Scientist in the Forum - Gillen Brown | Building the Universe

All right, thank you all for stopping by, I’m gonna go ahead and get started today. So my name is Gillen Brown. I’m a grad student here at the University of Michigan in the Department of Astronomy So I’m gonna be talking about all kinds of stuff astronomy related today, but I’m gonna start with the earth. Because here on earth there’s all kinds of things and one thing we’re gonna talk about is what different things are made of. It’s a kind of an interesting question. We’ll talk about more later, but I want to start with two things So I’m gonna have this side of the room I want you to talk about what water is made of and what gold is made of You might know the answers to these and then this side of the room. I’m gonna have you talk about air and then aluminum foil.

00:37 - So talk amongst yourselves for like ten seconds, thirty seconds. And then I’ll ask you if you have any ideas here in just a second. So Guest : Water? yeah, Oh Get to use the mic Guest: It’s made of hydrogen and oxygen. Cool what about gold? Guest: it’s made of gold. Made of gold Excellent! that’s a trick question. All right, you know you all do you have an idea of what’s in air? Anyone want to volunteer? Oxygen you say it into the microphone? Guest: Oxygen.

Awesome that’s true, you know anything else that’s in there. There’s all kinds of stuff, water, cool. So yeah, those are all great answers and Kind of oh, did you talk about aluminum foil to do you know what’s in aluminum foil? It’s also a trick question Say it again, minerals. Okay good. That’s true. You guys know? Yeah Guest: Alu-mini-um. Exactly aluminum is made of aluminum So kind of the point of this is that some things are made of other things Like air it has all kinds of stuff in it. But some things like gold are just they’re not made of anything more they’re just what they are and so…

01:54 - What we can do as scientist is make a list of all the things that are what they are like all the things like gold, or like aluminum that we can break other things down into and So we can do that and it turns out that we can put our list into a big table like this Or this is a list of all the elements We call them elements that different things made of So I see you pointing out some things I’m going to point some out to and that this water that we talked about it’s made of hydrogen which is the number one the very top left and Oxygen which is number eight here. So water is just two of these things you put them together and you get water. Air is a mixture of all these other things so we said water vapor. So that’s, you get your hydrogen your oxygen you get some oxygen. There’s also things like carbon dioxide so that is that C and the O and then there’s lots of nitrogen in the air to most of the air is actually nitrogen this element N up there, and then there’s also a little bit of argon Which is another gas that you may not hear about.

That 02:55 - I didn’t realize was The top five or six. but it is! And there’s all kinds of other stuff too that I didn’t put on here. But this is just some of the few things that are in air we can break it down into. While, gold Number 79 here has a weird symbol AU. This is some Latin name and then a aluminum It’s it’s own thing. Also number 13 up there.

And so the idea behind this is that you can break things down into similar things 03:23 - Things that can’t be broken down any further that we call elements and so with all these elements the question that I’m kind of asking in this talk is when you may not even think to ask and that’s Where do these elements come from? If we have aluminum or we have gold, how do we get that gold in the first place? Where did it come from? so as an astronomer what I can do or Other astronomers can do more accurately is to look at the very beginning of universe to see what was around when the universe started Right after the Big Bang, so we know how that worked we can do the math and figure out what elements there were and it turns out there are only these first two. There was only Hydrogen, that was in part of water and Helium, elements, so balloons, so we could have had balloons after the beginning in universe But basically nothing else we couldn’t have air right? We don’t have oxygen We couldn’t have aluminum or gold so these had to be made Somehow throughout the history of the universe And so how does this happen? well It turns out galaxies are a big part of this and this is kind of what I want to talk about next So galaxies are beautiful things. They have there’s these spiral galaxies. There’s several examples here I’m going to show but there’s a huge variety of galaxies. So they have different colors from one another slightly different shapes There’s a ton of these beautiful spiral galaxies. I can show a million pictures of these and I have quite a few here But you can also notice the different colors some of these are because of the way the picture was taken But galaxies really are different colors from each other.

You have some that are different shapes 04:47 - This one’s a little more fuzzy in the center that some of the other ones were then you have some like this that are just basically a big ball of stars without these nice pretty spiral arms like other galaxies have Some of them have these like shells around them almost a bunch of weird shapes of galaxies can have you have a ring shaped galaxies? really the variety of galaxies is endless but I want to kind of transition into what galaxies are made of so we talked about what stuff on earth is made of and What we can do to look at galaxies is to zoom in on them. So this is a picture of a nearby galaxy This is the Andromeda galaxy so closest big galaxy to us in the Milky Way And this is a picture of it taken with the telescope on the ground like the one there on the left And we’re gonna zoom in on it as far as we can and you can see that it starts to get blurry You can’t really see it as much as we might like and that’s because we’re on the ground There’s the air between us and the stars and it basically blurs out the image So what we can do to fix that is to go to a space telescope like Hubble Space Telescope You might have heard of that and it can see a whole lot more than telescopes on the ground You can see them in much sharper vision And so we zoom in and the closer we get ahead You’ll start to see that what was kind of a fuzz earlier is actually a ton of individual stars like our Sun And even though stars are like our Sun you can see there’s a variety of stars too. Some are red Some are blue when a pause this real quick But you just see some red stars some blue stars. Some are brighter or fainter than others so there’s a huge variety of stars that exist in galaxies, but really galaxies are made of stars and Stars do all kinds of interesting things So stars have their own life cycle kind of like humans doing it. They are born and then they die And so we’re gonna walk through all this whole life cycle here It tells us about how elements form which is kind of the goal of our talk here But I want to start with this. How stars form in the first place. So they form in these things.

We call a nebula 06:49 - It’s basically a big cloud. These are a couple of examples you might have seen before where it’s a bunch of hydrogen gas. Basically that’s has gravity That’s basically pulling it together and in some spots if you look really closely with Hubble Space Telescope You can see these little stars are about to form, these little tiny clumps. So here are some more examples This big cloud is made up of little smaller clouds. These are all individual stars as they’re about to form.

So 07:18 - Gravity turns this giant cloud that’s beautiful into these individual stars. And so You get stars out of this process and on this diagram We basically split them into small stars like our Sun even though our Sun is huge compared to the earth It’s smaller compared to other stars out there and big stars and we’ll go through these both because they’re both super interesting But let’s start with stars like our Sun because that’s what we’re most familiar with So the Sun shines it gives us light that lets us live But the Sun is powered by this thing we call nuclear fusion, where you’re basically taking elements and smashing them together. So in the center of their Sun there’s lots of this element We talked about earlier called hydrogen, and if you take a bunch of hydrogen and smash it together really hard. Harder than you could possibly do as a human you can turn it into the next element called helium. And so this is happening in the Sun right now.

08:10 - it’s taking hydrogen smashing it together and making helium and that’s how the Sun shines so doing this releases a bunch of energy that the Sun can use to give us light. And so, the Sun will do this for like ten billion years and Then once it’s done. It basically runs that a hydrogen they’ll do another thing or it takes three helium’s smashes those together you can get carbon another atom on this table that we talked about - so This powers a Sun for a while And what’s interesting is that we took hydrogen That was around at the beginning in the universe and we turned it into carbon, which was not So this process of stars powering themselves is how you get all these other elements that are out there in the universe so once these stars The Sun runs out of energy at the end of its life. It goes through this thing. We call a red giant. It basically becomes super huge even by Star standards It’ll get so large They’ll eat several of the planets possibly earth. For example So it gets big and then it basically gets way too big and it puffs off all the outer layers.

So it loses 09:13 - its All the material that had. And so when you do this you get beautiful things like this These are some stars that are undergoing this process right now Where they’re taking the material that they made like this carbon and putting it back out into the universe. So if you look at our diagram again, you can see that these this process that we call planetary nebula. This material can go back into a star-forming nebula for future generations of stars to be made of So the carbon that one star makes can used by another star - maybe seed life on one of its planets, for example. And you’ll also notice this little thing at the bottom called the white dwarf If you look in the center of each of these images, you can see a little dot the bright one there there It’s hard to see but here there looks like there might be two But each of these is a tiny little leftover star that we call a white dwarf and we’ll talk about those a little later Too.

But they’re very interesting in their own right but that’s basically how stars like our Sun live their lives 10:11 - They take hydrogen put it into helium and then into carbon that they can then put out to the universe for other things to use. So next we’ll talk about big stars as you might imagine big stars can do a lot more Fusion than our Sun can because they’re bigger. They have more gravity basically. So for example, they can do the same stuff our Sun did but then they can keep going so they can take carbon They’ll smash it together with helium. You can make oxygen. oxygen is obviously a very important element that We need to breathe and for water and all that stuff so we couldn’t live with that oxygen and it’s made in these big stars And then it does this a bunch of times I’m not going to show all the things that happen, but one that happens at the end that is super interesting is that you take This element called chromium, which is a very big element put it with the helium and you get iron Iron is an important one and it’s special in stars because iron is as far as you can go Normally stars give normally the process gives off energy, but once you get to iron that stops happening So your star can’t shine anymore it basically collapses and then explodes so you get this thing that we call supernova which is when a star blows up and So it takes all the elements that it created: like chromium and oxygen and iron and it spews them out into the universe for again future generations of stars to use and it leaves behind these things that are (I think I highlighted it here) Oh, yeah, so it does this, they have these huge remnants of supernovae left behind For future generations of stars to use and there is a bit of a there’s a star in the center of each of these It’s too hard to see these stars are even smaller than white dwarfs. These are the neutron stars There might be black holes that are left behind by supernovae too.

11:55 - So supernovae are very interesting because you get all kinds of cool stuff out of them All right So that’s most of the ways that we get elements. there’s one more I want to talk about and that involves these last couple things The leftovers of stars these neutron stars or white dwarfs and sometimes these can run into each other So what, two white dwarfs can collide with each other or two neutron stars can collide it’ll It looks something like this, these huge explosions. We’ve seen these things happen. So we know this really does happen This is obviously an artist drawing of what this might look like, but we can observe this happening and they leave behind their own Remnants, too. And these things like any other are full of new elements that are created in the explosions That were not present beforehand. So you can create elements in these type of things, too.

12:43 - And so, with that we can fill in the periodic table based on where these elements come from. So The yellow here, the elements in yellow were made by these big stars as they lived their lives and then blew up the blue ones are stars like our Sun so they made a few elements plus some other ones by another thing that I didn’t talk about and then These other green elements are these merging neutron stars that I talked about, and similarly the oranges these white dwarfs when they merge and Explode. So to go back to what we talked about at the beginning We talked about water, its made of hydrogen So hydrogen was one of the elements that was around since the beginning of the universe It was made in the Big Bang and then oxygen was made in stars as they explode at the end of their lives These big stars Air, we have: hydrogen, carbon, nitrogen oxygen, argon. These are made, hydrogen, in the Big Bang. Carbon and nitrogen, Those are essential to life. So carbon is what we’re mostly made of. It was mostly made in stars like our Sun with a little bit from these big stars similar with oxygen or sorry nitrogen and Then argon another part of the air that’s like 1% I think It comes from these big stars and a little bit from these exploding white dwarfs Gold, gold is obviously nice element jewelry coins, etc. Those come from these two neutron stars as they collide So if you have a piece of gold jewelry That’s a leftover of two stars as they collided and blew up and that’s really cool, to me.

14:17 - that you, you have something that is a remnant of something that happen in space and our whole bodies are really Made of things that happen in space. So we’re really connected to the universe in a way that you might not have thought of before And then our last one. Aluminum, it was another one that’s made in these big stars so big stars are really super important for A lot of what happens in the universe and this kind of ties in to what I do as an astronomer I am interested in how elements are Put into galaxies and where they are in galaxies and one that we use a lot in astronomy is oxygen. We’ve talked about oxygen quite a bit. This is element number eight. And one thing that we can observe about galaxies is something like this… So this is a little diagram that I made. So on the Left we have a small galaxy on the right we have a big galaxy and I put a false color on here to basically color code the amount of oxygen each point in the galaxy So red means there’s a lot of oxygen at this point.

Blue means there’s not a lot of oxygen at this point 15:16 - And so, there’s a couple things you might notice about this anyone wants to volunteer anything. They see happening. Yes The red presents more oxygen. Good and which, yes, in which galaxy has more? Guest: The big galaxy. Exactly, awesome. So the big galaxies have more oxygen in the small galaxies. Why is this the case? We don’t really know there’s we can do a lot about it, but it’s still an open question what about like the center of the galaxy compared to the outside and Then the center of each galaxy has more oxygen than the outside as well so if you look on the big galaxy, for example It’s it’s red in the center and kind of fades to bluish on the outside And so this is a thing that we can observe the center of galaxies have more action on the outside. Why is this the case? It’s not easy to think about how this would happen.

So what I do is run computer simulations of galaxies. So this is an example This is not my movie. It’s a movie someone else made. It’s beautiful though, which I like to use it So what you basically do is put all the rules You know about how galaxies form into a computer so we know gravity’s important. We know that stars form we know the galaxies merged. All these things and when you do this You put them in the computer and have it solve all these equations and you can get out of galaxies That’s pretty realistic in a lot of ways.

So here we’re flying through a galaxy to 16:41 - Look at it as it spins around Basically, and so it’s nice about these computer simulations is that we can’t observe this in real life This takes millions and billions of years to take to do this process But in a computer you can look at in a movie in 30 seconds like this So we can really see how galaxies change over time In a way that we can’t otherwise and we can use this to learn about how galaxies formed So I’ll play this again here And so this is what I do. I basically put oxygen into these simulations Tell it to track how much there is and then we can compare to the the real galaxies We observe to see if our answers are right or not about how we think this happens and then we can learn about the processes that make more oxygen being the center than the outsides for example, or Big galaxies to have more oxygen than small galaxies. These are the kind of questions. We’re asking by doing these computer simulations, so Once this finishes I will leave it here and I will we’ll take anymore questions Thank you all .