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Exoplanets: The Cosmic Neighbours We Never Knew In this special episode of Space Nuts, hosts Andrew Dunkley and Professor Jonti Horner delve into the fascinating world of exoplanets. With over 6,200 confirmed exoplanets and counting, the duo explores the diversity and complexity of these distant worlds, challenging our assumptions about planetary systems beyond our own.
Episode Highlights:
- The Birth of Exoplanet Discovery: Andrew and Jonty reflect on the first confirmed exoplanets in the early 1990s and how our understanding of planetary systems has evolved since then. From the initial excitement to the current reality of thousands of discoveries, they discuss the implications of these findings.
- Planetary Diversity: The hosts highlight the remarkable variety of exoplanets, including hot Jupiters, super-Earths, and even pulsar planets. They explore how these discoveries have shattered the notion that our solar system is typical, revealing a vast array of planetary types and characteristics.
- Methods of Discovery: Andrew and Jonty explain the different techniques used to find exoplanets, including the radial velocity and transit methods. They discuss the technological advancements that have made these discoveries possible and the role of amateur astronomers in the search for new worlds.
- Future Prospects: The conversation shifts to the future of exoplanet research, with a focus on upcoming missions like the Nancy Chris Roman Telescope and the Gaia satellite. The hosts speculate on the potential for discovering Earth-like planets and the ongoing quest to find life beyond our planet.
- Philosophical Implications: Andrew and Jonty ponder the profound questions surrounding the existence of life in the universe, considering the statistical likelihood of life on other planets given the vast number of stars and planets in the cosmos.
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- Introduction to Exoplanets
- The Evolution of Exoplanet Discovery
- The Diversity of Exoplanets
- Techniques for Discovering New Worlds
- The Future of Exoplanet Research
- Philosophical Implications of Life Beyond Earth
00:00:00 --> 00:00:00 Jonti Horner: Hi there.
00:00:00 --> 00:00:02 Andrew Dunkley: Thanks for joining us yet again. This is
00:00:02 --> 00:00:05 Space Nuts. My name is Andrew Dunkley. Great
00:00:05 --> 00:00:08 to have your company one more time. Well,
00:00:08 --> 00:00:09 hopefully it's more than one more time, but
00:00:09 --> 00:00:12 on this occasion, uh, now with Fred Watson
00:00:12 --> 00:00:15 away, uh, we are doing a series of
00:00:15 --> 00:00:17 little specials and today the focus
00:00:18 --> 00:00:20 will be on exoplanets.
00:00:20 --> 00:00:23 We've known about them since the early 90s
00:00:24 --> 00:00:26 and since then we have found
00:00:27 --> 00:00:30 thousands of them. But what is there to
00:00:30 --> 00:00:32 know? I mean, we've got our own planets.
00:00:32 --> 00:00:34 Surely that just means everything else around
00:00:34 --> 00:00:37 the galaxy is the same. That's
00:00:37 --> 00:00:40 probably not true. And we're going to talk
00:00:40 --> 00:00:42 about all of it today on this, uh, episode of
00:00:42 --> 00:00:45 space nuts. 15 seconds. Guidance is
00:00:45 --> 00:00:48 internal. 10, 9,
00:00:48 --> 00:00:50 ignition sequence.
00:00:50 --> 00:00:52 Jonti Horner: Star. Space nuts. 5, 4, 3, 2.
00:00:52 --> 00:00:55 Andrew Dunkley: 1. 2, 3, 4, 5, 5, 4, 3,
00:00:55 --> 00:00:58 2, 1. Space nuts. Astronauts report
00:00:58 --> 00:01:01 at and with us while
00:01:01 --> 00:01:04 Fred Watson is away is Jonty Horner,
00:01:04 --> 00:01:06 professor of astrophysics at the University
00:01:06 --> 00:01:08 of Southern Queensland. Hi, Jonty.
00:01:08 --> 00:01:09 Jonti Horner: Good afternoon. How are you going?
00:01:09 --> 00:01:11 Andrew Dunkley: I am quite well. And you?
00:01:11 --> 00:01:13 Jonti Horner: I can't complain. I'm enjoying us having a
00:01:13 --> 00:01:15 public holiday today, which is great. I mean,
00:01:15 --> 00:01:17 I'm still off anyway, so it doesn't really
00:01:17 --> 00:01:19 matter, but it means I'm taking one day's
00:01:19 --> 00:01:21 less of sick leave, I guess. Uh, well, it's
00:01:21 --> 00:01:21 all good.
00:01:22 --> 00:01:25 Andrew Dunkley: I'm retired, so public holidays mean nothing
00:01:25 --> 00:01:28 to me now. I
00:01:28 --> 00:01:30 used to so look forward to having a few days
00:01:30 --> 00:01:32 off or, you know, an extra long weekend if
00:01:32 --> 00:01:35 they combined the two in April because we
00:01:35 --> 00:01:37 get, uh, east sometimes, get Easter and Anzac
00:01:37 --> 00:01:40 Day in April. And if, um, you jam them
00:01:40 --> 00:01:43 together, you get a nice free holiday. But,
00:01:43 --> 00:01:45 uh, it doesn't mean squat to me anymore.
00:01:45 --> 00:01:47 Jonti Horner: I keep finding it bizarre. At least in
00:01:47 --> 00:01:49 Toowoomba. I'm sure this is reproduced
00:01:49 --> 00:01:51 everywhere. If the shop shut for one day, the
00:01:51 --> 00:01:54 day after is absolutely feral. So
00:01:54 --> 00:01:56 last week we had Anzac Day, which tells you
00:01:56 --> 00:01:58 how long ago these were recorded, by the way.
00:01:58 --> 00:02:01 Um, but yeah, last week we had Anzac Day. And
00:02:01 --> 00:02:03 obviously, Franz, act quite rightly, the
00:02:03 --> 00:02:04 shops, the supermarkets and everything are
00:02:04 --> 00:02:06 shut. It's one of the biggest holidays in
00:02:06 --> 00:02:09 Australia of the lot of them. But we, we tend
00:02:09 --> 00:02:11 to do our shopping on a Sunday anyway, so it
00:02:11 --> 00:02:13 didn't really matter. Went to the shops on
00:02:13 --> 00:02:14 the Sunday and it was almost people fighting
00:02:14 --> 00:02:16 in the aisles because heaven forfend that one
00:02:16 --> 00:02:18 day you don't, you know, you don't get food
00:02:18 --> 00:02:21 for one day and the shops start running empty
00:02:21 --> 00:02:24 of bread. And it's like people buy more when
00:02:24 --> 00:02:25 they've had one day without the Shops being
00:02:25 --> 00:02:27 open, very, very strange phenomenon.
00:02:28 --> 00:02:30 Andrew Dunkley: They panic by and there's no toilet paper on
00:02:30 --> 00:02:31 the shelves. Is also.
00:02:32 --> 00:02:34 Jonti Horner: Well, the best thing about that. That led us
00:02:34 --> 00:02:37 to subscribing to who Gives a Crap which
00:02:37 --> 00:02:40 panel started online.
00:02:40 --> 00:02:42 Um, and they've been brilliant. We've
00:02:42 --> 00:02:44 recommended them to everyone because it works
00:02:44 --> 00:02:45 out cheaper than getting it from the
00:02:45 --> 00:02:47 supermarket and they're better quality. I
00:02:47 --> 00:02:49 mean it's, it feels like very much a no, uh,
00:02:49 --> 00:02:51 brainer. And we'd never have come across them
00:02:51 --> 00:02:54 if it wasn't for Covid and the
00:02:54 --> 00:02:56 incredibly smart people of Toowoomba going,
00:02:56 --> 00:02:58 oh my God, Covid's happening. We're going to
00:02:58 --> 00:03:00 run out of toilet paper. Of all the things
00:03:00 --> 00:03:02 for the shop to run out of, happened
00:03:02 --> 00:03:05 everywhere. Why toilet paper? Uh,
00:03:05 --> 00:03:08 I mean Covid affect my
00:03:08 --> 00:03:11 memory was that Covid was a, was something
00:03:11 --> 00:03:12 that made things come out of your head, not
00:03:12 --> 00:03:14 things that came out anywhere else. It's not
00:03:14 --> 00:03:15 like there will be an expectation it would
00:03:15 --> 00:03:18 make you use more. No, bread was
00:03:18 --> 00:03:20 fine, eggs were fine, perishables were fine.
00:03:20 --> 00:03:23 But toilet paper, I don't understand.
00:03:24 --> 00:03:26 Andrew Dunkley: I never, I never got it either. But uh, uh,
00:03:26 --> 00:03:28 our shelves were devoid of the stuff.
00:03:29 --> 00:03:30 We better get down to business.
00:03:30 --> 00:03:33 We're talking exoplanets today.
00:03:33 --> 00:03:35 And I did a little bit of research. Uh, the
00:03:35 --> 00:03:38 first exoplanets were confirmed in
00:03:38 --> 00:03:41 1992. In fact, they suspected they existed
00:03:41 --> 00:03:43 before that, but they couldn't prove it. But
00:03:43 --> 00:03:45 1992, uh, they
00:03:45 --> 00:03:48 found two planets that were later named
00:03:48 --> 00:03:51 Poltergeist and um, Phobitor
00:03:52 --> 00:03:55 Phoebe. Uh, so they were
00:03:55 --> 00:03:58 officially the first two exoplanets. And then
00:03:58 --> 00:04:01 the first one that was
00:04:01 --> 00:04:03 orbiting a sun like star was found in
00:04:03 --> 00:04:05 1995. That was
00:04:06 --> 00:04:08 um, 51 Pegasi B.
00:04:08 --> 00:04:08 Jonti Horner: Yes.
00:04:09 --> 00:04:11 Andrew Dunkley: So, uh, those were the first few. And of
00:04:11 --> 00:04:14 course now we've reached a point where
00:04:14 --> 00:04:16 as at 30
00:04:17 --> 00:04:19 April 2026,
00:04:19 --> 00:04:22 6278 confirmed
00:04:22 --> 00:04:24 exoplanets with another 8000
00:04:25 --> 00:04:28 waiting to be, um, officially
00:04:28 --> 00:04:31 catalogued. I suppose. So we've
00:04:31 --> 00:04:33 found a lot of them. And the other thing
00:04:33 --> 00:04:36 we've been discovering about, um, finding
00:04:36 --> 00:04:38 these things is how very different
00:04:39 --> 00:04:42 a lot of solar systems are and how very
00:04:42 --> 00:04:44 different some of the planets are. Ah,
00:04:46 --> 00:04:49 what we always thought was basically the
00:04:49 --> 00:04:51 standard for solar systems,
00:04:51 --> 00:04:54 which was ours. Doesn't appear to be very
00:04:54 --> 00:04:55 standard at all.
00:04:56 --> 00:04:58 Jonti Horner: No, it's an incredible time to live through.
00:04:58 --> 00:05:00 I think the way I always budge this is we've
00:05:00 --> 00:05:03 lived through one of the great scientific
00:05:03 --> 00:05:05 revolutions almost without noticing it.
00:05:05 --> 00:05:08 And I think it sheds A light into how people
00:05:08 --> 00:05:09 would have reacted in previous scientific
00:05:09 --> 00:05:11 revolutions, which is that when it's
00:05:11 --> 00:05:13 happening in your lifetime, it just happens.
00:05:13 --> 00:05:15 So we look back and think that was such a
00:05:15 --> 00:05:17 fundamental change. And at the time it was
00:05:17 --> 00:05:19 just Tuesday, you know. And
00:05:19 --> 00:05:22 yes, it's like that with exoplanets. I
00:05:22 --> 00:05:25 grew up in a world where one of the big
00:05:25 --> 00:05:27 science questions was, is a solar system
00:05:27 --> 00:05:29 unique? Are there planets around other stars?
00:05:29 --> 00:05:32 Or are we alone? And there were good
00:05:32 --> 00:05:34 reasons for some people to suspect that we
00:05:34 --> 00:05:36 might be the only planetary system in the
00:05:36 --> 00:05:38 universe. There were kind of, at that time,
00:05:38 --> 00:05:40 two broadly competing models of planet
00:05:40 --> 00:05:42 formation that could both explain the solar
00:05:42 --> 00:05:45 system as we see it to a fair degree. And one
00:05:45 --> 00:05:48 was what's almost described as the
00:05:48 --> 00:05:51 Laplace model, the disc model, which is now
00:05:51 --> 00:05:53 what we favour, that has developed a lot
00:05:53 --> 00:05:55 since then. But the other was this idea that
00:05:55 --> 00:05:57 you had a close encounter between the sun and
00:05:57 --> 00:06:00 a protostar. Ah, that was close enough that
00:06:00 --> 00:06:02 the two stars almost collided and a tongue of
00:06:02 --> 00:06:04 material was pulled out of the sun, which
00:06:04 --> 00:06:05 went on to condense from the planets. And
00:06:05 --> 00:06:07 that was championed by people like Martin
00:06:07 --> 00:06:09 Wolfson of York University, among others.
00:06:10 --> 00:06:12 At, uh, this time we're talking in the late
00:06:12 --> 00:06:15 80s, it was kind of widely held that, uh,
00:06:15 --> 00:06:18 Wolfson's suggestion had problems.
00:06:18 --> 00:06:21 It was probably not the right solution, but
00:06:21 --> 00:06:23 it potentially could be. We'd found a few
00:06:23 --> 00:06:25 debris discs, debris around stars, a bit like
00:06:25 --> 00:06:27 the asteroid belt around the sun, but much
00:06:27 --> 00:06:30 more massive in the early 80s. And that
00:06:30 --> 00:06:33 was kind of hinting that planets could be
00:06:33 --> 00:06:36 common, that the disc model could be the one.
00:06:36 --> 00:06:38 But at the time I was growing up, and at the
00:06:38 --> 00:06:40 time, going into the early 90s, you have
00:06:40 --> 00:06:42 these two models of planet formation that
00:06:42 --> 00:06:45 predicted vastly different outcomes. If
00:06:45 --> 00:06:47 the disc model was right, planets would be
00:06:47 --> 00:06:49 ubiquitous, planets would just be the
00:06:49 --> 00:06:51 leftovers from star formation, and
00:06:51 --> 00:06:53 effectively every star would have planets or
00:06:53 --> 00:06:56 close to it. If the encounter
00:06:56 --> 00:06:58 model was right, then planetary systems would
00:06:58 --> 00:07:01 be exceedingly rare, because to get two stars
00:07:01 --> 00:07:03 to come sufficiently close together at just
00:07:03 --> 00:07:05 the right speed for that to draw a tongue out
00:07:05 --> 00:07:08 and form a planetary system is vanishingly
00:07:08 --> 00:07:11 unlikely. So that was arguing that we were
00:07:11 --> 00:07:14 effectively the result of a freak encounter.
00:07:14 --> 00:07:17 And if that prediction was right, then if
00:07:17 --> 00:07:18 that method was right, sorry, it would
00:07:18 --> 00:07:20 predict that planetary systems were
00:07:20 --> 00:07:22 exceedingly rare and that we wouldn't find
00:07:22 --> 00:07:25 them. So going into the 90s, you had these
00:07:25 --> 00:07:27 two theories that could both explain in broad
00:07:27 --> 00:07:30 brushstrokes, what we see at home, but that
00:07:30 --> 00:07:31 predicted very, very, very different
00:07:31 --> 00:07:34 outcomes. And as I say, The Wolfson idea was
00:07:34 --> 00:07:37 already losing a bit of seam. But in the time
00:07:37 --> 00:07:40 since we found that planets are under the
00:07:40 --> 00:07:41 stars and, um, that they are ubiquitous,
00:07:41 --> 00:07:43 basically every star you see in the night
00:07:43 --> 00:07:46 sky, no matter how complex system, no
00:07:46 --> 00:07:48 matter what's that, there are going to be
00:07:48 --> 00:07:50 planetary objects around it, pretty much all
00:07:50 --> 00:07:53 cases. And that's a death knell, of course,
00:07:53 --> 00:07:55 for the Wolfson model of freak planetary
00:07:55 --> 00:07:58 system formation and its support for the
00:07:58 --> 00:08:00 model we now know and love, which has been
00:08:00 --> 00:08:02 refined over the years because of all the
00:08:02 --> 00:08:04 oddities we found. Now, it's really
00:08:04 --> 00:08:06 interesting, storey, but it goes way back
00:08:06 --> 00:08:08 before that. We've got a long history of
00:08:09 --> 00:08:11 the things that led to finding the first
00:08:11 --> 00:08:13 planets. What we take it a bit for granted
00:08:13 --> 00:08:15 now. We're finding so many planets and I have
00:08:15 --> 00:08:17 the good fortune of getting to be involved
00:08:17 --> 00:08:19 peripherally in some of the discoveries. I'
00:08:19 --> 00:08:21 have the very entertaining job of killing
00:08:21 --> 00:08:23 some planetary systems. So it should be said
00:08:23 --> 00:08:25 that the number you gave at the start can go
00:08:25 --> 00:08:28 down as well as going up. Some of
00:08:28 --> 00:08:30 the planets that get confirmed later on get
00:08:30 --> 00:08:32 redacted, get killed. And I've probably,
00:08:32 --> 00:08:35 certainly as lead author, I've never led a
00:08:35 --> 00:08:36 planet discovery, but I've been involved with
00:08:36 --> 00:08:38 them. But I've led a number of research
00:08:38 --> 00:08:40 projects that killed planets that other
00:08:40 --> 00:08:42 people claimed. So I've probably been net
00:08:42 --> 00:08:44 responsible as an individual for a negative
00:08:44 --> 00:08:47 number of planet discoveries that can happen.
00:08:47 --> 00:08:49 But it's really important that we do that
00:08:49 --> 00:08:50 kind of work. I've always been really
00:08:50 --> 00:08:52 passionate about that because all of the
00:08:52 --> 00:08:55 things that we do to talk about how common
00:08:55 --> 00:08:58 planets are, to look into how they form and,
00:08:58 --> 00:09:00 um, further down the line to try and find
00:09:00 --> 00:09:02 planets that could be like the Earth and to
00:09:02 --> 00:09:04 try and look for life on them. All of that is
00:09:04 --> 00:09:06 based on the catalogue of the known. What do
00:09:06 --> 00:09:09 we know? What's the variety? And so if you've
00:09:09 --> 00:09:11 got planets that are in that catalogue that
00:09:11 --> 00:09:13 don't exist, they're polluting that catalogue
00:09:13 --> 00:09:15 and confusing and obscuring the truth. So
00:09:15 --> 00:09:18 it's really important to not just accept that
00:09:18 --> 00:09:20 when a planet is claimed and marked as
00:09:20 --> 00:09:22 confirmed, that's the end of the storey. But
00:09:22 --> 00:09:23 we need to follow it up and say, does it make
00:09:23 --> 00:09:25 sense? Could there be something else going
00:09:25 --> 00:09:27 on? And in those cases we do learn more about
00:09:27 --> 00:09:30 it. So it's a fascinating field. I'm really
00:09:30 --> 00:09:32 fortunate to have gone from being a kid who
00:09:32 --> 00:09:34 wondered to an adult who gets to be involved
00:09:34 --> 00:09:36 in the process. That's incredibly
00:09:36 --> 00:09:39 wonderful for me, but it's a fabulous Storey
00:09:39 --> 00:09:41 we have lived through a great scientific
00:09:41 --> 00:09:44 revolution in many ways. One that's as big as
00:09:44 --> 00:09:46 the acceptance of continental drift or uh,
00:09:47 --> 00:09:49 the origin of species and Darwin or general
00:09:49 --> 00:09:52 relativity and Einstein. It's one of those
00:09:52 --> 00:09:53 revolutions. And when you talk about the
00:09:53 --> 00:09:56 other ones, you think about how epochal
00:09:56 --> 00:09:58 and incredible and how they change the world
00:09:58 --> 00:10:00 and we've just lived through one. Um, it's
00:10:00 --> 00:10:01 amazing.
00:10:01 --> 00:10:03 Andrew Dunkley: Yeah, it's incredible. And, and
00:10:04 --> 00:10:06 will it never end? I mean the thought of
00:10:06 --> 00:10:08 looking up into the night sky and seeing
00:10:09 --> 00:10:12 billions of stars and knowing that there
00:10:12 --> 00:10:15 are probably multi, billions of planets is
00:10:15 --> 00:10:17 just, it's mind blowing.
00:10:17 --> 00:10:19 Jonti Horner: And the rest, I mean to me it's a numbers
00:10:19 --> 00:10:20 game and we talk about this when we talk
00:10:20 --> 00:10:23 about life elsewhere, but the numbers get
00:10:23 --> 00:10:26 ridiculous really, really quickly. Now we've
00:10:26 --> 00:10:28 been heavily biassing what we found to
00:10:28 --> 00:10:30 finding planets closer to their stars than
00:10:30 --> 00:10:31 the Earth is to the sun. The overwhelming
00:10:31 --> 00:10:33 majority of planets. We found a very close
00:10:33 --> 00:10:36 end, but there will be planets further out as
00:10:36 --> 00:10:37 well. You're not going to have a situation
00:10:37 --> 00:10:39 very often where you've got a few planets
00:10:39 --> 00:10:41 near the star and nothing further out. So a
00:10:41 --> 00:10:43 lot of the very tentative estimates you get
00:10:43 --> 00:10:46 of the number of planets in the universe say,
00:10:46 --> 00:10:48 well, imagine there's just one planet per I.
00:10:48 --> 00:10:50 Based on what we found so far, I think it's
00:10:50 --> 00:10:52 fairer to say there are probably nearer to 10
00:10:52 --> 00:10:54 planets per star. And depending on whether
00:10:55 --> 00:10:58 Jared Isaacson, the guy who's taken
00:10:58 --> 00:11:00 over NASA who is not an astronomer, gets his
00:11:00 --> 00:11:02 way and restores Pluto. If he restores
00:11:02 --> 00:11:05 Pluto, then you have to argue that Ceres,
00:11:05 --> 00:11:07 Makemake, Haumea, Eris, all these other
00:11:07 --> 00:11:09 things are planets in the solar system. You
00:11:09 --> 00:11:12 could have 20 planets in the solar system. So
00:11:12 --> 00:11:15 let's assume 10 per star. You
00:11:15 --> 00:11:17 know whether Pluto is arisen. Leave that for
00:11:17 --> 00:11:19 aside. I have strong opinions on that. Other
00:11:19 --> 00:11:20 opinions are available. They're wrong, but
00:11:20 --> 00:11:22 they're available. As Matt come out always
00:11:22 --> 00:11:25 says, um, ignoring
00:11:25 --> 00:11:27 that though, if you assume 10 planets per
00:11:27 --> 00:11:28 star, because it's going to be nearer to 10
00:11:28 --> 00:11:30 than when an astronomer's working factors of
00:11:30 --> 00:11:33 10. In our galaxy alone, um, we have
00:11:34 --> 00:11:37 somewhere around 400 million
00:11:37 --> 00:11:39 stars. Now that number also is only accurate
00:11:39 --> 00:11:41 to a factor of 2 or 3. So it could be 200, it
00:11:41 --> 00:11:44 could be 600, but call it 400
00:11:44 --> 00:11:46 million stars means 10 planets per star.
00:11:46 --> 00:11:49 You'd have 4 trillion planets in our
00:11:49 --> 00:11:51 galaxy, ignoring the free floating ones that
00:11:51 --> 00:11:54 don't have a star to call their own. 4
00:11:54 --> 00:11:55 trillion planets in our galaxy.
00:11:56 --> 00:11:58 There are more galaxies in the observable
00:11:58 --> 00:12:01 universe than there are stars in our galaxy
00:12:01 --> 00:12:03 by orders of magnitude. Which means you start
00:12:03 --> 00:12:05 getting to the point which, in the observable
00:12:05 --> 00:12:08 universe alone, um, ignoring the part of the
00:12:08 --> 00:12:09 universe that we can't see because that's
00:12:09 --> 00:12:11 utterly unquantifiable, but just in the part
00:12:11 --> 00:12:14 we can see, you'll have planets numbered in
00:12:14 --> 00:12:16 the sextillions of septillions.
00:12:17 --> 00:12:19 So a trillion is 10 to the 12, a trillion is
00:12:19 --> 00:12:22 a thousand billion, a quadrillion is 10 to
00:12:22 --> 00:12:25 the 15, which is a thousand trillion, and so
00:12:25 --> 00:12:28 on. So these numbers are utterly,
00:12:28 --> 00:12:31 astonishingly, overwhelmingly, mind boggling.
00:12:31 --> 00:12:33 And that's where I come to with this thing,
00:12:33 --> 00:12:35 that if we're the only place with life in the
00:12:35 --> 00:12:37 universe, then there's something very unusual
00:12:37 --> 00:12:37 going on.
00:12:38 --> 00:12:41 Andrew Dunkley: Absolutely, yeah. Um, and
00:12:41 --> 00:12:44 it was the movie Contact where they said, uh,
00:12:44 --> 00:12:47 space is really big. So if it's just stuff,
00:12:47 --> 00:12:49 just us, it seems like an awful waste of
00:12:49 --> 00:12:49 space.
00:12:50 --> 00:12:50 Jonti Horner: It is.
00:12:51 --> 00:12:52 Andrew Dunkley: I always like that line.
00:12:52 --> 00:12:54 Jonti Horner: Yeah, well, the question of life elsewhere is
00:12:54 --> 00:12:56 one that really polarises people. I mean,
00:12:56 --> 00:12:58 everybody's interested to know the answer.
00:12:58 --> 00:13:00 Arthur C Clarke said something along the
00:13:00 --> 00:13:02 lines of, there are two possibilities. Either
00:13:02 --> 00:13:04 we're alone in the universe or we are not.
00:13:04 --> 00:13:07 Both equally terrifying. Um,
00:13:08 --> 00:13:10 a lot of people. Stephen Hawking was very
00:13:10 --> 00:13:11 adamantly, we shouldn't try and contact
00:13:11 --> 00:13:13 aliens because they will kill us in the face.
00:13:14 --> 00:13:16 I don't tend to agree with them, but
00:13:17 --> 00:13:19 it is one of those discussions that really
00:13:19 --> 00:13:22 fires people up, gets people energised. And
00:13:22 --> 00:13:24 for me, it would be actually far more
00:13:24 --> 00:13:26 terrifying to know we're alone in the
00:13:26 --> 00:13:27 universe, because that means life is such an
00:13:27 --> 00:13:30 impossible fluke that given planets
00:13:30 --> 00:13:33 numbering in the sextillions or septillions,
00:13:33 --> 00:13:35 in the known universe, we're the only one
00:13:35 --> 00:13:38 with life. Which means that only one planet
00:13:38 --> 00:13:41 in 10 followed by 20 zeros or more
00:13:41 --> 00:13:43 gets life on it. And that seems infeasible to
00:13:43 --> 00:13:46 me, but m. We won't really know until
00:13:47 --> 00:13:50 we move forward and we actually proceed with
00:13:50 --> 00:13:51 the search for life elsewhere. And as I've
00:13:51 --> 00:13:54 said in a previous episode, absence of
00:13:54 --> 00:13:56 evidence is not evidence of absence. So if we
00:13:56 --> 00:13:58 find life, then we'll know we're not alone.
00:13:58 --> 00:14:00 We'll know that life's common in the
00:14:00 --> 00:14:02 universe. The longer it takes us to find life
00:14:03 --> 00:14:05 doesn't mean that there is nothing to be
00:14:05 --> 00:14:08 found, it just means that life is scarcer,
00:14:08 --> 00:14:10 basically. So the longer we take to find it,
00:14:10 --> 00:14:12 the better we'll get at doing it. The further
00:14:12 --> 00:14:14 we'll be able to look, the more planets we
00:14:14 --> 00:14:16 can Sample. And that will then give us a
00:14:16 --> 00:14:18 handle for the commonality of life.
00:14:18 --> 00:14:18 Andrew Dunkley: Life.
00:14:18 --> 00:14:20 Jonti Horner: So we find life in our lifetime. All well and
00:14:20 --> 00:14:22 good. If we're still looking in a thousand
00:14:22 --> 00:14:25 years. I'd be gobsmacked, but that just tells
00:14:25 --> 00:14:26 you life is a lot rarer than we thought.
00:14:27 --> 00:14:30 Andrew Dunkley: Indeed. And we will talk about that more in
00:14:30 --> 00:14:32 another, uh, special episode when we do part
00:14:32 --> 00:14:35 two of Astrobiology. Uh, we kind
00:14:35 --> 00:14:38 of had, we didn't have enough time to
00:14:38 --> 00:14:39 talk about it last time, so we're going to do
00:14:39 --> 00:14:40 a part two.
00:14:40 --> 00:14:42 Jonti Horner: But uh, I can talk too much.
00:14:43 --> 00:14:45 Andrew Dunkley: It's also an area that um, uh, makes
00:14:45 --> 00:14:48 your brain hurt. So we, we decided to,
00:14:49 --> 00:14:51 you know, give it a miss this week and go
00:14:51 --> 00:14:52 back, uh, next week.
00:14:53 --> 00:14:56 Um, so where do you want to go with this?
00:14:56 --> 00:14:58 Like, um, everyone knows there's
00:14:58 --> 00:15:01 exoplanets. Everyone knows there are, um, you
00:15:01 --> 00:15:03 know, powder puff planets. And um,
00:15:04 --> 00:15:06 they've actually got names for them. I've got
00:15:07 --> 00:15:10 named, um. So you know, we can
00:15:10 --> 00:15:13 officially say that uh, as far as
00:15:13 --> 00:15:14 planets are concerned, we have
00:15:15 --> 00:15:17 um, specific types of
00:15:17 --> 00:15:19 planets in our solar system, and that is
00:15:20 --> 00:15:22 rocky planets, gas giants, and
00:15:23 --> 00:15:25 for want of a better term, ice giants. But in
00:15:25 --> 00:15:28 the exoplanet world there are
00:15:28 --> 00:15:31 several other types. Um,
00:15:31 --> 00:15:34 you've got um, uh, Neptunian,
00:15:34 --> 00:15:37 like planets, super Earths, uh, you've
00:15:37 --> 00:15:40 got uh, hot Jupiters, you've got super cold
00:15:40 --> 00:15:42 worlds, you've got pulsar planets, and
00:15:42 --> 00:15:44 there's even uh, uh,
00:15:44 --> 00:15:47 circumbinary planets where they're
00:15:47 --> 00:15:49 orbiting two stars. We don't have that
00:15:49 --> 00:15:51 thankfully. Uh, that could be messy,
00:15:51 --> 00:15:53 especially when it comes to trying to predict
00:15:53 --> 00:15:56 the tides. But um, it's, you know, there's so
00:15:56 --> 00:15:58 much more going on out there.
00:15:58 --> 00:16:00 Jonti Horner: There is, and it reflects something that's
00:16:00 --> 00:16:03 incredibly human. And it again goes back to
00:16:03 --> 00:16:06 that discussion about Pluto and many other
00:16:06 --> 00:16:08 things in human experience. What we find
00:16:09 --> 00:16:11 in every field of study, but you know, in
00:16:11 --> 00:16:14 astronomy in particular, is you have a
00:16:14 --> 00:16:16 continuum of things you've got from the very
00:16:16 --> 00:16:18 small to the very big with no obvious sharp
00:16:18 --> 00:16:21 gaps. You know, you'll find everything in
00:16:21 --> 00:16:23 planetary systems from stuff the size of a
00:16:23 --> 00:16:25 grain of dust to things more massive than the
00:16:25 --> 00:16:27 sun, depending on the planetary system you're
00:16:27 --> 00:16:30 in. What we tend to do as humans is we tend
00:16:30 --> 00:16:33 to break down that which we
00:16:33 --> 00:16:36 see as a continuum into manageable bite sized
00:16:36 --> 00:16:38 chunks by grouping like with like in order
00:16:38 --> 00:16:41 that we can then better study objects.
00:16:42 --> 00:16:44 And so for example, you'd say that the Earth
00:16:44 --> 00:16:46 is more like Venus or Mars than it is Like
00:16:46 --> 00:16:47 Jupiter. So you categorise them into
00:16:47 --> 00:16:50 different subgroups. For humans, we do this
00:16:50 --> 00:16:53 all around the world. You've got babies and
00:16:53 --> 00:16:55 toddlers, children, teenagers, adults,
00:16:55 --> 00:16:58 retirees, pensioners, and you set boundaries.
00:16:58 --> 00:17:00 And those boundaries don't always agree from
00:17:00 --> 00:17:02 country to country. You know, you remember
00:17:02 --> 00:17:04 the incredible day that you suddenly wake up
00:17:04 --> 00:17:06 and you're able to drive legally when the day
00:17:06 --> 00:17:08 before you weren't. And fundamentally you'
00:17:08 --> 00:17:11 changed as a human. You're one day older out
00:17:11 --> 00:17:14 of what, you know, several thousand days at
00:17:14 --> 00:17:16 that point, about 5, 6 days. But
00:17:16 --> 00:17:18 miraculously you've crossed this arbitrary
00:17:18 --> 00:17:21 threshold which we've put there to separate
00:17:21 --> 00:17:23 people who can't drive and people who can but
00:17:23 --> 00:17:25 maybe shouldn't. You know, that's kind of
00:17:25 --> 00:17:26 where the division is.
00:17:28 --> 00:17:29 We do this as humans all the time to
00:17:29 --> 00:17:32 categorise things. And that's kind of where
00:17:32 --> 00:17:34 Pluto fallafal and it's where all these
00:17:34 --> 00:17:36 groups of different types of planets come
00:17:36 --> 00:17:37 from. You've got hot Jupiters and warm
00:17:37 --> 00:17:40 Jupiters, super puff planets and all
00:17:40 --> 00:17:43 sorts of quirky things. And those terms
00:17:43 --> 00:17:46 are taking the broad spectrum of planets that
00:17:46 --> 00:17:48 we've got and trying to group apples with
00:17:48 --> 00:17:50 apples and oranges with oranges, things that
00:17:50 --> 00:17:53 are similar to one another. And the diversity
00:17:53 --> 00:17:55 just continues to ascend, as every time we
00:17:55 --> 00:17:57 think we've found the most extreme of
00:17:57 --> 00:17:58 whatever, we find something that's even more
00:17:58 --> 00:18:01 so. Like I said, we found planets who we
00:18:01 --> 00:18:04 can calculate their size by how much light of
00:18:04 --> 00:18:05 their star they block. We can calculate their
00:18:05 --> 00:18:07 mass by how much they pull their star around.
00:18:09 --> 00:18:11 We've got a subset of stars and planets where
00:18:11 --> 00:18:12 we can do both those, uh, things which lets
00:18:12 --> 00:18:15 us figure out the density. And from them we
00:18:15 --> 00:18:18 found planets that are less dense than cotton
00:18:18 --> 00:18:20 candy, which are the super puffs,
00:18:20 --> 00:18:22 fluffy ones, probably coming towards the end
00:18:22 --> 00:18:24 of their lives because they're so low density
00:18:24 --> 00:18:26 that they are probably being stripped away by
00:18:26 --> 00:18:28 their star stellar winds. We found planets
00:18:28 --> 00:18:31 that are effectively like comets with tails
00:18:31 --> 00:18:33 as their atmosphere stripped off. I mean, to
00:18:33 --> 00:18:35 some degree, actually, the planet Mercury in
00:18:35 --> 00:18:37 the solar system is a comet. It's got a
00:18:37 --> 00:18:39 beautiful long sodium tail. One of my
00:18:39 --> 00:18:42 favourite astrophotos I've ever seen is a
00:18:42 --> 00:18:44 picture of Mercury near the Pleiades, where
00:18:44 --> 00:18:46 somebody's done some imaging in a sodium
00:18:46 --> 00:18:48 filter and you can see Mercury's tail
00:18:48 --> 00:18:51 visible on the image. It's an astonishing
00:18:51 --> 00:18:53 thing. So we found planets like comets. We've
00:18:53 --> 00:18:55 even found planets around pulsars and they
00:18:55 --> 00:18:57 were the first three planets we found around
00:18:57 --> 00:19:00 other stars. There were um, Phoebe Toe,
00:19:00 --> 00:19:03 Poltergeist and Rao, these stars orbiting a
00:19:03 --> 00:19:05 pulsar named after three kinds of the, um,
00:19:05 --> 00:19:07 undead. So there's this huge variety that
00:19:07 --> 00:19:09 worth mentioning actually from the names. The
00:19:09 --> 00:19:12 names are being allocated by the
00:19:12 --> 00:19:13 International Astronomical Union, just as
00:19:13 --> 00:19:16 names of asteroids and names of satellites
00:19:16 --> 00:19:18 and things like that are. What they're trying
00:19:18 --> 00:19:20 to do with them is to be very
00:19:21 --> 00:19:24 democratic globally, to try and represent
00:19:24 --> 00:19:26 multiple cultures rather than just have all
00:19:26 --> 00:19:29 the planets draw from a single cultural base,
00:19:29 --> 00:19:31 a single kind of background. And so they've
00:19:31 --> 00:19:33 been running a series of competitions over
00:19:33 --> 00:19:36 the years for the general public where a
00:19:36 --> 00:19:39 given planetary system is to a given country.
00:19:39 --> 00:19:41 And, um, then people from that country get to
00:19:41 --> 00:19:43 nominate names, and then people from that
00:19:43 --> 00:19:46 country get to vote on it. And I think we've
00:19:46 --> 00:19:47 now got more than 100 planets named. We've
00:19:47 --> 00:19:49 had a few of them from Australia named. And
00:19:49 --> 00:19:52 I'm actually just trying to look up, um, the
00:19:52 --> 00:19:54 planet names from the iau. They're the
00:19:54 --> 00:19:56 official ones. Now, what's interesting is
00:19:56 --> 00:19:59 these are, uh, official names. They're
00:19:59 --> 00:20:01 the IAU's official names. I
00:20:01 --> 00:20:04 therefore try to use them in my purpose.
00:20:04 --> 00:20:06 Um, and I've had pushback from astronomers
00:20:06 --> 00:20:08 because everyone's so used to the catalogue
00:20:08 --> 00:20:10 numbers. So what I've been trying to do
00:20:10 --> 00:20:12 is you give both names, you give the
00:20:12 --> 00:20:14 catalogue name on the proper now. And I think
00:20:14 --> 00:20:16 where it will go long term is it'll become a
00:20:16 --> 00:20:18 bit like comets. You know, I've been trying
00:20:18 --> 00:20:20 to get images through the cloud and cursing
00:20:20 --> 00:20:22 the weather of Comet Pan Stars at the minute.
00:20:22 --> 00:20:24 And we talk about Comet Pan Stars, but it's
00:20:24 --> 00:20:26 real name that I'd write down, if I'm writing
00:20:26 --> 00:20:29 it is C20, 26 R3
00:20:29 --> 00:20:31 brackets, pan stars. And I think
00:20:32 --> 00:20:34 in the long term, I can see exoplanet names
00:20:34 --> 00:20:36 going that kind of way once people get used
00:20:36 --> 00:20:38 to it. So 51 Pegasi B,
00:20:39 --> 00:20:41 for example, is dimidium. That's the name
00:20:41 --> 00:20:44 that's been given there. And you can use both
00:20:44 --> 00:20:46 interchangeably. But because astronomers are
00:20:46 --> 00:20:49 used to 51 Pegasi B, that's where it
00:20:49 --> 00:20:51 sticks. Now, the names come from lots of
00:20:51 --> 00:20:53 different cultures. They come from lots of
00:20:53 --> 00:20:55 different groups. There are planets that have
00:20:55 --> 00:20:57 been discovered by Australians that are named
00:20:57 --> 00:20:59 after Australians. There are planets that are
00:20:59 --> 00:21:01 named after people. You know, you've got the
00:21:01 --> 00:21:03 planet Galileo going around 55 Cancri.
00:21:04 --> 00:21:06 So 55 Cancer's five named planets are all
00:21:06 --> 00:21:08 named after astronomers. You've got Galileo,
00:21:08 --> 00:21:11 Brahe, Lipper, Hay Janssen,
00:21:11 --> 00:21:13 Harriet, and, um, that's it. So Five
00:21:13 --> 00:21:16 planets, five names. Lots of different names
00:21:16 --> 00:21:19 from different cultures. We've got names that
00:21:19 --> 00:21:21 are controversial, names from different
00:21:21 --> 00:21:24 folklore, names from different cultures all
00:21:24 --> 00:21:26 around. That list is growing. But you don't
00:21:26 --> 00:21:28 say, see used all that much yet because a
00:21:28 --> 00:21:31 planet needs to be confirmed and
00:21:31 --> 00:21:34 then very confidently there and well studied
00:21:34 --> 00:21:36 for it to get onto the list for the name. So
00:21:36 --> 00:21:37 I think like I said, we've got a bit more
00:21:37 --> 00:21:39 than 100 names and a bit more than 6
00:21:39 --> 00:21:42 planets. Those 6 planets, that
00:21:42 --> 00:21:44 number will go up as well as down, but it's
00:21:44 --> 00:21:45 not going to be too long until we're 10
00:21:45 --> 00:21:46 plus.
00:21:46 --> 00:21:49 Andrew Dunkley: Yeah, I figured out why, uh, some of these,
00:21:49 --> 00:21:52 um, sometimes the number goes down. They're
00:21:52 --> 00:21:54 the ones that have been discovered by Monty
00:21:54 --> 00:21:55 Python. It's a planet.
00:21:55 --> 00:21:56 Jonti Horner: No it's not, it's not.
00:21:56 --> 00:21:59 Um, so that's why we'll also lose
00:21:59 --> 00:22:02 some with Gaia. So Gaia has been this
00:22:02 --> 00:22:04 amazing satellite measuring positions of
00:22:04 --> 00:22:07 stars and it can measure the
00:22:07 --> 00:22:10 wobble on the sky side to side of
00:22:10 --> 00:22:12 stars as a result of their planets. Now
00:22:12 --> 00:22:15 historically, the two, by far the two most
00:22:15 --> 00:22:16 successful methods of finding planets are the
00:22:16 --> 00:22:19 radial velocity method where we measure the
00:22:19 --> 00:22:21 star speed towards our away from us and see
00:22:21 --> 00:22:23 it wobbling along the line of sight, and the
00:22:23 --> 00:22:24 transit method where we see it pass between
00:22:24 --> 00:22:26 us and the star. And that means the orbit is
00:22:26 --> 00:22:28 edge on to us. And but for those radial
00:22:28 --> 00:22:30 velocity planets, we're measuring the
00:22:30 --> 00:22:32 fraction of the wobble towards or away from
00:22:32 --> 00:22:35 the observer. And um, the orbit could be
00:22:35 --> 00:22:37 tilted almost edge on or almost face on to
00:22:37 --> 00:22:39 give that same amount of wobble along our
00:22:39 --> 00:22:41 line of sight. Gaia will give us the other
00:22:41 --> 00:22:43 dimension. It'll give us a side by side,
00:22:43 --> 00:22:45 which means it'll find us the tilts of all
00:22:45 --> 00:22:48 those planets. Some of those planets will be
00:22:48 --> 00:22:51 on orbits very tilted to ours and therefore
00:22:51 --> 00:22:52 the mass that they have will be much higher
00:22:52 --> 00:22:55 than that we think they probably have. And
00:22:55 --> 00:22:56 that there'll be certain amount of attrition
00:22:56 --> 00:22:58 where planets that we think are planets are
00:22:58 --> 00:23:01 actually brown water dwarfs. And that is
00:23:01 --> 00:23:02 another of these arbitrary boundaries which
00:23:02 --> 00:23:05 we set roughly at 13 Jupiter masses. But we
00:23:05 --> 00:23:07 will have planets falling off at the top end.
00:23:08 --> 00:23:11 When Gaia comes out. I suspect he won't see
00:23:11 --> 00:23:12 the number drop though, because Gaia will
00:23:12 --> 00:23:14 also lead to so many new discoveries that,
00:23:14 --> 00:23:16 that will overwhelm the ones that fall, uh,
00:23:16 --> 00:23:17 off the top end.
00:23:18 --> 00:23:20 Andrew Dunkley: I, yes, that's a fair point. So, um,
00:23:20 --> 00:23:23 it's, it's going to be one of those waveforms
00:23:24 --> 00:23:26 that goes up and down
00:23:26 --> 00:23:29 as, as situations change. Yeah,
00:23:29 --> 00:23:31 let's take a. I was going
00:23:31 --> 00:23:33 Jonti Horner: to say I've been responsible for a number of
00:23:33 --> 00:23:35 systems getting killed because people propose
00:23:35 --> 00:23:38 planets in places that they seemed unlikely
00:23:38 --> 00:23:40 and they didn't make sense from orbital
00:23:40 --> 00:23:42 mechanics point of view. So I ran simulations
00:23:42 --> 00:23:44 and showed that if these planetary systems
00:23:44 --> 00:23:46 are real, wetting them in the last 10 years
00:23:46 --> 00:23:49 of a 4 billion year lifetime before
00:23:49 --> 00:23:50 the planets crash into each other or reject
00:23:50 --> 00:23:52 each other. And that's not feasible. So there
00:23:52 --> 00:23:53 must be something else going on. So on the
00:23:53 --> 00:23:55 one hand, hand, boohoo, you've killed a
00:23:55 --> 00:23:57 planet. That's not good, you naughty boy. Um,
00:23:57 --> 00:23:59 on the flip side though, it's really cool
00:23:59 --> 00:24:01 because there's something there creating the
00:24:01 --> 00:24:04 signal that people have measured and it
00:24:04 --> 00:24:06 isn't planets, so what is it? So there's
00:24:06 --> 00:24:08 always. Science always gives you more
00:24:08 --> 00:24:09 questions.
00:24:09 --> 00:24:12 Andrew Dunkley: Indeed it does. And you're listening to Space
00:24:12 --> 00:24:15 Nuts with Andrew Dunkley. Andrew Dunkley, I
00:24:15 --> 00:24:17 do know my name. And Professor Johnty Horner.
00:24:19 --> 00:24:21 Let's take a short break from the show to
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00:26:10 --> 00:26:11 Jonti Horner: Space Nuts.
00:26:11 --> 00:26:12 Andrew Dunkley: I'm gonna have to write it down so I can read
00:26:12 --> 00:26:13 it properly.
00:26:13 --> 00:26:16 Um, Jonty, where do you want to go next? I
00:26:16 --> 00:26:19 mean, we've found so many, uh, I don't think
00:26:19 --> 00:26:21 we will ever, never stop finding
00:26:21 --> 00:26:24 exoplanets, uh, because as
00:26:24 --> 00:26:25 technology improves they're just going to
00:26:25 --> 00:26:26 keep stacking up, aren't they?
00:26:26 --> 00:26:29 Jonti Horner: Yeah. I mean, if we talk about the 6000ish we
00:26:29 --> 00:26:32 found so far, uh, 6278
00:26:32 --> 00:26:34 I think it was. We said earlier on there are
00:26:34 --> 00:26:37 probably 4 trillion give or take in our
00:26:37 --> 00:26:40 galaxy, which means we've only found about
00:26:40 --> 00:26:43 one planet for every billion planets
00:26:43 --> 00:26:46 that are in our galaxy. We've barely
00:26:46 --> 00:26:48 scratched the surface in doing that. We've
00:26:48 --> 00:26:51 utterly revolutionised our knowledge of the,
00:26:51 --> 00:26:53 the variety of planets that'll be out there,
00:26:53 --> 00:26:56 of how planets form. We have still for
00:26:56 --> 00:26:58 me, not found something truly Earth like. I
00:26:58 --> 00:27:00 think that's the next hurdle. Now you'll see
00:27:00 --> 00:27:02 a number of media articles over the years
00:27:02 --> 00:27:04 saying the most Earth like planet yet has
00:27:04 --> 00:27:06 been found. All the bloody.
00:27:06 --> 00:27:08 Andrew Dunkley: I, I actually read an article yesterday
00:27:09 --> 00:27:12 which said, uh, oh, super Earth found
00:27:12 --> 00:27:14 potential life. Da, da, da, da, da. And I
00:27:14 --> 00:27:15 thought, yeah, here we go again. And I read
00:27:15 --> 00:27:17 it and of course when you get down to the
00:27:17 --> 00:27:19 second last paragraph, it says, of course
00:27:19 --> 00:27:21 there's no confirmation that this is even a
00:27:21 --> 00:27:21 rocky planet.
00:27:21 --> 00:27:24 Jonti Horner: But yeah, and to me it's like
00:27:24 --> 00:27:26 imagining that you're an alien visiting the
00:27:26 --> 00:27:27 Earth. Ah, and you're flying over the oceans
00:27:27 --> 00:27:29 and you say, we found the most human like
00:27:29 --> 00:27:31 animal yet. It's about two metres long, it's
00:27:31 --> 00:27:33 a couple of hundred kilos, 100 kilos. I mean,
00:27:33 --> 00:27:36 it's a dolphin, it's nothing like humans, but
00:27:36 --> 00:27:38 it, you know, it's that kind of thing. And I
00:27:38 --> 00:27:41 think I understand the urge, uh,
00:27:41 --> 00:27:44 for scientists to talk about things in the
00:27:44 --> 00:27:45 context of the habitable zone, in the
00:27:45 --> 00:27:47 purpose, because that's interesting. Is it
00:27:47 --> 00:27:50 too warm? Is it too cold? I understand the
00:27:50 --> 00:27:52 thing of saying this planet has similarities
00:27:52 --> 00:27:54 to the Earth. It's about the same size, size,
00:27:54 --> 00:27:56 or it would be about the same temperature.
00:27:56 --> 00:27:58 What tends to happen though then is that the
00:27:58 --> 00:28:00 pressure release from the universities gets a
00:28:00 --> 00:28:01 little bit more hyperbolic in it because they
00:28:01 --> 00:28:04 want to get the reads and the clicks, want to
00:28:04 --> 00:28:06 get the word out there. It then gets into the
00:28:06 --> 00:28:09 media, who again are being more hyperbolic,
00:28:09 --> 00:28:11 and we're seeing it at, ah, the minute, with
00:28:11 --> 00:28:13 the articles about the meteor shower that's
00:28:13 --> 00:28:14 active at the minute, where people are
00:28:14 --> 00:28:16 building it up and blowing it up to a level
00:28:16 --> 00:28:19 that is not practical and not observable and
00:28:19 --> 00:28:22 leads to this point. It's not helped by the
00:28:22 --> 00:28:23 fact that there are people who are making
00:28:23 --> 00:28:25 careers out of
00:28:26 --> 00:28:28 discussing how Earth like planets are that
00:28:28 --> 00:28:30 they didn't discover, that they weren't
00:28:30 --> 00:28:32 involved with to get themselves clicked and
00:28:32 --> 00:28:33 to get money. And a lot of the beautiful
00:28:33 --> 00:28:36 visuals you get cropping up online about
00:28:36 --> 00:28:38 Earth like planets come from one resource,
00:28:38 --> 00:28:40 which is called the Planetary Habitability
00:28:40 --> 00:28:43 Laboratory in Puerto Rico, which has been
00:28:43 --> 00:28:45 an ongoing source of frustration for me and
00:28:45 --> 00:28:48 colleagues because there's been storeys that
00:28:48 --> 00:28:49 people I know have published about planets.
00:28:49 --> 00:28:52 And then this entity
00:28:52 --> 00:28:54 puts out their own press release saying,
00:28:54 --> 00:28:56 we've calculated this magic number and this
00:28:56 --> 00:28:57 is the most Earth like planet found and it's
00:28:57 --> 00:28:59 probably got life. And the scientists who
00:28:59 --> 00:29:01 discovered it have said none of those things.
00:29:01 --> 00:29:04 Yeah. Um, and all the coverage is, look
00:29:04 --> 00:29:06 at this beautiful AI generated artwork. Isn't
00:29:06 --> 00:29:09 this amazing? So I do, and I
00:29:09 --> 00:29:11 had a fun storey about this a few months ago.
00:29:11 --> 00:29:13 I had a. An author get in touch with me,
00:29:13 --> 00:29:14 asking me to proofread a chapter of the book.
00:29:14 --> 00:29:16 A book, A book that they're doing. And they'd
00:29:16 --> 00:29:18 got a little bit in there about all the
00:29:18 --> 00:29:20 potentially Earth like habitable planets that
00:29:20 --> 00:29:21 have been found out there. And they use that
00:29:21 --> 00:29:24 as a resource. And I had to back them off on
00:29:24 --> 00:29:25 it and say, look, it's brilliant to talk
00:29:25 --> 00:29:27 about this. Please don't use this as a
00:29:27 --> 00:29:30 resource. If you use their equations,
00:29:30 --> 00:29:32 Venus would be the most habitable planet
00:29:32 --> 00:29:34 we've discovered other than the Earth.
00:29:35 --> 00:29:37 And I certainly wouldn't want to have a
00:29:37 --> 00:29:37 holiday there.
00:29:38 --> 00:29:41 Andrew Dunkley: No, no. Um, you'd need. Need 20
00:29:41 --> 00:29:44 gazillion plus sunscreen
00:29:44 --> 00:29:46 for starters or something like
00:29:46 --> 00:29:49 that. Now that'd be Mercury. But, um, it's.
00:29:49 --> 00:29:49 Yeah, it's.
00:29:49 --> 00:29:52 Jonti Horner: It's impossible unless it's impossible, you
00:29:52 --> 00:29:54 know, and we could live among the clouds.
00:29:54 --> 00:29:56 That'd be a bit different. But yeah, there's
00:29:56 --> 00:29:59 a lot of stuff around it. And it. We've
00:29:59 --> 00:30:01 talked before about other things. We talked
00:30:01 --> 00:30:03 about interstellar comets and the obfuscation
00:30:03 --> 00:30:04 of science when it comes to those. And
00:30:04 --> 00:30:06 they're definitely not aliens. And I'll say
00:30:06 --> 00:30:09 again, they definitely are not aliens. In
00:30:09 --> 00:30:12 this case, the exo Earth
00:30:12 --> 00:30:15 fatigue is real. People in the general public
00:30:15 --> 00:30:17 are convinced that we found planets like the
00:30:17 --> 00:30:19 Earth already. And I mean, it's great, it
00:30:19 --> 00:30:21 keeps people interested, but it also
00:30:21 --> 00:30:23 diminishes the impact when we finally do,
00:30:24 --> 00:30:25 you know, astronomers will finally find a
00:30:25 --> 00:30:27 planet that could genuinely be truly Earth.
00:30:27 --> 00:30:29 Like. We'll then need to do a lot of work to
00:30:29 --> 00:30:31 characterise it, but you can imagine in 10
00:30:31 --> 00:30:34 years time, we get data back from a planet
00:30:34 --> 00:30:37 that shows not only that it could be Earth
00:30:37 --> 00:30:38 like, but the surface temperature is right,
00:30:38 --> 00:30:39 and that there is liquid water in the
00:30:39 --> 00:30:42 atmosphere. And the scientific community will
00:30:42 --> 00:30:44 be, wow, this is our best discovery ever.
00:30:44 --> 00:30:46 This is so cool. And nobody'll care because,
00:30:46 --> 00:30:48 well, you've done it 10 times already. The
00:30:48 --> 00:30:49 media told me.
00:30:49 --> 00:30:51 Andrew Dunkley: So, yeah, I think I've found
00:30:51 --> 00:30:54 it. Um, a potentially habitable
00:30:54 --> 00:30:57 new planet has been discovered 146 light
00:30:57 --> 00:31:00 years away. Um, but then it goes.
00:31:00 --> 00:31:02 It goes on to say, but it might be minus 70
00:31:02 --> 00:31:05 degrees Celsius, um, but there's a storey
00:31:05 --> 00:31:06 like that coming out every other week.
00:31:07 --> 00:31:09 Jonti Horner: Um, and if you want to play that game, our
00:31:09 --> 00:31:11 definitions of habitability, based very much
00:31:11 --> 00:31:13 as we talked about in the previous episode,
00:31:13 --> 00:31:16 on our understanding of where
00:31:16 --> 00:31:18 Earth life could thrive and in the solar
00:31:18 --> 00:31:20 system. We've got potentially habitable
00:31:20 --> 00:31:22 worlds all over the place. Mars is
00:31:22 --> 00:31:23 potentially habitable on the borderline.
00:31:24 --> 00:31:26 Depending on what you think about bacteria in
00:31:26 --> 00:31:27 the atmosphere, Venus could be habitable for
00:31:27 --> 00:31:30 that type of life. We've got all the icy
00:31:30 --> 00:31:32 objects with buried subsurface oceans that
00:31:32 --> 00:31:34 are habitable, but not detectably habitable
00:31:34 --> 00:31:37 because there's ice in the way. I don't think
00:31:37 --> 00:31:40 it. It benefits people to overplay
00:31:40 --> 00:31:41 these discoveries, even though I fully
00:31:41 --> 00:31:44 understand the reason why people do,
00:31:45 --> 00:31:47 and I don't think it does anybody a service
00:31:47 --> 00:31:50 long term. Um, it is the unfortunate
00:31:50 --> 00:31:53 reality of what it is. But, hey,
00:31:53 --> 00:31:55 people are interested. Of course, you'll play
00:31:55 --> 00:31:57 to that in the kind of modern media cycle.
00:31:57 --> 00:31:59 Nobody remembers the retraction. They all
00:31:59 --> 00:32:01 remember the discovery. You know, everybody
00:32:01 --> 00:32:03 remembers cold fusion back from when I was a
00:32:03 --> 00:32:06 kid and a teenager. Um, that was, of course,
00:32:06 --> 00:32:07 published in the Journal of Irreproducible
00:32:07 --> 00:32:10 Results, otherwise known as Nature. Um,
00:32:10 --> 00:32:11 these things happen.
00:32:13 --> 00:32:14 Andrew Dunkley: Yeah, they do.
00:32:14 --> 00:32:16 Um, so, all right, where to next? With
00:32:17 --> 00:32:20 exoplanets, with, uh, so many
00:32:20 --> 00:32:22 discovered, um, that that's provided a
00:32:22 --> 00:32:25 baseline for the probability that every star
00:32:25 --> 00:32:28 has at least 10 planets around us.
00:32:29 --> 00:32:31 Jonti Horner: Um, we're finding them in a growing variety
00:32:31 --> 00:32:33 of ways. It's instructive a little bit to
00:32:33 --> 00:32:35 look back at history. You know, if I took you
00:32:35 --> 00:32:38 back to the early 1800s, our telescopes
00:32:38 --> 00:32:41 had finally got good enough to measure the
00:32:41 --> 00:32:43 motion of nearby stars against the background
00:32:43 --> 00:32:45 stars. Um, that allowed us to start measuring
00:32:45 --> 00:32:47 the distance to nearby stars using
00:32:47 --> 00:32:49 trigonometric parallax, where you look at a
00:32:49 --> 00:32:50 star from one side of the Earth's orbit, then
00:32:50 --> 00:32:52 the other and see it move against the
00:32:52 --> 00:32:54 background just like your finger moves if you
00:32:54 --> 00:32:56 look from one eye or the other. That same
00:32:56 --> 00:32:59 trick at ah, that time people start measuring
00:32:59 --> 00:33:01 it and they realise that nearby stars also
00:33:01 --> 00:33:04 moved through space. They were
00:33:04 --> 00:33:06 undergoing what we now know as proper motion,
00:33:06 --> 00:33:08 moving against the background stars in a
00:33:08 --> 00:33:10 straight line, which is their true space
00:33:10 --> 00:33:13 movement through the galaxy as seen by people
00:33:13 --> 00:33:15 on Earth. A guy called Friedrich
00:33:15 --> 00:33:18 Wilhelm Bessel, who was a fabulous astronomer
00:33:18 --> 00:33:20 in the early 1800s was doing
00:33:20 --> 00:33:23 observations of Sirius, which is our, uh, one
00:33:23 --> 00:33:25 of our class's star systems. It's a brightest
00:33:25 --> 00:33:28 star in the night sky and he found that once
00:33:28 --> 00:33:30 he took away the parallax Martian, the wobble
00:33:30 --> 00:33:31 left and right because of the Earth going
00:33:31 --> 00:33:34 around the sun, that Sirius was wobbling
00:33:34 --> 00:33:35 as it moved across the night sky. And it
00:33:35 --> 00:33:37 looked as though it was being pulled around
00:33:37 --> 00:33:39 by something as massive as the sun, but you
00:33:39 --> 00:33:42 could see nothing there. There obviously was
00:33:42 --> 00:33:44 something there pulling it around. It turns
00:33:44 --> 00:33:46 out that was the indirect discovery of what
00:33:46 --> 00:33:48 we now know as Sirius B, the white dwarf
00:33:48 --> 00:33:50 star. It wasn't the first white dwarf to be
00:33:50 --> 00:33:53 found, but in this case it was discovered
00:33:53 --> 00:33:55 indirectly. We saw Sirius doing something
00:33:55 --> 00:33:58 unexpected. We saw it wobbling and we used
00:33:58 --> 00:34:00 that to infer the presence of the white dwarf
00:34:00 --> 00:34:03 star around it. And of course we got another
00:34:03 --> 00:34:05 example of this a little bit later in the
00:34:05 --> 00:34:08 1800s with the discovery of Neptune, not
00:34:08 --> 00:34:10 through direct observation, but initially
00:34:10 --> 00:34:13 through mathematics, through John, um,
00:34:13 --> 00:34:15 Couch, Adams and Urban, uh, Le
00:34:15 --> 00:34:18 Verrier, doing calculations of how Uranus
00:34:18 --> 00:34:21 was moving across the sky, seeing that it was
00:34:21 --> 00:34:24 moving as though something we couldn't see
00:34:24 --> 00:34:26 was pulling on it. Predicting where that
00:34:26 --> 00:34:27 thing will be in Neptune was duly found. So
00:34:27 --> 00:34:30 they set this heritage of inferring
00:34:30 --> 00:34:32 the presence of something we cannot see
00:34:32 --> 00:34:35 because of its effect on something else. And
00:34:35 --> 00:34:38 that has been foundational to how we find
00:34:38 --> 00:34:40 planets around other stars. That's
00:34:40 --> 00:34:42 fundamentally how for more than 99% of
00:34:42 --> 00:34:45 them we've discovered them. There have been
00:34:45 --> 00:34:48 slip ups on the way in the 1940s,
00:34:48 --> 00:34:50 1950s, Edwin Vanderkamp, who's director of
00:34:50 --> 00:34:52 Spruill Observatory, thought he'd found
00:34:52 --> 00:34:54 planets around Barnard's Star, which is a
00:34:54 --> 00:34:56 star with the biggest proper motion in the
00:34:56 --> 00:34:58 sky. Turned out that he'd actually discovered
00:34:58 --> 00:35:00 the cleaner because what was happening was
00:35:00 --> 00:35:03 that his telescope was getting dirty. He used
00:35:03 --> 00:35:05 a lens telescope, a refracting telescope
00:35:06 --> 00:35:08 as the front Objective lens got
00:35:08 --> 00:35:11 Grottier the way in which it meant red light
00:35:11 --> 00:35:13 compared to blue light changed, causing
00:35:13 --> 00:35:15 Barnard's star position to shift against the
00:35:15 --> 00:35:16 background sounds. And when it got cleaned,
00:35:16 --> 00:35:19 it all went back to normal. He went very sad.
00:35:19 --> 00:35:21 But he went to his grave in the 70s convinced
00:35:22 --> 00:35:23 he was a victim of an injustice and he'd
00:35:23 --> 00:35:26 found planets around Barnassar. We now have
00:35:26 --> 00:35:27 found planets around Barnard, sir, but
00:35:27 --> 00:35:29 they're very different to the ones he
00:35:29 --> 00:35:32 proposed. We also had the fabulous
00:35:32 --> 00:35:34 Storey just prior to the pulsar planets
00:35:34 --> 00:35:36 actually being found, the same researchers
00:35:37 --> 00:35:38 thought they'd found a planet around a
00:35:38 --> 00:35:40 different pulsar and announced it at a
00:35:40 --> 00:35:42 conference. And someone went away and said a
00:35:42 --> 00:35:44 little bit, bit. Something a bit odd about
00:35:44 --> 00:35:46 this. What had been done was they were
00:35:46 --> 00:35:49 measuring the timing of the pulsars. So
00:35:49 --> 00:35:51 pulsars are super, ah, condensed
00:35:51 --> 00:35:54 neutron stars, leftovers from the explosion
00:35:54 --> 00:35:56 of star as a supernova, which have a couple
00:35:56 --> 00:35:58 of magnetic hotspots on their surface. And as
00:35:58 --> 00:36:00 they spin, they beam radio waves into space
00:36:00 --> 00:36:02 like lighthouse beams. And when the beam
00:36:02 --> 00:36:05 sweeps across as we get pulses of radio waves
00:36:05 --> 00:36:06 like the ticking of a clock.
00:36:07 --> 00:36:09 Andrew Dunkley: Yep. With this pulse, they're very, they're
00:36:09 --> 00:36:10 very precise, aren't they?
00:36:10 --> 00:36:11 Jonti Horner: Yeah, they're viewed as being the most
00:36:11 --> 00:36:13 accurate clocks in the universe, aside from
00:36:13 --> 00:36:15 when they have the old glitch or. And I've
00:36:15 --> 00:36:18 had plenty of watchers that do that in this
00:36:18 --> 00:36:20 case, uh, he was observing this pulsar and
00:36:20 --> 00:36:22 sometimes the pulses arrived a little early,
00:36:22 --> 00:36:23 sometimes they arrived a little there. And
00:36:23 --> 00:36:26 this was happening periodically, so
00:36:26 --> 00:36:28 ruled everything else out. There must be
00:36:28 --> 00:36:29 something causing the distance between the
00:36:29 --> 00:36:31 pulsar and the solar system to vary
00:36:31 --> 00:36:33 periodically though, uh, it must be a planet.
00:36:34 --> 00:36:36 Turned out that after the conference someone
00:36:36 --> 00:36:38 said, there's something a little bit odd
00:36:38 --> 00:36:39 here, maybe you should just do a double
00:36:39 --> 00:36:41 cheque before you publish it. Went away and
00:36:41 --> 00:36:43 found a single typo in their code that meant
00:36:43 --> 00:36:45 they didn't properly account for the motion
00:36:45 --> 00:36:47 of the Earth around the sun. So they had
00:36:47 --> 00:36:49 discovered a planet, but they discovered that
00:36:49 --> 00:36:50 the one that they were set on, they
00:36:50 --> 00:36:53 discovered the Earth. I mean it's a
00:36:53 --> 00:36:56 fabulous discovery. Now we laugh about this,
00:36:56 --> 00:36:58 but it shows how hard these observations are.
00:36:58 --> 00:37:00 Uh, finding planets around other stars is
00:37:01 --> 00:37:02 incredibly difficult. We've had the
00:37:02 --> 00:37:05 wherewithal to understand the methods
00:37:05 --> 00:37:07 that we would use for a couple of hundred
00:37:07 --> 00:37:10 years, but it was only in the
00:37:10 --> 00:37:13 90s it really became feasible to do them. And
00:37:13 --> 00:37:15 in those early days in particular, there were
00:37:15 --> 00:37:17 two methods that hugely
00:37:17 --> 00:37:20 dominated. For the first, probably 10
00:37:20 --> 00:37:23 years, 12 years of the exoplanet area era,
00:37:23 --> 00:37:25 the main way we found planets was what you
00:37:25 --> 00:37:27 call the radial velocity technique, the
00:37:27 --> 00:37:29 wobble technique, which is using the Doppler
00:37:29 --> 00:37:32 effect. And you see a distance star. And, um,
00:37:32 --> 00:37:33 we can measure its light and we can break
00:37:33 --> 00:37:35 that light to its component colours, seeing
00:37:35 --> 00:37:37 what we call the Fraunhofel lines littered
00:37:37 --> 00:37:39 across it, which are dark lines that are the
00:37:39 --> 00:37:41 chemical fingerprint of what the star's made
00:37:41 --> 00:37:43 of. And, um, we can measure their positions
00:37:43 --> 00:37:45 in the lab incredibly precisely. And if the
00:37:45 --> 00:37:47 star's moving towards us, its light gets a
00:37:47 --> 00:37:49 bit blue shifted and all those lines move a
00:37:49 --> 00:37:51 little bit to the blue. And if it's moving
00:37:51 --> 00:37:52 away from us, they move a little bit to the
00:37:52 --> 00:37:54 red. And if you can monitor it for long
00:37:54 --> 00:37:56 enough, you can see the star coming backward
00:37:56 --> 00:37:59 and forward, it's wobbling. You can infer the
00:37:59 --> 00:38:01 presence of something massive pulling it
00:38:01 --> 00:38:03 round. You can figure out the, the orbital
00:38:03 --> 00:38:06 distance of that object by how
00:38:06 --> 00:38:08 long it takes for the wobble. So it comes
00:38:08 --> 00:38:10 towards us, goes away, comes towards us again
00:38:10 --> 00:38:13 as it does one full lap. That gives you the
00:38:13 --> 00:38:16 orbital period. You can infer the mass based
00:38:16 --> 00:38:18 on the size of the wobble. But we're only
00:38:18 --> 00:38:19 measuring that component along our line of
00:38:19 --> 00:38:21 sight. So you get a minimum mass that it
00:38:21 --> 00:38:23 could be, and it could be higher than that.
00:38:23 --> 00:38:25 So we can learn about the orbit. That's the
00:38:25 --> 00:38:27 radial velocity technique. And that is an
00:38:27 --> 00:38:29 indirect method. You see the station wobbling
00:38:29 --> 00:38:31 and infer the presence of a planet or planets
00:38:31 --> 00:38:33 around it. The technique that's taken over
00:38:33 --> 00:38:36 from it is the transit technique. That's
00:38:36 --> 00:38:38 where a planet's going around its star and
00:38:38 --> 00:38:39 its orbits just lined up right, that every
00:38:39 --> 00:38:41 time it goes around, it blocks a bit of the
00:38:41 --> 00:38:43 star's light. The star dims and then
00:38:43 --> 00:38:45 brightens again periodically. And, um, by
00:38:45 --> 00:38:47 measuring the periodic dimming, you can infer
00:38:47 --> 00:38:49 the presence of something blocking the star's
00:38:49 --> 00:38:51 light. Again, that gives you the orbital
00:38:51 --> 00:38:54 period, because you get one dip per orbit and
00:38:54 --> 00:38:56 it gives you the size, the diameter of the
00:38:56 --> 00:38:57 planet, because a bigger planet will block,
00:38:57 --> 00:38:59 block more light. But fundamentally, again,
00:38:59 --> 00:39:02 it's an indirect method. You see a star doing
00:39:02 --> 00:39:04 something odd and infer the presence of a
00:39:04 --> 00:39:07 planet. Now, both these methods
00:39:08 --> 00:39:10 were known and were used for hundreds of
00:39:10 --> 00:39:12 years. We saw binary
00:39:12 --> 00:39:15 stars being observed because of the
00:39:15 --> 00:39:18 dimming during the eclipses. Um, John
00:39:18 --> 00:39:20 Goodrick, um, a British astronomer who died
00:39:20 --> 00:39:22 at a very young age, explained Algol. The
00:39:22 --> 00:39:24 Wink of Kingdom star has been a binary star
00:39:24 --> 00:39:27 back in the early 1700s. That is effectively
00:39:27 --> 00:39:29 the same as A transit technique, it's just
00:39:29 --> 00:39:32 you've got a bigger, uh, blocker. Problem is
00:39:32 --> 00:39:34 our eyes are only sensitive to variations in
00:39:34 --> 00:39:37 light at about the 20% level. Smaller
00:39:37 --> 00:39:38 variations than that, we just don't pick up.
00:39:38 --> 00:39:40 Your lights can be flickering by 20% and
00:39:40 --> 00:39:43 you'll barely notice it. For a binary star,
00:39:43 --> 00:39:45 the brightness can change by a factor of two
00:39:45 --> 00:39:48 or more. For an exoplanet, Jupiter,
00:39:48 --> 00:39:51 uh, blocks about 1% of the light from the sun
00:39:51 --> 00:39:53 on that is just something you cannot see with
00:39:53 --> 00:39:56 a naked eye. So to be able to use the transit
00:39:56 --> 00:39:58 technique, we had to wait for detectors that
00:39:58 --> 00:40:00 were sensitive enough to measure incredibly
00:40:00 --> 00:40:02 fine variations in brightness to come along,
00:40:02 --> 00:40:04 which is why we've only been able to use a
00:40:04 --> 00:40:07 transit technique this millennium. It wasn't
00:40:07 --> 00:40:09 really possible before that. Similarly, with
00:40:09 --> 00:40:12 the radial velocity technique, we could
00:40:12 --> 00:40:14 measure the wobble of stars from binary
00:40:14 --> 00:40:17 stars for decades. Because the movement of
00:40:17 --> 00:40:18 the lines were sufficiently big, you could
00:40:18 --> 00:40:20 measure it on a photographic plate and you
00:40:20 --> 00:40:21 could measure speeds of kilometres per
00:40:21 --> 00:40:23 second. Fairly easy.
00:40:23 --> 00:40:25 Planets like Jupiter going around the sun
00:40:25 --> 00:40:28 cause wobbles measured in metres per second,
00:40:28 --> 00:40:31 maybe 10 metres per second. That is, again,
00:40:31 --> 00:40:33 this such a small wobble that taking photos
00:40:33 --> 00:40:36 on photographic plates of the spectral lines,
00:40:36 --> 00:40:38 the resolution isn't good enough. Our
00:40:38 --> 00:40:41 spectrograph we've got up at Matt Kent in our
00:40:41 --> 00:40:43 facility, Merv Ross Rallis. Typically, the
00:40:43 --> 00:40:45 measurements we're making are measurements of
00:40:45 --> 00:40:48 a thousandth of a pixel shift
00:40:48 --> 00:40:50 in a given line. And the only way we can do
00:40:50 --> 00:40:52 that is because you're seeing thousands of
00:40:52 --> 00:40:54 lines at once and you can work out
00:40:54 --> 00:40:56 statistically what they're doing. So even
00:40:56 --> 00:40:58 with the most modern cameras and most modern
00:40:58 --> 00:41:00 technology, it's still hard. And that's why,
00:41:00 --> 00:41:03 even though we had the wherewithal to
00:41:03 --> 00:41:05 understand the physics and, um, to know how
00:41:05 --> 00:41:07 to do the techniques, 200 years ago,
00:41:08 --> 00:41:10 we were stuck in a technology gap. We just
00:41:10 --> 00:41:12 had to wait for the technology to reach the
00:41:12 --> 00:41:14 right place. And that's why finding the first
00:41:14 --> 00:41:16 was hard. But once you found one, you'll find
00:41:16 --> 00:41:18 tech 10, you'll find 100, you'll find a
00:41:18 --> 00:41:20 thousand. I'd m point people, incidentally,
00:41:20 --> 00:41:23 to the astonishingly beautiful videos by
00:41:23 --> 00:41:25 System Sounds, in partnership with NASA, that
00:41:25 --> 00:41:28 were put out to celebrate the 4 and 5000th
00:41:28 --> 00:41:31 discovered exoplanets, where they run the
00:41:31 --> 00:41:33 discoveries over time on a, on a map of the
00:41:33 --> 00:41:35 sky where the discoveries are marked with a
00:41:35 --> 00:41:38 little ring. And every planet gets its own
00:41:38 --> 00:41:40 musical note, where the musical note tells
00:41:40 --> 00:41:42 you the orbital period of that planet around
00:41:42 --> 00:41:44 the star. So a high Pitched note like a ding
00:41:45 --> 00:41:46 will be a planet really close and going
00:41:46 --> 00:41:48 around really quick and low pitch note like a
00:41:48 --> 00:41:51 ding that'll be a planet a long, long way
00:41:51 --> 00:41:53 away going around really slowly. And um, it
00:41:53 --> 00:41:56 shows you the diversity we found but it also
00:41:56 --> 00:41:59 shows you this incredibly accelerating
00:41:59 --> 00:42:01 rate at which we're getting better at doing
00:42:01 --> 00:42:03 it because now we've crossed that threshold
00:42:03 --> 00:42:06 where the technology wasn't good enough. And
00:42:06 --> 00:42:08 now the technology keeps getting better, we
00:42:08 --> 00:42:09 get better at doing it and the numbers
00:42:09 --> 00:42:11 continue m to rise. And depending who you
00:42:11 --> 00:42:13 talk to, there are people who suggest we may
00:42:13 --> 00:42:15 well actually we'll certainly cross the
00:42:15 --> 00:42:17 10 count by 2030.
00:42:18 --> 00:42:20 Might not be long after that before we cross
00:42:20 --> 00:42:22 100 mark. That will all depend on Gaia,
00:42:22 --> 00:42:24 but also the Nancy Grace Roman telescope
00:42:24 --> 00:42:26 that's due to launch in a few years time.
00:42:27 --> 00:42:30 Andrew Dunkley: Yeah, it's going to be amazing. Uh,
00:42:30 --> 00:42:32 and uh, who knows what we will find.
00:42:33 --> 00:42:35 And we'll talk about uh, a bit more in a
00:42:35 --> 00:42:37 moment here on Space Nuts.
00:42:40 --> 00:42:42 Three, two, one.
00:42:43 --> 00:42:44 Jonti Horner: Space Nuts.
00:42:44 --> 00:42:46 Andrew Dunkley: And you're with Andrew Dunkley and Professor
00:42:46 --> 00:42:49 Jonty Horner. We're talking exoplanets on
00:42:49 --> 00:42:52 this special episode. Uh, it's
00:42:52 --> 00:42:55 our last segment. So, um, over to you
00:42:55 --> 00:42:57 Jonty. Where do you, where do you want to go
00:42:57 --> 00:42:59 to finish off this particularly interesting
00:42:59 --> 00:42:59 topic?
00:42:59 --> 00:43:02 Jonti Horner: Well, I think it's also worth flagging out
00:43:02 --> 00:43:04 the diversity places that are doing this work
00:43:04 --> 00:43:05 as well. I mean amateur astronomers are
00:43:05 --> 00:43:07 contributing a huge amount. We're now at the
00:43:07 --> 00:43:09 point where, where the technology's moved on
00:43:09 --> 00:43:12 enough that you can observe and measure
00:43:12 --> 00:43:15 exoplanet transits using a fairly cheap off
00:43:15 --> 00:43:17 the shelf telescope. Many amateur astronomers
00:43:17 --> 00:43:19 will occasionally observe the transit of one
00:43:19 --> 00:43:21 of our bright planets. There was an article
00:43:21 --> 00:43:23 on Australia's ABC News recently about some
00:43:23 --> 00:43:25 amateur astronomers who banded together to be
00:43:25 --> 00:43:28 involved in planet discovery. I'm
00:43:29 --> 00:43:32 increasingly proud of the facility we've got
00:43:32 --> 00:43:34 at Uni sq, which is as far as we know, the
00:43:34 --> 00:43:37 only dedicated Southern Hemisphere exoplanet
00:43:37 --> 00:43:38 observatory in the Southern Hemisphere.
00:43:38 --> 00:43:40 There's a lot of facilities looking for them,
00:43:40 --> 00:43:43 but we've got our own facility at Matt Kent
00:43:43 --> 00:43:46 Observatory just outside Toowoomba that all
00:43:46 --> 00:43:47 it does is look for planets and learn more
00:43:47 --> 00:43:49 about them. It doesn't split its time with
00:43:49 --> 00:43:52 other tasks. Its job is planet search.
00:43:52 --> 00:43:54 And it's really important to stress that
00:43:54 --> 00:43:56 particularly for the younger listeners from
00:43:56 --> 00:43:58 Australia, there's this perception
00:43:59 --> 00:44:01 that the only place you can go to do real
00:44:01 --> 00:44:03 science and to become a scientist is to go to
00:44:03 --> 00:44:05 the big cities, the big capital cities, to
00:44:05 --> 00:44:08 the group Fake Universities and for people in
00:44:08 --> 00:44:09 regional Australia, and particularly people
00:44:09 --> 00:44:12 from less prestigious
00:44:12 --> 00:44:14 backgrounds, lower socioeconomic backgrounds,
00:44:14 --> 00:44:16 all the rest of it, there's this very much
00:44:16 --> 00:44:18 feeling that it's a big city thing and you've
00:44:18 --> 00:44:19 got to go to the right schools. But we're at
00:44:19 --> 00:44:22 a small regional university in regional
00:44:22 --> 00:44:24 Australia and we're leading the world in
00:44:24 --> 00:44:27 this. You know, we have two of my colleagues,
00:44:27 --> 00:44:29 um, Professor George Zhao and Associate
00:44:29 --> 00:44:31 Professor Chelsea Huang are, uh, between them
00:44:31 --> 00:44:34 responsible for 30% of all time Australia
00:44:34 --> 00:44:36 has ever had allocated on the James Webb
00:44:36 --> 00:44:39 Space Telescope. And, uh, they've sat to
00:44:39 --> 00:44:41 study planets around other stars. So I do
00:44:41 --> 00:44:43 want to stress to people listening that this
00:44:43 --> 00:44:45 is not just something that's done in the US
00:44:45 --> 00:44:47 or it's not just something that's done at the
00:44:47 --> 00:44:49 world's top 10 universities. It's something
00:44:49 --> 00:44:51 that you can participate in yourself. There's
00:44:51 --> 00:44:53 some fabulous citizen science programmes out
00:44:53 --> 00:44:55 there and uh, there is going to be an
00:44:55 --> 00:44:58 increasing extreme wealth
00:44:58 --> 00:45:00 of data coming out in the coming years that
00:45:00 --> 00:45:02 uh, astronomers simply won't have enough
00:45:02 --> 00:45:04 hands to go through. So I'm sure that, that
00:45:04 --> 00:45:06 if people keep their eyes out, there will be
00:45:06 --> 00:45:08 other citizen science programmes pop up in
00:45:08 --> 00:45:10 the coming years. You know, we've got,
00:45:10 --> 00:45:12 currently I'm looking at the wonderful NASA
00:45:12 --> 00:45:15 Rexoplanet archive here, looking at the
00:45:15 --> 00:45:16 different methods planets have been
00:45:16 --> 00:45:18 discovered by, and we've now got, I think
00:45:18 --> 00:45:20 it's 11 different methods that have been
00:45:20 --> 00:45:22 used. Of our
00:45:22 --> 00:45:25 6283 planets,
00:45:25 --> 00:45:28 4640 have been found by the
00:45:28 --> 00:45:30 transit method. That's overwhelmingly the
00:45:30 --> 00:45:32 most successful now. And that's because you
00:45:32 --> 00:45:33 can play a numbers game. You can look at
00:45:33 --> 00:45:36 thousands of stars at once, looking to see if
00:45:36 --> 00:45:38 any of them wink. And that's what the Kepler
00:45:38 --> 00:45:40 spacecraft and more recently NASA's test
00:45:40 --> 00:45:43 spacecraft did. We've got nearly
00:45:43 --> 00:45:44 1200 planets found with the radial velocity
00:45:44 --> 00:45:47 method, the wobbled method. Now should be
00:45:47 --> 00:45:49 said this is a discovery method and a lot of
00:45:49 --> 00:45:51 these planets have then been studied using
00:45:51 --> 00:45:52 other methods. But this is how they were
00:45:52 --> 00:45:55 found. So between those two were, uh, what,
00:45:55 --> 00:45:58 5800 of the known
00:45:58 --> 00:46:00 planets, 6200 were found by those.
00:46:01 --> 00:46:03 That's 90 odd percent of the
00:46:03 --> 00:46:06 remainder. We, uh, know of 278 planets that
00:46:06 --> 00:46:08 were found by microlensing. This is where you
00:46:08 --> 00:46:11 look at very distant stars like the middle of
00:46:11 --> 00:46:13 the galaxy and look for planets and stars
00:46:13 --> 00:46:15 that we can't see passing along our line of
00:46:15 --> 00:46:18 sight and their mass bending light to
00:46:18 --> 00:46:20 cause that background star to brighten then
00:46:20 --> 00:46:23 fade. Very small number found so far.
00:46:23 --> 00:46:25 But the Nancy Grace Roman telescope will
00:46:25 --> 00:46:28 likely discover thousands, if not tens of
00:46:28 --> 00:46:30 thousands of microlensing planets in the
00:46:30 --> 00:46:32 coming years. Because that telescope's going
00:46:32 --> 00:46:33 to go and stare at the middle of the galaxy,
00:46:33 --> 00:46:36 among other things, and should be very useful
00:46:36 --> 00:46:39 at that. We've got nearly a hundred planets
00:46:39 --> 00:46:41 now discovered by direct imaging,
00:46:41 --> 00:46:43 and they're really interesting because
00:46:43 --> 00:46:44 they're the ones where we actually see the
00:46:44 --> 00:46:46 planet and we find it by seeing the light
00:46:46 --> 00:46:48 from the planet. So it's amazing that we're
00:46:48 --> 00:46:51 nearly at 100 there. And my favourite movie
00:46:51 --> 00:46:53 of all time Time is really the
00:46:54 --> 00:46:57 movie of the planets orbiting the star HR
00:46:57 --> 00:46:59 8799, where observations spanning
00:46:59 --> 00:47:01 more than decade now have been made, where
00:47:01 --> 00:47:03 you can see four planets around that star and
00:47:03 --> 00:47:06 watch them move in their orbits. And you
00:47:06 --> 00:47:08 think from where we were when I was a kid,
00:47:08 --> 00:47:10 where we didn't even know if there were any
00:47:10 --> 00:47:12 planets out there, we can now watch some of
00:47:12 --> 00:47:15 them go around their stars in real time.
00:47:15 --> 00:47:16 That's just astonishing.
00:47:17 --> 00:47:19 There's a lot of other really niche methods
00:47:19 --> 00:47:20 that have been used news, but they're kind of
00:47:20 --> 00:47:23 the big four, I'd say. And I think the one
00:47:23 --> 00:47:25 that's going to grow over the coming decade
00:47:25 --> 00:47:28 more than any other is astrometry. So at the
00:47:28 --> 00:47:30 minute there is a grand total of six planets
00:47:30 --> 00:47:32 that have been discovered by astrometry. This
00:47:32 --> 00:47:34 is measuring the positions of stars in the
00:47:34 --> 00:47:36 sky and seeing them wobble side to side. It's
00:47:36 --> 00:47:39 what Bessel did with Sirius to find Sirius B.
00:47:39 --> 00:47:41 We've only found six so far, but the Gaia,
00:47:41 --> 00:47:44 uh, spacecraft observed for a long time,
00:47:44 --> 00:47:45 finished observing, but we're still getting
00:47:45 --> 00:47:47 new data releases from. From it. Gaia data
00:47:47 --> 00:47:50 release number four is coming allegedly in
00:47:50 --> 00:47:52 December this year. Maybe push back a little
00:47:52 --> 00:47:55 bit, but that's where they will have enough
00:47:55 --> 00:47:57 quality and analysis of the data and enough
00:47:58 --> 00:48:00 time period the data covers to start finding
00:48:00 --> 00:48:03 planets in the Gaia data doing astrometry
00:48:04 --> 00:48:06 and people are still predicting that could
00:48:06 --> 00:48:08 yield tens of thousands of planets. Even if
00:48:08 --> 00:48:11 you're a pessimist, it's easy that Gaia
00:48:11 --> 00:48:14 could take over from Kepler and TESS as a
00:48:14 --> 00:48:16 tool that found the most planets. That's just
00:48:16 --> 00:48:18 in the next year or two. And what we're doing
00:48:18 --> 00:48:21 then we're finding more, but where we're
00:48:21 --> 00:48:22 shifting to is not just finding them, but
00:48:22 --> 00:48:25 learning more about them, characterising
00:48:25 --> 00:48:27 them. And that's where the future of
00:48:27 --> 00:48:29 exoplanet science is. It's not just enough
00:48:29 --> 00:48:31 now to find a planet, we want to learn more
00:48:31 --> 00:48:33 about it. What's its atmosphere made of?
00:48:34 --> 00:48:36 What's its internal composition? What's it
00:48:36 --> 00:48:39 like? That's where we're going. And
00:48:39 --> 00:48:42 um, we're making great leaps in that we are
00:48:42 --> 00:48:44 finding out what chemical species are in the
00:48:44 --> 00:48:45 atmospheres of different planets. Currently
00:48:45 --> 00:48:47 only really doing it for the very biggest
00:48:47 --> 00:48:49 ones because of the easiest to observe. But
00:48:49 --> 00:48:51 that's very much the future. And that's what
00:48:51 --> 00:48:53 will lead to the search for life elsewhere,
00:48:53 --> 00:48:55 which I think is what really hooks a lot of
00:48:55 --> 00:48:56 people into the subject.
00:48:57 --> 00:48:59 Andrew Dunkley: Yeah, it's fascinating. For the record, the
00:48:59 --> 00:49:02 first actual photograph of an
00:49:02 --> 00:49:03 Exoplanet was in
00:49:03 --> 00:49:05
00:49:07 --> 00:49:08 Jonti Horner: and
00:49:08 --> 00:49:10 Andrew Dunkley: it was 2m, um, 1207b.
00:49:10 --> 00:49:10 Jonti Horner: Yes.
00:49:11 --> 00:49:13 Andrew Dunkley: Which apparently is an exoplanet, uh,
00:49:13 --> 00:49:15 orbiting a gas giant.
00:49:16 --> 00:49:18 Yes. Which is a big, a big one,
00:49:18 --> 00:49:21 about five times the mass of Jupiter. So, um,
00:49:21 --> 00:49:23 yeah, so that was the first one ever
00:49:23 --> 00:49:25 photographed that we actually got to see a
00:49:25 --> 00:49:28 picture of rather than just identified
00:49:28 --> 00:49:29 through some.
00:49:29 --> 00:49:30 Jonti Horner: I mean we're still just seeing them as a
00:49:30 --> 00:49:33 single pixel. We're not going to be at the
00:49:33 --> 00:49:35 point of Star Trek type images of the surface
00:49:35 --> 00:49:37 for a long, long, long time because the
00:49:37 --> 00:49:39 resolutions are challenged there. But that
00:49:39 --> 00:49:42 was a breathtaking thing. And it is worth
00:49:42 --> 00:49:44 noting that the overwhelming majority of the
00:49:44 --> 00:49:46 direct imaging planets that we've imaged are
00:49:46 --> 00:49:49 um, massive and um, young. And the thing
00:49:49 --> 00:49:50 about them being young is they're still
00:49:50 --> 00:49:52 hotter, which means they glow brighter and
00:49:52 --> 00:49:53 therefore are easier to see.
00:49:54 --> 00:49:57 Andrew Dunkley: M okay, um,
00:49:57 --> 00:50:00 last chance to talk about exoplanets.
00:50:00 --> 00:50:01 We're going to wrap it up in a sec. Any, any
00:50:01 --> 00:50:02 final comments?
00:50:02 --> 00:50:05 Jonti Horner: Well, I think, I think there is so much more
00:50:05 --> 00:50:07 we could talk about. I mean like every topic
00:50:07 --> 00:50:09 we get onto, I talk too much. But we could
00:50:09 --> 00:50:10 fill several hours worth of excitement
00:50:10 --> 00:50:13 digging into the nitty gritty. But I think
00:50:13 --> 00:50:14 the thing that leaps out to me probably even
00:50:14 --> 00:50:17 more than the ubiquity of planets, the fact
00:50:17 --> 00:50:19 that they're everywhere, is the diversity.
00:50:19 --> 00:50:22 You know, when I was growing up, we thought
00:50:22 --> 00:50:24 that there would be other planetary systems,
00:50:24 --> 00:50:25 but we weren't sure. But we assumed they'd be
00:50:25 --> 00:50:26 like the solar system, you know, rocky
00:50:26 --> 00:50:28 planets on the interior, giant planets on the
00:50:28 --> 00:50:31 outside. Yeah. And the first planets
00:50:31 --> 00:50:33 discovered shattered that you had planets
00:50:33 --> 00:50:35 around a pulsar, which makes no sense.
00:50:36 --> 00:50:37 Um, we think there are probably a second
00:50:37 --> 00:50:39 generation of planets. The initial planets
00:50:39 --> 00:50:41 there were destroyed and new ones formed
00:50:41 --> 00:50:43 after the supernova, but we're not sure. You
00:50:43 --> 00:50:45 then found a hot Jupiter, a planet the size
00:50:45 --> 00:50:47 of Jupiter, going around a star like the sun
00:50:47 --> 00:50:49 every few days and that was enough to
00:50:49 --> 00:50:51 revolutionise our understanding of how
00:50:51 --> 00:50:53 planetary systems form. And with every new
00:50:53 --> 00:50:55 technique and with every new facility and
00:50:55 --> 00:50:58 with every new way of finding planets, we
00:50:58 --> 00:51:00 find planets that are more different to the
00:51:00 --> 00:51:02 solar system than we could ever possibly
00:51:02 --> 00:51:04 imagine. The lightest, well, not the
00:51:04 --> 00:51:06 lightest, the fluffiest planets, the lowest
00:51:06 --> 00:51:08 density planets are so fluffy that they're
00:51:08 --> 00:51:10 being torn apart by their stars. We mentioned
00:51:10 --> 00:51:13 them early on. The highest density
00:51:13 --> 00:51:16 of any planet in the exoplanet catalogue is
00:51:16 --> 00:51:18 denser than any metal or mineral or anything
00:51:18 --> 00:51:21 known on Earth by such a large distance. Uh,
00:51:21 --> 00:51:22 there is speculation that it could be a
00:51:22 --> 00:51:24 fragment of a white dwarf or something. That
00:51:24 --> 00:51:27 it could be actually not a lump
00:51:27 --> 00:51:29 of iron but a lump of white dwarf material or
00:51:29 --> 00:51:32 something. We just don't know. And everything
00:51:32 --> 00:51:34 in between. We're finding that the planets in
00:51:34 --> 00:51:37 our solar system are pretty
00:51:37 --> 00:51:39 average. We still don't have a handle on
00:51:40 --> 00:51:42 how common are planets like the Earth. How
00:51:42 --> 00:51:44 common are planets on, like the Earth? On
00:51:44 --> 00:51:47 Earth like orbits. We also don't really have
00:51:47 --> 00:51:49 a handle yet on how common are ah, planets
00:51:49 --> 00:51:50 like Jupiter and Saturn, in other words
00:51:50 --> 00:51:53 called Jupiters planets that take a decade
00:51:53 --> 00:51:55 um, or more to orbit their star because
00:51:55 --> 00:51:56 finding them hard you need to watch for a
00:51:56 --> 00:51:59 long time. So we know much more about planets
00:51:59 --> 00:52:01 close in and planets very different to our
00:52:01 --> 00:52:04 own than we do about planet planetary systems
00:52:04 --> 00:52:05 similar to the solar system. So I think one
00:52:05 --> 00:52:08 of the big questions now is not is the solar
00:52:08 --> 00:52:11 system unique but rather how
00:52:11 --> 00:52:13 unusual or usual is the solar system,
00:52:14 --> 00:52:17 our planetary systems like our one common or
00:52:17 --> 00:52:19 are we a bit of an exception? We're not
00:52:19 --> 00:52:21 really in a position to answer um, that yet.
00:52:21 --> 00:52:24 It seems that the frequency of
00:52:24 --> 00:52:26 Jupiter like planets around other stars is
00:52:26 --> 00:52:29 somewhere between 5 and 20%. And by Jupiter
00:52:29 --> 00:52:32 like, I mean Jupiter mass on a Jupiter like
00:52:32 --> 00:52:34 orbit around stars like the sun.
00:52:34 --> 00:52:37 But that's a big variety of,
00:52:37 --> 00:52:39 you know, possibilities we just don't know
00:52:39 --> 00:52:42 yet. And so even though we now
00:52:42 --> 00:52:44 know that planets are everywhere, we've
00:52:44 --> 00:52:46 barely scratched the surface. And it's the
00:52:46 --> 00:52:47 kind of thing where if we had this chat again
00:52:47 --> 00:52:49 in five years time the numbers would be
00:52:49 --> 00:52:51 different but there would be whole swathes of
00:52:51 --> 00:52:54 new knowledge then that we can't even predict
00:52:54 --> 00:52:56 now. There will be things that surprise us
00:52:56 --> 00:52:58 just as much in the years to come as hot
00:52:58 --> 00:53:00 Jupiter's and pulsar planets did at the dawn
00:53:00 --> 00:53:02 of the era. And that's part of the fun.
00:53:03 --> 00:53:05 Andrew Dunkley: Yeah, and there'll probably be planets we
00:53:05 --> 00:53:08 can't even imagine that would
00:53:08 --> 00:53:10 be discovered that we couldn't have even
00:53:10 --> 00:53:13 contemplated, contemplated existing.
00:53:14 --> 00:53:17 Um, and I can't even pretend to make one up
00:53:17 --> 00:53:18 at the moment. But there will be. Of course
00:53:18 --> 00:53:21 the search, as you mentioned, is for an Earth
00:53:21 --> 00:53:24 like planet. A planet, a, uh,
00:53:24 --> 00:53:26 rocky planet in the right place orbiting a
00:53:26 --> 00:53:29 star like ours, um, that
00:53:29 --> 00:53:31 basically duplicates Earth. We just haven't
00:53:31 --> 00:53:33 found one of those yet, have we?
00:53:33 --> 00:53:36 Jonti Horner: No, no. With a caveat we may
00:53:36 --> 00:53:38 have done and it have not been picked up.
00:53:38 --> 00:53:40 There's more to learn about these things.
00:53:40 --> 00:53:43 Things I still think of the planets
00:53:43 --> 00:53:45 we've found so far. Venus is more like the
00:53:45 --> 00:53:48 Earth than anything we've found so far. I
00:53:48 --> 00:53:51 also think though, that that's even a
00:53:51 --> 00:53:52 difficult question because what do we mean by
00:53:52 --> 00:53:54 it being like the Earth? If you went and
00:53:54 --> 00:53:57 looked at the solar system 4 billion years
00:53:57 --> 00:53:59 ago, I don't think you'd have considered the
00:53:59 --> 00:54:01 Earth an Earth like planet. It would have had
00:54:01 --> 00:54:03 this incredibly thick atmosphere, very
00:54:03 --> 00:54:04 different to ours, with a very different
00:54:04 --> 00:54:07 composition. It would have been outside
00:54:07 --> 00:54:09 the edge of the habitable zone because the
00:54:09 --> 00:54:11 sun was that much fainter. But it would
00:54:11 --> 00:54:12 probably still have liquid water on the
00:54:12 --> 00:54:14 surface because it had such an intense
00:54:14 --> 00:54:17 greenhouse effect. So there could
00:54:17 --> 00:54:18 almost be a philosophical question about how
00:54:18 --> 00:54:20 long would you consider the Earth to have
00:54:20 --> 00:54:21 been an Earth like planet?
00:54:22 --> 00:54:25 Andrew Dunkley: That's a really good point. Yeah. And
00:54:26 --> 00:54:28 the possibility that we have observed planets
00:54:28 --> 00:54:30 that just, ah, aren't where we are yet
00:54:30 --> 00:54:32 because of the time differences in,
00:54:32 --> 00:54:35 in, in the travel, uh, time of our vision.
00:54:35 --> 00:54:38 So again, it mightn't be there yet
00:54:38 --> 00:54:40 and it could be billions of years before it
00:54:40 --> 00:54:42 is and we won't be around to confirm it.
00:54:42 --> 00:54:45 There's all sorts of weirdisms that go into
00:54:45 --> 00:54:48 this. My, the bottom line for me is if they
00:54:48 --> 00:54:49 find one, it's got to have kangaroos on it.
00:54:49 --> 00:54:51 Otherwise there's just no Earth like planets.
00:54:51 --> 00:54:53 Jonti Horner: Oh, absolutely. I mean, would be very
00:54:53 --> 00:54:55 interesting to imagine kangaroos in space. I
00:54:55 --> 00:54:57 talk a lot about, um, the Dragonfly mission
00:54:58 --> 00:55:00 going to Titan, and the fact that Titan is
00:55:00 --> 00:55:01 the only other body we know of with permanent
00:55:01 --> 00:55:03 liquid water on the surface. Well, not
00:55:03 --> 00:55:05 permanent liquid water, permanent liquid on
00:55:05 --> 00:55:07 the surface. The water there is harder than
00:55:07 --> 00:55:09 granite frozen solid, but it's got liquid
00:55:09 --> 00:55:11 methane and Ethernet there. But on Titan,
00:55:12 --> 00:55:14 unlike on Earth, you could fly under your own
00:55:14 --> 00:55:16 power. If you strapped a pair of wings on.
00:55:16 --> 00:55:18 The gravity is low enough in the atmosphere,
00:55:18 --> 00:55:21 dense enough that you could flap around and
00:55:21 --> 00:55:23 saw. I have never thought about how a
00:55:23 --> 00:55:26 kangaroo would react if you took it to Titan.
00:55:26 --> 00:55:28 It would just, uh, launch itself. Just launch
00:55:28 --> 00:55:31 itself. Um, it Would, of course, need a very,
00:55:31 --> 00:55:33 very good space suit because it's so cold
00:55:33 --> 00:55:35 there and kangaroos are not fans of the cold.
00:55:35 --> 00:55:37 But, yeah, that would be the shock. If
00:55:37 --> 00:55:39 Dragonfly hops around, flying around on the
00:55:39 --> 00:55:41 surface of Titan, and then gets attacked by a
00:55:41 --> 00:55:43 kangaroo when it comes into land. Like, we
00:55:43 --> 00:55:45 see some of the videos online of kangaroos
00:55:45 --> 00:55:47 being territorial. That would be the most
00:55:47 --> 00:55:48 bizarre discovery of life elsewhere that I
00:55:48 --> 00:55:50 think I could imagine. Kangaroos on Titan.
00:55:51 --> 00:55:53 Andrew Dunkley: I wait with bated breath. Although kangaroos,
00:55:53 --> 00:55:56 uh, do have one particular problem in this
00:55:56 --> 00:55:58 country. They do not know how to get out of
00:55:58 --> 00:56:00 the way of a car. Even when they do, they go,
00:56:00 --> 00:56:02 oh, no, no, hang on, I want to get back in
00:56:02 --> 00:56:05 front of you. Bang. Okay, see ya. Uh,
00:56:05 --> 00:56:07 anyway, um, that's our problem. I'm sure it's
00:56:07 --> 00:56:09 the same in other countries without other
00:56:09 --> 00:56:11 animals and other planets, probably that
00:56:11 --> 00:56:14 we're unaware of as yet. Uh, Jonty, that's
00:56:14 --> 00:56:17 been a lot of fun. It's a, it's a fascinating
00:56:17 --> 00:56:19 topic and it's one that will keep evolving, I
00:56:19 --> 00:56:20 think is probably, probably the best way to
00:56:20 --> 00:56:22 describe it. Thank you so much and we'll
00:56:22 --> 00:56:23 catch you again real soon.
00:56:23 --> 00:56:24 Jonti Horner: It's a pleasure and I look forward to it.
00:56:25 --> 00:56:28 Andrew Dunkley: Professor Jonty Horner from the University of
00:56:28 --> 00:56:31 Southern Queensland. And thanks, uh, to Huw
00:56:31 --> 00:56:32 in the studio. Couldn't be with us today.
00:56:32 --> 00:56:35 Made a fatal error. He's back in hospital. He
00:56:35 --> 00:56:37 ran into an ex. And, uh, he called
00:56:37 --> 00:56:39 his ex a planet.
00:56:40 --> 00:56:42 Think about that. It's terrible. And don't
00:56:42 --> 00:56:44 forget to visit us online if you dare, at
00:56:44 --> 00:56:47 spacenutspodcast.com or spacenuts
00:56:47 --> 00:56:49 IO until next time, thanks for your company.
00:56:49 --> 00:56:51 We'll see you on the very next episode of
00:56:51 --> 00:56:53 Space Nuts. Bye.
00:56:53 --> 00:56:55 Jonti Horner: Bye. You've been listening to
00:56:55 --> 00:56:57 the Space Nuts podcast,
00:56:58 --> 00:57:01 available at Apple Podcasts, Spotify,
00:57:02 --> 00:57:04 iHeartRadio or your favourite podcast
00:57:04 --> 00:57:06 player. You can also stream on
00:57:06 --> 00:57:08 demand@bytes.com.
00:57:08 --> 00:57:10 Andrew Dunkley: this has been another quality podcast
00:57:10 --> 00:57:12 production from bytes.com.
00:57:12 --> 00:57:12 Jonti Horner: um,