10:14:41 Yeah, so now we have Barbara Castanheira from Baylor University who's going to tell us how to listen to the stars. 10:14:48 Barbara, take it away. Yes, thank you Hi Hi everybody, sorry. 10:15:27 there is somebody putting a door inside my house right now so that's always. 10:15:38 There's always, I would love, I can't wait to come back to normal lives that I can actually go to conferences so anyway so today I'm going to be talking about astroseismology apply to us and how we can listen to start so you probably heard about heard some 10:15:58 Every time that we start giving a presentation we want to put up a picture in front and in the first slide, but of course the pretty pictures of white dwarfs are not necessarily very pretty. 10:16:11 So, it because it's just a side by itself so I actually have a pretty picture of what will become a white dwarf so here we have a planetary nebula. 10:16:21 And this planetary nebula is the sewage acting its outer layer so this is a pretty white dwarfs right at the center here that we are, we're looking at. 10:16:31 But if I want to really see a white dwarf. 10:16:36 We can actually look at a picture from Sirius B. So this is Sirius A, we can all see Sirius A from Earth. It's a very bright star Sirius B we actually stumbled across it. 10:16:50 And that's how white was our first discovered, because we were actually seeing the gravitational influence of of something on Sirius, a Sirius A was actually moving in the sky a little bit, and that motion. 10:17:08 We actually calculated and attribute it to a body that we were actually should be orbiting that star so that's how we first discovered white dwarfs, and we call them white because they were white, right, and doors because they were tiny in comparison 10:17:25 to the main sequence dice. 10:17:29 Now, I'm not going to be talking about white dwarfs. 10:17:33 In general, but I'm actually going to be talking about pulsating white dwarfs. So this is another one that we basically just stumbled across, and this is HL Tau, 76, which was the first DAV ever observed. 10:17:49 So I know, Landolt was actually making a catalogue of standard stars and studying the variability of those, studying actually the photography of those stars. 10:18:01 And what he actually measured here for this particular style was that the in this plot we have here. 10:18:10 modulation in milli amplitude so it's something as intensity of the star as a function of time. Okay and then you can see here that this star is actually changing its brightness, over time, so then we found this to be and it's cyclical it's repeating 10:18:27 itself. So we started seeing maybe this is not a constant star the first pulsating stars that was discovered is a class of stars, called the virial, and they were miracle stars because they were changing it there variability. 10:18:44 And we could see that with naked eye, even, but the time scales were completely different those virial stars actually pulsate like this, they become bigger and smaller and bigger and smaller and we can see that change for white dwarfs is as here it's the 10:19:01 it's the milli modulation so the amplitude is very very small for us to detect with naked eyes so we really have to go ahead and and and and see, you know, with, with very precise instruments so naked eye, we would never ever be able to detect this pulsations. 10:19:22 So fortunately, there are some questions in the chat I don't know if I should answer. Oh yes, I'll go back to the thanks to thank you for the answer, the DAV is the one that has hydrogen. 10:19:37 So JJ actually show the spectra. 10:19:39 How we can get back to have those stars. And for. 10:19:44 Here we have two columns of spectra so the DAs, which are the most common white dwarf so something like 80 90% of all white dwarfs will be the ace, which means that in the photo sphere of those stars, we still have a lot of hydrogen as JJ also mentioned before, 10:20:04 there is the gravitation settling so everything which is heavier than hydrogen has already sink down towards the center. So, in rough terms these stars carbon and oxygen in the center, helium and hydrogen outwards. 10:20:21 So we have here some additional types of of things that can be seen on those DAs, which can be able to generate hydrogen. we can have magnetic field. 10:20:36 Therefore we have an age here, so the fact of the magnetic field on those those hydrogen lines was split up so so there was split them. We can also have DAZ are white dwarfs we just heard about that, and some white dwarfs may have a companion so this, the 10:20:52 the bottom one is a DA with a main sequence style. So, this we see the component of the white dwarf. And then the component of the main sequence that. 10:21:02 The second most common type of white dwarfs is the DBs, and the Generate B stands for helium. So, whenever the protoplanetary event happened this time ejected pretty much always hydrogen, as well. 10:21:19 So, there is basically carbon and oxygen, and then a thin layer of Helium, and we don't see any hydrogen lines here. So we see a very similar. 10:21:32 Similar spectrum here so the DBS the DBs with magnetic field. The DBs with matters. This is an interesting one, it's a DB with a tiny tiny little amount of a hydrogen so DBA. 10:21:48 So, we are mostly talking about the DAVs, because those are the white dwarfs of hydrogen that failsafe, but we also have the DBV. We have the DOBs and so on. 10:22:09 So, you probably heard about the gaia mission. 10:22:17 The gaia is a satellite that will have a goal of of serving billions of stars. And by this observations is actually measuring the distance, and the photometery three of those stops, so we can measure distance with parallax. 10:22:29 And so we measure the stars, compare them with the background stars and try to determine the distance of those stars as well measuring the photometry. 10:22:39 And by doing so, we are able to make this kind of plots for stars and this is the plot that comes straight from the gaia mission, which has lots and lots of stars, and we astronomers like to organize things right by brightness so on the top here. 10:22:55 We put to the brightest stars. And then we also organize those things based on colors. So on the bottom here we have bluer, and to the other end we have redder stars, stars, don't fall in. 10:23:12 We've seen this plot with luminosity in the y axis and temperature in the, in the x axis, we don't find stars randomly distributed they actually fall into those very specific sequences. 10:23:28 So this is the main sequence, which is, you know, where we see most of the stars. We also have giants and super giants and then we have this a faint, and hot sequence, which is where the white dwarfs are found here. 10:23:44 Okay, so see this. 10:23:48 And another thing is about pulsation so what are the stars that pulsate I talked to you about the virus which were the ones that actually pulsate, but we see we inside this hr diagram, this, this diagram is called HR diagram, we said that the pulsations 10:24:04 throughout all the evolutionary phases. So this is, let me just find out this is the white dwarf cooling sequence. And as the stars are cooling down, then white dwarfs are basically cooling down, they will cross those instability strips, and they will 10:24:23 show variations on their brightness, depending on the element that is dominant in the photo sphere of the star. So in this case here they if the white dwarfs have helium. 10:24:33 Then we will have them pulsating at this temperatures here between 30,000 and 22,000 Calvin, if they have hydrogen, they will pulsate in a very narrow instability strip between starting at around 12,500 Kelvin, down to 10,000 Kelvin, basically very very 10:24:56 narrow. 10:24:59 Sorry. 10:25:01 So what are the types of pulsations that you have. So for most of the stars, we're going to have two types of pulsations gravity waves, g modes, or gravity modes, or pressure modes. 10:25:12 So pressure modes are like the sound. So we have for instance the pressure is a longitudinal wave that propagates like that so that's how we. 10:25:22 That's how we claim this to be pressure modes and gravity waves are transverse waves, and that basically, the ones that we observe for instance in the water. 10:25:36 There are basically two types of pulsations that we can observe on Star so the stars can actually pulsate radially, so they change their size, or we can have the pulsation non radially, that they will go through this stuff. 10:25:51 But what can we really learn about pulsations. 10:26:06 It depends, it can tell us, for instance, the composition of this style, the type of this star, and so on. Now I actually have it at home, guitar, and I am just going to show you here, a guitar, if you don't have it at home, and I also have a ukulele. 10:26:25 so they are basically the same instrument. Right. But this ukulele is a shrunk version of the guitar. So if I play the guitar. In one string here, just show you. 10:26:28 So this is a see 10:26:33 everybody can hear that if I pluck one of the chords here. 10:26:41 It changes the sound. 10:26:50 And I have other chords here that will sound differently. 10:26:54 And if I look at the chords, I don't know if you guys can see very well. They are made of different thicknesses, so that's why they sound completely different, so I can identify by the sound that I'm producing if they get on. 10:27:22 This is a small instrument then the other one. 10:27:23 This is coming from the guitar. So now if I want to play a ukulele sounds a little bit different. Okay, let's get a little. 10:27:25 And this is this same analogy that we are doing for stars and pulsations on stars, if you can hear the frequency. 10:27:36 Of course, you cannot hear the frequency from the, from the stars because that's not how electromagnetic waves will will travel, but if we detect the frequencies we can tell this is coming from a small star This is coming from a big star This is coming 10:27:50 from this star that has more carbon less carbon more hydrogen less hydrogen, and so on. Okay, so that's the basic idea of doing doing Astro seismology. 10:28:03 Let me check there's some questions in. 10:28:12 Alright, so the non radial pulsations that you observe on white dwarfs will look like those light signals that will travel the light is traveling here. 10:28:17 Okay. 10:28:26 So, in this diagram here we are seeing kind of one darker region and an inter region so we have orange and and yellow. So this is basically a difference in temperature, and we are seeing that it doesn't deform this time, it doesn't change the size 10:28:43 of this star is just that the wave is traveling around this time. 10:28:48 T his is something that Mike Montgomery does quite a bit I stole it from him this See here, which is modeling the amplitude of the pulsations. So what we are seeing here this star is now fainter and then it will become brighter again. 10:29:03 So we have here one. 10:29:07 One type of one spot traveling around this star. And this is basically what's happening here. And it's well identified the blue one so the waves are doing this, but it's not really changing the size of this box. 10:29:24 So, what, what is our understanding on pulsations on white dwarfs, we actually, when we do observations we see that there are two types of light curves and very distinct ones. 10:29:37 So we have this one here that is very peaky. 10:29:39 In terms of the, the shape of those, the pulse that we are observing. and we have the other one that it's very sinusoidal. And we also see that the sinusoidal one has a smaller amplitude, and the other ones have a bigger amplitude. 10:29:56 So, what is our idea and again back to the understanding of the pulsations, so it happens in a cavity, where the cavity like the cavity off the guitar, the body of the guitar right so there is a cavity here, and this cavity is changing, becoming bigger 10:30:14 as this tie cools down. And it's also becoming deeper. So that's why the pulsations are basically a way for this dog to release energy. So that's so a way that the energy is being transported from the interior of the star outwards. 10:30:32 So the stars are cooling down and then therefore the internal structure of this tower is changing. So there is convection in those layers so the conductive cavity, we're actually deepen and becoming bigger. 10:30:57 So that's what we are seeing here and that's why we have the differences between the hot, the DAVs. And the cool DAVs. We also call the DAVs ZZ Ceti, Despite that with this the first Dav that discover was a HL Tau 76, and the second one was ZZ Ceti 10:31:14 said, We named the class. After this, he said, I don't know, I mean I honestly don't know why, but our understanding of the mechanisms that drive pulsations is so great that back in the 80s Don ranges, who was my co advisor the advisor of Mike and advisor 10:31:26 He actually predicted that this is happening because in that cavity that we observed for the DAVs. Hydrogen is becoming partially ionized, so the hydrogen. 10:31:35 of JJ. 10:31:39 When the side is very hot is fully ionized as the stars are cooling down, we start to see some of these electrons recombining into the atom. So he thought, maybe, maybe this is equivalent to, the re-ionization of Helium, and he went on 10:32:01 to look for a pulsating whitewash that had just a photo sphere of helium. And he looked for them so he made calculations predicted the temperature, and he was looking for them, so he had like a program at McDonald 10:32:16 Observatory, and he at some point he said well why don't we look at the brightest one so do the DBV 358 is the brightest what pulsating the brightest dB. And it's also the prototype of the class of conversations. 10:32:31 So that's, that's a very powerful thing to say that we really understand the mechanisms that will drive the pulsations. 10:32:40 Now, when we actually doing astro seismology instead of looking at the light curves, we actually do mathematical process called Fourier transform. 10:32:50 So instead of looking in terms of time as a function of intensity. We go to a different space of frequency as a function of power. Okay. And, or amplitude, sometimes this will see amplitude here. 10:33:06 So, when you do this Fourier Transform, everything that we are seeing here in this graph is what they call the noise right so everything above this line here so we set the limit the tech stability limit to see all those are real pulsations of these star. 10:33:23 So we have to first of all detect the pulsations of the stars, and we have to our models usually use independent modes, so we will see when we have pulsations we'll see harmonics sub harmonics we'll see linear combinations and so on, but we just want to 10:33:42 actually look at the independent modes, and we will compare them with models, and then we determine the stellar structure so it's simple process right. 10:33:51 The problem is most white dwarfs will have very few pulsation modes. So in this particular one do you want 1716 eight. We have only three modes. And if we have three things that we observed, we can only determine three other things. 10:34:07 So, I look at this plot here at the bottom, and we want to see the amount of carbon the amount of oxygen the amount of helium the amount of hydrogen the temperature the mass. 10:34:20 And in real life those those transitions are not shocked when we make a drawing cartoon like this one at the bottom. This is just a cartoon for us to have an idea of gravitation sadly, but each one of the transitions will have a certain function. 10:34:34 And we can see here, the transition between hydrogen and helium. So a little bit of helium will be entering also diffuse towards the hydrogen layer. And the same thing will happen here. 10:34:47 So what if this function is a little bit steeper. What if it is like these are like that so you can we, in, in theory, we want also to be able to constrain how the transition zones actually happened. 10:35:01 So we would need to observe I don't know 20 models here maybe 50 models, the more the better, but why it was done pulsating those many modes. So that's one of the. 10:35:18 Because we can constrain right so here is a model on top for a dB. And we have this mass here point 565 solar masses and 24,600 and this is for a da. 10:35:35 okay. So, with, we found some very interesting stars, and this one here is what we call the super diamond, it's the BPM 37093. 10:35:29 It's a sad thing but again we keep on working that there are better things that we can try to do right. 10:35:47 And this super diamond. Actually, it's a little bit. There's a whole lot of stories that we can tell about this star, but mainly, if you look at this cartoon that has been done this solid part here, which is the super diamonds is at the center. 10:36:06 So the pulsation modes will propagate only to here. So the amplitude of the observed pulsations will be much much smaller. Then if this star. If the pulsation could go all the way to the center of this star. 10:36:20 So that's why we see that this indication of very low amplitude. 10:36:26 We're actually tells us that the structure is a little bit different. Another thing that we observe here for this particular star from spectra. We know that the mass of the star is about one solar mass, which means it's a very dense very small star already, 10:36:43 so it's probably already crystallize at the temperatures of the stability strip. 10:36:49 So, in terms of the crystallization This is not the only way that we see that, but for instance for this globular cluster NGC6397, we can actually see the stars. 10:37:01 This cooling sequence here. And I don't know if you can, unfocus your eyes, but statistically this region here is where crystallization happens, which means the stars, pretty much stop cooling, and they are actually clumping that particular region. 10:37:19 We all know that if you boil water, whenever the water is boiling, and we go from, you know, from a liquid to gas, the temperature will remain constant. 10:37:29 So, this is basically what's happening here the stars are cooling down. And every time there is a phase change the stars who actually maintain their temperature so this is the latent heat, that we are looking, but for stars and I think this is pretty cool 10:37:44 with a very it's very amazing to be able to see that now know that the magnitude we could only detect that with Hubble. Okay, for this year for this globalar class and look at the magnitude here is 26 27 so it's really really really faint so we are pushing 10:38:01 pushing the limits of what we can definitely see. 10:38:06 Now, when we want to observe the stars in the tech more mode so you can actually, we did this for many decades to actually it's a it's an interesting idea, because we can only observe the stars at night. 10:38:20 So if you are at one side, you're going to be able to observe the size for eight hours. But what about trying to observe the stars for longer. So this whole earth telescope data, which starts back in 1990s. 10:38:34 We were able to keep track of the star, for, for a very long time, right for two weeks of data, open the door and tell that mommy is coming. Okay, put a mask on, say that I'm coming. 10:38:49 And we are able to track this stuff for up to two weeks so that was pretty cool So if, for instance, what did you do GD358 we're able to see many other modes as well. 10:38:59 And either Same thing for this size actually changed. so this is data from different campaigns or different year so we have here 1990 1994 1996 and 2000, and actually Mike coined the name for this change here. 10:39:15 He, I mean I have instruments, but he's the musician, and he actually called it this for some mode because all the energy of the pulsations was actually tuned towards one mode here to this K equals eight. 10:39:29 Ok so this mode right here, so there was like this star change, and a month later this guy came back to its normal, normal thing. 10:39:39 Now, even better than observing on earth we can actually look in space. So Kepler mission was a mission designed to detect the frequency of earth like planets around solar like stars. 10:39:50 So we, the idea was to stare at a field for 40 years and and sample 160,000 starts now to get for instance a transit, a planetary transit. 10:40:05 So, what, what actually was very cool for us doing astro seismology is that since you have this light curves that we are trying to detect planets. We can also detect pulsations in stars. 10:40:21 We can also detect pulsations in stars. And one of the most amazing result results I think that came from the Kepler data was this detection of this outbursts. 10:40:35 So this is for sun like events, also happen, but we missed them, because here we have Look how many days we were able to observe this star. So, for two months that's just unbelievable that's really really amazing. 10:40:42 On the bottom here we have the Fourier transform of the light curves that we are seeing here so the, the, the black ones and the green ones as well. 10:40:54 But that was something interesting happen of unfortunate but fortunate at the same time with Kaplan, so one of, so Kepler had the reaction we use for reaction wheels to keep it tracking and position and looking at staring at the same time. 10:41:09 So when Kepler actually two of those reaction wheels failed so that the telescope was drifting down so it couldn't maintain its its its field of observation. 10:41:20 So, what actually happened is we they repurpose the. 10:41:30 Kepler into k two and K two they were actually observing with less precision, but they could point K two at different fields and they were able to do that for a few more years, until fuels ran out and the. 10:41:43 And then we were able to find even more white dwarfs that was, that was something very, very, very cool. And this one here that I'm plotting, I don't have a name. 10:41:54 I didn't put a name yet, because this is one that I found in my kitchen. So I can actually go into the K two data download the K two data and just keep on looking at that so there's still a lot of things that can be done. 10:42:06 And, yeah, so we can look back and look for data and download data all the time. 10:42:16 And this paper here is, is a, is, is from this year, published by my, mainly led by my PhD advisor of G117 B15A. So this has been observed for 45 years 45 years so and whenever Kepler Kepler is the name of my PhD advisor came to to started his PhD, 10:42:39 the first observing run was to look at this star. So what is he doing here, so we actually observe the period of pulsation to have 215 seconds. 10:42:48 And that period is becoming slightly longer so it's a very stable period of pulsation but it's becoming slightly longer over time. So, it is not the most stable clock, but it's the most stable optical clock, and this is a measurement of the cooling 10:43:06 of the stars. So now we are with white dwarfs and pulsations we're even able to determine the cooling times of stars, that's something that, you know, in astronomy, we have a very hard time trying to pin, pin point how the star evolution will happen and 10:43:23 so on because we cannot observe a star in and follow its, its life, basically the timescales are just too long, but for white dwarfs, we can actually do that. 10:43:35 The change here is very small, right. So, but, but it's still significant and we can tell you know the fate of this star pretty much so that's something very, very impressive. 10:43:48 and very difficult to do. Basically, and. 10:44:04 But if you go outside. This, this meeting here, the most, you know, exciting things will come from supernovas planets galaxies and so on. But you know, we can learn so much about white dwarfs, and it's still the quote for the first director of McDonald 10:44:20 Observatory Otto Struve was that one of the first tasks to be undertaken by the staff at McDonald Observatory between investigate further the mysteries of the white dwarfs and we're still doing that so and there's still lots and lots of things to see 10:44:33 with the white dwarfs. 10:44:34 Okay, well thank you so much. 10:44:38 Do I have any , Barbara. Thank you so much. 10:44:42 Thanks to your kids for being so patient while you are giving us this lecture and talk. 10:44:50 Okay, so a lot of new concept have been brought up in terms of self solutions and composition of the, of the inner layers, so maybe it's time to open up for questions. 10:45:17 I know there's been some discussions on the chat that you know, to con recently people were very interested in. In the diamond like nature of the in the region of the stars. 10:45:28 And so the question was, how, how really diamond like are we talking about at end of the day, this regions are, plasma is like this ionized electrons of freedom all so so JJ, maybe you want to share what you answer to the BBC radio interview. 10:45:54 I think it was Mike. 10:45:56 It was Mike, Yeah, it was Mike, looks like. Yeah, sorry it was. So, a collaborator of ours Travis Metcalf had just sort of did a minor story like local to Harvard he was a postdoc there, but it was right around Valentine's Day and so it got subsumed into 10:46:13 Hey giant diamond in the sky Valentine's Day oh this is popular now. And it just sort of blew up in 2003 and I was in Cambridge at the time and so they call me. 10:46:24 I was on the paper but you know the BBC they know their stuff. So you're doing the interview and then the science guy said. So, is this really like a diamond of the year. 10:46:38 And I said, Well, not exactly. Because, electronic bonds, hold carbon atoms in certain places on the earth but all the electrons are just free so that the thing that's holding the thing together is that you're forcing all of them to be close and they're 10:46:52 just getting as far away from each other as they can. So it's not the same thing but it's really the astrophysical equivalent of a diamond, you know, in the center of the star. 10:47:02 And it really is a solid. So it really is the same thing but if you took it out of the center of the star it would blow up because there'd be no pressure on it would just spring apart, whereas the diamond just sits there. 10:47:13 So it's the difference between chemical bonds and just, just the electrical forces repelling each other. 10:47:26 Anyway, I hope that helps people. Can I ask a follow up on that, though. So, the diamond has a specific structure with the location of the nuclei. 10:47:30 The question I was really trying to get at was, how is that what the arrangement is like inside the yeah so yeah so this is a lot more compact then diamond. 10:47:44 So carbon itself. You can see carbon has graphite, for example in those structures liking layers. Then if you do the diamonds on Earth, the structure becomes this cubic kind of structure. 10:47:56 So this is much more complex than that so it would be like cubes inside cubes if you, if you want to have an idea. And again, I, I took out I had a talk that I gave for, you know, for the kids, usually give talks for my kids classrooms and, actually, 10:48:14 the density of white dwarfs is like a white great white shark inside the little, tiny, playing dice. 10:48:23 That's the best. 10:48:25 And it's great white shark never forget that. So, it is like imagine like cubes inside cubes because you can fit many more carbon, carbon atoms inside that. 10:48:38 And sorry I should have mentioned I think we think that the interior of a white dwarf is like a body centered cubic lattice. I actually don't know what diamonds are so if that's the same then they would share that as well but I don't know. 10:48:54 Yes, the, the diamonds are cubic not layered like graphite. 10:48:59 But yeah, but they're missing those two spaces that you can put more, because if you think about a cube it has just those those edges right. But then you can put something in between them so it's like cubes inside cubes. 10:49:18 Yeah. 10:49:18 And then was a discussion about the conductivity which I thought was interesting because, in a sense, the material is as tough as a diamond but also more conductive that graphite. 10:49:31 So in a sense you you get both properties of carbon layering that you get on earth. And the same form which I thought it was, I never thought about it but it's actually kind of, kind of interesting. 10:49:48 Thank you. 10:49:53 Okay, more questions about Astro seismology of white dwarfs. 10:50:02 I saw one question here on the chat about the optical clock. Yes, the correct they correct for everything, even from the motion of the battery centric motion of our solar system so we collect everything. 10:50:15 So this is purely coming from the, from the, from the motion, relative motion of the star for everything that we are seeing. That's collected. Yeah. And this is purely from the pulsation of this. 10:50:30 And Barbara, I mean, for this type of pulsation since the period is of the order of minutes to hours. I guess you know the frequency doesn't really change due to Doppler effect, because the orbit of the Earth around the Sun is you know occurring on a much 10:50:50 longer timescale. 10:50:52 So in a sense, you know, we, that shouldn't matter too much, the audit effect that might matter but that one shouldn't be important. Yeah, no, definitely, but if you actually forget to correct the bi centric emotion you will find a doppler again. 10:51:12 That's true. 10:51:15 Those, Robert. Is there any gravitational lensing from this kind of from the white dwarf. And can you see anything from there. 10:51:27 Thank you. 10:51:31 Can you see the gravitational ANC 10:51:35 well. 10:51:38 Does, Does the white dwarf cause gravitational lensing that we could see. And is there anything that we could get any information that we could get from, um, well if we could she could use that the lensing for that you could get information of whatever 10:51:56 object behind that. It is right. So that would be. 10:52:03 Yeah, I don't work with gravitational lensing on the white dwarfs but in principle, if it is working as a lens, you could see whatever is causing the effect of the bigger so but this is a planet, you can find that but I don't see that much the 10:52:19 relation with the pulsations but. 10:52:35 Any other questions. 10:52:44 Okay. 10:52:50 I think people are ready to. Oh, actually we got Mark. 10:52:55 I have just one more quick question. 10:52:58 So if you can take for a spectra of vibrations. Are you thinking that eventually you'll be able to sort of map out like changes in layers or something like what you would do with FDIR spectroscopy and molecules. 10:53:17 So, we can by doing the Fourier transform, I can see for instance, if the modes are beating with each other, because if you start having tons of modes, they can start interfering with each other. 10:53:29 So in this respect, we can see how I can try to model and infer how the layers going on inside this though. Yeah. So, it's a, it's a, it's a good thing. 10:53:42 It's also a bad thing to have tons of modes because if you have tons of modes, it means that you have a lot of information, but you have to do also if the bad part of, of having tons of modes because they interact with each other, and that becomes way 10:53:56 too complex to even understand. So like the sun has, you know, Thousands of nodes and then things become even more complicated but but again we, it's it's a process like the more we have always trying to push the boundaries of getting better data detecting 10:54:14 mode so going to space is definitely better. And, yeah, so, and the models are becoming better, because we have better computers. So, calculating Stella model nowadays would take. 10:54:29 I don't know, minutes, you know, in comparison to what it would take like 2030 years ago that we would have to do a whole lot of calculate and spend months trying to figure out how these stars look like so. 10:54:42 So there's a lot of development in astronomy but yeah things, walk at a certain pace. So, thank you, Thank you. 10:54:57 Okay. 10:54:59 Any more questions for Barbara. 10:55:11 Okay, So, I think everybody deserves. 10:55:16