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Comets, Meteors, and Celestial Wonders In this engaging episode of Space Nuts, hosts Andrew Dunkley and Professor Jonti Horner dive deep into the fascinating world of comets and meteors. With Professor Fred Watson away, Jonti brings his expertise to explore these celestial phenomena, their historical significance, and the science behind them.
Episode Highlights:
- Understanding Comets and Meteors: Andrew and Jonti kick off the episode by discussing the importance of comets and meteors in both ancient cultures and modern astronomy. They delve into how these celestial objects have been perceived throughout history and their impact on human events.
- Recent Discoveries and Predictions: The hosts share insights on recent comet discoveries, including the intriguing Comet Chichin Chan, and discuss what we can expect from this comet in the near future. They also touch on the challenges of predicting comet brightness and visibility.
- Meteor Showers Explained: Jonti explains how meteor showers occur, the significance of radiant points, and what conditions are best for viewing these spectacular events. They discuss the most notable meteor showers and when listeners can catch them in action.
- The Impact of Media on Public Perception: The conversation takes a turn as Andrew and Jonti address the role of media in shaping public understanding of astronomical events, particularly the sensationalism surrounding potential alien encounters and the importance of relying on scientific facts.
For more Space Nuts, including our continuously updating newsfeed and to listen to all our episodes, visit our website. Follow us on social media at SpaceNutsPod on Facebook, Instagram, and more. We love engaging with our community, so be sure to drop us a message or comment on your favourite platform.
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Stay curious, keep looking up, and join us next time for more stellar insights and cosmic wonders. Until then, clear skies and happy stargazing.
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00:00:00 --> 00:00:01 Andrew Dunkley: Hello again. Thank you for joining us on
00:00:01 --> 00:00:04 another episode of Space Nuts. My name is
00:00:04 --> 00:00:06 Andrew Dunkley, your host. It's great to have
00:00:06 --> 00:00:09 your company. As I mentioned last episode,
00:00:09 --> 00:00:12 Fred is away for a few weeks or
00:00:12 --> 00:00:15 a couple of years. Now it's a few weeks. And,
00:00:15 --> 00:00:17 uh, in his stead, we'll be joined by
00:00:17 --> 00:00:20 Professor Jonti Horner, who you know and love
00:00:20 --> 00:00:22 because he's been with us before and uh, he's
00:00:22 --> 00:00:25 a part of the team. So, uh, we will be
00:00:25 --> 00:00:28 doing over the next, uh, several episodes,
00:00:28 --> 00:00:31 um, taking a different approach. Uh, we're
00:00:31 --> 00:00:34 going to, to uh, focus on specific topics
00:00:34 --> 00:00:37 within each of the episodes. Uh,
00:00:37 --> 00:00:40 we could call them specials if you like. And
00:00:40 --> 00:00:42 today our focus will be on
00:00:42 --> 00:00:45 comets and meteors. Stick around.
00:00:45 --> 00:00:47 We're doing all of that on this episode of
00:00:47 --> 00:00:50 space nuts. 15 seconds. Guidance
00:00:50 --> 00:00:53 is internal. 10, 9,
00:00:53 --> 00:00:55 ignition sequence start.
00:00:55 --> 00:00:57 Jonti Horner: Space nuts. 5, 4, 3, 2.
00:00:57 --> 00:01:00 Andrew Dunkley: 1, 2, 3, 4, 5, 5, 4, 3,
00:01:00 --> 00:01:01 2, 1.
00:01:01 --> 00:01:02 Jonti Horner: Space nuts.
00:01:02 --> 00:01:05 Andrew Dunkley: Astronauts. Feels good and
00:01:05 --> 00:01:07 it's great to have him back. Professor Jonti
00:01:07 --> 00:01:10 Horner, professor of Astrophysics at the
00:01:10 --> 00:01:13 University of Southern Queensland. Jonti,
00:01:13 --> 00:01:13 hello.
00:01:13 --> 00:01:15 Jonti Horner: Ah, uh, hey, how are you going? Good.
00:01:15 --> 00:01:16 Andrew Dunkley: Great to see you again.
00:01:17 --> 00:01:19 Jonti Horner: Well, it's good to be back. It's something
00:01:19 --> 00:01:20 nice to keep me entertained while I'm having
00:01:20 --> 00:01:22 a little bit of a restful couple of weeks.
00:01:22 --> 00:01:24 I'm, you know, I've got a bit of leave, so
00:01:24 --> 00:01:27 I'm recovering from a minor surgery and
00:01:27 --> 00:01:29 therefore I can give my entire forecast to.
00:01:29 --> 00:01:31 Talking about fun things rather than doing
00:01:31 --> 00:01:34 admin effectively means I get to see a little
00:01:34 --> 00:01:35 bit of the life Fred gets to live.
00:01:35 --> 00:01:38 Andrew Dunkley: Yeah, maybe. Yes. Although he doesn't seem to
00:01:38 --> 00:01:41 slow down much. Um, in fact, I think
00:01:41 --> 00:01:43 the worst thing you can do when you retire is
00:01:43 --> 00:01:46 slow down because the brain matter decides to
00:01:46 --> 00:01:48 give up the ghost and that's when it's all
00:01:48 --> 00:01:51 over. Red Rover. But, uh, no, he, he's going,
00:01:51 --> 00:01:52 going great guns.
00:01:52 --> 00:01:55 And um, you didn't mention that you're having
00:01:55 --> 00:01:58 a little bit of a recuperation. Are
00:01:58 --> 00:02:00 you in a position to talk about that or
00:02:01 --> 00:02:02 too embarrassing?
00:02:03 --> 00:02:04 Jonti Horner: Well, it's one of those things that when I,
00:02:04 --> 00:02:06 when I first had this pointed out, I a bit
00:02:06 --> 00:02:08 embarrassed about it, but I don't think as
00:02:08 --> 00:02:10 bloats we ever talk about health that much
00:02:10 --> 00:02:13 until it's worth muscling past a little bit
00:02:13 --> 00:02:16 of embarrassment. So I'm in my late 40s and
00:02:16 --> 00:02:18 I went to the doctor about a year ago
00:02:18 --> 00:02:20 because, had a little bit of bleeding when I
00:02:20 --> 00:02:21 was sitting down and stuff like this and
00:02:21 --> 00:02:24 nothing dramatic. Um, But I found out two
00:02:24 --> 00:02:26 things. Firstly, in Australia, and I don't
00:02:26 --> 00:02:27 know about the rest of the world, you should
00:02:27 --> 00:02:29 look this up. But when you're in your 40s,
00:02:30 --> 00:02:32 the Medicare system here affords the
00:02:32 --> 00:02:34 opportunity for you to get health checks.
00:02:34 --> 00:02:36 Yep. Which is brilliant. So you basically get
00:02:36 --> 00:02:38 what in the UK they'd call an MOT for a car.
00:02:39 --> 00:02:41 You get everything run over and you get your
00:02:41 --> 00:02:43 blood pressure done and your heart rate done
00:02:43 --> 00:02:44 and everything else. And then you go back
00:02:44 --> 00:02:46 every three months and do it again and again
00:02:46 --> 00:02:48 and again, and it's basically you're at an
00:02:48 --> 00:02:50 edge where things start to break. Let's get
00:02:50 --> 00:02:52 on top of it early so that you can enjoy the
00:02:52 --> 00:02:55 rest of your life in peace, effectively. I
00:02:55 --> 00:02:56 think it's a really good idea and I suspect
00:02:56 --> 00:02:58 from a government point of view, makes a lot
00:02:58 --> 00:03:00 of sense, because if you find things easy
00:03:00 --> 00:03:02 earlier, they're easier and quicker and
00:03:02 --> 00:03:05 cheaper to solve. Um, what it turned out from
00:03:05 --> 00:03:07 that was I spent about two months going back
00:03:07 --> 00:03:09 and forth with a doctor who thought I had one
00:03:09 --> 00:03:11 thing wrong, which is not what it was. And
00:03:11 --> 00:03:13 then I got. Got sent to this specialist who
00:03:13 --> 00:03:15 said, you've got something called a fistula
00:03:15 --> 00:03:18 down near your backside, which, not life
00:03:18 --> 00:03:19 threatening, not the end of the world, not
00:03:19 --> 00:03:22 doomed, but it's uncomfortable. Um, and, you
00:03:22 --> 00:03:24 know, it's been slightly embarrassing in that
00:03:24 --> 00:03:27 I've had to learn more about sanitary pads
00:03:27 --> 00:03:29 and, you know, um, you would have expected,
00:03:29 --> 00:03:32 you know, which the women in the audience are
00:03:32 --> 00:03:33 going, about bloody time a man learned about
00:03:33 --> 00:03:36 this. Um, but it's a weird
00:03:36 --> 00:03:38 one because it's not life threatening. It's
00:03:38 --> 00:03:40 nothing of a problem, something 10 or 20% of
00:03:40 --> 00:03:42 guys apparently get them, but they contain
00:03:42 --> 00:03:45 multiple surgeries to fix. And when I went in
00:03:45 --> 00:03:48 for the first surgery in January, there was
00:03:48 --> 00:03:50 another guy there who was on surgery number
00:03:50 --> 00:03:50 seven.
00:03:50 --> 00:03:51 Andrew Dunkley: Wow.
00:03:51 --> 00:03:54 Jonti Horner: Which he had deep and joyous, um, kind of day
00:03:54 --> 00:03:55 surgery. But you get a full general and you
00:03:55 --> 00:03:57 go under and Dr. Does snippy, snippy things
00:03:57 --> 00:03:59 and you get a couple of weeks off work, which
00:03:59 --> 00:04:01 is where I am now. So I've just had surgery
00:04:01 --> 00:04:04 number two and the doctor is hopeful,
00:04:04 --> 00:04:05 confident, whatever, that surgery number
00:04:05 --> 00:04:08 three will be the final fix. And it's one of
00:04:08 --> 00:04:09 these weird things because people say, what's
00:04:09 --> 00:04:11 wrong with you? And if it's a sore arm, you
00:04:11 --> 00:04:13 just say, I've hurt my arm, or you've broken
00:04:13 --> 00:04:15 your arm or something. Or in Australia, a
00:04:15 --> 00:04:17 really common one, a melanoma. People have
00:04:17 --> 00:04:19 been in the sun too much going into hospital.
00:04:19 --> 00:04:20 What do you get, I've, ah, got a melanoma
00:04:20 --> 00:04:22 taken off. But as soon as it's anywhere
00:04:22 --> 00:04:24 between about your belly button and your
00:04:24 --> 00:04:25 knee, people are bashful about talking about
00:04:25 --> 00:04:28 it. And I first few months I was mortified
00:04:28 --> 00:04:30 and like, wouldn't talk about it. And
00:04:30 --> 00:04:32 realization is that if you don't talk about
00:04:32 --> 00:04:35 it, people don't get checked. And we as
00:04:35 --> 00:04:37 men are terrible for that. And so, yeah,
00:04:37 --> 00:04:39 worth talking about. I'm a bit embarrassed
00:04:39 --> 00:04:41 about it, but I shouldn't be. And it's good,
00:04:41 --> 00:04:42 it's going to tune up. And it means that in
00:04:42 --> 00:04:45 40 years time I'll still be up and kicking
00:04:45 --> 00:04:47 and having a lot of fun rather than in
00:04:47 --> 00:04:48 discomfort and grumbling about a problem I
00:04:48 --> 00:04:49 could have got fixed.
00:04:49 --> 00:04:52 Andrew Dunkley: Yeah, yeah. And, um, I think you're
00:04:52 --> 00:04:55 right. I think men do tend to keep things to
00:04:55 --> 00:04:58 themselves. Uh, a lot of them go into denial
00:04:58 --> 00:05:00 or they just think, well, no, that won't
00:05:00 --> 00:05:03 happen to me, so no problem. But,
00:05:04 --> 00:05:06 uh, when I was diagnosed with prostate
00:05:06 --> 00:05:09 cancer, it was like a bolt from the blue. And
00:05:09 --> 00:05:12 I didn't, I never expected
00:05:12 --> 00:05:14 to get it because there was next to no
00:05:14 --> 00:05:17 history of it in my family. So, um, that was
00:05:17 --> 00:05:20 a bit of a shock. And this is. How long is
00:05:20 --> 00:05:23 it now? Three years. Three years. And I'm
00:05:23 --> 00:05:26 still working my way through it. So,
00:05:27 --> 00:05:30 um, but the latest scans are all good.
00:05:30 --> 00:05:32 So fingers crossed that we've, you know,
00:05:33 --> 00:05:36 reached a good position. But, um, it's
00:05:36 --> 00:05:37 just an ongoing thing in your life. You just
00:05:37 --> 00:05:40 got to get used to it. But you. My
00:05:40 --> 00:05:42 advice to men is go and get checked. If
00:05:42 --> 00:05:45 you're over 50, go and get a
00:05:45 --> 00:05:48 prostate exam, go and get your PSA tests
00:05:48 --> 00:05:51 done. Because if you don't and
00:05:51 --> 00:05:53 then they find it, it might be too far along.
00:05:54 --> 00:05:57 Um, and then the treatment becomes more
00:05:57 --> 00:06:00 dramatic. So anyway, um, it's a good
00:06:00 --> 00:06:01 thing to bring up.
00:06:01 --> 00:06:03 Jonti Horner: It is. And it goes for the mental health
00:06:03 --> 00:06:05 stuff as well. I have a former partner of
00:06:05 --> 00:06:07 mine, kind of 20 years ago, who was very
00:06:07 --> 00:06:10 severely bipolar, had a lot of challenges
00:06:10 --> 00:06:12 and she was continually frustrated by
00:06:12 --> 00:06:14 people's responses to that in public, in that
00:06:14 --> 00:06:17 it's a hidden illness there. She's getting
00:06:17 --> 00:06:19 treatment. But what she always said is, it's
00:06:19 --> 00:06:21 really frustrating. If I, if I had a broken
00:06:21 --> 00:06:23 leg or I had an injury to my arm and people
00:06:23 --> 00:06:26 could see it, they'd be supportive. But with
00:06:26 --> 00:06:27 mental health, she got a hell of a lot of,
00:06:27 --> 00:06:29 I'll just get over it, uh, or toughen up or.
00:06:29 --> 00:06:30 Andrew Dunkley: Yep. Yeah.
00:06:30 --> 00:06:33 Jonti Horner: And, yeah, and, you know, she was female,
00:06:33 --> 00:06:35 so she's more likely to go to the doctor and
00:06:35 --> 00:06:38 talk about it. Statistically, men with mental
00:06:38 --> 00:06:40 health challenges tend to avoid that even
00:06:40 --> 00:06:42 more than they'll go to the doctor with
00:06:42 --> 00:06:44 physical health challenges. And it's
00:06:44 --> 00:06:46 something I'd like to change. I come from a
00:06:46 --> 00:06:48 working class background in Yorkshire where
00:06:48 --> 00:06:49 men m. Don't talk about anything. You know,
00:06:49 --> 00:06:52 you're meant to be stoic and the only, the
00:06:52 --> 00:06:53 only expression of emotion you're allowed is
00:06:53 --> 00:06:56 rage or a single manly tear. You know, it's,
00:06:56 --> 00:06:58 it's really creative the way we're
00:06:58 --> 00:07:00 conditioned. And even though I'm, you know, I
00:07:00 --> 00:07:02 went to uni, I've had a life, I've grown up.
00:07:02 --> 00:07:03 All this stuff still there at the back of
00:07:03 --> 00:07:05 your head and you've got to fight against it
00:07:05 --> 00:07:07 because the instinct is, ah, there's nothing
00:07:07 --> 00:07:09 wrong. I won't bother, you know. Yeah.
00:07:09 --> 00:07:11 Andrew Dunkley: And, um, yeah, you see it way too often.
00:07:12 --> 00:07:14 Um, I know it's a departure from what this
00:07:14 --> 00:07:16 podcast is all about, but I,
00:07:17 --> 00:07:19 when given the opportunity, will
00:07:20 --> 00:07:23 openly, um, say to men, um, you know,
00:07:23 --> 00:07:26 don't, don't hesitate to go to the
00:07:26 --> 00:07:29 doctor. Not, not when you think something's
00:07:29 --> 00:07:32 wrong. Just preemptively go and get. Once a
00:07:32 --> 00:07:33 year, go and get checked and make sure
00:07:33 --> 00:07:35 everything's where it's supposed to be or
00:07:36 --> 00:07:38 whatever. Um, we do it, do it for
00:07:38 --> 00:07:40 Jonti Horner: our cars, we do it for our pets.
00:07:40 --> 00:07:40 Andrew Dunkley: Yeah.
00:07:40 --> 00:07:42 Jonti Horner: Do it for yourself as well.
00:07:42 --> 00:07:43 Andrew Dunkley: Yeah, exactly.
00:07:43 --> 00:07:44 Jonti Horner: And yeah, I think it's probably a record for
00:07:44 --> 00:07:46 the quickest we've ever got off topic. And
00:07:46 --> 00:07:48 possibly we shouldn't have a trigger warning
00:07:48 --> 00:07:49 at the front of it and all the rest of it,
00:07:49 --> 00:07:51 but no good way to start even though it is
00:07:51 --> 00:07:52 off topic.
00:07:52 --> 00:07:54 Andrew Dunkley: It's okay, we'll get on to topic right now
00:07:54 --> 00:07:57 because, uh, uh, as I mentioned, these,
00:07:57 --> 00:08:00 these, uh, next, uh, several, uh,
00:08:00 --> 00:08:02 episodes are going to be dedicated to
00:08:02 --> 00:08:04 singular topics each. And today
00:08:05 --> 00:08:07 it's, uh, well, related topics. Comets and
00:08:07 --> 00:08:10 meteors. Uh, this is a, this is pet
00:08:11 --> 00:08:12 topic of yours, I imagine.
00:08:13 --> 00:08:15 Jonti Horner: It is. I, I've always been a bit more into
00:08:15 --> 00:08:17 the nearby stuff than the more distant stuff.
00:08:17 --> 00:08:19 So it always tickles me a little bit that
00:08:19 --> 00:08:21 when questions come in when I'm on the show,
00:08:21 --> 00:08:23 we get all the Big bang and cosmology ones.
00:08:23 --> 00:08:25 And I'm sure if you've got uh, someone like
00:08:25 --> 00:08:26 the wonderful Tamara Davis on to talk
00:08:26 --> 00:08:28 cosmology, she get all the planets questions.
00:08:28 --> 00:08:31 It's always the way it goes. Yeah, but comets
00:08:31 --> 00:08:33 and meteors are a big part of what hooked me
00:08:33 --> 00:08:35 into astronomy as A kid. And, um, my thinking
00:08:35 --> 00:08:38 behind this is that we're recording in
00:08:38 --> 00:08:41 advance. You know, um, obviously Fred
00:08:41 --> 00:08:43 is away, but you've got recordings with Fred
00:08:43 --> 00:08:45 already. And so the news that we would
00:08:45 --> 00:08:47 normally talk about hasn't happened yet. So
00:08:48 --> 00:08:50 I, I have many talents, but seeing into the
00:08:50 --> 00:08:52 future isn't one of them to that degree. And
00:08:52 --> 00:08:54 so I thought it better to have a discussion
00:08:54 --> 00:08:56 about the general stuff in a bit more depth
00:08:57 --> 00:08:59 than go into particular news topics. And
00:08:59 --> 00:09:01 it's. It could almost be a bit of an
00:09:01 --> 00:09:03 explainer, a bit of the background, and
00:09:03 --> 00:09:05 hopefully at least gives my insight into why
00:09:05 --> 00:09:07 a given topic's interesting, but also what
00:09:07 --> 00:09:09 people can look out for in the future and how
00:09:09 --> 00:09:12 they can get more into and more out
00:09:12 --> 00:09:15 of that particular topic, if that makes
00:09:15 --> 00:09:17 sense. Yeah, Um, a little bit different, I
00:09:17 --> 00:09:19 understand. For some listeners it might be a
00:09:19 --> 00:09:22 bit of an abrupt departure and a change. So
00:09:22 --> 00:09:23 it'll be interesting to see what feedback you
00:09:23 --> 00:09:26 get. But hopefully people like it as a little
00:09:26 --> 00:09:28 bit of a change in a breath of fresh air. And
00:09:28 --> 00:09:29 if they don't, well, there's only a couple of
00:09:29 --> 00:09:31 episodes and Fred's back anyway, so you'll
00:09:31 --> 00:09:33 have to deal with it and we'll see.
00:09:33 --> 00:09:34 Andrew Dunkley: I'm sure it'll be fine.
00:09:34 --> 00:09:37 Uh, comets and meteors are a very popular,
00:09:37 --> 00:09:40 uh, topic. So, um, uh, where do we
00:09:40 --> 00:09:41 start? Maybe, maybe look at a bit of the
00:09:41 --> 00:09:42 history of this.
00:09:43 --> 00:09:45 Jonti Horner: Yeah, I think that is always a good place.
00:09:46 --> 00:09:48 It sets the context of where we are now. And,
00:09:48 --> 00:09:51 um, for both comets and meteors, there's a
00:09:51 --> 00:09:53 kind of global connection societally that
00:09:53 --> 00:09:56 really predates by a long, long way
00:09:56 --> 00:09:59 our scientific knowledge. Essentially the
00:09:59 --> 00:10:01 modern scientific viewpoint and the
00:10:01 --> 00:10:03 scientific method. All cultures across the
00:10:03 --> 00:10:05 world, from our wonderful, uh, traditional
00:10:05 --> 00:10:07 owners here in Australia to the peoples of
00:10:07 --> 00:10:09 every continent and every land, um, both
00:10:09 --> 00:10:12 current and past, historically had a
00:10:12 --> 00:10:14 really firm connection to the night sky. They
00:10:14 --> 00:10:15 knew the night sky better than most people
00:10:15 --> 00:10:17 these days do because it wasn't light
00:10:17 --> 00:10:19 pollution, there weren't TVs and Xboxes.
00:10:20 --> 00:10:22 So the sky was something people much more
00:10:22 --> 00:10:25 exposed to. A lot of cultures have
00:10:25 --> 00:10:27 this kind of idea of as above, so below, as
00:10:27 --> 00:10:30 below, so above. So they were very firmly of
00:10:30 --> 00:10:32 the idea that major events on the Earth were
00:10:32 --> 00:10:35 reflected in the sky. And, uh, major events
00:10:35 --> 00:10:37 in the sky would have their counterparts on
00:10:37 --> 00:10:40 the Earth. And that's where astrology
00:10:40 --> 00:10:42 was born. And for a long time, astrology and
00:10:42 --> 00:10:44 astronomy were one and the same. You know,
00:10:44 --> 00:10:47 people doing astronomy studies were doing it
00:10:47 --> 00:10:48 because they wanted to understand the events
00:10:48 --> 00:10:51 that would influence what's on the Earth. And
00:10:51 --> 00:10:53 there are good examples of this in terms of
00:10:53 --> 00:10:55 the nominally fixed stars, uh, things like
00:10:55 --> 00:10:58 the ancient Egyptians using the rising of
00:10:58 --> 00:11:01 Sirius in the dawn sky after it disappeared
00:11:01 --> 00:11:03 in the evenings as a predictor of the
00:11:03 --> 00:11:04 flooding of the Nile, for example, the use of
00:11:04 --> 00:11:07 the night sky as a calendar, lots of stuff
00:11:07 --> 00:11:10 like that. But because people are so aware of
00:11:10 --> 00:11:12 the night sky, anything that was ephemeral,
00:11:13 --> 00:11:15 anything that was transitory, that appeared
00:11:15 --> 00:11:17 and then disappeared, that was unexpected,
00:11:17 --> 00:11:19 was often seen as kind of a portent or an
00:11:19 --> 00:11:22 omen, something that was an
00:11:22 --> 00:11:24 indication either of major change and
00:11:24 --> 00:11:26 upheaval currently happening or one soon to
00:11:26 --> 00:11:28 come. And really bright comets and, um,
00:11:28 --> 00:11:31 spectacular meteor showers kind of often fill
00:11:31 --> 00:11:33 this role. And you can go back through
00:11:33 --> 00:11:36 ancient history where we have the records and
00:11:36 --> 00:11:38 see good examples of this. I've got, in one
00:11:38 --> 00:11:41 of my talks, talks about a
00:11:41 --> 00:11:43 guy called, uh, Mithridates,
00:11:44 --> 00:11:46 um, Jupiter 6, I think his name was. He was
00:11:46 --> 00:11:48 one of the great enemies of the Roman Empire.
00:11:48 --> 00:11:51 And there are quotes ascribed to him saying
00:11:51 --> 00:11:54 things like, um, even the heavens predicted
00:11:54 --> 00:11:56 the greatness of this man. For in the year in
00:11:56 --> 00:11:57 which he was born and the year in which he
00:11:57 --> 00:12:00 came to reign, a comet shone through Both
00:12:00 --> 00:12:02 periods for 70 days as
00:12:02 --> 00:12:04 bright as the sun. Um, each rising and
00:12:04 --> 00:12:07 setting took four hours each. And that's kind
00:12:07 --> 00:12:09 of hyperbolic, but it gives this idea that
00:12:09 --> 00:12:12 people saw something in the sky that was
00:12:12 --> 00:12:15 unusual and tied it to events on Earth.
00:12:15 --> 00:12:17 Another good example would be the alleged
00:12:17 --> 00:12:20 comet called Caesar's Comet in 44 BC
00:12:20 --> 00:12:23 43-43, which
00:12:23 --> 00:12:26 is recorded in Roman writings from
00:12:26 --> 00:12:28 a century or two later, talking
00:12:29 --> 00:12:31 about after the death of Caesar, a comet
00:12:31 --> 00:12:34 blazed in the sky for seven days that was
00:12:34 --> 00:12:36 spectacularly bright, then disappeared and
00:12:36 --> 00:12:38 was never seen again. Now, that comet is a
00:12:38 --> 00:12:40 really good example of the challenge people
00:12:40 --> 00:12:42 have with historical records,
00:12:43 --> 00:12:45 because on the one hand you've got these
00:12:45 --> 00:12:48 clear reports from the Roman Empire, none of
00:12:48 --> 00:12:50 them at the time, though, all of them a bit
00:12:50 --> 00:12:52 later on. But that comet is not recorded from
00:12:52 --> 00:12:54 anywhere else on the planet. And there were
00:12:54 --> 00:12:56 cultures around the globe leaving records
00:12:56 --> 00:12:58 like ancient China and ancient Korea, who
00:12:58 --> 00:13:01 would have seen it. So was that comet real,
00:13:02 --> 00:13:04 or was it a case of after the event, people
00:13:04 --> 00:13:07 inventing a night sky phenomena to tie
00:13:07 --> 00:13:09 with the soul of the emperor rising to
00:13:09 --> 00:13:11 heaven? It's one of the challenges people in
00:13:11 --> 00:13:13 the kind of cultural astronomy space face, I
00:13:13 --> 00:13:16 think, in terms of disentangling the
00:13:16 --> 00:13:18 narrative from the events that prompted it,
00:13:18 --> 00:13:21 if that kind of makes sense. Yeah, but what's
00:13:21 --> 00:13:23 certainly true is, uh, for as long as we've
00:13:23 --> 00:13:25 looked at the sky, really bright comets and,
00:13:25 --> 00:13:28 um, unusually powerful meteor showers
00:13:28 --> 00:13:30 were things that people took note of. And
00:13:30 --> 00:13:32 recently there was a lot of media, media
00:13:32 --> 00:13:35 coverage of the April Lyrid meteor shower,
00:13:35 --> 00:13:37 which is not one of the strongest of the
00:13:37 --> 00:13:40 year, but one of the reasonable, moderate
00:13:40 --> 00:13:41 ones. It's kind of one that if you're a
00:13:41 --> 00:13:43 meteor enthusiast, you'll go out and watch,
00:13:43 --> 00:13:45 but isn't worth going out if you're not that
00:13:45 --> 00:13:46 interested because there's too few.
00:13:48 --> 00:13:49 I had to grumble about some of the coverage
00:13:49 --> 00:13:51 here in Australia because it's not a great
00:13:51 --> 00:13:53 shower for us. But that meteor shower
00:13:53 --> 00:13:56 was recognized by the traditional owners in
00:13:56 --> 00:13:57 Australia. And there are stories from
00:13:57 --> 00:14:00 Victoria, from, I think, the Burong people,
00:14:00 --> 00:14:01 although I stand to be corrected on that,
00:14:02 --> 00:14:04 that associate this meteor shower with the
00:14:04 --> 00:14:05 Mallee Fowl, one of the big ground nesting
00:14:05 --> 00:14:08 birds in Australia, which nests around that
00:14:08 --> 00:14:10 time of year. The meteors seen shrieking from
00:14:10 --> 00:14:12 low in the northern sky were viewed as being
00:14:12 --> 00:14:15 the dust being kicked up by the nesting bird
00:14:15 --> 00:14:17 celestially. So they recorded this meteor
00:14:17 --> 00:14:19 shower, even though it isn't a particularly
00:14:19 --> 00:14:21 strong one. But our oldest
00:14:22 --> 00:14:24 written record of any meteor shower is the
00:14:24 --> 00:14:26 April Lyrids, and it's dated back to
00:14:26 --> 00:14:28 something like 687 BCE, when
00:14:28 --> 00:14:30 stars fell like rain, when there was a major
00:14:30 --> 00:14:33 storm from the Lyrids, and it was significant
00:14:33 --> 00:14:36 enough for people to record. So comets
00:14:36 --> 00:14:39 and meteors, way before the modern
00:14:39 --> 00:14:41 scientific understanding of them really had
00:14:41 --> 00:14:44 this important cultural role,
00:14:44 --> 00:14:46 um, even in the Battle of Hastings. If you
00:14:46 --> 00:14:48 ever go to see the Bayer Tapestry, this
00:14:48 --> 00:14:50 wonderful woven record of the Battle of
00:14:50 --> 00:14:52 Hastings and the invasion of William the
00:14:52 --> 00:14:55 Conqueror, Comet Hallie features prominently
00:14:55 --> 00:14:57 on that, because in 1066,
00:14:58 --> 00:15:00 you had the second best apparition of Comet
00:15:00 --> 00:15:02 Hallie in the last 2 years. Arguably, it
00:15:02 --> 00:15:04 was very spectacular in the sky at the time
00:15:04 --> 00:15:06 the conquest was going on. And, um, that was
00:15:06 --> 00:15:09 considered important enough to be recorded in
00:15:09 --> 00:15:12 the tapestry that was woven at the time. You
00:15:12 --> 00:15:14 know, it's amazing that you've got this panel
00:15:14 --> 00:15:16 where there's all the peasants pointing up at
00:15:16 --> 00:15:18 this thing in the sky and somebody whispering
00:15:18 --> 00:15:20 in King Harold's ear about the comet that's
00:15:20 --> 00:15:23 visible. So, yeah, don't know whether the
00:15:23 --> 00:15:25 invading forces took it as a good sign or a
00:15:25 --> 00:15:26 bad sign, but they thought it was important
00:15:27 --> 00:15:29 enough to include. So that in
00:15:29 --> 00:15:31 itself is fairly breathtaking. And so when we
00:15:31 --> 00:15:33 see these objects, it's a lovely connection
00:15:33 --> 00:15:36 to thousands of years of our heritage of
00:15:36 --> 00:15:39 people looking at the night sky in wonder I
00:15:39 --> 00:15:42 think the first step we had really,
00:15:43 --> 00:15:46 in moving from cultural
00:15:46 --> 00:15:48 cometary astronomy to modern scientific
00:15:48 --> 00:15:51 astronomy, in a way, came with the Great
00:15:51 --> 00:15:54 Comet of 1577, which was
00:15:54 --> 00:15:56 another of the really amazing, spectacular,
00:15:56 --> 00:15:59 bright comets that was widely
00:15:59 --> 00:16:02 observed, hence why it's a great comet.
00:16:02 --> 00:16:04 But it was observed by the great astronomer
00:16:04 --> 00:16:07 Tycho Brahe. And, um, I'm sure Brahe is
00:16:07 --> 00:16:09 featured on the podcast many times before,
00:16:09 --> 00:16:11 but the quirky individual he was, it's well
00:16:11 --> 00:16:14 worth looking up. His Wikipedia record is
00:16:14 --> 00:16:17 this wealthy nobleman with a silver
00:16:17 --> 00:16:19 replacement nose after he lost half his nose
00:16:19 --> 00:16:22 in a duel. He's that guy. Yes,
00:16:22 --> 00:16:24 yes. Um, he had a pet moose that died when it
00:16:24 --> 00:16:26 fell down the steps because it got drunk at a
00:16:26 --> 00:16:29 banquet. He really odd, odd
00:16:29 --> 00:16:32 man. Um, but probably viewed as being
00:16:32 --> 00:16:35 the last great pre telescope astronaut,
00:16:35 --> 00:16:36 astronomical observer, if that makes sense.
00:16:36 --> 00:16:39 Naked eye observer. Now, at this time,
00:16:39 --> 00:16:41 comets were kind of thought to be probably
00:16:41 --> 00:16:44 atmospheric phenomenon. They were nearby,
00:16:44 --> 00:16:47 high in the atmosphere, and so
00:16:47 --> 00:16:49 that was what was going on. People had that
00:16:49 --> 00:16:52 kind of idea. He realized that if that were
00:16:52 --> 00:16:55 true, these things would display a noticeable
00:16:55 --> 00:16:57 parallax if people observe them from
00:16:57 --> 00:16:59 different locations. Uh-huh. So in other
00:16:59 --> 00:17:01 words, people looking from different
00:17:01 --> 00:17:03 locations would see the comet in a different
00:17:04 --> 00:17:06 place in the sky because it was in the
00:17:06 --> 00:17:08 foreground. It's the same technique we use to
00:17:08 --> 00:17:10 measure the distance to the nearest stars. If
00:17:10 --> 00:17:12 you put your finger in front of your face and
00:17:12 --> 00:17:13 look at it through one eye and then look
00:17:13 --> 00:17:15 through the other, you'll see your finger
00:17:15 --> 00:17:18 blinking side to side. And the further away
00:17:18 --> 00:17:20 your finger is, the less it moves. We use
00:17:20 --> 00:17:22 that to measure the distance to stars by
00:17:22 --> 00:17:24 observing from one side of the Earth's orbit,
00:17:24 --> 00:17:26 then the other. But what Brahe did was
00:17:26 --> 00:17:28 collect observations from around Europe of
00:17:28 --> 00:17:31 where the comet was in the sky. With those
00:17:31 --> 00:17:33 observations, he would have been able to
00:17:33 --> 00:17:36 detect a parallax for the comet if it were
00:17:36 --> 00:17:39 closer than the orbit of the Moon. So if it
00:17:39 --> 00:17:40 was atmospheric, absolutely, definitely would
00:17:40 --> 00:17:43 do. But no measurable parallax was found
00:17:44 --> 00:17:45 which showed the comet had to be at least a
00:17:45 --> 00:17:47 couple of million kilometers away. And in
00:17:47 --> 00:17:49 fact, it was probably several tens of
00:17:49 --> 00:17:52 millions of kilometers distant. He got this
00:17:52 --> 00:17:54 beautiful figure, and I've. I use this in my
00:17:54 --> 00:17:57 talks occasionally. That is his drawing of
00:17:57 --> 00:17:59 the motion of the comet. And it's fascinating
00:17:59 --> 00:18:01 from a cultural point of view because it's
00:18:01 --> 00:18:03 clearly at the time when you still have the
00:18:03 --> 00:18:05 geocentric model, the Earth was the center of
00:18:05 --> 00:18:06 the universe. So you've got the Earth in the
00:18:06 --> 00:18:09 middle, the sun going around the Earth but
00:18:09 --> 00:18:11 then Mercury, Venus and the moon going around
00:18:11 --> 00:18:13 the sun. This kind of weird hybrid thing.
00:18:13 --> 00:18:15 Yeah, but you've got the path of the comet
00:18:15 --> 00:18:17 moving through there that he's determined.
00:18:17 --> 00:18:19 And what's really interesting to me, what's
00:18:19 --> 00:18:22 really fascinating is he's got the tails
00:18:22 --> 00:18:24 pointing away from the sun all the time. So
00:18:24 --> 00:18:26 he's got the phenomenology of where the comet
00:18:26 --> 00:18:28 is in the solar system. Modular.
00:18:30 --> 00:18:32 The sun's going around the Earth and the
00:18:32 --> 00:18:34 tails pointing the right way as it moves.
00:18:34 --> 00:18:36 Tails of comets always pointing away from the
00:18:36 --> 00:18:39 sun. And to me that kind of marks the
00:18:39 --> 00:18:42 dawn of the modern scientific view
00:18:42 --> 00:18:45 of comets from the cultural. We don't
00:18:45 --> 00:18:48 know what they are, but they are important.
00:18:50 --> 00:18:52 That's a real kind of boundary point for me.
00:18:52 --> 00:18:53 Andrew Dunkley: Yeah, yeah, fascinating.
00:18:53 --> 00:18:55 I was actually going to ask you about the uh,
00:18:55 --> 00:18:57 you know, the point in time where we went
00:18:57 --> 00:18:59 from the mythology m to the
00:19:00 --> 00:19:03 understanding that this, this was something
00:19:03 --> 00:19:05 else. And yeah, you covered that beautifully.
00:19:05 --> 00:19:08 Gonna just take a breath on space nuts. Uh,
00:19:08 --> 00:19:10 you're with Andrew Dunkley and Professor
00:19:10 --> 00:19:11 Jonti Horner.
00:19:14 --> 00:19:17 Jonti Horner: 0G and I feel fine. Space nuts.
00:19:17 --> 00:19:18 Andrew Dunkley: I did say a breath. That was quick.
00:19:18 --> 00:19:21 Um, let's continue talking about, uh, comets
00:19:21 --> 00:19:24 and meteors. There have been a lot of them in
00:19:24 --> 00:19:26 the news of late. Um, Comet
00:19:26 --> 00:19:29 Pan Stars is, um, you know, it was very,
00:19:29 --> 00:19:32 very popular, uh, late
00:19:32 --> 00:19:35 April. Uh, and uh,
00:19:35 --> 00:19:38 we've seen in recent times, um, a
00:19:38 --> 00:19:40 new kind of comet. And those are the ones
00:19:40 --> 00:19:43 that are coming from other systems, uh,
00:19:43 --> 00:19:45 not the ones that are
00:19:45 --> 00:19:48 continually rotating through our own solar
00:19:48 --> 00:19:51 system. We've had these exo comets that have
00:19:52 --> 00:19:54 been quite intriguing and um,
00:19:54 --> 00:19:56 opening up all sorts of new ideas and
00:19:56 --> 00:19:59 questions about, uh, comets and other
00:19:59 --> 00:20:02 parts of the universe and what we could learn
00:20:02 --> 00:20:05 from them. Um, and
00:20:05 --> 00:20:07 new comets are being discovered all the time.
00:20:08 --> 00:20:09 That doesn't mean they haven't been here
00:20:09 --> 00:20:12 before, but it does mean that they've got
00:20:12 --> 00:20:15 very longitudinal travel times.
00:20:15 --> 00:20:18 So, um, you know, some we won't ever see
00:20:18 --> 00:20:20 because we'll have been and gone before they
00:20:20 --> 00:20:22 get here and others we'll
00:20:23 --> 00:20:25 maybe see several times during our lifetimes.
00:20:26 --> 00:20:29 Jonti Horner: Absolutely. Now historically, people broke
00:20:29 --> 00:20:31 the comets we found down into two categories.
00:20:31 --> 00:20:34 We had short period comets, which are
00:20:34 --> 00:20:36 comets. The definition when I was a kid was
00:20:36 --> 00:20:38 comets whose orbital periods were less than
00:20:38 --> 00:20:41 200 years shorter than that and you were a
00:20:41 --> 00:20:42 short period comet, longer than that and you
00:20:42 --> 00:20:44 were a long period comet. Now there are
00:20:44 --> 00:20:46 subtleties within that, within the short
00:20:46 --> 00:20:48 period comets. We have comets like Comet
00:20:48 --> 00:20:49 Hallie, which are called the Hallie type
00:20:49 --> 00:20:52 comets which come round with a period
00:20:52 --> 00:20:54 comparable to a human lifetime or a bit
00:20:54 --> 00:20:56 longer. The two brightest and most famous of
00:20:56 --> 00:20:57 those are Comet Hallie and Comet Swift
00:20:57 --> 00:20:59 Tuttle. You then have the Jupiter family
00:20:59 --> 00:21:01 comets, which are comets whose orbits, uh,
00:21:01 --> 00:21:04 are just a few years and are typically under
00:21:04 --> 00:21:06 Jupiter's control. And when I was a kid,
00:21:06 --> 00:21:08 anything longer than 200 years was considered
00:21:08 --> 00:21:11 long period. Now that kind of got smashed
00:21:11 --> 00:21:13 into the ground a bit in the early 2000s when
00:21:13 --> 00:21:16 Comet IKEA Jang was sighted, because Comet
00:21:16 --> 00:21:19 Ikea Zhang was very well observed,
00:21:19 --> 00:21:20 its orbit was well calculated and it was
00:21:20 --> 00:21:23 found to have a period of 366 years, I think
00:21:23 --> 00:21:26 it is. And that allowed people to identify
00:21:26 --> 00:21:28 the previous observations of that comet from
00:21:28 --> 00:21:30 the last time it was around. So that's
00:21:30 --> 00:21:33 currently the record holder where we're
00:21:33 --> 00:21:36 absolutely certain that it's been seen on
00:21:36 --> 00:21:38 multiple occasions and it has a
00:21:38 --> 00:21:41 periodic comet designation now. Now a
00:21:41 --> 00:21:43 subtlety to that is we do have the Kreutz sun
00:21:43 --> 00:21:45 grazing comets. I can talk more about them a
00:21:45 --> 00:21:47 little later where we have a strong
00:21:47 --> 00:21:50 identification between an observation of
00:21:50 --> 00:21:52 the comet, say with comedy kaya Seki in
00:21:52 --> 00:21:55 1965 and um, a previous
00:21:55 --> 00:21:58 apparition in the 1100s, which is about
00:21:58 --> 00:22:00 an 800 year return. Yeah, that's a bit
00:22:00 --> 00:22:03 woolier because the comets we observe now are
00:22:03 --> 00:22:06 fragments of one comet back then, and
00:22:06 --> 00:22:08 so therefore several comets tied to that
00:22:08 --> 00:22:09 initial apparition. So there's all that
00:22:09 --> 00:22:12 complexity there. We then have the long
00:22:12 --> 00:22:14 period comets, which, like I say were
00:22:14 --> 00:22:17 200 years or more. It still kind
00:22:17 --> 00:22:19 of is. But with those objects that are both
00:22:19 --> 00:22:22 long period and short period thanksgiang,
00:22:22 --> 00:22:23 you've got these objects whose orbital
00:22:23 --> 00:22:26 periods are so long that they are markedly
00:22:26 --> 00:22:28 longer than a human lifetime, even if they're
00:22:28 --> 00:22:30 comets that have been through before. So a
00:22:30 --> 00:22:32 good example of a really bright comet that is
00:22:32 --> 00:22:35 considered long period but has been through
00:22:35 --> 00:22:38 many times before is Comet Hale Bopp. Yes,
00:22:38 --> 00:22:41 was spectacular in 96, 97. It was visible
00:22:41 --> 00:22:43 with a naked eye for 18 months, shattering
00:22:43 --> 00:22:45 all the records. It will be back in about the
00:22:45 --> 00:22:47 year 4400. It was the last round when the
00:22:47 --> 00:22:50 Egyptians were building pyramids. And that is
00:22:50 --> 00:22:53 perversely a long period comet with a
00:22:53 --> 00:22:55 relatively short period orbit for a long
00:22:55 --> 00:22:58 period of comet. And so scientifically we'd
00:22:58 --> 00:23:01 call that dynamically old or not a
00:23:01 --> 00:23:02 new comet because it's been around a number
00:23:02 --> 00:23:05 of times at the very long period
00:23:05 --> 00:23:07 end of the long period comets, you get things
00:23:07 --> 00:23:09 that are coming in from halfway to the
00:23:09 --> 00:23:12 nearest star from a region we describe as the
00:23:12 --> 00:23:14 Oort Cloud or the Opic Oort cloud. And
00:23:14 --> 00:23:17 those things on their way in have
00:23:17 --> 00:23:20 calculated orbital periods of hundreds of
00:23:20 --> 00:23:23 thousands or even millions of years. And many
00:23:23 --> 00:23:25 of those actually only come through once. And
00:23:25 --> 00:23:27 then they get nudged and ejected from the
00:23:27 --> 00:23:29 solar system, never to return, going out to
00:23:29 --> 00:23:32 wander among the stars. And it's objects like
00:23:32 --> 00:23:34 that that will become the interstellar comets
00:23:34 --> 00:23:37 for other stars, in the same way that
00:23:37 --> 00:23:38 this third group of comets that you alluded
00:23:38 --> 00:23:41 to that we found recently are interstellar
00:23:41 --> 00:23:43 comets in our system. So these are the
00:23:43 --> 00:23:45 objects coming through so quickly that they
00:23:45 --> 00:23:47 are not gravitationally bound to the sun,
00:23:47 --> 00:23:49 but also so quickly that there is no
00:23:49 --> 00:23:52 possibility that they ever were. They've been
00:23:52 --> 00:23:54 flung in so quickly that they must come from
00:23:55 --> 00:23:58 another place. The most recent one was Three
00:23:58 --> 00:24:00 Eye Atlas, which got talked about a huge
00:24:00 --> 00:24:03 amount. Yes. Was definitely not an alien
00:24:03 --> 00:24:05 spaceship. And to avoid getting too
00:24:05 --> 00:24:07 political, just a very brief comment on that
00:24:07 --> 00:24:09 because it needs to be stated and restated,
00:24:09 --> 00:24:12 which is, uh, the arguments of that being an
00:24:12 --> 00:24:14 alien spaceship were the work of one person.
00:24:15 --> 00:24:17 One person who is not a solar system
00:24:17 --> 00:24:19 astronomer historically, but has reached that
00:24:19 --> 00:24:22 age and level of senility that they believe
00:24:22 --> 00:24:24 they can be an expert in things that they are
00:24:24 --> 00:24:27 not and has a certain financial interest in
00:24:27 --> 00:24:29 keeping people interested in aliens because
00:24:29 --> 00:24:31 they buy his book.
00:24:31 --> 00:24:31 Andrew Dunkley: Click.
00:24:32 --> 00:24:35 Jonti Horner: The community of astronomers has been very
00:24:35 --> 00:24:37 upset and very Shrek about that because it
00:24:37 --> 00:24:39 diverts attention from what is a really
00:24:39 --> 00:24:41 fascinating object on the fact that it's
00:24:41 --> 00:24:44 really fascinating, but also breeds a certain
00:24:44 --> 00:24:45 amount of fear. And I genuinely had people
00:24:45 --> 00:24:48 reaching out to me when he was pushing
00:24:48 --> 00:24:50 this narrative of it being aliens that were
00:24:50 --> 00:24:51 going to invade because they were frightened,
00:24:51 --> 00:24:54 heightened, they were genuinely worried
00:24:54 --> 00:24:55 because a Harvard astronomer was saying
00:24:55 --> 00:24:58 aliens were going to come and beat us all up.
00:24:58 --> 00:24:59 Andrew Dunkley: Yeah.
00:24:59 --> 00:25:01 Jonti Horner: And it's problematic because it hides the
00:25:01 --> 00:25:03 science, but it's also more widely
00:25:03 --> 00:25:06 problematic at a time when we have lowering
00:25:06 --> 00:25:09 levels of engagement with science and very
00:25:09 --> 00:25:11 much lowering levels of trust in science and
00:25:11 --> 00:25:14 scientists. It's very bad to have someone
00:25:14 --> 00:25:17 acting disingenuously, telling lies
00:25:17 --> 00:25:19 on muddying the water. Um, and then
00:25:19 --> 00:25:21 arguing that everybody else is wrong and mean
00:25:21 --> 00:25:23 to me and I'm the only one telling the truth.
00:25:23 --> 00:25:26 And it's part of that whole fake news thing
00:25:26 --> 00:25:29 that I think is dangerous and damaging.
00:25:29 --> 00:25:32 You know, we need people to have trust and
00:25:32 --> 00:25:33 faith in science because it's so integral to
00:25:33 --> 00:25:36 our lives. And it's good to question. But
00:25:36 --> 00:25:38 it's bad when people say things that they
00:25:38 --> 00:25:40 fundamentally know are not true just to get
00:25:40 --> 00:25:42 hits or clicks or money. Yeah.
00:25:43 --> 00:25:46 Andrew Dunkley: And it's important to debunk that
00:25:46 --> 00:25:49 kind of, uh, approach because
00:25:49 --> 00:25:51 I've had people come up to me very recently
00:25:51 --> 00:25:54 who know I do this podcast, uh,
00:25:54 --> 00:25:56 who've said to me, oh, what do you think of
00:25:56 --> 00:25:58 that alien spaceship? And I go, it's,
00:25:59 --> 00:26:01 it's, that's what I think
00:26:01 --> 00:26:04 because it's, it's somebody trying to get
00:26:04 --> 00:26:05 media attention. It's got nothing. It's a
00:26:05 --> 00:26:08 rock. It's actually, it's, it's a, it's an
00:26:08 --> 00:26:10 ice conglomerate. It's, it's not a, it's not
00:26:10 --> 00:26:13 a spaceship at all. It's not behaving like a
00:26:13 --> 00:26:15 spaceship would. It's behaving like something
00:26:15 --> 00:26:17 passing through our solar system.
00:26:18 --> 00:26:21 Um, and people, people. The thing is,
00:26:21 --> 00:26:22 Jonti, people are buying
00:26:22 --> 00:26:25 Jonti Horner: this rubbish, but there's an old saying
00:26:25 --> 00:26:28 that you know, like, and run around the
00:26:28 --> 00:26:30 world before the truth has got its boots on,
00:26:30 --> 00:26:32 especially when it's an attractive light.
00:26:32 --> 00:26:35 It's, I mean, again, digging into my
00:26:35 --> 00:26:36 memories of Terry Pratchett stuff which
00:26:36 --> 00:26:39 happens a lot. It's the old quote when
00:26:39 --> 00:26:41 they're talking about newspapers and nobody
00:26:41 --> 00:26:43 really ever wants to hear a story about dog
00:26:43 --> 00:26:44 bites mum because it happens all the time.
00:26:44 --> 00:26:46 But if you've got a story that says Mum bites
00:26:46 --> 00:26:48 dog, everybody's fascinated.
00:26:48 --> 00:26:48 Andrew Dunkley: Yeah.
00:26:48 --> 00:26:51 Jonti Horner: And this story has all the elements. It's so
00:26:51 --> 00:26:53 salacious that it gets coverage and people
00:26:53 --> 00:26:56 who don't normally read or digest science
00:26:56 --> 00:26:58 are not interested, will see this and hook
00:26:58 --> 00:27:00 into it. And when the byline is Harvard
00:27:00 --> 00:27:03 astronomer, that gives it a huge amount of
00:27:03 --> 00:27:03 credence.
00:27:03 --> 00:27:04 Andrew Dunkley: It does.
00:27:04 --> 00:27:06 Jonti Horner: Uh, and nobody hears the rebuttals. It's
00:27:07 --> 00:27:09 a bit like, you know, when there are claims
00:27:09 --> 00:27:10 of life on a planet around another star.
00:27:10 --> 00:27:13 Nobody remembers the, the follow
00:27:13 --> 00:27:15 ups that say actually it wasn't. They just
00:27:15 --> 00:27:17 remember, oh, we found aliens and we haven't.
00:27:18 --> 00:27:20 I mean, I think that story that,
00:27:20 --> 00:27:23 Andrew Dunkley: uh, the most recent story
00:27:23 --> 00:27:26 that I recall where that, that claim was made
00:27:26 --> 00:27:29 was um, the one about the
00:27:29 --> 00:27:31 something they. What was it they found in
00:27:31 --> 00:27:33 the, in the atmosphere of Venus. It was
00:27:34 --> 00:27:34 phosphine.
00:27:34 --> 00:27:37 Jonti Horner: Yes. I can go on a little bit of a side rant
00:27:37 --> 00:27:39 about that. My heart broke. Um, the
00:27:39 --> 00:27:42 lead author on that study was Jane Greaves in
00:27:42 --> 00:27:44 the uk, who's someone I knew very well when I
00:27:44 --> 00:27:46 was in the uk and she's a fabulous science
00:27:46 --> 00:27:49 and just all around wonderful individual. And
00:27:49 --> 00:27:51 the story was led by a UK team
00:27:52 --> 00:27:54 who, if you actually read the paper, don't
00:27:54 --> 00:27:57 say anything that is, this is life. What they
00:27:57 --> 00:28:00 say is we found a very weak signal of
00:28:00 --> 00:28:02 this gas in Venus's atmosphere. It's right
00:28:02 --> 00:28:04 down in the noise. So there is a chance it's
00:28:04 --> 00:28:07 a false positive anyway, so there needs to be
00:28:07 --> 00:28:09 a bit of extra work done. It's a little bit
00:28:09 --> 00:28:12 interesting because on the Earth, the only
00:28:12 --> 00:28:15 processes that produce this peculiar gas
00:28:15 --> 00:28:18 are, uh, technology and industry or life.
00:28:19 --> 00:28:20 Yeah. We don't know of any other way that
00:28:20 --> 00:28:22 it's made, but that doesn't mean that there
00:28:22 --> 00:28:23 aren't other ways that it's made.
00:28:23 --> 00:28:25 Andrew Dunkley: Isn't that a tasty morsel for the popular
00:28:25 --> 00:28:26 press?
00:28:26 --> 00:28:26 Jonti Horner: Absolutely.
00:28:26 --> 00:28:28 But what happened then was that there is an
00:28:29 --> 00:28:32 American outreach journal,
00:28:32 --> 00:28:34 um, science communication journal, that broke
00:28:34 --> 00:28:37 embargo on this story, didn't talk to Jane
00:28:37 --> 00:28:39 and her colleagues, but instead ran a story
00:28:39 --> 00:28:41 saying British scientists found life on
00:28:41 --> 00:28:43 Venus. Which is not what they'd said at all.
00:28:43 --> 00:28:45 No, that's what started the absolute bum
00:28:45 --> 00:28:48 fight. And the vitriol on the hair and the
00:28:48 --> 00:28:50 death threats, believe it or not, that Jane
00:28:50 --> 00:28:53 Grieves got because of this were
00:28:53 --> 00:28:55 astonishing. It was absolutely terrible. And
00:28:55 --> 00:28:58 instead of being able to managed to deploy
00:28:58 --> 00:29:00 this wonderful story about this fascinating
00:29:00 --> 00:29:02 new result they got, they spent all their
00:29:02 --> 00:29:05 time in damage control because this
00:29:06 --> 00:29:08 publication chose to break the embargo
00:29:08 --> 00:29:11 early and run a story that was not factually
00:29:11 --> 00:29:13 true, but again would get them clicks. Yep.
00:29:13 --> 00:29:16 Andrew Dunkley: Yeah. And that's unfortunately, the modern
00:29:16 --> 00:29:19 media and, um, the Internet's to
00:29:19 --> 00:29:21 blame. Well, it's not the Internet that's to
00:29:21 --> 00:29:23 blame. It's the people who use it that are to
00:29:23 --> 00:29:26 blame. And it's one of the, um,
00:29:26 --> 00:29:27 one of the things you've really got to be
00:29:27 --> 00:29:30 careful of when you are, uh, following
00:29:30 --> 00:29:33 a story, whether it's an exocomet that's not
00:29:33 --> 00:29:36 a spaceship or, uh, life that's
00:29:36 --> 00:29:38 not in Venus's atmosphere,
00:29:38 --> 00:29:41 um, and even to a lesser
00:29:41 --> 00:29:43 degree, and you and I mentioned this before
00:29:43 --> 00:29:45 we started, the way the media gets its
00:29:45 --> 00:29:48 information confused, such as
00:29:48 --> 00:29:51 reporting, uh, on, um, upcoming spectacular
00:29:51 --> 00:29:54 meteor showers that, uh, everyone
00:29:54 --> 00:29:56 gets excited about and then they realize
00:29:56 --> 00:29:57 they're on the wrong side of the planet.
00:29:57 --> 00:30:00 Jonti Horner: Absolutely. And this is a caution I give to
00:30:00 --> 00:30:02 everybody, both for comets and for meteors
00:30:02 --> 00:30:03 actually, but particularly for those of us in
00:30:03 --> 00:30:06 the Southern hemisphere, um, meteor showers
00:30:07 --> 00:30:10 and comets are things that are best seen
00:30:10 --> 00:30:12 from some latitudes and not from others. And
00:30:12 --> 00:30:13 for each comet or for each meteor shower
00:30:13 --> 00:30:16 that's different. Now, I'll talk later on
00:30:16 --> 00:30:18 about a newly discovered comet that might be
00:30:18 --> 00:30:20 very spectacular in late 2028.
00:30:21 --> 00:30:22 That comet is primarily going to be a
00:30:22 --> 00:30:25 Southern hemisphere object. So it will
00:30:25 --> 00:30:26 probably be better for us in Australia and
00:30:26 --> 00:30:28 New Zealand than it will be for people in the
00:30:28 --> 00:30:30 UK or the us Just as an example,
00:30:31 --> 00:30:33 when events are happening that are, uh,
00:30:33 --> 00:30:35 primarily good for the Northern Hemisphere.
00:30:35 --> 00:30:36 The Northern Hemisphere has more people and
00:30:36 --> 00:30:39 more media. And what I've seen happen more
00:30:39 --> 00:30:41 and more is that, uh, the media in Australia,
00:30:42 --> 00:30:44 and I know the Australian stuff because
00:30:44 --> 00:30:46 that's local to us. It's probably just the
00:30:46 --> 00:30:48 same in New Zealand, South Africa, South
00:30:48 --> 00:30:50 America, all these other places. But the
00:30:50 --> 00:30:52 media there will pick up these stories and
00:30:52 --> 00:30:54 just run them without running
00:30:54 --> 00:30:57 the sanity filter. So the April
00:30:57 --> 00:30:59 Lyrids are a really good example of this. But
00:30:59 --> 00:31:01 a better one is probably the Perseid meteor
00:31:01 --> 00:31:03 shower in August. Now, it's a little bit of
00:31:03 --> 00:31:06 background here. When we've got a meteor
00:31:06 --> 00:31:08 shower, we're getting bits of dust and debris
00:31:08 --> 00:31:11 hitting the Earth's atmosphere and ablating
00:31:11 --> 00:31:13 at an altitude of about 80 km. Now,
00:31:14 --> 00:31:16 ablation is a slightly weird thing. People
00:31:16 --> 00:31:18 often describe this as burning up, but it's
00:31:18 --> 00:31:20 not burning up in the sense of a flame being
00:31:20 --> 00:31:22 lit and a fire burning. It's rather that
00:31:22 --> 00:31:24 these things push into the atmosphere at
00:31:24 --> 00:31:26 really high speed, pile the air up in front
00:31:26 --> 00:31:28 of them, getting the air superheated,
00:31:28 --> 00:31:30 creating a load of plasma. And the heat from
00:31:30 --> 00:31:33 that makes and vaporizes the bit of debris.
00:31:33 --> 00:31:35 So it's not burning up in the traditional
00:31:35 --> 00:31:37 sense. And anytime you see a meteor, you see
00:31:37 --> 00:31:39 a shooting star, that's what you're seeing.
00:31:39 --> 00:31:40 And, uh, the bigger the bit of dust, the
00:31:40 --> 00:31:43 brighter it will be. The faster it's moving
00:31:43 --> 00:31:45 at a given size, the more energy it's got. So
00:31:45 --> 00:31:47 again, the brighter it'll be. Yeah. And you
00:31:47 --> 00:31:50 see shooting stars on any night of the year,
00:31:50 --> 00:31:53 typically, uh, three or four an hour in the
00:31:53 --> 00:31:55 evenings, five or six an hour in the
00:31:55 --> 00:31:57 mornings, potentially. And that difference is
00:31:57 --> 00:31:58 just because in the mornings you're facing
00:31:58 --> 00:32:00 the direction the Earth's moving. So you're
00:32:00 --> 00:32:02 getting collisions that are head on. So the
00:32:02 --> 00:32:05 average collision speed is higher. So a grain
00:32:05 --> 00:32:07 of dust that's the same size will be a bit
00:32:07 --> 00:32:09 brighter. Therefore, the things that in the
00:32:09 --> 00:32:11 evening that will be too faint to see become
00:32:11 --> 00:32:13 visible. So you get a slight increase in the
00:32:13 --> 00:32:15 rate towards morning. Then in the evening,
00:32:16 --> 00:32:17 um, it's also you're probably getting a
00:32:17 --> 00:32:19 slightly increased amount of stuff entering
00:32:19 --> 00:32:20 the atmosphere because you always see more
00:32:20 --> 00:32:22 flies hit your windscreen than your air
00:32:22 --> 00:32:24 windscreen. Same kind of idea. Yeah.
00:32:25 --> 00:32:27 When we get a meteor shower, what's happening
00:32:27 --> 00:32:30 is we're passing through the area of
00:32:30 --> 00:32:32 space where the Earth passes near the orbit
00:32:32 --> 00:32:34 of either a comet or an asteroid. And
00:32:34 --> 00:32:36 typically it's a comet. Now, every time a
00:32:36 --> 00:32:39 comet goes around the sun, that dirty
00:32:39 --> 00:32:42 snowball or snowy dirt ball gets hot. The
00:32:42 --> 00:32:44 volatile material on the surface is too hot
00:32:44 --> 00:32:47 to stay solid, so becomes a gas in a
00:32:47 --> 00:32:50 process called sublimation. And you get jets
00:32:50 --> 00:32:52 erupting from the comet, shrouding in gas,
00:32:53 --> 00:32:55 which is then blown away from the sun to give
00:32:55 --> 00:32:57 you the tails. Those jets erupting into
00:32:57 --> 00:32:59 space carry with them dust.
00:33:00 --> 00:33:03 Now, biggest bits of dust are pushed away so
00:33:03 --> 00:33:04 gently, they'll fall back to the comet and
00:33:04 --> 00:33:06 clog it up. And some comets eventually turn
00:33:06 --> 00:33:08 off because of. This also is the reason most
00:33:08 --> 00:33:11 comets are only active from a few locations
00:33:11 --> 00:33:13 on the surface, not uniformly, because most
00:33:13 --> 00:33:15 of the surface is clogged up and you've just
00:33:15 --> 00:33:17 got a few active areas where volatile
00:33:17 --> 00:33:20 material is exposed. Yeah, but that dust
00:33:20 --> 00:33:22 that's ejected from the comet is ejected with
00:33:22 --> 00:33:24 speeds measured in meters per second or
00:33:24 --> 00:33:27 centimetres per second from an object that's
00:33:27 --> 00:33:28 traveling at a speed measured in tens of
00:33:28 --> 00:33:31 kilometers a second. So what that means is
00:33:31 --> 00:33:34 that, uh, that dust is moving away from
00:33:34 --> 00:33:36 the comet at a speed almost identical to the
00:33:36 --> 00:33:39 speed the comet's traveling itself. I guess
00:33:39 --> 00:33:41 it's like if you. You're driving along the
00:33:41 --> 00:33:43 road and you drop a tennis ball out of the
00:33:43 --> 00:33:45 window until the wind resistance pushes it
00:33:45 --> 00:33:47 back. If there wasn't a wind resistance
00:33:47 --> 00:33:50 there, it would move along with the car, just
00:33:50 --> 00:33:51 drifting away very slightly based on the
00:33:51 --> 00:33:53 speed you pushed it out of the window. Same
00:33:53 --> 00:33:54 idea. Yeah.
00:33:54 --> 00:33:57 Andrew Dunkley: I actually saw a really great experiment once
00:33:57 --> 00:33:59 where they were.
00:34:01 --> 00:34:03 How did they do it? They had a guy on the
00:34:03 --> 00:34:06 back of a truck, and they
00:34:06 --> 00:34:08 were driving at, like, uh, 100
00:34:08 --> 00:34:11 kilometers an hour, and they shot him
00:34:11 --> 00:34:14 off the truck in the opposite direction at
00:34:14 --> 00:34:17 the same speed, and he just stopped where he
00:34:17 --> 00:34:17 landed.
00:34:17 --> 00:34:19 Jonti Horner: Well, it's brilliant. I think mythbusters did
00:34:19 --> 00:34:22 something similar, and it's amazing. Our
00:34:22 --> 00:34:24 common sense is physics, really
00:34:25 --> 00:34:27 simple physics is great, but our common sense
00:34:27 --> 00:34:30 breaks down in some situations because our
00:34:30 --> 00:34:32 common sense is a naturally inherited thing
00:34:32 --> 00:34:34 about the world at the speeds we experience
00:34:34 --> 00:34:37 it. And so we tend to think if you're running
00:34:37 --> 00:34:39 forwards at 10km an hour and you throw
00:34:39 --> 00:34:41 something forwards, it will travel a bit
00:34:41 --> 00:34:43 faster. That breaks down when you get to
00:34:43 --> 00:34:45 relativity. There's all these weird things
00:34:45 --> 00:34:47 around it where our common sense gets it
00:34:47 --> 00:34:50 wrong for comets and for the dust. And it
00:34:50 --> 00:34:51 took me a long while to get my head around
00:34:51 --> 00:34:54 this because it's a bit counterintuitive if
00:34:54 --> 00:34:56 you eject Dust from a comet. You can eject
00:34:56 --> 00:34:58 the dust forward or backwards. So you can
00:34:58 --> 00:35:00 imagine this jet from the comet working a bit
00:35:00 --> 00:35:03 like a geyser, turning off when it gets dark
00:35:03 --> 00:35:05 and it gets cold, and then turning off again
00:35:05 --> 00:35:07 in the morning when it gets hot again. That
00:35:07 --> 00:35:09 can throw dust forwards, sidewards, and, um,
00:35:09 --> 00:35:12 backwards, or any combination of the above.
00:35:12 --> 00:35:14 So that means this comet is throwing out dust
00:35:14 --> 00:35:17 at a speed of meters per second, a bit like a
00:35:17 --> 00:35:19 sprinkler into space. The
00:35:19 --> 00:35:22 dust has a forward component to its speed.
00:35:22 --> 00:35:24 So it could be going sideways but a little
00:35:24 --> 00:35:25 forward, or it could be going head on in
00:35:25 --> 00:35:28 front of the comet that is now traveling
00:35:28 --> 00:35:30 around the sun faster than the comet is,
00:35:30 --> 00:35:32 which means it will move onto, um, an orbit
00:35:32 --> 00:35:35 with a longer period than the comet. So the
00:35:35 --> 00:35:36 next time the comet comes round, that grain
00:35:36 --> 00:35:39 of dust will arrive after the comet. So dust
00:35:39 --> 00:35:42 thrown forward ends up behind. And similarly,
00:35:42 --> 00:35:44 dust thrown backwards is moving slower than
00:35:44 --> 00:35:45 the comet, which puts it on a slightly
00:35:45 --> 00:35:48 shorter period orbit, and therefore it will
00:35:48 --> 00:35:50 arrive ahead of the comet next time. And that
00:35:50 --> 00:35:52 little bit of sidewards motion also means it
00:35:52 --> 00:35:54 will spread out a little bit in space. What
00:35:54 --> 00:35:57 this means over, uh, time periods is that,
00:35:57 --> 00:35:58 uh, comets, every time they come round,
00:35:59 --> 00:36:01 essentially shed what becomes like a javelin
00:36:01 --> 00:36:04 shape, a spear of dust into space with a
00:36:04 --> 00:36:07 comet at the center, like a
00:36:07 --> 00:36:09 spike. And that spike gradually diffuses over
00:36:09 --> 00:36:11 time, spreads out further and further ahead
00:36:11 --> 00:36:13 and behind the comet. And so over a long time
00:36:13 --> 00:36:16 scale, you eventually end up with the comet's
00:36:16 --> 00:36:18 orbit shrouded in dust. And the dust can be
00:36:18 --> 00:36:20 quite spread out over millions of kilometers.
00:36:21 --> 00:36:23 Yeah, these orbits are oriented randomly in
00:36:23 --> 00:36:26 space. So many of them don't intersect the
00:36:26 --> 00:36:28 Earth. Even if the comet gets closer to the
00:36:28 --> 00:36:31 sun than we are at its closest, passes above
00:36:31 --> 00:36:33 or below the Earth's orbit, nothing happens.
00:36:33 --> 00:36:36 But for a subset of them, the comet
00:36:37 --> 00:36:39 will, in its orbit, have the potential to get
00:36:39 --> 00:36:41 very close to the Earth. So its orbit and the
00:36:41 --> 00:36:43 Earth get very close together. And in those
00:36:43 --> 00:36:46 cases, every time we go around the sun, if
00:36:46 --> 00:36:47 that comet's been laying dust down for a
00:36:47 --> 00:36:50 while, we'll run into the dust every time we
00:36:50 --> 00:36:52 go around. And that dust will hit the Earth's
00:36:52 --> 00:36:54 M atmosphere, which means we're going through
00:36:54 --> 00:36:56 a dirtier bit of the solar system and we get
00:36:56 --> 00:36:58 more meteors. That's when we get a meteor
00:36:58 --> 00:37:00 shower. But the other telltale thing for the
00:37:00 --> 00:37:03 meteor shower is all the dust grains that hit
00:37:03 --> 00:37:05 the Earth in a meteor shower are moving
00:37:05 --> 00:37:07 essentially parallel to each other.
00:37:07 --> 00:37:08 They're all following the same Orbit around
00:37:08 --> 00:37:09 the sun, hitting the Earth, the Earth from
00:37:09 --> 00:37:11 the same direction at the same speed.
00:37:13 --> 00:37:15 So all this dust is coming towards you from a
00:37:15 --> 00:37:17 single point in space. So from your point of
00:37:17 --> 00:37:19 view, looking at the sky, when you see those
00:37:19 --> 00:37:22 meteors, part of a meteor shower, they appear
00:37:22 --> 00:37:25 to appear anywhere in the sky. But if
00:37:25 --> 00:37:26 you trace them back, they'll all point to a
00:37:26 --> 00:37:28 single point in the sky, that something we
00:37:28 --> 00:37:31 call the radiant. And that's effectively the
00:37:31 --> 00:37:33 point in space they're traveling towards us
00:37:33 --> 00:37:35 from. And um, they diverge because they
00:37:35 --> 00:37:37 perspective, they're coming closer to you. So
00:37:37 --> 00:37:40 every meteor shower has a radiant in the sky.
00:37:40 --> 00:37:42 The April Lyrids have their radiant in
00:37:43 --> 00:37:45 Lyra, although for a fair part of their time
00:37:45 --> 00:37:47 it's actually in Hercules, it m drifts a bit.
00:37:47 --> 00:37:49 The Perseids have their radiant in Perseus,
00:37:50 --> 00:37:52 the Geminids in Gemini and so on.
00:37:53 --> 00:37:56 So that's all well and good. If the
00:37:56 --> 00:37:59 radiant is below the horizon, that means the
00:37:59 --> 00:38:00 meteors are hitting the other side of the
00:38:00 --> 00:38:02 Earth and you can't see them because the
00:38:02 --> 00:38:04 Earth's in the way. So first point with a
00:38:04 --> 00:38:07 meteor shower is unlike some of the media
00:38:07 --> 00:38:09 reports, you can't see meteors for that
00:38:09 --> 00:38:12 meteor shower at any time of night. You can
00:38:12 --> 00:38:13 only see them when the radiance above the
00:38:13 --> 00:38:15 horizon point, number one
00:38:16 --> 00:38:18 point. The second is the higher in the sky
00:38:18 --> 00:38:21 that radiant is, the more head on into the
00:38:21 --> 00:38:23 stream you're going. So the more meteors
00:38:23 --> 00:38:26 you'll see. Now the analogy I'd ah, use here
00:38:26 --> 00:38:28 is if you imagine getting your hose pipe and
00:38:28 --> 00:38:30 having it on that shower mode, you know,
00:38:30 --> 00:38:32 where water's coming out from many holes all
00:38:32 --> 00:38:35 at once. If you hold that hose pipe
00:38:35 --> 00:38:37 vertically and turn the tap on, all the water
00:38:37 --> 00:38:38 from that hose pipe will hit a relatively
00:38:38 --> 00:38:41 small area of the ground. If you turn that
00:38:41 --> 00:38:44 hose pipe to 45 degrees, that water will
00:38:44 --> 00:38:46 spread out over a larger surface area.
00:38:47 --> 00:38:47 Andrew Dunkley: Yep.
00:38:47 --> 00:38:49 Jonti Horner: Now if you imagine the meteors, the dust in a
00:38:49 --> 00:38:51 meteor shower coming in towards the Earth,
00:38:52 --> 00:38:54 the more directly overhead
00:38:54 --> 00:38:57 your point that they're coming from is the
00:38:57 --> 00:38:59 more meteors you'll get in a certain volume
00:38:59 --> 00:39:01 of the atmosphere and the lower to the
00:39:01 --> 00:39:03 horizon that point is, the more you'll spread
00:39:03 --> 00:39:05 those same number of grains of dust out.
00:39:06 --> 00:39:09 So the higher in the sky the radiant is, the
00:39:09 --> 00:39:10 more dust is hitting the part of the
00:39:10 --> 00:39:13 atmosphere you can see from your location. So
00:39:13 --> 00:39:15 the more meteors you get, and what this means
00:39:15 --> 00:39:17 is that the lower in the sky the rating is a
00:39:17 --> 00:39:20 few meteors you see. And so you see the most
00:39:20 --> 00:39:22 Meteors. For a given meteor shower, when the
00:39:22 --> 00:39:24 radiant is near what we call culmination,
00:39:24 --> 00:39:26 where it's nearly highest in the sky. For the
00:39:26 --> 00:39:28 southern hemisphere, when it's nearly due
00:39:28 --> 00:39:31 north, for the northern hemisphere rain, the
00:39:31 --> 00:39:33 radiant's nearly due south. So
00:39:33 --> 00:39:36 all well and good, but what that means is
00:39:36 --> 00:39:38 that ah, from different locations on the
00:39:38 --> 00:39:40 earth, a given meteor shower will give you a
00:39:40 --> 00:39:42 different strength of display. The April
00:39:42 --> 00:39:45 Lyrids, their radiant is
00:39:46 --> 00:39:48 34 degrees north of the equator. So that
00:39:48 --> 00:39:50 means if you lived 34 degrees north of the
00:39:50 --> 00:39:53 equator at about 2am in the morning, the
00:39:53 --> 00:39:55 radiant will be overhead and you're in the
00:39:55 --> 00:39:56 best place on the planet to see the meteors.
00:39:57 --> 00:40:00 If you had perfect vision, perfectly dark
00:40:00 --> 00:40:03 sky, you'd see a number of meteors, 15
00:40:03 --> 00:40:05 to 20 per hour for the April Lyrids and
00:40:05 --> 00:40:07 that's called the zenithal hourly rate.
00:40:07 --> 00:40:09 That's the number of meters you'd see in
00:40:09 --> 00:40:11 perfect conditions with perfect eyesight,
00:40:11 --> 00:40:13 with no light pollution if the radiant was
00:40:13 --> 00:40:16 overhead. The lower the radiant is in the
00:40:16 --> 00:40:18 sky, the more that number shrinks. So the
00:40:18 --> 00:40:21 ZHR is the theoretical maximum number
00:40:21 --> 00:40:23 you'd see. So good
00:40:23 --> 00:40:25 meteor shower, not a great one from the
00:40:25 --> 00:40:27 northern hemisphere, but for us in Brisbane,
00:40:27 --> 00:40:29 let's say 26 degrees south.
00:40:30 --> 00:40:32 The radiant of the April Lyrids at its
00:40:32 --> 00:40:34 highest in the sky is only 30 degrees above
00:40:34 --> 00:40:37 the horizon. That means that the
00:40:37 --> 00:40:40 volume of space where the dust is arriving is
00:40:40 --> 00:40:42 doubled. So you'd only see half the number of
00:40:42 --> 00:40:45 meteors. So instead of 20 per
00:40:45 --> 00:40:46 hour, you're down to 10 an hour
00:40:47 --> 00:40:50 immediately before anything else kicks in.
00:40:50 --> 00:40:52 And the further south you go, the lower the
00:40:52 --> 00:40:55 rates are. But the problem is the journalists
00:40:55 --> 00:40:56 covering this will pick up on a Northern
00:40:56 --> 00:40:58 hemisphere article and just repeat it.
00:40:58 --> 00:41:00 There's this meteor shower happening. You can
00:41:00 --> 00:41:02 see them all night, every night. Well that's
00:41:02 --> 00:41:04 not right. If the radiance below the horizon,
00:41:04 --> 00:41:06 you can't see them and you'll see 100 per
00:41:06 --> 00:41:08 hour and M that's because they've seen the
00:41:08 --> 00:41:10 zenithal hourly rate, quoted as 100 per hour.
00:41:10 --> 00:41:12 And they just use it as a number.
00:41:12 --> 00:41:13 Andrew Dunkley: Yeah.
00:41:13 --> 00:41:15 Jonti Horner: Unless you are incredibly, incredibly
00:41:15 --> 00:41:18 fortunate, you will never see the same number
00:41:18 --> 00:41:20 of meteors as the ZHR predicts
00:41:21 --> 00:41:23 because the radiant might be directly
00:41:23 --> 00:41:25 overhead. So the rate gets lower. Your eyes
00:41:25 --> 00:41:27 are not perfect unless you're one of the very
00:41:27 --> 00:41:30 rare observers. The rates will get lower,
00:41:30 --> 00:41:32 there might be light pollution. The phantom
00:41:33 --> 00:41:35 meteors are not seen, the rates get lower.
00:41:35 --> 00:41:37 The moon might be in the sky. The phantom
00:41:37 --> 00:41:39 meters are not seen. The rates are lower. So
00:41:40 --> 00:41:42 you will never see a number of meteors in the
00:41:42 --> 00:41:45 sky equal to the ZHR unless the meteor
00:41:45 --> 00:41:48 shower is more active than predicted in which
00:41:48 --> 00:41:49 case the ZHR will be higher and you'd see
00:41:49 --> 00:41:52 more. Where this really comes in is for
00:41:52 --> 00:41:54 meteor showers like the Perseids. The
00:41:54 --> 00:41:56 Perseids are one of the big three. There are
00:41:56 --> 00:41:59 AH3 awesome meteor showers a year that are by
00:41:59 --> 00:42:01 far the best in a given year.
00:42:01 --> 00:42:03 They're the highest rates, the most dust
00:42:04 --> 00:42:06 coming in. Other high speed, the Quadrantids
00:42:06 --> 00:42:09 in early January are very, very short
00:42:09 --> 00:42:11 lived. They're a wage shower. You've got a
00:42:11 --> 00:42:13 very low rate of meteors for most of the time
00:42:13 --> 00:42:14 they're active and then a very narrow spike
00:42:14 --> 00:42:17 that can be very big. But if you manage
00:42:17 --> 00:42:19 to see that spike there's a lot of meteors.
00:42:19 --> 00:42:21 They're only really visible from the northern
00:42:21 --> 00:42:24 hemisphere. The Perseids in August are
00:42:24 --> 00:42:26 probably uh, the most storied meteor shower
00:42:27 --> 00:42:30 with long history of observations
00:42:31 --> 00:42:32 linked to comet Swift Tuttle which goes
00:42:32 --> 00:42:34 around every 120. 130 years
00:42:35 --> 00:42:37 incidentally will be incredibly spectacular
00:42:37 --> 00:42:39 in the year 2126 if people hang around to see
00:42:39 --> 00:42:40 it.
00:42:40 --> 00:42:42 Andrew Dunkley: Yeah, okay, I'll write that in my diary.
00:42:43 --> 00:42:45 Jonti Horner: Um, Perseids are brilliant but their radiant
00:42:45 --> 00:42:48 is at about 55 degrees north in the sky.
00:42:49 --> 00:42:51 Fabulous from northern Europe, fabulous from
00:42:51 --> 00:42:53 North America, places north of the equator to
00:42:53 --> 00:42:55 get a really good show. But we get articles
00:42:55 --> 00:42:58 every year on commercial media here in
00:42:58 --> 00:43:00 Australia saying the persons are happening go
00:43:00 --> 00:43:02 up tonight and you'll see 100 meters an hour.
00:43:02 --> 00:43:04 And for most of Australia the radiant never
00:43:04 --> 00:43:07 even rises, never, you know, south of about
00:43:07 --> 00:43:10 35 degrees south the radiant will never rise.
00:43:10 --> 00:43:12 I think that's about the latitude of Sydney.
00:43:13 --> 00:43:15 North of that it will rise but it'll be very
00:43:15 --> 00:43:16 low to the horizon. So you'll see a much
00:43:16 --> 00:43:19 lower rate unless you're in the top, top end.
00:43:19 --> 00:43:20 If you're in the top end of Australia it's a
00:43:20 --> 00:43:23 bit different. And so when you see
00:43:23 --> 00:43:26 articles like this you need to engage
00:43:26 --> 00:43:28 your science brain and say the journalist
00:43:28 --> 00:43:30 wrong. Yeah, where's my location?
00:43:30 --> 00:43:33 What's the radiance? Declination which
00:43:33 --> 00:43:36 is latitude in the sky effectively figure out
00:43:36 --> 00:43:38 how high in the sky it'll get and that will
00:43:38 --> 00:43:39 give you a feel for what you might actually
00:43:39 --> 00:43:42 see. Now if you want to um, look
00:43:42 --> 00:43:44 at the meteor shower calendar and figure out
00:43:44 --> 00:43:46 when there are good ones happening, the
00:43:46 --> 00:43:48 International Meteor Organization is my go to
00:43:48 --> 00:43:51 on this. They're a fabulous organization that
00:43:51 --> 00:43:53 put together every year a calendar and that
00:43:53 --> 00:43:55 calendar lists all the meteor showers from
00:43:55 --> 00:43:57 the incredibly minor ones that give one
00:43:57 --> 00:43:59 meteor every two hours, you know, to the
00:43:59 --> 00:44:02 major ones. And every year it writes about
00:44:02 --> 00:44:05 the conditions in terms of moonlight as well.
00:44:05 --> 00:44:08 Because if the moon is bright, you will see
00:44:08 --> 00:44:11 far fewer meteors. And coming up in a couple
00:44:11 --> 00:44:13 of weeks from when we're having this
00:44:13 --> 00:44:15 discussion, but in the past, as we actually
00:44:15 --> 00:44:17 go live to air, you've got the peak of the
00:44:17 --> 00:44:19 Ytraquarids. Now the Yter Aquarids are one of
00:44:19 --> 00:44:21 the few showers that's better for Southern
00:44:21 --> 00:44:22 hemisphere than Northern Hemisphere
00:44:22 --> 00:44:24 hemisphere. Fragments of Comet Hallie, and
00:44:24 --> 00:44:26 they're at their peak around the 3rd to the
00:44:26 --> 00:44:29 7th may have quite a broad peak, but
00:44:29 --> 00:44:32 this year the moon is a waning
00:44:32 --> 00:44:34 gibbous. So at the time of night when you
00:44:34 --> 00:44:36 could see these meteors, the sky will be
00:44:36 --> 00:44:38 really bright and so far fewer will be
00:44:38 --> 00:44:41 visible than normal. And you can get that
00:44:41 --> 00:44:42 from these calendars. But the highlight of
00:44:42 --> 00:44:44 every year for meteor showers is the Geminids
00:44:45 --> 00:44:48 in December. And they are pretty much global
00:44:48 --> 00:44:50 as a phenomenon and they're brilliant
00:44:50 --> 00:44:52 everywhere. Obviously better for the Northern
00:44:52 --> 00:44:53 hemisphere than the south. That's like a
00:44:53 --> 00:44:55 recurring theme, but
00:44:56 --> 00:44:59 they are great every year. And this year,
00:44:59 --> 00:45:01 Moon will be effectively new. So if you want
00:45:01 --> 00:45:03 to go see the Geminids peaking on the 14th or
00:45:03 --> 00:45:06 15th of December, they're the highlight this
00:45:06 --> 00:45:07 year and pretty much every year.
00:45:08 --> 00:45:10 Andrew Dunkley: Okay, uh, we're going to take another breath
00:45:10 --> 00:45:12 and then we'll come back and wrap it all up
00:45:12 --> 00:45:14 in this episode of Space Nuts with Andrew
00:45:14 --> 00:45:15 Dunkley and Jonti Horner.
00:45:20 --> 00:45:21 Jonti Horner: Tranquility Base here.
00:45:21 --> 00:45:23 Andrew Dunkley: The eagle has landed.
00:45:23 --> 00:45:23 Jonti Horner: Space gnats.
00:45:24 --> 00:45:27 Andrew Dunkley: One of my big frustrations, uh,
00:45:27 --> 00:45:29 when I want to observe comets is I live on a
00:45:29 --> 00:45:32 very flat area of the planet. Uh,
00:45:32 --> 00:45:35 we don't have mountains nearby, we barely
00:45:35 --> 00:45:38 have hills. And a lot of the comets
00:45:38 --> 00:45:41 are visible, uh, in the low
00:45:41 --> 00:45:44 horizon just after sunset or
00:45:45 --> 00:45:47 thereabouts. And they're short lived
00:45:48 --> 00:45:51 and they're below the horizon way too
00:45:51 --> 00:45:53 quick. Uh, which makes astrophotography a
00:45:53 --> 00:45:56 real pain in the butt for me. But it is
00:45:57 --> 00:45:59 just a quirk of where I live.
00:45:59 --> 00:46:01 Um, I believe
00:46:02 --> 00:46:05 that we do have some pretty spectacular ones
00:46:05 --> 00:46:08 coming up. The one that I've seen
00:46:08 --> 00:46:11 in my life that was the most spectacular for
00:46:11 --> 00:46:13 me was in 2007, January
00:46:13 --> 00:46:16 2007. Uh, the, it
00:46:16 --> 00:46:19 was Comet McNaught. It was amazing,
00:46:19 --> 00:46:22 like naked eye, comet wise. It
00:46:22 --> 00:46:25 was unmissable. Uh, it dominated
00:46:25 --> 00:46:28 the sky for quite some time. Uh, we don't see
00:46:28 --> 00:46:29 many like that though, do we?
00:46:30 --> 00:46:32 Jonti Horner: We don't now. Comet McNaught was probably the
00:46:32 --> 00:46:35 brightest comet since the 1960s and it was
00:46:35 --> 00:46:37 truly a great comet. Now when we talk
00:46:37 --> 00:46:40 about the brightest comets and the ones
00:46:40 --> 00:46:42 people want to see, great comet is the
00:46:42 --> 00:46:44 Appalachian people attached to comets. And
00:46:44 --> 00:46:46 it's got a woolly ish definition. It's
00:46:46 --> 00:46:48 basically the comet was bright enough and
00:46:48 --> 00:46:50 spectacular enough that even people who
00:46:50 --> 00:46:51 weren't that interested could just step
00:46:51 --> 00:46:53 outside and see it. Comet McNaughts
00:46:53 --> 00:46:56 definitely like that. Arguably Comet Chichin
00:46:56 --> 00:46:59 Chan Atlas in 2024 and Comet Atlas in
00:46:59 --> 00:47:02 early 2025 just made that threshold.
00:47:02 --> 00:47:04 So if you saw those comets, you'd probably
00:47:04 --> 00:47:07 say they are right at the lower end of what
00:47:07 --> 00:47:10 we consider a great comet. On average,
00:47:10 --> 00:47:12 if you go back through historical comic
00:47:12 --> 00:47:14 records, you'd probably get about 10 great
00:47:14 --> 00:47:17 comets per century with very wide
00:47:17 --> 00:47:20 variants. And that's not one every 10 years.
00:47:20 --> 00:47:22 They're like buses. You wait 30 years and two
00:47:22 --> 00:47:24 come along at once. And you saw that back in
00:47:24 --> 00:47:27 1996 with Comet Hale Bop and Comet Hyakitake,
00:47:27 --> 00:47:29 which were visible in the sky at the same
00:47:29 --> 00:47:32 time as great comets. It's really
00:47:32 --> 00:47:33 hard to predict when they're going to come
00:47:33 --> 00:47:35 in. But we've seen some really fascinating
00:47:35 --> 00:47:38 advances in the last few years on two fronts.
00:47:38 --> 00:47:41 Firstly, our ability to find things
00:47:41 --> 00:47:43 early has improved. We've got better
00:47:43 --> 00:47:46 telescopes, more automated surveys, and,
00:47:46 --> 00:47:48 um, comet maps earlier this year, which
00:47:48 --> 00:47:49 turned out to be a bit of a disappointment
00:47:49 --> 00:47:51 for many people, is a really good example of
00:47:51 --> 00:47:53 that. That's a member of the Kreutz
00:47:53 --> 00:47:56 sungrazing family. And the Kreuz sungrazers
00:47:56 --> 00:47:58 have numbered many of the brightest great
00:47:58 --> 00:48:00 comets of the last couple of thousand years.
00:48:01 --> 00:48:03 Comet maps was the earliest we've ever found
00:48:03 --> 00:48:06 a Kreutz sungrazer on the way in, earlier
00:48:06 --> 00:48:09 even than Comedike Oseci, which was probably
00:48:09 --> 00:48:11 the brightest comet in the 20th century back
00:48:11 --> 00:48:14 in the late 1960s. And so people's hopes were
00:48:14 --> 00:48:16 high. But in reality it was quite a small
00:48:16 --> 00:48:18 fragment of the Kreutz parents
00:48:19 --> 00:48:20 sungrazer. These Kreutz comets are all
00:48:20 --> 00:48:23 fragments of a bigger comet in the past, and
00:48:23 --> 00:48:25 it just fell apart on its way in. Nothing to
00:48:25 --> 00:48:28 see here. But our ability to find
00:48:28 --> 00:48:30 things earlier means that we get more
00:48:30 --> 00:48:32 warning when a bright comet's coming. Now
00:48:32 --> 00:48:35 that's not absolutely guaranteed. We had a
00:48:35 --> 00:48:37 comet and the name of it slipped my mind. Um,
00:48:37 --> 00:48:40 Comet 12, 18 months ago. Um, no,
00:48:40 --> 00:48:43 I think it was like last September
00:48:44 --> 00:48:46 that was discovered when it was almost naked
00:48:46 --> 00:48:49 eye visibility. It just about became naked
00:48:49 --> 00:48:51 eye visible wasn't great by any means. Swan.
00:48:51 --> 00:48:54 We got no warning. That's it, Comet Swan. And
00:48:54 --> 00:48:56 the reason that that was found so late was it
00:48:56 --> 00:48:58 came at us from behind the sun and suddenly
00:48:58 --> 00:49:01 popped into view. So that does still happen,
00:49:01 --> 00:49:04 but with facilities like Vera Rubin coming
00:49:04 --> 00:49:05 online, we're going to find comets earlier
00:49:05 --> 00:49:08 and earlier, which means we get more prior
00:49:08 --> 00:49:10 warning. But it also means that the
00:49:10 --> 00:49:12 uncertainty about how bright they're going to
00:49:12 --> 00:49:13 get is possibly even higher because we're
00:49:13 --> 00:49:16 almost finding them now before they've really
00:49:16 --> 00:49:18 started to become active. While they're far
00:49:18 --> 00:49:19 enough from the sun that we're almost seeing
00:49:19 --> 00:49:22 a bare nuclear nucleus, or we're seeing
00:49:22 --> 00:49:24 a much smaller comet that's had a little bit
00:49:24 --> 00:49:26 of an outburst at that distance and whether
00:49:26 --> 00:49:28 that far away, we effectively can't tell the
00:49:28 --> 00:49:30 difference. They're still like a single
00:49:30 --> 00:49:32 pixel. There's a really good example of this
00:49:32 --> 00:49:35 in the form of Comet Chu Chin Shan. Um,
00:49:35 --> 00:49:37 not come to Chin Chan ATLAS from a couple of
00:49:37 --> 00:49:38 years ago, but Comet Chu Chin Shan that has
00:49:38 --> 00:49:40 just been discovered in the last couple of
00:49:40 --> 00:49:42 months, Comet C 2026
00:49:42 --> 00:49:45 C1. As we record this, that
00:49:45 --> 00:49:48 comet is still more distant from the sun than
00:49:48 --> 00:49:50 the orbit of Saturn. It was found a couple of
00:49:50 --> 00:49:52 months ago. It will not be at its closest to
00:49:52 --> 00:49:55 some perihelion until November
00:49:55 --> 00:49:57 2028. So we've got two and a half years to
00:49:57 --> 00:50:00 wait. Now, what factors
00:50:00 --> 00:50:01 into a comet's brightness is very
00:50:01 --> 00:50:04 complicated. Um, but it can boil down to a
00:50:04 --> 00:50:06 few different things. Firstly, if everything
00:50:06 --> 00:50:09 else is equal. So imagine we only change one
00:50:09 --> 00:50:11 thing. Typically, the bigger the nucleus of
00:50:11 --> 00:50:14 the comet, the bigger its surface area is. So
00:50:14 --> 00:50:17 the more dust and gas it can produce. And we
00:50:17 --> 00:50:19 see the comet from the light that is
00:50:19 --> 00:50:21 reflected from the dust and gas. That's what
00:50:21 --> 00:50:23 makes the tails and the coma. The snowballs,
00:50:23 --> 00:50:24 ah, at the head were actually pretty small.
00:50:24 --> 00:50:27 Comet McNaught was only about 5km across
00:50:27 --> 00:50:30 for the nucleus, but it grew tails more than
00:50:30 --> 00:50:31 300 million kilometers long.
00:50:32 --> 00:50:33 Andrew Dunkley: Yeah, that's a little bit different.
00:50:33 --> 00:50:34 Incredible.
00:50:34 --> 00:50:36 Jonti Horner: So if you have two cometary nuclei that, uh,
00:50:36 --> 00:50:39 are in all senses identical other than their
00:50:39 --> 00:50:41 size, the bigger one will typically be more
00:50:41 --> 00:50:43 active and produce more gas and dust.
00:50:44 --> 00:50:47 However, some comets have a m larger fraction
00:50:47 --> 00:50:49 of their surface active than others. Some
00:50:49 --> 00:50:51 comets are almost dormant because they're
00:50:51 --> 00:50:53 clogged up and there's very little activity
00:50:53 --> 00:50:55 even from a larger nucleus. So already a bit
00:50:55 --> 00:50:58 complex. But first rule of thumb, um, the
00:50:58 --> 00:50:59 bigger the nucleus, the more likelihood there
00:50:59 --> 00:51:01 is that it will be able to produce a lot of
00:51:01 --> 00:51:03 gas and Dust and be more spectacular. With
00:51:03 --> 00:51:06 Comet Chu Chen Shan, that's interesting. We
00:51:06 --> 00:51:08 found it so far away, which suggests it is
00:51:08 --> 00:51:10 either a comet with quite a large nucleus,
00:51:10 --> 00:51:12 because it's probably not that active at that
00:51:12 --> 00:51:15 distance, but it may have just had a bit of
00:51:15 --> 00:51:17 an outburst of activity driven by something
00:51:17 --> 00:51:20 like carbon monoxide, which can turn from
00:51:20 --> 00:51:22 solid gas at a very low temperature. So it
00:51:22 --> 00:51:24 might be masquerading as a bigger comet than
00:51:24 --> 00:51:25 it is, and we don't know.
00:51:26 --> 00:51:27 Andrew Dunkley: Okay.
00:51:27 --> 00:51:29 Jonti Horner: The next thing that factors into how bright a
00:51:29 --> 00:51:30 comet gets is how close it gets to the Sun.
00:51:30 --> 00:51:33 So the closer it gets to the sun, the hotter
00:51:33 --> 00:51:35 its surface gets and the more strongly it
00:51:35 --> 00:51:38 will be active. So with Comet McNaught, you
00:51:38 --> 00:51:40 had a five kilometer nucleus, which is fairly
00:51:40 --> 00:51:42 respectable, but not as big as Hale Bopp,
00:51:42 --> 00:51:45 which was 50km. Hale Bok was ridiculous.
00:51:45 --> 00:51:48 But Comet McNaught got very close into the
00:51:48 --> 00:51:50 Sun. Um, so it got really incredibly
00:51:50 --> 00:51:52 intensely active, was throwing off huge
00:51:52 --> 00:51:55 amounts of gas and dust. So that contributed
00:51:55 --> 00:51:57 again to more stuff to reflect sunlight. And
00:51:57 --> 00:51:59 also being nearer to the sun, the intensity
00:51:59 --> 00:52:01 of light reflecting off its higher as well.
00:52:01 --> 00:52:03 So kind of get a double whammy there. The
00:52:03 --> 00:52:05 other factor is how close they get to the
00:52:05 --> 00:52:07 Earth. So if you have two comets that are the
00:52:07 --> 00:52:09 same size and the same distance from the sun,
00:52:10 --> 00:52:11 and, um, one is closer to the Earth than the
00:52:11 --> 00:52:13 other, the one closer to the Earth will be
00:52:13 --> 00:52:15 brighter, but will also potentially be more
00:52:15 --> 00:52:17 spread out and more diffuse in the sky. So
00:52:17 --> 00:52:19 that brightness might be spread over a
00:52:19 --> 00:52:21 different area. You've then got
00:52:21 --> 00:52:24 subtleties of how dusty or gassy they are.
00:52:24 --> 00:52:27 Some comets, like Comet Pan, stars seem
00:52:27 --> 00:52:29 to be more gassy. Some comets like Church and
00:52:29 --> 00:52:31 Chan Atlas was more dusty. And that can have
00:52:31 --> 00:52:33 an impact on how they brighten. Bringing all
00:52:33 --> 00:52:35 this back together, though, for Comet Chu
00:52:35 --> 00:52:38 Chin Chan, at its closest to the sun,
00:52:38 --> 00:52:40 it will be a little bit further from the sun
00:52:40 --> 00:52:41 than the Earth, uh, is. So it's not like
00:52:41 --> 00:52:43 Comet McNaught that's going to get really
00:52:43 --> 00:52:46 close in. But one AU from the Sun's fairly
00:52:46 --> 00:52:48 respectable. It can still maintain a fairly
00:52:48 --> 00:52:49 decent level of activity at that distance.
00:52:49 --> 00:52:51 Comet Hale Bopp didn't get much closer than
00:52:51 --> 00:52:54 that and was fantastic. So that's in its
00:52:54 --> 00:52:56 favorite. It's going to get close enough in
00:52:56 --> 00:52:57 that you could get a decent level of
00:52:58 --> 00:53:01 activity. Also, because
00:53:01 --> 00:53:03 it's only going to get that close to the sun,
00:53:03 --> 00:53:04 it'll take a bit longer to pass through the
00:53:04 --> 00:53:06 inner solar system. Comets that get really
00:53:06 --> 00:53:08 close to the sun get traveling incredibly
00:53:08 --> 00:53:10 quickly at that point. So they tend to whip
00:53:10 --> 00:53:11 in and whip out fairly quickly. Whereas with
00:53:11 --> 00:53:14 cometary chinchan, it's going to hang around
00:53:14 --> 00:53:16 for a fair while. It is
00:53:16 --> 00:53:19 potentially quite a large cometary nucleus,
00:53:19 --> 00:53:22 but we don't know yet. This is the caution I
00:53:22 --> 00:53:24 give. If it turns out that we've caught it
00:53:24 --> 00:53:25 during an outburst, it may be a bit of a
00:53:25 --> 00:53:27 disappointment. If we've actually seen it as
00:53:27 --> 00:53:30 a bare nucleus. That augurs very, very
00:53:31 --> 00:53:33 well. What this all suggests is that Comet
00:53:33 --> 00:53:35 Chichin Shan, um, has a potential to be
00:53:35 --> 00:53:37 bright in late 2028.
00:53:38 --> 00:53:40 Depending on which fit to its current
00:53:40 --> 00:53:43 brightness you use. It could become barely
00:53:43 --> 00:53:45 naked eye visible, which is still pretty
00:53:45 --> 00:53:47 good. You know, we see 20 or 30 comets a year
00:53:48 --> 00:53:50 and very, uh, only maybe one will get to
00:53:50 --> 00:53:52 naked eye visibility. Or it could get as
00:53:52 --> 00:53:54 bright as the brightest stars. And if it gets
00:53:54 --> 00:53:56 as bright as the brightest stars, then it
00:53:56 --> 00:53:58 gets into great comet type territory.
00:53:59 --> 00:54:01 That's a factor of 100 difference in
00:54:01 --> 00:54:03 brightness between those two extremes. And,
00:54:03 --> 00:54:05 um, it could get brighter than the brightest
00:54:05 --> 00:54:06 extreme there or fainter than the faintest
00:54:06 --> 00:54:09 extreme. We just don't know yet. But having
00:54:09 --> 00:54:11 found it so early augurs well. But typically,
00:54:12 --> 00:54:14 predicting the next great comet is a fool's
00:54:14 --> 00:54:17 bargain until it's discovered. What we can
00:54:17 --> 00:54:20 say is that there are a few periodic comets
00:54:20 --> 00:54:23 that will be great in the future. Comet
00:54:23 --> 00:54:25 Hallie will be a lot better in 2061 than it
00:54:25 --> 00:54:28 was in 1986. In 1986, we had the
00:54:28 --> 00:54:30 worst separation of Comet Hallie for 2
00:54:30 --> 00:54:30 years.
00:54:30 --> 00:54:31 Andrew Dunkley: Tell me about it.
00:54:31 --> 00:54:34 Jonti Horner: Yeah, a bit disappointing. 2071
00:54:34 --> 00:54:35 will be better.
00:54:35 --> 00:54:38 Andrew Dunkley: Oh, good. I don't know if I'll be around by
00:54:38 --> 00:54:40 then, but, um, probably not.
00:54:40 --> 00:54:43 Jonti Horner: I'll be 99, make everybody
00:54:43 --> 00:54:45 feel really cheerful. It's now closer to
00:54:45 --> 00:54:47 Comet Hallie's next apparition than the last
00:54:47 --> 00:54:49 one. It turned around, I think, last year. So
00:54:49 --> 00:54:51 it's on its way back. Yeah, Comet Hallie will
00:54:51 --> 00:54:54 be even better in 21:35, will
00:54:54 --> 00:54:55 be really good that year. And that will be
00:54:55 --> 00:54:57 the best apparition for a couple of hundred
00:54:57 --> 00:55:00 years. Comet Swift Tuttle will be incredible
00:55:00 --> 00:55:02 in 21:26. We know that because we know pretty
00:55:02 --> 00:55:03 much exactly when it'll come back. We know
00:55:03 --> 00:55:05 where it will be compared to the Earth and
00:55:05 --> 00:55:07 the Sun. There is a suggestion that in
00:55:07 --> 00:55:10 2097 we may have the comet of the century, or
00:55:10 --> 00:55:12 close to it. This is research that came out
00:55:12 --> 00:55:15 last year. One of the greatest comets of the
00:55:15 --> 00:55:18 last thousand years was Comet De chezo, uh,
00:55:18 --> 00:55:21 in 1744, also called Comet
00:55:21 --> 00:55:23 Clinkenberg comet that is famous for having
00:55:23 --> 00:55:26 had six tails, incredibly bright, almost
00:55:26 --> 00:55:28 visible in broad daylight. A couple of
00:55:28 --> 00:55:30 astronomers, I think the lead researcher on
00:55:30 --> 00:55:33 this was Mike Meyer, published a paper last
00:55:33 --> 00:55:35 year that went back through historical
00:55:35 --> 00:55:38 observations and found a number of previous
00:55:38 --> 00:55:40 comets over the last 2 years that were
00:55:40 --> 00:55:42 all incredibly bright, really spectacular,
00:55:43 --> 00:55:45 but seem to have been moving the same as that
00:55:45 --> 00:55:47 comet. Linked them together and it's a very
00:55:47 --> 00:55:50 compelling tale that if their research is
00:55:50 --> 00:55:52 correct, that comet actually has an orbital
00:55:52 --> 00:55:55 period of just a little bit less. Just around
00:55:55 --> 00:55:57 450 years, I think. 400 years?
00:55:57 --> 00:56:00 No, 350 years. Wouldn't it do the mental
00:56:00 --> 00:56:03 arithmetic? Yeah, about 350 years,
00:56:03 --> 00:56:05 which means it should return in 2097.
00:56:06 --> 00:56:09 And if it does, it will be awesome.
00:56:09 --> 00:56:11 Um, sadly I don't think you or I will be
00:56:11 --> 00:56:12 around for that.
00:56:12 --> 00:56:14 Andrew Dunkley: Probably not, probably not.
00:56:14 --> 00:56:16 Jonti Horner: But things like that we can predict. But most
00:56:16 --> 00:56:18 Fred will be. But um, absolutely, Fred is
00:56:18 --> 00:56:20 indestructible and I'll stand um, by that.
00:56:21 --> 00:56:23 But most of the big cometary nuclei coming
00:56:23 --> 00:56:26 through are on such long period orbits, with
00:56:26 --> 00:56:28 the exception of Hallie and Swift Tuttle,
00:56:28 --> 00:56:30 that their apparitions are so infrequent that
00:56:30 --> 00:56:32 we've not identified them as periodic
00:56:32 --> 00:56:34 visitors. And many of them have periods of
00:56:34 --> 00:56:37 thousands or tens of thousands of years. So
00:56:37 --> 00:56:39 we typically only find them on their way in a
00:56:39 --> 00:56:42 few weeks or a few months before
00:56:42 --> 00:56:44 apparition. In case of Comet Hale Bopp, it
00:56:44 --> 00:56:47 was two years, which was exceptional at the
00:56:47 --> 00:56:49 time. Case of Comet Chichin Shan, it's more
00:56:49 --> 00:56:51 than two and a half years away, but our
00:56:51 --> 00:56:54 technology has improved hugely. So I don't
00:56:54 --> 00:56:56 think it's fair necessarily to say that
00:56:56 --> 00:56:59 Church and Chan will be another hell bop. But
00:56:59 --> 00:57:01 if you look at the brighter end of the
00:57:01 --> 00:57:02 predictions, it could be naked eye visible
00:57:02 --> 00:57:04 for three, four, five months.
00:57:04 --> 00:57:04 Andrew Dunkley: Wow.
00:57:04 --> 00:57:06 Jonti Horner: Would be awesome. And it would potentially be
00:57:06 --> 00:57:08 circumpolar for us in the Southern Hemisphere
00:57:08 --> 00:57:10 because at its closest to the center of the
00:57:10 --> 00:57:12 Earth, it's going to be way south, not going
00:57:12 --> 00:57:15 to be good for the Northern Hemisphere. But
00:57:15 --> 00:57:16 we can't really predict that. It's the same
00:57:16 --> 00:57:18 with meteor showers. We can predict the
00:57:18 --> 00:57:20 annual ones roughly how good they're going to
00:57:20 --> 00:57:23 be. And if you go back to when I was a
00:57:23 --> 00:57:25 kid, we couldn't really predict meteor
00:57:25 --> 00:57:27 storms, meteor outbursts, and that's one of
00:57:27 --> 00:57:28 the things people really love to see. So
00:57:28 --> 00:57:30 Geminids are great Northern Hemisphere,
00:57:30 --> 00:57:33 you'll see maybe even 80 or 100 an hour at
00:57:33 --> 00:57:35 their peak in the early hours of the morning.
00:57:35 --> 00:57:37 I've seen 50 an hour from our latitude near
00:57:37 --> 00:57:38 Brisbane.
00:57:38 --> 00:57:40 They're really good. But what people really
00:57:40 --> 00:57:42 want to see are meteor storms and they're
00:57:42 --> 00:57:45 much rarer. There's a few amazing ones.
00:57:45 --> 00:57:47 Historically. There was one in
00:57:47 --> 00:57:50 1833 that was linked to the Leonid meteor
00:57:50 --> 00:57:53 shower that had a rate in excess
00:57:53 --> 00:57:56 of a hundred thousand an hour, was best seen
00:57:56 --> 00:57:59 from the contiguous US and
00:57:59 --> 00:58:01 um, it was bright enough. There were
00:58:01 --> 00:58:04 sufficient meteors in the sky that miners in
00:58:04 --> 00:58:07 the US were woken from their campsites
00:58:07 --> 00:58:09 by the light shining through their tents. And
00:58:09 --> 00:58:11 people were convinced that the end times had
00:58:11 --> 00:58:14 come. The Apocalypse was here because he were
00:58:14 --> 00:58:16 getting as many as 20 meteors per second.
00:58:17 --> 00:58:17 Andrew Dunkley: Incredible.
00:58:17 --> 00:58:20 Jonti Horner: Um, now that in the way that kind of Tycho's
00:58:20 --> 00:58:23 observations in 1577 were probably the birth
00:58:23 --> 00:58:25 of modern cometary astronomy.
00:58:25 --> 00:58:28 1833, I think was possibly the birth of
00:58:28 --> 00:58:30 modern meteor astronomy. Because there'd been
00:58:30 --> 00:58:33 a storm from the Leonidas in 1799. People
00:58:33 --> 00:58:35 predicted that there might be another one in
00:58:35 --> 00:58:37 1866 because maybe this was happening every
00:58:37 --> 00:58:40 33 years when the comet came back. And indeed
00:58:40 --> 00:58:42 that happened in 1866.
00:58:43 --> 00:58:45 And so that was a bit like the birth of
00:58:45 --> 00:58:48 modern meteor science. And after that people
00:58:48 --> 00:58:50 said, well, there'll be one in 1899 and there
00:58:50 --> 00:58:52 wasn't. So that then tripped people up.
00:58:52 --> 00:58:55 So thanks to that we've gradually developed
00:58:55 --> 00:58:57 a better understanding of the physics of how
00:58:57 --> 00:59:00 meteor showers work. And I'm aware time is
00:59:00 --> 00:59:02 running away from us, but for people
00:59:02 --> 00:59:05 interested in this, in the run up to, uh, the
00:59:05 --> 00:59:08 heavily activity in 1999 through to
00:59:08 --> 00:59:10 2002, there was some amazing research
00:59:11 --> 00:59:13 done by um, David Asher
00:59:13 --> 00:59:16 from Amar Observatory and I think fondly on
00:59:16 --> 00:59:18 David because he was a lovely mentor to me
00:59:18 --> 00:59:20 when I visited Armagh in 1999. Very
00:59:20 --> 00:59:22 quiet guy, but incredibly talented
00:59:22 --> 00:59:25 scientists. And he did this remarkable
00:59:25 --> 00:59:28 work making predictions of when we would
00:59:28 --> 00:59:31 and wouldn't get Leonid storms by
00:59:31 --> 00:59:33 modeling the ejection of dust from the
00:59:33 --> 00:59:35 cometary nucleus and evolving the dust
00:59:35 --> 00:59:38 forward in time and go back. Way earlier on I
00:59:38 --> 00:59:40 mentioned these javelin spikes.
00:59:41 --> 00:59:43 He effectively modelled those and figured out
00:59:43 --> 00:59:45 where the spikes will be in a slight nudge up
00:59:45 --> 00:59:47 or down means that, uh, the Earth will run
00:59:47 --> 00:59:48 through the spike or not. And the great
00:59:48 --> 00:59:51 Leonid storms are produced by dust left
00:59:51 --> 00:59:54 behind just one or two revolutions ago. So
00:59:54 --> 00:59:56 the activity between 1999 and
00:59:56 --> 00:59:59 2002 resulted from a few different
00:59:59 --> 01:00:02 streams. The older they are, the more diffuse
01:00:02 --> 01:00:04 they get. But now we have the ability for
01:00:04 --> 01:00:06 comets we know well and meteor showers we
01:00:06 --> 01:00:08 know well to figure out where those spikes
01:00:08 --> 01:00:10 are roughly going to be how long they are
01:00:10 --> 01:00:13 and, uh, make predictions going forward. Now,
01:00:13 --> 01:00:15 there aren't any great meteor storms
01:00:15 --> 01:00:17 predicted in the relatively near future. The
01:00:17 --> 01:00:19 Leonids are not likely to give major storms
01:00:19 --> 01:00:22 in 2033 or 2066, but will give
01:00:22 --> 01:00:25 increased activity. The reason for that is
01:00:25 --> 01:00:27 Jupiter and Saturn are pulling those javelins
01:00:27 --> 01:00:29 around and making them miss the Earth.
01:00:30 --> 01:00:32 The leanings will probably return in force
01:00:32 --> 01:00:35 in, I think, 2097 with the possibility of a
01:00:35 --> 01:00:38 storm of like 20 an hour. But
01:00:38 --> 01:00:40 we're getting to understand that. So with
01:00:40 --> 01:00:42 meteor showers, we can predict the annual
01:00:42 --> 01:00:45 showers. They're very reliable. They
01:00:45 --> 01:00:46 gradually get better and worse with time as
01:00:46 --> 01:00:49 the streams move around and we intersect more
01:00:49 --> 01:00:51 of the material or less. But they're pretty
01:00:51 --> 01:00:54 reliable. Outbursts are harder
01:00:54 --> 01:00:56 to predict, but we're getting better at doing
01:00:56 --> 01:00:59 it. But predicting an
01:00:59 --> 01:01:00 outburst from a shower we've never seen
01:01:00 --> 01:01:03 before or a shower that's incredibly rare,
01:01:03 --> 01:01:06 we typically can't do until it happens
01:01:06 --> 01:01:08 because we need to have a feel for what it's
01:01:08 --> 01:01:10 done in the past. So we occasionally will get
01:01:10 --> 01:01:12 an outburst of a meteor shower we've never
01:01:12 --> 01:01:15 seen before. And you can't predict that. And
01:01:15 --> 01:01:17 that's when it's really exciting because then
01:01:17 --> 01:01:19 you can start to learn about a new meteor
01:01:19 --> 01:01:21 shower being born. You can learn about the
01:01:21 --> 01:01:23 comet that birthed it. It put all that
01:01:23 --> 01:01:24 together. And, um, that's one of the things
01:01:24 --> 01:01:26 where I'll go out and I love my meteor
01:01:26 --> 01:01:28 showers. I'll sit out under the sky and watch
01:01:28 --> 01:01:30 them. But I would love to just be outside
01:01:30 --> 01:01:31 when there's an unexpected outburst, when we
01:01:31 --> 01:01:33 see something new like a meteor shower being
01:01:33 --> 01:01:35 born for the first time.
01:01:35 --> 01:01:38 Andrew Dunkley: And, and that's what we recommend to all our
01:01:38 --> 01:01:40 Spacenads listeners. Uh, get up at 2 o' clock
01:01:40 --> 01:01:43 every morning, every day and go
01:01:43 --> 01:01:45 out and just wait and, you know, one day
01:01:45 --> 01:01:48 you'll get lucky. Might take 20 years, but it
01:01:48 --> 01:01:48 doesn't
01:01:48 --> 01:01:51 Jonti Horner: have to be 2:00am I mean, there is a little
01:01:51 --> 01:01:53 bit of a preference for meteor showers to be
01:01:53 --> 01:01:56 more active in the morning hours, in the
01:01:56 --> 01:01:57 evening hours. But that's purely a geometry
01:01:57 --> 01:01:59 thing. It's linked a little bit to the
01:01:59 --> 01:02:01 direction of the Earth's motion and the
01:02:01 --> 01:02:02 direction things are crossing the Earth's
01:02:02 --> 01:02:04 orbit in that if you think about something
01:02:04 --> 01:02:07 crossing the Earth's orbit at right angles to
01:02:07 --> 01:02:09 the Earth because the Earth's Moving forward
01:02:09 --> 01:02:12 at 30km a second, the direction you would see
01:02:12 --> 01:02:14 that coming from is actually a bit ahead of
01:02:14 --> 01:02:15 you because you've got the addition of the,
01:02:15 --> 01:02:17 the speed the debris is going on the speed
01:02:17 --> 01:02:20 the Earth's moving. So meteor showers
01:02:21 --> 01:02:24 that are uh, visible with radiance that will
01:02:24 --> 01:02:26 be in the morning sky, you've got a little
01:02:26 --> 01:02:27 bit of an additive effect between the speed
01:02:27 --> 01:02:29 the debris is going and the speed the Earth's
01:02:29 --> 01:02:32 moving, which means the average impact speed
01:02:32 --> 01:02:33 of the debris is higher and you get more
01:02:33 --> 01:02:36 meteors. But also you get this effect of
01:02:36 --> 01:02:37 the Earth's motion being a bit like you're
01:02:37 --> 01:02:40 driving into a snowstorm. You know, if you're
01:02:40 --> 01:02:42 driving into a snowstorm where there's no
01:02:42 --> 01:02:43 wind and the snowflakes are falling down
01:02:43 --> 01:02:45 vertically, vertically, you will perceive
01:02:45 --> 01:02:47 them as coming from in front of your car, not
01:02:47 --> 01:02:49 overhead. And so there's a preference for
01:02:49 --> 01:02:51 meteor showers to be slightly more likely to
01:02:51 --> 01:02:53 have activity that peaks in the morning hours
01:02:53 --> 01:02:55 in the evening. But that's not a guarantee.
01:02:55 --> 01:02:58 There are some meteor showers that are at the
01:02:58 --> 01:02:59 highest where the radiant culminates in the
01:02:59 --> 01:03:02 evening sky. It just depends. Some
01:03:03 --> 01:03:05 like the Utrecht, are only visible for a
01:03:05 --> 01:03:06 couple of hours before dawn. Um, there's even
01:03:06 --> 01:03:08 a few meteor showers that are daylight
01:03:08 --> 01:03:10 showers where the radiance only really above
01:03:10 --> 01:03:12 the horizon during the hours of daylight. And
01:03:12 --> 01:03:14 we know about them primarily from radio
01:03:14 --> 01:03:17 observations. Radar, well not radar. People
01:03:17 --> 01:03:20 listening to radio reflecting off the ionized
01:03:20 --> 01:03:22 streaks that the meteors leave in the
01:03:22 --> 01:03:24 ionosphere. That allows you to see over the
01:03:24 --> 01:03:27 horizon to radio sessions that are
01:03:27 --> 01:03:28 broadcasting that you don't normally get. So
01:03:28 --> 01:03:31 you can hear meteor showers? Yeah, so we know
01:03:31 --> 01:03:33 there are daytime showers that uh, we cannot
01:03:33 --> 01:03:35 see at night. And some of them are possibly
01:03:35 --> 01:03:37 as active as the Geminids of the Perseids.
01:03:37 --> 01:03:40 If, you know, if we could turn the sun off, I
01:03:40 --> 01:03:41 mean that would be a bad thing. Please don't
01:03:41 --> 01:03:43 do it. If you're a super villain listening,
01:03:43 --> 01:03:46 do not take this as an idea, but if we
01:03:46 --> 01:03:47 could turn the sun off and see there are a
01:03:47 --> 01:03:49 couple of meteor showers in the daytime that
01:03:49 --> 01:03:51 could be pretty spectacular.
01:03:52 --> 01:03:54 Andrew Dunkley: It is all very fascinating and I suppose the
01:03:54 --> 01:03:57 best advice would be to go and look for the,
01:03:58 --> 01:04:01 the better sources of forecasting rather than
01:04:01 --> 01:04:02 trying to figure it out for yourself.
01:04:02 --> 01:04:04 And uh, and, and you've mentioned a couple of
01:04:04 --> 01:04:07 already comet, uh, maps and, and uh,
01:04:07 --> 01:04:09 what was the other one about meteors?
01:04:09 --> 01:04:11 Jonti Horner: For meteors, I really strongly recommend the
01:04:11 --> 01:04:13 International Meteor Organization. If you go
01:04:13 --> 01:04:16 to their website, hover over the resources
01:04:16 --> 01:04:18 link, click on it to get the drop down. Click
01:04:18 --> 01:04:20 on meteor shower calendar. They have on the
01:04:20 --> 01:04:23 right hand side the best showers of the year
01:04:23 --> 01:04:25 with information and what the moon will be
01:04:25 --> 01:04:27 like. But there's also on the left side a PDF
01:04:27 --> 01:04:29 that you can download that goes into much
01:04:29 --> 01:04:31 more minute detail and talks about even the
01:04:31 --> 01:04:33 more minor showers. Um, and that's a very
01:04:33 --> 01:04:36 good point of truth for meteor showers. Well,
01:04:36 --> 01:04:38 I kind of describe them being like three
01:04:38 --> 01:04:40 tiers of meteor showers, ignoring the
01:04:40 --> 01:04:42 outbursts. There are the big three, which are
01:04:42 --> 01:04:44 the Quadrantids, the Persons and the
01:04:44 --> 01:04:47 Geminids, which are uh, even if you're not
01:04:47 --> 01:04:49 that interested at all in space, and if you
01:04:49 --> 01:04:51 are, thanks for listening to the podcast
01:04:51 --> 01:04:53 anyway, but it's not really our target
01:04:53 --> 01:04:55 audience. But even people who are not that
01:04:55 --> 01:04:57 interested, that's a spectacle you can go out
01:04:57 --> 01:04:58 and see with them and share with them them.
01:04:59 --> 01:05:00 Just make sure that you figure out when the
01:05:00 --> 01:05:02 radiant rises from your location because you
01:05:02 --> 01:05:05 don't want to turn people off by looking at a
01:05:05 --> 01:05:07 time when you can't see meteors. So for the
01:05:07 --> 01:05:10 Geminids the best time is around 2am but
01:05:10 --> 01:05:12 depending on where you are in the world, from
01:05:12 --> 01:05:15 our latitude you're looking at, you can't see
01:05:15 --> 01:05:17 any before 9:30, 10:00 clock at night.
01:05:17 --> 01:05:18 Obviously if you're somewhere with daylight
01:05:18 --> 01:05:20 savings in the southern hemisphere, add an
01:05:20 --> 01:05:23 hour to that. So for you down in New South
01:05:23 --> 01:05:24 Wales, where the clocks change, you're
01:05:24 --> 01:05:26 talking after 11pm for you. But if you're in
01:05:26 --> 01:05:29 Northern Europe, the Geminid radiant never
01:05:29 --> 01:05:31 sets. So where I grew up in the uk, as soon
01:05:31 --> 01:05:33 as it got dark I could see them. The rate
01:05:33 --> 01:05:35 still got better through the night. Similarly
01:05:35 --> 01:05:37 for the Perseids in particular. Perseids are
01:05:37 --> 01:05:40 a northern hemisphere only thing. It's light
01:05:40 --> 01:05:41 until quite late, certainly for the high
01:05:41 --> 01:05:43 northern latitudes like the uk, but as soon
01:05:43 --> 01:05:45 as it gets dark you can see them. So they're
01:05:45 --> 01:05:48 the showers that uh, are well worth going out
01:05:48 --> 01:05:50 to look at as a beginner and you just sit out
01:05:50 --> 01:05:52 there. I would figure out where the radiant
01:05:52 --> 01:05:55 is and look 30 or 40 degrees to the left or
01:05:55 --> 01:05:57 right of it to get the best balance between a
01:05:57 --> 01:06:00 lot of meteors but decent ones to see and
01:06:00 --> 01:06:03 just get a comfy chair, lie back, wrap up
01:06:03 --> 01:06:05 warm m with the people you love and tell
01:06:05 --> 01:06:07 stories and relax and occasionally you'll see
01:06:07 --> 01:06:08 something good and it's quite addictive. You
01:06:08 --> 01:06:10 think, you know, I'll go to bed, but I just
01:06:10 --> 01:06:12 want to see one more and then, well, that's
01:06:12 --> 01:06:14 rubbish. So uh, I want to see another one
01:06:14 --> 01:06:16 that's actually good. You've then got like
01:06:16 --> 01:06:19 the mid tier showers which can be decent but
01:06:19 --> 01:06:21 you need to be a bit more dedicated for these
01:06:21 --> 01:06:23 are the ones where you might see 10 or 15 an
01:06:23 --> 01:06:26 hour instead of 50 an hour. And I, um,
01:06:26 --> 01:06:27 wouldn't recommend people who were beginners
01:06:27 --> 01:06:29 go out and see them because it's, there's not
01:06:29 --> 01:06:32 enough happening. And that's why I worry
01:06:32 --> 01:06:34 about coverage for the April Lyrids, even in
01:06:34 --> 01:06:36 the Northern Hemisphere, because they're just
01:06:36 --> 01:06:39 not that good. If you're someone who's really
01:06:39 --> 01:06:41 keen, you'll enjoy them. But for most people
01:06:41 --> 01:06:43 there'll be a letdown and you don't want to
01:06:43 --> 01:06:45 turn people off the subject. Then there are
01:06:45 --> 01:06:48 the minor showers that you frankly need to be
01:06:48 --> 01:06:49 very obsessive to follow. And I've seen
01:06:49 --> 01:06:52 stories of a lot of the science of this has
01:06:52 --> 01:06:54 been done by amateur astronomers and, um,
01:06:54 --> 01:06:56 quite often by people who are quite obsessive
01:06:56 --> 01:06:59 about the topic. And I
01:06:59 --> 01:07:02 saw one guy who was in North America where it
01:07:02 --> 01:07:04 gets brutal, brutal cold in the winter,
01:07:05 --> 01:07:08 who built himself a, an insulated coffin with
01:07:08 --> 01:07:10 an incredibly transparent glass lid that he
01:07:10 --> 01:07:12 would carry out with him that was big enough
01:07:12 --> 01:07:14 for him to have a notebook and write down the
01:07:14 --> 01:07:17 details of every meteor he saw. He could lie
01:07:17 --> 01:07:19 out in minus 40 degrees and I think
01:07:19 --> 01:07:21 that's, um, units ambivalent. I think
01:07:21 --> 01:07:23 Fahrenheit and Centigrade are very similar at
01:07:23 --> 01:07:26 that point. But he's in an insulated box that
01:07:26 --> 01:07:28 keeps him warm and he'd lie out all night
01:07:28 --> 01:07:31 recording 2 meters, 3 meters an hour. That
01:07:31 --> 01:07:34 isn't for me, but it is for some people. But
01:07:34 --> 01:07:36 when you see a meteor shower with a ZHR of
01:07:36 --> 01:07:38 less than about 20, I'd probably leave that
01:07:38 --> 01:07:41 unless you're really keen. If it's got a zhr
01:07:41 --> 01:07:44 of 50 plus, well worth looking out for. But
01:07:44 --> 01:07:46 look for when the time of maximum is for most
01:07:46 --> 01:07:49 meteor showers, they've got what we call a
01:07:49 --> 01:07:51 full width half maximum of about 24 hours.
01:07:51 --> 01:07:54 What that means is that, uh, the rate only
01:07:54 --> 01:07:56 stays above half of the peak rate for about
01:07:56 --> 01:07:59 24 hours for 48 hours, then it'd stay above
01:07:59 --> 01:08:01 a quarter of the rate and so on. For the
01:08:01 --> 01:08:03 Quadrantids, it's full width at quarter
01:08:03 --> 01:08:06 maximum of about 12 hours. So that means
01:08:06 --> 01:08:08 if you're six hours away from the peak, the
01:08:08 --> 01:08:10 rate is already down to a quarter of that
01:08:10 --> 01:08:12 peak. It's a very sharp peak and if you're
01:08:12 --> 01:08:14 looking at the wrong time, the show won't be
01:08:14 --> 01:08:16 as good as you'd like it to be and you'll be
01:08:16 --> 01:08:17 disappointed.
01:08:18 --> 01:08:20 Andrew Dunkley: So much to consider, Jonti, but fascinating.
01:08:20 --> 01:08:22 Uh, copper and meteors.
01:08:22 --> 01:08:24 Um, there's so much to talk about and we
01:08:24 --> 01:08:27 probably didn't really cover absolutely
01:08:27 --> 01:08:29 everything. Although we did, uh, we did hit
01:08:29 --> 01:08:31 on quite a fair bit of info. And of course,
01:08:31 --> 01:08:34 we do welcome questions and comments. So, uh,
01:08:34 --> 01:08:36 please, um, go to our website and,
01:08:36 --> 01:08:39 um, click that little AMA button at
01:08:39 --> 01:08:41 the top and you can send us, uh, questions
01:08:41 --> 01:08:44 and comments, uh, in text and audio form.
01:08:44 --> 01:08:46 Don't forget to tell us who you are and where
01:08:46 --> 01:08:47 you're from, but we're going to wrap it up
01:08:47 --> 01:08:49 there. Jonti, thank you so much. We'll catch
01:08:49 --> 01:08:50 you on the next show.
01:08:50 --> 01:08:51 Jonti Horner: Thank you very much.
01:08:52 --> 01:08:54 Andrew Dunkley: Professor Jonti Horner, professor of
01:08:54 --> 01:08:57 Astrophysics at the University of Southern
01:08:57 --> 01:08:59 Queensland, our, uh, special, uh, guest
01:08:59 --> 01:09:02 commentator. While Fred's, uh, on the other
01:09:02 --> 01:09:04 side of the planet looking at meteors. And,
01:09:04 --> 01:09:07 uh, just a special word for, uh, for Huw in
01:09:07 --> 01:09:10 the studio. He's been a little unwell lately.
01:09:10 --> 01:09:12 Huw, get well soon, mate. We're all thinking
01:09:12 --> 01:09:15 of you. And from me, Andrew Dunkley. Thanks
01:09:15 --> 01:09:16 for your company. We'll catch you on the next
01:09:16 --> 01:09:18 episode of Space Nuts.
01:09:19 --> 01:09:21 Jonti Horner: You'll be listening to the Space Nuts
01:09:21 --> 01:09:24 podcast, available at
01:09:24 --> 01:09:26 Apple Podcasts, Spotify,
01:09:27 --> 01:09:29 iHeartRadio or your favorite podcast
01:09:29 --> 01:09:31 player. You can also stream on
01:09:31 --> 01:09:33 demand@bytes.com.
01:09:33 --> 01:09:35 Andrew Dunkley: this has been another quality podcast
01:09:35 --> 01:09:37 production from bytes.com.