In this captivating episode of Space Nuts, hosts Andrew Dunkley and Professor Jonti Horner explore the dynamic forces shaping our solar system and beyond. From the pivotal role of Jupiter in planetary formation to the intriguing behaviors of white dwarfs and the rapid evolution of Chiron's ring system, this episode is packed with cosmic revelations and scientific insights.
Episode Highlights:
- Jupiter's Role in the Solar System: Andrew and Jonti discuss a recent study that sheds light on how Jupiter's formation influenced the architecture of our solar system, potentially determining the locations and characteristics of the terrestrial planets. They delve into the gravitational effects Jupiter has on the inner solar system and how it may have created conditions favorable for planet formation.
- White Dwarf Devours Planetary Material: The hosts examine a fascinating case of a white dwarf star that has been observed consuming heavy elements from a planetesimal. They explain the implications of this discovery, including the potential for ongoing planetary activity around aging stars and what it suggests about the fate of planetary systems.
- Chiron's Evolving Ring System: The episode features a discussion about Chiron, the icy centaur that has recently been found to have a developing ring system. Andrew and Jonti explore the significance of this discovery, the potential origins of the rings, and what this tells us about the dynamic processes at play in the outer solar system.
- Exoplanet Life Candidates: The hosts wrap up with a critical look at claims surrounding a newly discovered exoplanet that is being touted as a potential candidate for life. They discuss the importance of scientific accuracy in media reporting and the implications of misrepresenting findings in the search for extraterrestrial life.
For more Space Nuts, including our continuously updating newsfeed and to listen to all our episodes, visit our website. Follow us on social media at SpaceNutsPod on Facebook, X, YouTube Music Music, Tumblr, Instagram, and TikTok. We love engaging with our community, so be sure to drop us a message or comment on your favorite platform.
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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: Hello, thanks for joining us. This is Space
00:00:02 --> 00:00:04 Nuts. My name is Andrew Dunkley, and we're
00:00:04 --> 00:00:07 here to talk astronomy and space science. And
00:00:07 --> 00:00:09 on this episode, we are going to look at a
00:00:09 --> 00:00:12 study into Jupiter's role in shaping
00:00:12 --> 00:00:15 our solar system. What shape is that?
00:00:15 --> 00:00:18 It's rhomboid. No, we don't know. we're also
00:00:18 --> 00:00:21 going to look at a, white dwarf star that's
00:00:21 --> 00:00:23 chowing down on a planetesimal. Sounds
00:00:23 --> 00:00:26 appetizing. observing a rapidly
00:00:26 --> 00:00:28 developing ring system, and it's not far
00:00:28 --> 00:00:31 away. And if we've got time, an exoplanet
00:00:31 --> 00:00:33 that in inverted commas may
00:00:34 --> 00:00:37 be a life candidate. That's all coming up on
00:00:37 --> 00:00:40 space nuts. 15 seconds. Guidance is
00:00:40 --> 00:00:42 internal. 10, 9.
00:00:43 --> 00:00:46 Ignition sequence start. space nuts. 5, 4,
00:00:46 --> 00:00:48 3, 2. 1, 2, 3, 4, 5, 5,
00:00:49 --> 00:00:50 4, 3, 2, 1.
00:00:50 --> 00:00:51 Jonti Horner: Space nuts.
00:00:51 --> 00:00:54 Andrew Dunkley: Astronauts report it feels good. And it's
00:00:54 --> 00:00:56 good to have Jonti Horner back with us again.
00:00:56 --> 00:00:58 Professor of astrophysics at the University
00:00:58 --> 00:01:01 of Southern Queensland. Hi, Jonti.
00:01:01 --> 00:01:02 Jonti Horner: Good evening. How are you going?
00:01:02 --> 00:01:04 Andrew Dunkley: I am well. Good to see you.
00:01:04 --> 00:01:06 Jonti Horner: Oh, it's good to be back. Although I'm
00:01:06 --> 00:01:08 admittedly a bit of a zombie, so I warn
00:01:08 --> 00:01:10 everybody, I've had less sleep than I should
00:01:10 --> 00:01:11 have done in the last couple of days because
00:01:11 --> 00:01:14 of the weather. we had some weather happen on
00:01:14 --> 00:01:17 Sunday, which led to the power here being
00:01:17 --> 00:01:19 knocked out for 24 hours during a mini heat
00:01:19 --> 00:01:21 wave. So I didn't get much sleep then. And
00:01:21 --> 00:01:23 then this morning I've got a colleague from
00:01:23 --> 00:01:25 Japan visiting, so I had to pick him, his
00:01:25 --> 00:01:27 wife and their two lovely daughters up from
00:01:27 --> 00:01:29 Brisbane Airport. So I've had six hours of
00:01:29 --> 00:01:31 driving today off the back of two nights of
00:01:31 --> 00:01:34 not much sleep. So if I seem less coherent
00:01:34 --> 00:01:35 than normal, and I appreciate I'm normally
00:01:35 --> 00:01:38 not that coherent to begin with, you know
00:01:38 --> 00:01:39 why, of course.
00:01:39 --> 00:01:42 Andrew Dunkley: Yes, we've all been there. we've had dreadful
00:01:42 --> 00:01:44 weather here too. But it hasn't been the
00:01:44 --> 00:01:46 extreme heat, it's been the extreme wind.
00:01:47 --> 00:01:49 I got woken up, last night about
00:01:49 --> 00:01:52 1am by the Fly, screens rattling. It
00:01:52 --> 00:01:55 was so windy. Yes, they, they were just
00:01:55 --> 00:01:56 shuddering. And I thought, I can't live with
00:01:56 --> 00:01:57 this.
00:01:57 --> 00:01:57 Jonti Horner: So I went outside.
00:01:58 --> 00:02:00 Andrew Dunkley: It was freezing cold, supposed to be late
00:02:00 --> 00:02:03 spring here, and I
00:02:03 --> 00:02:05 just jammed some wood chips
00:02:06 --> 00:02:09 into the. I just went off to the
00:02:09 --> 00:02:11 garden and grabbed some mulch and shoved it
00:02:11 --> 00:02:14 in the wind in, in the fly screens to stop
00:02:14 --> 00:02:14 them rattling.
00:02:14 --> 00:02:15 Jonti Horner: It worked.
00:02:15 --> 00:02:17 Andrew Dunkley: I've done it better during the day, but,
00:02:17 --> 00:02:19 well, that's just Been ridiculous.
00:02:19 --> 00:02:21 Jonti Horner: I know your parents. I mean having said that
00:02:21 --> 00:02:23 we had heat wave conditions and couldn't
00:02:23 --> 00:02:25 sleep because of the heat, I'm happ confess
00:02:25 --> 00:02:26 that I've had the wood serve on today because
00:02:26 --> 00:02:29 having had 36, 38 degrees so
00:02:29 --> 00:02:32 that's around 100 for our American friends
00:02:33 --> 00:02:36 last few days. Today has been a toasty kind
00:02:36 --> 00:02:38 of 15 degrees. and we've got a rain event
00:02:38 --> 00:02:41 happening. so we've had everything in the
00:02:41 --> 00:02:44 last week we've had kind of almost tornadic
00:02:44 --> 00:02:46 storms, we've had hailstones the size of your
00:02:46 --> 00:02:48 fists, we've had under a kilometer an hour
00:02:48 --> 00:02:50 gusts and now we've got random cold that
00:02:50 --> 00:02:53 makes me feel like I'm back in the uk. So
00:02:53 --> 00:02:55 yeah, all happening. And this is why
00:02:55 --> 00:02:56 Australia is an interesting place to live
00:02:56 --> 00:02:58 even to the extent that with the
00:02:58 --> 00:03:00 thunderstorms. We had got an email through
00:03:00 --> 00:03:02 yesterday that our wonderful observatory,
00:03:02 --> 00:03:04 Queensland's only professional astronomical
00:03:04 --> 00:03:06 observatory in Mount Kent was closed
00:03:06 --> 00:03:07 yesterday. We weren't allowed to go there
00:03:08 --> 00:03:10 because there was a bushfire within 10km of
00:03:10 --> 00:03:12 it that had been sparked by the lightning
00:03:12 --> 00:03:15 from the storms and fanned by the heat wave
00:03:15 --> 00:03:18 in a place that got lightning but no rain. So
00:03:18 --> 00:03:19 ah, it's all happening here.
00:03:20 --> 00:03:23 Andrew Dunkley: Yes, dry storms are not uncommon where I am.
00:03:23 --> 00:03:25 We we do get quite a few storms every year
00:03:25 --> 00:03:28 with lightning and thunder and nothing else.
00:03:28 --> 00:03:31 and they, yeah, they're very well known for
00:03:31 --> 00:03:32 sparking bushfires.
00:03:32 --> 00:03:33 Jonti Horner: Yeah.
00:03:33 --> 00:03:34 So while we're on the diversion of the
00:03:34 --> 00:03:36 weather, actually I'll apologize for Maya the
00:03:36 --> 00:03:38 dog chirping in the background but my
00:03:38 --> 00:03:40 partner's just got home. But we're also
00:03:40 --> 00:03:42 sitting here with an incredibly heartbreaking
00:03:42 --> 00:03:45 record, record breaking storm in the
00:03:45 --> 00:03:48 Caribbean. Yes, I know she's just come
00:03:48 --> 00:03:50 home. Thank you for joining me with the
00:03:50 --> 00:03:53 podcast Happy Dog. but yeah, there's
00:03:53 --> 00:03:55 borderline record breaking storm in the
00:03:55 --> 00:03:57 Caribbean which is going to be a Category 5
00:03:57 --> 00:03:59 hurricane hitting Jamaica and doing a, ah,
00:04:00 --> 00:04:01 hell of a lot of damage. And it's one of
00:04:01 --> 00:04:03 these that from a scientist point of view,
00:04:03 --> 00:04:06 fascinating watching it looking at the radar
00:04:05 --> 00:04:08 footage and all the satellite footage and on
00:04:08 --> 00:04:10 one hand you've got this thing of incredible
00:04:10 --> 00:04:12 exceptional beauty and on the other hand the
00:04:12 --> 00:04:14 devastation it's going to cause. So the
00:04:14 --> 00:04:16 people in the, in the firing line for that.
00:04:16 --> 00:04:18 Andrew Dunkley: Yeah, I saw the satellite images this
00:04:18 --> 00:04:20 afternoon. It is enormous.
00:04:20 --> 00:04:23 Jonti Horner: Yeah, you look at the false color one
00:04:23 --> 00:04:24 with the color of the clouds which is an
00:04:24 --> 00:04:26 indication of the severity of the storm and
00:04:26 --> 00:04:28 the shape and it's the kind of thing that you
00:04:28 --> 00:04:30 only see with the strongest storms we've ever
00:04:30 --> 00:04:33 seen, typically in the Pacific. So for this
00:04:33 --> 00:04:36 thing to not only be happening in the
00:04:36 --> 00:04:38 Atlantic, which is less common, but
00:04:38 --> 00:04:41 to be, you know, crosshairs on Jamaica,
00:04:41 --> 00:04:43 which has had a bit of a charmed life with
00:04:43 --> 00:04:45 some sacks of the high mountains that tend to
00:04:45 --> 00:04:47 bounce and go around a bit. This one looks
00:04:47 --> 00:04:49 like it's not so much going to bounce a
00:04:49 --> 00:04:49 splat.
00:04:49 --> 00:04:52 Andrew Dunkley: So yeah, when we were in Panama earlier
00:04:52 --> 00:04:55 this year, we did the Panama Canal and
00:04:55 --> 00:04:57 they were saying that they never get
00:04:57 --> 00:04:58 hurricanes ever.
00:05:00 --> 00:05:02 Jonti Horner: Too equatorial is my understanding. You need
00:05:02 --> 00:05:04 to be far enough away from the equator to get
00:05:04 --> 00:05:06 enough spin so. So it's very rare that you
00:05:06 --> 00:05:09 get storms getting right up to the equator
00:05:09 --> 00:05:11 because coriolis force and things like that.
00:05:11 --> 00:05:13 Andrew Dunkley: Yeah, yeah, it's interesting, isn't it?
00:05:13 --> 00:05:16 Very interesting. Okay, we better get
00:05:16 --> 00:05:19 on with what we came here to get on with. And
00:05:19 --> 00:05:22 we're going to start with a study that's
00:05:22 --> 00:05:24 been released into Jupiter's role in shaping
00:05:24 --> 00:05:26 the solar system. Now I do recall Fred
00:05:26 --> 00:05:29 mentioning that Jupiter, if Jupiter
00:05:29 --> 00:05:32 didn't exist we wouldn't. And this study
00:05:32 --> 00:05:35 basically adds a lot of fuel to that claim.
00:05:35 --> 00:05:38 Jonti Horner: It does. Now where Fred said,
00:05:38 --> 00:05:40 Fred and other people talk about if Jupiter
00:05:40 --> 00:05:43 didn't exist then we probably wouldn't. Ties
00:05:43 --> 00:05:45 into something that's a pretty big
00:05:46 --> 00:05:49 myth in science communication, Ansel in
00:05:49 --> 00:05:51 science papers and stuff, which is the idea
00:05:51 --> 00:05:54 of Jupiter shielding us from impacts. And my
00:05:54 --> 00:05:57 most favorite piece of research I ever did in
00:05:57 --> 00:05:58 my career is proving that to be a lot of
00:05:58 --> 00:06:00 cobblers and it's actually a lot more
00:06:00 --> 00:06:02 complicated. Jupiter throws things at us as
00:06:02 --> 00:06:05 well as protecting us. So I've always got a
00:06:05 --> 00:06:07 bit of an eye on any study that says, hey
00:06:07 --> 00:06:09 guys, if Jupiter wasn't there, neither would
00:06:09 --> 00:06:11 we. But this is a really interesting one that
00:06:11 --> 00:06:14 looks an entirely different aspect of
00:06:14 --> 00:06:16 Jupiter, which is the role that Jupiter
00:06:16 --> 00:06:18 played on the formation and evolution of the
00:06:18 --> 00:06:21 early solar system, the formation of the
00:06:21 --> 00:06:23 planets. And I've actually been teaching
00:06:23 --> 00:06:25 planet formation this week to my undergrad
00:06:25 --> 00:06:27 students. I've just, prior to recording this,
00:06:27 --> 00:06:29 had a two hour tutorial with them where I've
00:06:29 --> 00:06:31 been talking about planet formation and
00:06:31 --> 00:06:34 brought this story up because it
00:06:34 --> 00:06:37 really highlights the fact that when we
00:06:37 --> 00:06:40 often see in documentaries and the stuff we
00:06:40 --> 00:06:43 get taught at school, we get the impression
00:06:43 --> 00:06:45 that everything's solved, that we know the
00:06:45 --> 00:06:47 answers, that we know full well how the
00:06:47 --> 00:06:49 planets formed in microscopic detail and
00:06:49 --> 00:06:52 we've got everything figured out and the
00:06:52 --> 00:06:54 Reality is that we haven't. We have a really
00:06:54 --> 00:06:57 good broad picture and we're getting better
00:06:57 --> 00:06:59 and better at understanding the processes
00:06:59 --> 00:07:01 that went on. But there's still a lot to
00:07:01 --> 00:07:02 learn. And part of that is that while we've
00:07:02 --> 00:07:04 known the solar system since the year dot,
00:07:05 --> 00:07:07 we've only known other planetary systems for
00:07:07 --> 00:07:10 the last 30 years. And in reality we're still
00:07:10 --> 00:07:11 learning an awful lot about the planetary
00:07:11 --> 00:07:14 systems we find elsewhere. And learning about
00:07:14 --> 00:07:16 them is cool and all, but it also gives us
00:07:16 --> 00:07:18 insights that help us better understand our
00:07:18 --> 00:07:20 planetary system and how it formed. And that
00:07:20 --> 00:07:23 ties into this because the more we
00:07:23 --> 00:07:25 study those other planetary systems, the more
00:07:25 --> 00:07:27 we're getting observations of really
00:07:27 --> 00:07:30 beautiful things like planetary systems that
00:07:30 --> 00:07:31 are in formation, where you've got a
00:07:31 --> 00:07:34 protoplanetary disk. And we're getting these
00:07:34 --> 00:07:37 gorgeous images from things like the
00:07:37 --> 00:07:39 ALMA array, the Ataccama Large Millimeter
00:07:39 --> 00:07:42 Array that shows disks of planet
00:07:42 --> 00:07:44 forming material around stars with gaps in
00:07:44 --> 00:07:46 them and ripples in them and bands in them,
00:07:46 --> 00:07:49 and all these beautiful structures. And some
00:07:49 --> 00:07:50 of these have been previous astronomy.
00:07:50 --> 00:07:53 Picture of the days where this ties into the
00:07:53 --> 00:07:56 solar system is if you imagine that kind of
00:07:56 --> 00:07:58 stereotypical image of a
00:07:58 --> 00:08:00 protoplanetary disk, a disk of gas and dust
00:08:00 --> 00:08:03 around a young star like the sun, where
00:08:03 --> 00:08:05 material is feeding in through that disk to
00:08:05 --> 00:08:08 the star. So while the gas and dust is
00:08:08 --> 00:08:09 orbiting the star, there is this kind of
00:08:09 --> 00:08:12 sense of inward motion where the stars kind
00:08:12 --> 00:08:14 of nominating at the inner edge of the disk,
00:08:14 --> 00:08:16 materials falling in, and more material from
00:08:16 --> 00:08:18 outside flowing in to replace it. Yeah, and
00:08:18 --> 00:08:21 some of the models of the formation of the
00:08:21 --> 00:08:23 solar system struggle to make the terrestrial
00:08:23 --> 00:08:26 planets as a result of that. Because the
00:08:26 --> 00:08:27 material in the inner solar system is
00:08:27 --> 00:08:30 destined to fall onto M the star. And how do
00:08:30 --> 00:08:32 you stop that happening to let that material
00:08:32 --> 00:08:35 hang around to actually form into planets?
00:08:35 --> 00:08:37 Now it's been pretty well established for a
00:08:37 --> 00:08:39 long time that the first planet that formed
00:08:39 --> 00:08:41 in the solar system and got to a good size
00:08:41 --> 00:08:43 was Jupiter. And there's good reasons for
00:08:43 --> 00:08:46 that. It formed far enough away from the sun
00:08:46 --> 00:08:48 that the temperature was cold enough that the
00:08:48 --> 00:08:51 disk was rich in ice, which at, the
00:08:51 --> 00:08:53 distance the Earth is from the sun, all that
00:08:53 --> 00:08:55 ice would be gas. when you're forming solid
00:08:55 --> 00:08:57 objects, you need solid objects to feed from.
00:08:58 --> 00:08:59 And so when you've got a lot of ice, you've
00:08:59 --> 00:09:01 got a lot more solids. So things grow
00:09:01 --> 00:09:04 quicker, there's a lot more to eat. And it's
00:09:04 --> 00:09:06 only when you get to about 10 or 12 times the
00:09:06 --> 00:09:08 Mass of the Earth that You're massive enough
00:09:08 --> 00:09:10 to effectively start gobbling up the gas as
00:09:10 --> 00:09:13 well. So Jupiter formed beyond this point
00:09:13 --> 00:09:14 called the snow line, where there's a lot
00:09:14 --> 00:09:17 more solid material. It got to grow really
00:09:17 --> 00:09:20 quickly. It grew quicker than things further
00:09:20 --> 00:09:21 out because the further out you go, the
00:09:21 --> 00:09:23 slower things happen. So Jupiter was very
00:09:23 --> 00:09:25 much in the sweet spot, grew really quickly
00:09:25 --> 00:09:27 and eventually got big enough that it started
00:09:27 --> 00:09:29 clearing the gas and the dust it could gather
00:09:29 --> 00:09:32 the gas as well. And it opened up a gap in
00:09:32 --> 00:09:34 the disk. And that's very analogous to what
00:09:34 --> 00:09:36 we're seeing with these beautiful images from
00:09:36 --> 00:09:38 ALMA places like this. So the team of
00:09:38 --> 00:09:41 researchers behind this work have run some
00:09:41 --> 00:09:44 really in depth computer modeling of the
00:09:44 --> 00:09:46 formation of the solar system formation of
00:09:46 --> 00:09:48 Jupiter, and showed that when Jupiter opens
00:09:48 --> 00:09:51 up the gap in the disk, its gravity will
00:09:51 --> 00:09:53 also have an impact on the inner solar
00:09:53 --> 00:09:55 system. It'll effectively create the
00:09:55 --> 00:09:58 gravitational equivalent of speed bumps,
00:09:58 --> 00:10:00 creating areas where the dust that's
00:10:00 --> 00:10:02 spiraling inwards can pile up and be
00:10:02 --> 00:10:05 stopped from traveling further in.
00:10:05 --> 00:10:08 Effectively. It also creates
00:10:08 --> 00:10:10 a gap between the in run out of solar system
00:10:10 --> 00:10:12 that nothing crosses because if anything gets
00:10:12 --> 00:10:15 in that gap, Jupiter noms on it. And that's
00:10:15 --> 00:10:17 really interesting because some studies that
00:10:17 --> 00:10:19 have looked at primordial material we've
00:10:19 --> 00:10:21 found from in the solar system suggests that
00:10:21 --> 00:10:23 there is a bit of a chemical difference
00:10:23 --> 00:10:25 between material that formed in the inner
00:10:25 --> 00:10:27 solar system and material that formed in the
00:10:27 --> 00:10:29 outer solar system. So this gap
00:10:29 --> 00:10:32 dividing the two gives a natural way for that
00:10:32 --> 00:10:35 to happen. But the really big exciting result
00:10:35 --> 00:10:38 from this is really that modeling of
00:10:38 --> 00:10:40 the structure that Jupiter would have imposed
00:10:40 --> 00:10:42 on the inner solar system. These kind of pile
00:10:42 --> 00:10:44 up regions where you get more m dust and
00:10:44 --> 00:10:47 debris than normal, the structures that, that
00:10:47 --> 00:10:49 would carve out ripples in the disk
00:10:49 --> 00:10:51 effectively and how that would then
00:10:51 --> 00:10:53 contribute to the formation of the
00:10:53 --> 00:10:55 terrestrial planets. and therefore suggesting
00:10:55 --> 00:10:57 that not only did Jupiter help the
00:10:57 --> 00:11:00 terrestrial planets form by creating sweet
00:11:00 --> 00:11:02 spots where material could pile up, but it
00:11:02 --> 00:11:04 may also have had a really strong influence
00:11:04 --> 00:11:06 on the architecture of the inner solar system
00:11:06 --> 00:11:08 by setting where the planets would form,
00:11:09 --> 00:11:11 which then would go through a bit of a
00:11:11 --> 00:11:13 randomization phase as everything collides
00:11:13 --> 00:11:15 with each other. But it kind of possibly set
00:11:15 --> 00:11:18 the blueprint for the inner solar system. And
00:11:18 --> 00:11:20 therefore, if Jupiter hadn't formed where it
00:11:20 --> 00:11:22 did and how it did, the Earth would look
00:11:22 --> 00:11:24 very, very different and we might not be
00:11:24 --> 00:11:24 here.
00:11:25 --> 00:11:27 Andrew Dunkley: Yeah, it's truly fascinating. And
00:11:27 --> 00:11:30 when you look at other systems that
00:11:30 --> 00:11:33 we've discovered, exoplanet solar systems,
00:11:33 --> 00:11:36 ours is starting to look a little bit more
00:11:36 --> 00:11:39 unusual than normal. and
00:11:39 --> 00:11:40 Jupiter may be the reason.
00:11:41 --> 00:11:43 Jonti Horner: It could well be. And it's one of those
00:11:43 --> 00:11:45 things, I'm reminded of the Monty Python
00:11:45 --> 00:11:47 thing. I think it's in Life of Brian, where
00:11:47 --> 00:11:48 you've got that thing of we're all
00:11:48 --> 00:11:50 individuals. Yes, we're. No, we're not. I'm
00:11:50 --> 00:11:53 not. Every
00:11:53 --> 00:11:55 planetary system is going to be unique
00:11:55 --> 00:11:58 because it is influenced by
00:11:58 --> 00:12:01 such a wide variety of things going on. Even
00:12:01 --> 00:12:03 the stars that form in the local
00:12:03 --> 00:12:04 neighborhood, whittling it away from the
00:12:04 --> 00:12:07 outside, it all starts going on. But what
00:12:07 --> 00:12:09 we're seeing is there's a commonality among a
00:12:09 --> 00:12:11 lot of the planetary systems that we find
00:12:11 --> 00:12:13 that look very different to ours.
00:12:14 --> 00:12:16 The thing that gives us a little bit of pause
00:12:16 --> 00:12:17 though, is that we have these observational
00:12:17 --> 00:12:19 biases that make us more likely to find
00:12:19 --> 00:12:22 systems that are different to ours than we
00:12:22 --> 00:12:24 are to find systems like ours. And so you've
00:12:24 --> 00:12:27 always got that question of do we look
00:12:27 --> 00:12:30 unusual because we are unusual,
00:12:30 --> 00:12:31 or do we look unusual because we're not yet
00:12:31 --> 00:12:33 very good at finding places that look like
00:12:33 --> 00:12:35 home? and that's where colleagues of mine,
00:12:35 --> 00:12:37 like professor, Rob Wittenmayer, my colleague
00:12:37 --> 00:12:40 at unisq, have done really interesting
00:12:40 --> 00:12:43 work where what they
00:12:43 --> 00:12:46 do is look at what we found, but work
00:12:46 --> 00:12:49 out what doesn't exist
00:12:49 --> 00:12:52 based on what we haven't found yet. So they
00:12:52 --> 00:12:54 can start getting an estimate of how common
00:12:54 --> 00:12:57 our, ah, planetary systems like ours based on
00:12:57 --> 00:12:59 the fact we haven't found them yet. And it's
00:12:59 --> 00:13:02 a really kind of weird type of science where
00:13:02 --> 00:13:05 the absence of finding thing places limits on
00:13:05 --> 00:13:08 how common that thing is. So if you said
00:13:08 --> 00:13:10 that every star had a planet exactly like the
00:13:10 --> 00:13:12 Earth, on an orbit that's one year long that
00:13:12 --> 00:13:14 is exactly the same size as us and all the
00:13:14 --> 00:13:16 rest of it, then we can work out
00:13:16 --> 00:13:18 statistically, based on how good our
00:13:18 --> 00:13:21 telescopes are and our techniques are, how
00:13:21 --> 00:13:23 many of those planets we would have found.
00:13:23 --> 00:13:24 And we wouldn't have found anywhere near all
00:13:24 --> 00:13:26 of them because it's really hard to do. But
00:13:26 --> 00:13:28 we'd have found X amount. And the fact that
00:13:28 --> 00:13:30 we've only found a very small number smaller
00:13:30 --> 00:13:33 than that places an upper limit on how common
00:13:33 --> 00:13:36 things can be. So you get this perverse
00:13:36 --> 00:13:39 science where you get the observations
00:13:39 --> 00:13:40 that tell us what we found and what we've
00:13:40 --> 00:13:43 seen, but you can also put inferences on
00:13:43 --> 00:13:45 what isn't there and what is there based on
00:13:45 --> 00:13:47 what we haven't found yet, which allows you
00:13:47 --> 00:13:49 to put limits on how common things are that
00:13:49 --> 00:13:52 you couldn't really find very easily. Which,
00:13:52 --> 00:13:54 if that makes your head hurt. it makes my
00:13:54 --> 00:13:56 head hurt a little bit as well. But it's a
00:13:56 --> 00:13:59 really kind of clever use of the data we get
00:13:59 --> 00:14:01 to extrapolate further and draw more
00:14:01 --> 00:14:04 conclusions. And the net result of that is
00:14:04 --> 00:14:07 that the solar system is not hugely rare, but
00:14:07 --> 00:14:10 it's not common either. It's usual.
00:14:10 --> 00:14:11 And, that's really cool. And that probably
00:14:11 --> 00:14:13 extends to everything. Like I say, we're all
00:14:13 --> 00:14:16 individuals. The Earth, even though it's
00:14:16 --> 00:14:18 peeing it down outside at the minute, the
00:14:18 --> 00:14:20 Earth's actually a very dry planet. If you
00:14:20 --> 00:14:22 took all the water off the Earth and made a
00:14:22 --> 00:14:23 little blob of it next to the Earth, that
00:14:23 --> 00:14:25 blob would be fairly tiny. And everybody
00:14:25 --> 00:14:27 views the Earth as being very wet, but I view
00:14:27 --> 00:14:30 it as being very dry because water is such a
00:14:30 --> 00:14:33 common compound in the universe. It's made of
00:14:33 --> 00:14:36 the first and third most common atom. You put
00:14:36 --> 00:14:37 them together. Yet water waters everywhere.
00:14:37 --> 00:14:40 So for the Earth to be as dry as it is is
00:14:40 --> 00:14:42 telling you a lot about the uniqueness of the
00:14:42 --> 00:14:44 solar system. And maybe that's partially
00:14:44 --> 00:14:46 because of Jupiter. Not, necessarily
00:14:46 --> 00:14:48 shielding us from impacts, but preventing
00:14:48 --> 00:14:51 that icy material spiraling in, preventing
00:14:51 --> 00:14:54 us from becoming an ocean world. It's also
00:14:54 --> 00:14:56 partly down to the moon forming impact. The
00:14:56 --> 00:14:57 moon forming impact would have stripped a lot
00:14:57 --> 00:14:59 of the primordial Earth's water away because
00:14:59 --> 00:15:02 it walked as light and sits near the surface.
00:15:02 --> 00:15:05 So a lot about our Earth and a lot about the
00:15:05 --> 00:15:08 solar system is down to the random nature of
00:15:08 --> 00:15:11 the events around us. When we formed the moon
00:15:11 --> 00:15:13 forming impact, a nearby star going
00:15:13 --> 00:15:15 supernova and lacing our solar system with
00:15:15 --> 00:15:17 radioactive aluminium. Things like this.
00:15:17 --> 00:15:19 There's all these oddities that made our
00:15:19 --> 00:15:22 solar system unique, but if those
00:15:22 --> 00:15:23 hadn't happened, other things would have
00:15:23 --> 00:15:25 happened and we'd have still ended up with
00:15:25 --> 00:15:26 something unique because of other random
00:15:26 --> 00:15:27 things happening.
00:15:28 --> 00:15:30 It's all fascinating and I just love this
00:15:30 --> 00:15:30 stuff.
00:15:31 --> 00:15:33 Andrew Dunkley: Yeah. And it adds more and more weight to the
00:15:33 --> 00:15:35 theory that we are just a freak accident.
00:15:36 --> 00:15:36 Jonti Horner: Yes.
00:15:37 --> 00:15:39 Andrew Dunkley: And probably a one off in the universe.
00:15:39 --> 00:15:41 That's one argument. So, yeah,
00:15:42 --> 00:15:45 who knows if, if we find a
00:15:45 --> 00:15:47 solar system just like ours, with a planet
00:15:47 --> 00:15:50 just like ours, orbiting a
00:15:50 --> 00:15:53 star just like ours. That would be
00:15:53 --> 00:15:56 the, you know, one of the greatest
00:15:56 --> 00:15:58 discoveries in astronomical history, I
00:15:58 --> 00:16:01 imagine. But no, we do that.
00:16:01 --> 00:16:02 Jonti Horner: We would have to get in touch with the planet
00:16:02 --> 00:16:04 builders at Magrathea and demand that money
00:16:04 --> 00:16:06 back. Because we thought we had a limited
00:16:06 --> 00:16:06 edition.
00:16:06 --> 00:16:09 Andrew Dunkley: Yes, yes. weren't they the white mice? Was
00:16:09 --> 00:16:10 that the white mice?
00:16:10 --> 00:16:11 Jonti Horner: Yes, it was.
00:16:11 --> 00:16:13 Andrew Dunkley: Yeah. All right, if you want to read all
00:16:13 --> 00:16:15 about it, you can find, the paper,
00:16:16 --> 00:16:19 which was published in the journal Science
00:16:19 --> 00:16:20 Advances.
00:16:23 --> 00:16:25 Jonti Horner: Roger, your labs are here. Also space nuts.
00:16:26 --> 00:16:28 Andrew Dunkley: now, Jonti, let's move on to our next story.
00:16:28 --> 00:16:31 And this one is about a planetismal,
00:16:32 --> 00:16:35 that appears doomed. According to the, paper
00:16:35 --> 00:16:37 I'm reading, it's a white dwarf that's
00:16:37 --> 00:16:39 chowing down very, very hungry, hungry
00:16:39 --> 00:16:40 individual is this one.
00:16:41 --> 00:16:44 Jonti Horner: It is. So just to remind the audience, a
00:16:44 --> 00:16:47 white dwarf is the kind of little husk
00:16:47 --> 00:16:48 that's left after a cell like our sun comes
00:16:48 --> 00:16:51 to the end of its life, burns all its
00:16:51 --> 00:16:53 hydrogen, becomes a red giant, and then
00:16:53 --> 00:16:55 eventually blows off its outer layers. And it
00:16:55 --> 00:16:58 leaves a big chunk of the star's mass
00:16:58 --> 00:17:00 compressed into an object about the size of
00:17:00 --> 00:17:03 the Earth. That whole process will
00:17:03 --> 00:17:05 have a fairly hefty impact on the
00:17:05 --> 00:17:07 planetary system that star's got around it.
00:17:08 --> 00:17:09 And of course, as we just discussed, we now
00:17:09 --> 00:17:11 know that pretty much every star has planets.
00:17:12 --> 00:17:14 The expectation is that when the sun reaches
00:17:14 --> 00:17:16 this stage, unfortunately it's in about 7
00:17:16 --> 00:17:18 billion years, so nothing to worry about.
00:17:18 --> 00:17:20 Immediately it will swell up and it will
00:17:20 --> 00:17:23 chow down on Mercury and chow down on Venus.
00:17:23 --> 00:17:25 They'll just be swallowed up and gone. Yeah,
00:17:25 --> 00:17:27 There is some debate over whether the Earth
00:17:27 --> 00:17:30 will be swallowed up or will survive. Just
00:17:31 --> 00:17:33 all the models of star, evolution suggest
00:17:33 --> 00:17:35 that the sun will swell up to be about the
00:17:35 --> 00:17:37 radius of the Earth's orbit. But whether the
00:17:37 --> 00:17:39 Earth is there to nominal or not is still
00:17:39 --> 00:17:41 open for debate. It may be that the loss of
00:17:41 --> 00:17:44 mass from the sun in the time before may just
00:17:44 --> 00:17:46 mean that the Earth nudges far enough away to
00:17:46 --> 00:17:48 survive as a burnt husk rather than be
00:17:48 --> 00:17:51 devoured. It still would be ideal
00:17:51 --> 00:17:53 to be around when that wouldn't be pleasant.
00:17:53 --> 00:17:54 I mean, that said, the Earth is going to
00:17:54 --> 00:17:56 become uninhabitable a lot sooner than that
00:17:56 --> 00:17:58 because the Sun's getting brighter and the
00:17:58 --> 00:18:01 Earth's oceans will boil and it'll all go
00:18:01 --> 00:18:04 downhill. But after all that process
00:18:04 --> 00:18:06 happens when the sun sheds its outer layers,
00:18:07 --> 00:18:09 that'll have a pretty cataclysmic event on
00:18:09 --> 00:18:12 the planets and the debris that are left. So
00:18:12 --> 00:18:14 suddenly the sun goes on the ultimate kind of
00:18:14 --> 00:18:16 weight loss kick loses mass. And that
00:18:16 --> 00:18:18 will mean that all of the objects going
00:18:18 --> 00:18:21 around the sun will be held less strongly.
00:18:21 --> 00:18:23 And so therefore their orbits will move
00:18:23 --> 00:18:25 outwards because the gravity pulling them in
00:18:25 --> 00:18:28 gets weaker. Now, if you suddenly Press the
00:18:28 --> 00:18:30 button and vanished half of the mass of the
00:18:30 --> 00:18:33 Sun. What had happened is that the speed that
00:18:33 --> 00:18:35 any of the objects are going in their orbit
00:18:35 --> 00:18:37 will be too quick for that orbit to be
00:18:37 --> 00:18:40 circular. So at that instant, at that
00:18:40 --> 00:18:43 point, they'd now be at their new perihelion,
00:18:43 --> 00:18:44 they'd be at their closest point to the sun,
00:18:44 --> 00:18:45 and they'd all move out onto much more
00:18:45 --> 00:18:48 elongated orbits with a longer orbital
00:18:48 --> 00:18:51 period, but orbits that would then cross one
00:18:51 --> 00:18:53 another. So if you imagine you lose half of
00:18:53 --> 00:18:56 the Sun's mass, Jupiter moves onto an orbit
00:18:56 --> 00:18:58 where its perihelion is 5 au from the sun,
00:18:58 --> 00:19:00 but its aphelion could be 15 au from the Sun.
00:19:01 --> 00:19:03 Saturn at the same time would have perihelion
00:19:03 --> 00:19:06 at 10 au and aphelion at say 20 au. And I'm
00:19:06 --> 00:19:08 making the numbers up a bit here. So suddenly
00:19:08 --> 00:19:11 Jupiter and Saturn are on orbits that
00:19:11 --> 00:19:14 cross one another. Their orbits
00:19:14 --> 00:19:16 will probably still have the same ratio of
00:19:16 --> 00:19:19 orbital periods, so 12 years to 29 years. But
00:19:19 --> 00:19:21 they'd scale up to be something like, I don't
00:19:21 --> 00:19:23 know, 30 to 70 or something like that,
00:19:23 --> 00:19:25 because they've both moved out by the same
00:19:25 --> 00:19:27 amount. But suddenly you've got these planets
00:19:27 --> 00:19:29 that are on orbits that cross each other and
00:19:29 --> 00:19:32 therefore can really strongly interact. They
00:19:32 --> 00:19:33 can stir everything else up because all of
00:19:33 --> 00:19:35 the objects in the asteroid belt, all of the
00:19:35 --> 00:19:37 objects beyond Neptune, this happens to
00:19:37 --> 00:19:39 everything. Now the mass loss is a bit more
00:19:39 --> 00:19:42 gradual than that in actuality. So what
00:19:42 --> 00:19:44 happens is you get the orbit spiraling out,
00:19:44 --> 00:19:46 but getting perturbed, being made more
00:19:46 --> 00:19:48 eccentric. You've also got these objects
00:19:48 --> 00:19:51 moving through the headwind of possibly half
00:19:51 --> 00:19:53 a solar mass of material being blown
00:19:53 --> 00:19:55 outwards. That provides friction and so
00:19:55 --> 00:19:57 causes them possibly to spiral inwards a bit.
00:19:58 --> 00:20:00 Causes Jupiter potentially to gather mass as
00:20:00 --> 00:20:03 it numbs on all that gas that's going out. At
00:20:03 --> 00:20:04 the same time, its atmosphere is probably
00:20:04 --> 00:20:07 being blasted away by all this wind blowing
00:20:07 --> 00:20:10 past. All of this complexity means
00:20:10 --> 00:20:12 that you couldn't predict with absolute
00:20:12 --> 00:20:14 certainty what the solar system would look
00:20:14 --> 00:20:16 like at the end of this, but certainly
00:20:16 --> 00:20:19 there'd be a period of chaos. A lot of stuff
00:20:19 --> 00:20:21 would survive, but it would survive on orbits
00:20:21 --> 00:20:24 that are now much more unstable. So you get a
00:20:24 --> 00:20:26 lot of material flung inwards and, some of
00:20:26 --> 00:20:29 that will be flung inwards far enough for it
00:20:29 --> 00:20:31 to impact on the Earth sized object in the
00:20:31 --> 00:20:33 middle and, for the white dwarf to get a
00:20:33 --> 00:20:36 snack. Now all that's expected to happen
00:20:36 --> 00:20:38 really early on. And over time everything
00:20:38 --> 00:20:41 stabilizes out, things get flung around and
00:20:41 --> 00:20:44 clean up happens a bit like the
00:20:44 --> 00:20:45 solar system. You know, we were talking early
00:20:45 --> 00:20:47 on about the early stages of planet
00:20:47 --> 00:20:49 formation. Everything gets flung around and
00:20:49 --> 00:20:51 by the time you get to now, four and a half
00:20:51 --> 00:20:52 billion years down the road, it's fairly
00:20:52 --> 00:20:55 quiet. There's a bit going on, but most of
00:20:55 --> 00:20:57 the drama's finished. So the
00:20:57 --> 00:20:59 expectation is you'd see white dwarfs that
00:20:59 --> 00:21:02 are very young occasionally eating things
00:21:02 --> 00:21:04 because things get flung in and they get a
00:21:04 --> 00:21:06 bit of a snack. And the material from that
00:21:06 --> 00:21:08 snack will be spattered over the surface of
00:21:08 --> 00:21:10 the white dwarf and be visible in its
00:21:10 --> 00:21:13 spectrum as anomalous added
00:21:14 --> 00:21:16 solid material, heavy elements.
00:21:17 --> 00:21:19 But that signal would only last a short time
00:21:19 --> 00:21:21 because the outer layer of the white dwarf is
00:21:21 --> 00:21:24 kind of a hydrogen soup and heavier elements
00:21:24 --> 00:21:27 would sink down. So any given time you'd eat
00:21:27 --> 00:21:29 something. The evidence for that meal would
00:21:29 --> 00:21:31 only remain for a few tens of thousands of
00:21:31 --> 00:21:34 years, SOPs before it goes away. Okay, so
00:21:34 --> 00:21:36 the fact is we've seen some white dwarfs
00:21:36 --> 00:21:38 which have these anomalous heavy element
00:21:38 --> 00:21:41 readings in their atmospheres. We can tell
00:21:41 --> 00:21:42 they're eating stuff, but typically they're
00:21:42 --> 00:21:45 young. So you'd expect that.
00:21:45 --> 00:21:48 The quirky thing here is that this white
00:21:48 --> 00:21:49 dwarf, which goes by the name of
00:21:49 --> 00:21:52 lspm, which I think is a survey name,
00:21:52 --> 00:21:54 m followed by
00:21:54 --> 00:21:57 J020733331.
00:21:58 --> 00:22:00 So that's a coordinate on the sky. So that's
00:22:00 --> 00:22:01 telling you where in the sky this is. It's
00:22:01 --> 00:22:04 catalog number. Yeah, this thing is an old
00:22:04 --> 00:22:06 white dwarf. It's thought to be about 3
00:22:06 --> 00:22:08 billion years old. So in other words, the
00:22:08 --> 00:22:11 star that formed it died 3
00:22:11 --> 00:22:13 billion years ago and it's been sitting there
00:22:13 --> 00:22:16 minding its own business. That's old enough
00:22:16 --> 00:22:18 that you'd expect everything to have calmed
00:22:18 --> 00:22:20 down around it. But what the new
00:22:20 --> 00:22:23 observations have shown is evidence of
00:22:23 --> 00:22:25 13 different heavy elements,
00:22:26 --> 00:22:28 including carbon, chromium,
00:22:29 --> 00:22:32 strontium, titanium, a lot of these different
00:22:32 --> 00:22:35 elements, roughly in the kind of abundance as
00:22:35 --> 00:22:37 you'd see on the Earth, added, to this white
00:22:37 --> 00:22:40 dwarf's atmosphere. So it's
00:22:40 --> 00:22:42 obviously just had a meal and we know it's a
00:22:42 --> 00:22:44 case of just had a meal rather than it's been
00:22:44 --> 00:22:47 a leftover from a long time ago, because this
00:22:47 --> 00:22:49 stuff will sink and disappear over the next
00:22:49 --> 00:22:52 few tens of thousands of years. So what
00:22:52 --> 00:22:54 that means is that this white dwarf
00:22:55 --> 00:22:57 has just had a snack. Now it might have had
00:22:57 --> 00:23:00 that snack 30 years ago, or it
00:23:00 --> 00:23:03 may still be in the process of eating as
00:23:03 --> 00:23:05 we speak. Now what the team have been able to
00:23:05 --> 00:23:08 do is look at the amount of material you'd
00:23:08 --> 00:23:10 need to give the strength of signal you've
00:23:10 --> 00:23:12 got in the spectrum of the star. And, what
00:23:12 --> 00:23:14 they've calculated is that to get this amount
00:23:14 --> 00:23:17 of material you'd need to eat an asteroid
00:23:17 --> 00:23:19 about 200 kilometers in diameter.
00:23:20 --> 00:23:22 So that's comparable to some of the larger
00:23:22 --> 00:23:24 asteroids in the asteroid belt, but not the
00:23:24 --> 00:23:26 largest by any means. It's within the bounds
00:23:26 --> 00:23:28 of possibility of what we see here at home.
00:23:29 --> 00:23:31 But the real question is why is it eating it
00:23:31 --> 00:23:33 now? Why is this happening now when you'd
00:23:33 --> 00:23:35 expect the system to have had plenty of time
00:23:35 --> 00:23:37 to calm down? What
00:23:37 --> 00:23:40 it suggests to me, and it suggests in the
00:23:40 --> 00:23:42 paper, it suggests in the articles about this
00:23:42 --> 00:23:45 as well, is that the only way you can get
00:23:45 --> 00:23:48 something eating this late, after 3 billion
00:23:48 --> 00:23:50 years have passed, is if you've still got a
00:23:50 --> 00:23:53 number of planet mass objects in the system
00:23:53 --> 00:23:56 serving things up, which is what we've got
00:23:56 --> 00:23:57 in the solar system. If we look at the inner
00:23:57 --> 00:24:00 solar system, fragments of comets and
00:24:00 --> 00:24:02 asteroids are falling onto the sun all the
00:24:02 --> 00:24:04 time. We've got near Earth asteroids, short
00:24:04 --> 00:24:06 period comets and long period comets whizzing
00:24:06 --> 00:24:08 around. And, they're being bounced around by
00:24:08 --> 00:24:10 the planets. Jupiter's throwing a lot of
00:24:10 --> 00:24:12 stuff away. Their orbits are constantly
00:24:12 --> 00:24:15 getting tweaked. And so therefore the sun
00:24:15 --> 00:24:18 is still getting this rain of solid material
00:24:18 --> 00:24:20 falling on it as a result of the planets
00:24:20 --> 00:24:23 stirring things up. Even though the solar
00:24:23 --> 00:24:25 system mostly quietened down, the planets are
00:24:25 --> 00:24:28 still injecting material to the inner solar
00:24:28 --> 00:24:30 system, which is why we're getting meteorites
00:24:30 --> 00:24:32 and it's why the sun occasionally gets to
00:24:32 --> 00:24:35 numb some stuff. The idea here is
00:24:35 --> 00:24:37 that this star reached the end of its life.
00:24:37 --> 00:24:40 Puff dots with its outer layers. You have
00:24:40 --> 00:24:42 this really chaotic period where everything
00:24:42 --> 00:24:44 had got stirred up, then it settled down. But
00:24:44 --> 00:24:46 because you still got planet mass objects
00:24:46 --> 00:24:49 there, they're still bouncing around what
00:24:49 --> 00:24:51 debris is left. And we're just catching this
00:24:51 --> 00:24:54 white dwarf just at the right time, when
00:24:54 --> 00:24:56 another asteroid has been flung inwards close
00:24:56 --> 00:24:59 enough to be torn apart by the star's gravity
00:24:59 --> 00:25:01 and to give it a snack. So in other words,
00:25:02 --> 00:25:04 seeing this snack happening this late in the
00:25:04 --> 00:25:07 life of this white dwarf is fairly strong
00:25:07 --> 00:25:09 evidence that planets survived the death of
00:25:09 --> 00:25:12 its star, have lived there for 3 billion
00:25:12 --> 00:25:14 years, which a is really cool in of itself.
00:25:14 --> 00:25:17 But it also means that here is a star that we
00:25:17 --> 00:25:19 should look at when the Gaia data release
00:25:19 --> 00:25:22 comes next year. Gaia Dr. AH4,
00:25:22 --> 00:25:24 which will have been measuring this star's
00:25:24 --> 00:25:26 position on the sky. And if there Are planets
00:25:26 --> 00:25:28 there, we'll be able to detect the wobble and
00:25:28 --> 00:25:31 confirm them. So it's also holding up a flag
00:25:31 --> 00:25:33 to exoplanet people saying,
00:25:33 --> 00:25:36 hey, folks, here's a target for you to look
00:25:36 --> 00:25:38 at when the data release comes out where you
00:25:38 --> 00:25:39 might be able to find some planets, because
00:25:39 --> 00:25:42 we think there's a smoking gun here that the
00:25:42 --> 00:25:44 planets are feeding the white dwarf, giving
00:25:44 --> 00:25:46 it little snacks every now and again.
00:25:47 --> 00:25:49 Andrew Dunkley: Okay, wow. All right.
00:25:49 --> 00:25:51 so are there many white dwarf
00:25:52 --> 00:25:54 stars out there? What, do they, sort of,
00:25:55 --> 00:25:58 percentage wise, inhabit the star field?
00:25:58 --> 00:26:01 Jonti Horner: There would be a fair few of them. So the
00:26:01 --> 00:26:03 more massive a star is, the shorter its life
00:26:03 --> 00:26:05 is. And, that's a really rapid function.
00:26:06 --> 00:26:08 Where that works is, if your star's more
00:26:08 --> 00:26:11 massive, its gravitational pull is stronger,
00:26:11 --> 00:26:14 so its ability to pull material into
00:26:14 --> 00:26:17 the middle of the star is higher, which means
00:26:17 --> 00:26:19 that that star's got to give off a lot more
00:26:19 --> 00:26:21 energy to balance that gravitational pull.
00:26:21 --> 00:26:24 And so stars in the main sequence part of
00:26:24 --> 00:26:26 their life are in equilibrium. The radiation
00:26:26 --> 00:26:28 coming out from the nuclear fusion in the
00:26:28 --> 00:26:31 middle balances gravity pulling in. The
00:26:31 --> 00:26:33 more massive you are, the hotter and denser
00:26:33 --> 00:26:35 you get in the middle, so the more energy you
00:26:35 --> 00:26:38 give off. And the result of that is that it
00:26:38 --> 00:26:40 roughly, it varies a little bit by star's
00:26:40 --> 00:26:42 mass, but roughly the brightness of a star,
00:26:42 --> 00:26:45 the luminosity of a star is proportional to
00:26:45 --> 00:26:47 the mass of the star to the power
00:26:47 --> 00:26:49 4.3.54. Which means if you
00:26:49 --> 00:26:52 double the mass of a star, it'll get between
00:26:52 --> 00:26:54 10 and 16 times brighter.
00:26:55 --> 00:26:58 So twice the mass, Call it a factor of 10
00:26:58 --> 00:26:59 just to keep it easy. If it's 10 times
00:26:59 --> 00:27:02 brighter, that means it's burning its fuel 10
00:27:02 --> 00:27:04 times quicker to produce 10 times as much
00:27:04 --> 00:27:07 energy. But it's only twice the mass, so it's
00:27:07 --> 00:27:09 only got twice as much fuel, so its
00:27:09 --> 00:27:11 life will be a factor of five times shorter.
00:27:12 --> 00:27:13 And the more massive you get, the shorter the
00:27:13 --> 00:27:16 life gets. Now, stars of different masses
00:27:16 --> 00:27:19 have different. A star like Proxima
00:27:19 --> 00:27:21 Centauri will never swell up to become a red
00:27:21 --> 00:27:23 giant. It'll just be a dull, glowing ember
00:27:23 --> 00:27:26 and eventually go out. But even the
00:27:26 --> 00:27:28 oldest stars like Proxima Centauri are still
00:27:28 --> 00:27:30 really in their youth because they're burning
00:27:30 --> 00:27:33 their fuel so slowly. Stars that are more
00:27:33 --> 00:27:35 massive eventually get stars like the sun,
00:27:35 --> 00:27:37 which are what form like dwarfs. And, they
00:27:37 --> 00:27:39 eventually swell up to become a red giant,
00:27:39 --> 00:27:41 puff off their outer layers. And for a star
00:27:42 --> 00:27:44 of the Sun's mass, that process from
00:27:44 --> 00:27:46 forming to the end of its life is thought to
00:27:46 --> 00:27:49 be about 12 billion years. It used to be 10
00:27:49 --> 00:27:51 billion models seem to have refined. So
00:27:51 --> 00:27:52 people nowadays seem to say it's about 12
00:27:52 --> 00:27:55 billion years. So a star of
00:27:55 --> 00:27:58 the mass of the sun that formed when our,
00:27:58 --> 00:28:00 Milky Way was very young will have lived and
00:28:00 --> 00:28:02 died and become a white dwarf more than a
00:28:02 --> 00:28:05 billion years ago. But stars more massive
00:28:05 --> 00:28:08 than the sun can form white dwarfs as well,
00:28:08 --> 00:28:10 up to maybe two or even three times the mass
00:28:10 --> 00:28:12 of the sun, depending how effective it is at
00:28:12 --> 00:28:14 shedding mass at the end. Yeah, the maximum
00:28:14 --> 00:28:17 mass for white dwarf, you can get about 1.4
00:28:17 --> 00:28:19 times the mass of the Sun. If stars lose half
00:28:19 --> 00:28:20 their mass, that gives you something about
00:28:20 --> 00:28:22 three times the mass of the sun before you
00:28:22 --> 00:28:25 start it. Three times the mass of the sun.
00:28:26 --> 00:28:28 Three to the power four is three times three
00:28:28 --> 00:28:30 times three times three. That's 81 if my
00:28:30 --> 00:28:33 mental arithmetic is correct. So three times
00:28:33 --> 00:28:35 the mass of the sun burns its fuel 81 times
00:28:35 --> 00:28:38 as quickly, which means it would live a 27th
00:28:38 --> 00:28:40 as long. Which means instead of 12 billion
00:28:40 --> 00:28:43 years, you get down to, 1.2 billion years,
00:28:43 --> 00:28:45 you get down to or like, 600 million years,
00:28:45 --> 00:28:48 500 million years. So there will have been a
00:28:48 --> 00:28:50 lot of stars that were more m massive than
00:28:50 --> 00:28:52 the sun that have lived and died and created
00:28:52 --> 00:28:54 white dwarfs. And so there's going to be a
00:28:54 --> 00:28:57 lot of white dwarfs out there. I saw
00:28:57 --> 00:29:00 someone talking a while back about how old
00:29:00 --> 00:29:02 the oldest white dwarf will be in how dim it
00:29:02 --> 00:29:04 will be, because white dwarfs just cool and
00:29:04 --> 00:29:07 gradually go from being blue to white to
00:29:07 --> 00:29:09 yellow to red. You know, gradually dim down.
00:29:09 --> 00:29:11 Yeah. but what that all means is that there
00:29:11 --> 00:29:14 are probably a really large population of
00:29:14 --> 00:29:16 white dwarfs out there. We know quite a large
00:29:16 --> 00:29:19 number, but we won't know anywhere near
00:29:19 --> 00:29:21 as many of them as we do stars that are
00:29:21 --> 00:29:22 actually the mass of the sun, that are in the
00:29:22 --> 00:29:24 prime of their life because they're much
00:29:24 --> 00:29:27 fainter and harder to spot because they've
00:29:27 --> 00:29:28 got a much smaller surface area. So even
00:29:28 --> 00:29:30 though they're hot, they're tiny and,
00:29:30 --> 00:29:31 therefore they're faint. and the best example
00:29:31 --> 00:29:33 of that, of course, is a white dwarf that is
00:29:33 --> 00:29:36 a companion to Sirius. Sirius is the
00:29:36 --> 00:29:38 brightest star in the night sky. It's more
00:29:38 --> 00:29:40 massive than the Sun. It's also nearby. Its
00:29:41 --> 00:29:44 white dwarf companion is something
00:29:44 --> 00:29:46 like a factor of a million times fainter than
00:29:46 --> 00:29:49 Sirius is. So even though the white dwarf is
00:29:49 --> 00:29:51 comparable in Master Sirius A,
00:29:52 --> 00:29:55 it is like a million times dimmer because
00:29:55 --> 00:29:57 it's so tiny. And that's why they're Hard to
00:29:57 --> 00:29:57 find.
00:29:58 --> 00:30:00 Andrew Dunkley: Yeah, even though there's probably a hell of
00:30:00 --> 00:30:02 a lot of them out there. Okay, if you would
00:30:02 --> 00:30:05 like to read more about this particular white
00:30:05 --> 00:30:08 dwarf star that is, you know, got a case of
00:30:08 --> 00:30:10 the munchies, probably spent too much time
00:30:10 --> 00:30:13 smoking the juju. you can read all about it
00:30:14 --> 00:30:17 in the Astronomical Journal. This is Space
00:30:17 --> 00:30:20 Nuts with Andrew Dunkley and Jonti Horner.
00:30:20 --> 00:30:22 Jonti Horner: Okay, we checked all four systems and being
00:30:22 --> 00:30:24 with the jerk space nets,
00:30:25 --> 00:30:26 Andrew Dunkley: Don'T know why we went down that road.
00:30:26 --> 00:30:29 Let's go to our next story. And this
00:30:29 --> 00:30:32 one is, this one's close to home.
00:30:32 --> 00:30:35 a, an object that is rapidly developing
00:30:35 --> 00:30:37 a ring system and it's it's in
00:30:37 --> 00:30:40 the outer solar system.
00:30:40 --> 00:30:43 Jonti Horner: It is, this is an object called Chiron,
00:30:43 --> 00:30:45 which was the first of the centaurs to be
00:30:45 --> 00:30:47 discovered. And I always like to talk about
00:30:47 --> 00:30:48 the centaurs because they're what I studied
00:30:48 --> 00:30:51 for my PhD, so, so I was at one
00:30:51 --> 00:30:54 point, 20 odd years ago, one of the world's
00:30:54 --> 00:30:56 experts in how these things move around the
00:30:56 --> 00:30:57 solar system. And then science has moved on
00:30:57 --> 00:31:00 and I haven't, so I probably can no longer
00:31:00 --> 00:31:02 claim that. But Chiron is
00:31:02 --> 00:31:04 an interesting object. It's an icy object,
00:31:05 --> 00:31:08 bit more than 200km across. It was
00:31:08 --> 00:31:10 one of, if not the first object to get both a
00:31:10 --> 00:31:12 classification as an asteroid and as a comet.
00:31:13 --> 00:31:15 So it was initially discovered as a tiny
00:31:15 --> 00:31:17 speck of light moving around. It's discovered
00:31:17 --> 00:31:19 by Cowell I think in 1970,
00:31:20 --> 00:31:22 moving on an orbit that spends nearly all its
00:31:22 --> 00:31:24 time between the orbits of Saturn and Uranus.
00:31:24 --> 00:31:25 At the minute. Long term it's an unstable
00:31:25 --> 00:31:28 orbit. There's about a, ah, one in three
00:31:28 --> 00:31:29 chance that this will eventually end up in
00:31:29 --> 00:31:31 the inner solar system at some point in the
00:31:31 --> 00:31:33 next few million years. And that's part of
00:31:33 --> 00:31:36 the work I did during my PhD was running
00:31:36 --> 00:31:37 simulations of where this thing's going to
00:31:37 --> 00:31:40 go. That in itself is interesting because
00:31:40 --> 00:31:42 it's about a bit more than 200km across.
00:31:43 --> 00:31:44 So if this thing got trapped in the inner
00:31:44 --> 00:31:46 solar system, it will be, be a comet like
00:31:46 --> 00:31:48 nothing we've seen in recorded history. Hale
00:31:48 --> 00:31:51 Bopp, which was ridiculous, had a 50
00:31:51 --> 00:31:54 kilometer nucleus. If this thing's 250
00:31:54 --> 00:31:56 kilometers across, that's five times the
00:31:56 --> 00:31:59 radius, which means it's something like 25
00:31:59 --> 00:32:01 times the surface area, which means it will
00:32:01 --> 00:32:04 be a lot more impressive. So it's obviously
00:32:04 --> 00:32:07 an interesting object. Back in
00:32:07 --> 00:32:10 2011, team of scientists
00:32:10 --> 00:32:13 traveled across the world to gather to
00:32:13 --> 00:32:15 watch Chiron block out the light from a
00:32:15 --> 00:32:18 background star. So as this thing's moving
00:32:18 --> 00:32:20 through space, it just happened to pass in
00:32:20 --> 00:32:23 front of a star, from a subset of locations
00:32:23 --> 00:32:25 across the Earth. Now the distant stars are
00:32:25 --> 00:32:27 effectively so far away, we can consider the
00:32:27 --> 00:32:30 light coming in perfectly parallel. And
00:32:30 --> 00:32:32 so a 200 kilometer
00:32:33 --> 00:32:35 centaur will cast a shadow on the earth
00:32:35 --> 00:32:37 that's 200 kilometers across. And that shadow
00:32:37 --> 00:32:39 will whip across our planet. As the object
00:32:39 --> 00:32:41 and the Earth move around the sun, the shadow
00:32:41 --> 00:32:43 moves, the Earth moves through it. And so you
00:32:43 --> 00:32:46 get a 200 kilometer roughly scale band on the
00:32:46 --> 00:32:48 Earth where that star will disappear, then
00:32:48 --> 00:32:51 reappear. We know how fast everything's
00:32:51 --> 00:32:53 moving. So if you can get in that location,
00:32:54 --> 00:32:56 have a lot of telescopes spread out in a
00:32:56 --> 00:32:58 line, you can observe that
00:32:58 --> 00:33:01 occultation event and, by how long the star
00:33:01 --> 00:33:03 vanishes from different locations, you can
00:33:03 --> 00:33:05 actually figure out the shape and the size of
00:33:05 --> 00:33:08 the centaur because you can essentially map
00:33:08 --> 00:33:11 that shadow. And if you're near the edge, the
00:33:11 --> 00:33:12 star will disappear and reappear really
00:33:12 --> 00:33:14 quickly. If you're near the middle, you'll
00:33:14 --> 00:33:17 get a longer period where it vanishes. So
00:33:17 --> 00:33:18 these kind of, ah, occultation observations
00:33:18 --> 00:33:21 are really valuable to scientists. What
00:33:21 --> 00:33:23 happened in 2011 was they set their
00:33:23 --> 00:33:25 telescopes up and started watching a bit
00:33:25 --> 00:33:26 early to make sure they were looking at the
00:33:26 --> 00:33:29 star. And they noticed the star flickered on
00:33:29 --> 00:33:31 and off a couple of times before it properly
00:33:31 --> 00:33:33 disappeared for the main occultation. Then
00:33:33 --> 00:33:35 after it reappeared, it flickered on and off
00:33:35 --> 00:33:37 again a couple of times. And that's really
00:33:37 --> 00:33:40 weird. Now there was a kind of
00:33:40 --> 00:33:42 precedent for this with observations that
00:33:42 --> 00:33:44 were made in 1977, I believe,
00:33:45 --> 00:33:47 of Uranus, which was being observed from, I
00:33:47 --> 00:33:49 think it was the Kuiper Airborne Observatory
00:33:49 --> 00:33:52 doing one of these occultations. And they'd
00:33:52 --> 00:33:54 observed Uranus for this occultation because
00:33:54 --> 00:33:57 they wanted to understand the atmosphere of
00:33:57 --> 00:33:59 Uranus. And they figured as a stalwart behind
00:33:59 --> 00:34:02 Uranus, you'd see it not just disappear, but
00:34:02 --> 00:34:03 actually fade out as the light passed through
00:34:03 --> 00:34:06 the atmosphere. So you could measure the
00:34:06 --> 00:34:08 atmosphere and with that occultation of
00:34:08 --> 00:34:11 Uranus, occultation by Uranus, sorry, they
00:34:11 --> 00:34:12 got this flickering on and off thing. And
00:34:12 --> 00:34:14 that was the discovery of Uranus, of ring
00:34:14 --> 00:34:17 system. So basically the star vanished behind
00:34:17 --> 00:34:19 the rings, then reappeared, then vanished
00:34:19 --> 00:34:20 again, then reappeared, then went behind the
00:34:20 --> 00:34:23 planet. Right. So with this
00:34:23 --> 00:34:26 2011 event, the same kind of thing applied.
00:34:27 --> 00:34:29 It was the discovery of a ring system around
00:34:29 --> 00:34:31 this icy object. So this is a tiny thing,
00:34:31 --> 00:34:34 smaller than even Mimas, that we talked about
00:34:34 --> 00:34:36 last week with the subsurface ocean,
00:34:36 --> 00:34:38 something so small that its gravity is
00:34:38 --> 00:34:39 probably not strong enough to make it
00:34:39 --> 00:34:42 spherical. It's probably peanut shaped or
00:34:42 --> 00:34:44 rugby ball shaped or something like this.
00:34:44 --> 00:34:46 It's probably not spherical. Around this
00:34:46 --> 00:34:48 object, it seems that there is a system of
00:34:48 --> 00:34:50 rings where there are three or four narrow
00:34:50 --> 00:34:52 rings at various distances. I think the
00:34:52 --> 00:34:55 distances are something like 273, 325, 438
00:34:55 --> 00:34:58 and 1400 kilometers from the
00:34:58 --> 00:35:01 center of Chiron. Got this ring
00:35:01 --> 00:35:03 system and it's been observed again since
00:35:03 --> 00:35:06 they did observations in 2018, 2022 and
00:35:06 --> 00:35:09 2023, where they again figured
00:35:09 --> 00:35:11 out that the shadow of Chiron was going to
00:35:11 --> 00:35:13 scan across the planet, got a load of
00:35:13 --> 00:35:16 telescopes, went on a road trip and observed
00:35:16 --> 00:35:18 it happen to get more information about the
00:35:18 --> 00:35:21 rings. Because having a ring system around an
00:35:21 --> 00:35:23 object that isn't a planet is really cool.
00:35:23 --> 00:35:23 Andrew Dunkley: Yeah.
00:35:24 --> 00:35:26 Jonti Horner: And how did it form? How long has it been
00:35:26 --> 00:35:28 there? What's going on? How common are ring
00:35:28 --> 00:35:31 systems like this? Incidentally, a former PhD
00:35:31 --> 00:35:33 student of mine, Jeremy Wood, did some really
00:35:33 --> 00:35:36 cool dynamical studies that basically showed
00:35:36 --> 00:35:38 that the ring system could be
00:35:38 --> 00:35:40 primordial. It could be as old as the solar
00:35:40 --> 00:35:43 system. From the point of view of Chiron has
00:35:43 --> 00:35:45 never been close enough to one of the planets
00:35:45 --> 00:35:48 to disrupt the rings. So that
00:35:48 --> 00:35:49 doesn't put an edge limit on it, but it was
00:35:49 --> 00:35:52 still quite cool. What the new observations
00:35:52 --> 00:35:53 have shown though, is that, the ring system
00:35:53 --> 00:35:56 now seems to be different to how it was in
00:35:56 --> 00:35:59 2011. In other words, the ring
00:35:59 --> 00:36:01 system is evolving before our very
00:36:01 --> 00:36:04 eyes and it actually seems to be a denser,
00:36:04 --> 00:36:06 stronger ring system now than it was 10 or 15
00:36:06 --> 00:36:09 years ago. So it's possible that we're
00:36:09 --> 00:36:11 actually witnessing this ring system as it is
00:36:11 --> 00:36:14 forming or as it's changing over time.
00:36:14 --> 00:36:16 Now I know Chiron has been quite active,
00:36:17 --> 00:36:19 it's been outgassing because it's been closer
00:36:19 --> 00:36:21 to the sun, hence the cometary type
00:36:21 --> 00:36:24 classification it got. Maybe some
00:36:24 --> 00:36:26 of the material it's ejecting in that
00:36:26 --> 00:36:28 outgassing is being ejected gently enough
00:36:28 --> 00:36:31 that it doesn't escape from Chiron and,
00:36:30 --> 00:36:33 that's repopulating the rings. We just don't
00:36:33 --> 00:36:36 know. But the only way we'll find
00:36:36 --> 00:36:38 out is by doing more of these observations.
00:36:38 --> 00:36:41 But I think it's just really exciting and
00:36:41 --> 00:36:44 it's a really good reminder again that we
00:36:44 --> 00:36:46 always kind of imagine the solar system as a
00:36:46 --> 00:36:48 very sad and boring, placid place where not
00:36:48 --> 00:36:50 much changing anymore because it's four and a
00:36:50 --> 00:36:52 half billion years old. And as you get older,
00:36:52 --> 00:36:53 you Get a bit more sedentary and not much
00:36:53 --> 00:36:56 happens. But in fact it's a reminder that
00:36:56 --> 00:36:59 the solar system's a really dynamic place and
00:36:59 --> 00:37:01 things are constantly influenced, constantly
00:37:01 --> 00:37:03 changing. We talked about it last week. The
00:37:03 --> 00:37:05 ocean on Mimas that is possibly
00:37:06 --> 00:37:08 only 15 million years old. Now, 50 million
00:37:08 --> 00:37:11 years sounds like a really long time, but in
00:37:11 --> 00:37:12 a system that's four and a half thousand
00:37:12 --> 00:37:15 million years old, that's like something
00:37:15 --> 00:37:17 that has happened to me in the last couple of
00:37:17 --> 00:37:20 weeks. That's a new feature, not something
00:37:20 --> 00:37:22 I've had since birth. And this is yet another
00:37:22 --> 00:37:24 example of the fact that the solar system
00:37:24 --> 00:37:26 just seems to be continually rapidly changing
00:37:26 --> 00:37:27 and evolving.
00:37:27 --> 00:37:29 Andrew Dunkley: Yeah, yeah, it's a really interesting
00:37:29 --> 00:37:32 situation. how far out is chiron?
00:37:33 --> 00:37:36 Jonti Horner: It varies. So it's closest to the sun, It's a
00:37:36 --> 00:37:37 little bit closer to the sun than the orbit
00:37:37 --> 00:37:39 of Saturn. at its furthest, it's a bit
00:37:39 --> 00:37:41 further away than the orbit of Uranus. And
00:37:41 --> 00:37:42 that's an unstable orbit. So it bounces
00:37:42 --> 00:37:45 around over time, it will have encounters
00:37:45 --> 00:37:47 with them that fling it around. But at the
00:37:47 --> 00:37:50 minute it's in the outer solar system
00:37:50 --> 00:37:53 between the orbits of Saturn and Uranus most
00:37:53 --> 00:37:55 of the time. Unstable solution. It probably
00:37:55 --> 00:37:57 originated out beyond the orbit of Neptune.
00:37:57 --> 00:38:00 And it's one of this population called the
00:38:00 --> 00:38:03 Centaurs that are, the future parents of the
00:38:03 --> 00:38:04 next generation of short period comets.
00:38:04 --> 00:38:06 Effectively in the same way that the near
00:38:06 --> 00:38:08 Earth asteroids have their origin in the
00:38:08 --> 00:38:10 asteroid belt, short period comets have their
00:38:10 --> 00:38:13 origin in the Transeptunian region. But to
00:38:13 --> 00:38:15 get here from there, they've got to pass
00:38:15 --> 00:38:16 through the outer solar system. And that's
00:38:16 --> 00:38:17 what the Centaurs are.
00:38:18 --> 00:38:20 Andrew Dunkley: Okay. Fascinating. Yeah, it's really
00:38:20 --> 00:38:22 interesting and probably not one that,
00:38:23 --> 00:38:25 too many people would be aware of. I remember
00:38:25 --> 00:38:28 when it was making the news some
00:38:28 --> 00:38:30 years ago, and that's why the name stuck when
00:38:30 --> 00:38:33 you, when you sent the story to me. But, you
00:38:33 --> 00:38:35 don't really hear much about it. But now
00:38:35 --> 00:38:37 we've got a very good reason to look at it.
00:38:38 --> 00:38:40 if you would like to look into that
00:38:40 --> 00:38:43 particular paper, it's been published in
00:38:43 --> 00:38:45 the Astrophysical Journal Letters.
00:38:51 --> 00:38:53 Our final story, Jonti, is,
00:38:54 --> 00:38:57 an exoplanet that the popular press are going
00:38:57 --> 00:38:59 to say has got, some kind of life on it. it's
00:38:59 --> 00:39:02 a, it's a maybe life candidate, story,
00:39:02 --> 00:39:05 this one. And Yeah, but they're still
00:39:05 --> 00:39:07 using the term super Earth.
00:39:07 --> 00:39:09 Jonti Horner: Yeah, I'll keep this one a little bit short
00:39:09 --> 00:39:12 and try not to get too grumpy. But one of my
00:39:12 --> 00:39:15 big bug bears all the way through my career
00:39:15 --> 00:39:18 is a good way for people to get media
00:39:18 --> 00:39:20 coverage of their new planet discovery is say
00:39:20 --> 00:39:23 it could be habitable. It's in the Goldilocks
00:39:23 --> 00:39:23 zone. Hooray.
00:39:24 --> 00:39:25 Andrew Dunkley: Using the L word.
00:39:25 --> 00:39:27 Jonti Horner: Rumble, rumble, grumble, grumble.
00:39:27 --> 00:39:28 Andrew Dunkley: It's a four letter word too, that one.
00:39:28 --> 00:39:30 Jonti Horner: It is, and it's one of the terrible four
00:39:30 --> 00:39:33 letter words. Part of the problem here is
00:39:33 --> 00:39:35 there's this concept of the Goldilocks zone,
00:39:35 --> 00:39:37 of the habitable zone, which has become
00:39:37 --> 00:39:38 really entrenched in the popular
00:39:38 --> 00:39:41 consciousness. And it's always viewed as
00:39:41 --> 00:39:43 being this sweet spot for life. And the idea
00:39:43 --> 00:39:45 is that if you have a planet in the habitable
00:39:45 --> 00:39:46 zone, it will have liquid water on its
00:39:46 --> 00:39:48 surface and all sorts of happy life things
00:39:48 --> 00:39:51 will happen and everything will be good.
00:39:52 --> 00:39:54 What it actually means is that if you took
00:39:54 --> 00:39:56 the Earth, as it is today and put it where
00:39:56 --> 00:39:59 that planet is, the Earth would still
00:39:59 --> 00:40:01 maintain its liquid water because planets are
00:40:01 --> 00:40:04 really diverse. If you took Venus and put
00:40:04 --> 00:40:06 Venus where the Earth is, With Venus's
00:40:06 --> 00:40:08 current atmosphere, Venus will be too hot to
00:40:08 --> 00:40:10 have liquid water. But if you observe the
00:40:10 --> 00:40:12 solar system from a long long way away and
00:40:12 --> 00:40:15 you discovered Venus on the Earth's
00:40:15 --> 00:40:17 orbit, it wouldn't look any different to the
00:40:17 --> 00:40:19 Earth. it's a planet about the size of the
00:40:19 --> 00:40:21 Earth, sat in the habitable sun. We, it's
00:40:21 --> 00:40:23 habitable. Hooray. Whereas Venus is actually
00:40:23 --> 00:40:25 so hot that on the surface it had melt lead.
00:40:25 --> 00:40:27 And I certainly wouldn't want to visit there.
00:40:27 --> 00:40:30 It's even hotter than my room was the other
00:40:30 --> 00:40:32 night when the power cut had happened. And
00:40:32 --> 00:40:35 that was bad enough and brutal enough. so
00:40:35 --> 00:40:38 what this means is that ah, people
00:40:38 --> 00:40:40 have become very fond of
00:40:41 --> 00:40:44 find a planet around a star, you can work out
00:40:44 --> 00:40:46 where the boundaries of the habitable zone
00:40:46 --> 00:40:48 will be based on a few assumptions. And this
00:40:48 --> 00:40:51 is work going back about a decade of the
00:40:51 --> 00:40:53 definitions we use now. And you've got the
00:40:53 --> 00:40:55 conservative and the optimistic habitable
00:40:55 --> 00:40:57 zone, which are basically loosely based
00:40:57 --> 00:40:59 around the fact that if you're as close to
00:40:59 --> 00:41:02 the star that you get an amount of radiation
00:41:02 --> 00:41:04 coming in comparable to Venus, you'll be too
00:41:04 --> 00:41:05 hot. If you're about where Mars is, you'll be
00:41:05 --> 00:41:07 too cold, but in the middle you'll be just
00:41:07 --> 00:41:09 right m. and that's about it.
00:41:10 --> 00:41:12 Now that definition doesn't really take any
00:41:12 --> 00:41:14 account of the mass of the planet or its
00:41:14 --> 00:41:17 atmosphere. What that
00:41:17 --> 00:41:20 means is that ah, when you find a planet that
00:41:20 --> 00:41:22 is a super Earth that Is four times the mass
00:41:22 --> 00:41:24 of the Earth. That is almost certainly
00:41:24 --> 00:41:27 nothing like our planet at all.
00:41:27 --> 00:41:30 You'll do a calculation and say it sits in
00:41:30 --> 00:41:32 the optimistic habitable zone. So there is a
00:41:32 --> 00:41:34 potential it could have liquid water on its
00:41:34 --> 00:41:37 surface. That's full of a whole heap
00:41:37 --> 00:41:39 of assumptions. But to me it's a really long
00:41:39 --> 00:41:41 stretch from saying it could have life.
00:41:41 --> 00:41:41 Andrew Dunkley: A.
00:41:41 --> 00:41:43 Jonti Horner: You're assuming it's got the right kind of
00:41:43 --> 00:41:45 atmosphere to have liquid water where it's
00:41:45 --> 00:41:46 four times the mass of the Earth. So its
00:41:46 --> 00:41:48 atmosphere is almost certainly much, much m
00:41:48 --> 00:41:50 thicker, Therefore
00:41:51 --> 00:41:53 likely has a much stronger greenhouse effect,
00:41:54 --> 00:41:55 Therefore probably runaway greenhouse. Not
00:41:55 --> 00:41:56 good.
00:41:56 --> 00:41:58 The other thing with this particular planet,
00:41:58 --> 00:42:01 GJ 251C is it's a super
00:42:01 --> 00:42:03 Earth orbiting a red dwarf star, ah,
00:42:04 --> 00:42:06 nearby, less than 20 light years away. And
00:42:06 --> 00:42:08 that's part of why people are excited. It's
00:42:08 --> 00:42:09 near enough that we'll learn a lot more about
00:42:09 --> 00:42:11 it in the future. However,
00:42:12 --> 00:42:15 planet orbiting a red dwarf star means that
00:42:15 --> 00:42:16 to be in the habitable zone, it's got to be
00:42:16 --> 00:42:18 close in. This thing goes around its star
00:42:18 --> 00:42:21 every 54 days, which means that it is
00:42:21 --> 00:42:23 closer to its star than Mercury is to the
00:42:23 --> 00:42:25 sun. And given the difference in the masses,
00:42:25 --> 00:42:28 it's actually much closer in than that. That
00:42:28 --> 00:42:30 means it's up close and personal with a red
00:42:30 --> 00:42:32 dwarf star, which are notorious for being
00:42:32 --> 00:42:35 active and flary and noisy, Particularly when
00:42:35 --> 00:42:37 they're young. They're tempestuous teenagers
00:42:37 --> 00:42:40 in their early days with mega stellar flares
00:42:40 --> 00:42:43 and stuff like this. So it seems to be
00:42:43 --> 00:42:44 fairly widely accepted that planets around
00:42:44 --> 00:42:47 red dwarf stars that are close enough to be
00:42:47 --> 00:42:50 warm enough to have liquid water will have a
00:42:50 --> 00:42:51 hard time holding onto their atmospheres,
00:42:51 --> 00:42:53 Particularly when the stars are young,
00:42:53 --> 00:42:55 because it'll be having all sorts of
00:42:55 --> 00:42:57 bonkers fun. And that's kind of borne out
00:42:57 --> 00:43:00 with the planets around Trappist 1, which for
00:43:00 --> 00:43:02 years have been people saying these are the
00:43:02 --> 00:43:04 most Earth like planets ever and we'll find
00:43:04 --> 00:43:06 life on them and hooray. And then when they
00:43:06 --> 00:43:08 finally got to use the James Webb space
00:43:08 --> 00:43:10 telescope and look at those planets, none of
00:43:10 --> 00:43:13 them have an atmosphere. Now I don't know
00:43:13 --> 00:43:15 about you, but I kind of like to breathe.
00:43:15 --> 00:43:17 It's a fairly important part of living. And a
00:43:17 --> 00:43:19 planet without an atmosphere is not going to
00:43:19 --> 00:43:21 have liquid water on the surface because if
00:43:21 --> 00:43:23 you take the atmosphere away, there's no
00:43:23 --> 00:43:25 pressure, the oceans boil and then are blown
00:43:25 --> 00:43:28 away by the red dwarfs, which makes that
00:43:28 --> 00:43:30 planet a desiccated husk, which not
00:43:30 --> 00:43:32 particularly habitable. The reason I Get
00:43:33 --> 00:43:35 energized and activated about this. It's a
00:43:35 --> 00:43:37 lovely discovery. It's a really interesting
00:43:37 --> 00:43:39 planet. We'll, learn a lot more about planets
00:43:39 --> 00:43:41 elsewhere. If there is an atmosphere, it's
00:43:41 --> 00:43:43 around us now that's near enough to us that
00:43:43 --> 00:43:45 with James Webb, we'll be able to study it,
00:43:45 --> 00:43:46 learn more about the atmosphere. We'll learn
00:43:46 --> 00:43:48 a whole heap from it. But I get really
00:43:48 --> 00:43:50 energized about this because there's only so
00:43:50 --> 00:43:52 many times that people can hear a story that
00:43:52 --> 00:43:54 says we found the most Earth like planet ever
00:43:55 --> 00:43:57 before they think we found the Earth before
00:43:57 --> 00:44:00 they think we found life elsewhere. And that
00:44:00 --> 00:44:02 then really devalues it. When we finally do
00:44:02 --> 00:44:04 find planets that are, ah, properly like the
00:44:04 --> 00:44:07 Earth, when we do find signs of life
00:44:07 --> 00:44:09 elsewhere, scientists will be getting really
00:44:09 --> 00:44:11 excited because we've finally done it. And
00:44:11 --> 00:44:13 everybody will be like, well, why bother?
00:44:13 --> 00:44:15 You've done this a million times before. The
00:44:15 --> 00:44:16 whole boy who cried wolf thing
00:44:18 --> 00:44:21 again, a big bugbear. And something that's
00:44:21 --> 00:44:22 really critically important these days is
00:44:22 --> 00:44:25 trust in science and trust in scientists. We,
00:44:25 --> 00:44:27 we've got all the controversies about topics
00:44:27 --> 00:44:29 that, are much more controversial than we're
00:44:29 --> 00:44:31 talking about with astronomy, with vaccine
00:44:31 --> 00:44:34 denial, with climate change denial, with
00:44:34 --> 00:44:36 people refusing to evacuate in the path of a
00:44:36 --> 00:44:38 hurricane that's coming because they don't
00:44:38 --> 00:44:41 believe the scientists. Anything that
00:44:41 --> 00:44:44 makes people less trusting of scientists
00:44:44 --> 00:44:46 because they're overblowing stories is
00:44:46 --> 00:44:49 damaging now far more than it has been in
00:44:49 --> 00:44:51 decades past. It's part of why I get so
00:44:51 --> 00:44:54 frustrated with Avi Loeb and Three Eye Atlas.
00:44:54 --> 00:44:56 It's why get frustrated with the media
00:44:56 --> 00:44:58 coverage of stories like this and the
00:44:58 --> 00:45:00 scientists pushing, I think, somewhat
00:45:00 --> 00:45:03 unethically an argument that this could be a
00:45:03 --> 00:45:06 habitable planet because it makes
00:45:06 --> 00:45:07 the rest of us look like fools. And it makes
00:45:07 --> 00:45:10 people, it gives them ammunition to say,
00:45:10 --> 00:45:12 well, scientists lie to us when they're not.
00:45:13 --> 00:45:15 They're saying that this meets the criteria
00:45:15 --> 00:45:16 for the Habitable Zone paper that was
00:45:16 --> 00:45:19 published 10 years ago. But
00:45:19 --> 00:45:21 it weakens that trust in science, which is so
00:45:21 --> 00:45:23 important now more than it ever has done. And
00:45:23 --> 00:45:25 I said I wouldn't go on a run and I'm now
00:45:25 --> 00:45:27 waving the flag and banging the table and all
00:45:27 --> 00:45:30 the rest of it. But it's a frustration that's
00:45:30 --> 00:45:32 wider than this story. And this story is
00:45:32 --> 00:45:34 lovely. It's an awesome discovery. They found
00:45:34 --> 00:45:36 a planet going around a star. That's very
00:45:36 --> 00:45:38 cool. We'll learn a lot more about it. It's a
00:45:38 --> 00:45:41 brilliant result. You don't need to tag every
00:45:41 --> 00:45:43 result like this and say that this planet
00:45:43 --> 00:45:43 could have life.
00:45:45 --> 00:45:47 Andrew Dunkley: And yet that's what, that's what happens.
00:45:47 --> 00:45:49 it's sort of like, what artificial
00:45:49 --> 00:45:51 intelligence is doing to social media. You
00:45:51 --> 00:45:53 don't know. You don't know what you're
00:45:53 --> 00:45:56 looking at anymore. And my
00:45:56 --> 00:45:59 trust levels have dropped significantly in
00:45:59 --> 00:46:00 recent months.
00:46:02 --> 00:46:04 Jonti Horner: My dad is, 80, and
00:46:04 --> 00:46:06 he's still on Facebook. And he doesn't like
00:46:06 --> 00:46:08 it, but he's on it because it's a way to
00:46:08 --> 00:46:10 communicate with people back in the uk. Moved
00:46:10 --> 00:46:12 over here a few years ago and he's constantly
00:46:12 --> 00:46:14 saying to me, he's getting so frustrated with
00:46:14 --> 00:46:16 these AI stories and fake news things that he
00:46:16 --> 00:46:18 doesn't know what to trust on there anymore
00:46:18 --> 00:46:21 because he'll see a story that some famous
00:46:21 --> 00:46:23 actors died and then he'll look up on
00:46:23 --> 00:46:25 Wikipedia and they're still alive and kicking
00:46:25 --> 00:46:26 and they've got a film coming out. But
00:46:26 --> 00:46:28 there's this thing of, you'd never believe
00:46:28 --> 00:46:31 the tragic photos. And it's
00:46:31 --> 00:46:33 bizarre. And at a time when we need fidelity
00:46:33 --> 00:46:36 and trust in our news and trust in our
00:46:36 --> 00:46:38 science, we've got to be careful about how
00:46:38 --> 00:46:41 much hyperbole we put into stories. I think.
00:46:41 --> 00:46:43 Andrew Dunkley: I totally agree. Yes. If you'd like to read
00:46:43 --> 00:46:46 about that, particular exoplanet, you can,
00:46:47 --> 00:46:49 pick up that yarn through the Astronomical
00:46:49 --> 00:46:51 Journal where they publish the paper. Or you
00:46:51 --> 00:46:53 can read up on all the stories we've talked
00:46:53 --> 00:46:53 about
00:46:53 --> 00:46:56 today@space.com
00:46:57 --> 00:46:59 and I'm sure a few other, platforms have
00:46:59 --> 00:47:00 published them as well.
00:47:01 --> 00:47:03 and that brings us to the end of, this
00:47:03 --> 00:47:05 program. Jonti, thank you so much.
00:47:05 --> 00:47:07 Jonti Horner: It's a pleasure. It's lovely to chat. Thanks
00:47:07 --> 00:47:09 for bearing with me, being a bit flighty and
00:47:09 --> 00:47:11 flirty thanks to the power cuts and the
00:47:11 --> 00:47:11 weather.
00:47:12 --> 00:47:15 Andrew Dunkley: You've done well. You've done well. We'll,
00:47:15 --> 00:47:17 catch you on the next program, a Q and A
00:47:17 --> 00:47:19 program. Johnty, Horn, a professor of
00:47:19 --> 00:47:21 astrophysics at the University University of
00:47:21 --> 00:47:24 Southern Queens. And thanks to Huw in the
00:47:24 --> 00:47:26 studio, who couldn't be with us today
00:47:27 --> 00:47:30 because he never tells me. I
00:47:30 --> 00:47:32 have no idea. I just make up the reasons he's
00:47:32 --> 00:47:34 not here. I honestly don't know why he didn't
00:47:34 --> 00:47:36 turn up this week. Probably because we didn't
00:47:36 --> 00:47:37 tell him when we were recording.
00:47:38 --> 00:47:39 Jonti Horner: That might have been it.
00:47:39 --> 00:47:41 Andrew Dunkley: and from me, Andrew Dunkley, thanks for your
00:47:41 --> 00:47:44 company. Catch you on the very next episode
00:47:44 --> 00:47:46 of Space Nuts. Bye.
00:47:46 --> 00:47:46 Jonti Horner: Bye.
00:47:47 --> 00:47:49 You've been listening to the Space Nuts
00:47:49 --> 00:47:52 podcast, available at
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00:47:54 --> 00:47:57 iHeartRadio or your favorite podcast
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00:48:01 --> 00:48:03 Andrew Dunkley: This has been another quality podcast
00:48:03 --> 00:48:05 production from Bytes. Com.