 our first figure today is joining us from out of the news going to say is going to share some very exciting news with you today. Her name is Dr. Jennifer Stobet she got her PhD at UT and she's here to tell us today a bit about where the blame on your finger came from. Join me in welcoming Jen. This slide switcher thing but hopefully this will all work out. So I'd like to welcome you to the October 2017 version of astronomy on tap. I want you to know this is a really relaxed environment obviously eight and five year so in case you have any questions please just raise your hand scream out my name Jen and we'll go through it the best that we can. Okay so the title of the talk is Hitchhiker's Guide to the Galaxy, Money Around the Milky Way and just so you know why I chose this theme. I hope it's not too dated I hope there are some Hitchhiker's Guide fans here. My survey is a big fan too and in fact we have a bunch of software, we have a bunch of databases, all named after the characters that you see here in Hitchhiker's Guide to the Galaxy. So for instance you can see, you go to Github and you can look up Marvin and you will find some of the software products that we actually have. In fact Marvin is just a really nice way to visualize some galaxies. So going a little more, I'm going to take a look at galaxies. Head on over to Marvin. So originally my talk was going to be all about stars. So it was going to be about stars, the Milky Way, and the telescopes that we actually used to observe these guys. So right here I have a photo of Proxima Centauri. Proxima Centauri is what to us. The closest star to us, exactly. And so I was going to have all focus on stars, their characteristics so forth and so on. And then we have a really nice space on you of our galaxy. You can see here is the center of our galaxy where there's a huge black hole. This is the bulge of our galaxy, a very dense concentration of stars. And then here are the disks, our spiral arms. And the location of our sun is just about here. Breathe this out of the way, you know, out from the center of the galaxy. This right here is Las Campanas. If you ever really want to see the Milky Way, you have to head down to the southern hemisphere. It's just absolutely beautiful. Plus the fact that going out to a place where there's not a lot of light, look up, and you'll be amazed by the number of stars that you can actually see out there. So this was my plan. And the one thing I was not going to do is talk about exoplanets. No exo, no plan, nothing, not a zipped zelch, because you guys have had some really wonderful presentations lately about exoplanets, but I wanted to take us somewhere different. And so the only time I was going to mention exoplanets is that they're objects that just work with stars, stars, stars. Five. See? A little over a week ago, there was a tiny, tiny announcement. Some of you guys heard about this. And because of that, we have the LIGO announcement right here. So LIGO, which is the laser, and we actually know what LIGO stands for, how many of these talks have you been to? Laser, the gravity gravitational wave observatory, Virgo and various partners made the detection of gravitational waves from colliding neutron stars. So what you can see right here is that typical, this typical chirp signal right here, both LIGO and Virgo did this detection. I'll talk about that in just a little bit. But since it's one of the few bits of positive news, because let's face back, it's time to put the ball right now. So we got a lot of plus coverage. So the New York Times called it LIGO to text a fierce collision of neutron stars for the first time. CNN wrote, first thing neutron star collision creates light, gravitational waves, and cold. And then New York Times wrote, it was a universe-shaking announcement. So I think my hand was worse at this point. So basically, what happened with this? So no more hitchhikers guide to the galaxy tour, unfortunately. So I'm a stellar astrophysicist by trade. I don't know much about gravitational waves, but I do know a lot about neutron stars. In fact, I'm a big fan. So you guys are ready? Let's go. I'll take you there. So gravitational wave detection. Now, you guys, you've been going to these AOTs. You've probably heard of LIGO talk or two. But essentially, this has to go right to my mouth. Okay, anyway. Essentially, it's two laser-based facilities, one located in the good old part of Washington State in Hanford, as you can see it's a really beautiful area in Washington State. The other part is Livingston. It's a place in Louisiana. And so they use tidal waves essentially to detect gravitational wave signals. And so here's that really stereotypical images that you've seen. The indication that gravitational wave detection has occurred. That's what you see right here. And this is a really beautiful artist rendering of just two not-neutron neutron stars colliding with one another. The detection of the actual signal was made on August 17, 2017. It's given the really lovely name of GW 107817, so something really iconic in the world. So like I mentioned, you have the LIGO facilities first detecting this particular signal, and then you have Virgo following that. So in this particular diagram, you kind of see all the gravitational waves observatories either operational or under construction. There's eventually going to be a LIGO India, which I think is going to be really cool, but all these things really truly help us to do a few things. First, it's signal verification. And second, it's signal localization, so it's really kind of cool. Virgo, thank God, had actually just undergone a major upgrade. So Virgo's been around for a while, but what they did is they updated a lot of their software and hardware components. And just two weeks before the signal came on, they went online. There was something else that was really unique about the signal, and something called Kiladopa, and that actually accompanied the gravitational wave. So, here we go, our first review of the event. Similarly, this really good little music that accompanies it. So what you see here are two neutron stars gravitationally attracted to one another. They're pulled into one another's gravitational wells. They circle around one another, and then they merge. Notice I'm not saying destruct from one another. They merge from one another. Now, there are a couple different possibilities that come out of that merger. It's something that we can talk about just in just a little bit. Anybody want to see the video again? I wish I could sing the music, but I would spare you that. So, here you go. Here, there are orbiting around one another. This is a video from NASA, so these are your tax dollars at work as long as NASA still exists across your universe. So now, what is unique about that signal? What kind of tip them off that this was something unique and new and different, and something that we really need to pay attention to? So what I've gone ahead and done is put out all the various gravitational wave signals that LIGO has received, and I want to show you that this is the one from the recent neutron star merger event. And the very first thing that you can tell, it's longer. Right? It's longer in duration. So here are the black hole, black hole mergers, and here's the actual neutron star gravitational wave signal. Another thing that kind of tip them off is the actual shape of the signal looks like it was coming from two compact objects merging together. So the very shape, plus the duration, said, hey, neutron star merger is going on. The thing about this and the thing that I hinted about is not only do you have gravitational waves, but you have this thing called a kilonova. Anybody ever heard of a supernova before? Supernova is a very huge, powerful, luminous explosion, right? This is the kilonova. What's bigger? A supernova or a kilonova? Supernova is bigger. So kilonova, don't keep it wrong. Kilonova's cool. Okay? Kilonova's cool. I don't want to downplay the kilonova. But it's a little bit less on the explosion scale, if you will, like I'm talking about stars and the universe and the cool stuff. So it's like big bang, okay, some black hole, cool collisions, maybe a few galaxy collisions, but supernova and then kilonova. So there is a scale, just so you guys can know. Kilonova means that we were able to have electromagnetic radiation across the spectrum that a whole bunch of facilities were actually able to monitor. So you can see here on this chart, I have the LIGO facilities, so here are the gravitational waves facilities right here. And there are a bunch of blue dots. And these blue dots all participated in the follow-up of this particular event. So you have stuff on the ground and stuff in space. And just in case you guys don't remember your EM spectrum or your basic medical physics, I just wanted to illustrate it really quickly. So we have short gamma rays, they are very, very high in energy. And they're very, very short in wavelength. And you go across the spectrum from gamma, x-ray, ultraviolet, visible, which is very crucial to us by the way, first for the glass, infrared, microwave, and radio. So radio waves have the longest wavelength and also the lowest energy. So this is just kind of key and just important to keep in mind. But the point is, is you're getting a different piece of information from all these parts of the spectrum. They all help to fill in that positive. So just to give you an idea of stuff that we have on the ground, so here's stuff like Keck, Gemini, Karma, and Ray Bank. And so here again are gamma rays. And here again is radio, so you kind of have like this EM spectrum view and the various actual satellites that observe at these different wavelengths. So for us, Fermi and Swift, we come to like, here's little Hubble and Hubble observes and the visible ultraviolet and infrared, actually. And so this is kind of all of you, all of the facilities that really truly helped to monitor this particular event. So like I mentioned, there was a participation in many facilities and one of the very first to do so was Fermi. So gravitational wave goes off, bam, ours received. And then 1.7 seconds later, Fermi picks up a gamma ray burst. So what's cool about this gamma ray burst? So here you can see the baseline signal, bam, burst. The burst is cool, but it's very short in duration, right? And it has a really truly just a weak signal that I used to. There's another facility, it's a Burmese NASA instrument. Interpol is a BSA instrument, so European space agency. So about 66 minutes later, the world comes online. Again, it sees the same detection right there. Between the LIGO, Virgo, gravitational wave observatories, plus also Fermi and Interpol, they were actually able to locate the source of the signal, at least to a patch of sky, right? This has never been done before. So if they were able to use these types of observations to really locate the source of the signal, and they mirrored it down to about 30 square degrees of sky, this is when the optical observatories come in. So has anybody ever visited an observatory? Okay, great. So first, if you haven't done it, I highly recommend it. Secondly, if you just ever want to be outside looking at the night sky, Unpluted, it's just a great place to go. So this is a place called Las Campanas. It's in Chile, it's in the Atacama Desert, and it's absolutely amazing. I've had a really good fortune that I've visited there many, many times. This is one of the telescopes, it's a one-meter swoop. I know the trend right now is to move to larger and larger telescopes, but these little guys, they're still powerhouses. So they were able to use optical detection, there was a particular pet about 11 hours later, and they were able to see first just through energy what was going on. So what they did is they pretty much said, hey, what are the most luminous, well-known galaxies in the sky and this 30-squared-degree patch, right? Let's just start looking. So they scanned the skies and they were actually able to find the source in NGC 4993, another memorable name. So just to show you the difference, only in the optical, here's a view of this particular galaxy right here on Able 28th. Here it is on Able 17th. You guys see that dot? That dot is the neutron star. Looking within just a little bit of a larger aperture, you're able to see here, here's the dot just one day later, and then on Able 31st, the dot is no longer there. So this two-in-a-bottom explosion lasted for a period of only 15 days. So NGC 4993, just to keep you updated, is a galaxy, but it's not a galaxy like ours. It's not that our spiral type of galaxy. It's an elliptical galaxy, and there's not much star information going on, and it's really heavily bulged on it. Remember that central portion of stars? It's completely dominated by that. So nothing like our own particular galaxy. And in fact, oh, sorry, this is a little dense, but I'll kind of walk you through it really quickly. Not only did we look in, you know, the gamma-ray range, we looked in x-rays, we looked in optical IR. So here's the timeline. So here this axis just represents time. So this is basically, you know, event occurrence right here, and you can see here's the term, right? And this is the several days afterward. You can notice gravitational wave follow-up occurred. The camera, the x-ray, and then radio. So radio is, again, the longest or the shortest of the wavelengths. Pay attention, I'm really looking at that. So anyway, so here's Chandra. Hubble got in on the axe. There's a great paper just based off of the Hubble observations. Here are all of the various optical observations right here. And then even in the radio, they were able to follow this up. But one thing that they were able to make clear with all of these observations is what the explosion actually looked like. That's just fascinating. To have that level of detail on the explosion, it's only possible through all these types of observations just kind of compiling that data together and really making sense of what we saw. So pretend we're here. And this is the line of sight on the explosion. As you can actually see, it was a bit off-axis, a bit tilted away from us, right? And so here's the original jet of gamma rays right here. Here's the kilonewla itself. It's slightly off-axis to us. We didn't receive quite the amount of radiation that we could have in an off-axis like this. So I've talked about all the cool stuff and now I'm going to talk about stars because I love stars, but primarily because this is a neutron star or neutron star we're driven. So again, in the other dense slide, I'm going to walk you through it. There are essentially two pathways that stars can take. There's a low mass path and a high mass path. Most stars take this low mass track right here. It's including our own star, right? There's a huge hydrogen cloud. Basically, it's a protostart in the forms. You spend the vast majority, like your adulthood, kind of existing to the dwarf star. You're doing this. You're burning hydrogen into healing. You're having a great time. Eventually, you get old. You no longer have the supply of hydrogen. You start turning to helium, and it's just not as efficient. So you become a red giant. Our own sun will become a red giant star. Where we currently sit right now will be evolved by the red giant star. So nice knowing you. Eventually, our sun, really true, doesn't have enough energy. There's just not enough to retain the outer layers of the atmosphere. So just cast it off and it all starts to float away. Contribute to the interstellar medium. Our sun lines up a light dwarf. This is the vast majority of stars. Here's the cool stuff. So if you're really high mass, we're talking in the range of roughly 4 to 8 times the solar mass right here. You go through this protostart and the dwarf is super giant. It's really quick. The more mass that you are, the faster you live. So that's the idea. The cool thing is, is that you super the buzz. So remember super the blow into this huge explosion. And if you're at the 4 to 8 solar masses, you become a neutron star. If you're larger than this, you become a black hole. So this is the really cool track that these particular stars actually took and they became neutron stars. But I can't emphasize enough how rare this actually is. So to come across this event is just really, really cool. We have about 4 billion years. So the question was how long the solar sun becomes a red giant? Don't worry, it's not my 30 days. About 4 billion years. So we have some time. So what is a neutron star exactly? Why is it so damn cool? So what I wanted to do is give you a little bit of perspective of what, you know, a neutron star, what the fate of this, you know, North Saint Louis wall, but high mass star actually becomes. So here's the stars. Rigel, Arcturus. Can't read that one. Polyx, sorry. Sirius, and this really little dot is our sun. So here's the sun. Here's Betelgeuse. Sun, Betelgeuse. Sun. Just to make it clear, so there's two things that play here in this diagram. One of course is just diameter and the other is mass. Betelgeuse happens to weigh, or happens to have the mass of the lines of our sun. So Betelgeuse will in fact become a neutron star. But Betelgeuse can be observed from the naked eye. So if you get a chance to get out of here, you'll be able to, you know, just go to the back country, you'll be able to observe it. So when Betelgeuse becomes a neutron star, it will be compacted down to the size of 12 miles in diameter. It is one of the most dense objects that we can observe in the universe. Here's Betelgeuse. Here's Manhattan. Betelgeuse is a neutron star, I should say. It is so incredibly dense that if you took one teaspoon of Betelgeuse's neutron star of matter, it would weigh more than every single person on the face of the earth. These are amazing, amazing stars. So what does that mean exactly if I'm taking something so enormous and so huge and I'm compacting it down? What is the line? That's right, that's right. That's right. It's just amazing to me. Anyway, the idea is that you have this neutron star and it's about still about a little more mass than the Sun, about 1.5 times the solar mass. It's 12 diameters, 12 miles in diameter, right? The actual exterior of the star, the upper layers are solid crust. It's not like the star, right? But don't think it wrong. Light can still permeate and reach us, but it's quite interesting to think about that. And then inside it's just basically a small, it's a hot mess, but everything's so compressed because of degenerate. What degenerate actually means is there are no more atoms. There are no more molecules. Those are all blown apart. It's just like a soup of neutrons. They're just tons of neutrons in the nucleus, down in the center. They think the pressures are so high that your reaction might hit works. So the subatomic level is really, really interesting. And here's just a view of neutron stars. They come in a couple different flavors. One of the flavors is called a pulsar. The other one is called a magnetron. Just absolutely fascinating. So now, if I talk about stars, I talk about elements and there's a reason why. So here's a really beautiful view of the periodic table. And basically, all of the elements that you see here were manufactured in some sort of way by stars. They're just a few exceptions and I'll get into those in just a second. But every single thing, everything that makes us up, everything that makes up the mentions, the beer thing kind, everything came from the stars. And so there's this really lovely quote from Carl Sagan, he says, we are made of star stuff. So if you get a chance, just go ahead to this website. It's right on your board, just click on stuff. You get a really nice introduction to all of the elements. I'm going to switch stuff on just a little bit. I'm going to flip this switch just a little bit and start talking about where these guys are actually made. And so this is from a friend of mine, Jennifer Johnson, and she wanted to really take the periodic table and actually make. Let me just kind of draw this and diagram it out. And so remember I mentioned those few stars that are the exceptions? It's these guys Hydrogen, Helium and Lithium. These guys were made in the Big Bang. All the Hydrogen that exists today, everything in the water, everything in the beer, comes from the Big Bang. So that's happening. I'm not in stars. But everything else, comes from stars. So things like War on, Carbon, Nitrogen, Oxygen these things all come from stars. They're stars that die that massive supernova death and they can make elements. They're stars that are white dwarfs and do something called a Type 1 Supernova that I can't get into. They can do stuff. Now just out of curiosity, I'll give you five seconds to answer this question. If there's anybody who can tell me what that is, I will bite you here. This one right here. Alright, shit, I go here. Get on that promise. I swear I won't. But anyway. So this is just kind of a diagram showing you the source of each of one of these elements. So here's my friend, Dr. Jennifer Johnson. We've been friends for longer than I could care to tell you guys. But the thing is this emerging neutron stars that it was just a hypothesis. I'm hoping that this was the case. What we didn't know for sure. So at this point, it was just your speculation. And so remember this vid? Here's CNN. They said, Neutron star, great. Cool, right? It's kind of like clickbait for sure, right? So... This is going to be the most technical slide that I have, but I'm going to justify their statement right now. So first, I'm going to go ahead and talk about here's the galaxy at GC4993. Here's that Exit, no, sorry, that Kilanova event right here. And the very first thing I want you to notice, so here are the dates, on August 17th and August 21st. So just four days apart. The first thing is it appears blue, right? And then just four days later, it's a bit red. Not just that, it's dimmed a bit. So this is a really fast occurring type of event. So we're focusing all of our telescopes and all the various scans on this particular event, trying to record as much information as possible. So this is a really nice plot from Drowden and all. And it's coming from that lost components of derivative that I was talking about. So there's a bunch of stuff on this plot, but I'm going to go ahead and try to dissect it really quickly. The first is apparent magnitude. So that's just basically a.k.a. brightness. The second on the x-axis right here is just time from the merger. So it's just basically a timeline. And what you see is a bunch of numbers here. But this is the bluest of wavelengths. This is the reddest of wavelengths up here. So you're going from almost near UV up to really deep near infrared right here. So you're looking from blue to red. And the things that they notice is, you know, yeah, at first there's there's a bit of blue radiation, right? Like light, right? But it very quickly dissipates. So again, this is showing, but with real data, we're looking at these various photometric band passes, right? These various wavelengths of light saying, hey, can I get blue or get red? Why does this mean you can do anything to me? I'll tell you about that in a second. So not to be outdone, the theorists got into the act and they're like, ah, I have an explanation for this. It actually turns out this time you're going to be right. But what they try to do is say, hey, here's this light curve behavior. What could possibly be contributing to that? And so if you go back and look at this picture, it's real clear. So remember when we were talking about these elements and the ones that are made in emerging neutron stars? These guys are primarily that they're called the lanthanides. And so, whoops. So what the theorists did is they said, hey, they took this series of lanthanides and they buried the actual concentration of what they expected to come out and be ejected from this kilonew event. So the two neutron stars work and then they eject stuff. And what is actually that eject they're made out of? And so they started with really low concentrations and then they pre-kept on increasing to very, very high. And then as you can see, so here again there's just a timeline, day since merger. This is basically brightness right here. The brightness actually changes with the concentration of these elements. Same idea here, right? Looking at the UV, the obstacle in the red. Based on the concentration of these elements, the light curve actually looks a little bit different. So they came up with a really nice cartoon. And in this case, it turns out to be really kind of blue and really kind of bright. What they show is that here's the actual neutron star merger event. Now, here's the thing I want to point out to you. Just because these guys have merged doesn't mean there's not anything left. They can merge and actually become just another big blue neutron star. But anyway, in this case, the light that comes out is very, very blue. The only way it's blue is if you have a high concentration of these elements. So like silver, cadmium, indium, and tin right here. But if the light is more red-focused, more red in appearance to us and our observatories, it really contains stuff like this. Platinum, gold, mercury, lead, and bismuth. And it turns out, as you guys remember, when I showed those two diagrams, this particular X and the red went from blue very, very quickly. To red. And it stayed red most of the time. So fence. We've got a bunch of gold in our hands. This particular event took place 130 million light years ago. I do believe that is a true big question just in case you guys want to know. And so 130 million light years ago, thanks to this particular supernova, gold and platinum were being produced. So the cool thing is it's a really wonderful thing just from a month and a half ago, a couple months ago, is that we found out that neutron star marches do make elements your rights. So, hello. Now, I know I'm probably over time because that's what I do. So, and we're very sorry about this. I hope you guys don't mind me going over. But there's just a couple things I wanted to do and just kind of bring it back to our original theme of Hitchhiker's Guide to the Galaxy. And so there's just a few quotes. So there's a moment never done when life floats. There's the possibility of magic. Creation holds its breath. And in this case, we held our breath. The neutron star merger. We got some really good shit out of it. And this is my actual work which I will not go into because I do not have enough time. But maybe next AOT. But basically, this is my experiment. And so my experiment works in the near-infrared. So if you guys kind of kept in mind, there's, you know, these X-rays, UV, you know, optical infrared microwaves and radio. So that's the spectrum, right? And I actually work in the near-infrared. And so here are two edge on use of our galaxy. And here's the Milky Way in one in the near-infrared and the Milky Way in the visible. You guys, can you see the difference? The near-infrared is really able to penetrate all of this dust and crap into our Milky Way galaxy. So we have a beautiful view on the galaxy we're really able to see directly along the midplane and actually into the center. And so, I will leave you with this quote. I hope you enjoyed it. And thank you very much. We have time for a handful of questions. Please stand up and project as loudly as you can with the questions that you have to join. No questions. There was one screen that showed there were satellites that detected something. One was like 16 seconds after the event and one was an hour. So this is different parts of the event, right? This is not catching the same data? Or how does that work? So it's a really good question. So basically this is just typing your satellites and making sure that they come online or open and receptive to the signal. That's the way of putting it. That it's kind of the truth. So for me, which had to be positioned so that it received the signal almost simultaneously right after the gravitational white event, integral is also an array of territory also in space. But they were able to come online and look at the signal 66 minutes at least be able to process this signal. That's probably the issue. Well, it's not necessarily that the way the gravitational waves are actually received or gamma rays are actually received. They're strong enough to trigger the detectors. It's more like being able to process, download and understand that this is what was going on here. But really the question is things. Alright, I saw another potential question here. So my question was why is it very important that the gravitational waves receive pretty much the exact same amount of data? So the question was why is it interesting that gamma rays and gravitational waves pretty much accompany one another? And that basically just said to us hey, this is a compact object event. That's what that indicated. So because we have gravitational waves, black hole, black hole mergers would give off gravitational waves. But there's no accompanying other electromagnetic radiation. So once they got this signal and they all kind of do it and they localize it to one area of space and it would wrap up. This is a compact object event. Easy to answer. So the question was how the hell do we know what neutron stars are actually made out of? It's a little bit of physics, a little bit of astronomy. We roll it up together and you kind of get the answer. But the idea is since we're able to understand both density and pressure we're able to extrapolate into these regimes what the actual structure of the star would look like. Now some of this is hypothesis, but we use another tool called spectroscopy. And spectroscopy essentially breaks apart the life. We saw some of this spectroscopy actually featured in some of the diagrams that we had. But that gives us competitions. That gives us concentrations. It's also able to give us densities. So we put all these pieces of puzzles together and just kind of understand hey, this is probably what this is supposed to. It is conjecture some of it. Like when I said a bit about the quarks, there's a bit of conjecture right now. But the apparent densities and pressures in this particular regime say hey, this is probably the existing and still intact at these particular pressures and densities. Thank you. So what is the crust of the neutron star? Why is that different than your interior? It's a good question. So hold on. Let me bring up my little cartoon diagram real quickly. So the thing is what I didn't talk about is that when you have something that's supernovae, the star that's supernovae, at this point it's actually made a lot heavier elements. So I only talked about hydrogen and aluminum, really. But when you have these massive stars you have this kind of fusion and nucleosynthesis going on, this element manufacture that starts to make things heavier and heavier like carbon, oxygen, magnesium, silicon, so forth and so on all the way up to iron. And it turns out iron is just a no-win process. It's just this that's a bad word. But anyway there's just no trying to fuse iron, a star can't do it and then bang on that supernovae. A lot of the outer layers are actually expelled from the interstellar medium. But what's normally left and captured by gravity is carbon and oxygen. There might be a little bit of neon and there might be a little bit of silicon but the primary composition is carbon and oxygen and that actually is what resides in the surface. That's what's really still able to remain intact right there and that's actually what emits and permits light to watch this carbon and oxygen from these guys. Everything below this is stuff that is just completely broken apart not even in atoms just kind of coming out in this kind of neutrality sewer basically. So obviously I know that happened in the past but how did we know that it was going to happen or how do we know to look in that area or to turn on all of our equipment to face it there to read all of the data? Good question. So essentially LIGO picks up anything. It is almost omnidirectional but that would be an okay way to say it. It just picks up everything from gravitational waves. What was necessary is to have a LIGO facility in Washington a LIGO facility in New Louisiana and then one in Virgo and the time delays coupled with a bit of additional information actually allowed for localization in the sky. We just keep those suckers on we're just waiting for a really cool day to come in. Join me in thanking Jim one more time.