 Hi, everyone. I'm Eloise. And this evening, I will be talking to you about how we can build baby planets. So luckily for me, if you've managed to hear parts of it, Jeff has already covered a couple of the things that I will be mentioning tonight, mostly around how planets are built. So first, I'm just going to introduce myself a little bit. Apologies, everyone. There we go. Sorry, technical difficulties. So I am a PhD student in astrophysics. And like Jeff, I am interested in space rocks because space rocks, normally I get a groan when I can hear the audience. So I'm assuming you all groaned at that. I study star and planet formation. So what that means is that I study baby stars. And to do that, I do simulations of baby stars. And what I mean by that is that I give a computer, in fact, I give this computer, Gadi at the National Computational Infrastructure, I give this computer a recipe and I'm like, hello, please make me some stars, please. And hopefully it does. Most of the time it does. So that's very good. But if we're trying to make a star and planet in real life, how would we go about that? So the first step that you need to go through is so you need to get all your ingredients together. It's kind of like making a cake or something. Then you've got to make a star. And then you've got to make planets. And then at the end, you get to enjoy your solar system. So this talk is going to have a few baking analogies in it. I already told you about my qualifications to talk to you about astronomy, but now I'm talking to you about baking as well. Basically, I really like baking. I do a lot of it. I managed to get some awards for it when I was a kid. So tonight we're going to have some helpers. So sometimes it's nice to have a helping chef when you're doing some cooking. So one of my helpers tonight is Hubble, the Hubble Space Telescope, which is in space. Now you may not know this, but Hubble is actually also an excellent chef. Very good at helping us find some stars. And this other helper I have tonight is Alma, the Atacama Large Millimeter Array in the Atacama Desert in Chile. And that's a handy little team of chefs. So I'm showing you these because a lot of the images I'm showing you tonight will be from either Hubble's kitchen or Alma's kitchen. So to make a star, you need some ingredients. So before you can make planets, you need to make a star because planets form at the same time as you're making stars. So you need lots and lots of gas. You need millions of cups of gas. You need some dust. You need the millions of tablespoons of dust. You need a cold, dense place. So basically it needs to be very cold. It needs to be, you know, if you think as hot as your oven can go, so that's 260 degrees, now make it negative. So it needs to be like minus 260 degrees for stars to be able to form. So, you know, that's a lot colder than you can get your freezer to go. And the final thing we need is gravity. Now gravity is sort of like the key ingredient, like the key tool you need in your cosmic kitchen because it helps you with everything. It can help you with forming your stars. It can help you with forming your planets. It's just like an all-round helpful tool. Now I took this photo at like a shop. So I, you know, it's a planetary mix master. The only thing I changed was branding it as gravity. So that I was very excited to see that. Apparently you can use a mix master to make planets. Who knew? Yeah. So that's what we need to make our stars. So now if we want to take a bit of a closer look and, you know, we've measured out, we're measuring out our ingredients, we've got them out of the pantry and now we're heading into the kitchen to get cooking. So the first thing you need to do if you're making your stars, you need your cold, dense place and you're going to collapse the cloud of dust and gas that you have. So it's going to collapse down and this is where you need to use your gravity. So gravity helps you draw everything in so that the core of where your star is forming is like a ball of, it sort of gathers together all the dust and gas and it's kind of like you've measured out all your ingredients and this is just starting to come together. So that takes around 10,000 years. So having a look a bit closer. So you can see these little, there's little points here. So I've just pointed to one there with a big arrow. Hopefully you can see that. So that little point there is actually where we might have one star forming. So they form in these little points at the edges of these big clouds. So the next thing we're going to do is once there's enough gas in that small area, a star will start to form. So the mix just come together. We're starting to get a dough and we're still adding stuff into the star and stuff might fall out as often happens when you turn the beat is on too high or when you're pouring flour into a bowl, you're pouring stuff in, pouring stuff in and then stuff just falls out everywhere. So you can see the sort of browner areas on this image that I've got here. So this is a real image of a baby star and then there's these yellow things pointing outwards from it. Now those yellow bits pointing outwards are where the stars just been like, nah, I don't want to throw it out. And this takes around 100,000 years for us to get to this stage. Now personally for me, this is my favorite stage of star formation because this is the stage that I work on. So here we have, I'm showing you some images of different baby stars. So when you have baby stars or when you're cooking, for example, and you cook and then you look at the recipe book example of what something should look like and then you look at yours and you're like, what? So that happens in space too. So here's one that looks all pointy. So the red thing coming out is the jet coming out of the star and the green is where there's lots of stuff around the star, what we call a disc. I'll talk about that in a minute. So here's another one. Again, the red stuff is what's coming out of the star and this one's my personal favorite where it's all blobby and a bit of a mess because that's what mine look like when I make them. So having a step, stepping into my, out of Hubble's kitchen and into my kitchen with the help of the Supercomputer Guardi, I have made these videos of some baby stars. So, you know, no cooking show is complete without a time lapse of maybe something rising in the oven or something. So we can think of it a bit like that. So in the image on the left, you're going to see sort of some rotation when I play the video and on the right you're going to see some jets of material going out from the star. So the stars in the middle of both of these images. So now I'm going to play the video and you should be able to see on the right it's sort of spreading out and on the left you're getting it swirling around. So I'm going to play that again because then I can make the sound effects and like it goes whoosh when all the stuff comes out the star. So you can see that there. Yes. So I mentioned that around these stars, so as you can see in the right image, there's sort of like this yellow squiggle in the middle and that's a disc. So basically when all the material is, when all the stuff's falling on to the start, the baby star, if you've ever seen someone throw pizza dough, so they start off with a ball and they throw it and it flattens out into a disc like it flattens out into a pizza, right? So that happens with all the material around the star, it's spinning and then it flattens out into a disc around the star. And this is actually what we make our planets out of and it takes us about a million years to get here. So you know, a long time. Now the ingredients that we need to make a planet are basically all the dust and gas that's in this disc around the young star. So this is where our building blocks come from. So after the star has formed, you end up with all these building blocks that you can, once the star's sort of forming, you can use all the leftovers from the, from, from building the star to build your planet. And this one's an artist impression, so unfortunately we can't get images quite that good yet. However, we do have these lovely images. So these discs are where planets grow and you can even see signs of planet formation in them. So this is, so we're stepping into Alma's kitchen now. So this is an image of HL Tau. So I just seen a question that says, how does it go whoosh in space when no one can hear you scream? So talking about the, the video I played where everything goes whoosh. Unfortunately, it probably doesn't go whoosh because it happens a lot slower than it happens in my video. But I like to make sound effects because otherwise you're just watching a video where nothing goes whoosh and that feels sad. So I like to make sounds to go with it. So this is an image of HL Tau that was taken with Alma in 2015. Now something that's really exciting about this image is, A, it was one of the first images where we could actually see this. There's these rings. And so in some of these dark rings, there could be baby planets. And then we kept studying different discs with Alma. And this is a survey of 20 of these baby stars with their discs. And you can see they have a variety of different, they all look different. They're all individual. And they've got all these different cool features. Some of them have spiral arms. Some of them have rings. Some of them have really strong asymmetries. There's all sorts of cool stuff happening in them. And these can all be different signs of planet formation. And really, it's, we're still trying to figure out how they all ended up looking like this. So the good thing about these sorts of asymmetries is that it can be really tricky for planets to grow. So you need to find places where it can make it easier for them. And when I say an asymmetry, I mean, see how you can see those two bright regions in this disc? There's two really bright regions. That's where there's a lot more stuff. Right. When there's a lot more stuff, it's more dense. So if you think of walking across, you know, pre, pre the current times, walking across a crowded room, you're more likely to run into people. Whereas if you're in an empty room, you're not going to run into anyone. That's because there's a higher density of people in the crowded room or on a crowded dance floor. And that's what's happening here. It's actually a lot easier for the little bits of dust to run into each other in these big, bright regions. And this is where gravity can come into its own. It can help pull everything together. So when you have your baby planets, basically the little bits of dust smash into each other and they keep smashing and smashing and smashing until they grow up bigger and bigger and bigger. So they collide to grow. And some will stay small like asteroids, but some will keep growing and they'll be able to come planet-sized or even here, moon-sized. But so that begs the question, you know, how did our moon come to be in this kind of environment? So just taking a step out of kitchens for the minute, let's just have a think about where, how we can make the moon. So basically we've got the early Earth, which is, you know, a baby Earth. And then we've got this, this thing about the size of Mars called Thayer. And Thayer kind of hit Earth. It went and hit it. So then it got a bit smashed. And then there was a lot of stuff that fell off. And then all those bits that fell off, you know, did the same thing as the extra bits from the staff, right? They flattened out into a pizza disc around, around the, the baby Earth. And then it was like, let's, let's be a moon. That's pretty neat. But not all moons form like this, right? So this is something that happened for our moon and our moon's a bit different. But if we think of one of our neighbors, Mars, who also has moons, Mars's moons at Deimos and Phobos, Mars's moons are actually asteroids like Jeff was talking about. So these are, instead of running into Mars like Thayer did to Earth, these moons were sort of moving past Mars. And then they were, they were like, you're cool. I want to be your friend. Gravity came into play. So they got pulled into Mars's gravity, but not so much so that they hit it. They just ended up around Mars. So that's a, that we digress to moons for a bit. They're kind of like putting sprinkles on your cake or maybe adding chocolate chips or something. But we still have to think about how we can get icing on our cakes. So if we think about the gas planets, so you know, the gas giants or ice giants, so the gas giants are Jupiter and Saturn and the ice giant giants are Neptune and Uranus. So you take this rocky core that you've made. So like the baby Earth, that rocky core that we had from all the planets smashing into each other. And you need to be out past what astronomers call the ice line. So that is basically where it gets cold enough that everything can be a gas. You know, if you want to freeze water, you don't put it in the oven, right? You put it in the freezer where it's cold. And if you're close to the sun, it's warm. It's like standing next to a campfire. It's nice and warm when you're standing there, but as soon as you move, move further away, it gets colder. So these sort of rocky cores, once they're out past the ice line, they can gobble up lots of gas and get bigger and bigger and bigger. And they can even act as a bit of an ice cream scoop sometimes, like we saw in the images I showed you of disks earlier, where there's those rings that have been carved out. So, you know, you put your icing on your cake. I did not make that cake. I wish I could do icing art like that. So the neat, the really cool thing that we've been able to do recently is we can actually, we've managed to take a picture of a gas giant forming. So this is a picture of PDS 70, which is a system. And they've blocked out the star so that they can see all the stuff around it. So I've just put the star back in for you. It's in the middle of that little black circle. And then this blob here, PDS 70B, is a baby planet. How cool is that? And this over here is PDS 70C, which actually has a ring of material around it still. So not only is it a baby planet, but it's a baby planet with a ring of material. And that's really, really cool because that's how we think Jupiter's moons formed. So similar to how when a star forms and there's stuff in the disk around the star, you get baby planets. Well, if you've got a big planet and it's got a disk of stuff around it, you can make, you know, moons from the leftovers. So that's pretty neat. Yeah. So at the end of making your solar system, so you built all your planets, you built all your stars, and you're like, dang, time to clean up. So, you know, you have all your leftovers, like are in the asteroid belt, like Jeff was saying earlier. So these leftovers in the asteroid belt, you know, they just sort of hang out, but some stuff does clear away so that you're left with a solar system. So here we are cleaning up. You know how cleaning up takes forever? Well, this takes 10 million years. So like, it actually does take forever. And yes, so basically, when you've done all that, you get to enjoy your solar system. And it's definitely a lot of work. But I think it's worth it and that our solar system deserves a 10 out of 10. So thank you. That is me. And I think now I can take questions. And potentially Jeff can also take questions. So if you can pop your questions in the comment section on the video, we've got someone relaying us those questions so we can have a look at them for you. So yeah, if you have any questions about something that I've spoken about tonight or that Jeff has spoken about, please, yeah, please let us know. Jeff says that he, if there's questions for him, he will type out the answer and I will read it out for you. Just because we're having a few technical difficulties with that, but he can get your questions. He just can't answer them in person. So yes, while we're waiting to see if there are any questions, we would like to thank you all for joining us tonight and for bearing with us with some of our technical difficulties that we've had. And we do have another one of these coming up next month. So we do have another public night coming up next month. That will be again online. We're not quite ready to go to in-person events yet. But yeah, if you've enjoyed this event, please come along to the next one or the next event is on the 17th of July and it will be in a similar format to this and we might be able to do some stargazing next time. Unfortunately, we couldn't get that to you tonight. Okay, we have a question about Mars. Did Mars capture its asteroid because they weren't travelling fast enough to escape the planet's pool? How did that happen? Yeah, so if something is travelling fast enough, it will go past the planet and it won't get captured. But that's interesting. So yeah, when things are flying past, if they're flying fast enough, they won't get caught. But if they're sort of going more towards something's gravitational pull and they are going slow enough, just through it, it can get caught around. Okay, the difference between, oh, okay, can a planet be made out of dust? Yes, Earth is made out of dust. Earth is a dusty, dusty planet because we refer to dust as anything that is rocky because astronomers are basically like anything that is not a gas is dust. So silica, iron, all the stuff that are in earth. Yeah, so yes, that's sorry, what was I answering? I was answering a planet being made out of dust, yes. So someone has asked, could you please tell us again the difference between a moon and an asteroid? Is the moon large enough to hold itself as a sphere? So our moon is large enough to hold itself as a sphere. But Jeff has answered that one. And he says a moon is orbiting a particular planet where asteroids orbit the star directly. So moons don't necessarily have to be spheres. So Mars's moons aren't spheres. And, you know, some moons are bigger than planets, like Titan is bigger than Mercury. So Titan is a moon of Saturn and it's larger than Mercury. It's just that they're orbiting the planet rather than orbiting the star. And someone made an interesting observation that spinning happens when you form mammal bodies as well. So it's, I don't know, maybe we've borrowed that from the universe. Yes, so if you have any more questions, stick them in the chat. Like I said there, sorry, in the comments. And yes, there is another event on the 17th of July. We'd love for you all to join us. There will be recordings of these talks made available on our Facebook page later. And also on our potentially on our website as well. I'm not sure about that because I'm not in charge of that. Oh, this is an interesting question. Is Jupiter a failed star? So this one's interesting because so Jupiter is made up of all the same stuff as the sun. So mostly hydrogen, a little bit of helium. But it's not quite big enough to be a star. So Jupiter, so there's different classes of stars, basically, basically. And something needs to be about 13 times heavier than Jupiter to be classed as a brown dwarf, which we class as sort of the smallest kind of star. They're not quite, they don't burn hydrogen. So they burn deuterium. So they're not quite, they're sort of what people would call almost a failed star. And then once it would, if something was, if Jupiter got up to be 80 times heavier than it is, so that's 8080, it would be, it would be, sorry, I'm just trying to think, yes. So it would be, it would become a very small star. But if Jupiter had been able to get a lot more mass instead of all the mass that went on to the sun, maybe it could have been a star. Someone asked, can a planet become a star like Jupiter in 2010, or 2010, a space Odyssey sequel? Okay. I'm not familiar with what happens in that, but if something like Jupiter was able to accumulate enough mass, you could actually get some kind of explosion happening, and you could potentially trigger burning. However, it would have to get quite a lot heavier, and I don't know where it would get all that material from. However, we do have situations where there's two stars next to each other, and once, once, if one star's a bit bigger, it'll evolve sooner, and it'll start sort of getting rid of its outer layers sooner. And the other star can start gobbling up some of that extra stuff that's coming off the other star, and then it sort of can explode, and there's a particular type of supernovae. Yes. So, like I said, thank you for joining us this evening. We will put a good recording of Jeff's talk up soon so that you can learn all about asteroids. Again, thank you for bearing us with our technical difficulties in this new brand new world of doing everything digitally. So yeah, we will get a recording of that for you, and it will be on our Facebook page. If there's no more questions, yeah, I'm just checking, sorry, trying to type while I'm talking to you. So, yes. Basically, I hope you've enjoyed being with us tonight. If it's not cloudy where you are, you can do some of your own stargazing and maybe go and have a look at the moon if it's still up. It was lovely earlier this evening. A nice crescent moon. So the fun thing about crescent moon, the crescent moon is if you look at it with a pair of binoculars or something and you look where it goes from light to dark, you can actually see the light and dark in the crater of the moon, in the different craters of the moon. And I think that's really exciting. And physically, since it's World Asteroid Day next Tuesday, it's fun to think of, like when you can see all those craters on the moon, you know, think of what might have happened to cause them all. Will the moons of Mars collide? What a wonderful question. I'm not 100% sure. So this is my image here that I've got is most certainly not to scale. Demos and Phobos are a lot smaller than Mars than that. And I don't think they're going to collide with each other. I think one might be trying to move away, actually. They're probably more likely to end up colliding with Mars than with each other. But I'm not 100% sure. So, oh dear. Sorry. Great. All right. If there's no more questions and no one is frantically typing at me, then yes. Oh, there's a question. Okay. Sorry. Yeah, it's a bit harder to see if people have got questions and you can't get them through to us as quickly. How big is the sun? Well, since I'm an astronomer and astronomer is like giving things in strange numbers, it is one solar radius and one solar mass. But that's not useful to most people. So the sun, I can tell you how much it weighs. The sun weighs two times 10 to the 30 kilograms. So that's two with 30 zeros. The sun is very heavy. And its radius, so from the centre of the sun to the edge, is at 696,000 kilometres. For comparison, the Earth's radius is about 6,000 or 6,000 in a bit, kilometres. Oh, there you go. Jeff has said that the sun is 109 times wider than the Earth. Yes, that definitely checks out. Yes. Yes. Okay. Cool. So thank you again, everyone, for joining us tonight. Like I said, a recording will be available on Facebook afterwards. We will have another event on the 17th of July that will be digital again. And hopefully that will go to plan. And hopefully we might be able to do some stargazing then.