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ontroversial Concepts: Sunlight Services, Near-Earth Asteroids, and the 6,000th Exoplanet
In this captivating episode of Space Nuts, hosts Andrew Dunkley and Professor Jonti Horner dive into a variety of cosmic topics that challenge our understanding of space and its implications for life on Earth. From a bold proposal for a satellite-based sunlight service to a near miss with an asteroid and the discovery of the 6,000th exoplanet, this episode is filled with intriguing discussions and scientific insights.
Episode Highlights:
- Sunlight Services Proposal: Andrew and Jonti explore the controversial idea of launching satellites to reflect sunlight back to Earth, discussing the practical challenges and potential environmental impacts of such a scheme. They raise critical questions about the feasibility and safety of this ambitious project.
- Asteroid Near Miss: The hosts analyze the recent close encounter with asteroid 2025 TF, emphasizing the importance of early detection in planetary defense and how light pollution from artificial satellites could hinder our ability to spot these potential threats in the future.
- Milestone in Exoplanet Discovery: Celebrating the discovery of the 6,000th exoplanet, Andrew and Jonti reflect on the journey of exoplanet research over the past three decades and the implications of finding planets beyond our solar system. They discuss the criteria for confirming these distant worlds and what the future holds for exoplanet exploration.
- Mimas and Subsurface Oceans: The episode concludes with a fascinating look at Saturn's moon Mimas, which may harbor a subsurface ocean. The discussion highlights the ongoing research into the moon's geological history and the potential for life beyond Earth in unexpected places.
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Stay curious, keep looking up, and join us next time for more stellar insights and cosmic wonders. Until then, clear skies and happy stargazing.
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00:00:00 --> 00:00:02 Andrew Dunkley: Hi there. Thanks for joining us on another
00:00:02 --> 00:00:04 edition of Space Nuts, where we talk
00:00:04 --> 00:00:06 astronomy and space science. My name is
00:00:06 --> 00:00:08 Andrew Dunkley, your host. It's good to have
00:00:08 --> 00:00:10 your company as always. Today,
00:00:11 --> 00:00:12 we're going to start off with something quite
00:00:12 --> 00:00:15 controversial. And in some
00:00:15 --> 00:00:17 parts of the world they probably call this
00:00:17 --> 00:00:20 dumb. But, a proposal to create
00:00:20 --> 00:00:23 a sunlight service. Yes. Using
00:00:23 --> 00:00:25 mirrors in orbit. It's a thing.
00:00:25 --> 00:00:28 also a near miss for Earth involving asteroid
00:00:28 --> 00:00:30 20, 2025 TF, the
00:00:30 --> 00:00:33 6th exoplanet has
00:00:33 --> 00:00:36 been discovered. And another potential
00:00:36 --> 00:00:38 subsurface ocean, this one
00:00:38 --> 00:00:41 involving the moon Mimas. That's all coming
00:00:41 --> 00:00:43 up on this edition of Space Nuts.
00:00:43 --> 00:00:46 Jonti Horner: 15 seconds. Guidance is internal.
00:00:46 --> 00:00:49 10, 9. Ignition
00:00:49 --> 00:00:51 sequence. Star. Space Nuts. 5, 4,
00:00:51 --> 00:00:54 3. 2. 1. 2, 3, 4, 5, 5, 4,
00:00:54 --> 00:00:57 3, 2, 1. Space Nuts astronauts,
00:00:57 --> 00:00:58 report.
00:00:58 --> 00:00:58 Andrew Dunkley: It feels good.
00:00:59 --> 00:01:02 And joining us, in the stead of Fred
00:01:02 --> 00:01:05 Watson, we are, joined by Jonti Horner,
00:01:05 --> 00:01:06 professor of astrophysics at the University
00:01:06 --> 00:01:08 of Southern Queensland. Hello again, Jonti.
00:01:09 --> 00:01:11 Jonti Horner: good morning. How are you going?
00:01:11 --> 00:01:13 Andrew Dunkley: I am well. And we should, just put a
00:01:13 --> 00:01:16 caveat to this episode. There might be noise
00:01:16 --> 00:01:17 because you're getting work done at the
00:01:17 --> 00:01:17 house.
00:01:18 --> 00:01:20 Jonti Horner: Yes. And of course we organized to record at
00:01:20 --> 00:01:22 this time prior to the trade is getting in
00:01:22 --> 00:01:23 touch and saying, you know what, we'll be
00:01:23 --> 00:01:25 there at 7am on Monday morning. It's like
00:01:25 --> 00:01:28 great, you know, want this done. Hopefully
00:01:28 --> 00:01:31 the wonders of the microphone will filter it
00:01:31 --> 00:01:33 all out. But given that some of the banging I
00:01:33 --> 00:01:35 can feel through my feet, I suspect the
00:01:35 --> 00:01:36 vibrations might go all the way through the
00:01:36 --> 00:01:38 desk and all the way up the microphone and
00:01:38 --> 00:01:40 we'll occasionally get bang, bang, bang,
00:01:40 --> 00:01:41 drill, drill, drill. So, yeah, I know.
00:01:42 --> 00:01:44 Consider it like we've got a craft work gig
00:01:44 --> 00:01:45 going on or something like that.
00:01:45 --> 00:01:47 Andrew Dunkley: Well, I can tell you we've, we've heard worse
00:01:47 --> 00:01:50 from Fred's house. So, yeah, it should, it
00:01:50 --> 00:01:52 shouldn't sound out of the ordinary, to be
00:01:52 --> 00:01:52 honest.
00:01:53 --> 00:01:55 All right, let's get, stuck into these
00:01:55 --> 00:01:57 stories because we've got a lot to talk
00:01:57 --> 00:02:00 about. This first one, I know you sent me
00:02:00 --> 00:02:02 the, information initially that came from, I
00:02:02 --> 00:02:05 believe, one of your students who's overseas.
00:02:05 --> 00:02:08 But this is, an idea of a Californian company
00:02:08 --> 00:02:10 who is applying to the federal,
00:02:11 --> 00:02:12 communications commission in the United
00:02:12 --> 00:02:15 States, the fcc, for permission to launch a
00:02:15 --> 00:02:17 satellite into space to reflect
00:02:18 --> 00:02:20 sunlight back down on Earth and
00:02:20 --> 00:02:22 charge people for the privilege.
00:02:24 --> 00:02:27 Jonti Horner: Yeah. Now I try very hard to be
00:02:27 --> 00:02:30 even handed and to not be too critical even
00:02:30 --> 00:02:32 when I'm talking About the people who shall
00:02:32 --> 00:02:33 not be named. You know, the ones who are
00:02:33 --> 00:02:36 putting up, Starlink satellites and abusing
00:02:36 --> 00:02:39 colleagues of mine, or people who are
00:02:39 --> 00:02:41 claiming that things that are not aliens are
00:02:41 --> 00:02:43 aliens in order to sell books. You know, I
00:02:43 --> 00:02:45 try and be even handed and it's very
00:02:45 --> 00:02:48 hard to talk about this one without getting a
00:02:48 --> 00:02:50 bit caustic. it reminds me
00:02:50 --> 00:02:53 of the late, great Terry Pratchett, who,
00:02:53 --> 00:02:55 in one of the books was talking about a
00:02:55 --> 00:02:58 certain subset of the landed gentry.
00:02:58 --> 00:03:00 You know, there's, political things going on
00:03:00 --> 00:03:02 and this is a time when the city's under
00:03:02 --> 00:03:05 siege and they're reforming the regiments and
00:03:05 --> 00:03:08 things like this. And it's talking about the
00:03:08 --> 00:03:09 boys who were dropped on their heads as
00:03:09 --> 00:03:12 babies, as this kind of subset of,
00:03:12 --> 00:03:15 you know, nice but dim gentry. Yeah, they're
00:03:15 --> 00:03:18 nice, but they're not all there. And this,
00:03:18 --> 00:03:20 to me, seems like an idea that was dropped on
00:03:20 --> 00:03:23 its head as a baby. It's so
00:03:23 --> 00:03:26 overwhelmingly dumb that you think it must be
00:03:26 --> 00:03:29 April 1st and it isn't. So the idea
00:03:29 --> 00:03:31 that this company called Reflector Orbital
00:03:31 --> 00:03:34 have. And it's an idea that has
00:03:34 --> 00:03:36 led to them getting tens of millions of
00:03:36 --> 00:03:38 dollars of funding. So it's not like,
00:03:39 --> 00:03:41 yeah, this is. It's
00:03:41 --> 00:03:43 not like these are people in the pub saying,
00:03:43 --> 00:03:45 we've had a few. You know what'd be funny?
00:03:45 --> 00:03:48 This is a company taking it seriously.
00:03:48 --> 00:03:50 They're getting interns in, they've got a
00:03:50 --> 00:03:52 very active social media presence and their
00:03:52 --> 00:03:55 whole business is. Isn't it sad that it's
00:03:55 --> 00:03:57 dark at nighttime? Wouldn't it be great if
00:03:57 --> 00:03:59 you could pay somebody and get sunshine
00:03:59 --> 00:04:02 delivered to you at night? And that could
00:04:02 --> 00:04:03 power your solar panels or it could help you
00:04:03 --> 00:04:06 grow your crops or, you know, help you
00:04:06 --> 00:04:08 illuminate your sporting event or your
00:04:08 --> 00:04:10 concert. And the idea that
00:04:10 --> 00:04:12 they've got is that they will launch
00:04:12 --> 00:04:14 satellites into low Earth orbit, maybe 400
00:04:14 --> 00:04:17 kilometers up, that will go around the Earth
00:04:17 --> 00:04:18 every 90 minutes. So they're going to be
00:04:18 --> 00:04:21 fleetingly above any given location, above
00:04:21 --> 00:04:23 the horizon for a few minutes. And if you
00:04:23 --> 00:04:26 send them a few of your dollary dues, they
00:04:26 --> 00:04:28 will make their satellite reflect light down
00:04:28 --> 00:04:31 to your location and deliver
00:04:31 --> 00:04:34 sunlight to you. Now, there's all sorts of
00:04:34 --> 00:04:35 problems with this. Firstly, you know, I
00:04:35 --> 00:04:38 live, in Toowoomba. I'm 27 degrees south and
00:04:38 --> 00:04:41 I can see satellites that are about 400 km up
00:04:41 --> 00:04:43 in about the first hour after sunset, the
00:04:43 --> 00:04:46 first hour before sunrise, the rest of the
00:04:46 --> 00:04:48 night, those satellites are in shadow too. So
00:04:48 --> 00:04:51 there isn't any sun to reflect. Oh.
00:04:51 --> 00:04:52 Andrew Dunkley: So, you know, fair point.
00:04:53 --> 00:04:55 Jonti Horner: Nobody seems to be really mentioning that in
00:04:55 --> 00:04:57 the narrative of how this will work. But even
00:04:57 --> 00:04:58 ignoring that, think about the International
00:04:59 --> 00:05:00 Space Station going overhead. And you can get
00:05:00 --> 00:05:02 predictions of this from wonderful websites
00:05:02 --> 00:05:05 like heavensabove.com and the space
00:05:05 --> 00:05:07 station becomes visible,
00:05:08 --> 00:05:10 passes over, and then goes into the shadow.
00:05:10 --> 00:05:12 And you might get five, six minutes of it
00:05:12 --> 00:05:15 going overhead, if you're lucky. Yeah. And
00:05:15 --> 00:05:18 then it's gone. So you have this idea that
00:05:18 --> 00:05:20 these mirrors, that they're going to launch
00:05:20 --> 00:05:22 at about that altitude, and
00:05:23 --> 00:05:25 if you want them to illuminate a single point
00:05:25 --> 00:05:26 on the ground, they've got to be turning. So
00:05:26 --> 00:05:29 they keep rotating the light to that point as
00:05:29 --> 00:05:31 they pass overhead. Mm. When they're
00:05:31 --> 00:05:33 passed overhead, what do they do? They can't
00:05:33 --> 00:05:36 just turn off the mirror. So is that
00:05:36 --> 00:05:39 suggesting that you're gonna have a beam of
00:05:39 --> 00:05:41 light sweeping across the countryside at
00:05:41 --> 00:05:44 orbital speed? Like when you're trying
00:05:44 --> 00:05:45 to entertain a cat and you're shining a laser
00:05:45 --> 00:05:47 pointer on the floor and the cat's chasing
00:05:47 --> 00:05:48 it, you've got a beam going across the Earth.
00:05:48 --> 00:05:51 yeah. Going across the skies of all these
00:05:51 --> 00:05:54 people who didn't pay for the service. Not
00:05:54 --> 00:05:56 just that, how do you get enough sunlight
00:05:56 --> 00:05:58 down to be functional? So
00:05:58 --> 00:06:00 these satellites are going to be small enough
00:06:00 --> 00:06:03 to launch. So you're talking about a mirror a
00:06:03 --> 00:06:06 few meters across, 400 kilometers away,
00:06:06 --> 00:06:08 trying to reflect sunlight down, and they,
00:06:08 --> 00:06:11 they talk about how the diameter of the
00:06:11 --> 00:06:13 beam will be about 5km across.
00:06:14 --> 00:06:17 So that means if I pay for them to deliver
00:06:17 --> 00:06:19 light to my backyard, anybody in a five
00:06:19 --> 00:06:22 kilometer diameter area around me also get
00:06:22 --> 00:06:24 illuminated as well, for free, whether they
00:06:24 --> 00:06:24 want to or not.
00:06:25 --> 00:06:26 Andrew Dunkley: Yeah, but not just that.
00:06:26 --> 00:06:27 Jonti Horner: The light's not going to be that bright,
00:06:27 --> 00:06:30 because if you've got a 1 meter sized mirror
00:06:30 --> 00:06:32 reflecting sunlight, and then you spread that
00:06:32 --> 00:06:35 light over an area that is 5km in diameter,
00:06:35 --> 00:06:37 you're spreading that light awfully thin. So
00:06:37 --> 00:06:40 any area on the ground there is not going to
00:06:40 --> 00:06:43 see broad daylight. They're going to see
00:06:43 --> 00:06:45 something that is comparable in brightness or
00:06:45 --> 00:06:46 a few times brighter than the full moon,
00:06:47 --> 00:06:50 which is. Okay, that's enough light for you
00:06:50 --> 00:06:52 to go out and do something in the backyard
00:06:52 --> 00:06:54 by. But it's not particularly enough light to
00:06:54 --> 00:06:56 get really effective solar power from. So if
00:06:56 --> 00:06:58 you want to make this effective, you're going
00:06:58 --> 00:07:01 to have to launch hundreds of thousands
00:07:01 --> 00:07:04 of these mirrors, all to work in
00:07:04 --> 00:07:06 concert to beam towards a given location,
00:07:07 --> 00:07:09 which doesn't sound that feasible. Add to
00:07:09 --> 00:07:11 that the fact that these are Big floating
00:07:11 --> 00:07:14 targets in space that space debris can hit
00:07:14 --> 00:07:17 and smash, which means that a, you could
00:07:17 --> 00:07:18 get all this debris scattered off in all
00:07:18 --> 00:07:21 sorts of different directions, but also that
00:07:21 --> 00:07:23 it's going to be hard for them to control the
00:07:23 --> 00:07:25 direction the mirror's pointing. So you've
00:07:25 --> 00:07:27 got all sorts of problems here. I mean, I
00:07:27 --> 00:07:29 think there's growing and
00:07:29 --> 00:07:32 demonstrated evidence, and Fred's talked
00:07:32 --> 00:07:34 about this to death, about all the negative
00:07:34 --> 00:07:36 effects artificial light at night has. We've
00:07:36 --> 00:07:38 got effects on people. You've got increased
00:07:38 --> 00:07:41 cancer rates, a very bizarre but
00:07:41 --> 00:07:44 very significant link between light at night
00:07:44 --> 00:07:45 and an increased risk of breast cancer for
00:07:45 --> 00:07:48 women. Believe it or not, just as one
00:07:48 --> 00:07:50 example, you've got the impact in our
00:07:50 --> 00:07:52 circadian rhythms, the fact that we need it
00:07:52 --> 00:07:55 to be dark to sleep, then you've got all the
00:07:55 --> 00:07:57 impact on flora and fauna. Now, I've visited
00:07:57 --> 00:07:59 some wonderful places on the coast of
00:07:59 --> 00:08:02 Queensland to do outreach sessions, you know,
00:08:02 --> 00:08:04 some kind of night sky observing. And a lot
00:08:04 --> 00:08:06 of these places are places where turtles
00:08:06 --> 00:08:09 nest. In fact, I'm going next weekend to the
00:08:09 --> 00:08:11 wonderful Lady Elliot island on the reef to
00:08:11 --> 00:08:13 do some outreach. And I go there several
00:08:13 --> 00:08:15 times a year. And all of their resort is
00:08:15 --> 00:08:18 designed to keep light down and pointed at
00:08:18 --> 00:08:19 the ground and have lights that get turned
00:08:19 --> 00:08:22 off because baby turtles, when they hatch,
00:08:23 --> 00:08:25 they navigate to the ocean by looking at the
00:08:25 --> 00:08:27 very faint light on the horizon, light
00:08:27 --> 00:08:29 reflecting off the ocean. And, that's what
00:08:29 --> 00:08:31 sets their internal compass as they start
00:08:31 --> 00:08:34 their lives. And if you have stray light,
00:08:34 --> 00:08:36 they go the wrong way and they end up under
00:08:36 --> 00:08:38 the buildings and on the road and things like
00:08:38 --> 00:08:41 this. Yeah, so there's huge impacts on life.
00:08:41 --> 00:08:44 But I think the biggest concern about this is
00:08:44 --> 00:08:46 the safety aspect. You know, you're driving
00:08:46 --> 00:08:48 around and I know here in regional Australia,
00:08:48 --> 00:08:50 most of our roads don't have street lights
00:08:50 --> 00:08:52 and that's perfectly fine. It's safer. As
00:08:52 --> 00:08:54 such, you drive along with your full beam on
00:08:54 --> 00:08:56 and any kangaroo that you see, you've got
00:08:56 --> 00:08:58 room to do something about it. So you're
00:08:58 --> 00:09:00 driving along on this pitch black road and,
00:09:00 --> 00:09:02 suddenly from nowhere, something brighter
00:09:02 --> 00:09:04 than the full moon shines full head on in
00:09:04 --> 00:09:06 your view. You're dazzled. That's
00:09:06 --> 00:09:09 hugely dangerous. Odd enough, if you're
00:09:09 --> 00:09:10 driving on the ground, if you're a pilot
00:09:10 --> 00:09:13 coming in to land, and suddenly somebody's
00:09:13 --> 00:09:15 trying to spotlight in your face, that's not
00:09:15 --> 00:09:18 going to be a particularly pleasant outcome
00:09:18 --> 00:09:21 for you and the passengers in your plane. And
00:09:21 --> 00:09:23 so there's all these issues there that
00:09:24 --> 00:09:26 any one of them will be enough for you to
00:09:26 --> 00:09:29 say, this is a really foolish idea. It
00:09:29 --> 00:09:31 is not something that is likely to work
00:09:31 --> 00:09:33 anyway, but it's a really foolish
00:09:33 --> 00:09:35 idea from the ground up. It's only going to
00:09:35 --> 00:09:37 work near twilight. You're going to have to
00:09:37 --> 00:09:39 launch thousands of satellites to make it
00:09:39 --> 00:09:42 work, but it isn't stopping people funding
00:09:42 --> 00:09:44 them. And, this company, like I say, has
00:09:44 --> 00:09:47 applied to the FCC in the US for
00:09:47 --> 00:09:48 permission to launch the first of these
00:09:48 --> 00:09:50 satellites, which they've named Earundel 1
00:09:50 --> 00:09:52 after the light from Lord of the Rings.
00:09:53 --> 00:09:56 Earundel 1. They're hoping to launch April,
00:09:56 --> 00:09:59 May time next year, 2026, to
00:09:59 --> 00:10:02 demonstrate that their wonderful great idea
00:10:02 --> 00:10:05 can work. And it's just yet another example
00:10:05 --> 00:10:07 of this kind of Wild west scenario we've got
00:10:07 --> 00:10:09 with the use of space around the Earth, where
00:10:09 --> 00:10:12 the use of space is really outstripping our
00:10:12 --> 00:10:14 ability to regulate and control that use.
00:10:14 --> 00:10:16 And, people are doing things because it
00:10:16 --> 00:10:17 seemed like a good idea at the time without
00:10:17 --> 00:10:20 any real thought about the practicality of
00:10:20 --> 00:10:22 it, whether it could work. And, normally you
00:10:22 --> 00:10:24 just think like, say you think this is an
00:10:24 --> 00:10:27 April Fool's Day kind of prank. But the
00:10:27 --> 00:10:29 fact that this company has raised tens of
00:10:29 --> 00:10:31 millions of dollars in kind of venture
00:10:31 --> 00:10:32 capital, it's supported by A M
00:10:32 --> 00:10:35 multibillionaire, is really, really
00:10:35 --> 00:10:37 concerning. And that's why a group of
00:10:37 --> 00:10:39 astronomers, including Jessica Heim, who's
00:10:39 --> 00:10:42 doing a PhD with me at UNISQ, have put
00:10:42 --> 00:10:45 out this fact sheet with lots of information,
00:10:45 --> 00:10:47 loads of links, number of astronomers in the
00:10:47 --> 00:10:49 US who people in the media can contact for
00:10:49 --> 00:10:52 more information and suggestions about what
00:10:52 --> 00:10:55 people can do to flag up how catastrophically
00:10:55 --> 00:10:57 dumb this is. And that includes submit
00:10:57 --> 00:10:59 comments on the application to the Federal
00:10:59 --> 00:11:02 Communications Commission in the US to demand
00:11:02 --> 00:11:04 an environmental review of reflected light
00:11:04 --> 00:11:06 from orbit. Contact government
00:11:06 --> 00:11:08 representatives, particularly in the US but
00:11:08 --> 00:11:10 also locally where you live, to try and raise
00:11:10 --> 00:11:13 noise about this, but also tell people about
00:11:13 --> 00:11:15 it and point out how dumb it is. Because I
00:11:15 --> 00:11:17 can understand that if you don't really think
00:11:17 --> 00:11:20 about this too much, you can think, yeah,
00:11:20 --> 00:11:21 there are times it'd be really nice to have a
00:11:21 --> 00:11:23 bit of extra light at night.
00:11:23 --> 00:11:24 I didn't get round to doing the gardening.
00:11:24 --> 00:11:26 It'd be good to mow the lawn tonight.
00:11:26 --> 00:11:27 Wouldn't it be great if I could just turn on
00:11:27 --> 00:11:29 the spotlight and have half an hour of my
00:11:29 --> 00:11:32 backyard being daily, at night for me to do
00:11:32 --> 00:11:35 that job? And you need to talk about it and
00:11:35 --> 00:11:37 you need to think about it to see why this is
00:11:37 --> 00:11:40 just so catastrophically dumb. In
00:11:40 --> 00:11:43 so, so many ways that you would have thought
00:11:43 --> 00:11:46 it'd be an unstarter, but yet they're getting
00:11:46 --> 00:11:46 money.
00:11:47 --> 00:11:49 Andrew Dunkley: I can't see or understand
00:11:50 --> 00:11:53 any logic in this. And,
00:11:54 --> 00:11:56 the way in low Earth orbit, as you said,
00:11:56 --> 00:11:58 there's only going to be a few minutes of
00:11:58 --> 00:12:00 light. It's not like they can light a stadium
00:12:00 --> 00:12:03 for four hours straight. Not yet, any. But,
00:12:03 --> 00:12:05 even if they could, that's going to take a
00:12:05 --> 00:12:07 lot of hardware up in space. And there's more
00:12:07 --> 00:12:09 light pollution on Earth.
00:12:09 --> 00:12:10 Jonti Horner: Which is a big problem.
00:12:10 --> 00:12:12 Andrew Dunkley: Fred and Marnie are so heavily involved in
00:12:12 --> 00:12:15 the Dark Skies project. This would just blow
00:12:15 --> 00:12:16 that out of the water.
00:12:16 --> 00:12:18 Jonti Horner: Well, it would. And I mean, to light that
00:12:18 --> 00:12:20 stadium for four hours, you would need
00:12:20 --> 00:12:23 mirrors going overhead continuously in a
00:12:23 --> 00:12:26 parade. You'd need that stadium to be near
00:12:26 --> 00:12:28 enough to the pole on it to be summertime
00:12:28 --> 00:12:31 that those satellites were always in sunlight
00:12:31 --> 00:12:33 or you'd need to put them further from the
00:12:33 --> 00:12:35 Earth. The further you move them from the
00:12:35 --> 00:12:37 Earth, the more spread out the light will be,
00:12:37 --> 00:12:39 and so therefore the more satellites you'll
00:12:39 --> 00:12:42 need, you know. And if you get
00:12:42 --> 00:12:44 to that stage, if you've got that many
00:12:44 --> 00:12:46 satellites in orbit around the Earth, you may
00:12:46 --> 00:12:48 as well build a mirror that
00:12:48 --> 00:12:51 is held in geostationary orbit that covers
00:12:51 --> 00:12:54 half of the size of the Earth, and bears the
00:12:54 --> 00:12:55 entirety of that side of the Earth in
00:12:55 --> 00:12:58 sunlight. And, you know, while you're at it,
00:12:58 --> 00:12:59 you're increasing the amount of heat coming
00:12:59 --> 00:13:00 to the Earth and we'll just speed up global
00:13:00 --> 00:13:01 warming and kill everybody.
00:13:03 --> 00:13:05 Andrew Dunkley: Yeah, there is a groundswell of discontent,
00:13:05 --> 00:13:08 as you mentioned. So people are starting to
00:13:08 --> 00:13:10 make some noise about this. I hope the fcc,
00:13:13 --> 00:13:15 you know, looks at both sides of the story.
00:13:15 --> 00:13:18 how, just quickly, how likely are they
00:13:18 --> 00:13:21 to get their license and start testing
00:13:21 --> 00:13:21 this?
00:13:22 --> 00:13:24 Jonti Horner: I mean, a pessimist would say it's almost
00:13:24 --> 00:13:26 certain to happen because, you know, the FCC
00:13:26 --> 00:13:28 are quite happy for sailing to be putting up
00:13:28 --> 00:13:30 the number of satellites. They are looking at
00:13:30 --> 00:13:33 42 long term. So it
00:13:33 --> 00:13:35 doesn't seem like there's much thought of
00:13:35 --> 00:13:37 that. And there's the added concern. I think
00:13:37 --> 00:13:39 one of the things that is hindering
00:13:39 --> 00:13:41 legislation is the fact that you can launch
00:13:41 --> 00:13:44 the space from many, many countries. And so
00:13:44 --> 00:13:46 companies can quite rightly say to, a given
00:13:46 --> 00:13:48 legislating body, if you don't give us this,
00:13:48 --> 00:13:50 we'll just take our business elsewhere and
00:13:50 --> 00:13:53 someone else will. And, you know, once you're
00:13:53 --> 00:13:55 launched from a given country, you're above
00:13:56 --> 00:13:58 all of the countries of the world as you move
00:13:58 --> 00:14:00 over them in your orbit. So it isn't like
00:14:00 --> 00:14:02 this thing is just going to affect people in
00:14:02 --> 00:14:03 the U.S. because it's been launched from the
00:14:03 --> 00:14:05 U.S. it's going to be going around the Earth,
00:14:05 --> 00:14:08 like say, running a five kilometer size beam
00:14:08 --> 00:14:10 of light across the surface of the earth,
00:14:11 --> 00:14:13 every 90 minutes as it goes round and round
00:14:13 --> 00:14:14 and round and round.
00:14:14 --> 00:14:17 Andrew Dunkley: It just doesn't, doesn't make much sense
00:14:17 --> 00:14:19 really. It sounds like pie in the sky. But,
00:14:20 --> 00:14:22 yeah, they're actually seriously considering
00:14:22 --> 00:14:25 doing this. And yeah, hopefully
00:14:25 --> 00:14:28 common sense will prevail, but, time will
00:14:28 --> 00:14:30 tell, I suppose we'll know next year whether
00:14:30 --> 00:14:32 or not they start testing these things.
00:14:33 --> 00:14:35 I know they did do this some years ago
00:14:36 --> 00:14:38 with a mirror array up in space and they,
00:14:38 --> 00:14:41 they lit up a spot on Siberia or something.
00:14:43 --> 00:14:45 yeah, I don't know why they did that then. I
00:14:45 --> 00:14:47 can't remember. But, it was, somewhat
00:14:47 --> 00:14:49 successful, although quite dim. But, This,
00:14:49 --> 00:14:52 this just. Yeah, I mean, I don't know where
00:14:52 --> 00:14:55 it stops. there seems to be this,
00:14:55 --> 00:14:58 this constant tug of war between what
00:14:58 --> 00:15:01 we need up there and what we don't need up
00:15:01 --> 00:15:03 there. And the. Yeah,
00:15:04 --> 00:15:06 it's swinging the wrong way at the moment, I
00:15:06 --> 00:15:08 suppose, would be the way to describe it.
00:15:08 --> 00:15:10 But, I dare say this will get a lot more
00:15:10 --> 00:15:13 press and a lot more pushback and maybe the
00:15:13 --> 00:15:16 fcc, will look at the
00:15:16 --> 00:15:17 problems associated with this.
00:15:18 --> 00:15:20 Jonti Horner: Really hope so. I mean, it reminds me, and
00:15:20 --> 00:15:22 I'm probably paraphrasing terribly, but
00:15:22 --> 00:15:23 there's a famous science fiction quote,
00:15:23 --> 00:15:25 something along the lines of, you know, they
00:15:25 --> 00:15:27 spent so much time and effort trying to show
00:15:27 --> 00:15:28 that they could, that they never put any
00:15:28 --> 00:15:31 thought into whether they should. It feels
00:15:31 --> 00:15:31 like all of those.
00:15:32 --> 00:15:35 Andrew Dunkley: Yes, yes, indeed. All right. yeah, it's
00:15:35 --> 00:15:37 a project, you might find online. It's only
00:15:37 --> 00:15:39 just sort of starting to emerge. I don't know
00:15:39 --> 00:15:41 how much press it's got yet, but, it will
00:15:41 --> 00:15:44 grow. Because it's one of those stories that,
00:15:45 --> 00:15:47 is also fascinating and they're the ones that
00:15:47 --> 00:15:49 generally get a lot of attention.
00:15:49 --> 00:15:51 Jonti Horner: Looking at the website, the company seems to
00:15:51 --> 00:15:52 have been around for quite a while and I
00:15:52 --> 00:15:54 think it's probably getting attention now
00:15:54 --> 00:15:57 because previously everybody thought, well,
00:15:57 --> 00:16:00 no, this will never fly. This is clearly not
00:16:00 --> 00:16:02 something we should be worried about. And now
00:16:02 --> 00:16:04 it's very clear that actually it is, because
00:16:04 --> 00:16:07 they're in for licenses and they've got a lot
00:16:07 --> 00:16:08 of money invested.
00:16:08 --> 00:16:09 Andrew Dunkley: Yeah.
00:16:09 --> 00:16:09 Jonti Horner: Yeah.
00:16:09 --> 00:16:11 Andrew Dunkley: And one wonders who's really going to pay
00:16:11 --> 00:16:14 them to shed a little light on their
00:16:14 --> 00:16:16 whatever. I mean, what would you use it for?
00:16:16 --> 00:16:18 Solar panels. You said they won't work.
00:16:19 --> 00:16:21 Football, matches. Well, we've got lights for
00:16:21 --> 00:16:23 that. I don't know. I don't know.
00:16:23 --> 00:16:25 Jonti Horner: We can do a bit of quick mental arithmetic to
00:16:25 --> 00:16:27 cheer everybody up. I mean, the brightness of
00:16:27 --> 00:16:30 the full moon to first order very roughly, is
00:16:30 --> 00:16:32 about magnitude -12 in the wonderful
00:16:32 --> 00:16:35 complex magnitude system astronomers are so
00:16:35 --> 00:16:37 fond of. The brightness of the noonday sun's
00:16:37 --> 00:16:40 about magnitude -27. So that's a 15
00:16:40 --> 00:16:43 magnitude difference. Now, that magnitude
00:16:43 --> 00:16:45 system is a logarithmic scale.
00:16:45 --> 00:16:47 So every five magnitudes you're brighter off
00:16:47 --> 00:16:50 enter than something is equivalent to a
00:16:50 --> 00:16:52 factor of 100 influx. So if you're
00:16:52 --> 00:16:55 15 magnitudes, that's three lots of 100. So
00:16:55 --> 00:16:58 100 times 100 times 100, that's 100
00:16:58 --> 00:17:01 becomes 10 becomes a million.
00:17:02 --> 00:17:04 So if the light from this thing is about the
00:17:04 --> 00:17:06 brightness of the full moon, it's a million
00:17:06 --> 00:17:08 times fainter than the sun is.
00:17:09 --> 00:17:12 So if you've got your solar panels that are
00:17:12 --> 00:17:15 generating in full sunlight, you know, a few
00:17:15 --> 00:17:17 hundred watts of power, right. they're
00:17:17 --> 00:17:20 generating a few hundred watts. Divide that
00:17:20 --> 00:17:23 by a million and you're not
00:17:23 --> 00:17:25 generating enough to register. Yeah,
00:17:25 --> 00:17:26 yeah.
00:17:26 --> 00:17:28 Andrew Dunkley: It would be like putting up a solar panel to
00:17:28 --> 00:17:31 power a light and using that light to
00:17:31 --> 00:17:33 generate the power to power that light.
00:17:33 --> 00:17:36 Jonti Horner: It's just absolutely. Or just holding a
00:17:36 --> 00:17:38 match, a lit match near your solar panels and
00:17:38 --> 00:17:41 expecting it to run your entire house. Yeah,
00:17:41 --> 00:17:41 yeah.
00:17:41 --> 00:17:43 Andrew Dunkley: Ah, it's crazy stuff. All right, yeah, keep
00:17:43 --> 00:17:45 an eye out for that story and if you feel
00:17:45 --> 00:17:47 strongly enough about it, maybe, get
00:17:47 --> 00:17:48 involved.
00:17:49 --> 00:17:50 let's move on to our next story. this
00:17:50 --> 00:17:53 involves a near miss for Earth with asteroid,
00:17:54 --> 00:17:56 2025 TF just skimming us,
00:17:56 --> 00:17:59 and we didn't see it till it was too late,
00:18:00 --> 00:18:02 technically speaking. And, it kind of
00:18:02 --> 00:18:05 dovetails into the previous story because if
00:18:05 --> 00:18:07 there's going to be more light up there, it's
00:18:07 --> 00:18:09 going to make us harder, make things harder
00:18:09 --> 00:18:11 for us in terms of, you know, getting these
00:18:11 --> 00:18:14 ready alerts for potential objects that could
00:18:14 --> 00:18:17 strike Earth. this one wasn't huge,
00:18:17 --> 00:18:20 but, yeah, it was, it was there and
00:18:20 --> 00:18:22 it was a detectable object and we didn't see
00:18:22 --> 00:18:22 it.
00:18:22 --> 00:18:25 Jonti Horner: Yes. And that's the issue. Now, this
00:18:25 --> 00:18:28 thing, you know, quite happy to say, straight
00:18:28 --> 00:18:30 up the size of this thing is such that it
00:18:30 --> 00:18:32 would have put on a nice light show as it,
00:18:32 --> 00:18:35 you know, was quite harmlessly destroyed in
00:18:35 --> 00:18:37 the atmosphere. It was probably about 1 to 3
00:18:37 --> 00:18:37 meters across.
00:18:38 --> 00:18:38 Andrew Dunkley: Yeah.
00:18:38 --> 00:18:40 Jonti Horner: But of the things that have not entered the
00:18:40 --> 00:18:43 Earth's atmosphere, but have come close, this
00:18:43 --> 00:18:45 is the second closest on record. Now,
00:18:46 --> 00:18:48 back in. I'm trying to remember exactly when
00:18:48 --> 00:18:50 the great daylight fireball was. But in the
00:18:50 --> 00:18:53 early 1970s, there was a fireball
00:18:54 --> 00:18:56 observed widely over, North America, which
00:18:56 --> 00:18:59 was what we call an earth grazing object, and
00:18:59 --> 00:19:00 it actually hit the atmosphere and skimmed
00:19:00 --> 00:19:03 back out. That is not counted when people
00:19:03 --> 00:19:05 talk about these two closest encounters that
00:19:05 --> 00:19:07 didn't hit Earth because technically that did
00:19:07 --> 00:19:09 hit the atmosphere. The fact that it skipped
00:19:09 --> 00:19:12 back out again is beside the point.
00:19:12 --> 00:19:14 And that was a daylight fireball. It created
00:19:14 --> 00:19:16 sonic booms over a couple of the US States
00:19:16 --> 00:19:18 and was really the first kind of fireball
00:19:18 --> 00:19:20 event that was widely captured because it was
00:19:20 --> 00:19:23 early in the era of modern holiday
00:19:23 --> 00:19:25 snaps. And this was a time when people were
00:19:25 --> 00:19:27 taking photos on holiday, then boring their
00:19:27 --> 00:19:28 friends when they came home.
00:19:28 --> 00:19:30 Andrew Dunkley: Yeah, yeah, 1972 it was.
00:19:30 --> 00:19:32 Jonti Horner: That's the one. Yeah, I thought it was. It
00:19:32 --> 00:19:35 was, probably something smaller than a house
00:19:35 --> 00:19:37 that came within about 57 km
00:19:37 --> 00:19:40 of the surface of the Earth. And put that in
00:19:40 --> 00:19:42 perspective, that's like, you know, the old
00:19:42 --> 00:19:43 William Tell thing of shooting an apple off
00:19:43 --> 00:19:45 somebody's head. That's like shooting the
00:19:45 --> 00:19:47 arrow at the apple and touching the skin of
00:19:47 --> 00:19:50 the apple without breaking it. It's coming
00:19:50 --> 00:19:52 within less than 1% of the diameter of the
00:19:52 --> 00:19:54 Earth of actually hitting our planet. This
00:19:54 --> 00:19:57 one wasn't quite that close. But it's an
00:19:57 --> 00:19:59 object that was discovered by the Catalina
00:19:59 --> 00:20:02 Sky Survey a few hours after
00:20:02 --> 00:20:04 its closest approach to the Earth,
00:20:05 --> 00:20:08 basically whizzed over Antarctica. So I think
00:20:08 --> 00:20:10 it's one of those that even if it had hit the
00:20:10 --> 00:20:11 atmosphere and burned up, very few people
00:20:11 --> 00:20:13 would have seen it, but a lot of penguins
00:20:13 --> 00:20:16 would have been impressed. at
00:20:16 --> 00:20:19 its closest, it was 428km above the
00:20:19 --> 00:20:21 Earth's surface. So that's slightly closer
00:20:21 --> 00:20:23 than reflector orbital. Want to put their
00:20:23 --> 00:20:25 mirrors. so if it had come through a few
00:20:25 --> 00:20:27 years later, we could have hoped it would
00:20:27 --> 00:20:28 have knocked a few of them out of the way.
00:20:28 --> 00:20:31 But it's a really close approach.
00:20:31 --> 00:20:33 And, yes, it's an object that in this case
00:20:33 --> 00:20:35 wouldn't have been big enough to cause any
00:20:35 --> 00:20:38 damage, wouldn't have had any impacts felt at
00:20:38 --> 00:20:41 ground level. It may have, if it was made of
00:20:41 --> 00:20:42 the right stuff, dropped a few little bits of
00:20:42 --> 00:20:45 meteorite on the surface, but that's about
00:20:45 --> 00:20:47 it. But it's a reminder,
00:20:48 --> 00:20:50 of the fact that as we're looking for things
00:20:50 --> 00:20:52 that come close enough to the Earth, to pose
00:20:52 --> 00:20:54 a threat. We haven't found them all yet.
00:20:54 --> 00:20:57 Now probably about 75% of the threat
00:20:57 --> 00:20:59 to the Earth, from impacts comes from the
00:20:59 --> 00:21:01 near Earth asteroids. And they're objects at
00:21:01 --> 00:21:04 the bottom of the asteroid belt, typically
00:21:04 --> 00:21:06 rocky or metallic objects moving on orbits at
00:21:06 --> 00:21:08 a relatively short period in the inner solar
00:21:08 --> 00:21:10 system. And they're short lived. You know, if
00:21:10 --> 00:21:12 you come back in a million years, most of the
00:21:12 --> 00:21:14 ones we currently know will have been
00:21:14 --> 00:21:15 removed. They'll have been ejected from the
00:21:15 --> 00:21:17 solar system or collided with a planet or
00:21:17 --> 00:21:20 fallen apart or fallen into the sun. But
00:21:20 --> 00:21:21 they're continually being repopulated from
00:21:21 --> 00:21:24 the asteroid belt. Some of them hide
00:21:24 --> 00:21:26 closer to the sun than we are and then pop
00:21:26 --> 00:21:28 out to say hello. We were talking about that
00:21:28 --> 00:21:30 last week with the objects near Venus.
00:21:31 --> 00:21:33 But there's this effort to try and find all
00:21:33 --> 00:21:36 of them. And the earlier you can find them,
00:21:36 --> 00:21:38 and the earlier you can figure out if there's
00:21:38 --> 00:21:40 going to be an encounter with the Earth that
00:21:40 --> 00:21:43 poses a threat, the better the odds of you
00:21:43 --> 00:21:45 doing something about it. And we saw this
00:21:46 --> 00:21:48 kind of a bright light shone on this back at
00:21:48 --> 00:21:50 the start of 2025 with the object
00:21:50 --> 00:21:53 2024 yr 4. I think the name M was
00:21:53 --> 00:21:55 that for a while we thought had a
00:21:56 --> 00:21:58 substantial possibility of hitting the Earth
00:21:58 --> 00:22:01 in 2032 that we now know is not going to
00:22:01 --> 00:22:02 hit the Earth, but might hit the moon in
00:22:02 --> 00:22:04 2032. And that was a big success because we
00:22:04 --> 00:22:06 found it early enough to get a lot of data.
00:22:06 --> 00:22:07 and over the course of about a month
00:22:07 --> 00:22:10 astronomers observed it repeatedly until
00:22:10 --> 00:22:12 eventually we showed that it definitely
00:22:12 --> 00:22:13 wasn't going to hit the Earth in eight year
00:22:13 --> 00:22:15 time. And everybody kind of basically jumped
00:22:15 --> 00:22:17 up and down and said hooray. And there was
00:22:17 --> 00:22:19 much rejoicing. So that's like the ideal
00:22:19 --> 00:22:22 scenario. We find something when it passes
00:22:22 --> 00:22:25 relatively nearby on one apparition a
00:22:25 --> 00:22:27 few years before it would realistically pose
00:22:27 --> 00:22:30 a threat. And that's what we want to achieve.
00:22:30 --> 00:22:32 And the stated goal of a lot of the agencies
00:22:32 --> 00:22:34 looking for these things is to find all the
00:22:34 --> 00:22:36 objects bigger than about 100 meters across
00:22:37 --> 00:22:38 that could pose a threat to the Earth, and
00:22:38 --> 00:22:41 catalog them. And we haven't managed
00:22:41 --> 00:22:44 that yet. We even more haven't managed that
00:22:44 --> 00:22:45 when you take into account things like
00:22:45 --> 00:22:47 comets. You know we were talking about, about
00:22:47 --> 00:22:50 Comet Swan last week, which appeared from
00:22:50 --> 00:22:52 hiding behind the sun and came and was
00:22:52 --> 00:22:54 suddenly the brightest comet in the sky.
00:22:54 --> 00:22:56 Comets are coming in on orbits that take
00:22:56 --> 00:22:59 hundreds, thousands, sometimes even tens of
00:22:59 --> 00:23:00 thousands or millions of years to complete.
00:23:01 --> 00:23:02 So even if we find all the near Earth
00:23:02 --> 00:23:05 asteroids, we're still going to have comets
00:23:05 --> 00:23:06 coming in. So we'll have to stay vigilant and
00:23:06 --> 00:23:09 keep watching forevermore. But this
00:23:09 --> 00:23:12 is a really good reminder that despite how
00:23:12 --> 00:23:15 you feel, we're not there yet. We are still
00:23:15 --> 00:23:17 in a position where these things are
00:23:17 --> 00:23:20 catching us by surprise. And the worst case
00:23:20 --> 00:23:22 scenario is what happened in 2013 with the
00:23:22 --> 00:23:24 Chelyabinsk impactor to a similar
00:23:24 --> 00:23:27 level of what happened with comets 1 earlier
00:23:27 --> 00:23:28 this year in that as, ah, the object
00:23:28 --> 00:23:30 approaches the Earth and eventually gets
00:23:30 --> 00:23:32 close enough that it was visible in the
00:23:32 --> 00:23:34 nighttime sky, would be able to detect it.
00:23:34 --> 00:23:36 It's coming from the sunward side of the
00:23:36 --> 00:23:37 Earth, so it's hidden in the glare of
00:23:37 --> 00:23:40 daylight. And so that's why you
00:23:40 --> 00:23:42 don't want to try and detect something the
00:23:42 --> 00:23:44 moment it's on an approach to hit you. You
00:23:44 --> 00:23:47 want to find it well in advance. And with
00:23:47 --> 00:23:48 Charlie Abinsky, it demonstrated something
00:23:48 --> 00:23:51 big enough to injure people, damage a city
00:23:51 --> 00:23:53 we didn't find until it was in the
00:23:53 --> 00:23:55 atmosphere. And it was kind of too late. It
00:23:55 --> 00:23:56 was seconds from disaster.
00:23:57 --> 00:23:57 Andrew Dunkley: Indeed.
00:23:58 --> 00:24:00 Jonti Horner: Now there's hope. We've got Vera Rubin
00:24:00 --> 00:24:02 coming online. We saw a beautiful picture
00:24:02 --> 00:24:05 from that earlier this year. Vera Rubin's
00:24:05 --> 00:24:06 going to start getting data regularly,
00:24:07 --> 00:24:09 continuously later this year, early next
00:24:09 --> 00:24:11 year, that's when the Mayan mission starts.
00:24:11 --> 00:24:13 And Vera Rubin is going to be an exceptional
00:24:13 --> 00:24:16 thing finding tool no matter what. The thing
00:24:16 --> 00:24:18 is, it will find more of them than anybody's
00:24:18 --> 00:24:20 found before. From a solar system point of
00:24:20 --> 00:24:22 view. We're really excited because it will
00:24:22 --> 00:24:24 increase the number of objects we know by a
00:24:24 --> 00:24:27 factor of several to an order of magnitude
00:24:27 --> 00:24:29 within a year or two. And it'll be great at
00:24:29 --> 00:24:32 finding these things, but it'll be less
00:24:32 --> 00:24:34 great than it would have been thanks to all
00:24:34 --> 00:24:35 the stuff we keep watching.
00:24:35 --> 00:24:36 Then this is where it ties into the previous
00:24:37 --> 00:24:40 story. Also ties in again to the wonderful
00:24:40 --> 00:24:42 student who sent me the information about the
00:24:42 --> 00:24:44 reflector orbital stuff. Jessica Heim
00:24:45 --> 00:24:47 is finishing up her PhD with us at UNESCO.
00:24:47 --> 00:24:50 She's based in North America and she's
00:24:50 --> 00:24:53 done a lot of her work about light pollution
00:24:53 --> 00:24:55 and artificial, light at night and things
00:24:55 --> 00:24:57 like this. And one of her papers early in a
00:24:57 --> 00:25:00 PhD that she was a co author on was in
00:25:00 --> 00:25:02 Nature Astronomy. And they actually did a
00:25:02 --> 00:25:05 study looking at just the starlink satellites
00:25:05 --> 00:25:07 that were in orbit at that time, so not the
00:25:07 --> 00:25:10 predicted number in the future, and tried to
00:25:10 --> 00:25:13 quantify how much harder they would make
00:25:13 --> 00:25:14 life for Vera Rubin, and particularly how
00:25:14 --> 00:25:16 much harder they make it for Vera Rubin to
00:25:16 --> 00:25:18 find objects like the one we're just talking
00:25:18 --> 00:25:20 about that was over Antarctica.
00:25:21 --> 00:25:23 And what they found was the Starlink
00:25:23 --> 00:25:25 satellites that were in orbit at the time. So
00:25:25 --> 00:25:27 not the constellation we have now, which is
00:25:27 --> 00:25:30 big and not the final constellation would
00:25:30 --> 00:25:32 make it 10% harder for Vera Rubin to do its
00:25:32 --> 00:25:33 job. So in other words, it would have to
00:25:33 --> 00:25:36 observe for 10% longer. Roughly. I think the
00:25:36 --> 00:25:37 number was actually slightly higher than that
00:25:38 --> 00:25:40 in order to achieve the same results. Now
00:25:40 --> 00:25:42 when you're talking about a facility that's a
00:25:42 --> 00:25:45 billion dollar level facility, hundreds of
00:25:45 --> 00:25:47 millions of dollars to build, having to take
00:25:47 --> 00:25:50 10% longer to do something is a cost measured
00:25:50 --> 00:25:52 in tens of millions of dollars. Yeah, that's
00:25:52 --> 00:25:54 real impact in this. And what it means is
00:25:54 --> 00:25:56 that things like this are going to be harder
00:25:56 --> 00:25:58 to find. And our ability to
00:25:59 --> 00:26:02 detect potential threats is really
00:26:02 --> 00:26:05 kind of confused and obfuscated by the
00:26:05 --> 00:26:07 stuff we're putting to hang around in the
00:26:07 --> 00:26:09 foreground. It's like, I guess it's really
00:26:09 --> 00:26:11 easy to see a road sign on a clear day, but
00:26:11 --> 00:26:13 when it's foggy, it's a lot harder to spot it
00:26:13 --> 00:26:14 until you're right on that side.
00:26:15 --> 00:26:18 Andrew Dunkley: Yeah, yeah, indeed. And
00:26:18 --> 00:26:20 if you want to read up on that story, about
00:26:20 --> 00:26:23 the near miss, you can do so@space
00:26:23 --> 00:26:25 space.com. this is Space Nuts with Andrew
00:26:25 --> 00:26:27 Dunkley and John T. Horner.
00:26:28 --> 00:26:30 Jonti Horner: Three, two, one.
00:26:31 --> 00:26:32 Andrew Dunkley: Space nuts.
00:26:33 --> 00:26:35 Now, Johnny, we have found the
00:26:35 --> 00:26:38 6th exoplanet.
00:26:38 --> 00:26:40 It took us 30 years, which is,
00:26:41 --> 00:26:43 you know, if you, if you look back at when we
00:26:43 --> 00:26:46 found the first one, it was quite a surprise
00:26:46 --> 00:26:49 for a bunch of reasons. mostly because
00:26:49 --> 00:26:51 we didn't even know they could have existed
00:26:51 --> 00:26:53 beyond our solar system. Logic suggests, you
00:26:53 --> 00:26:56 know, if it's. We've got planets around our
00:26:56 --> 00:26:59 sun, other stars must have planets too.
00:26:59 --> 00:27:02 And 30 years ago, that was proven. Well, now
00:27:02 --> 00:27:04 we're up to number 6. When are we going
00:27:04 --> 00:27:06 to stop counting? Because it's going to reach
00:27:06 --> 00:27:08 a point where we're going to find millions
00:27:08 --> 00:27:10 upon millions of these things, isn't it?
00:27:10 --> 00:27:12 Jonti Horner: It is. And even the counting's a little bit
00:27:12 --> 00:27:15 confused because the resource I
00:27:15 --> 00:27:18 trust as kind of being the authoritative word
00:27:18 --> 00:27:20 on this is the NASA exoplanet archive, which
00:27:20 --> 00:27:22 is a wonderful resource. And they've got a
00:27:22 --> 00:27:25 certain threshold for what they consider a
00:27:25 --> 00:27:27 confirmed planet. And we've got all these
00:27:27 --> 00:27:29 candidate planets as well, of which there are
00:27:29 --> 00:27:31 thousands more where we're fairly Confident
00:27:31 --> 00:27:33 there's a planet there, but it doesn't meet
00:27:33 --> 00:27:36 that rigorous criterion. There is a
00:27:36 --> 00:27:38 different exoplanet catalog run out of Europe
00:27:38 --> 00:27:40 that has a number higher because they are
00:27:40 --> 00:27:42 less strict on their criterion for
00:27:43 --> 00:27:45 confirmation. part of the reason I'm more
00:27:45 --> 00:27:47 skeptical about that catalog is that there's
00:27:47 --> 00:27:49 a number of planetary systems I've helped to
00:27:49 --> 00:27:52 kill and they've left them in their catalog.
00:27:52 --> 00:27:53 So we know for a fact those planets aren't
00:27:53 --> 00:27:55 there. I did some of that work and they still
00:27:55 --> 00:27:57 include them in their catalog, which puts
00:27:57 --> 00:27:59 them m on my naughty list. So I prefer the
00:27:59 --> 00:28:02 NASA one and the NASA one is the more
00:28:02 --> 00:28:04 cautious of them. It's really
00:28:04 --> 00:28:06 interesting how this has come though. You
00:28:06 --> 00:28:08 know, I'm, I'm 47 now. I don't feel it, but
00:28:08 --> 00:28:11 I'm getting on a little bit. I was a kid who
00:28:11 --> 00:28:13 was mad about astronomy. You know, like some
00:28:13 --> 00:28:14 of the people who send in their questions,
00:28:14 --> 00:28:16 some of the youngsters who send in questions.
00:28:16 --> 00:28:18 And when I was growing up, one of the
00:28:18 --> 00:28:19 questions I'd have been asking is do you
00:28:19 --> 00:28:21 think there are planets around other stars?
00:28:22 --> 00:28:24 We'd had observations from satellites like
00:28:24 --> 00:28:27 IRAS in the 1980s that indicated there was
00:28:27 --> 00:28:30 dust and debris around some stars. But at
00:28:30 --> 00:28:33 the time our models of planet formation fell
00:28:33 --> 00:28:35 into kind of two camps. So whereas what's now
00:28:35 --> 00:28:37 become kind of the standard baseline with
00:28:37 --> 00:28:39 some tweaks, which was that you get a disc of
00:28:39 --> 00:28:42 material around every young star and planets
00:28:42 --> 00:28:44 forming it. So most stars will have planets.
00:28:44 --> 00:28:47 But there was a competing theory that said
00:28:47 --> 00:28:49 that the planets were formed by a very close
00:28:49 --> 00:28:51 encounter between the sun and a passing star
00:28:51 --> 00:28:54 that pulled material out of the sun like a
00:28:54 --> 00:28:56 tongue of material, and the planets formed
00:28:56 --> 00:28:59 from that. and there are people who were
00:28:59 --> 00:29:02 very strong advocates of that. Now
00:29:02 --> 00:29:04 the test of those theories
00:29:05 --> 00:29:07 it would have been, are, ah, there planets
00:29:07 --> 00:29:09 around other stars, Are they common? Because
00:29:09 --> 00:29:10 the idea that two stars get close enough
00:29:10 --> 00:29:13 together to have this tidal interaction pull
00:29:13 --> 00:29:15 out a ton of material and planets form from
00:29:15 --> 00:29:17 that would suggest that planets would be
00:29:17 --> 00:29:20 overwhelmingly rare in the cosmos. So
00:29:20 --> 00:29:21 likelihood of 2 stars getting that close
00:29:21 --> 00:29:23 together and having exactly the right
00:29:23 --> 00:29:25 conditions would mean that planets were
00:29:25 --> 00:29:28 pretty much non existent, that they were a
00:29:28 --> 00:29:31 fluke of nature. The other model
00:29:31 --> 00:29:33 suggested that planets are common. And so one
00:29:33 --> 00:29:36 of the goals in the early 1990s with the
00:29:36 --> 00:29:39 search for planets elsewhere was to see
00:29:39 --> 00:29:40 whether there were any at all. And we just
00:29:40 --> 00:29:43 didn't know. The discovery of
00:29:43 --> 00:29:45 three planets around a pulsar in the early
00:29:45 --> 00:29:48 1990s broke everybody's heads. Those
00:29:48 --> 00:29:50 planets have now, incidentally, been called
00:29:50 --> 00:29:53 drow, Phoebeta and poltergeist, which are
00:29:53 --> 00:29:54 names of different types of undead from
00:29:54 --> 00:29:56 different cultures around the world. And I
00:29:56 --> 00:29:57 think that's kind of cute because you've got
00:29:57 --> 00:30:00 zombie planets around a dead star. That's all
00:30:00 --> 00:30:03 good. But 30 years ago, and actually 30 years
00:30:03 --> 00:30:05 ago last week on the 6th of October
00:30:05 --> 00:30:08 1995, we saw the announcement
00:30:08 --> 00:30:10 of the first confirmed planet around a star
00:30:10 --> 00:30:13 like the sun. And that planet was 51 Pegasi
00:30:13 --> 00:30:16 b. So it's a planet going around the south 51
00:30:16 --> 00:30:19 Pegasi. And it immediately broke
00:30:19 --> 00:30:20 everybody's heads because it was not what we
00:30:20 --> 00:30:23 expected. So both our models of planet
00:30:23 --> 00:30:26 formation that were based on a grand total of
00:30:26 --> 00:30:28 one planetary system, our own, predicted
00:30:28 --> 00:30:30 you'd have rocky planets close to the star
00:30:30 --> 00:30:33 and big gas giants a long way from the star,
00:30:33 --> 00:30:34 because that's what we see at home. And that
00:30:34 --> 00:30:37 makes sense. So to find a planet
00:30:37 --> 00:30:39 similar to Jupiter, but going around its star
00:30:39 --> 00:30:41 every four days with a surface temperature in
00:30:41 --> 00:30:44 excess of a thousand degrees C was not
00:30:44 --> 00:30:46 what was expected, I think would be the
00:30:46 --> 00:30:48 polite way to put it. Now, that forced people
00:30:48 --> 00:30:51 to immediately go back and start revisiting
00:30:51 --> 00:30:53 and improving that disk model of planet
00:30:53 --> 00:30:55 formation, which has kind of led us to where
00:30:55 --> 00:30:57 we are now. But that was kind of
00:30:57 --> 00:31:00 fundamental and foundational. For the first
00:31:01 --> 00:31:03 decade or so after that
00:31:03 --> 00:31:06 discovery, new planets were found in dribs
00:31:06 --> 00:31:08 and drabs, and the rate at which they were
00:31:08 --> 00:31:10 discovered gradually increased. And in that
00:31:10 --> 00:31:12 first decade, the best technique for finding
00:31:12 --> 00:31:14 planets, the one that was most successful,
00:31:14 --> 00:31:16 was what we call the radial velocity method,
00:31:17 --> 00:31:19 which Australia really played a leading role
00:31:19 --> 00:31:21 in with the Anglo Australian Planet Search.
00:31:21 --> 00:31:23 There was this beautiful spectrograph
00:31:23 --> 00:31:25 attached to the 3.9 meter telescope at Siding
00:31:25 --> 00:31:28 Spring, which I know Fred loves daily. It's a
00:31:28 --> 00:31:31 real icon of Australian astronomy. And, that
00:31:31 --> 00:31:33 telescope was used to point at one star,
00:31:33 --> 00:31:35 measure that star speed, then point at
00:31:35 --> 00:31:38 another, and gradually survey this collection
00:31:38 --> 00:31:40 of stars and then keep coming back to them
00:31:40 --> 00:31:41 every now and again and measure their speed
00:31:41 --> 00:31:43 again. And, by measuring the speed of these
00:31:43 --> 00:31:46 stars to the level that you can see them
00:31:46 --> 00:31:49 wobbling with changes of
00:31:49 --> 00:31:51 speed measured in a few meters per second. So
00:31:51 --> 00:31:53 comparable to speed, people walk or jog
00:31:53 --> 00:31:56 around stars that are trillions or
00:31:56 --> 00:31:57 quadrillions of kilometers away, measuring
00:31:57 --> 00:31:59 their wobbles to a precision of meters per
00:31:59 --> 00:32:02 second. That just makes my head hurt. But by
00:32:02 --> 00:32:04 doing that, you can spot the telltale wobble
00:32:04 --> 00:32:07 of a star rocking back and forward in space
00:32:07 --> 00:32:09 and infer the presence of a planet. But it's
00:32:09 --> 00:32:12 a really time consuming, challenging
00:32:12 --> 00:32:14 method where you can only observe a few stars
00:32:14 --> 00:32:15 at once, because you've got to gather light
00:32:15 --> 00:32:18 for an hour or more to get enough
00:32:18 --> 00:32:20 light, to get an accurate enough spectrum to
00:32:20 --> 00:32:22 get a single measurement. And you can only
00:32:22 --> 00:32:24 point at one star at once. By
00:32:25 --> 00:32:27 the late part of the first decade of the
00:32:27 --> 00:32:30 21st century, the transit method started to
00:32:30 --> 00:32:32 take over. And this is where we look at a lot
00:32:32 --> 00:32:35 of stars all at once and look for the
00:32:35 --> 00:32:37 few of them that are winking at us. So
00:32:37 --> 00:32:39 they've got a planet going around them that's
00:32:39 --> 00:32:40 lined, up just right that every time it goes
00:32:40 --> 00:32:42 around that star, it will block a bit of that
00:32:42 --> 00:32:44 star's light and the star will dim and then
00:32:44 --> 00:32:47 brighten again. And that started to
00:32:47 --> 00:32:49 take over from the radial velocity method
00:32:49 --> 00:32:51 purely because of the numbers. Again, because
00:32:51 --> 00:32:53 you can look at a large number of stars at
00:32:53 --> 00:32:56 the same time. And even if only
00:32:56 --> 00:32:58 1% of those stars have a planet oriented in
00:32:58 --> 00:33:00 the right direction for you to have it line
00:33:00 --> 00:33:03 up and give us a dip by looking at 100
00:33:03 --> 00:33:05 stars at once, you'll have plenty of
00:33:05 --> 00:33:07 candidates. The Kepler spacecraft
00:33:07 --> 00:33:10 launched in about 2008 and became
00:33:10 --> 00:33:13 this first census of the night sky. And
00:33:13 --> 00:33:15 it discovered on its own more than 3
00:33:15 --> 00:33:17 planets around other stars using this transit
00:33:17 --> 00:33:20 method. So we've got better and better at
00:33:20 --> 00:33:22 doing it. And over time what's happened is
00:33:22 --> 00:33:24 we've not only found the low hanging fruit,
00:33:24 --> 00:33:26 the really big planets close to their stars
00:33:26 --> 00:33:28 that give a whopping great signal that you
00:33:28 --> 00:33:30 can find, but with each generation of new
00:33:30 --> 00:33:31 instrument that's gone up there, we've got
00:33:31 --> 00:33:33 better at finding planets that are further
00:33:33 --> 00:33:35 from their stars, better at finding planets
00:33:35 --> 00:33:37 that are ever smaller, finding planets that
00:33:37 --> 00:33:40 are weird, or other techniques are coming
00:33:40 --> 00:33:41 online that allow us to do things another
00:33:41 --> 00:33:43 way. And I still think one of the greatest
00:33:43 --> 00:33:45 movies that never won an Oscar are, ah, the
00:33:45 --> 00:33:48 wonderful Images of the SAHR 8799 that
00:33:48 --> 00:33:51 shows four planets going around it. And we've
00:33:51 --> 00:33:53 got kind of a live movie of those planets
00:33:53 --> 00:33:56 orbiting that star that runs back more than a
00:33:56 --> 00:33:57 decade now. It's just breathtaking.
00:33:57 --> 00:33:59 Andrew Dunkley: Yeah, I saw it.
00:33:59 --> 00:34:02 Jonti Horner: Yeah, it's awesome. And we've basically lived
00:34:02 --> 00:34:04 through this awesome scientific
00:34:04 --> 00:34:07 revolution without really realizing it. You
00:34:07 --> 00:34:09 know, we've gone from a world where nobody
00:34:09 --> 00:34:10 knew if there were planets around other stars
00:34:11 --> 00:34:13 to a fact that there is nobody younger than
00:34:13 --> 00:34:15 the age of 30 now who grew up in that world
00:34:15 --> 00:34:18 that you and I grew up in, where we wondered
00:34:18 --> 00:34:19 if there were planets around other stars.
00:34:19 --> 00:34:22 It's absolutely breathtaking. We've had
00:34:22 --> 00:34:24 real big involvement with this here in
00:34:24 --> 00:34:26 Australia. The Anglo Australian Planet Search
00:34:26 --> 00:34:29 was one of the leaders for the first 10 or 15
00:34:29 --> 00:34:31 years of this exoplanet era. We've got a
00:34:31 --> 00:34:33 facility here in Queensland that is now
00:34:33 --> 00:34:34 leading the way, one of the leading
00:34:34 --> 00:34:37 facilities in the entire planet. You
00:34:37 --> 00:34:40 know, the only dedicated exoplanet search
00:34:40 --> 00:34:41 facility in the Southern hemisphere. And we
00:34:41 --> 00:34:44 work with NASA to do this. We've been
00:34:44 --> 00:34:47 directly involved with 41 planet discoveries
00:34:47 --> 00:34:49 in the last couple of years, using NASA's
00:34:49 --> 00:34:52 test mission and working with them. But it's
00:34:52 --> 00:34:54 this kind of ongoing exploration, this
00:34:54 --> 00:34:57 ongoing search. And, you know, what will the
00:34:57 --> 00:34:59 next 30 years bring? That's kind of what I
00:34:59 --> 00:35:02 wonder. Where will we go with it? And
00:35:02 --> 00:35:05 it's not so much when will we stop counting,
00:35:05 --> 00:35:07 but when will we start to get things that
00:35:08 --> 00:35:10 really potentially could be like the Earth?
00:35:10 --> 00:35:12 And I've said this before, I don't think
00:35:12 --> 00:35:13 we've found an Earth like planet yet. We
00:35:13 --> 00:35:15 found things about as big as the Earth that
00:35:15 --> 00:35:18 are very different. Like saying, I went
00:35:18 --> 00:35:19 swimming last week and I saw the most human
00:35:19 --> 00:35:21 like creature I've ever seen. And it was a
00:35:21 --> 00:35:23 dolphin. It was about the same size and
00:35:23 --> 00:35:25 weight as a human, but it's fundamentally not
00:35:25 --> 00:35:27 a human being. Yeah, but we're going to be
00:35:27 --> 00:35:29 moving forward and we're going to be moving
00:35:29 --> 00:35:30 from just finding these things to learning
00:35:30 --> 00:35:32 more about them. We're moving into this era
00:35:32 --> 00:35:35 of characterization and I think the number's
00:35:35 --> 00:35:36 going to gradually lose importance.
00:35:36 --> 00:35:39 You know, when we find 10 or 100,
00:35:40 --> 00:35:42 the difference will be a lot less significant
00:35:42 --> 00:35:44 than the difference between 0 and 1. But
00:35:44 --> 00:35:46 it'll start being which of the planets we
00:35:46 --> 00:35:49 know the most about. What are they like? What
00:35:49 --> 00:35:52 can we learn about them? And that's, I think,
00:35:52 --> 00:35:53 the journey for the next 30 years.
00:35:53 --> 00:35:56 Andrew Dunkley: Yes. And finding, and as you said, finding
00:35:56 --> 00:35:59 that, one planet that is so
00:35:59 --> 00:36:01 like ours in size and proximity,
00:36:02 --> 00:36:04 orbiting a sun like ours,
00:36:05 --> 00:36:08 maybe with liquid water, et cetera, et
00:36:08 --> 00:36:08 cetera.
00:36:08 --> 00:36:08 Jonti Horner: Yeah.
00:36:09 --> 00:36:11 Andrew Dunkley: that's the golden goose, isn't it, really?
00:36:11 --> 00:36:12 Jonti Horner: Absolutely.
00:36:12 --> 00:36:14 And we've got this really interesting
00:36:14 --> 00:36:17 question about how long has the
00:36:17 --> 00:36:20 Earth being in a condition that if we looked
00:36:20 --> 00:36:22 at it, it would look like the Earth. So in
00:36:22 --> 00:36:24 other words, how long has the Earth been an
00:36:24 --> 00:36:26 Earth like planet? Because when we're talking
00:36:26 --> 00:36:29 about a planet like the Earth, when it's
00:36:29 --> 00:36:30 something like the Earth is today, with, you
00:36:30 --> 00:36:32 know, beautiful blue sparkling oceans and A
00:36:32 --> 00:36:35 thin oxygen rich atmosphere and life
00:36:35 --> 00:36:37 teeming in abundant continents that are
00:36:37 --> 00:36:39 mottled brown and green and icy polar
00:36:39 --> 00:36:41 caps. But for the vast majority of the
00:36:41 --> 00:36:44 Earth's history it has looked nothing like it
00:36:44 --> 00:36:45 does now. It's had an entirely different
00:36:45 --> 00:36:48 atmosphere. It's not had free
00:36:48 --> 00:36:50 oxygen in the atmosphere. It's had periods
00:36:50 --> 00:36:52 when it was an enormous snowball, you know,
00:36:52 --> 00:36:55 snowball Earth episodes. So it's quite likely
00:36:55 --> 00:36:57 that for the majority of the Earth's history
00:36:58 --> 00:37:00 we wouldn't recognize it as an Earth like
00:37:00 --> 00:37:02 planet because it would look totally, totally
00:37:02 --> 00:37:03 different.
00:37:03 --> 00:37:05 Andrew Dunkley: Yeah, that's an interesting point. And that
00:37:05 --> 00:37:08 could exist elsewhere in the
00:37:08 --> 00:37:10 universe. And we may have seen a planet
00:37:10 --> 00:37:13 already that could one day be like
00:37:13 --> 00:37:15 ours, but it might be tens of thousands or
00:37:15 --> 00:37:17 hundreds of thousands of years before it
00:37:17 --> 00:37:19 reaches that point. So
00:37:20 --> 00:37:23 that's a really interesting factor to bring
00:37:23 --> 00:37:24 into the equation.
00:37:24 --> 00:37:27 you said some odd planets. I thought I'd do a
00:37:27 --> 00:37:29 bit of a search. these exoplanets that we've
00:37:29 --> 00:37:31 discovered in the last 30 years. Wasp
00:37:31 --> 00:37:34 76B. It's a hot
00:37:34 --> 00:37:37 Jupiter which rains molten iron. I think Fred
00:37:37 --> 00:37:38 and I talked about that one. Wasp,
00:37:39 --> 00:37:42 107B. A gas giant, with
00:37:42 --> 00:37:44 a density so low it's been described as a
00:37:44 --> 00:37:45 marshmallow planet.
00:37:47 --> 00:37:47 HD,
00:37:48 --> 00:37:51 189773B. It's a planet
00:37:51 --> 00:37:53 with an atmosphere that contains clouds of
00:37:53 --> 00:37:54 molten glass.
00:37:54 --> 00:37:57 Jonti Horner: Yeah, that's often described as a blue marble
00:37:57 --> 00:37:58 planet, I think.
00:37:58 --> 00:38:01 Andrew Dunkley: Yeah, yeah. Hat P7B is an ultra
00:38:01 --> 00:38:03 hot Jupiter that's so dark it's nearly
00:38:03 --> 00:38:05 charcoal and 5,
00:38:06 --> 00:38:08 5 Cancri E I think it's
00:38:08 --> 00:38:11 pronounced a, super Earth with a lava world,
00:38:11 --> 00:38:14 and sparkling skies. And there's probably
00:38:14 --> 00:38:17 more weird ones out there. We yet defined
00:38:17 --> 00:38:19 that, defy explanation. It's a really
00:38:19 --> 00:38:21 fascinating part of astronomy.
00:38:21 --> 00:38:23 Jonti Horner: it is. And it's that realization that the
00:38:23 --> 00:38:25 diversity of things that are out there is far
00:38:25 --> 00:38:26 greater than we could have possibly imagined.
00:38:26 --> 00:38:29 And it really forces us to revisit
00:38:29 --> 00:38:31 and refine our definitions of what a planet
00:38:31 --> 00:38:34 is. So we historically people have this
00:38:34 --> 00:38:37 idealized boundary at 13 Jupiter masses where
00:38:38 --> 00:38:39 if you're more massive than that, you're a
00:38:39 --> 00:38:41 brown dwarf and you're a fail star. And if
00:38:41 --> 00:38:42 you're less massive than that, you're a
00:38:42 --> 00:38:43 planet.
00:38:43 --> 00:38:43 Andrew Dunkley: Yeah.
00:38:43 --> 00:38:45 Jonti Horner: And we're now finding things that people are
00:38:45 --> 00:38:47 claiming a brown dwarfs that are only twice
00:38:47 --> 00:38:49 the mass of Jupiter and things people are
00:38:49 --> 00:38:50 claiming are planets that are 20 Jupiter
00:38:50 --> 00:38:53 masses. You know, there's a real blurring of
00:38:53 --> 00:38:56 that Boundary. You've then got one weird
00:38:56 --> 00:38:58 object. If you look at what the most dense
00:38:58 --> 00:39:00 planet we found is, there's one planet that
00:39:00 --> 00:39:03 has a density that is something like
00:39:03 --> 00:39:06 150 times the density of water or something
00:39:06 --> 00:39:09 like this. And it's a few Jupiter
00:39:09 --> 00:39:11 masses. And we know the density, we know the
00:39:11 --> 00:39:13 size because of transits and we know the mass
00:39:13 --> 00:39:15 because of radial velocity. And if you've got
00:39:15 --> 00:39:16 the size and the mass, you get the density.
00:39:18 --> 00:39:20 This thing is so dense so that it doesn't
00:39:20 --> 00:39:22 confirm with any known material.
00:39:23 --> 00:39:25 You know, it's many times denser than the
00:39:25 --> 00:39:27 densest metal. Gravity pulling things in
00:39:27 --> 00:39:30 can't explain it. And so
00:39:30 --> 00:39:32 is it really a planet? There is some
00:39:32 --> 00:39:34 speculation that it's actually something that
00:39:34 --> 00:39:36 was probably a white dwarf that has somehow
00:39:36 --> 00:39:39 been bombarded and fractured. So there's only
00:39:39 --> 00:39:41 a few Jupiter masses left.
00:39:42 --> 00:39:45 So it's not a planet. You know,
00:39:46 --> 00:39:47 if it was a white.
00:39:47 --> 00:39:49 Andrew Dunkley: Dwarf that's been culver, I would say no, but
00:39:49 --> 00:39:51 gosh, yeah, there's.
00:39:51 --> 00:39:53 Jonti Horner: All these other things. Planets that are less
00:39:53 --> 00:39:56 dense than cotton candy and yeah, it's
00:39:56 --> 00:39:58 awesome from a speculation point of view. And
00:39:58 --> 00:40:00 it's a, a lot of the planets we've found are
00:40:00 --> 00:40:02 things that if you saw them in an episode of
00:40:02 --> 00:40:05 Star Trek or you know, any of these sci fi
00:40:05 --> 00:40:08 series, you'd think that they jumped the
00:40:08 --> 00:40:09 shark, that that kind of thing just wasn't
00:40:09 --> 00:40:12 possible anymore. They'd obviously been
00:40:12 --> 00:40:14 enjoying themselves a little bit too much in
00:40:14 --> 00:40:17 the pre writing session. And yet we're
00:40:17 --> 00:40:19 finding these objects are just so diverse
00:40:19 --> 00:40:21 and bonkers. It's untrue. That's part of the
00:40:21 --> 00:40:23 fun of it. You never know what we're going to
00:40:23 --> 00:40:23 find next.
00:40:23 --> 00:40:24 Andrew Dunkley: Absolutely not.
00:40:25 --> 00:40:27 and that sort of takes us into our final
00:40:27 --> 00:40:30 story because this is an object that
00:40:30 --> 00:40:32 a little bit weird in our solar system.
00:40:33 --> 00:40:35 It's the moon Mimas. But it's also been
00:40:35 --> 00:40:38 called the Death Star because it does have
00:40:38 --> 00:40:40 that Death Star look about it. It's got a
00:40:40 --> 00:40:43 dish like depression, in it where it
00:40:43 --> 00:40:46 must have got hit at some stage. But the
00:40:46 --> 00:40:49 reason it's in the news now is because it
00:40:49 --> 00:40:51 is yet another object in our solar system
00:40:52 --> 00:40:54 that may contain a subsurface
00:40:54 --> 00:40:55 ocean.
00:40:56 --> 00:40:58 Jonti Horner: Yes. And it's probably of all the moons where
00:40:58 --> 00:41:01 subsurface oceans have been suspected or
00:41:01 --> 00:41:03 detected, it is the smallest of them and
00:41:03 --> 00:41:06 it's probably the most surprising of the lot.
00:41:07 --> 00:41:10 The evidence for this has built up over
00:41:10 --> 00:41:12 a bit more than a decade and comes from the
00:41:12 --> 00:41:14 Cassini mission that Spent all that time
00:41:14 --> 00:41:16 orbiting Saturn making wonderful discoveries,
00:41:16 --> 00:41:19 most famously, of course, being the geysers
00:41:19 --> 00:41:21 of liquid water erupting from the south pole
00:41:21 --> 00:41:23 of another of the small icy moons, Enceladus,
00:41:24 --> 00:41:26 which was a shock because Enceladus is so
00:41:26 --> 00:41:28 small that it should be frozen to the core.
00:41:28 --> 00:41:29 So it's a bit of a surprise there's liquid
00:41:29 --> 00:41:32 water there. Mimas is even smaller.
00:41:32 --> 00:41:35 It's the smallest object in the solar system
00:41:36 --> 00:41:39 that is spherical because its gravity has
00:41:39 --> 00:41:40 overcome the strength of the material it's
00:41:40 --> 00:41:43 made from. And when you look at the
00:41:43 --> 00:41:45 calculations people have made at what the
00:41:45 --> 00:41:48 minimum size something would have to be to be
00:41:48 --> 00:41:51 in hydrostatic equilibrium to be an object
00:41:51 --> 00:41:53 where gravity overcomes the strength. Mimas
00:41:53 --> 00:41:55 is actually a little bit smaller than that,
00:41:55 --> 00:41:58 which is interesting. It's a real edge case.
00:41:59 --> 00:42:01 And, you know, the fact that it is spherical
00:42:01 --> 00:42:03 like it is would suggest that at some point
00:42:03 --> 00:42:05 it has not been that strong in the past. So
00:42:05 --> 00:42:07 it was probably fairly liquid early on in its
00:42:07 --> 00:42:10 formation. But any ocean it had when it was
00:42:10 --> 00:42:13 born should have frozen out
00:42:13 --> 00:42:16 long, long, long, long, long ago. And, that's
00:42:16 --> 00:42:18 kind of borne out when you see the photos
00:42:18 --> 00:42:20 that are taken of Mimas. It doesn't look like
00:42:20 --> 00:42:22 Enceladus. It doesn't look like AR were
00:42:22 --> 00:42:24 talking about last week. It doesn't look like
00:42:24 --> 00:42:26 Europa. They're all places that have
00:42:26 --> 00:42:29 obviously been resurfaced, that have flat
00:42:29 --> 00:42:31 areas with cracks that look like ice that has
00:42:31 --> 00:42:33 been broken by plate tectonics. Because it's
00:42:33 --> 00:42:36 floating on an ocean, Mimas just looks like
00:42:36 --> 00:42:37 another cratered ice ball.
00:42:37 --> 00:42:38 Andrew Dunkley: Yes.
00:42:38 --> 00:42:40 Jonti Horner: So there's a few oddities that have built up.
00:42:40 --> 00:42:41 One of them is that, enormous crater,
00:42:41 --> 00:42:44 Herschel. Now, Herschel, as a crater, is
00:42:44 --> 00:42:46 almost big enough that the impactor could
00:42:46 --> 00:42:48 have shattered me. And if it had been only
00:42:48 --> 00:42:50 slightly larger, Mimas would have been
00:42:50 --> 00:42:53 destroyed. So it's right at the limit of
00:42:53 --> 00:42:56 how big a crater can be before things get
00:42:56 --> 00:42:58 seriously bad. But a lot of calculations
00:42:58 --> 00:43:01 have shown that if the Herschel crater had
00:43:01 --> 00:43:04 formed when the Moon was frozen solid to its
00:43:04 --> 00:43:07 core, it shouldn't have a central peak.
00:43:07 --> 00:43:10 But it has a central peak. Now, that suggests
00:43:10 --> 00:43:13 that Mimas was a bit slushy. But if you do
00:43:13 --> 00:43:15 the calculations and assume Mimas had a very,
00:43:15 --> 00:43:18 very well developed ocean, that
00:43:18 --> 00:43:19 crater wouldn't look like it did either,
00:43:19 --> 00:43:21 because it would have dug down into the ocean
00:43:21 --> 00:43:24 and splashed liquid water everywhere. So
00:43:24 --> 00:43:25 there are suggestions that the Herschel
00:43:25 --> 00:43:28 crater formed when Mimas was slushy rather
00:43:28 --> 00:43:30 than ocean, when it was fluid enough to get
00:43:30 --> 00:43:33 this central peak form, but not so fluid that
00:43:33 --> 00:43:35 an ocean was breached. And with the size of
00:43:35 --> 00:43:36 that M impact, it would have breached one if
00:43:36 --> 00:43:39 one was there. Now I've seen some suggestions
00:43:39 --> 00:43:41 from that saying that Herschel must therefore
00:43:41 --> 00:43:44 be a young crater because it's tied
00:43:44 --> 00:43:45 to this young ocean that is thought to be
00:43:45 --> 00:43:48 there on Mimas. Now that's one of the
00:43:48 --> 00:43:50 suggestions. I'm not necessarily sure that's
00:43:50 --> 00:43:51 the case. It may be that Herschel may be
00:43:51 --> 00:43:53 older than there was an ocean in the past.
00:43:53 --> 00:43:56 That's still to be sorted. But aside from
00:43:56 --> 00:43:58 that, there's been a lot of the data from
00:43:58 --> 00:44:01 Cassini linked to how Mimas is
00:44:01 --> 00:44:04 rotating and wobbling, suggested that
00:44:04 --> 00:44:07 it couldn't be solid to the core unless the
00:44:07 --> 00:44:09 core was not in her static equilibrium. The
00:44:09 --> 00:44:11 core was elongated and pancake shaped. and
00:44:11 --> 00:44:13 that just doesn't make sense. And as they got
00:44:13 --> 00:44:14 more and more data, more and more
00:44:14 --> 00:44:17 observations, that just doesn't work. And
00:44:17 --> 00:44:19 so from the rotation and the wobble of this
00:44:19 --> 00:44:22 moon, it suggests that as much as
00:44:22 --> 00:44:24 50% of its volume is liquid water.
00:44:25 --> 00:44:27 Wow. Which is an enormous subsurface ocean.
00:44:27 --> 00:44:30 That's an absolutely incredible ocean. But
00:44:30 --> 00:44:32 because of the thermodynamics of it, that
00:44:32 --> 00:44:34 ocean can't be old because if it was old, it
00:44:34 --> 00:44:37 would have frozen out already. Now, part of
00:44:37 --> 00:44:39 the supporting evidence for this is that the
00:44:39 --> 00:44:42 orbit of Mimas around Saturn is not perfectly
00:44:42 --> 00:44:44 circular. It's actually a little bit more
00:44:44 --> 00:44:46 eccentric than the orbit of the Earth around
00:44:46 --> 00:44:49 the Sun. That is not a
00:44:49 --> 00:44:51 situation that's tenable long term. The orbit
00:44:51 --> 00:44:53 should be circularized by tidal
00:44:53 --> 00:44:56 effects with Saturn. And so the suggestion
00:44:56 --> 00:44:58 seems to be that at some point, probably in
00:44:58 --> 00:45:01 the last 15 million years, something
00:45:01 --> 00:45:04 happened to stir, Mimas's orbit upper Mechi
00:45:04 --> 00:45:06 more eccentric, to actually make it a bit
00:45:06 --> 00:45:09 more elongated. That increased
00:45:09 --> 00:45:11 eccentricity means that Mimas now experience
00:45:11 --> 00:45:13 a significant tidal heating
00:45:14 --> 00:45:16 from being squashed and squeezed effectively
00:45:18 --> 00:45:20 by the gravity of Saturn and also by the
00:45:20 --> 00:45:21 other moons. It's in mean motion resonance
00:45:21 --> 00:45:23 with a couple of the other saturnian moons.
00:45:24 --> 00:45:25 And all of that means that you're going to
00:45:25 --> 00:45:27 get a significant amount of heat dumped into
00:45:27 --> 00:45:30 the interior of Mimas, melting that interior
00:45:30 --> 00:45:33 and creating this ocean. And the argument
00:45:33 --> 00:45:35 for the fact that the surface is not yet
00:45:35 --> 00:45:38 smooth and resurfaced is that a, that
00:45:38 --> 00:45:41 ocean is young and it's a still developing
00:45:41 --> 00:45:44 situation. But also that the crust of
00:45:44 --> 00:45:46 Mimas is 20 or 30 kilometers thick and
00:45:46 --> 00:45:48 that's thick enough that it hasn't yet
00:45:48 --> 00:45:51 responded to the liquid underneath
00:45:51 --> 00:45:53 and so you've almost got this hidden ocean in
00:45:53 --> 00:45:56 a place you wouldn't expect, but where all
00:45:56 --> 00:45:59 our observations, all our data is suggesting
00:45:59 --> 00:46:01 that the only explanation that works for all
00:46:01 --> 00:46:03 of the different things we've observed for it
00:46:03 --> 00:46:05 is that this is yet another of this growing
00:46:05 --> 00:46:08 catalog of places where there's a huge volume
00:46:08 --> 00:46:10 of liquid water buried beneath an icy
00:46:10 --> 00:46:12 surface. It's absolutely breathtaking work
00:46:12 --> 00:46:14 and it's a really good example of the
00:46:14 --> 00:46:17 iterative nature of science because it's not
00:46:17 --> 00:46:19 like this is a new discovery this week.
00:46:20 --> 00:46:21 There've been whispers about this for years
00:46:21 --> 00:46:23 and papers published about it for years and
00:46:24 --> 00:46:26 alternative hypotheses proposed and
00:46:26 --> 00:46:29 disproved and all the rest of it. And all
00:46:29 --> 00:46:31 the way through we're getting more and more
00:46:31 --> 00:46:33 certain that this ocean's there. We're
00:46:33 --> 00:46:36 learning more about the history. And I guess
00:46:36 --> 00:46:38 again, not only are we learning that liquid
00:46:38 --> 00:46:39 water is more common than the solar system,
00:46:39 --> 00:46:41 but we're getting reminded once again that
00:46:42 --> 00:46:44 the solar system's a very dynamic place. And
00:46:44 --> 00:46:47 it's not like everything of interest happened
00:46:47 --> 00:46:48 four and a half thousand million years ago.
00:46:48 --> 00:46:50 And now we're in the kind of mop up phase
00:46:50 --> 00:46:52 where nothing interesting happens. There's
00:46:52 --> 00:46:55 still a lot going on. And the solar system's
00:46:55 --> 00:46:57 dynamic in a way that if we were around when
00:46:57 --> 00:47:00 the dinosaurs walked the Earth, it would have
00:47:00 --> 00:47:01 looked like a very different place than the
00:47:01 --> 00:47:03 place we see today. It's that changeable.
00:47:03 --> 00:47:05 Andrew Dunkley: Yeah, absolutely. Yeah. And
00:47:06 --> 00:47:07 Mimas is also,
00:47:09 --> 00:47:11 if indeed it is another,
00:47:13 --> 00:47:15 water moon, let's say ice moon, whatever you
00:47:15 --> 00:47:17 want to call it, it's starting to show that
00:47:17 --> 00:47:20 it's probably more normal than we ever
00:47:20 --> 00:47:23 thought. You've got so many others that are
00:47:23 --> 00:47:26 starting to be found. obviously
00:47:26 --> 00:47:28 Europa Enceladus would be the top two, but
00:47:28 --> 00:47:30 Ganymede's now in there.
00:47:32 --> 00:47:35 Andrew Dunkley: Most of the dwarf moons,
00:47:35 --> 00:47:37 or dwarf planets in the outer solar system
00:47:37 --> 00:47:40 are starting to show these signs. So
00:47:40 --> 00:47:43 it could be quite normal here. And
00:47:43 --> 00:47:46 as we've already discussed, you know, there
00:47:46 --> 00:47:47 was a time where we weren't sure whether or
00:47:47 --> 00:47:50 not there were other planets in other solar
00:47:50 --> 00:47:53 systems in the universe. Well, it's
00:47:53 --> 00:47:55 probably going to be discovered that there
00:47:55 --> 00:47:58 are probably a lot more ice moons out there
00:47:58 --> 00:48:00 than we could possibly imagine. So.
00:48:00 --> 00:48:02 Jonti Horner: Absolutely. And the other interesting thing
00:48:02 --> 00:48:04 about this to me is it's not just suggesting
00:48:04 --> 00:48:06 that you get oceans and the oceans go away.
00:48:06 --> 00:48:09 It's suggesting you can get episodic oceans
00:48:10 --> 00:48:12 because m. If this Ocean is only 10 or 15
00:48:12 --> 00:48:15 million years old. We've had a lot of 10 and
00:48:15 --> 00:48:17 15 million year old windows
00:48:17 --> 00:48:20 in four and a half thousand million years of
00:48:20 --> 00:48:23 time. And, what is the likelihood that we
00:48:23 --> 00:48:24 just happen to be in the only one of those
00:48:24 --> 00:48:26 windows where you've got two temporary oceans
00:48:26 --> 00:48:29 at the same time, Where Enceladus and
00:48:29 --> 00:48:32 Mimas have temporary transient oceans that
00:48:32 --> 00:48:35 have only formed in recent times. And for
00:48:35 --> 00:48:37 both of them, the logic is the same. They're
00:48:37 --> 00:48:38 too small to have had this ocean since
00:48:38 --> 00:48:39 they're formed. It's got to be a recent
00:48:40 --> 00:48:42 thing. What is the likelihood that we catch
00:48:42 --> 00:48:44 two of them going off at once, just by
00:48:44 --> 00:48:46 random, when there have never been any
00:48:46 --> 00:48:48 others? So that's suggesting that these
00:48:48 --> 00:48:50 subsurface oceans on the smaller moons come
00:48:50 --> 00:48:52 and go and come again, which means
00:48:52 --> 00:48:55 that again, from the point of view of life
00:48:55 --> 00:48:57 elsewhere, life that can
00:48:57 --> 00:49:00 survive the long freeze is ready to take over
00:49:00 --> 00:49:03 during the short summer. And we see that on
00:49:03 --> 00:49:05 Earth. It's a really interesting thing that
00:49:06 --> 00:49:08 if this is a temporary transient ocean now,
00:49:09 --> 00:49:11 it's possibly been there multiple times in
00:49:11 --> 00:49:13 the past. And that's why I
00:49:13 --> 00:49:15 suspect that the Herschel Crater may not have
00:49:15 --> 00:49:18 formed with the latest recent ocean. But
00:49:18 --> 00:49:20 maybe it's a previous episode of it. We will
00:49:20 --> 00:49:22 only know when we get more studies. And of
00:49:22 --> 00:49:24 course, it's a really good reason to go back
00:49:24 --> 00:49:25 to Saturn to find out.
00:49:25 --> 00:49:28 Andrew Dunkley: Absolutely true. Yes, indeed. All right, if
00:49:28 --> 00:49:30 you want to read about that story and the,
00:49:30 --> 00:49:33 previous story, about exoplanets, you
00:49:33 --> 00:49:35 can go to space.com
00:49:36 --> 00:49:38 and we are done. Jonti, thank you so much.
00:49:39 --> 00:49:41 Jonti Horner: It's a pleasure. It's a lot to talk about.
00:49:41 --> 00:49:42 It's always good fun.
00:49:42 --> 00:49:44 Andrew Dunkley: It is great fun. Good, to see you. that's
00:49:44 --> 00:49:46 Jonti Horner, professor of Astrophysics at
00:49:46 --> 00:49:48 the University of Southern Queensland. And
00:49:48 --> 00:49:50 don't forget to visit our website while
00:49:50 --> 00:49:53 you're online and check us out. you can do
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00:50:22 --> 00:50:24 check it all out on our, space,
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00:50:28 --> 00:50:30 and I would say thanks to Huw in the studio.
00:50:30 --> 00:50:33 But he's out counting, exoplanets. And he got
00:50:33 --> 00:50:36 to 10, and you can't count any higher.
00:50:36 --> 00:50:38 And from me, Andrew Dunkley, thanks for your
00:50:38 --> 00:50:39 company. We'll see you on the next episode of
00:50:39 --> 00:50:41 Space Nuts real soon. Bye. Bye.