Episode 11: Mike Brown on Killing Pluto and Replacing It with Planet 9

hello everyone and welcome to the mindscape podcast I'm your host Sean Carroll you may have heard that one sign of an open rationally minded thinker is the ability to change one's mind to have an opinion and change it to something else in the face of new arguments or evidence personally I don't even remember usually when I change my mind about things one of the ways my brain works and I don't think I'm unusual in this is that I convinced myself that I always believed that thing that I believe right now even though I did change my mind but there's one example where I remember very vividly in science that I changed my mind from a strong belief one way to another and that's in whether or not Pluto is a planet you may have heard you may remember where you were when you first learn the news back in 2006 the International Astronomical Union got together and decided that we would no longer classify Pluto as a planet but instead as a dwarf planet this caused outrage across the globe as people school children and older folks said look we know what the planets are there are nine of them and Pluto is one of them this is you even made it into an episode of Rick and Morty the animated feature but they're on Rick and Morty the reason why puto had gotten demoted is because it was getting smaller that the Plutonians were mining their own central core so that Pluto itself was shrinking over time that's not why in the real world Pluto got demoted it's not that Pluto changed is that our understanding of the solar system changed Pluto didn't get smaller the rest of the solar system got bigger out there beyond the orbit of Neptune there's something called the Kuiper belt which is a collection of a large number of objects many many many objects some of them get pretty big it's only fairly recently that we discovered that there are a number of objects in the Kuiper belt that are comparable in size to Pluto so basically the choice for astronomers war was either to expand the solar system to include all of these new discoveries as new planets or to demote Pluto from the ranks of course there's another option which is the one that I originally believed which is you could just grand father Pluto aim right you could say the planets are the nine planets that we know about and Pluto discovered in 1930 is the last one we're gonna let into the club we've known for a long time the Pluto is small Pluto is smaller than Earth's moon but the important thing upon reflection is that Pluto is not even the most important object in its orbit around the Sun Pluto's orbit crosses that of Neptune it's at an angle it's sort of not that important dynamically speaking in the solar system so rationally there was really no reason to keep Bluto as a planet and exclude the other ones the IAU the International Astronomical Union eventually decided to just invent a new category call them all dwarf planets if anyone is responsible for this change in attitude towards the status of Pluto is today's guest dr. Michael Brown an astronomer and colleague of mine at Caltech Mike was the one who led the team that discovered these other large Kuiper belt objects that are now joining Pluto in the dwarf planet Club he's received a lot of scorn for being the person who demoted Pluto but he owns it rather than denies it Mike's Twitter handle is Pluto killer and his book is called how I killed Pluto and why it had it coming that's actually the book that I read that finally changed my mind as a scientist it's important to be rational to try to understand things to categorize them properly and when you face up to the evidence Pluto does not belong in the planet club these days Mike is trying to make up for what he did to the solar system by finding a new planet he and our colleague konstantin batygin a Caltech claimed there is evidence in the motion of known Kuiper belt objects for a new planet out there far beyond the orbit of Neptune which they have dubbed planet 9 just to remind us that Pluto is not one of the planets we already have you can make up your own mind these draw numbers have made up theirs today we're gonna figure out why we think the polluter doesn't belong and what that tells us about the future of understanding what's going on in our solar system so let's go [Music] Mike Brown welcome to the mindscape podcast thanks for having me so you're technically an astronomer but you're in a planetary sciences department here at Caltech like what do you tell people you are when you meet them on an airplane so I will say if if someone says what do you do I say I'm an astronomer but my official title is professor of planetary astronomy so I get to kind of have it both ways but I'm an astronomer who looks at planets in our solar system yeah you don't look at stars or galaxies like a real astronomer you know I they get in the way and I have to somehow figure out ways to ignore them but but I look at the real planets how did you get interested in that what was it what that's the imagination it is not what I thought I was going to do and I when I went into to graduate school to be an astronomer I I went to Berkeley for graduate school and I went to Berkeley because I wanted to work on the most distant galaxies known to man and you made a terrible mistake yeah so these these most distant galaxies at the time where the goal was to find things at a redshift of 3 which is funny to people who know these days that like people are finding things I don't even know how much further away these days but at the time that was that was the big quest find things that redshift of 3 one of the people doing this the best in the in the world was high-spin read at Berkeley and so I went to Berkeley to work with high-spin read I spend rad had a hobby of looking at comets in addition to looking at galaxies and he just he just liked he I'm not sure why actually his wife claims that the reason he'd like to look at comets is because he couldn't tell the difference between galaxies and comets they look the same in fact today we didn't even know right nebulae yeah well so I back in the day wasn't that long ago so we did actually but he would take spectra of comets took the composition of comets and he he always tried to get his grad students interested in studying comets in addition to galaxies and he could never get anybody interested because at the time and it's still sort of this way at the time in astronomy there is a rank order of who is the coolest and who is the least cool and the coolest kids are the ones who study the very most distant things that's what I wanted to do so if you study very distant galaxies super cool if you study nearby galaxies you're probably okay if you study stars and our galaxies you're kind of a loser and if you study planets or anything in our solar system like why are you even there exoplanets are cool but like planets that are in actual our solar system yeah so so at the time there were no known exoplanet so so even the fact that exoplanets have now have made nearby things because they're exoplanets are closer than distant galaxies so now the the ranking is a little bit different but at the time if you study planets you're you're a loser so he forced his students to study comets for one summer before they could look at galaxies because he just wanted them to you know get some work done for a hazing ritual yeah so I so I did mostly I wanted to work on comets but I worked I mean galaxies it worked on this comet stuff and then a moderately bright comet came by at the time and we went up to the telescope Lick Observatory to study it and I remember this moment forever we were we were looking at comet Austin I can't remember what year come with Austin was looking at comet Austin through the telescope getting a spectrum it's coming out we're seeing the composition and I walk out into the dome of the telescope and I can I can sight up the barrel of the telescope and I see the comet there in the sky yeah and that was it it was like oh my god this this is not an abstract thing like a distant galaxy with coordinates that we're measuring this is that thing in the sky and and I was I was stuck since then I have always your heart beat a little bit it really did so I from my for my thesis my PhD thesis I studied Jupiter and its moons and I would be there the telescope and I would get out my binoculars and stand outside and look at the moons and see the same thing I was seeing and it's just I I love that visceral feeling that that what I'm studying is actually real as opposed to this very distant smudge those are also real by the way less real they're further ok so yeah you can't see them almost everything I've studied these days I studied some pretty faint things but at the time they were all bright enough that you could take out your binoculars and see them and that was pretty cool and you mentioned spectra I mean one of the things that well I was an undergraduate astronomy major I don't know if you need to think but I have no degrees in physics all my PhD investors agree are both in astronomy all right I forgotten it all by now but one of the things that absolutely was drilled into me was the ability of astronomers to take a incredibly tiny amount of data and spend an incredibly elaborate story about what they were looking at so why don't you say a little bit about like so we take a picture of a comet what does that tell us how do we get information about yeah so it's the for the studies that we were doing in particular it's it's the it's the spectrum you take a the Comets up in the sky you collect the light from this the comet you you stick it into a big elaborate prism and you split it up into all its colors and all of the chemicals in the comet in the atmosphere of the comet and that coma that makes a comment a comet each one of them has a different fingerprint of basically colors that it emits and so we were we were simply trying to see what all the the chemicals were in in that coma by looking at their very we had a very very very fine spectrograph it's called you know elaborate prison where we could we could really break up the light into incredible number of colors and we could really in very detail see not just what the chemicals were but they slightly change their characteristics based on their temperatures and their velocities and so we could we could map out all these things just by looking at that one little spot because these comets are moving around the Sun and you're catching them not when they're at their farthest away but when they're more or less close to the Sun and yeah so there because we needed it to be pretty bright to be able to break up the light into all those components so the Comets that people tend to study in detail are ones that are pretty much the same distance away from the Sun as the earth is that's that's when they really start to get the heat up they their surfaces evaporate they get all that stuff in the atmosphere and that's when you can really study their details and their dirty snowballs roughly speaking that's what I remember they are dirty snowballs and then the interesting question is what is the dirt and what is the snow right because it's yes it's mostly water in the snow and it's mostly we don't know what it's mostly on the dirty part but it's a that studying the other parts of the comet or what's really done and it's not really snow there was never a snowfall on the comment its insights ice yeah yeah so you moved on though from comments to I did find it like things well so I that as my you know my PhD I studied the the volcanic emissions from Jupiter's moon Io okay as they exploded off the surface of Io and then they would go into orbit around Jupiter and then the magnetic field of Jupiter would grab ahold of them and start spitting it around and so I was studying this elaborate dance of all these objects that you could do in the same thing as actually the same instrument that broke up the light into very small components that allowed me to see here's this and here's that and here's what's going in here was that so it was just it was it was fantastic looking all the chemicals that I oh I always did yo is it really I I can say both in the same sentence you're professional okay so yeah so the volcanoes is huge volcano right on there a bunch of them a bunch of them yeah viewing stuff out into the atmosphere yeah the whole neighborhood of Jupiter is like a mess with magnetic fields and radiation and whole life and junk from IO actually junk from IO is one of the main components of the the magnetosphere that's that's going on which would make it tough to like go visit Jupiter and hang around the new spaceship this is actually why when spacecraft go to Jupiter they usually spend most their time pretty far away in fact the the Juno spacecraft that's there right now it's on this very very very elongated orbit it comes in really close but then it goes off super far away and it does that because you cannot spend that much time very close because it'll get smacked basically by stuff that came from volcanoes on Io ha okay so you still though studying things that we know to have existed so Galileo yes yes that was a long time ago that is true what made you move on to the further reaches of the solar system so in while I was a graduate student at Berkeley the very first object beyond Neptune since Pluto was discovered the first first new Kuiper belt objects 1992 qb1 second is its license plate number and at the time I remember hearing about at the time from the discoverer actually the day before I went public Jane Lew told me about it she was in an office right down the hall for me and I thought oh that's interesting but you know who cares he's a rock so yeah ice ball a big deal and very quickly it became apparent that this region beyond Neptune was full of stuff and that it was it's in a sense the most pristine region of the solar system it's not pristine but it's the most pristine it's like these things are cold they've been they've been in deep freeze since the beginning in the solar system and you can study more and more about how the solar system formed by finding these very distant things and so I thought this is this is an interesting thing to think about but the big change was when I arrived at Caltech and looking around at Caltech as an astronomer at Caltech I suddenly had access to telescopes that I had never had access to before the the big telescope at Palomar Observatory the relatively new at the time Keck telescopes out on Mauna Kea are big telescopes that are really good at seeing faint objects I made a deliberate decision to stop studying these relatively bright planetary objects because I had unique ability to study these faint ones and I sort of changed paths entirely and decided to start studying the outer parts of the solar system so let's set the stage here what the solar system looks like maybe have your planets you have your asteroids you mentioned the word Kuiper belt like what is the scale of all these things and where does the planetary system end and stuff like yeah so you know we the the inner part of the solar system most people would say the inner part of the solar system is is everything inside the orbit of Jupiter so we've got Mercury Venus and Earth and Mars all the line there and then between Mars and Jupiter is this big region of relatively small rocky asteroids the asteroid belt you know in the asteroid belt is not the star wars version where you have to dodge while you're flying through it there's now every time the spacecraft goes to the outer solar system they try desperately to fly near an asteroid so they can take a picture of an asteroid and it's hard it's hard to find them unless you try that's not what the movies ago no it's it doesn't it's nothing quite like a dangerous place as far as yeah so you could you could go through there a million times and and miss every asteroid unless you were trying hard when I was a kid I was absolutely convinced that it used to be a planet that got too destroyed somehow and I still kind of cling to that belief so apparently astronomers don't believe that the asteroid belt used to be a planet no but they but they did believe that at first so the first asteroid was discovered January 1st 1801 it was Ceres and then in quick succession three more were discovered and you know imagine how strange this was there were you could you could look up in the sky there were the most recent discovery had been Uranus and Uranus was the first thing discovered with a telescope the first you know object that we knew about in the sky that we didn't know about before found with the telescope and kind of blew people's minds well sorry Galileo and the moons right yeah okay so there were so that they were there were moons of things that were being found that's actually doing Saturn's moons Herschel discovered them I can't think of the year that Herschel discovered but you're absolutely Reynes is out there all by itself all by itself and so it actually led people to search for a new planet systematically and you know at the time there was this sort of numerology the the bodes law that suggested there should be a planet right about where it turns out the asteroid belt is because it's easy to make up numbers that make you think something might be true and so people started looking they call themselves the celestial police and they started scanning the skies actually the celestial police did not find the first asteroid there was an accidental discovery from of the first one but the celestial police found many of the well then the next three so they found three they found four in quick succession for maybe four years three years four years and they all had very similar orbits so people were looking for a planet at about this location and they find four small things okay and that was the the not unreasonable at the time assumption like well must have been a planet that exploded seamless plausible as exploded yeah something has blown up yeah so no and nothing else was found until actually don't know when the fifth asteroid was found but it was 1840s I think it was how many do we know about now Oh 300,000 maybe you know down to the size of a desk or something you know there's there's there's tiny things out there that are found and and now we know that there was no planet that formed there it in fact it's the opposite it's that a planet would have formed there but Jupiter messed with everything you know whenever there's anything going on in the inner solar system it's probably Jupiter's voice yeah exactly and I think that there's this a lesson that will we'll come back to I think you know we think of the solar system is big the planets are relatively tiny and we sort of treat them independently I think in the mind of an on astronomy mmm yeah but the lessons are over these millions and billions of year timescales there's a lot of influence on what's going on in different parts of the solar system from the planets that are there and this fact that there's a whole bunch of things in more or less similar orbits between Mars and Jupiter has to do with gravity and dynamics and how do butter does things yeah so it's so it if it hadn't been for Jupiter all these objects would have been able to coagulate together to form a planet but instead Jupiter is so close by every time an object gets close but not even really that close to Jupiter it gets a little tug and its orbit is kind of perturbed and shaken up so basically as these things are trying to coagulate Jupiter comes by and shakes them they try to coagulate Jupiter shakes I mean in the end they're never able to form a planet or the Jovians didn't want the competitions they destroyed the planet it's early it's actually possible on we shouldn't be as close minded the establishment is having some things here I've read them so good so that's the inner so let's that's the inner solar system and then we get to Jupiter so Jupiter so then there's the the realm of the giant planet so Jupiter and Saturn are the two really big giant planets you know it's funny people people have a very poor understanding of the sizes of planets because mostly they see them like on kids lunchboxes where they're all more or less the same as as you know and pretty close mercury is a little smaller than Jupiter but not that much more so Jupiter and Saturn are huge and so they these are you know so the distances we measure everything is in is astronomical units one being the distance from the earth the Sun is one astronomical unit Jupiter is at five so it's five times further from the Sun and then then the giant planets are nicely arranged Jupiter's of five Saturn's at ten Uranus is at twenty it'd be nice of Neptune we're at 40 but no it's at 30 but no okay close enough so there's those are pretty easy to remember so Neptune is the end of this realm of the giant planets but you're innocent have to we're actually not nearly as large as Jupiter and Saturn are they they are I think you know Uranus and Neptune or maybe three or four times the physical size of the earth you know they're they're big but they're not I didn't think they were that small yeah they're really kind of small Jupiter Saturn huge Jupiter Jupiter is as is 315 I think is the number of times more massive than the earth Neptune is about 17 times more mass than the earth and they're all gas giants so doesn't mean they're all gas or there's little rocky core so the big ones well so this is actually the one of the prime reasons that the Juno spacecraft is at Jupiter right now in orbit around Jupiter is trying to answer that exact question we think probably that they all have rocky cores but we don't know for sure and we're we're trying to find the answer that with with these sorts of spacecraft I mean the Great Red Spot has been on Jupiter for hundreds of years yeah isn't it do people think that maybe it's the reflection of that there's some feature on the surface of the core no so the early atmosphere yeah purely atmospheric the core is the core is tiny the core so I said that the Jupiter way is about 315 times more than Earth the core might be 15 Earth masses of that so it's really a very tiny fraction a critical fraction that actually leads to the formation of Jupiter itself but but in terms of what's going on with Jupiter it's actually a pretty insignificant chunk going on so that's Jupiter and Saturn is very much like a slightly smaller version of Jupiter Uranus and Neptune are very very different although we think of them all as gas giants many astronomers call Uranus and Neptune ice giants so it'sit's a better description of Uranus and Neptune or let me let me step back the a good description of Jupiter and Saturn is mostly gas with a little bit of core right Uranus and Neptune are mostly core with a little bit of gas okay it's not like you could stand on their surface and it's not like they have a solid surface in the chords this weird metastable liquid that I understand the physics of but I don't really even understand what it means when I say it so some people say they have that that they're they're liquid and the interior not really liquid in the interior but they're very different from Jupiter's I never landed on any of these play well we've sent probes into a probe into Jupiter it it you know scratch the tiniest bit of the surface before it was imploded through the to the pressure of the United Oracle surface it didn't actually reach the hour it went and went in a tiny tiny bit people would love to send probes into the other ones in particular Uranus and Neptune would be fascinating because they're so different and we know so little about them and because planets like those seem to be very common throughout the galaxy and so it would be very interesting to learn about what those planets are more like we you know so you're insane Epton have been flown by once by Voyager one or two I forget which one went one of them diverted so it could do a flyby of the rings of Saturn and and to do that it had to go and it had to basically go up out of the solar system and never go by anymore but one of them went by earrings nepeta and that's it we we know very little about these planets which means there's a lot of room for young astronomers to grow up and study these nothing we don't know right yeah okay and then it was always true about Pluto that it was a little weird if you saw a picture of the solar system that was a little bit more accurate the orbit was way more eccentric these planets have circular orbits right ludos in a very strong ellipse if tilted compared to everything else and it's not even its own orbit it crosses inside Neptune occasionally yeah so weird so I remember before we understood Pluto's place and the rest of the Soler's it really was just considered sort of this oddball at the edge of the solar system no one really knew why I was there how it got there didn't really make any sense but everyone was like well I guess I was found kind of by accident like they were looking for it yeah so well so this is this is this is how the whole problem with Pluto and planet hood started is that people were looking for Planet X now when you say Planet X people just think that means anything out there that you don't know about but Planet X it was an actual thing there was a prediction of a specific planet from Percival Lowell Percival Lowell had letters for all of his predictions and X just happened to be the number the one that he was predicting and and the reason he thought that there was a planet out there is because he looked at the orbits of Uranus and Neptune and they appeared to be being tugged by something and of course this is how Neptune itself was found and so it the day that Neptune Neptune was found in 1845 astronomers everywhere were like oh wow the very a predicted a planet based on perturbations and dude got super famous I'm gonna do the same and so I mean literally from that day people have been saying I predict a planet I predict a planet I predict the planet every single one of them has been wrong until very recently but Lowell had predicted that there was this planet and set off to find it and he he actually said that one of the very first times he looked for it he sent a team up to Mount Wilson right here above us here in Pasadena you know you can look out the window and see the telescopes the big telescopes didn't exist yet this was like something like 1916 there was a small station up there and he said it he said go look in this location and they took a big photographic plate of the sky right there and brought it back down and he looked at it and like and I don't see this giant planet that I'm looking for so he eventually passed away but he had founded Lowell Observatory with one of the goals was to find his Planet X that he predicted and that's that's why Clyde Tombaugh was hired off the farm to come take pictures of the sky looking for this planet Clyde Tombaugh took a couple pictures and and realized that he didn't know what a planet looked like because he just looked it looks like a star right Percival Lowell thought that it was gonna be big so he thought he would know that it would it looked like it would be a big spot instead of a smaller Clyde Tombaugh said you know I don't know and so he realized that you take a picture one night and you take a picture the next night and all the stars and all the galaxies are in the same place planets move so we did that so we took photographic plates looked for things that moved and very quickly and very close to the predicted location of Planet X he found Pluto there's a little dot moving and you know this is I think about this a lot because this is one of the ways that science can get it wrong at first and then eventually correct itself there was a prediction of a giant planet at this location something was found at this location therefore it must be that thing so if you go to the New York Times headlines of the when they announced the discovery ninth planet discovered the solar system blah blah blah and in right below the headline new planet 4 billion miles from the Sun I think that's the right number I can't do mile as well but that's 4 billion miles from the Sun possibly as large as Jupiter and meets predictions and that's the meets predictions is where science can get itself in trouble so so because it was a prediction people and so people thought at first that Pluto was as big as Jupiter that is only wrong by a factor of 250,000 but it but it you know if you think it's as big a Jupiter if it were as big as Jupiter it would be no question that it's that it's a planet and its own right it took a long time for that that mass of Pluto to slowly work its way down to the realization now that it's like it's it's a tiny fraction it's smaller than our moon and it's a tiny fraction of the mass of the moon because it's just a little ice ball so it's in the grand scheme of things in the solar system it's pretty small and then there's this thing called the Kuiper belt which has a kind of interesting history of its own right like it wasn't discovered by Kuiper it was vaguely predicted by Kuiper so it was named after Kuiper I think this is a long-standing and good tradition in astronomy that the it was basically named by those people who found 1992 qb1 which was I would say the second Kuiper belt object after Pluto being the first but we didn't know at the time and they said possible Kuiper belt object and they named it after pepper because Kuiper had written a paper that suggested that possibly there is this belt of ice balls out beyond Pluto they said at the time out beyond Pluto that's a source one of the sources of comets that come into the inner solar system the the Kuiper paper was really nearly a throwaway it was not a very detailed calculation or a really much of prediction but it was you know Kuiper is a large figure in planetary astronomy so I'm actually very happy that it's that it was named for him there people who argue oh that was the inappropriate name it should be called the blah-blah-blah-blah-blah but it's not should be as the the discoverers named it and I think that's I respect the naming of the discovery absolutely and it's different than the Oort cloud which we've heard about in terms of where comets come from also so why do we need more cloud and a Kuiper belt because there are two flavors of common one flavor of Comet comes in basically in the disk of the solar system and we see a lot of comets that are that are basically on the same types of orbits as all the planets are tilted by a little bit but not very much and then we see a second set of comets that come from everywhere all directions equally with no no preference those come from the Oort cloud and cloud because it's it's this uniform very distant cloud around the Sun and the Kuiper belt belt because it's a it's a a Taurus of material out beyond Neptune just like the asteroid belt is mostly stuff that's in the plane of the solar system the Kuiper belt is the same way and are these really two clearly distinct populations do they kind of blend in well so this is a an active question that we would like to know the answer to they they probably come from the same original source but we don't we don't know very much about the transition from the Kuiper belt to the Oort cloud I used to think I did and now I know less than I used to science yeah it's true so so the Kuiper belt is as we're continuing our tour of the solar system so Neptune it's the the edge of the what we know of as the the realm of the giant planets and then out beyond Neptune there is this belt of icy material if it is that is completely analogous to the asteroid belt it's not the same as the asteroid belt it's icy instead of rocky but the reasons for it the way it behaves are exactly the same the reason there is a Kuiper belt instead of a planet beyond Neptune is because Neptune messed with stuff Neptune did the same thing to the Kuiper belt that Jupiter did to the asteroid belt there would have been a planet beyond Neptune had Neptune not formed fast and then shook up everything out there and didn't let it form into a planet so there's no planet out there there's just a belt of debris basically that never never got a chance to form a planet and some of the moons and things of the planets we know about in the solar system might have been captured from the Kuiper belt so the movies of all hypotheses yeah so the moon's the moon's that you generally know of like the big ones and like the Galilean satellites Titan around Saturn those all formed in place so those are all those are all part of the the planetary system but but all of the giant planets have what's called irregular satellites regular meaning that the regular satellites are in the plane of the planet there they rotate in the same direction as the rotation of the planet so they're they're all part of that initial disk but they all have you know it almost sounds like the Oort cloud that I was talking about they all have these clouds of small moons around them that are just going in all kinds of crazy directions and those are absolutely captured from the Kuiper belt or from the region where the Kuiper belt got started to begin with some of them were probably probably captured early on before there was even a Kuiper belt but it's the same stuff it's the same icy things that are out there okay all right good so I think that more or less finishes our tour we're able to catch up where Jane Lew I think it was had discovered a new this new yeah object and then what year was that 1992 that's why it gets that license-plate number of 1992 qb1 okay and is that in a similar orbit to Pluto or similar size it's about 200 kilometers across so it's small compared to Pluto which is about 2,400 kilometers across and it's it's does not have the same sort of orbit as Pluto it's a little further away further out it's a it's a little bit more circular than Pluto is what we now know is that there are several different classes of objects in the Kuiper belt there are many many many many objects with orbits just like Pluto and an orbit just like Pluto I don't mean it's exactly the same orbit I mean it is it comes inside the orbit of Neptune it's tilted by you know anywhere from 0 to 30 degrees it's elongated like Pluto is elongated if I if I if I drew a diagram of all those objects and put Pluto's orbit in there too you could not distinguish so there's one flavor that's like that they're a little bit further out there's a flavor of ones that are like this 1992 qb1 they're a little bit more circular a little bit more they don't cross the orbit of Neptune across to cross the orbit of Neptune and to live you have to be on a very special orbit on a resonance it's called so Pluto and all of these other objects that are called blue Tino's Latino yeah that I think is a good name to all of those objects Neptune they go around two times the Sun they go around the Sun two times precisely for every three times Neptune goes around the Sun so they're locked into this very precise dance that they are through complicated gravitational mechanism they're forced to be locked into that they can't escape it but by being locked into that they never come close to Neptune so they're there every time they cross the orbit of Neptune Neptune is on the other side son so actually Pluto comes closer to Uranus than it ever does to Neptune crosses now and it's another example of this sort of gentle but crucially important dynamical influence that the planets have on each other and random objects in the solar system can't be in any old orbit there's certain orbits that are happy to for a planet to be in yeah and good so but this is uh this discovery of more Kuiper belt objects this is somewhat your fault or in Celtx vault anyway for giving you telescope yeah something so uh so yeah so this is when I when I started here there were boy I probably when I started as a young naive assistant professor there might have been a hundred known Kuiper belt objects okay which is you know going from from one in nineteen ninety to two-hundred was a lot of work for a lot of people and I and I realized this is this is going to be big I want to I want to get into this and so I started doing a couple projects studying the known objects and what I really got excited about was the realization that that it was very clear it was it was obvious to people who had looked carefully at it that there would be some large Kuiper belt objects out there they they might like large I mean Pluto size bigger than Pluto size we didn't know but that that Pluto was not an outlier it just happened to be the one that was found first by Clyde Tombaugh but there there should be other things very much less like Pluto the hard thing is that finding objects that the small number of large objects is a lot harder to find than the large number of small objects the the the analogy I used to always make when I was doing this is that if you you know if you go out into the ocean and you get a big net and you scoop it you'll find a ton of small fish but you're probably not gonna get a whale okay finding a whale is a lot harder that analogy you you have to go sail all around so we didn't have a good way of you know we didn't have a big net astronomers of the time we're really good and they were they're just developing these electronic detectors this the CCD that everybody now has in their their cameras we're pretty new then and they're pretty small if you remember your first digital camera might have been one of those like 380 by 500 pixels that was you know tiny compared to what we have now astronomers were the same way we could we could only look at a tiny area of the sky but these things were so good this is late 90s late 90s so if you wanted to cover large swaths of the sky you couldn't with these these digital detectors so I actually I did one of the very last projects I think with photographic plates that I'm probably the youngest astronomer to ever do a project using photographic plates that might actually be a true statement I'm not I'm not a hundred percent sure that's true but I used this old telescope at Palomar Observatory which had been built at the same time as the big 200-inch telescope it's the the 48 inch Schmidt telescope had been built basically to take widefield pictures of the sky to help the 200-inch know where to look right what was interesting in the sky and there are these famous at the time the these these famous sky pictures that you could go to any astronomical library and they would all have drawers that you would pull out and get the the Palomar prints for that point of the sky and you could see what was in the sky now you can get them all online and it's less fun but at the time if you were gonna look at something you would go library you'd pull out the print you would take a picture of it because you're about to go to the telescope when you need to make sure you were looking at the right thing they had these you know Polaroid cameras designed specifically to you Mountain it here and you could take a picture and you'd walk back with your picture of where you were looking in the sky you're finding chart we called him now you know kids these days they just look on there they're through this and their Twitter yeah but it was it was it was pretty fun back then so it was built to do that sort of thing and it was nobody was doing things with photographic plates anymore so it was spending a lot of time just sitting around doing nothing I don't like it when telescopes sit around and do nothing makes me very upset so I realized that I could use it to take pictures of vast areas of the sky the disadvantage is photographic plates are not very sensitive compared to digital detectors and so in a the the the differences in about a half an hour of exposing a photographic plate on the sky I can see things about the same faintness as I can now from the same telescope that's still being used but with digital detectors in about 30 seconds okay so so it was a lie you're the last one gainfully inefficient but that means I could cover big areas of sky so so I spent a couple years doing that and I and and just sort of caught the bug like I really was pretty convinced that we were gonna find something big you just hate bring this guy you're just looking all over the place we didn't have enough time to paper the whole sky and so we had to pick word of paper and so we went we did a swath right along the the clip take the plane of the the planets and we know if we look up in the sky and you see where the moon is and where Mars is and where Jupiter is they make this line across the sky that's the line across the sky that we looked at okay and we looked a little bit of a little below and went along there and spent three years and it was pretty exciting because we found not a thing zero literally zero there was there were no objects in the sky bright enough that we could find them in that part of the survey that we did turns out had we wait so I tell you we looked at the ecliptic and we looked a little bit above and a little below had we gone 50 percent more below or 50 percent more above we would have found things back in 1998 okay but we didn't know that at the time it turns out the bright copper belt objects are preferentially above and below the ecliptic not on the ecliptic who knew so we didn't find anything but but I just it just really reinforced to me that this is something that you just we just needed to do somebody needs to go out there and cover the whole sky photographic plates were a little bit of a pain but but it this was right about the time when the the digital detectors were getting better and bigger they weren't great but you could start you could kind of string a bunch of them together it's kind of like you know taking a hundred of those 580 by 300 camera and and mounting them all on a big board and pointing about the sky I mean it was his sort of kludgy as that yeah but in the end we could cover inefficiently still but we could cover vast parts of the sky and so it took about six more years seven more years to cover the whole sky but we covered the whole sky - much better than we could do with the photographic plates and slowly as we were covering the whole sky we would find we found a lot of moderately big Kuiper belt objects I'll say moderately big to me is a 500 kilometer object in the sky which is kind of cool you you know you're sitting there looking and you're in your office looking at the images from the night before and suddenly you see this thing that's a big chunk of ice that no human has ever seen before and he literally billions of miles away yeah it's pretty hanging out in the middle I still get a charge every time I find one of these new ones but but every once in a while and actually more as we get got further and further off of the ecliptic there would be one that you would you know you're just looking through the data and you'd be like oh oh oh and you know I would do quick calculations of how big it was how far away what was going on and it was pretty cool because we would find it started out we found one that was half the size of Pluto we thought that was pretty good that's pretty good we didn't know how big it was at the time we we thought maybe was gonna be bigger than Pluto but we've learned later is about half the size Pluto it was the biggest new thing that had been found at the time it was the largest new object that had been found since I think it still is true the largest object found in the solar system since 1845 ok well other than Pluto I guess large oh that's when we found air I was felt like I used to say that phrase what was I talking about I was talking about Eris when a founders which is lighter and it's not actually the largest so I was wrong but so at the time 1845 it was like the the it was the largest objects found since Pluto how about thing that's pretty good that was good and we found you know once time went on we'd find one that was slightly bigger like 3/4 the size of Pluto they just they just kept stacking up and it just by chance we found the smaller ones first and the bigger ones next and then one of the last ones we found was in fact eros eros was this one that I remember seeing it on my screen when I first saw it and it's it's it was moving very slowly across the screen and it was really bright and my reaction was we're all good what did I do wrong this time because you know 90% of your best discoveries yes yeah yeah maybe 95 maybe 99 percent I mean I make a lot of really exciting discoveries and most of them I've had some really great theoretical ideas too yeah so same thing so I was like what did I do it's it's moving slowly our typical sequence was we would take an image every hour and a half we would take three images over the course of three hours and see how fast the things were moving so I thought you know what what if I just screwed up and I accidentally took them every 10 minutes and I see this thing not moving very much it's because it's actually an asteroid really close by moving fast that's why it's bright what did I do wrong I went and checked everything I'm like well that actually is right oh that was right - oh that's right - and I was like it's real Oh so I called it my wife and I said I just found a planet because it was obviously as big as Pluto yeah and if Pluto is a planet right it's pretty clear that this thing was a planet Eris the Eris he didn't name it that I did at the time I did not name it that because it didn't we we had code names for all the things that we found at the time that we would talk about just because we needed you know the first thing that it was called was the the name that the computer gave it which was so I can't believe I can't even remember this one anyway some string of letters and numbers most of which used to mean a lot to me and now I can't remember but we gave it code name zina which one reserved for something something bigger than or your princess like thing yeah something that was I'm soaked you know what the idea being that people had always talked about Planet X I wanted an X I thought you know be nice to have an X I wanted to have it you know good mythological name and so okay so it's TV mythology but let Pluto was named after owed you know a cartoon dog so that seemed no content that's not actually true but it's it's mostly true and then there were you know there were there were not enough female planet names and so I thought good what if you wanted a X mythological X female name choices are limited you can't good letter you cannot do better it wasn't awesome we found a satellite there was an obvious name for the satellite satellite was Gabrielle so that's what we called it for the first the the time while we were still studying at before we were we were working on our papers to announce it to the world by the time it got announced it still didn't have a name so I told I believe I told one reporter that we called it Xena and that story got out and everybody now knows the lead right there for many years it was mostly known as as Xena or the other official license plate was 2003 you be three one three that was the International Astronomical unions license plate number clearly the stuffed shirts at the International Islamic Lee Union I'm not gonna let you get away with Xena as a long term name for an important celestial object yeah yeah probably not although it's an L terrace so notes eros which is have to say a fantastic name it's a good so we didn't get to name it they they they held off on allowing us to name it until I could decide what it was right there were some people who were pushing very hard that it be called a planet when we announced it we said 10th planet because I figured I don't even at the time I did I did not think Pluto deserved be a planet and so I didn't actually believe the arastoo's ever be a planet but I'd like look if you guys are gonna call Pluto planet I'm gonna call this planet and the worst that can happen is you can say no it's not and then Pluto doesn't get to be planet either so I you know it's win-win for me so we call it we call it the tenth planet there were other people who were very adamant that it should be classified as a planet and other people were like no way that's ridiculous and we just got to hang out and watch the arguments go but it meant that we couldn't name it because if it was a planets well nobody knows how different and it's yeah if it's just a regular Kuiper belt object there's ways to name it so so look when Pluto was officially relabeled uh yeah we're playing it not a planet billions of hearts were broken yeah people got very upset you're you're considered to be a bad person because of all this and yet you kind of revel in that you don't back down you lean into it if they say today yeah yeah what it what is the best sales pitch for saying no we shouldn't call these things planets or at least we shouldn't call Pluto a planet why can't we just let Pluto be a planet and call these other things post Plutonian objects or something like that so so you will often hear arguments from astronomers who are tired of talking about this that it doesn't matter Pluto is Pluto no matter what you call it bla bla bla it's semantics it doesn't matter and and I get what they're trying to say but I actually disagree completely with the statement that this is just semantics it doesn't matter it's not semantics though the word planet the word that you use is semantics but it's but it's classification right and classification is what we do as scientists to try to understand phenomena in whatever field we're studying and bad classification leads to a lack of understanding of what you're going on you you could be somebody who studies birds and you decide to classify them all and you might classify them as you know seabirds and and birds that live here and birds at burrow in the ground and all these things and you know you would study them in different ways than that because or you could be scientist who studies birds and you could say I'm gonna study them all the ones that have blue on their heads and you know that's a classification and it's a perfectly valid classification it just not doesn't mean very much latch on to anything it does allowed there eight world doesn't late lead you to ask any important questions and so when you look at the solar system and you think about a classification in the solar system the classification should lead you to the important questions so if so if you had the eight planets plus plus Pluto as a planet the main question you would ask about the solar system is what the heck is Pluto tweet there it doesn't it doesn't you you can't ask any questions about because planet the word is the classification it is sort of meaningless there are other people who suggested that you should have all round things should be planets which would include Pluto and Eris and 200 other objects in the Kuiper belt the moon the moon many moons so there there are many things and and it's true they are different because the the being round means you have enough gravity that you have pulled yourself into a sphere which is very different and so the question you would ask yourself about the difference between round things and not round things is why are there round things that seems like the obvious question well I just told you it's gravity we know the answer to that actually if if instead you classify the solar system and if you were to say there are four terrestrial planets rocky planets Mercury Venus Earth Mars there are four giant planets already maybe two giant planets and two ice giants Jupiter Saturn Uranus Neptune between Mars and Jupiter between the terrestrials and the giant planets there's an asteroid belt beyond Neptune there's a tie per belt even further out there's a Nord cloud that leads to profound questions and the profound question the obvious question is why and that why is the main question that we as planetary scientists are trying to answer how did the solar system get to be the way that it is and by classifying it correctly you you are led to that question and but and by not you know we as scientists would still ask the right questions but I still feel like it's a public disservice to pretend that we're gonna call all these other things planet it doesn't it doesn't help people understand what the solar system is like it I would like people to understand what the solar systems like and before we forget what is the definition of a planet because the definition I mean there are people like God just stupid definition and like okay yes it is a stupid definition the fact that there is a definition is is stupid in astronomy I mean can you think of anything else have a phenomenon in astronomy and object type in astronomy in the sky for which there is a definition that somebody has to check is this value a planet has a three-part definition that you have to fulfill all three parts and the lawyers can argue about whether you lay down this tell us through the eye you says you have to be around so that's the last one you have to be an orbit around Sun so this says people get confused by this one - yeah the definition of a planet in the solar system is that you have to be in orbit around Sun I mean I felt part of the motivation for going through these arguments was that we thought we would be discovering planets elsewhere the only motivation for this argument is to deal with Pluto ok literally that if there is no other reason for this definition of planet and then we know how to be dealt with one way or the other so the definition is in orbit around the Sun round big enough to be round and then the third part kicker which is where all the arguments come about and and it's phrased terribly but it's I understand what they're trying to say it has to clear its orbit clear its orbit of other stuff of other stuff right so the you know instantly the amateur astronomical lawyers say well so Neptune is not a planet because Pluto and it's you know yes it's because it's because the the it's it's not because empty is not a planet it's because the definition is both poorly worded and a bad idea to have to begin with what so what the but there I mean what they're trying to say is that the planets are the gravitationally dominant things out there and it's super easy to make a calculation of something that you would call gravitational dominance and see that the eight planets are incredibly different from everything else in the solar system they are big dominant bodies that kick around everybody else you know you could say the argument is the the planets all the things that are not planets are sort of flitting in and out of the orbits of all the planets getting kicked around by the planets and the planets are the ones doing the kick in and nobody kicks planets around right that's that's a pretty good definition and so by this definition we have the eight planets and Pluto is just one of the various dwarf planets in the Kuiper belt and as you sort of alluded to alternatively the only sensible alternative that didn't sort of just make Pluto a thing all by itself would be to have dozens of planets and hundreds hundreds in beauty to discover of many many plans yeah this is what's what I always find funny when people like you just hey Pluto so you don't want them to be like dude do you know that if if I used your definition I would be the biggest planet discover in human history do you know that and the answer's no they don't know that you just don't want to be like someone asked me back in that first year when Xena was still being generally called the tenth planet I was doing an interview and somebody said you know what does it feel like to have discovered the tenth planet I stopped and I thought about it and I said you know how it feels it feels fraudulent you know Impostors in it no I wouldn't even say it's imposter syndrome I'd say it actually feels fraudulent and that it's soso Herschel you know opened up his brand-new fancy telescope pointed to the sky and found Uranus this thing that's 17 times more massive than the earth you know big chunk of the solar system the very a did calculations on how the orbits were going realized it was something else out there had someone pointed telescope and boom there was Neptune those are those are significant things in our solar system and if you removed any of them our solar system would be a different place if you removed eros or Pluto or any of these other objects the solar system exactly the same place these are these are you know they don't define the solar system in the same way so it just it really did feel fraudulent to pretend that this was a major part of the solar system and you really had to pretend if you wanted to call it the tenth planet but the good news is now we're basically done right we have the Kuiper belt we have eight planets and there's no more planets ever to be found we're not older sister yeah so we're not done so you're saying there could be other I landed so here's what I'm saying there is at least one other planet I'm not saying could be both I'm not saying might be I am I am as close to a hundred percent convinced as you can be in this business that we have found gravitational evidence for a ninth planet if you recall I am about the five hundred and seventy fifth person to say this since 1845 it's an long distinguished lineage yes it's not distinguished it is really scary to say this it was it was scary for a for me and my colleague who came up with idea konstantin batygin he and I came up with this idea a couple years ago and we were very reluctant you know we started doing the calculations we started seeing what we seeing and we're like god it really really kind of makes sense it's a planet like we do not want to be that 547 person saying we we predict a planet and we're right and everybody else was wrong but here's the interesting thing is that we predict a planet and we're right and everybody else is wrong well let's just pause for a moment before getting to the evidence that you're right I mean I want to just say again or highlight the this way that science works I mean not only do we look for evidence and so forth but we have prior beliefs right and part of those prior beliefs are colored by history and what has happened kinda salutely and so rather than you and Constantine just running out and saying hey maybe there's a planet you say look we all know that this has been claimed before we should be extremely cautious and really make sure the I's are dotted in the T's are crossed we also knew that there were no other planets I was in graduate school when the final nail was put in the coffin of Planet X I should have mentioned this when we were talking about the discovery of Pluto and the perturbations and all this stuff is in the end the reason that Percival Lowell thought there was a Planet X is because some of the early observations of planetary positions were not exactly right and and he didn't have the precise mass of Uranus and Neptune and we didn't have those until Voyager flew by uranus and neptune so at the final neptune flyby we got the precise mass of Neptune and we did all those calculations of where the planets are and they're where they're supposed to be so there is no planet done with perturbation and I move that in in graduate school that paper came out and we all knew there were no new planets to be found and to think otherwise was heresy yeah and so of course there are no new planets and so this is this this lead when when Colleen and I first started looking at these phenomenon it was to prove that there wasn't a planet right so what kind of phenomena do you look at so it's so it's one specific thing that we eventually found it took us a while it's that if you look at the most distant objects in the Kuiper belts so most the Kuiper belt objects are in these kind of either kind of circular ish orbits a little outside of Neptune or maybe a mildly elongated like like Pluto but some of them actually are on hugely elongated orbit and orbits and go out go out 1020 times further than the orbit of Neptune and then come back so they're on these these big elipses like this if you look at the ones that go the farthest we realized something unexpected which is the ones that go the farthest are preferentially lined up in a particular way the direction that they're going when they go out the farthest is a specific direction there's no reason that should be so where the aliens put them when they left there so even if the aliens even if the aliens put them there they would very quickly untangle themselves so each of the objects in the in the whole solar system but in particular these distant ones their orbits change over time and they they precess is what it's called the direction of their orbits changes over you know couple tens to hundreds of millions time period and so all these objects are like hands on a clock that are moving at different speeds and we happen to look up and they're all aligned and so it could be you just happen to look up when they're all aligned or there's something else going on and so we sort of split into my job was to decide whether or not it could be that they just happen to be all aligned and it was a kind of sentence and Constantine started doing calculation that he's starting math if he actually started out by like writing equations on his board and he's like well what do you think about this I'm like it's like the Greek letter those are my favorite and so we we really were trying to figure out what could have done this we know a planet could do it you see that and you're like oh my god must be a planet that's kind of the last 150 years because of the D symbol to how these trans-neptunian objects are sort of there's certain places they could fit in without being disturbed by that's exactly right you're saying is simply exactly right and we didn't know the details but we kind of knew like yeah we get that there must be some some gravitational perturbation that it'll make them it'll work we know that let's like of course that works but that's that's a crazy thing to jump to initially so let's figure out what's really going on because it's not a planet and we tried really hard to make it not be a planet yeah and there's nothing else there is no other way to make those objects line up the way that they do and the story got more convincing over time so the the convincing aspect of it so so this has been two and a half years now our paper has been out planet nine Planet nine as we called it the time you secretly in the back of your mind have the name you want to get no no I am suspicious suspicious but I'm superstitious but definitely suspicious too I'm superstitious enough to do feel like if you really start to think about a name you will not find okay and so I really I honestly do not have a name which is pretty amazing to have blocked that part of my brain so I'll do this so it's a planet 9 I you know we did have a nickname like we have nicknames for everything we the nickname was fatty ok at the time spelled with a pH and it was because that was gonna that was the ELSA when I had a daughter she had a nickname before she was born I seem to make a habit of that and we had we had one picked out in case it was a boy it was gonna be fatty because that's an old family name of mine is Jehosaphat there were many jehosophat's and we always talked about naming our son Jehoshaphat but we would call him fatty because I just thought that and and we would make sure that he was like a jazz saxophonist because he'd be like fatty Brown doesn't that sound pretty good night yeah yeah so what that was what we called Planet nine at first but eventually Planet nine was such a good name that we just kept with Planet nine so two and a half years also is a little poke to people who think that Pluto's that was totally unintentional I promised two and a half years so one of the things that always happens in astronomy sure in physics everything else is that theorists are really good at explaining anything oh yeah yeah so if you felt differently yeah and if you said oh no I'm sorry I didn't mean that I actually found that instead like oh okay then I can explain that too so there I mean theories are good that's their job so we knew that as soon as we published both the observations that these things are lined up and our hypothesis of planet 9 very quickly there would be papers coming up with alternative explanations alternative physics and we were curious what they were gonna be because we couldn't come up with any and in two and a half years there are zero and that baffles me that no one has come up with another way to make that alignment I mean Dark Matter cosmic strings aliens black holes I have a dozen yeah but I write that paper okay so it has to actually point at level of that's actually what does it work yeah so no I always get the explanations as like what if it's yeah yeah but but real physics really working okay I've seen no explanation so the one potential explanation and one part that that we still worried about is the idea that it was just a random coincidence and not only a random coincidence but a random coincidence can be helped along by some sort of bias in your observations and there there are many ways that these observations could have been biased you can imagine that if you if you're saying that all of your objects are lined up in one particular way well what if that's the only place you do that for example I mean that would be an extreme version of the bias but but we worried about that and it turns out to be very difficult to do that calculation right and it has taken us in fact two and a half years to do that calculation right and I just finished the paper on the final calculation this morning literally Mazel Tov and and the answer is the probability that it's just due to chance taking into account all the biases of all the observations and everything else is a 0.1% point one four percent I think so means as possible as things happen but it it's a small number yeah so so here's what I say and paper I say look you don't have to believe in Planet nine I'll punch you but you don't have to clean an attitude but the effect is real and if you if you don't believe in Planet nine there needs to be another explanation for right and so why don't you go look for it well so we are looking for it okay so I've spent the two-and-a-half years has been both understanding those biases because understand the biases is critical to then using the observations to predict where it is so as of right now now that I understand the biases I have a very tight prediction of the orbit of Planet nine in the sky do you know where it should be so I know the path that its orbit traces out in the sky and that is not the same as where it should be that is where it should be except that I don't know where you know along the path when it should be yeah so so the bad news is were not as good as Lovera a very a said there's a planet it's right there and they literally looked one night and found it it was right at the very I said it was I got a little lucky he had a couple things going for him one is he could make some assumptions like it's a circular orbit in the plane of the solar system ours is definitely not a circular orbit and it's actually not in the plane of the solar system it's tilted by by you know 20 30 degrees okay and so does it per turbine empty it does not perturbed Neptune it's so far out is its orbit far away it's it's not a circular orbit it's an eccentric orbit centric and it's average distance away is about 500 au member of Neptune was 30 so it's nearly 20 times further away than Neptune it has no effect on Neptune or even the the relatively nearby Kuiper belt objects the only thing that affects are these very distant ones that go out into that realm and so they go out and into where it is and get a find how big is planets so now we know it's it's right around seven times the mass of the earth might be six might be five might be eight but it's not it's not that much different than that so seven times mass the earth is is again Neptune is about seventeen so it's smaller than Neptune bigger than the earth probably it's like Neptune and then it's a mostly it's it's an ice giant it's a it's mostly a core a sort of liquid Ecore surrounded by by gas so it's way bigger than the Death Star for example it's it could swallow the Death Star quite easily because I mean you must be thinking why is there such a thing out there why is it in the wrong orbit yeah that's so far away so we think we know that we we have ideas so the idea that there's an object out there is agnostic as to how it got there you know so what's our evidence for its existence its solid then we just get to make up stories on how it could have gotten there interestingly as soon as we figured out that it was it was something like seven earth masses ten earth masses and on this eccentric orbit Constantine and I both just the same light bulb went off on our heads at the same time it's like oh I know where it came from like yep me too and the answer is ten earth masses is a special mass in the solar system ten earth masses is as we've talked about the mass of the cores of the giant planets Constantine and I actually had written this paper six or seven or eight years ago now about what would happen in the solar system if instead of four giant planets you start out with five giant planets in the regular giant planet region and the answer is nearly all the time one of those giant planets gets destabilized gets a little too close to Jupiter and gets tossed out and we were interested in how that affects the outer solar system and everything else and we didn't really want once it got tossed out we never worried about it so the solar system is full in some sense planet wise planet wise yeah so you can't stick new ones inside where the old ones are and if you try they they are most likely PD ejected there's no reason why there should have only been four cores for them there should have been actually many many cores for them so probably they were cores being tossed out all the time and we never really thought about what happens when they get tossed out the idea that one gets tossed out and then gets is there's still a little bit of a waving of a magic wand that has to happen because it has to then get stabilized in the outer part of the solar system and not come back in and not go back out and so that's we think that happens when the Sun is formed in a giant cluster of other stars so we think we know how that be well you know our hypothesis is that that's how it happens but it all kind of makes sense it fits perfectly doesn't mean it's true but it but it's the idea that there was a core that got ejected and recaptured is so uncontroversial that you know when you suggest that to theorists working on the solar system like oh yeah sure yeah that's what yeah sure and once it's out there it is planned at 9:00 sometimes perturbed Kuiper belt objects and turn them into comments the government absolutely and it does something really interesting to them it does that by twisting their orbits instead of just perturbing them and throwing them in it slowly perturbed and so things that used to be in more or less the same plane as the solar system get their orbits twisted by about 90 degrees and so they're plunging into the solar system and back out again and then it drives them into the into the Sun in past Neptune and the the reason the the transition that Constantine and I took from thinking this was a cute theory that could explain things it's easy to come up with theories that explain things but you don't believe them most the time when we started believing it is when we realized that we were predicting these these orbits twisting and coming into the solar system and then we went out and realized that those things exist and that nobody else nobody had an explanation for them they would they would be found and people would just say so weird I don't know why these things are coming in and now so so our hypothesis now explains you know the the alignment some of the other detailed dynamics these other objects were like it's fitting together at that moment I mean literally the moment we did that I think both of us just kind of looked at each other like oh oh there's actually oh this there's a oh there's a planet out there and it went from just you know cute idea to holy cow there's a planet let's go find it you're optimistic about finding it you can buy find it we mean literally yeah yes I mean in the end it's a hypothesis that I am convinced is true no one else need believe it until we go see it our people basically up to me or people's coffee some of each there's a whole group of people who are desperately trying to find it because they're convinced we had a we had a workshop here at Caltech in late spring of all the people around the globe who are in search of it and exchanged ideas and where we thought it was and how to and who was searching and how they were finding it but there are people who are like so the there are the general skeptics like I think most scientists should be who probably not looked very hard at the evidence you know until you look at it really carefully you are your default it's always gonna be come on the planet and that's that's right that's the way to be and then there are the no way it's impossible I'm going to prove you wrong and they try and yeah they haven't I haven't succeeded yet but but meanwhile you're flying to Hawaii going up on top of the mountain yes big telescope yes and taking snapshots and yes to see a dot moving yeah it's what I started in 1978 with photographic plates and now we're we're continuing yet now looking for something even more distant and a lot fainter do you really have to fly to Hawaii I mean don't they have robots so depends on the telescope actually so the telescope that we're using the Subaru telescope on top of Mauna Kea is the Japanese National telescope and they require you to be there they don't need to require you to be there but but they do as a philosophical dilemma of necessity and it would be it would there's no actual reason for us to be there it would it would work just fine with us on video link somewhere else and sometimes they actually do do that but they do make us come up there which I don't I don't mind at all it's a spectacular place to go when you see a moving dot how quickly will you know and with what level of certainty that it actually is the planet you've been beautiful so I I think that if I if we found a moving dot in the in the Subaru Survey the things that you want to know are how fast is it moving because that tells you how far away it is and how bright it is because that tells you about how big it is basically if we find anything that is five or six or seven hundred au way we we can't see things that far away unless their planets basically so if we see something moving at the predicted speed and you know we won't see it that night at the telescope we bring all the data home and to have it cranked through computer but it but AC I'll be sitting my office I'll be looking through candidates and one will come up and it'll be consistent with everything and I will be 98 percent certain at that point very quickly really okay and so but what we'll do one is all assume it's real and I'll think about what I'm doing about it but the other thing we'll do is we'll very quickly predict where it should be you know this will probably be a week or two later it took us will predict where it should be that night based on what we did and we will find some astronomer somewhere in the world at some telescope and say go take a picture right here and tell me nothing to tell you why but no no it is well there you know I have enough friends who would it would do it and if it's where we predict then it is 100% no questions it is there we know it and then the fun starts because finding it is fun yeah but it's but it's actually studying it and learning about this new giant planet that you know we only have four we got a new one yeah pretty cool so we have we have our day zero things that we want to do that we'll start doing immediately well you know you killed Pluto for which we can't really forgive you but it will compensate somewhat if you find another replacement this is you know it was all suggested by my daughter about four years ago she said she said she said daddy do you know how to get people to stop hating you I was like gosh no I don't nobody knows how should i do why is my four-year-old daughter she said oh you should go find a new planet and then people wouldn't hate you anymore and I laughed and said hahaha but there's no new planets and now I realize it was she she knew what she was talking about alright well we are rooting for you Mike Brown thanks so much for coming on the plug it was fun [Music] you [Music]

Channel: Sean Carroll

Views: 21,759

Rating: 4.877193 out of 5

Keywords: astronomy, planets, pluto

Id: 9cZMFyRgx4w

Length: 77min 47sec (4667 seconds)

Published: Mon Aug 27 2018