# Exploring Moons with Atmospheres, Hot Jupiters, and the Mysteries of Black Holes

An episode of [Space Nuts: Astronomy Insights & Cosmic Discoveries](https://invisiblenetwork.ai/podcast/1080090608), 17 Aug 2026, 34 min.

Audio: https://dts.podtrac.com/redirect.mp3/pscrb.fm/rss/p/op3.dev/e/api.spreaker.com/download/episode/74177571/exploring_moons_with_atmospheres_hot_jupiters_and_the_mysteries_of_black_holes_nordvpn_sponsor.mp3

Sponsor Link: This Q&A episode of Space Nuts is brought to you with the support of NordVPN. When you decide to get serius about your security online, do what we did and get NordVPN. We have a special deal for you too, chck out the details at www.nordvpn.com/spacenuts In this episode of Space Nuts, hosts Andrew Dunkley and Professor Fred Watson delve into a captivating Q&A session, tackling a range of intriguing questions from listeners. From the possibility of moons having atmospheres to the mysteries surrounding hot Jupiters and the fascinating realm of black holes, this episode promises to ignite your curiosity about the cosmos. Key topics include: - Chris from Exmouth wonders if moons can have atmospheres and if they can share these with their parent planets, leading to a discussion on Titan and Pluto's unique characteristics. - An anonymous listener poses a thought-provoking question about 'secret astronomy' and the potential for military satellite technology to advance our understanding of the universe. - Fenton from Minnesota asks about the likelihood of rocky planets existing in solar systems with hot Jupiters, prompting a discussion on planetary migration and the diversity of solar systems. - Ed raises a classic black hole question regarding the merger of black holes and the concept of mass escaping, leading to an exploration of gravitational waves and their implications. Join Andrew and Fred Watson as they navigate these fascinating topics, providing insights and sparking further exploration into the wonders of space. 00:00 01:18 04:13 05:37 11:35 16:34 20:35 27:11 31:31 Become a supporter of this podcast: https://www.spreaker.com/podcast/space-nuts-astronomy-insights-cosmic-discoveries--2631155/support.

## Transcript

[0:00] Andrew Dunkley: Hello again and thank you for joining us on
[0:02] yet another episode of Space Nuts. I don't
[0:04] know what we're up to.652.
[0:07] Blimey. And we only started yesterday.
[0:10] Uh, coming up in this Q and A episode, we
[0:13] will be answering questions about, uh, moons
[0:15] with atmospheres, secret
[0:18] astronomy. This is a fascinating question.
[0:21] Uh, we've also got, uh, a question about hot
[0:24] Jupiters. We've talked about them before. And
[0:26] a very rare, never before
[0:29] asked black hole question that's
[0:32] coming up in this Q and A edition of space
[0:34] nuts. 15 seconds.
[0:36] Professor Fred Watson: Guidance is internal. 10,
[0:39] 9, ignition sequence start. Uh,
[0:42] space nuts. 5, 4, 3, 2. 1, 2,
[0:45] 3, 4, 5, 5, 4, 3, 2, 1.
[0:48] Andrew Dunkley: Space nuts.
[0:49] Professor Fred Watson: Astronauts report it feels good.
[0:52] Andrew Dunkley: Joining us again to resolve all of that is
[0:54] Professor Fred Watson Watson, astronomer at
[0:57] large. Hi, Fred Watson.
[0:58] Professor Fred Watson: Hello, Andrew. How are you? Good to see you
[1:00] again.
[1:00] Andrew Dunkley: I'm as well as I was the last time you saw
[1:03] me.
[1:05] Professor Fred Watson: Yes. All those years ago. That's right, yeah.
[1:08] Andrew Dunkley: Minutes or seconds, whichever comes first.
[1:12] Uh, we've got some good questions today and,
[1:14] uh, I thought we might just get straight into
[1:16] it if you're, uh, ready to.
[1:18] Oh, no, I've got an announcement.
[1:20] Professor Fred Watson: Oh, yes, Better do that then.
[1:23] Andrew Dunkley: It's a bit of shameless self promotion. I've
[1:25] finally released my science fiction trilogy.
[1:30] Yes, it's out there. Um, I'm just putting the
[1:33] final touches on a few bits and bobs. But the
[1:35] ebook is out. Uh, the paperback
[1:38] should be out by the time you hear this.
[1:42] Um, unless you're watching us live on
[1:44] YouTube.
[1:44] Professor Fred Watson: Hello.
[1:45] Andrew Dunkley: It's called the Human Epoch.
[1:48] M which I did look up to see if there are
[1:51] any other science fiction books with that
[1:53] name, and there are not. So the human
[1:56] epoch, parts 1, 2 and 3. I released them all
[1:58] at once.
[1:58] Andrew Dunkley: Oops.
[1:59] Andrew Dunkley: I, uh, nearly released the microphone. Yeah,
[2:01] all at once. I thought, I'm gonna write the
[2:03] whole thing and release it as a batch rather
[2:06] than write one book and then
[2:08] release it and then make people wait a year.
[2:11] Now the whole bang lot's out there already
[2:14] on its way.
[2:15] Professor Fred Watson: Seasons one, two and three.
[2:16] Andrew Dunkley: Yes, exactly. I hope people enjoy it. Can't
[2:19] wait to get the feedback. Good, bad or
[2:22] indifferent. So the Human Epoch.
[2:24] Professor Fred Watson: Look for it.
[2:25] Andrew Dunkley: Uh, and you should be able to order it from
[2:27] bookshops. I don't know. I don't know how it
[2:29] works. Um, but you know, looking
[2:32] at the cost of printing and the
[2:35] sharing of spoils, um, if you
[2:38] sell a book for 20 bucks these days, you
[2:40] might get two or three dollars out of that.
[2:42] It's a Tough industry.
[2:44] Professor Fred Watson: Very. Yeah.
[2:46] Andrew Dunkley: I mean, you've really got to sell
[2:49] m tens of thousands of books to even scratch
[2:51] the surface. Which I have not done.
[2:55] Professor Fred Watson: Yeah, neither have I.
[2:56] Andrew Dunkley: No, no. But anyway, I
[2:59] thought I'd give it a mention. I've mentioned
[3:01] that I was writing it times. I thought I
[3:03] might as well people. It's out there. So
[3:06] there. That's, um, done.
[3:07] Professor Fred Watson: So you're not emulating Douglas Adams with a
[3:10] trilogy in four parts?
[3:13] Andrew Dunkley: No, but, you know, I
[3:15] might. Yeah, I might continue the
[3:18] storey because I became very. Isn't.
[3:21] Andrew Dunkley: Uh.
[3:21] Andrew Dunkley: I don't know if this happens to other
[3:23] authors. I'm sure it does.
[3:24] Professor Fred Watson: Oh, there you are.
[3:24] Andrew Dunkley: It happens to Earth.
[3:26] Professor Fred Watson: Yes, it does. He's a bit late.
[3:27] Andrew Dunkley: We could have used him in the last episode.
[3:28] Professor Fred Watson: We could. That's right. With the dogs.
[3:31] Andrew Dunkley: Um, you get a bit attached to some of
[3:34] the characters you create.
[3:35] Professor Fred Watson: Yes. I believe that happens when you write
[3:38] fiction.
[3:38] Andrew Dunkley: Um, the main character in this trilogy,
[3:42] um, I've come to adore. I really. I love his
[3:45] attitude. That's all I say.
[3:48] Professor Fred Watson: Okay. All right.
[3:49] Andrew Dunkley: Okay. He's
[3:53] a different kind of character.
[3:55] Professor Fred Watson: Is he based on anybody real?
[3:57] Andrew Dunkley: No, I made him up. Um, and I made him
[4:00] Canadian. Uh, I don't know why. I just did.
[4:03] Professor Fred Watson: I just thought Canadian.
[4:05] Andrew Dunkley: Canadians never get much of a mention in
[4:07] science fiction novels. So I thought, I'll
[4:08] make my hero a Canadian.
[4:10] Professor Fred Watson: Good on you. Yeah.
[4:13] Andrew Dunkley: All right.
[4:14] Professor Fred Watson: Before we do that, I better just go and see
[4:16] what's, um. Because I'm home alone at the
[4:18] moment. Jordy, I won't be a sec.
[4:21] All right?
[4:22] Andrew Dunkley: Okay. This doesn't happen very often. He
[4:25] could have done that while I was spruiking
[4:27] the book, you know, because, um, that would
[4:29] have been a nice filler. But now he's
[4:32] just left me swinging in the breeze.
[4:35] Which, um, happens occasionally.
[4:39] This used to happen on radio. I remember
[4:41] once, uh, years ago, um, we were
[4:43] expecting some guests, so I played an
[4:45] appropriate song. I think they were circus
[4:47] performers. And I played
[4:50] circus by Britney Spears in the hope that
[4:53] they would actually arrive while the song was
[4:54] on. And, uh, I got lucky. They
[4:57] walked in the door just as it was finishing.
[4:59] So I got the interview on air in time. It's
[5:02] sometimes a bit scary like that. Anyway,
[5:05] welcome, uh, back, Fred Watson. Is Jordie
[5:06] okay?
[5:07] Professor Fred Watson: Yes. I don't know what was causing
[5:10] the howling. Uh, ruckus.
[5:12] Andrew Dunkley: A butterfly, probably.
[5:13] Professor Fred Watson: Could have been. Honestly, it's that level
[5:15] that sets him off. You know, a leaf
[5:18] moves two, uh, hundred metres away across
[5:21] the forest and off he goes. That's right.
[5:23] Andrew Dunkley: He could probably use a GPS collar.
[5:26] Professor Fred Watson: There were times when he could use a muzzle,
[5:29] I think to speak.
[5:32] Andrew Dunkley: Um, now let's get into some questions. I
[5:34] think that's why we're here.
[5:35] Professor Fred Watson: Oh, I suppose it is, yes. Yes.
[5:37] Andrew Dunkley: Um, so first question comes from Chris
[5:40] in Exmouth in the uk. Just
[5:42] wondering, could a moon ever have
[5:45] an atmosphere and is it possible for a moon
[5:48] to be close enough to a planet to share
[5:51] an atmosphere? Really enjoy the show. Thank,
[5:54] uh, you Chris for sending that in. Um,
[5:57] look, we already know in our solar system
[6:00] there are moons with atmospheres and I do
[6:02] believe they do share their stuff with their
[6:05] home planets, some of them.
[6:06] Professor Fred Watson: Uh, correct. That's right. Although
[6:09] it's sort of um, probably not quite
[6:12] what Chris has, his mind. So yes. Uh, I mean
[6:15] the classic example is Saturn's moon Titan,
[6:18] that has a very thick atmosphere,
[6:21] um, atmospheric pressure I think one and a
[6:23] half times that of the Earth. It's a dense
[6:25] atmosphere and um, also
[6:27] opaque because it's rich in um,
[6:31] ah, hydrocarbons. The same
[6:34] stuff that makes smog in a city. Uh, is why
[6:37] we can't see through Titan's atmosphere. So
[6:39] yes, a moon can have an atmosphere, um,
[6:42] but you can't have a situation where
[6:45] uh, you had a planet and a
[6:48] moon which were sort of embedded in a much
[6:51] larger dense atmosphere. Uh,
[6:54] and that's because the, you basically
[6:57] slow down the moon as it orbits the planet,
[7:00] uh, and it doesn't last very long. Uh, in
[7:02] fact that's what brings satellites down uh,
[7:04] from orbit. Low Earth orbit above the Earth.
[7:08] They are slowed down by the Earth's
[7:09] atmosphere, even though it's very tenuous up
[7:12] there. And uh, nevertheless it slows them
[7:14] down and they fall deeper into the atmosphere
[7:16] and the deceleration continues.
[7:19] But the example that you've mentioned is the
[7:22] one that came to mind when I read this
[7:24] question as well. Uh, which is
[7:27] the dwarf planet Pluto, uh,
[7:30] which has a large moon. It's uh,
[7:34] about half the size of Pluto actually. It's
[7:35] called Charon, uh, or Charon, not
[7:38] Charon. Some people call it Charon.
[7:40] Andrew Dunkley: They do.
[7:42] Professor Fred Watson: Charon, Shaz for short.
[7:45] Shaza. Yeah, um,
[7:48] it's uh, it's a large moon, as
[7:51] I said, half the size of Pluto.
[7:54] Uh, and so they are in a sense a
[7:56] binary dwarf planet system because
[8:00] they orbit around a point which
[8:03] is outside the body of Pluto, uh,
[8:06] which is the kind of definition of a binary
[8:08] system, something orbiting around a common
[8:10] centre of gravity. Uh, so you've
[8:13] got that ah, unusual situation to start
[8:16] with, but um,
[8:19] it Appears that because of that
[8:22] geometry,
[8:25] the atmosphere of
[8:27] Pluto, which is very, very thin, but it is
[8:30] there. I was once helping a project that
[8:33] measured the atmosphere of Pluto not from
[8:35] space, but by Pluto passing in front of a
[8:37] star as observed with the Anglo Australian
[8:40] telescope. We could see it dimmed gradually,
[8:42] the light of the star rather than just
[8:44] switching off as it would have been if
[8:46] there'd been no atmosphere. So, uh, that
[8:48] atmosphere is mostly nitroge gas,
[8:51] uh, or the part that's
[8:54] escaping. Uh, and
[8:56] apparently it is basically
[8:59] captured by Charon. There's
[9:02] this flow of the nitrogen
[9:05] from Pluto to its dwarf
[9:08] planet companion. Um,
[9:10] there's probably something similar happens
[9:13] with the Earth and Moon, but very, very much
[9:17] less intense. Uh, there's probably a
[9:20] bit of gas transfer, uh, from
[9:25] the Earth, uh, to the Moon. Given that
[9:28] the pressure of the Earth's atmosphere
[9:31] doesn't just stop suddenly, it falls away
[9:33] very gradually. And in fact there are some of
[9:35] the molecules of the Earth's atmosphere that
[9:37] are out at the distance of the Moon. Uh, so
[9:40] they probably do exchange, you
[9:42] know, some low levels of gas, but
[9:45] not very much. And it is, yes, it's
[9:48] a different situation from perhaps what Chris
[9:50] had in mind with an atmosphere, with a planet
[9:52] and its moon both orbiting within it.
[9:55] Andrew Dunkley: Yeah, I understand what he was saying. Uh,
[9:57] and as you suggested, um, it
[10:00] would be an impossible situation. Although
[10:03] we do see, I think around the gas giants,
[10:06] some of those planets, particularly the ice
[10:08] worlds, do shed some of their
[10:10] material, which is picked up by
[10:13] um, um, the gas giant, I think.
[10:17] Is it Enceladus?
[10:19] Professor Fred Watson: Uh, yeah, that forms, um, that's correct.
[10:22] So that's solid matter. Actually it's the
[10:24] ice crystals that come from Enceladus
[10:27] Ocean. They form, uh, Saturn's E
[10:30] ring, uh, which is a very, um,
[10:33] non dense, very, uh, rarefied ring.
[10:36] One. I think it's the outermost ring of
[10:38] Saturn. Um, and it's basically,
[10:41] uh, the orbit of uh, Enceladus is embedded in
[10:43] that. So, yes, that's a sort of similar sort
[10:46] of situation. Yeah, that's right.
[10:47] Andrew Dunkley: It's not sharing atmosphere, but it's sharing
[10:50] material in a way.
[10:53] So, uh, the answer to both of your points,
[10:55] Chris, is definite. Yes, um,
[10:59] but no, in terms of them both sharing the
[11:01] same atmosphere. Hold us,
[11:04] Bolus. As we say so. Yeah, but great
[11:07] question, uh, Christian Exmouth. Where's
[11:10] Exmouth, Fred Watson?
[11:11] Professor Fred Watson: Uh, down in Devon. It's a lovely part of the
[11:13] country. Uh, and um, it's
[11:16] uh, not far from Exeter. The River X
[11:19] runs through both of them, as you'd expect.
[11:21] Andrew Dunkley: Uh, and the River X owned by Elon
[11:23] Musk.
[11:25] Professor Fred Watson: Probably, yes. It's spelled
[11:27] slightly differently from Elon Musk's X, but
[11:29] yes, probably still the same thing.
[11:33] Andrew Dunkley: Thanks for the question, Chris.
[11:35] Next question comes from, uh, somebody
[11:38] who's keeping their name a secret. And it's,
[11:40] uh, it's about secret astronomy. Oh, hang
[11:43] on, That's. I've got to change pages. Here we
[11:45] go. Here we go.
[11:46] Professor Fred Watson: I have a question about secret
[11:49] astronomy. We know that gamma
[11:51] ray bursts were first detected by spy
[11:53] satellites looking for nuclear testing. We
[11:56] know that satellites use star tracking and
[11:58] star catalogues for calculating their
[12:00] position. And we, uh, know that the Nancy
[12:03] Grace Roman launching, hopefully in August,
[12:06] uses, um, is built out of a,
[12:09] um, spy satellite the National Reconnaissance
[12:11] Office, the US Uh spy satellite agency,
[12:14] donated to NASA because they weren't going to
[12:16] launch it. They donated two and only one is
[12:19] being used yet. And we know that the Space
[12:21] Force released, um, a bunch of observational
[12:24] data around bolides to, um, help with
[12:26] planetary defence and asteroid detection
[12:29] and understanding. So by their nature, spy
[12:32] satellites tend to point at the Earth. Um,
[12:35] but obviously they push into a lot of
[12:37] astronomy and astronomy adjacent, um, things.
[12:41] I just wondered if you could speculate, given
[12:44] their budgets and um,
[12:46] constantly improving capabilities, where they
[12:49] might be ahead of public astronomy or running
[12:51] into things that, um. Uh,
[12:54] yeah, it might be pretty interesting in a few
[12:56] years. Thank you so much.
[12:59] Andrew Dunkley: Thank you for the question.
[13:01] Professor Fred Watson: Um,
[13:03] Andrew Dunkley: yeah, I don't know who that was, but, um.
[13:05] That's okay. Happens from time to time. But
[13:07] interesting, uh, question, Fred Watson.
[13:10] Professor Fred Watson: Really, it's, uh, not just an interesting
[13:12] question, but a very well posed one as well.
[13:14] Because everything our anonymous questioner
[13:16] said is true. Uh, and so we are being
[13:19] invited to speculate on what, what else
[13:22] might be up and running. Uh, we didn't know
[13:25] for a long time that there were two more
[13:27] Hubble telescopes, uh, because,
[13:30] you know, the company kept their. Built
[13:33] it. I think it might have been perkinelmer.
[13:35] I'm, um, not sure. But they kept their cards
[13:38] very close to their chest, uh, in terms
[13:40] of, uh, the existence of the Hubble
[13:43] telescope. But it turned out subsequently we
[13:45] found out there were two more built for
[13:48] surveillance. Um, something else
[13:51] that did find its way into astronomy
[13:54] that was originally secret was, um,
[13:56] President Reagan's Star wars technology,
[13:59] uh, which, um, required
[14:02] adaptive optics. And those are optical
[14:05] surfaces that change in response to, um,
[14:08] basically things like, um,
[14:11] uh, scintillation in the atmosphere or
[14:14] twinkling for a star. So that adaptive
[14:16] optics technology is now used very commonly
[14:19] in astronomy. Uh, it's not Used
[14:22] here in Australia we don't have a
[14:25] site that is naturally good enough um,
[14:28] to be able to compensate for um,
[14:31] this um, atmospheric turbulence. Whereas some
[14:33] of the better sites in the world like Mauna
[14:36] Kea in Hawaii and Ceropa
[14:38] Paranal, uh, in Chile, they do. And
[14:41] so they use um, adaptive optics
[14:44] very, very uh, commonly for their work.
[14:47] Basically allows you to take out the
[14:49] twinkling of a star which is something that
[14:51] ruins the images as you see them through
[14:53] telescopes. Uh and um,
[14:56] as I said, came from Star wars technology.
[14:58] Uh, that technology by the way, this is uh.
[15:01] Not really along the lines of the question
[15:04] but uh. It's leapfrogged as well from
[15:06] astronomy into um,
[15:09] ophthalmology. So uh, people are now using
[15:12] adaptive optics to compensate for
[15:15] the turbulence inside your eye
[15:18] when they're doing sort of retinoscopy and
[15:21] things like that. Uh, so that adaptive optics
[15:23] technology is now uh, gone from
[15:27] defence through astronomy and is
[15:29] now um, being developed for uh,
[15:33] health reasons, which is very, very good.
[15:35] Andrew Dunkley: Don't know if it's quite the same thing but
[15:37] my optometrist was telling me they've
[15:40] invented a new um, kind of
[15:42] um, lens that replaces human
[15:45] lens that can now
[15:49] do the same thing as a human lens. Like okay,
[15:52] when you have a cataract operation they
[15:54] replace the human lens. That's all fogged up
[15:56] with generally a plastic lens of some
[15:59] kind. But it was a fixed lens. It could only
[16:02] do one thing. They've now advanced the
[16:05] technology to the point where they can put a
[16:07] lens in that will be able to
[16:10] be controlled by your brain and give you
[16:13] various focal lengths.
[16:15] Professor Fred Watson: Yeah.
[16:15] Andrew Dunkley: Which I think is amazing.
[16:17] Professor Fred Watson: It's what you. What your eye naturally does.
[16:19] It's called accommodation you that the eye
[16:21] accommodates to different distances by
[16:23] changing the shape of the lens. Yeah, yeah.
[16:25] So um, that's pretty. Yes. Quite remarkable
[16:28] and um. Would be a real breakthrough for
[16:31] um. You know, for vision, uh, for poor
[16:34] vision.
[16:34] Anyway, we've strayed off the topic here. We
[16:36] have a bit and uh.
[16:38] Andrew Dunkley: I do, I'm sure never happens usually.
[16:43] Professor Fred Watson: I'm sure that um. Uh. Our uh.
[16:45] Listener is on the money suggesting that
[16:47] there are technologies that are being used
[16:51] in secrets, um.
[16:53] Professor Fred Watson: Ah.
[16:53] Professor Fred Watson: Or restricted environments.
[16:56] Uh, that would be of great
[16:59] value for astronomy. I uh.
[17:02] Guess the kind of thing that comes to mind is
[17:05] quantum detectors and. And things of that
[17:08] sort. Um, there is no. I don't think there's
[17:11] any equivalent uh, for example in the
[17:14] field of gravitational wave astronomy. I
[17:16] don't think there's anything that the
[17:18] military are doing that could feed into that.
[17:19] Although quantum optics are being used in
[17:21] that now. So, um, I
[17:24] suspect it's in, you know, in relation to the
[17:26] tools that are developed for, uh,
[17:30] our observations. Um,
[17:32] we owe infrared detectors,
[17:35] the things that see redder than red light or
[17:37] heat radiation. We owe them to the military.
[17:40] That's a spin off from military work. Um,
[17:43] I do remember, uh, one of the first
[17:46] infrared instruments on the Anglo Australian
[17:48] telescope. When it was being delivered.
[17:51] Uh, I think,
[17:54] um, the detector came under armed guard
[17:56] almost. It wasn't quite like that. But there
[17:58] was a lot of hoops to jump through when this
[18:01] detector was delivered. Because it had to be
[18:03] certain not to stray into the hands
[18:06] of certain foreign nations who the
[18:09] Americans who developed this detector didn't
[18:12] want, uh, them to get hold of.
[18:15] So those technologies do eventually
[18:19] kind of sprinkle down to astronomy where the
[18:21] poor relations in that regard, uh, although
[18:24] we do push the limits perhaps more than
[18:25] anybody else, uh, in technology.
[18:29] So, um, yes,
[18:31] I, I don't have any
[18:35] definite, um, speculations, uh,
[18:38] except to say that nothing would
[18:40] surprise me in that regard
[18:43] when it comes.
[18:45] Andrew Dunkley: I'm not a conspiracy theorist, but I do
[18:47] believe there's a heck of a lot going on up
[18:50] there that we do not and probably will
[18:53] not know about. Um, and
[18:56] I truly believe that the technology
[18:59] available today in space and on
[19:02] the planet, um, in those
[19:05] dark corners of government buildings
[19:08] is far, far more advanced than we
[19:11] could possibly imagine. I think given what
[19:14] we've got access to in a domestic sense in
[19:16] the public arena today,
[19:19] uh, what's been developed already behind
[19:22] closed doors that we're unaware of. And
[19:25] it's probably up. They're circling the planet
[19:27] as we speak.
[19:29] Professor Fred Watson: Yeah, I think it works both ways though,
[19:31] because I think, um, we're now
[19:34] seeing, uh, the military adopting
[19:37] what would have been thought of as commercial
[19:39] products before. Uh,
[19:42] and that's happened certainly in Ukraine.
[19:45] There's been an adaptation of
[19:48] all sorts of commercial products for
[19:51] military purposes. Um, so
[19:54] what I guess I'm saying is that the
[19:55] technology that we use every day is not
[19:58] as far removed from what the military use
[20:01] as it would have been 20 or 30 years ago.
[20:05] Uh, I think that's probably fair to say, but
[20:08] that's me going out on a limb. And who can
[20:09] prove me wrong?
[20:11] Andrew Dunkley: Well, that's a good point too. Yeah, it's a,
[20:14] uh, really interesting question. Thank you
[20:16] for sending it in. This is Space Nuts Andrew
[20:18] Dunkley here with Professor Fred Watson
[20:20] Watson.
[20:22] Professor Fred Watson: I believe that this nation should commit
[20:25] itself to achieving the goal
[20:27] before this decade is out of landing A man
[20:30] on the moon and returning him safely
[20:33] Andrew Dunkley: to the Earth face nuts.
[20:35] Another audio question from Fred.
[20:39] Andrew Dunkley: Hi, this is Fred calling you from St. Paul,
[20:41] Minnesota in the US I have a question for
[20:44] you regarding the solar systems that contain
[20:48] uh, so called hot Jupiter planets, those
[20:50] which are very close, ah, around their
[20:53] suns. Is it reasonable at all to
[20:55] expect that they will have
[20:58] smaller planets, rocky planets,
[21:01] or are there good reasons that
[21:04] come to mind where that should not be the
[21:06] case? Um, I'd uh, appreciate hearing
[21:09] your theories on this, uh, what the variables
[21:12] would be in this and I of course enjoy
[21:15] listening to your show. Thank you very much.
[21:18] Goodbye.
[21:19] Andrew Dunkley: Thank you Fred. Uh, Fred's one of our semi
[21:22] regular sender inners and um,
[21:24] he's always got a very interesting question
[21:27] in mind. Um, so uh, yeah, I'm
[21:30] guessing that what he is asking is if you've
[21:32] got a solar system with hot Jupiters, uh,
[21:35] that are orbiting their parent star in
[21:38] close proximity, could those systems
[21:41] have rocky planets further out? Now, uh, the
[21:43] downside of exoplanet detection is rocky
[21:45] planets are very hard to find at a distance.
[21:47] You generally find the gas giants
[21:50] fast or first. Um,
[21:53] we do know there are a lot of hot Jupiters
[21:55] out there because we've talked about them.
[21:58] Um, but uh, yeah,
[22:01] uh, what's the likelihood that that's a
[22:04] common thing? Um, not that there's
[22:06] anything absolutely common about anything you
[22:09] find when you start looking around at other
[22:12] solar systems?
[22:13] Professor Fred Watson: Yeah, that's exactly right. Our solar
[22:16] system is very neat and tidy compared with
[22:18] most of the other ones that we've detected.
[22:20] But you're absolutely right Andrew. Um, the
[22:23] rocky planets are the, the tricky ones to
[22:25] observe. And so it might well be that
[22:28] what we're seeing is effectively a selection
[22:31] effect. We're selecting the easiest ones,
[22:34] uh, to discover. Uh, and that's why we see a
[22:37] lot of hot Jupiters without any evidence
[22:40] of rocky planets in the same solar systems,
[22:43] I think, and I haven't looked at this for
[22:46] some time but um, one of the ideas
[22:49] for why we've got this
[22:52] situation with hot Jupiters is basically
[22:56] a planetary migration. This is where planets
[22:59] change their positions in the solar system.
[23:02] Uh, and that might have happened to some
[23:04] extent in our solar system, but not
[23:07] in um, a really sort
[23:10] of existential way. Not in a way that will
[23:13] totally alter the shape of the solar system
[23:16] because we've got four rocky planets which
[23:17] are the innermost ones and they exist within
[23:20] a zone where um,
[23:23] water exists as a
[23:26] gas, whereas beyond the orbit of Mars,
[23:29] and we sometimes call that the frost line or
[23:31] the ice line water exists
[23:34] uh, as ice and that ice is what
[23:37] has allowed the gas giants to grow
[23:40] to the size that they have because the ice
[23:43] basically collects and uh, the
[23:46] planets absorb it. So you've got ah,
[23:50] not just a massive rock being formed but ice
[23:52] as well. And then you end up with a gas
[23:55] giant planet. Uh so the four gas giants
[23:58] we think are ah, like that because they're
[24:00] outside the frost line. Now if you've got
[24:03] planetary migration taking place then
[24:06] some of those planets could wander in to the
[24:08] inner solar system. Uh and
[24:11] it may essentially leave your solar
[24:14] system looking like some of the ones that we
[24:16] see with a hot Jupiter orbiting very close
[24:19] to Paris star. But also
[24:22] perhaps with some rocky planets lingering
[24:25] uh, moaning around or moping around
[24:28] uh, where they've been uh, projected
[24:31] to by the rearrangement of the planets
[24:33] because some of them could be ejected by
[24:35] planetary migration. If you've got your gas
[24:38] giant wanders too near your little rocky
[24:40] planet, it's going to boot it out the solar
[24:42] system altogether. Uh but um, I
[24:45] suspect that there will be solar systems uh,
[24:48] ah that will turn out to have both hot
[24:50] Jupiters and rocky planets. And as our
[24:54] um, technology improves and allows us to
[24:56] detect these things uh, at lower masses, I
[24:59] think we'll be finding them as well. So um,
[25:01] watch this space phantom. That's the bottom
[25:03] line there.
[25:04] Andrew Dunkley: Theo was a wandering planet.
[25:06] Professor Fred Watson: Yes, that's right. Theo wandered into the
[25:08] Earth back in the uh, literally
[25:11] late 4,000 B.C. yeah,
[25:15] 4,000 million BCS. I beg your pardon. Four
[25:17] billion. Yeah.
[25:19] Andrew Dunkley: I think um, the train of thought these days
[25:22] is that uh, in terms of solar systems,
[25:25] um, just about every star has at least got
[25:28] one planet. Um, that's based
[25:31] on an average assumption. But um,
[25:34] it also stands to reason that uh,
[25:37] solar systems are as many and as varied as
[25:40] there are stars in the sky. Ours
[25:43] which has the four rocky planets, then the
[25:45] gas giants as you move out and then the dwarf
[25:47] planets beyond that um, ours
[25:50] seems to be quite different
[25:53] from most.
[25:54] Professor Fred Watson: It does, that's what I meant. It's very neat
[25:56] and tidy compared with uh, what we see
[25:59] elsewhere. Um, certainly
[26:02] if you were on uh, the planet of
[26:05] a star 100 light years away, our rocky
[26:08] planets would be very difficult to detect.
[26:10] And you just think, you'd probably think all
[26:12] it had was Jupiter, uh because you'd be
[26:15] able to detect Jupiter relatively easily. If
[26:17] it passed in front of the sun it would, would
[26:19] produce a 1% drop in the um, light
[26:22] of the sun. And that's easy to
[26:25] measure. So yes. So um,
[26:28] uh is the future
[26:31] of our solar system, one that does involve
[26:33] planetary migration. Um, it doesn't seem
[26:36] to be. The planets seem to be in very, very
[26:38] stable orbits. And maybe that's just
[26:40] something to do with the geometry of the
[26:42] solar system itself. But maybe it's something
[26:44] to do also with why intelligent
[26:47] life has evolved on one of those planets.
[26:49] Because we've had this idea long term
[26:51] stability over many millions of years,
[26:54] which
[26:54] Andrew Dunkley: is why it's going to be near impossible to
[26:56] find another intelligent, communicative
[26:59] civilization. Because, um, the circumstances
[27:02] are unique.
[27:03] Professor Fred Watson: Could be, probably, yeah, could be almost
[27:05] unique. Yes.
[27:06] Andrew Dunkley: Thank you, Fred.
[27:10] Professor Fred Watson: Roger, you're allowed to clear here.
[27:11] Andrew Dunkley: Also space nuts. Our final question
[27:14] comes from Ed. Now this is not dissimilar to
[27:17] a question we had recently, but it's not
[27:19] quite the same either. Uh, we believe
[27:22] that nothing can escape from a black hole.
[27:25] And yet when two black holes merge, the mass
[27:27] of the surviving black hole is significantly
[27:30] less than the combined mass of the two
[27:31] merging black holes. It would appear this
[27:34] missing mass, which I understand is converted
[27:36] to gravitational waves, has to come from the
[27:39] black holes, hence energy. Matter does
[27:42] escape from black holes. Is this
[27:44] wrong? Ed asks. Hello, Ed, thanks for the
[27:47] question. Uh, black hole questions,
[27:50] Fred Watson. It's not. A week goes by we
[27:52] don't get a black hole.
[27:54] Professor Fred Watson: A great one, though. It's a good question
[27:56] that Ed's raised. Um, so it's.
[27:59] Yes, the uh, gravitational radiation
[28:03] is
[28:06] quite different from
[28:09] uh, the electromagnetic radiation that's
[28:12] coming from a black hole which does get
[28:14] trapped. It can't pass the event horizon.
[28:16] That's what the event horizon is all about.
[28:18] Because gravitation is a property
[28:22] not of the black hole, but of
[28:25] the universe itself. Ah. It's
[28:28] the underlying sort of fabric of space that
[28:30] is what carries gravity. Um,
[28:33] and so if you've got these colliding
[28:36] black holes, they shake the space
[28:39] itself rather than emit
[28:43] something. So that's the
[28:45] difference. The gravitational waves. Uh,
[28:48] yes, indeed. They're caused by, uh, the,
[28:51] by a loss of mass from the black holes. But
[28:54] they're not a property of the black holes. If
[28:56] I can put it that way. Yes, it's an
[28:59] effect rather than something being emitted.
[29:02] So, um, um, Ed's quite right that
[29:05] nothing can escape a black hole, but
[29:07] gravitational waves apparently do. But
[29:10] they're not. Basically what you're seeing is,
[29:13] uh, something to do with the universe, not
[29:15] the black hole.
[29:17] Andrew Dunkley: Okay, yeah, I get it. It's the old pebble in
[29:20] the pond trick.
[29:21] Professor Fred Watson: Yeah, that's right. Yes it is, yeah.
[29:24] The ripples in the pond, uh, don't come
[29:27] from the pebble. They come from the fact that
[29:30] the pebble has disturbed the underlying
[29:33] fabric. Uh, of the water, in fact. Put it
[29:35] that way. Yeah, it's a really good analogy.
[29:39] Andrew Dunkley: I come up with all sorts.
[29:41] Professor Fred Watson: You do, but that's a cracking good one,
[29:43] Andrew. Well done. I like that.
[29:45] Andrew Dunkley: I think you told it to me once before.
[29:48] Maybe.
[29:49] Professor Fred Watson: Maybe.
[29:49] Andrew Dunkley: Um, so that's the simplicity of it, really.
[29:52] There's not much more to tell.
[29:53] Professor Fred Watson: No, no, that's right. It's not. You know, it
[29:55] doesn't defy the logic of nothing being able
[29:58] to escape a black hole. Uh, it's, um,
[30:01] because you, um. Yes, Ed's right. Nothing
[30:04] can. Nothing solid or,
[30:07] um, electromagnetic or particles
[30:09] can't either. Uh, but the
[30:12] gravitational field is different. It's
[30:15] something to do with the underlying universe.
[30:18] Andrew Dunkley: Indeed it is. Uh, thanks, Ed. Great question.
[30:21] And, um, yeah, answered
[30:24] very simply in the end. Which
[30:27] doesn't happen often, does it, really?
[30:29] Professor Fred Watson: No, usually they're not answered at all.
[30:32] Andrew Dunkley: Or just adequately.
[30:33] Professor Fred Watson: Yes, adequately. That's right.
[30:36] Andrew Dunkley: Thanks, Ed. Uh, thanks to everyone who's sent
[30:38] in questions. And if you would like to send a
[30:39] question to us, please do go to our website,
[30:41] spacenutspodcast.com or spacenuts
[30:44] IO and there's a little button, uh, up the
[30:47] top top. Uh, or a tab or a link or whatever.
[30:49] It's a link. Uh, AMA stands for Ask me
[30:52] Anything. And you can send your questions in
[30:54] through that particular interface,
[30:57] text or audio. Don't forget to tell us who
[31:00] you are or where you're from. Although
[31:01] sometimes people forget. And you're not going
[31:03] to get into trouble for that. We're not that
[31:06] kind of people. M
[31:08] Nobody there. Have a look around. Visit the
[31:10] shop, become a supporter. And don't forget to
[31:13] leave, uh, reviews wherever you listen to us.
[31:15] Maybe the people listening live right now
[31:18] via YouTube could leave reviews. That'd be
[31:20] nice. Unless they hated us. Just don't do
[31:23] anything. No, I'm just kidding. They've stuck
[31:26] around, so we must be doing something right.
[31:28] Professor Fred Watson: Yeah.
[31:28] Andrew Dunkley: And we're all done, Fred Watson. Thank you
[31:30] very much.
[31:31] Professor Fred Watson: Thank you, Andrew. Um, we'll talk again soon.
[31:34] I, uh, look forward to it.
[31:35] Andrew Dunkley: I hope so. Uh, Professor Fred Watson Watson,
[31:37] astronomer at large, thanks to Huw in the
[31:39] studio, um, who couldn't be with
[31:42] us today because, uh, he's got a black
[31:45] hole problem. He called a plumber and neither
[31:48] of them can get out. And from me, Andrew
[31:50] Dunkley. Thanks for your company. I'll catch
[31:52] you on the next episode of Space Nuts. Until
[31:55] then, bye bye. You've been
[31:58] listening to the Space Nuts podcast
[32:01] available at Apple Podcasts, Spotify,
[32:05] iHeartRadio or your favourite podcast
[32:07] player. You can also stream on
[32:09] demand@bytes.com um,
[32:11] Professor Fred Watson: this has been another quality podcast
[32:13] production from bytes.um com.

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