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Comets, Meteors & Celestial Wonders : A Cosmic Special | Space Nuts: Astronomy Insights & Cosmic... · Space News Today

• 0:00
  Hello again. Thank you for joining us on
• 0:01
  another episode of Space Nuts. My name
• 0:04
  is Andrew Dunley, your host. It's great
• 0:06
  to have your company. As I mentioned
• 0:08
  last episode, Fred is away for a few
• 0:11
  weeks or a couple of years. No, it's a
• 0:13
  few weeks. And uh in hisstead, we'll be
• 0:16
  joined by Professor Jonty, who you know
• 0:19
  and love because he's been with us
• 0:21
  before and uh he's a part of the team.
• 0:24
  So, uh, we will be doing over the next,
• 0:27
  uh, several episodes, um, taking a
• 0:30
  different approach. Uh, we we're going
• 0:31
  to focus on specific topics within each
• 0:35
  of the episodes. Uh, we could call them
• 0:38
  specials if you like. And today, our
• 0:41
  focus will be on comets and meteors.
• 0:44
  Stick around. We're doing all of that on
• 0:47
  this episode of Space Nuts.
• 0:49
  >> 15 seconds. Guidance is internal. 10 9
• 0:54
  Ignition sequence start.
• 0:55
  >> Space Nuts.
• 0:56
  >> 5 4 3 2
• 0:59
  >> 1 2 3 4 5 5 4 3 2 1
• 1:01
  >> Space Nuts.
• 1:02
  >> Astronauts report. It feels good.
• 1:05
  >> And it's great to have him back.
• 1:06
  Professor Jonty her, professor of
• 1:08
  astrophysics at the University of
• 1:11
  Southern Queensland. Jonty, hello.
• 1:14
  >> Ah, hey. How are you going?
• 1:15
  >> Good. Great to see you again.
• 1:17
  >> Well, it's good to be back. It's
• 1:19
  something nice to keep me entertained
• 1:20
  while I'm having a little bit of a a
• 1:21
  restful couple of weeks. I'm, you know,
• 1:23
  I've got a bit of leave so I'm um
• 1:25
  recovering from a minor surgery and
• 1:27
  therefore I can give my entire forecast
• 1:29
  to talking about fun things rather than
• 1:31
  doing Adam in effectively. But means I
• 1:33
  get to see a little bit of the life Fred
• 1:34
  gets to live.
• 1:35
  >> Yeah, maybe. Yes. Although he he doesn't
• 1:38
  seem to slow down much. Um, in fact, I
• 1:41
  think the worst thing you can do when
• 1:42
  you retire is slow down because um that
• 1:44
  the brain matter decides to give up the
• 1:46
  ghost and that's when it's all over Red
• 1:49
  Rover. But, uh, no, he he's going going
• 1:52
  great guns and um, you didn't mention
• 1:54
  that you're having a little bit of a
• 1:56
  recuperation. Um, are you in a position
• 1:59
  to talk about that or is it too
• 2:01
  embarrassing? Oh, well, it's one of
• 2:03
  those things that when I when I first
• 2:05
  had this pointed out, I a bit
• 2:06
  embarrassed about it, but I don't think
• 2:08
  as blossing
• 2:12
  past a little bit of embarrassment. So,
• 2:14
  I'm in my late 40s and I went to the
• 2:17
  doctor about a year ago cuz I had a
• 2:19
  little bit of bleeding when I was
• 2:20
  sitting down and stuff like this. And
• 2:21
  nothing dramatic. Um, but I found out
• 2:24
  two things. Firstly, in Australia, and I
• 2:26
  don't know about the rest of the world,
• 2:27
  you should look this up, but when you're
• 2:28
  in your 40s, the Medicare system here
• 2:32
  affords the opportunity for you to get
• 2:33
  health checks.
• 2:34
  >> Yep.
• 2:34
  >> Which is brilliant. So, you basically
• 2:36
  get what in the UK they'd call an MOT
• 2:38
  for a car. You get everything run over
• 2:40
  and you get your blood pressure done and
• 2:42
  your heart rate done and everything
• 2:43
  else. And then you go back every 3
• 2:45
  months and do it again and again and
• 2:47
  again. And it's basically, you're at an
• 2:48
  age where things start to break. Let's
• 2:50
  get on top of it early so that you can
• 2:52
  enjoy the rest of your life in peace.
• 2:54
  effectively. I think it's a really good
• 2:55
  idea and I suspect from a government
• 2:57
  point of view makes a lot of sense cuz
• 2:59
  if you find things easy earlier they're
• 3:01
  easier and quicker and cheaper to solve.
• 3:04
  Um, what it turned out from that was I
• 3:06
  spent about two months going back and
• 3:07
  forth with a doctor who thought I had
• 3:09
  one thing wrong, which is not what it
• 3:10
  was. And then I got got sent to this
• 3:12
  specialist who said, "You've got
• 3:14
  something called a fistula down near
• 3:15
  your backside."
• 3:17
  >> Which not life-threatening, not the end
• 3:19
  of the world, not doomed, but it's
• 3:20
  uncomfortable. Um, and you know, it's
• 3:23
  been slightly embarrassing in that I've
• 3:24
  had to learn more about sanitary pads
• 3:27
  than, you know, um, you would have
• 3:29
  expected, you know, which the women in
• 3:31
  the audience are going about bloody
• 3:32
  time. a man learned about this. Um, but
• 3:35
  it's a weird one because it's not
• 3:37
  life-threatening. It's nothing of a
• 3:38
  problem. Something 10 or 20% of guys
• 3:40
  apparently get them, but they can take
• 3:42
  multiple surgeries to fix. And when I
• 3:45
  went in for the first surgery in
• 3:46
  January, the there was another guy there
• 3:48
  who was on surgery number seven.
• 3:50
  >> Wow.
• 3:51
  >> Um, which Yeah. deep and joyous. Um,
• 3:53
  it's kind of day surgery, but you get a
• 3:55
  full general and you go under and doctor
• 3:56
  does snippy snippy things and you get a
• 3:58
  couple of weeks off work, which is where
• 3:59
  I am now. So, I've just had surgery
• 4:01
  number two and the doctor is hopeful,
• 4:04
  confident, whatever that surgery number
• 4:05
  three will be the final fix. And it's
• 4:08
  one of these weird things cuz people
• 4:09
  say, "What's wrong with you?" And if
• 4:10
  it's a sore arm, you just say, "I've
• 4:12
  hurt my arm or you've broken your arm or
• 4:13
  something like that." Or in Australia, a
• 4:15
  really common one, a melanoma. People
• 4:17
  have been in the sun too much. Going
• 4:19
  into hospital, what do you get? Oh, I've
• 4:20
  got a melanoma taken off. But as soon as
• 4:22
  it's anywhere between about your belly
• 4:23
  button and your knee, people are bashful
• 4:25
  about talking about it. And I
• 4:27
  >> first few months I was mortified and
• 4:28
  like wouldn't talk about it. And I
• 4:30
  realization is that if you don't talk
• 4:32
  about it, people don't get checked and
• 4:34
  we as men are terrible for that. And so,
• 4:37
  yeah, worth talking about. I'm a bit
• 4:38
  embarrassed about it, but I shouldn't
• 4:40
  be. And it's good to tune up. And it
• 4:42
  means that in 40 years time, I'll still
• 4:44
  be up and kicking and having a lot of
• 4:45
  fun rather than in discomfort and
• 4:47
  grumbling about a problem I could have
• 4:49
  got fixed.
• 4:50
  >> Yeah. Yeah. And um I think you're right.
• 4:53
  I think men do tend to keep things to
• 4:55
  themselves. uh a lot of them go into
• 4:57
  denial uh or they just think well no
• 5:00
  that won't happen to me so no problem
• 5:03
  but uh when I was diagnosed with
• 5:05
  prostate cancer it was like a bolt from
• 5:08
  the blue and I didn't I I I never
• 5:12
  expected to get it because there was
• 5:14
  next to no history of it in my family so
• 5:16
  um that was that was a bit of a shock
• 5:18
  and this is what how long is it now 3
• 5:21
  years 3 years and I'm still working my
• 5:25
  way through it. So, um, but the latest
• 5:29
  scans are all good. So, fingers crossed
• 5:31
  that we've, you know, reached a a good
• 5:34
  position. But, um, it it's just an
• 5:36
  ongoing thing in your life. You just got
• 5:38
  to get used to it. But, you my my advice
• 5:41
  to men is go and get checked. If you're
• 5:42
  over 50, go and get a prostate exam. Go
• 5:46
  and get your PSA tests done because if
• 5:49
  you don't
• 5:50
  and then they find it, it might be too
• 5:53
  far along. Um and then then the then the
• 5:57
  treatment becomes more dramatic.
• 5:59
  >> So anyway um it's a good thing to bring
• 6:01
  up.
• 6:02
  >> It is and it goes for the mental health
• 6:03
  stuff as well. I have a former partner
• 6:05
  of mine kind of 20 years ago who was
• 6:07
  very severely bipolar. Had a lot of
• 6:09
  challenges and she was continually
• 6:11
  frustrated by people's responses to that
• 6:13
  in public in that it's a hidden illness.
• 6:16
  It's there. She's getting treatment. But
• 6:18
  what she always said is, "It's real
• 6:20
  frustrating. If I if I had a broken leg
• 6:21
  or I had an injury to my arm and people
• 6:23
  could see it, they'd be supportive." But
• 6:26
  with mental health, she got a hell of a
• 6:27
  lot of, "Oh, just get over it or toughen
• 6:29
  up or
• 6:30
  >> Yep."
• 6:30
  >> And
• 6:31
  >> and you know, she was female, so she's
• 6:34
  more likely to go to the doctor and talk
• 6:35
  about it statistically. Men with mental
• 6:38
  health challenges tend to avoid that
• 6:40
  even more than they'll go to the doctor
• 6:41
  with physical health challenges. And
• 6:44
  it's something I'd like to see change. I
• 6:45
  come from a workingass background in
• 6:47
  Yorkshire where men don't talk about
• 6:49
  anything. You know, you're meant to be
• 6:50
  stoic and the only the only expression
• 6:52
  of emotion you're allowed is rage or a
• 6:54
  single manly tear. You know, it's
• 6:57
  >> really crazy the way we're conditioned.
• 6:58
  And even though I'm, you know, I went to
• 7:00
  uni, I've had a life, I've grown up, all
• 7:02
  this stuff still there at the back of
• 7:03
  your head and you've got to fight
• 7:04
  against it because the instinct is, ah,
• 7:06
  there's nothing wrong. I won't bother.
• 7:08
  >> Yeah.
• 7:08
  >> Yeah. And uh yeah, you see it way too
• 7:11
  often. Um, I I know it's a departure
• 7:14
  from what this podcast is all about, but
• 7:15
  I I
• 7:17
  when given the opportunity will, um,
• 7:21
  openly say to men, um, you know, don't
• 7:25
  don't hesitate to go to the doctor, not
• 7:28
  not when you think something's wrong,
• 7:30
  just preemptively go and get once a
• 7:32
  year, go and get checked and make sure
• 7:33
  everything's where it's supposed to be
• 7:35
  or whatever. Um,
• 7:38
  >> we do it do it for our cars, we do it
• 7:39
  for our pets.
• 7:40
  >> Yeah. Yeah, do it for yourself as well.
• 7:42
  >> Yeah, exactly.
• 7:43
  >> And yeah, I think it's probably a record
• 7:44
  for the quickest we've ever got off
• 7:45
  topic and possibly we should have a
• 7:47
  trigger warning at the front of it and
• 7:49
  all the rest of it, but no, good way to
• 7:50
  start even though it is off topic.
• 7:52
  >> It's okay. We'll get on to topic right
• 7:54
  now because uh what uh as I mentioned
• 7:57
  these these uh next uh several uh
• 8:00
  episodes are going to be dedicated to
• 8:02
  singular topics each and today it's uh
• 8:06
  well related topics, comets and meteors.
• 8:09
  Uh, this is a this is a pet topic of
• 8:11
  yours. I imagine
• 8:13
  >> it is. I I've always been a bit more
• 8:14
  into the nearby stuff than the more
• 8:16
  distant stuff. So, it always tickles me
• 8:18
  a little bit that when questions come in
• 8:20
  when I'm on the show, we get all the big
• 8:22
  bang and cosmology ones. And I'm sure if
• 8:24
  you got someone like the wonderful
• 8:25
  Tamara Davis on to talk cosmology, she'd
• 8:27
  get all the planets questions. It's
• 8:29
  always the way it goes. Yeah.
• 8:30
  >> But comets and meteors a big part of
• 8:32
  what hooked me into astronomy as a kid.
• 8:34
  And my thinking behind this is that
• 8:37
  we're recording in advance. You know, um
• 8:39
  obviously Fred is away, but you've got
• 8:42
  recordings with Fred already. And so the
• 8:44
  news that we would normally talk about
• 8:46
  hasn't happened yet. So I I have many
• 8:49
  talents, but seeing Into the Future
• 8:50
  isn't one of them to that degree. And so
• 8:52
  I thought it better to have a discussion
• 8:54
  about the general stuff in a bit more
• 8:55
  depth
• 8:57
  than go into particular news topics. And
• 8:59
  it's it could almost be a bit of an
• 9:01
  explainer, a bit of the background, and
• 9:03
  hopefully at least gives my insight into
• 9:05
  why a given topic's interesting, but
• 9:07
  also what people can look out for in the
• 9:09
  future and how they can get more into
• 9:12
  more out of that particular topic, if
• 9:14
  that makes sense.
• 9:15
  >> Yeah.
• 9:16
  >> Um, a little bit different. I understand
• 9:18
  for some listeners it might be a bit bit
• 9:20
  of an abrupt departure and a change. So,
• 9:22
  it'll be interesting to see what
• 9:23
  feedback you get. But hopefully people
• 9:25
  like it as a little bit of a change in a
• 9:27
  breath of fresh air. And if they don't,
• 9:28
  well, there's only a couple of episodes
• 9:30
  and Fred's back anyway, so you'll have
• 9:32
  to deal with it and we'll see.
• 9:33
  >> I'm sure it'll be fine. Comets and
• 9:35
  meteors are a very uh popular topic. So,
• 9:39
  um, where do we start? Maybe maybe look
• 9:41
  at a bit of the history of this.
• 9:43
  >> Yeah, I think that is a always a good
• 9:45
  place to start because it sets the
• 9:46
  context of where we are now. And for
• 9:49
  both comets and meteors, there's a kind
• 9:51
  of global connection society that really
• 9:54
  predates by a long long way our
• 9:57
  scientific knowledge essentially the
• 9:59
  modern scientific viewpoint and the
• 10:01
  scientific method. All cultures across
• 10:03
  the world from our wonderful traditional
• 10:05
  owners here in Australia to the peoples
• 10:07
  of every continent and every land both
• 10:09
  current and past historically had a
• 10:12
  really firm connection to the night sky.
• 10:14
  They knew the night sky better than most
• 10:15
  people these days do because it wasn't
• 10:17
  light pollution. There weren't TVs and
• 10:19
  Xboxes. So the sky was something people
• 10:21
  were much more exposed to.
• 10:24
  A lot of cultures had this kind of idea
• 10:25
  of as above so below, as below so above.
• 10:28
  So they were very firmly of the idea
• 10:30
  that major events on the earth were
• 10:32
  reflected in the sky and major events in
• 10:35
  the sky would have their counterparts on
• 10:37
  the earth. And that's where astrology
• 10:40
  was born. And for a long time astrology
• 10:42
  and astronomy were one and the same. You
• 10:44
  know, people doing astronomy studies
• 10:46
  were doing it because they wanted to
• 10:48
  understand the events that would
• 10:49
  influence what's on the earth. And there
• 10:51
  are good examples of this in terms of
• 10:53
  the nominally fixed stars. Things like
• 10:55
  the ancient Egyptians using the rising
• 10:58
  of Sirius in the dawn sky after it
• 11:00
  disappeared in the evenings as a
• 11:02
  predictor of the flooding of the Nile,
• 11:04
  for example, the use of the night sky as
• 11:05
  a calendar. Lots of stuff like that. But
• 11:08
  because people were so aware of the
• 11:10
  night sky, anything that was ephemeral,
• 11:13
  anything that was transitory that
• 11:15
  appeared and then disappeared that was
• 11:16
  unexpected was often seen as kind of a
• 11:19
  potent or an omen. Something that was an
• 11:22
  indication either of major change and
• 11:24
  upheaval currently happening or one soon
• 11:26
  to come. And really bright comets and
• 11:28
  spectacular meteor showers kind of often
• 11:30
  filled this role. And you can go back
• 11:33
  through ancient history where we have
• 11:35
  the records and see good examples of
• 11:37
  this. I've got in one of my talks talks
• 11:40
  about a guy called Mithridatis um up 6 I
• 11:45
  think his name was. He was one of the
• 11:46
  great enemies of the Roman Empire. And
• 11:48
  there are quotes ascribed to him saying
• 11:51
  things like um even the heavens
• 11:53
  predicted the greatness of this man. For
• 11:55
  in the year in which he was born and the
• 11:57
  year in which he came to reign, a comet
• 11:59
  shone through both periods for 70 days
• 12:02
  as bright as the sun. Each rising and
• 12:04
  setting took four hours each. And that's
• 12:06
  kind of hyperbolic, but it gives this
• 12:08
  idea that people saw something in the
• 12:11
  sky that was unusual and tied it to
• 12:14
  events on Earth. Another good example
• 12:16
  would be the alleged comet called
• 12:18
  Caesar's comet in 44 BC 43US 43
• 12:23
  which is recorded in Roman writings from
• 12:26
  a century or two later talking about
• 12:30
  after the death of Caesar a comet blazed
• 12:32
  in the sky for seven days that was
• 12:34
  spectacularly bright. then disappeared
• 12:36
  and was never seen again. Now, that
• 12:38
  comet is a really good example of the
• 12:40
  challenge people have with historical
• 12:42
  records
• 12:44
  >> because on the one hand, you've got
• 12:45
  these clear reports from the Roman
• 12:46
  Empire. None of them at the time though,
• 12:49
  all of them a bit later on. But that
• 12:51
  comet is not recorded from anywhere else
• 12:53
  on the planet and there were cultures
• 12:54
  around the globe leaving records like
• 12:56
  ancient China and ancient Korea who
• 12:58
  would have seen it. So, was that comet
• 13:01
  real? Or was it a case of after the
• 13:03
  event people inventing a night sky
• 13:05
  phenomena to tie with the soul of the
• 13:08
  emperor rising to heaven? It's one of
• 13:10
  the challenges people in the kind of
• 13:12
  cultural astronomy space face, I think,
• 13:13
  in terms of disentangling
• 13:15
  the narrative from the events that
• 13:17
  prompted it, if that kind of makes
• 13:19
  sense.
• 13:19
  >> Yeah. But what's certainly true is that
• 13:22
  for as long as we've looked at the sky,
• 13:24
  really bright comets and unusually
• 13:26
  powerful meteor showers were things that
• 13:29
  people took note of. And recently there
• 13:31
  was a lot of meteor media coverage of
• 13:33
  the April Lyid meteor shower, which is
• 13:36
  not one of the strongest of the year,
• 13:37
  but one of the reasonable moderate ones.
• 13:40
  It's a kind of one that if you're a
• 13:41
  meteor enthusiast, you'll go out and
• 13:43
  watch, but isn't worth going out if
• 13:44
  you're not that interested cuz there's
• 13:46
  too few. M
• 13:48
  >> I had to grumble about some of the
• 13:49
  coverage here in Australia cuz it's not
• 13:50
  a great shower for us. But that meteor
• 13:53
  shower was recognized by the traditional
• 13:55
  owners in Australia and there are
• 13:57
  stories from Victoria from I think the
• 13:59
  Bong people although I stand to be
• 14:01
  corrected on that that associate this
• 14:03
  meteor shower with the Malifile one of
• 14:04
  the big grand nesting birds in Australia
• 14:07
  which nests around that time of year.
• 14:09
  The meteors seen shrieking from low in
• 14:11
  the northern sky were viewed as being
• 14:12
  the dust being kicked up by the nesting
• 14:15
  bird celestially. So they recorded this
• 14:17
  meteor shower, even though it isn't a
• 14:18
  particularly strong one. But our oldest
• 14:22
  written record of any meteor shower is
• 14:24
  the Aprils and it's dated back to
• 14:26
  something like 687 B.CE when stars fell
• 14:29
  like rain when there was a major storm
• 14:31
  from the Lyids and it was significant
• 14:33
  enough for people to record. So comets
• 14:36
  and meteors way before the modern
• 14:39
  scientific understanding of them really
• 14:41
  had this important cultural role. Um,
• 14:45
  even in the Battle of Hastings, if you
• 14:46
  ever go to see the bio tapestry, this
• 14:48
  wonderful woven record of the Battle of
• 14:51
  Hastings and the invasion of William the
• 14:52
  Conqueror, Comet Hi features prominently
• 14:55
  on that because in 1066,
• 14:58
  >> you had the second best apparition of
• 14:59
  Comet Halley in the last 2,000 years.
• 15:01
  Arguably, it was very spectacular in the
• 15:03
  sky at the time the conquest was going
• 15:05
  on. And that was considered important
• 15:07
  enough to be recorded in the tapestry
• 15:10
  that was woven at the time. You know,
• 15:12
  it's amazing that you've got this panel
• 15:14
  where there's all the peasants pointing
• 15:16
  up at this thing in the sky and somebody
• 15:18
  whispering King Harold's ear about the
• 15:20
  comet that's visible. So yeah, don't
• 15:22
  know whether the invading forces took it
• 15:24
  as a good sign or a bad sign, but they
• 15:26
  thought it was important enough to
• 15:27
  include.
• 15:29
  >> So that in itself's fairly breathtaking.
• 15:31
  And so when we see these objects, it's a
• 15:32
  lovely connection to thousands of years
• 15:35
  of our heritage of people looking at the
• 15:37
  night sky in wonder. I think the first
• 15:41
  step we had really in moving from
• 15:45
  cultural commentary astronomy to modern
• 15:48
  scientific astronomy in a way came with
• 15:50
  the great comet of 1577
• 15:53
  which was another of the really amazing
• 15:56
  spectacular bright comets that was
• 15:58
  widely observed hence why it's a great
• 16:01
  comet but it was observed by the great
• 16:03
  astronomer Tiko Brahhe and I'm sure
• 16:06
  Brahe is featured on the podcast many
• 16:08
  times before, but the quirky individual
• 16:10
  he was. It's well worth looking up his
• 16:12
  Wikipedia record. Is this wealthy
• 16:15
  nobleman with a silver replacement nose
• 16:18
  after he lost half his nose in a duel?
• 16:20
  He's that guy.
• 16:21
  >> Yes.
• 16:22
  >> Yes. Um he had a pet moose that died
• 16:24
  when it fell down the steps because it
• 16:25
  got drunk at a banquet. He
• 16:27
  >> really odd odd man. Um but probably
• 16:31
  viewed as being the last great pre-
• 16:33
  telescope astron astronomical observer
• 16:36
  if that makes sense. Naked eye observer.
• 16:38
  Now, at this time, comets were kind of
• 16:40
  thought to be probably atmospheric
• 16:42
  phenomenon. They were nearby, high in
• 16:44
  the atmosphere,
• 16:46
  and so that was what was going on.
• 16:48
  People had that kind of idea. He
• 16:50
  realized that if that were true, these
• 16:53
  things would display a noticeable
• 16:55
  parallax if people observed them from
• 16:57
  different locations.
• 16:58
  >> Uhhuh.
• 16:59
  >> So, in other words, people looking from
• 17:01
  different locations would see the comet
• 17:03
  in a different place in the sky because
• 17:05
  it was in the foreground. It's the same
• 17:07
  technique we use to measure the distance
• 17:09
  to the nearest stars. If you put your
• 17:11
  finger in front of your face and look at
• 17:12
  it through one eye and then look through
• 17:14
  the other, you'll see your finger
• 17:15
  blinking side to side. And the further
• 17:18
  away your finger is, the less it moves.
• 17:20
  >> We use that to measure the distance to
• 17:21
  stars by observing from one side of the
• 17:23
  Earth's orbit than the other. But what
• 17:25
  Brah did was collect observations from
• 17:27
  around Europe of where the comet was in
• 17:29
  the sky. With those observations, he
• 17:33
  would have been able to detect a
• 17:34
  parallax for the comet if it were closer
• 17:37
  than the orbit of the moon. So if it was
• 17:39
  atmospheric, absolutely definitely would
• 17:40
  do. But no measurable parallax was
• 17:43
  found, which showed the comet had to be
• 17:45
  at least a couple of million km away.
• 17:47
  And in fact, it was probably several
• 17:48
  tens of millions of kilome distant. He
• 17:51
  got this beautiful figure and I've I use
• 17:53
  this in my talks occasionally that is
• 17:56
  his drawing of the motion of the comet
• 17:58
  and it's fascinating from cultural point
• 18:00
  of view because it's clearly at the time
• 18:02
  when you still have the geocentric model
• 18:04
  the earth was the center of the
• 18:05
  universe. So you've got the Earth in the
• 18:07
  middle, the Sun going around the Earth,
• 18:09
  but then Mercury, Venus, and the Moon
• 18:10
  going around the Sun,
• 18:12
  >> this kind of weird hybrid thing, but
• 18:14
  you've got the path of the comet moving
• 18:15
  through there that he's determined. And
• 18:17
  what's really interesting to me, what's
• 18:20
  really fascinating is he's got the tails
• 18:22
  pointing away from the sun all the time.
• 18:24
  So he's got the phenomenology of where
• 18:26
  the comet is in the solar system,
• 18:28
  modular, the the sun's going around the
• 18:31
  Earth, and the tails pointing the right
• 18:33
  way as it moves. tales of comets always
• 18:36
  pointing away from the sun. And to me
• 18:38
  that kind of marks the dawn of the
• 18:41
  modern scientific view of comets from
• 18:44
  the cultural we don't know what they are
• 18:46
  but they are important.
• 18:49
  >> I think that's a real kind of boundary
• 18:51
  point for me.
• 18:52
  >> Yeah. Yeah. Fascinating. I was actually
• 18:54
  going to ask you about the uh you know
• 18:56
  the point in time where we went from the
• 18:58
  mythology to the understanding that this
• 19:01
  this was something else and yeah you
• 19:04
  covered that beautifully. Going to just
• 19:06
  take a breath on Space Nuts. Uh you're
• 19:08
  with Andrew Dunley and Professor Jonty
• 19:10
  Horner.
• 19:13
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• 21:01
  >> G. And I feel
• 21:02
  >> Space Nuts.
• 21:03
  >> I did say a breath. That was quick. Um,
• 21:05
  let's continue talking about comets and
• 21:07
  meteors. There have been a lot of them
• 21:10
  in the news of late uh comet pan stars
• 21:14
  is um you know it was very very uh
• 21:17
  popular late April. uh and uh we we've
• 21:22
  seen in recent times u a new kind of
• 21:25
  comet and those are the ones that are
• 21:27
  coming from other systems uh not not the
• 21:31
  ones that are con continually rotating
• 21:34
  through our own solar system. We've had
• 21:35
  these exo comets that have been quite
• 21:39
  intriguing and and uh opening up all
• 21:42
  sorts of new ideas and questions about
• 21:44
  uh comets and other other parts of the
• 21:47
  the universe and what we could learn
• 21:49
  from them. Um and and new comets are
• 21:53
  being discovered all the time. That
• 21:54
  doesn't mean they haven't been here
• 21:56
  before, but it does mean that they've
• 21:58
  got very longitudinal travel times. So,
• 22:02
  um, you know, some we won't ever see
• 22:04
  because we'll have been and gone before
• 22:06
  they get here, and others we'll maybe
• 22:10
  see several times during our lifetimes.
• 22:12
  >> Absolutely. Now, historically, people
• 22:15
  broke the comets we found down into two
• 22:17
  categories. We had short period comets,
• 22:20
  which are comets. The definition when I
• 22:22
  was a kid was comets whose orbital
• 22:24
  periods were less than 200 years.
• 22:26
  Shorter than that and you were a short
• 22:27
  period comet. Longer than that, and you
• 22:29
  were a long period comet. Now there are
• 22:31
  subtleties within that. Within the short
• 22:33
  period comets we have comets like comet
• 22:34
  Halley which are called the Halley type
• 22:36
  comets which come around with a period
• 22:38
  comparable to a human lifetime or a bit
• 22:40
  longer. And the two brightest and most
• 22:42
  famous of those are comet Halley and
• 22:43
  comet Swift Tuttle.
• 22:44
  >> You then have the Jupiter family comets
• 22:46
  which are comets whose orbits are just a
• 22:48
  few years and are typically under
• 22:50
  Jupiter's control. And when I was a kid,
• 22:52
  anything longer than 200 years was
• 22:54
  considered long period. Now that kind of
• 22:57
  got smashed into the ground a bit in the
• 22:58
  early 2000s when comet Eaya Jang was
• 23:01
  cited because comet Eaya Jang was very
• 23:04
  well observed. Its orbit was well
• 23:06
  calculated. It was found to have a
• 23:07
  period of 366 years I think it is and
• 23:10
  that allowed people to identify the
• 23:13
  previous observations of that comet from
• 23:14
  the last time it was around. So that's
• 23:17
  currently the record holder where we're
• 23:19
  absolutely certain that it's been seen
• 23:22
  on multiple occasions and it has a a
• 23:25
  periodic comet designation. Now now a
• 23:27
  subtlety to that is we do have the crot
• 23:30
  sungrazing comets and I can talk more
• 23:31
  about them a little later where we have
• 23:33
  a strong identification between an
• 23:36
  observation of the comet say with comedy
• 23:38
  Keki in 1965
• 23:40
  and a previous apparition in the 1100s
• 23:44
  which is about an 800year return. Yeah,
• 23:46
  >> that's a bit woolly because the comets
• 23:48
  we observe now are fragments of one
• 23:50
  comet back then and so therefore several
• 23:53
  comets tied to that initial apparition.
• 23:55
  So there's all that complexity there. We
• 23:57
  then have the long period comets which
• 24:00
  like I say were 200 years or more. It
• 24:03
  still kind of is but with those objects
• 24:06
  that are both long period and short
• 24:07
  period thanks to a jang. You've got
• 24:08
  these objects whose orbital periods are
• 24:10
  so long that they are marketkedly longer
• 24:12
  than a human lifetime. even if they're
• 24:15
  comets that have been through before. So
• 24:16
  a good example of a really bright comet
• 24:18
  that is considered long period but has
• 24:21
  been through many times before is comet
• 24:23
  Hailbop. Comet Hailbop was spectacular
• 24:25
  in 9697. It was visible with a naked eye
• 24:28
  for 18 months shattering all the
• 24:30
  records. It will be back in about the
• 24:32
  year 4400. It was the last round when
• 24:34
  the Egyptians were building pyramids.
• 24:36
  And that is perversely a long period
• 24:39
  comet with a relatively short period
• 24:40
  orbit for a long period of comet. And so
• 24:43
  scientifically we'd call that
• 24:45
  dynamically old or not a new comet
• 24:48
  because it's been around a number of
• 24:49
  times. At the very long period end of
• 24:52
  the long period comets you get things
• 24:54
  that are coming in from halfway to the
• 24:56
  nearest star from a region we describe
• 24:58
  as the or cloud or the opic cloud. And
• 25:01
  those things on their way in have
• 25:04
  calculated orbital periods of hundreds
• 25:06
  of thousands or even millions of years.
• 25:09
  And many of those actually only come
• 25:10
  through once and then they get nudged
• 25:12
  and ejected from the solar system never
• 25:14
  to return
• 25:15
  >> going out to wander among the stars. And
• 25:18
  it's objects like that that will become
• 25:19
  the interstellar comets for other stars
• 25:22
  in the same way that this third group of
• 25:24
  comets that you alluded to that we found
• 25:26
  recently are interstellar comets in our
• 25:28
  system. So these are the objects coming
• 25:30
  through so quickly that they are not
• 25:32
  gravitationally bound to the sun, but
• 25:34
  also so quickly that there is no
• 25:36
  possibility that they ever were. They've
• 25:38
  been flung in so quickly that they must
• 25:40
  come from another place. The most recent
• 25:44
  one was ThreeI Atlas, which got talked
• 25:46
  about a huge amount. Yes. Was definitely
• 25:49
  not an alien spaceship. And to avoid
• 25:51
  getting too political, just a very brief
• 25:53
  comment on that because it needs to be
• 25:55
  stated and restated, which is that the
• 25:57
  arguments of that being an alien
• 25:59
  spaceship were the work of one person. M
• 26:02
  >> one person who is not a solar system
• 26:04
  astronomer historically but has reached
• 26:06
  that age and level of senility that they
• 26:08
  believe they can be an expert in things
• 26:10
  that they are not and has a certain
• 26:12
  financial interest in keeping people
• 26:14
  interested in aliens because they buy
• 26:16
  his book. And the community of
• 26:20
  astronomers has been very upset and very
• 26:22
  stressed about that cuz it diverts
• 26:24
  attention from what is a really
• 26:25
  fascinating object on the fact that it's
• 26:28
  really fascinating but also breeds a
• 26:30
  certain amount of fear. And I genuinely
• 26:31
  had people reaching out to me when he
• 26:34
  was pushing this narrative of it being
• 26:36
  aliens that were going to invade because
• 26:37
  they were frightened. They were
• 26:39
  genuinely worried because a Harvard
• 26:41
  astronomer was saying aliens were going
• 26:43
  to come and beat us all up.
• 26:45
  >> Yeah. And it's problematic because it
• 26:47
  hides the science, but it's also more
• 26:49
  widely problematic at a time when we
• 26:51
  have lowering levels of engagement with
• 26:54
  science and very much lowering levels of
• 26:56
  trust in science and scientists. It's
• 26:59
  very bad to have someone acting
• 27:01
  disingenuously,
• 27:02
  telling lies or muddying the water and
• 27:06
  then arguing that everybody else is
• 27:07
  wrong and mean to me and I'm the only
• 27:09
  one telling the truth. And it's part of
• 27:11
  that whole fake news thing that I think
• 27:13
  is dangerous and damaging. You know, we
• 27:16
  need people to
• 27:18
  >> have trust and faith in science because
• 27:19
  it's so integral to our lives. And it's
• 27:21
  good to question, but it's bad when
• 27:23
  people say things that they
• 27:25
  fundamentally know are not true just to
• 27:26
  get hits or clicks or money.
• 27:28
  >> Yeah. I and it's important to debunk
• 27:32
  that kind of uh approach because I I've
• 27:36
  had people come up to me very recently
• 27:38
  who know I do this podcast
• 27:40
  uh who've said to me, "Oh, what do you
• 27:42
  think of that alien spaceship?" And I
• 27:44
  go, "It's it's bullshit." That's what I
• 27:47
  think because it's it's somebody trying
• 27:50
  to get media attention. It's got
• 27:51
  nothing. It's a rock. It it's actually
• 27:53
  it's it's an it's an ice conglomerate.
• 27:56
  It's it's not a it's not a spaceship at
• 27:58
  all. It's not behaving like a spaceship
• 28:00
  would. It's behaving like something
• 28:02
  passing through our solar system
• 28:04
  >> and
• 28:06
  and people people the thing is Johnny
• 28:08
  people are buying this rubbish.
• 28:10
  >> But there's a old saying that you know a
• 28:12
  lie can run around a lie can run around
• 28:14
  the world before the truth has got its
• 28:16
  boots on.
• 28:17
  >> Especially when it's an attractive lie.
• 28:19
  It's I mean again digging into my
• 28:21
  memories of Terry Pratchett stuff which
• 28:23
  happens a lot. It's the old quote when
• 28:25
  they're talking about newspapers and
• 28:27
  nobody really ever wants to hear a story
• 28:29
  about dog bites man because it happens
• 28:31
  all the time. But if you got a story
• 28:32
  that says man bites dog, everybody's
• 28:34
  fascinated.
• 28:34
  >> Yeah.
• 28:35
  >> And this story has all the elements.
• 28:37
  It's so salacious that it gets coverage
• 28:39
  and people who don't normally read or
• 28:42
  digest science are not interested will
• 28:44
  see this and hook into it. And when the
• 28:46
  by line is Harvard astronomer that gives
• 28:48
  it a huge amount of credence. It does
• 28:50
  >> and nobody hears the rebuttals. It's
• 28:53
  A bit like, you know, when there are
• 28:55
  claims of life on a planet around
• 28:56
  another star, nobody remembers the t the
• 28:59
  follow-ups that say actually it wasn't.
• 29:01
  They just remember, oh, we found aliens
• 29:03
  and we haven't.
• 29:05
  >> I mean, I think that the story that uh
• 29:08
  the most recent story that I recall
• 29:11
  where that that claim was made was um
• 29:14
  the one about the something they what
• 29:17
  was it they found in the in the
• 29:18
  atmosphere of Venus? It was
• 29:20
  >> phosphine. Yes. Now I I can go on a
• 29:22
  little bit of a side rant about that. My
• 29:24
  heart broke. Um the lead author on that
• 29:27
  study was Jane Greavves in the UK who's
• 29:29
  someone I knew very well when I was in
• 29:31
  the UK and she's a fabulous science and
• 29:32
  just all around wonderful individual and
• 29:35
  the story was led by a UK team who if
• 29:39
  you actually read the paper don't say
• 29:41
  anything that is this is life. What they
• 29:44
  say is we found a very weak signal
• 29:46
  >> of this gas in Venus's atmosphere. It's
• 29:49
  right down in the noise. So there is a
• 29:50
  chance it's a false positive anyway. So
• 29:53
  there needs to be a bit bit of extra
• 29:54
  work done. It's a little bit interesting
• 29:56
  because on the earth the only processes
• 29:59
  that produce this peculiar gas are
• 30:03
  technology and industry or life.
• 30:05
  >> Yeah.
• 30:06
  >> We don't know of any other way that it's
• 30:07
  made. But that doesn't mean that there
• 30:08
  aren't other ways that it's made.
• 30:10
  >> Isn't that a tasty morsel for the
• 30:12
  popular press?
• 30:12
  >> Absolutely. But what happened then was
• 30:14
  that there is an American
• 30:17
  outreach journal um science
• 30:19
  communication journal that broke embargo
• 30:21
  on this story. Didn't talk to Jane and
• 30:24
  her colleagues, but instead ran a story
• 30:26
  saying British scientists find life on
• 30:28
  Venus, which is not what they'd said at
• 30:29
  all. No,
• 30:30
  >> that's what started the absolute bum
• 30:32
  fight. And the vitrial and the hate and
• 30:35
  the death threats, believe it or not,
• 30:36
  that Jen Greavves got because of this
• 30:39
  >> were astonishing. It was absolutely
• 30:41
  terrible. And instead of being able to
• 30:43
  manage the deployment of this wonderful
• 30:45
  story about this fascinating new result
• 30:47
  they got, they spent all their time in
• 30:49
  damage control because this publication
• 30:54
  chose to break the embargo early and run
• 30:56
  a story that was not factually true but
• 30:58
  again would get them clicks.
• 30:59
  >> Yep. Yeah. And and that's unfortunately
• 31:02
  the modern media and um the the
• 31:05
  internet's to blame. Well, it's not the
• 31:07
  internet that's to blame. It's the
• 31:08
  people who use it that are to blame. And
• 31:11
  it's one of the um one of the things you
• 31:13
  really got to be careful of when you are
• 31:16
  following a story, whether it's an exoc
• 31:18
  comet that's not a spaceship or uh life
• 31:22
  that's not in Venus's atmosphere. Um and
• 31:25
  and even to a lesser degree, and you and
• 31:28
  I mentioned this before we started, the
• 31:30
  way the media gets its information
• 31:33
  confused, such as uh reporting on uh you
• 31:37
  upcoming spectacular meteor showers that
• 31:40
  uh everyone gets excited about and then
• 31:42
  they realize they're on the wrong side
• 31:43
  of the planet.
• 31:44
  >> Absolutely. And this is a caution I give
• 31:46
  to everybody both for comets and for
• 31:48
  meteors actually, but particularly for
• 31:50
  those of us in the southern hemisphere.
• 31:51
  Um, meteor showers and comets are things
• 31:55
  that are best seen from some latitudes
• 31:57
  and not from others. And for each comet
• 31:59
  or for each meteor shower, that's
• 32:00
  different. Now, I'll talk later on about
• 32:02
  a newly discovered comet that might be
• 32:04
  very spectacular in late 2028.
• 32:07
  That comet is primarily going to be a
• 32:09
  southern hemisphere object. So, it will
• 32:11
  probably be better for us in Australia
• 32:13
  and New Zealand than it will be for
• 32:14
  people in the UK or the US, just as an
• 32:16
  example.
• 32:18
  when events are happening that are
• 32:20
  primarily good for the northern
• 32:21
  hemisphere. The northern hemisphere has
• 32:22
  more people and more media. And what
• 32:24
  I've seen happen more and more is that
• 32:26
  the media in Australia and I know the
• 32:30
  Australian stuff because that's local to
• 32:31
  us. It's probably just the same in New
• 32:33
  Zealand, South Africa, South America,
• 32:35
  all these other places. But the media
• 32:37
  there will pick up these stories and
• 32:38
  just run them without running the sanity
• 32:42
  featur filter. So the April lyids are a
• 32:44
  really good example of this, but a
• 32:46
  better one is probably the Percid meteor
• 32:47
  shower in August. Now, as a little bit
• 32:50
  of background here, when we've got a
• 32:52
  meteor shower, we're getting bits of
• 32:54
  dust and debris hitting the Earth's
• 32:55
  atmosphere and ablating at an altitude
• 32:58
  of about 80 km. Now, ablation is a
• 33:02
  slightly weird thing. People often
• 33:03
  describe this as burning up, but it's
• 33:05
  not burning up in the sense of a flame
• 33:06
  being lit and a fire burning. It's
• 33:09
  rather that these things push into the
• 33:10
  atmosphere at really high speed, pile
• 33:12
  the air up in front of them, getting the
• 33:14
  air superheated, creating a load of
• 33:16
  plasma, and the heat from that bakes and
• 33:18
  vaporizes the bit of debris. So, it's
• 33:20
  not burning up in the traditional sense.
• 33:22
  And anytime you see a meteor, you see a
• 33:24
  shooting star, that's what you're
• 33:25
  seeing. And the bigger the bit of dust,
• 33:27
  the brighter it will be. The faster it's
• 33:29
  moving at a given size, the more energy
• 33:31
  it's got. So, again, the brighter it'll
• 33:32
  be.
• 33:33
  >> Yeah.
• 33:33
  >> And you see shooting stars on any night
• 33:36
  of the year. typically three or four an
• 33:39
  hour in the evenings, five or six an
• 33:41
  hour in the mornings potentially. And
• 33:43
  that difference is just because in the
• 33:44
  mornings you're facing the direction the
• 33:45
  earth's moving. So you getting
• 33:47
  collisions that are headon. So the
• 33:49
  average collision speed is higher. So a
• 33:51
  grain of dust that's the same size will
• 33:53
  be a bit brighter. Therefore, the things
• 33:55
  that in the evening that will be too
• 33:56
  faint to see become visible. So you get
• 33:58
  a slight increase in the rate towards
• 34:00
  morning than in the evening. Um, it's
• 34:03
  also you're probably getting a slightly
• 34:04
  increased amount of stuff entering the
• 34:06
  atmosphere cuz you always see more flies
• 34:07
  hit your windscreen than your air
• 34:08
  windscreen. Same kind of idea.
• 34:11
  >> When we get a meteor shower, what's
• 34:13
  happening is we're passing through the
• 34:16
  area of space where the Earth passes
• 34:18
  near the orbit of either a comet or an
• 34:20
  asteroid. And typically, it's a comet.
• 34:22
  >> Now, every time a comet goes around the
• 34:24
  sun, that dirty snowball or snowy dirt
• 34:27
  ball gets hot. The volatile material on
• 34:30
  the surface is too hot to stay solid. So
• 34:32
  becomes a gas in a process called
• 34:34
  sublimation. And you get jets erupting
• 34:36
  from the comet, shrouding in gas, which
• 34:40
  is then blown away from the sun to give
• 34:41
  you the tails. Those jets erupting into
• 34:44
  space carry with them dust.
• 34:47
  Now biggest bits of dust are pushed away
• 34:49
  so gently they'll fall back to the comet
• 34:50
  and clog it up. And some comets
• 34:52
  eventually turn off because of this.
• 34:54
  also is the reason most comets are only
• 34:56
  active from a few few locations on the
• 34:58
  surface, not uniformly because most of
• 35:00
  the surface is clogged up and you've
• 35:02
  just got a few active areas where
• 35:03
  volatile material is exposed.
• 35:05
  >> Yeah.
• 35:06
  >> But that dust that's ejected from the
• 35:07
  comet is ejected with speeds measured in
• 35:10
  meters/s or centimeters/s
• 35:12
  from an object that's traveling at a
• 35:14
  speed measured in tens of kilometers/ a
• 35:15
  second. So, what that means is that that
• 35:18
  dust is moving away from the comet at a
• 35:21
  speed almost identical to the speed the
• 35:23
  comet's traveling itself. I guess it's
• 35:25
  like if you you're driving along the
• 35:28
  road and you drop a tennis ball out of
• 35:29
  the window until the wind resistance
• 35:32
  pushes it back. If there wasn't a wind
• 35:33
  resistance there, it would move along
• 35:35
  with the car just drifting away very
• 35:37
  slightly based on the speed you pushed
• 35:39
  it out of the window. Same idea.
• 35:41
  >> Yeah. I actually saw a a really great
• 35:43
  experiment once where they were um how
• 35:48
  did they do it? They had a guy on the
• 35:49
  back of a truck and they were driving at
• 35:53
  like 100 kilometers an hour and they
• 35:57
  shot him off the truck in the opposite
• 35:59
  direction at the same speed and he just
• 36:03
  stopped where he landed.
• 36:04
  >> Oh, it's brilliant. I think Mythbusters
• 36:06
  did something similar.
• 36:07
  >> It's amazing.
• 36:08
  >> Our common sense is physics really.
• 36:11
  >> Yeah, simple physics is great, but our
• 36:13
  common sense breaks down in some
• 36:15
  situations because our common sense is a
• 36:17
  naturally inherited thing about the
• 36:19
  world at the speeds we experience it.
• 36:22
  >> And so we tend to think if you're
• 36:23
  running forwards at 10 km an hour and
• 36:25
  you throw something forwards, it will
• 36:27
  travel a bit faster. That breaks down
• 36:29
  when you get to relativity. There's all
• 36:30
  these weird things around it. where our
• 36:33
  common sense gets it wrong for comets
• 36:35
  and for the dust. And it took me a long
• 36:37
  while to get my head around this because
• 36:38
  it's a bit counterintuitive.
• 36:40
  If you eject dust from a comet, you can
• 36:43
  eject the dust forward or backwards. So
• 36:44
  you can imagine this jet from the comet
• 36:46
  working a bit like a geyser turning off
• 36:48
  when it gets dark and it gets cold and
• 36:50
  then turning off again in the morning
• 36:51
  when it gets hot again.
• 36:53
  >> That can throw dust forwards, sidewards,
• 36:55
  and backwards or any combination of the
• 36:58
  above. So that means this comet is
• 37:00
  throwing out dust at a speed of
• 37:01
  meters/s, a bit like a sprinkler into
• 37:04
  space. The dust that has a forward
• 37:07
  component to its speed. So it could be
• 37:09
  going sidewards but a little forward or
• 37:11
  it could be going head-on in front of
• 37:12
  the comet. That is now traveling around
• 37:14
  the sun faster than the comet is, which
• 37:17
  means it will move onto an orbit with a
• 37:19
  longer period than the comet. So the
• 37:21
  next time the comet comes around, that
• 37:23
  grain of dust will arrive after the
• 37:24
  comet. So dust thrown forward ends up
• 37:27
  behind. And similarly does thrown
• 37:29
  backwards is moving slower than the
• 37:30
  comet which puts it on a slightly
• 37:32
  shorter period orbit and therefore it
• 37:34
  will arrive ahead of the comet next
• 37:36
  time. And that little bit of sidewards
• 37:37
  motion also means it will spread out a
• 37:39
  little bit in space. What this means
• 37:42
  over time periods is that comets every
• 37:44
  time they come round essentially shed
• 37:46
  what becomes like a javelin shape, a
• 37:48
  spear of dust into space with a comet at
• 37:51
  the center
• 37:53
  like a spike. And that spike gradually
• 37:55
  diffuses over time, spreads out further
• 37:57
  and further ahead and behind the comet.
• 37:59
  And so over a long time scale, you
• 38:01
  eventually end up with the comet's orbit
• 38:03
  shrouded in dust. And the dust can be
• 38:05
  quite spread out over millions of
• 38:06
  kilometers.
• 38:07
  >> Yeah,
• 38:08
  >> these orbits are oriented randomly in
• 38:10
  space. So many of them don't intersect
• 38:12
  the Earth. Even if the comet gets closer
• 38:14
  to the sun than we are at its closest,
• 38:16
  passes above or below the Earth's orbit,
• 38:18
  nothing happens. But for a subset of
• 38:21
  them, the comet will in its orbit have
• 38:25
  the potential to get very close to the
• 38:26
  Earth. So its orbit and the Earth get
• 38:28
  very close together. And in those cases,
• 38:30
  every time we go around the sun, if that
• 38:32
  comet's been laying dust down for a
• 38:34
  while, we'll run into the dust every
• 38:36
  time we go around. And that dust will
• 38:38
  hit the Earth's atmosphere, which means
• 38:40
  we're going through a dirtier bit of the
• 38:41
  solar system, and we get more meteors.
• 38:43
  That's when we get a meteor shower. But
• 38:45
  the other telltale thing for the meteor
• 38:47
  shower is all the dust grains that hit
• 38:49
  the earth in a meteor shower are moving
• 38:52
  essentially parallel to each other.
• 38:53
  They're all following the same orbit
• 38:54
  around the sun hitting the earth from
• 38:56
  the same direction at the same speed.
• 38:59
  So all this dust is coming towards you
• 39:01
  from a single point in space. So from
• 39:03
  your point of view looking at the sky
• 39:05
  when you see those meteors part of a
• 39:06
  meteor shower they appear to appear
• 39:09
  anywhere in the sky. But if you trace
• 39:12
  them back they'll all point to a single
• 39:13
  point in the sky. something we call the
• 39:15
  radiant and that's effectively the point
• 39:18
  in space they're traveling towards us
• 39:19
  from and they diverge because of
• 39:21
  perspective they're coming closer to you
• 39:23
  so every meteor shower has a radiant in
• 39:26
  the sky the April lids have their
• 39:28
  radiant in Lyra although for a fair part
• 39:31
  of their time it's actually in Hercules
• 39:32
  it drifts a bit the perids have their
• 39:35
  radiant in Perseus the Geminids in
• 39:37
  Gemini and so on
• 39:40
  >> so that's all well and good if the
• 39:42
  radiant is below the horizon horizon.
• 39:45
  That means the meteors are hitting the
• 39:46
  other side of the Earth and you can't
• 39:47
  see them because the Earth's in the way.
• 39:50
  So, first point with a meteor shower is
• 39:52
  unlike some of the media reports, you
• 39:55
  can't see meteors for that meteor shower
• 39:56
  at any time of night. You can only see
• 39:58
  them when the radiant's above the
• 39:59
  horizon. Point number one. Point the
• 40:03
  second is the higher in the sky that
• 40:05
  radiant is, the more head on into the
• 40:07
  stream you're going. So, the more
• 40:09
  meteors you'll see. Now, the analogy I
• 40:11
  I'd use here is if you imagine getting
• 40:13
  your hose pipe and having it on that
• 40:16
  shower mode, you know, where water's
• 40:17
  coming out from many holes all at once.
• 40:20
  If you hold that hose pipe vertically
• 40:22
  and turn the tap on, all the water from
• 40:24
  that hose pipe will hit a relatively
• 40:25
  small area of the ground.
• 40:27
  >> If you turn that hose pipe to 45°, that
• 40:30
  water will spread out over a larger
• 40:32
  surface area.
• 40:33
  >> Yep. Now, if you imagine the meteors,
• 40:35
  the dust in a meteor shower coming in
• 40:37
  towards the Earth, the more directly
• 40:40
  overhead your point that they're coming
• 40:42
  from is, the more meteors you'll get in
• 40:45
  a certain volume of the atmosphere. And
• 40:47
  the lower to the horizon that point is,
• 40:49
  the more you'll spread those same number
• 40:50
  of grains of dust out. So, the higher in
• 40:53
  the sky the radiant is, the more dust is
• 40:56
  hitting the part of the atmosphere you
• 40:58
  can see from your location. So, the more
• 40:59
  meteors you get. And what this means is
• 41:02
  the lower in the sky the radiant is the
• 41:04
  fewer meteors you see. And so you see
• 41:06
  the most meteors for a given meteor
• 41:08
  shower when the radiant is near what we
• 41:10
  call culmination where it's nearly
• 41:11
  highest in the sky.
• 41:13
  >> For the southern hemisphere when it's
• 41:14
  nearly due north for the northern
• 41:16
  hemisphere the radiant nearly due south.
• 41:19
  So all well and good. But what that
• 41:22
  means is that from different locations
• 41:24
  on the earth a given meteor shower will
• 41:26
  give you a different strength of
• 41:27
  display. The April lyids, their radiant
• 41:32
  is 34 degrees north of the equator. So
• 41:34
  that means if you lived 34 degrees north
• 41:37
  of the equator, at about 2:00 a.m. in
• 41:39
  the morning, the radiant would be
• 41:40
  overhead and you're in the best place on
• 41:42
  the planet to see the meteors. If you
• 41:44
  had perfect vision, perfectly dark sky,
• 41:47
  you'd see a number of meteors 15 to 20
• 41:50
  per hour for the Aprils. And that's
• 41:52
  called the zenithl hourly rate. That's
• 41:54
  the number of meters you'd see in
• 41:56
  perfect conditions with perfect eyesight
• 41:58
  with no light pollution if the radiant
• 42:00
  was overhead. The lower the radiant is
• 42:02
  in the sky, the more that number
• 42:03
  shrinks. So the ZHR is the theoretical
• 42:07
  maximum number you'd see. So good meteor
• 42:10
  shower, not a great one from the
• 42:12
  northern hemisphere, but for us in
• 42:13
  Brisbane, let's say 26° south, the
• 42:17
  radiant of the April Lyids at its
• 42:19
  highest in the sky is only 30° above the
• 42:21
  horizon. That means that the volume of
• 42:24
  space where the dust is arriving is
• 42:26
  doubled. So you'd only see half the
• 42:28
  number of meteors.
• 42:30
  >> So instead of 20 per hour, you're down
• 42:32
  to 10 an hour immediately before
• 42:35
  anything else kicks in. And the further
• 42:37
  south you go, the lower the rates are.
• 42:39
  But the problem is the journalist
• 42:41
  covering this will pick up on a northern
• 42:42
  hemisphere article and just repeat it.
• 42:45
  There's this meteor shower happening.
• 42:46
  You can see them all night every night.
• 42:48
  Well, that's not right. If the radiant's
• 42:50
  below the horizon, you can't see them.
• 42:51
  and you'll see 100 per hour and that's
• 42:53
  because they've seen the zenithal rate
• 42:55
  quoted as 100 per hour and they just use
• 42:58
  it as a number.
• 42:59
  >> Yeah.
• 42:59
  >> Unless you are incredibly incredibly
• 43:01
  fortunate, you will never see the same
• 43:04
  number of meteors as the ZHR predicts
• 43:07
  because the radiant won't be directly
• 43:09
  overhead. So the rate gets lower. Your
• 43:12
  eyes are not perfect unless you're one
• 43:13
  of the very rare observers. The rates
• 43:15
  will get lower.
• 43:17
  >> There might be light pollution. The
• 43:18
  phentto meteors are not seen. the rates
• 43:21
  get lower. The moon might be in the sky.
• 43:23
  The faint meters are not seen. The rates
• 43:24
  are lower. So you will never see a
• 43:28
  number of meters in the sky equal to the
• 43:29
  ZHR unless the meteor shower is more
• 43:32
  active than predicted in which case the
• 43:34
  ZHR will be higher and you'd see more.
• 43:37
  Where this really comes in is for meteor
• 43:39
  showers like the perids. The perids are
• 43:41
  one of the big three. There are three
• 43:43
  awesome meteor showers a year that are
• 43:45
  by far the best in a given year. They're
• 43:48
  the highest rate. So most dust coming in
• 43:51
  or the highest speed. The quadrantids in
• 43:53
  early January
• 43:55
  are very very shortlived. They're a wage
• 43:57
  shower. You've got a very low rate of
• 43:58
  meteors for most of the time they're
• 43:59
  active and then a very narrow spike that
• 44:01
  can be very big. But if you manage to
• 44:04
  see that spike, there's a lot of
• 44:05
  meteors. They're only really visible
• 44:07
  from the northern hemisphere. The perids
• 44:10
  in August are probably the most storied
• 44:12
  meteor shower with long history of
• 44:16
  observations
• 44:17
  linked to comet Swift Tuttle which goes
• 44:19
  around every 120 130 years incidentally
• 44:22
  will be incredibly spectacular in the
• 44:24
  year 2126 if people hang around to see
• 44:26
  it.
• 44:26
  >> Yeah. Okay. I'll I'll write that in my
• 44:28
  diary.
• 44:29
  >> Um Percids are brilliant but their
• 44:31
  radiant is at about 55° north in the
• 44:34
  sky.
• 44:36
  Fabulous from Northern Europe, fabulous
• 44:37
  from North America, places north of the
• 44:39
  equator to get a really good show. But
• 44:41
  we get articles every year on commercial
• 44:44
  media here in Australia saying the
• 44:45
  persons are happening. Go out tonight
• 44:47
  and you'll see 100 meters an hour. And
• 44:49
  for most of Australia, the radiant never
• 44:51
  even rises. Never. You know, south of
• 44:54
  about 35° south, the radiant will never
• 44:56
  rise. I think that's about the latitude
• 44:58
  of Sydney.
• 44:59
  >> North of that, it will rise, but it'll
• 45:01
  be very low to the horizon. And so
• 45:02
  you'll see a much lower rate unless
• 45:04
  you're in the top top end. If you're in
• 45:06
  the top end of Australia, it's a bit
• 45:07
  different. And so when you see articles
• 45:10
  like this, you need to engage your
• 45:12
  science brain and say the journal is
• 45:14
  wrong.
• 45:15
  >> Yeah.
• 45:15
  >> Where's my location? What's the radiance
• 45:19
  declination, which is latitude in the
• 45:21
  sky effectively? Figure out how high in
• 45:23
  the sky it'll get, and that will give
• 45:24
  you a feel for what you might actually
• 45:26
  see. Now, if you want to um look at the
• 45:29
  meteor shower calendar and figure out
• 45:31
  when there are good ones happening, the
• 45:32
  International Meteor organization is my
• 45:35
  go-to on this. They're a fabulous
• 45:37
  organization that put together every
• 45:38
  year a calendar. And that calendar lists
• 45:41
  all the meteor showers from the
• 45:42
  incredibly minor ones that give one
• 45:43
  meteor every two hours, you know, to the
• 45:46
  major ones. And every year it writes
• 45:48
  about the conditions in terms of
• 45:50
  moonlight as well. Because if the moon
• 45:52
  is bright, you will see far fewer
• 45:55
  meteors. And coming up in a couple of
• 45:57
  weeks from when we're having this
• 45:59
  discussion, but in the past as we
• 46:01
  actually go live to air, you've got the
• 46:03
  peak of the Aquarids. Now the Aquarids
• 46:05
  are one of the few showers that's better
• 46:07
  for southern hemisphere than northern
• 46:08
  hemisphere. Fragments of comet Hali and
• 46:10
  they're at their peak around the 3rd to
• 46:13
  the 7th of May. Have quite a broad peak.
• 46:16
  But this year the moon is a waning
• 46:18
  gibbus. So at the time of night when you
• 46:21
  could see these meteors, the sky will be
• 46:22
  really bright and so far fewer will be
• 46:25
  visible than normal and you can get that
• 46:27
  from these calendars. But the highlight
• 46:29
  of every year for me showers is the
• 46:30
  Geminids in December and they are pretty
• 46:34
  much global as a phenomenon and they're
• 46:36
  brilliant everywhere. Obviously better
• 46:38
  for the northern hemisphere than the
• 46:39
  south. That's like a recurring theme,
• 46:42
  but they are great every year and this
• 46:45
  year moon will be effectively new. So,
• 46:48
  if you want to go see the Geminids
• 46:49
  peaking on the 14th or 15th of December,
• 46:51
  they're the highlight this year and
• 46:53
  pretty much every year.
• 46:54
  >> Okay. Uh, we're going to take another
• 46:56
  breath and then we'll come back and wrap
• 46:58
  it all up in this episode of Space Nuts
• 47:00
  with Andrew Dunley and Jonty Horner.
• 47:05
  >> Swift
• 47:07
  base here. The angle has landed.
• 47:09
  >> Space Nuts. One of my big frustrations
• 47:13
  uh when I want to observe comets is I
• 47:16
  live on a very flat area of the planet.
• 47:19
  Uh we don't have mountains nearby. We
• 47:22
  barely have hills and a lot of the
• 47:24
  comets are visible in the low horizon
• 47:29
  just after sunset or thereabouts. And
• 47:33
  they're short-lived and they're they're
• 47:35
  below the horizon way too quick. uh
• 47:38
  which makes astrophotography a real pain
• 47:40
  in the butt for me. But it is just a a
• 47:44
  quirk of where I live. Um I believe the
• 47:49
  that we do have some pretty spectacular
• 47:51
  ones coming up. I I the one that I've
• 47:54
  seen in my life that was the most
• 47:56
  spectacular for me was in 2007, January
• 48:00
  2007.
• 48:01
  Uh the it was Comet McNort. It was
• 48:05
  amazing. like naked eye comet wise it
• 48:08
  was unmissable. Uh it dominated the sky
• 48:12
  for quite some time. Uh we don't see
• 48:14
  many like that though do we? We don't.
• 48:17
  Now comet McNaugh was probably the
• 48:18
  brightest comet since the 1960s and it
• 48:21
  was truly a great comet. Now when we
• 48:24
  talk about the brightest comets and the
• 48:26
  ones people want to see great comet is
• 48:29
  the Appalachian people attached to
• 48:30
  comets and it's got a woollyish
• 48:32
  definition. It's basically the comet was
• 48:34
  bright enough and spectacular enough
• 48:36
  that even people who weren't that
• 48:37
  interested could just step outside and
• 48:39
  see it. Comet McNot's definitely like
• 48:40
  that. Arguably Comet Chuchchin Chan
• 48:43
  Atlas in 2024 and Comet Atlas in early
• 48:46
  2025 just made that threshold. So if you
• 48:50
  saw those comets, you'd probably say
• 48:51
  they are right at the lower end of what
• 48:54
  we consider a great comet. M
• 48:56
  >> on average if you go back through
• 48:58
  historical comic records you'd probably
• 49:00
  get about 10 great comics per century
• 49:02
  with very wide variance and that's not
• 49:05
  one every 10 years though like buses you
• 49:07
  wait 30 years and two come along at once
• 49:09
  and you saw that back in 1996 with comet
• 49:12
  Hailbop and comet H high kitaki which
• 49:14
  were visible in the sky at the same time
• 49:16
  as great comets.
• 49:18
  >> It's really hard to predict when they're
• 49:19
  going to come in but we've seen some
• 49:21
  really fascinating advances in the last
• 49:23
  few years on two fronts. Firstly, our
• 49:26
  ability to find things early has
• 49:28
  improved. We've got better telescopes,
• 49:31
  more automated surveys, and comet maps
• 49:34
  earlier this year, which turned out to
• 49:35
  be a bit of a disappointment for many
• 49:36
  people, is a really good example of
• 49:38
  that. That's a member of the CO
• 49:39
  sungrazing family. And the CO sungrazers
• 49:42
  have numbered many of the brightest
• 49:44
  great comets of the last couple of
• 49:46
  thousand years. Comet maps was the
• 49:49
  earliest we've ever found a crot
• 49:50
  sungrazer on the way in earlier even
• 49:53
  than comedy kayeki which was probably
• 49:56
  the brightest comet in the 20th century
• 49:58
  back in the late 1960s and so people's
• 50:00
  hopes were high but in reality it was
• 50:02
  quite a small fragment of the crot's
• 50:04
  parents sunraer these crots comets are
• 50:07
  all fragments of a bigger comet in the
• 50:08
  past and it just fell apart on its way
• 50:10
  in nothing to see here but our ability
• 50:14
  to find things earlier means that we get
• 50:17
  more warning
• 50:18
  when a bright comet's coming. Now,
• 50:19
  that's not absolutely guaranteed. We had
• 50:21
  a comet and the name of it slipped my
• 50:23
  mind um comet 12 18 months ago. Um no, I
• 50:27
  think it was like last September that
• 50:31
  was discovered when it was almost naked
• 50:33
  eye visibility. It just about became
• 50:35
  naked eye visible. Wasn't great by any
• 50:37
  means.
• 50:38
  >> Swan,
• 50:38
  >> but we got no warning. That's it. Comet
• 50:40
  swan. And the reason that that was found
• 50:42
  so late was it came at us from behind
• 50:44
  the sun and suddenly popped into view.
• 50:46
  So that does still happen. But with
• 50:49
  facilities like Vera Rubin coming
• 50:50
  online, we're going to find comets
• 50:52
  earlier and earlier, which means we get
• 50:54
  more prior warning, but it also means
• 50:56
  that the uncertainty about how bright
• 50:58
  they're going to get is possibly even
• 50:59
  higher cuz we're almost finding them now
• 51:02
  before they've really started to become
• 51:03
  active while they're far enough from the
• 51:05
  sun that we're almost seeing a bare
• 51:06
  nucleus or we're seeing a much smaller
• 51:09
  comet that's have a little bit of an
• 51:10
  outburst at that distance. And whether
• 51:12
  that far away, we effectively can't tell
• 51:14
  the difference. they're still like a
• 51:16
  single pixel. There's a really good
• 51:18
  example of this in the form of comet
• 51:20
  Chuch Chin Chan. Um, not comet Chuchchan
• 51:22
  Atlas from a couple of years ago, but
• 51:24
  comet Chuch Chin Chan that has just been
• 51:25
  discovered in the last couple of months.
• 51:27
  Comet C/2026C1.
• 51:30
  As we record this, that comet is still
• 51:32
  more distant from the sun than the orbit
• 51:34
  of Saturn.
• 51:36
  >> It was found a couple of months ago. It
• 51:38
  will not be at its closest to some
• 51:39
  perihelion until November 2028. So,
• 51:42
  we've got two and a half years to wait.
• 51:45
  Now, what factors into a comet's
• 51:47
  brightness is very complicated. Um, but
• 51:49
  it can boil down to a few different
• 51:51
  things. Firstly, if everything else is
• 51:53
  equal. So, imagine we only change one
• 51:55
  thing. Typically, the bigger the nucleus
• 51:58
  of the comet, the bigger its surface
• 52:00
  area is, so the more dust and gas it can
• 52:03
  produce. And we see the comet from the
• 52:05
  light that is reflected from the dust
• 52:06
  and gas. That's what makes the tails in
• 52:08
  the coma. The snowballs at the head are
• 52:10
  actually pretty small. Comet McNaugh was
• 52:12
  only about 5 km across for the nucleus,
• 52:14
  but it grew tails more than 300 million
• 52:17
  km long.
• 52:18
  >> Yeah, that's different. Incredible.
• 52:21
  >> So, if you have two comet nuclei that
• 52:23
  are in all senses identical other than
• 52:25
  their size, the bigger one will
• 52:27
  typically be more active and produce
• 52:29
  more gas and dust. However, some comets
• 52:32
  have a larger fraction of their surface
• 52:34
  active than others. Some comets are
• 52:36
  almost dormant because they're clogged
• 52:38
  up and there's very little activity even
• 52:39
  from a larger nucleus. So already a bit
• 52:42
  complex, but first rule of thumb, the
• 52:44
  bigger the nucleus, the more likelihood
• 52:46
  there is that it will be able to produce
• 52:47
  a lot of gas and dust and be more
• 52:48
  spectacular. With comet Chuch Chen Shan,
• 52:51
  that's interesting. We found it so far
• 52:53
  away, which suggests it is either a
• 52:55
  comet with quite a large nucleus because
• 52:57
  it's probably not that active at that
• 52:59
  distance, but it may have just had a bit
• 53:01
  of an outburst of activity driven by
• 53:04
  something like carbon monoxide, which
• 53:06
  can turn from solid to gas at a very low
• 53:08
  temperature. So, it might be
• 53:09
  masquerading as a bigger comet than it
• 53:11
  is, and we don't know.
• 53:13
  >> Okay.
• 53:13
  >> The next thing that factors into how
• 53:15
  bright a comet gets is how close it gets
• 53:16
  to the sun. So the closer it gets to the
• 53:18
  sun,
• 53:19
  >> the hotter its surface gets and the more
• 53:21
  strongly it will be active. So with
• 53:23
  comet McNaut, you had a 5 km nucleus
• 53:26
  which is fairly respectable but not as
• 53:28
  big as Hailbot which was 50 km. Hailbot
• 53:31
  was ridiculous. But comet McNaut got
• 53:33
  very close into the sun. So it got
• 53:35
  really incredibly intensely active was
• 53:38
  throwing off huge amounts of gas and
• 53:39
  dust. So that contributed again to more
• 53:42
  stuff to reflect sunlight and also being
• 53:44
  nearer to the sun, the intensity of
• 53:46
  light reflecting off it's higher as
• 53:47
  well. So kind of get a double whammy
• 53:49
  there. The other factor is how close
• 53:51
  they get to the earth. So if you have
• 53:53
  two comets that are the same size and
• 53:55
  the same distance from the sun and one
• 53:57
  is closer to the earth than the other,
• 53:59
  the one closer to the earth will be
• 54:00
  brighter, but will also potentially be
• 54:01
  more spread out and more diffuse in the
• 54:03
  sky. So that brightness might be spread
• 54:05
  over a different area.
• 54:07
  You've then got subtleties of how dusty
• 54:09
  or gassy they are. Some comets like
• 54:12
  comet Pan Stars seem to be more gassy.
• 54:15
  Some comets like Chuch Chin Chan Atlas
• 54:16
  was more dusty and that can have an
• 54:18
  impact on how they brighten. Bringing
• 54:20
  all this back together though for comet
• 54:21
  Chuch Chin Chan. At its closest to the
• 54:24
  Sun, it will be a little bit further
• 54:26
  from the Sun than the Earth is. So, it's
• 54:28
  not like comet McNaugh that's going to
• 54:29
  get really close in. But 1 AU from the
• 54:32
  Sun's fairly respectable. it can still
• 54:33
  maintain a fairly decent level of
• 54:35
  activity at that distance. Comet hellbop
• 54:37
  didn't get much closer than that and was
• 54:38
  fantastic.
• 54:40
  So that's in its favor. It's going to
• 54:41
  get close enough in that you could get a
• 54:43
  decent level of activity.
• 54:46
  Also, because it's only going to get
• 54:48
  that close to the sun, it'll take a bit
• 54:50
  longer to pass through the inner solar
• 54:51
  system. Comets that get really close to
• 54:53
  the sun get traveling incredibly quickly
• 54:55
  at that point. So they tend to whip in
• 54:57
  and whip out fairly quickly. Whereas
• 54:58
  with cometry chinchan, it's going to
• 55:00
  hang around for a fair while. It is
• 55:03
  potentially quite a large cometry
• 55:05
  nucleus, but we don't know yet. This is
• 55:07
  the the caution I give. If it turns out
• 55:10
  that we've caught it during an outburst,
• 55:11
  it may be a bit of a disappointment. If
• 55:13
  we've actually seen it as a bare
• 55:14
  nucleus, that orers very very very well.
• 55:18
  What this all suggests is that comet
• 55:20
  chaan has the potential to be bright in
• 55:23
  late 2028. Depending on which fit to its
• 55:26
  current brightness you use, it could
• 55:28
  become barely naked eye visible, which
• 55:30
  is still pretty good. You know, we see
• 55:33
  20 or 30 comets a year and very only
• 55:36
  maybe one will get to naked eye
• 55:37
  visibility. Or it could get as bright as
• 55:39
  the brightest stars. And if it gets as
• 55:40
  bright as the brightest stars, then it
• 55:43
  gets into great comet type territory.
• 55:45
  That's a factor of a 100 difference in
• 55:47
  brightness between those two extremes.
• 55:50
  And it could get brighter than the
• 55:51
  brightest extreme there or fainter than
• 55:52
  the faintest extreme. We just don't know
• 55:55
  yet. But having found it so early or as
• 55:57
  well, but typically predicting the next
• 56:00
  great comet is a fool's bargain until
• 56:02
  it's discovered. What we can say is that
• 56:04
  there are a few periodic comets that
• 56:07
  will be great in the future. Comet
• 56:09
  Halley will be a lot better in 2061 than
• 56:12
  it was in 1986. In 1986, we had the
• 56:15
  worst operation of comet Hali for 2,000
• 56:16
  years.
• 56:17
  >> Tell me about it.
• 56:18
  >> Yeah. Bit disappointing. 2061 will be
• 56:21
  better.
• 56:22
  >> Oh, good. Well, I don't know if I'll be
• 56:24
  around by then, but um probably not.
• 56:27
  I'll be 99.
• 56:29
  >> Make everybody feel really cheerful.
• 56:31
  It's now closer to Comet Hall's next
• 56:32
  apparition than the last one. It turned
• 56:34
  around, I think, last year. So, it's on
• 56:35
  its way back. Yeah.
• 56:36
  >> Comet Halley will be even better in
• 56:38
  2135.
• 56:40
  Will be really good that year. And that
• 56:42
  will be the best apparition for a couple
• 56:43
  of hundred years. Comet Swift Tuttle
• 56:45
  will be incredible in 2126. We know that
• 56:48
  cuz we know pretty much exactly when
• 56:49
  it'll come back. We know where it will
• 56:50
  be compared to the Earth and the Sun.
• 56:52
  There is a suggestion that in 2097 we
• 56:55
  may have the comet of the century or
• 56:57
  close to it. This is research that came
• 56:58
  out last year. One of the greatest
• 57:01
  comets of the last thousand years was
• 57:03
  comet dishes in 1744. Also called comet
• 57:07
  Clinkenberg. Comet that is famous for
• 57:09
  having had six tails. Incredibly bright
• 57:12
  almost visible in broad daylight. A
• 57:15
  couple of astronomers, I think the lead
• 57:16
  researcher on this was Mike Meyer,
• 57:19
  published a paper last year that went
• 57:20
  back through historical observations and
• 57:23
  found a number of previous comets over
• 57:25
  the last 2,000 years that were all
• 57:27
  incredibly bright, really spectacular,
• 57:29
  but seem to have been moving the same as
• 57:31
  that comet, linked them together, and
• 57:33
  it's a very compelling tale that if
• 57:35
  their research is correct, that comet
• 57:38
  actually has an orbital period of just a
• 57:40
  little bit less, just around 450 years,
• 57:43
  I think 400 years. No, 350 years,
• 57:45
  wouldn't it? Do the mental arithmetic.
• 57:47
  Yeah, about 350 years, which means it
• 57:50
  should return in 2097.
• 57:53
  And if it does, it will be awesome. Um,
• 57:56
  sadly, I don't think you or I will be
• 57:58
  around for that.
• 57:59
  >> Probably not.
• 58:00
  >> Probably not. But things like that we
• 58:01
  can predict. But most
• 58:02
  >> Fred will be, but
• 58:04
  >> absolutely. Fred is indestructible, and
• 58:06
  I'll stand by that. But most of the big
• 58:09
  cometry nuclei coming through are on
• 58:11
  such long period orbits with the
• 58:13
  exception of Halley and Swift Tuttle
• 58:15
  that their apparitions are so infrequent
• 58:17
  that we've not identified them as
• 58:18
  periodic visitors and many of them have
• 58:20
  periods of thousands or tens of
• 58:22
  thousands of years. So we typically only
• 58:24
  find them on their way in a few weeks or
• 58:27
  a few months before apparition in case
• 58:30
  of comet hellopet was 2 years which was
• 58:32
  exceptional at the time. KZ of comet
• 58:34
  Chuchin Shan it's more than two and a
• 58:36
  half years away but our technology has
• 58:39
  improved hugely so I don't think it's
• 58:41
  fair necessarily to say that Chuchin
• 58:43
  Shan will be another hail bop
• 58:45
  >> but if you look at the brighter end of
• 58:47
  the predictions it could be naked eye
• 58:48
  visible for 3 four 5 months
• 58:50
  >> wow
• 58:51
  >> which would be awesome and it would
• 58:52
  potentially be circumpolar for us in the
• 58:54
  southern hemisphere because at its
• 58:56
  closest to the sun of the earth it's
• 58:57
  going to be way south not going to be
• 58:59
  good for the northern hemisphere but we
• 59:01
  can't really predict that it's the same
• 59:03
  with meteor showers, we can predict the
• 59:05
  annual ones roughly how good they're
• 59:06
  going to be.
• 59:07
  >> Y
• 59:08
  >> and if you go back to when I was a kid,
• 59:10
  we couldn't really predict meteor
• 59:12
  storms, meteor outbursts, and that's one
• 59:13
  of the things people really love to see.
• 59:15
  So Geminids are great. Northern
• 59:17
  hemisphere, you'll see maybe even 80 or
• 59:19
  100 an hour at their peak in the early
• 59:20
  hours of the morning. I've seen 50 an
• 59:22
  hour from our latitude near Brisbane.
• 59:25
  They're really good. But what people
• 59:27
  really want to see are meteor storms,
• 59:28
  and they're much rarer. There's a few
• 59:31
  amazing ones historically. There was the
• 59:33
  one in 1833 that was linked to the
• 59:36
  Leonid meteor shower that had a rate in
• 59:39
  excess of 100,000 an hour was best seen
• 59:43
  from the contiguous US and it was bright
• 59:47
  enough there were sufficient meteors in
• 59:49
  the sky that miners in the US were woken
• 59:52
  from their campsites by the light
• 59:54
  shining through their tents and people
• 59:56
  were convinced that the end times had
• 59:58
  come the apocalypse was here because he
• 1:00:00
  were getting as many as 20 meteors per
• 1:00:02
  second.
• 1:00:03
  >> Incredible.
• 1:00:04
  >> Um, now that in the way that kind of
• 1:00:06
  Taiko's observations in 1577 were
• 1:00:09
  probably the birth of modern cometry
• 1:00:11
  astronomy, 1833, I think, was possibly
• 1:00:14
  the birth of modern meteor astronomy
• 1:00:16
  because there had been a storm from the
• 1:00:17
  lineage in 1799. People predicted that
• 1:00:20
  there might be another one in 1866
• 1:00:23
  because maybe this was happening every
• 1:00:24
  33 years when the comet came back and
• 1:00:26
  indeed that happened in 1866.
• 1:00:29
  And so that was a bit like the birth of
• 1:00:32
  modern meteor science. And after that,
• 1:00:34
  people said, "Well, there'll be one in
• 1:00:35
  1899." And there wasn't. So that then
• 1:00:38
  tricked people up. So thanks to that,
• 1:00:41
  we've gradually developed a better
• 1:00:42
  understanding of the physics of how
• 1:00:44
  meteor showers work. And I'm aware time
• 1:00:46
  is running away from us. But it for
• 1:00:48
  people interested in this, in the run-up
• 1:00:50
  to the Leonid heavy leanid activity in
• 1:00:53
  1999 through to 2002, there was some
• 1:00:56
  amazing research done by um David Asher
• 1:01:00
  from Amar Observatory and I think fondly
• 1:01:02
  on David because he was a lovely mentor
• 1:01:04
  to me when I visited Amar in 1999. very
• 1:01:07
  quiet guy but incredibly talented
• 1:01:09
  scientist and he did this remarkable
• 1:01:12
  work making predictions of when we would
• 1:01:15
  and wouldn't get Leonid storms by
• 1:01:17
  modeling the ejection of dust from the
• 1:01:20
  cometry nucleus and evolving the dust
• 1:01:22
  forward in time and go back way earlier
• 1:01:24
  on I mentioned these javelin sh spikes
• 1:01:27
  he event he effectively modeled those
• 1:01:29
  and figured out where the spikes will be
• 1:01:31
  and a slight nudge up or down means that
• 1:01:32
  the earth will run through the spike or
• 1:01:34
  not and the great lean zones are
• 1:01:36
  produced by dust left behind just one or
• 1:01:38
  two revolutions ago. So the activity
• 1:01:41
  between 1999 and 2002 resulted from a
• 1:01:45
  few different streams. The older they
• 1:01:47
  are, the more diffuse they get. But now
• 1:01:49
  we have the ability for comets we know
• 1:01:51
  well and meteor showers we know well to
• 1:01:54
  figure out where those spikes are
• 1:01:55
  roughly going to be, how long they are,
• 1:01:57
  and make predictions going forward. Now,
• 1:02:00
  there aren't any great meteor storms
• 1:02:02
  predicted in the relatively near future.
• 1:02:03
  The Leonids are not likely to give major
• 1:02:05
  storms in 2033 or 2066, but will give
• 1:02:09
  increased activity. The reason for that
• 1:02:11
  is Jupiter and Saturn are pulling those
• 1:02:13
  javelins around and making them miss the
• 1:02:16
  Earth. The leanings will probably return
• 1:02:18
  in force in I think 2097 with a
• 1:02:21
  possibility of a storm of like 20,000 an
• 1:02:23
  hour. But we're getting to understand
• 1:02:26
  that. So with meteor showers, we can
• 1:02:28
  predict the annual showers. They're very
• 1:02:30
  reliable. They gradually get better and
• 1:02:32
  worse with time as the streams move
• 1:02:34
  around and we insect more of the
• 1:02:35
  material or less, but they're pretty
• 1:02:38
  reliable.
• 1:02:39
  Outbursts are harder to predict, but
• 1:02:41
  we're getting better at doing it. But
• 1:02:44
  predicting an outburst from a shower
• 1:02:46
  we've never seen before or a shower
• 1:02:48
  that's incredibly rare, we typically
• 1:02:50
  can't do until it happens because we
• 1:02:53
  need to have a feel for what it's done
• 1:02:55
  in the past. So, we occasionally will
• 1:02:57
  get an outburst of a meteor shower we've
• 1:02:58
  never seen before. and you can't predict
• 1:03:01
  that. And that's when it's really
• 1:03:02
  exciting because then you can start to
• 1:03:04
  learn about a new meteor shower being
• 1:03:06
  born. You can learn about the comet that
• 1:03:08
  birthed it. Put all that together. And
• 1:03:10
  that's one of the things where I'll go
• 1:03:12
  out and I love my meteor showers. I'll
• 1:03:13
  sit out under the sky and watch them.
• 1:03:15
  But I would love to just be outside when
• 1:03:16
  there's an unexpected outburst when we
• 1:03:18
  see something new like a meteor shower
• 1:03:20
  being born for the first time. Just
• 1:03:22
  >> and and and that's what we recommend to
• 1:03:24
  all our space listeners. uh get up at
• 1:03:26
  2:00 every morning every day and go out
• 1:03:30
  and just wait. And you know, one day
• 1:03:32
  you'll get lucky. Might take 20 years,
• 1:03:34
  but
• 1:03:34
  >> doesn't have to be 2 a.m. I mean, there
• 1:03:36
  is a little bit of a preference for
• 1:03:38
  meteor showers to be more active in the
• 1:03:41
  morning hours and the evening hours, but
• 1:03:43
  that's purely a geometry thing. Yeah,
• 1:03:45
  >> it's linked a little bit to the
• 1:03:46
  direction of the Earth's motion and the
• 1:03:47
  direction things are crossing the
• 1:03:48
  Earth's orbit in that if you think about
• 1:03:51
  something crossing the Earth's orbit at
• 1:03:52
  right angles to the Earth because the
• 1:03:55
  Earth's moving forward at 30 km a
• 1:03:57
  second, the direction you would see that
• 1:03:59
  coming from is actually a bit ahead of
• 1:04:00
  you because you've got the addition of
• 1:04:01
  the speed the debris is going and the
• 1:04:03
  speed the Earth's moving. M so meteor
• 1:04:06
  showers
• 1:04:08
  that are visible with radiance that will
• 1:04:10
  be in the morning sky. You've got a
• 1:04:12
  little bit of an additive effect between
• 1:04:14
  the speed the debris is going and the
• 1:04:15
  speed the earth's moving which means the
• 1:04:17
  average impact speed of the debris is
• 1:04:19
  higher and you get more meteors. But
• 1:04:21
  also you get this effect of the earth's
• 1:04:23
  motion being a bit like you're driving
• 1:04:24
  into a snowstorm. You know if you're
• 1:04:26
  driving into a snowstorm where there's
• 1:04:28
  no wind and the snowflakes are falling
• 1:04:30
  down vertically you will perceive them
• 1:04:32
  as coming from in front of your car not
• 1:04:33
  overhead. And so there's a preference
• 1:04:36
  for meteor showers to be slightly more
• 1:04:37
  likely to have activity that peaks in
• 1:04:39
  the morning hours and the evening, but
• 1:04:41
  that's not a guarantee. There are some
• 1:04:43
  meteor showers that are at the highest
• 1:04:45
  where the radiant culminates in the
• 1:04:46
  evening sky. It just depends. Some like
• 1:04:50
  the Aquarids are only visible for a
• 1:04:51
  couple of hours before dawn. There's
• 1:04:53
  even a few meteor showers that are
• 1:04:54
  daylight showers where the radiance's
• 1:04:56
  only really above the horizon during the
• 1:04:58
  hours of daylight. And we know about
• 1:04:59
  them primarily from radio observations.
• 1:05:01
  Radar pe well not radar people listening
• 1:05:04
  to radio reflecting off the ionized
• 1:05:06
  streaks that the meteors leave in the
• 1:05:09
  ionosphere that allows you to see over
• 1:05:11
  the horizon to radio stations that are
• 1:05:13
  broadcasting that you don't normally
• 1:05:14
  get. So you can hear meteor showers.
• 1:05:16
  >> Yeah.
• 1:05:17
  >> So we know there are daytime showers
• 1:05:18
  that we cannot see at night and some of
• 1:05:20
  them are possibly as active as the
• 1:05:22
  Geminis of the Percids. If you know if
• 1:05:24
  we could turn the sun off I mean that
• 1:05:26
  would be a bad thing. Please don't do
• 1:05:28
  it. If you're a super villain listening,
• 1:05:29
  do not take this as an idea. But if we
• 1:05:32
  could turn the sun off and see, there
• 1:05:34
  are a couple of meteor showers in the
• 1:05:35
  daytime that could be pretty
• 1:05:36
  spectacular.
• 1:05:38
  It is all very fascinating. And I
• 1:05:41
  suppose the best advice would be to uh
• 1:05:43
  go and look for the the better sources
• 1:05:46
  of forecasting rather than trying to
• 1:05:48
  figure it out for yourself. And uh and
• 1:05:50
  you've mentioned a couple of them
• 1:05:51
  already, uh comet maps and what was the
• 1:05:54
  other one about meteors? For meteors, I
• 1:05:56
  really strongly recommend the
• 1:05:58
  International Meteor Organization. If
• 1:06:00
  you go to their website, hover over the
• 1:06:02
  resources link, click on it to get the
• 1:06:04
  drop down. Click on meteor shower
• 1:06:06
  calendar. They have on the right hand
• 1:06:07
  side the best showers of the year with
• 1:06:10
  information and what the moon will be
• 1:06:12
  like. But there's also on the left side
• 1:06:13
  a PDF that you can download that goes
• 1:06:16
  into much more minute detail and talks
• 1:06:17
  about even the more minor showers. And
• 1:06:20
  that's a very good point of truth for
• 1:06:21
  meteor showers. Well, I I kind of
• 1:06:24
  describe them being like three tiers of
• 1:06:25
  meteor showers, ignoring the outbursts.
• 1:06:28
  There are the big three, which are the
• 1:06:29
  quadrantids, the perids, and the
• 1:06:31
  geminids, which are even if you're not
• 1:06:33
  that interested at all in space. And if
• 1:06:36
  you are, thanks for listening to the
• 1:06:37
  podcast anyway, but it's not really our
• 1:06:39
  target audience. But even people who are
• 1:06:41
  not that interested, that's a spectacle
• 1:06:43
  you can go out and see with them and
• 1:06:44
  share with them. Just make sure that you
• 1:06:46
  figure out when the radiant rises from
• 1:06:48
  your location because you don't want to
• 1:06:49
  turn people off by looking at a time
• 1:06:51
  when you can't see meteors. So for the
• 1:06:53
  Geminids, the best time is around 2:00
• 1:06:55
  a.m. But depending on where you are in
• 1:06:57
  the world, from our latitude, you're
• 1:07:00
  looking at you can't see any before
• 1:07:02
  9:30, 10:00 at night. Obviously, if
• 1:07:04
  you're somewhere with daylight savings
• 1:07:05
  in the Southern Hemisphere, add an hour
• 1:07:07
  to that. So for you down in New South
• 1:07:09
  Wales where the clocks change, you're
• 1:07:11
  talking after 11:00 p.m. for you. But if
• 1:07:13
  you're in Northern Europe, the Geminid
• 1:07:15
  radiant never sets. So where I grew up
• 1:07:17
  in the UK, as soon as it got dark, I
• 1:07:18
  could see them. The rates still got
• 1:07:20
  better through the night. Similarly for
• 1:07:21
  the Percids in particular, Percids are a
• 1:07:24
  northern hemisphere only thing. It's
• 1:07:26
  light until quite late. Certainly for
• 1:07:28
  the high northern latitudes like the UK,
• 1:07:29
  but as soon as it gets dark, you can see
• 1:07:31
  them. So they're the showers that are
• 1:07:33
  well worth going out to look at as a
• 1:07:35
  beginner. And you just sit out there. I
• 1:07:38
  would figure out where the radiant is
• 1:07:39
  and look 30 or 40 degrees to the left or
• 1:07:41
  right of it to get the best balance
• 1:07:43
  between a lot of meteors but decent ones
• 1:07:45
  to see and just get a comfy chair, lie
• 1:07:48
  back, wrap up warm with the people you
• 1:07:51
  love and tell stories and relax and
• 1:07:53
  occasionally you'll see something good
• 1:07:54
  and it's quite addictive. You think, you
• 1:07:55
  know, I'll go to bed but I just want to
• 1:07:57
  see one more and then well that was
• 1:07:59
  rubbish so I want to see another one
• 1:08:00
  that's actually good. You've then got
• 1:08:02
  like the mid-tier showers which can be
• 1:08:05
  decent but you need to be a bit more
• 1:08:06
  dedicated for. These are the ones where
• 1:08:08
  you might see 10 or 15 an hour instead
• 1:08:10
  of 50 an hour. And I wouldn't recommend
• 1:08:13
  people who are beginners go out and see
• 1:08:14
  them because it's there's not enough
• 1:08:16
  happening. And that's why I worry about
• 1:08:18
  coverage for the April liids even in the
• 1:08:21
  northern hemisphere because they're just
• 1:08:23
  not that good. If you're someone who's
• 1:08:25
  really keen, you'll enjoy them, but for
• 1:08:27
  most people they'll be a let down and
• 1:08:29
  you don't want to turn people off the
• 1:08:30
  subject. Then there are the minor
• 1:08:32
  showers that you frankly need to be very
• 1:08:34
  obsessive to follow. And I've seen
• 1:08:36
  stories of a lot of the science of this
• 1:08:38
  has been done by amateur astronomers and
• 1:08:41
  quite often by people who are quite
• 1:08:42
  obsessive about the topic. And I saw one
• 1:08:46
  guy who was in North America where it
• 1:08:48
  gets brutal, brutal cold in the winter,
• 1:08:51
  who built himself a an insulated coffin
• 1:08:54
  with an incredibly transparent glass lid
• 1:08:56
  that he would carry out with him that
• 1:08:58
  was big enough for him to have a
• 1:09:00
  notebook and write down the details of
• 1:09:01
  every meteor he saw. So he could lie out
• 1:09:03
  in minus40°
• 1:09:05
  and I think that's um units ambivalent.
• 1:09:08
  I think Fahrenheit and centigrade are
• 1:09:09
  very similar at that point. But he's in
• 1:09:11
  an insulated box that keeps him warm and
• 1:09:13
  he'd lie out all night recording 2
• 1:09:15
  meters 3 meters an hour.
• 1:09:17
  >> That isn't for me, but it is for people.
• 1:09:20
  But when you see a meteor shower with a
• 1:09:22
  ZHR of less than about 20, I'd probably
• 1:09:25
  leave that unless you're really keen. If
• 1:09:27
  it's got a ZHR of 50 plus, well worth
• 1:09:30
  looking out for. But look for when the
• 1:09:31
  time of maximum is. For most meteor
• 1:09:33
  showers, they've got what we call a full
• 1:09:35
  width half maximum of about 24 hours.
• 1:09:38
  What that means is that the rate only
• 1:09:41
  stays above half of the peak rate for
• 1:09:42
  about 24 hours. For 48 hours, then it
• 1:09:45
  would stay above a quarter of the rate
• 1:09:46
  and so on. For the quadrantids, it's
• 1:09:48
  full width at quarter maximum of about
• 1:09:50
  12 hours. So that means if you're 6
• 1:09:53
  hours away from the peak, the rate is
• 1:09:55
  already down to a quarter of that peak.
• 1:09:57
  It's a very sharp peak. And if you're
• 1:09:59
  looking at the wrong time, the show
• 1:10:00
  won't be as good as you'd like it to be,
• 1:10:02
  and you'll be disappointed.
• 1:10:05
  So much to consider, Jonty, but uh
• 1:10:06
  fascinating cockpits and meteors. Um
• 1:10:10
  there's so much to talk about and we
• 1:10:11
  probably didn't really cover absolutely
• 1:10:13
  everything, although we did uh we did
• 1:10:15
  hit on quite a fair bit of info. And of
• 1:10:18
  course, we do welcome questions and
• 1:10:20
  comments. So, please u go to our website
• 1:10:22
  and um click that little AMA button at
• 1:10:26
  the top and you can send us questions
• 1:10:27
  and comments uh in text and audio form.
• 1:10:30
  Don't forget to tell us who you are and
• 1:10:32
  where you're from. But we're going to
• 1:10:33
  wrap it up there. Jonty, thank you so
• 1:10:35
  much. We'll catch you on the next show.
• 1:10:37
  >> Thank you very much.
• 1:10:38
  >> Professor Jonty her, professor of
• 1:10:40
  astrophysics at the University of
• 1:10:43
  Southern Queensland, our special guest
• 1:10:46
  commentator, while Fred's uh on the
• 1:10:48
  other side of the planet looking at
• 1:10:49
  meteors. And uh just a special word for
• 1:10:53
  uh for Hugh in the studio. He's been a
• 1:10:55
  little unwell lately. Hugh, get well
• 1:10:58
  soon, mate. We're all thinking of you.
• 1:11:00
  And from me, Andrew Dunley, thanks for
• 1:11:01
  your company. We'll catch you on the
• 1:11:03
  next episode of Space Nuts.
• 1:11:05
  >> Space Nuts.
• 1:11:06
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• 1:11:08
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• 1:11:10
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• 1:11:16
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• 1:11:21
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