Extremes of the Universe by Andy Fabian

I'm Andy Fabian I am the acting director of the Institute of astronomy here at the University of so tonight's voyage we turn from the oceans to astronomy now in his essay on the era Areopagus the hill of Mars John Milton the poet tells us that he had found and visited the famous Galileo grown old a prisoner to the Inquisition for thinking in astronomy he participated in the Italian academies these were the ones who went to the extreme who by finding new worlds changed our world and thinking Milton there defines what we hope to be here in Cambridge not slow and dull but of a quick ingenious and piercing spirit acute to invent subtle and sinewy to discourse not beneath the reach of any point the highest that human capacity can soar to the highest point that's the extreme where astronomy pulls us that's what we hope this university is doing now but Mars I expect you know that most people may think of a couple of things that I say Mars one of course Mars rover that the planet the Red Planet the other of course though is the chocolate bar made in slough Slough was where William and Caroline Herschel lived keenly supported by their neighbor across the Thames in Windsor Castle William was George the Third's astronomer Caroline put together the new general catalogue of thousands of nebulae and star clusters including many of her own discoveries and our modern study of the universe comes from that catalog for which the Royal Astronomical Society awarded her their gold medal she was the first woman to be awarded that astronomy fascinates us unimaginable worlds beyond our own and tonight to explore those extremes we have one of the world's eminent astronomers astrophysicists professor Andy Fabian director of the Institute of astronomy here in Cambridge like Caroline Herschel he's a gold medalist of the Royal Astronomical Society he's also a fellow of the Royal Society and a foreign affiliate of the US National Academy these are the descendants of Galileo's Academy the lynce or link side the farsighted ones and he's a fellow of Darwin College and the central guiding individual behind this annual Darwin College lecture series from the very first series in 1986 so please welcome Andy Fabian to speak on extremes of the universe [Applause] well thank you very much talking about the extremes of the universe I'm spoilt for choice one of the extremes of course is the Big Bang which is the origin of space and time that started at all but I'm not going to go and talk about cosmology I'm going to talk about the extremes of power in the universe and the most powerful things I'm looking at our nearby powerhouse the Sun in this little movie and you can see all these eruptions of material above it these are solar prominences which are visible the light of hydrogen-alpha and we're going to go on and look a bit at those things but in a sense what the theme is it's going to be about power in the universe what are the most powerful objects in the universe that we can see and often it's involving magnetism sometimes it's gravity most often gravity and magnetism that is driving what I'm going to talk about so I'll move ahead talking now looking at these eruptions from the Sun connected with solar flares the Sun is actually a very inactive star compared to many stars out there we it's a dwarf star and things about our solar system are not very eruptive like this thankfully for us I think but what we've got on the Sun of this the Sun as you know has not got a solid surface but it's a gas ball and it's rotating not this fast in this little x-ray image up here it rotates at 26 days at the equator and at 30 days at the poles this means it's differentially rotating and if you differentially rotate a magnetized plasma it's like winding up a basket full of rubber bands eventually they start springing out and here are the rubber bands that the magnetic field lines springing out from the surface of the Sun in this picture down here taken in the ultraviolet but sometimes there are really in norm eruptions on the Sun so-called solar flares and perhaps the brightest solar flare seen in historical times was recorded by RC Richard Carrington Esquire while engaged in the forenoon how many of us talk about the forenoon of Thursday September the 1st in taking my customary observation of the forms and positions of the solar spots the appearance was witnessed which I believed to be exceedingly rare and that is in this drawing here it's these white bits just here and what we refer to is a white light flare now white light flares on the Sun a very rare he's the only one to have seen one and it was verified by somebody else so it's a genuine observation but it coincided with the observation of the Aurora this is a painting of observation of the Aurora as far south as the Caribbean also back in those days they had Telegraph's connecting cities ran along railway lines and things they were long wires and people were getting sparks off them and things worse being set on fire by them this is because there was an enormous eruption from the Sun at the same time of plasma coming out directly towards the Earth and that plasma striking the earth of a few days later giving rise to all these phenomena essentially what you've got is the Earth's magnetic field is encased in this solar wind all the time but there's a big eruption passing through it it squeezes the Earth's magnetic field and everybody knows from Faraday's law if you move a magnetic field you generate an electric field and those electric fields lead to all of this phenomena and also the sparks and well one to happen today it could easily wipe out many of our transmission systems and wipe out our satellites particularly the GPS satellites the next time one happens and they're not predictive we can't predict when they occur the next time when happens I don't want to be landing in an aeroplane now it was thought that these were extremely rare and haven't happened recently but actually we have got two satellites monitoring the Sun one ahead of us in our orbit one behind us in our orbit by about 60 degrees and they're called stereo a and stereo B you're now seeing the whole of at the July the 23rd 2012 that's the Sun in the center is just a it's not an image it's just an image pasted on this is a disc blotting out the image of the Sun and you can see in this speeded up movie you can see that something is erupted from the Sun here it goes this vast coronal mass ejection it's called but notice how that this image suddenly gets terrible it's full of spots that's because there's a vast cloud of very energetic particles coming out as well and those energetic particles which come out only slightly slower than the speed of light are then bombarded that satellite with this intense array it's very intensely irradiated that's what causes a lot of damage to satellites it's what we don't want so this was 23rd of July 2012 had it happened just a week earlier it would have happened directly at us so 2012 would be known to all of you this date would have been known to all of you had it happened well or let's say it would be 16th of July 2012 would be known to all of you if that the alignment had been different so our solar flares the biggest things that happen on the Sun well this is just a technical plot but this is the frequency at which flares occur versus their energy and don't worry about the units but what we've got each of these ticks is a factor of 10 so you know this is 10 to the 24 10 to the 26 that's a factor of a hundred that's a factor of a hundred that's a factor of hundred in order to plot anything and I'm going to show you only a few plots but I'm going to talk about big numbers and the only way I can talk about big numbers in astronomy because they are astronomically huge is to talk about them in powers of 10 so when I say 10 to the 20 that means a 1 followed by 20 North's 10 to the 40 is a 1 followed by 40 knots 10 to the 52 Watts we're gonna get there 10 to the 52 watts is a 1 followed by 50 to zeros Watts well here we're talking about 10 to the 32 it's a total energy and a flair and you see people have looked at the rate at which flares occur there do they also occur up here well you can if you work it out these flares up here where they to occur would occur once every thousand years or so so we have to look at the Sun for a thousand years to see one of these super flares but another way to do it is to actually look at a thousand stars like the Sun for a year and that's what's been done with the Kepler satellite just staring at a thousand solar-type stars and they do see these flares and it continues up there so we don't quite know where this ends and there's probably some physical limitation but they can be extremely energetic and this is just a dwarf star unlike the Sun it's smaller than the Sun a small red dwarf star actually had a flare that big in 2014 now I'm going to go on now with I'm doing the preliminaries before we get into all the exciting details of all the powerful events in the universe I want to talk you through a little bit about what I what how big power can be how much how large can you think about the maximum power and I'm going to send you all out of the room because I'm going to give you an equation which everybody says one shouldn't do but this is a very simple equation it's just what is the maximum power that you can get from an object of mass M and so it's very simple but if you've not seen it it's very cute as at least in terms I think it's cute but this is the power or luminosity it's defined as energy divided by time you all know about light bulbs 100 watt light bulbs or 15 watt light bulbs that you use saying that's that's a unit of power so it's energy divided by time what's the maximum energy you can get from mass M Einstein gave us the answer it's MC squared and I'm sure everybody in this room knows e equals MC squared so there's energy equals MC squared what's the shortest time that you can get it out on it's what we call the light crossing time it's how long light takes to cross the object because the fastest you can remove the energy is at the speed of light and of course if you want to get a a pulse from it you've got to have the light from the back side and you've got to see the light from the front side and there's a time difference between the two so that's our oversee rearrange that we get MC cubed over R and then what's the smallest radius it can be what's the smallest radius and mass can be it's a black hole what's the size of a black hole it's GM over C squared if it's spinning okay so I now rearrange it and the M cancels and I get C to the fifth over G and that's the maximum power that you can generate from an object C to the fifth C is the speed of light which is a very large number G is the gravitational constant gravity is not a very strong force it's a small number a very large number divided by a small number it turns out to be three point six times ten to the fifty-two watts okay that sounds utterly ridiculous utterly utterly ridiculous but it's not completely ridiculous it turns out to be the maximum power is ten to the twenty six times the luminosity of the Sun okay now it turns out that in our galaxy there's a hundred billion stars and there's about a hundred billion galaxies in the universe so if I take the power of all the stars in the universe and I'll add them all together that's going to be a hundred billion times 100 billion that's ten to the twenty two so this maximum power is ten thousand times bigger than all the luminosity of all the stars and all the galaxies in the universe but this is my maximum another limitation on power in the universe comes from what we call Eddington limit 100 years ago one of the most prominent astronomers in the last century was Sir Arthur Eddington Columbian professor in the here in the University of Cambridge this is named after Eddington pointed out there's a limitation to how powerful something can be because power that because radiant radiation and if you've got something radiating radiation exerts a pressure we've all seen pictures of this this is this is comet hale-bopp that the older members of the audience will remember from about 20 years ago and this is its tail or tails this is the so-called iron tail which I'm not interested in this is the dust tail and basically the Sun is way over on the left here and the radiation from the Sun is blowing the tail away from the comet and this is very visible visibly demonstrating that radiation pressure can push things and what you can get there's a limit to how powerful something can be in terms of radiation when the radiation is so powerful it blows the thing to pieces so that if radiation outwards is equal to the gravitational pull inwards or is sorry greater than the gravitational pull inwards then obviously the object will blow itself to pieces and that's called the Eddington limit when you're there and this is a plot showing power up there versus mass of objects in the universe and I'm again using this logarithmic unit so zero means one it's ten to the naught that's ten billion and so on the sun's down this bottom part this is the Eddington limit there's the ultimate or maximum power and it turns out stars are down here galaxies up here and all stars in the universe up there now we're going to start thinking about exploding stars so I'm in order to talk about exploding stars I want you to think about what stars are on what's going on in Stars and I'm going to do this in terms of this mass radius plot don't get too worried about it but this is mass and radius and astronomers like plotting everything in the universe all on one plot and so we've got rock logarithmic units again okay and stars are over here with the Sun they're on one one of these units and these are black holes these are planets and when you get up here this sort of turns round it goes down to these objects called white dwarfs incidentally white dwarfs were first understood by the Masters grandfather ray Fowler this turning point here is known as the Chandrasekhar mass that's there's a maximum mass to a white dwarf and it's up here down here there's another point at which things you can have stable objects these are this defines where stable objects occur white dwarfs planets that's Jupiter that's the earth and neutron stars are over here just before you get to black holes there's nothing that is made that what we would see is a solid object above in this part of the diagram above the white dwarfs and neutron stars you then have the black holes which objects which I'll get to later where they've collapsed in on themselves stars are over here and they're held out over there because they have nuclear reactions in their cores which have generated pressure in them which balances gravity and so in the Sun we've got the outward pressure thermal pressure due to the creation of all the helium in the core of the Sun from the hydrogen their nuclear fusion that's actually inflating this the Sun keeping it in balance and the sun's been like that for the last five billion years but eventually you end up using up all the hydrogen in the core of the star and it then collapses the core collapses and starts burning helium to carbon and eventually the Sun will die as a carbon-oxygen white dwarf so there I represented this by an arrow the Sun will end its life as a white dwarf it will throw some of its outer envelope away but it goes like that and it will get stuck on that bit there but if you're a more massive star somewhere up here then what happens is the only thing the core of the star can do is collapse all the way down and form the black hole there's nothing else for it to do and in doing so because the material of the star the core of the star there's collapses inwards there's nothing to stop it collapsing down and there's an enormous amount of energy being released and it does it very quickly it collapses down in a matter of minutes and seconds enormous amount of energy vast explosion that's what we call a supernova explosion there is just one other one of these and that is if you're a medium sized star then you can actually go across here throwing off some of the mass on the way and you can end up as a neutron star so I'm now going to introduce you to supernova and neutron stars starting off with the only supernova that's the supernova explosion as that star exploded that's what it looked like before hand it's this thing in the middle this star exploded in 1987 in February in the nearby galaxy called the Large Magellanic Cloud it's a satellite galaxy of our own this nebula is a nebula of gas and you can see it in the light of hydrogen there it's called the tarantula nebula because it looks a bit like a squash spider anyway this thing was extremely bright and visible to the naked eye it's the last one that's been visible to the naked eye and this is just a plot of its brightness versus time that's a year and you can see the thing actually was not observed down there and then suddenly very quickly it brightened up and made this brightness and drop down like that and when it's below this level it's to faith faith for the human eye I actually was observing at the anglo-australian telescope in late 87 and saw this supernova through binoculars I didn't come early enough to see it with the naked eye so I'm not I've never seen a naked eye supernova the this part of the curve in this plot which is straight like this is due to radioactive decay when you get a supernova explosion the temperature is extremely high and they go and in the ejector as it's all thrown out there are lots of neutrons and that leads to many of the heavy elements the elements greater than hydrogen helium that we have around us most of us are I don't know if you know this but the dominant element in your body by mass if I was to go round and ask you most people would say carbon actually you're wrong is oxygen okay now if I was to get a stone and do the same what's the dominant element in a stone it's mostly oxygen I'm geologist in the front there is nodding in approval so I think I've got that right anyway so so oxygen but in our bodies okay most of the oxygen in our bodies was formed in one of these supernova explosions so you know all of this we are Stardust etc etc but that's where most of the oxygen comes from and about half of the iron in your blood comes from what's called a core collapse supernova these are the supernovae where the core of the star has collapsed as I've shown you and this is a wonderful image is made by the eros to collaboration and this is speeded up images of the region the supernova occurred here and this is this is speeded up images over the subsequent over the seven years from 1996 to 2002 can you see these ripples going outwards these are just where the light from the supernova is now reflecting off the nebulae here okay these nebulae have got dust in and if you shine a bright light on dust it shows up and it can reflect and so you're seeing the reflections and you can see them going across here so they circle around there so in a way this means you can look back in time if you see that and you can actually go and measure its color and so forth you're actually looking at a reflection of the original supernova so when you're out there in a clear night and you shine a torch around that torch light goes out into space and may reflect off dust grains and if your torch was really powerful you could see it back again but these you can see this is a another core collapse supernova in our own galaxy in the constellation of Cassiopeia and this occurred in the 17th century and it's not clear that anybody saw it there still a squabble about whether anybody saw the flash from it but you can see the outer shock wave as it's propagating out into the gas between the stars and you can see the inside of it there now there's another class of supernova I just wanted to mention because I'll be talking about mergers of binaries again later in the talk and this these are white dwarfs I said how the Sun is going to end its life as a white dwarf now our Sun is unusual in a way because it's a single lone star most stars in the galaxy more than half of the stars in the galaxy are multiple stars meaning there's not just one star there's several stars and sometimes there are two stars which are close together and both of them can evolve and become white dwarfs and they can be driven together by the radiation of by gravitational radio which is something I'll get to near the end of the lecture and they can spiral together like this and when they do that it leads to a giant thermonuclear explosion where the brightness when it goes bang is about a billion times as bright as the Sun that's his power not how bright it appears to us but is a billion times the loop power from the Sun and there is a nearby galaxy m82 with before and after when a supernova occurred back in 2012 in that galaxy and that was this kind of merger of white dwarf supernovae and those super no be mostly leave ion behind and the other half of the iron in your blood comes from that kind of supernova now the brightest flash that's been recorded by anybody flash to the eye occurred a generation of this supernova remnant this is the remnant of a supernova that occurred in 1006 and it was seen the flash the supernova explosion was actually seen by Korean Chinese and other astronomers and recorded and that's where it where it is now this is the remnant of a core collapse supernova and it's called the Crab Nebula because Herschel thought it looked a bit like a crab but I can't see that myself but it's a very strange object and this is the remnant of the supernova that occurred in 1054 ad this is in the constellation of Taurus and when it was going off it would have been easily visible in the daytime there are absolutely no records from England maybe everybody was going around looking at the ground all the time or maybe it was cloudy all the time but anyway it was not seen but it was again recorded by Asian astronomers and I think it was also recorded by some monks in Switzerland now this supernova ad to 1054 which is only 48 years after the 1006 one so it was possible to for somebody to have seen two supernovae in their lifetime this this one has left behind a neutron star and it was long thought that there's something funny about one of the stars in the center of it and it wasn't until 1968 it was realised it was a pulsar a pulsar is essentially this collapsed object at the center only it's highly magnetized and as it spins round it flashes at us and it flashes in all wave bands from the radio through to the gamma ray bands and here is this is the Pulsar that thing there and you can see that it's done something to the nebula around it and that's because it's a highly magnetized neutron star the neutron star has got a size of a radius of only 10 kilometers so it's about as big as London it's rotating at 30 times a second so it's going spinning pretty fast and it's got a magnetic field of a million million Gauss or million million times that magnetic field in this room I'm now going to just play you what it sounds like that's 30 times a second there are pulsars out there that are much faster and I'm now going to remind you of last your last visit to the dentist because this one is 600 times a second you ready I thought you'd like it so these are pulsars pulsars are the remnants of explosions exploded massive or medium mass stars and they're quite common in our galaxy there are also kinds of neutron stars which have got extremely high magnetic fields there are a thousand times higher than the one I just talked about so there are a thousand million million times the magnetic field in this room these extremely high magnetic fields mean that the crust of the star is incredibly stressed by the magnetic field and sometimes it cracks and breaks and that leads to a tense flash of radiation most of it in the gamma ray and hard x-ray bounce and these objects are known as magnet ARS and this is the most intense flash that's ever been recorded most powerful flash well its brightest flash this one and it occurred in 2004 in December and this is just a time running along there where that is a minute another minute and so forth and this is this incredibly intense flash and indeed that in this instrument it's totally saturated and the only way they got good measurements of the brightness of this flash is by looking at gamma rays reflected off the moon and the moon is not very shiny at all in gamma rays in fact it mainly absorbs them so this is a really intense flash and as they say it's it's the brightest flash that's been seen and it comes from the other side of the galaxy and as it decayed it showed a pulsation okay can you see the pulsations there every five seconds that's due to its spinning these flashes of gamma rays hitting the Earth's atmosphere ionized the atmosphere and indeed the oscillations could be picked up by radio measurements of the outer atmosphere I took out our ionosphere of the earth so it set the Earth's outer atmosphere ringing like a bell so something the size of London the other side of the galaxy goes bang and causes our atmosphere to ring like a bell okay if you wanted to do real astrology we should all do gamma-ray astrology because these are the things that really do affect you I'm absolutely 100% convinced that the position of Saturn in the solar system of the day you were born has got no influence whatsoever whatsoever on you personally I'm now going to turn to black holes and just to show you the evidence for the one in the centre of our galaxy these are all stars in our galaxy this is the Milky Way the dark bands are due to dust and the center of our galaxy is there everything in our galaxy rotates around the center at about 230 kilometers per second if you go in and look at the cluster of stars at the center of our galaxy particularly in the infrared band you could this is where the center is just there you need to remove the flickering the the deviations caused by the Earth's atmosphere in order to do this and this is called adaptive optics where basically you have you create a star in the atmosphere outer atmosphere of the earth and you sharpen your images up on that and as they switch it on you can see the image gets very sharp here so that you can actually see the motion of the stars you make the artificial star using these laser beams these are the Keck telescopes on Hawaii shining laser beams at the galactic center the galactic center is 25,000 light-years away so if they would have send a signal it would take 25,000 years to get there so I don't think if there's anybody at the galactic center they're going to take much notice of that but anyway here is what they can see in terms of the motion of the Stars and you see the stars are doing something moving around the center here if we now look that the these are the actual a plot of all the motion of those stars and there's one of the stars I'll go back it's this one is orbiting this Center about once every 15 years and that's this star and when it was going close to this point it's orbiting around this point in an elliptical orbit when it's close to this point it's traveling at 4,000 kilometers per second this is the radial velocity of it and these are the positions of it using Newton's equations of gravity you can work out the mass of the object there that mass turns out to be 4 million times the mass of the Sun 4 million times the mass of the Sun and yet it has to be a very compact region because it follows an orbit very precisely how compact does it have to be it has to have a density which is more than 10 to the 19 point 5 times the mass of a Sun per cubic parsec you probably don't know what a cubic parsec is it's a distance measurement in astronomy but essentially it's the distance a parsec is a distancing us to the next star approximately so a local density of stars is 1 in these units this is a hundred million million million times higher than the density locally to us it can't possibly be native stars because it will be incredibly bright you can't even make it out of neutron stars without the neutron stars colliding with each other there's nothing known to physics that can be there other than a black hole now black holes also are powering quasars but let me go on to the concept of the black hole the is from Einstein the idea that mass warps space-time and here it's shown warping the space in just in a two dimensional representation and it's something where the the center is collapsed warping the space around it and there is an event horizon around it a little bit like a water portal this is Niagara Falls of course but you've got to think about this edge round here as being a point beyond which you you can't come back and we call that the event horizon as you approach the event horizon and are observed by an outside observer you go from looking yellow to red you appear red shifted and eventually time appears to stop if you had a clock your clock would appear to stop by the time it gets here you never actually appear to the outside observer to fall into the black hole so black holes were originally a theoretical concept and originated in the 1780s by John Mitchell who was a fellow of Queens College but spent most of his time looking after a parish in Yorkshire but he theorized that if he was to pack lots of Suns together lots of stars together eventually they would have an escape velocity from the surface bigger than the speed of light and therefore you couldn't see them that's a Newtonian argument which isn't right nowadays but he essentially got the right answer but then Einstein came up with his general theory of relativity and that gave rise to the concept of black holes that they the equations were solved the following year just 101 years ago by Karl Schwarzschild for us a stationary point mass and then for a spinning object back in 1963 by Roy Kerr I now want to show you about black holes by just showing you a picture of the sky this is the visible sky and if there are any amateur astronomers amongst you you'll recognize this pattern this is the constellation of Orion with Betelgeuse there and Rigel there and that's the brightest Scot star at the star in the sky Sirius this is the moon and that's the constellation of Taurus the Bull I'm going to switch now to what the sky the same patch of sky looks like in the x-ray band there it is and then you can see the stars and Orion's belt flip back you can see Orion's belt and they're showing up because of magnetic activity like we can see on the Sun you cannot find Betelgeuse in this picture the moon is that thing this bright thing here is the Crab Nebula which I've already shown you which is got the Pulsar in so it's a dead star and this is serious but not serious eh this is it's white dwarf companion Sirius B so in x-rays you see Sirius B not this bright star which is Sirius a then they orbit each other every 50 years so in this picture in x-rays you see dead objects white dwarfs neutron stars some active stars magnetically active stars and many many black holes most of the objects you can see are black holes and here we can see black holes now I've just said things can fall into a black hole and you can't see them they can't go out how do can you see black holes you see black holes because material falls into them they are the ultimate thing to drop material into and you can release the greatest amount of energy by dropping material into a black hole and this is just an x-ray image of a patch of sky and 95% of the dots there are black holes accreting material from their host galaxies some of these things are clusters of galaxies are big fluffy ones there is an artist image of one of these black holes accrete accreting material in the form of an accretion disk we expect the matter to swirl around and sometimes the magnetic fields generate powerful jets that come out of them so accretion dropping matter into black holes generates enormous amounts of power and just to go through some numbers with you this is equals MC squared but with an efficiency factor and in for chemical reactions that is 5 times 10 to the minus 11 it's a very small number chemical reactions are very inefficient in e equals mc-squared nuclear fusion is a hundred million times better that's what powers the Sun so clearly you're getting a lot of energy out for your mass and indeed if you were to you you take your petrol from your car and enable it to undergo nuclear fusion rather than chemical reactions you go a hundred million miles per gallon or should we say a billion miles per gallon you can go even 20 times better than that if you can go to black hole accretion if you drop matter into a black hole you can release more than 10% of its rest mass so small amounts of matter in galaxies falling in to black holes at the Centers produces an enormous amount of power I've shown you pictures of the black hole at the center of our galaxy it is not very bright somehow it's not got much material falling into it in many other galaxies they are very bright and what they do in this brightness is essentially blast all the gas out of the galaxy and we think that this is the reason why many of the elliptical galaxies the most massive galaxies in the universe are mainly these big balls of stars they are all look now red and dead and like spiral galaxies which have got lots of star formation we think that's because the black hole at the Centers of these galaxies has blown all the gas out of the galaxy in blowing all the gas out of the galaxy they stopped any new stars forming there's no gas to form new stars this is amazing this is been a realization in the last 20 years it's the black hole at the center of the galaxy that controls the mass of the whole galaxy when a galaxy ends its life is due to this tiny little thing spatially tiny it's actually got 1,000 for the mass of the galaxy but it's physically very tiny it's got a size the black hole at the center has a size compared to the size of the galaxy a bit like the size of an orange compared to the size of the earth okay that's an extreme for you okay imagine something that small controlling something that big it's got a thousandth of the mass but small amounts of matter falling into it blasts all gas out of the galaxy that's what we think is happening in quasars moving on there are these Jets that come out of them often powered by the magnetic fields and if we happen to look down the jet those objects can look even brighter so this is very bright but if you look downward it's going to look very very bright and actually one of these objects act quite a high distance and for anybody who's an amateur astronomer they might know about redshifts and redshift one there was a quasar at redshift one visible in binoculars just over Christmas because it's jet pointing at us underwent an enormous flare these Jets can go out beyond the galaxies this is a large galaxy and it's squirting these Jets out either side making these enormous lobes this is actually emissions seen in radio wavelengths overlaying on an optical picture of that region now these Jets can lead to interesting phenomena this is the nearest jet that has been seen it's in the constellation it's in the constellation of Virgo in a galaxy called m87 and here's this jet sticking out that side you cannot see a jet the other side this was found a hundred years ago by Heba curseth Curtis who wrote that there is a thin white ray emerging from the nucleus of m87 he didn't know what it was and do you know we don't actually know exactly what it is even now a hundred years later we know it's squirting electrons out we know that because of all sorts of things including the fact that light is polarized I'm not going to define what that is if you don't know but basically that means it's got negative particles coming out we don't know what the positive particles are coming out whether they're protons or positrons maybe it's squirting antimatter out I think it's squirting antimatter out which is rather interesting we cannot see the other side we think they're jets going out equally either side we can see that one why can't we see the other one well we can perhaps start to understand it if we see look at this Hubble image of it it's been tipped round in to make it level here and there's the jet I've just shown you there we're going to look at this bit of it here and can you see in the 90s Hubble saw there's clearly something emitted and has moved across like that if you work out the distance it's moved it's gone 24 light-years he's gone 24 light-years in 4 years so it's traveling at 6 times the speed of light okay is that all right I'll have one of those please because you know that's how I can travel around in space it's superluminal it's actually an optical illusion even those ripples from the supernova we're traveling faster than the speed of light okay it's due to the fact in this case that this jet is pointing towards us and the matter in the Jets is traveling very very fast it's going very close to the speed of light it's chasing the light beams and you can do a very simple geometrical calculation which I am NOT going to do here show that you can end up with this apparent superluminal assuming luminal motion now the most amazing Jets that we see these ones and they associated with gamma-ray bursts these are intense flashes which were first found in the 1960s by the military both the Russian the sorry the Soviet and the US military were monitoring outer space hoping to check that they each other were not letting off nuclear bombs in space these are monitoring satellites they did find ashes of gamma-rays that you would expect to see from a nuclear bomb accepting these flashes of gamma rays clearly came from beyond the solar system they did not come from nuclear weapons I mean people did at one point say well maybe there other intelligent life as letting off nuclear bombs but no that's not the answer these flashes like this are associated with the birth of black holes in stars and basically what happens is during the supernova collapse forming a black hole if the material is spinning very fast it's able to make Jets which squirt through the whole star and out through the star and if it's shining at us and I'm not gonna point this laser beam at you but you know a laser beam pointed is very bright along the laser beam it's like having a laser being shone at you that's what we're seeing here these things are very bright in gamma rays they're gamma-ray bursts and for anybody who knows about relativity these Jets have got a Lorentz factor of a hundred and this thing has got a Lorentz factor of ten but I'm not going to go any further in defining it these are extreme objects in the sense they've got extreme powers now I'm going to around my last ten minutes and going to go through two final classes of objects these are fast radio bursts they're the mystery of 2017 they made the cover of nature in January the first issue of nature this year these fast radio bursts were discovered in first discovered in 2007 these slides were given to me by Jason hassles over Dutch astronomer now that's the Parkes radio telescope here in Australia and it picked up intense flashy at one intense flash in 2007 that's when it was published by duncan Lorimer so known as the Lorimer burst it's an intense very bright flash these are hundreds of that's a hundred milliseconds to hundred milliseconds so that is half a second so it's a very sharp flash it also changed this is now frequency and it changed in frequency so essentially in radio frequency it was first detected at high frequencies and then you know it decayed and was seen in the lower frequencies this is called dispersion of the radiation is characteristic of radio signals going through ionized gas and this looks like it could be the gas between the galaxies or it could be gas associating with the thing itself apart from the fact that the radio telescope was pointed at a particular region they Duncan Lorimer had no idea what this is due to it was clearly very sharp and very bright people then began to wonder whether they there were any other ones time passes people are getting frustrated they can't find anymore bursts nobody found any more bursts and then there was some bursts seen also from the Parkes radio telescope they looked a bit like the original one excepting they were a bit sort of spotty it's something funny about they don't quite look right and what they would do to was somebody opening a microwave door nearby it took a while to work this out but they're pretty certain that this one is not due to a somebody opening a microwave door okay and so it remained as a big puzzle but what's going on here until in 2013 another burst was seen or and a few other this meant there's a population of Farr's radio bursts people didn't know what they were because these radio telescopes are only looking at a tiny patch of sky there must be thousands of these over the whole sky per day but what are they and these are all the ideas can't they pernicious radio frequency interference or atmospheric effects flare stars we've already heard about flares are the micro phasers pulsars man guitars or are they sati are they little green people okay can they be something new gamma-ray bursts supergiant pulsars from pulsars of operating black holes Stephen Hawking supernova merging black holes I'm going to talk about that in a minute we don't know and then another one was found from the Arecibo telescope you can see it's not a great one but there it is and this is the start of making of working out more what they are this came from this Arecibo telescope which many of you remember if you like watching Bond films they fought on here during the film and which film was it hmm Goldeneye well done thank you yes yeah I always remember the I bit because this is an eye on the sky okay so there we are anyway it came from there okay this is a globular cluster this is the plane of our galaxy the Milky Way so it came along the plane of our galaxy but it's not obvious it's galactic and then they found more from the same position so it's not due to a cataclysmic explosion something blowing itself to pieces it's repeating and you can see there many more of them you may wonder why they're not all shaped like that that's because somebody's straighten them all up just to pack them all onto a simple plot so really important it rules out the cataclysmic source it's not a single explosion it's due to a pulsar on steroids perhaps and they even worked out where it came from because it repeats they even found there was a constant source at the same position they were able to combine a whole load of radio telescopes Arecibo of the european VLBI network and there's a map of it and you probably can't read this but this one here is it's that this one is Cambridge so anybody who drove up the Barton Road will have driven past the telescope the big the big dish there is part of this this European very long baseline interferometry network by using all these telescopes at the same time looking at the same patch of sky they can get a very accurate position and the net result is it came from this object okay it came from that object and you can see it doesn't look very exciting does it so this burst came from there this is the cover of the first nature of the year and so this is where it comes from it's a very faint object it's a hundred million times fainter than the naked eye limit the galaxy it comes from is a thousand times less massive than the Milky Way I showed you that supernova 8780 came from the Large Magellanic Cloud the small Magellanic Cloud has about this mass so it came from a little tiny galaxy and each burst when it goes briefly outshines all the other stars in the galaxy and it looks like this object is the small Magellanic Cloud only at three billion light years so these bursts we're looking at happen three billion years ago what are they we don't know I think and many people think they are actually due to a very young magnetar okay if a magnetar were formed you know maybe 20 years ago we don't mean dem a sort of supernova from there but then maybe we wouldn't have done and maybe it's left behind one of these magnet ours it remains a puzzle now into the last part one other class of flare that you can get is when a star strays close to a black hole and is ripped apart by the tides I don't have time to talk about those but I'm going to talk now briefly about gravitational waves when you get binary stars spiraling together when they orbit each other they cause warping of space-time and they cause gravitational radiation and this is meant to represent ripples of space-time flowing away from this binaries system you can get binary stars of different types white dwarfs we've already spoken about but you can also get neutron star neutron star binaries here they are and these are the temperatures of going up to 10,000 no 100,000 million degrees when you merge two neutron stars together like this you probably get a gamma-ray burst and you also generate a lot of heavy elements it turns out that in a generation of these heavier elements I've talked about oxygen I've talked about iron but it's very difficult to get significant elements beyond iron out of supernova and it's been a big puzzle where gold comes from I've got some gold you many of you will be wearing a bit of gold that's where they come from neutron star neutron star mergers that's the only way we can explain gold and when they do this they generate a significant mass of mock gold about the moon's mass of gold now before you sort of thinking about a gold moon it's probably spread in a load of bits and it'll be a very difficult thing to get hold of but anyway I'm just trying to say many of the things I'm talking about are actually connected with you not you in your current form but the atoms out of which you are made and the atoms out of which your jewelry is made now go on to the final one this is the ultimate one this is the gravitational wave mergers of black holes two black holes can spiral together and as they spiral together they go faster and faster and then leave behind a black hole and the LIGO Virgo consortium have got instruments now which are the ultimate rulers which rulers in the sense of you know measuring inches should we say these things are this is like Oh which consists of this cross of laser beams are shining up there up there they are comparing these laser beams all the time if you stretch that and don't stretch that one then they'll get out of sync and you can detect that down here and you can detect changes in length equivalent to an atom the size of an atom versus the distance between the Earth and the Sun that's that's the precision that they're making okay with these gravitational wave detectors ten to the minus twenty-one okay and they switched advanced LIGO on in September of 2015 and within three days they had measured a merger this is what it looks like there's the oscillation this is just a plot of theoretical plot of the strain that's the the relative motion of it you can see the oscillation gets faster and faster as these two spiral closes close to each other they merge and then ring down and so we've got it like this just to show you the data here's the data like that you can see this is frequency that's time you're seeing it for only 0.2 of a second but there's a it starts off with a frequency of somewhere like 40 Hertz and at the end it's gone up to almost 300 Hertz and this is this detector which was in in Hanford in Washington State and this is the detector they had in Livingston Louisiana so they've got two of these interferometers in the US and they were both working at the same time they both saw the same signal and in fact you can take the signal from that one and plop it on top of the signal from that one and you see that they match so they're looking at the same event they were extremely lucky because this was the merger of two 13 solar mass black holes two black holes of 30 solar masses merging together and they presumably formed one of a mass of about 60 solar masses I say about because three solar masses was lost it went into radiation not into electromagnetic radiation it went into gravitational radiation and this is where it sits in this plot here's the ultimate power here's gravitational waves that merger is up here I put it at low mass because it's 30 solar mass objects I've given it green because it's not electromagnetic it just for 0.2 of a second the amount of power out of this merging system in terms of rippling space-time the power involved exceeded by more than a factor of 10 the total power from all the stars in all the galaxies in the universe so that it got within 8 percent of the ultimate power seen to the fourth over gee I've now put everything else I've talked on about on this plot there are quasars apparently can look brighter with Jets supernovae gamma-ray bursts supernovae actually most of the power of the supernova comes out in neutrinos and 1987 a supernova collapse did create neutrinos of which 30 were detected on earth neutrinos if you know anything about them you know that they're ghostly particles which in gunk can go right through the earth many times so that that's a power there but this is where power lies in the universe and I'll just I'm going to finish with a demonstration but this is just a again representation of two black holes merging if you were close enough to look at them against the Milky Way it would look a bit like this you wouldn't want to be this close but okay and here it goes you get closer and closer and space-time stops wriggling and there we are okay and there's just a nice picture of the Milky Way there's the Large Magellanic Cloud and there's the small Magellanic Cloud now I'm going to show you just a chirp what happens the oscillations got faster and faster and stopped that's called a chirp and that device I'm about to show you actually produces a chirp and you this is your take-home experiment okay okay now don't be worried about it's actually a toy don't be worried about playing with toys these are three Nobel Prize winners in physics Richard Feynman Wolfgang Pauli Niels Bohr two great physicists of the last century they're looking at a toy it's a top a tippy top one that you spend and it flips over if you know what I mean and they're trying to work out what's going on this guy Richard Feynman was actually watching somebody's spinning a plate in the Cornell cafeteria and realized that the motion of the plate was peculiar and he worked out what it was doing and in his autobiography he points out that it that took him broke through in his thoughts and ideas that led to his Nobel Prize so what I want to do now is to show you a simple toy and it's this thing here it just consists of a heavy disc and just a plate to put it on and I'm going to spin it now and hopefully the camera will okay it's now spinning and you can do this at home with our dinner plate okay do it on the floor and the way in which it gets faster and faster the rate of change of it is the same rate of change form as the merger of two black holes or two white dwarfs together so it's going faster and faster and faster and it takes a long time but when you do when you do the plate on the floor don't worry it will happen quickly and you'll do it again because you realize you have the plate the wrong way around and this will end up with a chart and that will be the end of the lecture yeah conservation angular momentum losses yeah and I hope you've been see this holographic things on top it's the actual things it's spinning faster than infinity from there yes I soon [Applause] [Music] so Andy thank you very very much that was absolutely wonderful lecture you know you've taken us through huge distances and and times powers of ten beyond most of our imaginings I'm a geophysicist powers of ten and the Earth's don't go up that high and yet at the end you end with effect demonstrating two black holes on what I thought was an orange from where I was sitting but I see a thing the head at the head of the microphone I mean that was talking about ultimate power I think you've this is the ultimate lecture on astronomy thank you so much [Applause] no I mentioned that Andy's been the person overseeing this lecture series this annual series for some thirty two years now as you all know in recent years they've been filmed and they're available online so actually sometime this next week you will to watch watch that again see all these images again I'm trying to figure out which one was ten to the twenty six and 10 to the 52 but each year this also a book is published with a chapter from each of the of the speakers that's published by Cambridge University Press obviously takes a little longer than a week to get a book out but hot off the press tonight I have kind of a record book because it's the first book in this series that has the images in color so it was the plagues book just published I think we have one copy here tonight hopefully far more it'll be readily available from now on it's got a chapter and in bowler it's got a chapter on our Vice Chancellor by Vice Chancellor lesyk for a savage on medicine and plagues he's not a plague he said he's an expert in medicine so watch out for this one now next week we come down from the stars we come back to earth and actually worrying aspects of modern life was a lecture from Professor Matthew Goodwin from the University of Kent on extreme politics but I think just let's just and again by thanking Andy both for tonight's lecture and for 32 years worth of lecture series Andy you you

Channel: Darwin College Lecture Series

Views: 15,049

Rating: 4.7872338 out of 5

Keywords: Professor Andy Fabian, University of Cambridge, Darwin College, Darwin College Lectures, Darwin College lecture series, Extremes, big bang, solar flares, exploding stars, magnetars, quasars, gravitational waves, black holes, observable universe

Id: zF3Caufuz4U

Length: 69min 31sec (4171 seconds)

Published: Sun Feb 16 2020