 Now, I will begin today by talking about explosions and collisions in space. It's one of my favorite things. It's one of the... It's not as dangerous as it seems, but there is a lot that happens in our universe, and we're going to explore that this morning. And firstly, we have to start near the Earth. Now, this is kind of an artistic image by the European Space Agency that maybe you're not usually familiar with, and this is Earth with all the satellites around it. Yes, there's a lot of satellites out there. There's over 6,000 satellites in orbit, more launched every day. Definitely every week. One of the problems that comes with launching satellites is that at some point, eventually, they run out of fuel and they can turn into space junk. And space junk is stuff in space that is human-made, artificial, that we don't have control over, and these things can crash and collide. In fact, in 2009, we saw the very first crash between two satellites. So over Russia, there is this Cosmos satellite, which was a Russian satellite, that they had lost control over, and this crashed into an iridium satellite phone satellite, and this produced thousands and thousands of pieces of debris, almost 10,000 pieces of debris. It was a very large crash or collision in space. And we do worry about this happening. In fact, in February, there's a near-miss between a satellite and an old space telescope coming within a few meters of each other, which in space terms is pretty close. So we do worry about these things. In fact, just two days ago, in the International Space Station, they had to do a maneuver to avoid a piece of space junk, and that was the third such maneuver that they've seen. If you've seen the movie Gravity, where it collides and, you know, we all win because George Clooney turns into space junk. Just kidding, but he does. They were trying to avoid something like that. Not as spectacular, obviously, but they were trying to avoid these impacts, because these impacts and collisions do happen. On the left here, in fact, is an image of glass from the space station, and that hole, which is centimeters deep. So glass in space is bulletproof, right? Because you're traveling into a very harsh place, lots of things. You want to make sure you don't explode, ultimately. Now, this hole was centimeters deep. A piece of paint, a flake of paint created a hole centimeters deep in this bulletproof glass in space. So that is a big collision that it can happen. One of the things we are doing at Mount Stromlo is with electro-optic systems, part of the space environment research center. You may have seen a talk about this this year. We use this laser firing out of one of the domes to track the space junk, track things down to the sides of a couple centimeters, and a new laser that will come online to actually remove that debris and actually burn it up by steering it into the Earth's atmosphere. So really cool post-technology, but collisions do happen in space. But there is another collision, and you may be surprised, and that is the moon. When you look at the moon, it's very beautiful. We obviously like to look at it. Firstly, I think people are surprised how big the moon is. If I were to ask you how big the moon is. Is it bigger, smaller, or about the same size of Australia? What would you say? Well, the answer is it's about the same size as Australia. So here's a picture taken of the far side of the moon. So there isn't a dark side of the moon. There's just a far side. So there's a side that we can't see, but it does get sunlight, as you can see here. And that, in our moon, was actually formed from a big collision billions of years ago. So billions of years ago when the Earth was just a melting planet and this nice ball, something about the size of Mars. It wasn't Mars, but something about the size of Mars crashing the Earth. Then a whole bunch of rock and stuff spilt out of the Earth. This formed a bunch of rock around the Earth that eventually gravity pulled together to form the moon. So in fact, the moon was formed from one of the biggest collisions that has happened on or really around the Earth. But we've seen similar kind of impacts recently. If you recognize this, this is a comet. This is Comet McNaught, sometimes called the Christmas Comets. We had a beautiful view of it about a decade ago here in Australia. And these comets, their comets are essentially kind of like dirty snowballs. There are bits of rock and ice lumped together. They're a couple kilometers wide. Well, in 1994, a particular comet called Shoemaker-Levy 9 crashed into Jupiter. So this video was taken at Siding Spring Observatory. So you can see here, here's Jupiter. Here's the great red spot. Here's one of the moons of Jupiter, Europa. And if we replay this, you can see this big flash on the side. Now, that's not a star. That's not a planet. That's not a moon coming around. That is an explosion from pieces of this comet smashing into Jupiter. And in fact, the Hubble Space Telescope took a bunch of images afterward. And you can see kind of the debris field. You can see these holes, these craters in Jupiter. In fact, the Hubble Space Telescope took a look at Jupiter. And it found this really big hole was about 12,000 kilometers wide. Now, 12,000 kilometers wide is a pretty big hole. That is essentially the size of the Earth. So here's the great red spot to scale. And that's that hole. That's that explosion from that collision of that comet. So imagine a comet creating a hole 12,000 kilometers wide, the size of the Earth. Now, that is a big impact. Now, luckily that didn't happen on Earth. But these things have definitely happened in our time. In fact, in 1908, a slightly different event, but related in Tunguska. So Tunguska, Russia, a massive explosion happened, knocking out a whole bunch of trees and forest, devastating a huge area in northern Russia. In fact, still leaving scarves from the event even today. And what we realized was this was actually from an asteroid. So this is a piece of rock or a meteor hit the Earth as it hits the Earth's atmosphere. It essentially exploded. So when you see a shooting star, that's about the size of a grain of sand or a small pebble. It's pretty tiny. Imagine you get a bigger one. They slam into the Earth and they can sometimes explode. We actually saw this back in 2013 as well. Also over Russia, completely overrated, over Chiblitzk. You may have seen the video is caught on dash cam about this meter. So this meteor was about 20 meters wide hitting the Earth's atmosphere. As it hits the Earth's atmosphere, it explodes. It's kind of like doing a belly flop into the water. It stacks the Earth's atmosphere. It explodes. And so this created like, you know, it injured about 1500 people because it shattered windows and all sorts of things. Now no one died. Luckily that was a great thing, but it definitely created some damage. And these are some real impacts that we can happen. You may have heard of the news actually that there was maybe this meteor or asteroid that was going to hit the Earth the day before the U.S. election coming this year. That one's only about two meters wide. So that's 10 times smaller than the one that hit over Chiblitzk in 2013. So it's not one that we necessarily have to worry about. But we do watch for these asteroids because when they hit, they can really cause some big explosions. What you're seeing in this image from NASA is all the yellow points are happening during the day. The blue points happen at night. So the bigger the circle, the bigger the explosion. And we measure this in joules or this case gigajoules. Now to put this in a scale, 63,000 gigajoules. So between this circle and this circle was the amount of energy released from the Hiroshima bomb, that nuclear bomb a long time ago. And you can actually see some of these impacts that someone in Russia we're just talking about are much bigger than a nuclear bomb. So these are things we actually have to think about. And as you see here, you may have asked, well, I talked about two in Russia, they happen all over the place. It just so happens that most of the earth is uninhabited, oceans and Antarctica, places like that. So we don't often see these impacts, but they definitely do happen. These explosions definitely do happen. Now, the coolest explosion I'd love to study are supernova. So supernova exploding stars and they go boom. So one exploding star is equal to 100 million billion billion billion lightning bolts. So imagine one lightning bolt, then imagine 100 million billion billion billion of them. That is what happens when one single star explodes. Now you may be asking, how often do stars explode? Well, in a galaxy like our Milky Way, we expect one about every 100 years. The last one that exploded in our Milky Way was in 1604. So we're actually overdue. Now when we think of all the stuff in the universe, all the two trillion galaxies in the universe and all the stars in those galaxies, about 50 stars explode every second. So 50 stars explode every second in our universe. That is a lot of stuff. That's a lot of explosions. And when these stars explode, it's kind of just like spotting the difference. We take an image, then we take an image a few days later and we look for something to change. So if you'd like playing I spy at home, this is the perfect job for you. And when these stars explode, it's pretty cool. So when the big stars explode, so this is an animation from data we took from the Kepler space telescope. On the inside of the star, the star is being squished into a ball and it's waking up. And at some point, a giant shockwave travels through the star, causing the star to ignite and explode. And you can see here, this happens in minutes. So our sun is too small to explode, but there's lots of big stars out there. In fact, Orion, in the constellation Orion, there's Betelgeuse, and we'll talk about that a little bit later about how you can see it in the nighttime sky, is due to explode any day. Now, when we say any day, we mean 20,000 to 50,000 years. That's as good as we get. But we do think it will explode relatively soon. I really hope it's something we can see. If Betelgeuse explodes, hopefully if I say it three times, it'll explode, it will be bright enough to be seen during the daytime, almost as bright as a full moon. This thing will be very bright. Now, there are some other types of explosions with stars, and that is sometimes you can get a very small star, what we call a white dwarf, and it uses its gravity to suck off the atmosphere of another star, and then essentially it eats too much, it swallows too much, and it detonates as a big nuclear bomb. And these nuclear bombs go off and essentially the entire star ignites. And some stars actually even crash together. In this case, we have two white dwarfs, two things our sun will be in billions of years, and they're going to smash into each other, ignite and explode, producing a giant explosion in space. So these are really cool. And as I said, these explosions happen every time. Something else that really collides, that is even more exciting I think recently, are black holes. There's been a lot of talk recently about black holes colliding, something that lots of scientists here at ANU are working on, and all over Australia. And that is if you get two black holes, this kind of looks like an owl almost, near each other, they'll eventually spiral into each other and collide. Now, they don't necessarily produce the biggest explosion, but they kind of produce a bigger black hole. So black holes kind of swallow other black holes. And we see these happening, and sometimes we see even bigger black holes colliding. And these are happening quite often in our universe. And when they do, these collisions produce ripples. So imagine you're standing in a lake and you drop a rock. As the rock causes ripples in the water, that ripples travel through it. And so our universe, what we call space time, it's like a giant sheet, it's like a giant lake. And as these black holes collide, they produce these ripples. Or, you know, if you put a heavy weight on your pillow, the pillow sinks. It's the same thing that happens when these black holes collide, they cause these ripples through space, from these big, massive collisions. And I think Naomi is going to talk a little bit about our neighboring galaxies, a large and small Magellanic cloud and the related activity. And these are examples of galaxies that will collide. Galaxies collide all the time. And I know Naomi is going to touch on this more. And it's an amazing thing to see that these giant things in space can actually collide as well. And so there's really a lot of things that go bump in the night. I think it's kind of cool because we think of the universe as this kind of boring static place, these things where not a lot of stuff happens. But it is, and there's things that are colliding, changing on real time. And even the big things like the Big Bang itself, and the Big Bang wasn't an explosion in the traditional sense, but it was a massive release of energy that gave birth to our universe. And in fact, our universe may end even in another big sort of explosion, what we call the big rip. Our universe is going to end at some point. Now, it could be that we believe for a long time that maybe the universe was going to crunch or collide back on itself. We don't think that's going to happen now. It could be that the universe just keeps growing, something called the Big Freeze or the Heat Death, and it just becomes so big nothing can happen. Or the universe can grow so fast it rips itself apart, releasing all of that energy. So there's a lot of these things that happen, a lot of these big explosions, collisions always happening in space. So I think it's fun. A, we're relatively safe, so don't worry. We're not in that much danger. The sun's not going to explode. We do have to worry about asteroids, but again, not anything to lose sleep over. Now, I know we have lots of questions I don't want to try to answer. Will the universe just become one enormous black hole at the end? One of the things that we think will happen is all of the galaxies will be separated. So ultimately, galaxies start forming, stop forming, and then you're just left with a bunch of supermassive black holes. But black holes actually leak radiation, something we call Hawking radiation over time. So black holes need to feed. So over time, if there's nothing else happens, eventually the black holes will get smaller and smaller and smaller until they eventually dissipate. So we won't end in one enormous black hole, we'll end with a bunch of big black holes that over time will evaporate. Will we see any event signs that beetle Jews are about to explode? The quickest we'll see is on order of maybe seconds to minutes. So one of the things that happens is when a star explodes, a bunch of neutrinos, so particles on the inside are released. And they don't travel fast in the speed of light, but it's kind of the first thing to escape. In 1987, a supernova exploded in the Large Magellant Cloud or neighboring galaxy, and 24 neutrinos arrived on Earth, and then we saw the explosion. So we would see these particles arriving on Earth, realize something's happened and be able to point our telescopes to it, but it won't be that far in advance. It won't be days or months in advance. We're really talking about a very small, short amount of time. But that is a good question. What instrument do we use for supernova hunting? I'd imagine it'd be a wide field to cover as much as possible. Yeah, to find supernova, because we don't know where they're going to happen. We don't know when they're going to go off or where. So we just like to look at a lot of stuff. So we use big telescopes. Sometimes that can see 20 to 30 times bigger than the full moon. So imagine the area of the full moon. You can see 20 to 30 times bigger than the full moon. And we just take image of the sky as much as we can. And we keep doing that repeatedly. And that's how we've tried to find these supernova, because as you're kind of hinting at it, we just don't know where they're going to go off. Sometimes there's a close meteor in the past few days. Yeah, there's kind of meteors happening all the time. There are great news stories because they make, they fit into the theme of 2020. But there are meteors that happen. You probably do see them when you see a bright fireball. And there was a good one over Canberra and the East Coast of Australia earlier this month. Lots of people saw it. That was maybe the size of about a meter. It wasn't actually that big. Another just related question, if Betelgeuse explodes will affect us? No. So that's a great question. So Betelgeuse is far enough away that it's going to be an awesome show, but we don't have to worry about it. It's not anything that's going to cause us any damage or really anything to worry about. And then related, someone asked, what is the closest star that may go supernova in the next few million years? Betelgeuse is one. There's also another star called Eta Carina that we see kind of burping or going through these small eruptions that we expect to explode. So these are thousands of light years away. So still pretty far, but close enough that there'll be the closest ones to us and a pretty good show for at least those people who like explosions, i.e. me. So what happened to the thing that impacted the Moon? So we talked about something crashing to the Earth to create the Moon. We don't know exactly what that is. We've looked for evidence. We think part of it lies in the asteroid belt. There's been groups that have been trying to pinpoint exactly what that is, but we haven't really seen or conclusively said this was the exact object that crashed in the Earth to create the Moon. How wide is Jupiter's red spot? Jupiter's red spot was observed first 130 years ago, and at that time is about five times the size of the Earth. Now it's shrinking. It's just about less than three times the size of the Earth. It is getting smaller over time. What is the closest black hole? Just earlier this year, the closest black hole to the Earth was announced at about a thousand light years away. It's still pretty far. So there is more than one black hole in our galaxy. We have the supermassive black hole. We call Sagittarius A star in the center of our Milky Way. That weighs about four million times the mass of our Sun, but there's lots of smaller ones. There's anywhere between a million or 10 million and 50 million small black holes in our own galaxy, the nearest one being about a thousand light years away. There may be closer ones, but that's the closest one that we found. And the Jupiter's question is a great chance to talk about what we can see in the nighttime sky. So let's talk about some of the things we can do, and let's do a little bit of virtual stargazing. So if you're up early in the morning, or sorry, early in the evening rather, a bit too cloudy tonight. If you look towards the west, and this can be seen all across the world essentially. So about maybe about a half hour after sunset, look towards the western sky where the sun is setting, and you'll notice there's a very bright dot, relatively bright, and that bright dot is Mercury. So right now we can actually see all five visible planets. So there's eight planets in our solar system. Uranus and Neptune are too faint to see, so you cannot just see them with your eyes. We obviously live on Earth, so that kind of doesn't count. So then there's Mercury, Venus, Mars, Jupiter, and Saturn. All five can be seen right around now with our naked eyes at some point. So Mercury only lasts for about an hour after sunset, so it's not very long, but we can definitely see it, and it's a really cool thing to check out. Now, tonight you may have noticed, and I definitely recommend checking it out. So right about 7 p.m., this started to become visible. You would have noticed the Moon, and the Moon is actually sandwiched between Jupiter and Saturn. So this has been happening the past few months that over a few days every month, the Jupiter, Saturn, and the Moon have actually been forming this nice trio. And that's because there's a cool, essentially line-up happening where Jupiter and Saturn are near each other, as viewed from the Earth. In fact, in December, they're all going to be so close. Jupiter and Saturn and the Moon will be all right next to each other that you could actually see it through the same telescope shot. So if you go out right now or anytime tonight, you'll see the Moon in between Jupiter and Saturn. So Jupiter is the bright object on the left, Saturn is the bright object on the right. Now, if you ever want to figure out how to find a planet in the nighttime sky, sorry, I lost my train of thought there, planets don't twinkle, and I've said this before, so planets don't twinkle in the nighttime sky. So stars twinkle, and stars twinkle because they're so far away, single points of light travel through our Earth's atmosphere or Earth's atmosphere turbulent, so the same reason you're a plane shake, bends and wobbles at light. Now, these planets have multiple points of light entering our Earth's atmosphere, and they actually do wobble. If you look through the telescope, you can see it. But because our eye blends it together, they appear as solid points. So if you see a bright object in the sky that's not twinkling, it's likely to be a planet. The other trick is our solar system is essentially a giant disk. And all of the objects in the solar system lie on this imaginary line we call the ecliptic. So this is the same path our sun takes in the sky. So if you can kind of trace how the sun moves to the sky, and as you see it going across, anything that is on that line and not twinkling is going to be a planet. And this alignment that we're seeing, and I see someone just asked this as well, it is actually kind of special. So we will get it the next few months. You'll get it in October and November with the best being in December. But this actually does only happen every 20 years. So if you miss it now, and if you miss it the past few months, it won't happen for 20 years. So isn't that common of a thing? So it's definitely worth taking a chance. And so tomorrow we'll have Jupiter and Saturn with the moon on the right side. The formation will be a bit different. You may have noticed last night the moon was on the left. Tomorrow night the moon will be on the right. And so this is some video I took of the moon the other day. When you look at the moon, it's really amazing. So this is through one of the telescopes we have. You can actually start to see really great detail of the craters. Now the line between the light and the dark is what we call the terminator. And you may notice even in this video that along the terminator, sorry, we're just repositioning it, you see a lot of craters on the terminator, the line between the dark and the light, and maybe less of the places. Now there's craters all over. But because the terminator gives you contrast, you actually see lots of craters. So if you have a telescope at home or pair binoculars, focus along the terminator, because that's where you're going to see the most craters. And that's the best chance of seeing something. And someone just asked, is it true there may be life on Venus? There was the exciting announcement the other week of phosphine. So phosphine is a mixture of phosphorus and hydrogen. Now the exciting thing about that was that after lots of study of Venus, they couldn't determine what or where this phosphine was being created. They measured it about 50 to 60 kilometers in the Venetian atmosphere, the atmosphere of Venus. It could be from life, but it is not necessarily. There's lots of things that could cause phosphine that they're trying to rule out. It just so happens that microbes, bacteria on Earth and caves also produce it. So it's really exciting because it may be a sign of life, but it by no means is from life. But it's a lot of exciting reasons to go and look at Venus. Someone has asked what causes the craters on the Moon that you're seeing here. These are asteroid impacts. These are meteor impacts. Now the Moon essentially has no atmosphere. It has a very, very, very small amount of atmosphere. Now as meteors crash into your atmosphere, they burn up. We see them as shooting stars. There's nothing to slow them down on. There's nothing to slow them down on the Moon. So they just crash and create meteorite impacts. Now let's take a look at some other stuff. This is what Saturn looks like right now. So one of the astronomers, Dave Weldrake, took this of Saturn through our telescope at Mount Stromlo. Saturn is really beautiful to see through a telescope. You can see the beautiful rings. You can see the gaps in the rings even. So you can see that the rings are clearly separated from the main planet body. And you can see that there's even a gap in the middle of this ring. And so the rings of Saturn are rock and ice. That's pretty much what they are. Eventually they could be or were parts of old moons. Saturn does have the most moons in the solar system at 82. Jupiter is second at 79. And when we see them, you can really see the detail. Now actually all four big planets. So the gas giants, Jupiter and Saturn, and what we call the ice giants, Uranus and Neptune. So all four of those outer planets actually all do have rings. Uranus and Neptune's rings are a bit bigger than Jupiter. And Jupiter has a very small rings. But Saturn, even through a small telescope or pair binoculars, you can start to see the rings. And here's obviously Jupiter. Jupiter looks fantastic in the nighttime sky. You can see some of the gas bands. And you can clearly see the Great Red Spot, as someone has asked, that big storm of Jupiter. Now, the Great Red Spot is a cyclone. It's a giant storm spinning hundreds of kilometers an hour. So no different to really the cyclones we get here on Earth. They just last for a really long time. And Saturn's actually really asked a good question. When was the last meteorite impact on the moon? We've actually seen them in recent times. Some small ones and big ones. There is even one captured during an event where people were monitoring the moon a couple of years ago. So we do see them, even if they're small. Would you be able to see a meteorite impact? It would have to be pretty big. I mean, you can't see the meteorite craters with your naked eye. So if you had a telescope, maybe. If it was a big one, that probably wouldn't be good because it would be a big meteorite impact. But hopefully, we don't have many of those. So it would probably be tricky to see one of those. But Jupiter, as we were just looking at, looks fantastic. Here's a little time lapse video of it. And you will notice it's a bit fuzzier and wobblier. So this is the turbulence of the atmosphere. Just because you can't see it with your eyes, it is happening. So if we kind of add all of these images together and take a nice, deep, still image, that's the one we get over here. Now there's some other things to see. Around 11 p.m., Mars is rising. So if you're up late or you're up early in the morning and you look straight above you, you'll see this nice red dot. And that is the planet Mars. And Mars looks like a red dot because it is red. That's what Mars is. Through a telescope, you can start to see detail on Mars. You can even notice this white thing. So this white thing is what we call the ice caps. Mars does have ice caps. We don't often think about it, but Mars does have an ice cap. And you can see it even through a good-sized telescope. Now some of the other things that you can see in the nighttime sky. We have the Southern Cross. This is just taken with my iPhone. Here's the Southern Cross. If you look next to the Southern Cross, we have Alpha and Beta Centauri, what we call the pointers. Now Alpha Centauri is quite cool because it's the nearest star to us. And we can use the pointers and the Southern Cross to find south. And this is always a favorite thing I like to point out to people. And there's kind of two cool ways. One, you take the long part of the cross and you go three times. One, two, three. That point is the South Celestial Pole. So if you look behind me, the Earth is rotating. And the stars appear to be going in a circle. That is the South Celestial Pole. That is the point our Earth is rotating. And so directly below it is south. The other way is you draw a line through the long part of the cross and along between the two pointers. And the line or the point those intersect is the South Celestial Pole as well. So it's another great thing to actually see in the nighttime sky. Near Alpha Centauri, which is here and here. That's Beta Centauri. It's a Mega Centauri. So if you kind of form a triangle from Alpha Centauri or Rigel Centaurus to this kind of object to the top of the Southern Cross, you may see there's this bright object. And that bright object is not actually even an object at all. It's a faint fuzzy ball called a Mega Centauri. And a Mega Centauri is what we believe to be an old dwarf galaxy. It's a globular cluster that's full of millions of stars. That through a telescope, as you see here, you can really see it. So all these little pinpoints of light are stars. Now before we move on to Naomi, I'll just take one or two more questions. Do most meteorites come from Saturn's rings? No, most meteorites come from the asteroid belt. So the asteroid belt, it is chaotic. There are a lot of asteroids. Sometimes they bump into each other. Bits of those asteroids break apart. They travel through space and sometimes hit the Earth's atmosphere. So it is something that really can happen. And it does happen that often. Where do the water for the ice come from and all the loose space debris? So it's actually been realized for a long time that water ice is quite common in the outer solar system. Moons of Jupiter and Saturn are rich in water. And so a lot of these things happen. So when you just have hydrogen and oxygen, that mixes to H2O. It is kind of as simple as that. And you can freeze it and condense it on these objects in space. But also ice is not just water ice. Ice is any gas that is frozen. So you can get methane ice. You can get carbon dioxide ice. So ice doesn't just necessarily apply to water ice. And I'll probably make this the last question because it's a great one. What would happen if the Earth didn't have a moon? We would be a very different place. So the moon obviously affects our tides. It also affects our daytime, how fast we spin. In fact, the moon is slowly moving away. So about every year, the moon is four centimeters further. And as the moon goes away, it is actually slowing down the Earth's rotation. So as the moon drifts away, the Earth is slowing down. So our days are getting longer. So yes, every Monday scientifically is a fractionally longer than the previous Monday. Not by something necessarily you can measure, but it really is happening. Millions of years ago, the day was much shorter. In fact, scientists have actually measured, using things in the ocean, that the day around the end of the dinosaurs were about 23 and a half hours long. Now I am going to stop there and I will hand it over to Professor Naomi McCurg-Glyphus. And she is going to talk about some great things to do with some of our neighbors, including an even better zoom backdrop than myself. And that is our Magellanic friends, the large and small Magellanic cloud and the Magellanic streams. And what she and others in Australia are doing to study our nearest galactic neighbors. So I will hand it over to Naomi. Okay. Thank you all. So hopefully you can all hear me now. So hi, I'm Naomi McCurg-Gryphus and I'm a professor at Mount Stromlo, at the Australian National University. 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 a 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 Parks Telescope that you can see in the center of your image there. And the Parks 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 Parks 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 about 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, if 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 I said this talk was about getting to know the neighbors. If we've just moved into this neighborhood, and 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 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 SNC 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% 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 it 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. And 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 and 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 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 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 6 kilometers or closer to 8 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 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 say 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 eyes 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 certainly tell a lot about 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 SK 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 it were a clear night where you were in the southern hemisphere and you stepped outside and you would 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 some place 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 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 tail 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 part 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 at the through the ASCAP telescope mounted on the ASCAP 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 6 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 that says 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 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 but we can tell how much is there 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 I 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 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 and 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 is there an estimate of when the Milky Way will buy them out the large and 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 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 kinds 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 would be meaning 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 if the infrared wavelength used for dust images so there's quite a few wavelengths that are put together but one of the ones that we look at often is about 150 microns the 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 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 stop it immediately so as bodies like galaxies and planets form they form by material that circulates inwards comes in and 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 big explosions we're talking about massive kinds of explosions and relating those explosions the types of 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 allowing kids interested when you talk about things exploding and I'll just wrap up 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 talk about 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'd 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