 And since I appear to you just as a little tiny head in a corner of a screen, I thought I might appear as a slightly bigger head in front of the screen and just tell you a bit about myself before I jump into telling you about what I do and some of the things that I find exciting. So I am a radio astronomer, which means that I use telescopes like the Parkes Telescope that you can see in the center of your image there. And the Parkes Telescope is often called the Grand Old Lady of Radio Astronomy. It's a 64-meter dish. And I tend to joke that I went into radio astronomy because I like big toys and there's not much that's bigger than the Parkes Telescope. But the telescope on the bottom left-hand corner in China is quite a bit bigger. It's a 500-meter telescope. So if you can imagine the size of your swimming pool at the Olympic pool, multiply that by a factor of 10. And that's how big that telescope is all the way across. So I spend my days and nights using radio telescopes in order to study both our own galaxy and our galactic friends, the Magellanic Clouds, that I'm going to tell you a little bit about tonight. So it's often said that every star you can see when you look up in the sky is part of the Milky Way. But that's not quite true. In fact, some of the stars that we see are part of the Magellanic Clouds, which were first written down by Magellan when Magellan came into the Southern Hemisphere, although they've been known by Indigenous cultures in the Southern Hemisphere for many, many, many tens of thousands of years before that. So the Magellanic Clouds are these little blobs of gas that we can see in the left-hand side of the image. So we see in this image that are you not able to see my slides? Sorry, okay. Make certain this is sharing my screen. Hopefully you've got my slides now. Okay, so hopefully we've got slides now. Sorry about that. I assumed that they were there, but now you are. So now you can see this wonderful picture of the Parkes Telescope. So the Parkes Telescope in the center here, the 64-meter telescope, and on the left-hand side is the fast 500-meter telescope. So these radio telescopes, they look sort of familiar to many of us because they look like satellite dishes, but these are much more sophisticated and looking much further out into the universe than your typical satellite dish. So the beautiful image of the night sky, which you didn't have the pleasure of seeing, but now you can see, is this is taken in one of the East Ocides, European Southern Observatory site for the very large telescope. And you can see the band of stars that stretches across the bottom of the screen there. That's the Milky Way, but the little smudges of stars that are on the left-hand side are the large and the small Magellanic clouds. And you can, if you are lucky enough to live in the Southern Hemisphere, you can step outside and see them on some nights. And they tend to look like clouds, which is why they got named that way. So you might think, oh, there's just a bit of cloud in that otherwise clear sky, but in fact, it is a nearby galaxy. So what is a galaxy? Well, a galaxy is a cluster of billions or millions of stars, millions, billions, even trillions of stars that are all joined together as one kind of grouping. And our galaxy, the Milky Way, is part of the local group of galaxies. So the local group of galaxies is all the galaxies that interact with our own galaxy. The Milky Way is the big fellow in that room. It has the largest amount of mass. And near to us are a couple of little dwarf galaxies called Canis Major and the Sagittarius Galaxy. The Sagittarius Galaxy is kind of pathetic. It's about 50,000 light years away from us. And it's pretty much old and red and dead. And it's not a terribly exciting galaxy. But if we step a little bit further out from the Milky Way, we step out to about 180,000 light years, we come across the Large Magellanic Cloud. And the Large Magellanic Cloud is about 30,000 light years in diameter. It's much smaller than the Milky Way. The Milky Way is more than 100,000 light years across. And then next to it is the Small Magellanic Cloud, which is kind of its friend. So when I said this talk was about getting to know the neighbors, if we've just moved into this neighborhood, we've landed on Galaxy Milky Way, you might want to go next door and see who's there and find out a little bit about them, find out whether they're interesting or whether they're going to be messy or noisy neighbors. And so hopefully through this talk, you'll get an idea a little bit about who is part of the the neighbors, who the Large and the Small Magellanic Clouds are. So there are a number of other galaxies that we can see through the local group. And this image here is meant to put them in the kind of relative sizing that they would look like on the sky. So the Milky Way is enormous, it's the enormous big spiraling, swirling, twisting bit of gas and stars on the bottom left. And the Magellanic Clouds sit off on the right hand side and you get an idea of the sense of scale on the sky relative to us. So the Large and Small Magellanic Clouds are nearest interesting neighbors. You might think of Draco and Sagittarius as kind of just interlopers, they've just dropped in, but the Large and Small Magellanic Clouds have been in the neighborhood for a while and they're kind of interesting ones. They have a lot going on. So the next door neighbor, the Large Magellanic Cloud on the left hand side there, about 180,000 light years away, it's interacting with both us and the next next door neighbor, the Small Magellanic Cloud, which is about 210,000 light years away. And what we're looking at when we're looking at these images of these galaxies are all of their stars and also a lot of the gas that exists in those galaxies themselves. So the big reddish purple regions, that's some of the hot gas that surrounds the very massive stars. And the kind of blurry bits that you can see, those are all the stars that sort of add up together to be one kind of smudge of stars. So the Large Magellanic Cloud is about 10 billion solar masses. So that means it's about 10 billion times the mass of our own sun. And the Small Magellanic Cloud is about six and a half billion solar masses. Now for comparison, the Milky Way, our own galaxy, the place where we live, is about one and a half trillion solar masses. So it's a lot bigger. It's almost 10 times, almost a thousand times bigger. It's a much, much bigger galaxy. And it kind of bosses these two little ones around. And so in fact, the the SMC and the LMC do interact with the Milky Way. And they interact by gravity. So the two little galaxies orbit around each other spinning around and their gravity pulls on each other and transfers a bit of material from one to the other. But then the whole pair of those galaxies is orbiting or coming into orbit around our own galaxy, the Milky Way. And a lot of the material from those galaxies is being pulled away by the gravity of the Milky Way, which is so strong compared with those two. So my field is not to look at stars, but to look at the stuff between the stars. And I personally think that it's much more interesting than the stars itself, because this is the stuff from which the stars form. So it's like the seeds and the dirt to make the stars. And it's also the soil to which they return when they die. So the interstellar matter is a very interesting part of galaxies and contains a lot of the clues about how galaxies are built up and how they lived their lives. But it's only a tiny fraction of the mass of the entire galaxy. So interstellar matter is about 10 percent of visible matter in terms of mass. And it's very, very low in density. It has densities that are anywhere between 0.001 to up to a million particles per cubic centimeter. So imagine a cubic centimeter. It's a little tiny box, one centimeter on a side. And inside that, you might be lucky to have a million atoms, but more likely you have one atom, only one atom. By contrast here on Earth, the atmosphere has 10 to the 19. So that's one with 19 zeros after there, molecules in every one of those cubic centimeter boxes. It's enormously more dense just in the air around us rather than the entire interstellar gas. And if you went from here to the nearest star with a butterfly net the size of a football field, you get a gram of material. So there's not very much of it. But it's exciting stuff and I'll show you why. The most abundant atom in interstellar gas is hydrogen. So hydrogen is a very, very simple atom. Physicists like me, we love hydrogen. It's very, very easy to understand. It's just a proton and electron. It's very simple. And it produces a little radio channel. It has its own radio channel at 1420 megahertz. So it produces just exactly at that frequency a little bit of a radio signal that we can detect with our radio telescopes. And the great thing about it is that if that hydrogen is moving with respect to us, if it's going away from us or it's coming towards us, it's Doppler shifted. And that means it changes its frequency just like the siren of an ambulance going away from you or coming towards you. It's pitch changes and that's by the Doppler effect. The same thing happens to the atomic hydrogen line. It's frequency changes. And so the frequency moves just a little bit. And that tells us about the velocity of the gas as it's moving with respect to us. So how quickly it's moving away from us or towards us. And we use this powerful technique to be able to understand how galaxies are rotating. And that tells us about how much matter is inside the galaxies that allows us to weigh galaxies. It also allows us to look further and further back in time and tell how far away something is by looking at its redshift. And it can also tell us just a lot about how things are moving inside a galaxy. It's a way of tracking things like we track the wind speed on the earth or how clouds are moving around. So we can detect the hydrogen gas with a radio telescope. And radio telescopes are a wonderful things of beauty, not the least because they can operate during the day, which is a wonderful thing if you happen to be an astronomer. It means you don't have to spend all of your nights observing. But the other thing about looking for atomic hydrogen is that the wavelength of the radiation that we're looking at is about 21 centimeters, which is, you know, a reasonably big size. And that goes through clouds and rainstorms and doesn't care about most of the weather. So one of our great new tools for being able to study the atomic hydrogen distribution in galaxies is the Australian SK Pathfinder. So this is a brand new telescope that's being constructed in Western Australia or has been constructed in Western Australia. And this is an image of it here. It's out in the middle of nowhere, quite literally really the middle of nowhere. There are about 250 people in an area the size of the Netherlands where this telescope is. And the telescope extends over about six kilometers or closer to eight kilometers. And it's made up of all these little dishes. And each one of the dishes has this very clever little camera on it. And this camera is a called a phased array feed. So the phased array feed is sort of a multipixel camera, like your camera on your phone or your iPad, which can see number of megapixels. This one has a number of hundreds of pixels. And it allows us to look at hydrogen much faster than we ever could before. So why would we care to look at hydrogen? Well, when we look at hydrogen in a galaxy, we get a very different view than we do when we just look at the stars. So if you look at a galaxy like M51 here, the center image is the optical image. That's what we see with our eyes. And that's what most of us are used to seeing a beautiful Hubble space telescope image of the galaxy in optical. And that shows us where the stars are and where the stars that are kind of boring stars like our sun. But if we go up into the ultraviolet to the right of that optical, it allows us to see the really hot stars, the really big massive stars that are 10, 15 times as massive as the sun. And they're quite powerful stars that live fast and die hard. If we go all the way up into the x-ray, we can see gas that's 10 million degrees in temperature. And it looks quite different. The same galaxy on the right-hand side looks very different than it does in the center. And if we go the other direction, we go through the infrared, which allows us to see smaller cooler stars than the sun and also dust in the galaxy. And all the way down into the radio where we can look at hydrogen gas and look at the stuff from which the stars are built. And whichever wavelength you choose, the galaxy looks quite different. So what happens if we look at our Magellanic friends? So this image shows the small Magellanic cloud, which is on the left hand side just shown in the stars. This is from the Gaia telescope. And it's got a bar-like structure across it. So it's sort of a long linear feature that's made up of stars. And we're looking kind of at the edge of the galaxy along it. Like little blobs that are off to the top above it are actually things that are in the foreground closer to us. So you look at it in the optical and the stars and, you know, it looks like a bunch of stars. It's kind of a blob. It's okay. But if you look at it in the dust, like the middle one, this is looking at interstellar dust, things between the stars that are in red there. And this is warm dust. It can be maybe well, it's warm in the sense that it's maybe minus 150 degrees Celsius. And some of the stuff that's greenish there is quite cool. That's all the way down to minus 260 degrees Celsius. But the minus 150 degrees Celsius, that's quite warm by interstellar standards. It's not too bad. It's pretty cold out there in space. And if you go over to the right hand side, this is where we get to really warm gas. This is gas that's about 10,000 degrees. And it shows up as these hot regions around stars in purple and then the stars themselves. But if we take our radio lies and we look at the atomic hydrogen, we get quite a different view. So this is an image that we made a couple of years ago using that new telescope, the Australian SK Pathfinder in Western Australia, to look at the atomic hydrogen. And you can see it looks kind of similar to the dust in some ways. It's sort of a triangular shape, but it has a lot of interesting bits that come off of it, fluffy things around it. And I said that one of the great advantages of looking at atomic hydrogen is that it allows you to look at the movement of the gas. So when you're looking at atomic hydrogen, you can measure its velocity moving away from us. And then movie that hopefully you're seeing there is a movie which slowly steps through this galaxy by its velocity. So what we get with atomic hydrogen is not just a two-dimensional image on the sky, just a flat picture of all the stars or all the dust. But we get a three-dimensional image where we're seeing the image on the sky, but then how that different parts of that image are moving with respect to us here on Earth. And that allows us to really understand what's going on inside a galaxy. How does the gas move to form new stars? How does stars blow the galaxy apart and suddenly tell a lot about the the galaxy by looking at the hydrogen gas? Now what about the large Magellanic Cloud? So the large Magellanic Cloud we can see on the left here as looking in the stars. So this is an image made with the Vista telescope of the European Southern Observatory in Chile. And you can see we have a sort of bar-like structure with some edges around it. But when you look in the dust it looks really, really different. It looks quite more extended, much more sort of circular, flat-on thing with big huge gaps in the dust which are filled with hot gas. And then on the right hand side it looks kind of like a mixture between those two. You can see where the stars are from the left hand side image, but you can also see where the purple blobs are and that's where the very hot gas is. So when we look in the atomic gas, again it looks a lot like the dust. So this is the atomic hydrogen gas made with the Australia Telescope Compact Array. And one of the things that we'll be doing over the next year is to go back and visit this galaxy with the new Australian SKA Pathfinder and look at it in much greater detail than we were able to see in the past. And it's like we're getting a whole new set of glasses moving from those glasses that don't really work and you're seeing everything blurry to really ones that are perfect prescription for your eyes and everything comes into sharp focus. And so I can show this image here of what we think the galaxy looks like, but what we'll know in a year's time will be way, way much better. So I said that the hydrogen gas tells us a little bit more about the galaxies and I showed you them individually, but what do they look like all together? The two Magellanic clouds together. So this is an image of the southern sky from in the optical and it looks kind of like what you would see if it were a clear night where you were in the southern hemisphere and you stepped out the side, you'd see a band of stars that would be the Milky Way, but you probably wouldn't see the Magellanic clouds very well. But if you go a bit further out to someplace where it's nice and dark, you would see the band of the Milky Way, which stretches across the sky there. And the two smudges of the large and the small Magellanic clouds, which are quite close to the center of your image there. But if you put on your hydrogen eyes, you see that those two galaxies, which look like they're just sitting separate from each other, the large and the small Magellanic cloud and separate from the Milky Way, are connected together with a band of gas. So the blue gas in the center, those are the large and the small Magellanic clouds and they're connected together with hydrogen gas. And furthermore, there's actually a whole tale of gas that streams up to the top and that's called the Magellanic stream. And this Magellanic stream of gas is the evidence that we have that these clouds are interacting with the Milky Way. And the band of gas that's between those two galaxies is the evidence that we have that they interact with each other. So by moving around each other, they're pulling gas off of each other and by moving around the Milky Way's halo, the Milky Way is pulling gas off of them. So you might think of them as rather untidy neighbors. They're the sort of neighbors you don't really want to move in next to because they throw their stuff all over the place. They've got their bits and bobs all over your garden and the next garden over and they're really causing a bit of a mess. So the Magellanic stream is shown here on the bottom of this image of them around the Milky Way. It wraps almost entirely around the Milky Way. It goes about 200 degrees on the sky. So it goes a long way around the sky. And it has about 800 million times the mass of the sun in gas spread out there. This was first discovered in the 1960s, but nobody really knew exactly what it was until the mid-1970s when Matthewson discovered that it was actually connected to the entire bits of the galaxies. And recently, about 10, 15 years ago, people mapped out the orbits of the Magellanic clouds and realized that they were only just coming into the Milky Way for the first time. So this is their first passage into the Milky Way. And yet the Milky Way has pulled the gas apart off of these galaxies most spectacularly. So you can just shift this around and look at it a different way. So the band that strips through on the left-hand side is the Milky Way. Plunging down towards it are the large and the small Magellanic cloud with this trailing bit of material coming off of the right-hand side and creating quite a mess around our neighborhood. So these are messy neighbors. So we've been wondering for quite a while how to explain all of the gas that exists around the Magellanic clouds and in the Milky Way's halo from the Magellanic clouds. It's quite difficult to pull off all of this gas and distribute it around the Milky Way. But just about a month ago, there was a new paper published with a set of simulations which show the gas of those galaxies in flowing. So the movie that you can see is a simulation designed to reproduce the observational information that we have on the left. So in this simulation they take the large and the small Magellanic clouds and they orbit each other and they drop those in to the Milky Way and the Milky Way pulls the gas off of those galaxies and makes the mess. So in fact it's not really the Magellanic clouds fault that they're messy neighbors. It's really kind of our fault. We pulled all the stuff out of their house and draped it all around our houses. So I'll just wrap up here with a couple of final points. So this image here is looking through the Azcap telescope with the nice camera that we have mounted on the Azcap telescope. And you can see in it the large and the small Magellanic clouds on either side of that white bar there. They are our closest living neighbors. There's a couple of other neighbor galaxies that are only just barely alive but these are very living active galaxies and they're about 200,000 light years away. They're pretty tiny. They're about six to 10 billion times the mass of the Sun and by comparison the Milky Way is one and a half trillion solar masses so it's a much bigger beast. They're flinging their stuff all over our garden. They're leaving their hydrogen gas all over the place and we can see it almost entirely around the sky of the Milky Way. And eventually this is one of the most fascinating parts. Eventually the Milky Way will buy them out or consume them is another way of putting it. And the Milky Way will gravitationally pull these galaxies in so that we pull all of the gas off of them and they merge in with our galaxy. And over the history of the universe this is how the big galaxies get bigger. They buy out the little ones by causing them to merge in and the Milky Way is a big galaxy for a reason. It does exactly this. It consumes other galaxies. It has consumed them in the past and it will consume them in the future. So I'll leave that summary up there and I can see I've got a bunch of questions here so I'll try to answer some of these questions. So hopefully I've convinced you that these galaxies do interact. Now we can get the mass of a galaxy. I've got a question. How do you get the mass of a galaxy? And one of the ways that we get the mass of the galaxy is by measuring the rotational velocity of gas in the galaxy or stars in the galaxy. And by seeing how fast it goes around we can use laws of physics in order to estimate how much matter is inside the orbit in the same way that we can tell how massive the Sun is by how quickly the Earth is going around the Sun. Then we can use that same process to understand the mass of a galaxy. So in terms of understanding studying interstellar matter the question is how do you study it if you can't reach it? And this is one of those great frustrations of astronomers that we have to sit here on Earth and try to figure out what's happening out there without being able to go to it and measure it. But we have these wonderful little signals that we can use and for hydrogen it's this particular spectral line this particular radio channel that hydrogen produces that allows us to know that it's there and to put it all together and figure out how much is there. And we can figure out how much is there so how do you measure the density of it. We can tell how much is there by looking at how strong the signal is. So if we see a really really bright spectral line then we know there's a lot of hydrogen and if it's very weak then we know there's not very much out there. I have a nice question about what made me decide to research the LMC and the SMC out of everything that's out there and I think that's a great question because as you know the universe is filled with an immense number of fascinating things to study. But I chose the SMC and the LMC and indeed our own galaxy as well because they're things that all of you everybody who's not a professional astronomer can relate to. They're things that you can see and I think it's more exciting in some ways to be able to look at something that all of us can access and then to be able to try to delve into the details of it and understand it a bit better and try to explain it to other people. Okay lots and lots of questions. So the gas that we're talking about is not quite a plasma. I have a question is this a plasma and it's not quite a plasma. A plasma we tend to use to refer to as a gas where the hydrogen has separated at least an interstellar space we use it that way. So the protons and the electrons are no longer together in an atom but if they're in an atom then we call it atomic hydrogen gas and that's where that comes from. There's a great question about how do you create an image from a radio telescope if you're only detecting the signals and I could give probably well I do give an entire course on this but what we look for is we're measuring an electrical signal of voltage from our telescopes and we look at every single position on the sky and then we see if we have more voltage or less voltage and we can put those together to create an image but it's quite a complicated process but we've mastered it over the last 70 years of radio astronomy almost 80 years of radio astronomy so that we can make beautiful images to rival some of the ones that we see in the optical. So yes and is there an estimate of when the Milky Way will buy them out meaning they're large in the small Magellanic clouds. There are rough estimates of this it depends a lot on exactly how massive the Milky Way is which believe it or not is something that's not completely decided but we're looking at billions of years before we actually merge the large and small Magellanic clouds into our own galaxy. There's a question are there planets in the Magellanic clouds and that is a wonderful question we don't know is the answer we don't know yet. Finding planets is very tricky and it tends to be done around the closer stars so these stars that are much more distant it's harder to look for the the signal of planets around them but from what we do know about how planets form I think we would guess that there probably are planets around at least in the large Magellanic cloud but they would be quite a bit different than the ones that we have here because there's a very different kind of dust in those galaxies. So if you looked out right now would you be able to see a galaxy we would definitely be able to see our own Milky Way as a galaxy and if you had super eyes everywhere you look your eyes would cross a galaxy but those super eyes are things like the Hubble Space Telescope eyes that can really look very very very far out but if we looked out right now well in Canberra I don't think we'd see anything that's been raining today and certainly we won't be seeing the large and small Magellanic clouds just just yet. Now let's see another question can tell us the infrared wavelength used for dust images so there's there's quite a few wavelengths that are put together but they're one of the ones that we look at often is about 150 microns so 150 micrometers and that gives us a good handle on a lot of the sort of warmish dust. Now what other questions are there that I can pull out here? Ah what keeps the earth spinning? Oh boy these are tough questions. So the earth is going to slow down eventually but it doesn't have to there's nothing to stop it immediately. So as bodies like galaxies and planets form they form by material that circulates inwards comes in a nice sort of spinning in fashion and that spinning in fashion puts some spin into the planet initially and it just keeps on going and doesn't slow down very quickly so there's nothing required to keep it spinning up but there's not a lot that makes it slow down. Other questions to pull out here? What is it about the stars that impresses you? How can I make images of explosions thousands of years ago relevant to my students? That's a very good question. I think you can make things relevant by talking about the atoms that come from explosions and stars and how those atoms come and find their way into us but not just can you make it relevant you can make it cool right? Big explosions we're talking about massive kinds of explosions and relating those explosions the types of stuff supernova explosions that we see in galaxies are much much more powerful than atomic bombs or any kind of explosions that we have here and it's usually easy to get things going kids interested when you talk about things exploding. And I'll just wrap up with a with a final question. What is the most impressive thing that you've seen in space which I think is a fun one because we can we can talk about our our own impressions of things and for me the most impressive thing that I have ever seen was the first time that I made the image of the small Magellanic cloud that I showed you earlier because I've worked really hard we'd worked for years planning to do this and we put the data together and made this image which showed that the galaxy was incredibly dynamic that gas was flinging all over the place and moving in different directions and to me that really was quite exciting.