 Alright, welcome back and hope you all have time to get yourself a beer and turn in your trivia sheet if you haven't already. Alright, let's get started with our next speaker. You're already here for tonight. Give it up for Dr. Daisy Lombard. I also do things called prototype planetary debris desks, but when I study massive stars, it's almost always through polar imagery, so tonight I'm going to show you one data set that I have on a massive star using polar imagery, sort of at the end of the talk, but at first I thought you guys might not exactly know what a massive star is, so I should explain that to begin with. And the easiest way to explain that is actually maybe through supernovae. So if you guys have come to astronomy on top before, I think you've probably heard about the different types of supernovae that go off. We typically classify them to the first order based on whether or not they have hydrogen in their spectrum, and then we further sub-classify them based on whether or not we see certain elements. So at type 1b supernova has no silicon, at type 1c has no silicon and also no helium. We also classify them based on how their light curves or how the amount of light changes over time with the light curve is, how their light curve evolves, and things like that. The weird thing about this is maybe it's good for putting things into bins, but it doesn't really tell us what kinds of things exploded. And so you can see I've color coded these lines, and these types of supernovae. So the red supernovae are from a thermonuclear reaction. So those are something different, and I'm not going to talk about them, but everything that's a massive star is going to explode in some other type of supernova. Every massive star ends its life as a supernova, and it ends its life as what we call a portap supernova. You need, if you're a star, between about 8 and 10 times the mass of our sun to do that. And so basically everything from there on up 90 times the mass of our sun, all of that, is going to explode as a supernova. So the holy grail for us in massive star research is basically to be able to take a massive star, at the beginning of its lifetime, figure out how massive it is. Is it big solar masses? Is it 15? Is it 50? Is it 100? And map out what its life is going to look like, and figure out what supernova it's going to end its life as. So we would like to be able to say that something between 30 and 40 solar masses starts off as an O type star. O just basically means really, really big. Then becomes maybe LBV. LBV stands for luminous blue variable. They are literally luminous, and they are literally blue. And that's about all we know about them. All things like we see it. We're not very imaginative when it comes to names. And then maybe it becomes a wolf ray star. So the WN stands for Nitrogen-rich wolf ray star. And then maybe it explodes as some type of supernova. And then we would like to be able to do the same thing for another mass band, and how they go through different states and stuff like that. But it turns out that is really hard, and it's complicated by the fact that most massive stars are probably in binary systems. And so this is just a pie chart to show you where they would fall. Basically about one third of all massive stars are either actually single stars off on their own, or they have a companion star that's orbiting so far away from it that it's never going to interact with it, and it's going to just act like it's equal. It's just not very friendly with the thing that's orbiting around it. But the other two thirds of massive stars have companions, and they're either going to merge with their companion star and make another even bigger star, or they're going to interact by like saying, I want to lose some weight. I'm going to dump a bunch of my mass onto you, and if you fat and heavier, they do that. And in fact, the star that what I'm going to talk about later on is doing that. It's super mean to its life partner. They can also... They also can accrete material from the companion. What happens when they accrete material and do material is they spin up and they spin faster and faster and faster and faster and faster, and so it's like having a friend at the Disney Tea Cup ride, and then they spin you so fast that you start to throw up. The stars will actually start to spin so fast that they actually start to lose material. So if two thirds of all stars, all massive stars, are binaries, then two thirds of all supernova, at least core collapse supernova, everything that the tech one is that we see should be coming from binary stars, right? That makes sense. Well, there's a problem, and that is we've only seen maybe like two or three core collapse supernova where we have evidence that suggests that it's come from a binary star. So this is supernova 1993 J. This is the explosion discovery image. You can see the supernova right here. It basically rivals the brightness of the galaxy that it did. And the reason, or at least one of the reasons we think that it was in a binary system was because several years later a team went back and it imaged the same galaxy with Hubble and they basically zoomed into that same region of the galaxy and then zoomed in some more and there's still a star there. And so we think that was the companion that did not get destroyed and then the original supernova went off when it's companion supernova, the companion star went off, right? So that's nice, except that like we should have more than one or two examples of this happening. We should have like tens of thousands of these happening. So why don't we have, why don't we see that? Why don't we see all of these binary stars going supernova? The answer is really that we don't know. We don't know how binary stars evolve. And so we kind of have a general picture, which I'm going to give you now, but the details of this picture are really, really uncertain. So basically what happens is you start off your life if you're a binary star with a companion or orbiting each other, everything is fine and dandy until the star that's the most massive star runs out of hydrogen. The most massive star is going to run out of hydrogen first. And when that happens, the star gets bigger and starts to pop up. And if the star fills a region around it called its rocheload, which is this tear drop shaped thing, if it can push material beyond that rocheload, that material is no longer bound gravitationally to the star and it can move around. And so this is where it gets mean and it's like I want to lose some weight and all of that material that it pushes out here transfers over to the companion and then the companion starts gaining material and becoming more massive. And eventually that star should explode as a supernova. Then we should have some sort of remnant either a black hole or a neutron star. But then that secondary star that hasn't really evolved yet that gained a bunch of mass is going to do the same thing. It might fill its rocheload. It might say, you know, what you may be gain weight before, I'm going to make you gain weight now because I can. That will evolve eventually into the supernova as well. And then you have two neutron stars or two black holes or a neutron star and a black hole orbiting each other that then coalesce. And then you get the LIGO signature that you've seen if you've come to a previous astronomy ontop of it. Show me that. What's the WR? WR stands for Formal Ray. And those are stars that lack hydrogen, which is interesting because about 75% of the stars should be hydrogen. And so they are just so big that they can either have been able to blow off with their summer winds, all of their outer layers of hydrogen, or if they're in a binary system, they use this rocheload overflow to just dump all of their hydrogen onto their companion star. So the star I'm going to talk to you tonight about is called Beta Lyra. This is a movie of the two stars orbiting each other. It's a massive star system. And so what we can do with Beta Lyra is we can try to hammer out the details of how that mass is transferring between the two stars and when the system is losing material to try to figure out how that affects its future evolution. And once we kind of start answering questions like that, we can start to tease out why aren't we seeing all of these binary supernova refrigerators that we think we should be seeing. Good question. I was just going to get to that. So every 14 days, the two stars equip each other and go around. The really cool thing about Beta Lyra is not only does this happen every 14 days, but you could go out tonight if you wanted to and find it. So this is the constellation Lyra. It is basically a triangle on top of a parallelogram. If you guys know, know your stars very well. This one up here is Beta. It's the brightest star in the constellation. And then this one down here is Beta Lyra. And it's Beta, literally because it's the second brightest. That's how it was named. So it's roughly like right above us. If it's not cloudy and rainy right now. And if you have an app, if you want to download one of the apps, then you can hold up and see what's in the sky and have it tell you what you're looking at. Sometimes those apps call it Sheelyac instead of Beta Lyra. So that's what you're looking for. But because you can see this with your naked eye and because the two stars are orbiting each other and closing each other every 13-ish days, if you went outside every single night for the next 13 days, you'll actually notice that it's getting brighter and dimmer compared to the stars around it. So you can go and look at this and do this tonight. And of course this guy doesn't have the lines nicely drawn on for you. So really quickly, good luck. This is this guy. That's what you're looking for. This is the parallelogram here. And then this is the triangle. And this is the brightest one. So what do we actually know about Beta Lyra besides that? We can go and see it and it's really cool. And there's two stars that orbit each other. Both stars in the system were originally massive stars. The more massive star evolved first and filled its brush load and is now actively using material to the secondary star. And in fact, it's lost so much material it's not really a massive star anymore. It's only about three solar masses. If you remember before, I told you massive stars are like sort of eight to ten or above. So it's now a wee, small star instead. That mass loss and transfer to the companion star has formed a very, very thick accretion disk around it of gas. And in fact, it's so thick that when we look at the star we don't actually, when we look at the two stars we don't actually see the star itself and actually what we were seeing in that movie earlier was one star and one disk orbiting each other. You weren't actually seeing the secondary star. It's just the light cannot get through that gas it's just so thick. We also know that you have some evidence for jets coming out of the system. But as you can see in that movie you didn't see any evidence of jets. You just saw sort of two blobs orbiting each other. So we don't really know exactly where the jets are. If they're located on the end of the disk like somebody drew and depicted here or if they're located more from the center due to in-fall of material onto the star and then they flop that kind of thing. But polar imagery can really help us answer some of these questions. So basically these are all features that we can't really see well with a regular telescope. We can't see the mass transfer stream between the two stars. We can't see the jets. But what we really want to know is how much material is moving between the two stars. We want to know if that transfer is kind of constant over time or if it's clumpy and happening in bursts of mass loss and transfer. And we want to know the same thing about the jets. Are they constant? Is a constant mass loss? How much material is being lost in the jets compared to how much is being transferred? So is the whole system losing mass as well? Or is it just the transfer happening? Those kinds of questions. So the key with being a liar or understanding it with the format of data that I'm going to show you is this slide and I'm going to explain it to you. So basically if you have a star like this orange blob here that's obviously very star like rounded by something gas or dust that is circularly symmetric what happens is the light comes out of the star unpolarized it interacts, magic happens and all of those wiggles of the light line up so that they're tangential in the edge of the gas and dust. And then if you go and look at that with a telescope remember we're not actually resolving this. We're using polarimetry as a trick to get us geometric information without ever having to resolve it. But so if you go and look at it with a telescope basically you see all of these lines all together and you see all of the wiggles in all of their directions and it looks like it's not polarized and so you don't get any, you don't actually get any coordinate signal. But if the gas around your star is elongated in some way and just like maybe the disc that's in data Lyra then your light still interacts in the same way it still gets scattered so that the wiggles are preferentially tangential to the edge of the gas. But when you add them all up to look at it with a telescope they no longer are all in one direction. There's a little bit of a preferred direction it's like they cancel with each other a little bit but not all the way so you get a preferred direction and that's the preferred wiggle direction is 90 degrees from the direction of elongation of the disc. So you can back out geometric information pretty quickly. So what I'm showing you now is a polarimetric light curve of data Lyra so if you've come to astronomy on top before you've seen light curves of planets as they transit in front of stars this is basically the same thing but with just a little extra information. So this top panel here is the regular light curve of data Lyra so if you look at the system at this time at day zero it doesn't have a lot of light coming from it and that's because the star in the system that's losing material is directly behind the disc and then the system rotates a little bit so that they're next to each other and then it rotates a little bit more and then the star is in front of the disc and so you have a little bit more light than you did at primary eclipse but less light than you did when the two stars were next to each other and then they continue to rotate until you're back at our primary eclipse again and again this happens every 13 days. When you look at this with polarimetry you basically get the same thing you get a polarized light curve which means you also get how much light was polarized over time just like you had how much light you were getting over time it's just how much light was total polarized and you also get the direction of that polarization with time so I'm going to walk you through what this graph is actually telling us and teaching us about beta Lyra and I want you to forget the top two panels for the time being I will come back to them and I'm only going to talk about the angle that the light is wiggling and in fact I'm actually going to ask you also to forget about this for a few seconds right that's here it doesn't look like everything else everything else looks nice and neat right it's kind of all nice and aligned there and in fact if you draw a line through there that angle if you can see the different angles here that angle is about 164 degrees and so like I said before that the angle that the light is wiggling at is 90 degrees off of the angle that the disc is at so if you just add 90 degrees to that you get 256 degrees and if you guys can see it if nobody's head is in your way that's what this angle is right here compared to the constellation right so this is the constellation this is the the parallelogram the orientation of the disc in the system is like this so right so directly just by looking at how the light is wiggling I can tell you how the disc is oriented on the sky which is pretty cool and pretty useful information and in fact if you go back to the movie that I showed you of the two globs orbiting each other and you figure out what the angle is from the two globs you get roughly the same number it's 253 degrees compared to 256 so we're doing pretty good and I should mention that this movie actually took multiple telescopes observing being a lyra at the same exact time to be able to see the two stars separated from each other normally you don't get to do that that's a pretty difficult thing to do and so we're getting that information with a very small telescope without ever having to you know do more complicated things so still still forget about this for a while so what is the other what is this other middle graph that I was showing you well it tells us a few things there's actually three features in here that are important and the first thing is that primary eclipse when the disc is in front of the star that's losing material you'll see that the amount of polarized light that we're getting has increased compared to other times during the star's orbits and basically what this graph is is actually not the amount of polarized light we're getting compared to the total amount of light we're getting so there's an unpolarized light source in our system which is the primary star that's the one that's losing all the material and then there's a source of polarized light in the system which is the disc and so what's happened is the disc is blocking out our unpolarized light source so we're not seeing that anymore so percentage-wise of the total light that we're getting percentage-wise more polarized light even though if you were to measure the intensity it's the same as when the primary star is not being eclipsed the second feature you see is there's these bumps right here and right here about a quarter, a little more than a quarter of a way through the orbit of the two stars and a little bit more than a quarter of a way through because of the material that the star, that the light is scattering off of and so when you have hot things it ionizes the gas that's around them and so in the case of beta lyra about the stars are very hot it's ionized the gas in the disc and when light scatters with hot ionized gas it prefers to scatter at a 90 degree angle and so it will scatter more light at that 90 degree angle than at 90 degrees or 91 degrees and so when the orientation of the system, so the orientation of the primary star which is our source of light the disc which is where that magic is happening in our telescope is at a 90 degree angle that's when we get the most polarized light coming into our telescope and so that gives us these bumps and then the third thing that you can see in the polarized light from here is that there's a secondary eclipse and if you really look closely that secondary eclipse is occurring just before the secondary eclipse in regular light and I know it's not very much but this is actually pretty important that secondary eclipse in polarized light is happening right about where the red line is and in regular total light it's happening more than the blue line is so what's up with that it's weird right and it turns out it's also doing this weird eclipse just before what you normally would expect it right when all of the wheels are doing odd things and not nice and oriented together anymore and it turns out that's a signature of something strange happening in the disc and so normally the disc is all nice and smooth and has nice edges to it but when you're transferring mass off of a primary star there's a mass stream there that runs into that edge of the disc and it's going to screw it up and it's going to basically create a giant splash zone and send material flying everywhere and that's what that signature is you're getting a little bit of a primary eclipse just beforehand and then the position angle is going walky because the structure of the disc is walking and what we call that is a hot spot because the actor material running into all our material basically walks it up and it's hot like I said before we're really terrible at naming things it's a hot spot because it's hot and we can also use we can use the light curve the polarized light curve to basically measure the size of the hot spot so what we just have to do to do that is go back to where this is happening where the minimum being the polarized light curve is the secondary eclipse and just figure out what the orientation of the system was and because it's an eclipse system that's really easy to do and it looks something like this so this blue and orange region is the disc and then this red blob is the star that's losing material and you can see it's not quite in the center if it were in the center we would be at exactly a secondary eclipse where the normal where you could see the normal total light and basically just everything in front of that star that's part of the disc that hasn't been eclipsed yet is hot spot material and it's part of the disc that is completely walking and not nice in disc shape anymore and so if you actually work out the math and figure out how big that is across the face of the disc it's actually 13 times the size of our sun so this is really really big we can fit 13 suns back to back to back as across this so it's quite huge so I hope what I've shown you is that obviously polarimetry is the coolest thing ever it's okay if you don't like that it's not really it's okay if you don't like it but importantly if you're not doing polarimetry you're throwing out free information about these objects about whatever you're studying for no good reason you're getting all of this extra information for free I didn't have to do anything to get it except point a telescope at it and look at how the light was weakling and on top of that because you're adding in this extra information you're getting information that you're not going to get any other way so I couldn't have gone and imaged the disc of beta lyra and seen that there was a hot spot on it no matter how many giant telescopes I got if I strung them together I was just never going to see it it doesn't matter if I decided to look at a spectra it's not going to happen so it's really in my mind it's really cool that you can basically figure out things you can see things that you can otherwise be able to see you can see invisible things to you and that gives you extra information about what's going on in different systems so I'm happy to take questions if you have any really fast so this is it's not an astronomy picture basically what somebody did was they looked at a crystal with a polarizing filter in front of their camera and different wavelengths of light are polarized differently and that's why you get this really cool color striation and stuff for it so the question was how expensive is a polarimeter compared to a regular instrument so a polarimeter is basically a regular instrument with a couple of extra optics parts in them so a lot of instruments can be turned into polarimeters if you have the right pieces it really depends on the size of the instrument and the wavelength you're at and what you're looking for for example I was on a telecon the other day we're talking about trying to revive a polarimeter we actually got put on a telescope and never used we want to check it out and see if it's still running and working if it is, commission it so astronomers can actually use it and somebody was telling us one of the pieces that we needed was missing because they could put it in a box and put it in a room and forgot in what room they put it in as one normally does with all of their expensive equipment and so we asked for some of the specs so we could get an idea of how much money we would need if they couldn't find it and had to replace it and it turns out that this is about $120,000 part and so when we told them that they said okay we're going to go look harder so it can be it can be much more expensive this is for an 8 meter class telescope a telescope that's maybe one meter big you could probably build a polarimeter for $100,000 or $150,000 and not just have this one part so the question is how does voron like work in radio they get um I don't know how I want to say this but I'll make it into complex so they get that information for free basically when they observe they get the up and down the goals for free and they get the left and right for free and they can back out from those what the whole polarization state is but they get it automatically with their receivers I'm not sure if we can talk about it more I don't have officers because I'm not a professor but come by so the question is what else can we use the technique for to study besides muscle stars well Q is going to talk to you about planets so those are really hot pool there's really magnetic fields around stars you can study galaxies basically any astronomical object you can think of we have an application for it yeah the question is do we know if gravity waves can be polarized in the same way um I'm basically no then that's a guess I don't know ask the like of the folks if they come back last question yes so the question is do we do experiments on earth to see how light gets polarized as it acts with different media people do that all the time in the lab and that happens quite often so I think it's time for trivia answers trivia is our title of the stage to perhaps this month's winners please come see us at the front to get your questions yes hi everybody so as soon as Trevor gets the slide alright so let's get the show on the road for our last talk we are here for tonight please give a warm welcome to Dr. Kim Ba to tell us about the most topic oh gee guys thank you oh jeez oh jeez okay I know you guys most of you are really disappointed right now because you didn't win at trivia but it's okay because we're going to talk about aliens now and that's fun typically what we're going to talk about is how you would use polarized light to figure out if a planet is habitable that's the same it has conditions sort of like earth does it have an ocean or whether or not a planet already has life on it whether or not it has biosignatures signatures of a bio or biology whether or not it has aliens the the first thing that we'll want to cover I'm totally blanking on my first slide I'm so sorry alright this was an introductory slide in case you don't know what an exoplanet is I'm guessing most people here are science enthusiasts and you know what an exoplanet is but just in case you don't that's perfectly okay an exoplanet just refers to any planets outside of our solar system so you know that we have a star that we call the sun and the 8 planets orbit around it well anything that orbits around another star even finding tons of these things since the mid 90s is an exoplanet orbiting one of the stars you can see or even the ones you can't see is an exoplanet and that's most of what I'll be talking about I'll talk a little bit about ways that you could detect lives in our own solar system so why would we use polarimetry in the first place to study planets we mentioned in the introduction that actually you kind of don't get polarized light from stars if it's a star that's kind of not being ripped apart and it's very much like our sun it's sort of main sequence it's not too young and active or old and fluffy then we don't get polarized light from that so this is just an image of our own star the sun and transving in front of it so if you want to look at something that's really freaking dim then you can just erase the star by looking at it so there's a whole bunch of different things lint off of an ocean and telling you whether or not there's an ocean there to mean water for life so that's useful we could be looking at really scattering the same thing that makes our sky blue we can look at on other planets and figure out what their atmospheres are like what sort of gases are in the atmospheres we can look for clouds and cases in some cases and we can look for rainbows even double rainbows in some as well and that will tell you about obviously what's raining down what the precipitants are on these planets as for actual life there's some indication that we could look for biosignatures so we could look at the gases in an atmosphere to figure out whether or not there's life there and that that might be enhanced if we look at linearly polarized light we talked earlier about linear and circularly polarized light with circularly polarized light we can detect something called pyromolecules and I will explain what that is very shortly another reason that this is a super useful thing for studying planets is I know that this schematic looks way too technical hopefully you've also already had free drinks so it's just too much but it's really quite simple OL is just referring to the orbital launch tooth it's just telling you how far on the star it's gone and the phases are just kind of like the moon like the space of the moon and things like that so the other reason that this is super useful for studying planets for studying exoplanets is because it's dependent on the angle of the planet so we're getting that directional information as well as the intensity the thing we talked about in the introduction so we can look at how the light is reflecting off or interacting with particles in the atmosphere of these planets so here in the middle you've got the star and you're looking at this from a top down angle you would of course be this planet finding satellite that's looking at its side on so if you're, if this is too much black and white for you instead just picture that you guys are all earthlings looking at the planet through a telescope and not my head my big shiny head is a star and then you have a planet that's orbiting around it it's not elliptical it's just how my hand moves but it's going around in a circular orbit so if you're looking for something like a rainbow you get that sort of like near full phase when it's pretty fully illuminated and the planet's kind of behind my head or behind the star and then if you're looking for something like really scattering that's producing that blue light in our sky and our red sunsets that's hitting a maximum in that polarized light when it's at 90 degrees so that's important you can tell the difference looking at polarized light by seeing whether you get a peek from the planet's back here or when it's at the side you can tell whether that's from a rainbow or if it's from the really scattering and then if you're looking at something like the water reflection that glints where off the ocean you can get that when the planet is closer to a crescent phase so when the planet has moved in front of the star you don't get a whole lot of polarized light when it's directly in front of the star but kind of out here you'll get a glint you get this kind of glimmer off the surface if the planet has an ocean now I want to do a quick aside this we're talking about astrobiology in terms of life as we know it and that's done for a very practical reason we need to have very detailed ideas about what we're looking for so when I'm talking about this I'm aware of the fact that I'm talking about looking for planets with water oceans, H2O oceans and scientists do know that you can have life that's a sentient ocean that takes the form of your dead ex-wife spaceship but the kind of life that we can look for would be something more akin to what we see on Earth so there's sort of three things that you can look for that you can look for when you're looking at polarized light of a planet when you're doing planetary polarimetry you can try to characterize the system just to figure out what the atmosphere is like, what the orbit is like you can try to judge habitability, it doesn't have an ocean it doesn't have an atmosphere like ours what is the rain like there is something I would want to be standing in and you can try to detect biosignatures those signatures of a bio signatures of biology but there's life already there so when we're talking about characterizing planets we can actually do that whether or not the planet is small or large we only expect life to be on small planets but we can kind of practice polarimetry with really large planets even with Jupiter size planets so we have these things called hot Jupiters who might have heard of and they're like the size of Jupiter or larger and then they're like a fraction of the distance that Mercury is to our own Sun they can orbit within like an Earth day so their gear is like less than an Earth day so they're super hot, they're getting tons of radiation from their star light bouncing off of them and they're also very large so they're really good at reflecting light and that gives us something to study in the meantime it was only very recently that we developed polarimeters things that could measure polarized light that were sensitive enough to start studying planets so these are sort of the first things that we've begun to look at and oh there's some math there let's get rid of that let's go so when you're looking to just kind of characterize a planet you're maybe looking for that Rayleigh scattering like we see in our own atmosphere so to look for Rayleigh scattering you're just kind of looking for this wiggle you're looking for that peak or maybe a dip because it can be positive or negative when the planet is in behind sorry at 90 degrees more or less you get the peak in polarized light for Rayleigh scattering and you can do that with those giant planets unfortunately so far we have we have started looking there's only really a couple polarimeters that can even do this in the world but we've started looking at this and we just kind of see this is kind of one of the better cases and you just see scattered so you can kind of fit that that wave to it but it doesn't fit very well so we think maybe we're seeing that but this is a totally new application of polarimeters it's not exciting it's really really new we're figuring out all the different things that we need to look at when we look at a planet to be sure that we're just getting polarized light from the planet itself so this is an example of a hot Jupiter real data from a hot Jupiter there and with measurements meant to detect the Rayleigh scattering from the atmosphere to see whether or not it has a blue atmosphere the reason you might care about whether or not planets have blue atmospheres and what the Rayleigh scattering is like is because it tells you something about the average size of the particles in the atmosphere so we have a lot of nitrogen and some oxygen in our atmosphere and we have a different sunset than what you might expect on different planets we have a blue sky that's produced by the Rayleigh scattering as well as our red sunsets and that's going to vary from planet to planet so looking at the Rayleigh scattering and polarized light really easy way relatively to detect Rayleigh scattering because you're knowing the star you don't get any light from the star we tell us something about what the bulk composition of the atmosphere is what it's like in general so we can move on from giant planets and sort of looking at the atmospheres and try to start judging habitability does this planet have gases in its atmosphere that are a similar composition are it doesn't have an ocean that produces blint, it doesn't have rainbows that are actual rain and are made of water and not like sulfuric acid or something we don't want to be standing in oh I'm going to see you take care of that, don't worry so if we're looking at something like rainbows the reason that looking for rainbows works is not only do you get a peak in the rainbow at a certain point in the orbit but that peak will change very slightly depending what that rain with the cloud that's producing the rainbow is made out of so if you have water you'll get that peak in your polarized light at a slightly different angle from if you have say raindrops made out of sulfuric acid like on Venus or if you have raindrops made out of methane like on Titan and that's all due to that math that I just covered up but basically all that math was saying was that the light will bend in the water droplets at a slightly different angle depending what the droplet is made out of if it's water it bends at a slightly different angle than anything and we all know that they are probably told at some point in their life that rainbows happen at a very specific angle and so when we're looking at polarized light we're just extending that to exoplanets that have rainbows happening at slightly different angles at different points in their orbits so one of the teams that I worked with has used models to reproduce this for a very famous case of Venus back from the day way back in the day people were like oh Venus it's around the same size as Earth it's probably pretty nice there it's probably got tropical jungles it's a little warm it's close to the star to our sun I'm sure it's great and then looking at more and more detail about the information and looking in fact at the polarized light at different wavelengths we were able to keep almost flipping we were able to tell what its rainbow is like so you can look in sort of like a red light a green light, a blue light and look for those peaks in the polarized light that rainbow is sort of like what I showed you on the last slide and prepare them and you can tell where your rainbow is happening and sort of how spread out the colors are what shape the rainbow has and that's going to tell you whether or not those rain droplets are made out of water like we have on Earth or sulfuric acid like we have on Venus and maybe we don't want to go there after all that was a bad idea so we're trying to create these really robust models that will take into consideration polarized light from really scattering in the atmosphere as well as from rainbows and if you've had a planet to see the surface, not like Venus you'd be able to see the signature from glint as well and we're able to kind of map the polarized light signature that we get across surface so this is sort of looking at Venus through different phases and then those blue dashes that don't show terribly well on the screen are those different polarized light vectors so there are little lines telling you how that light is aligned so it's giving you the directional information as well as the intensity and then if you were able to look at a planet through different phases you'd be able to tell things like if it had an atmosphere made out of nitrogen and oxygen or carbon dioxide and whether or not it had rain drops made from water or made from sulfuric acid so speaking of looking at planets through phases another way to detect habitability or to judge habitability is to look for glint so this is a real planet called Earth I know this is real observations of a planet and so you can kind of see the light from the sun kind of bouncing back as it moves across and you can see a peak in that light right when it's kind of in presence so I said you would see the peak in glint when the planet's kind of in front of you, kind of in front of my pit when it would look like a compressive to you and that's when you're going to see that peak in polarized light so we can look for that as well as well as the rainbow and the really scattering you can start to get a really robust picture of what the planet is like of course in reality we have all these other things going on we have clouds that are getting in the way of the continents which I guess are good but you can start ideally you can start mapping this right you can look at when you see the glint and when you don't see the glint and get an idea of maybe where the continents lie and that might give you an idea of where you should play tectonics and some other things that we want to know to get an idea of whether or not a planet is habitable you can also figure out whether or not those oceans that are producing the glint are something nice like water that we think life as we know it would be happy in or something a little different that maybe other life would be happy in or maybe life would be happy in at all and once again that's all to do with math but it all comes down to the fact that different things bend white at different angles so last bend is like at a different angle than water and similarly on earth we have light going from air bouncing off of H2O water and that's going to produce a maximum and polarized light at a different angle than on