Planet Nine from Outer Space - K. Batygin - 12/7/2016

presented by Caltech it's my pleasure to introduce tonight's speaker konstantin batygin konstantin is an assistant professor of planetary science here at Caltech he was born in Russia and partly educated in Japan but speaks English with a California beach bum accent since he got his undergraduate education at UC Santa Cruz when he applied to Caltech to be a graduate student here we were not sure what to make of him but we accepted him and he came and we have no regrets less than four years later he completed his PhD here at that time we did something very unusual for us we offered him a faculty position here at Caltech and to our delight he accepted and we have no regrets we did send him off for a year or two to our farm team and Harvard to get a bit of seasoning Constantin works mainly on planetary dynamics a subject that has its roots in something very classical celestial mechanics which has to do with the behavior of bodies interacting under gravity in the simplest version of it bodies that are treated as point masses a very classical problem some aspects of which are still unsolved indeed in Constantine's very first paper he worked on a problem of long standing the stability of the solar system and here at Caltech both as a student and subsequently as a faculty member he has continued his passionate interest in planetary dynamics though he has worked on other things as well a wide variety of problems that involve various aspects of planets including magnetic fields the disks from which planets form and so on a very rich set of problems motivated to a significant extent by the remarkable explosion in information that we have received in the past decade or so about planets around other stars one of the interesting features of the way that Konstantin does science is that he's working on problems that many people would seek to solve by throwing them at a computer by running a big computer code constant ins not afraid of computers but one of the distinctive features of his style of doing science is that wherever possible he tries to do things with pencil and paper or on the blackboard and this of course is the way that you get a deeper insight into what is going on it also means that he is an excellent teacher I should mention an aspect of constant endure does not have to do with the science and that is that he is the lead singer of a band it's called the seventh season google it but do so after the show as for this show it's not going to be hard rock although there are some aspects of chaos in it it is perhaps music of the spheres although you can debate whether planet 9 is in harmony with the rest or even whether it's playing in the same band but with no further ado let me now ask Constantine to come out and give his presentation please welcome constant thanks very much thank you it's a it's a really special moment for me to be introduced by Dave when I was a grad student here which by the way I always wondered how I got in now I know it was a close call rightfully so when I was a grad student Dave was my was my mentor my my PhD advisor and before we dive into all this I just want to tell a quick story but the first time ever I talked to Dave and went like this I walked into his office and I said Dave I'm Konstantin I want to do some research and Dave said you know what you should do you should calculate the magnetic Reynolds number for a highly irradiated exoplanet atmosphere so I already do that and then come back and we'll talk I don't even know what a regular Reynolds number is let alone a magnetic one anyway I spent like the day figuring out what they was talking about and at the end of the day I calculated and the answer was three so it's swagger I walked back in two days odds that the answer is three and they said three no way I don't believe it and then he stared blankly into space for like five seconds it was like yeah I also get three but what is this place you know what how it so anyway now that I'm a prof I do the exactly the same thing I tell my grad students why don't you go calculate something then I spend all day calculating but when they come back you know I pretend I didn't man all right so speaking of speaking of exoplanets right over the last couple decades the number of planets that we have discovered around other stars has just been staggering thousands of planets around other stars really interesting stuff but meanwhile in the solar system we've been losing okay in 2006 we went from nine planets to eight planets right we lost a planet so today I would like to talk about how to make the solar system great again and restore it to its former rightful nine planet glory okay so this is work I should acknowledge done alongside my friend and also mentor Mike Brown and before we talk about 2016 let's sort of turned the clock back a little bit to the year 1781 which was the first time this planet was discovered in the solar system and it was discovered by a guy named Herschel simply through the meticulous process of using the telescope to look at the night sky and just make a drawing of what he saw so in principle discovering objects in the solar system is kind of easy right the kind of basic idea is that night after night galaxies and stars that are far away don't move relative to one another but things in the solar system move ever so slightly so Herschel discovered the first big object that moved across the night sky and said great this is a new planet of the solar system we will call it George okay so we can have my earth Venus Mars Jupiter Saturn and George so the the astronomical community did not exactly agree and said we will instead of calling it George call it Uranus so one of the remarkable things about George was that immediately upon his discovery astronomers realized that it had been spotted a bunch of times before right a numerous astronomers had jotted it down and didn't recognize that it was a moving star right they just kind of drew it so immediately after the formal discovery of Uranus its orbit was reconstructed by going to legacy observations and something that astronomers noted is that it was deviating away from its predicted path here's a set of tables which was published in 1821 rather compiled in 1821 by alexis Bovard who was the director of the persian observatory and as you can clearly see from this slide Uranus is not where it's supposed to be right there is signs and co-signs over here on the left-hand side and there's a table some French words and pluses and minuses so what people that speak French tell me is that in here what Brevard writes is that as a good theorist I will not dismiss the possibility that the data is bad right after all is just astronomers drawing what they saw at night for nose I said but let's sort of for the sake of argument also consider the possibility that the data is right and that Uranus really is deviating away from its predicted course what would that mean that would mean that there exists another planet in the solar system that is gravitationally perturbing it that is causing it to go off course so this was again 1821 like I said I don't speak French but I have enough skill to define the word Uranus and it appears here another spot on the slide so at least I know that they're taught up this is the right page where they're talking about Uranus so the promise of this data the promise of Bovard x' tables didn't come to fruition for about 20 years it took more than two decades for the promise of using existing data the deviation from the predicted path of uranus to lead to the discovery of the next object and the man who's typically credited with the discovery the theoretical discovery of Neptune is this guy orb on delivery who live between 1811 and 1877 now - to the untrained eye he looks like a pretty fancy French guy but as Dave mentioned when I was an undergrad I lived in Santa Cruz kind of a questionable part of Santa Cruz so I can spot a gangster from afar and it was absolutely clear that lavare EI was a gangsta because he's bling right is it wearing his bling on the outside his stage name is urban so I went through the process of reconstructing what he actually looked like which is this and by the way you too can download the thug life app onto your iPhone and yeah we you know they work they work assistant professor is hard here right so this is what this is a page from lavare EA's manuscript where he went through the calculation they the painful meticulous calculation of using existing locations right existing observations of where Uranus was in the night sky to deduce where the next planet was it took years for him to complete his calculation and interestingly at the same time there was another gentleman by the last name Adams in England who basically had the same set of calculations but got scooped baile varier and this is what this is what happened in 1846 when live area completed his his prediction he went to Paris to the to the observing crowd right where I gave this big talk we're in the audience there were lots of observational astronomers where he tried to explain to them exactly where the next planet is said Neptune is like right there all you have to do is find it please someone find it and in the in the audience there were some big names Airy for example it was very famous geophysicist of the time who said I cannot attempt to convey the impression which was made on me by the author's undoubting confidence but the firmness with which he proclaimed to the observing astronomers look into the place which I have indicated and you will see the planet well so laverre EA was absolutely certain that his prediction was right and remarkably he generated very little enthusiasm among the observing astronomers because they said you know you're kind of making us asking us for a big commitment like we have to stay up at night all night okay like it's not easy to do so interestingly Neptune was not discovered by a French astronomer observational ela very a had sent a telegram to gal who was a German observed observer and gal put together this plan for finding Neptune and on the first night of their observational campaign the sky went dark they opened up the dome and within an hour found Neptune right just remarkable it was probably it's probably one of the most remarkable instances where theoretical calculations lead led to something that was kind of immediately and very immediately observable and very dramatic another really interesting thing about lavare EA's miracle was that it was all about timing the reason it worked was because it happened in 1846 okay so both lavare EI and adams assumed the so-called bodes law for the size of the orbit right they said so in the solar system things are roughly spaced in a geometrical sequence so by that assumption okay with that assumption built into the calculations the predicted orbits that both atoms and lavare EA got were these big circles on the slide whereas the real Neptune is the smaller orbit okay but they got the location in the night sky correctly because Neptune and Uranus were almost at conjunction in 1846 so it's all about Sciences just like show business it's all about timing right it's all about being in the right place at the right time so in the modern day you don't have to spend years doing this type of a calculation you can use computer algebra and if you will if all of this was happening in 2011 which is by the way exactly one Neptunian year later Neptune completed one revolution since 1846 Adams would have predicted Neptune to be here and the very a would have predicted it'd be there so they would still have gotten the correct notion that indeed a planet exists beyond Uranus but it would wouldn't have been nearly as dramatic they wouldn't have gotten the part of the night sky where to observe it correctly so I'm not the first person to point this out in fact this was first I think pointed out by this hipster from Harvard College Observatory who said the various calculations nothing but a happy accident and he together with Parsifal Lowell of my understanding of the history is correct set out to find the next planet using the same methodology and I said now that we know that this method works you can discover planets with math rather than the telescope then we can just keep on doing this right so and in fact lavare EA's neptune even the observed neptune didn't fully resolve all of the issues with with the iranian orbit urania nor it resolved most of them but Uranus was still deviating away a little bit from its predicted path so chasing those residuals parsable Lowell set out to defined the famed Planet X in fact when you type in Planet X into Google that notion tip actually dates back to this guy so he spent decades employing people to do the laverre EA calculations and his family was very wealthy so I'm making this up but this is probably exactly what happened he probably one day woke up when like dad you buy me a telescope and I was like yeah come on so it built him a Lowell Observatory right Lowell observatories dates back from that time so right Lowell spent his life looking for Planet X published all of the calculations in 1915 and then died in 1960 so the search for Planet X kept going and the planet the man who invented is covered Planet X was this guy clyde tombaugh who only died in 1997 this is a real picture of him standing by the telescope this is a children's book version of his biography pitched at my intellectual level so we can choose you can choose that or Wikipedia so what Clyde Tombaugh found was really remarkable right if this is 1930 front page of New York Times Sunday edition if you zoom in here by the discovery made it above the fold it's pretty big pretty big deal that's how you know it's a big deal right it says here astronomers hail finding the sphere possibly larger than Jupiter and four billion miles away meets predictions right so the various miracle has been successfully redone now we know that what Clyde Tombaugh found was not a sphere larger than Jupiter what he found was Pluto and if you put Pluto on top of Australia it fits right so it's not it's not a big it's not a big deal right Pluto is is a really small planet it's it's smaller than the moon by a large factor so it's really sad actually in the way that the planet X story unraveled okay and actually the interesting thing is that it was really put to put the rest in 1992 when the flyby data of Voyager 2 spacecraft was analyzed Voyager 2 encountered Neptune and measured its mass directly what was recognized is that we had the mass of Neptune wrong by half a percent and if you fix it then all of those residuals that parsable Lowell was chasing almost a hundred years ago simply go away right so Planet X was really killed by unmanned space flight and I think because it was such a letdown in time this notion that a planet it can exist beyond the solar beyond the orbit of Neptune kind of downgraded itself to the point where if you talk about it you're crazy okay so this is a one of the first hits from from the internet okay which which I pulled up on October 24th 2015 so a little bit over a year ago when I typed in something like planet beyond Neptune right it says that we're all going to die because the planet X is coming in for and if you read the common section and then there's some real literary masterpieces of our time right who says hear me and many folk with me have been waiting for this to show up for years declares commenter Socrates rare amore ancient records state that once the destroyer is visible to the world we have 40 days to prepare and it's definitely Nibiru and it's time to freak out so what I'm getting to here is that if in 2000 I don't know 13 somebody had walked into my office and said it's totally evidence for a planet beyond Neptune I'm like take what you want okay just just leave so indeed we haven't found any planets in the solar system no matter no matter how hard we search the night sky but what astronomers did discover is the so-called Kuiper belt and this is actually the thing that led to Pluto's demotion right this is the solar system viewed from top down that little green sorry that little blue circle is the earth in pink there Jupiter Saturn Uranus and Neptune Pluto is is appearing here right now we're going to switch to the frame of the solar system go into into the plane and clipped ik plane and what's going to appear all of the well-known well characterized Kuiper belt object of which we now know of thousands right there they all are right so in the last two decades concurrently with the discovery of extrasolar planets astronomers have discovered that the solar system has another belt of debris not just the asteroid belt but the Kuiper belt which resides beyond the orbit of Neptune individually each of these objects is not very significant visually there may be average size of these guys is about 100 kilometers roughly the size of La Plus Orange County combined the none of these things are planets they're just space debris really cumulatively this belt only weighs about 0.1 Earth masses so it's not a huge gravitational deal but the orbits are interesting now if you look at all each one of these orbits individually they're they each tell their own story some of them including Pluto exhibit chaotic motion fundamentally unpredictable this is actually really neat we can't predict the orbit of Pluto 500 million years into the future we know we have some statistical idea but not the exact orbit itself but if you were to examine each one of them a uniting feature that you would find is that each of these orbits are gravitationally tethered to Neptune they have the shape that they have because Neptune says so so to speak right and one of the kind of interesting things that you can almost see by eye here is that at perihelion at closest approach to the Sun all of these orbits hug the orbit of Neptune why is that if there's a simple explanation gravity is a conservative force which means that if neptune perturbs you right kicks you on this really long elliptical orbit you must come back to to the place from which you started so these all of these orbits evolve chaotically in time but they're all gravitationally tied to the orbit of Neptune so imagine the surprise of Mike Brown and company in 2004 when they found an object called that they that we now call Sedna right this is the orbit of Sedna and you don't have to be a sophisticated astronomer to kind of realize that something is something is wrong right first of all at aphelion at farthest approached from the Sun Sedna thousand times as far away from the Sun as is the earth so it's really really out there orbit is really elliptical but the really staggering thing about Sedna is that its orbit is not elliptical enough okay look at the closest approach at closest approach it doesn't go anywhere near Neptune okay that's pretty pretty remarkable and strange why because Neptune could not have them placed Sedna into its orbit if they never see each other so to speak then in fact they never interact and you can demonstrate this on your laptop right you can you can code up the gravitational equations of motion and just evolve the system forward all that will happen to Sedna is it'll just keep going round and round on it's highly elliptical orbit and the orbit will really slowly rotate but that's it so Sedna was the first hint in about a hundred and sixty years that the solar system has still has some tricks up its sleeve and the distant as we unveil the Kuiper belt as we hadn't veiled the most distant orbits that we we know of some interesting surprises are going to appear now for a decade Sedna was the only example of a so-called detached Kuiper belt object detached meaning that its closest approach is nowhere near the orbital radius of Neptune but in 2014 a team of two astronomers Chatt Trujillo and Scott Shepherd announced the discovery of Joe Biden orbiting the Sun the Sun and this is Joe Biden's orbit right so this object which they nicknamed Joe Biden also never comes anywhere close to the Sun in fact at closest approach it's even further away than said it's at 80 astronomical units it's really weird in in science if you have one data point that's weird you tend to ignore it if you have two data points there's we make a really big deal out of it because it takes two points to to draw a line I think that's why so this was really the inspiration for our for our work the work that that Mike and I have done over the last three years or so and it was F in fact with this paper by trujillo and sheppard that mike whose office is only couple down a couple doors down from mine so he didn't it wasn't a dramatic stroll but anyway he would this paper in hand he came into my office said this is really weird we should figure out what's going on so we looked into it and here's what we found effectively immediately we found that if you zoom out in the solar system and if you only concentrate on the most distant orbits which include Sedna and Biden then what then they all exhibit a really interesting clustering right all of them roughly lie in the same plane you could almost put a piece of paper through all of those orbits and equally as dramatically they all point to the right okay so I know I'm gravitationally attractive but not attractive enough to deform all those Kuiper belt orbits so this is this is really weird if orbits are clustered that way something is doing it right this is in stark contrast with the rest of the Kuiper belt where orbits were facing every which way something is gravitationally confining this set of distant bodies so what can it be right well it can be a number of things okay you could say first of all the number of ellipses in that previous slide was not that big it's like six okay and maybe you just randomly chose you know it just so randomly happened that the six most distant orbits that we know of are all pointed in the same direction could be a coincidence fortunately we can calculate the statistical likelihood that that's the case and it clocks in at about zero point zero zero seven percent okay so it's not exactly a great gamble could it be because a star passed near the solar system four billion years ago and kind of perturb these distant orbits into into an aligned cluster if you make that argument then that star would have passed by the solar system really recently okay and the kind of rate of encounters with stars is incompatible with that idea why because if as it turns out if you take all of those orbits that are all pointing in the same direction and allow them to evolve forward then they differentially process it will all come out of this confinement in only a hundred million years a geologically short time so something is keeping the orbits confined right now as I already mentioned if you talk about planets beyond Neptune you're kind of chances are you're crazy so we spent the first year of this project ruling out every possible you know every possible other mechanism that could have caused confinement so I think my favorite model from our real of out takes is a model where we thought maybe the distant Kuiper belt actually has enough gravity where all of those pieces of debris are creating this mean gravitational field which is self confining and turns out that would even work if there was ten thousand times more debris out there than we know there is so so cool it's a cool calculation but turns out turns out to be wrong so having exhausted all reasonable all normal kind of models that we could come up with we said okay what if we join the land of the bloggers and you know consider the existence of a planet because after all you know the only reason why why we hesitate with with introducing planets is because it's failed so many times after the very a got it right something that we immediately discovered is that you run into a problem when you say okay we're going to introduce a planet into our solar system it's not clear where to put it right Oh or it's not even clear what its orbit should be so the thing to do is to make it up right so we thought okay what if I don't know all of these orbits face that way what if we just introduce a planet into the cluster of the orbits maybe that'll keep them confined now the good news about this type of calculation is that you can pretty much do it on the board you can do a similar thing to what live area did so so for the rest of the talk I want to go through this in just painful detail the really the important parts are these three terms here I'm not really going to go through you know I once I was gave this talk at a math department and I made the similar joke and they're like no no no stop this is the only slide that makes any sense so actually I will say this about this calculation with this calculation you can you can immediately find out a couple things if a planet is causing the confinement that we see then the planet must be at least 10 Earth masses that's something that comes out of this relatively simple set of calculations and another thing that you know is that the planetary orbit must be eccentric you can't do it with a typical solar system type you know circular orbit now the good news about 2016 is that it's no longer 1846 despite well so so anyway it's no longer 1846 is what I keep telling myself and we can in fact use the vast computational resources that are available to us here at Caltech in fact the supercomputer that we use the one hosted by the GPS division is literally beneath me it's two floors below my office so it was so this is what we did we considered the following evolutionary picture we thought if the solar system started out with a ninth planet that had an eccentric orbit and about ten earth masses and we started out with a Kuiper belt this this field of debris which was initially completely random right was occupied all of these eccentric orbits that went every which way will let it evolve self consistently for the lifetime of the solar system four and a half billion years then would it produce the pattern that we see and so you can judge for yourself this is the simulation not in real time it takes like weeks for this to to compute and what we did is we iterated on the parameters of the planet we tried many many different cases this is one of the the better outcomes and right about now so we're about two and a half billion years to the solar system's lifetime right about now a pattern begins to emerge where you can see that the orbits are starting to cluster on the opposite side of the planet good right I'm not crazy right you guys see this - certainly right typically the orbits are that are anti aligned with respect to the orbit of planet nine are the ones that survive we now have a pretty good understanding of why that is and as it turns out the physical mechanism is is that it that of mean motion resonance it's actually the same mechanism that keeps Pluto stable even though Pluto's orbit overlaps Neptune's orbit slightly so I won't go into the details of the physical picture but just kind of empirically you can at this point we're getting towards modern day tell that okay indeed the simulation is producing a synthetic solar system that looks a lot like the real one you can do the same type of statistics on this synthetic solar system and kind of convince yourself that that you're only mildly crazy so one of the things I want to point out as we rotate the set of orbits through is are these guys see how these guys have come out of the plane quite a bit we'll come back to those stragglers later so what does this all mean this whole means that given that these are the real orbits we can use their properties to calculate what the orbit of Planet nine looks like and it looks roughly like this it's anti aligned with respects to this cluster of distant ellipses it lies roughly in the same plane as these distant orbits themselves so it's inclined with respect to the rest of the solar system by about 2030 degrees and it has a mass of about 10 maybe 15 earth masses that's pretty cool at that point we had a good story right this was I guess about a year ago maybe a little bit less than maybe a little bit more than a year ago that we had attained these results and we felt pretty confident because we had explained the existence of this clustering of the orbits as it turns out as the orbits rattle around within the cluster some of them become detached like Sedna like Joe Biden and then reattach back to Neptune so what this means is that if you were to come back to the solar system 200 or 300 million years from now then Sedna and Biden would go back to being regular Kuiper belt objects and some of those regular Kuiper belt objects would detach and be attained Sedna or Joe Biden type orbits that kind of cyclic nature is kind of satisfactory from a you know from an almost Zen point of view and then we ran into this okay so this was was a real surprise and this was actually already when we were starting to write up the paper that we noticed that not only does Planet 9 confined the distant orbits into this cluster and caused them to periodically detach from the orbit of Neptune it's also generating this type of dynamics so on the x axis of this plot what's being shown is the physical orientation of the orbit which way it's pointing in physical space and on the y axis is the inclination the extent to which the orbit is inclined right and these these curves are just the theoretical paths that the model has produced the staggering thing that you might note is just a range of the y axis it goes from 0 to 180 degrees and those that mountain of of trajectories reaches numbers that are like 120 what this means is that Planet 9 is taking some of those distant orbits and twisting them onto states that are effectively perpendicular to the plane of the solar system so when I first noted this I thought well maybe this is just a weird simulation turns out every simulation has this feature this is actually the most robust effect of planet nines dynamics I thought huh this is really odd and wouldn't it be cool if one day somebody discovered a little Kuiper belt object that was orbiting her in a perpendicular sense to the plane to the plane of the solar system that would be in direct evidence that Planet 9 really exists so I took this down the hall to Mike's office and I said look what I found and Mike said should we see what dr 30 does have said is dr 30 a street drug in which case we should take it and see what it does mice turns out dr 30 is not a street drug it's an asteroid so Mike had noticed right somewhere in the in the back of his mind that there was this discovery of a body called 2012 dr 30 which was in fact spotted crossing the ecliptic plane the plane of the solar system going from south to north I believe so it was going perpendicular to the plane of the solar system so we thought we would do the following experiment okay because this is because you have to be honest with yourself we took effectively this graph right put it on Mike's computer and then said we're going to plot all of the data that's available not make any cuts not not filter it anyhow and see if there are any objects that fall into that into that structure that appears in the middle and this is what we found we found that turns out there have been five discoveries of bodies in the solar system small bodies at 50 kilometers across that orbit perpendicularly to the plane of the solar system and they're exactly where the model is predicting them to be this is what they look like in real life right if you zoom out of the solar system as it turns out and kind of have a top-down view they look like wings on which the solar system is flying towards you but really the staggering thing is look at the orbit of this of this guy on the right and it's huge it's way bigger than orbit of Sedna and as it turns out all of them were spotted by accident by near-earth asteroid survey and the reason they were discovered was that a new earth asteroid survey Scott scans the entire night sky right it doesn't discriminate on where it's going to find bodies whereas when you look for Kuiper belt objects you typically focus on the plane of the solar system because well you want to discover something and you know that nothing is going to be on a highly inclined orbit so this was a really interesting moment in the development of our story because the model made a prediction which we confirmed 10 minutes later by dumpster diving into the data set but this was the moment really where it went from just a cute story in our minds to to I think a theory where where you can really start to believe that planet 9 is really out there so this was published in January and in August I was on a run with my with my iPhone which is also serves as my iPod and I got a call from from a nice woman who said there's huge news about the solar system this is in August ok then we they've discovered this object that totally revolutionized everything it's called niku can you come on our radio show on Friday and talk about it can you research what it does and so that you can say some interesting things about niku ok so I looked up what niku is and they had found this body in the Kuiper belt which was again individually not that significant right about a hundred kilometers across and it's tilt its orbital tilt is a hundred and ten degrees they made a big deal out of the fact it orbits the solar system on its side and I thought this is not a big deal they just discovered another one of those perpendicular orbits was really extended perpendicular orbits that our model predicted right it turns out no turns that that's not what they found they found something much more weird this for scale those blue orbits are Jupiter Saturn Uranus and Neptune and that yellow ring is the orbit of niku it's totally not extended right in fact it's orbital semi-major axes the size of its orbit is roughly that of Neptune okay so it's completely unaware of Planet nine Planet nine is so far away that it does not affect its orbit I mean an analogy would be you know that that niku is loose Nico's effect rather planet 9s effect on niku is like if you're standing next to a Marshall amp you know turned up to 11 and you're trying to make out what somebody's saying in the corner of the bar right it's just planet nines effect it's completely negligible today on the orbit of niku so we were a little bit puzzled because this is really interesting in its own right even if it's not part of the planet nine story but even if you're logical kind of intuition tells you that this is not this phenomenon is not part of Planet nine you should resist that okay because everything is always part of the Planet nine story so we didn't stop we continued calculating and here's what we found right what we found is that some of those distant orbits can be turned in to Nicko's through in the following way all right so again now this pink orbit is planet nine yellow is just a random Kuiper belt object that starts out in that type of orbital state if you let things go it will evolve in this rather unpredictable and crazy way where periodically tilt on its side then go back into the plane so we're going to zoom in right now into the solar system the biggest pink circle is Neptune and notice how every time the closest approach reaches Neptune the orbit shrinks right that's because this object is suffering close encounters with the planets and the planets are shrinking their orbit so little by little the orbit becomes smaller and smaller and smaller and starts rotating like crazy and eventually when we're done this body that we simulated again this is just this is a simple calculation all there's all that's going on is GMM over R squared it's just gravity right at the end of the day what planet 9 does is turns these really distant bodies into highly inclined members of the traditional Kuiper belt so what we realized is that planet 9 even though it doesn't have a direct effect on these objects that are entrained in the current and kind of the closer part of the Kuiper belt it has an evolutionary effect so niku used to be much much further away in the solar system Planet 9 caused its orbit to tilt and then encounters with Neptune and other giant planets shrunk it's it's magnificent orbit so we thought okay maybe mini coup is not alone in fact we knew that it was not alone because there was an object called drak which shared a similar type of orbit and we decided to look into the inclination dispersion of the Kuiper belt so again on the y-axis this is the how inclined the objects are on the x axis is the semi-major axis how big the orbits our planet nines influence starts basically on the street outside of outside of this auditorium but if you just examine what the evolutionary effects of Planet nine are as it turns out it explains every data point on this plot okay it's pretty remarkable including that thing up there all the way up there which was just discovered in September that thing is called 2016 nm 56 so this is pretty interesting right the effects of planet 9 could be felt effectively everywhere in the Kuiper belt but wouldn't it be cool if planet 9 affected also something something else something outside of the Kuiper belt turns out it does and this was work which was led by a graduate student named Elizabeth Bailey who's working with both myself and Mike and the problem that the three of us tackled is the following one okay if planet nines orbit is inclined by about 30 degrees then what we'll do is it'll exert a torque on the rest of the planets it will act to kind of misaligned very very slowly misalign the plane of the known giant planets and the Earth and Venus and Mars and Mercury from its initial orientation and the reason we looked into this is because it's been known since 1850 that the Sun is inclined with respect to the plane of the solar system by six degrees and now I'd say six degrees it's not that many degrees and indeed you would be right six is a small number compared to like 90 but 6 is a big number compared to one in fact by a factor of six that's that's the kind of math that I can do all right and if you ask yourself by what extent are the planets misaligned with respect to one another the answer is less than the degree so the Sun stands out as a weird anomaly right it's it splits spin axis right the sense into which it rotates is significantly misaligned with respect to the plane of the solar system we thought what if what if planet nine has over the lifetime of the solar system tilted the plane of the solar system by some number of degrees right what I mean a priori we didn't know what that number was it could have been 0.001 or it could have been 45 in which case we would have been in trouble turns out if you plug in the numbers that we derive for planet 9 from the Kuiper belt that answer is 6 degrees okay if you take the current state of the solar system and reverse time okay and compute the gravitational interactions that the giant planets have with planet 9 then in 4 and a half billion years the giant planets return to being exactly coplanar with the Sun right so we think that the Sun is tilted it's actually our our entire plane or the plane of the solar system that's been slowly misaligned right I think that's pretty remarkable because what it means is that both the obliquity of the Sun and the direction into which its tilted is inherently connected by the thing that's at the center of our solar system the way it's tilted is it's inherently connected to the most distant of orbits that we know of these Kuiper belt orbits and where they point and how they are tilted and that connection is planet 9 so over the last year additional objects have been discovered in the solar system they all fit in beautifully with our with our model this is sort of the new census of distant Kuiper belt objects as you can see the cluster that that's anti aligned with respect to Planet nine has gotten only more statistically significant they have even found a couple objects that point toward Planet nine that was a prediction that we made in the original paper that such objects would in fact exist and wha-la they're there okay so I'm out of time effectively I want to quickly summarize the properties of Planet nine Planet nine is on a really really extended orbit its orbital period is about 20,000 years right it's eccentricity is unlike that of any other planet in our solar system 0.6 we don't know how big planet 9 is physically but we know of a lot of exoplanets that are about 10 earth masses and those exoplanets routinely have radii between 2 and 4 times that of the earth and finally we know that its orbit is tilted by about 30 degrees what are the lines of evidence for planet 9 for the existence of Planet 9 they are now 5 right so in this talk we talked about the clustering of the distant orbits it explains that it explains the detachment of Sedna type bodies those weird objects that don't come to hug the orbit of Neptune said Joe Biden right really weird it produces those highly inclined centaurs that were detected by accident right by the near-earth asteroid survey and some of those objects over time evolved on to Niko type orbits and finally and quite dramatically planet 9 explains this long-term this long-standing question of why is the Sun spinning in a sense that's slightly misaligned with the rest of the solar system so I think that the case for planet 9 is pretty strong and we are on the observational hunt for it along with many other groups this is the top of Mauna Kea in Hawaii and these are telescopes I'm not a observer Mike as the observer so this part of the talk will be short and superficial we are using that one too to try and find planet 9 when you go inside it it's huge okay so there's the the telescope itself that gigantic metal blue thing and this is Mike and that's me right so it's it's pretty remarkable turns out you have to stay up all night but I'll tell you where it is right so I only know of one constellation because my cat is named Orion so I learned where a Ryan is turns out luckily Planet 9 is in the Orion constellation so that's the Orion constellation right here and that star in the top right corner is not Planet nine but Planet 9 is really close to it I think okay I am completely out of time so I think at this point I'll finish up and take any questions thanks very much you

Channel: caltech

Views: 75,458

Rating: 4.849391 out of 5

Keywords: Caltech, science, technology, research

Id: 5-J6gW_w_Hs

Length: 57min 1sec (3421 seconds)

Published: Mon Dec 12 2016