Planet Nine from Outer Space - Mike Brown - 03/15/2019

good evening everyone thanks for coming sorry about the delays this is the first time we've tried to do this live broadcasting on the back patio so thank you for your patience welcome to our public lecture and stargazing event for March my name is dr. Cameron Hummels I'm a postdoctoral researcher here and also organized these events and there are oh I didn't grab a poster but these occur once a month they're open to everyone there they're open to the public they're free and sponsored by Caltech astronomy and the National Science Foundation the as you may have seen up at the front door we have our schedule of events for the remainder of the semester the next one I think is April 12th on the spitzer space telescope in addition we organized a number of other events including astronomy on tap which is also the schedule of astronomy on tap is on the back side of the flyer that you may have picked up it these are events that take place at a local bar in Old Town Pasadena with informal talks 15-minute talks on different astronomical topics as well as astronomy themed pub trivia that's also free and it happens once a month on a Monday night our next one is a week from a week and a half from now on black holes and big numbers so should be awesome tomorrow there's a special event called science for March that is occurring on the Beckman lawn from 10:00 a.m. until 3:00 p.m. it's kind of like a science fair with a bunch of different science booths that are that are going on you can you can show up it's open to everyone the target is anything from K to 12 as well as adults so there are science demos we'll have a booth there where we're getting to use optics to light marshmallows on fire with the Rays of the Sun which will be super cool we'll also have a solar telescope so you can safely look at the surface of the Sun and then afterwards there are a number of Ted style talks that are going on from 1:00 until 3:00 in the Beckman auditorium and I'm giving one of those too so you should come and boo me throw tomatoes so tonight's schedule will have about a 30-minute lecture from our speaker and then after a few questions you guys are adjourned we'll set up telescopes on the fields right behind us so if you follow the signs out and into the North Atlantic fields we'll have telescopes set up finally we've got some clear weather we haven't had for the last three months but there will be lots of good viewing and at the same time that that's going on that goes on until 10 o'clock at the same time that's going on we'll have a panel of experts in different areas of astrophysics and planetary science set up in here to answer your questions on whatever topic you can think of you can ask a question about space science or planetary science or astronomy or physics or whatever and we'll do our best to answer so and feel free to go back and forth between in the auditorium and out stargazing if you want and I think oh and the only other announcements are if you go on the fields there are these rules or else we get banished from the field so no litter no food no drink no smoking no pets and no high heels interestingly enough because it can puncture the artificial turf and they'll banish us from the land so for those of you wearing high heels it's really nice to take off your shoes anyway even if you aren't wearing high heels you can take off your shoes and it's really comfortable so please I encourage you to remove your shoes so we we can continue to use the fields and I think those are all the announcements so our speaker for tonight on honored to present is he's a professor here dr. Mike Brown he he's been a he did his PhD at Princeton no his undergrad at Princeton his PhD at Berkeley and he's been a faculty member here in the Planetary Sciences Department since 1998 he he gained a lot of notoriety and his Twitter handle is called Pluto killer because he he played a significant role in the discovery of many other objects in the outer solar system and the Kuiper belt that that that took away some of the shine of Pluto and resulted in the demotion from Planet to dwarf planet of Pluto but he's going to talk tonight about planet 9 the worthy successor to Pluto that's potentially much more massive but we haven't yet detected it so please welcome our speaker dr. Mike Brown [Applause] so it's uh it's great to see such a huge crowd out here I'm kind of amazed did anybody follow my advice on Twitter and go and have dinner at Pine burger before coming here anybody one person okay well you know I try to get my kickbacks from Pine burger and they're not going to be very high tonight but yeah maybe next time around so I'm gonna I'm not going to talk very much about the the old story of Pluto beginning demoted though I have to admit that it is impossible for me to give a talk without giving little subtle digs to Pluto at the same time so you'll see them I admit but we really are going to talk tonight about this this new idea that there is a ninth planet which I would not say as a worthy successor to Pluto it's a so much more massive than Pluto that that it would stomp on Pluto sad Pluto hardly exists I'm gonna tell you why we think it's out there and I'm gonna tell you how how we're trying to go about finding it and give you some idea of when we think we might find it but to tell a story I really think it's important to step back and think about the discovery of planets in our solar system and the the history of predicting that there are new planets in our solar system this goes back a long time if you go back to about 1780 in 1780 you could look up in the sky like a nice clear night like tonight and you could see all the planets all the planets were visible to the eye they extended as far as Saturn and that was that was all there was and as far as I can tell I've gone back and tried to read old historic documents as far as I could tell people really never thought very much about the fact that there might be more planets out there to be found the telescope had been invented people were realizing that there were stars that they couldn't see without a telescope people were realizing that there were things like Jupiter had moons that you couldn't see without a telescope but there's no written speculation that there might be more planets to be found and so at this moment in time William Herschel had built what was the best telescope in the world made these very very super crisp images and he was simply cataloguing the Stars he was he was making a map he would see a star he didn't write it down he'd see a star right position make a map of that and because his telescope was so good one night he was looking and he realized that something he saw was was not a star it was a little bit extended a little bit fuzzy and there are many things in the sky that are not little points of light like stars there are things that we call planetary nebulae or their galaxies or their comets or their other things so he didn't know what it was but he noted that there was something strange there and he was smart enough to go back and look the next day when he went back and looked the next day it was in a different spot the second that you realized it's in a different spot you you instantly realize that this is not some nebula some galaxies they didn't know what galaxies were at the time but it was not something external this is something in our solar system it's moving around the Sun and because of its because it's close and because it's moving you can see that motion in the sky in one night Herschel himself didn't really want to call it a planet he said you know there's a thing it's moving maybe it's a comet maybe it's something else everybody else was was trying to explain to convince him that he had discovered this new planet but he was he was reluctant just because I think it was the idea that there was a new planet it was just so hard to imagine so fast forward about 30 years and people are still trying to answer the question is it a planet or is it not and and to them the way to answer the question of is it a plan or not dependent on its orbit around the Sun planets as they all knew at the time go on these nice circular orbits around the Sun the alternative was that it might be a comet Comets if you ever look at the orbit of a comet they come in close to the Sun and then go further out and so the fact that it might have been out here could mean it's on its way back in and on its way out or it could be on a circular orbit they didn't have any way to find out in 1820 a an astronomer in Paris named Alexis boob bard who has the best title ever I I need all these every time I write a paper I'm going to use all these titles order of the Royal Legion of Honour member of the Academy Royal Sciences Bureau of longitudes actually no I know a guy who's a member of the longitudes in Paris these days it's some honorific title I need that one Academy Royal Sciences London society many anything etcetera etc so good but more importantly he was its a tables you know the exciting title here tables of Jupiter Saturn and Uranus and they were basically tables of where the planets were and the reason that you wanted to know where the planets were is because you wanted to understand how they went around the Sun and calculate how much if we could figure out where their positions we're supposed to be and what he realized here's the the key table on Uranus is right here and I mean it's astounding right oh wait okay so let me tell you why it's astounding first thing is he does all this math over here to figure out exactly where Uranus should be you know we all know it goes in a circle around the Sun now we know it goes in a circle around the Sun but it's not a it's not a circle really it's an ellipse really and it's not even a perfect ellipse because Jupiter and Saturn tug on it a little bit so sometimes it's a little faster and sometimes a little slower and that's what all this math over here does it figures out where precisely Uranus should be in the sky and he did something really amazing he went back in time here's the discovery of Uranus 1782 and he goes backwards in time 1781 1771 69 all the way back to 1690 she might ask how he figured out how to go backwards in time he found out that there were astronomers as early as 1690 who were cataloging stars and they did two things that were not quite as good they they catalogued positions of stars the telescope's weren't as good so they didn't notice that Uranus was fuzzy and they never went back a second night to see if the stars had moved so they just catalogued in one night cataloged him the next night and so in 1690 an astronomer actually found Uranus and thought it was a star and put it on the catalog Bouvard went back realized that and realized that there's no star there and and mapped its position all the way back to here the interesting thing about this table from 1690 up to 1819 is that you see these pluses and minuses and pluses and pluses and minuses the string of numbers these are how our Uranus is a way from where it's supposed to be if if his theory was perfect these should all be zero it's not perfect they're actually fairly large numbers and I don't know if any of you know any theoretical astrophysicists anybody have friends who's a theoretical astrophysicist so you'll you'll get it if you if you know these people this is what they would say okay clearly there are discrepancies here my theory is perfect it must be the bad observations those astronomers are terrible this continues to this day but he does say down here they're Mia there is all if there's an alternative possibly maybe also there's another planet out there that's pulling Uranus along in its orbit but probably not probably it's just bad data you crummy astronomers do better and and show that it's in the right spot so the crummy astronomers observe Uranus for another twenty years and it kept on being in the wrong place and by about 1840 it was pretty well understood that there must be something else out there beyond Uranus basically Uranus would go along a little bit fast and its orbit for a while a little bit slow a little bit fast and they realized it's because something else is pulling it along nobody knew how to do the math to figure out where it was though until Urbain the very a also working at the same observatory came along developed an entirely new set of mathematics to try to predict where the planet was he went to the Academy in Paris presented his paper on all the mathematics of where this planet was and they all clapped their hands and he he suggested that they go look for this planet and they know they did so nobody wanted to really look for the planet because I think this is my interpretation of what was going on in 18 1845 is that they they really were not convinced they liked his math his math was beautiful and made a nice theory and all these numbers went to zero they didn't really think you could use math to predict planets that's kind of ridiculous so they didn't want to go look he eventually sent a telegram to Berlin and got some astronomers in Berlin to go take a look at it and make in one night they opened up the telescope and it was right there there was Neptune the discovery of Neptune based on his predictions he got really really really famous overnight there's a statue of him in Paris anybody seen the Statue of Liberty in Paris what do you guys do when you go to Paris I go visit I have a picture of myself right next to the Statue of the Vario in Paris he got very very famous and astronomers immediately said you know I want to be famous so they decided to start predicting more planets and so they kept on trying a quick announcement we fixed the audio problems on the back patio so now it should be working seamlessly so if you want to go back out there and set a crowded in here you can sorry for the brief interruption and the technical difficulties sorry for the back patio people high back patio people we're talking about Neptune Oh up there high back patio people so what were we talking about Neptune various statues of laverra a famous astronomers everybody wanted to be famous it took approximately three months before the next planet was predicted because people were like okay I can do the same math the variation do the math and they figured out that well these aren't actually zeros and it doesn't exactly work and so there must be yet another planet and then it just kept going from from 1845 until when we took town in about 2015 we have found something like 25 to 30 separate predictions of planets for some reason or another and it turns out every single one of these was wrong until ours we'll get to that every single one of these was wrong and all for different reasons often the reasons that they were wrong was because the data were actually wrong the most famous of these comes from the prediction that many people know about which is from Percival Lowell who predicted what's now called Planet X a lot of people think Planet X means just kind of anything out there Planet X is with an actual prediction by Percival Lowell of Pluto here's Jupiter Saturn Uranus Neptune he didn't predict Pluto he predicted a giant planet out here somewhere and people went out and looked and found Pluto at the time and thought Pluto was Planet X when turned out Pluto was not actually merely big enough to be this thing that was the the Planet X out there and people spent decades looking for planet acts there's no planet x they realized it was the data were bad there's no evidence for Planet X there's no evidence for any other of these planets that people were finding and so by about 1992 I was in graduate school in 1992 and I remember learning about this in 1990 to 1919 we learned that there are absolutely positively or no planets no no planets beyond Neptune and anybody who says there aren't as crazy we learned that and we also learned something even more interesting is that though there are a lot of planets out there there's a lot of out beyond the orbit of Neptune all these little objects that you see out here are things that astronomers have found out beyond Neptune in this region that these days we call the the Kuiper belt they have orbits that look like this and that's much better thank you they have orbits that look like this they have crazy orbits like Pluto because they're tilted compared to everything else and it's very clear I mean in the end this is why Pluto ended up getting demoted it's because Pluto is clearly a member of this vast population as opposed to being a member of these sorts of things like this so that's that's the location where Pluto fits and so it was it was fun to have found all these new objects and here's let me just throw a few digs at Pluto just for fun just to remember here's here's the planets the real sizes Mercury Venus Earth Mars huge Jupiter Saturn Uranus Neptune there's Pluto it's really really really tiny and not only is it really tiny when we started finding these other objects in the Kuiper belt they you know they they fill in the sizes they're - there's just a ton of things like Pluto out there it really made no sense to call it a planet but what did what when we found all of these objects out in the Kuiper belt one thing we realized is that we had yet another set of objects that we could look at the way they're perturbed and see if there's a new planet out there it's just this obsession that astronomers seem to have I don't know why they're so crazy but we kept on looking and for the most part these objects in the Kuiper belt seemed pretty thing they were going where they were supposed to they they're in they're not in circular orbits but they're pretty uniformly distributed around the Sun they're in this ring here there was no hint in the early data that there was anything funny going on the first hints of anything funny came in 2003 when we discovered this one crazy object this crazy object goes way way out there it has a it's about a 10,000 year orbit around the Sun really really long and it rarely even gets close to the Sun it's a it's a bizarre object that it took us a while and at the time we knew it was strange we didn't know how it got there and we spent a lot of a decade trying to figure out how it got there and how objects like it formed it took another ten years after that discovery of Neptune to realize that something was funny was going on we found other objects like Sedna which go really far away from the Sun and come back in and the really strange thing about them it was totally unexpected is they all go off in one direction and if you look at and actually that little blue circle is Neptune that's the orbit of Neptune these are the orbits of all these objects they all go off in one direction and the way that they're all tilted slightly with respect to the plane of the solar system and they're all tilted in about the same direction and it's really weird they should not do that if you if if there was nothing keeping them in place like that over the course of just a blink of an eye 100 million years they should basically disperse randomly once again so either there was something funny going on and we just got lucky and they happen to be lined up like that or there was something even funnier going on and they were all lined up for one particular reason so this this is where we started with our trying to develop the idea of what what was going on out here and when I say we and I'll often say we on this this is me and konstantin batygin konstantin is another professor of planetary science across the street and he has an office about three doors down from mine and in this time period we wore out the carpeting between our two offices we would just like walk back and we like did you see how what is co and and we would argue and people thought we hated each other because we would be like what about this I'm like that's the stupidest thing I've ever heard and and I know it's fun we were having a great time and we tried everything we could think of because the one thing we did not want to stand up and say is well I guess it has to be a planet because that's dumb and we had we knew that only dumb astronomers stand up and say it must be a planet and if as soon as we stood up and said it must be a planet people were just gonna throw tomatoes at us and so we tried every other possibility and at the end we couldn't make it work without a planet so here's here's the idea the idea is you saw those objects show anyone here that you saw those objects all lined up like this and our idea was if you had a planet like this with an orbit that kind of hugged the outside of all those those really distant Kuiper belt objects that it would kind of keep them from wandering so we worked out the math the way I nicely say we worked out the math Constantine did all the math okay and it all worked and we thought that's cute but let's let's do a computer simulation and see if it works and I'm going to show you this computer simulation because it's entertaining and here's here's what I'm showing you in pink right here you can't see it all the way near is is the we we place a planet a massive planet on an eccentric orbit around the Sun the orbit of Neptune and you can't even see it it's right there so this is a huge region of the solar system the earth isn't right about there each one of these blue things is a random object that we put in into a crazy orbit so we can we can do with this all on the computer very easily we just put all the objects in and we turn on gravity we say go what happens and we sit back and we wait for billion years and hope you guys have a long time because here we go four billion years the first thing that happens is notice that a lot of these objects disappear that's because they get too close to the planet and they the gravity of the planet flings them out of the solar system remember what we're looking for we're looking for things that get trapped into orbits like this and stick around the other thing that you notice is things that don't go very far I'm highlighting him in green here nothing really happens to them they just kind of their orbits just kind of move around the orbits change position nothing really happens but these start to get captured over here like this like like that one no this one this one this next one was gonna do it this one's no okay this one stays this next one no no this one stays so none of them stay it didn't work at all actually our computer simulations showed that our initial hypothesis was completely wrong planets do not do what we thought planets did but planets do something entirely different from what we first thought which is that nothing is getting captured over here at all because they're all over here these are the objects that are this is four billion years later this looks an awful lot like what we see in the solar system right now rather than a planet hugging everything and keeping it together they actually it almost like it repels it it doesn't actually repel it but it almost looks like it's repelling it at first we thought this is ridiculous there's no way this can be right and then we thought ah we're idiots this this is obvious we should have known this from the begin what to begin with and and it's just for the simple reason that the planet this planet that we put here is big and massive and anytime an object gets close to it it gets ejected if you had something in a planets when they go around the Sun they face they go slowly out through here and then they go fast slow like this so it spends most of its time out here and these are the same thing slow so imagine an object that was like this it would spend most of its time here the planet spends most of its time here they're close together a lot of the time that's bad news it gets ejected the only way to stay as far as possible from this planet is to actually be over here you spend most your time over here it spends most of its time over here you stick around so a planet explains something like this if the planet is something like this and the other thing that we found is that for how those objects are kind of tilted funny as long as the planet is tilted in the same way it all works out just perfectly so this would this was cute but I would say it was it was a nice explanation explanations are actually pretty easy in astronomy you know somebody shows you something weird and you can make up some story about why it happened and this wasn't this was a good story what the physics works but it but it it was not enough for us to want to stand up and say we think there's a planet out there because again for 170 years people have been saying that and they're always wrong and usually ridiculous we don't mind being wrong but it's less fun to be ridiculous and so we tried to think of was there anything it's easy to make an explanation what you really want in science is to make a prediction and have the prediction come true and one very strong prediction that this theory had is that in addition to having these objects like this the theory predicted that there should be another set of objects lined perpendicularly so going this way and this way and and it's it's hard to picture it but imagine the planets like this all these objects are like this and then a set of objects with orbits like this and like this they almost look like wings of a butterfly or something the theory predicted that very strongly and there's there was no way that they couldn't be there and we had never seen them and we we actually this was enough to make us officially worried that we were about ready to throw away the entire theory and just think okay we're wrong I don't know why I don't know what's going on and one day we were sitting in my office and I suddenly had this idea to look at this other set of collection of objects we had never looked at which was not smart on my part now look at him but when we did look at him we realized that they were in fact exactly what I just described these things are perpendicular often these in these directions these directions and perpendicular this way these are the objects that were predicted by our computer simulations that nobody had any explanation for otherwise this is the point where both of us were sitting in my office at this point and our jaws hit the ground I think both of us have the same thought at the same time which is oh my god this is this is actually this is actually a planet this is not just a cute theory that we just came up with this is actually a planet out there and we gotta go find it so this was the point in which nearly three years ago now we wrote a paper we wrote down our prediction and the paper paper was published about three years ago and we made a couple of predictions we made a prediction of where the planet should be what it should be like how we're going to find it but we also said look if this is true people will continue to find more objects in this direction and and it is still true that a few will be found in this direction but there should be most of them should be in the direction only a couple in this direction and more like this so let's fast forward a few years that was our prediction here's the original objects one two three four five six a year later there was a new one was found they're hard to find they don't come quickly three new words were found one two finally one in the wrong direction which was good I was getting worried that there weren't there's a fourth one in the right direction there are six more that are about to be published all in the right direction and one more going off in this direction so it's something like 16 in one direction - in the other direction it's exactly what we predicted it's is gratifying every time I go and see a paper that says there's a new object off in this direction like yeah it's good it's what I wanted to see okay so at this point the data are so good the predictions have all come true the explanation is it's not even that crazy I'm gonna tell you there's a planet out there it's not I don't I don't think that there's a question at this point I think this is more or less like 1840 where everybody more or less knows there's a planet out there and now the trick is to predict where it is better so that we can go find it so for the last three years that's the main thing we've been doing trying to predict where it is better so that we can go find it so in doing that predicting where it is better we take those same sorts of computer simulations that I showed you one of at this point we now have about 3000 of those we actually have a cluster of computers in the basement of the building across the street from us that has been sitting for two years non-stop running these simulations trying to pinpoint exactly where it is and we've learned a lot about where we need to be looking at we've learned a lot about what that planet is so the first thing that we learned is how big it is how massive it is so we detect it by its gravitational pull which means that we're detecting it by its by its mass so how big is that mass well three years ago at first we thought it was something like 10 times the mass of the earth which puts it comfortably between Earth which is precisely 1 times the mass of the Earth and Neptune and Uranus which are about 15 times mast it's actually an interesting mass because five years ago I would always be teaching my planetary science class again across the street and I would always say isn't it interesting that in that between one and about 50 North masses we don't have any planets but if you look at stars in our galaxy something like 10 earth masses is about the most common type of planet that there is out there isn't it weird we don't have one well the answer is it would be weird if we didn't have one but we caught one there it is but it's not ten turns out we now know better and the answer is about six six plus or minus one I mean this is we're getting to like real real numbers and real uncertainties so the the mass is six times the mass of the earth with an uncertainty of about one you could probably get away with eight if you had to but but about six six is a really interesting number at ten I was perfectly willing to say ten is pretty close to Neptune and Uranus and I we had the artists draw these pictures and we said make it look like Neptune and put some Lightning on it for fun so that's that's why that picture looks like that six is not six has really kind of could go either direction and around other stars six earth masses tends to be more like Neptune and then like the earth but around other stars that the six earth mass things that we see are really close to those stars so they're hot this is really far away so it's cold so I'm a little unsure what we're looking for let's just give you a little perspective here here was that picture I showed you again Uranus Neptune all the things in the Kuiper belt here's here's how big it is if it's a kind of a Neptune ish like planet it's something like this and it's also really probably quite bright like this if it's more like a giant version of an icy satellite like Ganymede Jupiter's the biggest satellite in the solar system Ganymede a big ice ball if it's more like that then it's kind of like that big again these are huge that looks like a real planet right none of this garbage like down here but there's a there's a big difference between this which is bright and big and this which is darker and smaller and that's that even though they're the same math one of them's a lot easier to find this is a lot easier to find than this we don't know which one it is so this is this is a current source of frustration the good news is we got telescopes Caltech runs the two Keck telescopes on the summit of Mauna Kea you you see Maui there in the background and I love the Keck telescopes and they are awful for trying to look for planet nine because the Keck telescopes really have specialized in being super good at studying detailed things once you find them they're not so good at looking at huge swaths of the sky looking for something new but this telescope the Subaru telescope is perfect for that the super telescope is the Japanese natural telescope Subaru not because of the car anybody knows Subaru and Japanese it's the Pleiades which you'll you'll see tonight it's also why the Subaru logo is the Pleiades they also and it's I was wondering if they're trying to get like sponsorship out of the car company but no I don't think so it's just the Subaru telescope has this great camera that is designed it's it's huge there it is here's the tethers me and Constantine this is the Subaru telescope this mirror is eight meters across this is a I don't even know this is this is about six stories maybe I think so it's about six stories high there's the camera the camera sits at the top and is collecting all the light that comes in from the big mirror down here covers huge swaths of the sky at once so that's great it's big telescope big camera and it will allow us to search vast regions of the sky for something that's very faint there's also another telescope in this picture that you can't see because it's over here on top of Haleakala on on the island of Maui and it's called the pan-starrs telescope it's been taking pictures of skies sky for six or seven years it's a much smaller telescope it's covered a lot bigger region of the sky already if planet nine is that big bright thing we are gonna find it in data that already exists from Haleakala if it's that small dark thing I think we're gonna find it from this one over here I'm working on both of these at the same time I'm striving driving me crazy but we're gonna we're gonna figure out which one it is I think relatively soon so let me show you where I think it is in the sky and I'm pretty excited about this tonight because you're gonna go see it tonight not planet 9 they're gonna go see this spot in the sky because I think it's alright I always say this but it's really true if you could name your favorite constellation everybody just say out loud your favorite constellation ready said go I heard a lot of Orion's I heard something else over here that I saying this is good actually saying this is great we'll give you signature but I think I heard more Orion's because I was looking listening for that so Ryan I mean come on and so Ryan is visible from everywhere on the earth I read once that it's like the only constellation that is the same in all mythologies that people know about constellations it's always a humanoid figure because it really looks like somebody up there in the sky doing something it's a fantastic place I mean if if I had to tell you the planet 9 was in the constellation Cetus only three of you would even know what Cena says one was one maybe you only want to do see this is a whale so is my favorite spot in the sky and you can see it tonight you look straight up there's Orion it's beautiful Taurus is over here and the cool thing well so planet 9 is not there but it's really close planet 9 I think is in this swath of the sky right here this swath of the sky right here it's actually right between a Ryan and Taurus you know the cosmic battle in the sky Oh Ryan is either depicted usually with a bow shooting at the bull or a shield protecting himself from the bull so there's this huge clash in the sky and in the middle of this clash in the sky is is planet nine what I want you to do when you go out tonight is to stare at that spot in the sky for a minute and and don't just think wow that was the best talk I've ever heard in my entire life what I want you to think is is there really is a planet out there there's a planet out there that no one's found and it's just right there I mean I literally do this when I go outside and see Orion I always just stop I'm like it is I can I mean really is right there I want you to just spend a second seeing if you can feel it out there we've been searching we we of us I think it's right there but but it might not be that's it this is our and and in the statistics we've done this is the most likely spot but it's not that much more likely than anywhere else in here our first year we covered about this much last year we've covered a little bit more we're gonna keep going I don't want to keep you guys here much longer because I want you to go and see it but I do want to end with one thing that I started with this is the poster of course we stole this fair and square from plan 9 from outer space which is famous why is it famous worst movie ever made I am this is this is not me this is some Critics Association voted it as the worst movie ever made and it really is I mean it's it's not even so bad that it's good it's just bad so there are zombies there's Dracula there's Vampira this is Constantine actually strange they know and and so it was it was a it was filmed in 1959 Ed Wood was a director and Ed Wood I think made this poster 1959 if you think about what was happening in the solar system 1959 Pluto had been discovered in 1930 there was some argument about it weather was a planet or not when it was discovered nobody knew what else to call it so they call it a planet but Ed Wood in addition to being you know making this terrible terrible terrible movie was generally considered kind of a genius and he was ahead of his time in many ways and the one that I never realized until I started looking this poster is I mean so see this graveyard scene right here there's the - there's if you look at the tombstone can anybody read that tombstone yeah okay please let me let me zoom that in Edward 1959 who knows so thank thanks for coming out please stick around for the for the for the stars go steamer plant at 9:00 is it planet 9 right now is basically right there I'm not even joking see the stars hang out talk to the astronomers something else they're supposed to do this blog panel Q&A at panel QA and ask me questions thank you dr. banner [Applause] I'll let I let everybody head out for a second then we'll take questions for anybody who's still around and I will take questions from the youngest person who raises his or her hand I think I got it I think I got one do I have a percentage chance that there isn't a planet nine that is a fabulous question and a lot of the last three years we've been spending trying to answer that precise question because we really want to know is it something that we just think is there or do we have is can we really do the the probabilities correctly and as of about three weeks ago we finally have the analysis finished the chance that there's not a planet nine is 0.2 percent so it's one in five hundred so I'd say yeah yeah any other any other youngsters no okay oldsters Oh such a good question is something funny going on because planet nine is being pulled along by a planet n and therefore we can't find it let me tell you we worry about that a lot like really a lot we think that even if there is a planet n which there may well be there's no reason there shouldn't be but there's also no evidence that there is we think that the effects that we're seeing from Planet nine will be the same even if Planet nine is being tugged around a little bit but we're actually doing that analysis right now because because we're worried about it yeah we've not there's nothing that we've seen that would lead us to say that there has to be another planet out there what I think is that if there is a planet even beyond planet nine that the way that it would eventually be found is similar to how we found Planet nine which is realizing that there are distant objects being perturbed even more and and we don't have a big enough telescope stance so I mean I think Planet nine is kind of perfectly suited for finding with the telescopes we have right now I think that if there's a plan of ten it's going to be up to you know the kids here to go find that one so well we'll leave that one for you guys yeah you can see it it's behind that it's behind the gate yeah you can I can I guess so I still go I go up to the gate and kind of stick my face and go so so it's a it's a but I'm gonna answer that even more general way which is so there are a lot of different big sets of data of things that have been taken in the sky pictures of the sky measurements of different things in the sky and a really interesting question is is there anything in those data that we can use either is planet night in those data or evidence for Planet nine and we have we're looking at pan stars as I said so that's one of similar set of things so one of these spacecraft missions called Gaia and Gaia has taken measurements around the entire sky it probably doesn't go faint enough to actually see Planet 9 itself but there are people who have suggested that if Planet 9 is there it might be able to see the perturbations of stars as planet noise as the star lights not the stars themselves but the star light we can't do that yet because the current data release doesn't give us give us that but maybe that's gonna be hard but it would be awesome if it if it worked out that way that'd be really cool let me look back in the back because I can't see the back usually I'm gonna go away in the back yes you know yes you you oh no you can't tell me that so so astronomers I think it's fair to say you can ask the other people around here astronomers I think of as very superstitious people and one of my superstitions and I think it's actually because of we're so dependent on the weather that's at least where all my superstitions are from that I'm gonna omit one of my very strong superstitions is is it if you name it before you find it you will not find it there's one example that I can think of that's a really good example which is La very a after finding Neptune himself went into the business of predicting new planets and he predicted this planet interior to mercury call a named it Vulcan doesn't exist the very a so I mean he was his was the interesting case where the data were good it's the physics were no good his the this is the reason he thought that was one inside of mercury is actually because of general relativity so well give him a pass on that one he didn't know about general relativity but still he named it so no if you'd like to give me suggestions just let me know so I can stick my fingers in my ears first know No yes with Clyde Tombaugh passed away just a few years before Pluto got demoted he was he was still alive when they were when when the first Kuiper belt object was discovered in 1992 well I would say he discovered the first Kuiper belt object but when the second Kuiper belt object was discovered in 1992 and that's when the grumblings kind of started so I think he was aware of the grumblings but he didn't he didn't live to see it tomorrow yes what what keeps all these planets in orbit so the the answer is always the same which is the Sun the Sun is as massive in the center of the solar system everything goes in orbit around the Sun because of the pole of the gravity of the Sun so even Planet 9 which is really far away it's still held very strongly in place by by the Sun all those orbits that I showed you were going around the Sun the Sun I should have made this more clear if it wasn't cleared the Sun was always at the very center of all those things I shouldn't so everything that I've been talking about is in orbit around the Sun have been being perturbed by something else at the same time way back here yeah did anybody go to the 7 o'clock talk yeah you can answer this question I didn't right right why can it why can you find these really distant planets and not find one in our own backyard and it's actually me so it's a good question and the answer is if you want to find a planet around the star where should you look a star we know where the stars are we know when the nearby stars are we know where the bright stars are that's where they're being found so if I wanted to find a planet if I wanted to find a start with the planet I probably just go outside and point the first star I see and it probably has a planet and I could probably find a planet around it but in if you wanted to find one planet in our solar system that we don't know about you have the whole sky to look for so it's a lot harder those guys have it easy cheaters I say it's where I'm from yeah so it's a good question which is how bright is planet 9 supposed to be and the answer is different depending on whether it's that large very bright Neptune II kind of thing or the darker red icy thing it's Neptuna thing it's like xx xx nine to twenty first nineteen so for astronomers out there so four four maybe backyard astronomers that might seem faint or something but for the for the astronomers out there that's like super bright it's there's almost embarrassingly bright it's it's so bright that it must be in data from the past and we should must be able to track it down that's if it's that'll brighten if it's on the thin end it could be as faint as twenty fourth magnitude which is pretty faint and so that's why we're using the Subaru for that so it's in this weird range of really easier really hard or somewhere between which is a stupid range to me how far away is playing at nine I didn't even show say that I showed the pictures it's it's about three times further than Neptune so Neptune is in the units that we use in the solar system is astronomical units astronomical unit is the distance from the Sun to the earth is one and Neptune is that thirty and planet nine is at three hundred three hundred and ten plus or minus twenty that's actually the semi-major axis so that's the average distance so it's right now it's probably at four hundred at its most distance distance and it comes in to about 280 so it's on that eccentric orbit so we'll call it four hundred eighty yes yeah so because I'm not very smart I think is the answer so we can detect its mass why can't we detect its location even better you know Lovera a predicted where neptune was in one night so what's wrong with me and the answer is is subtle but it's important which is lavera a predicted the location of neptune by taking uranus and looking at its full orbit and saying it's a little slow here little slow speeds up over here aha that must mean that Neptune is here so he could do it that way we don't have the luxury of having a full orbit of any of these objects they have they take a hundred thousand years ten thousand years to go around the Sun if you gave me ten thousand years and I could track one of these objects I could pinpoint precisely where Planet nothing was so instead we have a ton of objects that are making a pattern in the sky that we're trying to match to theories of where it should be and it's it's just it's harder to get it precise we've narrowed the area down pretty a lot not quite a lot enough yet every you know every minute that we wait and the computers across the street are churning I think we narrow it down a little bit more so I'm convinced we're gonna find it soon but I'm today I'm optimistic tomorrow I might say we're never good not sure yes I came sorry I cannot here so I don't believe that Planet X exists as I said Planet X is the thing that Clyde Tom that Percival Lowell predicted that he thought was perturbing Uranus and Neptune Planet 9 is not Planet X they are entirely different things people get confused and call it Planet X or call everything Planet X but there really was a prediction of Planet X this is a different thing so I'll answer the real question you're asked which is do I think that Planet 9 has an eccentric and inclined orbit it has two so the eccentricities required to cluster all those other objects in the other direction if we're not eccentric it wouldn't do that and the tilt of Planet nines orbit is required to make all those other objects tilted to so we can read those patterns and try to determine exactly how Planet 9 is tilted in fact I will tell you right now it is tilted by 17 degrees plus or minus 3 and it's eccentricities to point to plus or minus 0.05 don't write that down nobody go find it yes so the question is is it is it possible that rather than a planet that it's maybe a pair of things orbiting each other so I'll answer that in two ways one is gravitationally yes it is absolutely possible because all we detect is that there's a gravitational pull and we don't know if it's two things we don't know if it's a planet we don't know what it's made out of and we know that there has to be six earth masses there could be six earth masses of hamburgers and it would still work in terms of the physics in terms of the sort of conceptual planetary science it kind of doesn't make any sense there's no I mean yes it could be why we don't we've never seen anything like that in our solar system around any other star and so it's kind of a weird unnatural hypothesis earth in the moon is not much different they're pretty different and it would be it would be hard to have I mean if if it were just two things that are about the same size we could still find them it wouldn't be that much harder to find these two different things because they would still just look like one big blob of light to us it's just it's it's not impossible I mean there's no reason that that can't work I don't think it's very likely all right I'm gonna go all the way in the back kid can give the computer simulations rule out of Planet n absolutely not at this point we could put a lot of stuff out there and not yet see the effects if you if you found another hundred of these distant objects you might be able to start to do that but right now there could be a lot that we don't know still to come out there which is kind of fun I started this back at the beginning talking about in 1992 that was in graduate school and the idea that there was a new planet was ridiculous and even if you would ask me in fact people asked me back when Pluto was demoted will there ever be another planet found I was like no this is it eight planets and I was a little sad and now it's pretty cool yeah there I am I am completely convinced there's a nine and we don't know what else is out there there's still plenty of the solar system left to find which i think is a lot more fun than when we just had eight and that was all there was anybody who has a question that has not asked one if you've asked one wait and see if I did that and just I think we have to just one more question okay I already pointed that way well I I pointed on the wall sorry oh it's a good question where did it come from why is there a Planet nine in a crazy orbit out there so we don't know the the fact that we see the gravitational pull tells us nothing about how it got there but we can we can come up with hypotheses that I think are reasonable and and and even not very controversial I think the most likely hypothesis is that it formed in the same region of the solar system as Uranus and Neptune back four-and-a-half billion years ago and as these things were all forming having three planets that close together is is a little bit unstable and so it probably came a little bit get got flung inward close to maybe Saturn or Jupiter and got flung outward and it's been kind of lurking at the edge of the solar system ever since then that's such a such an uncontroversial idea that that Konstantin and I actually wrote a paper about that when he was in graduate school but we didn't we didn't talk about planet 9 being out there we talked about what would happen if there were a fifth giant planet what would happen and we showed they would get ejected and then that's all we did and then you know a decade later we're like oh yeah that's oh yeah then it goes here oh yeah so I I think that's likely it's not it doesn't have to be that there are ways that it could have actually formed out there I don't think it's true but there are ways to make it happen and it's also ways we could have stolen it from another star I don't think that's true either but because we live here in LA I have been approached by at least one producer who wants to make a movie where Planet nine is stolen from a nearby star and it had a moon with the civilization on it but then goes extend it it's a long story it's gonna be good though when it comes out top notch I hope this III hopefully yeah I hope you guys are all there let's let's thank our speak too so the members of our panel Sicilian Sanders is a graduates a PhD student in planetary sciences department and she's happy to answer questions related to astrobiology life on Earth and beyond geochemistry and figuring out the ages of very old things we've also got Nicole Wallach yes I pronounced it ok awesome also a PhD student in the Planetary Sciences Department who's happy to answer questions about exoplanets that is planets orbiting around other stars planet formation and how to use really big telescopes we've got Katherine Plant who is a graduate student in the astronomy and physics department happy to answer questions about building radio telescopes fast radio bursts which are these distant flashes of radio waves that come from some unknown objects and cosmic rays oh yeah things that make really short flashes of radio waves and then I'm dr. Cameron Hummels I'm a postdoc I do research in galaxy evolution so I can I can try and fill in the cracks we're where we we get questions on on things unrelated to that so yeah so we opened the floor up to questions from all of you yeah so the question was whether or not astrobiology takes inspiration from our shares resources and ideas and things with the field of paleontology which is an excellent question for me because secretly I am NOT in planetary science but in geo biology and planetary science so my day-to-day life I am more much more of a paleontologist than or more closer to the spectrum of paleontology earth science studying history of life on Earth than I am to observational astronomy but I got into that because of my interest in astrobiology so as it turns out if you want to look for life in the universe one of the best places to start is looking at the only confirmed world where we know life evolved which is our own which is our own and so a lot of the tools that we use for understanding the history of life on Earth are the same tools that we the same tools that we take with us when we go to Mars and eventually when we go to Europa potentially one day outside of our own solar system looking for life in the deep past of Earth is actually extremely difficult as you might imagine if you leave a living thing that has that has died and is decaying just sitting out on a hot sidewalk in the middle of a hot day in summer in Los Angeles it will slowly degrade it will slowly be eaten by a number of things its carbon will go back into the terrestrial carbon cycle and very little will be left behind to be potentially fossilized or preserved in the geochemical record things like that so paleontologists work very hard to figure out the rate at which those various processes happen what are the circumstances under which those processes are stalled and even when those processes happen is there any signature physical or chemical that the living thing might have left behind that might survive for hundreds of millions of years beyond to be discovered by a paleontologist so those questions are still very relevant on other planetary surfaces and so long answer to a short but excellent question paleontology is astrobiology but we just applied to a slightly different slightly different Rock ready for dress yeah so the the question was well the premise of your a very very excellent question is that the moon enceladus which is one of the many moons of the planet Saturn has these huge spectacular geysers that shoot off into space and are responsible for the production of the e ring around the planet Saturn so you have this huge ring of ice crystals and sometimes colloidal silica apparently and other interesting things that are sourced from the subsurface of the moon Enceladus and so this is obviously of great interest to planetary scientists because it tells an interesting story about just how icy worlds form and evolved and the physics and chemistry of cryovolcanism but it's also of great interest to astrobiologists because these geysers are associated with a temperature anomaly a hot spot in the southern hemisphere of Enceladus and so explanations for that hot spot can be as simple as oh it's it's tidal flexing because it's a small moon around a very big massive planet it's just getting pushed and pulled around and it's developed and that heat is being dissipated in the ice shell and it's a way of melting the ice and making this water and you know that's all very exciting but it's not specific enough really for scientists so it's actually a big mystery are can it get hot enough in there to have a hydrothermal system of the kinds that we know support life on our own plant so this is all premise enceladus super interesting guys geyser systems possible hydrothermal activity all the stuff but your question was is anything like that happening on other water ice moons water ice dominated moons in our solar system like Europa and the answer as far as I know is no we have not observed we have not observed plumes of nearly that magnitude on any other body in the soul of any other body in the solar system and Earth included we don't have giant plumes that spread into space but you think new developments are happening all the time and you know I'm not directly familiar with the most recent work on Europa so there's some tentative evidence for some flumes on Europa depending on who you ask mostly so I think there was some Hubble data that showed some possible tentative detection but nothing to the extent of Enceladus so I think these sorts of outer bodies are just super interesting to what we know to happen on these icy worlds and what we don't know so worlds that we think should have plumes we don't necessarily know if they're gonna have flames and things like that so I think it just kind of speaks volumes to how little we really know about these sort of outer body is in general yeah it really does depend on who you ask how much you believe it oh I'm sorry the question was about the Hubble the Hubble data that showed the possible plume on Europa and it's still up for debate and that's actually a really big thing in most of planetary science is that everything is kind of up for debate and we don't know as much as we wish we knew about our own solar system and like Mike Brown alluded to before sometimes we know a lot more about exoplanets or about things that are outside of the solar system and it's kind of scary in a lot of ways but it's kind of look how much we have to look out to basically and look how much we have left to learn about our own world it's actually not the innermost that's being yes a is the star and also if there's a binary system it's a P then but the lowercase letters are in the order in which they're discovered so that's why you sometimes have planets that are discovered in sort of the wrong order you think but it just so happens that the closer in planets tend to be easier to find so that's why you do tend to have you know BCDE out but it is just the order in which they were discovered is a is capital they're always capital so yeah this party's gonna be capital letters so if there's a binary system or a triple star system it'll be ABC if its surrounding all of those there's a whole other series of problems but no it would just get a little confusing to have you know happy 26 AAA so okay yeah so the for anyone who didn't pay the question the question is how do you know life when you see it and this can be as philosophical or a scientifical question as anyone likes and there are a lot of different opinions about what constitutes life so one of the first things that you do when you first start learning about astrobiology as a field is just try to answer the question what is life and there are a lot of possible definitions the one that I feel I subscribe the most to is life is something that is not only not only capable of sustaining disequilibrium chemical conditions um as some astrobiologists who come more from the Astronomy side prefer to think of it I think that you need to add that additional layer of complexity that life can make a plan for itself and perpetuate that plan there has to be some dimension of heredity and self-replication in order to really be life as we know it and think about it on our own world but that said that definition doesn't exclude things like viruses that definition doesn't necessarily exclude things like like dormant spores or egg cells and things like that so yeah so first part of that question is like establishing what is life to begin with before we go looking for it and then another dimension of that is maybe it's not enough to just say do we find something that's capable of sustaining chemical disequilibrium and making plans and expressing excel for multiple multiple times it might just be simple enough to say life is a cell you know and then start to and then start to talk about well what's inside of a cell what are the fundamental structures that define or make up a cell and that sort of thing so when we talk about detecting life on this or other worlds in the modern or in deep time we're usually looking for some evidence of cellular metabolism and so metabolism is both how you make energy how you make usable energy for yourself and how you use that energy to assemble structures so in our case assemble biomolecules proteins and nucleic acids and that sort of thing of course exactly what those proteins and nucleic acids and carbohydrates and such look like in other organisms is certainly up for debate so looking for life on another world involves looking for you know first you look at where energy might be available might be available to something like a cell and then how how favorable kinetically and if thermodynamically are those reactions that might supply energy to the cell and then think about if the cell was using was using those energy sources what would it leave behind is it depleting something is it enriching something is it is it leaving a physical imprint of itself or you know my favorite my favorite instance of the preservation of life it doesn't leave a fossil you know so leaving a physical structure behind is a kind of gold standard for like discovering life on a discovering life on another world because as you might imagine there various ways of assembling certain structures or depleting certain reservoirs and enriching other reservoirs of particular isotope or a particular compound or something like that that might not necessarily involve life so having like a physical structure that can't be assembled in the absence of so in metabolism is another that's the best yeah so what I would like to see as a proof of extant life on Europa which is to say life that is currently living today and not necessarily evidence of some ancient extinct biosphere I would want to see I would probably want to see lipid lipid biomarkers so lipids are another type of complex biomolecule that we make it's essential to the formation of all of our cells every single cell in your body is made up of lipids and yes yeah so every cell requires so one of one of the can do this gets back to what is the definition of life so one of the conditions for being a living thing as being somewhat compartmentalized so separated from your environment and maintaining homeostasis in the face of a changing environment so if you are a so one of the best ways of sort of encapsulating yourself is by building a lipid membrane so that take many forms it can develop like structural complexities and things but every living thing on earth every cell makes a lipid membrane and so but it's not just the membrane lipids are also extremely useful for building structures inside of the cell extremely useful as secretions that help communicate between multiple cells in a community it's another interesting hallmark of life on our planet is that it interacts with other life and interesting complicated ways and so lipids are just special in this context because they are a lot more resilient to the test of time and there's such a variety of lipid structures that you can actually if you find certain if you find certain lipids in the dirt or inside of an ancient organic rich shale or floating in seawater then certain lipids their structure is impossible to accomplish without certain so a machinery of a Sun for assembly and so you can actually distinguish between different organisms different metabolic strategies by what lipids they leave behind so it's a it would be so if if there is extant life on in the oceans of Europa that would be one of the best things to look for that would be the most definitive finding actual cells would also be great um but is potentially harder to if you are going to look for actual cells with some of the tools that we send to other planetary surfaces you would still be looking for lipids so whether those lipids are assembled into a membrane or a different structure or whether those lipids are floating free on their own because the cell that made them has lice and died what you would do is you'd probably put like a flow cytometry or something like that on your on your instrument so you could look through the water look through the water that the instrument is and analyze it for those particular structures so lipid biomarkers would be my answer if you could get a look at the sedimentary geologic record of Europa which I'm not so sure that such a thing exists um but if you could then there's a bunch of other interesting sedimentary structures that are indicative of microbial life as you might imagine if you've ever if you've ever had a fish tank or looked in a pond or a puddle or something like you there's that kind of slimy stuff that grows on the sides or on sometimes a skim on the surface of the water microorganisms like to form these biofilms or even assemble them into thick mats and those mats provide a cohesiveness that is difficult to achieve with just mineral substrates alone so you could potentially look at the rocks look at sedimentary rocks deep beneath the ocean on Europa it's more of a favorite favorite activity for search for life on planets like Mars and stuff so we should probably move on to yes yes so lipids are fat yeah so yeah yeah so biologists slash biochemists will typically talk about life we talk about the the building blocks for life the building blocks for life are these different classes of biomolecules and so the classes classically are lipids carbohydrates proteins and nucleic acids and the differences between those are structural probably the best way the best way to define them would be to just draw the structure on the board but since people didn't necessarily come for a biochemistry lecture I won't do that but it's it's very easy to look up and the you know so when we think of dietary or nutritional like proteins and fats and things like that technically they are the things that we're talking about fall under those categories of biomolecule but certainly the range of proteins that exist in nature is much much larger than the range of proteins that are important for building our own our own biomass or biological structures of things so lipid does mean the same thing as fat but dietary fat as we think of it is just a small subset of that much larger group of biomolecules and you know they some of your some of our intuition that comes from our definition of like dietary fat is uh does applies lipids as well the way that it is sort of hydrophobic doesn't that usually like that is a property of what of all limits that sort of thing so sorry I just started throwing out jargon and did not explain it but thank you for your question there's a gentleman who's been waiting yeah so I think you're you're absolutely spot-on if we had a planet very much like Earth that was yeah oh man yeah so what would the question is what would alien life be like on an earth orbiting a star of a different color than our own yeah yes yeah yeah so there's a there's a lot of differences that we could possibly imagine if it was exactly like Earth in every way and the history of life the evolution of land plants if all of that happened in the exact in the exact same way yeah you would still get up to a point where just fundamentally the the photosynthesis synthetic organisms so organisms that derive their energy ultimately from the Sun but then use that energy to assemble their own biomass independently they do not consume their reduced carbon from other organisms those photosynthetic organisms would have to be sensitive to a part of the electromagnetic spectrum our Sun has a broad spectrum emission but it is brightest part of the spectrum and so if you were around a red dwarf star that brought that spectrum that peak would be shifted to longer wavelengths to lower energy wavelengths so so certainly like the plants would end up looking a different color because they're the pigments that they use to harvest to collect and light energy and turn that into usable chemical energy would be sensitive to a different to that different part of the spectrum that's yeah yeah so that's certainly a very interesting possibility and almost more likely I think is that plant life just would not evolve the way that we understand it ourselves like photosynthesis on land is already a wildly cool and improbable metabolic strategy photosynthesis is a strategy that evolved in marine environment and marine environments on a planet around a yellow star so I think that I'm you know certainly it could change the colors of the plants but I think I would expect I think that I would expect like non-oxygen 'ok photosynthesis which often uses pigments that are sensitive to this different set this different part of the electromagnetic spectrum I think those organisms would do much better than the organisms that eventually became the land plants on our own world so more likely than not I think that life around a red planet sorry a red star is probably going to look a little bit more like the pond scum around like yeah yeah so yeah so the most abundant star that you have are these smaller redder stars so it's important to note though that I don't usually come at this from a life perspective so we'll leave that to Cecilia but there are other factors that will influence the ability in general for life to evolve on these types of planets around these stars and one is that you as you related to before they're much smaller and they're cooler so you're gonna have a habitable zone a place where liquid water could be present on a surface of a planet a lot closer in there are a number of other factors also for these types of systems things like availability of solids in the prenatal disk just means the building blocks for planets around stars like that the age of these stars are very different the time that they've had to evolve planets in life to evolve around these stars so I think that there's a lot of things to consider when you're talking about planets around these the most abundant of all stars that's another interesting thing about sorry another interesting thing about red dwarfs as well as that they planets in this closer in habitable zone being the people that's warm enough water at the surface given a range of atmospheric compositions that zone is also subject to a much higher energy radiation environment than our world is necessarily and our sort of pop culture intuition is correct that if you're getting bathed in higher energy radiation all the time it's a lot harder to maintain your nucleic acids that are responsible for transferring for encoding all the things that a living thing needs to do so maybe you don't evolve life at the service at all and maybe life ends up hanging out in the immediate subsurface and the soil and the rock beneath the particular critical zone of the water column they're not as deep as you might think because water indeed is the penetration depth of this longer wavelength lower energy light is also much shorter our planet so this in addition to leading to interesting variations the type of life you can expect which we from planet to planet different types of stars leads to complications for the detection of life around those planets if it's all gonna be underground and maybe there's a lot a lot of the things that we think of as being atmospheric biomarkers around other stars like methane or oxygen or something like that maybe there's just a lot more maybe all of that is getting broken down and recycled and that you know a few meters of rock and topsoil and maybe it's not making it into the atmosphere for us to detect it so so yeah just a quick sign on that so when you hear about bio signatures or for those who don't know it's basically something that we'd assume would generate life like what I've generated by life rather so things like oxygen that we expect due to you know plants producing oxygen things like that that really present in the atmosphere of a planet so it's important when you hear in pop science or in you know on the news somewhere it's like oh we detect bio signatures but doesn't necessarily mean there's life there it's an important caveat to you know pop science is that we don't really understand everything about atmospheres of planets and there's a lot of confounding variables when you're talking about atmospheric bio signatures so you know chemistry produces a lot of these things chemistry produces methane and co2 and oxygen just you know the planet being around its star and being hot so just you know exactly so we actually have no idea when we're talking about you know an earth twin it's like this is the most earth-like planet we've ever found most of the time that's kind of nonsense when you think about it because it could be a planet that's the same mass and radius as the earth we know nothing about its atmosphere most of the time for these types of planets and even if we did the likelihood of it being very similar to earth given how close they are to their host stars for most of the planets that have been detected in the ways that we're talking about we're talking about Earth twins it doesn't really lend itself to being able to be studied in the way that we would need to in order to actually detect life on another planet so just you know important caveat it depends on what your idea of life is is a big thing so according to what we know about the earth yeah but we have a sample size of one basically so we know that given our conditions at this very moment we have been able to form life on this planet and a diversity of life and amazing diversity of life but we don't really know what life will take in different kind of forms life will take in other places it could absolutely be like star checking you could have silicon-based life forms you don't know we have absolutely no idea the astrobiologist is now gonna be the pessimist not on silicon-based life but the just like clarify for any when the audience who hasn't heard this idea before there's obviously a lot that life needs not just water not just an atmosphere of the particular composition that we've got but also it turns out that life might require a planet with a geodynamo a planet that has a molten a dynamic interior where you have where you have electrons that are being cycled in such a way that they are generating a magnetic field in that magnetic field extends wide enough around the planet to encompass its atmosphere so the gases that it's capable of holding on to because of its innate gravity and so if you don't have an active geodynamo for example on mars which is a planet that is it doesn't look all that much smaller than Earth but it's critically smaller than Earth and it's the differentiation of its core and its mantle and its crust preceded in a different way and so it's interior doesn't have that same flux of electrons going or going around and generating a magnetic field so it's my Nanuk field is much weaker and is part of the reason combined with the fact that smaller that it wasn't able to hold on to nearly as robust an atmosphere as the earth has so doesn't mean that life can't be there and in fact you know many forms of life on our own planet do not necessarily have to interact directly with an atmosphere with nitrogen and oxygen in significant abundance but it does it does add this other caveat that if you see a planet that's just a little bit smaller than Earth you're probably not gonna see any earth like you're not probably not going to see the kinds of interesting so one way that people are interested in testing and looking for planets that have magnetic fields is by looking for the Aurora like the the Northern Lights or Southern Lights I but looking for that around other stars because the charged particles from a star's space weather when it hits an atmosphere with a magnetic field you get bright auroral emission and this would be a very faint for many planets except in extreme space weather events but if you look around enough stars enough planets you might be able to detect it and not yet so far it's it's required building a special dedicated array which is built about four hours north of here when they're still looking yes there's a telescope looking for it yes Oh Jupiter Aurora's have been observed for sure and a viewed from a distant star Jupiter would be much easier to see in its Aurora mission than earth and actually there was a public lecture here given about three years ago that was all about Aurora around other planets in the solar system and it's on YouTube so if you look on our YouTube page Caltech Astro you can find this lecture that's all about planetary magnetic fields throughout the solar system in their Aurora but you're right it's Jupiter's the primary one so you're asking how how could radio telescopes be used to look for extra yes yeah yeah yes I think I some things that could be distinctive would be something that confines a lot of energy to a very very specific frequency range and people who work on this come up with all kinds of ways for looking for really unusual signals and that's what what I like best about those efforts is they come up with these signal processing algorithms that lets us find weird stuff and then we go and find weird stuff and it turns out to be new physical phenomenon scenarios to go look for and the discovery of pulsars is an example of that there was this regular flash of radio emission coming periodically as periodic as a clock and at first I when Jocelyn Bell found this I people thought maybe it is it aliens what else could make flashes as regular as a clock and it turned out it was a spinning neutron star emitting radiation like a lighthouse so thinking of when we try to think of what what's something that the physical universe couldn't what's something that couldn't naturally occur and then we go look for that thing we find a new parameter space of naturally-occurring weird physics I yes so magnet ours are that the question was I about the types of emission that magnet ours make and how they relate to neutron stars is that so magnet ours are a specific type of neutron star and a neutron star is the remnant that's left behind after a very massive star has burned up all of its fuel and and and goes out and the giant explosion what's left behind is a dense core of neutrons it's so dense it's almost like one big atomic nucleus and often these are highly magnetized and often they're admitting bright radiation out of their magnetic poles if they are spinning around an axis that isn't that magnetic pole then you see a beam of radiation sweep by like a lighthouse every time you pass the spot and that's a pulsar I normally be the energy that's being emitted comes from something's you can calculate how much energy it should be emitting by noticing that you have something spinning very fast and it's slowing down so it's losing energy and that is the energy source that's emitting some of them are emitting too much energy for that to be the explanation and the energy source that we understand for those objects is that they have a lot of energy in their magnetic fields and those are the magnet ours so there a specific subclass of neutron stars yes so the question relates to the orbit of planet 9 and how far away the planet Norbit of a planet could be so we have something called directly image planets so planets that are actually just pictures are taken of them and there are hundreds of a you that was the I think the I want to see 600 at you kind of thing there are a couple hundred at you from their host star they can be up to that and it depends on the star the gravitational well of the stars you know depend on how massive the star is for one but yeah I mean that's perfectly within the read the region of you know gravitational pull of the host of our Sun so yeah of the Oort cloud sort of represent like the boundaries of the gravitational influence pretty much yeah yes is I'm sorry I'm passionate is it on the order of civil so if it's a difference between where a planet can form and where a planet can be in its gravitational pull the host star so when you have planets that are forming we're gonna talk about you know four directly much- the planets that are kind of the farthest out for what we've seen mostly with respect to the existence from their star where a planet can form is very different than where it can be so the gravitational pull of a host star can be much further out but the problem is that planets form in a disk that surrounds the star you need to have enough of material to form those planets so something like Planet nine if it was captured by from another star then yeah it could be at the outer boundary of where the host star of where our Sun you can pull in but I think that's an important nuance issue is that where a planet can form and where a planet is found aren't the same thing necessarily so I guess the answer is it depends pretty much range of what I think is realistic for a planet that formed from our own proto stellar disk yes and strictly speaking the gravitational influence of an object gravity is an inverse square law so it falls off with the square of the distance but that extends to infinity so if you had just like a single star in the universe and nothing else except this planet it could be arbitrarily long distance away and actually be orbiting around but that isn't realistic because there's a lot of other massive objects in the in the vicinity that'll steal it away or perturb it so it wouldn't actually orbit so mine is just like a technical point that's there their answers the the right answer the question is what size is the heliosphere and astronomical units well Voyager just got outside the heliosphere and I don't know how far away Voyager is P the PI of Voyager is in this building probably not right now it's done it's probably sleeping but yeah it's on it's in a few it's it's in the hundreds I think I don't actually know the actual just do you know Mike about 100 okay about a hundred au well just because you're outside the heliosphere that that's just the the region that the magnetic field of the solar system is more powerful than the than the surrounding inner planet or interstellar magnetic field so it's getting buffeted by the ice m and so on and so forth so it doesn't mean that objects can't exist out there and still feel the gravitational influence of the of the Sun it just means that it's not shielded by the magnetic field right exactly yeah sorry I don't mean to steal planet questions from you guys Arvin's kind of unique so the bonding and the bonding environments that carbon is capable of that carbon is capable of assuming are conducive to the assembly of these important structural molecules like lipids carbs etc if you substitute in something like silicon which is you know one of the exciting and fun it's you know they if you've ever looked at a periodic table the periodic table very nicely lays out like oh here here's our attempt at organ a organizing elements in a way that explains some of the similarities and the bonding environments that they're capable of taking up so silicon is one of these that people say like oh well this is similar enough to carbon that we can substitute in but functionally the nature of those bonds if you start trying to make the same kinds of bonds that you do with carbon using silicon you end up with rocks instead which you know for a variety of reasons don't necessarily fit the the definition of life that we were talking that we were talking about earlier so their carbon is definitely the best the best element that we have for assembling biologic biologically relevant structures and because it is the best even if you could substitute in some others those others would not be stable enough or as effective it's self perpetuating themselves and so that is one of the other criteria for life is that they're able to perpetuate themselves and so the the reason that we have some of the ubiquitous structures that we have reason why all living things use DNA is because it's that much more stable and that much more robust when you start pulling arising it and making increasingly long sequences then it's then the related molecule RNA for example and so it persists is our primary way of transferring of storing the plans to assemble biological material and transferring that to our progeny so carbon has become so there's a reason that all life is carbon-based there's a reason that all life uses DNA there's a reason that all life uses these structural lipids and it's because they're the most they went out kind of in a competition of who is the best and who is the best at doing this thing and perpetuating itself so it's weird because I'm using some of the language of evolution and natural selection to talk about the molecules themselves and not necessarily something intentional that a living thing is trying to do to survive but the I think that the language still translates well from the one to the other and indeed one of the things that one of the important parts of astrobiology is not just the search for life on other worlds but also the understanding of the origins of life and so before you have a cell before you're assembling complex biological structures you're just trying to assemble molecules that are effective it's sticking around for long enough to make more of themselves and carbon compounds are really good at that I'm sorry could you could you repeat the question yeah no yeah so there have been some attempts experimentally to create molecules with similar structures to DNA and structural proteins using nitrogen mostly are the experiments that I'm familiar with and I feel like arsenic to arsenic based life is something that people have also done experiments with so it is possible to massage energetic conditions to make some of these molecules structurally stable and to get them to mimic some of the functions of important biomolecules on our own planet but a lot of those conditions are not necessarily I won't say that they aren't naturally occurring because obviously with the range of planets that we've been talking about around other stars and you know you could maybe alter a lot of things about the geological history of a world in order to yeah yeah you've got to be a lot colder for one I think in order to get like the nitrogenous like yeah nitrogenous like protein like structures in order to to stabilize them so there there are some experiments doing that which i think is super interesting and certainly expands our view of possible stories for the origin of life possibly around other planets but at this point it's pretty purely speculative because we haven't observed such an environment where those things could be sustained it's a it's a very popular idea though for the planet Titan we're sorry I say the planet Titan the the world Titan the moon and Titan one of the other extremely large extremely popular moons in our solar system it's the only other body in the solar system that has liquid oceans at its surface but it's much much farther out from the Sun than Earth is so this ocean instead of being made of water are made of well mostly methane and ethane and interesting complex hydrocarbons and things like that so it's a lot colder and that's a place where maybe carbon because carbon compounds are sort of forming the basis for the equivalent rock or ices on that world that maybe carbons not the best molecule for as the basis for a biosphere so maybe it's nitrogen instead and so that was sort of I think the motivation behind some of behind some of those experiments yeah yeah which is very interesting though that you know the whole range of interesting consequences for the the climate weather system is on on a hydrocarbon facsimile earth are yeah it's it's a very fascinating and rich field of study that is not my own but sorry unfortunately it is 10 past 10 and I'm about to pass out because I have to be back here at 9 for this science for March thing so thank you all for sticking around thank you all for coming I hope you got something out of both the panel as well as the stargazing and Mike's talk and yeah I encourage you to come to one of our other events we have the next public lecture on the schedule up front April 12th on the Spitzer Space Telescope and the next astronomy on tap in a week and a half on black holes and very large numbers so thank you all for coming

Channel: Caltech Astro

Views: 37,011

Rating: 4.6408978 out of 5

Keywords: Planet X, Planet 9, Mike Brown, universe, astronomy, science, Caltech Astronomy Outreach, Pluto, astrophysics, planetary science

Id: Zw5MDh_wpnI

Length: 109min 43sec (6583 seconds)

Published: Sun Mar 17 2019