Ronald Ekers

Transcription

>> Thank you Curtin University for organising this and giving me an opportunity to tell you about something, which I think, is quite exciting and also happened in my career. So I'm going to talk about Quasars, their discovery, and the key date here when key paper was published in "Nature" was on the 16th of March, 1963, so that was 50 years ago last Saturday. And this is perhaps one of the biggest events, which has happened in astronomy. There are a few other big events but this one has had a huge impact on the way we think about the universe and on astronomers and so I'm going to tell you some of that story, quite a bit about how it happened and about some of the machines that led to it. As you see, this issue of "Time Magazine", Martin Schmidt who was one of the key astronomers using the fabulous 200-inch optical telescope. Biggest optical telescope in the world for many, many decades and discovered the Quasar. And that's the 50th anniversary, was on March 16th. One of the huge paradigm shifts which was triggered by the discovery of Quasars and that's part of the story I'll tell you was the realisation that black holes weren't just a figment of the imagination of theorists but are real objects which play an important role in the universe so we'll get to that later. So why am I telling you this story? It's really pretty special to me because it was on March 1963, the month when those papers came out in "Nature" that I started my PhD in astronomy at the Australia National University and I used the facilities at the Parkes Radio Telescope and worked -- my supervisor was John Bolton who features throughout this story, so it has been my career this 50 years of Quasars, in fact, exactly. Here when I was a little bit younger in a jumper knitted by my wife -- well wife to be -- I hadn't actually gotten married quite then and I'm at the focus of a small telescope, a 60-foot telescope that's near Parkes and was the interferometer I used in my thesis. That doesn't feature anymore; however, all of a sudden, radio astronomy caught the imagination of pretty much everyone and the BBC, for example filmed "The Violent Universe". This was part of the realisation that our universe is formed in my very violent activities, Quasars are one. The big bang of course itself, stars exploding making the elements from which you have all evolved. So this whole idea was really come to life and especially with these radio observations I'll talk about. So very brief summary here and in going through these things, I've tried to cater for both from time to time the scientists of you in the audience. I'm trying to use when I can simple language and please at least at the end ask me questions about anything but we also I'm delighted to see we have some young people in the audience and so I hope you bear with me because I'm also trying a little bit to make sure they can get some feel of what we're talking about as well. So the discovery of Quasars is a bizarre story. It's nothing like the way you're taught that science progresses. It was full of wrong directions, mistakes, people not understanding what they were seeing and to me that is a really important part of science and a reason for looking at the history of science is it's no different today. We might think we understand all this but we have things like dark matter, dark energy and as you hear this story, those of you either thinking or wanting to stretch your imaginations, think about the way that our predecessors here went wrong and the way they made their mistakes because we are surely making similar mistakes now and the real directions are going to be different from what people think they are. The Quasars brought the black holes into mainstream science and astronomy and I'll talk a bit about that and then at the end I'll give you only a glimpse because -- take me quite a bit of time to cover all the history -- a glimpse of what we might do in the future. Now this talk is going to have a fairly strong focus on the astronomy we do using radio wavelengths. You're more used to thinking about what you see with your eyes, what you can photograph with a camera, that's the astronomy you do using visual light; but as this diagram on the left shows, there are many different electromagnetic waves which come to us from space and as astronomers we usually can't go out and do experiments. We can only interpret the information that comes to us so we want to use all the possible wavelengths and you can see it goes radio waves, inferred. There's the tiny little visible spectrum where all of our past knowledge came from and then the ultraviolet and the X-ray and I'll show you a few images at these wavelengths. But the radio is going to play an important role and so why is radio being so important for discovering Quasars? Well the real reason are the two points here written on the screen. The brightest Quasar in the sky and the one we're going to talk about a lot, 3C273, is the 6th strongest, brightest source in the sky at radio wavelengths. So if you're going through radio objects to find something interesting you've only got to count down to number 6 and you find a Quasar and as I will show you numbers 2, 3 and 4 are incredibly interesting as well. However, if you were going to look at the stars that you see when you go out in the dark sky you've got to get to 3 million before you find a Quasar so you've got to do an awful lot of searching and that's really the reason why it was the radio wavelength that highlighted this very unusual phenomena. So here is a picture taken through a reasonably good telescope of a piece of the Milky Way, like you would see with your eyes at night and the dark band across the centre of the Milky Way and all the little dots sprinkled all over it. These are stars. These are stars like our sun further away, billions and billions of them as Carl Sagan would say. The radio sky if you had radio eyes looks totally different and here is a -- is a Recent picture of the radio sky. The band you see across the middle is our galaxy and that's very bright in the radio. That's where in light you have the dark rift caused by all of the dust then outside of that, you see the haze, which is radio emission coming from our entire galaxy. That was what was first detected when the universe was first seen in radio waves and as you will find out as I go through this talk, all the little spots sprinkled around the screen, they're not stars. The radio astronomers thought they were going to be stars and that's going to be part of this story. They are almost all galaxies at huge distances and so it's very different. So both universes are real. The universe you see with your eyes and this universe you see with the radio waves and it's perhaps also interesting to think of the two wavelengths that we can observe through the atmosphere, it's the radio and the visible, why we've evolved to use eyes and light but there's no biological entity which actually using radio waves to sense or communicate and two reasons for this, one is radio wavelengths are rather long from centimetres to meters. They're very -- sort of a human size but it's kind of difficult to build an optics system like your eye which can work with radio waves; however, a piece of wire -- I meant to bring a piece, I forgot -- just a piece of wire will pick up radio waves so that's not very complicated. But the other problem is, no biological system has been able to separate metallic conductors out because of the electric potentials involved. So even dinosaurs which were big enough still didn't use radio waves. Okay. Let's go on. Now we're going to go through the entire universe in looking at this story of the Quasars and as I said, my apologies for some of you who know all this but I think it's always useful to think about these scales again. Astronomers get quite used to talking about huge distances, small distances and we do it often enough that it means something to us, but unless you are used to doing that, the distances we talk about won't mean very much but we are pretty good at thinking about how far back in time things happened. We can think about how long ago, you know, when -- when various things happened, you know, when your grandfather was born. Those are kind of time scales we can understand and because of the study of the earth and the rocks and the things on the earth people have a pretty good feel for time. So the way we talk about the scale of the universe and make it fairly easy to understand is to talk about things in terms of how long it took the light to get here. The light travels pretty fast. 186,000-kilometers per -- miles per second, sorry. So for example, it can go all the way around -- around the earth in a 7th of a second. So we would call that a 7th of a light second. That's the distance around the earth. It takes light about 8 minutes to get to the earth from the sun. So that's 8 light minutes away. It takes about 40 minutes for the light to get from the planet Jupiter to the earth so that's 40 light minutes away. And then within -- within an hour you've got a good part of the solar system. Then big jump. Nearest star, 4 light years. So we've got this little village of objects just here in the solar system and then we have a big gap until we get to other stars, which very probably have solar systems too. So I'm just trying to get you that feel of how empty space is and how far away things are. Now as I go through my talk, every now and then I will tell you how far away things are using light years and giving some analogy to something that you can refer to. Okay. Now the other thing I have to do is go back a little bit further in time to set the scene. This is a normal human time. So during the war, there was a lot of developments of the kind of instruments you need to pick up radio waves and Stanley Hey was one of the key people doing this in the United Kingdom using the strange little thing to the right there which is the telescope he used. And what he discovered amongst all the radio emission coming from space was in one part of the sky in the constellation of Cygnus there was a spot which was fluctuating in intensity and so that told him straight away if it's going to be changing intensity it cannot be on a time scale of minutes, in this case. It cannot be more than a few light minutes across because otherwise one side of it wouldn't know what the other side was doing so he was able to quite correctly say that object has got to be pretty small and maybe it's even something like -- like our sun but much further away. So that's when they started talking about radio stars. However, this brightest radio object in the sky there was no -- nothing obviously visible there. There was nothing that you could see. So what was it? It wasn't known and the question was asked is all of that emission coming from the galaxy? Is that because there are lots of objects, lots of stars like this? And for the specialists here just in case you don't remember there was no theory for synchrotron emission, no non-thermal radiation theory at that time. That didn't come for another 10 plus years after this before there was any knowledge of how these radio waves were made. So that was happening in Cambridge. At the end of the war there were lots of people who had been involved in building radar for the Second World War including a group in Australia and I picked one lady Ruby Payne-Scott who is kind of special. You will find out there's quite a few characters in this story and they're interesting people and I'll talk a little bit about some of them. So Ruby Payne-Scott had been looking with CSIR in the radar systems that were developed in World War II. And these funny antennas here, one here, another one here that you see on the cliffs, this is Dover Heights just near Sidney Harbour, they were antennas that had been used for doing World War II radar. But what they put together was a very clever scheme. Here's the antenna here, that's this guy sitting on top of the cliff and When you look up at the sky you might see the radio waves coming in down here but there would be a reflected one which would come bounce off the sea and you would also see that. And these two radio waves would interfere with each other. This was a standard thing done by the radar people off the ships doing radar they would see the direct reflection. They would also get one bounced off the sea and that already worked out from that interference pattern you could calculate quite accurately the angle. Now radio waves are very long so determining exactly where they came from was quite difficult and this was one of the ways of doing it. When the sun comes up, it's daylight of course; you can't see the stars at all. Now radio wavelengths the sun is reasonably bright but it isn't the brightest thing in the sky normally and you wouldn't have the day/night difference at radio waves that you have in light. But every now and then, the sun was making quite a lot of radio waves and this was known. And so Ruby used this system to try and work out where those radio waves were coming from on the sun. Are they coming from the whole disk of the sun? The sun isn't actually hot enough to make the radio waves by processes that were known and this is what they found in the radio. This is an image -- usually I'll show you modern images rather than ones from the time because they're more interesting, more exciting. So this is an image of where the radio emission comes from and it turns out it was coming from the sunspots and it was Ruby Payne-Scott, first woman radio astronomer, who actually deduced that. So the radio waves were actually coming from these little tiny spots on the sun. Now as we get better telescopes, we look in the UV and we look from satellites from above the atmosphere, what it was actually finding were these incredible loops. There are huge magnetic explosions in the sun and as that material explodes out of the surface there's a lot of particles, high-energy electrons and they were the ones that were making the radio waves. Now the step that's important for my story here I'm not going to say any more about the sun, but this was the first time people connected radio waves with explosive events happening out there in space. It wasn't the actual heat of the sun making the radio waves. It does make some radio waves. It was these explosions and radio waves are very easily excited by explosive activity. So what were these other radio sources? Like the small one that Hey had found and I'm going through this story because it mimics what's going to happen in the Quasar story a bit later. People were getting most of the interpretation wrong. They'd found one small radio source. That was correct and then they jumped to the collusion that all of the radio emission would be made of those. They had seen these sun spots making radio flares and so they thought, ah, other stars are going to have even bigger sunspots and so these radio waves will all be coming from maybe better stars than our sun, ones that are more violent and that was the model that prevailed for almost a decade. As you will see it was completely wrong. They got two steps wrong. The unresolved emission wasn't the stars and the one star that they had studied well, which was the sun, was not an example of any of the things that were to come. Now the story of what was to come next involves an expedition by another group that was working in CSIR in Australia. And they had been looking not at the sun but at some of these radio sources to measure their accurate position so that they could try and work out what is it out there in space that's making all these radio signals. But with just one cliff at Dover Heights, they could only get one piece of information from the interference pattern so they went to New Zealand. And New Zealand has wonderful cliffs and it has them on both the east and the west coast. Here is a little portable antenna that was shipped across to New Zealand. John Bolton who was my supervisor, by the way, later after this and Gordon Stanley set this up in New Zealand on a place called Pakiri Hill, which is on a cliff above Lee. That's kind of famous because of "The Piano" the film was filmed on the beach just below that cliff. That's got nothing to do with the story of course. [laughter] So what happens? They've drawn one line in the sky from the Australian observations and saying those radio sources lie somewhere along that line. The New Zealand expedition, which was completely successful, drew another line. Now you look where the two lines cross and if you look at that point up in space, that's where you should find something. And the four strongest sources in the sky they could see, the one in Cygnus, I already told you about, it was a strong source in the constellation of Taurus, one in the constellation of Virgo and one in Centaurus. They measured four positions and they got the surprise of their life. The one in Taurus turned out to be pointing at something that's called the crab nebula. There's a beautiful new image made with a VLA, which I'm showing rather than of course the very crude image that they had at the time. And that is in the position where the Chinese saw a star explode in 1054 A.D. And this star was so bright that it was easily visible. When we get the next supernova that close in our galaxy everybody will see a bright star appear but it only happens every 3 or 400 years so who knows when. But the Chinese recorded this one as a gas star. We are now looking at things much further away. The light from this one left when the pyramids were being built 6000 years ago. So I've taken a pretty big jump already. We've gone from the nearest stars and we don't find an interesting radio source until we get out to 6000 light years away. So we're jumping out in space in huge steps and this is one of the brightest radio sources in the sky. Let's put the Hubble space telescope and point it at it and that's what we see in optical light with the Hubble telescope. It all matches up beautifully. But this object you could have an entire lecture about. In the middle of that, this is a telescope which takes pictures in the X-ray and has produced this incredible picture, something swirling around in the centre and in fact something that is indeed a jet poking out of it. You point a radio telescope at it, connect it to the earphones or even connect it to a loudspeaker if you're a radio astronomer and when you point at it, [noise] they're the radio pulses coming from the centre of this object. And that is an object which is rotating once every beat in that sound and I won't tell you much about that story, but -- but it's a thing called a neutron star. As I said it's an entirely different lecture. So there you can see that this detection of this particular radio source just led to such a wealth of phenomena and just think for a moment something the mass of our sun spinning at the rate at which you could hear that -- that pulse. All right. Let's go to the next one they measured. The brightest source in the constellation of Centaurus, low and behold there's this incredibly beautiful but rather strange galaxy and you see 5128. Now we have, assuming that's a galaxy, moved totally out of our entire galaxy. That light left 10 million light years ago. For that object, we are back at when the first humans were evolving on earth. And the radio emission in a modern image looks like this. There's a spot in the middle and the radio plasma seems to be funnelled out from the centre. But it's way more dramatic even than that because -- let's try and get the scale right and I've got to shrink this image way down. This is an object the size of our entire galaxy and then when we do a modern radio image, this is what we see. So there's an object out there generating radio waves, which is hundreds of times bigger than our entire galaxy. So right away, these radio waves were picking up some absolutely remarkable things out there in the universe. Here are the three people that were involved in that paper which measured the first positions. John Bolton, Gordon Stanley, and Bruce Slee. They had just discovered a couple of the most important discoveries in astronomy. The crab nebula, they nailed it. They got it right. But this Centaurus A hundreds of times more luminous than our galaxy. Hundreds of times bigger than our galaxy. Who's ever going to believe this? This -- this maybe can't be real. John Bolton told me when I was a student and this is an example also of how people can misremember, they had problems with the referees so they had to put this statement in the paper that says it's a pretty weird galaxy. It's got this funny dust laying across it so maybe it's really in our galaxy after all and the optical astronomers have got it wrong. That's the statement in the paper. John says, just had to do that for the referees. Of course we knew what was going on. But in those days people wrote letters and some of those letters still exist and you can find them and my colleague, Milligauss in particular, has been doing the research in the archives and came across this little gem, which was written just at the time -- a few months after that paper was submitted by John Bolton and he's writing to somebody called Rudolph Minkowski at Cal Tech, one of the top scientists working on galaxies in the world and what it says is, "In a letter to "Nature", written before I had a chance to consult with you, I have suggested that these objects may be within our own galaxy. On the basis that a close freak is more probable than a large collection of freaks at great distance." You see, as soon as they acknowledged it was at great distance all the others were going to be at great distance too. And this was a step too far. They weren't at that point willing to make that step, but who did he have to talk to? He says, this galaxy looks weird to me. He's a radio engineer. He's not even an astronomer. So you say, oh well you talked to somebody next door who knows about galaxies. In 1949 in Australia, there wasn't anybody who knew about galaxies. Close to 0. So he's got nobody to tell him, that's a real galaxy. It's not going to be -- it's not going to be in our galaxy and Minkowski replied immediately, saying come on, you have found the galaxy and this is way more incredible than what you even said in "Nature". So the message here was, you need to have this network of connections to people who know about all kinds of things. That group in Australia had worked on the sun and they did know a bit about supernova remnants and exploding stars, but there was nobody in the group who new anything about galaxies and so they missed, in fact, in terms of the paper, they missed this incredible discovery. Everybody who knew about galaxies it was within months that the original story was changed. Everybody knew that galaxies were detected perhaps with the exception of Martin Rile, he hung on a bit longer. Our Cambridge friends. So by five years later, these things are being called radio galaxies and they are being found by the dozens. And every time you measure an accurate position, you find a big galaxy often with these lobes like the ones shown here outside. And finally, in 1954 the brightest one in the sky which is this one called Cygnus A was discovered and as you see it's a bit like the picture I showed you of Centaurus A. Now these things are another factor of 10 further away. We are now back to the light living in the age of the dinosaurs. So if you're thinking back in time, we have gown that much further out in the universe and we're seeing all of these objects. Here is Walter Barter and Minkowski, both the experts in what galaxies were and the people who were using the great 200-inch and 100-inch telescopes at Palma to study them. What they saw in the middle here in the photograph here taken with the 200-inch, Minkowski -- well Barter first and Minkowski together they thought it looked like two galaxies had banged Into each other and they came up with a theory that they were colliding galaxies and that's when two entire galaxies crash into each other. That's what provides all the energy to make these incredibly luminous sources. So now they knew that the radio could pick up these things so the next step was people want to see things further and further away so the idea was, find really small radio sources and they're going to be at even greater distance because the further away things are, the smaller they're going to be. So there was a huge team of people started measuring the sizes of radio sources. Should have included they're doing this on the famous Lovell Telescope at Jodrell Bank and they're finding the really small ones, they're measuring accurate positions of some of those small objects because if you're trying to find something very small like a star and your position is only as good as that, you've got lots of choices and to study all of them with a 200-inch telescope is actually impossible because it takes sometimes all night to get a spectrum of each of them so they had to get much better positions. They were doing that with an interferometer at the Owens Valley in California. An interferometer built by no less than the same John Bolton who discovered the radio galaxies. See the Americans after the war didn't go into radio astronomy and they fell behind the UK, Europe and Australia so they actually got John Bolton to come to Cal Tech to build a radio astronomy observatory there for them. So that's also interesting in case you imagine that Australia's the underdog. Sometimes yes but sometimes no. So John Bolton built that and one of the ideas were to use those two telescopes to get the interference pattern to measure the accurate positions and as John Bolton again and one of his students Tom Matthews got the position for object number 48 in the Cambridge catalog and this turns out to be a pretty interesting object. So once they had nailed which star-like object it was, they got a spectrum of it with the 200-inch and across the bottom are three of the luminaries in measuring light from -- from objects in -- out in -- in astronomy out in space Jesse Greenstein, Guido Munch was involved in this and here's Allan Sandage, famous for the cosmology you could do with a 200-inch. So they got a spectrum of 3C48. It had lots and lots of what we call emission lines. You analyse the light from a star. You can tell what kind of elements are in it because they make what's called lines in the spectrum I guess I'll show you one in a minute. And you can tell what kind of elements they are and if the object is moving, you can measure the Doppler shift and see how fast it's moving. So they measured -- there were lots of lines in the spectrum. They couldn't work out what they were and in 1960, Allan Sandage here as a paper to the double American astronomical meeting saying there's this weird object with weird lines. Possibly it could be a remote galaxy of stars with some strange red shift but it's most likely that this really is a star in our galaxy. So here they go they're actually heading down exactly the same path and the same trap that we had already seen before. And furthermore this object was variable. Like in the beginning of my talk the one in Cygnus and if something varies, then it can't be very big and this thing was changing in its optical brightness from night to night. So the thinking was if it was distant as a galaxy then it would have -- and you can see it -- it would have to have as much light as all of the stars in an entire galaxy. So here's the object 3C48; if they imagine -- this is a very distant version of this galaxy -- oh that's what I did. Good. Then if it varies in a week that means that every star in the galaxy would have to vary in a week and of course that's nonsense. How that possibly happen? They can't possibly know about each other. They are thousands of light years apart. So the view was because of the variability this cannot be an extra galactic object it has to be something nearby. And so that was the situation in 1960 and it was considered to be the first radio star. Greenstein, one of the most famous spectroscopists an expert in analysing what the light means, how you can go from the light to what kind of elements and what kind of conditions there were that made it and he had written a paper for the Astrophysical Journal with totally weird kinds of elements in a very weird kind of star that he thought might be some offshoot of the stellar revolution process. So -- and the paper had been accepted by ApJ but hadn't come out yet. By the way, from this point on, things are happening really fast. And even though there's no email in this era just think about that also a little bit people are writing era grams back and forth on a time scale of about a week. The groups in Cal Tech, Manchester, Australia are all talking to each other and there's a lot going on and you'll see there's a lot packed in to the next five minutes of my talk. A hell of a lot happens really fast now. Well this John Bolton who had gone to Cal Tech to build that Owens Valley Observatory had decided to return to Australia, which he did. And in a history, which John wrote in 1989, he made a statement saying that this 3C48 could have been fit with a red shift of .37. Now I already gave you one example of the same John Bolton, in fact telling us what he -- a change he made in a paper because of a referee and that was -- maybe the referee was tough as well but it was a small mis-remembery of what had happened. So everybody said, ah John is making it up. Nobody knew that it had that red shift. Well guess what's been found in the archive of letters? And my God what are we going to do in the email age? Who's going to actually find these gems among the millions of worthless bits of information [laughter] that plug up all of our databases well think about that too. Here's John Bolton. He's actually left and I think he was in Hu Wei, and he was on a boat to Australia and he's written this letter to Joe Pawsey who would -- it would be his boss when he arrives in Australia. "I thought we had a star but it is not a star. Measurements on high dispersion spectrum suggests that these various lines neon, argon need a red shift of .367. The absolute magnitude is then minus 24 which is two magnitudes brighter than anything known." So he did do it and he wrote it down. This is -- this is 60 so this actually is -- is three years before the discovery of Quasars. This was a Quasar no doubt about it, but one month later he writes another letter -- that's right, this letter he was still at Cal Tech. A month later he writes saying, "No, the experts have told me that these lines are not possible it can't have this kind of ionisation. Such an object cannot exist. I was wrong. So must be a star after all." So that was the effect of having the most expert person in the world saying what that spectrum was. So this is an example of too much knowledge becomes a problem. Previously we had the problem with the galaxy it was too little knowledge. Here clearly, there was too much knowledge and now, let's proceed into the next step. This is the Parkes Radio Telescope and we were actually observing the moon when this beautiful paragraph was taken by Seth Shostak. I was inside so I'm very proud of it. We were looking for very high-energy neutrinos but that's something totally different. It's got the telescope and the moon. Now if a radio source goes behind the moon then if you time very exactly when the radio source disappears and when it reappears you can measure an incredibly accurate position. So this was an alternate way of being able to pin down the identifications of some of these radio sources and thank you Diviar, I stole that from your Power Point presentation the other day. Cyril Hazard had become the master of doing these occultation's. He was doing it at Jodrell Bank using what's now called the Lovell Telescope but he had come to Australia and he was aware of the fact that a source called number 273 in the third Cambridge catalog was going to be occulted by the moon and that would be visible from Australia, not from the northern hemisphere. So he asked if he could get access to CSRO's radio telescope to observe this occultation and it was -- there were actually a sequence of occultations throughout 1962. Here is one of about 6. In this case, the radio source is emerging from the side of the moon down here you see nothing then you see an increase then you see a little step which turns out to be real and that's part of what I'll show you next and then it continues to increase and then you get this beautiful diffraction pattern. It is an absolute classic knife-edge frenal diffraction. It's the radio waves being diffracted because they're half blocked by the moon and half not so it's a classic diffraction pattern. That tells you straight away that the thing that's being occulted by the moon has got to be extremely small to make this pattern and it also tells you it's got another lump in it and that lump doesn't come with a pattern so that other lump has got to be not small. So they pull all these observations together. They can draw this little picture. So in this direction of the sky there is a point source, which is making this pattern and down here there's another blob, which has to be a little bit elongated. Here's the photograph taken with a 200-inch and now by the way, this is happening in February by now '63 and lots of things are happening very quickly. They knew this source was going to be occulted so they already got a good quality photograph with the 200-inch but this is what they found. Previously they thought this source was identified with a completely different object. This very point like object is that star and see a little faint wisp. That's exactly where the other thing has to land. The first thing the optical astronomers thought of when they saw this was, well, we've got a mixture here. This must be a background very faint galaxy and this is going to be another one -- whoops, where's my pointer going? And this is going to be another one of these galactic stars and that's just a chance coincidence. That was the first reaction. August '62 Martin Schmidt gets the photograph I showed you. Martin Schmidt had come from the Netherlands and by the way, that is absolute typical Martin Schmidt any time you meet him it will be looking elegant with a bow tie. I've never not seen Martin with his bow tie. He'd come -- Minkowski had just retired and he was taking over the program in the 200-inch to measure faint galaxies and so his job would really be to try and see what that faint wispy thing was. But it was immediately obvious from the occultation that there was radio emission from the star and from the wisp. Martin said he took the spectrum of the star first because he wanted to get that out of the way and then he'd do the difficult job of trying to get the wisp but when we took the spectrum of the star, this is the spectrum down here, it's now February the 5th. He's actually taken the spectrum in December. He looks at it straight away. All of these black bands are these emission lines I told you about. There's something in the star, which is some elements, which are making these lines. They didn't make any sense. They didn't make any sense to Martin Schmidt but he straight away said it's another thing like 3C48 which doesn't make sense but he didn't know about the high red shift of 3C48. And then in -- he was then writing the paper up to put together with the occultation paper, put it in "Nature" and he went back and he looked at the spectrum again and he suddenly saw that this line, this line, this line and a faint one you can't see in here but you can see on a different spectrum were in a certain ratio and it suddenly realised it was the Balmer sequence of hydrogen lines if you multiply them by 1.16. So if you gave them a huge red shift they all fell into place. And not only that, this is now science making predictions. Here is a hypothesis. If that thing was going at this incredible velocity then the lines would all fall in that place. A guy called Baboak had an infrared spectrograph and then you could predict that the strongest line of all which is H alpha would be in the infrared. He looked spot on. So there's almost no doubt at that point. They have found the red shift of this thing. Next door is Greenstein's office. So Martin says, "Hey look at this, this thing looks a bit like your 3C48 but I know what its red shift is." and Jesse Greenstein says, "Oh shit." Canceled his paper in ApJ and within days had written another paper on the second Quasar 3C48 which indeed have a red shift of .37, which was what John Bolton had said but was talked out of 3 years ago. So the bizarre twists and turns. Now, these Quasars, they are really bright and if the red shift is part of the expanding universe, then our -- so many billion light years away we are actually talking about the first life -- evidence of life on earth. So we're now out to about 10% of the age of the earth and the universe. So we have suddenly gone to these vast distances in space. That's a summary and furthermore, this thing wasn't just as bright as the galaxy it was 100 times brighter than the most luminous galaxy known. And of course that is what triggered my opening slide and the enormous excitement about the Quasars. There's a bit of a problem. This is one of the major discoveries. There's no Nobel Prize for discovering Quasars but if you've been listening to my story, you can see, it's a very confused story. Who discovered 3C273? And in fact, we've been trying to find who was actually the first person that said, looked at that 200-inch photograph and said the star in the jet line up. Martin Schmidt says this was not me. I just observed the thing that you guys told me to look at. Tom Matthews who he says did it. Tom Matthews said no I didn't do it at all. So did Cyril Hazard do it? But Cyril Hazard there's no evidence but he almost certainly didn't and so on. And perhaps -- probably I think John Bolton did, Benkowski was in Australia. He had a copy of that picture with him but I'm not sure we're ever going to find out who actually identified it. But as you can see, there's so many people involved in so many steps. The Noble Committee doesn't handle that very well when giving out Nobel's. To move from there to the future, here's a sketch of what they thought the radio emission looked like based on that occultation. Small thing up here and down here a more extended object and the other piece of the sketch, which is actually being done by Jan Auton in the Netherlands. Oh by the way, there's people in Australia talking to the people at Cal Tech, talking to people at Manchester, here talking to Jan Auton of the Netherlands. This is international game. This is a world game. This is not played by any one group and the information to sort this out is spread over all these places around the world. This is international science, which is my other thing I love and working very well. So this is what they measured. For those of you who study radio emission from AGM this is the paradigm AGM. They measured the spectrum. They had a number of frequencies. Compact one is flat. This thing down here is steep. That was the first time that was found in a radio source. This is where it started with that occultation. There is a modern image taken with the VLA and so you see they got it pretty good in the old occultation record. So 30 years later with a big fancy telescope, you got perhaps a better picture and then you look at it with a Hubble Space Telescope and this is what you see. Beautiful picture with very bright Quasar up here and here is the optical jet broken out into a whole string of knots and today we still try to understand exactly what's going on especially in the jet. But we will mostly now talk about what's going on in the stars. Today we call them Quasars. The astronomers didn't introduce that term. It was a populariser of science writing in physics today got sick of writing quasi stellar radio sources and called them Quasars but the journal, ApJ in particular, refused to use the word Quasar and there's a little story here which comes from Martin Schmidt. He then decided that they were optically loud -- optically radio loud radio quiet Quasars and they needed different names and he wanted a term to apply to everything so he wrote a paper to ApJ and said we really got to use this term and here's the reply by Chandrasekhar pointing out that this very reputable journal hadn't used this popular term but they feel that it can no longer be ignored. So that's when Quasars came into the literature. These things were bright. They were relatively easy to observe. You didn't even need a 200-inch and look what happened immediately after 1963. This thing called Z is proportional to how far away they are and so there was a race basically of people all over the world trying to find an object at the greatest distance. So there was a huge amount of activity and going up to as you can see red shifts of 7, which we believe is the time in the universe when Quasars were probably first made. None have been found beyond that and beyond that we now have other things gamma Ray bursts but I won't talk about that. This same Quasar, I had a few other surprises and I just wanted to show you this one quickly. If you look at this picture, it shows images taken of this Quasar with its -- with its jet. It's a very central part of it and pictures are taken about once every year and the sizes in light years are written on. Does anybody see that there's something pretty unusual, amazing about this photograph? In a time scale of roughly a year, this thing keeps changing in size by 5 or 6 light years. That means it's been expanding at 5 or 6 times the speed of light. That was always observed. Is this a problem or not for special relativity? The answer is not because you can do it with an optical illusion and I think you either know about this or else I don't have time to explain it but because the objects are moving apart at about the speed of light and the light is coming to us at the speed of light you can make an illusion in which you get this apparent expansion but of course there's another "Nature" paper and a whole business of measuring what's called now the superluminal expansions in AGN. But I wanted to look at a deferent aspect of the discovery of Quasars. So just recapitulating, Parkes did the occultation, Schmidt got the spectrum and I am actually sitting at Cal Tech at about this point in time and I was watching what I thought was an incredible collision of two cultures. Astronomers all of a sudden had to get in bed with general relativity theorists. A kind of theorists and normal astronomer would not even think about talking to because you have no idea what they were talking about. These were the theorists who work on Einstein's Theory of General Relativity and space-time and coordinate transformations and what was generally thought to be pretty weird stuff. But the Quasars caused something enormously interesting to happen. Because how did you get this much energy not now from an entire galaxy but from a small region? Remember. It fluctuated night to night. It's only a few light days across. You got to get this energy not from an entire galaxy but from a very small region. And if you think about that, there's only one source of energy, which works and it's gravity by having an incredibly massive object in the nucleus of the galaxy. By December in that same year a symposium had been convened only you can't work this fast. It was the first Texas symposium on relativistic astrophysics. If you're interested in history and excitement you read this and it bubbles with the excitement that's going on in that year 1963. And here's a statement, a quote, which was attributed to Fred Hoyle. I assume it is. "So relativists with their sophisticated work were not only magnificent cultural ornaments but might actually be useful to science." So there was a transformation occurring. The other thing that was happening, this is in the nucleus of a galaxy. Well everybody now thinks well of course the nucleus of the galaxy that's where the action's all going to be. What's surprising about that? Well the surprising thing is that this was a big surprise. Carl Seyfert perhaps one of the best known astronomers these days because there's things called Seyfert galaxies which are named after him which are hugely important. In 1943 he made a catalog of them, small catalog. He had 6 of them. For 16 years his paper received not a single citation and that's even worse than most of the statistics we worry about. And furthermore when he did get some citations, none of them came from the west. Not from all the people working on galaxies in Europe or the U.S. but from old Victor Ambartsumian who said the nuclei of galaxies aren't just the place where they're brightest. Maybe something important is happening there. And followed a few years later by Vitaly Ginzburg who got the Noble Prize by the way for super conductivity. Think broad look at many subjects. As far as I can tell he is the first one that said, gravity can supply the energy. He's not normally credited with it, but I think you'll find it was probably him. So if you get into the nucleus of galaxy and you've got a lot of gravity you can really make things happen. Very quickly, all of the old ideas of colliding galaxies to provide the energy disappeared within a year; I would say they were gone. One controversy lasted for decades, that was a rather strange one. A subset of the scientists said, objects cannot naturally be that luminous. This is unreasonable. We would rather have a red shift due to some phenomena we don't understand so we'll invent something like dark energy and say that's going to explain away the red shift and not have to put them at great distance. That persisted for quite a long time. It's interesting that theories which were making good sense were nevertheless so different from what anybody was thinking that they were considered less credible than a theory that you made up saying well we don't understand what the red shift is so that will be magic and let's go on from there. [laughter] Not surprisingly, the magic theories failed to predict much of anything. Where as the gravitational energy from collapsed objects had become a really big thing. And in the years -- even in '62-'62 there are papers by a string of people saying gravity can do wonderful things. There could be accretion disks around massive objects. But notice I said, what kind of object? Nearly all these people are saying really massive objects. Maybe you can have a star, which is a million times more massive than our sun. And then it could -- could accrete the stuff and we could get all the energy. What about the black holes? You know all about black holes now, but black holes then were even more esoteric than other bits of general relativity and it's also 50 years this week since black holes became credible. Have a very quick look at the black hole history. We can go way back. Chandrasekhar said -- this is Chandrasekhar eventually the editor of ApJ by the way in 1931, young -- young -- young scientist. "A star of a large mass cannot pass into a white dwarf stage when one is left speculating on other possibilities. The idea is if something is so massive that its gravity overcomes the atomic repulse forces then what happens to it?" And so he's wondering what happens. The expert, here's the authority steps in, Eddington is basically saying there's going to be something in "Nature" to stop crazy things happening. It's not going to turn into are black hole or anything weird like this. There'll be some law of "Nature" because that would be totally weird. Oppenheimer more famous for his role in the development of the atomic bomb worked for many years on the theory of black holes and he called it an exercise in abstraction. And most of the theory was there but was considered to be irrelevant and wildly speculative. I also thought it was interesting when Chandrasekhar eventually got his Noble Prize and you read the citation. The citation was for his work on white dwarfs neutron stars but included in the citation is this statement that he had predicted that there would be a black hole but in the noble committee, they're still so called black holes in '83. Kavli Prize 2008 Schmidt for the discovery of Quasars and then they added Donald Lyden-Bell. Now when my friend Donald added to the story was a couple of rather interesting steps. He wasn't the first one to come up with the idea that if you had a black hole and things accreted onto it you'd get lots of energy but he did realise there was so many of those things out there in space and the black hole all the mass may have been used up, you may have big black holes which aren't doing anything. So he said maybe all the galaxies may have to have black holes in them. Otherwise we can't explain the number of Quasars seen at great distance. And so that was when the nuclei now will not only weird occasionally when they have these blasts of energy in AGN but maybe all the nuclei maybe even our galaxy has a black hole in it. I also thought it relevant to pop this in. This is the VLA, the -- one of the largest radio telescopes on earth at the moment. And when you build a radio telescope you have to make up a story of what you're building it for. The VLA was built to observe Quasars with optical resolution. So if the Quasars hadn't been discovered, I guess we wouldn't of had a VLA. Now VLA did observe Quasars with optical resolution but it did a hell of a lot more. Lyden-Bell said, hey, look in the centre of our galaxy, there might be a black hole there. Centre of our galaxy's a pretty messy place. Here's a picture of it, which I was involved in making but I don't have time to talk about. And at really high resolution little white dot there and when you do look at the stars in the infrared where you can see through the dust and what this is showing, the different dates is the way these stars are all looping around the galactic centre you can apply Newtonian mechanics and you can work out there is indeed at exactly that point there a black hole with 3 million times the mass of the sun. And I was going to get the movie of this but I didn't get around to it which looks quite dramatic but it reminded me of these little black hole machines where you drop the coin, right, and circles around and around and around and goes down the black hole. And so that's a very nice illustration of just what's happening in the galaxy and by the way, all this gas you see is just spiralling around the hole as it goes down into the black hole. But when I looked up this image or actually my wife found it for me, there was an amazing caption on it. It said, "These things may gather more money than any of the other sponsorship devices which are out there." And so for the commercial people here, here's a spin off from black holes and excuse the pun. They are making money because the shape of that is designed based on a black hole. There's a beautiful picture of a couple of galaxies colliding with each other and swirling off the stars and doing a kind of dance before they finally merge. Well if each of these have a nucleus and here in this picture you can see they do in the Hubble picture and they each have black holes then you're going to have two black holes in orbit about each other. And if there are two black holes in orbit that gives interesting possibilities. Because they can generate gravitational waves and those gravitational waves can be sensed by timing pulsars and see the distortion in space and time as the gravity wave goes past. And this is our now moving quickly to the future and here's a plot, which says can we see these gravity waves? Well of all the places in Australia, Perth in Western Australia, is where much of the research on detecting gravity waves is being done. There's a machine in Perth like LIGO to try and detect them. This has got to do with the frequency and big black holes have a different frequency than small black holes. These pulsar and these are the prediction all along here and these little loopy things are the limits. None have been detected yet. These are looking at pulsars today and the best you can do and the next one in here is what this telescope called the SKA will do and it should get us to the point where we'll see these double black holes orbiting around each other because of the gravitational waves they make. In order to do this kind of experiment, we now need telescopes which are in order of magnitude bigger than what we had before so we need to go from the VLA to things like the SKA and here's an artist impression of one part of the SKA as it may look like in Western Australia. And in conclusion let me just comment on these new telescopes. Of course there are many things it can do. I showed you just one tiny example because it linked into the black hole talk. But like the VLA, it will not just image Quasars, these telescopes will test the predictions we're making but the exciting thing and I think the exciting thing about this story is it's not the old questions which we are answering, but it's the new things which they are going to find to which we don't know anything about yet. And I think the Quasar story has got this interesting twist in the tail. The power of science is surely its ability to make predictions which you can test. That's the foundation of science and why it works, but don't get confused. Science itself evolves in completely unpredictable ways so we cannot predict what the exciting science will be in the future but we have every reason to believe that it will be just as exciting as the period I've just told you about. Thank you. [ Applause ]