 All right. So just before I start off, I'd like to take a moment to thank the traditional owners of the land in Canberra, the Nonnawall, and Nambi people. We would like to acknowledge their elders past, present, and emerging. So let's get started and start talking about eclipses and shadows in space. And remember to leave any questions you have in the comment section below. So before we talk about eclipses and shadows in space, let's have a bit of an idea of who's talking to you. Who am I? Well, my name is Ryan. I'm an astronomer. I finished my PhD in astronomy at the Australian National University, studying at Mount Strong Observatory, which was an incredible place to study. In my spare time, I make some videos for YouTube, and for my work, I look for exploding stars out in the universe. Now I'm working at the Space Telescope Science Institute. You may not have heard of this place before, but it's the place in America that handles the operation of space telescopes, like the Hubble Space Telescope. Now I don't really use the Hubble Space Telescope for my work. I use some other space telescopes, like the Kepler Space Telescope, which tragically died and is now drifting in space since 2018, and the Transiting Exoplanet Survey satellite, which is very useful for finding exploding stuff all across the night sky. But enough about me. Let's start talking about shadows and eclipses. So before we get into shadows, we first need to talk about some kind of light source. In space, this light source is usually a star, like our sun, and these light sources are big shining balls of light in space, and they emit light in every direction. So these stars will just happily shine out light. But what would happen if we put a planet in the way, something that doesn't shine light? A light coming from the star would fall upon the planet and illuminate one side, you get daytime and the other side could be nighttime. So you also might think that this planet blocking all this light would cast a shadow that looks like this. Everything in that rectangle behind that planet won't get any light from a star. Well, it's actually a little more complicated than that, and that's not the case, because the star is a big ball. And it's complicated like this. If you looked at light coming from the top of the star, a lot of it will run into the planet or move past it. Some of it will move above the planet and some of it will move below it. So it could pass on by the planet like that. And likewise, if you had light coming from the bottom of the star, it could pass above and below the planet like that as well. So you end up with this one region, this triangle or cone behind the planet where there's no light coming from the star. It's like a big shadow in space, but it's only this cone. It's not that rectangle that we had before. And either side of this cone, we have two other cones which are partially shaded. We call these different areas the penumbra for the partially shaded areas and the umbra for the completely shaded areas. What would happen though if we put a moon orbiting this planet? Well, the moon would orbit around the planet and sometimes it would pass through the shadow of the planet. In reality, the scales are much more different and it's not so easy to have a moon pass through the shadow of a planet. But in this case, we can just tweak it and make it go where we want. So let's put the moon inside of the penumbra. What we end up with here is a penumbra lunar eclipse. So in this case, the moon is slightly fainter than what it would have been otherwise. But if we move the moon slightly further along and have it obscured by the planet's shadow, then we end up with something called a partial lunar eclipse. And you may have heard of those before where half or part of the Earth's shadow will block out part of the moon. But if we move the moon even further still, we'll get to a total lunar eclipse. Whereas the moon is completely in the Earth's shadow and actually appears this kind of red color from light being bent around by the Earth's atmosphere and shone onto the moon indirectly from the sun. So to see what this looks like in real life, I've got this lovely video here from Colin Legge. So the moon starts and the penumbra shadow moves through to a partial and then to a complete solar eclipse. And then once it's passed to a tally, it'll move to a partial eclipse and back out to a penumbra eclipse. So you can see where the Earth's shadow crossing the moon. And then it turns that lovely red color from all of the light bending through the Earth's atmosphere and falling onto the moon in the Earth's shadow. So the cool thing about this is we've actually got a penumbra lunar eclipse coming up on the 6th of June. So the moon will look a little bit fainter starting at 3.45am Australian Eastern Standard Time. And I'll reach midpoint through the Earth's penumbra at 5.24 and it will cross out the other side at 7am. So the moon will look a little bit fainter during these times, but if you're up while this is happening, it would be worthwhile to check it out. But it's not just planets that can cast shadows. We can have moons in space and just like a planet, it will block out some light. So the moon will cast a shadow similar to what the planet does as well. And we end up with something looking like this, where we have the penumbra here. And if you found yourself inside the penumbra of the moon's shadow, you would be seeing something called a partial solar eclipse. If you were inside the umbra of the moon's shadow, you would be in a total solar eclipse. So again, to show you what this would look like in real life, let's look at another amazing video from again Colin Legg. So this is a total lunar eclipse that happened in 2012 in the northern territory of Australia. You can see that the moon blocks out some for a moment, then moves on again. So this is an incredible event that I haven't seen myself, but I'm often recommended to try and spot a total solar eclipse at some point. So while I'm going through this talk, remember to put your questions down in the comments if you have anything you want me to answer. So it's not just a planet or the earth and moon that have eclipses. You can have eclipses happening all over the place. Here's a cool example of an eclipse happening on a neighboring planet. Jupiter, of course, the biggest planet in our solar system. It has a lot of moons orbiting it and it has four big moons, one of which is shown here is Io. It's the closest moon to Jupiter. And you can see that it's casting a very perfect circular shadow onto Jupiter's clouds. So if you were to find yourself floating in Jupiter's atmosphere underneath this black shadow, you would see a total solar eclipse just like you would on the earth. So these eclipses can happen all over the place and they happen fairly regularly on Jupiter with all of its lovely moons. But eclipses aren't just property of planets and moons. You can have them on rings as well. Here's another incredible example from Saturn. Now this image is taken by the Cassini space probe, which has burned up in Saturn's atmosphere. But you can see a lot of cool stuff going on. You can see Saturn's shadow being cast on Saturn's rings. And you can also see the rings of Saturn casting a shadow on Saturn itself. So all of these objects in space can cast shadows all over the place. But shadows aren't just pretty things that you might see in space. They can be very useful for science as well. So here's a quick example of how we can use shadows and eclipses in science. And it's to do with finding planets around other stars. So if you imagine a star sitting in the sky and you want to study it very closely, in particular how bright it appears to you. So you might want to measure it and plot it on a graph where the vertical or y axis is the brightness and the x or horizontal axis is time. And if you had a normal star, the brightness would kind of mill around and not really do too much. It would be very boring. But what would happen if we had a planet? Well, let's see. We'll send the planet across the star. So you can see that as the planet goes across the star, it casts a shadow on us more or less and blocks out some of the light coming from that star. And the brightness of that star dips. Very small amount, but it does dip. And with very sensitive instruments, we can actually detect these things. And so far we've found thousands of planets orbiting distant stars. They're called exoplanets. And there's many thousands more waiting to be discovered. So eclipses are more than just pretty things that we can take pictures of. So just to summarize these things, we talked about the lunar eclipses. There are three different kinds. They're penumbral lunar eclipse, the partial lunar eclipse and the total lunar eclipse. And there's a penumbral lunar eclipse that's going to happen on the 6th of June. And there are solar eclipses, which is when the moon gets between the Earth and the sun or any other star. And we can have lovely eclipses and shadows being cast on anything in the solar system. And they're very useful for finding things out in the universe. So eclipses are generally very interesting, very pretty and very useful objects. So with that said, I'll have some time now to take any questions you might have. So while we're waiting for some questions to come through, I'll just take this moment to show you all about this event that's going to be happening tomorrow afternoon. The Young Stars program has a lecture if you haven't gone enough of astronomy this evening. The universe beginning to end by Professor Brian Schmidt. It starts at 1 p.m. Australian Eastern Standard Time. And you can still register for this event through Eventbrite or watch it live on Facebook. All you need to do is search for the Young Stars program and you should be able to find it in either of those places. So let's answer some questions. So one question here is, can we detect exomoons? That is a very good question. And at the moment, there might be, there are some contested claims of exomoon detection, but it's really tricky to detect it. Let's go back to this slide here where I've kind of exaggerated what happens. In reality, the dip in brightness of a planet going in front of a star is only around 1% or less of the star's total brightness. So we need incredibly sensitive equipment to detect these tiny dips in brightness. And so far, we haven't been able to detect conclusively an exomoon through this transiting method. There are other methods as well of using radial velocity, which is a fancy way of telling us how objects move. Again, there hasn't been any conclusive evidence. So exomoons might be something or definitely is something left to discover in the future. It's a very hard thing to find. Another question is, how often does Australia experience total solar eclipses? Well, total solar eclipses are reasonably common on the Earth, but the tricky thing is most of the Earth is ocean. So almost all of the total solar eclipses will fall somewhere in the middle of an ocean. And I'm not sure exactly when the next one in Australia is. I think there might be one in the 2030s, but I'd need to look that up. The next question is, oh, I've just gotten in some help from the internet. Apparently in the 22nd of July, 2028, over Sydney, thank you, Brittany, is when the next total solar eclipse will happen in Australia. So the next question is, if you could see any eclipse in the universe, what would it be? So we can see lots of eclipses in the universe. There are lots of different kinds of things like I showed in the talk. Any object that blocks light from another object that we can see would cause an eclipse. And we can see them from a whole lot of different things, including planets, ones that may not even be around stars. The next question is, how frequent are lunar eclipses? Lunar eclipses are pretty common. There's one coming up in the near future in the next year or so. Again, I'm a bit rusty on the dates of these things. So perhaps one of my friendly internet helpers can give me a date on that one. The morning of the 6th, apparently. Yeah, so that's when the next penumbral solar eclipse will happen in the morning of the 6th of June. Okay, next question. Has Juno captured any eclipses at Jupiter? It has actually. There are lots of amazing photos from the Juno spacecraft. For those that don't know, Juno is a spacecraft which is orbiting around Jupiter, trying to understand among many things how Jupiter formed, how the storms operate on Jupiter's big atmosphere. And it does this by taking lots of amazing pictures. And of some of those pictures, some of them are eclipses. There are some I almost put in this talk, but decided on that other one. Okay, next question is, can space junk make a sun or planet less bright? Well, that's an interesting question. They can eclipse things as well. Anything that blocks out light coming from something else can eclipse an object. So, there was a YouTuber by the name of Smarter Every Day, who's sharing the American total solar eclipse, found a spot in America where both the moon crossed in front of the sun and the International Space Station crossed in front of the sun, and took images and videos of both objects eclipsing the sun more or less simultaneously. So anything in space can block light, but the amount of light that gets blocked by space junk and space stations is incredibly small. Here's another question. Do eclipses occur with other parts of the spectrum? Yeah, so eclipses, whatever kind of light you look at, the object passing in front of something else will pretty much block all the light coming from it. Eclipses can get really interesting, though, if there is an atmosphere surrounding, say, an exoplanet. Because atmospheres interact with light, I said earlier that the light coming from the sun gets bent around the earth, and that's why the moon turns red during a total lunar eclipse. The same kind of thing can happen if there's atmospheres around planets orbiting other stars. And the effect of that would be that on the same plot here, if you had observed the transit of a planet in one color, it would take out a certain amount of light. And if you observed with another color, it might take out maybe a little bit more of that light. And you can use computer models and atmospheric simulations to work out exactly what that means the planet's atmosphere is made of. And there have been a few really cool identifications of different atmospheres out there around exoplanets. Okay, do we have any more questions coming through? Ah, does a black hole cause an eclipse? That's a very good question. Right, so eclipses, another really useful tool for eclipses is, which was testing theories of gravity. So we're all used to how gravity works on the earth. If we jump up, we get pulled back down, and we don't go flying off into space. But in extreme environments around stars or around black holes, gravity can do some pretty strange things. It can bend and warp space so that light itself bends as it travels around these objects. Now this principle was observed for the first time during a solar eclipse where stars had shifted position during the solar eclipse that were sitting right next to the sun, from where we expected them to be to where we observed them to be. That shift was due to the sun's gravitational influence. Now with black holes, because they have extreme gravity, the shifts that they cause light is pretty astounding. And if you've seen a movie called Interstellar, there's a really cool model of a black hole in that where the black hole lenses, it's called, bends light up above and below itself. So if an object sits behind a black hole, copies of that object will get made above and below it. So you could imagine a kind of duplicate image around the black hole. So instead of blocking out the object's light, it will actually amplify the object's light and make it brighter than it would have been without the black hole in the way. On to the next question. Are there exoplanets in our solar system? So in our solar system, we have planets and the way an exoplanet is defined is it must be a planet orbiting a star that's not our sun. So by definition, we don't have any exoplanets in our solar system. So the nearest exoplanet we have is around the nearest star to our sun called Proxima Centauri. And there's a little planet that's about the size of the Earth running around Proxima Centauri, which is about 3.4 or so light years away from us. So that's the nearest exoplanet that we know of. Next question is what kind of mineral deposits may be on the far side of the moon? That's a very good question and one which starts to stray out of things I know. But in general, the surface of the moon is made out of the same stuff as the surface of the Earth or the crust of the Earth. So you would expect to see a lot of the same stuff that the Earth is made of. One of the things that you would also find that's not so common on the Earth is lots of helium on the surface of the moon. And that's because the moon catches helium that the sun emits out in great big solar winds. So particles streaming away from the sun will land on the moon and make these little helium deposits. So that's one of the very interesting materials that you might be able to find on the far side of the moon. The next question is what's space traffic like at the moment? How many astronauts are in space right now? So space traffic is getting more busy as more and more satellites go up into space, things get more complicated, more crowded. And you've got to be very careful that satellites don't run into other things. So space traffic is okay at the moment, but it may get pretty tricky in the future. At the moment there are three people on the space station and there are two more which were supposed to be launched into space yesterday, but got delayed because a big storm came through and they should be trying to relaunch again. I think it's tomorrow morning. So the next question is where do black holes lead to? Answer one question on black holes and then you're bound to fall into another. So black holes are of course the big exciting mystery of physics and astronomy. There are these strange objects that sit in space which kind of break our understanding of physics because they need to obey the laws of gravity, which are defined by general relativity and quantum and the laws of the very small things which are defined by quantum physics. And we can't mix those two correctly at the moment. The question of where the black hole leads to is a question that we have no real answer to. If you were to fall into a black hole, you would get torn to pieces before you had a chance to see what might be on the other side. And if you don't get killed, I guess by being torn to pieces by the black hole, time will slow down to an incredible crawl so that you might never actually fall into the black hole from an outside perspective at least. The last question that we have is can we use the helium on the moon to do nuclear fusion? Yeah, that was actually an argument that's been around for a while is that this helium deposits we have on the moon and specifically helium three is very useful for making fusion reactors. So you slam the helium atoms together along with some other things like lithium and you can make a lot of very clean energy that way. But it's very tricky to get up to the moon and mine things off the moon. So at the moment I don't think, I think it will be a while before we can use helium from the moon in nuclear fusion reactors. So anyway, thank you all for coming along and listening to my talk. Hope you learned a little bit about eclipses and I really enjoyed all the questions you had. So I'm going to hand over now to Brad Tucker. Hello everyone. So thanks for tuning in and thanks Ryan for your great talk. So what we're going to do now for the next about 15-ish minutes, 20 minutes before Marta Yebro speaks after me about some really cool things about how we're using space to help with bushfires is we're going to do some virtual stargazing. Now the way this is going to work is you can play along at home. You can do this wherever you want. I will explain how we're going to see a few things in the sky. And using the magic of technology, i.e. I've taken some photos and videos just a few minutes ago, we're going to look at what it kind of looks at outside and it's pretty clear. And you know, hopefully where you are, it's clear and if not, you can join home right now, hopefully on your couch and it's quite warm and cozy. It's a bit cold here in Canberra. It's not too bad. It's brisk. It keeps us alive. And you know, I always like starting with this photo here and this is taken at Mount Stromlo at night and and one of the cool things you see here are these stars swirling around. And that's because this is taken at what we call the South Celestial Pole. Now the South Celestial Pole is the point where the earth actually spins. So the earth spins on an axis. It's about 23.8 degrees. So we're built tilt tilted over. And because of that, when it spins, you see stars kind of trailing around in a very interesting pattern. And so the way to take something like this, this photo of this is to find south aim south, and you just leave your camera you do an exposure, you know, your DLR or some DSLR or something like that. You know, take a photo every 10, 20 seconds, and you'll see over time, the star trails the stars moving. And so it's a very easy way of seeing literally the rotation of the planet, that nice circle ball that we are on and seeing how the stars move with it. Now one of the other reasons I really like showing this photo and it also happens to be my virtual background is when we notice here, you know, this yellow bit. So this photo is taken pointing southwest roughly. Pretty south more south southwest, and that yellow bit isn't you may think oh that's the sunset. No, this is light pollution from the suburbs of Canberra. This photo is taken in the dead of the night I think is roughly around one or 2am. And that glow is purely from light pollution from our houses and buildings and those sorts of things and it's always a good point to show that, you know, we obviously need light. We need to see at night and it plays a very important role into us, but we don't want to lose the ability to see the nighttime sky. Something that we can do here in Canberra, which is rare compared to other places, we can go outside and we can see, you know, the Milky Way, for instance, with their own eyes. And some of these things that we can see, and I'll show you tonight, it's because we have pretty dark skies. You know, there are parts of the world where they've never even seen with their own eyes the Milky Way, yet we're, you know, we're great opportunity as a great chance for us to go outside and see it. And part of that is making sure light pollution is reduced. And we all play a part in turning off lights at home, making sure either lights are on timers or things like shielding downward facing lights so we don't actually bleed into the sky because the more light goes up, the more it reduces our visibility to see the beautiful nighttime sky, something that is a great thing that we have here in Canberra and Australia in general. Now, let's start off a bit with what we could see. So this is a kind of a snapshot I took from a program called Stellarium. Stellarium is free to download. It's a great tool to use to try and find things in the nighttime sky. And if you're out anytime tonight or the next few nights in the early evening and when I say the early evening, we're talking about right after sunset. So about right after sunset, so around 536 o'clock. This is taken just before six o'clock. So this kind of plot animation. What you'll see is a couple of things. If you look west, do west. There will be a very bright dots just sitting below the horizon. That's Venus. So Venus is sometimes called the evening or the morning star rather. It's been out in the evening skies for the past better part of a couple months. So if you've gone out and you've seen, hey, there's a really bright object in the western skies after sunset, that's Venus. Now right now, we're also gracing the skies with the planet Mercury. Now, the great thing about both Mercury and Venus, if you have a pair of binoculars or small telescope is they have phases. Just like the moon. And this is kind of a cool thing that really shows how the phase of Venus moves. So even though it looks like a little bright circle, a bright dot on the western skies over time, as you see, starting all the way from November, getting different all the way down to just about now. It's gone from a full circle to just a sliver. It actually looks more like the moon rather than what you think a planet might look like. Now, if you have some binoculars or small telescope, you pointed at Venus, Mercury the same as well. You won't see that full circle. You really will see just, it's like Pac-Man or a bit taken off of it that most of it has been removed. And so this is quite a unique thing. And that's the phases of the inner planets. Now, in fact, the phases of Venus is something Galileo actually used to prove that the Earth, not the Sun, not the Earth was the center of the solar system. And because of the motion of planets, you realize that the only way to explain the phases of Venus and Mercury is if Earth was not at the center, but the Sun. Now, the cool thing about this is because of the way the planets work, the further out on the planet you go, the more phases of other planets you see. So if you're on Mars, you see phases of Mercury, you see phases of Venus, and you see phases of Earth. If you're on Jupiter, you see phases of Mercury, Venus, Earth, Mars, and so on and so on and so on. And so the phases are a really fundamental thing that not only prove and understand how our solar system works, but also greater how the universe works. And some people, when Ryan was talking about seeing eclipses with the satellite Juno around Jupiter and some of its moons, we've seen phases of the moons of Jupiter, we've seen phases of the moons of Saturn, for instance. So it's a really cool thing that you can see just looking to the western skies with these two bright things. Now, of course, if you're looking out tonight, you'll notice a very beautiful moon. But before we get to the moon, there's also something that just is in the western skies. And that is Orion's Nebula. Now Orion is a famous constellation. So some people in Australia might call it the saucepan because we have the handle here and the three lines. So some people call this the saucepan. In Greek mythology, this is called Orion. So here are the shoulders going down to the belt, the sword down to the knees and legs. So this is famously known as Orion's Belt. Now, one of the big stars in Orion is Beetlejuice. Now, Beetlejuice was in the news a couple of months ago because it was getting dim and it was acting a bit funny. And some people thought that Beetlejuice may explode. Now, it's not like the movie, if you say Beetlejuice three times, it explodes. Otherwise, astronomers would have. One of the things I specialize in is exploding stars and I really want Beetlejuice to blow up. That's because when Beetlejuice does blow up and it will blow up any day now, any day being 10,000 years. So, you know, don't hold your breath, unfortunately. It will be very bright in the nighttime sky. Now, Beetlejuice is what we call a red super giant. So it goes through phases of slightly brightening and slightly dimming. And if you looked at the constellation Orion late last year, you would have noticed that Beetlejuice is actually much fainter than the other star, Rigel. But nowadays, it's getting brighter. It's getting back to its normal state. But when, if and when, Beetlejuice blows up, the brightness will approach the full moon. So it'd be like going outside in the night and all of a sudden you see a bright object like the moon, but it's actually Beetlejuice. That's how bright it will get. No lasts for months. So it's a really great thing that we all hope to see. But the real reason I think we want to focus on Orion tonight is in the middle of the handle or the sword. So we have the three stars of Orion's belt. And we have the three stars of the handle or the sword in the middle is not actually a star. This is Orion's nebula. So this is the photo care courtesy of Dave Weldrake who took it using the 12 inch telescope we have. So if you have a telescope at home and point to that middle star of the handle, this is what you'll see. So this is just putting a camera next to the telescope, the telescopes that we use for every other public night. These are the sorts of views you get to see. And so what you're kind of seeing is a bunch of gas and the gases lit up in different colors and what those colors are are actually different elements. So Orion's nebula is caused by a star that's actually puffed out. It's essentially burped and it shed all of this gas into space. And so this fuzzy kind of milky hazy glow is because all that gas is expanding and eventually gravity will pull it back together and they'll form new stars. So nebula are quite a common thing. Now some people call Orion's nebula M42, Mezier 42. And it's a very easy object to find. One of the easiest objects I think, besides some of the planets to find with your own telescope, because it's easy to find the constellation Orion. You just go to that middle object in the handle or the sword and there you go. You get Orion's nebula. And so this is kind of the essentially the view we're getting of Orion's nebula right now. If you could go outside and you could do it or as I said, I hope you're comfortable wherever you are and enjoying something warm. Now as I said before, we had phases of Mercury and Venus and obviously right now we're in the phase of the moon. So this is a video I just captured. And so what you'll see is we're going to be moving around the surface of the moon. Now the moon is in a waxing crescent phase. So the moon can either be waxing or waning. Waxing means it's getting brighter towards a full moon. Once you get a full moon, it starts to wane. Crescent is when it's less than half. And gibbous is more than half. So waxing crescent means we're getting brighter going from 0% moon to 50% moon, 50% being essentially a half moon. Now, one of the cool things I think about looking at the moon is the shadow, the line between the dark light and the dark. In fact, in astronomy, we call that line the terminator. No, it's not named after Arnold Schwarzenegger who used to be my governor, the great governator. The terminator is just a term we use for the termination between the light and the dark side. I mean, it's kind of a cool name obviously, so we really like it. But it's the technical term for that shadow between the light and the dark. And one of the cool things you'll notice along the terminator is you see lots of craters. Now, the reason you're seeing lots of craters along the terminator is not because there's more there, but we get contrast. So because we're getting that light and dark, we're getting the contrast between the light and the dark, and it's able to accentuate those craters more. The craters are fairly even across the surface of the moon, except a couple places I'll explain in a second. But it really is a way of accentuating these features. And what you see already is, you know, we're really zoomed in on the moon here, and you can really see the scales of these craters. Some are quite big, some are small. And if you look here right now, this crater in particular, you see how it has the little bump in the middle. So we have the giant circle, and we have the little bump in the middle. Now, the cool thing that happens is there's actually a little mountain that forms in the middle of the craters of the moon, or any object that has a big crater impact, including meteorites that strike here on Earth. And what happens simply is when the rock hits the object, the moon or the Earth, it travels through space, it slams into the ground, and it's traveling tens if not hundreds of thousands of kilometers fast. And it hits with so much force and so much power, it actually turns the ground into a liquid. It actually liquidifies the ground. And so it has a wave travel through it. So a good way of thinking about this is, imagine you're standing in the water and you drop a rock in the water. Well, the water will go out, and then the wave will stop, and it'll come back in, and then you get the little dollop in the middle. So imagine you're in the bath or something like that. You drop the rock or something in, the wave goes out, and then it comes back in and you get the little boop in the middle. That little bump in the middle, that little loop, is literally that same thing happening. It's the ground moving as water traveling through it. And what you'll notice as we zoom around here is that some of the bigger craters have it and some of the smaller ones don't. And that's kind of exactly what we think. When you get to a certain size, you have enough force, enough energy, you slam into the surface of the moon, and you create this dollop. So it's kind of a really cool thing we get to see. Now obviously one of the things that's famous for looking at the moon is that there's lots of craters obviously. But why does the moon have so many craters? Well, it simply has so many craters because it has very little atmosphere. It's been bombarded by things, the atmosphere doesn't slow anything down, nothing stops it, and it just slams into the ground. Now the earth gets hit with tons of stuff all the time. There's about 200 tons, literally 200 tons worth of rock and stuff that hits the earth every single day. Now most of this is very small things that burns up in the Earth's atmosphere. And because of it, we don't get these cratering effects. We also have lots of oceans, so they land in the ocean, we don't see it. Whereas the moon, lots of all land, very little atmosphere, so it just crashes into it. So it's not that it's more unlucky or anything like that compared to the earth, it's just the way the moon is structured. Now one of the other big features you see of the moon are these dark areas. These are called Mari. So if you notice right here, we have this dark area here, and we'll go back to another one, but we can compare it to this other area. So this part is not dark, it's that light area of the moon, and you can go out right now and see the moon. We have the darker areas and the lighter areas. So here are the darker areas of Mari, here are the lighter areas. Do you notice the darker area has very little to no craters? So even right here, tons of craters, the darker Mari, very few craters, maybe one or two. Why is that? One of the interesting things is these Mari are actually the most recent volcanic lava flows on the moon. The ground is actually a little bit different. So Mari actually means sea. So some of them are called Sea of Tranquility, one of the landing spots for the Apollo mission. And because the ground, imagine, you know, think about like volcanoes and Hawaii or something like that. The ground's a bit harder, but it's also a bit younger. It's a bit younger, so it's had less time to be bombarded by craters. And therefore it appears a bit smoother and also less cratering. And so this is kind of a cool thing that you can just see even with your own eyes, you don't need a telescope to see that, that there's less craters on the Mari as opposed to the rest of the surface. Now someone has asked, how do we get a super moon? So this is a great question. So the moon has phases. So the moon goes around the earth about every 29 and a half days. So every 29 and a half days, we go through the full phase cycle. So we go from new moon to half moon to full moon and back. The moon also varies, it wobbles in its orbit. And that's because the moon is not in a perfect circle around the earth. So sometimes it gets closer and sometimes it's further. So when the moon is closer, we call it perigee. When it's further, it's called apogee. So the average distance of the moon is 384,400 kilometers. But the orbit varies by almost 50,000 kilometers. So sometimes it's literally almost 50,000 kilometers closer, about 340,000, sometimes much further, about 430,000 kilometers. And so a super moon is when you get a perigee moon and what we call a sigi. So sigi is when three objects line up in space. And to get a full moon, you have to have the sun, the earth in the middle, and the moon on the other side. So we see that side of the moon, it lights up, and we see it full. So you'll always A have a lunar eclipse when it's a full moon. So if you notice on the six, when we have that partial lunar eclipse, it will also be a full moon. So a perigee sigi is the technical term for what we call super moon. And so the moon, because it does an orbit every 29 and a half days, every 29 and a half days it has a point of perigee and apogee. So it's actually more common than we hear of sometimes the moon or the news. But when it is closer, it is a bit closer. And therefore it is a bit bigger and it is a bit brighter. And if you can kind of compare side by side between super moon and micro moon, micro moon being apogee sigi moon, you can really see the difference. And just a question before, before I hand it over to Marta. What does the moon also have? One of the things the moon has a lot of is ice. Yes, just like the thing that you can drink and freeze and will go on and frost on our lawns overnight. The moon, especially in these crater areas has lots of ice. And this is the big thing. The whole return to the moon effort is about extracting the ice because we can use ice for rocket fuel. We can also use ice for drinking because ice is hydrogen and oxygen. That can be converted into rocket fuel. In fact, if you go into the Facebook feed of Mount Shermlow, you can see a demo by Caitlyn talking about how to create your own hydrogen. This is exactly the same process that we're planning to do around the moon. So that's going to be the biggest thing that we can have and use there. And last question is, have any meteorites crashed the ACT that I know of? No, I don't. There may have been some. Probably the most famous meteorite in eastern Australia was the Merchantson meteorite that crashed 51 years ago in 1969. 1969 was a big year for space Apollo 11 and Merchantson. And it's big because that has actually been dated to come from something that is 7 billion years old. That's a big deal. The solar system is 4.626 billion years old. This is 7 billion years old. This did not come from the solar system. It actually predates the solar system. So it's one of the most important discoveries that we've actually recently had. And it's because that meteorite crashed into a town in Victoria 51 years ago. So stay tuned. I will stop this and I'm going to hand it over to Marta. And so Marta Yebra is going to talk about some really exciting things. And, you know, after the summer that we've had, I think we all realize, you know, the response from the bushfires that Australia faced this past summer. One of the people who you didn't probably realize was in the middle of it helping was Marta. She's using what she's going to talk about here to help to predict those fire maps. When you see those fire maps that really were, you know, saving lives and I'm not trying to be dramatic, you know, we used to understand what the fire was doing, how it was moving. It was Marta and others in that team who did it. And so she's going to talk about some, I mean, it's probably some of the most important work you'll hear that is actually happening, I think, in Canberra right now. And that is how we're going to use satellites to help not only plan and mitigate, but hopefully monitor bushfires. And Marta is the person. So Marta Yebra is a senior lecturer at the Finner School of Environment and the Research School of Mechanical and Environmental Engineering at ANU. And yeah, I think you'll enjoy this talk. And after Marta, we'll do a little bit more virtual stargazing. So I'll hand it over to her. Hi, Brad. Thank you for the introduction and thank you everyone for joining me tonight. And I hope you enjoy the first talks as much as I did. And over the next about 30 minutes or so, instead of you looking up to the sky, I'm going to make you looking down. So I'm going to send you to the space and look down to the earth. So I'm going to be talking and giving you a brief overview of the current available and the next generation of the space-based data and mapping technologies that are helping bushfire managements to better prepare and respond to bushfires. So well, unfortunately, I said I will go to take you to space, but I cannot do that. And anyway, I'm not sure you prefer to be at home or at the space of the now. But then we already have ice in the skies. So there are a lot of satellite instruments that are imaging our planet and are helping us to observe and understand the earth processes. So this animation here is from the NASA's, the United States Space Agency, which is the template of Earth conservation spacecraft. And currently the satellites instruments such as these ones here in the animations and other instruments launched by other international space agencies issue an immense amount of data. So terabytes per day. So that remotely sends experts like me profess and convert into information or products that are useful in decision-making and planning. So when it comes to bushfire management, this basal right of data collected from space can be used to inform different phases of fire management. So in a nutshell, this slide showed that before the fire remote sensing data can be used to monitor fuel condition, which will affect a far danger likelihood. For example, during the fires, we can use remote sensing data or satellite data to identify areas of the land with anomalous high temperatures or to visualize smoke which help to detect active fires. And also to know how the fire will spread based, for example, on the fuel condition and the weather conditions. And this information helped to most efficiently direct separation and evacuation decisions. So finally, after the fire, a remote sensing data can be used to assess the fire stand, the mission from the fires, and the impact in terms of fire severity and also to tell us how the vegetation is recovering after fire. So moving to the applications of satellite data to assess profile conditions, the main objective here is around estimating fire danger. So this is the risk of bushfire occurring. So a good fire danger rating system is of very important as it supports a range of critical decisions such as prepositioning firefighting resources, issuing public safety warnings and information, or limiting the potential of emissions through the use of total fire bans. And we know very well what this means as we've been going through these total fire bans very often here in Australia and sometimes it prevents us to do that barbecue we wanted to do. And this slide gives an overview of the new fire danger rating system that is under development. That includes factors for fire weather, fuel condition, fire behavior, ignition, likelihood, fire suppression, and fire impact. So under this complex framework, remote sensing data is mainly used to estimate a fuel condition. And in case you don't know what a fuel condition is, I will explain now. So fuel is all life of the vegetation that accumulates over time and therefore can potentially burn at any time. And its condition includes moisture content, structure and quantity or load. So all these components of fuel condition affect the flammability of the landscape and therefore the potential severity of a bushfire. So for example, thinking about fuel structure or the arrangement of the fuel that is separated is the fuel that is separated is less likely to carry a fire than a fuel that is continuous and packed. In addition, more fuel means larger flames and greater fire intensity. Finally, when fuel is high, there is less chance of a fire ignition than if the fuel is low. Fuel moisture is low if the vegetation is high. So let's start with the fuel moisture content. There are various methods that have been developed to estimate this variable from remote sensing data or data collected from satellites. And I'm going to try to briefly explain why this is possible because I thought perhaps some of you were curious to know the physics behind this. So well, when the solar radiation hits the surface of a leaf, part of it is absorbed, or there is transmitting to other layers in the plant and most importantly, other fraction of this incoming solar radiation is reflected from the leaf's surface back to the sensor that are on board of the satellites in the space. So this fraction of the solar radiation that travels back to the sensor is called reflectance and is represented in this figure in the life. So basically this figure shows the reflectance for two plants with different moisture content. And as you can see, there are big difference mainly in this region here of the spectra. And this is because the water in the leaves absorbs a lot of the radiation in this area of the spectrum. So depending on the leaf tissue again, sorry, depending on the leaf tissue water content, the reflectance is therefore reduced to a varying extent. And based on these principles, we can create algorithms that convert the reflectance measured by the satellite into few moisture content values. And this is happening in near real time. So this animation here presents as an example the dynamics, the dynamic variation of few moisture content for Australia for 2019. And these maps were derived from data collected by a satellite from NASA and that is called MODIS. And this animation show us, as expected, the few moisture content values are constantly low in the desert in the central areas of Australia. But there are strong seasonality elsewhere. For example, in January, well, now we are moving towards summer. We can see how the southeast coast get more red pixels. Well, now where are we? Hold on. This is September, December. So we are moving towards summer and as we move into summer, there is more red areas in the coastal area. But as we move into summer, there are less values. And the total, the temporal pattern is the opposite in the tropical region. So in the north of the country, higher life moisture contents are preserved during the northern wet season. That is December to March. And lower values are during the dry season. So this seasonal patterns of few moisture content have been demonstrated to be linked to far landscape flammability and the far occurrence. For example, unusually dry, few land hot weather was one of the factors that explained the high far activity we had in the south is Australia during the last five seasons. So this map, this figure here, for example, shows you the few moisture content nationally for the different years. And we can see how in 2019, the few moisture content was the lowest in record. When focusing in the southeast forest, these figures tells a similar story. So in black, we see the satellite base average few moisture content for the southeast forest during 2000 and 2018. And in blue, we see the low moisture values at the same forest, the same forested areas reached during the 2019-2020 far season. So anybody can get access to these maps if you were wondering. And here I show a screenshot of the public website we have developed to facilitate the access to this information. As a quick tour, for example, you can search for any... Where's my mouse? Sorry. Yeah. So you can search for any date. Since 2001, you can search for any location here and you will have the map of Australia that you can zoom in any area of Australia. So as an example, here, what you can also see is in black, the areas in black are represented total burned extent reported by the emergency authorities at a given time and the red flames are the active parts as reported. This is basically the same information that you may have seen in the farge near me. But with this website, we also provide information of the few moisture content. So this screenshot that I prepared I searched for the few moisture content maps during one of the days of the Oral Valley fire in the 25th of January. And as you can see, the fuel was very dry that day and that they may have the intensity of this fire. As a comparison, I also included the same the map of the same day but in 2011 and you can see a huge difference. So now the map is pretty much blue. That means it has very high values. And again, if we go back to this map we can see how red everything was. So the dryness of the landscape was quite. So moving into mapping a fuel structure and load. So this is best captured with a remote sensing method that we call LiDAR. So the principle behind LiDAR is really simple. It's a lot simpler than what I explained before. So basically the LiDAR is an active sensor or an instrument that fires rapid pulse of a laser light at the surface and measures the time it takes to return to its source. So as the light moves at a constant unknown speed, the LiDAR measurements can calculate the distance between itself and the target with high accuracy. But repeating this quickly in succession several times the instrument can build a complex map of the surface that is measuring and this is called a point cloud. So up to a few years ago you could only have created LiDAR data on ground sensors such these two that I display here on the bottom of this slide that nowadays there are satellite LiDAR observations that are great. I am now greatly increasing with the written launch of for example the Jedi mission that is an NASA mission on board of the International Space Station. So LiDAR can reconstruct the three-dimensional structure of a forest providing extremely detailed information of the forest structure and load and here I show you an example of a point cloud of the Black Mountain that you can see the Telstra tower up there and here this animation and yes is a specific location assuming to this point cloud and to this point cloud we have basically run a complex automatic algorithm to classify the different points into the different layers of the forest and then from this we can start to extract properties of the fuel and different few layers that are relevant for fire behavior like the authenticity of cover of the near surface fuel or the elevated fuel or the height of the trees or things like that. By the way, I just take a time to remember you that you have questions remember to write them in Facebook and I will answer them when I finish. So apart from using LiDAR the right information on fuel structure and load in fire behavior modeling also the maps are very important to provide useful information for separation of cities. For example, this is a map of the the elevated fuel load so basically in red you see areas with high loads and in blue you see areas of low fuels and these maps were used for example in 2019 you may remember that there was a small fire small in comparison with what we had the year of course around the square rocks so these LiDAR maps were used to locate a site free of trees to win the special firefighters in because it was a remote fire and also it was used to try to pick up the easy line to construct the walking track okay so now moving into the applications of remote sensing during the fires the objective here is to use a satellite based data to detect the fires and determine how the fire is going to spread and also find both what we call soft and hard containment lines so soft lines, containment lines can be for example differential in fuel moisture content so there is a part of the forest that has that is wet air that can have like a soft containment line so when the fire hits that wet area it may spread slowly and it will be easier to contain and the hard containment lights normally refer to roads and paths and things like that so most people may have seen you see this is an animation so most people may have seen these maps here on the right during the last fire season as they were very popular in the media so these maps are hotspots so what it is really is thermal anomalies used to identify active fire so this animation I have borrowed from Robi so as a time series of the active fire during the last fire season and it is just spectacular to see how the activity grows over time so one of the important aspects when it comes to detect active fire using satellite observation is the frequency in image acquisition so of course the more frequently the satellite collect imagery of a specific area the higher the chances that you will be able to detect a fire as soon as it ignites so this animation so you on the left active fires detected by the NASA modis satellite I mentioned before that this sensor is on board of the Terra and Aqua platforms that views the entire surface every one or two days and therefore the frequency of observation is a bit limited for active fire detection so on the right under the hand you have the detections detected by Imawari-8 that is just Japanese geostationary weather satellite so this means that the satellite is pointing always to the same location on the earth and therefore offers general improvements in the frequency of observations this satellite provides an image every 10 minutes and therefore it is more useful when it comes to the spread of a fire as you can see in this animation these are other images offered by satellites but I'm sure most of you might be familiar with them because they were also in the media during this last fire session and these images here are from high resolution optical data over Bayman's Bay during the 31st of December and you can clearly see the smoke of the fire front and even the cumulus clouds of what we call fire clouds associated with the fire activity after the fire season you can use this information about fire activity or hotspots during a specific period to know how the season was and this slide that comes out of a report on the state of the environment we released a few weeks ago summarized the rank of fire activity by a region in Australia and clearly shows us that while fire activity last year was below or average across most of the inland due to low fuel loads because of the dryness it was the highest since at least 2000 in Tasmania, the east coast and parts of western Australia so finally during the sorry post fire phase of fire management the objective here is to map the effect of the fire basically how much area is being burned in with severity and then also to compute the missions resulting from the fire and also to look at how the vegetation is recovering after the fire so in the same way the reflect changes in fuel moisture content because plants with different water content have different response here we can detect fire severity because the reflect or burning area because the reflectance spectra for unburned vegetation canopy and fires affecting different vegetation strata are very different and those differences can be used to map the total burn so these animations show an example of the total burn of the fires with Sydney last season the yellows indeed show the active fires similarly as I previously show the time of the active season and the black shows the area damage at its time so using that also from the NASA Modi sensor we recently analysed in this report I mentioned on the Australian environment in 2009 we estimate the burn area per land cover to clearly show that the bush fires we just had were unprecedented in the forested environments of Australia and this analysis only included the area burn up to 2019 that was the period of the study but as I mentioned before fire is not really a binary process so the analysis of fire impacts require better discrimination of the variation of burn severity and satellite data can also generate information for example this is a map of the severity of the 50 fires that happen in Queensland so this fire went a bit of convective on the 18th of November and burned right up to two significant dams which are water resources for two areas in Queensland so we provided these maps because they help the Queensland agencies to talk to the local council about targeting remediation efforts to protect the water supply so basically it tells you where you need to be more quicker in making remediation activities because the fire has been affected this area more severe than others so one important aspect of any satellite based maps of any kind of variable is validation we need to remember that the satellites record some information that then needs to be converted into the collect data that then need to be converted into useful information and for that we use algorithms so once we derive maps of whatever we are targeting in this case for severity then we need to do remediation and these are some images some of the observations we took of the severity of the fire the overall valley fire here in the city in February basically we flew with an helicopter and we took visual estimates of the fire severity at the same time that we also took photos with a normal camera so the tracks we did during one of the days we flew so this is the sample of the severity map for the overall valley that we derived using in this specific case we use data from the european space agencies sent to sensor that provides imagery every five days at 10 meters as a resolution on the ground and again overlapping this map I have those that are the observations we took from the helicopter so again once you do the modeling and you have a map you always need to do some field validation and here for example this spot that is in the green area that this area affected with low severity this picture taken from the helicopter that shows that indeed that area was not heavily affected we only have a few panophys that were scored this other dot that is in the yellow area that are medium severity here we see that most of the all the panophys are scored and if we take up dot in the red area we see how the vegetation is completely gone so there is no fuel left so the fire was more intense so I guess just to finalize my take home message I guess is that the increasing challenging fire management situation are calling for proactive approaches to reduce the likelihood of catastrophic bushfires emotional sensing information has already and will be in the future support fire management in Australia providing additional intelligence and to better plan, prepare and response to bushfires but I guess my key message is that on top of using better information technologies governments and individuals also need to take serious actions to tackle the underlying problem with these climate change so I think that was everything I wanted to cover tonight I hope you enjoy my talk and now I'm ready to take questions thank you for listening alright so we have a few questions already so the first question is whether in the future how can we reduce the potential for bushfires well this is an excellent question and that really touches in my last point so with better information we can be better prepared and we can better plan and better respond but we will no stop fires to happen in the future so for that really we need to tackle climate change and make a serious efforts to reduce the increase in the future so the next question is whether there are predictions for the next summer 2021 well I don't think we have predictions yet but it's very difficult to know what is going to happen because in one as I said at the beginning fire risk depends on many factors so one is the fuel load the other is the brightness of the fuel in one hand there has been so many fires that the fuel has been reduced dramatically so there is not much fuel to be left to be burned but on the other hand the areas that have not been burned may be drier if we still have a dry dry winter dry spring and dry summer there is still a bit early to know what is going to happen so another question is if more prescribed burns have been conducted in the areas burned last fire season would the burn areas be low and not have resulted in fires we had well there is a very hot debate around that and the answer to that is not simple it really depends on a specific case so for the oral ballet specifically we show that the areas that were recently burned with prescribed burns in recent years were affected with less severity than areas that were not burned in recent years but this has not been observed in all the fires so it is very hard to have a direct relationship between radiation of fuel and the effect on the fire severity and occurrence will you always need to verify the satellite data or will you eventually be able to rely on satellites alone well that is an excellent question and I think we always need to verify the satellite data at least in the research development phase so once you have validated your algorithm and you know how it works and how accurate it is then you can just run it and forget about the validation but again that initial evaluation is very important to keep an idea of the uncertainty of the algorithm okay so it seems that there are no more questions coming so thank you for your time tonight and I hand it to Brad now yeah thanks Marcia thanks for doing that that was fantastic and so you know we'll finish right now with looking a bit backwards and a bit up instead of looking down and we'll just do a few more objects and then we'll call it for the night just keeping in mind that the next public night will be in about a month 26th June that again will be virtual so stay tuned for the speakers and we'll also do some different objects with the virtual telescope there's a few other events happening in the meantime so feel free to check out the page now obviously one of the big things to see especially right now it's very clear above us and that is the southern cross you can see that right in the middle it's pretty high in the sky now one of the cool things about the southern cross is actually what we call the pointers so these are two stars that point as we call that to the southern cross and the brightest this bottom one is what we call alpha centauri are Rigel centauri now so some stars are called alpha or beta and you'll hear omega later one of the things that we do in astronomy is the brightest object in the constellation is alpha and then the second is beta and then delta gamma so on then we get to omega and then we go A through Z and then we just start calling them numbers so alpha centauri just simply means the brightest object in the constellation centauri because that's alpha crux beta crux delta crux gamma crux epsilon crux now alpha crux or alpha centauri rather it's a very special object the reason it is special it is the closest star to us besides the Sun so it's the closest thing to our solar system and beyond now it's 4.2 light years away so that means if you're staring outside right now and you're looking at alpha centauri the light you're seeing now left 4.2 years ago it left in 2016 2016 seems like a much simpler time but that's a different story it left 4 years ago it literally takes 4 years to reach us and then to return so it's interesting because let's imagine you're standing on alpha centauri let's say I transfer you there and you send a message pick up a phone say hey hello I'm here I won't hear for 4.2 years and then I have to reply back it's an 8 and a half year conversation 8 and a half years just to say hello you know that is really bad internet lag I know we complain about the internet speeds here in Australia but that puts it a bit into perspective in my opinion now alpha centauri is also special it's not only just it's not a single star there's actually three stars there's alpha centauri a and b and then there's proximus centauri the proximus centauri is a much smaller what we call m-dwarf or red giant that orbits around it now the two main stars alpha centauri a and b one of the great things you can see is through a telescope you can actually start to see that it's not one star that is two stars now this looks weird you're imagining you're staring down a road and you see the car headlights and as the car gets closer you start to see the two lights becoming clearer and clearer so it starts as one light starts to be smudged and becoming two so through the telescope I just took an image and you start to see here is kind of one circle and here is another instead of just a nice round circle there too now in fact it's actually even more clear with your eye my phone my camera rather I wasn't really able to grasp just a great detail through the telescope you can really see these two bright dots and these are this is the closest solar system to us and we can see those two objects for our own eyes now there's also something else to look at in the constellation centaurus and that is a mega centauri so the way to find this is we have the southern cross we have the bright pointers and they point to the southern cross now if you kind of follow up from beta centauri or Hadar and you follow a straight line we get to another bright star let me get to it will look like a star to your own eyes but it's actually kind of a fuzzy blob and that fuzzy blob is what we call a mega centauri and a mega centauri is not a star at all it's a globular cluster so this is another image from Dave Weldrake with our telescope recently so what you're seeing here is what it looks like through the telescope it's amazing this globular cluster has 10 million stars in this little ball 10 million solar systems 10 million suns not quite the same size of our sun but it's a range 10 million objects in this little ball and yet even though it appears as a bright dot on the sky it is this beautiful globular cluster now a mega centauri is quite interesting a mega centauri is it's a very dense it's a very big globular cluster and it's also different than the other globular clusters and one of the things that has been studied at Mount Sharumlow for the better part of 70 years is this globular cluster and what people think is that in fact it actually used to be the center of an entire other galaxy a dwarf galaxy and as that galaxy came into our Milky Way the Milky Way started to pull it apart and swallowed it and the rest of the outside kind of got destroyed and what's left is just this little core the little inside ball of the remaining stars so we think that a mega centauri may have is the remnant of a galaxy that's been destroyed by our own Milky Way and when you look at also this photo you see a couple things you notice immediately there's different colors here and these colors are real now when you go into the sky whether it's looking at beetle juice an Orion or you know anywhere else in the night time sky stars color relate to their temperature so imagine flame so imagine a flame as the hotter the flame gets it gets from red to yellow to orangey to that bluey white flame where that white blue fame is really the hottest so hot things burn bluer, cooler things burn redder so when you see these blue stars they're actually burning hotter the red stars are burning cooler so we can actually measure and see their temperature differences with our own eyes and there's another thing we can relate to this hotter things also are younger things so the younger stars burn more hotter bluer, the older stars are a bit cooler redder so immediately just by seeing the range we can see where the hot young stars are in the older cooler stars are and so someone just asks why there's so many suns in the area and that's again so we think because this was a condensed galaxy that as the dwarf galaxy came into our Milky Way the rest of the outside started to get ripped apart and what's left is just a very bound through gravity a very contained area in there and someone actually asks a very good question how can we tell there are 10 million stars now we don't know the exact number we don't sit there counting them here's a great example we estimate there's 300 billion stars in our Milky Way and if you can count a star so imagine this, so imagine you count 5 stars per second so you go 1, 2, 3, 4, 5 and that's the second and then 6, 7, 8, 9, 10 and so on and imagine you just did that your entire life and that's all you did it would take thousands of years to count the stars in our Milky Way so the way we can estimate it is through two things we can measure its mass we can feel how heavy it is and get an estimate of that so we can kind of weigh it and we weigh it based on measuring how fast it's spinning and moving and a few other ways and we can also then measure we can take chunks we can take density chunks we can take a very small portion and a couple smart portions see actually how many stars are in that small portion and then figure out and estimate overall so that's a really good question we think there's about 10 million stars give or take and both of that estimate has arrived by a couple of different ways but Omega Centauri is a really great thing to see in the nighttime sky and in a very dark sky like tonight it was really great and easy to see this and again you can even through a pair of binoculars if you start to focus in on it you see it's not a dot you see it's fuzzy compared to the other stars and that's a great thing about it is if you take a pair of binoculars and you look at Alpha Centauri or Alpha Crux it looks like a star and then you start to look at Omega Centauri and you're like hmm that's kind of fuzzy why is it looks that way so someone just asked what are the hottest stars called and what are the coolest stars called so we classify stars in a category we go from O B A it used to be it's an old archaic system where someone thought they ordered it in A to B or A through O you realize it's not the case so the hottest stars, the youngest stars are O and B type stars and then you get to the more middle stars like G so our Sun is in the middle of its life it's a yellow dwarf giant or yellow dwarf star so it's a G type, a G3 type star the cooler ones become M dwarfs or we also call them red super giants so some of the big blue stars will be blue super giants some of the big red stars will be red super giants so great question now in about 10 minutes if you look towards the east you'll start to see two bright things pop up in the night time sky and that's Jupiter and Saturn so what you'll see of Saturn is I took it last night so I did have to cheat and take this last night because we couldn't stay up that late but if you'll stay out and if you go outside in a few minutes especially in about an hour from now you'll see two bright objects in the eastern horizon and that will be Jupiter and Saturn now firstly one of the cool things is how do you just see or tell if a planet is a planet in the night time sky planets don't twinkle so if you look in the sky right now you'll see some stars are twinkling especially as you go towards the horizon where there's more turbulence so turbulence the same reason your aeroplane shake is the same reason a star twinkles and as you get more towards the horizon there's more turbulence and you see the stars twinkling the color slightly flicking and changing planets don't twinkle why don't they twinkle well the cool thing is it actually really isn't to do with our atmosphere or astronomy or space so these stars that we see pretty much just single points of light come through the atmosphere and that atmosphere is twinkling around so we see it moving now Jupiter and Saturn are a bit closer now because they're a bit closer they actually have more points of light coming into our atmosphere now our eye is not sensitive enough to see that our eye just kind of blends it together and we see it as a bright point and if you remember when we looked it back at the moon a little bit later there were actually parts where the moon appeared to wobble and you can actually kind of see a bit of the turbulence in the moon itself now if you go out tonight or any night you stare at the moon you don't see the moon twinkling but we can actually see a bit of the effects of the atmosphere looking to the moon through a telescope so Jupiter and Saturn you can pinpoint it as those bright dots and the other thing with planets is they form what's called a line across the sky we call the ecliptic so if you know kind of roughly where the sun rises and sets our solar system is a big disk or a plate and the planets form and travel along the same mine that go across an arc across the sky so if you're going to make an imaginary line connecting the movement of the sun all the way across setting in the west what you'll see is any bright dot that's not twinkling and along that line roughly will be a planet so you can actually I'll actually predict so the sun will set right there or the sun will rise right there tomorrow that's where the sun will rise so it's a really cool way of figuring out planets with your own eyes it's just by seeing them um now Saturn so you can actually already see here here's a bit of the rings of Saturn and the gap now I'm going to zoom in on the second we don't see the color as well unfortunately my eye pitched it up really well but the quick picture I took in it but you can already see the gaps here now the great thing about Saturn is it does tilt so sometimes we see Saturn beautifully the main bit of the planet and the rings but sometimes it's almost face on that it looks like a straight line and someone just asked how good does your telescope need to be to be able to see Saturn or Jupiter now I'll just put that in the scale the telescope that Galileo used to see the four moons of Jupiter was four centimeters it doesn't actually have to be that big to start resolving Jupiter and Saturn even with a good pair of binoculars you can start to see the moons of Jupiter you'll see the bright circle of Jupiter and four bright dots around it and next month we're going to take a very cool look at Jupiter we should be able to see some of the gas bands and we can see some of the moons and hopefully if we can take a few time lapses of it we can actually see the moons moving around Jupiter so they actually do move around Jupiter it's really cool now when you look at Saturn I really love Saturn because it's exactly what it looks like this isn't fake this is exactly what it looks like and we zoom in we can really start to see here is the gap of Saturn you can even see the main ball here the main part of the planet and clearly the rings around it Saturn looks exactly as described now one of the great things about rings of Saturn is Saturn is not the only planet with rings in fact all four gas giants Jupiter, Saturn, Uranus and Neptune all have ring system Saturn just has the biggest rings and so obviously we see it the best but the others have just as many rings now one of the other things that I think is really cool of Saturn and next month we'll try and take a closer look at to make out is it has a very big moon called Titan and Titan is a very interesting place where we think has water and ice and it could host life now Saturn actually has the most moons in our solar system Saturn has 82 moons Jupiter only has 79 so Saturn took back the title of most moons in the solar system about 18 months ago and as I said next month we'll take a look at Jupiter and we'll take a little bit closer look at some of its moons and we'll talk about it a little bit earlier now we have time just for a few minute questions and I hope we've all enjoyed our virtual thing and I look forward to the day and we're all back at Stromlo and we can look at the telescope because I still get excited seeing Saturn and being like yes that's exactly how it looks like just as described that's what we like in astronomy just as described so someone just asked how far away the closest black hole to Earth is yes we do know the answer to this and this was a recent discovery a couple weeks ago a black hole a thousand light years away was recently discovered so that to date is the closest black hole that we can get and now a thousand light years is still pretty far away the Milky Way is a hundred thousand light years across so if you stood on one side turn on a torch and take a hundred thousand years to get to the other side in this case it's only a thousand years but the star system can actually be resolved with the eyes and in fact what we'll do is next month we'll take a look and actually try and see the exact spot where the closest black hole is to the Earth and I'll show you how to find it so it's a really cool thing we can now do now it is far away so how long to take to drive well a thousand light years so let's put this in a scale I won't drive there we'll send Voyager now Voyager will take about so Voyager just to get to Alpha Centauri so Voyager is the furthest probe we sent to get to Alpha Centauri which is four light years away would take 75,000 years so to get to a thousand light years you're talking about a very very very long time talking about over a million years to get to the nearest black hole now we do think there's a lot of black holes in the Milky Way anywhere between tens of millions upwards 100 million and we do have the supermassive black hole but most of the black holes are quite small because this black hole that's near to us this thousand light year distance black hole is only four times the mass of our sun so it's actually quite small and I'll end on this question because I think it's always a nice one what got me interested in astronomy I wasn't someone who looked at the telescope when I was a kid I wasn't really interested in astronomy when I was younger is when I went to university and I didn't really know what I wanted to do I did some physics I did philosophy, I did theology and I tried different areas of physics and then I said hey asher physics yeah that sounds fun I emailed a few professors in the department one replied and that was pretty much it and so some people know and feel they're destined to be an astronomer and they're amazing people there's a lot of people who we work with I wasn't one and I think that's kind of important to hear because sometimes especially kids if you're listening you think that you have to know what you're going to be in the future you don't it's okay it's okay to change your mind just do something that's fun because if you're doing something that's fun you'll enjoy it and then you'll succeed at it I think that's the coolest thing that you can have so we're going to end it there I think thank you everyone for tuning in thanks to our amazing speakers Ryan and Marta and again next month on the 26th of June we'll have another virtual public night we'll have a few different talks and I hope everyone has a rest of the great weekend and be safe and be well take care