Latest / Space Nuts: Astronomy Insights & Cosmic Discoveries / Earth's Core, Hypervelocity Stars & Cosmic Dandruff: #497 - Unraveling the Mysteries Below and Beyond

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Earth's Core, Hypervelocity Stars & Cosmic Dandruff: #497 - Unraveling the Mysteries Below and Beyond · Space Nuts: Astronomy Insights & Cosmic Discoveries

• 0:00
  Speaker 1: Hi there, thanks for joining us. This is Space Nuts.
• 0:03
  Speaker 1: My name is Andrew Dunkley, your hosts. Great to have
• 0:06
  Speaker 1: your company. Coming up on this episode, we are going
• 0:09
  Speaker 1: to look at Earth's core and it's sort of hit
• 0:12
  Speaker 1: the news lately, but this is not a news story,
• 0:14
  Speaker 1: but we thought we'd better talk about it just in
• 0:16
  Speaker 1: case you're wondering Earth's core is slowing down or not
• 0:23
  Speaker 1: doing what you'd think it would normally do.
• 0:25
  Speaker 2: So we'll talk about that.
• 0:27
  Speaker 1: There's a hyperactive star out there and it's got a planet.
• 0:30
  Speaker 1: What does that mean? It means it's pretty darn quick.
• 0:34
  Speaker 1: We're going to talk space dandruff. Yes, it's true, and
• 0:38
  Speaker 1: a new planet that's sparking a bit of debate on
• 0:41
  Speaker 1: its status.
• 0:42
  Speaker 2: If we've got time.
• 0:43
  Speaker 1: If we've got time, we'll do that one. That's all
• 0:45
  Speaker 1: coming up on this episode of Space Nuts Channel ten
• 0:51
  Speaker 1: nine Ignition Space Nuts or three two Space Nussen actually
• 1:02
  Speaker 1: bought it real good.
• 1:04
  Speaker 3: Respect for more.
• 1:05
  Speaker 2: Professor John D.
• 1:06
  Speaker 1: Horner, Professor of vestrophysics at the University of Selling Queensland.
• 1:09
  Speaker 2: Hi, Johnny, Hey, how are you going? I am well,
• 1:12
  Speaker 2: how are you?
• 1:13
  Speaker 3: I'm getting them I'm not a morning person, as I
• 1:16
  Speaker 3: was saying I got woken up earlier than I was
• 1:18
  Speaker 3: planning this morning by phone call that said, can you
• 1:21
  Speaker 3: go on live on the radio for five minutes? So
• 1:23
  Speaker 3: I got to be a zombie on live radio, which
• 1:25
  Speaker 3: all was good fun.
• 1:26
  Speaker 2: There's PESTI journalists, yeah, grade ever since.
• 1:29
  Speaker 3: Yeah, I have great sympathy for anybody who works the
• 1:32
  Speaker 3: morning show. And we I think we're talking about this
• 1:35
  Speaker 3: last week, but it must be had. But I'm not
• 1:38
  Speaker 3: at my best at twenty to seven in the morning.
• 1:41
  Speaker 3: This is a more reasonable time, but this is still morning.
• 1:43
  Speaker 3: It's twenty to twelve.
• 1:44
  Speaker 2: At the minute. I used to work Rapy the Deeping Conscience.
• 1:47
  Speaker 1: I used to work with the journalists who used to
• 1:50
  Speaker 1: have to do the police rounds first thing in the
• 1:52
  Speaker 1: morning to get any news from around the various police
• 1:55
  Speaker 1: districts in car crashes, all that horrible stuff.
• 1:59
  Speaker 2: Fires, et cetera.
• 2:00
  Speaker 1: And after a council meeting, they used to have to
• 2:02
  Speaker 1: ring the mayor at sparrows in the morning. We had
• 2:06
  Speaker 1: one particular mayor who was always nearly asleep when they called,
• 2:12
  Speaker 1: and they could never get a good quote from him
• 2:14
  Speaker 1: because he was just non compassmentus, not of the day.
• 2:19
  Speaker 2: It was a frustration to the journalist.
• 2:21
  Speaker 3: I can tell you I'm going to do something at
• 2:22
  Speaker 3: five am. I'd rather have said.
• 2:23
  Speaker 2: Up all night to do it than sat my a
• 2:25
  Speaker 2: larm oler.
• 2:26
  Speaker 1: Yes, yes, well I never had a choice for thirty
• 2:30
  Speaker 1: odd years, but anyway, that was that was my choice,
• 2:33
  Speaker 1: even though I didn't.
• 2:34
  Speaker 3: Have a choice.
• 2:34
  Speaker 2: I know you have your freedom, so I do. Now,
• 2:39
  Speaker 2: let's get down to business.
• 2:41
  Speaker 1: Earth's core, the rotation thereof This is a story that's
• 2:44
  Speaker 1: been around a little while, but it keeps popping up.
• 2:46
  Speaker 1: It popped up again on the weekend and I thought, well,
• 2:49
  Speaker 1: let's talk about it. We may have talked about it
• 2:51
  Speaker 1: with Fred. I've got an inkling that when it first
• 2:54
  Speaker 1: came up we went there. But yes, it's something that
• 2:59
  Speaker 1: the press is certainly honing in on.
• 3:01
  Speaker 2: Yeah.
• 3:02
  Speaker 3: Well, there's a few little fact words about this that
• 3:05
  Speaker 3: really caught my arch. So when you sent me the
• 3:06
  Speaker 3: link through, I've managed to miss this one. These are
• 3:10
  Speaker 3: researchers at the University of Southern California so USC, and
• 3:15
  Speaker 3: they've been looking at earthquake data. So if we want
• 3:18
  Speaker 3: to study the interior of the Earth with the best
• 3:21
  Speaker 3: wall in the world, we can't drill down there. You know.
• 3:23
  Speaker 3: The deepest hole ever drilled was less than ten kilometers
• 3:26
  Speaker 3: I believe, and the earth is frustrating the opaque. We
• 3:29
  Speaker 3: can't see the interiors grounds in the way. So we've
• 3:32
  Speaker 3: learned everything that we know about.
• 3:33
  Speaker 2: The interior structure of the Earth.
• 3:35
  Speaker 3: The call the mantle, how they all behave through earthquakes.
• 3:38
  Speaker 3: So you get an earthquake and seismic wave travel outwards
• 3:41
  Speaker 3: in all directions. There are two different types of seismic
• 3:44
  Speaker 3: waves in a very rough sense, and when they go
• 3:47
  Speaker 3: from one medium to another, their speed changes and they're
• 3:49
  Speaker 3: refract in just the same way, likeness when it enters
• 3:52
  Speaker 3: a swimming pool, same kind of idea. So if you're
• 3:55
  Speaker 3: measuring these earthquakes using seismic grass from all around the world,
• 4:00
  Speaker 3: you can back out what the interior of the Earth
• 4:02
  Speaker 3: looks like and its properties by the time it takes
• 4:05
  Speaker 3: the different tax seismic waves to reach you, essentially, and
• 4:08
  Speaker 3: by doing that over an incredible long time, we've got
• 4:10
  Speaker 3: a very detailed picture of the Earth's interior even now
• 4:13
  Speaker 3: to you know the temperatures, the pressures, the compositions, and
• 4:17
  Speaker 3: people are monitoring this all the time. But the finer
• 4:19
  Speaker 3: the detail you want, the more challenging it is to
• 4:22
  Speaker 3: disentangle the information about the earthquake itself from the information
• 4:25
  Speaker 3: you're learning about the interior. And this is something we
• 4:28
  Speaker 3: see a lot with finding X up on. It says
• 4:30
  Speaker 3: a perverse analogy here that we're looking at the light
• 4:33
  Speaker 3: from stars, and to get a really good idea of
• 4:35
  Speaker 3: what the planet's like, you've got to understand the star first,
• 4:38
  Speaker 3: because that is overlaid on the data and you've got
• 4:41
  Speaker 3: to disentangle them so to get a real handle on
• 4:44
  Speaker 3: the fine details of what's going in in terms of
• 4:47
  Speaker 3: the Earth. Your ideal situation will be to have every
• 4:49
  Speaker 3: earthquake be identical to the last, so that all the
• 4:53
  Speaker 3: earthquakes were the same, and you could take that out
• 4:55
  Speaker 3: of your analysis. You could essentially account for that. And
• 4:58
  Speaker 3: that was the first thing I say this that I
• 5:00
  Speaker 3: thought was really interesting. I mean, obviously the results are cool,
• 5:02
  Speaker 3: but it's the way they got them. They looked at
• 5:05
  Speaker 3: this sample of what are described as repeating earthquakes. They
• 5:10
  Speaker 3: got data from these earthquakes near the South Sandwich Islands,
• 5:14
  Speaker 3: one hundred and twenty one of these that occurred between
• 5:16
  Speaker 3: nineteen ninety one and twenty twenty three, and it says,
• 5:20
  Speaker 3: repeating earthquakes as seismic events that occur at the same
• 5:23
  Speaker 3: location and produce identical seismogrants. So rather than using all
• 5:27
  Speaker 3: the earthquakes from all around the world, they use this
• 5:30
  Speaker 3: one subset that gave them very controlled data and that
• 5:33
  Speaker 3: lets you get very fine resolution on the things you're
• 5:37
  Speaker 3: looking at because you're not adding extra noise essentially, and
• 5:40
  Speaker 3: by doing all this they'll learned a couple of new
• 5:42
  Speaker 3: things about the Earth in a core. So we've known
• 5:45
  Speaker 3: for a while that while the Earth has a call,
• 5:47
  Speaker 3: the core actually has two layers. It's got a molten
• 5:49
  Speaker 3: outer core, which the iron and the nickel are essentially liquid.
• 5:53
  Speaker 3: They're moving while they're molten, so they're a fluid. They
• 5:56
  Speaker 3: move around, and that movement is tied to the formation
• 5:59
  Speaker 3: of the earth magnet field. You get the induced magnetism
• 6:03
  Speaker 3: that gives us a magnetic field interior to that why
• 6:06
  Speaker 3: the pressures hing. Even though the temperature is so high,
• 6:08
  Speaker 3: the pressure is such that the inner core has been
• 6:10
  Speaker 3: thought to be solid, and so you've got a solid
• 6:14
  Speaker 3: with a liquid layer outside, and then the multen layer
• 6:16
  Speaker 3: of the mantle, then the solid layer of the crust.
• 6:18
  Speaker 2: As a rough kind of structure.
• 6:21
  Speaker 3: What these new results have shown is the headline act
• 6:23
  Speaker 3: is that that inner core doesn't spin perfectly constantly. It
• 6:28
  Speaker 3: had apparently from a long period of time which I
• 6:30
  Speaker 3: wasn't aware of, people were are that the spin speed
• 6:33
  Speaker 3: of that inner care was gradually increasing. It was speeding
• 6:36
  Speaker 3: up a little bit, almost imperceptibly. But what this research
• 6:39
  Speaker 3: has shown is that more recently it has now started
• 6:42
  Speaker 3: to slow down again. So that's a headline act. The
• 6:45
  Speaker 3: inner core has slowed down a little bit. And they're
• 6:47
  Speaker 3: talking about here on a scale of about one thousandth
• 6:50
  Speaker 3: of a second for the rotation period, so it's a
• 6:52
  Speaker 3: tiny effect, but they can measure it thanks to these
• 6:56
  Speaker 3: repeating earthquakes that have the same signature. That allows them
• 6:59
  Speaker 3: to get and much better resolution on the data.
• 7:02
  Speaker 2: The other thing.
• 7:03
  Speaker 3: Which I think is very interesting that isn't in the
• 7:06
  Speaker 3: main pressure is but is in a couple of the
• 7:07
  Speaker 3: other articles, is that the same data suggests that the
• 7:10
  Speaker 3: inner core is not totally solid but actually has molten
• 7:13
  Speaker 3: areas within it. So this is a bit of a
• 7:16
  Speaker 3: change to the paradigm we had of this very simple
• 7:19
  Speaker 3: model of a solid inner core than a molten outer
• 7:22
  Speaker 3: core that there's actually a bit of moltenness to the
• 7:25
  Speaker 3: inner core as well, which probably makes a bit of
• 7:28
  Speaker 3: sense in the context of this thing's rotation changing over time.
• 7:31
  Speaker 3: If you've got bits that are melting, bits that are
• 7:34
  Speaker 3: moving around a little bit, you're moveing angular momentum around.
• 7:38
  Speaker 3: So therefore you'll change the rotation period in just the
• 7:41
  Speaker 3: same way that the rotation period of the Earth as
• 7:43
  Speaker 3: a whole will change if the ice caps melt, will
• 7:46
  Speaker 3: change in a measurable way because you're moving mass from.
• 7:48
  Speaker 2: The poles to the equator.
• 7:50
  Speaker 3: Redistributing that mass will mean that the spin will slow
• 7:53
  Speaker 3: a little bit to conserve angular momenta. So it's a
• 7:57
  Speaker 3: fascinating story, and I think, yes, the head line side
• 8:00
  Speaker 3: of it, the inner core has slowed down. That's interesting.
• 8:04
  Speaker 3: That's the headline story. But to me, the really interesting
• 8:06
  Speaker 3: stuff was how of how they figured that out, and
• 8:09
  Speaker 3: those subtleties of the choice of earthquakes to use and
• 8:13
  Speaker 3: the additional things they can figure out. It really shows
• 8:15
  Speaker 3: the benefit of continuing to get longer data sets in
• 8:19
  Speaker 3: reanalyzing what you thought you knew when you've got better
• 8:22
  Speaker 3: data and better instruments. So it's a very cool story
• 8:24
  Speaker 3: and do encourage people to have a look around. There's
• 8:27
  Speaker 3: a few different versions of the story out there on
• 8:29
  Speaker 3: the web. Even CNN covered.
• 8:31
  Speaker 2: It at one point, so it's a good one. Interesting.
• 8:34
  Speaker 3: By reading a variety of stories, you can get some
• 8:37
  Speaker 3: of the different cool facts that maybe the main pressure
• 8:39
  Speaker 3: release didn't pick up on.
• 8:40
  Speaker 1: Yeah, they figured this out by studying what is one
• 8:45
  Speaker 1: hundred and twenty one earthquakes between nineteen ninety one and
• 8:48
  Speaker 1: twenty twenty four.
• 8:49
  Speaker 3: Yes, help accurate. Do you perceive their data to be well?
• 8:56
  Speaker 3: I trust at the end of the day, it's peer
• 8:57
  Speaker 3: reviewed and published, so there's a and confidence of fidelity there.
• 9:02
  Speaker 2: That's good.
• 9:02
  Speaker 3: And I find their data selection really interesting. There the
• 9:06
  Speaker 3: fact that you've got thousands of earthquakes happening all the time.
• 9:09
  Speaker 3: You know, we see what's happening in Santaurini at the
• 9:11
  Speaker 3: minute with what is probably a very large motion of
• 9:14
  Speaker 3: magma underneath that ancient volcano that suggests it may well
• 9:19
  Speaker 3: erupt again at some point, seeing similarly under aples. So
• 9:22
  Speaker 3: earthquakes are happening all the time all around the world.
• 9:25
  Speaker 3: And what I loved about this was finding this subset
• 9:27
  Speaker 3: of earthquakes that are happening recurrently at the same place
• 9:31
  Speaker 3: that are giving them the same signal, which makes a
• 9:34
  Speaker 3: data analysis much much much better. I just really like that,
• 9:38
  Speaker 3: and it's why, in exactly the same way that we
• 9:41
  Speaker 3: can find planets using our radial.
• 9:43
  Speaker 2: Velocity of the wobble method much.
• 9:45
  Speaker 3: More easily around quiet stars and active starts because active
• 9:50
  Speaker 3: stars are roiling and bubbling and boiling, so the lines
• 9:53
  Speaker 3: of the spectrum of the star are moving around because
• 9:56
  Speaker 3: of the properties of the star. That introduces a lot
• 9:59
  Speaker 3: of noise. When you've got a quiet SAA South that
• 10:02
  Speaker 3: isn't very active a bit like the Sun, is that
• 10:05
  Speaker 3: noise is much less, which means that you can resolve
• 10:08
  Speaker 3: much smaller motions thanks to the planets, and so you
• 10:11
  Speaker 3: can detect smaller planets around stars that are less active.
• 10:15
  Speaker 3: And it's a.
• 10:16
  Speaker 2: Direct parallel here.
• 10:17
  Speaker 3: By getting a much simpler set of earthquakes that all
• 10:20
  Speaker 3: behave the same way, you reduce the noise and therefore
• 10:23
  Speaker 3: you can get a much more accurate pressure of what's
• 10:25
  Speaker 3: going on in the interior. So I guess if you
• 10:27
  Speaker 3: want to look at timescale changes in the mantle and
• 10:30
  Speaker 3: stuff like that, you can use all the data set
• 10:33
  Speaker 3: and map it that way. But for something like this way,
• 10:35
  Speaker 3: you need that really fine tooth comb. It's a beautiful
• 10:37
  Speaker 3: way of doing it.
• 10:39
  Speaker 2: Yeah. Yeah, it's fascinating story.
• 10:40
  Speaker 1: It's you know, we're so close to it compared to
• 10:43
  Speaker 1: everything else we study, but it's it's.
• 10:47
  Speaker 4: Invisible to us to Yeah, we have to dig deep
• 10:52
  Speaker 4: instead of getting developed from this then applying astronomy and
• 10:56
  Speaker 4: in planet for science.
• 10:57
  Speaker 3: You know, we talked previously about Insight, which sat on
• 11:00
  Speaker 3: Mars and recorded Mars quakes and that much just single station.
• 11:03
  Speaker 3: I would love at some point in the future, perhaps
• 11:06
  Speaker 3: when Syrielon decides that he's finally going to move to Mars,
• 11:09
  Speaker 3: if he could text some seismometers with him and drop
• 11:12
  Speaker 3: them in a variety of positions, that'll give us a
• 11:15
  Speaker 3: lot more information on Mars's interior. Similar with these kind
• 11:18
  Speaker 3: of techniques are very similar to what my colleagues at
• 11:20
  Speaker 3: the University of Southern Queensland and elsewhere around the sphere
• 11:24
  Speaker 3: of academia used to study the interiors of starsks. You've
• 11:27
  Speaker 3: got the same problem. You look at the Sun and
• 11:29
  Speaker 3: it's our near as star, but always see it's a surface.
• 11:32
  Speaker 3: You can't see inside it because the surfaces in the
• 11:34
  Speaker 3: way now, how do we know about the structure of
• 11:36
  Speaker 3: the interior. It's exactly the same kind of thing they're
• 11:39
  Speaker 3: doing here, but using star quakes and star wobbles rather
• 11:42
  Speaker 3: than earthquakes.
• 11:44
  Speaker 2: Yeah, really interesting stuff.
• 11:46
  Speaker 1: And if you'd like to read more about the core
• 11:49
  Speaker 1: of our own planet slowing down, just do a.
• 11:52
  Speaker 2: Search for that. It's everywhere.
• 11:54
  Speaker 1: You can find it on Discover magazine and a few
• 11:57
  Speaker 1: other sites. Let's take a little break from the show
• 12:01
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  Speaker 1: Now back to the show three Space Nuts. Now, let's
• 13:48
  Speaker 1: go to this story that is talking about a star
• 13:52
  Speaker 1: that's been described as hyperactives.
• 13:54
  Speaker 2: This is a star that's moving well. It's probably one
• 13:57
  Speaker 2: of the.
• 13:58
  Speaker 1: Fastest, if not the fastest, ever discovered. This story is
• 14:02
  Speaker 1: quite amazing.
• 14:04
  Speaker 3: So this is what's called a hypervelost is Sara, and
• 14:07
  Speaker 3: we do know a few of these in the Milky Way.
• 14:10
  Speaker 3: These are stars that are traveling at such a high
• 14:12
  Speaker 3: speed that they're traveling faster than the local escape velosity
• 14:16
  Speaker 3: for the galaxy at their location. So we're on the
• 14:19
  Speaker 3: surface of the Earth, and if I throw a tennis
• 14:20
  Speaker 3: ball up in the air, it will fall back down.
• 14:23
  Speaker 2: I'll catch it, or I'll fail to catch it.
• 14:24
  Speaker 3: Bex and English and the English cricket team is doing
• 14:27
  Speaker 3: terribly at them, and it's I'll probably fail to catch
• 14:29
  Speaker 3: it because that's where I'm from. Originally, if I threw
• 14:32
  Speaker 3: it hard enough, the Earth's gravity wouldn't be able to
• 14:35
  Speaker 3: hold on twit and it would escape. And for the Earth,
• 14:38
  Speaker 3: that's about eleven kilometers a second. The more massive you are,
• 14:43
  Speaker 3: the higher that veloci is, but the further you are
• 14:45
  Speaker 3: from the.
• 14:45
  Speaker 2: Mass, the lower that veloci is.
• 14:47
  Speaker 3: I mean, it's the kind of thing we teach in
• 14:48
  Speaker 3: first year astrophysics as an equation for the escape velocity
• 14:52
  Speaker 3: where you can work it out, and I think it's
• 14:54
  Speaker 3: a square of two gm over r now sounds about
• 14:59
  Speaker 3: right though. That's basically it's related to the mass of
• 15:02
  Speaker 3: the thing you're going around that and it's investly proportional
• 15:05
  Speaker 3: to the distance that you are away from that thing
• 15:08
  Speaker 3: with a square rout there. What that means is that
• 15:12
  Speaker 3: anything that has mass has an escape velocity. So technically
• 15:16
  Speaker 3: I have an escape velosity. If you put me in
• 15:18
  Speaker 3: the vacuum of space far away from any star and
• 15:22
  Speaker 3: give me that tennis ball, I could, in theory nudge
• 15:24
  Speaker 3: it gently and make it orbit me. But if I
• 15:27
  Speaker 3: knowdge too hard, it would escape. But even though I'm
• 15:30
  Speaker 3: far too heavy, my gravitational pull is incredibly weak because
• 15:33
  Speaker 3: I'm only one hundred and thirty kilos, not the mass
• 15:36
  Speaker 3: of the Earth. What that means from the point of
• 15:39
  Speaker 3: view of our galaxy is that our galaxy has an
• 15:42
  Speaker 3: escape velosity that varies depending on where you are in
• 15:44
  Speaker 3: the galaxy mayor you are to the middle. The higher
• 15:47
  Speaker 3: the speed you need to be traveling is to escape.
• 15:50
  Speaker 3: Just as in the Solar System, it's harder to escape
• 15:53
  Speaker 3: from the Sun when your name Mercury is orbit than
• 15:55
  Speaker 3: it is when you're.
• 15:56
  Speaker 2: Know Neptron's orbit.
• 15:58
  Speaker 3: So that's how stars move, and a small fraction of
• 16:01
  Speaker 3: the stars in our galaxy, because they're constantly moving around
• 16:04
  Speaker 3: all the other stars because of things going on, a
• 16:07
  Speaker 3: small number of those stars will eventually get ejected from
• 16:10
  Speaker 3: the galaxy entirely.
• 16:12
  Speaker 2: Now.
• 16:12
  Speaker 3: Quite a few of these actually that are previously known
• 16:15
  Speaker 3: are linked to stars that were in a binary star
• 16:18
  Speaker 3: system that was quite close and then one of the
• 16:20
  Speaker 3: components went super and over and suddenly like the lead
• 16:24
  Speaker 3: was cut, so suddenly they're rejected at very high speed. Right,
• 16:27
  Speaker 3: But that's not the only way you can form that
• 16:30
  Speaker 3: hypervelocity stars. And are these stars whose speed is so
• 16:33
  Speaker 3: high that they will probably escape and never return, that
• 16:36
  Speaker 3: will wonder the void between the galaxies in a very
• 16:38
  Speaker 3: lonely life forevermore. The other side of this story is
• 16:44
  Speaker 3: planet detection. We've talked before about how the two most
• 16:47
  Speaker 3: successful methods for finding planets are the transit method and
• 16:50
  Speaker 3: the radio lossy method, essentially seeing stars warbble and wink.
• 16:54
  Speaker 3: There is a method of technique called gravitational microlensing that
• 16:58
  Speaker 3: if you went back to the Latin nineties, people were
• 17:00
  Speaker 3: really hoping it would find gazillions of planets, that it
• 17:04
  Speaker 3: would be really successful, and it's never quite found as
• 17:07
  Speaker 3: many as people expected because it's fundamentally hard to do.
• 17:11
  Speaker 3: It's not that these events aren't happening, it's just that
• 17:13
  Speaker 3: they're very hard to observe. But going back to twenty eleven,
• 17:16
  Speaker 3: a team of scientists that were looking towards the galactic core,
• 17:20
  Speaker 3: where you've got the most stars on the sky in
• 17:22
  Speaker 3: the smallest area, observed a gravitational micro lensing event. They
• 17:26
  Speaker 3: saw a background star brightened and then faded away again,
• 17:30
  Speaker 3: but it had a double peak in the brightness, so
• 17:32
  Speaker 3: there were two peaks as it went up, and then
• 17:35
  Speaker 3: it went up further and then it fell away again,
• 17:37
  Speaker 3: and that was indicating that in the foreground between us
• 17:40
  Speaker 3: and that star, something had passed in front that had mass.
• 17:44
  Speaker 3: That mass curving space time acted as a lens bent
• 17:47
  Speaker 3: a little bit more of the light from the background
• 17:49
  Speaker 3: star towards us, and that's why we saw the star brighton.
• 17:52
  Speaker 3: And then as the thing in the foreground moved away again,
• 17:54
  Speaker 3: the lens went away and it faded away again. And
• 17:57
  Speaker 3: when these events happened quite a lot from studying the
• 18:01
  Speaker 3: degree to which the thing brightened and faded and also
• 18:04
  Speaker 3: the timescale over which it happened, and the team at
• 18:08
  Speaker 3: the time announce the results. This is really exciting, but
• 18:11
  Speaker 3: there's a little bit of what we call a degeneracy.
• 18:13
  Speaker 3: There are two different models that can equally well explain
• 18:17
  Speaker 3: what we've observed. The first is that you've got a
• 18:20
  Speaker 3: star that's about a fifth of the mass of the
• 18:22
  Speaker 3: Sun with a planet that is about twenty nine times
• 18:25
  Speaker 3: the mass of the Earth. That's scenario one, so you've
• 18:29
  Speaker 3: got a star with a planet. The other scenario is
• 18:32
  Speaker 3: that you had a planet the mass of Jupiter with
• 18:35
  Speaker 3: a tiny little moon, and in either case, the ratio
• 18:38
  Speaker 3: of the mass between the big thing and the little
• 18:40
  Speaker 3: things about twenty three hundred times. Either of these scenarios
• 18:44
  Speaker 3: could explain perfectly well what was seen. So how do
• 18:48
  Speaker 3: we differentiate between them. Well, one thing we can do
• 18:51
  Speaker 3: now that we've got better telescopes and better technology, is
• 18:54
  Speaker 3: to use the Keck telescopes, which are among the biggest
• 18:57
  Speaker 3: in the world. There are incredible instruments in South America,
• 19:01
  Speaker 3: and also the Geyer spacecraft, which has been should finish
• 19:04
  Speaker 3: its mission, but it spent twelve years in orbit mapping
• 19:07
  Speaker 3: the positions of the motions of up to two billion
• 19:10
  Speaker 3: stars with unprecedented mind boggling accuracy. So the team that
• 19:15
  Speaker 3: found this object in twenty eleven saw this signal in
• 19:18
  Speaker 3: the gravitational micro lensing said, one way that we could
• 19:21
  Speaker 3: distinguish between those two different models. Is to look for
• 19:26
  Speaker 3: the thing that caused the lensing. If it's a star,
• 19:30
  Speaker 3: in theory, there'll be a point of light there that's
• 19:32
  Speaker 3: moving that we can see that we can track back
• 19:34
  Speaker 3: and say it was in the right place at the
• 19:35
  Speaker 3: right time. We'll be able to see it, and that
• 19:38
  Speaker 3: shows that the thing that did the lensing was a star.
• 19:40
  Speaker 3: So it's a star and a planet. If we see nothing,
• 19:44
  Speaker 3: then the star doesn't work because if there was a
• 19:45
  Speaker 3: star there, we'd see it, so it must be the
• 19:47
  Speaker 3: other scenario. So they went away and dug through that data,
• 19:50
  Speaker 3: and it took them a bit longer than expected, but
• 19:53
  Speaker 3: they finally found a star that is moving ridiculously quickly
• 19:56
  Speaker 3: but was in exactly the right place at the right
• 19:59
  Speaker 3: time caused a micro lensing event. And that star is
• 20:02
  Speaker 3: also quite near the middle of the galaxy, so it's
• 20:04
  Speaker 3: quite it was quite far from us, quite near the
• 20:07
  Speaker 3: thing it was lensing at the time. They've tracked it
• 20:09
  Speaker 3: back and it turns out that the movement of this
• 20:12
  Speaker 3: star just at right angle to all ainosites, so the
• 20:14
  Speaker 3: movement across the sky gives it a speed that is
• 20:18
  Speaker 3: almost two million kilometers per hour five hundred and forty kilometers.
• 20:24
  Speaker 2: Per second glimy. That is ridiculous.
• 20:27
  Speaker 3: You know, stars nearby near the some moving around. We
• 20:31
  Speaker 3: typically talk of speeds of tens of kilometers a second,
• 20:33
  Speaker 3: maybe a bit more than one hundred, So five hundred
• 20:36
  Speaker 3: and forty is ridiculously extreme and is already almost the
• 20:39
  Speaker 3: escape lossary of the galaxy at that point. Now, the
• 20:42
  Speaker 3: unknown here is that there could be some movement towards
• 20:45
  Speaker 3: are away from us as well, So we only see
• 20:47
  Speaker 3: the movement on the sky, and essentially any movement that
• 20:52
  Speaker 3: is radial towards are away from us would be enough
• 20:55
  Speaker 3: to mean that this thing is unbound by the galaxy,
• 20:57
  Speaker 3: that it will eventually escape. It is therefore a hyper
• 21:01
  Speaker 3: velocity star, and this is the very first time a
• 21:04
  Speaker 3: planet has been confirmed around the hypervelosity stat. Now, planets
• 21:08
  Speaker 3: will form around the stats, that's fine. But to get
• 21:10
  Speaker 3: the very first one, that's kind of cool, and that's
• 21:13
  Speaker 3: the planet that is signific cooking massive than the Earth.
• 21:17
  Speaker 3: That's our probably has other planets. Where you find one planet,
• 21:20
  Speaker 3: there will be more. So this is a planetary system
• 21:23
  Speaker 3: that is on a one way ticket out of our galaxy,
• 21:25
  Speaker 3: never to return.
• 21:27
  Speaker 2: Wow.
• 21:28
  Speaker 1: Yeah, that's quite a fine isn't it, And such an
• 21:31
  Speaker 1: incredible speed. Have they worked out how long it will
• 21:35
  Speaker 1: take to exit the galaxy? Probably a long time even
• 21:37
  Speaker 1: at that speed.
• 21:39
  Speaker 3: Very very long time, even at that speed. So we
• 21:41
  Speaker 3: can probably try and back of the envelope mental arithmetically.
• 21:44
  Speaker 3: So I'll get everybody on line to forgive me. But
• 21:48
  Speaker 3: speed of light is three hundred thousand kilometers a second.
• 21:52
  Speaker 3: I'm going to say that this is six hundred klometers
• 21:54
  Speaker 3: a second because that just keeps the mouths easier, right,
• 21:57
  Speaker 3: six hundred over three hundred thousand is six hundred, which
• 22:00
  Speaker 3: is two percent thereabouts. So this thing's traveling at two
• 22:04
  Speaker 3: percent of the speed of light. That's fairly significant. Now
• 22:08
  Speaker 3: the galaxy is going to be pointing back as long
• 22:10
  Speaker 3: down as it goes. But if you think about the
• 22:13
  Speaker 3: diameter of the milky ways, about one hundred thousand light years,
• 22:16
  Speaker 3: so that means the radius of the milky way's about
• 22:18
  Speaker 3: fifty thousand light years. If you're traveling at two percent
• 22:22
  Speaker 3: of the speed of light, that means it will take
• 22:24
  Speaker 3: you fifty years to travel one light year, right, right,
• 22:28
  Speaker 3: So fifty years per light year for fifty thousand light
• 22:31
  Speaker 3: years is two point five million years. Now, that is
• 22:37
  Speaker 3: a long time for us. But where compuere it to
• 22:40
  Speaker 3: the fact that it takes to some two hundred and
• 22:42
  Speaker 3: fifty million years or so to go around the middle
• 22:44
  Speaker 3: of the galaxy. That gives you a sense of how
• 22:46
  Speaker 3: quickness is actually moving.
• 22:49
  Speaker 1: Fascinating. All right, Yeah, so far the fastest found, but
• 22:54
  Speaker 1: maybe others will probably find another one that's faster at
• 22:57
  Speaker 1: some stage. Yes, you can read about that. It's based
• 23:00
  Speaker 1: dot com. If you want to read the actual paper.
• 23:03
  Speaker 1: It was published this month in the Astronomical Journal. There's
• 23:07
  Speaker 1: a space nuts with Andrew Dunkley and Professor John T.
• 23:09
  Speaker 2: Horner.
• 23:12
  Speaker 1: Okay, we take a space nuts now.
• 23:17
  Speaker 2: Johnny, let's move on to this problem with.
• 23:21
  Speaker 1: Dandriff in space that's what it's described as. It's not
• 23:24
  Speaker 1: really Dandriff. It's just neighboring solar systems dumping their stuff
• 23:30
  Speaker 1: on us.
• 23:31
  Speaker 2: So I didn't know. I didn't know that.
• 23:33
  Speaker 3: Was a thing Amber's doing exactly the same back at
• 23:35
  Speaker 3: the BIT.
• 23:35
  Speaker 2: Should have said no, only.
• 23:37
  Speaker 3: Ask one of those things that I talk about a lot.
• 23:40
  Speaker 3: In the context of our solar system, we have comets
• 23:42
  Speaker 3: and asteroids, and the main where that comets get removed
• 23:46
  Speaker 3: from the Solar System to no longer pose a threat
• 23:48
  Speaker 3: to the Earth. Is that many of the mess get
• 23:50
  Speaker 3: the Solar System never to return, usually flung out by
• 23:53
  Speaker 3: one of the giant planets or by subtle gravitational perturbations
• 23:57
  Speaker 3: like that. So you can look back over the edge
• 23:59
  Speaker 3: of the Cellar System and it has continually been shedding
• 24:01
  Speaker 3: comets and asteroids into the void of space, creating these
• 24:05
  Speaker 3: interstellar wonderers essentially, And that will have been particularly strongly
• 24:09
  Speaker 3: the case, incidentally, when the Solar System was still forming,
• 24:13
  Speaker 3: because big part of the formation of the planets and
• 24:15
  Speaker 3: the cleanup afterwards was getting rid of most of the
• 24:17
  Speaker 3: stuff that was left over. So the Solar System over
• 24:20
  Speaker 3: it some will have shed uncountered objects into space, and
• 24:24
  Speaker 3: it continues to do so today. And I've often said,
• 24:27
  Speaker 3: in those socks, it's almost certain that every other star
• 24:30
  Speaker 3: will be doing the same thing. Any star that has
• 24:32
  Speaker 3: a planetary system, those planets will be staring things up
• 24:35
  Speaker 3: and throwing things out. So it's one of those things
• 24:38
  Speaker 3: that I've just taken for granted. But it's only recently
• 24:41
  Speaker 3: that we've actually been able to detect the products of
• 24:45
  Speaker 3: this from other stars. Like I said, for decades people
• 24:48
  Speaker 3: have talked about the possibility of us finding interstellar objects
• 24:51
  Speaker 3: in the Solar System. So seeing comets or asteroids coming
• 24:54
  Speaker 3: through that could be absolutely indefinitively shown not to have
• 24:59
  Speaker 3: an origin in it our source system, how do we
• 25:01
  Speaker 3: do that while we look at how quick they're moving.
• 25:03
  Speaker 3: It's just like what we were talking about a minute
• 25:05
  Speaker 3: ago with the escape velocity. Objects moving around the Sun
• 25:09
  Speaker 3: are gravitationally bound. If they get a nudge and they're
• 25:12
  Speaker 3: going to escape, they will be traveling a bit too
• 25:14
  Speaker 3: quick to be gravitationally bound, but only just by a
• 25:18
  Speaker 3: tiny amount. So when we find an object that comes in,
• 25:22
  Speaker 3: we can work out what speed it would travel at
• 25:25
  Speaker 3: if it was infinitely far from the Sun.
• 25:27
  Speaker 2: Top call this the velocity of infinity.
• 25:29
  Speaker 3: So and once the Sun has slowed it down as
• 25:31
  Speaker 3: much as it can, how much speed has it got left?
• 25:34
  Speaker 3: And two objects that were found in the last decade
• 25:38
  Speaker 3: met this criteria have been interstellar. There were Umau Mau
• 25:42
  Speaker 3: which came through in twenty seventeen. And despite what a
• 25:44
  Speaker 3: certain eminent person at Harvard, and I'm trying to choose
• 25:48
  Speaker 3: my words carefully here because I have a certain opinion,
• 25:50
  Speaker 3: despite what he keeps trying to tell you to sell
• 25:53
  Speaker 3: his books and make a lot of money. That was
• 25:55
  Speaker 3: not an alien spaceship. It never would be an alien spaceship.
• 25:58
  Speaker 3: It absolutely was not aliens. That was just a lump
• 26:01
  Speaker 3: of rock and debris. We then had commit Borisov back
• 26:05
  Speaker 3: in twenty nineteen, which was our second interstellar object. Yeah,
• 26:08
  Speaker 3: we found two of them. Now the odds are that
• 26:10
  Speaker 3: in the coming decade we will find hundreds because the
• 26:13
  Speaker 3: Vera Ruben Observatory is going to come online. Vera Ruben Observatory,
• 26:17
  Speaker 3: of course, named for one of the grade astronomers of
• 26:19
  Speaker 3: twentieth century who was a woman in astronomy, And that's
• 26:24
  Speaker 3: a challenging thing to discuss at the moment with what's
• 26:26
  Speaker 3: going on in the US. I will just mention in
• 26:28
  Speaker 3: passing that that is itself a controversy this week because
• 26:32
  Speaker 3: with the new government in the US, they've been forced
• 26:35
  Speaker 3: to change the biography of Vera Rubin on the website
• 26:39
  Speaker 3: because one of the things that she was very active
• 26:41
  Speaker 3: on was advocating for women in science and you know,
• 26:44
  Speaker 3: setting up schemes to try and help women get more
• 26:45
  Speaker 3: involved in astronomy. Now you can't talk about that anyway,
• 26:49
  Speaker 3: that's an aside, but it's a bit of a frustration
• 26:51
  Speaker 3: of the human element of this. Yeah, vera Rubin Observatory
• 26:55
  Speaker 3: named after this incredible astronomer. It's going to come online
• 26:58
  Speaker 3: in the next year or two, and it's for has
• 27:00
  Speaker 3: to find tens or hundreds of these objects, because we'll
• 27:02
  Speaker 3: just be much better at spotting them. What the new
• 27:06
  Speaker 3: research is is some computer modeling. A group has had
• 27:09
  Speaker 3: the same idea that we're just talking about and said,
• 27:11
  Speaker 3: let's model this. Let's try and get a handle on
• 27:14
  Speaker 3: just how much stuff nearby star systems are throwing our
• 27:18
  Speaker 3: way to fill the space around us. And they're looked
• 27:21
  Speaker 3: at our nearest companions. The Alpha Centauri system, which is
• 27:25
  Speaker 3: the binary star of Alpha Centauri AMB, and then the
• 27:28
  Speaker 3: red dwarf Proximma, which is currently a bit closer to us,
• 27:31
  Speaker 3: are the two biggest starts.
• 27:33
  Speaker 2: They ransom simulations very much of the ILK.
• 27:35
  Speaker 3: That I do in my day job running on the
• 27:38
  Speaker 3: supercomputing cluster here saying if this star system has the
• 27:43
  Speaker 3: kind of objects in it we'd expect for system of
• 27:45
  Speaker 3: that age, how many getting ejected in our general direction?
• 27:49
  Speaker 3: And what they have found is that their simulation suggests
• 27:52
  Speaker 3: there could be as many as a million objects bigger
• 27:55
  Speaker 3: than one hundred meters across passing through our Solar system
• 27:59
  Speaker 3: out of the current time that departed from the Alpha
• 28:03
  Speaker 3: Centaurus system. Now the circulty here is a lot of
• 28:06
  Speaker 3: the time when we talk about passing through the Solar system,
• 28:09
  Speaker 3: we think of our local part of the Solar system,
• 28:11
  Speaker 3: the orbits of the planets, But in reality, the volume
• 28:13
  Speaker 3: of space we're considering to be the Solar system here
• 28:16
  Speaker 3: is the entirety of the Oat cloud. So this is
• 28:18
  Speaker 3: a volume of space something like two light years in
• 28:22
  Speaker 3: every direction from us. It's an unimaginably vast sphere of
• 28:26
  Speaker 3: space that has these objects passing through it. So the
• 28:30
  Speaker 3: likelihood of one getting closer for us to detective the
• 28:32
  Speaker 3: near future is pretty low, but it's not being the
• 28:35
  Speaker 3: bounds of possibility. And again, when Vera Rubin comes online,
• 28:40
  Speaker 3: if any of these are in the domain of the planets,
• 28:43
  Speaker 3: they're coming close enough to the sum that they are detectable,
• 28:47
  Speaker 3: Vera Rubin will find them. Now a million objects spread
• 28:52
  Speaker 3: over the Oat Cloud, to be honest, means that it's
• 28:54
  Speaker 3: very unlikely one of them will be close enough to see.
• 28:57
  Speaker 3: But these things are going to be traveling faster than
• 28:59
  Speaker 3: the escape loss the Sun, so they'll come through fairly quickly,
• 29:03
  Speaker 3: and that means if they're moving through, just because we
• 29:05
  Speaker 3: don't see them now doesn't mean if we look again
• 29:07
  Speaker 3: in five years time, there wouldn't be one that's appeared.
• 29:09
  Speaker 2: The other thing that.
• 29:10
  Speaker 3: Came out of this is that they talked about the
• 29:12
  Speaker 3: smaller particles more common, and it's quite likely that there
• 29:16
  Speaker 3: may be as many as ten meteas per year on
• 29:19
  Speaker 3: the Earth that are bits of dust from the off
• 29:21
  Speaker 3: Centaurus system hitting our planet. Now ten per year across
• 29:25
  Speaker 3: the entire surface of the Earth means that you're very
• 29:27
  Speaker 3: unlikely to find them, but it reminded me of stories
• 29:30
  Speaker 3: that go back much further, because we have these wonderful
• 29:32
  Speaker 3: networks of cameras across the Earth that look up at
• 29:35
  Speaker 3: shooting stav and try and get multi session observations so
• 29:39
  Speaker 3: you can do trigonometry and figure out what their orbit was,
• 29:42
  Speaker 3: how they were moving, and they've detected over the years
• 29:45
  Speaker 3: a very small number of definitively interstellar meteors, so Metea's
• 29:49
  Speaker 3: coming into the Earth's atmosphere with a speed significantly higher
• 29:52
  Speaker 3: than seventy two kilometers a second, which means that they
• 29:55
  Speaker 3: can't have been bound to the Solar system. One of
• 29:59
  Speaker 3: the things that those papers discussed for a long time
• 30:01
  Speaker 3: is that there is one dominant source of dust through
• 30:04
  Speaker 3: our Solar system that gives us more than all of
• 30:07
  Speaker 3: the sources combined. A famous star called Beta Pictoris, which
• 30:12
  Speaker 3: back in nineteen eighty three was one of three stars
• 30:14
  Speaker 3: the Infrared Astronomical Satellite was confused about because it found
• 30:18
  Speaker 3: an infrared excess around that star. It is three light
• 30:22
  Speaker 3: years away, It's more massive than the Sun and hotter,
• 30:24
  Speaker 3: but it's very young, and it's still got a disc
• 30:26
  Speaker 3: of debris around it forming planets. It's got planets in
• 30:29
  Speaker 3: that disk that we've discovered. But then incredibly active stellar
• 30:32
  Speaker 3: wind that that massive star has is blowing lots of
• 30:35
  Speaker 3: the dust into space, streaming off in all directions, and
• 30:39
  Speaker 3: the enough of that dust is traveling to reach us
• 30:42
  Speaker 3: sixty three light years away that we can detect that
• 30:46
  Speaker 3: as a distinct source of debris crashing into the s atmosphere.
• 30:51
  Speaker 3: That really boggles my mind that a star that far
• 30:54
  Speaker 3: away can be putting dust into our atmosphere at a
• 30:57
  Speaker 3: subfigent level that people have detected that dustry.
• 31:02
  Speaker 1: It is it's amazing, and this must be happening just
• 31:05
  Speaker 1: about everywhere. We've probably got systems exchanging junk constantly.
• 31:11
  Speaker 2: Yeah.
• 31:11
  Speaker 3: Absolutely, And it ties into the panspermia idea that we've
• 31:15
  Speaker 3: talked about before as well. If you are constantly ejecting
• 31:18
  Speaker 3: dust and debris from every planetary system, if you have
• 31:22
  Speaker 3: somewhere with life in that system, eventually that life has
• 31:26
  Speaker 3: the potential to travel. And you know, yeah, most of
• 31:30
  Speaker 3: it will. Most of the debris ejected from the Earth
• 31:32
  Speaker 3: will never land on any other world. It will just
• 31:34
  Speaker 3: float in space for forever more. But enough has been
• 31:37
  Speaker 3: ejected that eventually something ejected from the Earth will land
• 31:42
  Speaker 3: on a planet around another SAR, or will be incorporated
• 31:45
  Speaker 3: in a planet forming region around a SATH that's just
• 31:47
  Speaker 3: been borught. You put enough material out there, with enough
• 31:51
  Speaker 3: bacteria buried in it, it's very reasonable to imagine that
• 31:54
  Speaker 3: you could get a situation where, at some point in
• 31:57
  Speaker 3: the distant future, there is a planet that has life
• 31:59
  Speaker 3: on it, and that life is having a discussion of
• 32:02
  Speaker 3: how did life get started, and someone suggests, well, Medley,
• 32:05
  Speaker 3: life came from the stars, and everybody says, well, that's
• 32:07
  Speaker 3: a lot of rubbis. Stop watching star trek and after
• 32:09
  Speaker 3: it was the case because it's earthlife.
• 32:12
  Speaker 1: Yes, indeed, And this story also proves that you shouldn't
• 32:15
  Speaker 1: get upset with your neighbors for throwing the grass clippings
• 32:18
  Speaker 1: over your fence because it happens right through the.
• 32:21
  Speaker 3: Cosmos absolutely, I mean times into the other space sand
• 32:25
  Speaker 3: rough thing.
• 32:25
  Speaker 2: Actually.
• 32:26
  Speaker 3: So the whole Nambrup connection here, of course, is the
• 32:29
  Speaker 3: stars shaking their head and comets flying through space, essentially
• 32:32
  Speaker 3: the beautiful analogy there. But every time you're walking around
• 32:35
  Speaker 3: outside or anytime you're doing the dust thing in your house,
• 32:38
  Speaker 3: a certain amount of the dust that is falling on
• 32:40
  Speaker 3: your shoulders or that is a crewing in your house
• 32:43
  Speaker 3: is dust from outer space. We have these tiny little
• 32:46
  Speaker 3: particles of dust, which are sometimes called brownly particles. They
• 32:50
  Speaker 3: are small enough that they are slowed down by the
• 32:52
  Speaker 3: very tenuous sout atmosphere before they get into a thick
• 32:55
  Speaker 3: enough flare of atmosphere that they get ablated that before
• 32:58
  Speaker 3: they burn up. So there's this steady little sleeked of
• 33:01
  Speaker 3: micro micro microscopic particles from space running down on the
• 33:05
  Speaker 3: Earth all the time. So when you do the best thing,
• 33:08
  Speaker 3: or when you go outside on a day and you're
• 33:10
  Speaker 3: getting dusts on you. A total fraction of one is
• 33:13
  Speaker 3: space that you've got spast under running down on you
• 33:16
  Speaker 3: at old times.
• 33:17
  Speaker 1: Yeah, it is fascinating to think about. I think we
• 33:20
  Speaker 1: have touched on that story once before a while ago,
• 33:23
  Speaker 1: but yeah, fascinating. I think if we're quick, we can
• 33:28
  Speaker 1: squeeze in one more little story, or if you want
• 33:30
  Speaker 1: to chase up the space Dandriff story, Life science dot
• 33:33
  Speaker 1: Com carries that one one last yarn and this one
• 33:39
  Speaker 1: is something we I think we touched on in the
• 33:42
  Speaker 1: last couple of weeks about you know, where does a
• 33:44
  Speaker 1: planet store start and a brown dwarf begin?
• 33:47
  Speaker 2: And we talked about thirteen jupiter masses.
• 33:51
  Speaker 1: Well, now our new planet has popped up in a
• 33:55
  Speaker 1: study that has sparked debate on that very issue.
• 33:59
  Speaker 3: Yes, so what we to do as humans in all
• 34:01
  Speaker 3: walks of life is trying to understand the universe. That's
• 34:04
  Speaker 3: just very fundamentally human thing to do. And to do that,
• 34:07
  Speaker 3: we break things that are continue up into discrete packets,
• 34:12
  Speaker 3: into discrete fractions. And we do this with a human lifetime.
• 34:15
  Speaker 3: You know, you grow up and then suddenly one magical
• 34:17
  Speaker 3: morning you wake up and you're legally able to drive.
• 34:20
  Speaker 3: Are you'llegally able to drink so long as you're not driving.
• 34:23
  Speaker 3: You know, you have these magical thresholds where we've said
• 34:25
  Speaker 3: one day you're an adult, the day before you were
• 34:28
  Speaker 3: a child. You're not fundamentally any different across that barrier,
• 34:31
  Speaker 3: but we're grouping like with like and keeping different things separated.
• 34:36
  Speaker 3: That's what's happened with definitions of planets. You know, this
• 34:38
  Speaker 3: was all the age, all the controversy two decades ago
• 34:42
  Speaker 3: with the emotion of Pluto. It was the same thing.
• 34:44
  Speaker 3: It was trying to group objects that are similar with
• 34:46
  Speaker 3: each other in groups so that you can study that.
• 34:50
  Speaker 3: And one of the great areas where this has happened
• 34:52
  Speaker 3: is you've got planets, you've got stars, and in between them,
• 34:56
  Speaker 3: you've got these curious objects that people call brown dwarfs,
• 35:00
  Speaker 3: which are things that they viewed as been too big
• 35:02
  Speaker 3: and too massive to be considered a typical planet, but
• 35:05
  Speaker 3: they're not massive enough to have hydrogen fusion and to
• 35:07
  Speaker 3: shine and become a star. So the boundary to be
• 35:10
  Speaker 3: a star is fairly clear. Cup If you get hydrogen
• 35:12
  Speaker 3: fusion going, you're a star, which leads to the slightly
• 35:16
  Speaker 3: quirky thing that white dwarfs and neutron stars are not stars.
• 35:20
  Speaker 3: They's cellar remnant, so they're dead stars, which is a
• 35:24
  Speaker 3: turtle a site. But between a planet and a star,
• 35:28
  Speaker 3: there's this domain where you are not massive enough to
• 35:30
  Speaker 3: burn hydrogen, but the temperature in your core will get
• 35:33
  Speaker 3: high enough that you will temporarily be able to burn
• 35:35
  Speaker 3: the uterium, which.
• 35:36
  Speaker 2: Is heavy hydrogen.
• 35:38
  Speaker 3: There's not much of that, so you'll get a very
• 35:39
  Speaker 3: short period of uterium burning and then you'll just fizzle
• 35:42
  Speaker 3: out and be a little glowing ember. Now where that
• 35:47
  Speaker 3: boundaries with a star is very clear cup it's a
• 35:49
  Speaker 3: hydrogen fusion and it's a very observable thing. But the
• 35:52
  Speaker 3: boundary at the lower end, where you no longer have
• 35:55
  Speaker 3: enough mass to burn the uterium, is much woolier. And
• 35:58
  Speaker 3: if people do modeling, it depends on the composition of
• 36:01
  Speaker 3: the object and how much solid material it's got and
• 36:04
  Speaker 3: how much deuterium it's got, and all sorts of things
• 36:06
  Speaker 3: going on. So what's happened historically, because we didn't really
• 36:10
  Speaker 3: have the capacity to find low mass objects is people
• 36:12
  Speaker 3: just put this arbitrary boundary of thirteen jupiter masses there
• 36:16
  Speaker 3: to say anything more massive than that is a brown dwarf.
• 36:19
  Speaker 3: Anything less massive as a planet. So that is setting
• 36:23
  Speaker 3: this boundary purely on the physical mass is taking no
• 36:26
  Speaker 3: account of the composition of the object or how it formed,
• 36:30
  Speaker 3: And as we finally got the ability to find objects
• 36:32
  Speaker 3: of this mass, people have started to question that because
• 36:35
  Speaker 3: the formation mechanism of the composition matters. A planet like
• 36:38
  Speaker 3: Jupiter has about thirty Earth masters of solid material as
• 36:41
  Speaker 3: a core because of the way it formed. A star
• 36:45
  Speaker 3: doesn't have that same kind of structure. So there's a
• 36:49
  Speaker 3: growing argument that maybe we should divide it by formation mechanism,
• 36:54
  Speaker 3: and something that formed like a planet is a planet,
• 36:56
  Speaker 3: even if it's more massive than this limit, and it
• 36:58
  Speaker 3: probably wouldn't undergo due TOI infusion because a lot of
• 37:01
  Speaker 3: the masses solid material, so it's got less utarium. Alternatively,
• 37:05
  Speaker 3: if it formed like a star, even if it's less
• 37:08
  Speaker 3: massive than thirteen juke to masses, maybe it should be
• 37:11
  Speaker 3: considered a brand war rather than a planet because of
• 37:13
  Speaker 3: the formation mechanism.
• 37:15
  Speaker 4: And it's a debate that.
• 37:16
  Speaker 3: So we're just starting to kick off because we're only
• 37:18
  Speaker 3: really able to find these objects now. It's been fired
• 37:21
  Speaker 3: up here by the discovery of what's known as GAYA
• 37:23
  Speaker 3: four B. So the guy in spacecraft we talked about
• 37:26
  Speaker 3: earlier is this incredible mission that was measuring the positions
• 37:29
  Speaker 3: of the motions of a billion stars with incredible precision.
• 37:33
  Speaker 3: Two billion stars, absolutely ridiculous. And what Gaya has promised
• 37:37
  Speaker 3: for a long time is that it would find one
• 37:39
  Speaker 3: hundred thousand to one million planets around other stars. That
• 37:43
  Speaker 3: was part of the marketing. So far it has found
• 37:46
  Speaker 3: four or five.
• 37:48
  Speaker 2: More will come.
• 37:48
  Speaker 3: Because they're still doing their big data really says, so
• 37:50
  Speaker 3: it will give us a deluge of planets at some point.
• 37:53
  Speaker 3: But the reason it can do this is that it
• 37:55
  Speaker 3: measures the positions of the stars in the sky so
• 37:58
  Speaker 3: accurately that it can see than wabbling as they move
• 38:02
  Speaker 3: as a result of the planets pulling them around. So
• 38:05
  Speaker 3: this is a counterpart to our radial loss in effort.
• 38:08
  Speaker 3: The radio lossy sees a movement back and forth on
• 38:10
  Speaker 3: a line of sight, guyas sees a movement at right
• 38:13
  Speaker 3: angles to that. So it's been looking at this star.
• 38:17
  Speaker 3: This star is less massive than the Sun, about two
• 38:19
  Speaker 3: thirds of the mass of the Sun, and this starts
• 38:21
  Speaker 3: moving across the night sky. Because it's moving through the
• 38:24
  Speaker 3: galaxy separately towards it's not what we call proper mation,
• 38:27
  Speaker 3: and Guy has identified that instead of that proper motion
• 38:30
  Speaker 3: ministrat line, it's following a corks grow path across the sky, zigzagging,
• 38:34
  Speaker 3: and that's a telltale sign it's got a planet going
• 38:36
  Speaker 3: around it. Now, because this sounds a bit like the Sun,
• 38:40
  Speaker 3: it's a bit cooler. You can do radio lossity observations,
• 38:43
  Speaker 3: which means you can measure the line of sight wobble
• 38:45
  Speaker 3: as well, which means you can perfectly constrain what's going
• 38:49
  Speaker 3: around it. And the evidence here is that this is
• 38:51
  Speaker 3: an object eleven point eight times a mass of Jupiter,
• 38:55
  Speaker 3: so it's just underneath that threshold to be a brown dwarf.
• 38:58
  Speaker 3: We would traditionally call it a planet. And job done.
• 39:01
  Speaker 3: The complexity comes out that this star is less massive
• 39:04
  Speaker 3: than the Sun and it's got a roughly similar composition
• 39:08
  Speaker 3: to the Sun. What that means is a material the
• 39:11
  Speaker 3: planets around it would have formed from would have been
• 39:14
  Speaker 3: similar to that around the Sun. It's not particularly metal rich,
• 39:18
  Speaker 3: so it wouldn't have had far more solid material around
• 39:20
  Speaker 3: it than the Sun did, which means is a really
• 39:23
  Speaker 3: difficult question to answer which is, how can a star
• 39:25
  Speaker 3: less massive than the Sun, which presumably formed from a
• 39:28
  Speaker 3: less massive cloud of material than the Sun, how can
• 39:31
  Speaker 3: it form a planet twelve times more massive than the
• 39:34
  Speaker 3: biggest planet we have in our system. That just doesn't
• 39:37
  Speaker 3: make much sense. It's really counter to our planet formation models,
• 39:41
  Speaker 3: which is more massive stars formed more massive planets. So
• 39:45
  Speaker 3: that then brings up the suggestion that maybe this thing
• 39:47
  Speaker 3: didn't form as a planet at all. Maybe instead what
• 39:50
  Speaker 3: we're seeing as a failed binary star system. And this
• 39:53
  Speaker 3: eleven point eight dupe to mass object formed in the
• 39:56
  Speaker 3: same way that binary stars would form, and it.
• 40:00
  Speaker 2: Wasn't core recretion.
• 40:01
  Speaker 3: You didn't get a load of solid material grow to
• 40:03
  Speaker 3: thirty times a mass of the Earth or ten times
• 40:05
  Speaker 3: a mass of the Earth and then sat gathering gas
• 40:08
  Speaker 3: because of the gravitational pull that instead it formed through
• 40:11
  Speaker 3: gravitational and instability in the cloud like another star would fall.
• 40:14
  Speaker 3: And therefore this could be considered a failed star, in
• 40:18
  Speaker 3: which case.
• 40:19
  Speaker 2: It should be called a brown dwarf.
• 40:21
  Speaker 3: Even though it's not massive enough because it didn't fall
• 40:24
  Speaker 3: as a planet. It may even be because it's so
• 40:26
  Speaker 3: class of the threshold that it could have almost got
• 40:29
  Speaker 3: to the deuterium Beurn, England. It could have had that happen.
• 40:32
  Speaker 3: Now we don't really know if we could go there,
• 40:35
  Speaker 3: If we could borrow Captain Kirk's spaceship and engage what
• 40:39
  Speaker 3: Brave and go there, we'd be able to answer this
• 40:41
  Speaker 3: after a little while. We'd put a mission up like
• 40:43
  Speaker 3: Juno that's going around Jupiter, that would allow you to
• 40:45
  Speaker 3: map the interior of the objective bit like the earthquakes
• 40:48
  Speaker 3: we were talking about the first topic, and figure out
• 40:51
  Speaker 3: if it had a core or not, and that would
• 40:52
  Speaker 3: tell you about its formation.
• 40:53
  Speaker 2: But we can't do that.
• 40:55
  Speaker 3: We just can't get there. So we at the minute
• 40:57
  Speaker 3: it's purely in the domain of speculation, but it's efficiently
• 41:00
  Speaker 3: odd discovery that it is just restarting that old discussion
• 41:05
  Speaker 3: about at what point do we need.
• 41:07
  Speaker 2: To look at this again? I guess at.
• 41:08
  Speaker 3: What point do we need to discuss whether we get
• 41:12
  Speaker 3: a more physically motivated difference between brand walls and planets,
• 41:16
  Speaker 3: or whether we're happy to sticking with this arbitrary mass limit.
• 41:19
  Speaker 3: And as the years go on, Geyer is going to
• 41:21
  Speaker 3: discover far more objects. We continue to find planets using
• 41:26
  Speaker 3: all the other methods, there will be more objects that
• 41:28
  Speaker 3: straddle that boundary. Because nature forms things of all sizes,
• 41:31
  Speaker 3: it doesn't say I'm going to leave a gap here
• 41:34
  Speaker 3: to make it massive. There'll be things of all masses,
• 41:37
  Speaker 3: and there will be things of identical masses that formed
• 41:39
  Speaker 3: in different ways, and so it's going to be an
• 41:42
  Speaker 3: ongoing question. I'm sure we could have a chat in
• 41:44
  Speaker 3: a couple of years time and they'd still be having
• 41:45
  Speaker 3: the same debates. But it's great when you get to
• 41:48
  Speaker 3: the point where our ability to find things is such
• 41:52
  Speaker 3: that it pushes the boundaries of how we define things
• 41:54
  Speaker 3: and we have to revisit them.
• 41:56
  Speaker 2: That's how signs works, and I.
• 41:57
  Speaker 3: Really love it, even if it means you get cranky
• 41:59
  Speaker 3: people all waving plugs and go Blueto should still be
• 42:01
  Speaker 3: a planet.
• 42:02
  Speaker 1: Yes, yes, and that's still happening two years indeed. Yeah,
• 42:07
  Speaker 1: all right, if you would like to look into Guaya
• 42:11
  Speaker 1: four B and five B. They've posted a report in
• 42:16
  Speaker 1: the Astronomical Journal. Yes, a fascinating discovery. And I imagine
• 42:20
  Speaker 1: the more we look, the more unusual things we'll find.
• 42:22
  Speaker 1: And yes, we probably will have to redefine where a
• 42:26
  Speaker 1: Brown law starts and a planet finishes. In the future,
• 42:29
  Speaker 1: it might come down to that. At the moment, we
• 42:32
  Speaker 1: just go with what we know until proof sends us
• 42:36
  Speaker 1: in a different direction. We are just about done. Johnny,
• 42:40
  Speaker 1: thank you so much.
• 42:41
  Speaker 2: That's absolute pleasure.
• 42:42
  Speaker 1: If I keep having me, always a pleasure. And we'll
• 42:45
  Speaker 1: see you real soon. Professor John T. Horner from the
• 42:48
  Speaker 1: University of Southern Queensland. And thanks to Hugh in the studio,
• 42:52
  Speaker 1: who couldn't be with us today.
• 42:53
  Speaker 2: It's very embarrassed.
• 42:54
  Speaker 1: He's got a severe case of space Dandriff.
• 42:57
  Speaker 2: Don't forget to visit.
• 42:58
  Speaker 1: Us online as well Space Nuts podcast dot com or
• 43:01
  Speaker 1: space Nuts dot io. And from me Andrew Uncley, thanks
• 43:04
  Speaker 1: for joining us. We'll see on the very next episode
• 43:07
  Speaker 1: of Space space Nuts come exert.
• 43:11
  Speaker 2: Until then, Bye bye to the Space Nuts podcast.
• 43:18
  Speaker 3: Available at Apple Podcasts, Spotify, iHeart Radio, or your favorite
• 43:23
  Speaker 3: podcast player.
• 43:24
  Speaker 1: You can also stream on demand at guides dot com.
• 43:27
  Speaker 3: This has been another quality podcast production from nights dot com.