 For our last talk, you are here for tonight. Please give a warm welcome to Dr. Kim Vah to tell us about the best topics it is. Good to see you guys. Thank you. Come on, cheeseburg. Okay. It's a bit of a trivia, but it's okay because we're going to talk about aliens now. We'll figure out if a planet is 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 first thing that we'll want to cover, I'm totally blanking on my first slide. I'm hot-braining, so sorry. Dr. E-slide. In case you don't know what an exoplanet is, 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 planet outside of our solar system, so you know that we have a star that we call the Sun and the 8th planet's orbit around it. Well, anything that orbits around another star, and we've been finding tons of these things since the mid-90s, is an exoplanet. According to that, that's what I'm talking about. Just any planet in a solar system that's not in our own, not in our 8th planet, if it was not a planet, any other, yeah, whatever. Forming one of the stars you can see, or even the ones we 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 can detect life on bodies in our own solar system. So why would we use polarimetry in the first place to study planets? Well, 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 like 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 Venus transiting in front of it. So if you want to look at something that's really freaking dim like, and you don't want the light from that super bright star, then you can just basically erase the star by looking at it and polarize light and study planets. So there's a whole bunch of different things that you could be looking at. A whole bunch of different things that you could be looking at and polarize light, these different stuff. So you could be looking for the glint off of an ocean from an exoplanet telling you whether or not there's an ocean there in the first place, and you think you need water for life, so that's useful. You 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. And that's a polarizing mechanism 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 chiral molecules, and I will explain what that is very shortly. So, 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. O-L is just referring to the orbital longitude. 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 githubus phase 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 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 that 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. 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 planets back here or when it's at the side. You can tell whether that's from a rainbow or if it's from the red light scattering. And then, if you're looking at something like the water reflection, that glimpse, that glare 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 glimpse. You get this kind of glimmer off the surface if the planet has an ocean. Now, I want to do a quick aside. 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 and tries to kill everyone in the 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. You can look for, when you're looking at polarized light of a planet, when you're doing planetary polar imagery, 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? It's something I would want to be standing in. And you can try to detect biosignatures. Those signatures of a biome, 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 polar imagery with really large planets, even with Jupiter-sized planets. So we have these things called hot Jupiters you 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. And so they're super hot. They're getting tons of radiation from their star, lots of 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 can 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 give it a five. 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 just 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 of polarized light for Rayleigh scattering. And you can do that with those giant planets. Unfortunately, so far, we have started looking, there's only really a couple of polarimeters that can even do this in the world, but we've started looking at this, kind of one of the better cases, and you just see scatter. So you can kind of fit 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 kind of 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 the 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, a really easy way, relatively, to detect Rayleigh scattering because you're nulling the star or you don't get any light from the star, would 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 to ours? Does it have an ocean that produces blint? Does it have rainbows that are actual rain and like made of water and not like sulfuric acid or something? We don't want to be standing in. Oh. So... I mean, I 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, rain drops made out of sulfuric acid like on Venus, or if you have rain drops 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 if it's methane. And we all know that there are, probably told at some point in our 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 in 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 supposed to start to our sun. I'm sure it's great. And then looking at more and more detail about the information, the light that we were getting from the atmosphere of Venus, 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 was 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 where you can see the surface, not like Venus, you'd be able to see the signature from the lens as well. And we're able to kind of map the polarized light signature that we get across the surface. So this is sort of looking at Venus through different phases and those blue dashes that don't show terribly well on the screen are those different polarized light vectors. So they're 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 glints when the planet's kind of in front of you, kind of in front of my pit when it would look like a crescent 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. We 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 and we have continents, which I guess would be good. But you can start, ideally, you can start mapping this, right? You could 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 they take on it, since 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, whether or not those oceans that are producing the glint are something nice like water that we think life as you know it would be happier or something a little different that maybe other life would be happier or maybe life would be happier 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, glass bends light 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, say, Titan, where you have light going from a methane atmosphere and then bouncing off of a hydrocarbon ocean. So we can actually, in theory, tell what the ocean and atmosphere are made out of by looking at where exactly we see this glint. So once again, we're going to look at where in orbit we see this peak. It's going to shift a little bit depending on what the light is bouncing off of, what the atmosphere and what the ocean are made out of. So finally, we're on to the aliens. How do we detect biosignatories, who's being polarized by it? We've talked about how to figure out if a planet would be friendly to life, whether or not it's habitable, but how are we going to tell if there's already light there and we can't just set up camp? There's a few different ways, actually. So there's the idea that you could enhance biosignatories to enhance the signature of the spectrum of the gases that you see in it. But the method that I'm more familiar with has to do with something called chirality, which we mentioned earlier. So you can have molecules in your body that are either left-handed or right-handed. We call that chirality. And so in this picture, that R is meant to be kind of forward and poking out at you, but you can also imagine the reason we call it left-handed or right-handed. If you take your left hand and flip it over, your thumb's on the same side as your right hand, but it's not the same as your right hand. I can't do it. If you do it like, palms up, and then flip it over, it's not the same. So the molecules in your body are the same sort of thing. They can be left-handed or right-handed. And so that you need really complicated molecules for life. And we know also that you want those molecules to kind of wind up the same way so that they can interact with each other. We think this is one of the most basic, most simplified examples of a biosignature, that this is a sign of life in its purest form. So in your own body, you have DNA that's wound the same way. All of your DNA is wound the same direction that my DNA is. You have sugars wound in the opposite way. You have amino acids wound the same way. All of these molecules that are very complicated in your body need to interact with each other. They need to be wound the right way. And we think that because when you have life on a planet, you're going to have a system that needs to interact that all of the molecules there will be wound the same way. And so we talk about, you know, your DNA could be right-handed or left-handed. It could, on other planets, though, be wound the other way. The important thing is that it's consistent. So in the future, you can have friends who have their DNA and their amino acids wound the opposite way from you and your friends, but it would be consistent on their planet. They would all have DNA or whatever their analogs DNA is wound the same way for all of the creatures on that planet. And it would be consistent. So that would produce circularly polarized light. Those molecules that are wound a particular way that are right-handed or left-handed will produce circularly polarized light. As Jamie mentioned earlier, that light that's linearly polarized but twisted in a particular way will be twisted one way or another. So the problem with that is that in the past we thought that this was a very weak signal. It turns out a recent research has suggested, I should say, that you might actually have an enhanced signal. You can have all of these molecules in a single cell sort of like enhancing, like amplifying your circularly polarized light signal. And it might be that if you had a whole mat of these things that you would get a very strong signal. So I was very fortunate earlier this year to be able to go to Yellowstone with a team that had a polarimeter that measures circularly polarized light, that twisted light, and measure the signatures that we get off different microbial mats. These different colors here are all different organisms that live at different temperatures. And we took measurements of these different micro-organisms to see what their circularly polarized light signatures were like. And so this in the future could be applied to exoplanets but in the near future it could certainly be applied to something more local like Europa. You could possibly send a polarimeter to look at the cracks in Europa to see if there's any gross microbial mats kind of growing there just like we find in Yellowstone or in other extreme environments. So once again, there's lots of different ways to use polarized light, linear and circularly polarized light to detect signs of life or even signs that a planet is habitable in the first place, and life as we know it would be happy living there. So we can look at whether or not it has liquid oceans and whether or not it's made of water, whether or not it has blue skies that would suggest it has molecules similar to the molecules in our atmosphere, clouds and gazes, whether or not it has rainbows and made of nice water rain. I kind of touched on this but didn't go into it in detail. We can look for biosignatures, the gases that come off of life from breathing out and burning the hole that might be enhanced using linearly polarized light and then we can look for that circularly polarized light when we have molecules that are kind of twisted and they can twist the light when it interacts with them. With that, I'll open it to questions. You should really ask me questions because I love talking about aliens when I'm drunk. So scientists don't really know that. They're trying to figure it out. There's a few different ideas that have been kind of good is that you have some random orientations to begin with but then once you have life, they have to line up one way or the other. So you'll have slightly more of one than the other and things will just work out so that that takes over because if you have life, things need to be able to line up, they need to be able to combine together in the same direction. There's some other theories that it could have to do with the circularly polarized light of the star that the planets orbit in the first place. It could kind of give it a preference but that's definitely an open question. Blue shirt in the back. So if you look... Sorry, I should be repeating my questions. If you look at a planet that doesn't have life, would you see a bright ahead in the left? That's sort of the idea that you don't really have anything driving the preference until you have life, you have things wanting to reproduce to copy information and to interact with each other. And so if you kind of think about life, how do you want to define it in the first place? Even the most rudimentary idea of life, you might think, I kind of need to have these molecules that can interact with each other and copy their information. I guess that's the most basic definition of life. So to have that, you would really want things facing the right way and that they can interact with each other and be consistent. So I guess you wouldn't have so much. You would have a mixed back unless that process of life has started. I think you're wearing a black shirt in the middle. Just did jump rope through a white picket fence and allergy work to explain circular polarization? I can't visualize it. Yeah, now I have a hard time visualizing it too. Jump rope through a white picket fence and allergy work to describe circular polarization. So you're basically, you're looking at linearly polarized light that's just kind of changing its angle through time. So if you wanted to measure that, you would have a white picket fence and know the time that you're taking the measurements and change its angle through time or if you could take two different angles at the same time. And you would just look to see if it sort of kept its face, if it was what you expected for a twisting over time. Does that make sense? How do the moving glasses filter? How do they filter for it? They measure linearly polarized light, basically. The glasses are measuring. We just started working on circular polarized light so it's pretty nice of you. We had the face changing over time like what's producing it. I would expect it to be constant, but I haven't really thought about what it would mean if it wasn't constant or if it changed in like predictable way through time. I mean, we're sort of just starting to explore that. So part of the science that we were doing at Yellowstone was just kind of trying to get measurements of mats like huge swaths of microbes rather than just trying to look in the lab at a small sample. It's all very new science. Yes, Dan? Goals? No, we have not measured. We haven't detected aliens yet. I would tell you guys. But it seems like doing this study to see if you really do get that sort of amplified signal from something like a microbe, we could use that in the near future as I said for something like Europa, but it's going to be a long way in the future. It's still going to be a weaker signal for circular polarizing. Of course, they're so far away, it's already quite weak. Space shirt? Almost done? Done? Space shirt? Are you using Rayleigh Scattery? Do you only get like a shell on the outside or do you get an average of people out of the sphere? Yeah, I mean, you can't necessarily probe. And that's another... You can't probe the surface. So you're getting information about the top of the atmosphere at least. And maybe some depth. And that can be hard to kind of lay across the atmosphere. You're masking everything below that. You're not getting a signal from below those clouds from the Rayleigh Scattering. So you might just be getting information about the top of an atmosphere and totally blow it. So you'd want to look at like rainbows and stuff like that too to get a more complete picture. Yeah, I can't tell what color your shirt is in the middle. What satellites are looking at them. So this is all super, super new stuff. So we've built a couple of polarimeters that are super sensitive and can actually measure this stuff at least for those hot Jupiter planets that I was talking about. And those so far have just been placed on small telescopes. We're trying to get people to let us put them on something that they're like Gemini or even to put them on space telescopes like Luar. And that would really open things up. We'd be able to get a lot more data over a short period of time and maybe be able to really pin down whether or not we can just have Rayleigh Scattering from hot Jupiter and maybe even start to look at terrestrial planets. They aren't really on any orbiting satellite telescopes right now. But there's a discussion about whether or not they should be included on some orbiting telescopes like what would be the next generation after JWST or whether or not we should include them on things that would probe and go to other places like Europa to look for signs of life and things like that. Thank you. Before I let you all go, just want to remind you our next month's event is October 25th. That's Wednesday at 7pm. Please, before you head out, make sure to bring those trivia pencils back up to the front to our trivia side. Tyler, thank you all so much. Let's give one more round of applause to our speakers. Thank you so much. Thank you so much.