 Can I both do polarimetry? And I'm sure you guys are wondering what that is. It's a special observing method that not everybody uses but is really really cool. So what we're going to do tonight is give you an introduction to what polarimetry is first before we give you our really cool science talks because our science talks feature polarimetry in them and so we don't want you to be lost when we get there. So if you guys are not too drunk yet, you will probably remember in high school learning about lights and learning that it's a wave. And so what that means is that it has an electric field and a magnetic field that vibrates or oscillates or wriggles, perpendicular to each other. So normally light from a star or light from any source is what we call unpolarized. And what that means is that the the wiggles that the light is doing, they're all randomly oriented. So as the light is coming towards you it can be wiggling vertically, it can be wiggling horizontally, and it can be wiggling at every angle in between there. But sometimes something happens to the light that causes it to be polarized. So that just means that it's wiggling in one direction. There's a preferred plane for that wiggle to happen in. And in polarimetry what we're doing is we're measuring that preferred plane and we're looking for light that has been polarized by something depending on what you're something like stars or gas or galaxies or planets. So there's actually two kinds of polarization. You can have linear polarization, which is when it's wiggling in the preferred plane like I showed you before, but there's also a kind of polarization called circular polarization. And you can think of that just like linear polarization, except it's twisting as it's moving towards you. So it's kind of doing this as it's coming at you. The question that must be in your head is why would we use polarimetry anyway? As Jamie was sort of pointing out before, it's giving you spatial information. It's giving you an angle as well as an intensity. So it's the fact that it's wiggling just in one plane is giving you some sort of spatial information. It can help you resolve shapes without or it can help you figure out the shape of things without having to resolve the objects. So we're always trying to improve resolving power in astronomy. And you can overcome some of that issue by using polarimetry. You can null the star. In some cases, stars won't produce polarized light, which is really great if you're trying to look at something dim like a planet. And the most important reason to use polarimetry, Jamie says it's the best thing ever. So what's happening? Why are things polarizing? You're starting with something like a star like if it's sort of the sun or some very simple star like that. That's a source of unpolarized light. And that light is wiggling that electric field that we were talking about is wiggling in whatever direction it wants. And then it goes through an atmosphere, excuse me, the ocean or something like that. It's a magic happens. And then giving you that directional information when you observe it, as well as its intensity. So just to really drive this home, no pun intended, we can think about it in terms of the car. Let's go if you're just sort of measuring the intensity of the light. You're measuring the intensity and its direction, some angular information about the light. So if you think about driving a car, you have a speed that you're going whoops, you have that extra information, which is why polarimetry is so great. You get bonus information that can help you do science. So that's why we use polarimetry. We're going to move on to where would we use it? So we actually use polarimetry, or a lot of us do in our everyday lives. You might use polarized light with your sunnies or sunglasses, and you might use it when you watch a 3D movie as well. Australian for sunglasses. If you go to the beach and you have polarized sunglasses, you might take them off and hold them up, and if there's a lot of glare coming off the water, your polarized sunglasses will cancel that out. It'll erase that polarized light. But because this is directional information that we're getting from polarized light, as well as intensity, if you turn your glasses to the side, it'll let that polarized light through, it'll let that glare that went through, because that's polarized light that's bouncing off the water. So just if you guys want, light from computer monitors and your laptop screens is also polarized, and I have a pair of polarized sunglasses. If you want after the talks and the laptops are still on, you can come up and rotate them. You can see, you'll be able to see at some angles the screen and at other angles it'll look completely black, because it's filtering out all the light. So if you want to, you can do that later. But the other place that you really use this a lot in your life is when you go to a 3D movie. And so Avatar was the first major movie in 3D. Cam and I give it two thumbs down. We had a bus like this, so that's our new movie. And I heard they're just coming, they're coming out with like four new ones. I don't know, they're coming for new ones. But you might also use it in gaming. There are some names nowadays that you can work special glasses for and also do it in 3D. So how does that work? What happens is they project two images on the screen and your glasses allow one, just one of those images to come through to each eye. So there's going to be a filter in front of one of your eyes that lets all of the light that's wiggling up and down go to one eye and all of that, the light that's wiggling horizontally going to the other eye. And in fact if you go to an iMacs movie, that's what's happening. You're using literally polarized light to see the movie. And if you move your head a little bit and tilt it because you're an hour and a half of the movie and you're a little tired of holding your head straight, you'll notice that you'll lose the 3D effect of your movie. You won't see it anymore. It's because your glasses are not lined up with what's being projected on the screen anymore. But if you go to just a regular movie theater and you watch a regular movie in 3D there, they use circular polarized light instead. So one of your eyes is seeing light that is coming at you clockwise and the other eye is seeing light that's coming at you counterclockwise. And so if you go to a regular theater and not an iMacs theater, you can move your head, you can relax, and you can save a few dollars and get a better movie experience. Just a tip. But what do we do in astronomy with polar imagery? We do a lot of things. Basically anything that you can study in astronomy, we're using polar imagery for. One of the things we do is we look at the cosmic microwave background with polar imagery to basically try to determine what the shape of the universe is and where inflation happened a little bit faster and a little bit slower. We look at galaxies to try to determine how the black holes that are in the center of them are oriented and how the jets are compared to the galaxy itself. We can map the structure of the ISM. And so if you, I don't know if people in the back can see it. The interstellar medium. The dust between the stars. Yes. You can see structure in lines in the interstellar medium. And in fact you can also use polar imagery to determine how the little dust grains are oriented and if they're all lined up or randomly oriented compared to other places in the interstellar medium. We study Nebulae around stars to get their shapes. And we also look at stars themselves with polar imagery. You can determine if they're spherically shaped or a little bit oblong. You can better detect material that's in falling onto the central star or material that's being blown off of that star and determine what the shape is of all of that kind of stuff. Right. And we can also study Deirides. So this is, this is planets being formed. You can get an idea of their structure. Which side of them is closer to you. And with planets we can look at their atmospheres and surfaces. We can figure out if they have a blue sky like ours, if they have an ocean on them. And we can even study boring things like comets. This is a picture of Halebop. It's a different ejection events of stuff fluffing off of the comet Halebop, a scene in polarized light. So with that brief introduction to colorometry, we are very happy to take any of your questions about the general idea of how colorometry works before we get into the nitty-gritty of what we do with it. Can you use any telescope to observe polarized light? You could, well you can, yeah, you can use like radio telescopes and optical telescopes. You can look at different wavelengths. Some telescopes are better geared for it. And you need to put something, you need to have like the detector, you need to have a particular instrument called a polarimeter on the telescope, at least for optical telescopes so that you can detect it. In the radio, you just get it for free. Yeah. And you don't have to have a special instrument necessarily like you do in optical. Anyone else? What causes the circular polarization? What causes circular polarization? I mean, I'm going to talk about that a little bit later, but there's a few different mechanisms. Yeah. So, Kim and I don't study the same exact things, but I study massive stars and around massive stars, it's almost always caused by a magnetic field. So you can use circular polarization to map the actual magnetic field structure of a massive star just like we could with the sun, except the sun is a lot closer and a lot easier to do. Yeah. So that makes sense if you were thinking about that first slide that we showed that you have the electric field wiggling and the magnetic field wiggling along with it perpendicular, that a magnetic field, if it's winding things up that it could cause circularly polarized light, but we see it from other things like molecules can cause circularly polarized light. And I'll talk a little bit about that. Eels? Can you determine elements or the material of what you're looking at through polarization? Can you determine elements or the material of what you're looking at through polarization? Yeah, in some ways. I mean, yeah, that's kind of part of the science that we're going to be talking about. So if you have gas, gas is what we call, if you're scattering with hot electrons and hot gas, that's what we call a brain process because it doesn't matter what wavelength you're at. It scatters just the same, but dust scatters differently and there's a wavelength dependence. And so different kinds of dust have different kinds of wavelength dependence, so you could back out information about the composition that way. In the back? So when you're measuring it, you're going to use something that would basically polarize the light itself, so it's like a filter that only lets light wiggling one way. So the way they often describe this is to think of like a picket fence and you have a rope going through it, and you can wiggle the rope up and down to let the waves on the rope go through it, but if you tried to wiggle it side to side and stop it, so basically when we're measuring it, we're taking that fence or something that does the same sort of thing as that fence and turning it at different angles so we can see what the orientation is, what angle that light is wiggling at and see if it's wiggling a little bit in another direction as well. Well, I mean like we can look at the cosmic microwave background. It depends what wave lengths you're using to look at it. I don't want to run too fast. Okay, I'm sorry, that's it. There will be more time for questions in a minute. All right, let's give a round of applause to our speakers. We're going to do a quick round of trivia, so we're going to switch over our slides to our trivia slides. If you've not gotten a trivia sheet and you would like one, please see our Trivias R Tyler, he's up here in the front, and before we let you over trivia out, tomorrow I draw the next month's event is going to be at 7 p.m.