 All right, I think we'll make a start. So, welcome to Digital Mount Stromlo Observatory live streams. My name is Adam Reigns. I'm a PhD student at the Observatory at the Australian National University where I study a variety of things and I'll be talking about one of them this morning. But before we get started, I'll just mention this talk will go for about 20 minutes to half an hour. We'll have time for questions afterwards. So, if you have any questions during the talk, just type them in the Facebook chat and I'll have a look and I'll get to them at the end. And I'll mention that a few other times throughout the talk. But yeah, if anything takes you fancy about what I'm talking about or something related, just pop it in the chat and I'll get to it. So, now to get started. So, what I'm going to talk about is a technique in astronomy where we combine the light from telescopes to essentially get more bang for our buck to make them greater than the sum of our parts because having one telescope is fantastic. But we can only build telescopes so big and sometimes in order to have a bigger telescope, we can combine them, combine the light from them in order to do really impressive things, really cool things. But get onto that right now. So, this here is a beautiful, I've got some sunset pictures and videos here because telescope observatories, I think make the best sunset pictures, but this is from Siding Spring Observatory, which in the telescope we can see here is the AAT. The AAT is the largest optical telescope in Australia. So, optical means light we can see with our eyes. And the AAT does some fantastic stuff. It studies stars in our local galaxy, figuring out what they're doing, studying their chemical, like the chemistry of them. They even looks to plants these days and even looks outside our galaxy to see distant galaxies. But sometimes even that's not big enough. So, the AAT has a mirror about four meters across. So, imagine your bathroom mirror, but now imagine a mirror that was four meters across, that's bigger than a car. And sometimes that's not enough because the reason we build telescopes is because we can see extra detail with them. And the reason for that is that the bigger your mirror or your lens, your light collecting area, the more detail you can see. This is why when you hold binoculars up to your eyes and take a look at distant mountain or whatever, you can see more detail because the binoculars, their lenses, make your eye bigger than your eyes. The collecting area is bigger. Because when it comes to astronomy, it's all about collecting lots of light, but also light over a large area. And so, what I'm gonna talk about today is a technique called interferometry, which is essentially telescope teamwork. We combine our telescopes together and we can do lots of stuff with them. So, we can only build telescopes so big. We can't actually make a telescope the size of a football field with a mirror. That's simply too big. But what we can do is put telescopes either end the football field and collect their light. And so, we'll get into that. But first of all, we need to talk a bit about sizes and resolution. This here is a scale picture. Well, not picture, but it's to scale of the Earth and the Moon. And so, the Moon is actually really far away. You could fit 30 Earths between the Earth and the Moon. And really, really big. But we can still see the Moon when we look into the night sky or the daytime sky. And as we all kind of know as humans, as things get further away, they get smaller and as they get closer to us, they get bigger. So, if the Moon was further away, it would look smaller in our sky. Or if it was closer, it would take up more size on the sky and our full moons would look much more interesting but our tides would be a bit weird as well. So, this lets something really cool happen on Earth because the Sun is much bigger than the Moon, but it's also much further away. So, by a quirk of nature, we're really fortunate here on Earth to be able to have the Moon be about the same size as the Sun. And when they overlap, that causes what's called the solar eclipse and the Moon blocks light from the Sun, which lets us see all the faint outer atmosphere of the Sun, which is really, really, really neat. And this is just a demonstration of that, the fact that you can, if you've got something smaller that's closer, you can cover something larger that's farther away. So, to bring this a bit closer to home, if we take an Australian dollar coin, it's 25 millimeters across, how far away would you need to hold that dollar coin from your eyes, such that you could exactly cover the Moon and the Sun? Well, the answer is about 2.8 meters. And so, you know, you can hold the dollar coin up close and see how big it is. And then if you put it on a big stick, you could hold it out and exactly cover the Moon or the Sun. And I'm gonna take this analogy a bit further. But let's zoom in a bit. So, this is the Moon and if we zoom in, well, not zoom in, this is the size of the planets in our solar system compared to the Moon. And all of these planets are bigger than our Moon. It's just that they're much further away, so they look smaller. And that green circle there, that's the resolution of the human eye, which means anything smaller than that, the human eye can't see any detail on. So, this is why if you look up at the night sky with your eyes, you can't see the strikes on Jupiter. But if you have a telescope, you make that green circle smaller because the resolution of the telescope is smaller, it's better, you can see more detail. So, when that circle is smaller than something, you can actually begin to see detail on. And this tiny dot, it's a bit hard to see, but that dot is about the average size of a twinkling star and a good observatory. So, Siding Spring Observatory that I mentioned, it's one of the best places in Australia to do astronomy. It's in the middle of New South Wales, in the middle of nowhere, where there's nice, dark skies. And the air is somewhat stable, which means the air is all moving all throughout our atmosphere. Some of it's going this way, that way, some of it's hot and wants to rise up and some of it's cool and comes down. And what this means is the air is very what we call turbulent. There's lots of motion there. And so, an analogy here is, if you have a nice painting canvas, like a canvas that you're gonna paint on, and you take your paintbrush, and you dip it in some paint, and you put a nice dot, a single small dot on the canvas, that's what a star would look like if the earth didn't have an atmosphere. But because of all the light everywhere, the light blows that out. So, it's like taking your wet dot of paint and smearing it out, and it makes the dot bigger. But just how much bigger? So, we zoomed in again, this is about the size of a twinkling star. And this is Betelgeuse. Betelgeuse is a star in the constellation of Orion, but we'll get to that in a bit. But it's a really, really big star. And it's actually one of the stars that looks biggest to us from the earth. It's not the biggest star, but just because of it's reasonably close to the earth, it looks reasonably big on our sky. But if you, even with a good telescope, Betelgeuse is going to get smeared out to much bigger than it actually is, which means you can't really tell anything about Betelgeuse, because it's, or you can't see detail on Betelgeuse because it's been smeared out. And so, here's a lovely picture from Chile of the night sky. And we're gonna zoom in a bit up here. And some of you, if you know anything about the night sky and constellations, might be able to pick out Betelgeuse. But for the others, I'll give this a hand. So, this is the constellation of Orion, the hunter. And we can see here in his shoulder that reddy star, that is Betelgeuse. And so, it's a red supergiant star. And if I took Betelgeuse and clicked my fingers and replaced the sun with Betelgeuse, so that the Betelgeuse was now in our solar system, we would all be inside of Betelgeuse and it wouldn't be a good time. Because Betelgeuse, its atmosphere extends out as far as about the orbit of Mars, which is really big. So, Mercury, Venus, Earth, and Mars would be inside of this really, really big star. And it's about, it's relatively close, 700 light years away, a light year is a distance. Like if I went outside with a torch and shot it at the sky at night, that light would take 700 years to get to Betelgeuse. That's what a light year is. And if we turn light years into kilometers, that's a really big number that I'm not even gonna bother reading out. But let's think back to our coin analogy. Betelgeuse was one of the biggest stars. How big would I need to make that coin, or half-far away, to be able to exactly cover Betelgeuse? And remind everyone here again that if you just joined us, I'll take questions at the end, so put any questions in the comments and I'll take them at the end. So, our coin would have to be 103 kilometers away to exactly cover Betelgeuse, the actual apparent size of Betelgeuse if we remove the twinkling, which is really far. I don't have a stick long enough to put the coin on the end of, that's a very long stick. I need to drive for like an hour, at 100 kilometers an hour, to go put that coin far enough away where it would exactly cover Betelgeuse. It's pretty far. But the thing is, how do we study these stars? And what stars do I study? So this is an actual picture of Betelgeuse. It may not look as pretty as one of the star pictures of the sun, for instance, but the sun's a lot closer. We can study it in a lot better detail. This here actually shows us that Betelgeuse has a lot of gas and dust that it's sort of billowing off it because it's a really big star and it's so spread out that it can't hold on to its atmosphere as well. So it kind of just throws it out into space. And so we can see that Betelgeuse has a pretty odd shape and it's quite bright in the middle and that green circle is about where we actually think the atmosphere of the star is. But this was taken with an eight meter telescope. So the stars that I've recently studied, these are some of them. My biggest star is the one at the bottom right, the Lambda Sanjiteria. And my smallest is HR7221. Not all stars get cool names, unfortunately, but keep HR7221 in mind because we'll come back to it in a bit. So how do we do this? So this is the BLT. This is the very large telescope in Chile. BLT, very large telescope. Astronomers are really good with names. So these four telescopes are 8.2 meters across. So that means they have a mirror that's 8.2 meters across. That's really, really big. And these are among the largest telescopes in the world. And this is what we took that picture of Betelgeuse with. And these telescopes have special technology on them and special mirrors that can change their shape that let us take the twinkle out of the stars. And so they were able to take that picture of Betelgeuse. But how do we do better? Because that picture of Betelgeuse is approaching the limit of what you can do with an 8-meter telescope. And our biggest optical telescopes currently in the world have mirrors about the size of 10 meters across. So it's hard to do much better with a single telescope. Well, what we can do and indeed what I did is we can combine the light from telescopes that are spread out. This is interferometry. And so I use these four 1.8-meter telescopes and you can move them around onto these tracks that you can see here. And when you spread them out, they can be up to 130 meters away from each other, which means that their resolution is the size of 130-meter telescope, which we can't actually build. We can't build a telescope that big, but we can spread our telescopes out and make one that big. Now, coming back to HR 7.221, what, how much detail can we see if we look at it with 130-meter telescope? Well, our coin, remember from before? The eye with this interferometer, I looked at the coin 4,600 kilometers away and measured its size. That's equivalent to the tip of Queensland in Australia to Wellington in New Zealand. And the size of the coin, how well I know its size? Well, I measured its size to about the precision of one of the kangaroo's eyes on the coin from 4,600 kilometers away. That's what you can do with an interferometer. But let's backtrack a bit. Let's talk about how telescopes work. So here's just a single-dish telescope. And what do I mean by single-dish? We have one big mirror and we have a secondary mirror. So what's gonna happen when we're looking at a star and we wanna get the light from that star to our camera? And so the light from the star comes off, bounces off the big mirror, hits the little mirror, and then goes down to our camera. You might have some extra mirrors, but this is how a single telescope works. How do you combine the light if you have two of these telescopes or more? And so the light has to travel exactly the same distance from the star to get to the camera, because otherwise it didn't leave the star at the same time and you can't really combine it sensibly. So you gotta make sure the light arrives at the same time. And so that makes, that's easy to do if your telescopes are here and your star's right overhead. But what happens if your star is over there? Like it's over near the horizon? Well, you've gotta move your camera, which is kind of hard to do. How do we do this? And the answer is we can do it with mirror trains. And so what you have is, you have essentially these big tunnels that sort of connect underneath your telescopes. And you have like a train or a cart on them, which have mirrors. And you can move that cart further away so that the light has to go further to bounce off the mirror and come back to your camera. So you can change the distance between your telescope and the mirror and sort of equalize the light. And here's another picture, like me looking inside one of these. So this cart system, this isn't at the BLT, but it's at another telescope, another interferometer that'll get to a little bit later. What about radio telescopes? Radio telescopes look really different to optical telescopes because they're using a different technology. Like with a radio telescope, as we'll see, they can look a bit strange, but they don't need to have as finely polished surface. They don't need to be reflective to our eyes. And this is Parks. It's a pretty famous telescope in Australia. There's only one of them. I've just duplicated the picture here, but if you wanna do interferometry with a radio telescope, they can do something neat is because of how radio technology works, radio telescopes can combine the signals later in a computer, which means we don't need those mirror trains, which makes it easy to put the telescopes really far away. Because think about it with an optical interferometer, like the BLT, I've got those telescopes 130 meters away, but that means that I need to have those mirror carts able to move a really, really big distance. If I wanted to put those telescopes kilometers away, I'd need to dig really long tunnels to be able to have those mirror trains move back and forth. And it's a bit hard to do, but with radio telescopes, because of the way that you can detect radio lights, and radio is a kind of light, we just can't see it with our eyes. The technology allows you to sense a bit extra about the lights, and so you can do it in a computer later. So, now we'll talk about some other interferometers. So this is Charo. This is an interferometer at Mount Wilson, near Los Angeles in California in America. And this is where I actually took that video of the mirror trains. And I'll just remind everyone again, if you've got any questions for those that have just joined us, pop them in the comments and I'll get to them at the end. So, what we can do with Charo. Charo can put their telescopes further away than the BLT. And so what they've actually done is something pretty cool. This is a star, zeta and drometer. And this is a model, an image that we've made of it by observing it. And we can see star spots like sunspots on zeta and drometer, which is really cool because sunspots are regions on the star where they sort of block the magnetic fields like magnets that stars have lots of magnetic fields. And what happens is they can block the heat which makes the star a bit cooler and thus appear darker because it's not glowing as brightly. And so something prior to observing the star, we didn't actually know that stars with strong magnetic fields could have sunspots on their North Pole and their South Pole. And so this is a map of that. And so what we're seeing here is the strange oval shape, that's the map and the dark spot and the color is temperature. And so the lightest color is about 4,600 degrees and the darkest color, which you can see right on the top of the star, is about 3,400 degrees. And so that's a pretty big difference in temperature, but the thing is we can't study this on the sun because the sun has changed in how much magnetic, how active its magnetic fields are over the years. And it used to be more active, but we don't have a time machine. But one of the good things about astronomy is there's lots of other stars out there that are all different ages. And so we can look at a star that's a bit like what the sun was in the past. And then we can see what it's like today and say maybe the sun was like that in the past. So what we can see here, I'm gonna flip between two images. One was taken in 2011, one was taken in 2013. And we can see that that big dark spot on the top of the star stayed there over those years, which means that this doesn't happen on the sun today, but it probably did in the past. And that's something that we can do within its parameter, see a star. All right, let's go back to the VLT. And so the VLT is in the Southern Hemisphere in Chile. And what we can do, we can look at a star Akina and it's spinning so quickly that it's not actually round anymore. The Earth sort of does this too, the Earth spins and it's about 21 kilometers bigger at its equator, but this is only 0.03%, which is pretty small. But this star is really flattened and this isn't a picture of a star, these are just some measurements, but we figured out that this is about the shape of the star. And parts of the star that are closer to the middle are going to be hotter than parts of the further away. This is why red giants are really red because their atmosphere is really spread out and it's colder, they can't be hot over the whole surface of the star. So all we can see here that the white bit of the star near its top and its bottom, that's 17,000 degrees. And the band around the equator is really thrown out because it's spinning so quickly, that's about only 13,000 degrees, which means there's 4,000 degrees difference in temperature on this star because it's spinning so quickly. This isn't a picture of the star, this is just a computer model, but we can only do this with interferometry, like measuring these things about the stars. Now that move on to something a little bit different, I've got to make a quick digression about how stars and planets are actually made. So here we've got a video playing and it's showing stars making planets and disks. So what happens? You have a big cloud of gas and dust and gravity wants to pull it together. But the thing is the cloud is spinning. And so much like if you've ever seen a chef with making pizza and it's sort of the dough in the air and it spins out and becomes flat, that's sort of like what's happening here. And so it becomes, gravity pulls it flat and it's spinning. There's a star in the middle and you're left with a big pancake around the star that is where the planets are going to be born. And so this is a computer simulation done by Professor Mark Kromholz at ANU. And this is the sort of stuff you use a big supercomputer for. I don't have a computer that's powerful. And so what, why I showed you that is because we can look for those disks. We can look for those pancakes in the sky. Now this is another telescope in Chile. This is Alma. And it has 66 telescopes and you can spread them out between 150 meters away from each other all the way out to like 16 kilometers which is much further than you can do with an optical telescope because these are like radio telescopes. And so this here is an image taken by Alma. And what it is is at one of those pancakes. There is a star in the middle of that, of that circle in the brightest bit and all the rings around it are gaps in the disk in this pancake. And those gaps might be planets that are traveling through the disk and gobbling up all the gas in the dust. Cause what we're seeing here is the gas that has grown glowing really brightly. And do you like that one? How about any of these? Pick one of them. They're all different shapes and the solar system could have looked like any combination of these. Some of these have really thin rings like the one at the top left. Some of them even have spirals sort of like our galaxy. And these are all baby stars. These are baby stars that are making planets and they haven't cleaned up their solar system yet. Like our asteroid belts in our solar system is sort of the leftovers of these disks. Cause once the star has finished making planets all the gas kind of gets blown away or eaten up onto the planets and the dust goes onto the planets or gets blown away and there's only a little bit left over. But with an interferometer, you can see these and very nice details. So let's go to Australia. So this is ASCAP, the Australian Square Kilometre Ray Pathfinder. And you've got 36 of these big telescopes, the big radio telescopes and they're big 12-meter dishes. And it's in the outback because if I went there with my mobile phone, the mobile phone, the telescopes would see the mobile phone and the mobile phone would be really, really, really bright and brighter than anything in the sky. So it's out in the outback where there's not as much mobile phone coverage so we can have clearer skies because that's the equivalence of looking up if you've got a big city and you look up in the sky how there's lots of light pollution. Light pollution for radio telescopes is mobile phones. And so what can we do with this? Well, researchers at ANU led by Professor Naomi McClure Griffiths studied the gas in two of our neighbouring galaxies the large and the small Magellanic clouds. And so with these, they've got extreme detail, three times smaller detail than ever before. And why is this important though? So what we're looking at here is like hydrogen gas which is the most common kind of stuff in the universe. So if you're in the Southern Hemisphere and you go outside to a dark site and you look to the south, you can see these, the large and the small Magellanic clouds and the large one is on the right and the small ones on the left. And these are small galaxies that orbit the Milky Way. But they're also kind of orbiting, they're tugging on each other, they're having like a tug of war. And between them, there's actually a big strip of gas that baby stars have been born from. And so by using different kinds of lights, study these galaxies and getting the extreme detail that you can only get with an interferometer we can learn about our close friends. So still in the Southern Hemisphere, how don't we look at a radio telescope that's a bit strange? It's not really what you'd expect a telescope to look like. This is the Murchison, this is WA, MWA sorry. And so this is a telescope or one tile from a telescope. It looks sort of more like a fence or an art exhibition but each of those white contractions is actually an antenna and you get a bunch of them together and put them on this big tile and that's a telescope. And then you have lots of these tiles spread out really far away and you can see stuff in the radio. And so what we're seeing here, this is what MWA would see what the sky would look like to MWA if or us if we had radio eyes. And so that big strip, that's the Milky Way and then off to the right you can see sort of something that looks a bit like an hourglass. What is that? Well, that is Centaurus A and it's a galaxy that didn't want its gas. And so Centaurus A has a supermassive black hole in the middle and that black hole is eating lots of stuff and it's a messy eater and it throws lots of stuff out the top and lots of stuff out the bottom. And what we see on the left is what MWA sees and on the right is what we would see if we looked with a telescope with our eyes. And you can see that everything there that we can see with our eyes is really small. That's tiny, it's in the middle of that and all this stuff coming out of the top and the bottom is all the gas, all like the hydrogen gas that Centaurus A has just thrown out and it's really, really, really long. Millions of light years long. Like if you was right next to the black hole and you shot a torch up, that light would take millions of years to get to the current top of all that gas. And your W.A. gives us an extreme amount of detail. So coming back to parks, this is what park sees if it looks at MWA. And so parks has a 64-meter ditch and it's a really big telescope. But let's jump back and forth between these a bit. This is the difference in resolution that you can get when you put your telescope really far apart, like three kilometers apart, like MWA. You can see much more detail. And this is what an interferometer can do. Parks is still a great telescope and actually can do some complimentary science because we need all kinds of telescopes, big and small, single and joined together to do astronomy that gives you a good idea. So to wrap up, talk about the biggest interferometer. So this here is a map of the Earth and all those little points on it are telescopes, radio telescopes that all observe the same thing. This is the event horizon telescope. And you may have heard about this in recent years or you may have seen this picture because this is a black hole. We used radio telescopes spread out across the entire planet, which means we essentially had a planet-sized telescope to look at a black hole. But what are we seeing here? So this shadow is the size of our solar system. And so the black hole is in here and there's a shadow around it because black holes are black because not even light can go fast enough to get out of them. So this is why we need a rocket to get off the Earth because you need to go fast to overcome gravity. But black holes have such strong gravity, they're not even light. The fastest thing there is, you've heard of the speed of light can go fast enough to get out. And so there's a shadow around that where any light that falls in never comes out. So this is a disk, like a pancake of hot gas that's orbiting the black hole and it's shining really brightly. So this is 25 times smaller than HR7-221, my smallest star that I looked at. What's that number? One and a half million times smaller than the human eye resolution and it's 45 million times smaller than the moon. This is really incredible and this is something we could have only done with an interferometer and a planet size interferometer at that. And so different wavelengths of light let us see different things. We use radio waves here because they can kind of see through the gas. This isn't our black hole, I should mention, it's a black hole in another galaxy, the Messier 87 galaxy. But by using radio light, we can kind of see through the gas and the dust that's in the way of the galaxy. And this study, this telescope also looked it out black hole and we'll get a picture about it at some point as well. But here's a completely unrelated sunset video that I took at Sighting Spring Observatory. But for resolution, two telescopes really are better than one. And so this brings me to the end of what I wanted to talk about. But by combining a light from multiple telescopes by doing telescope teamwork, getting our telescopes to get together, this lets us do something called interferometry, which allows us to get telescopes that are greater than the sum of their parts and see things that we can't with our own eyes because we need gigantic telescopes to see it. But it lets us study stars and how stars make planets and even galaxies and clouds of gas in space in fantastic detail. So thank you all for listening and I'll take any questions now. And so I've got a question here about what's my favorite interferometer and why? So I've only used two interferometers. I used the BLT in Chile to do my science, to measure the sizes of like HR7221 in the land of Sagittarius, M16 stars. And so that was really fun and interesting. And the way that works is I didn't actually go to Chile because astronomy is really international. And what you can do with that observatory is you can say, hey, I'd like you to observe these stars for me when the sky is pretty clear and there's no clouds and the air is pretty still, the stars aren't twinkling much. And what'll happen is they'll observe for me those stars when the conditions arrive. And so there was another astronomer using those telescopes in Chile that observed for me. I'd observed with Chara though three times now. And been pretty unsuccessful. Like I actually went to Los Angeles, like LA, California, went up to Mount Wilson and was on Mount Wilson Observatory in the observatory control room, picking the stars we wanted to observe. But as happens with astronomy, the sky was cloudy and it was rainy and it was too humid to open our telescope domes. Because if it's too humid, then the water can drop on the telescope mirror. And so that wasn't a very good time. We lost three nights, I think, to weather. And then I observed again last year and weren't very successful that time either. Like the sky was just really, really, really turbulent. And so what we were trying to use Chara for is Chara has a better resolution than the BLT, but it's in the Northern Hemisphere. So there are benefits and trade-offs to both of them, but you can see stars that are in the North that you can't see with the BLT in the South. But we were trying to look at red dwarf stars, which are stars much smaller than the Sun. And they're pretty hard to understand because they're really faint and their atmospheres are a bit weird. And so they're really hard to model in computers. So we're trying to observe them and measure how big they were to get their sizes so that we can put them into the computer models and see what happens. I'll just mention as well, if there's any more questions, keep putting them in the comments and I'll take them as long as you're giving them to me. But yeah, but because these red dwarf stars are so faint, like these stars are maybe 10%, like 10 times smaller than the Sun or smaller. And as a result, they're much, much fainter. And so we need much, much better weather to see them. These aren't stars, you can just walk outside and see, yeah, that's a red dwarf and that's a red dwarf, which makes it a little difficult. And we did have, this week actually, were the world not currently locked down because we've had to close all our observatories in the pandemic to make sure that we're safe and all the astronomers and people who work on the telescopes, the technicians are safe. And so I would actually be observing with Chara this afternoon to look at these red dwarfs, but Chara is closed. So not having very luck with, much luck with Chara, but I have hope for the future that we'll eventually be able to get some data on these red dwarfs and figure out just what's going on with them. Ah, so we have another question. Why can't we have optical interferometers the size of radio interferometers? And so I've touched on this a bit earlier, but the reason is that we need to make sure that the light arrives at the camera at the same time for optical telescopes, but like we can see with our eyes. But the problem is that we can't combine it at a computer. So if I wanted to have an optical telescope here in Canberra, say, and put one in New South Wales or one in Sydney or something like that, those are really far apart and I would need to bring the light from one telescope from both telescopes to probably like the middle, like where they are. So if I had a telescope in, you know, if we said to say one in Canberra, one in Sydney, I would need to bring the light 150 kilometers to the middle from Canberra and another 150 kilometers from the middle from Sydney, have the light there in a laboratory, combine it and have my camera there. And so I'd essentially need to have tunnels under the earth or I guess on top of the earth where I'm shining this light through to bring it to the center. And that gets a bit tricky. It's a really big distance and it makes it a really big construction project to build. Whereas with the radio telescope, because they have antennas and radio technology is a bit different, it's, you can combine the light in a computer. So about a radio telescope here in Canberra and a radio telescope in Sydney, I don't actually need to build that big tunnel. I can just save the data on a hard drive at one end and a hard drive at the other and like bring it together and then like line up the lights in a computer and it makes it much easier. And so that's just a limitation with optical telescopes. So we've got a question about what is my favorite planet? I like Jupiter. Jupiter's gorgeous to look at. I had a very small picture of Jupiter before which didn't really do it justice but looking at it even through a relatively small telescope, you can see the stripes on Jupiter which are the bands of clouds that go around the planet. And you can see the Great Red Spot which is a big storm that's been raging for hundreds of years and might actually be getting a bit smaller. And you can see the moons of Jupiter. So Jupiter has, you know, some 60 plus 70 moons now, I think and you can see the four biggest ones, the Galilean moons and each of these moons is about the same size as our own moon. And if you crawl back to the beginning, I showed you the size of the Earth compared to the moon and so each of those moons is about the size of our moon. But around Jupiter. And so you can see them just going around Jupiter and if you check back, like you've looked at it a few now and then a few hours later, for instance, you could see the moons actually change position because they all that pretty quickly. But yeah, the first time I actually saw those moons was just with a pair of binoculars as well because remember, binoculars let you get that extra detail leaning against the gum tree at my parents house. Just looking up at Jupiter and that was really exciting just seeing those moons for the first time. It doesn't actually take much to see them. But yeah, any other questions? Otherwise we'll probably wrap up soon but thank you for everyone who has joined us. I hope you learned something. I guess if we're not getting any more questions that all do us for now. Thank you everyone for tuning in. We'll be having more of these chats with some of the other astronomers from the observatory. You can watch this later or again if you want. If you only just quarter or you can catch it the first time. You can come ask me questions on Twitter if you want. So I'm at Adam D. Reigns. If you want to ask me any astronomy question, I can either do my best to answer it or point you to another astronomer on Twitter who knows better than I do because there's a lot to learn and we all know very little of it because the universe is really big. But anyway, thank you for joining us and I'll catch everyone next time.