History In the Making

Space Nuts 247 Transcript

[00:00:00]15 seconds. Guidance is internal gen nine ignition sequence

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Andrew: feels good. Hello, once again. Thank you for joining us. This is the space nuts podcast episode 247. I am your host, Andrew Dunkley. Great to be with you again. And joining me as always is professor Fred Watson astro nomer at large. Hello, Fred

Fred: Lou. Hi, Andrew. How are you doing?

Andrew: Oh, I'm well, thanks.

How was your Easter?

Fred: Uh, busy, um, with, uh, the, uh, right at the pointy end of the children's book. And, uh, the last bit is the cartoons, which I'm drawing. That would the fun, it's a, it's absolutely heaps of fun, and I really enjoy it, but they take kind of longer than you expect. So I'm really up against the deadline.

Um, but we'll see how I go. [00:01:00] I have a bit of an extension from the publisher. To the middle of this month to get the cartoons done. And, um, I'm getting there the middle of this month, which is a week. It is actually a week. That's right, exactly. Um, I might do some, I'll just have to see if I can do some fast-talking.

Oh, nobody from new South. The press is listening to this book. We're in good shape. I'm about to send off the, um, the text, which I'll. Hopefully you do today and probably the cartoons for the first four chapters, which are the ones that are actually complete. Terrific. Yep. Yep. Can't wait. Yeah. What about your Easter, Andrew?

How did you go? My

Andrew: boys came up from Sydney. Um, my eldest and my youngest lived down there. My middle child. Also a boy, uh, lives just down the road from us, with the three grandchildren. And, uh, we all got together and it's the first time they've all seen each other in three years. And it's the first time that my, um, two Sydney boys have met their, uh, their niece, the youngest niece.

So that [00:02:00] was all very exciting. And, and it went well. So your family barbecues sitting around the fire pit, although it wasn't. Really cold enough for a fire pit, but we did the marshmallow thing and that was a disaster, but, uh, it was, it was pretty good fun. It was really nice to just sit back and do nothing and just talk about whatever we felt like talking about at the time we usually end up, we usually end up having these big discussions about movies.

I don't know why, but that seems to be the family topic whenever we get together. And I got to talk about something it's better than talking about it. Politics.

Fred: Although we do that too, most people talk about what's wrong with auntie Mabel or, you know, something like that. So it's good that you've got how we did that too.

We did that

Andrew: too. And how did you know I had an anti-male. Coming up in this episode, Fred, we're just going to touch on ingenuity. The helicopter, the test is about to happen and, uh, they they're being super duper careful about this, but, uh, who can [00:03:00] blame them? They can't send the mechanic out. If the wheels fall off.

There's also some new data that's come out of examining the Chick-fil-A crater. That's that big asteroid impact that polished off the dinosaurs about 66 million years ago. Actually, it's been about a year since we talked about this. So at 66 million, one years ago, uh there's um, Also been a discovery of one of those elusive, intermediate black holes we think.

And we're going to tackle some text questions today. We haven't done any for ages, but we're going to do a couple today actually to double bangers. Andre from the Netherlands has sent us two questions. And so has David from Springfield. So we will get into those on this week's episode. But first Fred let's, uh, let's go back to Mars and talk about this, uh, this, this test flight that's coming up soon for ingenuity.

Uh, the news I hear is that they have dropped the helicopter from the belly of the beast perseverance, and it is, [00:04:00] um, getting ready to be. You know, ramped up almost

Fred: literally. Exactly. That's right. Um, there's a, there's a tweet, uh, from NASA jet propulsion laboratory, which I liked. This was a at the weekend.

I liked very much. It said Mars helicopter, touchdown confirmed it's 293 million mile or 471 million kilometer journey, a board NASA perseverance. And did with the final drop of four inches, 10 centimeters from the Rover's belly to the surface of Mars today, next milestone survive the night. And that's because, um, as of, uh, I think it was Saturday, uh, Per the ingenuity helicopter has been now relying on its own power for the heaters that keep the electronics warm, because until then it was taking power from perseverance itself.

Now it's on its own. And so, um, you know, it relies on the batteries, the internal [00:05:00] batteries and the solar panel, which sits on top of the, uh, the two rotor blades. Uh, so, uh, hopefully that will all keep going well. Um, the heater apparently keeps the inside at about 70 degrees Celsius or 45 degrees Fahrenheit, uh, because the, you know, the temperature on Mars drops to way, way below zero.

It can be as low as minus minus 90 Celsius, about 130 minus 130 ferry Fahrenheit. So. Look, it's, um, I think all is going well. As far as I know, they've checked out the solar panels and we haven't heard anything to the contrary, uh, the first flight now I read somewhere that it was planned for the 8th of April, but the latest is not before the 11th of April.

So we still have a few more days to wait, but, uh, isn't it going to be fantastic. The first flight is going to be climbing, uh, 10, uh, roundabout 10 feet. Uh, three meters or so, and a hopper that perseverance,

Andrew: which has [00:06:00] gone six meters,

Fred: it's probably gone further now because it's hard to drive over the yeah.

Drive over the helicopter. So it doesn't accidentally back into something

Andrew: like that. Going to be fascinating, Fred, in that the, um, the atmosphere being so thin, uh, it takes a lot more effort to get off the ground than it would on earth. Surprisingly, but, uh, the, the thing in their favor is the lesser gravity.

So, uh, I'm not sure that will counter the thin atmosphere, but it will to a degree, I imagine.

Fred: Yeah. I mean, it's, it's really going to be very interesting to see whether it works or not given the 1% that, uh, you know, it was fake pressure, uh, on Mars, but look, it's, uh, it, it, the engineers have done their job.

My bet is that it will work. Just fine.

Andrew: Yes. I, well, everything's gone so well so far, we've just got to keep that momentum going and to get off the [00:07:00] ground. They've got to, they've got to achieve some massive rotational rate haven't they? Yeah, it's quite

Fred: astonishing. 2,400 RPM is the, is the rotor speed. It's pretty fast, certainly faster than copter.

If it

Andrew: doesn't get off the ground, uh, we can wait until Mars is Terraform to turn it upside down and turn it into a law.

Fred: Uh, you might have a long way. Cause terraforming, Mars is physically impossible because the atmosphere just flies away.

Andrew: Yes. Yes, indeed. All right. So, and I notice a lot of people have been talking about this on the space nuts podcast group.

Good. Uh, so there's a lot of excitement. Everyone's really looking forward to this and look, why not? I mean, it's never been done before. This is, this is all brand new science in terms of. Flying an aircraft on another planet. So, um, we can't, uh, we, can't not be excited about this I'm sure. But, uh, yeah, hopefully in the next week or two, we'll be able to [00:08:00] tell you, um, what happened because no one else will, no one else will, it'll just be asked now.

So move on to our next topic and, and, uh, we're revisiting an old friend, the, uh, the asteroid that, um, came down in what is now the Gulf of Mexico and obliterated the planet, not just the dinosaurs, it finished them off, but there's some new research that's come out that suggested that, uh, other things happened as a consequence of this impact that, um, Probably had a bigger effect on why the earth is the way it

Fred: is today.

Yeah, that's right. You know, this is something that certainly I've never thought about before. Um, but, uh, scientists at various institutions think deeply about this kind of thing. One of the effects of the, uh, the asteroid, sorry. Dinosaur killing asteroid. If I can call it that we usually call it the Cretaceous tertiary event.

Uh, in fact, it's got a slightly different name, but yeah, the KT event, uh, when, [00:09:00] um, 66 million years ago, when something, we think about 15 kilometers across. Hit the earth at about 30 kilometers per second, and caused not just a big explosion, but you know, all the, the, the absolute devastation that you'd expect, including a blanket of Ash that would have, uh, uh, stopped the solar radiation, probably got a kind of nuclear, winter effect, all of that.

Uh, and so, um, I think actually come to think of it. You and I have spoken before about the effects on the fossil record, um, in terms of the microorganisms, because, um, It's, you know, we, we know the dinosaurs don't appear above that layer of the strata in, in the, uh, in the, uh, uh, in the us, across the, the, the fossil level is different fossil levels.

Um, so, uh, people have analyzed other things. It's not just the, uh, the traces of the dinosaurs. They've looked at fossils for example of leaves and, [00:10:00] and pollen, uh, and. Leaves tell you something really interesting because, uh, often they've got insect bites in them and, um, it's apparently this is one of the things that they've looked at insect bikes on foster live fossilized leaves, uh, essentially show that, uh, insect diversity, uh, fell dramatically after the event.

As did plant life. In fact, the same is true with the leaves themselves. You know, you, you, you get this decline in fact, by, uh, an assumed roughly 45%, uh, that's diversity of plant life. It's not the number of plants. It's the number of species of plants, uh, shut down by it. Forty-five percent after the impact.

Uh, and, and the, the fossil record shows, it took about 6 million years to recover to something like it was. But, um, the, the other really interesting aspect of this work and it comes from, uh, a scientist called Carlos [00:11:00] Herrera, Emilio. I think he's probably how you pronounce his name, um, in the Smithsonian tropical research Institute in Panama, um, he, he.

He says, if you return to the day before the asteroid fell, the forests of South America would have been an open canopy with a lot of firms, many conifers and dinosaurs. Of course. Yeah. Yeah. The forest we have today. Is a product of that one event 66 million years ago. And essentially what they're suggesting is that, uh, the, the, the conifers and the firms, uh, basically disappeared and.

The, they were replaced by essentially flowering power plants, but that it, it actually increased the canopy. The canopy, the forest canopy is much greater now than it was before. Um, [00:12:00] actually another comment from one of the other scientists selling could know she's at the university of Wyoming. I think the one.

Number one lesson here is unpredictability. When you have these major perturbations, they changed the rules of the whole ecosystem. And one of the things that they're suggesting is that, uh, in the, in the lower levels of the forest, uh, the dinosaurs before the impact were treading out, trampling everything down and kind of eating stuff.

So the lower levels were much more sparsely, uh, much more sparsely. Um, uh, variated or what's the word for populated by, by plants. Um, but it's more, much more sparsely covered. Um, so the dinosaurs are gone, so that change what was happening to the, the forest floor. But at the other side of the coin is, and I mentioned the Ash that came because of the impact a minute ago, but when that [00:13:00] settled on the ground, cause it all basically falls out of the atmosphere effectively.

Yeah, they're suggesting that, uh, it's uh, does a fertilizer. So you end up with a much more nutrient rich soil and you get these fast-growing flowering plants, uh, and you know, um, they, they sort of bounce back in a way that some of the other plants don't. Um, and, uh, actually another quote from somebody called Bonnie Jacobs, who was at the Southern Methodist university in Texas.

She says, we love the way it ended up this incredibly diverse, really structurally complex forest. But right now we should be aware that we're living through a mass extinction caused by humans. Once again, ecosystems are being set on a different path. So there's a lesson in this, um, you know, that, uh, that.

It comes back to us from the Cretaceous tertiary boundary that events like, uh, asteroids can change the whole ecosystem for another, uh, another 60 bill at 66 [00:14:00] million years. Um, and we are kind of mucking around a bit too. Yeah. What

Andrew: I found interesting was we draw a line where the dinosaurs stop and then life, as we know, it starts to begin, I guess.

But the other interesting factor that came out of this is that, uh, you spoke of the conifers and the firms that. Disappeared. But they were replaced by legume trees, trees that produce pods and seeds and, and, uh, and, and they sort of don't exist prior to this impact. So it, it changed the planet to a point where.

Um, w you'd have to say it was an extremely dramatic change in the entire ecosystem and developers of the planets life cycles and the types of, um, life that that came about. And one wonders. What humans might or might not be like had that thing never hit

Fred: it. So yeah. Yeah. We, it [00:15:00] may well not have been here because, uh, maybe, uh, dinosaurs rule the earth at that time, they were a big ferocious and mammals were small creatures that kind of cowered under the, under the.

W w what a cover they could find on the, on the forest floor. Uh, yeah, we, um, we, we may be a product, uh, indirectly a product of that event.

Andrew: And another thing that comes to my mind is I wonder if there was anything in that asteroid that ended up in the atmosphere after the impact that settled down and perhaps caused.

Certain factors of life to change or alter. I don't know. It's, it's a bit of a bit out there.

Fred: There is certainly one thing that that was in it is what told us it was there at all. And that's the Iridium that was present in the, um, in the asteroid, which is not really found, uh, in any great quantity on the Earth's crust, but it is, uh, it's.

Essentially, uh, [00:16:00] something that you do find in extra terrestrial objects and it was, um, uh, basically Luis Alvarez and his son whose name? I can never remember. It's terrible. It's shocking, Louie. Jr. Walter Walter Alvara. Is it close to me? Yeah. Uh, Louis and Walter Alavarez. Um, they were essentially. Um, you know, geophysicists, but they, they discovered this layer of Iridium that corresponds to the boundary where between, uh, strata, that's got dinosaur fossils and strata that hasn't, and that was when they actually, they alerted to colleagues of mine, uh, in Edinburgh who were working on this at the time.

I've probably mentioned this before bill Napier and Victor Kluber were working on the same thing. And, uh, they, um, you know, basically the, uh, the information was, um, was shared, although in fact bill and. Victor really didn't share in the glory of it all. It was the Alvarez. Uh, do you have, uh, shared in the glory because they, they [00:17:00] had a press release very quickly after that.

Yeah. Well, fair enough. Yep. Pete who hesitates is lost well that's right. Well, of course we are terribly British in Edinburgh. We were. Well, we were a scientist, actually. I should say we were terribly British in Edinburgh, um, because that's in Scotland, but yeah, it was, um, it was, uh, an unhappy time for Victrum, but I remember it very clearly because I was working with them, not on that topic actually on other stuff.

Andrew: Fair enough, but, uh, it's more information coming out of, uh, the, um, study into the Chick-fil-A crater and, uh, yeah. Who knows what else we'll discover, but, uh, the, the, the rainforest, as we know them, uh, just didn't look anything like that or have the plant life than they have today. They were very, very different in indeed.

Uh, so what else are we going to learn? I wonder we'll, we'll tell you when

Fred: we find out, hopefully this. Yes.

Andrew: This is the space nuts podcast with Andrew Dunkley and Fred Watson. [00:18:00] Space nuts. This is episode 247 of the space nuts podcast and Andrew Dunkley, who was Fred Watson and a big shout out to our patrons.

The people who put a little bit of money every month into the kitty to feed Fred's cap. And to, um, you know, keep the website, running, things like that. Uh, we thank you from the bottom of our hearts that you, you think we are worthy of a few dollars. If you would like to become a patron, just go to our website space, NATS podcast.com and click on the subscribe button.

It's. Up in the top right-hand corner, whichever one that is because I'm facing a camera and it could all be reversed. I have no idea, but, uh, you can click on there and see what options are available to you. You can subscribe to package deals, which gives you two or three podcasts, depending on what you want to do.

Uh, or you can just make a one-off donation or you can become a patron through Patrion or through super cast. What we're [00:19:00] ultimately aiming to do is to make the podcast 100%. Reliant on listeners only. And that means getting as many patrons as we can. And it's good to see a few more have signed up in the last week or so Fred, so fantastic.

And thank you. Thank you so much. Let's move on to our next topic, Fred. And, uh, this headline has got me. I'm scratching my head. We're talking about, uh, intermediate black holes. Now we've, we've spoken about those before. Um, there up until recently have been only two kinds. Find, found little tiny ones. And others that are about, I dunno, 55,000 times the mass of the sun or something, or maybe a bigger, I don't know.

Some of the millions times bigger. Uh, some of them are as big as galaxies as we talked about last year, but the ones that are middle-sized the ones that are, you know, somewhere around the 150 times, the mass of the sun are few and far between. And until recently we didn't even know [00:20:00] if they existed. Well, This headline, Fred in cosmos, uh, reads astronomers, find Goldie locks, black hole, Goldilocks black hole.

What does that mean?

Fred: That's a really good question. It's not a headline. I would have used golden Lux, usually refers to things being not, not, not too cold and not too hot budgets. Right. But maybe it's a Goldilocks black hole because, um, it has been, uh, you know, it's, it's the sort of. For who has been sitting in my chair kind of side of it could be, could be.

Um, but no, you're right. Uh, that, uh, it is one of the puzzles of astronomy that we find what we call stellar mass black holes, which are up to about a hundred times the mass. Of the sun and, um, the supermassive black holes, which started something like a hundred thousand times, the mass of the sun, probably usually bigger.

We, most of the ones that we know about and millions of times the mass of the sun and some are billions of times like the, the one in  [00:21:00] that was imaged by the event, horizon telescope, that 6.5 billion times the mass of the sun. So there's, there's this gap in, in the middle, uh, the elusive, uh, Intermediate mass black holes as they're called.

And there are a few, um, a few suggestions of where these things might be found. There's there's, uh, some people have suggested they might be in the centers of what we call globular clusters. These are clusters of stars that we think are. Well, they may be the remnants of, uh, of the nuclear either centers of some galaxies that are galaxy has gobbled up smaller dwarf galaxies, but the field is still wide open.

Um, this story though relates to. Uh, probable detection of an intermediate black mass black hole. And in fact, its mass is right in the middle of that range. It's about 55,000 times the mass of the sun. That's the, uh, the estimated [00:22:00] mass, but it has been detected by gravitational lensing. Uh, so, uh, which is a really neat.

Trick that relativity allows us to do, um, when you've got a massive object in space, it distorts the space around it. Um, and that can act as a, as a lens magnifying, what you see beyond it. It's a, it's a way we study very, very distinct clusters of galaxies. If a very distant cluster of galaxy has a nearer.

Large cluster of galaxies in front of it that near a cluster will bend this, the space around it and act as a kind of natural telescope for the cluster beyond. It's a very, very powerful technique. Um, but this story starts with something called a gamma Ray burst and went and talked much about those recently, but they're thought to be the, uh, basically the, uh, emission of a pulse of gamma rays.

Uh, very, short-lived not as short as fast radio bursts, but. Short [00:23:00] seconds sort of length of time. Um, they are thought to be basically the result of stars colliding, uh, that they were stars basically annihilate, and you get these gamma rays. Um, but, um, but they're short enough that, uh, if you had. Uh, gravitational lens, um, these policies of gamma rays pass through it.

Uh, you could find that you get two images of the gamma Ray source because of the bending of the light. It's not a perfect lens. It can actually produce multiple images of the same object. Um, and because it's a pulse that you getting, you can look for the time delay between one arriving, uh, uh, one, one of the images arriving.

And the, and another one, um, which has taken whose light or whose gamma Ray light has taken a different path through the gravitational lens. I'm not really explaining this one. No, really. I get this.

Andrew: You're seeing the same thing [00:24:00] twice at different intervals because of the disturbance to the space.

Fred: Uh, and around traveling through.

Yep, exactly that. And so what's happened is that by looking at the various quantities and they are specifically how far apart, the, the two images of this gamma Ray pulse are and what the time delay is in between them, uh, the scientists who've done this work, uh, have been able to determine, um, that. They are seeing the effect of gravitational lensing around a black hole.

And you can put the numbers into the, uh, you know, into the formula that relate to gravitational lensing to get out the mass of the black coal. And it turns out to be. Intermediate mass 55,000 solar masses. And I might add as a footnote, Andrew, to this research, it comes from [00:25:00] Australia. Um, one of the, so this is from, uh, Monash university, Eric , uh, and, uh, Monash is, uh, is, uh, The university in Melbourne that has actually a very, very strong, uh, school of theoretical astronomy in there that one of the theoretic theoreticians is somebody I know very well, John Lattanzio, uh, and they do calculations about the way stars work and about, you know, the way.

Um, th th the stars evolved. This is I suspect from the same group, but we're talking now about gravitational lenses, which is, um, a remarkable, remarkable science. So this could be the first really concrete, uh, evidence of an intermediate mass. Black hole being discovered by, um, gravitational lensing. One of the curious freaks of, of relativity.

It's a very, very nice story and I'll shut up for a minute, but there is a postscript to it, which we might get to in a second.

[00:26:00] Andrew: No, I was just going to say, it's interesting that they, they have. Perhaps discovered this through the observation of something else by the sound of it. So an event that, um, that, that, that headed our way in, on two different paths.

So we received the information at two different times and the by-product is, Oh, hang on a minute. The cause of that was

Fred: an intermediate black hole. Yes, that's right. Exactly. Yeah. Yeah. So it's, that's always very nice when something happens, serendipitously and you get this a result that is something that you didn't expect.

No. Um, the, the postscript I mentioned is that one of the. Possibilities for the origin of intermediate black calls is that they may be primordial. That means they're remnants from the big bang, uh, and the, uh, big bang remnants are not something that we've really got any proof of. It was suggested actually originally by [00:27:00] Stephen Hawking, many years ago that the big bang might've spurred spawned many, many, um, black calls ranging in size from tiny ones.

To, uh, what were they called? Slabs, I think super large black holes. We talked about that a few, few weeks ago. Um, they, they were also thought to be primordial black holes. So, uh, an intermediate mass black hole, because it's too big to have been formed by a single star. Turning into a supernova, but it's too small to be found at the center of a galaxy, um, may well have been formed, uh, in the big bang itself.

So they might be primordial ones. And in fact, one of the, uh, one of the, um, uh, other side effects of this study that, uh, that we were talking about, the one from Monash is that maybe there are very large numbers of these. Black holes in our neighborhood of the Milky way. And of course, some people have suggested that planet nine is actually a primordial black hole.

It's not a planet at all. It's something, um, much [00:28:00] more interesting, uh, or we're seeing around the sun. Anything's

Andrew: possible. And I, I suppose it sort of brings us back to that, that thing, uh, whereby we suspect certain things exist, but we've never found evidence of them, but. Ultimately, we probably will. And just like we suspect that life might be quite prolific in the universe, at least at a microbial level, intermediate black holes are probably quite prolific too.

We just haven't been able to track them down as yet. That would be my theory.

Fred: Exactly. That's that, that, that's pretty cool. Pretty well sums up the view of astronomers that, you know, these things are probably out there. Uh, but we're not finding them in anything like the numbers we might expect. And maybe it's because they're, you know, that the fact that this thing has no evidence of any other, uh, anything bright surrounding it, the, uh, all the, [00:29:00] all they know is that the.

The signal from the gamma Ray burst arrived by two different pathways. Uh, but there's nothing to see, uh, that in itself suggests that, you know, you're not seeing something that's gobbling up material from its surrounding galaxy. You're seeing something that's perhaps just lurking in space, which is what you would expect primordial black holes to do.

So, yeah, it does kind of make sense.

Andrew: Just hanging around on a street corner, doing drug deals, just, you know, minding its own business and hoping it doesn't get caught,

Fred: but it has been, it's been caught

Andrew: deed and we'll go to court and we'll be sentenced is, yeah. Fascinating. Very interesting. Then hopefully more to learn about the elusive intermediate black hole.

This is space nuts. Cast Andrew directly here with Fred Watson.

Fred: Space

Andrew: nuts now. Um, I wanted to, uh, [00:30:00] say hi to everybody who gets together on Facebook, uh, on the podcast group and talks to each other. Uh, if you want to meet like-minded people that listen to space and that's, uh, do a search for the space and that's podcast group. And, and join, uh, fellow listeners because, uh, that they're a great community.

They have a lot of fun and they, uh, they often have a lot of, uh, interesting discussions about this, that, and the other, I occasionally will pop in and say hello, and maybe answer a question. Sometimes questions are directed towards us and I make, I make Fred's answers up because I just think that's a lot of fun, but, uh, yes, it's the space and that's poker.

Podcast group, and you can find it on, on Facebook. Just put a search in for that. And while we're at it, uh, also hello to our YouTube viewers who for some reason or another are increasing in number, even though they can see our faces, that is really lovely. So if you prefer the vodcast [00:31:00] over the podcast, you can find us on YouTube as well.

Now, Fred something a little bit different this week, we're going to read some questions. We've felt we finally transposed our massive text questions that came on a spreadsheet that basically was three kilometers long, one big string and, and managed to. Whittle it down into manageable edible parts. Uh, so let's get into our first question.

Actually, it's a, it's a double banger, perfect questions. A double bangers this week. First one is from Andre in the Netherlands, holler, Andre. He says, hello space in that. So I have a few questions for your show, which have been bothering me for a while. I'm sorry to hear that. Uh, first our Milky way has a diameter of about 150,000 light years.

I would like to know how. Think it is well, it is pretty dumb. I will say that. Uh, so how high is the cake is his question? Second. I would like to [00:32:00] know if the plane of our own solar system is aligned with or tilted in comparison with the center of our galaxy. And how is this? For other solar systems in our galaxy, are they all the same or different?

Thank you. And keep up the good work. A fan of your show. Andre. Thank you so much. Well, we might as well start with, uh, how thick the Milky way is.

Fred: Um, I think you're, I'm guessing he means the bottom in your thinking you means in terms of its intellectual capacity. I guess that it's pretty dumb. I'm thinking I'm thinking is yeah.

Have you got, have you got any guesses, Andrew?

Andrew: Um, well, if it's spread out 150,000 light years, I'm going to guess probably a quarter

Fred: of that. Yeah. That's an interesting guest. So we should make it clear that we're talking about the disc itself rather than the halo, because there is this halo, which. Is nowhere near as dense as the disc.

It's [00:33:00] much more, you know, the stars are much more sparsely spread out. It's where the globular clusters are that I mentioned a few minutes ago and that's more or less. Very cool. Um, so, you know, yeah, it's probably 150,000 light years, top to bottom, but when you come to the disc, um, the answer is a lot more interesting and just a little bit more complicated, um, because we define, and this actually comes from work that.

Um, I wasn't directly involved, but friends of mine, people I worked closely with certainly where, um, it's, it's got various components, uh, and it depends which ones you're talking about. So, um, yes, 150,000, maybe even 200,000 light years in diameter it's growing all the time or at least our estimate of it is yeah.

Um, the, the thinnest component of the disc is called the young thin disc. So there's two bits, there's the thin disk and the thick desk, but the young thin desk is where staff formation itself is taking place [00:34:00] now. And, um, you know, the Milky ways youngest stars are as well as most of the gas and dust. It's the, the bit that we see when we look along the, the center of the Milky way.

And that the thickness of that is only about, you know, up to about 500 light years, maybe less, maybe more like 300 light years. It's, it's really very, very thin, uh, almost like a blade through space. When you think about it, given how big the diameter is. Um, and then there is an older component which is called the old thing disc, um, and that's.

Stars that have basically migrated away from the young thin desks or their oldest stars. And that's roughly a thousand light years thick. Um, okay. And then there is what we call the thick disk, which, uh, and it was the difference between the thin disc and the thickness discovered by scientists who I used to work with in Edinburgh actually, um, uh, years ago, uh, [00:35:00] about.

Gosh, it's more than 30 years ago. It's a long time ago, but that the idea of the thin and thick this is, as I said, it's been around for quite a long time. Um, Neil Reed and Jerry Gilmore, I think were the proponents of that people I worked with in Edinburgh, uh, still going strong in the world of astronomy.

The thick disc, uh, is thicker and it is roundabout, um, something in the region of five to 10,000. Light is so, you know, it's probably about 5,000 light years thick, um, compared with a thousand for the old thin disc and something like 300 for the young thin disc. So, um, the thick disc is very, definitely a separate component.

The work, um, that I did with colleagues in the. In the rave project, the radio lusty, the experiment that we did using the United Kingdom Schmidt telescope, we collected the speeds and physical parameters of half a million stars. [00:36:00] And it was possible from the results of that, to see that the delineation between the thin disc and the disc, um, Even though we actually tried to avoid the disk because it's too many stars in it.

Uh, we were mostly looking at the halo of the galaxy with that experiment. Anyway, a great question. And thank you for that. Moving on.

Andrew: Sorry. Sorry. I just needed to clarify when we're talking FIC disc and thin disc, are we talking layers?

Fred: Yes, in a sense we are. I mean, it's all done because, because you're talking about stars, which are individual objects and not, uh, you know, something like, uh, gas, you're, you're really talking about statistical things.

But so the statistics are that there are a lot more stars in the thin disc than the thick disc. Uh, and you can imagine it as a layer between one and the other. It's um, it's probably not a very flat layer because. Once again, there's probabilities involved, uh, but really [00:37:00] remarkable that, that we can now recognize these two characteristics of the, of the disc.

Um, in fact, we recognize too that the halo itself is not uniform this and the Annina halo and an outer halo, and they've got quite different rotational characteristics. So, uh, as we find out more about our galaxy, we realize its structure is more and more complicated. Yeah. Well,

Andrew: why am I surprised? Yeah, he also wants to know about how the solar system is aligned, uh, or tilted in comparison with the galaxy.

And is it the same for him? Other solar systems,

Fred: uh, danced to that is no, uh, no. Uh, the answer to the tilt of our own solar system is that the, the plane of the planets, what we call the ecliptic plane is tilted to the plane of the galaxy. In other words, to the thin desk, it's tilted at an angle of 60 degrees.

So it's sitting at the, you know, an unusual angle, [00:38:00] uh, No where near the same plane. And that is true of all solar systems. We find that they are various different angles. I think people have looked for, uh, the kind of, um, correlations that might say, Oh, 60 degrees is the most popular and it must be a reason for that.

That's not been found. Uh, so yes, you have, uh, you have, uh, You know, quite a strong tilt of the solar system to the plain of the galaxy. And it seems normal. Yes. And that's normal. And it seems to be, you know what, you've got you remember how the, the solar system was formed. You, you start off with a cloud of gas and dust that collapses under its own gravity and.

It's the illegal random rotations within that cloud that eventually take on a preferred direction and a preferred plane of rotation. So the whole thing starts rotating. That could be in any direction. And that's why we get this. Randomness is a great question. Very nice to [00:39:00] have Andre's question about it.

Indeed.

Andrew: Thank you for the question, Andrea, and, uh, hope we adequately covered your two elements today. Let's move on to a question. Now, a couple of questions from David in Springfield. He describes it as a dark meta quandary evidence for dark matter was found by abs serving that the stars of galaxies all move at the same speed, regardless of whether they are near or far from the galactic center.

Uh, how then does a spiral galaxy even form with all stars moving at the same rate, like water spiraling down a drain. The spiral shape requires the stuff towards the outer edge to be moving more slowly than the staff needs to. Right. Uh, dark matter should make it formation of spiral, gal galaxies, impossible.

Why aren't all galaxies of the non spiral globular type. If dark matter is real. And another question from David on the subject of terraforming Mars, which we touched on earlier, the red planet has a very [00:40:00] thin atmosphere. Terraforming would have to invoke creating a practical atmosphere at a density.

More like, uh, it used, uh, used to have a long time ago with Mars having such low gravity wouldn't any increase in its atmosphere. We engineer just evaporate back into space like its original one did. If so, would the rate of that evaporation be at such a slow rate that we could maintain it kind of like having a slow leak in a tie.

You just keep adding air once in a while. Yeah. I liked that question to get back to that. But, uh, yeah, I, I got a feeling the answer to the first question is that spiral galaxies are a trick of the eye, which I think we talked about a few weeks ago. They, uh, the spirals can only be seen under certain circumstances and that all galaxies aren't actually spiral galaxies.

Is that right? We said it

Fred: that's more or less it yes. In the sense that the spirals, uh, in some way, and in an optical illusion, um, what David says is absolutely right. Um, although, [00:41:00] uh, he's. I think the premise of what he's saying is, is wrong. Um, because, uh, yes, we've, we've, he's correct in that, uh, the rotational speed of stars near the center is more or less the same at the outer edge.

Um, but the, if the, if the spiral was a physical property of stars, uh, then. Uh, you would still get the winding up effect because the inner stars have got much. They have a much shorter distance to go to go around once. Then the outer stars, even though they're all rotating at the same speed, um, it's not rotating like a solid body.

It's rotating. With the linear velocity of all the stars being effectively the same speed, roughly 250 kilometers per second. Um, and even in that circumstance, you would get a wind up of the spiral arms. And in fact it will be wound up so tightly, [00:42:00] uh, that that's how we know that spiral alarms are not just strings of stars.

Uh, and as you alluded to it's something else, um, and what we're seeing with the spiral. Is this wave of, uh, higher density moving through the disk of stars and gas. And as it moves through the gas, the pressure triggers, staph formation, you get all these high mass short-lived stars, which burn over only a few tens of millions of years and blow up a supernovae.

Um, and you get this brilliance of forming along the spiral alarm. So the, the spiral arm is a wave. We call it a density wave. And that's why you've got these beautiful, gentle spirals rather than something really tightly wound, uh, in, uh, in, in a galaxy, which is what you'd get if there really were strings of stars.

Um, because they're, you know, they're moving up. Uh, the same linear speed, but they would, that the inner stars have got far less to go distance to go than the Alto ones so that they [00:43:00] immediately pull it into something, looking like a clock spring, whatever a clock spring is. People don't know what a clock Springs are these days.

Yeah. I remember the world, but anyway, that's what young

Andrew: whippersnappers don't know what a clock Springs,

Fred: right? Yes, indeed. Um, so, uh, It's, it's not the case that dark matter would make the formation of spiral galaxies. Impossible. In fact, it probably enhances it by, uh, it may well be that the dark matter halo of galaxy stabilizes, the density wave and gives it a, you know, that, uh, stunning property that we see in galaxies, like  one, which is one of my favorites.

So it's got a beautiful spiral structure. Sure. Uh, hope that answers the question. Um, hopefully moving along to terraforming March. Now

Andrew: you said earlier impossible, but he brings up a couple of interesting concepts, uh, which we, we should discuss, but let's say we [00:44:00] did Terraform Mars, and we did create an atmosphere.

It couldn't hold

Fred: that's right. So what he's saying is exactly right. Um, the density, the gravitational pull of Mars is insufficient to hang on to a, an Earth-like atmosphere. You lose the oxygen and the nitrogen very quickly. Um, the. The, the evidence for that is, is sort of ongoing as well because the last remnants of Mars is thick.

Atmosphere is still disappearing into space. The Marvin spacecraft can detect, uh, oxygen, I think hydrogen oxygen, uh, leaving the planet, uh, being. Basically released from the planet now. So, uh, terraforming is, um, a challenge. If you want to turn its atmosphere into an Earth-like atmosphere, you've got to do what, uh, David suggests at the end of his, his, uh, question there.

Um, Could, [00:45:00] could we still maintain it because of the slow rate of evaporation? Well, I think the answer is maybe, um, but you know, where are you going to get all this carbon dioxide from that you need to stabilize the atmosphere. And, uh, my guess. Uh, you know, he's lovely, um, analog of a slow leak in a tire, which I liked very much.

Uh, you just got to keep pumping it up. I think you'd probably have to pump it up faster than, uh, you know, uh, I think you'd struggle to pump it up faster than the leak. That's the bottom line. Yeah,

Andrew: I think, I think you're right. I, I, my theory is if we ever did. Uh, go to Mars to, uh, put a permanent human presence.

There you'd probably live in domed communities or something. You'd, you'd create an artificial environment and living in domes over the surface. And I, I think that'd be the only way to make it feasible. And even that would be a major engineering challenge, [00:46:00] but who knows one day, that might just

Fred: be that case.

Yeah. Well, you know, my view on all this, that, um, the ethical way to colonize space is to build mega structures, uh, you know, like halo worlds, which has engineering. That's probably not that. Much different from trying to Terraform of planet. In fact, terraforming a planet will be much more of a challenge.

Um, yeah. Interesting, interesting stuff. But, uh, yeah, I think you're right. I think domes on miles are what we're going to see. Eventually when we get research stations there, perhaps I hope we never try and colonize the planet, but if we get research stations, which I think is a good idea without humans living there and, uh, In in they'd have to be radiation protected as well.

You know, that's the other problem with Terraform again? How do you generate a magnetic field? Cause you need that to protect the atmosphere as well as, as well as everything else, we,

Andrew: we get lots of space, wheel Barrows, and we just, uh, demolish mercury or something and add it to Mars.

Fred: That's what [00:47:00] I've heard, that sort of thing before we took mercury out tomorrow as well,

Andrew: just, just Ram them together and just wait a couple of billion years for it to

Fred: work.

Andrew: Anyway, there you are, David. Um, hopefully we helped you out with your inquiry and thanks for sending in your questions. And that brings us to the end, but don't forget if you do have. Uh, some questions for us. You can do that on our website, just go to space and that's podcast.com and you can click on the little tab that says AMA.

Which I'm doing right now as we speak. And it brings up the, uh, the interface where you can either type a question in the old fashioned way using our email interface, whoever would have thought the day would come when I refer to typing an email as old fashioned. But, uh, the other option is if you've got a device with a microphone, you just press the start recording button and [00:48:00] it will record what you're saying.

Uh, don't forget to tell us who you are and where you're from and ask you a question and boom, all done, simple as that. And while you're there, don't forget to visit the space in that shop. There's all sorts of goodies there that you might like to add to your repertoire of useless junk at your place. Um, but you know, you'll be helping us out at the same time.

But, uh, yeah, check it all out. It's space now, podcast.com and Fred, that brings us to the conclusion of another episode, 247 of the space and that's podcasts. Thank you, sir. And it's been great fun. Yeah. As

Fred: always. And thanks to all our listeners for sending in their questions and we will get two more next week, like willing to

Andrew: see you later.

See you next time. Fred Watson astronomer at large part of the, uh, the trio that creates this podcast. And hello, back in the studio to hue, it's not actually a studio, it's a back shed and he shares it with the dog. Um, but, uh, that's okay. Plenty of dust there to put on Mars. Uh, but for me, thank you again for watching or [00:49:00] listening and contributing and we'll see you again.

Next time. Bye-bye.

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