# Strange Spins and Cosmic Rings: Exploring NGC 4698 and Chariklo's Secrets

An episode of [Space Nuts: Astronomy Insights & Cosmic Discoveries](https://invisiblenetwork.ai/podcast/1080090608), 12 Oct 2026, 35 min.

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Sponsor Link: This episode of Space Nuts is brought to you with the support of NordVPN. To check out our special money-saving deal, visit www.nordvpn.com/spacenuts Space Nuts: Unraveling the Mysteries of NGC 4698 and Chariklo's Rings In this exciting episode of Space Nuts, hosts Andrew Dunkley and Professor Fred Watson explore some truly peculiar cosmic phenomena. They kick off with a deep dive into the strange behaviour of the galaxy NGC 4698, known for its unusual rotational patterns and mysterious bulge, leading to discussions about possible galactic mergers. Next, the duo ventures into the intriguing world of Chariklo, a centaur object with changing rings, as they discuss the latest observations from the James Webb Space Telescope and the implications of its unique ring structure. Join Andrew and Fred Watson as they navigate these captivating astronomical tales with their signature blend of humour and insight. Key topics - The peculiar characteristics of NGC 4698: What makes this galaxy behave strangely? - Insights into the dynamics of galaxy mergers and their effects on structure. - Chariklo's rings: How have they changed since their discovery, and what does this mean for our understanding of ring systems? - The potential existence of a hidden moon influencing the structure of Chariklo's rings. Timestamps 00:00 - Introduction and overview of today's topics 01:20 - Discussion on the peculiar galaxy NGC 4698 and its unusual features 15:30 - Exploring Chariklo and the changes in its ring system 25:00 - Insights from the James Webb Space Telescope and the hidden moon hypothesis 35:15 - Final thoughts and listener engagement Wanting a commercial free option of Space Nuts? Become a supporter of this podcast: https://www.spreaker.com/podcast/space-nuts-astronomy-insights-cosmic-discoveries--2631155/support.

## Transcript

[0:00] Andrew Dunkley: Hi there. Thanks for joining us on yet
[0:01] another edition of the Space Nuts
[0:04] podcast. My name is Andrew Dunkley, your host
[0:06] and it's good to have your company as we look
[0:09] into these, uh, issues, you call them issues
[0:12] stories. Uh, there's a really weird
[0:15] galaxy out there. It's got a really
[0:17] odd rotational pattern, uh, and
[0:20] one wonders why.
[0:21] I have a theory, but it's probably wrong. Uh,
[0:24] we're also going to look at the changing
[0:27] rings of Chariklo. What is
[0:30] that? It's a weird thing in a weird
[0:32] place I think is the best way to describe it.
[0:35] And we don't need to talk about it anymore.
[0:37] And we've got a juicy story from ESA as well.
[0:40] That's all coming up on this episode of
[0:43] Space Nuts.
[0:44] Professor Fred Watson: 15 seconds. Guidance within channel
[0:47] N9. Ignition
[0:49] sequence star.
[0:50] Professor Fred Watson: Uh, SpaceNets.
[0:51] Professor Fred Watson: 5, 4, 3, 2, 1. 3, 3, 4,
[0:54] 5, 5, 4, 3, 2', 1. Space
[0:57] Nuts astronauts reported. Neil.
[0:59] Good.
[1:01] Andrew Dunkley: Actually, we've got a couple of stories from
[1:02] ESA today. Joining us to explain all
[1:05] of that mystery that I just unveiled is
[1:08] Professor Fred Watson Watson, astronomer at
[1:10] large. Hello Fred Watson.
[1:11] Professor Fred Watson: Good morning. Uh, uh, what's your name again?
[1:13] Andrew. Yeah, that's it, sorry. Dave.
[1:16] Andrew Dunkley: Dave. I've copped that many times. I still
[1:19] get that now. That was years ago that
[1:21] somebody accidentally calls me Dave. And
[1:24] it's still going.
[1:25] Professor Fred Watson: Part of Space Nuts legend is that
[1:28] Andrew Dunkley: my best friend's name is Dave. So I'm not
[1:31] offended.
[1:31] Professor Fred Watson: Uh, could be, actually. Um, I've got several
[1:34] really close friends who are Dave's as well,
[1:35] so must be what it is.
[1:39] Anyway, Dave, it's nice to talk to you again.
[1:41] Andrew Dunkley: Thank you, Fred Watson.
[1:43] Professor Fred Watson: Um,
[1:45] Professor Fred Watson: I usually get Frank.
[1:47] Andrew Dunkley: Do you?
[1:47] Professor Fred Watson: Uh, sometimes I get Greg. Yeah. When people
[1:50] m. Mishear the consonants.
[1:53] Okay, so it's when you, you know
[1:56] when you go and order a coffee and they say
[1:58] what's your name? So they can yell out your
[2:00] name when your coffee's ready. Yeah.
[2:01] And um, so I expect Greg or
[2:05] you know, Ted or anything that's got
[2:07] different consonants. And occasionally I get
[2:09] Frank as well.
[2:10] Andrew Dunkley: Well, my elder, I've got a better one than
[2:12] that. Uh, my eldest son's name is Kyle. K
[2:15] Y L E. And uh,
[2:18] this turned into a Facebook, um,
[2:20] epidemic, uh, at one stage where
[2:23] he'd go and order a coffee down in Sydney
[2:25] somewhere and then they'd call out Kylie,
[2:29] Kylie. And they'd even
[2:32] written Kylie on the car.
[2:33] Professor Fred Watson: Ah, yeah, yeah.
[2:34] Andrew Dunkley: And every time it happened he'd take a photo
[2:36] and go put it on Facebook and go what the
[2:39] bleep? And it still
[2:41] happens. To him. But he's been down there
[2:44] for, I don't know, 15 years now. And, um,
[2:47] he still gets called Kylie.
[2:50] Professor Fred Watson: I don't understand. Could be there.
[2:52] Andrew Dunkley: Anyway, he hates us because we named him, so.
[2:55] Anyway.
[2:55] Professor Fred Watson: Yeah, yeah.
[2:56] Professor Fred Watson: Why did he call him Kyle?
[2:58] Andrew Dunkley: Uh, that's a funny story too, because, uh,
[3:01] when Judy fell pregnant and I'm
[3:04] still trying to find the man that did it.
[3:05] Anyway, um, when
[3:08] Judy fell pregnant, we were sitting in the
[3:10] lounge room saying, what are we going to call
[3:12] him? And we were watching the movie the
[3:15] Terminator. And the original one, the
[3:18] very first one, and the. And the, um,
[3:20] hero's name in that was Kyle. I said, that's
[3:23] a nice name. And Judy said, yeah, yeah, let's
[3:25] go with that.
[3:26] So it's from the mo Movie the Terminator.
[3:28] There's. There's no family connection
[3:31] whatsoever with the name. We just liked it
[3:34] from the film.
[3:37] Professor Fred Watson: I thought you might. There might be a link
[3:39] with Scotland there. Uh, no, Kyle is
[3:42] an estuary. Oh, is it kind of
[3:45] local? Of Sutherland. Yeah. So he's an
[3:47] estuary. That's his name.
[3:49] Andrew Dunkley: I mean, there's a bit of Scottish heritage in
[3:51] our family, so that probably works.
[3:53] Professor Fred Watson: That'll.
[3:53] Andrew Dunkley: That'll do.
[3:54] Professor Fred Watson: Yeah.
[3:55] Professor Fred Watson: Yeah.
[3:56] Andrew Dunkley: And our other two, we. We picked Morgan for a
[3:58] girl and never had a girl.
[3:59] So when we had our second boy, we went, well,
[4:01] let's just use that just in case.
[4:04] And then the third one came along and we
[4:06] were. We were still devoid of names. And I
[4:08] said, well, why not Lachlan? You know, we're
[4:11] not far from the Lachlan River. Let's just
[4:13] stick with Lachlan. So that's how that
[4:15] happened as well.
[4:17] Professor Fred Watson: Yeah.
[4:18] Andrew Dunkley: Yeah, it is. It is, yeah.
[4:20] Professor Fred Watson: There you go.
[4:21] Andrew Dunkley: Hmm. Yeah. I hadn't thought about
[4:24] how we named our kids, and I haven't thought
[4:26] about it for years. And they never asked, so
[4:29] I. We don't go there.
[4:32] Professor Fred Watson: We'll do another episode, uh, down the track
[4:35] and I'll tell you how, uh, we. Why we
[4:37] named our kids. All right. Yeah,
[4:40] no, we won't do it now. We won't do it now.
[4:42] Andrew Dunkley: We'll do it in the next episode.
[4:43] Professor Fred Watson: Do it in the next episode.
[4:45] Andrew Dunkley: We should do some stories, though. Um, now
[4:48] this.
[4:48] This one's really weird and it's
[4:51] all to do with observ of a
[4:54] very strange, uh, galaxy,
[4:57] uh, that's behaving badly. Or is it just
[5:00] behaving strangely? Has it had too much to
[5:02] drink? Fred Watson?
[5:03] Professor Fred Watson: It could be. Certainly. It probably is a
[5:06] digestive issue, uh, for the galaxy.
[5:08] Andrew Dunkley: I was gonna Say that that was my theory. I
[5:10] bet this is a result of a galaxy merger.
[5:13] Professor Fred Watson: Yeah, I think that's right. That's the
[5:15] general view of it. So the galaxy we're
[5:17] talking about, it's actually not. It's a
[5:19] nearby galaxy. It's um, 55
[5:22] million light years away. That's very
[5:24] much uh, our uh, local backyard. So the
[5:26] images that we see of it are very, very
[5:28] detailed. There's a beautiful image, uh,
[5:31] which I think is on both the ESA and NASA
[5:33] website because it's a Hubble telescope
[5:36] image. And of course the Hubble telescope is
[5:39] um, um, funded by both and uh,
[5:41] operated by both. Um. Uh,
[5:44] it's a spiral galaxy, uh, in
[5:47] the constellation Virgo. As I said, 55
[5:49] million light years away. Uh, it's one
[5:52] member of the Virgo Cluster, which
[5:55] is one of the biggest nearby galaxy clusters
[5:58] that we can see. Um, there's something like a
[6:00] thousand galaxies in it. Um, there are a
[6:03] few really big ones, the Coma Cluster, uh,
[6:06] Virgo Cluster, a few in our locality. And
[6:09] they're big, they're big, um, galaxy
[6:11] clusters.
[6:12] So um, when you look at
[6:15] this, there's a lovely Hubble telescope image
[6:18] that I guess is the centre of uh,
[6:21] attention on this story. Um,
[6:24] beautiful image of this galaxy, spiral
[6:27] arms, which unlike
[6:30] the spiral arms of our Milky Way
[6:32] galaxy, we think they are at their
[6:35] inner edge firmly pinned down to the
[6:39] um, central bar of the galaxy. That
[6:41] means when you look at it, and we clearly
[6:44] can't look at our own galaxy in a photograph
[6:47] because we're right inside it. Uh, we can't
[6:49] look at the whole thing but we can map it
[6:51] through infrared and radio astronomy. And um,
[6:54] the evidence seems to be that there is a bar,
[6:57] uh, at the centre. Now that's not a bar you
[6:59] lean against. It's an elongated distribution
[7:02] of stars, uh, and
[7:04] um, with some really interesting dynamics,
[7:06] really interesting movement in it. Uh, but
[7:09] our spiral arms, uh, are uh, sort of
[7:12] fixed to the end of the bar. That's where
[7:14] they seem to originate from. Um,
[7:16] whereas with ah, this particular galaxy, and
[7:19] I haven't given it its name, it is NGC
[7:22] 4698. A uh, lovely,
[7:24] um, meaningless name. Um,
[7:28] uh, NGC stands for New General Catalogue
[7:30] which if I remember rightly was published in
[7:32] 1888. Uh, so it's still pretty new
[7:35] really. NGC
[7:37] 4698. Uh, the point
[7:40] about this galaxy is when you look at it you
[7:42] can see spiral arms, but they're sort of
[7:44] only in the outer, I guess the
[7:47] outer third of the galaxy.
[7:49] And in the middle there's no sign of
[7:52] spiral arms. So that straight away
[7:55] tells you that there's something different
[7:57] about this object. Um, the
[7:59] other thing, and the thing that is, I guess,
[8:02] really remarkable is what we
[8:05] slightly unflatteringly refer to as the bulge
[8:07] of the galaxy. Um, our galaxy has a bulge.
[8:10] Uh, it's, uh, what is often known as a
[8:13] peanut bulge because it's kind of vaguely
[8:16] peanut shaped. And that probably comes about
[8:18] because of the, the bar in the centre of our
[8:20] galaxy. Uh, we see it from our vantage point
[8:23] here in the solar system. We see it in the
[8:26] constellation of Sagittarius. And,
[8:28] um, if you look on winter nights
[8:31] at the Milky Way, when it's nearly overhead,
[8:34] that's where it is at its widest. There is a
[8:37] sort of big swath of stars there
[8:40] and that's the bulge of our own galaxy. So
[8:42] you can kind of see it with the naked eye.
[8:45] Uh, this one has a bulge as well, which is
[8:48] elongated a bit like ours, but
[8:51] it's elongated in the wrong direction.
[8:54] It stretches out
[8:56] perpendicular to the disc of the
[8:58] galaxy. And that is a rarity.
[9:01] I don't think it's unique, but I think it's
[9:04] pretty rare. Uh, and
[9:07] so what, um, is
[9:10] perhaps the smoking
[9:13] gun about how this originated
[9:16] is that when you look at the movement of
[9:19] stars within that perpendicular bulge,
[9:22] um, you find that the motion of the stars is
[9:25] perpendicular to the rest of the galaxy as
[9:27] well. So it's not just that it looks as
[9:29] though it's at right angles, it really is
[9:31] because the stars are moving in that
[9:34] direction, uh, up and down through the centre
[9:37] of the galaxy, rather than, uh,
[9:40] swirling around in the same plane as the disc
[9:43] of the galaxy.
[9:44] Andrew Dunkley: Yeah, I don't, you know,
[9:47] is that possibly a rarity or is
[9:50] this most likely more common than we think
[9:52] we've just happened to find? The first one
[9:55] that looks this way.
[9:56] Professor Fred Watson: Uh, yeah, that's a good question.
[9:57] Is it, um, you know, is it a selection effect
[10:00] that we normally don't see that. But I
[10:03] think it is more likely that this is
[10:06] quite rare because, um, certainly the
[10:09] imagery of this object, uh, is
[10:12] very striking. When you look at it, you can
[10:14] see straight away that its bulge is
[10:17] different from, uh, normal
[10:20] galaxies, that it's got this, uh,
[10:23] sprinkling of stars which are well above the
[10:26] plane of the galaxy and that's not what you
[10:27] expect from, uh, the bulge.
[10:30] Andrew Dunkley: So you can see it in the image. It's a
[10:32] beautiful image, by the way, isn't it?
[10:34] Professor Fred Watson: Isn't it lovely? Um, there's other
[10:37] fainter galaxies in the background, which,
[10:39] um, are always nice to see, it looks as
[10:41] though, um, uh,
[10:44] the dust is showing up very clearly, uh,
[10:48] reddish in this image. And that's
[10:51] probably a true colour as well. So it looks
[10:53] like the dust looks like gravy swirling
[10:55] around, uh, the spiral arms at the outer side
[10:57] of the galaxy. But, um, yes, it's a
[11:00] very, very, uh, attractive image.
[11:04] So, um, the reason
[11:06] possibly is that
[11:09] maybe there was a collision.
[11:12] Uh, and we know that galaxies
[11:15] have grown by sort of gobbling up smaller
[11:18] galaxies. And if this collision
[11:21] took place at, uh, this high angle,
[11:23] uh, so that you've got a dwarf galaxy perhaps
[11:26] being absorbed by, uh, uh,
[11:29] NGC 4698, um,
[11:32] then you might very well get
[11:35] these velocities which are perpendicular to
[11:37] the disc of the galaxy. Um, we've
[11:40] got a similar situation in our own
[11:43] galaxy with the Two Magellanic Clouds,
[11:46] the dwarf galaxies. They're quite big for
[11:49] dwarf galaxies, actually. Uh, but they still
[11:52] count as that. Uh, they are visible in our
[11:54] southern hemisphere sky. They are being
[11:57] absorbed by our own galaxy. And there's a
[11:59] sort of something called the Magellanic, uh,
[12:01] stream, which is a stream of stars between
[12:04] them and connecting with the disc of our
[12:06] galaxy. And they're at a relatively high
[12:08] angle. So maybe in a few
[12:12] hundred million years, when space nuts will
[12:14] still be going, uh, we might have a
[12:17] similar phenomenon in our own galaxy. A bulge
[12:20] that's modified, that sticks up. Uh, although
[12:22] we've got a bar as well in the middle, which
[12:24] is a fairly robust feature. I think as
[12:27] the galaxy evolves, that will stay pretty
[12:30] solidly there. So we might end up with two
[12:32] bulges.
[12:32] Who knows?
[12:33] Andrew Dunkley: You never know. Yeah, so this one's, uh,
[12:36] quite, quite amazing. And, uh, uh, you
[12:39] can read all about it on the
[12:41] European Space agency website. That's
[12:44] ESA.int and just do
[12:47] a search for, uh, NGC
[12:49] 4698, I think, would be probably the easiest
[12:52] thing to do, Fred Watson.
[12:53] Professor Fred Watson: Yeah, Or, I mean, the title of their press
[12:56] release is lovely. A Galaxy Spinning out of
[12:59] Sink. I like that.
[13:00] Andrew Dunkley: Yes.
[13:01] Professor Fred Watson: Yeah.
[13:01] Andrew Dunkley: Or it fell down a sink or something.
[13:04] Those tend to spiral as well.
[13:06] Professor Fred Watson: Yes, well, they do. That's right. Yeah.
[13:08] Andrew Dunkley: Indeed.
[13:09] Professor Fred Watson: Two different sinks.
[13:11] Andrew Dunkley: Have a look for it. Uh, this is Space Nuts
[13:13] with Andrew Dunkley and Professor Fred Watson
[13:15] Watson. Okay, we've had a problem here.
[13:18] Professor Fred Watson: This is Houston. Say again, please.
[13:20] Professor Fred Watson: We've had a problem.
[13:21] Professor Fred Watson: We've had a B pup on a vault.
[13:24] So we're looking at it.
[13:26] Andrew Dunkley: Space Muffs. And I've got to say
[13:29] hello to a couple of our live viewers.
[13:31] Uh, Emily is, uh, watching us from a
[13:34] taxi in Perth at the moment on her way to a
[13:37] conference or a training course, I think.
[13:40] And, uh, yeah, so, um, yeah, the
[13:42] places we tune in from, I guess we're all
[13:45] nuts. She says, hi
[13:47] Emily.
[13:48] And, uh, Sophie's listening to us, uh, from,
[13:51] uh. Now, where did she say? Doesn't, uh,
[13:54] say where she's from, but she does ask if
[13:56] we'd heard about the potential closure of the
[13:59] Jodrell bank facility. Oh, she's in
[14:01] Somerset in the uk. Hi, Sophie. Yes, we, we
[14:04] were very much aware of that. That's been
[14:06] brought to our attention by a couple of
[14:07] listeners recently. Yes, and very
[14:10] sad news. Very sad news indeed.
[14:13] Professor Fred Watson: Except that we think it's been the, the, the
[14:16] prime. The Prime Minister mentioned it in
[14:17] Parliament about two weeks ago, saying that,
[14:21] uh, every school kid of his generation
[14:23] went to visit Jodrell bank and there's no way
[14:25] he was going to see it being closed in his
[14:27] watch.
[14:28] Andrew Dunkley: That's good news. There you go, Sophie. So,
[14:30] um, it may well be saved. Yeah, that
[14:33] would be wonderful.
[14:35] Um, lovely to have a live audience. It's
[14:37] becoming a new trend for us.
[14:38] Professor Fred Watson: Isn't it great? Yeah, it's absolutely
[14:40] fantastic.
[14:41] Andrew Dunkley: Terrific. Let's go to our next story,
[14:44] and this one's a little bit weird,
[14:47] and I'll try and pronounce this correctly,
[14:49] but we're talking about an object named
[14:52] Carricklo. Uh, now, um,
[14:55] the story is about the rings around
[14:58] Chariklo that are. That are changing. But
[15:01] we better firstly explain what this
[15:03] object actually is.
[15:06] Professor Fred Watson: Uh, yes, that's a, uh, nice way to
[15:09] introduce the story because, um, Chariklo is
[15:11] not one that we talk about very much.
[15:13] Uh, its full name is one zero one. Um, nine.
[15:16] Nine Chariklo. And the fact that it's
[15:18] preceded by a number tells you that it's an
[15:20] asteroid. Uh, uh,
[15:22] every asteroid, uh, has a number as well as a
[15:25] name like 5691. Fred Watson Watson.
[15:28] Sorry, couldn't resist it. So
[15:31] 10199 curriculo. Um, but
[15:33] it's not, uh, an asteroid. Ah, Fred Watson
[15:36] Watson, by the way, is probably the single
[15:38] most boring object in the solar system.
[15:41] It is in the main asteroid belt. It never
[15:44] does anything, uh, just sort of circulates
[15:46] around the sun. Um, there's not really
[15:48] anything to, you know, to make it stand out
[15:50] and it definitely won't hit the Earth anytime
[15:53] soon. Uh,
[15:55] Cariklo, on the other hand.
[15:57] Andrew Dunkley: Wouldn't it be ironic though if it hit Earth
[15:59] and hit your house?
[16:03] Professor Fred Watson: I probably told you this story before when
[16:06] more than 20 years ago now, when it was
[16:08] announced that the IAU was naming an
[16:11] asteroid after me. I went home from the
[16:13] observatory, told my two young sons that
[16:16] that was what had happened. They said, dad,
[16:18] that was terrible. If it hits the Earth,
[16:20] it'll be your fault. Um, and, um.
[16:23] So, yes, I've had that hanging over my head,
[16:25] uh, ever since. It will never, ever hit the
[16:27] Earth. The dynamics of the solar system are
[16:29] such that it will remain, as I said, probably
[16:32] the single most boring object in the entire
[16:34] solar system. Unlike Curriculo, um,
[16:36] which, uh, is, uh. Actually,
[16:39] it's called a centaur.
[16:41] That's a class of asteroids and this
[16:44] is the biggest of them. Curriculo. It's
[16:45] probably 250 kilometres across itself. A
[16:48] large ish asteroid. Um, and they
[16:51] orbit, uh, between the orbits of Saturn
[16:54] and Uranus. Uh, ah,
[16:56] that's the centaurs. Uh, this particular one,
[16:59] Chariklo, has an orbital period of
[17:02] 62 and a half years. That's how long it takes
[17:04] to go around. Once actually discovered back
[17:07] in the 1990s at Kitt Peak National
[17:09] Observatory in Arizona. Uh, it's
[17:12] got a, uh, dark reddish surface.
[17:15] Um, uh, uh, this brief
[17:19] update comes from Wikipedia just
[17:21] so I can get all the facts in there. It's got
[17:24] water, ice, silicate minerals, amorphous
[17:26] carbon and various complex organic
[17:29] compounds known as solins. Actually, uh, so
[17:32] these are the things that make
[17:35] many of those very distant trans. Neptunian
[17:38] objects, like, um,
[17:40] our old friend Arrokoth, the most distant
[17:42] object that's yet been visited by a
[17:44] spacecraft. Quite a, uh, reddish reddy
[17:47] brown surface.
[17:49] Andrew Dunkley: Yeah, SEDNA is like that too, apparently.
[17:52] Professor Fred Watson: That's right, yeah. It's common. It
[17:55] comes about because of the, uh,
[17:58] um, bombardment by
[18:01] subatomic particles from the sun and also
[18:04] cosmic rays, which come from outside the
[18:06] solar system, uh, over, uh, many billions
[18:09] of years. Like the four billion year history
[18:11] of the solar system. A four and a half
[18:13] billion year history. Um, and that modifies
[18:16] these chemicals to give you this brownish
[18:18] colour. So, um,
[18:21] there are, uh, uh, rings around
[18:24] Curriculo. I think it may have a
[18:26] moon. Um, I have that
[18:29] wrong, but it certainly has
[18:33] rings.
[18:34] Uh, maybe it doesn't have a moon. Sorry, M. I
[18:37] don't want to mislead anybody.
[18:38] Andrew Dunkley: Um, I'll tell you in a second. No,
[18:42] it does not have a confirmed moon yet,
[18:45] is the answer.
[18:46] Professor Fred Watson: Yeah, well, that's right. It's a long way
[18:48] away. It's beyond the orbit of Saturn.
[18:51] An object only a couple of hundred kilometres
[18:53] across, uh, smallish object.
[18:56] Um, uh, but it's got
[18:59] rings. And uh, how do we know that?
[19:02] By this marvellous technique, uh, that I
[19:05] always think is a great way to find solar
[19:07] system objects and measure them. Sometimes
[19:10] what we call occultations. When,
[19:12] uh, a solar system object passes in front
[19:15] of uh, a distant star and
[19:18] so its light is blocked, the light of the
[19:20] star is blocked. And if you have enough
[19:22] people observing the occultation, you spread
[19:25] them out across, well, sometimes across a
[19:27] nation like Australia, uh,
[19:30] you can essentially uh,
[19:33] see the dip in light, uh,
[19:36] and map it. Map m whatever it is that's uh,
[19:39] obscuring over uh, this area
[19:42] of the land where you've got observers.
[19:45] So you get all the observers to
[19:48] time when the background star
[19:51] seems to disappear and reappear. And by
[19:53] doing that, by plotting all those timings
[19:56] on a map, you can actually get the shape of
[19:59] whatever it is that's occulting or blocking
[20:01] out the light of the star. And back in
[20:04] 2013, uh, Kuriklo,
[20:06] uh occulted a star and it
[20:09] was seen that there were
[20:12] sort of symmetric occultations on either side
[20:15] of the main object which tell you that you've
[20:18] got rings. So
[20:21] that's the backstory. Uh, the front
[20:24] story is that uh,
[20:26] curricula has now been observed or
[20:29] occultations have now been
[20:31] observed by the James Webb Telescope, which
[20:34] of course is a very powerful instrument.
[20:36] And so you get very, very sensitive light
[20:38] curves or very detailed light curves. And
[20:41] what they're finding is, uh, that its
[20:44] rings have changed.
[20:47] They've changed significantly since that
[20:50] um, 2013 discovery.
[20:54] Uh, um, it
[20:57] basically uh, is a very nice
[20:59] occultation because it misses the
[21:02] curricula itself. Curricula, uh, didn't dim
[21:05] the star, uh, because the
[21:08] line of sight to the star from the James Webb
[21:10] telescope was uh, about seven kilometres
[21:13] above the Curriculo's surface. We're talking
[21:15] in very small distances here. So that the
[21:18] rings of Curriculo, and I didn't mention that
[21:21] there are two, not just one, there are two,
[21:23] uh, which crossed, uh, passed in
[21:26] front of the star, uh, and uh, were
[21:29] able to be measured um, by
[21:32] the James Webb Space Telescope. Some very
[21:34] nice observations, uh, of that. And
[21:38] uh, what we now know, uh, is
[21:41] that the rings have changed, as I said, since
[21:44] 20. Um, and so what
[21:47] we've got is a darkening of
[21:50] the inner ring, uh
[21:53] m sort of more so than would be
[21:56] expected. Uh, there have been other
[21:58] observations since 2013, uh, in 2014
[22:01] and 2017. Um, so
[22:04] these, you know, uh, the observations allow
[22:07] uh, us to see the way things uh,
[22:10] change. The astronomers who've done
[22:13] this work do make the comment though
[22:16] that maybe these rings are unequal in
[22:19] density. Uh, so if you've got, you know, the
[22:22] rings are made of material, just
[22:24] dusty material, uh, in orbit around the
[22:27] parent star. Uh, but there can be regions
[22:30] where there's more dust than there is further
[22:32] along the ring. And so it may be
[22:35] that uh, we've, you know, that
[22:39] they, that's what they've seen, a more dense
[22:41] region. Uh, but um, doing a
[22:44] statistical um, analysis of that
[22:47] suggests that that's probably not the case.
[22:49] That it probably is a real effect
[22:52] that the rings are actually
[22:55] um, that you know, the rings themselves are
[22:58] changing in structure.
[22:59] Andrew Dunkley: Yeah. Interestingly Fred Watson, we
[23:02] mentioned um, earlier about whether or not it
[23:05] had a moon. There is a hidden moon
[23:07] hypothesis, uh. Ah, yes, attached to this
[23:10] uh, object. And um, uh, some
[23:13] astronomers believe a tiny moon about two
[23:15] miles across, three kilometres, ish,
[23:19] uh, is orbiting inside or near the
[23:21] rings. And its gravity acts like
[23:24] a sheepdog, cosmic sheepdog they say,
[23:27] containing the icy particles so the rings
[23:29] stay intact. That's one theory,
[23:32] yes.
[23:33] Professor Fred Watson: Uh, and
[23:36] um,
[23:39] certainly um, this research
[23:42] uh, mentions that partly because
[23:45] um, there are resonances here and we've
[23:48] talked about resonances before. When you've
[23:50] got one thing that orbits, for
[23:53] example, um.
[23:54] Well, if you've got moons orbiting like
[23:57] Saturn as resonances, one moon will
[23:59] orbit uh, twice for
[24:02] another moon going around three times. These
[24:04] are uh, what we call resonances. And
[24:09] apparently uh, one of the rings is a uh, one
[24:12] to three resonance with curricula itself.
[24:15] So you've got a ring particle going around
[24:17] once for every three rotations of
[24:20] curricula. And that could shape the
[24:23] structure of the rings. Um, but
[24:25] that in itself might be caused, exactly as
[24:28] you've just said, by what they call a
[24:30] shepherd satellite. An unseen moon
[24:33] could perhaps uh, help to keep the
[24:35] ring intact. Uh, exactly as we
[24:38] see in some of the tiny moons of Saturn,
[24:41] which are almost embedded in Saturn's ring
[24:43] system. So yeah, this is um,
[24:46] really interesting stuff. Uh, if you're an
[24:49] asteroid fanatic, uh, um,
[24:52] with these possibilities, um, imagine what
[24:54] something like that would look like if you
[24:56] could stand close to it. Because curricula
[24:58] itself is probably a fairly irregular object.
[25:00] It is big enough to be more or less
[25:02] spherical, but um, we don't know its true
[25:05] shape. That's something else that can be
[25:07] gained by the way, by occultation
[25:08] measurements.
[25:10] Professor Fred Watson: Mhm.
[25:10] Andrew Dunkley: The other interesting thing is um,
[25:13] the belief is those rings will disperse
[25:16] eventually.
[25:18] Professor Fred Watson: Yeah, exactly as we think with Saturn. Ah,
[25:21] but I think these might have a relatively
[25:24] short timescale. I can't remember what sort
[25:25] of timescale.
[25:27] Andrew Dunkley: Uh, a few million years
[25:30] Is the, the theory.
[25:32] Professor Fred Watson: Relatively short. Saturn's rings are expected
[25:35] to disperse within the next hundred million
[25:38] years or so. It's in the diary. I've got it
[25:40] in my diary. I hope you have too.
[25:42] Andrew Dunkley: Uh, yes, I have, yes. Um, when they say
[25:45] disperse, what does that mean? They're just
[25:46] going to go drifting off into space.
[25:48] Professor Fred Watson: And probably in um, maybe,
[25:51] I suspect in both cases it will be a question
[25:54] of them collapsing onto the, gradually
[25:56] collapsing onto the surface of the body
[25:59] itself. We know that um, the inner edge
[26:02] of Saturn's rings are uh, basically raining
[26:05] down into Saturn. We saw that with the
[26:07] Cassini spacecraft. Direct evidence of that.
[26:10] A kind of rainfall of ice
[26:13] from the inner edge of the rings, uh,
[26:16] heading down towards the planet. And I
[26:18] suspect that's what will happen with
[26:20] Curriculo. Uh, the rings will end up on the
[26:22] surface. We think, and you and I have covered
[26:24] this on space knots, there might be evidence
[26:27] that the same thing happened on Earth
[26:29] billions of years ago.
[26:31] Andrew Dunkley: Interesting. If you'd like to read all about
[26:34] it, you can find out about uh,
[26:36] Curriculo's rings on the
[26:38] Brighterside News website.
[26:42] This is Space Nuts. Andrew Dunkley here,
[26:45] Fred Watson Watson there.
[26:49] Professor Fred Watson: Amen.
[26:50] Professor Fred Watson: Space Nuts.
[26:52] Andrew Dunkley: Now Fred Watson, we turn our attention to the
[26:55] JUICE mission. This is an ESA mission to
[26:58] Jupiter, uh, to look at its uh,
[27:01] it's moons and uh, it's about
[27:04] to do something. By the time this podcast is
[27:07] out, um, Juice will have done the, something
[27:09] that we're talking about doing.
[27:11] Professor Fred Watson: Right? It will, it'll have
[27:13] done it, it'll have done its thing and uh,
[27:16] uh, successfully, we hope so. Juice, uh,
[27:18] it's a really juicy topic of course. We can't
[27:21] resist, uh, that. I uh, had a nice glass of
[27:23] orange juice a couple of hours ago as well,
[27:25] which was good.
[27:26] Anyway, um, it's um, uh, it is
[27:29] the European Space Agency's Jupiter
[27:31] Icy Moons Explorer. That's where the name
[27:34] comes from. Uh, and uh, it's heading for
[27:37] Jupiter. Uh, if I remember rightly, it
[27:39] will orbit the planet itself, making
[27:42] frequent flybys. Um,
[27:46] uh, there is NASA's probe which is also
[27:50] uh, looking at the ice moons. Uh,
[27:54] that is Europa Clipper, that's called.
[27:56] Andrew Dunkley: That's right, yeah.
[27:57] Professor Fred Watson: That will also be in orbit around
[28:00] Jupiter. Anyway, Juice, um, is
[28:03] heading out to Jupiter but it's been on its
[28:06] way there for three and a half years. Uh,
[28:08] and um, given that it was
[28:11] launched in April 2023, uh, in
[28:14] French Guiana. That's where, uh, the
[28:17] ESA Space Port is. And
[28:20] what it's done in the time since
[28:22] then. Uh, first of all, it did,
[28:26] uh, a lunar Earth flyby. Um,
[28:29] in other words, kind of taking
[28:31] the gravitational pull of both the Moon and
[28:34] the Earth into account. Uh, then
[28:37] it did a Venus flyby and you think, wait a
[28:39] minute, Venus isn't on the way to Jupiter.
[28:42] It's the other way.
[28:43] Andrew Dunkley: Here we go again.
[28:44] Professor Fred Watson: Yeah, here we go again. But that's how you do
[28:46] these gravitational assists, uh, that um,
[28:49] actually increased its speed. Uh,
[28:52] and I think I'm right in saying as we stand
[28:54] here now, there are two more flybys of Earth.
[28:57] Uh, one on the 28th of September,
[29:01] um, which is as we're speaking now in the
[29:03] future, but perhaps won't be by the time our
[29:05] listeners hear this, except for our live
[29:07] audience who are hearing it now. Um, and
[29:09] welcome again.
[29:11] Andrew Dunkley: By the time this one goes out, this episode
[29:14] goes out, what we're talking about will have
[29:15] happened last week.
[29:17] Professor Fred Watson: Okay, so last week there was another flyby
[29:20] of the Earth, um, coming
[29:23] within, uh, actually less than 9,000
[29:26] kilometres of the Earth's surface. That is
[29:28] very close. Uh, and that sets it
[29:31] up for a, uh, gravitational.
[29:34] Final gravitational assist in January
[29:37] 2029. A, uh, couple of
[29:40] years down the track, three years down the
[29:42] track, um, or two and a half. Um,
[29:45] and that will put Juice on its,
[29:48] uh, sort of, um. I guess the
[29:51] best way to describe it is on the
[29:53] fastest part of its journey because it will
[29:55] then head off towards Jupiter, uh, and
[29:58] intercepting the orbit of Jupiter in July
[30:01] 2031. Uh, so a long
[30:04] and complicated journey. Still simple
[30:06] compared with BepiColombo, uh, which is now
[30:09] in the region of Mercury after I think. Was
[30:11] it eight or nine gravitational assists?
[30:13] Andrew Dunkley: It was nine. Yeah.
[30:14] Professor Fred Watson: Nine. Yeah. Um, so, uh,
[30:18] it's actually um, one of these things
[30:21] that uh, uh, we almost
[30:24] certainly won't notice it. Uh, but
[30:26] at that height, uh, it's uh,
[30:29] possible that people who know
[30:32] how to find the trajectory in the sky
[30:36] using, uh, telescopes or even binoculars
[30:39] might be able to track it. And there is a
[30:41] link on the European Space
[30:43] Agency's, uh, media
[30:46] brief on this, a link to tell you how to find
[30:49] the trajectory. So, uh, head
[30:52] to, uh, the page called Juice to fly past
[30:54] Earth for a third gravity assist. Uh,
[30:58] which might have been revised to Juice flew
[31:01] past Earth for a third gravity assist.
[31:03] Andrew Dunkley: It might.
[31:05] Professor Fred Watson: In which case you don't need to know where
[31:07] its trajectory is. But anybody who's
[31:09] listening live now can find that trajectory
[31:11] data on that website.
[31:12] I think there's at least two people who are
[31:13] listening.
[31:15] Andrew Dunkley: It's a very exciting mission.
[31:16] Professor Fred Watson: Can't wait. It is, isn't it? Yeah.
[31:19] Andrew Dunkley: And, and such a complicated way to get
[31:21] somewhere. But, uh, probably no more
[31:23] complicated than catching suburban trains.
[31:26] So, um, you know, sometimes you have to
[31:29] go out there to get back there, but.
[31:31] Professor Fred Watson: Yeah, that's right. Yeah, indeed.
[31:33] Andrew Dunkley: But, yeah, yes, uh, it's on the ESA website
[31:35] if you want to check it out. The Juice
[31:38] mission. Um, yeah. Uh, and who
[31:41] knows what it will reveal? We just gotta be a
[31:43] bit patient.
[31:43] We've got a few more years to wait yet. That,
[31:46] uh, brings us to the end. Fred Watson, thank
[31:48] you very much.
[31:50] Professor Fred Watson: Uh, you're welcome, Andrew. It's been a joy
[31:52] to talk to you again and to our, uh,
[31:54] listeners and to the audience who will
[31:56] eventually see this, uh, long after Juice has
[31:59] come and gone.
[32:00] Andrew Dunkley: Yes, indeed, professor, um, Fred Watson
[32:03] Watson, astronomer at large, part of the team
[32:05] here at Space Nuts. Don't forget to visit our
[32:07] website. Uh, in the meantime, you can send us
[32:10] a message on the Ask me Anything link at the
[32:12] top that's labelled ama. Uh, you can check
[32:15] out the shop. Uh, you can, um,
[32:18] subscribe to the Astronomy newsletter
[32:21] or, or. And, uh, you can, um,
[32:24] do something else that I've completely
[32:25] forgotten about. Hate it
[32:28] when that happens. Anyway,
[32:31] and thanks to Huw in the studio who couldn't
[32:33] be with us today. He, um, he
[32:36] grabbed some juice and now he's
[32:38] 156.7 million kilometres away.
[32:41] He'll be back next week and from me, Dunkley,
[32:44] thanks for your company.
[32:45] We'll see you on the next episode of Space
[32:47] Nuts.
[32:47] Professor Fred Watson: Bye.
[32:48] Andrew Dunkley: Bye.

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