instead of being able to managed to deploy

754
00:28:58.430 --> 00:29:00.790
this wonderful story about this fascinating

755
00:29:00.790 --> 00:29:02.790
new result they got, they spent all their

756
00:29:02.790 --> 00:29:05.790
time in damage control because this

757
00:29:06.030 --> 00:29:08.950
publication chose to break the embargo

758
00:29:08.950 --> 00:29:11.030
early and run a story that was not factually

759
00:29:11.030 --> 00:29:13.470
true, but again would get them clicks. Yep.

760
00:29:13.550 --> 00:29:16.270
Andrew Dunkley: Yeah. And that's unfortunately, the modern

761
00:29:16.270 --> 00:29:19.030
media and, um, the Internet's to

762
00:29:19.030 --> 00:29:21.630
blame. Well, it's not the Internet that's to

763
00:29:21.630 --> 00:29:23.660
blame. It's the people who use it that are to

764
00:29:23.660 --> 00:29:26.460
blame. And it's one of the, um,

765
00:29:26.460 --> 00:29:27.700
one of the things you've really got to be

766
00:29:27.700 --> 00:29:30.420
careful of when you are, uh, following

767
00:29:30.500 --> 00:29:33.260
a story, whether it's an exocomet that's not

768
00:29:33.260 --> 00:29:36.220
a spaceship or, uh, life that's

769
00:29:36.220 --> 00:29:38.020
not in Venus's atmosphere,

770
00:29:38.680 --> 00:29:41.340
um, and even to a lesser

771
00:29:41.340 --> 00:29:43.140
degree, and you and I mentioned this before

772
00:29:43.140 --> 00:29:45.860
we started, the way the media gets its

773
00:29:45.860 --> 00:29:48.500
information confused, such as

774
00:29:48.980 --> 00:29:51.900
reporting, uh, on, um, upcoming spectacular

775
00:29:51.900 --> 00:29:54.630
meteor showers that, uh, everyone

776
00:29:54.630 --> 00:29:56.150
gets excited about and then they realize

777
00:29:56.150 --> 00:29:57.630
they're on the wrong side of the planet.

778
00:29:57.950 --> 00:30:00.430
Jonti Horner: Absolutely. And this is a caution I give to

779
00:30:00.430 --> 00:30:02.590
everybody, both for comets and for meteors

780
00:30:02.590 --> 00:30:03.950
actually, but particularly for those of us in

781
00:30:03.950 --> 00:30:06.590
the Southern hemisphere, um, meteor showers

782
00:30:07.150 --> 00:30:10.030
and comets are things that are best seen

783
00:30:10.110 --> 00:30:12.190
from some latitudes and not from others. And

784
00:30:12.190 --> 00:30:13.990
for each comet or for each meteor shower

785
00:30:13.990 --> 00:30:16.150
that's different. Now, I'll talk later on

786
00:30:16.150 --> 00:30:18.310
about a newly discovered comet that might be

787
00:30:18.310 --> 00:30:20.590
very spectacular in late 2028.

788
00:30:21.360 --> 00:30:22.720
That comet is primarily going to be a

789
00:30:22.720 --> 00:30:25.280
Southern hemisphere object. So it will

790
00:30:25.280 --> 00:30:26.920
probably be better for us in Australia and

791
00:30:26.920 --> 00:30:28.560
New Zealand than it will be for people in the

792
00:30:28.560 --> 00:30:30.480
UK or the us Just as an example,

793
00:30:31.520 --> 00:30:33.350
when events are happening that are, uh,

794
00:30:33.400 --> 00:30:35.320
primarily good for the Northern Hemisphere.

795
00:30:35.320 --> 00:30:36.919
The Northern Hemisphere has more people and

796
00:30:36.919 --> 00:30:39.320
more media. And what I've seen happen more

797
00:30:39.320 --> 00:30:41.760
and more is that, uh, the media in Australia,

798
00:30:42.800 --> 00:30:44.560
and I know the Australian stuff because

799
00:30:44.560 --> 00:30:46.440
that's local to us. It's probably just the

800
00:30:46.440 --> 00:30:48.120
same in New Zealand, South Africa, South

801
00:30:48.120 --> 00:30:50.240
America, all these other places. But the

802
00:30:50.240 --> 00:30:52.000
media there will pick up these stories and

803
00:30:52.000 --> 00:30:54.920
just run them without running

804
00:30:54.920 --> 00:30:57.320
the sanity filter. So the April

805
00:30:57.320 --> 00:30:59.440
Lyrids are a really good example of this. But

806
00:30:59.440 --> 00:31:01.200
a better one is probably the Perseid meteor

807
00:31:01.200 --> 00:31:03.920
shower in August. Now, it's a little bit of

808
00:31:03.920 --> 00:31:06.000
background here. When we've got a meteor

809
00:31:06.000 --> 00:31:08.440
shower, we're getting bits of dust and debris

810
00:31:08.440 --> 00:31:11.000
hitting the Earth's atmosphere and ablating

811
00:31:11.320 --> 00:31:13.560
at an altitude of about 80 km. Now,

812
00:31:14.200 --> 00:31:16.520
ablation is a slightly weird thing. People

813
00:31:16.520 --> 00:31:18.520
often describe this as burning up, but it's

814
00:31:18.520 --> 00:31:20.570
not burning up in the sense of a flame being

815
00:31:20.570 --> 00:31:22.890
lit and a fire burning. It's rather that

816
00:31:22.890 --> 00:31:24.370
these things push into the atmosphere at

817
00:31:24.370 --> 00:31:26.730
really high speed, pile the air up in front

818
00:31:26.730 --> 00:31:28.450
of them, getting the air superheated,

819
00:31:28.930 --> 00:31:30.730
creating a load of plasma. And the heat from

820
00:31:30.730 --> 00:31:33.410
that makes and vaporizes the bit of debris.

821
00:31:33.730 --> 00:31:35.410
So it's not burning up in the traditional

822
00:31:35.410 --> 00:31:37.770
sense. And anytime you see a meteor, you see

823
00:31:37.770 --> 00:31:39.210
a shooting star, that's what you're seeing.

824
00:31:39.210 --> 00:31:40.730
And, uh, the bigger the bit of dust, the

825
00:31:40.730 --> 00:31:43.130
brighter it will be. The faster it's moving

826
00:31:43.130 --> 00:31:45.130
at a given size, the more energy it's got. So

827
00:31:45.130 --> 00:31:47.540
again, the brighter it'll be. Yeah. And you

828
00:31:47.540 --> 00:31:50.500
see shooting stars on any night of the year,

829
00:31:50.740 --> 00:31:53.340
typically, uh, three or four an hour in the

830
00:31:53.340 --> 00:31:55.580
evenings, five or six an hour in the

831
00:31:55.580 --> 00:31:57.140
mornings, potentially. And that difference is

832
00:31:57.140 --> 00:31:58.700
just because in the mornings you're facing

833
00:31:58.700 --> 00:32:00.420
the direction the Earth's moving. So you're

834
00:32:00.500 --> 00:32:02.700
getting collisions that are head on. So the

835
00:32:02.700 --> 00:32:05.340
average collision speed is higher. So a grain

836
00:32:05.340 --> 00:32:07.340
of dust that's the same size will be a bit

837
00:32:07.340 --> 00:32:09.540
brighter. Therefore, the things that in the

838
00:32:09.540 --> 00:32:11.220
evening that will be too faint to see become

839
00:32:11.220 --> 00:32:13.180
visible. So you get a slight increase in the

840
00:32:13.180 --> 00:32:15.660
rate towards morning. Then in the evening,

841
00:32:16.130 --> 00:32:17.700
um, it's also you're probably getting a

842
00:32:17.700 --> 00:32:19.420
slightly increased amount of stuff entering

843
00:32:19.420 --> 00:32:20.820
the atmosphere because you always see more

844
00:32:20.820 --> 00:32:22.260
flies hit your windscreen than your air

845
00:32:22.260 --> 00:32:24.940
windscreen. Same kind of idea. Yeah.

846
00:32:25.100 --> 00:32:27.300
When we get a meteor shower, what's happening

847
00:32:27.300 --> 00:32:30.180
is we're passing through the area of

848
00:32:30.180 --> 00:32:32.940
space where the Earth passes near the orbit

849
00:32:32.940 --> 00:32:34.540
of either a comet or an asteroid. And

850
00:32:34.540 --> 00:32:36.980
typically it's a comet. Now, every time a

851
00:32:36.980 --> 00:32:39.500
comet goes around the sun, that dirty

852
00:32:39.500 --> 00:32:42.500
snowball or snowy dirt ball gets hot. The

853
00:32:42.500 --> 00:32:44.580
volatile material on the surface is too hot

854
00:32:44.580 --> 00:32:47.580
to stay solid, so becomes a gas in a

855
00:32:47.580 --> 00:32:50.020
process called sublimation. And you get jets

856
00:32:50.020 --> 00:32:52.740
erupting from the comet, shrouding in gas,

857
00:32:53.380 --> 00:32:55.180
which is then blown away from the sun to give

858
00:32:55.180 --> 00:32:57.939
you the tails. Those jets erupting into

859
00:32:57.939 --> 00:32:59.460
space carry with them dust.

860
00:33:00.660 --> 00:33:03.100
Now, biggest bits of dust are pushed away so

861
00:33:03.100 --> 00:33:04.620
gently, they'll fall back to the comet and

862
00:33:04.620 --> 00:33:06.460
clog it up. And some comets eventually turn

863
00:33:06.460 --> 00:33:08.970
off because of. This also is the reason most

864
00:33:08.970 --> 00:33:11.370
comets are only active from a few locations

865
00:33:11.370 --> 00:33:13.850
on the surface, not uniformly, because most

866
00:33:13.850 --> 00:33:15.930
of the surface is clogged up and you've just

867
00:33:15.930 --> 00:33:17.810
got a few active areas where volatile

868
00:33:17.810 --> 00:33:20.290
material is exposed. Yeah, but that dust

869
00:33:20.290 --> 00:33:22.330
that's ejected from the comet is ejected with

870
00:33:22.330 --> 00:33:24.530
speeds measured in meters per second or

871
00:33:24.530 --> 00:33:27.210
centimetres per second from an object that's

872
00:33:27.210 --> 00:33:28.730
traveling at a speed measured in tens of

873
00:33:28.730 --> 00:33:31.410
kilometers a second. So what that means is

874
00:33:31.410 --> 00:33:34.410
that, uh, that dust is moving away from

875
00:33:34.410 --> 00:33:36.730
the comet at a speed almost identical to the

876
00:33:36.730 --> 00:33:39.130
speed the comet's traveling itself. I guess

877
00:33:39.130 --> 00:33:41.530
it's like if you. You're driving along the

878
00:33:41.530 --> 00:33:43.330
road and you drop a tennis ball out of the

879
00:33:43.330 --> 00:33:45.970
window until the wind resistance pushes it

880
00:33:45.970 --> 00:33:47.770
back. If there wasn't a wind resistance

881
00:33:47.770 --> 00:33:50.210
there, it would move along with the car, just

882
00:33:50.210 --> 00:33:51.930
drifting away very slightly based on the

883
00:33:51.930 --> 00:33:53.690
speed you pushed it out of the window. Same

884
00:33:53.690 --> 00:33:54.770
idea. Yeah.

885
00:33:54.770 --> 00:33:57.450
Andrew Dunkley: I actually saw a really great experiment once

886
00:33:57.450 --> 00:33:59.230
where they were.

887
00:34:01.230 --> 00:34:03.230
How did they do it? They had a guy on the

888
00:34:03.230 --> 00:34:06.150
back of a truck, and they

889
00:34:06.150 --> 00:34:08.670
were driving at, like, uh, 100

890
00:34:08.670 --> 00:34:11.470
kilometers an hour, and they shot him

891
00:34:11.470 --> 00:34:14.230
off the truck in the opposite direction at

892
00:34:14.230 --> 00:34:17.190
the same speed, and he just stopped where he

893
00:34:17.190 --> 00:34:17.630
landed.

894
00:34:17.790 --> 00:34:19.830
Jonti Horner: Well, it's brilliant. I think mythbusters did

895
00:34:19.830 --> 00:34:22.150
something similar, and it's amazing. Our

896
00:34:22.150 --> 00:34:24.990
common sense is physics, really

897
00:34:25.959 --> 00:34:27.959
simple physics is great, but our common sense

898
00:34:27.959 --> 00:34:30.079
breaks down in some situations because our

899
00:34:30.079 --> 00:34:32.559
common sense is a naturally inherited thing

900
00:34:32.559 --> 00:34:34.359
about the world at the speeds we experience

901
00:34:34.519 --> 00:34:37.479
it. And so we tend to think if you're running

902
00:34:37.479 --> 00:34:39.279
forwards at 10km an hour and you throw

903
00:34:39.279 --> 00:34:41.759
something forwards, it will travel a bit

904
00:34:41.759 --> 00:34:43.559
faster. That breaks down when you get to

905
00:34:43.559 --> 00:34:45.239
relativity. There's all these weird things

906
00:34:45.239 --> 00:34:47.839
around it where our common sense gets it

907
00:34:47.839 --> 00:34:50.359
wrong for comets and for the dust. And it

908
00:34:50.359 --> 00:34:51.919
took me a long while to get my head around

909
00:34:51.919 --> 00:34:54.400
this because it's a bit counterintuitive if

910
00:34:54.400 --> 00:34:56.960
you eject Dust from a comet. You can eject

911
00:34:56.960 --> 00:34:58.320
the dust forward or backwards. So you can

912
00:34:58.320 --> 00:35:00.240
imagine this jet from the comet working a bit

913
00:35:00.240 --> 00:35:03.200
like a geyser, turning off when it gets dark

914
00:35:03.200 --> 00:35:05.000
and it gets cold, and then turning off again

915
00:35:05.000 --> 00:35:07.280
in the morning when it gets hot again. That

916
00:35:07.280 --> 00:35:09.410
can throw dust forwards, sidewards, and, um,

917
00:35:09.519 --> 00:35:12.120
backwards, or any combination of the above.

918
00:35:12.440 --> 00:35:14.440
So that means this comet is throwing out dust

919
00:35:14.440 --> 00:35:17.120
at a speed of meters per second, a bit like a

920
00:35:17.120 --> 00:35:19.810
sprinkler into space. The

921
00:35:19.810 --> 00:35:22.530
dust has a forward component to its speed.

922
00:35:22.690 --> 00:35:24.370
So it could be going sideways but a little

923
00:35:24.370 --> 00:35:25.970
forward, or it could be going head on in

924
00:35:25.970 --> 00:35:28.210
front of the comet that is now traveling

925
00:35:28.210 --> 00:35:30.450
around the sun faster than the comet is,

926
00:35:30.930 --> 00:35:32.610
which means it will move onto, um, an orbit

927
00:35:32.610 --> 00:35:35.289
with a longer period than the comet. So the

928
00:35:35.289 --> 00:35:36.890
next time the comet comes round, that grain

929
00:35:36.890 --> 00:35:39.530
of dust will arrive after the comet. So dust

930
00:35:39.530 --> 00:35:42.410
thrown forward ends up behind. And similarly,

931
00:35:42.410 --> 00:35:44.370
dust thrown backwards is moving slower than

932
00:35:44.370 --> 00:35:45.930
the comet, which puts it on a slightly

933
00:35:45.930 --> 00:35:48.260
shorter period orbit, and therefore it will

934
00:35:48.260 --> 00:35:50.620
arrive ahead of the comet next time. And that

935
00:35:50.620 --> 00:35:52.300
little bit of sidewards motion also means it

936
00:35:52.300 --> 00:35:54.980
will spread out a little bit in space. What

937
00:35:54.980 --> 00:35:57.180
this means over, uh, time periods is that,

938
00:35:57.180 --> 00:35:58.860
uh, comets, every time they come round,

939
00:35:59.340 --> 00:36:01.780
essentially shed what becomes like a javelin

940
00:36:01.780 --> 00:36:04.700
shape, a spear of dust into space with a

941
00:36:04.700 --> 00:36:07.380
comet at the center, like a

942
00:36:07.380 --> 00:36:09.620
spike. And that spike gradually diffuses over

943
00:36:09.620 --> 00:36:11.580
time, spreads out further and further ahead

944
00:36:11.580 --> 00:36:13.950
and behind the comet. And so over a long time

945
00:36:13.950 --> 00:36:16.190
scale, you eventually end up with the comet's

946
00:36:16.190 --> 00:36:18.750
orbit shrouded in dust. And the dust can be

947
00:36:18.750 --> 00:36:20.790
quite spread out over millions of kilometers.

948
00:36:21.190 --> 00:36:23.630
Yeah, these orbits are oriented randomly in

949
00:36:23.630 --> 00:36:26.230
space. So many of them don't intersect the

950
00:36:26.230 --> 00:36:28.430
Earth. Even if the comet gets closer to the

951
00:36:28.430 --> 00:36:31.070
sun than we are at its closest, passes above

952
00:36:31.070 --> 00:36:33.110
or below the Earth's orbit, nothing happens.

953
00:36:33.990 --> 00:36:36.630
But for a subset of them, the comet

954
00:36:37.270 --> 00:36:39.630
will, in its orbit, have the potential to get

955
00:36:39.630 --> 00:36:41.430
very close to the Earth. So its orbit and the

956
00:36:41.430 --> 00:36:43.730
Earth get very close together. And in those

957
00:36:43.730 --> 00:36:46.210
cases, every time we go around the sun, if

958
00:36:46.210 --> 00:36:47.850
that comet's been laying dust down for a

959
00:36:47.850 --> 00:36:50.290
while, we'll run into the dust every time we

960
00:36:50.290 --> 00:36:52.380
go around. And that dust will hit the Earth's

961
00:36:52.380 --> 00:36:54.050
M atmosphere, which means we're going through

962
00:36:54.050 --> 00:36:56.610
a dirtier bit of the solar system and we get

963
00:36:56.610 --> 00:36:58.370
more meteors. That's when we get a meteor

964
00:36:58.370 --> 00:37:00.530
shower. But the other telltale thing for the

965
00:37:00.530 --> 00:37:03.330
meteor shower is all the dust grains that hit

966
00:37:03.330 --> 00:37:05.610
the Earth in a meteor shower are moving

967
00:37:05.610 --> 00:37:07.010
essentially parallel to each other.

968
00:37:07.010 --> 00:37:08.530
They're all following the same Orbit around

969
00:37:08.530 --> 00:37:09.730
the sun, hitting the Earth, the Earth from

970
00:37:09.730 --> 00:37:11.930
the same direction at the same speed.

971
00:37:13.050 --> 00:37:15.290
So all this dust is coming towards you from a

972
00:37:15.290 --> 00:37:17.410
single point in space. So from your point of

973
00:37:17.410 --> 00:37:19.610
view, looking at the sky, when you see those

974
00:37:19.610 --> 00:37:22.370
meteors, part of a meteor shower, they appear

975
00:37:22.370 --> 00:37:25.290
to appear anywhere in the sky. But if

976
00:37:25.290 --> 00:37:26.850
you trace them back, they'll all point to a

977
00:37:26.850 --> 00:37:28.930
single point in the sky, that something we

978
00:37:28.930 --> 00:37:31.410
call the radiant. And that's effectively the

979
00:37:31.410 --> 00:37:33.250
point in space they're traveling towards us

980
00:37:33.250 --> 00:37:35.150
from. And um, they diverge because they

981
00:37:35.380 --> 00:37:37.660
perspective, they're coming closer to you. So

982
00:37:37.660 --> 00:37:40.420
every meteor shower has a radiant in the sky.

983
00:37:40.420 --> 00:37:42.980
The April Lyrids have their radiant in

984
00:37:43.300 --> 00:37:45.180
Lyra, although for a fair part of their time

985
00:37:45.180 --> 00:37:47.300
it's actually in Hercules, it m drifts a bit.

986
00:37:47.380 --> 00:37:49.780
The Perseids have their radiant in Perseus,

987
00:37:50.020 --> 00:37:52.580
the Geminids in Gemini and so on.

988
00:37:53.700 --> 00:37:56.300
So that's all well and good. If the

989
00:37:56.300 --> 00:37:59.260
radiant is below the horizon, that means the

990
00:37:59.260 --> 00:38:00.780
meteors are hitting the other side of the

991
00:38:00.780 --> 00:38:02.800
Earth and you can't see them because the

992
00:38:02.800 --> 00:38:04.880
Earth's in the way. So first point with a

993
00:38:04.880 --> 00:38:07.520
meteor shower is unlike some of the media

994
00:38:07.520 --> 00:38:09.680
reports, you can't see meteors for that

995
00:38:09.680 --> 00:38:12.040
meteor shower at any time of night. You can

996
00:38:12.040 --> 00:38:13.440
only see them when the radiance above the

997
00:38:13.440 --> 00:38:15.520
horizon point, number one

998
00:38:16.240 --> 00:38:18.400
point. The second is the higher in the sky

999
00:38:18.400 --> 00:38:21.240
that radiant is, the more head on into the

1000
00:38:21.240 --> 00:38:23.680
stream you're going. So the more meteors

1001
00:38:23.680 --> 00:38:26.160
you'll see. Now the analogy I'd ah, use here

1002
00:38:26.160 --> 00:38:28.760
is if you imagine getting your hose pipe and

1003
00:38:28.760 --> 00:38:30.280
having it on that shower mode, you know,

1004
00:38:30.280 --> 00:38:32.600
where water's coming out from many holes all

1005
00:38:32.600 --> 00:38:35.160
at once. If you hold that hose pipe

1006
00:38:35.160 --> 00:38:37.280
vertically and turn the tap on, all the water

1007
00:38:37.280 --> 00:38:38.920
from that hose pipe will hit a relatively

1008
00:38:38.920 --> 00:38:41.600
small area of the ground. If you turn that

1009
00:38:41.600 --> 00:38:44.520
hose pipe to 45 degrees, that water will

1010
00:38:44.520 --> 00:38:46.640
spread out over a larger surface area.

1011
00:38:47.040 --> 00:38:47.560
Andrew Dunkley: Yep.

1012
00:38:47.560 --> 00:38:49.600
Jonti Horner: Now if you imagine the meteors, the dust in a

1013
00:38:49.600 --> 00:38:51.440
meteor shower coming in towards the Earth,

1014
00:38:52.080 --> 00:38:54.160
the more directly overhead

1015
00:38:54.980 --> 00:38:57.660
your point that they're coming from is the

1016
00:38:57.660 --> 00:38:59.660
more meteors you'll get in a certain volume

1017
00:38:59.660 --> 00:39:01.700
of the atmosphere and the lower to the

1018
00:39:01.700 --> 00:39:03.460
horizon that point is, the more you'll spread

1019
00:39:03.460 --> 00:39:05.380
those same number of grains of dust out.

1020
00:39:06.260 --> 00:39:09.140
So the higher in the sky the radiant is, the

1021
00:39:09.140 --> 00:39:10.940
more dust is hitting the part of the

1022
00:39:10.940 --> 00:39:13.100
atmosphere you can see from your location. So

1023
00:39:13.100 --> 00:39:15.540
the more meteors you get, and what this means

1024
00:39:15.540 --> 00:39:17.620
is that the lower in the sky the rating is a

1025
00:39:17.620 --> 00:39:20.260
few meteors you see. And so you see the most

1026
00:39:20.260 --> 00:39:22.440
Meteors. For a given meteor shower, when the

1027
00:39:22.440 --> 00:39:24.560
radiant is near what we call culmination,

1028
00:39:24.560 --> 00:39:26.920
where it's nearly highest in the sky. For the

1029
00:39:26.920 --> 00:39:28.640
southern hemisphere, when it's nearly due

1030
00:39:28.640 --> 00:39:31.200
north, for the northern hemisphere rain, the

1031
00:39:31.200 --> 00:39:33.840
radiant's nearly due south. So

1032
00:39:33.920 --> 00:39:36.320
all well and good, but what that means is

1033
00:39:36.320 --> 00:39:38.040
that ah, from different locations on the

1034
00:39:38.040 --> 00:39:40.360
earth, a given meteor shower will give you a

1035
00:39:40.360 --> 00:39:42.960
different strength of display. The April

1036
00:39:42.960 --> 00:39:45.920
Lyrids, their radiant is

1037
00:39:46.000 --> 00:39:48.600
34 degrees north of the equator. So that

1038
00:39:48.600 --> 00:39:50.830
means if you lived 34 degrees north of the

1039
00:39:50.830 --> 00:39:53.310
equator at about 2am in the morning, the

1040
00:39:53.310 --> 00:39:55.070
radiant will be overhead and you're in the

1041
00:39:55.070 --> 00:39:56.870
best place on the planet to see the meteors.

1042
00:39:57.510 --> 00:40:00.310
If you had perfect vision, perfectly dark

1043
00:40:00.310 --> 00:40:03.190
sky, you'd see a number of meteors, 15

1044
00:40:03.190 --> 00:40:05.350
to 20 per hour for the April Lyrids and

1045
00:40:05.350 --> 00:40:07.270
that's called the zenithal hourly rate.

1046
00:40:07.750 --> 00:40:09.390
That's the number of meters you'd see in

1047
00:40:09.390 --> 00:40:11.350
perfect conditions with perfect eyesight,

1048
00:40:11.670 --> 00:40:13.710
with no light pollution if the radiant was

1049
00:40:13.710 --> 00:40:16.150
overhead. The lower the radiant is in the

1050
00:40:16.150 --> 00:40:18.460
sky, the more that number shrinks. So the

1051
00:40:18.460 --> 00:40:21.220
ZHR is the theoretical maximum number

1052
00:40:21.220 --> 00:40:23.900
you'd see. So good

1053
00:40:23.900 --> 00:40:25.580
meteor shower, not a great one from the

1054
00:40:25.580 --> 00:40:27.940
northern hemisphere, but for us in Brisbane,

1055
00:40:27.940 --> 00:40:29.780
let's say 26 degrees south.

1056
00:40:30.740 --> 00:40:32.860
The radiant of the April Lyrids at its

1057
00:40:32.860 --> 00:40:34.820
highest in the sky is only 30 degrees above

1058
00:40:34.820 --> 00:40:37.580
the horizon. That means that the

1059
00:40:37.580 --> 00:40:40.300
volume of space where the dust is arriving is

1060
00:40:40.300 --> 00:40:42.620
doubled. So you'd only see half the number of

1061
00:40:42.620 --> 00:40:45.350
meteors. So instead of 20 per

1062
00:40:45.350 --> 00:40:46.910
hour, you're down to 10 an hour

1063
00:40:47.550 --> 00:40:50.030
immediately before anything else kicks in.

1064
00:40:50.350 --> 00:40:52.110
And the further south you go, the lower the

1065
00:40:52.110 --> 00:40:55.070
rates are. But the problem is the journalists

1066
00:40:55.070 --> 00:40:56.550
covering this will pick up on a Northern

1067
00:40:56.550 --> 00:40:58.710
hemisphere article and just repeat it.

1068
00:40:58.710 --> 00:41:00.670
There's this meteor shower happening. You can

1069
00:41:00.670 --> 00:41:02.590
see them all night, every night. Well that's

1070
00:41:02.590 --> 00:41:04.230
not right. If the radiance below the horizon,

1071
00:41:04.230 --> 00:41:06.750
you can't see them and you'll see 100 per

1072
00:41:06.750 --> 00:41:08.190
hour and M that's because they've seen the

1073
00:41:08.190 --> 00:41:10.490
zenithal hourly rate, quoted as 100 per hour.

1074
00:41:10.960 --> 00:41:12.320
And they just use it as a number.

1075
00:41:12.720 --> 00:41:13.200
Andrew Dunkley: Yeah.

1076
00:41:13.200 --> 00:41:15.440
Jonti Horner: Unless you are incredibly, incredibly

1077
00:41:15.440 --> 00:41:18.160
fortunate, you will never see the same number

1078
00:41:18.160 --> 00:41:20.640
of meteors as the ZHR predicts

1079
00:41:21.280 --> 00:41:23.440
because the radiant might be directly

1080
00:41:23.440 --> 00:41:25.800
overhead. So the rate gets lower. Your eyes

1081
00:41:25.800 --> 00:41:27.920
are not perfect unless you're one of the very

1082
00:41:27.920 --> 00:41:30.240
rare observers. The rates will get lower,

1083
00:41:30.560 --> 00:41:32.720
there might be light pollution. The phantom

1084
00:41:33.040 --> 00:41:35.200
meteors are not seen, the rates get lower.

1085
00:41:35.280 --> 00:41:37.080
The moon might be in the sky. The phantom

1086
00:41:37.080 --> 00:41:39.890
meters are not seen. The rates are lower. So

1087
00:41:40.370 --> 00:41:42.690
you will never see a number of meteors in the

1088
00:41:42.690 --> 00:41:45.650
sky equal to the ZHR unless the meteor

1089
00:41:45.650 --> 00:41:48.090
shower is more active than predicted in which

1090
00:41:48.090 --> 00:41:49.930
case the ZHR will be higher and you'd see

1091
00:41:49.930 --> 00:41:52.810
more. Where this really comes in is for

1092
00:41:52.810 --> 00:41:54.410
meteor showers like the Perseids. The

1093
00:41:54.410 --> 00:41:56.210
Perseids are one of the big three. There are

1094
00:41:56.600 --> 00:41:59.010
AH3 awesome meteor showers a year that are by

1095
00:41:59.010 --> 00:42:01.730
far the best in a given year.

1096
00:42:01.970 --> 00:42:03.970
They're the highest rates, the most dust

1097
00:42:04.380 --> 00:42:06.860
coming in. Other high speed, the Quadrantids

1098
00:42:06.860 --> 00:42:09.740
in early January are very, very short

1099
00:42:09.740 --> 00:42:11.300
lived. They're a wage shower. You've got a

1100
00:42:11.300 --> 00:42:13.060
very low rate of meteors for most of the time

1101
00:42:13.060 --> 00:42:14.820
they're active and then a very narrow spike

1102
00:42:14.820 --> 00:42:17.780
that can be very big. But if you manage

1103
00:42:17.780 --> 00:42:19.660
to see that spike there's a lot of meteors.

1104
00:42:19.979 --> 00:42:21.700
They're only really visible from the northern

1105
00:42:21.700 --> 00:42:24.540
hemisphere. The Perseids in August are

1106
00:42:24.540 --> 00:42:26.780
probably uh, the most storied meteor shower

1107
00:42:27.500 --> 00:42:30.140
with long history of observations

1108
00:42:31.150 --> 00:42:32.790
linked to comet Swift Tuttle which goes

1109
00:42:32.790 --> 00:42:34.830
around every 120. 130 years

1110
00:42:35.230 --> 00:42:37.230
incidentally will be incredibly spectacular

1111
00:42:37.230 --> 00:42:39.830
in the year 2126 if people hang around to see

1112
00:42:39.830 --> 00:42:40.110
it.

1113
00:42:40.270 --> 00:42:42.510
Andrew Dunkley: Yeah, okay, I'll write that in my diary.

1114
00:42:43.330 --> 00:42:45.870
Jonti Horner: Um, Perseids are brilliant but their radiant

1115
00:42:45.870 --> 00:42:48.350
is at about 55 degrees north in the sky.

1116
00:42:49.390 --> 00:42:51.590
Fabulous from northern Europe, fabulous from

1117
00:42:51.590 --> 00:42:53.550
North America, places north of the equator to

1118
00:42:53.550 --> 00:42:55.830
get a really good show. But we get articles

1119
00:42:55.830 --> 00:42:58.230
every year on commercial media here in

1120
00:42:58.230 --> 00:43:00.390
Australia saying the persons are happening go

1121
00:43:00.390 --> 00:43:02.270
up tonight and you'll see 100 meters an hour.

1122
00:43:02.750 --> 00:43:04.830
And for most of Australia the radiant never

1123
00:43:04.910 --> 00:43:07.790
even rises, never, you know, south of about

1124
00:43:07.790 --> 00:43:10.070
35 degrees south the radiant will never rise.

1125
00:43:10.070 --> 00:43:12.030
I think that's about the latitude of Sydney.

1126
00:43:13.310 --> 00:43:15.150
North of that it will rise but it'll be very

1127
00:43:15.150 --> 00:43:16.990
low to the horizon. So you'll see a much

1128
00:43:16.990 --> 00:43:19.110
lower rate unless you're in the top, top end.

1129
00:43:19.110 --> 00:43:20.670
If you're in the top end of Australia it's a

1130
00:43:20.670 --> 00:43:23.270
bit different. And so when you see

1131
00:43:23.270 --> 00:43:26.050
articles like this you need to engage

1132
00:43:26.050 --> 00:43:28.010
your science brain and say the journalist

1133
00:43:28.010 --> 00:43:30.130
wrong. Yeah, where's my location?

1134
00:43:30.930 --> 00:43:33.850
What's the radiance? Declination which

1135
00:43:33.850 --> 00:43:36.730
is latitude in the sky effectively figure out

1136
00:43:36.730 --> 00:43:38.210
how high in the sky it'll get and that will

1137
00:43:38.210 --> 00:43:39.730
give you a feel for what you might actually

1138
00:43:39.810 --> 00:43:42.730
see. Now if you want to um, look

1139
00:43:42.730 --> 00:43:44.570
at the meteor shower calendar and figure out

1140
00:43:44.570 --> 00:43:46.250
when there are good ones happening, the

1141
00:43:46.250 --> 00:43:48.930
International Meteor Organization is my go to

1142
00:43:48.930 --> 00:43:51.330
on this. They're a fabulous organization that

1143
00:43:51.330 --> 00:43:53.890
put together every year a calendar and that

1144
00:43:53.890 --> 00:43:55.530
calendar lists all the meteor showers from

1145
00:43:55.530 --> 00:43:57.210
the incredibly minor ones that give one

1146
00:43:57.210 --> 00:43:59.490
meteor every two hours, you know, to the

1147
00:43:59.490 --> 00:44:02.490
major ones. And every year it writes about

1148
00:44:02.490 --> 00:44:05.050
the conditions in terms of moonlight as well.

1149
00:44:05.290 --> 00:44:08.170
Because if the moon is bright, you will see

1150
00:44:08.170 --> 00:44:11.050
far fewer meteors. And coming up in a couple

1151
00:44:11.050 --> 00:44:13.010
of weeks from when we're having this

1152
00:44:13.010 --> 00:44:15.410
discussion, but in the past, as we actually

1153
00:44:15.410 --> 00:44:17.490
go live to air, you've got the peak of the

1154
00:44:17.490 --> 00:44:19.610
Ytraquarids. Now the Yter Aquarids are one of

1155
00:44:19.610 --> 00:44:21.170
the few showers that's better for Southern

1156
00:44:21.170 --> 00:44:22.220
hemisphere than Northern Hemisphere

1157
00:44:22.290 --> 00:44:24.290
hemisphere. Fragments of Comet Hallie, and

1158
00:44:24.290 --> 00:44:26.730
they're at their peak around the 3rd to the

1159
00:44:26.730 --> 00:44:29.690
7th may have quite a broad peak, but

1160
00:44:29.690 --> 00:44:32.370
this year the moon is a waning

1161
00:44:32.370 --> 00:44:34.770
gibbous. So at the time of night when you

1162
00:44:34.770 --> 00:44:36.410
could see these meteors, the sky will be

1163
00:44:36.410 --> 00:44:38.810
really bright and so far fewer will be

1164
00:44:38.810 --> 00:44:41.090
visible than normal. And you can get that

1165
00:44:41.090 --> 00:44:42.970
from these calendars. But the highlight of

1166
00:44:42.970 --> 00:44:44.930
every year for meteor showers is the Geminids

1167
00:44:45.250 --> 00:44:48.170
in December. And they are pretty much global

1168
00:44:48.170 --> 00:44:50.710
as a phenomenon and they're brilliant

1169
00:44:50.710 --> 00:44:52.390
everywhere. Obviously better for the Northern

1170
00:44:52.390 --> 00:44:53.910
hemisphere than the south. That's like a

1171
00:44:53.910 --> 00:44:55.910
recurring theme, but

1172
00:44:56.950 --> 00:44:59.030
they are great every year. And this year,

1173
00:44:59.270 --> 00:45:01.750
Moon will be effectively new. So if you want

1174
00:45:01.750 --> 00:45:03.950
to go see the Geminids peaking on the 14th or

1175
00:45:03.950 --> 00:45:06.230
15th of December, they're the highlight this

1176
00:45:06.230 --> 00:45:07.910
year and pretty much every year.

1177
00:45:08.150 --> 00:45:10.590
Andrew Dunkley: Okay, uh, we're going to take another breath

1178
00:45:10.590 --> 00:45:12.630
and then we'll come back and wrap it all up

1179
00:45:12.630 --> 00:45:14.550
in this episode of Space Nuts with Andrew

1180
00:45:14.550 --> 00:45:15.830
Dunkley and Jonti Horner.

1181
00:45:20.380 --> 00:45:21.660
Jonti Horner: Tranquility Base here.

1182
00:45:21.660 --> 00:45:23.020
Andrew Dunkley: The eagle has landed.

1183
00:45:23.020 --> 00:45:23.900
Jonti Horner: Space gnats.

1184
00:45:24.380 --> 00:45:27.370
Andrew Dunkley: One of my big frustrations, uh,

1185
00:45:27.370 --> 00:45:29.980
when I want to observe comets is I live on a

1186
00:45:29.980 --> 00:45:32.970
very flat area of the planet. Uh,

1187
00:45:32.970 --> 00:45:35.940
we don't have mountains nearby, we barely

1188
00:45:35.940 --> 00:45:38.780
have hills. And a lot of the comets

1189
00:45:38.860 --> 00:45:41.700
are visible, uh, in the low

1190
00:45:41.700 --> 00:45:44.690
horizon just after sunset or

1191
00:45:45.170 --> 00:45:47.890
thereabouts. And they're short lived

1192
00:45:48.050 --> 00:45:51.050
and they're below the horizon way too

1193
00:45:51.050 --> 00:45:53.850
quick. Uh, which makes astrophotography a

1194
00:45:53.850 --> 00:45:56.850
real pain in the butt for me. But it is

1195
00:45:57.090 --> 00:45:59.250
just a quirk of where I live.

1196
00:45:59.710 --> 00:46:01.730
Um, I believe

1197
00:46:02.930 --> 00:46:05.370
that we do have some pretty spectacular ones

1198
00:46:05.370 --> 00:46:08.330
coming up. The one that I've seen

1199
00:46:08.330 --> 00:46:11.210
in my life that was the most spectacular for

1200
00:46:11.210 --> 00:46:13.442
me was in 2007, January

1201
00:46:13.618 --> 00:46:16.490
2007. Uh, the, it

1202
00:46:16.490 --> 00:46:19.210
was Comet McNaught. It was amazing,

1203
00:46:19.370 --> 00:46:22.170
like naked eye, comet wise. It

1204
00:46:22.170 --> 00:46:25.130
was unmissable. Uh, it dominated

1205
00:46:25.130 --> 00:46:28.130
the sky for quite some time. Uh, we don't see

1206
00:46:28.130 --> 00:46:29.690
many like that though, do we?

1207
00:46:30.090 --> 00:46:32.370
Jonti Horner: We don't now. Comet McNaught was probably the

1208
00:46:32.370 --> 00:46:35.050
brightest comet since the 1960s and it was

1209
00:46:35.050 --> 00:46:37.970
truly a great comet. Now when we talk

1210
00:46:37.970 --> 00:46:40.510
about the brightest comets and the ones

1211
00:46:40.510 --> 00:46:42.790
people want to see, great comet is the

1212
00:46:42.790 --> 00:46:44.830
Appalachian people attached to comets. And

1213
00:46:44.830 --> 00:46:46.350
it's got a woolly ish definition. It's

1214
00:46:46.350 --> 00:46:48.110
basically the comet was bright enough and

1215
00:46:48.110 --> 00:46:50.550
spectacular enough that even people who

1216
00:46:50.550 --> 00:46:51.950
weren't that interested could just step

1217
00:46:51.950 --> 00:46:53.750
outside and see it. Comet McNaughts

1218
00:46:53.750 --> 00:46:56.630
definitely like that. Arguably Comet Chichin

1219
00:46:56.630 --> 00:46:59.510
Chan Atlas in 2024 and Comet Atlas in

1220
00:46:59.510 --> 00:47:02.510
early 2025 just made that threshold.

1221
00:47:02.670 --> 00:47:04.990
So if you saw those comets, you'd probably

1222
00:47:04.990 --> 00:47:07.450
say they are right at the lower end of what

1223
00:47:07.450 --> 00:47:10.450
we consider a great comet. On average,

1224
00:47:10.450 --> 00:47:12.570
if you go back through historical comic

1225
00:47:12.570 --> 00:47:14.730
records, you'd probably get about 10 great

1226
00:47:14.730 --> 00:47:17.170
comets per century with very wide

1227
00:47:17.170 --> 00:47:20.130
variants. And that's not one every 10 years.

1228
00:47:20.130 --> 00:47:22.130
They're like buses. You wait 30 years and two

1229
00:47:22.130 --> 00:47:24.410
come along at once. And you saw that back in

1230
00:47:24.410 --> 00:47:27.330
1996 with Comet Hale Bop and Comet Hyakitake,

1231
00:47:27.650 --> 00:47:29.490
which were visible in the sky at the same

1232
00:47:29.490 --> 00:47:32.260
time as great comets. It's really

1233
00:47:32.260 --> 00:47:33.620
hard to predict when they're going to come

1234
00:47:33.620 --> 00:47:35.580
in. But we've seen some really fascinating

1235
00:47:35.660 --> 00:47:38.180
advances in the last few years on two fronts.

1236
00:47:38.180 --> 00:47:41.180
Firstly, our ability to find things

1237
00:47:41.340 --> 00:47:43.740
early has improved. We've got better

1238
00:47:43.740 --> 00:47:46.550
telescopes, more automated surveys, and,

1239
00:47:46.550 --> 00:47:48.300
um, comet maps earlier this year, which

1240
00:47:48.300 --> 00:47:49.700
turned out to be a bit of a disappointment

1241
00:47:49.700 --> 00:47:51.460
for many people, is a really good example of

1242
00:47:51.460 --> 00:47:53.260
that. That's a member of the Kreutz

1243
00:47:53.260 --> 00:47:56.060
sungrazing family. And the Kreuz sungrazers

1244
00:47:56.060 --> 00:47:58.590
have numbered many of the brightest great

1245
00:47:58.590 --> 00:48:00.630
comets of the last couple of thousand years.

1246
00:48:01.510 --> 00:48:03.950
Comet maps was the earliest we've ever found

1247
00:48:03.950 --> 00:48:06.630
a Kreutz sungrazer on the way in, earlier

1248
00:48:06.790 --> 00:48:09.550
even than Comedike Oseci, which was probably

1249
00:48:09.550 --> 00:48:11.870
the brightest comet in the 20th century back

1250
00:48:11.870 --> 00:48:14.750
in the late 1960s. And so people's hopes were

1251
00:48:14.750 --> 00:48:16.750
high. But in reality it was quite a small

1252
00:48:16.750 --> 00:48:18.950
fragment of the Kreutz parents

1253
00:48:19.190 --> 00:48:20.950
sungrazer. These Kreutz comets are all

1254
00:48:20.950 --> 00:48:23.070
fragments of a bigger comet in the past, and

1255
00:48:23.070 --> 00:48:25.030
it just fell apart on its way in. Nothing to

1256
00:48:25.030 --> 00:48:28.010
see here. But our ability to find

1257
00:48:28.010 --> 00:48:30.770
things earlier means that we get more

1258
00:48:30.770 --> 00:48:32.970
warning when a bright comet's coming. Now

1259
00:48:32.970 --> 00:48:35.210
that's not absolutely guaranteed. We had a

1260
00:48:35.210 --> 00:48:37.990
comet and the name of it slipped my mind. Um,

1261
00:48:37.990 --> 00:48:40.970
Comet 12, 18 months ago. Um, no,

1262
00:48:40.970 --> 00:48:43.810
I think it was like last September

1263
00:48:44.210 --> 00:48:46.650
that was discovered when it was almost naked

1264
00:48:46.650 --> 00:48:49.330
eye visibility. It just about became naked

1265
00:48:49.330 --> 00:48:51.830
eye visible wasn't great by any means. Swan.

1266
00:48:51.830 --> 00:48:54.350
We got no warning. That's it, Comet Swan. And

1267
00:48:54.350 --> 00:48:56.630
the reason that that was found so late was it

1268
00:48:56.630 --> 00:48:58.910
came at us from behind the sun and suddenly

1269
00:48:58.910 --> 00:49:01.350
popped into view. So that does still happen,

1270
00:49:01.830 --> 00:49:04.270
but with facilities like Vera Rubin coming

1271
00:49:04.270 --> 00:49:05.950
online, we're going to find comets earlier

1272
00:49:05.950 --> 00:49:08.550
and earlier, which means we get more prior

1273
00:49:08.550 --> 00:49:10.430
warning. But it also means that the

1274
00:49:10.430 --> 00:49:12.230
uncertainty about how bright they're going to

1275
00:49:12.230 --> 00:49:13.950
get is possibly even higher because we're

1276
00:49:13.950 --> 00:49:16.590
almost finding them now before they've really

1277
00:49:16.590 --> 00:49:18.310
started to become active. While they're far

1278
00:49:18.310 --> 00:49:19.670
enough from the sun that we're almost seeing

1279
00:49:19.670 --> 00:49:22.560
a bare nuclear nucleus, or we're seeing

1280
00:49:22.560 --> 00:49:24.200
a much smaller comet that's had a little bit

1281
00:49:24.200 --> 00:49:26.320
of an outburst at that distance and whether

1282
00:49:26.320 --> 00:49:28.520
that far away, we effectively can't tell the

1283
00:49:28.520 --> 00:49:30.000
difference. They're still like a single

1284
00:49:30.000 --> 00:49:32.520
pixel. There's a really good example of this

1285
00:49:32.520 --> 00:49:35.410
in the form of Comet Chu Chin Shan. Um,

1286
00:49:35.410 --> 00:49:37.160
not come to Chin Chan ATLAS from a couple of

1287
00:49:37.160 --> 00:49:38.840
years ago, but Comet Chu Chin Shan that has

1288
00:49:38.840 --> 00:49:40.240
just been discovered in the last couple of

1289
00:49:40.240 --> 00:49:42.440
months, Comet C 2026

1290
00:49:42.600 --> 00:49:45.520
C1. As we record this, that

1291
00:49:45.520 --> 00:49:48.000
comet is still more distant from the sun than

1292
00:49:48.000 --> 00:49:50.960
the orbit of Saturn. It was found a couple of

1293
00:49:50.960 --> 00:49:52.600
months ago. It will not be at its closest to

1294
00:49:52.600 --> 00:49:55.040
some perihelion until November

1295
00:49:55.040 --> 00:49:57.480
2028. So we've got two and a half years to

1296
00:49:57.480 --> 00:50:00.320
wait. Now, what factors

1297
00:50:00.320 --> 00:50:01.840
into a comet's brightness is very

1298
00:50:01.840 --> 00:50:04.080
complicated. Um, but it can boil down to a

1299
00:50:04.080 --> 00:50:06.720
few different things. Firstly, if everything

1300
00:50:06.720 --> 00:50:09.280
else is equal. So imagine we only change one

1301
00:50:09.280 --> 00:50:11.960
thing. Typically, the bigger the nucleus of

1302
00:50:11.960 --> 00:50:14.940
the comet, the bigger its surface area is. So

1303
00:50:14.940 --> 00:50:17.860
the more dust and gas it can produce. And we

1304
00:50:17.860 --> 00:50:19.460
see the comet from the light that is

1305
00:50:19.460 --> 00:50:21.180
reflected from the dust and gas. That's what

1306
00:50:21.180 --> 00:50:23.450
makes the tails and the coma. The snowballs,

1307
00:50:23.450 --> 00:50:24.620
ah, at the head were actually pretty small.

1308
00:50:24.620 --> 00:50:27.100
Comet McNaught was only about 5km across

1309
00:50:27.580 --> 00:50:30.140
for the nucleus, but it grew tails more than

1310
00:50:30.140 --> 00:50:31.980
300 million kilometers long.

1311
00:50:32.060 --> 00:50:33.340
Andrew Dunkley: Yeah, that's a little bit different.

1312
00:50:33.580 --> 00:50:34.300
Incredible.

1313
00:50:34.700 --> 00:50:36.900
Jonti Horner: So if you have two cometary nuclei that, uh,

1314
00:50:36.900 --> 00:50:39.340
are in all senses identical other than their

1315
00:50:39.340 --> 00:50:41.700
size, the bigger one will typically be more

1316
00:50:41.700 --> 00:50:43.420
active and produce more gas and dust.

1317
00:50:44.650 --> 00:50:47.450
However, some comets have a m larger fraction

1318
00:50:47.450 --> 00:50:49.650
of their surface active than others. Some

1319
00:50:49.650 --> 00:50:51.730
comets are almost dormant because they're

1320
00:50:51.730 --> 00:50:53.170
clogged up and there's very little activity

1321
00:50:53.170 --> 00:50:55.530
even from a larger nucleus. So already a bit

1322
00:50:55.530 --> 00:50:58.050
complex. But first rule of thumb, um, the

1323
00:50:58.050 --> 00:50:59.969
bigger the nucleus, the more likelihood there

1324
00:50:59.969 --> 00:51:01.370
is that it will be able to produce a lot of

1325
00:51:01.370 --> 00:51:03.770
gas and Dust and be more spectacular. With

1326
00:51:03.770 --> 00:51:06.130
Comet Chu Chen Shan, that's interesting. We

1327
00:51:06.130 --> 00:51:08.450
found it so far away, which suggests it is

1328
00:51:08.450 --> 00:51:10.250
either a comet with quite a large nucleus,

1329
00:51:10.790 --> 00:51:12.950
because it's probably not that active at that

1330
00:51:12.950 --> 00:51:15.350
distance, but it may have just had a bit of

1331
00:51:15.350 --> 00:51:17.990
an outburst of activity driven by something

1332
00:51:17.990 --> 00:51:20.430
like carbon monoxide, which can turn from

1333
00:51:20.430 --> 00:51:22.830
solid gas at a very low temperature. So it

1334
00:51:22.830 --> 00:51:24.870
might be masquerading as a bigger comet than

1335
00:51:24.870 --> 00:51:25.990
it is, and we don't know.

1336
00:51:26.469 --> 00:51:27.030
Andrew Dunkley: Okay.

1337
00:51:27.110 --> 00:51:29.030
Jonti Horner: The next thing that factors into how bright a

1338
00:51:29.030 --> 00:51:30.750
comet gets is how close it gets to the Sun.

1339
00:51:30.750 --> 00:51:33.230
So the closer it gets to the sun, the hotter

1340
00:51:33.230 --> 00:51:35.510
its surface gets and the more strongly it

1341
00:51:35.510 --> 00:51:38.110
will be active. So with Comet McNaught, you

1342
00:51:38.110 --> 00:51:40.910
had a five kilometer nucleus, which is fairly

1343
00:51:40.910 --> 00:51:42.710
respectable, but not as big as Hale Bopp,

1344
00:51:42.710 --> 00:51:45.510
which was 50km. Hale Bok was ridiculous.

1345
00:51:45.830 --> 00:51:48.030
But Comet McNaught got very close into the

1346
00:51:48.030 --> 00:51:50.630
Sun. Um, so it got really incredibly

1347
00:51:50.630 --> 00:51:52.270
intensely active, was throwing off huge

1348
00:51:52.270 --> 00:51:55.230
amounts of gas and dust. So that contributed

1349
00:51:55.230 --> 00:51:57.870
again to more stuff to reflect sunlight. And

1350
00:51:57.870 --> 00:51:59.710
also being nearer to the sun, the intensity

1351
00:51:59.710 --> 00:52:01.470
of light reflecting off its higher as well.

1352
00:52:01.470 --> 00:52:03.970
So kind of get a double whammy there. The

1353
00:52:03.970 --> 00:52:05.650
other factor is how close they get to the

1354
00:52:05.650 --> 00:52:07.930
Earth. So if you have two comets that are the

1355
00:52:07.930 --> 00:52:09.850
same size and the same distance from the sun,

1356
00:52:10.170 --> 00:52:11.890
and, um, one is closer to the Earth than the

1357
00:52:11.890 --> 00:52:13.970
other, the one closer to the Earth will be

1358
00:52:13.970 --> 00:52:15.570
brighter, but will also potentially be more

1359
00:52:15.570 --> 00:52:17.690
spread out and more diffuse in the sky. So

1360
00:52:17.690 --> 00:52:19.169
that brightness might be spread over a

1361
00:52:19.169 --> 00:52:21.610
different area. You've then got

1362
00:52:21.690 --> 00:52:24.170
subtleties of how dusty or gassy they are.

1363
00:52:24.250 --> 00:52:27.210
Some comets, like Comet Pan, stars seem

1364
00:52:27.210 --> 00:52:29.610
to be more gassy. Some comets like Church and

1365
00:52:29.610 --> 00:52:31.330
Chan Atlas was more dusty. And that can have

1366
00:52:31.330 --> 00:52:33.880
an impact on how they brighten. Bringing all

1367
00:52:33.880 --> 00:52:35.320
this back together, though, for Comet Chu

1368
00:52:35.320 --> 00:52:38.280
Chin Chan, at its closest to the sun,

1369
00:52:38.360 --> 00:52:40.120
it will be a little bit further from the sun

1370
00:52:40.120 --> 00:52:41.920
than the Earth, uh, is. So it's not like

1371
00:52:41.920 --> 00:52:43.480
Comet McNaught that's going to get really

1372
00:52:43.480 --> 00:52:46.400
close in. But one AU from the Sun's fairly

1373
00:52:46.400 --> 00:52:48.120
respectable. It can still maintain a fairly

1374
00:52:48.120 --> 00:52:49.920
decent level of activity at that distance.

1375
00:52:49.920 --> 00:52:51.840
Comet Hale Bopp didn't get much closer than

1376
00:52:51.840 --> 00:52:54.720
that and was fantastic. So that's in its

1377
00:52:54.720 --> 00:52:56.000
favorite. It's going to get close enough in

1378
00:52:56.000 --> 00:52:57.960
that you could get a decent level of

1379
00:52:58.200 --> 00:53:01.090
activity. Also, because

1380
00:53:01.090 --> 00:53:03.050
it's only going to get that close to the sun,

1381
00:53:03.050 --> 00:53:04.490
it'll take a bit longer to pass through the

1382
00:53:04.490 --> 00:53:06.090
inner solar system. Comets that get really

1383
00:53:06.090 --> 00:53:08.850
close to the sun get traveling incredibly

1384
00:53:08.850 --> 00:53:10.450
quickly at that point. So they tend to whip

1385
00:53:10.450 --> 00:53:11.970
in and whip out fairly quickly. Whereas with

1386
00:53:11.970 --> 00:53:14.010
cometary chinchan, it's going to hang around

1387
00:53:14.010 --> 00:53:16.570
for a fair while. It is

1388
00:53:16.570 --> 00:53:19.170
potentially quite a large cometary nucleus,

1389
00:53:19.170 --> 00:53:22.130
but we don't know yet. This is the caution I

1390
00:53:22.130 --> 00:53:24.410
give. If it turns out that we've caught it

1391
00:53:24.410 --> 00:53:25.930
during an outburst, it may be a bit of a

1392
00:53:25.930 --> 00:53:27.690
disappointment. If we've actually seen it as

1393
00:53:27.690 --> 00:53:30.490
a bare nucleus. That augurs very, very

1394
00:53:31.030 --> 00:53:33.670
well. What this all suggests is that Comet

1395
00:53:33.670 --> 00:53:35.590
Chichin Shan, um, has a potential to be

1396
00:53:35.590 --> 00:53:37.910
bright in late 2028.

1397
00:53:38.390 --> 00:53:40.670
Depending on which fit to its current

1398
00:53:40.670 --> 00:53:43.110
brightness you use. It could become barely

1399
00:53:43.110 --> 00:53:45.150
naked eye visible, which is still pretty

1400
00:53:45.150 --> 00:53:47.990
good. You know, we see 20 or 30 comets a year

1401
00:53:48.230 --> 00:53:50.230
and very, uh, only maybe one will get to

1402
00:53:50.230 --> 00:53:52.510
naked eye visibility. Or it could get as

1403
00:53:52.510 --> 00:53:54.230
bright as the brightest stars. And if it gets

1404
00:53:54.230 --> 00:53:56.590
as bright as the brightest stars, then it

1405
00:53:56.590 --> 00:53:58.980
gets into great comet type territory.

1406
00:53:59.380 --> 00:54:01.100
That's a factor of 100 difference in

1407
00:54:01.100 --> 00:54:03.530
brightness between those two extremes. And,

1408
00:54:03.530 --> 00:54:05.220
um, it could get brighter than the brightest

1409
00:54:05.220 --> 00:54:06.980
extreme there or fainter than the faintest

1410
00:54:06.980 --> 00:54:09.340
extreme. We just don't know yet. But having

1411
00:54:09.340 --> 00:54:11.940
found it so early augurs well. But typically,

1412
00:54:12.660 --> 00:54:14.900
predicting the next great comet is a fool's

1413
00:54:14.900 --> 00:54:17.620
bargain until it's discovered. What we can

1414
00:54:17.620 --> 00:54:20.580
say is that there are a few periodic comets

1415
00:54:20.660 --> 00:54:23.260
that will be great in the future. Comet

1416
00:54:23.260 --> 00:54:25.620
Hallie will be a lot better in 2061 than it

1417
00:54:25.620 --> 00:54:28.420
was in 1986. In 1986, we had the

1418
00:54:28.420 --> 00:54:30.320
worst separation of Comet Hallie for 2,000

1419
00:54:30.400 --> 00:54:30.800
years.

1420
00:54:30.960 --> 00:54:31.920
Andrew Dunkley: Tell me about it.

1421
00:54:31.920 --> 00:54:34.880
Jonti Horner: Yeah, a bit disappointing. 2071

1422
00:54:34.880 --> 00:54:35.600
will be better.

1423
00:54:35.920 --> 00:54:38.280
Andrew Dunkley: Oh, good. I don't know if I'll be around by

1424
00:54:38.280 --> 00:54:40.480
then, but, um, probably not.

1425
00:54:40.480 --> 00:54:43.480
Jonti Horner: I'll be 99, make everybody

1426
00:54:43.480 --> 00:54:45.560
feel really cheerful. It's now closer to

1427
00:54:45.560 --> 00:54:47.400
Comet Hallie's next apparition than the last

1428
00:54:47.400 --> 00:54:49.120
one. It turned around, I think, last year. So

1429
00:54:49.120 --> 00:54:51.280
it's on its way back. Yeah, Comet Hallie will

1430
00:54:51.280 --> 00:54:54.160
be even better in 21:35, will

1431
00:54:54.160 --> 00:54:55.800
be really good that year. And that will be

1432
00:54:55.800 --> 00:54:57.480
the best apparition for a couple of hundred

1433
00:54:57.480 --> 00:55:00.030
years. Comet Swift Tuttle will be incredible

1434
00:55:00.030 --> 00:55:02.230
in 21:26. We know that because we know pretty

1435
00:55:02.230 --> 00:55:03.830
much exactly when it'll come back. We know

1436
00:55:03.830 --> 00:55:05.230
where it will be compared to the Earth and

1437
00:55:05.230 --> 00:55:07.670
the Sun. There is a suggestion that in

1438
00:55:07.670 --> 00:55:10.470
2097 we may have the comet of the century, or

1439
00:55:10.470 --> 00:55:12.470
close to it. This is research that came out

1440
00:55:12.470 --> 00:55:15.390
last year. One of the greatest comets of the

1441
00:55:15.390 --> 00:55:18.200
last thousand years was Comet De chezo, uh,

1442
00:55:18.200 --> 00:55:21.150
in 1744, also called Comet

1443
00:55:21.150 --> 00:55:23.310
Clinkenberg comet that is famous for having

1444
00:55:23.310 --> 00:55:26.130
had six tails, incredibly bright, almost

1445
00:55:26.130 --> 00:55:28.850
visible in broad daylight. A couple of

1446
00:55:28.850 --> 00:55:30.890
astronomers, I think the lead researcher on

1447
00:55:30.890 --> 00:55:33.610
this was Mike Meyer, published a paper last

1448
00:55:33.610 --> 00:55:35.370
year that went back through historical

1449
00:55:35.370 --> 00:55:38.250
observations and found a number of previous

1450
00:55:38.250 --> 00:55:40.290
comets over the last 2,000 years that were

1451
00:55:40.290 --> 00:55:42.890
all incredibly bright, really spectacular,

1452
00:55:43.370 --> 00:55:45.210
but seem to have been moving the same as that

1453
00:55:45.210 --> 00:55:47.770
comet. Linked them together and it's a very

1454
00:55:47.770 --> 00:55:50.090
compelling tale that if their research is

1455
00:55:50.090 --> 00:55:52.500
correct, that comet actually has an orbital

1456
00:55:52.500 --> 00:55:55.060
period of just a little bit less. Just around

1457
00:55:55.060 --> 00:55:57.780
450 years, I think. 400 years?

1458
00:55:57.860 --> 00:56:00.860
No, 350 years. Wouldn't it do the mental

1459
00:56:00.860 --> 00:56:03.220
arithmetic? Yeah, about 350 years,

1460
00:56:03.620 --> 00:56:05.940
which means it should return in 2097.

1461
00:56:06.420 --> 00:56:09.300
And if it does, it will be awesome.

1462
00:56:09.660 --> 00:56:11.460
Um, sadly I don't think you or I will be

1463
00:56:11.460 --> 00:56:12.100
around for that.

1464
00:56:12.500 --> 00:56:14.140
Andrew Dunkley: Probably not, probably not.

1465
00:56:14.140 --> 00:56:16.180
Jonti Horner: But things like that we can predict. But most

1466
00:56:16.340 --> 00:56:18.620
Fred will be. But um, absolutely, Fred is

1467
00:56:18.620 --> 00:56:20.500
indestructible and I'll stand um, by that.

1468
00:56:21.130 --> 00:56:23.850
But most of the big cometary nuclei coming

1469
00:56:23.850 --> 00:56:26.330
through are on such long period orbits, with

1470
00:56:26.330 --> 00:56:28.490
the exception of Hallie and Swift Tuttle,

1471
00:56:28.810 --> 00:56:30.770
that their apparitions are so infrequent that

1472
00:56:30.770 --> 00:56:32.530
we've not identified them as periodic

1473
00:56:32.530 --> 00:56:34.570
visitors. And many of them have periods of

1474
00:56:34.730 --> 00:56:37.290
thousands or tens of thousands of years. So

1475
00:56:37.290 --> 00:56:39.970
we typically only find them on their way in a

1476
00:56:39.970 --> 00:56:42.090
few weeks or a few months before

1477
00:56:42.730 --> 00:56:44.530
apparition. In case of Comet Hale Bopp, it

1478
00:56:44.530 --> 00:56:47.090
was two years, which was exceptional at the

1479
00:56:47.090 --> 00:56:49.260
time. Case of Comet Chichin Shan, it's more

1480
00:56:49.260 --> 00:56:51.660
than two and a half years away, but our

1481
00:56:51.660 --> 00:56:54.620
technology has improved hugely. So I don't

1482
00:56:54.620 --> 00:56:56.060
think it's fair necessarily to say that

1483
00:56:56.060 --> 00:56:59.020
Church and Chan will be another hell bop. But

1484
00:56:59.020 --> 00:57:01.020
if you look at the brighter end of the

1485
00:57:01.020 --> 00:57:02.700
predictions, it could be naked eye visible

1486
00:57:02.700 --> 00:57:04.100
for three, four, five months.

1487
00:57:04.420 --> 00:57:04.900
Andrew Dunkley: Wow.

1488
00:57:04.900 --> 00:57:06.780
Jonti Horner: Would be awesome. And it would potentially be

1489
00:57:06.780 --> 00:57:08.820
circumpolar for us in the Southern Hemisphere

1490
00:57:08.980 --> 00:57:10.740
because at its closest to the center of the

1491
00:57:10.740 --> 00:57:12.980
Earth, it's going to be way south, not going

1492
00:57:12.980 --> 00:57:15.110
to be good for the Northern Hemisphere. But

1493
00:57:15.110 --> 00:57:16.710
we can't really predict that. It's the same

1494
00:57:16.710 --> 00:57:18.550
with meteor showers. We can predict the

1495
00:57:18.550 --> 00:57:20.590
annual ones roughly how good they're going to

1496
00:57:20.590 --> 00:57:23.390
be. And if you go back to when I was a

1497
00:57:23.390 --> 00:57:25.510
kid, we couldn't really predict meteor

1498
00:57:25.510 --> 00:57:27.230
storms, meteor outbursts, and that's one of

1499
00:57:27.230 --> 00:57:28.790
the things people really love to see. So

1500
00:57:28.790 --> 00:57:30.950
Geminids are great Northern Hemisphere,

1501
00:57:30.950 --> 00:57:33.590
you'll see maybe even 80 or 100 an hour at

1502
00:57:33.590 --> 00:57:35.070
their peak in the early hours of the morning.

1503
00:57:35.150 --> 00:57:37.870
I've seen 50 an hour from our latitude near

1504
00:57:37.870 --> 00:57:38.510
Brisbane.

1505
00:57:38.510 --> 00:57:40.750
They're really good. But what people really

1506
00:57:40.750 --> 00:57:42.870
want to see are meteor storms and they're

1507
00:57:42.870 --> 00:57:45.600
much rarer. There's a few amazing ones.

1508
00:57:45.600 --> 00:57:47.160
Historically. There was one in

1509
00:57:47.560 --> 00:57:50.560
1833 that was linked to the Leonid meteor

1510
00:57:50.560 --> 00:57:53.520
shower that had a rate in excess

1511
00:57:53.520 --> 00:57:56.360
of a hundred thousand an hour, was best seen

1512
00:57:56.600 --> 00:57:59.420
from the contiguous US and

1513
00:57:59.420 --> 00:58:01.760
um, it was bright enough. There were

1514
00:58:01.760 --> 00:58:04.600
sufficient meteors in the sky that miners in

1515
00:58:04.600 --> 00:58:07.520
the US were woken from their campsites

1516
00:58:07.520 --> 00:58:09.480
by the light shining through their tents. And

1517
00:58:09.560 --> 00:58:11.480
people were convinced that the end times had

1518
00:58:11.480 --> 00:58:14.150
come. The Apocalypse was here because he were

1519
00:58:14.150 --> 00:58:16.590
getting as many as 20 meteors per second.

1520
00:58:17.230 --> 00:58:17.900
Andrew Dunkley: Incredible.

1521
00:58:17.900 --> 00:58:20.870
Jonti Horner: Um, now that in the way that kind of Tycho's

1522
00:58:20.870 --> 00:58:23.430
observations in 1577 were probably the birth

1523
00:58:23.430 --> 00:58:25.310
of modern cometary astronomy.

1524
00:58:25.710 --> 00:58:28.310
1833, I think was possibly the birth of

1525
00:58:28.310 --> 00:58:30.550
modern meteor astronomy. Because there'd been

1526
00:58:30.550 --> 00:58:33.430
a storm from the Leonidas in 1799. People

1527
00:58:33.430 --> 00:58:35.430
predicted that there might be another one in

1528
00:58:35.430 --> 00:58:37.870
1866 because maybe this was happening every

1529
00:58:37.870 --> 00:58:40.470
33 years when the comet came back. And indeed

1530
00:58:40.470 --> 00:58:42.110
that happened in 1866.

1531
00:58:43.360 --> 00:58:45.760
And so that was a bit like the birth of

1532
00:58:45.840 --> 00:58:48.120
modern meteor science. And after that people

1533
00:58:48.120 --> 00:58:50.120
said, well, there'll be one in 1899 and there

1534
00:58:50.120 --> 00:58:52.800
wasn't. So that then tripped people up.

1535
00:58:52.880 --> 00:58:55.800
So thanks to that we've gradually developed

1536
00:58:55.800 --> 00:58:57.560
a better understanding of the physics of how

1537
00:58:57.560 --> 00:59:00.200
meteor showers work. And I'm aware time is

1538
00:59:00.200 --> 00:59:02.200
running away from us, but for people

1539
00:59:02.200 --> 00:59:05.200
interested in this, in the run up to, uh, the

1540
00:59:05.680 --> 00:59:08.280
heavily activity in 1999 through to

1541
00:59:08.280 --> 00:59:10.970
2002, there was some amazing research

1542
00:59:11.130 --> 00:59:13.530
done by um, David Asher

1543
00:59:13.770 --> 00:59:16.450
from Amar Observatory and I think fondly on

1544
00:59:16.450 --> 00:59:18.090
David because he was a lovely mentor to me

1545
00:59:18.090 --> 00:59:20.810
when I visited Armagh in 1999. Very

1546
00:59:20.810 --> 00:59:22.730
quiet guy, but incredibly talented

1547
00:59:22.730 --> 00:59:25.730
scientists. And he did this remarkable

1548
00:59:25.730 --> 00:59:28.570
work making predictions of when we would

1549
00:59:28.570 --> 00:59:31.290
and wouldn't get Leonid storms by

1550
00:59:31.290 --> 00:59:33.490
modeling the ejection of dust from the

1551
00:59:33.490 --> 00:59:35.450
cometary nucleus and evolving the dust

1552
00:59:35.450 --> 00:59:38.000
forward in time and go back. Way earlier on I

1553
00:59:38.000 --> 00:59:40.240
mentioned these javelin spikes.

1554
00:59:41.680 --> 00:59:43.760
He effectively modelled those and figured out

1555
00:59:43.760 --> 00:59:45.480
where the spikes will be in a slight nudge up

1556
00:59:45.480 --> 00:59:47.120
or down means that, uh, the Earth will run

1557
00:59:47.120 --> 00:59:48.920
through the spike or not. And the great

1558
00:59:48.920 --> 00:59:51.360
Leonid storms are produced by dust left

1559
00:59:51.360 --> 00:59:54.240
behind just one or two revolutions ago. So

1560
00:59:54.240 --> 00:59:56.760
the activity between 1999 and

1561
00:59:56.760 --> 00:59:59.520
2002 resulted from a few different

1562
00:59:59.680 --> 01:00:02.160
streams. The older they are, the more diffuse

1563
01:00:02.160 --> 01:00:04.490
they get. But now we have the ability for

1564
01:00:04.570 --> 01:00:06.490
comets we know well and meteor showers we

1565
01:00:06.490 --> 01:00:08.810
know well to figure out where those spikes

1566
01:00:08.810 --> 01:00:10.570
are roughly going to be how long they are

1567
01:00:10.890 --> 01:00:13.530
and, uh, make predictions going forward. Now,

1568
01:00:13.770 --> 01:00:15.450
there aren't any great meteor storms

1569
01:00:15.450 --> 01:00:17.170
predicted in the relatively near future. The

1570
01:00:17.170 --> 01:00:19.730
Leonids are not likely to give major storms

1571
01:00:19.730 --> 01:00:22.570
in 2033 or 2066, but will give

1572
01:00:22.570 --> 01:00:25.090
increased activity. The reason for that is

1573
01:00:25.090 --> 01:00:27.810
Jupiter and Saturn are pulling those javelins

1574
01:00:27.810 --> 01:00:29.890
around and making them miss the Earth.

1575
01:00:30.840 --> 01:00:32.800
The leanings will probably return in force

1576
01:00:32.800 --> 01:00:35.600
in, I think, 2097 with the possibility of a

1577
01:00:35.600 --> 01:00:38.600
storm of like 20,000 an hour. But

1578
01:00:38.600 --> 01:00:40.160
we're getting to understand that. So with

1579
01:00:40.160 --> 01:00:42.680
meteor showers, we can predict the annual

1580
01:00:42.680 --> 01:00:45.120
showers. They're very reliable. They

1581
01:00:45.120 --> 01:00:46.960
gradually get better and worse with time as

1582
01:00:46.960 --> 01:00:49.040
the streams move around and we intersect more

1583
01:00:49.040 --> 01:00:51.320
of the material or less. But they're pretty

1584
01:00:51.400 --> 01:00:54.360
reliable. Outbursts are harder

1585
01:00:54.360 --> 01:00:56.120
to predict, but we're getting better at doing

1586
01:00:56.120 --> 01:00:59.060
it. But predicting an

1587
01:00:59.060 --> 01:01:00.580
outburst from a shower we've never seen

1588
01:01:00.580 --> 01:01:03.260
before or a shower that's incredibly rare,

1589
01:01:03.580 --> 01:01:06.420
we typically can't do until it happens

1590
01:01:06.420 --> 01:01:08.460
because we need to have a feel for what it's

1591
01:01:08.460 --> 01:01:10.900
done in the past. So we occasionally will get

1592
01:01:10.900 --> 01:01:12.500
an outburst of a meteor shower we've never

1593
01:01:12.500 --> 01:01:15.220
seen before. And you can't predict that. And

1594
01:01:15.220 --> 01:01:17.140
that's when it's really exciting because then

1595
01:01:17.140 --> 01:01:19.460
you can start to learn about a new meteor

1596
01:01:19.460 --> 01:01:21.180
shower being born. You can learn about the

1597
01:01:21.180 --> 01:01:23.270
comet that birthed it. It put all that

1598
01:01:23.270 --> 01:01:24.870
together. And, um, that's one of the things

1599
01:01:24.870 --> 01:01:26.670
where I'll go out and I love my meteor

1600
01:01:26.670 --> 01:01:28.230
showers. I'll sit out under the sky and watch

1601
01:01:28.230 --> 01:01:30.070
them. But I would love to just be outside

1602
01:01:30.070 --> 01:01:31.950
when there's an unexpected outburst, when we

1603
01:01:31.950 --> 01:01:33.990
see something new like a meteor shower being

1604
01:01:33.990 --> 01:01:35.190
born for the first time.

1605
01:01:35.670 --> 01:01:38.349
Andrew Dunkley: And, and that's what we recommend to all our

1606
01:01:38.349 --> 01:01:40.870
Spacenads listeners. Uh, get up at 2 o' clock

1607
01:01:40.870 --> 01:01:43.750
every morning, every day and go

1608
01:01:43.750 --> 01:01:45.710
out and just wait and, you know, one day

1609
01:01:45.710 --> 01:01:48.430
you'll get lucky. Might take 20 years, but it

1610
01:01:48.430 --> 01:01:48.750
doesn't

1611
01:01:48.750 --> 01:01:51.230
Jonti Horner: have to be 2:00am I mean, there is a little

1612
01:01:51.230 --> 01:01:53.350
bit of a preference for meteor showers to be

1613
01:01:53.670 --> 01:01:56.070
more active in the morning hours, in the

1614
01:01:56.070 --> 01:01:57.830
evening hours. But that's purely a geometry

1615
01:01:57.830 --> 01:01:59.750
thing. It's linked a little bit to the

1616
01:01:59.750 --> 01:02:01.030
direction of the Earth's motion and the

1617
01:02:01.030 --> 01:02:02.510
direction things are crossing the Earth's

1618
01:02:02.510 --> 01:02:04.990
orbit in that if you think about something

1619
01:02:04.990 --> 01:02:07.030
crossing the Earth's orbit at right angles to

1620
01:02:07.030 --> 01:02:09.390
the Earth because the Earth's Moving forward

1621
01:02:09.390 --> 01:02:12.350
at 30km a second, the direction you would see

1622
01:02:12.350 --> 01:02:14.230
that coming from is actually a bit ahead of

1623
01:02:14.230 --> 01:02:15.640
you because you've got the addition of the,

1624
01:02:15.710 --> 01:02:17.430
the speed the debris is going on the speed

1625
01:02:17.430 --> 01:02:20.190
the Earth's moving. So meteor showers

1626
01:02:21.390 --> 01:02:24.390
that are uh, visible with radiance that will

1627
01:02:24.390 --> 01:02:26.390
be in the morning sky, you've got a little

1628
01:02:26.390 --> 01:02:27.990
bit of an additive effect between the speed

1629
01:02:27.990 --> 01:02:29.670
the debris is going and the speed the Earth's

1630
01:02:29.670 --> 01:02:32.030
moving, which means the average impact speed

1631
01:02:32.030 --> 01:02:33.510
of the debris is higher and you get more

1632
01:02:33.510 --> 01:02:36.470
meteors. But also you get this effect of

1633
01:02:36.470 --> 01:02:37.950
the Earth's motion being a bit like you're

1634
01:02:37.950 --> 01:02:40.310
driving into a snowstorm. You know, if you're

1635
01:02:40.310 --> 01:02:42.150
driving into a snowstorm where there's no

1636
01:02:42.150 --> 01:02:43.630
wind and the snowflakes are falling down

1637
01:02:43.630 --> 01:02:45.530
vertically, vertically, you will perceive

1638
01:02:45.530 --> 01:02:47.410
them as coming from in front of your car, not

1639
01:02:47.410 --> 01:02:49.850
overhead. And so there's a preference for

1640
01:02:49.850 --> 01:02:51.850
meteor showers to be slightly more likely to

1641
01:02:51.850 --> 01:02:53.410
have activity that peaks in the morning hours

1642
01:02:53.410 --> 01:02:55.650
in the evening. But that's not a guarantee.

1643
01:02:55.890 --> 01:02:58.210
There are some meteor showers that are at the

1644
01:02:58.210 --> 01:02:59.930
highest where the radiant culminates in the

1645
01:02:59.930 --> 01:03:02.850
evening sky. It just depends. Some

1646
01:03:03.250 --> 01:03:05.330
like the Utrecht, are only visible for a

1647
01:03:05.330 --> 01:03:06.810
couple of hours before dawn. Um, there's even

1648
01:03:06.810 --> 01:03:08.810
a few meteor showers that are daylight

1649
01:03:08.810 --> 01:03:10.530
showers where the radiance only really above

1650
01:03:10.530 --> 01:03:12.900
the horizon during the hours of daylight. And

1651
01:03:12.900 --> 01:03:14.580
we know about them primarily from radio

1652
01:03:14.580 --> 01:03:17.340
observations. Radar, well not radar. People

1653
01:03:17.340 --> 01:03:20.340
listening to radio reflecting off the ionized

1654
01:03:20.340 --> 01:03:22.380
streaks that the meteors leave in the

1655
01:03:22.380 --> 01:03:24.860
ionosphere. That allows you to see over the

1656
01:03:24.860 --> 01:03:27.140
horizon to radio sessions that are

1657
01:03:27.140 --> 01:03:28.700
broadcasting that you don't normally get. So

1658
01:03:28.700 --> 01:03:31.300
you can hear meteor showers? Yeah, so we know

1659
01:03:31.300 --> 01:03:33.060
there are daytime showers that uh, we cannot

1660
01:03:33.060 --> 01:03:35.020
see at night. And some of them are possibly

1661
01:03:35.180 --> 01:03:37.140
as active as the Geminids of the Perseids.

1662
01:03:37.140 --> 01:03:40.050
If, you know, if we could turn the sun off, I

1663
01:03:40.050 --> 01:03:41.570
mean that would be a bad thing. Please don't

1664
01:03:41.570 --> 01:03:43.170
do it. If you're a super villain listening,

1665
01:03:43.170 --> 01:03:46.050
do not take this as an idea, but if we

1666
01:03:46.050 --> 01:03:47.930
could turn the sun off and see there are a

1667
01:03:47.930 --> 01:03:49.530
couple of meteor showers in the daytime that

1668
01:03:49.530 --> 01:03:51.050
could be pretty spectacular.

1669
01:03:52.170 --> 01:03:54.930
Andrew Dunkley: It is all very fascinating and I suppose the

1670
01:03:54.930 --> 01:03:57.850
best advice would be to go and look for the,

1671
01:03:58.250 --> 01:04:01.170
the better sources of forecasting rather than

1672
01:04:01.170 --> 01:04:02.450
trying to figure it out for yourself.

1673
01:04:02.450 --> 01:04:04.890
And uh, and, and you've mentioned a couple of

1674
01:04:04.890 --> 01:04:07.820
already comet, uh, maps and, and uh,

1675
01:04:07.820 --> 01:04:09.230
what was the other one about meteors?

1676
01:04:09.390 --> 01:04:11.670
Jonti Horner: For meteors, I really strongly recommend the

1677
01:04:11.670 --> 01:04:13.750
International Meteor Organization. If you go

1678
01:04:13.750 --> 01:04:16.630
to their website, hover over the resources

1679
01:04:16.630 --> 01:04:18.590
link, click on it to get the drop down. Click

1680
01:04:18.590 --> 01:04:20.910
on meteor shower calendar. They have on the

1681
01:04:20.910 --> 01:04:23.790
right hand side the best showers of the year

1682
01:04:23.950 --> 01:04:25.630
with information and what the moon will be

1683
01:04:25.630 --> 01:04:27.750
like. But there's also on the left side a PDF

1684
01:04:27.750 --> 01:04:29.910
that you can download that goes into much

1685
01:04:29.910 --> 01:04:31.870
more minute detail and talks about even the

1686
01:04:31.870 --> 01:04:33.970
more minor showers. Um, and that's a very

1687
01:04:33.970 --> 01:04:36.970
good point of truth for meteor showers. Well,

1688
01:04:36.970 --> 01:04:38.930
I kind of describe them being like three

1689
01:04:38.930 --> 01:04:40.450
tiers of meteor showers, ignoring the

1690
01:04:40.450 --> 01:04:42.930
outbursts. There are the big three, which are

1691
01:04:42.930 --> 01:04:44.930
the Quadrantids, the Persons and the

1692
01:04:44.930 --> 01:04:47.130
Geminids, which are uh, even if you're not

1693
01:04:47.130 --> 01:04:49.570
that interested at all in space, and if you

1694
01:04:49.570 --> 01:04:51.450
are, thanks for listening to the podcast

1695
01:04:51.450 --> 01:04:53.450
anyway, but it's not really our target

1696
01:04:53.450 --> 01:04:55.170
audience. But even people who are not that

1697
01:04:55.170 --> 01:04:57.090
interested, that's a spectacle you can go out

1698
01:04:57.090 --> 01:04:58.700
and see with them and share with them them.

1699
01:04:59.020 --> 01:05:00.820
Just make sure that you figure out when the

1700
01:05:00.820 --> 01:05:02.780
radiant rises from your location because you

1701
01:05:02.780 --> 01:05:05.340
don't want to turn people off by looking at a

1702
01:05:05.340 --> 01:05:07.380
time when you can't see meteors. So for the

1703
01:05:07.380 --> 01:05:10.140
Geminids the best time is around 2am but

1704
01:05:10.140 --> 01:05:12.140
depending on where you are in the world, from

1705
01:05:12.380 --> 01:05:15.340
our latitude you're looking at, you can't see

1706
01:05:15.340 --> 01:05:17.260
any before 9:30, 10:00 clock at night.

1707
01:05:17.340 --> 01:05:18.900
Obviously if you're somewhere with daylight

1708
01:05:18.900 --> 01:05:20.580
savings in the southern hemisphere, add an

1709
01:05:20.580 --> 01:05:23.100
hour to that. So for you down in New South

1710
01:05:23.100 --> 01:05:24.460
Wales, where the clocks change, you're

1711
01:05:24.460 --> 01:05:26.870
talking after 11pm for you. But if you're in

1712
01:05:26.870 --> 01:05:29.310
Northern Europe, the Geminid radiant never

1713
01:05:29.310 --> 01:05:31.430
sets. So where I grew up in the uk, as soon

1714
01:05:31.430 --> 01:05:33.430
as it got dark I could see them. The rate

1715
01:05:33.430 --> 01:05:35.110
still got better through the night. Similarly

1716
01:05:35.110 --> 01:05:37.470
for the Perseids in particular. Perseids are

1717
01:05:37.470 --> 01:05:40.270
a northern hemisphere only thing. It's light

1718
01:05:40.270 --> 01:05:41.790
until quite late, certainly for the high

1719
01:05:41.790 --> 01:05:43.630
northern latitudes like the uk, but as soon

1720
01:05:43.630 --> 01:05:45.870
as it gets dark you can see them. So they're

1721
01:05:45.870 --> 01:05:48.030
the showers that uh, are well worth going out

1722
01:05:48.030 --> 01:05:50.390
to look at as a beginner and you just sit out

1723
01:05:50.390 --> 01:05:52.900
there. I would figure out where the radiant

1724
01:05:52.900 --> 01:05:55.100
is and look 30 or 40 degrees to the left or

1725
01:05:55.100 --> 01:05:57.540
right of it to get the best balance between a

1726
01:05:57.540 --> 01:06:00.380
lot of meteors but decent ones to see and

1727
01:06:00.380 --> 01:06:03.140
just get a comfy chair, lie back, wrap up

1728
01:06:03.140 --> 01:06:05.100
warm m with the people you love and tell

1729
01:06:05.100 --> 01:06:07.500
stories and relax and occasionally you'll see

1730
01:06:07.500 --> 01:06:08.940
something good and it's quite addictive. You

1731
01:06:08.940 --> 01:06:10.700
think, you know, I'll go to bed, but I just

1732
01:06:10.700 --> 01:06:12.460
want to see one more and then, well, that's

1733
01:06:12.460 --> 01:06:14.220
rubbish. So uh, I want to see another one

1734
01:06:14.220 --> 01:06:16.480
that's actually good. You've then got like

1735
01:06:16.630 --> 01:06:19.470
the mid tier showers which can be decent but

1736
01:06:19.470 --> 01:06:21.230
you need to be a bit more dedicated for these

1737
01:06:21.230 --> 01:06:23.190
are the ones where you might see 10 or 15 an

1738
01:06:23.190 --> 01:06:26.150
hour instead of 50 an hour. And I, um,

1739
01:06:26.190 --> 01:06:27.790
wouldn't recommend people who were beginners

1740
01:06:27.790 --> 01:06:29.790
go out and see them because it's, there's not

1741
01:06:29.790 --> 01:06:32.110
enough happening. And that's why I worry

1742
01:06:32.110 --> 01:06:34.790
about coverage for the April Lyrids, even in

1743
01:06:34.790 --> 01:06:36.870
the Northern Hemisphere, because they're just

1744
01:06:36.870 --> 01:06:39.030
not that good. If you're someone who's really

1745
01:06:39.030 --> 01:06:41.870
keen, you'll enjoy them. But for most people

1746
01:06:41.870 --> 01:06:43.270
there'll be a letdown and you don't want to

1747
01:06:43.270 --> 01:06:45.230
turn people off the subject. Then there are

1748
01:06:45.230 --> 01:06:48.080
the minor showers that you frankly need to be

1749
01:06:48.080 --> 01:06:49.840
very obsessive to follow. And I've seen

1750
01:06:49.840 --> 01:06:52.200
stories of a lot of the science of this has

1751
01:06:52.200 --> 01:06:54.710
been done by amateur astronomers and, um,

1752
01:06:54.760 --> 01:06:56.760
quite often by people who are quite obsessive

1753
01:06:56.760 --> 01:06:59.520
about the topic. And I

1754
01:06:59.520 --> 01:07:02.040
saw one guy who was in North America where it

1755
01:07:02.040 --> 01:07:04.960
gets brutal, brutal cold in the winter,

1756
01:07:05.200 --> 01:07:08.160
who built himself a, an insulated coffin with

1757
01:07:08.160 --> 01:07:10.680
an incredibly transparent glass lid that he

1758
01:07:10.680 --> 01:07:12.870
would carry out with him that was big enough

1759
01:07:12.870 --> 01:07:14.470
for him to have a notebook and write down the

1760
01:07:14.470 --> 01:07:17.030
details of every meteor he saw. He could lie

1761
01:07:17.030 --> 01:07:19.750
out in minus 40 degrees and I think

1762
01:07:19.750 --> 01:07:21.830
that's, um, units ambivalent. I think

1763
01:07:21.830 --> 01:07:23.630
Fahrenheit and Centigrade are very similar at

1764
01:07:23.630 --> 01:07:26.150
that point. But he's in an insulated box that

1765
01:07:26.150 --> 01:07:28.270
keeps him warm and he'd lie out all night

1766
01:07:28.270 --> 01:07:31.150
recording 2 meters, 3 meters an hour. That

1767
01:07:31.150 --> 01:07:34.150
isn't for me, but it is for some people. But

1768
01:07:34.150 --> 01:07:36.310
when you see a meteor shower with a ZHR of

1769
01:07:36.310 --> 01:07:38.960
less than about 20, I'd probably leave that

1770
01:07:38.960 --> 01:07:41.800
unless you're really keen. If it's got a zhr

1771
01:07:41.800 --> 01:07:44.480
of 50 plus, well worth looking out for. But

1772
01:07:44.480 --> 01:07:46.520
look for when the time of maximum is for most

1773
01:07:46.520 --> 01:07:49.160
meteor showers, they've got what we call a

1774
01:07:49.160 --> 01:07:51.480
full width half maximum of about 24 hours.

1775
01:07:51.880 --> 01:07:54.600
What that means is that, uh, the rate only

1776
01:07:54.600 --> 01:07:56.520
stays above half of the peak rate for about

1777
01:07:56.520 --> 01:07:59.480
24 hours for 48 hours, then it'd stay above

1778
01:07:59.480 --> 01:08:01.560
a quarter of the rate and so on. For the

1779
01:08:01.560 --> 01:08:03.240
Quadrantids, it's full width at quarter

1780
01:08:03.240 --> 01:08:06.060
maximum of about 12 hours. So that means

1781
01:08:06.220 --> 01:08:08.620
if you're six hours away from the peak, the

1782
01:08:08.620 --> 01:08:10.420
rate is already down to a quarter of that

1783
01:08:10.420 --> 01:08:12.700
peak. It's a very sharp peak and if you're

1784
01:08:12.700 --> 01:08:14.780
looking at the wrong time, the show won't be

1785
01:08:14.780 --> 01:08:16.580
as good as you'd like it to be and you'll be

1786
01:08:16.580 --> 01:08:17.260
disappointed.

1787
01:08:18.460 --> 01:08:20.310
Andrew Dunkley: So much to consider, Jonti, but fascinating.

1788
01:08:20.310 --> 01:08:22.300
Uh, copper and meteors.

1789
01:08:22.510 --> 01:08:24.900
Um, there's so much to talk about and we

1790
01:08:24.900 --> 01:08:27.100
probably didn't really cover absolutely

1791
01:08:27.100 --> 01:08:29.020
everything. Although we did, uh, we did hit

1792
01:08:29.020 --> 01:08:31.980
on quite a fair bit of info. And of course,

1793
01:08:31.980 --> 01:08:34.010
we do welcome questions and comments. So, uh,

1794
01:08:34.140 --> 01:08:36.490
please, um, go to our website and,

1795
01:08:36.790 --> 01:08:39.770
um, click that little AMA button at

1796
01:08:39.770 --> 01:08:41.490
the top and you can send us, uh, questions

1797
01:08:41.490 --> 01:08:44.090
and comments, uh, in text and audio form.

1798
01:08:44.090 --> 01:08:46.210
Don't forget to tell us who you are and where

1799
01:08:46.210 --> 01:08:47.570
you're from, but we're going to wrap it up

1800
01:08:47.570 --> 01:08:49.370
there. Jonti, thank you so much. We'll catch

1801
01:08:49.370 --> 01:08:50.170
you on the next show.

1802
01:08:50.410 --> 01:08:51.290
Jonti Horner: Thank you very much.

1803
01:08:52.010 --> 01:08:54.370
Andrew Dunkley: Professor Jonti Horner, professor of

1804
01:08:54.370 --> 01:08:57.250
Astrophysics at the University of Southern

1805
01:08:57.250 --> 01:08:59.850
Queensland, our, uh, special, uh, guest

1806
01:08:59.850 --> 01:09:02.370
commentator. While Fred's, uh, on the other

1807
01:09:02.370 --> 01:09:04.960
side of the planet looking at meteors. And,

1808
01:09:04.970 --> 01:09:07.720
uh, just a special word for, uh, for Huw in

1809
01:09:07.720 --> 01:09:10.400
the studio. He's been a little unwell lately.

1810
01:09:10.400 --> 01:09:12.800
Huw, get well soon, mate. We're all thinking

1811
01:09:12.800 --> 01:09:15.120
of you. And from me, Andrew Dunkley. Thanks

1812
01:09:15.120 --> 01:09:16.720
for your company. We'll catch you on the next

1813
01:09:16.720 --> 01:09:18.560
episode of Space Nuts.

1814
01:09:19.759 --> 01:09:21.880
Jonti Horner: You'll be listening to the Space Nuts

1815
01:09:21.880 --> 01:09:24.840
podcast, available at

1816
01:09:24.840 --> 01:09:26.800
Apple Podcasts, Spotify,

1817
01:09:27.040 --> 01:09:29.620
iHeartRadio or your favorite podcast

1818
01:09:29.929 --> 01:09:31.529
player. You can also stream on

1819
01:09:31.529 --> 01:09:33.209
demand@bytes.com.

1820
01:09:33.529 --> 01:09:35.609
Andrew Dunkley: this has been another quality podcast

1821
01:09:35.609 --> 01:09:37.609
production from bytes.com.