How the Universe Made the Elements in the Periodic Table

I'm Matt Baker I'm associate dean here in the College of Sciences and we're very happy to be bringing you this year-long lecture series frontiers in science lectures in honor of the one hundred and fiftieth birthday of the periodic table so in 1869 Dmitri Mendeleev discovered formulated the periodic table of the chemical elements and it's had a tremendous impact on science ever since and we are joining the International celebration of this with a series of events we have some entertaining events we've already had an athletic event and we will have some arts related events and a scavenger hunt and some other fun things throughout the year so you can go to periodic table dot got techy D U and see all the things that we have planned but the academic core of our celebration this year is a series of seven lectures on different aspects of the periodic table so there are many different schools within the College of Sciences and we're trying to show how the periodic table is not just influential in chemistry but it's impacted all kinds of things throughout the world of science and even beyond we even have a lecture about geopolitics and the impact of rare chemical elements on the geopolitics of today's world but we also have a talk about the mathematics of the periodic table we have a talk about global warming and ocean chemistry and we have a historical talk about discoveries related to the periodic table and just some kind of fun anecdotes and trivia next month we have a lecture all about silicon its past present and future in all the different ways in which silicon impacts our daily lives so I hope that you all will come out for all of the events not just today's and help us celebrate this year so without further ado I'm going oh yes thank you I forgot the most important thing which is that there are t-shirts for ten lucky winners available after the Q&A session so please stick around for that we'll also have a reception with some some food and snacks outside here after the Q&A session after the lecture so please stick around for that and you might be a lucky winner now without further ado I will introduce dr. Pablo Laguna who is the chair of the School of Physics here at Georgia Tech and he will introduce today's speaker thank you for coming I'm delighted to introduce our first distinguished speaker dr. Jean Sawa Jame arrived in Georgia Tech thirty years ago he was the first astronomer in Georgia Tech he got his bachelor's and master's from binder Vanderbilt and a PhD from Michigan he does research in observational stellar astronomy and he is the director of the observatory here at Georgia Tech that is at the roof of Howie he's also been teaching for many years the introductory courses in astronomy and of course a more advanced course in stellar astronomy and he is strongly committed to outreach and K to 12 education he has these monthly public lectures are hopefully some of you have attended and he has been a huge success there are hundreds of people come in every semester so please join me in welcoming dr. Tsao who is going to tell us about how the universe made the elements of the periodic table can you hear me okay okay good I just have to get oriented a little bit with where everything is thank you for coming out tonight I do appreciate it I hope you will find tonight in all of this series not only educational but also entertaining and that you'll be very glad that you came so I'm gonna be talking to you as dr. Laguna's said regarding how the universe made the elements I haven't necessarily done any research in this I just taught it a lot so I feel pretty comfortable and I want to tell the story to you so I some of the steps we're gonna go through we're gonna have to look at the Big Bang low mass stars high mass stars supernova explosions and a new mechanism that our department is associated with which is a collision of neutron stars what I am NOT going to talk about is the periodic table okay I am NOT going to talk about its structure the periodic table is very much based for chemical reasons and we're gonna be looking at the nucleus primarily I'm also not going to talk about the man-made elements okay so we're gonna stick with what the universe did and not mankind necessarily okay now before we get going because I know we have a very mixed audience let's review the definitions we're gonna need to deal with so first atoms consist of nuclei which have a positive charge surrounded by bound electrons which have a negative charge and this is the electromagnetic force which is holding those two together the nuclei which is what I'm going to spend most of my time on consists of protons and neutrons held together the protons have a positive charge the neutrons do not have a charge they're neutral these two are about 2,000 times more massive than the electrons and the nuclei are held together by a different force called the strong force think about it we'll talk about all these positively charged protons being held together protons and neutrons are made out of bound quarks and they can change in the fourth force of nature the weak force and we'll just have to touch on for a second so that atoms nuclei protons and neutrons and then a few other terms an element is defined by the number of protons so hydrogen is one helium has two and its be the the charge but isotopes are elements that have a variety of Neutron numbers so they're hydrogen could be just a proton but there's also something called deuterium proton plus a neutron and then there's trinium proton plus two nucleons and I'm going to be looking at these various isotopes for certain elements also okay so let's begin and we got to begin at the beginning a long time ago not necessarily in a galaxy but certainly at the beginning and so here is a simulation this is the universe which is about as big as an atom and these are photons imagine these are photons and quarks streaming by some are made out of matter so I'm out of antimatter there's no such thing yet as protons and neutrons and electrons but the early universe is just this seething cauldron it's made up of quarks and photons it's extremely dense okay it consists of both matter and antimatter and I've talked about that and the four forces of nature exists that we went through including gravity as the fourth one all right now this is what it's like when T equals about one millionth of a second okay now we get down to about T equals one ten thousandth of a second we have a couple of things going on it's an wonderful balance now I purposely am NOT going to show you any equations okay but I am going to show you a few reactions along the way but I am going to talk through a few things and you've all heard of e equals MC squared okay and what that says is that energy and matter can be transformed back and forth and this is a diagram showing two gamma rays gamma rays are fo tons unique characteristic about photons shorter the wavelength the more energetic they are so here you've got two Mac trucks hitting each other when you have that happening they can create two particles now in this case though it's a batter particle and an antimatter particle and yes the antimatter is real it's not just for Star Trek warp drives okay it really does exist out in the universe and primarily in a few reactions in the cores of stars but this is a reversible process in that matter an antimatter if you have a proton and antiproton come together they can annihilate themselves so they do not get along okay and they will create two photons so in that first millionth of a second this is what is occurring it would be a wonderful balance in a way except there's a major change the universe is expanding and it's expanding rapidly chemistry students will touch on that okay if you have a volume of gas and you make the volume larger the temperature goes down for physicists and chemists temperature means speed okay so if it's cooling things are slowing down that's for the particles what we need to look at though are the photons the light photons travel I love to use this expression and by the way most of the physicists in the audience are ready to strangle me because I'm giving you very classical very somewhat inaccurate but I'm trying to get the picture across okay accurately enough but photons are moving through the fabric of space think of space as something different than matter literally you could think of it as a sheet and as the sheet the fabric of space is expanding it will stretch the photons the photons are getting longer so the energy is going down okay so the photons are changing but the particles are not so that reaction that was balanced a millionth of a second ago at ten thousandth of a second is no longer balanced the only thing that can happen is you can destroy particles so there were particles that were made and suddenly they're being destroyed because the photons don't have the energy the equivalent mass to create new particles so at about a ten thousandth of a second all of the protons and neutrons that could be made have been made and down at about t equals one second you now have all of the electrons okay there are problems and one of the problems that I know I can't solve is the question of what happened to all the antimatter in the universe because the best thoughts are it should have been the same amount and we have a few ideas but none of them are really that good and I'm just gonna have to say somehow it happens that the antimatter is all gone and I'm not gonna worry about this okay so we're stuck now with matter particles time is about one second and so what is the condition of the universe now give me a second to check my notes well at one second this is the periodic table we have protons okay and technically this isn't a periodic table yet because there's no periodicity and second these aren't atoms okay they're just the nuclei an atom remember has the electron bound around it so there isn't a chemical aspect right now well can we do more than this can we make better heavier elements in order to make the heavier elements what we're going to have to do is take protons and smash them into protons and get them to fuse get the strong force to work to hold it together now I think all of you have done this this activity before where you take two magnets and you take the two north ends and you try to push them together and they repel it just doesn't attach well that's the electromagnetic force and that's the at the atomic level we want to get down to the nuclear level so that the strong force which is very strong but very short can capture this so what we've got to do is or the universe has to send the protons at a very fast speed so that the strong force is able to catch it to get close enough before the electromagnetic force repulses it the only way to do that is to have a high temperature a very high speed so the question is did the early universe have a high enough temperature and a high enough speed to do this well I'm not going to talk to you for a moment about at time equal one second I'm going to tell you about right now now this is a picture and this is the evidence that most people use to say the Big Bang seems to be the right theory this is a picture of temperature across the entire universe now it looks very scattered but the deviation from the red which would be I guess the hottest to the blue which would be the coolest the deviation is a thousandth of a degree so if I was showing this as a one degree variation it would all be one color this is called the three degree background radiation that's in all directions of the universe and the reason the scientists love this for the Big Bang is because it is isotropic it doesn't matter which way you look there is this glow well if you take this three degree radiation the background and say okay I have an idea how big the universe is right now and as I look at this it seems to follow what physicists call a blackbody curve you see how beautiful the curve fits through here and here's a case where we have take something that we know in the laboratory very well and apply it to the universe this mathematical equation I'm not showing you the equation just the graph and if you crank it back to that T equal one second the first early time of the universe we see that the temperatures are hot enough for fusion of helium for helium to be created so we do think the early universe also creates helium and the extra check on this is when we get finished tonight and I'm talking about abundances the people that work in this field go oxygen yep done in stars iron yep done in stars uranium okay we may be two mechanisms but when it comes to helium they go there's too much we could not have created the amount of helium in the universe that we see in stars so that's great evidence that the early universe had to have also created helium so how long did it make helium well for a long time maybe fifteen minutes okay and here's our periodic table at about 15 minutes into the age of the universe again these are not atoms they are just the nuclei now once now this is the easiest to make to make the heavier elements still heavier it's going to require higher temperatures and the universe is getting cooler and so what happens now well the universe continues to cool at about 400,000 years okay so we jump from a 15 minutes now to 400,000 years this is when it's cool enough that the protons and helium can start grabbing the electrons the electrons start becoming bound and you really have atoms and at that time though this soup that was hot photons and particles now the photons can get through because the atomic spectra can only grab certain wavelengths and now they get through and that's what forms that three degree background radiation that was when the light decoupled from most of the matter that's at 400,000 the universe is getting cooler and in order to fuse we got to have some hot spots we got to make some furnaces we got to make some stars so now here's a big question when did the first stars begin to form and fortunately we have a person in our department dr. John Weiss who works on the early universe and so I had some discussions with him and it's interesting discussions because 25 years ago he was a Georgia Tech student and took some of my courses so now I'm asking him for advice on some of these topics well the first star is probably formed at about 400 to 500 million years into the age of the universe again we're taking a gigantic step and this is a picture of some of the oldest stars in these globular clusters but we really don't know anything about these first stars these first stars should have been made out of hydrogen and helium and I forgot to mention this so the amount of helium that was created in the first 15 minutes there's about 12 hydrogen particles for one helium particle okay so it's approximately the abundance that we see we have never found a star that has just hydrogen and helium okay so that tells us that even the oldest stars we have if the story is correct are not first generation stars okay so how how was a star form so take your favorite proton okay and watch it and for about half of its life it's going to be in a star or a planet or human or a cat something like that and then the other half of its life it's going to be in the interstellar medium it's going to be out there as a gas cloud and the interstellar medium is produced by the deaths of stars and that's where newer elements are created so the original cloud is just hydrogen helium the next cloud will have some other elements in it and then the next one after that other elements and so I was asking dr. wise well look at the abundance of elements in the Sun right now and our Sun is five billion years old we think the universe is about 14 billion years old so the Sun formed when the universe was about 9 billion years old so what happened between those first stars to get us to the abundances that we have today so how many generations were needed for a start of stars to form to die creating enriched material then that makes a new star and to build up the periodic table and our back the envelope calculation is that our stars may be a tenth generation but we don't know about those stars we don't now I understand fusion reactions you're going to see them they have changed but the evolution of the universe during the first you know eight billion years as far as creating the elements I mean we have a good idea but where the star is different than they are today because the mass of the star determines its evolution I think this would be the the most challenging part of what we're talking about tonight but as also if I had to do it over again something I might consider spending some time and I think this would be a very interesting aspect for studying the the elements now the other thing about stars is they are a microcosm of the universe the war in the universe and there is a war going on is between gravity and pressure is there enough pressure in the Big Bang that it's a one-and-done or is gravity gonna slow the expansion and the universe is going to contract and in stars we have self gravity pulling down on the material and we have the fusion reactions creating energy a temperature of pressure which is fighting against that and most stars there's a truce right now and that's good in case of our Sun that is fantastic because we don't want the Sun to go changing honest our bodies cannot adapt fast enough and this is so what's happening inside the star and so we want to see the fusion reactions okay because the fusion reactions are creating this energy and they're also giving us the elements that we want so here is a model of our Sun and a typical star and an excellent way to model this is if you could imagine a spherical egg birds egg there's a shell and then there's a large region of that mucus I don't a quite know what you'd call it and then there's the yolk and for us the yolk is the core and the Sun everything is well mixed so even in the core which is the only place where the fusion reactions are occurring the hydrogen and the existing helium's already mixed well and the new helium being produced is also being mixed well and this is about 30% the diameter of the Sun okay now I also have to add that for a moment there are two types of stars when it comes to stellar wealth its mass and there are low mass stars and high mass stars and they live their lives differently just like the wealthy and the poor live their lives differently the Sun is a low-mass star it gets up to about the low mass stars go up to about four times the mass of the Sun and then the high mass stars are can go up to maybe fifty times the mass of the Sun but there aren't many of those whereas there's gazillions of the low mass stars including the ones smaller than us the lowest mass stars are about 8% the mass of the Sun Jupiter is one thousandth the mass of the Sun so there's a big jump between planets until though you can get to the smallest of the stars so we're gonna look for the moment at just these low mass stars and let's make some helium okay so I'm going to show you some reaction rates so this is one of the ways to make helium so we're gonna start with two hydrogen protons they smash in together they're fast enough so the strong force wins out and I mentioned quickly the weak force one of the protons changes into a neutron and in the process gives off this exotic particle called a neutrino hold that thought I'm gonna come back to it and it gives off a positron that unfortunate positron as antimatter has been born into a matter universe it travels all of about a centimeter before it's annihilated with an electron so we get a little extra energy from that and then the next step is we hit this this is deuterium we hit the deuterium with a third proton so not much difference here okay and now everybody's thinking okay I know what you're gonna say then it gets it with a fourth proton and we make helium not it's not what happens apparently it takes two of these helium Tannis so here's a case of an isotope and by the way you see the number is indicating how many protons and neutrons are in the core in the nucleus and it creates helium four which is the stable the common helium and then two protons get given back so if you're in my class the answer is it take four to make one helium okay even though you see six ultimately involved it takes one to two get to here and then a third one to get to here so it's three here three here we get four and we get two back and so this is the step now there are all kinds of side branches and you can make a few more elements that are a little bit higher in mass and our periodic table can actually get up to lithium beryllium and boron but these guys don't live long they just they fall apart other reactions occur and so their abundances even though they're so close to these two that are so abundant their abundances are some of the smallest in the universe well I want to tell a good story but I also want to give you data so I showed you aspects of the Big Bang three degree background radiation so that you can believe that story when it comes to understanding how the insides of stars are working we still have a problem we we can't scoop we can't go down into the core and say that we've got it absolutely right and the problem with the light that's created in the core is the light also only goes about a centimeter and then it gets involved in another reaction and a new photon is created and it goes in a different direction so it might take a million years for your favorite photon to work its way out and that doesn't tell you what's happening in the core but that little neutrino that I mentioned it passes right through just about everything and here is the first neutrino detector look at the size compared to the men and this was filled with dry-cleaning fluid this is from the 1960s and the this is back in the days when groups were not a hundred and fifty people but three and one of the three was a professor here at Georgia Tech who has unfortunately passed away a few years ago and I said this is referred to as the Ray Davis experiment Don Harmar was the number two guy and I said Don so here's this picture which ones you and he looked at it and goes that's ray Davis here's the third guy I'm the one who took the picture this is a mile down in a gold mine and I would love to tell you these stories but there is a problem here to this detector and all the other neutrino detectors are only getting about a third of the number of neutrinos that we say are coming from the Sun so there is a chance we the story I just told you what's happening in the Sun we don't have quite right but most scientists feel it's because the neutrino can change into three different flavors and that only one of those three and cause the correct reaction but because of a Georgia Tech connection I wanted to mention this and I could spend a whole hour talking about that so let's continue on so let's go back to the Sun and so I said everything is well mixed and one day the sun's gonna wake up and go a wonderful change has occurred that heavier helium has precipitated down to the very center of the star and at this point this is a good five billion years from now but the Sun will be a red giant and it now has an extra layer the centermost region of helium is not reacting it's not hot enough yet because now you got a positive two charge and a positive two charge you've got to ram together that's a lot harder than the two protons so this is gonna take a while the hydrogen shell it's no longer the core continues to burn continues to dump more helium into the core but then someday this finally does kick in and we have helium being created okay and here are the steps so again I'm not only going to show you a few check the math so the helium has two protons two neutrons so it's a four and carbon has six protons six neutrons so 3 times 4 gives us carbon this is referred to as the triple alpha process but you can also make oxygen it's pretty easy in fact there's more oxygen in the universe than there is carbon and you can even go a little bit further and get some neon neon is pretty abundant to now something you're gonna notice you might hear another talks to about the periodic table there is definitely a difference if it's odd versus even you can see that the even-numbered species are getting created and not the odd numbers not to the same extent and it goes back to the helium is kind of the building block as we move along here so the Sun and the low mass stars eventually have was Yogi Berra someone who said deja vu all over again so exactly the same thing of a core this case is carbon and oxygen that's not burning yet surrounded by a helium burning shell surrounded by a hydrogen burning shell and so we have definitely been creating elements heavier than the lithium beryllium and boron but unfortunately low mass stars just don't have the gravity the umph to make this fusion reaction occur and whenever I say the core can't then that means the death of the star is coming okay and unfortunately we still have a lot of periodic table to make - so we got a death and a periodic table problem now when low mass stars die they do it by a very non violent but not necessarily well understood process where the outer part which is Suns may be gonna be 20 to 50 times larger than it is now it's very low density it just kind of blows off this outer shell and this would be a three-dimensional shell but from our perspective it's only bright when you're looking through the thicker part so it ends up looking like a ring and that's the name of this object the ring nebula and it's just gently been blown off and left behind what's called a white dwarf is that inert carbon oxygen core that just could not ever get to fuse it's a very dense core it's much denser than a diamond but it just didn't work now we have a little bit of a problem here - this is where most of the heavier elements are that we've just created there aren't that many in the remnant of planetary nebula so it's not the most efficient way for increasing the abundance of the heavier elements but how do we see that this happens we can do spectroscopy of these guys and we see the heavier elements and by heavy I only mean a slight way up these low mass stars can get us up to carbon nitrogen oxygen and neon the fluorine doesn't really get developed so that's why it's down with color-wise with these other two so these are the more abundant of the elements and so that's what the low mass stars can do for us the high mass stars there's a huge difference between a 10 so a star with 10 times the mass of the Sun and the Sun the core of the Sun its temperature is about 15 million degrees okay the core temperature of the 10 million 10 mass 10 solar mass star is probably closer to a billion degrees these guys are hot they make a much larger bonfire it's not that we both they have we have 15 million dollars in the bank and they have a billion and they can live a lot longer they spend it so much faster they live a shorter time than a lower mass star because they're just burning and eating themselves but at least that cauldron is extremely hot so I'm gonna pick it up where the low mass stars are the high mass stars will quickly fuse hydrogen to helium quickly fuse helium to carbon and oxygen and then they just keep going the carbon and oxygen here's carbon burning now remember your environment is basically pure carbon and oxygen so there's not a lot of other stuff in there so you can't really have a carbon plus a helium reaction it has to be itself against itself and now you've got a positive six charge against a positive six so the temperatures do have to be immense and we make we can make magnesium and this is a Raymond off and you can make a few others as long as you balance this this is 24 on this side of the equation this side has to be 24 and you can play the games and you can see magnesium and neon and this one's pretty popular too but this is the one of interest but there's also a great deal of oxygen and the oxygen it's reactions we can make sulfur and a little bit of phosphorous and silicon and the silicon is the one I'm a little bit more interested in and finally we're gonna do silicon burning so silicon plus silicon makes nickel and the nickel is a little bit unstable nickel decays what happens as you see the 56 doesn't change but nickel has two protons two more protons than iron and two of those protons change to neutrons so it changes its charge it's number number of protons goes down number of neutrons goes up and so the mass stays the same by the way the silicon is so important that next month speaker that's all he's going to talk about so I'll give a little push for that so I hope you'll come back to hear that so so we're moving along and look what we're doing and so the star at this point and now this is a more massive star to begin with it also extends out I mean it can get out to the orbit of Jupiter the single star and this region is extremely low density in fact the outer edge is probably less dense than the best vacuums we can make on the earth okay it is just so thin but the core if you or did a density profile this is where everything is and it has this onion shell appearance as the different elements are creating and then the next one begins and we're here at this point with the iron core and the I got a pause for a second let's see where is our periodic table so we're now up to these high mass stars have gotten us up to iron and again highlighting magnesium and silicon okay and you're going why did you stop okay so the next thing is you're gonna take iron and iron smash it together and you're just going to complete the rest of this and the problem is mother nature changes the rules okay and so how's that for a teaser as we now have our intermission and during the intermission and I do this with my classes I need everybody to stand up and begin to stretch and take another sip of coffee check the basketball score reintroduce yourself to the person next to you okay I I hope that my chairman will institute this in all of our colloquium okay because I can certainly use it all right thank you I hope that helps I'll try talking to this side a little bit too it's just my notes are way down there so sometimes if I'm wandering back got to make certain I'm telling the story well alright so as I said mother nature changes the rules when we get to iron the reason that fusion reactions have work is because the two things you want to smash together weigh more than the final product okay all the way up to iron this is true now scientists don't want to see something unbalanced right conservation laws so how do you balance this out well it's that e equals MC squared there was a little bit of mass I can't see my pointer now a little bit of mass from here got converted to energy and that's the energy that the star is releasing in the court to fight the gravity okay so the fusion reactions are not only building our periodic table it's releasing energy it's fighting the gravity of the stars but now if I were going to try to smash to iron to make Teller rhenium I believe that is they don't weigh as much okay to balance this we would have to put some energy in here a star doesn't want to do that the energy in the core is going this way and if you suddenly say no no you've got to put some energy in this way you're going the same way as gravity so a star isn't going to do that and so we're once again faced with the star is faced with its death because it's core isn't going to want to do what we need to do and we still have to have half the periodic table to make so our high mass stars inside can get up to iron but now what we've got to do is in a minute we're gonna have to do a supernova explosion but first I got to give you a little bit more scientific diagram what's being plotted here is this is how strong the pull of the nucleus is how or if want to think of maybe well how strong the pool is the best way say it and then this is the various elements so what's happening is if I were to take a helium four and I rip out the two protons how much energy did it take to pull out the first one and to pull out the second one that energy and because there were two I divide through by two and if I do the same thing for iron I got to pull out twenty six take that total energy divided by twenty six and I will see that iron is the most tightly bound nucleus so up to iron fusion works you see iron is the most tightly bound and these begin to decay this is also a dividing line if you want energy released you use fission on this side as elements are moving toward a more compact state okay so that's the real physics that's happening so as I said we need a supernova to come along now and create what we're not able to do so let's learn about supernova [Music] [Music] [Music] all right now you know everything you need to know about super okay so here's a supernova explosion I'm going to explain in a second how it happened but this is the remnant from a supernova doesn't look like that beautiful planetary nebula this is very violent very jumbled and mixed up and in here is where higher elements higher than iron are made this also is has a blue glow hidden down in the center is a neutron star that's acting as a pulsar with a jet illuminating this and we're getting into the realm of our department as we get to these very dense objects such as neutron stars and black holes well and then so that's a close-up view this supernova the Crab Nebula is in our galaxy much of the supernova that we have studied are in other galaxies this star is actually a member of this galaxy you can see the single supernova vent can become almost as bright as the entire galaxy and we can watch the brightness change it's going to fade over time and we can see the effect of radioactive decay of certain elements certain elements have maybe a 77 day decay half-life and we can see that there is a plateau and then after the 77 days maybe a different radioactive element kicks in again how do we know this happens we take spectra and we can see the elements that are in the supernova remnant the material and we do have elements higher than iron now I didn't say though how does that supernova explosion occur so let me just go through this very quickly because I don't want to go too long on this but in that supergiant there was this iron nucleus that was getting formed right and it's extremely dense and let's think about the early universe extremely dense and extremely hot and this core becomes so hot in about a day it only lasts for about a day before this event occurs it gets so hot that the photons now being created have enough energy they're like a hammer they can smash an iron nucleus and split a single iron nucleus into thirteen helium and four neutrons and if you ever have neutrons in a reaction like this you think bomb and this is an explosion okay so you've got to have those free neutrons going and then there's enough energy that even the helium gets broken back down into protons and neutrons and there's all these free electrons that are always around to because it has to be electrically balanced and the electrons and protons get smashed into each other and that creates even more neutrons and some neutrinos so suddenly volume the size of the earth neutrons everywhere but where did the energy go it went in words and gravity is relentless and so suddenly you have this implosion and these neutrons are slamming into each other at a speed of about a tenth the speed of light and we think a neutron star will stop that the density of a neutron star a neutron star has a size of Atlanta okay the density if you were to take a sugar of neutron star material because it's just a giant nucleus there's no space well that's equal to Mount Everest okay sugar cube so now you've got this extremely hard object much harder than a diamond again and you've got all this other material that suddenly realized hey we're falling this way well it's just like 100 mile an hour fastball pitch you hit it just right with a bat even though it's going this way it's suddenly going that way and you have this gigantic rebound and so this material the innermost region is what rips through the star and creates that bright supernova and this is where all those elements are created but I haven't told you how right this is what's happened but I said we can't do iron to iron now we're gonna switch over and we're gonna use the neutrons the neutrons don't have a charge so we can push them together we don't have to worry about the electromagnetic force so much so I'm going to show you a different kind of periodic table now this is technically not a periodic table because there isn't any periodicity and I realized about a week ago as preparing this talk you know it's called the periodic table of the elements it's not called the elements table the chemists have a periodicity because they see that there are chemical properties this metal and this metal and this metal all behave the same so that is why it is a periodic table this table is showing proton number going this way Neutron number going this way and the color coding is the black are the stable isotopes right here this is hydrogen this is a free Neutron so this is helium and then lithium and so as you go up up up you get so high and then we're gonna start down here and continue going and you can see there's a wide variety of non stable isotopes remember the isotope is a neutron number Changez and then we get up to about uranium about here and then these become natural and man-made now there's a little just too much information to look there so I'm gonna zoom in on a region that's kind of like this because we see that two different processes are occurring you see a lot of symbols let's look at the s and the are S stands for slow our stands for rapid in a supernova it's only the rapid well what's rapid well here's a silicon nucleus that just is now getting hit by this burst of neutrons and maybe the silicon goes from having 14 neutrons to 114 neutrons all in once I was very rapid and then this is very unstable so a neutron changes to a proton and then another one doesn't and another one does it and on this kind of graph when you get hit with the neutrons you go way over here and as you change to proton protons are in this direction so then you start coming down and so that's what these wiggly lines are these are these isotopes that are not stable until it gets to a point in the periodic table this chart of the isotopes that is stable and then you got your isotope it's formed but notice that there's also some guys back here well this guy is a blocker so the technique of a supernova could create this isotope but for this element it can't and so what is the slow process we think that's in some stars where you get hit with a neutron takes its time decays it with another neutron takes its time to case and so it's a very slow walk the rapid supernova explosion is going to give us this wealth of very heavy elements being created okay notice one other thing about this remember I talked about the odd-even effect okay this is an odd-numbered element this isn't even five stable isotopes odd just one five even odd for one so we still are seeing this odd-even effect with the isotopes and it will go back again somewhat because of the helium being involved with many of these reactions this is a simulation and I'm gonna be telling you about another mechanism in a second but this simulation is showing 39 seconds worth and so here your stable isotopes and a rapid processes just occurred and so let me go ahead and start it and I'll talk over it there we go and so in 39 seconds all of these isotopes are being created and they're decaying and they're getting closer and closer to the stable time and at the very end they're gonna go fast and then look what happens up in the upper right and then those which have a very short half-life decay down to uranium let me show this and I don't know if I can show it a second time I think you saw it okay okay and so it's really the elements higher than iron now you can obviously make more of the ones lower than it but the elements higher than iron are going to require something like a supernova explosion and so that gives us the complete table I'm not finished with the story yet but a complete table by the way I went past uranium because when this table was made the farthest known planet in the Solar System was Uranus and when this next element was found discovered they decided to name it after the next planet timing was right about the time that Pluto was being discovered that this is named Neptunian and then here's evil plutonium named after Pluto which was then the last one and I've read articles it's not so evil okay so we don't have to worry about it so much but this isn't the only story this isn't the only way to do this the and this is a woman from our department I'm gonna play this video for you in a second but a few years ago with the gravity wave studies done in our department they have found a neutron star hitting a neutron star and believe that that can also create the heavy elements above iron and that simulation that I showed you was based on this phenomena which I'm about to show you stars both left after a star most of its fuel and enclosed under its own weight 135 million years ago in a galaxy far far away called NGC or 993 two neutron stars were in spiraling they were rotating around each other they got his closest distance between Atlanta Nashville when they started merging as they were spiraling faster and faster they were stretching and squeezing space-time they produce a gravitational wave signal that kept traveling under which was and then they merged as they merged introduced in fireball of gamma radiation that light also traveled all the way to us and the recipient matter that was left behind started merging in nuclear reactions in this process is called the Q Nova and they produce heavy elements such as and that's only like two and a half years old right I mean so is this is the first so new scenarios are being discovered and there are some other theories out there I saw one about primordial black holes eating neutron stars and maybe the reactions that can occur there you know the problem is we can't replicate these in laboratories so these are a little bit harder to study alright I'm getting near the end so this is a chart showing the abundances of the elements in the universe as best we can tell at the moment okay and again a different kind of scientific chart to get all this information here this axis is logarithmic which means if you go from nine to eight which you think is just one that's actually a factor of 10 to the 1 to go from 9 to 6 a difference of 3 that's 10 to the 3rd power or a thousand and this is going down and these it's not even plotted hydrogen is always set at 12 and then helium is at about ten point nine those are by far and away the two biggest and we see oxygen is third and neon fourth and nitrogen beats out carbon and then look at some of these I talked about magnesium and silicon and it's jumping that's falling down until we get to iron which this big peak again and then past iron a little bit of nickel and then the bottom just drops out and that's partly because what creates this these events are much rarer right we had helium hydrogen being created in the Big Bang and we've got lots of stars out there creating these elements in this particular region you can again see the odd-even effects the saw two effects the even ones are going to be higher of the particular bunch here's lithium beryllium boron is right about here I don't know why I didn't quite plot it very rare and then you can see these are all rare gold is 79 on this chart so it's way down here it's over somewhere kind of in the same region so this is where we're at today now we can talk about the future and how things will change but we're gonna have to go many billions of years before we see that happen so as I've getting to the end well what are some of the flaws in the story well the first one we talked about right I mean know what to do about antimatter to handle that issue really how much hydrogen was helium was produced in the Big Bang maybe there was a little bit of lithium too but to handle that but we think we have good ideas how long before the first stars and really everything about the first stars if they were instead of 10 solar masses I mean today's stars the most massive or 50 times the mass of the Sun what if these stars were 250 they would live for maybe a thousand years I'm the calculation and gigantic supernova explosion so maybe the early part of the in and it was much denser so maybe this cycle could occur a much faster so we're just not certain what happened in there and this relates to it how many generations were between we actually think we know our stellar interiors well of all the ones we think we know that and we think we know some of these supernovae process is pretty well too well we've opened the door to these other mechanisms we need to worry about the frequency right now we have one detection just because we haven't detected them doesn't mean that they're not occurring all the time but you know it's wonderful to see these other ways to do this and in astronomy that's the best thing we can usually see is that you can get a result from more than one way and hopefully you're consistent and then finally I didn't even talk about this subject but Dark Matter we can tell that for every particle that you can see in the universe there's probably 10 particles of equal mass 10 whatever and we don't know what it is because it's dark we haven't been able to detect it anyway other than gravity and one favorite theory is that there are these other particles and the nickname is wimps stands for weakly interacting which is why you can't detect them massive particles well maybe they're not a big deal you know maybe there's a lot of pink elephants in this room we just don't see them until somebody yells fire and everybody's trying to get through those doors and the pink elephants are stopping you from flowing like that so it could be that these are in the way inside the Sun and so we don't have as many reactions or maybe these massive particles have their own reactions or they decay into something so if you want a Nobel Prize answer that question okay so and that will be a great day when we get it so do we really need to care about this well the answer is yes there are some heavy elements in our body do you know what the heaviest one is think about it for a second so I picked a picture of people feeling sunlight and here are some of the heavier elements oh there's iron so everything above iron was created in a supernova or collision of neutron stars where is it going to stop what's the highest mass object that our human body has to have in order to live and that's iodine and that's according to Wikipedia there might be something even again even heavier that we have to have so this is very important and so if these elements are all created by supernovae then you have supernova dust in you we all do in order to have life we've got to have these particular elements so I'll show you again the periodic table and again thank you for coming and I'll take some questions [Applause] explain that doesn't work does it work oh it does work oops so you said that gamma rays come together to make matter and antimatter and then when you were talking about making stuff like magnesium and silicon and all that jazz the carbon or oxygens come together make that atom and a gamma ray how does that work okay so those are two different things the matter and antimatter they come and go okay so they're gonna destroy each other and we're gonna forget about that for the rest of the universe after the first second so inside stars you want to know how a fusion reaction would occur no like where does that gamma right come back from okay so if you've been in chemistry high school chemistry and you had to balance the charge in a reaction you had to have the same number of positives and negatives on both sides in these physics reactions there's several other charges that you put several other conservation laws and the equals MC squared is one of them and so if you can figure out how much mass is involved on the one end and then you've got your final product and the two don't match then that could be a gamma ray okay that's one possible output if a proton changes to a neutron then you're always going to have that antimatter and the neutrino but if it's just collisions and they don't change then you're usually gonna get a gamma ray okay so Jim the example you gave was a core collapse supernova yeah are the abundances about the same produced by a type 1a supernova or are they similar that's so type 1a supernova is a white dwarf that gets too much mass on it and it collapses when the white dwarf collapses we think everything gets fused but it's starting at carbon and oxygen and so the fusion reactions would maybe make at the most so you're not going to get the higher levels I'm just thinking off top of my head the disadvantage about supernovas though is there's no nobody's ever made a chart that says if it's a 10 solar mass this is what you get and if it's a 12 this is what you get it's just to unknown at this point as to what are the reactions what would be the final output we have a question from Miami Florida and the question is what are the elements that naturally exist on earth and if it doesn't include all of the elements how are the other elements formed okay so all of the elements we were showing are on the earth and you're pushing my expertise level here I think there is one element that's very radioactive it's hard to find I think it starts with an S okay and then once you get up into this range although everybody thinks uranium apparently there might be a few of these from other decay processes but there's so few of them on the earth but they probably do exist but everything I've shown you is on the earth okay and rather uniformly distributed in our solar neighborhood there aren't any big changes you're not gonna have one star that's full of barium and another one that's full of iron so it's pretty the in homogeneity abundance is pretty well distributed you have the same in all stars and then it's whatever's left over for the system this kind of a follow-up to this question I think you said that the Nova the supernovae are a neutron stars are somewhat are fairly rare how do you get the distribution of all these elements that they produce throughout the universe assuming they're well distributed I've got some gravitational astronomers over here that can astrophysicists that can answer your question that's what I was saying is and people are starting to fall into two camps oh no supernovas can do it Oh No the colliding neutron stars can do it they both have their advantages and they both have their disadvantage that the colliding neutron stars you've got a lot of neutrons right there a very dense environment so you could have a gigantic rapid process occurring on the other hand it took two supernova explosions to produce those two neutron stars so you know which one has contributed the most but right now with the colliding neutron stars which were very well studied once the first observation came out it's it's in its infancy but that is what a lot of people are jumping on now and hopefully we will get a better feel altima but I think we're a little too new into this to start to answer your kind of questions all right but I'll I'll get you to somebody whoever catches it ask to ask a question okay so say like edit Caron a the the that superstar would to collapse into a supernova like it will in the next million years when that happens is it possible that the supernova would release enough energy and have enough a high enough temperature to produce elements we have never seen before like is there a possibility to still discover stable elements that we that are outside the realm of the periodic table so the elements that are down here I think the answer is yes they could possibly be formed but because of the strong force and the weak force there's kind of a limit as to how big a nucleus can get because the strong force can't reach to the other side very well and from what I understand these elements are going to have half-lives that are on the order of milliseconds so there is kind of a limit that even if it got created it's not it's so unstable you wouldn't see it collapse back down so you mentioned when you were building the periodic table that's something right now that they're not really atoms it's just the nuclei so where do those electrons come into play okay so in the early universe that T equal one second the electrons have all been formed because now the universe is cool enough that even the gamma rays to make electrons don't have sufficient energy so but you've always got electrons out there too because we have to be electrically balanced we don't have half of the universe positive and half negative so they're always mixed in there not necessarily bound you got protons doing this and electrons doing that at a time of about 400,000 it's cool enough that the protons could start grabbing the electrons and they become bound and now you have an atom okay but when you get back like into the interiors of stars they're and they're not atoms that's nuclei and free electrons swarming around so it's not atomic in the nuclei adain the cores of stars I think we're gonna have quite two more questions and that's all we have time for all right is this on now at the higher limit numbers there are hypothetical islands of stability at about one hundred and twelve hundred and fourteen protons so my question would be with the new evidence on neutron star collisions is there any evidence of say a higher neutron count isotope of the rhodium coming out of that something that really is we can't produce in the lab but we can get some kind of special scopic evidence of although I can't answer the question that way I don't think enough would be created that a we could see it in a spectrum and B that we would know what the spectrum looks like in fact it wouldn't have a spectrum because it wouldn't have any life spectrum without having created it in the lab first right okay we wouldn't be able to identify it and I some of these supernova remnants are still plasmas they don't have all of the electrons yet being bound and creating the spectrum they're pretty they're gonna be faint so it's a tough what are the processes that bring this down to us an earth from the core of stars off in the universe and so how does it get to a planet okay so yes in a certain volume of space eventually there should be some supernova explosions and there should be a lot of planetary nebulae and so you get a mixture of the gases and eventually there will be enough self gravity that these gas clouds will begin to contract and you'll make a new generation of stars and you tend to make clusters like that first diagram I showed you they're gonna live their lives and then depending upon their mass they die at different times so it's the same process you're gonna either so I sort of saying following your favorite proton it's either gonna be trapped in a star or a stellar environment or that it's gonna be kicked back out to the interstellar medium but as you do this over and over again the elemental abundances are growing because the Stars have been creating heavier elements and so and especially with the supernova explosions if you get them in your environment then it's just in your environment so when our solar system formed the abundance that we see in the Sun we feel the same abundances in the earth same abundances in Jupiter now the Sun has changed it because of fusion reactions but basically whatever the Sun started with we had the same thing here but we've had the iron sink toward the core and we've lost hydrogen and helium helium okay got me talking to helium was first discovered in the Sun not on the earth and it was named after the Sun Helios and eclipses like we had a year and a half ago so there is a relationship of the elements with astronomy and where it's being found so so we here was a case where we did it backwards celestial object before finding it on the in the earth I hope I answered your question well on that note I'd really like to thank Jim for this amazing lecture one more time and and Jim we have a little gift for you from the College of Sciences to thank you for giving this lecture thank you so much and I'd like to bring up our interim dean David colored who has an important announcement to make very important announcement so it's a real pleasure to be serving as interim dean of the College of Sciences especially as a chemist this special year being the International Year of the periodic table and you know that the College of Sciences has a year-long celebration of this special year and everyone needs to know who Moines Ruhi is where's Maureen she's out in the lobby so you can all meet Maureen out there she really is the driving force behind this entire series of events not just the lecture series monthly that that Matt is really taking leadership role on but we've got concerts we've got a party over the summer for the summer students and the first day of classes in the fall will be a special day for us with lots of activities based around elements in their place on the periodic table so the most important thing right now is probably food but before food there's t-shirts thanks Julia so how are we going to get t-shirts out I don't see any t-shirts in the room so I was wearing one where are the t-shirts well if you reach under your chair there might be an envelope no t-shirt that gets you a t-shirt at the at the table of the bag and if you're sitting next to an empty chair you get two chances of winning a t-shirt and so with that again I'd like to thank dr. Sal for an illuminating lecture to kick off the kick off this series and I hope that we can continue the conversation in the lobby where you can talk to Jim some more and amongst each other about elements and periodic table thank you for attending this evening [Applause]

Channel: Georgia Tech Physics

Views: 25,621

Rating: 4.7493978 out of 5

Keywords: Gatech, Universe, Physics, Georgia Tech

Id: uXOQZl3J5v4

Length: 71min 53sec (4313 seconds)

Published: Thu Feb 14 2019