Exoplanets and Cosmology - Nobel Prize in Physics 2019

it's that time of the year again it's the Nobel Prizes always tells my phone up you you never know I do you again overlooked yeah just need to check the number I called it yes I'm feeling a bit smug about this because about five minutes before the announcement I suddenly had this feeling who was going to win and sure enough they did or at least they won't half the prize anyway and the other half of the prize went to a guy called Jim Peebles and a good call that says see Jim Peebles get past the Nobel Prize he's regarded I think as the father of modern cosmology did you put a bet on or any I should have done should not really yeah but no I didn't and it was literally five minutes before the announcement it wasn't that clever of a prediction because I was certainly wasn't the only person predicting it and it's be they've been sort of one of the runners and riders for a number of years now but I sort of thought it was their time it's a slightly strange award and actually so the citation reads was awarded for contributions to our understanding of the evolution of the universe in Earth's place in the cosmos which could be pretty much for anything really because that covers pretty much everything there is but Jim Peebles is a cosmologists and he's really one of the towering founding figures of modern cosmology in that he did a lot of the work he was part of the group that was predicting the existence of the Cosmic Microwave Background he did a lot of work about the growth of structure in the universe the impact of dark matter on how structure would grow so really I mean he is if you if you teach a course on cosmology in large part you're talking about his work the model which is fitting the data so well has his influence on every single part of it he is a theorist but he's one of those theorists who actually maintains a very close link to the observation so some of his work you know has actually he's written papers which are presenting observational data but more in a fairly theoretical framework so you would think of him as a theoretical astrophysicist he's just demonstrated that in modern cosmology these are the key ingredients we look like we need and he was there at the start of each one of them playing a role so he can be and properly regarded as the father of the subject and the expert says there on your board did a tutorial today we have tutorial system here at Nottingham where all the first-years get to have a this usually six in the group I screwed up prior to do twelve cuz and so I thought well you've got to tell them about the Nobel Prize at least the bit I know about it if you were talking about Jim Peebles you wouldn't say our he did so-and-so because there is just so much he's contributed so the other half of the prize was shared between michel mayor and didier caleb and they worked on studying exoplanets they still work on studying exoplanets of planets outside the solar system and it was awarded for and then we could get the exact wording here for the discovery of an exoplanet orbiting a solar type star so it was really their discovery in 1995 was what kicked off the entire field of exoplanet studies because like exoplanets these days are like candy I don't know they're like there are many many thousands of them at that point it was only one actually that's not quite true because there were other planets and that's it's interesting the way they worded the citation they says an exoplanet orbiting a solar type star the first exoplanet was actually found orbiting a pulsar a neutron star rotating neutron star which is a very weird system and no one really expected to find planets around pulsars and so it was clearly something very strange and so although it was interesting it was like everyone was well it's nothing like the solar system so it's not really a planet in the sense that we would understand it there were also tentative discoveries of planets orbiting giant stars that preceded the Maya and kalo discovery but this was really the first announcement of one which we would sort of equate with something like the solar system so it was a solar type star very like the Sun with a planet in orbit around it do you happen to know like what star was it was obviously in near bias it was it's 51 Pegasus is the star and the planet is called 51 Pegasus B it's about 50 light years away it's very ordinary stars I say it's a g-type stars are very like the Sun a little bit more massive I think 1.1 times the mass of the Sun so tiny bit more massive but really almost a twin of the Sun very bog-standard kind of star what method did they use to discover it so they use this radial velocity method there are now a whole slew of methods that are used for discovering and studying exoplanets but one of the foundational techniques and the one that made this first discovery was this radial velocity technique where ever if you've got a star and you think of a planet in orbit around it the sort of simple picture is the star is stationary in the middle on the planets orbiting around but of course they're actually tugging each other and sort of orbiting around their mutual center of gravity what that means is that the planet is tugging the star backwards and forwards as well as the the the star tugging the planet backwards and forwards so the star is actually oscillating and so sometimes it's moving towards you and sometimes it's moving away from you and by studying the spectra of the star and looking there those little dips where there are a spectral lines in the star you can see whether they're being shifted Doppler shifted towards the red end of the spectrum or the blue end of the spectrum so you measure that backwards and forwards wobble of the star and that gives you a measure of the mass of the thing that's all between around it as well as how rapidly it's orbiting around it by how quickly the thing oscillates backwards and forwards you know that's a that's a good method I imagine I imagine that method had been thought of for quite a while and all the astronomers in the world have access to telescopes and telescope time what did they scientists do that made them a would be first like what what method or trick or idea that they have that made them the winners so there's a couple of aspects here firstly people weren't really looking that hard at the time because there was no expectation that you'd actually be able to detect much because we had this and so if you think about what's easy what's easy to detect in this case you want something where there's a strong gravitational pull between your planet and the star to tug it a long way so it's got to be a big planner so there's two things you want it to be a big planet so it's massive so it'll talk the thing backwards and actually you want them close together so the pull of gravity strong so that the movements are bigger and so what you really want is a planet like Jupiter close to the star now at the time we only knew about one solar system and Jupiter in our solar system is a long way out as is the way with scientists you know if you've only got one of example of something you convince yourself that that's the way the universe works so we had all these ideas at the time back in the 1990s and before that actually jupiter-like planets only existed in the outer reaches of solar systems and things close to their stars were all little things like Mercury and earth which you wouldn't be able to detect and so because of that there wasn't really a huge expectation that we'd be able to detect this kind of effect and what these guys actually found was something that's about half the mass of Jupiter very close to a star and so actually and subsequently of course we found many of these hot Jupiters like planets so jupiter-like planets which are close to the star and so it turns out that actually the universe doesn't work the way we thought it did back then and there are mechanisms where even if a big planet forms a long way out in a solar system or there are mechanisms by which you can kind of my group migrated inwards towards its star so they found something that no one was really that much expecting to find which is why there wasn't a huge rush to try and find these things the other thing is they had some very clever instrumentation they actually built a custom-built spectrograph that allowed them to measure very small Doppler shifts they were down at sort of tens of meters per second that they were measuring these wobbles in these stars which did require very good instrumentation very stable instrumentation where you can actually calibrate things with that kind of accuracy to really measure those very small shifts so you couldn't have just had like an off-the-shelf night of VLT and have found that sort of thing you probably could now with VLT but in the 1990s no you really wanted a custom-built instrument it wasn't on that large you telescope it was I think it was a two meter telescope so even by then those standards the standards of the 1990s it wasn't a particularly huge telescope but it was just a very clever spectrograph and they were looking for something that no one else is really looking for as an astronomer and you're an astronomer in the 90s I was yes do you kick yourself and think oh I could have done that that would have been like a week's work and I could have I could have been the one to find it so the interesting thing is before their paper in the 1990s in the 1980s let me show you another so let me show you their paper so here's their paper published in 1995 a jupiter-mass companion to a solar type star and it's you know it's actually not a particularly long paper it's not got many pretty pictures in it few graphs not even a picture of the star even a picture no nothing spectacular about it at all I mean you know nice looking data there here's there so here's the the wobble backwards and forwards of the star so sometimes it's going away from us sometimes it's coming towards us you can see so that here's the scale 50 meters per seconds are their small ships that you actually measuring here so that's the wobble that they were measuring so here's the interesting thing that was the 1990s in 1989 this paper came out the unseen companion of telephone number a probable brown dwarf and it turns out they had actually also discovered a jupiter-like planet he's on there as well there that he's actually my always on there as well he's one of the authors but the primary mover of this guy called Dave Latham was actually in an office just over the corridor for me at the time because I was a PhD student and he was a proper serious scientist at that point at the CFA in Boston he wasn't very excited about this result I mean he was a bit excited but he was actually you know because and again it comes back to the fact that no one was expecting to find planets and the reason why he didn't know that he'd found a planet so brown dwarfs are sort of one up from planets they're sort of failed stars and no one was you know people were expecting to find brown dwarfs because we find binary stars quite a lot of the time and they have different mass ratios and it wouldn't be terribly surprising if once in a while the littler one turned out to be not quite making it as a star so people were not that surprised to be finding stars with brown dwarfs in orbit around them because they basically just very closely related binary stars that we know exist a fire would binary it's a 1/2 of its kind of failed to ignite so 1/2 is a star the other half didn't quite make it because they weren't expecting to find planets he convinced himself he hadn't found a planet and the reason why there's an ambiguity because you might think well you know we know what mass is brown dwarfs are we know on masses planets are wouldn't even known turns out there's an ambiguity in this method and the ambiguity in this method is I kind of drew this you know what I wasn't waving my hands around I did it like that but we don't know whether the systems like that or whether it's sort of I can't do it that way that way like that and of course if the planets orbiting that way you don't see that the star is still moving it's but it's being tugged in the plane in the sky so you don't see these Doppler shifts so this is an bu and of course you can have anything in between so actually if you see a certain movement it could be like if it's you know you see a certain movement it could be a relatively low mass thing that's in the plane of the sky so we're seeing all the movement of the sky or it could be it's almost in the play a much more massive thing and actually these things mean jerking around all over the place but we don't see most of the motion because most of it's in the plane of the sky rather than towards us or away from us you've got to get lucky it's kind of you need it to be punching you face rather than wobbling around to get the biggest signal you really want to be lucky and just catch catch the thing edge on so you see the biggest signal because this has had less ambiguity you you can't tell really directly from the observation whether you're seeing a brown dwarf kind of in the plane in the sky close to the plane the sky or a planet close to a John and because they had this expectation that they shouldn't be finding these planets they convinced themselves that they were seeing a brown dwarf star binary fairly close on and it was a bit unlikely because actually it has to be surprisingly close to face on for it to work but they sort of convinced themselves they do actually say somewhere in the paper or it could be a large planet so they do actually at least make you know say we might have found a planet the extra thing that Maya and Kahlo did is they also looked at the properties of the star so they actually couldn't measure how fast the star is rotating because you can see one half of if the stars rotating one half of its coming towards you the other half is going away from you and so you can actually see you what you end up seeing is a kind of a broadening of the lines so instead of seeing the line wobbling you see part of the line being shifted one way part of it the other way they met effect of that is you see a slightly broader line so they could measure the rotation at the star kind of the the at least but again that's the same thing right is it a star that's rotating in the plane in the sky or is it rotating edge-on but they knew some of the properties of the star you could just make observations of it find out what kind of star it is and we know how fast stars typically actually rotate that are of that type so they have this measurement of this kind of one component of how fast the things are rotating and that could be either a very fast rotating star that's sort of pole on or it could be a relatively slowly rotating star that's a John but we know intrinsically how far stars like this actually rotate from that you can figure out that actually this system is relatively close to a John so there's one more leap here which is that as long as the Stars axis of rotation is the same as the planets axis of rotation which for example it is pretty much in the solar system the Sun rotating about kind of the same axis that the solar system is then that actually tells you that the system has to be relatively close to a John and once you've got that then you know you've found a planet so that was the sort of the extra bit that I guess though is what really got them the Nobel Prize Plus actually just the confidence to say found something that no one expected to find so in the future of one day we go and visit other systems and other planets and we can somehow do this this will be this plant this particular Nobel Prize want to be a good one to visit wouldn't it to be like historic want it to be like visiting like for Humanity this was a this was a historic site for us it probably I mean it's not the easiest one to get to because it is 50 light years away and we know no we now know about planets you know there are only a few light-years away so it's probably not the first one that would ever get visited but yeah when it becomes routine it will become one of the stops on the tourist trail I suspect those of course there could be other planets in the system we've just seen this one fairly massive jupiter-like planet very close to the star which really wouldn't be very hospitable because it's going to be a gas giant and it's going to be very hot and very unpleasant but who knows there could be other planets further out in the solar system father of modern cosmology does that mean there's an older cosmology like where does it read it weird an old cosmology transition to modern cosmology I'm giving the transition time around the 1960s which by the way is another important time for the that's what the epoch of Higgs and kibble and Brout and on blarin people the discovery of the cosmic microwave background radiation I think that kind of transformed the field from being one that was full of speculation and promise in solving Einstein's equations without really knowing what the background material was in the universe - first the first time we established that this radiation this remnant of the hot Big Bang that emerged when the first atoms were formed say 400,000 years after the Big Bang and then just propagated outwards for the next 3.8 billion years that the detection of that in the 1960s 1965 in fact it was announced by Penzias and Wilson that where the associated a temperature - this radiation that I think is what you might come calling here that it's kind of the start of modern cosmology and Peebles was there in fact it's not very well known but the paper by Penzias and Wilson which is one page long we are busting a gut writing all these lumpy one-page paper about the third or fourth line having announced that they discovered this radiation that they don't really know what it is they say that in the preceding paper in the journal which is Jim Peebles paper with decay and roll and Wilkinson they say they've come up with an explanation for what this could be and it is in fact you know the microwave background radiation at a temperature of around at the time they say 3.5 kelvin and soda it's now about seen as about 2.7 Kelvin but that's that's okay it was 3.5 plus or minus no point one so they when they were perfectly okay but people's was there and in fact not only was he there he's the one that actually in the previous paper the one that literally appears before it which is a mind-blowing four pages long that's a huge paper by comparison he's the one along with his co-authors who suggest that actually this remnant radiation is linked to the hot Big Bang and he and that it's got these thermal properties it's that I think which is really key that that you can pin down as being one of people's main contributions here that he he recognizes ever significance of the the radiation has been linked to the early universe and and the second thing that he does which I hadn't seen done before he points out that because we now know the temperature of that radiation and because we believe in the idea of general relativity and we can understand how that radiation changes its temperature as the universe changes scale because it gets red shifted it cools down as the universe expands it means it's hotter earlier on and so he's able to link the temperature you've got today to an estimate of what the amount of matter must be in the universe today because he knows what it must be sort of in the around the time of nucleosynthesis he's got a bound he can use and and by doing that he actually in this paper without I don't think necessarily really realizing that they're saying there must be some sort of Dark Matter he's actually points out that the estimate for the amount of baryons matter in the universe in terms of baryons is actually lower than the critical matter amount that you need that we see today we believe the universe today is spatially flat that means as a critical amount of matter in there and he said in his calculations there's not there's not enough and in fact the end of his first paper the one that appears with Penzias and Wilson comes up with ways of trying to increase the amount but he was there he was pointing out this connection between measurement of the radiation and the density of matter in the universe and that's absolutely integral to the rest of cosmology in fact the man in the street probably hasn't heard of the to CDN model but I think if you said the standard model of cosmology that's what you would say people's was a responsible for the standard model of cosmology has various contributions to the overall energy budget so before Peebles was around we knew that there were baryons right and and but we didn't necessarily know how many and Peebles began to put a bound on that from this paper but then he made some even bigger contributions in some sense the next thing he sort of realized was that again using the fact that you've got this Cosmic Microwave Background that had been detected by Penzias and Wilson he was aware of the fact that there's fluctuations to be expected in this Cosmic Microwave Background and he's the one along with you who actually was the first to fully do sort of numerical simulations of different types of cosmology and predict what these the Doppler the acoustic oscillations were that we see in the microwave background remember those peak structures there are big Peaks and then they go down as you as in the CMB he was the first to numerically show what different cosmologies would predict and so he in in amongst that he showed what a flat universe would do and that's the one that pretty much is observed by first of all by W map and then by Planck the initial anisotropies were demonstrated by Kobe but the original work solving the numerical codes to show roughly what they would look like is from Peebles what made him good like why is he why is he good at this what is it about him that all the other cosmologists haven't got I don't think anybody has his overview his a is very very strong mathematically he he's developed the statistics that are you that's used in much of the analysis of the CMB and of large scale structure when you're looking at correlations of different regions of the sky he developed the techniques you need more than that and there's ability to solve equations and do integrals and things he had this he has still there he's 85 but he's still very active and really on the ball he has this overview this he can see the bigger picture he can see how a given calculation a given observation tells you something about something else in the universe by extracting out from that small initial observation that sort of its impact on the whole of the background evolution and and to do that is not easy because there's so many balls in the air and he's able to juggle them all in the end I think that in many ways is his big skill have you ever met him oh yeah I've met him many times at conferences he's such a nice guy he's one of these people that he's always prepared to give to you his time if you're walking for dinner or having lunch or 'add he's you know he asks really pertinent questions and but he's I've always found him to be somebody that it's easy to get on with that when he asked questions is very polite and but he's not afraid to tell you it for you if you think you're wrong which he's done to me that's right professor right now in cosmology there are kind of different camps and schools of thought you know people who like string theory and a B and C and all that is is his peoples in your on your side or on the opposite side people sit sort of above it all I don't think he's worried about the camps to be honest he's he goes where the science tells him really excited Neil because it's for Litton batteries and so he's gone on a battery Safari some of you know that Neil is a motorcyclist he has an electric motorcycle

Channel: Sixty Symbols

Views: 123,137

Rating: 4.9588585 out of 5

Keywords: sixtysymbols, exoplanets, cosmology, nobel prize

Id: Gq-atYZFKPQ

Length: 22min 28sec (1348 seconds)

Published: Sat Oct 12 2019