Exploring Space Lecture: Gamma Ray Bursts and the Birth of Black Holes

okay good evening everybody my name is Paul sárosi I'm the chairman of the space history division here at the National Air and Space Museum and I want to welcome you to the third installment of the 2012 exploring space lecture series and I hope you those of you who've come early I hope you've been enjoying the various activities that we've had not just here but also out in the floor of the museum and perhaps you had some encounter with our education people who are demonstrating black holes which is kind of cool and really appreciate their contribution to these if I thought yes really we really do appreciate it so I'm definitely and we also want to thank our sponsors as they have for the past nine years the science Mission Directorate of NASA continues to be a great friend in supporting this series and tonight NASA's represented by John Grunsfeld associate administrator for the science Mission Directorate and I think that's a name it's probably familiar to many of you if you know anything about the servicing missions of the Hubble Space Telescope you know the name of John Grunsfeld and we also want to welcome back Michael O'Hara of the Aerojet Corporation who just joined NASA for the 2012 season so why don't you just stand up very briefly John and Michael there you go yes thank you very much okay tonight's speaker is dr. Neil Gerald's chief of the astra particle physics laboratory at the NASA Goddard Space Flight Center dr. Gerald's is well known as an experimental physicist and a leader in gamma-ray astronomy he studied gamma-ray bursts and supernovae and his presently principal investigator for the Swift gamma-ray burst mission he's held many positions at NASA including project scientist for the Compton Observatory from 1991 to 2000 he's held post of the chair of the American Astronomical Society high energy astrophysics division chair of the American Physical Society z-- Division of astrophysics a member of the American Academy of Arts and Science Sciences and the National Academy of Sciences now to share a few things of thoughts about dr. Gerald's though I want to first introduce John Grunsfeld who will say a few remarks and then introduce our speaker tonight so take it away John thank you very much it was fun to hear Neil talking a little bit informally before the start of our formal activities tonight and it's really a pleasure to represent the National Aeronautics and Space Administration here tonight and I'm just thrilled to see you know all of you coming out to learn something about the nature of our cosmos you know I as you heard took a little bit of risk going up in the Space Shuttle to trying to enable great science and I like to say to to help unlock the mysteries of the universe and Neil has made his career doing that for the young man who asked about you know heroes in science I can't help you no I want to sort of wanted to answer we all have our own answers but my my heroines science was Enrico Fermi who is an American physicist first person to develop the or with a team first atomic pile but before that he was a cosmic ray physicist I went into cosmic grade physicist physics worked on you know all kinds of cosmic questions put thought into extraterrestrial life which is something I'm very interested the question of are we alone in the universe but he was also a great Mountaineer he liked to go out and have great adventures and we recently named a satellite after Enrico Fermi the Fermi Observatory something neil has worked on Neil as as you heard chief of the astroparticle physics laboratory at the Goddard Space Flight Center has had a very long and distinguished career in in high-energy astrophysics he and I both have an interest in doing imaging and hard x-rays and gamma rays in fact he and I worked on the Compton Observatory together as young researchers I worked on the Burstyn transit source experiment looking at gamma-ray bursts which will be a topic tonight he was working at much higher energy something I was interested in babsi was not an imaging detector egret was an imaging detector and we also share a little bit of educational background I was a postdoc at a small Technical School on the west coast called the California Institute of Technology a few years earlier working with the same advisor edge stone Neal was a PhD student that's where he got his his doctorate from Caltech he's received many awards and I don't want to go into all of them but one in particular the Bruno Rossi award the Rossi award of the American Astronomical Society which is a very prestigious award for somebody in high-energy astrophysics well deserved and also the National exceptional scientific achievement award or metal but there's a different side of deal that I've learned to appreciate but it's very consistent with his scientific curiosity and his love of exploring science and if you could bring up the slide a slide that's neil on your right that's me on the left at nineteen thousand feet on the flanks of a mountain called aconcagua the highest mountain in this hemisphere and there's a large glacier behind us and we're trying to keep warm he as an ice axe in his hand and you know many people would say that you know this is sort of an adverse environment but you know neil has a high tolerance for adversity and in fact you know enjoys being in tough conditions he was my tent-mate for our two weeks on the mountain there and you know being in the mountains you know trying to achieve hard things you know the question about what do you tell your science students when when they say hey this is hard and one of the answers is that when you strive for something that's hard and you achieve it you know that's the best satisfaction you can possibly get but also I hope you appreciate this maybe well maybe you're not it's also the most fun and and I think I can speak for Neil I know I can speak for Neil and saying you know one of the reasons Neil has been so successful is because he finds the science you know compelling engaging and fun you know it's so personally rewarding that it gives you that great sense of pleasure you know that others would find you know perhaps playing softball or or other endeavors and believe it or not mountaineering you know living freezing cold conditions and no showers for weeks and needing freeze-dried food and all the rest is also a lot of fun sometimes it's more fun afterwards thinking back on it but it's also a lot of fun somebody asked about funding my job now is to make sure brilliant people like Neal have good funding and I take that very seriously and we we do have very strong bipartisan support for the funding for NASA for the science we do you know in the 50 years of NASA's history you know science has provided the real backbone the great consistent interest through our missions through missions like the Compton Observatory the Hubble Space Telescope somebody asked about archival research half of the scientific results that come out of Hubble now come from data in the archive and I think that'll be true for for Swift and all and all the other missions now you all came here to the National Air and Space Museum and I you know again thank you for coming out you didn't pay an admission coming in but unfortunately again you know we talked about funding I have to break the news to that actually tonight's event is not free and you're thinking oh yeah he's going to say we pay taxes and things like that and you do and I appreciate that and it allows us to fund the great research but actually there's a specific tax for all of you tonight and it's more your homework assignment you've come out here to learn something tonight and again I think that's just terrific I'm excited that we're not looking at a bunch of empty seats we're looking at mostly full seats but your fee for coming here tonight or your homework assignment if you choose to take it if you find Neil's talk interesting tonight is that I want you to go out and share that knowledge that you've gained share it with your neighbors with your friends you know with your school mates you know whoever you interact with over the next week or two is you know that I'd like to extract that payment from you as you know go out and share this knowledge because what you're going to hear tonight about gamma-ray bursts and black holes and the birth of black holes is really fascinating story and retell that story Neal thank you that was a great introduction thank you okay so I'm going to be talking about gamma-ray bursts and the birth of black holes and we're going to have some fun tonight I'm going to be talking about results from the Swift observatory which is one of these Explorer observatories at the moment it's actually the only Explorer that the astronomical Explorer that's flying but John is working hard on bringing up some new ones in the near future we've had as many as four at a time in orbit we proposed Swift to NASA I led an international team I was at a NASA center but we included universities and people in the UK and Italy we proposed this as a mission and it was one of 40 that went in at that round in 1998 and two of them were selected for study and in the end only one of them is on orbit so it was very hard competition and we were we were delighted that we won we had some new technology that we were bringing forth and I think that was a factor and I'll show you a little bit about that after many hard years of development you know five years although that isn't very long by space standards we launched in 2004 and here's a beautiful picture of the launch I'm going to show a movie of the of the launch as we get into the talk the science of the Swift Observatory is to study gamma-ray bursts a few minutes I'll tell you what gamma rays are and what gamma-ray bursts are so don't worry if you don't understand that jargon but just to put it in a nutshell we're studying the biggest explosions in the universe with Swift that we think are caused by the birth of black holes mario livio at the Space Telescope Institute calls it the birth cries of black holes and so I thought you would be quite interested to learn about black holes so I'm going to start this lecture by really talking about black holes the history of black holes the people that were involved what we now know and what we don't know about black holes you know what is a black hole the observational evidence we have that there are black holes and then go into the results from Swift and and talk about Swift gamma-ray bursts the birth of black holes and get back to in the end and I think you'll find this really interesting a kind of philosophical scientific question again what is a black hole so in the beginning there was Einstein everything else goes back to Einstein 1905 honest mirabile is the miracle year he had three major papers that year explaining the photoelectric effect which gave us the particle nature of light light can both be a wave and a particle Brownian motion which supported the atomic nature of matter suspended small particles in a liquid are bouncing around do the atomic interactions with them and special relativity which says that the physics is the same in any non accelerating frame that you're in so if you walk down the aisle of a of an airplane going 600 miles an hour you can't tell that you're in an airplane unless you look outside you know it feels the same as walking on the ground and that's special relativity and one of the consequences of that is that the speed of light is the same in all frames and another outcome of that is the famous law e equals mc-squared well 1907 Einstein had what he called the happiest thought of his life okay so you know was something profound for Einstein to be happy and here's what his thought was this is eventually leading to his general relativity theory his thought was if you're in an elevator and you're accelerating it feels just the same in fact all the laws of physics are the same and all of the forces are the same as if you're on a gravitating planet or some gravitating object so the force of gravity and acceleration are equivalent and you know we know this all the time if you're in an elevator and starts going up it feels like you're being pulled more to the ground and it even comes into our language fighter pilots talk about pulling three GS when they go through an acceleration and they're pushed into their seat you know by three times the the force of gravity and so okay so that's a happy thought but what did it mean and it actually took him nine years to fully develop this this theory and that is essentially that mass massive objects like stars or any kind of mass caused deflections and curvature in space and time so you can see in this nice little drawing here on the on the screen you can think of a particle let's say an asteroid going by the earth and gravity pulls it in and so it deflects its course and it goes out in a different direction that it came in but another completely mathematically equivalent way of talking about this is that the Sun or this star causes a curvature of space around it and so this asteroid comes in it goes into this curvature this curved well and comes back out and they're exactly the same so it took nine years for him to realize and this you know put this all into mathematical terms and it became the theory of general relativity and his his Einstein field equations describe this and he developed this theory really for understanding the cosmos and cosmology the next person that's important for the black hole story is Karl Schwarzschild because Einstein hadn't thought about this in terms of stars and objects he was thinking about the whole universe and it you know whether it's accelerating or constant he thought it was constant but Karl Schwarzschild is the first person who produced the solution to Einstein's equations in an astronomical setting for a spherical star at rest there's a pretty interesting story about Karl Schwarzschild he was 41 years old he was the director of the Potsdam observatory in germany and this is the time of World War one and he volunteered at this fairly late age to go fight on the Russian Russian front which was you know a really tough assignment and he was an artillery officer so he was serving on the front and he was getting some kind of messages still from the home country and he heard about Einstein's theory of general relativity and he sat in his tent and actually worked out this solution the Schwartz field equations to you know solve the equations for this start rest and he came up with a really interesting solution it describes you know the curvature of space around the star but it has a singularity in it now what does that mean that means that the equation blows up it has a zero in the dynamic of the dynamic denominator this occurs for a very sort of bizarre case and it wasn't appreciated at the time of his theory if you can take a star like the mass of our Sun and crunch it down into a really small size then for the mass of our Sun at a distance of three kilometers from this crunch down star the equation blows up time becomes infinite space you know crunches down to zero and it wasn't understood to realize that there was a singularity this radius was called the Schwarzschild radius this will eventually become the event horizon of a black hole but we at that time they had no idea that you could actually get a star into that smaller region so it was more of a curiosity in fact Einstein never believed that this singularity would have any effect he didn't even think it was real and the Schwarzschild radius is also the distance at which light could not escape from this convinced star Karl Schwarzschild got ill when he was on the front and within a year after coming back to Germany he was dead so he did this one thing a really important thing so then we move on to Oppenheimer Robert Oppenheimer the father of the atom bomb who actually spent the rest of his life after World War two convincing the world to not use nuclear weapons again he became a pacifist and very effective although he was he was persecuted by many people and he with a student Schneider showed that you actually could get a star a really compact star they didn't have any real evidence that there were such things and they didn't know exactly how it happened but he showed that if there was no forces and the mass of the star was was large enough there's nothing to stop it from contracting and going all the way essentially contracting to a point source in certain circumstances which I'll show you in a minute the whole star can collapse to a single point essentially a black hole he called it a dark star or a frozen star the name black hole hadn't been invented and so here here I'm showing you this is a SOHO movie of the Sun I'm not sure why it's rotating so fast but it's a beautiful image of the Sun by the Soho satellite every star has nuclear burning taking place inside of it this nuclear fusion and what's its what produces the energy inside the star that holds it up from collapsing so this is happening inside our star star starts out being mostly helium and hydrogen and then it ends up in this onion kind of configuration which you can see on the screen here where the nuclear burning transforms the elements from hydrogen to helium to carbon the silicon to oxygen and all the way to iron at the core the whole time that this is going on there's energy produced and it holds up the star but when the core becomes iron is the most tightly bound nucleus and there's no other burning that can create energy and so the core you know grows and grows and it's not producing any light and eventually it becomes overwhelmed by the force of gravity in a star like our Sun this cup this star will collapse and quantum mechanical effects effects will hold it up becomes a white dwarf but if it's a massive star greater than 2 or 3 times the mass of our Sun it will over those quantum mechanical effects and it'll actually collapse in the center and so this is this is the kind of process that can produce a black hole and since we're looking at stars I thought of this cartoon that I really like again Jones's colleagues named the telescope sneekly at the Sun a person who came up with the name of black holes was John Archibald Archibald wheeler he's a famous physicist he did many different things and this is a picture of him actually emerging from a conference in black hole Nova Scotia which is was a pirate it's actually was a Pirates Cove on the Bay of Fundy with these really high tides you may have heard of it and he was giving a talk in 1967 in response to questions he coined the term black holes so maybe we could coin some some new term tonight I'm not planning on it but you never know what will happen and black holes had been used before you know that name had come along it's really a negative kind of term if you're an astronomer you know just think about it about these objects but if you listen to the vernacular you know you'll hear people say oh you're your room is like a black hole or you know even worse my job is a black hole you know it's not good and and and going way back in history the very first usage of this name was was really negative the black hole of Calcutta it was the British East Indies tea trade company that was in India and some of the rulers in India were very much opposed to them so there was a minor war always going on and the Nawab of Bengal in 1756 imprisoned 146 British POWs into this tiny little cell and you read here the dungeon was strongly barred room was not intended four to five hundred more than two or three men at a time there were only two windows and thick iron bars which impeded the ventilation the prisoners were packed so tightly that the door was difficult to close and when they opened the doors the next day of the hundred forty six only twenty-three were alive this is the first actual use of the word black holes so it is kind of a squalid history what actually is a black hole we'll start talking more a little bit about science here so mathematically it's a star or an object that's collapsed to a point it's actually my mathematical singularity it's a single point no light can escape from this object there's a Schwarzschild radius for the silence of three kilometers it grows linear with the mass of the black hole and it's a it's a mathematical construct of general relativity you know that we now have evidence that I'll show you in a minute that there are black holes in the universe but when this was first realized you know especially by John Wheeler even going back to Karl Schwarzschild people didn't think that it that it would that there really would be black holes and John Wheeler came up with this interesting theorem which we now believe is really true that black holes have no hair now what that means is that there are only very few properties that a black hole can have it can't have color you can't see oceans on it you can't see any kind of texture it can only have mass and spin and charge in astrophysics we don't usually end up with a charged object object because if something is positively charged it'll suck in negative charges and become neutral but we do see that black holes have different masses and we are just beginning to be able to measure their spin rate and I'll show you some evidence here of black holes when when John and I were students and you know in the 1970s there was an object in the universe that everybody sort of talked about as a candidate black hole we had no strong evidence that it was a black hole but it had behaviors that made us think it was it's called Cygnus x1 it's actually we now know it is a black hole with a massive star orbiting it and gas is flowing on to this compact object and the x-ray was x-ray flux from this object was flickering all the time so if you look with an x-ray telescope you see flickering on and off very rapid timescales down to hundreds of milliseconds and so it's hard you already realize that you're dealing with a very compact and energetic object when you see this kind of variability you wouldn't see our Sun turning on and off the whole Sun turning on and off it's on second timescales you know it's way too large so this is telling us that there's the source of the emission is sort of like that time times the speed of light so you know 100 milliseconds times the speed of light it's a very compact object that's what made us think it was a black hole people eventually got to measuring the velocity of this object around it and by Doppler measurements were able to see how massive that object was and you know it's something like 10 times the mass of our Sun and so it became pretty believed that it was a black hole there's some nice data that I'll show you here black holes can have all different kinds of sizes you can have ones that are a few times the mass of our Sun a million times the mass of our Sun and the Centers of galaxies even a billion and the way that we really understand that their black holes is by looking at objects orbiting them and if they're orbiting you know this really tight compact mass we start to think it's a black hole so we think that there's a black hole at the center of our galaxy and this is a really nice movie it's taken decades to have the technology and infrared astronomy to be able to make this movie because the center of our galaxy is a very cloudy crowded obscured area you have to look in the infrared band to see this but here are traces of stars all orbiting around this central object and you know they come in and they come whipping around you see the when you trace out all of these different orbits you can make a measurement of how much mass there is there and we think it's about three million times the mass of our Sun but there's no light coming from that central object so we think that there's a black hole at the center of our galaxy and we see with the Hubble Space Telescope that John was talking about and enabled it to to make these beautiful images we make images of galaxies outside of our own and many of them have this compact object at the center that seems to be a creating matter glowing brightly sometimes having jets like this m87 image here's the black hole we don't have the technology yet to image all the way down to the black hole so I can't show you a picture of one you know we hope in 20 years or something with x-ray astronomy we'll be able to really take a picture right around the black hole so all of the evidence is circumstantial but I would say you know every astrophysicist that I know you know feels very strongly that there must be black holes do the circumstantial evidence we talked about Stephen Hawking due to the nice question that came up black holes do not radiate the only you know light cannot escape from them well Stephen Hawking proved that wrong and he came up with this idea for Hawking radiation and here's how it works if you have a vacuum in space you know you think there's nothing there but quantum mechanics tells us there's always little fluctuations burbling around you just can't see them there's little bits of energy and then it comes and goes and these you can make virtual pairs in the vacuum so there will be an electron and it's antiparticle a positron that are created they come back together they disappear you never see them but they're there if you have a black hole Stephen Hawking realized that it can it has a strong enough gravity to actually pull one of the particles into it and so you know you make this virtual pair but then the electron disappears and suddenly you've just got this positron a real positron flying out and so a black hole does radiate we've never tested this because the radiation is so faint you know we it's very hard to detect but over the age of the universe smaller black holes can radiate away you know some fraction of their their mass and this is a nice picture Stephen Hawking getting the comple matter metal and this is Michael Griffin the administrator from from NASA this is in the 1990s martin rees a colleague of ours in england giving him this medal stephen hawking was a real space buff and he flew he flew on the Vomit Comet once which was really hard for somebody in his physical condition this is the airplane that flies in parabolic orbits and gives you a weightless time at the top of the orbit I don't know do astronauts all get trained on that yeah okay so but he flew wanted just two experiences and as I understand it I haven't done it myself but John could tell us later you know it's it's it's pretty violent experience because it isn't just one arc it goes 20 or 30 times and you're weightless and then a few minutes later you're slammed down to the ground at 1.8 GS and then you're weightless again and this goes over and over again so it takes it's called the vomit comment by the way and there's one other before I get to Swift I wanted to tell you one other interesting thing this curious episode of Walter Wagner so Walter Wagner is a I hope he's not in the audience but if he is he can speak up for himself a dangerous combination of a lawyer and a physicist and and he had this idea that the Large Hadron Collider it in Switzerland on the border of Switzerland and France when it would turn on would be able to make energy in these collisions that would be so great that you'd form a black hole and if you formed a black hole it could grow and grow and swallow up the earth so it was actually you know his idea was it was quite dangerous and he brought a lawsuit to prevent them from turning on CERN and he actually brought it in San Francisco it was you know it was out of jurisdiction so it was thrown out and the LHC turned on and no black holes were formed even if there were mic microscopic black holes form they would have such a short lifetime to Hawking radiation that they would you know disappear right away so no one no physicists really believe this but I read an interesting news art interview that he did and he said well you know I calculate the the probability for this is 50/50 and you know that's a pretty high probability for something catastrophic like that and they said well how did you do that said well on the one hand it might happen and on the other hand it might not so 5050 okay so now we're going to talk about Swift my favorite topic and in gamma-ray bursts so first of all what are gamma rays I've been talking we even during the questions we were talking about gamma rays so I think you already have an idea and maybe you knew before you came here that gamma rays are light just like the light we're seeing with our eyes but they're very short wavelength light very high frequency they're at the shortest wavelength highest frequency end of the electromagnetic spectrum at the other end is infrared and then radio waves you know which are very long waves and light has a this duality principle that it behaves both like waves and particles and in the visible band that you really do treat you know you do think about it you can see the effects of waves if you see the a distant light coming through a screen and your door you'll see a diffraction pattern but you can also do photon counting with some cameras where you detect the individual photons of light and the gamma ray band we always think of them as particles they behave much more like individual objects arriving these they're actually packets of ways but they they come as objects that we can count so we actually count the gamma rays that come in to Swift and you can see here that there's a lot of different satellites only the optical band you know gets down to the ground in radio waves at very high energies you can measure gamma rays because of their effect in the atmosphere most of the electromagnetic spectrum you have to be above the word the Earth's atmosphere to study and so astronomy and astrophysics has gone through a revolution in our understanding of the universe as we've been able to launch these satellites above the Earth's atmosphere and make these measurements satellites like HST Chandra and the x-ray band Spitzer and and in the gamma ray band we have swift and we also have a that the John mentioned called Fermi that's flying right now so that's what gamma rays are and and then what are gamma ray bursts gamma-ray bursts are flashes of gamma rays really bright flashes they dominate everything else in the sky when they occur and they last very short time they only last like a hundred seconds so we don't have anything similar in the optical band that we see you know where you look up in the sky and you just see a star come for 10 seconds and disappear that the closest thing I can think of are these glints off of satellites they'll sometimes make a bright flash I don't know if you've ever seen any of those but they are visible to the human eye we're not very familiar with that kind of transient sky like we have in the gamma ray band they occur about once a day with Swift we see one every few days we don't see the whole sky and they were discovered by the veil of satellites that were built at Los Alamos so John F Kennedy signed a test ban treaty with the Soviets in 1962 he actually signed it you know just the year before he died and it was to prohibit testing of nuclear weapons above the Earth's atmosphere and Los Alamos was tasked with building these valus satellites they were launched in pairs you can see two of them here and and they have gamma ray detectors on them gamma-ray bursts make gamma-ray flashes will so do bombs when they go off in fact it's the gamma rays from a bomb the x-rays and the gamma rays are the most fatal part of it like in Hiroshima and Nagasaki people got radiation damage mostly from from x-rays and gamma rays so they had gamma ray detectors on the satellites and they started detecting flashes of gamma rays which you know lucky for all of us it was not nuclear weapons testing they did discover gamma ray bursts this is what a gamma-ray burst looks like to to an astrophysicist it's the counting rate in the detector that suddenly goes up it's County a thousand counts per second of these individual gamma rays coming in and then it dies away this one lasted for six seconds is the first gamma-ray burst that they saw and since they were so bright occurred fairly often everybody even when we were students were thinking that these must be coming from somewhere nearby our own solar system or somewhere within our galaxy just because they were so bright and that that was thrown out of the window by discoveries in the late 1990s both with the Compton gamma-ray Observatory the Batsy instrument that John mentioned and also by an Italian Dutch satellite they were able to position a gamma-ray burst very accurately on the sky and then follow it up this is a little bit later in time but it's the most nicest image I have that shows you with the Hubble Space Telescope here's the gamma-ray burst was detected it's dying away and here it is in a distant galaxy it's not nearby our solar system it's not even in our own Milky Way these gamma-ray bursts are coming from far out in the universe and so if you put that together they're bright they're really far away you realize that they're a huge amount of energy so they're the the most energetic explosions in the universe people say after the Big Bang they're about ten times as much energy as a normal supernova and you know they're really fascinating objects my friend at Atlas Alamos Edie Fenimore put it in this way which is maybe you know one way you can sort of appreciate the energy a nuclear bomb which has a huge amount of energy you know tons of TNT is equivalent to just taking a raisin of mass and converting it into e equals MC squared of energy so you know mass converts into a lot of energy without much but a gamma-ray burst is the equivalent of taking four hundred thousand Earth's and having them you know that much mass just suddenly vaporize equals MC squared so there's really a huge amount of energy in these gamma ray bursts well that's what motivated us to propose the Swift mission because this was the late 1990s and we we realized that these were really neat we don't understand what they are they're important and understanding the universe because they're so bright they have a lot of effects that I'll show you and we can use them as tools to study the early universe because they're these bright beacons that come from far away and so we can use them to study the distant universe in a way you can't do with other techniques but they were poorly understood we didn't have any really good set of observations and so we needed first of all a good gamma ray detector and I'll show you about that and we needed a rapidly responding spacecraft that's why this whole mission is called Swift because we proposed a mission it's an astronomical robot it can control itself and point at the gamma ray burst what we had and I think this is one of the reasons we were able to win this big competition in 98 was this new technology we didn't invent it at Goddard it was invented by the medical imaging community it's the solid-state detectors called CAD Zink tell detectors this is the size of them they're very small but they're solid-state they can run at room temperature they have a lot of advantages over other things like silicon detectors and we found a way to build very large arrays of this so on Swift we have 32,000 of these detectors and I brought one of the modules this is a hundred and twenty eight of them that you can come down and see afterwards this is actually a flight module week so we fly it says 128 detectors and we have 256 of these modules in our array so it's a you know it's about this size it's a size of a coffee table all with these precision solid-state detectors it's by far the most sensitive gamma ray camera that's ever been built this is what Swift looks like this is the instrument that says gamma ray camera with all of those CAD zinc tail detectors in it it views the sky through this thing called a coated mask which is a big mask with lead elements on it it allows us to do imaging in the gamma rays and then we have an an optical telescope called UV UV optical and an x-ray telescope so the way the satellite works is this wide field gamma ray instrument is looking up at the sky doesn't matter where it's looking is waiting waiting then a gamma-ray burst goes off and we're able on the fly with the high-power that we have on board to calculate where the position was we tell the spacecraft and it on autonomously slew is to point the you've odd and the XR t added and we can look and see the dying away x-ray and optical emission after this flash of gamma-rays that's how swift works and it also sends the data right down to the ground immediately through a relay satellite called t dress that nasa runs and so astronomers on the ground can point their telescopes at the gamma-ray burst and they do whenever we have a gamma-ray burst twice a day and every time i mean twice a week sorry we wish i was twice a day and you know every time we have one there's people scrambling to make observations you have to observe this x-ray and optical afterglow lasts only for about a day you have to observe quickly but what when you observe it can be very bright nice to have this advertisement from these Swift trucks that you may see rumbling around the beltway although that can have its downside we put this satellite together it was a busiest time of my life you know building the satellite with this team of about a hundred scientists a hundred engineers and managers that we had but it was a wonderful time because you could see it come together in the clean rooms at goddard we bought this spacecraft bus they call it it's basically the structures and the solar arrays from a company in Arizona it's now owned by orbital but it was called General Dynamics at the time and then we built these telescopes we got parts from our European partners in the UK and Italy and and then we assembled them here in the US and we built a large gamma-ray bat instrument right at Goddard and here it is all put together still at Goddard that that's me pointing where we want to go and so then we shipped it down to Kennedy Space Center and that was it that was a fascinating time I've been to other launches but this is the first time you know was sort of our own satellite that we were launching and we launched on a delta rocket delta ii rocket here's the solid rocket booster so this is full basically it has 10,000 gallons of Kara's seen in 10,000 gallons of liquid oxygen and it's a solid rocket so you can you can turn on and off the rocket and steer the nozzle that's what's nice about a solid of the the liquid rocket it's surrounded by these three solid rocket boosters and these have a tremendous amount of energy they're solid explosive essentially they're solid nitrogen nitroglycerin but the you know what's what's good about them is you get a huge amount of power what's bad about them is you when you light them you can't turn them off or steer them you know so when you light them they're like firecrackers and you're going and here was our precious satellite you know it wasn't my life on the line but I felt like it was John this is the satellite you know this instrument that we'd been building for seven years and was on top of this bomb there's a nice picture of it when we went down to Florida in 2004 it happened that this was the most hurricane active time and all these hurricanes happened after we shipped so we were sitting down there at Kennedy Space Center this was where we launched from from Cape Canaveral and and some of them you know tore the siding off of the Vehicle Assembly Building they were violent toward her Akane's and so we had to hunker down in our hotel room we actually had to put Swift back in his shipping container to protect it and and all we could think of is we want to launch so we had this idea we launch right through the eye of the hurricane why not because it's calm right have to push the button at the right time well finally the double rainbow came out and we knew it was good good omen and and that's when we launched so I'm now going to show this video I think it's still on mute okay so this is a picture of the launch a movie of the launch of the Swift it's a really nice movie because in addition to the cameras on the ground they have to yield telescope a quest star setup and so you'll see the rocket go up you'll be able to see the solid rocket boosters fly off of it it was a beautiful clear day fifteen fifteen ten nine eight seven seven five six five three three once we have ignition we had we should lift and reassess we also has a swimming phase for studying my position so it understands gamma-ray yours throughout the universe everything continues to look good I'm going to turn it on to you now so I can talk over it so we're going to see the rocket go through the sound barrier at that time if you're able to see it well enough you'll see a cloud of vapor form around the nose cone that's coming up soon here there okay there we are going through the sound barrier and here's what this quest our telescope you see the soccer solids flying off it was kind of an interesting experience because that was the shroud coming off after the we launched by on a delta ii which was managed by boeing it was a boeing rocket and after we launched and got on orbit all the boeing guys stood up and started shaking each other's hands and we're all clapping and everyone was happy but you know for us the the rocket was very reliable we were that stressed about the ride we're more stressed about all of our own deployables coming out in the telescope turning on those guys just walked out of the room and left us with our telescope luckily everything worked well and this is some beautiful pictures we have from the UV optical telescope and the x-ray telescope of different galaxies we don't spend all of our time looking at gamma ray bursts although i'll be showing you those data and when we're not looking at gamma-ray bursts we're looking at objects that people in the community asked us to look at and so we get requests and we schedule about seven different observations a day and everywhere you point Swift you get a multi-wavelength view of the sky you can see in the optical you can see in the UV you can see in the x-ray look how different galaxies look in these different bands and the optical you see the whole galaxy in the ultraviolet which is the are the middle panels you see the star formation regions in the galaxy these are all spirals and then in the x-ray band you don't see that at all you tend to see neutron stars and black holes and compact objects that are making high-energy emission this is what the gamma ray burst data look like so when we we get the bursts detected by the bad instrument there it is on the sky and position it right away get this position to a small fraction of a degree then almost every one of them has an x-ray afterglow and so there's the x-ray source and this x-ray telescope is really nice because it can persist position them really precisely to arcsecond positions so about a factor of 100 better than the bad instrument and then we take a picture of the whole sky with this optical telescope it's not as big a telescope as the HST but it's very capable and we can point it all over the sky so so we do a lot of different optical Astronomy observations with the UV ot this is what a gamma-ray burst looks like as I mentioned earlier to to a gamma-ray astronomer this is counting rate versus time now that look at this one this one lasted 30 seconds you know it turns on it turns off sort of looks like Cygnus x1 with much brighter it's very erratic well here's another one very short one this whole thing lasted only a second and yet it still has these really high time fluctuations and although we don't really understand what causes all these fluctuations I'll give you some speculation in a few minutes what we've learned was Swift and and here it is it's this is heaven to my eyes it looks like a bunch of squiggly lines to you but here's a whole page of gamma-ray bursts and all of their light curves and this is just a fraction we now have 700 of them that we've detected and perform these detailed observations on so let's see what we're learning from this first of all I mentioned that you see a gamma-ray flash it lasts for a minute or so or tens of seconds and then afterwards through this afterglow in the x-ray and gamma rays and here you see the x-rays fading this is over about a thousand seconds so here's an hour turns it's very bright for a while and it kind of flattered and decays away one of the things that we've learned is that a gamma-ray burst actually lasts much longer it's just that we never had an x-ray telescope that could look that quickly and so the real show is still going on for hundreds of seconds and then in the optical we've looked with HST which has the prettiest images but we look with a lot of other telescopes too and there's something really important about this afterglow that we see in the optical band it's extremely bright it can be a billion times a million times - a billion times brighter than the galaxy it's in and so we're getting a lot of light from this distant galaxy in the universe you have to be able to observe it quickly but if you can you can use it to study that galaxy in a way that you can't in any other way because if these distant galaxies are so faint you can't see them even until the gamma ray bursts lights them up now this is the record holder that we had and this is actually the most distant object that's known in the universe with a so-called spectroscopic redshift a very accurate measurement of its distance and it occurred 13 billion years ago so the universe is 13.7 billion years old this curd from one of the early stars that were being four that were formed in the universe in early galaxies and it's the light has been traveling to us remarkably for 13 billion years and when we were talking at dinner tonight beforehand you know a lot of different objects have exploded and their waves of light or hanging tortoise we don't even know what's on the way but it's all been launched was you know especially with these gamma ray bursts they were launched a long time ago we're just sitting here waiting for them to to hit the earth and for us to study them this is a beautiful picture how bright that is you know even it's such a great distance what you can do with these is a lot of great science I'm not going to go into the details but I wanted to show you this one beautiful plot this is a spectrum that's taken of one of these gamma-ray bursts it's a very faraway object and it's in the optical band this one is taken with the Keck telescope on Mauna Kea in Hawaii it's a huge optical telescope what we're looking at is how much light is coming from the gamma ray burst as a function of the wavelength so this is very red light this is more into the visible light what I want you to see are all of these absorption lines so as the gamma ray bursts signs through the gas of its galaxy it's absorbed by different elements in the galaxy you can see iron magnesium silicon nitrogen we can see by which lines are there how much nitrogen there was how much there is how much night carbon there is and so we can measure the elemental abundances of this object that's at the very early part of the universe and that's one of the great tools of gamma-ray bursts is to study the early universe and try to see how the elements were formed when they were formed when the first stars occurred it's kind of a nice maybe a nicer picture to look at this so here's the history of the universe all in one panel so first of all there's the Big Bang as shown as this glowing white light and then eventually it cooled down in the U the whole universe became there were no stars or galaxies yet and all the electrons found protons and became hydrogen atoms and it became neutral they call this the Dark Ages because any star that formed its light would travel through the medium and it would get absorbed and absorbed and you wouldn't see this star even because it couldn't the light couldn't travel very far but then stars started forming in galaxies and try to understand when that happened and how it happened is one of the major problems in astrophysics right now and they emitted light that reaiiy annoys the universe and made it transparent in the to the way we see it now so we can see across the universe and you can see stars and galaxies you can see here these are red shifts these are the millions of years ago the gamma-ray bursts are probing back into these very early times that we can't see with other satellites it'll be neat when JWST this future satellite beyond the Hubble Space Telescope is on orbit because it's also going to probe back into this very early time in the universe we hope we hope Swift is still up at that time you know knock on wood at least that we have some way of detecting gamma-ray bursts when JWST is there now one more result I wanted to show you and that is on the opposite end and this is the very nearest gamma-ray burst that we detected they have names this is 2006 February 18th that's the date that we detected this one and it's probably our most famous gamma-ray bursts in fact they did an interview with science magazine yesterday about this burst that occurred you know six years ago and what's so special about it is that it lasted a long time this one actually lasted 35 minutes and when a gamma-ray burst goes off the signal comes to the ground and goes to the telescopes but it also comes to our cellphones and so we get paged and we go running to our computers and I still remember this was at 2:00 a.m. and you know try to figure out what is this object it's lasting 35 minutes it doesn't seem like a gamma-ray burst it had a very smooth curve it wasn't jagged II like the other ones and then we had an aha moment around 4:00 a.m. when we said oh it's just a really long gamma ray burst it must be nearby or something strange so we sent out astronomical telegrams to the whole world saying look at this with your telescope there's a really odd object in the in the sky and so everybody was observing this and the next day a supernova started to occur in that part of the sky and so this was a tie-in between these gamma-ray bursts that we were seeing and exploding stars and it wasn't just any old supernova it was a very high velocity a supernova is a star that explodes people have seen them historically we haven't had a nearby one in the sky when they go off they can be so bright that everybody you'll see them it'll be as bright as Venus hopefully sometime in your lifetime you'll be able to see a supernova and our gal see but there's a tie between these gamma-ray bursts and supernovae I'll show you a little movie in a minute and they're very high velocity we call them hypernova and you can see here this is an image it doesn't look very bright but it's a it's still at a pretty good distance it's 450 million light years away it's much brighter than its a galaxy and it's shining there this is a nearby supernova and you can see how they occur in galaxies then we see them in external ones they appear for a while they last for about a month and then they disappear okay so so that gave us the tie between gamma-ray bursts and exploding stars so now this is what we learned so this is what happens to a star I showed you this onion structure of a star the core burns to iron and it collapses there's no more radiation their gravitational weight of the star pushes down it collapses and in a new normal new star a massive star this core collapses to what's called a neutron star it's a hard core of a star it's not a black hole it has about a 10 kilometer diameter sort of the size of our Beltway but it's a lot of mass within that small region but it's a neutron star and then the rest of the star goes shooting off making this bright explosion we call the supernova and here's what we strongly believe now happens in a gamma ray burst it's a more massive star the pressure is larger in the center and so it presses all the way down beyond this limit the Swart shield found in that Robin that Oppenheimer found and so this neutron star collapses down to form a black hole and when you form a black hole at the center of a star a lot of things happen first of all all the mass starts falling into it it's a really strong gravitational pull it forms this disk it makes Jets that beat their way out through the star and these Jets are aimed at us and make the gamma-ray burst and then it also explodes the star in this this very high velocity hypernova so here's the video so we're going to ride on a camera into the this star we're going to see the black hole form you will see the Jets come shooting out hope it plays looks like it's good so there we are in the center there's the iron core collapses to a neutron star and then all the way to a black hole and actually which should be just a point gas is flowing down onto this black hole jets are shooting out they have such high velocity they burst their way out of this star and these Jets are what are making the gamma ray the gamma ray emission in the gamma ray bursts and so one thing you'll learn from this movie if you looked at it is that we see a gamma ray burst when that jet is coming at us and there's a lot of these exploding stars aimed somewhere else you know some other civilization may be seeing them but we don't we only see about it one in a thousand of them we've learned a lot of things kind of to view graphs to show you just the kind of things we can learn about black holes from gamma-ray bursts so counting the GRBs gives us an estimate of how many black holes there are in the universe we know of a few dozen from these velocity measurements but that's so few when we take the current GRB rate observed by swift and assume that that's been going on for like ten billion years of the universe you come up with about a million black holes in every galaxy people think there may be between a million or ten or even a hundred million they have no idea but these gamma-ray bursts are telling us the number and then sort of bringing it closer to home gamma-ray bursts extinctions gets everyone worried well you don't have to worry but there is a there's real science here actually we've done this at Goddard where people study the ozone hole they've developed computer codes to understand you know how ionizing radiation hitting the the atmosphere can affect it and confess own for solar flares if you have a gamma-ray burst that's near a planet with an atmosphere it can destroy the ozone layer if it's close enough it can blast the atmosphere right off the planet the GRB must be really close it has to be within a thousand light-years that sounds like a big distance but it's not that many stars within that distance and so we worked out the probabilities and we think that this kind of gamma-ray burst blowing the atmosphere off the earth or at least destroying the ozone layer probably has happened a couple of times during the time that there's been life on Earth since the Paleozoic era causing some extinctions this is a new field it may be one of the causes of extinctions but the probability that it happens you know in your lifetime is minuscule much less than an asteroid hitting the earth so you don't have to worry about one of these but another way of looking at it though is every time you know every two times a week when we detect a gamma-ray burst some poor planet nearby got completely vaporized so it is happening okay so now I'm going to close I wanted just to discuss a few of these sort of mind-boggling things about what really is a black hole well of course it's it's an object that's just full of unmatched socks and we all know that they're actually a lot of different ideas of what in physics is a black hole I talked about general relativity in that case the black hole is just a point of mass the whole star is collapsed to a mathematical point a singularity I gave one of these lectures kind of similar to this one that for a different audience and somebody in the audience that wait a second black hole can't be a singularity there's only one singularity that's what the word means so I don't know it's a mathematical term that means everything is concentrated at a point we call it a singularity that's the general relativity view of a black hole and then there's a Schwarzschild radius around it and light can't get out from it then there's also the idea that it's not just complete what's it like inside the black hole well it's not just completely black because there's radiation that's coming there's matter that's falling into the black the the event horizon of the black hole I'm falling in and so it's radiating it would be lit up inside with a lot of things falling by you all the time sort of a really violent place now each of these actually these are not just sort of ideas somebody had but these are real papers of people have written so these are serious ideas this is another one all the masses accumulated at the event horizon there actually isn't anything inside okay here's a way of looking at that and this comes about because if you watch matter falling into a black hole you'll see the Tut it gets time dilated which means the time slows down more and more is this matter gets closer and closer to the black hole and when it gets the event horizon from our external point of view time has stopped and so Wow maybe nothing ever actually goes through the event horizon it's just all piled up there well they're good arguments why that probably isn't the case if you have a star that collapses to a black hole or already was mass inside there so there must be something inside and also looking at it in a proper quantum mechanical calculation and well actually it's proper calculation taking into account general relativity an observer or some of this mass that's falling in in the frame of that object does go through the event horizon and eventually you know does plunge through okay this is one of my favorites I think and that's it we haven't we really haven't we don't have a theory of everything that we were discussing in the questions before the talk so maybe there must be quantum mechanics that comes in when you have such a tight gravitational field such a strong field that it's not going to be a point it's going to be some kind of quantum fuzzy ball in the center and other people say that the whole black hole is sort of filled with with quantum funds these last two I think are kind of fascinating one is that the black holes are portholes to a parallel universe and the other is that every black hole forms a new universe so let's talk about that for a minute so you can have these things called wormholes we don't we don't believe there really are any but mathematically you can have them or you can transfer between one point of the universe to another through this through a black hole so the idea is that these black holes whenever one forms it's essentially giving you a path to a different place the universe the trouble with that theory is that there's no way to ever test it this other one is pretty fascinating too and that is every time a black hole forms there's a new universe the whole universe is within that black hole you can think of our universe as being a black hole and then there's the idea of cosmic evolution so the universe develops in such a way to make black holes ah that's interesting we live in this universe where really bizarre things happen you know these massive stars evolve and collapse into black holes you know who could have ever thought of that well these preposterous things are happening because they make black holes and we're in a part of the universe where black holes are being formed because there's a kind of natural evolution towards the creation of black holes so think about that for a while so now what would it be like to fall into a black hole so I've talked about clocks moving slower and slower from an external observer but if you're actually traveling into the black hole you in your frame you don't see that you see the rest of the universe between become more and more redshifted and their clocks slowing down but your clocks are going just fine you can plunge right through but if you look at the Schwartz yield equation what happens when you go through this singularity is that the coefficients in front of the time term in front of the space term change signs and so you actually get a swap between space and time inside the black hole this is the mathematical structure that you come out with with the short-shorts field equations and so we're used to in our world time is inexorably moving on but you can move around in space from one place to another well inside a black hole space is inexorably moving along and you can't change that your space path but you can move around in time so that's another kind of bizarre do okay there is something kind of fun that happens or bad that happens if you're in that if you're the person this thing called spaghettification and so what happens is that if you're a person falling into a black hole you get close to the black hole and the gravitational field at your force at your feet the gravitational pull of your feet is so much stronger than it is at your head that it stretches you out and so this happens actually we believe to all matter falling into a black hole and for a very small black hole with just a few times the mass of our Sun there's a really big gradient and it would just tear any astronaut falling into the black hole but if you had a massive black hole at the center of a galaxy it would be a more gentle ride and you'd be able to plunge right through I like to collect pictures and these are ideas sort of what people think about black holes this is a gamma-ray burst with this guy shooting out along the jet here you see the black hole at the center with these Jets this is a star falling into to become a black hole and this is also more of a sort of gamma-ray burst kind of picture and you can see with time that the way people have viewed black holes has changed this is a 70s artists impression of a black hole it looks kind of like The Wizard of Oz I would say you know kind of everything you can see the cows and the barn falling into the black hole but here we are nowadays you know anime of course and so this is what it looks like nowadays falling into a black hole I have my conclusions I have one more slide after that so objects exist that look and behave like black holes that were predicted by general relativity we haven't been able image one directly I hope you know hopefully in my lifetime we'll be able to do that but we have a lot of indirect evidence and all points in the same direction that there really are black holes they're common in the universe we know by name a few hundred but we can tell by extrapolating out in space that they're you know millions in our own galaxy and and billions in the universe but we still don't know really what the true nature of these black hole monsters so with Swift we're observing the fiery birth of black holes we have these gr bees that are a new tool for studying the universe and we very much with Swift hope that we can detect one of these gamma-ray bursts from an even more distant object hopefully from the very first generation of stars in the universe this is a meeting that we had recently and I just wanted to sort of thank publicly thank this this team that's working on Swift we have 200 team members all around the world about 100 are in the US and then we also have about five times that many observer users of the observatory that are just out there in the astronomical community that put in requests and it's a great lot of fun working with this satellite and we hope that it stays in orbit for quite a ways still thank where you go well thank you very much hello okay we have some time for Q&A I imagine there might be a question or two right here in the middle the question is are gamma mate gamma-ray bursts associated with magnet ours and blazed ours no boy this is a topic that may be closer to John's expertise but indeed these very magnetized neutron stars what a magnetar is do make flashes of gamma rays and in the early days there was a really bright flash of gamma rays in 1979 that I remember in fact everybody in the community knew about it we thought it was a regular gamma-ray burst it turned out to be one of these magnet ARS that was near in our own in a nearby galaxy and so they're different the physics is different the observations look very similar way in the back okay the question is what is the youngest black hole that you know of well every time we observe a gamma-ray burst there's a brand new informing so you know those are really young okay yeah I understand I understand what you're talking about light travel time so the youngest in terms of this time frame oh boy there's no way to really measure their age very accurately these very massive stars don't live very long they only live about a million years before they collapse and make neutron stars and black holes but then they sit there and there they can either be dark if there's nothing around them or if there's some other star around them they'll be a creating matter and so we don't know their age we can tell how long they've been lit up sometimes by sort of the age of the star that's on them okay question here on all the plots that he showed seem to have two peaks and the question is why or what does it mean well that was just a selection effect of my picking some to show you you know there are there are a good number they have two peaks you know this one has maybe three or four or five and they're also ones and of course you won't be able to see this very well but there's some that just have you know a single spike and so if you can maybe scan your eyes over this you'll realize that there are some really interesting one with two peaks but they don't seem to be a separate population that we know of over here are the far right yes I am so the question the question is are the is there one family of events causing this one particular mechanism or is different mechanisms causing much longer bursts than shorter bursts it's one of the main questions we wanted to answer with Swift and bursts that are longer than about two seconds seem to be all the same these ones that are really long that lasts many minutes we think maybe the jet is just barely getting out of the star and so it's taking longer so the basic idea is the same but it's the you know look but it's a little bit different in its tuning but then what about less than two seconds if I haven't gotten into that but we think there's a different complete mechanism for making bursts that are less than two seconds and it's the results that have come out of Swift and those are actually probably do two neutron stars that are orbiting each other and then merge in a fiery collision also making a jet it's fairly preliminary data but it's a very interesting question that you asked we actually believe that there's two different ways of making gamma-ray bursts and I'm glad you asked because I didn't you know have time to get into that okay a question right above him yeah I didn't here's a question he was asking are we tracking any objects that might become gamma-ray burst near enough to harm the earth and actually we have been doing some studies to see where there really massive stars that could explode that are in the neighborhood this isn't really to predict one because you know there's still thousands of light-years away and there is a very massive explosive object called a de Carina which is we talked about during dinner which had some explosions in the past and when it goes it's a hundred solar mass star it's going to make this huge explosion and it's just a few thousand light years away so people have gotten interested in this topic it's a good question we're not tracking them in the way that we do asteroids though there was right here yes and then we have time for one or two more but that's it and we don't know if it's clear outside but if it is if you can see Mars if you can see Saturn just two bright spots in the sky our telescope is open for your pleasure yes yeah the question is is there any distribution pattern over the sky or do they appear everywhere in the sky they appear uniformly in the sky the bats the instrument that was on the compet observatory that we talked about at the beginning and john mentioned was the first instrument to measure a large population of gamma-ray bursts and to see what their distribution was on the sky they were looking to see if there would be a concentration along the Milky Way plane just to determine the origin and it's very uniform everything statistical we go three month we went three months once without seeing one and we've got other date you know there were days where we had four in a day but on the average it's two a week and if you look at the distribution it's just like rolling the dice you know it's just a statistical so it seems to be a uniform rate and time and uniform on the sky I just want to add that that is exactly the same logic that William Herschel used for the distribution of nebulae realizing that they'd had no concentration toward the Milky Way or the galaxy and he started making him think in the 1780s that there's something else out there and that's what we're faced with here the galaxies right and they were the galaxies that's right back in the red there could you talk about supernova 1987a that was the nearest as you know the nearest supernova that we've had in our lifetimes and it did not make a gamma-ray burst we're pretty sure it was a kind of very interesting supernova because of its proximity to earth we've been observing it with HST and Chandra seeing rings come out of it and I actually did in my postdoc we flew a balloon instrument a high-altitude balloon instrument in Australia to observe gamma rays from supernova 1987a so it's one of my favorite topics quite a quite a supernova vent okay one more question then we will those of you who wish to see the detector and you can come on down here after that maybe ask a few more questions yes what causes the Jets what's the mechanism that causes the Jets and gives them their high velocity yeah that's a hot topic right now we seem Jets and many different kinds of sources you know we see them not just in gamma-ray bursts but also from the Centers of galaxies I had this one image here and it probably used magnetic fields actually that so you have a black hole at the center possibly even with a neutron star but let's talk about a black hole mass is orbiting it and accreting onto it and it's this magnetic field in this disk that gets twisted up by this rotational motion and it can make a kind of funnel that that'll collimate the particles that come streaming out so that's that's our best guess right now what makes these Jets I've often thought I've given lectures on the topic that you know whenever there's a black hole that's a creating matter you have some kind of jet coming out of it they seem to be very common and they may be a signature of black holes the particles charged or neutral we think that there's charged particles coming out you know electrons and and some people even talk about protons coming out there are other models where people have mostly photons making the pressure so Mesa mostly light that's created in there so it's an open question right now exactly what's streaming out the gamma-ray burst comes from the streaming out particles that radiate gamma rays at us for those of you are interested in the micro physics well on that especially it's lovely to end on an open question don't you think I want to thank all of you for a great set of questions and certainly give another round of applause for our speaker once again thank our sponsors NASA I want to invite you back for the final session that will be on June 5th where Dave Latham from a Smithsonian Astrophysical Observatory will be talking about the Kepler mission and of course that is very nicely timed with the last transit of Venus across the face of the Sun that any of us will probably see in our lifetimes and you're all welcome to come thank you very much

Channel: Smithsonian

Views: 30,330

Rating: 4.5923567 out of 5

Keywords: National Air and Space Museum, Smithsonian, gamma-ray, satellite, black holes

Id: DtAWoC5BjoY

Length: 80min 50sec (4850 seconds)

Published: Tue May 29 2012